Sheet feeding device and image forming apparatus

Abstract

To provide a sheet feeder capable of suppressing double feeding of sheets and an image forming device equipped with the same.SOLUTION: The sheet feeder comprises: a sheet loading part; a feeding part provided so as to be lifted / lowered to a feeding position and an upper position; a conveyance part; a separation member provided so as to be movable between an abutment position for forming a separation nip for separating sheets fed by the feeding part one by one and a separation position separated from the conveyance part; a return part that is provided so as to be movable between a projection position projecting to a conveyance path through which the sheets pass and a retreat position retreating from the conveyance path between the feeding part and the separation nip in a sheet conveying direction and that moves from the retreat position to the projection position to push back the sheets toward the sheet loading part; and a pressing part that presses the sheets toward the return part located below the sheets from above when the return part is set at the projection position.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] A sheet feeding device has been proposed that includes an ASF base on which sheets are stacked, a feed roller that feeds the sheets stacked on the ASF base, a torque limiter that contacts the feed roller to separate the sheets one by one, and a return lever (see Patent Document 1). A pressure plate is attached to the ASF base to press the sheets toward the feed roller. The torque limiter is provided so as to be able to move toward and away from the feed roller, and the return lever is configured to push the sheets back toward the ASF base. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-332130 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the ASF base described in Patent Document 1 is inclined downward, and if a sheet on the ASF base unintentionally passes over the return lever and advances, there is a risk of double sheet feeding occurring.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet feeding device capable of suppressing double feeding of sheets, and an image forming apparatus including the same. [Means for solving the problem]

[0006] a sheet feeding device including: a sheet stacking section on which sheets are stacked; a feeding section that is provided to be able to move up and down to a feeding position where it contacts the sheets stacked on the sheet stacking section and an upper position spaced above the sheets stacked on the sheet stacking section, and that feeds the sheets by rotating at the feeding position; a transport section that transports the sheets fed by the feeding section; a separating member that is provided to be able to move between a contact position where it contacts the transport section to form a separation nip that separates the sheets fed by the feeding section one by one, and a spaced position spaced from the transport section; a return section that is provided to be able to move between a protruding position where it protrudes into a transport path through which sheets pass and a retracted position where it retracts from the transport path, between the feeding section and the separation nip in the sheet transport direction, and that pushes the sheets back toward the sheet stacking section by moving from the retracted position to the protruding position; and a pressing section having a contact portion that can come into contact with the sheets. an elevation holder that supports the feeding unit so that the feeding unit can be elevated between the feeding position and the upper position; The pressing portion is configured to press the returning portion to the protruding position. and When positioned under the seat, the seat Return The sheet is pressed from above via the contact portion so as to be pressed toward the contact portion. the pressing portion has a rotating portion supported by the lift holder so as to be rotatable about a rotating shaft, and the contact portion provided on the rotating portion, and the rotating shaft is disposed upstream of the contact portion in the sheet conveying direction. It is characterized by: The present invention also provides a sheet feeding device including: a sheet stacking section on which sheets are stacked; a feeding section that is provided to be able to move up and down to a feeding position where it contacts the sheets stacked on the sheet stacking section and an upper position spaced above the sheets stacked on the sheet stacking section and feeds the sheets by rotating at the feeding position; a transport section that transports the sheets fed by the feeding section; a separating member that is provided to be able to move between a contact position where it contacts the transport section to form a separation nip that separates the sheets fed by the feeding section one by one and a spaced position spaced from the transport section; and a separating member that is provided to be able to move between a contact position where it contacts the transport section to form a separation nip that separates the sheets fed by the feeding section one by one and a spaced position spaced from the transport section in a sheet transport direction. Between the nip, the sheet transport device is provided with a return section that is movable between a protruding position that protrudes into the transport path through which the sheet passes and a retracted position that retracts from the transport path, and that pushes the sheet back toward the sheet stacking section by moving from the retracted position to the protruding position, and a pressing section that has a contact section that can come into contact with the sheet, wherein the pressing section is configured to press the sheet from above via the contact section when the return section is positioned in the protruding position and below the sheet, and the contact section is positioned at a position closer to the transport section than the feeding section in the sheet transport direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent double feeding of sheets. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an overall configuration of a printer according to an embodiment of the present invention; [Figure 2] FIG. [Figure 3] 1A is a perspective view showing a feeding unit, FIG. 1B is a perspective view showing a pressing unit, and FIG. 1C is another perspective view showing the pressing unit. [Figure 4] FIG. 2A is a perspective view showing the drive mechanism, and FIG. 2B is a plan view showing the drive mechanism. [Figure 5]FIG. 1( a ) is a side view showing the manual feed device before feeding begins, FIG. 1( b ) is a side view showing the manual feed device during feeding, and FIG. 1( c ) is a side view showing the manual feed device after the missing tooth gear has rotated once. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Overall structure] 1, the printer 1 as an image forming apparatus is an electrophotographic laser beam printer, and has an image forming section 20 that forms an image on a sheet S, a cassette feeding device 50, a manual feeding device 70, and a fixing device 30. The image forming section 20 has four process cartridges PY, PM, PC, and PK that form toner images of four colors, yellow (Y), magenta (M), cyan (C), and black (K), respectively, a scanner unit 2, and an intermediate transfer belt 21.

