HK1094602B

HK1094602B - Process cartridge and image forming apparatus

Info

Publication number: HK1094602B
Application number: HK07101886.8A
Authority: HK
Inventors: 出口英明
Original assignee: 兄弟工业株式会社
Priority date: 2005-01-28
Filing date: 2007-02-16
Publication date: 2010-02-12

Description

Process cartridge and image forming apparatus

Cross Reference to Related Applications

This application claims priority to Japanese patent application Nos. 2005-021992 and 2005-021993, both filed on 28.1.2005, the subject matter of which is herein incorporated by reference in its entirety.

Technical Field

The present invention relates to an image forming apparatus such as a laser printer and a process cartridge included in the image forming apparatus.

Background

In general, a process unit that causes a photosensitive drum to carry a toner image by developing an electrostatic latent image is removably attached to an image forming apparatus such as a laser printer. The photosensitive drum is disposed in contact with and opposed to a transfer roller, and transfers toner to paper when the paper passes between the photosensitive drum and the transfer roller, thereby forming an image on the paper.

However, when a gap is generated between the paper and the photosensitive drum on the upstream side of the transfer position where the photosensitive drum and the transfer roller contact each other in the paper conveyance direction, discharge may occur in the gap. When such discharge occurs, particularly when the paper is thin, a spot-like discharge pattern called penetration through the paper appears.

Therefore, it is proposed to mount a guide for guiding the leading end of the paper closer to the surface of the photosensitive drum on the upstream side of the transfer position in the paper conveying direction.

Fig. 31A to 32C show the paper conveyance state of the conventional process cartridge 90 in stages. The process cartridge 90 holds a photosensitive drum 91 and a transfer roller 92 opposed to the photosensitive drum 91 in contact with a housing 93. A guide 95 is mounted in the housing 93 for guiding the sheet 94 to a transfer position where both the photosensitive drum 91 and the transfer roller 92 contact each other.

A bottom end 96 of the guide 95 (i.e., an upstream side end in the conveying direction of the paper 94, which is used in the following description in the same sense) is fixed to the housing 93 such that the guide 95 is inclined upward in the direction from the upstream side toward the downstream side in the conveying direction of the paper 94 (hereinafter, the upstream side or the downstream side in the conveying direction of the paper 94 is simply referred to as upstream or downstream in some cases). A leading end 97 of the guide 95 (i.e., one end on the downstream side in the conveying direction of the paper 94, which is used for explanation in the following description in the same sense) is disposed close to the photosensitive drum 91 upstream of the transfer position.

As shown in fig. 31A and 31B, when the paper 94 is conveyed to the process cartridge 90, the leading end of the paper 94 is guided to the downstream along the top surface of the guide 95, reaches the leading end 97 from the bottom end 96 of the guide 95, and is then guided into contact with the upstream side of the transfer position in the photosensitive drum 91.

The paper 94 then closely adheres to the photosensitive drum 91 on the upstream side of the transfer position from the leading end thereof, and is guided to the position near the trailing end thereof while closely adhering to the photosensitive drum 91 as shown in fig. 32A. Therefore, the paper 94 does not allow a gap to be generated between the paper on the upstream side of the transfer position and the photosensitive drum 91, and the generation of discharge between the paper and the photosensitive drum is suppressed. As a result, discharge with a mottled pattern in the paper 94 can be prevented.

However, according to the guide 95, when the rear end of the sheet 94 passes the front end 97 of the guide 95, the rear end of the sheet 94 drops from the front end 97 of the guide 95 as shown in fig. 32B and 32C and is guided to the transfer position. Thus, the trailing end of the paper 94 undulates to cause a trailing end transfer defect.

Therefore, it has been proposed to provide first and second guides formed of polyester having the same thickness in parallel with each other on the upstream side of the image carrier in the conveying direction of the transfer paper (see, for example, japanese patent laid-open No. 8-036313). According to this proposal, the rear end of the transfer paper having passed through the first guide is guided to the image carrier by a second guide provided in the vicinity of the transfer position. As a result, transfer defects at the trailing end of the transfer paper are reduced.

However, thin paper such as insufficiently flat paper is easily discharged, and thus needs to be closely adhered to the photosensitive drum on the upstream side of the transfer position to prevent such discharge as described above. While a thick sheet of paper such as a thick postcard is less likely to discharge than a thin sheet of paper, it needs to be conveyed as correctly as possible because the thick sheet of paper will bend when it adheres closely to the photosensitive drum as described above.

However, according to the arrangement disclosed in japanese patent application laid-open No. 8-036313, the second guide member is provided in parallel with the first guide member, so that the transfer paper passing through the first guide member comes into contact with the second guide member provided at the same inclination angle as the first guide member at a large angle. In this case, the resistance of the second guide against the transfer paper increases, and the transfer paper is firmly pressed against the image carrier by the second guide. Therefore, in the case of such thick paper, the transfer paper is bent by such pressing, resulting in transfer defects.

Further, according to the arrangement disclosed in japanese patent application laid-open No. 8-036313, the second guide is provided in parallel with the first guide, and therefore the second guide, which is brought into contact with the transfer sheet passing through the first guide, is provided separately from the first guide, is inclined in the same direction as the first guide, and is brought into contact from the same direction as the inclined direction.

In this case, the transfer sheet is pressed by the second guide from a direction approaching the image carrier to the upstream side in the transfer medium conveyance direction. Thus, the thick transfer paper is bent by the pressing, resulting in transfer defects.

Disclosure of Invention

One aspect of the present invention can provide a process cartridge and an image forming apparatus that can prevent transfer defects in any of a thin transfer medium and a thick transfer medium.

Another aspect of the present invention can provide a process cartridge and an image forming apparatus that can prevent transfer defects by smoothly guiding a thinner or thicker transfer medium to a transfer position.

A process cartridge includes: an image carrier carrying the developer image transferred to the transfer medium at the transfer position; a first guide member provided with a first guide surface that guides the transfer medium to the image carrier, the first guide surface having flexibility; and a second guide member provided with a second guide surface that guides the transfer medium to the image carrier, the second guide surface having flexibility. The first guide surface has a first base end fixed on an upstream side in a transfer medium conveyance direction with respect to the transfer position, and a first leading end of the image carrier extending to the upstream side of the transfer position. The second guide surface has a second base end fixed to the upstream side of the transfer position, and a second leading end extending from the second base end to the image carrier between the first leading end and the transfer position. The second guide member is provided such that a first plane connecting the first leading end and the first base end and a second plane connecting the second leading end and the second base end intersect each other at the first base end or an upstream side of the first base end.

An image forming apparatus includes: an image carrier carrying the developer image transferred to the transfer medium at the transfer position; a developing unit for carrying a developer, supplying the developer to the image carrier, and forming a developer image on the image carrier; a transfer unit for transferring the transfer medium to a transfer position; a first guide member provided with a first guide surface that guides the transfer medium to the image carrier, the first guide surface having flexibility; and a second guide member provided with a second guide surface that guides the transfer medium to the image carrier, the second guide surface having flexibility. The first guide surface has a first base end fixed on an upstream side in a transfer medium conveyance direction with respect to the transfer position, and a first leading end of the image carrier extending to the upstream side of the transfer position. The second guide surface has a second base end fixed to the upstream side of the transfer position, and a second leading end extending from the second base end to the image carrier between the first leading end and the transfer position. The second guide member is provided such that a first plane connecting the first leading end and the first base end and a second plane connecting the second leading end and the second base end intersect each other at the first base end or an upstream side of the first base end.

A process cartridge includes: an image carrier carrying the developer image transferred to the transfer medium at the transfer position; a first guide member provided with a first guide surface that guides the transfer medium to the image carrier, the first guide surface having flexibility; and a second guide member provided with a second guide surface that guides the transfer medium to the image carrier, the second guide surface having flexibility. The first guide surface has a first base end fixed on an upstream side in a transfer medium conveyance direction with respect to the transfer position, and a first leading end of the image carrier extending to the upstream side of the transfer position. The second guide surface has a second base end fixed to the upstream side of the transfer position, and a second leading end extending from the second base end to the upstream side opposite to the first leading end.

An image forming apparatus includes: an image carrier carrying the developer image transferred to the transfer medium at the transfer position; a developing unit for carrying a developer, supplying the developer to the image carrier, and forming a developer image on the image carrier; a transfer unit contacting the image carrier at a transfer position and transferring the developer image to a transfer medium; a transfer unit for transferring the transfer medium to a transfer position; a first guide member provided with a first guide surface that guides the transfer medium to the image carrier, the first guide surface having flexibility; and a second guide member provided with a second guide surface that guides the transfer medium to the image carrier, the second guide surface having flexibility. The first guide surface has a first base end fixed on an upstream side in a transfer medium conveyance direction with respect to the transfer position, and a first leading end of the image carrier extending to the upstream side of the transfer position. The second guide surface has a second base end fixed to the upstream side of the transfer position, and a second leading end extending from the second base end to the upstream side opposite to the first leading end.

Drawings

Included in the drawings are:

fig. 1 is a side sectional view showing a laser printer as an image forming apparatus in a first exemplary manner;

fig. 2 is a side sectional view showing a main part in a process cartridge of the laser printer shown in fig. 1;

fig. 3A and 3B are schematic plan views showing first and second guides, wherein fig. 3A shows the first and second guides arranged continuously in the width direction thereof, and fig. 3B shows the first and second guides divided in the width direction thereof;

fig. 4A and 4B are side cross-sectional views schematically showing the action of guiding the thinner paper to the transfer position in stages, in which fig. 4A shows that the leading end of the thinner paper reaches the first leading end of the first guide surface, and fig. 4B shows that the leading end of the thinner paper is closely adhered to the photosensitive drum;

FIGS. 5A to 5C are side sectional views schematically showing the action of guiding the thin paper to the transfer position in stages, in which FIG. 5A shows the rear end of the thin paper closely adhered to the photosensitive drum, FIG. 5B shows the rear end of the thin paper elastically received by the second front end of the second guide surface, and FIG. 5C shows the rear end of the thin paper guided to the transfer position;

fig. 6A and 6B are side cross-sectional views schematically showing the action of guiding the thick paper to the transfer position in stages, in which fig. 6A shows that the leading end of the thick paper reaches the first leading end of the first guide surface, and fig. 6B shows that the leading end of the thick paper is in contact with the photosensitive drum;

FIGS. 7A and 7B are side cross-sectional views schematically showing the action of guiding the thick paper to the transfer position in stages, in which FIG. 7A shows the rear end of the thick paper in contact with the photosensitive drum, and FIG. 7B shows the rear end of the thick paper being guided to the transfer position;

fig. 8 is a side sectional view showing a main portion of the front ends of the first and second guides;

fig. 9 is a schematic top view showing different structures (i.e., respective cutout shapes) of the first and second guides;

fig. 10 is a schematic plan view showing separation preventing bodies formed at respective ends in different structures (i.e., respective cutout shapes) of the first and second guides;

fig. 11A to 11D are schematic plan views showing different structures (i.e., respective slit shapes) of the first and second guides, wherein fig. 11A shows that the slits are substantially rectangular when viewed from a top view, fig. 11B shows that the slits are substantially V-shaped when viewed from a top view, fig. 11C shows that the slits are substantially U-shaped when viewed from a top view, and fig. 11D shows a separation preventing body formed by end portions of the slits which are substantially V-shaped when viewed from a top view;

fig. 12 is a perspective view showing a different structure of the first and second guides 71 and 72 (in which the first and second guides are formed as one plate member);

fig. 13 is a side view showing a different structure of the first and second guides 71 and 72 (in which the first and second guides are formed as a single sponge assembly);

fig. 14 is a side sectional view of a main portion in a process cartridge of a laser printer as an image forming apparatus in a second exemplary manner;

fig. 15A and 15B are plan views of a first guide member and a second guide member, in which fig. 15A shows the first and second guide members formed continuously with each other in the width direction, and fig. 15B shows the first and second guide members divided in the width direction;

fig. 16A and 16B are side cross-sectional views showing the action of guiding the thin paper to the transfer position by stages using the first and second guides, in which fig. 16A shows that the leading end of the thin paper reaches the first leading end of the first guide surface, and fig. 16B shows that the leading end of the thin paper is in a state of close contact with the photosensitive drum;

fig. 17A to 17C are side cross-sectional views showing in stages the action of guiding the thin paper to the transfer position by the first and second guides, in which fig. 17A shows a state in which the trailing end of the thin paper is in close contact with the photosensitive drum, fig. 17B shows that the trailing end of the thin paper is elastically received by the second leading end of the second guide surface, and fig. 17C shows that the trailing end of the thin paper is guided to the transfer position;

fig. 18A and 18B are side cross-sectional views showing the action of guiding the thick paper to the transfer position by stages using first and second guides, in which fig. 18A shows that the leading end of the thick paper reaches the first leading end of the first guide surface, and fig. 18B shows that the leading end of the thick paper is in close contact with the photosensitive drum;

FIGS. 19A and 19B are side cross-sectional views showing in stages the action of guiding a thick sheet to a transfer position by means of first and second guides, in which FIG. 19A shows a state in which the trailing end of the thick sheet is in close contact with the photosensitive drum, and FIG. 19B shows the trailing end of the thick sheet being guided to the transfer position;

fig. 20 is a side sectional view showing a main portion of the leading ends of the first and second guides;

fig. 21 is a schematic top view showing different structures (i.e., respective cutout shapes) of the first and second guides;

fig. 22 is a schematic plan view showing separation preventing bodies formed at respective ends in different structures (i.e., respective cutout shapes) of the first and second guides;

fig. 23A to 23D are schematic plan views showing different structures (i.e., respective slit shapes) of the first and second guides, in which fig. 23A shows that the slits are substantially rectangular when viewed from a top view, fig. 23B shows that the slits are substantially V-shaped when viewed from a top view, fig. 23C shows that the slits are substantially U-shaped when viewed from a top view, and fig. 23D shows a separation preventing body formed by end portions of the slits which are substantially V-shaped when viewed from a top view;

fig. 24 is a perspective view showing a different structure of the first and second guides 71 and 72 (in which the first and second guides are formed as one plate member);

fig. 25 is a side sectional view of such a main portion of a process cartridge of a laser printer of the third illustrative aspect that the first and second guides are integrally formed with each other;

fig. 26A and 26B are side sectional views showing in stages the action of guiding the thin paper to the transfer position by the first and second guide members shown in fig. 25, in which fig. 26A shows that the leading end of the thin paper reaches the first leading end of the first guide surface, and fig. 26B shows that the leading end of the thin paper is in close contact with the photosensitive drum;

fig. 27A to 27C are side cross-sectional views showing in stages the action of guiding the thin paper to the transfer position by the first and second guides shown in fig. 25, in which fig. 27A shows a state in which the trailing end of the thin paper is in close contact with the photosensitive drum, fig. 27B shows that the trailing end of the thin paper is elastically received by the second leading end of the second guide surface, and fig. 27C shows that the trailing end of the thin paper is guided to the transfer position;

