JP2018012591A - Sheet feeding device and image forming apparatus having the sheet feeding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeding device which can determine abnormality of a lift rise mechanism without using a position sensor, and to provide an image forming apparatus.SOLUTION: An image forming apparatus 10 has a control unit 80 which performs abnormality determination processing. The control unit 80 performs a feeding operation of print sheets from a manual insertion tray 38 by a second feeding unit 39 when the print sheets are not detected by a sheet sensor 44 after the feeding operation of the print sheets by a first feeding unit 32, and determines rise abnormality of a lift plate 45 when the print sheet is detected by the sheet sensor 44 after the feeding operation.SELECTED DRAWING: Figure 13

Description

  The present invention relates to a sheet feeding apparatus that accommodates a plurality of sheet materials, and an image forming apparatus including the sheet feeding apparatus.

  The image forming apparatus includes a paper feed cassette (sheet storage unit) that stores paper (sheet material) on which an image is printed. The paper feed cassette stores a plurality of papers in a stacked manner. The paper stored in the paper feed cassette is fed to the image forming unit by the feeding mechanism. Specifically, when the pickup roller of the feeding mechanism comes into contact with the uppermost sheet of the sheet bundle stored in the sheet feeding cassette and rotates, the pickup roller feeds the sheet in the feeding direction. Then, the sheet is fed downstream in the feeding direction by the feeding roller and the retard roller disposed downstream of the pickup roller in the feeding direction.

  When the number of sheets in the sheet feeding cassette decreases, the position of the uppermost sheet gradually decreases, and the sheet cannot be fed out by the pickup roller. Therefore, the image forming apparatus is provided with a lift plate for lifting the sheet bundle in the paper feed cassette and a lift raising mechanism for raising the lift plate.

  Conventionally, as a detection of whether there is an abnormality in the lift of the lift plate, the position sensor detects whether the lift plate has reached a predetermined position after the lift plate lift operation by the lift lift mechanism, An apparatus that determines an abnormality of a lift raising mechanism when it cannot be detected within a predetermined time is known (see Patent Document 1).

JP-A-62-88727

  However, the conventional configuration that determines the abnormality of the lift raising mechanism using the position sensor cannot determine the abnormality of the lift raising mechanism when the position sensor fails. In addition, since a position sensor is required, the number of parts increases and the cost increases.

  An object of the present invention is to provide a sheet feeding apparatus and an image forming apparatus that can perform abnormality determination of a lift raising mechanism without using a position sensor.

  A sheet feeding device according to one aspect of the present invention includes a first sheet storage unit, a lift raising mechanism, a first feeding unit, a second sheet storage unit, a second feeding unit, and a sheet detection unit. And a determination unit. The first sheet storage unit includes a lift plate that supports a sheet material to be stored. The lift raising mechanism raises the lift plate from a first position on the bottom side of the first sheet storage portion to a second position where the sheet material can be fed. The first feeding unit feeds the sheet material at the second position toward the first conveyance path on the downstream side in the feeding direction. The second sheet accommodating portion is configured to accommodate the sheet material. The second feeding unit feeds the sheet material from the second sheet storage unit to the first conveyance path through a second conveyance path on the downstream side in the feeding direction from a connection point with the first conveyance path. To do. The sheet detection unit detects the sheet material passing through a detection position on the downstream side in the feeding direction with respect to the connection point in the first conveyance path. The determination unit determines abnormality of the lift raising mechanism. The determination unit determines the second sheet material by the second feeding unit when the sheet material is not detected by the sheet detection unit after the first feeding operation of the sheet material by the first feeding unit. A feeding operation is performed, and when the sheet material is detected by the sheet detection unit after the second feeding operation, it is determined that the lift raising mechanism is abnormal.

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

  According to the present invention, it is possible to determine abnormality of the lift raising mechanism without using a position sensor.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a control configuration of the image forming apparatus. FIG. 3 is a perspective view illustrating a configuration of a paper feed cassette included in the image forming apparatus. FIG. 4 is a cross-sectional view showing the configuration of the paper feed cassette. FIG. 5 is a top view illustrating a configuration of a lift drive unit included in the image forming apparatus. FIG. 6 is a perspective view showing the lift drive unit. FIG. 7 is a perspective view showing the lift drive unit. FIG. 8 is a diagram for explaining the operation of the lift drive unit. FIG. 9 is a diagram for explaining the operation of the lift drive unit. FIG. 10 is a diagram for explaining the operation of the lift drive unit. FIG. 11 is a diagram for explaining the operation of the lift drive unit. FIG. 12 is a diagram for explaining the operation of the lift drive unit. FIG. 13 is a flowchart illustrating a procedure of abnormality determination processing executed by the control unit of the image forming apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. Embodiment described below is only an example which actualized this invention, and does not limit the technical scope of this invention. For convenience of explanation, the vertical direction is defined as the vertical direction 7 in the installation state in which the image forming apparatus 10 can be used (the state shown in FIG. 1). Also, the front-rear direction 8 is defined with the front surface (front surface) being the surface into which the paper feed cassette 24 shown in FIG. Further, a left-right direction 9 is defined with reference to the front surface of the installed image forming apparatus 10.

  The image forming apparatus 10 according to the embodiment of the present invention is an apparatus having at least a printing function. The image forming apparatus 10 is a so-called tandem type color printer. The image forming apparatus 10 prints an image on printing paper using a developer containing toner. The image forming apparatus 10 is not limited to a simple printer as long as it includes a paper feed cassette 24 and a manual feed tray 38, which will be described later. For example, the image forming apparatus 10 may be a multifunction machine, a FAX apparatus, a copying machine, or the like. . Of course, not a color image but a single color image may be formed.

  As shown in FIG. 1, the image forming apparatus 10 includes a housing 10A. Each part constituting the image forming apparatus 10 is provided inside the housing 10A. The image forming apparatus 10 includes four image forming units 4, a transfer belt 5, an optical scanning device 13, a secondary transfer roller 20, a fixing device 16, a paper discharge tray 18, a paper feed cassette 24 (first sheet storage unit of the present invention). Example), container unit 31, first feeding unit 32, lift drive unit 60 (an example of the pressing unit of the present invention), operation display unit 25, manual feed tray 38 (an example of the second sheet storage unit of the present invention), A second feeding unit 39, a sheet sensor 44 (an example of the sheet detection unit of the present invention), a control unit 80 (see FIG. 2), and the like are provided. The printing paper is a sheet material such as paper, coated paper, postcard, envelope, and OHP sheet.

  Each of the image forming units 4 includes a photosensitive drum 11, a charging device 12, a developing device 14, a primary transfer roller 15, and the like, and forms an image according to an electrophotographic method. The image forming unit 4 is arranged in parallel along the front-rear direction 8 inside the housing 10A. The image forming unit 4 forms a color toner image on the transfer belt 5 by superimposing and transferring the toner images of the respective colors on the surface of the transfer belt 5. The toner image on the transfer belt 5 is transferred by the secondary transfer roller 20 to the printing paper conveyed from the paper feed cassette 24 via the vertical conveyance path 26 (an example of the first conveyance path of the present invention).

  The optical scanning device 13 is provided below the image forming unit 4. The optical scanning device 13 scans the peripheral surface of the photosensitive drum 11 with a laser beam corresponding to the image data, and forms an electrostatic latent image on the peripheral surface.

