Image forming apparatus

Abstract

To provide an image forming apparatus that can stably convey a sheet even when it comprises a fixing shutter.SOLUTION: An image forming apparatus 1 comprises: an apparatus body 2; a fuser 6; a fixing chute 28 that is located upstream of the fuser 6 in a sheet conveyance direction; a fixing guide 66 that is located upstream of a heating unit 61 in the sheet conveyance direction, and has a guide conveyance surface 661 inclined in a direction approaching the fixing chute 28 toward the downstream in the sheet conveyance direction; and a fixing shutter 64 that is movable to a closed position where it covers the upstream side of the heating unit 61 in the sheet conveyance direction and an open position where it opens the upstream side. The fixing shutter 64 has a shutter conveyance surface 643 that, with the fixing shutter 64 being located at the open position, is inclined in the direction approaching the fixing chute 28 toward the downstream in the sheet conveyance direction, so that an end 643a on the downstream side in the sheet conveyance direction is located closer to the fixing chute 28 than an end 661a of the guide conveyance surface 661 on the upstream side in the sheet conveyance direction.SELECTED DRAWING: Figure 23

Description

Technical Field

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

Background Art

[0002] Conventionally, as disclosed in Patent Document 1, in an image forming apparatus, in order to prevent a user's hand from contacting a fixing device having a heating unit, a fixing shutter that can move between a closed position covering the heating unit and an open position exposing the heating unit is provided in front of the fixing device.

[0003] The fixing shutter is configured to be located at a position retracted from the sheet conveyance path when normally located at the open position.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the conveyed sheet is curled or the behavior of the conveyed sheet becomes unstable, the sheet may hit the fixing shutter, etc., and there is a risk of jamming without being properly conveyed.

[0006] Therefore, in the present invention, there is provided an image forming apparatus capable of stably conveying a sheet even when a fixing shutter is provided.

Means for Solving the Problems

[0007] The image forming apparatus for solving the above problems has the following features.

[0008] That is, the image forming apparatus includes a device main body, a fixing unit having a heating unit for fixing a toner image on a conveyed sheet, a fixing chute that is located upstream of the fixing unit in the sheet conveyance direction and forms a sheet conveyance path, and a fixing guide that is located upstream of the heating unit in the sheet conveyance direction and on the opposite side of the fixing chute across the sheet conveyance path in the sheet thickness direction, and has a guide conveyance surface that inclines in a direction approaching the fixing chute as it goes downstream in the sheet conveyance direction. The fixing guide guides the sheet. A fixing shutter is located on the opposite side of the fixing chute across the sheet conveyance path in the sheet thickness direction, and is movable between a closed position that covers the upstream side of the heating unit in the sheet conveyance direction and an open position that opens the upstream side of the heating unit in the sheet conveyance direction. The fixing shutter has a shutter conveyance surface that can guide the sheet upstream of the fixing guide in the sheet conveyance direction when the fixing shutter is in the open position, and the shutter conveyance surface inclines in a direction approaching the fixing chute as it goes downstream in the sheet conveyance direction when the fixing shutter is in the open position, so that the end portion on the downstream side in the sheet conveyance direction is located closer to the fixing chute than the end portion on the upstream side in the sheet conveyance direction of the guide conveyance surface.

[0009] As a result, a step is formed between the shutter conveyance surface and the guide conveyance surface, and the end portion on the downstream side in the sheet conveyance direction of the shutter conveyance surface is located closer to the fixing chute than the end portion on the upstream side in the sheet conveyance direction of the guide conveyance surface. Therefore, when the sheet guided by the shutter conveyance surface is taken over from the shutter conveyance surface to the guide conveyance surface, the leading edge of the conveyed sheet is prevented from being caught by the fixing guide, and the sheet can be stably conveyed even when the fixing shutter is provided.

[0010] Also, when the fixing shutter is in the open position, the end portion on the downstream side in the sheet conveyance direction of the shutter conveyance surface overlaps the guide conveyance surface in the sheet conveyance direction.

[0011] As a result, the sheet guided on the shutter conveyance surface can smoothly transfer onto the guide conveyance surface, and it is possible to prevent the sheet from being caught by the fixing guide.

[0012] In addition, the inclination angle of the shutter conveyance surface with respect to the sheet conveyance direction is larger than the inclination angle of the guide conveyance surface with respect to the sheet conveyance direction.

[0013] As a result, a large space can be ensured between the shutter conveyance surface and the fixing chute, and it is possible to prevent jams from occurring in the conveyed sheet.

[0014] In addition, the shutter conveyance surface of the fixing shutter faces the fixing device in a state where the fixing shutter is in the closed position.

[0015] As a result, when the fixing shutter is in the closed position, the shutter conveyance surface faces the side of the fixing device where the user's hand is less likely to touch. Therefore, it is possible to prevent the user's hand from touching the shutter conveyance surface and getting dirty, and then prevent the sheet from getting dirty when it contacts the shutter conveyance surface during subsequent conveyance.

[0016] In addition, the fixing shutter has a shielding surface that covers the upstream side in the sheet conveyance direction from the heating unit in a state where the fixing shutter is in the closed position, and the shielding surface extends in a direction intersecting the direction in which the shutter conveyance surface extends.

[0017] As a result, when the fixing shutter is in the closed position, the heating unit is covered by the shielding surface, so it is possible to prevent the user from touching the heating unit.

[0018] The apparatus further includes a cartridge detachable from the apparatus main body, and a shutter link provided on the apparatus main body and connected to the fixing shutter, the shutter link moving the fixing shutter between the open position and the closed position in conjunction with the attachment / detachment operation of the cartridge with respect to the apparatus main body.

[0019] Accordingly, the fixing shutter can be opened and closed by attaching and detaching the cartridge to and from the apparatus main body without performing a unique operation for opening and closing the fixing shutter.

[0020] Further, it has an upstream guide capable of guiding the sheet upstream in the sheet conveyance direction from the shutter conveyance surface of the fixing shutter, and an end portion on the downstream side in the sheet conveyance direction of the upstream guide is located closer to the fixing chute than an end portion on the upstream side in the sheet conveyance direction of the shutter conveyance surface.

[0021] As a result, a step is formed between the upstream guide and the shutter conveyance surface, in which an end portion on the downstream side in the sheet conveyance direction of the upstream guide is located closer to the fixing chute than an end portion on the upstream side in the sheet conveyance direction of the shutter conveyance surface. Therefore, when the sheet guided by the upstream guide transfers onto the shutter conveyance surface, it can be suppressed from being caught by the fixing shutter, and the sheet can be stably conveyed.

[0022] Also, in the sheet conveyance direction, it is downstream of a transfer unit that transfers an image onto the sheet and upstream of the fixing device, and includes a movable chute that is movable between a first position and a second position where an end portion on the downstream side in the sheet conveyance direction from the first position is separated from the sheet conveyance path.

[0023] Accordingly, the sheet conveyed from the transfer unit can be properly guided to the fixing device by the movable chute.

[0024] Further, the movable chute has a sheet conveyance surface for guiding the sheet, and in a state where the movable chute is located at the first position, a virtual plane obtained by extending the sheet conveyance surface at an end portion on the downstream side in the sheet conveyance direction of the movable chute passes through the fixing guide.

[0025] When the sheet guided on the sheet conveyance surface of the movable chute is straight paper without curl or curled paper that curls toward the side away from the shutter conveyance surface, the tip of the sheet guided by the movable chute abuts against the guide conveyance surface located downstream of the shutter conveyance surface. As a result, the sheet can be more stably guided to the fixing device.

[0026] Further, a perpendicular line to the shutter conveyance surface in the fixing shutter passes through the movable chute.

[0027] As a result, the sheet conveyed from the movable chute can be appropriately guided toward the fixing device by the shutter conveyance surface.

[0028] Also, a drive source for moving the movable chute and a control unit for controlling the operation of the drive source are provided. The control unit controls the drive source to move the movable chute from the first position toward the second position after the tip of the conveyed sheet has passed through the fixing device.

[0029] After the tip of the sheet has passed through the fixing device, during the period when the sheet is conveyed by both the fixing device and the transfer unit, the conveyance speed of the sheet by the transfer unit is greater than the conveyance speed of the sheet by the fixing device, and the sheet between the fixing device and the transfer unit bends. Therefore, by moving the movable chute toward the second position away from the sheet conveyance path under the control of the control unit, a large space can be secured between the fixing device and the transfer unit, and it is possible to suppress the bent sheet from interfering with other components of the apparatus main body.

[0030] Also, a chute link that is connected to the drive source and moves the movable chute from the first position to the second position is provided. The drive source is a solenoid actuator that drives the chute link. The movable chute has a sheet conveyance surface for guiding the sheet. The chute link drives the movable chute from the first position to the second position by being driven by the drive source and pressing the movable chute from the side of the sheet conveyance surface.

[0031] As a result, the movable chute can be quickly and stably moved from the first position to the second position.

[0032] Further, the fixing guide is located at an end portion in a direction orthogonal to the sheet conveyance direction of the guide conveyance surface, and has a guide protrusion protruding toward the fixing chute side from the guide conveyance surface. The guide protrusion is inclined in a direction approaching the fixing chute as it goes downstream in the sheet conveyance direction, and the inclination angle of the guide protrusion with respect to the sheet conveyance direction is larger than the inclination angle of the shutter conveyance surface with respect to the sheet conveyance direction.

