Fixing device

Abstract

To appropriately control the deviation of a fixing belt when a pressure rotating body is in a separation state.SOLUTION: A fixing device has a pressure rotating body separation and contact mechanism, and steering control to reciprocate a fixing belt in a width direction. In a non-paper feed state in which paper is not fed through a nip part of the fixing device, when a pressure rotating body is in a separation state, the steering control performed by a steering mechanism reciprocates the fixing belt within a narrower range in the width direction than in a contact state.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to a fixing device for fixing a toner image on a recording material onto the recording material. [Background technology]

[0002] The image forming apparatus has a fixing device that fixes an unfixed toner image on a recording material onto the recording material.

[0003] The fixing device has a pair of rotors, including a fixing belt that applies heat to unfixed toner and is driven to rotate, and a pressure rotor that applies pressure to the fixing belt to form a nip between the fixing belt and the pressure rotor, which is driven to rotate. When a recording material with unfixed toner on it is conveyed to the nip, the heat of the fixing belt and the pressure of the pressure rotor are applied to the recording material, and the unfixed toner is fixed to the recording material.

[0004] The fixing device also has a contact / separation mechanism that enables the pressure rotator to move between a position where it contacts the fixing belt and a position where it is separated from the fixing belt.

[0005] Patent Document 1 (JP 2015-59964 A) discloses a steering control that reciprocates the fixing belt in the width direction. By repeatedly reciprocating the fixing belt within a predetermined area, it is possible to prevent the fixing belt from coming off the steering roller. In addition, it is possible to prevent the edge of the recording material from repeatedly passing through the same area of ​​the fixing belt. As a result, it is possible to prevent deterioration of the fixing belt surface. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2015-59964 Summary of the Invention [Problem to be solved by the invention]

[0007] During image formation, the pressure rotating body presses the fixing pad via the fixing belt with a force of 170 kg, applying the pressure required for fixing to the recording material.

[0008] When the recording material is not passed through the fixing nip for several seconds, the pressure rotating body is separated from the fixing belt (separated state) to prevent the temperature of the pressure rotating body from increasing. When the fixing belt is reciprocated in the width direction by steering control in the separated state, the reciprocating speed of the fixing belt increases by 2 to 3 times compared to the contact state.

[0009] Conventionally, the conditions for steering control in the contact state were also applied to the separated state, so that appropriate steering control was not performed in the separated state.

[0010] This could result in steering control not being able to keep up when the wheel is separated, which could result in a steering error.

[0011] Therefore, an object of the present invention is to appropriately perform steering control in the separated state. [Means for solving the problem]

[0012] In order to solve the above problems, a fixing device according to the present invention includes a rotatable endless fixing belt, of a heating roller that contacts the inner circumferential surface of the fixing belt and applies heat to the fixing belt; ofA fixing device which forms a nip portion with a steering roller contacting an inner circumferential surface of a fixing belt and a pressure rotating body which presses the fixing belt, sandwiches and conveys a recording material carrying unfixed toner through the nip portion, and fixes an unfixed toner image onto the recording material, comprises: a contact / separation mechanism which can move the pressure rotating body between a position in contact with the fixing belt and a position in a separated state, a belt position detection unit which detects the position of the fixing belt in the width direction of the fixing belt, and a control unit which controls, based on a detection result of the belt position detection unit, to swing the steering roller so as to move the fixing belt to a predetermined position in the width direction, In the width direction, after the center position of the fixing belt moves away from the center of the moving range of the fixing belt, the distance between the center position of the fixing belt where the steering roller is first tilted and the center position of the moving range of the fixing belt is smaller in the separated state than in the contact state. It is characterized by: Effect of the Invention

[0013] In the separated state, steering control can be performed appropriately. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus. [Diagram 2] FIG. [Diagram 3] FIG. 2 is a schematic diagram showing a steering mechanism. [Figure 4] 4 is a schematic diagram showing a sensor unit that detects the position of a fixing belt. FIG. [Diagram 5] FIG. 4 is a block diagram for explaining a control unit. [Figure 6] 4 is a schematic diagram showing a belt position detector for detecting the position of a fixing belt; FIG. [Figure 7] 5 is a schematic diagram showing a fixing belt position in a width direction on one end side of the fixing belt. FIG. [Figure 8] 10 is a flowchart showing a steering control in a state in which a pressurizing rotor is in contact with the steering wheel; [Figure 9] 11 is a diagram showing the relationship between the position of the fixing belt when the pressure rotating member is in contact with the steering roller and the inclination angle of the fixing belt; [Figure 10] FIG. 2 is a diagram showing the inclination angles (A and -A) of the steering roller. [Figure 11] FIG. 2 is a diagram showing the inclination angles (B and -B) of the steering roller. [Figure 12] FIG. 11 is a diagram showing the inclination angles (C and -C) of the steering roller. [Figure 13] 5 is a flowchart showing a steering control in a pressurizing rotor separated state in the first embodiment. [Figure 14] 6 is a diagram showing the relationship between the fixing belt position and the inclination angle of the steering roller in a state in which the pressure rotator is separated in the first embodiment. FIG. [Figure 15] 10 is a flowchart showing a steering control in a state in which the pressurizing rotor is separated from the steering wheel in a modified example. [Figure 16] 13A and 13B are diagrams illustrating the relationship between the fixing belt position and the inclination angle of the steering roller in a modified example when the pressure rotator is separated from the fixing belt. [Figure 17] 13 is a table showing the relationship between fixing belt positions and substituted values ​​in a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Image forming device> Fig. 1 is a schematic diagram showing the configuration of an image forming apparatus 100. As shown in Fig. 1, the image forming apparatus 100 has four image forming units of yellow, magenta, cyan, and black arranged along the moving direction of an intermediate transfer belt 6. First, the process in which a toner image is formed on the intermediate transfer belt 6 will be described using the yellow image forming unit PY as an example.

[0016] The surface of the photosensitive drum 3, which is rotated by the charger 2, is uniformly charged (charging). After that, the exposure device 5 irradiates the surface of the photosensitive drum 3 with a laser according to the input image data, and an electrostatic latent image is formed on the surface of the photosensitive drum 3 (exposure). After that, the development device 1 forms a yellow toner image on the photosensitive drum (development). The primary transfer roller 24 applies a voltage of a polarity opposite to the potential polarity of the yellow toner image to the intermediate transfer belt 6. As a result, the yellow toner on the photosensitive drum 3 is transferred to the intermediate transfer belt 6 (primary transfer). The yellow toner remaining on the photosensitive drum surface without being transferred is scraped off by the toner cleaner 4 and removed from the surface of the photosensitive drum 3. This series of processes is performed in the same way for magenta, cyan, and black. As a result, a full-color toner image is formed on the intermediate transfer belt 6.

[0017] The toner image on the intermediate transfer belt 6 is transported to a secondary transfer portion n2 formed by a pair of secondary transfer rollers 11 and 14. In accordance with the timing at which the toner image is transported, recording material A is taken out one by one from a recording material cassette 10 and fed to the secondary transfer portion n2. Then, the toner image on the intermediate transfer belt 6 is transferred to the recording material A (secondary transfer). Specific examples of the recording material A include plain paper, a resin sheet, coated paper, thick paper, and a sheet for an overhead projector.

[0018] The recording material A onto which the toner image has been transferred is conveyed to the fixing device 30, where it is fixed by heat and pressure (fixing). The recording material A onto which the toner image has been fixed is discharged onto the discharge tray 8.

[0019] Image forming apparatus 100 can also form monochrome images. When forming monochrome images, only the black image forming station PK is driven among the multiple image forming stations.

[0020] A double-sided printing process in which images are formed on both sides of a recording material will now be described. Recording material A with an image formed on one side is discharged from fixing device 30 and then guided to paper path 18 by flapper 7. Recording material A is transported from paper path 18 to reversing path 19, where it is switched back and transported on reversing path 19. Recording material A then passes through double-sided path 20 and is transported to paper path 21. At this time, recording material A is in an inverted state. Recording material A is then transported again to secondary transfer section n2, where a toner image is transferred and fixed by fixing device 30. Recording material A that has been double-sided printed is then discharged to output tray 8.

