Sheet storage device and image forming apparatus

Abstract

This invention provides a sheet storage device and an image forming apparatus. The sheet storage device includes a sheet storage unit for storing sheets, an adjustment unit within the sheet storage unit, and a lifting unit. The adjustment unit adjusts the position of the rear edge of the sheet in the sheet conveying direction and includes a support portion, a pressing member, and a pressing portion having a pressing surface. In the pressing surface, the lower part of the pressing surface contacts the sheet below, and the upper part of the pressing surface contacts the sheet above, which is located at a higher position than the sheet below. The pressing surface can be in a first state or a second state. In the first state, the upper part of the pressing surface is downstream of the lower part of the pressing surface in the pressing direction. In the second state, the lower part of the pressing surface is downstream of the upper part of the pressing surface in the pressing direction.

Description

Technical Field

[0001] The present invention relates to image forming apparatuses such as copiers and printers, and sheet storage devices for image forming apparatuses. Background Technology

[0002] Image forming apparatuses that transport sheets to an image forming unit to form an image on the sheets typically include: a sheet storage device including a sheet stacking tray for stacking sheets; and a sheet feed roller (sheet feed member) that transports the sheets from the sheet storage device in a transport direction. One type of such sheet storage device has an adjustment unit (rear edge adjustment unit) for adjusting the rear edge of the sheet in the transport direction.

[0003] Another type of sheet storage device has a lifting plate that lifts the sheet toward the sheet feed roller. The lifting plate lifts the leading edge of the sheet in the conveying direction, thereby maintaining the leading edge of the sheet at a height that allows it to contact the sheet feed roller.

[0004] When the number of sheets stacked on the sheet stacking tray decreases, both the leading and trailing edges of the stacked sheets are positioned low in the conveying direction. If the lifting amount of the lifting plate increases to bring the sheet feed roller and the leading edge of the sheet closer together, the distance from the trailing edge of the sheet to the sheet feed roller also increases. Consequently, the position of the leading edge of the sheet relative to the sheet feed roller shifts upstream in the conveying direction. As a result, image defects or paper jams may occur due to sheet conveying delays.

[0005] To solve this problem, a structure was discussed in which a pressing part, which is pushed toward the rear edge of the sheet by a pressing member, is arranged in the rear edge adjustment unit, and the pressing part pushes the rear edge of the sheet upward according to the lifting angle of the stacked sheets (Japanese Patent Application Publication No. 9-118439).

[0006] However, in the construction described in Japanese Patent Application Publication No. 9-118439, there is a problem that the pushing force of the pushing member is difficult to adjust. Details will be described below.

[0007] The pressing part of the rear edge adjustment unit is configured to move all the sheets stacked on the sheet stacking tray. Therefore, when the number of stacked sheets is large, a large pushing force is desired to push the sheets out. At the same time, it is desirable to set a pushing force to prevent sheet warping when the number of stacked sheets is small. If a pushing force is set to prevent sheet warping when the number of stacked sheets is small, the following situation may occur: when the number of stacked sheets is large, the sheets cannot be pushed out. Summary of the Invention

[0008] According to one aspect of the present invention, a sheet storage device includes: a sheet storage unit configured to store a sheet; an adjustment unit disposed in the sheet storage unit and configured to adjust the position of a rear edge portion of the sheet in a sheet conveying direction, wherein the adjustment unit includes a pressing portion, a supporting portion, and a pushing member, the pressing portion having a pressing surface configured to press the rear edge portion, the supporting portion being configured to support the pressing portion, and the pushing member being configured to push the pressing portion so that the pressing surface presses the sheet; and a lifting unit configured to lift a front edge portion of the sheet in the conveying direction. In the pressing surface, the position that contacts the lower sheet is the lower part of the pressing surface, and the position that contacts the upper sheet located at a higher position than the lower sheet is the upper part of the pressing surface. When the pressing direction is parallel to the horizontal direction and downstream of the conveying direction, and depending on the number of sheets stored in the sheet storage unit, the pressing surface can be in a first state or a second state. In the first state, the upper part of the pressing surface is downstream of the lower part of the pressing surface in the pressing direction, and in the second state, the lower part of the pressing surface is downstream of the upper part of the pressing surface in the pressing direction.

[0009] Other features of the invention will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0010] Figure 1 It is a cross-sectional view of the overall structure of the main body of the image forming apparatus.

[0011] Figure 2 It is a schematic plan view of the structure of a sheet storage device installed in an image forming apparatus.

