Fixing apparatus and image forming apparatus

Abstract

Thoroughly clean the fixing member in the longitudinal direction. [Solution] The fuser 8 of the image forming apparatus 1 is provided with a fuser belt 28 extending in the longitudinal direction, a cleaning roller extending in the left-right direction and contacting the fuser belt 28 for cleaning, an opposing member 52 extending in the left-right direction and facing the cleaning roller in the cleaning roller contact-to-contact direction Dc with the fuser belt 28 in between, forming a cleaning nip portion NP2 with the cleaning roller 50, and a fuser frame 30 that supports the opposing member 52. When the opposing member 52 and the fuser frame 30 are removed from the fuser 8, the opposing member 52 is restricted from moving in the left-right direction relative to the fuser frame 30, while being supported to be movable in the cleaning roller contact-to-contact direction Dc.

Description

Technical Field

[0001] The present invention relates to a fixing device and an image forming apparatus, and is suitable for application to, for example, an electrophotographic printer.

Background Art

[0002] Conventionally, as an image forming apparatus (also called a printer), based on image data supplied from a computer device or the like, a developer image is formed by an image forming unit using toner (also called a developer), transferred to a medium such as paper, and heat and pressure are applied thereto in a fixing device to fix it, whereby a printing process is widely performed. In the fixing device, for example, a planar heater is used to achieve quick start or energy saving, and a belt member may be adopted for the fixing member. Conventionally, a fixing device provided with a cleaning member is also known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As such a fixing device, it is required to sufficiently clean the fixing member in the longitudinal direction.

[0005] The present invention has been made in consideration of the above points, and intends to propose a fixing device and an image forming apparatus capable of sufficiently cleaning a fixing member in the longitudinal direction.

Means for Solving the Problems

[0006] To solve these problems, the fixing device of the present invention is provided with a belt member extending in a first direction, a cleaning member extending in the first direction and contacting the belt member for cleaning, an opposing member extending in the first direction and facing the cleaning member in a second direction across the belt member, forming a nip portion with the cleaning member, and a support member that supports the opposing member. When the opposing member and the support member are removed from the fixing device, the opposing member is supported by the support member so that its movement in the first direction is restricted, while its movement in the second direction is permitted.

[0007] Furthermore, the image forming apparatus of the present invention is provided with the fixing device described above.

[0008] The present invention prevents singularities from occurring in the longitudinal pressure distribution at the nip portion by moving the opposing member in a direction other than the longitudinal direction relative to the support member, even if a difference in thermal expansion coefficient occurs between the opposing member and the support member, while positioning the opposing member in the longitudinal direction relative to the support member. [Effects of the Invention]

[0009] According to the present invention, even if a difference in thermal expansion coefficient occurs between the opposing member and the support member, while positioning the opposing member in the longitudinal direction relative to the support member, it is possible to prevent singularities from occurring in the longitudinal pressure distribution at the nip portion by moving the opposing member in a direction other than the longitudinal direction relative to the support member. Thus, the present invention makes it possible to realize a fixing device and an image forming device that can thoroughly clean the fixing member in the longitudinal direction. [Brief explanation of the drawing]

[0010] [Figure 1] This is a left side view showing the configuration of an image forming apparatus. [Figure 2] This is a perspective view showing the configuration of the fuser unit (1). [Figure 3] Figure 2 shows a cross-sectional view taken along the line AA in Figure 2, illustrating the configuration of the fuser according to the first embodiment (1). [Figure 4]The configuration of the fuser according to the first embodiment (2) is shown, and is a partial cross-sectional view of the bearing in the direction of arrow BB in Figure 2. [Figure 5] This is a plan view showing the configuration (1) of the opposing member and fixing frame according to the first embodiment. [Figure 6] The configuration of the opposing member and fixing frame according to the first embodiment (2) is shown in the cross-sectional view taken along the arrow AA in Figure 5. [Figure 7] This is area A in Figure 3, and is an enlarged view showing only the cleaning roller, opposing member, and fixing frame. [Figure 8] This is a perspective view showing the configuration of the opposing members according to the first embodiment. [Figure 9] This is a plan view showing the configuration (3) of the fuser according to the first embodiment. [Figure 10] This is area A in Figure 3, and is an enlarged view showing only the flange, opposing member, and anchoring frame. [Figure 11] This is a rear view showing the crown shape of the refresh roller, cleaning roller, opposing member, and fixing frame. [Figure 12] This is a cross-sectional view showing the measurement of the crown amount of the opposing member. [Figure 13] This is a plan view showing the configuration (1) of the opposing member, fixing frame, and stepped screw according to the second embodiment. [Figure 14] The configuration of the opposing member, fixing frame, and stepped screw according to the second embodiment (2) is shown in the cross-sectional view taken along the arrow AA in Figure 13. [Figure 15] The configuration of the opposing member, fixing frame, and stepped screw according to the second embodiment (3) is shown in a cross-sectional view taken along the arrow BB in Figure 13. [Modes for carrying out the invention]

[0011] The embodiments for carrying out the invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

[0012] [1. First Embodiment] [1-1. Configuration of the Image Forming Apparatus] As shown in FIG. 1, the image forming apparatus 1 is a printer that uses, for example, an electrophotographic method, and forms a black-and-white image or a color image on a printing medium P such as paper by performing an image forming operation using a developer such as toner. Hereinafter, a position close to the paper feed cassette 3 as viewed from an arbitrary position on the conveyance path along which the printing medium P is conveyed, or a direction toward the paper feed cassette 3 is referred to as upstream. Also, a position close to the stacker 11 on which the discharged printing medium P is stacked as viewed from an arbitrary position on the conveyance path, or a direction toward the stacker 11 is referred to as downstream. Further, the direction from upstream to downstream is referred to as the conveyance direction. Further, hereinafter, the right end portion in FIG. 1 is taken as the front of the image forming apparatus 1, and the vertical direction, the left-right direction, and the front-back direction when viewed facing this front are defined and then described. The image forming apparatus 1 has a so-called direct transfer method, that is, a configuration in which a toner image as a developer image is directly transferred from a photoreceptor drum 20 (described later) of an image forming unit 14 (described later) to the printing medium P.

[0013] The image forming apparatus 1 is overall controlled by a print control unit (not shown). This print control unit has a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. not shown, and executes various processes by reading and executing a predetermined program. Also, the image forming apparatus 1 has a paper feed cassette 3, a hopping roller 4, a registration roller 5, a conveyance roller 6, an image forming unit 7, a fixing unit 8, and discharge rollers 9 and 10 inside a box-shaped housing 2.

[0014] The paper feed cassette 3 is arranged at the lower part of the housing 2 and accommodates a plurality of printing media P to be stacked. A hopping roller 4 is provided downstream of the paper feed cassette 3. The hopping roller 4 rotates while being in pressure contact with the surface of the printing medium P, and feeds out the printing medium P downstream along the conveyance path.

[0015] A registration roller 5 is provided downstream of the hopping roller 4. The registration roller 5 transports the printing medium P toward the transport roller 6. When the registration roller 5 transports the printing medium P, it corrects the skew of the printing medium P by abutting the leading edge of the printing medium P against it. A transport roller 6 is provided downstream of the registration roller 5. The transport roller 6 transports the printing medium P toward the image forming unit 7 located downstream. The image forming unit 7 transfers an image to the printing medium P and transports it to the fuser 8.

[0016] The fuser 8 applies heat and pressure to the toner image transferred onto the printing medium P, which has been transported from the transfer belt unit 16 of the image forming unit 7, thereby fixing the toner image onto the printing medium P, and also transports the printing medium P along the transport path toward the discharge roller 9.

[0017] A discharge roller 9 is provided downstream of the fuser 8. The discharge roller 9 transports the printing medium P toward a discharge roller 10 located downstream. The discharge roller 10 transports the printing medium P toward the stacker 11. As a result, the image forming apparatus 1 loads the printing medium P, on which the toner image has been fixed, into the stacker 11 located on the outside of the housing 2.

[0018] [1-2. Configuration of the Image Forming Unit] The image forming unit 7 is a mechanism that forms an image (toner image) and transfers that image to the printing medium P. This image forming unit 7 has four image forming units 14 (image forming units 14K, 14Y, 14M, and 14C), four LED heads 15 (LED heads 15K, 15Y, 15M, and 15C), and a transfer belt unit 16. The image forming units 14K, 14Y, 14M, and 14C are arranged in this order along the transport direction of the printing medium P. Hereinafter, the image forming units 14K, 14Y, 14M, and 14C will be collectively referred to as the image forming unit 14, and the LED heads 15K, 15Y, 15M, and 15C will be collectively referred to as the LED head 15.