  The paper feed cassette 24 is provided below the optical scanning device 13. The paper feed cassette 24 is mounted on the bottom of the housing 10A. A printing paper of a specified size is stored in the paper feed cassette 24. The printing paper accommodated in the paper feeding cassette 24 is fed in the feeding direction toward the longitudinal conveyance path 26 side (rear side) by the first feeding unit 32 as will be described later. In the present embodiment, the configuration of one sheet feeding cassette 24 is illustrated, but a configuration in which a plurality of sheet feeding cassettes 24 capable of individually accommodating a plurality of sizes of sheets may be provided.

  A vertical conveyance path 26 is formed on the rear side inside the housing 10A. The vertical conveyance path 26 is a space sandwiched between a pair of guide members provided to face each other in the front-rear direction. The vertical conveyance path 26 extends from the paper feed cassette 24 to the sheet discharge port 27 through the secondary transfer roller 20 and the fixing device 16. A plurality of transport rollers 22 are provided along the vertical transport path 26. A part of the guide surface at the lower end of the vertical conveyance path 26 is formed by a guide member 41. Specifically, the lower guide surface at the lower end of the vertical conveyance path 26 is formed by a guide member 41 provided on the lower back side of the housing 10A.

  The first feeding unit 32 takes out the printing sheets stacked in the sheet feeding cassette 24 one by one and feeds them toward the vertical conveyance path 26 formed on the downstream side in the feeding direction.

  The first feeding unit 32 includes a pickup roller 51, a paper feed roller 52, and a retard roller 53. The pickup roller 51 is provided in the vicinity of the paper feed cassette 24. Specifically, a pickup roller 51 is provided above the rear portion of the paper feed cassette 24. The pickup roller 51 is provided at the rear portion of the paper feed cassette 24 so as to face the upper surface of the bundle of print sheets stored therein. The pickup roller 51 is a rotating body that is rotationally driven by receiving a rotational driving force transmitted from a first motor 54 (see FIG. 2) as a driving source. The pickup roller 51 contacts the printing paper stored in the paper feeding cassette 24 and rotates in the contacted state, thereby feeding the printing paper in the feeding direction toward the entrance of the vertical conveyance path 26.

  The paper feed roller 52 conveys the printing paper fed by the pickup roller 51 downstream in the feeding direction. The paper feed roller 52 is provided on the rear side of the pickup roller 51. The paper feed roller 52 is a rotating body that is rotationally driven in response to the rotational driving force transmitted from the first motor 54 (see FIG. 2). Below the paper feed roller 52, a retard roller 53 is provided in pressure contact with the roller surface of the paper feed roller 52. When the paper feed roller 52 is rotated, the retard roller 53 is driven by the paper feed roller 52 and rotated. When the leading edge of the printing paper fed by the pickup roller 51 reaches the nip portion between the paper feeding roller 52 and the retard roller 53, the printing paper is fed while being sandwiched between the paper feeding roller 52 and the retard roller 53. It is sent out to the downstream side in the direction and conveyed to the vertical conveyance path 26.

  The secondary transfer roller 20 is provided at a position facing the drive roller 5A on the rear side of the housing 10A. The toner image is transferred from the transfer belt 5 to the printing paper by the secondary transfer roller 20.

  The fixing device 16 applies heat to the printing paper to fix the toner image on the printing paper. The fixing device 16 includes a heating roller 16A, which is a pair of rollers, and a pressure roller 16B. Heat is transmitted from the heating roller 16A to the printing paper, and the toner on the printing paper is melted and fixed on the printing paper. Thereby, a color image is formed on the printing paper. The printing paper that has passed through the fixing device 16 is discharged from the sheet discharge port 27 to the paper discharge tray 18 by the paper discharge roller 23.

  A relay conveyance path 28 (an example of the second conveyance path of the present invention) is formed between the optical scanning device 13 and the paper feed cassette 24. The relay conveyance path 28 is a space sandwiched between a pair of guide members provided so as to face each other vertically. The relay conveyance path 28 extends rearward from the front surface of the image forming apparatus 10 inside the housing 10A, and is connected to the vertical conveyance path 26 on the rear side inside the housing 10A. Accordingly, the printing paper conveyed rearward along the relay conveyance path 28 is conveyed upward through the vertical conveyance path 26 when entering the vertical conveyance path 26 from the connection point P1 between the relay conveyance path 28 and the vertical conveyance path 26. The

  A manual feed tray 38 is provided on the front surface of the image forming apparatus 10. In addition, a second feeding unit 39 is provided between the manual feed tray 38 and the relay conveyance path 28 inside the housing 10A. The manual feed tray 38 stores printing paper fed by the second-level layer unit 39. The manual feed tray 38 also serves as a cover on the front surface of the housing 10 </ b> A of the image forming apparatus 10. The manual feed tray 38 is configured to be able to open and close the entrance of the relay conveyance path 28 with respect to the front surface of the housing 10A. In FIG. 1, a state where the manual feed tray 38 is closed with respect to the front surface of the housing 10A is shown by a solid line, and a state where the manual feed tray 38 is opened is shown by a broken line. When the manual feed tray 38 is opened with respect to the front surface of the housing 10A, the inner surface of the manual feed tray 38 is directed upward. In this state, printing paper of a predetermined size can be placed on the inner surface. The printing paper placed on the manual feed tray 38 is fed to the vertical conveyance path 26 through the relay conveyance path 28 by the second feeding unit 39.

  The second feeding unit 39 takes out the printing paper placed on the manual feed tray 38 one by one, feeds it to the relay conveyance path 28, and further connects the printing paper fed into the relay conveyance path 28 to the connection point. The sheet is fed from P1 to the vertical conveyance path 26. The second feeding unit 39 includes a pickup roller 391 and a paper feed roller 392. The second feeding unit 39 further includes a plurality of transport rollers 393 provided along the relay transport path 28. The pickup roller 391, the paper feed roller 392, and the transport roller 393 are rotating bodies that are rotationally driven by receiving a rotational driving force transmitted from a second motor 43 (see FIG. 2) as a driving source.

  The sheet sensor 44 is provided in the vertical conveyance path 26. The sheet sensor 44 is provided on the downstream side in the feeding direction from the connection point P1. The sheet sensor 44 is used to detect the leading edge of the printing paper that passes the detection position P2 on the downstream side in the feeding direction from the connection point P1. The sheet sensor 44 is, for example, a reflective phototransistor that can detect printing paper passing through the detection position P2. Alternatively, a detector that is displaced according to the passage of the printing paper and a transmissive phototransistor whose optical path is blocked or transmitted according to the displacement of the detector may be combined. The sheet sensor 44 may have any configuration as long as it can detect the presence or absence of printing paper conveyed downstream from the connection point 1 of the vertical conveyance path 26.

  The sheet sensor 44 is used for the purpose of determining the timing for rotationally driving a registration roller 22A described later. When the leading edge of the printing paper reaches the detection position P2, the output signal of the sheet sensor 44 changes from LOW level to HIGH level. The sheet sensor 44 is connected to the control unit 80, and the control unit 80 determines that the leading edge of the printing paper has reached the detection position P2 when the output signal of the sheet sensor 44 changes from the LOW level to the HIGH level. .

