Sheet discharge device and image forming device

Abstract

To provide a sheet discharge device which improves a discharge property of sheets and which can suppress damage to the sheets, and to provide an image forming device including the same.SOLUTION: A sheet discharge device includes: a first roller; and a second roller rotating around a second rotation axis extending in a second axial direction. The second roller includes: a first surface and a second surface configured to push out a sheet toward a loading part; and a roller part including a peripheral surface. When the radius of rotation of the peripheral surface at a first end is defined as a first radius, the radius of rotation of the peripheral surface at a second end is defined as a second radius, the radius of rotation of the first surface is defined as a third radius and the radius of rotation of the second surface is defined as a fourth radius, (i) the peripheral surface is inclined with respect to the second axial direction so that the first radius becomes larger than the second radius, (ii) the third radius is larger than the first radius and (iii) the fourth radius is smaller than the second radius.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a sheet discharging device that discharges sheets and an image forming apparatus including the same.

Background Art

[0002] Conventionally, a pair of discharge rollers configured by a first roller and a second roller and discharging a sheet to the outside of an image forming apparatus has been proposed (see Patent Document 1). The first roller has a cylindrical portion that is in pressure contact with the second roller and a flange portion, and a plurality of convex portions are formed on the outer peripheral portion of the flange portion. The plurality of convex portions are for pushing the rear end of the sheet discharged by the first roller and the second roller toward the discharge portion, and are formed to have a size equal to or smaller than the radius of the cylindrical portion of the first roller.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the first roller is inclined with respect to the second roller in a direction in which the convex portion approaches the second roller, the convex portion may protrude radially outward with respect to the cylindrical portion of the first roller. When the convex portion protrudes significantly with respect to the cylindrical portion, the possibility that the sheet is damaged increases.

[0005] An object of the present invention is to provide a sheet discharging device that can improve the dischargeability of sheets and suppress damage to the sheets, and an image forming apparatus including the same.

Means for Solving the Problems

[0006] The present invention relates to a sheet discharging device, which includes a stacking portion on which sheets are stacked, a first roller that rotates about a first rotation axis extending in a first axial direction, and a second roller that rotates about a second rotation axis extending in a second axial direction and is configured to discharge a sheet toward the stacking portion together with the first roller. The second roller includes: a first surface that extends so as to intersect a circle centered on the second rotation axis when viewed in the second axial direction and is configured to push the sheet toward the stacking portion; a second surface that extends so as to intersect a circle centered on the second rotation axis when viewed in the second axial direction and is configured to push the sheet toward the stacking portion; and a roller portion that is disposed between the first surface and the second surface in the second axial direction and includes a circumferential surface that contacts the first roller so as to form a discharge nip therebetween. The circumferential surface has a first end and a second end opposite to the first end in the second axial direction. A distance between the first end and the first surface in the second axial direction is shorter than a distance between the second end and the first surface in the second axial direction. When a rotation radius of the circumferential surface at the first end is a first radius, a rotation radius of the circumferential surface at the second end is a second radius, a rotation radius of the first surface is a third radius, and a rotation radius of the second surface is a fourth radius, (i) the circumferential surface is inclined with respect to the second axial direction such that the first radius is larger than the second radius, (ii) the third radius is larger than the first radius, and (iii) the fourth radius is smaller than the second radius.

[0007] Furthermore, the present invention relates to a sheet discharging device, which includes a stacking portion on which sheets are stacked, a first roller that rotates about a first rotation axis extending in a first axis direction, and a second roller that rotates about a second rotation axis extending in a second axis direction and is configured to discharge the sheets toward the stacking portion together with the first roller. The second roller includes an extrusion surface that extends so as to intersect a circle centered on the second rotation axis when viewed in the second axis direction and is configured to extrude the sheets toward the stacking portion, and a roller portion that is disposed at a position different from the extrusion surface in the second axis direction and includes a circumferential surface that contacts the first roller so as to form a discharge nip therebetween. The circumferential surface has a first end and a second end opposite to the first end in the second axis direction. A distance between the first end and the extrusion surface in the second axis direction is shorter than a distance between the second end and the extrusion surface in the second axis direction. When a rotation radius of the circumferential surface at the first end is a first radius and a rotation radius of the circumferential surface at the second end is a second radius, (i) the circumferential surface is inclined with respect to the second axis direction such that the first radius is larger than the second radius, and (ii) a rotation radius of the extrusion surface is larger than the first radius.

[0008] In addition, the present invention relates to a sheet discharging device, which includes a stacking unit on which sheets are stacked, a first roller that rotates about a first rotation axis extending in a first axis direction, and a second roller that rotates about a second rotation axis extending in a second axis direction and is configured to discharge the sheet toward the stacking unit together with the first roller. The second roller includes an extrusion surface that extends so as to intersect a circle centered on the second rotation axis when viewed in the second axis direction and is configured to extrude the sheet toward the stacking unit, and a roller portion that is disposed at a position different from the extrusion surface in the second axis direction and includes a circumferential surface that abuts against the first roller so as to form a discharge nip therebetween. The circumferential surface has a first end and a second end opposite to the first end in the second axis direction. A distance between the first end and the extrusion surface in the second axis direction is longer than a distance between the second end and the extrusion surface in the second axis direction. When a rotation radius of the circumferential surface at the first end is a first radius and a rotation radius of the circumferential surface at the second end is a second radius, (i) the circumferential surface is inclined with respect to the second axis direction such that the first radius is larger than the second radius, and (ii) a rotation radius of the extrusion surface is smaller than the second radius.

Advantages of the Invention

[0009] According to the present invention, it is possible to improve the dischargeability of sheets and suppress damage to the sheets.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0011] <First Embodiment> [Overall Configuration] First, the first embodiment of the present invention will be described. The image forming apparatus 100 according to this embodiment is an electrophotographic monochrome laser beam printer. Note that the image forming apparatus includes a printer, a copier, a facsimile machine, and a multifunction machine, and refers to an apparatus that forms an image on a sheet used as a recording medium based on image information input from an external PC or image information read from a document. In addition, in addition to the main body having an image forming function, an image forming apparatus may be connected with accessory devices such as an optional feeder, an image reading device, and a sheet processing device. However, the entire system to which such accessory devices are connected is also a kind of image forming apparatus.

