Fixing device and image forming apparatus

Abstract

To provide a fixing device including a cleaning member that can clean a fixing member without adversely affecting rotation or replacement of the fixing member.SOLUTION: A fixing device comprises: a rotatable fixing member 21; a pressing member 27 that forms a pressing region with the fixing member 21; a pressure changing mechanism 29 that changes pressure of the pressing region; and a cleaning member 31 that cleans an end portion of the fixing member 21. The pressure changing mechanism 29 comprises a support plate 41 that supports the fixing member 21 and a cam 43 that abuts on the support plate 41. By rotation of a shaft 45 of the cam 43 within a predetermined angle, the support plate 41 is guided by the cam 43 so that the fixing member 21 moves and pressure of the pressing region is changed. The cleaning member 31 is fixed to the shaft 45 of the cam 43, and during rotation around the shaft 45 of the cam 43 within the predetermined angle for changing the pressure of the pressing region, the cleaning member contacts the end portion of the fixing member 21 to clean the end portion.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present invention relates to a fixing device that fixes a toner image on a sheet of paper and an image forming apparatus equipped with the fixing device. [Background technology]

[0002] The fixing device includes a fixing member heated by a heater and a pressure member that contacts the fixing member to form a pressure area. The fixing member and pressure member rotate to fix a toner image on paper transported to the pressure area. In such a fixing device, paper dust generated from the side edges of the paper tends to adhere to both ends of the fixing member in the width direction of the paper. When paper dust adheres to the fixing member, it can cause image defects such as vertical streaks on the paper.

[0003] For this reason, for example, the fixing device described in Patent Document 1 is provided with a cleaning roller that is pressed against a rotating member (fixing member or pressure member) to remove paper dust and the like. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-145929 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the fixing device described in Patent Document 1, the cleaning roller is constantly pressed against the rotating member, which places a load on the rotation of the rotating member. Furthermore, when replacing the rotating member, the cleaning roller must be retracted, which makes the replacement process time-consuming. Furthermore, there is a risk of heat being generated due to friction between the cleaning roller and the rotating member.

[0006] In consideration of the above circumstances, the present invention aims to provide a fixing device equipped with a cleaning member that can clean the fixing member without adversely affecting the rotation or replacement of the fixing member, and an image forming apparatus equipped with this fixing device. [Means for solving the problem]

[0007] In order to solve the above problem, the fixing device of the present invention comprises a rotatable fixing member heated by a heat source, a pressure member that forms a pressure area between the fixing member and heats and pressurizes paper onto which a toner image has been transferred, thereby fixing the toner image to the paper, a pressure change mechanism that changes the pressure in the pressure area, and a cleaning member that cleans the end of the fixing member in the width direction of the paper, wherein the pressure change mechanism comprises a support plate that supports the fixing member and has one end rotatably supported, and a cam having a cam surface that abuts the support plate, and when the cam shaft rotates in one direction or the other within a predetermined angle, the support plate is guided by the cam surface and the fixing member moves in a direction toward or away from the pressure member, thereby changing the pressure in the pressure area, and the cleaning member is rotatably fixed integrally with the cam shaft, and when the pressure in the pressure area is changed, it comes into contact with the end of the fixing member while rotating in one direction or the other within the predetermined angle around the cam shaft, thereby cleaning the end.

[0008] In the present invention, the fixing member may be rotated while the cleaning member is in contact with the end portion of the fixing member.

[0009] In the present invention, the cleaning member may be characterized in that it contacts the end of the fixing member when the pressure in the pressure area is increased from a state where the pressure is reduced below a predetermined pressure at which a toner image can be fixed to paper to the predetermined pressure.

[0010] In the present invention, the fixing member may be a flexible, endless fixing belt including a support member that supports the fixing belt from the inside, and the cleaning member may be in contact with a portion of the fixing belt that is not supported by the support member.

[0011] In the present invention, the predetermined angle may be 180 degrees, the cleaning member may have a fan shape with a central angle of 45 degrees centered on the cam shaft, and may be fixed to the cam shaft between the maximum diameter portion and the minimum diameter portion of the cam.