[0019] The image forming unit 14 forms an image using toner, which is a developer, based on print data transmitted from a higher-level device such as a personal computer. The image forming units 14K, 14Y, 14M, and 14C form images in black, yellow, magenta, and cyan, respectively. The image forming units 14K, 14Y, 14M, and 14C have the same configuration except that they form images using toners of different colors. Each image forming unit 14 mainly includes a charging roller 19, a photosensitive drum 20, and a toner cartridge 21.

[0020] The photoreceptor drum 20 is a cylindrical component that carries an electrostatic latent image on its surface (surface layer), and is constructed using a photoreceptor (for example, an organic photoreceptor). This photoreceptor drum 20 rotates in direction a, which is clockwise in Figure 1, by power transmitted from a motor (not shown). The photoreceptor drum 20 is charged by a charging roller 19 and exposed by the corresponding LED head 15. As a result, an electrostatic latent image is formed on the surface of the photoreceptor drum 20. Then, toner is supplied from a developing roller (not shown), and a toner image corresponding to the electrostatic latent image is formed (developed) on the photoreceptor drum 20.

[0021] The toner cartridge 21 is configured to contain toner. Specifically, the toner cartridge 21 for each of the image forming units 14K, 14Y, 14M, and 14C contains black, yellow, magenta, and cyan toners, respectively.

[0022] The LED heads 15 (LED heads 15K, 15Y, 15M, and 15C) are mechanisms that irradiate light onto the photosensitive drums 20 of the image forming units 14K, 14Y, 14M, and 14C, respectively, and are constructed using LEDs (Light Emitting Diodes).

[0023] The transfer belt unit 16 is a mechanism that transfers the toner image formed on the surface of the photoreceptor drum 20 to the surface of the printing medium P by Coulomb force, and also transports the printing medium P in the transport direction b. This transfer belt unit 16 transports the printing medium P, on which the image has been transferred, toward the fuser 8. The transfer belt unit 16 has a transfer belt 22, a drive roller 23, a driven roller 24, and four transfer rollers (not shown).

[0024] The transfer belt 22 is a seamlessly formed annular belt capable of carrying the printing medium P. This transfer belt 22 is tensioned by a drive roller 23 and a driven roller 24. The drive roller 23 is a rotating member that rotates to transport the printing medium P toward the fuser 8 by power transmitted from a motor (not shown), and rotates the transfer belt 22 in a circulating manner. The driven roller 24 is a member that tensions the transfer belt 22 together with the drive roller 23 and adjusts the tension applied to the transfer belt 22.

[0025] A transfer roller (not shown) is a rotating member that transfers the toner image formed on the surface of the photoreceptor drum 20 of the corresponding image forming unit 14 onto the transfer surface of the printing medium P. Each transfer roller is positioned opposite the photoreceptor drum 20 of the image forming units 14K, 14Y, 14M, and 14C via a transfer belt 22. A predetermined transfer voltage is applied to each transfer roller, thereby transferring the toner image formed on the photoreceptor drum 20 by the image forming unit 14 onto the transfer surface of the printing medium P.

[0026] [1-3. Fuser Unit Configuration] As shown in Figures 2 and 3, the fuser 8 is broadly composed of a fuser belt 28 positioned above the transport path of the printing medium P and a pressure roller 29 positioned below the transport path. In addition to the fuser belt 28 and the pressure roller 29, the fuser 8 is also equipped with a main lever 38 (main levers 38L and 38R), flanges 40 (flanges 40L and 40R), sub-levers 42 (sub-levers 42L and 42R), springs 44 (springs 44L and 44R), bearings 46 (bearings 46L and 46R), a refresh roller 48, and a cleaning roller 50.

[0027] Incidentally, the fuser unit 8 is generally surrounded by a housing (not shown). This housing has holes and other features appropriately formed to allow the printing medium P to pass along the transport path. As shown in Figure 1, the central axis of the fuser belt 28 of the fuser unit 8 is positioned in front of the central axis of the pressure roller 29, but for the sake of explanation, in the following description, the central axis of the fuser belt 28 and the central axis of the pressure roller 29 of the fuser unit 8 will be described as being at the same position in the front-rear direction.

[0028] [1-3-1. Configuration of the fixing belt] The fixing belt 28 is an endless belt made of a tubular film composed of a flexible and heat-resistant material, and is formed in a substantially cylindrical shape with its central axis aligned in the left-right direction. This fixing belt 28 has a multi-layer structure in which a heat-resistant resin such as PI (polyimide) or a metal such as SUS (stainless steel) is used as the base material, and an elastic layer made of silicone rubber is superimposed on it, and a surface layer made of a fluororesin coating represented by PFA (perfluoroalkoxyalkane) or a tube made by processing these materials is superimposed on it. In addition, a sliding grease mainly composed of PFPE (perfluoropolyether) is applied to the inner circumferential surface of the fixing belt 28. The shape of this fixing belt 28 is maintained at both the left and right ends by flanges 40L and 40R. Inside the fixing belt 28, mainly a fixing frame 30, a heater holding member 32, a planar heater 34, a heat diffusion member 36, and an opposing member 52 are provided. This fixing belt 28 rotates along with the rotation of the pressure roller 29 and also transfers the heat from the planar heater 34 to the printing medium P.

[0029] [1-3-2. Configuration of the fixing frame] As shown in Figures 2, 3, and 7, the fixing frame 30 extends in the longitudinal direction, which is the left-right direction, and its cross-section has a shape like a capital English letter "U" rotated by 180° when viewed from the left side, and it holds the opposing member 52. That is, the fixing frame 30 has a recess that faces the heater holding member 32. This fixing frame 30 is made of galvanized steel plate, and both left and right ends are fixed to the main levers 38L and 38R. The fixing frame 30 is also biased toward the pressure roller 29 via the main levers 38L and 38R by a pressure means (not shown).

[0030] The fixing frame 30 is broadly composed of an upper fixing frame plate 30U and a fixing frame wall plate 30W, with an opening formed at its lower end. The upper fixing frame plate 30U is a plate-like member that extends in the longitudinal direction (left-right direction) and is thin in the vertical direction with a constant thickness. The upper surface of the upper fixing frame plate 30U, the fixing frame upper surface 30UUS, and the lower surface of the upper fixing frame plate 30U, the fixing frame lower surface 30UDS, are planar in shape. The planar width WF, which is the width in the longitudinal direction (left-right direction) on which the upper fixing frame surface 30UUS and the outer surface 30WS of the fixing frame wall plate (described later) are formed, is wider than the paper width WP, which is the width in the left-right direction for borderless printing that the image forming apparatus 1 supports, as shown in Figure 9. Hereafter, the direction perpendicular to the upper fixing frame plate 30U will also be called the upper plate orthogonal direction D1 (Figure 7).

[0031] The anchoring frame wall panel 30W extends downward from both sides of the upper anchoring frame panel 30U in the front-rear direction (only the rear anchoring frame wall panel 30W is shown in Figure 7) perpendicular to the upper anchoring frame panel 30U. It is a plate-like member that is long and narrow in the left-right direction, thin in the front-rear direction, and has a constant thickness. The rear side surface of the rear anchoring frame wall panel 30W, which is the outer surface surface 30WS of the rear anchoring frame wall panel 30W, and the front side surface of the front anchoring frame wall panel 30W, which is the outer surface surface 30WS of the front anchoring frame wall panel 30W (not shown in Figure 7), are planar in shape. Hereinafter, the direction perpendicular to the anchoring frame wall panel 30W will also be called the wall panel orthogonal direction D2. The wall panel orthogonal direction D2 is perpendicular to the top panel orthogonal direction D1.

[0032] A bent portion 30B is formed at the connection point between the upper fixing frame plate 30U and the rear and front fixing frame wall plates 30W. The rear upper surface of the bent portion 30B has a curved shape.

[0033] In the upper plate 30U of the fixing frame, a hook locking hole 30UA1 (Figures 4 and 5) is formed at the same location as the hook portion 52HF (described later) of the opposing member 52 in the front-rear, left-right, and right directions, penetrating from the upper surface 30UUS of the fixing frame to the lower surface 30UDS of the fixing frame.

[0034] On the upper surface 30UUS of the fixing frame, a roughly cylindrical projection 30P protrudes upward from the same location as the positioning hole 52BA (described later) of the opposing member 52 in the front-rear, left-right, and right directions. The outer diameter of this projection 30P is approximately the same as the width in the left-right direction of the positioning hole 52BA of the opposing member 52, and is shorter than the length in the front-rear direction of the positioning hole 52BA.