[0012] As shown in FIG. 1, the image forming apparatus 100 includes an image forming unit 30 that forms an image on a sheet P, a sheet feeding unit 40, a fixing device 50, and a sheet discharging device 60. The image forming unit 30 includes four process cartridges 31Y, 31M, 31C, and 31K that form toner images of four colors: yellow (Y), magenta (M), cyan (C), and black (K), and a laser scanner 8.

[0013] The four process cartridges 31Y, 31M, 31C, and 31K have the same configuration except for the colors of the images they form. Therefore, only the configuration of the process cartridge 31Y and the image forming process will be described, and the descriptions of the process cartridges 31M, 31C, and 31K will be omitted.

[0014] The process cartridge 31Y includes a photosensitive drum 7, a charging roller 32, and a developing roller 33. The photosensitive drum 7 as a photoreceptor is configured by applying an organic photoconductive layer to the outer periphery of an aluminum cylinder and rotates by a drive motor (not shown). Note that a photosensitive belt may be used instead of the photosensitive drum 7. Further, the image forming unit 30 is provided with an intermediate transfer belt 9 wound around a drive roller 5, a tension roller 10, etc., and the intermediate transfer belt 9 rotates clockwise in the figure by the drive roller 5. An primary transfer roller (not shown) is provided inside the intermediate transfer belt 9.

[0015] The fixing device 50 includes a heating unit 11 heated by a heater and a pressure roller 12 pressed against the heating unit 11. The heating unit 11 according to the present embodiment includes a heater and a fixing film heated by the heater, but is not limited thereto. For example, the heating unit 11 may be a fixing roller having a built-in heater, or a fixing belt having a heat generating layer heated by induction heating. Further, various heaters such as a ceramic heater and a halogen heater can be applied to the heater.

[0016] The sheet feeding unit 40 is provided at the lower part of the image forming apparatus 100 and includes a feeding cassette 1 that can be pulled out and attached to the apparatus main body 100A. The sheet discharging device 60 has a pair of discharging rollers 61 and a discharging tray 15 on which the sheet P discharged by the pair of discharging rollers is stacked. Note that the sheet P includes paper such as paper and envelopes, plastic films such as overhead projector sheets (OHP), cloth, and the like.

[0017] Next, the image forming operation of the image forming apparatus 100 configured as described above will be described. When an image signal is input from a personal computer or the like (not shown) to the laser scanner 8, laser light corresponding to the image signal is irradiated from the laser scanner 8 onto the photosensitive drum 7 of the process cartridge 31Y.

[0018] At this time, the surface of the photosensitive drum 7 is uniformly charged in advance to a predetermined polarity and potential by the charging roller 32, and an electrostatic latent image is formed on the surface by irradiation with laser light from the laser scanner 8. The electrostatic latent image formed on the photosensitive drum 7 is developed by the developing roller 33, and a yellow (Y) toner image is formed on the photosensitive drum 7.

[0019] Similarly, laser light is irradiated from the laser scanner 8 onto the photosensitive drums of the process cartridges 31M, 31C, and 31K, and magenta (M), cyan (C), and black (K) toner images are formed on the respective photosensitive drums. The toner images of each color formed on each photosensitive drum are transferred to the intermediate transfer belt 9 by a primary transfer roller corresponding to each process cartridge, and are conveyed to the secondary transfer roller 6 by the intermediate transfer belt 9 rotated by the driving roller 5.

[0020] Note that the image forming process for each color is performed at a timing when it is superimposed on the upstream toner image primarily transferred onto the intermediate transfer belt 9. Further, after the toner images of each color are transferred to the intermediate transfer belt 9, the toner remaining on the surface of the photosensitive drum 7 is removed by a cleaning device (not shown).

[0021] In parallel with this image forming process, the sheet P accommodated in the supply cassette 1 of the sheet feeding unit 40 or the sheet P supplied from the manual feeding unit 41 is fed by the feeding roller 3. The sheet P fed by the feeding roller 3 is conveyed upward by the pair of conveying rollers 4.

[0022] The sheet P is conveyed at a predetermined conveying timing by the pair of conveying rollers 4 in accordance with the image forming process. Then, the full-color toner image on the intermediate transfer belt 9 is transferred to the sheet P by the secondary transfer bias applied to the secondary transfer roller 6. Note that the pair of conveying rollers 4 may be a pair of registration rollers that correct the skew of the sheet P.

[0023] The sheet P onto which the toner image has been transferred is given a predetermined heat and pressure by the heating unit 11 and the pressure roller 12 of the fixing device 50, and the toner is melted and fixed (fixed). The sheet P that has passed through the fixing device 50 is discharged to the discharge tray 150 by the pair of discharge rollers 61.

[0024] [Sheet Discharge Device] Next, the sheet discharge device 60 will be described with reference to FIGS. 2(a) to 3. FIG. 2(a) is a cross-sectional view showing the state in which the sheet P is discharged toward the discharge tray 15. FIG. 2(b) is a cross-sectional view showing the state in which the sheet P is conveyed toward the duplex conveyance path 17. FIG. 3 is a front view showing the pair of discharge rollers 61.

[0025] As shown in FIG. 2(a), for example, when single-sided printing is performed, the sheet P that has passed through the fixing device 50 is discharged outside the image forming apparatus 100 by the pair of discharge rollers 61 and stacked on the discharge tray 15 (see FIG. 1).

[0026] Also, as shown in FIG. 2(b), for example, when double-sided printing is performed, the sheet P with an image formed on the first side is first conveyed outward by the discharge roller pair 61. Here, the discharge roller pair 61 has a driving roller 13 driven by a driving motor M as a driving source, and a driven roller 14 that rotates in a driven manner with respect to the driving roller 13. The driving roller 13 is configured to be capable of normal rotation or reverse rotation. Further, between the fixing device 50 and the discharge roller pair 61, a guide member 16 capable of changing the conveyance path of the sheet P is arranged.

