Sheet feeding device and image forming device

Abstract

To improve separability of a sheet bundle.SOLUTION: A sheet feeding device comprises: a separation part for separating a plurality of sheets fed by a feeding part into each sheet; a blowing part, above a sheet bundle, which blows air from one side in a sheet width direction W via a blowing port 83 to separate a sheet at an upper part of the sheet bundle; and a rotary part 90 which is provided rotatably with respect to a sheet tray 31 with a sheet feeding direction Df as a rotary axis, and is disposed on one side in the sheet width direction W in a support area of the sheet in the sheet tray 31, and can displace by rotating to a close position at which it is positioned on a plane equal to or lower than a sheet support surface 31a and to an open position at which it opens one side in the sheet width direction W above the sheet support surface 31a and has a space Sp below itself between with the sheet tray 31. The rotary part 90 has a partition part 93 for partitioning the sheet support surface 31a and the space Sp when it is positioned at the open position.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a sheet feeding device that feeds sheets and an image forming apparatus that uses the same. [Background technology]

[0002] Conventionally, a sheet feeding device is known that blows loosening air and separation air onto sheets stacked on a sheet tray that rises and falls depending on the number of sheets in the tray to reliably feed each sheet one by one. In this sheet feeding device, loosening air is blown onto the side edges of a stack of sheets stacked on the sheet tray, the floating sheets are sucked onto a suction belt, and separation air is blown onto the downstream side of the sucked sheets in the conveyance direction. In this way, by blowing separation air onto the sheets sucked onto the suction belt, air is blown between the top sheet and the sheets stuck below it, reliably separating only the top sheet from the stack of sheets, and the separated sheets are fed by the suction belt.

[0003] However, when most of the sheets in the sheet tray are fed and there are fewer than 10 sheets remaining, there is a risk that the separating air will pass over the sheet stack, preventing the sheets from being separated, potentially resulting in a deterioration in separation performance. To solve this problem, a configuration has been developed in which a rotating plate is provided in the sheet tray opposite the blowing port. The rotating plate is rotatable and opens and closes, forming a space between the sheet tray and the plate when in the open position (see Patent Document 1). When a large number of sheets are placed in the sheet tray, the rotating plate is in the closed position. However, when there are fewer than 10 sheets remaining, the plate is raised by the blowing of separating air and rotates to the open position, lifting the side edges of the sheets. This ensures that the separating air is reliably blown to the sides of the sheet stack with only a few remaining sheets. As a result, even when there are fewer than 10 sheets remaining in the sheet tray, the separating air is less likely to pass over the sheet stack, and the sheet stack is separated using the separating air, thereby avoiding a deterioration in separation performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-70122 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the sheet feeding device described in Patent Document 1 above may have the following problem. Specifically, when the number of remaining sheets on the sheet tray falls below 10 and the rotating plate rises, separating air may flow from the space between the rotating plate and the sheet tray into the gap between the bottom sheet and the sheet tray. In this case, because the sheet stack is light (fewer than 10 sheets), the entire sheet stack rises, and in this state, the sheet stack is pressed from below toward the suction belt. Therefore, when the blowing of separating air is stopped and the suction belt starts suctioning the sheets, the second and subsequent sheets may remain tightly attached below the top sheet, potentially preventing them from being separated even when separation air is blown.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet feeding device and an image forming apparatus that can improve the separation performance of a sheet stack. [Means for solving the problem]

[0007] One aspect of the present invention is a sheet feeding device comprising: a sheet tray that supports sheets on a sheet support surface; a feeding unit that feeds the top sheet of a sheet stack supported on the sheet support surface; a separation unit that separates the multiple sheets fed by the feeding unit into individual sheets; a blowing unit that blows air through a blowing port onto the top of the sheet stack from one side in a sheet width direction perpendicular to the sheet feeding direction to handle the top sheets of the sheet stack; and a rotating unit that is rotatable relative to the sheet tray with the sheet feeding direction as its rotation axis, is positioned on the one side in the sheet width direction in a sheet support area of ​​the sheet tray, and is displaceable by rotating between a closed position where the one side in the sheet width direction is located at a level below the sheet support surface, and an open position where the one side in the sheet width direction is opened above the sheet support surface and a space is formed between the sheet tray and the rotating unit below, wherein the rotating unit has a partition that separates the sheet support surface and the space when positioned in the open position.

