JP4052990B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an information recording apparatus.

2. Description of the Related Art Conventionally, in some image forming apparatuses to which an electrophotographic system is applied, an image forming cartridge is detachably disposed.
This image forming cartridge includes a photosensitive drum therein, and includes a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit around the photosensitive drum.
An image forming cartridge is formed by covering each member with a cartridge case.

  In the photosensitive drum, a rotating shaft is fitted in a bearing portion formed at the center of the flange, whereby the photosensitive drum is grounded (refer to Patent Document 1). ).

The structure of the conventional image forming cartridge will be described below.
FIG. 6 is a cross-sectional view of the main part of a conventional image forming cartridge.
In FIG. 6, a photosensitive drum 3 is provided inside the cartridge case 2 that covers the entire image forming cartridge 1.
The photosensitive drum 3 is configured by forming a charge generation layer and a charge transport layer on a conductive base material made of a cylindrical aluminum alloy material or the like.
The drum support members 4 and 5 made of metal or conductive resin are press-fitted or bonded to both ends of the photosensitive drum 3.
The shaft portion of the drum support member 4 is rotatably engaged in a bearing hole 2a formed in the cartridge case 2.
Thus, the photosensitive drum 3 is rotatably supported with respect to the cartridge case 2 by the bearing hole 2a.
A gear 6 is disposed on a part of the peripheral surface of the drum support member 4.

Positioning pins 8 and 9 are attached to the frame 7 constituting the image forming apparatus in a state of protruding toward the inside of the apparatus.
The positioning pins 8 and 9 are fitted in rotation center holes formed at the centers of the drum support members 4 and 5.
A conductive annular conductive spring member 10 is attached to the inner end face of the drum support member 4.

  The peripheral edge of the conductive spring member 10 is in contact with the inner peripheral surface of the photosensitive drum 3, and the protruding portion 10 a extending from the peripheral edge of the conductive spring member 10 toward the center is in contact with the distal end portion of the positioning pin 8. It is arranged like this.

  As described above, the photosensitive drum 3 is electrically connected to the frame 7 via the conductive spring member 10 and the positioning pin 8, and is grounded by the frame 7.

By the way, when the roundness error between the inner peripheral wall surface forming the rotation center hole of the drum support member 4 and the peripheral surface of the positioning pin 8 is large, the drum support member 4 rotates as the photosensitive drum 3 rotates. Since the peripheral surface of the positioning pin 8 is in sliding contact with the inner peripheral wall surface forming the rotation center hole, the rotational speed of the photosensitive drum 3 may vary.
Although it is conceivable to arrange a bearing between the positioning pin 8 and the rotation center hole, the number of parts is increased by that amount, resulting in an increase in cost.

On the other hand, it is possible to reduce the amount of sliding contact by reducing the contact area of the peripheral surface of the positioning pin 8 by reducing the thickness dimension of the drum support member 4 or the like.
However, when the drum support member 4 is formed from a conductive resin, if the contact area is reduced, the conductivity is inferior to that of the conductive metal, and thus the photosensitive drum 3 cannot be stably grounded.
As a result, there is a possibility that the image quality deteriorates or noise is generated and the apparatus malfunctions.

A means for solving the above problem is disclosed in Patent Document 2.
FIG. 7 shows a cross-sectional view of the main part of another conventional image forming cartridge.
In FIG. 7, a photosensitive drum 15 is provided inside the cartridge case 14 that covers the entire image forming cartridge 12.

The photosensitive drum 15 is configured by forming a charge generation layer and a charge transport layer on a conductive base material made of a cylindrical aluminum alloy material or the like.
A metal drum shaft 16 serving as a shaft member made of a conductor is disposed in the photosensitive drum 15.
Both end portions 16 a and 16 b of the drum shaft 16 pass through bearing holes 14 c and 14 c formed in the side walls 14 a and 14 b of the cartridge case 14.

Both end portions 16a and 16b of the drum shaft 16 are engaged with the engaging slots 19c and 19c of the frame 19 (19a and 19b) in a state of protruding from the side walls 14a and 14b of the cartridge case 14.
Thereby, the drum shaft 16 is positioned with respect to the frame 19 of the image forming apparatus.
A part of the drum shaft 16 is formed with a groove 16d into which a part of an E-ring 22 described later enters.

