JP6535154B2 - Sheet feeding apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet feeding device for feeding a sheet, and an image forming apparatus provided with the same.

  This type of sheet feeding apparatus includes a sheet feeding tray on which sheets are stacked, a sheet feeding roller, and a separating member in contact with the sheet feeding roller, and the sheet is pulled out of the sheet feeding tray to be separated from the sheet feeding roller and the separating member. The sheet is sent to the sheet conveyance path through the gap. When a plurality of sheets are pulled out from the sheet feeding tray with overlapping, the sheets are separated and conveyed one by one as they pass between the sheet feeding roller and the separating member.

  Further, in Patent Document 1, a pair of auxiliary rollers disposed on both sides of the sheet feeding roller and freely rotated and having a diameter smaller than the sheet feeding roller are provided, and each auxiliary roller is used to convey the sheet by the sheet feeding roller. The sheet is contacted to prevent skewing of the sheet.

  Further, in Patent Document 2, a pair of auxiliary rollers disposed on both sides of the sheet feeding roller and rotationally driven with the sheet feeding roller, a separating member in contact with the sheet feeding roller, and disposed between the sheet feeding roller and each auxiliary roller Provided with the respective auxiliary auxiliary members, conveying the sheet by the feed roller and each auxiliary roller, preventing double feeding of the respective sheets overlapped by the auxiliary members and the auxiliary members, and the auxiliary members and the auxiliary members The paper undulates the sheets to promote separation of the overlapping sheets.

Japanese Utility Model Application Publication 1-152936 JP, 2010-105774, A

  By the way, in the sheet feeding apparatus, when the number of sheets (the thickness of a sheet bundle) stacked in the sheet feeding tray changes, the uppermost sheet of the sheet bundle is between the sheet feeding roller and the separating member or separating member. The intruding angle (referred to as the paper entering angle) may change. In this case, the separating ability of each sheet by the sheet feeding roller and the separating member may not be stable, and a sheet feeding error or double feeding of sheets may occur.

  However, in any of Patent Documents 1 and 2, the change in the paper input angle between the paper feed roller and the separating member or the separating member is not taken into consideration, and the change in the paper input angle is The solution to the paper feed error and the double feed of the paper which is the cause has not been achieved.

  Therefore, the present invention has been made in view of the above-described conventional problems, and even if the number of sheets (the thickness of a sheet bundle) changes, the sheet entering angle between the sheet feed roller and the separating member. It is an object of the present invention to provide a sheet feeding device and an image forming apparatus capable of preventing sheet feeding errors and double feeding of sheets while maintaining the substantially constant.

In order to solve the above problems, a sheet feeding device according to the present invention includes a sheet feeding tray on which sheets are stacked, a sheet feeding roller for conveying the sheets, and a separating member for separating sheets conveyed by the sheet feeding rollers. A sheet feeding apparatus for pulling out the sheet from the sheet feeding tray and feeding the sheet to a sheet conveyance path through the space between the sheet feeding roller and the separating member, wherein the sheet is fed on an axis of the sheet feeding roller. An auxiliary member made of an elastic body having a diameter larger than that of a paper roller and the paper feed roller are provided side by side, an end of the paper feed roller in the axial direction of the paper feed roller and the auxiliary member facing the end The distance from the end, or the distance between the end of the separating member in the axial direction and the end of the auxiliary member opposed to the end is the length of the sheet feeding roller in the axial direction or the shaft Length of the separating member in the direction Rimotan rather, when the paper a nip region between the separating member and the feed roller is conveyed, the auxiliary member to which the paper corresponds to the nip area in the conveyance direction conveyed through the nip zone The portion of the outer peripheral surface of the sheet is in a direction away from the axis of the sheet feeding roller than the nip area in the direction orthogonal to the conveying direction .

In such an embodiment of the present invention, since the auxiliary member made of an elastic body having a diameter larger than that of the sheet feeding roller and the sheet feeding roller are provided side by side on the shaft of the sheet feeding roller Before reaching between the roller and the separating member, it is pressed against the separating member by the auxiliary member having a larger diameter than the feeding roller, and guided between the feeding roller and the separating member while being guided by the separating member. Therefore, even if the number of sheets (sheet bundle thickness) stacked in the sheet feeding tray changes, the sheet entering angle between the sheet feeding roller and the separating member is maintained substantially constant. It is possible to prevent sheet feeding errors and double sheet feeding caused by changes in the sheet angle.
Further, in the sheet feeding device of the present invention, the end of the sheet feeding roller in the axial direction is in contact with the end of the auxiliary member opposed to the end.

  Further, in the sheet feeding device of the present invention, the auxiliary member is in the form of a roller, and rotates with the sheet feeding roller.

  In this case, since the sheet is conveyed not only by the sheet feeding roller but also by the roller-shaped auxiliary member, it is possible to further reduce the sheet feeding error.

  Furthermore, in the sheet feeding device of the present invention, the auxiliary member is in the form of a roller and is made of foam.

  The sheet is pressed against the separating member with an appropriate force by the auxiliary member made of such a roller-shaped foam, and the paper entering angle between the sheet feeding roller and the separating member is effectively maintained substantially constant. can do.

