Fixing device

Abstract

To provide a configuration capable of suppressing occurrence of unevenness in a supply amount of lubricant in a width direction of an inner peripheral surface of a fixing belt 301 by skew control of the fixing belt 301.SOLUTION: A steering roller 308 is in contact with an inner peripheral surface of a fixing belt 301, is arranged so that a rotation axis is tiltable with respect to a direction parallel to a rotation axis direction of a heating roller 307, and controls a position of the fixing belt 301 with respect to the rotation axis direction of the heating roller 307 by being tilted. A lubricant supply roller 501 is arranged inside the fixing belt 301 so as to contact the steering roller 308 and be tiltable together with the steering roller 308 with respect to the direction parallel to the rotation axis direction of the heating roller 307 and supplies lubricant to the steering roller 308.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 has also been known in the past in which the belt member is tilted by a roller that stretches the belt member to control the shift of the belt member, in order to prevent the belt member from shifting to one side in the width direction when the belt member rotates, thereby preventing damage to the widthwise end of the belt member (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 the past, a lubricant supply roller was positioned to contact the inner peripheral surface of the belt member between a roller tensioning the belt member and a nip-forming member, and was configured to supply lubricant to the inner peripheral surface of the belt member by being pressed against the belt member. In this configuration, when the lubricant supply roller is in contact with the inner peripheral surface of the belt member, the amount of lubricant supplied across the width of the inner peripheral surface of the belt member may be uneven due to changes in the belt trajectory caused by belt deviation control. This may result in unstable belt deviation control or a shortened lifespan of the belt member.

[0007] An object of the present invention is to provide a configuration that can suppress unevenness in the amount of lubricant supplied to the inner circumferential surface of the belt member in the width direction due to deviation control of the belt member. [Means for solving the problem]

[0008] 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, comprising: an endless belt member; a rotating body that rotates in contact with the outer surface of the belt member; a nip forming member that is arranged inside the belt member so as to face the rotating body via the belt member and forms a nip between the belt member and the rotating body to sandwich and transport the recording material; a tension roller that contacts the inner surface of the belt member and tensions the belt member; a steering roller that contacts the inner surface of the belt member and is arranged so that its rotation axis can tilt in a direction parallel to the rotation axis direction of the tension roller, and tilts to control the position of the belt member relative to the rotation axis direction of the tension roller; and a lubricant supply roller that contacts the steering roller inside the belt member and is arranged so that it can tilt together with the steering roller in a direction parallel to the rotation axis direction of the tension roller, and supplies lubricant to the steering roller. [Effects of the Invention]

[0009] According to the present invention, by controlling the deviation of the belt member, it is possible to suppress unevenness in the amount of lubricant supplied in the width direction of the inner circumferential surface of the belt member. [Brief explanation of the drawings]

[0010] [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 perspective view of the vicinity of a steering roller according to the embodiment, and FIG. 2B is a schematic diagram illustrating tilting of the steering roller according to the embodiment. [Figure 4] 5A and 5B are schematic diagrams for explaining problems that occur when a lubricant supply roller is brought into contact with the inner circumferential surface of a fixing belt. [Figure 5] FIG. 10 is a cross-sectional view showing a schematic configuration of a fixing device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The embodiment will be described with reference to Figures 1 to 4. First, the schematic configuration of an image forming apparatus according to the present embodiment will be described with reference to Figure 1.

[0012] [Image forming equipment] 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.

[0013] 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.

[0014] 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.

[0015] 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 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] [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.

[0022] 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.

[0023] 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, 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.

[0024] The fixing belt 301 has thermal conductivity, heat resistance, and the like, and is a thin 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.

[0025] 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 LCP (liquid crystal polymer) resin.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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).

[0030] 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.

[0031] The lubricant supply roller 501 is in contact with the steering roller 308 on the inner side of the fixing belt 301, and 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. The lubricant supply roller 501 supplies lubricant to the steering roller 308. The lubricant supplied to the steering roller 308 is supplied to the inner circumferential surface of the fixing belt 301. That is, in this embodiment, the lubricant supply roller 501 supplies lubricant to the fixing belt 301 via the steering roller 308.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Lower separation guide 402 is disposed downstream of nip portion N in the recording material conveyance direction and vertically below nip portion N, with its tip closely facing the pressure roller 305 near nip portion N. When recording material P sticks to pressure roller 305, lower separation guide 400b separates this recording material P from pressure roller 305. Lower separation guide 400b also supports the underside of recording material P discharged from nip portion N and guides this recording material P to discharge roller pair 400. Discharge roller pair 400 discharges recording material P discharged from nip portion N to the outside of fixing device 8.

[0036] [Steering roller] The steering roller 308 will be described with reference to FIGS. 2 to 3(b). The steering roller 308 is disposed so that its rotation axis can tilt in a direction parallel to the rotation axis direction (width direction, longitudinal direction) of the heating roller 307. The tilting of the steering roller 308 controls the position (offset 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 (longitudinal direction) of the steering roller 308, and tilts in the longitudinal 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 fixing belt 301 in the longitudinal direction, causing the fixing belt 301 to move in the longitudinal direction.