[0027] When the rear end of the sheet P passes through the guide member 16, the conveyance path of the sheet P is switched by the rotation of the guide member 16. Also, when the driving roller 13 rotates reversely, the sheet P is conveyed toward the double-sided conveyance path 17. Thereafter, the sheet P that has passed through the double-sided conveyance path 17 has an image formed on the second side by the image forming unit 30 and is discharged to the discharge tray 15 by the discharge roller pair 61. The sheet P discharged outside by the discharge roller pair 61 is stacked on the discharge tray 15 as a stacking unit.

[0028] FIG. 3 is a front view of the discharge roller pair 61 viewed in the horizontal direction. The discharge roller pair 61 has a driving roller 13 and a plurality (four in this embodiment) of driven rollers 14. In other words, the discharge roller pair 61 includes a plurality of extrusion rollers, and each of the plurality of extrusion rollers is a driven roller 14. The driving roller 13 has a driving shaft 13b driven by a driving motor M (see FIG. 2(a)) and a plurality of roller portions 13a fixed to the driving shaft 13b.

[0029] Each driven roller 14 is supported by a holder 62 so as to be relatively movable with respect to the driving roller 13. And each driven roller 14 is in pressure contact with the roller portion 13a of the corresponding driving roller 13. Since the plurality of driven rollers 14 have the same or left-right symmetric shapes with respect to each other, hereinafter, only one driven roller 14 (for example, the leftmost driven roller 14 in FIG. 3) among the plurality of driven rollers 14 will be described.

[0030] [Driven roller] Next, the driven roller 14 will be described with reference to FIGS. 4(a) to 6. FIG. 4(a) is a left side view showing the driven roller 14 and a partially enlarged view thereof, FIG. 4(b) is a front view showing the driven roller 14, and FIG. 4(c) is a right side view showing the driven roller 14 and a partially enlarged view thereof. FIG. 5 is a diagram showing the peripheral speed of the driven roller 14 and the conveyance speed of the sheet P.

[0031] As shown in FIGS. 4(a) to 4(c), the driven roller 14 has a roller shaft 14s, a roller portion 14r as a first roller portion, and flange portions 14b and 14c. The roller portion 14r and the flange portions 14b and 14c are fixed to the roller shaft 14s and rotate integrally about a rotation axis 14p as a second rotation axis of the roller shaft 14s. Note that the roller shaft 14s may be divided into a plurality of shafts. In the present embodiment, the driven roller 14 is made of resin, and the roller shaft 14s, the roller portion 14r, and the flange portions 14b and 14c are integrally formed. The driven roller 14 is formed by injection molding. Note that the direction in which the rotation axis 14p extends can be referred to as an axial direction AD as a second axial direction.

[0032] The roller portion 14r of the driven roller 14 forms a discharge nip N together with the roller portion 13a of the driving roller 13. At the discharge nip N, the sheet P is discharged in a sheet discharge direction DD (see FIG. 2(a)). The roller portion 14r has a peripheral surface 14a that contacts the roller portion 13a of the driving roller 13 and is formed in a frustum shape. The sheet discharge direction DD at the discharge nip N can be referred to as the moving direction of the sheet P at the discharge nip N. Therefore, the sheet discharge direction DD is parallel to the tangent of the roller portion 13a passing through the discharge nip N. Also, the sheet discharge direction DD is parallel to the tangent of the roller portion 14r passing through the discharge nip N.

[0033] The flange portion 14b has a plurality (four in this embodiment) of first surfaces 14d configured to extrude the sheet P toward the discharge tray 15. Similarly, the flange portion 14c has a plurality (four in this embodiment) of second surfaces 14e configured to extrude the sheet P toward the discharge tray 15. The first surface 14d is an example of an extrusion surface or a first extrusion surface, and the second surface 14e is an example of an extrusion surface or a second extrusion surface. These first surface 14d and second surface 14e extend in a direction intersecting the axial direction AD of the rotation axis 14p, and face the downstream side in the rotation direction of the driven roller 14 when the discharge nip N discharges the sheet P in the sheet discharge direction DD.

[0034] As shown in FIG. 4(a), the first surface 14d extends in a direction intersecting a circle 14v, which is a virtual circle centered on the rotation axis 14p, when viewed in the axial direction AD. In other words, when a first virtual point and a second virtual point are arranged on the first surface 14d when viewed in the axial direction AD, the distance between the first virtual point and the rotation axis 14p is different from the distance between the second virtual point and the rotation axis 14p.

[0035] As shown in FIG. 4(c), the second surface 14e extends in a direction intersecting a circle 14w, which is a virtual circle centered on the rotation axis 14p, when viewed in the axial direction AD. In other words, when a third virtual point and a fourth virtual point are arranged on the second surface 14e when viewed in the axial direction AD, the distance between the third virtual point and the rotation axis 14p is different from the distance between the fourth virtual point and the rotation axis 14p.

[0036] The circumferential surface 14a of the roller portion 14r is disposed between the flange portion 14b and the flange portion 14c in the axial direction AD. In the axial direction AD, the roller portion 14r is separated from the flange portion 14b and the flange portion 14c. In other words, in the axial direction AD, gaps are formed between the roller portion 14r and the flange portion 14b and between the roller portion 14r and the flange portion 14c. Further, the circumferential surface 14a as the first circumferential surface has a first end 14f close to the flange portion 14b and a second end 14g located on the side opposite to the first end 14f in the axial direction AD and close to the flange portion 14c.

[0037] That is, the distance 14h between the first end 14f of the circumferential surface 14a and the first surface 14d is shorter than the distance 14i between the second end 14g of the circumferential surface 14a and the first surface 14d (distance 14h < distance 14i).

[0038] Here, let the radius of rotation of the circumferential surface 14a at the first end 14f be the first radius 14m, the radius of rotation of the circumferential surface 14a at the second end 14g be the second radius 14n, the radius of rotation of the first surface 14d be the third radius 14j, and the radius of rotation of the second surface 14e be the fourth radius 14k. Note that the third radius 14j is the distance between the rotation axis 14p and the outermost position in the radial direction of the first surface 14d, and the fourth radius 14k is the distance between the rotation axis 14p and the outermost position in the radial direction of the second surface 14e.

