Sheet discharge device and image forming apparatus

Abstract

To smoothly discharge sheets even when the number of stacked sheets is increased.SOLUTION: A stacking part (170) of the sheet discharge device includes a fixed member (20) forming a first stacking surface inclined upward in the vertical direction toward the downstream in the sheet discharge direction, and a movable member (21) forming a second stacking surface and rotatable with respect to the fixed member. The movable member is located at a first position where at least a part of the second support surface protrudes upward in the vertical direction from the first support surface in a state where no sheet is supported on the support portion, and rotates toward a second position lower than the first position in accordance with an increase in the number of sheets supported on the support portion. A rotation fulcrum (P) of the movable member is provided upstream of an intermediate position (U) between an upstream end (W) and a downstream end (X) of the stacking portion in the sheet discharge direction, and a distance in the sheet discharge direction from the rotation fulcrum of the movable member to the upstream end of the stacking portion is smaller than a distance in the sheet discharge direction from the rotation fulcrum of the movable member to the intermediate position of the stacking portion.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a sheet discharge device that discharges a sheet and an image forming apparatus that forms an image on a sheet. [Background technology]

[0002] In image forming devices such as printers, copiers, and multifunction devices, sheets on which images are formed using an electrophotographic mechanism or an inkjet printing unit are discharged to the outside of the device body by a pair of discharge rollers and stacked on a discharge tray as a finished product. At this time, it is preferable that the discharged sheets are stacked on the discharge tray in a state that makes them easy for the user to remove. Patent Document 1 describes a technique that provides a rib guide that protrudes above the discharge tray and is configured to descend depending on the number of sheets loaded, making it easy to remove the sheets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-38247 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the rib guide described in the above document rotates around the downstream end in the paper discharge direction as a pivot point. In this case, as the number of sheets increases and the rib guide descends, the inclination of the rib guide relative to the horizontal plane becomes steeper, and the height of the top sheet rises near the pivot point. As a result, when a large number of sheets are loaded, newly discharged sheets encounter significant resistance from the already loaded sheets, which can lead to poor discharge or misalignment of the sheets.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet discharge device that can smoothly discharge sheets even when a large number of sheets are stacked, and an image forming apparatus equipped with the same. [Means for solving the problem]

[0006] One aspect of the present invention is a sheet discharge device comprising a discharge means for discharging sheets and a stacking section on which the sheets discharged by the discharge means are stacked, wherein the stacking section has a fixed member forming a first stacking surface that is inclined vertically upward toward downstream in the sheet discharge direction, and a movable member that forms a second stacking surface and is rotatable relative to the fixed member, wherein when no sheets are loaded on the stacking section, the movable member is at a first position in which at least a portion of the second stacking surface protrudes vertically upward beyond the first stacking surface, and is configured to rotate toward a second position lower than the first position as the number of sheets loaded on the stacking section increases, wherein the rotational fulcrum of the movable member is located upstream of a midpoint between the upstream and downstream ends of the stacking section in the sheet discharge direction, and wherein the distance in the sheet discharge direction from the rotational fulcrum of the movable member to the upstream end of the stacking section is smaller than the distance in the sheet discharge direction from the rotational fulcrum of the movable member to the midpoint of the stacking section. [Effects of the Invention]

[0007] According to the present invention, it is possible to smoothly discharge sheets even when the number of stacked sheets is large. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of the upper surface side of the discharge tray (first discharge tray) according to the first embodiment. [Figure 3] FIG. 3 is a perspective view of the lower surface side of the discharge tray according to the first embodiment. [Figure 4] FIG. 3 is a cross-sectional view of the discharge tray according to the first embodiment (standby state). [Figure 5] FIG. 2 is a cross-sectional view of the discharge tray according to the first embodiment (fully loaded state). [Figure 6] 5A and 5B are cross-sectional views illustrating a state of a sheet discharging operation in the first embodiment. [Figure 7] 5A and 5B are cross-sectional views illustrating the movement of a sheet discharged onto a discharge tray in the first embodiment. [Figure 8] FIG. 3 is a cross-sectional view showing a state in which a plurality of sheets are stacked in the first embodiment. [Figure 9] FIG. 10 is a cross-sectional view illustrating a state in which a plurality of sheets are stacked in a comparative example. [Figure 10] FIG. 10 is a perspective view of a movable tray according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. [Example]

[0010] 1 is a schematic diagram of an image forming apparatus 100 according to Example 1. An apparatus body 101 of the image forming apparatus 100 houses an image forming unit 140 as an intermediate transfer tandem type electrophotographic mechanism in which four image forming stations 1Y, 1M, 1C, and 1K that form four-color toner images are arranged along an intermediate transfer belt 145.

[0011] At each of the image forming stations 1Y, 1M, 1C, and 1K, a toner image is formed by an electrophotographic process. That is, a photoconductor 141, which serves as an image carrier, is uniformly charged in advance by a charger and then scanned and exposed to light from an exposure device 142, thereby writing an electrostatic latent image onto the surface of the photoconductor 141. This electrostatic latent image is developed into a toner image by charged toner particles supplied from a developer 143. The toner image carried by the photoconductor 141 is temporarily transferred by a primary transfer roller 144 to an intermediate transfer belt 145, which serves as an intermediate transfer member. At this time, the yellow, magenta, cyan, and black toner images formed at each of the image forming stations 1Y, 1M, 1C, and 1K are superimposed on the intermediate transfer belt 145, thereby forming a full-color toner image. This full-color toner image is carried by the intermediate transfer belt 145 and transported to the secondary transfer unit 130.