[0035] [1-3-3. Configuration of the heater holding member] As shown in Figure 3, the heater holding member 32 is fixed to the fixing frame 30, and a portion of it fits into a recess in the fixing frame 30 on the underside of the fixing frame 30. This heater holding member 32 is made of heat-resistant sliding resin and holds the heat diffusion member 36 and the planar heater 34.

[0036] [1-3-4. Configuration of a planar heater] As shown in Figures 2 and 3, the planar heater 34 is a thin, plate-shaped planar heating element that extends in the longitudinal direction (left-right) and is thin in the vertical direction. A heating pattern is formed on a stainless steel (SUS) substrate, and the heating pattern is protected by a glass coating. This planar heater 34 generates only the amount of heat necessary for the fixing operation by power supply means and control means (not shown).

[0037] [1-3-5. Configuration of the heat diffusion member] As shown in Figure 3, the heat diffusion member 36 is a substantially flat plate that extends horizontally along the planar heater 34 and is held by the heater holding member 32. Its upper surface is in contact with the lower surface of the planar heater 34, and its lower surface is in contact with the inner circumferential surface of the fixing belt 28. This heat diffusion member 36 is made of a metal such as SUS (stainless steel) and is a metal plate with high thermal conductivity. The cross-section of the heat diffusion member 36 is shaped like the capital letter "U," and both the front and rear ends are bent upwards in the vertical direction, which is the thickness direction. In other words, the heat diffusion member 36 has a recess facing the planar heater 34. Due to the properties of the metal material, the heat diffusion member 36 efficiently transfers heat, diffusing the heat emitted by the planar heater 34 evenly in the longitudinal direction, reducing uneven heating, and conducting heat to the fixing belt 28.

[0038] [1-3-6. Composition of the pressure roller] On the other hand, the pressure roller 29 is formed in a cylindrical shape with its central axis aligned in the left-right direction, and has a multi-layered structure in which an elastic layer and a PFA tube layer are superimposed on a hollow metal core. This pressure roller 29 is rotatably supported by a support member (not shown). As a result, in the fuser 8, the fuser belt 28 is pressed against the pressure roller 29, and a fuser nip NP1 is formed between them, which holds the printing medium P conveyed from the transfer belt 22 (Figure 1). This pressure roller 29 rotates by a driving means (not shown), and moves the fuser belt 28 along with it.

[0039] [1-3-7. Main Lever Configuration] As shown in Figures 2 and 3, the main levers 38L and 38R are provided on the left and right sides, respectively, which are outward in the left-right direction relative to the fixing belt 28. The main lever 38R is made of galvanized steel and is configured to rotate around a main lever pivot point 38F located at its front-down end. The main levers 38L and 38R are biased by a pressurizing means (not shown) in the main lever pressurizing direction Dm, which is counterclockwise in Figure 3, with the main lever pivot point 38F as the pivot point. As a result, the main levers 38L and 38R bias the fixing belt 28 toward the pressurizing roller 29 via the fixing frame 30.

[0040] [1-3-8. Flange Configuration] As shown in Figure 2, flanges 40L and 40R are fastened to main levers 38L and 38R with screws on the inside in the left-right direction relative to the main levers 38L and 38R, respectively. These flanges 40L and 40R are made of heat-resistant sliding resin and are provided on both the left and right outer sides relative to the fixing belt 28. As shown in Figure 10, only flange 40R has a belt support portion 40H protruding inward on both sides, and the shape of the fixing belt 28 is restricted by bringing the outer circumferential surface of the belt support portion 40H into contact with the inner circumferential surface of the fixing belt 28. The outer circumferential surface of the belt support portion 40H on flange 40R is almost identical to the right end of the nip surface 52NTS1 (described later) of the opposing member 52 when viewed from the left side, resulting in a state of surface alignment. Since flange 40L is configured symmetrically with flange 40R, its explanation will be omitted. However, the outer surface of the belt support portion 40H on flange 40L is almost identical to the left end of the nip surface 52NTS1 (described later) of the opposing member 52 when viewed from the left side, resulting in a state of surface alignment.

[0041] [1-3-9. Sub-lever configuration] As shown in Figures 2 and 3, the sub-levers 42L and 42R are rotatably held by the main levers 38L and 38R, respectively, on the inside in the left-right direction relative to the main levers 38L and 38R, with the sub-lever rotation pivot point 42F on the main levers 38L and 38R as the pivot point. These sub-levers 42L and 42R are made of galvanized steel plates and are biased by springs 44L and 44R, respectively, in the sub-lever pressurizing direction Ds, which is the clockwise direction in Figure 3, with the sub-lever rotation pivot point 42F as the pivot point. Therefore, in the fuser 8, when the opposing portion 52N (described later) of the opposing member 52 is pressed against the cleaning roller 50 via the fuser belt 28, the sub-levers 42L and 42R press the cleaning roller 50 against the fuser belt 28 in the cleaning roller biasing direction Dp along the cleaning roller contact / disconnection direction Dc shown in Figure 7 via the bearings 46L and 46R and the refresh roller 48, forming a cleaning nip portion NP2 (Figure 3) between the opposing member 52 and the cleaning roller 50. The cleaning roller contact / disconnection direction Dc is inclined at approximately 45° with respect to the direction D1 perpendicular to the top plate and the direction D2 perpendicular to the wall plate, and is a downward-sloping direction inclined at approximately 45° with respect to the direction D2 perpendicular to the wall plate.

[0042] [1-3-10. Bearing Configuration] As shown in Figures 2 and 3, bearings 46L and 46R are fixed to sub-levers 42L and 42R, respectively, and rotatably hold the refresh roller 48 on the rear-upward side relative to the fixing belt 28. These bearings 46L and 46R are made of heat-resistant sliding resin, and as shown in Figure 4, they hold the cleaning roller 50 so that it can move in the cleaning roller's moving-away direction Dc, while restricting the circumferential movement of the fixing belt 28. Bearing 46L is configured symmetrically with bearing 46R, so its description is omitted.

[0043] [1-3-11. Refresh Roller Configuration] The refresh roller 48 is formed in a cylindrical shape with its central axis aligned in the left-right direction, positioned on the rear-upper side relative to the fixing belt 28, and is made of a solid metal such as SUS (stainless steel). The refresh roller 48 also has a centrally convex crown shape, which is curved as a whole so that the central part in the left-right direction bulges outwards (details will be described later). Fine grooves (cutting marks) are engraved along the circumferential direction on the circumferential surface of the refresh roller 48, and it rotates while contacting the circumferential surface of the cleaning roller 50, causing the toner on the cleaning roller 50 to adhere to the circumferential surface and be collected.

[0044] [1-3-12. Cleaning Roller Configuration] The cleaning roller 50 is formed in a cylindrical shape with its central axis aligned in the left-right direction, and is positioned between the refresh roller 48 and the fuser belt 28. It has a multi-layered structure in which an elastic layer made of silicone rubber is superimposed on a metal core made of SUS (stainless steel). The cleaning roller 50 is also straight, with the same diameter from one end to the other in the left-right direction. This cleaning roller 50 rotates while contacting the outer surface of the fuser belt 28, and collects the toner on the fuser belt 28 by adhering it to the outer surface.

[0045] [1-3-13. Configuration and fixing method of opposing members] The opposing member 52 extends in the longitudinal direction, which is the left-right direction, and is positioned above the fixing frame 30 and fixed to the fixing frame 30. In this embodiment, the opposing member 52 is made of the same heat-resistant sliding resin as the flanges 40L and 40R, and supports the load of the cleaning roller 50 from inside the fixing belt 28, forming the cleaning nip portion NP2 (Figure 7). As shown in Figures 5, 6, 7, and 8, the opposing member 52 is broadly composed of a support portion 52H, an opposing portion 52N, and a slit 52S.

[0046] [1-3-13-1. Configuration of the fixing part] The support portion 52H is a plate-like member that extends in the longitudinal direction, which is the left-right direction, and is thin in the vertical direction, and has a flexible portion 52B, a hook portion 52HF, and a positioning hole portion 52BA formed therein, and is supported by the fixing frame 30.

[0047] The flexible portion 52B is formed approximately in the center of the longitudinal direction of the support portion 52H. The flexible portion 52B has gaps between it and the support portion 52H on its front, rear, and left sides, and is connected to the support portion 52H only on its right side. This allows the left end to flex so that it moves up and down with the right end as the pivot point. The gap behind the flexible portion 52B also functions as a slit 52S.

[0048] A positioning hole 52BA is formed slightly to the left of the flexible portion 52B, and approximately in the center of the support portion 52H in the left-right direction. The positioning hole 52BA is an elongated hole that extends linearly along the front-rear direction, which is the shorter direction, and penetrates from the top surface to the bottom surface of the support portion 52H.