[0039] At this time, the circumferential surface 14a is inclined with respect to the axial direction AD such that the first radius 14m is larger than the second radius 14n. Also, the third radius 14j is larger than the first radius 14m, and the fourth radius 14k is smaller than the second radius 14n. That is, the magnitude relationship of each radius is as follows. Third radius 14j > First radius 14m > Second radius 14n > Fourth radius 14k ··· (1)

[0040] As shown in FIG. 5, the four driven rollers 14 in the present embodiment are arranged symmetrically with respect to the center CT of the conveyance path in the sheet width direction W orthogonal to the sheet discharge direction DD. And each driven roller 14 is arranged such that the second end 14g with a smaller radius is closer to the center CT than the first end 14f with a larger radius. The sheet width direction W is a direction orthogonal to the sheet discharge direction DD and is parallel to the axial direction (the direction of the rotation axis 13p described later) as the first axial direction of the drive roller 13.

[0041] Note that the number of the driven rollers 14 does not have to be four. Also, they do not have to be arranged in strict left - right symmetry with respect to the center CT of the conveyance path. That is, the angle formed by the axial direction AD with respect to the axial direction of the drive roller 13 (the direction in which the rotation axis 13p described later extends) may be different among the driven rollers 14.

[0042] Here, one driven roller 14 (for example, the leftmost driven roller 14 in FIG. 3) disposed on one side with respect to the center CT of the conveyance path is referred to as the second roller, and one driven roller 14 (for example, the rightmost driven roller 14 in FIG. 3) disposed on the other side with respect to the center CT of the conveyance path is referred to as the third roller. The rotation radius of the circumferential surface 14a (the second circumferential surface) at the first end 14f (the third end) of the third roller is the first radius 14m (the fifth radius), the rotation radius of the circumferential surface 14a at the second end 14g (the fourth end) is the second radius 14n (the sixth radius), the rotation radius of the first surface 14d (the third surface, the second extrusion surface) is the third radius 14j (the seventh radius), and the rotation radius of the second surface 14e (the fourth surface, the second extrusion surface) is the fourth radius 14k (the eighth radius). Further, the third roller has a roller portion 14r (the second roller portion) including the circumferential surface 14a (the second circumferential surface) that contacts the roller portion 13a of the driving roller 13, and rotates about a third rotation axis extending in the third axis direction. At this time, the circumferential surface 14a is inclined with respect to the axial direction AD such that the first radius 14m is larger than the second radius 14n. Also, the third radius 14j is larger than the first radius 14m, and the fourth radius 14k is smaller than the second radius 14n. Also, the second end 14g of the second roller and the second end 14g of the third roller are disposed between the first end 14f of the second roller and the first end 14f of the third roller.

[0043] At this time, when the conveyance speed of the sheet P is the conveyance speed A, the circumferential speed of the circumferential surface 14a at the first end 14f is the circumferential speed B, and the circumferential speed of the circumferential surface 14a at the second end 14g is the circumferential speed C, the magnitude relationship between the conveyance speed A and the circumferential speeds B and C is as follows. Circumferential speed B > Conveyance speed A > Circumferential speed C ··· (2)

[0044] By configuring the driven roller 14 in this way, when conveying the sheet P, since the conveyance speed A of the sheet P and the circumferential speeds B and C of the circumferential surface 14a are different, the sheet P and the circumferential surface 14a rub against each other, and it is possible to suppress the toner from adhering to the circumferential surface 14a. Therefore, it is possible to suppress the toner adhering to the circumferential surface 14a from adhering to the subsequent sheets, and it is possible to suppress the sheets from being soiled by the toner.

[0045] Further, as shown in FIG. 5, by arranging a plurality of driven rollers 14, the components of the plurality of driven rollers 20 can be made common, and the cost can be reduced. Further, the sheet P can be conveyed while being extended outward in the sheet width direction W, and the generation of wrinkles in the sheet P can be suppressed.

[0046] In the present embodiment, each driven roller 14 is arranged such that the second end 14g with a smaller radius is closer to the center CT than the first end 14f with a larger radius, but the present invention is not limited thereto. For example, each driven roller 14 may be arranged such that the first end 14f with a larger radius is closer to the center CT than the second end 14g with a smaller radius. In this case, in the axial direction of the drive roller 13, the first end 14f of one driven roller 14 and the first end 14f of another driven roller 14 are arranged between the second end 14g of the one driven roller 14 and the second end 14g of the other driven roller 14.

[0047] [Posture of Driven Roller During Sheet Conveyance] FIG. 6 is a front view showing the posture of the driven roller 14 when the sheet P is being conveyed. As described above, the peripheral surface 14a of the roller portion 14r of the driven roller 14 is formed so as to intersect the rotation axis 14p of the driven roller 14. The roller portion 13a of the drive roller 13 rotates about the rotation axis 13p as the first rotation axis. Therefore, when the peripheral surface 14a of the driven roller 14 comes into contact with the roller portion 13a of the drive roller 13, the rotation axis 14p of the driven roller 14 is inclined with respect to the rotation axis 13p of the drive roller 13. The axial direction AD1 of the rotation axis 13p can be referred to as the first axial direction. In other words, the rotation axis 13p extends in the axial direction AD1.

[0048] Then, the sheet P is conveyed by the roller portion 13a of the driving roller 13 and the roller portion 14r of the driven roller 14. When the rear end of the sheet P passes through the discharge nip N, at least one of the first surface 14d and the second surface 14e pushes out the rear end of the sheet P. As a result, it is possible to prevent the rear end of the sheet P from being draped over and held on the circumferential surface 14a of the roller portion 14r of the driven roller 14, and the sheet P can be reliably loaded onto the discharge tray 15. That is, the discharge performance of the sheet P can be improved.

[0049] In addition, in the present embodiment, as shown in FIG. 1, the rotation axis 14p of the driven roller 14 is closer to the discharge tray 15 in the horizontal direction than the rotation axis 13p of the driving roller 13. As a result, the sheet P discharged from the discharge nip N is discharged along the inclination of the discharge tray 15, and the loadability of the sheet P onto the discharge tray 15 can be improved. Further, since the discharge port from which the sheet P is discharged faces obliquely upward, the moist air near the discharge nip N is easily discharged to the outside of the apparatus main body 100A, and the occurrence of dew condensation can be suppressed. Also, in the vertical direction VD, the rotation axis 14p is located below the rotation axis 13p.

