Image forming apparatus

Abstract

To provide an image forming apparatus that can accurately move a shutter of a fuser to a closing position.SOLUTION: An image forming apparatus 1 comprises: a fuser 6 that has a heating member 61, a pressure roller 62, a fixing frame 63 formed with a first opening 63a on the upstream side in a sheet conveyance direction of the heating member 61, and a shutter 64 moving between a closing position where it closes the first opening 63a and an opening position where it opens the first opening 63a; and an opening and closing link 4 that is connected with the shutter 64 and moves the shutter 64 to the opening position and the closing position. The fixing frame 63 has a first contact surface 631 with which the shutter 64 at the closing position is brought into contact. A link cam 42 of the opening and closing link 4 is movable in a first direction W1 to move the shutter 64 to the closing position and a second direction W2 to move the shutter to the opening position. When the shutter 64 is in contact with the first contact surface 631 and at the closing position, the movement of the link cam 42 in the first direction W1 is allowed with the shutter 64 remained at the closing position.SELECTED DRAWING: Figure 7

Description

Technical Field

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

Background Art

[0002] Conventionally, in an image forming apparatus provided with a detachable cartridge, in order to prevent a user's hand from contacting a fixing device having a heating member, a shutter is provided in front of the fixing device.

[0003] For example, in the image forming apparatus disclosed in Patent Document 1, a link member that is connected to the shutter and can abut against the cartridge is provided. When the cartridge is mounted, the link member abuts against the cartridge and moves, and the shutter is configured to open along with the movement of the link member. Further, when the cartridge is detached, the link member moves to the opposite side by the spring force, and the shutter is configured to close.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, which discloses a configuration in which a shutter opens and closes in conjunction with a cartridge that is a movable member operated by a user, it is disclosed that when the shutter opens, the shutter abuts against a regulating portion of the apparatus main body and does not rotate any further. However, when the shutter performs a closing operation, how the shutter operates is not disclosed. Therefore, when the shutter closes, there is a possibility that the shutter may not move accurately to the closed position.

[0006] Therefore, the present invention provides an image forming apparatus that can move the shutter to the closed position with high precision in a configuration in which the shutter opens and closes in conjunction with a movable member operated by the user, such as a cartridge or a front cover. [Means for solving the problem]

[0007] The image forming apparatus that solves the above problems has the following features.

[0008] That is, the image forming apparatus is a fuser for fixing a toner image transferred to a conveyed sheet, and comprises a heating member, a pressing member that nips the sheet together with the heating member, a fixing frame that covers the heating member and the pressing member and has an opening formed on the upstream side of the heating member in the sheet conveying direction, and a shutter that moves between a closed position that closes the opening and an open position that opens the opening, and an opening / closing link connected to the shutter that moves the shutter between the open position and the closed position, wherein the fixing frame has a first contact surface that the shutter in the closed position contacts, and the opening / closing link is movable in a first direction that moves the shutter to the closed position and a second direction that moves the shutter to the open position, and when the shutter is in the closed position contacting the contact surface, movement of the opening / closing link in the first direction is permitted while maintaining the shutter in the closed position.

[0009] As a result, when the shutter is in the closed position, in contact with the first contact surface, and the opening / closing link is pressed in the first direction, the shutter will not move any further in the first direction, and only the opening / closing link will move in the first direction. Therefore, the shutter in the closed position will always be in contact with the first contact surface, and the shutter can be moved to the closed position accurately in a stable posture.

[0010] Furthermore, the first contact surface of the fixing frame faces the upstream side in the sheet transport direction.

[0011] This allows for improved positioning accuracy when the shutter is closed.

[0012] Furthermore, the opening and closing link includes a shutter link connected to the shutter and moving the shutter between the open and closed positions, a link cam connected to the shutter link and movable in the first and second directions, and a spring that moves along the movement of the link cam and presses the shutter link. When the shutter is in the closed position, in contact with the first contact surface, the spring is in contact with the shutter link and presses the shutter link in the first direction. As the spring elastically deforms while the shutter remains in the closed position, movement of the link cam in the first direction is permitted.

[0013] As a result, when the shutter is in the closed position, contacting the first contact surface, and the link cam is pressed in the first direction, the shutter will not move any further in the first direction while being biased in the first direction by the spring, and only the link cam will move in the first direction. Therefore, the shutter in the closed position will always be in contact with the first contact surface, and the shutter can be moved to the closed position accurately in a stable posture.

[0014] Furthermore, the shutter has a pivot shaft that is rotatably supported by the fixing frame and a connecting shaft that protrudes in a direction parallel to the pivot shaft, and the shutter link is connected to the connecting shaft.

[0015] As a result, when the shutter opens or closes, a connecting shaft parallel to the pivot axis, which is rotatably supported by the fixing frame, is operated by the shutter link, allowing for precise opening and closing of the shutter.

[0016] Furthermore, the shutter link has an elongated hole, and the connecting shaft of the shutter is located within the elongated hole.

[0017] This allows the connecting shaft 2 to slide within the elongated hole when the shutter link opens and closes, thus enabling smooth operation of the shutter by the shutter link.

[0018] The device also includes a main body for housing the fuser, the link cam having a link cam body that is rotatably supported on the fuser frame and has a through hole that penetrates along the rotation axis direction, and a projection that protrudes from the link cam body along the rotation axis direction, the shutter link having a boss that protrudes along the rotation axis direction and is located in the through hole, and the main body has a main body-side link that engages with the projection and moves the link cam.

[0019] This allows for greater flexibility in the location where the shutter is opened and closed within the image forming apparatus.

[0020] Furthermore, the shutter link and the link cam are rotatably supported on the fixing frame coaxially, and the spring is a coil spring having a coil supported by the link cam body and a spring arm extending outward from the coil, the spring arm being located within the through hole, and the link cam body having a locking groove that engages with the spring arm to restrict its movement to one side in the circumferential direction.

[0021] As a result, for example, when moving the shutter to the closed position via the shutter link by the link cam, the shutter link is driven by pressing the boss of the shutter link with a spring arm located inside the through hole. Therefore, the biasing force of the spring arm makes it possible to press the shutter against the first contact surface, allowing the shutter to be held in the closed position with precision.

[0022] Furthermore, the locking groove of the link cam body is cut out in the circumferential direction of the rotational movement of the link cam body, and by contacting the spring arm at the bottom of the locking groove, it restricts the movement of the spring arm in the first direction relative to the link cam body, and allows the link cam body to move in the first direction relative to the spring arm as the spring arm elastically deforms inside the locking groove while the shutter remains in the closed position.

[0023] In this way, within the locking groove, the spring arm elastically deform, allowing the link cam body to move in the first direction, so the link cam body can move smoothly in the first direction.

[0024] Further, the link cam is movable to a first position that moves in the first direction to move the shutter to the closed position and a second position that moves in the second direction to move the shutter to the open position. The through hole has a first end face located on the first direction side in the circumferential direction and a second end face located on the second direction side in the circumferential direction. The second end face is at a position where it does not contact the boss of the shutter link when the shutter moves from the closed position to the open position while the link cam is in the first position.

[0025] Thereby, when the link cam is in the first position and the shutter is in the closed position, even if the shutter moves to the open position, the boss of the shutter link does not contact the link cam, and damage to the opening and closing link can be suppressed.

[0026] Also, the main body side link moves the shutter link in the second direction in response to the attachment of a cartridge attached to the apparatus main body, and moves the shutter link in the first direction in response to the detachment of the cartridge from the apparatus main body.

[0027] In this way, since the main body side link operates in response to the attachment and detachment of the cartridge attached to the apparatus main body, the shutter 64 can be opened and closed via the opening and closing link at an appropriate timing.

[0028] Also, in the sheet conveyance direction, the connection point between the shutter link and the shutter is located on the opposite side of the connection point between the shutter link and the link cam, sandwiching the nip point of the sheet between the heating member and the pressing member.

[0029] This allows for an increase in the length of the shutter link in the sheet transport direction, and reduces the amount of movement of the link cam required to open and close the shutter.

[0030] Furthermore, the fuser has a rotating shaft supported by the fuser frame, and is equipped with a nip pressure changing mechanism that changes the nip pressure between the heating member and the pressurizing member by rotating the rotating shaft, and the link cam is located coaxially with the rotating shaft.

[0031] This allows the rotating shaft that operates the nip pressure changing mechanism to also serve as the shaft that supports the link cam, enabling the link cam to be positioned in a space-saving manner.

[0032] Furthermore, the fixing frame has a second contact surface against which the shutter in the open position abuts, and when the shutter is in the open position with the second contact surface abutting, the spring abuts against the shutter link and presses the shutter link in the second direction, and as the spring elastically deforms while the shutter remains in the open position, movement of the link cam in the second direction is permitted.

[0033] As a result, when the shutter is in the open position, contacting the second contact surface, and the link cam is pressed in the second direction, the shutter will not move further in the second direction due to the spring bias, and only the link cam will move in the second direction. Therefore, the shutter in the open position will always be in contact with the second contact surface, and the shutter can be moved to the open position accurately in a stable posture. Furthermore, a single spring allows for the movement of the link cam in both the closed and open positions of the shutter.

[0034] Furthermore, the second contact surface of the fixing frame faces the upstream side in the sheet transport direction.