FIGS. 28A and 28B are side cross-sectional views showing in stages the action of guiding the thick paper to the transfer position by the first and second guides shown in FIG. 25, in which FIG. 28A shows that the leading end of the thick paper reaches the first leading end of the first guide surface, and FIG. 28B shows that the leading end of the thick paper is in close contact with the photosensitive drum;

FIGS. 29A to 29C are side cross-sectional views showing in stages the action of guiding the thick paper to the transfer position by the first and second guides shown in FIG. 25, in which FIG. 29A shows a state in which the trailing end of the thick paper is in close contact with the photosensitive drum, FIG. 29B shows the trailing end of the thick paper being elastically received by the second leading end of the second guide surface, and FIG. 29C shows the trailing end of the thick paper being guided to the transfer position;

fig. 30 is a side view showing a different structure of the first and second guides 71 and 72 (in which the first and second guides are formed as a single sponge assembly);

fig. 31A and 31B are side sectional views schematically showing a state where a sheet is conveyed in stages in a conventional process cartridge, in which fig. 31A shows that a leading end of the sheet reaches a leading end of a guide member, and fig. 31B shows that the leading end of the sheet is closely adhered to a photosensitive drum; and

fig. 32A to 32C are side sectional views schematically showing a state of conveying a sheet in stages in a conventional process cartridge, in which fig. 32A shows that a trailing end of the sheet is closely adhered to a photosensitive drum, fig. 32B shows that the trailing end of the sheet falls from a leading end of a guide, and fig. 32C shows that the trailing end of the sheet is guided to a transfer position.

Detailed Description

Exemplary aspects of the present invention are described below with reference to the accompanying drawings.

First exemplary mode

General structure of laser printer

Fig. 1 is a side sectional view showing a laser printer as an image forming apparatus in a first exemplary manner.

Referring to fig. 1, a laser printer 1 includes a sheet feeder 4 for feeding a sheet 3 as a transfer medium, and an image forming unit 5 for forming an image on the fed sheet 3 in a main body casing 2.

Paper feeder structure

The paper feeder 4 includes: a paper feeding tray 6 removably attached to the bottom of the main body casing 2; a paper pressing plate 7 disposed in the paper feeding tray 6; a paper feed roller 8 and a paper feed pad 9 as a conveying unit provided above one end portion of the paper feed tray 6; paper dust removing rollers 10 and 11 provided downstream of the paper feed roller 8 in the conveying direction of the sheet 3 (hereinafter, the upstream side or the downstream side in the conveying direction of the sheet 3 is simply referred to as upstream or downstream in some cases); and an abutment roller 12 disposed downstream of the paper dust removing rollers 10 and 11.

The platen 7 allows the sheet 3 to be stacked with its distal end relative to the feed roller 8 being supported to be bendable, and with its proximal end relative to the feed roller 8 being movable in the up-down direction, with a force being applied upward from the rear surface of the platen 7 by a spring (not shown). Thus, when the number of stacked sheets 3 increases, the paper pressing plate 7 swings downward against the spring pressure with the distal end with respect to the paper feeding roller 8 as a fulcrum. The paper feed roller 8 and the paper feed pad 9 are opposed to each other, and the paper feed pad 9 is pressed to the paper feed roller 8 by a spring 13 provided on the rear surface of the paper feed pad 9.

The paper 3 on the top surface of the platen 7 is pressed by a spring (not shown) from the rear surface of the platen 7 to the paper feed roller 8, and is sandwiched between the paper feed roller 8 and the paper feed pad 9 by the rotation of the paper feed roller 8, and then fed one by one.

Paper dust of the fed sheet 3 is removed by the paper dust removing rollers 10 and 11, and then the fed sheet is conveyed to the resist roller 12. The counter roller 12 is composed of a pair of rollers opposed to each other so that the sheet 3 is sent to the image forming position after being pressed. In addition, the image forming position is a transfer position at which the toner image on the photosensitive drum 27 is transferred to the sheet 3, and is a position at which the photosensitive drum 27 and the transfer roller 30 are in a state of contact with each other in the present exemplary embodiment.

The sheet feeder 4 includes a multipurpose sheet feeding tray 14, a multipurpose sheet feeding roller 15, and a multipurpose sheet feeding pad 25 for feeding sheets 3 stacked on the multipurpose sheet feeding tray 14. The multipurpose paper feed roller 15 and the multipurpose paper feed pad 25 are disposed opposite to each other, and the multipurpose paper feed pad 25 is pressed against the multipurpose paper feed roller 15 by a spring 26 disposed on the rear surface of the multipurpose paper feed pad 25.

The sheets 3 stacked on the multi-purpose sheet feeding tray 14 are sandwiched between the multi-purpose sheet feeding roller 15 and the multi-purpose sheet feeding pad 25 by the rotation of the multi-purpose sheet feeding roller 15, and are then fed one by one.

Structure of image forming unit

The image forming unit 5 includes a scanning unit 16, a process cartridge 17, and a fixing unit 18

Structure of scanning unit

The scanner unit 16 is disposed at an upper position in the main body casing 2, and includes a laser light emitting unit (not shown), a polygonal mirror 19 driven by rotation, lenses 20 and 21, and mirrors 22, 23 and 24, and the like. The laser beam emitted by the laser light emitting unit according to the image data passes through the polygon mirror 19, the lens 20, the mirrors 22 and 23, the lens 21, and the mirror 24 in this order as indicated by the locklines, thereby rapidly scanning on the surface of the photosensitive drum 27 of the process cartridge 17. Structure of processing box

The process cartridge 17 is disposed below the scanner unit 16, and the housing 51 is provided therein with a housing 51 that is freely removable with respect to the main body casing 2, a developing cartridge 28, a photosensitive drum 27 as an image carrier, a scorotron type charger 29, a conductive brush 52, and a transfer roller 30 as a transfer unit.

The housing 51 has an upper housing 53 and a lower housing 54 with a passage for the sheet 3 therebetween. The photosensitive drum 27, the scorotron type charger 29, and the conductive brush 52 are accommodated in an upper casing 53, on which the developing cartridge 28 is attached in a freely removable manner. In addition, the transfer roller 30 is accommodated in the lower case 54.

The developing cartridge 28 is removably attached to the casing 51, and has a developing roller 31 as a developing unit, a layer thickness regulating blade 32, a supply roller 33, and a toner hopper 34.

The toner hopper 34 has an internal space on one side of the housing 51. The positive polarity electrostatic non-magnetic single component toner is housed as a developer in the toner hopper 34. Such a toner may be an example of a toner obtained by copolymerizing a styrene-based monomer such as styrene, or an acrylic monomer such as acrylic acid, alkyl (C1-C4) acrylate, alkyl (C1-C4) metacrylate, by a known polymerization method such as suspension polymerization. This polymerized toner is substantially spherical and has excellent fluidity. Colorants such as carbon black or paraffin are formulated into the toner and provide external additives such as silica to improve flow. The particle size of the toner is about 6 to 10 microns.

The toner in the toner hopper 34 is stirred by an agitator 36 supported by a rotary shaft 35 provided at the center of the toner hopper 34 and discharged from a toner supply port 37 opened at the side portion on the other side of the toner hopper 34. In addition, a window 38 is provided on a side wall of the toner hopper 34 for detecting the remaining amount of toner and is cleaned by a cleaner 39 supported by the rotary shaft 35.

The supply roller 33 is rotatably provided on the other side portion of the toner supply port 37, and the developing roller 31 opposed to the supply roller 33 is also rotatably provided. The above-mentioned supply roller 33 and the developing roller 31 are pressed against each other with a predetermined pressure while being in a state of contact with each other.

The supply roller 33 is composed of a metal roller shaft and a roller body coated with a conductive foam material.

The developing roller 31 is composed of a metallic roller shaft and a roller body coated with a conductive rubber material. Specifically, the roller body of the developer 31 is made of conductive urethane rubber or silicone rubber containing carbon particles, and the surface thereof is covered with a coating layer made of fluorine-containing urethane rubber or silicone rubber. In addition, a developing bias is applied to the developing roller 31 at the time of development.

The layer thickness regulating blade 32 is disposed close to the developing roller 31. The layer thickness regulating blade 32 has a pressing portion 40 formed of insulating silicone rubber and having a semicircular shape in a sectional view at a tip end of the blade formed of a metal reed, and is supported by the developing cartridge 28 near the developing roller 31 so that the pressing portion 40 is pressed against the developing roller 31 by an elastic force of the blade.

The toner discharged from the toner supply port 37 is supplied to the developing roller 31 by rotation in the direction indicated by the arrow (counterclockwise direction) while the toner carries a positive polarity triboelectric charge between both the supply roller 33 and the developing roller 31. The toner supplied onto the developing roller 31 moves between the developing roller 31 and the pressing portion 40 of the layer thickness regulating blade 32 as the developing roller 31 rotates in the direction indicated by the arrow (counterclockwise direction), so that the toner carried on the developing roller 31 is formed into a thin layer having a predetermined thickness.

The photosensitive drum 27 rotatably supported in the direction indicated by the arrow (clockwise direction) in the upper casing 53 is opposed to the developing roller 31 at a lateral portion on the other side of the developing roller 31. The photosensitive drum 27 has its drum body grounded and its surface portion is composed of a positive electrostatic photosensitive layer made of polycarbonate.

A scorotron (scorotron) type charger 29 is disposed on the upper surface of the photosensitive drum 27 opposite to the photosensitive drum 27 with a predetermined gap, and is supported by the upper casing 53. The scorotron charger 29 is a positive polarity electrostatic scorotron charger that generates corona discharge from an electrostatic filament such as tungsten and is configured to charge the surface of the photosensitive drum 27 with a uniform positive polarity.

Further, a conductive brush 52 is provided at a side portion on the other side of the photosensitive drum 27 (a side portion on the opposite side of the developing roller 31) opposite to the photosensitive drum 27. The conductive brush 52 is fixed to the upper case 53 in a state of being in contact with the surface of the photosensitive drum 27.

The transfer roller 30 is disposed in contact with the photosensitive drum 27, and is supported below the photosensitive drum 27 so as to be rotatable in a direction indicated by an arrow (counterclockwise direction). The transfer roller 30 is an ion conductive transfer roller having a metal roller shaft covered with a roller body made of a conductive rubber material. A transfer bias is applied to the transfer roller 30 by constant current control at the time of transfer. In addition, a transfer position is formed at a contact position (nip portion) between the transfer roller 30 and the photosensitive drum 27.

The surface of the photosensitive drum 27 is charged with a uniform positive polarity by a scorotron type charger 29, and then exposed to a laser beam emitted from the scanner unit 16 by fast scanning, thereby forming an electrostatic latent image in accordance with image data.

Next, when the positively charged toner carried on the developing roller 31 is brought into opposed contact with the photosensitive drum 27 by the rotation of the developing roller 31, the toner is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 27, and the exposed portion exposed to the laser beam has a reduced potential on the surface of the photosensitive drum 27 having a uniform positive charge, thus selectively carrying the toner to be visible, so that the toner image is formed into a developer image by reverse development.

Then, the sheet 3 held between the photosensitive drum 27 and the transfer roller 30 is conveyed with respect to the transfer position by rotationally driving the photosensitive drum 27 and the transfer roller 30, and the sheet 3 is conveyed between the photosensitive drum 27 and the transfer roller 30, whereby the toner image carried on the surface of the photosensitive drum 27 is transferred to the sheet 3.

After the transfer, the paper dust adhering to the surface of the photosensitive drum 27 due to the contact with the paper 3 is removed by the brush portion of the conductive brush 52 when the surface of the photosensitive drum 27 is opposed to the brush portion as the photosensitive drum 27 rotates.

The laser printer 1 adopts a cleaning-free method of transferring toner onto the sheet 3 by the transfer roller 30 and then recovering residual toner on the surface of the photosensitive drum 27 by the developing roller 31. When this cleaning-free arrangement is adopted to recover the toner remaining on the photosensitive drum 27, a toner cleaning unit or a reservoir for used toner is no longer required, so that the apparatus structure can be simplified.

Structure of fixing unit

The fixing unit 18 is disposed on the other downstream side of the process cartridge 17, and has a heating roller 41, a pressing roller 42 opposed to the heating roller 41 and pressing the heating roller 41, and a pair of conveying rollers 43 disposed on the downstream sides of the heating roller 41 and the pressing roller 42.

A heating roller 41 made of metal and having a halogen lamp is used for heating, and the toner transferred to the sheet 3 is thermally fixed while the sheet 3 passes between the heating roller 41 and the pressing roller 42 in the process cartridge 17, and then the sheet 3 is conveyed to the conveying path 44 by a conveying roller 43. The sheet 3 sent to the conveying path 44 is conveyed to the conveying roller 45, and then conveyed to the sheet discharge tray 46 by the conveying roller 45.

Description of the Duplex printing Unit

An inversion conveyance unit 47 as a duplex printing unit is provided in the laser printer 1 for forming images on both sides of the sheet 3. The inversion conveyance unit 47 has a conveyance roller 45, an inversion conveyance path 48, a flap 48, and a plurality of inversion conveyance rollers 50.

The conveying roller 45 is composed of a pair of rollers, and is configured to switch between normal rotation and inversion rotation. The conveying rollers 45 rotate in the normal direction when the sheet 3 is conveyed onto the sheet discharge tray 46, but rotate in the reverse direction when the sheet 3 is reversed as described above.

