Image forming apparatus

Abstract

To provide an image forming apparatus that prevents a fixing nip from unintentionally shifting from a pressure-released state to a pressurized state after pressure release.SOLUTION: In the process of opening the door, when the pressurizing force adjusting means is in the second position, the second interlocking member is separated from the door engaging portion, and further, the second interlocking member is movable with respect to the first interlocking member in the second state of the pressurizing force adjusting means, and in the process of closing the door, the first interlocking member moves the pressurizing force adjusting means to the first position by moving the first interlocking member regardless of the movement of the second interlocking member.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus in which pressure applied to a fixing device is released in conjunction with the opening and closing of a user access door during jam clearance. [Background technology]

[0002] For example, image forming devices such as printers and facsimiles are equipped with a fixing device that applies heat and pressure to a toner image formed on a sheet to fix it to the sheet. The fixing device is configured to form a nip portion with a pressure roller and a heating unit, and to fix the toner image by applying heat and pressure to the sheet as it passes through the nip portion.

[0003] Generally, the pressure applied to the nip of the fixing device is greater than that of other conveying rollers, so if a sheet jam occurs in the fixing device, it is more difficult to clear the jam than with other conveying rollers. Also, if a jam is cleared while a large pressure is applied to the nip, the sheet may tear and the remaining sheet fragments may be difficult to clear, or parts of the fixing device may be damaged if the jam is cleared with too much force.

[0004] Therefore, a technology has been proposed in which, when a user opens and closes the door of an image forming apparatus to clear a jam in the fixing device, the pressure applied to the fixing device is released in conjunction with the opening and closing of the door (see Patent Document 1). In the technology described in Patent Document 1, a pressure release lever on the fixing device is pushed by a pressure release shaped portion provided on the door in conjunction with the action of opening the door, causing the lever to rotate and release the pressure. After the pressure is released, the pressure release lever and the pressure release shaped portion on the door are configured to separate. This allows the fixing pressure to be released when clearing a jam. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2006-48005 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the image forming apparatus described in Patent Document 1, if a user touches the pressure release lever after releasing the pressure in the fixing nip, there is a risk that the image forming apparatus may unintentionally transition from a pressure-released state to a pressure-applied state.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image forming apparatus that prevents an unintended transition from a pressure-released state to a pressure-applied state after pressure is released from the fixing nip. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides an image forming apparatus having an apparatus main body, a door that is provided so as to be openable and closable relative to the apparatus main body, a fixing unit that fixes a toner image formed on a sheet to the sheet, the fixing unit having a pressure member, a pressure-receiving member that forms a fixing nip portion between itself and the pressure member, and pressure adjusting means for reducing or releasing the pressure applied to the fixing nip portion, and interlocking means that is engageable with the pressure adjusting means and interlocks opening and closing of the door with the pressure adjusting means, the door having a door engaging portion that engages with the interlocking means, and the interlocking means having a first interlocking member and a second interlocking member that engage with each other, the fixing unit having two states: a first state in which a predetermined pressure is applied to the fixing nip portion and the pressure adjusting means is in a first position, and a second state in which the pressure applied to the fixing nip portion is reduced below the predetermined pressure. or a second state in which the door is in a released state and the pressure adjustment means is in a second position, and the door engagement portion and the second interlocking member are engaged in the process of opening the door from a closed state, and the first interlocking member and the pressure adjustment means are engaged and the first interlocking member moves the pressure adjustment means, thereby moving the pressure adjustment means from the first position to the second position, and during the process of opening the door, the second interlocking member moves away from the door engagement portion when the pressure adjustment means is in the second position, and the second interlocking member is movable relative to the first interlocking member when the pressure adjustment means is in the second state, and during the process of closing the door, the first interlocking member moves the pressure adjustment means to the first position by moving the first interlocking member regardless of the movement of the second interlocking member. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an image forming apparatus that can prevent an unintended transition from a pressure-released state to a pressure-applied state after pressure in the fixing nip is released. [Brief explanation of the drawings]

[0010] [Figure 1]Schematic diagram of an image forming apparatus according to the first embodiment [Figure 2] Schematic diagram of a fixing device in the first embodiment [Figure 3] 1 is a cross-sectional view showing a configuration of a heating unit in the first embodiment. [Figure 4] Schematic diagram of a pressure-applied state and a pressure-released state of a fixing device in the first embodiment. [Figure 5] FIG. 1 is a perspective view of a pressure release mechanism of a fixing device according to a first embodiment of the present invention; [Figure 6] An explanatory diagram of a pressure release cam in the first embodiment. [Figure 7] FIG. 1 is an explanatory diagram of a pressure release arm in the first embodiment. [Figure 8] FIG. 1 is an explanatory diagram of a fixing left cover in the first embodiment; [Figure 9] FIG. 10 is an explanatory diagram of a fixing interlocking lever in the first embodiment; [Figure 10] FIG. 10 is an explanatory diagram of a rear door interlocking lever in the first embodiment; [Figure 11] FIG. 10 is an explanatory diagram illustrating the configuration of an interlocking member in the first embodiment. [Figure 12] FIG. 1 is an explanatory diagram illustrating a configuration of a rear door in the first embodiment. [Figure 13] An explanatory diagram of a latch in the first embodiment. [Figure 14] FIG. 1 is an explanatory diagram of a latch cover according to the first embodiment; [Figure 15] FIG. 10 is an explanatory diagram showing a state in which the latch, the latch spring, and the latch cover are attached in the first embodiment. [Figure 16] FIG. 1 is an explanatory diagram of a state in which a rear door is closed in the first embodiment; [Figure 17] FIG. 10 is an explanatory diagram of the interlocking of the latch and the rear door interlocking lever when the rear door is opened in the first embodiment. [Figure 18] FIG. 10 is an explanatory diagram of the interlocking of the rear door interlocking lever and the fixing interlocking lever when the rear door is opened in the first embodiment; [Figure 19] FIG. 10 is an explanatory diagram of a state in which pressure release of the fixing device is completed when the rear door is opened in the first embodiment; [Figure 20] FIG. 10 is an explanatory diagram of a state when the latch separates from the rear door interlocking lever in the first embodiment; [Figure 21] FIG. 10 is an explanatory diagram of the movement of the rear door interlocking lever after separation in the first embodiment. [Figure 22] FIG. 10 is an explanatory diagram of the relationship between the rear door guide and the fixing interlocking lever when the rear door is closed in the first embodiment. [Figure 23] FIG. 10 is an explanatory diagram of the operation of the pressure release cam when the rear door is closed in the first embodiment. [Figure 24] FIG. 10 is an explanatory diagram of a state in which the latch and the rear door interlocking lever are separated when the rear door is closed in the first embodiment. [Figure 25] FIG. 10 is an explanatory diagram of the relationship between the latch and the rear door interlocking lever when the rear door is closed in the first embodiment. [Figure 26] FIG. 10 is an explanatory diagram of a state in which the latch is retracted when the rear door is closed in the first embodiment. [Figure 27] FIG. 10 is an explanatory diagram of a state in which the latch and the rear door interlocking lever are returned to an engaged state when the rear door is closed in the first embodiment. [Figure 28] FIG. 10 is an explanatory diagram of the fixing left cover in the second embodiment. [Figure 29] FIG. 10 is an explanatory diagram of a rear door interlocking lever in the second embodiment. [Figure 30] FIG. 10 is an explanatory diagram of the movement of the rear door interlocking lever after separation in the second embodiment. [Figure 31] FIG. 10 is an explanatory diagram of a fixing interlocking lever in the third embodiment. [Figure 32] FIG. 10 is an explanatory diagram of a rear door interlocking lever in the third embodiment. [Figure 33] FIG. 10 is an explanatory diagram of the movement of the rear door interlocking lever after separation in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Example 1] As an example of the configuration of an image forming apparatus according to the present invention, an embodiment in which the image forming apparatus is applied to an electrophotographic laser printer will be specifically described. In this description, the overall configuration of the image forming apparatus according to the present invention will be described first, and then the configuration of the fixing device of the image forming apparatus according to the present invention will be described.

