JP6237505B2 - Sheet feeding apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet feeding apparatus that feeds out a sheet stored in a sheet cassette mounted in a cassette storage section from an end side in an insertion direction, and an image forming apparatus including the sheet feeding apparatus.

  As a sheet feeding device mounted on an image forming apparatus, there is known a sheet feeding device that feeds out a sheet stored in a sheet cassette inserted in a cassette storage unit from an end in an insertion direction by a feeding roller. In this type of sheet feeding apparatus, when the sheet cassette is pulled out from the cassette accommodating portion, the feeding roller is in contact with the uppermost sheet in the sheet cassette, so that the uppermost sheet is in the cassette accommodating portion. May be left behind. This is because a frictional force acts between the uppermost sheet of the sheet cassette and the roller surface of the feeding roller, and this frictional force prevents movement of the uppermost sheet.

  As a conventional technique for solving this problem, a sheet feeding device is disclosed in which when a sheet cassette is pulled out from a cassette housing portion, the sheet comes into contact with the sheet to be popped out from the sheet cassette and returns the sheet to the sheet cassette (Patent Document). 1).

JP 2011-68476 A

  However, in the conventional technology, it is necessary to provide a new complicated push-back mechanism in the sheet feeding device. Therefore, a new member constituting the push-back mechanism is required, and new problems such as member failure, member variation, and cost increase occur.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet feeding device and an image forming apparatus capable of suppressing the uppermost sheet from jumping out of the sheet cassette using the conventional configuration as it is when the sheet cassette is pulled out from the cassette housing portion. Is to provide a device.

  A sheet feeding apparatus according to one aspect of the present invention includes a sheet cassette, a cassette housing unit, a feeding roller, a feeding roller, a detection unit, and a control unit. The sheet cassette stores sheets. The cassette housing portion supports the sheet cassette so that it can be inserted and removed. The feeding roller is provided in the cassette housing portion so as to be able to rotate in the forward and reverse directions, and contacts the upper surface of the sheet stored in the mounted sheet cassette and rotates forward so that the sheet with respect to the cassette housing portion is fed to the sheet cassette. The sheet is fed out to the downstream side in the sheet feeding direction, which is the same direction as the insertion direction. The feeding roller feeds the sheet fed by the feeding roller to the downstream side in the sheet feeding direction. The detection unit detects whether the sheet cassette is mounted at a predetermined position with respect to the cassette housing unit or pulled out from the predetermined position. The control unit controls the rotation of the feeding roller and the feeding roller, and reversely rotates the feeding roller for a predetermined time when the detection unit detects that the sheet cassette is pulled out from the predetermined position. Let

  An image forming apparatus according to another aspect of the present invention includes the sheet feeding device and an image forming unit capable of forming an image on a sheet fed by the sheet feeding device.

  According to the present invention, when the sheet cassette is pulled out, the uppermost sheet can be prevented from jumping out of the sheet cassette.

FIG. 1 is a perspective view showing an external appearance of a multifunction peripheral according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the configuration of the multifunction peripheral according to the embodiment of the present invention. FIG. 3 is a perspective view showing the sheet cassette. FIG. 4 is a diagram illustrating a configuration of a sheet size setting unit of the sheet cassette. FIG. 5 is a block diagram illustrating a configuration of a control unit of the sheet feeding apparatus. FIG. 6 is a schematic side view showing the structure around the feeding roller. FIG. 7 is a cross-sectional view showing an operation state when the sheet cassette is pulled out. FIG. 8 is a cross-sectional view showing an operation state when the feeding roller rotates in the reverse direction when the sheet cassette is pulled out.

  Embodiments of the present invention will be described below with reference to the drawings as appropriate. In addition, the following embodiment is only an example which actualized this invention, and does not limit the technical scope of this invention.

[Image forming apparatus 10]
FIG. 1A is a perspective view showing the appearance of the image forming apparatus 10 with the paper feed cassette 40 mounted. FIG. 1B is a perspective view illustrating an appearance of the image forming apparatus 10 in a state in which the paper feed cassette 40 is pulled out. A schematic configuration of the image forming apparatus 10 according to the embodiment of the present invention shown in FIG. For convenience of explanation, the vertical direction is defined as the vertical direction 8 in the installation state in which the image forming apparatus 10 is installed so as to be usable (the state shown in FIG. 1A). 1A is defined as the front-rear direction 7 (FIG. 1A), and the surface in which the paper feed cassette 40 shown in FIG. A left-right direction 9 is defined with reference to the front of the apparatus 10.

  The housing 10A of the image forming apparatus 10 is a substantially rectangular parallelepiped housing as a whole. Each part constituting the image forming apparatus 10 is disposed inside the housing 10A. As shown in FIGS. 1A and 1B, the housing 10A includes a front cover 51, side covers 52, 53, and 54 other than the front cover 51, and a ceiling wall on which the sheet tray 18 is formed. 55. An opening 56 that is wide in the left-right direction 9 is formed below the front cover 51 in the front-rear direction 7 of the housing 10A. The paper feed cassette 40 can be accommodated in the cassette accommodating portion 31 formed in the housing 10 </ b> A from the opening 56.

  As shown in FIG. 2, the image forming apparatus 10 includes a control unit 2, a plurality of image forming units 4 (an example of the image forming unit of the present invention), an intermediate transfer belt 5, an optical scanning device 13, and a secondary transfer roller 20. The color printer includes a fixing device 16, a sheet tray 18, a paper feed cassette 40, an operation display unit 25, and a conveyance path 26. The image forming apparatus 10 forms a monochrome image or a color image on the sheet S based on the input image data. The sheet S is an example of the sheet of the present invention, and is a sheet material such as paper, coated paper, postcard, envelope, and OHP sheet. Other examples of the image forming apparatus according to the present invention include a facsimile machine, a copier, and a multifunction machine. The operation display unit 25 is a touch panel that displays various types of information in accordance with control instructions from the control unit 2 and inputs various types of information to the control unit 2 in response to user operations.

