Image forming device

Abstract

To provide an image forming device that can be downsized and manufactured at a lower cost.SOLUTION: An image forming device 1 includes: a first detector 100 that detects a sheet SH between a first conveyance roller 23 and a merging position J1 in a conveyance path P1, the first detector 100 having a first actuator 110 that rotates while being in contact with the sheet SH and a first optical sensor 101 that detect the rotation of the first actuator 110; a second detector 200 that detects the sheet SH between a second conveyance roller 26 and the merging position J1 in a re-conveyance path P2, the second detector 200 having a second actuator 210 that rotates while being in contact with the sheet SH and a second optical sensor 201 that detects the rotation of the second actuator 210; and a sensor substrate 400 that supports the first and second sensors 101 and 201 and has a wiring pattern 400 W to which the first and second sensors 101 and 201 are connected.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] An example of a conventional image forming apparatus is disclosed in Patent Document 1. This image forming apparatus includes an image forming section, a conveying path, a re-conveying path, a conveying roller 24, a conveying roller 62, and a registration roller 26.

[0003] The image forming unit forms an image on a sheet. The transport path is a path for transporting the sheet toward the image forming unit. The re-transport path is a path for transporting the sheet, one side of which has an image formed thereon, toward the image forming unit again. The re-transport path merges with the transport path at a junction.

[0004] The conveying rollers 24 convey the sheet toward the joining position on the conveying path. The conveying rollers 62 convey the sheet toward the joining position on the re-conveying path. The registration rollers 26 are located between the joining position on the conveying path and the image forming unit, and convey the sheet toward the image forming unit.

[0005] Although not disclosed in Patent Document 1, this image forming apparatus generally includes a first detection unit that detects a sheet between the conveying roller 24 and the joining position on the conveying path. The first detection unit includes an actuator that rotates in contact with the conveyed sheet, and an optical sensor that detects the rotation of the actuator.

[0006] Furthermore, by adding a second detection section that detects the sheet between the conveying roller 62 on the re-conveying path and the junction position, this image forming device can appropriately control the conveying timing for each of the sheet conveyed on the conveying path and the sheet conveyed on the re-conveying path. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2013-50698 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the conventional image forming apparatus, the addition of the second detection unit requires an actuator and an optical sensor, similar to the first detection unit, and further requires a sensor board for supporting the sensor of the first detection unit, a sensor board for supporting the sensor of the second detection unit, and space for installing these sensor boards. Therefore, it may be difficult to realize miniaturization and low manufacturing costs for this image forming apparatus.

[0009] SUMMARY OF THE PRESENT DISCLOSURE The present invention has been made in consideration of the above-mentioned conventional circumstances, and has an object to provide an image forming apparatus that can be made compact and inexpensive to manufacture. [Means for solving the problem]

[0010] The image forming apparatus of the present invention includes an image forming unit that forms an image on a sheet, a conveying path for conveying a sheet toward the image forming unit; a re-conveying path for conveying the sheet having an image formed on one side thereof toward the image forming unit again, the re-conveying path joining the conveying path at a joining position; a first conveying roller that conveys the sheet along the conveying path toward the joining position; a second conveying roller that conveys the sheet toward the joining position in the re-conveying path; a third conveying roller located between the joining position on the conveying path and the image forming unit, the third conveying roller being configured to convey the sheet toward the image forming unit; An image forming apparatus comprising: a first detection unit that detects a sheet between the first conveying roller and the joining position in the conveying path, the first detection unit having a first actuator that rotates in contact with the sheet conveyed by the first conveying roller, and an optical first sensor that detects the rotation of the first actuator; a second detection unit that detects a sheet between the second conveying roller and the joining position in the re-conveying path, the second detection unit having a second actuator that rotates in contact with the sheet conveyed by the second conveying roller, and a second optical sensor that detects the rotation of the second actuator; a sensor substrate having a wiring pattern to which the first sensor and the second sensor are connected and supporting the first sensor and the second sensor; The present invention is characterized in that it is provided with:

[0011] The image forming apparatus of the present invention realizes a common substrate for the first sensor and the second sensor by using one sensor substrate, which eliminates the need for a sensor substrate supporting the first sensor and a sensor substrate supporting the second sensor, and eliminates the need for separate spaces for installing these sensor substrates.

[0012] Therefore, the image forming apparatus of the present invention can be made smaller and its manufacturing costs can be reduced. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a schematic cross-sectional view of the image forming apparatus according to the embodiment. [Diagram 2] 4 is a partial cross-sectional view mainly showing first and second frame members and first to third actuators. FIG. [Diagram 3] FIG. 2 is a partial side view mainly showing the first and second frame members, the first to third actuators, the first to third sensors, and the sensor substrate. [Figure 4] 4 is a partial perspective view mainly showing first and second frame members, first to third actuators, first to third sensors, and a sensor substrate. FIG. [Diagram 5]FIG. 3 is a perspective view showing first to third actuators. [Figure 6] 4 is a partial front view showing first to third actuators, first to third sensors, and a sensor substrate. FIG. [Figure 7] FIG. 2 is a side view showing the first and second actuators, illustrating a state in which the first actuator has rotated. [Figure 8] FIG. 8 is a side view similar to FIG. 7, showing a state in which the second actuator has rotated. [Figure 9] FIG. 4 is a perspective view showing a rear cover and a re-feed tray. [Figure 10] FIG. 4 is a partial cross-sectional view showing the rear cover and the re-feed tray. [Figure 11] FIG. 2 is a perspective view of a transfer belt unit. [Figure 12] FIG. 4 is a partial perspective view showing a state in which the transfer belt unit is positioned on the side frame. [Figure 13] FIG. 4 is a partial perspective view showing a state in which the transfer belt unit is detached from the side frame. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0015] (Example) 1, an image forming apparatus 1 according to an embodiment is an example of a specific aspect of the image forming apparatus of the present invention. The image forming apparatus 1 is a laser printer that forms an image on a sheet SH by electrophotography.

[0016] 1, the left side of the paper is defined as the front of the image forming apparatus 1, and the upper side of the paper is defined as the upper side of the image forming apparatus 1. The directions shown in each of the figures from FIG. 2 onwards are shown corresponding to FIG.

[0017] <General Configuration of Image Forming Apparatus> As shown in FIG. 1, the image forming apparatus 1 includes an apparatus main body 2, a sheet tray 2C, a control unit C1, a supply unit 20, an image forming unit 3, a discharge unit 29, and a re-feed tray 500.

[0018] The device main body 2 is a substantially box-shaped body, and detachably houses a sheet tray 2C at its bottom. The sheet tray 2C houses sheets SH in a stacked state before being conveyed by the supply unit 20. The sheets SH are paper, overhead projector sheets, etc.

[0019] The device body 2 also has a discharge tray 2T. The discharge tray 2T is located on the upper surface of the device body 2. The discharge tray 2T supports the sheet SH on which image formation has been completed. The device body 2 also has a rear cover 400. The rear cover 400 constitutes a part of the rear surface of the device body 2.

[0020] The control unit C1 has a calculation unit mainly including a CPU, ROM, and RAM (not shown), and hardware for controlling the semiconductor laser, motors, etc. The ROM stores programs for the CPU to control various operations of the image forming apparatus 1, programs for executing the recognition process, etc. The RAM functions as a storage area for temporarily recording data and signals used when the CPU executes the programs, or as a working area for data processing.

[0021] The control unit C1 controls the entire image forming apparatus 1 including the supply unit 20, the image forming unit 3, the discharge unit 29, and the re-feed tray 500.