  The plurality of transport rollers 22 include a registration roller 22A. The registration roller 22 </ b> A includes a driving roller and a driven roller provided between the secondary transfer roller 20 and the sheet sensor 44. The registration roller 22A is driven to rotate by obtaining a driving force from the first motor 54 (see FIG. 2), and thereby conveys the printing paper that has reached the registration roller 22A to the downstream side. The registration roller 22A is used for a purpose of performing a registration operation on the printing paper conveyed through the vertical conveyance path 26 and a purpose of conveying the printing paper after the registration operation to the downstream side in the conveyance direction. When a preset time (registration time) elapses after the leading edge of the printing paper is detected by the sheet sensor 44, the driving force is transmitted to the stopped registration roller 22A. Until the driving force is transmitted, the leading edge of the printing paper is abutted against the nip portion of the registration roller 22A (the nip portion between the driving roller and the driven roller). In this state, when a conveying force is continuously applied to the printing paper by the conveying roller 22, the leading edge of the printing paper is aligned at the nip portion of the registration roller 22A. Thereby, the skew of the printing paper being conveyed is corrected. The registration roller 22A is provided with an electromagnetic clutch (not shown), and the rotation of the registration roller 22A is controlled by the controller 80 controlling on / off of the electromagnetic clutch.

  The control unit 80 performs overall control of the image forming apparatus 10. As shown in FIG. 2, the control unit 80 includes a CPU 81, a ROM 82, a RAM 83, an internal memory 84, a motor driver 85, and the like.

  As shown in FIG. 2, the control unit 80 is electrically connected to the first motor 54, the second motor 43, the electromagnetic clutches 57, 58, and the like by an internal bus, a signal line, and the like. The control unit 80 controls the driving of the first motor 54 and the second motor 43, and controls the on / off of the electromagnetic clutches 57 and 58.

  In the present embodiment, the control unit 80 performs an abnormality determination process described later according to the flowchart of FIG. This abnormality determination process is a process for determining whether or not the lift-up operation of the lift drive unit 60 is abnormal. The ROM 82 stores a control program for performing the abnormality determination process. The internal memory 84 is a non-volatile storage device such as a flash memory, for example, and stores data such as a threshold value, a set value, and a count value used for the abnormality determination process.

  The abnormality determination process by the control unit 80 may be realized by an electronic circuit such as an integrated circuit (ASIC, DSP).

  The first motor 54 is, for example, a DC motor or a stepping motor. The first motor 54 outputs a rotational driving force for rotating the pickup roller 51, the paper feed roller 52, the transport roller 22, and the like. The first motor 54 also supplies a rotational driving force to the two-stage cam 65 provided in the lift drive unit 60. That is, the rotational driving force of the first motor 54 is also used as a force for driving the two-stage cam 65. Accordingly, the pickup roller 51 and the two-stage cam 65 are rotationally driven by the first motor 54 that is the same drive source.

  The second motor 43 outputs a rotational driving force that rotates the pickup roller 391, the paper feed roller 392, the transport roller 393, and the like.

  The first motor 54 and the second motor 43 are connected to a motor driver 85 provided in the control unit 80, and are driven and controlled by the motor driver 85. In the present embodiment, an example in which the pickup motor 51, the paper feed roller 52, the transport roller 22, and the two-stage cam 65 are driven by the first motor 54 will be described. A configuration in which the motor is driven may be adopted.

  The drive transmission mechanisms 55 and 56 transmit the rotational driving force of the first motor 54 to other driving devices. The drive transmission mechanism 55 transmits the rotational driving force to the paper feed roller 52, the pickup roller 51, the transport roller 22, and the like. The drive transmission mechanism 56 transmits the rotational driving force to the two-stage cam 65 of the lift drive unit 60. As the drive transmission mechanisms 55 and 56, for example, a gear transmission mechanism constituted by a shaft coupling or a gear, a belt transmission mechanism constituted by a belt or a pulley, a wire transmission mechanism constituted by a wire or a pulley, etc. are considered. It is done.

  The electromagnetic clutches 57 and 58 are clutches that are turned on or off in response to a control signal from the control unit 80. The electromagnetic clutch 57 is provided in the transmission path between the first motor 54 and the pickup roller 51. The electromagnetic clutch 58 is provided in a transmission path between the first motor 54 and the two-stage cam 65 of the lift drive unit 60. The electromagnetic clutch 57 may be incorporated in the drive transmission mechanism 55, and the electromagnetic clutch 58 may be incorporated in the drive transmission mechanism 56. When the electromagnetic clutches 57 and 58 are on, the rotational driving force supplied from the drive transmission mechanisms 55 and 56 is transmitted to other driving devices. When the electromagnetic clutches 57 and 58 are off, the transmission path from the drive transmission mechanisms 55 and 56 to other drive devices is blocked. That is, when the electromagnetic clutch 58 is turned off by the control unit 80, the rotational driving force of the first motor 54 is not transmitted to the two-stage cam 65, and when the electromagnetic clutch 58 is turned on, the first motor 54 is rotationally driven. A force is transmitted to the two-stage cam 65.

  Hereinafter, the paper feed cassette 24 and the lift drive unit 60 will be described in detail.

  The paper feed cassette 24 is provided at the lowermost part of the housing 10A. As shown in FIG. 3, the paper feed cassette 24 is formed in a tray shape having an opening on the upper surface so that a plurality of print sheets can be accommodated. The paper feed cassette 24 stacks printing paper on which an image is formed by the image forming unit 4.

  A bottom plate 46 of the paper feed cassette 24 is provided with a lift plate 45 that supports printing paper to be stored and a lift raising mechanism 34 that raises the lift plate 45. The lift plate 45 is provided on the rear side at the bottom 46. Printing paper is stacked on the lift plate 45. A front end 47 (see FIG. 4) of the lift plate 45 is rotatably supported by the bottom 46 of the paper feed cassette 24, and a rear end 48 (see FIG. 4) is a free end. When the lift plate 45 rotates about the front end portion 47 of the lift plate 45, the lift plate 45 can be raised and lowered in the vertical direction 7. In the present embodiment, the lift plate 45 has a first position where the rear end portion 48 is close to the bottom portion 46 of the paper feed cassette 24 (the position shown in FIG. 4C) and a first position above the first position. It can be displaced between two positions (position shown in FIG. 4A). The first position and the second position will be described later.

  The lift raising mechanism 34 raises the lift plate 45 from the first position on the bottom 46 side of the paper feed cassette 24 to the second position where the printing paper can be fed. As shown in FIG. 4, the lift raising mechanism 34 has an elastic member 34 </ b> A (an example of an urging member according to the present invention) provided on the upper surface of the bottom 46 of the sheet feeding cassette 24. The lift plate 45 is attached to the upper surface of the bottom 46 of the paper feed cassette 24 via an elastic member 34A. The elastic member 34A is a so-called compression spring, for example, a coil spring in a compressed state. The lift plate 45 is always urged upward by the elastic member 34A. In other words, the elastic member 34A urges the lift plate 45 from the first position toward the second position by its elastic force. By this urging force, the lift plate 45 in the first position is lifted to the second position. Thereby, even when the printing paper is stacked on the lift plate 45, the printing paper located at the uppermost position can always contact the outer peripheral surface of the pickup roller 51.

  The paper feed cassette 24 is detachably supported on the housing 10A. Specifically, the paper feed cassette 24 is slidably supported by a well-known rail support mechanism so that it can be inserted and removed in the front-rear direction 8 from the front surface of the image forming apparatus 10 to the inside of the housing 10A. For example, the rail support mechanism may be composed of a support rail provided in the housing 10A and a supported portion that slides along the support rail while being supported by the support rail.

