Image forming device

Abstract

To provide an image forming apparatus equipped with a fixing device capable of easily removing paper jammed in a fixing nip when a shutter is closed. [Solution] The image forming apparatus comprises a heating rotor 81 and a pressure rotor 63, a removably attached mounting member, a shutter 65 that rotates vertically, a protrusion attached to the mounting member that rotates the shutter 65 upward to expose the heating rotor 81 when the mounting member is attached to the apparatus main body, a pressure change unit 69 that reduces the pressure in the fixing nip, and a transport guide 103 that is tiltable upward in conjunction with the pressure change unit 69 and guides paper to the fixing nip, and when the mounting member is removed from the apparatus main body, the shutter 65 rotates downward, and the pressure change unit 69 reduces the pressure in the fixing nip and tilts the transport guide 103 upward to contact the shutter 65.

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus equipped with a fixing device having a shutter that covers a heating rotor. [Background technology]

[0002] The fixing device includes a heating rotor and a pressure rotor that form a fixing nip. For safety reasons, the fixing device may be equipped with an openable shutter. When removing a paper jammed in the fixing nip, the shutter is closed to prevent the user from touching the heating rotor.

[0003] Patent Document 1 describes an image forming apparatus that includes a cartridge that is removably mounted in the apparatus main body, and that moves a shutter from a closed position to an open position when the cartridge is mounted in the apparatus main body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-101165 Summary of the Invention [Problem to be solved by the invention]

[0005] In an image forming apparatus such as that described in Patent Document 1, if a paper jam occurs in the fixing nip, the paper must be removed from the fixing nip with the shutter closed. If the paper comes into contact with the closed shutter at this time, a large force may be required to pull the paper out, or the paper may be torn.

[0006] SUMMARY OF THE INVENTION In consideration of the above circumstances, it is an object of the present invention to provide an image forming apparatus equipped with a fixing device that can easily remove paper jammed in the fixing nip when the shutter is closed. [Means for solving the problem]

[0007] In order to achieve the above object, the image forming apparatus of the present invention comprises a heating rotor and a pressure rotor that are supported within the device main body and form a fixing nip for fixing a toner image to paper; a mounting member that is removably attached to the device main body; a shutter that is positioned upstream of the fixing nip in the removal direction of the mounting member and rotates vertically to expose or cover the heating rotor; a protrusion that is attached to the mounting member and rotates the shutter upward to expose the heating rotor when the mounting member is attached to the device main body; a pressure change unit that reduces the pressure in the fixing nip; and a transport guide that is tiltable upward toward the downstream side in the removal direction in conjunction with the pressure change unit and guides paper to the fixing nip, wherein when the mounting member is removed from the device main body, the shutter rotates downward to cover the heating rotor, and the pressure change unit reduces the pressure in the fixing nip and tilts the transport guide upward to contact the shutter.

[0008] In the present invention, the contact portion between the shutter and the transport guide and the fixing nip may be at substantially the same height.

[0009] In the present invention, the transport guide may be inclined so that an end portion of the transport guide downstream of the fixing nip in the removal direction faces upward.

[0010] In the present invention, the shutter may be provided with a roller that rotates in contact with the paper pulled out of the fixing nip when a paper jam occurs in the fixing nip.

[0011] The present invention may be characterized by further comprising a biasing member that biases the shutter so as to rotate downward.

[0012] In the present invention, the mounting member may be a drum unit including a photosensitive drum and a housing that accommodates the photosensitive drum, and the protrusion may be provided on the housing. [Effects of the Invention]

[0013] According to the present invention, paper jammed in the fixing nip can be pulled out in an almost straight line from the fixing nip through the contact area between the shutter and the conveying guide, so that the paper can be pulled out smoothly without resistance. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a front view schematically illustrating an internal structure of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a perspective view showing a drum unit in an image forming apparatus according to an embodiment of the present invention; [Figure 3] 1 is a cross-sectional view showing a fixing device (with a drum unit removed) in an image forming apparatus according to one embodiment of the present invention. [Figure 4] 1 is a cross-sectional view showing a fixing device (with a drum unit attached) in an image forming apparatus according to one embodiment of the present invention. [Figure 5] FIG. 2 is a perspective view showing a shutter in the image forming apparatus according to the embodiment of the present invention. [Figure 6] 1 is a perspective view showing a conveyance guide (a fixed guide and a movable guide) in an image forming apparatus according to an embodiment of the present invention. [Figure 7] 1 is a side view showing a pressure changing unit (in a state where the fixing nip is set to a predetermined pressure) in an image forming apparatus according to an embodiment of the present invention. FIG. [Figure 8] 1 is a side view showing a pressure changing unit (in a state where the fixing nip is decompressed) in an image forming apparatus according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[0016] First, the overall configuration of image forming apparatus 1 will be described with reference to Fig. 1. Fig. 1 is a front view schematically showing the internal configuration of image forming apparatus 1. The symbols Fr, Rr, L, and R used in the following drawings represent front, rear, left, and right, respectively.