[0022] The supply unit 20, the image forming unit 3, and the discharge unit 29 are located above the sheet tray 2C in the apparatus body 2. The re-feed tray 500 is located below the image forming unit 3 and above the sheet tray 2C in the apparatus body 2.

[0023] The image forming apparatus 1 includes a conveying path P1 and a re-conveying path P2.

[0024] The conveying path P1 is a path for conveying the sheets SH accommodated in the sheet tray 2C toward the image forming unit 3.

[0025] More specifically, the conveying path P1 is a path that makes an upward U-turn from the front end of the sheet tray 2C, passes through the supply unit 20, then proceeds rearward approximately horizontally, passes through the image forming unit 3, and then makes an upward U-turn to reach the discharge tray 2T via the discharge unit 29. The conveying direction of the sheet SH conveyed on the conveying path P1 is designated as D1.

[0026] The re-conveying path P2 is a path for reversing the sheet SH, one side of which has an image formed by the image forming unit 3, and transporting the sheet SH again toward the image forming unit 3. The re-conveying path P2 merges with the transport path P1 at a junction position J1.

[0027] More specifically, the re-conveying path P2 proceeds downward from the discharge unit 29, changes direction at a position below the image forming unit 3 and above the sheet tray 2C, proceeds forward substantially horizontally, passes through the re-conveying tray 500, and then joins the conveying path P1 at a joining position J1 to reach the supply unit 20. The re-conveying direction of the sheet SH conveyed on the re-conveying path P2 is designated as D2.

[0028] The re-conveyance path P2 has a curved section P21 and a horizontal section P22.

[0029] In the curved section P21, the re-conveying direction D2 of the sheet SH transported on the re-conveying path P2 changes from a downward direction to a direction proceeding horizontally toward the joining position J1.

[0030] The horizontal section P22 is connected to a downstream end P21E of the curved section P21 in the re-conveying direction D2. In the horizontal section P22, the re-conveying direction D2 is a direction that advances horizontally toward the joining position J1.

[0031] The re-conveying path P2, downstream of the horizontal section P22 in the re-conveying direction D2, advances in an upwardly inclined forward direction and reaches a joining position J1.

[0032] The width direction of the sheet SH transported on the transport path P1 and the re-transport path P2 is a direction perpendicular to the front-rear direction and the up-down direction, and is a direction perpendicular to the paper plane of Figures 1 to 3. The front side of the paper plane of Figures 1 to 3 is regarded as one side of the width direction, and the width direction is appropriately indicated in each of Figures from Figure 4 onwards.

[0033] 1, the supply unit 20 has a supply roller 21, a separation roller 22, and a separation pad 22A. The supply roller 21 is located at the upstream end of the conveying path P1 in the conveying direction D1. The supply roller 21 sends out the sheets SH stored in the sheet tray 2C to the conveying path P1. When multiple sheets SH are stacked, the separation roller 22 and the separation pad 22A separate the sheets SH sent out by the supply roller 21 one by one.

[0034] The supply unit 20 also includes a conveying roller 23, a pinch roller 23P, a registration roller 24, and a pinch roller 24P. The conveying roller 23 is an example of a "first conveying roller" in the present invention. The registration roller 24 is an example of a "third conveying roller" in the present invention.

[0035] The conveying roller 23 is located between the separation roller 22 and the joining position J1 on the conveying path P1. The pinch roller 23P is pressed toward the conveying roller 23. The conveying roller 23 cooperates with the pinch roller 23P to convey the sheet SH on the conveying path P1 toward the joining position J1.

[0036] The registration rollers 24 are positioned between the joining position J1 on the conveying path P1 and the image forming unit 3. The pinch rollers 24P are pressed against the registration rollers 24. The registration rollers 24 cooperate with the pinch rollers 24P to convey the sheet SH toward the image forming unit 3 on the conveying path P1.

[0037] The image forming section 3 is of a direct transfer type color electrophotographic system, and includes a process cartridge 7, a transfer belt 6, a scanner section 8, a fixing unit 9, and the like, which are well-known configurations.

[0038] The process cartridge 7 corresponds to four colors of toner, black, yellow, magenta, and cyan, and is a collection of four cartridges arranged in series along a substantially horizontal portion of the transport path P1. The process cartridge 7 has four photoconductors 5 corresponding to the four colors of toner, a developing roller, a charger, a toner storage unit, etc. (not shown). The axis of each photoconductor 5 extends in the width direction.

[0039] The transfer belt 6 faces each of the photoconductors 5 from below. The transfer belt 6 circulates while sandwiching the sheet SH conveyed from the sheet tray 2C together with each of the photoconductors 5.

[0040] The scanner unit 8 has a laser light source, a polygon mirror, an fθ lens, a reflecting mirror, etc. The scanner unit 8 irradiates each photoconductor 5 in the process cartridge 7 with a laser beam from above.

[0041] The fixing unit 9 is located behind the process cartridge 7. The fixing unit 9 has a heating roller 9A and a pressure roller 9B. The fixing unit 9 heats and presses the sheet SH that has passed below the process cartridge 7 with the heating roller 9A and the pressure roller 9B.

[0042] The image forming unit 3 forms an image on the sheet SH transported along the transport path P1 in the following manner. That is, the surface of each photoconductor 5 is uniformly positively charged by a charger as it rotates, and then exposed to high-speed scanning of a laser beam emitted from the scanner unit 8. As a result, an electrostatic latent image corresponding to the image to be formed on the sheet SH is formed on the surface of each photoconductor 5. Next, toner is supplied from the toner storage unit to the surface of each photoconductor 5 in correspondence with the electrostatic latent image. Then, when the sheet SH is transported along the transport path P1 and passes through the image forming unit 3, one side of the sheet SH faces upward and faces the photoconductor 5. Then, the toner carried on the surface of each photoconductor 5 is transferred to one side of the sheet SH, and is heated and pressed by the fixing unit 9. As a result, the toner is fixed to the sheet SH.

[0043] The discharge section 29 includes a discharge roller 29A, a pinch roller 29P, and a flapper 29F.

[0044] The discharge roller 29A is located at the most downstream side of the conveying path P1. The pinch roller 29P is pressed toward the discharge roller 29A. The discharge roller 29A is controlled by the control unit C1 to rotate forward and backward.

[0045] The flapper 29F is located at a portion of the transport path P1 that makes an upward U-turn behind the fixing unit 9. The flapper 29F can swing between a position shown by a solid line in FIG. 1 and a position shown by a two-dot chain line in FIG.

[0046] The flapper 29F is held by a spring (not shown) at the position shown by the two-dot chain line in Fig. 1. The biasing force of the spring is weak enough that the flapper 29F swings to the position shown by the solid line in Fig. 1 when the sheet SH transported along the transport path P1 abuts against the flapper 29F.

[0047] When an image is formed on only one side of the sheet SH, the discharge roller 29A cooperates with the pinch roller 29P to rotate forward while pinching the sheet SH that has passed through the fixing unit 9, thereby discharging the sheet SH onto the discharge tray 2T. At this time, the flapper 29F is pushed by the sheet SH and swings to the position shown by the solid line in Fig. 1, and returns to the position shown by the two-dot chain line in Fig. 1 after the sheet SH has passed.

[0048] When performing image formation on both sides of the sheet SH, the discharge roller 29A, the pinch roller 29P and the flapper 29F function as a reversing mechanism for the sheet SH, and reverse the sheet SH having an image formed on one side thereof.

[0049] That is, while the discharge roller 29A and the pinch roller 29P are nipping the sheet SH and discharging it to the discharge tray 2T, the control unit C1 switches the discharge roller 29A from forward rotation to reverse rotation at a predetermined timing after the sheet sensor (not shown) no longer detects the trailing edge of the sheet SH passing through the fixing unit 9. As a result, the discharge roller 29A and the pinch roller 29P reverse the sheet SH.