[0012] 1 is a cross-sectional view showing the configuration of an electrophotographic laser printer having a double-sided image forming function as an example of an image forming apparatus according to an embodiment of the present invention. However, unless otherwise specified, the dimensions, materials, shapes, and relative positions of the components described in this embodiment are not intended to limit the scope of the present invention. Furthermore, the image forming apparatus according to the present invention is not limited to laser printers, but may also be applied to other image forming apparatuses such as copiers and facsimiles.

[0013] The image forming apparatus 101 shown in FIG. 1 is broadly composed of a sheet feeder, an image forming unit that forms an image on a sheet, a fixing unit, a paper discharge / reversal unit, and a duplex conveyance unit. The image forming apparatus 101 is equipped with a process cartridge 1 that is detachable from the main body of the apparatus. The process cartridge 1 is a process unit required to form a toner image on a sheet using an electrophotographic process, and is composed of a photosensitive drum 2 and process means such as a developing unit (not shown) and a charging roller. A scanner unit 3 is disposed vertically above the process cartridge 1, and exposes the photosensitive drum 2 based on an image signal. After the photosensitive drum 2 is charged to a predetermined negative potential by a charging roller (not shown), an electrostatic latent image is formed by the scanner unit 3. This electrostatic latent image is reverse-developed by a developing unit (not shown) inside the process cartridge 1, and negative toner is attached to form a toner image.

[0014] The sheet feeding unit is made up of a paper feed roller 4 attached to the image forming apparatus 101 and a paper feed cassette 5 that stores sheets and is detachable from the image forming apparatus 101. The sheets S stored in the paper feed cassette 5 are separated and fed one by one from the paper feed cassette 5 by the paper feed roller 4 that is rotated by the power of a paper feed drive unit (not shown). The fed sheet S is transported to a registration roller pair 7 by a transport roller pair 6, where skew correction is performed, and the sheet S is transported to the transfer unit.

[0015] In the transfer section, a bias voltage of positive polarity is applied by a bias applying means (not shown) to the transfer roller 8. As a result, the toner image is transferred as an unfixed image onto the sheet S conveyed to the transfer section.

[0016] The sheet S onto which the toner image has been transferred is transported to a fixing device (fixing unit) 9 provided downstream in the transport direction of the transfer section. The fixing device 9 fixes the toner image transferred onto the sheet S, and has a heating unit (pressurized member) 10, which is a fixing member heated by a heater, which is a heating means (not shown), and a pressure roller (pressurizing member) 11 that rotates while being pressed against the heating unit 10. The sheet S is sandwiched and transported in a fixing nip formed by the heating unit 10 and the pressure roller 11, and the toner image is fixed to the surface of the sheet S by applying heat and pressure. Note that the pressure member may be heated by a heater instead of the pressure member.

[0017] The sheet S on which the toner image has been fixed is transported from the fixing device 9 to a paper discharge reversal section. In the case of single-sided image formation (single-sided printing), a double-sided flapper 12 waits at a position (solid line position) where it guides the sheet material S toward a pair of intermediate conveying rollers 13. The sheet material S on which the toner image has been fixed is transported from the fixing device 9 to the pair of intermediate conveying rollers 13, and is discharged onto a paper discharge stacking tray 16 by a pair of paper discharge rollers 14.

[0018] In the case of double-sided image formation (double-sided printing), the double-sided flapper 12 waits at a position (dotted line position) that guides the sheet S toward the double-sided reversing roller pair 15, and the fixing device 9 conveys the sheet S toward the double-sided reversing roller pair 15. When the trailing edge of the sheet S reaches a predetermined position, the double-sided reversing roller pair 15 is rotated in reverse by a rotation direction switching means (not shown). As a result, the sheet S passes through the double-sided conveying roller pair 17 and the re-feed roller pair 18 with the trailing edge at the front, and is re-fed in an inverted state with respect to the registration roller pair 7. Then, as with single-sided printing, the second side of the sheet S is corrected for skew by the registration roller pair 7, transferred by the transfer roller 8, and fixed by the fixing device 9. The sheet is then ejected onto the paper ejection tray 16 by the paper ejection roller pair 14, completing the double-sided printing. If a jam occurs inside the device body during sheet transport, the front door 19 or rear door 20 is opened depending on the location of the jam.