[0012] In parallel with this image formation process, a conveyance process for sheets S, which are recording materials, is carried out. The sheets S are stored in a cassette that can be inserted into and removed from the main body 101 of the image forming apparatus, with the sheets S stacked on a lift-up device of the sheet feeding device. Various sheet materials of different sizes and materials can be used as the sheets S, including paper such as plain paper and cardboard, surface-treated sheets such as plastic film, cloth, and coated paper, and specially shaped sheets such as envelopes and index paper. The sheets S stored in the cassette are fed one by one by a feeding unit 110, which serves as a feeding means, based on the progress of the image formation operation by the image forming stations 1Y, 1M, 1C, and 1K.

[0013] The sheet S fed by the feeding unit 110 is transported to the skew correction device 120 via a transport path, and after undergoing skew correction and timing correction in the skew correction device 120, is sent to the secondary transfer section 130. The secondary transfer section 130 is a nip formed by a secondary transfer inner roller 131 and a secondary transfer outer roller 132 that face each other with an intermediate transfer belt 145 sandwiched therebetween. The toner image carried on the intermediate transfer belt 145 is transferred to the sheet S in the secondary transfer section 130 by applying a mechanical pressure and an electrostatic load bias.

[0014] The sheet S that has passed through the secondary transfer unit 130 is conveyed to the fixing unit 150. The fixing unit 150 has a pair of rotating bodies that rotate while sandwiching the sheet S, and a heat source such as a halogen lamp, and heats and pressurizes the toner image on the sheet while conveying the sheet S. This melts the toner particles and then solidifies the toner image onto the sheet S. The sheet S with the fixed image is guided by a first flap 151, which is a switching member, to a path toward first discharge rollers 160 (lower discharge path) or a path toward second discharge rollers 161 (upper discharge path).

[0015] The image forming apparatus 100 of this embodiment is provided with a first discharge tray 170 and a second discharge tray 171 as discharge destinations for sheets S on which an image has been formed. The sheets S guided to the lower discharge path are discharged to the outside of the apparatus body 101 by first discharge rollers 160 and stacked on the first discharge tray 170. The sheets S guided to the upper discharge path are discharged to the outside of the apparatus body 101 by second discharge rollers 161 and stacked on the second discharge tray 171. The first discharge rollers 160 and the first discharge tray 170 form a first discharge section 190, and the second discharge rollers 161 and the second discharge tray 171 form a second discharge section 191. Both the first discharge section 190 and the second discharge section 191 are examples of sheet discharge devices that discharge sheets.

[0016] On the other hand, when double-sided printing is performed, the sheet S, on which an image has been formed on its first side, is guided to the upper discharge path by the first flap 151, and then is switched back and conveyed by the reversing operation of the second discharge roller 161. The second flap 152 guides the sheet S after the switchback to the double-sided conveying path 180. Then, the sheet S reaches the skew correction device 120 again via the double-sided conveying path 180, and an image is formed on its second side in the same process as on the first side, and then the sheet is discharged to the first discharge tray 170 or the second discharge tray 171.

[0017] Both the first discharge tray 170 and the second discharge tray 171 have an inclined surface that slopes vertically upward toward the downstream side in the discharge direction (left side in the figure). Therefore, the sheet S discharged onto each discharge tray is returned to the upstream side in the discharge direction by its own weight and is aligned by abutting against an alignment reference wall provided on the device main body 101.

[0018] The image forming apparatus 100 of this embodiment has a so-called internal discharge type configuration in which a sheet discharge space is provided between the image reading device 102, which is installed at the top of the apparatus main body 101 in the vertical direction, and the image forming unit 140. Of the first discharge tray 170 and second discharge tray 171, which are installed in two levels, one above the other, in this discharge space, the lower first discharge tray 170 is attached to the top of the apparatus main body 101. The image reading device 102 is a device that scans an original document using an image sensor unit equipped with an image sensor, reads image information, and transfers it to a control circuit in the apparatus main body 101.

[0019] [Output tray] The configuration of the first discharge section 190, which is the sheet discharge device of this embodiment, will be described below. In the following description, the first discharge tray 170 will be simply referred to as the "discharge tray 170," and the first discharge roller 160 will be simply referred to as the "discharge roller 160." Furthermore, the horizontal direction in which a sheet discharged from the discharge roller 160 moves will be referred to as the "sheet discharge direction D1," and the axial direction of the discharge roller 160 (the vertical direction and the direction perpendicular to the sheet discharge direction D1) will be referred to as the "width direction D2."

[0020] Fig. 2 is a perspective view of the discharge tray 170 as seen from above (from the front side), and Fig. 3 is a perspective view of the discharge tray 170 as seen from below (from the back side). The discharge tray 170, which is the stacking section in this embodiment, is a tray unit having a fixed tray 20 as a fixed member that forms a first stacking surface, and a movable tray 21 as a movable member that forms a second stacking surface and is movable relative to the fixed member. The sheets S discharged by the discharge rollers 160 are stacked on the stacking surface formed by the fixed tray 20 and movable tray 21.