[0008] Another aspect of the present invention is an image forming apparatus including the sheet feeding device described above and an image forming section that forms an image on a sheet. [Effects of the Invention]

[0009] According to the present invention, the separation performance of the sheet stack can be improved. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing an image forming apparatus according to an embodiment; [Figure 2] FIG. 2 is a block diagram showing a control system of the sheet feeding device according to the embodiment. [Figure 3] FIG. 1 is a perspective view showing a sheet feeding device according to an embodiment. [Figure 4] 10A and 10B are left side views showing a state in which a stack of multiple sheets is supported on a sheet feeding device according to an embodiment, in which (a) is before the blowing of separating air, (b) is when the blowing of separating air, and (c) is when the blowing of separating air is stopped, after the sheets are adsorbed by the suction belt, and when the blowing of separating air. [Figure 5] 10 is a flowchart showing a procedure for blowing loosening air, suction by a suction belt, and blowing separation air in the sheet feeding device according to the embodiment. [Figure 6] 1A and 1B are perspective views showing a rotating part according to an embodiment, in which FIG. 1A shows the rotating part in a closed position and FIG. 1B shows the rotating part in an open position. [Figure 7] 1A is a perspective view showing a rotating section according to an embodiment of the present invention alone, and FIG. 1B is a perspective view showing a storage section of a sheet tray. [Figure 8] FIG. 10 is a plan view showing a state in which the rotating portion according to the embodiment is located at an open position. [Figure 9] 10A and 10B are left side views showing a state in which a stack of a small number of sheets is supported in a sheet feeding device according to a comparative example, in which FIG. 10A shows a state before loosening air is blown, and FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] This embodiment will be described below with reference to the drawings. First, the schematic configuration of an image forming apparatus 1 according to this embodiment will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view showing the schematic configuration of the image forming apparatus 1 according to this embodiment. The image forming apparatus 1 is a tandem-intermediate transfer laser beam printer that uses an electrophotographic process. In this embodiment, the front side (front side) of the image forming apparatus 1 is the near side on the paper surface of FIG. 1, the side where a user is positioned when operating the operation unit, and is indicated as the front direction F. The side opposite the front direction F is indicated as the rear direction B, the left side when viewing the image forming apparatus 1 from the front is indicated as the left direction L, the right side is indicated as the right direction R, the upper side in the direction of gravity is indicated as the upper direction U, and the lower side is indicated as the downward direction D.

[0012] [Image forming equipment] The image forming apparatus 1 has an image forming unit 2 that forms an image on a sheet S, a sheet feeding device 3 that supplies the sheet S to the image forming unit 2, a sheet conveying unit 4 that conveys the sheet S, and a control unit 5 that controls these. The image forming apparatus 1 can form and output a full-color or monochrome image corresponding to print image data output from a host device (not shown) connected to the control unit 5 on the sheet S, which is a recording medium.

[0013] The image forming unit 2 forms an image on a sheet S fed by a sheet feeding device 3. The image forming unit 2 is a four-drum full-color system and includes a laser scanner 20 and four process cartridges PY, PM, PC, and PK that form toner images in four colors: yellow (Y), magenta (M), cyan (C), and black (K). Each process cartridge PY, PM, PC, and PK includes a photosensitive drum 21, a charger (not shown), and a developing unit 22. Toner is supplied to the developing unit 22 from a toner cartridge (not shown). The image forming unit 2 also includes an intermediate transfer belt 23 that rotates in the D1 direction, a primary transfer roller 24 that is disposed opposite each photosensitive drum 21 of the process cartridges PY, PM, PC, and PK across the intermediate transfer belt 23, a secondary transfer unit 25, and a fixing unit 26.

[0014] The sheet feeding device 3 has cassette units 30, which are two sheet cassettes arranged one above the other. Each cassette unit 30 has a sheet tray 31 that can be raised and lowered. The top sheet of a stack of sheets loaded and supported on the sheet tray 31 is attracted to a feeding belt 33 provided in the device body 7 of the image forming apparatus 1 and fed to the outside of the cassette unit 30.