[0019] Next, the fixing device according to the present invention will be described with reference to FIGS. 2 to 11. Note that in the following description, illustrations of fastening members such as screws are omitted. FIGS. 2 to 3 are schematic diagrams of the fixing device according to the first embodiment, with FIG. 2 being a perspective view and FIG. 3 being a side view of FIG. 2 as viewed from direction A. As shown in FIG. 2, the fixing device 9 comprises a frame including a first fixing side plate 21, a second fixing side plate 22, an upper fixing stay 23, and a lower fixing stay 24. To protect the edges of the metal plates from the user, a left fixing cover (cover member) 25 and a right fixing cover 26 are fastened to the first fixing side plate 21 and the second fixing side plate 22, respectively, with screws (not shown). As shown in FIG. 3, the pressure roller 11 is rotatably supported relative to the first fixing side plate 21 and the second fixing side plate 22 via a ball bearing 27 and a pressure roller bearing 28. The heating unit 10 is attached to the first fixing side plate 21 and the second fixing side plate 22 via a flange member 30 and is positioned opposite the pressure roller 11 to form a nip portion and clamp the sheet.

[0020] 4 is a cross-sectional view showing the configuration of the heating unit. The heating unit 10 is mainly composed of a heater 31, a pressure stay 32, a fixing film 33, and a film guide 34. The fixing film 33 is cylindrical (endless belt-like or sleeve-like) and flexible, and is loosely fitted around the film guide 34. The heater 31, which serves as a heat source, is fitted into a recessed groove provided along the length of the outer surface of the film guide 34 and fixed therein. The pressure stay 32 has a roughly U-shaped cross section and is positioned inside the film guide 34. When pressure is applied, it presses the film guide 34 and heater 31 toward the pressure roller 11.

[0021] 5 is a side view of FIG. 2 seen from direction A, showing the pressure-applied and pressure-released states of the fixing device. Fig. 5(a) shows the contact state where a predetermined pressure is applied to the fixing nip portion, and Fig. 5(b) shows the pressure-released state where the pressure applied to the fixing nip portion is reduced from the contact state or released. For convenience of explanation, the fixing left cover 25 is not shown.

[0022] In the pressure mechanism of the fixing device 9, the heating unit 10 is biased against the pressure roller 11 by a pressure spring 35 via a pressure plate 29 and a flange member 30. The pressure adjustment means of the fixing device 9 is composed of a pressure release cam (cam member) 36, the pressure plate 29, a pressure release arm 39, and a pressure release arm holder 40. The fixing device 9 also has a rear door interlocking lever (second interlocking member) 37 and a fixing interlocking lever (first interlocking member) 38 as interlocking members. When the pressure of the fixing device 9 is released, the rotation of the rear door interlocking lever 37 rotates the pressure release cam 36, which rotates around a bearing member (not shown), via the fixing interlocking lever 38. The rotation of the pressure release cam 36 in the radial direction is converted into a movement in the Y direction by the pressure release arm 39, thereby switching the position of the pressure plate 29 from the abutting state shown in FIG. 5A to the pressure-released state shown in FIG. 5B. Here, the pressure release arm 39 is held by a pressure release arm holder 40 so that it can move only in the Y direction.

[0023] The pressure plate 29, pressure spring 35, pressure release cam 36, rear door interlocking lever 37, fixing interlocking lever 38, pressure release arm 39, and pressure release arm holder 40 are arranged on both sides in the longitudinal direction of the fixing device 9. Here, the pressure release arm 39 is not limited to being made up of a single component, but may be made up of multiple components, and may also be made up of a power transmission system such as multiple gears.

[0024] 6 and 7 are detailed explanatory diagrams of the components of the pressure adjusting means, with FIG. 6 being an explanatory diagram of the pressure release cam and FIG. 7 being an explanatory diagram of the pressure release arm. As shown in FIG. 6, pressure release cam 36 has a first arcuate portion 36A that contacts pressure release arm 39 when the nip portion is in the abutting state, and a second arcuate portion 36B that contacts pressure release arm 39 when the nip portion is in the pressure-released state. Here, first arcuate portion 36A and second arcuate portion 36B are both concentric with the cam's rotation axis, and second arcuate portion 36B has a larger radius than first arcuate portion 36A. Pressure release cam 36 also has a first engaged portion 36C and a second engaged portion 36D that are interlocked with the opening and closing of rear door 20 via rear door interlock lever 37 and fixation interlock lever 38.

[0025] 7, pressure release arm 39 has a cam contact portion 39A that contacts pressure release cam 36, and a pressure plate contact portion 39B that contacts pressure plate 29. Figures 8 to 10 are detailed explanatory diagrams of each component of the interlocking member, with Fig. 8 being an explanatory diagram of the fixing left cover, Fig. 9 being an explanatory diagram of the fixing interlocking lever, and Fig. 10 being an explanatory diagram of the rear door interlocking lever. As shown in Fig. 8, fixing left cover 25 has a substantially circular cover rotation central shaft 25A for rotatably supporting fixing interlocking lever 38, and abutment portion 25B for preventing rotation of rear door interlocking lever 37.

[0026] 9, the fixing interlocking lever 38 has a substantially circular first rotation center hole 38A for fitting with the cover rotation center shaft 25A of the fixing left cover 25, an engaged portion 38B for interlocking with the rear door interlocking lever 37 when the rear door 20 is opened, a substantially circular second rotation center hole 38C for rotatably supporting the rear door interlocking lever 37, and a first engaging portion 38D and a second engaging portion 38E for interlocking the opening and closing of the rear door 20 with the pressure release cam 36. The fixing interlocking lever 38 also has a pressed portion 38F for rotating when pressed by the rear door guide 44 when the rear door 20 is closed.

[0027] 10, rear door interlocking lever 37 has an engaging portion (third engaging portion) 37A for interlocking with rear door 20 when rear door 20 is opened, a second lever engaging portion 37B for interlocking the opening operation of rear door 20 with fixing interlocking lever 38, a substantially circular rotation center shaft 37C for fitting with second rotation center hole 38C of fixing interlocking lever 38, and a rotation stopper portion 37D for abutting against abutted portion 25B of fixing left cover 25 to be stopped from rotating. Rear door interlocking lever 37 also has a surface 37E that comes into contact with rear door 20 when rear door 20 is closed.

[0028] 11 is an explanatory diagram showing the configuration of the interlocking member. As shown in FIG. 11, the first rotation center hole 38A of the fixing interlocking lever 38 is fitted over the cover rotation center shaft 25A of the fixing left cover 25, and the fixing interlocking lever 38 is rotatably supported. The rotation center shaft 37C of the rear door interlocking lever 37 is fitted over the second rotation center hole 38C of the fixing interlocking lever 38, and the rear door interlocking lever 37 is rotatably supported. The second lever engaging portion 37B of the rear door interlocking lever 37 engages with the engaged portion 38B of the fixing interlocking lever 38. The relationship between the second lever engaging portion 37B and the engaged portion 38B is such that the second lever engaging portion 37B and the engaged portion 38B butt against each other and engage in the rotation direction CW (first rotation direction) that releases pressure on the fixing device 9, but do not engage in the opposite direction CCW (second rotation direction). Therefore, the rear door interlocking lever 37 can rotate in the CCW direction independently of the fixing interlocking lever 38 and the pressure release cam 36.