  As shown in FIG. 3, the paper feed cassette 24 includes a front wall 35 at the front end, a pair of side walls 36 on the left and right sides, and a regulation wall 37 that regulates the movement of the paper on the rear side. Yes. An opening 36 </ b> A is formed on the rear side of the side wall 36. Further, the regulation wall 37 is provided with an engaging portion 70 described later. As shown in FIG. 6, rectangular wing portions 48 </ b> A that protrude outward in the left-right direction 9 are provided on both side ends of the rear end portion 48 of the lift plate 45. The wing portion 48A is inserted through the opening 36A, whereby the wing portion 48A is disposed outside the side wall 36.

  As shown in FIG. 4, the paper feed cassette 24 has an engaging portion 70. The engaging portion 70 is provided at the lower end of the regulation wall 37 of the paper feed cassette 24. The engaging portion 70 engages with the rear end portion 48 of the lift plate 45 in the unmounted state in which the paper feed cassette 24 is detached from the mounting position in the housing 10 </ b> A, and the rear end portion 48 is close to the bottom portion 46. It can be held at the position (the position shown in FIG. 4C). In the present embodiment, the lift plate 45 is in contact with the bottom 46 at the first position, and is in a posture substantially parallel to the bottom 46. Further, the engaging portion 70 can be disengaged from the rear end portion 48 when the paper feed cassette 24 is mounted on the housing 10A. Specifically, the engaging portion 70 includes a lock member 71 and an elastic member 72. An insertion hole 74 is formed at the center of the lower end of the regulation wall 37 in the width direction, and a groove 75 continuous with the insertion hole 74 is formed at the rear end of the bottom portion 46 so as to extend in the front-rear direction 8. The lock member 71 is inserted through the insertion hole 74. An elastic member 72 is attached to the groove 75. The elastic member 72 is a compressed coil spring, one end is fixed to the front end of the groove 75, and the other end is fixed to the lock member 71. As a result, as shown in FIG. 4A, the lock member 71 is pulled to the inside of the paper feed cassette 24 by the elastic member 72.

  The lock member 71 has an engagement piece 71A protruding forward and a stopper portion 71B protruding downward. An inclined surface is formed on the front side of the engaging piece 71A. The engagement piece 71 </ b> A forms a gap in which the lift plate 45 can be inserted between the engagement piece 71 </ b> A and the upper surface of the bottom 46. The stopper portion 71B protrudes downward from the bottom surface of the paper feed cassette 24 on the outer side of the regulation wall 37, and the engagement piece 71A projects forward from the inner surface of the regulation wall 37 to the front of the lock member 71. Stop movement.

  Since the engaging portion 70 is configured as described above, the printing paper is stored in the paper feeding cassette 24 removed from the housing 10A in order to store the printing paper in the paper feeding cassette 24. When the lift plate 45 is pressed downward, the rear end portion 48 of the lift plate 45 comes into contact with the inclined surface of the engagement piece 71A. When the lift plate 45 is further pressed downward, the lock member 71 moves rearward (see FIG. 4B). As a result, the rear end portion 48 of the lift plate 45 enters the gap on the lower side of the engagement piece 71A. When the rear end portion 48 enters the gap, the lock member 71 returns to the original posture, and the engagement piece 71 </ b> A is disposed on the upper surface of the rear end portion 48. As a result, the lift plate 45 is held at the first position in contact with the bottom 46 (see FIG. 4C).

  On the other hand, when the paper feed cassette 24 is mounted on the housing 10A with the lift plate 45 held at the first position, the release member 49 provided on the housing 10A is stopped by the stopper portion 71B in the mounting process. Press the lower end of to the front. Specifically, when the paper feed cassette 24 reaches the mounting position in the housing 10A, the release member 49 presses the stopper portion 71B forward. At this time, as indicated by a dotted line in FIG. 4C, the stopper portion 71B is inclined backward, and the engagement piece 71A is displaced rearward, so that the engagement between the rear end portion 48 and the engagement piece 71A. The match is released. As a result, the lift plate 45 is lifted upward by receiving the urging force of the elastic member 34A, and the lift plate 45 is moved to the second position (position shown in FIG. 4A) above the first position. Be placed. Here, the second position is a position where the printing paper accommodated in the paper feeding cassette 24 can be fed in contact with the peripheral surface of the pickup roller 51.

  By the way, when the paper feed cassette 24 is mounted on the housing 10A and the engagement by the engaging portion 70 is released, the lift plate 45 is moved upward by receiving the urging force of the elastic member 34A. At this time, when the lift plate 45 rises vigorously, the upper surface of the sheet collides with the pickup roller 51 and a collision sound is generated. In particular, when a relatively small number of printing sheets are stored in the paper feed cassette 24, the printing sheet does not function as an impact sound absorbing material, and a relatively large impact sound is generated. In order to reduce such a collision sound, the lift drive unit 60 is provided in this embodiment.

  The lift drive unit 60 is provided on the rear side of the paper feed cassette 24 inside the housing 10A. A guide member 41 that constitutes a guide surface of the vertical conveyance path 26 is provided in the housing 10A. As shown in FIG. 5, the lift drive unit 60 is provided on each of both side surfaces 42 in the left-right direction 9 of the guide member 41.

  The lift drive unit 60 gradually reduces the displacement speed at which the lift plate 45 is displaced upward in the mounted state in which the paper feed cassette 24 is mounted on the housing 10A. When the paper feed cassette 24 is mounted on the housing 10A and the engagement of the lift plate 45 by the engaging portion 70 is released, the lift plate 45 tends to rise from the first position to the second position. The rising speed at this time is decelerated by the lift drive unit 60.

  As shown in FIGS. 5 to 7, the lift drive unit 60 includes an actuator 64 and a two-stage cam 65. 6 and 7 show the right-side lift drive unit 60. FIG.

  The actuator 64 is rotatably supported on the side surface 42. Specifically, the first rotating shaft 61 is provided on the side surface 42. The first rotating shaft 61 protrudes from the side surface 42. The actuator 64 is supported so as to be rotatable about the first rotation shaft 61. The actuator 64 is provided with a bearing portion 91, and the first rotating shaft 61 is inserted through the bearing portion 91. That is, the first rotating shaft 61 is a support shaft for rotatably supporting the actuator 64. As shown in FIGS. 5 and 6, the first rotating shaft 61 is provided at a position separated rearward from the rear end portion 48 of the lift plate 45 in the first position. More specifically, the first rotating shaft 61 is provided at the rear end of the side surface 42.

  As shown in FIG. 5, the guide member 41 is provided with a second rotating shaft 62 extending in the left-right direction 9. The second rotating shaft 62 is rotatably supported by the guide member 41. The second rotating shaft 62 passes through each side surface 42 of the guide member 41 and protrudes outward from each side surface 42. The second rotation shaft 62 is provided behind the rear end portion 48 of the lift plate 45 in the first position and ahead of the first rotation shaft 61. That is, the second rotation shaft 62 is provided between the rear end portion 48 and the first rotation shaft 61 on the side surface 42.

  The actuator 64 includes a cylindrical bearing portion 91, a base portion 95 in which a substantially circular through hole 92 is formed, and an arm-shaped arm portion 93 protruding from the base portion 95. The projecting length of the arm part 93 is determined to be a dimension capable of contacting the lift plate 45. As shown in FIG. 6, the through hole 92 is formed substantially at the center of the base portion 95 of the actuator 64. The bearing portion 91 is rotatably supported by the first rotation shaft 61 in a state where the second rotation shaft 62 is inserted through the through hole 92. As described above, the first rotating shaft 61 is inserted into the inner hole of the bearing portion 91, whereby the actuator 64 is rotatably supported on the side surface 42.

