Sheet conveying device and image forming apparatus

Abstract

To provide a sheet conveying device capable of performing smooth jam processing without installing a complicated mechanism in driving force transmission means.SOLUTION: A sheet conveying device T of the invention includes a motor 4, a pressurizing roller 62, and a one-way clutch 90. The one-way clutch 90 has: a fixed shaft 91; an input gear 92 that can be rotated by the driving force of the motor 4; an output gear 94 that is connected to the pressurizing roller 62 and can transmit the driving force to the pressurizing roller 62; and a transmission gear 93 that is movable between a first position separated from the output gear 94 and a second position connected to the output gear 94. The input gear 92 rotates in a first direction W1 to move the transmission gear 93 from the first position to the second position and transmit a driving force in the first direction to the output gear 94, and rotates in a second direction W2 to move the transmission gear 93 from the second position to the first position and break the transmission of driving force to the output gear 94, thereby the transmission gear 93 in the first position is not connected to the output gear 94 when the output gear 94 is rotated.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a sheet conveying device and an image forming apparatus. [Background technology]

[0002] Conventionally, there is known a one-way clutch that transmits rotational force in only one direction, as described in Patent Document 1. In a sheet conveying device provided in an image forming apparatus such as a laser printer, such a one-way clutch is incorporated into a drive train that conveys a sheet and transmits driving force from a motor to a fixing device that fixes an image on the sheet.

[0003] However, in such a fixing unit, a sheet may get stuck between the fixing rollers, and when a jam occurs, it is necessary to manually remove the jammed sheet. If the fixing roller and the motor are connected during jam removal, the rotation of the fixing roller is subjected to a load from the motor and drive train, which may hinder smooth jam removal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-87611 [Patent Document 2] Japanese Patent Application Publication No. 3-148684 Summary of the Invention [Problem to be solved by the invention]

[0005] To address the above-mentioned problem, Patent Document 2 discloses a configuration in which a drive force transmission means that transmits drive force from a drive source to the fixation roller includes a one-way clutch and a drive force transmission release mechanism that transmits and releases drive force between the fixation roller and the drive source, thereby enabling the fixation roller to be disconnected from the drive source when clearing a jam. However, providing such a drive force transmission release mechanism may complicate the configuration of the drive force transmission means.

[0006] Therefore, the present invention provides a sheet transporting device and an image forming apparatus that can perform smooth jam removal without providing a complex mechanism in the drive force transmission means. [Means for solving the problem]

[0007] The sheet conveying device and image forming apparatus that solve the above problems have the following features.

[0008] That is, the sheet conveying device includes a drive source, a roller for conveying a sheet, and a one-way clutch capable of transmitting a drive force from the drive source to the roller, and the one-way clutch includes a fixed shaft, an input gear rotatably supported on the fixed shaft and rotatable by receiving a drive force from the drive source, an output gear rotatably supported on the fixed shaft, connected to the roller, and capable of transmitting the drive force to the roller, and a transmission gear supported on the fixed shaft, which, when engaged with the input gear, moves between a first position where it is separated from the output gear and a second position where it is connected to the output gear. and a transmission gear that is movable in the axial direction of a fixed shaft, wherein the input gear receives driving force from the driving source and rotates in a first direction, thereby moving the transmission gear from the first position to the second position, and transmits the driving force in the first direction to the output gear via the transmission gear, and receives driving force from the driving source and rotates in a second direction opposite to the first direction, thereby moving the transmission gear from the second position to the first position, and cancels the transmission of the driving force to the output gear, and when the output gear rotates while positioned at the first position, the transmission gear is not connected to the output gear.

[0009] With this configuration, when the transmission gear is in the first position, the transmission gear and the output gear are separated and not connected, so that even if the output gear is rotated, the transmission gear does not rotate with the output gear and the output gear rotates freely. Therefore, the output gear connected to the roller is not subjected to the load of the drive source and the drive force transmission means between the drive source and the input gear. This makes it possible to easily rotate the roller when clearing a jammed sheet, and to smoothly clear the jammed sheet, without providing a complex mechanism such as a one-way clutch or a drive force transmission release mechanism in the drive force transmission means that transmits the drive force from the drive source to the roller.

[0010] Furthermore, when the roller rotates with the transmission gear positioned at the first position, the roller is not coupled to the driving source.

[0011] As a result, when the transmission gear is in the first position, the one-way clutch cuts off the transmission of driving force from the drive source to the roller, so that even when the roller is rotated during jam clearance, the load of the drive source is not placed on the roller, allowing for smooth jam clearance.

[0012] Furthermore, the fixed shaft supports the transmission gear located at the first position with a first sliding resistance of a predetermined magnitude between the fixed shaft and the transmission gear, and supports the transmission gear located at the second position with a second sliding resistance between the fixed shaft and the transmission gear that is smaller than the first sliding resistance, and when the input gear rotates in the first direction, the transmission gear located at the first position is moved from the first position to the second position by the input gear by maintaining a state in which rotation relative to the fixed shaft is suppressed by the first sliding resistance, and the transmission gear located at the second position rotates together with the input gear relative to the fixed shaft against the second sliding resistance when the input gear rotates in the first direction.

[0013] As a result, when the input gear rotates in the first direction, the first sliding resistance prevents the transmission gear located in the first position from rotating at the same speed as the input gear, thereby enabling movement from the first position to the second position. Furthermore, when the input gear rotates in the first direction, the transmission gear located in the second position rotates together with the input gear against the second sliding resistance, thereby enabling transmission of driving force from the transmission gear to the output gear.

[0014] The fixed shaft also includes a first shaft portion having a first outer diameter and a second shaft portion having a second outer diameter smaller than the first outer diameter, and the first shaft portion supports the transmission gear positioned at the first position with the first sliding resistance, and the second shaft portion supports the transmission gear positioned at the second position with the second sliding resistance.

[0015] In this way, by making the first outer diameter of the first shaft portion supporting the transmission gear located in the first position different from the second outer diameter of the second shaft portion supporting the transmission gear located in the second position, the magnitude of the first sliding resistance and the magnitude of the second sliding resistance are changed, thereby simplifying the configuration of the one-way clutch.