[0017] The device body 3 of the image forming device 1 is provided with a paper feed cassette 5 that stores paper, a paper feed device 7 that feeds paper from the paper feed cassette 5, an image forming unit 9 that forms a toner image on paper using an electrophotographic method, a fixing device 11 that fixes the toner image on the paper, a discharge device 13 that discharges paper, and a discharge tray 15 on which the discharged paper is stacked. In addition, a pair of registration rollers 17 is arranged between the paper feed device 7 and the image forming unit 9.

[0018] The paper feed cassette 5 is housed in a cassette housing section provided at the bottom inside the device main body 3. The paper feed device 7 is located above the front end of the cassette housing section. The registration roller pair 17 is located above the paper feed device 7. The image forming section 9 is located behind the registration roller pair 17. The fixing device 11 is located behind the image forming section 9. The discharge device 13 is located above the fixing device 11. The discharge tray 15 is provided on the top surface of the device main body 3.

[0019] Furthermore, the apparatus main body 3 is formed with a main transport path 19a and a duplex transport path 19b along which paper is transported. The main transport path 19a is formed so as to extend from the paper feed device 7, through the image forming unit 9 and the fixing device 11, toward the discharge device 13. Specifically, the main transport path 19a curves upward toward the rear from the paper feed device 7, passes through the image forming unit 9 and the fixing device 11, and then curves upward toward the discharge device 13. The duplex transport path 19b branches off from the main transport path 19a downstream of the fixing device 11 in the transport direction and merges with the main transport path 19a upstream of the registration roller pair 17 in the transport direction. Specifically, the duplex transport path 19b branches off downward from the main transport path 19a between the fixing device 11 and the discharge device 13, extends forward below the main transport path 19a, and merges with the main transport path 19a between the paper feed device 7 and the registration roller pair 17.

[0020] Next, the image forming unit 9 will be further described. The image forming unit 9 is made up of a drum unit 21, a developing unit 23, an exposure device 25, a toner container 27, and a transfer roller 29. The drum unit 21, the developing unit 23, and the toner container 27 are removably attached to the apparatus main body 3.

[0021] First, the drum unit 21 will be described with reference to FIGS. 1 and 2. FIG. 2 is a perspective view showing the drum unit 21. As shown in FIG. 1, the drum unit 21 includes a photosensitive drum 31, a charging device 33, a cleaning device 35, and a drum housing 37 that supports these. The photosensitive drum 31 is rotatably supported by the drum housing 37. A portion of the outer circumferential surface of the photosensitive drum 31 is exposed through an opening formed in the drum housing 37. The charging device 33 and the cleaning device 35 are arranged around the photosensitive drum 31 along the rotation direction of the photosensitive drum 31.

[0022] The drum unit 21 is removably mounted at a predetermined position upstream of the fixing device 11 in the conveyance direction through an opening 3a formed in the front surface of the device main body 3. Specifically, as shown in FIG. 1, rails 3b are formed on the left and right side plates of the device main body 3, extending from the opening 3a toward a predetermined position. Also, as shown in FIG. 2, guide pins 39 are provided on the left and right side plates of the drum housing 37. The drum unit 21 is positioned at a predetermined position by engaging these guide pins 39 with the rails 3b and moving the drum unit 21 along the rails 3b. The drum unit 21 is an example of a mounting member removably mounted to the device main body 3 in the present invention. Thus, the removal direction X of the drum unit 21 is from the rear to the front. The fixing device 11 is disposed upstream of the drum unit 21 in the removal direction X.

