JP4195680B2 - Paper feeding device and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet feeding device that supplies a recording medium on a sheet to the image forming unit side, and more specifically, a friction pad type sheet feeding device, and a printer, a copier, a fax machine, and the like equipped with the sheet feeding device. The present invention relates to an image forming apparatus.

  Conventionally, in image forming apparatuses such as printers, copiers, facsimiles, etc., a friction pad type paper feeding device is used as a mechanism for separating and feeding one by one from stacked recording papers and originals. ing. The friction pad is affixed to the lower surface of the upper part of the friction pad holder and affixed so that the front surface of the front end, which is a convex portion just before the lower surface, slides against the paper surface and slides it. Yes. The friction pad holder pivotally supported about the shaft is always pressed against the sheet feed roller by the separation spring. With such a configuration, the sheet is fed out by the rotation of the paper feed roller, and the front end of the paper slides on the front part of the front end of the portion serving as a guide for the friction pad, and enters the nip portion between the paper feed roller and the friction pad. It is conveyed and separated and sent out due to the friction coefficient of the friction pad, paper, and paper feed roller.

  As this type of technology, for example, the inventions disclosed in Patent Documents 1 and 2 are known. Among these, in Patent Document 1, when the paper is separated, the paper is caught on both ends of the friction pad portion, or the occurrence of jamming, non-feeding or multi-feeding caused as a load is prevented. In order to make it possible to easily change the length of a guide for sliding paper, in a friction pad type paper feeding device that separates paper with a paper feed roller and a friction pad, the friction pad section and the friction pad for holding the friction pad section It has a guide plate that covers the front end of the paper-passing side of the holder and friction pad holder, both ends of the paper-passing surface of the friction pad, and the front of the front end of the friction pad holder. Techniques to do this are disclosed.

In Patent Document 2, a cylindrical body is attached to the outer peripheral surface of the core and the core is fixed to the support shaft in order to suppress the occurrence of abnormal noise without impairing the separation conditions set at the time of designing the paper feeder. Furthermore, a collar is provided on both sides of the core so that the collar can be rotated with respect to the support shaft, so that the feed roller is configured, and the separation pad that faces the feed roller is a high friction part with a high friction coefficient in the center. And a low-friction part with a low friction coefficient at both ends, and the separation pad is arranged so that the roller surface of the paper feed roller faces the high-friction part and the collar and collar are in contact with the low-friction part It is disclosed.
JP-A-6-144619 JP2002-335766

  By the way, when the paper passes over the friction pad, the portion of the paper that is not placed on the friction pad is in a suspended state. If it passes in this state, the paper may be scratched or turned up by the left and right edges of the friction pad. What can be considered here is that scratches and turns do not occur unless the paper is rubbed against the left and right edges of the friction pad. As countermeasures, in order to cover this edge, a tape or the like is applied to the edge part, or measures such as disposing other members outside the left and right ends of the edge as disclosed in Patent Document 1, can be considered, Separation is performed on the surface of the friction pad. If the tape is applied, the tape may catch on the tape itself and may not be transported due to the thickness of the tape, or may affect transport performance such as double feeding. The same applies to the case where separate members are arranged at the left and right ends. Furthermore, as disclosed in Patent Document 2, it cannot be denied that partially changing the friction coefficient of one separation pad leads to an increase in cost.

  The present invention has been made in view of the actual situation of such a conventional technique, and its purpose is to prevent the paper from being rubbed at the left and right ends of the friction pad with a simple configuration without affecting the transport performance. An object of the present invention is to provide an inexpensive sheet feeding device that does not cause scratches or turning on a sheet, and an image forming apparatus including such a sheet feeding device.

In order to achieve the above object, the first means is provided on both sides of the paper feed roller in a paper feed device that separates the paper at the nip portion between the paper feed roller and the friction pad held by the friction pad holder. A pressure roller having a smaller diameter than the paper feed roller, and provided at both ends in the width direction of the friction pad holder on the downstream side of the paper feed direction from the nip portion of the paper feed roller and the friction pad along the paper transport direction. And a protrusion for avoiding interference with the end of the friction pad in the width direction, the protrusion being located outside both end faces of the pressure roller, and the protrusion being the friction It protrudes from the upper surface of the pad, and the outer peripheral surface of the pressure roller is located between the upper surface of the friction pad and the upper surface of the protrusion .