[0016] Further, the transmission gear is positioned between the input gear and the output gear in the axial direction, and the input gear has input teeth to which the driving force is input, a transmission portion engageable with the transmission gear, and an inclined cam surface facing the output gear in the axial direction, the inclined cam surface extending along the circumferential direction and positioned closer to the output gear in the axial direction on the upstream side in the first direction than on the downstream side, and the transmission gear has a transmitted portion engageable with the transmission portion when the input gear rotates in the first direction, an abutment surface that abuts against the inclined cam surface when the input gear rotates in the first direction, and a ratchet pawl that protrudes toward the output gear in the axial direction, and the output gear has a ratchet recess that engages with the ratchet pawl when the transmission gear rotates in the first direction and does not engage with the ratchet pawl when the transmission gear rotates in the second direction, and output teeth connected to the roller.

[0017] This makes it possible, with a simple configuration, to switch from a state in which transmission of the driving force to the output gear is released to a state in which the driving force is transmitted to the output gear via the transmission gear.

[0018] The input gear also has an inclined engagement surface facing the opposite side to the output gear in the axial direction, extending along the circumferential direction, with the downstream side in the second direction being closer to the output gear in the axial direction than the upstream side, and the transmission gear has an engagement claw that engages with the inclined engagement surface when the input gear rotates in the second direction.

[0019] As a result, by rotating the input gear in the second direction, the inclined engagement surface and the engagement pawl are engaged with each other, and the transmission gear can be moved from the second position to the first position.

[0020] The apparatus further includes a control unit, and when the control unit determines that a sheet jam has occurred, the control unit drives the drive source in a direction in which the input gear rotates in the second direction.

[0021] As a result, when a sheet jam occurs, the control unit drives the drive source to rotate the input gear in the second direction, thereby moving the transmission gear from the second position to the first position and separating the transmission gear from the output gear. Therefore, even when the roller is rotated during jam clearance, the load of the drive source is not applied to the roller, allowing for smooth jam clearance.

[0022] The image forming apparatus also includes a sheet conveying device according to any one of claims 1 to 7, an image forming unit that forms an image on a sheet, and a fixing unit that conveys and heats the sheet sent from the image forming unit, and the roller is provided in the fixing unit.

[0023] This allows the sheet to be smoothly removed from the fixing unit when a sheet jam occurs in the fixing unit.

[0024] The fixing unit has a flat heater, and the roller is a pressure roller that heats and presses the sheet together with the heater.

[0025] When the fixing unit has a flat heater, the rotational torque of the pressure roller tends to be large, but by moving the transmission gear to the first position where the transmission gear and the output gear are separated, the load on the pressure roller does not increase, allowing for smooth jam handling. [Effects of the Invention]

[0026] According to the present invention, the roller can be easily rotated when clearing a jammed sheet without providing a complex mechanism in the driving force transmission means that transmits the driving force from the driving source to the roller, and the jammed sheet can be cleared smoothly. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 2 is a central cross-sectional view showing the image forming apparatus. [Figure 2] FIG. [Figure 3] FIG. 2 is a perspective view showing a heating unit and a pressure roller of the fixing unit. [Figure 4] FIG. [Figure 5] FIG. 2 is an exploded perspective view showing a one-way clutch. [Figure 6] 1A is a side cross-sectional view showing the one-way clutch when the transmission gear is in a first position, and FIG. 1B is a side cross-sectional view showing the one-way clutch when the transmission gear is in a second position. [Figure 7] FIG. 4 is a rear view showing the fixed shaft of the one-way clutch. [Figure 8] FIG. 4 is a perspective view showing an input gear of a one-way clutch. [Figure 9] FIG. 1 is an exploded perspective view of a one-way clutch with the inclined engagement surface of the input gear visible. [Figure 10] FIG. 4 is a perspective view showing a transmission gear of a one-way clutch. [Figure 11] FIG. 4 is a perspective view showing an output gear of the one-way clutch. [Figure 12] FIG. 2 is a block diagram showing a control unit to which a motor and a paper discharge sensor are connected. DETAILED DESCRIPTION OF THE INVENTION

[0028] Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0029] [Image forming device] An image forming apparatus 1 shown in FIG. 1 is an embodiment of an image forming apparatus equipped with a sheet conveying device according to the present invention, and is a laser printer that forms an image on a sheet S by electrophotography.

[0030] In the following description, the right side in Fig. 1 is defined as the front side of the image forming apparatus 1, the left side in Fig. 1 is defined as the rear 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.

[0031] The image forming apparatus 1 includes an apparatus main body 2, a paper feed section 3, an image forming section 5, a fixing device 6, a paper discharge section 7, and a sheet conveying device T.

[0032] The apparatus main body 2 accommodates a paper feed section 3, an image forming section 5, a fixing device 6, a paper discharge section 7, and a sheet transport device T.

[0033] The paper feed unit 3 includes a paper feed tray 10 that supports the sheet S, a sheet conveying unit 30, a conveying roller pair 34, and a registration roller pair 35. The paper feed unit 3 is disposed at the bottom of the apparatus main body 2, and conveys the sheet S supported on the paper feed tray 10 to the image forming unit 5. The image forming apparatus 1 has a conveying path P for the sheet S that runs from the paper feed unit 3 to the paper discharge unit 7 via the image forming unit 5.

[0034] The sheet feed tray 10 has a pressure plate 12 and a pressing plate 13. The pressure plate 12 is a plate-shaped member that supports the sheets S from below. The pressure plate 12 is rotatable around a pivot point 12a at its rear end, and by rotating around the pivot point 12a, the pressure plate 12 can be raised and lowered between a lowered position and an upper position. The pressing plate 13 is located below the pressure plate 12, and can raise and lower the pressure plate 12 between the lowered position and the upper position.

[0035] The sheet conveying unit 30 is a conveying mechanism that separates and picks up the sheets S supported on the paper feed tray 10 one by one and conveys them toward the image forming unit 5, and is equipped with a paper feed roller 31, a separation roller 32, and a separation pad 33.