[0012] Figure 3 It is a cross-sectional view of a schematic structure of a sheet storage device arranged in an image forming apparatus.

[0013] Figure 4 This is a perspective view of the adjustment unit according to a first exemplary embodiment of the present invention.

[0014] Figure 5 This is a cross-sectional view of the adjustment unit according to a first exemplary embodiment of the present invention.

[0015] Figures 6A to 6C Each of these is a cross-sectional view showing the sheet storage device in use according to a first embodiment of the present invention.

[0016] Figures 7A to 7C Each of these is a cross-sectional view showing the usage state of the adjustment unit according to the first embodiment of the present invention.

[0017] Figure 8 This is a perspective view of the adjustment unit according to a second exemplary embodiment of the present invention.

[0018] Figure 9 This is a cross-sectional view of the adjustment unit according to a second exemplary embodiment of the present invention.

[0019] Figures 10A to 10C Each of these is a cross-sectional view showing the sheet storage device in use according to a second embodiment of the present invention.

[0020] Figures 11A to 11C Each of these is a cross-sectional view showing the usage state of the adjustment unit according to the second embodiment of the present invention. Detailed Implementation

[0021] [Overall Structure]

[0022] Figure 1 This is a schematic cross-sectional view of the overall structure of the image forming apparatus 1. The image forming apparatus 1 forms an image using an electrophotographic recording method. The image forming apparatus 1 feeds a sheet (recording material) S to the image forming unit 5 to transfer a toner image onto the sheet S, feeds the sheet S to the fixing unit 6 to fix the toner image onto the sheet S, and then discharges the sheet S to the discharge unit.

[0023] Sheets S are stacked and stored on the stacking surface of sheet storage unit 21 in sheet storage device 2, which is mounted at the bottom of image forming apparatus 1. Sheets S are sequentially fed out from the topmost sheet by sheet feed roller 31, which serves as a conveying unit for conveying the sheets in the conveying direction. Sheet feed roller 31 is arranged in supply unit 3 for supplying sheets S to image forming unit 5. Sheets S fed out by sheet feed roller 31 are conveyed to conveying unit 4 and subsequently transferred to image forming unit 5 by conveying roller pair 41, which is arranged downstream of sheet storage device 2 in the conveying direction.

[0024] In the image forming unit 5, a laser beam based on image information is used by the laser scanner 52 to irradiate the photosensitive drum 51, thereby forming an electrostatic latent image on the photosensitive drum 51. Subsequently, toner development is performed in the developing unit (not shown) in the processing cartridge P, thereby forming a toner image. By applying a bias voltage to the transfer roller 531 in the transfer unit 53, the toner image is transferred as an unfixed image onto the sheet S that has been conveyed to the image forming unit 5. Subsequently, the sheet S is conveyed to the fixing unit 6.

[0025] The fixing unit 6 forms a fixing roller gap through a heating unit 61 and a pressure roller 62 that is in pressure contact with the heating unit 61. The heating unit 61 consists of a fixing film and a heating element (such as a ceramic heater) disposed on the inner surface of the fixing film. The sheet S passes through the fixing roller gap, so that the unfixed image is permanently fixed on the sheet S. Then, the sheet S is discharged from the image forming apparatus 1 by the discharge roller pair 7 via the sheet discharge path and placed on the discharge tray 8.

[0026] In this exemplary embodiment, an electrophotographic image forming process using a transfer unit and a fixing unit is employed as the image forming unit for forming an image on the sheet S, but the present invention is not limited thereto.

[0027] For example, the present invention can use an inkjet image forming process that forms an image on a sheet by ejecting ink from a nozzle that serves as an image forming unit for forming an image on a sheet S.

[0028] [Sheet storage equipment]

[0029] Now refer to Figure 2 and Figure 5 The detailed structure of the sheet storage device 2 installed on the image forming apparatus 1 is described. Figure 2 This is a schematic plan view of the structure of a sheet storage device 2 capable of storing sheets S of different sizes, and Figure 5 This is a cross-sectional view of the adjustment unit 24.

[0030] Figure 2 The sheet storage device 2 shown includes: a sheet storage unit 21 for stacking and storing sheets S of different sizes; a pair of width adjustment units 22 and 23 for adjusting the position of the side edges of the sheets S; and an adjustment unit 24 for adjusting the position of the rear edge of the sheets S. The sheet storage device 2 also includes an intermediate plate 25, which contacts the stacked sheets S with a pivotally mounted lifting arm 26, pushes the sheets S upward by pivoting about the main shafts 251 and 252 of the intermediate plate, and contacts the stacked sheets S with the sheet feed roller 31. The width adjustment units 22 and 23 and the adjustment unit 24 are all positioned in a way that does not interfere with the pivoting operation of the intermediate plate 25.

