JP2020033115A - Medium transport device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent poor transport and double feed regardless of the rigidity of a medium. A medium transfer device includes a medium mounting portion on which a medium is placed, a first roller that comes into contact with a medium mounted on the medium mounting section, and feeds the medium in the transport direction, and a first roller. It is located on the downstream side in the transport direction with respect to the rollers, and is arranged in a transport path between a second roller that further transports the medium unwound by the first roller and between the first roller and the second roller. It has a medium contact portion that comes into contact with the medium. The medium contact portion has a plurality of contact surfaces having different shapes that can be switched according to the type of medium. [Selection diagram] FIG. 11

Description

  The present invention relates to a medium transport device that transports a medium, and an image forming apparatus including the medium transport device.

  2. Description of the Related Art A medium conveyance device used in an image forming apparatus feeds out a sheet (medium) stacked on a tray by a pickup roller, separates the sheets (sheets) one by one by a feed roller and a separation roller, and sends the sheet to a conveyance path. reference).

  Here, in order to prevent a double feed in which a plurality of sheets are conveyed in an overlapping manner, it is conceivable to provide a rib (abutting portion) in contact with the leading end of the sheet in the sheet conveying path from the pickup roller to the feed roller. .

JP 2013-129481 (FIG. 4)

  However, the stiffness (Clark stiffness: stiffness) varies depending on the type of paper, and the difficulty in bending varies. High-rigidity paper such as thick paper cannot easily get over the ribs, and transport failure tends to occur. Low-rigidity paper such as thin paper easily gets over the ribs and is double-fed.

  The present invention has been made to solve the above-described problems, and has as its object to suppress poor conveyance and double feeding of both a high-rigidity medium and a low-rigidity medium.

  A medium conveyance device according to the present invention includes a medium placement unit on which a medium is placed, a first roller that comes into contact with the medium placed on the medium placement unit, and feeds out the medium in a conveyance direction. A second roller that is located downstream of the roller in the transport direction and further transports the medium fed by the first roller; and a second roller that is disposed on a transport path between the first roller and the second roller. , And a medium contact portion that contacts the medium. The medium contact portion has a plurality of contact surfaces having different shapes that can be switched according to the type of the medium.

  An image forming apparatus according to the present invention includes the above-described medium transport device, and an image forming unit that forms an image on the medium transported by the medium transport device.

  According to the present invention, the medium contact portion has a plurality of contact surfaces having different shapes, and these are switched according to the type of the medium. Poor transport and double feed can be suppressed.

FIG. 1 is a diagram illustrating a basic configuration of an image forming apparatus according to a first embodiment. FIG. 2 is a schematic diagram illustrating a process unit of the image forming apparatus according to the first embodiment. FIG. 3A is a perspective view illustrating a portion including a manual feed tray of the image forming apparatus according to the first embodiment, and FIG. 2B is a perspective view illustrating a state where a manual feed tray cover is opened. FIG. 3 is a perspective view illustrating a state in which a manual feed tray cover of the image forming apparatus according to the first embodiment is opened and a lever is pulled up. FIG. 2 is a perspective view illustrating the medium transport device according to the first embodiment. FIG. 2 is a side sectional view illustrating the medium transport device according to the first embodiment. It is a perspective view showing a retard roller and a retard frame of a 1st embodiment. FIG. 3A is a perspective view illustrating a retard frame according to the first embodiment and a periphery thereof, and FIG. 3B is a perspective view illustrating a state where a cover is removed from the retard frame. It is the perspective view (A) and the enlarged view (B) which show the retard frame of 1st Embodiment, a restriction | limiting rib, and a separation block, and those circumference | surroundings. It is the perspective view (A) and the enlarged view (B) which show the state in which the separation bar of the 1st embodiment was in the lowered position. FIG. 2 is a cross-sectional view illustrating the medium conveyance device according to the first embodiment. FIG. 2 is a block diagram illustrating a control system of the image forming apparatus according to the first embodiment. FIGS. 3A and 3B are a schematic diagram illustrating a transport state of thick paper and a schematic view illustrating a transport state of thin paper by the medium transport apparatus according to the first embodiment. FIGS. FIGS. 3A and 3B are a cross-sectional view and a magnified view illustrating a state in which the medium transport device according to the first embodiment is transporting thick paper. FIGS. FIGS. 4A and 4B are a cross-sectional view and a magnified view illustrating a state in which the medium transport device according to the first embodiment is transporting thin paper. FIGS. FIG. 10 is a cross-sectional view illustrating a medium transport device according to a second embodiment. FIG. 5A is a cross-sectional view illustrating a medium transport device according to a second embodiment, and FIGS.

First Embodiment <Configuration of Image Forming Apparatus>
First, the image forming apparatus 1 including the manual feed tray 30 according to the first embodiment will be described. FIG. 1 is a diagram illustrating an image forming apparatus 1 according to the first embodiment. The image forming apparatus 1 is a printer that forms a color image using an electrophotographic method.

  The image forming apparatus 1 includes a paper tray 50 that stores the paper S, a feeding unit 51 that feeds the paper S from the paper tray 50, a manual feed tray 30 that feeds the paper P (FIG. 14A) as a medium, A medium transport unit 55 that transports the paper S (P) fed from the paper tray 50 or the manual feed tray 30, an image forming unit 60 that forms a toner image on the paper S (P), and toner on the paper S (P) The image forming apparatus includes a fixing device 80 that fixes an image, and a discharge unit 85 that discharges the sheet S (P) on which the toner image is fixed.

  The sheet tray 50 is arranged below the image forming apparatus 1 and stores stacked sheets S (medium). The feeding unit 51 includes a pickup roller 52 that feeds out the paper S stored in the paper tray 50, a feed roller 53 that separates and feeds the paper S fed out by the pickup roller 52 one by one, and a separation piece 54.

  The manual feed tray 30 is arranged on a side of the image forming apparatus 1. The manual feed tray 30 includes a paper mounting plate 32 on which the stacked paper P (medium) is mounted, a manual feed tray cover 31 that rotatably holds the paper mounting plate 32, and a paper on the paper mounting plate 32. It has a pickup roller (first roller) 34 for feeding P, a feed roller (second roller) 35 and a retard roller (separation roller) 36 for separating the sheets P fed by the pickup roller 34 one by one.