The second means is characterized in that the image forming apparatus includes the paper feeding device according to the first means.

According to the present invention, it is possible to prevent the sheet from floating at the left and right ends of the friction pad with a simple configuration without affecting the conveyance performance, and to prevent the sheet from being rubbed. It is possible to prevent scratches and turning.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 6 is a diagram illustrating a configuration of an image forming apparatus including a friction pad type sheet feeding device according to an embodiment of the present invention.

  The image forming apparatus shown in FIG. 6 schematically includes an automatic document feeder (hereinafter referred to as ADF) 200 and an image forming apparatus main body 100. A sheet document bundle placed on the document table 220 in the ADF 200 with the image surface of the document 210 facing upward is detected by the document set detection sensor 209, and when a start (PRINT) key on an operation unit (not shown) is pressed, The document is fed from the top document and stops when the leading edge of the document reaches the position where the registration sensor 205 is disposed. The document that has reached the position of the registration sensor 205 is restarted and read at the ADF document reading position 110 on the image forming apparatus main body 100 side. In the case of single-sided reading, the original is discharged directly to the document discharge tray 207. In the case of double-sided reading, the reverse side is read by reversing the paper on the document discharge tray 207 by the document branching claw 206 and feeding again. A book document or the like is placed on the contact glass 108 and read by the reading unit 150.

  The transfer sheets loaded on the first paper feed cassette 111, the second paper feed cassette 112, and the third paper feed cassette 113 on the image forming apparatus main body side are the first paper feed device 114, the second paper feed device 115, and the second paper feed device, respectively. Paper is fed from one of the three paper feeders 116 and conveyed to a position where it contacts the photoconductor 118 by a common vertical conveyance unit 117. At that time, the transfer paper is sent out at the timing of the leading edge position of the image formed on the photosensitive member 118 by the registration roller 117a. Reference numeral 26 denotes a registration sensor 26. The image data read by the reading unit 150 is written on the photosensitive member 118 by the laser beam from the writing unit 157 and passes through the developing unit 127 to form a toner image. The toner image on the photoconductor 118 is transferred while the transfer paper is conveyed by the conveyance belt 119 at the same speed as the rotation of the photoconductor 118. Thereafter, the image on the transfer paper is fixed by the fixing unit 120, and the transfer paper on which the image is fixed is discharged to the paper discharge tray 121.

  When images are to be formed on both sides of the transfer paper, the image is once conveyed to the double-sided conveyance path 132 by the branching claw 131 for switching the path without being guided from the fixing unit 120 to the paper discharge tray 121 side. Thereafter, the transfer sheet in the double-sided conveyance path 132 is again fed to transfer the toner image formed on the photosensitive member 118 again. When the toner image is transferred, the discharge tray 121 passes through the fixing unit 120. Led to. In this way, the double-sided conveyance path 132 is used when images are created on both sides of the transfer paper.

  The reading unit 150 includes a contact glass 108 on which an original is placed and an optical scanning system. The optical scanning system includes an exposure lamp 151, a first mirror 152, a second mirror 155, a third mirror 156, and a lens 153. , A CCD image sensor 154 and the like. The exposure lamp 151 and the first mirror 152 are fixed on a first carriage (not shown), and the second mirror 155 and the third mirror 156 are fixed on a second carriage (not shown).

  When the original image on the contact glass 108 is read, the first carriage and the second carriage are mechanically scanned at a relative speed of 2: 1 so that the optical path length does not change. This optical scanning system is driven by a scanner drive motor (not shown). On the other hand, when the original image is read while the original is fed by the ADF 200, the first carriage having the exposure lamp 151 and the first mirror 152 and the second carriage having the second mirror 155 and the third mirror 156 are shown in FIG. Fixed at the indicated position. The document image is read by the CCD image sensor 154, converted into an electrical signal, and processed.