  Further, in the sheet feeding device of the present invention, the outer peripheral surface of the auxiliary member is made of a coating layer for adjusting the frictional force between the sheet and the auxiliary member.

  In this case, the frictional force between the auxiliary member and the sheet is increased, the sheet is effectively conveyed by the auxiliary member, and the sheet feeding error is further reduced.

  Furthermore, in the sheet feeding device of the present invention, the auxiliary member is in the form of a hollow roller made of rubber.

  With a hollow roller-shaped auxiliary member made of such rubber, the sheet is pressed against the separating member with an appropriate force to effectively keep the sheet entering angle between the sheet feeding roller and the separating member substantially constant. Can be maintained. In addition, the frictional force between the auxiliary member and the sheet is increased, and the sheet is effectively conveyed by the auxiliary member, and the feeding error is further reduced.

  Further, in the sheet feeding device of the present invention, the auxiliary member is provided outside the area of the separating member in the axial direction of the sheet feeding roller.

  In this case, the sheet comes in contact with the sheet feeding roller and the auxiliary member having a diameter larger than that of the sheet feeding roller on both sides of the separating member, and the sheet is bent. This facilitates separation of each sheet when multiple sheets overlap and are pulled out.

  Next, the image forming apparatus of the present invention includes the sheet feeding device of the present invention, and a printing unit that forms an image on a sheet fed from the sheet feeding device.

  Also in such an image forming apparatus of the present invention, the same effects as those of the sheet feeding apparatus of the present invention can be obtained.

  In the present invention, since the auxiliary member made of an elastic material having a diameter larger than the paper feeding roller and the paper feeding roller are provided side by side on the shaft of the paper feeding roller, the leading end of the paper is separated from the paper feeding roller. Before reaching the space between them, it is pressed against the separating member by an auxiliary member having a larger diameter than the feeding roller, and guided between the feeding roller and the separating member while being guided by the separating member. Therefore, even if the number of sheets (sheet bundle thickness) stacked in the sheet feeding tray changes, the sheet entering angle between the sheet feeding roller and the separating member is maintained substantially constant. It is possible to prevent sheet feeding errors and double sheet feeding caused by changes in the sheet angle.

FIG. 1 is a cross-sectional view showing an image forming apparatus to which a first embodiment of a sheet feeding device of the present invention is applied. FIG. 2 is an enlarged side view schematically showing the sheet feeding device of the first embodiment. FIG. 3 is a front view showing a sheet feeding roller, a separation pad, and each auxiliary roller in the sheet feeding device as viewed from the upstream side in the sheet conveyance direction. FIG. 6 is a cross-sectional view showing an example of an auxiliary roller in the sheet feeding device. FIG. 7 is a cross-sectional view showing another example of the auxiliary roller in the sheet feeding device. FIG. 6 is an enlarged cross-sectional view showing a pressure contact state between the recording sheet on the uppermost layer of the sheet bundle on the sheet feeding tray and the sheet feeding roller and each auxiliary roller in the sheet feeding device. (A) is an enlarged sectional view showing a pressure contact state between the uppermost recording sheet and the sheet feeding roller and each auxiliary roller when the thickness of the sheet bundle on the sheet feeding tray becomes thick, (b) FIG. 6 is an enlarged cross-sectional view showing a pressure contact state between the uppermost recording sheet and the sheet feed roller and each auxiliary roller when the thickness of the sheet bundle on the sheet feed tray is reduced. (A) is an enlarged sectional view showing a state in which the recording sheet of the sheet bundle on the sheet feeding tray is curled downward; (b) is a state in which the recording sheet of the sheet bundle on the sheet feeding tray is curled upward FIG. 7C is an enlarged cross-sectional view showing a state in which the recording sheet is pressed against the separation pad by each auxiliary roller. FIG. 6A is an enlarged cross-sectional view showing a pressure contact state between the uppermost recording sheet and the sheet feeding roller and each auxiliary roller when the sheet bundle on the sheet feeding tray in the comparative example has a medium thickness; FIG. 7B is an enlarged cross-sectional view showing a pressure contact state between the uppermost recording sheet and the sheet feeding roller and each auxiliary roller when the thickness of the sheet bundle on the sheet feeding tray in the comparative example becomes thick; FIG. 7C is an enlarged cross-sectional view showing a pressure contact state between the uppermost recording sheet and the sheet feeding roller and each auxiliary roller when the thickness of the sheet bundle on the sheet feeding tray in the comparative example is reduced. (A) is an enlarged sectional view showing the recording sheet of the sheet bundle on the sheet feeding tray in the comparative example curled downward, and (b) is a recording sheet of the sheet bundle on the sheet feeding tray in the comparative example Is an enlarged sectional view showing a state of curling upward. It is a side view which expands a sheet feeding device of a 2nd embodiment, and is shown typically. It is a side view which expands a sheet feeding device of a 3rd embodiment, and is shown typically.

  Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

  FIG. 1 is a cross-sectional view showing an image forming apparatus to which a first embodiment of a sheet feeding device of the present invention is applied. The image forming apparatus 1 has a copying function of reading a document and printing it on a recording sheet, and includes a document reading device 2, a document conveying device (ADF) 3, a printing unit 4, a sheet feeding device 5 and a manual feeding device 7. , And the sheet conveyance unit 8 and the like. The document reading device 2 and the document conveying device 3 are mounted on the upper side of the main body of the image forming apparatus 1, and the printing unit 4, the paper feeding device 5 and the sheet conveying unit 8 are built in the main body of the image forming device 1, Furthermore, the manual feed device 7 is attached to the side wall of the main body of the image forming apparatus 1.

  The image data handled in this image forming apparatus 1 corresponds to a color image using each color of black (K), cyan (C), magenta (M) and yellow (Y), or a single color (for example, black) It corresponds to the monochrome image used. Therefore, in the printing unit 4, four developing devices 12, a photosensitive drum 13, a drum cleaning device 14, and a charging device 15 are provided to form four types of toner images according to the respective colors. Four image stations Pa, Pb, Pc, and Pd are configured in correspondence with black, cyan, magenta, and yellow, respectively.

  In any of the image stations Pa, Pb, Pc, and Pd, after the residual toner on the surface of the photosensitive drum 13 is removed and collected by the drum cleaning device 14, the surface of the photosensitive drum 13 is set to a predetermined potential by the charging device 15. The surface of the photosensitive drum 13 is exposed by the light scanning device 11 to form an electrostatic latent image on the surface, and the electrostatic latent image on the surface of the photosensitive drum 13 is developed by the developing device 12. A toner image is formed on the surface of the photosensitive drum 13. As a result, toner images of the respective colors are formed on the surfaces of the respective photosensitive drums 13.

  Thereafter, while moving the intermediate transfer belt 21 in the arrow direction C, the belt cleaning device 22 removes and recovers the residual toner of the intermediate transfer belt 21, and the toner image of each color formed on the surface of each photosensitive drum 13 is The toner image is transferred onto the intermediate transfer belt 21 to form a color toner image on the intermediate transfer belt 21.

  A nip area is formed between the intermediate transfer belt 21 and the transfer roller 23a of the secondary transfer device 23, and the recording paper conveyed through the S-shaped paper conveyance path R1 is sandwiched in the nip area. While being conveyed, the color toner image on the surface of the intermediate transfer belt 21 is transferred onto the recording sheet. Then, the recording sheet is nipped between the heating roller 24 and the pressure roller 25 of the fixing device 17 to be heated and pressurized to fix the color toner image on the recording sheet.

  On the other hand, in the sheet conveyance unit 8, the recording sheet is fed from the sheet feeding device 5 or the manual feeding device 7 and conveyed through the sheet conveyance path R1, and the recording sheet is discharged via the secondary transfer device 23 or the fixing device 17. The sheet is discharged to the sheet discharge tray 39 through the sheet roller 36. After temporarily stopping the recording sheet and aligning the leading end of the recording sheet along the sheet conveyance path R1, the recording sheet is conveyed according to the transfer timing of the toner image in the nip area between the intermediate transfer belt 21 and the transfer roller 23a. The registration rollers 34 for starting the recording, the conveyance rollers 35 for urging the conveyance of the recording sheet, the paper discharge rollers 36 and the like are arranged.

  The sheet feeding device 5 includes a cassette 51 disposed in the lower part of the image forming apparatus 1, a sheet feeding tray 52 on which recording sheets are stacked, a sheet feeding roller 53 provided above one end of the sheet feeding tray 52, The auxiliary rollers 54 provided on both sides of the paper roller 53, the separation pad 55 pressed against the paper feed roller 53, and the like are provided. In the sheet feeding device 5, the recording sheet is pulled out of the sheet feeding tray 52 by the sheet feeding roller 53, and the recording sheet is passed between the sheet feeding roller 53 and the separation pad 55 and separated one by one for sheet conveyance route R1. It is sending out to.

  The manual feed device 7 is disposed on the side wall of the main body of the image forming apparatus 1 and includes a manual feed tray 71 on which recording sheets are stacked, a feed roller 73 provided at one end of the manual feed tray 71, and a feed roller 73. And a separation pad 74 or the like which is pressure-welded. In this manual feeding device 7, the recording sheet is pulled out from the manual feeding tray 71 by the sheet feeding roller 73, and the recording sheet is passed between the sheet feeding roller 73 and the separation pad 74 and separated one by one to the sheet conveyance path R1. And sending out.

  Next, the sheet feeding device 5 of the first embodiment will be described in detail. FIG. 2 is an enlarged side view schematically showing the sheet feeding device 5. FIG. 3 is a front view showing the sheet feeding roller 53, the separation pad 55, and each auxiliary roller 54 in the sheet feeding device 5 as viewed from the upstream side in the sheet conveyance direction.

  As shown in FIGS. 2 and 3, supporting pieces 52b are provided on both sides of the rear end 52a of the sheet feeding tray 52, and shafts 51a provided on the inner walls (not shown) on both sides of the cassette 51 are provided. The paper feed tray 52 is rotatably supported in the arrow direction D about the shaft 51a by passing through the hole of the support piece 52b.

