Sheet Feeding Device and Image Forming Apparatus

Abstract

To provide a sheet feeder capable of improving conveyance stability of sheets, and an image formation apparatus comprising the same.SOLUTION: A sheet feeder comprises: a sheet support surface which supports sheets; a feed rotary body which feeds the sheets supported on the sheet support surface; a separation part which separates the sheets fed by the feed rotary body, individually; and a conveyor guide which guides the sheets fed by the feed rotary body toward the separation part. The conveyor guide has a first inclined surface and a second inclined surface for guiding the sheets fed by the feed rotary body toward the separation part. At least a part of the second inclined surface is placed overlapping with the first inclined surface in a sheet conveyance direction. When viewed in a width direction orthogonal to the sheet conveyance direction, the angle on the side of the feed rotary body that the sheet support surface and the second inclined surface contain is larger than the angle on the side of the feed rotary body that the sheet support surface and the first inclined surface contain.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a sheet feeding device for feeding a sheet and an image forming apparatus including the same.

Background Art

[0002] Conventionally, a sheet feeding device has been proposed that feeds a sheet placed on a placement unit by a pickup roller and guides the sheet to a separation nip unit by a separation front slope (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the sheet feeding device of Patent Document 1, when the number of sheets stacked on the placement unit decreases, the sheet is conveyed while slidingly contacting the separation front slope. Then, friction acts between the separation front slope and the sheet, increasing the conveyance resistance of the sheet. Since the conveyance resistance increases as the rigidity of the conveyed sheet increases, depending on the type of sheet, there is a risk that the conveyance force by the pickup roller will be overcome by the conveyance resistance and the sheet cannot be stably conveyed.

[0005] Therefore, an object of the present invention is to provide a sheet feeding device capable of improving the conveyance stability of a sheet and an image forming apparatus including the same.

Means for Solving the Problems

[0006] The present invention relates to a sheet feeding device, comprising a sheet support surface for supporting a sheet, a feeding rotating body for feeding the sheet supported on the sheet support surface, a separating unit for separating the sheets fed by the feeding rotating body one by one, and a conveying guide for guiding the sheet fed by the feeding rotating body toward the separating unit. The conveying guide has a first inclined surface and a second inclined surface for guiding the sheet fed by the feeding rotating body toward the separating unit, at least a part of the second inclined surface is disposed at a position overlapping the first inclined surface in the sheet conveying direction, and when viewed in the width direction orthogonal to the sheet conveying direction, the angle on the feeding rotating body side formed by the sheet support surface and the second inclined surface is larger than the angle on the feeding rotating body side formed by the sheet support surface and the first inclined surface. く , The second inclined surface is composed of a plurality of ribs integrally formed on the first inclined surface. The plurality of ribs include a first rib provided at a position overlapping the feeding rotating body in the width direction, a second rib disposed on one side of the first rib in the width direction, and a third rib disposed on the other side of the first rib in the width direction. It is characterized by this. Moreover, the present invention relates to a sheet feeding device, comprising a sheet support surface for supporting a sheet, a feeding rotating body for feeding the sheet supported on the sheet support surface, a separating unit for separating the sheets fed by the feeding rotating body one by one, and a conveying guide for guiding the sheet fed by the feeding rotating body toward the separating unit. The conveying guide has a first inclined surface and a second inclined surface for guiding the sheet fed by the feeding rotating body toward the separating unit. At least a part of the second inclined surface is disposed at a position overlapping the first inclined surface in the sheet conveying direction. When viewed in the width direction orthogonal to the sheet conveying direction, the angle on the feeding rotating body side formed by the sheet support surface and the second inclined surface is larger than the angle on the feeding rotating body side formed by the sheet support surface and the first inclined surface. At least a part of the region where the second inclined surface is disposed is provided at a position overlapping the feeding rotating body in the width direction, and the length of the region where the second inclined surface is disposed in the width direction is shorter than twice the length of the feeding rotating body in the width direction. Further, the present invention provides a sheet feeding device including a sheet support surface for supporting a sheet, a feeding rotating body for feeding the sheet supported on the sheet support surface, a separating unit for separating the sheets fed by the feeding rotating body one by one, and a conveying guide for guiding the sheet fed by the feeding rotating body toward the separating unit. The conveying guide has a first inclined surface and a second inclined surface for guiding the sheet fed by the feeding rotating body toward the separating unit. At least a part of the second inclined surface is disposed at a position overlapping the first inclined surface in the sheet conveying direction. When viewed in the width direction orthogonal to the sheet conveying direction, the angle on the feeding rotating body side formed by the sheet support surface and the second inclined surface is larger than the angle on the feeding rotating body side formed by the sheet support surface and the first inclined surface. The conveying guide includes a first guide member and a second guide member detachably supported by the first guide member. The first inclined surface is provided on the first guide member and the second guide member, and the second inclined surface is provided on the second guide member.

