Fixing device

Abstract

To provide a configuration facilitating replacement operations of a fixing belt 301 in a miniaturized fixing device 8.SOLUTION: A steering roller 308 is movable to a first urging position where it urges a fixing belt 301 and a first urging release position where it does not urge the fixing belt 301. A lubricant supply roller 501 is movable to a second urging position where the lubricant supply roller 501 urges the fixing belt 301 while the steering roller 308 is located at the first urging position, and a second urging release position where it does not urge the fixing belt 301. A tapered part moves the lubricant supply roller 501 from the second urging position to the second urging release position in conjunction with the movement of the steering roller 308 from the first urging position to the first urging release position.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fixing device that heats a toner image carried on a recording material and fixes the toner image to the recording material. [Background technology]

[0002] Image forming devices such as copiers, printers, facsimiles, and multifunction devices having multiple functions of these include a fixing device that fixes a toner image carried on a recording material to the recording material. As a fixing device, a configuration in which a toner image on a recording material is heated and conveyed in a nip formed by an endless belt member and a rotating body has been conventionally known (Patent Document 1).

[0003] The fixing device described in Patent Document 1 forms a nip using a nip-forming member that sandwiches a belt member between itself and a rotating body. When a nip is formed using such a nip-forming member, it is known that the sliding resistance between the belt member and the nip-forming member increases at the nip, resulting in image defects and wear on the inner surface of the belt. For this reason, a configuration that reduces sliding resistance by disposing a lubricant supply roller inside the belt member and applying the lubricant to the inner surface of the belt member is widely adopted.

[0004] Furthermore, as a fixing device using a belt member, a configuration including a tension roller that contacts the inner peripheral surface of the belt member and applies tension to the belt member has also been known (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-195671 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-59964 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, in order to reduce running costs, there has been a demand for fixing devices that can be replaced individually, rather than replacing the entire fixing device or individual units (e.g., fixing belt units) inside the fixing device. For this reason, fixing devices that use the belt member described above are required to be able to replace the belt member individually.

[0007] When replacing a belt member, the tension applied to the belt member by the tension roller is released before replacement. Meanwhile, in recent years, there has been a demand for smaller fixing devices using belt members, and as fixing devices become smaller, the outer diameter of the belt member tends to become smaller. When the outer diameter of the belt member becomes smaller, even if the tension roller is retracted from the inner circumferential surface of the belt member to release the tension of the tension roller, the amount of retraction becomes smaller. As a result, it becomes difficult to ensure sufficient slack for attaching and detaching the belt member, making the replacement of the belt member more difficult.

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a structure that allows easy replacement of a belt member in a compact fixing device. [Means for solving the problem]

[0009] One aspect of the present invention is a fixing device that heats a toner image carried on a recording material and fixes it to the recording material, the fixing device comprising: an endless belt member; a rotating body that rotates in contact with the outer peripheral surface of the belt member; a nip portion forming member that is arranged inside the belt member so as to face the rotating body across the belt member and forms a nip portion between the belt member and the rotating body to sandwich and transport the recording material; a tension roller that contacts the inner peripheral surface of the belt member and stretches the belt member; a tension roller that contacts the inner peripheral surface of the belt member; a first biasing member that biases the tension roller toward the belt member and applies tension to the belt member via the tension roller; a lubricant supply roller that contacts the inner peripheral surface of the belt member and supplies lubricant to the belt member; and a second biasing member that biases the lubricant supply roller toward the belt member. and an interlocking unit, wherein the tension roller is movable between a first biasing position where the tension roller biases the belt member with the first biasing member and a first bias-release position where the tension roller does not bias the belt member regardless of the biasing force of the first biasing member, and the lubricant supply roller is movable between a second biasing position where the lubricant supply roller biases the belt member with the second biasing member when the tension roller is located at the first biasing position, and a second bias-release position where the lubricant supply roller does not bias the belt member regardless of the biasing force of the second biasing member, and the interlocking unit moves the lubricant supply roller from the second biasing position to the second bias-release position in conjunction with the movement of the tension roller from the first biasing position to the first bias-release position. [Effects of the Invention]

[0010] According to the present invention, in a compact fixing device, the belt member can be easily replaced. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming apparatus according to an embodiment. [Figure 2]FIG. 2 is a cross-sectional view showing a schematic configuration of a fixing device according to the embodiment. [Figure 3] FIG. 2A is a side view showing a schematic configuration of a steering roller according to an embodiment, and FIG. 2B is a cross-sectional view taken along the line AA in FIG. [Figure 4] FIG. 2 is a perspective view showing an end configuration of the fixing device according to the embodiment. [Figure 5] 1A and 1B are views of the vicinity of the end of the tension roller according to an embodiment, showing a state in which tension is applied to the fixing belt by the tension roller and the lubricant supply roller, and a state in which tension applied to the fixing belt by the tension roller and the lubricant supply roller is released. [Figure 6] 1A is a perspective view of a heating unit according to an embodiment in a state where a steering roller is tilted, and FIG. 1B is a perspective view of the heating unit in a state where the steering roller is tilted in a direction different from that in FIG. 1A. [Figure 7] 1A and 1B are views of the vicinity of the end of the lubricant supply roller according to an embodiment, viewed from the width direction, showing a state in which tension on the lubricant supply roller is released, a state in which the oscillating arm is rotated to a position in which the lubricant supply roller can be replaced, and a state in which the lubricant supply roller is removed together with the oscillating arm. DETAILED DESCRIPTION OF THE INVENTION

[0012] The embodiment will be described with reference to Figures 1 to 7(c) First, the schematic configuration of the image forming apparatus of the present embodiment will be described with reference to Figure 1.