The turn-over conveying path 48 is provided in the upward and downward directions, so that the sheet 3 can be conveyed from the conveying roller to a plurality of turn-over conveying rollers 50 provided below the image forming portion, the upstream end of which is provided near the conveying roller 45 and the downstream end of which is provided near the turn-over conveying rollers 50.

The flap 49 is swingable to reach a branch portion between the reversing conveyance path 48 and the conveyance path 44, and is switched by whether or not a solenoid (not shown) is energized, and the conveyance direction of the sheet 3 is switched to the direction toward the reversing conveyance path 48 by the conveyance roller 45.

A plurality of turn-over conveying rollers 50 are disposed in a substantially horizontal direction above the paper feeding tray 6. The turn-over conveying roller 50 located most upstream is disposed at a position closer to the rear end of the turn-over conveying passage 48, and the turn-over conveying roller 50 located most downstream is disposed below the counter roller 12.

When images are formed on both sides of the sheet 3, the reversing conveyance unit 47 operates as follows. Specifically, when the sheet having an image formed on one surface is returned from the conveying path 44 to the conveying roller 45 by the conveying roller 43, the conveying roller 45 normally rotates with the sheet 3 sandwiched therebetween, so that the sheet 3 is conveyed to the outside (the sheet discharge tray 46 side), and most of the sheet 3 is discharged to the outside, so that the normal rotation is stopped when the rear end of the sheet 3 is sandwiched by the conveying roller 45. Next, the conveying direction is switched while the conveying roller 54 performs reverse rotation to allow the sheet 3 to be conveyed to the inside out conveying path 48, so that the sheet 3 is conveyed to the inside out conveying path 48 in the reverse direction before and after switching. Further, the movable flap 49 can be switched to a conveyance state in which the sheet 3 is conveyed from the conveying roller 43 to the conveying roller 45 when conveyance of the sheet 3 is stopped.

Subsequently, the sheet 3 reversely conveyed to the reversing conveyance path 48 is conveyed to the reversing conveyance roller 50, reversed by the reversing conveyance roller 50, and conveyed to the counter roller 12. The sheet 3 conveyed in its inverted state to the counter roller 12 is subjected to a predetermined squeezing and shaping and then conveyed again to the image forming portion, whereby images are formed on both sides of the sheet 3.

Structure of main part in process cartridge

Fig. 2 is a side sectional view showing a main portion in the process cartridge 17 of the laser printer 1 shown in fig. 1.

As shown in fig. 2, the lower case 54 of the process cartridge 17 is integrally provided with a transfer roller housing unit 55 housing the transfer roller 30, and a paper guide unit 56 disposed on the upstream side of the transfer roller housing unit 55 for guiding the paper 3 to the photosensitive drum 27.

The transfer roller housing unit 55 is recessed in a cross-sectional view in a width direction (hereinafter simply referred to as a width direction) orthogonal to the conveyance direction of the sheet 3, and the transfer roller 30 is housed by the recessed transfer roller housing unit 55, is rotatably supported by the transfer roller housing unit 55, and is disposed below the photosensitive drum 27 so as to be in opposed contact with the photosensitive drum 27.

The sheet guide unit 56 is substantially flat plate-shaped, slightly inclined upward from the rear end (i.e., the upstream side end portion in the conveying direction of the sheet 3, which will be described in the following description) to the front end (i.e., the downstream side end portion in the conveying direction of the sheet 3, which will be described in the following description), and is integrally provided with a holding portion 57 that holds the first guide member 71 and the second guide member 72, and an introduction portion 59 that is provided with the rib member 58.

The holding portion 57 is fixed to the transfer roller housing unit 55, and has a front end continuous with a rear end of the transfer roller housing unit 55 and a rear end continuous with a front end of the introduction portion 59. A step unit 61 for holding the first guide 71 is provided at the rear end of the holding portion 57. The step unit 61 is formed as a step recessed in a substantially L-shape with its height set to the thickness of the first guide 71 or more so as to avoid adhesion of the upstream conveyed sheet in the step.

As shown in fig. 2, the introduction portion 59 has a front end connected to the rear end of the holding portion 57 and a rear end extending toward the abutment roller 12. The rib assembly 58 is disposed in the lead-in portion 59. The rib member 58 is formed to reinforce the lower case 54 and reduce frictional resistance when conveying the paper, and has a plate shape, is provided upright in the vertical direction in the conveying direction of the paper 3 in the introduction portion 59, and is formed with a plurality of rib members at predetermined intervals in the width direction of the paper 3. In addition, the front end of each rib assembly 58 is set substantially to the height of the rear end of the step unit 61 or more, i.e., the upper surface between the upper surface having the step and the lower surface having the step.

The first guide 71 and the second guide 72 in the process cartridge 17 are supported by the holding portion 57.

The first guide 71 and the second guide 72 are formed of an insulating material having flexibility, such as a resin like polyethylene terephthalate, and are composed of a substantially rectangular film member formed by a punching process.

The first base end 73 as the rear end is fixed to the step surface of the step unit 61 of the holding portion 57 so that the first guide 71 is inclined upward from upstream to downstream. The first guide member 71 extends from the first bottom end 73 thereof to the photosensitive drum 27, so that the top surface of the first guide member 71 constitutes a first guide surface 71A for guiding the sheet 3 to the photosensitive drum 27. A first leading end 74 as a leading end of the first guide 71 is disposed close to the photosensitive drum 27 above the leading end of the holding portion 57 on the upstream side of the transfer position. The first guide 71 is formed to have a thickness of 0.100 to 0.200 mm, preferably 0.125 mm.

The second base end 75 as the rear end is fixed to the top surface of the front end of the holding portion 57 downstream of the first base end 73 of the first guide 71, so that the second guide 72 is inclined upward from upstream to downstream. The second guide member 72 extends from the second bottom end 75 thereof to the photosensitive drum 27, so that the top surface of the second guide member 72 constitutes a second guide surface 72A for guiding the paper 3 to the photosensitive drum 27. A second leading end 76 as a leading end of the second guide 72 is disposed close to the photosensitive drum 27 between both the transfer position and the first leading end 74 of the first guide 71. The second guide member 72 is formed to have a thickness of 0.075 to 0.125 mm, preferably 0.100 mm.

When the surface of each of the first guide 71 and the second guide 72 on the side in contact with the cutting blade in press working is a front surface and the opposite side surface thereof is a back surface, the front surface, i.e., the sagging surface in press working, is set as a top surface (a first guide surface 71A and a second guide surface 72A) in contact with the paper 3 and the back surface thereof is set as a bottom surface opposite to the top surface of the holding portion 57.

The edge of the first leading end 74 of the first guide surface 71A and the edge of the second leading end 76 of the second guide surface 72A are disposed above a line L connecting a contact position (transfer position) between the photosensitive drum 27 and the transfer roller 30 and a contact position between two opposing rollers 12 opposing each other.

The first guide 71 and the second guide 72 may be disposed in a width direction orthogonal to the conveying direction of the sheet 3, specifically, in a direction parallel to the axial direction of the photosensitive drum 27, as shown in fig. 3A.

The first guide 71 and the second guide 72 may be divided as shown in fig. 3B by being arranged in parallel with each other at predetermined intervals in the orthogonal direction to the conveying direction of the sheet 3.

The first guide 71 may set a contact position between the paper 3 and the photosensitive drum 27 by the curvature of the first leading end 74, and is provided as a portion capable of guiding the paper at a contact angle θ 1 between the paper 3 and the photosensitive drum 27 smaller than 90 °. The second guide 72 may set a contact position between the paper 3 and the photosensitive drum 27 by the curvature of the second leading end 76, and is provided as a portion capable of guiding the paper at a contact angle θ 2 between the paper 3 and the photosensitive drum 27 smaller than 90 °. Each inclination angle of the first guide 71 and the second guide 72 with respect to the holding portion 57 is set so that θ 1 is larger than θ 2.

The first guide 71 is formed with an elastic modulus of extension E in a direction parallel to the conveying direction of the sheet 3₁And a geometrical moment of inertia I in a direction parallel to the longitudinal direction of the photosensitive drum 27 and perpendicular to the maximum plane (top or bottom surface) of the first guide 71₁Product E of the two₁I₁At 3.49X 10^-5≤E₁I₁≤1.18×10^-3Within the range. The second guide member 72 is formed with an elastic modulus of extension E in a direction parallel to the conveying direction of the sheet 3 therein₂And a geometrical moment of inertia I in a direction parallel to the axial direction of the photosensitive drum 27 and perpendicular to the maximum plane (top or bottom surface) of the second guide 72₂Product E of the two₂I₂At 3.49X 10^-5≤E₂I₂≤1.18×10^-3Within the range.

The length from the first front end 74 to the first bottom end 73 of the first guide face 71A is longer than the length from the second front end 76 to the second bottom end 75 of the second guide face 72A. The second leading end 76 of the second guide surface 72A is provided on the first guide surfaceThe sheet guided by the guide surface 71A presses the downstream of the projection plane in such a (downward) direction of the first guide member 71. Also, the first guide 71 is formed thicker than the second guide 72 as described above, so that the geometric moment of inertia I of the first guide 71₁Set to be larger than the geometrical moment of inertia I of the second guide 72₂。

But the geometrical moment of inertia I of the first guide 71₁Set to be larger than the geometrical moment of inertia I of the second guide 72₂The method of (3) is not limited to the method of forming the first guide 71 thicker than the second guide 72 as described above, and the width direction length of the first guide 71 may be formed longer than the width direction length of the second guide 72.

The inclination angle θ 3 of the first guide 71 with respect to the holder 57 is about 30 ° to 45 °, and preferably about 30 ° (see fig. 5C). The inclination angle θ 4 of the second guide 72 with respect to the holding portion 57 is about 10 ° to 40 °, and preferably about 20 °. (refer to fig. 5C). An inclination angle θ 4 of the second guide 72 with respect to the holding portion 57 is set smaller than an inclination angle θ 3 of the first guide 71 with respect to the holding portion 57 so that a plane 77 connecting the first front end 74 and the first bottom end 73 of the first guide 71 and a plane 78 connecting the second front end 76 and the second bottom end 75 of the second guide 72 intersect with each other on the upstream side of the first bottom end 73.

The following specifically describes an operation of guiding the thin paper sheet 3 and the thick paper sheet 3 to the transfer position in the process cartridge 17. In the present exemplary embodiment, when the weight per square meter of the paper 3 (plain paper) is 75 to 105 g/m, such plain paper or paper (for example, recording paper) having a weight of 56 to 75 g/m is referred to as thin paper, and paper (for example, postcard or the like) having a weight of 105 to 200 g/m or more is referred to as thick paper.

Description of the operation of guiding a thinner sheet to a transfer position

Fig. 4A to 5C show the operation of guiding the thinner paper 3 to the transfer position in stages. As shown in fig. 4A, in this process cartridge 17, when the thin paper 3 is first conveyed, the leading end of the paper 3 is guided downstream along the first guide surface 71A of the first guide member 71, reaches the first leading end 74 from the first bottom end 73 of the first guide surface 71A, and is then guided into contact with the upstream side of the transfer position of the photosensitive drum 27.

However, the thin paper 3 is weak, and therefore even when the leading end of the thin paper 3 comes into contact with the photosensitive drum 27 as shown in fig. 4B, the first leading end 74 of the first guide 71 is not bent significantly, and is guided to the transfer position as it is when the paper 3 closely adheres to the photosensitive drum 27.

Next, the thin paper 3, as shown in fig. 5A, is closely adhered to the photosensitive drum 27 from the leading end on the upstream side of the transfer position until the vicinity of the trailing end thereof is guided to the transfer position in a state of being closely adhered to the photosensitive drum 27.

Therefore, a gap between the thin paper 3 and the photosensitive drum 27 is not formed on the upstream side of the transfer position, and thus the occurrence of electric discharge between the two can be suppressed. As a result, a spot-like discharge pattern, which is referred to as a penetrated through sheet 3, on the sheet 3 can be prevented from occurring.

Further, when the thin paper 3 is guided from the front end to the rear end thereof by the first guide 71, the bottom surface of the paper 3 may be slidably guided to the transfer position on the second guide surface 72A of the second guide 72, or may not be slidably guided to the transfer position on the second guide surface 72A of the second guide 72.

The second leading end 76 of the second guide surface 72A is provided downstream of a projection plane in a direction in which the sheet 3 guided by the first guide surface 71A presses the first guide member 71. Thus, when the rear end of the thin paper 3 passes the first front end 74 of the first guide surface 71A, as shown in fig. 5B and 5C, the rear end of the thin paper 3 drops from the first front end 74 of the first guide surface 71A, and is elastically received by the second front end 76 of the second guide surface 72A to be guided to the transfer position. Therefore, the swing of the rear end of the thin paper 3 can be suppressed, and the occurrence of the transfer defect at the rear end can be prevented.

Description of the operation of guiding a thick sheet to a transfer position

Fig. 6A to 7B show the operation of guiding the thick paper 3 to the transfer position in stages. As shown in fig. 6A, in this process cartridge 17, when the thick paper 3 is first conveyed, the leading end of the paper 3 is guided downstream along the first guide surface 71A of the first guide member 71, reaches the first leading end 74 from the first bottom end 73 of the first guide surface 71A, and is then guided into contact with the upstream side of the transfer position of the photosensitive drum 27.

However, the thick paper 3 is thick, and when the leading end of the thick paper 3 comes into contact with the photosensitive drum 27 as shown in fig. 6B, the second guide 72 is bent significantly in the downward direction due to the contact with the leading end of the paper 3, and the thick paper 3 is guided to the transfer position by the first guide 71 and the second guide 72 in a state where both the first guide 71 and the second guide 72 are in contact with or close to each other.

As shown in fig. 2, the plane 78 connecting the second front end 76 and the second bottom end 75 of the second guide member 72 and the plane 77 connecting the first front end 74 and the first bottom end 73 of the first guide member 71 intersect each other on the upstream side of the first bottom end 73, so that the sheet 3 comes into contact with the second guide surface 72A at a smaller angle when the sheet 3 is guided from the first guide surface 71A to the second guide surface 72A than in the case where the second guide member is parallel to the first guide member 71. Thus, the resistance of the second guide surface 72A against the sheet 3 is reduced, so that the sheet 3 can strongly press the second guide surface 72A, so that the second guide surface 72A is significantly curved in a direction corresponding to the direction in which the thick sheet 3 is directed.

