Sheet feeding apparatus and image forming apparatus

Abstract

To provide a sheet feeder and an image forming device of a new form related to a return member for pushing back a sheet.SOLUTION: A feeding member configured to feed the sheet accommodated in the cassette in a sheet feeding direction, the feeding member forming a nip portion with the feeding member and allowing a first sheet with which the feeding member is in contact to pass through the nip portion, the feeding member including a return member movable between a first position and a second position; And a separating member configured to prevent the at least one second sheet from passing through the nip portion when the at least one second sheet is conveyed to the nip portion together with the first sheet, wherein the returning member is movable from the second position to the first position so as to push back the at least one second sheet upstream of the nip portion in the sheet feeding direction in a state where the cassette is attached to the apparatus body.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 forms images on sheets. [Background technology]

[0002] Patent Document 1 describes a feeding device that includes a feeding cassette that is detachable from the main body of an image forming apparatus, a feeding roller and a feed roller that feed sheets from the feeding cassette, and a separation roller that forms a separation nip together with the feed roller. This document also describes a return lever that pushes the sheet back to the upstream side of the separation nip. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-116367 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above document, the return lever is disposed on the device body.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet feeding device and an image forming apparatus having a new configuration related to a return member that pushes back a sheet. [Means for solving the problem]

[0006] One aspect of the present invention is a sheet feeding device comprising: an apparatus main body; a cassette that stores sheets and is attached to the apparatus main body so that it can be pulled out, the cassette having a return member that can move between a first position and a second position; a feeding member that feeds the sheets stored in the cassette in a sheet feeding direction; and a separating member that forms a nip portion together with the feeding member, allows a first sheet that the feeding member abuts to pass through the nip portion, and prevents at least one second sheet from passing through the nip portion when the at least one second sheet is transported to the nip portion together with the first sheet; and when the cassette is attached to the apparatus main body, the return member is movable from the second position to the first position so as to push back the at least one second sheet upstream of the nip portion in the sheet feeding direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a sheet feeding device and an image forming apparatus having a new configuration related to a return member that pushes back a sheet. [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 cross-sectional view of a sheet feeding section according to the first embodiment. [Figure 3] FIG. 2 is a perspective view of a feeding unit and a driving device according to the first embodiment. [Figure 4] 3A and 3B are explanatory views of a feeding unit according to the first embodiment. [Figure 5] 1A and 1B are perspective views of a separation unit according to a first embodiment. [Figure 6] 4A to 4C are explanatory views of a feeding operation according to the first embodiment. [Figure 7] 3A to 3C are explanatory views of a separation unit according to the first embodiment. [Figure 8] FIG. 2 is an explanatory view of a stopper according to the first embodiment. [Figure 9] FIG. 10 is a perspective view of a separation unit according to a second embodiment. [Figure 10] 10A to 10C are explanatory diagrams of a separation unit according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0010] Example 1 1 is a schematic diagram showing a cross section of a printer 1 as an image forming apparatus according to Example 1. The printer 1 is an electrophotographic color laser beam printer that forms an image on a sheet S as a recording material.

[0011] As shown in FIG. 1, the X, Y, and Z directions are defined. The Z direction is the up-down direction (vertical direction) when the printer 1 is installed on a horizontal surface. The Y direction is the direction of the rotation axis of the photosensitive drum 61 provided in the printer 1. The X direction is a direction that intersects with both the Z direction and the Y direction. The X direction, Y direction, and Z direction are preferably perpendicular to each other. With respect to the printer 1 of this embodiment, the X direction may be referred to as the front-to-rear direction, the Y direction as the left-to-right direction, and the Z direction as the up-to-down direction. Furthermore, in this embodiment, the right direction in FIG. 1 is the front direction (front) of the printer 1.

[0012] As shown in FIG. 1, the printer 1 includes a device main body 1A (housing), a scanner 2 (exposure device), a control unit 3, a sheet feeding unit 30, a transfer unit 40, a cartridge tray unit 50, and a fixing device 80. The scanner 2, the control unit 3, the sheet feeding unit 30, and the fixing device 80 are housed in the device main body 1A. The transfer unit 40 and the cartridge tray unit 50 are each attached to the device main body 1A so that they can be pulled out. The cartridge tray unit 50 and the transfer unit 40 are examples of an image forming unit that forms an image on a sheet S. Note that instead of the intermediate transfer type image forming unit, a direct transfer type image forming unit may be used, or an image forming unit other than an electrophotographic type (for example, an inkjet type) may be used.

[0013] The sheet feeding section 30 has a sheet cassette 31 (also called a sheet tray or storage) for stacking sheets S as recording materials, a feeding unit 35 as a feeding means for feeding the sheets S, and a separation unit 36 ​​for separating the sheets S one by one. Details of the sheet feeding section 30 will be described later.

[0014] The cartridge tray unit 50 has a tray 51 and the cartridges PY, PM, PC, and PK, and the tray 51 has a tray handle 52. The cartridges PY, PM, PC, and PK are removably attached to the tray 51. In this embodiment, the cartridges PY, PM, PC, and PK can be attached to and detached from the tray 51 independently of each other.

[0015] The cartridges PY, PM, PC, and PK contain yellow (Y), magenta (M), cyan (C), and black (K) toner (developer), respectively. The cartridges PY, PM, PC, and PK have the same configuration except for the toner colors they contain. Therefore, the configuration and operation of only one of the cartridges PY, PM, PC, and PK will be described, and descriptions of the others will be omitted. Also, when there is no need to distinguish between the cartridges PY, PM, PC, and PK, the cartridges PY, PM, PC, and PK may be simply referred to as cartridge P.

[0016] The cartridge tray unit 50 has four photosensitive drums (image carriers) 61, four charging rollers 62 (charging members), and four developing rollers (developer carriers) 71. The rotational axis directions of the photosensitive drums 61, the developing rollers 71, and the charging rollers 62 are parallel to one another and are the same as the Y direction.

[0017] In the cartridge tray unit 50, the portion where a black (K) image is formed is called the black station (first station). The photosensitive drum 61 of the first station is called the first photosensitive drum, the developing roller 71 is called the first developing roller, and the charging roller 62 is called the first charging roller. In the cartridge tray unit 50, the portion where a cyan (C) image is formed is called the cyan station (second station). In the second station, the photosensitive drum 61 is called the second photosensitive drum, the developing roller 71 is called the second developing roller, and the charging roller 62 is called the second charging roller. In the cartridge tray unit 50, the portion where a magenta (M) image is formed is called the magenta station (third station). In the third station, the photosensitive drum 61 is called the third photosensitive drum, the developing roller 71 is called the third developing roller, and the charging roller 62 is called the third charging roller. In the cartridge tray unit 50, the portion where a yellow (Y) image is formed is called the yellow station (fourth station). The photosensitive drum 61 of the fourth station is called a fourth photosensitive drum, the developing roller 71 is called a fourth developing roller, and the charging roller 62 is called a fourth charging roller.

[0018] The photosensitive drum 61, the charging roller 62, and the developing roller 71 may be provided in either the cartridge P or the tray 51. In this embodiment, the cartridge P has the photosensitive drum 61, the charging roller 62, and the developing roller 71.

[0019] The transfer unit 40 includes a belt (intermediate transfer belt) 41, a primary transfer roller 42, a cleaning unit 43, a drive roller 46 that drives the belt 41, and a tension roller (driven roller) 47. The printer 1 in this embodiment is provided with an optical sensor 44 that detects the toner image transferred to the belt 41. In this embodiment, the belt 41 is disposed below the photosensitive drum 61 and can come into contact with the photosensitive drum 61 so as to form a primary transfer unit.

[0020] The printer 1 also has a secondary transfer roller 45 that contacts the belt 41 to form a secondary transfer section. The rotational axes of the primary transfer roller 42, drive roller 46, tension roller 47, and secondary transfer roller 45 are parallel to one another and are the same as the Y direction. A registration roller pair 4 is arranged before the secondary transfer section on the sheet transport path.

[0021] The fixing device 80 has a fixing section 81 and a discharge / reversal section 5. The fixing device 80 is configured to apply pressure and heat to the sheet S. In this embodiment, the fixing section 81 includes a heating section (heating roller) 82 including a heater, and a pressure section (pressure roller) 83. The heater (heat source) may be, for example, a halogen lamp, or a heater substrate on which a pattern of a resistance heating element is printed. The discharge / reversal section 5 has a pair of discharge rollers 6, a pair of reversal rollers 8, and a switching member 84.

[0022] [Image formation operation] 1, a series of operations (image forming operations) in which the printer 1 forms an image on a sheet S while conveying the sheet S will be described. The control unit 3 of the printer 1 starts the image forming operation based on an image signal received from an external host device 400. The external host device 400 is, for example, a personal computer, an image reader, or a facsimile machine.

