fixing device

Abstract

A fixing device is disclosed. The fixing device includes a fixing belt, a deflection roller, a pressure rotating member, and a contact-separation mechanism. The contact-separation mechanism moves the pressure rotating member to a position where the pressure rotating member is in contact with the fixing belt and a position where the pressure rotating member is separated from the fixing belt. The deflection roller is controlled to swing so that the fixing belt moves to a predetermined position in a width direction. In the separated state, a distance between a center position of the fixing belt when the deflection roller is tilted for the first time after the center position of the fixing belt in the width direction is separated from a center position of a moving range of the fixing belt is smaller than the distance in the contact state.

Description

Technical Field

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

[0002] The image forming apparatus includes a fixing device for fixing an unfixed toner image on a recording material onto the recording material.

[0003] The fixing device includes a pair of rotating members, which includes a fixing belt and a pressure rotating member. The fixing belt heats the unfixed toner image and is driven to rotate. The pressure rotating member presses against the fixing belt to form a clamping portion with the fixing belt and is driven to rotate. If recording material carrying the unfixed toner image is conveyed to the clamping portion, heat from the fixing belt and pressure from the pressure rotating member are applied to the recording material, thereby fixing the unfixed toner image onto the recording material.

[0004] The fixing unit also includes a contact separation mechanism, which can move the pressure rotating member to a position where the pressure rotating member contacts the fixing belt and to a position where the pressure rotating member separates from the fixing belt.

[0005] Japanese Patent Application Publication No. 2015-59964 discusses steering control of a fusing belt that reciprocates in the width direction. Repeatedly reciprocating the fusing belt within a predetermined area prevents it from slipping off the steering roller. Furthermore, it prevents the edge of the recording material from continuously passing through the same area of ​​the fusing belt. Therefore, degradation of the fusing belt surface can be reduced.

[0006] During image formation, the pressure rotating member presses the fixing pad with a force of 170 kgf through the fixing belt, thereby applying appropriate fixing pressure to the recording material.

[0007] If no material is recorded passing through the fixing clamping section for several seconds, the pressure rotating member separates from the fixing belt to prevent the temperature of the pressure rotating member from rising (separation state). In the separation state, if the fixing belt is moved back and forth in the width direction by steering control, the reciprocating speed of the fixing belt is two or three times higher than that in the contact state.

[0008] Traditionally, steering control conditions in the contact state also apply to the separation state.

[0009] Therefore, proper steering control was not performed in the separated state.

[0010] Therefore, since there is no time for steering control in the separated state, there is a possibility of a complete deviation error. Summary of the Invention

[0011] The object of this invention is to perform appropriate steering control to cause the fixing belt of the fixing device to reciprocate along the width direction. For example, under steering control, when the pressure rotating member is in a disengaged state, the fixing belt reciprocates within a narrower range than under steering control when the pressure rotating member is in a contact state.

[0012] A fixing apparatus includes: a fixing belt, which is rotatable and annular; a heating roller configured to contact the inner peripheral surface of the fixing belt and apply heat to the fixing belt; a deflector roller configured to contact the inner peripheral surface of the fixing belt together with the heating roller; a pressure rotating member configured to press the fixing belt, wherein the pressure rotating member and the fixing belt form a clamping portion and, in order to fix an unfixed toner image onto recording material, recording material carrying the unfixed toner image is conveyed to the clamping portion and clamped between the pressure rotating member and the fixing belt; and a contact-separation mechanism configured to move the pressure rotating member to contact the fixing belt. The system includes a position where the belt is in contact and a position where the pressure rotating member is separated from the fixing belt; a belt position detection unit configured to detect the position of the fixing belt in the width direction; and a control unit configured to control the oscillation of the guide roller based on the detection result of the belt position detection unit, so that the fixing belt moves to a predetermined position in the width direction, wherein, in the separated state, the distance between the center position of the fixing belt and the center position of the fixing belt's movement range when the tilting guide roller is first performed after the separation of the center position of the fixing belt from the center position of the fixing belt's movement range in the width direction is less than the distance in the contact state.

[0013] Other features of the invention will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0014] Figure 1 This is a schematic diagram showing the configuration of the image forming apparatus.

[0015] Figure 2 This is a schematic cross-sectional view of the fixing device.

[0016] Figure 3 This is a schematic diagram showing the steering mechanism.

[0017] Figure 4 This is a schematic diagram showing a sensor unit used to detect the position of the fixing belt.

[0018] Figure 5 It is a block diagram used to describe the control unit.

[0019] Figure 6A This is a schematic diagram showing a belt position detection unit used to detect the position of the fixing belt. Figure 6B This is a table showing the combinations of output signals.

[0020] Figure 7 This is a schematic diagram showing the position of the fixing tape in the width direction at one end of the fixing tape.

[0021] Figure 8 This is a flowchart illustrating the steering control when the pressure rotating component is in contact.

[0022] Figure 9 This is a diagram showing the relationship between the belt position and the tilt angle of the steering roller when the pressure rotating component is in contact.

[0023] Figure 10 This is a diagram showing the tilt angles (angles A and -A) of the steering rollers.

[0024] Figure 11 This is a diagram showing the tilt angles (angles B and -B) of the steering rollers.

[0025] Figure 12 This is a diagram showing the tilt angles (angles C and -C) of the steering rollers.

[0026] Figure 13 This is a flowchart illustrating steering control when the pressure rotating member is in a disengaged state according to a first exemplary embodiment.

[0027] Figure 14 This is a diagram showing the relationship between the belt position and the tilt angle of the steering roller when the pressure rotating member is in the separated state according to the first exemplary embodiment.

[0028] Figure 15 This is a flowchart illustrating the steering control when the pressure rotating member is in a separated state according to a variant example.

[0029] Figure 16 This is a diagram showing the relationship between the belt position and the tilt angle of the steering roller when the pressure rotating member is in the separated state according to a variant example.

[0030] Figure 17 This is a table showing the relationship between the position and the assigned value of the band according to the variant example. Detailed Implementation

[0031] Image forming apparatus

[0032] Figure 1 This is a schematic diagram showing the configuration of the image forming apparatus 100. (As shown) Figure 1 As shown, the image forming apparatus 100 includes four types of image forming units, PY, PM, PC, and PK, arranged in the moving direction of the intermediate transfer belt 6, for yellow, magenta, cyan, and black respectively. First, taking the yellow image forming unit PY as an example, the process of forming a toner image on the intermediate transfer belt 6 will be explained.