[0031] When sheets of different sizes S are to be stored in the sheet storage unit 21, width adjustment units 22 and 23 and adjustment unit 24 are all positioned corresponding to the sheet S to be stored. Thus, the sheet S can be stored in the appropriate location. The sheet storage device 2 can be attached by moving it relative to the image forming apparatus 1 in the direction of arrow A. When conveying the sheet S, the lifting arm 26 pivots via a pivoting mechanism (not shown) in the main body, causing the intermediate plate 25 to pivot upwards about the intermediate plate main shafts 251 and 252. As a result, the sheet positioned by the width adjustment units 22 and 23 and adjustment unit 24 is pressed against the sheet feed roller 31.

[0032] A pair of adjustment units 22 and 23 each have rack portions 221 and 231 extending in the width direction (arrow B direction) at the bottom of the sheet storage unit 21. Rack teeth (not shown) formed in rack portion 221 and rack teeth (not shown) formed in rack portion 231 mesh with each other via a pinion (not shown). When any one of these width adjustment units moves in the width direction, the other width adjustment unit moves in the opposite direction in an interlocking manner under the action of the pinion and rack portions 221 and 231. The positions of the width adjustment units 22 and 23 are fixed by assembling the fixing units (not shown) provided in each of the width adjustment units 22 and 23 into the grooves of the sheet storage unit 21.

[0033] The adjustment unit 24 can move within a recess 27 provided in the direction C. The recess 27 has a protrusion 28 extending in the direction C, and the adjustment unit 24 is positioned by engaging the protrusion 28 with the protrusion 2412 of the adjustment unit 24. The engagement between the protrusion 2412 and the protrusion 28 is released by user operation of the lever member 244. In this state, the adjustment unit 24 moves on the recess 27 and is positioned at any position corresponding to the size of the sheet S.

[0034] Now refer to Figures 3 to 7C A first exemplary embodiment of the present invention is described. Figure 3 This is a cross-sectional view of the sheet storage device 2 according to the first exemplary embodiment. Figure 4 This is a perspective view of the adjustment unit 24 that positions the rear edge of the sheet S stacked in the sheet storage unit 21. Figure 5 This is a cross-sectional view of the adjustment unit 24. Figures 6A to 6C and Figures 7A to 7C This is a diagram showing the movement of the pressing part 200.

[0035] The adjustment unit 24 includes a pressing part 200, a support part 241, and a pushing member 243. The pressing part 200 has a first portion 245 and a second portion 246. The first portion 245 and the second portion 246 are pivotable relative to the support part 241, and the second portion 246 is located below the first portion 245. The first portion 245 and the second portion 246 have pressing surfaces that press the rear edge of the sheet S. However, the pressing surfaces here refer to the surface of the sheet S being pressed and vary depending on the number of sheets S stacked.

[0036] The adjustment unit 24 has a pushing member 243 that pushes the pressing portion 200, causing the sheet S to be pressed by the pressing surface. The first surface 245c of the first portion 245 is the surface that presses the sheet S at the third quantity described later. The second surface 246c of the second portion 246 is the surface that can contact the bottommost sheet among the sheets stacked in the sheet storage unit 21. The second surface 246c is the surface that presses the sheet when the quantity of sheets is each of the first and second quantities described later. In this exemplary embodiment, the second surface 246c is a flat surface.

[0037] The first part 245 is held by the support 241, and a portion of the first part 245 is fitted into the shaft (not shown) of the support 241, such that the first part 245 can pivot about the shaft.

[0038] The second part 246 is held by the first part 245, and the joint 246a of the second part 246 engages with the connecting part 245a of the first part 245, so that the second part 246 can pivot about the joint 246a.

[0039] According to this exemplary embodiment, the joint 246a is located in the vertical direction closer to the upper end 248 than the lower end 249 of the adjustment unit 24. When the sheet S is not stored in the sheet storage device 2, as... Figure 5 As shown, the first part 245 and the second part 246 are in a state of being pushed by the pushing member 243, and pivot relative to the support part 241. Figure 5 The position is further to the right. The pivot movement of the second part 246 is adjusted by bringing the contact surface 246b of the second part 246 into contact with the pivot movement adjustment unit 241b of the support part 241, thereby determining the maximum pivot movement position.