[0023] 2, the drum housing 37 is provided with a protrusion 41. The protrusion 41 protrudes from the rear surface (the surface on the upstream side in the removal direction X) of the drum housing 37 toward the rear (the upstream side in the removal direction X), that is, toward the fixing device 11. The protrusion 41 has a substantially triangular plate shape when viewed from the left and right.

[0024] Next, the developing unit 23 will be described. As shown in Fig. 1, the developing unit 23 includes an agitating roller 51, a supply roller 53, a developing roller 55, and a developing housing 57 that supports these rollers and contains the developer. Each roller is rotatably supported by the developing housing 57. A portion of the outer circumferential surface of the developing roller 55 is exposed through an opening formed in the developing housing 57.

[0025] The developing unit 23 is removably mounted at a predetermined position upstream of the drum unit 21 in the transport direction through the opening 3a of the device main body 3. Guide pins (not shown) are provided on the left and right side plates of the developing housing 57. The developing unit 23 is positioned at a predetermined position by engaging these guide pins with the rails 3b and moving the developing unit 23 along the rails 3b. When the developing unit 23 is positioned, a portion of the outer circumferential surface of the developing roller 55 exposed from the opening of the developing housing 57 faces, with a predetermined gap between them, a portion of the outer circumferential surface of the photosensitive drum 31 exposed from the opening of the drum housing 37 of the drum unit 21.

[0026] Next, we will explain the exposure device 25. The exposure device 25 is disposed above the drum unit 21 and the developing unit 23. The exposure device 25 irradiates the outer peripheral surface of the photosensitive drum 31 with laser light based on image data, thereby forming an electrostatic latent image on the photosensitive drum 31.

[0027] Next, a description will be given of the toner container 27. The toner container 27 is disposed above the developing unit 23. The toner container 27 can communicate with the developing housing 57 of the developing unit 23, and supplies toner to the developing housing 57.

[0028] Next, we will explain the transfer roller 29. The transfer roller 29 is arranged to face the photosensitive drum 31 exposed from the opening of the drum housing 37 of the drum unit 21, across the main transport path 19a. A transfer nip is formed between the transfer roller 29 and the photosensitive drum 31.

[0029] Next, a brief description of the image forming operation will be given. In the case of single-sided printing, a sheet of paper fed from the paper feed cassette 5 by the paper feed device 7 is transported along the main transport path 19a, where skew is corrected by the pair of registration rollers 17 before being transported to the image forming unit 9. In the image forming unit 9, a toner image is formed on the sheet of paper. Specifically, in the drum unit 21, the photosensitive drum 31 is charged to a predetermined potential by the charging device 33. Then, the exposure device 25 irradiates the photosensitive drum 31 with laser light based on image data, forming an electrostatic latent image on the photosensitive drum 31. In the development unit 23, toner supplied from the toner container 27 is stirred and charged with the developer housed in the development housing 57 by the stirring roller 51. The charged toner is then supplied to the development roller 55 by the supply roller 53 and held on the development roller 55. The held toner is supplied to the electrostatic latent image formed on the photosensitive drum 31, and the electrostatic latent image is developed into a toner image. The toner image is transferred from the photosensitive drum 31 to the paper at the transfer nip. Any toner remaining on the photosensitive drum is removed by a cleaning device 35.

[0030] The paper on which the toner image has been formed is transported along main transport path 19a to fixing device 11, where the toner image is fixed to the paper. The paper on which the toner image has been fixed is discharged onto discharge tray 15 by discharge device 13.

[0031] During double-sided printing, after a toner image has been fixed on one side of the paper by fixing device 11, the paper passes through fixing device 11, switches back, and is transported to double-sided conveying path 19b. The paper passes through double-sided conveying path 19b and is transported along main conveying path 19a. After the pair of registration rollers 17 corrects the skew of the paper, the toner image is transferred to the other side of the paper in image forming unit 9. The paper with the transferred toner image is transported along main conveying path 19a to fixing device 11, where the toner image is fixed to the other side of the paper. The paper with the fixed toner image is transported along main conveying path 19a to discharge device 13, and is discharged by discharge device 13 onto discharge tray 15.

[0032] Next, the fixing device 11 will be further described with reference to Figures 3 and 4. Figures 3 and 4 are cross-sectional views showing the fixing device 11.

[0033] The fixing device 11 includes a belt assembly 61, a pressure roller 63, a shutter 65, a conveying guide 67, a pressure changer 69, and a fixing housing 71 that supports these components.