[0033] The surface of the driven rotating photosensitive drum 3 is uniformly charged by the charging device 2. Then, the exposure device 5 irradiates the surface of the photosensitive drum 3 with a laser beam based on the input image data, thereby forming an electrostatic latent image on the surface of the photosensitive drum 3 (exposure). Then, the developing device 1 forms a yellow toner image on the photosensitive drum 3 (development). The primary transfer roller 24 applies a voltage with the opposite potential polarity to the intermediate transfer belt 6. As a result, the yellow toner image on the photosensitive drum 3 is transferred to the intermediate transfer belt 6 (primary transfer). Yellow toner that is not transferred to the surface of the photosensitive drum 3 is scraped off by the toner cleaner 4 and removed from the surface of the photosensitive drum 3. Similarly, such a series of processes are performed in the magenta, cyan, and black image forming units PM, PC, and PK. As a result, a full-color toner image is formed on the intermediate transfer belt 6.

[0034] The toner image on the intermediate transfer belt 6 is transferred to the secondary transfer section n2 formed by the secondary transfer rollers 11 and 14. Recording materials S are removed one by one from the recording material cassette 10 and fed into the secondary transfer section n2 in time with the transfer of the toner image. The toner image on the intermediate transfer belt 6 is transferred to the fed recording material S (secondary transfer). Specific examples of recording materials include plain paper, resin sheets, coated paper, thick paper, and overhead projector sheets.

[0035] The recording material S, on which the toner image has been transferred, is conveyed to the fixing unit 30. The toner image is fixed onto the recording material S by heat and pressure in the fixing unit 30 (fixing). The recording material S with the fixed toner image is discharged into the discharge tray 8.

[0036] The image forming apparatus 100 can also form monochrome images. When forming a monochrome image, only the black image forming unit PK among the plurality of image forming units is driven.

[0037] The following describes duplex printing for forming images on both sides of a recording material S. The recording material S, with an image formed on one side, is discharged from the fixing unit 30 and then guided by the baffle 7 to the sheet path 18. The recording material S is conveyed from the sheet path 18 to the reversing path 19 and rotated back on the reversing path 19. Then, the recording material S passes through the duplex path 20 and is conveyed to the sheet path 21. Here, the recording material S is in a reversed state. Then, the recording material S is again conveyed to the secondary transfer section n2, and the toner image is transferred onto it. The toner image is fixed by the fixing unit 30. Then, the duplex printing recording material S is discharged into the discharge tray 8.

[0038] The series of processes from the moment the image is charged to the point where the recording material S containing the toner image is ejected into the ejection tray 8 is referred to as the image forming process (print job). The period during which image forming is performed is referred to as the image forming process period (print job period).

[0039] <Fixing Device>

[0040] Next, we will refer to Figure 2 Describes the fixing device 30 according to this exemplary embodiment.

[0041] In this exemplary embodiment, a fixing device using a circular fixing belt 310 is used. Figure 2 In this process, the recording material is conveyed in the direction indicated by arrow α. The fixing device 30 includes a heating rotating member 300 and a pressure rotating member 330. The heating rotating member 300 includes a fixing belt 310. The pressure rotating member 330 forms a clamping portion N with the fixing belt 310 by contacting it and applying pressure thereto.

[0042] The pressure rotation component 330 includes a fixing belt 310, a guide roller 350, a fixing pad 380 as a pad component, and a heating roller 340. The guide roller 350, the fixing pad 380, and the heating roller 340 are in contact with the inner circumferential surface of the fixing belt 310. The fixing belt 310 extends around the guide roller 350, the fixing pad 380, and the heating roller 340.

[0043] The heating roller 340 is formed into a cylindrical shape from metals such as aluminum and stainless steel. In this exemplary embodiment, the heating roller 340 is made of an aluminum tube with an outer diameter of 80 mm. A halogen heater 341, which serves as a heating unit for heating the fixing belt 310, is arranged inside the heating roller 340. The halogen heater 341 heats the heating roller 340 to a predetermined temperature. The heating roller 340, heated by the heat from the halogen heater 341, heats the fixing belt 310. Based on the temperature detection result of a fixing temperature detection sensor (not shown), the fixing belt 310 is controlled to a predetermined target temperature corresponding to the weight of the recording material to be fixed.

[0044] The heating unit is not limited to a halogen heater. For example, the heating unit can be configured to generate heat by induction heating (IH) of the heating roller 340. The heating roller 340 is driven by a drive motor M1 to rotate in the direction of arrow R1.

[0045] The fixing belt 310 has excellent thermal conductivity and heat resistance. For example, the fixing belt 310 is a thin annular belt with an inner diameter of 120 mm. In this exemplary embodiment, the fixing belt 310 has a three-layer structure, including a stack of a base layer, an elastic layer outside the base layer, and a release layer outside the elastic layer. The base layer is made of polyimide resin with a thickness of 60 μm. The elastic layer is made of silicone rubber with a thickness of 300 μm. The release layer is made of fluorocarbon resin tetrafluoroethylene perfluoroalkoxyalkane (PFA) with a thickness of 30 μm. The pressure rotation member 330, described below, contacts the fixing belt 310 and is driven to rotate, thereby driving the fixing belt 310 to rotate. Since the heating roller 340 is driven to rotate by the drive motor M1, it can be said that the fixing belt 310 is also driven to rotate by the rotation of the heating roller 340.

[0046] The fixing pad 380 is configured to contact the inner circumferential surface of the fixing belt 310 and to be opposite the pressure rotating member 330, with the fixing belt 310 located between them.

[0047] The pressure rotating component 330 includes a cylindrical aluminum core, a 1mm thick elastic layer outside the core, and a release layer outside the elastic layer. The release layer is designed to improve the release properties of the toner.

[0048] The pressure rotating member 330 can be moved by a contact separation mechanism, which can move the pressure rotating member 330 to contact or move away from the fixing belt 310. The contact separation mechanism includes a frame 385 and a drive motor (not shown). The frame 385 is supported by the main body of the image forming apparatus 100. The frame 385 supports the pressure rotating member 330. The frame 385 is driven to rotate about a rotation axis 332 by the drive motor (not shown). When the frame 385 rotates about the rotation axis 332 by the drive motor (not shown), the pressure rotating member 330 moves in the direction of arrow P. As a result, the pressure rotating member 330 contacts the fixing pad 380 (contact state) in a direction perpendicular to the transport direction α of the recording material, with the fixing belt 310 located between them. This forms a clamping portion N. In this exemplary embodiment, the fixing belt 310 is pressed with a total pressure of 2000 N, wherein the width of the clamping portion N is 24 mm. If the frame 385 rotates in the opposite direction to the contact direction with the rotation axis 332 as the rotation axis, the pressure rotation member 330 separates from the fixing belt 310 (separation state).