[0010] The four process cartridges PY, PM, PC, and PK have the same configuration except for the colors of the images they form. Therefore, only the configuration and image forming process of the process cartridge PY will be described, and descriptions of the process cartridges PM, PC, and PK will be omitted.

[0011] The process cartridge PY has a photosensitive drum 11a, a charging roller (not shown), and a developing roller 12a. The photosensitive drum 11a is constructed by coating the outer periphery of an aluminum cylinder with an organic photoconductive layer and is rotated by a drive motor (not shown). An intermediate transfer belt 21 is stretched by a drive roller 22, a driven roller 24, and a tension roller 23, and is rotated by the drive roller 22. Primary transfer rollers 25a, 25b, 25c, and 25d are provided inside the intermediate transfer belt 21. The fixing device 30 has a fixing film 31 heated by a heater and a pressure roller 32 that presses against the fixing film 31.

[0012] The cassette feeding device 50 is provided at the bottom of the printer 1 and stores sheets S. The manual feeding device 70 as a sheet feeding device has a door 82 supported on the device body 1A of the printer 1 so as to be able to open and close, a stacking tray 81 supported on the door 82, a feeding unit 100 that feeds the sheets S stacked on the stacking tray 81, and a separation roller 73.

[0013] Next, we will explain the image forming operation of the printer 1 configured as above. When an image signal is input to the scanner unit 2 from a personal computer (not shown) or the like, the scanner unit 2 irradiates the photosensitive drum 11a of the process cartridge PY with a laser beam corresponding to the image signal.

[0014] At this time, the surface of the photosensitive drum 11a is uniformly charged to a predetermined polarity and potential by a charging roller, and an electrostatic latent image is formed on the surface by irradiating it with laser light from the scanner unit 2. The electrostatic latent image formed on the photosensitive drum 11a is developed by the developing roller 12a, and a yellow (Y) toner image is formed on the photosensitive drum 11a.

[0015] Similarly, the scanner unit 2 irradiates the photosensitive drums of the process cartridges PM, PC, and PK with laser light, and magenta (M), cyan (C), and black (K) toner images are formed on the photosensitive drums. The toner images of each color formed on each photosensitive drum are transferred onto the intermediate transfer belt 21 by primary transfer rollers 25a, 25b, 25c, and 25d, and are transported to the secondary transfer roller 26 by the intermediate transfer belt 21, which is rotated by a drive roller 22. The image formation process for each color is performed at a timing to overlap the upstream toner image that has been primarily transferred onto the intermediate transfer belt 21.

[0016] In parallel with this image forming process, sheets S are fed from cassette feeding device 50 or manual feeding device 70. For example, when sheets S are fed from cassette feeding device 50, sheets S stored in cassette 51 are sent out by pickup roller 52 and then separated one by one by conveyance roller 53 and separation roller 54. When sheets S are fed from manual feeding device 70, sheets S stacked on stacking tray 81 as a sheet stacking section are fed by pickup roller 71 and then separated one by one by conveyance roller 72 and separation roller 73. Then, sheets S are conveyed toward registration roller pair 61 by conveyance roller pairs 62, 63, and 64.

[0017] The sheet S is conveyed in accordance with the transfer timing after the skew is corrected by the registration roller pair 61. Then, the full-color toner image on the intermediate transfer belt 21 is transferred onto the sheet S by the secondary transfer bias applied to the secondary transfer roller 26.

[0018] The sheet S onto which the toner image has been transferred is subjected to predetermined heat and pressure by the fixing film 31 and pressure roller 32 of the fixing device 30, thereby melting and fixing (fixing) the toner. The sheet S that has passed through the fixing device 30 is discharged onto a discharge tray 43 by a pair of discharge rollers 41 of the discharge section 40. The dashed arrows shown in FIG. 1 indicate an example of the transport path along which the sheet S is transported from the cassette feeding device 50 to the pair of discharge rollers 41.

[0019] [Manual feeder] Next, the manual feed device 70 will be described with reference to Figures 2 to 3(c). As shown in Figures 2 to 3(c), the manual feed device 70 has a feed unit 100 detachably supported on the device main body 1A (see Figure 1), and a separation roller 73.

[0020] 2, a conveying guide frame 98 is fixed to the apparatus main body 1A (see FIG. 1), and a conveying guide 99 is fixed to the conveying guide frame 98. The conveying guide 99 constitutes a part of a conveying path CP through which the sheet S fed by the pickup roller 71 passes.