[0049] The ejected part 30P of the fixing frame 30 is fitted into the positioning hole 52BA. The width of the positioning hole 52BA in the left-right direction is approximately the same as the outer diameter of the ejected part 30P, and the length in the front-back direction is longer than the outer diameter of the ejected part 30P. Therefore, when the ejected part 30P is fitted into the positioning hole 52BA, no gap is formed between the left end of the ejected part 30P and the left end of the positioning hole 52BA, and no gap is formed between the right end of the ejected part 30P and the right end of the positioning hole 52BA. On the other hand, when the ejected part 30P of the fixing frame 30 is fitted into the positioning hole 52BA, for example in the center in the front-back direction, gaps are formed between the front end of the ejected part 30P and the front end of the positioning hole 52BA, and between the rear end of the ejected part 30P and the rear end of the positioning hole 52BA. Therefore, the ejected part 30P of the fixing frame 30 is fitted into the positioning hole 52BA so that it cannot move in the left-right direction but can move in the front-back direction. As a result, the opposing member 52 is positioned relative to the fixing frame 30 so as not to move in the longitudinal direction, while being fixed in a state that allows for some degree of play in the short direction within the front-to-back range of the positioning hole 52BA.

[0050] The hook portion 52HF is located on the lower surface of the support portion 52H, in the front-to-back direction, at the center of the support portion 52H, and protruding downward from the right side of the right end of the flexible portion 52B in the left-to-right direction. The hook portion 52HF has a shape like the capital letter "L" rotated 90° counterclockwise in Figure 6, and is formed of a hook portion hole through portion 52HF1 extending downward from the lower surface of the support portion 52H, and a hook portion locking portion 52HF2 extending from the hook portion hole through portion 52HF1, bending at a right angle to the left.

[0051] The opposing member 52 is fixed to the fixing frame 30 by the hook portion 52HF sandwiching the upper plate 30U of the fixing frame 30, with the hook portion 52HF inserted into the hook locking hole portion 30UA1 of the fixing frame 30, the hook portion hole penetration portion 52HF1 reaching below the hook locking hole portion 30UA1 of the fixing frame 30, and the left end of the hook portion locking portion 52HF2 reaching to the left of the hook locking hole portion 30UA1.

[0052] The vertical length between the lower surface of the support portion 52H and the upper end of the hook portion locking portion 52HF2 is greater than the thickness of the upper plate 30U of the fixing frame. Therefore, there is a certain amount of space between the upper end of the left tip of the hook portion locking portion 52HF2 and the lower surface 30UDS of the fixing frame. For this reason, the opposing member 52 is fixed to the fixing frame 30 in a manner that allows for a certain amount of vertical play, so as not to come off due to impact when the transport or cleaning nip portion NP2 is not in a nip state.

[0053] In this configuration, during the assembly of the fuser 8, the opposing member 52 moves downward from the upper side of the fuser frame 30, the hook portion 52HF is inserted into the hook locking hole portion 30UA1, and slides to the left. At this time, the flexible portion 52B flexes so that its left end moves upward with its right end as the pivot point, thereby overcoming the projectile 30P. When the positioning hole portion 52BA reaches the projectile 30P, the flexible portion 52B returns to its original shape so that its left end moves downward with its right end as the pivot point, causing the projectile 30P to fit into the positioning hole portion 52BA. At this time, the left end of the hook locking portion 52HF2 reaches to the left of the hook locking hole portion 30UA1, and the opposing member 52 is fixed to the fuser frame 30.

[0054] [1-3-13-2. Configuration of the opposing section] The opposing portion 52N is a plate-shaped member that extends in the longitudinal direction, which is the left-right direction, and has front and rear plates 52NH, an inclined plate 52NT, and upper and lower plates 52NV, and faces the cleaning roller 50.

[0055] The front and rear plates 52NH extend from the upper side of the rear end of the support portion 52H toward the rear in the front-rear direction to the rear end of the upper fixing frame plate 30U (the front end of the bent portion 30B). At the lower front end surface of the front plate 52NH, a planar front and rear plate lower surface 52NHS is formed parallel to the upper fixing frame surface 30UUS of the fixing frame 30, and the front and rear plate lower surface 52NHS is in contact with the upper fixing frame surface 30UUS without any gaps. The front and rear plate lower surface 52NHS is parallel to the direction D2 perpendicular to the wall plate.

[0056] The inclined plate 52NT extends from the rear end of the front and rear plates 52NH in a downward-rear direction, bent at approximately 45°, and extends in the vertical direction to the upper end of the fixing frame wall plate 30W (the lower end of the bent portion 30B). The inclined plate 52NT has a nip surface 52NTS1 formed on its upper rear side and a non-contact surface 52NTS2 formed on its lower front side. The nip surface 52NTS1 has a curved shape that protrudes upward-rear in cross-section and faces the cleaning roller 50 via the fixing belt 28 at the cleaning nip portion NP2. The non-contact surface 52NTS2 has a planar shape from one end to the other in the longitudinal direction and faces the bent portion 30B of the fixing frame 30 with a gap between them.

[0057] The upper and lower plates 52NV extend downward from the lower end of the inclined plate 52NT, bent at approximately 45°. On the front side, the upper and lower plates 52NV have a planar rear surface 52NVS that is parallel to the outer surface 30WS of the fixing frame wall plate of the fixing frame 30, and the rear surface 52NVS of the upper and lower plates abuts against the outer surface 30WS of the fixing frame wall plate without any gaps. The rear surface 52NVS of the upper and lower plates is parallel to the direction D1 perpendicular to the upper plate.

[0058] In this manner, the opposing member 52 brings the lower surfaces 52NHS of the front and rear plates and the rear surfaces 52NVS of the upper and lower plates into contact with the fixing frame 30. The width of the planar portion WF (Figure 9), which is the width in the longitudinal direction (left-right direction) where the lower surfaces 52NHS of the front and rear plates and the rear surfaces 52NVS of the upper and lower plates are formed, is wider than the paper width WP described above.

[0059] On the other hand, the fixing frame 30 and the opposing member 52 are separated from each other in the bent portion 30B, which is located between the lower surfaces 52NHS of the front and rear plates and the rear surfaces 52NVS of the upper and lower plates. In other words, the fixing frame 30 and the opposing member 52 form a gap in the bent portion 30B, which is located between the lower surfaces 52NHS of the front and rear plates and the rear surfaces 52NVS of the upper and lower plates. Furthermore, a straight line L1 extending parallel to the cleaning roller biasing direction Dp from the rotation axis of the cleaning roller 50 intersects with the bent portion 30B, which is the region where the fixing frame 30 and the opposing member 52 are separated, as described above.

[0060] [1-3-13-3. Slit Configuration] Five slits 52S are formed at the connection point between the support portion 52H and the opposing portion 52N, extending in the left-right direction and penetrating from the top surface to the bottom surface of the support portion 52H. As a result, the cross-sectional area (also called the contact cross-sectional area) of the connection portion between the support portion 52H and the opposing portion 52N is smaller when viewed in a vertical section extending in the left-right direction compared to a case where the slits 52S are not provided.

[0061] [1-3-14. Regarding the crown shape of each component] Figure 11 schematically shows the crown shapes of each component involved in the cleaning operation using thick lines. Here, the term "crown shape" originally refers to a shape in which the overall outer shape is curved such that the diameter of the central part in the longitudinal direction of a cylindrical component is longer than the diameters of both ends, or a shape in which the overall outer shape is curved such that the diameter of the central part in the longitudinal direction of a cylindrical component is shorter than the diameters of both ends. However, in this embodiment, the term "crown shape" is not limited to cylindrical components, but also refers to a shape in which the overall part of a component (e.g., the lower end) is curved such that the central part in the longitudinal direction of a part of the component (e.g., the lower end) protrudes downward more than the ends. In reality, the opposing component 52, cleaning roller 50, and refresh roller 48 are arranged along a straight line of approximately 45° in the rear-upward direction relative to the fixing frame 30, but in Figure 11, for convenience, the way in which force is applied in the vertical direction and the crown shape are shown, especially for the opposing component 52 and the fixing frame 30.

[0062] The fixing frame 30 is pressurized downwards toward the pressure roller 29 by the main levers 38L and 38R at both ends in the left-right direction. Therefore, the fixing frame 30 has a downward-convex crown shape, where the lower end of the fixing frame wall plate 30W is curved downwards so that the central part in the left-right direction protrudes downwards. This compensates for the pressure in the central part in the left-right direction where pressure tends to escape, and makes the pressure uniform across the left-right direction.