  Each of the image forming units 4 (4C, 4M, 4Y, 4K) includes an electrophotographic image forming apparatus including a photosensitive drum 11, a charging device 12, a developing device 14, a primary transfer roller 15, a cleaning device (not shown), and the like. Is a unit. The image forming units 4 are arranged side by side along the traveling direction (horizontal direction) of the intermediate transfer belt 5 and constitute a so-called tandem type image forming unit. Specifically, a toner image corresponding to C (cyan) in the image forming unit 4C, M (magenta) in the image forming unit 4M, Y (yellow) in the image forming unit 4Y, and K (black) in the image forming unit 4K is formed. Is done. The cyan image forming unit 4C, the magenta image forming unit 4M, the yellow image forming unit 4Y, and the black image forming unit 4K are arranged in this order from the downstream side in the moving direction (arrow 19 direction) of the intermediate transfer belt 5. They are arranged in a line in that order.

  The intermediate transfer belt 5 is an intermediate transfer member to which toner images of respective colors formed on the photosensitive drums 11 of the image forming units 4 are intermediately transferred. The intermediate transfer belt 5 is supported by a driving roller 6A and a driven roller 6B so as to be rotationally driven. By being supported by the driving roller 6 </ b> A and the driven roller 6 </ b> B, the intermediate transfer belt 5 can move (run) while the surface thereof is in contact with the surface of each photosensitive drum 11. Then, when the surface of the intermediate transfer belt 5 passes between the photosensitive drum 11 and the primary transfer roller 15, the toner images are sequentially superimposed and transferred from the photosensitive drums 11. The optical scanning device 13 includes a laser light source that emits laser light of each color, a polygon mirror that scans the laser light, and mirrors 13C, 13M, 13Y, and 13K that emit the scanned laser light. The optical scanning device 13 forms an electrostatic latent image on each photoconductive drum 11 by irradiating the photoconductive drum 11 of each image forming unit 4 with laser light based on the input image data of each color.

  In the image forming apparatus 10 configured as described above, a color image is formed on the sheet S supplied along the conveyance path 26 from the paper feed cassette 40 (an example of the sheet cassette of the present invention) by the following procedure, and image formation is performed. The subsequent sheet S is discharged to the sheet tray 18. The transport path 26 is provided with various transport rollers that transport the sheets S stacked on the paper feed cassette 40 to the sheet tray 18 via the secondary transfer roller 20 and the fixing device 16.

  First, in each image forming unit 4, the photosensitive drum 11 is uniformly charged to a predetermined potential by the charging device 12. Next, the optical scanning device 13 irradiates the surface of each photoconductive drum 11 with laser light based on the image data, thereby forming an electrostatic latent image on the surface of each photoconductive drum 11. The electrostatic latent images on the photosensitive drums 11 are developed (visualized) as toner images of respective colors by the developing devices 14. Each developing device 14 is supplied with toner (developer) from removable toner containers 3 (3C, 3M, 3Y, 3K) corresponding to the respective colors.

  Subsequently, the toner images of the respective colors formed on the photosensitive drums 11 of the image forming units 4 are sequentially superimposed and transferred onto the intermediate transfer belt 5 by the primary transfer rollers 15. As a result, a color image based on the image data is formed on the intermediate transfer belt 5. Next, the color image on the intermediate transfer belt 5 is transferred by the secondary transfer roller 20 to the sheet S conveyed from the paper feed cassette 40 via the conveyance path 26. The sheet S on which the color image has been transferred is conveyed to the fixing device 16 by a conveying unit (not shown). The fixing device 16 includes a heating roller 16A heated to a high temperature, and a pressure roller 16B disposed to face the heating roller 16A. The sheet S conveyed to the fixing device 16 is conveyed while being sandwiched between the heating roller 16A and the pressure roller 16B. As a result, the color image is welded to the sheet S. Thereafter, the sheet S is discharged to the sheet tray 18. The toner remaining on the surface of each photosensitive drum 11 is removed by each of the cleaning devices.

  Further, the image forming apparatus 10 is provided with a separation mechanism (not shown) for bringing the photosensitive drum 11 and the primary transfer roller 15 of the image forming units 4C, 4M, and 4Y into contact with and separating from the intermediate transfer belt 5. . When the image forming apparatus 10 prints a monochrome image, the photosensitive drum 11 and the primary transfer roller 15 of the image forming units 4C, 4M, and 4Y and the intermediate transfer belt 5 are separated by the separation / contact mechanism. . As a result, only the black toner image is transferred from the image forming unit 4K to the intermediate transfer belt 5, and a monochrome image is transferred from the intermediate transfer belt 5 to the sheet S. In the present embodiment, the electrophotographic image forming unit 4 has been described as an example. However, the image forming unit 4 is not limited to the electrophotographic method, and may be an ink jet recording method or other than that. The recording method or the printing method may be used.

  The control unit 2 performs overall control of the image forming apparatus 10. The control unit 2 is configured as a microcomputer whose main components are a CPU, ROM, RAM, EEPROM, and the like. The control unit 2 is connected to each image forming unit 4, the secondary transfer roller 20, the fixing device 16, and the driving roller 6 </ b> A in the image forming apparatus 10, and controls these components. The control unit 2 is connected to each element constituting the image forming unit 4, specifically, the charging device 12, the optical scanning device 13, the developing device 14, the primary transfer roller 15, the cleaning device, and the like. . Furthermore, as will be described later, the control unit 2 controls the stepping motor 36A (an example of the driving motor of the present invention, see FIG. 5), the clutch 36B (see FIG. 5), and the paper feed for controlling the feeding roller 33 and the feeding roller 34. It is connected to a paper size detection unit 37 that detects the size of the sheet S stored in the cassette 40.

  As described above, the image forming apparatus 10 transfers the color image by superimposing the toner images of the respective colors onto the running intermediate transfer belt 5 by the plurality of image forming units 4 (4C, 4M, 4Y, 4K). It is formed on the surface of the intermediate transfer belt 5. Further, the image forming apparatus 10 forms a color image on the sheet S by transferring the formed color image from the intermediate transfer belt 5 to the sheet S by the secondary transfer roller 20. The intermediate transfer belt 5 is used as a conveying belt, and a color image is directly superimposed and transferred onto the sheet S conveyed on the conveying belt, or a roller-shaped intermediate transferring member is used instead of the intermediate transferring belt 5 The use of is also considered as another embodiment.

