Image forming apparatus and fixing unit

Abstract

To provide an image formation apparatus and a fixation unit which can highly accurately position a shutter when the shutter is opened.SOLUTION: An image formation apparatus comprises: an image formation part which forms a toner image on a sheet; a fixation part which heats and presses the sheet formed with the toner image to fix the toner image on the sheet; a shutter which is provided so as to be movable between the open position for opening an opening through which the sheet conveyed toward the fixation part can pass and the close position for closing the opening; a biasing part which biases the shutter toward the open position; and an abutting part which positions the shutter at the open position with abutting by the shutter biased toward the open position by the biasing part.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and a fixing unit. [Background technology]

[0002] Conventionally, there has been known an image forming apparatus that includes a fixing unit that becomes hot and a fixing frame that surrounds the fixing unit. This type of fixing frame generally has an opening through which a sheet passes. Patent Document 1 discloses an image forming apparatus that includes a shutter that opens and closes the opening of the fixing frame so that a user's fingers do not touch the fixing unit through the opening of the fixing frame when the user opens an opening / closing member of the exterior. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-140480 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the shutter described in Patent Document 1 is biased toward a closed position that closes the opening, so when opening the shutter, it must be moved by an interlocking member that interlocks with the opening / closing member. For this reason, when opening the shutter, it is difficult to position the shutter with high precision due to manufacturing tolerances of the interlocking member and the opening / closing cover.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus and a fixing unit that are capable of positioning a shutter with high precision when the shutter is opened. [Means for solving the problem]

[0006] The image forming apparatus of the present invention includes an image forming unit that forms a toner image on a sheet, a fixing unit that heats and pressurizes the sheet on which the toner image has been formed to fix the toner image to the sheet, a shutter that is provided so as to be movable between an open position that opens an opening through which a sheet conveyed toward the fixing unit can pass and a closed position that closes the opening, a biasing unit that biases the shutter toward the open position, and an abutting unit that positions the shutter at the open position by abutting against the shutter biased toward the open position by the biasing unit. an opening / closing member that constitutes at least a part of the exterior of the image forming apparatus; and a link mechanism that moves the shutter to the closed position against the biasing force of the biasing portion in conjunction with an opening operation of the opening / closing member. The present invention is characterized by comprising:

[0007] The fixing unit of the present invention includes a fixing section that applies heat and pressure to a sheet on which a toner image has been formed to fix the toner image to the sheet; a shutter that is provided so as to be movable between an open position that opens an opening through which a sheet conveyed toward the fixing section can pass and a closed position that closes the opening; a biasing section that biases the shutter toward the open position; and an abutting section that positions the shutter at the open position by abutting against the shutter biased toward the open position by the biasing section. a link mechanism that moves the shutter to the closed position against the biasing force of the biasing portion in conjunction with an opening operation of an opening / closing member that constitutes at least a part of the exterior of the image forming apparatus; The present invention is characterized by comprising: [Effects of the Invention]

[0008] According to the present invention, the shutter can be positioned with high precision when it is opened. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a printer as an example of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 2 is a perspective view of a fixing unit according to the first embodiment. [Figure 3] 3A and 3B are cross-sectional views of a fixing unit according to the first embodiment. [Figure 4] FIG. 2 is a perspective view of a link mechanism and a fixing unit according to the first embodiment. [Figure 5] 5A and 5B are cross-sectional views of a link mechanism and a fixing unit according to the first embodiment. [Figure 6] 5A and 5B are cross-sectional views of a fixing unit, a link mechanism, and an opening / closing cover according to the first embodiment. [Figure 7] FIG. 10 is a cross-sectional view of a fixing unit according to a first modified example. [Figure 8] FIG. 10 is a perspective view of a fixing unit, a link mechanism, and a front opening / closing cover of a printer that is an example of an image forming apparatus according to a second embodiment. [Figure 9] 10(a) and 10(b) are cross-sectional views of a fixing unit, a link mechanism, and a front opening / closing cover according to a second embodiment. [Figure 10] FIG. 11 is a perspective view of a fixing unit, a link mechanism, and a rear opening / closing cover of a printer that is an example of an image forming apparatus according to a third embodiment. [Figure 11] 10(a) and 10(b) are cross-sectional views of a fixing unit, a link mechanism, and a rear opening / closing cover according to a third embodiment. [Figure 12] FIG. 10 is a perspective view of a fixing unit, a link mechanism, and a process cartridge of a printer that is an example of an image forming apparatus according to a fourth embodiment. [Figure 13] 10A and 10B are cross-sectional views of a fixing unit, a link mechanism, and a process cartridge according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] [First embodiment] 1 is a schematic diagram showing a vertical cross section of a printer 100, which is an example of an image forming apparatus according to the first embodiment. The printer 100 is an electrophotographic laser beam printer that forms monochrome toner images.

[0012] The printer 100 includes a device main body 101 and an exterior casing 102 that covers the device main body 101. The device main body 101 includes a body frame 110, a sheet feeding section 120 that feeds a sheet S, and a pair of transport rollers 130 that transport the sheet S fed by the sheet feeding section 120. The device main body 101 also includes an image forming section 140 that forms a toner image on the sheet S transported by the pair of transport rollers 130, and a fixing unit 150 that includes a fixing section 300 that fixes the toner image formed on the sheet S. The device main body 101 also includes a pair of discharge rollers 160 that can discharge the sheet S to a discharge tray 161. The sheet S includes recording media such as paper, such as plain paper or envelopes, plastic film (OHT) for overhead projectors, and cloth.

[0013] At least a part of the exterior 102, in the first embodiment, a part of the upper part of the exterior 102, is an opening / closing cover 103, which is an example of an opening / closing member. The opening / closing cover 103 is supported by the main body frame 110 so as to be openable and closable in the vertical direction.

[0014] The main body frame 110 is a frame made of sheet metal and includes a pair of side plates (not shown). The main body frame 110 supports the sheet feeding section 120, the pair of conveying rollers 130, the image forming section 140, the fixing unit 150, and the pair of discharging rollers 160 directly or indirectly via members (not shown).

[0015] When an image formation job is output to the printer 100, an image formation process is started by the image forming unit 140 based on image information input from an external computer or the like connected to the printer 100. The image forming unit 140 has a process cartridge 200 which is an example of a cartridge, a laser scanner 250 which is an example of an exposure unit, and a transfer roller 202 which is an example of a transfer unit.

[0016] The process cartridge 200 is removably inserted into the main body frame 110 along a guide (not shown). When the process cartridge 200 is inserted into the main body frame 110, it is biased by a pressing member (not shown) so that it abuts against an abutment portion (not shown) and is positioned relative to the main body frame 110.

[0017] In this embodiment, by opening the opening / closing cover 103, the process cartridge 200 can be exposed to the outside, allowing the user to insert or remove the process cartridge 200. The process cartridge 200 has a photosensitive drum 201 as an image carrier, and a charging unit (not shown) and a developing unit (not shown) arranged around the photosensitive drum 201.