[0063] The downwardly convex crown shape of the fixing frame 30 deforms into a straight shape during nipping at the fixing nip portion NP1. However, the upper part of the fixing frame 30 that contacts the opposing member 52 becomes an upwardly convex crown shape, with the upper part curving upward so that the central part in the left-right direction protrudes upward. As a result, the opposing member 52 receives a force from the fixing frame 30 that causes the upper part to curve, with the central part in the left-right direction protruding upward. The opposing member 52 takes this upward protrusion of the central part on the upper side of the fixing frame 30 into account, and the thickness of the central part in the left-right direction of the nip surface 52NTS1 is reduced, resulting in an upwardly concave crown shape, with the upper part curving downward so that the central part in the left-right direction is concave.

[0064] The cleaning roller 50 is sandwiched between the opposing member 52 and the refresh roller 48. If it were crown-shaped, the pressure on either the opposing member 52 or the refresh roller 48 would be lost, so it has a straight shape. The refresh roller 48 is pressurized toward the cleaning roller 50 at both ends in the left-right direction by the sub-levers 42L and 42R. For this reason, the refresh roller 48 has a crown shape with a central convex curve, where the central part in the left-right direction bulges outwards, thereby compensating for the pressure in the central part in the left-right direction where pressure tends to escape easily, and making the pressure uniform across the left-right direction.

[0065] [1-3-15. Regarding the measurement method of crown shape] The crown shape of such an opposing member 52 is determined by sandwiching the inclined plate 52NT of the opposing portion 52N between the spindle 54S and the anvil 54A of the micrometer 54, as shown in Figure 12, and measuring the thickness of the inclined plate 52NT of the opposing portion 52N of the opposing member 52 at a predetermined location along the longitudinal direction, thereby measuring the crown amount. The thickness of the inclined plate 52NT is the thickness from the nip surface 52NTS1 to the non-contact surface 52NTS2.

[0066] Here, the non-contact surface 52NTS2 has a planar shape without irregularities from one end to the other in the longitudinal direction. Therefore, the opposing member 52 can measure the crown amount without being affected by the longitudinal curvature of the opposing member 52. This makes it easier for the image forming apparatus 1 to control the distribution of nip pressure from one end to the other in the longitudinal direction of the cleaning nip section NP2 during mass production.

[0067] However, in Figure 12, the width from the top to the bottom of the non-contact surface 52NTS2 is too narrow for the spindle 54S of the micrometer 54 to fit, so a narrow gauge block 56 is sandwiched between the non-contact surface 52NTS2 and the spindle 54S.

[0068] [1-4. Fuser Cleaning Operation] In this configuration, during the printing operation of the image forming apparatus 1, when the printing medium P carrying unfixed toner passes through the fixing nip section NP1 and the unfixed toner is fixed to the printing medium P, a portion of the unfixed toner, particularly that resting on the left and right edges of the printing medium P, adheres to the fixing belt 28. If there is no cleaning roller 50, when the next printing medium P passes through the fixing nip section NP1, a portion of the unfixed toner attached to the fixing belt 28 adheres to the printing medium P, resulting in staining on the printing medium P.

[0069] On the other hand, in the case of an image forming apparatus 1 with a cleaning roller 50, when the fuser belt 28 passes the cleaning nip NP2, unfixed toner adheres from the fuser belt 28 to the cleaning roller 50 and is removed from the fuser belt 28 (hereinafter referred to as the cleaning action). The toner that adheres from the fuser belt 28 to the cleaning roller 50 moves from the cleaning roller 50 to the refresh roller 48 when the cleaning roller 50 passes the nip with the refresh roller 48, thus keeping the surface of the cleaning roller 50 clean. Incidentally, the toner on the refresh roller 48 remains without being collected until the end of the fuser unit 8's lifespan.

[0070] However, this cleaning action is limited to areas where a certain level of nip pressure is applied between the cleaning roller 50 and the fixing belt 28 in the longitudinal direction. Therefore, if the nip pressure becomes weaker than specified (also called pressure loss) for various reasons, such as the axial shape of the cleaning roller 50 being uneven or bent, the cleaning action will not work in the area where the pressure loss occurs, and unfixed toner will remain on the fixing belt 28 and adhere to the next printing medium P, causing contamination of the printing medium P.

[0071] [1-5. Effects, etc.] In the above configuration, the image forming apparatus 1 positions the opposing portion 52N of the opposing member 52, which is located near the rear upper side of the bent portion 30B of the fixing frame 30 provided inside the fixing belt 28, opposite the cleaning roller 50 provided outside the fixing belt 28. In the nip state of the cleaning nip portion NP2, the cleaning roller 50 is biased in the cleaning roller biasing direction Dp, and the positional relationship is such that the opposing portion 52N receives the load from the cleaning roller 50. Specifically, the central axis of the cleaning roller 50 is located in a range between the direction extending upward from the upper fixing frame plate 30U of the fixing frame 30 toward the direction D1 perpendicular to the top plate, and the direction extending backward from the fixing frame wall plate 30W of the fixing frame 30 toward the direction D2 perpendicular to the wall plate, with respect to the bent portion 30B of the fixing frame 30.

[0072] Therefore, the force that the cleaning roller 50 applies to the opposing part 52N (i.e., the opposing member 52) in the cleaning nip portion NP2 in the cleaning roller biasing direction Dp, which is in the forward downward direction, includes a component of force acting downward toward the direction D1 perpendicular to the top plate and a component of force acting forward toward the direction D2 perpendicular to the wall plate.

[0073] Furthermore, the image forming apparatus 1 is configured to bring the fixing frame 30 into contact with the lower front and rear plate surfaces 52NHS, which serve as the first surface, and the rear upper and lower plate surfaces 52NVS, which serve as the second surface, of the opposing member 52, while separating the bent portion 30B located between the lower front and rear plate surfaces 52NHS and the rear upper and lower plate surfaces 52NVS from the opposing member 52.

[0074] Here, it is conceivable that the opposing member 52 could be fixed to the fixing frame 30 by fastening it with screws (i.e., screwing it in) so that it cannot move in any direction relative to the fixing frame 30, such as in the front-to-back, left-to-right, or up-to-down directions. However, in that case, the position of the opposing member 52 in the cleaning roller contact-to-contact direction Dc relative to the fixing frame 30 would be fixed, and the opposing member 52 would not be able to move in the cleaning roller contact-to-contact direction Dc relative to the fixing frame 30.

[0075] Therefore, in the cleaning nip section NP2, the nip pressure increases locally only at the screw-fastened portion in the longitudinal direction, causing a singularity in the distribution of nip pressure in the longitudinal direction. This can result in the nip pressure not changing smoothly from one end to the other in the longitudinal direction. In that case, the image forming apparatus 1 will be unable to collect the toner on the fixing belt 28 from one end to the other in the longitudinal direction as designed by the cleaning roller 50.

[0076] In contrast, the image forming apparatus 1, in the non-nip state, inserts the hook locking portion 52HF2 into the hook locking hole portion 30UA1 of the fixing frame 30 so that the opposing member 52 can rattle relative to the fixing frame 30 in the direction D1 perpendicular to the top plate, and fits the positioning hole portion 52BA into the projection 30P of the fixing frame 30 so that the opposing member 52 can rattle relative to the fixing frame 30 in the direction D2 perpendicular to the wall plate, but cannot move in the longitudinal direction, thereby fixing the opposing member 52 to the fixing frame 30 in a movable manner. As a result, in the non-nip state of the cleaning nip portion NP2, the opposing member 52 is positioned only in the longitudinal direction relative to the fixing frame 30, but is not positioned in any other direction, including the direction D1 perpendicular to the top plate and the direction D2 perpendicular to the wall plate, which are the directions in which it receives load from the cleaning roller 50, and is therefore movable. Thus, in the non-nip state of the cleaning nip portion NP2, the opposing member 52 is movable relative to the fixing frame 30 in the cleaning roller moving away direction Dc.

[0077] On the other hand, the image forming apparatus 1, in the nip state of the cleaning nip section NP2, biases the cleaning roller 50 toward the cleaning roller biasing direction Dp, and applies a load to the opposing section 52N by causing the lower front and rear plate surfaces 52NHS to abut against the upper surface 30UUS of the fixing frame, and the rear upper and lower plate surfaces 52NVS to abut against the outer surface 30WS of the fixing frame wall plate, thereby pressing the opposing member 52 against the fixing frame 30, and thereby positioning the opposing member 52 relative to the fixing frame 30 in the direction perpendicular to the upper plate D1 and the direction perpendicular to the wall plate D2 (i.e., the cleaning roller moving away direction Dc).