  Further, the conical coil spring 56 is fixed to the bottom 51 b of the cassette 51, and the conical coil spring 56 is sandwiched between the leading end 52 c of the sheet feeding tray 52 and the bottom 51 b of the cassette 51. The portion 52c is urged upward. When the recording sheet P is placed on the sheet feeding tray 52, the leading end 52c of the sheet feeding tray 52 is biased upward by the conical coil spring 56, and the recording sheet P on the sheet feeding tray 52 is fed. The roller 53 and each auxiliary roller 54 are pressed against each other.

  The drive shaft 53a passes through the center of the paper feed roller 53, and is fixed to the drive shaft 53a. Further, the drive shaft 53a is passed through the centers of the two auxiliary rollers 54, and the two auxiliary rollers 54 are fixed to the drive shaft 53a. The driving force of the motor is transmitted through the gear unit and the driving shaft 53a is rotationally driven, and the sheet feeding roller 53 and each auxiliary roller 54 rotate in the arrow direction F together with the driving shaft 53a.

  In the longitudinal direction of the drive shaft 53a, the width J1 of the feed roller 53 and the width J2 of the separation pad 55 are substantially the same, and the feed roller 53 and the separation pad 55 overlap each other. And the outer side of the separation pad 55 (outside the area of the separation pad 55).

  For example, the paper feed roller 53 is made of cylindrical rubber, and its diameter φa is 28 mm, and its width J1 in the longitudinal direction of the drive shaft 53a is 50 mm.

Each auxiliary roller 54 is made of an elastic body having a diameter φb (φb> φa) larger than the diameter φa of the feed roller 53. For example, the auxiliary rollers 54 have their diameter φb is in 29～30Mm, their width J3 in the longitudinal direction of the drive shaft 53a is approximately 10 mm, an interval of 0~30mm from both ends of the paper feed roller 3 Are arranged. Further, as shown in the cross-sectional view of FIG. 4, the auxiliary roller 54 has a column-shaped elastic synthetic resin (e.g., urethane foam rubber) 54a and a rubber layer 54b covering the outer periphery of the synthetic resin 54a. It consists of The foamed synthetic resin 54 a is for enabling elastic deformation of the auxiliary roller 54, and the rubber layer 54 b is for increasing the frictional force between the auxiliary roller 54 and the recording sheet P. Alternatively, as shown in the cross-sectional view of FIG. 5, the auxiliary roller 54 is formed of a hollow rubber member 54c having a cylindrical appearance. The rubber member 54 enables elastic deformation of the auxiliary roller 54 and increases the frictional force between the auxiliary roller 54 and the recording sheet P.

  As shown in FIG. 2, the separation pad 55 is fixed to the end face of the support member 57. The support member 57 is movably supported in the arrow direction E and urged toward the sheet feeding roller 53 by the coil spring 58, and the separation pad 55 of the end face of the support member 57 is fed by the urging force of the coil spring 58. A nip area H is formed between the paper feed roller 53 and the separation pad 55 by pressure contact with the roller 53. The surface of the separation pad 55 pressed against the sheet feed roller 53 is substantially flat, and the nip area H is flat.

  Further, at the end of the separation pad 55 on the sheet feeding tray 52 facing the sheet bundle, one end of a guide piece 59 is provided in an overlapping manner. The guide piece 59 is made of, for example, a metal plate.

  In the sheet feeding apparatus 5 having such a configuration, assuming that a sheet bundle of recording sheets P is stacked on the sheet feeding tray 52, the leading end 52c of the sheet feeding tray 52 is biased upward by the conical coil spring 56. As shown in FIG. 6, the uppermost recording sheet P of the sheet bundle on the sheet feeding tray 52 is brought into pressure contact with the sheet feeding roller 53 and the respective auxiliary rollers 54. At this time, the leading end side of the recording sheet P in the uppermost layer of the sheet bundle is positioned in the height direction by being brought into pressure contact with the sheet feeding roller 53. Further, the outer peripheral portion of each auxiliary roller 54 facing the recording sheet P on the top layer is pressed by the recording sheet P on the top layer and is deformed into a planar shape.

  Further, a fixed space (distance) sp is provided from the press-contacting position of the sheet feed roller 53 and the respective auxiliary rollers 54 to the uppermost recording sheet P to the nip area H between the sheet feed roller 53 and the separation pad 55. ing.

  In this state, when the sheet feeding roller 53 and the respective auxiliary rollers 54 are rotationally driven in the arrow direction F, the sheet P on the uppermost layer of the sheet bundle on the sheet feeding tray 52 is the sheet by the sheet feeding roller 53 and the respective auxiliary rollers 54. The leading edge of the recording sheet P is guided to the nip area H between the feed roller 53 and the separation pad 55 through the space sp. At this time, before reaching the nip area H, the leading edge of the recording paper P is sequentially pressed against the guide piece 59 and the separation pad 55 by the respective auxiliary rollers 54 having a diameter φb larger than the diameter φa of the paper feeding roller 53 It slides on the surface of the guide piece 59 and is guided to the surface of the separation pad 55 and is guided to the nip area H while being slidably guided on the surface of the separation pad 55.