[0035] This allows for improved positioning accuracy at the shutter's open position. [Effects of the Invention]

[0036] According to the present invention, the shutter in the closed position can always be kept in contact with the first contact surface, and the shutter can be moved to the closed position accurately in a stable posture. [Brief explanation of the drawing]

[0037] [Figure 1] This is a central cross-sectional view showing an image forming apparatus. [Figure 2] This is a perspective view showing an image forming apparatus with the front cover in the open position. [Figure 3] This is a side cross-sectional view showing the fuser. [Figure 4] This is a perspective view showing the heating element and pressure roller of the fuser. [Figure 5] (a) is a perspective view showing the fuser with the shutter in the closed position, and (b) is a perspective view showing the fuser with the shutter in the open position. [Figure 6] This is a side cross-sectional view showing the fuser. [Figure 7] (a) is a side view showing the fuser with the shutter in the closed position, and (b) is a side view showing the fuser with the shutter in the open position. [Figure 8] (a) is a front view showing the fuser with the shutter in the closed position, and (b) is a front view showing the fuser with the shutter in the open position. [Figure 9] (a) is a front view showing the shutter, and (b) is a side view showing the shutter. [Figure 10] This is an exploded perspective view showing the opening and closing links. [Figure 11] This is a perspective view showing the open / close link. [Figure 12] This is a side cross-sectional view showing the opening and closing link when the shutter is in the closed position. [Figure 13] This is a side cross-sectional view showing the opening and closing link when the shutter is in the open position. [Figure 14] This is a side view showing the nip pressure changing mechanism. [Figure 15] This is a perspective view showing the process cartridge. [Figure 16] This is a side view showing the process cartridge. [Figure 17] This is a side view showing the left side of the first main frame. [Figure 18] This is a side view showing the right side of the first main frame. [Figure 19] This is a side view showing the main body side link in a state where the first projection of the contact piece is located in the middle of the contact piece rail and the second projection is located in the front of the contact piece rail. [Figure 20] This is a side view showing the first main frame in a state where the process cartridge is in the mounting start position, the first projection of the contact piece is located in the middle of the contact piece rail, and the second projection is located in the front of the contact piece rail. [Figure 21] This is a diagram showing the contact piece. [Figure 22] This is a side view showing the main body side link in a state where the drum shaft is in contact with the contact piece, and both the first and second projections of the contact piece are located in the middle of the contact piece rail. [Figure 23] This is a side view showing the first main frame in a state where the drum shaft is in contact with the contact piece, and both the first and second projections of the contact piece are located in the middle of the contact piece rail. [Figure 24] This is a side view showing the main body side link in a state where the drum shaft is in contact with the contact piece, the first projection of the contact piece is located at the rear of the contact piece rail, and the second projection is located in the middle of the contact piece rail. [Figure 25] This is a side view showing the first main frame in a state where the drum shaft is in contact with the contact piece, the first projection of the contact piece is located at the rear of the contact piece rail, and the second projection is located in the middle of the contact piece rail. [Figure 26] This is a side view showing the first main frame in a state where the drum shaft is separated from the contact piece and the process cartridge is in the mounting position. [Figure 27]This is a side cross-sectional view showing the positional relationship between the boss of the shutter link and the second end face of the through hole when the shutter moves from the closed position to the open position, with the link cam in the first position. [Modes for carrying out the invention]

[0038] Next, embodiments for carrying out the present invention will be described with reference to the attached drawings.

[0039] [Image forming apparatus] The image forming apparatus 1 shown in Figure 1 is an embodiment of an image forming apparatus equipped with a sheet transport device according to the present invention, and is a laser printer that forms an image on a sheet S by an electrophotographic method.

[0040] In the following explanation, the right side of Figure 1 is defined as the front side of the image forming apparatus 1, the left side of Figure 1 is defined as the rear side of the image forming apparatus 1, the front of the page in Figure 1 is defined as the left side of the image forming apparatus 1, and the back of the page in Figure 1 is defined as the right side of the image forming apparatus 1. Furthermore, the top and bottom sides of Figure 1 are defined as the top and bottom sides of the image forming apparatus 1, respectively.

[0041] The image forming apparatus 1 comprises a main body 2, a paper feeding unit 3, an image forming unit 5, a fuser 6, and a paper discharge unit 7.

[0042] The main body 2 houses the paper feeding unit 3, the image forming unit 5, the fuser unit 6, and the paper discharge unit 7. An opening 2A is located on the front of the main body 2, and the main body 2 has a front cover 21 that can open and close the opening 2A. The front cover 21 is configured to rotate around a pivot axis 21a at its lower end, and by rotating around the pivot axis 21a, it can move between a closed position that closes the opening 2A and an open position that opens the opening 2A.

[0043] The paper feeding unit 3 comprises a paper feeding tray 10 that supports the sheet S, a sheet transport unit 30, a transport roller pair 34, and a registration roller 35a. The paper feeding unit 3 is located at the bottom of the main body 2 of the device and transports the sheet S supported by the paper feeding tray 10 to the image forming unit 5. The image forming apparatus 1 has a transport path P for the sheet S from the paper feeding unit 3 through the image forming unit 5 to the paper discharge unit 7.

[0044] The paper 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 sheet S from below. The pressure plate 12 is rotatable about a pivot point 12a at its rear end, and by rotating about the pivot point 12a, it can move up and down between a lowered position and an elevated position. The pressing plate 13 is located below the pressure plate 12 and can move the pressure plate 12 up and down between a lowered position and an elevated position.

[0045] The sheet transport unit 30 is a transport mechanism that separates and removes sheets S supported by the paper feed tray 10 one by one and transports them toward the image forming unit 5, and includes a paper feed roller 31, a separation roller 32, and a separation pad 33. The paper feed roller 31 is a roller that feeds the sheets S supported by the paper feed tray 10 toward the separation roller 32. The separation roller 32 is positioned downstream of the paper feed roller 31 in the sheet transport direction, and the separation pad 33 is positioned opposite the separation roller 32 and is biased toward the separation roller 32.

[0046] The sheets S, fed towards the separation roller 32 by the paper feed roller 31, are separated one by one between the separation roller 32 and the separation pad 33. The separated sheets S are then fed into the transport path P.

[0047] The sheet S, which has been sent onto the transport path P, is transported toward the image forming unit 5 by the transport roller pair 34, the resist roller 35a, and the pinch roller 35b positioned opposite the resist roller 35a. The resist roller 35a restricts the movement of the leading edge of the transported sheet S, stopping it temporarily, and then transports the sheet S toward the image forming unit 5 at a predetermined timing.

[0048] The image forming unit 5 is located downstream of the paper feeding unit 3 in the sheet transport direction and forms an image on the sheet S transported 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 transported from the paper feeding unit 3, a transfer roller 55 positioned opposite the photosensitive drum 54 of the process cartridge 50, and an exposure unit 56 that exposes the surface of the photosensitive drum 54.

[0049] The process cartridge 50 is located above the paper feed section 3 in the main body of the device 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 driven roller, which is a pinch roller 35b.

[0050] The process cartridge 50 comprises a drum cartridge having a photosensitive drum 54 and a developing cartridge mounted on the drum cartridge and having a developing roller 53, and is detachably mounted on the device body 2. In this case, the process cartridge 50 is mounted on the device body 2 by inserting the drum cartridge and the developing cartridge mounted on the drum cartridge into the device body 2 as a single unit, and is detached from the device body 2 by removing the drum cartridge and the developing cartridge mounted on the drum cartridge from the device body 2 as a single unit.

[0051] The process cartridge 50 is an example of a cartridge that is detachably attached to the main body of the device and is a movable component operated by the user. The process cartridge 50 can be attached to and detached from the main body of the device 2 when the front cover 21 is in the open position.

[0052] The photosensitive drum 54 is positioned such that its axis X is aligned in the left-right direction when the process cartridge 50 is mounted on the main body 2 of the apparatus. The photosensitive drum 54 has a metal drum shaft 54a that extends along the direction of the axis X.

[0053] In this embodiment, the process cartridge 50 comprises a drum cartridge having a photosensitive drum 54 and a developing cartridge mounted on the drum cartridge and having a developing roller 53. However, it can also be configured to include a cartridge having the photosensitive drum 54 and the developing roller 53, and a toner box mounted on the cartridge for containing toner. Furthermore, in an 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 mounted separately on the main body 2 of the apparatus.

[0054] The exposure unit 56 is equipped with a laser diode, a polygon mirror, a lens, and a reflector, 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.

[0055] The developer chamber 51 contains toner, which is the developer. The toner contained in the developer chamber 51 is agitated by an agitator (not shown) and sent to the supply roller 52. The supply roller 52 then supplies the toner sent from the developer chamber 51 to the developing roller 53.

[0056] The developing roller 53 is positioned in close contact with the supply roller 52 and carries positively charged toner supplied from the supply roller 52 by a sliding contact member (not shown). A developing bias is also applied to the developing roller 53 by a bias application means (not shown).

[0057] The photosensitive drum 54 is positioned 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, positively charged toner is supplied from the developing roller 53 to the surface of the photosensitive drum 54 where the electrostatic latent image has been formed, causing the electrostatic latent image to become visible as a toner image.

[0058] The transfer roller 55 is positioned opposite the photosensitive drum 54, and a transfer bias is applied by a bias application means (not shown). With the transfer bias applied to the surface of the transfer roller 55, the sheet S is transported while being sandwiched between the photosensitive drum 54 on which the toner image has been formed and the transfer roller 55, thereby transferring the toner image formed on the surface of the photosensitive drum 54 to the surface of the sheet S. The sheet S on which the toner image has been transferred is then transported to the fuser 6.

[0059] The fuser 6 comprises a heating element 61 and a pressure roller 62, and fixes the image transferred to the sheet S by the process cartridge 50. The heating element 61 is heated by power supplied from a power source (not shown). The pressure roller 62 is an example of a pressure element. The pressure roller 62 and the heating element 61 are positioned opposite each other, and the heating element 61 is biased against the pressure roller 62 by a nip pressure changing mechanism (see Figure 14). The pressure roller 62 nips the sheet together with the heating element 61.

[0060] When the sheet S on which the toner image has been transferred is transported to the fuser unit 6, the sheet S is heated while being held between the heating element 61 and the pressure roller 62, thereby fixing the toner image to the sheet S. In this way, the fuser unit 6 fixes the toner image transferred to the transported sheet S.