  The medium transport unit 55 has two transport roller pairs 56 and 57. The transport roller pair 56 transports the paper P fed by the feed unit 51. The transport roller pair 57 transports the paper P transported from the transport roller pair 56 or the paper S fed from the manual feed tray 30 to the image forming unit 60.

  The image forming unit 60 includes four process units 61K, 61Y, 61M, and 61C that form toner images of black (K), yellow (Y), magenta (M), and cyan (C), and a toner image on the surface of a sheet. And a transfer unit 70 for transferring the image to the printer.

  The process units 61K, 61Y, 61M, and 61C are arranged from the upstream side to the downstream side in the transport direction of the paper P (S) (from right to left in the drawing). The process units 61K, 61Y, 61M, and 61C are referred to as a process unit 61 unless it is necessary to distinguish them.

  FIG. 2 is a schematic diagram illustrating a configuration example of the process unit 61. The process unit 61 includes a photoconductor drum 62 as an image carrier, a charging roller 63 as a charging member for uniformly charging the surface of the photoconductor drum 62, and an electrostatic latent image by irradiating the photoconductor drum 62 with light. A print head 64 as an exposure device for forming an image, a developing roller 65 as a developer carrier for developing an electrostatic latent image on the photosensitive drum 62, and a supply member for supplying toner (developer) to the developing roller 65 And a toner cartridge 67 as a developer container for supplying toner to the developing roller 65 and the supply roller 66.

  Returning to FIG. 1, the transfer unit 70 includes a transfer belt 71 that conveys the sheet S (P), four transfer rollers 72 that face the photosensitive drum 62 of each process unit 61 via the transfer belt 71, and a transfer belt. The transfer belt 71 includes a drive roller 73 that drives the transfer belt 71 and a tension roller 74 that applies tension to the transfer belt 71. The transfer unit 70 transfers the toner image of each color formed on the photosensitive drum 62 of each process unit 61 to the sheet S (P) by Coulomb force.

  The fixing device 80 includes, for example, a fixing roller 81 having a built-in heat source, and a pressure roller 82 pressed by the fixing roller 81. The fixing roller 81 and the pressure roller 82 apply heat and pressure to the toner image transferred to the sheet S (P) to fix the toner image on the sheet S (P).

  The discharge unit 85 includes a pair of conveying rollers 83 and a pair of discharge rollers 84 that convey the sheet S (P) that has passed through the fixing device 80, and discharges the sheet S (P) on which fixing has been completed. The upper cover of the image forming apparatus 1 is provided with a stacker unit 86 for stacking the sheets S (P) discharged by the discharge unit 85.

  The image forming apparatus 1 includes a duplex printing unit 87 that transports the sheet S (P) that has passed through the fixing device 80 toward the medium transport unit 55 for duplex printing. Omitted.

  In FIG. 1, the moving direction when the sheet S (P) passes through the image forming unit 60 is defined as the X direction, and the direction of the rotation axis of the photosensitive drum 62 is defined as the Y direction. The Y direction is the same as the width direction of the sheet S (P). A direction orthogonal to both the X direction and the Y direction is defined as a Z direction. Here, the Z direction is a vertical direction.

<Configuration of medium transport device>
FIGS. 3A and 3B are perspective views of a portion including the manual feed tray 30 of the image forming apparatus 1 as viewed obliquely from above. FIG. 3A shows a state in which the manual feed tray 30 is in the storage position, that is, a state in which the manual feed tray cover 31 is closed. FIG. 3B shows a state in which the manual feed tray 30 is in the use position, that is, a state in which the manual feed tray cover 31 is opened. FIG. 4 shows a state where the manual feed tray 30 is in the use position and the lever 33 is further pulled up.

  As shown in FIG. 3B, the manual feed tray cover 31 is rotatably attached to the apparatus frame 10 as a frame member fixed to the main body of the image forming apparatus 1. The manual feed tray cover 31 rotates between a closed position shown in FIG. 3A and an open position shown in FIG. The paper placing plate 32 is rotatably provided on the manual feed tray cover 31 as described later, and the paper P is placed thereon.

  Further, on both sides in the Y direction of the manual feed tray cover 31, lock portions 31b for locking the manual feed tray cover 31 to the main body of the image forming apparatus 1 at a closed position are formed. In the closed position shown in FIG. 3A, when the user operates the lock portion 31b to release the lock and pulls the manual feed tray cover 31 toward the user, the manual feed tray cover 31 moves to the rotation support portion 10a of the apparatus frame 10. (FIG. 8 (A)) is rotated toward the open position.

  The manual feed tray 30 and the device frame 10 constitute a medium transport device. The manual tray cover 31 and the paper placing plate 32 constitute a medium placing portion. Portions of the image forming apparatus 1 other than the medium transport device (manual tray 30 and apparatus frame 10) are referred to as a main body (base) of the image forming apparatus 1.

  The holding member 11 for rotatably holding the pickup roller 34 is rotatably held on the apparatus frame 10. The holding member 11 extends in the Y direction, and has a pair of arms 11a (only one arm 11a is shown in FIG. 3B) on both sides in the Y direction. The distal end of each arm 11a is slidably engaged with a guide groove 31a (FIG. 5) formed in the manual feed tray cover 31, thereby limiting the rotation range of the manual feed tray cover 31.

  As shown in FIG. 4, a lever 33 is rotatably held by the holding member 11. The lever 33 extends in the Y direction and has a pair of arms 33a at both ends (only one arm 33a is shown in FIG. 4). The tip of the arm 33a is engaged with a groove 32a provided at the end of the sheet mounting plate 32 in the Y direction. As shown in FIG. 3B, when the user rotates the lever 33, the paper loading plate 32 moves up and down due to the engagement between the arm 33a and the groove 32a.

  FIG. 5 is a perspective view showing the manual feed tray 30 and the apparatus frame 10 in the open position. FIG. 6 is a cross-sectional view of the manual feed tray 30 and the apparatus frame 10 viewed from the direction indicated by the arrow VI in FIG. 5 (that is, the + Y side). In FIG. 5, a part of the holding member 11 and the lever 33 are omitted.

  In FIG. 5, a pickup roller 34 as a first roller is rotatably held by the holding member 11. The pickup roller 34 is provided so as to come into contact with a contact portion 32b (FIG. 6) provided at the center in the Y direction of the paper placing plate 32.