[0023] In the image forming operation, first, the photosensitive drums 61 and the belt 41 start to be rotated. A charging voltage is applied to each charging roller 62, thereby charging the surface of the corresponding photosensitive drum 61. A laser corresponding to the image information is irradiated from the scanner 2 onto each photosensitive drum 61, exposing the surface of the photosensitive drum 61. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of each photosensitive drum 61.

[0024] Each developing roller 71 carries toner and supplies the toner to the corresponding photosensitive drum 61. A developing voltage is applied to the developing roller 71, and the electrostatic latent image formed on the photosensitive drum 61 is developed with the toner supplied from the developing roller 71, forming a toner image on the surface of the photosensitive drum 61. In this embodiment, the developing roller 71 develops the electrostatic latent image while in contact with the photosensitive drum 61 (contact development method), but the developing roller 71 may also develop the electrostatic latent image while there is a gap between the developing roller 71 and the photosensitive drum 61.

[0025] In this embodiment, the developing roller 71 is movable between a contact position where it contacts the photosensitive drum 61 and a spaced position where it is spaced from the photosensitive drum 61. Specifically, a switching device (not shown) provided in the apparatus main body 1A switches between a state where the developing roller 71 is in the contact position and a state where the developing roller 71 is in the spaced position. This allows the developing roller 71 to be spaced from the photosensitive drum 61 when no image forming operation is being performed.

[0026] When a full-color image is formed by the image forming operation, four-color toner images are formed on the four photosensitive drums 61. The printer 1 can form a full-color image with the photosensitive drums 61 corresponding to the cartridges PY, PM, PC, and PK in contact with the belt 41. The printer 1 can also form a monochrome image with the developing roller 71 corresponding to the cartridge PK in contact with the photosensitive drum 61 and the developing roller 71 corresponding to each of the cartridges PY, PM, and PC separated from the photosensitive drum 61.

[0027] The toner image formed on each photosensitive drum 61 is transferred onto the belt 41 by the primary transfer roller 42 and conveyed toward a secondary transfer portion formed by the belt 41 and a secondary transfer roller 45 .

[0028] Meanwhile, the sheet S is fed from the sheet feeding section 30 toward the secondary transfer section. The feeding operation will be described in detail later.

[0029] The toner image is transferred from the belt 41 to the sheet S transported to the secondary transfer section. Note that the toner that has not been transferred to the sheet S is removed from the belt 41 by a cleaning blade (cleaning member) 43A provided in the cleaning section 43. The sheet S onto which the toner image has been transferred in the secondary transfer section is transported toward the fixing device 80. In the fixing device 80, the sheet S is heated and pressurized in the fixing section 81, and the toner image is fixed to the sheet S.

[0030] After passing through the fixing unit 81, the sheet S is guided by a switching member 84 to either the discharge path 12 or the duplex path 11. In the case of single-sided printing, the sheet S is guided to the discharge path 12, discharged from the device main body 1A by the discharge roller pair 6, and stacked on the discharge tray 7 provided on the top surface of the device main body 1A. In the case of double-sided printing, the sheet S, on which an image has been formed on the first side by passing through the secondary transfer unit and the fixing unit 81, is guided to the duplex path 11, reversed (switched back) by the reversing roller pair 8, and then transported again toward the secondary transfer unit. Then, after the sheet S passes through the secondary transfer unit and the fixing unit 81 for the second time and an image has been formed on the second side, the sheet S is discharged from the device main body 1A by the discharge roller pair 6 and stacked on the discharge tray 7 provided on the top surface of the device main body 1A.

[0031] [Sheet Feeder] Next, the configuration of the sheet feeding section 30 will be described with reference to Figures 2 to 6. Figure 2 is a cross-sectional view showing the entire sheet feeding section 30. Figure 3 is a perspective view of the feeding unit 35. Figures 4(a) and 4(b) are diagrams showing the operation of the feeding unit 35. Figures 5(a) and 5(b) are diagrams showing the operation of the separation unit 36 ​​and the feeding cam 220. Figures 6(a) to 6(c) are diagrams showing the operation of the separation unit 36 ​​and the feeding unit 35.

[0032] 2 to 6(c), the sheet feeding section 30 includes a sheet cassette 31 (cassette), a feeding unit 35, a driving device 20, and a separation unit 36. In this embodiment, the separation unit 36 ​​is disposed in the sheet cassette 31, and the feeding unit 35 and the driving device 20 are disposed in the apparatus main body 1A.

[0033] (sheet cassette) 2, the sheet cassette 31 has a cassette frame 310, a lift plate 311 (sheet support portion) swingably attached to the cassette frame 310, and a lift arm 312 that raises and lowers the lift plate 311. The cassette frame 310 is formed with a storage space 310a that stores the sheets S.

[0034] The sheet cassette 31 is mounted in the device main body 1A so that it can be pulled out toward the front side of the printer 1 (to the right in FIG. 1). In this embodiment, the pull-out direction Dd of the sheet cassette 31 faces downstream in the sheet feeding direction Df (FIG. 2) of the sheets S fed from the sheet cassette 31. In other words, the sheet cassette 31 (cassette) is configured to be pulled out from the device main body 1A toward downstream in the sheet feeding direction Df. In this embodiment, the stopper 101 and separation roller 34, which are located downstream in the sheet feeding direction Df with respect to the storage space 310a of the sheet cassette 31, are disposed in the sheet cassette 31. In other words, the sheet cassette 31 has the stopper 101 and the separation roller 34, and when the sheet cassette 31 is moved relative to the device main body 1A, the stopper 101 and the separation roller 34 also move relative to the device main body 1A. Therefore, when the sheet cassette 31 is pulled out downstream in the sheet feeding direction Df, the sheet cassette 31 does not interfere with the stopper 101 or the separation roller .

[0035] When the sheet cassette 31 is attached to the apparatus main body 1A, the lift arm 312 is connected to a drive source provided in the apparatus main body 1A. The lift arm 312 rotates around the shaft 313 by the driving force of the drive source, and can raise the lift plate 311 to a position where the topmost sheet S in the sheet cassette 31 can be fed by the feeding unit 35.

[0036] The sheet cassette 31 is provided with a feeding guide 314. The feeding guide 314 is a guide member that guides the lower surface of the sheet S between the pickup roller 32 and the feed roller 33.

[0037] (feeding unit) 2 and 3, the feeding unit 35 includes a pickup roller 32, a feed roller 33, a feed shaft 206, a roller drive gear 205, a feed gear 207, an idler gear 208, and a pickup gear 209. The feeding unit 35 also includes a roller lifting member 210 and a roller lifting link 211.

[0038] The pickup roller 32 is disposed above a storage space 310a provided in the sheet cassette 31 for storing sheets S, and rotates while coming into contact with the uppermost sheet S in the sheet cassette 31, thereby feeding the sheet S in the sheet feeding direction Df. The feed roller 33 is a feeding member that feeds the sheets S stored in the sheet cassette 31 in the sheet feeding direction Df. The feed roller 33 in this embodiment is disposed downstream of the pickup roller 32 in the sheet feeding direction Df, and conveys the sheet S received from the pickup roller 32.

[0039] The feed gear 207 is attached to one end of the feed shaft 206, which is a roller shaft that supports the feed roller 33. The roller drive gear 205 is attached to the other end of the feed shaft 206. The roller drive gear 205 is an input unit that receives the driving force from the drive device 20 to rotate the feed roller 33 and the pickup roller 32. The feed roller 33, the feed gear 207, and the roller drive gear 205 are rotatable integrally around the central axis of the feed shaft 206. In other words, the driving force input to the roller drive gear 205 is transmitted to the feed roller 33 via the feed shaft 206.

[0040] The pickup gear 209 is attached to a roller shaft that supports the pickup roller 32, and rotates integrally with the pickup roller 32. The pickup gear 209 is connected to the feed gear 207 via an idler gear 208. In other words, a portion of the driving force input to the roller drive gear 205 is transmitted to the pickup roller 32 via the feed shaft 206, the feed gear 207, the idler gear 208, and the pickup gear 209.

[0041] One-way clutches may be disposed between the feed gear 207 and the feed roller 33, and between the pickup gear 209 and the pickup roller 32. The one-way clutches allow the feed roller 33 and the pickup roller 32 to rotate due to the pull of the sheet S moving in the sheet feeding direction Df, even when the rotation of the motor M1, which will be described later, is stopped.

[0042] The pickup roller 32, feed roller 33, pickup gear 209, idler gear 208, and feed gear 207 are attached to a roller lifting member 210 via holders (not shown). The roller lifting member 210 is configured to be swingable (liftable) around the feed shaft 206. That is, the pickup roller 32 is swingable (liftable) around the feed shaft 206. The pickup roller 32 is movable between a feeding position where it contacts the uppermost sheet of the sheet stack on the lifting plate 311, and a standby position where it is spaced above the uppermost sheet.

