Image forming device

Abstract

To provide an image forming apparatus that can prevent reduction in throughput.SOLUTION: A switching mechanism 8 has a planetary differential gear 8A that has a planetary gear carrier 83, a sun gear 80, and an internal tooth gear 81; a first drive transmission part 8B having a first bi-directional clutch 84 that transmits driving force from the sun gear 80 to an intermediate ejection roller 72a and does not transmit driving force from the intermediate ejection roller 72a to the sun gear 80; a second drive transmission part 8C having a second bi-directional clutch 85 that transmits driving force from the internal tooth gear 81 to the intermediate ejection roller 72a and does not transmit driving force from the intermediate ejection roller 72a to the internal tooth gear 81; and a switching part 8D that switches a state between a first state in which the driving force is output to the first drive transmission part 8B and the driving force is not output to the second drive transmission part 8C to rotate the intermediate ejection roller 72a in a first direction, and a second state in which the driving force is not output to the first drive transmission part 8B and the driving force is output to the second drive transmission part 8C to rotate the intermediate ejection roller 72a in a second direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] As disclosed in Patent Document 1, there has been known an image forming device that includes an image forming unit, and intermediate discharge rollers and discharge rollers that are located downstream of the image forming unit in the sheet transport direction and discharge the sheet transported from the image forming unit or transport it back to the image forming device.

[0003] In such an image forming device, the intermediate discharge roller and discharge roller are driven by a motor, and by switching the rotation direction of the motor, the rotation direction of the intermediate discharge roller and discharge roller is switched between forward and reverse rotation to discharge and reverse transport the sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-140114 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, in a configuration in which the rotation direction of the motor is changed to switch between forward and reverse rotation of the intermediate discharge rollers and discharge rollers, the rotation direction of the motor must be changed every time the rotation direction of the intermediate discharge rollers and discharge rollers is changed between forward and reverse rotation, which increases the time required to change the rotation direction of the motor, resulting in a decrease in the throughput of the image forming apparatus.

[0006] Furthermore, because the motors that drive the intermediate discharge rollers and discharge rollers need to switch their rotation directions, it is difficult to drive the intermediate discharge rollers, discharge rollers, and other drive units with a common motor. Therefore, the image forming apparatus of Patent Document 1 is provided with dedicated motors for driving the intermediate discharge rollers and discharge rollers, which increases costs.

[0007] Therefore, the present invention provides an image forming apparatus that uses a common motor to drive the intermediate discharge roller and discharge roller and the motor to drive other drive units, and that can suppress a decrease in throughput when switching the rotation direction of the intermediate discharge roller and discharge roller. [Means for solving the problem]

[0008] The image forming apparatus that solves the above problem has the following features.

[0009] That is, the image forming apparatus includes an image forming unit that forms an image on a conveyed sheet, a reversing roller that is located downstream of the image forming unit in the sheet conveying direction and is rotatable in a first direction and a second direction opposite to the first direction, a motor that is a drive source for the reversing roller, and a switching mechanism that switches the rotation direction of the reversing roller when the motor is rotating in one direction, the switching mechanism including an input gear that is rotated by receiving a driving force from the motor, first and second output gears that are capable of outputting a driving force, a planetary differential gear having planetary gears that transmit the driving force from the input gear to the first and second output gears, and a first drive transmission unit that connects the first output gear and the reversing roller, and that transmits the driving force to the reversing roller when the driving force from the first output gear is input, and a first drive transmission unit having a first clutch that does not transmit a driving force to the first output gear when the second output gear is in a driven state; a second drive transmission unit connecting the second output gear and the reversing roller, the second drive transmission unit having a second clutch that transmits a driving force to the reversing roller when the driving force from the second output gear is input and does not transmit the driving force to the second output gear when the driving force from the reversing roller is input; and a switching unit that switches between a first state in which the driving force is output from the first output gear to the first drive transmission unit and is not output from the second output gear to the second drive transmission unit, thereby rotating the reversing roller in the first direction, and a second state in which the driving force is not output from the first output gear to the first drive transmission unit and is output from the second output gear to the second drive transmission unit, thereby rotating the reversing roller in the second direction.

[0010] This allows the rotation direction of the reversing roller to be switched without switching the rotation direction of the motor, thereby preventing a decrease in throughput during printing by the image forming apparatus. Also, the motor that drives the reversing roller can be shared with the motors that drive other drive units, thereby reducing costs.

[0011] The first clutch has a first shaft connected to the first output gear and a second shaft connected to the reversing roller, and is a bidirectional clutch that transmits the driving force from the first output gear transmitted to the first shaft to the second shaft and does not transmit the driving force from the reversing roller transmitted to the second shaft to the first shaft; the second clutch has a third shaft connected to the second output gear and a fourth shaft connected to the reversing roller, and is a bidirectional clutch that transmits the driving force from the second output gear transmitted to the third shaft to the fourth shaft and does not transmit the driving force from the reversing roller transmitted to the fourth shaft to the third shaft.

[0012] This eliminates the need for a power source or control device for operating the electromagnetic clutches, as is the case when electromagnetic clutches are used as the first clutch and the second clutch, and allows the switching mechanism to have a simple configuration.

[0013] The switching unit selectively stops one of the rotation of the first output gear and the rotation of the second output gear.

[0014] This makes it possible to easily stop either the output of the driving force from the first output gear or the output of the driving force from the second output gear.

[0015] The switching unit also has a clutch lever having a first engagement pawl that engages with the first output gear to stop rotation of the first output gear and a second engagement pawl that engages with the second output gear to stop rotation of the second output gear, and the clutch lever is movable between a first position where the first engagement pawl is separated from the first output gear and the second engagement pawl is engaged with the second output gear, and a second position where the first engagement pawl engages with the first output gear and the second engagement pawl is separated from the second output gear.

[0016] This makes it possible to easily switch between stopping the rotation of the first output gear and stopping the rotation of the second output gear.

[0017] The switching unit also has a tension spring that biases the clutch lever to the first position and a solenoid that moves the clutch lever from the first position toward the second position, and further includes a control unit that controls the operation of the solenoid, and the control unit turns on the solenoid when the solenoid moves the clutch lever from the first position toward the second position.

[0018] This allows the stopping of rotation of the first output gear and the stopping of rotation of the second output gear to be switched over in a short time.

[0019] In addition, the input gear is a planetary gear carrier that rotatably holds the planetary gear, the first output gear is one of a sun gear and an internal gear that meshes with the planetary gear, and the second output gear is the other of the sun gear and the internal gear.

[0020] This allows the first output gear to rotate in the same direction as the second output gear when it outputs driving force, and also allows the rotation speeds of the first output gear and the second output gear to be increased relative to the rotation speed of the input gear.

[0021] The rotational speed controller further includes a reversing roller gear that rotates integrally with the reversing roller, wherein the first drive transmission unit is composed of only the first clutch, and the second drive transmission unit is composed of the second clutch and an idle gear that meshes with the reversing roller gear, wherein the first clutch is a first bidirectional clutch that has a first gear that meshes with the first output gear and a second gear that meshes with the reversing roller gear and transmits the driving force from the first output gear that has been transmitted to the first gear to the second gear and does not transmit the driving force from the reversing roller that has been transmitted to the second gear to the first gear, and wherein the second clutch is a second bidirectional clutch that has a third gear that meshes with the second output gear and a fourth gear that meshes with the idle gear and transmits the driving force from the second output gear that has been transmitted to the third gear to the fourth gear and does not transmit the driving force from the reversing roller that has been transmitted to the fourth gear to the third gear.

[0022] This makes it possible to switch the rotation direction of the reversing roller while simplifying the configuration of the first drive transmission unit and the second drive transmission unit.

[0023] Furthermore, the input gear is one of the sun gear and the internal gear that meshes with the planetary gear, the first output gear is the other of the sun gear and the internal gear, and one of the planetary gear carriers that rotatably holds the planetary gear, and the second output gear is the other of the sun gear and the internal gear, and the other of the planetary gear carrier.

[0024] This allows the first output gear to rotate in the opposite direction to the direction in which the second output gear outputs driving force, and also allows the rotation speeds of the first output gear and the second output gear to be different.