[0029] Although only one side of the fixing device 9 in the longitudinal direction is described here, the relationship between the fixing right cover 26, rear door interlocking lever 37, and fixing interlocking lever 38 on the opposite side in the longitudinal direction is also configured in the same way.

[0030] 12 is an explanatory diagram showing the configuration of the rear door. The rear door 20 is composed of a latch 41, which is an engaging member, a latch spring (second biasing member) 42, a latch cover 43, and a rear door guide 44. The latch 41, latch spring 42, and latch cover 43 are housed in a latch housing portion 20A located in the rear door 20, and are respectively disposed at longitudinal positions corresponding to the two rear door interlocking levers 37 disposed in the longitudinal direction of the fixing device 9. The rear door guide 44 also has a pressing portion 44A that presses the pressed portion 38F of the fixing interlocking lever 38 when the rear door 20 is closed. Here, in this embodiment, the rear door guide 44 is a separate part from the rear door, but the shape of the rear door guide 44 may be formed integrally with the rear door 20.

[0031] Figures 13 and 14 are detailed explanatory diagrams of the components of the rear door, with Figure 13 being an explanatory diagram of the latch and Figure 14 being an explanatory diagram of the latch cover. Note that Figure 13(b) is a view of Figure 13(a) viewed from direction B. As shown in Figure 13, the latch 41 has a door engagement portion 41A for engaging with the first lever engagement portion 37A to link the opening operation of the rear door 20 to the rear door interlocking lever 37, a receiving hole 41B for locating the latch spring 42 and receiving the biasing force of the spring, and a protrusion 41C for preventing the latch 41 from coming out of the storage portion 20A due to the biasing force of the latch spring 42. The latch 41 also has a contact portion 41D that comes into contact with the rear door interlocking lever 37 when the rear door 20 is closed, to retract the latch 41.

[0032] As shown in Figure 14, the latch cover 43 has a spring seat 43A for positioning the latch spring 42, a regulating portion 43B for preventing the latch 41 from coming out of the storage portion 20A due to the biasing force of the latch spring 42, and a retaining portion 43C for preventing the latch cover 43 from coming out of the latch storage portion 20A due to the biasing force of the latch spring 42.

[0033] FIG. 15 shows the latch 41, latch spring 42, and latch cover 43 in an attached state, with FIG. 15(a) being a front view and FIG. 15(b) being a cross-sectional view taken along line AA in FIG. 15(a). As shown in FIG. 15, the latch 41 is biased in the direction A by the biasing force of the latch spring 42. Furthermore, the protrusion 41C and the restricting portion 43B of the latch cover 43 come into contact with each other to prevent the latch 41 from falling out of the latch storage portion 20A due to the biasing force of the latch spring 42. Furthermore, the latch cover 43 is prevented from falling out by the biasing force of the latch spring 42, and the retaining portion 43C is caught on the latch cover restricting portion 20B of the rear door, preventing it from falling out. With this configuration, the latch 41 is biased in the direction of engagement with the rear door interlocking lever 37 by the biasing force of the latch spring 42.

[0034] 16 to 21, the linkage between the rear door and the fixing device when the rear door is opened will be described. Note that FIGS. 16 to 21 are cross-sectional views of the pressure release cam 36 in the longitudinal direction of the fixing device 9. For convenience of explanation, the shape of the rear door interlocking lever 37 has been partially omitted. FIG. 16 illustrates a state in which the rear door is closed, FIG. 17 illustrates a state in which the rear door begins to open and the latch and rear door interlocking lever begin to interlock, FIG. 18 illustrates a state in which the rear door interlocking lever and the fixing device interlocking lever begin to interlock, FIG. 19 illustrates a state in which pressure release of the fixing device is completed, FIG. 20 illustrates a state in which the latch separates from the rear door interlocking lever, and FIG. 21 illustrates a state in which the rear door interlocking lever moves after the latch and rear door interlocking lever separate. The pressure adjusting means in FIG. 16 is, for example, in the first position, and the fixing unit is, for example, in the first state. Also, the pressure adjusting means in FIG. 21 is, for example, in the second position, and the fixing unit is, for example, in the second state.

[0035] 16, when the rear door 20 is closed, the door engaging portion 41A of the latch 41 and the first lever engaging portion 37A of the rear door interlocking lever 37 are not in contact. Also, the second lever engaging portion 37B of the rear door interlocking lever 37 is not in contact with the engaged portion 38B of the fixing interlocking lever 38. When the rear door 20 is closed, the nip portion of the fixing device 9 is in contact.

[0036] 17, the door engagement portion 41A of the latch 41 comes into contact with the first lever engagement portion 37A of the rear door interlocking lever 37. That is, from this state, the latch 41 and the rear door interlocking lever 37 begin to interlock. At this timing, the rear door interlocking lever 37 and the fixing interlocking lever 38 have not yet rotated, so the nip portion of the fixing device 9 remains in contact.

[0037] 17, the rear door interlocking lever 37 is engaged with the latch 41 and therefore rotates in conjunction with the rear door 20. When the rear door 20 opens to the state shown in FIG. 18, the second lever engaging portion 37B of the rear door interlocking lever 37 comes into contact with the engaged portion 38B of the fixing interlocking lever 38, and from this point on, the rear door interlocking lever 37 and the fixing interlocking lever 38 begin to interlock with each other. Therefore, when the rear door 20 is opened further from this state, the first engaging portion 38D of the fixing interlocking lever 38 presses the first engaged portion 36C of the pressure releasing cam 36, causing the pressure releasing cam 36 to rotate, and pressure release of the fixing device 9 begins.

[0038] Thereafter, when the rear door 20 is opened further, the latch 41 rotates the rear door interlocking lever 37 and the fixing interlocking lever 38 in conjunction with the opening movement of the rear door, and the pressure release cam 36 also rotates. When the rear door 20 is opened to the state shown in FIG. 19, the second arc portion 36B of the pressure release cam 36 comes into contact with the cam contact portion 39A of the pressure release arm (moving member) 39. When the pressure release cam 36 rotates to this state, pressure release of the fixing device 9 is completed. At this timing, the latch 41 and the rear door interlocking lever 37 are still engaged.