[0015] The sheet conveying unit 4 has a pull-out roller pair 41, a conveying roller pair 42, a skew correction unit 43, a discharge roller pair 44, a switching unit 45, and a re-conveying unit 46. The pull-out roller pair 41 is provided opposite the sheet discharge unit of each cassette unit 30, and conveys the sheet S handed over from the cassette unit 30. The conveying roller pair 42 conveys the sheet S conveyed from the pull-out roller pair 41 to the skew correction unit 43. The skew correction unit 43 has a registration roller pair 47, and corrects skew of the sheet S by abutting the leading edge of the sheet S against the stopped registration roller pair 47, and adjusts the timing at which the sheet S is conveyed to the secondary transfer unit 25 by the rotation of the registration roller pair 47.

[0016] The control unit 5 controls the overall operation of the image forming apparatus 1 and exchanges information with the host device and the operation unit. The control unit 5 also performs signal processing and sequence control for various process devices. Here, the host device is a personal computer, image scanner, facsimile, etc. The control unit 5 has a CPU, RAM, and ROM, and controls each unit within the image forming apparatus 1. The CPU outputs output signals to each electrical component to operate the electrical component at the desired timing and with the required control amount based on detection signals input from each sensor and information stored in the ROM. Therefore, it is the CPU that actually controls the electrical components. The ROM and RAM store information data necessary for controlling each unit, and the CPU reads information data stored in the ROM and writes it to the RAM.

[0017] As shown in FIG. 2, the image forming apparatus 1 has an air supply unit 60 that sucks sheets, a separation blower unit 70 that blows separation air, and a separation blower unit 80 that blows separation air. The detailed configuration of each will be described later. The control unit 5 is connected to a suction fan motor 61 that performs suction in the air supply unit 60, a separation fan motor 71 that blows separation air in the separation blower unit 70, and a separation fan motor 81 that blows separation air in the separation blower unit 80. The control unit 5 is also connected to an elevation motor 51 that is a drive source for raising and lowering the sheet tray 31, and a height position sensor 52 that detects the height position of the top sheet of the sheet stack supported on the sheet tray 31. The elevation motor 51 and the power transmission mechanism from the elevation motor 51 to the sheet tray 31 are an example of an elevation unit that raises and lowers the sheet tray 31.

[0018] Next, the image forming operation of the image forming apparatus 1 will be described with reference to Figure 1. First, when the image forming apparatus 1 receives image data of an original to be printed, the image information is processed, converted into an electrical signal, and transmitted to the laser scanner 20 of the image forming unit 2. In the image forming unit 2, the surface of the photosensitive drum 21, the surface of which has been uniformly charged to a predetermined polarity and potential by a charger, is sequentially exposed to a laser. As a result, electrostatic latent images of yellow, magenta, cyan, and black are sequentially formed on the photosensitive drum 21 of each process cartridge PY, PM, PC, and PK, respectively.

[0019] Thereafter, the electrostatic latent images are developed and visualized with toner of each color, and the toner images of each color on each photosensitive drum 21 are sequentially superimposed and transferred onto the intermediate transfer belt 23 by a primary transfer bias applied to the primary transfer roller 24. As a result, a toner image is formed on the intermediate transfer belt 23.

[0020] In parallel with this toner image forming operation, the sheets S are transported one by one from the cassette unit 30 to the pair of registration rollers 47, and skew is corrected by the pair of registration rollers 47. After skew is corrected, the sheets S are transported by the pair of registration rollers 47 to the secondary transfer section 25, where the toner images are transferred onto the sheets S all at once by a secondary transfer bias.

[0021] Next, the sheet S onto which the toner image has been transferred in the secondary transfer unit 25 is transported to the fixing unit 26, where heat and pressure are applied to the fixing nip formed by a heating roller and a pressure roller, causing the toners of each color to melt and mix, and a color image is fixed on the sheet S. The sheet S with the fixed image is discharged and stacked on the discharge tray 6 by a pair of discharge rollers 44 provided downstream of the fixing unit 26. When forming images on both sides of the sheet S, after the images are fixed, a switching unit 45 selects a path that guides the sheet S to a re-conveyance unit 46, and the sheet S is reversed via the re-conveyance unit 46 and transported again to the pair of registration rollers 47.

[0022] [Cassette unit] Next, the cassette unit 30 will be described with reference to Fig. 3. Fig. 3 is a perspective view of the cassette unit 30. In this embodiment, the image forming apparatus 1 has two cassette units 30 (see Fig. 1), and although they are configured similarly to each other and are used to store different sheet sizes or types, only one of the cassette units 30 will be described.