[Sheet feeding device 30]
FIG. 3A is a perspective view of the sheet feeding apparatus 30 showing a state in which the paper feed cassette 40 is mounted at a predetermined position determined in the cassette housing portion 31. FIG. 3B is a perspective view of the sheet feeding apparatus 30 showing a state in the middle of insertion and removal of the paper feed cassette 40 from the cassette housing portion 31. As shown in FIGS. 3A and 3B, the image forming apparatus 10 is formed with a sheet feeding apparatus 30 for supplying a sheet S for forming an image. The sheet feeding apparatus 30 includes a paper feed cassette 40, a cassette housing unit 31, a paper feed mechanism 32, a paper size detection unit 37 (an example of the detection unit of the present invention, see FIG. 3B), and the like.

  As shown in FIG. 2, a cassette housing portion 31 that supports the paper feed cassette 40 so as to be insertable / removable is formed in the lower portion of the housing 10A. In FIG. 2, only one stage of the paper feed cassettes 40 is illustrated, but the cassette housing unit 31 may be configured to accommodate a plurality of paper feed cassettes 40 in the vertical direction. The cassette housing portion 31 can be loaded and unloaded from the paper feed cassette 40 through the opening 56 on the front side in the front-rear direction 7 of FIG. The paper feed cassette 40 is inserted and removed in the front-rear direction 7 of FIG.

  As shown in FIGS. 3A and 3B, the paper feed cassette 40 includes a rectangular bottom plate 45, a front wall 41, a back wall 42, and a rear wall 42 erected along each side of the bottom plate 45. It has a right side wall 43 and a left side wall 44. The paper feed cassette 40 stores a sheet S on which an image is formed by the image forming unit 4. The paper feed cassette 40 can store a plurality of sheets in a stacked state. The arrow Y1 indicates the insertion direction in which the paper feed cassette 40 is inserted. Hereinafter, it is referred to as an insertion direction Y1. An arrow Y2 is opposite to the arrow Y1, and indicates a drawing direction in which the sheet feeding cassette 40 is drawn. Hereinafter, it is referred to as a drawing direction Y2. The predetermined position is a position where the sheet feeding cassette 40 is mounted in the cassette housing unit 31 and the sheet S can be fed from the sheet feeding cassette 40.

  As shown in FIG. 2, the paper feed cassette 40 includes a lift plate 46 and a push-up member 49. Sheets S are stacked on the lift plate 46. The push-up member 49 is connected to the end of the bottom plate 45 of the lift plate 46 on the back wall 42 side of the paper feed cassette 40, and rotates when the paper feed cassette 40 is mounted at the predetermined position. The end of the shaft 49A and the transmission gear (not shown) are connected. The transmission gear is connected to a drive motor (not shown). When the paper size detection unit 37 described later detects that the paper feed cassette 40 is mounted at the predetermined position, the drive motor is driven.

  The push-up member 49 rotates by receiving a driving force from a driving motor (not shown). The lift plate 46 is moved up and down at the end in the insertion direction Y <b> 1 by the rotation of the push-up member 49. When the paper feed cassette 40 is mounted at the predetermined position of the cassette housing 31, the lift plate 46 is displaced to a position where the lift plate 46 is pushed up by the push-up member 49 (hereinafter referred to as the first position). The stacked sheets S are brought into contact with a feeding roller 33 described later. The sheet S is pressed against the feeding roller 33 with a predetermined force by the lift plate 46.

  On the other hand, when the paper feed cassette 40 is pulled out from the cassette housing portion 31, the connection between the rotary shaft 49 </ b> A and the transmission gear is released, and the force for supporting the lift plate 46 is not applied to the push-up member 49. The lift plate 46 is lowered by its own weight. The lift plate 46 is displaced to a lowered position (hereinafter referred to as a second position), and the sheets S stacked on the lift plate 46 are separated from the feeding roller 33. The lift plate 46 is supported by the push-up member 49 so as to be displaceable between the first position and the second position.

  The paper feed cassette 40 has a pair of paper guides 47 that support the stacked sheets S from the width direction (left-right direction 9) orthogonal to the insertion direction Y1. The sheet S can maintain the feeding position suitable for the sheet width by the sheet guide 47. For example, the paper guide 47 has a predetermined position for supporting the sheet S from the width direction in accordance with JIS standard A4 size, A5 size, postcard size, and the like. The paper guide 47 is a sheet corresponding to a letter (letter, 11 × 8.5 inch) or folio (FOLIO, 220.0 × 330.0 mm), which is a paper size standard of the American National Standards Institute (American National Standards Institute). The position where S is supported from the width direction may be determined in advance.

  As shown in FIG. 3B, the paper feed cassette 40 includes a size dial 39 in the internal space near the left end of the front wall 41 in the left-right direction 9. The size dial 39 is a dial indicating the size of the sheet S accommodated therein, and the size of the sheet S is set by the user. The size set in the size dial 39 is visible from a window 41A provided on the left side in the left-right direction 9 of the front wall 41 of the paper feed cassette 40. Since it is set by the user, it may be set to a size different from the size of the sheet S actually stored in the paper feed cassette 40.

  FIG. 4A is a perspective view of the paper feed cassette 40, and shows the outer surface 44A of the left wall 44. FIG. FIG. 4B is an enlarged view of the size dial 39. FIG. 4C is an enlarged view of the paper size detection unit 37. As shown in FIGS. 4A and 4B, the size dial 39 includes a shaft 39E parallel to the vertical direction 8 and a plurality of actuators 39A, 39B, 39C, 39D, etc. around the shaft 39E. ing. In the size dial 39, the shaft 39E rotates in accordance with the set size of the sheet S. When any of the actuators 39A to 39D corresponding to the size is located on the left side in the left-right direction 9 and the paper feed cassette 40 is mounted at the predetermined position of the cassette housing unit 31, the paper size detection unit 37 (to be described later) Abut.

  As shown in FIG. 3B, a paper size detection unit 37 is provided below the front cover 51 of the housing 10A. A more detailed position of the paper size detection unit 37 is located at the front cover 51 which is the left side of the opening 56 in the left-right direction 9. As shown in FIG. 4C, the paper size detection unit 37 includes dip switches 37A, 37B, and 37C. The dip switches 37A, 37B, and 37C are arranged in order from the top to the bottom in the vertical direction 8 and project forward in the front-rear direction 7. When the paper feed cassette 40 is mounted at the predetermined position of the cassette housing portion 31, any of the actuators 39A to 39D contacts with any of the dip switches 37A, 37B, and 37C.