[0012] The image forming apparatus of the present invention is characterized by comprising: an image forming unit that transfers a toner image onto a sheet; and a fixing device that fixes the toner image transferred by the image forming unit onto the sheet. [Effects of the Invention]

[0013] According to the present invention, the cleaning member is not in contact with the fixing belt during the fixing operation and when the fixing device is on standby, so that no load is applied to the rotation of the fixing belt during the fixing operation, allowing the fixing belt to rotate smoothly and the fixing belt to be removed and installed without interfering with the cleaning member. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a side view schematically illustrating an internal configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically illustrating an internal configuration of a fixing device according to an embodiment of the present invention. [Figure 3] FIG. 1 is a perspective view showing a fixing device according to an embodiment of the present invention. [Figure 4A] FIG. 2 is a perspective view showing a pressure changing mechanism of the fixing device (when a pressure region is formed) according to one embodiment of the present invention. [Figure 4B] FIG. 2 is a perspective view showing a pressure changing mechanism of the fixing device (when the pressure region is decompressed) according to one embodiment of the present invention. [Figure 5] FIG. 2 is a perspective view showing a cleaning member of a fixing device according to an embodiment of the present invention. [Figure 6A] 10 is a side view showing the cleaning member when the pressure in the pressure region is reduced in the fixing device according to one embodiment of the present invention. FIG. [Figure 6B]10 is a side view showing the cleaning member during pressure change in the pressure region in the fixing device according to one embodiment of the present invention; FIG. [Figure 6C] FIG. 4 is a side view showing the cleaning member when forming a pressure area in the fixing device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an image forming apparatus and a fixing device according to the present invention will be described with reference to the drawings.

[0016] First, the overall configuration of image forming apparatus 1 will be described using Figure 1. Figure 1 is a front view that schematically shows the internal configuration of image forming apparatus 1. Hereinafter, the right side of the paper in Figure 1 will be referred to as the front side (front side) of image forming apparatus 1. Fr, Rr, L, and R written in each figure indicate the front side, rear side, left side, and right side of the image forming apparatus.

[0017] The device body 3 of the image forming device 1 is provided with a paper feed cassette 5 that stores paper sheets S, a paper feed device 7 that feeds paper sheets S from the paper feed cassette 5, an image forming section 9 that forms a toner image on paper sheets S by electrophotography, a fixing device 11 that fixes the toner image on paper sheets S, a paper discharge device 13 that discharges paper sheets S, and a paper discharge tray 15 on which the discharged paper sheets S are stacked. Furthermore, the device body 3 is formed with a transport path 17 for paper sheets S that runs from the paper feed device 7, through the image forming section 9 and the fixing device 11, and toward the paper discharge device 13.

[0018] The image forming operation will be briefly explained. First, paper S is sent out from paper feed cassette 5 to transport path 17 by paper feed device 7. The sent paper S is transported along transport path 17 to image forming unit 9, where a toner image is formed on the paper S by electrophotography. The paper S with the toner image formed is transported along transport path 17 to fixing device 11. Fixing device 11 fixes the toner image on the paper S. The paper S with the fixed toner image is transported along transport path 17 to paper discharge device 13. Paper discharge device 13 discharges the paper S onto paper output tray 15.

[0019] Next, the fixing device 11 will be described with reference to Figures 2, 3, 4A, and 4B. Figure 2 is a cross-sectional view that schematically shows the internal configuration of the fixing device 11, Figure 3 is a perspective view that shows the fixing device 11, and Figures 4A and 4B are perspective views that show the pressure change mechanism 29.

[0020] As shown in Figure 2, the fixing device 11 includes a fixing belt 21 as a fixing member, a heater 23 as a heat source for heating the fixing belt 21, a support member 25 that holds the heater 23 and supports the fixing belt 21, a pressure roller 27 as a pressure member that forms a pressure area N between the fixing belt 21 and the support member 25, left and right pressure change mechanisms 29 (see Figures 4A and 4B) that change the pressure in the pressure area N, and a cleaning member 31 (see Figure 3).

[0021] First, the fixing belt 21 will be described. The fixing belt 21 is an endless belt having a predetermined inner diameter and a width greater than the width of the paper-passing area (for example, A4 landscape size). The fixing belt 21 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 a metal such as SUS or Ni. The elastic layer is made of silicone rubber or the like. The release layer is made of a PFA tube or the like. A sliding layer may be formed on the inner surface of the base layer. The sliding layer is made of polyimide amide, PTFE or the like.