[0023] The cassette unit 30 has a fixed frame 34, a front cover 35, and a sheet tray 31. The cassette unit 30 is attached to the device body 7 (see FIG. 1) of the image forming apparatus 1 so as to be removable on the front side F. The front cover 35 is fixed to the fixed frame 34 and exposed on the front side F of the device body 7 of the image forming apparatus 1, and by pulling it out towards the front, the entire cassette unit 30 can be pulled out together with the fixed frame 34.

[0024] On the right side (R) of the sheet tray 31, a leading edge regulating plate 36 is fixed to the fixed frame 34. The leading edge regulating plate 36 regulates and positions the downstream edge of the sheet stack in the sheet feeding direction Df. On the left side (L) of the sheet tray 31, a trailing edge regulating plate 37 is provided movably in the left-right direction relative to the fixed frame 34. The trailing edge regulating plate 37 regulates and positions the upstream edge of the sheet stack in the sheet feeding direction Df. On the front side (F) and rear side (B) of the sheet tray 31, side edge regulating plates 38 are provided movably in the front-rear direction relative to the fixed frame 34. The side edges of the sheet stack in the sheet width direction W are regulated and positioned. The sheet width direction W is perpendicular to the sheet feeding direction Df.

[0025] The sheet tray 31 is provided with a fixed frame 34 so as to be movable up and down by the driving force of a lift motor 51 (see FIG. 2), and supports sheets S stacked on a sheet support surface 31a, which is the upper surface. When the cassette unit 30 is pulled out from the device main body 7, the sheet tray 31 is lowered by the lift motor 51 so as to be located at the lowest position. The sheet tray 31 is raised by the lift motor 51 based on the position of the uppermost sheet of the sheet stack supported by the sheet tray 31. Specifically, the height position sensor 52 is set to detect whether the uppermost sheet S is located at a predetermined height at which it can be attracted to the underside of the feed belt 33. The control unit 5 drives the lift motor 51 to raise the uppermost sheet so as to be located at the predetermined height, depending on the detection result of the height position sensor 52.

[0026] Around the cassette unit 30, there are arranged an air feeding section 60, a feeding belt 33, a separating air blowing section 70, and a separating air blowing section 80 (see FIG. 2). The topmost sheet of the sheet stack stacked and supported on the sheet tray 31 is separated by separating air from the separating air blowing section 80 and is attracted to the feeding belt 33. The attracted sheets S are separated one by one by separating air from the separating air blowing section 70 and fed.

[0027] The air feeding unit 60 and the feed belt 33 are examples of a feeding unit and a suction feeding unit, and they suck and feed the top sheet of a stack of sheets supported on the sheet support surface 31a. The air feeding unit 60 has a suction fan motor 61 that sucks air (see FIG. 2), a duct 62 connected to the suction fan motor 61, and a chamber 63 connected to the tip of the duct 62 and having a suction port around its periphery. The chamber 63 is located on the inner periphery of the feed belt 33. The feed belt 33 is located above the end of the sheet support surface 31a on the right side R. The feed belt 33 has many holes on its surface and is located so as to surround the chamber 63. By rotating the feed belt 33 with the sheet S sucked, the sheet S can be transported downstream.

[0028] The separation blower 70 has a separation fan motor 71 that blows out air (see FIG. 2), a duct 72 connected to the separation fan motor 71, and a blowing port 73 that opens in the duct 72 (see FIG. 4(a)). The duct 72 is thin in the vertical direction and is disposed between the uppermost sheet and the feed belt 33, and opens on the upstream side in the sheet feeding direction Df to form the blowing port 73. The separation blower 70 is an example of a separation section and a second blowing section, and blows air (separation air) from the downstream side to the upstream side in the sheet feeding direction Df toward the sheet S adsorbed to the air feeding section 60, thereby separating the multiple sheets S adsorbed to the air feeding section 60 one by one.

[0029] The separating air blower 80 includes a separating fan motor 81 (see FIG. 2 ) that blows out air, a duct 82 connected to the separating fan motor 81, and a blowing port 83 opening in the duct 82. The separating air blower 80 is an example of a blowing section and a first blowing section, and blows air (separating air) from one side (rearward direction B) in the sheet width direction W to the upper part of the sheet stack supported on the sheet support surface 31a through the blowing port 83 to separate the upper sheets of the sheet stack. In this embodiment, the blowing port 83 is disposed opposite the downstream end of the support area supporting the maximum-sized sheets in the sheet feeding direction Df, as viewed from a direction perpendicular to the sheet feeding direction Df and the sheet width direction W. Therefore, blowing separating air to the leading edge of the sheet stack facilitates separation. Here, the relative positions of the duct 82 and the side end regulating plate 38 are determined in the front-rear direction. That is, the duct 82 is attached to the side end restricting plate 38, or the duct 82 is connected to the side end restricting plate 38. In this way, even if the width size of the sheet S changes, the distance from the side edge of the sheet S to the duct 82 is always kept constant.