A conductive drum support member 20 is fixed inside the photosensitive drum 15 by press-fitting or a conductive adhesive.
The drum support member 20 and a gear 25 described later are rotatably mounted on the drum shaft 16.

The drum support member 20 has a cone-shaped hole 20 a that is not in contact with the peripheral surface of the drum shaft 16, and only the small diameter portion 20 b facing the collar 21 made of a conductive metal is in contact with the peripheral surface of the drum shaft 16. Yes.
Thereby, the rotational friction resistance generated between the drum shaft 16 and the drum support member 20 is reduced.

The collar 21 is mounted on the end of the drum shaft 16 protruding from the photosensitive drum 15 so as to be rotatable and movable.
Further, an E-ring 22 is attached to the end of the drum shaft 16 so as to be fitted in the groove 16d.
The end face of the collar 21 is in contact with the E-ring 22.
The E-ring 22 is a stopper that prevents the collar 21 from moving when the collar 21 is pressed by a thrust force, which will be described later, via the drum support member 20. The E-ring 22 reliably contacts the collar 21 and the drum support member 20. Connect electrically.

A conductive spring member 23 is attached to the frame 19 a by pins 24.
The spring member 23 is grounded, and its free end is in contact with the end surface 16c of the drum shaft 16 in pressure contact.
Therefore, the end surface 16c of the drum shaft 16 and the spring member 23 are reliably electrically connected.

  As a result, the photosensitive drum 15 is electrically connected to the drum shaft 16 via the drum support member 20 or is electrically connected via the drum support member 20, the collar 21 and the E ring 22. It will be grounded via.

On the other end of the photosensitive drum 15, a gear 25, which is a rotation transmitting means serving also as a drum support member, is fixed with a conductive adhesive.
A drive gear 26 is engaged with the gear 25, and the drive gear 26 is rotatably fitted to a fixed shaft 27 fixed to the frame 19b.

Here, the gear 25 and the drive gear 26 are formed of helical gears, and are set to generate a thrust force in a direction in which the drum support member 20 is pressed against the collar 21.
Japanese Utility Model Publication No. 62-49175 JP 2002-149007 A

  However, in the configuration shown in FIG. 7, since the collar 21 is made of metal, the elasticity in the thrust direction is poor, and it is relatively easy to make a stable electrical connection by reliably contacting the end surface of the drum support member 20. A large thrust force is required, and the sliding contact resistance at the end surface of the drum support member 20 may be increased.

  Further, when the thrust force fluctuates, the sliding contact resistance at the end face of the drum support member 20 may greatly fluctuate.

  Therefore, the present invention has been made in view of the above circumstances, and even with a small thrust force, it is possible to stably ground the image carrier, and further, when the thrust force fluctuates. Even so, an object of the present invention is to provide an image forming apparatus having good image quality without noise by adopting a configuration in which the variation in sliding resistance of the image carrier is small.

The image forming apparatus of the present invention includes an apparatus main body that is electrically grounded, and an image carrier that is rotatably disposed on the apparatus main body, and the image carrier is disposed on a rotation center axis thereof. A conductive shaft member that is connected to the apparatus main body and rotatably supports the image carrier, and a conductive member that is attached to the shaft member and electrically connects the image carrier and the shaft member. First connecting means having the characteristics. Further, the shaft member and the second connecting means consisting of a compression coil spring having conductivity for electrically connecting the device body and the shaft member to the machine end, the composed than the compression coil spring And a stopper having conductivity for preventing movement of the connecting means relative to the shaft member, and the apparatus main body is provided with a body-side support shaft for rotatably connecting the shaft member. When the shaft member of the image carrier is coupled to the main body side support shaft , the compression coil spring as the second connection means contacts the main body side support shaft, and the image carrier is the first connection means, the shaft. It has a configuration in which it is electrically connected to the apparatus main body via a second connecting means comprising a member, a stopper, a compression coil spring , and a main body side support shaft.

According to the present invention, the image carrier disposed rotatably on the apparatus main body is electrically connected to the front apparatus main body, so that the rotational sliding resistance of the image carrier is reduced and the image carrier is provided. Can be reliably grounded, noise can be eliminated, and image quality can be improved.