  The writing unit 157 includes a laser output unit 158, an imaging lens 159, and a mirror 160. Inside the laser output unit 58, a rotating polygon mirror (polygon mirror) that rotates at a high speed at a high speed by a laser diode and a motor as a laser light source. ). Laser light emitted from the laser output unit 158 is deflected by a polygon mirror that rotates at a constant speed, passes through an imaging lens 159, is folded by a mirror 160, and is focused on the surface of the photoconductor 118. The deflected laser light is exposed and scanned in a direction (main scanning direction) orthogonal to the direction in which the photosensitive member 118 rotates, and recording is performed in units of lines of an image signal output from an output data selector of an image processing unit (not shown). An image (electrostatic latent image) is formed on the surface of the photoconductor 118 by repeating main scanning at a predetermined cycle corresponding to the rotational speed and recording density of the photoconductor 118.

  As described above, the laser beam output from the writing unit 157 is applied to the image forming photoconductor 118. Although not shown, a beam sensor for generating a main scanning synchronization signal is disposed at a position where a laser beam near one end of the photosensitive member 118 is irradiated. Based on the main scanning synchronization signal, control of image recording start timing in the main scanning direction and generation of a control signal for inputting / outputting the image signal are performed.

  FIG. 1 is an enlarged cross-sectional view showing a paper feeding unit of the first to third paper feeding devices 114 to 116 provided in the image forming apparatus, FIG. 2 is a front view, and FIG. 3 is an enlarged view of FIG. 4 is a perspective view of the friction pad holder, and FIG. 5 is an enlarged view of the paper feed roller and the friction pad holder.

  In these drawings, on the bottom plate 40 of the paper feed cassette 111 (which will be described below as a representative example of the first paper feed cassette 111, but the same applies to the second and third paper feed cassettes 112 and 113). Sheets 50 are stacked, and the stacked uppermost sheet 50 is elastically urged toward the sheet feed roller 30 disposed above the sheet feed cassette 111 by a bottom plate spring (not shown) that lifts the bottom plate 40 upward. It is pressed by the paper feed roller 30. The friction pad holder 1 is provided immediately after the downstream side of the paper 50 in the carry-out direction, at a position facing the paper feed roller 30 below the paper feed roller 30, and swings on the shaft 1b on the downstream side in the paper transport direction. It is pivotally supported. The friction pad holder 1 is elastically biased to the paper feed roller 30 by the separation spring 3, and the friction pad 2 is pressed against the paper feed roller 30 with a predetermined pressure. This state is a set state, and the paper 50 is not fed in this state.

  As shown in FIG. 4, the friction pad 2 is provided with an inclined guide portion 1c at a portion where the paper is carried in, and the friction pad 2 is disposed on the downstream side of the guide portion 1c in the paper conveyance direction. Further, as shown in FIG. 3, ribs 1 a that rise higher than the upper surface of the friction pad 2 are provided on both sides of the portion corresponding to the rear end of the portion where the friction pad 2 is disposed in the sheet conveyance direction. . The paper feed roller 30 is disposed at the center of the outer periphery of the paper feed roller collar 32 provided coaxially with the shaft 31, and the narrow pressure rollers 7 are provided at both ends of the paper feed roller 30. Yes. As shown in FIG. 3, the pressure roller 7 is set to have a slightly smaller diameter than the paper feed roller 30, and can be pressed so that both side portions parallel to the conveyance direction of the paper 50 do not float.

  When the paper feed roller 30 rotates clockwise (in the direction of arrow B) from the state shown in FIG. 1, the paper 50 set on the bottom plate 40 moves in the direction of arrow A, and the guide 1b on the front surface of the friction pad holder 1 is moved. Is advanced to the nip portion between the friction pad 2 and the paper feed roller 30. At this time, even if several sheets are simultaneously fed by the top sheet due to friction between the sheets 50, the top sheet 50 is always fed at the nip portion between the feed roller 30 and the friction pad 2. Since the roller 30 is pulled in the transport direction, and the friction between the sheets 50 is smaller than the friction force between the friction pad 2 and the sheet 50, the uppermost sheet 50 is separated from the sheet located below it. Only one sheet is conveyed.