[0021] This process, which starts from charging and ends when the recording material A with the fixed toner image is discharged onto the discharge tray 8, is called an image forming process (print job). The period during which the image formation is being performed is called an image forming process in progress (a print job in progress).

[0022] <Fixing device> Next, the fixing device 30 of the present embodiment will be described with reference to FIG.

[0023] In this embodiment, a fixing device using an endless fixing belt 310 is used. In Fig. 2, the recording material is transported in the direction indicated by the arrow α. The fixing device 30 has a heating rotor 300 having the fixing belt 310, and a pressure rotor 330 that comes into contact with the fixing belt 310 and applies pressure to it to form a nip portion N with the fixing belt 310.

[0024] The heating rotator 300 has a fixing belt 310, a steering roller 350, a fixing pad 380 which is a pad member, and a heating roller 340. The fixing pad 380 and the heating roller 340 are in contact with the inner circumferential surface of the fixing belt. The fixing belt 310 is stretched by the fixing pad 380 and the heating roller 340.

[0025] The heating roller 340 is formed in a cylindrical shape from a metal such as aluminum or stainless steel. In this embodiment, it is formed from an aluminum pipe with an outer diameter of 80 mm. A halogen heater 341 is installed inside the heating roller 340 as a means for heating the fixing belt 310. The heating roller 340 is heated to a predetermined temperature by the halogen heater 341. The fixing belt 310 is heated by the heating roller 340 heated by the heat of the halogen heater 341. The fixing belt 310 is controlled to a predetermined target temperature according to the basis weight of the recording material to be fixed, based on the temperature detection result by a fixing temperature detection sensor (not shown). Note that the heating means is not limited to a halogen heater, and may be configured to heat the heating roller 340 by electromagnetic induction heating (IH), for example. The heating roller 340 is driven to rotate in the direction of the arrow R1 by receiving drive from a drive motor M1.

[0026] The fixing belt 310 has excellent thermal conductivity and heat resistance, and is, for example, a thin endless belt with an inner diameter of 120 mm. In this embodiment, the fixing belt 310 has a three-layer structure including a base layer, an elastic layer on the outside of the base layer, and a release layer on the outside of the elastic layer. The base layer is 60 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 310 is rotated by a pressure rotating body 330 (described later) that comes into contact with the fixing belt 310 and is rotated. In addition, since the heating roller 340 is rotated by receiving drive from the driving motor M1, the fixing belt 310 is also rotated by the rotation of the heating roller 340.

[0027] Fixing pad 380 is disposed on the inner circumferential surface of fixing belt 310 so as to face pressure rotor 330 with fixing belt 310 therebetween.

[0028] The pressure rotating body 330 has a cylindrical aluminum core, an elastic layer having a thickness of 1 mm on the outside of the core, and a release layer for improving separation from the toner on the outside of the elastic layer.

[0029] The pressure rotator 330 can be moved by a contact / separation mechanism that moves the pressure rotator 330 so that the pressure rotator 330 can be brought into contact with or separated from the fixing belt 310. The contact / separation mechanism has a frame 385 and a drive motor (not shown). The frame 385 is supported by the image forming apparatus 100. The frame 385 supports the pressure rotator 330. The frame 385 is rotated by receiving drive from a drive motor (not shown) about a rotation axis 332 as a rotation axis. When the frame 385 is rotated about the rotation axis 332 by a drive motor (not shown), the pressure rotator 330 is moved in the direction of the arrow P. As a result, the pressure rotator 330 is brought into contact with the fixing pad 380 with the fixing belt 310 sandwiched therebetween in a direction perpendicular to the conveying direction α of the recording material (contact state). As a result, a nip portion N is formed. In this embodiment, a total pressure of 2000 N is applied, and the width of the nip portion N is 24 mm. When the frame 385 is rotated about the rotation shaft 332 in the direction opposite to the contact direction, the pressure rotator 330 is separated from the fixing belt 310 (separated state).

[0030] Further, the pressure rotating body 330 is rotated in the direction of the arrow R2. Therefore, the fixing belt 310 sandwiched between the pressure rotating body 330 and the fixing pad 380 is rotated in response to the rotation of the pressure rotating body 330.

[0031] As described above, the recording material carrying the unfixed toner image is sandwiched and conveyed at the nip portion N by the heating rotator 300 and the pressure rotator 330, and heat and pressure are applied to the recording material, thereby performing fixing.

[0032] <Steering roller> Next, the steering roller 350 in this embodiment will be described with reference to FIGS.

[0033] In this embodiment, in the contact state, a force of 2000 N is applied to the fixing belt 310. Therefore, the surface of the fixing belt 310 may be damaged by the edge of the recording material, which may cause uneven gloss. The details of this will be described later.

[0034] <Uneven gloss due to scratches on the edge of the paper> Paper edge scratches are scratches on the surface of the fixing belt caused by a cut portion (edge) of the recording material. When unfixed toner is fixed to the recording material, the portion of the fixing belt 310 that comes into contact with the edge (edge ​​contact portion) is subjected to greater stress than the portion that does not come into contact with the edge (edge ​​non-contact portion). There is a risk that the area scratched by the edge of the recording material will have a more concave shape than the edge non-contact portion. Such a concave caused on the surface of the fixing belt 310 by the edge of the recording material is called a paper edge scratch.

[0035] When fixing the unfixed toner to the recording material, the fixing device 30 applies pressure and heat to the recording material. At this time, the surface condition of the fixing belt 310 is reflected in the gloss of the image surface after fixing. If there are irregularities on the surface of the fixing belt 310, the state of the irregularities is reflected in the gloss of the image surface, resulting in uneven gloss (gloss unevenness) on the image surface.

[0036] Therefore, if unfixed toner is fixed to a recording material in a state where the fixing belt surface has scratches on the edge of the paper, gloss unevenness like straight lines will occur on the surface of the image.

[0037] In this embodiment, in order to prevent scratches on the edge of the surface of the fixing belt 310, a steering control by a steering mechanism 400 is used, which reciprocates the fixing belt 310 in the width direction.

[0038] The steering control will be described with reference to FIG.

[0039] 3, the steering mechanism 400 has a steering roller 350, a steering motor 401, a worm 402, a worm wheel 403, and a fork plate 404. The steering motor 401 can rotate in a forward direction and a reverse direction. When the steering motor 401 receives a signal from the control unit 600 and is driven to rotate, the worm 402 attached to the steering motor 401 is rotated.

[0040] The rotation of the worm 402 is converted into a swing in the direction of the rotation axis of the steering motor 401 around the rotating shaft 405 by the drive conversion unit 410 in which the worm wheel 403 and the fork plate 404 are integrally formed. That is, the worm wheel 403 is engaged with the worm 402 and is provided so as to be able to move back and forth in the direction of the rotation axis of the steering motor 401 in accordance with the rotation of the worm 402. To achieve this, the engagement surface of the worm wheel 403 is formed in an arc shape so as to engage with the worm 402 at the center in the direction of the rotation axis. In this way, the drive conversion unit 410 can swing around the rotating shaft 405 via the worm 402 and the worm wheel 403 in accordance with the rotation of the steering motor 401.

[0041] Further, the steering mechanism 400 has a steering operation shaft 406, a steering roller support arm 351, and a bearing portion 352. The steering operation shaft 406, the steering roller support arm 351, and the bearing portion 352 are integrally formed and attached to the steering roller 350. The bearing portion 352 rotatably supports the rotation shaft of the steering roller 350. The steering roller support arm 351 is provided rotatably, and rotatably supports the steering roller 350 by holding the bearing portion 352.

[0042] A steering operation shaft 406 that is fitted to the drive conversion unit 410 is fixed to the steering roller support arm 351. The steering operation shaft 406 is fitted to the fork plate 404 of the drive conversion unit 410, and can move together with the drive conversion unit 410 while being maintained in a state of being fitted to the drive conversion unit 410. In this way, the inclination of the steering roller 350 changes in conjunction with the swing of the drive conversion unit 410. That is, by driving the steering motor 401, the arrangement angle of the steering roller 350 with respect to the heating roller 340 (see FIG. 2) can be changed steplessly. In this way, when the steering angle of the steering roller 350 is adjusted, the fixing belt 310 stretched by the steering roller 350 and the heating roller 340 is reciprocated in the width direction. Therefore, the fixing belt 310 can be reciprocated within a predetermined region in the width direction, and steering control of the fixing belt 310 can be realized. The fixing belt 310 moves back and forth such that the moving direction is exactly opposite when the steering motor 401 is rotated forward to tilt the steering roller 350 and when the steering motor 401 is rotated backward to tilt the steering roller 350.