[0013] [Image forming device] Image forming apparatus 1 is an electrophotographic full-color printer having four image forming units Pa, Pb, Pc, and Pd corresponding to the four colors of yellow, magenta, cyan, and black. In this embodiment, the image forming units Pa, Pb, Pc, and Pd are arranged in tandem along the rotation direction of an intermediate transfer belt 204 (described later). Image forming apparatus 1 forms a toner image (image) on a recording material in response to an image signal from an image reading unit (document reading device) 2 connected to image forming apparatus main body 3 or from a host device such as a personal computer connected to image forming apparatus main body 3 so as to be able to communicate with the image forming apparatus main body 3. Examples of recording materials include sheet materials such as paper, plastic film, and cloth.

[0014] The image forming apparatus 1 comprises an image reading unit 2 and an image forming apparatus main body 3. The image reading unit 2 reads an original placed on a platen glass 21. Light emitted from a light source 22 is reflected by the original and forms an image on a CCD sensor 24 via optical components 23 such as a lens. This optical unit scans in the direction of the arrow, converting the original into a line-by-line electrical signal data stream. The image signal obtained by the CCD sensor 24 is sent to the image forming apparatus main body 3, where it is subjected to image processing in accordance with each image forming unit (described later) by a control unit 30. The control unit 30 also receives external inputs as image signals from external host devices such as a print server.

[0015] The image forming apparatus main body 3 includes multiple image forming units Pa, Pb, Pc, and Pd, and each image forming unit forms an image based on the image signal. That is, the image signal is converted into a laser beam that is PWM (pulse width modulation) controlled by a control unit 30. A polygon scanner 31 serving as an exposure device scans the laser beam in accordance with the image signal. The laser beam is then irradiated onto photosensitive drums 200a to 200d serving as image carriers of each image forming unit Pa to Pd.

[0016] Note that Pa is a yellow (Y) image forming unit, Pb is a magenta (M) image forming unit, Pc is a cyan (C) image forming unit, and Pd is a black (Bk) image forming unit, each forming an image of the corresponding color. Since the image forming units Pa to Pd are substantially identical, the yellow (Y) image forming unit Pa will be described in detail below, and descriptions of the other image forming units will be omitted. In the image forming unit Pa, a toner image is formed on the surface of the photosensitive drum 200a based on an image signal, as will be described below.

[0017] A charging roller 201a, which serves as a primary charger, charges the surface of the photosensitive drum 200a to a predetermined potential to prepare for the formation of an electrostatic latent image. A laser beam from a polygon scanner 31 forms an electrostatic latent image on the surface of the photosensitive drum 200a, which has been charged to a predetermined potential. A developing unit 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. A primary transfer roller 203a discharges electricity from the back surface of the intermediate transfer belt 204 and applies a primary transfer bias of opposite polarity to the toner, transferring the toner image on the photosensitive drum 200a onto the intermediate transfer belt 204. After transfer, the surface of the photosensitive drum 200a is cleaned by a cleaner 207a.

[0018] The toner image on intermediate transfer belt 204 is then conveyed to the next image forming station, where the toner images of each color formed at each image forming station are transferred in the order of Y, M, C, and Bk, forming a four-color image on the surface. The toner image that has passed through Bk image forming station Pd, which is located at the most downstream side in the rotation direction of intermediate transfer belt 204, is conveyed to a secondary transfer station made up of a pair of secondary transfer rollers 205 and 206. In the secondary transfer station, a secondary transfer electric field of opposite polarity to the toner image on intermediate transfer belt 204 is applied, thereby secondarily transferring the toner image onto the recording material.

[0019] The recording material is stored in a cassette 9, and the recording material fed from the cassette 9 is transported to a registration unit 208, which is made up of, for example, a pair of registration rollers, and waits at the registration unit 208. Thereafter, the timing of the registration unit 208 is controlled to align the position of the toner image on the intermediate transfer belt 204 with the position of the paper, and the recording material is transported to a secondary transfer unit.

[0020] The recording material onto which the toner image has been transferred in the secondary transfer section is transported to a fixing device 8, where the toner image carried on the recording material is fixed to the recording material by heating and pressing. The recording material that has passed through the fixing device 8 is discharged onto a discharge tray 7. When forming images on both sides of the recording material, after the toner image has been transferred and fixed onto the first side (front side) of the recording material, the recording material is turned over via a reversing conveyance section 10, and the toner image is transferred and fixed onto the second side (rear side) of the recording material, and the recording material is then stacked on the discharge tray 7.

[0021] As described above, the control unit 30 controls the entire image forming apparatus 1. The control unit 30 can also perform various settings based on input from the operation unit 4 of the image forming apparatus 1. The control unit 30 has a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU controls each unit by reading a program corresponding to a control procedure stored in the ROM. The RAM stores working data and input data, and the CPU performs control by referring to the data stored in the RAM based on the aforementioned programs.

[0022] [Fusing device] Next, the configuration of the fixing device 8 in this embodiment will be described with reference to FIG. 2. FIG. 2 is a cross-sectional view that schematically shows the general configuration of the fixing device 8. In this embodiment, a belt heating type fixing device using an endless belt is adopted. In FIG. 2, the X direction indicates the conveyance direction of the recording material P, the Y direction indicates the width direction that intersects with the conveyance direction of the recording material P (orthogonal in this embodiment), and the Z direction indicates the pressure direction of the pressure roller 305, which will be described later. These directions are perpendicular to each other. Furthermore, one side of the width direction (Y direction) is the front side of the image forming apparatus 1, for example, the side where the operation unit 4 is located and operated by the user. On the other hand, the other side of the width direction is the rear side of the image forming apparatus 1.

[0023] The fixing device 8 includes a heating unit 300 having a fixing belt 301 as an endless rotatable belt member, and a pressure roller 305 as a rotating body that contacts the fixing belt 301 and forms a nip portion N together with the fixing belt 301.