[0021] The front side of the fixed tray 20 (FIG. 2) is provided with an upper surface 20s constituting a first stacking surface and a plurality of slits 20b aligned in the width direction D2 from the upstream end to the center in the sheet discharge direction D1. As will be described later, arc ribs 21d of the movable tray 21 protrude from each slit 20b formed in the upper surface 20s. Note that, on the upper surface 20s, a plurality of guide ribs 20g extend along the sheet discharge direction D1 at positions corresponding to each slit 20b in the width direction D2. In other words, the arc ribs 21d of the movable tray 21 and the guide ribs 20g of the fixed tray 20 are aligned in the sheet discharge direction D1.

[0022] A rotation hole 20d is provided on the rear side (FIG. 3) of the fixed tray 20 at the upstream end in the sheet discharge direction, and two fixed tray hook portions 20e for attaching the biasing springs 22 are provided in the center in the sheet discharge direction. The fixed tray 20 is attached to the image forming apparatus and fixed to the apparatus main body 101 by engaging four attachment portions 20c provided on the rear side with engagement portions of the apparatus main body 101 (FIG. 1).

[0023] The movable tray 21 includes a plurality of arcuate ribs 21d (FIG. 2) that form the second stacking surface. The plurality of arcuate ribs 21d are provided at positions corresponding to the slits 20b in the width direction D2 of the fixed tray 20, and at least some of them extend from the upstream end to the downstream end of the movable tray 21 in the sheet discharge direction D1. The upper ends of the arcuate ribs 21d are inclined upward toward the downstream side in the sheet discharge direction D1, and are curved in a substantially arc shape so that the angle of inclination with respect to the horizontal plane decreases toward the downstream side in the sheet discharge direction D1. In this embodiment, nine arcuate ribs 21d are disposed. The distance M between the five central arcuate ribs 21d in the width direction is narrower than the distance N between the two arcuate ribs 21d on both sides in the width direction.

[0024] Furthermore, the movable tray 21 has, on the rear side (FIG. 3) of the fixed tray 20, a plate-shaped main body 21f that connects the multiple arc ribs 21d, two rotation shafts 21a that serve as rotation fulcrums for the movable tray 21, and two movable tray hook portions 21b. Each arc rib 21d extends vertically upward from the main body 21f and can protrude above the fixed tray 20 through a slit 20b in the fixed tray 20.

[0025] The two rotation shafts 21a are provided at the upstream end of the movable tray 21 in the sheet discharge direction D1 and are fitted into rotation holes 20d of the fixed tray 20, respectively. This allows the movable tray 21 to rotate relative to the fixed tray 20 around a rotation axis (a virtual line passing through the two rotation shafts 21a) extending in the width direction D2. The two movable tray hook portions 21b are provided at the downstream end of the movable tray 21 in the sheet discharge direction D1. A biasing spring 22 is attached between each of the two sets of movable tray hook portions 21b and fixed tray hook portion 20e, and biases the movable tray hook portions 21b toward the fixed tray hook portions 20e (i.e., so that the movable tray 21 moves upward). The downstream end of the movable tray 21 in the sheet discharge direction D1 is provided with abutment portion 21c (see FIGS. 4 and 5) that abuts against the rear surface of the fixed tray 20. The position where the abutting portion 21c abuts against the fixed tray 20 (FIG. 4) is the upper limit position of the rotation range of the movable tray 21.

[0026] The discharge tray 170 assembled as described above is attached to the apparatus main body 101 by the four attachment portions 20c of the fixed tray 20. Note that the discharge tray 170 (and the second discharge tray 171 above it) in this embodiment are detachable from the apparatus main body 101, and by removing both discharge trays, a space for installing a post-processing device is secured in the discharge space within the body of the image forming apparatus 100.

[0027] [Tray shape details] Next, the shape of the stacking surface formed by the discharge tray 170 including the movable tray 21 and its operation will be described. FIG. 4 is a cross-sectional view of the discharge tray 170 when the movable tray 21 is in a standby state, and FIG. 5 is a cross-sectional view of the discharge tray 170 when the movable tray 21 is in a maximum rotation state. Note that the standby state refers to a state in which no sheets are stacked on the discharge tray 170, and the maximum rotation state refers to a state in which the movable tray 21 has rotated downward to the maximum extent from the standby state position. The position of the movable tray 21 in the standby state is the first position in this embodiment, and the position of the movable tray 21 in the maximum rotation state is the second position in this embodiment. Furthermore, unless otherwise specified in the following description, "upstream" and "downstream" refer to the upstream or downstream positional relationship in the sheet discharge direction D1.

[0028] The first stacking surface WX is a surface formed by the fixed tray 20 from position W to position X. Position W is the upstream end position in the sheet discharge direction D1 of the area on the upper surface of the fixed tray 20 that can support the lower surface of a sheet, and position X is the downstream end position of that area.

[0029] The second stacking surface YZ is a surface formed by the arc ribs 21d of the movable tray 21 from position Y to position Z. That is, in this embodiment, the second stacking surface YZ is a virtual surface that connects the upper ends of the multiple arc ribs 21d aligned in the width direction in the width direction. Position Y is the upstream end position in the sheet discharge direction D1 of the area where the upper ends of the arc ribs 21d can support the underside of a sheet, and position Z is the downstream end position thereof.