[0043] In this way, the steering mechanism 400 causes the fixing belt 310 to reciprocate in the width direction within the area of ​​the steering roller 350. The reciprocating movement of the fixing belt 310 can prevent the edge of the recording material from repeatedly passing through the same area on the surface of the fixing belt 310. This can prevent scratches on the edge of the paper that are generated on the surface of the fixing belt 310.

[0044] <Fixing belt position detection> 2, 3, and 4, a belt position detector for detecting the position of fixing belt 310 in the width direction will be described.

[0045] In this embodiment, a sensor unit 390 is provided for detecting the position of the end of the fixing belt 310 in the width direction. The position of the end of the fixing belt 310 is detected based on an output signal from the sensor unit 390. The steering mechanism 400 described above is operated based on the detected end position of the fixing belt 310, thereby changing the tilt angle of the steering roller 350. The configuration of the sensor unit 390 will be described with reference to FIG. 4.

[0046] 4, the sensor unit 390 of this embodiment has a contact member 391 that contacts the end of the fixing belt 310, an arm member 392 for supporting the contact member 391, a belt position detection unit 393 as a moving member, and three sensors 394, 395, and 396 for detecting the positions of the ends of the fixing belt 310. For example, optical sensors are used as the sensors 394, 395, and 396 as the belt position detection units. The contact member 391 is disposed on one end side of the arm member 392 so as to contact the end in the width direction.

[0047] The arm member 392 is biased by a coil spring (not shown) from the end portion of the fixing belt 310 toward the center portion in the width direction. The arm member 392 is provided rotatably so as to follow the movement in the width direction via the contact member 391. A belt position detection unit 393 is provided on the other end side of the arm member 392 as a moving member. The belt position detection unit 393 is, for example, a fan-shaped column member, and has a plurality of openings 393a and a plurality of detection target portions 393b formed on its arc-shaped outer peripheral surface. Three sensors 394, 395, and 396 are arranged at predetermined intervals along the rotational movement direction of the belt position detection unit 393 so as to face the outer peripheral surface on which the openings 393a and the detection target portions 393b are formed with respect to the belt position detection unit 393.

[0048] In this embodiment, when the fixing belt 310 moves from one end side to the other end side in the width direction, the belt position detection unit 393 rotates in accordance with the movement of the fixing belt 310. In response to the rotation of the belt position detection unit 393, the positional relationship between the sensors 394, 395, 396 and the detected portion 393b (or the opening 393a) changes. Specifically, a detection state in which the sensors 394, 395, 396 detect the detected portion 393b and a non-detection state in which the sensors 394, 395, 396 face the opening 393a and therefore do not detect the detected portion 393b are switched.

[0049] In this embodiment, optical sensors are used for the sensors 394, 395, and 396. The sensors 394, 395, and 396 have a light-emitting unit that emits light and a light-receiving unit that receives reflected light of the light emitted from the light-emitting unit. The sensors 394, 395, and 396 emit a predetermined amount of light toward the belt position detection unit 393 using the light-emitting unit. If the emitted light is blocked by the detection target unit 393b of the belt position detection unit 393, the light-receiving units of the sensors 394, 395, and 396 do not receive the light emitted from the light-emitting unit. On the other hand, if the emitted light is not blocked by the opening 393a of the belt position detection unit 393, the light-receiving unit receives the light emitted from the light-emitting unit. In this way, the presence or absence of light reception in each of the sensors 394, 395, and 396 is determined according to the movement of the belt position detection unit 393.

[0050] <Control Unit> As shown in Fig. 1, the image forming apparatus 100 includes a control unit 600. The control unit 600 will be described using Fig. 5 with reference to Figs. 2 to 4. However, in addition to those shown in the figure, various devices such as a motor and a power supply for operating the image forming apparatus 100 are connected to the control unit 600, but as this is not the main point of the invention, illustration and description of these will be omitted here.

[0051] The control unit 600 as a control means performs various controls such as image forming operations, and has, for example, a CPU 601 (Central Processing Unit) and a memory 602. The memory 602 is composed of a ROM (Read Only Memory) and a RAM (Random Access Memory). The memory 602 stores various programs and various data for controlling the image forming apparatus 100. The CPU 601 can execute various programs stored in the memory 602, and can operate the image forming apparatus 100 by executing the various programs.

[0052] In this embodiment, the CPU 601 can execute "image formation job processing (program)" stored in the memory 602, "steering control" to be described later, and the like.

[0053] The memory 602 stores, for example, a "sensor value table" (see FIG. 9 described later) that is referenced to specify the end position of the fixing belt 310 that is reciprocated by steering control during the belt deviation control process, and to determine whether or not there is a malfunction in the sensor unit 390. The memory 602 can also temporarily store the results of calculations associated with the execution of various programs.

[0054] The control unit 600 is connected to the operation unit 40 via an input / output interface. The operation unit 40 has, for example, a touch panel type liquid crystal screen (display unit) that allows the user to give instructions to start various programs such as image forming job processing, and input various data such as the size of recording material (A3, B4, etc.). This liquid crystal screen can display various screens including software keys, and various functions such as instructions to start various programs that have been assigned in advance can be executed in response to the user's touch operation of the software keys. In addition, the liquid crystal screen can display various information such as the operating status of the image forming apparatus and error information in order to notify the user. That is, in the case of this embodiment, the operation unit 40 can function as a notifying means. Note that the notification of various information such as error information is not limited to the above-mentioned notification method by display, and may be an appropriate method such as a notification method by sound using a sound generating means such as a speaker.

[0055] The control unit 600 is further connected to the driving motor M1, the steering motor 401, the temperature sensor 370, the halogen heater 341, the sensor unit 390, the position sensor 407, and a motor for driving the pressure rotating body 330 via an input / output interface. When an instruction to start an image forming job is given from the operation unit 40, the control unit 600 (more specifically, the CPU 601) executes an "image forming job" stored in the memory 602. The control unit 600 controls the image forming apparatus 100 based on the execution of the "image forming job". Accordingly, the control unit 600 drives the driving motor M1 to rotate the heating roller 340, thereby rotating the fixing belt 310. In addition, the control unit 600 controls the halogen heater 341 based on the detection result of the temperature sensor 370 so that the surface temperature of the fixing belt 310 becomes a desired target temperature (180° C. in this embodiment). Since the control unit 600 controls the motor that drives the pressure rotating body 330, it is also possible to determine whether the pressure rotating body 330 is in contact with the fixing belt 310 or separated therefrom.

[0056] In this embodiment, the control unit 600 controls the steering motor 401 based on the detection result of the sensor unit 390, specifically, based on a combination of output signals from three sensors 394, 395, and 396 (see FIG. 6(b) described later). That is, the control unit 600 detects the end position of the fixing belt 310 based on the detection result of the sensor unit 390, and rotates the steering motor 401 forward or backward according to the rotation amount determined accordingly. In this way, the control unit 600 can operate the steering mechanism 400 described above by the steering motor 401 to steer the fixing belt 310.

[0057] <Belt position detection unit> The belt position detector 393 will be described with reference to Figs. 6(a) and 6(b). Fig. 6(a) is a top view for explaining the belt position detector 393, and Fig. 6(b) shows a combination of output signals from the sensors 394, 395, and 396 when the belt position detector 393 is used. The 27 regions in Fig. 6(a) are used when nine positions of the fixing belt 310 in the width direction are detected by three sensors (394, 395, and 396). For example, when the sensors 394, 395, and 396 are in a detection state where they detect the detection target portions 393b1 to 393b5, in other words, when they are in a shielded state where they are shielded by the detection target portions 393b1 to 393b5, they output an output signal of "0". On the other hand, when each sensor 394, 395, 396 is in a non-detection state in which it is not detecting the detection targets 393b1-393b5, in other words, in an open state (also called a non-obstructed state) facing the openings 393a1-393a4, it outputs an output signal "1".