[0037] 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.

[0038] The steering roller 308 of this embodiment will be described in more detail. 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. The steering section 321 rotates with respect to the frame 320 of the heating unit 300 around a rotation shaft 322 as a fulcrum, thereby supporting the steering roller 308 so that the angle of contact with the fixing belt 301 can be changed.

[0039] In addition, both ends of the steering roller 308 are urged toward the fixing belt 301 by urging springs 309 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.

[0040] [Steering movement] The steering operation of the steering roller 308 will be described with reference to Figures 3(a) and (b). Figure 3(a) is a perspective view of the vicinity of the steering roller 308 around which the fixing belt 301 is stretched, and Figure 3(b) is a schematic diagram showing the tilting of the steering roller 308 together with the fixing belt 301. Note that, for simplicity of explanation, the lubricant supply roller 501 is not shown in Figures 3(a) and (b).

[0041] As described above, the steering roller 308 is rotatably supported by the frame 320 (FIG. 2) of the heating unit 300 via the steering section 321. The frame 320 supports the heating roller 307, the stay 302, and the fixing pad 303. The steering section 321 has a steering main body 323 as a steering support that supports the steering roller 308, a steering shaft 324 provided at an end of the steering main body 323, and a steering arm 325. The steering main body 323 is rotatably supported by the frame 320 around a rotation shaft 322 (FIG. 2). The steering arm 325 is driven by a motor M2 and swings the steering shaft 324 in the direction of arrow A in FIGS. 3(a) and 3(b). As a result, the steering main body 323 rotates around the rotation shaft 322 (FIG. 2) via the steering shaft 324, allowing the angle of the lubricant application roller 308A to be changed with respect to the fixing belt 301.

[0042] By changing the angle of the steering roller 308 in this way, the fixing belt 301 stretched around it moves along the width direction (longitudinal direction) W. When the steering roller 308 tilts in the direction of arrow A+ in FIGS. 3(a) and 3(b), the fixing belt 301 is moved in the direction of arrow W- in FIGS. 3(a) and 3(b), which is the front side of the fixing device 8 (belt frontward control). On the other hand, when the steering roller 308 tilts in the direction of arrow A- in FIGS. 3(a) and 3(b), the fixing belt 301 is moved in the direction of arrow W+ in FIGS. 3(a) and 3(b), which is the rear side of the fixing device 8 (belt rearward control). By repeating this operation, the fixing belt 301 reciprocates within a predetermined area in the width direction W.

[0043] [Lubricant supply roller 501] As shown in FIG. 2, the lubricant supply roller 501 is disposed inside the fixing belt 301. The lubricant supply roller 501 abuts against the steering roller 308 that stretches the fixing belt 301, and is supported together with the steering roller 308 by the steering unit 321. Specifically, the lubricant supply roller 501 is supported by a steering main body 323 (see FIG. 3(a)) that supports the steering roller 308. Because the lubricant supply roller 501 is supported by the steering main body 323, it can tilt together with the steering roller 308 in a direction parallel to the rotation axis direction of the heating roller 307. Note that the lubricant supply roller 501 may be supported by a structure separate from the steering main body 323, for example, a structure that tilts only the lubricant supply roller 501.

[0044] The lubricant supply roller 501 has, 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 provided around the core of the lubricant supply roller 501, so that it comes into contact with the outer surface of the steering roller 308. The oil-impregnated layer is formed by wrapping 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, or a woven fabric of organic or inorganic fibers such as polyester fiber.

[0045] Here, problems that arise when lubricant supply rollers are brought into contact with various points on the inner circumferential surface of the fixing belt will be described with reference to Fig. 4. Fig. 4 is a diagram illustrating an image of lubricant supply rollers 502 arranged at various points on the inner circumferential surface of fixing belt 301. At each position, lubricant supply roller 502 is urged toward the inner circumferential surface of fixing belt 301 by urging spring 503.

[0046] First, if the lubricant supply roller 502 is disposed between the fixing pad 303 and the heating roller 307 (position B in FIG. 4), the fixing belt 301 will be deformed so as to protrude outward downstream of the nip portion N in the rotation direction of the fixing belt 301. In this case, the distance between the fixing belt 301 and the separation plate 401, which is disposed close to the fixing belt 301 to separate the recording material P from the fixing belt 301, becomes unstable, which affects the separation performance of the recording material P from the fixing belt 301. Also, there is a risk that the fixing belt 301 will come into contact with the separation plate 401 and be damaged.

[0047] Next, if the lubricant supply roller 502 is disposed between the fixing pad 303 and the steering roller 308 (position C in FIG. 4), the fixing belt 301 will be deformed so as to bulge outward upstream of the nip portion N in the rotation direction of the fixing belt 301. In this case, the width of the entrance of the nip portion N will be narrowed, and unfixed toner carried on the recording material P may come into contact with the fixing belt 301 before the nip portion N. As a result, there is a risk of image defects occurring.