  The arm portion 93 protrudes in a direction away from the first rotation shaft 61. The arm portion 93 can abut on the upper surface of the wing portion 48 </ b> A provided at both side ends of the rear end portion 48 of the lift plate 45. A protrusion 94 that protrudes downward is provided at the tip of the arm portion 93. The protrusion 94 has an inclined surface 94A that is inclined downward from the tip of the arm portion 93. The inclined surface 94A is a portion where the wing portion 48A of the lift plate 45 is brought into contact when the paper feed cassette 24 is mounted at the mounting position in the housing 10A. When the wing portion 48A comes into contact with the inclined surface 94A, the arm portion 93 is pushed upward, the wing portion 48A moves rearward, and the sheet feeding cassette 24 is disposed at the mounting position. Further, a concave portion 48B is provided on the upper surface of the wing portion 48A. When the arm portion 93 is brought into contact with the wing portion 48A, the protrusion 94 enters the recess 48B. Thereby, the arm part 93 and the wing part 48A engage so that contact / separation is possible.

  The actuator 64 rotates between a third position and a fourth position described later. Specifically, as described above, since the arm portion 93 is in contact with the upper surface of the wing portion 48A, when the lift plate 45 rises from the first position to the second position, the rise follows (follow). Then, the arm portion 93 rotates so as to be lifted upward. When the lift plate 45 is in the first position, the position of the actuator 64 when the arm portion 93 is in contact with the wing portion 48A is the third position (position shown in FIG. 8). That is, the third position is a position corresponding to the first position of the lift plate 45. Further, when the lift plate 45 rises and reaches the second position, the arm portion 93 is lifted upward and lifted to the fourth position (position shown in FIG. 11). That is, the fourth position is a position corresponding to the second position of the lift plate 45.

  In the present embodiment, the two-stage cam 65 applies a stepwise load to the actuator 64 in the process in which the actuator 64 rotates from the third position to the fourth position as the lift plate 45 rises. This stepwise load is transmitted to the wing portion 48A via the arm portion 93, whereby the lifting speed of the lift plate 45 is reduced.

  The two-stage cam 65 is attached to both ends of the second rotating shaft 62. The two-stage cam 65 is fixed to the second rotating shaft 62. Therefore, when the second rotating shaft 62 rotates, the two-stage cam 65 also rotates in the same direction. An input gear 68 to which the rotational driving force transmitted from the drive transmission mechanism 56 is input is connected to the left end portion of the second rotation shaft 62. When the rotational driving force is transmitted to the input gear 68, the rotational driving force is input (transmitted) to the two-stage cam 65 via the second rotating shaft 62.

  As shown in FIG. 7, the two-stage cam 65 includes a first cam 101 and a second cam 102. The two-stage cam 65 is a resin molded product in which the first cam 101 and the second cam 102 are integrally formed. In the two-stage cam 65, the first cam 101 is formed on the outer side in the axial direction of the second rotating shaft 62, and the second cam 102 is formed on the inner side in the axial direction (side surface 42 side). Each of the first cam 101 and the second cam 102 is a so-called eccentric cam. That is, the center of each of the first cam 101 and the second cam 102 is determined at a position shifted from the second rotation shaft 62.

  When the rotational driving force is input to the input gear 68, the second rotating shaft 62 is rotated at a constant speed in the counterclockwise rotation direction D5 in FIG. Thereby, the two-stage cam 65 is also rotated at a constant speed in the same direction. In the present embodiment, as will be described later, the two-stage cam 65 moves from the initial position (position shown in FIG. 8) to the relay start position (position shown in FIG. 9, the fifth position) and the relay end position (FIG. 10). It is rotated to the release position (position shown in FIG. 11) via the position shown, the sixth position). The first cam 101 and the second cam 102 act in contact with the actuator 64 according to each position at each position that the two-stage cam 65 can take.

  Specifically, as shown in FIGS. 6 and 7, the base portion 95 of the actuator 64 has a first boss 64 </ b> A that is an example of a first protrusion and a second boss that is an example of a second protrusion. 64B is provided. The first boss 64 </ b> A and the second boss 64 </ b> B are projecting members that protrude vertically from the side surface of the actuator 64. The first boss 64A is a portion where the first cam 101 is brought into contact with the second cam 65 until the second cam 65 rotates in the counterclockwise rotation direction D5 from the initial position and reaches the relay start position. In the first boss 64A, the contact surface with the first cam 101 is formed in a curved surface. The second boss 64B is a portion where the second cam 102 is brought into contact with the second cam 65 until the second cam 65 rotates in the counterclockwise rotation direction D5 from the relay start position and reaches the relay end position. In the second boss 64B, the contact surface with the second cam 102 is formed in a curved surface.

  FIGS. 8 to 12 are diagrams illustrating the operating state of the lift drive unit 60, and more specifically, illustrating the operating state of the actuator 64 that operates according to the rotation of the two-stage cam 65. FIG. Here, in FIG. 8 (A), FIG. 9 (A), FIG. 10 (A), FIG. 11 (A), and FIG. 12 (A), the first cam 101 of the two-stage cam 65 is shown. 8B, FIG. 9B, FIG. 10B, FIG. 11B, and FIG. 12B show the second cam 102 of the two-stage cam 65. FIG. FIG. 8 shows a state in which the two-stage cam 65 is in the initial position. FIG. 9 shows a state where the two-stage cam 65 is at the relay start position, and FIG. 10 shows a state where the two-stage cam 65 is at the relay end position. FIG. 11 shows a state in which the two-stage cam 65 is in the release position.

  The first cam 101 and the second cam 102 are annular members formed so as to surround the second rotation shaft 62. As shown in FIG. 8A, the first cam 101 has a locking portion 111 that is an example of an engagement surface and a first action portion 112 that is an example of the first cam surface on the outer peripheral surface thereof. . Further, as shown in FIG. 8B, the second cam 102 has a second action portion 113 that is an example of a second cam surface on the outer peripheral surface thereof.

  When the two-stage cam 65 is in the initial position shown in FIG. 8, the locking portion 111 is in contact with the first boss 64A. The locking portion 111 is formed in a slightly recessed shape with respect to the outer peripheral surface of the first cam 101. The initial position is a state where the locking portion 111 is in contact with the first boss 64A. At this time, the locking portion 111 abuts so as to push the upper end of the first boss 64A downward. The downward acting force at this time is defined as F1. In the present embodiment, the actuator 64 is disposed at the third position in a state where the two-stage cam 65 is at the initial position, and the actuator 64 is held at the third position by the acting force F1 of the locking portion 111. Has been. Therefore, when the two-stage cam 65 is in the initial position, even if the upward biasing force F10 by the elastic member 34A is applied from the lift plate 45 to the arm portion 93, the acting force F1 is larger, so the actuator 64 is The third position is held. In other words, the upward displacement (rise) of the lift plate 45 from the first position is regulated by the arm portion 93 of the actuator 64, and the lift plate 45 is held at the first position.

  The locking portion 111 is also formed continuously on the second cam 102. Accordingly, at the initial position, the first cam 101 and the second cam 102 are in contact with the first boss 64 </ b> A via the locking portion 111. In other words, the two-stage cam 65 has the locking portion 111 in the region from the first cam 101 to the second cam 102 in the width direction. The locking portion 111 may not be formed continuously with the second cam 102, and the locking portion 111 that contacts the first boss 64A at least at the initial position is provided on the first cam 101. That's fine.