[0034] First, a description will be given of the belt assembly 61. The belt assembly 61 includes a fixing belt 81, a support member 83, a heater 85, and an end holder 87.

[0035] The fixing belt 81 is an endless belt having a predetermined inner diameter and a width greater than the width of the paper. The fixing belt 81 is made of a flexible material and has a base layer, an elastic layer provided on the outer surface of the base layer, and a release layer provided on the outer surface of the elastic layer. The base layer is made of resin. The elastic layer is made of silicone rubber or the like. The release layer is made of PFA tubing or the like. The fixing belt 81 is an example of a heating rotator of the present invention.

[0036] The support member 83 has a sliding surface that faces the inner circumferential surface of the fixing belt 81. The sliding surface has a width wider than the width of the fixing belt 81 and is formed to follow the circumferential direction of the fixing belt 81. The support member 83 is supported by a stay 89 that passes through the hollow portion of the fixing belt 81. The support member 83 is fixed to the lower surface of the stay 89, and the sliding surface faces the inner circumferential surface of the fixing belt 81.

[0037] Heater 85 is, for example, a plate-shaped ceramic heater that generates heat when electricity is applied. The heating area of ​​heater 85 is slightly wider than the width of the paper. Heater 85 is housed in a groove formed in the sliding surface of support member 83 and is in contact with the inner circumferential surface of fixing belt 81.

[0038] The end holders 87 support both ends of the fixing belt 81 and both ends of the stays 89. The end holders 87 are supported by the pressure change unit 69, as will be described later.

[0039] Next, the pressure roller 63 will be described. The pressure roller 63 has a rotating shaft, an elastic layer provided on the outer peripheral surface of the rotating shaft, and a release layer provided on the outer peripheral surface of the elastic layer. The pressure roller 63 is an example of a pressure rotating body of the present invention.

[0040] The left and right ends of the rotation shaft of the pressure roller 63 are rotatably supported by the left and right side plates of the fixing housing 71 below the belt assembly 61. The pressure roller 63 faces the heater 85 with the fixing belt 81 of the belt assembly 61 sandwiched therebetween. This forms a fixing nip N between the fixing belt 81 and the pressure roller 63. A drive gear (not shown) is fixed to one end of the rotation shaft of the pressure roller 63. The drive gear is connected to a motor (not shown) via a gear train (not shown).

[0041] When the motor is driven, the drive gear rotates clockwise in FIGS. 3 and 4 via a gear train, causing the pressure roller 63 to rotate in one direction (clockwise in this example). This causes the fixing belt 81, which is in contact with the pressure roller 63 at the fixing nip N, to rotate in the other direction (counterclockwise in this example). As a result, the paper guided into the fixing nip N passes through the fixing nip N. At this time, the toner image is heated and pressurized and fixed to the paper.

[0042] Next, the shutter 65 will be described with reference to Fig. 5. Fig. 5 is a perspective view showing the shutter 65. The shutter 65 includes a rotation shaft 91 and a shutter plate 93 provided integrally with the rotation shaft 91.

[0043] The rotation shaft 91 has a length longer than the width of the fixing belt 81. At the center of the rotation shaft 91, a protrusion 95 is formed that protrudes upward.

[0044] The shutter plate 93 is formed in the shape of a rectangular plate having a width slightly shorter than the length of the rotary shaft 91 and a predetermined length. Two rectangular notches are formed at the lower end of the shutter plate 93 with a predetermined distance between them. A roller 97 is rotatably housed in each notch. The roller 97 protrudes downward from the lower edge of the shutter plate 93.

[0045] 3 and 4, the shutter 65 is disposed downstream (in front of) the fixing device 11 in the removal direction X. Both ends of the rotation shaft 91 are rotatably supported by the left and right side plates of the fixing housing 71 above the fixing nip N. This allows the shutter 65 to rotate vertically around the rotation shaft 91. More specifically, the shutter 65 can rotate upward toward the downstream side in the removal direction X (see FIG. 3). The shutter 65 is also biased by a biasing member 99 to rotate downward. The biasing member 99 is, for example, a torsion coil spring, and is provided at one end of the rotation shaft 91.