[0078] Thus, the image forming apparatus 1 is configured to allow the opposing member 52 to move relative to the fixing frame 30 in the cleaning roller contact / disconnection direction Dc when the cleaning nip section NP2 is in a non-nip state. Therefore, while the longitudinal direction of the opposing member 52 is positioned relative to the fixing frame 30, even if a difference in thermal expansion coefficient occurs between the resin opposing member 52 and the galvanized steel plate fixing frame 30, the image forming apparatus 1 can move the opposing member 52 in a direction other than the longitudinal direction, the cleaning roller contact / disconnection direction Dc, thereby preventing any physical interference between the opposing member 52 and the fixing frame 30. Thus, the image forming apparatus 1 can prevent singularities from occurring in the longitudinal pressure distribution in the cleaning nip section NP2, and can suppress deformation of the opposing member 52 and damage such as cracking due to the difference in thermal expansion coefficients. This allows the image forming apparatus 1 to smoothly change the nip pressure in the cleaning nip section NP2 from one end to the other in the longitudinal direction, preventing singularities from occurring in the distribution of nip pressure in the longitudinal direction. Thus, the image forming apparatus 1 obtains a smooth nip pressure distribution without singularities from one end to the other in the longitudinal direction, and the cleaning roller 50 can collect the toner on the fixing belt 28 from one end to the other in the longitudinal direction as designed.

[0079] Furthermore, since the image forming apparatus 1 fixes the opposing member 52 so that it can move relative to the fixing frame 30 in directions other than the longitudinal direction, when the cleaning nip portion NP2 is in the non-nip state, the opposing member 52 is not positioned relative to the fixing frame 30 in directions other than the longitudinal direction. However, the range in which the opposing member 52 can move relative to the fixing frame 30 is limited to the range in which the hook portion locking portion 52HF2 can wobble in the direction D1 perpendicular to the top plate, and limited to the range in which the positioning hole portion 52BA can wobble relative to the ejection 30P in the direction D2 perpendicular to the wall plate.

[0080] Therefore, the image forming apparatus 1 can prevent the opposing member 52 from detaching from the fixing frame 30 due to impacts during the release operation that changes the cleaning nip portion NP2 from a nipped state to a non-nipped state, or during the transport of the image forming apparatus 1. At the same time, when the cleaning nip portion NP2 is in a nipped state, the image forming apparatus 1 can return the position of the opposing member 52 relative to the fixing frame 30 to the correct position by pressing the cleaning roller 50 against the nip surface 52NTS1.

[0081] Furthermore, the image forming apparatus 1 positions the longitudinal position of the opposing member 52 relative to the fixing frame 30 using only a positioning hole 52BA and an ejection 30P located at only one location in the longitudinal direction. Therefore, compared to a case where the longitudinal position of the opposing member 52 relative to the fixing frame 30 is positioned at multiple locations in the longitudinal direction, the image forming apparatus 1 can suppress deformation and cracking of the opposing member 52 due to the difference in thermal expansion coefficients between the opposing member 52 and the fixing frame 30.

[0082] Furthermore, compared to the case where the opposing member 52 is fixed to the fixing frame 30 with screws (i.e., screwed in), the image forming apparatus 1 can prevent the screws from loosening due to heating and cooling, thereby extending its lifespan.

[0083] Furthermore, the image forming apparatus 1 is configured to bring the fixing frame 30 into contact with the lower front and rear plate surfaces 52NHS and the rear upper and lower plate surfaces 52NVS of the opposing member 52, and to separate the bending portion 30B located between the lower front and rear plate surfaces 52NHS and the rear upper and lower plate surfaces 52NVS from the opposing member 52. In addition, the image forming apparatus 1 is configured such that a straight line L1 along the cleaning roller's moving direction Dc from the rotation axis of the cleaning roller 50 passes through (i.e., intersects) the bending portion 30B, which is the point where the fixing frame 30 and the opposing member 52 are separated. As a result, even if the opposing member 52N receives a load from the cleaning roller 50 on the nip surface 52NTS1, the image forming apparatus 1 can maintain a non-contact state between the non-contact surface 52NTS2 on the back side of the nip surface 52NTS1 and the bending portion 30B of the fixing frame 30, and the lower front and rear plate surfaces 52NHS and the rear upper and lower plate surfaces 52NVS located on both sides of the bending portion 30B can be brought into contact with the fixing frame 30. This allows the image forming apparatus 1 to eliminate the influence of the bending portion 30B on the distribution of longitudinal nip pressure in the cleaning nip portion NP2.

[0084] Furthermore, the image forming apparatus 1 forms the longitudinal planar width WF of the upper surface 30UUS of the fixing frame, the outer surface 30WS of the fixing frame wall plate, the lower surfaces 52NHS of the front and rear plates, and the rear surfaces 52NVS of the upper and lower plates (Figure 9) over a wider area than the paper width WP, resulting in a planar shape without irregularities. As a result, the image forming apparatus 1 can smoothly change the nip pressure in the cleaning nip section NP2 from one end to the other in the longitudinal direction, and can prevent singularities from occurring in the distribution of nip pressure in the longitudinal direction.

[0085] Furthermore, the image forming apparatus 1 has a support portion 52H in which the opposing member 52 is supported by the fixing frame 30, and an opposing portion 52N in which the opposing member 52 faces the cleaning roller 50. A slit 52S is provided between the support portion 52H and the opposing portion 52N, extending in the left-right direction and penetrating from the top surface to the bottom surface of the support portion 52H. In this way, the image forming apparatus 1 separates the function of being supported by the fixing frame 30 and the function of facing the cleaning roller 50 in the opposing member 52, and the connection portion between the support portion 52H and the opposing portion 52N is provided with a slit 52S to reduce the cross-sectional area.

[0086] Therefore, although the opposing portion 52N of the opposing member 52 has a long, slender concave crown shape in the longitudinal direction and its wall thickness is uneven with respect to the central axis, making it prone to warping in the longitudinal direction during molding and shrinkage, the force required to correct the warping of the opposing portion 52N on the opposing member 52 due to the load of the cleaning roller 50 during nipping can be reduced, and the influence of the warping of the opposing portion 52N on the distribution of longitudinal nip pressure in the cleaning nip portion NP2 can be reduced.

[0087] Here, in the support portion 52H, the opposing member 52 is in contact with the fixing frame 30 over a wide area of ​​its lower surface, while in the opposing portion 52N, only the lower surfaces 52NHS of the front and rear plates and the rear surfaces 52NVS of the upper and lower plates are in contact with the fixing frame 30, avoiding the bent portion 30B. In contrast, the image forming apparatus 1 has a slit 52S at the connection point between the support portion 52H and the opposing portion 52N to reduce the cross-sectional area. As a result, the image forming apparatus 1 can prevent heat transferred from the fixing belt 28 to the opposing portion 52N from being transferred to the fixing frame 30 (i.e., it prevents heat from escaping), thus maintaining the quickness (speed of heating) which is an advantage of the fixing belt system.

[0088] Furthermore, the image forming apparatus 1 is configured to align the nip surface 52NTS1 of the opposing member 52 with the outer circumferential surface of the belt support portion 40H of the flanges 40L and 40R. As a result, the image forming apparatus 1 can minimize deformation of the fixing belt 28 during driving and maintain durability. In particular, it is preferable that the nip surfaces 52NTS1 at both the left and right ends, which are close to the outer circumferential surface of the belt support portion 40H, are aligned with the outer circumferential surface of the belt support portion 40H. The central part of the nip surface 52NTS1 in the longitudinal direction has a concave crown shape, so it is slightly concave than the ends in the longitudinal direction, but it is sufficient that the shape changes smoothly from the central part in the longitudinal direction to the ends.

[0089] With the above configuration, the fuser 8 of the image forming apparatus 1 is provided with a fuser belt 28 extending in the left-right direction (longitudinal direction) as a first direction, a cleaning roller 50 extending in the left-right direction and contacting the fuser belt 28 for cleaning, an opposing member 52 extending in the left-right direction and facing the cleaning roller 50 in the cleaning roller contact-away direction Dc as a second direction, with the fuser belt 28 in between, and forming a cleaning nip portion NP2 with the cleaning roller 50, and a fuser frame 30 that supports the opposing member 52. When the opposing member 52 and the fuser frame 30 are removed from the fuser 8, the opposing member 52 is restricted from moving in the left-right direction relative to the fuser frame 30, while being supported to move in the cleaning roller contact-away direction Dc.

[0090] As a result, the fuser 8 can position the opposing member 52 in the longitudinal direction relative to the fuser frame 30, and even if a difference in thermal expansion coefficient occurs between the opposing member 52 and the fuser frame 30, it can move the opposing member 52 in a direction other than the longitudinal direction relative to the fuser frame 30, namely the cleaning roller contact / return direction Dc, thereby preventing the occurrence of singularities in the longitudinal pressure distribution at the cleaning nip portion NP2.