Effect of the Invention

[0007] According to the present invention, the conveyance stability of the sheet can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Best Mode for Carrying Out the Invention

[0009] 〔Overall Configuration〕 First, a first embodiment of the present invention will be described. The printer 200 as an image forming apparatus is a laser beam printer using an electrophotographic method. In the present embodiment, the sheet includes various sheets with different sizes and materials, such as paper such as plain paper and thick paper, plastic film, cloth, sheet materials with surface treatment such as coated paper, and special-shaped sheet materials such as envelopes and index paper.

[0010] As shown in FIG. 1, it has an image forming unit 19 that forms an image on a sheet, a cassette feeding unit 10, a multi-feeding device 100, and a fixing device 40. The image forming unit 19 includes four process cartridges 20Y, 20M, 20C, and 20BK that form toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (BK), respectively, and a scanner unit 23.

[0011] Note that the four process cartridges 20Y, 20M, 20C, and 20BK have the same configuration except that the colors of the images they form are different. Therefore, only the configuration and image forming process of the process cartridge 20Y will be described, and the descriptions of the process cartridges 20M, 20C, and 20BK will be omitted.

[0012] The process cartridge 20Y has a photosensitive drum 21, a charging roller 22, and a developing roller 24. The photosensitive drum 21 is configured by applying an organic photoconductive layer to the outer periphery of an aluminum cylinder and rotates by a drive motor (not shown). In addition, the image forming unit 19 is provided with an intermediate transfer belt 31 wound around a drive roller 32, a tension roller 35, etc., and primary transfer rollers 26Y, 26M, 26C, and 26BK are provided inside the intermediate transfer belt 31.

[0013] The fixing device 40 has a fixing film 41 heated by a heater (not shown) and a pressure roller 42 that presses against the fixing film 41. The cassette feeding unit 10 is provided at the lower part of the printer 200 and includes a cassette 11 for storing sheets and a feeding roller 12 for feeding the sheets.

[0014] Next, the image forming operation of the printer 200 configured as described above will be explained. When an image signal is input from a personal computer or the like (not shown) to the scanner unit 23, laser light corresponding to the image signal is irradiated onto the photosensitive drum 21 of the process cartridge 20Y from the scanner unit 23.

[0015] At this time, the surface of the photosensitive drum 21 is uniformly charged to a predetermined polarity and potential in advance by the charging roller 22, and an electrostatic latent image is formed on the surface when the laser light is irradiated from the scanner unit 23. The electrostatic latent image formed on the photosensitive drum 21 is developed by the developing roller 24, and a yellow (Y) toner image is formed on the photosensitive drum 21.

[0016] Similarly, the photosensitive drums of the process cartridges 20M, 20C, and 20BK are also irradiated with laser light from the scanner unit 23, and toner images of magenta (M), cyan (C), and black (BK) 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 31 by the primary transfer rollers 26Y, 26M, 26C, and 26BK, and are conveyed to the secondary transfer roller 33 by the intermediate transfer belt 31 rotated by the driving roller 32. Note that the image forming process of each color is performed at a timing to overlap with the upstream toner image primarily transferred onto the intermediate transfer belt 31.