[0030] [Sheet feeding operation] Next, the operation of feeding sheets S will be described with reference to FIGS. 4(a) to (c) and the flowchart of FIG. 5. As shown in FIG. 4(a), when a sheet stack is placed on sheet tray 31, control unit 5 drives lift motor 51, which raises and lowers sheet tray 31, based on the detection result of height position sensor 52, and moves it to a predetermined height suitable for feeding. As shown in FIG. 4(b), control unit 5 drives separating air blower 80, which blows separating air from blowing port 83 of duct 82 toward the side edge of the upper part of the sheet stack (S1 in FIG. 5). As a result, about 5 to 10 sheets S from the top of the sheet stack are lifted up.

[0031] The control unit 5 drives the air feeding unit 60, and starts the operation of adsorbing the uppermost sheet by the feeding belt 33 (S2 in FIG. 5). At the same time, the control unit 5 stops the air blowing unit 80, as shown in FIG. 4(c), and stops the blowing of air from the duct 82 (S3 in FIG. 5).

[0032] Furthermore, at the same time, the control unit 5 drives the separation blower unit 70 to blow separation air from the blowing port 73 of the duct 72 and blow it onto the floating sheet S (S4 in FIG. 5). As a result, the top sheet is further lifted toward the feed belt 33, and the top sheet S1 is adsorbed to the feed belt 33. At this time, separation air enters between the top sheet adsorbed to the feed belt 33 and the second sheet immediately below it, separating the second and subsequent sheets from the top sheet.

[0033] Thereafter, the control unit 5 stops the blowing operation of the separation blower unit 70, and all of the floating sheets fall toward the sheet tray 31. At this timing, the control unit 5 drives the feed belt 33 to rotate, thereby feeding only the topmost sheet S1 (S5 in FIG. 5). By repeating the above operation, it becomes possible to feed the sheets one by one separately.

[0034] [Rotating part] Here, when most of the sheet stack placed on the sheet tray 31 has been fed and there are fewer than 10 sheets remaining, there is a risk that the separating air will pass over the sheet stack, making it impossible to separate the sheets, and this could result in a decrease in separating performance. To address this issue, as shown in FIG. 9( a), a pivoting unit 190 can be provided at a location on the sheet tray 31 opposite the blowing port 83 of the separating air blowing unit 80. The pivoting unit 190 is in the closed position when a large number of sheets are placed on the sheet tray 31, but when there are fewer than 10 sheets remaining, the pivoting unit 190 is raised by the blowing of separating air and rotates to the open position, lifting the side edges of the sheets. This ensures that the separating air is blown reliably to the sides of the sheet stack with only a few remaining sheets. As a result, even when the number of sheets remaining on the sheet tray 31 is less than 10, the separating air is less likely to pass above the sheet stack, and the sheet stack is separated by the separating air, thereby avoiding a drop in separating performance.

[0035] However, even with the rotating unit 190, depending on the sheet weight, the temperature, and humidity of the operating environment, the following problem may occur when most of the sheets in a sheet stack are fed and only about 10 sheets remain. In this case, as shown in the comparative example in FIG. 9(a), the rotating unit 190 can be operated upward to blow separating air onto the side edges of the sheet stack. However, there is a risk that the air will subsequently enter between the bottom sheet and the sheet tray 31, causing the entire stack (less than 10 sheets) to float up, as shown in FIG. 9(b). Normally, separating air is blown from the leading edge of the sheets, between the top sheet and the second sheet below it, ensuring the top sheet is separated from the stack. However, in the example in FIG. 9(b), the air cannot enter between the top sheet and the sheet below it. This can result in poor sheet separation, preventing the sheets from sticking together, and increasing the risk of double feeding. Therefore, in this embodiment, a partition 93 is provided below the rotating portion 90 to prevent the clearance air from flowing between the lowermost sheet and the sheet tray 31.