[0025] The rotational speed controller further includes a reversing roller gear that rotates integrally with the reversing roller, wherein the first drive transmission unit is composed only of the first clutch, and the second drive transmission unit is composed only of the second clutch, wherein the first clutch has a first gear that meshes with the first output gear and a second gear that meshes with the reversing roller gear, and is a first bidirectional clutch that transmits the driving force from the first output gear that has been transmitted to the first gear to the second gear and does not transmit the driving force from the reversing roller that has been transmitted to the second gear to the first gear, and the second clutch has a third gear that meshes with the second output gear and a fourth gear that meshes with the reversing roller gear, and is a second bidirectional clutch that transmits the driving force from the second output gear that has been transmitted to the third gear to the fourth gear and does not transmit the driving force from the reversing roller that has been transmitted to the fourth gear to the third gear.

[0026] This makes it possible to switch the rotation direction of the reversing roller while simplifying the configuration of the first drive transmission unit and the second drive transmission unit.

[0027] The image forming unit further includes a fixing device that has a photosensitive drum and a transfer roller, is located downstream of the image forming unit in the sheet transport direction, and fixes the toner image formed on the sheet to the sheet, and the reversing roller is located downstream of the fixing device in the sheet transport direction.

[0028] This makes it possible to suppress a decrease in throughput during printing in the image forming apparatus. [Effects of the Invention]

[0029] According to the present invention, it is possible to suppress a decrease in throughput of an image forming apparatus and reduce costs. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 2 is a central cross-sectional view showing the image forming apparatus. [Figure 2] FIG. 2(a) is a side view showing the switching mechanism when the switching unit is in a first state, and FIG. 2(b) is a side view showing the switching mechanism when the switching unit is in a second state. [Figure 3] FIG. 4 is a plan cross-sectional view showing a switching mechanism. [Figure 4] FIG. 4 is a diagram showing the relationship between the input and output of a planetary differential gear. [Figure 5] FIG. 2 is a block diagram showing a control unit to which a motor and a solenoid are connected. [Figure 6] 10A is a side view showing a switching mechanism according to a second embodiment, in which FIG. 10A is a side view showing a switching mechanism in which a switching unit is in a first state, and FIG. 10B is a side view showing a switching mechanism in which a switching unit is in a second state. [Figure 7] FIG. 10 is a plan cross-sectional view showing a switching mechanism according to a second embodiment. [Figure 8] 10A is a side view showing a switching mechanism according to a third embodiment, in which FIG. 10A is a side view showing the switching mechanism with a switching unit in a first state, and FIG. 10B is a side view showing the switching mechanism with a switching unit in a second state. [Figure 9] FIG. 10 is a plan cross-sectional view showing a switching mechanism according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0032] [Image forming equipment] The image forming apparatus 1 shown in Figure 1 is one embodiment of the image forming apparatus according to the present invention, and is configured as a color laser printer that forms an image by superimposing multiple color developer images on a sheet S such as paper or an OHP sheet using an electrophotographic method. However, the image forming apparatus 1 can also be configured as a monochrome laser printer that forms an image on a sheet using a single color developer image. The image forming apparatus 1 can also be configured as an inkjet printer.

[0033] In the following description, the left side in Fig. 1 is defined as the rear side of the image forming apparatus 1, the right side in Fig. 1 is defined as the front side of the image forming apparatus 1, the front side of the paper in Fig. 1 is defined as the left side of the image forming apparatus 1, and the back side of the paper in Fig. 1 is defined as the right side of the image forming apparatus 1. In addition, the upper and lower sides in Fig. 1 are defined as the upper and lower sides of the image forming apparatus 1, respectively.

[0034] The image forming apparatus 1 includes a device main body 2, a paper feed unit 3 that supplies sheets S, an image forming unit 5 that forms an image on the conveyed sheets S, and a conveying unit 7 that conveys the sheets S conveyed from the image forming unit 5. The device main body 2 is a box formed in a substantially rectangular parallelepiped shape, and houses the paper feed unit 3, the image forming unit 5, and the conveying unit 7. An ejection tray 23a that is recessed and slopes downward from the front side to the rear side is formed on an upper surface 23 of the device main body 2.

[0035] The paper feed unit 3 includes a sheet cassette 31, a paper feed roller 32, a conveying roller pair 34, and a registration roller pair 35. A paper feed path P0 for feeding the sheet S from the sheet cassette 31 to the image forming unit 5 is configured within the device main body 2.

[0036] The sheet cassette 31 supports a plurality of sheets S in a stacked state. The sheets S supported by the sheet cassette 31 are sent out one by one to a sheet feed path P0 by a sheet feed roller 32. The sheets S sent out to the sheet feed path P0 are conveyed toward the image forming unit 5 by a conveyance roller pair 34 and a registration roller pair 35.

[0037] The image forming unit 5 includes four drum units 51 arranged side by side in the front-to-rear direction. Each drum unit 51 corresponds to one of the colors: black, yellow, magenta, and cyan. Each drum unit 51 includes a photosensitive drum 51a and a developing roller 51b.

[0038] The image forming section 5 also includes a scanner unit 52. The scanner unit 52 is provided in the upper part of the device main body 2, and laser light based on image data is irradiated onto the surface of the photosensitive drum 51a corresponding to each color by high-speed scanning through a polygon mirror, a lens, a reflecting mirror, etc.

[0039] A transfer belt 40 is disposed below the drum unit 51 in the image forming section 5. The transfer belt 40 is stretched between a drive roller 41a and a driven roller 41b disposed in front of the drive roller 41a. Transfer rollers 42 are disposed at positions facing each photosensitive drum 51a across the transfer belt 40.

[0040] In the image forming unit 5, the photosensitive drums 51a, which are uniformly charged by a charger (not shown), are selectively exposed to light by the scanner unit 52. This exposure selectively removes charge from the surfaces of the photosensitive drums 51a, and an electrostatic latent image is formed on the surfaces of the photosensitive drums 51a.

[0041] A developing bias is applied to the developing roller 51b, and when the electrostatic latent image formed on the photosensitive drum 51a faces the developing roller 51b, the potential difference between the electrostatic latent image and the developing roller 51b causes toner to be supplied from the developing roller 51b to the electrostatic latent image, thereby forming a toner image on the surface of the photosensitive drum 51a.

[0042] When the sheet S is conveyed toward the image forming unit 5 and is conveyed onto the transfer belt 40, it is conveyed by the transfer belt 40 and passes sequentially between the transfer belt 40 and each photosensitive drum 51a. Then, when the toner image on the surface of the photosensitive drum 51a faces the sheet S, it is transferred onto the sheet S by a transfer bias applied to the transfer roller 42.

[0043] A fixing unit 6 is provided downstream in the sheet conveying direction of the image forming unit 5. The fixing unit 6 includes a heating roller 61 that heats the sheet S, and a pressure roller 62 that is disposed opposite the heating roller 61.

[0044] The sheet S onto which the toner image has been transferred is transported to the fixing device 6. The sheet S transported to the fixing device 6 passes between a heating roller 61 and a pressure roller 62 which are pressed against each other, thereby thermally fixing the toner image. In this way, the fixing device 6 fixes the toner image formed on the sheet S to the sheet S.

[0045] The sheet S on which the toner image has been thermally fixed is transported downstream of the fixing unit 6 by the transport unit 7. The transport unit 7 has a transport path P1, a discharge path P2, and a re-transport path P3. The transport path P1 is a path along which the sheet S is transported from the image forming unit 5 to the downstream of the fixing unit 6. The discharge path P2 branches off from the transport path P1 at a branch point Ps, and is a path along which the sheet S is transported to the discharge tray 23a. The re-transport path P3 branches off from the transport path P1 and the discharge path P2 at the branch point Ps, and is a path along which the sheet S is transported to the image forming unit 5.

[0046] A post-fixing roller 71a for transporting the sheet S and a driven roller 71b arranged opposite the post-fixing roller 71a are provided downstream of the fixing unit 6 in the sheet transport direction on the transport path P1.