[0017] In parallel with this image forming process, sheets are fed from the cassette feeder 10 or the multi-feeder 100. For example, the sheets stored in the cassette 11 of the cassette feeder 10 are sent out by the feed roller 12 and then conveyed to the registration roller pair 14 via the conveyance roller pair 13. An upstream top sensor 16 in the sheet conveyance direction of the registration roller pair 14 is provided, and the top sensor 16 detects the positions of the leading and trailing edges of the conveyed sheet. The sheet whose skew has been corrected by the registration roller pair 14 is conveyed at a predetermined conveyance timing based on the detection result of the top sensor 16. Then, a full-color toner image on the intermediate transfer belt 31 is transferred onto the sheet by a secondary transfer bias applied to the secondary transfer roller 33.

[0018] The sheet onto which the toner image has been transferred is given a predetermined heat and pressure by the fixing film 41 and the pressure roller 42 of the fixing device 40, and the toner is melted and fixed (fixed). The sheet that has passed through the fixing device 40 is discharged to the discharge tray 51 by the discharge roller pair 15. The arrow CP shown in FIG. 1 is an example of the conveyance path along which the sheet is conveyed from the cassette 11 to the discharge roller pair 15.

[0019] Further, the printer 200 has a cover 70 that is supported so as to be openable and closable with respect to the printer main body 201 as the apparatus main body for performing jam processing, and a multi-feeder 100. The cover 70 is separable from the printer main body 201 at the boundary portion 70b, and opening the cover 70 facilitates jam processing.

[0020] [Multi-feeder] Next, the multi-sheet feeding device 100 as a sheet feeding device will be described with reference to FIGS. 1 to 3. FIG. 2 is a perspective view of the multi-sheet feeding device 100 viewed from below. As shown in FIGS. 1 and 2, the multi-sheet feeding device 100 includes a tray 105 that is supported so as to be openable and closable with respect to the cover 70 or the printer main body 201, a pickup roller 101, a feeding roller 102, and a separating roller 103. The drive configuration of these pickup roller 101, feeding roller 102, and separating roller 103, and the lifting mechanism for raising and lowering the pickup roller 101 will be described in detail.

[0021] The multi-sheet feeding device 100 includes a feed drive gear 111 that is driven by the driving force of a drive motor M, and a cam drive gear 110 that meshes with the feed drive gear 111. The feed drive gear 111 is fixed to one end of a feed roller shaft 102A, and a feed roller 102 is fixed to the other end of the feed roller shaft 102A. A lifting plate 106 is rotatably supported on the feed roller shaft 102A, and a pickup roller shaft 101A is rotatably supported on the lifting plate 106. A pickup roller 101 as a feed rotating body is rotatably supported on the pickup roller shaft 101A.

[0022] A drive gear train 116 is provided between the feed roller shaft 102A and the pickup roller shaft 101A, and the driving force of the feed roller shaft 102A is transmitted to the pickup roller 101 via the drive gear train 116. The lifting plate 106 is biased by a spring (not shown) so that the pickup roller 101 is biased toward the sheet S (see FIG. 3) stacked on the tray 105.

[0023] The cam drive gear 110 is fixed to a camshaft 108A that extends parallel to the feed roller shaft 102A, and a cam 108 is fixed to the camshaft 108A. Further, between the camshaft 108A and the feed roller shaft 102A, an arm shaft 109A that extends parallel to the camshaft 108A and the feed roller shaft 102A is provided, and an arm 109 is fixed to the arm shaft 109A. The arm 109 is configured to rotate when pressed by the cam 108 and to be able to contact an abutting portion 106a provided at the end of the lifting plate 106. Each shaft of the multi-feed device 100 such as the feed roller shaft 102A extends in the width direction W orthogonal to the sheet conveyance direction X (see FIG. 3).

[0024] The cam 108 is in contact with the arm 109 in the home position. At this time, the cam 108 receives a force by which the arm 109 is pushed from the abutting portion 106a of the lifting plate 106 biased by a biasing portion (not shown). Thereby, the pickup roller 101 is held at a position separated from the tray 105, and the sheet S can be loaded on the tray 105.

[0025] Further, below the feed roller 102, a separation roller shaft 103A and a roller holder 107 are arranged. The roller holder 107 is rotatably supported with respect to the printer main body 201 about a shaft 107a, and the separation roller shaft 103A is fixed to the roller holder 107. The separation roller 103 is attached to the separation roller shaft 103A via a torque limiter 104. The roller holder 107 is biased upward by a pressing spring 112, and due to the biasing force of the pressing spring 112, the separation roller 103 is in contact with the feed roller 102 with a predetermined nip pressure. The feed roller 102 and the separation roller 103 form a separation nip NP as a separation portion.