[0040] The second portion 246 is attached to be pivotable relative to the first portion 245, such that the second portion 246 is configured such that when a pushing force is applied by the pushing member 243, the upper portion can pivot even if the lower portion does not move. With this configuration, the second portion 246 preferentially pushes out the upper side of the stacked sheets S.

[0041] Although the force used by the pressing part 200 to push out the topmost sheet of the stacked sheets S is independent of the height of the stacked sheets S, when the number of stacked sheets is large, it is desirable to push out the lower sheets together with the upper sheets. Therefore, as the height of the stacked sheets S increases, the pressing force applied by the second part 246 near the topmost sheet of the sheets S needs to increase. Conversely, when the number of stacked sheets S is small, it is desirable to limit the load to a level that prevents the bundle of sheets S from warping due to the pressing force of the second part 246. The pressing position and pressing force are set to satisfy both of the above conditions.

[0042] The pressing member 243 presses against the pressed portion 247 of the second part 246. In this exemplary embodiment, the pressed portion 247 is positioned below the joint portion 246a and closer to the upper end 248 than the lower end 249 of the adjusting unit 24. It is desirable to position the pressed portion 247 in such a way to achieve a greater effect of preferentially pushing out the upper sheet S. However, the pressed portion 247 can be positioned anywhere, as long as it is located above the lowermost sheet of the sheet S stored in the sheet storage unit 21.

[0043] The pivoting posture of the pressing part 200 is determined so that the required amount of pressing force is ensured according to the height of the stacked sheets S. The support part 241 is also provided with a stacked sheet contact surface 241a that contacts the rear edge of the sheet S when the number of stacked sheets S is large.

[0044] Reference Figures 6A to 6C and Figures 7A to 7C The description describes the states of the first portion 245 and the second portion 246 when the number of stacked sheets S is in one of three modes (i.e., the third quantity, the first quantity, and the second quantity). Figure 6A and Figure 7A The third quantity case is shown. Figure 6B and Figure 7B The first quantity case is shown, and Figure 6C and Figure 7C The second quantity is shown. The third quantity is greater than the first quantity, and the first quantity is greater than the second quantity. Specifically, in this exemplary embodiment, the third quantity, the first quantity, and the second quantity are described as a state of 90% storage, a state of 50% storage, and a state of 10% storage, respectively, for the permissible quantity of sheet S that can be stored in the sheet storage unit 21. However, this exemplary embodiment is not limited to these quantities.

[0045] Before describing the construction of this exemplary embodiment, consider a construction in which the pressing part 200 is absent, the rear edge of the sheet S is adjusted by the adjusting unit, and the front edge of the sheet S is raised. In a state where the number of sheets S is a third number, as... Figure 6A As shown, the distance L1 is the distance along the surface of the sheet from the rear edge of the topmost sheet in the stacked sheets to the contact point between the sheet and the sheet feed roller 31. When the number of sheets S is a first quantity, as... Figure 6B As shown, the distance is distance L2, which is longer than distance L1. Furthermore, when the number of sheets S is the second number, as... Figure 6C As shown, the distance is distance L3, which is longer than distance L2.

[0046] The construction of this exemplary embodiment with the pressing part 200 will be described. When the number of stacked sheets S is a third number, as... Figure 7A As shown, the first part 245 and the second part 246 contact the rear edge of the sheet S while pressing the sheet S, without protruding from the support part 241.

[0047] At this point, the angle formed by the pressing surface of the pressing sheet S with the vertical direction is smaller than that in the first and second states described below (third state).

[0048] Here, in the pressing surface, the position that contacts the lower sheet S stacked in the sheet storage unit 21 is called the lower part of the pressing surface, and the position that contacts the sheet S at a higher position than the lower sheet S is called the upper part of the pressing surface. In other words, the pressing surface has a lower part that contacts the sheet S and an upper part that contacts the sheet S at a higher position than the lower part of the pressing surface.

[0049] When the number of stacked sheets S is the first quantity, the pressing surface is as follows: Figure 7B The tilt shown causes the first part 245 and the second part 246 to be inclined along... Figure 7B The sheet S pivots to the right from the support 241. Here, the distance from the rear edge of the uppermost sheet to the point where the sheet S contacts the sheet feed roller 31 is called the contact distance. The contact distance is increased by reducing the number of stacked sheets S and raising the intermediate plate 25. When the pressing surface pivots, the uppermost sheet S, which will be fed next by the sheet feed roller 31, moves in the conveying direction, and the contact distance decreases. In this way, the increased contact distance is adjusted.