[0018] A pair of longitudinal ends of the photosensitive drum 201 are rotatably supported by the housing of the process cartridge 200. The driving force of a drive motor (not shown) is transmitted to one end of the photosensitive drum 201 via a drive transmission mechanism (not shown), thereby driving the photosensitive drum 201 to rotate in the direction of arrow A in FIG.

[0019] The surface of the photosensitive drum 201 is made of an organic photoconductor layer, and is uniformly charged by applying a charging bias to a charging roller (not shown) of a charging unit. A laser scanner 250 irradiates the photosensitive drum 201 with laser light based on input image information. The surface of the photosensitive drum 201 is exposed to the laser light emitted from the laser scanner 250, and an electrostatic latent image is formed on the surface of the photosensitive drum 201. A developing unit (not shown) applies toner to the surface of the photosensitive drum 201 on which the electrostatic latent image has been formed, thereby developing the electrostatic latent image. As a result, a monochrome toner image is formed on the surface of the photosensitive drum 201.

[0020] In parallel with the image formation process described above, sheets S are fed from the sheet feeding unit 120. The sheet feeding unit 120 includes a feed tray (not shown), a middle plate 121, a pickup roller 122, a feed roller 123, and a separation roller 124. The middle plate 121 is supported on the feed tray (not shown) so as to be able to move up and down, and is pressed upward by a middle plate lifting mechanism (not shown). When the middle plate 121 is pushed up by the middle plate lifting mechanism (not shown), the downstream ends of the sheets S stacked on the middle plate 121 are pressed against the pickup roller 122. In this state, the pickup roller 122 feeds the uppermost sheet S of the sheets S stacked on the middle plate 121 to the feed roller 123. The feed roller 123 is driven at a predetermined timing by a drive motor (not shown) and a drive transmission mechanism (not shown), and conveys the sheet S fed by the pickup roller 122 to the conveyance roller pair 130. When a plurality of sheets S are fed by the pickup roller 122, the plurality of sheets S are separated by a separation roller 124, and only the uppermost sheet S is conveyed to the conveying roller pair 130.

[0021] The sheet S conveyed to the conveying roller pair 130 is conveyed by the conveying roller pair 130 to a transfer nip where the photosensitive drum 201 and the transfer roller 202 come into contact with each other. A predetermined bias is applied to the transfer roller 202, so that the toner image on the photosensitive drum 201 is transferred onto the sheet S conveyed to the transfer nip.

[0022] The fixing unit 150 has a fixing frame 310 that supports the fixing section 300. The fixing frame 310 is supported by the main body frame 110 by being attached and fixed to the main body frame 110. This makes the fixing unit 150 attachable to and detachable from the main body frame 110, improving the ease of assembly and maintenance of the printer 100.

[0023] The fixing frame 310 has a front side portion 311 facing the transfer roller 202 and an upper portion 312 facing the pair of discharge rollers 160. An opening H1 through which the sheet S can pass is formed in the front side portion 311 of the fixing frame 310. A conveying guide 170 extending in a substantially horizontal direction is disposed between the transfer roller 202 and the opening H1 of the fixing frame 310. The sheet S onto which the toner image has been transferred is guided by the conveying guide 170 to the fixing unit 150 and then led to the fixing section 300 through the opening H1.

[0024] The fixing unit 300 has a heating roller 301 and a pressure roller 302. The heating roller 301 is heated by a heat source such as a heating element such as a halogen lamp or a ceramic heater, or a heating mechanism using an induction heating method. A fixing nip N is formed when the heating roller 301 and the pressure roller 302 come into contact with each other. The sheet S onto which the toner image has been transferred is sandwiched and conveyed through the fixing nip N of the fixing unit 300, whereby a predetermined amount of heat and pressure are applied. As a result, the toner image is fused and fixed (fixed) onto the sheet S, and an image is formed on the sheet S.

[0025] An opening H2 through which the sheet S can pass is formed in the upper portion 312 of the fixing frame 310. Transport guides 181 and 182 extending in a substantially vertical direction are arranged between the opening H2 of the fixing frame 310 and the pair of discharge rollers 160. The sheet S on which an image has been formed by the fixing unit 300 is transported to the outside of the fixing frame 310 through the opening H2, guided by the transport guides 181 and 182 to the pair of discharge rollers 160, and then discharged onto the discharge tray 161 by the pair of discharge rollers 160.

[0026] Although the printer 100 of the first embodiment is configured to be capable of single-sided printing, in which an image is formed on the first side of the sheet S, it may also be configured to be capable of double-sided printing, in which an image is formed on both the first and second sides of the sheet S. That is, a double-sided conveying path may be provided downstream of the fixing unit 300 in the sheet conveying direction, and the sheet S with an image formed on its first side may be guided again to the transfer nip by the double-sided conveying path.

[0027] Furthermore, although the fixing unit 300 has been described as having a heating roller 301, this is not limited to this, and instead of the heating roller 301, the fixing unit 300 may have a fixing film made of a flexible sleeve that has a built-in heater (not shown).

[0028] When the open / close cover 103 is opened and the process cartridge 200 is pulled out from the main body frame 110, the transfer roller 202, the conveying guide 170, and the front side portion 311 of the fixing frame 310 are exposed. This makes it easy for the user to remove a jammed sheet inside the printer 100.

[0029] Fig. 2 is a perspective view of the fixing unit 150 according to the first embodiment. Fig. 3(a) and Fig. 3(b) are cross-sectional views of the fixing unit 150 according to the first embodiment.

[0030] The heating roller 301 and the pressure roller 302, especially the heating roller 301, have portions that become hot because they are heated by a heat source such as a heater (not shown). The fixing frame 310 is disposed so as to surround the fixing unit 300. The fixing frame 310 is made of, for example, sheet metal.

[0031] The longitudinal direction of the fixing unit 300, i.e., the longitudinal direction of the heating roller 301 and the pressure roller 302, is defined as the X direction. The X direction is also the width direction of the sheet S. The fixing unit 300 is disposed inside the fixing frame 310, and both ends of the fixing unit 300 in the X direction are supported by the fixing frame 310. As described above, the fixing frame 310 has two openings H1 and H2 through which the sheet S can pass. The opening H1 is formed on the inlet side of the fixing frame 310 for the sheet S, and the opening H2 is formed on the outlet side of the fixing frame 310 for the sheet S.

[0032] The fact that the fixing frame 310 surrounds the fixing unit 300 means that the fixing frame 310 does not seal the fixing unit 300 but partially covers it. That is, the fixing frame 310 may have openings other than the openings H1 and H2, or may not cover a portion of the fixing unit 300, as long as it is difficult for a user's hands to touch the high-temperature portion of the fixing unit 300. For example, as shown in FIG. 2 , both sides of the fixing frame 310 in the X direction may be open. Alternatively, the fixing frame 310 may have openings large enough to prevent a user's fingers from passing through. Alternatively, the fixing frame 310 may have openings in a position that is difficult for a user to reach. Alternatively, a gap may be formed between the fixing frame 310 and the main frame 110, and the end of the fixing unit 300 in the X direction may be exposed through the gap.