  Here, when the leading edge of the recording paper P is in sliding contact with the surface of the separation pad 55 and is led to the nip area H, the leading edge of the recording paper P is the separation pad 55 when viewed from the side as shown in FIG. 9 (b) and 10 (a). The angle formed between the surface (or nip area H) of the separation pad 55 and the leading edge of the recording paper P is in sliding contact with the surface (or nip area H) of the The paper angle α) is approximately 0 °. Further, as viewed from the upstream side in the sheet conveyance direction as shown in FIG. 3, the leading end of the recording sheet P is curved downward at both sides of the separation pad 55 by the respective auxiliary rollers 54. In this case, it becomes difficult to cause a double feeding such that a feeding error such that the pulling out and sending out of the recording sheet P by the sheet feeding roller 53 is interrupted and a plurality of recording sheets P are conveyed while overlapping.

  Since the sheet bundle of the recording paper P is cut at the peripheral edge, burrs and burrs occur on the end sides of the recording paper P, and the recording paper P is difficult to separate. Therefore, the leading end of the recording sheet P is brought into sliding contact with the surface of the separation pad 55 by the sheet feeding roller 53 and conveyed, and the recording sheets P are separated one by one. At this time, if the paper input angle α formed by the surface (or the nip area H) of the separation pad 55 and the front end of the recording paper P is 0 °, the front end of the recording paper P slides uniformly on the surface of the separation pad 55. The contact causes a large frictional force between the leading edge of the recording paper P and the surface of the separation pad 55. Thus, even if the plurality of recording sheets P overlap and are pulled out, the recording sheets P can be reliably separated in the nip area H between the sheet feeding roller 53 and the separation pad 55.

  In the sheet feeding device 5 of the first embodiment, the leading edge of the recording sheet P is pressed against the separation pad 55 by each auxiliary roller 54, and the leading edge of the recording sheet P is brought into sliding contact with the surface of the separation pad 55 and guided while nipping Since the sheet is guided to H and the paper input angle α formed by the surface (or nip area H) of the separation pad 55 and the front end of the recording paper P is maintained at 0 °, the front end of the recording paper P and the separation pad 55 A large frictional force is generated with the surface, and even if a plurality of recording sheets P are overlapped and pulled out, each recording sheet P can be reliably separated, and double feeding of the recording sheets P is effectively prevented. Can.

  Further, since the leading edge of the recording sheet P is curved downward on both sides of the separation pad 55 by the respective auxiliary rollers 54, separation of the recording sheet P is promoted, and double feeding of the recording sheet P is effective. To prevent.

  Further, when the paper input angle α formed by the surface (or the nip area H) of the separation pad 55 and the leading end of the recording paper P is maintained at 0 °, the recording paper P quickly intrudes into the nip area H and The conveyance of the recording sheet P by the roller 53 is surely performed, and the feeding error of the recording sheet P is effectively prevented.

  Further, as shown in FIG. 7A, even if the thickness of the sheet bundle on the sheet feeding tray 52 is increased and the inclination angle of the sheet feeding tray 52 around each shaft 51a with respect to the bottom 51b of the cassette 51 is decreased. Or, as shown in FIG. 7B, even if the thickness of the sheet bundle on the sheet feeding tray 52 becomes thin and the inclination angle of the sheet feeding tray 52 around each shaft 51a with respect to the bottom portion 51b of the cassette 51 becomes large. Before the leading edge of the recording sheet P reaches the nip area H, the leading edge of the recording sheet P is pressed against the separation pad 55 by each auxiliary roller 54, and the leading edge of the recording sheet P is in sliding contact with the surface of the separation pad 55 Since the sheet H is guided to the area H, the sheet entrance angle α of the leading end of the recording sheet P is held at 0 °, and sheet feeding errors and double feeding hardly occur.

  Furthermore, even if the leading edge of each recording sheet P of the bundle of sheets curls downward as shown in FIG. 8A, or as shown in FIG. 8B, the leading edge of each recording sheet P of the bundle of sheets upwards 8C, the leading end of the recording sheet P is pressed against the separation pad 55 by the respective auxiliary rollers 54, and the leading end of the recording sheet P is in sliding contact with the surface of the separation pad 55. Since the sheet is guided to the nip area H, the sheet entrance angle α of the leading end of the recording sheet P is held at 0 °, so that feeding errors and double feeding hardly occur.

  Next, the sheet feeding device of the comparative example will be described. The sheet feeding device of this comparative example is different from the sheet feeding device 5 of the first embodiment in that a sheet corresponding to each auxiliary roller 54 is not provided. 9A to 9C are enlarged side views showing the sheet feeding tray 52, the sheet feeding roller 53, and the separation pad 55 in the sheet feeding device of the comparative example.

  In the sheet feeding device of this comparative example, as shown in FIG. 9A, the sheet bundle on the sheet feeding tray 52 has a medium sheet thickness, and the sheet feeding tray around each shaft 51a with respect to the bottom 51b of the cassette 51. When the inclination angle of 52 is medium, the separation pad 55 is set such that the paper input angle α of the leading edge of the recording sheet P on the uppermost layer of the sheet bundle with respect to the surface (or nip area H) of the separation pad 55 is 0 °. The inclination angle of the surface of the is set. Therefore, when the thickness of the sheet bundle on the sheet feeding tray 52 is medium, the leading end of the recording sheet P is uniformly in sliding contact with the surface of the separation pad 55, and the tip of the recording sheet P and the separation pad 55 A large frictional force is generated between the recording sheet P and the surface, and even if the plurality of recording sheets P overlap and are pulled out, the recording sheets P are separated well.