[0050] At this time, the upper and lower parts of the pressing surface will be referred to as the upper pressing surface 2411b and the lower pressing surface 2410b, respectively. The lower pressing surface 2410b is positioned such that it corresponds in the height direction to the bottommost sheet among the sheets stacked in the sheet storage unit 21. The upper pressing surface 2411b is positioned corresponding to the topmost sheet. The pressing direction is parallel to the horizontal direction and faces downstream in the conveying direction. Regarding the contact surface (pressing surface) between the second part 246 and the sheet S, the upper pressing surface 2411b is located downstream of the lower pressing surface 2410b in the pressing direction (first state). In other words, the second surface 246c of the second part 246 is in an inclined state, such that the upper end of the second surface 246c is located downstream of the lower end of the second surface 246c in the pressing direction. In this state, the pressing surface and the second surface 246c face downward in the vertical direction.

[0051] The reason for this tilt is that the force applied from the sheet S to the upper part 2411b of the pressing surface is less than the force applied to the lower part 2410b of the pressing surface. Therefore, the lower part 2410b of the pressing surface is not pivoted by the sheet S, while the upper part 2411b of the pressing surface is pivoted by the pushing force, and as... Figure 7B The inclination is shown.

[0052] Because the second surface 246c and the pressing surface are inclined as described above, the second part 246 can press the upper sheet S to move the upper sheet S toward the sheet feeding roller 31. In other words, because the second surface 246c and the pressing surface are inclined as described above, the second surface 246c will not move the entire bundle of sheets stored in the sheet storage unit 21 when the number of sheets is large.

[0053] When the number of stacked sheets S is the second number, the position corresponding to the bottommost sheet among the sheets S stacked in the sheet storage unit 21 in the height direction is the lower part 2410c of the pressing surface, and the position corresponding to the topmost sheet is the upper part 2411c of the pressing surface. Regarding the contact surface (pressing surface) between the second part 246 and the sheet S, the lower part 2410c of the pressing surface is located downstream of the upper part 2411c of the pressing surface in the pressing direction (second state).

[0054] In other words, it is in the following state: the second surface 246c of the second part 246 is inclined such that the lower end of the second surface 246c is downstream of the upper end of the second surface 246c in the pressing direction. In this state, the pressing surface and the second surface 246c face upward in the vertical direction.

[0055] Even in this state, the pressing surface pivots, causing the uppermost sheet S, which will be fed next by the sheet feed roller 31, to move in the conveying direction, and the contact distance decreases. Furthermore, the distance for pushing out the uppermost sheet in the second state is longer than the distance in the first state. As described above, the increased contact distance has been adjusted.

[0056] In this exemplary embodiment, the positions of the upper and lower parts of the pressing surface correspond to the positions of the topmost and bottommost sheets among the sheets stacked in the sheet storage unit 21, respectively, but are not limited thereto. For example, when the second portion 246 does not contact the bottommost sheet among the sheets stacked in the sheet storage unit 21, the position corresponding to the bottommost sheet among the sheets contacted by the second portion 246 is the position of the lower part of the pressing surface. Similarly, when the second portion 246 does not contact the topmost sheet among the sheets stacked in the sheet storage unit 21, the position corresponding to the topmost sheet among the sheets contacted by the second portion 246 is the position of the upper part of the pressing surface. In other words, the topmost and bottommost parts of the pressing surface can be referred to as the upper part of the pressing surface and the lower part of the pressing surface, respectively.

[0057] In summary, based on the number of sheets stored in the sheet storage unit, the pressing surface can be in a first state and a second state: in the first state, the upper part of the pressing surface is downstream of the lower part of the pressing surface in the pressing direction, while in the second state, the lower part of the pressing surface is downstream of the upper part of the pressing surface in the pressing direction. Here, if the number of sheets in the first state is a first quantity and the number of sheets in the second state is a second quantity, then the first quantity is greater than the second quantity. Furthermore, when the number of sheets is a third quantity, the pressing surface can be in a third state where the angle formed by the pressing surface and the vertical direction is smaller than the angle formed by the pressing surface and the vertical direction in the first state and the angle formed by the pressing surface and the vertical direction in the second state. The third quantity is greater than the first quantity. The angle formed by the pressing surface and the vertical direction is the same as the angle formed by the second surface 246c and the vertical direction.