[0024] The heating unit 300 includes the above-mentioned fixing belt 301, a fixing pad 303 serving as a nip portion forming member and a pad member, a stay 302, a heating roller 307 serving as a tension roller, a steering roller 308 serving as a tension roller, and a lubricant supply roller 501. The pressure roller 305 rotates in contact with the outer peripheral surface of the fixing belt 301 and is also a driving rotor that applies a driving force to the fixing belt 301.

[0025] The fixing belt 301 has thermal conductivity, heat resistance, and the like, and is a thin-walled cylindrical shape. In this embodiment, it has a three-layer structure consisting of a base layer, an elastic layer on the outer periphery of the base layer, and a release layer on the outer periphery of the elastic layer. The base layer is 80 μm thick and made of polyimide resin (PI), the elastic layer is 300 μm thick and made of silicone rubber, and the release layer is 30 μm thick and made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin. The fixing belt 301 is stretched by a fixing pad 303, a heating roller 307, and a steering roller 308. A lubricant supply roller 501 is disposed on the inner periphery of the fixing belt 301 between the heating roller 307 and the steering roller 308, and is pressed against the fixing belt 301.

[0026] The fixing pad 303 is disposed inside the fixing belt 301 and is non-rotating so as to face the pressure roller 305 with the fixing belt 301 sandwiched therebetween. The fixing pad 303 forms a nip portion N between the fixing belt 301 and the pressure roller 305, which sandwiches and conveys the recording material. In this embodiment, the fixing pad 303 is a substantially plate-shaped member that is long in the width direction of the fixing belt 301 (the longitudinal direction intersecting the rotation direction of the fixing belt 301, the direction of the rotation axis of the heating roller 307). The fixing pad 303 is pressed against the pressure roller 305 with the fixing belt 301 sandwiched therebetween, thereby forming the nip portion N. The fixing pad 303 is made of a material made of LCP (liquid crystal polymer).

[0027] The fixing pad 303 is supported by a stay 302 serving as a support member disposed inside the fixing belt 301. That is, the stay 302 is disposed on the opposite side of the fixing pad 303 from the pressure roller 305, and supports the fixing pad 303. The stay 302 is a reinforcing member having long rigidity along the longitudinal direction of the fixing belt 301, and contacts the fixing pad 303 to back it up. That is, the stay 302 provides strength to the fixing pad 303 when the fixing pad 303 is pressed by the pressure roller 305, thereby ensuring the pressure force at the nip N.

[0028] Between the fixing pad 303 and the fixing belt 301, there is interposed a lubricating sheet 310 whose surface is coated with PTFE (polytetrafluoroethylene), and silicone oil S (hereinafter referred to as oil S) as a lubricant, allowing the fixing belt 301 to slide smoothly against the fixing pad 303. The lubricating sheet 310 is formed by coating the surface of a 70 μm-thick polyimide base material with PTFE. Note that the lubricating sheet 310 is arranged to improve the sliding properties between the fixing pad 303 and the fixing belt 301, so it is possible to substitute the lubricating sheet 310 by applying a coating that improves sliding properties to the surface layer of the fixing pad 303.

[0029] Heating roller 307 is disposed inside fixing belt 301, and stretches fixing belt 301 together with fixing pad 303 and steering roller 308. Heating roller 307 is formed into a cylindrical shape from a metal such as aluminum or stainless steel, and is provided inside with halogen heater 306 as a heating unit for heating fixing belt 301. Heating roller 307 is heated to a predetermined temperature by halogen heater 306.

[0030] In this embodiment, the heating roller 307 is formed of, for example, a stainless steel pipe having a thickness of 1 mm. The halogen heater 306 may be one or more. The heating unit that heats the heating roller 307 is not limited to a halogen heater, and may be another heater capable of heating the heating roller 307, such as a carbon heater. The fixing belt 301 is heated by the heating roller 307 heated by the halogen heater 306, and is controlled to a predetermined target temperature according to the type of recording material based on temperature detection by a thermistor (not shown).

[0031] The steering roller 308 is disposed inside the fixing belt 301, stretches the fixing belt 301 together with the fixing pad 303 and the heating roller 307, and is rotated by the fixing belt 301. In this embodiment, the steering roller 308 is biased toward the fixing belt 301 by a biasing spring 309 serving as a biasing member, and also serves as a tension roller that applies a predetermined tension to the fixing belt 301.

[0032] The lubricant supply roller 501 is disposed inside the fixing belt 301, contacts the inner circumferential surface of the fixing belt 301, and supplies lubricant to the fixing belt 301. In this embodiment, the lubricant supply roller 501 is disposed so as to be tiltable together with the steering roller 308 in a direction parallel to the rotation axis direction of the heating roller 307, as will be described in detail later.

[0033] The pressure roller 305 rotates in contact with the outer peripheral surface of the fixing belt 301, applying a driving force to the fixing belt 301. In this embodiment, the pressure roller 305 is a roller having an elastic layer formed on the outer periphery of its shaft and a release layer formed on the outer periphery of the elastic layer. The shaft is made of stainless steel with a diameter of 72 mm, the elastic layer is made of conductive silicone rubber with a thickness of 8 mm, and the release layer is made of PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin) as a fluororesin with a thickness of 100 μm. The pressure roller 305 is rotatably supported by a pressure arm that is movable relative to the fixing frame (not shown) of the fixing device 8, and has a gear fixed to one end thereof. The pressure roller 305 is connected to a motor M1, which serves as a pressure roller drive source, via the gear, and is driven to rotate.