[0033] When the rear end of the conveyed sheet passes through the guide conveyance surface, the rear end portion of the sheet may bounce. However, since the fixing guide has the guide protrusion, it is possible to press the conveyed sheet with the guide protrusion and suppress the bounce generated at the rear end portion of the sheet. In this case, since the inclination angle of the guide protrusion is formed larger than the inclination angle of the shutter conveyance surface, even if the guide protrusion protrudes from the guide conveyance surface, the upstream end portion of the guide protrusion in the sheet conveyance direction can be positioned farther from the fixing chute than the downstream end portion of the shutter conveyance surface in the sheet conveyance direction, and it is possible to prevent the conveyed sheet from being caught by the guide protrusion.

Advantages of the Invention

[0034] According to the present invention, when the sheet is taken over from the shutter conveyance surface to the guide conveyance surface, it is possible to suppress the leading end of the conveyed sheet from being caught by the fixing guide and stably convey the sheet.

Brief Description of the Drawings

[0035]

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[0036] Next, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

[0037] [Image Forming Apparatus] The image forming apparatus 1 shown in FIG. 1 is an embodiment of an image forming apparatus provided with a sheet conveying apparatus according to the present invention, and is a laser printer that forms an image on a sheet S by an electrophotographic method.

[0038] 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 surface in FIG. 1 is defined as the left side of the image forming apparatus 1, and the back side of the paper surface in FIG. 1 is defined as the right side of the image forming apparatus 1. Also, the upper side and the lower side in FIG. 1 are defined as the upper side and the lower side of the image forming apparatus 1, respectively.

[0039] The image forming apparatus 1 includes an apparatus main body 2, a paper feeding unit 3, an image forming unit 5, a fixing unit 6, and a paper discharging unit 29.

[0040] The apparatus main body 2 houses the paper feeding unit 3, the image forming unit 5, the fixing unit 6, and the paper discharging unit 29. An opening 2A is open on the front surface of the apparatus main body 2, and the apparatus main body 2 has a front cover 21 that can open and close the opening 2A. The front cover 21 is configured to be rotatable about a rotation axis 21a at the lower end, and by rotating about the rotation axis 21a, it can move between a closed position where the opening 2A is closed and an open position where the opening 2A is opened.

[0041] The paper feeding unit 3 includes a paper feeding tray 10 that supports the sheet S, a sheet conveying unit 30, a pair of conveying rollers 34, and a registration roller 35a. The paper feeding unit 3 is disposed at the lower part of the apparatus main body 2 and conveys the sheet S supported by the paper feeding tray 10 to the image forming unit 5. The image forming apparatus 1 has a conveyance path P of the sheet S that extends from the paper feeding unit 3, passes through the image forming unit 5, and reaches the paper discharging unit 29. The conveyance path P is an example of a sheet conveyance path.

[0042] The paper feed tray 10 has a pressure plate 12 and a pressing plate 13. The pressure plate 12 is a plate-like member that supports the sheet S from below. The pressure plate 12 is rotatable about a rotation fulcrum 12a at the rear end, and can be lifted and lowered between a lowered position and a raised position by rotating about the rotation fulcrum 12a. The pressing plate 13 is located below the pressure plate 12 and can lift and lower the pressure plate 12 between a lowered position and a raised position.

[0043] The sheet conveyance unit 30 is a conveyance mechanism that separates and takes out the sheets S supported by the paper feed tray 10 one by one and conveys them toward the image forming unit 5, and includes a paper feed roller 31, a separation roller 32, and a separation pad 33.

[0044] The paper feed roller 31 is a roller for sending out the sheet S supported by the paper feed tray 10 toward the separation roller 32. The separation roller 32 is arranged on the downstream side in the sheet conveyance direction from the paper feed roller 31, and the separation pad 33 is arranged opposite to the separation roller 32 and is biased toward the separation roller 32.

[0045] The sheet S sent out toward the separation roller 32 by the paper feed roller 31 is separated one by one between the separation roller 32 and the separation pad 33. The sheets S separated one by one are sent out to the conveyance path P.

[0046] The sheet S sent out to the conveyance path P is conveyed toward the image forming unit 5 by a pair of conveyance rollers 34, a registration roller 35a, and a pinch roller 35b arranged opposite to the registration roller 35a. The registration roller 35a restricts the movement of the leading end of the conveyed sheet S and once stops it, and then conveys the sheet S toward the image forming unit 5 at a predetermined timing.

[0047] The image forming apparatus 1 has a post-registration sensor 98 that detects the sheet S conveyed along the conveyance path P downstream of the resist roller 35a in the sheet conveyance direction. The post-registration sensor 98 can be configured to detect the leading edge of the sheet S and turn on when the leading edge of the sheet S passes through the post-registration sensor 98, and to detect the trailing edge of the sheet S and turn off when the trailing edge of the sheet S passes through the post-registration sensor 98.

[0048] The image forming unit 5 is disposed downstream of the paper feeding unit 3 in the sheet conveyance direction, and forms an image on the sheet S conveyed from the paper feeding unit 3. The image forming unit 5 includes a process cartridge 50 that transfers an image to the surface of the sheet S conveyed from the paper feeding unit 3, a transfer roller 55 disposed opposite to the photosensitive drum 54 of the process cartridge 50, and an exposure unit 56 that exposes the surface of the photosensitive drum 54. The process cartridge 50 is an example of a cartridge that is detachable from the apparatus main body.

[0049] The process cartridge 50 is disposed above the paper feeding unit 3 in the apparatus main body 2, and includes a developer storage chamber 51, a supply roller 52, a developing roller 53, a photosensitive drum 54, and the like. The process cartridge 50 supports the pinch roller 35b.

[0050] The process cartridge 50 includes a drum cartridge having a photosensitive drum 54 and a developing cartridge having a developing roller 53 attached to the drum cartridge, and is detachably attached to the apparatus main body 2. In this case, the process cartridge 50 is attached to the apparatus main body 2 by integrally inserting the drum cartridge and the developing cartridge attached to the drum cartridge into the apparatus main body 2, and is detached from the apparatus main body 2 by integrally extracting the drum cartridge and the developing cartridge attached to the drum cartridge from the apparatus main body 2.

[0051] The process cartridge 50 is an example of a cartridge and can be configured to include at least one of a photosensitive drum, a developing roller, and a toner container. The process cartridge 50 can be attached to and detached from the apparatus main body 2 when the front cover 21 is in the open position.

[0052] The photosensitive drum 54 is arranged in a posture where the axis X is along the left - right direction in a state where the process cartridge 50 is attached to the apparatus main body 2. The photosensitive drum 54 has a metal drum shaft 54a extending along the axis X direction. The photosensitive drum 54 rotates about the drum shaft 54a.

[0053] In the present embodiment, the process cartridge 50 includes a drum cartridge having the photosensitive drum 54 and a developing cartridge having the developing roller 53 attached to the drum cartridge. However, it can also be configured to include a cartridge having the photosensitive drum 54 and the developing roller 53 and a toner box for accommodating toner attached to the cartridge.

[0054] Also, in the image forming apparatus, the drum cartridge having the photosensitive drum 54 and the developing cartridge having the developing roller 53 can be configured to be separately attached to the apparatus main body 2. That is, the process cartridge 50 can be configured to include at least one of a photosensitive drum, a developing roller, and a toner container and be detachably attached to the apparatus main body.

[0055] The exposure unit 56 includes a laser diode, a polygon mirror, a lens, a reflecting mirror, etc., and exposes the surface of the photosensitive drum 54 by irradiating laser light toward the photosensitive drum 54 based on the image data input to the image forming apparatus 1.

[0056] The developing agent storage chamber 51 stores toner which serves as the developing agent. The toner stored in the developing agent storage chamber 51 is sent to the supply roller 52 while being agitated by an agitation member (not shown). The supply roller 52 further supplies the toner sent from the developing agent storage chamber 51 to the developing roller 53.

[0057] The developing roller 53 is disposed in close contact with the supply roller 52, and carries the toner supplied from the supply roller 52 and positively charged by a sliding contact member (not shown). Further, a developing bias is applied to the developing roller 53 by bias applying means (not shown).

[0058] 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 other portions, and an electrostatic latent image based on the image data is formed on the photosensitive drum 54. Then, the positively charged toner is supplied from the developing roller 53 to the surface of the photosensitive drum 54 on which the electrostatic latent image is formed, and the electrostatic latent image is developed into a toner image.

[0059] The transfer roller 55 is disposed opposite to the photosensitive drum 54, and a transfer bias is applied thereto by bias applying means (not shown). While the transfer bias is applied to the surface of the transfer roller 55, the sheet S is sandwiched and conveyed between the photosensitive drum 54 on which the toner image is 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 photosensitive drum 54 and the transfer roller 55 of the process cartridge 50 constitute a transfer portion that transfers an image to the sheet S. The sheet S on which the toner image is transferred is conveyed to the fixing device 6.

[0060] The fixing device 6 includes a heating unit 61 and a pressure roller 62, and fixes the image transferred to the sheet S by the process cartridge 50. The heating unit 61 is heated by supplying power from a power source (not shown). The heating unit 61 is an example of a heating part, and the pressure roller 62 is an example of a pressure part. The pressure roller 62 is disposed opposite to the heating unit 61. One of the heating unit 61 and the pressure roller 62 is biased against 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.