  The separated paper 50 passes through the nip portion between the paper feed roller 30 and the friction pad 2 and further moves in the arrow A direction. At this time, the front end portion and both side portions of the sheet 50 are supported by the ribs 1 a and can pass through without strongly contacting the left and right edges 2 a of the friction pad 2. As a result, the sheet 50 is not rubbed against the left and right edges 2a of the friction pad 2, so that the generation of scratches and turns on the sheet 50 can be minimized. Further, as can be seen from FIG. 5, the rib 1 a is arranged in the transport downstream direction from the nip portion between the paper feed roller 30 and the friction pad 2, so that the separation performance is not affected.

  In this embodiment, the height of the rib 1a is configured to be higher than the upper surface of the friction pad 2 as described above, but may be set to an equivalent height. In this case, as shown in FIG. 3, the sheet is not separated from the friction pad 2 due to the influence of the rib 1a, and the separation performance is not affected by the rib 1a.

  Furthermore, in the above-described embodiment, the height of the rib 1a is configured to be higher than the upper surface of the friction pad 2 as described above. However, the height of the rib is previously projected from the surface of the friction pad 2 in this way. By repeating the paper feeding operation, the rib 1a can be scraped by the passing paper, and the height can finally be the same as the surface of the friction pad 2. In this case, the friction pad holder 1 is formed of a general resin such as ABS, PC, or PS. When such a material is used, the rib 1a is scraped by repeating the paper feeding operation, but eventually becomes the same height as the surface of the friction pad 2 and is not scraped thereafter. When the height is equal to the surface of the friction pad 2 in this way, the paper is not separated from the friction pad 2 by the rib 1a, and the paper separation performance is not affected.

  As described above, according to the present embodiment, the nip portion between the feed roller 30 and the friction pad 2 that affects the conveyance performance is avoided, and the sheet does not rub against the left and right edges 2 a of the friction pad 2. As a result, it is possible to reduce the occurrence of scratches and turns on the paper without affecting the transport performance.

  In addition, if the rib height is too high, there is a high possibility that double feeding will occur, and if it is too low, there will be no effect on scratches or turning, but by making the rib shape as described above, By using a material such as this so that it can be scraped over time, there is no need to increase processing accuracy and the paper does not rub against the left and right edges of the friction pad without affecting the transport performance. And can exhibit stable performance over time.

FIG. 4 is an enlarged cross-sectional view illustrating a paper feeding unit of first to third paper feeding devices provided in an image forming apparatus according to an embodiment of the present invention. It is a front view of FIG. FIG. 3 is an enlarged view of FIG. 2. It is a perspective view of the friction pad holder which concerns on embodiment of this invention. It is an enlarged view of a paper feed roller and a friction pad holder. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Friction pad holder 1a Rib 2 Friction pad 2a Friction pad right and left edge 3 Separation spring 7 Pressure roller 30 Paper feed roller 31 Paper feed roller shaft 32 Paper feed roller color 40 Cassette bottom plate 50 Paper 100 Image forming apparatus main body 200 Automatic document feeding Equipment (ADF)

Claims (2)

In a paper feeding device that performs paper separation at a nip portion between a paper feeding roller and a friction pad held by a friction pad holder,
A pressure roller having a smaller diameter than the paper feed roller provided on both sides of the paper feed roller;
Provided along the paper transport direction at both ends in the width direction of the friction pad holder on the downstream side in the paper transport direction from the nip portion of the paper feed roller and the friction pad, and with the end in the width direction of the friction pad. A protrusion to avoid interference ,
With
The protrusion is located outside both end surfaces of the pressure roller, the protrusion protrudes from the upper surface of the friction pad, and the outer peripheral surface of the pressure roller is formed between the upper surface of the friction pad and the upper surface of the protrusion. A sheet feeding device that is located between the two . An image forming apparatus characterized by comprising a sheet feeding apparatus according to 請 Motomeko 1.

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