[0034] In the fixing device 8 configured as above, the toner image is heated in the nip portion N formed between the fixing belt 301 and the pressure roller 305 while the recording material P carrying the toner image is sandwiched and conveyed. The toner image is then fixed to the recording material P. Therefore, the fixing device 8 needs to have both the function of applying heat and pressure and the function of conveying the recording material P. The pressure roller 305 is pressed against the fixing pad 303 via the fixing belt 301 by a drive source (not shown). In this embodiment, the pressure force (NF) at the nip portion N during image formation is set to 1600 N, and the length of the nip portion N in the X direction (conveyance direction) is set to 24.5 mm, and the length in the Y direction (width direction) is set to 326 mm.

[0035] Further, downstream of the nip portion N in the conveying direction of the recording material P, there are arranged a pair of discharge rollers 400, a separation plate 401, and a lower separation guide 402 for discharging the recording material P that has passed through the nip portion N out of the fixing device 8. The separation plate 401 is arranged downstream of the nip portion N in the conveying direction of the recording material and vertically above the nip portion N, with its leading edge closely facing the vicinity of the nip portion N of the fixing belt 301. Then, the separation plate 401 separates the recording material P from the fixing belt 301 after it has passed through the nip portion N.

[0036] The lower separation guide 402 is disposed downstream of the nip portion N in the recording material conveyance direction and vertically below the nip portion N, with its tip closely facing the pressure roller 305 near the nip portion N. When the recording material P sticks to the pressure roller 305, the lower separation guide 402 separates the recording material P from the pressure roller 305. The lower separation guide 402 also supports the lower surface of the recording material P discharged from the nip portion N and guides the recording material P to the discharge roller pair 400. The discharge roller pair 400 discharges the recording material P discharged from the nip portion N to the outside of the fixing device 8.

[0037] [Steering roller] 3(a) and (b) show a side view and a cross-sectional view of the steering roller 308. Fig. 3(a) is a side view of the steering roller 308 seen from the direction of the rotation axis, and Fig. 3(b) is a cross-sectional view of the steering roller 308 cut in the direction along the rotation axis. The steering roller 308 has a cylindrical member 308a as a rotation shaft portion, and an elastic layer 308b arranged around the cylindrical member 308a.

[0038] In this embodiment, the steering roller 308 is supported around a rotation support shaft 308c via a bearing 308d. For example, the cylindrical member 308a is a stainless steel pipe having an outer diameter of 20 mm and a thickness of 1 mm. The elastic layer 308b is a silicone rubber layer having a thickness of 100 μm.

[0039] 3(b), both ends of the steering roller 308 in the longitudinal direction (direction of the rotation axis) are rotatably supported by bearings 308d. That is, bearings 308d are disposed at both ends of the rotation support shaft 308c in the longitudinal direction, and the cylindrical member 308a is rotatably supported by the rotation support shaft 308c via the bearings 308d at both ends. Therefore, the steering roller 308 rotates in response to the rotation of the fixing belt 301 while being supported by the rotation support shaft 308c via the bearings 308d.

[0040] The steering roller 308 is disposed so that its rotation axis can tilt in a direction parallel to the rotation axis direction (width direction, lengthwise direction) of the heating roller 307. The tilting of the steering roller 308 controls the position (shift position) of the fixing belt 301 in the rotation axis direction of the heating roller 307. That is, the steering roller 308 has a rotation center at the center or one end of the rotation axis direction (lengthwise direction) of the steering roller 308, and tilts in the lengthwise direction of the heating roller 307 by swinging around this rotation center. This generates a tension difference between one side and the other side of the lengthwise direction of the fixing belt 301, causing the fixing belt 301 to move in the lengthwise direction.

[0041] Fixing belt 301 tends to shift to one end during rotation depending on the outer diameter accuracy of the rollers that tension it and the alignment accuracy between the rollers. For this reason, such shifting is controlled by steering roller 308. Note that steering roller 308 may be oscillated by a drive source such as a motor, or may be configured to oscillate by automatic centering.

[0042] The steering roller 308 of this embodiment will be described in more detail with reference to Figures 2, 4, 5(a) and 5(b). The steering roller 308 is disposed inside the fixing belt 301. The steering roller 308 stretches the fixing belt 301 and is supported by a steering section 321 serving as a support section. Specifically, the steering roller 308 is rotatably supported by a frame 320 of the heating unit 300 via the steering section 321. The frame 320, the heating roller 307, the stay 302 and the fixing pad 303 are supported by front and rear side plates (not shown) to form a unit.

[0043] The steering unit 321 rotates relative to the frame 320 around a rotation shaft 322, whereby the steering roller 308 is supported so as to be able to change the angle of contact with the fixing belt 301. This changes the alignment of the steering roller 308 with the other tension members, generating a tension difference between one side and the other side of the fixing belt 301 in the longitudinal direction, and controlling the position of the fixing belt 301 in the width direction.

[0044] In addition, both ends of the steering roller 308 are urged toward the fixing belt 301 by urging springs 309 serving as first urging members supported by the steering unit 321. That is, the urging springs 309 are disposed between the steering roller 308 and the steering unit 321, and urge the steering roller 308 toward the inner circumferential surface of the fixing belt 301. The steering roller 308 also serves as a tension roller that applies a predetermined tension to the fixing belt 301.

[0045] As shown in FIGS. 4 to 5(b), the rotation support shaft 308c of the steering roller 308 is rotatably supported at both ends in the direction of the rotation axis by a pair of first bearings 330. The first bearings 330 are made of a resin material that can be used in high-temperature environments, such as PPS (polyphenylene sulfide). The first bearings 330 are movably attached along the side walls of the box-shaped steering unit 321. The side walls of the steering unit 321 are formed in a direction that follows the biasing direction of the biasing spring 309. The biasing spring 309 is disposed between the first bearings 330 and the steering unit 321.