[0030] The movable tray 21 is disposed near the upstream side of the discharge tray 170 in the sheet discharge direction D1. For example, the intermediate position V of the second stacking surface in the sheet discharge direction D1 (the midpoint between positions Y and Z) is located upstream of the intermediate position U of the first stacking surface (the midpoint between positions W and X), which is also the midpoint of the entire discharge tray 170. The distance from the upstream end of the first stacking surface WX to the upstream end of the second stacking surface YZ is shorter than the distance from the downstream end of the first stacking surface WX to the downstream end of the second stacking surface YZ (WY <XZ)。

[0031] Furthermore, the upstream end (Y) of the second stacking surface YZ is located in an upstream end region of the discharge tray 170. For example, the upstream end (Y) of the second stacking surface YZ is located upstream of an upstream quarter point Q1 when the range of the stacking surface of the discharge tray 170 in the sheet discharge direction D1 is divided into four equal parts. On the other hand, the downstream end (Z) of the second stacking surface YZ extends downstream of the intermediate position U of the discharge tray 170. However, the downstream end (Z) of the second stacking surface YZ is located upstream of a downstream quarter point Q3 when the range of the stacking surface of the discharge tray 170 is divided into four equal parts.

[0032] The pivot point P of the movable tray 21 is provided near the upstream end of the discharge tray 170. Specifically, the pivot point P is located upstream of the intermediate position U of the discharge tray 170 in the sheet discharge direction D1, and the distance from the pivot point P to position X is shorter than the distance from the pivot point P to the intermediate position U. In other words, the pivot point P is located upstream of the upstream quarter point Q1 of the stacking surface of the discharge tray 170.

[0033] Furthermore, the rotation support point P of the movable tray 21 is provided near the upstream end of the movable tray itself. Specifically, the rotation support point P is located upstream of the intermediate position V of the movable tray 21 in the sheet discharge direction D1, and the distance from the rotation support point P to position Y is shorter than the distance from the rotation support point P to the intermediate position V. In other words, the rotation support point P is located upstream of the upstream quarter point q1 when the range of the second stacking surface in the sheet discharge direction D1 is divided into four equal parts.

[0034] In the illustrated configuration example, the pivot point P of the movable tray 21 is located at a position within the above-mentioned range that is closer to the upstream end of the discharge tray 170 and the upstream end of the movable tray itself. For example, the distance (PW) in the sheet discharge direction D1 from the pivot point P to the upstream end of the discharge tray 170 is less than one-eighth of the entire range (WX) of the stacking surface of the discharge tray 170. Furthermore, the distance (PY) in the sheet discharge direction D1 from the pivot point P to the upstream end of the second stacking surface YZ is less than one-eighth of the entire range (YZ) of the stacking surface of the discharge tray 170.

[0035] In the standby state, the first stacking surface WX and the second stacking surface YZ are both configured as inclined surfaces that are inclined vertically upward toward the downstream side in the sheet discharge direction D1. In other words, the fixed tray 20 and the movable tray 21 are inclined so as to generate a force that returns the sheets discharged onto the discharge tray 170 in the standby state to the upstream side in the discharge direction.

[0036] The inclination angles of the first loading surface WX and the second loading surface YZ will be described in detail. The first loading surface WX has different average inclination angles between the section (W-Z) upstream of the downstream end of the second loading surface YZ and the section (Z-X) downstream of the downstream end of the second loading surface YZ. When the inclination angle of the upstream section (W-Z) of the first loading surface WX is θa [degrees] and the inclination angle of the downstream section (Z-X) is θb [degrees], θa > θb. Note that in this embodiment, both the upstream and downstream sections of the first loading surface WX are formed in a flat shape inclined at a constant inclination angle of θa or θb. When the inclination angles of each section are not constant, θa and θb represent the average inclination angles.

[0037] The second stacking surface YZ is configured so that the inclination angle of at least its upstream portion is greater than the inclination angle θa of the upstream section of the first stacking surface WX where the second stacking surface YZ and the sheet discharge direction D1 overlap. In other words, if the inclination angle of the tangent of the arc rib 21d relative to the horizontal plane is θc [degrees], the inclination angle θc gradually decreases from the upstream side to the downstream side. At this time, the second stacking surface YZ is configured so that θc > θa at least in the upstream end region where the inclination angle θc is maximum. In other words, if the inclination angle θc of the second stacking surface YZ in the upstream end region of the second stacking surface YZ is θcmax, θcmax is greater than θa.

[0038] In the illustrated configuration example, the settings are θa=20[degrees], θb=6[degrees], and θcmax=32[degrees]. However, the inclination angle of the stacking surface is not limited to this, and can be changed as appropriate depending on the material and size of the main sheets expected to be used, the surface properties of the material that makes up the discharge tray 170, etc.

[0039] When no sheets are stacked on the discharge tray 170, the biasing force of the biasing spring 22 keeps the movable tray 21 in a standby state in which the second stacking surface YZ protrudes most upward from the first stacking surface WX. At this time, as shown in FIG. 4, the entire second stacking surface YZ is positioned above the first stacking surface WX. The movable tray 21 rotates downward as shown by arrow B in FIG. 5 in response to a force from above, that is, the weight of the discharged sheets. The biasing force of the biasing spring 22 is set so that even when a small force is applied, the abutment portion 21c of the movable tray 21 remains in contact with the fixed tray 20, and vibration noise is not easily generated.