  As shown in FIG. 5, the control unit 2 is electrically connected to the paper size detection unit 37. Each of the abutted dip switches 37A, 37B, and 37C is pushed rearward in the front-rear direction 7, and a signal indicating that the dip switches 37A, 37B, and 37C are pushed is transmitted to the control unit 2. The control unit 2 detects the size of the sheet S stored in the paper feed cassette 40 according to the combination of the DIP switches 37A, 37B, and 37C to which the signal is input, and the paper feed cassette 40 is mounted at the predetermined position. It is detected that On the other hand, when the paper feed cassette 40 is pulled out in the pull-out direction Y2 with respect to the cassette housing portion 31, all the dip switches 37A, 37B, and 37C are separated from the actuators 39A to 39D. All the DIP switches 37A, 37B, and 37C do not transmit signals to the control unit 2 due to the separation. When the signals from all the DIP switches 37A, 37B, and 37C are not received, the control unit 2 determines that the paper feed cassette 40 has been pulled out from the predetermined position. The sheet size detection unit 37 and the control unit 2 correspond to an example of the detection unit of the present invention.

  As shown in FIGS. 5 and 6, the paper feed mechanism 32 includes a feed roller 33, a feed roller 34, a separation roller 35, a stepping motor 36A, a clutch 36B, a transmission gear 33A, a one-way clutch 34A, a holder 38A, and a holder. 38B and the like.

  The feeding roller 33 is provided in the vicinity of the end portion in the insertion direction Y1 of the paper feed cassette 40 mounted at the predetermined position of the cassette housing portion 31, and the end portion of the mounted paper feed cassette 40 on the back wall 42 side. Located in the vicinity of The feeding roller 33 is disposed at a position spaced upward from the upper end of the back wall 42 in the vertical direction 8, specifically, above the tip of the lift plate 46. The feeding roller 33 includes a rotating shaft 61 and is supported so as to be able to rotate forward and reverse. The feeding roller 33 is in contact with the upper surface of the uppermost sheet S among the sheets pushed up by the lift plate 46, and feeds out the sheet S in contact with the feeding roller 33 by being rotated forward. The feeding direction is fed to the downstream side in the sheet feeding direction, which is the same direction as the insertion direction Y1 in which the sheet feeding cassette 40 is inserted into the cassette housing portion 31.

  The feeding roller 34 is provided on the downstream side in the feeding direction (insertion direction Y1) with respect to the feeding roller 33. The feeding roller 34 includes a rotation shaft 62 and is supported so as to be able to rotate forward. The feeding roller 34 forms a separation roller 35 and a nip portion 35 </ b> A, and sandwiches the sheet S. The feeding roller 34 contacts the sheet S fed by the feeding roller 33 and rotates forward to feed the sheet S downstream in the sheet feeding direction.

  The separation roller 35 is provided below the feeding roller 34 in the vertical direction 8. The separation roller 35 includes a rotation shaft 63 and is rotatably supported via a torque limiter. The torque limiter enables the separation roller 35 to rotate when a load of a certain threshold value or more is applied, and restricts the rotation of the separation roller 35 to be stationary when it takes less than the certain threshold value. When a load equal to or greater than the predetermined threshold is applied, the separation roller 35 releases the restriction by the torque limiter and is driven to rotate, and the sheet S fed by the feeding roller 33 is pinched by the feeding roller 34. When only a load less than the predetermined threshold is applied, the separation roller 35 stops without being driven to rotate due to the limitation of the torque limiter. The constant threshold is a load applied to the separation roller 35 when one sheet S is conveyed. The friction between the sheets when the two sheets S are double fed is smaller than the friction when the one sheet S is conveyed. Therefore, the separation roller 35 separates the uppermost sheet S from the other sheets S when the driven rotation is stopped, and when the plurality of sheets are fed out by the feeding roller 33. . Accordingly, the sheet S is fed one by one by the feeding roller 34 and the separation roller 35 to the image forming unit 4 on the downstream side in the sheet feeding direction.

  The rotation axes of the feeding roller 33, the feeding roller 34, and the separation roller 35 are parallel to each other. The feeding roller 33 and the feeding roller 34 are supported by a holder 38A. The holder 38 </ b> A can rotate the feeding roller 33 and the feeding roller 34 while maintaining the relative positional relationship between the feeding roller 33 and the feeding roller 34 (the distance between the rollers 33 and 34 and the positional relationship in the axial direction). To support. The holder 38 </ b> A is provided with a swing support shaft 64 provided coaxially with the rotation shaft 62 of the feeding roller 34. The swing support shaft 64 is rotatably supported by a main body frame (not shown). Thus, the holder 38A is supported by the swing support shaft 64 so as to be swingable. The holder 38 </ b> A is swung between a position where the feeding roller 33 contacts the sheet S in the sheet feeding cassette 40 and a position where the feeding roller 33 is separated from the sheet S in the sheet feeding cassette 40. By such swinging of the holder 38A, the feeding roller 33 can be displaced while the position of the feeding roller 34 remains constant.

  The separation roller 35 is rotatably supported by the holder 38B. The holder 38B is supported by a swing support shaft (not shown), and supports the separation roller 35 in a displaceable manner. The holder 38 </ b> B is swung between a position when the separation roller 35 comes into contact with the feeding roller 34 and a position when the separation roller 35 is separated from the feeding roller 34 by a predetermined amount. As the support mechanism of the holder 38B, a displacement support mechanism that displaces between the contact position and the separation position in conjunction with the drawer of the paper feed cassette 40 can be considered. The contact position is a position where the nip portion 35 </ b> A is formed by the feeding roller 34 and the separation roller 35. The separation position is a position where the feeding roller 34 and the separation roller 35 are separated to eliminate the nip portion 35A. The displacement support mechanism displaces the paper feed cassette 40 from the contact position to the separation position when the paper feed cassette 40 is pulled out from the predetermined position. The displacement support mechanism may not be one that displaces the holder 38B in conjunction with the paper feed cassette 40, but may be a mechanism that is driven by a drive motor or the like in response to the paper feed cassette 40 being pulled out. .