[0026] FIG. 3 is a view showing a state where the sheet S is fully loaded on the tray 105. When a sheet feeding instruction is issued to feed a sheet from the multi-sheet feeding device 100, as shown in FIGS. 2 and 3, the drive motor M is driven. Then, upon receiving the driving force of the drive motor M, the feed roller 102 and the pickup roller 101 rotate. Further, as the cam shaft 108A rotates by the driving force of the drive motor M, the cam 108 presses the arm 109, and the arm 109 rotates. When the arm 109 rotates and disengages from the contact portion 106a of the lifting plate 106, the lifting plate 106 rotates downward about the feed roller shaft 102A by the biasing force of a spring (not shown).

[0027] When the lifting plate 106 rotates downward, the pickup roller 101 abuts on the uppermost sheet St stacked on the tray 105. As a result, the sheet St is fed by the pickup roller 101 and guided toward the separation nip NP by the conveyance guide 121. The conveyance guide 121 also has a function of guiding the sheets fed by the pickup roller 101 one by one.

[0028] At this time, when a plurality of sheets enter the separation nip NP, while the sheet St is conveyed in the sheet conveyance direction X by the feed roller 102, the other sheets are prevented from moving in the sheet conveyance direction X by the frictional force received from the separation roller 103. In other words, the torque value of the torque limiter 104 is set to a magnitude capable of overcoming the frictional force between the overlapping sheets and restricting the rotation of the separation roller 103.

[0029] On the other hand, when only the sheet St enters the separation nip NP, the torque limiter 104 slips due to the force received by the separation roller 103 from the sheet St, and the separation roller 103 rotates following the feed roller 102. The sheet St that has passed through the separation nip is further conveyed by a pair of conveyance rollers 13 (see FIG. 1) provided downstream in the sheet conveyance direction X. The sheet conveyed from the separation nip NP toward the pair of conveyance rollers 13 is detected by a sensor 120 (see FIG. 1).

[0030] After the tip of the sheet St reaches the separation nip NP, the lifting plate 106 swings upward again when the arm 109 presses the contact portion 106a of the lifting plate 106, and the pickup roller 101 separates from the sheet S. As a result, the sheet S under the sheet St is prevented from being continuously fed out. Then, the above operation is repeated by repeating the lifting operation of the lifting plate 106 by the rotation of the feed drive gear 111, and the sheets S stacked on the tray 105 are fed one by one while being separated.

[0031] Note that the pickup roller 101 can swing to the lower position shown by the broken line in FIG. 3 by a spring (not shown) that biases the lifting plate 106, and at the lower position, it can feed to the last sheet on the tray 105.

[0032] Also, in the present embodiment, the sheets are separated one by one at the separation nip NP formed by the feed roller 102 and the separation roller 103, but it is not limited to this. For example, instead of the separation roller 103, a retard roller to which a driving force is input so as to convey the sheet in a direction opposite to the sheet conveyance direction X may be applied. Also, instead of the separation roller 103, a pad-shaped friction member may be used. Further, instead of the pickup roller 101 or the feed roller 102, it may be configured to convey the sheet while adsorbing it to a rotating belt.

[0033] [Conveyance Guide] Next, the conveyance guide 121 that guides the sheet fed by the pickup roller 101 to the separation nip NP will be described in detail. Hereinafter, the tray 105 is located at a predetermined open position. As shown in FIGS. 3 to 5, the conveyance guide 121 has a first inclined surface portion 121a as a first inclined surface and a second inclined surface portion 121b as a second inclined surface. The first inclined surface portion 121a is provided across substantially the entire width of the sheet conveyance region (conveyance path) in the width direction W.

[0034] The second inclined surface portion 121b is composed of three ribs 121C, 121L, and 121R formed integrally with the first inclined surface portion 121a. The three ribs 121C, 121L, and 121R constituting the second inclined surface portion 121b are arranged so as to overlap the first inclined surface portion 121a in the sheet conveyance direction X. Note that the three ribs 121C, 121L, and 121R may be arranged so that at least a part thereof overlaps the first inclined surface portion 121a in the sheet conveyance direction X.

