Fixing device

Abstract

To provide a fixing device in which the alignment of a stretching roller can be easily adjusted.SOLUTION: A fixing device is provided with a pressing mechanism 401 operable by a worker from outside a fixing frame 8A. In accordance with an operation performed by the worker, a pressing force of the pressing mechanism 401 applied to a belt unit side plate 313 is changed, thereby deforming each of left and right belt unit side plates 313. By deforming each of the left and right belt unit side plates 313, the alignment of a heating roller 307, a steering roller 308, and a fixing pad unit 300 supported by the belt unit side plates 313 is adjusted. Since the worker can operate the pressing mechanism 401 from outside the fixing frame 8A, alignment adjustment can be easily performed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fixing device suitable for use in an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine. [Background technology]

[0002] In an image forming apparatus, an unfixed toner image is formed on a recording material, and the toner image is fixed to the recording material by applying heat and pressure using a fixing device. One example of a fixing device proposed is a belt-heating fixing device (Patent Document 1). In the case of a belt-heating fixing device, if the rotation axes of the tension rollers that support the belt are not parallel and misaligned (called an alignment error), the rotating belt may shift in the width direction, which intersects with the direction of rotation, causing belt misalignment toward the end of the tension roller. Belt misalignment can cause the shifted belt to come into contact with other components, potentially damaging the belt or other components. To address this issue, a steering control system is used to adjust the belt misalignment by using a sensor to detect the widthwise position of the belt end and swinging one of the tension rollers (called a steering roller) based on the detection result to change the relative angle of the steering roller with respect to the other tension rollers. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-33227 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-mentioned tension roller alignment error is primarily caused by the precision of the components that make up the fixing device. Recently, with the increasing speed of image formation, alignment errors have occurred due to deformation of a portion of the belt unit containing the belt and tension roller caused by the driving force of the tension roller. In such cases, a service technician or user manually adjusts the alignment of the tension roller. However, the fixing device has a cover member, and when the cover member is closed for thermal insulation, the alignment adjustment unit for adjusting the alignment of the tension roller is covered by the cover member. Therefore, the service technician or user must open the cover member to adjust the alignment, which increases the number of work steps.

[0005] SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a fixing device in which the alignment of the tension roller can be easily adjusted. [Means for solving the problem]

[0006] A fixing device according to one embodiment of the present invention is a fixing device that fixes a toner image formed on a recording material to the recording material, and includes a belt unit having: a rotating endless belt; a tension roller that stretches the belt inside the belt; a tension member that stretches the belt together with the tension roller inside the belt; a first support plate that supports one end of the tension roller in the rotational axis direction and one end of the tension member in the rotational axis direction; and a second support plate that supports the other end of the tension roller in the rotational axis direction and the other end of the tension member in the rotational axis direction; a pressure rotor that is disposed outside the belt and presses the belt toward the tension member to form a nip portion that can sandwich and convey the recording material; and a frame that supports the first support plate and the second support plate. the belt unit includes a drive transmission member supported by the frame and transmitting a driving force of a drive source to the tension roller; a first pressing mechanism provided on the frame and capable of pressing the first support plate in a first direction intersecting the rotation axis direction; a second pressing mechanism provided on the frame and capable of pressing the second support plate in a second direction intersecting the rotation axis direction; and a cover member that covers the belt unit, the frame, the first pressing mechanism, and the second pressing mechanism, wherein the first pressing mechanism has a first adjustment unit that can adjust the pressing force, the second pressing mechanism has a second adjustment unit that can adjust the pressing force, and the cover member has a first opening formed at a position corresponding to the first adjustment unit and communicating with the outside, and a second opening formed at a position corresponding to the second adjustment unit and communicating with the outside. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a fixing device in which the alignment of the tension roller can be easily adjusted. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an image forming apparatus suitable for using the fixing device of the present embodiment. [Figure 2] FIG. 2 is a schematic diagram showing a fixing device according to the first embodiment. [Figure 3]FIG. 2 is a schematic diagram showing a belt unit. [Figure 4] FIG. 2 is a cross-sectional view showing a pressing mechanism according to the first embodiment. [Figure 5] FIG. 10 is a schematic diagram showing a fixing device according to a second embodiment. [Figure 6] FIG. 10 is a cross-sectional view showing a pressing mechanism according to a second embodiment. [Figure 7] FIG. 10 is a schematic diagram showing a fixing device according to a third embodiment. [Figure 8] FIG. 10 is a cross-sectional view showing a pressing mechanism according to a third embodiment. [Figure 9] FIG. 10 is a schematic diagram showing a case where a gripping portion is provided in the pressing mechanism. [Figure 10] FIG. 4 is a schematic diagram showing the cover member in an open position. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] <Image forming device> This embodiment will be described. First, the configuration of an image forming apparatus suitable for using the fixing device of this embodiment will be described with reference to FIG. 1. The 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. This embodiment is a tandem-type image forming apparatus 1 in which the image forming units Pa, Pb, Pc, and Pd are arranged along the rotation direction of an intermediate transfer belt 204. The image forming apparatus 1 forms a toner image (image) on a recording material in response to an image signal from a document reading device 2 connected to the main body 3 of the image forming apparatus 1 or an external host device such as a print server connected to the main body 3 so as to be able to communicate with the main body 3. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.