[0049] The pressure rotating member 330 is driven to rotate in the direction of arrow R2. Therefore, the fixing belt 310 sandwiched between the pressure rotating member 330 and the fixing pad 380 is driven to rotate by the rotation of the pressure rotating member 330.

[0050] As described above, the recording material carrying the unfixed toner image is clamped in the clamping portion N and conveyed through the clamping portion N. Heat and pressure are applied by the heating rotating member 300 and the pressure rotating member 330, and the unfixed toner image is fixed onto the recording material by heat and pressure.

[0051] <Steering Roller>

[0052] Next, we will refer to Figure 2 and Figure 3 Describes the steering roller 350 according to this exemplary embodiment.

[0053] In the contact state according to this exemplary embodiment, 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 edges of the recording material, resulting in uneven gloss. A detailed description of this will now be provided.

[0054] Uneven gloss caused by scratches on the paper edge.

[0055] Paper edge scratches refer to scratches caused by the cut portion (edge) of the recording material on the surface of the fixing belt 310. When fixing an unfixed toner image onto the recording material, the portion of the fixing belt 310 in contact with the edge (edge-contact portion) experiences higher stress than the portion not in contact with the edge (edge-non-contact portion). Compared to the edge-non-contact portion, the area of ​​edge damage to the recorded material may be recessed. Such recesses on the surface of the fixing belt 310 due to the edge of the recording material are called paper edge scratches.

[0056] When fixing an unfixed toner image onto recording material, the fixing device 30 applies pressure and heat to the recording material.

[0057] The surface condition of the fixing belt 310 is reflected in the gloss of the fixed image surface. If the surface of the fixing belt 310 is uneven, this unevenness will be reflected in the gloss of the image surface. Therefore, uneven gloss will appear on the image surface.

[0058] If an unfixed toner image is fixed onto the recording material while the surface of the fixing belt 310 has paper edge scratches, the image surface may appear unevenly glossy, as if a straight line has been drawn.

[0059] In this exemplary embodiment, a steering mechanism 400 for reciprocating movement of the fixing belt 310 in the width direction is used for steering control to reduce the occurrence of paper edge scratches on the surface of the fixing belt 310.

[0060] Reference Figure 3 Describe steering control.

[0061] like Figure 3 As shown, the steering mechanism 400 includes a steering roller 350, a steering motor 401, a worm gear 402, a worm wheel 403, and a fork 404. The steering motor 401 can rotate in both forward and reverse directions. When the steering motor 401 is driven to rotate by a signal from the control unit 600, the worm gear 402 attached to the steering motor 401 rotates.

[0062] The drive conversion unit 410, which has a worm gear 403 and a fork plate 404 integrally formed thereon, converts the rotation of the worm gear 402 into oscillation in the direction of the rotation axis of the steering motor 401, with the rotation axis portion 405 serving as the center of oscillation. More specifically, the worm gear 403 meshes with the worm 402 and is arranged to reciprocate in the direction of the rotation axis of the steering motor 401 as the worm gear 402 rotates. For this purpose, the worm gear 403 is formed with an arcuate meshing surface such that the meshing surface meshes with the worm 402 at the center in the direction of the rotation axis. Therefore, the drive conversion unit 410 can oscillate with the rotation axis portion 405 as the center of oscillation via the worm 402 and the worm gear 403 as the steering motor 401 rotates.

[0063] The steering mechanism 400 also includes a steering operating shaft 406, a steering roller support arm 351, and a bearing unit 352. The steering operating shaft 406, the steering roller support arm 351, and the bearing unit 352 are integrally formed with each other and attached to the steering roller 350. The bearing unit 352 rotatably supports the rotation axis of the steering roller 350. The steering roller support arm 351 is rotatably arranged and rotatably supports the steering roller 350 by retaining the bearing unit 352.

[0064] The steering operating shaft 406, mounted on the aforementioned drive conversion unit 410, is fixed to the steering roller support arm 351. The steering operating shaft 406 is mounted on the fork plate 404 of the drive conversion unit 410 and can move with the drive conversion unit 410 while maintaining its mounted position. Therefore, the tilt of the steering roller 350 changes in conjunction with the oscillation of the drive conversion unit 410. More specifically, the steering roller 350 relative to the heating roller 340 (see [link to steering motor]) can be continuously changed by driving the steering motor 401. Figure 2 The arrangement angle of the guide roller 350 is adjusted in this way. If the steering angle of the guide roller 350 is adjusted in this way, the fixing belt 310 stretched around the guide roller 350, the heating roller 340, and the fixing pad 380 will reciprocate in the width direction. This allows for steering control on the fixing belt 310, causing the fixing belt 310 to reciprocate within a predetermined area in the width direction. If the guide roller 350 is tilted by rotating the guide motor 401 forward, or if the guide roller 350 is tilted by rotating the guide motor 401 backward, the fixing belt 310 will move in the opposite direction of movement.

[0065] As described above, the steering mechanism 400 moves the fixing belt 310, causing it to reciprocate along its width within the area of ​​the steering roller 350. This reciprocating movement of the fixing belt 310 prevents the edges of the recording material from continuously passing through the same area on the surface of the fixing belt 310. This reduces the appearance of paper edge scratches on the surface of the fixing belt 310.

[0066] <Fixing Tape Position Detection>

[0067] Reference Figure 2 , 3 Section 4 describes a belt position detection unit for detecting the position of the fixing belt 310 in the width direction.

[0068] In this exemplary embodiment, the fixing device 30 includes a sensor unit 390 for detecting the position of the end of the fixing belt 310 in the width direction (hereinafter referred to as the end position). The end position of the fixing belt 310 is detected based on the output signal of the sensor unit 390. The tilt angle of the steering roller 350 is changed by operating the aforementioned steering mechanism 400 based on the detected end position of the fixing belt 310. (Refer to...) Figure 4 Describe the configuration of sensor unit 390.