[0035] Further, a metal plate 117 is attached to the conveyance guide 121 so as to overlap the separation roller 103 in the sheet conveyance direction X and guide the sheet to the separation nip NP. The metal plate 117 is formed in a thin plate shape so as to extend up to immediately before the separation nip NP, and rigidity is ensured by being composed of a metal material. The rib 121C as the first rib is shorter than the ribs 121L and 121R in the sheet conveyance direction X because the metal plate 117 is attached to the conveyance guide 121.

[0036] The three ribs 121C, 121L, and 121R constituting the second inclined surface portion 121b are arranged in parallel with a predetermined gap in the width direction W. The rib 121C is provided at the center of the conveyance path or the conveyance guide 121 in the width direction W and is arranged so as to overlap the pickup roller 101 in the width direction W.

[0037] In the width direction W, the rib 121L is arranged on one side of the rib 121C, and the rib 121R is arranged on the other side of the rib 121C. The rib 121L as the second rib and the rib 121R as the third rib are arranged at positions that do not overlap the pickup roller 101 in the width direction W. In other words, the second inclined surface portion 121b is arranged in the region AR between the rib 121L and the rib 121R in the width direction W, and at least a part of the region AR is arranged so as to overlap the pickup roller 101 in the width direction W.

[0038] In addition, in the present embodiment, the length L1 in the width direction W of the region AR is shorter than twice the length L2 in the width direction W of the pickup roller 101. L1 < L2 × 2 ····· (1)

[0039] Also, in the width direction W, the length from the end face 101a of the pickup roller 101 to the rib 121L and the length from the end face 101b of the pickup roller 101 to the rib 121R are both the length L3. That is, the length L1 in the width direction W of the region AR is the sum of the length L2 in the width direction W of the pickup roller 101 and twice the length L3. L1 = L2 + L3 × 2 ····· (2)

[0040] From the above formulas (1) and (2), the following formula (3) is derived. L2 > L3 × 2 ····· (3) In the present embodiment, the length L3 is set to 7 mm. However, for example, the length L3 may be set to a value of 10 mm or less.

[0041] Also, in the present embodiment, the distance L4 between the rib 121C and the rib 121L and the distance L5 between the rib 121C and the rib 121R are shorter than the length L2 of the pickup roller 101 in the width direction W. Therefore, when the sheet passes through the ribs 121C, 121L, and 121R, it is difficult for the sheet to curve and contact the first inclined surface portion 121a between the ribs 121C, 121L, and 121R. Thereby, the friction between the sheet and the conveyance guide 121 can be reduced, and the conveyance resistance can be reduced.

[0042] As shown in FIG. 3, the sheet support surface 105a of the tray 105 is inclined downward as it goes downstream in the sheet conveyance direction X. On the other hand, the first inclined surface portion 121a and the second inclined surface portion 121b are inclined upward as they go downstream in the sheet conveyance direction X.

[0043] Here, the transport guide 121 of the present embodiment will be described while comparing it with the comparative examples shown in FIGS. 8(a) and 8(b). As shown in FIGS. 8(a) and 8(b), the transport guide 1121 in the comparative example does not have the second inclined surface portion 121b and has only the first inclined surface portion 121a.

[0044] As viewed in the width direction W as shown in FIG. 8(a), the angle formed by the sheet support surface 105a and the first inclined surface portion 121a on the pickup roller 101 side is the angle θ1. As viewed in the width direction W as shown in FIG. 3, the angle formed by the sheet support surface 105a and the second inclined surface portion 121b on the pickup roller 101 side is an angle θ2 that is larger than the angle θ1. The difference between the angle θ1 and the angle θ2 is the angle α formed by the first inclined surface portion 121a and the second inclined surface portion 121b.