[0021] A separation holder 87 is supported on the conveying guide 99 so as to be rotatable about a separation shaft 87a (see FIG. 4(a)), and a separation roller 73 is rotatably supported on the separation holder 87. The separation roller 73 as a separating member is provided so as to be able to swing (move) between an abutment position where it abuts against the conveying roller 72 as a conveying section, and a spaced position where it is spaced from the conveying roller 72, as the separation holder 87 rotates about the separation shaft 87a.

[0022] The separation roller 73 comes into contact with the conveyance roller 72 at the contact position to form a separation nip N that separates the sheets S fed by the pickup roller 71 serving as a feeding unit one by one. The separation roller 73 incorporates a torque limiter (not shown), and when multiple sheets S are present in the separation nip N, it has the function of separating the other sheets from the sheet being conveyed by the conveyance roller 72. On the other hand, when only one sheet S is present in the separation nip N, the torque limiter rotates idly, and the separation roller 73 is rotated in accordance with the conveyance roller 72.

[0023] The conveyance guide 99 is also provided with return claws 91L and 91R as return sections, and the return claws 91L and 91R are respectively arranged on one side and the other side of the separation roller 73 in the width direction W perpendicular to the sheet conveyance direction. The return claws 91L and 91R are provided between the pickup roller 71 and the separation nip N in the sheet conveyance direction, and are movable between a protruding position (see FIG. 5A) where they protrude into the conveyance path CP and a retracted position where they retract from the conveyance path CP. The return claws 91L and 91R push back the sheet S located near the separation nip N toward the stacking tray 81 by moving from the retracted position to the protruding position. The distance between the return claws 91L and 91R in the width direction W is set to be smaller than the width of the smallest size sheet that can be fed by the manual feed device 70.

[0024] 3(a), the feeding unit 100 has a feed shaft 90, a conveying roller 72 rotatably supported on one end of the feed shaft 90, a feed gear 92 integral with the conveying roller 72, and a cylindrical lifting arm shaft 97 that houses the feed shaft 90. The feeding unit 100 also has a lifting arm 74 that is rotatably supported on the feed shaft 90 and connected to the lifting arm shaft 97, and a roller cover 105 that is provided to cover the lifting arm 74. The feeding unit 100 also has a pickup roller 71 and a pickup gear 101 rotatably supported by the lifting arm 74 and the roller cover 105, and a pressing unit 120.

[0025] The feed shaft 90 has a connecting portion 95 at the end opposite the conveying roller 72, and is connected to the apparatus main body 1A so that a driving force can be input. When the feed shaft 90 rotates, the conveying roller 72 and the feed gear 92 rotate. Then, the rotation of the feed gear 92 is transmitted to the pickup gear 101 via a drive train (not shown) supported by the lifting arm 74, causing the pickup roller 91 to rotate.

[0026] The lifting arm shaft 97 is rotatable relative to the feed shaft 90 and has a connecting portion 96 that is connected to a lifting mechanism provided in the apparatus main body 1A (see FIG. 1). When the lifting arm shaft 97 is rotated via the connecting portion 96, the lifting arm 74 and roller cover 105 that are connected to the lifting arm shaft 97 are lowered. This allows the pickup roller 71 to rise and fall between a feeding position (see FIG. 5(b)) where the pickup roller 71 abuts against sheets stacked on the stacking tray 81 and an upper position (see FIG. 5(a)) where the pickup roller 71 is spaced above the sheets stacked on the stacking tray 81. In other words, the lifting arm 74 and the roller cover 105 form a lifting holder 130 that supports the pickup roller 71 so that the pickup roller 71 can rise and fall between the feeding position and the upper position.

[0027] The lifting arm 74 and the roller cover 105 may be configured to be biased upward by a biasing member (not shown), or to be raised and lowered by driving the lifting arm shaft 97 .

[0028] As shown in FIGS. 3(b) and 3(c), the pressing unit 120 includes a pressing lever 107 as a rotating portion, a pressing roller 108, and a torsion coil spring 109 as a biasing portion. The pressing lever 107 is formed in a substantially L-shape and includes a rotation shaft 107a rotatably supported on the roller cover 105 and a lever portion 107b extending perpendicular to the rotation shaft 107a. That is, the lever portion 107b swings about the rotation shaft 107a relative to the lifting holder 130 including the roller cover 105. A pressing roller 108, which functions as a contact portion and a roller, is rotatably supported on the end of the lever portion 107b opposite the rotation shaft 107a. The pressing roller 108 is located between the conveying roller 72 and the pickup roller 71 in the sheet conveying direction CD, which will be described later. As will be described later, the pressing roller 108 is configured to press the sheet S toward the return claws 91L and 91R. The pressure roller 108 is disposed in a position closer to the conveying roller 72 and the return claws 91L, 91R than the pickup roller 71 in the sheet conveying direction CD. Therefore, the pressure roller 108 can press the sheet S in the vicinity of the return claws 91L, 91R. Furthermore, the rotation shaft 107a is located upstream of the pickup roller 71 in the sheet conveying direction CD. This allows the lever portion 107b to be configured long, and prevents the pressure roller 108 from pressing the sheet S too strongly.