[0091] [2. Second Embodiment] [2-1. Configuration of the image forming apparatus] As shown in Figure 1, the image forming apparatus 101 according to the second embodiment differs from the image forming apparatus 1 according to the first embodiment in that it has a fuser 108 instead of a fuser 8, but is otherwise configured similarly.

[0092] [2-2. Fuser Unit Configuration] As shown in Figure 2, the fuser 108 according to the second embodiment differs from the fuser 8 according to the first embodiment in that it has a fuser frame 130 instead of a fuser frame 30 and an opposing member 152 instead of an opposing member 52, but is otherwise configured similarly.

[0093] [2-2-1. Configuration of the fixing frame] As shown in Figures 13, 14, and 15, which use the same reference numerals as in Figure 5, the fixing frame 130 according to the second embodiment differs from the fixing frame 30 according to the first embodiment in that it has a fixing frame upper plate 130U instead of the fixing frame upper plate 30U, but is otherwise configured similarly. The fixing frame upper plate 130U according to the second embodiment differs from the fixing frame upper plate 30U according to the first embodiment in that the projection 30P and hook locking hole portion 30UA1 are omitted, and a positioning frame side hole portion 130UA2 is added, but is otherwise configured similarly.

[0094] The positioning frame side hole 130UA2 is formed so as to align its center with the front-to-back center of the positioning hole 52BA of the opposing member 152, approximately in the left-to-right center of the upper plate 130U of the fixing frame. This positioning frame side hole 130UA2 is a cylindrical round hole that penetrates from the upper surface 30UUS of the fixing frame to the lower surface 30UDS of the fixing frame, with a diameter shorter than the front-to-back length of the positioning hole 52BA and a diameter shorter than the cylindrical portion 60C of the stepped screw 60.

[0095] [2-2-2. Configuration of opposing members] The opposing member 152 according to the second embodiment differs from the opposing member 52 according to the first embodiment in that it has a support portion 152H instead of the support portion 52H, but is otherwise configured similarly. The support portion 152H according to the second embodiment differs from the support portion 52H according to the first embodiment in that the hook portion 52HF and the flexible portion 52B are omitted, but is otherwise configured similarly.

[0096] A positioning hole 52BA, similar to that in the first embodiment, is formed approximately in the center of the support portion 152H in the left-right direction. The positioning hole 52BA is an elongated hole that extends linearly along the front-rear direction, which is the shorter direction of the opposing member 152, and penetrates from the top surface to the bottom surface of the support portion 152H.

[0097] The opposing member 152 is fixed to the fixing frame 130 by inserting and fastening a stepped screw 60 into the positioning hole 52BA and the positioning frame side hole 130UA2 of the fixing frame upper plate 130U. The stepped screw 60 has a threaded portion 60S, a cylindrical portion 60C, and a head 60H formed from the bottom tip to the top. The threaded portion 60S has threads cut into its circumferential surface and is fastened to the positioning frame side hole 130UA2 of the fixing frame upper plate 130U.

[0098] The cylindrical portion 60C is fitted into the positioning hole 52BA. This cylindrical portion 60C has a diameter longer than the nominal diameter of the threaded portion 60S, and its outer diameter is approximately the same as the width in the left-right direction of the positioning hole 52BA of the opposing member 152, and shorter than the length in the front-rear direction of the positioning hole 52BA. Therefore, when the cylindrical portion 60C of the stepped thread 60 is fitted into the positioning hole 52BA, no gap is formed between the left end of the cylindrical portion 60C and the left end of the positioning hole 52BA, and between the right end of the cylindrical portion 60C and the right end of the positioning hole 52BA. On the other hand, when the cylindrical portion 60C of the anchoring frame 130 is fitted into, for example, the center in the front-rear direction of the positioning hole 52BA, gaps are formed between the front end of the cylindrical portion 60C and the front end of the positioning hole 52BA, and between the rear end of the cylindrical portion 60C and the rear end of the positioning hole 52BA. Therefore, the cylindrical portion 60C of the fixing frame 130 is fitted into the positioning hole 52BA so that it cannot move in the left-right direction but can move in the front-back direction. As a result, the opposing member 152 is positioned relative to the fixing frame 130 so that it cannot move in the longitudinal direction, while being fixed in a state that allows for some play in the short direction within the front-back range of the positioning hole 52BA.

[0099] The head portion 60H has an outer diameter longer than the width in the left-right direction and the length in the front-back direction of the positioning hole portion 52BA, and a tool hole for inserting a screwdriver or the like is formed on its upper surface. On the other hand, the cylindrical portion 60C has a diameter longer than the positioning frame side hole portion 130UA2, and its vertical length is longer than the vertical length (i.e., thickness) of the support portion 152H. Therefore, when the stepped screw 60 is fastened to the positioning frame side hole portion 130UA2, the lower surface of the cylindrical portion 60C comes into contact with the upper surface 30UUS of the fixing frame, restricting the downward movement of the stepped screw 60, and a certain amount of gap is formed between the head portion 60H and the upper surface of the support portion 152H. For this reason, the opposing member 152 is fixed to the fixing frame 130 in a state that allows for a certain amount of vertical play so as not to come off due to impact when the transport or cleaning nip portion NP2 is in a non-nip state.

[0100] [2-3. Effects, etc.] In this way, the fuser 108 is fastened to the upper plate 130U of the fuser frame by inserting stepped screws 60 into the positioning holes 52BA of the opposing member 152 and the positioning frame side holes 130UA2 of the upper plate 130U of the fuser frame, thereby fixing the opposing member 152 to the upper plate 130U of the fuser frame in a state where the cleaning nip portion NP2 is not nipped, allowing for some play in the front-to-back and up-and-down directions relative to the fuser frame 130. For this reason, the fuser 108 can be assembled without a portion of the opposing member 52 being bent, unlike the bending portion 52B of the fuser 8 in the first embodiment. This allows the fuser 108 to use materials for the opposing member 152 that have low toughness and are undesirable to bend during the assembly of the fuser 108. This is particularly useful when applying heat-resistant resin materials to the opposing member 152, as many heat-resistant resin materials are hard and brittle. Furthermore, even if there is no space above the opposing member 152 to allow it to bend during assembly of the fuser unit 108, the opposing member 152 can still be fixed to the fuser frame 130.

[0101] In other respects as well, the image forming apparatus 101 according to the second embodiment can achieve the same effects as the image forming apparatus 1 according to the first embodiment.

[0102] [3. Other Embodiments] In the first embodiment described above, the image forming apparatus 1 fixes the opposing member 52 to the fixing frame 30 so as to be movable in the direction D1 perpendicular to the top plate and the direction D2 perpendicular to the wall plate, and in the nip state of the cleaning nip section NP2, the cleaning roller 50 presses the opposing member 52 in the cleaning roller biasing direction Dp to position the opposing member 52 relative to the fixing frame 30 in the direction D1 perpendicular to the top plate and the direction D2 perpendicular to the wall plate. The present invention is not limited to this, and the image forming apparatus 1 may position the opposing member 52 relative to the fixing frame 30 in only one direction, either the direction D1 perpendicular to the top plate or the direction D2 perpendicular to the wall plate, with the cleaning roller 50 in the nip state of the cleaning nip section NP2, and position the opposing member 52 relative to the fixing frame 30 in only the other direction, either the direction D1 perpendicular to the top plate or the direction D2 perpendicular to the wall plate, with respect to the fixing frame 30, with respect to the cleaning roller 50. The same applies to the second embodiment.

[0103] Furthermore, in the first embodiment described above, the image forming apparatus 1 positioned the opposing member 52 in the longitudinal direction relative to the fixing frame 30 by fitting a positioning hole 52BA, provided in approximately the center of the longitudinal direction of the opposing member 52, into an ejection 30P of the fixing frame 30. The present invention is not limited to this, and the image forming apparatus 1 may also position the opposing member 52 in the longitudinal direction relative to the fixing frame 30 by fitting positioning holes 52BA, provided at various other locations in the longitudinal direction of the opposing member 52, into ejection 30P provided in the fixing frame 30 at positions corresponding to the positioning holes 52BA. The same applies to the second embodiment.

[0104] Furthermore, the above-described embodiment describes the application of the present invention to an image forming apparatus 1 or 101 in which a cylindrical cleaning roller 50 is brought into contact with the outer circumferential surface of the fixing belt 28 to collect toner on the fixing belt 28. The present invention is not limited to this, and may also be applied to an image forming apparatus in which a cleaning belt, which is an endless belt stretched over an internally provided roller, is brought into contact with the outer circumferential surface of the fixing belt to collect toner on the fixing belt.