[0040] On the other hand, the biasing force of the biasing spring 22 is set so that when a certain number of sheets are stacked on the discharge tray 170, the tray 21 rotates to its maximum rotational position in accordance with the weight of the sheets. As described below, when the number of stacked sheets is small, the second stacking surface YZ, which has a steeper inclination, supports the sheets, increasing the return force acting on the sheets and providing better alignment. When the sheet load increases, the lower end 21g of the movable tray 21 abuts against the mounting surface 210 of the device main body 101, restricting downward rotation and causing the movable tray 21 to rotate to its maximum rotational position. At this time, the biasing spring 22 is set to its maximum extension but not to enter a plastic deformation range. This prevents the function of the biasing spring 22 from being impaired even if the movable tray 21 is accidentally rotated manually. Furthermore, in the maximum rotational position, the second stacking surface retracts below the first stacking surface at least in the range from the intermediate position V of the second stacking surface to the downstream end (Z) of the second stacking surface.

[0041] The movable tray 21 configured as described above has its rotation fulcrum located at the upstream end of the discharge tray 170 in the sheet discharge direction, so that the inclination angle θc of the second stacking surface YZ gradually approaches the inclination angle θa from θcmax as the number of stacked sheets increases. Therefore, as the number of stacked sheets increases, the return force that the second stacking surface YZ applies to the sheets decreases, while the second stacking surface YZ descends and the inclination of the portion of the sheets supported by the second stacking surface YZ decreases. In other words, the posture of the sheet stack stacked on the discharge tray 170 becomes closer to horizontal, and the position of the bottom surface of the sheet stack becomes lower. Therefore, as will be described later, it is possible to smoothly discharge sheets even when the number of sheets stacked on the tray increases.

[0042] The tilt angle θb of the downstream portion of the fixed tray 20 is set smaller than the tilt angle θa of the upstream portion and the maximum tilt angle (θcmax) of the movable tray 21. This is to prevent the vertical occupation area of ​​the discharge tray 170 from becoming too large, and in this embodiment, this is to ensure space for the second discharge tray 171 provided above the discharge tray 170 and the sheets stacked thereon. Furthermore, by setting the tilt angle θb of the downstream portion to a small value, it is possible to prevent relatively large sheets from experiencing large conveyance resistance from the stacking surface during sheet discharge, which can lead to discharge failures. However, the reason why θb is not set to 0 degrees or less even in the downstream portion of the fixed tray 20 is to generate a return force on the sheet at any position on the discharge tray 170.

[0043] The fixed tray 20 and movable tray 21 that form the first stacking surface WX and the second stacking surface YZ each have ribs extending in the discharge direction, and in particular, the second stacking surface is formed by arc ribs 21d. Such ribs are effective in reducing the transport resistance that the tray surface experiences on sheets being discharged onto the discharge tray 170. Furthermore, because the second stacking surface YZ is curved so that the inclination decreases toward the downstream side, it is possible to prevent large steps or grooves that could cause sheets to get caught at the boundary between the second stacking surface YZ and the first stacking surface, regardless of the rotation angle of the movable tray 21.

[0044] Furthermore, the arc rib 21d of the movable tray 21 protrudes slightly above the first stacking surface WX (i.e., above the guide rib of the fixed tray 20) near the upstream end position Y and the downstream end position Z of the second stacking surface YZ. By forming the arc rib 21d slightly higher, it is possible to prevent the leading or trailing end of a sheet in the sheet discharge direction from getting caught on the longitudinal ends of the slit 20b of the fixed tray 20. Furthermore, the downstream end of the slit 20b in the sheet discharge direction is formed in a tapered shape that narrows toward the downstream. This prevents the sheet from getting caught on the downstream end of the slit 20b even if the movable tray 21 is rotated downward from the standby state and the downstream portion of the arc rib 21d is below the slit 20b and a new sheet is discharged.

[0045] Furthermore, the first stacking surface WX is formed by the upper surface of the fixed tray 20, which is a plate-like member extending in the sheet discharge direction and width direction, and the second stacking surface YZ is formed by a rib-like member extending in the sheet discharge direction and protruding through a slit provided in the plate-like member. Therefore, when the movable tray 21 is in a standby state, most of the opening of the slit 20b is blocked by the arc rib 21d, and when the movable tray 21 rotates downward due to the weight of the sheet, at least a portion of the opening of the slit 20b is blocked by the sheet. Therefore, when an opening is provided in the fixed tray 20 to allow the movable tray 21 to appear and disappear, the possibility of foreign matter falling to the back side of the discharge tray 170 can be reduced.

[0046] The fixed tray 20 is provided with a removal groove 20a for removing sheets. The removal groove 20a extends toward one end of the discharge tray 170 (the front side of the image forming apparatus) in the width direction D2. The removal groove 20a is provided at a position overlapping with the movable tray 21 in the sheet discharge direction D1, and the upper surface 20s of the fixed tray 20 is formed as a concave shape recessed downward. To enable a user to access the sheets through the removal groove 20a, some of the arc ribs 21d that overlap with the removal groove 20a in the width direction D2 are formed only outside the removal groove 20a in the sheet discharge direction D1. The wall surface on the downstream side of this removal groove 20a is also set at an inclination angle that can prevent the leading edge of the sheet from getting caught.

[0047] Furthermore, the slits 20b formed in the fixed tray 20 are of the minimum necessary length, and the fixed tray 20 is formed as a member that is connected in the width direction D2 on both the upstream and downstream sides of the movable tray 21. This not only has the advantage of ensuring the rigidity of the fixed tray 20, but also takes into consideration the fluidity when the fixed tray 20 is injection molded from a resin material. An example of the resin material is PC+ABS (an alloy of polycarbonate and acrylonitrile-butadiene-styrene copolymer). The fixed tray 20 may be a single member as a whole, or may be formed by molding an upstream portion and a downstream portion as separate members and then combining them.