[0010] As shown in FIG. 1, image forming apparatus 1 includes document reading device 2 and device main body 3. Document reading device 2 reads a document placed on document glass 21. Light emitted from light source 22 is reflected by the document and forms an image on CCD sensor 24 via optical components 23, such as lenses. When this optical unit is scanned in the direction indicated by the arrow under the control of a reader control unit, it reads the document line by line and converts it into an electrical signal data stream. The image signal obtained by CCD sensor 24 is sent to device main body 3, where it is processed by control unit 30 in accordance with the image forming units described below. Control unit 30 also receives external inputs as image signals from external host devices, such as a print server.

[0011] The 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.

[0012] Image forming unit Pa forms a toner image of yellow (Y), image forming unit Pb forms a toner image of magenta (M), image forming unit Pc forms a toner image of cyan (C), and image forming unit Pd forms a toner image of black (Bk), respectively. Since these image forming units Pa to Pd have approximately the same configuration, the following description will be given taking image forming unit Pa, which forms a toner image of yellow (Y), as an example, and descriptions of the other image forming units Pb to Pd will be omitted. In image forming unit Pa, a toner image is formed on the surface of photosensitive drum 200a based on an image signal.

[0013] The charging roller 201a 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 the polygon scanner 31 forms an electrostatic latent image on the surface of the photosensitive drum 200a, which has been charged to a predetermined potential. The developing unit 202a develops the electrostatic latent image on the photosensitive drum 200a to form a toner image. The primary transfer roller 203a discharges from the back side 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.

[0014] 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 image forming stations Pa to Pd 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 image forming station Pd, which is located at the most downstream position in the rotation direction of intermediate transfer belt 204, is conveyed to secondary transfer station T2, which is composed of a pair of secondary transfer rollers 205 and 206. At secondary transfer station T2, 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 from intermediate transfer belt 204 to the recording material.

[0015] 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 T2.

[0016] The recording material onto which the toner image has been transferred at secondary transfer section T2 is transported to fixing device 8, where heat and pressure are applied to fix the toner image to the recording material. The recording material that has passed through fixing device 8 is discharged onto 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 reversing conveyance section 10, and the toner image is transferred and fixed onto the second side (back side) of the recording material, and the recording material is discharged onto discharge tray 7.

[0017] The control unit 30 controls the entire image forming apparatus 1. The control unit 30 has a CPU (Central Processing Unit), ROM (Read Only Memory), and 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 work data and input data, and the CPU performs control by referring to the data stored in the RAM based on the above-mentioned programs, etc. The control unit 30 can perform various settings based on input from an operation unit 4 of the image forming apparatus 1. The operation unit 4 may be, for example, a touch panel, and accepts inputs such as the start of various programs such as an "image formation job" and various data inputs in response to a user's touch operation.

[0018] <Fixing device> Next, the fixing device 8 of this embodiment will be described with reference to FIGS. 2 and 3. This embodiment employs a belt-heating fixing device 8 using an endless fixing belt 301. In FIG. 2, "X" indicates the conveyance direction of the recording material S, "Y" indicates the width direction, and "Z" indicates the pressure direction. In this specification, the width direction (left-right direction) refers to the direction intersecting the conveyance direction of the recording material S at the fixing nip N (described later), in other words, the direction of the rotation axis of the pressure roller 305. Furthermore, the fixing device 8 viewed from the upstream side in the conveyance direction is referred to as the "front (or front)," the side opposite the front is referred to as the "rear," the left side as viewed from the front is referred to as the "left," and the right side as viewed from the front is referred to as the "right." FIGS. 2 and 3 each show the fixing device 8 and belt unit 309 viewed from the left.

[0019] As shown in FIG. 2, the fixing device 8 includes a fixing frame 8A, a belt unit 309, a pressure roller 305, a discharge unit 500, and a pressing mechanism 401. Although not shown, the fixing frame 8A is composed of support columns extending vertically at its four corners and connecting stays that connect the support columns in the left-right (width) direction or the front-to-rear direction. Frame side plates 311, which form part of the fixing frame 8A, are disposed on both left and right ends of the fixing frame 8A. The frame side plates 311 support the belt unit 309, the pressure roller 305, and the discharge unit 500. A cover member 312 is attached to the fixing frame 8A so as to cover the belt unit 309. The cover member 312 is fastened to the fixing frame 8A with screws in a closed position.