[0029] Furthermore, a coil portion 109a of a torsion coil spring 109 is attached to the rotary shaft 107a, one end portion 109b of the torsion coil spring 109 engages with the roller cover 105, and the other end portion 109c of the torsion coil spring 109 engages with the lever portion 107b. As a result, the pressure lever 107 is biased in a direction in which the pressure roller 108 moves away from the roller cover 105, i.e., downward.

[0030] [Drive mechanism] Next, a description will be given of the drive mechanism 200 for driving the manual sheet feeder 70, with reference to Figures 4(a) and (b). As shown in Figures 4(a) and (b), the drive mechanism 200 has a motor M as a drive source, a first transmission gear G1, a second transmission gear G2, a solenoid unit 79, a partially toothed gear 78 as a control gear, and an interlocking unit 80.

[0031] In this embodiment, the motor M is capable of transmitting driving force to both the cassette feeding device 50 and the manual feeding device 70. The motor M is engaged with a first transmission gear G1 and a second transmission gear G2, and the first transmission gear G1 is capable of transmitting driving force to the cassette feeding device 50. The second transmission gear G2 is capable of transmitting driving force to the manual feeding device 70. The second transmission gear G2 transmits driving force to a connecting portion 95 of the feed shaft 90 (see FIG. 3(a)) via a drive train (not shown). Note that a clutch may be provided between the motor M and the first transmission gear G1 or between the motor M and the second transmission gear G2. Note that the motor M, the first transmission gear G1, and the second transmission gear G2 are merely an example of a drive transmission configuration, and the present invention is not limited to this.

[0032] The solenoid unit 79 has a solenoid 79a and an engagement claw 79b driven by the solenoid 79a. The engagement claw 79b engages with the missing tooth gear 78 when the solenoid 79a is not energized. At this time, the missing tooth portion 78a of the missing tooth gear 78 faces the second transmission gear G2. In other words, when the solenoid 79a is not energized, the rotation of the second transmission gear G2 is not transmitted to the missing tooth gear 78.

[0033] When the solenoid 79a is energized, the engaging claw portion 79b moves away from the missing tooth gear 78, and a spring built into the missing tooth gear 78 causes the missing tooth gear 78 to rotate slightly, causing the gear portion 78b of the missing tooth gear 78 to mesh with the second transmission gear G2. The solenoid 79a is de-energized as soon as the engaging claw portion 79b moves away from the missing tooth gear 78, so after the missing tooth gear 78 rotates once, the missing tooth gear 78 is again locked by the engaging claw portion 79b. In this way, the missing tooth gear 78 is driven by the driving force from the motor M and is controlled to rotate once so as to stop after each rotation.

[0034] The interlocking unit 80 has a control cam 84 connected to the missing tooth gear 78, a reciprocating gear 77, an idler gear 85, a left return claw drive member 75a, a separation holder drive member 75b, a connecting member 76, and a right return claw drive member 86. The reciprocating gear 77 is configured to reciprocate like a pendulum around a swing center 77a in conjunction with the control cam 84. The reciprocating gear 77 meshes with the idler gear 85, and the idler gear 85 meshes with the left return claw drive member 75a. This causes the left return claw drive member 75a to reciprocate in the width direction W.

[0035] The left-side return claw driving member 75a is connected to the right-side return claw driving member 86 by a connecting member 76, and the right-side return claw driving member 86 reciprocates integrally with the left-side return claw driving member 75a in the width direction W. The left-side return claw driving member 75a and the right-side return claw driving member 86 have cam portions (not shown) that engage with the return claws 91L, 91R, respectively, to move the return claws 91L, 91R between a protruding position and a retracted position.

[0036] The left-side return claw drive member 75a is also connected to a separation holder drive member 75b, which reciprocates integrally with the left-side return claw drive member 75a in the width direction W. The separation holder drive member 75b is provided with a cam portion 75c that engages with the separation holder 87 to rotate the separation holder 87 about a separation shaft 87a. In other words, as the separation holder drive member 75b reciprocates in the width direction W, the separation roller 73 held by the separation holder 87 is swung between a contact position and a separation position.

[0037] More specifically, the left return claw drive member 75a is biased in the width direction W by a biasing member (not shown). In this embodiment, the left return claw drive member 75a is biased in a direction approaching the separation roller 73 (to the right in FIG. 4B). The separation holder 87 is also biased by a biasing member (not shown) in a direction in which the separation roller 73 approaches the conveying roller 72. When the control cam 84 presses the reciprocating gear 77, the reciprocating gear 77 rotates counterclockwise in FIG. 4B, and the left return claw drive member 75a moves leftward in FIG. 4B against the biasing force biasing the left return claw drive member 75a. In this state, the cam portion 75c and the separation holder 87 come into contact with each other, and the separation roller 73 is positioned in the separated position against the biasing force biasing the separation holder 87. At this time, the return claws 91L and 91R are positioned in the protruding position.