[0047] Discharge rollers 73a that convey the sheet S and driven rollers 73b that are arranged opposite the discharge rollers 73a are provided at the downstream end of the discharge path P2 in the sheet conveying direction. Intermediate discharge rollers 72a that convey the sheet S and driven rollers 72b that are arranged opposite the intermediate discharge rollers 72a are provided upstream of the discharge rollers 73a and driven rollers 73b in the discharge path P2 in the sheet conveying direction when the sheet S is discharged.

[0048] The intermediate discharge rollers 72a and the discharge rollers 73a are located downstream of the image forming unit 5 and the fixing unit 6 in the conveying direction of the sheet S discharged onto the discharge tray 23a. The intermediate discharge rollers 72a and the discharge rollers 73a are an example of a reversing roller.

[0049] The re-conveying path P3 is provided with an intermediate reversing roller 74a that transports the sheet S and a driven roller 74b that is arranged opposite the intermediate reversing roller 74a, a first re-conveying roller 75a and a driven roller 75b that is arranged opposite the first re-conveying roller 75a, and a second re-conveying roller 76a and a driven roller 76b that is arranged opposite the second re-conveying roller 76a.

[0050] The first re-conveying roller 75a and the driven roller 75b are arranged downstream in the sheet conveying direction from the intermediate reversing roller 74a and the driven roller 74b, and the second re-conveying roller 76a and the driven roller 76b are arranged downstream in the sheet conveying direction from the first re-conveying roller 75a and the driven roller 75b.

[0051] The image forming apparatus 1 includes a motor 91. The motor 91 is a drive source that drives the paper feed roller 32, the post-fixing roller 71a, the intermediate discharge roller 72a, the discharge roller 73a, the intermediate reversing roller 74a, the first re-conveyance roller 75a, the second re-conveyance roller 76a, the heating roller 61, and the like.

[0052] The intermediate discharge rollers 72a and discharge rollers 73a, driven by a motor 91, are configured to be rotatable in a forward rotation direction and a reverse rotation direction opposite to the forward rotation direction. When rotating in the forward rotation direction, the intermediate discharge rollers 72a and discharge rollers 73a transport the sheet S toward the discharge tray 23a, and the transported sheet S is discharged to the discharge tray 23a. When rotating in the reverse rotation direction, the intermediate discharge rollers 72a and discharge rollers 73a can transport the sheet S toward the re-conveyance path P3. This allows the transport direction of the sheet S on the discharge path P2 to be reversed. One of the forward rotation direction and the reverse rotation direction is a first direction, and the other of the forward rotation direction and the reverse rotation direction is a second direction opposite to the first direction.

[0053] [Switching mechanism] 2, the image forming apparatus 1 includes a switching mechanism 8 that switches the rotation direction of the intermediate discharge rollers 72a when the motor 91 is rotating in one direction. The switching mechanism 8 includes a planetary differential gear 8A, a first drive transmission unit 8B, a second drive transmission unit 8C, and a switching unit 8D.

[0054] A driving force from a motor 91 is input to the planetary differential gear 8A through a driving gear 92 connected to the motor 91. The planetary differential gear 8A is configured to be able to output the driving force to a first driving force transmission unit 8B and a second driving force transmission unit 8C.

[0055] 3, the planetary differential gear 8A has a sun gear 80, an internal gear 81, planet gears 82, and a planet gear carrier 83. The sun gear 80 has a rotary shaft 801, and a first sun gear 802 and a second sun gear 803 that can rotate integrally with the rotary shaft 801. The internal gear 81 is rotatably supported by the rotary shaft 801, and has external teeth 811 formed on its outer circumferential surface and internal teeth 812 formed on its inner circumferential surface.

[0056] The planetary gear 82 is provided between the second sun gear 803 of the sun gear 80 and the internal teeth 812 of the internal gear 81, and is in mesh with both the second sun gear 803 and the internal teeth 812. In the planetary differential gear 8A, a plurality of planetary gears 82 are provided.

[0057] The planetary gear carrier 83 is rotatably supported by the rotation shaft 801, and has a carrier gear 831 and a support shaft 832. The support shaft 832 rotatably holds the planetary gear 82, and the planetary gear 82 is rotatable around the support shaft 832. When the planetary gear carrier 83 rotates around the rotation shaft 801, the planetary gear 82 revolves around the rotation shaft 801.

[0058] A drive gear 92 meshes with the carrier gear 831, and the drive force from the motor 91 can be transmitted to the carrier gear 831 via the drive gear 92. The planetary gear 82 transmits the drive force from the carrier gear 831 to the sun gear 80 and the internal gear 81.

[0059] In the planetary differential gear 8A, for example, when a driving force is transmitted to the planetary gear carrier 83 with the internal gear 81 fixed and the planetary gear carrier 83 rotates, the planetary gears 82 held by the planetary gear carrier 83 rotate, and the sun gear 80 meshing with the planetary gears 82 also rotates. In this case, the planetary gears 82 rotate in the direction opposite to the rotational direction of the planetary gear carrier 83, and the sun gear 80 rotates in the same direction as the rotational direction of the planetary gear carrier 83 at an accelerated speed (see R1 in FIG. 4). As the sun gear 80 rotates, a driving force is output from the sun gear 80.

[0060] Furthermore, when a driving force is transmitted to the planetary gear carrier 83 with the sun gear 80 fixed and the planetary gear carrier 83 rotates, the planetary gears 82 held by the planetary gear carrier 83 rotate, and the internal gear 81 meshing with the planetary gears 82 also rotates. In this case, the planetary gears 82 rotate in the same direction as the rotational direction of the planetary gear carrier 83, and the internal gear 81 rotates in the same direction as the rotational direction of the planetary gear carrier 83, but at an increased speed (see R2 in FIG. 4). The rotation of the internal gear 81 causes the internal gear 81 to output a driving force.

[0061] The planetary gear carrier 83 is an example of an input gear that rotates when driving force from the motor is transmitted. The input gear is a gear that meshes with the drive gear 92. The sun gear 80 is an example of a first output gear that can output driving force. The internal gear 81 is an example of a second output gear that can output driving force.

[0062] The first drive transmission unit 8B has a first bidirectional clutch 84. The first drive transmission unit 8B is composed of only the first bidirectional clutch 84. The first bidirectional clutch 84 is an example of a first clutch. The first bidirectional clutch 84 has a clutch body 841, a first shaft 842, a second shaft 843, a first gear 844, and a second gear 845.

[0063] The first shaft 842 is rotatably supported by the clutch body 841, and a first gear 844 is fixed to the first shaft 842 so as to be integrally rotatable. The second shaft 843 is rotatably supported by the clutch body 841, and a second gear 845 is fixed to the second shaft 843 so as to be integrally rotatable.

[0064] The first gear 844 meshes with the first sun gear 802 of the sun gear 80, and the first shaft 842 is connected to the sun gear 80 via the first gear 844. In other words, the first gear 844 meshes with the first output gear, and the first shaft 842 is connected to the first output gear.

[0065] The image forming apparatus 1 includes a roller gear 72A that rotates integrally with the intermediate discharge roller 72a, and the second gear 845 meshes with the roller gear 72A. The second shaft 843 is connected to the intermediate discharge roller 72a via the second gear 845 and the roller gear 72A. The roller gear 72A is an example of a reversing roller gear.

[0066] The first bidirectional clutch 84 is a bidirectional clutch that transmits the driving force transmitted to the first shaft 842 to the second shaft 843 by the clutch body 841, and does not transmit the driving force transmitted to the second shaft 843 to the first shaft 842 by the clutch body 841. Therefore, when the driving force from the first sun gear 802 is transmitted to the first gear 844, the driving force transmitted to the first gear 844 is transmitted to the second gear 845. On the other hand, when the driving force from the roller gear 72A is transmitted to the second gear 845, the driving force transmitted to the second gear 845 is not transmitted to the first gear 844.

[0067] In other words, the first drive transmission unit 8B connects the sun gear 80, which is the first output gear, to the intermediate discharge roller 72a, and has a first bidirectional clutch 84 that transmits the drive force to the intermediate discharge roller 72a when drive force is input from the sun gear 80, and does not transmit the drive force to the sun gear 80 when drive force is input from the intermediate discharge roller 72a.