  As shown in FIG. 6, the end of the sheet placing plate 32 in the −X direction (that is, the end on the upstream side in the transport direction indicated by the arrow A) is rotatably held by the manual feed tray cover 31. A spring 45, which is a coil spring, is arranged below the abutting portion 32b of the paper placing plate 32 in a compressed state. The spring 45 urges the contact portion 32b of the sheet mounting plate 32 toward the pickup roller 34.

  The feed roller 35 as a second roller is rotatably supported by the apparatus frame 10. When the manual feed tray 30 is at the open position, the feed roller 35 is located downstream of the pickup roller 34 in the transport direction (indicated by the arrow A). The feed roller 35 is rotated clockwise in the figure by a paper feed motor 224 (FIG. 12) via an electromagnetic clutch 225 (FIG. 12).

  The holding member 11 that rotatably holds the pickup roller 34 is rotatably held by the apparatus frame 10 about a rotation shaft that is coaxial with the feed roller 35. The pickup roller 34 and the feed roller 35 are connected by an idle roller 38 (FIG. 4) rotatably held by the holding member 11.

  Therefore, the pickup roller 34 rotates in the same direction following the rotation of the feed roller 35. Further, the pickup roller 34 rotates around the feed roller 35 while maintaining the connection state with the feed roller 35 with the rotation of the holding member 11.

  The retard roller 36 as a separation roller is disposed below the feed roller 35 so as to face the same. FIG. 7 is a perspective view showing the retard roller 36 and the retard frame 40 that holds the retard roller 36.

  As shown in FIG. 7, the retard frame 40 has a pair of side plates 41 facing each other in the Y direction, and each side plate 41 is formed with a groove 41a. The retard roller 36 is attached to the rotating shaft 42 via a torque limiter 37, and both ends of the rotating shaft 42 are fitted in the grooves 41a. Therefore, when receiving a rotational force from the outside, the retard roller 36 rotates in the direction of the rotational force while generating a predetermined rotational load by the torque limiter 37.

  Each side plate 41 of the retard frame 40 is formed with a groove 41b that engages with the shaft 15 (FIG. 8A) formed on the device frame 10. The retard frame 40 is rotatably supported by the apparatus frame 10 below the feed roller 35 by the engagement between the shaft 15 and the groove 41b. The rotation axis of the retard frame 40 and the rotation axis of the retard roller 36 are both parallel to the rotation axis of the feed roller 35 (that is, the Y direction).

  Returning to FIG. 6, the transport guide 13 that guides the sheet S fed from the feeding section 51 (FIG. 1) and the sheet P fed from the manual feed tray 30 to the transport roller pair 57 is arranged on the apparatus frame 10. I have.

  The transport rollers 57a and 57b in the image forming apparatus 1 are a pair of transport rollers 57 (FIG. 1) that transport the sheet S fed from the feed section 51 (FIG. 1) and the sheet P fed from the manual feed tray 30. Is configured. The transport rollers 57a and 57b are rotatably attached to the main body of the image forming apparatus 1, and are rotated by the transport motor 226 (FIG. 12).

  FIG. 8A is a perspective view showing the retard frame 40 and the regulating rib 21 and the periphery thereof. In FIG. 8A, the device frame 10 is cut off on the near side (+ Y side) of the retard frame 40. The same applies to FIGS. 9A and 10A described later.

  As shown in FIG. 8A, an inclined surface 14 facing the manual feed tray 30 (FIG. 6) is formed on the apparatus frame 10. The retard frame 40 is arranged at the center of the inclined surface 14 in the Y direction. As described above, the shaft portion 15 of the device frame 10 is engaged with the groove portion 41b of the retard frame 40, whereby the retard frame 40 is supported so as to be rotatable about the rotation axis in the Y direction.

  A spring seat 43 is formed below the retard frame 40 in the device frame 10. Between the spring seat 43 and the retard frame 40, a spring 44, which is a coil spring, is arranged in a compressed state. The spring 44 urges the retard frame 40 in a direction in which the retard roller 36 is pressed against the feed roller 35.

  A cover 46 that covers the upstream side of the retard roller 36 in the transport direction (indicated by an arrow A) is attached to an upper portion of the retard frame 40. The cover 46 is attached to the side plate 41 of the retard frame 40 so as to expose the upper part of the retard roller 36 (that is, the feed roller 35 side).

  FIG. 8B is a perspective view showing the retard frame 40 shown in FIG. 8A with the cover 46 removed. As shown in FIG. 8B, a pair of regulating ribs 21 are formed on the device frame 10 adjacent to both sides of the pair of side plates 41 of the retard frame 40 in the Y direction. FIGS. 8A and 8B show only one regulating rib 21. The regulating rib 21 is formed in a flat plate shape having a plate surface parallel to the XZ plane.

  The regulating rib 21 has an abutment surface 21a having a radius of curvature R1 facing the conveyance path of the sheet P. The contact surface 21a is formed at the upstream end of the regulating rib 21 in the transport direction (indicated by the arrow A) and at the upper end (the end in the + Z direction).

  The contact surface 21a of the regulating rib 21 is located between the pickup roller 34 and the feed roller 35 in the transport direction indicated by the arrow A, as shown in FIG. The contact surface 21a of the regulating rib 21 has a function of guiding the paper P and suppressing double feeding of the paper P.

  FIG. 9A is a perspective view showing the retard frame 40, the regulating rib 21, the separation rib 22, and the periphery thereof. As shown in FIG. 9A, separation ribs 22 are provided on both sides in the Y direction of the pair of regulating ribs 21. The separation bar 22 is a plate-like member having a plate surface parallel to the XZ plane, and has a protruding piece 22c that protrudes in the transport direction indicated by the arrow A.

  The separation block 22 has a contact surface 22a having a radius of curvature R2 (<R1) facing the conveyance path of the sheet P. The contact surface 22a is formed at the end in the −X direction (that is, the end on the upstream side in the transport direction) and the end in the + Z direction (that is, the upper end) of the separation slot 22. The contact surface 22a of the separation block 22 has a function of guiding the sheet P and suppressing double feeding of the sheet P.

  The restricting rib 21 and the separation groove 22 constitute a medium contact portion that contacts the sheet P in a transport path between the pickup roller 34 and the feed roller 35. The restricting rib 21 forms a fixed portion of the medium contact portion, and the separation rib 22 forms a movable portion of the medium contact portion.