[0038] On the other hand, when the solenoid 79a is energized, the missing tooth gear 78 rotates, and the control cam 84 moves away from the reciprocating gear 77. As a result, the biasing force that biases the left return pawl drive member 75a moves the left return pawl drive member 75a in a direction approaching the separation roller 73 (to the right in FIG. 4(b)). Then, the cam portion 75c and the separation holder 87 move away from each other, and the biasing force that biases the separation holder 87 positions the separation roller 73 in the abutment position. At this time, the return pawls 91L and 91R are positioned in the retracted position.

[0039] In this way, when the motor M is driven, a driving force is input to the feed shaft 90 via the second transmission gear G2, the missing tooth gear 78, and an idler gear (not shown), causing the conveyance roller 72 and the pickup roller 71 to rotate. When the solenoid 79a is energized, the missing tooth gear 78 rotates once, and the lifting mechanism (not shown), which operates in conjunction with the rotation of the missing tooth gear 78, rotates the lifting arm shaft 97 and the lifting arm 74 via the connecting portion 96. Therefore, with each rotation of the missing tooth gear 78, the pickup roller 71 moves up and down in the order of the upper position, the feeding position, and the upper position. Furthermore, with each rotation of the missing tooth gear 78, the separation roller 73 moves in the order of the separation position, the abutment position, and the separation position, and the return claws 91L and 91R move in the order of the protruding position, the retracted position, and the protruding position.

[0040] That is, the interlocking unit 80 includes the above-mentioned lifting mechanism (not shown) and lifting arm shaft 97, and works in conjunction with the missing tooth gear 78 to lift and lower the pickup roller 71, move the separation roller 73, and move the return claws 91L and 91R.

[0041] [Feeding operation sequence and pressure roller movement] Next, the feeding operation sequence of the manual feeder 70 and the movement of the pressure roller 108 will be described with reference to Figures 5(a) to 5(c). Figure 5(a) is a side view showing the manual feeder 70 before feeding begins. Figure 5(b) is a side view showing the manual feeder 70 during feeding. Figure 5(c) is a side view showing the manual feeder 70 after the missing tooth gear 78 has made one rotation.

[0042] As shown in Fig. 5(a), when the door 82 is opened from the device main body 1A, the pickup roller 71 is in the upper position, the separation roller 73 is in the separated position, and the return claws 91L and 91R are in the protruding position. At this time, the pickup roller 71 protrudes outward from the device main body 1A when viewed in the direction of the rotation axis of the pickup roller 71 (width direction W) (see Fig. 1). Then, by closing the door 82 from the device main body 1A, the feeding unit 100 is stored inside the device main body 1A.

[0043] Before a feeding instruction is input to the manual feeding device 70, the pickup roller 71 is located at the upper position and is separated from the stacking surface 81a of the stacking tray 81. This makes it easy for the user to place the sheet S on the stacking surface 81a.

[0044] Furthermore, before the sheets S are loaded onto the loading surface 81a, the pressure roller 108 is also separated from the loading surface 81a. In other words, when no sheets S are loaded onto the loading surface 81a, a gap is formed between the pressure roller 108 and the loading surface 81a. This reduces the possibility of the sheets stopping short of the set position due to resistance from the pressure roller 108, resulting in poor loading, even when a user slides a small number of sheets onto the loading surface 81a from the front. Furthermore, after the last sheet on the loading surface 81a is fed, noise caused by the pressure roller 108 colliding with the loading surface 81a can be prevented. In this embodiment, the roller cover 105 of the lifting holder 130 prevents the pressure lever 107 from moving beyond a predetermined position to prevent the pressure roller 108 from contacting the loading surface 81a.

[0045] When the stacking tray 81 is in the open position relative to the apparatus main body 1A, the stacking surface 81a is inclined downward toward the downstream side in the sheet conveying direction CD. Therefore, the sheet S on the stacking surface 81a slides down by gravity toward the return claws 91L, 91R positioned in the protruding position. The sheet S then waits with its leading edge positioned near the return claws 91L, 91R.

[0046] Depending on the amount of sheets S that the user places on the stacking surface 81a, the sheets S may come into contact with the pressure roller 108. However, the pressure roller 108 is rotated by the sheets S placed on the stacking surface 81a. In other words, the pressure roller 108 is rotated by friction with the sheets S. Furthermore, because the rotation shaft 107a of the pressure lever 107 is disposed upstream of the pressure roller 108 in the sheet conveying direction CD, even if the pressure roller 108 comes into contact with the sheets S, the pressure lever 107 and the pressure roller 108 can be retracted upward. This allows the user to easily place the sheets S on the stacking surface 81a without damaging the sheets S.