[0068] The second drive transmission unit 8C has a second bidirectional clutch 85 and an idle gear 86. The second drive transmission unit 8C is also composed of the second bidirectional clutch 85 and the idle gear 86. The second bidirectional clutch 85 is an example of a second clutch. The second bidirectional clutch 85 has a clutch body 851, a third shaft 852, a fourth shaft 853, a third gear 854, and a fourth gear 855.

[0069] The third shaft 852 is rotatably supported by the clutch body 851, and a third gear 854 is fixed to the third shaft 852 so as to be rotatable integrally with the third shaft 852. The fourth shaft 853 is rotatably supported by the clutch body 851, and a fourth gear 855 is fixed to the fourth shaft 853 so as to be rotatable integrally with the fourth shaft 853.

[0070] The third gear 854 meshes with the external teeth 811 of the internal gear 81, and the third shaft 852 is connected to the internal gear 81 via the third gear 854. In other words, the third gear 854 meshes with the second output gear, and the third shaft 852 is connected to the second output gear.

[0071] The idle gear 86 meshes with the roller gear 72A, and the fourth gear 855 meshes with the idle gear 86. The fourth shaft 853 is connected to the intermediate discharge roller 72a via the fourth gear 855, the idle gear 86, and the roller gear 72A.

[0072] The second bidirectional clutch 85 is a bidirectional clutch that transmits the driving force transmitted to the third shaft 852 to the fourth shaft 853 by the clutch body 851, but does not transmit the driving force transmitted to the fourth shaft 853 to the third shaft 852 by the clutch body 851. Therefore, when the driving force from the external teeth 811 is transmitted to the third gear 854, the driving force transmitted to the third gear 854 is transmitted to the fourth gear 855. On the other hand, when the driving force from the roller gear 72A is transmitted to the fourth gear 855, the driving force transmitted to the fourth gear 855 is not transmitted to the third gear 854.

[0073] In other words, the second drive transmission unit 8C connects the internal gear 81, which is the second output gear, to the intermediate discharge roller 72a, and has a second bidirectional clutch 85 that transmits the drive force to the intermediate discharge roller 72a when the drive force is input from the internal gear 81, and does not transmit the drive force to the internal gear 81 when the drive force is input from the intermediate discharge roller 72a.

[0074] The switching unit 8D has a clutch lever 87, a tension spring 88, and a solenoid 89. The clutch lever 87 has a rotation center 87a, a first lever 87b, a second lever 87c, and a third lever 87d that are rotatable about the rotation center 87a, a first engagement claw 871 fixed to the first lever 87b, and a second engagement claw 872 fixed to the second lever 87c.

[0075] The first lever 87b, the second lever 87c, and the third lever 87d extend radially outward from the rotation center 87a at different phases, and are arranged in the counterclockwise direction in this order in Fig. 2. In the circumferential direction around the rotation center 87a, the planetary differential gear 8A is located between the first lever 87b and the second lever 87c.

[0076] The first engagement claw 871 can be engaged with the first sun gear 802 of the sun gear 80 to stop the rotation of the sun gear 80. The second engagement claw 872 can be engaged with the external teeth 811 of the internal gear 81 to stop the rotation of the internal gear 81. In other words, the first engagement claw 871 can be engaged with the first output gear, and the second engagement claw 872 can be engaged with the second output gear.

[0077] The clutch lever 87 can rotate around a rotation center 87a to move between a first position (position shown in FIG. 2(a)) where the first engagement claw 871 is separated from the sun gear 80 of the planetary differential gear 8A and the second engagement claw 872 is engaged with the internal gear 81 of the planetary differential gear 8A, and a second position (position shown in FIG. 2(b)) where the first engagement claw 871 is engaged with the sun gear 80 of the planetary differential gear 8A and the second engagement claw 872 is separated from the internal gear 81 of the planetary differential gear 8A.

[0078] The tension spring 88 is connected to the first lever 87b and biases the clutch lever 87 to the first position. The solenoid 89 is connected to the third lever 87d and is configured to be able to move the clutch lever 87 from the first position toward the second position.

[0079] 5, the image forming apparatus 1 includes a control unit 90, which is connected to a motor 91 and a solenoid 89. The control unit 90 can control the operations of the motor 91 and the solenoid 89. The control unit 90 turns on the solenoid 89 when the solenoid 89 moves the clutch lever 87 from the first position toward the second position.

[0080] [Operation of switching mechanism 8] As shown in Figure 2(a), when the solenoid 89 is off, the switching unit 8D can be set to a first state in which the tension spring 88 biases the clutch lever 87 to a first position, causing the first engagement claw 871 to move away from the sun gear 80, allowing the sun gear 80 to rotate, and the second engagement claw 872 to engage with the internal gear 81, stopping the rotation of the internal gear 81.

[0081] In the first state, when the driving force from the motor 91 rotating counterclockwise is transmitted to the planetary gear carrier 83 and the planetary gear carrier 83 rotates clockwise, the sun gear 80 rotates clockwise and the driving force is output from the sun gear 80 to the first drive transmission unit 8B. On the other hand, because the rotation of the internal gear 81 is stopped by the second engagement pawl 872, the driving force is not output from the internal gear 81 to the second drive transmission unit 8C.

[0082] When the driving force output from the sun gear 80 is transmitted to the first gear 844 of the first bidirectional clutch 84 in the first drive transmission unit 8B, the driving force transmitted to the first gear 844 is then transmitted to the second gear 845. In this case, the first gear 844 and the second gear 845 rotate counterclockwise. As the second gear 845 rotates counterclockwise, the driving force is transmitted to the roller gear 72A and the intermediate discharge roller 72a, and the roller gear 72A and the intermediate discharge roller 72a rotate clockwise.

[0083] 2, in which the roller gear 72A and the intermediate discharge roller 72a rotate in the first state, is the first direction. That is, the roller gear 72A and the intermediate discharge roller 72a rotate in the first direction in the first state.

[0084] When roller gear 72A rotates in the clockwise direction, which is the first direction, idle gear 86 meshing with roller gear 72A rotates counterclockwise, and the driving force from roller gear 72A is transmitted to fourth gear 855 of second bidirectional clutch 85. However, the driving force from roller gear 72A transmitted to fourth gear 855 is not transmitted to third gear 854, and therefore third gear 854 meshing with external teeth 811 of internal gear 81 is held stationary.

[0085] As shown in Figure 2(b), when the solenoid 89 is turned on by the control unit 90, the switching unit 8D causes the solenoid 89 to move the clutch lever 87 from the first position to the second position, so that the first engagement claw 871 engages with the sun gear 80 to stop the rotation of the sun gear 80, and the second engagement claw 872 moves away from the internal gear 81 to enter a second state in which the internal gear 81 can rotate.

[0086] In the second state, the driving force from the motor 91 rotating in the counterclockwise direction, which is the same direction as in the first state, is transmitted to the planetary gear carrier 83, and when the planetary gear carrier 83 rotates clockwise, the internal gear 81 rotates clockwise and the driving force is output from the internal gear 81 to the second driving force transmission unit 8C. On the other hand, because the rotation of the sun gear 80 is stopped by the first engagement claw 871, the driving force is not output from the sun gear 80 to the first driving force transmission unit 8B.

[0087] When the driving force output from the internal gear 81 is transmitted to the third gear 854 of the second bidirectional clutch 85 in the second driving force transmission unit 8C, the driving force transmitted to the third gear 854 is then transmitted to the fourth gear 855. In this case, the third gear 854 and the fourth gear 855 rotate counterclockwise. As the fourth gear 855 rotates counterclockwise, the driving force is transmitted to the roller gear 72A and the intermediate discharge roller 72a via the idle gear 86. In this case, the idle gear 86 rotates clockwise, and the roller gear 72A and the intermediate discharge roller 72a rotate counterclockwise.

[0088] 2, in which the roller gear 72A and the intermediate discharge roller 72a rotate, is a second direction that is opposite to the first direction. That is, the roller gear 72A and the intermediate discharge roller 72a rotate in the second direction in the second state.

[0089] When roller gear 72A rotates in one of two directions, counterclockwise, the driving force from roller gear 72A is transmitted to second gear 845 of first bidirectional clutch 84, which meshes with roller gear 72A. However, the driving force from roller gear 72A transmitted to second gear 845 is not transmitted to first gear 844, and therefore first gear 844, which meshes with first sun gear 802 of sun gear 80, is held stationary.