[0020] The cover member 312 is movable between a closed position shown in FIG. 2 where the belt unit 309 is not exposed and an open position shown in FIG. 10 where the belt unit 309 is exposed. The cover member 312 is fastened to the fixing frame 8A with screws (not shown) while in the closed position, and the fixing device 8 can perform fixing operations with the cover member 312 fastened with the screws. On the other hand, the belt unit 309 must be exposed during maintenance work on the fixing device 8. Therefore, the cover member 312 is movable from the closed position to the open position with the screws removed. For example, as shown in FIG. 10, the cover member 312 is configured so that an operator can open it from the front to the rear around a rotation shaft 312a, which is located downstream of the discharge unit 500 in the conveyance direction of the recording material S.

[0021] <Pressure roller> The pressure roller 305 as a pressure rotating body is rotatably supported at both ends in the width direction by the left and right frame side plates 311 so as to be able to come into contact with and apply pressure to the fixing belt 301 of the belt unit 309. A gear (not shown) is fixed to one end of the pressure roller 305, and the pressure roller 305 is connected to a motor M1 via the gear and is driven to rotate.

[0022] The pressure roller 305 is a roller that has a cylindrical core, an elastic layer on the outer periphery of the core, and a release layer on top of the elastic layer. As an example, the core is made of stainless steel (SUS) 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 tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA) with a thickness of 100 μm.

[0023] The pressure roller 305 contacts the outer peripheral surface of the fixing belt 301 so as to sandwich the fixing belt 301 between itself and a pressure pad 303 of the belt unit 309, forming a fixing nip N capable of nipping and conveying the recording material S in order to fix a toner image to the recording material S. To do this, the pressure roller 305 is provided so as to be movable toward the pressure pad 303 by a drive source (not shown). In the present embodiment, the pressure roller 305 presses the fixing belt 301 so that, for example, during image formation, the pressure of the fixing nip N is "1600 N," and the length of the fixing nip N in the conveyance direction is "24.5 mm" and the length in the width direction is "326 mm." The belt unit 309 receives a force corresponding to the drive force of the pressure roller 305 in the fixing nip N in the direction of arrow F1.

[0024] <Discharge unit> A discharge unit 500 is disposed downstream in the conveying direction of the fixing nip portion N for discharging the recording material S that has passed through the fixing nip portion N to the outside of the fixing frame 8A. The discharge unit 500 has an air nozzle 501 that blows compressed air to separate the recording material S that has passed through the fixing nip portion N from the fixing belt 301, a lower separation guide 502 that separates the recording material S from the pressure roller 305, and a pair of conveying rollers 503 that convey the separated recording material S.

[0025] <Belt unit> Fig. 3 is a schematic diagram showing a belt unit. As shown in Fig. 3, belt unit 309 has an endless fixing belt 301, a heating roller 307, a steering roller 308, a fixing pad unit 300, and belt unit side plates 313. Belt unit side plates 313 (first support plate, second support plate) are arranged opposite both ends in the width direction (front-rear direction), and support one end and the other end of each of heating roller 307, steering roller 308, and holding stay 302.

[0026] The holding stays 302 of the fixing pad unit 300 are formed to a length that protrudes outward in the width direction beyond the left and right belt unit side plates 313, and the belt unit side plates 313 are fixed midway along the holding stays 302 of the fixing pad unit 300. The frame side plates 311 are provided with fitting portions (not shown) into which both ends of the holding stays 302 can fit. Furthermore, the belt unit side plates 313 are formed with fitting grooves 700 on the upper, downstream side (left side in this example) in the conveyance direction. Meanwhile, the frame side plates 311 are provided with protruding portions 701 that protrude so as to be able to fit into the fitting grooves 700, as shown in FIG. 2 . In this embodiment, as the belt unit 309 moves from front to rear relative to the side plates 131, that is, in the conveyance direction (direction of arrow X), the holding stays 302 fit into the fitting portions, and the protruding portions 701 fit into the fitting grooves 700. In other words, the portions of the retaining stays 302 that protrude outward beyond the belt unit side plates 313 in the width direction function as support portions that support the belt unit side plates 313 on the frame side plates 311. In this way, the belt unit 309 is supported on the frame side plates 311 via the retaining stays 302 and the protruding portions 701. Therefore, the heating roller 307 and the steering roller 308 are supported only by the belt unit side plates 313, and are not supported by the frame side plates 311.

[0027] <Fixing belt> Fixing belt 301 is stretched by two tension rollers, a heating roller 307 and a steering roller 308, and a fixing pad unit 300. Fixing belt 301 has thermal conductivity, heat resistance, and the like, and is formed in a thin cylindrical shape. Fixing belt 301 has a three-layer structure in which, from the inner periphery, a base layer, an elastic layer, and a release layer are formed on a substrate such as rubber. As an example, 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.