[0050] Further, if, in FIG. 4(b), the third radius 14j < the first radius 14m, the rear end of the sheet P cannot be pushed out toward the discharge tray 15 by the first surface 14d. Also, if, in FIG. 4(b), the second radius 14n < the fourth radius 14k, the second surface 14e may deeply push in the sheet P sandwiched by the discharge nip N, which may damage the sheet P.

[0051] However, in the present embodiment, since the magnitude relationship of the respective radii of the driven roller 14 is set as in the above formula (1), the first surface 14d and the second surface 14e are located substantially on the same plane with respect to the conveyance path of the sheet P. In other words, as shown in FIG. 6, when viewed in the sheet discharge direction DD, the first surface 14d and the second surface 14e are arranged at positions overlapping a straight line ST parallel to the rotation axis 13p of the driving roller 13 passing through the discharge nip N. As a result, the discharge performance of the sheet can be improved and damage to the sheet P can be suppressed.

[0052] Incidentally, the arrangements of the first surface 14d and the second surface 14e can also be defined as follows. As shown in FIG. 4(b), when viewed in a direction perpendicular to the axial direction of the rotation axis 13p and parallel to the tangent line of the roller portion 13a passing through the discharge nip N, the first surface 14d and the second surface 14e are arranged at positions overlapping a straight line ST that is parallel to the rotation axis 13p and passes through the discharge nip N.

[0053] Also, when viewed in a direction perpendicular to the axial direction AD, at least one of the first surface 14d and the second surface 14e is arranged at a position overlapping a straight line that is parallel to the circumferential surface 14a and passes through the circumferential surface 14a (see FIG. 4(b)).

[0054] <Second Embodiment> Next, a second embodiment of the present invention will be described. The second embodiment is configured by omitting the flange portion 14c of the driven roller 14 in the first embodiment. Therefore, for the same configurations as in the first embodiment, illustration is omitted or the same reference numerals are given in the figures for explanation.

[0055] [Driven Roller] The driven roller 18 according to the second embodiment will be described with reference to FIGS. 7(a) to 7(c). As described above, the driven roller 18 is configured by omitting the flange portion 14c from the driven roller 14 in the first embodiment. FIG. 7(a) is a left side view showing the driven roller 18 and a partially enlarged view thereof, FIG. 7(b) is a front view showing the driven roller 18, and FIG. 7(c) is a right side view showing the driven roller 18.

[0056] As shown in FIGS. 7(a) to 7(c), the driven roller 18 as the second roller has a roller shaft 14s, a roller portion 14r, and a flange portion 14b. The roller portion 14r and the flange portion 14b are fixed to the roller shaft 14s and rotate integrally about the rotation axis 14p of the roller shaft 14s. Note that the roller shaft 14s may be divided into a plurality of shafts. In the present embodiment, the driven roller 18 is made of resin, and the roller shaft 14s, the roller portion 14r, and the flange portion 14b are integrally formed. The driven roller 18 is formed by injection molding.

[0057] The circumferential surface 14a of the roller portion 14r is disposed at a position different from that of the flange portion 14b in the axial direction AD. Further, the circumferential surface 14a has a first end 14f close to the flange portion 14b and a second end 14g located on the side opposite to the first end 14f in the axial direction AD and farther from the flange portion 14b than the first end 14f.

[0058] That is, the distance 14h between the first end 14f of the circumferential surface 14a and the first surface 14d is shorter than the distance 14i between the second end 14g of the circumferential surface 14a and the first surface 14d (distance 14h < distance 14i).

[0059] Here, let the rotation radius of the circumferential surface 14a at the first end 14f be the first radius 14m, the rotation radius of the circumferential surface 14a at the second end 14g be the second radius 14n, and the rotation radius of the first surface 14d be the third radius 14j.

[0060] At this time, the circumferential surface 14a is inclined with respect to the axial direction AD such that the first radius 14m is larger than the second radius 14n. Further, the third radius 14j as the rotation radius is larger than the first radius 14m. That is, the magnitude relationship of each radius is as follows. Third radius 14j > First radius 14m > Second radius 14n ··· (3)

[0061] As described above, since the driven roller 18 of the second embodiment has only one flange portion 14b, for example, it is easy to manufacture parts when molding the driven roller 18 with a mold, and the cost can be reduced. Also, similar to the first embodiment, the dischargeability of the sheet can be improved and damage to the sheet P can be suppressed.

[0062] <Third Embodiment> Next, a third embodiment of the present invention will be described. The third embodiment is configured by omitting the flange portion 14b of the driven roller 14 of the first embodiment. Therefore, for the same configurations as those in the first embodiment, illustration will be omitted or the same reference numerals will be given in the drawings for explanation.

[0063] [Driven Roller] The driven roller 19 according to the third embodiment will be described with reference to FIGS. 8(a) to 8(c). As described above, the driven roller 19 is configured by omitting the flange portion 14b from the driven roller 19 of the first embodiment. FIG. 8(a) is a left side view showing the driven roller 19, FIG. 8(b) is a front view showing the driven roller 19, and FIG. 8(c) is a right side view showing the driven roller 19 and a partially enlarged view thereof.

[0064] As shown in FIGS. 8(a) to 8(c), the driven roller 19 as the second roller has a roller shaft 14s, a roller portion 14r, and a flange portion 14c. The roller portion 14r and the flange portion 14c are fixed to the roller shaft 14s and rotate integrally about the rotation axis 14p of the roller shaft 14s. Note that the roller shaft 14s may be divided into a plurality of shafts. In the present embodiment, the driven roller 19 is made of resin, and the roller shaft 14s, the roller portion 14r, and the flange portion 14c are integrally formed. The driven roller 19 is formed by injection molding.

[0065] The circumferential surface 14a of the roller part 14r is arranged at a position different from that of the flange part 14c in the axial direction AD. Further, the circumferential surface 14a has a first end 14f and a second end 14g which is located on the side opposite to the first end 14f in the axial direction AD and is closer to the flange part 14c than the first end 14f.

[0066] That is, the distance 19g between the first end 14f of the circumferential surface 14a and the second surface 14e is longer than the distance 19f between the second end 14g of the circumferential surface 14a and the second surface 14e (distance 19g > distance 19f).