[0090] In this way, the switching unit 8D can switch between a first state in which the intermediate discharge roller 72a rotates in a first direction by outputting the driving force from the sun gear 80, which is the first output gear, to the first drive transmission unit 8B, and not outputting the driving force from the internal gear 81, which is the second output gear, to the second drive transmission unit 8C, and a second state in which the intermediate discharge roller 72a rotates in a second direction by not outputting the driving force from the sun gear 80 to the first drive transmission unit 8B, and outputting the driving force from the internal gear 81 to the second drive transmission unit 8C.

[0091] This makes it possible to switch the rotation direction of the intermediate discharge roller 72a without switching the rotation direction of the motor 91, thereby suppressing a decrease in throughput during printing by the image forming apparatus 1. Furthermore, the motor 91 that is the drive source for the intermediate discharge roller 72a can be shared with the motor 91 that is the drive source for the other drive units, such as the paper feed roller 32, the post-fixing roller 71a, the intermediate reversing roller 74a, the first re-conveyance roller 75a, the second re-conveyance roller 76a, and the heating roller 61, thereby enabling cost reductions.

[0092] In this case, the switching unit 8D selectively stops either the rotation of the sun gear 80, which is the first output gear, or the rotation of the internal gear 81, which is the second output gear, so that either the output of driving force from the sun gear 80 or the output of driving force from the internal gear 81 can be easily stopped.

[0093] Furthermore, because the switching mechanism 8 uses the first bidirectional clutch 84 as the first clutch of the first drive transmission unit 8B and the second bidirectional clutch 85 as the second clutch of the second drive transmission unit 8C, a power source or control device for operating the electromagnetic clutches is not required, as would be the case if electromagnetic clutches were used as the first clutch of the first drive transmission unit 8B and the second clutch of the second drive transmission unit 8C. This allows the switching mechanism 8 to have a simple configuration. However, in the switching mechanism 8, electromagnetic clutches can also be used as the clutches of the first drive transmission unit 8B and the second drive transmission unit 8C.

[0094] In addition, the switching mechanism 8 is configured to switch between stopping the rotation of the sun gear 80 and stopping the rotation of the internal gear 81 by moving the clutch lever 87, which has a first engagement claw 871 and a second engagement claw 872, between a first position and a second position, making it possible to easily switch between stopping the rotation of the sun gear 80 and stopping the rotation of the internal gear 81.

[0095] In this case, the clutch lever 87 is biased to the first position by the tension spring 88, and is moved from the first position to the second position when the solenoid 89 is turned on by the control unit 90, so that it is possible to switch between stopping the rotation of the sun gear 80 and stopping the rotation of the internal gear 81 in a short period of time.

[0096] Furthermore, in the switching mechanism 8 of this embodiment, the planetary gear carrier 83 is used as the input gear to which the driving force from the motor 91 is transmitted, the sun gear 80 is used as the first output gear capable of outputting driving force, and the internal gear 81 is used as the second output gear capable of outputting driving force, but when the planetary gear carrier 83 is used as the input gear, it is also possible to use the internal gear 81 as the first output gear and the sun gear 80 as the second output gear.

[0097] When the internal gear 81 is used as the first output gear and the sun gear 80 is used as the second output gear, the external teeth 811 of the internal gear 81 mesh with the first gear 844 of the first bidirectional clutch 84, and the first sun gear 802 of the sun gear 80 meshes with the third gear 854 of the second bidirectional clutch 85. In addition, the first engagement pawl 871 of the clutch lever 87 engages with the external teeth 811 of the internal gear 81, and the second engagement pawl 872 of the clutch lever 87 engages with the first sun gear 802 of the sun gear 80.

[0098] When the internal gear 81 is used as the first output gear and the sun gear 80 is used as the second output gear, when the switching unit 8D is in the first state, the roller gear 72A and the intermediate discharge roller 72a rotate in a first direction, which in this case is the clockwise direction in Fig. 2. When the switching unit 8D is in the second state, the roller gear 72A and the intermediate discharge roller 72a rotate in a second direction, which in this case is the counterclockwise direction in Fig. 2.

[0099] In this way, when the planetary gear carrier 83 is used as the input gear, one of the sun gear 80 and the internal gear 81 is used as the first output gear, and the other of the sun gear 80 and the internal gear 81 is used as the second output gear, the rotation direction when the first output gear outputs a driving force can be made the same as the rotation direction when the second output gear outputs a driving force. Also, the rotation speeds of the first output gear and the second output gear can be increased relative to the rotation speed of the input gear.

[0100] Furthermore, in the switching mechanism 8, the first drive transmission unit 8B is composed only of the first bidirectional clutch 84, and the second drive transmission unit 8C is composed of the second bidirectional clutch 85 and the idle gear 86. Therefore, it is possible to switch the rotation direction of the intermediate discharge roller 72a while keeping the first drive transmission unit 8B and the second drive transmission unit 8C simple in configuration.

[0101] However, the first drive transmission unit 8B and the second drive transmission unit 8C may be configured to have one or more idle gears, as long as the intermediate discharge roller 72a rotates in a first direction when the switching unit 8D is in a first state, and the intermediate discharge roller 72a rotates in a second direction opposite to the first direction when the switching unit 8D is in a second state.

[0102] By connecting the roller gear 72A and the discharge roller 73a with a drive transmission train, the discharge roller 73a can be rotated in the same direction and at the same speed as the intermediate discharge roller 72a by the driving force from the roller gear 72A. Also, by applying a switching mechanism similar to the switching mechanism 8, the discharge roller 73a can be rotated in the same direction and at the same speed as the intermediate discharge roller 72a by the driving force from the motor 91.

[0103] [Second embodiment of switching mechanism] 6 and 7, a switching mechanism 8-1 according to the second embodiment uses the sun gear 80 of the planetary differential gear 8A as an input gear, the planetary gear carrier 83 as a first output gear, and the internal gear 81 as a second output gear, which differs from the switching mechanism 8 that uses the planetary gear carrier 83 of the planetary differential gear 8A as an input gear, the sun gear 80 as a first output gear, and the internal gear 81 as a second output gear. The switching mechanism 8-1 also differs from the switching mechanism 8 in that it includes a second drive transmission unit 8E instead of the second drive transmission unit 8C.

[0104] The second drive transmission unit 8E has a second bidirectional clutch 85. The second drive transmission unit 8E is composed of the second bidirectional clutch 85 alone.

[0105] In the switching mechanism 8-1, the first sun gear 802 of the sun gear 80, which is the input gear, meshes with the drive gear 92. The carrier gear 831 of the planetary gear carrier 83, which is the first output gear, meshes with the first gear 844 of the first bidirectional clutch 84.

[0106] The external teeth 811 of the internal gear 81, which is the second output gear, mesh with the third gear 854 of the second bidirectional clutch 85. The fourth gear 855 of the second bidirectional clutch 85 meshes with the roller gear 72A. The fourth shaft 853 of the second bidirectional clutch 85 is connected to the intermediate discharge roller 72a via the fourth gear 855 and the roller gear 72A.

[0107] Other configurations of the switching mechanism 8-1 are the same as those of the switching mechanism 8, and therefore description thereof will be omitted.

[0108] [Operation of switching mechanism 8-1] As shown in Figure 6(a), when the solenoid 89 is off, the switching unit 8D biases the clutch lever 87 to a first position using a tension spring 88, thereby causing the first engagement claw 871 to move away from the planetary gear carrier 83, allowing the planetary gear carrier 83 to rotate, and the second engagement claw 872 to engage with the internal gear 81, stopping the rotation of the internal gear 81, thereby entering a first state.

[0109] In the first state, when the driving force from the motor 91 rotating counterclockwise is transmitted to the sun gear 80 and the sun gear 80 rotates clockwise, the planetary gear carrier 83 rotates clockwise and the driving force is output from the planetary gear carrier 83 to the first drive transmission unit 8B. In this case, the planetary gear carrier 83 rotates in the same direction as the rotation direction of the sun gear 80 at a reduced speed (see R3 in FIG. 4). On the other hand, because the rotation of the internal gear 81 is stopped by the second engagement pawl 872, the driving force is not output from the internal gear 81 to the second drive transmission unit 8E.