[0058] The first exemplary embodiment is constructed such that the pressing part 200 can push the stacked sheets upward, so that the sheet feeding roller 31 can contact the predetermined position of the stacked sheets, regardless of the number of stacked sheets S. Therefore, the positional change of the sheets S at the start of conveying can be reduced, and stable sheet feeding can be achieved.

[0059] When setting a small number of sheets S or setting thin sheets as sheets S, the adjustment unit 24 can also properly set the sheets S without causing the sheets S to flex. It can push the sheets S upwards during transport, regardless of the number of stacked sheets S.

[0060] In this exemplary embodiment, a helical compression spring is used for the pushing member 243, but other types of members such as torsion helical springs or plate springs can be used, as long as the member generates pushing force.

[0061] Now refer to Figures 8 to 11C A second exemplary embodiment of the present invention will be described. In the first exemplary embodiment, a structure for pushing out sheet S using two connected pressing portions was described, but the present invention is not limited to this structure. In the second exemplary embodiment, an example in which the pressing portion is composed of a single component and produces a similar effect will be described.

[0062] In this exemplary embodiment, the adjustment unit 94 includes a support portion 941, a stacked sheet contact surface 941a, a pressing portion 900, a pressing member 945, a surface 945c, and a pressed portion 947. The pressing portion 900 includes the pressing member 945, and the pressing member 945 has a surface 945c. Surface 945c is a surface corresponding to the second surface 246c in the first exemplary embodiment. Surface 945c is a surface capable of contacting the lowermost sheet among the sheets stacked in the sheet storage unit 21. Surface 945c is the surface for pressing the sheets when the number of sheets is each of a first number and a second number. In this exemplary embodiment, surface 945c is a flat surface.

[0063] Components having the same construction and function as in the first exemplary embodiment are indicated by the same reference numerals as in the first exemplary embodiment, and repeated descriptions will be omitted. Figure 8 This is a perspective view of the adjustment unit 94 that positions the rear edge of the sheet S stacked in the sheet storage unit 21. Figure 9 This is a cross-sectional view of the adjustment unit 94. Figures 10A to 10C and Figures 11A to 11C A second exemplary embodiment of the present invention is shown.

[0064] The pressing member 945 has a pressing member shaft portion 945a located at both ends and fitted into the opening 941c of the support portion 941, such that the pressing member 945 can move linearly in the direction d extending from the opening 941c and rotate about the pressing member shaft portion 945a. The length of the opening 941c in the direction of linear movement of the pressing member 945, which serves as the pressing part, is longer than the length of the opening 941c in the direction orthogonal to the direction of linear movement of the pressing member 945.

[0065] In other words, the pressing member 945 is supported by the support portion 941 and its opening portion 941c, so that the pressing member 945 can move linearly and rotate.

[0066] Compared to the lower end 249 of the adjustment unit 94, the opening 941c is also located closer to the upper end 248 in the vertical direction. In the pressing member 945, as in the first exemplary embodiment, the pressed portion 947 is pushed toward the sheet S by the pressing member 243 of the adjustment unit 94.

[0067] When sheet S is not present in sheet storage device 2, such as Figure 9 As shown, the pressing member 945 is pressed by the pushing member 243 and is in the following state: the pressing member 945 is... Figure 9 It protrudes further to the right than the support portion 941. The pivotal movement of the pressing member 945 is adjusted by bringing the pressing member contact portion 945b of the pressing member 945 into contact with the contacted portion 941b of the support portion 941.

[0068] The pressed portion 947 is located lower than the opening 941c and is closer to the upper end 248 in the vertical direction than the lower end 249 of the adjusting unit 94. It is desirable to position the pressed portion 947 in this way to preferentially push out the upper sheet S. However, the pressed portion 947 can be positioned anywhere, as long as it is higher than the lowermost sheet of the sheets S stored in the sheet storage unit 21.

[0069] The pressing member 945 is configured such that when the pushing force of the pressing member 243 is applied, the upper part can pivot even if the lower part does not move. Based on the above configuration, the pressing member 945 preferentially pushes out the upper side of the stacked sheet S.

[0070] Similar to the first exemplary embodiment, the pressing position and pressing force are set to balance the force that pushes the upper sheet out of the stacked sheets S and the force that prevents the bundle of sheets S from warping. The pivoting posture of the pressing part is determined so that the required amount of pressing force can be ensured at each height of the stacked sheets S.