[0033] Each of the openings H1, H2 is formed to a size that allows both ends in the X direction of the largest size sheet S on which an image can be formed in the printer 100 to pass through without contacting the fixing frame 310, and in this embodiment is a rectangular slot extending in the X direction. Note that the shape of the openings H1, H2 is not limited to this, and for example, the ends in the X direction of the openings H1, H2 may extend to the ends of the fixing frame 310 in the X direction.

[0034] When the opening / closing cover 103 is open and the process cartridge 200 is pulled out from the main body frame 110, the opening H1 is in a position that is within the user's reach, and the opening H2 is in a position that is difficult for the user to reach. In this embodiment, the fixing unit 150 has a shutter (hereinafter referred to as the "fixing shutter") 320 that opens and closes the opening H1. Note that FIG. 3(a) illustrates the fixing shutter 320 in an open state, and FIG. 3(b) illustrates the fixing shutter 320 in a closed state.

[0035] The fixing shutter 320 is provided so as to be movable between an open position P1 shown in Fig. 3(a) where the opening H1 is open, and a closed position P2 shown in Fig. 3(b) where the opening H1 is closed. Here, when the fixing shutter 320 moves to the closed position P2, the entire opening H1 may be blocked by the fixing shutter 320, but a portion of the opening H1 may not be blocked by the fixing shutter 320 as long as the user's finger does not fit through it. For example, the end of the opening H1 in the X direction may not be blocked by the fixing shutter 320, or an opening such as a hole or slit large enough to prevent the user's finger from passing through may be formed in the fixing shutter 320.

[0036] The fixing unit 150 has a holder 330 that supports the fixing shutter 320 so that the fixing shutter 320 can move between an open position P1 and a closed position P2. The holder 330 is attached and fixed to the fixing frame 310. As a result, the fixing shutter 320 is supported by the main body frame 110 via the holder 330 and the fixing frame 310. In this embodiment, the fixing shutter 320 is rotatably (swingably) supported by the holder 330. The fixing shutter 320 can move between the open position P1 and the closed position P2 by rotating relative to the holder 330, i.e., the fixing frame 310. More specifically, the fixing shutter 320 has a shutter main body 321 that extends in the X direction and a support shaft 322 provided on the shutter main body 321. The support shaft 322 is rotatably supported by the holder 330. As a result, the fixing shutter 320 is supported by the holder 330 so as to be rotatable about the support shaft 322 .

[0037] The fixing unit 150 also has a fixing shutter spring 340, which is an example of a biasing portion, and an abutment portion 335 against which the fixing shutter 320 abuts, thereby positioning the fixing shutter 320 at the open position P1. The fixing shutter spring 340 is a spring that biases the fixing shutter 320 toward the open position P1 with a biasing force F1, and in this embodiment is a torsion coil spring. A coil portion of the fixing shutter spring 340 is attached to the support shaft 322, one end of the fixing shutter spring 340 abuts against the shutter body 321 of the fixing shutter 320, and the other end of the fixing shutter spring 340 abuts against the fixing frame 310. As a result, the biasing force F1 of the fixing shutter spring 340 acts on the fixing shutter 320. Then, the fixing shutter 320 rotates counterclockwise due to the biasing force F1 of the fixing shutter spring 340, and abuts against the abutment portion 335, as shown in FIG.

[0038] The abutment portion 335 is fixed to a holder 330 which is fixed to the fixing frame 310. In other words, by being fixed to the holder 330, the abutment portion 335 is indirectly fixed to the fixing frame 310 via the holder 330, and is indirectly fixed to the main body frame 110 via the holder 330 and the fixing frame 310. In this way, the abutment portion 335 is positioned and fixed to the fixing frame 310, i.e., the main body frame 110, with high precision. Therefore, the fixing shutter 320 abuts against the abutment portion 335 which is positioned with high precision, and is thereby positioned at the open position P1 with high precision.

[0039] As shown in FIG. 3A, the fixing shutter 320 moves to the open position P1 due to the biasing force F1 of the fixing shutter spring 340, thereby exposing the fixing nip N of the fixing unit 300 to the outside of the fixing frame 310 through the opening H1 during image formation. Then, the shutter body 321 of the fixing shutter 320 abuts against the abutment portion 335, thereby positioning the fixing shutter 320 at the open position P1 with high precision. This allows a sheet transport path at the opening H1 wide enough for the sheet S to pass through without increasing the size of the printer 100. This prevents the sheet S, guided to the fixing nip N through the opening H1, from contacting the fixing frame 310 or the fixing shutter 320 during image formation. This prevents the sheet S from jamming at the opening H1 and the toner image formed on the sheet S from being distorted.

[0040] Furthermore, since the fixing shutter 320 moves between the open position P1 and the closed position P2 by rotating around the support shaft 322, the printer 100 can be made smaller than when the fixing shutter moves linearly to move between the open position and the closed position.

[0041] As shown in FIG. 3B, the fixing shutter 320 has a contact portion 323 provided at the end of the shutter body 321 in the X direction. The contact portion 323 is arranged outside the sheet conveying path. The fixing frame 310 is provided with an abutment portion 336 against which the contact portion 323 of the fixing shutter 320 abuts when the fixing shutter 320 moves to the closed position P2. The abutment portion 323 of the fixing shutter 320 abuts against the abutment portion 336, thereby positioning the fixing shutter 320 at the closed position P2 with high accuracy. When the fixing shutter 320 moves to the closed position P2, the fixing nip N of the fixing unit 300 is shielded by the fixing shutter 320.

[0042] 1, the printer 100 includes a link mechanism 350 that opens and closes the fixing shutter 320 in conjunction with the opening and closing operation of the opening and closing cover 103. The link mechanism 350 moves the fixing shutter 320 to the closed position P2 against the biasing force F1 of the fixing shutter spring 340 in conjunction with the opening operation of the opening and closing cover 103.

[0043] Fig. 4 is a perspective view of the link mechanism 350 and the fixing unit 150 according to the first embodiment. Fig. 5(a) and Fig. 5(b) are cross-sectional views of the link mechanism 350 and the fixing unit 150 according to the first embodiment. Fig. 5(a) shows the fixing shutter 320 in an open state, and Fig. 5(b) shows the fixing shutter 320 in a closed state.

[0044] The link mechanism 350 is disposed at a position corresponding to the contact portion 323 of the fixing shutter 320. The link mechanism 350 has a switching link 351 which is an example of a first link member, a moving link 352 which is an example of a second link member, and a switching link spring 353 which is an example of a link biasing portion.

[0045] The switching link 351 is connected to the contact portion 3 of the fixing shutter 320. 2 5A, the fixing shutter 320 is spaced from the contact portion 3. 2 3, and an abutment position P4 shown in FIG. 5(b) where the switching link 351 abuts against the holder 110. In this embodiment, the switching link 351 is rotatably (swingably) supported by a holder (not shown). The holder (not shown) is fixed to the main body frame 110 of FIG. 1. The switching link 351 rotates relative to the holder (not shown), thereby moving between the separation position P3 and the abutment position P4. More specifically, the switching link 351 has a link body 3511 and a support shaft 3512 provided on the link body 3511. The support shaft 3512 is rotatably supported by the holder (not shown). As a result, the switching link 351 is supported by the holder (not shown) so as to be rotatable about the support shaft 3512.