[0061] When the sheet S with the toner image 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 to heat the sheet S and fix the toner image on the sheet S. In this way, the fixing device 6 fixes the toner image transferred to the conveyed sheet S.

[0062] The paper discharge unit 29 is located on the downstream side in the sheet conveyance direction from the image forming unit 5, and discharges the sheet S on which the image is formed by the image forming unit 5 to the outside of the image forming apparatus 1. The paper discharge unit 29 includes a pair of paper discharge rollers 291 and a paper discharge tray 292. The pair of paper discharge rollers 291 is configured to be able to discharge the sheet S conveyed along the conveyance path P from the fixing device 6 to the outside of the apparatus main body 2. The paper discharge tray 292 is formed on the upper surface of the apparatus main body 2 and supports the sheet S discharged to the outside of the apparatus main body 2 by the pair of paper discharge rollers 291.

[0063] As shown in FIGS. 2 to 4, the apparatus main body 2 includes a first main body frame 24 and a second main body frame 25 that are spaced apart from each other in the left-right direction. The first main body frame 24 is located at the right end of the apparatus main body 2, and the second main body frame 25 is located at the left end of the apparatus main body 2. The first main body frame 24 extends in the front-rear direction and the up-down direction, and is disposed in a posture in which the plate surface faces in the left-right direction. The second main body frame 25 extends in the front-rear direction and the up-down direction, and is disposed in a posture in which the plate surface faces in the left-right direction.

[0064] The process cartridge 50 and the fixing device 6 are disposed between a first main body frame 24 and a second main body frame 25. The first main body frame 24 is disposed on the right side of the process cartridge 50 and the fixing device 6, and the second main body frame 25 is disposed on the left side of the process cartridge 50 and the fixing device 6. The process cartridge 50 is detachably supported by the first main body frame 24 and the second main body frame 25.

[0065] The first main body frame 24 supports a fan 27 that discharges the air inside the apparatus main body 2 to the outside of the apparatus main body 2. The second main body frame 25 supports a control board 951 on which electronic components such as a CPU 951A are mounted. The control board 951 constitutes a control unit 95 (see FIG. 26) for controlling the operation of the image forming apparatus 1.

[0066] An air duct 26 extending along the left - right direction is disposed between the first main body frame 24 and the second main body frame 25. The air duct 26 is provided across the first main body frame 24 and the second main body frame 25. The right end portion of the air duct 26 is supported by the first main body frame 24, and the left end portion of the air duct 26 is supported by the second main body frame 25. The air duct 26 is located between the process cartridge 50 and the fixing device 6 in the front - rear direction.

[0067] The air duct 26 is disposed at a position overlapping the fan 27 when viewed from the left - right direction. Air can flow inside the air duct 26. The air duct 26 guides the air inside the apparatus main body 2 toward the fan 27.

[0068] [Fixing device] As shown in FIGS. 5 and 6, 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 heater extending in the left - right direction. The heater 611 has a first surface 611A and a second surface 611B on the opposite side of the first surface 611A, and the first surface 611A is supported by the holder 612.

[0069] The holder 612 is made of, for example, a resin member, and has a guide surface 612a and a support wall 612b. The guide surface 612a contacts the inner peripheral surface 614a of the belt 614 to guide the belt 614. The support wall 612b has a support surface 612A that supports the heater 611. The support surface 612A of the support wall 612b is in contact with the first surface 611A of the heater 611. The stay 613 is a member that supports the holder 612, and is formed by bending a plate material having a higher rigidity than the holder 612, such as a steel plate, into a substantially U-shaped cross section.

[0070] The belt 614 is an endless belt having heat resistance and flexibility, and has a metal base tube made of a metal such as stainless steel and a fluororesin layer covering the metal base tube. The heater 611, the holder 612, and the stay 613 are disposed inside the belt 614. The belt 614 is configured to rotate around the heater 611, the holder 612, and the stay 613. The inner peripheral surface 614a of the belt 614 contacts the heater 611.

[0071] The pressure roller 62 has a metal shaft 62A and an elastic layer 62B covering the shaft 62A. The pressure roller 62 is pressed against the heater 611 via the belt 614. The pressure roller 62 forms a nip NP for heating and pressing the sheet S by sandwiching the belt 614 between the pressure roller 62 and the heater 611. That is, the pressure roller 62 forms the pressure roller 62 and the nip NP, and at the nip NP, the sheet S is heated and pressed together with the heater 611.

[0072] The pressure roller 62 is configured to be rotationally driven by the transmission of a driving force from a motor included in the image forming apparatus 1. By rotationally driving the pressure roller 62, the belt 614 is driven to rotate passively by the frictional force with the sheet S sandwiched between the belt 614 or the nip NP. As a result, the sheet S on which the toner image is transferred is conveyed between the pressure roller 62 and the heated belt 614, and the toner image is thermally fixed.

[0073] As shown in FIGS. 1, 7 to 9, the fixing device 6 has a fixing frame 63 that covers the heating unit 61 and the pressure roller 62, and a fixing shutter 64 supported by the fixing frame 63. The fixing frame 63 holds the heating unit 61 and the pressure roller 62. The fixing frame 63 covers the periphery of the heating unit 61 and the pressure roller 62, and has a first opening 63a formed on the upstream side in the sheet conveyance direction of the heating unit 61 and the pressure roller 62, and a second opening 63b formed on the downstream side in the sheet conveyance direction of the heating unit 61 and the pressure roller 62.

[0074] The fixing frame 63 has an upper frame 63A and a lower frame 63B. The upper frame 63A is located above the lower frame 63B. The upper frame 63A covers the heating unit 61, and the lower frame 63B covers the pressure roller 62.

[0075] The fixing shutter 64 is located on the upstream side in the sheet conveyance direction of the first opening 63a in the fixing frame 63, and has a rotation shaft 641 extending along the left-right direction and a connection shaft 642 protruding in a direction parallel to the rotation shaft 641. The rotation shaft 641 is rotatably supported by the fixing frame 63. The rotation shaft 641 is provided at both the left and right ends of the fixing shutter 64, and the connection shaft 642 protrudes rightward from the right end of the fixing shutter 64.

[0076] The fixing shutter 64 is configured to be rotatable about the rotation shaft 641, and by rotating about the rotation shaft 641, it can move between a closed position (the position shown in FIGS. 7(a), 8(a), 9(a)) where the first opening 63a is closed and an open position (the position shown in FIGS. 7(b), 8(b), 9(b)) where the first opening 63a is opened. When the fixing shutter 64 is in the closed position, the nip NP between the heating unit 61 and the pressure roller 62 is covered by the fixing shutter 64, and when the fixing shutter 64 is in the open position, the nip NP between the heating unit 61 and the pressure roller 62 is exposed to the outside of the fixing frame 63 through the first opening 63a.

[0077] Also, the fixing shutter 64 covers the upstream side in the sheet conveyance direction from the heating unit 61 when in the closed position, and opens the upstream side in the sheet conveyance direction from the heating unit 61 when in the open position. That is, the fixing shutter 64 is movable between a closed position that covers the upstream side in the sheet conveyance direction from the heating unit 61 and an open position that opens the upstream side in the sheet conveyance direction from the heating unit 61.

[0078] In this embodiment, the fixing device 6 includes a heating unit 61 having a heater 611 and a belt 614, and a pressure roller 62. However, the fixing device 6 can also be configured to include a heating roller with a built-in heater and a pressure roller pressed against the heating roller. Further, the fixing device 6 can also be configured to include a heating roller with a built-in heater and a pressure belt pressed against the heating roller by an elastic member.

[0079] [Drum shaft] As shown in FIGS. 10 and 11, the drum shaft 54a of the photosensitive drum 54 protrudes rightward along the axial direction X from the right end portion of the process cartridge 50. That is, the drum shaft 54a protrudes toward the first main body frame 24 side along the axial direction X.

[0080] [First main body frame] As shown in FIGS. 12 and 13, the first main body frame 24 has a cartridge rail 241 and a contact piece rail 242. The cartridge rail 241 is formed in a groove shape with an open left side. The cartridge rail 241 extends in the front-rear direction and is inclined in a direction of descending from the front to the rear.

[0081] The drum shaft 54a of the photosensitive drum 54 can enter the cartridge rail 241. When the process cartridge 50 is attached to the apparatus main body 2 and when the process cartridge 50 is detached from the apparatus main body 2, the cartridge rail 241 guides the drum shaft 54a. The drum shaft 54a guided by the cartridge rail 241 enters the cartridge rail 241 from the left side. Note that the process cartridge 50 is attached to the apparatus main body 2 from the front to the rear and is detached from the apparatus main body 2 from the rear to the front.

[0082] The contact piece rail 242 is formed in a groove shape with the right side open. The contact piece rail 242 extends in the front-rear direction and is inclined in a direction of descending as it goes from the front to the rear. The contact piece rail 242 is located on the right side of the cartridge rail 241 in the left-right direction.

[0083] The cartridge rail 241 has a front portion 241a located in the front, a rear portion 241c located in the rear, and a middle portion 241b located between the front portion 241a and the rear portion 241c. The contact piece rail 242 has a front portion 242a located in the front, a rear portion 242c located in the rear, and a middle portion 242b located between the front portion 242a and the rear portion 242c.