[0061] The paper discharge unit 7 is located downstream of the image forming unit 5 in the sheet transport direction and discharges the sheets S, on which images have been formed in the image forming unit 5, to the outside of the image forming apparatus 1. The paper discharge unit 7 comprises a pair of paper discharge rollers 71 and a paper discharge tray 72. The pair of paper discharge rollers 71 is configured to discharge the sheets S, which have been transported from the fuser 6 along the transport path P, toward the outside of the apparatus body 2. The paper discharge tray 72 is formed on the upper surface of the apparatus body 2 and supports the sheets S that have been discharged to the outside of the apparatus body 2 by the pair of paper discharge rollers 71.

[0062] As shown in Figure 2, the device body 2 comprises a first main frame 24 and a second main frame 25, which are spaced apart from each other in the left-right direction. The first main frame 24 is located at the right end of the device body 2, and the second main frame 25 is located at the left end of the device body 2. The first main frame 24 extends in the front-rear and up-down directions and is positioned so that its plate surface faces the left-right direction. The second main frame 25 extends in the front-rear and up-down directions and is positioned so that its plate surface faces the left-right direction.

[0063] The process cartridge 50 and fuser unit 6 are positioned between the first main frame 24 and the second main frame 25. The first main frame 24 is positioned to the right of the process cartridge 50 and fuser unit 6, and the second main frame 25 is positioned to the left of the process cartridge 50 and fuser unit 6. The process cartridge 50 is detachably supported by the first main frame 24 and the second main frame 25.

[0064] [Fuser] As shown in Figures 3 and 4, the heating element 61 of the fuser 6 comprises 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, with the first surface 611A being supported by the holder 612.

[0065] The holder 612 is made of, for example, a resin material and has a guide surface 612a and a support wall 612b. The guide surface 612a contacts the inner circumferential surface 614a of the belt 614 and guides 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 with greater rigidity than the holder 612, such as a steel plate, into a roughly U-shape in cross-section.

[0066] The belt 614 is an endless belt having heat resistance and flexibility, and comprises 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 arranged inside the belt 614. The belt 614 is configured to rotate around the heater 611, holder 612, and stay 613. The inner circumferential surface 614a of the belt 614 is in contact with the heater 611.

[0067] The pressure roller 62 has a metal shaft 62A and an elastic layer 62B covering the shaft 62A. The pressure roller 62 is pressed relative to the heater 611 via a belt 614. The pressure roller 62, by sandwiching the belt 614 between itself and the heater 611, forms a nip point NP for nipping the sheet S and heating and pressurizing it. In other words, at the nip point NP, the pressure roller 62 heats and pressurizes the sheet S together with the heater 611.

[0068] The pressure roller 62 is configured to rotate when a driving force is transmitted from the motor 4 of the image forming apparatus 1. By rotating, the pressure roller 62 causes the belt 614 to rotate due to the frictional force between the belt 614 and the sheet S sandwiched between the nip points NP. As a result, the sheet S on which the toner image has been transferred is transported between the pressure roller 62 and the heated belt 614, and the toner image is heat-fixed.

[0069] As shown in Figures 1, 5 to 9, the fuser 6 has a fuser frame 63 that covers the heating element 61 and the pressure roller 62, and a shutter 64 supported by the fuser frame 63. The fuser frame 63 holds the heating element 61 and the pressure roller 62. The fuser frame 63 covers the periphery of the heating element 61 and the pressure roller 62 and has a first opening 63a formed on the upstream side in the sheet conveying direction of the heating element 61 and the pressure roller 62, and a second opening 63b formed on the downstream side in the sheet conveying direction of the heating element 61 and the pressure roller 62. The first opening 63a is an example of an opening.

[0070] The shutter 64 is located upstream of the first opening 63a in the sheet transport direction in the fixing frame 63, and has a pivot shaft 641 extending along the left-right direction and a connecting shaft 642 projecting in a direction parallel to the pivot shaft 641. The pivot shaft 641 is rotatably supported by the fixing frame 63. The shutter 64 is configured to be rotatable about the pivot shaft 641, and by rotating about the pivot shaft 641, it can move between a closed position that closes the first opening 63a and an open position that opens the first opening 63a. The pivot shaft 641 is provided at both the left and right ends of the shutter 64, and the connecting shaft 642 projects to the right from the right end of the shutter 64.

[0071] The fixing frame 63 has a first contact surface 631 against which the shutter 64 in the closed position abuts, and a second contact surface 632 against which the shutter 64 in the open position abuts. The first contact surface 631 faces the upstream side in the sheet conveying direction, and the stopper 643 of the shutter 64 abuts against it when the shutter 64 is in the closed position. The stopper 643 abutting against the first contact surface 631 restricts the shutter 64 from moving any further in the closing direction. The second contact surface 632 faces the upstream side in the sheet conveying direction, and the connecting shaft 642 of the shutter 64 abuts against it when the shutter 64 is in the open position. The connecting shaft 642 abutting against the second contact surface 632 restricts the shutter 64 from moving any further in the opening direction.

[0072] In this embodiment, the heating element 61 has a heater 611 and a belt 614, but it is not limited to this, and for example, it may be a heating roller with a heater built in as the heating element. Also, in this embodiment, there is a pressure roller 62 as a pressure element, but it is not limited to this, and the pressure element may also be configured to include a pressure belt that is pressed against the heating roller by an elastic member.

[0073] [Open / Close Link] As shown in Figures 5, 7, 8, and 10, the image forming apparatus 1 is equipped with an opening / closing link 4 that is connected to the shutter 64 and moves the shutter 64 between an open position and a closed position. The opening / closing link 4 includes a shutter link 41, a link cam 42, and a coil spring 43.

[0074] The shutter link 41 is connected to the shutter 64 and moves the shutter 64 between the open and closed positions. The fuser 6 has a rotating shaft 65 that extends along the left-right direction and is rotatably supported by the fuser frame 63, and the shutter link 41 is rotatably supported by the rotating shaft 65. The rotating shaft 65 protrudes to the right from the right end of the fuser frame 63. An operating lever 67 is integrally and rotatably fixed to the right end of the rotating shaft 65. The operating lever 67 can rotate the rotating shaft 65. The shutter link 41 is located at the right end of the fuser 6 and has a support portion 411, an arm portion 412, an engaging portion 413, and a boss 414.

[0075] The support portion 411 is cylindrical in shape with a hole that penetrates in the left-right direction, is located at the rear end of the arm portion 412, and is rotatably supported by the rotation shaft 65. The arm portion 412 is rod-shaped extending forward from the support portion 411, and more specifically, it extends forward from the support portion 411 and is bent downward midway. The engaging portion 413 is located at the front end of the arm portion 412 and has an elongated oval-shaped slot 413a that is long in the front-rear direction. The connecting shaft 642 of the shutter 64 is located inside the slot 413a. When the connecting shaft 642 is located inside the slot 413a, the connecting shaft 642 and the engaging portion 413 engage, connecting the connecting shaft 642 and the shutter link 41.

[0076] The shutter link 41 is rotatable around the support portion 411 in a direction in which the engaging portion 413 moves up and down. When the shutter link 41 rotates and the engaging portion 413 moves downward, the shutter 64 moves to the closed position (see Figures 5(a) and 7(a)). When the shutter link 41 rotates and the engaging portion 413 moves upward, the shutter 64 moves to the open position (see Figures 5(b) and 7(b)). The boss 414 protrudes to the right from the support portion 411 side end of the arm portion 412.

[0077] The link cam 42 is connected to the shutter link 41 and is movable in a first direction W1 and a second direction W2 opposite to the first direction W1. The link cam 42 is rotatably supported on the rotation axis 65 of the fuser 6, and the link cam 42 and the rotation axis 65 are coaxially located. The link cam 42 is rotatable about the rotation axis 65 in the first direction W1 and the second direction W2. In this embodiment, the first direction W1 is the counterclockwise direction in Figure 7, and the second direction W2 is the clockwise direction in Figure 7. Both the shutter link 41 and the link cam 42 are supported on the rotation axis 65 and are rotatably supported on the fuser frame 63 coaxially.

[0078] The link cam 42 has a link cam body 421 that is rotatably supported on the rotation axis 65, and a projection 422 that protrudes to the right from the link cam body 421. The link cam body 421 has an operating cam 421a. The operating cam 421a is located in a different phase from the projection 422 in the circumferential direction of the link cam body 421. The operating cam 421a of the link cam body 421 has a through hole 423 that penetrates along the left-right direction. The left-right direction is an example of the direction of the rotation axis. The boss 414 of the shutter link 41 is located within the through hole 423 of the link cam 42.

[0079] As shown in Figures 7 and 10-13, the coil spring 43 is formed by bending an elastic metal wire and has a coil 431, a first spring arm 432, and a second spring arm 433. The coil spring 43 is an example of a spring that presses against a shutter link. The first spring arm 432 and the second spring arm 433 are examples of spring arms that extend outward from the coil.

[0080] The coil 431 is formed by winding a wire in a ring shape and is fitted into a support groove 421b formed in the link cam body 421 of the link cam 42. The coil 431 is supported by the link cam body 421 by being fitted into the support groove 421b of the link cam body 421. In the link cam body 421, the operating cam 421a is located on the outer diameter side of the support groove 421b. The projection 422 protrudes from a portion of the link cam body 421 that is located on the outer diameter side of the support groove 421b.

[0081] The first spring arm 432 extends outward from the coil 431. The first spring arm 432 enters the through hole 423 in the link cam 42 from the inner diameter side to the outer diameter side and is located within the through hole 423. The second spring arm 433 extends outward from the coil 431 at a different phase than the first arm portion 861 in the circumferential direction. The second spring arm 433 enters the through hole 423 in the link cam 42 from the inner diameter side to the outer diameter side and is located within the through hole 423.

[0082] The first spring arm 432 is located above the boss 414 within the through hole 423, and the second spring arm 433 is located below the boss 414 within the through hole 423. The through hole 423 is formed in an elongated shape extending along the circumferential direction, and has a first end face 423a located on the first direction W1 side in the circumferential direction, and a second end face 423b located on the second direction W2 side in the circumferential direction.