[0058] 6(b), the "first sensor" refers to sensor 394, the "second sensor" refers to sensor 395, and the "third sensor" refers to sensor 396, and the belt position is a value determined by a combination of the output signals of the sensors 394, 395, and 396. In this embodiment, the control unit 600 can detect the end position of the fixing belt 310 at nine subdivided positions according to the above-mentioned belt position determined according to a combination of the output signals (0 or 1) of the sensors 394, 395, and 396.

[0059] The nine positions obtained by dividing the end position of the fixing belt 310 will be described with reference to FIG. 7. FIG. 7 is a diagram showing one end side of the fixing belt 310 from the conveying direction α, with the pressure rotator 330 positioned on the lower side. The detectable positions are a "first close-in" position where the fixing belt 310 has moved to one end side to the maximum, a "second close-in" position where the fixing belt 310 has moved to the other end side to the maximum, and seven positions obtained by equally dividing the area between the "first close-in" position and the "second close-in" position. The seven positions are, in order from the position closest to the "first close-in" position, a "front 3" position, a "front 2" position, a "front 1" position, a "middle" position, a "rear 1" position, a "rear 2" position, and a "rear 3" position. The "front" and "rear" positions here refer to the positions based on the operation unit 40.

[0060] In this embodiment, the detected portions 393b1-393b5 are arranged so that two or more of the sensors 394, 395, and 396 are simultaneously in a detection state (0) or a non-detection state (1) depending on the above-mentioned movement position of the sensor flag 393. Also, the detected portions 393b1-393b5 are arranged so that all of the sensors 394, 395, and 396 are in a detection state (or a non-detection state) when the fixing belt 310 is in the "first approach" position or the "second approach" position.

[0061] In this embodiment, the "front 3" position is the first predetermined position, and the "front 1" position is the second predetermined position. The "front 1" position is located on the "middle" position side relative to the "front 3" position.

[0062] When the fixing belt 310 is located at the "middle" position, it indicates that the center position of the fixing belt 310 in the width direction is at the center position of the steering roller 350. When the fixing belt 310 is located at the "front 1-3" position, it indicates that the center position of the fixing belt 310 in the width direction is located on one end side of the center position of the steering roller 350. Conversely, when the fixing belt 310 is located at the "rear 1-3" position, it indicates that the center position of the fixing belt 310 in the width direction is located on the other end side of the center position of the steering roller 350. Therefore, when the belt position detection unit 393 detects that the fixing belt 310 is located at the second predetermined position in the width direction, it indicates that the fixing belt 310 is located on the central position side of the steering roller 350 compared to when the fixing belt 310 is located at the first predetermined position.

[0063] Furthermore, the center position of the fixing belt 310 and the center position of the steering roller 350 may be slightly misaligned due to variations in assembly accuracy.

[0064] 7 shows nine positions from the first close-in position to the second close-in position. The nine positions are arranged at equal intervals, and in this embodiment, the intervals between each are 3 mm (see FIG. 7). In this embodiment, the first close-in position is on one end side of the steering roller 350. The "middle" position is the center position of the nine positions arranged at equal intervals. Therefore, when the belt position detector 393 detects that the end of the fixing belt 310 is at the "middle" position, it means that the fixing belt is at the center position of the steering roller 350 in the width direction.

[0065] As shown in FIG. 6(a), the sensor flag 393 is a sector-shaped columnar member, and five detection target portions 393b1-393b5 are formed on the outer peripheral surface on which the sensors 394, 395, and 396 are arranged to face each other. In other words, four openings 393a1-393a4 are formed on the outer peripheral surface so that the five detection target portions 393b1-393b5 are formed. In this embodiment, the three sensors 394, 395, and 396 are arranged at a predetermined interval along the movement direction (arrow X direction) of the sensor flag 393. It is sufficient that the detection target portions 393b1-393b5 are formed in the number of four or more, which is more than the number of sensors.

[0066] The five detection target portions 393b1 to 393b5 are formed in the sensor flag 393 so that one of the sensors 394, 395, and 396 switches between a detection state and a non-detection state as the sensor flag 393 moves. That is, the detection target portions 393b1 to 393b5 are formed so that only one of the output signals of the sensors 394, 395, and 396 changes as shown in FIG. 6(b) when the fixing belt 310 moves in the width direction. The detection target portions 393b1 to 393b5 are formed with widths as shown in FIG. 6(a) when the sensor flag 393 is divided into 27 regions at equal angles in the circumferential direction starting from the rotation center O of the sensor flag 393. Specifically, the detection target portions 393b1 and 393b2 are formed to occupy two regions, the detection target portions 393b3 and 393b5 are formed to occupy four regions, and the detection target portion 393b4 is formed to occupy three regions.

[0067] As shown in FIG. 6B, when the sensor flag 393 shown in FIG. 6A is used, when the fixing belt 310 (specifically, the end position) is in the "second close-in" position, the output signals of the three sensors 394, 395, and 396 are all "0". That is, the three sensors 394, 395, and 396 are in a detection state in which they detect the detection target portions 393b1, 393b3, and 393b4, respectively. Then, when the fixing belt 310 moves from the "second close-in" position to the "rear 3" position, the output signal of the sensor 396 changes from "0" to "1", and the output signals of the other sensors 394 and 395 remain unchanged at "0". That is, only the output signal of the sensor 396 changes. At this time, the sensor 396 faces the opening 393a4.

[0068] When the fixing belt 310 moves from the "rear 3" position to the "rear 2" position, only the output signal of the sensor 394 changes from "0" to "1". At this time, the sensor 394 faces the opening 393a1. When the fixing belt 310 moves from the "rear 2" position to the "rear 1" position, only the output signal of the sensor 395 changes from "0" to "1". At this time, the sensor 395 faces the opening 393a3. That is, all of the three sensors 394, 395, and 396 face the openings 393a1, 393a3, and 393a4, respectively, and are in a non-detection state in which none of the detection target portions 393b1 to 393b5 are detected. Therefore, all of the output signals of the three sensors 394, 395, and 396 become "1".

[0069] When the fixing belt 310 moves from the "rear 1" position to the "middle" position, only the output signal of the sensor 394 changes from "1" to "0". At this time, the sensor 394 detects the detection target portion 393b2. When the fixing belt 310 moves from the "middle" position to the "front 1" position, only the output signal of the sensor 396 changes from "1" to "0". At this time, the sensor 396 detects the detection target portion 393b5. When the fixing belt 310 moves from the "front 1" position to the "front 2" position, only the output signal of the sensor 394 changes from "0" to "1". At this time, the sensor 394 faces the opening 393a2. When the fixing belt 310 moves from the "front 2" position to the "front 3" position, only the output signal of the sensor 395 changes from "1" to "0". At this time, the sensor 395 detects the detection target portion 393b4. Furthermore, when the fixing belt 310 moves from the "near 3" position to the "first close-in" position, only the output signal of the sensor 394 changes from "1" to "0". At this time, the sensor 394 detects the detection target 393b3. When the fixing belt 310 is in the "first close-in" position, the output signals of all the sensors are "0". In other words, all of the three sensors 394, 395, and 396 are in a detection state in which they detect the detection target portions 393b3, 393b4, and 393b5, respectively. Note that when the fixing belt 310 moves from the "first close-in" position to the "second close-in" position, it is only necessary to reverse the change in the output signals of the above-mentioned sensors 394, 395, and 396, and therefore the description here will be omitted.

[0070] In order to prevent the fixing belt 310 from coming off the steering roller 350, when the belt position detection unit 393 detects that the fixing belt 310 is in the "first close-in" position or the "second close-in" position, the control unit 600 judges via the sensor unit 390 that there is a close-in error. When the control unit 600 judges that there is a close-in error, it stops the image forming process and the pressure rotor 330 is in a separated state. In addition, in order to inform the user that there is a close-in error, the operation unit 40 may display that there is a close-in error. By putting the belt in the separated state, it becomes easier for a serviceman to perform an operation to restore the image forming apparatus 100 from the close-in error to a state in which image formation is possible, that is, to recover. In this embodiment, it is an operation to move the fixing belt 310 to the "middle" position side from the "first close-in" position or the "second close-in" position.