[0028] <Heating roller> Heating roller 307, which serves as a tension roller, is disposed inside fixing belt 301 and is rotatably supported on belt unit side plate 313 so as to tension fixing belt 301 together with fixing pad unit 300. Heating roller 307 is a cylindrical metal roller made of metal such as aluminum or stainless steel, with a thickness of, for example, 1 mm, and has a halogen heater 306 disposed inside for heating fixing belt 301. Heating roller 307 to a predetermined temperature by halogen heater 306 heats fixing belt 301. A gear (not shown) is fixed to the right end of heating roller 307 and is driven to rotate by motor M2 via drive gear 322 installed on fixing frame 8A. Drive gear 322, which serves as a drive transmission member, transmits the driving force of motor M2, which serves as a drive source, to heating roller 307 in the direction of arrow W, thereby rotating heating roller 307. The heating roller 307 and the pressure roller 305 may be driven to rotate by using either the motor M1 or the motor M2 as a common drive source. For example, when the motor M1 is the common drive source, the drive gear portion 322 is rotated in the direction of the arrow W by the motor M1.

[0029] <Fixing pad unit> Fixing pad unit 300, which serves as a tension member, has a holding stay 302 and a pressure pad 303, and is disposed inside fixing belt 301 and attached to a belt unit side plate 313. Holding stay 302 is a rigid member made of, for example, metal that extends in the width direction of fixing belt 301 and holds pressure pad 303. Pressure pad 303, which serves as a pad member, is provided non-rotatably inside fixing belt 301. Pressure pad 303 is a resin member that extends in the width direction, and the width direction length of pressure pad 303 is longer than the width direction length of the maximum size recording material on which an image can be formed. Pressure pad 303 is formed from a resin with good insulating properties and heat resistance, such as LCP (liquid crystal polymer resin).

[0030] In order to reduce the frictional force between the fixing belt 301 and the pressure pad 303, it is preferable to provide a sliding member (not shown) between the pressure pad 303 and the fixing belt 301. The sliding member is disposed at a position facing the pressure roller 305 with the fixing belt 301 sandwiched therebetween. It is also preferable to apply a lubricant such as silicone oil to the inner circumferential surface of the fixing belt 301 in order to allow the fixing belt 301 to slide smoothly against the sliding member.

[0031] In this embodiment, the fixing belt 301 is pressed from the outside by the pressure roller 305 against the pressure pad 303 held by the holding stay 302. In this manner, a wide fixing nip N is formed between the pressure roller 305 and the fixing belt 301, ensuring the above-mentioned length in the conveyance direction and width direction. In addition, by holding the resin pressure pad 303 on the metal holding stay 302, which has greater rigidity, deflection that occurs in the pressure pad 303 when pressed is reduced, thereby achieving a fixing nip width that is uniform in the width direction.

[0032] <Steering roller> In the belt unit 309, due to component precision issues, the rotation axes of the tension rollers that tension the fixing belt 301 may not be parallel but may be misaligned, resulting in a so-called alignment error. In such a case, the rotating fixing belt 301 is likely to shift toward one of the widthwise edges, potentially damaging the fixing belt 301 or other components. Therefore, in this embodiment, to prevent belt shift, one of the tension rollers that tension the fixing belt 301 is a steering roller 308. The steering roller 308 is a hollow metal shaft (e.g., a stainless steel shaft) with a diameter of, for example, 20 mm, on the surface of which a rubber material is provided to increase the grip force on the fixing belt 301.

[0033] In this embodiment, the steering roller 308 is disposed downstream of the heating roller 307 and upstream of the pressure pad 303 in the rotation direction of the fixing belt 301. The steering roller 308 controls the widthwise position of the rotating fixing belt 301. The steering roller 308 has a swing center at the center in the widthwise direction and is provided so as to be tiltable with respect to the fixing belt 301 by a steering mechanism (not shown). As the steering roller 308 tilts, a tension difference occurs between both ends of the fixing belt 301, causing the fixing belt 301 to move in the widthwise direction. In this way, in this embodiment, as in the conventional case, the steering roller 308 can suppress belt misalignment when an alignment error occurs due to component precision.

[0034] Recently, in order to accommodate faster image formation, the rotational speed of the fixing belt 301 is sometimes increased and the pressure applied to the fixing nip N is sometimes increased. In such cases, the drive torque of the heating roller 307 must be increased, so the rotational drive force that the heating roller 307 receives from the drive gear portion 322 is increased. However, depending on the magnitude of the rotational drive force, the belt unit 309 may receive a large force in the direction of arrow F2 (see FIG. 2) on the drive gear portion 322 side, which may deform the belt unit side plate 313 on the drive gear portion 322 side (here, the right side). If one of the left and right belt unit side plates 313 is deformed, a larger alignment error may occur, making it difficult to suppress belt misalignment using the steering roller 308.

[0035] In view of the above, in this embodiment, an operator is allowed to manually adjust the alignment between the tension rollers in the belt unit 309 from outside the fixing frame 8A to the extent that the steering roller 308 can suppress belt misalignment. A pressing mechanism 401 for achieving this will be described below with reference to Figures 2 and 4. Figure 4 is a cross-sectional view showing the pressing mechanism of the first embodiment.