[0022] As shown in Fig. 3, both ends of the fixing belt 21 are rotatably supported by left and right end holders 33. The left and right end holders 33 are supported by a fixing housing 35 (see Figs. 4A and 4B). As shown in Fig. 2, a stay 37 penetrates the hollow portion of the fixing belt 21. Both ends of the stay 37 are supported by the left and right end holders 33.

[0023] Next, the heater 23 will be described. The heater 23 is a flat plate-shaped member having a width equal to that of the fixing belt 21, a predetermined length along the circumferential direction X of the fixing belt 21, and a predetermined thickness. The heater 23 is composed of a stainless steel or ceramic substrate, an electrical insulating layer made of glass or the like, a resistance heating element layer, and a protective layer, laminated in this order from the back side to the front side. The resistance heating element layer has multiple resistance heating elements and electrodes that are electrically connected to the resistance heating elements. The resistance heating element layer generates heat when electricity is passed through the electrodes to the resistance heating elements. The surface of the protective layer is formed flat and serves as the belt contact surface that comes into contact with the inner circumferential surface of the fixing belt.

[0024] Next, we will explain the support member 25. The support member 25 is a substantially semi-cylindrical member that has a width equal to that of the fixing belt 21 and a predetermined length along the circumferential direction X. The support member 25 is made of a heat-resistant resin such as a liquid crystal polymer.

[0025] The outer peripheral surface of the support member 25 is curved so as to fit substantially along the inner peripheral surface of the lower half of the fixing belt 21. The outer peripheral surface of the top portion of the support member 25 is formed flat. A rectangular parallelepiped accommodation recess 25a for accommodating the heater 23 is formed in this top portion. When the heater 23 is accommodated in the accommodation recess 25a, the belt contact surface of the heater 23 is flush with the outer peripheral surface of the top portion of the support member 25.

[0026] Next, the pressure roller 27 will be described. The pressure roller 27 has a core, an elastic layer provided on the outer peripheral surface of the core, and a release layer provided on the outer peripheral surface of the elastic layer. The elastic layer is made of silicone rubber or the like. The release layer is made of a PFA tube or the like.

[0027] The pressure roller 27 is supported so as to be pressed against the heater 23 from below the fixing belt 21. This forms a pressure area N between the fixing belt 21 and the pressure roller 27. The pressure roller 27 is driven by a motor (not shown) to rotate counterclockwise in FIG. 2. When the pressure roller 27 rotates, the fixing belt 21 is driven to rotate clockwise in FIG. 2, which is opposite to the rotation of the pressure roller 27. This allows the paper S to pass through the pressure area N.

[0028] Next, the left and right pressure change mechanisms 29 will be described with reference to Figures 4A and 4B. The left and right pressure change mechanisms 29 reduce the pressure in the pressure region N from a predetermined pressure by moving the fixing belt 21, supported by the end holder 33, in a direction away from the pressure roller 27. The left and right pressure change mechanisms 29 include left and right support plates 41 that support the left and right end holders 33, respectively, and left and right cams 43 that have cam surfaces that abut against the left and right support plates 41. Figures 4A and 4B show the right side of the pressure change mechanism 29.

[0029] First, the support plate 41 will be described. The support plate 41 is a plate-like member with a flat lower surface, and includes a linear portion 41a and a curved portion 41b that curves upward in an arc shape from one end of the linear portion 41a. The upper end of the end holder 33 is fixed to the lower surface of the linear portion 41a. The other end of the linear portion 41a is inserted into an opening formed in the rear plate of the fixing housing 35. This allows the support plate 41 to rotate vertically relative to the fixing housing 35 around the other end of the linear portion 41a. In other words, the fixing belt 21 supported by the end holder 33 fixed to the support plate 41 can move vertically together with the support plate 41.