[0046] Next, the conveying guide 67 will be described with reference to FIG. 6. FIG. 6 is a perspective view showing the conveying guide 67 (fixed guide 101, movable guide 103). The conveying guide 67 includes the fixed guide 101 and the movable guide 103. As shown in FIGS. 3 and 4, the conveying guide 67 is disposed below the shutter 65, and guides the paper onto which the toner image has been transferred in the image forming unit 9 to the fixing nip N.

[0047] The fixed guide 101 has a guide portion 101a that is inclined upward toward the downstream side in the conveying direction (upstream side in the removal direction X) toward the fixing nip N, and a leg portion 101b that is supported by the fixing housing 71. The guide portion 101a has a plurality of ribs formed along the conveying direction at predetermined intervals in the width direction perpendicular to the conveying direction.

[0048] A plurality of ribs extending in the conveying direction are formed at predetermined intervals in the width direction on the upper surface of the movable guide 103. As shown in Fig. 6, a drive shaft 105 extending in the width direction is formed at the upper end of one side of the movable guide 103. Furthermore, a protrusion 107 is formed at the upper end of the other side of the movable guide 103.

[0049] 3 and 4, the movable guide 103 is disposed upstream in the transport direction (downstream in the removal direction X) of the guide portion 101a of the fixed guide 101. A drive shaft 105 of the movable guide 103 is rotatably supported by the fixing housing 71, and a protrusion 107 is supported by the fixed guide 101. A drive gear 109 (see FIGS. 7 and 8) is fixed to the drive shaft 105. When the drive gear 109 rotates, the drive shaft 105 rotates and the movable guide 103 rotates, tilting upward or downward toward the downstream side in the removal direction X.

[0050] 4, when the movable guide 103 is tilted downward, the upper surface of the movable guide 103 and the upper surface of the guide portion 101a of the fixed guide 101 are smoothly continuous. As shown in Fig. 3, when the movable guide 103 is tilted upward, the lower end portion of the movable guide 103 (the end portion on the upstream side in the removal direction X) rises to approximately the same height as the fixing nip N. The rotation range of the movable guide 103 and the rotation range of the shutter 65 partially overlap.

[0051] Next, the pressure changing unit 69 will be described with reference to Figures 7 and 8. Figures 7 and 8 are cross-sectional views showing the pressure changing unit 69. The pressure changing unit 69 reduces the pressure at the fixing nip N to a predetermined pressure while an image forming operation is not being performed (including during standby, when the drum unit 21 is detached from the device main body 3, and when a paper jam is being cleared at the fixing nip N). The pressure changing unit 69 includes a support arm 111, a biasing member 113, a cam 115, and a cam gear 117.

[0052] First, the support arm 111 will be described. The support arm 111 is supported by the fixing housing 71 in a cantilevered manner so as to be able to swing. The upper surface of the end holder 87 of the belt assembly 61 is fixed to the center of the lower surface of the support arm 111. When the support arm 111 swings upward, the belt assembly 61 moves upward relative to the pressure roller 63. When the support arm 111 swings downward, the belt assembly 61 moves toward the pressure roller 63.

[0053] Next, we will explain the urging member 113. The urging member 113 urges the support arm 111 downward. That is, it urges the belt assembly 61 downward to press the fixing belt 81 against the pressure roller 63, and sets the fixing nip N at a predetermined pressure.

[0054] Next, the cam 115 will be described. The cam 115 abuts against the tip of the lower surface of the support arm 111 from below. When the maximum diameter portion of the cam 115 is separated from the lower surface of the support arm 111 (see FIG. 7), the cam 115 moves downward away from the support arm 111. As a result, the support arm 111 is urged downward by the urging member 113, and the fixing nip N is set to a predetermined pressure. On the other hand, when the cam 115 rotates and the maximum diameter portion of the cam 115 faces the lower surface of the support arm 111 (see FIG. 8), the support arm 111 is lifted by the maximum diameter portion and swings upward against the urging force of the urging member 113. As a result, the pressure in the fixing nip N becomes lower than the predetermined pressure.

[0055] Next, the cam gear 117 will be described. The cam gear 117 is provided coaxially with the cam 115 and can rotate integrally with the cam 115. The cam gear 117 is driven to rotate by a motor (not shown). The cam gear 117 meshes with a drive gear 109 fixed to a drive shaft 105 of the movable guide 103 of the conveying guide 67 via a first transmission gear 121 and a second transmission gear 123.