[0039] As the rear door 20 is further opened from the state shown in FIG. 19, the latch 41 causes the rear door interlocking lever 37, the fixing interlocking lever 38, and the pressure release cam 36 to further rotate. When the rear door 20 is opened to the state shown in FIG. 20, the door engagement portion 41A of the latch 41 and the first lever engagement portion 37A of the rear door interlocking lever 37 separate. Here, the pressure release cam 36 has further rotated from the state shown in FIG. 19, but the pressure release cam 36 remains in the pressure release state even in the state shown in FIG. 20 because the second arc portion 36B is in contact with the cam contact portion 39A of the pressure release arm 39. Furthermore, because the second arc portion 36B is concentric with the center of the cam rotation axis, the fixing device 9 remains in the pressure release state even after the latch 41 and the rear door interlocking lever 37 separate. In addition, during the process from Figure 19 to Figure 20, the first engagement portion 38D of the fixing interlocking lever 38 and the first engaged portion 36C of the pressure release cam 36 are separated, and the engagement point switches to the second engagement portion 38E of the fixing interlocking lever 38 and the second engaged portion 36D of the pressure release cam 36, and they are interlocked.

[0040] In the state shown in FIG. 20, the rear door interlocking lever 37 separates from the latch 41, eliminating the biasing force in the CCW direction in FIG. 20. The second lever engaging portion 37B of the rear door interlocking lever 37 and the engaged portion 38B of the fixing interlocking lever 38 are engaged only in the CCW direction. In other words, the rear door interlocking lever 37 can rotate independently in the CW direction without rotating the fixing interlocking lever 38 or the pressure release cam 36. Therefore, for example, the rear door interlocking lever 37 can be rotated by a user or other operation until the rotation stopper portion 37D of the rear door interlocking lever 37 abuts against the abutment portion 25B of the fixing left cover 25, as shown in FIGS. 20 and 21. In this state, the rear door interlocking lever 37 is subjected to a force by its own weight that rotates it in the direction of abutting against the fixing left cover 25, so the state shown in FIG. 21 is maintained.

[0041] Next, the operation of the fixing interlocking lever and the pressure adjusting means when the rear door is closed will be described using Figures 22 and 23. Figure 22 shows the timing when the rear door guide and fixing interlocking lever come into contact, and Figure 23 shows the timing when the fixing interlocking lever rotates and comes into contact with the pressure release cam. When the rear door 20 is closed from the state shown in Figure 21, the pressing portion 44A of the rear door guide 44 comes into contact with the pressed portion 38F of the fixing interlocking lever 38, as shown in Figure 22. When the rear door 20 is further closed from this state, the pressing portion 44A presses the pressed portion 38F, causing the fixing interlocking lever 38 to rotate. When the rear door 20 is rotated to the state shown in Figure 23, the second engaging portion 38E of the fixing interlocking lever 38 again presses the second engaged portion 36D of the pressure release cam 36, causing the pressure release cam 36 to rotate in the direction of the abutment state. 16, the first arc portion 36A of the pressure release cam 36 comes into contact with the cam contact portion 39A of the pressure release arm, and the fixing device 9 returns to the abutting state. Also, the rear door interlocking lever 37 returns to the abutting state shown in FIG. 16 while the rotation stopper portion 37D slides on the abutted portion 25B of the fixing left cover 25.

[0042] Next, the operation of the latch when the rear door is closed will be described using Figures 24 to 27. Figures 24 to 27 are views of Figure 21 viewed from the Z direction, with Figure 24 showing the state when the latch and rear door interlocking lever are separated, Figure 25 showing the state at the moment when the latch and rear door interlocking lever are in contact, Figure 26 showing the state when the latch is retracted, and Figure 27 showing the state when the latch and rear door interlocking lever are back in the engaged state. Note that for convenience of explanation, the shape of the rear door interlocking lever 37 has been partially removed. When the rear door 20 is closed from the state shown in Figure 24, the contact portion (contacted portion) 41D of the latch 41 comes into contact with the surface (abutting portion) 37E of the rear door interlocking lever 37, as shown in Figure 25. When the rear door is further closed from this state, the contact portion 41D of the latch 41 is pressed by the surface 37E, overcoming the biasing force of the latch spring 42, as shown in Figure 26, and the latch 41 is retracted. Thereafter, when the latch 41 overcomes the surface 37E, the latch 41 returns to its original state by the biasing force of the latch spring 42, as shown in Figure 27. Then, the door engagement portion 41A of the latch 41 and the first lever engagement portion 37A of the rear door interlocking lever 37 return to the engaged state. The relationship between the door engagement portion 41A of the latch 41 and the first lever engagement portion 37A of the rear door interlocking lever 37 in Figure 27 is the same as the abutting state of the fixing device 9 in Figure 16, and when the rear door 20 is returned to the closed state, it returns to the state in Figure 16.

[0043] In this way, in a configuration in which the pressure force of the fixing device 9 is released in conjunction with the opening and closing of the rear door 20, by making it possible for the rear door interlocking lever 37 to rotate independently without rotating the pressure release cam 36 after the rear door interlocking lever 37 and the latch 41 separate, it is possible to achieve a configuration in which the pressure force is released in conjunction with the opening and closing of the door and which is also easy to use.

[0044] The configuration of the present invention can provide an image forming apparatus that can release the fixing pressure in conjunction with the opening and closing of the door, while also achieving usability.

[0045] [Example 2] Next, a second embodiment of the present invention will be described with reference to Figures 28 to 30. In this embodiment, explanations of parts common to the first embodiment will be omitted. The difference from the first embodiment is the configuration related to the movement of the rear door interlocking lever after the latch and the rear door interlocking lever are separated.

[0046] Fig. 28 is an explanatory diagram showing the shape of the fixing left cover, and Fig. 29 is an explanatory diagram showing the shape of the rear door interlocking lever. As shown in Fig. 28, fixing left cover 125 has a substantially circular cover rotation center shaft 125A for rotatably supporting fixing interlocking lever 38, and abutment portion 125B for preventing rotation of rear door interlocking lever 137. Fixing left cover 125 also has holding portion 125C for holding rear door interlocking lever 137.