[0050] The predetermined timing is set so that it occurs after the trailing edge of the sheet SH passes the flapper 29F and the flapper 29F returns to the position shown by the two-dot chain line in Fig. 1. When the flapper 29F is in the position shown by the two-dot chain line in Fig. 1, the upper end side of the flapper 29F straddles the conveying path P1 and is aligned with the re-conveying path P2. As a result, the flapper 29F guides the inverted sheet SH to the re-conveying path P2.

[0051] The re-conveying tray 500 has a regulating member 530, a first re-conveying roller 25, an oblique feed roller 25P, a second re-conveying roller 26, and a pinch roller 26P. The second re-conveying roller 26 is an example of the "second conveying roller" in the present invention.

[0052] The regulating member 530 is located in the horizontal section P22 of the re-conveying path P2, and is located on the other side in the width direction. The regulating member 530 is for shifting the sheet SH in the width direction.

[0053] The first re-conveying roller 25 is located near the downstream end P21E of the curved section P21 in the horizontal section P22 of the re-conveying path P2. The oblique feed roller 25P is pressed toward the first re-conveying roller 25. The first re-conveying roller 25 cooperates with the oblique feed roller 25P to convey the sheet SH toward the second re-conveying roller 26 in the re-conveying path P2. At this time, the oblique feed roller 25P obliquely feeds the sheet SH toward the regulating member 530.

[0054] The second re-conveying roller 26 is located on the most downstream side of the horizontal section P22 of the re-conveying path P2. The pinch roller 26P is pressed toward the second re-conveying roller 26. The second re-conveying roller 26 cooperates with the pinch roller 26P to transport the sheet SH toward the joining position J1 on the re-conveying path P2.

[0055] As a result, the re-conveyed sheet SH merges with the transport path P1 at the junction position J1. Then, the image forming unit 3 forms an image on the other side of the re-conveyed sheet SH, and the discharge unit 29 discharges the sheet SH with the images formed on both sides onto the discharge tray 2T.

[0056] <First frame member and second frame member> 2 to 4, the image forming apparatus 1 includes a first frame member 91 and a second frame member 92. The first frame member 91 and the second frame member 92 are each a resin molded product manufactured by injection molding of a thermoplastic resin or the like.

[0057] Although not shown in the figure, the first frame member 91 and the second frame member 92 are connected to each other by fastening them with screws at one and the other widthwise positions relative to the conveying path P1 and the re-conveying path P2 while being precisely positioned by fitting portions, engagement portions, etc.

[0058] As shown in FIG. 2, the first frame member 91 and the second frame member 92 separate a part of the conveying path P1 from a part of the re-conveying path P2.

[0059] More specifically, the surface of the first frame member 91 facing forward and downward defines a portion of the transport path P1 from the most upstream side in the transport direction D1 to the joining position J1.

[0060] The upward and rearward facing surface of the first frame member 91 and the downward and forward facing surface of the second frame member 92 define a portion of the re-conveyance path P2 that slopes upward and forward to reach the joining position J1.

[0061] The surface of the second frame member 92 facing upward and forward defines a portion of the transport path P1 that extends from the junction J1 toward the image forming unit 3.

[0062] The first frame member 91 rotatably supports the separation roller 22 and the transport roller 23. The second frame member 92 rotatably supports the registration roller 24 and the pinch roller 26P.

[0063] <One sensor board> 3, 4 and 6, the image forming apparatus 1 includes one sensor board 400. The sensor board 400 is a small-sized printed circuit board.

[0064] 3 and 4, the sensor substrate 400 has a first positioning hole 400A and a second positioning hole 400B. The first positioning hole 400A is a circular hole located on the upper side of the sensor substrate 400. The second positioning hole 400B is an oval hole located on the lower side of the sensor substrate 400.

[0065] The second frame member 92 has a first positioning protrusion 92A and a second positioning protrusion 92B. The first positioning protrusion 92A and the second positioning protrusion 92B are each a cylindrical protrusion protruding toward one side in the width direction from one side surface in the width direction of the second frame member 92. The second positioning protrusion 92B is located lower than the first positioning protrusion 92A.

[0066] The sensor substrate 400 is precisely positioned relative to the second frame member 92, with the first positioning protrusion 92A fitting into the first positioning hole 400A and the second positioning protrusion 92B fitting into the second positioning hole 400B, so that the sensor substrate 400 is positioned to one side in the width direction relative to the conveying path P1 and the re-conveying path P2.

[0067] Then, the screw 400F passes through an insertion hole (not shown) located approximately in the center of the sensor board 400 and is screwed into the second frame member 92. In this manner, the second frame member 92 supports the sensor board 400.

[0068] As shown in FIG. 3, the sensor board 400 is located downstream of the transport roller 23 and the second re-transport roller 26 and upstream of the registration rollers 24 in the transport direction D1.

[0069] The sensor board 400 has a wiring pattern 400W to which a first sensor 101, a second sensor 201, and a third sensor 301, which will be described later, are connected. The wiring pattern 400W is connected to the controller C1 via a connector 400C and a wire harness 400H.

[0070] <First detection unit, second detection unit, and third detection unit> As simply shown in FIG. 1, the image forming apparatus 1 includes a first detection unit 100, a second detection unit 200, and a third detection unit 300. The first detection unit 100, the second detection unit 200, and the third detection unit 300 are arranged in a row and a column.

[0071] The first detection unit 100 detects the sheet SH between the conveying roller 23 and the junction J1 on the conveying path P1. The second detection unit 200 detects the sheet SH between the second re-conveying roller 26 and the junction J1 on the re-conveying path P2. The third detection unit 300 detects the sheet SH between the registration roller 24 and the image forming unit 3 on the conveying path P1.

[0072] The first detection unit 100, the second detection unit 200, and the third detection unit 300 each transmit a detection result to the control unit C1. Based on the detection results, the control unit C1 appropriately controls the transport timing of the sheet SH transported along the transport path P1 and the sheet SH transported along the re-transport path P2.

[0073] The configurations of the first detection section 100, the second detection section 200 and the third detection section 300 will be described in detail below with reference to FIGS.

[0074] The first detection unit 100 has a first sensor 101 shown in Figures 3, 4 and 6, a first actuator 110 shown in Figures 2 to 8, and a tension coil spring 150 shown in Figure 3. The tension coil spring 150 is an example of the "first biasing member" in the present invention.

[0075] The second detection unit 200 has a second sensor 201 shown in Figures 3, 4 and 6, a second actuator 210 shown in Figures 2 to 8, and a torsion coil spring 250 shown in Figure 5. The torsion coil spring 250 is an example of the "second biasing member" of the present invention.

[0076] The third detection section 300 has a third sensor 301 shown in FIGS. 3, 4 and 6, a third actuator 310 shown in FIGS. 2 to 6, and a torsion coil spring 350 shown in FIG.

[0077] <First sensor, second sensor and third sensor> 3, the first sensor 101, the second sensor 201, and the third sensor 301 are all photointerrupters, and the same product is used. The photointerrupter is a well-known optical sensor that detects the opening and closing of the optical path from the light-emitting part to the light-receiving part.

[0078] The sensor substrate 400 supports a first sensor 101, a second sensor 201, and a third sensor 301. The first sensor 101 is located at a front and lower corner of the sensor substrate 400. The second sensor 201 is located at a rear and lower corner of the sensor substrate 400. The third sensor 301 is located at a rear and upper corner of the sensor substrate 400.

[0079] The first sensor 101, the second sensor 201, and the third sensor 301 each have a plurality of terminals connected to a wiring pattern 400W.