[0036] The paper feed roller 31 is a roller for sending the sheet S supported on the paper feed tray 10 toward the separation roller 32. The separation roller 32 is disposed downstream of the paper feed roller 31 in the sheet conveying direction, and the separation pad 33 is disposed opposite the separation roller 32 and is urged toward the separation roller 32.

[0037] The sheets S sent out by the paper feed roller 31 toward the separation roller 32 are separated one by one between the separation roller 32 and the separation pad 33. The separated sheets S are sent out to a conveying path P.

[0038] The sheet S sent to the conveying path P is conveyed toward the image forming unit 5 by a pair of conveying rollers 34 and a pair of registration rollers 35. The pair of registration rollers 35 regulates the movement of the leading edge of the sheet S being conveyed, temporarily stops the sheet S, and then conveys the sheet S toward the image forming unit 5 at a predetermined timing.

[0039] The image forming unit 5 is disposed downstream of the paper feed unit 3 in the sheet transport direction, and forms an image on the sheet S transported from the paper feed unit 3. The image forming unit 5 includes a process cartridge 50 that transfers an image onto the surface of the sheet S transported from the paper feed unit 3, and an exposure unit 56 that exposes the surface of a photosensitive drum 54 in the process cartridge 50.

[0040] The process cartridge 50 is disposed above the paper feed unit 3 in the device main body 2, and includes a developer storage chamber 51, a supply roller 52, a developing roller 53, a photosensitive drum 54, a transfer roller 55, and the like.

[0041] The exposure unit 56 is equipped with a laser diode, a polygon mirror, a lens, a reflecting mirror, etc., and exposes the surface of the photosensitive drum 54 by irradiating the photosensitive drum 54 with laser light based on image data input to the image forming apparatus 1.

[0042] Toner that will become the developer is stored in the developer storage chamber 51. The toner stored in the developer storage chamber 51 is stirred by a stirring member (not shown) and sent to the supply roller 52. The supply roller 52 further supplies the toner sent from the developer storage chamber 51 to the developing roller 53.

[0043] The developing roller 53 is disposed in close contact with the supply roller 52, and carries toner supplied from the supply roller 52 and positively charged by a sliding contact member (not shown). A developing bias is applied to the developing roller 53 by a bias application means (not shown).

[0044] The photosensitive drum 54 is disposed adjacent to the developing roller 53. The surface of the photosensitive drum 54 is uniformly charged by a charger (not shown) and then exposed by the exposure unit 56. The exposed portion of the photosensitive drum 54 has a lower potential than the other portions, and an electrostatic latent image based on the image data is formed on the photosensitive drum 54. Then, positively charged toner is supplied from the developing roller 53 to the surface of the photosensitive drum 54 on which the electrostatic latent image has been formed, thereby visualizing the electrostatic latent image into a toner image.

[0045] The transfer roller 55 is disposed opposite the photosensitive drum 54, and a transfer bias is applied to it by a bias application means (not shown). With the transfer bias applied to the surface of the transfer roller 55, the sheet S is conveyed while being sandwiched between the photosensitive drum 54 on which the toner image has been formed and the transfer roller 55, whereby the toner image formed on the surface of the photosensitive drum 54 is transferred to the surface of the sheet S. The sheet S on which the toner image has been transferred is conveyed to the fixing device 6.

[0046] The fixing device 6 includes a heating unit 61 and a pressure roller 62, and fixes the image transferred onto the sheet S by the process cartridge 50. The heating unit 61 is heated by supplying power from a power source (not shown). The pressure roller 62 is disposed opposite the heating unit 61. One of the heating unit 61 and the pressure roller 62 is biased toward the other by a biasing mechanism (not shown), and the heating unit 61 and the pressure roller 62 are in close contact with each other.

[0047] When the sheet S onto which the toner image has been transferred is conveyed to the fixing device 6, the sheet S is conveyed while being sandwiched between the heating unit 61 and the pressure roller 62, and the sheet S is heated, thereby fixing the toner image onto the sheet S. In this way, the fixing device 6 conveys and heats the sheet S sent from the image forming unit 5.

[0048] The paper discharge unit 7 is located downstream of the image forming unit 5 in the sheet transport direction, and discharges the sheet S on which an image has been formed in the image forming unit 5 to the outside of the image forming apparatus 1. The paper discharge unit 7 includes a pair of paper discharge rollers 71 and a paper discharge tray 72. The pair of paper discharge rollers 71 is configured to be able to discharge the sheet S transported from the fixing unit 6 along the transport path P to the outside of the device main body 2. The paper discharge tray 72 is formed on the top surface of the device main body 2, and supports the sheet S discharged to the outside of the device main body 2 by the pair of paper discharge rollers 71.

[0049] [Fuser] 2 and 3, the heating unit 61 of the fixing device 6 includes a heater 611, a holder 612, a stay 613, and a belt 614. The heater 611 is a flat plate-shaped heater extending in the left-right direction. The heater 611 has a first surface 611A and a second surface 611B opposite to the first surface 611A, and the first surface 611A is supported by the holder 612.

[0050] Holder 612 is made of, for example, a resin member, and has a guide surface 612a and a support wall 612b. Guide surface 612a contacts an inner circumferential surface 614a of belt 614 to guide belt 614. Support wall 612b has a support surface 612A that supports heater 611. Support surface 612A of support wall 612b abuts against first surface 611A of heater 611. Stay 613 is a member that supports holder 612, and is formed by bending a plate material that is more rigid than holder 612, such as a steel plate, into a generally U-shaped cross section.

[0051] The belt 614 is an endless belt that is heat-resistant and flexible, and includes a metal tube made of a metal such as stainless steel and a fluororesin layer covering the metal tube. The heater 611, holder 612, and stay 613 are disposed inside the belt 614. The belt 614 is configured to rotate around the heater 611, holder 612, and stay 613. An inner peripheral surface 614a of the belt 614 contacts the heater 611.