[0036] <Pressing mechanism> 2 and 4, the pressing mechanism 401 is composed of a contact member 402, a spring member 403, an adjustment screw 404, an adjustment piece 405, a mounting member 311a, and a rotation restricting member 311b. The pressing mechanism 401 is attached to the fixing frame 8A via two mounting members 311a that are fixed to the fixing frame 8A (more specifically, the frame side plates 311) in advance. The mounting members 311a are arranged side by side with a gap between them in the front-to-rear direction. A through-hole 311c is formed in the mounting member 311a, and the shank of the adjustment screw 404 is inserted into this through-hole 311c, so that the adjustment screw 404 is supported by the mounting member 311a so as to be reciprocable in the front-to-rear direction.

[0037] An adjustment screw 404 is supported by two mounting members 311a, one behind the other, and an adjustment piece 405 is disposed between the mounting members 311a. The adjustment piece 405 is formed in a polygonal shape, such as a hexagon. A spiral groove is formed in the shaft of the adjustment screw 404, and a threaded hole 405a that meshes with the shaft of the adjustment screw 404 is formed in the adjustment piece 405. In other words, the adjustment piece 405 is provided so that it can move along the shaft of the adjustment screw 404 as the adjustment screw 404 rotates.

[0038] In this embodiment, the rotation restricting member 311b is fixed to the fixation frame 8A in the same manner as the mounting member 311a. The rotation restricting member 311b abuts against one surface of the outer circumferential surface of the adjustment screw 405, restricting the rotation of the adjustment screw 405 so that the adjustment screw 405 does not rotate together with the adjustment screw 404 when the adjustment screw 404 is rotated. In this manner, the adjustment screw 405 can move back and forth on the shaft of the adjustment screw 404 within a range H in the front-to-rear direction of the rotation restricting member 311b in response to the rotation of the adjustment screw 404. As a result, the position of the adjustment screw 405 on the shaft of the adjustment screw 404 changes in response to the rotation of the adjustment screw 404. For example, when the adjustment screw 404 is rotated clockwise, the adjustment screw 405 moves from the rear to the front with respect to the shaft, and when the adjustment screw 404 is rotated counterclockwise, the adjustment screw 405 moves from the front to the rear with respect to the shaft.

[0039] Then, with the shafts of the adjustment screws 404 inserted through the front and rear mounting members 311a, spring members 403 (first elastic member, second elastic member) inserted through the shafts of the adjustment screws 404 are disposed between the adjustment piece 405 and the front mounting member 311a. The spring members 403 are provided to bias the contact members 402 toward the belt unit side plates 313, and the adjustment screws 404 can adjust the biasing force of the spring members 403.

[0040] In this embodiment, one end of the spring member 403 is connected to the adjustment top 405, and the other end of the spring member 403 is connected to the front mounting member 311a. The spring member 403 applies a force that pulls the adjustment top 405 forward relative to the front mounting member 311a. As described above, when the adjustment top 405 moves relative to the shaft of the adjustment screw 404 in response to the rotation of the adjustment screw 404, the distance between the adjustment top 405 and the front mounting member 311a changes, causing the spring member 403 to expand and contract. The rear tip of the adjustment screw 404 is provided with a contact member 402 (first contact portion, second contact portion) that abuts against the belt unit side plate 313. Therefore, the force that pulls the adjustment top 405 forward changes in response to the expansion and contraction of the spring member 403, and the force that pushes the contact member 402 from the front to the rear changes accordingly. For example, when the gap between the adjustment piece 405 and the front mounting member 311a narrows and the spring member 403 contracts, the pressing force of the abutting member 402 pressing the belt unit side plate 313 increases. Conversely, when the gap between the adjustment piece 405 and the front mounting member 311a widens and the spring member 403 expands, the pressing force of the abutting member 402 pressing the belt unit side plate 313 decreases. The belt unit side plate 313 is deformed by being pressed by the abutting member 402.

[0041] The pressing mechanisms 401 are arranged one on each side (first pressing mechanism, second pressing mechanism) at positions where they can press the left and right belt unit side plates 313 from the front. In this embodiment, one of the two pressing mechanisms 401 can press the left belt unit side plate 313 in a first direction intersecting the rotational axis direction of the heating roller 307, and the other pressing mechanism 401 can press the right belt unit side plate 313 in a second direction intersecting the rotational axis direction of the heating roller 307. Note that the first direction and the second direction may be the same.

[0042] As shown in FIG. 2, the cover member 312 has adjustment openings 406 (first opening and second opening) that communicate with the outside at left and right positions that overlap the heads of the adjustment screws 404 (first adjustment portion and second adjustment portion) when viewed from the front. The adjustment openings 406 are sized to allow insertion of a tool for rotating the adjustment screws 404 to access the adjustment screws 404 inside the fixing frame 8A. An operator can insert, for example, a screwdriver through the adjustment opening 406 and use the screwdriver to rotate the adjustment screws 404. The operator can adjust the pressing force of the pressing mechanisms 401 against the belt unit side plates 313 by changing the rotation direction of the adjustment screws 404. Adjusting the pressing force of the pressing mechanisms 401 installed on the left and right changes the amount of deformation of the left and right belt unit side plates 313.