[0043] The roller lifting member 210 is biased in the downward direction of the pickup roller 32 by the biasing force of a biasing member (not shown). The biasing member is, for example, a spring member having one end engaged with a spring hook portion of the apparatus main body 1A and the other end engaged with the roller lifting member 210.

[0044] The roller lifting link 211 is configured to swing around the feed shaft 206 integrally with the roller lifting member 210. The roller lifting link 211 has a cam abutment portion 211a that abuts against a roller lifting cam portion 221 (FIG. 4(a)) of the feed cam 220, which will be described later. The roller lifting link 211 is a driven portion (drive input portion) that receives a driving force from the drive device 20 to lift and lower the pickup roller 32.

[0045] (Drive unit) The drive device 20 is a mechanism that transmits a driving force generated by a motor M1 as a driving source to the feeding unit 35. As shown in Fig. 3, the drive device 20 includes a motor M1 (driving source), a first driving gear 201, a second driving gear 202, a missing tooth gear 203, a feeding cam 220, and an idler gear 204.

[0046] The first drive gear 201 is connected to a motor M1 and rotates by the driving force of the motor M1. The second drive gear 202 meshes with the first drive gear 201. The missing tooth gear 203 can mesh with the second drive gear 202 and an idler gear 204. The idler gear 204 meshes with a roller drive gear 205 of the feeding unit 35.

[0047] The feed cam 220 is attached to a side surface of the partially toothed gear 203 and is rotatable together with the partially toothed gear 203. The feed cam 220 has a disk-shaped base portion 220a, a roller lifting cam portion 221 (FIG. 4(a)) as a first cam, and a separation cam portion 222 as a second cam. The roller lifting cam portion 221 and the separation cam portion 222 are provided on opposite surfaces of the base portion 220a. The feed cam 220 equipped with the separation cam portion 222 is disposed in the apparatus main body 1A and is an example of a drive member connected to a motor M1 (drive source).

[0048] Here, the missing tooth gear 203 is configured to be switchable between a state in which its rotation is restricted and a state in which its rotation is permitted by an actuator such as a solenoid, and is configured to selectively mesh with the second drive gear 202. That is, when the rotation of the missing tooth gear 203 is restricted by the solenoid at a predetermined rotational phase, the missing tooth region of the missing tooth gear 203 faces the second drive gear 202, and the meshing between the second drive gear 202 and the missing tooth gear 203 is released. When the restriction on the rotation of the missing tooth gear 203 by the solenoid is released, the missing tooth gear 203 rotates by a biasing means (not shown) to a rotational phase in which the teeth of the missing tooth gear 203 mesh with the second drive gear 202, and the second drive gear 202 and the missing tooth gear 203 can mesh with each other.

[0049] (separation unit) 5(a)(b) and 6(a) to 6(c), the separation unit 36 ​​includes a separation roller 34, a roller holder 341, a nip pressure spring 342 (FIG. 2), and a separation frame 343 (FIG. 2). The separation unit 36 ​​also includes a stopper 101, a stopper shaft 102, a roller holder gear 103, a separation gear 104, a stopper gear 105, a separation lever 106, and a separation shaft 107.

[0050] The separation roller 34 is positioned opposite the feed roller 33 and is held by a roller holder 341 via a torque limiter. The roller holder 341 is a holder member that holds the separation roller 34 as a separating member. A separation nip Ns is formed as a nip portion where the feed roller 33 and the separation roller 34 come into contact. The torque limiter allows the separation roller 34 to rotate when a torque equal to or greater than a predetermined value acts on the separation roller 34. The separation roller 34 is an example of a separating member that forms a nip portion together with the feed roller 33 (feeding member) and allows the top sheet against which the feed roller 33 abuts to pass through the nip portion while preventing sheets other than the top sheet from passing through the nip portion. In other words, when multiple sheets are conveyed to the separation nip Ns, the top sheet of the multiple sheets can be referred to as the first sheet, and the sheets other than the top sheet can be referred to as at least one second sheet. The at least one second sheet separated from the first sheet by the separating member can be a single sheet or multiple sheets.

[0051] The separation roller 34 in this embodiment is an example of a separating member, and the separating member is not limited to this. A pad-shaped elastic member (separation pad) that contacts the feed roller 33 may also be used as the separating member. A roller (retard roller) to which a driving force in the retard direction is input via a torque limiter may also be used as the separating member. The retard direction is a rotation direction in which the movement direction of the roller circumferential surface at the separation nip Ns is opposite to the sheet feeding direction Df. In other words, the "separating member" may be any member that forms a separation nip Ns with the feed roller 33, applies frictional force to the sheets S at the separation nip Ns, separates the multiple sheets S, and allows the sheets S to pass through the separation nip Ns one by one.

[0052] The roller holder 341 and the nip pressure spring 342 are attached to a separation frame 343. The nip pressure spring 342 biases the roller holder 341 so as to press the separation roller 34 against the feed roller 33. In this embodiment, the biasing force of the nip pressure spring 342 causes the separation roller 34 to come into contact with the feed roller 33, thereby forming the separation nip Ns. At least a portion of the feeding guide 314 of the sheet cassette 31 described above is configured to guide the leading edge of the sheet S fed by the pickup roller 32 to the separation nip Ns.

[0053] The roller holder gear 103 is rotatable around a common rotation axis with the roller holder 341. The roller holder gear 103 is in mesh with the separation gear 104. The roller holder gear 103 has an engagement portion 103a (FIG. 5(a)) that engages with the roller holder 341. The engagement portion 103a presses the roller holder 341, causing the roller holder 341 to rotate integrally with the roller holder gear 103. The rotation of the roller holder 341 allows the separation roller 34 to move between an abutment position where it abuts against the feed roller 33 and a separation position where it is separated from the feed roller 33.

[0054] The separation shaft 107 extends in a direction (Y direction) parallel to the rotation axis of the separation roller 34. The separation lever 106 is attached to one end of the separation shaft 107, and the separation gear 104 is attached to the other end of the separation shaft 107. The separation shaft 107 is rotatably held by a separation frame 343. The separation lever 106 can abut against a separation cam portion 222 of the feed cam 220. When the separation cam portion 222 presses the separation lever 106, the separation lever 106, separation shaft 107, and separation gear 104 rotate integrally around the central axis of the separation shaft 107. The separation lever 106 is an example of a driven member (drive input portion) that receives a driving force from the drive device 20 of the device main body 1A. The separation lever 106, which is a driven member in this embodiment, is configured as a cam follower that moves when pressed by the feed cam 220 (cam).

[0055] The stopper 101 is an example of a returning member that pushes back sheets other than the uppermost sheet contacting the feed roller 33 (feeding member) upstream of the separation nip Ns (nip portion) in the sheet feeding direction Df. In this embodiment, the stopper 101 is disposed in the sheet cassette 31 as part of the separation unit 36.

[0056] The stopper 101 is attached to a stopper shaft 102 extending in a direction (Y direction) parallel to the rotation axis of the separation roller 34. The stopper 101 has a contact surface 101a that can contact the leading edge of the sheet S. In this embodiment, one stopper 101 is disposed on each side of the separation roller 34 in the Y direction. The direction in which the contact surface 101a presses the sheet S is preferably approximately parallel to the sheet S. Therefore, while the stopper 101 moves, it is preferable that the direction in which the contact surface 101a presses the sheet S be approximately parallel to the sheet S. While the stopper 101 moves, in order to keep the direction in which the contact surface 101a presses the sheet S within a predetermined range, the contact surface 101a may include at least one of a curved surface, a plurality of flat surfaces with different angles, and a plurality of curved surfaces with different curvatures.

[0057] A stopper gear 105 is also attached to the stopper shaft 102. The stopper gear 105 is engaged with a separation gear 104. The stopper shaft 102 is rotatably held by a separation frame 343.

[0058] The separation shaft 107, the stopper shaft 102, the roller holder gear 103, the separation gear 104, and the stopper gear 105 function as a transmission mechanism that transmits the driving force received by the separation lever 106 (driven member) from the feed cam 220 (driving member) of the apparatus main body 1A. This transmission mechanism transmits the driving force received by the separation lever 106 (driven member) to the roller holder 341 (holder member) and the stopper 101 (returning member). As will be described later, when the sheet cassette 31 is attached to the apparatus main body 1A, this transmission mechanism moves the roller holder 341 in conjunction with the movement of the stopper 101 from the restriction position P1 (first position) to the restriction release position P2 (second position). At that time, the transmission mechanism moves the roller holder 341 so that the separation roller 34 abuts against the feed roller 33.

[0059] The transmission mechanism of this embodiment includes a separation shaft 107 as a first shaft portion to which a separation lever 106 (driven member) is attached, and a stopper shaft 102 as a second shaft portion to which a stopper 101 (return member) is attached. The transmission mechanism of this embodiment also includes an engagement portion 103a that engages with a roller holder 341 (holder member), and a gear train (103, 104, 105) that transmits driving force from the separation shaft 107 (first shaft portion) to the stopper shaft 102 (second shaft portion) and the engagement portion 103a.