[0052] The pressure roller 62 has a metal shaft 62A and an elastic layer 62B that covers the shaft 62A. The pressure roller 62 is pressed against the heater 611 via a belt 614. The pressure roller 62 sandwiches the belt 614 between itself and the heater 611, thereby forming a nip portion NP for heating and pressurizing the sheet S. That is, the pressure roller 62 heats and pressurizes the sheet S together with the heater 611 at the nip portion NP.

[0053] The pressure roller 62 is configured to be rotationally driven by a driving force transmitted from the motor 4 provided in the image forming apparatus 1. When the pressure roller 62 is rotationally driven, the pressure roller 62 rotates the belt 614 due to friction with the belt 614 or the sheet S sandwiched in the nip portion NP. As a result, the sheet S onto which the toner image has been transferred is transported between the pressure roller 62 and the heated belt 614, whereby the toner image is thermally fixed. The pressure roller 62 is an example of a roller that transports a sheet.

[0054] [Sheet transport device] The sheet conveying device T includes a motor 4, a driving force transmission train 8, a pressure roller 62, etc., and conveys the sheet S. The motor 4 is an example of a driving source.

[0055] [Drivetrain] 4, the driving force transmission train 8 is a driving force transmission train for transmitting the driving force from the motor 4 to the pressure roller 62 of the fixing unit 6. The driving force transmission train 8 is disposed at the left end of the apparatus main body 2, and has a motor gear 81, a first idle gear 82, a second idle gear 83, a third idle gear 84, a one-way clutch 90, a fourth idle gear 85, and a pressure roller gear 86.

[0056] The motor gear 81 is fixed to the output shaft 4a of the motor 4, and the first idle gear 82 meshes with the motor gear 81. The second idle gear 83 meshes with the first idle gear 82, and the third idle gear 84 meshes with the second idle gear 83. The input side of the one-way clutch 90 is connected to the third idle gear 84. The fourth idle gear 85 is connected to the output side of the one-way clutch 90. The pressure roller gear 86 meshes with the fourth idle gear 85. The pressure roller gear 86 is fixed to the shaft 62A of the pressure roller 62 so as to be rotatable integrally therewith.

[0057] [One-way clutch] 5 and 6, the one-way clutch 90 is configured to be able to transmit driving force from the motor 4 to the pressure roller 62, and includes a fixed shaft 91, an input gear 92, a transmission gear 93, and an output gear 94. The input gear 92 is the input gear of the one-way clutch 90, and the output gear 94 is the output gear of the one-way clutch 90.

[0058] In the one-way clutch 90, an input gear 92, a transmission gear 93, and an output gear 94 are arranged in this order from left to right. That is, in the axial direction X, the transmission gear 93 is located between the input gear 92 and the output gear 94.

[0059] As shown in FIGS. 5 to 7, the fixed shaft 91 is a long shaft member extending in the left-right direction and has a first shaft portion 911 and a second shaft portion 912. The direction along the left-right direction in which the fixed shaft 91 extends is the axial direction X of the fixed shaft 91. The first shaft portion 911 has a first outer diameter D1, and the second shaft portion 912 has a second outer diameter D2 that is smaller than the first outer diameter D1 (D1>D2). The second shaft portion 912 is formed contiguous to the right of the first shaft portion 911.

[0060] 5, 6, and 8, the input gear 92 is rotatably supported on a first shaft portion 911 of the fixed shaft 91, and is rotatable by receiving a driving force from the motor 4. The input gear 92 is rotatable in a first direction W1 and a second direction W2 opposite to the first direction W1. The input gear 92 has a main body portion 920, an input teeth portion 921, a transmission portion 922, an inclined cam surface 923, and an inclined engagement surface 924.

[0061] The main body 920 is formed of a cylindrical member having a bottom 920a, and the bottom 920a is located at the left end of the main body 920. The input teeth portion 921 is formed in a cylindrical shape that protrudes leftward from the bottom 920a of the main body 920, and input teeth 921a are formed on the outer circumferential surface of the input teeth portion 921. The input teeth 921a mesh with the third idle gear 84. A driving force from the motor 4 is input to the input teeth 921a via the motor gear 81, the first idle gear 82, the second idle gear 83, and the third idle gear 84.

[0062] The transmission portion 922 is a protruding piece that protrudes radially inward from the inner circumferential surface of the main body portion 920, and is configured to be able to engage with the transmission gear 93. In this embodiment, the transmission portions 922 are formed in two locations, and the two transmission portions 922 are arranged at positions where the distance from one transmission portion 922 to the other transmission portion 922 in the circumferential direction is equal to the distance from the other transmission portion 922 to one transmission portion 922.

[0063] The inclined cam surface 923 is formed on the bottom 920a of the main body 920, and is an inclined surface facing the output gear 94 side in the axial direction X. Here, "the inclined cam surface 923 is an inclined surface facing the output gear 94 side" means that the inclined cam surface 923 is an inclined surface that is visible when viewed from the output gear 94 side in the axial direction X, that is, from the right side.

[0064] The inclined cam surface 923 extends in the circumferential direction. The inclined cam surface 923 is inclined with respect to a direction perpendicular to the axial direction X so that the upstream side in the first direction W1 is closer to the output gear 94 in the axial direction X than the downstream side. The inclined cam surface 923 has a downstream end 923a in the first direction W1 and an upstream end 923b in the first direction W1. In the axial direction X, the upstream end 923b is closer to the output gear 94 than the downstream end 923a.

[0065] The inclined engagement surface 924 is formed inside the main body 920 and is located upstream of the transmission part 922 in the first direction W1. The inclined engagement surface 924 is an inclined surface facing the side opposite to the output gear 94 side in the axial direction X. Here, as shown in FIG. 9 , "the inclined engagement surface 924 is an inclined surface facing the side opposite to the output gear 94 side" means that the inclined engagement surface 924 is an inclined surface that is visible when viewed from the side opposite to the output gear 94 side in the axial direction X, that is, from the left side (see the inclined engagement surface 924 surrounded by a dotted line in FIG. 9). Note that the input gear 92 shown in FIG. 9 is drawn with the bottom 920a thereof seen through so that the inclined engagement surface 924 can be seen.