  The first action part 112 is a curved surface formed in the clockwise rotation direction D6 side with respect to the locking part 111 in FIG. The 1st action part 112 is formed so that the distance with the 2nd axis of rotation 62 may become short as it goes away from the stop part 111 side. When a rotational driving force is input to the second rotating shaft 62 and the two-stage cam 65 is rotated in the counterclockwise direction D5, the locking portion 111 acts on the first boss 64A, and the actuator 64 slightly moves in the same direction. Only rotate. As a result, the first boss 64 </ b> A of the actuator 64 gets over the locking portion 111. At this time, the actuator 64 is allowed to rotate in the clockwise direction D6 in FIG. 8, and the first boss 64A rotates in the clockwise direction D6 while sliding on the curved surface of the first action part 112. That is, when the two-stage cam 65 rotates in the counterclockwise rotation direction D5, when the locking portion 111 passes the first boss 64A and reaches the position where the first boss 64A faces the curved surface of the first action portion 112, The distance between the 1 boss 64A and the second rotation shaft 62 is reduced. As a result, the engaging portion 111 does not receive the acting force F1 that pushes the actuator 64 in the counterclockwise rotation direction D5, and the restriction of the rotation of the actuator 64 in the clockwise rotation direction D6 by the locking portion 111 is released. Is done. As a result, the first boss 64A of the actuator 64 rotates in the clockwise direction D6 while sliding on the curved surface of the first action portion 112. Hereinafter, a load such as a sliding resistance generated between the first boss 64A and the curved surface of the first action part 112 at this time is referred to as a first load F21. That is, the first load F21 causes the first cam 101 to move to the first boss 64A when the two-stage cam 65 is rotated in the counterclockwise direction D5 from the initial position with the actuator 64 in the third position. The force in the clockwise direction D6 is applied to the actuator 64 through the first boss 64A at the time of contact. As shown in FIG. 9, the first load F <b> 21 acts in a direction that inhibits the rotation of the actuator 64 in the clockwise direction D <b> 6, and the rear end portion 48 of the lift plate 45 is moved via the arm portion 93. Acts as a downward pressing force.

  The first load F21 occurs until the two-stage cam 65 reaches the relay start position (see FIG. 9) from the initial position (see FIG. 8). The first load F21 is smaller than the biasing force F10 that biases the lift plate 45 upward. Therefore, the actuator 64 starts to rotate in the clockwise direction D6 by receiving the urging force F10. That is, the lift plate 45 whose rise has been suppressed by the actuator 64 starts to move from the first position toward the second position. The rising speed of the lift plate 45 at this time is V1. The first load F21 decreases as the two-stage cam 65 approaches the relay start position, so that the first boss 64A approaches the second rotating shaft 62. However, the urging force F10 decreases as the lift plate 45 rises. Become. Accordingly, there is no significant change in the speed V1 of the lift plate 45 until the two-stage cam 65 reaches the relay start position from the initial position.

  FIG. 9 shows a state where the two-stage cam 65 is rotated to the relay start position. The relay start position is a position when the two-stage cam 65 is rotated by a predetermined angle θ1 from the initial position in the counterclockwise rotation direction D5. In the present embodiment, the angle θ1 is 60 °. That is, the relay start position is a position that is separated from the initial position by an angle θ1 in the counterclockwise rotation direction D5. At the relay start position, the first action part 112 is in contact with the first boss 64A. Further, when the two-stage cam 65 reaches the relay start position, the second action portion 113 of the second cam 102 contacts the second boss 64B.

  In the present embodiment, when the two-stage cam 65 is further rotated in the counterclockwise direction D5 from the relay start position, the first cam 101 is separated from the first boss 64A (see FIG. 10). On the other hand, the second action portion 113 of the second cam 102 contacts the second boss 64B until the two-stage cam 65 reaches the relay end position (see FIG. 10) from the relay start position. When the two-stage cam 65 is further rotated in the counterclockwise rotation direction D5 from the relay end position and reaches the release position, the second action portion 113 of the second cam 102 is separated from the second boss 64B.

  That is, the first cam 101 exerts the first load F21 on the actuator 64 through the first action part 112 from the initial position to the relay start position. The first cam 101 does not act on the first load F21. Instead, taking over the role of the first cam 101, after the relay start position, the second cam 102 applies a second load F22 (described later) to the actuator 64 through the second action portion 113. Here, when the two-stage cam 65 is further rotated in the counterclockwise direction D5 from the relay start position, the second boss 64B slides on the curved surface of the second action portion 113. A load such as a sliding resistance generated at this time is the second load F22. That is, the second load F22 is such that the second cam 102 contacts the second boss 64B when the two-stage cam 65 is rotated in the counterclockwise rotation direction D5 from the relay start position. This is the force in the clockwise rotation direction D6 that is applied to the actuator 64 through it. The second load F22 acts in a direction that inhibits the rotation of the actuator 64 in the clockwise direction D6, and acts as a force that presses the rear end portion 48 of the lift plate 45 downward via the arm portion 93. . The second load F22 is a force larger than the first load F21.

  In the present embodiment, the inclination angle θ12 (see FIG. 10B) of the contact surface passing through the contact point between the second cam 102 and the second boss 64B is the contact point passing through the contact point between the first cam 101 and the first boss 64A. It is smaller than the inclination angle θ11 of the surface (see FIG. 9A). Specifically, the inclination angle θ12 is approximately 20 °, while the inclination angle θ11 is approximately 85 °. For this reason, in the state shown in FIG. 9A, the first load F21 is generated by the pressing force that the first cam 101 of the two-stage cam 65 presses the first boss 64A downward. In the state shown in B), a larger pressing force is applied than the second cam 102 of the two-stage cam 65 presses the second boss 64B downward. Therefore, the second load F22 is equivalent to the pressing force. It becomes larger than the first load F21.

  The second load F22 is generated until the two-stage cam 65 reaches the relay end position. That is, the second action portion 113 of the second cam 102 contacts the second boss 64B until the relay end position, and is separated from the second boss 64B after the relay end position. The relay end position is a position separated from the initial position by an angle θ2 (> θ1) in the counterclockwise rotation direction D5. In the present embodiment, the angle θ2 is 80 °. The second load F22 is larger than the first load F21, but smaller than the urging force F10 that urges the lift plate 45 upward. Therefore, the actuator 64 continuously rotates in the clockwise rotation direction D6 by receiving the urging force F10, but the rotation speed at that time is reduced due to the influence of the second load F22. Therefore, the lifting speed of the lift plate 45 is also decelerated to a speed V2 that is slower than the speed V1.

  When the two-stage cam 65 is further rotated to reach the release position (see FIG. 11), the two-stage cam 65 is not in contact with either the first boss 64A or the second boss 64B. The state at this time is the release position. At this time, the actuator 64 receives only the urging force F <b> 10 from the lift plate 45 without receiving a load from the two-stage cam 65. Depending on the number of print sheets stored in the paper feed cassette 24, the lift plate 45 has reached the second position between the relay end position and the release position, and the uppermost print sheet. Is in contact with the pickup roller 51. The release position is a position separated from the initial position by an angle θ3 (> θ2) in the counterclockwise rotation direction D5. In the present embodiment, the angle θ3 is 90 °.