  As shown in FIG. 5, the stepping motor 36 </ b> A can rotate in either the first direction corresponding to the forward rotation of the feeding roller 33 or the second direction corresponding to the reverse rotation. The stepping motor 36A is connected to the feeding roller 33 via the clutch 36B and the transmission gear 33A. The stepping motor 36A is connected to the feeding roller 34 via a clutch 36B, a transmission gear 33A, and a one-way clutch 34A. The stepping motor 36 </ b> A is a drive source that rotates the feeding roller 33 and the feeding roller 34 forward and backward by rotating in the first direction or the second direction. The stepping motor 36A is connected to the control unit 2. The control unit 2 controls the rotation direction of the stepping motor 36A to rotate the stepping motor 36A in either the first direction or the second direction. In the description of the present embodiment, the case where the drive motor of the present invention is the stepping motor 36A will be described. However, the drive motor of the present invention is not limited to the stepping motor 36A, and various types of motors can be applied. The stepping motor 36 </ b> A may also serve as a drive source for other transport rollers in the transport path 26.

  The transmission gear 33A transmits the rotational driving force of the stepping motor 36A from the stepping motor 36A to the feeding roller 33. The clutch 36B connects or disconnects the transmission path between the stepping motor 36A and the transmission gear 33A. The clutch 36 </ b> B is connected to the control unit 2, and is switched by the control unit 2 between a connected state that connects the transmission paths and a disconnected state that blocks the transmission paths. The connected state is a state in which the stepping motor 36A and the transmission gear 33A are connected to transmit the rotational driving force of the stepping motor 36A to the feeding roller 33. The shut-off state is a state in which the stepping motor 36A and the transmission gear 33A are disconnected and the feeding roller 33 and the feeding roller 34 are driven to rotate by the rotational driving force of the other transport rollers.

  For example, when the sheet S is fed from the sheet feeding cassette 40, the control unit 2 switches the state of the clutch 36B from the connected state to the disconnected state while the sheet S is being conveyed. Specifically, the control unit 2 rotates the stepping motor 36 </ b> A in the first direction and turns the clutch 36 </ b> B in the connected state to feed out the sheet S from the paper feed cassette 40. Thereafter, the fed sheet S is sandwiched between the other transport rollers and the feeding roller 34 in the transport path 26, and the sheet S can be transported by the other transport rollers. At that time, the control unit 2 causes the feeding roller 33 and the feeding roller 34 to take over the conveyance of the sheet S to the other conveyance rollers. After the conveyance of the sheet S is taken over, the control unit 2 stops the stepping motor 36A and puts the clutch 36B in the disconnected state. Thereby, even if the downstream side of the sheet S in the sheet feeding direction is sandwiched between the feeding roller 33 or the feeding roller 34, both the rollers 33 and 34 are driven to rotate. The transport of is not hindered. In addition, this makes it possible to prevent the sheet S from being conveyed without a gap between the sheets by feeding the next sheet S from the sheet feeding cassette 40 by the feeding roller 33.

  The feeding roller 33 is connected to the stepping motor 36A via the clutch 36B and the transmission gear 33A. The stepping motor 36 </ b> A is driven to rotate in the first direction and the clutch 36 </ b> B is connected, so that a force that is fed downstream in the sheet feeding direction is applied to the sheet S. In other words, the control unit 2 feeds the uppermost sheet S out of the plurality of sheets S downstream in the sheet feeding direction by rotating the feeding roller 33 forward and connecting the clutch 36B. On the other hand, the control unit 2 reversely rotates the feeding roller 33 and connects the clutch 36 </ b> B, so that the sheet S positioned downward in order from the uppermost sheet S among the plurality of sheets S is returned to the sheet feeding cassette 40. Giving the power of. The control unit 2 that controls each unit of the sheet feeding device 30 by a predetermined program corresponds to the control unit of the present invention.

  As shown in FIGS. 5 and 6, the feed roller 34 is connected to the stepping motor 36A via a clutch 36B, a transmission gear 33A, and a one-way clutch 34A. The one-way clutch 34A is provided between the transmission gear 33A and the feeding roller 34, and transmits only the rotational driving force that rotates in the first direction from the stepping motor 36A. Therefore, when the clutch 36B is engaged, only the rotational driving force that rotates in the first direction is transmitted from the stepping motor 36A to the feeding roller 34. On the other hand, when the clutch 36B is connected, the feeding roller 33 receives the rotational driving force rotating in the first direction and the rotational driving force rotating in the second direction from the stepping motor 36A. For this reason, when the stepping motor 36A rotates in the first direction, both the feeding roller 33 and the feeding roller 34 rotate forward, and the sheets S are fed one by one downstream in the sheet feeding direction. However, the rotational driving force by which the stepping motor 36 </ b> A rotates in the second direction is transmitted only to the feeding roller 33 and not to the feeding roller 34. In other words, when the stepping motor 36A rotates in the second direction, only the feeding roller 33 rotates in the reverse direction, and the feeding roller 34 is stopped. In the present invention, when the paper feed cassette 40 is pulled out from the cassette housing unit 31, the control unit 2 connects the clutch 33A when rotating the feeding roller 33 in the reverse direction by rotating at least the stepping motor 36A in the second direction. . Thus, the sheet S is prevented from jumping out of the paper feed cassette 40 when the paper feed cassette 40 is pulled out from the cassette housing unit 31.

[Drawing operation of sheet feeding device 30]
With reference to FIGS. 7 and 8, the operation of the feeding roller 33 and the state of the sheet S accompanying the drawing of the sheet feeding cassette 40 of the sheet feeding apparatus 30 will be described. FIGS. 7A to 7D show the state of the sheet S when the paper feeding cassette 40 is pulled out from the cassette housing portion 31 with the feeding roller 33 stopped. On the other hand, FIGS. 8A to 8D show the state of the sheet S when the paper feed cassette 40 is pulled out from the cassette housing portion 31 while the feeding roller 33 is rotated in the reverse direction. In FIG. 8, it is assumed that the clutch 36 </ b> B has been switched to the connected state by the control unit 2.

  As shown in FIGS. 7A and 8A, in a state in which the paper feed cassette 40 is mounted at the predetermined position of the cassette housing portion 31, the sheet S stored in the paper feed cassette 40 is fed out. The roller 33 is fed out. The uppermost sheet S is stopped before the nip portion 35 </ b> A formed by the feeding roller 34 and the separation roller 35.