  FIG. 9B is an enlarged view showing the retard frame 40, the regulating rib 21, and the separation bar 22. As shown in FIG. 9B, the separation bar 22 is a plate-like member having a plate surface parallel to the XZ plane. A substantially square guide hole 22b is formed substantially at the center of the separation bar 22. A rectangular guide rib 21b formed on the regulating rib 21 is engaged with the guide hole 22b.

  The dimension of the guide hole 22b in the X direction is substantially the same as or slightly larger than the dimension of the guide rib 21b in the X direction. On the other hand, the dimension of the guide hole 22b in the Z direction is larger than the dimension of the guide rib 21b in the Z direction.

  That is, the separation rib 22 is supported by the regulating rib 21 so as to be movable in the Z direction by the engagement between the guide rib 21b and the guide hole 22b. In the state shown in FIGS. 9A and 9B, the separation bar 22 is at the upper end position (end position in the + Z direction) of the movement range.

  When the separation rib 22 is at the upper end position, the contact surface 22 a of the separation rib 22 is located above the contact surface 21 a of the regulating rib 21. Therefore, the contact surface 22a of the separation bar 22 protrudes into the sheet P conveyance path.

  FIG. 10A is a perspective view showing the retard frame 40, the regulating rib 21, and the separation groove 22 when the separation groove 22 is at the lower end position, and the periphery thereof. FIG. 10B is an enlarged perspective view showing the retard frame 40, the regulating rib 21, and the separation slot 22 when the separation slot 22 is at the lower end position.

  As shown in FIG. 10B, when the separation bar 22 is at the lower end position of the movement range, the contact surface 22 a of the separation bar 22 retreats below the contact surface 21 a of the regulating rib 21. Therefore, the contact surface 21 a of the regulating rib 21 protrudes into the transport path of the sheet P.

  FIG. 11 is a sectional view showing the apparatus frame 10 and the manual feed tray 30. As shown in FIG. 11, the protruding pieces 22c of the pair of separation sticks 22 are connected to each other by a connecting bar 23 extending in the Y direction.

  The apparatus frame 10 is provided with a rotatable switching lever 25. The switching lever 25 is arranged below the connecting bar 23, a rotating shaft 25a, an operating portion 25b extending in the -X direction from the rotating shaft 25a, and protruding from the rotating shaft 25a toward the connecting bar 23. And an action portion 25c. The operation unit 25b and the operation unit 25c are combined in an L shape.

  The rotation shaft 25a is parallel to the Y direction. The operation unit 25b protrudes from the device frame 10 in the −X direction, and is operated by the user. The action portion 25c contacts the connection bar 23 from below.

  In the state shown in FIG. 11, the action portion 25 c of the switching lever 25 contacts the connection bar 23 from below, and urges the connection bar 23 including the connection bar 23 upward. Therefore, the separation bar 22 is located at the upper end position of the movement range in the Z direction.

  On the other hand, when the user pushes down the operation portion 25b of the switching lever 25 downward, the switching lever 25 rotates clockwise around the rotation shaft 25a. Thereby, the position where the action part 25c contacts the connection bar 23 also moves downward. Therefore, the separation bar 22 moves to the lower end position of the movement range in the Z direction.

  As described above, when the separation stick 22 is at the upper end position of the movement range, the contact surface 22a of the separation stick 22 is located above the contact surface 21a of the regulating rib 21, and the contact of the separation stick 22 is The surface 22a protrudes into the sheet P conveyance path. In other words, when the separation stick 22 is at the lower end position of the movement range, the contact surface 22a of the separation stick 22 retreats below the contact surface 21a of the regulating rib 21, and the contact surface 21a of the regulating rib 21 Protrudes into the paper P transport path.

<Control system of image forming apparatus>
Next, a control system of the image forming apparatus 1 will be described. FIG. 12 is a block diagram illustrating a control system of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 200, an I / F (interface) control unit 201, a reception memory 202, an image data editing memory 203, an operation unit 204, a sensor group 205, a power control unit 206, A head control unit 211, a drive control unit 212, a belt drive control unit 214, a fixing control unit 216, a fixing drive control unit 219, and a paper feed control unit 221 are provided.

  The control unit 200 includes a microprocessor, a ROM (Read Only Memory), a RAM (Random Access Memory), an input / output port, a timer, and the like. The control unit 200 receives print data and a control command from the host device via the I / F control unit 201, and performs the printing operation of the image forming apparatus 1.

  The reception memory 202 temporarily stores print data input from the host device via the I / F control unit 201. The image data editing memory 203 receives the print data stored in the reception memory 202, and records the image data formed by editing the print data, that is, the image data.

  The operation unit 204 includes a display unit (for example, an LED) for displaying a state of the image forming apparatus 1 and an operation unit (for example, a switch) for an operator to input an instruction. The sensor group 205 includes various sensors for monitoring the operation state of the image forming apparatus 1, such as a paper position sensor, a temperature and humidity sensor, and a density sensor.

  The power supply control unit 206 includes a charging voltage power supply 207 for applying a charging voltage to the charging roller 63, a developing voltage power supply 208 for applying a developing voltage to the developing roller 65, a supply voltage power supply 209 for applying a supply voltage to the supply roller 66, and a transfer. A transfer voltage power supply 210 for applying a transfer voltage to the roller 72 is controlled. The head control unit 211 sends the image data recorded in the image data editing memory 203 to the print head 64, and controls the light emission of the print head 64.

  The drive control unit 212 controls a drive motor 213 that rotates the photosensitive drum 62 of each process unit 61. The charging roller 63 rotates following the rotation of the photosensitive drum 62, and the developing roller 65 and the supply roller 66 rotate by transmitting rotation from the photosensitive drum 62. The belt drive control unit 214 controls a belt motor 215 that rotates a drive roller 73 for driving the transfer belt 71.

  The fixing control unit 216 has a temperature adjustment circuit, and supplies a current to the heater 217 of the fixing roller 81 based on the output signal of the thermistor 218 of the fixing device 80. The fixing drive control unit 219 controls a fixing motor 220 that rotates the fixing roller 81 of the fixing device 80. The transport roller pair 83 and the discharge roller pair 84 are rotated by rotation transmitted from the fixing motor 220.