[0045] Then, as shown in FIG. 3, the upstream end 121bQ of the second inclined surface portion 121b in the sheet transport direction X is disposed below the upstream end 121aU of the first inclined surface portion 121a in the sheet transport direction X. Further, the downstream end 121bJ of the second inclined surface portion 121b in the sheet transport direction X joins the first inclined surface portion 121a at a position upstream of the separation nip NP in the sheet transport direction X. Further, in order to transfer the sheet from the tray 105 to the transport guide 121 without catching, the upstream end 121aU of the first inclined surface portion 121a and the upstream end 121bQ of the second inclined surface portion 121b are disposed below the downstream end 105aT of the sheet support surface 105a. Also, as viewed in the width direction W, the extension line LN of the sheet support surface 105a intersects the first inclined surface portion 121a and the second inclined surface portion 121b.

[0046] Hereinafter, the operation and effect of the transport guide 121 of the present embodiment will be described while comparing it with the comparative example. FIGS. 6 and 8(a) are diagrams showing the force relationship when transporting a sheet St which is a single piece of cardboard. As shown in FIGS. 6 and 8(a), the pickup roller 101 abuts on the sheet St supported by the sheet support surface 105a of the tray 105 at point P and applies a transport force F to the sheet St. The transport force F is the same in FIGS. 6 and 8(a).

[0047] The leading end of the sheet St moves toward the separation nip NP while contacting the conveyance guide 121. Here, in the comparative example, as shown in FIG. 8(a), the leading end of the sheet St contacts the first inclined surface portion 121a at the contact point G'. When the conveyance force F is resolved in the horizontal and vertical directions of the first inclined surface portion 121a with the vector origin of the conveyance force F being the contact point G', the horizontal component of the conveyance force F becomes the guide ascending conveyance force Fs', and the vertical component of the conveyance force F becomes the vertical resistance force N'.

[0048] Similarly, in the present embodiment, as shown in FIG. 6, the leading end of the sheet St contacts the second inclined surface portion 121b at the contact point G. When the conveyance force F is resolved in the horizontal and vertical directions of the second inclined surface portion 121b with the vector origin of the conveyance force F being the contact point G, the horizontal component of the conveyance force F becomes the guide ascending conveyance force Fs, and the vertical component of the conveyance force F becomes the vertical resistance force N.

[0049] Here, since the angle θ2 is larger than the angle θ1 by the angle α, the guide ascending conveyance force Fs is larger than the guide ascending conveyance force Fs'. Fs > Fs’ ····· (4)

[0050] Next, the conveyance resistance of the sheet St with respect to the conveyance guide 121 in the present embodiment and the comparative example will be described. Assuming that the friction coefficient between the sheet and the conveyance guide 121 is the friction coefficient μ, the conveyance resistance in the comparative example is the conveyance resistance μN' as shown in FIG. 8(a). Also, the conveyance resistance in the present embodiment is the conveyance resistance μN as shown in FIG. 6. These conveyance resistances μN and μN' act in the direction opposite to the guide ascending conveyance forces Fs and Fs'.

[0051] Here too, since the angle θ2 is larger than the angle θ1 by the angle α, N < N', and the conveyance resistance μN' is larger than the conveyance resistance μN. μN < μN’ ····· (5)

[0052] The conveyance margin, which is the margin of force for the sheet St to be conveyed along the conveyance guide 121, is represented by (guide uphill conveyance force) - (conveyance resistance). The conveyance margin of the present embodiment is Fs - μN, and the conveyance margin of the comparative example is Fs' - μN'. Therefore, when comparing the conveyance margins of the present embodiment and the comparative example, according to the above-described formulas (4) and (5), Fs - μN >> Fs' - μN' ····· (6) is obtained. From the above formula (6), in the present embodiment, the conveyance performance when conveying a smaller number of sheets of cardboard can be improved compared to the comparative example. Also, as shown in FIG. 3, since the downstream end 121bJ of the second inclined surface portion 121b joins the first inclined surface portion 121a, the sheet St can be smoothly guided in the conveyance guide 121.

[0053] In the comparative example, since the second inclined surface portion 121b is not provided, as shown in FIG. 8(b), the entire area in the width direction W of the sheet St abuts on the first inclined surface portion 121a. For this reason, the friction between the sheet St and the conveyance guide 1121 increases, and the conveyance resistance of the sheet St increases.

[0054] On the other hand, in the present embodiment, as shown in FIG. 5, since the second inclined surface portion 121b is provided only at the central portion in the width direction W of the conveyance guide 121, both end portions in the width direction W of the tip of the sheet St have a gap C between them and the first inclined surface portion 121a. For this reason, the friction between the sheet St and the conveyance guide 121 can be reduced, and the conveyance resistance of the sheet St can be suppressed.