[0060] When the sheet cassette 31 is attached to the apparatus main body 1A, the stopper 101 can move between a restricting position (first position, return position) shown in FIGS. 5A and 6A and a non-restricting position (second position, permitting position, passing position) shown in FIGS. 5B and 6B. The restricting position is a position where at least a part of the contact surface 101a of the stopper 101 is upstream of the separation nip position Ps in the sheet feeding direction Df. The separation nip position Ps is the position where the distance between the circumferential surface of the feed roller 33 and the circumferential surface of the separation roller 34 is narrowest in the sheet feeding direction Df. In other words, the restricting position is the position of the stopper 101 when the stopper 101 pushes back the sheet S upstream of the separation nip Ns (FIG. 6B) in the sheet feeding direction Df. The restriction release position is the position of the stopper 101 when the contact surface 101a is retracted downstream of the separation nip Ns in the sheet feeding direction Df. That is, the restriction release position is a position where the stopper 101 allows the sheet S conveyed by the feed roller 33 (feeding member) to pass through. In other words, when the stopper 101 is in the restriction release position, the sheet conveyed by the pickup roller 32 is allowed to reach the separation nip Ns.

[0061] As will be described below, the stopper 101 and the separation roller 34 move in conjunction with the operation of the feeding unit 35 during the sheet feeding operation. In addition, as will be described later, the stopper 101 can move to a retracted position (third position) different from the restricting position and the unrestricting position in association with the insertion or removal of the sheet cassette 31.

[0062] [Feeding operation] A series of operations (feeding operations) in which the sheet feeding unit 30 feeds the sheets S one by one during the image forming operation will be described below. First, the state before the start of the feeding operation will be described with reference to FIGS. 4(a), 5(a), and 6(a).

[0063] Before the start of the feeding operation, as shown in Fig. 4(a), the roller lifting cam portion 221 of the feeding cam 220 abuts against the roller lifting link 211. Due to the abutment between the roller lifting cam portion 221 and the roller lifting link 211, the feeding unit 35 is held in a standby position where the pickup roller 32 is spaced upward from the uppermost sheet S1 of the sheet cassette 31 (Fig. 6(a)).

[0064] 5(a) and 6(a), before the start of the feeding operation, the separation cam portion 222 of the feeding cam 220 is in contact with the separation lever 106. Due to the contact between the separation cam portion 222 and the separation lever 106, the roller holder gear 103 is maintained in a state where it presses down the roller holder 341 against the biasing force of the nip pressure spring 342, and the separation roller 34 is held in the separated position.

[0065] Furthermore, before the start of the feeding operation, the stopper gear 105 is held at a predetermined rotational phase by the abutment of the separation cam portion 222 and the separation lever 106 so that the stopper 101 is positioned at the restricting position.

[0066] When the feeding operation starts, the solenoid releases the rotation restriction on the missing tooth gear 203 (FIG. 3), and driving force begins to be transmitted by the driving device 20. When driving force transmission by the driving device 20 begins, the feeding cam 220 starts to rotate together with the missing tooth gear 203.

[0067] The feed cam 220 rotates in a predetermined rotation direction (clockwise in the figure) as shown in FIG. 4(b). Due to the rotation of the feed cam 220, the roller lifting cam portion 221 begins to disengage from the cam abutment portion 211a of the roller lifting link 211. Then, the roller lifting member 210 swings together with the roller lifting link 211 around the feed shaft 206 in the clockwise direction in the figure, causing the pickup roller 32 to descend from the standby position to the feeding position. Furthermore, due to the rotation of the missing tooth gear 203, a driving force is also input to the roller drive gear 205 (FIG. 3), so that the feed roller 33 and the pickup roller 32 are driven to rotate. Then, with the pickup roller 32 abutting the uppermost sheet S1 of the sheet cassette 31 at the feeding position, the pickup roller 32 and the feed roller 33 rotate, and the uppermost sheet S1 is fed in the sheet feeding direction Df.

[0068] Furthermore, when the feeding operation is started, the separation cam portion 222 of the feeding cam 220 disengages from the separation lever 106 as shown in FIGS. 5(b) and 6(b). When the separation lever 106 is released from the separation cam portion 222, the restriction on rotation of the separation shaft 107 is released, and the restriction on rotation of the roller holder 341 due to the meshing of the separation gear 104 and the roller holder gear 103 is also released. Then, due to the biasing force of the nip pressure spring 342 (FIG. 2), the roller holder 341 is allowed to rotate around the rotation shaft 341a in the direction in which the separation roller 34 approaches the feed roller 33 (clockwise direction in FIG. 5(b)). Due to the rotation of the roller holder 341, the separation roller 34 moves from the separated position to the abutting position, and the separation nip Ns is formed. Meanwhile, the biasing force of the nip pressure spring 342 is transmitted to the separation shaft 107 via the roller holder 341, the roller holder gear 103, and the separation gear 104, causing the separation shaft 107 to rotate, and the separation lever 106 moves along the cam surface of the separation cam portion 222. When the separation roller 34 reaches the contact position, the rotation of the separation shaft 107 and the separation lever 106 stops.

[0069] Furthermore, when the feeding operation is started, the separation shaft 107 rotates due to the biasing force of the nip pressure spring 342, and the separation gear 104 on the separation shaft 107 rotates the stopper gear 105. The rotation of the stopper gear 105 causes the stopper 101 to move around the stopper shaft 102 in a direction from the restricting position toward the unrestricted position (clockwise in FIG. 5(b)). The stopper 101 is configured to move from the restricting position to the unrestricted position while the separation roller 34 moves from the separated position to the abutting position.

[0070] The topmost sheet S1, which has begun to be fed by the pickup roller 32, is conveyed through the separation nip Ns. At this time, due to friction between the sheets, sheet S2 overlapping the topmost sheet S1 may be pulled out by the topmost sheet S1 and enter the separation nip Ns. However, the separation roller 34 applies a frictional force in the opposite direction of the sheet feeding direction Df to the sheets S2 other than the topmost sheet S1 at the separation nip Ns, preventing the sheets S2 other than the topmost sheet S1 from passing through the separation nip Ns. In other words, when at least one second sheet is conveyed to the separation nip Ns together with the topmost sheet S1, the separation roller 34 prevents at least one second sheet from passing through the separation nip Ns. On the other hand, when only the topmost sheet S1 has entered the separation nip Ns, the separation roller 34 rotates following the topmost sheet S1, allowing the topmost sheet S1 to pass through the separation nip Ns.

[0071] When the feed cam 220 rotates further, the roller lift cam portion 221 of the feed cam 220 comes into contact with the roller lift link 211 again (FIG. 4(a)). Then, due to the contact between the roller lift cam portion 221 and the roller lift link 211, the feed unit 35 is held in a state in which the pickup roller 32 is in the standby position (FIG. 6(a)).

[0072] Furthermore, when the feed cam 220 rotates to a predetermined angle from the start of the feeding operation, the separation cam portion 222 of the feed cam 220 abuts against the separation lever 106 again, as shown in FIG. 6(c). The separation cam portion 222 presses against the separation lever 106 to rotate the separation shaft 107. As the separation shaft 107 rotates, the separation gear 104 rotates the roller holder gear 103, and the roller holder gear 103 presses down the roller holder 341 against the biasing force of the nip pressure spring 342. As a result, the separation roller 34 moves from the abutment position toward the separation position and separates from the feed roller 33.

[0073] Furthermore, when the feed cam 220 rotates to a predetermined angle from the start of the feed operation, the separation gear 104 rotates the stopper gear 105 in accordance with the rotation of the separation shaft 107. As the stopper gear 105 rotates, the stopper 101 swings counterclockwise around the stopper shaft 102 in FIG. 6(c). In other words, the stopper 101 swings from the restriction release position toward the restriction position.

[0074] As the stopper 101 moves from the restriction release position to the restriction position, the contact surface 101a of the stopper 101 comes into contact with the leading edge of the sheet S2 that was brought to the vicinity of the separation nip Ns when the uppermost sheet S1 was fed. Then, the stopper 101 moves to the restriction position while pushing back the leading edge of the sheet S2 to a position upstream of the separation nip Ns (FIG. 6(a)).

[0075] When the missing tooth gear 203 rotates once from the state before the start of the feeding operation, the solenoid again restricts the rotation of the missing tooth gear 203. As a result, the drive transmission of the drive device 20 is interrupted, and the feeding unit 35 and the separation unit 36 ​​return to the states before the start of the feeding operation shown in Figures 4(a), 5(a), and 6(a). This completes the feeding operation for one sheet.