[0069] like Figure 4 As shown, the sensor unit 390 according to this exemplary embodiment includes a contact member 391, an arm member 392, a position detection unit (hereinafter referred to as a sensor marker) 393, and three sensors 394, 395, and 396. The contact member 391 contacts the end of the fixing belt 310. The arm member 392 supports the contact member 391. The position detection unit 393 serves as a moving member. Sensors 394, 395, and 396 are used to detect the position of the end of the fixing belt 310. For example, optical sensors are used as sensors 394, 395, and 396. The contact member 391 is located at one end of the arm member 392 to contact the end of the fixing belt 310 in the width direction.

[0070] An arm member 392 is biased from the end of the fixing belt 310 toward its center in the width direction by a helical spring (not shown). The arm member 392 is rotatably arranged to follow the movement of the fixing belt 310 in the width direction via a contact member 391. A belt position detection unit 393, which serves as a moving member, is located at the other end of the arm member 392. For example, the belt position detection unit 393 is a fan-shaped columnar member with a plurality of openings 393a and a plurality of detection portions 393b in / on its arcuate outer periphery. Three sensors 394, 395, and 396 are arranged at a predetermined distance in the rotational movement direction of the belt position detection unit 393, such that the sensors 394, 395, and 396 are opposite to the outer periphery of the belt position detection unit 393, on which the openings 393a and detection portions 393b are formed.

[0071] In this exemplary embodiment, when the fixing belt 310 moves from one end to the other in the width direction, the belt position detection unit 393 rotates along with the movement of the fixing belt 310. As the belt position detection unit 393 rotates, the positional relationship between the sensors 394, 395, and 396 and the portion to be detected 393b (or the opening 393a) changes. Specifically, this involves switching between a detection state where the sensors 394, 395, and 396 detect the portion to be detected 393b and a non-detection state where the sensors 394, 395, and 396 are opposite the opening 393a and therefore do not detect any portion to be detected 393b.

[0072] In this exemplary embodiment, optical sensors are used as sensors 394, 395, and 396. Each of sensors 394, 395, and 396 includes a light-emitting unit for emitting light and a light-receiving unit for receiving light emitted from the light-emitting unit. Sensors 394, 395, and 396 emit a predetermined amount of light from their respective light-emitting units towards the position detection unit 393. If the emitted light is blocked by the detection portion 393b of the position detection unit 393, the light-receiving units of sensors 394, 395, and 396 do not receive the light emitted from the light-emitting unit. Conversely, if the emitted light is not blocked by the detection portion 393b but passes through the opening 393a of the position detection unit 393, the light-receiving units receive the light emitted from each light-emitting unit. In this way, whether each sensor 394, 395, and 396 receives light depends on the movement of the position detection unit 393.

[0073] <Control Unit>

[0074] like Figure 1 As shown, the image forming apparatus 100 includes a control unit 600. (Refer to...) Figure 5 as well as Figures 2 to 4 The control unit 600 will now be described. The control unit 600 is also connected to various devices other than those shown, such as motors and power supplies for operating the image forming apparatus 100. Since such devices are not relevant to the essential points of this exemplary embodiment, their description will be omitted.

[0075] The control unit 600, serving as a control device, performs various types of control, such as image forming operations. The control unit 600 includes, for example, a central processing unit (CPU) 601 and a memory 602. The memory 602 includes read-only memory (ROM) and random access memory (RAM). The memory 602 stores various programs and various types of data used to control the image forming apparatus 100. The CPU 601 can execute the various programs stored in the memory 602, and the image forming apparatus 100 can be operated by executing these programs.

[0076] In this exemplary embodiment, CPU 601 executes an image forming job processing program and a steering control program stored in memory 602, which are described below.

[0077] Memory 602 stores sensor value tables (see description below) Figure 6B This table will be referenced, for example, during deviation control processing, when identifying the end position of the fixing belt 310, which moves reciprocally by steering control, and when determining whether the sensor unit 390 is faulty. The memory 602 can also temporarily store the results of computational processing resulting from the execution of various programs.

[0078] The operation unit 40 is connected to the control unit 600 via an input / output interface. For example, the operation unit 40 includes a touch panel LCD screen (display unit) so that a user can input start commands for various programs, such as image forming job processing programs, and various types of data, such as the dimensions of the recording material (A3, B4, etc.). The LCD screen can display various screens, including software keys. Various functions can be performed based on the user's touch operation of the software keys, such as giving start commands for various previously assigned programs. The LCD screen can also display various types of information, such as the operating status of the image forming apparatus 100 and error messages for user notification. In other words, in this exemplary embodiment, the operation unit 40 can be used as a notification unit. The method for notifying the user of various types of information, such as error messages, is not limited to the aforementioned display-based method; any suitable notification method can be used. Examples include sound-based notification methods using a sound generation unit (e.g., a speaker).

[0079] The drive motor M1, steering motor 401, temperature sensor 370, halogen heater 341, sensor unit 390, position sensor 407, and motor for driving the pressure rotation member 330 are further connected to the control unit 600 via an input / output interface. If an instruction to start an image forming operation is issued from the operation unit 40, the control unit 600 (more specifically, CPU 601) executes the image forming operation processing program stored in the memory 602. The control unit 600 controls the image forming apparatus 100 based on the execution of the image forming operation processing program. Therefore, the control unit 600 drives the drive motor M1 to rotate the heating roller 340, thereby rotating the fixing belt 310. The control unit 600 also controls the halogen heater 341 based on the detection result of the temperature sensor 370, such that the surface temperature of the fixing belt 310 reaches the desired target temperature (180°C in this exemplary embodiment). The control unit 600 also controls the motor driving the pressure rotation member 330, and thus can determine whether the pressure rotation member 330 is in contact with or separated from the fixing belt 310.

[0080] In this exemplary embodiment, the control unit 600 bases its detection results on the sensor unit 390, or more specifically, on the combination of the output signals from the three sensors 394, 395, and 396 (see description below). Figure 6B The control unit 600 controls the steering motor 401. More specifically, the control unit 600 detects the end position of the fixing belt 310 based on the detection results of the sensor unit 390, and rotates the steering motor 401 forward or backward based on the amount of rotation determined from the detected position. Therefore, the control unit 600 can perform steering control on the fixing belt 310 by operating the aforementioned steering mechanism 400 using the steering motor 401.