[0030] Next, the cam 43 will be described. The cam 43 has an egg shape in plan view, with the maximum diameter portion and the minimum diameter portion disposed at a central angle of approximately 180 degrees around the shaft 45. The shaft 45 is disposed below the support plate 41, and both ends are rotatably supported by the left and right side plates of the fixing housing 35. A motor is connected to one end of the shaft 45. When the motor is driven, the shaft 45 rotates in one direction and then in the opposite direction.

[0031] A light blocking plate 47 is fixed to one end of the shaft 45 so as to be rotatable integrally therewith. The light blocking plate 47 has a small-diameter semicircular portion and a large-diameter semicircular portion. The fixing housing 35 is provided with an optical sensor 49 that blocks or forms an optical path by the large-diameter semicircular portion as the light blocking plate 47 rotates. The optical sensor 49 is electrically connected to a control unit (not shown). When the light blocking plate 47 rotates and blocks the optical path, the optical sensor 49 outputs an OFF signal to the control unit (not shown), and when the optical path is formed, the optical sensor 49 outputs an ON signal to the control unit.

[0032] The lower surface of the curved portion 41b of the support plate 41 abuts against the cam surface of the cam 43. In addition, a coil spring 51 is disposed between the linear portion 41a of the support plate 41 and the top plate of the fixing housing 35. The coil spring 51 presses the lower surface of the curved portion 41b of the support plate 41 against the cam surface of the cam 43.

[0033] 4A, when shaft 45 rotates so that the cam surface of the smallest diameter portion of cam 43 abuts against the underside of curved portion 41b of support plate 41, support plate 41 rotates to a predetermined position. In this state, the pressure in pressure region N is a predetermined pressure that can fix the toner image. Also, the optical path of optical sensor 49 is blocked by the large diameter semicircular portion of light-shielding plate 47, and optical sensor 49 outputs an OFF signal to the control unit.

[0034] When shaft 45 starts to rotate in one direction (counterclockwise, see arrow A), the lower surface of curved portion 41b of support plate 41 moves along the cam surface from the minimum diameter portion of cam 43 to the maximum diameter portion. As a result, fixing belt 21 supported by end holder 33 together with support plate 41 starts to move upward relative to pressure roller 27. In addition, the large diameter semicircular portion of light shielding plate 47 moves away from the optical path of optical sensor 49, and the output of optical sensor 49 switches from an OFF signal to an ON signal.

[0035] When the shaft 45 rotates approximately 180 degrees in one direction (counterclockwise, see arrow A), the large-diameter semicircular portion of the light-shielding plate 47 eventually blocks the optical path of the optical sensor 49 (FIG. 4B shows the state immediately before the light-shielding plate 47 blocks the optical path). This causes the output of the optical sensor 49 to switch from an ON signal to an OFF signal. When the ON signal switches to an OFF signal, the control unit stops the rotation of the shaft 45. Furthermore, as the shaft 45 rotates in this manner, the support plate 41 is lifted by the maximum diameter portion of the cam 43 and rotates to the uppermost position. As a result, the fixing belt 21, supported by the end holder 33 together with the support plate 41, moves upward relative to the pressure roller 27. As a result, the pressure in the pressure region N is reduced below the predetermined pressure. Note that even in this state, the fixing belt 21 and the pressure roller 27 remain in contact with each other.

[0036] In this way, shaft 45 rotates in one direction (counterclockwise, see arrow A) from a position where the cam surface of the smallest diameter portion of cam 43 abuts against support plate 41 (reference position P1, see Figure 4A) to a position where the cam surface of the largest diameter portion of cam 43 abuts against support plate 41 (maximum rotation position P2, see Figure 4B), and then rotates in the other direction opposite to the one direction (clockwise, see arrow B) from the maximum rotation position to the reference position.

[0037] The reference position P1 and the maximum rotation position P2 are determined by the control unit based on the switching of the optical sensor 49 between an ON state and an OFF state. When the shaft 45 rotates from the reference position P1 to the maximum rotation position P2, the output of the optical sensor 49 switches from an OFF signal to an ON signal, and then switches from an ON signal to an OFF signal. On the other hand, when the shaft 45 rotates from the maximum rotation position P2 to the reference position P1, the output of the optical sensor 49 switches from an OFF signal to an ON signal, and then switches from an ON signal to an OFF signal. In this way, when the output of the optical sensor 49 switches from an OFF state to an ON state, and then switches from an ON state to an OFF state, the control unit determines that the shaft 45 has rotated from the reference position P1 to the maximum rotation position P2, or from the maximum rotation position P2 to the reference position P1.