[0071] In this embodiment, a method for detecting the widthwise position of the belt using the belt position detection unit 393 and the sensors 394, 395, and 396 has been described. However, the means for detecting the widthwise position of the belt is not limited to this, and a line sensor, an eddy current sensor, or the like may also be used.

[0072] <When in contact with the pressurized rotating body> When the fixing device 30 applies heat and pressure to a recording material carrying an unfixed toner image to perform fixing, the pressure rotating body 330 comes into contact with the fixing belt 310 to form a fixing nip N. In the contact state, the pressure rotating body 330 presses the fixing pad 380 with a force of 2000 N through the fixing belt 310. This causes paper edge scratches on the surface of the fixing belt 310. When the paper edge scratches are made on the surface of the fixing belt 310, gloss unevenness like lines are drawn on the image surface occurs. Therefore, when the pressure rotating body 330 is in the contact state, the fixing belt 310 is steered and controlled by the steering mechanism 400 to suppress deterioration of the surface of the fixing belt 310 due to the paper edge scratches.

[0073] In order to prevent scratches on the edge of the paper, the edge of the recording material is prevented from repeatedly passing over the same area on the surface of the fixing belt 310. To achieve this, when the pressure rotating body 330 is in the contact state, the fixing belt 310 is configured to reduce the number of positions at which the steering roller 350 is tilted, compared to when the pressure rotating body 330 is in the separated state.

[0074] In this embodiment, there are two positions on the fixing belt 310 where the steering roller 350 is tilted. In addition, by increasing the angle of inclination of the steering roller 350, it is possible to prevent the edge of the recording material from repeatedly passing through the same area on the surface of the fixing belt 310. This makes it possible to prevent deterioration of the surface of the fixing belt 310 due to scratches on the edge of the paper.

[0075] The steering control by the steering mechanism 400 when the pressure rotating body 330 is in the contact state will be described in detail later with reference to FIGS.

[0076] When performing image forming processing, the pressure rotating body 330 is in a contact state.

[0077] When the control unit 600 determines that the pressure rotator 330 is in the contact state, the control unit 600 tilts the steering roller 350 in accordance with the position of the fixing belt 310, as shown in FIG.

[0078] The explanation will be given with reference to the flowchart in FIG.

[0079] First, the control unit 600 determines that the pressurizing rotator 330 is in a contact state.

[0080] S001 In the contact state, the belt position detector 393 performs a first detection of the position of the fixing belt 310. When the belt position detector 393 detects that the fixing belt 310 is located at the first or second shift position (shift position), the controller 600 issues a shift error. When it is detected that the fixing belt 310 is not located at the shift position, the process proceeds to S002.

[0081] S002 If the first detection by belt position detection unit 393 detects that fixing belt 310 is located at the "front 1", "front 2", or "front 3" position, the process proceeds to S003. If the first detection by belt position detection unit 393 detects that fixing belt 310 is located at the "middle", "rear 1", "rear 2", or "rear 3", the process proceeds to S006.

[0082] S003 By the steering control, the steering roller 350 is inclined at the first inclination angle, which allows the fixing belt 310 to be used widely in the width direction, and prevents deterioration of the surface of the fixing belt 310.

[0083] The first inclination angle will be described with reference to FIG. 10. FIG. 10 is a view seen from the direction of the arrow α in FIG. 2, and the fixing belt 310 is not illustrated in order to describe the inclination angle of the steering roller 350. The pressure rotating body 330 is located at the lower side on the paper. 350a in FIG. 10 indicates the case where the steering roller is parallel to the heating roller 340. The first inclination angle is an angle at which the steering roller 350 is inclined with respect to the steering roller 350a in order to move the fixing belt 310 to the other end side of the steering roller 350 in the contact state. In this embodiment, an operation is performed to incline the steering roller 350a to the position of 350b in a counterclockwise direction on the paper of FIG. 10. The direction in which the steering roller 350a is inclined counterclockwise on the paper is defined as a first direction. Then, the fixing belt 310 is moved to the other end side of the steering roller 350. The inclination angle from the steering roller 350a to 350b at this time is defined as a first inclination angle (angle A). In this embodiment, 350a is parallel to the heating roller 340, but it may be slightly misaligned due to variations in assembly precision.

[0084] As a result of the operation of tilting the steering roller 350a to the position of 350b, the steering roller 350 is inclined at a first tilt angle.

[0085] It takes about 1.5 seconds to change the tilt angle of the steering roller 350. Therefore, the fixing belt 310 may go beyond the "near 3" position toward the first shift position (overshoot). When the belt position detector 393 detects that the fixing belt 310 has reached the first shift position and is positioned at the first shift position, the controller 600 issues a shift error.

[0086] On the other hand, a case may also be considered in which the fixing belt 310 has passed the "in front 3" position toward the first close-in position but has not yet reached the first close-in position. In this case, the steering roller 350 is tilted at the first tilt angle, so that the fixing belt 310 is moved from between the "in front 3" position and the first close-in position toward one end of the steering roller 350. As a result, the belt position detection unit 393 detects that the fixing belt 310 has reached the "in front 3" position, but the tilt angle of the steering roller 350 is tilted at the first tilt angle A, which is the first direction.

[0087] Since the steering roller 350 is inclined at the first inclination angle, the fixing belt 310 is moved to the positions "front 2", "front 1" (second predetermined position), "middle", "back 1", and "back 2" in that order. While the fixing belt 310 is being moved to the other end side, the belt position detection unit 393 detects the position of the fixing belt 310 at the positions "front 2", "front 1" (second predetermined position), "middle", "back 1", and "back 2", but no operation is performed to change the inclination angle of the steering roller 350 by steering control. The steering roller 350 is inclined at the first inclination angle.

[0088] Furthermore, the configuration may be such that the belt position detection unit 393 does not detect that the fixing belt 310 is located at the “front 2”, “front 1” (second predetermined position), “middle”, “rear 1”, or “rear 2” position, and no operation of tilting the steering roller 350 by steering control is performed.

[0089] S004 When the belt position detector 393 detects that the fixing belt 310 has been moved to the other end side of the steering roller 350 and positioned at the "rear 3" position, the process proceeds to S006. When the belt position detector 393 does not detect that the fixing belt 310 has been positioned at the "rear 3" position, the process proceeds to S005.

[0090] S005 If it is detected that the fixing belt 310 is in the overturn position, a overturn error is issued. If it is not detected that the fixing belt 310 is in the overturn position, the process returns to S003.

[0091] S006 By the steering control of the steering mechanism 400, an operation of tilting the steering roller 350 at an angle −A is performed so as to move the fixing belt 310 to one end side.

[0092] 350a in FIG. 10 indicates the state when the steering roller is parallel to the heating roller 340. The -A angle is an angle at which the steering roller 350 is inclined with respect to the steering roller 350a in order to move the fixing belt 310 to one end side of the steering roller 350. In this embodiment, an operation is performed to incline the steering roller 350a clockwise on the paper surface of FIG. 10 to the position of 350c. The direction in which the steering roller 350a is inclined clockwise on the paper surface is defined as a second direction. That is, the second direction is a direction in which the steering roller 350a is inclined clockwise, which is the opposite direction to the first direction in which the steering roller 350a is inclined counterclockwise on the paper surface. Then, the fixing belt 310 is moved to one end side of the steering roller 350. The inclination angle from the steering roller 350a to the steering roller 350c at this time is defined as angle -A.

[0093] As a result of the operation of tilting the steering roller 350a to the position of 350c, the steering roller 350 is inclined at the angle -A.

[0094] It takes about 1.5 seconds to change the tilt angle of the steering roller 350. Therefore, the fixing belt 310 may exceed the "rear 3" position toward the second shift position (overshoot). When the fixing belt 310 reaches the second shift position and the belt position detector 393 detects that the fixing belt 310 is at the second shift position, the controller 600 issues a shift error.