[0110] When the driving force output from the planetary gear carrier 83 is transmitted to the first gear 844 of the first bidirectional clutch 84 in the first drive transmission unit 8B, the driving force transmitted to the first gear 844 is transmitted to the second gear 845, causing the first gear 844 and the second gear 845 to rotate counterclockwise. As the second gear 845 rotates counterclockwise, the driving force is transmitted to the roller gear 72A and the intermediate discharge roller 72a, causing the roller gear 72A and the intermediate discharge roller 72a to rotate clockwise.

[0111] 6, in which the roller gear 72A and the intermediate discharge roller 72a rotate in the first state, is the first direction. That is, the roller gear 72A and the intermediate discharge roller 72a rotate in the first direction in the first state.

[0112] When roller gear 72A rotates in the first direction, i.e., clockwise, the driving force from roller gear 72A is transmitted to fourth gear 855, which meshes with roller gear 72A. However, the driving force from roller gear 72A transmitted to fourth gear 855 is not transmitted to third gear 854, and therefore third gear 854, which meshes with external teeth 811 of internal gear 81, is held stationary.

[0113] As shown in Figure 6(b), when the solenoid 89 is turned on by the control unit 90, the switching unit 8D causes the solenoid 89 to move the clutch lever 87 from the first position to the second position, so that the first engagement claw 871 engages with the planetary gear carrier 83 to stop the rotation of the planetary gear carrier 83, and the second engagement claw 872 moves away from the internal gear 81 to enter a second state in which the internal gear 81 can rotate.

[0114] In the second state, the driving force from the motor 91, which rotates in the counterclockwise direction, which is the same direction as in the first state, is transmitted to the sun gear 80. When the sun gear 80 rotates clockwise, the internal gear 81 rotates counterclockwise and the driving force is output from the internal gear 81 to the second driving force transmission unit 8E. In this way, the internal gear 81 rotates in the direction opposite to the rotation direction of the sun gear 80 (see R4 in FIG. 4). On the other hand, because the rotation of the planetary gear carrier 83 is stopped by the first engagement pawl 871, the driving force is not output from the planetary gear carrier 83 to the first driving force transmission unit 8B.

[0115] When the driving force output from the internal gear 81 is transmitted to the third gear 854 of the second bidirectional clutch 85 of the second driving force transmission unit 8E, the driving force transmitted to the third gear 854 is then transmitted to the fourth gear 855. In this case, the third gear 854 and the fourth gear 855 rotate clockwise. As the fourth gear 855 rotates clockwise, the driving force is transmitted to the roller gear 72A and the intermediate discharge roller 72a. In this case, the roller gear 72A and the intermediate discharge roller 72a rotate counterclockwise.

[0116] 6, in which the roller gear 72A and the intermediate discharge roller 72a rotate in the second state, is the second direction. That is, the roller gear 72A and the intermediate discharge roller 72a rotate in the second direction in the second state.

[0117] When roller gear 72A rotates in the second direction, i.e., counterclockwise, the driving force from roller gear 72A is transmitted to second gear 845 of first bidirectional clutch 84, which meshes with roller gear 72A. However, the driving force from roller gear 72A transmitted to second gear 845 is not transmitted to first gear 844, and therefore first gear 844, which meshes with carrier gear 831 of planetary gear carrier 83, is held stationary.

[0118] In this way, the switching unit 8D can switch between a first state in which the intermediate discharge roller 72a rotates in a first direction by outputting the driving force from the planetary gear carrier 83, which is the first output gear, to the first drive transmission unit 8B, and not outputting the driving force from the internal gear 81, which is the second output gear, to the second drive transmission unit 8E, and a second state in which the intermediate discharge roller 72a rotates in a second direction by not outputting the driving force from the planetary gear carrier 83 to the first drive transmission unit 8B, and outputting the driving force from the internal gear 81 to the second drive transmission unit 8E.

[0119] The switching mechanism 8-1 can also switch the rotation direction of the intermediate discharge roller 72a without switching the rotation direction of the motor 91, thereby preventing a decrease in throughput during printing in the image forming apparatus 1. Furthermore, the motor 91 that is the drive source for the intermediate discharge roller 72a can be shared with the motor 91 that is the drive source for the other drive units, thereby reducing costs.

[0120] Furthermore, in the switching mechanism 8-1, the sun gear 80 is used as the input gear to which the driving force from the motor 91 is transmitted, the planetary gear carrier 83 is used as the first output gear capable of outputting driving force, and the internal gear 81 is used as the second output gear capable of outputting driving force; however, when the sun gear 80 is used as the input gear, it is also possible to use the internal gear 81 as the first output gear and the planetary gear carrier 83 as the second output gear.

[0121] When the internal gear 81 is used as the first output gear and the planetary gear carrier 83 is used as the second output gear, the external teeth 811 of the internal gear 81 mesh with the first gear 844 of the first bidirectional clutch 84, and the carrier gear 831 of the planetary gear carrier 83 meshes with the third gear 854 of the second bidirectional clutch 85. In addition, the first engagement pawl 871 of the clutch lever 87 engages with the external teeth 811 of the internal gear 81, and the second engagement pawl 872 of the clutch lever 87 engages with the carrier gear 831 of the planetary gear carrier 83.

[0122] When an internal gear 81 is used as the first output gear and a planetary gear carrier 83 is used as the second output gear, when the switching unit 8D is in the first state, a driving force is output from the internal gear 81, which is the first output gear, to the first drive transmission unit 8B, and the roller gear 72A and the intermediate discharge roller 72a rotate in the first direction, which in this case is the counterclockwise direction in Figure 6.

[0123] In other words, when the sun gear 80 rotates clockwise due to the driving force from the motor 91 rotating counterclockwise, the internal gear 81, which is the first output gear, rotates counterclockwise, the opposite direction to the sun gear 80, and the first gear 844 and second gear 845 of the first bidirectional clutch 84 rotate clockwise, so that the roller gear 72A and intermediate discharge roller 72a rotate counterclockwise.

[0124] Also, when the switching unit 8D is in the second state, a driving force is output from the planetary gear carrier 83, which is the second output gear, to the second drive transmission unit 8E, causing the roller gear 72A and the intermediate discharge roller 72a to rotate in the second direction, which in this case is the clockwise direction in Figure 6.

[0125] In other words, when the sun gear 80 rotates clockwise due to the driving force from the motor 91 rotating counterclockwise, the planetary gear carrier 83, which is the second output gear, rotates at a reduced speed in the clockwise direction, which is the same direction as the sun gear 80, and the third gear 854 and fourth gear 855 of the second bidirectional clutch 85 rotate counterclockwise, so that the roller gear 72A and intermediate discharge roller 72a rotate clockwise.

[0126] In this way, when the sun gear 80 is used as the input gear, one of the planetary gear carrier 83 and the internal gear 81 is used as the first output gear, and the other of the planetary gear carrier 83 and the internal gear 81 is used as the second output gear, the rotation direction when the first output gear outputs driving force can be opposite to the rotation direction when the second output gear outputs driving force. Also, the rotation speed of the first output gear can be made different from the rotation speed of the second output gear.

[0127] Furthermore, in the switching mechanism 8-1, the first drive transmission unit 8B is composed only of the first bidirectional clutch 84, and the second drive transmission unit 8E is composed only of the second bidirectional clutch 85. Therefore, there is no need to provide idle gears in the first drive transmission unit 8B and the second drive transmission unit 8E, and it is possible to switch the rotation direction of the intermediate discharge roller 72a while keeping the first drive transmission unit 8B and the second drive transmission unit 8E simple in configuration.

[0128] However, the first drive transmission unit 8B and the second drive transmission unit 8E may be configured to have one or more idle gears, as long as the intermediate discharge roller 72a rotates in a first direction when the switching unit 8D is in a first state, and the intermediate discharge roller 72a rotates in a second direction opposite to the first direction when the switching unit 8D is in a second state.