[0066] The inclined engagement surface 924 extends along the circumferential direction. The inclined engagement surface 924 is inclined with respect to a direction perpendicular to the axial direction X, such that the downstream side in the second direction W2 is closer to the output gear 94 in the axial direction X than the upstream side. In the present embodiment, the inclined engagement surfaces 924 are formed in two locations, and the two inclined engagement surfaces 924 are disposed at positions where the distance from one inclined engagement surface 924 to the other inclined engagement surface 924 in the circumferential direction is equal to the distance from the other inclined engagement surface 924 to one inclined engagement surface 924.

[0067] 5, 6, and 10, the transmission gear 93 is supported on a fixed shaft 91 so as to be movable in the axial direction X. The transmission gear 93 is rotatable in a first direction W1 and a second direction W2. The transmission gear 93 has a cylindrical portion 930, a transmitted portion 931, an abutment surface 932, a ratchet pawl 933, and an engagement pawl 934.

[0068] The cylindrical portion 930 is formed in a cylindrical shape and has a small-diameter portion 930a that is smaller in diameter than other portions at the end on the output gear 94 side in the axial direction X. The transmitted portion 931 is a protruding piece that protrudes radially outward from the outer circumferential surface of the cylindrical portion 930.

[0069] In this embodiment, the transmitted portion 931 is formed in two locations, and the two transmitted portions 931 are arranged at positions where the distance in the circumferential direction from one transmitted portion 931 to the other transmitted portion 931 is equal to the distance from the other transmitted portion 931 to the one transmitted portion 931. The transmitted portion 931 is configured to be able to engage with the transmission portion 922 of the input gear 92 when the input gear 92 rotates in the first direction W1.

[0070] The abutment surface 932 is located at the end of the transmitted part 931 on the input gear 92 side in the axial direction X, and is configured to abut against the inclined cam surface 923 of the input gear 92 when the input gear 92 rotates in the first direction W1.

[0071] The ratchet pawl 933 protrudes from the end of the cylindrical portion 930 on the output gear 94 side in the axial direction X toward the output gear 94. The ratchet pawl 933 has an engagement surface 933a and a sliding surface 933b formed continuous with the engagement surface 933a in the circumferential direction. A plurality of ratchet pawls 933 are formed along the circumferential direction, and the engagement surfaces 933a and the sliding surfaces 933b are arranged alternately in the circumferential direction.

[0072] The engaging claws 934 protrude from the transmitted portion 931 in the circumferential direction toward the downstream side in the first direction W1. In this embodiment, the engaging claws 934 are formed in two locations, and the two engaging claws 934 are arranged at positions where the distance from one engaging claw 934 to the other engaging claw 934 in the circumferential direction is equal to the distance from the other engaging claw 934 to the one engaging claw 934. The engaging claws 934 are configured to engage with the inclined engaging surface 924 of the input gear 92 when the input gear 92 rotates in the second direction.

[0073] When engaged with the input gear 92, the transmission gear 93 is movable in the axial direction X between a first position (position shown in Figure 6(a)) in which the small diameter portion 930a of the cylindrical portion 930 is supported by the first shaft portion 911 of the fixed shaft 91, and a second position (position shown in Figure 6(b)) in which the small diameter portion 930a of the cylindrical portion 930 is supported by the second shaft portion 912 of the fixed shaft 91.

[0074] The small diameter portion 930a of the transmission gear 93 located at the first position is supported by the first shaft portion 911 with a first sliding resistance between the small diameter portion 930a and the first shaft portion 911. The small diameter portion 930a of the transmission gear 93 located at the second position is supported by the second shaft portion 912 with a second sliding resistance between the small diameter portion 930a and the second shaft portion 912, the second sliding resistance being smaller than the first sliding resistance.

[0075] In other words, the first shaft portion 911 of the fixed shaft 91 supports the transmission gear 93 located at the first position with a first sliding resistance of a predetermined magnitude between the fixed shaft 91 and the transmission gear 93, and the second shaft portion 912 of the fixed shaft 91 supports the transmission gear 93 located at the second position with a second sliding resistance between the fixed shaft 91 and the transmission gear 93 that is smaller than the first sliding resistance.

[0076] As shown in Figures 5, 6, and 11, the output gear 94 is rotatably supported on the second shaft portion 912 of the fixed shaft 91. The output gear 94 is connected to the pressure roller 62 of the fixing unit 6 and is capable of transmitting driving force from the motor 4 to the pressure roller 62. The output gear 94 is rotatable in a first direction W1 and a second direction W2. The output gear 94 has a main body portion 940, a ratchet recess 941, output teeth 942, and a spacer 943.

[0077] The main body 940 is formed in a cylindrical shape. The ratchet recess 941 is located at an end of the main body 940 on the input gear 92 side in the axial direction X. The ratchet recess 941 is engageable with the ratchet pawl 933 of the transmission gear 93. Specifically, the ratchet recess 941 engages with the ratchet pawl 933 when the transmission gear 93 rotates in the first direction W1 relative to the output gear 94, and does not engage with the ratchet pawl 933 when the transmission gear 93 rotates in the second direction W2 relative to the output gear 94.

[0078] The ratchet recess 941 has an engagement surface 941a and a sliding surface 941b formed continuously with the engagement surface 941a in the circumferential direction. A plurality of ratchet recesses 941 are formed along the circumferential direction, and the engagement surfaces 941a and the sliding surfaces 941b are arranged alternately in the circumferential direction.

[0079] When the transmission gear 93 is in the first position, the ratchet recess 941 is spaced apart from the ratchet pawl 933 of the transmission gear 93 in the axial direction X, and when the transmission gear 93 is in the second position, the ratchet recess 941 can be connected to the ratchet pawl 933 of the transmission gear 93 in the axial direction X.

[0080] When the transmission gear 93 is in the second position and rotates in the first direction W1 relative to the output gear 94, the engagement surface 933a of the ratchet pawl 933 engages with the engagement surface 941a of the ratchet recess 941, causing the transmission gear 93 and the output gear 94 to rotate integrally.