[0056] When the cam gear 117 rotates counterclockwise in FIG. 7 so that the maximum diameter portion of the cam 115 faces the lower surface of the support arm from a state in which the fixing nip N is set to a predetermined pressure as shown in FIG. 7, the pressure in the fixing nip N decreases below the predetermined pressure, as described above. Furthermore, as shown in FIG. 8, the drive gear 109 rotates clockwise via the first transmission gear 121 and the second transmission gear 123. As a result, the drive shaft 105 rotates clockwise, and the movable guide 103 of the conveying guide 67 tilts upward (see FIG. 3).

[0057] In the image forming apparatus 1 having the above configuration, the opening and closing operation of the shutter 65 of the fixing device 11 will be described.

[0058] When the drum unit 21 and the developing unit 23 are removed from the apparatus main body 3, the pressure at the fixing nip N is reduced by the pressure change unit 69, as described above. Furthermore, the pressure change unit 69 tilts the movable guide 103 of the conveying guide 67 upward. Meanwhile, the shutter 65 is urged downward by its own weight and the urging member 99. Then, as shown in FIG. 3, the lower end of the shutter 65, i.e., the roller 97, contacts the upwardly tilted movable guide 103. In other words, the shutter 65 does not rotate until it hangs down vertically from the rotation shaft 91. The contact point P between the shutter 65 and the movable guide 103 is at approximately the same height as the fixing nip N. As a result, the shutter 65 and the movable guide 103 can be seen through the opening 3a (see FIG. 1) on the front surface of the apparatus main body 3 through the space (referred to as the storage space) where the drum unit 21 and the developing unit 23 were installed. In other words, the fixing belt 81 is covered by the shutter 65 and the movable guide 103. This prevents the worker from accidentally touching the fixing belt 81.

[0059] From this state, the worker installs the drum unit 21. The worker engages the guide pin 39 of the drum housing 37 of the drum unit 21 with the rail 3b and moves the drum unit 21 along the rail 3b toward a predetermined position. The drum unit 21 moves, with the protrusion 41 (see FIG. 2) leading, toward a predetermined position, i.e., a position upstream of the fixing device 11 in the transport direction. The protrusion 41 then abuts against the front surface of the protrusion 95 of the shutter 65. When the drum unit 21 is further moved and installed in the predetermined position, the protrusion 41 pushes the protrusion 95 rearward. Then, as shown in FIG. 4, the shutter plate 93 rotates upward about the pivot shaft 91, creating a gap between the shutter 65 and the transport guide 67 through which paper can pass. The developing unit 23 is then installed in the predetermined position.

[0060] When an instruction to perform an image forming operation is issued, the motor in the pressure changing unit 69 is driven to rotate the cam gear 117, which moves the cam 115 away from the support arm 111. As a result, the support arm 111 is urged downward by the urging member 113, and the fixing nip N is set to a predetermined pressure. Furthermore, the rotation of the cam gear 117 rotates the drive gear 109 via the first transmission gear 121 and the second transmission gear 123. The drive shaft 105 then rotates together with the drive gear 109, causing the movable guide 103 to tilt downward. As a result, as shown in FIG. 4 , a guide surface toward the fixing nip N is formed by the upper surface of the movable guide 103 and the upper surface of the guide portion 101a of the fixed guide 101. When an image forming operation is performed in this state, the paper onto which the toner image has been transferred is guided toward the fixing nip N along the conveyance guide 67.

[0061] If a paper jam occurs in the fixing nip N during image formation, the developing unit 23 is first pulled out, and then the drum unit 21 is pulled out. Then, the protrusion 41 separates from the protruding piece 95, and the shutter plate 93 rotates downward by its own weight and the biasing force of the biasing member 99.

[0062] Furthermore, in the pressure changing unit 69, the motor is driven to rotate the cam gear 117, and the maximum diameter portion of the cam 115 lifts the support arm 111. This causes the support arm 111 to swing upward, and the belt assembly 61 moves upward relative to the pressure roller 63, reducing the pressure in the fixing nip N.

[0063] Furthermore, when the cam gear 117 rotates, the drive gear 109 of the movable guide 103 of the conveying guide 67 rotates via the first transmission gear 121 and the second transmission gear 123. The drive shaft 105 rotates together with the drive gear 109, and the movable guide 103 tilts upward.