[0046] The steering roller 308 is in contact with the fixing belt 301 with a force of, for example, 20 N, as the first bearing portion 330 is pressed by the biasing spring 309 supported by the steering portion 321. Such a steering roller 308 is movable between a first biasing position (position in FIG. 5(a)) where the steering roller 308 biases the fixing belt 301 by the biasing spring 309, and a first bias-release position (position in FIG. 5(b)) where the steering roller 308 does not bias the fixing belt 301 regardless of the biasing force of the biasing spring 309. In other words, the steering roller 308 is movable between the first biasing position and the first bias-release position along the side wall of the steering portion 321.

[0047] [Lubricant supply roller 501] As shown in FIG. 2, the lubricant supply roller 501 is disposed inside the fixing belt 301 and contacts the inner circumferential surface of the fixing belt 301 to supply lubricant to the fixing belt 301. The lubricant supply roller 501 includes, for example, a core and an oil-impregnated layer as a lubricant-impregnated layer disposed around the core. The core is a roller shaft made of, for example, aluminum, iron, or stainless steel. The oil-impregnated layer is a layer impregnated with a lubricant and is disposed around the core of the lubricant supply roller 501 to contact the inner circumferential surface of the fixing belt 301. The oil-impregnated layer has a thickness of, for example, 100 μm and is formed by winding a nonwoven fabric impregnated with a lubricant (for example, silicone oil) around the core. However, the oil-impregnated layer is not limited to this. The oil-impregnated layer may also be made of, for example, an organic or inorganic porous material such as a sponge or porous ceramic body, cloth, or a woven fabric of organic or inorganic fibers such as polyester fiber.

[0048] 4 to 5(b), second bearing portions 502 are disposed at both ends of the lubricant supply roller 501 in the direction of its rotation axis, and the second bearing portions 502 at both ends are held by swing arms 503, which serve as rotation support portions. Therefore, the lubricant supply roller 501 is rotatably supported by the second bearing portions 502 relative to the swing arms 503. Furthermore, the swing arms 503 are disposed so as to be swingable (rotatable) around the rotation support shaft (rotation shaft) 308c of the steering roller 308. Therefore, the swing arms 503 support the second bearing portions 502 swingably relative to the steering roller 308.

[0049] Additionally, a pressure spring 504 serving as a second biasing member is disposed between the first bearing portion 330 and the swing arm 503. The pressure spring 504 biases the lubricant supply roller 501 toward the inner circumferential surface of the fixing belt 301, and the pressure spring 504 causes the lubricant supply roller 501 to abut against the inner circumferential surface of the fixing belt 301 with a force of 3.0 N.

[0050] The lubricant supply roller 501 is movable between a second urging position (position shown in FIG. 5A) where the lubricant supply roller 501 urges the fixing belt 301 by the pressure spring 504 with the steering roller 308 positioned at the first urging position, and a second force-release position (position shown in FIG. 5B) where the lubricant supply roller 501 does not urge the fixing belt 301 regardless of the urging force of the pressure spring 504. That is, the lubricant supply roller 501 can be moved between the second urging position and the second force-release position by the swinging arm 503 swinging. The pressure spring 504 urges the swinging arm in the direction in which the lubricant supply roller 501 moves from the second force-release position toward the second urging position.

[0051] The lubricant supply roller 501 is supported by the steering roller 308 via a swing arm 503. Therefore, the lubricant supply roller 501 can tilt together with the steering roller 308 in a direction parallel to the rotation axis direction of the heating roller 307. That is, when the steering roller 308 tilts to perform deviation control, the lubricant supply roller 501 tilts together with the steering roller 308.

[0052] [Operation of the steering roller and lubricant supply roller during steering] Next, the movements of the steering roller 308 and the lubricant supply roller 501 during the steering operation in this embodiment will be described with reference to Fig. 2 and Figs. 6(a) and 6(b). Figs. 6(a) and 6(b) are perspective views of the heating unit 300 during the steering operation, showing two patterns with different tilt angles of the steering roller 308. Note that the fixing belt 301 is not shown in Figs. 6(a) and 6(b).

[0053] As described above, the steering unit 321 is supported so as to be tiltable and changeable in contact angle with the fixing belt 301 by rotating with respect to the frame 320 around the rotation shaft 322 as a fulcrum. When the steering roller 308 tilts, the lubricant supply roller 501, which is supported by the swing arm 503 together with the rotation support shaft 308c, also tilts integrally with the steering roller 308, approximately parallel to the steering roller 308.

[0054] During the steering operation, the fixing belt 301 near the steering roller 308 also twists accordingly, which is suitable for stabilizing the contact pressure of the lubricant supply roller 501 against the fixing belt 301 and stabilizing the rotational movement of the fixing belt 301. Furthermore, it is desirable that the steering roller 308 and the lubricant supply roller 501 operate integrally in the pressure release operation, which will be described later.

[0055] [Release pressure on steering roller and lubricant supply roller] Next, a configuration for releasing the pressure of the steering roller 308 and the lubricant supply roller 501 against the fixing belt 301 in this embodiment will be described with reference to Figures 5(a) and 5(b). Figure 5(a) shows a state in which pressure is being applied to the fixing belt 301 by the steering roller 308 and the lubricant supply roller 501. Figure 5(b) shows a state in which the pressure of the steering roller 308 and the lubricant supply roller 501 against the fixing belt 301 is released.

[0056] In this embodiment, the lubricant supply roller 501 has a tapered portion 503a as an interlocking portion that moves the lubricant supply roller 501 from the second biased position to the second bias-released position in conjunction with the movement of the steering roller 308 from the first biased position to the first bias-released position. The tapered portion 503a is provided on the swing arm 503. When the steering roller 308 moves from the first biased position to the first bias-released position, the tapered portion 503a engages with the steering portion 321, thereby swinging the swing arm 503 so that the lubricant supply roller 501 moves from the second biased position to the second bias-released position.