[0076] When multiple sheets S are fed continuously, the above-described feeding operation is repeatedly performed for each sheet. Even when the feeding operation is repeatedly performed, the stopper 101 repeatedly pushes back the sheets S2 other than the uppermost sheet S1, which is the target of the current feeding operation, upstream of the separation nip Ns for each sheet. Therefore, it is possible to more reliably prevent double feeding of sheets than when the stopper 101 is not used.

[0077] In this way, when the sheet cassette 31 is attached to the apparatus main body 1A, the feed cam 220 (driving member) of the apparatus main body 1A engages with the separation lever 106 (driven member) of the sheet cassette 31 to transmit the driving force of the motor M1 (driving source). This drive transmission moves the stopper 101 (returning member) between the restricting position (first position) and the unrestricting position (second position).

[0078] [Operation when inserting or removing a cassette] Next, the operation of the separation unit 36 ​​when the sheet cassette 31 is pulled out and attached to the apparatus main body 1A (hereinafter collectively referred to as insertion and removal) will be described with reference to Figures 7(a) to 7(c) and 8. Figures 7(a) to 7(c) are perspective views showing the operation of the separation unit 36 ​​when the sheet cassette 31 is pulled out from the apparatus main body 1A. Figure 8 is a cross-sectional view showing the state when sheets S are refilled into the sheet cassette 31.

[0079] Fig. 7(a) shows a state in which the sheet cassette 31 is installed in a predetermined installation position in the apparatus main body 1A (a position where the sheet feeding unit 30 can feed sheets from the sheet cassette 31). Fig. 7(b) shows a state in which the sheet cassette 31 has been pulled out several millimeters in the pull-out direction Dd from the installation position. Fig. 7(c) shows a state in which the sheet cassette 31 has been further pulled out in the pull-out direction Dd from the state in Fig. 7(b).

[0080] As described above, the feeding unit 35 and the drive device 20 are disposed in the apparatus main body 1A, and the separation unit 36 ​​is disposed in the sheet cassette 31. Therefore, when the sheet cassette 31 is pulled out from the apparatus main body 1A, as will be described in detail below, the separation cam portion 222 of the feeding cam 220 of the drive device 20 moves away from the separation lever 106 of the separation unit 36. In other words, when the sheet cassette 31 is pulled out from the apparatus main body 1A, the feeding cam 220 (driving member) of the apparatus main body 1A moves away from the separation lever 106 (driven member) of the sheet cassette 31.

[0081] 7(a) and 7(b), when the sheet cassette 31 starts to move in the pull-out direction Dd from the installation position, the separation lever 106 moves in the pull-out direction Dd relative to the separation cam portion 222. Then, the separation lever 106 is gradually released from the separation cam portion 222, so that the rotation restriction on the separation shaft 107 is released, and the rotation restriction on the roller holder 341 due to the meshing of the separation gear 104 and the roller holder gear 103 is also released. Then, due to the biasing force of the nip pressure spring 342, the roller holder 341 rotates in a direction (clockwise direction in the figure) in which the separation roller 34 approaches the feed roller 33. Furthermore, as the biasing force of the nip pressure spring 342 rotates the separation shaft 107, the separation gear 104 on the separation shaft 107 rotates the stopper gear 105, and the stopper 101 moves in a direction (clockwise direction in FIG. 7(b)) from the restricted position toward the unrestricted position.

[0082] In other words, when the sheet cassette 31 starts to move from the mounting position toward the pull-out direction Dd, the separation roller 34 starts to move from the separation position toward the abutment position, and the stopper 101 starts to move from the restriction position toward the release position, just as at the start of the feeding operation.

[0083] However, unlike the case of the feeding operation, when the sheet cassette 31 is pulled out from the device main body 1A, the roller holder 341 does not stop at the position where the separation roller 34 abuts against the feed roller 33. During the feeding operation, the roller holder 341 rotates clockwise in the drawing beyond the position where the separation roller 34 abuts against the feed roller 33, and stops when it abuts against the feed guide 314. Specifically, the stopping position of the roller holder 341 when the sheet cassette 31 is pulled out from the device main body 1A is the position where part of the roller holder 341 abuts against the surface 314b (downward surface, see FIG. 8) opposite to the guide surface 314a (upward surface) of the feed guide 314.

[0084] 7C and 8, the stopper 101 rotates clockwise in the figure while the roller holder 341 rotates clockwise in the figure beyond the position where the separation roller 34 contacts the feed roller 33 during the feeding operation. Therefore, as shown in Figures 7C and 8, the retracted position P3 (solid line), which is the position of the stopper 101 when the sheet cassette 31 is pulled out from the apparatus main body 1A, is the position where the stopper 101 has swung from the restricting position P1 beyond the unrestricted position P2. In other words, when the sheet cassette 31 is pulled out from the apparatus main body 1A, the stopper 101 (returning member) is located at the retracted position (third position) downstream of the unrestricted position P2 in the movement direction from the restricting position P1 (first position) toward the unrestricted position P2 (second position).

[0085] In other words, the rotation angle of the roller holder 341 about the rotation shaft 341a when the sheet cassette 31 is pulled out from the apparatus main body 1A is larger than the rotation angle of the roller holder 341 about the rotation shaft 341a during the feeding operation. Also, the rotation angle of the stopper 101 about the stopper shaft 102 when the sheet cassette 31 is pulled out from the apparatus main body 1A is larger than the rotation angle of the stopper 101 about the stopper shaft 102 during the feeding operation.

[0086] In this way, when the sheet cassette 31 is pulled out from the apparatus main body 1A, the stopper 101 is positioned at a retracted position P3, which is further retracted from the restriction release position P2 that allows the passage of the sheets S during the feeding operation. This makes it less likely that the stopper 101 will interfere with the operation of refilling the sheet cassette 31 with sheets when the sheet cassette 31 is pulled out from the apparatus main body 1A, thereby improving workability.

[0087] In this embodiment, when the feed cam 220 (driving member) and the separation lever 106 (driven member) are separated by the extraction of the sheet cassette 31, the stopper 101 (returning member) is positioned at the retracted position P3 (third position) by the biasing force of the nip pressure spring 342 as a biasing member. Also, in this embodiment, the nip pressure spring 342 not only biases the stopper 101 but also serves as a spring member for pressing the separation roller 34 against the feed roller 33 to form the separation nip Ns, thereby reducing the number of parts. However, the biasing member is not limited to this, and for example, a spring member that biases the stopper 101 toward the retracted position P3 may be provided separately from the nip pressure spring 342.

[0088] As shown in FIG. 8, the retracted position of the stopper 101 is preferably a position retracted from the feed guide 314, which is a guide member that guides the lower surface of the sheet S on the upstream side of the separation roller 34 in the sheet feeding direction Df. Specifically, when the stopper 101 is in the retracted position, it is preferable that the entire stopper 101 be located below the guide surface 314a (upper surface) of the feed guide 314 when viewed in the direction of the rotation axis of the feed roller 33 (Y direction). In other words, when the returning member is located at the retracted position P3 (third position), it is preferable that the entire stopper 101 (returning member) be located below the upper surface (guide surface 314a) of the guide member when viewed in the direction of the rotation axis of the feed roller 33 (feeding member).

[0089] This prevents the sheet S from getting caught on the stopper 101 when the user attempts to set the sheet S in the storage space 310a of the sheet cassette 31 along the guide surface 314a, for example. Furthermore, even when the user sets the sheet S from a different direction, the user can be prevented from accidentally coming into contact with the stopper 101, and damage to the separation unit 36 ​​can be prevented.

[0090] In this embodiment, since the sheet cassette 31 is pulled out from the apparatus main body 1A toward the downstream side in the sheet feeding direction Df, it is assumed that the user will mainly access the sheet cassette 31 from above the sheet cassette 31 and from the downstream side in the sheet feeding direction Df. In such a case, even when the sheet S is set obliquely downward along the guide surface 314a of the feeding guide 314, the sheet S can be prevented from getting caught on the stopper 101. Note that the user may set the sheet S in the storage space 310a of the sheet cassette 31 while a part of the sheet cassette 31, including the upstream end of the cassette frame 310 in the sheet feeding direction Df, remains inside the apparatus main body 1A.

[0091] When the sheet cassette 31 that has been pulled out from the device main body 1A is inserted into the device main body 1A, the separation unit 36 ​​operates in the reverse order to the operation when pulling out the sheet cassette 31 described above (in the order of (c) → (b) → (a) in Figure 7).

[0092] That is, before the separation lever 106 abuts against the separation cam portion 222, the roller holder 341 abuts against the surface 314b of the feeding guide 314 and the stopper 101 is positioned at the retracted position as shown in FIG. 7(c).