[0080] The first sensor 101 detects the rotation of a first interlocking portion 120 (described later) of the first actuator 110. The second sensor 201 detects the rotation of a second interlocking portion 220 (described later) of the second actuator 210. The third sensor 301 detects the rotation of a third interlocking portion 320 (described later) of the third actuator 310.

[0081] The detection results of the first sensor 101, the second sensor 201, and the third sensor 301 are transmitted to the control unit C1 via the wiring pattern 400W, the connector 400C, and the wire harness 400H.

[0082] <First actuator and tension coil spring> 5, the first actuator 110 is a resin molded product manufactured by injection molding of a thermoplastic resin, etc. The first actuator 110 has a first rotation shaft 130, a first arm 111, a first interlocking portion 120, and a spring locking portion 119.

[0083] The first rotating shaft 130 extends in a generally cylindrical shape around a first rotating axis X110 extending in the width direction. The first rotating shaft 130 connects the first arm 111, the first interlocking portion 120, and the spring locking portion 119.

[0084] 2, the first rotating shaft 130 is supported by the first frame member 91. This allows the first rotating shaft 130, the first arm 111, the first interlocking portion 120 and the spring locking portion 119 to rotate integrally around the first rotating axis X110.

[0085] As shown in FIGS. 2 and 5, the first arm 111 protrudes from the other end of the first rotating shaft 130 in the width direction in a radially outward direction of the first rotating axis X110.

[0086] As shown in FIGS. 3 to 5, the first interlocking portion 120 and the spring locking portion 119 extend in mutually different directions from one end in the width direction of the first rotating shaft 130 in the radially outward direction of the first rotating axis X110.

[0087] The first interlocking portion 120 and the spring locking portion 119 are located on the sensor board 400 side in the width direction. More specifically, the first interlocking portion 120 and the spring locking portion 119 are located on the opposite side of the sensor board 400 to the transport path P1 and the re-transport path P2.

[0088] 3, the spring locking portion 119 locks one end of the tension coil spring 150 in a state of extending downward. The first frame member 91 has a spring locking portion 91S. The spring locking portion 91S protrudes rearward at a position spaced rearward and downward from the first rotation axis X110 on one side surface of the first frame member 91 in the width direction. The spring locking portion 91S locks the other end of the tension coil spring 150.

[0089] The tension coil spring 150 biases the first actuator 110 in a counterclockwise direction on the paper surface of Fig. 3. As a result, the first arm 111 is held in a state in which it crosses the transport path P1, as shown in Fig. 2.

[0090] The first arm 111 comes into contact with the sheet SH being conveyed by the conveyance roller 23 and rotates in the clockwise direction on the paper surface of Fig. 2. In other words, the tension coil spring 150 biases the first actuator 110 in the direction opposite to the direction in which the first actuator 110 comes into contact with the sheet SH and rotates.

[0091] The description of the shape of the first interlocking portion 120 will be based on the state where the first arm 111 crosses the transport path P1.

[0092] As shown in FIG. 5, the first interlocking portion 120 has a first curved portion 121, a first connecting portion 122, and a first reinforcing portion 123.

[0093] The first curved portion 121 has a curved plate shape that extends in an arc shape in the circumferential direction of the first rotation axis X110 and also in the width direction. As shown in Fig. 3, the upper end of the first curved portion 121 is located near the first sensor 101 and forward of the first sensor 101. The lower end of the first curved portion 121 is located forward and below the first rotation axis X110.

[0094] As shown in FIG. 5, the first connection portion 122 extends in the radial direction of the first rotation axis X110 and also in the width direction, and connects one end of the first rotation axis 130 in the width direction and the lower end of the first curved portion 121.

[0095] The first reinforcing portion 123 is connected to a portion of one widthwise edge of the first curved portion 121 that is close to the upper end of the first curved portion 121 and to one widthwise edge of an intermediate portion of the first connecting portion 122, thereby reinforcing the first curved portion 121. The first reinforcing portion 123 is recessed forward so as to escape from a second rotation shaft 230 (described later) of the second actuator 210.

[0096] 2, in a state in which the first arm 111 crosses the transport path P1, the first curved portion 121 of the first interlocking portion 120 opens the optical path of the first sensor 101 as shown in FIG 3. This allows the first sensor 101 to detect that the sheet SH is not present between the transport roller 23 and the joining position J1 on the transport path P1.

[0097] Although not shown, when the first arm 111 comes into contact with the sheet SH being conveyed by the conveying roller 23 and rotates in the clockwise direction on the paper in Fig. 2, the first interlocking portion 120 also rotates in the clockwise direction on the paper in Fig. 3 in conjunction with the first arm 111. As a result, the first curved portion 121 of the first interlocking portion 120 blocks the optical path of the first sensor 101. This causes the first sensor 101 to detect that the sheet SH is present between the conveying roller 23 and the joining position J1 on the conveying path P1.

[0098] <Second actuator and torsion coil spring> 5, the second actuator 210 is a resin molded product manufactured by injection molding of a thermoplastic resin, etc. The second actuator 210 has a second rotation shaft 230, a second arm 211, a second interlocking portion 220, and a spring locking portion 219.

[0099] The second rotating shaft 230 extends in a substantially cylindrical shape around a second rotating axis X210 extending in the width direction. The second rotating shaft 230 connects the second arm 211, the second interlocking portion 220, and the spring locking portion 219.

[0100] 2, the second rotating shaft 230 is supported by the first frame member 91. This allows the second rotating shaft 230, the second arm 211, the second interlocking portion 220 and the spring locking portion 219 to rotate integrally around the second rotating axis X210.

[0101] The second rotating shaft 230 is located slightly rearward of directly above the first rotating shaft 130. A range EA1 in which the first rotating shaft 130 exists in the front-rear direction and a range EA2 in which the second rotating shaft 230 exists in the front-rear direction at least partially overlap with each other.

[0102] As shown in FIGS. 2 and 5, the second arm 211 protrudes radially outward from a position close to the other end of the second rotation shaft 230 in the width direction about the second rotation axis X210.

[0103] As shown in FIG. 5, the spring locking portion 219 extends from the other end of the second rotating shaft 230 in the width direction in the radially outward direction of the second rotating axis X210.

[0104] 3 to 5, the second interlocking portion 220 extends radially outward from one end of the second rotation shaft 230 in the width direction about the second rotation axis X210. More specifically, the second interlocking portion 220 is located on the opposite side of the sensor substrate 400 to the transport path P1 and the re-transport path P2.

[0105] 5, coil portion 250C of torsion coil spring 250 is extrapolated onto the other end in the width direction of second rotating shaft 230. Spring locking portion 219 locks one end 250A of torsion coil spring 250. Although not shown, first frame member 91 locks the other end 250B of torsion coil spring 250.

[0106] The torsion coil spring 250 biases the second actuator 210 in a clockwise direction on the paper surface of Fig. 2. As a result, the second arm 211 is held in a state in which it intersects with the re-transport path P2.

[0107] The second arm 211 comes into contact with the sheet SH being transported by the second re-transport roller 26 and rotates counterclockwise in the plane of the drawing in Fig. 2. In other words, the torsion coil spring 250 biases the second actuator 210 in a direction opposite to the direction in which the second actuator 210 comes into contact with the sheet SH and rotates.

[0108] The tension coil spring 150 shown in FIG. 3 and the torsion coil spring 250 shown in FIG. 5 are located at positions separated from each other in the width direction.

[0109] The description of the shape of the second interlocking portion 220 will be based on the state where the second arm 211 crosses the re-conveyance path P2.

[0110] As shown in FIG. 5, the second interlocking portion 220 has a second curved portion 221, a second connecting portion 222, and a second reinforcing portion 223.