[0067] Here, let the rotation radius of the circumferential surface 14a at the first end 14f be the first radius 14m, the rotation radius of the circumferential surface 14a at the second end 14g be the second radius 14n, and the rotation radius of the second surface 14e be the fourth radius 14k.

[0068] At this time, the circumferential surface 14a is inclined with respect to the axial direction AD such that the first radius 14m is larger than the second radius 14n. Further, the fourth radius 14k as the rotation radius is smaller than the second radius 14n. That is, the magnitude relationship of each radius is as follows. First radius 14m > second radius 14n > fourth radius 14k ··· (4)

[0069] As described above, since the driven roller 19 of the third embodiment has only one flange part 14c, for example, it is easy to manufacture parts when molding the driven roller 19 with a mold, and the cost can be reduced. Also, similar to the first embodiment, the discharge property of the sheet can be improved and damage to the sheet P can be suppressed.

[0070] <Fourth Embodiment> Next, a fourth embodiment of the present invention will be described. The fourth embodiment is configured by adding extrusion surfaces 20f and 20g to the flange parts 14b and 14c of the driven roller 14 of the first embodiment, respectively. Therefore, for the same configurations as those in the first embodiment, illustration is omitted or the same reference numerals are given in the drawings for explanation.

[0071] [Driven roller] The driven roller 20 according to the fourth embodiment will be described with reference to FIGS. 9(a) to (c) and FIG. 10. FIG. 9(a) is a left side view of the driven roller 20 and a partially enlarged view thereof, FIG. 9(b) is a front view of the driven roller 20, and FIG. 9(c) is a right side view of the driven roller 20 and a partially enlarged view thereof. FIG. 10 is a diagram showing the arrangement relationship of the four driven rollers 20.

[0072] As shown in FIGS. 9(a) to (c), the driven roller 20 as the second roller has a roller shaft 14s, a roller portion 14r, and flange portions 20b and 20c. As described above, the driven roller 20 in the fourth embodiment is obtained by adding extrusion surfaces 20f and 20g to the driven roller 14 in the first embodiment.

[0073] More specifically, the flange portion 20b in the present embodiment has two first surfaces 14d and two extrusion surfaces 20f. These first surfaces 14d and extrusion surfaces 20f are alternately arranged every 90 degrees in the rotation direction of the flange portion 20b.

[0074] Further, the flange portion 20c has two second surfaces 14e and two extrusion surfaces 20g. These second surfaces 14e and extrusion surfaces 20g are alternately arranged every 90 degrees in the rotation direction of the flange portion 20c.

[0075] And the extrusion surfaces 20f and 20g as surfaces extend in a direction intersecting the axial direction AD, and when the discharge nip N discharges the sheet in the sheet discharge direction DD (see FIG. 2(a)), they face the upstream side in the rotation direction of the driven roller 20. Further, the extrusion surface 20f is arranged to face the first surface 14d in the rotation direction of the driven roller 20. Similarly, the extrusion surface 20g is arranged to face the second surface 14e in the rotation direction of the driven roller 20.

[0076] The radius of the extrusion surface 20f is the third radius 14j, similar to the first surface 14d, and the radius of the extrusion surface 20g is the fourth radius 14k, similar to the second surface 14e. Also in this embodiment, the magnitude relationship of the radii shown in the formula (1) described in the first embodiment is satisfied.

[0077] As shown in FIG. 10, the four driven rollers 20 in this embodiment are arranged symmetrically with respect to the center CT of the conveyance path. For this reason, when attempting to apply the driven roller 20 described in FIG. 9(b) to the two driven rollers 20 on the right side in FIG. 10, the driven roller 20 will be turned over left and right from the posture in FIG. 9(b). Then, when the discharge nip N discharges the sheet in the sheet discharge direction DD, the first surface 14d and the second surface 14e will face the upstream side in the rotation direction of the driven roller 20.

[0078] Therefore, in this embodiment, extrusion surfaces 20f and 20g facing the opposite sides of the first surface 14d and the second surface 14e are provided on the flange portions 20b and 20c of the driven roller 20, respectively. For this reason, the two driven rollers 20 on the left side with respect to the center CT of the conveyance path in FIG. 10 and the two driven rollers 20 on the right side with respect to the center CT can be configured from the same components.

[0079] By sharing the components in this way, the cost can be reduced. Also, similar to the first embodiment, the discharge property of the sheet can be improved and damage to the sheet P can be suppressed.

[0080] In this embodiment, each driven roller 14 is arranged such that the second end 14g with a smaller radius is closer to the center CT than the first end 14f with a larger radius, but it is not limited to this. For example, each driven roller 14 may be arranged such that the first end 14f with a larger radius is closer to the center CT than the second end 14g with a smaller radius.

[0081] <Other Embodiments> In addition, in any of the above-described embodiments, although the first surface 14d and the second surface 14e extend so as to be orthogonal to the rotational direction of the flange portions 14b and 14c, the present invention is not limited thereto. For example, if the first surface 14d and the second surface 14e extend so as to intersect the axial direction AD, they may be inclined with respect to the rotational direction of the flange portions 14b and 14c. Further, if the extrusion surfaces 20f and 20g in the fourth embodiment also extend so as to intersect the axial direction AD, they may be inclined with respect to the rotational direction of the flange portions 14b and 14c.

[0082] Also, in any of the above-described embodiments, although the electrophotographic image forming apparatus 100 has been described, the present invention is not limited thereto. For example, the present invention can also be applied to an inkjet image forming apparatus that forms an image on a sheet by ejecting an ink liquid from a nozzle.