[0046] The switching link spring 353 is a spring that urges the switching link 351 toward the abutment position P4 with a urging force F2, and in this embodiment is a torsion coil spring. The urging force F2 of the switching link spring 353 is set to be greater than the urging force F1 of the fixing shutter spring 340. The switching link spring 353 is provided on a support shaft 3512 of the switching link 351.

[0047] The movable link 352 is a link member that moves the switching link 351 to the separated position P3 against the biasing force F2 of the switching link spring 353 in conjunction with the closing operation of the open / close cover 103 in Fig. 1. The movable link 352 is supported by a holder (not shown) so as to be able to move linearly. The holder (not shown) is fixed to the main body frame 110 in Fig. 1. The movable link 352 can come into contact with or separate from the switching link 351 by moving linearly relative to the holder (not shown).

[0048] 5A, the movable link 352 abuts against the switching link 351 and presses the switching link 351, thereby rotating the switching link 351 counterclockwise, i.e., in the first direction, against the biasing force F2 of the switching link spring 353, and moving the switching link 351 to the separated position P3. As a result, when the switching link 351 is located at the separated position P3, the fixing shutter 320 is biased by the fixing shutter spring 340 and is positioned at the open position P1. That is, the fixing shutter 320 is released from the restriction by the switching link 351, rotates counterclockwise due to the biasing force F1 of the fixing shutter spring 340, and abuts against the abutment portion 335, and is positioned at the open position P1 with high accuracy.

[0049] 5B, when the moving link 352 moves away from the switching link 351, the switching link 351 rotates clockwise, which is a second direction opposite to the first direction, due to the biasing force F2 of the switching link spring 353, and comes into contact with the contact portion 323. The biasing force F2 of the switching link spring 353 is greater than the biasing force F1 of the fixing shutter spring 340. Therefore, the switching link 351 presses the contact portion 323 of the fixing shutter 320 with the biasing force F2 of the switching link spring 353 against the biasing force F1 of the fixing shutter spring 340, rotating the fixing shutter 320 clockwise and moving to the contact position P4. As a result, when the switching link 351 is located at the contact position P4, the fixing shutter 320 is pressed by the switching link 351 against the biasing force F1 of the fixing shutter spring 340 and is located at the closed position P2. That is, the fixing shutter 320 rotates clockwise around the support shaft 322 as the contact portion 323 is pressed by the rotating switching link 351. Then, as the switching link 351 rotates to the contact position P4, the contact portion 323 abuts against the abutment portion 336, and the fixing shutter 320 is positioned at the closed position P2 with high accuracy.

[0050] 6(a) and 6(b) are cross-sectional views of the fixing unit 150, link mechanism 350, and opening / closing cover 103 according to the first embodiment. Note that FIG. 6(a) shows a state in which the fixing shutter 320 is open, and FIG. 6(b) shows a state in which the fixing shutter 320 is closed. The opening / closing cover 103 is supported by the main body frame 110 so as to be rotatable about a support shaft 1031. The opening / closing cover 103 has a recess 1032 into which one end of the moving link 352 can be fitted and detached.

[0051] As shown in FIG. 6(a), when the opening / closing cover 103 changes from the open state to the closed state, one end of the moving link 352 fits into the recess 1032 of the opening / closing cover 103, causing the moving link 352 to move in the direction of arrow A1. closedIn conjunction with this operation, the switch link 351 moves in the direction of arrow A1, coming into contact with the switching link 351 and rotating the switching link 351 counterclockwise against the biasing force F2 of the switching link spring 353. As a result, the switching link 351 moves to a separated position P3 where it is separated from the abutment portion 323 of the fixing shutter 320. As the switching link 351 separates from the fixing shutter 320, the fixing shutter 320 is abutted against the abutment portion 335 by the biasing force F1 of the fixing shutter spring 340, and is positioned at the open position P1. As a result, the fixing nip N is exposed from the opening H1.

[0052] 6(b), when the opening / closing cover 103 changes from the closed state to the open state, one end of the moving link 352 is released from the recess 1032 of the opening / closing cover 103, and is pressed against the opening / closing cover 103 in the direction of arrow A2, which is opposite to the direction of arrow A1. Open The moving link 352 moves in the direction of arrow A2 in conjunction with the operation of the fixing shutter 320. As the moving link 352 moves in the direction of arrow A2, it separates from the switching link 351, and the switching link 351 rotates clockwise due to the biasing force F2 of the switching link spring 353. As the switching link 351 moves to the abutting position P4 against the biasing force F1 of the fixing shutter spring 340, the abutting portion 323 of the fixing shutter 320 abuts against the abutting portion 336, and the fixing shutter 320 is positioned at the closed position P2. As a result, the fixing nip N is shielded by the fixing shutter 320.

[0053] As described above, according to the first embodiment, closing the open / close cover 103 causes the switching link 351 of the link mechanism 350 to move away from the fixing shutter 320. Since the fixing shutter 320 is biased toward the open position P1 by the biasing force F1 of the fixing shutter spring 340, the fixing shutter 320 rotates and abuts against the abutment portion 335, and is positioned at the open position P1 with high accuracy.

[0054] Furthermore, the member that moves the fixing shutter 320 to the open position P1 is the fixing shutter spring 340 provided on the support shaft 322 of the fixing shutter 320. Therefore, compared to a configuration in which the fixing shutter is retracted from the sheet transport path by an interlocking member that is interlocked with the closing operation of the open / close cover, the configuration for retracting the fixing shutter 320 from the sheet transport path can be simplified, making it possible to reduce the size of the printer 100. In this way, even if the printer 100 is made smaller, the fixing shutter 320 can be reliably retracted from the sheet transport path.

[0055] In the first embodiment, the biasing force F2 of the switching link spring 353 is set to be larger than the biasing force F1 of the fixing shutter spring 340. When a user opens the open / close cover 103 to clear a jammed sheet or replace the process cartridge 200, the inside of the apparatus main body 101 is exposed. In this state, the fixing shutter 320 is positioned at the closed position P2 by the biasing force F2 of the switching link spring 353 against the biasing force F1 of the fixing shutter spring 340. This prevents the user's fingers from touching a high-temperature portion of the fixing unit 300 through the opening H1.

[0056] Furthermore, if a sheet jams upstream of the fixing unit 300 while being sandwiched therein, the user must clear the jam by pulling the sheet out through the opening H1. The biasing force F1 of the fixing shutter spring 340 supplements the pulling force applied by the user when pulling out the jammed sheet, reducing the biasing force F2 of the switching link 351, making it easier to pull out the jammed sheet. This improves usability when clearing a jam upstream of the fixing unit 300.