[0038] When the shaft 45 is rotated to the reference position P1, the pressure in the pressure region N is a predetermined pressure capable of fixing the toner image, as described above. On the other hand, when the shaft 45 is rotated to the maximum rotation position P2, the fixing belt 21 moves upward relative to the pressure roller 27, as described above, and the pressure in the pressure region N is reduced.

[0039] Next, the cleaning member 31 will be described with reference to Figures 3, 4A, 4B, and 5. Figure 5 is a perspective view showing the cleaning member 31.

[0040] As shown in FIG. 3 , the cleaning members 31 are disposed corresponding to both widthwise ends of the fixing belt 21 (both ends of the paper passage area) and fixed to the shaft 45. As shown in FIG. 5 , the cleaning member 31 has a main body 61 fixed to the shaft 45 and a contact portion 63 that contacts the fixing belt 21. When viewed in the axial direction of the shaft 45, the main body 61 has a fan-like shape that widens radially outward from the shaft 45 and has a predetermined width in the axial direction of the shaft 45. The central angle of the main body 61 is, for example, approximately 45 degrees. The main body 61 is formed with a pair of support pieces 65 that are spaced apart in the circumferential direction. The main body 61 is made of heat-resistant resin. When viewed in the axial direction of the shaft 45, the contact portion 63 has an arc shape centered on the shaft 45. The corners between the outer circumferential surface and both side surfaces of the contact portion 63 are curved. The contact portion 63 is made of a heat-resistant sponge and is adhered to the outer circumferential surface of the main body portion 61 with a heat-resistant resin adhesive.

[0041] The two cleaning members 31 are fixed to the shaft 45 at the same circumferential position on the shaft 45, between the maximum diameter portion and the minimum diameter portion of the cam 43. A D-cut portion is formed in a predetermined position on the shaft 45. The cleaning members 31 are fixed to the shaft 45 by sandwiching the D-cut portion between a pair of support pieces 65 of the main body 61 of the cleaning members 31 and fastening the support pieces 65 to the shaft 45 with screws in a direction intersecting the axial direction of the shaft 45. As the shaft 45 rotates, the cleaning members 31 rotate around the shaft 45.

[0042] As shown in FIG. 4A , when the shaft 45 rotates to the reference position P1, the cleaning member 31 is spaced apart from the fixing belt 21 to one side (the upstream side in the rotation direction of the fixing belt 21, which is referred to as the upstream separation position C1). When the shaft 45 rotates counterclockwise (see arrow A) from the reference position P1 to the maximum rotation position P2, the cleaning member 31 rotates counterclockwise and separates from the fixing belt 21 to the other side (the downstream side in the rotation direction of the fixing belt 21, which is referred to as the downstream separation position C2) as shown in FIG. 4B (note that the position of the cleaning member 31 depicted in FIG. 4B differs from the actual position). While the cleaning member 31 rotates in this manner, the outer circumferential surface of the cleaning member 31 (contact portion 63) comes into contact with the outer circumferential surface of the fixing belt 21. Specifically, the outer circumferential surface of the cleaning member 31 comes into contact with the portion of the fixing belt 21 that is not supported by the support member 25 (the upper half of the fixing belt 21).

[0043] The fixing operation of the fixing device 11 having the above configuration and the cleaning operation of the fixing belt 21 by the cleaning member 31 will be described with reference to FIGS. 6A to 6C. FIGS. 6A to 6C are side views showing the cleaning member 31. As shown in FIG. 6A, during standby when no image forming operation is being performed, the shaft 45 rotates to the maximum rotation position P2. That is, the pressure in the pressure region N is in a reduced pressure state lower than the predetermined pressure at which fixing operation is possible. However, the fixing belt 21 and the pressure roller 27 remain in contact. The cleaning member 31 also rotates to the downstream separation position C2 and is separated from the fixing belt 21.