[0048] [Moveable tray operation] The state when a sheet is discharged onto the stacking surface of the discharge tray 170 configured as described above will be described. Fig. 6 is a cross-sectional view of the first discharge section 190 showing the state in which the first sheet S is being discharged by the discharge rollers 160, and Fig. 7 is a cross-sectional view of the first discharge section 190 showing the state in which the discharged first sheet S is aligned by the stacking surface of the discharge tray 170.

[0049] As shown in FIG. 6, the discharge rollers 160 are configured to discharge the sheet S in a position inclined upward toward the downstream side in the sheet discharge direction D1 in the horizontal direction. In other words, the discharge rollers 160 are a pair of rollers arranged at a nip angle (the angle in the direction perpendicular to the inter-roller axis direction when the pair of rollers feeds the sheet from the nip portion) that faces slightly upward. The discharge rollers 160 are also provided with a stiffening member that imparts rigidity to the sheet S by curving (wavinessing) the sheet S when viewed from the downstream side in the sheet discharge direction D1. Therefore, the sheet S is discharged downstream in the sheet discharge direction D1 while tracing an arch-shaped trajectory from the position where it is nipped by the discharge rollers 160 toward its leading edge. The leading edge of this sheet S comes into contact with the movable tray 21 of the discharge tray 170, which is in a standby state, at position P1, and moves while sliding against the fixed tray 20 and the movable tray 21, and the trailing edge of the sheet S is kicked out by the discharge rollers 160.

[0050] 7, the sheet S, whose trailing end has been kicked out, returns to the upstream side in the sheet discharge direction D1 (arrow R) according to the inclination of the stacking surface of the discharge tray 170, particularly the inclination of the inclined surface (second stacking surface) formed by the movable tray 21. Then, the sheet S stops when the trailing end in the sheet discharge direction D1 hits an alignment wall 162 provided on the apparatus main body 101. The alignment wall 162 is a reference surface that aligns the sheet position by coming into contact with the trailing end of the sheet discharged onto the discharge tray 170.

[0051] The behavior of the first sheet S as it moves toward the alignment wall 162 is affected by the magnitude of the frictional force acting between the sheet S and the stacking surface of the discharge tray 170. For the second and subsequent sheets S, the influence of the friction between the sheet S and the discharge tray 170 becomes smaller, and instead the influence of the friction between the sheets becomes greater.

[0052] The position P1 (the position where the leading edge of the first sheet is expected to first contact the stacking surface of the discharge tray 170) is preferably a position some distance away from the discharge roller 160 in the sheet discharge direction D1 and at approximately the same height as the nip height of the discharge roller 160. Furthermore, the movable tray 21 is configured so that the angle of contact between the leading edge of the sheet S and the second stacking surface does not become too large. In the standby state, the movable tray 21 of this embodiment has a maximum inclination angle (32 degrees) at the upstream end, and the inclination angle at the downstream end is approximately equal to the inclination angle (6 degrees) of the downstream portion of the fixed tray 20. This configuration reduces the conveyance resistance that the sheet S receives from the stacking surface, ensures the maximum number of sheets that can be stacked on the discharge tray 170, enables stable discharge of low-rigidity sheets, and improves the alignment of the stacked sheets.

[0053] Incidentally, the sheets S discharged by the discharge roller 160 include sheets such as recycled paper and thin paper, and these sheets tend to have a large degree of curl at the sheet edges, for example, in a high-humidity environment. A case where a relatively large number of such highly curled sheets are stacked will be described with reference to FIGS. 8 and 9. FIG. 8 is a cross-sectional view of the first discharge section 190 and the second discharge section 191, showing a state in which a plurality of curled sheets S are stacked on the discharge tray 170. FIG. 9 is a cross-sectional view of the first discharge section 190 and the second discharge section 191, showing a state in which the movable tray 21 is fixed in a standby state position, as a reference example. However, the number of sheets S shown in FIGS. 8 and 9 is not intended to specify the actual number of sheets.

[0054] The image forming apparatus of this embodiment can handle both small-size sheets, such as A4, and large-size sheets, such as A3. Curl occurs in both sizes, but the edges of the curled sheets tend to rise upward due to the curvature. Small-size sheets are particularly short compared to large-size sheets, making them more likely to form a steeply inclined surface due to curl. Additionally, as mentioned above, the stacking surface of the discharge tray 170 is configured such that the inclination angle on the upstream side of the sheet discharge direction is greater than that on the downstream side. Small-size sheets are primarily supported by the upstream stacking surface, which has a steeper inclination, and the combined effect of the inclination of the stacking surface makes the effects of sheet curl more pronounced.

[0055] 8, small-size sheets S are stacked in a curled state. In the case of small-size sheets S, when the trailing edge of the sheet in the sheet discharge direction D1 abuts against the alignment wall 162, the leading edge of the sheet is located upstream of the downstream end of the movable tray 21. The sheets S are curled so that the lower surface (the surface facing the stacking surface of the discharge tray 170), which is the image surface, is convex. Therefore, the middle portion of the stacked stack T of sheets S is supported by contacting the stacking surfaces of the fixed tray 20 and the movable tray 21, while the end portion in the sheet discharge direction D1 stands up.