[0043] Note that no opening is formed in the cover member 312 in a portion connecting the left and right adjustment openings 406 (first opening, second opening). That is, a wall portion 3121 is provided between the left and right adjustment openings 406 in the cover member 312, separating the inside and outside of the cover member 312 (see FIG. 10 ). The adjustment opening 406 is provided so that an operator can operate the pressing mechanism 401 even when the cover member 312 is closed. However, providing an opening reduces the heat insulating performance, which is the original purpose of the cover member 312. Therefore, the openings formed in the cover member 312 should be kept to a minimum, and no opening is formed in a portion connecting the left and right adjustment openings 406. In other words, the left and right adjustment openings 406 (between the first opening and the second opening) are blocked in the cover member 312.

[0044] As described above, this embodiment provides the pressing mechanism 401 that can be operated by an operator from outside the fixing frame 8A. The pressing force of the pressing mechanism 401 against the belt unit side plates 313 can be adjusted by the operator's operation, thereby deforming the left and right belt unit side plates 313. By deforming the left and right belt unit side plates 313 in this manner, the alignment between the heating roller 307 and the steering roller 308 supported by the belt unit side plates 313 is adjusted. The alignment adjustment by deforming the belt unit side plates 313 need only be sufficient to prevent the steering roller 308 from shifting the belt after the adjustment. Because the operator can operate the pressing mechanism 401 from outside the fixing frame 8A, the alignment adjustment can be easily performed.

[0045] [Second embodiment] Next, a second embodiment will be described with reference to Figures 5 and 6. Figure 5 shows a fixing device of the second embodiment, and Figure 6 shows a pressing mechanism of the second embodiment. The fixing device 80 of the second embodiment shown in Figure 5 is different from the fixing device 8 of the first embodiment shown in Figure 2 only in the configuration of the pressing mechanism 410, and the other configurations are the same. Therefore, the same components as those of the fixing device 8 of the first embodiment described above are denoted by the same reference numerals, and their description will be simplified or omitted.

[0046] 5 and 6, the pressing mechanism 410 is made up of an adjustment screw 411, a swing lever 412, a spring member 413, and an attachment member 321. In the second embodiment, as in the first embodiment, one pressing mechanism 410 is disposed on each of the left and right belt unit side plates 313 at a position where it can press the left and right belt unit side plates 313 from the front. The pressing mechanism 401 is attached to the fixing frame 8A via the attachment member 321, which is fixed to the fixing frame 8A (more specifically, the frame side plate 311) in advance, and the swing lever 412. The swing lever 412 is supported so as to be swingable around a swing shaft 412a protruding from the frame side plate 311.

[0047] A spiral groove is formed in the shaft of the adjustment screw 411, and a threaded hole 321a that meshes with the shaft of the adjustment screw 411 is formed in the mounting member 321. In other words, the adjustment screw 411 can move back and forth in the front-to-rear direction relative to the mounting member 321 as it rotates. A through hole 412c is formed in the swing lever 412, and the shaft of the adjustment screw 411 is inserted through this through hole 412c. With the shaft of the adjustment screw 411 inserted through the through hole 412c of the swing lever 412, a spring member 413 that is inserted through the shaft of the adjustment screw 411 is disposed between the swing lever 412 and the head of the adjustment screw 411. One end of the spring member 413 is connected to the swing lever 412, and the other end is connected to the head of the adjustment screw 411, and the spring member 413 is provided to swing the swing lever 412 back and forth.

[0048] The swing lever 412 has a protruding portion 414 that protrudes rearward between the through-hole 412c and the swing shaft 412a. This protruding portion 414 abuts against the belt unit side plate 313. When the adjustment screw 421 is rotated and moved rearward, the protruding portion 414 abuts against the belt unit side plate 313, narrowing the gap between the swing lever 412 and the head of the adjustment screw 411, and the spring member 403 contracts. When the spring member 403 contracts, the force pushing the swing lever 412 rearward increases, and the pressing force of the protruding portion 414 pressing against the belt unit side plate 313 increases. Conversely, when the adjustment screw 404 is rotated and moved frontward, the gap between the swing lever 412 and the head of the adjustment screw 411 increases, and the spring member 403 expands. When the spring member 403 expands, the force pushing the swing lever 412 rearward decreases, and the pressing force of the protrusion 414 pressing the belt unit side plate 313 increases. In this way, the belt unit side plate 313 is deformed by being pressed by the protrusion 414 of the swing lever 412.

[0049] As shown in FIG. 5 , the cover member 312 has an adjustment opening 406 formed at a position overlapping the head of the adjustment screw 411 when viewed from the front. Therefore, an operator can insert, for example, a screwdriver through the adjustment opening 406 and use the screwdriver to rotate the adjustment screw 411. By changing the direction of rotation of the adjustment screw 411, the operator can change the pressing force of the pressing mechanism 410 against the belt unit side plate 313. Changing the pressing force of the pressing mechanisms 410 installed on the left and right changes the amount of deformation of the left and right belt unit side plates 313. This adjusts the alignment between the heating roller 307 and the steering roller 308 supported by the belt unit side plate 313. Because the operator can operate the pressing mechanism 410 from outside the fixing frame 8A, alignment adjustment can be easily performed.