[0071] Reference Figures 10A to 10C and Figures 11A to 11C The description describes the state of the pressing member 945 when the stacked sheets S are in one of three modes (i.e., a third quantity, a first quantity, and a second quantity) in the sheet storage device 2. The quantities and their relationships are similar to those in the first exemplary embodiment, but the second exemplary embodiment is not limited to these quantities.

[0072] Consider the following state, where the pressing part 900 is absent, the rear edge of the sheet S is adjusted by the adjusting unit, and the front edge of the sheet S is raised. In the state where the number of sheets S is the third, as follows... Figure 10AAs shown, the shortest distance L4 is the distance along the surface of the sheet from the rear edge of the topmost sheet in the stacked sheets to the contact point between the sheet and the sheet feed roller 31. The distance L5 is the distance when the number of sheets S is the first quantity. Figure 10B As shown, this distance is longer than distance L4. Furthermore, when the number of sheets S is the second quantity, the distance is distance L6, as shown... Figure 10C As shown, this distance is longer than distance L5.

[0073] The construction of this exemplary embodiment with the pressing part 900 will now be described. When the number of stacked sheets S is a third number, as... Figure 11A As shown, the pressing member 945 contacts the rear edge of the sheet S while pressing the sheet S, without protruding from the support 941 (third state).

[0074] When the number of stacked sheets S is the first quantity, the pressing component 945 is as follows. Figure 11B The pressure surface is tilted as shown. The upper and lower parts of the pressure surface at this time will be referred to as the upper pressure surface 2411b and the lower pressure surface 2410b, respectively. Here, the lower pressure surface 2410b is positioned such that it corresponds in the height direction to the lowermost sheet among the sheets stacked in the sheet storage unit 21. The upper pressure surface 2411b is positioned corresponding to the uppermost sheet. Furthermore, as in the first exemplary embodiment, the pressing direction is parallel to the horizontal direction and faces downstream in the conveying direction. Regarding the contact surface (pressing surface) between the pressing member 945 and the sheet S, the upper pressure surface 2411b is located downstream of the lower pressure surface 2410b in the pressing direction (first state). In other words, the surface 945c of the pressing member 945 is tilted such that the upper end of the surface 945c is downstream of the lower end of the surface 945c in the pressing direction. In this state, the pressing surface and the surface 945c face downwards in the vertical direction.

[0075] Even in this state, the pressing surface pivots, causing the uppermost sheet S, which will be fed next by the sheet feed roller 31, to move in the conveying direction, and the contact distance to decrease. As described above, the increased contact distance has been adjusted.

[0076] The reason for this tilt is that the force applied from the sheet S to the upper part 2411b of the pressing surface is less than the force applied to the lower part 2410b of the pressing surface. Therefore, the lower part 2410b of the pressing surface is not pivoted by the sheet S, while the upper part 2411b of the pressing surface is pivoted by the pushing force, and as... Figure 11B The inclination is shown.

[0077] Because the surface 945c and the pressing surface are inclined as described above, the pressing member 945 can press the upper sheet S to move the upper sheet S toward the sheet feeding roller 31. In other words, because the surface 945c and the pressing surface are inclined as described above, the pressing member 945 does not need to move the entire bundle of sheets stored in the sheet storage unit 21 when the number of sheets is large.

[0078] When the number of stacked sheets S is the second number, the position corresponding to the lowest sheet among the sheets S stacked in the sheet storage unit 21 in the height direction is the lower part 2410c of the pressing surface, and the position corresponding to the uppermost sheet is the upper part 2411c of the pressing surface. Regarding the contact surface (pressing surface) between the pressing member 945 and the sheet S, the lower part of the pressing surface is located downstream of the upper part of the pressing surface in the pressing direction (second state). In other words, this is a state in which the surface 945c of the pressing member 945 is inclined such that the lower end of the surface 945c is located downstream of the upper end of the surface 945c in the pressing direction. In this state, the pressing surface and the surface 945c face upward in the vertical direction.

[0079] Even in this state, the pressing surface pivots, causing the uppermost sheet S, which will be fed next by the sheet feed roller 31, to move in the conveying direction, and the contact distance decreases. In the second state, the distance used to push out the uppermost sheet is longer than in the first state. In this way, the increased contact distance is adjusted.