Explanation of Reference Numerals

[0083] 13: First roller (driving roller) / 13p: First rotation axis (rotation axis) / 14, 18, 19, 20: Second roller, third roller (driven roller) / 14a: Peripheral surface, first peripheral surface, second peripheral surface / 14d: First surface, third surface, extrusion surface, second extrusion surface / 14e: Second surface, fourth surface, extrusion surface, second extrusion surface / 14f: First end, third end / 14g: Second end, fourth end / 14h, 14i: Distance / 14j: Third radius, seventh radius, rotation radius / 14k: Fourth radius, eighth radius, rotation radius / 14m: First radius, fifth radius / 14n: Second radius, sixth radius / 14p: Second rotation axis (rotation axis) / 14r: Roller portion, first roller portion / 14v, 14w: Circle / 15: Loading portion (discharge tray) / 20f, 20g: Surface (extrusion surface) / 30: Image forming portion / 60: Sheet discharge device / 100: Image forming apparatus / AD: Second axial direction (axial direction) / AD1: First axial direction (axial direction) / DD: Sheet discharge direction / M: Driving source (driving motor) / N: Discharge nip / ST: Straight line / VD: Vertical direction

Claims

1. A loading part on which a sheet is loaded, A first roller that rotates about a first rotation axis extending in the first axis direction, A second roller that rotates about a second rotation axis extending in the second axis direction and is configured to discharge the sheet toward the loading part together with the first roller, The second roller includes, when viewed in the second axis direction, a first surface that extends so as to intersect a circle centered on the second rotation axis and is configured to push the sheet toward the loading part, a second surface that extends so as to intersect a circle centered on the second rotation axis and is configured to push the sheet toward the loading part, and a roller part disposed between the first surface and the second surface in the second axis direction and including a circumferential surface that abuts the first roller so as to form a discharge nip between the first roller and the second roller, The circumferential surface has a first end and a second end opposite to the first end in the second axis direction, The distance between the first end and the first surface in the second axis direction is shorter than the distance between the second end and the first surface in the second axis direction, When the rotation radius of the circumferential surface at the first end is a first radius, the rotation radius of the circumferential surface at the second end is a second radius, the rotation radius of the first surface is a third radius, and the rotation radius of the second surface is a fourth radius, (i) The circumferential surface is inclined with respect to the second axis direction such that the first radius is larger than the second radius, (ii) The third radius is larger than the first radius, (iii) The fourth radius is smaller than the second radius, A sheet discharge device characterized by the above.

2. When viewed in a direction parallel to the tangent of the first roller passing through the discharge nip and orthogonal to the first axis direction, the first surface and the second surface are arranged at positions overlapping a straight line parallel to the first rotation axis and passing through the discharge nip, The sheet discharge device according to claim 1, characterized by the above.

3. The second roller has a surface disposed at a position different from the roller part in the second axis direction, The surface extends in a direction intersecting the second axis direction and faces upstream in the rotation direction of the second roller when the second roller discharges the sheet toward the loading part together with the first roller, The sheet discharge device according to claim 1, characterized by the above.

4. Further comprising a third roller configured to rotate about a third rotation axis extending in the third axis direction and discharge the sheet toward the stacking portion together with the first roller, The circumferential surface and the roller portion are a first circumferential surface and a first roller portion, respectively, The third roller includes a third surface configured to extend so as to intersect a circle centered on the third rotation axis when viewed in the third axis direction and push out the sheet toward the stacking portion, and a fourth surface configured to extend so as to intersect a circle centered on the third rotation axis when viewed in the third axis direction and push out the sheet toward the stacking portion, and a second roller portion disposed between the third surface and the fourth surface in the third axis direction and including a second circumferential surface that contacts the first roller, The second circumferential surface has a third end and a fourth end opposite to the third end in the third axis direction, The distance between the third end and the third surface in the third axis direction is shorter than the distance between the fourth end and the third surface in the third axis direction, When the rotation radius of the second circumferential surface at the third end is a fifth radius, the rotation radius of the second circumferential surface at the fourth end is a sixth radius, the rotation radius of the third surface is a seventh radius, and the rotation radius of the fourth surface is an eighth radius, (i) The second circumferential surface is inclined with respect to the third axis direction such that the fifth radius is larger than the sixth radius, (ii) The seventh radius is larger than the fifth radius, (iii) The eighth radius is smaller than the sixth radius, In the first axis direction, the second end of the second roller and the fourth end of the third roller are disposed between the first end of the second roller and the third end of the third roller, The sheet discharge device according to claim 1, characterized in that.

5. The second roller is configured to be relatively movable with respect to the first roller, The sheet discharge device according to any one of claims 1 to 4, characterized in that.

6. Further comprising a drive source for driving the first roller, The second roller is rotated by the first roller by contacting the first roller, The sheet discharge device according to any one of claims 1 to 4, characterized in that.

7. The second rotation axis is closer to the stacking portion in the horizontal direction than the first rotation axis, The sheet discharge device according to any one of claims 1 to 4, characterized in that.

8. The second rotation axis is located below the first rotation axis in the vertical direction. The sheet discharging device according to any one of claims 1 to 4, characterized in that.

9. An image forming unit that forms an image on a sheet, A sheet discharging device according to any one of claims 1 to 4, which discharges a sheet on which an image has been formed by the image forming unit, An image forming apparatus characterized by that.

10. A stacking unit on which sheets are stacked, A first roller that rotates about a first rotation axis extending in a first axis direction, A second roller that rotates about a second rotation axis extending in a second axis direction and is configured to discharge a sheet toward the stacking unit together with the first roller, The second roller has a pushing-out surface that extends so as to intersect a circle centered on the second rotation axis when viewed in the second axis direction and is configured to push out the sheet toward the stacking unit, and a roller portion that is disposed at a position different from the pushing-out surface in the second axis direction and includes a circumferential surface that abuts against the first roller so as to form a discharge nip between the second roller and the first roller. The circumferential surface has a first end and a second end opposite to the first end in the second axis direction. The distance between the first end and the pushing-out surface in the second axis direction is shorter than the distance between the second end and the pushing-out surface in the second axis direction. When the rotation radius of the circumferential surface at the first end is a first radius and the rotation radius of the circumferential surface at the second end is a second radius, (i) The circumferential surface is inclined with respect to the second axis direction such that the first radius is larger than the second radius. (ii) The rotation radius of the pushing-out surface is larger than the first radius. A sheet discharging device characterized by that.

11. When viewed in a direction parallel to the tangent line of the first roller passing through the discharge nip and orthogonal to the first axis direction, the pushing-out surface is disposed at a position parallel to the first rotation axis and overlapping a straight line passing through the discharge nip. The sheet discharging device according to claim 10, characterized in that.