[0111] The second curved portion 221 has a curved plate shape that extends in an arc shape in the circumferential direction of the second rotation axis X210 and also in the width direction. As shown in Fig. 3, the upper end of the second curved portion 221 is located near the second sensor 201 and below the second sensor 201. The lower end of the second curved portion 221 is located rearward and below the second rotation axis X210.

[0112] As shown in FIG. 5, the second connection portion 222 extends in the radial direction of the second rotation axis X210 and also in the width direction, and connects one end of the second rotation axis 230 in the width direction and the lower end of the second curved portion 221.

[0113] The second reinforcing portion 223 is connected to a portion of one widthwise edge of the second curved portion 221 that is close to the upper end of the second curved portion 221 and to one widthwise end of the second rotating shaft 230, thereby reinforcing the second curved portion 221.

[0114] 2, in a state in which the second arm 211 crosses the re-conveying path P2, the second curved portion 221 of the second interlocking portion 220 opens the optical path of the second sensor 201 as shown in Fig. 3. This allows the second sensor 201 to detect that the sheet SH is not present between the second re-conveying roller 26 and the joining position J1 on the re-conveying path P2.

[0115] Although not shown, when the second arm 211 comes into contact with the sheet SH transported by the second re-conveying roller 26 and rotates counterclockwise on the paper surface of Fig. 2, the second interlocking portion 220 also rotates counterclockwise on the paper surface of Fig. 3 in conjunction with the second arm 211. As a result, the second curved portion 221 of the second interlocking portion 220 blocks the optical path of the second sensor 201. As a result, the second sensor 201 detects that the sheet SH is present between the second re-conveying roller 26 and the joining position J1 on the re-conveying path P2.

[0116] As shown in FIG. 6, a range EW1 in the width direction in which the first interlocking portion 120 exists and a range EW2 in the width direction in which the second interlocking portion 220 exists at least partially overlap with each other.

[0117] The second interlocking portion 220 protrudes from the first interlocking portion 120 to one side in the width direction. The second interlocking portion 220 is an example of the "first specific portion" of the present invention. The first interlocking portion 120 is an example of the "second specific portion" of the present invention.

[0118] 7 and 8 show a rotation locus RP1 of the first interlocking part 120 when the first arm 111 abuts against the seat SH and rotates. Fig. 8 shows a rotation locus RP2 of the second interlocking part 220 when the second arm 211 abuts against the seat SH and rotates.

[0119] As shown in FIG. 8, when viewed in the width direction, a rotation locus RP1 of the first interlocking portion 120 and a rotation locus RP2 of the second interlocking portion 220 at least partially overlap with each other.

[0120] As shown in Figure 7, the second interlocking portion 220 has a hollowed-out shape due to the second curved portion 221, the second connection portion 222, and the second reinforcing portion 223 so that the first interlocking portion 120 can enter the second interlocking portion 220 when the first interlocking portion 120 rotates.

[0121] Although not shown in the drawings, the first interlocking portion 120 and the second interlocking portion 220 are designed not to interfere with each other even when the first interlocking portion 120 and the second interlocking portion 220 rotate simultaneously.

[0122] <Third actuator and torsion coil spring> 5, the third actuator 310 is a resin molded product manufactured by injection molding of a thermoplastic resin, etc. The third actuator 310 has a third rotation shaft 330, a third arm 311, and a third interlocking part 320.

[0123] The third rotating shaft 330 extends in a substantially cylindrical shape around a third rotating axis X310 extending in the width direction. The third rotating shaft 330 connects the third arm 311 and the third interlocking portion 320.

[0124] 2, the third rotating shaft 330 is supported by the second frame member 92. This allows the third rotating shaft 330, the third arm 311 and the third interlocking part 320 to rotate integrally around the third rotating axis X310. The third rotating shaft 330 is located above and rearward away from the second rotating shaft 230.

[0125] As shown in FIGS. 2 and 5, the third arm 311 protrudes from the other end of the third rotating shaft 330 in the width direction in a radially outward direction of the third rotating axis X310.

[0126] 3 to 5, the third interlocking portion 320 extends downward from one end in the width direction of the third rotation shaft 330 in the radially outward direction of the third rotation axis X310. More specifically, the third interlocking portion 320 is located on the opposite side of the sensor substrate 400 to the transport path P1 and the re-transport path P2.

[0127] 5, coil portion 350C of torsion coil spring 350 is extrapolated onto the other end in the width direction of third rotating shaft 330. An intermediate portion of third arm 311 locks one end 350A of torsion coil spring 350. Although not shown, second frame member 92 locks the other end 350B of torsion coil spring 350.

[0128] The torsion coil spring 350 biases the third actuator 310 in a counterclockwise direction on the paper surface of Fig. 2. This causes the third arm 311 to be held in a state in which it intersects with the transport path P1.

[0129] The third arm 311 comes into contact with the sheet SH being conveyed by the registration rollers 24 and rotates in the clockwise direction on the paper surface of Fig. 2. In other words, the torsion coil spring 350 biases the third actuator 310 in the direction opposite to the direction in which the third actuator 310 comes into contact with the sheet SH and rotates.

[0130] The description of the shape of the third interlocking portion 320 will be based on the state where the third arm 311 crosses the transport path P1.

[0131] As shown in FIG. 5, the third interlocking portion 320 has a third curved portion 321 , a third connection portion 322 and a third reinforcing portion 323 .

[0132] The third curved portion 321 has a curved plate shape that extends in an arc shape in the circumferential direction of the third rotation axis X310 and also in the width direction. As shown in Fig. 3, the front end of the third curved portion 321 is located near the third sensor 301 and forward of the third sensor 301. The rear end of the third curved portion 321 is located near the third sensor 301 and rearward of the third sensor 301.

[0133] As shown in FIG. 5, the third connection portion 322 extends radially about the third rotation axis X310 and also extends in the width direction, and connects one end of the third rotation axis 330 in the width direction to the front end of the third curved portion 321.

[0134] The third reinforcing portion 323 is connected to one edge of the third curved portion 321 in the width direction and one end of the third rotation shaft 330 in the width direction, thereby reinforcing the third curved portion 321.

[0135] 2, in a state where the third arm 311 crosses the transport path P1, the third curved portion 321 of the third interlocking portion 320 blocks the optical path of the third sensor 301 as shown in FIG 3. This allows the third sensor 301 to detect that the sheet SH is not present between the registration rollers 24 and the image forming unit 3 on the transport path P1.

[0136] Although not shown, when the third arm 311 comes into contact with the sheet SH transported by the registration rollers 24 and rotates in the clockwise direction on the paper in Fig. 2, the third interlocking portion 320 also rotates in the clockwise direction on the paper in Fig. 3 in conjunction with the third arm 311. As a result, the third curved portion 321 of the third interlocking portion 320 opens the optical path of the third sensor 301. As a result, the third sensor 301 detects that the sheet SH is present between the registration rollers 24 and the joining position J1 on the transport path P1.

[0137] <First guide rib and second guide rib> 9 and 10, the rear cover 400 has a plurality of first guide ribs 410. The re-transport tray 500 has a plurality of second guide ribs 520. The plurality of first guide ribs 410 and the plurality of second guide ribs 520 are an example of the "plurality of guide ribs" of the present invention.

[0138] 9 and 10, the first guide rib 410 and the second guide rib 520 located at one side in the width direction and the first guide rib 410 and the second guide rib 520 located at the other side in the width direction are given symbols, and symbols are omitted for the first guide rib 410 and the second guide rib 520 located between them.

[0139] Each of the first guide ribs 410 is located in an upstream portion of the curved section P21 in the re-conveying direction D2.