  As shown in FIG. 7B, when the paper feeding cassette 40 is pulled out from the cassette housing portion 31 in the pulling-out direction Y2, the lift plate 46 starts to descend. However, since it takes time to lower the lift plate 46, the feeding roller 33 contacts the uppermost sheet S for a while even when the paper feed cassette 40 is moved in the drawing direction Y <b> 2. At this time, if the feeding roller 33 is not rotated, the rear end S1 of the uppermost sheet S on the back wall 42 side receives a frictional force from the roller surface of the feeding roller 33. Here, the rear end portion S1 of the sheet S is the rear of the sheet S in the front-rear direction 7 in FIG. The frictional force that the rear end portion S <b> 1 of the uppermost sheet S receives from the roller surface of the feeding roller 33 is larger than the frictional force that the uppermost sheet S receives from the lower sheet S stacked on the sheet feeding cassette 40. For this reason, the sheet feeding cassette 40 moves in the drawing direction Y2, but the rear end portion S1 of the uppermost sheet S is subjected to a force that tries to remain stationary at a position in contact with the feeding roller 33. As the paper feed cassette 40 is pulled out in the pull-out direction Y2, the holder 38A that supports the feed roller 33 and the feed roller 34 starts to swing in the direction of the arrow Y3, and the holder 38B that houses the separation roller 35 Begins to drop in the direction of arrow Y4.

  As shown in FIG. 7C, the holder 38 </ b> A starts from the sheet S in the sheet feeding cassette 40 from the position where the holder 38 </ b> A contacts the sheet S stacked on the lift plate 46 on which the feeding roller 33 is lifted. Oscillates to a position where they are separated (see arrow Y3). Further, the holder 38B is lowered from the position where the separation roller 35 forms the nip portion 35A with the feeding roller 34 (see arrow Y4), and the nip portion 35A is eliminated. Further, the lift plate 46 of the paper feed cassette 40 is lowered. However, there is a case where the rear end S1 of the uppermost sheet S rides on the back wall 42 due to a frictional force received from the roller surface of the feeding roller 33. The rear end S1 of the uppermost sheet S riding on the back wall 42 may come into contact with the feeding roller 33. When receiving the frictional force of the roller surface of the feeding roller 33, the trailing edge S 1 of the sheet S tries to remain stationary at a position in contact with the feeding roller 33, and the trailing edge S 1 of the uppermost sheet S is fed to the paper feed cassette 40. There is a possibility of jumping over the rear wall 42 of the vehicle.

  Here, when the rear wall 42 of the paper feed cassette 40 reaches the lowermost position of the feed roller 33, the distance that the paper feed cassette 40 is drawn from the predetermined position in the drawing direction Y2 is L2. In general, the trailing end S1 of the sheet S tries to remain stationary at a position in contact with the feeding roller 33 until the distance L2 in the drawing direction Y2 of the sheet feeding cassette 40 is reached. On the other hand, as will be described later, in the sheet feeding device 30 of the present invention, the feeding roller 33 is reversely rotated to store the sheet S in the sheet feeding cassette 40 (see FIG. 8).

  As shown in FIG. 7D, when the paper feeding cassette 40 is further pulled out from the cassette housing portion 31 in the pulling-out direction Y2, the uppermost sheet S is brought out from the paper feeding cassette 40. At this time, the distance that the sheet feeding cassette 40 is pulled out from the predetermined position in the pulling direction Y2 is L3. Furthermore, when the paper feed cassette 40 is pulled out from the cassette housing unit 31, the uppermost sheet S may be wrinkled or bent.

[Reverse rotation of feed roller 33]
When the sheet feeding cassette 40 is pulled out in the pulling-out direction Y2 with respect to the cassette housing portion 31 as shown in FIG. 8B from the state where it is mounted at the predetermined position as shown in FIG. The control unit 2 does not receive a signal from the paper size detection unit 37. Accordingly, the control unit 2 detects that the paper feed cassette 40 is pulled out from the predetermined position of the cassette housing unit 31. At this time, the distance that the paper feed cassette 40 is pulled out from the predetermined position in the pull-out direction Y2 is L1. Further, when the paper feeding cassette 40 is pulled out from the predetermined position of the cassette housing portion 31 in the pulling direction Y2, the lift plate 46 starts to be displaced from the first position to the second position. As the paper feed cassette 40 is pulled out in the pull-out direction Y2, the holder 38A that supports the feed roller 33 and the feed roller 34 starts to swing in the direction of the arrow Y3, and the holder 38B that houses the separation roller 35 Begins to drop in the direction of arrow Y4.

  However, since it takes time to lower the lift plate 46, the feeding roller 33 contacts the uppermost sheet S for a while even when the paper feed cassette 40 is moved in the drawing direction Y <b> 2. If the sheet feeding cassette 40 is pulled out from the predetermined position as it is, the uppermost sheet S jumps out from the sheet feeding cassette 40. Therefore, the controller 2 reversely rotates the feeding roller 33 for a predetermined reverse rotation time (an example of the predetermined time of the present invention) (arrow Y5). For example, the reverse rotation time is a time obtained by adding a margin time to the time until the back wall 42 of the paper feed cassette 40 passes the lowest point of the feed roller 33 when being pulled out. The reverse rotation time may be determined based on the time required for the lift plate 46 to move from the first position to the second position.

  In addition, by measuring in advance, the speed at which the paper feed cassette 40 is pulled out from the predetermined position of the cassette housing unit 31 can be set to an appropriate value. For example, the speed drawn from the predetermined position by the user is measured in advance, and the measured average speed is set as the drawing speed. A speed obtained by adding a predetermined amount to the average speed is predetermined as a reverse rotation speed for reverse rotation. When the feeding roller 33 is reversely rotated at a rotation speed faster than the drawing speed, the uppermost sheet S is easily returned to the sheet feeding cassette 40. Therefore, the control unit 2 reversely rotates the feeding roller 33 at the reverse rotation speed faster than the predetermined average speed corresponding to the speed at which the paper feed cassette 40 is pulled out from the predetermined position. As described above, when the control unit 2 detects that the paper feed cassette 40 is pulled out from the predetermined position based on a signal from the paper size detection unit 37, the control unit 2 reversely rotates the feeding roller 33 to thereby rotate the uppermost sheet. S is fed in the direction of returning to the paper feed cassette 40. As a result, the uppermost sheet S is prevented from jumping out of the paper feed cassette 40.