[0057] [Variation 1] In the first embodiment, the case where the holder 330 is attached and fixed to the fixing frame 310 has been described, but the present invention is not limited to this. Fig. 7 is a cross-sectional view of the fixing unit 150 of Modification 1. For example, as shown in Fig. 7, the holder 330 to which the abutment portion 335 is fixed may be fixed to the main body frame 110. Furthermore, although not shown in the drawings, the abutment portion 335 may be attached and fixed directly to the fixing frame 310 without using the holder 330.

[0058] [Second embodiment] A printer, which is an example of an image forming apparatus according to the second embodiment, will be described. Fig. 8 is a perspective view of a fixing unit 150, a link mechanism 350A, and a front opening / closing cover 103A of a printer, which is an example of an image forming apparatus according to the second embodiment. Figs. 9(a) and 9(b) are cross-sectional views of the fixing unit 150, the link mechanism 350A, and the front opening / closing cover 103A according to the second embodiment.

[0059] In the first embodiment, a configuration was described in which the fixing shutter 320 of the fixing unit 150 opens and closes the opening H1 in conjunction with the opening and closing operation of the opening and closing cover 103. In the second embodiment, a configuration will be described in which the fixing shutter 320 of the fixing unit 150 opens and closes the opening H1 in conjunction with the opening and closing operation of the front opening and closing cover 103A. Note that the configuration of the printer of the second embodiment, other than the front opening and closing cover 103A and the link mechanism 350A, is substantially the same as the configuration of the printer 100 of the first embodiment, except for the opening and closing cover 103 and the link mechanism 350, and therefore a description thereof will be omitted.

[0060] The printer of the second embodiment has a fixing unit 150, a link mechanism 350A, and a front opening / closing cover 103A. The front opening / closing cover 103A is an example of an opening / closing member. The front opening / closing cover 103A is part of the exterior of the printer, and is the front part of the exterior. The front opening / closing cover 103A is supported by the main body frame 110 (FIG. 1) so as to be openable and closable.

[0061] As described in the first embodiment, the fixing unit 150 includes a fixing section 300, a fixing frame 310, a fixing shutter 320, a fixing shutter spring 340, a holder 330, abutment sections 335 and 336. The opening and closing operation of the fixing shutter 320 is the same as that described in the first embodiment. Note that Fig. 9(a) illustrates the state in which the fixing shutter 320 is open, and Fig. 9(b) illustrates the state in which the fixing shutter 320 is closed.

[0062] The front opening / closing cover 103A is supported by the main body frame 110 so as to be rotatable around a support shaft 1031A. The link mechanism 350A has a switching link 351 and a switching link spring 353 configured as described in the first embodiment. The switching link 351 is an example of a first link member, and the switching link spring 353 is an example of a link biasing portion. The link mechanism 350A also has a moving link 352A, which is an example of a second link member, and a holding link 354A.

[0063] The movable link 352A is a link member that moves linearly in the horizontal direction in conjunction with the opening and closing operation of the front opening cover 103A, and is supported by a holder (not shown) so that it can move linearly. The holder (not shown) is fixed to the main body frame 110 in FIG. 1. The movable link 352A moves linearly relative to the holder (not shown), so that it can come into contact with or move away from the switching link 351.

[0064] In the second embodiment, the front opening / closing cover 103A, which is operated to open or close, linearly moves the movable link 352A via the retaining link 354A. The retaining link 354A is supported by the support shaft 1032A of the front opening / closing cover 103A so as to be rotatable about the support shaft 1032A. The retaining link 354A has an elongated hole 3541A. A pin 3521A provided at one end of the movable link 352A is inserted into the elongated hole 3541A of the retaining link 354A so as to be slidable along the elongated hole 3541A of the retaining link 354A. This causes the movable link 352A to linearly move horizontally in conjunction with the opening or closing operation of the front opening / closing cover 103A.

[0065] As shown in FIG. 9A, the movable link 352A moves in the direction of arrow A1 in conjunction with the closing operation of the front openable cover 103A. The movable link 352A, moving in the direction of arrow A1, abuts against the switching link 351 and moves the switching link 351 to the separated position P3 against the biasing force F2 of the switching link spring 353. As a result, when the switching link 351 is located at the separated position P3, the fixing shutter 320 is biased by the fixing shutter spring 340 to abut against the abutment portion 335 and is positioned at the open position P1. That is, the fixing shutter 320 is released from the restriction by the switching link 351 and rotates due to the biasing force F1 of the fixing shutter spring 340 to abut against the abutment portion 335 and is positioned at the open position P1 with high accuracy. This makes it possible to ensure a sheet transport path wide enough for a sheet to pass through the opening H1 without increasing the size of the printer. This prevents the sheet guided to the fixing nip N through the opening H1 from contacting the fixing frame 310 or the fixing shutter 320 during image formation, thereby preventing the sheet from jamming at the opening H1 and the toner image formed on the sheet from being distorted.

[0066] 9(b), the moving link 352A moves in the direction of arrow A2, which is opposite to the direction of arrow A1, in conjunction with the opening operation of the front opening / closing cover 103A. 2As the moving link 352A, which moves in the forward direction, moves away from the switching link 351, the switching link 351 rotates due to the biasing force F2 of the switching link spring 353. The biasing force F2 of the switching link spring 353 is greater than the biasing force F1 of the fixing shutter spring 340. Therefore, the switching link 351 presses the abutment portion 323 of the fixing shutter 320 with the biasing force F2 of the switching link spring 353 against the biasing force F1 of the fixing shutter spring 340, thereby rotating the fixing shutter 320 and moving to the abutment position P4. As a result, when the switching link 351 is located at the abutment position P4, the fixing shutter 320 is pressed by the switching link 351 against the biasing force F1 of the fixing shutter spring 340 and is located at the closed position P2. That is, when pressed by the switching link 351, the fixing shutter 320 rotates about the support shaft 322 and abuts against the abutment portion 336, and is positioned at the closed position P2 with high accuracy. This prevents the user's fingers from touching the high-temperature portion of the fixing unit 300 through the opening H1.

[0067] [Third embodiment] A printer, which is an example of an image forming apparatus according to the third embodiment, will be described. Fig. 10 is a perspective view of a fixing unit 150B, a link mechanism 350B, and a rear opening / closing cover 103B of a printer, which is an example of an image forming apparatus according to the third embodiment. Figs. 11(a) and 11(b) are cross-sectional views of the fixing unit 150B, the link mechanism 350B, and the rear opening / closing cover 103B according to the third embodiment.

[0068] In the first and second embodiments, a configuration for opening and closing an opening on the sheet inlet side of the fixing frame was described. In the third embodiment, a configuration for opening and closing an opening on the sheet outlet side of the fixing frame will be described. Note that the configuration of the printer of the third embodiment, other than the fixing unit 150B, the rear opening / closing cover 103B, and the link mechanism 350B, is substantially the same as the configuration of the printer 100, except for the fixing unit 150B, the opening / closing cover 103B, and the link mechanism 350B, and therefore a description thereof will be omitted.