[0050] [Third embodiment] Next, a second embodiment will be described with reference to Figures 7 and 8. Figure 7 shows a fixing device of the third embodiment, and Figure 8 shows a pressing mechanism of the third embodiment. The fixing device 800 of the third embodiment shown in Figure 7 is different from the fixing device 8 of the first embodiment shown in Figure 2 only in the configuration of the pressing mechanism 420, and the other configurations are the same. Therefore, the same components as those of the fixing device 8 of the first embodiment described above are denoted by the same reference numerals, and their description will be simplified or omitted.

[0051] As shown in FIGS. 7 and 8 , the pressing mechanism 420 is composed of an adjustment screw 421, an adjustment block 422, a spring member 423, a swing lever 424, a mounting member 331, and a rotation restriction member 332. In the third embodiment, as in the first embodiment, two pressing mechanisms 420 are disposed on the left and right sides of the belt unit side plates 313, one at a time, so as to be able to press the respective belt unit side plates 313 from the front. The pressing mechanisms 420 are attached to the fixing frame 8A via two mounting members 331 that are fixed to the fixing frame 8A (specifically, the frame side plates 311) in advance. The mounting members 331 are arranged side by side with a gap between them in the front-rear direction. A through-hole 331a is formed in the mounting member 331, and the shaft of the adjustment screw 421 is inserted into the through-hole 331a, so that the adjustment screw 421 is supported by the mounting member 331 so as to be able to reciprocate in the front-rear direction.

[0052] An adjustment screw 421 is supported by two mounting members 331, one behind the other, and an adjustment piece 422 is disposed between the mounting members 331. The adjustment piece 422 is formed in a polygonal shape, such as a hexagon. A spiral groove is formed in the shaft of the adjustment screw 421, and a threaded hole 422a that meshes with the shaft of the adjustment screw 421 is formed in the adjustment piece 422. In other words, the adjustment piece 422 is provided so that it can move along the shaft of the adjustment screw 421 as the adjustment screw 421 rotates.

[0053] In this embodiment, the rotation restricting member 332 is fixed to the fixation frame 8A in the same manner as the mounting member 331. The rotation restricting member 332 abuts against one surface of the outer circumferential surface of the adjustment screw 422, and restricts the rotation of the adjustment screw 422 so that the adjustment screw 422 does not rotate together with the adjustment screw 421 when the adjustment screw 421 is rotated. This allows the adjustment screw 422 to move back and forth on the shaft of the adjustment screw 421 as the adjustment screw 421 is rotated, changing the position of the adjustment screw 422 on the shaft of the adjustment screw 421. For example, when the adjustment screw 421 is rotated clockwise, the adjustment screw 422 moves from the rear to the front with respect to the shaft, and when the adjustment screw 421 is rotated counterclockwise, the adjustment screw 422 moves from the front to the rear with respect to the shaft.

[0054] One end of a spring member 423 is connected to the outer circumferential surface of the adjustment top 422, on the surface opposite to the surface restricted by the rotation restricting member 332. In this embodiment, a swing lever 424 is supported so as to be swingable about a swing shaft 424a protruding from the frame side plate 311. The other end of the spring member 423 is connected to one end of the swing lever 424. In other words, the spring 423 is stretched between the adjustment top 422 and the swing lever 424. An abutting member 425 is provided on the other end of the swing lever 424 opposite to the one end connected to the spring member 423. This abutting member 425 abuts against the belt unit side plate 313.

[0055] When the adjustment top 422 moves forward relative to the shaft of the adjustment screw 421 in response to the rotation of the adjustment screw 421, the abutting member 425 abuts against the belt unit side plate 313, causing the spring member 423 to expand. As the spring member 423 expands, the force pulling one end of the swing lever 424 forward increases, and the pressing force of the abutting member 425 on the other end pressing against the belt unit side plate 313 increases. Conversely, when the adjustment top 422 moves rearward in response to the rotation of the adjustment screw 421, the spring member 423 contracts. As the spring member 423 contracts, the force pulling one end of the swing lever 424 forward decreases, and the pressing force of the abutting member 425 on the other end pressing against the belt unit side plate 313 decreases. In this way, the belt unit side plate 313 is deformed by being pressed by the abutting member 425 of the swing lever 424.

[0056] As shown in FIG. 7 , the cover member 312 has an adjustment opening 406 formed at a position that overlaps the head of the adjustment screw 421 when viewed from the front. Therefore, an operator can insert, for example, a screwdriver through the adjustment opening 406 and use the screwdriver to rotate the adjustment screw 421. By changing the direction of rotation of the adjustment screw 421, the operator can change the pressing force of the pressing mechanism 420 against the belt unit side plate 313. Changing the pressing force of the pressing mechanisms 420 installed on the left and right changes the amount of deformation of the left and right belt unit side plates 313. This adjusts the alignment between the heating roller 307 and the steering roller 308 supported by the belt unit side plate 313. Because the operator can operate the pressing mechanism 420 from outside the fixing frame 8A, alignment adjustment can be easily performed.