12. The second roller has a surface that is disposed at a position different from the roller portion in the second axis direction. The surface extends in a direction intersecting the second axis direction and faces upstream in the rotation direction of the second roller when the second roller discharges a sheet toward the stacking unit together with the first roller. The sheet discharging device according to claim 10, characterized in that...

13. Further comprising a third roller that rotates about a third rotation axis extending in the third axis direction and is configured to discharge the sheet toward the stacking portion together with the first roller. The extrusion surface, the circumferential surface, and the roller portion are a first extrusion surface, a first circumferential surface, and a first roller portion, respectively. The third roller includes a second extrusion surface that extends so as to intersect a circle centered on the third rotation axis when viewed in the third axis direction and is configured to extrude the sheet toward the stacking portion, and a second roller portion that is disposed at a position different from the second extrusion surface in the third axis direction and includes a second circumferential surface that contacts the first roller. The second circumferential surface has a third end and a fourth end opposite to the third end in the third axis direction. The distance between the third end and the second extrusion surface in the third axis direction is shorter than the distance between the fourth end and the second extrusion surface in the third axis direction. When the rotation radius of the second circumferential surface at the third end is a fifth radius and the rotation radius of the second circumferential surface at the fourth end is a sixth radius. (i) The second circumferential surface is inclined with respect to the third axis direction such that the fifth radius is larger than the sixth radius. (ii) The rotation radius of the second extrusion surface is larger than the fifth radius. In the first axis direction, the second end of the second roller and the fourth end of the third roller are disposed between the first end of the second roller and the third end of the third roller. The sheet discharging device according to claim 10, characterized in that...

14. The second roller is configured to be relatively movable with respect to the first roller. The sheet discharging device according to any one of claims 10 to 13, characterized in that...

15. Further comprising a drive source for driving the first roller. The second roller is rotated by the first roller by contacting the first roller. The sheet discharging device according to any one of claims 10 to 13, characterized in that...

16. The second rotation axis is closer to the stacking portion in the horizontal direction than the first rotation axis. The sheet discharging device according to any one of claims 10 to 13, characterized in that...

17. The second rotation axis is located below the first rotation axis in the vertical direction. The sheet discharging device according to any one of claims 10 to 13, characterized in that...

18. An image forming unit that forms an image on a sheet, The sheet discharging device according to any one of claims 10 to 13, which discharges the sheet on which the image is formed by the image forming unit, and An image forming apparatus characterized in that...

19. A stacking unit on which sheets are stacked, A first roller that rotates about a first rotation axis extending in a first axis direction, A second roller that rotates about a second rotation axis extending in a second axis direction and is configured to discharge the sheet toward the stacking unit together with the first roller, The second roller has a pushing-out surface that extends so as to intersect a circle centered on the second rotation axis when viewed in the second axis direction and is configured to push out the sheet toward the stacking unit, and a roller portion that is disposed at a position different from the pushing-out surface in the second axis direction and includes a circumferential surface that abuts against the first roller so as to form a discharge nip between the first roller and the second roller. The circumferential surface has a first end and a second end opposite to the first end in the second axis direction. The distance between the first end and the pushing-out surface in the second axis direction is longer than the distance between the second end and the pushing-out surface in the second axis direction. When the rotation radius of the circumferential surface at the first end is a first radius and the rotation radius of the circumferential surface at the second end is a second radius, (i) The circumferential surface is inclined with respect to the second axis direction such that the first radius is larger than the second radius. (ii) The rotation radius of the pushing-out surface is smaller than the second radius. A sheet discharging device characterized in that...

20. When viewed in a direction parallel to the tangent line of the first roller passing through the discharge nip and orthogonal to the first axis direction, the pushing-out surface is disposed at a position parallel to the first rotation axis and overlapping a straight line passing through the discharge nip. The sheet discharging device according to claim 19, characterized in that...

21. The second roller has a surface that is disposed at a position different from the roller portion in the second axis direction. The surface extends in a direction intersecting the second axis direction and faces upstream in the rotation direction of the second roller when the second roller discharges the sheet toward the stacking unit together with the first roller. The sheet discharging device according to claim 19, characterized in that...

22. Further comprising a third roller configured to rotate about a third rotation axis extending in the third axis direction and discharge the sheet toward the stacking portion together with the first roller, The extrusion surface, the circumferential surface, and the roller portion are a first extrusion surface, a first circumferential surface, and a first roller portion, respectively, The third roller includes a second extrusion surface configured to extend so as to intersect a circle centered on the third rotation axis when viewed in the third axis direction and to extrude the sheet toward the stacking portion, and a second roller portion disposed at a position different from the second extrusion surface in the third axis direction and including a second circumferential surface that contacts the first roller, The second circumferential surface has a third end and a fourth end opposite to the third end in the third axis direction, The distance between the third end and the second extrusion surface in the third axis direction is longer than the distance between the fourth end and the second extrusion surface in the third axis direction, When the rotation radius of the second circumferential surface at the third end is a fifth radius and the rotation radius of the second circumferential surface at the fourth end is a sixth radius, (i) The second circumferential surface is inclined with respect to the third axis direction such that the fifth radius is larger than the sixth radius, (ii) The rotation radius of the second extrusion surface is smaller than the sixth radius, In the first axis direction, the second end of the second roller and the fourth end of the third roller are disposed between the first end of the second roller and the third end of the third roller, The sheet discharging device according to claim 19, characterized in that.

23. The second roller is configured to be relatively movable with respect to the first roller, The sheet discharging device according to any one of claims 19 to 22, characterized in that.

24. Further comprising a drive source for driving the first roller, The second roller is rotated by the first roller by contacting the first roller, The sheet discharging device according to any one of claims 19 to 22, characterized in that.

25. The second rotation axis is closer to the stacking portion in the horizontal direction than the first rotation axis, The sheet discharging device according to any one of claims 19 to 22, characterized in that.

26. The second rotation axis is located below the first rotation axis in the vertical direction, The sheet discharging device according to any one of claims 19 to 22, characterized in that.

27. An image forming unit that forms an image on a sheet; A sheet discharging device according to any one of claims 19 to 22, which discharges the sheet on which the image has been formed by the image forming unit; and An image forming apparatus characterized by the above.

Images