[0093] As the sheet cassette 31 is inserted into the apparatus main body 1A, the separation lever 106 comes into contact with the separation cam portion 222 as shown in FIG. 7B. Then, the separation lever 106 is pressed by the separation cam portion 222, causing the separation shaft 107 to rotate in the clockwise direction in the figure. Then, due to the meshing of the separation gear 104 and the roller holder gear 103, the roller holder 341 rotates in a direction (counterclockwise direction in the figure) in which the separation roller 34 moves away from the feed roller 33 against the biasing force of the nip pressure spring 342, and moves away from the feeding guide 314. In addition, as the separation shaft 107 rotates, the separation gear 104 on the separation shaft 107 rotates the stopper gear 105, and the stopper 101 moves from the retracted position P3 toward the release position P2 and the restricting position P1 (counterclockwise direction in FIGS. 7B and 8).

[0094] When the sheet cassette 31 is further inserted and reaches the installation position, as shown in FIG. 7(a), the separation unit 36 ​​returns to the state it was in before the start of the feeding operation. That is, with the separation roller 34 positioned at the abutment position, the roller holder 341 is positioned, and the stopper 101 is positioned at the restriction position P1 (FIG. 8). In this way, when the sheet cassette 31 pulled out from the apparatus main body 1A is inserted into the apparatus main body 1A, the feeding cam 220 (driving member) abuts against the separation lever 106 (driven member). This moves the stopper 101 (returning member) from the retracted position P3 (third position) to the restriction position P1 (first position).

[0095] [Summary of this Example] As described above, the configuration of this embodiment can provide a new type of sheet feeding device and image forming apparatus in which the stopper 101 (returning member) is arranged in the sheet cassette 31 rather than in the apparatus main body 1A.

[0096] Furthermore, according to this embodiment, when the sheet cassette 31 is pulled out from the apparatus main body 1A, the stopper 101 (returning member) is positioned at a retracted position P3 (third position) that is further retracted from the restriction release position P2. Therefore, when replenishing or removing sheets S from the sheet cassette 31, the user's hand or the sheets S will not come into contact with the stopper 101, and the work can be performed smoothly without damaging the sheets S.

[0097] Furthermore, when the sheet cassette 31 is attached to the apparatus main body 1A, the stopper 101 moves between a restricting position P1 (first position) and a derestricting position P2 (second position) that is closer to the restricting position P1 than the retracted position P3 (third position). Therefore, the movement amount of the stopper 101 during the feeding operation is less than the movement amount of the stopper 101 when the sheet cassette 31 is inserted into or removed from the apparatus main body 1A. This makes it possible to improve the throughput (number of sheets fed per unit time) of the sheet feeding section 30, and to accommodate higher speeds of the printer 1.

[0098] Example 2 Next, a description will be given of Example 2. Example 2 differs from Example 1 in that the separation unit is driven by a drive source independent of the motor M1 (FIG. 3) of Example 1. Hereinafter, elements with the same reference symbols as Example 1 will be considered to have basically the same configurations and functions as those described in Example 1 unless otherwise specified, and differences from Example 1 will be mainly described.

[0099] [Separation unit] 9 is a perspective view showing the configuration of a separation unit 36A in Example 2. The separation unit 36A has a separation roller 34, a roller holder 341, a nip pressure spring 342 (FIG. 2), and a separation frame 343 (FIG. 2). The separation unit 36A also has a stopper 101, a stopper shaft 112, a roller holder gear 103, a stopper gear 105, an idler gear 108, a separation lever 121, and a rotation restriction lever 122.

[0100] In the second embodiment, the apparatus main body 1A is provided with a solenoid unit (232, 233, 235) including a solenoid 232 as a drive source, and abutment portion 234. The solenoid unit has the solenoid 232, a solenoid lever 233 rotatable around a support shaft 235, and a biasing spring that biases the solenoid lever 233 in a predetermined direction (the direction of the arrow in the figure). The solenoid lever 233 rotates around the support shaft 235 in accordance with the movement of a plunger 236 of the solenoid 232. The solenoid lever 233 is an example of a drive member connected to the solenoid 232 (drive source). The abutment portion 234 is fixed to the frame of the apparatus main body 1A.

[0101] The stopper 101 is fixed to a stopper shaft 112. In this embodiment, one stopper 101 is arranged on each side of the separation roller 34 in the direction of the rotation axis of the separation roller 34 (Y direction). The stopper shaft 112 is supported by a separation frame 343 so as to be rotatable around an axis in the Y direction. A separation lever 121 and a rotation restriction lever 122 are provided at the end of the stopper shaft 112. The separation lever 121 and the rotation restriction lever 122 each protrude in a direction intersecting the central axis of the stopper shaft 112 and in different directions. The separation lever 121 is an example of a driven member to which a driving force is transmitted from a solenoid lever 233 serving as a driving member. In this embodiment, the separation lever 121 serving as a driven member is a pressed portion pressed by the solenoid lever 233.

[0102] The stopper 101 and the stopper shaft 112 are biased in a predetermined rotational direction R1 by a biasing member (not shown). The biasing member that biases the stopper 101 and the stopper shaft 112 may be the nip pressure spring 342, or may be a spring separate from the nip pressure spring 342. The rotational direction R1 is the direction in which the stopper 101 moves from the restricted position P1 toward the unrestricted position P2 (FIGS. 10(a) and 10(b)).

[0103] The stopper gear 105 is fixed to a stopper shaft 112. The stopper gear 105 is connected to the roller holder gear 103 via an idler gear .

[0104] The stopper shaft 112, roller holder gear 103, stopper gear 105, and idler gear 108 function as a transmission mechanism that transmits the driving force received by the separation lever 121 (driven member) from the solenoid lever 233 (driving member) of the apparatus main body 1A. The transmission mechanism of this embodiment includes the stopper shaft 112 as a shaft portion to which the separation lever 121 (driven member) and the stopper (101) are attached. The transmission mechanism of this embodiment also includes an engagement portion 103a that engages with the roller holder 341 (holder member), and a gear train (103, 105, 108) that transmits the driving force from the stopper shaft 112 (shaft portion) to the engagement portion 103a.

[0105] [Feeding operation] The operation of the separation unit 36 ​​in this embodiment during the feeding operation will be described using Figures 10(a) and (b). Figure 10(a) is a diagram showing the separation unit 36 ​​when the sheet cassette 31 is attached to the apparatus main body 1A and before the feeding operation begins. Figure 10(b) is a diagram showing the separation unit 36 ​​when the sheet cassette 31 is attached to the apparatus main body 1A and during the feeding operation. Note that the viewpoints of Figures 10(a) to (c) are on the opposite side in the Y direction from the viewpoints of Figures 6(a) to (c) and Figures 7(a) to (c).

[0106] As shown in FIG. 10(a), before the start of the feeding operation, the solenoid 232 is energized, causing the plunger 236 to retract to the left in the figure. The retraction of the plunger 236 maintains the solenoid lever 233 rotated counterclockwise around the support shaft 235. The tip of the solenoid lever 233 presses the separation lever 121 of the separation unit 36A, maintaining the stopper shaft 112 at a predetermined rotation angle rotated in the direction opposite to the rotation direction R1 against the biasing force of the biasing member, and the stopper 101 at the restricted position P1. While the stopper 101 is maintained at the predetermined rotation angle, rotation of the roller holder gear 103, which is connected to the stopper gear 105 on the stopper shaft 112 via the idler gear 108, is also restricted. In this case, the roller holder 341 is positioned with the separation roller 34 in the separated position.

[0107] In this way, the power supply to the solenoid 232 is controlled so that the stopper 101 is held at the regulating position P1 and the separation roller 34 is held at the separated position before the start of the feeding operation.

[0108] When the feeding operation starts, the solenoid 232 is de-energized at a predetermined timing synchronized with the drive of the feeding unit 35 by the motor M1 (FIG. 3). The de-energization of the solenoid 232 causes the plunger 236 to stop retracting. Then, as shown in FIG. 10(b), the stopper shaft 112 and the stopper 101 rotate in a rotation direction R1 (counterclockwise in the drawing), which is the biasing direction of the biasing member. The rotation of the stopper shaft 112 and the stopper 101 is stopped when the rotation restriction lever 122 abuts against the abutment portion 234. As a result, the stopper 101 moves from the restriction position P1 to the restriction release position P2. Furthermore, as the stopper shaft 112 rotates, the roller holder gear 103 rotates via the stopper gear 105 and the idler gear 108, and the roller holder 341 rotates so that the separation roller 34 moves from the separation position to the abutment position.

[0109] In this way, the power supply to the solenoid 232 is controlled so that after the start of the feeding operation, the stopper 101 is moved from the restricting position P1 to the unrestricted position P2 and the separation roller 34 is moved from the separated position to the abutting position.