  The paper feed conveyance control unit 221 includes a paper feed motor 222 and an electromagnetic clutch 223 for rotating the feed roller 53 of the feeding unit 51, a paper feed motor 224 and an electromagnetic clutch 225 for rotating the feed roller 35 of the manual feed tray 30, The transport motor 226 for rotating the transport roller pairs 56 and 57 of the section 55 is controlled.

<Operation of Image Forming Apparatus>
Next, the operation of the image forming apparatus 1 will be described with reference to FIG. 1, FIG. 11, and FIG. When the control unit 200 of the image forming apparatus 1 receives a print command and print data from the host device via the I / F control unit 201, the control unit 200 starts an image forming (printing) operation. The control unit 200 temporarily records the print data in the reception memory 202, edits the recorded print data to generate image data, and records the image data in the image data editing memory 203.

  Here, a case where paper P is fed from the manual feed tray 30 based on a print command will be described. When setting the paper P on the manual feed tray 30, the user rotates the lever 33 in the closing direction indicated by the arrow B2 with the manual feed tray 30 in the open position as shown in FIG. When the lever 33 rotates in the closing direction, the arm 33 a of the lever 33 (FIG. 4) pushes down the sheet placing plate 32 against the urging force of the spring 45.

  When the arm 33a of the lever 33 is fitted into the groove 32a of the paper placing plate 32, the paper placing plate 32 is maintained in a depressed state. Thereby, a predetermined number of sheets P can be set between the sheet placing plate 32 and the pickup roller 34.

  Further, when the user rotates the lever 33 in the opening direction shown by the arrow B1, the pressing down of the sheet placement plate 32 by the arm 33a of the lever 33 is released. Thereby, the upper surface of the sheet P placed on the sheet placing plate 32 is pressed against the pickup roller 34 by the urging force of the spring 45. That is, the sheet P can be transported.

  In this state, the control unit 200 drives the paper feed motor 224 and the electromagnetic clutch 225 by the paper feed / transport control unit 221 to rotate the feed roller 35 clockwise in the drawing. The rotation of the feed roller 35 is transmitted to the pickup roller 34 via the idle roller 38. Thereby, the pickup roller 34 rotates clockwise in the drawing.

  Due to the rotation of the pickup roller 34, the paper P pressed against the pickup roller 34 is fed out and sent to the nip portion between the feed roller 35 and the retard roller 36. The feed roller 35 sends out the paper P toward the medium transport unit 55, and the retard roller 36 separates the paper P one by one.

  The sheet P that has passed through the feed roller 35 and the retard roller 36 reaches the medium transport unit 55. The paper feed conveyance control unit 221 drives the conveyance motor 226 to rotate the conveyance roller pairs 56 and 57. The transport roller pairs 56 and 57 transport the paper P toward the image forming unit 60.

  The control unit 200 drives the belt motor 215 by the belt drive control unit 214, rotates the drive roller 73, and causes the transfer belt 71 to run. The transfer belt 71 conveys the paper P while holding it by suction. The paper P passes through the process units 61K, 61Y, 61M, and 61C in this order.

  The control unit 200 forms a toner image of each color in each process unit 61. That is, the control unit 200 causes the power supply control unit 206 to apply the charging voltage, the developing voltage, and the supply voltage to the charging roller 63, the developing roller 65, and the supply roller 66 of each process unit 61, respectively.

  The control unit 200 causes the drive control unit 212 to rotate the drive motor 213 to rotate the photosensitive drum 62. As the photosensitive drum 62 rotates, the charging roller 63, the developing roller 65, and the supply roller 66 also rotate. The charging roller 63 uniformly charges the surface of the photosensitive drum 62 by the charging voltage.

  The control unit 200 further controls the light emission of the print head 64 by the head control unit 211 based on the image data recorded in the image data editing memory 203. The print head 64 exposes the surface of the photosensitive drum 62 to form an electrostatic latent image.

  The electrostatic latent image formed on the surface of the photosensitive drum 62 is developed by the toner attached to the developing roller 65, and a toner image is formed on the surface of the photosensitive drum 62. When the toner image approaches the surface of the transfer belt 71 due to the rotation of the photosensitive drum 62, the power supply control unit 206 applies a transfer voltage to the transfer roller 72. Thus, the toner image formed on the photosensitive drum 62 is transferred to the sheet P on the transfer belt 71.

  In this manner, the toner images of each color formed by the process units 61K, 61Y, 61M, and 61C are sequentially transferred to the paper P and are superimposed on each other. The paper P on which the toner images of each color have been transferred is further conveyed by the transfer belt 71 and reaches the fixing device 80.

  In the fixing device 80, the heater 217 is heated by the fixing control unit 216, and the fixing roller 81 has reached a predetermined fixing temperature. The sheet P conveyed to the fixing device 80 is heated and pressed between the fixing roller 81 and the pressure roller 82, and the toner image is fixed on the sheet P.

  The sheet P on which the toner image has been fixed is discharged to the outside of the image forming apparatus 1 by the pair of conveying rollers 83 and the pair of discharge rollers 84, and is stacked on the stacker unit 86. Thus, the formation of the color image on the paper P is completed.

<Paper transport operation in the manual feed tray>
Next, the paper transport operation in the manual feed tray 30 according to the first embodiment will be described with reference to the schematic diagram of FIG. The medium transport device according to the first embodiment transports paper P (for example, thick paper) having high rigidity (Clark rigidity) as shown in FIG. 13A, and rigidity as shown in FIG. Paper P (for example, plain paper or thin paper) may be conveyed.

  In order to suppress the intrusion of the plurality of sheets P into the nip portion between the feed roller 35 and the retard roller 36, a contact surface C that contacts the leading end of the sheet P fed out by the pickup roller 34 is provided on the upstream side thereof. It is necessary to provide. The larger the radius of curvature of the contact surface C, the easier the paper P can get over the contact surface C.

  As shown in FIG. 13A, when the radius of curvature of the contact surface C is small, the highly rigid paper P cannot get over the contact surface C, and there is a possibility that conveyance failure may occur. On the other hand, as shown in FIG. 13B, when the radius of curvature of the contact surface C is large, the paper P having low rigidity is likely to be bundled over the contact surface C, and a double feed may occur. There is.

  Therefore, in the first embodiment, when the paper P having high rigidity is used, the contact surface 21a of the regulating rib 21 having a large curvature radius R1 is projected into the conveyance path, and the paper P having low rigidity is used. , The contact surface 22a of the separation block 22 having a small radius of curvature R2 is projected into the transport path.