[0083] The operating cam 421a of the link cam body 421 has a first locking groove 424 and a second locking groove 425 located on the outer diameter side of the through hole 423. The first locking groove 424 and the second locking groove 425 are examples of locking grooves. The first locking groove 424 is an example of a locking groove that restricts the movement of the spring arm in a first direction relative to the link cam body.

[0084] The first locking groove 424 is a groove cut out from the end on the second direction W2 side toward the first direction W1 in the circumferential direction of the rotational movement of the operating cam 421a, and the first spring arm 432 can abut against the first groove bottom 424a located at the end on the first direction W1 side of the first locking groove 424. By abutting against the first groove bottom 424a, the first spring arm 432 is restricted from moving toward the first direction W1 relative to the link cam body 421. On the other hand, the first spring arm 432, which abuts against the first groove bottom 424a, is allowed to move toward the second direction W2 by elastically deforming inside the first locking groove 424. In other words, the first locking groove 424 locks with the first spring arm 432 and restricts the movement of the first spring arm 432 toward one side in the circumferential direction.

[0085] The second locking groove 425 is a groove cut out from the end on the first direction W1 side toward the second direction W2 in the circumferential direction of the rotational movement of the operating cam 421a, and the second spring arm 433 can abut against the second groove bottom 425a located at the end on the second direction W2 side of the second locking groove 425. By abutting against the second groove bottom 425a, the second spring arm 433 is restricted from moving toward the second direction W2 relative to the link cam body 421. On the other hand, the second spring arm 433, which abuts against the second groove bottom 425a, is allowed to move toward the first direction W1 by elastically deforming inside the first locking groove 424. In other words, the second locking groove 425 locks with the second spring arm 433 and restricts the movement of the second spring arm 433 toward one side in the circumferential direction.

[0086] The coil spring 43 is movable along with the rotation of the link cam 42, and as the link cam 42 rotates, the first spring arm 432 or the second spring arm 433 presses against the boss 414. As the first spring arm 432 or the second spring arm 433 presses against the boss 414, the shutter link 41 moves along with the rotation of the link cam 42, moving the shutter 64 between the closed and open positions.

[0087] For example, when the shutter 64 is in the open position, if the link cam 42 rotates in the first direction W1, the coil spring 43 moves along with the rotation of the link cam 42, and the first spring arm 432 presses the boss 414 downward. When the boss 414 is pressed downward, the shutter link 41 rotates in the first direction W1, in which the engaging portion 413 moves downward, and the shutter 64 moves from the open position to the closed position. The first direction W1 is the direction in which the link cam 42 moves the shutter 64 to the closed position, and the rotational position of the link cam 42 when it has moved in the first direction W1 and moved the shutter 64 to the closed position is the first position (the position shown in Figure 7(a)).

[0088] In this case, when the shutter 64 moves to the closed position, the stopper 643 contacts the first contact surface 631 of the fixing frame 63, restricting it from moving any further in the closing direction. On the other hand, when the shutter 64 is in the closed position, contacting the first contact surface 631, the link cam 42 is allowed to move in the first direction W1 while maintaining the shutter 64 in the closed position.

[0089] In other words, when the shutter 64 is in the closed position, contacting the first contact surface 631, the first spring arm 432 of the coil spring 43 contacts the boss 414 of the shutter link 41, pressing the shutter link 41 in the first direction W1. In this state, when a force is applied to the link cam 42 in the direction of movement in the first direction W1, the first spring arm 432 elastically deforms within the first locking groove 424 in a direction away from the bottom 424a of the first groove, while the shutter 64 remains in the closed position. This allows the link cam body 421 to move in the first direction W1 relative to the first spring arm 432.

[0090] Thus, when the shutter 64 is in the closed position, in contact with the first contact surface 631, and the link cam 42 is pressed in the first direction W1, the shutter 64 will not move any further in the first direction W1, and only the link cam 42 will move in the first direction W1. Therefore, the shutter 64 in the closed position will always be in contact with the first contact surface 631, making it possible to move the shutter 64 to the closed position accurately in a stable posture.

[0091] In particular, when the shutter 64 is in the closed position, in contact with the first contact surface 631, and the link cam 42 is pressed in the first direction W1, the shutter 64 will not move any further in the first direction W1 while being biased in the first direction W1 by the coil spring 43, and only the link cam 42 will move in the first direction W1. Therefore, the shutter 64 in the closed position will always be in contact with the first contact surface 631, making it possible to move the shutter 64 to the closed position accurately in a stable posture.

[0092] Furthermore, the shutter 64, which is provided on the upstream side of the fixing frame 63 in the sheet transport direction, is configured to contact the first contact surface 631 facing the upstream side in the sheet transport direction when in the closed position. This makes it possible to further improve the positioning accuracy of the shutter 64 in the closed position.

[0093] Furthermore, when the shutter 64 is moved to the closed position via the shutter link 41 by the link cam 42, the shutter link 41 is driven by the first spring arm 432 located in the through hole 424 pressing against the boss 414 of the shutter link 41. This makes it possible to press the shutter 64 against the first contact surface 631 with the biasing force of the first spring arm 432, thereby accurately holding the shutter 64 in the closed position.

[0094] Furthermore, in the opening / closing link 4, the first spring arm 432 elastically deforms within the first locking groove 424 while the shutter 64 remains in the closed position, allowing the link cam body 421 to move in the first direction W1 relative to the first spring arm 432. In this way, the elastic deformation of the first spring arm 432 within the first locking groove 424 allows the link cam body 421 to move in the first direction W1, enabling smooth movement in the first direction W1.

[0095] Furthermore, when the shutter 64 is in the closed position, if the link cam 42 rotates in the second direction W2, the coil spring 43 moves along with the rotation of the link cam 42, and the second spring arm 433 presses the boss 414 upward. When the boss 414 is pressed upward, the shutter link 41 rotates in the second direction W2, in which the engaging portion 413 moves upward, and the shutter 64 moves from the closed position to the open position. The second direction W2 is the direction in which the link cam 42 moves the shutter 64 to the open position, and the rotational position of the link cam 42 when it has moved in the second direction W2 and moved the shutter 64 to the open position is the second position (the position shown in Figure 7(b)).

[0096] In this case, when the shutter 64 moves to the open position, the connecting shaft 642 comes into contact with the second contact surface 632 of the fixing frame 63, restricting it from moving any further in the opening direction. On the other hand, when the shutter 64 is in the open position due to contact with the second contact surface 632, the link cam 42 is allowed to move in the second direction W2 while maintaining the shutter 64 in the open position.

[0097] In other words, when the shutter 64 is in the open position, contacting the second contact surface 632, the second spring arm 433 of the coil spring 43 contacts the boss 414 of the shutter link 41, pressing the shutter link 41 in the second direction W2. In this state, when a force is applied to the link cam 42 in the direction of movement in the second direction W2, the second spring arm 433 elastically deforms within the second locking groove 425 in a direction away from the bottom 425a of the second groove, while the shutter 64 remains in the open position. This allows the link cam body 421 to move in the second direction W2 relative to the second spring arm 433.

[0098] Thus, when the shutter 64 is in the open position, in contact with the second contact surface 632, and the link cam 42 is pressed in the second direction W2, the shutter 64 will not move any further in the second direction W1, and only the link cam 42 will move in the second direction W2. Therefore, the shutter 64 in the open position will always be in contact with the second contact surface 632, making it possible to move the shutter 64 to the open position accurately in a stable posture.

[0099] In particular, when the shutter 64 is in the open position, in contact with the second contact surface 632, and the link cam 42 is pressed in the second direction W2, the shutter 64 will not move any further in the second direction W2 while being biased in the second direction W2 by the coil spring 43, and only the link cam 42 will move in the second direction W2. Therefore, the shutter 64 in the open position is always in contact with the second contact surface 632, making it possible to move the shutter 64 to the open position accurately in a stable posture. Furthermore, a single coil spring 43 allows for the movement of the link cam 64 both when the shutter 64 is in the closed position and when it is in the open position.

[0100] Furthermore, the shutter 64, which is provided on the upstream side of the fixing frame 63 in the sheet transport direction, is configured to contact a second contact surface 632 facing the upstream side in the sheet transport direction when in the open position. This makes it possible to further improve the positioning accuracy of the shutter 64 in the open position.

[0101] Furthermore, when the shutter 64 is moved to the open position via the shutter link 41 by the link cam 42, the shutter link 41 is driven by the second spring arm 433 located in the through hole 424 pressing against the boss 414 of the shutter link 41. This allows the shutter 64 to be pressed against the second contact surface 632 by the biasing force of the second spring arm 433, enabling the shutter 64 to be held in the open position with precision.

[0102] Furthermore, when the shutter 64 opens or closes, the connecting shaft 642, which is parallel to the pivot shaft 641 rotatably supported by the fixing frame 63, is operated by the shutter link 41, making it possible to perform the opening and closing operation of the shutter 64 accurately.

[0103] Furthermore, the connecting shaft 642 of the shutter 64 is located within the elongated hole 413a of the shutter link 41, and when the shutter link 41 opens and closes, the connecting shaft 642 can slide within the elongated hole 413a, thereby enabling smooth operation of the shutter 64 by the shutter link 41.

[0104] Furthermore, as shown in Figure 6, in the sheet transport direction, the connecting shaft 642 of the shutter 64, which is the connection point between the shutter link 41 and the shutter 64, is located on the opposite side of the boss 414 of the link cam 42, which is the connection point between the shutter link 41 and the link cam 42, with the nip point NP between the heating member 61 and the pressure roller 62 in between. This makes it possible to increase the length of the shutter link 41 in the sheet transport direction and reduce the amount of movement of the link cam 42 required to open and close the shutter 64.