[0044] When an image forming operation (fixing operation) is performed, the pressure roller 27 is driven by a motor to rotate, and the fixing belt 21 rotates clockwise in the figure, driven by the pressure roller 27. Furthermore, as shown in FIG. 6B, the shaft 45 is driven by the motor to rotate in the counterclockwise direction (clockwise, see arrow B) from the maximum rotation position P2 toward the reference position P1. This causes the fixing belt 21 to move closer to the pressure roller 27, and the pressure in the pressure region N is increased to a predetermined pressure that enables fixing. Furthermore, the rotation of the shaft 45 causes the cleaning member 31 to rotate clockwise from the downstream separation position C2 to the upstream separation position C1. During this rotation, the cleaning member 31 comes into contact with the outer peripheral surface of the fixing belt 21. As shown in FIG. 6C, when the shaft 45 rotates to the maximum rotation position P2, the cleaning member 31 separates from the outer peripheral surface of the fixing belt 21.

[0045] In this way, the cleaning member 31 comes into contact with the rotating fixing belt 21. Because the rotation speed of the cleaning member 31 is slower than that of the fixing belt 21, the fixing belt 21 rotates at least one revolution while the cleaning member 31 is in contact with the fixing belt 21. As a result, the outer circumferential surface of the cleaning member 31 (contact portion 63) is rubbed by the cleaning member 31, and paper dust and the like adhering to the edge is removed. Furthermore, the rotation direction of the fixing belt 21 and the rotation direction of the cleaning member 31 are the same, but are opposite directions in the contact area between the two. This increases the effectiveness of removing paper dust in the contact area.

[0046] During the image forming operation, the shaft 45 is maintained at the reference position P1 (see FIG. 6C), and a predetermined pressure is applied to the pressure region N. The cleaning member 31 rotates to the upstream separation position C1 and is separated from the outer peripheral surface of the fixing belt 21.

[0047] If a paper jam occurs during image formation, shaft 45 rotates counterclockwise from reference position P1 (see FIG. 6C) to maximum rotation position P2 (see FIG. 6A). As a result, fixing belt 21 moves away from pressure roller 27, and pressure in pressure area N is reduced from a predetermined pressure. This makes it easier to remove the jammed paper in pressure area N.

[0048] Furthermore, the rotation of the shaft 45 moves the cleaning member 31 from the upstream separation position C1 to the downstream separation position C2. When a paper jam is detected, the rotation of the pressure roller 27 stops, and the rotation of the fixing belt 21 also stops. During rotation, the cleaning member 31 comes into contact with the stopped fixing belt 21.

[0049] When the paper jam is cleared and the image forming operation resumes, the pressure roller 27 is driven by the motor to rotate, and the fixing belt 21 rotates in response to the pressure roller 27. Furthermore, the motor is driven to rotate the shaft 45 clockwise from the maximum rotation position P2 (see FIG. 6A) to the reference position P1 (see FIG. 6C). This causes the fixing belt 21 to move closer to the pressure roller 27, increasing the pressure in the pressure region N. Furthermore, the rotation of the shaft 45 causes the cleaning member 31 to rotate from the downstream separation position C2 to the upstream separation position C1. During this rotation, the cleaning member 31 comes into contact with the outer peripheral surface of the rotating fixing belt 21 (see FIG. 6B). This causes the cleaning member 31 to rub against the edge of the outer peripheral surface of the fixing belt 21, removing paper dust and other particles adhering to the edge.

[0050] When the image forming operation is completed, the pressure roller 27 stops rotating, and the fixing belt 21 also stops rotating. Furthermore, the shaft 45 rotates counterclockwise from the reference position P1 to the maximum rotation position P2. This reduces the pressure in the pressure region N from a predetermined pressure. Furthermore, the cleaning member 31 rotates from the upstream separation position C1 to the downstream separation position C2. Because the fixing belt 21 is stopped from rotating, the cleaning member 31 comes into contact with the stopped fixing belt 21 during movement.

[0051] As described above, according to the fixing device 11 of the present invention, the cleaning member 31 is not in contact with the fixing belt 21 during the fixing operation, i.e., when the fixing belt 21 is rotating, and when the fixing device 11 is on standby. Therefore, no load is applied to the rotation of the fixing belt 21 during the fixing operation, and the fixing belt 21 can rotate smoothly. Furthermore, when replacing the fixing belt 21 during standby, the fixing belt 21 can be removed and installed without interfering with the cleaning member 31.