[0080] Even though in this exemplary embodiment, the positions of the upper part of the pressing surface and the lower part of the pressing surface are respectively the positions corresponding to the uppermost sheet and the lowermost sheet among the sheets stacked in the sheet storage unit 21, they are not limited thereto.

[0081] As described above, similar to the first exemplary embodiment, the second exemplary embodiment is constructed such that the pressing part 900 can push the stacked sheets upward, allowing the sheet feeding roller 31 to contact a predetermined position of the stacked sheets, regardless of the number of stacked sheets S. Therefore, the positional change of the sheets S at the start of conveying can be reduced, and stable sheet feeding can be achieved.

[0082] In this exemplary embodiment, as in the first exemplary embodiment, a helical compression spring is used for the pushing member 243, but other types of members such as torsion helical springs or plate springs can be used, as long as the member generates pushing force.

[0083] According to an exemplary embodiment of the present invention, the pressing part can push the stacked sheets upward so that the sheet feeding roller can contact a predetermined position of the stacked sheets, regardless of the number of stacked sheets. Therefore, the change in the sheet position at the start of conveying can be reduced.

[0084] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The appended claims should be interpreted in the broadest possible sense to encompass all such variations and equivalent structures and functions.

Claims

1. A sheet storage device, comprising: Sheet storage unit, which is constructed as a storage sheet; An adjustment unit is disposed in the sheet storage unit and configured to adjust the position of the rear edge of the sheet in the sheet conveying direction. The adjustment unit includes a pressing part, a supporting part, and a pushing member. The pressing part has a pressing surface configured to press the rear edge. The supporting part is configured to support the pressing part. The pushing member is configured to push the pressing part so that the pressing surface presses the sheet. as well as The lifting unit is configured to lift the leading edge of the sheet in the conveying direction. Specifically, in the pressing surface, the lower part of the pressing surface is the position that contacts the sheet below, and the upper part of the pressing surface is the position that contacts the sheet above, which is located at a higher position than the sheet below. Depending on the number of sheets stored in the sheet storage unit, the pressing surface can be in either a first state or a second state. Wherein, in the case that the pressing direction is parallel to the horizontal direction and faces downstream of the conveying direction, in the first state, the upper part of the pressing surface is located downstream of the lower part of the pressing surface in the pressing direction, and In the second state, the lower part of the pressing surface is located downstream of the upper part of the pressing surface in the pressing direction, and Wherein, when the pressing surface is in the first state and the number of sheets stored in the sheet storage unit is a first number, and when the pressing surface is in the second state and the number of sheets stored in the sheet storage unit is a second number, the first number is greater than the second number. Where the number of sheets stored in the sheet storage unit is a third number greater than the first number, the pressing surface can be in a third state, and Wherein, when the pressing surface is in the third state, the third angle formed by the pressing surface and the vertical direction is smaller than the first angle formed by the pressing surface and the vertical direction when the pressing surface is in the first state and the second angle formed by the pressing surface and the vertical direction when the pressing surface is in the second state.

2. The sheet storage apparatus according to claim 1, wherein The pressing part includes a first portion pivotally supported by the support portion and a second portion pivotally engaged with the first portion and located below the first portion in the vertical direction.

3. The sheet storage apparatus according to claim 2, wherein The first part and the second part are joined together at the joint, and the joint is located closer to the upper end of the adjustment unit than the lower end of the adjustment unit in the vertical direction.

4. The sheet storage device according to claim 3, wherein, The pressing member is configured to press the pressed portion of the pressing part, and the pressed portion is positioned lower than the joint and closer to the upper end of the adjustment unit in the vertical direction than the lower end of the adjustment unit.

5. The sheet storage apparatus according to claim 1, wherein The support portion has an opening that is configured to support the pressing portion so that the pressing portion can move linearly and rotate.

6. The sheet storage apparatus according to claim 5, wherein In the opening, the length of the pressing part in the direction of linear movement is longer than the length in the direction orthogonal to the direction of linear movement of the pressing part.

7. The sheet storage apparatus according to claim 5, wherein The opening is located vertically closer to the upper end of the adjustment unit than to the lower end of the adjustment unit.

8. The sheet storage apparatus according to claim 7, wherein The pressing member is configured to press the pressed portion of the pressing part, and the pressed portion is positioned in the vertical direction lower than the opening and closer to the upper end of the adjusting unit than the lower end of the adjusting unit.

9. An image forming apparatus comprising: The sheet storage device according to any one of claims 1 to 8; as well as An image forming unit is configured to form an image on a sheet.

Images