[0105] Furthermore, in the first embodiment described above, the case in which the image forming apparatus 1 extends the slit 52S along the left-right direction was described. The present invention is not limited to this, and the image forming apparatus 1 may extend the slit 52S along a direction inclined with respect to the left-right direction. In short, the image forming apparatus 1 only needs to extend the slit 52S in a direction that includes a component in the left-right direction. The same applies to the second embodiment.

[0106] Furthermore, in the first embodiment described above, the image forming apparatus 1 may, in various other configurations, fix the opposing member 52 to the fixing frame 30 so as not to move in the longitudinal direction, while fixing it so as to be movable in the direction perpendicular to the top plate D1 and the direction perpendicular to the wall plate D2. The same applies to the second embodiment.

[0107] Furthermore, in the second embodiment described above, the image forming apparatus 101 is fixed to the fixing frame 130 so as to be movable in the direction D1 perpendicular to the top plate and the direction D2 perpendicular to the wall plate using a stepped screw 60. The present invention is not limited to this, and the image forming apparatus 101 may also fix to the fixing frame 130 so as to be movable in the direction D1 perpendicular to the top plate and the direction D2 perpendicular to the wall plate by using a normal screw that does not have a cylindrical portion 60C and using a spacer instead of the cylindrical portion 60C, or by providing a step on the upper surface 30UUS of the fixing frame that protrudes upward from around the cylindrical portion 60C.

[0108] Furthermore, the above-described embodiment describes the application of the present invention to an image forming apparatus 1 or 101 of a so-called direct transfer method, in which toner images are directly transferred from the photoreceptor drum 20 of the image forming unit 14 to the printing medium P. The present invention is not limited to this, and may also be applied to an image forming apparatus of a so-called intermediate transfer method (or secondary transfer method), in which toner images of each color are sequentially transferred from the photoreceptor drum 20 of the image forming unit 14 to an intermediate transfer belt, and the toner images are transferred from this intermediate transfer belt to the printing medium P.

[0109] Furthermore, the embodiments described above describe the application of the present invention to an image forming apparatus 1 or 101 using a one-component developing agent. The present invention is not limited to this, and may also be applied to an image forming apparatus using a two-component developing agent, which is a method of imparting an appropriate amount of charge to the toner by utilizing the friction between the carrier and the toner after mixing the carrier and the toner.

[0110] Furthermore, the above-described embodiment described the case in which the present invention is applied to an image forming apparatus 1 or 101 having four image forming units 14 and forming a color image using four toners. The present invention is not limited to this, and may also be applied to an image forming apparatus having three or fewer or five or more image forming units 14 and forming an image using a predetermined number of toners.

[0111] Furthermore, the above-described embodiments described the case in which the present invention is applied to an image forming apparatus 1 or 101, which is a single-function printer. The present invention is not limited to this, and may be applied to image forming apparatuses with various other functions, such as MFPs (Multi-Function Peripherals) that have the functions of a copier or a facsimile machine. The present invention may also be applied to various electronic devices that form images on a printing medium P such as paper using an electrophotographic method and a developer.

[0112] Furthermore, the present invention is not limited to the embodiments described above and other embodiments. That is, the scope of the present invention also extends to embodiments obtained by arbitrarily combining some or all of the embodiments described above and other embodiments. In addition, the scope of the present invention also extends to embodiments obtained by extracting a part of the configuration described in any embodiment from the embodiments described above and other embodiments and substituting or adapting it for a part of the configuration of any embodiment from the embodiments described above and other embodiments, or by adding a part of the extracted configuration to any embodiment.

[0113] Furthermore, in the first embodiment described above, we have described a case in which the fixing device 8 is configured with a fixing belt 28 as a belt member, a cleaning roller 50 as a cleaning member, an opposing member 52 as an opposing member, and a fixing frame 30 as a support member. The present invention is not limited to this, and the fixing device may be configured with a belt member, cleaning member, opposing member, and support member having various other configurations. [Industrial applicability]

[0114] This invention can be used when printing an image onto a medium using an electrophotographic image forming apparatus. [Explanation of Symbols]

[0115] 1, 101...Image forming apparatus, 2...Housing, 3...Paper feed cassette, 4...Hopping roller, 5...Registration roller, 6...Conveyor roller, 7...Image forming unit, 8, 108...Fuser, 9, 10...Discharge roller, 11...Stacker, 14...Image forming unit, 15...LED head, 16...Transfer belt unit, 19...Charging roller, 20...Photoconductor drum, 21...Toner cartridge, 22...Transfer belt, 23...Drive roller, 24...Driven roller, 28...Fuser belt, 29...Pressure roller, 30, 130...Fuser frame Frame, 30U, 130U... Upper side plate of the fixing frame, 30UUS... Top surface of the fixing frame, 30UDS... Bottom surface of the fixing frame, 30UA1... Hook locking hole, 130UA2... Positioning frame side hole, 30B... Bending part, 30W... Fixing frame wall plate, 30WS... Outer surface of the fixing frame wall plate, 30P... Embellishment, 32... Heater holding member, 34... Planar heater, 36... Heat diffusion member, 38L, 38R... Main lever, 38F... Main lever rotation pivot point, 40L, 40R... Flange, 40H... Belt support part, 42L, 42R... ...Sub-lever, 42F...Sub-lever pivot point, 44L, 44R...Spring, 46L, 46R...Bearing, 48...Refresh roller, 50...Cleaning roller, 52, 152...Opposite members, 52H, 152H...Support part, 52HF...Hook part, 52HF1...Hook part hole through part, 52HF2...Hook part locking part, 52B...Flexible part, 52BA...Positioning hole part, 52N...Opposite part, 52NH...Front and rear plates, 52NHS...Underside of front and rear plates, 52NT...Inclined plate, 52NTS1...Nip surface, 52NTS2...Non-contact surface 52NV...Upper and lower plates, 52NVS...Rear surface of upper and lower plates, 52S...Slit, 54...Micrometer, 54S...Spindle, 54A...Anvil, 56...Block gauge, Dm...Main lever pressurization direction, Ds...Sub lever pressurization direction, D1...Direction perpendicular to the upper plate, D2...Direction perpendicular to the wall plate, Dp...Cleaning roller biasing direction, Dc...Cleaning roller moving away / away direction, NP1...Fixing nip section, NP2...Cleaning nip section, 60...Stepped screw, 60S...Screw section, 60C...Cylindrical section, 60H...Head, P...Printing medium.

Claims

1. In a fixing device, A belt member extending in the first direction, A cleaning member extending in the first direction and contacting the belt member to clean it, An opposing member extending in the first direction, facing the cleaning member in the second direction with the belt member in between, and forming a nip portion with the cleaning member, Support member that supports the opposing member and It has, When the opposing member and the support member are removed from the fixing device, the opposing member is supported by the support member so as to be movable in the second direction, while its movement in the first direction is restricted. A fixing device characterized by the following features.

2. The opposing member is, When the opposing member and the support member are attached to the fixing device, the cleaning member pressurizes the nip portion and positions the support member in the second direction. The fixing device according to feature 1.

3. The aforementioned support member is It contacts the first and second surfaces of the opposing member, and is separated from the opposing member between the first and second surfaces. A straight line extending from the rotation axis of the cleaning member along the second direction intersects with the region where the support member and the opposing member are separated. The fixing device according to feature 1.

4. The hypothetical straight line along the first surface and the hypothetical straight line along the second surface intersect, The support member supports the opposing member so as to be movable in a direction parallel to the first surface, and also supports the opposing member so as to be movable in a direction parallel to the second surface. The fixing device according to feature 3.

5. The opposing member is, A hook that engages with the surface of the support member opposite to the surface that contacts the first surface, leaving a gap in a direction parallel to the second surface, The projection of the support member is movably fitted into an elongated hole that extends in a direction other than the first direction parallel to the first surface, and a flexible portion that bends in a direction parallel to the second surface. The fixing device according to claim 4, characterized by having the following features.

6. The opposing member is, Elongated holes extending in directions parallel to the first surface, other than the first direction. It has, With the screw head leaving a gap with respect to the surface of the opposing member opposite to the surface in contact with the support member in a direction parallel to the second surface, the screw is fitted into the elongated hole so as to be movable in a direction intersecting the first direction among the directions parallel to the first surface, from the head to the tip of the screw, and the opposing member is held by the support member. The fixing device according to feature 4.

7. The opposing member is, With respect to the support member, movement in the first direction is restricted at one location in the first direction. The fixing device according to feature 1.

8. The opposing member is, The system has a support portion supported by the support member and a facing portion facing the cleaning member, and a slit extending in the first direction between the support portion and the facing portion. The fixing device according to feature 1.

9. An image forming apparatus having a fixing device according to any one of claims 1 to 8.

Images