[0052] Furthermore, the contact time between the cleaning member 31 and the fixing belt 21 can be minimized during the cleaning operation of the fixing belt 21. Specifically, the cleaning operation is performed when the image forming operation (fixing operation) starts during standby or after clearing a paper jam. This reduces wear on the cleaning member 31 and the fixing belt 21 due to friction between them, thereby extending the lifespan of both.

[0053] Furthermore, the cleaning member 31 comes into contact with the upper half of the fixing belt 21. The upper half of the fixing belt 21 is not supported by the support member 25, and is a flexible portion maintained by the rigidity of the fixing belt itself, so the resistance generated when the cleaning member 31 comes into contact with the fixing belt 21 is small. Therefore, wear between the cleaning member 31 and the fixing belt 21 can be further reduced.

[0054] Furthermore, by rotating shaft 45 by approximately 180 degrees, the pressure in pressure region N is reduced from a predetermined pressure at which fixing can be performed. Also, the central angle of cleaning member 31 is approximately 45 degrees, and cleaning member 31 is fixed to shaft 45 between the maximum diameter portion and the minimum diameter portion of cam 43. This allows cleaning member 31 to reliably contact fixing belt 21 while the pressure in pressure region N is being changed.

[0055] Furthermore, in the above embodiment, the cleaning member 31 for the fixing belt 21 has been described, but the same cleaning member 31 may also be provided to clean the pressure roller 27 .

[0056] Furthermore, the above-mentioned description of the embodiments of the present invention describes preferred embodiments of the present invention, and therefore may include various technically preferable limitations, but the technical scope of the present invention is not limited to these aspects unless there is a description that specifically limits the present invention. [Explanation of symbols]

[0057] 1. Image forming device 9 Image forming unit 11 Fixing device 21 Fixing belt (fixing member) 23 Heater (heat source) 25 Support member 27 Pressure roller (pressure member) 29 Pressure change mechanism 31 Cleaning materials 41 Support plate 43 Cam 45 shaft

Claims

1. a rotatable fuser member heated by a heat source; a pressure member that forms a pressure region between the fixing member and the sheet of paper by applying heat and pressure to the sheet of paper onto which the toner image has been transferred, thereby fixing the toner image to the sheet of paper; a pressure change mechanism for changing the pressure in the pressurized region; a cleaning member that cleans an end portion of the fixing member in the width direction of the paper, The pressure change mechanism includes: a support plate supporting the fixing member and rotatably supported at one end, and a cam having a cam surface that abuts against the support plate, wherein when the shaft of the cam rotates in one direction or the other within a predetermined angle, the support plate is guided by the cam surface, and the fixing member moves in a direction approaching or moving away from the pressure member, thereby changing the pressure in the pressure region; The cleaning member is fixed rotatably integrally with the cam shaft, and cleans the end of the fixing member by contacting the end while rotating in one direction and the other direction within the specified angle around the cam shaft when the pressure in the pressure region is changed.

2. 2. The fixing device according to claim 1, wherein the fixing member is rotating while the cleaning member is in contact with the end portion of the fixing member.

3. 3. The fixing device according to claim 2, wherein the cleaning member contacts an end of the fixing member when the pressure in the pressure region is increased from a state where the pressure is reduced below a predetermined pressure capable of fixing a toner image to paper to the predetermined pressure.

4. the fixing member is a flexible endless fixing belt, a support member that supports the fixing belt from the inside, 2. The fixing device according to claim 1, wherein the cleaning member comes into contact with a portion of the fixing belt that is not supported by the support member.

5. The predetermined angle is 180 degrees, 2. The fixing device according to claim 1, wherein the cleaning member has a fan-shaped configuration with a central angle of 45 degrees around the cam shaft, and is fixed to the cam shaft between the maximum diameter portion and the minimum diameter portion of the cam.

6. an image forming unit that transfers a toner image onto a sheet; a fixing device according to claim 1 that fixes the toner image transferred by the image forming unit onto a sheet of paper; An image forming apparatus comprising:

Images