  In addition, the control unit 80 sets the two-stage cam 65 to the initial stage when the first feeding unit 32 does not instruct the lift driving unit 60 configured as described above to perform the printing paper feeding operation. Control to place in position. When an instruction to execute the feeding operation is input, the electromagnetic clutch 58 is turned on, and the two-stage cam 65 is moved from the initial position (position shown in FIG. 8) to the release position (position shown in FIG. 11). ) Until the release position is reached, the electromagnetic clutch 58 is turned off. Whether the two-stage cam 65 has reached the initial position or the release position can be determined based on, for example, a rotation angle sensor such as a rotary encoder provided on the second rotation shaft 62 and the sensor output.

  The 1st cam 101 has the 3rd operation part 114 (an example of the press provision part of this invention) in the outer peripheral surface. As shown in FIG. 11, the third action part 114 is a step part formed on the outer peripheral surface of the first cam 101, the two-stage cam 65 is in the release position, and the actuator 64 is in the second position. In the vicinity of the first boss 64A. The third action portion 114 is in contact with the first boss 64A through the arm portion 93 in the process in which the two-stage cam 65 is rotated in the counterclockwise rotation direction D5 from the release position and returns to the initial position. A pressing force F30 (see FIG. 12) is applied to displace the rear end 48 of 45 downward. Specifically, as shown in FIG. 12, the third action portion 114 contacts the first boss 64A when the two-stage cam 65 is rotated in the counterclockwise rotation direction D5 from the release position. Thereby, the 3rd action part 114 presses the 1st boss 64A in the counterclockwise rotation direction. The pressing force F <b> 30 at this time acts on the rear end portion 48 of the lift plate 45 from the arm portion 93. The pressing force F30 is larger than the urging force F10 that urges the lift plate 45 upward. In response to this pressing force F30, the actuator 64 starts to rotate in the counterclockwise direction D5. When the actuator 64 rotates to the third position, the third action part 114 passes through the first boss 64A. Instead, the curved face 115 from the third action part 114 to the locking part 111 biases the first boss 64A. Press against F10. When the two-stage cam 65 reaches the initial position where the locking portion 111 contacts the first boss 64A, the two-stage cam 65 is stopped by the control unit 80. At this time, the actuator 64 is held at the third position by the locking portion 111.

  Since the lift drive unit 60 is configured in this way, the lift plate 45 is biased by the elastic member 34A when the paper feed cassette 24 is mounted on the housing 10A and the engagement by the engagement portion 70 is released. Even if it moves upward in response, the moving speed is gradually reduced. Specifically, immediately after the engagement is released, the speed increases at the speed V1, but when the two-stage cam 65 of the lift drive unit 60 reaches the relay start position, the speed increases at the speed V2 slower than the speed V1. For this reason, since the lift plate 45 is decelerated before coming into contact with the pickup roller 51, a collision sound at the time of contact is not generated.

  Further, the lift plate 45 can be moved up and down in the up-down direction 7 using the rotational driving force at a constant speed of the first motor 54 shared with the pickup roller 51 and the like, compared with the case where an individual driving source is provided. Space saving around the lift drive unit 60 can be realized, and the apparatus can be made compact.

  By the way, even when the paper feed cassette 24 is mounted on the housing 10A and reaches the mounting position, if the release member 49 (see FIG. 4) or the lock member 71 is defective, the lift plate 45 is It remains held in the first position (position shown in FIG. 4C). In this case, since the printing paper stored in the paper feeding cassette 24 cannot come into contact with the peripheral surface of the pickup roller 51 of the lift plate 45, the printing paper is fed even if the feeding operation to the paper feeding cassette 24 is performed. The problem of not being sent arises. This problem can be caused when the lift drive unit 60 stops working due to a failure or the like, and the arm portion 93 of the actuator 64 always presses the lift plate 45 downward, or when the elastic member 34A has a problem and the biasing force is reduced. It also occurs when it is no longer applied to the lift plate 45. In particular, when the driving force is transmitted using the two-stage cam 65 as in the lift drive unit 60, the contact points between the members and the members and the drive transmission locations increase, so that the members and the members are fixed and the actuator 64 is connected to the actuator 64. There is a risk of sticking at three positions. The above problem can also occur when the sheet sensor 44 is out of order and printing paper passing through the detection position P2 cannot be detected.

  On the other hand, based on the change in the detection signal of the sheet sensor 44 after the feeding operation, the control unit 80 indicates that the printing paper has not reached the detection position P2 of the sheet sensor 44 in the vertical conveyance path 26 (hereinafter referred to as “no paper feed”). ").) Can be determined. For example, when there is no change in the output of the sheet sensor 44 until a predetermined time has elapsed after the feeding operation, the control unit 80 determines that there is no paper feeding. However, in the image forming apparatus having the conventional configuration, the control unit 80 determines whether the cause of the non-feeding is a feeding error due to an abnormal rise of the lift plate 45, or the feeding has occurred in the vertical conveyance path 26. Cannot determine if a paper jam (jam) has occurred. In the image forming apparatus 10 according to the present embodiment, the control unit 80 performs an abnormality determination process, which will be described later, to determine whether the lift plate 45 has risen without using a position sensor that detects the position of the lift plate 45. It is possible.

  Hereinafter, an example of the procedure of the abnormality determination process executed by the control unit 80 will be described with reference to the flowchart of FIG. In FIG. 13, S11, S12,... Represent processing procedure (step) numbers. By executing the abnormality determination process by the control unit 80, the determination unit of the present invention is realized. Note that the following abnormality determination process is performed in a state where the paper feed cassette 24 is mounted at the mounting position in the housing 10A.

  When an instruction signal for a feeding operation for feeding printing paper from the paper feeding cassette 24 is input to the image forming apparatus 10 together with the image forming operation, the motor driver 85 of the control unit 80 drives the first motor 54. Thus, the first feeding unit 32 is operated to perform a feeding operation (first feeding operation) for feeding printing paper from the paper feed cassette 24 to the vertical conveyance path 26. Specifically, the control unit 80 drives the first motor 54 to rotate the paper feed roller 52, the transport roller 22, and the paper discharge roller 23 (S11). Moreover, the control part 80 outputs an ON signal with respect to the electromagnetic clutch 57, and controls the electromagnetic clutch 57 to an ON state (fitting state). As a result, the pickup roller 51 is rotated, and the printing paper can be fed from the paper feed cassette 24 to the vertical conveyance path 26. Here, the operation of feeding printing paper from the paper feed cassette 24 corresponds to the first feeding operation by the first feeding unit 32 of the present invention. The pickup roller 51 can feed printing paper when the lift plate 45 is in the second position. However, when the lift plate 45 is abnormally raised and the lift plate 45 is in the first position. Can not feed printing paper. When the printing paper is fed to the position where it is transported by the transport roller 22, the controller 80 turns off the electromagnetic clutch 57 and stops the rotation of the pickup roller 51.

  Next, the control unit 80 determines whether the leading edge of the printing paper has reached the detection position P2 of the sheet sensor 44 (S12). Specifically, the control unit 80 determines that the leading edge of the printing paper has reached the detection position P2 when the output signal of the sheet sensor 44 changes from the LOW level to the HIGH level within a predetermined set time. To do. Here, when it is determined that the sheet sensor 44 has detected the leading edge of the printing paper, the control unit 80 ends the abnormality determination process. On the other hand, when the output signal of the sheet sensor 44 does not change from the LOW level to the HIGH level within the set time, the control unit 80 determines that the leading edge of the printing paper has not reached the detection position P2. That is, the control unit 80 determines that the leading edge of the printing paper field is not detected as the no-paper feeding.