[0048] Furthermore, if the lubricant supply roller 502 is disposed between the heating roller 307 and the steering roller 308 (position D in FIG. 4), it may be affected by the deviation control of the fixing belt 301 performed by the steering roller 308. That is, if the trajectory of the fixing belt 301 changes due to deviation control, unevenness may occur in the amount of lubricant supplied from the lubricant supply roller 502 in the width direction of the inner circumferential surface of the fixing belt 301. As a result, deviation control of the fixing belt 301 may become unstable, and the life of the fixing belt 301 may be shortened. Note that even if the lubricant supply roller 502 is disposed at position C in FIG. 4, it may also be affected by the deviation control of the fixing belt 301.

[0049] In contrast, in this embodiment, the lubricant supply roller 501 is disposed inside the fixing belt 301, in contact with the steering roller 308, and tiltable together with the steering roller 308 in a direction parallel to the rotational axis of the heating roller 307. The lubricant supply roller 501 supplies lubricant to the fixing belt 301 via the steering roller 308. Therefore, even if the path of the fixing belt 301 changes due to the deviation control by the steering roller 308, the amount of lubricant supplied from the lubricant supply roller 501 to the steering roller 308 does not vary in the width direction. The lubricant supplied from the lubricant supply roller 501 to the steering roller 308 is then supplied from the steering roller 308 to the inner circumferential surface of the fixing belt 301. As a result, it is possible to prevent deviation control of the fixing belt 301 from becoming unstable and to prevent a shortened life of the fixing belt 301.

[0050] 4, the fixing belt 301 does not protrude outward and come into contact with the separation plate 401 or the unfixed toner image on the recording material P. This prevents damage to the fixing belt 301 and the occurrence of image defects.

[0051] Furthermore, in this embodiment, the lubricant supply roller 501 is supported by the steering unit 321 so as to be tiltable together with the steering roller 308. Therefore, compared to a case where the lubricant supply roller 501 is supported at a position different from the steering unit 321, space efficiency inside the fixing belt 301 can be improved. This allows the fixing device 8 to be made more compact. In this way, in this embodiment, the lubricant supply roller 501 is brought into contact with the steering roller 308, which controls the deviation of the fixing belt 301. This allows for stable supply of lubricant to the inner circumferential surface of the fixing belt 301 and control of the deviation of the fixing belt 301, while also achieving both a compact fixing device 8 and a long life.

[0052] [Other embodiments] In the above-described embodiment, one lubricant supply roller 501 is in contact with the steering roller 308, but multiple lubricant supply rollers 501 may be in contact with the steering roller 308. For example, as in the fixing device 8A shown in FIG. 5, two lubricant supply rollers 501a and 501b may be in contact with the steering roller 308. Specifically, the lubricant supply roller 501a as the first lubricant supply roller and the lubricant supply roller 501b as the second lubricant supply roller are in contact with the steering roller 308 on the inner side of the fixing belt 301, and are arranged 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.

[0053] 2, the lubricant supply rollers 501a and 501b are supported by the steering main body 323 and supply lubricant to the steering roller 308. The lubricant supply rollers 501a and 501b may have the same configuration, or may have different outer diameters, for example.

[0054] 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.

[0055] 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]

[0056] 8, 8A... Fixing unit 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 309.... Spring (biasing member) 320...frame 323 Steering body (steering support part) 501 Lubricant supply roller 501a: Lubricant supply roller (first lubricant supply roller) 501b: Lubricant supply roller (second lubricant supply roller)

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 that is disposed inside the belt member so as to face the rotating body with the belt member interposed therebetween and forms 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 steering roller that contacts the inner peripheral surface of the belt member, has a rotation axis that is tiltable relative to a direction parallel to the rotation axis of the tension roller, and tilts to control the position of the belt member relative to the rotation axis of the tension roller; a lubricant supply roller that is in contact with the steering roller on the inside of the belt member, and is arranged so as to be tiltable together with the steering roller in a direction parallel to the rotation axis direction of the tension roller, and that supplies lubricant to the steering roller.

2. a biasing member that biases the steering roller toward the belt member; 2. The fixing device according to claim 1, wherein the steering roller applies tension to the belt member.

3. a frame supporting the tension roller and the nip portion forming member; a steering support portion that is rotatably supported by the frame and supports the steering roller, 2. The fixing device according to claim 1, wherein the lubricant supply roller is supported by the steering support portion.

4. 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.

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

6. the lubricant supply roller is a first lubricant supply roller, The fixing device described in claim 1 further comprises a second lubricant supply roller that contacts the steering roller on the inside of the belt member, and is arranged so as to be tiltable together with the steering roller and the first lubricant supply roller in a direction parallel to the rotation axis direction of the tension roller, and supplies lubricant to the steering roller.

Images