[0055] In the present embodiment, the length L3 (see FIG. 4) is set to 7 mm. However, if the length L3 is set to about 3 mm to 10 mm, a high effect can be exhibited with respect to the improvement of the conveyance margin.

[0056] In addition, a configuration may be considered in which the inclination angles of the first inclined surface portion 121a of the comparative example and the tray 105 are made gentle to improve the guide ascending conveyance force. However, in this case, since the sheet contacts the entire region in the width direction W of the first inclined surface portion 121a, the conveyance resistance increases. Therefore, compared with such a configuration, the present embodiment can increase the conveyance margin and improve the conveyance stability of the sheet. Further, in the above configuration, the elevating plate 106 becomes larger and the installation area of the printer 200 increases.

[0057] As described above, in the present embodiment, the second inclined surface portion 121b is provided at the central portion in the width direction W of the conveyance guide 121. Thereby, while improving the conveyance force (guide ascending conveyance force) of the sheet for being conveyed along the second inclined surface portion 121b, the conveyance resistance of the sheet can be reduced. Further, since both end portions in the width direction W of the sheet float with respect to the first inclined surface portion 121a, the conveyance resistance can be further reduced. From these, the conveyance margin can be improved, and the conveyance stability can be improved particularly for a sheet having high rigidity.

[0058] Further, the length L1 in the width direction W of the region AR where the second inclined surface portion 121b is disposed is set to be shorter than twice the length L2 in the width direction W of the pickup roller 101. Thereby, when conveying a sheet having particularly high rigidity (cardboard), it is possible to suppress the sheet from being curved and contacting the first inclined surface portion 121a between the ribs of the second inclined surface portion 121b, thereby increasing the conveyance resistance.

[0059] [Modification Example] FIG. 7 is a perspective view showing a modification example of the present embodiment. As shown in FIG. 7, in the modification example, the conveyance guide 121 includes a first guide member 121H and a second guide member 121U detachably supported by the first guide member 121H. The first inclined surface portion 121a is provided on the first guide member 121H and the second guide member 121U, and the second inclined surface portion 121b is provided only on the second guide member 121U.

[0060] By removing the second guide member 121U provided near the separation roller 103 from the first guide member 121H, the maintainability for replacing the separation roller 103 or the like can be improved.

[0061] <Other Embodiments> In the above-described embodiment, the second inclined surface portion 121b is constituted by the three ribs 121C, 121L, and 121R. However, the present invention is not limited thereto. For example, the second inclined surface portion 121b may be constituted by two or four or more ribs, or may be constituted by one protrusion.

[0062] Further, the second inclined surface portion 121b may be formed of a material having a small coefficient of friction, such as polyacetal resin. Thereby, the conveyance resistance of the sheet can be further reduced.

[0063] Also, in any of the above-described embodiments, the electrophotographic printer 200 has been described. However, the present invention is not limited thereto. For example, the present invention can also be applied to an inkjet method or an offset printing method image forming apparatus that forms an image on a sheet by discharging an ink liquid from a nozzle. Further, the present invention may be applied to a sheet feeding device provided in an ADF (Auto Document Feeder) or an option feeder.

Description of Reference Numerals

[0064] 19: Image forming unit / 100: Sheet feeding device (multi-feeding device) 101: Feeding rotating body (pickup roller) / 105a: Sheet support surface / NP: Separation unit (separation nip) / 121: Conveyance guide / 121a: First inclined surface (first inclined surface portion) / 121aU, 121bQ: Upstream end / 121b: Second inclined surface (second inclined surface portion) / 121bJ: Downstream end / 121C: Rib, first rib / 121H: First guide member / 121L: Rib, second rib / 121R: Rib, third rib / 121 U : Second guide member / 200: Image forming apparatus (printer) / AR: Region / L1, L2: Length / L4, L5: Distance / LN: Extension line / W: Width direction / X: Sheet conveyance direction / θ1, θ2: Angle