[0069] The printer of the third embodiment has a fixing unit 150B, a link mechanism 350B, and a rear opening / closing cover 103B. The rear opening / closing cover 103B is an example of an opening / closing member. The fixing unit 150B has a fixing section 300 configured as described in the first embodiment. The fixing unit 150B also has a fixing frame 310B that surrounds the fixing section 300. The fixing frame 310B has an opening H11 on the sheet entrance side and an opening H12 on the sheet exit side. The rear opening / closing cover 103B is part of the exterior of the printer and is the rear part of the exterior. The rear opening / closing cover 103B is supported by the main body frame 110 so as to be rotatable about a support shaft 1031B. As a result, the rear opening / closing cover 103B can be opened and closed relative to the main body frame 110 (FIG. 1) by rotating about the support shaft 1031B. The rear opening / closing cover 103B and the transport guide 181 are integrally configured, and the transport guide 181 can be opened and closed together with the rear opening / closing cover 103B.

[0070] When the transport guide 181 is opened together with the rear openable cover 103B, the sheet transport path formed by the transport guide 181 and the transport guide 182 (FIG. 1) can be opened. This makes it easy to remove a sheet that has jammed in the transport guides 181 and 182. To prevent the user's fingers from touching the high-temperature part of the fixing section 300 through the opening H12 during the jam clearance operation, the fixing unit 150B of the third embodiment has a fixing shutter 320B that opens and closes the opening H12. Note that FIG. 11(a) illustrates a state in which the fixing shutter 320B is open, and FIG. 11(b) illustrates a state in which the fixing shutter 320B is closed.

[0071] The fixing shutter 320B is provided so as to be movable between an open position P11 shown in Fig. 11(a) where the opening H12 is open, and a closed position P12 shown in Fig. 11(b) where the opening H12 is closed. Here, when the fixing shutter 320B moves to the closed position P12, the entire opening H12 may be blocked by the fixing shutter 320B, but as long as the user's finger does not get inside, only a portion of the opening H12 does not have to be blocked by the fixing shutter 320B.

[0072] The fixing unit 150B has a holder 330B that supports the fixing shutter 320B so that the fixing shutter 320B can move between an open position P11 and a closed position P12. The holder 330B is fixedly attached to the fixing frame 310B. As a result, the fixing shutter 320B is supported by the main body frame 110 of FIG. 1 via the holder 330B and the fixing frame 310B. In this embodiment, the fixing shutter 320B is rotatably (swingably) supported by the holder 330B. The fixing shutter 320B can move between the open position P11 and the closed position P12 by rotating relative to the holder 330B, i.e., the fixing frame 310B. Specifically, the fixing shutter 320B has a shutter main body 321B extending in the X direction and a support shaft 322B provided on the shutter main body 321B. The support shaft 322B is rotatably supported by the holder 330B, so that the fixing shutter 320B is supported by the holder 330B so as to be rotatable around the support shaft 322B.

[0073] The fixing unit 150B also has a fixing shutter spring 340B, which is an example of a biasing portion, and an abutment portion 335B, which the fixing shutter 320B abuts against and positions the fixing shutter 320B at the open position P11. The fixing shutter spring 340B is a spring that biases the fixing shutter 320B toward the open position P11 with a biasing force F3, and in this embodiment is a torsion coil spring. The fixing shutter spring 340B is provided on the support shaft 322B so as to apply the biasing force F3 to the fixing shutter 320B.

[0074] The abutment portion 335B is fixed to a holder 330B that is fixed to the fixing frame 310B. In other words, by being fixed to the holder 330B, the abutment portion 335B is indirectly fixed to the fixing frame 310B via the holder 330B, and is indirectly fixed to the main body frame 110 via the holder 330B and the fixing frame 310B. In this way, the abutment portion 335B is positioned and fixed to the fixing frame 310B, i.e., the main body frame 110, with high precision. Therefore, the fixing shutter 320B abuts against the abutment portion 335B, which is positioned with high precision, and is thereby positioned at the open position P11 with high precision. Note that the abutment portion 335B may be provided directly on the fixing frame 310B.

[0075] Furthermore, the fixing shutter 320B has a contact portion 323B provided at the end of the shutter main body 321B in the X direction. The link mechanism 350B is disposed at a position corresponding to the contact portion 323B. The link mechanism 350B has a switching link 351B which is an example of a first link member, a pressing portion 352B which is an example of a second link member, and a switching link spring 353B which is an example of a link biasing portion.

[0076] The switching link 351B is provided so as to be movable between a separation position P13 shown in FIG. 11(a) where it is separated from the contact portion 323B of the fixing shutter 320B and a contact position P14 shown in FIG. 11(b) where it is in contact with the contact portion 323B of the fixing shutter 320B. In this embodiment, the switching link 351B is rotatably (swingably) supported by a holder (not shown). The holder (not shown) is fixed to the main body frame 110 shown in FIG. 1. The switching link 351B can move between the separation position P13 and the contact position P14 by rotating relative to the holder (not shown). Specifically, the switching link 351B has a support shaft 3512B rotatably supported by a holder (not shown).

[0077] The switching link spring 353B is a spring that biases the switching link 351B toward the abutment position P14 with a biasing force F4, and in this embodiment is a torsion coil spring. The biasing force F4 of the switching link spring 353B is set to be greater than the biasing force F3 of the fixing shutter spring 340B. The switching link spring 353B is provided on the support shaft 3512B of the switching link 351B.

[0078] The pressing portion 352B is a link member that moves the switching link 351B to the separated position P13 against the biasing force F4 of the switching link spring 353B in conjunction with the closing operation of the rear opening / closing cover 103B. The pressing portion 352B is fixed to the rear opening / closing cover 103B. When the rear opening / closing cover 103B is opened or closed, the pressing portion 352B separates from or comes into contact with the switching link 351B.

[0079] As shown in FIG. 11A, when the rear cover 103B is closed, the pressing portion 352B contacts the switching link 351B and moves the switching link 351B to the separated position P13 against the biasing force F4 of the switching link spring 353B. As a result, when the switching link 351B is positioned at the separated position P13, the fixing shutter 320B is biased by the fixing shutter spring 340B to abut against the abutting portion 335B and is positioned at the open position P11. That is, the fixing shutter 320B is released from the restriction imposed by the switching link 351B and rotates due to the biasing force F3 of the fixing shutter spring 340B to abut against the abutting portion 335B and is positioned at the open position P11 with high accuracy. This prevents the sheet leading out of the fixing nip N through the opening H12 from contacting the fixing frame 310B or the fixing shutter 320B during image formation. Therefore, the sheet is prevented from jamming at the opening H12.