[0064] As described above, the shutter plate 93 of the shutter 65 rotates downward. Therefore, when the movable guide 103 tilts upward, the lower end (roller 97) of the shutter plate 93 abuts against the upper surface of the upwardly tilted movable guide 103 (see FIG. 3). As described above, the tip of the movable guide 103 rises to approximately the same height as the fixing nip N, so that the contact point P between the shutter plate 93 and the movable guide 103 is approximately the same height as the fixing nip N.

[0065] As a result, the paper S jammed in the fixing nip N is pinched at the contact point P between the shutter plate 93 and the movable guide 103, and assumes a substantially straight position. Because the pressure in the fixing nip N is reduced, the paper can be smoothly pulled out of the fixing nip N. During this time, the roller 131 rotates as the paper S is pulled out. Furthermore, when viewed from the front through the storage space, the fixing belt 81 and the fixing nip N are covered by the shutter 65 and the movable guide 103. Therefore, even when the drum unit 21 is removed to clear a paper jam, the fixing belt 81 can be prevented from accidentally coming into contact with the worker's fingers.

[0066] As described above, according to the image forming apparatus 1 of the present invention, a sheet jammed in the fixing nip N can be pulled out in a substantially straight line from the fixing nip N through the contact area P between the shutter 65 and the movable guide 103. In addition, because the fixing nip N is depressurized, the sheet can be pulled out smoothly without resistance.

[0067] Furthermore, the movable guide 103 swings so that the end portion downstream (farther) from the fixing device 11 in the removal direction X faces upward, so a predetermined distance can be provided along the conveyance direction between the fixing nip N and the contact portion P. Therefore, even if the fixing nip N and the contact portion P are at different heights, the paper is not suddenly curved, and the load applied to the paper can be reduced.

[0068] Furthermore, the contact portion P is actually formed between the roller 97 of the shutter 65 and the movable guide 103. Therefore, even if the shutter 65 is urged downward by the urging member 99, the roller 97 rotates, allowing the paper to be pulled out through the contact portion P without encountering significant resistance.

[0069] Furthermore, in the present embodiment, the drum unit 21 is an example of an attachment member that is detachably attached to the apparatus main body 3, but it may also be a cover that opens and closes the opening 3a of the apparatus main body 3.

[0070] Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above embodiments, and those skilled in the art may modify the above embodiments without departing from the scope and spirit of the present invention. [Explanation of symbols]

[0071] 1. Image forming device 3. Device body 21 Drum unit (mounting part) 31 Photosensitive drum 37 Drum housing 41 protrusion 63 Pressure roller (pressure rotating body) 65 Shutter 67 Transport guide 69 Pressure change section 81 Fixing belt (heating rotor) 97 Roller 99 biasing member

Claims

1. a heating rotor and a pressure rotor that are supported within the device body and form a fixing nip for fixing a toner image onto a sheet of paper; a mounting member that is removably mounted on the device body; a shutter that is disposed upstream of the fixing nip in the removal direction of the mounting member and that rotates vertically to expose or cover the heating rotor; a protrusion provided on the mounting member, the protrusion rotating the shutter upward to expose the heating rotor when the mounting member is mounted on the device body; a pressure change unit that reduces the pressure in the fixing nip; a conveyance guide that is inclined upward toward the downstream side in the removal direction in conjunction with the pressure change unit and that guides the paper to the fixing nip, When the mounting member is removed from the device main body, the shutter rotates downward to cover the heating rotor, and the pressure change unit reduces the pressure in the fixing nip and tilts the conveying guide upward to contact the shutter.

2. 2. The image forming apparatus according to claim 1, wherein the contact portion between the shutter and the conveying guide and the fixing nip are at substantially the same height.

3. 2. The image forming apparatus according to claim 1, wherein the conveying guide is inclined so that an end portion of the conveying guide downstream of the fixing nip in the removal direction faces upward.

4. 2. The image forming apparatus according to claim 1, wherein the shutter includes a roller that rotates in contact with the paper pulled out from the fixing nip when a paper jam occurs in the fixing nip.

5. 2. The image forming apparatus according to claim 1, further comprising a biasing member that biases the shutter so as to rotate downward.

6. the mounting member is a drum unit including a photosensitive drum and a housing that accommodates the photosensitive drum, 2. The image forming apparatus according to claim 1, wherein the protrusion is provided on the housing.

Images