[0056] Here, due to the weight of the stack of sheets T, the movable tray 21 has rotated downward from its standby position (FIGS. 6 and 7), and a portion of the arc rib of the movable tray 21 has retreated below the upper surface of the fixed tray 20 via the slit. The inclination of the stacking surface formed by the movable tray 21 is also gentler than in the standby state. In other words, due to the increased amount of stacked sheet stacks, at least a portion of the second stacking surface has retreated below the first stacking surface, and the inclination of the second stacking surface relative to the horizontal plane is reduced. Therefore, when the discharged sheets S are curled, a situation in which the discharge space above the discharge tray 170 is occupied by the stack of sheets T consisting of a relatively small number of sheets S is avoided.

[0057] 9, the movable tray 21 is fixed in a standby position using the spacer 203, and the height and inclination of the second stacking surface do not change even if the weight of the stacked sheet T increases. Therefore, if the discharged sheets S are curled, the downstream ends of the sheets rise upward, and the stacked sheet T consisting of a relatively small number of sheets S occupies the discharge space above the discharge tray 170.

[0058] In this case, the angle of contact when the leading edge of the sheet S discharged from the discharge rollers 160 contacts the top surface of the stack of sheets T becomes larger than when the movable tray 21 is rotated as shown in FIG. 8 . As a result, the sheet S is likely to collide with the top surface of the stack of sheets T and receive a large force. Furthermore, the conveyance resistance increases when the sheet S slides against the top surface of the stack of sheets T (especially the curled portion downstream of the stack of sheets T) as it is discharged. As a result, the sheet S may not be properly kicked out from the discharge rollers 160, and the trailing edge of the sheet S may remain in the nip of the discharge rollers 160, preventing it from falling onto the discharge tray 170 (rear-edge leaning). Furthermore, if the trailing edge of the preceding sheet remains near the nip of the discharge rollers 160 when the following sheet reaches the discharge rollers 160, the leading edge of the following sheet may collide with the trailing edge of the preceding sheet, preventing the preceding and following sheets from being properly discharged.

[0059] In contrast, in this embodiment, as described above, the movable tray 21 rotates around a pivot point provided near the upstream end of the discharge tray 170, thereby lowering the height of the top surface of the stack of stacks T to ensure discharge space and reduce the inclination of the stack of stacks T. As a result, compared to the reference example shown in Fig. 9, the resistance force applied to the discharged sheets is reduced, preventing discharge failures and enabling smooth discharge of sheets.

[0060] Furthermore, since this embodiment is an internal discharge type configuration, there is a limit to the height of the discharge space of the discharge tray 170. In such a case, a configuration in which the movable tray 21 rotates about a pivot point provided near the upstream end of the discharge tray 170 has the advantage of ensuring the discharge space. In particular, in this embodiment, the second discharge tray 171, which is another second stacking section, is provided above the discharge tray 170, which is the first stacking section, so there is a great advantage in being able to ensure the discharge space. In this embodiment, the distance M between the five central arc ribs 21d in the width direction is narrow, so that sheets that are small in size in the width direction can be stably supported by the central arc ribs 21d. [Example]

[0061] In the second embodiment, instead of the configuration of the first embodiment in which the movable tray 21 rotates due to the weight of the sheets, a configuration example will be described in which a drive source is provided to drive and rotate the movable tray 21. Hereinafter, elements having the same configuration and function as those in the first embodiment will be assigned the same reference numerals as those in the first embodiment, and descriptions thereof will be omitted.

[0062] 10 is a perspective view showing the movable tray 21 and its drive configuration of this embodiment. The movable tray 21 is provided with fan gears 21e, 21e at two locations in the width direction at the downstream end in the sheet discharge direction D1 opposite the rotation shaft 21a. The fan gears 21e, 21e are connected to an input / output shaft 220 via output gears 222, 222. An input gear 221 that meshes with a gear 211 of a rotation motor 212, which is a drive source, is provided at the end of the input / output shaft 220. Therefore, when the rotation motor 212 rotates forward and backward, the movable tray 21 is driven via a gear train and rotates up and down around the rotation shaft 21a.

[0063] A stepping motor is preferably used for this rotation motor 212. In this case, the rotation amount of the movable tray 21, i.e., the tilt angle, can be set with high precision to any value that does not depend on the weight of the sheets on the tray. Therefore, even if the number of stacked sheets is the same, it is possible to set different rotation amounts of the movable tray 21 depending on conditions such as whether the environment is high humidity, which makes sheets more likely to curl, or whether the stack height per sheet is large. In other words, it is possible to set an appropriate rotation amount according to the operating conditions of the image forming apparatus.

[0064] By using a sensor that detects the position of the movable tray 21 (for example, a switch that detects that the movable tray 21 is in a standby position), it is possible to more accurately control the amount of rotation of the movable tray 21. In addition, by arranging a sensor that detects the height of the top surface of the sheet stack loaded on the discharge tray 170 above the movable tray 21 and controlling the amount of rotation of the movable tray 21 based on the detection result, it is possible to more accurately control the height of the top surface of the sheet stack.

[0065] In this embodiment, the rotary motor 212 is used as a drive source, and the movable tray 21 is rotated by a gear transmission mechanism shown in FIG. 10, but other drive configurations may also be used.

[0066] (Variation) In the above-described first and second embodiments, it has been described that the first loading surface is configured by the upper surface 20s of the fixed tray 20, and the second loading surface is formed by a plurality of arc ribs 21d provided on the movable tray 21. However, the first loading surface may be formed by a plurality of rib-shaped members, and the second loading surface may be a plate-shaped member having slits that allow such rib-shaped members to pass through.