[0084] The middle portion 241b of the cartridge rail 241 and the middle portion 242b of the contact piece rail 242 overlap and communicate with each other. The middle portion 241b and the middle portion 242b form a through hole 24C that penetrates the front frame 24A in the left-right direction. In the through hole 24C, when the process cartridge 50 is attached to the apparatus main body 2 and when the process cartridge 50 is detached from the apparatus main body 2, the drum shaft 54a enters.

[0085] The front portion 242a of the contact piece rail 242 is located above the front portion 241a of the cartridge rail 241, and the rear portion 242c of the contact piece rail 242 is located above the rear portion 241c of the cartridge rail 241.

[0086] [Link] As shown in FIGS. 8, 14, and 15, the apparatus main body 2 is capable of abutting against the process cartridge 50 and includes a shutter link 8 that moves the fixing shutter 64 between an open position and a closed position. The shutter link 8 is connected to the fixing shutter 64.

[0087] When the process cartridge 50 is attached to the apparatus main body 2, the shutter link 8 abuts against the process cartridge 50 to move the fixing shutter 64 from the closed position to the open position. When the process cartridge 50 is detached from the apparatus main body 2, the shutter link 8 abuts against the process cartridge 50 to move the fixing shutter 64 from the open position to the closed position. That is, the shutter link 8 is configured to move the fixing shutter 64 between the open position and the closed position in conjunction with the attachment / detachment operation of the process cartridge 50 with respect to the apparatus main body 2.

[0088] The shutter link 8 includes a contact piece 80, a first swing link 81, a linear motion link 82, a second swing link 83, a third swing link 84, an opening / closing link 85, and a coil spring 86.

[0089] The contact piece 80 moves in contact with the drum shaft 54a of the photosensitive drum 54. The contact piece 80 is slidably fitted to a contact piece rail 242, and the contact piece rail 242 guides the contact piece 80 that moves in contact with the drum shaft 54a.

[0090] The contact piece 80 includes a main body portion 801, a connecting portion 802, a first boss 803, and a second boss 804. The main body portion 801 is formed of a plate-like member whose plate surface faces in the left-right direction. The connecting portion 802 is a protrusion that projects rightward from the right surface of the main body portion 801.

[0091] The first boss 803 and the second boss 804 are protrusions that project leftward from the left surface of the main body portion 801. The first boss 803 and the second boss 804 enter the contact piece rail 242 of the first main body frame 24 from the right side and are guided by the contact piece rail 242.

[0092] The second boss 804 is located upstream of the first boss 803 in the mounting direction of the process cartridge 50. The mounting direction is the direction in which the process cartridge 50 moves toward the mounting position when the process cartridge 50 is mounted on the apparatus main body 2.

[0093] The first boss 803 abuts against the drum shaft 54a when the process cartridge 50 is mounted on the apparatus main body 2, and the second boss 804 abuts against the drum shaft 54a when the process cartridge 50 is detached from the apparatus main body 2.

[0094] The first boss 803 abuts against the drum shaft 54a of the process cartridge 50 mounted on the apparatus main body 2 when it is located at the middle portion 242b (through hole 24C) of the contact piece rail 242. Also, the second boss 804 abuts against the drum shaft 54a of the process cartridge 50 detached from the apparatus main body 2 when it is located at the middle portion 242b (through hole 24C) of the contact piece rail 242.

[0095] The first rotating link 81 is a substantially linear member that is rotatably connected to the contact piece 80. The first rotating link 81 has a fitting portion 811 located at the front end portion, into which the connecting portion 802 of the contact piece 80 is rotatably fitted, and a boss 812 located at the rear end portion and protruding leftward. The first rotating link 81 is arranged in an inclined posture in which the fitting portion 811 is located above and in front of the boss 812. The first rotating link 81 is connected to the contact piece 80 by fitting the connecting portion 802 into the fitting portion 811, and rotates along with the movement of the contact piece 80.

[0096] The linear motion link 82 is a substantially linear member that is rotatably connected to the first rotating link 81 and extends in the front-rear direction. The linear motion link 82 has a fitting portion 821 located at the front end portion, into which the boss 812 of the first rotating link 81 is rotatably fitted, and a connecting hole 822 located at the rear end portion. The linear motion link 82 is connected to the first rotating link 81 by fitting the boss 812 into the fitting portion 821, and linearly moves in the front-rear direction along with the rotation of the first rotating link 81.

[0097] The second rotating link 83 is connected to the linear motion link 82 and supported by the first main body frame 24. The second rotating link 83 has a support portion 831 rotatably supported by the first main body frame 24, a first arm 832 extending substantially downward from the support portion 831, and a second arm 833 extending substantially upward from the support portion 831. An engagement pin 832a protruding leftward is formed at the tip of the first arm 832, and a connection hole 833a is formed at the tip of the second arm 833.

[0098] The engagement pin 832a of the first arm 832 enters the connection hole 822 of the linear motion link 82 from the right, and engages with the connection hole 822 along the forward and backward movement of the linear motion link 82. The second rotating link 83 is connected to the linear motion link 82 when the engagement pin 832a and the connection hole 822 engage with each other, and rotates about the support portion 831 along the movement of the linear motion link 82.

[0099] The third rotating link 84 is connected to the second rotating link 83 and rotatably supported by the support shaft 65 of the fixing device 6. The third rotating link 84 has a support portion 841 rotatably supported by the support shaft 65, an engagement pin 842 protruding rightward from the support portion 841, an operation cam 843 formed at a phase different from that of the engagement pin 842 in the circumferential direction of the support portion 841, and a connection hole 844 formed in the operation cam 843. The connection hole 844 penetrates the operation cam 843 along the left - right direction.

[0100] The engagement pin 842 of the third rotating link 84 enters the connection hole 833a of the second rotating link 83 from the left, and engages with the connection hole 833a along the rotation of the second rotating link 83. The third rotating link 84 is connected to the second rotating link 83 when the engagement pin 842 and the connection hole 833a engage with each other, and rotates about the support shaft 65 along the rotation of the second rotating link 83.

[0101] As shown in FIGS. 7 and 8, the opening and closing link 85 is connected to the third rotating link 84 and is rotatably supported by the support shaft 65 of the fixing device 6. The opening and closing link 85 moves along with the movement of the third rotating link 84 to move the fixing shutter 64 of the fixing device 6 between the closed position and the open position. The opening and closing link 85 is located at the right end of the fixing device 6 and has a support portion 851, an arm portion 852, an engaging portion 853, and an engaging pin 854.

[0102] The support portion 851 is rotatably supported by a support shaft 65 that protrudes rightward from the right end portion of the fixing frame 63. The arm portion 852 is an arm member that extends forward from the support portion 851. The engaging portion 853 is located at the front end portion of the arm portion 852 and has an elliptical engaging hole 853a that is long in the front-rear direction. A connecting shaft 642 that protrudes rightward from the right end portion of the fixing shutter 64 is engaged with the engaging hole 853a.

[0103] The opening and closing link 85 is rotatable about the support portion 851 in the direction in which the engaging portion 853 moves up and down. When the opening and closing link 85 rotates and the engaging portion 853 moves downward, the fixing shutter 64 moves to the closed position (see FIGS. 7(a) and 8(a)). When the opening and closing link 85 rotates and the engaging portion 853 moves upward, the fixing shutter 64 moves to the open position (see FIGS. 7(b) and 8(b)).

[0104] The engaging pin 854 protrudes rightward from the end portion of the arm portion 852 on the support portion 851 side. The engaging pin 854 of the opening and closing link 85 enters the connecting hole 844 of the third rotating link 84 from the left.

[0105] The coil spring 86 is supported by the support portion 841 of the third rotating link 84. The coil spring 86 has an arm portion 861. The arm portion 861 extends from the inner diameter side to the outer diameter side of the connecting hole 844 and enters the connecting hole 844.

[0106] The wrist portion 861 is located above the engagement pin 854 within the connection hole 844. The coil spring 86 is rotatable along with the rotation of the third rotation link 84. The edge of the lower end of the connection hole 844 in the operation cam 843 of the third rotation link 84 forms an engagement surface 844a. The engagement surface 844a is located below the engagement pin 854.

[0107] The engagement surface 844a of the connection hole 844 engages with the engagement pin 854 when the third rotation link 84 rotates in the direction in which the operation cam 843 moves upward. The wrist portion 861 of the coil spring 86 engages with the engagement pin 854 when the third rotation link 84 rotates in the direction in which the operation cam 843 moves downward.

[0108] The opening and closing link 85 is connected to the third rotation link 84 when the engagement pin 854 engages with the wrist portion 861 or the engagement surface 843a, and moves along with the rotation of the third rotation link 84 to move the fixing shutter 64 between the closed position and the open position.

[0109] In the image forming apparatus 1, when the process cartridge 50 is attached to or detached from the apparatus main body 2, the contact piece 80 of the shutter link 8 contacts the drum shaft 54a and moves along the contact piece rail 242, so that a driving force is transmitted to the fixing shutter 64 via the shutter link 8, and the fixing shutter 64 moves between the closed position and the open position.

[0110] In this embodiment, the shutter link 8 has a configuration including the contact piece 80, the first rotation link 81, the linear motion link 82, the second rotation link 83, the third rotation link 84, the opening and closing link 85, and the coil spring 86, but is not limited thereto, and may be configured by one link that is connected to the fixing shutter 64 and contacts the process cartridge 50 to open and close the fixing shutter 64. Also, the movement of the shutter link 8 is not limited to rotation or sliding, and any movement that appropriately opens and closes the fixing shutter 64 according to the insertion and removal of the process cartridge 50 is acceptable.