[0140] Each first guide rib 410 is a rib that protrudes forward from the front surface of the rear cover 400 and extends in the vertical direction. Each first guide rib 410 is arranged at intervals in the width direction. The front end edge of each first guide rib 410 is curved so that the middle part in the vertical direction is located rearward of the upper end and the lower end.

[0141] Each second guide rib 520 is located downstream of each first guide rib 410 in the curved section P21 in the re-conveying direction D2, and extends to a downstream end P21E of the curved section P21.

[0142] Each second guide rib 520 is a rib that protrudes upward rearward from the downstream end P21E of the curved section P21 of the re-conveying tray 500 and extends in the front-rear direction. The second guide ribs 520 are arranged at intervals in the width direction. The upper edge of each second guide rib 520 has a height of zero at the downstream end P21E of the curved section P21, and is curved so as to gradually increase the inclination angle while inclining upward toward the rear.

[0143] The first guide ribs 410 and the second guide ribs 520 guide the sheet SH so as to change the re-conveying direction D2 from a downward direction to a direction proceeding horizontally toward the joining position J1.

[0144] Each of the first guide ribs 410 and each of the second guide ribs 520 are configured to gradually decrease in height as they move away from the regulating member 530 located on the other side of the width direction of the re-conveying tray 500 in one direction in the width direction.

[0145] The lower end of the front end edge of each of the first guide ribs 410 is configured so as to gradually move away from the regulating member 530 toward the rear as it moves away from the regulating member 530 in one direction in the width direction.

[0146] The upper ends of the upper edges of the second guide ribs 510 are also configured to gradually move away from the regulating member 530 toward the rear as they move away from the regulating member 530 in one direction in the width direction.

[0147] Due to such a shape of each of the first guide ribs 410 and each of the second guide ribs 510, the space that allows deformation of the sheet SH can be increased as it moves away from the regulating member 530 in the width direction.

[0148] <Transfer belt positioning structure> The transfer belt 6 shown in Fig. 1 constitutes a part of the transfer belt unit 600 shown in Fig. 11 and Fig. 12. As shown in Fig. 12, the transfer belt unit 600 is supported in a positioned state by a side frame 900 located on the other side in the width direction within the device main body 2 and a side frame (not shown) located on one side in the width direction.

[0149] The side frame 900 is a resin molded product manufactured by injection molding of a thermoplastic resin or the like.

[0150] 13, the transfer belt unit 600 is removable from the apparatus main body 2. The transfer belt unit 600 has a unit side frame 610 that extends in the front-rear direction on the other side of the width direction.

[0151] As shown in FIG. 11, the unit side frame 610 has a first positioning portion 611 , a second positioning portion 612 , a third positioning portion 613 , a fourth positioning portion 614 and a fifth positioning portion 615 .

[0152] The first positioning portion 611 is a convex portion that protrudes downward from the front end portion of the unit side frame 610. As shown in Fig. 12 and Fig. 13, the first positioning portion 611 fits into a fitting boss 901 formed on the side frame 900, thereby positioning the front end portion of the transfer belt unit 600 in the width direction.

[0153] 11, the second positioning portion 612 is a flat surface facing downward and located rearward of the first positioning portion 611 in the unit side frame 610. As shown in Fig. 13, the second positioning portion 612 abuts against a receiving surface 902 formed on the side frame 900 from above, thereby positioning the front end portion of the transfer belt unit 600 in the up-down direction.

[0154] 11, the third positioning portion 613 is a downwardly pointed protrusion that protrudes from the middle portion in the front-rear direction of the unit side frame 610 in the other width direction. As shown in Fig. 13, the third positioning portion 613 abuts against a receiving surface 903 formed on the side frame 900 from the rear, and is pressed against the receiving surface 903 by a pressing member 903P, thereby positioning the transfer belt unit 600 in the front-rear direction.

[0155] 11, the fourth positioning portion 614 is a flat surface located at the rear end of the unit side frame 610 and facing the other side in the width direction. The fifth positioning portion 615 is a flat surface located below the fourth positioning portion 614 at the rear end of the unit side frame 610 and facing downward.

[0156] As shown in FIG. 13, the fourth positioning portion 614 is biased by a biasing spring (not shown) to abut against a receiving surface 904 formed on the side frame 900 from one side in the width direction, thereby positioning the rear end portion of the transfer belt unit 600 in the width direction.

[0157] The fifth positioning portion 615 abuts against a receiving surface 905 formed on the side frame 900 from above, thereby positioning the rear end portion of the transfer belt unit 600 in the up-down direction.

[0158] Since the transfer belt unit 600 is positioned in the front-rear, up-down and width directions by the single side frame 900, the accumulation of errors can be suppressed compared to a case where the transfer belt unit 600 is positioned by a plurality of members. As a result, the image forming apparatus 1 can improve the positioning accuracy of the transfer belt unit 600.

[0159] <Action and effect> 3 and 4, the image forming apparatus 1 of the embodiment realizes a common substrate for the first sensor 101 and the second sensor 201 by using one sensor substrate 400. As a result, the image forming apparatus 1 does not need to provide a sensor substrate supporting the first sensor 101 and a sensor substrate supporting the second sensor 201 separately, and does not need to secure separate spaces for installing these sensor substrates.

[0160] Therefore, the image forming apparatus 1 of the embodiment can be made smaller and the manufacturing costs can be reduced.

[0161] 3, in the image forming apparatus 1, the sensor board 400 is located downstream of the conveying roller 23 and the second re-conveying roller 26 and upstream of the registration roller 24 in the conveying direction D1. This configuration makes it easy to secure free space around the sensor board 400 in the image forming apparatus 1, and by utilizing this free space, it is possible to improve the layout freedom of other components. As a result, the image forming apparatus 1 can be made even more compact.

[0162] Furthermore, in this image forming apparatus 1, the sensor board 400 is located on one side in the width direction with respect to the transport path P1 and the re-transport path P2. The first actuator 110 has a first arm 111 and a first interlocking portion 120. The second actuator 210 has a second arm 211 and a second interlocking portion 220. The first sensor 101 detects the rotation of the first interlocking portion 120. The second sensor 201 detects the rotation of the second interlocking portion 220. With this configuration, the image forming apparatus 1 can easily realize a layout of the first interlocking portion 120, the second interlocking portion 220, the sensor board 400, the first sensor 101, and the second sensor 201 that does not interfere with the transport path P1 and the re-transport path P2.

[0163] 8, in the image forming apparatus 1, the rotation locus RP1 of the first interlocking portion 120 and the rotation locus RP2 of the second interlocking portion 220 at least partially overlap when viewed in the width direction. This configuration makes it easy to lay out the image forming apparatus 1 with the first actuator 110 and the second actuator 210 close to each other in the front-rear or up-down direction. As a result, the image forming apparatus 1 can be made even more compact.

[0164] Further, in the image forming apparatus 1, as shown in FIG. 6, the range EW1 in which the first interlocking portion 120 exists in the width direction and the range EW2 in which the second interlocking portion 220 exists in the width direction at least partially overlap. The second interlocking portion 220 protrudes from the first interlocking portion 120 to one side in the width direction. As shown in FIG. 7, the second interlocking portion 220 has a hollow shape so that the first interlocking portion 120 can enter the second interlocking portion 220 when the first interlocking portion 120 rotates. With this configuration, the image forming apparatus 1 can be easily laid out with the first actuator 110 and the second actuator 210 closer to each other in the front-rear direction or the up-down direction. As a result, the image forming apparatus 1 can be made even more compact.