[0047] When a feeding command is input to the manual feed device 70, a sheet presence / absence sensor (not shown) determines whether or not there is a sheet S on the stacking tray 81. When it is determined that there is a sheet S on the stacking tray 81, the motor M is driven and the solenoid 79a is energized, causing the missing tooth gear 78 to start rotating. As a result, as shown in FIG. 5(b), the lifting arm 74 and the interlocking unit 80 are driven, and the pickup roller 71 is lowered to the feeding position where it contacts the sheet S. In addition, the separation roller 73 moves to the contact position, and the return claws 91L and 91R move to retracted positions where they are retracted from the conveying path CP.

[0048] The return claws 91L, 91R may move to the retracted position by their own weight when the cam portions of the left return claw drive member 75a and the right return claw drive member 86 move away from the return claws 91L, 91R, or may move to the retracted position when pressed by the sheet S. Because the movement of the return claws 91L, 91R in the retracted direction is not restricted, they can be retracted from the conveying path CP without damaging the leading edge of the sheet S, even when they are retracted after being contacted by the sheet S.

[0049] Rotation of the feed shaft 90 rotates the pickup roller 71 and the conveying roller 72, so that the sheet S is fed by the pickup roller 71 located at the feeding position. The pickup roller 71 only needs to convey the leading edge of the sheet S to the separation nip N, and is configured to be raised to the upper position by the lifting arm 74 after conveying a predetermined amount of the sheet S.

[0050] The separation roller 73 moves from the contact position to the separation position after the leading edge of the sheet S is conveyed to the nip between the pair of registration rollers 61. After the separation nip N is released, the return claws 91L and 91R move from the retracted position to the protruding position, and push back the sheet remaining near the separation nip N toward the stacking tray 81.

[0051] As shown in FIG. 5(c), the sheet conveyed by the registration roller pair 61 (see FIG. 1) serving as the downstream conveyance section is referred to as the leading sheet S1, and the sheet pushed back by the return claws 91L and 91R is referred to as the trailing sheet S2. The trailing sheet S2 tends to move downstream in the sheet conveyance direction CD due to the frictional force it receives from the leading sheet S1 during conveyance and the sheet's own weight. In particular, in a configuration in which the stacking surface 81a is inclined downward toward the downstream side in the sheet conveyance direction CD, the trailing sheet S2 tends to move downstream in the sheet conveyance direction CD. When the trailing sheet S2 passes over the return claws 91L and 91R and moves downstream in the sheet conveyance direction CD, the separation nip N is released, resulting in double feeding.

[0052] To reduce such double feeding, the pressure roller 108 supported by the pressure lever 107 presses the preceding sheet S1 from above so that the preceding sheet S1 is pressed toward the return claws 91L and 91R when the return claws 91L and 91R are positioned below the preceding sheet S1. In other words, a pressure unit 120 (see FIG. 3B) as a pressing section including the pressure lever 107 and the pressure roller 108 presses the preceding sheet S1 from above via the pressure roller 108 so that the preceding sheet S1 is pressed toward the return claws 91L and 91R. At this time, the pressure roller 108 is positioned closer to the stacking surface 81a than the tips of the return claws 91L and 91R that come into contact with the sheet. In other words, the pressure roller 108 is positioned closer to the bases of the return claws 91L and 91R than the tips of the return claws 91L and 91R. The pressure lever 107 supporting the pressure roller 108 is biased downward about the pivot shaft 107a by its own weight and a torsion coil spring 109 (see FIG. 3(b)). Note that, as long as the preceding sheet S1 is pressed toward the return claws 91L and 91R, the direction in which the pressure roller 108 presses the preceding sheet S1 may be deviated from the direction toward the return claws 91L and 91R. In this embodiment, the movement direction in which the pressure roller 108 is moved by the lever portion 107b may be deviated from the direction toward the return claws 91L and 91R.

[0053] The pressure roller 108 presses the preceding sheet S1 from above, thereby reducing the gap D1 between the preceding sheet S1 and the return claws 91L and 91R, and preventing the subsequent sheet S2 from climbing over the return claws 91L and 91R. As shown in FIGS. 2 and 3, conveying ribs 74a and 97a are provided on both sides of the return claw 91L in the width direction W. The conveying rib 74a is provided on the lifting arm 74, and the conveying rib 97a is provided on the lifting arm shaft 97. Similar to the pressure roller 108, these conveying ribs 74a and 97a also press the preceding sheet S1 from above toward the return claws 91L and 91R, thereby reducing the gap D1. When the trailing edge of the preceding sheet S1 passes through the pressure roller 108, the state returns to that shown in FIG. 5(a).

[0054] Manual feed device 70 of this embodiment repeats the above-described operation for each sheet to transport sheets on stacking tray 81. Stacking tray 81 is provided integrally with door 82, and moves between an open position and a closed position as door 82 is opened and closed relative to device main body 1A. Feeding unit 100 including pressing unit 120 is linked to the opening and closing of door 82, and is accommodated within device main body 1A by closing door 82 when not in use. Therefore, providing pressing unit 120 does not increase the size of printer 1.