  FIG. 14A is a diagram illustrating a medium transport device when a sheet of paper P having low rigidity (for example, plain paper or thin paper) is fed. FIG. 14B is an enlarged view of a portion surrounded by a dashed-dotted line circle in FIG. Here, the first sheet on the sheet mounting plate 32 is referred to as a sheet P1, and the second and subsequent sheets P from the top are referred to as sheets P2.

  As shown in FIG. 14A, when feeding the paper P having low rigidity, the user turns the switching lever 25 (FIG. 11) to the upper position. When the switching lever 25 is at the upper position, as described with reference to FIG. 11, the separation arm 22 is located at the upper end position of the movement range.

  Therefore, as shown in FIG. 14B, the contact surface 22a of the separation rib 22 is located higher than the contact surface 21a of the regulating rib 21. In other words, the contact surface 22 a of the separation block 22 protrudes from the pickup roller 34 toward the feed roller 35 in the transport path of the sheet P. In other words, the contact surface 22a of the separation block 22 is located at a position for guiding the sheet P from the pickup roller 34 to the feed roller 35.

  In this state, the pickup roller 34 rotates and sends out the paper P in the transport direction indicated by the arrow A. When a plurality of papers P are sent out in the transport direction due to friction between the papers P, the leading ends of the papers P come into contact with the contact surfaces 22 a of the separation pegs 22. Most of the paper P is dammed by the contact surface 22a of the separation block 22, and the uppermost paper P1 in contact with the pickup roller 34 is transported in the transport direction indicated by the arrow A. In some cases, several sheets P2 following the top sheet P1 may be conveyed in the same direction.

  The sheet P sent out by the pickup roller 34 is sent to a nip portion between a feed roller 35 and a retard roller 36. A predetermined rotational load is generated on the retard roller 36 by a torque limiter 37 (FIG. 6). Therefore, even if a plurality of papers P enter the space between the feed roller 35 and the retard roller 36, only one sheet P1 in contact with the feed roller 35 is conveyed, and the second and subsequent sheets P2 are transported by the retard roller 36. Entry into the nip is prevented.

  In this way, the paper P is separated one by one and transported in the transport direction indicated by the arrow A. The sheet P <b> 1 transported by the feed roller 35 is transported to the image forming unit 60 via the transport roller pair 57.

  FIG. 15A is a diagram illustrating a medium conveyance device when a highly rigid sheet P (for example, thick sheet) is fed. FIG. 15B is an enlarged view of a portion surrounded by a dashed-dotted line circle in FIG.

  In the case of paper P having high rigidity, the user turns the switching lever 25 (FIG. 11) to the lower position. When the switching lever 25 is at the lower position, as described with reference to FIG. 11, the separation arm 22 is located at the lower end position of the movement range.

  Therefore, as shown in FIG. 15B, the contact surface 22a of the separation rib 22 retreats below the contact surface 21a of the regulating rib 21. Thereby, the contact surface 21a of the regulating rib 21 having the large curvature radius R1 protrudes into the transport path. In other words, the contact surface 21 a of the regulating rib 21 is located at a position for guiding the sheet P from the pickup roller 34 to the feed roller 35.

  In this state, the pickup roller 34 rotates and sends out the paper P in the transport direction indicated by the arrow A. As described above, when a plurality of papers P are sent in the transport direction due to friction between the papers P, the leading ends of the papers P come into contact with the contact surfaces 21 a of the regulating ribs 21. Most of the paper P is dammed by the contact surface 21 a of the regulating rib 21, and the uppermost paper P <b> 1 in contact with the pickup roller 34 is transported in the transport direction indicated by the arrow A. In some cases, several sheets P2 following the top sheet P1 may be conveyed in the same direction.

  The sheet P sent out by the pickup roller 34 is sent to a nip portion between a feed roller 35 and a retard roller 36. As with the low-rigidity sheet P, the high-rigidity sheet P also conveys only one sheet P1 in contact with the feed roller 35, and the second and subsequent sheets P2 are prevented from entering the nip by the retard roller 36. You. In this way, the paper P is separated one by one, transported in the transport direction indicated by the arrow A, and transported to the image forming unit 60 via the transport roller pair 57.

  As described above, when the paper P having high rigidity is used, the contact surface 21a of the regulating rib 21 having a large curvature radius R1 is projected into the transport path, so that the paper P can easily get over the contact surface 21a, and the transport is performed. It controls defects. When a sheet P having low rigidity is used, the contact surface 22a of the separation block 22 having a small radius of curvature R2 is protruded into the conveyance path, so that a plurality of sheets are bundled and get over the contact surface 22a. That is, double feed is suppressed.

  By using the contact surfaces 21a and 22a having different radii of curvature in accordance with the rigidity of the paper P, it is possible to effectively suppress the double feed and the poor conveyance of the high rigidity paper P and the low rigidity paper P. Can be.

  The height of the contact surface 21a when the contact surface 21a of the regulating rib 21 is located on the transport path is the same as the contact surface when the contact surface 22a of the separation rib 22 is located on the transport path. Slightly lower than the height of 22a. This makes it easy for the highly rigid paper P to get over the contact surface 21a.

  The curvature radii R1 and R2 of the contact surface 21a of the regulating rib 21 and the contact surface 22a of the separation rib 22 are determined according to the type of the sheet P to be conveyed. For example, when the range of the basis weight of the paper P used in the image forming apparatus 1 is 64 to 250 sgm, it is desirable that the curvature radius R1 is 2.0 mm or more and the curvature radius R2 is 0.3 mm or less. In this case, the regulating rib 21 is used for the paper P having a basis weight of 68 to 250 sgm, and the separation block 22 is used for the paper P having a basis weight of 64 to 68 gsm.

  In the above description, the control rib 21 and the separation rib 22 are switched by using the manual switching lever 25. However, the present invention is not limited to such a configuration. For example, the restriction rib 21 and the separation rod are separated by using an actuator such as a motor. 22 may be switched.

  In the above description, the regulating rib 21 has the contact surface 21a having a large radius of curvature R1, and the separation rib 22 has the contact surface 22a having a small radius of curvature R2. May have a contact surface with a small radius, and the separation groove 22 may have a contact surface with a large radius of curvature.