[0105] As shown in Figure 14, the fuser 6 is equipped with a nip pressure changing mechanism 66 that changes the nip pressure at the nip point NP between the heating element 61 and the pressure roller 62. The nip pressure changing mechanism 66 is provided at the left end and the right end of the fuser 6. The nip pressure changing mechanism 66 includes a guide 661, an arm 662, a spring 663, and a cam 664.

[0106] The guide 661 is located above the heating element 61 and is in contact with the heating element 61. The guide 661 is supported by the fixing frame 63 so as to be vertically movable. Specifically, the guide 661 is supported by the fixing frame 63 so as to be movable in a direction that presses the heating element 61 toward the pressure roller 62 and in a direction that moves away from the heating element 61.

[0107] The arm 662 is a roughly L-shaped metal member and is configured to press against the heating member 61 via the guide 661. The arm 662 has an outer fitting portion 662a that is rotatably fitted onto the boss 633 of the fixing frame 63, a pressing portion 662b that presses against the upper surface 661a of the guide member 661, a support portion 662c that supports the upper end of the spring 663, and a contact portion 662d that can contact the cam 664.

[0108] The arm 662 is movable between a pressing position (shown by a solid line in Figure 14) in which the pressing portion 662b presses against the upper surface 661a of the guide 661 so that the nip pressure between the pressure roller 62 and the heating member 61 is large, and a release position (shown by a dashed line in Figure 14) in which the pressing portion 662b is separated from the upper surface 661a of the guide 661 so that the nip pressure is smaller than that of the pressing position. In the fuser 6, thermal fixing to the sheet S is possible when the arm 662 is in the pressing position, and jamming of the sheet S is possible when the arm 662 is in the release position.

[0109] The spring 663 is, for example, a tension coil spring, with its upper end supported by the support portion 662c of the arm 662 and its lower end supported by the anchoring frame 63. The spring 663 biases the arm 662 in the direction from the release position to the pressed position.

[0110] The cam 664 is fixed integrally and rotatably to the rotating shaft 65, and rotates together with the rotating shaft 65 to move the arm 662 between a pressed position and a released position. The cam 664 is formed in a D-shape in cross-section and has a first cam surface 664a which is composed of a flat surface and a second cam surface 664b which is composed of an arcuate surface formed continuously with the first cam surface 664a.

[0111] When the first cam surface 664a is in a position opposite the contact portion 662d of the arm 662, it is spaced apart from the contact portion 662d. In this state, the arm 662 is pulled by the spring 663 to the pressed position. The first cam surface 664a is the surface that guides the arm 662 to the pressed position. When the second cam surface 664b is in a position opposite the contact portion 662d of the arm 662, it contacts the contact portion 662d and pushes the arm 662 upward. In this state, the arm 662 is pushed upward against the biasing force of the spring 663 and moves to the release position. The second cam surface 664b is the surface that guides the arm 662 to the release position.

[0112] Thus, the fuser 6 is equipped with a nip pressure changing mechanism 66 that changes the nip pressure between the pressure roller 62 and the heating element 61 by rotating a rotating shaft 65 operated by an operating lever 67, and the link cam 42 is located coaxially with the rotating shaft 65. This allows the rotating shaft 65 that operates the nip pressure changing mechanism 66 to also serve as the shaft that supports the link cam 42, making it possible to arrange the link cam 42 in a space-saving manner. Note that the nip pressure changing mechanism 66 is not limited to this configuration, and any configuration that is provided in the fuser 6 and can act on the heating element 61 or the pressure roller 62 to change the nip pressure between the heating element 61 and the pressure roller 62 is acceptable.

[0113] [Drum shaft] As shown in Figures 15 and 16, the drum shaft 54a of the photosensitive drum 54 protrudes to the right from the right end of the process cartridge 50 along the axial X direction. In other words, the drum shaft 54a protrudes toward the first main body frame 24 along the axial X direction.

[0114] [First main frame] As shown in Figures 17 and 18, the first main frame 24 has a front frame 24A located in front of it and a rear frame 24B located behind the front frame 24A. The front frame 24A and the rear frame 24B are formed integrally and continuously in the front-rear direction.

[0115] The front frame 24A of the first main frame 24 has a cartridge rail 241 and a contact rail 242. The cartridge rail 241 is formed in a groove shape with the left side open. The cartridge rail 241 extends in the front-rear direction and is inclined downwards as it moves from front to rear.

[0116] The drum shaft 54a of the photosensitive drum 54 can enter the cartridge rail 241, and the cartridge rail 241 guides the drum shaft 54a when the process cartridge 50 is mounted to the device body 2 and when the process cartridge 50 is removed from the device body 2. The drum shaft 54a guided by the cartridge rail 241 enters the cartridge rail 241 from the left side. The process cartridge 50 is mounted to the device body 2 from front to rear and removed from the device body 2 from rear to front.

[0117] In this manner, the front frame 24A guides the drum shaft 54a by the cartridge rail 241 when the process cartridge 50 is mounted to the apparatus body 2 and when it is detached from the apparatus body 2.

[0118] The contact rail 242 is formed in a groove shape with the right side open. The contact rail 242 extends in the front-rear direction and is inclined downwards from front to rear.

[0119] The cartridge rail 241 has a front portion 241a located forward, a rear portion 241c located backward, 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 forward, a rear portion 242c located backward, and a middle portion 242b located between the front portion 242a and the rear portion 242c.

[0120] The central portion 241b of the cartridge rail 241 and the central portion 242b of the abutment rail 242 overlap and communicate with each other. The central portions 241b and 242b form a through hole 24C that penetrates the front frame 24A in the left-right direction.

[0121] In other words, the middle section 241b, which is part of the cartridge rail 241, and the middle section 242b, which is part of the contact rail 242, overlap, and the overlapping portion between the cartridge rail 241 and the contact rail 242 is the through hole 24C. In this way, because a portion of the cartridge rail 241 and the contact rail 242 overlap, it is possible to use the same components for forming the cartridge rail 241 and the contact rail 242.

[0122] The drum shaft 54a enters the through-hole 24C when the process cartridge 50 is mounted to the apparatus body 2 and when the process cartridge 50 is removed from the apparatus body 2.

[0123] The front portion 242a of the contact rail 242 is located above the front portion 241a of the cartridge rail 241, and the rear portion 242c of the contact rail 242 is located above the rear portion 241c of the cartridge rail 241.

[0124] [Main unit link] As shown in Figures 19 and 20, the main body 2 of the device is connected to the opening / closing link 4 by engaging with the projection 422 of the link cam 42 and is equipped with a main body-side link 8 that moves the link cam 42. The main body-side link 8 moves the shutter 64 from the closed position to the open position when the process cartridge 50 is mounted on the main body 2 of the device, and moves the shutter 64 from the open position to the closed position when the process cartridge 50 is detached from the main body 2 of the device. In other words, the main body-side link 8 moves the shutter 64 between the open and closed positions via the opening / closing link 4 by operating in response to the attachment and detachment of the process cartridge 50 to and from the main body 2 of the device.

[0125] The main body side link 8 is located in the left-right direction, on the opposite side of the process cartridge 50 mounted on the device body 2, relative to the front frame 24A of the first main body frame 24. The main body side link 8 has a contact piece 80, a first rotational link 81, a linear link 82, and a second rotational link 83.

[0126] The contact piece 80 moves in contact with the drum shaft 54a of the photosensitive drum 54. The contact piece 80 is slidably fitted into the contact piece rail 242, which guides the contact piece 80 as it moves in contact with the drum shaft 54a.

[0127] As shown in Figure 21, the contact piece 80 has a main body portion 801, a connecting portion 802, a first projection 803, and a second projection 804. The main body portion 801 is formed of a plate-shaped member with its plate surface facing in the left-right direction. The connecting portion 802 is a boss that protrudes to the right from the right side of the main body portion 801.

[0128] The first projection 803 and the second projection 804 are pins that protrude to the left from the left side of the main body portion 801. The first projection 803 and the second projection 804 enter the contact rail 242 of the first main body frame 24 from the right side and are guided by the contact rail 242.

[0129] When the first projection 803 and the second projection 804 are engaged with the contact rail 242, the second projection 804 is located upstream of the first projection 803 in the direction in which the process cartridge 50 is mounted to the device body 2. The mounting direction is the direction in which the process cartridge 50 moves toward the mounting position when it is inserted into the device body 2.

[0130] The contact piece 80 is located on the opposite side of the process cartridge 50 mounted on the device body 2 relative to the front frame 24A of the first main frame 24. The first projection 803 and the second projection 804 are positioned so that, when they are engaged with the contact piece rail 242, they do not protrude further toward the process cartridge 50 than the front frame 24A of the first main frame 24.

[0131] The first projection 803 contacts the drum shaft 54a when the process cartridge 50 is mounted on the device body 2, and the second projection 804 contacts the drum shaft 54a when the process cartridge 50 is detached from the device body 2. In other words, the first projection 803 contacts the drum shaft 54a of the process cartridge 50 when it is mounted on the device body 2, and the second projection 804 contacts the drum shaft 54a of the process cartridge 50 when it is detached from the device body 2.

[0132] In this case, when the first projection 803 is located in the middle portion 242b (through hole 24C) of the contact rail 242, it contacts the drum shaft 54a of the process cartridge 50 mounted on the device body 2 via the through hole 24C. Also, when the second projection 804 is located in the middle portion 242b (through hole 24C) of the contact rail 242, it contacts the drum shaft 54a of the process cartridge 50 being detached from the device body 2 via the through hole 24C.

[0133] The drum shaft 54a, which contacts the first projection 803 and the second projection 804 through the through hole 24C, may contact the first projection 803 and the second projection 804 inside the through hole 24C, or it may contact the first projection 803 and the second projection 804 at a position that extends to the right of the through hole 24C in the left-right direction.