[0055] As described above, in this embodiment, the pressure roller 108 of the pressure unit 120 presses the sheet S from above, thereby making it possible to reduce the gap D1 between the conveyed sheet and the return claws 91L, 91R. This prevents the subsequent sheet S from passing through the gap D1 and climbing over the return claws 91L, 91R, thereby preventing double feeding of sheets.

[0056] Furthermore, by configuring the pickup roller 71 to be liftable, the pickup roller 71 can be projected outside the device body 1A together with the stacking tray 81 only when in use, allowing the diameter of the pickup roller 71 to be reduced. This allows the device to be made more compact. Generally, when a configuration is adopted in which the stacking tray is lifted and lowered rather than the pickup roller, heavy sheets are loaded on the lifting tray, resulting in a loud operating noise from the motor that lifts and lowers the stacking tray. In this embodiment, by configuring the pickup roller 71 to be lifted and lowered without lifting and lowering the stacking tray 81, the operating noise during sheet feeding can be reduced.

[0057] Furthermore, since not only the pickup roller 71 but also the separation roller 73 moves toward and away from the conveyance roller 72 each time a sheet is fed, wear on the pickup roller 71, conveyance roller 72, and separation roller 73 can be reduced, resulting in longer lifespans. Also, since the pickup roller 71 is positioned at the upper position and the separation nip N is released when a sheet is conveyed by the registration roller pair 61, conveyance resistance can be reduced and the drive motor can be made smaller. Furthermore, the lifting and lowering of the pickup roller 71 and the movement of the separation roller 73 and return claws 91L and 91R are controlled by the solenoid 79a, costs can be reduced.

[0058] <Other embodiments> In this embodiment, the separation roller 73 employs a torque limiter system, but is not limited to this. For example, the separation roller 73 may employ a retard roller system that inputs a driving force to rotate in the direction opposite to the sheet conveying direction, and may be replaced with a separation pad or the like without being limited to a roller.

[0059] In addition, in this embodiment, a pair of left and right return claws 91L, 91R are provided, but the present invention is not limited to this. For example, the number of return claws may be one or three or more.

[0060] In addition, in this embodiment, pressure roller 108 is provided at the tip of pressure lever 107 in consideration of feeding sheets such as glossy paper whose surfaces are easily scratched, but this is not limiting. For example, depending on the type of sheet to be fed, pressure lever 107 may be configured to slide directly on the sheet. In other words, a contact portion that can come into contact with the sheet may be provided on a part of pressure lever 107.

[0061] In addition, in this embodiment, the pressing lever 107 is biased so as to rotate downward by the torsion coil spring 109, but this is not limiting. For example, instead of the torsion coil spring 109, an elastic body that applies a biasing force, such as a compression spring, may be applied, or the torsion coil spring 109 may be omitted, and the pressing lever 107 may be configured to rotate downward by its own weight.

[0062] In addition, in the present embodiment, the rotation shaft 107a of the pressing lever 107 is disposed upstream of the pressing roller 108 in the sheet conveying direction CD, but this is not limiting. For example, the rotation shaft 107a may be disposed downstream of the pressing roller 108. Furthermore, the pressing unit 120 including the pressing lever 107 may be supported by the apparatus main body 1A instead of the lifting holder 130.

[0063] In addition, in this embodiment, the solenoid unit 79 is configured to stop the missing tooth gear 78 after each rotation, but this is not limiting. For example, the driving force from the motor M may be transmitted or not transmitted to the manual feed device 70 by a clutch such as an electromagnetic clutch.

[0064] Although the present embodiment has been described using an electrophotographic printer 1, the present invention is not limited to this. For example, the present invention can also be applied to an inkjet image forming apparatus that forms an image on a sheet by ejecting ink liquid from nozzles. [Explanation of symbols]

[0065] 1: Image forming apparatus (printer) / 1A: Device body / 20: Image forming unit / 61: Downstream transport unit (pair of registration rollers) / 70: Sheet feeding device (manual feed device) / 71: Feeding unit (pickup roller) / 72: Transport unit (transport roller) / 73: Separation member (separation roller) / 78: Control gear (missing tooth gear) / 80: Interlocking unit / 81: Sheet stacking unit (loading tray) / 81a: Loading surface / 91L, 91R: Return unit (return claw) / 107: Rotating unit (pressure lever) / 107a: Rotating shaft / 108: Contact unit, roller (pressure roller) / 109: Pressing unit (torsion coil spring) / 120: Pressing unit (pressure unit) / 130: Lifting holder / CD: Sheet transport direction / CP: Transport path / M: Drive source (motor) / N: Separation nip / S1: Sheet (preceding sheet)