[0081] On the other hand, when the transmission gear 93 is in the second position and rotates in the second direction W2 relative to the output gear 94, the sliding surface 933b of the ratchet pawl 933 slides circumferentially against the sliding surface 941b of the ratchet recess 941, thereby disengaging the engagement surface 933a from the engagement surface 941a. In this case, even if the transmission gear 93 rotates in the second direction W2, the output gear 94 does not rotate.

[0082] Furthermore, when the transmission gear 93 is in the first position, the ratchet recess 941 and the ratchet pawl 933 are separated from each other, and therefore the output gear 94 does not rotate when the transmission gear 93 rotates in the first direction W1 and when the transmission gear 93 rotates in the second direction W2. Furthermore, when the output gear 94 rotates while the transmission gear 93 is in the first position, the transmission gear 93 is not coupled to the output gear 94.

[0083] The output teeth 942 are formed on the outer peripheral surface of the main body 940 and mesh with the fourth idle gear 85. The output teeth 942 are connected to the pressure roller 62 of the fixing unit 6 via the fourth idle gear 85 and the pressure roller gear 86. The output teeth 942 can transmit the driving force from the motor 4 to the pressure roller 62 via the fourth idle gear 85 and the pressure roller gear 86.

[0084] The spacer 943 protrudes from the input gear 92 side end of the main body 940 in the axial direction X toward the input gear 92, and is configured to be able to abut against the input gear 92. A plurality of spacers 943 are formed discontinuously along the circumferential direction on the outer circumferential edge of the main body 940.

[0085] The spacer 943 abuts against the input gear 92, thereby restricting the position of the output gear 94 in the axial direction X relative to the input gear 92. By restricting the position of the output gear 94 relative to the input gear 92 with the spacer 943, the transmission gear 93 is movable in the axial direction X between the input gear 92 and the output gear 94.

[0086] [One-way clutch operation] Next, the operation of the one-way clutch 90 will be described.

[0087] 6(a), the transmission gear 93 is located at a first position, and the contact surface 932 of the transmission gear 93 is in contact with the downstream end 923a of the inclined cam surface 923 of the input gear 92. The transmission gear 93 located at the first position is separated from the output gear 94 in the axial direction X.

[0088] In this state where the transmission gear 93 is positioned at the first position, even if the output gear 94 rotates in the first direction W1 and the second direction W2, the output gear 94 and the transmission gear 93 are not connected to each other. Therefore, when the transmission gear 93 is positioned at the first position, even if the pressure roller 62 connected to the output gear 94 rotates, the pressure roller 62 is not connected to the motor 4 connected to the input gear 92.

[0089] Furthermore, when the transmission gear 93 is positioned in the first position, the small diameter portion 930a of the cylindrical portion 930 in the transmission gear 93 is supported on the first shaft portion 911 of the fixed shaft 91 with a first sliding resistance.

[0090] When the input gear 92 receives driving force from the motor 4 and rotates in the first direction W1 from the state shown in Figure 6(a), the inclined cam surface 923 abutting against the abutment surface 932 of the transmission gear 93 moves circumferentially, and a circumferential sliding resistance acts on the transmission gear 93 between the inclined cam surface 923.

[0091] On the other hand, the transmission gear 93 is supported by the first shaft portion 911 with a first sliding resistance between the small diameter portion 930a and the first shaft portion 911, and the first sliding resistance is set to be larger than the circumferential sliding resistance generated between the transmission gear 93 and the inclined cam surface 923. Therefore, when the input gear 92 rotates in the first direction W1 with the abutment surface 932 of the transmission gear 93 abutting against the inclined cam surface 923, the transmission gear 93 maintains a state in which its rotation relative to the fixed shaft 91 is suppressed, and does not rotate together with the input gear 92 at the same speed.

[0092] As a result, the phase of the transmission gear 93 relative to the inclined cam surface 923 in the first direction W1 shifts, and the position of the inclined cam surface 923 abutting against the abutment surface 932 of the transmission gear 93 moves from the downstream end 923 a to the upstream side in the first direction W1. Because the inclined cam surface 923 is located closer to the output gear 94 on the upstream side than on the downstream side in the first direction W1, when the position of the inclined cam surface 923 abutting against the abutment surface 932 of the transmission gear 93 moves upstream in the first direction W1, the transmission gear 93 is pressed by the inclined cam surface 923 toward the output gear 94 in the axial direction X and moves.

[0093] As shown in FIG. 6(b), when the position of the inclined cam surface 923 abutting against the abutment surface 932 of the transmission gear 93 reaches the upstream end 923b, the transmission gear 93 moves to the second position.

[0094] In this way, when the input gear 92 rotates in the first direction W1, the transmission gear 93 located at the first position is prevented from rotating at the same speed as the input gear 92 due to the first sliding resistance between the small diameter portion 930a and the first shaft portion 911, thereby enabling movement from the first position to the second position.

[0095] After the transmission gear 93 moves to the second position, the transmission portion 922 of the input gear 92, which rotates in the first direction W1, comes into contact with the transmitted portion 931 of the transmission gear 93. As the transmission portion 922 comes into contact with the transmitted portion 931, a force in the first direction W1 acts from the input gear 92 to the transmission gear 93, and the input gear 92 and the transmission gear 93 rotate integrally in the first direction W1.

[0096] In this case, the second sliding resistance between the small diameter portion 930a of the transmission gear 93 located in the second position and the second shaft portion 912 is smaller than the first sliding resistance, so the transmission gear 93 can rotate smoothly against the second sliding resistance.

[0097] In the one-way clutch 90, the magnitude of the first sliding resistance and the magnitude of the second sliding resistance are changed by making different the first outer diameter D1 of the first shaft portion 911 that supports the transmission gear 93 located in the first position and the second outer diameter D2 of the second shaft portion 912 that supports the transmission gear 93 located in the second position, thereby making it possible to simplify the configuration of the one-way clutch 90.