[0111] [Pressing portion] As shown in FIG. 14, the apparatus main body 2 includes a pressing portion 9. The pressing portion 9 presses the shutter link 8 in a direction in which the fixing shutter 64 moves to the open position before the fixing shutter 64 moves to the open position in the process of the shutter link 8 moving the fixing shutter 64 from the closed position to the open position. Further, the pressing portion 9 restricts the movement of the shutter link 8 that has moved the fixing shutter 64 to the open position or the closed position by pressing the shutter link 8.

[0112] The pressing portion 9 has a pressing spring 92 and a pressing arm 91 that is pressed by the pressing spring 92 and abuts on the upper surface 82A of the linear motion link 82. The pressing spring 92 presses the tip of the pressing arm 91 toward the upper surface 82A side of the linear motion link 82.

[0113] The upper surface 82A of the linear motion link 82 has a link protrusion 823 that protrudes upward. The link protrusion 823 is formed in a mountain shape having a first pressed surface 823a, a second pressed surface 823b, and a third pressed surface 823c.

[0114] The first pressed surface 823a is located at the apex portion of the mountain shape and extends in the horizontal direction. The second pressed surface 823b is located in front of the first pressed surface 823a and is formed as an inclined surface that rises as it goes rearward. The third pressed surface 823c is located behind the first pressed surface 823a and is formed as an inclined surface that descends as it goes rearward.

[0115] The linear motion link 82 can be positioned at a position where the pressing arm 91 presses the first pressed surface 823a, a position where the pressing arm 91 presses the second pressed surface 823b, and a position where the pressing arm 91 presses the third pressed surface 823c by moving in the front-rear direction.

[0116] Since the first pressed surface 823a is a surface that extends in the horizontal direction, when the pressing arm 91 presses the first pressed surface 823a from above, the pressing force by the pressing arm 91 does not act in both the backward and forward directions.

[0117] Since the second pressed surface 823b is a surface that slopes upward from below along the backward direction, when the pressing arm 91 presses the second pressed surface 823b from above, the pressing force by the pressing arm 91 acts backward. Also, in a state where the pressing arm 91 is pressing the second pressed surface 823b from above, the forward movement of the linear motion link 82 is restricted.

[0118] Since the third pressed surface 823c is a surface that slopes downward from above along the backward direction, when the pressing arm 91 presses the third pressed surface 823c from above, the pressing force by the pressing arm 91 acts forward. Also, in a state where the pressing arm 91 is pressing the third pressed surface 823c from above, the backward movement of the linear motion link 82 is restricted.

[0119] In the present embodiment, the pressing portion 9 has a pressing spring 92 and a pressing arm 91 that is pressed by the pressing spring 92 and contacts the upper surface 82A of the linear motion link 82. However, it is not limited to this, and as long as it is a configuration that presses the shutter link 8, it does not have to be in the form of a spring or an arm.

[0120] [Link operation] Next, the operation of the shutter link 8 will be described.

[0121] (Operation when the process cartridge is installed) When installing the process cartridge 50 onto the apparatus main body 2, when the drum shaft 54a enters the front portion 241a of the cartridge rail 241 (see FIG. 15), it then enters the middle portion 241b (through hole 24C) and contacts the first boss 803 of the contact piece 80. As shown in FIG. 16, the contact piece 80 that has contacted the drum shaft 54a is pressed by the drum shaft 54a and moves to the downstream side in the installation direction of the process cartridge 50.

[0122] When the contact piece 80 moves, the first swing link 81 moves backward while rotating in a direction in which the inclination angle with respect to the horizontal direction becomes smaller. When the first swing link 81 rotates and moves, the linear motion link 82 connected to the first swing link 81 moves linearly backward.

[0123] When the linear motion link 82 moves rearward, the engagement hole 822 of the linear motion link 82 engages with the engagement pin 832a of the second rotating link 83, and the second rotating link 83 rotates in the direction in which the engagement pin 832a moves rearward. When the second rotating link 83 rotates, the engagement hole 833a of the second rotating link 83 engages with the engagement pin 842 of the third rotating link 84, and the third rotating link 84 rotates in the direction in which the engagement pin 842 moves forward.

[0124] When the third rotating link 84 rotates, the engagement surface 844a of the engagement hole 844 in the operation cam 843 engages with the engagement pin 854 of the opening / closing link 85 from below. By the engagement surface 844a of the engagement hole 844 engaging with the engagement pin 854, the opening / closing link 85 rotates in the direction in which the engaging portion 853 moves upward, and the fixing shutter 64 moves from the closed position toward the open position.

[0125] As shown in FIG. 17, the drum shaft 54a that has moved the contact piece 80 rearward at the middle portion 241b (through hole 24C) of the cartridge rail 241 moves from the middle portion 241b to the rear portion 241c of the cartridge rail 241 and separates from the contact piece 80.

[0126] As shown in FIG. 18, after the drum shaft 54a contacts the contact piece 80 and the linear motion link 82 moves rearward, in a state where the drum shaft 54a and the contact piece 80 are separated, the pressing arm 91 contacts the second pressed surface 823b of the linear motion link 82.

[0127] After the contact piece 80 and the drum shaft 54a are separated, the drum shaft 54a does not move the contact piece 80. However, since the pressing arm 91 is in contact with the second pressed surface 823b, a pressing force in the direction toward the second position is applied to the linear motion link 82 from the pressing arm 91, and the linear motion link 82 moves rearward.

[0128] As shown in FIG. 8(b), when the linear motion link 82 moves rearward due to the pressing force from the pressing arm 91, the opening / closing link 85 rotates in the direction in which the engaging portion 853 moves upward, and the fixing shutter 64 moves to the open position. As shown in FIG. 19, when the process cartridge 50 is mounted on the apparatus main body 2, the drum shaft 54a separated from the contact piece 80 moves to the mounting position located at the rear end of the rear portion 241c of the cartridge rail 241.

[0129] (Operation when process cartridge is detached) When the shutter link 8 detaches the process cartridge 50, it operates in the reverse manner to the operation when the process cartridge 50 is mounted.

[0130] When the process cartridge 50 at the mounting position shown in FIG. 19 is detached from the apparatus main body 2 forward, the drum shaft 54a moves in the rear portion 241c of the cartridge rail 241 toward the downstream side in the detachment direction. Note that the detachment direction is the direction in which the process cartridge 50 withdrawn from the apparatus main body 2 moves toward the outside of the apparatus main body 2 when the process cartridge 50 is detached from the apparatus main body 2. As shown in FIG. 16, when the drum shaft 54a moving in the cartridge rail 241 reaches the middle portion 241b (through hole 24C), the drum shaft 54a contacts the second boss 804 of the contact piece 80.

[0131] The contact piece 80 contacting the drum shaft 54a moves in the downstream side in the detachment direction of the process cartridge 50 within the middle portion 242b (through hole 24C). When the contact piece 80 moves, the first rotation link 81 moves forward while rotating in the direction in which the inclination angle with respect to the horizontal direction increases, and the linear motion link 82 moves linearly forward.

[0132] When the linear motion link 82 moves, the engagement hole 822 of the linear motion link 82 engages with the engagement pin 832a of the second rotating link 83, and the second rotating link 83 rotates in the direction in which the engagement pin 832a moves forward. When the second rotating link 83 rotates, the engagement hole 833a of the second rotating link 83 engages with the engagement pin 842 of the third rotating link 84, and the third rotating link 84 rotates in the direction in which the engagement pin 842 moves backward.

[0133] When the third rotating link 84 rotates, the coil spring 86 rotates along with the rotation of the third rotating link 84, and the arm portion 861 of the coil spring 86 engages with the engagement pin 854 of the opening and closing link 85 from above. When the arm portion 861 engages with the engagement pin 854, the opening and closing link 85 rotates in the direction in which the engaging portion 853 moves downward. As a result, the fixing shutter 64 moves from the open position toward the closed position side. In a state where the process cartridge 50 is detached from the apparatus main body 2, the fixing shutter 64 is located at the closed position.

[0134] As described above, the shutter link 8 connected to the fixing shutter 64 is configured to move the fixing shutter 64 between the open position and the closed position in conjunction with the attachment / detachment operation of the process cartridge 50 with respect to the apparatus main body 2. Thereby, it is possible to open and close the fixing shutter 64 by the attachment / detachment operation of the process cartridge 50 with respect to the apparatus main body 2 without performing a separate operation for opening and closing the fixing shutter 64.

[0135] In the present embodiment, the fixing shutter 64 is opened and closed by the drum shaft 54a of the process cartridge 50 coming into contact with the shutter link 8. However, the present invention is not limited to this, and other portions of the process cartridge 50 may be configured to come into contact with the shutter link 8.

[0136] [Position relationship among fixing chute, fixing guide, and fixing shutter] As shown in FIGS. 20 to 22, the apparatus main body 2 has a fixing chute 28 and a fixing guide 66.