  Further, when the feeding speed of the sheet cassette 40 is high and the frictional force between the sheets S is strong, the rear end portions S1 of the plurality of sheets S including the uppermost sheet S are placed on the back wall 42. It is possible to become. In this case, the control unit 2 can reversely rotate the feeding roller 33 to feed the plurality of sheets S in a direction to return to the paper feed cassette 40. When the control unit 2 reversely rotates the feeding roller 33 when a plurality of sheets S ride on the rear wall 42 of the sheet feeding cassette 40, the rear end S1 of the uppermost sheet S is fed in the returning direction. The feeding roller 33 comes into contact with the rear end S1 of the lower sheet S. In this state, when the control unit 2 continues to rotate the feeding roller 33 in the reverse direction, the rear end portion S1 of the sheet S positioned below is also fed back. In this way, the control unit 2 feeds the sheet S positioned downward in order from the uppermost sheet S among the plurality of sheets S in the direction of returning to the sheet feeding cassette 40 by rotating the feeding roller 33 in the reverse direction. Let

  As shown in FIG. 8C, the holder 38 </ b> A starts from the sheet S in the sheet feeding cassette 40 from the position where the holder 38 </ b> A contacts the sheet S stacked on the lift plate 46 on which the feeding roller 33 is lifted. Is swung to a position where they are separated (see arrow Y3). Further, the holder 38B is lowered from the position where the separation roller 35 forms the nip portion 35A with the feeding roller 34 (see arrow Y4), and the nip portion 35A is eliminated. Further, the lift plate 46 of the paper feed cassette 40 is lowered.

  However, the rear end S <b> 1 of the uppermost sheet S may ride on the back wall 42 and come into contact with the feeding roller 33 due to the frictional force received from the roller surface of the feeding roller 33. Therefore, the control unit 2 reversely rotates the feeding roller 33 until the rear wall 42 of the sheet feeding cassette 40 passes the lowest point of the feeding roller 33, and the rear end S 1 of the uppermost sheet S is moved to the sheet feeding cassette 40. Feed in the direction to return to. In general, the rear end S1 of the sheet S continues to contact the feeding roller 33 until the distance L2 in the drawing direction Y2 of the sheet feeding cassette 40 is reached. Therefore, the control unit 2 reversely rotates the feeding roller 33 until the distance at which the paper feeding cassette 40 is pulled out from the predetermined position in the pulling direction Y2 reaches L2. The direction in which the sheet cassette 40 is pulled out and the sheet S is fed are the same direction. If the feeding speed of the sheet S is faster than that of the sheet feeding cassette 40, the sheet S stays inside the sheet feeding cassette 40, and the sheet S may jump out of the sheet feeding cassette 40 due to contact with the feeding roller 33. Is suppressed. The uppermost sheet S bends inside the sheet feeding cassette 40 by feeding in the reverse direction, but the rear end portion S1 of the uppermost sheet S is in the inside of the sheet feeding cassette 40.

  As shown in FIG. 8D, even when the sheet feeding cassette 40 is further pulled out from the cassette accommodating portion 31 in the pulling direction Y2 to reach the distance L3, the rear end S1 of the uppermost sheet S is still in the sheet feeding cassette. It is within 40. Therefore, when the bent uppermost sheet S extends straight due to its own weight, it is stacked on the lower sheet S. At that time, since the position of the sheet S is regulated by the sheet guide 47 and the like, the uppermost sheet S is in a correct position in the sheet feeding cassette 40.

[Effect of the embodiment]
As described above, according to the image forming apparatus 10 and the sheet feeding apparatus 30 of the present invention, when the paper feeding cassette 40 is pulled out from the cassette housing unit 31, the uppermost sheet S is ejected from the paper feeding cassette 40. This can be suppressed.

  In the description of the embodiment described above, the case where the reverse rotation speed of the feeding roller 33 is higher than the speed at which the paper feed cassette 40 is pulled out has been described. However, the reverse rotation speed is the same as the speed at which the reverse rotation speed is pulled out. Slow speed is acceptable. When the reverse rotation speed is the same as the drawing speed, the uppermost sheet S moves in the drawing direction Y2 at the same speed as the paper feed cassette 40. In FIG. 8C, the uppermost sheet S is stacked on the lower sheet S without being bent. On the other hand, when the reverse rotation speed is slower than the drawing speed, the uppermost sheet S moves in the drawing direction Y <b> 2 at a speed slower than that of the sheet feeding cassette 40. In FIG. 8C, the rear end S <b> 1 of the uppermost sheet S is on the back wall 42 of the paper feed cassette 40. However, the trailing end S <b> 1 of the uppermost sheet S is prevented from hanging outward from the back wall 42 of the sheet feeding cassette 40. As described above, even when the reverse rotation speed of the feeding roller 33 is not higher than the rotation speed at which the paper feed cassette 40 is pulled out, the uppermost sheet S is suppressed from jumping out of the paper feed cassette 40.

[Modification of Embodiment]
In the description of the above-described embodiment, the case where the one-way clutch 34A is provided to rotate the feeding roller 34 in one direction has been described, but the present invention is not limited to this. For example, both the feeding roller 33 and the feeding roller 34 may rotate forward and backward. Further, the drive source that rotates the feeding roller 33 and the drive source that rotates the feeding roller 34 may be different drive sources.

  In the above description of the embodiment, the reverse rotation speed of the feeding roller 33 is described as the reverse rotation speed obtained by adding a predetermined amount to the average speed, but the present invention is not limited to this. The reverse rotation speed may be equal to or slower than the average speed. By rotating the feeding roller 33 in the reverse direction, the uppermost sheet S receives a feeding force in the drawing direction Y <b> 2 without receiving a stationary frictional resistance from the roller surface of the feeding roller 33. Therefore, the uppermost sheet S is likely to stay inside the paper feed cassette 40.