[0081] <With position detection unit>

[0082] Reference Figure 6A and Figure 6B The above-mentioned position detection unit 393 is described. Figure 6A This is a top view used to describe the position detection unit 393. Figure 6B Possible combinations of the output signals of sensors 394, 395, and 396 are shown when using position detection unit 393. Figure 6A The diagram illustrates twenty-seven regions at nine locations on the fixing belt 310 in the width direction, configured to use three sensors 394, 395, and 396. For example, when in a detection state that detects any one of the portions 393b1 to 393b5, sensors 394, 395, and 396 each output a signal "0". In other words, when in a blocked state where the sensors are obscured by any one of the portions 393b1 to 393b5, each sensor outputs a signal "0". Conversely, when in a non-detection state that does not detect any of the portions 393b1 to 393b5, sensors 394, 395, and 396 each output a signal "1". In other words, when in an open state (also called an unblocked state) where the sensors are opposite one of the openings 393a1 to 393a4, each sensor outputs a signal "1".

[0083] exist Figure 6B In this embodiment, sensor 394 is referred to as the "first sensor," sensor 395 as the "second sensor," and sensor 396 as the "third sensor." The belt position is a value determined by the combination of the output signals of sensors 394, 395, and 396. In this exemplary embodiment, control unit 600 can detect the end position of the fixing belt 310 in nine subdivided positions based on the aforementioned belt position determined according to the combination of the output signals ("0" or "1") of sensors 394, 395, and 396.

[0084] Reference Figure 7Nine subdivisions describe the end position of the fixing tape 310. Figure 7 This diagram shows one end of the fixing belt 310 as seen in the conveying direction α with the pressure rotating member 330 facing downwards. Detectable positions include the "first full deviation" position where the fixing belt 310 is fully moved to one end, the "second full deviation" position where the fixing belt 310 is fully moved to the other end, and seven average subdivision positions between the "first full deviation" and "second full deviation" positions. These seven positions, in order of proximity to the "first full deviation" position, are the "near 3" position, "near 2" position, "near 1" position, "center" position, "far 1" position, "far 2" position, and "far 3" position. As used herein, a "near" position refers to a position close to the operating unit 40, and a "far" position refers to a position far from the operating unit 40.

[0085] In this exemplary embodiment, the arrangement of the parts to be detected 393b1 to 393b5 is such that if the fixing belt 310 is in the "first full deviation" position or the "second full deviation" position, all sensors 394, 395 and 396 are in the detection state.

[0086] In this exemplary embodiment, the "near 3" position will be referred to as the first predetermined position, and the "near 1" position will be referred to as the second predetermined position. The "near 1" position is located on the "center" position side of the "near 3" position.

[0087] The fixing belt 310 being in the "center" position means that the center of the fixing belt 310 in the width direction falls on the center of the guide roller 350. The fixing belt 310 being in the "near 1" to "near 3" position means that the center of the fixing belt 310 in the width direction falls on one end of the center of the guide roller 350. In contrast, the fixing belt 310 being in the "far 1" to "far 3" position means that the center of the fixing belt 310 in the width direction falls on the other end of the center of the guide roller 350. Therefore, compared to when the fixing belt 310 is in the first predetermined position, the sensor unit 390 detecting that the fixing belt 310 is in the second predetermined position in the width direction means that the fixing belt 310 is near the center of the guide roller 350.

[0088] Due to assembly precision requirements, the center positions of the fixing belt 310 and the guide roller 350 may differ.

[0089] Figure 7 Nine positions are shown, ranging from the "first full deviation" position to the "second full deviation" position. These nine positions are arranged at equal intervals. In this exemplary embodiment, the distance is 3 mm (see [link to example]. Figure 7In this exemplary embodiment, the "first full deviation" position is located at one end of the guide roller 350. The "center" position is the center of nine positions arranged at equal intervals. The sensor unit 390 detecting that the end of the fixing belt 310 is located at the "center" position means that the fixing belt 310 is located at the center of the guide roller 350 in the width direction.

[0090] like Figure 6A As shown, sensor mark 393 is a fan-shaped columnar member, and its outer periphery opposite sensors 394, 395, and 396 includes five detectable portions 393b1 to 393b5. In other words, four openings 393a1 to 393a4 are formed in the outer periphery to form the five detectable portions 393b1 to 393b5. In this exemplary embodiment, three sensors 394, 395, and 396 are arranged at a predetermined distance along the direction of movement of sensor mark 393 (the direction of arrow X). The number of detectable portions formed can be greater than or equal to the number of sensors, or four.

[0091] The five detectable portions 393b1 to 393b5 are configured such that, as the sensor mark 393 moves, one of the sensors 394, 395, and 396 switches between a detection state and a non-detection state each time. In other words, the detectable portions 393b1 to 393b5 are configured such that, when the fixing belt 310 moves in the width direction, only one of the output signals of sensors 394, 395, and 396 changes at any given time, such as... Figure 6B As shown. For example, suppose sensor marking 393 is divided into 27 regions at equal angles around the rotation center O. The detectable portions 393b1 to 393b5 are formed with, as shown... Figure 6A The width is shown. Specifically, the parts to be detected 393b1 and 393b2 are each formed to occupy two regions, the parts to be detected 393b3 and 393b5 are each formed to occupy four regions, and the part to be detected 393b4 is formed to occupy three regions.

[0092] like Figure 6B As shown, if using Figure 6AWith sensor marker 393 shown and fixing belt 310 (more specifically, its end position) in the "second full deviation" position, the output signals of the three sensors 394, 395, and 396 are all "0". In other words, the three sensors 394, 395, and 396 are in a detection state, detecting the parts to be detected 393b1, 393b3, and 393b4, respectively. If fixing belt 310 moves from the "second full deviation" position to the "far 3" position, the output signal of sensor 396 changes from "0" to "1". The output signals of the other sensors 394 and 395 remain unchanged from "0". In other words, only the output signal of sensor 396 changes. Here, sensor 396 is opposite to opening 393a4.

[0093] If the fixing belt 310 moves from the "far 3" position to the "far 2" position, only the output signal of sensor 394 changes from "0" to "1". Here, sensor 394 is opposite to opening 393a1. If the fixing belt 310 moves from the "far 2" position to the "far 1" position, only the output signal of sensor 395 changes from "0" to "1". Here, sensor 395 is opposite to opening 393a3. In other words, all three sensors 394, 395, and 396 are in a non-detection state, opposite openings 393a1, 393a3, and 393a4 respectively, and do not detect any of the parts to be detected 393b1 to 393b5. Therefore, all output signals of the three sensors 394, 395, and 396 are "1".