[0057] The steering unit 321 has an engaged portion 321a that can freely engage with the tapered portion 503a. The engaged portion 321a is, for example, an end portion of a side wall of the steering unit 321 that is formed in a box shape. The tapered portion 503a has an inclined surface 503b that engages with the engaged portion 321a. The inclined surface 503b is inclined so that when the swing arm 503 moves in the direction opposite to the biasing direction of the biasing spring 309 (the direction of arrow B in FIG. 5A), the tapered portion 503a engages with the engaged portion 321a, causing the swing arm 503 to move in the direction of arrow C in FIG. 5B, i.e., in the direction in which the lubricant supply roller 501 moves away from the inner circumferential surface of the fixing belt 301.

[0058] The interlocking portion is not limited to the tapered portion 503a provided integrally with the swing arm 503, but may be, for example, a portion provided separately from the swing arm 503 and engaging with the steering portion 321 to move the lubricant supply roller 501 from the second biasing position to the second bias-released position. The interlocking portion may also be something like a link mechanism that swings the swing arm 503 in conjunction with the movement of the steering roller 308. In other words, the interlocking portion may be provided integrally or separately with the swing arm 503 so that the lubricant supply roller 501 and the steering roller 308 move integrally.

[0059] In this embodiment, the steering roller 308 is further provided with a locking member 331 that locks the steering roller 308 in the first bias release position. The locking member 331 is provided on the steering unit 321 and holds the steering roller 308 in the first bias release position by hooking onto a hook portion 330a of the first bearing unit 330 of the steering roller 308 that has been moved to the first bias release position. The locking member 331 is a generally ring-shaped member rotatably supported by the steering unit 321, and a portion of the ring can be hooked onto the hook portion 330a. The hook portion 330a is a flat surface formed on the outer peripheral surface of a portion of the first bearing unit 330 into which the rotation support shaft 308c is fitted, on the downstream side in the biasing direction of the biasing spring 309 (the direction opposite to the arrow B direction in FIG. 5(a)). The locking member 331 has a straight portion 331a that facilitates engagement with the flat hook portion 330a. Then, the straight portion 331a of the locking member 331 is caught on the catch portion 330a, so that the position of the steering roller 308 relative to the steering portion 321 is determined, and the steering roller 308 is held in the first bias release position.

[0060] Next, the operation of releasing the pressure of the steering roller 308 and the lubricant supply roller 501 against the fixing belt 301 will be described. First, as shown in Fig. 5(a), with the steering roller 308 in the first biasing position, a force is applied to the first bearing portion 330 in a direction opposite to the biasing force of the biasing spring 309 (the direction of arrow B in Fig. 5(a)), and the steering roller 308 is moved to the first bias-release position shown in Fig. 5(b). Then, at this position, the locking member 331 is hooked onto the first bearing portion 330 to restrict the movement of the steering roller 308, thereby making it possible to release the pressure of the steering roller 308 against the fixing belt 301.

[0061] The swing arm 503 is disposed so as to be swingable around the rotation support shaft 308c of the steering roller 308. Therefore, as the first bearing portion 330 moves as described above, the rotation support shaft 308c of the steering roller 308 also moves, and the swing arm 503 also moves in the direction of arrow B in conjunction with this.

[0062] As described above, the swing arm 503 is formed with the tapered portion 503a as an interlocking portion, and when the swing arm 503 moves in the direction of arrow B, the inclined surface 503b of the tapered portion 503a comes into contact with the engaged portion 321a of the steering unit 321. Then, when the swing arm 503 moves further in the direction of arrow B from this state, the inclined surface 503b and the engaged portion 321a rub against each other, causing the swing arm 503 to rotate in a direction (the direction of arrow C in FIG. 5B ) in which the lubricant supply roller 501 moves away from the fixing belt 301, making it possible to release the pressure of the lubricant supply roller 501 on the fixing belt 301.

[0063] In this way, by releasing the pressure on the steering roller 308 and the lubricant supply roller 501, the fixing belt 301 can be sufficiently bent, and the fixing belt 301 can be removed from the heating unit 300 by pulling it out longitudinally from the fixing pad 303, stay 302, heating roller 307, steering roller 308 and lubricant supply roller 501.

[0064] When removing the fixing belt 301 and attaching a new fixing belt 301 to the heating unit 300 in this manner, as described above, the pressure of the lubricant supply roller 501 on the fixing belt 301 is released, and the fixing belt 301 is attached in the longitudinal direction so that the fixing pad 303, stay 302, heating roller 307, steering roller 308, and lubricant supply roller 501 are positioned inside the fixing belt 301. Then, the locking member 331 is unlocked. That is, the straight portion 331a of the locking member 331 is disengaged from the hook portion 330a. Then, the steering roller 308 moves toward the inner circumferential surface of the fixing belt 301 due to the biasing force of the biasing spring 309. As the steering roller 308 moves, the swing arm 503 also moves, disengaging the tapered portion 503a from the steering portion 321. As a result, the steering roller 308 biases the fixing belt 301 with the biasing spring 309, and the lubricant supply roller 501 biases the fixing belt 301 with the pressure spring 504, and tension is applied to the fixing belt 301 by the steering roller 308 and the lubricant supply roller 501.

[0065] In recent years, the outer diameter of fixing belt 301 has tended to become smaller due to the downsizing of fixing device 8, making it difficult to ensure the retraction amount of the rollers that apply tension to fixing belt 301 when replacing fixing belt 301. In contrast, in this embodiment, the tension applied to fixing belt 301 is released by retracting two rollers from fixing belt 301. Therefore, even if the outer diameter of fixing belt 301 has become small due to the downsizing of fixing device 8 and the retraction amount of each roller cannot be ensured, fixing belt 301 can be sufficiently slackened.