[0098] Furthermore, when the transmission gear 93 rotates in the first direction W1 while positioned in the second position, the engagement surface 933a of the ratchet pawl 933 on the transmission gear 93 engages with the engagement surface 941a of the ratchet recess 941 on the output gear 94, causing the transmission gear 93 and the output gear 94 to rotate integrally in the first direction W1.

[0099] In this way, the input gear 92 receives driving force from the motor 4 and rotates in the first direction W1, thereby moving the transmission gear 93 from the first position to the second position, connecting the transmission gear 93 and the output gear 94, and transmitting the driving force from the motor 4 in the first direction W1 to the output gear 94 via the transmission gear 93.

[0100] In other words, when the input gear 92 rotates in the first direction W1, the transmission gear 93, which is located at the second position and connected to the output gear 94, rotates together with the input gear 92 relative to the fixed shaft 91 against the second sliding resistance. This makes it possible to transmit driving force from the transmission gear 93 to the output gear 94.

[0101] Furthermore, in the one-way clutch 90, when the input gear 92 rotates in the first direction W1, the transmission gear 93 is pressed toward the output gear 94 by the inclined cam surface 923, moving from the first position to the second position. Therefore, with a simple configuration, it is possible to switch from a state in which the transmission of driving force to the output gear 94 is released to a state in which the driving force is transmitted to the output gear 94 via the transmission gear 93.

[0102] Conversely, in the one-way clutch 90, when the transmission gear 93 is positioned at the second position shown in Figure 6(b), the input gear 92 receives driving force from the motor 4 and rotates in the second direction W2, thereby moving the transmission gear 93 from the second position to the first position and releasing the transmission of driving force to the output gear 94.

[0103] Specifically, when the input gear 92 receives a driving force from the motor 4 and rotates in the second direction W2 while the transmission gear 93 is in the second position, the inclined engagement surface 924 of the input gear 92 engages with the engagement claw 934 of the transmission gear 93. Because the downstream side of the inclined engagement surface 924 in the second direction W2 is closer to the output gear 94 than the upstream side, when the engagement claw 934 engages with the inclined engagement surface 924 and is pressed in the second direction W2, the position of the inclined engagement surface 924 abutting against the engagement claw 934 moves upstream in the second direction W2, and the transmission gear 93 is pulled by the inclined engagement surface 924 toward the input gear 92 in the axial direction X.

[0104] In other words, when the input gear 92 rotates in the second direction W2 while the transmission gear 93 is located at the second position, the inclined engagement surface 924 pulls the transmission gear 93 toward the input gear 92 in the axial direction X, and moves the transmission gear 93 to the first position. This separates the transmission gear 93 and the output gear 94, and the transmission of the driving force from the input gear 92 to the output gear 94 is released.

[0105] In this way, in the one-way clutch 90, by rotating the input gear 92 in the second direction, the inclined engagement surface 924 and the engagement claw 934 can be engaged, and the transmission gear 93 can be moved from the second position to the first position.

[0106] In the one-way clutch 90, when the transmission gear 93 is in the first position, the transmission gear 93 and the output gear 94 are not connected but are separated, so that even if the output gear 94 is rotated, the transmission gear 93 does not rotate with it, and the output gear 94 rotates freely.

[0107] Therefore, the output gear 94 connected to the pressure roller 62 is not subjected to the load of the motor 4 and the gear train between the motor 4 and the input gear 92. As a result, the pressure roller 62 can be easily rotated when clearing jammed sheets S without providing the drive force transmission train 8 with a complex mechanism such as a drive force transmission release mechanism in addition to the one-way clutch 90, and jammed sheets S can be cleared smoothly.

[0108] Furthermore, when the transmission gear 93 is in the first position, the one-way clutch 90 cuts off the transmission of driving force from the motor 4 to the pressure roller 62, so that even when the pressure roller 62 is rotated during jam clearance, the load of the motor 4 is not applied to the pressure roller 62, making it possible to clear the jam smoothly.

[0109] Furthermore, since the one-way clutch 90 is connected to the pressure roller 62 of the fixing device 6, when a jam of the sheet S occurs in the fixing device 6, the sheet S can be smoothly removed from the fixing device 6.

[0110] Furthermore, since the heating unit 61 of the fixing device 6 has a flat heater 611 and the pressure roller 62 is pressed against the heater 611, the rotation torque of the pressure roller 62 tends to be larger than when the heating unit 61 is composed of a roller member. However, in the one-way clutch 90, by moving the transmission gear 93 to the first position where the transmission gear 93 and the output gear 94 are separated, the load on the pressure roller 62 does not increase, and jam clearance can be carried out smoothly.

[0111] [Motor drive control when a jam occurs] 12, the image forming apparatus 1 includes a control unit C and a paper discharge sensor 98. The control unit C is connected to the motor 4 and is configured to be able to control the operation of the motor 4. As shown in FIG. 1, the paper discharge sensor 98 is disposed between the fixing unit 6 and the pair of paper discharge rollers 71 in the sheet conveying direction and is configured to be able to detect the sheet S that has passed through the fixing unit 6.

[0112] For example, when the detection of the sheet S by the paper discharge sensor 98 continues for a predetermined time or longer, the control unit C can determine that a jam of the sheet S has occurred in the fixing unit 6. When the control unit C determines that a jam of the sheet S has occurred, it executes control to drive the motor 4 in a direction in which the input gear 92 rotates in the second direction W2.

[0113] When the input gear 92 is rotated in the second direction W2 by the driving of the motor 4, the inclined engagement surface 924 and the engagement claw 934 engage with each other, the transmission gear 93 moves to the first position, and the transmission gear 93 and the output gear 94 move away from each other.

[0114] In this way, when a jam occurs in the sheet S, the motor 4 is driven under the control of the control unit C to rotate the input gear 92 in the second direction W2, thereby moving the transmission gear 93 from the second position to the first position and separating the transmission gear 93 from the output gear 94. As a result, even when the pressure roller 62 is rotated during jam clearance, the load of the motor 4 is not applied to the pressure roller 62, making it possible to clear the jam smoothly.