[0094] If the fixing belt 310 moves from the "far 1" position to the "center" position, only the output signal of sensor 394 changes from "1" to "0". Here, sensor 394 detects the portion to be detected 393b2. If the fixing belt 310 moves from the "center" position to the "near 1" position, only the output signal of sensor 396 changes from "1" to "0". Here, sensor 396 detects the portion to be detected 393b5. If the fixing belt 310 moves from the "near 1" position to the "near 2" position, only the output signal of sensor 394 changes from "0" to "1". Here, sensor 394 is opposite to the opening 393a2. If the fixing belt 310 moves from the "near 2" position to the "near 3" position, only the output signal of sensor 395 changes from "1" to "0". Here, sensor 395 detects the portion to be detected 393b4. If the fixing belt 310 moves from the "near 3" position to the "first full deviation" position, only the output signal of sensor 394 changes from "1" to "0". Here, sensor 394 detects the portion to be detected 393b3. If the fixing belt 310 is at the "first full deviation" position, the output signals of all sensors 394, 395, and 396 are "0". In other words, all three sensors 394, 395, and 396 are in detection mode, detecting the portions to be detected 393b3, 393b4, and 393b5 respectively. If the fixing belt 310 moves from the "first full deviation" position to the "second full deviation" position, the output signals of sensors 394, 395, and 396 change in the reverse order. Therefore, a description of this will be omitted.

[0095] If sensor unit 390 detects that the fixing belt 310 is in the "first full deviation" position or the "second full deviation" position, control unit 600 determines that a full deviation error has occurred. This is to prevent the fixing belt 310 from detaching from the guide roller 350. If control unit 600 determines that a full deviation error has occurred, control unit 600 stops the image forming process and puts pressure rotation member 330 into a separated state. Furthermore, control unit 600 can display a message indicating a full deviation error on operation unit 40 to notify the user. The separated state facilitates the resumption of operation by maintenance personnel, allowing the image forming apparatus 100 to return from a full deviation error to a state capable of forming an image.

[0096] In this exemplary embodiment, a method for detecting the position of the fixing belt 310 in the width direction using a position detection unit 393 and sensors 394, 395, and 396 is described. However, the unit used to detect the position of the fixing belt 310 in the width direction is not limited thereto. A line sensor or an eddy current sensor can be used.

[0097] When the pressure rotating component is in contact:

[0098] When the fixing unit 30 performs fixing by applying heat and pressure to the recording material carrying the unfixed toner image, the pressure rotating member 330 enters a contact state, in which it contacts the fixing belt 310 to form a clamping portion N. In the contact state, the pressure rotating member 330 presses the fixing pad 380 with a force of 2000N through the fixing belt 310. This leaves paper edge scratches on the surface of the fixing belt 310. Paper edge scratches on the surface of the fixing belt 310 may produce uneven gloss, like drawing lines on the image surface. If the pressure rotating member 330 is in the contact state, the steering mechanism 400 is therefore used to perform steering control on the fixing belt 310 to reduce the deterioration of the surface of the fixing belt 310 due to paper edge scratches.

[0099] To reduce paper edge scratches and prevent the edges of the recording material from repeatedly crossing the same area on the surface of the fixing belt 310, a configuration is used when the pressure rotating member 330 is in contact, compared to when the pressure rotating member 330 is in the separated state, to reduce the number of positions of the fixing belt 310 that perform the operation of the tilting guide roller 350.

[0100] In this exemplary embodiment, the operation of the tilting guide roller 350 is performed at two positions on the fixing belt 310. Furthermore, the tilt angle of the guide roller 350 is increased, thereby reducing the frequency with which the edge of the recorded material passes over the same area on the surface of the fixing belt 310. As a result, surface degradation of the fixing belt 310 due to paper edge scratches can be reduced.

[0101] The following will refer to Figure 8 , 9 Sections 1 and 10 describe the details of the steering control performed by the steering mechanism 400 when the pressure rotating member 330 is in the contact state.

[0102] During image forming processing, the pressure rotating member 330 enters a contact state.

[0103] If the control unit 600 determines that the pressure rotating member 330 is in a contact state, then as follows Figure 8 As shown, the control unit 600 performs steering control via a position tilting steering roller 350 based on the position of the fixing belt 310.

[0104] Reference Figure 8 The flowchart provides an explanation.

[0105] In step S000, the control unit 600 determines that the pressure rotating member 330 is in a contact state.

[0106] In step S001, with the pressure rotating member 330 in contact, the sensor unit 390 first detects the position of the fixing belt 310. If the sensor unit 390 detects that the fixing belt 310 is in the "first full deviation" position or the "second full deviation" position (full deviation position) ("Yes" in step S001), the process proceeds to step S009. In step S009, the control unit 600 issues a full deviation error. If the fixing belt 310 is detected not to be in the full deviation position ("No" in step S001), the process proceeds to step S002.

[0107] In step S002, if sensor unit 390 detects through the first detection that the fixing belt 310 is located at a "near 1", "near 2", or "near 3" position ("Yes" in step S002), the process proceeds to step S003. If sensor unit 390 detects through the first detection that the fixing belt 310 is located at a "center", "far 1", "far 2", or "far 3" position ("No" in step S002), the process proceeds to step S006.

[0108] In step S003, the control unit 600 performs steering control to tilt the steering roller 350 at a first tilt angle. This allows for the use of a large area of ​​the fixing belt 310 in the width direction and reduces surface degradation of the fixing belt 310.

[0109] Reference Figure 10 Describe the first tilt angle. Figure 10 yes Figure 2 The view in the direction of the middle arrow α. Because... Figure 10 This is intended to illustrate the tilt angle of the guide roller 350, therefore the fixing belt 310 is not shown. The pressure rotating member 330 is shown at the bottom. Figure 10 In this embodiment, the guide roller 350a refers to the guide roller 350 that is parallel to the heating roller 340. The first tilt angle refers to the angle at which the guide roller 350 is tilted relative to the guide roller 350a so that the fixing belt 310 moves toward the other end of the guide roller 350 in the contact state. In this exemplary embodiment, the guide roller 350a is in Figure 10 Tilting counterclockwise upwards to position 350b of the steering roller. Figure 10 In this embodiment, the direction in which the guide roller 350a tilts counterclockwise will be referred to as the first direction. As a result, the fixing belt 310 moves toward the other end of the guide roller 350. The tilt angle from the guide roller 350a to the guide roller 350b is called the first tilt angle (angle A). In this exemplary embodiment, the guide roller 350a is described as parallel to the heating roller 340. However, due to variations in assembly precision, the guide roller 350a and the heating roller 340 may not be entirely parallel.