[0036] 6(a) to 8, the rotating unit 90 of this embodiment will be described in detail below. As shown in FIGS. 6(a) and 6(b), the rotating unit 90 is provided rotatably relative to the sheet tray 31 with the sheet feeding direction Df as a rotation axis, and is disposed on one side (rear direction B side) in the sheet width direction W in the support area for the sheets S in the sheet tray 31. That is, when viewed from a direction perpendicular to the sheet feeding direction Df and the sheet width direction W, the rotating unit 90 is disposed at the downstream end in the sheet feeding direction in the support area for supporting maximum-size sheets.

[0037] The pivoting portion 90 can be pivotally displaced between a closed position where it is flush with or below the sheet support surface 31a and an open position where the rearward direction B side in the sheet width direction W is open above the sheet support surface 31a and a space Sp is formed below it between the sheet tray 31. Fig. 6(a) shows the pivoting portion 90 in the closed position, and Fig. 6(b) shows the pivoting portion 90 in the open position.

[0038] As shown in FIG. 7A, the rotating unit 90 includes a support plate 91 capable of supporting a sheet on its upper surface, two hinges 92 that form a rotating shaft, and a partition 93. The partition 93 is flange-shaped and protrudes downward from the rear side of the support plate 91. The partition 93 has a thickness in the left-right direction and separates the sheet support surface 31a from the space Sp when the rotating unit 90 is in the open position. The partition 93 is formed at the upstream end of the rotating unit 90 in the sheet feeding direction Df. As a result, the entire space Sp below the rotating unit 90 is separated from the sheet support surface 31a by the partition 93. The partition 93 is disposed upstream of the blowing port 83 in the sheet feeding direction Df when viewed from a direction perpendicular to the sheet feeding direction Df and the sheet width direction W. The space Sp is formed downstream of the partition 93 in the sheet feeding direction Df. In this embodiment, the partition 93 is formed at the upstream end of the rotating unit 90 in the sheet feeding direction Df, but this is not limiting. For example, the partition 93 may be provided slightly downstream of the upstream end of the rotating unit 90 in the sheet feeding direction Df. In this case, a space may be formed between the partition 93 and the sheet support surface 31a upstream of the partition 93 in the sheet feeding direction Df, and a very small amount of clearance air may be introduced between the bottom sheet and the sheet support surface 31a.

[0039] As shown in FIG. 7B, the sheet tray 31 has a sheet support surface 31a formed on its upper surface and a generally plate-shaped upper plate 31b that forms the upper portion of the sheet tray 31. The upper plate 31b has a storage compartment 32 recessed from the sheet support surface 31a to accommodate the pivoting unit 90 when the sheet tray 31 is in the closed position. The storage compartment 32 is located adjacent to a duct 82 attached to the side end restricting plate 38. The storage compartment 32 has a bottom 32a and a hole 32b formed in the bottom 32a. The hole 32b is provided so that when the pivoting unit 90 is in the closed position and accommodated in the storage compartment 32, the partition 93 penetrates downward through the upper plate 31b, retracting the partition 93 and allowing the entire support plate 91 to be accommodated in the storage compartment 32. When the support plate 91 is accommodated in the storage compartment 32, the upper surface of the pivoting unit 90 is positioned flush with the sheet support surface 31a. In this embodiment, the sheet tray 31 is positioned on the same plane, but this is not limiting and the sheet tray 31 may be positioned lower than the sheet support surface 31a. By positioning the sheet tray 31 below the sheet support surface 31a, a gap is not formed between the bottom sheet of the sheet stack supported by the sheet tray 31 and the sheet support surface 31a, which is preferable.

[0040] In this embodiment, the shape of the storage section 32 is such that the upper surface of the bottom 32a is open to the rearward direction B in the sheet width direction W in the surface direction (direction included in the surface) of the upper surface and is also open downstream in the sheet feeding direction Df. That is, the storage section 32 is not a recess closed on all four sides in the horizontal direction, but is open on the rearward direction B side and the rightward direction R side, and the separating air blown from the rearward direction B side flows through the space Sp, bends, and can flow out toward the rightward direction R side.

[0041] Next, the mechanism for rotating the rotating unit 90 will be described. When there are fewer than 10 sheets remaining, the rotating unit 90 rises to a position facing the duct 82, allowing air blown out from the duct 82 to flow between the rotating unit 90 and the tray's storage unit 32, causing the rotating unit 90 to move upward. Even when there are fewer than 10 sheets remaining, the rising of the rotating unit 90 allows air to properly hit the side edges of the sheet stack, causing the sheets to float and improving sheet separation performance.