[0047] 29, rear door interlocking lever 137 has a first lever engaging portion 137A for interlocking with rear door 20 when rear door 20 is opened, a second lever engaging portion 137B for interlocking the opening movement of rear door 20 with fixing interlocking lever 38, and a substantially circular rotation center shaft 137C for fitting with second rotation center hole 38C of fixing interlocking lever 38. It also has a rotation stop portion 137D for abutting against abutted portion 125B of fixing left cover 125 to stop rotation, and a hook portion 137E for hooking on holding portion 125C of fixing left cover 125 to maintain its position. Furthermore, rear door interlocking lever 137 has a surface 137F that comes into contact with latch 41 when rear door 20 is closed and causes latch 41 to retract.

[0048] FIG. 30 is an explanatory diagram of the configuration of the movement of the rear door interlocking lever after the latch and the rear door interlocking lever are separated. After the rear door interlocking lever 137 is separated from the latch 41, the second lever engaging portion 137B of the rear door interlocking lever 137 and the engaged portion 38B of the fixing interlocking lever 38 are engaged only in the CW direction in FIG. 30(a). Therefore, the rear door interlocking lever 137 can be rotated by a user or other operation from FIG. 30(a) to FIG. 30(b) until the rotation stopper portion 137D of the rear door interlocking lever 137 abuts against the abutment portion 125B of the fixing left cover 125. In addition, in the state of FIG. 30(b), the hook portion 137E of the rear door interlocking lever 137 is hooked on the holding portion 125C of the fixing left cover 125. This allows the rear door interlocking lever 137 to maintain the state of FIG. 30(b).

[0049] In this embodiment, when the rear door interlocking lever 137 moves after separating from the latch 41 and hits the fixing left cover 125, the position of the rear door interlocking lever 137 is maintained by a hook portion 137E provided on the rear door interlocking lever 137 and a holding portion 125C of the fixing left cover 125. As a result, even when the weight of the rear door interlocking lever 137 generates a rotational force that rotates the lever in the CCW direction in FIG. 30 in the state shown in FIG. 30(b), the position of the rear door interlocking lever 137 can be maintained.

[0050] [Example 3] Next, a third embodiment of the present invention will be described with reference to Figures 31 to 33. In this embodiment, explanations of parts common to the first embodiment will be omitted. The difference from the first embodiment is the configuration related to the movement of the rear door interlocking lever after the latch and the rear door interlocking lever are separated.

[0051] Fig. 31 is an explanatory diagram showing the shape of the fixing interlocking lever, and Fig. 32 is an explanatory diagram showing the shape of the rear door interlocking lever. As shown in Fig. 31, fixing interlocking lever 238 has a substantially circular first rotation center hole 238A for fitting with cover rotation center shaft 25A of fixing left cover 25, an engaged portion 238B for interlocking with rear door interlocking lever 237 when rear door 20 is opened, a substantially circular second rotation center hole 238C for rotatably supporting rear door interlocking lever 237, and a first engaging portion 238D and a second engaging portion 238E for interlocking the opening and closing of rear door 20 with pressure release cam 36. Fixing interlocking lever 238 also has a pressed portion 238F that is pressed by rear door guide 44 and rotates when rear door 20 is closed. Furthermore, the fixing interlocking lever 238 has a cylindrical portion 238G that holds the coil portion of the rear door interlocking lever spring (first biasing member) 244, a fixed arm regulating portion 238H that regulates the fixed arm 244B of the rear door interlocking lever spring 244, and an abutment portion 238J that comes into contact with the fixing first side plate 221.

[0052] 32, the rear door interlocking lever 237 has a first lever engaging portion 237A for interlocking with the rear door 20 when the rear door 20 is opened, a second lever engaging portion 237B for interlocking the opening operation of the rear door 20 with the fixing interlocking lever 238, a substantially circular rotation center shaft 237C for fitting with a second rotation center hole 238C of the fixing interlocking lever 238, and a rotation stopper portion 237D for abutting against the abutted portion 25B of the fixing left cover 25 to stop the rotation. The rear door interlocking lever 237 also has a surface 237F that comes into contact with the latch 41 when the rear door 20 is closed and causes the latch 41 to retract. The rear door interlocking lever 237 also has a spring engaging portion 237G for engaging with the operating arm 244A of the rear door interlocking lever spring 244.

[0053] FIG. 33 is an explanatory diagram of the configuration of the movement of the rear door interlock lever after the latch and the rear door interlock lever are separated. After the rear door interlock lever 237 is separated from the latch 41, the second lever engaging portion 237B of the rear door interlock lever 237 and the engaged portion 238B of the fixing interlock lever 238 are engaged only in the CW direction. The fixing device 9 also has a rear door interlock lever spring 244. The rear door interlock lever spring 244 has a coil portion held by a cylindrical portion 238G of the fixing interlock lever 238. The fixed arm 244B of the spring is fixed to the fixed arm restricting portion 238H of the fixing interlock lever 238, and the operating arm 244A is engaged with the spring engaging portion 237G of the rear door interlock lever 237. In this state, the operating arm 244A of the rear door interlock lever spring 244 applies a rotational force to the rear door interlock lever 237 in the CCW direction in FIG. 33(a). At this time, a rotational force to rotate in the CW direction is also applied to the fixing interlocking lever 238 by the fixed arm 244B of the rear door interlocking lever spring 244, but the fixing interlocking lever 238 does not rotate because the abutting portion 238J is in abutment with the lever contact portion 221A of the fixing first side plate 221. Therefore, only the rear door interlocking lever 237 rotates, and the rear door interlocking lever 237 changes from the state shown in Figure 33(a) to the state shown in Figure 33(b), and the state shown in Figure 33(b) is maintained.

[0054] In this embodiment, the rear door interlocking lever 237 moves by the rotational force of the rear door interlocking lever spring 244 after it separates from the latch 41. Therefore, after the rear door interlocking lever 237 separates from the latch 41, it can move to the state shown in FIG. 33(b) without any operation by the user, etc. This results in a configuration with better usability than the first and second embodiments.

[0055] Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments. The present invention is not limited to the above, and various modifications are possible based on the technical concept of the present invention.

[0056] [Note] The disclosure of the present embodiment also includes the following configuration examples and method examples.