[0129] [Third embodiment of switching mechanism] 8 and 9, a switching mechanism 8-2 according to the third embodiment uses the internal gear 81 of the planetary differential gear 8A as an input gear, the planetary gear carrier 83 as a first output gear, and the sun gear 80 as a second output gear, which differs from the switching mechanism 8 that uses the planetary gear carrier 83 of the planetary differential gear 8A as an input gear, the sun gear 80 as the first output gear, and the internal gear 81 as the second output gear. Also, like the switching mechanism 8-1, the switching mechanism 8-2 differs from the switching mechanism 8 in that it includes a second drive transmission unit 8E instead of the second drive transmission unit 8C.

[0130] The second drive transmission unit 8E has a second bidirectional clutch 85. The second drive transmission unit 8E is composed of the second bidirectional clutch 85 alone.

[0131] In the switching mechanism 8-2, the external teeth 811 of the internal gear 81, which is the input gear, mesh with the drive gear 92. The carrier gear 831 of the planetary gear carrier 83, which is the first output gear, meshes with the first gear 844 of the first bidirectional clutch 84.

[0132] The first sun gear 802 of the sun gear 80, which is the second output gear, is meshed with the third gear 854 of the second bidirectional clutch 85. The fourth gear 855 of the second bidirectional clutch 85 is meshed with the roller gear 72A. The fourth shaft 853 of the second bidirectional clutch 85 is connected to the intermediate discharge roller 72a via the fourth gear 855 and the roller gear 72A.

[0133] Other configurations of the switching mechanism 8-2 are the same as those of the switching mechanism 8, and therefore description thereof will be omitted.

[0134] [Operation of switching mechanism 8-2] As shown in Figure 8(a), when the solenoid 89 is off, the switching unit 8D biases the clutch lever 87 to a first position using a tension spring 88, thereby causing the first engagement claw 871 to move away from the planetary gear carrier 83, allowing the planetary gear carrier 83 to rotate, and the second engagement claw 872 to engage with the sun gear 80, stopping the rotation of the sun gear 80, thereby entering a first state.

[0135] In the first state, when the driving force from the motor 91 rotating counterclockwise is transmitted to the internal gear 81 and the internal gear 81 rotates clockwise, the planetary gear carrier 83 rotates clockwise and the driving force is output from the planetary gear carrier 83 to the first drive transmission unit 8B. In this case, the planetary gear carrier 83 rotates in the same direction as the rotation direction of the internal gear 81 at a reduced speed (see R5 in FIG. 4). On the other hand, because the rotation of the sun gear 80 is stopped by the second engagement claw 872, the driving force is not output from the sun gear 80 to the second drive transmission unit 8E.

[0136] When the driving force output from the planetary gear carrier 83 is transmitted to the first gear 844 of the first bidirectional clutch 84 in the first drive transmission unit 8B, the driving force transmitted to the first gear 844 is transmitted to the second gear 845, causing the first gear 844 and the second gear 845 to rotate counterclockwise. As the second gear 845 rotates counterclockwise, the driving force is transmitted to the roller gear 72A and the intermediate discharge roller 72a, causing the roller gear 72A and the intermediate discharge roller 72a to rotate clockwise.

[0137] 8, in which the roller gear 72A and the intermediate discharge roller 72a rotate in the first state, is the first direction. That is, the roller gear 72A and the intermediate discharge roller 72a rotate in the first direction in the first state.

[0138] When roller gear 72A rotates in the first direction, that is, clockwise, the driving force from roller gear 72A is transmitted to fourth gear 855, which meshes with roller gear 72A. However, the driving force from roller gear 72A transmitted to fourth gear 855 is not transmitted to third gear 854, and therefore third gear 854, which meshes with first sun gear 802 of sun gear 80, is held stationary.

[0139] As shown in Figure 8(b), when the solenoid 89 is turned on by the control unit 90, the switching unit 8D causes the solenoid 89 to move the clutch lever 87 from the first position to the second position, so that the first engagement claw 871 engages with the planetary gear carrier 83 to stop the rotation of the planetary gear carrier 83, and the second engagement claw 872 moves away from the sun gear 80 to enter a second state in which the sun gear 80 can rotate.

[0140] In the second state, the driving force from the motor 91, which rotates in the counterclockwise direction, which is the same direction as in the first state, is transmitted to the internal gear 81. When the internal gear 81 rotates clockwise, the sun gear 80 rotates counterclockwise and the driving force is output from the sun gear 80 to the second driving force transmission unit 8E. In this way, the sun gear 80 rotates in the direction opposite to the rotation direction of the internal gear 81 (see R6 in FIG. 4). On the other hand, because the rotation of the planetary gear carrier 83 is stopped by the first engagement pawl 871, the driving force is not output from the planetary gear carrier 83 to the first driving force transmission unit 8B.

[0141] When the driving force output from the sun gear 80 is transmitted to the third gear 854 of the second bidirectional clutch 85 of the second driving force transmission unit 8E, the driving force transmitted to the third gear 854 is then transmitted to the fourth gear 855. In this case, the third gear 854 and the fourth gear 855 rotate clockwise. As the fourth gear 855 rotates clockwise, the driving force is transmitted to the roller gear 72A and the intermediate discharge roller 72a. In this case, the roller gear 72A and the intermediate discharge roller 72a rotate counterclockwise.

[0142] 8, in which the roller gear 72A and the intermediate discharge roller 72a rotate in the second state, is the second direction. That is, the roller gear 72A and the intermediate discharge roller 72a rotate in the second direction in the second state.

[0143] When roller gear 72A rotates in the second direction, i.e., counterclockwise, the driving force from roller gear 72A is transmitted to second gear 845 of first bidirectional clutch 84, which meshes with roller gear 72A. However, the driving force from roller gear 72A transmitted to second gear 845 is not transmitted to first gear 844, and therefore first gear 844, which meshes with carrier gear 831 of planetary gear carrier 83, is held stationary.

[0144] In this way, the switching unit 8D can switch between a first state in which the intermediate discharge roller 72a rotates in a first direction by outputting the driving force from the planetary gear carrier 83, which is the first output gear, to the first drive transmission unit 8B, and not outputting the driving force from the sun gear 80, which is the second output gear, to the second drive transmission unit 8E, and a second state in which the intermediate discharge roller 72a rotates in a second direction by not outputting the driving force from the planetary gear carrier 83 to the first drive transmission unit 8B, and outputting the driving force from the sun gear 80 to the second drive transmission unit 8E.

[0145] The switching mechanism 8-2 can also switch the rotation direction of the intermediate discharge roller 72a without switching the rotation direction of the motor 91, thereby preventing a decrease in throughput during printing in the image forming apparatus 1. Furthermore, the motor 91 that is the drive source for the intermediate discharge roller 72a can be shared with the motor 91 that is the drive source for the other drive units, thereby reducing costs.

[0146] Furthermore, in the switching mechanism 8-2, an internal gear 81 is used as the input gear to which the driving force from the motor 91 is transmitted, a planetary gear carrier 83 is used as the first output gear capable of outputting driving force, and a sun gear 80 is used as the second output gear capable of outputting driving force; however, when an internal gear 81 is used as the input gear, it is also possible to use the sun gear 80 as the first output gear and the planetary gear carrier 83 as the second output gear.

[0147] When the sun gear 80 is used as the first output gear and the planetary gear carrier 83 is used as the second output gear, the first sun gear 802 of the sun gear 80 meshes with the first gear 844 of the first bidirectional clutch 84, and the carrier gear 831 of the planetary gear carrier 83 meshes with the third gear 854 of the second bidirectional clutch 85. In addition, the first engagement pawl 871 of the clutch lever 87 engages with the first sun gear 802 of the sun gear 80, and the second engagement pawl 872 of the clutch lever 87 engages with the carrier gear 831 of the planetary gear carrier 83.

[0148] When the sun gear 80 is used as the first output gear and the planetary gear carrier 83 is used as the second output gear, when the switching unit 8D is in the first state, a driving force is output from the sun gear 80, which is the first output gear, to the first drive transmission unit 8B, and the roller gear 72A and the intermediate discharge roller 72a rotate in the first direction, which in this case is the counterclockwise direction in Figure 8.

[0149] In other words, when the internal gear 81 rotates clockwise due to the driving force from the motor 91 rotating counterclockwise, the sun gear 80, which is the first output gear, rotates counterclockwise, the opposite direction to the internal gear 81, and the first gear 844 and second gear 845 of the first bidirectional clutch 84 rotate clockwise, so that the roller gear 72A and intermediate discharge roller 72a rotate counterclockwise.