[0042] In this embodiment, the lower edge of the rotating unit 90 on the rearward direction B side of the support plate 91 is chamfered. This allows the cleaning air blown from the blowing port 83 to flow into the gap between the underside of the rotating unit 90 and the storage unit 32, thereby allowing the rotating unit 90 to be positioned in the open position by the cleaning air. Whether the rotating unit 90 rotates depends on the relationship between the weight of the rotating unit 90 itself, the weight of the sheets placed on it, and the air volume. In this embodiment, the lower edge of the support plate 91 on the rearward direction B side is chamfered to allow the cleaning air to flow in. However, this is not limited to this, and the lower edge on the rearward direction B side of the bottom 32a of the storage unit 32 of the sheet tray 31 may also be chamfered. Alternatively, the chamfered shape is not limited to a chamfered shape, and any gap structure such as a groove may be used.

[0043] In this embodiment, the rotating portion 90 receives the sweeping air and moves to the open position when at least a portion of the rotating portion 90 faces the front of the blowing port 83. That is, when viewed from the sheet width direction W, the rotating portion 90 is located in the open position when at least a portion of the rotating portion 90 overlaps with the blowing port 83, and is located in the closed position when it does not overlap with the blowing port 83.

[0044] As shown in FIG. 8 , the air used to move the rotating unit 90 upward flows in the direction of arrow f1 because the partition 93 of the rotating unit 90 and the portion where the hinge 92 is pivotally supported by the storage unit 32 of the sheet tray 31 act as walls. As a result, almost no air flows in the direction of arrow f2, which is downstream in the sheet feeding direction Df of the sheet stack. In other words, the separating air blown onto the side edges of the sheet stack is less likely to flow between the bottom sheet and the sheet tray 31, preventing the entire stack (a small number of sheets, such as less than 10) from floating up. As a result, the separating air blown from the duct 72 of the separating air blowing unit 70 in the direction of arrow f3 is blown between the top sheet and the second sheet below it, improving separation performance and preventing double feeding.

[0045] As described above, in the sheet feeding device 3 of this embodiment, when the rotating unit 90 is in the open position, the rotating unit 90 has a partition 93 that separates the sheet support surface 31a from the space Sp below the rotating unit 90. Therefore, when the rotating unit 90 is in the open position, the separating air blown onto a small stack of sheets is less likely to flow from the space Sp toward the sheet support surface 31a. This makes it less likely for the air to get between the bottom sheet of the sheet stack and the sheet support surface 31a, preventing the sheet stack from floating and improving the ability to separate the sheet stack.

[0046] In addition, in this embodiment, a simple configuration of simply providing a partition section 93 on the rotating section 90 can prevent the flow of separating air between the bottom sheet of the sheet stack and the sheet support surface 31a, thereby reducing costs.

[0047] In the above-described embodiment, the rotating unit 90 is configured to rotate to the open position by blowing loosening air. However, this is not limited to this. That is, it is sufficient if a biasing unit is provided that applies a biasing force to the rotating unit 90 to rotate it from the closed position to the open position. This biasing unit biases the rotating unit 90 to rotate from the closed position to the open position when the biasing force is greater than the weight of the rotating unit 90 and the sheet stack supported above the rotating unit 90. For example, the biasing unit may be a cam that rotates in accordance with the height of the sheet tray 31, and the rotating unit 90 may also move in conjunction with this cam in accordance with the height position of the sheet tray 31. Alternatively, a spring may be provided to bias the rotating unit 90 to the open position, and the rotating unit 90 may rotate to the open position when the biasing force of the spring exceeds the weight of the remaining sheets.

[0048] In the above-described embodiment, the feeding unit is the air feeding unit 60 and the feeding belt 33, and the separating unit is the separation air blowing unit 70. However, the present invention is not limited to this. For example, the feeding unit may be a feeding roller, and the separating unit may be a separation roller.