[0095] On the other hand, a case may also be considered in which the fixing belt 310 has passed the "rear 3" position toward the second close-in position but has not yet reached the second close-in position. In this case, the steering roller 350 is tilted at an angle -A, so that the fixing belt 310 is moved from between the "rear 3" position and the second close-in position toward one end of the steering roller 350. As a result, the belt position detection unit 393 detects that the fixing belt 310 has reached the "rear 3" position, but the steering roller 350 is inclined at an angle of -A.

[0096] Since the steering roller 350 is tilted at the angle -A, the fixing belt 310 is moved to the positions "rear 2", "rear 1", "middle", "front 1" (second predetermined position), and "front 2" in that order. While the fixing belt 310 is being moved to the one end side, the belt position detector 393 detects the position of the fixing belt 310 at the positions "front 2", "front 1" (second predetermined position), "middle", "rear 1", and "rear 2", but no operation is performed to tilt the steering roller 350 by steering control. The steering roller 350 is inclined at the angle -A.

[0097] Furthermore, the configuration may be such that the belt position detection unit 393 does not detect that the fixing belt 310 is located at the positions "rear 2," "rear 1," "middle," "front 1" (second predetermined position), or "front 2," and no operation of tilting the steering roller 350 by steering control is performed.

[0098] S007 When the belt position detector 393 detects that the fixing belt 310 has been moved to one end side of the steering roller 350 and that the fixing belt 310 has reached the "Front 3" position (first predetermined position), the process proceeds to S003. When the belt position detector 393 does not detect that the fixing belt 310 has reached the "Front 3" position (first predetermined position), the process proceeds to S008.

[0099] S008 If it is detected that the fixing belt 310 is in the overturn position, a overturn error is issued. If it is not detected that the fixing belt 310 is in the overturn position, the process returns to S006.

[0100] As shown in FIG. 9, when the pressure rotor 330 is in the contact state, the steering roller 350 is inclined at an angle A or an angle -A. In addition, when the fixing belt 310 is in the "front 1", "front 2", "rear 1", or "rear 2" positions, the steering roller 350 is not inclined, but when the fixing belt 310 is in the "front 3" or "rear 3" positions, the steering roller 350 is inclined. Therefore, the fixing belt 310 is moved back and forth between the "front 3" (first predetermined position) position and the "rear 3" position. In other words, in the width direction, the fixing belt 310 can be moved back and forth in a wider range than in the case of the separated state described later, within a range in which no edge-cutting error occurs. Therefore, deterioration of the surface of the fixing belt 310 due to scratches on the paper edge can be suppressed.

[0101] Although the steering control is performed at the "front 3" position and the "rear 3" position, the steering control may also be performed at the "front 2" and "rear 2" positions. In this case, when the belt position detection unit 393 detects that the fixing belt 310 is located at the "front 2" position, an operation to tilt the steering roller 350 is performed. The position of the steering roller 350 at this time is tilted toward the 350a side with respect to 350b. Similarly, when the belt position detection unit 393 detects that the fixing belt 310 is located at the "rear 2" position, an operation to tilt the steering roller 350 is performed. The position of the steering roller 350 at this time is tilted toward the 350a side with respect to 350c.

[0102] It is not necessary to configure the above steering control when the pressure rotator 330 is in the contact state. For example, the range in which the fixing belt 310 reciprocates may be changed depending on the type of recording material used. Also, the inclination angle of the steering roller 350 is set to A or -A, but is not limited thereto, and the inclination angle may be changed depending on the type of recording material used.

[0103] <Pressurized rotating body separated state> During a print job, the recording material is continuously transported to the nip portion N and fixed. Therefore, during a print job, the pressure rotating body 330 is in a contact state. However, even during a print job, the pressure rotating body 330 may be in a separated state. For example, this may be the case when different print jobs are continuously printed and an image formation signal is delayed. Also, this may be the case when post-processing such as stapling operation by an accessory takes time. In addition, when fixing a recording material with a large basis weight to a recording material with a small basis weight, the pressure rotating body 330 may be separated from the fixing belt to lower the temperature of the fixing belt 310 in order to lower the fixing temperature. In such cases, the paper is not transported to the nip portion N, resulting in a non-paper passing state.

[0104] When the non-paper passing state occurs, the surface temperature of the pressure rotating body 330 rises excessively due to the heat of the fixing belt 310. When fixing is performed on the recording material in a state in which the temperature of the pressure rotating body 330 has risen excessively, the toner is excessively dissolved. The excessively dissolved toner adheres to the surface of the pressure rotating body 330 or the fixing belt 310, and there is a risk that it will be re-adhered to the succeeding recording material. The area of ​​the recording material to which the toner has re-adhered may result in a defective image.

[0105] In order to suppress image defects caused by an increase in temperature of the pressure rotating body 330, the pressure rotating body 330 is kept in a separated state when no paper is passing through.

[0106] In the pressure rotator 330 separated state, the pressure of 2000N applied to the fixing belt 310 is released. Then, the reciprocating speed of the fixing belt 310 in the width direction due to the steering control increases by about 2 to 3 times compared to the pressure rotator 330 contact state. When the steering control is performed to change the tilt angle of the steering roller 350 between the "front 3" (first predetermined position) position and the "rear 3" position, which are the same conditions as the pressure rotator 330 contact state, there is a risk that the fixing belt 310 will overshoot the close-in position and cause a close-in error. There is also a risk that the fixing belt 310 will exceed the close-in position and deviate from the steering roller 350.

[0107] It is possible to suppress the overhang error by slowing down the rotation speed of the fixing belt 310. However, the non-paper passing state considered here is a paper gap of several seconds (about 4 seconds). Therefore, if the rotation speed of the fixing belt 310 is sufficiently slowed down to the extent that the overhang error does not occur, it takes time to return to the original speed just before the non-paper passing state. If the rotation speed of the fixing belt 310 cannot be returned in time before the succeeding recording material is conveyed to the nip portion N, productivity will inevitably decrease. Therefore, it was desired to suppress the occurrence of the overhang error while maintaining productivity.

[0108] When the pressure rotating body 330 is in the separated state, the nip portion N is not formed, and the surface of the fixing belt 310 is not deteriorated by the edge of the recording material. Therefore, in the width direction, when the pressure rotating body 330 is in the separated state, it is not necessary to reciprocate the fixing belt 310 over a wide range as in the steering control when the pressure rotating body 330 is in contact with the fixing belt 310. In other words, the reciprocating movement of the fixing belt 310 may be narrower than the reciprocating movement of the fixing belt 310 when the pressure rotating body 330 is in contact with the fixing belt 310.

[0109] When the pressure rotator 330 is in the separated state, the reciprocating speed of the fixing belt 310 is two to three times faster than when the pressure rotator 330 is in the contact state. Also, when the pressure rotator 330 is in the separated state, the surface of the fixing belt 310 is not deteriorated by the edge of the recording material. For these reasons, when the pressure rotator 330 is in the separated state, steering control is performed so that the center position of the fixing belt 310 is maintained at the center position of the steering roller. This makes it possible to suppress a shift error that occurs when the pressure rotator 330 is in the separated state and the fixing belt 310 reaches the shift position. In this embodiment, a configuration is used in which the number of positions of the fixing belt 310 at which the steering roller 350 is tilted is more than two, compared to two positions when the pressure rotator 330 is in the contact state.

[0110] In this embodiment, the rotation speed of the fixing belt 310 when the pressure rotator 330 is in the separated state is equal to the rotation speed of the fixing belt 310 when the pressure rotator 330 is in the contact state. Moreover, in order to suppress the overshooting error, the fixing belt 310 is reciprocated in an area narrower than in the contact state. Here, "equal" may mean that the rotation speed of the fixing belt 310 is reduced to a degree that does not reduce productivity.

[0111] The control performed when the control unit 600 determines that the pressurizing rotator 330 is in the separated state will be described in detail later.

[0112] <Example 1> A belt position detector 393 detects the position of the fixing belt 310. Depending on the position of the fixing belt 310 in the width direction, an operation of tilting the steering roller 350 is performed.

[0113] The method for determining the tilt angle in this embodiment will be described in detail below.

[0114] In this embodiment, a target position of the fixing belt 310 is set (the target position in this embodiment is the "middle" position), and an operation of tilting the steering roller 350 is performed so that the fixing belt 310 is moved to the target position. A specific method of determining the tilt angle in the separated state will be described with reference to the flowchart of FIG.