<Effects of Embodiment>
As described above, in the first embodiment, the restricting rib 21 and the separation bar 22 (medium contact portion) can be switched according to the type of the sheet P (medium), and can be switched according to the type of the sheet P (medium). It has contact surfaces 21a and 22a. For this reason, it is possible to suppress poor conveyance and double feed for both the rigid paper P such as thick paper and the rigid paper P such as thin paper. Therefore, it is possible to ease the restriction on the usable paper.

  Further, the separation rib 22 is movable with respect to the regulation rib 21, and the movement of the separation rib 22 causes the contact surface 21 a of the regulation rib 21 to protrude into the transport path, and the contact between the separation rib 22 and the first state. The second state in which the surface 22a protrudes into the transport path is switched. Therefore, the contact surfaces 21a and 22a can be switched according to the type of paper with a simple configuration.

  In addition, since the switching between the first state and the second state is performed by the switching lever 25 as a moving operation unit, the user can select an appropriate contact surface 21a, 22a according to the type of paper to be used. You can choose.

  Further, the height at which the contact surface 21a of the regulating rib 21 contacts the sheet P is lower than the height at which the contact surface 22a of the separation rib 22 contacts the sheet P. 22a can be easily overcome, and defective transport can be effectively prevented.

  In addition, since the regulating rib 21 and the separation rib 22 are disposed on both sides in the Y direction with respect to the feed roller 35, it is possible to abut the paper P at two locations in the width direction to enhance the effect of separating the paper P. it can.

  Here, the configuration in which the contact surfaces 21a and 22a of the regulating rib 21 and the separation rib 22 have different radii of curvature has been described. However, the configuration is not limited to the radius of curvature, and the shapes of the contact surfaces 21a and 22a may be different. For example, the contact surfaces 21a, 22a of the regulating rib 21 and the separation rib 22 may both be tapered surfaces, and the taper angles may be different from each other.

Second embodiment.
Next, a second embodiment of the present invention will be described. FIG. 16 is a side sectional view showing a medium transport device according to the second embodiment. Note that, in the components of the second embodiment, the same components as those of the first embodiment are denoted by the same reference numerals.

  In the second embodiment, the configuration of the restricting rib 21 is the same as that of the first embodiment, but the configuration of the separation bar (referred to as a rotary bar 26) is different from that of the first embodiment. The turning mechanism 26 according to the second embodiment has a shaft hole 26b that fits into the turning shaft 16 (FIG. 17B) provided in the device frame 10 so that the device frame 10 can turn. Installed.

  The rotating wheel 26 has an arc-shaped guide groove 26c centered on the shaft hole 26b. A guide pin 17 provided on the device frame 10 is fitted into the guide groove 26c. By the engagement between the guide groove 26c and the guide pin 17, the rotation range of the rotation bar 26 is restricted.

  The rotating wheel 26 has an abutting surface 26a that protrudes into a transport path between the pickup roller 34 and the feed roller 35. The radius of curvature R3 of the contact surface 26a of the rotating wheel 26 is smaller than the radius of curvature R1 of the contact surface 21a of the regulating rib 21.

  A spring 48, which is a coil spring, is arranged between the rotary wheel 26 and a spring seat 47 formed on the apparatus frame 10 in a compressed state. The spring 48 urges the rotary arm 26 in a direction in which the contact surface 26a protrudes into the transport path.

  Under normal conditions, the contact surface 26a of the rotary wheel 26 is located above the contact surface 21a of the regulating rib 21 due to the urging force of the spring 48, and protrudes into the transport path. On the other hand, when the turning stick 26 is turned in the direction shown by the arrow D against the urging force of the spring 48, the contact surface 26a of the turning stick 26 is retracted downward from the transport path. In this state, the contact surface 21a of the regulating rib 21 projects into the transport path.

  Here, if the leading end of the low-rigidity paper P (for example, plain paper) abuts on the contact surface 26a of the rotary stiffness 26, the rotary stiffness 26 does not rotate, and the rigid stiffness paper P (for example, thick paper) is used. The biasing force of the spring 48 is set such that the tip of the spring 48 abuts on the contact surface 26a of the rotary saw 26, and the rotary saw 26 rotates in the direction of arrow D. In other words, the rotary wheel 26 swings according to the rigidity of the sheet P, and the contact surfaces 21a and 26a are switched.

  Therefore, in the second embodiment, the switching lever 25 (FIG. 11) described in the first embodiment is not provided. Other configurations of the second embodiment are the same as those described in the first embodiment.

  Next, a sheet conveying operation according to the second embodiment will be described. FIG. 17A is a diagram illustrating a medium transporting device when a sheet P having low rigidity (for example, plain paper) is fed. FIG. 17B is an enlarged view of a portion surrounded by a dashed-dotted line circle in FIG. FIG. 17C is an enlarged view showing a case where a highly rigid sheet P is fed.

  As shown in FIG. 17B, when the pickup roller 34 rotates, the paper P is fed out in the transport direction indicated by the arrow A, and the leading end of the paper P comes into contact with the contact surface 22a of the rotary arm 26. In the case of a sheet P having low rigidity, the urging force of the spring 48 is larger than the force received by the contact surface 22a of the turning sheet 26 from the leading end of the sheet P, and thus the turning sheet 26 does not turn.

  For this reason, the contact surface 22a of the rotary saw 26 is kept in a state of protruding into the transport path. The contact surface 22a of the rotary wheel 26 dams most of the paper P, and the uppermost paper P1 that is in contact with the pickup roller 34 is transported in the transport direction indicated by the arrow A. In some cases, several sheets P2 following the top sheet P1 may be conveyed in the same direction.

  The paper P sent in the transport direction indicated by the arrow A is separated by the feed roller 35 and the retard roller 36 one by one as described in the first embodiment, and is transported in the image forming apparatus 1. The sheet is conveyed to the roller pair 57.

  On the other hand, in the case of the paper P having a high rigidity, the force received from the leading end of the paper P by the contact surface 22a of the rotation bar 26 is larger than the urging force of the spring 48, and as shown in FIG. The moving wheel 26 rotates in the direction indicated by the arrow D.

  For this reason, the contact surface 26a of the rotary wheel 26 retreats from the transport path, and the contact surface 21a of the regulating rib 21 projects into the transport path. The contact surface 21a of the regulating rib 21 dams most of the paper P, and the uppermost paper P1 in contact with the pickup roller 34 is transported in the transport direction indicated by the arrow A. In some cases, several sheets P2 following the top sheet P1 may be conveyed in the same direction.