  However, as shown in FIG. 9B, when the thickness of the sheet bundle on the sheet feeding tray 52 becomes thick and the inclination angle of the sheet feeding tray 52 around each shaft 51a with respect to the bottom 51b of the cassette 51 becomes small, The leading end of the recording sheet P in the uppermost layer of the bundle abuts on the surface of the separation pad 55 in a substantially straight line and is easily caught, and the paper entrance angle α of the leading end of the recording sheet P does not become 0 °. In this case, the rate of occurrence of paper feed errors increases.

  Further, as shown in FIG. 9C, when the thickness of the sheet bundle on the sheet feeding tray 52 becomes thin and the inclination angle of the sheet feeding tray 52 around each shaft 51a with respect to the bottom 51b of the cassette 51 becomes large, As the leading end of the recording sheet P in the uppermost layer of the bundle goes substantially linearly in the direction away from the surface of the separation pad 55, the leading end of the recording sheet P hardly contacts the surface of the separation pad 55. The paper feed angle α does not become 0 °. In this case, the occurrence rate of double feeding increases.

  Furthermore, as shown in FIG. 10A, when the leading end of each recording sheet P of the sheet bundle is curled downward, the leading end of the recording sheet P abuts on the surface of the separation pad 55 and is caught. The sheet entrance angle α at the leading end does not become 0 °, and the incidence of sheet feeding errors increases. Alternatively, as shown in FIG. 10B, when the leading end of each recording sheet P of the sheet bundle is curled upward, the leading end of the recording sheet P becomes difficult to contact the surface of the separation pad 55, and double feeding occurs. The rate goes up.

  That is, as is clear from the comparison with the sheet feeding device shown in FIGS. 9A to 9C and FIGS. 10A and 10B, the sheet feeding device 5 of the first embodiment is the sheet feeding tray 52. Regardless of the thickness of the upper bundle of sheets, regardless of the curled state of the leading edge of the recording paper P, the leading edge of the recording paper P is brought into sliding contact with the surface of the separation pad 55 by each auxiliary roller 54 Of the leading edge of the recording paper P can always be maintained at 0.degree., So that the occurrence of paper feeding error and double feeding can be favorably suppressed.

  Further, since each auxiliary roller 54 is elastically deformed, the pressing force of each auxiliary roller 54 against the recording sheet P on the uppermost layer of the sheet bundle on the sheet feeding tray 52 does not become excessive. There is no double feed caused by pressure.

  Further, since the frictional force between the outer periphery of the auxiliary roller 54 and the recording sheet P is increased, the recording sheet P of the uppermost layer of the sheet bundle is pulled out not only by the sheet feeding roller 53 but also by each auxiliary roller 54 Feeding can be performed, and the occurrence rate of feeding errors can be further reduced.

  Next, a second embodiment of the sheet feeding device of the present invention will be described. FIG. 11 is an enlarged side view schematically showing the sheet feeding device 5A of the second embodiment. Similar to the sheet feeding device 5 of the first embodiment, the sheet feeding device 5A of the second embodiment includes the cassette 51, the sheet feeding tray 52, and the conical coil spring 56, and the sheet feeding tray 52 is centered on the shaft 51a. And the tip end portion 52c of the sheet feeding tray 52 is urged upward by the conical coil spring 56, but the pickup roller 61 is mainly added in the first embodiment. It differs from the sheet feeding device 5.

  As shown in FIG. 11, the drive shaft 53 a of the paper feed roller 53 is passed through the hole at one end of the swing support piece 62 to rotatably support the swing support piece 62. The drive shaft 61 a of the pickup roller 61 is supported by passing through the hole at the other end of the swing support piece 62. The pickup roller 61 is rotationally driven in the arrow direction F in the same manner as the sheet feeding roller 53 and the respective auxiliary rollers 54.

  In the sheet feeding device 5A having such a configuration, the swinging support piece 62 is biased in the arrow direction G centering on the drive shaft 53a of the sheet feeding roller 53, and the pickup roller 61 takes the sheet bundle on the sheet feeding tray 52. It is in pressure contact with the uppermost recording sheet P. In this state, when the pickup roller 61, the sheet feeding roller 53, and the respective auxiliary rollers 54 are rotationally driven in the arrow direction F, the recording sheet P of the uppermost layer of the sheet bundle on the sheet feeding tray 52 is pulled out by the pickup roller 61. The leading end of the recording sheet P is guided to the nip area H between the feed roller 53 and the separation pad 55. At this time, the leading end of the recording paper P is sequentially pressed against the guide piece 59 and the separation pad 55 by the respective auxiliary rollers 54 before reaching the nip area H, and slips on the surface of the guide piece 59 and moves to the surface of the separation pad 55 And guided to the nip area H while being guided in sliding contact with the surface of the separation pad 55. For this reason, the paper input angle α formed by the surface (or the nip area H) of the separation pad 55 and the leading end of the recording paper P becomes 0 °, which makes it difficult to cause a feeding error or double feeding.