[0115] S30 First, the belt position detector 393 detects the position of the fixing belt 310 .

[0116] S31 If the fixing belt 310 is in the overhang position, the process proceeds to S35, and an overhang error is issued.

[0117] If the fixing belt 310 is not at the close-to-center position, the process proceeds to S32.

[0118] S32 Based on the detection result (B.Pnow) of the belt position detection unit 393, the difference B.Pdif from the target position "middle" is calculated.

[0119] A number between 1 and 7 is assigned to B.Pnow. The relationship between the position of the fixing belt 310 and the number assigned to B.Pnow is as shown in Fig. 15. For example, when the fixing belt 310 is at the front 3 (first predetermined position), 1 is assigned, and when the fixing belt 310 is at the rear 3, 7 is assigned. B.Pdif = 4 - B.Pnоw Equation 1 S33 The integral gain I and the cumulative integral value Itotal of the previous step are added to the difference BPdif. Here, the initial value of Itotal is 0. Itotal(n) = I×BPdif + Itotal(n-1)...Equation 2 S34 The steering angle is the sum of the difference BPdif multiplied by the proportional gain P and the cumulative integral Itotal(n). Steering angle = P×BPdif + Itotal(n) Equation 3 In this embodiment, the proportional gain P is 100, the integral gain I is 1, and the calculation is performed every 0.2 seconds. For example, if the detection result of the belt position detection unit 393 is 1, 5 is substituted for B.Pnow. In this case, the steering angle is as follows:

[0120] Rudder angle = 100×(4-5)+ 1×(4-5) = -101 The inclination angle of the steering roller 350 is determined by the steering angle value obtained from the above calculation.

[0121] The tilt angle has positive and negative tilt angles with the steering roller 350a as the reference. When the value obtained from the formulas 1 to 3 is positive, the steering roller 350 is tilted in order to move the fixing belt 310 to the other end side of the steering roller 350. The steering roller 350 is tilted counterclockwise on the paper surface of FIG. 10. Similarly, when the steering angle value is negative, the steering roller 350 is tilted in order to move the fixing belt 310 to one end side of the steering roller 350. The steering roller 350 is tilted clockwise on the paper surface of FIG. 10.

[0122] 10 shows a case where the steering roller 350a has a steering angle of 0 and is parallel to the heating roller 340, but this is not limited to the case. Because the steering roller 350a may not be parallel to the heating roller 340 due to variations in assembly precision, some deviation is acceptable.

[0123] The greater the absolute value of the determined steering angle, the greater the amount of clockwise or counterclockwise movement of 350a shown in FIG.

[0124] That is, the farther the fixing belt 310 is from the target "middle" position in the width direction, the larger the inclination angle of the steering roller 350. From the formulas 1, 2, and 3, when the fixing belt 310 is located at the target "middle" position, in this embodiment, the steering angle is 0. At this time, the steering roller 350 is inclined so that the fixing belt 310 is maintained at the "middle" position. As a result, when the fixing belt 310 is located at the target "middle" position, the fixing belt 310 is prevented from moving from the target position to the other end side or one end side of the steering roller 350.

[0125] The above steering control involves performing an operation to tilt the steering roller 350 in the width direction in accordance with the position of the fixing belt 310. In other words, an operation to tilt the steering roller 350 is performed so that the fixing belt 310 is maintained at the "middle" position in the width direction.

[0126] The position of the fixing belt 310 where the steering roller 350 is tilted in the width direction is on the "middle" side or at the "middle" position with respect to the position in the contact state, as compared with the contact state. This indicates that the position of the fixing belt where the steering roller 350 is tilted in the width direction is more frequent when the pressure rotator 330 is in the separated state than when the pressure rotator 330 is in the contact state.

[0127] In the contact state of this embodiment, no operation is performed to tilt the steering roller 350 at the "near 1" (second specified position) position, and in the separated state, an operation is performed to tilt the inclination angle of the steering roller 350 to the second inclination angle (B in the figure) at the "near 1" (second specified position) position.

[0128] On the paper surface of FIG. 11, the second inclination angle is an angle at which the steering roller 350 is inclined with respect to the steering roller 350a in order to move the fixing belt 310 to the other end side of the steering roller 350. When the steering roller 350 is inclined in the counterclockwise direction on the paper surface, which is the first direction, the fixing belt 310 is moved to the other end side of the steering roller 350. When the belt position detection unit 393 detects that the fixing belt 310 is located at the front 1 (second predetermined position) position, the steering roller 350a is inclined to the position 350d on the 350a side with respect to the position 350b. The inclination angle at this time is the second inclination angle (angle B). In other words, the relationship is the first inclination angle>the second inclination angle.

[0129] Similarly, when the belt position detector 393 detects that the fixing belt 310 is at the "rear 1" position, the steering roller 350 is tilted in the second direction, that is, clockwise on the paper, and the fixing belt 310 is moved to one end side of the steering roller 350. In this case, compared to when the steering roller 350 is tilted at the angle -A, the steering roller 350 is tilted to the position 350e (angle -B) toward the side of 350a.

[0130] In addition, in the separated state, an operation is performed to tilt the inclination angle of the steering roller 350 to a third inclination angle at the "front 2" (third predetermined position) position.

[0131] On the paper surface of FIG. 12, the third inclination angle is an angle at which the steering roller 350 is inclined with respect to the steering roller 350a in order to move the fixing belt 310 to the other end side of the steering roller 350. When the steering roller 350 is inclined counterclockwise on the paper surface, the fixing belt 310 is moved to the other end side of the steering roller 350. When the belt position detection unit 393 detects that the fixing belt 310 is located at the position of "front 2" (third predetermined position), the steering roller 350 is inclined to the position 350f, which is inclined toward the 350b side, compared to when the steering roller 350 is inclined at the second inclination angle. The inclination angle at this time is the third inclination angle (C). In other words, the relationship is that the third inclination angle is greater than the second inclination angle.

[0132] Similarly, when the belt position detector 393 detects that the fixing belt 310 is at the "rear 2" position, the steering roller 350 is tilted in the second direction, that is, clockwise on the page, and the fixing belt 310 is moved to one end side of the steering roller 350. In this case, compared to when the steering roller 350 is tilted at the angle -B, the steering roller 350 is tilted to the 350c side, that is, to the position 350g (angle -C).

[0133] The steering roller 350 is tilted at angles B, -B, C, and -C. The amount of change in one tilt operation of the steering roller 350 in the contact state is from angle A to angle -A, whereas the amount of change in one tilt operation of the steering roller 350 in the separated state is from angle C to angle -C at most. Thus, the amount of change in one tilt operation of the steering roller 350 in the separated state is smaller than that in the contact state. This makes it easier to keep the fixing belt 310 in the center of the steering roller 350.

[0134] When the pressure rotating body 330 is in the contact state, the steering roller 350 is not tilted at the "front 1", "front 2", "rear 1", and "rear 2" positions. In contrast, when the pressure rotating body 330 is in the separated state, the steering roller 350 is tilted at the "front 1", "front 2", "rear 1", and "rear 2" positions.

[0135] By carrying out the above steering control, as shown in FIG. 14, it becomes possible to reciprocate fixing belt 310 within a narrow range, compared to the case where pressure rotator 330 is in a contact state.

[0136] Specifically, in this embodiment, when the pressure rotating body 330 is in a separated state, the movement range in the width direction of the fixing belt 310 is between the "front 1" position and the "rear 1" position. In contrast, when the pressure rotating body 330 is in a contact state, the movement range in the width direction of the fixing belt 310 is between the "front 3" position and the "rear 3" position.

[0137] In the width direction, the distance between the center position of the moving range of the fixing belt 310 and the center position of the fixing belt 310 increases as the fixing belt 310 moves from the "rear 1" position to the "rear 3" position. Similarly, the distance increases as the fixing belt 310 moves from the "front 1" position to the "front 3" position. After the fixing belt 310 moves from the "middle" position, the first operation of tilting the steering roller is performed when the fixing belt is in the "front 1" position or the "rear 1" position in the separated state. On the other hand, in the abutting state, the position of the fixing belt is in the "front 3" position or the "rear 3" position. Therefore, it can be said that the distance between the center position of the fixing belt where the operation of tilting the steering roller is first performed after the center position of the fixing belt 310 moves away from the center of the moving range of the fixing belt 310 in the width direction and the center position of the moving range of the fixing belt is smaller when the pressure rotating body is in the separated state than when the pressure rotating body is in the abutting state.