Thus, as shown in fig. 7A, the thick paper 3 is guided relatively directly to the transfer position, so that it is possible to prevent the occurrence of transfer defects due to the bending of the thick paper 3. In addition, the friction of the sheet 3 in contact with the second guide surface 72A can be reduced, so that the sheet 3 can be prevented from being vibrated by the friction between the second guide surface 72A and the sheet 3, thereby preventing transfer defects caused by the vibration.

Further, even if a gap appears between the sheet and the photosensitive drum 27 as compared with the thin sheet 3, the discharge is less likely to occur in the thick sheet 3, and even if the thick sheet 3 is relatively directly guided to the transfer position, the discharge pattern due to the discharge is less likely to occur.

Next, the thick paper 3 is guided to the vicinity of the rear end as shown in fig. 7A, and since the first guide member 71 is bent significantly to come into contact with or approach the second guide member 72, it is continuously received from the first front end of the first guide surface 71A to the second front end 76 of the second guide surface 72A, whereby the thick paper is guided to the transfer position as shown in fig. 7B. Thus, the rear end of the thick paper 3 can be prevented from wobbling, thereby preventing transfer defects at the rear end.

In this way, the simple structure of the process cartridge 17 using the first guide 71 and the second guide 72 formed of the flexible films can prevent the transfer defect regardless of whether the paper 3 is thinner or thicker. Moreover, an image is formed on a sheet by the laser printer 1 including the process cartridge 17, so that reliable image formation can be achieved.

In this case, at least one of the first guide 71 and the second guide 72 may be composed of a deformable component such as a sponge other than the membrane member.

Geometrical moment of inertia I of the first guide 71₁Set to be larger than the geometrical moment of inertia I of the second guide 72₂So that the first guide 71 is stronger than the second guide 72. Thus, in the case of guiding the thin paper 3, the leading end of the thin paper 3 can be guided to a position as close as possible to the photosensitive drum 27 by the relatively strong first guide 71. Therefore, the discharge pattern caused by the discharge of the thin paper 3 can be further prevented.

The second guide member 72 is thinner than the first guide member 71, so that the pressing force with which the second guide surface 72A can press the paper 3 to the photosensitive drum 27 is relatively weak, so that friction between the paper 3 and the second guide surface 72A is relatively small. Thus, the thick paper 3 is guided to the transfer position more correctly, thereby further preventing the thick paper 3 from suffering transfer defects due to bending. In addition, it is possible to further prevent the occurrence of transfer defects due to vibrations caused by friction between the sheet 3 and the second guide 72.

The length from the first leading end 74 to the first bottom end 73 of the first guide surface 71A is longer than the length from the second leading end 76 to the second bottom end 75 of the second guide surface 72A, but the second guide surface 72A is provided closer to the transfer position than the first guide surface 71A, and therefore even if the second guide surface 72A is shorter than the first guide surface 71A, the second leading end 76 can be sufficiently close to the photosensitive drum 27. Thus, the sheet 3 can be smoothly guided to the transfer position.

In addition, the geometric moment of inertia I of the first guide 71₁And modulus of elasticity E₁Product E of the two₁I₁At 3.49X 10^-5≤E₁I₁≤1.18×10^-3In range, and the geometric moment of inertia I of the second guide 72₂And modulus of elasticity E₂Product E of the two₂I₂At 3.49X 10^-5≤E₂I₂≤1.18×10^-3Within the range, the first guide 71 and the second guide 72 can be thereby well deformed according to the thickness of the sheet 3, respectively. Thus, the sheet 3 can be smoothly guided to the transfer position.

When the contact angle θ 1 between the photosensitive drum 27 and the sheet 3 guided by the first guide 71 is 90 °, the leading end of the sheet 3 is nipped when the sheet 3 is in contact with the photosensitive drum 27, and when the contact angle θ 1 exceeds 90 °, the sheet is guided to the opposite side of the transfer position with respect to the contact position. The first guide 71 is provided at such a position that the contact angle θ 1 between the photosensitive drum 27 and the sheet 3 is smaller than 90 °. Thus, when the sheet 3 comes into contact with the photosensitive drum 27, the sheet is guided so that the contact angle θ 1 between the photosensitive drum 27 and the sheet 3 is less than 90 °, and the sheet 3 can be smoothly guided to the transfer position.

Further, the first guide surface 71A and the second guide surface 72A are formed of a drooping surface formed by press working, so that the sheet can be smoothly guided without being caught by the edge 65 of the first guide surface 71A and the second guide surface 72A.

Specifically, when the first guide 71 and the second guide 72 are formed by press working, the end portion 65 of the back surface 64 on the opposite side of the surface 63 formed as the drooping surface is cut by a shearing force of a cutting blade at the time of press forming, and is formed into a protruding shape (burr) as shown in fig. 8. When the rear surface 64 is arranged as a top surface (the first guide surface 71A and the second guide surface 72A) that contacts the sheet 3, the sheet 3 is caught by the end 65 (burr) having the protruding shape, and thus smooth conveyance cannot be achieved.

However, according to this process cartridge 17, since the surface 63 formed as a hanging surface by press working is a top surface and the back surface 64 on the opposite side is a bottom surface, and the bottom surface is opposed to the top surface of the holding portion 57, that is, the back surface 64 is not in contact with the sheet 3, the sheet 3 can be smoothly guided without being caught by the edge 65 of the back surface 64, as described above.

In addition, the transfer roller 30 is included in the process cartridge 17, and thus the relative positions of the first guide 71 and the second guide 72 with respect to the transfer position can be maintained with high accuracy. Thus, the occurrence of transfer defects can be further prevented regardless of whether the sheet 3 is thin or thick.

The edge of the first leading end 74 of the first guide surface 71A is disposed higher than the line L connecting the contact position between the photosensitive drum 27 and the transfer roller 30 and the contact position between the two counter rollers 12, so that the paper sheet 3 can be guided to the upstream side of the transfer position in the rotational direction of the photosensitive drum 27. Therefore, the discharge pattern caused by the discharge of the thinner paper sheet 3 can be reliably prevented.

The first and second guides 71 and 72 are formed of a material such as a resin film, so that the photosensitive drum 27 can be prevented from conducting electricity through the sheet 3. Therefore, the transfer of the toner image can be reliably achieved.

In addition, the first bottom end 73 of the first guide member 71 and the second bottom end 75 of the second guide member 72 are fixed to the housing 51, so that the photosensitive drum 27, the first and second guide members 71 and 72 can be integrally held by the housing, thus allowing the first and second guide surfaces 71A and 72A to be reliably arranged with respect to the photosensitive drum 27.

As shown in fig. 3B, the first guide 71 and the second guide 72 are divided in the width direction thereof, so that the frictional resistance when the sheet 3 is conveyed in the first guide 71 and the second guide 72 can be reduced, and smooth guidance can be achieved.

Exemplary manner of deformation

Fig. 9 is a schematic plan view showing another structure of the first guide 71 and the second guide 72. A plurality of cutouts 66 are formed in the first leading end 74 of the first guide 71 and the second leading end 76 of the second guide 72 at substantially equal intervals in the width direction orthogonal to the conveying direction of the sheet 3. Each slit 66 extends from an edge of the first leading end 74 or an edge of the second leading end 76 to halfway toward the first bottom end 73 or the second bottom end 75 in the conveying direction of the sheet 3 (refer to fig. 2).

By forming such a cutout 66, the first guide 71 and the second guide 72 can be assembled to the holding portion 57 with high accuracy without wrinkles on the first guide 71 and the second guide 72 (refer to fig. 2).

Specifically, the first guide 71 and the second guide 72 are thin and elongated in the width direction, so that when both ends in the width direction of the first guide 71 and the second guide 72 are fitted (connected) to the aligned positions of the holding portions 57, the center portions in the width direction of the first guide 71 and the second guide 72 are displaced. On the other hand, when the first guide 71 and the second guide 72 are aligned with each other at one end in the width direction with respect to the holding portion 57 and are sequentially assembled from the one end in the width direction to the other end in the width direction, the first guide 71 and the second guide 72 are prevented from being displaced at the center in the width direction, but wrinkles are likely to occur in the first guide 71 and the second guide 72.

According to the first guide 71 and the second guide 72 of the present exemplary embodiment, a plurality of cutouts 66 are formed therein, and thus wrinkles generated when the first guide 71 and the second guide 72 are fitted to the holding portion 57 in order from one end portion in the width direction thereof can be absorbed by the respective cutouts 66. Thus, it is possible to fit the first guide 71 and the second guide 72 to the holding portion 57 with high accuracy without occurrence of wrinkles on the first guide 71 and the second guide 72.

Further, by dividing the first leading end 74 of the first guide 71 and the second leading end 76 of the second guide 72 into a plurality of portions in the width direction of the slit 66, the first guide 71 and the second guide 72 can be deformed only at a portion in contact with the sheet 3 when the sheet 3 having a narrow width is continuously conveyed. Therefore, when the sheet 3 having a narrow width is continuously conveyed, the first guide 71 and the second guide 72 as a whole can be prevented from being deformed by bending of the portion in contact with the sheet 3, and the reliability of the first guide 71 and the second guide 72 in terms of durability can be enhanced.

In addition, only one cutout 66 may be formed at the first front end 74 of the first guide 71 or the second front end 76 of the second guide 72. In the case of forming the plurality of slits 66, the intervals between the slits in the width direction do not necessarily have to be substantially equal intervals, and may be different intervals. For example, the cutouts 66 may be formed in the first front end 74 of the first guide 71 or the second front end 76 of the second guide 72 at positions corresponding to both edges in the width direction of the paper 3 of various sizes conveyed on the first guide 71 or the second guide 72 so as to correspond to various sizes of the paper 3 usable in the laser printer 1. In this case, the first guide 71 or the second guide 72 may be deformed only at a portion in contact with the sheet 3 when the sheet 3 is conveyed.

Fig. 10 is a schematic plan view showing another structure of the first guide 71 and the second guide 72. Referring to fig. 10, the same reference numerals as in fig. 9 are given to portions corresponding to those shown in fig. 9, and detailed description thereof will be omitted.

In the first guide 71 and the second guide 72 shown in fig. 10, the separation preventing body 67 is formed at the end of the first bottom end 73 or the second bottom end 75 of each cutout 66. The separation preventing body 67 is formed as a hole having a substantially circular hole shape in a plan view at an end portion of each slit 66, and penetrates from a top surface of the first guide 71 and the second guide 72, which are in contact with the sheet 3, to a bottom surface of the opposite side thereof in the conveying direction of the sheet 3.

Thus, the first guide 71 and the second guide 72 can be prevented from being separated from the end of each cutout 66.

Fig. 11A to 11D are schematic plan views showing another structure of the first guide 71 and the second guide 72. The first and second leading ends 74 and 76 of the first and second guides 71 and 72 shown in fig. 11A to 11D are respectively provided with a plurality of slits 68 side by side with each other at substantially equal intervals in the width direction orthogonal to the sheet conveying direction. Each slit 68 extends from an edge of the first leading end 74 or an edge of the second leading end 76 to halfway toward the first bottom end 73 or the second bottom end 75 in the conveying direction of the sheet 3 (refer to fig. 2).

By forming such a slit 68, as in the case of the slit 66, the first guide 71 and the second guide 72 can be fitted to the holding portion 57 with high accuracy without wrinkles on the first guide 71 and the second guide 72. In addition, when the sheet 3 having a narrow width is continuously conveyed, the first and second guides 71 and 72 can be prevented from being deformed in their entirety with the bending of the portion in contact with the sheet 3, and the reliability of the first guide 71 and the second guide 72 in terms of durability can be enhanced.

Moreover, the slit 68 has a width in a direction orthogonal to the conveying direction of the sheet 3 unlike the slit 66, and thus the portions between the first and second guides 71 and 72, which sandwich the slit 68 therebetween, can be further prevented from overlapping each other when the first guide 71 and the second guide 72 are fitted to the holding portion 57.

Each slit 68 may have a substantially rectangular shape in plan view as shown in fig. 11A, a substantially V-shape in plan view as shown in fig. 11B, or a substantially U-shape in plan view as shown in fig. 11C.

When each slit 68 has a substantially rectangular shape or a substantially U-shape in plan view, the first guide 71 and the second guide 72 can be prevented from being separated from the end of the first bottom end 73 or the second bottom end 75 of each slit 68 (refer to fig. 2).

In addition, when each slit 68 has a substantially V-shape in plan view, the portions between the first and second guides 71 and 72, which sandwich the slit 68, are sequentially distant from the rear end to the front end, and thus the portions between the first and second guides 71 and 72, which sandwich the slit 68, can be further prevented from overlapping each other when the first and second guides 71 and 72 are assembled to the holding portion 57.

In this case, as shown in fig. 11D, the separation preventing body 69 is desirably formed at an end of the first bottom end 73 or the second bottom end 75 of the slit 68. The separation preventing body 69 is formed as a hole having a substantially circular hole shape in a plan view at an end portion of each slit 68, and penetrates from a top surface of the first guide 71 and the second guide 72, which are in contact with the sheet 3, to a bottom surface of the opposite side thereof in the conveying direction of the sheet 3. By forming the separation preventing body 69, the first guide 71 and the second guide 72 can be prevented from being separated at the deepest portion of each slit 68.

Also, only 1 slit 68 may be provided at the first front end 74 of the first guide 71 or the second front end 76 of the second guide 72. When the plurality of slits 68 are formed, the intervals between the slits in the width direction do not necessarily have to be substantially equal intervals, and may be different intervals. For example, the slits 68 may be formed in the first front end 74 of the first guide 71 or the second front end 76 of the second guide 72 at positions corresponding to both edges in the width direction of the paper 3 of various sizes conveyed on the first guide 71 or the second guide 72 so as to correspond to various sizes of the paper 3 usable in the laser printer 1. In this case, the first guide 71 or the second guide 72 may be deformed only at a portion in contact with the sheet 3 when the sheet 3 is conveyed.

Fig. 12 is a perspective view showing another structure of the first guide 71 and the second guide 72.