[0110] As part of the operation of tilting the steering roller 350a to the position of the steering roller 350b, the steering roller 350 is tilted at a first tilt angle.

[0111] Changing the tilt angle of the steering roller 350 takes approximately 1.5 seconds. Therefore, it is possible for the fixing belt 310 to move beyond the "near 3" position towards the "first full deviation" position (overshoot). If the fixing belt 310 reaches the "first full deviation" position, and the sensor unit 390 detects that the fixing belt 310 is in the "first full deviation" position, the control unit 600 issues a full deviation error.

[0112] The fixing belt 310 may sometimes move beyond the "near 3" position toward the "first full deviation" position without reaching it. In this case, because the guide roller 350 is tilted at a first tilt angle, the fixing belt 310 moves from between the "near 3" position and the "first full deviation" position toward the other end of the guide roller 350. Here, the sensor unit 390 detects that the fixing belt 310 is at the "near 3" position, and the guide roller 350 is tilted in a first direction at a first tilt angle (angle A).

[0113] Because the guide roller 350 is tilted at a first tilt angle, the fixing belt 310 moves sequentially to positions "near 2", "near 1" (second predetermined position), "center", "far 1", and "far 2". When the fixing belt 310 moves to the other end, the sensor unit 390 detects that the fixing belt 310 is at positions "near 2", "near 1" (second predetermined position), "center", "far 1", and "far 2". Simultaneously, the control unit 600 does not perform the operation of changing the tilt angle of the guide roller 350 through steering control; the guide roller 350 remains tilted at the first tilt angle.

[0114] Alternatively, the sensor unit 390 can be configured not to detect that the fixing belt 310 is in the "near 2", "near 1" (second predetermined position), "center", "far 1" or "far 2" position, so that the operation of tilting the steering roller 350 by steering control is not performed.

[0115] In step S004, if the fixing belt 310 moves toward the other end of the guide roller 350 and the sensor unit 390 detects that the fixing belt 310 is in the "far 3" position (yes in step S004), the process proceeds to step S006. If the sensor unit 390 does not detect that the fixing belt 310 is in the "far 3" position (no in step S004), the process proceeds to step S005.

[0116] In step S005, if the fixing belt 310 is detected to be at the full deviation position (“second full deviation” position) (“Yes” in step S005), the process proceeds to step S010. In step S010, the control unit 600 issues a full deviation error. If the fixing belt 310 is not detected to be at the full deviation position (“No” in step S005), the process returns to step S003.

[0117] In step S006, the control unit 600 performs an operation to tilt the steering roller 350 at an angle of -A via steering control on the steering mechanism 400. The purpose is to move the fixing belt 310 toward one end.

[0118] Figure 10 In this embodiment, the guide roller 350a refers to the guide roller 350 that is parallel to the heating roller 340. Angle-A refers to the angle at which the guide roller 350 is tilted relative to the guide roller 350a to move the fixing belt 310 toward one end of the guide roller 350. In this exemplary embodiment, in Figure 10 In this process, the control unit 600 performs the operation of tilting the steering roller 350a clockwise to the position of the steering roller 350c. Figure 10 In this context, the direction in which the steering roller 350a tilts clockwise will be referred to as the second direction. In other words, the second direction is the direction in which the steering roller 350 tilts clockwise, and... Figure 10 The first direction of the counterclockwise tilt of the middle guide roller 350 is reversed. The fixing belt 310 thus moves towards one end of the guide roller 350. Here, the tilt angle from guide roller 350a to guide roller 350c is called angle A.

[0119] As a result of the operation of tilting the steering roller 350a to the position of the steering roller 350c, the steering roller 350 is tilted at an angle -A.

[0120] Changing the tilt angle of the steering roller 350 takes approximately 1.5 seconds. Therefore, the fixing belt 310 may move beyond the "far 3" position towards the "second full deviation" position (overshoot). If the fixing belt 310 reaches the "second full deviation" position, and the sensor unit 390 detects that the fixing belt 310 is in the "second full deviation" position, the control unit 600 issues a full deviation error.

[0121] The fixing belt 310 sometimes moves beyond the "far 3" position towards the "second full deviation" position, but does not reach it. In this case, because the guide roller 350 is tilted at angle -A, the fixing belt 310 moves from between the "far 3" position and the "second full deviation" position towards one end of the guide roller 350. Here, the sensor unit 390 detects that the fixing belt 310 is at the "far 3" position and the guide roller 350 is tilted at angle -A.

[0122] Because the guide roller 350 is tilted at angle -A, the fixing belt 310 moves sequentially to positions "far 2", "far 1", "center", "near 1" (second predetermined position) and "near 2". When the fixing belt 310 moves to one end, the sensor unit 390 detects that the position of the fixing belt 310 is at positions "far 2", "far 1", "center", "near 1" (second predetermined position) and "near 2". At the same time, the control unit 600 does not perform the operation of changing the tilt angle of the guide roller 350 through steering control, and the guide roller 350 remains tilted at angle -A.

[0123] Alternatively, the sensor unit 390 can be configured not to detect that the fixing belt 310 is in the "far 2", "far 1", "center", "near 1" (second predetermined position) or "near 2" position, so that the operation of tilting the steering roller 350 by steering control is not performed.

[0124] In step S007, if the fixing belt 310 moves toward one end of the guide roller 350 and the sensor unit 390 detects that the fixing belt 310 is in the "near 3" position (first predetermined position) (yes in step S007), then the process proceeds to step S003. If the sensor unit 390 does not detect that the fixing belt 310 is in the "near 3" position (first predetermined position) (no in step S007), then the process proceeds to step S008.

[0125] In step S008, if the fixing belt 310 is detected to be at the full deviation position (“first full deviation” position) (“Yes” in step S008), the process proceeds to step S011. In step S011, the control unit 600 issues a full deviation error. If the fixing belt 310 is not detected to be at the full deviation position (“No” in step S008), the process returns to step S006.