[0067] Furthermore, instead of the arc-shaped arc rib 21d, a rib whose upper end is formed by a curve other than an arc may be arranged on the movable tray 21. In this case as well, it is preferable that the upper end of the rib is inclined upward toward the downstream in the sheet discharge direction D1 in the standby state, and is curved (including bent in a broken line) so that the angle of inclination with respect to the horizontal plane decreases toward the downstream in the sheet discharge direction D1.

[0068] Although the present embodiment has been described with respect to a sheet discharge device used in an image forming apparatus having an electrophotographic image forming means, the present technology is also useful in other image forming apparatuses. For example, the present technology can be suitably applied to an image forming apparatus having an inkjet printing unit as an image forming means, since curling of the sheet may occur during image formation.

[0069] Furthermore, the sheet discharge device in this disclosure is not limited to a device that discharges sheets as recording materials from the main body of an image forming apparatus. For example, it may be a sheet discharge device that discharges read sheets in an image reading apparatus that reads image information using an image sensor while automatically feeding original sheets. It may also be a sheet discharge device that discharges processed sheets in a sheet processing apparatus that is connected to an image forming apparatus and receives image-formed sheets from the image forming apparatus and performs processes such as punching and folding. [Explanation of symbols]

[0070] 20...Fixed member (fixed tray) / 21...Movable member (movable tray) / 100...Image forming apparatus / 101...Apparatus main body / 140...Image forming means (image forming section) / 160...Discharge means (discharge roller) / 162...Alignment wall / 170...Stacking section, first stacking section (discharge tray) / 171...Second stacking section (discharge tray) / 190...Sheet discharge device (first sheet discharge section) / P...Pivot fulcrum

Claims

1. Image forming means for forming an image on a sheet, Discharge means for discharging the sheet on which the image has been formed by the image forming means in the sheet discharge direction, A loading member having an inclined portion that slopes upward toward the downstream direction in the sheet discharge direction, on which the sheets discharged by the discharge means are loaded, An image reading device for reading an image of a document is positioned above the aforementioned loading member, and is positioned so as to overlap with the aforementioned loading member in the horizontal direction. A wall portion that abuts the rear end of the sheet loaded on the loading member in the direction of sheet discharge, An image forming apparatus having, The loading member is provided with a downwardly recessed retrieval groove, which allows the user to access the sheets loaded on the loading member. The upstream edge of the removal groove in the sheet discharge direction is separated from the wall and extends along the sheet width direction perpendicular to the sheet discharge direction. The downstream edge of the removal groove in the sheet discharge direction is inclined with respect to the sheet width direction such that it moves downstream in the sheet discharge direction as it moves outward in the sheet width direction. An image forming apparatus characterized by the following features.

2. A protruding member extending in the sheet discharge direction, which is capable of protruding upward from the loading member through an opening provided in the loading member, and on which sheets discharged by the discharge means are loaded, A motor that moves the protruding member so that the amount of protrusion of the protruding member from the loading member is changed, It further possesses, The width of the opening in the sheet width direction is narrower than the width of the sheet discharged to the loading member. The width of the protruding member in the sheet width direction is narrower than the width of the sheet discharged to the loading member. The upstream end of the opening in the sheet discharge direction is separated from the wall portion. In the sheet discharge direction, the upstream edge of the extraction groove is located downstream of the upstream end of the opening and the upstream end of the protruding member, and the downstream edge of the extraction groove is located upstream of the downstream end of the opening and the downstream end of the protruding member. The image forming apparatus according to feature 1.

3. A protruding member extending in the sheet discharge direction, which is capable of protruding upward from the loading member through an opening provided in the loading member, and on which sheets discharged by the discharge means are loaded, A biasing means for biasing the protruding member upward, It further possesses, The width of the opening in the sheet width direction is narrower than the width of the sheet discharged to the loading member. The width of the protruding member in the sheet width direction is narrower than the width of the sheet discharged to the loading member. The upstream end of the opening in the sheet discharge direction is separated from the wall portion. In the sheet discharge direction, the upstream edge of the extraction groove is located downstream of the upstream end of the opening and the upstream end of the protruding member, and the downstream edge of the extraction groove is located upstream of the downstream end of the opening and the downstream end of the protruding member. The image forming apparatus according to feature 1.

4. The opening is provided in the inclined portion, The image forming apparatus according to feature 2 or 3.

5. The upper part of the protruding member is inclined upward toward the downstream direction in the sheet discharge direction, The image forming apparatus according to any one of claims 2 to 4.

6. The removal groove portion is The bottom and, The bottom portion and the portion of the inclined portion located downstream of the bottom portion in the sheet discharge direction are connected, and the inclined surface is inclined upward toward the downstream direction of the sheet discharge direction, Includes, The inclination of the inclined surface with respect to the horizontal is greater than the inclination of the inclined portion with respect to the horizontal. The image forming apparatus according to any one of claims 1 to 5.

7. The motor is positioned downstream of the removal groove in the sheet discharge direction. The image forming apparatus according to feature 2.

8. The loading member has a plurality of mounting parts and is attached to the main body of the image forming apparatus via the plurality of mounting parts. The plurality of mounting portions include mounting portions located upstream of the removal groove portion in the sheet discharge direction, The image forming apparatus according to any one of claims 1 to 7.

Images