[0138] <Example 2> The modified example will be described with reference to the flow chart of FIG.

[0139] FIG. 13 is a flowchart of the contact state in FIG. 8, in which "Belt position 3 nearer?" in S007 is changed to "Belt position 1 nearer?", and "Belt position 3 farther?" in S004 is changed to "Belt position 1 farther?".

[0140] Explanations of parts that overlap with the first embodiment will be omitted.

[0141] S014 Since the steering roller 350 is inclined at the first inclination angle, the fixing belt 310 passes through the center position and is moved to the other end side. While the fixing belt 310 is being moved to the other end side, the belt position detection unit 393 detects the position of the fixing belt 310, but at the center position, control to change the inclination angle of the steering roller 350 by steering control is not performed. The steering roller 350 is in a state of maintaining the first inclination angle. When the fixing belt 310 is moved to the other end side of the steering roller 350 and the belt position detection unit 393 detects that the fixing belt 310 is located at the rear 1 position, the process proceeds to S006. When the belt position detection unit 393 does not detect that the fixing belt 310 is located at the rear 1 position, the process proceeds to S005.

[0142] S017 When the belt position detector 393 detects that the fixing belt 310 has been moved to one end side of the steering roller 350 and is positioned at the front 1 position, the process proceeds to S003. When the belt position detector 393 does not detect that the fixing belt 310 has been positioned at the front 1 position, the process proceeds to S008.

[0143] It takes about 1.5 seconds to change the tilt angle of the steering roller 350. Therefore, as shown in Fig. 11, the steering control may not be completed in time, causing an "overshoot" in which the fixing belt 310 moves to the first shift position. However, by performing the steering control even at the front 1 and rear 1 positions, it is possible to prevent the fixing belt 310 from moving to the shift position.

[0144] By carrying out the above steering control, as shown in FIG. 16, it is possible to move fixing belt 310 back and forth within a narrower range than when pressure rotator 330 is in a contact state. [Explanation of symbols]

[0145] 30 Fixing device 100 Image forming device 300 Heating Rotary Body 310 Fixing belt 330 Pressurized Rotating Body 340 Heating Roller 350 Steering roller 350a Steering roller when parallel to the heating roller 350b Steering roller when inclined at an inclination angle A 350c Steering roller when inclined at an angle of -A 350d Steering roller when inclined at an angle B 350e Steering roller when inclined at an inclination angle of -B 390 Detection Unit 393 Belt position detector 400 Steering mechanism N Nip section Arrow α: Recording material conveying direction

Claims

1. A rotatable endless fixing belt; a heating roller that contacts an inner circumferential surface of the fixing belt and applies heat to the fixing belt; a steering roller that contacts the inner circumferential surface of the fixing belt together with the heating roller; a pressure rotating member that presses the fixing belt to form a nip portion, a recording material carrying unfixed toner is nipped and conveyed through the nip portion, and an unfixed toner image is fixed to the recording material, a contact / separation mechanism that can move the pressure rotating body to a position where the pressure rotating body is in contact with the fixing belt and a position where the pressure rotating body is in a separated state from the fixing belt; a belt position detection unit that detects a position of the fixing belt in a width direction of the fixing belt; a control unit that controls the steering roller to swing so as to move the fixing belt to a predetermined position in the width direction based on a detection result of the belt position detection unit, In the width direction, after the center position of the fixing belt moves away from the center of the moving range of the fixing belt, the distance between the center position of the fixing belt where the steering roller is first tilted and the center position of the moving range of the fixing belt is smaller in the separated state than in the contact state. A fixing device comprising:

2. In a certain job, the rotation speed of the fixing belt when the pressure rotating body is in the separated state is equal to the rotation speed of the fixing belt when the pressure rotating body is in the contact state.

2. The fixing device according to claim 1,

3. Based on the detection result of the belt position detection unit, in one tilting operation in which the steering roller is tilted, the amount of change in the tilt angle of the steering roller in the separated state is smaller than the amount of change in the tilt angle in the abutting state.

3. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing roller.

4. a pad that contacts the inner circumferential surface of the fixing belt and forms the nip portion together with the pressure rotating body via the fixing belt; 4. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing roller.

5. A drive motor for rotating the heating roller is provided.

5. The fixing device according to claim 1, wherein the fixing member is a fixing member having a fixing roller.

6. The steering roller is disposed downstream of the heating roller in the rotation direction of the fixing belt. The fixing device according to claim 1 .

7. In the rotation direction of the fixing belt, the belt position detection unit is disposed between the steering roller and the heating roller.

7. The fixing device according to claim 6,

8. A rotatable endless fixing belt; a heating roller that contacts an inner circumferential surface of the fixing belt and applies heat to the fixing belt; a steering roller that contacts the inner circumferential surface of the fixing belt together with the heating roller; a pressure rotating member that presses the fixing belt to form a nip portion, a recording material carrying unfixed toner is nipped and conveyed through the nip portion, and an unfixed toner image is fixed to the recording material, a contact / separation mechanism that can move the pressure rotating body to a position where the pressure rotating body is in contact with the fixing belt and a position where the pressure rotating body is in a separated state from the fixing belt; a belt position detection unit that detects a position of the fixing belt in a width direction of the fixing belt; a control unit that controls the steering roller to swing so as to move the fixing belt to a predetermined position in the width direction based on a detection result of the belt position detection unit, the steering roller is movable between a position inclined at a first inclination angle and a position inclined at a second inclination angle smaller than the first inclination angle with respect to a position in which the steering roller is parallel to the heating roller; the belt position detection unit is capable of detecting whether the fixing belt is at a first predetermined position and whether the fixing belt is at a second predetermined position in the width direction, the first predetermined position and the second predetermined position are such that a center of the fixing belt in the width direction is located on one end side of the steering roller with respect to a center of the steering roller, a center position of the fixing belt at the first predetermined position is located on one end side of the steering roller with respect to a center position of the fixing belt at the second predetermined position, When it is detected that the pressure rotating body is in the contact state and the fixing belt is positioned at a first predetermined position, an operation of tilting the steering roller is performed, and the steering roller is inclined at the first tilt angle so as to be inclined in a first direction, When it is detected that the pressure rotating body is in the contact state and the fixing belt is located at a second predetermined position, the operation of tilting the steering roller is not performed, When it is detected that the pressure rotating body is in the separated state and the fixing belt is located at a second predetermined position, an operation of tilting the steering roller is performed, and the steering roller is inclined at the second tilt angle so as to be inclined in a first direction, which is a predetermined direction. A fixing device comprising:

9. When the pressure rotating body is in the contact state and the fixing belt moves from the first predetermined position to the second predetermined position, no operation of tilting the steering roller is performed, and the steering roller is inclined in the first direction. The fixing device according to claim 8 .

10. When the pressure rotating body is in the abutting state and the center of the fixing belt is moved from a position at the center of the steering roller to the second predetermined position, no operation of tilting the steering roller is performed, and the steering roller is inclined in a second direction opposite to the first direction. The fixing device according to claim 9 .

11. When the pressure rotor is in the separated state and it is detected that the fixing belt is located at a first predetermined position, an operation of tilting the steering roller is performed, and the steering roller is inclined at the first tilt angle so as to be inclined in the first direction. The fixing device according to claim 10 .

12. The belt position detection unit is capable of detecting that the fixing belt is at a third predetermined position in the width direction, a center position of the fixing belt at the third predetermined position is located on the other end side of a center position of the fixing belt at the first predetermined position and on the one end side of a center position of the fixing belt at the second predetermined position in the width direction, When the pressure rotating body is in the separated state and the fixing belt is in the third predetermined position, the control unit inclines the steering roller at an inclination angle larger than the second inclination angle and smaller than the first inclination angle so as to move the fixing belt toward the other end side. The fixing device according to claim 8 .

Images