[0137] The fixing chute 28 is located upstream of the fixing device 6 in the sheet conveyance direction and forms the lower side of the conveyance path P of the sheet S. The fixing chute 28 is supported by the lower frame 63B of the fixing frame 63. The fixing chute 28 is located below the conveyance path P. The fixing chute 28 has a sheet conveyance surface 28A facing upward, and the sheet conveyance surface 28A guides the lower side of the sheet S conveyed along the conveyance path P.

[0138] The fixing guide 66 is located upstream of the heating unit 61 of the fixing device 6 in the sheet conveyance direction and is located on the opposite side of the fixing chute 28 across the conveyance path P in the thickness direction of the sheet S conveyed along the conveyance path P. The fixing guide 66 is located above the conveyance path P and guides the upper side of the sheet S conveyed along the conveyance path P. The fixing guide 66 is supported by the upper frame 63A of the fixing frame 63.

[0139] The fixing guide 66 has a guide conveyance surface 661 facing downward. The guide conveyance surface 661 is an inclined surface that inclines in a direction approaching the fixing chute 28 as it goes downstream in the sheet conveyance direction. When the sheet S conveyed downstream in the sheet conveyance direction from the photosensitive drum 54 abuts against the guide conveyance surface 661, the sheet S is guided by the guide conveyance surface 661 to the first opening 63a of the fixing frame 63.

[0140] The fixing shutter 64 is located upstream of the fixing guide 66 in the sheet conveyance direction and is located on the opposite side of the fixing chute 28 across the conveyance path P in the thickness direction of the sheet S conveyed along the conveyance path P.

[0141] The fixing shutter 64 has a shutter conveyance surface 643 capable of conveying the sheet S on the upstream side in the sheet conveyance direction of the fixing guide 66 in a state where the fixing shutter 64 is in the open position. The shutter conveyance surface 643 is a surface facing downward in a state where the fixing shutter 64 is in the open position.

[0142] The shutter conveyance surface 643 is an inclined surface that slopes in a direction approaching the fixing chute 28 as it goes downstream in the sheet conveyance direction in a state where the fixing shutter 64 is located at the open position. When the sheet S conveyed downstream in the sheet conveyance direction from the photosensitive drum 54 abuts on the shutter conveyance surface 643, the sheet S is guided by the shutter conveyance surface 643 and then taken over by the guide conveyance surface 661.

[0143] As shown in FIG. 23, in a state where the fixing shutter 64 is located at the open position, the end portion 643a on the downstream side in the sheet conveyance direction of the shutter conveyance surface 643 is located closer to the fixing chute 28 than the end portion 661a on the upstream side in the sheet conveyance direction of the guide conveyance surface 661. That is, the distance D1 between the end portion 643a on the downstream side in the sheet conveyance direction of the shutter conveyance surface 643 and the sheet conveyance surface 28A of the fixing chute 28 is smaller than the distance D2 between the end portion 661a on the upstream side in the sheet conveyance direction of the guide conveyance surface 661 and the sheet conveyance surface 28A of the fixing chute 28.

[0144] Since the distance D1 is smaller than the distance D2, a step is formed between the shutter conveyance surface 643 and the guide conveyance surface 661 such that the end portion 643a is located closer to the fixing chute 28 than the end portion 661a. Therefore, when the sheet S conveyed downstream in the sheet conveyance direction from the photosensitive drum 54 and guided by the shutter conveyance surface 643 is taken over from the shutter conveyance surface 643 to the guide conveyance surface 661, it is possible to suppress the leading end of the conveyed sheet S from being caught by the fixing guide 66, and thus the sheet S can be stably conveyed even when the fixing shutter 64 is provided.

[0145] Also, with the fixing shutter 64 in the open position, the end portion 643a on the downstream side in the sheet conveyance direction of the shutter conveyance surface 643 overlaps with the guide conveyance surface 661 in the sheet conveyance direction. That is, the end portion 643a on the downstream side in the sheet conveyance direction of the shutter conveyance surface 643 is located on the downstream side in the sheet conveyance direction from the end portion 661a on the upstream side in the sheet conveyance direction of the guide conveyance surface 661. Thereby, the sheet S guided by the shutter conveyance surface 643 can smoothly transfer onto the guide conveyance surface 661, and it is possible to suppress the sheet S from getting caught on the fixing guide 66.

[0146] Also, the inclination angle θ1 of the shutter conveyance surface 643 with respect to the direction along the conveyance path P in the sheet conveyance direction is formed larger than the inclination angle θ2 of the guide conveyance surface 661 with respect to the direction along the conveyance path P. Thereby, a large space can be secured between the shutter conveyance surface 643 and the fixing chute 28, and it is possible to suppress jamming from occurring in the conveyed sheet S.

[0147] As shown in FIG. 22, in a state where the fixing shutter 64 is in the closed position, the shutter conveyance surface 643 faces the fixing device 6 and is in a position where it is hidden and not visible from the front. When the process cartridge 50 is detached from the apparatus main body 2, it is possible to insert the user's hand into the apparatus main body 2 from the front, but the fixing shutter 64 is in the closed position and the shutter conveyance surface 643 faces the fixing device 6 side where the user's hand is difficult to touch. Therefore, it is possible to prevent the user's hand from touching the shutter conveyance surface 643 and getting dirt attached, and then the conveyed sheet S coming into contact with the shutter conveyance surface 643, thereby preventing the sheet S from getting dirty.

[0148] [Shielding surface of the fixing shutter] Further, as shown in FIG. 22, the fixing shutter 64 has a shielding surface 644 that covers the upstream side in the sheet conveyance direction from the heating unit 61 in a state where the fixing shutter 64 is in the closed position. The shielding surface 644 extends in a direction intersecting the direction in which the shutter conveyance surface 643 extends. For example, the angle θ3 formed by the shutter conveyance surface 643 and the sheet conveyance surface 28A in the fixing chute 28 is smaller than the angle θ4 formed by the shielding surface 644 and the sheet conveyance surface 28A in the fixing chute 28, and the angle θ3 and the angle θ4 are different.

[0149] In this way, since the fixing shutter 64 has the shielding surface 644, when the fixing shutter 64 is in the closed position, the heating unit 61 is covered by the shielding surface 644, so that it is possible to prevent the user from touching the heating unit 61.

[0150] [Guide projection of the fixing guide] Further, as shown in FIGS. 23 and 24, the fixing guide 66 provided on the upper frame 63A of the fixing frame 63 has guide projections 662 located at the left and right ends in the lateral direction of the guide conveyance surface 661. The guide projections 662 protrude toward the fixing chute 28 side from the guide conveyance surface 661. The lateral direction is an example of a direction orthogonal to the sheet conveyance direction. The guide projections 662 can press the left and right ends of the conveyed sheet S from above.

[0151] The guide projections 662 are inclined in a direction approaching the fixing chute 28 as they go downstream in the sheet conveyance direction, and the inclination angle θ5 of the guide projections 662 with respect to the direction along the conveyance path P is formed larger than the inclination angle θ2 of the guide conveyance surface 661 with respect to the direction along the conveyance path P.

[0152] When the rear end of the conveyed sheet S passes through the guide conveyance surface 661, the rear end of the sheet S may bounce. However, since the fixing guide 66 has the guide projections 662, it is possible to press the conveyed sheet S with the guide projections 662 and suppress the bounce occurring at the rear end of the sheet S.

[0153] In this case, since the inclination angle θ5 of the guide projection 662 is formed to be larger than the inclination angle θ2 of the guide conveyance surface 661, even if the guide projection 662 protrudes more than the guide conveyance surface 661, the upstream end of the guide projection 662 in the sheet conveyance direction can be positioned farther from the fixing chute 28 than the downstream end of the guide conveyance surface 661 in the sheet conveyance direction, and it is possible to prevent the conveyed sheet S from being caught by the guide projection.

[0154] [Upstream guide] As shown in FIGS. 21, 23, and 25, the air duct 26 has an upstream guide 261. The upstream guide 261 is located on the opposite side of the fixing chute 28 across the conveyance path P in the thickness direction of the sheet S conveyed along the conveyance path P.

[0155] The upstream guide 261 is formed in a rib shape extending along the front-rear direction, and a plurality of upstream guides 261 are arranged with gaps in the left-right direction. A ventilation port 262 through which air can flow is formed between the upstream guides 261 in the left-right direction, and the air inside the apparatus main body 2 can flow into the air duct 26 through the ventilation port 262.

[0156] The upstream guide 261 can guide the sheet S upstream in the sheet conveyance direction from the shutter conveyance surface 643 of the fixing shutter 64. When the sheet S guided by the upstream guide 261 is conveyed downstream in the sheet conveyance direction from the upstream guide 261, it transfers from the upstream guide 261 to the shutter conveyance surface 643.

[0157] The lower end of the upstream guide 261 is inclined in a direction approaching the fixing chute 28 as it goes downstream in the sheet conveyance direction. The end portion 261a on the downstream side in the sheet conveyance direction of the upstream guide 261 is located closer to the fixing chute 28 than the end portion 643b on the upstream side in the sheet conveyance direction of the shutter conveyance surface 643. That is, the distance D3 between the end portion 261a on the downstream side in the sheet conveyance direction of the upstream guide 261 and the sheet conveyance surface 28A of the fixing chute 28 is smaller than the distance D4 between the end portion 643b on the upstream side in the sheet conveyance direction of the shutter conveyance surface 643 and the sheet conveyance surface 28A of the fixing chute 28.