Referring to fig. 12, the first guide 71 and the second guide 72 are formed of an insulating material having flexibility, such as a resin like polyethylene terephthalate, and are composed of a substantially single rectangular plate member 80 formed of a film member formed by a punching process.

The plate member 80 has a longitudinal direction oriented in the width direction, and a bottom surface of a base end 183 as a short-side direction rear end portion thereof is fixed along a rear end portion of the holding portion 57 shown in fig. 2. A leading end 184, which is a short-side direction leading end portion of the plate member 80, is disposed close to the photosensitive drum on the upstream side of the transfer position.

A plurality of cutouts 181 extending from the edge of the front end 184 to halfway toward the bottom end 183 in the short side direction of the plate member 80 are formed in the width direction, so that a plurality of front end pieces 182 are formed in the width direction.

The plurality of front end pieces 182 have different lengths alternately with each other in the width direction. In this case, the length is from the rear end portion to the front end portion of the front end piece. The front end piece 182 having a short length from the front end portion (first front end 74) to the rear end portion (first bottom end 73) constitutes the first guide 71, and the front end piece 182 having a long length from the front end portion (second front end 76) to the rear end portion (second bottom end 75) constitutes the second guide 72. The top surface of the first guide member 71 constitutes a first guide surface 71A, and the top surface of the second guide member 72 constitutes a second guide surface 72A. Thus, the first guide 71 and the second guide 72 can be simply formed with only a single plate member 80.

The first guide 71 and the second guide 72 are bent at different angles from each other centering on the edge of the rear end portion of the cutout 81 in the opposite (upward) direction to the direction in which the sheet 3 presses the first guide 71 and the second guide 72.

The inclination angle formed by the first guide 71 extending in the direction of the short side thereof with respect to the bottom end 183 of the plate member 80, i.e., the inclination angle θ 3 of the first guide 71 with respect to the holder 57, is about 30 ° to 45 °, preferably about 30 °. The inclination angle formed by the second guide 72 extending in the direction of the short side thereof with respect to the bottom end 183 of the plate member 80, i.e., the inclination angle θ 4 of the second guide 72 with respect to the holder 57, is about 10 ° to 40 °, preferably about 20 °, which is smaller than the inclination angle θ 3 of the first guide 71 with respect to the holder 57.

In this way, the inclination angle θ 4 of the second guide 72 with respect to the holding portion 57 is set smaller than the inclination angle θ 3 of the first guide 71 with respect to the holding portion 57, so that the plane 77 connecting the first front end 74 and the first bottom end 73 of the first guide 71 and the plane 78 connecting the second front end 76 and the second bottom end 75 of the second guide 72 intersect each other on the edge of the rear end portion of the cutout 81, which is the straight line 85 connecting the first bottom end 73. Thus, in the case of either the thin paper sheet 3 or the thick paper sheet 3, the transfer defect can be prevented from occurring by virtue of the same action as the first guide 71 and the second guide 72 in the above-described exemplary manner.

Fig. 13 is a side view showing another structure of the first guide 71 and the second guide 72. Referring to fig. 13, a first guide 71 and a second guide 72 are integrally formed by a deformable member 70 such as a sponge. Specifically, the deformable member 70 is provided with a bottom surface opposite to a top surface of the holding portion 57, and a top surface formed with a first guide surface 71A and a second guide surface 72A at different inclination angles from each other. The portion forming the first guide surface 71A of the transformable assembly 70 constitutes the first guide surface 71, and the portion forming the second guide surface 72A of the transformable assembly 70 constitutes the second guide surface 72.

A plane 77 connecting the first front end 74 and the first bottom end 73 of the first guide face 71A and a plane 78 connecting the second front end 76 and the second bottom end 75 of the second guide face 72A intersect each other on the upstream side of the first bottom end 73. Thus, in the case of either the thin paper sheet 3 or the thick paper sheet 3, the transfer defect can be prevented from occurring by virtue of the same action as the first guide 71 and the second guide 72 in the above-described exemplary manner.

In addition, in each of the exemplary modes and the modified exemplary modes, the transfer roller 30, the first guide 71, and the second guide 72 are provided in the process cartridge 17, but may be provided in the main body casing 2.

In the modification, physical properties (geometrical moment of inertia, length, product of elastic modulus and geometrical moment of inertia, material, etc.) and arrangement (contact angle between paper and the photosensitive drum, orientation of a sag formed by press working, etc.) similar to those of the modification may be combined.

Second exemplary mode

A laser printer 1 of a second exemplary mode is explained below with reference to the drawings.

In the following description of the second exemplary embodiment and the drawings, the same portions as those of the first exemplary embodiment are denoted by the same reference numerals as those of the first exemplary embodiment, and detailed description thereof will be omitted for the same portions and configurations as those of the first exemplary embodiment.

As shown in fig. 14, the second guide 72 of the laser printer according to the second exemplary embodiment is arranged to incline upward from downstream to upstream, and is fixed to the top surface of the front end portion of the support portion 57. A second bottom end 75 as a front end portion of the second guide 72 is provided downstream of the first bottom end 73 of the first guide 71. An extension 60 having a rectangular cross section is provided to protrude from the upper side of the transfer roller support 55 at the front end of the support portion 57. The first bottom end 73 of the first guide member 71 is fixed to the top surface of the extension portion 60. The second guide 72 extends from the second bottom end 75 to the upstream side. The top surface of the second guide 72 forms a second guide surface 72A for guiding the paper 3 to the photosensitive drum 27. Specifically, the second guide surface 72A extends to the opposite direction of the direction in which the first guide surface 71A extends. The second guide member 72 is formed to have a thickness of 0.075 to 0.125 mm, preferably 0.100 mm.

A second front end 76 as a rear end portion of the second guide 72 is disposed below the first front end 74 of the first guide 71 and is separated from the first front end 74. Specifically, the second leading end 76 of the second guide face 72A is provided in the projection plane of the first guide face 71A in the direction (downward direction) in which the sheet 3 guided by the first guide face 71A presses the first guide face 71A.

The second front end 76 of the second guide 72 may be disposed in contact with the first front end 74 of the first guide 71. The second leading end 76 of the second guide 72 may be disposed apart from or in contact with the first leading end 74 on the downstream side (photosensitive drum 27 side) of the first leading end 74 of the first guide 71.

When the surface of each of the first guide 71 and the second guide 72 on the side in contact with the cutting blade at the time of press working is a front surface and the opposite side surface thereof is a back surface, the front surface thereof, i.e., the drooping surface at the time of press working, is set as a top surface (a first guide surface 71A and a second guide surface 72A) in contact with the paper 3 and the back surface thereof is set as a bottom surface opposite to the top surface of the holding portion 57.

The first guide 71 and the second guide 72 may be disposed in a width direction orthogonal to the conveying direction of the sheet 3, specifically, in a direction parallel to the axial direction of the photosensitive drum 27, as shown in fig. 15A.

The first guide 71 and the second guide 72 may be divided as shown in fig. 15B by being arranged in parallel with each other at predetermined intervals in the orthogonal direction to the conveying direction of the sheet 3.

The length between the first front end 74 and the first bottom end 73 of the first guide surface 71A is formed longer than the length between the second front end 76 and the second bottom end 75 of the second guide surface 72A. Also, the first guide 71 is formed thicker than the second guide 72 as described above, so that the geometric moment of inertia I of the first guide 71₁Set to be larger than the geometrical moment of inertia I of the second guide 72₂。

The inclination angle θ 3 (see fig. 17C) of the first guide 71 with respect to the support 57 and the inclination angle θ 4 (see fig. 17C) of the second guide 72 with respect to the support 57 are about 30 ° to 45 °, respectively, and preferably about 30 °. Since the inclination angle θ 3 of the first guide 71 with respect to the support portion 57 and the inclination angle θ 4 of the second guide 72 with respect to the support portion 57 are both set to be smaller than 45 °, the plane 71 formed by connecting the first front end 74 and the first bottom end 73 of the first guide 71 and the plane 78 formed by connecting the second front end 76 and the second bottom end 75 of the second guide 72 intersect each other at an obtuse angle θ 2 therebetween (refer to fig. 14).

Further, the inclination angles θ 3 and θ 4 may be angles relative to a line connecting both the upstream side P1 immediately following the first guide 71 and the transfer position P2 in the sheet conveying path (see fig. 17C). The inclination angles θ 3 and θ 4 may also be angles relative to a line connecting both the edge of the first bottom end 73 of the first guide 71 and the edge of the second bottom end 75 of the second guide 72.

The operation of guiding the thin paper 3 and the thick paper 3 to the transfer position by the first and second guides 71 and 72 in the thus configured process cartridge 17 is specifically described below. In the present exemplary embodiment, when the weight per square meter of the paper 3 (plain paper) having a normal thickness is 75 to 105 g/m, the paper having a normal thickness or the paper (e.g., recording paper) having a weight of 56 to 75 g/m is hereinafter referred to as a thin paper, and the paper (e.g., postcard or the like) having a weight of 105 to 200 g/m or more is hereinafter referred to as a thick paper.

Action of guiding thinner paper to transfer position by first and second guide members

Fig. 16 and 17 show the action of guiding the thinner paper sheet 3 to the transfer position by the first and second guides 71 and 72 in stages. As shown in fig. 16A, in this process cartridge 17, when the thin paper 3 is first conveyed, the leading end of the paper 3 is guided downstream along the first guide surface 71A of the first guide member 71, reaches the first leading end 74 from the first bottom end 73 of the first guide surface 71A, and is then guided into contact with the upstream side of the transfer position of the photosensitive drum 27.

However, the thin paper 3 is weak, and therefore even when the leading end of the thin paper 3 comes into contact with the photosensitive drum 27 as shown in fig. 16B, the first leading end 74 of the first guide 71 is not bent significantly, and is guided to the transfer position as it is when the paper 3 closely adheres to the photosensitive drum 27.

Next, the thin paper 3, as shown in fig. 17A, is closely adhered to the photosensitive drum 27 from the leading end on the upstream side of the transfer position until the vicinity of the trailing end thereof is guided to the transfer position in a state of being closely adhered to the photosensitive drum 27.

The second leading end 76 of the second guide surface 72A is provided downstream of a projection plane in a direction in which the sheet 3 guided by the first guide surface 71A presses the first guide member 71. Thus, when the rear end of the thin paper 3 passes the first front end 74 of the first guide surface 71A, as shown in fig. 17B and 17C, the rear end of the thin paper 3 drops from the first front end 74 of the first guide surface 71A, and is elastically received by the second front end 76 of the second guide surface 72A to be guided to the transfer position. Therefore, the swing of the rear end of the thin paper 3 can be suppressed, and the occurrence of the transfer defect at the rear end can be prevented.

Action of guiding thick paper to transfer position by first and second guide members

Fig. 18A to 19B show the operation of guiding the thick paper 3 to the transfer position in stages. As shown in fig. 18A, in this process cartridge 17, when the thick paper 3 is first conveyed, the leading end of the paper 3 is guided downstream along the first guide surface 71A of the first guide member 71, reaches the first leading end 74 from the first bottom end 73 of the first guide surface 71A, and is then guided into contact with the upstream side of the transfer position of the photosensitive drum 27.

However, as shown in fig. 18B, the thick paper 3 is thick, and therefore when the leading end of the thick paper 3 comes into contact with the photosensitive drum 27, the first leading end 74 is bent significantly with respect to the first base end 73, and thus the second guide 72 guides the paper 3 in a state of close contact with the photosensitive drum 27.

The second guide surface 72A extends in the opposite direction to the direction in which the first guide surface 71A extends, and the second leading end 76 is disposed below the first leading end 74 of the first guide surface 71A. Thus, as shown in fig. 18B, when the thick paper 3 is guided from the first guide surface 71A to the second guide surface 72A, it comes into contact with the second guide surface 72A from the second front end 76 to the second bottom end 75. The thick paper 3 is pressed by the second guide surface 72A in a direction from the direction approaching the photosensitive drum 27 to the downstream. Thus, as the sheet 3 is conveyed to the transfer position, the second leading end 76 can be made to have a large curve relative to the second bottom end 75 on the second guide surface 72A.

Thus, as shown in fig. 19A, the thick paper 3 is guided relatively directly to the transfer position, so that it is possible to prevent the occurrence of transfer defects due to the bending of the thick paper 3. In addition, the friction of the sheet 3 in contact with the second guide surface 72A can be reduced, so that the sheet 3 can be prevented from being vibrated by the friction between the second guide surface 72A and the sheet 3, thereby preventing transfer defects caused by the vibration.

As shown in fig. 19A, the first guide 71 has a large curvature, and is in contact with or close to the second guide 72. Thus, after the trailing end of the thick paper 3 is guided to the transfer position, the paper 3 is continuously conveyed from the first leading end 74 of the first guide surface 71A to the second guide surface 72A as shown in fig. 19B, and is guided to the transfer position. Thus, it is possible to prevent the rear end of the thick paper 3 from being swung to smoothly guide the thick paper 3 to the transfer position, thereby preventing transfer defects.

Specifically, the process cartridge 17 uses the first and second guides 71 and 72 formed of deformable film members, and thus can smoothly guide the thin or thick paper 3 to the transfer position. Thus, transfer defects can be prevented. In addition, an image is formed on a sheet with the printer 1 equipped with the process cartridge 17, and thus a stable image can be formed.

At least one of the first and second guides 71 and 72 may be formed of a deformable member other than a membrane, such as a sponge.

The second front end 76 of the second guide 72 in the process cartridge 17 is separated from the first guide 71, so that the first and second guides 71 and 72 can be disposed at a predetermined inclination angle, respectively. Thus, the paper 3 can be reliably guided to the transfer position without transfer defects.

In addition, the first bottom end 73 of the first guide 71 and the second bottom end 75 of the second guide 72 are provided with a gap therebetween, and thus the first and second guides 71 and 72 are independently formed. Thus, the first and second guide faces 71A and 72A can be reliably provided.

In addition, the second leading end 76 of the second guide 72 is disposed below the first guide 71, and thus the leading end of the sheet 3 can be smoothly guided without contacting the second leading end 76 of the second guide 72.