Claims

1. a sheet support surface for supporting a sheet; a feeding rotator for feeding the sheet supported on the sheet support surface; a separating unit for separating the sheets fed by the feeding rotator one by one; a conveying guide for guiding the sheet fed by the feeding rotator toward the separating unit, comprising: the conveying guide has a first inclined surface and a second inclined surface for guiding the sheet fed by the feeding rotator toward the separating unit; at least a part of the second inclined surface is disposed at a position overlapping the first inclined surface in the sheet conveying direction; when viewed in the width direction orthogonal to the sheet conveying direction, the angle on the feeding rotator side formed by the sheet support surface and the second inclined surface is larger than the angle on the feeding rotator side formed by the sheet support surface and the first inclined surface; the second inclined surface is composed of a plurality of ribs integrally formed with the first inclined surface; the plurality of ribs include a first rib provided at a position overlapping the feeding rotator in the width direction, a second rib disposed on one side of the first rib in the width direction, and a third rib disposed on the other side of the first rib in the width direction; A sheet feeding device characterized by the above.

2. The second rib and the third rib are disposed at positions not overlapping the feeding rotator in the width direction. The sheet feeding device according to claim 1, characterized by the above.

3. The distance between the first rib and the second rib and the distance between the first rib and the third rib are shorter than the length of the feeding rotator in the width direction. The sheet feeding device according to claim 1 or 2, characterized by the above.

4. A sheet support surface for supporting a sheet; a feeding rotator for feeding the sheet supported on the sheet support surface; a separating unit for separating the sheets fed by the feeding rotator one by one; a conveying guide for guiding the sheet fed by the feeding rotator toward the separating unit, comprising: the conveying guide has a first inclined surface and a second inclined surface for guiding the sheet fed by the feeding rotator toward the separating unit; at least a part of the second inclined surface is disposed at a position overlapping the first inclined surface in the sheet conveying direction; When viewed in the width direction orthogonal to the sheet conveyance direction, the angle on the feed rotator side formed by the sheet support surface and the second inclined surface is larger than the angle on the feed rotator side formed by the sheet support surface and the first inclined surface. At least a part of the region where the second inclined surface is disposed is provided at a position overlapping the feed rotator in the width direction. The length of the region where the second inclined surface is disposed in the width direction is shorter than twice the length of the feed rotator in the width direction. A sheet feeding device characterized by the above.

5. A sheet support surface for supporting a sheet, A feed rotator for feeding the sheet supported by the sheet support surface, A separating unit for separating the sheets fed by the feed rotator one by one, A conveyance guide for guiding the sheet fed by the feed rotator toward the separating unit, comprising: The conveyance guide has a first inclined surface and a second inclined surface for guiding the sheet fed by the feed rotator toward the separating unit. At least a part of the second inclined surface is disposed at a position overlapping the first inclined surface in the sheet conveyance direction. When viewed in the width direction orthogonal to the sheet conveyance direction, the angle on the feed rotator side formed by the sheet support surface and the second inclined surface is larger than the angle on the feed rotator side formed by the sheet support surface and the first inclined surface. The conveyance guide has a first guide member and a second guide member detachably supported by the first guide member. The first inclined surface is provided on the first guide member and the second guide member. The second inclined surface is provided on the second guide member. A sheet feeding device characterized by the above.

6. The sheet support surface is inclined downward as it goes downstream in the sheet conveyance direction. The first inclined surface and the second inclined surface are inclined upward as they go downstream in the sheet conveyance direction. The sheet feeding device according to any one of claims 1 to 5, characterized by the above.

7. When viewed in the width direction, the extension line of the sheet support surface intersects the first inclined surface and the second inclined surface. The sheet feeding device according to any one of claims 1 to 6, characterized by the above.

8. The upstream end of the second inclined surface in the sheet conveyance direction is disposed above the upstream end of the first inclined surface in the sheet conveyance direction. The downstream end of the second inclined surface in the sheet conveyance direction joins the first inclined surface at a position upstream of the separation portion in the sheet conveyance direction. The sheet feeding device according to any one of claims 1 to 7, characterized in that.

9. A sheet feeding device according to any one of claims 1 to 8, an image forming unit that forms an image on the sheet fed from the sheet feeding device, and is provided with. An image forming apparatus, characterized in that.

Images