[0110] With the stopper 101 positioned at the restriction release position P2 and the separation roller 34 positioned at the abutment position, the feeding unit 35 feeds the sheet S from the sheet cassette 31. At this time, similar to the first embodiment, the separation roller 34 allows the top sheet to pass through the separation nip Ns and prevents sheets other than the top sheet from passing through the separation nip Ns, thereby separating the sheets S. In addition, the stopper 101 is positioned at the restriction release position P2, where it is retracted from the conveyance path of the sheet S, and allows the sheet S to be conveyed through the separation nip Ns.

[0111] Thereafter, when the solenoid 232 is energized again, the plunger 236 is retracted to the left as shown in FIG. 10A. The retraction of the plunger 236 rotates the solenoid lever 233 counterclockwise around the support shaft 235. The tip of the solenoid lever 233 presses the separation lever 121 of the separation unit 36A, causing the stopper shaft 112 to rotate in the direction opposite to the rotation direction R1 against the biasing force of the biasing member, and the stopper 101 moves from the restriction release position P2 to the restriction position P1. As the stopper 101 moves from the restriction release position P2 to the restriction position P1, the contact surface 101a of the stopper 101 comes into contact with the leading edge of the sheet that has been brought to the vicinity of the separation nip Ns during the feeding of the topmost sheet S1. The stopper 101 then moves to the restriction position while pushing back the leading edge of the sheet to a position upstream of the separation nip Ns (FIG. 6A).

[0112] Furthermore, the rotation of the stopper shaft 112 accompanying the resumption of power supply to the solenoid 232 rotates the roller holder gear 103, which is connected to the stopper gear 105 on the stopper shaft 112 via the idler gear 108. This rotates the roller holder 341 so that the separation roller 34 moves from the contact position to the separation position. This completes the feeding operation for one sheet.

[0113] When multiple sheets S are fed continuously, the above-described feeding operation is repeatedly performed for each sheet. Even when the feeding operation is repeatedly performed, the stopper 101 repeatedly pushes back, for each sheet, the sheets other than the uppermost sheet that is the target of the current feeding operation, upstream of the separation nip Ns. This makes it possible to more reliably prevent double feeding of sheets than when the stopper 101 is not used.

[0114] [Operation when inserting or removing a cassette] Next, the operation of the separation unit 36 ​​when the sheet cassette 31 is inserted into or removed from the apparatus main body 1A will be described with reference to Figures 10(b) and 10(c). Figure 10(c) is a diagram showing the state in which the sheet cassette 31 is being pulled out from the apparatus main body 1A.

[0115] As shown in FIG. 10(c), when the sheet cassette 31 starts to move in the pull-out direction Dd from the installed position, the separation lever 121 of the separation unit 36A moves away from the solenoid lever 233 of the apparatus main body 1A. Then, the separation lever 121 is released from the solenoid lever 233, and the rotation restriction of the stopper shaft 112 is released, and the biasing force of the biasing member causes the stopper shaft 112 to rotate in the direction opposite to the rotation direction R1. In other words, the stopper 101 moves from the restricted position P1 (FIG. 10(a)) toward the unrestricted position P2. Furthermore, as the stopper shaft 112 rotates, the roller holder 341 rotates in a direction in which the separation roller 34 approaches the feed roller 33.

[0116] That is, when the sheet cassette 31 is pulled out from the apparatus main body 1A, the separation roller 34 starts to move from the separated position toward the abutting position, just as when the power supply to the solenoid 232 is stopped during the feeding operation. Also, when the sheet cassette 31 is pulled out from the apparatus main body 1A, the stopper 101 starts to move from the restricting position P1 toward the unrestricted position P2, just as when the power supply to the solenoid 232 is stopped during the feeding operation.

[0117] However, unlike the case of the feeding operation, when the sheet cassette 31 is pulled out from the apparatus main body 1A, the roller holder 341 does not stop at the position where the separation roller 34 abuts against the feed roller 33. During the feeding operation, the roller holder 341 rotates beyond the position where the separation roller 34 abuts against the feed roller 33, and stops when it hits the feeding guide 314.

[0118] 10(b) while the roller holder 341 rotates past the position where the separation roller 34 contacts the feed roller 33 during the feeding operation. Therefore, as shown in FIG. 10(c), the retracted position P3, which is the position of the stopper 101 when the sheet cassette 31 is pulled out from the apparatus main body 1A, is a position downstream of the restriction release position P2 in the movement direction of the stopper 101 from the restriction position P1 toward the restriction release position P2.

[0119] In other words, the rotation angle of the roller holder 341 about the rotation shaft 341a when the sheet cassette 31 is pulled out from the apparatus main body 1A is larger than the rotation angle of the roller holder 341 about the rotation shaft 341a during the feeding operation. Also, the rotation angle of the stopper 101 about the stopper shaft 112 when the sheet cassette 31 is pulled out from the apparatus main body 1A is larger than the rotation angle of the stopper 101 about the stopper shaft 112 during the feeding operation.

[0120] In this way, when the sheet cassette 31 is pulled out from the apparatus main body 1A, the stopper 101 is positioned at a retracted position P3, which is further retracted from the restriction release position P2 that allows the passage of the sheets S during the feeding operation. This makes it less likely that the stopper 101 will interfere with the operation of refilling the sheet cassette 31 with sheets when the sheet cassette 31 is pulled out from the apparatus main body 1A, thereby improving workability.

[0121] [Summary of this Example] As described above, the configuration of this embodiment can provide a new type of sheet feeding device and image forming apparatus in which the stopper 101 (returning member) is arranged in the sheet cassette 31 rather than in the apparatus main body 1A.

[0122] Furthermore, according to this embodiment, when the sheet cassette 31 is pulled out from the apparatus main body 1A, the stopper 101 (returning member) is positioned at a retracted position P3 (third position) that is further retracted from the restriction release position P2. Therefore, when replenishing or removing sheets S from the sheet cassette 31, the user's hand or the sheets S will not come into contact with the stopper 101, and the work can be performed smoothly without damaging the sheets S.

[0123] Furthermore, when the sheet cassette 31 is attached to the apparatus main body 1A, the stopper 101 moves between a restricting position P1 (first position) and a derestricting position P2 (second position) that is closer to the restricting position P1 than the retracted position P3 (third position). Therefore, the movement amount of the stopper 101 during the feeding operation is less than the movement amount of the stopper 101 when the sheet cassette 31 is inserted into or removed from the apparatus main body 1A. This makes it possible to improve the throughput (number of sheets fed per unit time) of the sheet feeding section 30, and to accommodate higher speeds of the printer 1.

[0124] Furthermore, in this embodiment, the separation unit 36 ​​is driven using a drive source (solenoid 232) separate from the drive source (motor M1) that drives the feeding unit 35. Therefore, the contact and separation of the separation roller 34 with respect to the feed roller 33 and the position of the stopper 101 can be controlled at desired timing regardless of the operating state of the feeding unit 35. For example, after the start of the feeding operation, the timing at which the separation roller 34 is separated from the feed roller 33 is controlled based on the timing at which a sensor disposed upstream of the registration roller pair 4 detects the leading edge of the sheet S. This makes it possible to control the timing at which the separation nip Ns is opened so as to reduce the back tension generated in the sheet S between the separation nip Ns and the registration roller pair 4, without being affected by variations (early arrival or delayed arrival) in the sheet transport timing.

[0125] [Variations] Instead of the solenoid 232 and solenoid lever 233 in the second embodiment, a rotatable cam (driving member), a cam motor (driving source) for rotating the cam, and a detector for detecting the phase of the cam may be used. The cam can contact and separate from the separation lever 121 of the separation unit 36. When the sheet cassette 31 is attached to the device main body 1A, the cam presses the separation lever 121 to move the stopper 101 from the restriction position P1 to the restriction release position P2. The control unit of the printer 1 then drives the cam motor based on the detection result of the detector, thereby achieving the same operation as the separation unit 36A during the feeding operation in the second embodiment. Also in this modification, when the sheet cassette 31 is pulled out from the device main body 1A, the separation lever 121 separates from the cam, causing the stopper 101 to move to the retracted position P3. Therefore, the same advantages as those of the second embodiment can be obtained.