  When it is determined that there is no paper feeding, the control unit 80 counts up the number of times when it is determined that there is no paper feeding, that is, the number of times that the paper is not fed (corresponding to the number of undetected times of the present invention) (S13). . The counted value counted up is stored in the internal memory 84.

  Next, the control unit 80 determines whether or not the number of occurrences of non-sheet feeding has reached a predetermined number of times (S14). In the present embodiment, the set number of times is set to 2 times, for example. Of course, the specific number of the set times can be arbitrarily determined.

  If it is determined in step S14 that the number of occurrences of non-feeding is less than the set number, the process returns to step S11, and the processes in and after step S11 are repeated. That is, the control unit 80 performs the feeding operation of the printing paper from the paper feeding cassette 24 until the number of occurrences (the number of detection times when the printing paper is not detected at the detection position P2) reaches the set number of times. On the other hand, when it is determined in step S14 that the number of occurrences of non-feeding has reached the set number, the control unit 80 prompts the user to set printing paper on the manual feed tray 38 on the display unit of the operation display unit 25. Is displayed (S15).

  Thereafter, when an instruction signal for a feeding operation for feeding printing paper from the manual feed tray 38 is input to the image forming apparatus 10, the motor driver 85 of the control unit 80 drives the second motor 43, The second feeding unit 39 is operated to perform a feeding operation (second feeding operation) for feeding printing paper from the manual feed tray 38 to the relay conveyance path 28. Specifically, the control unit 80 drives the second motor 43 to rotate the pickup roller 391, the paper feed roller 392, and the transport roller 393 (S16). At this time, the first motor 54 is driven, and the electromagnetic clutch 57 is turned off.

  When the feeding operation in step S16 is performed, the printing paper on the manual feed tray 38 is fed to the relay conveyance path 28, further conveyed to the vertical conveyance path 26 through the connection point P1, and conveyed to the detection position P2. Is done. Then, similarly to step S12, the control unit 80 determines whether the leading edge of the printing paper fed from the manual feed tray 38 has reached the detection position P2 of the sheet sensor 44 (S17).

  If it is determined in step S17 that the sheet sensor 44 has detected the leading edge of the printing paper, the control unit 80 causes the lift plate 45 to rise due to the non-feeding during the feeding operation from the paper feeding cassette 24. It is determined that there is an error, and an error output indicating the rise abnormality is output (S18). In this manner, the control unit 80 performs printing from the manual feed tray 38 by the second feeding unit 39 when the printing paper is not detected by the sheet sensor 44 after the printing paper feeding operation by the first feeding unit 32. When a sheet feeding operation is performed and a printing sheet is detected by the sheet sensor 44 after the feeding operation, it is determined that the lift plate 45 is not lifted properly. In this case, the image forming apparatus 10 performs a process for prohibiting the use of the paper feed cassette 24 (S19). For example, the paper feed cassette 24 cannot be selected in the image forming apparatus 10. In addition, a message that prompts an operation check of the lift raising mechanism 34 and the lift drive unit 60 may be displayed on the display unit of the operation display unit 25.

  On the other hand, if it is determined in step S17 that the sheet sensor 44 has not detected the leading edge of the printing paper, the control unit 80 determines that the cause of the non-feed is a paper jam in the vertical conveyance path 26 or a failure of the sheet sensor 44. Then, an error output indicating a paper jam or a sensor abnormality is performed (S20), and a message prompting to remove the paper or a message prompting the operation check of the sheet sensor 44 is displayed on the display unit of the operation display unit 25.

  In this way, the control unit 80 can determine whether the lift plate 45 has risen without providing a position sensor that detects the position of the lift plate 45. Accordingly, it is possible to determine whether the lift plate 45 is abnormally raised without increasing the number of components in the image forming apparatus 10 and without increasing the cost.

  Further, as described above, when it is determined that the number of occurrences of non-feeding is less than the set number of times, the process returns to step S11, and from the sheet feeding cassette 24 until the number of occurrences reaches the set number of times. By performing the printing paper feeding operation, it is possible to improve the certainty of the determination of the lift abnormality of the lift plate 45.

  In the above-described embodiment, the manual feed tray 38 is illustrated as an example of the second sheet storage unit of the present invention. However, for example, another sheet feeding unit having the same configuration as that of the sheet feeding cassette 24 at the upper stage or the lower stage of the sheet feeding cassette 24. When a cassette is provided, the second sheet storage unit of the present invention may be the other sheet feeding cassette.

  In the above-described embodiment, the image forming apparatus 10 that performs the abnormality determination process is exemplified. However, the present invention includes a control unit that performs the abnormality determination process, and further includes a sheet sensor 44, a paper feed cassette 24, a lift. It may be a sheet feeding device that includes the raising mechanism 34, the first feeding unit 32, the manual feed tray 38, and the second feeding unit 39.

10: Image forming apparatus 10A: Housing 24: Paper feed cassette 32: First feeding unit 34: Lift raising mechanism 34A: Elastic member 39: Second feeding unit 44: Sheet sensor 45: Lift plate 60: Lift drive unit 64: Actuator 65: Two-stage cam 70: Engagement part 80: Control part 93: Arm part 95: Base part

Claims (6)

A first sheet storage portion having a lift plate for supporting the stored sheet material;
A lift raising mechanism that raises the lift plate from a first position on the bottom side of the first sheet storage portion to a second position where the sheet material can be fed;
A first feeding unit that feeds the sheet material at the second position toward the first conveyance path on the downstream side in the feeding direction;
A second sheet accommodating portion for accommodating the sheet material;
A second feeding unit that feeds the sheet material from the second sheet storage unit to a first conveyance path from a connection point with the first conveyance path via a second conveyance path on the downstream side in the feeding direction;
A sheet detection unit that detects the sheet material passing through a detection position on the downstream side in the feeding direction from the connection point in the first conveyance path;
A determination unit for determining an abnormality of the lift raising mechanism,
The determination unit determines the second sheet material by the second feeding unit when the sheet material is not detected by the sheet detection unit after the first feeding operation of the sheet material by the first feeding unit. A sheet feeding device that performs a feeding operation and determines that the lift raising mechanism is abnormal when the sheet detection unit detects the sheet material after the second feeding operation.   The determination unit repeatedly performs the first feeding operation until an undetected number of times when the sheet material is not detected by the sheet detecting unit reaches a predetermined set number of times, and the undetected number of times is the set number of times. 2. The second feeding operation is performed when reaching the position, and when the sheet material is detected by the sheet detection unit after the second feeding operation, it is determined that the lift raising mechanism is abnormal. The sheet feeding apparatus described in 1.   The sheet feeding apparatus according to claim 1, wherein the first sheet storage unit is a manual feed tray. The first sheet storage unit is engaged with the lift plate when the first sheet storage unit is not attached to the housing of the sheet feeding device, and the lift plate is moved to the first sheet storage unit. An engagement portion that is held in position and can be disengaged from the lift plate when mounted on the housing;
The lift raising mechanism is
4. The sheet feeding device according to claim 1, further comprising a biasing member that biases the lift plate from the first position toward the second position. 5.   The lift plate is pressed downward to hold the lift plate in the first position, and when the engagement by the engagement portion is released in the mounted state, the lift plate is moved from the first position to the first position. The sheet feeding device according to claim 4, further comprising: a pressing portion that follows displacement to two positions. A sheet feeding device according to any one of claims 1 to 4,
An image forming apparatus comprising: an image forming unit that forms an image on a sheet material fed by the sheet feeding device.

Images