[0057] (Item 1) A device body, a door that is provided so as to be openable and closable relative to the device body; a fixing unit for fixing a toner image formed on a sheet to the sheet, the fixing unit including a pressure member, a pressure-receiving member that forms a fixing nip portion between the pressure member and the pressure member, and pressure adjusting means for reducing or canceling the pressure applied to the fixing nip portion; an interlocking means engageable with the pressure adjusting means for interlocking the opening and closing of the door with the pressure adjusting means; An image forming apparatus having the door has a door engaging portion that engages with the interlocking means; the interlocking means includes a first interlocking member and a second interlocking member that are engaged with each other; the fixing unit is switchable between a first state in which a predetermined pressure is applied to the fixing nip portion and the pressure adjusting means is in a first position, and a second state in which the pressure applied to the fixing nip portion is reduced to less than the predetermined pressure or is released and the pressure adjusting means is in a second position; In the process of opening the door from a closed state, the door engagement portion and the second interlocking member are engaged with each other, and further, the first interlocking member and the pressure force adjusting means are engaged with each other, and the first interlocking member moves the pressure force adjusting means, whereby the pressure force adjusting means moves from the first position to the second position, During the process of opening the door, when the pressure adjusting means is in the second position, the second interlocking member is separated from the door engaging portion, and further, when the pressure adjusting means is in the second state, the second interlocking member is movable relative to the first interlocking member, An image forming apparatus characterized in that, during the process of closing the door, regardless of the movement of the second interlocking member, the first interlocking member is moved, and the first interlocking member moves the pressure adjustment means to the first position.

[0058] (Item 2) Item 1, the image forming apparatus according to item 1, an image forming apparatus characterized in that, in the process of closing the door, the door presses the first interlocking member, thereby moving the first interlocking member, and the first interlocking member moves the pressure adjustment means to the first position.

[0059] (Item 3) The image forming apparatus according to items 1 and 2, the fixing unit has a pressure plate for applying pressure to the fixing nip portion, the pressure adjusting means includes a cam member engageable with the first interlocking member, and a moving member that abuts against the cam member and the pressure plate, An image forming apparatus characterized in that, when the first interlocking member and the cam member are engaged, the cam member rotates in conjunction with the first interlocking member, the cam member abuts the moving member, the moving member abuts the pressure plate, and the position of the pressure plate changes, thereby switching the fixing unit between the first state and the second state.

[0060] (Item 4) The image forming apparatus according to items 1 to 3, the first interlocking member has a first engaging portion and a second engaging portion, the cam member has a first engaged portion, the second interlocking member has a second engaged portion and a third engaging portion, when the door is opened, the third engaging portion and the door engaging portion, the second engaging portion and the second engaged portion, and the first engaging portion and the first engaged portion engage with each other, and the door engaging portion moves and the cam member rotates, thereby switching the fixing unit from the first state to the second state; The image forming apparatus is characterized in that, when the fixing unit is in the second state, the third engagement portion and the door engagement portion are separated from each other.

[0061] (Item 5) The image forming apparatus according to any one of items 1 to 4, the first interlocking member and the second interlocking member rotate in conjunction with the door opening operation, thereby moving the pressure adjusting means from the first position to the second position; the first engaging portion and the first engaged portion are engaged with each other when the first interlocking member and the second interlocking member rotate in either a first rotation direction in which the first interlocking member and the second interlocking member rotate when the pressure adjusting means moves from the first position to the second position, or a second rotation direction opposite to the first rotation direction; When the second interlocking member rotates in the first rotation direction, the second engaging portion and the second engaged portion engage with each other, When the second interlocking member rotates in the second rotation direction, the second engaging portion and the second engaged portion are not engaged with each other, an image forming apparatus characterized in that, after the third engagement portion and the door engagement portion separate in conjunction with the door opening operation, the second interlocking member is capable of rotating in the second rotation direction without moving the pressure force adjustment means.

[0062] (Item 6) The image forming apparatus according to any one of items 1 to 5, the fixing unit has a cover member, the second interlocking member has an abutment portion, The cover member has an abutted portion, After the third engaging portion and the door engaging portion are separated in conjunction with the opening of the door, the second interlocking member rotates in the second rotation direction until the abutting portion abuts against the abutted portion, The image forming apparatus is characterized in that, after the second interlocking member abuts against the abutted portion, the second interlocking member maintains its abutted position due to its own weight.

[0063] (Item 7) The image forming apparatus according to any one of items 1 to 6, the fixing unit has a cover member, the second interlocking member has a butting portion and a hook portion, The cover member has an abutted portion and a holding portion, After the third engaging portion and the door engaging portion are separated in conjunction with the opening of the door, the second interlocking member rotates in the second rotation direction until the abutting portion abuts against the abutted portion, An image forming apparatus characterized in that when the second interlocking member abuts against the abutted portion, the hooking portion is hooked on the holding portion, thereby maintaining its posture.

[0064] (Item 8) The image forming apparatus according to any one of items 1 to 7, the interlocking means includes a first biasing member that biases the second interlocking member in the second rotation direction, an image forming apparatus characterized in that, after the third engagement portion and the door engagement portion separate in conjunction with the opening of the door, the second interlocking member rotates in the second rotation direction by the biasing force of the first biasing member without moving the pressure force adjustment means.

[0065] (Item 9) The image forming apparatus according to any one of items 1 to 8, The door engagement portion is provided with an engagement member that engages with the third engagement portion, The image forming apparatus according to claim 1, wherein the door has a second biasing member that biases the engaging member in a direction in which the engaging member engages with the third engaging portion.

[0066] (Item 10) The image forming apparatus according to any one of items 1 to 9, The door has a pressing portion, the first interlocking member has a pressed portion, the second interlocking member has a contact portion, The engaging member has an abutted portion, In conjunction with the closing operation of the door, the pressing portion presses the pressed portion, the first interlocking member rotates, thereby rotating the cam member, and the pressure adjusting means switches from the second position to the first position, The image forming apparatus is characterized in that the engaging member moves when the abutted portion abuts against the abutting portion, and when the abutted portion and the abutting portion are separated by closing the door, the engaging member is biased by the second biasing member to move so that the third engaging portion and the engaging member engage.