In addition, a plane 77 formed by the first front end 74 and the first bottom end 73 of the first guide 71 and a plane 78 formed by the second front end 76 and the second bottom end 75 of the second guide 72, which are connected to each other, intersect each other at an obtuse angle θ 2 therebetween, and thus the sheet 3 is not bent, as compared to the case where the planes are at an acute angle or a right angle to each other. Thus, the sheet 3 can be smoothly guided to the transfer position.

Geometrical moment of inertia I of the first guide 71₁Set to be larger than the geometrical moment of inertia I of the second guide 72₂And thus the first guide 71 is stronger than the second guide 72. Thus, the guide is thinnerWhen the sheet 3 is fed, the leading end of the thin sheet 3 can be guided to a position as close as possible to the photosensitive drum 27 by the first guide 71. Therefore, the thin paper 3 can be prevented from being discharged.

Specifically, when the first guide 71 and the second guide 72 are formed by press working, the end portion 65 of the back surface 64 on the opposite side of the surface 63 formed as the drooping surface is cut by a shearing force of a cutting blade at the time of press forming, and is formed into a protruding shape (burr) as shown in fig. 20. When the rear surface 64 is arranged as a top surface (the first guide surface 71A and the second guide surface 72A) that contacts the sheet 3, the sheet 3 is caught by the end 65 (burr) having the protruding shape, and thus smooth conveyance cannot be achieved.

As shown in fig. 15B, the first guide 71 and the second guide 72 are divided in the width direction thereof, and frictional resistance in conveying the sheet 3 in the first guide 71 and the second guide 72 can be reduced, so that smooth guidance can be achieved.

Exemplary manner of deformation

Fig. 21 is a schematic plan view showing another structure of the first guide 71 and the second guide 72. A plurality of cutouts 66 are formed in the first leading end 74 of the first guide 71 and the second leading end 76 of the second guide 72 at substantially equal intervals in the width direction orthogonal to the conveying direction of the sheet 3. Each slit 66 extends from an edge of the first leading end 74 or an edge of the second leading end 76 to halfway toward the first bottom end 73 or the second bottom end 75 in the conveying direction of the sheet 3 (refer to fig. 14).

By forming such a cutout 66, the first guide 71 and the second guide 72 can be assembled to the support portion 57 with high accuracy without wrinkles on the first guide 71 and the second guide 72 (see fig. 14).

Specifically, the first guide 71 and the second guide 72 are thin and elongated in the width direction, so that when both ends in the width direction of the first guide 71 and the second guide 72 are fitted (connected) to the aligned positions of the support portions 57, the center portions in the width direction of the first guide 71 and the second guide 72 are displaced. On the other hand, when the first guide 71 and the second guide 72 are aligned with each other at one end in the width direction with respect to the support portion 57 and are sequentially assembled from the one end in the width direction to the other end in the width direction, the first guide 71 and the second guide 72 are prevented from being displaced at the center in the width direction, but wrinkles are likely to occur in the first guide 71 and the second guide 72.

According to the first guide 71 and the second guide 72 of the present exemplary embodiment, a plurality of cutouts 66 are formed therein, and thus wrinkles generated when the first guide 71 and the second guide 72 are fitted to the support portion 57 in order from one end portion in the width direction thereof can be absorbed by the respective cutouts 66. Thus, it is possible to fit the first guide 71 and the second guide 72 to the support portion 57 with high accuracy without occurrence of wrinkles on the first guide 71 and the second guide 72.

Fig. 22 is a schematic plan view showing another structure of the first guide 71 and the second guide 72. Referring to fig. 22, the same reference numerals as in fig. 21 are given to portions corresponding to those shown in fig. 21, and detailed description thereof will not be repeated.

In the first guide 71 and the second guide 72 shown in fig. 22, the separation preventing body 67 is formed at the end of the first bottom end 73 or the second bottom end 75 of each cutout 66. The separation preventing body 67 is formed as a hole having a substantially circular hole shape in a plan view at an end portion of each slit 66, and penetrates from a top surface of the first guide 71 and the second guide 72, which are in contact with the sheet 3, to a bottom surface of the opposite side thereof in the conveying direction of the sheet 3.

Fig. 23A to 23D are schematic plan views showing another structure of the first guide 71 and the second guide 72. The first and second leading ends 74 and 76 of the first and second guides 71 and 72 shown in fig. 23A to 23D are respectively provided with a plurality of slits 68 side by side with each other at substantially equal intervals in the width direction orthogonal to the sheet conveying direction. Each slit 68 extends from an edge of the first leading end 74 or an edge of the second leading end 76 to halfway toward the first bottom end 73 or the second bottom end 75 in the conveying direction of the sheet 3 (refer to fig. 14).

By forming such a slit 68, as in the case of the slit 66, the first guide 71 and the second guide 72 can be fitted to the support portion 57 with high accuracy without wrinkles on the first guide 71 and the second guide 72. In addition, when the sheet 3 having a narrow width is continuously conveyed, the first and second guides 71 and 72 can be prevented from being deformed in their entirety with the bending of the portion in contact with the sheet 3, and the reliability of the first guide 71 and the second guide 72 in terms of durability can be enhanced.

Further, the slit 68 has a width in a direction orthogonal to the conveying direction of the sheet 3 unlike the slit 66, and thus the first guide 71 and the second guide 72 can be further prevented from overlapping each other when the first guide 71 and the second guide 72 are fitted to the supporting portion 57 with the slit 68 interposed therebetween.

Each slit 68 may have a substantially rectangular shape in plan view as shown in fig. 23A, a substantially V-shape in plan view as shown in fig. 23B, or a substantially U-shape in plan view as shown in fig. 23C.

When each slit 68 has a substantially rectangular shape or a substantially U-shape in plan view, the first guide 71 and the second guide 72 can be prevented from being separated from the end of the first bottom end 73 or the second bottom end 75 of each slit 68 (refer to fig. 14).

In addition, when each slit 68 has a substantially V-shape in plan view, the portions between the first and second guides 71 and 72, which sandwich the slit 68, are sequentially distant from the rear end to the front end, and thus the portions between the first and second guides 71 and 72, which sandwich the slit 68, can be further prevented from overlapping each other when the first and second guides 71 and 72 are assembled to the support portion 57.

In this case, as shown in fig. 23D, the separation preventing body 69 is desirably formed at an end of the first bottom end 73 or the second bottom end 75 of the slit 68. The separation preventing body 69 is formed as a hole having a substantially circular hole shape in a plan view at an end portion of each slit 68, and penetrates from a top surface of the first guide 71 and the second guide 72, which are in contact with the sheet 3, to a bottom surface of the opposite side thereof in the conveying direction of the sheet 3. By forming the separation preventing body 69, the first guide 71 and the second guide 72 can be prevented from being separated at the deepest portion of each slit 68.

Fig. 24 is a side view showing another structure of the first and second guides 71 and 72.

In fig. 24, the first and second guides 71 and 72 are formed of an insulating material having flexibility, for example, a resin such as polyethylene terephthalate, and are composed of 1 plate member 80 formed into a substantially rectangular film member by a press working.

The first guide 71 is formed in an inclined shape by bending the front end portion of the plate member 80 to one side (upper side) thereof and turning back to the downstream side. The second guide 72 is formed in an inclined shape by bending the rear end portion of the plate member 80 to one side (upper side) thereof and turning back to the upstream side. Specifically, the plate member 80 includes a first guide 71, a second guide 72, and a connecting portion 81 that are integrally formed with each other. In this case, the first guide 71 is formed to be inclined upward from upstream to downstream, and its first leading end 74 is disposed adjacent to the photosensitive drum 27. The second guide 72 is formed to be inclined upward from upstream to downstream, and a second leading end 76 thereof is disposed to be separated from the first leading end 74 of the first guide 71 below the first leading end 74. The connection portion 81 connects the first front end 73 of the first guide 71 and the second bottom end 75 of the second guide 72 to each other. The top surface of the first guide 71 forms a first guide surface 71A for guiding the paper 3 to the photosensitive drum 27. The top surface of the second guide 72 forms a second guide surface 72A for guiding the paper 3 to the photosensitive drum 27.

The bottom surface of the connecting portion 81 in the plate member 80 is fixed in contact with the top surface of the supporting portion 57 so that the first bottom end 73 of the first guide 71 and the second bottom end 75 of the second guide 72 are fixed to the upstream side of the transfer position. The inclination angle θ 3 (see fig. 17C) of the first guide 71 with respect to the connection portion 81 and the inclination angle θ 4 (see fig. 17C) of the second guide 72 with respect to the connection portion 81 are about 30 ° to 45 °, respectively, and preferably about 30 °. Since the inclination angle θ 3 of the first guide 71 with respect to the connecting portion 81 and the inclination angle θ 4 of the second guide 72 with respect to the connecting portion 81 are set to be smaller than 45 °, a plane 77 formed by connecting the first front end 74 and the first bottom end 73 of the first guide 71 and a plane 78 formed by connecting the second front end 76 and the second bottom end 75 of the second guide 72 intersect each other at an obtuse angle θ 2 therebetween.

The second front end 76 of the second guide 72 may be disposed in contact with the first front end 74 of the first guide 71. In addition, the second leading end 76 of the second guide 72 may be disposed apart from or in contact with the first leading end 74 on the downstream side (photosensitive drum 27 side) of the first leading end 74 of the first guide 71.

As with the first and second guides 71 and 72 of the above-described exemplary aspect, the first leading end 74 of the first guide 71 and the second leading end 76 of the second guide 72 in the plate member 80 face each other, and thus the thinner paper sheet 3 and the thicker paper sheet 3 can be smoothly guided to the transfer position, thereby preventing transfer defects.

In addition, the first bottom end 73 of the first guide 71 and the second bottom end 75 of the second guide 72 in the plate member 80 are connected to each other by a connection portion 81, so that the first and second guides 71 and 72 are formed integrally with each other. Thus, the number of parts can be reduced, or the first and second guides 71 and 72 can be easily assembled.

In addition, the first front end 74 of the first guide 71 and the second front end 76 of the second guide 72 in the plate member 80 may include each configuration shown in fig. 21 to 23.

Third exemplary mode

A laser printer 1 of a third exemplary mode is explained below with reference to the drawings.

In the following description of the third exemplary embodiment and the drawings, the same portions as those of the first and second exemplary embodiments are denoted by the same reference numerals as those of the first exemplary embodiment, and detailed descriptions thereof are omitted for the same portions and configurations as those of the first and second exemplary embodiments.

As shown in fig. 25, the process cartridge 17 of the third exemplary embodiment is configured such that a first guide 83 and its leading end, i.e., a first guide end 86, which are inclined upward from upstream to downstream are disposed adjacent to the photosensitive drum 27, and a second guide 84 and its trailing end, i.e., a second guide end 88 (which is opposed to and continuously formed from the first leading end 86 of the first guide 83) which are inclined upward from upstream to downstream are formed integrally with each other by a sheet member 82. The plate member 82 is formed of a flexible insulating material, for example, a resin such as polyethylene terephthalate, and is composed of a rectangular film member formed by press working. The front and rear end portions (first and second bottom ends 85 and 87) of the plate member 82 are fixed to the top surface of the support portion 57, wherein the plate member 82 is formed in an arc shape with a central portion thereof being upwardly arched.

The first guide 83 includes: a first base end 85 fixed to the step portion 61 of the support portion 57; and a first guide surface 83A for guiding the sheet 3 to the photosensitive drum 27. The first guide member 83 extends from the first bottom end 85 to the photosensitive drum 27.

The second guide member 84 includes: a second bottom end 87 fixed to the top surface of the extension 60 formed on the front end of the support portion 57; and a second guide surface 84A for guiding the sheet 3 to the photosensitive drum 27. The second guide member 84 extends from the second bottom end 87 to the upstream side.

When the portion in contact with the blade in the punching process is the front surface and the opposite side portion thereof is the back surface, the plate member 82 is provided in which the front surface is provided as the top surface (the first guide surface 83A and the second guide surface 84A) in contact with the sheet 3 and the back surface is provided as the bottom surface opposite to the top surface of the support portion 57.

The first guide end 86 of the first guide surface 83A and the second guide end 88 of the second guide surface 84A are disposed above a line L connecting both a contact position (transfer position) between the photosensitive drum 27 and the transfer roller 30 and a contact position between two opposing rollers 12 opposing each other.

The first guide member 83 can set the contact position of both the leading end of the paper 3 and the photosensitive drum 27 by the curvature of the first guide end 86, and is disposed at a guidable position such that the contact angle θ 4 between the photosensitive drum 27 and the paper 3 satisfies θ 4<90 °.

The plate member 82 is formed such that the product EI of Young's modulus E, which is an elastic modulus in a direction parallel to the conveying direction of the sheet 3, and geometric moment of inertia I, which has a direction parallel to the axial direction of the photosensitive drum 27 and a direction perpendicular to the widest plane (top or bottom surface), satisfies 3.49X 10^-5≤EI≤1.18×10^-3。

The inclination angle θ 5 (see fig. 27C) of the first guide 83 with respect to the support 57 and the inclination angle θ 6 (see fig. 27C) of the second guide 84 with respect to the support 57 are about 30 ° to 45 °, respectively, and preferably about 30 °. The inclination angles θ 5 and θ 6 may be angles at which the upstream side P3 immediately adjacent to the first guide 83 and the transfer position P2 are connected to each other in the sheet conveying path (see fig. 27C). The inclination angles θ 5 and θ 6 may be angles such that they are connected with respect to both the edge of the first bottom end 85 of the first guide member 83 and the edge of the second bottom end 87 of the second guide member 84.

The following specifically describes the action of guiding the thinner paper sheet 3 and the thicker paper sheet 3 to the transfer position by the first and second guides 83 and 84 with respect to the process cartridge 17 of this arrangement.

Fig. 26A to 27C show the action of guiding the thinner paper sheet 3 to the transfer position by the first and second guides 83 and 84 in stages. As shown in fig. 26A, in this process cartridge 17, when the thin paper 3 is conveyed, the leading end of the paper 3 is guided to the downstream along the first guide surface 83A of the first guide member 83, conveyed from the first bottom end 85 to the first guide end 86 of the first guide surface 83A, and then guided to contact the upstream side of the transfer position of the photosensitive drum 27.