[0049] In the above-described embodiment, the sheet feeding device is applied to the cassette unit 30 of the image forming apparatus 1, but the present invention is not limited to this and may be applied to, for example, a manual feed tray. Also, the present invention is not limited to being provided in the image forming apparatus 1 and may be applied to a standalone large-capacity sheet feeding device. [Explanation of symbols]

[0050] 1...image forming apparatus, 2...image forming section, 3...sheet feeding device, 7...apparatus main body, 30...sheet cassette, 31...sheet tray, 31a...sheet support surface, 31b...upper plate section, 32...storage section, 32a...bottom section, 32b...hole section, 33...feed belt (feed section), 51...lifting motor (lifting section), 60...air feeding section (feed section, suction feeding section), 70...separation blowing section (separation section, second blowing section), 80...separation blowing section (blowing section, first blowing section), 90...rotating section, 91a...urging section, 93...partition section, Df...sheet feeding direction, S...sheet, S1...topmost sheet, Sp...space, W...sheet width direction

Claims

1. a sheet tray that supports a sheet on a sheet support surface; a feeding section that feeds the top sheet of the sheet stack supported on the sheet support surface; a separating unit that separates the plurality of sheets fed by the feeding unit into individual sheets; a blowing unit that blows air onto an upper portion of the sheet stack from one side in a sheet width direction perpendicular to a sheet feeding direction through a blowing port to separate the upper sheets of the sheet stack; a rotating unit that is rotatable relative to the sheet tray with the sheet feeding direction as a rotation axis, that is disposed on one side in the sheet width direction in a sheet support area of ​​the sheet tray, and that can be displaced by rotating between a closed position that is positioned at a level below the sheet support surface and an open position that opens the one side in the sheet width direction above the sheet support surface and forms a space below it between the sheet tray and the rotating unit, the rotating portion has a partition portion that separates the seat support surface from the space when the rotating portion is located at the open position; A sheet feeding device characterized by:

2. The sheet tray is liftable and lowerable, a lifting unit that lifts and lowers the sheet tray; the lifting unit lifts the sheet tray based on the position of the top sheet of the sheet stack supported by the sheet tray.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

3. a biasing unit that applies a biasing force to the rotating unit to rotate the rotating unit from the closed position to the open position, and biases the rotating unit to rotate from the closed position to the open position when the biasing force is greater than the weight of the rotating unit and the sheet stack supported above the rotating unit; 2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

4. the biasing portion is formed on at least one of the rotating portion and the sheet tray, and has an inflow shape that causes the air blown from the blowing port to flow into a gap between the lower surface of the rotating portion and the sheet tray.

4. The sheet feeding device according to claim 3, wherein the sheet feeding device is a sheet feeding device.

5. When viewed from the seat width direction, the pivoting portion is positioned at the open position when at least a portion thereof overlaps the blowing port, and is positioned at the closed position when at least a portion thereof does not overlap the blowing port.

5. The sheet feeding device according to claim 4.

6. the blowing port is disposed to face a downstream end portion in the sheet feeding direction of the support region that supports a maximum size sheet, when viewed from a direction perpendicular to the sheet feeding direction and the sheet width direction.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

7. the rotating portion is disposed at a downstream end in the sheet feeding direction of the support region that supports a maximum size sheet when viewed from a direction perpendicular to the sheet feeding direction and the sheet width direction.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

8. the partition portion is formed at an upstream end portion of the rotating portion in the sheet feeding direction, the space is formed downstream of the partition portion in the sheet feeding direction; 2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

9. the partition portion is disposed upstream of the blowing port in the sheet feeding direction when viewed from a direction perpendicular to the sheet feeding direction and the sheet width direction.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

10. the sheet tray has an upper plate portion having a receiving portion recessed from the sheet support surface so as to receive the rotating portion positioned at the closed position, The storage section has a bottom and a hole formed in the bottom, through which the partition section passes below the upper plate section when the pivot section is located at the closed position and stored in the storage section.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

11. an upper surface of the bottom of the storage section is open to the one side in the sheet width direction and is open to a downstream side in the sheet feeding direction; 11. The sheet feeding device according to claim 10.

12. The spraying unit is a first spraying unit, the feeding unit is a suction feeding unit that sucks and feeds the top sheet of the sheet stack, the separating unit is a second blowing unit that blows air from the downstream side to the upstream side in the sheet feeding direction against the sheets sucked to the suction feeding unit, thereby separating the sheets sucked to the suction feeding unit one by one.

2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

13. a sheet feeding device according to any one of claims 1 to 12; an image forming unit that forms an image on a sheet, An image forming apparatus characterized by:

14. the sheet feeding device is housed in the device body and has a sheet cassette that feeds sheets to the image forming unit; 14. The image forming apparatus according to claim 13.

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