[0066] Furthermore, in this embodiment, the pressure of the lubricant supply roller 501 on the fixing belt 301 is released in conjunction with the operation of the steering roller 308 to release the pressure on the fixing belt 301. Therefore, the tension applied to the fixing belt 301 can be released without moving the steering roller 308 and the lubricant supply roller 501 separately. Also, when attaching the fixing belt 301, by releasing the lock member 331, the lubricant supply roller 501 moves in conjunction with the movement of the steering roller 308. As a result, the state in which the tension is released can be easily shifted to a state in which the steering roller 308 and the lubricant supply roller 501 apply tension to the fixing belt 301. Therefore, the fixing belt 301 can be easily replaced in the compact fixing device 8.

[0067] [How to replace the lubricant supply roller] A mechanism for replacing the lubricant supply roller 501 alone in the above-described configuration will be described with reference to FIGS. 7(a) to 7(c). FIGS. 7(a) to 7(c) show the engagement between the steering roller 308 and the swing arm 503. As described above, the rotation support shaft 308c of the steering roller 308 rotatably supports the swing arm 503. The swing arm 503 is detachable from the rotation support shaft 308c at a predetermined phase relative to the rotational direction around the rotation support shaft 308c. The predetermined phase is a position where the lubricant supply roller 501 supported by the swing arm 503 cannot move when the fixing belt 301 is stretched across the fixing pad 303, the heating roller 307, and the steering roller 308, and where the lubricant supply roller 501 supported by the swing arm 503 can move when the fixing belt 301 is not stretched across the fixing pad 303, the heating roller 307, and the steering roller 308. This will be described in detail below.

[0068] The rotation support shaft 308c of the steering roller 308 has, on its outer circumferential surface, an arc-shaped rotation support portion 308f and a small-diameter portion 308e whose outer diameter is smaller than that of the rotation support portion 308f at a partial phase in the rotation direction. Specifically, the rotation support shaft 308c has a pair of arc-shaped rotation support portions 308f at positions 180° out of phase with each other. Each of the pair of rotation support portions 308f is formed in a partially cylindrical shape. The pair of small-diameter portions 308e is formed so as to connect both ends of the pair of rotation support portions 308f with a linear surface. The pair of small-diameter portions 308e are formed approximately parallel to each other. Note that the small-diameter portions 308e may be curved as long as their distance (radius) from the central axis of the rotation support shaft 308c is smaller than that of the rotation support portions 308f.

[0069] The swing arm 503 supporting the lubricant supply roller 501 has an arc-shaped rotation support portion 503c, and an opening 503d is formed in the swing arm 503 at a certain phase in the rotation direction, penetrating to the outer shape of the swing arm 503. Specifically, the base end of the swing arm 503, which is supported by the rotation support shaft 308c, has the rotation support portion 503c into which the rotation support shaft 308c is fitted. The rotation support portion 503c is formed in a cylindrical shape so that the rotation support portion 308f of the rotation support shaft 308c can slide and rotate relative to it, and the opening 503d is formed in a part of the rotation support portion 503c. The opening 503d has a width that allows the rotation support shaft 308c to pass through when the swing arm 503 is at a predetermined phase in the rotation direction around the rotation support shaft 308c.

[0070] In this embodiment, a phase in which one of the pair of rotary support portions 308f overlaps with the opening 503d as viewed in the radial direction (the state in FIG. 7(b)) is a predetermined phase. As a result, the pair of small-diameter portions 308e are located inside the opening end portion of the opening 503d as viewed in the radial direction. Here, the interval (width) W1 between the pair of small-diameter portions 308e is set to be smaller than the width W2 of the opening 503d (W1 < W2). Therefore, the rotary support shaft 308c can pass through the opening 503d from the rotary support portion 308f on the opening 503d side. Hereinafter, a procedure for replacing the lubricant supply roller 501 alone will be described.

[0071] First, as shown in FIG. 7(a), in a state where the lubricant supply roller 501 is in the second biasing position or the second biasing release position, the rocking arm 503 can rock about the rotary support shaft 308c of the steering roller 308 by sliding relative to each other in a state where the rotary support portion 308f and the rotary support portion 503c are fitted.

[0072] Next, as shown in FIG. 7(b), in a state where the fixing belt 301 is removed, the rocking arm 503 can be rotated in the direction of arrow D to a region where the lubricant supply roller 501 is located outside the outer diameter of the fixing belt 301 when the fixing belt 301 was mounted. By rotating the rocking arm 503 to this position, the phases in the rotational direction of the pair of small-diameter portions 308e and the opening end portion of the opening 503d can be aligned. At this time, by passing the pair of small-diameter portions 308e inside the opening 503d, the rocking arm 503 can be moved in the direction of arrow E as shown in FIG. 7(c), and the rocking arm 503 can be removed from the rotary support shaft 308c. Since the lubricant supply roller 501 is supported by the rocking arm 503, the lubricant supply roller 501 can also be removed together. Then, by removing the lubricant supply roller 501 from the rocking arm 503, the lubricant supply roller 501 can be removed from the heating unit 300.

[0073] On the other hand, when attaching the replaced lubricant supply roller 501 to the heating unit 300, the above-described steps can be reversed. The lubricant supply roller 501 and the swing arm 503 may be replaced as a unit without removing the lubricant supply roller 501 from the swing arm 503. In this manner, in this embodiment, the lubricant supply roller 501 can be replaced without adding any dedicated parts or mechanisms for attachment or retaining. In particular, in this embodiment, the swing arm 503 can be removed from the rotation support shaft 308c by rotating the swing arm 503 to a reachable position with the fixing belt 301 removed. Therefore, the swing arm 503 will not accidentally come off during operation of the fixing device.