[0080] 11(b), when the rear openable cover 103B is opened, the pressing portion 352B moves away from the switching link 351B. As a result, the switching link 351B rotates due to the biasing force F4 of the switching link spring 353B and abuts against the abutting portion 323B of the fixing shutter 320B. The biasing force F4 of the switching link spring 353B is greater than the biasing force F3 of the fixing shutter spring 340B. Therefore, the switching link 351B presses against the abutting portion 323B of the fixing shutter 320B with the biasing force F4 of the switching link spring 353B against the biasing force F3 of the fixing shutter spring 340B, and moves to the abutting position P14 while rotating the fixing shutter 320B. As a result, when the switching link 351B is located at the contact position P14, the fixing shutter 320B is pressed by the switching link 351B against the biasing force F3 of the fixing shutter spring 340B, and is thereby located at the closed position P12. That is, when pressed by the switching link 351B, the fixing shutter 320B rotates about the support shaft 322B and abuts against the abutment portion 336B, and is positioned at the closed position P12 with high accuracy.

[0081] In this way, the fixing shutter 320B moves between the open position P11 and the closed position P12 by rotating around the support shaft 322B, which allows the printer to be made smaller than when the fixing shutter moves linearly to move between the open position and the closed position.

[0082] As described above, according to the third embodiment, closing the rear openable cover 103B causes the switching link 351B of the link mechanism 350B to move away from the fixing shutter 320B. Because the fixing shutter 320B is biased toward the open position P11 by the biasing force F3 of the fixing shutter spring 340B, the fixing shutter 320B rotates and abuts against the abutment portion 335B, and is positioned at the open position P11 with high accuracy.

[0083] Furthermore, the member that moves the fixing shutter 320B to the open position P11 is the fixing shutter spring 340B provided on the support shaft 322B of the fixing shutter 320B. Therefore, compared to a configuration in which the fixing shutter is retracted from the sheet transport path by an interlocking member that is interlocked with the closing operation of the open / close cover, the configuration for retracting the fixing shutter 320B from the sheet transport path can be simplified, making it possible to reduce the size of the printer. In this way, even if the printer is made smaller, the fixing shutter 320B can be reliably retracted from the sheet transport path.

[0084] In the third embodiment, the biasing force F4 of the switching link spring 353B is set to be larger than the biasing force F3 of the fixing shutter spring 340B. When a user opens the rear openable cover 103B to clear a jammed sheet, the sheet conveyance path formed by the conveyance guide 108 is exposed. In this state, the fixing shutter 320B is positioned at the closed position P12 by the biasing force F4 of the switching link spring 353B against the biasing force F3 of the fixing shutter spring 340B. This prevents the user's fingers from touching the high-temperature portion of the fixing unit 300 through the opening H12.

[0085] Furthermore, if a sheet jams downstream of the fixing unit 300 while being sandwiched therebetween, the user must clear the jam by pulling the sheet out through the opening H12. The biasing force F3 of the fixing shutter spring 340B supplements the pulling force applied by the user when pulling out the jammed sheet, reducing the biasing force F4 of the switching link 351B, making it easier to pull out the jammed sheet. This improves usability when clearing a jam downstream of the fixing unit 300.

[0086] [Fourth embodiment] A printer, which is an example of an image forming apparatus according to the fourth embodiment, will be described. Fig. 12 is a perspective view of a fixing unit 150, a link mechanism 350C, and a process cartridge 200 of a printer, which is an example of an image forming apparatus according to the fourth embodiment. Figs. 13(a) and 13(b) are cross-sectional views of the fixing unit 150, the link mechanism 350C, and the process cartridge 200 according to the fourth embodiment.

[0087] In the first to third embodiments, a configuration has been described in which the fixing shutter is moved in conjunction with the opening and closing operation of the opening and closing member. In the fourth embodiment, a configuration will be described in which the fixing shutter 320 is moved in conjunction with the insertion and removal operation of the process cartridge 200. Note that the configuration of the printer of the fourth embodiment, other than the link mechanism 350C, is substantially the same as the configuration of the printer 100 of the first embodiment, except for the link mechanism 350, and therefore description thereof will be omitted.

[0088] The printer of the fourth embodiment has a fixing unit 150, a process cartridge 200, and a link mechanism 350C. The configurations of the fixing unit 150 and the process cartridge 200 are the same as those described in the first embodiment.

[0089] The link mechanism 350C has a switching link 351 and a switching link spring 353. The switching link 351 is an example of a first link member. The switching link spring 353 is an example of a link biasing portion. The configurations of the switching link 351 and the switching link spring 353 are as described in the first embodiment. That is, the switching link 351 is supported by a holder (not shown) so as to be movable between a separation position P3 separated from the fixing shutter 320 and a contact position P4 contacting the fixing shutter 320. The switching link spring 353 is a spring that biases the switching link 351 toward the contact position P4. The biasing force F2 of the switching link spring 353 is greater than the biasing force F1 of the fixing shutter spring 340. When the switching link 351 is located at the separation position P3, the fixing shutter 320 is biased by the fixing shutter spring 340 to be located at the open position P1. When the switching link 351 is located at the contact position P4, the fixing shutter 320 is pressed by the switching link 351 against the biasing force F1 of the fixing shutter spring 340, and is thereby located at the closed position P2.

[0090] The link mechanism 350C also has a movable link 352C, which is an example of a second link member. The movable link 352C is a link member that moves the switching link 351 to the separated position P3 against the biasing force F2 of the switching link spring 353 in conjunction with the insertion of the process cartridge 200 into the main body frame 110. The process cartridge 200 has a pressing portion 210 that is disposed at a position corresponding to the link mechanism 350C. The pressing portion 210 is part of a side plate included in the housing of the process cartridge 200.

[0091] When the process cartridge 200 is inserted into the main body frame 110, as shown in FIG. 13A, the pressing portion 210 of the process cartridge 200 abuts against the moving link 352C and presses the moving link 352C in the direction of arrow A1. Then, the moving link 352C moves in the direction of arrow A1 and abuts against the switching link 351, pressing the switching link 351. The switching link 351 rotates counterclockwise in FIG. 13A against the biasing force F2 of the switching link spring 353. As a result, the switching link 351 moves away from the abutting portion 323 of the fixing shutter 320, and the fixing shutter 320 rotates counterclockwise in FIG. 13A due to the biasing force F1 of the fixing shutter spring 340. Then, the fixing shutter 320 abuts against the abutting portion 335 and is positioned at the open position P1. When the fixing shutter 320 is positioned at the open position P1, the fixing nip N of the fixing unit 300 is exposed through the opening H1.

[0092] Furthermore, when the process cartridge 200 is pulled out from the main body frame 110, the pressing portion 210 of the process cartridge 200 moves away from the moving link 352C, as shown in FIG. 13B. As a result, the switching link 351 rotates clockwise in FIG. 13B due to the biasing force F2 of the switching link spring 353, and the moving link 352C is pressed by the switching link 351 and moves in the direction of arrow A2. The switching link 351 then abuts against the abutting portion 323 of the fixing shutter 320, thereby pressing the fixing shutter 320, and rotates clockwise until the abutting portion 323 of the fixing shutter 320 abuts against the abutting portion 336. When the abutting portion 323 abuts against the abutting portion 336, the fixing shutter 320 is positioned at the closed position P2. When the fixing shutter 320 is positioned at the closed position P2, the fixing nip N of the fixing unit 300 is blocked by the fixing shutter 320.