The second connecting means of the image forming apparatus of the present invention is a compression coil spring in which at least one inner diameter thereof is narrowed to be smaller than the outer diameter of the shaft member, and the compression coil spring and the stopper are provided on the shaft member. A conductive material having an electric resistance smaller than the electric resistance is included .

According to the present invention described above, the contact electrical resistance with the stopper of the compression coil spring can be reduced, and the image carrier can be grounded reliably and stably.

  In the image forming apparatus of the present invention, the compression coil spring and the stopper are gold-plated using iron as a base material.

  According to the present invention, since the compression coil spring and the stopper are plated with gold using iron as a base material, the contact electrical resistance with the stopper of the compression coil spring can be further reduced.

  In the image forming apparatus of the present invention, when the compression coil spring attaches the image carrier to the apparatus main body, the thrust load contacting the end surface of the main body side support shaft provided on the apparatus main body side is 0.04 kgf. That's it.

  According to the present invention, when the compression coil spring attaches the image carrier to the apparatus main body, the thrust load that contacts the end surface of the main body side support shaft provided on the apparatus main body side is 0.04 kgf. As described above, the fluctuation of the contact electric resistance with the stopper with respect to the thrust load of the compression coil spring can be reduced, and the image carrier can be stably grounded.

  The image forming apparatus of the present invention further includes a driving force transmitting means for transmitting a driving force to the image carrier, and the driving force transmitting means is an outer member fixed coaxially to the main body side support shaft. A first joint body having teeth, and a second joint body coaxially fixed to an end portion of the image carrier and having internal teeth that mesh with external teeth of the first gear. The outer teeth of the joint body of 1 and the inner teeth of the second joint body are a screw for generating a thrust force in the direction in which the compression coil spring is compressed along with the transmission of the driving force.

  According to the present invention, the driving force transmission means for transmitting the driving force to the image carrier is further provided, and the driving force transmission means is coaxially fixed to the body-side support shaft. A first joint body having teeth, and a second joint body coaxially fixed to an end portion of the image carrier and having internal teeth that mesh with external teeth of the first gear. The outer teeth of the joint body of 1 and the inner teeth of the second joint body are helical for generating a thrust force in the direction of compressing the compression coil spring in accordance with the transmission of the driving force. The variation in the contact electric resistance with the stopper with respect to the thrust load of the compression coil spring can be further reduced.

  As described above, according to the present invention, it is possible to stably ground the image carrier even with a small thrust force, and even when the thrust force fluctuates, By adopting a configuration in which the variation in the sliding contact resistance of the carrier is small, an image forming apparatus with no noise and good image quality can be obtained.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  The image forming apparatus of the present invention is disposed on an apparatus main body (not shown), a photosensitive drum 30 which is an image carrier rotatably disposed on the apparatus main body, and a rotation center axis in the photosensitive drum 30. The drum shaft 31, which is a conductive shaft member for supporting both ends of the photosensitive drum 30, and the first conductive connection for electrically connecting the photosensitive drum 30 and the drum shaft 31. And a terminal member 32 as means.

  The image forming apparatus of the present invention is further provided on the drum shaft 31, and is provided on the drum shaft 31, and is provided with a conductive second connection means for electrically connecting the drum shaft 31 and the apparatus main body. A stopper 34 having conductivity for preventing movement of the second connecting means relative to the drum shaft 31, and the second connecting means restricts at least the inner diameter of one end thereof to be smaller than the outer diameter of the drum shaft 31. The compression coil spring 33 is provided.

  In the image forming apparatus of the present invention, the compression coil spring 33 and the stopper 34 are made of a conductive material having an electric resistance smaller than the electric resistance of the drum shaft 31, or the substrate has an electric resistance smaller than the electric resistance of the drum shaft 31. A conductive coating agent having resistance is coated.

  In the image forming apparatus of the present invention, the compression coil spring 33 and the stopper 34 are gold-plated using iron as a base material.

  In the image forming apparatus of the present invention, when the compression coil spring 33 is mounted on the apparatus main body, the thrust load that contacts the end surface of the main body side support shaft 35 provided on the apparatus main body side is 0.04 kgf or more. It is.