[0165] 2, in the image forming apparatus 1, the range EA1 in which the first rotating shaft 130 exists in the front-rear direction and the range EA2 in which the second rotating shaft 230 exists in the front-rear direction at least partially overlap. With this configuration, the image forming apparatus 1 can be easily laid out with the first actuator 110 and the second actuator 210 close to each other in the front-rear direction. As a result, the image forming apparatus 1 can be made even more compact.

[0166] Furthermore, in this image forming apparatus 1, both the first rotating shaft 130 and the second rotating shaft 230 are supported by the first frame member 91. With this configuration, this image forming apparatus 1 can achieve improved relative positional accuracy for the first actuator 110 and the second actuator 210.

[0167] In addition, in this image forming apparatus 1, the second frame member 92 supports the sensor board 400. The first frame member 91 and the second frame member 92 are connected to each other to partition a part of the transport path P1 and a part of the re-transport path P2. With this configuration, the first frame member 91 and the second frame member 92 are connected to each other in a state where they are positioned with high precision. This allows the image forming apparatus 1 to improve the relative positional precision between the first actuator 110, the second actuator 210, and the sensor board 400. As a result, the image forming apparatus 1 can improve the relative positional precision between the first interlocking unit 120 and the first sensor 101, and between the second interlocking unit 220 and the second sensor 201.

[0168] Furthermore, in this image forming apparatus 1, the tension coil spring 150 shown in Fig. 3 and the torsion coil spring 250 shown in Fig. 5 are located at positions separated in the width direction. With this configuration, the space for installing the tension coil spring 150 and the space for installing the torsion coil spring 250 are unlikely to overlap. As a result, this image forming apparatus 1 can be made even more compact.

[0169] The image forming apparatus 1 also includes a third detection unit 300. The sensor board 400 has a wiring pattern 400W to which the third sensor 301 of the third detection unit 300 is connected, and supports the third sensor 301. With this configuration, the image forming apparatus 1 realizes commonality of the board for the first sensor 101, the second sensor 201, and the third sensor 301 by using one sensor board 400. As a result, the image forming apparatus 1 does not need to separately provide a sensor board supporting the first sensor 101, a sensor board supporting the second sensor 201, and a sensor board supporting the third sensor 301, and does not need to separately secure space for installing these sensor boards. As a result, the image forming apparatus 1 can achieve miniaturization and low manufacturing costs.

[0170] Furthermore, in this image forming apparatus 1, the re-conveying path P2 passes below the image forming unit 3 and above the sheet tray 2C to reach the joining position J1. With this configuration, this image forming apparatus 1 can be easily laid out with the first actuator 110 and the second actuator 210 close to each other, thereby achieving further miniaturization.

[0171] In addition, in the image forming apparatus 1, as shown in FIG. 9 and FIG. 10, each of the first guide ribs 410 and each of the second guide ribs 520 is configured so that the height gradually decreases as it moves away from the regulating member 530 in the width direction. When the sheet SH is moved toward the regulating member 530 in the horizontal section P22 while passing through the curved section P21, the sheet SH is likely to be deformed three-dimensionally, including bending and twisting, and the deformation tends to be large especially on the side farther away from the regulating member 530 in the width direction. Therefore, by configuring each of the first guide ribs 410 and each of the second guide ribs 520 as described above, the space that allows the deformation of the sheet SH can be made larger as it moves away from the regulating member 530 in the width direction. As a result, the image forming apparatus 1 can suppress the excessive conveyance resistance acting on the sheet SH from each of the first guide ribs 410 and each of the second guide ribs 520, and as a result, the behavior of the sheet SH moved toward the regulating member 530 can be suppressed from becoming unstable.

[0172] Although the present invention has been described above with reference to the embodiments, it goes without saying that the present invention is not limited to the above embodiments and can be modified as appropriate without departing from the spirit of the present invention. [Industrial Applicability]

[0173] The present invention can be used in, for example, an image forming apparatus or a multifunction peripheral. [Explanation of symbols]

[0174] 1... image forming apparatus, SH... sheet, 3... image forming section P1: Transport path, P2: Re-transport path, J1: Junction position 23...First conveying roller (conveying roller) 26...Second conveying roller (second re-conveying roller) 24...Third conveying roller (registration roller) 100: first detection unit, 110: first actuator, 101: first sensor 200: second detection unit, 210: second actuator, 201: second sensor 400W...Wiring pattern, 400...Sensor board, D1...Transport direction X110: first rotating shaft center, 111: first arm, 120: first interlocking portion X210: second rotating shaft, 211: second arm, 220: second interlocking portion RP1: Rotation trajectory of the first interlocking part, RP2: Rotation trajectory of the second interlocking part EW1: Range in the width direction where the first interlocking part exists EW2: Range in the width direction where the second interlocking part exists 220…1st specific part (2nd interlocking part) 120…Second specific part (first interlocking part) 130: first rotating shaft, 230: second rotating shaft EA1: Range in which the first rotation axis exists in the front-rear direction EA2: Area in which the second rotation axis exists in the front-rear direction 91: first frame member, 92: second frame member 150...First biasing member (tension coil spring) 250...Second biasing member (torsion coil spring) 300: third detection unit, 310: third actuator, 301: third sensor 2C: Sheet tray, D2: Re-feed direction, P21: Curved section P21E: downstream end of the curved section in the re-feeding direction, P22: horizontal section 410, 520... Guide rib (410... First guide rib, 520... Second guide rib) 530...Regulation parts

Claims

1. an image forming unit that forms an image on a sheet; a conveying path for conveying a sheet toward the image forming unit; a re-conveying path for conveying the sheet having an image formed on one side thereof toward the image forming unit again, the re-conveying path joining the conveying path at a joining position; a first conveying roller configured to convey the sheet along the conveying path toward the joining position; a second conveying roller that conveys the sheet toward the joining position in the re-conveying path; a third conveying roller located between the joining position on the conveying path and the image forming unit, the third conveying roller being configured to convey the sheet toward the image forming unit; An image forming apparatus comprising: a first detection unit that detects a sheet between the first conveying roller and the joining position in the conveying path, the first detection unit having a first actuator that rotates in contact with the sheet conveyed by the first conveying roller, and an optical first sensor that detects the rotation of the first actuator; a second detection unit that detects a sheet between the second conveying roller and the joining position in the re-conveying path, the second detection unit having a second actuator that rotates in contact with the sheet conveyed by the second conveying roller, and a second optical sensor that detects the rotation of the second actuator; a sensor substrate having a wiring pattern to which the first sensor and the second sensor are connected and supporting the first sensor and the second sensor; Equipped with the sensor board is located on one side of the conveying path and the re-conveying path in a width direction of a sheet conveyed on the conveying path and the re-conveying path, the first actuator is rotatable about a first rotation axis extending in the width direction, and includes a first arm that rotates in contact with a sheet conveyed by the first conveying roller, and a first interlocking portion that is located on a side of the sensor board in the width direction and interlocks with the first arm, the second actuator is rotatable about a second rotation axis extending in the width direction, and includes a second arm that rotates in contact with the sheet conveyed by the second conveying roller, and a second interlocking portion that is located on the sensor board side in the width direction and interlocks with the second arm, The first sensor detects the rotation of the first interlocking part, The second sensor detects the rotation of the second interlocking portion, an image forming apparatus, wherein a rotation locus of the first interlocking portion and a rotation locus of the second interlocking portion at least partially overlap each other when viewed from the width direction;

2. 2 . The image forming apparatus according to claim 1 , wherein the sensor board is located downstream of the first transport roller and the second transport roller and upstream of the third transport roller in a transport direction of the sheet transported along the transport path.