However, as shown in fig. 26B, the thinner paper sheet 3 is weak, and thus even when the leading end of the thinner paper sheet 3 comes into contact with the photosensitive drum 27, the first leading end 86 of the first guide 83 and the second leading end 88 of the second guide 84 are not greatly bent, so that the paper sheet 3 is guided to the transfer position in close contact with the photosensitive drum 27.

Next, the thin paper 3, as shown in fig. 17A, is closely adhered to the photosensitive drum 27 from the leading end on the upstream side of the transfer position until the vicinity of the trailing end thereof is guided to the transfer position in a state of being closely adhered to the photosensitive drum 27. Therefore, a gap between the thin paper 3 and the photosensitive drum 27 is not formed on the upstream side of the transfer position, and thus the occurrence of electric discharge between the two can be suppressed. As a result, a spot-like discharge pattern, which is referred to as a penetrated through sheet 3, on the sheet 3 can be prevented from occurring.

Further, when the thin paper 3 is guided from the front end to the rear end thereof by the first guide 83, the bottom surface of the paper 3 may be slidably guided to the transfer position on the second guide surface 84A of the second guide 84, or may not be slidably guided to the transfer position on the second guide surface 84A of the second guide 84.

The first leading end 86 of the first guide face 83A is formed continuously with the second leading end 88 of the second guide face 84A on the downstream side. Thus, when the rear end of the thin paper 3 passes the first leading end 86 of the first guide surface 83A, as shown in fig. 27B and 27C, the rear end of the thin paper 3 is elastically guided to the transfer position by the second guide surface 84A. Therefore, it is possible to suppress the swing of the rear end of the thin paper 3 to smoothly guide the thin paper 3 to the transfer position, thereby preventing the transfer defect.

Fig. 28A to 29C show the action of guiding the thick paper 3 to the transfer position by the first and second guides 83 and 84 in stages. As shown in fig. 28A, in this process cartridge 17, when the thick paper 3 is conveyed, the leading end of the paper 3 is guided to the downstream along the first guide surface 83A of the first guide member 83, conveyed from the first bottom end 85 to the first leading end 86 of the first guide surface 83A, and then guided to contact the upstream side of the transfer position of the photosensitive drum 27.

At this time, as shown in fig. 28A, as the leading end of the thick paper 3 is conveyed to the photosensitive drum 27, the first leading end 86 of the first guide 83 and the second leading end 88 of the second guide 84 are bent downward by the weight of the thick paper 3. In addition, as shown in fig. 28B, the thick paper 3 is thick and solid, and therefore when the leading end of the thick paper 3 comes into contact with the photosensitive drum 27, the first leading end 86 of the first guide 83 and the second leading end 88 of the second guide 84 are greatly curved in an arch shape, and thus the paper 3 is guided in a state of close contact with the photosensitive drum 27.

The second guide surface 84A extends to the opposite direction of the direction in which the first guide surface 83A extends, and the second leading end 88 is formed continuously with the first leading end 86 of the first guide surface 83A. Thus, as shown in fig. 28B, when the thick paper 3 is guided from the first guide surface 83A to the second guide surface 84A, it comes into contact with the second guide surface 84A from the second guide end 88 to the second bottom end 87. The thick paper 3 is pressed by the second guide surface 84A in such a direction as to approach the photosensitive drum 27 to the downstream side. Thus, as the sheet 3 is conveyed to the transfer position, the second leading end 88 can be bent largely with respect to the second bottom end 87 on the second guide surface 84A.

Thus, as shown in fig. 29A, the thick paper 3 is guided relatively directly to the transfer position, so that it is possible to prevent the occurrence of transfer defects due to the bending of the thick paper 3. In addition, the friction of the sheet 3 in contact with the second guide surface 84A can be reduced, so that the vibration of the sheet 3 due to the friction between the second guide surface 84A and the sheet 3 can be suppressed, thereby preventing the transfer defect caused by the vibration.

Further, even if a gap appears between the thick paper 3 and the photosensitive drum 27, the thick paper 3 is less likely to generate electric discharge than in the case of the thin paper 3, and even if the thick paper 3 is relatively directly guided to the transfer position, an electric discharge pattern due to the electric discharge is less likely to be generated.

As shown in fig. 29A and 29B, the first guide face 83A of the first guide member 83 and the second guide face 84A of the second guide member 84 are continuous with each other. Thus, after the trailing end of the thick paper 3 is guided to the transfer position, the paper 3 is continuously conveyed from the first leading end 86 of the first guide surface 83A to the second guide surface 84A as shown in fig. 29B, and is guided to the transfer position. Thus, it is possible to prevent the rear end of the thick paper 3 from being swung to smoothly guide the thick paper 3 to the transfer position, thereby preventing transfer defects.

Specifically, the process cartridge 17 uses one sheet plate member 82 formed of a deformable film member, and thus can smoothly guide the thin or thick paper sheet 3 to the transfer position. Thus, transfer defects can be prevented. In addition, an image is formed on a sheet with the printer 1 equipped with the process cartridge 17, and thus a stable image can be formed.

In particular, the first leading end 86 of the first guide member 83 and the second leading end 88 of the second guide member 84 in the process cartridge 17 are continuous with each other, and thus the sheet 3 can be continuously guided. Thus, the paper 3 can be reliably guided to the transfer position without transfer defects.

In addition, the product EI of Young's modulus E and geometric moment of inertia I of plate member 82 satisfies 3.49 × 10^-5≤EI≤1.18×10^-3And the first and second guides 83 and 84 are formed integrally with each other so that they can be satisfactorily bent in accordance with the thickness of the sheet 3. Thus, the sheet 3 can be smoothly guided to the transfer position.

In addition, the geometric moment of inertia I of the first guide 83₁May be set to be larger than the geometrical moment of inertia I of the second guide member 84₂. For example, the first guide 83 may be formed thicker than the second guide 84. Alternatively, the length of the first guide 83 in the width direction may be longer than the length of the second guide 84 in the width direction。

When the contact angle θ 4 between the sheet 3 guided by the first guide 83 and the photosensitive drum 27 is 90 °, the leading end of the sheet 3 is pinched when the sheet 3 comes into contact with the photosensitive drum 27. And the contact angle θ 4 exceeds 90 °, the sheet 3 is guided to the opposite side of the transfer position. The first guide 83 is disposed such that the contact angle θ 4 between the paper 3 and the photosensitive drum 27 satisfies θ 4<90 °. Thus, the paper 3 is guided while the paper 3 is in contact with the photosensitive drum 27 such that the contact angle θ 4 between the paper 3 and the photosensitive drum 27 satisfies θ 4<90 °, so that the paper 3 can be smoothly guided to the transfer position.

Further, the first and second guide surfaces 83A and 84A are drooping surfaces formed by press working, so that the sheet 3 can be smoothly guided without being caught by the edges of the first and second guide surfaces 83A and 84A.

In addition, the transfer roller 30 is included in the process cartridge 17, and thus the relative positions of the first and second guides 83 and 84 with respect to the transfer position can be maintained with high accuracy. Thus, the occurrence of transfer defects can be prevented regardless of whether the sheet 3 is thin or thick.

The first guide end 86 of the first guide surface 83A is disposed above a line L connecting a contact position between the photosensitive drum 27 and the transfer roller 30 and a contact position between the two abutment rollers 12, so that the paper 3 can be guided to the upstream side of the transfer position in the rotational direction of the photosensitive drum 27. Therefore, the discharge pattern caused by the discharge of the thinner paper sheet 3 can be reliably prevented.

The first and second guides 83 and 84 are formed of an insulating material such as a resin film, so that the photosensitive drum 27 can be prevented from being electrically conductive through the sheet 3. Thus, reliable transfer of the toner image can be achieved.

In addition, the first bottom end 85 of the first guide member 83 and the second bottom end 87 of the second guide member 84 are fixed to the housing 51, so that the photosensitive drum 27, the first guide member 83, and the second guide member 84 can be integrally provided with the housing 51. Thus, the first and second guide surfaces 83A and 84A can be reliably arranged with respect to the photosensitive drum 27.

The plate member 82 (first and second guides 83 and 84) may be continuously formed in a width direction perpendicular to the sheet conveying direction, i.e., a direction parallel to the axial direction of the photosensitive drum 27. Alternatively, the plate-like member 82 may be divided into a plurality of portions and arranged side by side at predetermined intervals in a direction perpendicular to the conveying direction of the sheet 3.

When the first and second guides 83 and 84 are divided in the width direction, the frictional resistance when the sheet 3 is conveyed on the first and second guides 83 and 84 can be reduced, thereby smoothly guiding the sheet 3.

The second bottom end 87 of the second guide member 84 is rotatably positioned. In this configuration, when the thick paper 3 is guided to the transfer position by the first and second guides 83 and 84, the thick paper 3 can be guided to the correct transfer position by rotating the second bottom end 87 of the second guide 84 in accordance with the bending of the plate member 82. Thus, transfer defects caused by the bending of the thick paper 3 can be effectively prevented.

In addition, the first guide end 86 of the first guide 83 and the second guide end 88 of the second guide 84 in the plate member 82 may include the configurations shown in fig. 21 to 23D. In this case, the slit or slit may be continuously formed from the first leading end 86 to the second leading end 88.

Modifications of the first and second guides

Fig. 30 is a side view of another structure of the first and second guide members 83 and 84.

In fig. 30, the first and second guides 83 and 84 are integrally formed by a deformable member 89 formed of, for example, a sponge or the like, and having a substantially half-elliptical shape in a side view. Specifically, the bottom surface of the deformable member 89 is opposed to the top surface of the support portion 57 shown in fig. 25. The top surface of the deformable member 89 includes a first guide surface 83A and a second guide surface 84A on the upstream side and the downstream side, respectively.

By fixing the bottom surface of the deformable member 89 to the top surface of the support portion 57, the first bottom end 85 of the first guide surface 83A and the second bottom end 87 of the second guide surface 84A are fixed on the upstream side of the transfer position. The inclination angle θ 5 of the first guide surface 83A with respect to the bottom surface of the deformable member 89 and the inclination angle θ 6 of the second guide surface 84A with respect to the bottom surface of the deformable member 89 are about 30 ° to 45 °, respectively, and preferably about 30 °.

Like the first and second guides 83 and 84 of the above-described exemplary aspect, the first leading end 86 of the first guide surface 83A and the second leading end 88 of the second guide surface 84A in the deformable member 89 are opposed to each other, and the thinner paper sheet 3 and the thicker paper sheet 3 can be smoothly guided to the transfer position, thereby preventing the transfer defect.

In addition, the transfer roller 30, the first guide 71, the second guide 72, the first guide 83, and the second guide 84 in the above exemplary embodiment and the modification are provided in the process cartridge 17, but the present invention is not limited thereto, and may be provided in the casing 2.

In the above modification, physical properties (geometrical moment of inertia, length, product of young's modulus and geometrical moment of inertia, material, etc.), arrangement (contact angle between paper and the photosensitive drum, orientation of a sag formed by press working, etc.) may be combined and applied within the scope of the appended claims.

The foregoing description of the exemplary manner is provided for illustration. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The exemplary manner of selecting and describing the invention is for the purpose of illustrating the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various exemplary ways and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims

1. A process cartridge characterized by comprising:

an image carrier carrying a developer image, the developer image being transferred to a transfer medium at a transfer position;

a first guide member provided with a first guide surface that guides the transfer medium to the image carrier, the first guide surface having flexibility; and

a second guide member provided with a second guide surface that guides the transfer medium to the image carrier, the second guide surface having flexibility,

wherein the first guide surface has a first base end fixed on an upstream side in a transfer medium conveying direction with respect to the transfer position, and a first leading end of the image carrier extending to the upstream side of the transfer position,

wherein the second guide surface has a second base end fixed to an upstream side of the transfer position, and a second leading end extending from the second base end toward the image carrier between the first leading end and the transfer position,

wherein the second guide member is disposed such that a first plane connecting the first leading end and the first base end and a second plane connecting the second leading end and the second base end intersect each other at the first base end or an upstream side of the first base end, an

Wherein the first and second guide members are formed in a predetermined shape by press working by being contacted by the blade at the first and second guide surfaces.

2. A cartridge according to claim 1, wherein at least one of the first and second guides is formed of a film member.

3. The process cartridge as claimed in claim 1, wherein the first guide has a geometrical moment of inertia I₁Greater than the geometrical moment of inertia I of the second guide₂Geometric moment of inertia I₁Having a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the first guide, a geometrical moment of inertia I₂Has a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the second guide.

4. A process cartridge according to claim 1, wherein a length from the first front end to the first bottom end of the first guide face is longer than a length from the second front end to the second bottom end of the second guide face.

5. The process cartridge as claimed in claim 1, wherein the first guide is formed such that the young's modulus E of the first guide is₁Geometric rotation inertiaQuantity I₁Product of E₁I₁Satisfies 3.49X 10^-5≤E₁I₁≤1.18×10^-3Young's modulus E₁For the modulus of elasticity in the direction parallel to the conveying direction, geometrical moment of inertia I₁Has a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the first guide, an

The second guide member is formed such that the Young's modulus E of the second guide member₂And geometrical moment of inertia I₂Product of E₂I₂Satisfies 3.49X 10^-5≤E₂I₂≤1.18×10^-3Young's modulus E₂For the modulus of elasticity in the direction parallel to the conveying direction, geometrical moment of inertia I₂Has a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the second guide.

6. A process cartridge according to claim 1, wherein the first guide member is provided at a position to guide the transfer medium such that a contact angle θ between the image carrier and the transfer medium satisfies θ <90 °.

7. A cartridge according to claim 1, wherein at least one of the first and second guides is divided in a width direction orthogonal to the conveying direction.

8. A cartridge according to claim 1, wherein at least one of the first and second guide members is provided with a cutout extending from an edge of the first front end or the second front end toward the first bottom end or the second bottom end in the conveying direction.

9. A process cartridge according to claim 8, wherein at least one of the first and second guides is provided with a separation preventing body provided at an end of the first bottom end or the second bottom end of the cutout, the separation preventing body preventing the first or second guide from being separated from the cutout.

10. A cartridge according to claim 1, wherein at least one of the first and second guides is provided with a slit extending from an edge of the first front end or the second front end toward the first bottom end or the second bottom end in the conveying direction.