[0115] In addition, even when the control unit C determines that a jam of the sheet S has occurred at a location other than the fixing unit 6, it can execute control to drive the motor 4 in a direction in which the input gear 92 rotates in the second direction W2. [Explanation of symbols]

[0116] 1. Image forming device 4 motors 5. Image forming unit 6 Fixing unit 8. Drivetrain 61 Heating unit 62 Pressure roller 90 one-way clutch 91 Fixed axis 92 Input gear 93 Transmission Gear 94 Output gear 611 Heater 911 First Axis 912 Second shaft 921a Input teeth 922 Transmission Unit 923 Inclined Cam Surface 924 Inclined engagement surface 931 Receiving part 932 Contact surface 933 Ratchet Claw 934 Engagement claw 941 Ratchet recess 942 output teeth C control section S seat T Sheet transport device W1 1st direction W2 Second direction X-axis direction

Claims

1. A driving source; a roller for conveying a sheet; a one-way clutch capable of transmitting a driving force from the driving source to the roller; Equipped with The one-way clutch is A fixed axis and an input gear rotatably supported on the fixed shaft and rotatable by receiving a driving force from the driving source; an output gear rotatably supported on the fixed shaft, the output gear being coupled to the roller and capable of transmitting the driving force to the roller; a transmission gear supported by the fixed shaft, the transmission gear being movable in an axial direction of the fixed shaft between a first position spaced apart from the output gear and a second position connected to the output gear while engaged with the input gear; and the input gear receives the driving force from the driving source and rotates in a first direction, thereby moving the transmission gear from the first position to the second position, and transmits the driving force in the first direction to the output gear via the transmission gear; and receives the driving force from the driving source and rotates in a second direction opposite to the first direction, thereby moving the transmission gear from the second position to the first position, and releases the transmission of the driving force to the output gear; When the output gear rotates in a state where the transmission gear is located at the first position, the transmission gear is not coupled to the output gear, the fixed shaft supports the transmission gear positioned at the first position with a first sliding resistance of a predetermined magnitude between the fixed shaft and the transmission gear, and supports the transmission gear positioned at the second position with a second sliding resistance smaller than the first sliding resistance between the fixed shaft and the transmission gear, When the input gear rotates in the first direction, the transmission gear located at the first position is moved from the first position to the second position by the input gear by maintaining a state in which rotation with respect to the fixed shaft is suppressed by the first sliding resistance, A sheet conveying device characterized in that the transmission gear located at the second position rotates together with the input gear relative to the fixed shaft against the second sliding resistance when the input gear rotates in the first direction.

2. 2. The sheet transport device according to claim 1, wherein when the roller rotates with the transmission gear positioned at the first position, the roller is not coupled to the driving source.

3. the fixed shaft includes a first shaft portion having a first outer diameter and a second shaft portion having a second outer diameter smaller than the first outer diameter; the first shaft portion supports the transmission gear positioned at the first position in a state in which the transmission gear has the first sliding resistance; 3. The sheet conveying device according to claim 1, wherein the second shaft portion supports the transmission gear positioned at the second position while providing the second sliding resistance.

4. the transmission gear is located between the input gear and the output gear in the axial direction, The input gear is an input tooth to which the driving force is input; a transmission portion engageable with the transmission gear; an inclined cam surface facing the output gear in the axial direction, the inclined cam surface extending along a circumferential direction, the inclined cam surface being located closer to the output gear in the axial direction on an upstream side than on a downstream side in the first direction; The transmission gear is a transmitted portion engageable with the transmitting portion when the input gear rotates in the first direction; a contact surface that contacts the inclined cam surface when the input gear rotates in the first direction; a ratchet pawl protruding toward the output gear in the axial direction, The output gear is a ratchet recess that engages with the ratchet pawl when the transmission gear rotates in the first direction and does not engage with the ratchet pawl when the transmission gear rotates in the second direction; 4. The sheet transport device according to claim 1, further comprising an output tooth connected to the roller.

5. the input gear has an inclined engagement surface facing a side opposite to the output gear side in the axial direction, the inclined engagement surface extending along a circumferential direction, and the downstream side in the second direction being located closer to the output gear in the axial direction than the upstream side, 5. The sheet transport device according to claim 4, wherein the transmission gear has an engagement claw that engages with the inclined engagement surface when the input gear rotates in the second direction.

6. A control unit is provided, A sheet conveying device described in any one of claims 1 to 5, wherein when the control unit determines that a sheet jam has occurred, it drives the drive source in a direction in which the input gear rotates in the second direction.

7. A drive source; a roller for conveying a sheet; a one-way clutch capable of transmitting a driving force from the driving source to the roller; Equipped with The one-way clutch is A fixed axis and an input gear rotatably supported on the fixed shaft and rotatable by receiving a driving force from the driving source; an output gear rotatably supported on the fixed shaft, the output gear being coupled to the roller and capable of transmitting the driving force to the roller; a transmission gear supported by the fixed shaft, the transmission gear being movable in an axial direction of the fixed shaft between a first position spaced apart from the output gear and a second position connected to the output gear while engaged with the input gear; and the input gear receives the driving force from the driving source and rotates in a first direction, thereby moving the transmission gear from the first position to the second position, and transmits the driving force in the first direction to the output gear via the transmission gear; and receives the driving force from the driving source and rotates in a second direction opposite to the first direction, thereby moving the transmission gear from the second position to the first position, and releases the transmission of the driving force to the output gear; When the output gear rotates in a state where the transmission gear is located at the first position, the transmission gear is not coupled to the output gear, the fixed shaft includes a first shaft portion having a first outer diameter and a second shaft portion having a second outer diameter smaller than the first outer diameter; the first shaft portion supports the transmission gear positioned at the first position, The sheet conveying device, wherein the second shaft portion supports the transmission gear positioned at the second position.

8. The sheet conveying device according to any one of claims 1 to 7, an image forming unit that forms an image on a sheet; a fixing unit that conveys and heats the sheet sent from the image forming unit, The roller is provided in the fixing unit of the image forming apparatus.

9. the fixing unit has a flat heater, 9. The image forming apparatus according to claim 8, wherein the roller is a pressure roller that heats and presses the sheet together with the heater.

Images