[0134] In this embodiment, the contact piece 80 is configured to move in contact with the drum shaft 54a. However, the process cartridge 50 may also be provided with a guide projection that protrudes toward the first main frame 24 side, separate from the drum shaft 54a, and the contact piece 80 may be configured to move in contact with this guide projection.

[0135] The first rotating link 81 is a substantially straight member connected to the contact piece 80. In the left-right direction, the first rotating link 81 is located to the right of the front frame 24A of the first main frame 24. The first rotating link 81 has a fitting portion 811 located at the front end into which the connecting portion 802 of the contact piece 80 fits, and a boss 812 located at the rear end that protrudes to the left. The first rotating link 81 is arranged in an inclined position 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 the fitting portion 811 into which the connecting portion 802 fits, and rotates along with the movement of the contact piece 80.

[0136] The linear motion link 82 is a substantially straight member that is connected to the first rotational motion link 81 and extends in the front-rear direction. In the left-right direction, the linear motion link 82 is located to the right of the front frame 24A of the first main frame 24. The linear motion link 82 has a fitting portion 821 at its front end into which the boss 812 of the first rotational motion link 81 fits, and a connecting hole 822 at its rear end. The linear motion link 82 is connected to the first rotational motion link 81 by the fitting of the boss 812 into the fitting portion 821, and moves linearly in the front-rear direction along with the rotation of the first rotational motion link 81.

[0137] The second pivot link 83 is connected to the linear link 82 and supported by the first main frame 24. The second pivot link 83 has a support portion 831 that is rotatably supported by the first main frame 24, a first arm 832 that extends substantially downward from the support portion 831, and a second arm 833 that extends substantially upward from the support portion 831. An engagement pin 832a that protrudes to the left is formed at the tip of the first arm 832, and a connecting hole 833a is formed at the tip of the second arm 833.

[0138] The engagement pin 832a of the first arm 832 enters the connecting hole 822 of the linear link 82 from the right and engages with the connecting hole 822 as the linear link 82 moves in the front-rear direction. The second pivot link 83 is connected to the linear link 82 by the engagement of the engagement pin 832a with the connecting hole 822 and rotates around the support portion 831 as the linear link 82 moves.

[0139] The projection 422 of the link cam 42 in the opening / closing link 4 enters the connecting hole 833a of the second rotating link 83 from the left, and the projection 422 and the connecting hole 833a engage as the second rotating link 83 rotates. The link cam 42 is connected to the second rotating link 83 by the engagement of the projection 422 and the connecting hole 833a, and rotates around the rotation axis 65 as the second rotating link 83 rotates. As the link cam 42 rotates, the shutter link 41 rotates in the vertical direction, moving the shutter 64 between the closed position and the open position.

[0140] In the image forming apparatus 1, when the process cartridge 50 is attached to or detached from the apparatus body 2, the contact piece 80 of the body-side link 8 comes into contact with the drum shaft 54a and moves along the contact piece rail 242, thereby transmitting driving force to the shutter 64 via the body-side link 8 and the opening / closing link 4, causing the shutter 64 to move between the closed position and the open position.

[0141] In this embodiment, the main body link 8 was configured to include a contact piece 80, a first rotational link 81, a linear link 82, and a second rotational link 83. However, it is not limited to this configuration and may be composed of a single link that connects to the opening / closing link 4 and opens and closes the shutter 64 by contacting the process cartridge 50.

[0142] Furthermore, while the opening / closing link 4 was configured to include a shutter link 41, a link cam 42, and a coil spring 43, it is not limited to this configuration. It may also consist of a single link that connects to the main body link 8 and the shutter 64, opening and closing the shutter 64 in accordance with the movement of the main body link 8. Moreover, the opening / closing link 4 may consist of a single link that connects to the shutter 64 and opens and closes the shutter 64 by contacting the process cartridge 50. In addition, the movement of the main body link 8 and the opening / closing link 4 is not limited to rotation or sliding, but may be any movement that opens and closes the shutter 64 in an appropriate manner in response to the insertion and removal of the process cartridge 50.

[0143] [rock] As shown in Figure 19, the device body 2 is equipped with a lock 9 that restricts the movement of the body-side link 8 when the shutter 64 is moved to the open or closed position. Specifically, the lock 9 restricts the movement of the linear motion link 82 in the forward and backward direction by pressing on the linear motion link 82. The lock 9 has an arm 91 that contacts the upper surface 82A of the linear motion link 82, and a lock spring 92 that biases the tip of the arm 91 toward the upper surface 82A of the linear motion link 82.

[0144] The arm 91 has a support portion 911 located at the base end of the arm 91 and rotatably supported by the first main frame 24, a contact portion 912 located at the tip of the arm 91 that abuts against the upper surface 82A of the linear link 82, and a fitting portion 913 into which the lock spring 92 is fitted. The contact portion 912 is an example of the tip of the arm 91. The arm 91 extends in the front-rear direction, with the support portion 911 located at the front end and the contact portion 912 located at the rear end. The fitting portion 913 is located above the contact portion 912. The contact portion 912 is rotatable in the vertical direction around the support portion 911.

[0145] The lock spring 92 is supported by the first main frame 24, and its lower end is fitted into the fitting portion 913 of the arm 91. The lock spring 92 biases the contact portion 912 of the arm 91 downward toward the upper surface 82A side of the linear link 82, and the contact portion 912 is pressed against the upper surface 82A.

[0146] The upper surface 82A of the linear link 82 has a link projection 823 that protrudes upward toward the lock 9 side between the fitting portion 821 and the connecting hole 822. The link projection 823 is formed in a mountain shape with a first inclined surface 823a that slopes downward toward the rear and a second inclined surface 823b that is formed continuously in front of the first inclined surface 823a and slopes downward toward the front.

[0147] The contact portion 912 of the arm 91 can overcome the link projection 823 against the biasing force of the lock spring 92 as the linear motion link 82 moves in the front-rear direction, and can be positioned on the rear side facing the first inclined surface 823a of the link projection 823, or on the front side facing the second inclined surface 823b of the link projection 823. The front side of the link projection 823 is an example of one side of the link projection, and the rear side of the link projection 823 is an example of the other side of the link projection.

[0148] When the contact portion 912 of the arm 91 is located behind the link projection 823, the contact portion 912 and the first inclined surface 823a engage, restricting the rearward movement of the linear link 82. When the contact portion 912 of the arm 91 is located in front of the link projection 823, the contact portion 912 and the second inclined surface 823b engage, restricting the forward movement of the linear link 82.

[0149] In other words, the arm 91 contacts the upper surface 82A of the linear link 82 at the rear of the link projection 823, pressing against the linear link 82 and thereby restricting the rearward movement of the linear link 82 and fixing the operation of the main body link 8. Also, the arm 91 contacts the upper surface 82A of the linear link 82 at the front of the link projection 823, pressing against the linear link 82 and thereby restricting the forward movement of the linear link 82 and fixing the operation of the main body link 8. In this way, the lock 9 restricts the movement of the linear link 82 by the arm 91 pressing against the linear link 82, so the lock 9 can be constructed with a simple structure.

[0150] The lock 9 is not limited to this embodiment. For example, the lock 9 may not be provided separately from the main body link 8, and the main body link 8 may maintain the shutter 64 in the open or closed position.

[0151] [Operation of the main unit link and the opening / closing link] Next, we will explain the operation of the main unit link 8 and the opening / closing link 4.

[0152] (Operation when process cartridge is installed) First, we will explain the operation of the main unit-side link 8 and the opening / closing link 4 when the process cartridge 50 is attached to the main unit 2 of the device.

[0153] As shown in Figures 19 and 20, when the process cartridge 50 is detached from the main body 2, and when the tip 50A of the process cartridge 50 in the insertion direction is in the mounting start position (the position shown in Figure 20) inserted into the main body 2, the drum shaft 54a is spaced apart from the contact piece 80, and the contact piece 80 is positioned across the front 242a and middle 241b of the contact piece rail 242. Specifically, the contact piece 80 is fitted into the contact piece rail 242 with the first projection 803 located in the middle 242b (through hole 24C) of the contact piece rail 242 and the second projection 804 located in the front 242a of the contact piece rail 242. The insertion direction of the process cartridge 50 is the same as the mounting direction.

[0154] When the contact piece 80 is in the position shown in Figure 20, the shutter 64 is moved to the closed position by the main body link 8 and the opening / closing link 4, as shown in Figure 7(a). This prevents the user's hand from touching the heating element 61 of the fuser unit 6, even if the user inserts their hand into the device body 2 through the opening 2A when the process cartridge 50 is detached from the device body 2.

[0155] Furthermore, when the contact piece 80 is in the position shown in Figure 20, the contact portion 912 of the arm 91 in the lock 9 is located behind the link projection 823 of the linear motion link 82, restricting the rearward movement of the linear motion link 82. As a result, when the shutter 64 is moved to the closed position by the main body link 8 and the opening / closing link 4, the linear motion link 82 is fixed by the lock 9, preventing the shutter 64 from unintentionally moving from the closed position to the open position. In other words, in the lock 9, the contact portion 912 located behind the link projection 823 engages with the link projection 823, thereby restricting the movement of the linear motion link 82, and thus stably maintaining the closed position of the shutter 64.

[0156] As shown in Figures 22 and 23, when the process cartridge 50, which is in the mounting starting position, is further inserted toward the mounting position, the drum shaft 54a enters the front part 241a of the cartridge rail 241 and moves within the cartridge rail 241. When the drum shaft 54a, which is moving within the cartridge rail 241, reaches the middle part 241b (through hole 24C), the drum shaft 54a comes into contact with the first projection 803 of the contact piece 80.

[0157] The contact piece 80, which comes into contact with the drum shaft 54a as it moves within the middle portion 241b (through hole 24C) of the cartridge rail 241, is pressed by the drum shaft 54a and moves downstream in the mounting direction of the process cartridge 50. In Figure 23, the first projection 803 and the second projection 804 of the contact piece 80, which moves in contact with the drum shaft 54a, are both located in the middle portion 242b (through hole 24C) of the contact piece rail 242.