[0126] (Other embodiments) In the above-described embodiments, the sheet feeding unit 30 is a sheet feeding device incorporated in the printer 1 (image forming apparatus). However, the present disclosure is not limited to this. It may also be applied to a sheet feeding device that has a housing independent of the main body of the image forming apparatus and is capable of feeding sheets to the main body of the image forming apparatus. In this case, the "main body" may be the housing of the sheet feeding device that is connected to the main body of the image forming apparatus. Summary of the Disclosure The present disclosure includes at least the following: (Configuration 1) A device body, a cassette that stores sheets and is attached to the device body so as to be removable, the cassette having a return member that is movable between a first position and a second position; a feeding member that feeds the sheets stored in the cassette in a sheet feeding direction; a separating member that forms a nip portion together with the feeding member, allows a first sheet that the feeding member abuts to pass through the nip portion, and prevents at least one second sheet from passing through the nip portion when the at least one second sheet is transported to the nip portion together with the first sheet; and When the cassette is attached to the apparatus main body, the returning member is movable from the second position to the first position so as to push back the at least one second sheet upstream of the nip portion in the sheet feeding direction. A sheet feeding device characterized by: (Configuration 2) the cassette is pulled out from the apparatus main body downstream in the sheet feeding direction; 2. The sheet feeding device according to configuration 1, (Configuration 3) When the cassette is pulled out from the apparatus main body, the returning member is positioned at a third position downstream of the second position in a moving direction from the first position toward the second position. 3. The sheet feeding device according to configuration 1 or 2. (Configuration 4) the cassette is disposed upstream of the nip portion in the sheet feeding direction and includes a guide member that guides a lower surface of the sheet from an accommodation space within the cassette toward the nip portion; When the returning member is positioned at the third position, the entire returning member is positioned below an upper surface of the guide member when viewed in the direction of the rotation axis of the feeding member. 4. The sheet feeding device according to configuration 3. (Configuration 5) a drive source disposed in the device body; a driving member disposed in the device body and connected to the driving source; a driven member disposed in the cassette and connected to the return member; Further provided with When the cassette is attached to the apparatus main body, the driving member engages with the driven member to transmit the driving force of the driving source, thereby moving the returning member between the first position and the second position; When the cassette is pulled out from the apparatus main body, the driving member and the driven member are separated from each other. 5. The sheet feeding device according to configuration 3 or 4. (Configuration 6) a biasing member disposed in the cassette and biasing the returning member in the movement direction from the first position toward the second position; When the driving member and the driven member are spaced apart from each other, the returning member is positioned at the third position by the biasing force of the biasing member. 6. The sheet feeding device according to configuration 5, (Configuration 7) the biasing member is a spring member that presses the separating member against the feeding member to form the nip portion. 7. The sheet feeding device according to configuration 6, (Configuration 8) When the cassette that has been pulled out from the apparatus main body is inserted back into the apparatus main body, the driving member comes into contact with the driven member, thereby moving the returning member from the third position to the first position. 8. The sheet feeding device according to any one of configurations 5 to 7. (Configuration 9) the drive source is a motor, the driving member is a cam that rotates by the driving force of the motor, the driven member is a cam follower that is moved by contact with the cam; 9. The sheet feeding device according to any one of configurations 5 to 8. (Configuration 10) the drive source is a solenoid, the driving member is a lever that swings due to the driving force of the solenoid, The driven member is a pressed portion that is pressed by the lever. 9. The sheet feeding device according to any one of configurations 5 to 8. (Configuration 11) a holder member disposed in the cassette, holding the separating member, and movable so that the separating member abuts against and moves away from the feeding member; a transmission mechanism disposed in the cassette and configured to transmit the driving force received by the driven member to the holder member and the returning member; Further provided with the transmission mechanism moves the holder member in conjunction with movement of the returning member from the first position to the second position when the cassette is attached to the apparatus main body, so that the separating member abuts against the feeding member. 11. The sheet feeding device according to any one of configurations 5 to 10. (Configuration 12) the transmission mechanism includes a first shaft portion to which the driven member is attached, a second shaft portion to which the returning member is attached, an engagement portion that engages with the holder member, and a gear train that transmits the driving force from the first shaft portion to the second shaft portion and the engagement portion. 12. The sheet feeding device according to configuration 11. (Configuration 13) the transmission mechanism includes a shaft portion to which the driven member and the returning member are attached, an engagement portion that engages with the holder member, and a gear train that transmits the driving force from the shaft portion to the engagement portion. 12. The sheet feeding device according to configuration 11. (Configuration 14) a pickup roller disposed above a storage space for storing sheets provided in the cassette, the pickup roller feeding the uppermost sheet of the sheets stored in the storage space in the sheet feeding direction; the feeding member is a feed roller disposed downstream of the pickup roller in the sheet feeding direction, the separating member is a separating roller connected to a shaft fixed to a frame of the cassette via a torque limiter; 14. The sheet feeding device according to any one of configurations 1 to 13. (Configuration 15) a sheet feeding device according to any one of configurations 1 to 14; an image forming unit that forms an image on the sheet fed from the sheet feeding device; An image forming apparatus comprising: [Explanation of symbols]

[0127] 31... cassette (sheet cassette) / 33... feeding member (feed roller) / 34... separation member (separation roller) / 101... return member (stopper) / Df... sheet feeding direction / Ns... nip portion (separation nip)

Claims

1. A device body, a cassette that stores sheets and is attached to the device body so as to be removable, the cassette having a return member that is movable between a first position and a second position; a feeding member that feeds the sheets stored in the cassette in a sheet feeding direction; a separating member that forms a nip portion together with the feeding member, allows a first sheet that the feeding member abuts to pass through the nip portion, and prevents at least one second sheet from passing through the nip portion when the at least one second sheet is transported to the nip portion together with the first sheet; and When the cassette is attached to the apparatus main body, the returning member is movable from the second position to the first position so as to push back the at least one second sheet upstream of the nip portion in the sheet feeding direction. A sheet feeding device characterized by:

2. the cassette is pulled out from the apparatus main body downstream in the sheet feeding direction; 2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

3. When the cassette is pulled out from the apparatus main body, the returning member is located at a third position downstream of the second position in a moving direction from the first position toward the second position.

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

4. the cassette is disposed upstream of the nip portion in the sheet feeding direction and includes a guide member that guides a lower surface of the sheet from an accommodation space within the cassette toward the nip portion; When the returning member is positioned at the third position, the entire returning member is positioned below an upper surface of the guide member when viewed in a direction of a rotation axis of the feeding member.

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

5. a drive source disposed in the device body; a driving member disposed in the device body and connected to the driving source; a driven member disposed in the cassette and connected to the return member; Further provided with When the cassette is attached to the apparatus main body, the driving member engages with the driven member to transmit the driving force of the driving source, thereby moving the returning member between the first position and the second position; When the cassette is pulled out from the apparatus main body, the driving member and the driven member are separated from each other.

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

6. a biasing member disposed in the cassette and biasing the return member in the movement direction from the first position toward the second position; When the driving member and the driven member are spaced apart from each other, the returning member is positioned at the third position by the biasing force of the biasing member.

6. The sheet feeding device according to claim 5, wherein the sheet feeding device is a sheet feeding device.

7. the biasing member is a spring member that presses the separating member against the feeding member to form the nip portion.

7. The sheet feeding device according to claim 6, wherein the sheet feeding device is a sheet feeding device.

8. When the cassette that has been pulled out from the apparatus main body is inserted back into the apparatus main body, the driving member comes into contact with the driven member, thereby moving the returning member from the third position to the first position.

6. The sheet feeding device according to claim 5, wherein the sheet feeding device is a sheet feeding device.

9. the drive source is a motor, the driving member is a cam that rotates by the driving force of the motor, the driven member is a cam follower that is moved by contact with the cam; 6. The sheet feeding device according to claim 5, wherein the sheet feeding device is a sheet feeding device.

10. the drive source is a solenoid, the driving member is a lever that swings due to the driving force of the solenoid, The driven member is a pressed portion that is pressed by the lever.

6. The sheet feeding device according to claim 5, wherein the sheet feeding device is a sheet feeding device.

11. a holder member disposed in the cassette, holding the separating member, and movable so that the separating member abuts against and moves away from the feeding member; a transmission mechanism disposed in the cassette and configured to transmit the driving force received by the driven member to the holder member and the returning member; Further provided with the transmission mechanism moves the holder member in conjunction with movement of the returning member from the first position to the second position when the cassette is attached to the apparatus main body, so that the separating member abuts against the feeding member.

6. The sheet feeding device according to claim 5, wherein the sheet feeding device is a sheet feeding device.

12. the transmission mechanism includes a first shaft portion to which the driven member is attached, a second shaft portion to which the returning member is attached, an engaging portion that engages with the holder member, and a gear train that transmits the driving force from the first shaft portion to the second shaft portion and the engaging portion.

12. The sheet feeding apparatus according to claim 11.

13. the transmission mechanism includes a shaft portion to which the driven member and the returning member are attached, an engagement portion that engages with the holder member, and a gear train that transmits the driving force from the shaft portion to the engagement portion.

12. The sheet feeding apparatus according to claim 11.

14. a pickup roller disposed above a storage space that stores sheets and that is provided in the cassette, for feeding the first sheet located at the top of the sheets stored in the storage space in the sheet feeding direction; the feeding member is a feed roller disposed downstream of the pickup roller in the sheet feeding direction, the separating member is a separating roller connected to a shaft fixed to a frame of the cassette via a torque limiter; 2. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

15. a sheet feeding device according to any one of claims 1 to 14; an image forming unit that forms an image on the sheet fed from the sheet feeding device; An image forming apparatus comprising:

Images