  Further, even if the thickness of the sheet bundle on the sheet feeding tray 52 becomes thick and the inclination angle of the sheet feeding tray 52 around each axis 51 a with respect to the bottom 51 b of the cassette 51 becomes small, or the sheet on the sheet feeding tray 52 Each auxiliary roller before the leading edge of the recording paper P reaches the nip area H even if the thickness of the bundle becomes thin and the inclination angle of the paper feed tray 52 around each axis 51a with respect to the bottom 51b of the cassette 51 becomes large. The leading edge of the recording sheet P is pressed against the separation pad 55 by the sheet 54, and the leading edge of the recording sheet P is guided to the nip area H while being in sliding contact with the surface of the separation pad 55. Is held at 0 °, so that feeding errors and double feeding are less likely to occur.

  Furthermore, even if the leading end of each recording sheet P of the sheet bundle curls downward, or even if the leading end of each recording sheet P of the sheet bundle curls upward, the leading end of the recording sheet P is turned by the respective auxiliary rollers 54. Since the leading edge of the recording paper P is guided to the nip area H while being in sliding contact with the surface of the separation pad 55 by being pressed against the separation pad 55, the paper entrance angle α of the leading edge of the recording paper P is maintained at 0 ° Paper errors and double feeding are unlikely to occur.

  Further, since the frictional force between the outer periphery of the auxiliary roller 54 and the recording sheet P is increased, the recording sheet P can be sent out not only by the sheet feeding roller 53 but also by each auxiliary roller 54, so that the sheet feeding error The incidence rate of can be lower.

  Next, a third embodiment of the sheet feeding device of the present invention will be described. FIG. 12 is an enlarged side view schematically showing the sheet feeding device 5B of the third embodiment. Similar to the sheet feeding device 5 of the first embodiment, the sheet feeding device 5B of the third embodiment includes the cassette 51, the sheet feeding tray 52, and the conical coil spring 56, and the sheet feeding tray 52 is centered on the shaft 51a. And the tip end portion 52c of the sheet feeding tray 52 is urged upward by the conical coil spring 56, but the pickup roller 61 is mainly added in the first embodiment. It differs from the sheet feeding device 5A of the second embodiment in that a separating roller 63 is provided instead of the sheet feeding device 5 and in place of the separating pad 55.

  As shown in FIG. 12, the shaft 63a of the separating roller 63 is parallel to the shaft 53a of the sheet feeding roller 53, and the bearing (not shown) of the shaft 63a of the separating roller 63 is fed by a spring (not shown). The separation roller 63 is pressed against the sheet feeding roller 53 while being urged toward the roller 53. The separation roller 63 is made of cylindrical rubber having a diameter of approximately 16 mm.

  Further, a torque limiter (not shown) is provided on the shaft 63 a of the separation roller 63. When the separation roller 63 is in direct pressure contact with the paper feed roller 53, or when the separation roller 63 is pressed by the paper feed roller 53 via one recording sheet, the rotational force of the paper feed roller 53 is the separation roller. The torque acting on the torque limiter of the separating roller 63 is increased as it is transmitted to the separating roller 63, the separating roller 63 is idled, and the separating roller 63 is driven to rotate by the sheet feeding roller 53.

  Therefore, when the recording sheet is sequentially taken out one by one from the sheet feeding tray 52 by the pickup roller 61, the recording sheet is guided to and nipped by the nip area H between the sheet feeding roller 53 and the separating roller 63. The separation roller 63 is idled and driven to rotate, and the recording sheet is conveyed by the paper feed roller 53.

  In addition, when a plurality of recording sheets are simultaneously pulled out from the sheet feeding tray 52 by the pickup roller 61, the sheet feeding roller 53 separates from the sheet feeding roller 53 even if the recording sheet directly in contact with the sheet feeding roller 53 is conveyed. Since the respective recording sheets interposed between the roller 63 shift, the torque acting on the torque limiter of the separation roller 63 does not increase, and the separation roller 63 stops and does not follow the feed roller 53. The conveyance of the other recording sheet not in direct contact with the sheet is stopped, and the other recording sheet is separated from the recording sheet conveyed by the sheet feeding roller 53.

  Also in the sheet feeding device 5B having such a configuration, in a state where the pickup roller 61 is in pressure contact with the uppermost recording sheet P of the sheet bundle on the sheet feeding tray 52, the pickup roller 61, the sheet feeding roller 53, and each auxiliary The roller 54 is rotationally driven in the arrow direction F, and the topmost recording sheet P of the sheet bundle on the sheet feeding tray 52 is pulled out by the pickup roller 61, and the leading end of the recording sheet P is the sheet feeding roller 53 and the separating roller 63. Leading to the nip area H between them. At this time, the leading end of the recording paper P is pressed against the peripheral surface of the separation roller 63 by the respective auxiliary rollers 54 before reaching the nip area H, and is guided to the nip area H while in sliding contact with the peripheral surface of the separation roller 63. It is eaten.

  Here, the nip area H between the feed roller 53 and the separation roller 63 is formed on the circumferential surface of the separation roller 63 and is always maintained in a fixed size and shape. Therefore, when the leading end of the recording sheet P is guided to the nip area H while being in sliding contact with the circumferential surface of the separation roller 63, the paper input angle α formed by the nip area H and the leading end of the recording sheet P is constant at around 0 °. As a result, paper feed errors and double feeding are less likely to occur.