[0158] As the contact piece 80 moves, the first pivot link 81 connected to the contact piece 80 rotates in a direction that reduces its angle of inclination with respect to the horizontal, and moves backward. As the first pivot link 81 rotates and moves, the linear link 82 connected to the first pivot link 81 moves linearly backward.

[0159] When the linear link 82 moves, the connecting hole 822 of the linear link 82 engages with the engagement pin 832a of the second pivot link 83, causing the second pivot link 83 to rotate in the direction in which the engagement pin 832a moves backward. When the second pivot link 83 rotates, the connecting hole 833a of the second pivot link 83 engages with the projection 422 of the link cam 42, causing the link cam 42 to rotate in the second direction W2, which is the direction in which the projection 422 moves forward.

[0160] In this case, as the linear link 82 moves backward, the contact portion 912 of the arm 91 in the lock 9 moves up the first inclined surface 823a of the link projection 823 of the linear link 82 against the biasing force of the lock spring 92, and rides up onto the top of the link projection 823.

[0161] When the contact portion 912 is riding on the top of the link projection 823, the lock spring 92 is compressed, increasing the biasing force on the contact portion 912 compared to when the contact portion 912 is located on the rear or front side of the link projection 823, and the pressing load of the contact portion 912 on the linear link 82 by the lock spring 92 becomes maximum.

[0162] As shown in Figures 24 and 25, when the process cartridge 50 is further inserted from the position shown in Figure 23 toward the mounting position, the contact piece 80 is moved further downstream in the mounting direction by the drum shaft 54a moving within the middle portion 241b (through hole 24C) of the cartridge rail 241. In Figure 25, the first projection 803 of the contact piece 80 is located at the rear portion 241c of the contact piece rail 242, and the second projection 804 is located in the middle portion 241b (through hole 24C) of the contact piece rail 242.

[0163] As the contact piece 80 moves, the first pivot link 81 moves backward while rotating in a direction that further reduces its inclination angle with respect to the horizontal. As the first pivot link 81 rotates and moves, the linear link 82 moves linearly further backward. As the linear link 82 moves, the second pivot link 83 rotates further in a direction that moves the engagement pin 832a backward. As the second pivot link 83 rotates, the link cam 42 rotates further in the second direction W2.

[0164] As shown in Figure 7(b), when the link cam 42 rotates in the second direction W2, the coil spring 43 moves along with the rotation of the link cam 42, and the second spring arm 433 of the coil spring 43 presses the boss 414 of the shutter link 41 upward. As the second spring arm 433 presses the boss 414 upward, the shutter link 41 rotates in the direction in which the engaging portion 413 moves upward, and the shutter 64 moves from the closed position to the open position.

[0165] In this case, as the linear link 82 moves backward, the contact portion 912 of the arm 91 in the lock 9 moves down the first inclined surface 823a of the link projection 823 of the linear link 82 due to the biasing force of the lock spring 92, and is positioned on the front side of the link projection 823. With the contact portion 912 positioned on the front side of the link projection 823, the contact portion 912 and the second inclined surface 823b are locked together, restricting the forward movement of the linear link 82.

[0166] As a result, when the main body link 8 moves the shutter 64 to the open position, the linear link 82 is fixed by the lock 9, preventing the shutter 64 from unintentionally moving from the open position to the closed position. In other words, the lock 9 restricts the movement of the linear link 82 by having the contact portion 912 located in front of the link projection 823 engage with the link projection 823, thereby stably holding the shutter 64 in the open position.

[0167] In the image forming apparatus 1, the main body link 8 and the opening / closing link 4 are composed of many components connected together, including the contact piece 80, the first rotational link 81, the linear link 82, the second rotational link 83, the shutter link 41, the link cam 42, and the coil spring 43. Consequently, when the process cartridge 50 is mounted on the apparatus body 2, an error may occur in the amount of rotation of the link cam 42, and after the shutter 64 moves to the open position, the link cam 42 may be further rotated in the second direction W2 by the main body link 8.

[0168] In this case, in the opening / closing link 4, the second spring arm 433 of the coil spring 43 elastically deforms away from the second groove bottom 425a of the second locking groove 425, thereby allowing the link cam 42 to rotate further in the second direction W2. Therefore, the link cam 42 can rotate further in the second direction W2 from the rotation position when the shutter 64 moves to the open position, while maintaining the state in which the shutter 64 is in the open position (see Figure 13). This prevents damage to the opening / closing link 4 even if the link cam 42 is rotated further in the second direction W2 by the main body side link 8 after the shutter 64 has moved to the open position.

[0169] As the process cartridge 50 is further inserted from the position shown in Figure 25 toward the mounting position, the drum shaft 54a moves from the middle 241b to the rear 241c of the cartridge rail 241, and then moves within the rear 241c toward the mounting direction. Meanwhile, the contact piece 80 remains in a position where the first projection 803 is at the rear 241c of the contact piece rail 242, and the contact piece 80 and the drum shaft 54a move apart. Subsequently, the process cartridge 50 reaches the mounting position as shown in Figure 26 and becomes mounted on the main body 2 of the apparatus.

[0170] Thus, the process cartridge 50 is movable from an installation start position in which the tip 50A in the installation direction is inserted into the device body 2, to an installation position in which it is installed in the device body 2. During the process of the process cartridge 50 moving from the installation start position to the installation position, the contact piece 80 comes into contact with the drum shaft 54a of the process cartridge 50 and moves, causing the shutter 64 to move from the closed position to the open position. Furthermore, when the process cartridge 50 is in the installation position after the shutter 64 has moved to the open position, the process cartridge 50 and the contact piece 80 are separated.

[0171] If the process cartridge 50 in the mounting position were in contact with the contact piece 80 of the main body-side link 8 connected to the shutter 64, there is a risk that unwanted force would be applied to the process cartridge 50 from the contact piece 80 when an opening or closing force is applied to the shutter 64. However, since the process cartridge 50 in the mounting position and the contact piece 80 are spaced apart, no unwanted force is applied to the process cartridge 50 mounted on the device body 2 from the contact piece 80, and it is possible to suppress the main body-side link 8 from adversely affecting the printing accuracy.

[0172] (Action taken when the process cartridge is removed) Next, the operation of the main body-side link 8 and the opening / closing link 4 when detaching the process cartridge 50 from the main body 2 will be described. When detaching the process cartridge 50, the main body-side link 8 and the opening / closing link 4 operate in the reverse direction to the operation when installing the process cartridge 50.

[0173] When the process cartridge 50, which is in the mounting position shown in Figure 26, is detached from the main body 2 of the apparatus toward the front, the drum shaft 54a moves downstream in the rear part 241c of the cartridge rail 241 in the direction of detachment. The detachment direction is the direction in which the process cartridge 50, when removed from the mounting body 2, moves toward the outside of the mounting body 2. As shown in Figure 25, when the drum shaft 54a moving within the cartridge rail 241 reaches the middle part 241b (through hole 24C), the drum shaft 54a comes into contact with the second projection 804 of the contact piece 80.

[0174] As shown in Figure 23, the contact piece 80, which is in contact with the drum shaft 54a, is pressed by the drum shaft 54a and moves downstream in the direction of departure of the process cartridge 50. In other words, the contact piece 80 moves from the position where the first projection 803 is at the rear 242c of the contact piece rail 242 to the position where it is at the middle 242b (through hole 24C).

[0175] As the contact piece 80 moves, the first pivot link 81 moves forward while rotating in a direction that increases its inclination angle with respect to the horizontal, and the linear link 82 moves linearly forward. As the linear link 82 moves, the connecting hole 822 of the linear link 82 engages with the engagement pin 832a of the second pivot link 83, causing the second pivot link 83 to rotate in the direction that the engagement pin 832a moves forward. As the second pivot link 83 rotates, the connecting hole 833a of the second pivot link 83 engages with the projection 422 of the link cam 42, causing the link cam 42 to rotate in the first direction W1, which is the direction that the projection 422 moves backward.

[0176] As the process cartridge 50 is further detached from the main body 2, the contact piece 80 is moved further downstream in the detachment direction by the drum shaft 54a, which moves within the middle portion 241b (through hole 24C) of the cartridge rail 241. As shown in Figure 20, when the contact piece 80 moves until the second projection 804 is positioned at the front portion 242a of the contact piece rail 242, the shutter link 41 rotates via the main body side link 8 and the opening / closing link 4 in a direction that moves the engaging portion 413 downward, as shown in Figure 7(a).

[0177] Specifically, the movement of the contact piece 80 causes the link cam 42 to rotate further in the first direction W1. As the link cam 42 rotates in the first direction W1, the coil spring 43 rotates along with the rotation of the link cam 42, and the first spring arm 432 of the coil spring 43 presses the boss 414 of the shutter link 41 downward. The downward press of the boss 414 by the first spring arm 432 causes the shutter link 41 to rotate in a direction that moves the engaging portion 413 downward. As a result, the shutter 64 moves from the open position to the closed position.

[0178] In the image forming apparatus 1, when the process cartridge 50 is detached from the apparatus body 2, an error may occur in the amount of rotation of the link cam 42, and after the shutter 64 moves to the closed position, the link cam 42 may be further rotated in the first direction W1 by the link 8 on the main body side.

[0179] In this case, in the opening / closing link 4, the first spring arm 432 of the coil spring 43 elastically deforms away from the first groove bottom 424a of the first locking groove 424, thereby allowing the link cam 42 to rotate further in the first direction W1. Therefore, the link cam 42 can rotate further in the first direction W1 from the rotation position when the shutter 64 moves to the closed position, while maintaining the state in which the shutter 64 is in the closed position (see Figure 12). This prevents damage to the opening / closing link 4 even if the link cam 42 is rotated further in the first direction W1 by the main body side link 8 after the shutter 64 has moved to the closed position.