11. The process cartridge as claimed in claim 10, wherein the slit is formed in a substantially rectangular shape in a plan view.

12. The process cartridge as claimed in claim 10, wherein the slit is formed substantially in a V-shape in a plan view.

13. A process cartridge according to claim 12, wherein at least one of the first and second guides is provided with a separation preventing body disposed at an end of the first bottom end or the second bottom end of the slit, the separation preventing body preventing the first or second guide from being separated from the slit.

14. The process cartridge as claimed in claim 10, wherein the slit is formed substantially in a U-shape in a plan view.

15. A process cartridge according to claim 1, further comprising a plate member having a base end fixed to an upstream side of the transfer position and a leading end of the image carrier extending to the upstream side of the transfer position,

wherein the plate member is provided with a plurality of front end pieces in a direction parallel to a longitudinal direction of the image carrier, each of the front end pieces being formed by forming a slit extending from an edge of the front end toward a bottom end in the conveying direction,

wherein the front end pieces are bent at different angles from each other with the edge of the bottom end of the cutout as a bending center to form first and second guides.

16. A cartridge according to claim 1, further comprising a transfer unit which contacts the image carrier at a transfer position.

17. A process cartridge according to claim 16, wherein an edge of the first leading end of the first guide surface is provided on an opposite side to a pressing direction in which the transfer medium guided by the first guide is pressed against the first guide, with respect to a connecting line connecting the transfer position and a contact position at which the pair of abutting units contact each other, and the abutting units are provided on an upstream side of the first guide and are opposed to each other.

18. A cartridge according to claim 1, wherein the first and second guides are each formed of an insulating material.

19. A cartridge according to claim 1, further comprising a housing holding the image carrier, the first and second guides,

wherein the first and second bottom ends are both fixed to the housing.

20. An image forming apparatus, characterized by comprising:

a developing unit that carries a developer, supplies the developer to the image carrier, and forms a developer image on the image carrier;

a transfer unit that comes into contact with the image carrier at a transfer position and transfers the developer image to a transfer medium;

a conveying unit that conveys the transfer medium to a transfer position;

wherein the second guide member is disposed such that a first plane connecting the first leading end and the first base end and a second plane connecting the second leading end and the second base end intersect with each other at the first base end or an upstream side of the first base end,

21. The image forming apparatus as claimed in claim 20, wherein at least one of the first and second guides is formed of a film member.

22. The imaging apparatus of claim 20, wherein the first guide has a geometric moment of inertia I₁Greater than the geometrical moment of inertia I of the second guide₂Geometric moment of inertia I₁Having a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the first guide, a geometrical moment of inertia I₂Has a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the second guide.

23. The image forming apparatus as claimed in claim 20, wherein a length from the first front end to the first bottom end of the first guide surface is longer than a length from the second front end to the second bottom end of the second guide surface.

24. The imaging apparatus of claim 20,

the first guide member is formed such that the Young's modulus E of the first guide member₁And geometrical moment of inertia I₁Product of E₁I₁Satisfies 3.49X 10^-5≤E₁I₁≤1.18×10^-3Young's modulus E₁For the modulus of elasticity in the direction parallel to the conveying direction, geometrical moment of inertia I₁Has a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the first guide, an

25. The image forming apparatus as claimed in claim 20, wherein the first guide is provided at a position to guide the transfer medium such that a contact angle θ between the image carrier and the transfer medium satisfies θ <90 °.

26. The image forming apparatus according to claim 20, wherein at least one of the first and second guides is divided in a width direction orthogonal to the conveying direction.

27. The image forming apparatus as claimed in claim 20, wherein at least one of the first and second guide members is provided with a cutout extending from an edge of the first front end or the second front end toward the first bottom end or the second bottom end in the conveying direction.

28. The image forming apparatus as claimed in claim 27, wherein at least one of the first and second guide members is provided with a separation preventing body disposed at an end of the first bottom end or the second bottom end of the cutout, the separation preventing body preventing the first or second guide member from being separated from the cutout.

29. The image forming apparatus as claimed in claim 20, wherein at least one of the first and second guides is provided with a slit extending from an edge of the first front end or the second front end toward the first bottom end or the second bottom end in the conveying direction.

30. The imaging apparatus of claim 29, wherein the slit is formed in a substantially rectangular shape in plan view.

31. The imaging apparatus of claim 29, wherein the slits are formed in a substantially V-shape in plan view.

32. The image forming apparatus as claimed in claim 31, wherein at least one of the first and second guides is provided with a separation preventing body disposed at an end of the first bottom end or the second bottom end of the slit, the separation preventing body preventing the first or second guide from being separated from the slit.

33. The imaging apparatus as claimed in claim 29, wherein the slit is formed in a substantially U-shape in a plan view.

34. The image forming apparatus according to claim 20, further comprising a plate member having a base end fixed to an upstream side of the transfer position and a leading end of the image carrier extending to the upstream side of the transfer position,

35. The image forming apparatus according to claim 20, wherein an edge of the first leading end of the first guide surface is provided on an opposite side to a pressing direction in which the transfer medium guided by the first guide member is pressed against the first guide member, with respect to a connection line connecting the transfer position and a contact position at which the pair of abutting units contact each other, and the abutting units are provided on an upstream side of the first guide member and are disposed opposite to each other.

36. The imaging apparatus of claim 20, wherein the first and second guides are each formed of an insulating material.

37. The image forming apparatus as claimed in claim 20, further comprising a housing holding the image carrier, the first and second guides,

wherein the first and second bottom ends are both fixed to the housing.

38. A process cartridge characterized by comprising:

wherein the second guide surface has a second bottom end fixed to an upstream side of the transfer position, and a second leading end extending from the second bottom end to the upstream side opposite to the first leading end,

39. A cartridge according to claim 38, wherein at least one of the first and second guides is formed of a film member.

40. A cartridge according to claim 38, wherein the first and second guides are formed integrally with each other such that the first and second leading ends are continuously formed.

41. A cartridge according to claim 38, wherein the first and second guides are disposed such that the second leading end is in contact with the first guide and separable.

42. A cartridge according to claim 41, wherein the first and second guides are formed independently of each other by providing a gap between the first and second bottom ends.

43. A process cartridge according to claim 41, wherein the first and second guides are integrally formed with each other by connecting the first and second bottom ends to each other.

44. A process cartridge according to claim 41, wherein the second leading end is disposed in a projection plane of the first guide surface in a direction in which the transfer medium guided to the first guide surface presses the first guide surface.

45. A cartridge according to claim 38, wherein the first and second guides are arranged such that a first plane connecting the first front end and the first bottom end and a second plane connecting the second front end and the second bottom end intersect each other to form an obtuse angle between the first plane and the second plane.

46. The process cartridge as claimed in claim 38, wherein the first guide has a geometrical moment of inertia I₁Greater than the geometrical moment of inertia I of the second guide₂Geometric moment of inertia I₁Having a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the first guide, a geometrical moment of inertia I₂Has a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the second guide.

47. A process cartridge according to claim 38, wherein a length from the first front end to the first bottom end of the first guide face is longer than a length from the second front end to the second bottom end of the second guide face.

48. The process cartridge as claimed in claim 38, wherein the first guide is formed such that the young's modulus E of the first guide is₁And geometrical moment of inertia I₁Product of E₁I₁Satisfies 3.49X 10^-5≤E₁I₁≤1.18×10^-3Young's modulus E₁For the modulus of elasticity in the direction parallel to the conveying direction, geometrical moment of inertia I₁Has a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the first guide, an

The second guide member is formed such that the Young's modulus E of the second guide member₂And geometrical moment of inertia I₂Product of E₂I₂Satisfies 3.49X 10^-5≤E₂I₂≤1.18×10^-3Young's modulus E₂For the modulus of elasticity in the direction parallel to the conveying direction, geometrical moment of inertia I₂Having a direction parallel to the axial direction of the image carrier and a vertex against the second guideThe surface or the bottom surface is vertical.

49. The process cartridge according to claim 38, wherein the first guide is provided at a position to guide the transfer medium such that a contact angle θ between the image carrier and the transfer medium satisfies θ <90 °.

50. A cartridge according to claim 38, wherein at least one of the first and second guides is divided in a width direction orthogonal to the conveying direction.

51. A cartridge according to claim 38, wherein at least one of the first and second guide members is provided with a cutout extending from an edge of the first front end or the second front end toward the first bottom end or the second bottom end in the conveying direction.

52. A cartridge according to claim 51, wherein at least one of the first and second guides is provided with a separation preventing body provided at an end of the first bottom end or the second bottom end of the cutout, the separation preventing body preventing the first or second guide from being separated from the cutout.

53. A cartridge according to claim 38, wherein at least one of the first and second guides is provided with a slit extending from an edge of the first front end or the second front end toward the first bottom end or the second bottom end in the conveying direction.

54. The process cartridge as claimed in claim 53, wherein the slit is formed in a substantially rectangular shape in a plan view.

55. The process cartridge as claimed in claim 53, wherein the slit is formed substantially in a V-shape in a plan view.

56. The process cartridge as claimed in claim 55, wherein at least one of the first and second guides is provided with a separation preventing body disposed at an end of the first bottom end or the second bottom end of the slit, the separation preventing body preventing the first or second guide from being separated from the slit.

57. The process cartridge as claimed in claim 55, wherein the slit is formed substantially in a U-shape in a plan view.

58. A cartridge according to claim 38, further comprising a transfer unit which comes into contact with the image carrier at a transfer position.

59. A process cartridge according to claim 58, wherein an edge of the first leading end of the first guide surface is provided on an opposite side to a pressing direction in which the transfer medium guided by the first guide is pressed against the first guide, with respect to a connecting line connecting the transfer position and a contact position at which the pair of the abutting units contact each other, and the abutting units are provided on an upstream side of the first guide and are opposed to each other.

60. A cartridge according to claim 38, wherein the first and second guides are each formed of an insulating material.

61. A cartridge according to claim 38, further comprising a housing holding the image carrier, the first and second guides,

wherein the first and second bottom ends are both fixed to the housing.

62. An image forming apparatus, characterized by comprising:

a conveying unit that conveys the transfer medium to a transfer position;

63. The image forming apparatus according to claim 62, wherein at least one of the first and second guides is formed of a film member.

64. The image forming apparatus according to claim 62, wherein the first and second guides are formed integrally with each other such that the first and second leading ends are formed continuously.

65. The image forming apparatus as claimed in claim 62, wherein the first and second guides are disposed such that the second leading end is in contact with the first guide and separable.

66. The image forming apparatus as claimed in claim 65, wherein the first and second guides are formed independently of each other by providing a gap between the first and second bottom ends.

67. The image forming apparatus as claimed in claim 65, wherein the first and second guides are integrally formed with each other by connecting the first and second bottom ends to each other.

68. The image forming apparatus according to claim 65, wherein the second leading end is disposed within a projection plane of the first guide surface in a direction in which the transfer medium guided to the first guide surface presses the first guide surface.

69. The image forming apparatus according to claim 62, wherein the first and second guides are disposed such that a first plane connecting the first front end and the first bottom end and a second plane connecting the second front end and the second bottom end intersect each other so as to form an obtuse angle between the first plane and the second plane.

70. The imaging apparatus of claim 62, wherein the first guide has a geometric moment of inertia I₁Greater than the geometrical moment of inertia I of the second guide₂Geometric moment of inertia I₁Having a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the first guide, a geometrical moment of inertia I₂Has a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the second guide.

71. The image forming apparatus as claimed in claim 62, wherein a length from the first front end to the first bottom end of the first guide face is longer than a length from the second front end to the second bottom end of the second guide face.

72. The image forming apparatus as claimed in claim 62, wherein the first guide member is formed such that the Young's modulus E of the first guide member₁And geometrical moment of inertia I₁Product of E₁I₁Satisfies 3.49X 10^-5≤E₁I₁≤1.18×10^-3Young's modulus E₁For the modulus of elasticity in the direction parallel to the conveying direction, geometrical moment of inertia I₁Has a direction parallel to the axial direction of the image carrier and a direction perpendicular to the top or bottom surface of the first guide, an

73. The image forming apparatus according to claim 62, wherein the first guide is provided at a position to guide the transfer medium such that a contact angle θ between the image carrier and the transfer medium satisfies θ <90 °.

74. The image forming apparatus according to claim 62, wherein at least one of the first and second guides is divided in a width direction orthogonal to the conveying direction.

75. The image forming apparatus as claimed in claim 62, wherein at least one of the first and second guide members is provided with a cutout extending from an edge of the first front end or the second front end toward the first bottom end or the second bottom end in the conveying direction.

76. The image forming apparatus according to claim 75, wherein at least one of the first and second guide members is provided with a separation preventing body provided at an end of the first bottom end or the second bottom end of the cutout, the separation preventing body preventing the first or second guide member from being separated from the cutout.

77. The imaging apparatus of claim 62, wherein at least one of the first and second guides is provided with a slit extending in the conveying direction from an edge of the first leading end or the second leading end to the first bottom end or the second bottom end.

78. The imaging apparatus of claim 77, wherein the slit is formed in a substantially rectangular shape in plan view.

79. The image forming apparatus as claimed in claim 77, wherein the slit is formed substantially in a V-shape in a plan view.

80. The image forming apparatus as claimed in claim 79, wherein at least one of the first and second guide members is provided with a separation preventing body disposed at an end of the first bottom end or the second bottom end of the slit, the separation preventing body preventing the first or second guide member from being separated from the slit.

81. The image forming apparatus as claimed in claim 77, wherein the slit is formed substantially in a U-shape in a plan view.

82. An image forming apparatus according to claim 62, wherein an edge of the first leading end of the first guide surface is provided on an opposite side to a pressing direction in which the transfer medium guided by the first guide member is pressed against the first guide member, with respect to a connection line connecting the transfer position and a contact position at which the pair of abutting units contact each other, and the abutting units are provided on an upstream side of the first guide member and are disposed opposite to each other.

83. The image forming apparatus as claimed in claim 62, wherein the first and second guides are each formed of an insulating material.

84. The image forming apparatus according to claim 62, further comprising a housing that holds the image carrier, the first and second guides,

wherein the first and second bottom ends are both fixed to the housing.