[0093] As described above, according to the fourth embodiment, by inserting the process cartridge 200 into the main body frame 110, the switching link 351 of the link mechanism 350C moves away from the fixing shutter 320. Because the fixing shutter 320 is biased toward the open position P1 by the biasing force F1 of the fixing shutter spring 340, the fixing shutter 320 rotates and abuts against the abutment portion 335, and is positioned at the open position P1 with high accuracy.

[0094] Furthermore, the member that moves the fixing shutter 320 to the open position P1 is the fixing shutter spring 340 provided on the support shaft 322 of the fixing shutter 320. Therefore, compared to a configuration in which the fixing shutter is retracted from the sheet transport path by an interlocking member that is interlocked with the insertion operation of the process cartridge, the configuration for retracting the fixing shutter 320 from the sheet transport path can be simplified, making it possible to make the printer more compact. In this way, even if the printer is made more compact, the fixing shutter 320 can be reliably retracted from the sheet transport path.

[0095] In the fourth embodiment, the biasing force F2 of the switching link spring 353 is set to be larger than the biasing force F1 of the fixing shutter spring 340. When the user pulls out the process cartridge 200 from the main body frame 110, the fixing unit 150 is exposed. In this state, the fixing shutter 320 is biased by the biasing force F1 of the fixing shutter spring 340. 1 The opening H1 is opposed to the biasing force F2 of the switching link spring 353, and the opening H1 is positioned at the closed position P2. This prevents the user's fingers from touching the high-temperature portion of the fixing unit 300 through the opening H1.

[0096] In addition, when the fixing unit 300 is clamped, above When a sheet jam occurs on the downstream side, the user must perform jam clearance work by pulling out the sheet through the opening H1. The biasing force F1 of the fixing shutter spring 340 assists the pulling force when the user pulls out the jammed sheet, and the biasing force F2 of the switching link 351 is reduced, making it easier to pull out the jammed sheet. aboveThis improves usability when clearing jams on the downstream side.

[0097] The present invention is not limited to the above-described embodiments, and many modifications are possible within the technical concept of the present invention. Furthermore, the effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments.

[0098] In the above embodiment, a monochrome electrophotographic printer has been described as an example of an image forming apparatus, but the present invention is not limited to this. For example, the present invention may be applied to a full-color electrophotographic printer having multiple process cartridges. Furthermore, the present invention is not limited to printers, but may also be applied to copiers, facsimile machines, and multifunction machines having these functions.

[0099] In the above embodiment, the image forming apparatus is an electrophotographic type, but the present invention is not limited to this. For example, the present invention may be applied to an electrostatic recording type or a magnetic recording type image forming apparatus.

[0100] In the above embodiment, the cartridge that can be inserted into and removed from the main body frame is a process cartridge, but the present invention is not limited to this. For example, the present invention can also be applied to a cartridge that supplies toner to a developing unit. [Explanation of symbols]

[0101] H1...opening, P1...open position, P2...closed position, 100...printer (image forming apparatus), 110...main body frame, 140...image forming section, 150...fixing unit, 300...fixing section, 310...fixing frame, 320...fixing shutter (shutter), 335...abutment section

Claims

1. an image forming unit that forms a toner image on a sheet; a fixing unit that applies heat and pressure to the sheet on which the toner image is formed to fix the toner image to the sheet; a shutter that is movable between an open position that opens an opening through which a sheet conveyed toward the fixing unit can pass and a closed position that closes the opening; a biasing portion that biases the shutter toward the open position; an abutment portion that positions the shutter at the open position by the abutment portion being abutted by the shutter that is biased toward the open position by the biasing portion; an opening / closing member that constitutes at least a part of the exterior of the image forming apparatus; a link mechanism that moves the shutter to the closed position against the biasing force of the biasing portion in conjunction with the opening operation of the opening / closing member, An image forming apparatus characterized by:

2. The shutter is rotatable between the open position and the closed position.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

3. a fixing frame having the opening formed therein; a holder attached to the fixing frame, the abutment portion is fixed to the fixing frame via the holder; 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

4. the shutter is supported by the fixing frame via the holder; 4. The image forming apparatus according to claim 3, wherein the image forming apparatus is a recording medium.

5. Further comprising a main body frame, The opening / closing member is supported by the main body frame so as to be openable and closable.

5. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

6. The link mechanism includes: a first link member that is movable between a spaced position away from the shutter and an abutting position in abutment with the shutter; When the first link member is located at the separated position, the shutter is urged by the urging portion to be located at the open position, and when the first link member is located at the abutting position, the shutter is pressed by the first link member against the urging force of the urging portion to be located at the closed position.

6. The image forming apparatus according to claim 5,

7. The link mechanism includes: a link biasing portion that biases the first link member toward the abutting position; a second link member that moves the first link member to the separated position against the biasing force of the link biasing portion in conjunction with the closing operation of the opening / closing member, 7. The image forming apparatus according to claim 6, wherein the image forming apparatus is a recording medium.

8. The biasing force of the link biasing portion is greater than the biasing force of the biasing portion.

8. The image forming apparatus according to claim 7,

9. Further comprising a main body frame, the image forming unit has a cartridge that can be inserted into and removed from the main body frame, the link mechanism moves the shutter to the closed position against the biasing force of the biasing portion in conjunction with the operation of pulling the cartridge out of the main body frame; 5. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

10. The link mechanism includes: a first link member that is movable between a spaced position away from the shutter and an abutting position in abutment with the shutter; When the first link member is located at the separated position, the shutter is urged by the urging portion to be located at the open position, and when the first link member is located at the abutting position, the shutter is pressed by the first link member against the urging force of the urging portion to be located at the closed position.

10. The image forming apparatus according to claim 9,

11. The link mechanism includes: a link biasing portion that biases the first link member toward the abutting position; a second link member that moves the first link member to the separated position against the biasing force of the link biasing portion in conjunction with the insertion of the cartridge into the main body frame, 11. The image forming apparatus according to claim 10.

12. The biasing force of the link biasing portion is greater than the biasing force of the biasing portion.

12. The image forming apparatus according to claim 11.

13. a fixing unit that applies heat and pressure to the sheet on which the toner image is formed to fix the toner image to the sheet; a shutter that is movable between an open position that opens an opening through which a sheet conveyed toward the fixing unit can pass and a closed position that closes the opening; a biasing portion that biases the shutter toward the open position; an abutment portion that positions the shutter at the open position by the abutment portion being abutted by the shutter that is biased toward the open position by the biasing portion; a link mechanism that moves the shutter to the closed position against the biasing force of the biasing portion in conjunction with an opening operation of an opening / closing member that constitutes at least a part of the exterior of the image forming apparatus, A fixing unit characterized by the above.

14. The shutter is rotatable between the open position and the closed position.

14. The fixing unit according to claim 13.

15. a fixing frame having the opening formed therein; a holder attached to the fixing frame, the abutment portion is fixed to the fixing frame via the holder; 15. The fixing unit according to claim 13 or 14.

16. the shutter is supported by the fixing frame via the holder; 16. The fixing unit according to claim 15.

Images