[0180] Furthermore, when the process cartridge 50 is detached from the main body 2 and the shutter 64 is in the closed position with the link cam 42 in the first position, the shutter 64 may be pushed towards the open position by a user or the like. In such cases, as shown in Figure 27, the first spring arm 432 of the coil spring 43 is pressed against the boss 414 of the shutter link 41, causing it to elastically deform away from the first groove bottom 424a of the first locking groove 424, without the link cam 42 rotating, thereby allowing the shutter 64 to move to the open position.

[0181] In this case, the boss 414 of the shutter link 41 moves in a second direction W2 that approaches the second end face 423b of the through hole 423, but does not come into contact with the second end face 423b, and a gap d exists between the boss 414 and the second end face 423b in the circumferential direction.

[0182] In other words, the second end face 423b of the through hole 423 is positioned so that it does not come into contact with the boss 414 of the shutter link 41 when the shutter 64 moves from the closed position to the open position while the link cam 42 is in the first position. As a result, even if the shutter 64 moves to the open position when the link cam 42 is in the first position and the shutter 64 is in the closed position, the boss 414 of the shutter link 41 will not come into contact with the link cam 42, thereby preventing damage to the opening / closing link 4.

[0183] In the image forming apparatus 1, when the process cartridge 50 is mounted on the apparatus body 2, the drum shaft 54a contacts the first projection 803 of the contact piece 80, and the body-side link 8 moves the opening / closing link 4 in the direction that the shutter 64 moves from the closed position to the open position. Also, when the process cartridge 50 is removed from the apparatus body 2, the drum shaft 54a contacts the second projection 804 of the contact piece 80, and the body-side link 8 moves the opening / closing link 4 in the direction that the shutter 64 moves from the open position to the closed position.

[0184] In this manner, the main unit-side link 8 operates in response to the attachment and detachment of the process cartridge 50 to and from the device body 2. Specifically, the main unit-side link 8 moves the shutter link 41 in the second direction W2 when the process cartridge 50 is attached to the device body 2, and moves the shutter link 41 in the first direction W1 when the process cartridge 50 is detached from the device body 2. This allows the main unit-side link 8 to open and close the shutter 64 via the opening / closing link 4 at the appropriate timing.

[0185] Furthermore, in this embodiment, the main body link 8 operates in accordance with the attachment and detachment of the process cartridge 50 to the main body 2 of the device. However, it is not limited to this, and can also be configured to operate in conjunction with other movable members, such as operating in accordance with the opening and closing of the front cover 21, which is a movable member operated by the user. In this way, the main body link 8 for moving the link cam 42 can operate in conjunction with various movable members, thereby increasing the degree of freedom of the location where the opening and closing operation of the shutter 64 is performed within the image forming apparatus 1.

[0186] Furthermore, in this embodiment, the shutter 64 was opened and closed via the link cam 42 and the shutter link 41, but this is not the only possible configuration. For example, an elastically deformable member may be connected between the main body link 8 and the shutter 64. For example, when the process cartridge 50, which is a movable member operated by the user, is pulled out, the shutter 64 moves in the closing direction together with the main body link 8, and after the shutter 64 closes and contacts the first contact surface 631, if the main body link 8 moves further, the elastically deformable member between the main body link 8 and the shutter 64 may deform while the shutter 64 remains in the closed position.

[0187] Furthermore, the link cam 42 is permitted to move in the first direction W1 while maintaining the shutter 64 in the closed position when the shutter 64 is in contact with the first contact surface 631, and is permitted to move in the second direction while maintaining the shutter 64 in the open position when the shutter 64 is in contact with the second contact surface 632, but is not limited to this. The link cam 42 only needs to be permitted to move in the first direction W1 while maintaining the shutter 64 in the closed position, and may be configured to restrict movement in the second direction while maintaining the shutter 64 in the open position when the shutter 64 is in contact with the second contact surface 632.

[0188] Furthermore, in this embodiment, the link cam 42 is supported by a rotating shaft 65 that operates the nip pressure changing mechanism 66, but this is not the only configuration. For example, the nip pressure changing mechanism 66 may be operated by a rotating shaft separate from the rotating shaft that supports the link cam 42.

[0189] Furthermore, in this embodiment, the main body side link 8 has a contact piece 80, a first rotational link 81, a linear link 82, and a second rotational link 83, but it is not limited to this and may be composed of a single link member. [Explanation of Symbols]

[0190] 1. Image forming apparatus 2. Main unit of the device 4 Open / Close Links 6. Fuser 8. Main unit link 41 Shutterlink 42 Link Cam 43 Coil spring 50 Process Cartridges 61 Heating element 62 Pressure rollers 63 Fixing Frame 63a 1st opening 64 shutters 65 Rotation axis 66. Nip pressure changing mechanism 413a long hole 414 Boss 421 Link Cam Body 421a Operating cam 422 Protrusion 423 Through hole 423a 1st end face 423b 2nd end face 424 First locking groove 424a Bottom of the first trench 425 Second locking groove 425a 2nd groove bottom 431 Coil 432 First spring arm 433 Second spring arm 631 1st contact surface 632 Second contact surface 641 Rotary shaft 642 Connecting shaft NP (Nippon Nip Point) S Seat W1 1st direction W2 Second direction

Claims

1. A fuser for fixing a toner image transferred to a conveyed sheet, comprising: a heating member; a pressurizing member that nips the sheet together with the heating member; a fuser frame covering the heating member and the pressurizing member, with an opening formed on the upstream side of the heating member in the sheet conveying direction; and a shutter that moves between a closed position that closes the opening and an open position that opens the opening. An opening / closing link connected to the shutter, which moves the shutter between the open position and the closed position, Equipped with, The fixing frame has a first contact surface against which the shutter in the closed position contacts, The opening / closing link is movable in a first direction that moves the shutter to the closed position and in a second direction that moves the shutter to the open position. An image forming apparatus characterized in that, when the shutter is in contact with the first contact surface and in the closed position, movement of the opening / closing link in the first direction is permitted while the shutter is maintained in the closed position.

2. The image forming apparatus according to claim 1, wherein the first contact surface of the fixing frame faces the upstream side in the sheet transport direction.

3. The aforementioned open / close link is A shutter link connected to the shutter, which moves the shutter between the open position and the closed position, A link cam connected to the shutter link and movable in the first and second directions, The system includes a spring that moves along the movement of the link cam and presses against the shutter link, When the shutter is in the closed position, in contact with the first contact surface, The spring contacts the shutter link and presses the shutter link in the first direction. The image forming apparatus according to claim 1 or claim 2, wherein the movement of the link cam in the first direction is permitted by the elastic deformation of the spring while the shutter remains in the closed position.

4. The shutter has a pivot shaft that is rotatably supported by the fixing frame and a connecting shaft that protrudes in a direction parallel to the pivot shaft. The image forming apparatus according to claim 3, wherein the shutter link is connected to the connecting shaft.

5. The shutter link has an elongated hole, The image forming apparatus according to claim 4, wherein the connecting shaft of the shutter is located within the elongated hole.

6. The device comprises a main body that houses the aforementioned fuser, The link cam comprises a link cam body having a through hole that penetrates along the rotation axis direction and is rotatably supported on the fixing frame, and a projection that protrudes from the link cam body along the rotation axis direction, The shutter link has a boss that protrudes along the rotation axis direction and is located within the through hole, The image forming apparatus according to claim 3, wherein the apparatus body has a body-side link that engages with the projection and moves the link cam.

7. The shutter link and the link cam are rotatably supported on the fixing frame in the same axis. The spring is a coil spring having a coil supported by the link cam body and a spring arm extending outward from the coil. The spring arm is located inside the through hole, The image forming apparatus according to claim 6, wherein the link cam body has a locking groove that locks with the spring arm and restricts the movement of the spring arm to one side in the circumferential direction.

8. The locking groove of the link cam body is cut out in the circumferential direction of the rotational movement of the link cam body. The image forming apparatus according to claim 7, wherein the spring arm abuts against the bottom of the locking groove, thereby restricting the movement of the spring arm in the first direction relative to the link cam body, and the link cam body is allowed to move in the first direction relative to the spring arm by elastic deformation of the spring arm while the shutter remains in the closed position inside the locking groove.

9. The link cam is movable to a first position in which it moves in the first direction to move the shutter to the closed position, and to a second position in which it moves in the second direction to move the shutter to the open position. The through hole has a first end face located on the first direction side in the circumferential direction and a second end face located on the second direction side in the circumferential direction. The image forming apparatus according to claim 6, wherein the second end face is positioned so as not to contact the boss of the shutter link when the shutter moves from the closed position to the open position while the link cam is in the first position.

10. The image forming apparatus according to claim 6, wherein the main body-side link moves the shutter link in the second direction in response to a cartridge being mounted on the main body of the apparatus, and moves the shutter link in the first direction in response to a cartridge being detached from the main body of the apparatus.

11. The image forming apparatus according to claim 3, wherein in the sheet transport direction, the connection point between the shutter link and the shutter is located on the opposite side from the connection point between the shutter link and the link cam, with the nip point of the sheet between the heating member and the pressurizing member in between.

12. The aforementioned fuser is The fixing frame has a rotating shaft, and the nip pressure changing mechanism changes the nip pressure between the heating member and the pressurizing member by rotating the rotating shaft, The image forming apparatus according to claim 3, wherein the link cam is located coaxially with the rotation axis.

13. The fixing frame has a second contact surface against which the shutter, in the open position, contacts, When the shutter is in the open position, in contact with the second contact surface, The spring contacts the shutter link and presses the shutter link in the second direction. The image forming apparatus according to claim 3, wherein the movement of the link cam in the second direction is permitted by the elastic deformation of the spring while the shutter remains in the open position.

14. The image forming apparatus according to claim 13, wherein the second contact surface of the fixing frame faces the upstream side in the sheet transport direction.

Images