[0150] Furthermore, when the switching unit 8D is in the second state, a driving force is output from the planetary gear carrier 83, which is the second output gear, to the second drive transmission unit 8E, causing the roller gear 72A and the intermediate discharge roller 72a to rotate in the second direction, which in this case is the clockwise direction in Figure 8.

[0151] In other words, when the internal gear 81 rotates clockwise due to the driving force from the motor 91 rotating counterclockwise, the planetary gear carrier 83, which is the second output gear, rotates at a reduced speed in the clockwise direction, which is the same direction as the internal gear 81, and the third gear 854 and fourth gear 855 of the second bidirectional clutch 85 rotate counterclockwise, so that the roller gear 72A and intermediate discharge roller 72a rotate clockwise.

[0152] In this way, when the internal gear 81 is used as the input gear, one of the sun gear 80 and the planetary gear carrier 83 is used as the first output gear, and the other of the sun gear 80 and the planetary gear carrier 83 is used as the second output gear, the rotation direction when the first output gear outputs driving force can be opposite to the rotation direction when the second output gear outputs driving force. Also, the rotation speed of the first output gear can be made different from the rotation speed of the second output gear.

[0153] Furthermore, in the switching mechanism 8-2, as in the case of the switching mechanism 8-1, there is no need to provide idle gears in the first drive transmission unit 8B and the second drive transmission unit 8E, and it is possible to switch the rotation direction of the intermediate discharge roller 72a while keeping the first drive transmission unit 8B and the second drive transmission unit 8E in a simple configuration. [Explanation of symbols]

[0154] 1. Image forming device 5. Image forming unit 6 Fixing unit 8 Switching mechanism 8A planetary differential gear 8B First drive transmission part 8C, 8E Second drive transmission section 8D switching section 42 Transfer roller 51a Photosensitive drum 72a Intermediate discharge roller 72A Roller Gear 73a Discharge roller 80 Sun Gear 81 Internal gear 82 Planetary gear 83 Planetary gear carrier 84 First two-way clutch 85 Second two-way clutch 86 Idle Gear 87 Clutch lever 88 Tension Spring 89 Solenoid 90 Control Unit 91 Motor 842 1st axis 843 2nd axis 844 1st Gear 845 2nd Gear 852 3rd axis 853 4th axis 854 3rd Gear 855 4th Gear 871 First engaging claw 872 Second engaging claw S seat

Claims

1. an image forming unit that forms an image on the conveyed sheet; a reversing roller located downstream of the image forming unit in a sheet conveying direction and rotatable in a first direction and a second direction opposite to the first direction; a motor that is a drive source for the reversing roller; a switching mechanism that switches the rotation direction of the reversing roller while the motor is rotating in one direction, The switching mechanism includes: a planetary differential gear including an input gear that rotates when a driving force from the motor is transmitted thereto, a first output gear and a second output gear that are capable of outputting a driving force, and a planetary gear that transmits the driving force from the input gear to the first output gear and the second output gear; a first drive transmission unit connecting the first output gear and the reversing roller, the first drive transmission unit including a first clutch that transmits a drive force to the reversing roller when the drive force is input from the first output gear and does not transmit the drive force to the first output gear when the drive force is input from the reversing roller; a second drive transmission unit connecting the second output gear and the reversing roller, the second drive transmission unit having a second clutch that transmits a drive force to the reversing roller when the drive force is input from the second output gear and does not transmit the drive force to the second output gear when the drive force is input from the reversing roller; a switching unit that switches between a first state in which a driving force is output from the first output gear to the first power transmission unit and a second state in which a driving force is not output from the first output gear to the second power transmission unit, thereby rotating the reversing roller in the first direction, and a second state in which a driving force is not output from the first output gear to the first power transmission unit and a driving force is output from the second output gear to the second power transmission unit, thereby rotating the reversing roller in the second direction; An image forming apparatus comprising:

2. the first clutch is a bidirectional clutch that has a first shaft connected to the first output gear and a second shaft connected to the reversing roller, and that transmits the driving force from the first output gear transmitted to the first shaft to the second shaft, but does not transmit the driving force from the reversing roller transmitted to the second shaft to the first shaft; 2. The image forming apparatus according to claim 1, wherein the second clutch is a bidirectional clutch having a third shaft connected to the second output gear and a fourth shaft connected to the reversing roller, which transmits the driving force from the second output gear transmitted to the third shaft to the fourth shaft, but does not transmit the driving force from the reversing roller transmitted to the fourth shaft to the third shaft.

3. 3. The image forming apparatus according to claim 1, wherein the switching unit selectively stops one of the rotation of the first output gear and the rotation of the second output gear.

4. The switching unit is a clutch lever having a first engagement pawl that engages with the first output gear to stop rotation of the first output gear, and a second engagement pawl that engages with the second output gear to stop rotation of the second output gear, 4. The image forming apparatus according to claim 3, further comprising a clutch lever movable between a first position in which the first engagement claw is spaced apart from the first output gear and the second engagement claw is engaged with the second output gear, and a second position in which the first engagement claw is engaged with the first output gear and the second engagement claw is spaced apart from the second output gear.

5. The switching unit is a tension spring that biases the clutch lever to the first position; a solenoid that moves the clutch lever from the first position toward the second position, Further, a control unit is provided to control the operation of the solenoid.

5. The image forming apparatus according to claim 4, wherein the control unit turns on the solenoid when the solenoid moves the clutch lever from the first position toward the second position.

6. the input gear is a planetary gear carrier that rotatably holds the planetary gear, the first output gear is one of a sun gear and an internal gear that meshes with the planetary gear, 6. The image forming apparatus according to claim 1, wherein the second output gear is the other of the sun gear and the internal gear.

7. Further provided is a reversing roller gear that rotates integrally with the reversing roller, the first drive transmission unit is composed of only the first clutch, the second drive transmission unit is composed of the second clutch and an idle gear that meshes with the reverse roller gear, the first clutch is a first bidirectional clutch that has a first gear that meshes with the first output gear and a second gear that meshes with the reversing roller gear, and that transmits the driving force from the first output gear that has been transmitted to the first gear to the second gear, but does not transmit the driving force from the reversing roller that has been transmitted to the second gear to the first gear; 7. The image forming apparatus according to claim 6, wherein the second clutch is a second bidirectional clutch having a third gear that meshes with the second output gear and a fourth gear that meshes with the idle gear, and which transmits the driving force from the second output gear transmitted to the third gear to the fourth gear, but does not transmit the driving force from the reversing roller transmitted to the fourth gear to the third gear.

8. the input gear is one of a sun gear and an internal gear that meshes with the planetary gear; the first output gear is one of the other of the sun gear and the internal gear, and a planetary gear carrier that rotatably holds the planetary gear; 6. The image forming apparatus according to claim 1, wherein the second output gear is the other of the sun gear and the internal gear, and the other of the planetary gear carrier.

9. Further provided is a reversing roller gear that rotates integrally with the reversing roller, the first drive transmission unit is composed of only the first clutch, the second power transmission unit is composed of only the second clutch, the first clutch is a first bidirectional clutch that has a first gear that meshes with the first output gear and a second gear that meshes with the reversing roller gear, and that transmits the driving force from the first output gear that has been transmitted to the first gear to the second gear, but does not transmit the driving force from the reversing roller that has been transmitted to the second gear to the first gear; 9. The image forming apparatus according to claim 8, wherein the second clutch is a second bidirectional clutch having a third gear that meshes with the second output gear and a fourth gear that meshes with the reversing roller gear, and which transmits the driving force from the second output gear transmitted to the third gear to the fourth gear, but does not transmit the driving force from the reversing roller transmitted to the fourth gear to the third gear.

10. the image forming unit has a photosensitive drum and a transfer roller, a fixing unit provided downstream of the image forming unit in a sheet conveying direction, the fixing unit fixing the toner image formed on the sheet to the sheet; 10. The image forming apparatus according to claim 1, wherein the reversing roller is located downstream of the fixing unit in the sheet conveying direction.

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