[0158] Note that the "fixing chute" in the "approaching the fixing chute 28" and "near the fixing chute 28" in this description includes a virtual plane obtained by extending the sheet conveyance surface 28A of the fixing chute.

[0159] Thus, since the distance D3 is smaller than the distance D4, a step is formed between the upstream guide 261 and the shutter conveyance surface 643, where the end portion 261a is located closer to the fixing chute 28 than the end portion 643b. Therefore, when the sheet S guided by the upstream guide 261 transfers to the shutter conveyance surface 643, it is possible to suppress the sheet S from being caught by the fixing shutter 64 and stably convey the sheet S.

[0160] [Movable chute] As shown in FIGS. 21 to 23 and FIG. 25, the image forming apparatus 1 has a movable chute 71. The movable chute 71 is located between the process cartridge 50 and the fixing device 6 in the front-rear direction. That is, the movable chute 71 is located downstream of the photosensitive drum 54 and the transfer roller 55 constituting the transfer unit and upstream of the fixing device 6 in the sheet conveyance direction.

[0161] The movable chute 71 is located on the opposite side of the upstream guide 261 across the conveyance path P in the thickness direction of the sheet S conveyed along the conveyance path P, and can guide the conveyed sheet S from below.

[0162] The movable chute 71 is rotatable about a rotation axis 711 located at the front end. By rotating about the rotation axis 711, the movable chute 71 can move between a first position (the position shown by the solid line in FIG. 21) and a second position (the position shown in FIG. 22 and the position shown by the two-dot chain line in FIG. 21) where the end 71a on the downstream side in the sheet conveyance direction is farther from the conveyance path P than in the first position.

[0163] The movable chute 71 has a sheet conveyance surface 71A for guiding the sheet S. The sheet conveyance surface 71A faces upward. When the movable chute 71 is in the first position, the sheet conveyance surface 71A guides the sheet S conveyed from the process cartridge 50 toward the fixing device 6. Also, when the movable chute 71 is in the second position, it is located farther from the conveyance path P than when the movable chute 71 is in the first position. When the sheet S is conveyed by the transfer unit composed of the photosensitive drum 54 and the transfer roller 55 and the fixing device 6, the conveyance speed of the sheet S by the transfer unit is greater than the conveyance speed of the sheet S by the fixing device 6, and the sheet S between the fixing device 6 and the transfer unit is bent. The sheet conveyance surface 71A when the movable chute 71 is in the second position guides the sheet S bent toward the sheet conveyance surface 71A side between the fixing device 6 and the transfer unit.

[0164] In this way, by guiding the sheet S with the movable chute 71 in the first position closer to the conveyance path P than the second position, it is possible to properly guide the sheet conveyed from the transfer unit composed of the photosensitive drum 54 and the transfer roller 55 to the fixing device 6 by the movable chute 71.

[0165] As shown in FIG. 21, in a state where the movable chute 71 is in the first position, a virtual plane VS extending the sheet conveyance surface 71A at the end 71a on the downstream side in the sheet conveyance direction of the movable chute 71 is configured to pass through the fixing guide 66.

[0166] The leading edge of the sheet S guided on the sheet conveyance surface 71A of the movable chute 71 may move downstream of the shutter conveyance surface 643 without contacting the shutter conveyance surface 643. Such a situation is likely to occur in the case of curled paper in which the sheet S curls away from the shutter conveyance surface 643, or straight paper that is not particularly curled.

[0167] In such a case, since the virtual plane VS of the sheet conveyance surface 71A is configured to pass through the fixing guide 66, the leading edge of the sheet S guided by the movable chute 71 comes into contact with the guide conveyance surface 661 located downstream of the shutter conveyance surface 643, and it is possible to guide the sheet S to the fixing device 6 more stably.

[0168] Also, as shown in FIG. 21, the perpendicular line VL of the shutter conveyance surface 643 in the fixing shutter 6 is configured to pass through the sheet conveyance surface 71A of the movable chute 71. In the present embodiment, the perpendicular line VL of the shutter conveyance surface 643 is configured to pass through both the sheet conveyance surface 71A of the movable chute 71 located at the first position and the sheet conveyance surface 71A of the movable chute 71 located at the second position.

[0169] Thereby, it is possible to suppress the contact angle of the sheet S guided by the movable chute 71 with respect to the shutter conveyance surface 643 from exceeding 90 degrees and the sheet S from being guided upstream in the sheet conveyance direction by the shutter conveyance surface 643. Therefore, it is possible to appropriately guide the sheet S conveyed from the movable chute 71 toward the fixing device 6 by the shutter conveyance surface 643.

[0170] [Operation of the Movable Chute] As shown in FIG. 23, the image forming apparatus 1 has a chute spring 72 that biases the movable chute 71. The chute spring 72 biases the movable chute 71 toward the first position side.

[0171] As shown in Fig. 26, the image forming apparatus 1 has a solenoid 97 which is a drive source for moving the movable chute 71. The solenoid 97 is a solenoid actuator for moving the movable chute 71 from the first position to the second position. The solenoid 97 is connected to the control unit 95, and the control unit 95 controls the operation of the solenoid 97.

[0172] After the leading edge of the conveyed sheet S has passed through the fuser 6, the control unit 95 controls the solenoid 97 to move the movable chute 71 from the first position to the second position. The solenoid 97 is configured to move the movable chute 71 via, for example, a chute link 75.

[0173] In this case, the control unit 95 determines that the leading edge of the sheet S has passed through the fuser 6 when a predetermined time has elapsed after the post-registration sensor 98 detects the leading edge of the sheet S, and controls the solenoid 97 to move the movable chute 71 from the first position to the second position.

[0174] Further, the control unit 95 determines that the trailing edge of the sheet S has passed through the fuser 6 when a predetermined time has elapsed after the post-registration sensor 98 detects the trailing edge of the sheet S, and controls the solenoid 97 to move the movable chute 71 from the second position to the first position.

[0175] [Chute link] As shown in Figs. 26 to 28, the chute link 75 is connected to the solenoid 97 and is driven by the solenoid 97 to press the movable chute 71, thereby moving the movable chute 71 from the first position to the second position.

[0176] The solenoid 97 has a main body 921 supported by the second main body frame 25 and a plunger 922 that can move in the left - right direction with respect to the main body 921. The plunger 922 is biased to the right from the main body 921 by a biasing member. In a state where the solenoid 97 is not driven by the control unit 95, the plunger 922 is in a state of moving to the right and protruding from the main body 921. On the other hand, in a state where the solenoid 97 is driven by the control unit 95, the plunger 922 is pulled into the main body 921 and moves to the left.

[0177] The shoot link 75 has a first link 751, a second link 752, and a third link 753. The first link 751 and the second link 752 are located inside the air duct 26, and the third link 753 protrudes downward from inside the air duct 26. Inside the air duct 26, a holder 77 for supporting the shoot link 75 is attached.

[0178] The first link 751 is an elongated member extending in the left - right direction and is supported by the holder 77 so as to be movable in the left - right direction. The first link 751 has a first end 751a which is the left - hand end and a second end 751b which is the right - hand end. The first end 751a is connected to the plunger 922 of the solenoid 97. The second end 751b is in contact with the second link 752.

[0179] The second link 752 is an elongated member extending in the left - right direction and is located below the first link 751. The second link 752 has a pivot shaft portion 752a located at the right - hand end, a contact portion 752b extending upward from the pivot shaft portion 752a, a tip portion 752c which is the left - hand end, and an engagement portion 752d extending obliquely upward to the right from the pivot shaft portion 752a. The second link 752 is supported by the holder 77 so as to be rotatable about the pivot shaft portion 752a.

[0180] The image forming apparatus 1 has a link spring 76 that biases the second link 752. The link spring 76 is attached to a holder 77. One end of the link spring 76 is engaged with a hook 771 of the holder 77, and the other end of the link spring 76 is engaged with an engaging portion 752d of the second link 752. The second link 752 is biased by the link spring 76 so as to rotate in a direction in which the tip portion 752c moves upward. The contact portion 752b is in contact with the second end portion 751b of the first link 751. When the first link 751 moves leftward, the contact portion 752b is pressed leftward by the second end portion 751b, and the second link 752 rotates in a direction in which the tip portion 752c moves downward.

[0181] The third link 753 is a long member extending in the vertical direction and is arranged to be movable in the vertical direction. The third link 753 has a connecting portion 753a located at the upper end and a pressing portion 753b located at the lower end. The connecting portion 753a is connected to the tip portion 752c of the second link 752, and the pressing portion 753b can press a portion 71B to be pressed of the movable chute 71.

[0182] The portion 71B to be pressed of the movable chute 71 is formed on the side of the sheet conveyance surface 71A and faces upward. The sheet conveyance surface 71A of the movable chute 71 is formed in a region through which the sheet S passes in the left-right direction, and the portion 71B to be pressed is located outside the left-right direction of the region where the sheet conveyance surface 71A is formed. In the present embodiment, the portion 71B to be pressed is located on the left side of the region where the sheet conveyance surface 71A is formed.

[0183] The pressing portion 753b of the third link 753 and the portion 71B to be pressed of the movable chute 71 face each other in the vertical direction. When the third link 753 moves downward, the pressing portion 753b presses the portion 71B to be pressed.

[0184] In the chute link 75 configured as described above, when the solenoid 97 is in the off state where it is not driven by the control unit 95, the first link 751 connected to the plunger 922 is in a state of having moved to the right, and the second link 752 is rotated in a direction in which the tip 752c moves upward by the biasing force of the link spring 76.