  The image forming apparatus of the present invention further includes driving force transmission means 36 for transmitting driving force to the photosensitive drum 30, and the driving force transmission means 36 is coaxially fixed to the main body side support shaft 35. A driving side coupling member 37, which is a first joint body having outer teeth 37a, and an inner tooth 38a that is coaxially fixed to the end of the photosensitive drum 30 and meshes with the outer teeth 37a of the driving side coupling member 37. And a passive side coupling member 38 which is a second joint body having the outer joint 37 and the external teeth 37a of the driving side coupling member 37 and the internal teeth 38a of the passive side coupling member 38 are compressed in accordance with transmission of the driving force. This is a screw for generating a thrust force in the direction in which the coil spring 33 is compressed.

FIG. 1 is a cross-sectional view of the main part showing the configuration of an image forming apparatus according to an embodiment of the present invention.
The photoreceptor drum 30 is configured by forming a charge generation layer and a charge transport layer on a conductive base material made of a cylindrical aluminum alloy material.

  Inside the photosensitive drum 30, a metal drum shaft 31 as a shaft member made of a conductor is disposed along the rotation center axis of the photosensitive drum 30.

  Drum support members 39 and 40 are fixed to both ends of the photosensitive drum 30 by press-fitting or an adhesive, and the drum shaft 31 passes through the centers of the drum support members 39 and 40.

FIG. 3 is an enlarged front view showing the main part of the shaft member of the image forming apparatus according to the embodiment of the present invention.
A locking pin 41 is press-fitted into the drum shaft 31 in a direction crossing the central axis (see FIG. 3). The locking pin 41 is locked in a locking groove 42 formed in the drum support member 39. Yes.

  A passive side coupling member 38 is coaxially disposed at one end of the photosensitive drum 30, and the passive side coupling member 38 is attached to the outer end surface of the drum support member 39, and the center of the passive side coupling member 38 is centered. One end of the drum shaft 31 passes therethrough.

  A main body side support shaft 35 made of a conductor is rotatably provided on a frame 43 of the apparatus main body, and a drive gear 44 is mounted on the shaft. The main body side support shaft 35 is connected to the drive motor via the drive gear 44. (Not shown).

  A shaft insertion hole 35a having an inner diameter that is the same as the diameter of one end of the drum shaft 31 or slightly larger than the diameter of one end of the drum shaft 31 is provided at the center of the main body side support shaft 35. When the drum 30 is mounted on the apparatus main body, the photosensitive drum 30 is supported by inserting one end portion of the drum shaft 31 into a shaft insertion hole 35 a provided in the main body side support shaft 35.

  A drive side coupling member 37 is attached to the base of the main body side support shaft 35 and transmits a rotational driving force to a passive side coupling member 38 provided on the drum support member 39.

  The driving side coupling member 37 has outer teeth 37a on the outer periphery, and the passive side coupling member 38 has inner teeth 38a meshing with the outer teeth 37a of the driving side coupling member 37 on the inner periphery. The coupling member 37 and the passive side coupling member 38 are connected to each other, and the driving side coupling member 37 and the passive side coupling member 38 as the driving force transmitting means 36 drive the photosensitive drum 30 to rotate at a constant speed with high accuracy. ing.

  An annular terminal member 32 having conductivity is attached to the inner end surface of the drum support member 39, the outer peripheral edge of the terminal member 32 is in contact with the inner peripheral surface of the photosensitive drum 30, and the terminal member 32. The protrusion 32 a provided from the inner peripheral edge toward the center is arranged so as to contact the outer peripheral surface of the drum shaft 31.

  The end of the drum shaft 31 on the main body side support shaft 35 side has conductivity, and the compression coil spring 33 and the movement of the compression coil spring 33 have an inner diameter that is narrower than the outer diameter of the drum shaft 31. The stopper 34 which has the electroconductivity for preventing this is provided, and the stopper 34 is attached in the state fitted in the annular groove 31a provided in the drum shaft 31 (refer FIG. 3).

FIG. 2 is a cross-sectional view of a principal part showing a state of mounting the image carrier of the image forming apparatus according to the embodiment of the present invention to the apparatus main body.
When the photosensitive drum 30 is mounted on the apparatus main body, the compression coil spring 33 contacts the end surface of the main body side support shaft 35 while being compressed by the stopper 34.