3. A range in which the first interlocking portion exists in the width direction and a range in which the second interlocking portion exists in the width direction at least partially overlap each other, A first specific portion, which is one of the first interlocking portion and the second interlocking portion, protrudes to one side in the width direction beyond a second specific portion, which is the other of the first interlocking portion and the second interlocking portion, 3. The image forming apparatus according to claim 1, wherein the first specific portion has a hollow shape so that the second specific portion can enter the first specific portion when the second specific portion rotates.

4. the first actuator has a first rotation shaft extending about the first rotation axis and connecting the first arm and the first interlocking portion; the second actuator has a second rotation shaft extending about the second rotation axis and connecting the second arm and the second interlocking portion; 4. The image forming apparatus according to claim 1, wherein a range in the front-rear direction in which the first rotation shaft exists and a range in the front-rear direction in which the second rotation shaft exists at least partially overlap with each other.

5. A first frame member is provided. the first actuator has a first rotation shaft extending about the first rotation axis and connecting the first arm and the first interlocking portion; the second actuator has a second rotation shaft extending about the second rotation axis and connecting the second arm and the second interlocking portion; 5. The image forming apparatus according to claim 1, wherein the first rotation shaft and the second rotation shaft are both supported by the first frame member.

6. a second frame member supporting the sensor substrate; 6. The image forming apparatus according to claim 5, wherein the first frame member and the second frame member are connected to each other to separate a part of the transport path and a part of the re-transport path.

7. the first detection unit has a first biasing member that biases the first actuator in a direction opposite to a direction in which the first actuator abuts against the seat and rotates, the second detection portion has a second biasing member that biases the second actuator in a direction opposite to a direction in which the second actuator abuts against the seat and rotates, 7. The image forming apparatus according to claim 1, wherein the first urging member and the second urging member are located at positions spaced apart from each other in a width direction of the sheet transported through the transport path and the re-transport path.

8. a third detection unit that detects a sheet between the third conveying roller and the image forming unit in the conveying path, the third detection unit having a third actuator that rotates in contact with the sheet conveyed by the third conveying roller, and a third optical sensor that detects the rotation of the third actuator; 8. The image forming apparatus according to claim 1, wherein the sensor substrate has the wiring pattern to which the third sensor is connected and supports the third sensor.

9. a sheet tray located below the image forming unit and configured to accommodate a sheet before being conveyed by the first conveying roller; 9. The image forming apparatus according to claim 1, wherein the re-conveying path passes below the image forming unit and above the sheet tray to reach the joining position.

10. the re-conveying path has a curved section in which a re-conveying direction of the sheet conveyed on the re-conveying path changes from a downward direction to a direction in which the sheet advances horizontally toward the joining position; a horizontal section that is connected to a downstream end of the curved section in the re-conveying direction, and the re-conveying direction is a direction in which the conveying direction advances horizontally toward the junction position, The image forming apparatus includes a plurality of guide ribs that are located in the curved section, are arranged at intervals in a width direction of a sheet transported through the transport path and the re-transport path, and guide the sheet so as to change the re-transport direction from a downward direction to a direction proceeding horizontally toward the joining position; a regulating member located in the horizontal section for aligning the sheet in the width direction; Further equipped with 10. The image forming apparatus according to claim 1, wherein the height of each of the guide ribs gradually decreases as the guide ribs move away from the regulating member in the width direction.

11. An image forming unit that forms an image on a sheet; a conveying path for conveying a sheet toward the image forming unit; a re-conveying path for conveying the sheet having an image formed on one side thereof toward the image forming unit again, the re-conveying path joining the conveying path at a joining position; a first conveying roller configured to convey the sheet along the conveying path toward the joining position; a second conveying roller that conveys the sheet toward the joining position in the re-conveying path; a third conveying roller located between the joining position on the conveying path and the image forming unit, the third conveying roller being configured to convey the sheet toward the image forming unit; An image forming apparatus comprising: a first detection unit that detects a sheet between the first conveying roller and the joining position in the conveying path, the first detection unit having a first actuator that rotates in contact with the sheet conveyed by the first conveying roller, and an optical first sensor that detects the rotation of the first actuator; a second detection unit that detects a sheet between the second conveying roller and the joining position in the re-conveying path, the second detection unit having a second actuator that rotates in contact with the sheet conveyed by the second conveying roller, and a second optical sensor that detects the rotation of the second actuator; a sensor substrate having a wiring pattern to which the first sensor and the second sensor are connected and supporting the first sensor and the second sensor; Equipped with the sensor board is located on one side of the conveying path and the re-conveying path in a width direction of a sheet conveyed on the conveying path and the re-conveying path, the first actuator is rotatable about a first rotation axis extending in the width direction, and includes a first arm that rotates in contact with a sheet conveyed by the first conveying roller, and a first interlocking portion that is located on a side of the sensor board in the width direction and interlocks with the first arm, the second actuator is rotatable about a second rotation axis extending in the width direction, and includes a second arm that rotates in contact with the sheet conveyed by the second conveying roller, and a second interlocking portion that is located on the sensor board side in the width direction and interlocks with the second arm, The first sensor detects the rotation of the first interlocking part, The second sensor detects the rotation of the second interlocking portion, the first actuator has a first rotation shaft extending about the first rotation axis and connecting the first arm and the first interlocking portion; the second actuator has a second rotation shaft extending about the second rotation axis and connecting the second arm and the second interlocking portion; 13. An image forming apparatus, comprising: a range in the front-rear direction in which the first rotation shaft exists and a range in the front-rear direction in which the second rotation shaft exists, the range at least partially overlapping each other.

12. An image forming unit that forms an image on a sheet; a conveying path for conveying a sheet toward the image forming unit; a re-conveying path for conveying the sheet having an image formed on one side thereof toward the image forming unit again, the re-conveying path joining the conveying path at a joining position; a first conveying roller configured to convey the sheet along the conveying path toward the joining position; a second conveying roller that conveys the sheet toward the joining position in the re-conveying path; a third conveying roller located between the joining position on the conveying path and the image forming unit, the third conveying roller being configured to convey the sheet toward the image forming unit; An image forming apparatus comprising: a first detection unit that detects a sheet between the first conveying roller and the joining position in the conveying path, the first detection unit having a first actuator that rotates in contact with the sheet conveyed by the first conveying roller, and an optical first sensor that detects the rotation of the first actuator; a second detection unit that detects a sheet between the second conveying roller and the joining position in the re-conveying path, the second detection unit having a second actuator that rotates in contact with the sheet conveyed by the second conveying roller, and a second optical sensor that detects the rotation of the second actuator; a sensor substrate having a wiring pattern to which the first sensor and the second sensor are connected and supporting the first sensor and the second sensor; Equipped with the sensor board is located on one side of the conveying path and the re-conveying path in a width direction of a sheet conveyed on the conveying path and the re-conveying path, the first actuator is rotatable about a first rotation axis extending in the width direction, and includes a first arm that rotates in contact with a sheet conveyed by the first conveying roller, and a first interlocking portion that is located on a side of the sensor board in the width direction and interlocks with the first arm, the second actuator is rotatable about a second rotation axis extending in the width direction, and includes a second arm that rotates in contact with the sheet conveyed by the second conveying roller, and a second interlocking portion that is located on the sensor board side in the width direction and interlocks with the second arm, The first sensor detects the rotation of the first interlocking part, The second sensor detects the rotation of the second interlocking portion, A first frame member is provided. the first actuator has a first rotation shaft extending about the first rotation axis and connecting the first arm and the first interlocking portion; the second actuator has a second rotation shaft extending about the second rotation axis and connecting the second arm and the second interlocking portion; an image forming apparatus, wherein the first rotation shaft and the second rotation shaft are both supported by the first frame member;

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