[0067] (Item 11) The image forming apparatus according to any one of items 1 to 10, the pressure member is a pressure roller, the pressurized member is a heating unit, An image forming apparatus characterized in that a sheet transported to the fixing nip portion formed by the pressure roller and the heating unit is sandwiched and transported between the pressure roller and the heating unit, and a toner image formed on the sheet is fixed by applying heat and pressure. [Explanation of symbols]

[0068] 9 Fixing device 10 Heating unit 11 Pressure roller 11 conveying roller pair 20 Rear door 21 First fixing side plate 22 Second side plate of fixing 23 Fixed upper stay 24 Fixed stay 25 Fixing left cover 26 Fixing right cover 29 Pressure plate 31 Heater 32 Compression Stay 35 Pressure spring 36 Pressure release cam 37 Rear door interlocking lever 38 Fixing link lever 39 Pressure release arm 40 Pressure release arm holder 41 Latch 42 Latch spring 43 Latch cover 44 Rear door guide 101 Image forming device 244 Rear door interlocking lever spring

Claims

1. A device body, a door that is provided so as to be openable and closable relative to the device body; a fixing unit for fixing a toner image formed on a sheet to the sheet, the fixing unit including a pressure member, a pressure-receiving member that forms a fixing nip portion between the pressure member and the pressure member, and pressure adjusting means for reducing or canceling the pressure applied to the fixing nip portion; an interlocking means engageable with the pressure adjusting means for interlocking the opening and closing of the door with the pressure adjusting means; An image forming apparatus having: the door has a door engaging portion that engages with the interlocking means; the interlocking means includes a first interlocking member and a second interlocking member that are engaged with each other; the fixing unit is switchable between a first state in which a predetermined pressure is applied to the fixing nip portion and the pressure adjusting means is in a first position, and a second state in which the pressure applied to the fixing nip portion is reduced to less than the predetermined pressure or is released and the pressure adjusting means is in a second position; In the process of opening the door from a closed state, the door engaging portion and the second interlocking member are engaged with each other, and further, the first interlocking member and the pressure force adjusting means are engaged with each other, and the first interlocking member moves the pressure force adjusting means, whereby the pressure force adjusting means moves from the first position to the second position, During the process of opening the door, when the pressure adjusting means is in the second position, the second interlocking member is separated from the door engaging portion, and further, when the pressure adjusting means is in the second state, the second interlocking member is movable relative to the first interlocking member, an image forming apparatus characterized in that, during the process of closing the door, the first interlocking member is moved, regardless of the movement of the second interlocking member, and the first interlocking member moves the pressure adjustment means to the first position.

2. 2. The image forming apparatus according to claim 1, wherein the door pushes the first interlocking member during the process of closing the door, thereby moving the first interlocking member, and the first interlocking member moves the pressure adjusting means to the first position.

3. the fixing unit has a pressure plate for applying pressure to the fixing nip portion, the pressure adjusting means includes a cam member engageable with the first interlocking member, and a moving member that abuts against the cam member and the pressure plate, 2. The image forming apparatus according to claim 1, wherein when the first interlocking member and the cam member are engaged, the cam member rotates in conjunction with the first interlocking member, the cam member abuts the moving member, the moving member abuts the pressure plate, and the position of the pressure plate changes, thereby switching the fixing unit between the first state and the second state.

4. the first interlocking member has a first engaging portion and a second engaging portion, the cam member has a first engaged portion, the second interlocking member has a second engaged portion and a third engaging portion, when the door is opened, the third engaging portion and the door engaging portion, the second engaging portion and the second engaged portion, and the first engaging portion and the first engaged portion engage with each other, and the door engaging portion moves and the cam member rotates, thereby switching the fixing unit from the first state to the second state; 4. The image forming apparatus according to claim 3, wherein the third engaging portion and the door engaging portion are separated from each other when the fixing unit is in the second state.

5. the first interlocking member and the second interlocking member rotate in conjunction with the door opening operation, thereby moving the pressure adjusting means from the first position to the second position; the first engaging portion and the first engaged portion are engaged with each other when the first interlocking member and the second interlocking member rotate in either a first rotation direction in which the first interlocking member and the second interlocking member rotate when the pressure adjusting means moves from the first position to the second position, or a second rotation direction opposite to the first rotation direction; When the second interlocking member rotates in the first rotation direction, the second engaging portion and the second engaged portion engage with each other, When the second interlocking member rotates in the second rotation direction, the second engaging portion and the second engaged portion are not engaged with each other, 5. The image forming apparatus according to claim 4, wherein after the third engagement portion and the door engagement portion separate in conjunction with the door opening operation, the second interlocking member is rotatable in the second rotation direction without moving the pressure adjusting means.

6. the fixing unit has a cover member, the second interlocking member has an abutment portion, The cover member has an abutted portion, After the third engaging portion and the door engaging portion are separated in conjunction with the opening of the door, the second interlocking member rotates in the second rotation direction until the abutting portion abuts against the abutted portion, 6. The image forming apparatus according to claim 5, wherein after the second interlocking member abuts against the abutted portion, the second interlocking member maintains its abutted position due to its own weight.

7. the fixing unit has a cover member, the second interlocking member has a butting portion and a hook portion, The cover member has an abutted portion and a holding portion, After the third engaging portion and the door engaging portion are separated in conjunction with the opening of the door, the second interlocking member rotates in the second rotation direction until the abutting portion abuts against the abutted portion, 6. The image forming apparatus according to claim 5, wherein when the second interlocking member abuts against the abutted portion, the hook portion is hooked on the holding portion, thereby maintaining the position.

8. the interlocking means includes a first biasing member that biases the second interlocking member in the second rotation direction, 6. The image forming apparatus according to claim 5, wherein after the third engagement portion and the door engagement portion separate in conjunction with the opening of the door, the second interlocking member rotates in the second rotation direction by the biasing force of the first biasing member without moving the pressure adjusting means.

9. The door engaging portion is provided with an engaging member that engages with the third engaging portion, 5. The image forming apparatus according to claim 4, wherein the door has a second biasing member that biases the engaging member in a direction in which the engaging member engages with the third engaging portion.

10. The door has a pressing portion, the first interlocking member has a pressed portion, the second interlocking member has an abutment portion, The engaging member has an abutted portion, In conjunction with the closing operation of the door, the pressing portion presses the pressed portion, the first interlocking member rotates, thereby rotating the cam member, and the pressure adjusting means switches from the second position to the first position, The image forming apparatus of claim 9, wherein the engaging member moves when the abutted portion abuts against the abutting portion, and when the abutted portion and the abutting portion are separated by closing the door, the engaging member is biased by the second biasing member to move so that the third engaging portion and the engaging member engage.

11. the pressure member is a pressure roller, the pressurized member is a heating unit, An image forming apparatus according to any one of claims 1 to 10, characterized in that a sheet transported to the fixing nip portion formed by the pressure roller and the heating unit is sandwiched and transported between the pressure roller and the heating unit, and a toner image formed on the sheet is fixed by applying heat and pressure.

Images