  The paper P sent out in the transport direction indicated by the arrow A is separated one by one by the feed roller 35 and the retard roller 36 similarly to the case of the paper P having low rigidity, and the transport roller in the image forming apparatus 1 is transported. It is transported to the pair 57.

  As described above, when the paper P having high rigidity is used, since the contact surface 21a of the regulating rib 21 having the large radius of curvature R1 protrudes into the conveyance path, the paper P can get over the contact surface 21a, and Defects are suppressed. Further, when the paper P having low rigidity is used, since the contact surface 26a of the rotary screwing 26 having the small radius of curvature R2 protrudes into the transport path, a plurality of sheets may be bundled and go over the contact surface 21a. That is, double feed is suppressed.

  As described in the first embodiment, when the basis weight of the paper P is in the range of 64 to 250 sgm, the radius of curvature R1 of the contact surface 21a of the regulating rib 21 is 2.0 mm or more, and It is desirable that the radius of curvature R3 of the abutment surface 26a of 26 is 0.3 mm or less.

  As described above, in the second embodiment, since the rotary wheel 26 swings according to the rigidity of the sheet P and the contact surfaces 21a and 26a are switched, the first embodiment is used. In addition to the effects described above, the switching lever 25 becomes unnecessary, and an actuator for driving the switching lever 25 becomes unnecessary. Therefore, manufacturing costs can be reduced. Further, since there is no need for the user to operate the switching lever, erroneous selection can be prevented.

  In the above description, the restricting rib 21 has the contact surface 21a having a small radius of curvature, and the turning knob 26 has the contact surface 26a having a large radius of curvature. The pivot wheel 26 may have a large contact surface and a contact surface with a small radius of curvature.

  In addition, here, the configuration in which the curvature radii of the contact surfaces 21a and 26a of the regulating rib 21 and the rotating stiffener 26 are different is described. However, the present invention is not limited to the curvature radii, and the shapes of the contact surfaces 21a and 26a are different. Good. For example, the abutment surfaces 21a and 26a of the regulating rib 21 and the rotation bar 26 may both be tapered surfaces, and the taper angles may be different from each other.

  In the above embodiment, the image forming apparatus for forming a color image has been described. However, the present invention can be applied to an image forming apparatus for forming a single color (monochrome) image. Further, the present invention can be used, for example, in an image forming apparatus (for example, a copying machine, a facsimile, a printer, a multifunction peripheral, etc.) for forming an image on a medium using an electrophotographic method, and a fixing device thereof.

REFERENCE SIGNS LIST 1 image forming apparatus, 10 apparatus frame, 11 holding member, 11 a arm, 13 transport guide, 15 shaft section, 16 rotation axis, 17 guide pin, 21 regulating rib (medium contact section, fixed section), 21 a contact surface (1st contact surface), 21b guide rib, 22 separation stick (medium contact portion, movable portion), 22a contact surface (second contact surface), 22b guide hole, 23 connecting bar, 25 switching lever ( (Movement operation unit), 26 rotating knob (movable part), 26a contact surface (second contact surface), 26b shaft hole, 26c guide groove, 30 manual feed tray (medium conveying device), 31 manual feed tray cover, 32 Paper loading plate (medium loading plate), 33 lever, 34 pickup roller (first roller), 35 feed roller (second roller), 36 retard roller (separation roller), 37 torr Limiter, 38 idle roller, 40 retard frame, 41 side plate, 44 spring (pressing member), 45 spring (biasing member), 50 paper tray, 51 feeding section, 55 medium transport section, 60 image forming section, 61, 61Y, 61M, 61C, 61K process unit, 62 photoconductor drum (image carrier), 70 transfer unit, 80 fixing device, 200 control unit.

Claims (12)

A medium placement unit on which a medium is placed,
A first roller that comes into contact with a medium placed on the medium placement unit and feeds out the medium in a transport direction;
A second roller that is located downstream of the first roller in the transport direction and that further transports the medium that has been fed by the first roller;
A medium contact portion that is disposed on a conveyance path between the first roller and the second roller and that contacts the medium;
The medium conveyance device, wherein the medium contact portion has a plurality of contact surfaces having different shapes that can be switched according to the type of the medium. The medium contact portion has a first contact surface and a second contact surface having a different curvature radius from the first contact surface,
The medium transport device according to claim 1, wherein the first contact surface and the second contact surface are switched according to a type of the medium. The radius of curvature of the first contact surface is 2.0 mm or more,
The medium transport device according to claim 2, wherein a radius of curvature of the second contact surface is 0.3 mm or less. The medium contact portion has a movable portion having one of the first contact surface and the second contact surface, and a fixed portion having the other.
By moving the movable portion with respect to the fixed portion, a first state in which the first contact surface is located in the transport path and a second state in which the second contact surface is located in the transport path. The medium transport device according to claim 2, wherein the medium transport device switches between the state and the state.   The medium transport device according to claim 4, further comprising a moving operation unit operated by a user to move the movable unit. The movable portion is movable in a direction protruding into the transport path and a direction retracting from the transport path, and is urged toward the transport path by an urging member,
When the movable portion is retracted from the transport path due to contact with the medium, the other of the first contact surface and the second contact surface projects into the transport path. The medium transport device according to claim 4.   The medium transport device according to claim 6, wherein the movable unit is rotatable with respect to the fixed unit.   The height at which the first contact surface comes into contact with the medium and the height at which the second contact surface comes into contact with the medium are different from each other. 3. The medium transport device according to claim 1. The first roller and the second roller are disposed at a central portion of the medium in a width direction of the medium,
The said medium contact part is each arrange | positioned with respect to the said 1st roller and the said 2nd roller on both sides of the width direction of the said medium. The any one of Claim 1 to 8 characterized by the above-mentioned. A medium transport device according to the item.   The medium transport device according to any one of claims 1 to 9, wherein a separation roller is arranged to face the second roller.   The medium conveyance device according to claim 10, wherein the separation roller is in contact with the second roller and is rotatably supported via a torque limiter. A medium transport device according to any one of claims 1 to 11,
An image forming unit that forms an image on the medium conveyed by the medium conveying device.

Images