[0057] [Other embodiments] In the above-described embodiments, the worker inserts a tool such as a screwdriver through the adjustment opening 406 to rotate the adjustment screws (404, 411, 421), but this is not limiting. For example, the worker may grip the adjustment screws (404, 411, 421) with his or her hand to rotate them. To achieve this, at least a portion of the adjustment screws (404, 411, 421) needs to be exposed to the outside of the cover member 312 through the adjustment opening 406. Furthermore, as shown in FIG. 9 , it is preferable to provide a grip portion 900 on the portion of the adjustment screw 404 that is exposed to the outside of the cover member 312, so that the worker can grip the grip portion 900 to rotate the adjustment screws (404, 411, 421). [Explanation of symbols]

[0058] 8...fixing device, 300...stretching member (fixing pad unit), 301...belt (fixing belt), 302...stay (holding stay), 303...pad member (pressure pad), 305...pressure rotating body (pressure roller), 307...stretching roller (heating roller), 308...steering roller, 309...belt unit, 311...frame (frame side plate), 312...cover member, 313...first support plate (second support plate, belt unit side plate), 322...drive transmission member (drive gear portion), 401...first pressing mechanism (second pressing mechanism, pressing mechanism), 402...first contact portion (second contact portion, contact member), 403...first elastic member (second elastic member, spring member), 404...first adjustment portion (second adjustment portion, adjustment screw), 406...first opening (second opening, adjustment opening), 3121...wall portion, M2...drive source (motor), S...recording material

Claims

1. A fixing device that fixes a toner image formed on a recording material to the recording material, a belt unit including: a rotating endless belt; a tension roller that stretches the belt inside the belt; a tension member that stretches the belt together with the tension roller inside the belt; a first support plate that supports one end of the tension roller in the rotational axis direction and one end of the tension member in the rotational axis direction; and a second support plate that supports the other end of the tension roller in the rotational axis direction and the other end of the tension member in the rotational axis direction; a pressure rotating member disposed outside the belt and pressing the belt toward the tension member to form a nip portion capable of sandwiching and conveying a recording material; a frame supporting the first support plate and the second support plate; a drive transmission member supported by the frame and configured to transmit a drive force of a drive source to the tension roller; a first pressing mechanism provided on the frame and capable of pressing the first support plate in a first direction intersecting the rotation axis direction; a second pressing mechanism provided on the frame and capable of pressing the second support plate in a second direction intersecting the rotation axis direction; a cover member that covers the belt unit, the frame, the first pressing mechanism, and the second pressing mechanism, the first pressing mechanism has a first adjustment unit that can adjust the pressing force, the second pressing mechanism has a second adjustment unit that can adjust the pressing force, The cover member has a first opening formed at a position corresponding to the first adjustment unit and communicating with the outside, and a second opening formed at a position corresponding to the second adjustment unit and communicating with the outside. A fixing device characterized by:

2. the first pressing mechanism further includes a first contact portion that contacts the first support plate and a first elastic member that biases the first contact portion toward the first support plate, the first adjustment unit is capable of adjusting the biasing force of the first elastic member, the second pressing mechanism further includes a second contact portion that contacts the second support plate and a second elastic member that biases the second contact portion toward the second support plate, The second adjustment unit is capable of adjusting the biasing force of the second elastic member.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

3. the first adjustment unit and the second adjustment unit are operable from outside the cover member by a tool inserted through the first opening and the second opening.

3. The fixing device according to claim 2, wherein the fixing device is a fixing device.

4. At least a portion of the first adjustment unit and the second adjustment unit is exposed to the outside of the cover member through the first opening and the second opening, and can be operated outside the cover member.

3. The fixing device according to claim 2, wherein the fixing device is a fixing device.

5. The belt unit further includes a steering roller that stretches the belt together with the tension roller and the tension member on the inside of the belt and tilts with respect to the rotation axis direction to control the position of the belt in the rotation axis direction.

2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

6. the steering roller is supported by the first support plate and the second support plate so as to be tiltable with respect to the direction of the rotation axis; 6. The fixing device according to claim 5,

7. The tension member has a pad member that contacts the inner circumferential surface of the belt and a stay that supports the pad member, the stay has both end portions in the rotation axis direction fixed to the first support plate and the second support plate, a portion of the stay that protrudes outward beyond the first support plate and the second support plate in the rotation axis direction functions as a support portion that supports the first support plate and the second support plate on the frame; 2. The fixing device according to claim 1, wherein the fixing device is a fixing device for fixing a toner image onto a recording medium.

8. The cover member has a wall portion between the first opening and the second opening, the wall portion separating the inside and outside of the cover member.

2. The fixing device according to claim 1, wherein:

Images