  In the above description of the embodiment, the case where the feeding roller 33 is reversely rotated when it is detected that the paper feed cassette 40 is pulled out has been described. However, the present invention is not limited to this. For example, when the paper size detection unit 37 detects that the paper feed cassette 40 has been pulled out, the control unit 2 may reversely rotate the feeding roller 33 after a predetermined waiting time has elapsed. . When the end of the rotating shaft 49A is connected to the transmission gear, the rotating shaft 49A is connected to a different position each time it is mounted depending on the state of the gear being rotated and the clearance between the end of the rotating shaft 49A and the gear. Therefore, when the position of the paper feed cassette 40 shown in FIG. 8B reaches the distance L1, even if the paper size detection unit 37 detects that the paper feed cassette 40 has been pulled out, In some cases, the lift plate 46 remains in the first position and does not start to descend. At this stage, if the feeding roller 33 is rotated at the reverse rotation speed, the uppermost sheet S may become wrinkled. For this reason, it may be desirable not to reversely rotate the feeding roller 33 until the time for which the paper feeding cassette 40 is always pulled out from the predetermined position has elapsed. Therefore, it is conceivable that the control unit 2 reversely rotates the feeding roller 33 when the waiting time has elapsed after the paper size detection unit 37 detects that the paper feed cassette 40 has been pulled out. For example, the waiting time is about 0.2 seconds to 0.3 seconds.

  Moreover, although the case where the sheet S stored in the paper feed cassette 40 is moved up and down by the lift plate 46 and the push-up member 49 has been described, the present invention is not limited to this. When the sheet feeding cassette 40 is mounted at the predetermined position of the cassette housing portion 31, the sheet S stored in the sheet feeding cassette 40 is supported so as to be displaceable between the first position and the second position. Any other mechanism may be used.

  Further, in the description of the above-described embodiment, the case where the feeding roller 33 is provided in the vicinity of the end portion in the insertion direction Y1 in the paper feeding cassette 40 mounted at the predetermined position of the cassette housing portion 31 has been described. It is not limited to. The feeding roller 33 may be provided in the vicinity of the end in the drawing direction Y2 or in the vicinity of the center in the insertion direction Y1 as long as the feeding roller 33 can be fed while being in contact with the uppermost sheet S of the paper feed cassette 40.

2: Control unit 10: Image forming apparatus 10A: Housing 30: Sheet feeding device 31: Cassette storage unit 32: Paper feed mechanism 33: Feeding roller 33A: Clutch 34: Feeding roller 34A: One-way clutch 35: Separation roller 36A : Stepping motor 36B: Transmission gear 37: Paper size detectors 38A, 38B: Holder 39: Size dial 40: Paper feed cassette 46: Lift plate 49: Push-up member

Claims (7)

A sheet cassette for storing sheets;
A cassette housing portion that supports the sheet cassette so that it can be inserted and removed;
The cassette housing portion is provided so as to be able to rotate forward and backward, and is brought into contact with the upper surface of the sheet stored in the mounted sheet cassette so as to rotate forward so that the sheet is inserted into the cassette housing portion in the insertion direction of the sheet cassette. A feeding roller that feeds downstream in the sheet feeding direction, which is the same direction;
A feeding roller for feeding the sheet fed by the feeding roller to the downstream side in the sheet feeding direction;
A detection unit that detects whether the sheet cassette is mounted at a predetermined position with respect to the cassette housing unit or pulled out from the predetermined position;
A controller that controls the rotation of the feeding roller and the feeding roller, and reversely rotates the feeding roller for a predetermined time when the detection unit detects that the sheet cassette is pulled out from the predetermined position; equipped with a,
The control unit is a sheet feeding device that reversely rotates the feeding roller at a rotation speed faster than a predetermined rotation speed corresponding to a speed at which the sheet cassette is pulled out from the predetermined position . 2. The sheet feeding according to claim 1 , wherein the control unit reversely rotates the feeding roller when a predetermined waiting time elapses after the detection unit detects that the sheet cassette is pulled out. apparatus. The sheet cassette has a first position where a sheet in the sheet cassette is brought into contact with the feeding roller when the sheet cassette is mounted at the predetermined position of the cassette housing portion, and the sheet cassette is separated from the cassette housing portion. A lift plate supported so as to be displaceable between a second position for separating the feeding roller from the sheet in the sheet cassette when the sheet is pulled out;
3. The sheet feeding apparatus according to claim 1, wherein the predetermined time is a time required until the sheet cassette is pulled out and the lift plate is displaced from the first position to the second position. A drive motor capable of rotating in either the first direction corresponding to the forward rotation of the feeding roller or the second direction corresponding to the reverse rotation ;
The feeding roller is connected to the drive motor,
The feeding roller is connected to the drive motor via a one-way clutch,
Wherein, the sheet feeding apparatus according to any of the driving motor 請 Motomeko 1-3 you want to rotate. Either of the first rotating direction or the second rotating direction. A transmission gear for transmitting the rotational driving force of the driving motor from the driving motor to the feeding roller;
A clutch that connects or disconnects a transmission path between the drive motor and the transmission gear;
With
The one-way clutch is provided between the transmission gear and the feeding roller, and transmits only the rotational driving force in the first direction from the transmission gear to the feeding roller.
The sheet feeding device according to claim 4 , wherein the control unit connects the clutch when rotating at least the drive motor in the second direction to reversely rotate the feeding roller. A sheet cassette for storing sheets;
A cassette housing portion that supports the sheet cassette so that it can be inserted and removed;
The cassette housing portion is provided so as to be able to rotate forward and backward, and is brought into contact with the upper surface of the sheet stored in the mounted sheet cassette so as to rotate forward so that the sheet is inserted into the cassette housing portion in the insertion direction A feeding roller that feeds downstream in the sheet feeding direction, which is the same direction;
A feeding roller for feeding the sheet fed by the feeding roller to the downstream side in the sheet feeding direction;
A detection unit that detects whether the sheet cassette is mounted at a predetermined position with respect to the cassette housing unit or pulled out from the predetermined position;
A controller that controls the rotation of the feeding roller and the feeding roller, and reversely rotates the feeding roller for a predetermined time when the detection unit detects that the sheet cassette is pulled out from the predetermined position; With
The control unit rotates the feeding roller forward to feed the uppermost sheet among the plurality of sheets stored in the sheet cassette downstream in the sheet feeding direction, and reversely rotates the feeding roller. A sheet feeding device that applies a force in a direction to return the sheets positioned below in order from the uppermost sheet among the plurality of sheets to the sheet cassette. The sheet feeding device according to any one of claims 1 to 6 ,
An image forming apparatus comprising: an image forming unit capable of forming an image on a sheet fed by the sheet feeding device.

Images