A conductive spring member 46 is attached to the frame 43 of the apparatus main body by screws 47.
The spring member 46 is grounded (earthed), and is in contact with the outer peripheral surface of the main body side support shaft 35 in a state where the free end side of the spring member 46 is in pressure contact.
Therefore, the main body side support shaft 35 and the spring member 46 are reliably electrically connected.

  As described above, the photosensitive drum 30 is electrically connected to the frame 43 of the apparatus main body via the terminal member 32, the drum shaft 31, the stopper 34, the compression coil spring 33, and the main body side support shaft 35. Grounded.

FIG. 4 is a graph showing the contact electric resistance with the stopper with respect to the thrust load of the compression coil spring of the image forming apparatus according to the embodiment of the present invention.
Regarding the compression coil spring 33, the material is stainless steel (SUS), the base material is iron plated with nickel (iron + Ni plating), and the base material is iron plated with gold (iron + Au plating). Three types of stoppers are available, and there are two types of stoppers 34: iron with nickel plating (iron + Ni plating) and iron with gold plating (iron + Au plating). , No. 1-1, the compression coil spring 33 is a combination of SUS and the stopper 34 is iron + Ni plating. 1-2, the compression coil spring 33 is a combination of SUS and the stopper 34 is iron + Au plating. 2-1, the compression coil spring 33 is a combination of iron + Ni plating and the stopper 34 is a combination of iron + Ni plating. 2-2, the compression coil spring 33 is a combination of iron + Ni plating and the stopper 34 is iron + Au plating. 3-1, the compression coil spring 33 is a combination of iron + Au plating and the stopper 34 is iron + Ni plating. 3-2, the compression coil spring 33 is a combination of iron + Au plating and the stopper 34 is a combination of iron + Au plating, and the contact electric resistance with the stopper 34 against the thrust load of the compression coil spring 33 is measured. Came to show.

As shown in FIG. 4, the compression coil spring 33 has a smaller contact electrical resistance in the order of (iron + Au plating) <(iron + Ni plating) <SUS, and the stopper 34 has (iron + Au plating) <(iron + Ni plating). It can be seen that the contact electric resistance is small in the order of).
In any combination, it can be seen that the thrust load of the compression coil spring 33 is 0.04 kgf or more, and the contact electric resistance with the stopper 34 is stable.

  In this embodiment, the compression coil spring 33 and the stopper 34 are plated with Au on an iron base, and the thrust load of the compression coil spring 33 is set to 0.1 kgf.

  Further, the outer teeth 37a of the driving side coupling member 37 and the inner teeth 38a of the passive side coupling member 38 are used to generate a thrust force in the direction in which the compression coil spring 33 is compressed in accordance with the transmission of the driving force. By using the configuration, the variation of the contact electric resistance during driving can be further reduced.

FIG. 5 is an explanatory view showing a method for measuring the contact electric resistance with the stopper against the thrust load of the compression coil spring of the image forming apparatus according to the embodiment of the present invention.
As shown in FIG. 5, stoppers 34 and 34 are respectively attached to a pressing portion 51 and a load measuring portion 52 that are arranged facing the top and bottom of a spring load measuring device (SPRING TEST MACHINE, manufactured by Fuji Seiki) 50 with double-sided tape. The compression coil spring 33 is sandwiched between the stoppers 34, 34, and compressed with an electric resistance measuring device (FLUKE tester) 55 while the spring load measuring device 50 pressurizes / measures the spring load of the compression coil spring 33. The electrical resistance with the stopper 34 with respect to the thrust load of the coil spring 33 was measured.

  With the above configuration, even if the thrust force is small, the photosensitive drum 30 can be connected via the terminal member 32, the drum shaft 31, the stopper 34, the compression coil spring 33, the main body side support shaft 35, and the spring member 46. Since it is electrically connected to the frame 43 of the main body, it is possible to stably ground the photosensitive drum 30. Further, even if the thrust force fluctuates, the sliding contact of the photosensitive drum 30 is possible. It is possible to provide an image forming apparatus that can reduce the variation in resistance, has no noise, and has high image quality.