[0074] [Other embodiments] In the above-described embodiments, a configuration has been described in which a halogen heater is provided on the heating roller as a heating unit for heating the fixing belt. However, the heating unit may be provided on another tension member instead of the heating roller. It may also be provided on the pad member. For example, a plate-shaped heat-generating member such as a ceramic heater may be provided on the fixing belt side of the pad member. The fixing belt may also be heated by electromagnetic induction (IH). In addition, in each of the above-described embodiments, instead of a heating unit disposed inside the roller, an external heating method may be adopted in which a separate heating member is brought into contact with the belt or roller from the outside for heating.

[0075] In the above-described embodiments, a pressure roller is used as the driving rotor. However, the driving rotor may be an endless belt that is tensioned by a plurality of tension rollers and driven by one of the tension rollers. In the above-described embodiments, a pressure roller as the driving rotor presses against the belt to form a nip, but the belt may be pressed against the driving rotor. Furthermore, in the above-described embodiments, a fixing pad is used as the nip-forming member, but the nip-forming member may be a roller. [Explanation of symbols]

[0076] 8. Fixing device 301 Fixing belt (belt member) 303 Fixing pad (nip forming member, pad member) 305 Pressure roller (rotating body) 306 Halogen heater (heating part) 307 Heating roller (tension roller) 308···Steering roller (tension roller) 309.... Urging spring (first urging member) 320...frame 321 Steering unit (support unit) 330...1st bearing part 331 Locking member 501 Lubricant supply roller 502...Second bearing part 503 Swing arm (rotation support part) 503a···Tapered section (interlocking section) 504 Pressure spring (second biasing member)

Claims

1. A fixing device that heats a toner image carried on a recording material and fixes the toner image to the recording material, an endless belt member; a rotating body that rotates in contact with the outer peripheral surface of the belt member; a nip portion forming member disposed inside the belt member so as to face the rotating body with the belt member interposed therebetween, and forming a nip portion between the belt member and the rotating body for nipping and conveying a recording material; a tension roller that contacts the inner peripheral surface of the belt member and tensions the belt member; a tension roller that contacts the inner circumferential surface of the belt member; a first biasing member that biases the tension roller toward the belt member, thereby applying tension to the belt member by the tension roller; a lubricant supply roller that contacts the inner circumferential surface of the belt member and supplies a lubricant to the belt member; a second biasing member that biases the lubricant supply roller toward the belt member; an interlocking portion; the tension roller is movable between a first biasing position where the tension roller biases the belt member by the first biasing member and a first bias-release position where the tension roller does not bias the belt member regardless of the biasing force of the first biasing member, the lubricant supply roller is movable between a second biasing position where the lubricant supply roller biases the belt member by the second biasing member while the tension roller is positioned at the first biasing position, and a second bias-release position where the lubricant supply roller does not bias the belt member regardless of the biasing force of the second biasing member, The interlocking portion moves the lubricant supply roller from the second urging position to the second urging release position in conjunction with the movement of the tension roller from the first urging position to the first urging release position.

2. a rotation support portion that is arranged rotatably about a rotation axis of the tension roller and that rotatably supports the lubricant supply roller, 2. The fixing device according to claim 1, wherein the interlocking portion is provided integrally with or separately from the rotation support portion so that the lubricant supply roller and the tension roller move integrally.

3. The fixing device according to claim 1, wherein the tension roller is arranged so that its rotation axis can be tilted relative to a direction parallel to the rotation axis of the tension roller, and the tilting controls the position of the belt member relative to the rotation axis of the tension roller.

4. a frame supporting the tension roller and the nip portion forming member; a support portion supported by the frame, the tension roller is supported by the support portion, 2. The fixing device according to claim 1, wherein the interlocking portion engages with the support portion when the tension roller moves from the first urging position to the first urging release position, thereby moving the lubricant supply roller from the second urging position to the second urging release position.

5. a first bearing portion that rotatably supports an end portion of the tension roller in a rotation axis direction; a second bearing portion that rotatably supports an end portion of the lubricant supply roller in a rotation axis direction; a swing arm that swingably supports the second bearing portion relative to the tension roller, The fixing device according to claim 4, characterized in that the interlocking portion is provided on the swing arm, and when the tension roller moves from the first biased position to the first bias-released position, it engages with the support portion to swing the swing arm so that the lubricant supply roller moves from the second biased position to the second bias-released position.

6. the first biasing member is disposed between the first bearing portion and the support portion, 6. The fixing device according to claim 5, wherein the second biasing member is disposed between the swing arm and the first bearing portion, and biases the swing arm in a direction in which the lubricant supply roller moves from the second bias release position toward the second bias position.

7. 2. The fixing device according to claim 1, further comprising a locking member that locks the tension roller in the first bias release position.

8. 2. The fixing device according to claim 1, wherein the tension roller is a heating roller having a heating section therein, the heating section heating the tension roller to thereby heat the belt member.

9. 2. The fixing device according to claim 1, wherein the nip portion forming member is a pad member.

10. a rotation support shaft that rotatably supports the swing arm, the swing arm is detachable from the rotation support shaft at a predetermined phase in a rotation direction around the rotation support shaft, The fixing device described in claim 5, characterized in that the specified phase is a position where the lubricant supply roller supported by the swing arm cannot move when the belt member is stretched across the nip portion forming member, the tension roller, and the tension roller, and where the lubricant supply roller supported by the swing arm can move when the belt member is not stretched across the nip portion forming member, the tension roller, and the tension roller.

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