[0185] The third link 753 is in a state of having been moved upward by the second link 752, and the pressing portion 753b of the third link 753 and the pressed portion 71B of the movable chute 71 are separated from each other. The movable chute 71 is moved to the first position by the biasing force of the chute spring 72.

[0186] On the other hand, when the solenoid 97 is in the on state where it is driven by the control unit 95, the first link 751 is moved to the left by the plunger 922 attracted by the main body 921. When the first link 751 moves to the left, the contact portion 752b of the second link 752 is pressed by the second end portion 751b of the first link 751, and the second link 752 rotates in a direction in which the tip 752c moves downward against the biasing force of the link spring 76.

[0187] As the second link 752 rotates, the third link 753 moves downward, and the pressing portion 753b of the third link 753 presses the pressed portion 71B of the movable chute 71 downward, so that the movable chute 71 moves from the first position to the second position against the biasing force of the chute spring 72.

[0188] In this way, the chute link 75 is configured to move the movable chute 71 from the first position to the second position by being driven by the solenoid 97 and pressing the movable chute 71 from the sheet conveyance surface 71A side. Thereby, it is possible to move the movable chute 71 from the first position to the second position quickly and stably.

[0189] Further, with such a configuration, after the leading edge of the conveyed sheet S has passed through the fixing device 6, the control unit 95 turns on the solenoid 97 and presses the movable chute 71 from the side of the sheet conveyance surface 71A by the chute link 75, thereby moving the movable chute 71 from the first position to the second position.

[0190] Furthermore, after the trailing edge of the conveyed sheet S has passed through the transfer unit composed of the photosensitive drum 54 and the transfer roller 55, the control unit 95 turns off the solenoid 97, separates the chute link 75 from the movable chute 71, and moves the movable chute 71 from the second position to the first position by the biasing force of the chute spring 72.

[0191] In the image forming apparatus 1, after the leading edge of the sheet S has passed through the fixing device 6, there is a period during which the sheet S is conveyed by both the fixing device 6 and the transfer unit composed of the photosensitive drum 54 and the transfer roller 55.

[0192] During this period, the conveyance speed of the sheet S by the photosensitive drum 54 and the transfer roller 55 constituting the transfer unit is higher than the conveyance speed of the sheet S by the fixing device 6, and the sheet S between the fixing device 6 and the transfer unit is bent. Therefore, by moving the movable chute 71 toward the second position away from the conveyance path P under the control of the control unit 95, a large space can be secured between the fixing device 6 and the transfer unit, and it is possible to suppress the bent sheet S from interfering with other components of the apparatus main body 2.

[0193] Also, after the trailing edge of the sheet S has passed through the transfer unit composed of the photosensitive drum 54 and the transfer roller 55, since there is no longer a sheet S conveyed by both the fixing device 6 and the transfer unit, by turning off the solenoid 97 under the control of the control unit 95 and moving the movable chute 71 to the first position, it is possible to achieve power saving of the image forming apparatus 1. Further, the sheet S conveyed from the transfer unit next can be appropriately guided by the movable chute 71 located at the first position.

Explanation of Reference Numerals

[0194] 1 Image forming apparatus 2 Apparatus main body 6 Fixer 8 Shutter link 26 Air duct 28 Fixing chute 50 Process cartridge 54 Photosensitive drum 54a Drum shaft 55 Transfer roller 61 Heating unit 64 Fixing shutter 66 Fixing guide 71 Movable chute 71a End (of the movable chute on the downstream side in the sheet conveyance direction) 71A Sheet conveyance surface 71B Pressed portion 75 Chute link 95 Control unit 97 Solenoid 261 Upstream guide 261a End (of the upstream guide on the downstream side in the sheet conveyance direction) 643 Shutter conveyance surface 643a End (of the shutter conveyance surface on the downstream side in the sheet conveyance direction) 643b End (of the shutter conveyance surface on the upstream side in the sheet conveyance direction) 644 Shielding surface 661 Guide conveyance surface 661a End (of the guide conveyance surface on the upstream side in the sheet conveyance direction) 662 Guide protrusion P Conveyance path S Sheet VL Perpendicular line (to the shutter conveyance surface in the fixing shutter) VS Virtual plane (of the movable chute) θ1 Inclination angle (of the shutter conveyance surface with respect to the sheet conveyance direction) θ2 Inclination angle (of the guide conveyance surface with respect to the sheet conveyance direction) θ5 Inclination angle (of the guide protrusion with respect to the sheet conveyance direction)

Claims

1. A device main body, A fixing device having a heating unit for fixing a toner image on a conveyed sheet, A fixing chute located upstream of the fixing device in the sheet conveyance direction and forming a sheet conveyance path, A fixing guide that is located upstream of the heating unit in the sheet conveyance direction and on the opposite side of the fixing chute across the sheet conveyance path in the sheet thickness direction, and guides the sheet. The fixing guide has a guide conveyance surface that inclines in a direction approaching the fixing chute as it goes downstream in the sheet conveyance direction. A fixing shutter that is located on the opposite side of the fixing chute across the sheet conveyance path in the sheet thickness direction, and is movable between a closed position that covers the upstream side of the heating unit in the sheet conveyance direction and an open position that opens the upstream side of the heating unit in the sheet conveyance direction. The fixing shutter has a shutter conveyance surface that can guide the sheet upstream of the fixing guide in the sheet conveyance direction when the fixing shutter is in the open position. In the state where the fixing shutter is in the open position, the shutter conveyance surface inclines in a direction approaching the fixing chute as it goes downstream in the sheet conveyance direction, so that the end portion on the downstream side in the sheet conveyance direction is located closer to the fixing chute than the end portion on the upstream side in the sheet conveyance direction of the guide conveyance surface. An image forming apparatus having the shutter conveyance surface.

2. The image forming apparatus according to claim 1, wherein, in the state where the fixing shutter is in the open position, the end portion on the downstream side in the sheet conveyance direction of the shutter conveyance surface overlaps with the guide conveyance surface in the sheet conveyance direction.

3. The image forming apparatus according to claim 1 or claim 2, wherein the inclination angle of the shutter conveyance surface with respect to the sheet conveyance direction is larger than the inclination angle of the guide conveyance surface with respect to the sheet conveyance direction.

4. The image forming apparatus according to claim 1 or claim 2, wherein the shutter conveyance surface of the fixing shutter faces the fixing device when the fixing shutter is in the closed position.

5. The image forming apparatus according to claim 1 or claim 2, wherein the fixing shutter has a shielding surface that covers the upstream side of the heating unit in the sheet conveyance direction when the fixing shutter is in the closed position, and the shielding surface extends in a direction intersecting the direction in which the shutter conveyance surface extends.

6. A cartridge detachable from the device main body, A shutter link provided on the apparatus main body and connected to the fixing shutter, the shutter link moving the fixing shutter between the open position and the closed position in conjunction with the attachment / detachment operation of the cartridge with respect to the apparatus main body. The image forming apparatus according to claim 5, comprising:

7. It has an upstream guide capable of guiding a sheet upstream in the sheet conveyance direction from the shutter conveyance surface of the fixing shutter, The image forming apparatus according to claim 6, wherein an end portion on the downstream side in the sheet conveyance direction of the upstream guide is located closer to the fixing chute than an end portion on the upstream side in the sheet conveyance direction of the shutter conveyance surface.

8. In the sheet conveyance direction, it is downstream of a transfer unit that transfers an image to a sheet, located upstream of the fixing unit, and includes a movable chute movable between a first position and a second position where an end portion on the downstream side in the sheet conveyance direction from the first position is separated from the sheet conveyance path. The image forming apparatus according to claim 1 or claim 2.

9. The movable chute has a sheet conveyance surface for guiding a sheet, The image forming apparatus according to claim 8, wherein in a state where the movable chute is located at the first position, a virtual plane extending the sheet conveyance surface at an end portion on the downstream side in the sheet conveyance direction of the movable chute passes through the fixing guide.

10. The image forming apparatus according to claim 8, wherein a perpendicular line to the shutter conveyance surface in the fixing shutter passes through the movable chute.

11. A drive source for moving the movable chute, and A control unit for controlling the operation of the drive source, The image forming apparatus according to claim 8, wherein the control unit controls the drive source to move the movable chute from the first position toward the second position after the leading edge of the conveyed sheet has passed through the fixing unit.

12. It includes a chute link connected to the drive source and moving the movable chute from the first position to the second position, The drive source is a solenoid actuator that drives the chute link, The movable chute has a sheet conveyance surface for guiding a sheet, The image forming apparatus according to claim 11, wherein the chute link is driven by the drive source to press the movable chute from the sheet conveyance surface side, thereby moving the movable chute from the first position to the second position.

13. The fixing guide is located at an end in a direction orthogonal to the sheet conveyance direction of the guide conveyance surface, and has a guide protrusion that protrudes toward the fixing chute side from the guide conveyance surface. The guide protrusion is inclined in a direction approaching the fixing chute as it goes downstream in the sheet conveyance direction. The image forming apparatus according to claim 1 or claim 2, wherein an inclination angle of the guide protrusion with respect to the sheet conveyance direction is larger than an inclination angle of the shutter conveyance surface with respect to the sheet conveyance direction.

Images