1 is a cross-sectional view of a main part showing a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of a main part showing a state in which the image carrier of the image forming apparatus according to the embodiment of the present invention is mounted on the apparatus body. 1 is an enlarged front view showing a main part of a shaft member of an image forming apparatus according to an embodiment of the present invention. 3 is a graph showing contact electrical resistance with a stopper with respect to a thrust load of a compression coil spring of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is an explanatory diagram illustrating a method for measuring a contact electric resistance with a stopper against a thrust load of a compression coil spring of the image forming apparatus according to the exemplary embodiment of the present invention. FIG. 10 is a cross-sectional view of a main part showing a conventional image forming cartridge. FIG. 6 is a cross-sectional view of a main part showing an image forming cartridge of another conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image formation cartridge 2 Cartridge case 2a Bearing hole 3 Photosensitive drum 4,5 Drum support member 6 Gear 7 Frame 8,9 Positioning pin 10 Conductive spring member 10a Protrusion part 12 Image formation cartridge 14 Cartridge case 14a, 14b Side wall 14c, 14c Bearing hole 15 Photosensitive drum 16 Drum shaft 16a, 16b End 16c End surface 16d Groove 19 Frame 19a, 19b Frame 19c, 19c Engagement long hole 20 Drum support member 20a Hole 20b Small diameter part 21 Color 22 E ring 23 Spring member 24 pin 25 gear 26 drive gear 27 fixed shaft 30 photosensitive drum (image carrier)
31 Drum shaft (shaft member)
31a annular groove 32 terminal member (first connecting means)
32a protrusion 33 compression coil spring (second connecting means)
34 Stopper 35 Main body side support shaft 35a Shaft insertion hole 36 Driving force transmission means 37 Driving side coupling member (first joint body)
37a External tooth 38 Passive side coupling member (second joint body)
38a Internal teeth 39 Drum support member 40 Drum support member 41 Locking pin 42 Locking groove 43 Frame 44 Drive gear 46 Spring member 47 Screw 50 Spring load measuring device 51 Pressurizing unit 52 Load measuring unit 55 Electrical resistance measuring device

Claims (5)

An apparatus main body that is electrically grounded, and an image carrier that is rotatably arranged on the apparatus main body, the image carrier being arranged on a rotation center axis thereof, connected to the apparatus main body, and Conductive shaft member for rotatably supporting the image carrier, and first conductive means attached to the shaft member for electrically connecting the image carrier and the shaft member In an image forming apparatus comprising:
The shaft member has a second connection means including a conductive compression coil spring for electrically connecting the shaft member and the apparatus main body to an end portion on the apparatus side, and the shaft of the second connection means. A conductive stopper for preventing movement relative to the member,
The apparatus main body is provided with a main body side support shaft for rotatably connecting the shaft member,
When the shaft member of the image carrier is coupled to the main body side support shaft, the second connection means contacts the main body side support shaft, and the image carrier has the first connection means, the shaft member, the stopper, the second An image forming apparatus electrically connected to the apparatus main body via a connecting means and a main body side support shaft. The compression coil spring as the second connection means has at least one inner diameter reduced to be smaller than the outer diameter of the shaft member, and the compression coil spring and the stopper are smaller than the electric resistance of the shaft member. The image forming apparatus according to claim 1, comprising a conductive material having electrical resistance.   The image forming apparatus according to claim 2, wherein the compression coil spring and the stopper are gold-plated using iron as a base material.   4. The compression coil spring has a thrust load of 0.04 kgf or more in contact with an end surface of a main body side support shaft provided on the apparatus main body when the image carrier is mounted on the apparatus main body. The image forming apparatus described in 1.   A driving force transmitting means for transmitting a driving force to the image carrier, the driving force transmitting means having a first joint body having external teeth fixed coaxially to the body-side support shaft; A second joint body having an inner tooth that is coaxially fixed to an end portion of the image carrier and meshes with an outer tooth of the first gear; and the outer tooth of the first joint body and the first tooth 3. The image forming apparatus according to claim 1, wherein the internal teeth of the joint body of 2 are helical parts for generating a thrust force in a direction in which the compression coil spring is compressed in accordance with transmission of the driving force.

Images