Claims

1. a sheet stacking section on which sheets are stacked; a feeding section that is provided to be movable up and down between a feeding position where the feeding section abuts against the sheets stacked on the sheet stacking section and an upper position that is spaced above the sheets stacked on the sheet stacking section, and that feeds the sheets by rotating at the feeding position; a conveying unit that conveys the sheet fed by the feeding unit; a separating member provided to be movable between a contact position where the separating member contacts the conveying unit to form a separation nip that separates the sheets fed by the feeding unit one by one, and a separation position where the separating member is spaced from the conveying unit; a return section that is provided between the feeding section and the separation nip in the sheet conveying direction and is movable between a protruding position that protrudes into a conveying path through which a sheet passes and a retracted position that retracts from the conveying path, and that pushes back the sheet toward the sheet stacking section by moving from the retracted position to the protruding position; a pressing portion having a contact portion capable of coming into contact with the sheet; a lifting holder that supports the feeding unit so that the feeding unit can be lifted and lowered between the feeding position and the upper position, the pressing portion is configured to press the sheet from above via the contact portion so that the sheet is pressed toward the returning portion when the returning portion is in the protruding position and positioned below the sheet, the pressing portion has a rotating portion supported rotatably about a rotation axis relative to the lifting holder, and the contact portion provided on the rotating portion, the rotation shaft is disposed upstream of the contact portion in the sheet conveying direction. A sheet feeding device characterized by:

2. When the returning portion is located at the protruding position, the feeding portion is located at the upper position, and the separating member is located at the separated position.

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

3. the contact portion is a roller rotatably supported by the rotating portion; 3. The sheet feeding device according to claim 1, wherein the sheet feeding device is a sheet feeding device.

4. The pressing portion has a biasing portion that biases the rotating portion so as to rotate downward about the rotation axis.

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

5. the contact portion is disposed at a position closer to the conveying portion than the feeding portion in the sheet conveying direction.

5. The sheet feeding device according to claim 1, wherein the sheet feeding device comprises: a first feeding unit;

6. A sheet stacking section on which sheets are stacked; a feeding section that is provided to be movable up and down between a feeding position where the feeding section abuts against the sheets stacked on the sheet stacking section and an upper position that is spaced above the sheets stacked on the sheet stacking section, and that feeds the sheets by rotating at the feeding position; a conveying unit that conveys the sheet fed by the feeding unit; a separating member provided to be movable between a contact position where the separating member contacts the conveying unit to form a separation nip that separates the sheets fed by the feeding unit one by one, and a separation position where the separating member is spaced from the conveying unit; a return section that is provided between the feeding section and the separation nip in the sheet conveying direction and is movable between a protruding position that protrudes into a conveying path through which a sheet passes and a retracted position that retracts from the conveying path, and that pushes back the sheet toward the sheet stacking section by moving from the retracted position to the protruding position; a pressing portion having a contact portion that can come into contact with the sheet, the pressing portion is configured to press the sheet from above via the contact portion so that the sheet is pressed toward the returning portion when the returning portion is in the protruding position and positioned below the sheet, the contact portion is disposed at a position closer to the conveying portion than the feeding portion in the sheet conveying direction. A sheet feeding device characterized by:

7. When the return portion is located at the protruding position, the feeding portion is located at the upper position, and the separating member is located at the separated position.

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

8. When no sheets are stacked on the sheet stacking portion, a gap is generated between the contact portion and the sheet stacking portion.

8. The sheet feeding device according to claim 1, wherein the sheet feeding device comprises: a first feeding unit;

9. the sheet stacking section has a stacking surface on which sheets are stacked, and is provided so as to be openable and closable with respect to the apparatus body between a closed position and an open position; the stacking surface is inclined downward toward the downstream in the sheet conveying direction when the sheet stacking portion is located at the open position; 9. The sheet feeding device according to claim 1, wherein the sheet feeding device comprises: a first feeding unit;

10. the feeding unit, at the feeding position, protrudes outward from the device body as viewed in a direction of a rotation axis of the feeding unit; 10. The sheet feeding device according to claim 9, wherein the sheet feeding device is a sheet feeding device.

11. the stacking surface does not move when the sheet stacking section is located at the open position; 11. The sheet feeding device according to claim 9, wherein the sheet feeding device is a sheet feeding device.

12. a control gear that is driven by a driving force from a driving source and stops after each rotation; a linking unit that, in conjunction with the control gear, moves the feeding unit up and down between the feeding position and the upper position, moves the separating member between the abutting position and the separating position, and moves the returning unit between the retracted position and the protruding position, 12. The sheet feeding device according to claim 1, wherein the sheet feeding device comprises: a first feeding unit;

13. a downstream conveying unit disposed downstream of the separation nip in the sheet conveying direction and configured to convey the sheet; the pressing portion presses the sheet from above via the contact portion when the returning portion is located at the protruding position and the returning portion is located below the sheet conveyed by the downstream conveying portion.

13. The sheet feeding device according to claim 1, wherein the sheet feeding device comprises: a first feeding unit;

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

Images