  Further, even if the thickness of the sheet bundle on the sheet feeding tray 52 becomes thick and the inclination angle of the sheet feeding tray 52 around each axis 51 a with respect to the bottom 51 b of the cassette 51 becomes small, or the sheet on the sheet feeding tray 52 Even if the thickness of the bundle becomes thin and the inclination angle of the sheet feeding tray 52 around each axis 51a with respect to the bottom 51b of the cassette 51 becomes large, the leading edge of the recording sheet P by the auxiliary roller 54 is the circumferential surface of the separating roller 63 Since the sheet is pressed to slide and guided to the nip area H, the sheet entrance angle α of the leading end of the recording sheet P is held constant near 0 °, so that feeding errors and double feeding hardly occur.

  Furthermore, even if the leading end of each recording sheet P of the sheet bundle curls downward, or even if the leading end of each recording sheet P of the sheet bundle curls upward, the leading end of the recording sheet P is turned by the respective auxiliary rollers 54. Since it is guided to the nip area H while being pressed against and in sliding contact with the circumferential surface of the separation roller 63, the paper input angle α at the leading end of the recording paper P is held constant near 0 °, causing sheet feeding errors and double feeding. hard.

  Further, since the frictional force between the outer periphery of each auxiliary roller 54 and the recording sheet P is increased, the recording sheet P can be fed out not only by the sheet feeding roller 53 but also by each auxiliary roller 54. It is possible to lower the incidence of mistakes.

  The present invention is not limited to the above first to third embodiments, and can be variously modified. For example, the first to third embodiments may be combined as appropriate. Further, the present invention can be applied not only to the sheet feeding device 5 but also to the sheet feeding device 7 for pulling out the recording sheet from the sheet feeding tray 71 and feeding it to the sheet conveyance path R1. Further, in the document conveying device 3, since the pickup roller, the sheet feeding roller, the separation pad and the like for drawing out the document from the document tray and feeding it out are provided, the present invention is applicable to the document conveying device 3.

  Although the preferred embodiments and modifications of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the appended claims, and of course these also fall within the technical scope of the present invention. It is understood.

Reference Signs List 1 image forming apparatus 2 document reading apparatus 3 document conveying apparatus 4 printing unit 5 sheet feeding apparatus 7 manual feeding apparatus 8 sheet conveying unit 51 cassette 52 sheet feeding tray 53 sheet feeding roller 54 auxiliary roller (auxiliary member)
55 Separation pad (separation member)
56 Conical coil spring 57 Support member 58 Coil spring 59 Guide piece 61 Pickup roller 62 Swing support piece 63 Separation roller (separation member)

Claims (8)

A sheet feeding tray on which sheets are stacked, a sheet feeding roller for conveying the sheet, and a separating member for separating the sheet conveyed by the sheet feeding roller, and the sheet is drawn from the sheet feeding tray to feed the sheet A sheet feeding device for feeding a sheet conveyance path through a space between a sheet roller and the separating member,
An auxiliary member made of an elastic body having a diameter larger than that of the sheet feeding roller and the sheet feeding roller are provided side by side on the shaft of the sheet feeding roller.
The distance between the end of the paper feed roller in the axial direction of the paper feed roller and the end of the auxiliary member facing the end, or the end of the separation member in the axial direction and the end distance between the end portion of the auxiliary member is rather short than a length of the separating member in the length or the axial direction of the paper feed roller in the axial direction,
When the sheet is conveyed through a nip area between the sheet feeding roller and the separating member,
The portion of the outer peripheral surface of the auxiliary member corresponding to the nip area in the transport direction in which the sheet is transported in the nip area is
A sheet feeding apparatus according to claim 1, wherein said sheet feeding apparatus is further in a direction away from the axis of said sheet feeding roller than said nip area in a direction orthogonal to said conveying direction . The sheet feeding device according to claim 1, wherein
A sheet feeding apparatus according to claim 1, wherein an end of the sheet feeding roller in the axial direction is in contact with an end of the auxiliary member opposed to the end. The sheet feeding device according to claim 1 or 2, wherein
The sheet feeding device according to claim 1, wherein the auxiliary member has a roller shape and rotates with the sheet feeding roller. The sheet feeding device according to claim 1 or 2, wherein
The sheet feeding device according to claim 1, wherein the auxiliary member has a roller shape and is made of foam. The sheet feeding device according to any one of claims 1 to 4, wherein
A sheet feeding device according to claim 1, wherein an outer peripheral surface of the auxiliary member comprises a coating layer for adjusting a frictional force between the sheet and the auxiliary member. The sheet feeding device according to claim 1 or 2, wherein
The sheet feeding device according to claim 1, wherein the auxiliary member is in the form of a hollow roller made of rubber. The sheet feeding device according to any one of claims 1 to 6, wherein
The sheet feeding device according to claim 1, wherein the auxiliary member is provided outside the area of the separating member in the axial direction of the sheet feeding roller.   An image forming apparatus comprising: the sheet feeding device according to any one of claims 1 to 7; and a printing unit that forms an image on a sheet fed from the sheet feeding device.

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