[0126] like Figure 9 As shown, if the pressure rotating member 330 is in contact, the guide roller 350 tilts at angle A or angle -A. When the fixing belt 310 is in the "near 1", "near 2", "far 1", or "far 2" position, the tilting of the guide roller 350 is not performed. The tilting of the guide roller 350 is performed in the "near 3" and "far 3" positions. Therefore, the fixing belt 310 reciprocates between the "near 3" position (first predetermined position) and the "far 3" position. In other words, compared to the separated state described below, the fixing belt 310 can therefore reciprocate over a wider range in the width direction without causing a complete deviation error. This reduces the deterioration of the fixing belt 310 surface due to paper edge scratches.

[0127] Although steering control is described as being performed at the "near 3" and "far 3" positions, steering control can also be performed at the "near 2" and "far 2" positions. In this case, if sensor unit 390 detects that the fixing belt 310 is at the "near 2" position, the tilting operation of the steering roller 350 is performed. Here, the tilting position of the steering roller 350 falls on the steering roller 350a side of the steering roller 350b. Similarly, if sensor unit 390 detects that the fixing belt 310 is at the "far 2" position, the tilting operation of the steering roller 350 is performed. Here, the tilting position of the steering roller 350 falls on the steering roller 350a side of the steering roller 350c.

[0128] If the pressure rotating member 330 is in contact, steering control as described above is not necessary. For example, the reciprocating range of the fixing belt 310 can be varied depending on the type of recording material used. Although the tilt angle of the steering roller 350 is described as angles A and -A, this is not limiting. The tilt angle can be varied depending on the type of recording material used.

[0129] <When the pressure rotating component is in the separated state>

[0130] During a printing job, the recording material is continuously fed into the clamping section N for fixing. Therefore, the pressure rotating member 330 remains in contact during the printing job. However, even during a printing job, the pressure rotating member 330 sometimes enters a separated state. Examples include when different printing jobs are printed consecutively and there is a delay in the image forming signal. Another example is when post-processing (such as binding operations in auxiliary equipment) takes a long time. Furthermore, when fixing low-basis-weight recording material after high-basis-weight recording material, the pressure rotating member 330 may separate from the fixing belt 310 to reduce the temperature of the fixing belt 310 or the fixing temperature. In this case, the fixing unit 30 enters a non-sheet-passing state, in which no sheet is fed to the clamping section N.

[0131] When the film is not passing through, the surface temperature of the pressure rotating member 330 may rise excessively due to the heat from the fixing belt 310. If fixing of the recording material is performed while the pressure rotating member 330 is overheated, the toner may melt excessively. The excessively melted toner may adhere to the surface of the pressure rotating member 330 or the fixing belt 310 and re-adhere to subsequent recording material. Areas of toner re-adhesion in the recording material may result in image defects.

[0132] To prevent image defects caused by temperature rise of the pressure rotating member 330, the pressure rotating member 330 is placed in a separated state during the non-sheet passage state.

[0133] When the pressure rotating member 330 is in the disengaged state, the fixing belt 310 is released from the 2000N pressure. Compared to when the pressure rotating member 330 is in the contact state, the lateral reciprocating speed of the fixing belt 310 is increased by approximately two to three times through steering control. Assuming steering control is performed under the same conditions as when the pressure rotating member 330 is in the contact state, i.e., changing the tilt angle of the steering roller 350 between the "near 3" position (first predetermined position) and the "far 3" position, this could cause the fixing belt 310 to overshoot to the full deviation position side, resulting in a full deviation error. Furthermore, the fixing belt 310 might even exceed the full deviation position and detach from the steering roller 350.

[0134] Complete deviation errors can be prevented by reducing the rotational speed of the fixing belt 310. However, the non-sheet passage state discussed here only lasts for a few seconds (approximately four seconds) between sheets. If the rotational speed of the fixing belt 310 is reduced sufficiently to prevent complete deviation errors, it takes a considerable amount of time to restore the rotational speed to its original speed immediately prior to the non-sheet passage state. If the rotational speed of the fixing belt 310 cannot be restored before the next recording material is conveyed to the clamping section N, productivity decreases. Therefore, it is desirable to prevent complete deviation errors while maintaining productivity.

[0135] When the pressure rotating member 330 is in the separated state, no clamping portion N is formed, and the surface of the fixing belt 310 is not degraded by the edges of the recording material. Therefore, when the pressure rotating member 330 is in the separated state, the fixing belt 310 does not need to reciprocate over a wide range in the width direction as it does when the steering control is in the contact state. In other words, the fixing belt 310 can reciprocate over a narrower range compared to when the pressure rotating member 330 is in the contact state.

[0136] If the pressure rotating member 330 is in the separated state, the reciprocating speed of the fixing belt 310 is two to three times that in the contact state. Furthermore, if the pressure rotating member 330 is in the separated state, the surface of the fixing belt 310 will not deteriorate due to the edges of the recording material. Therefore, if the pressure rotating member 330 is in the separated state, steering control is performed to maintain the center position of the fixing belt 310 at the center position of the steering roller 350. This prevents complete deviation errors caused by the fixing belt 310 reaching a complete deviation position when the pressure rotating member 330 is in the separated state. This exemplary embodiment is configured such that the number of positions where the tilting steering roller 350 is performed is greater than the number (i.e., two) when the pressure rotating member 330 is in the contact state.

[0137] In this exemplary embodiment, when the pressure rotating member 330 is in the separated state, the rotational speed of the fixing belt 310 is the same as when the pressure rotating member 330 is in the contact state. Furthermore, to prevent complete deviation errors, the fixing belt 310 reciprocates over a narrower area than in the contact state. As employed herein, the same rotational speed can cover a configuration that reduces the rotational speed of the fixing belt 310 without reducing productivity.

[0138] The control details will be described below when the control unit 600 determines that the pressure rotating member 330 is in a disengaged state.

[0139] Sensor unit 390 detects the position of fixing belt 310. Control unit 600 performs operation of tilting guide roller 350 based on the position of fixing belt 310 in the width direction.

[0140] The details of the method for determining the tilt angle according to the first exemplary embodiment will now be described in detail.

[0141] In this exemplary embodiment, a target position is set for the fixing belt 310 (in this exemplary embodiment, the target position is the "center" position), and the tilting guide roller 350 is operated to move the fixing belt 310 to the target position. (Refer to...) Figure 13 The flowchart describes the specific method used to determine the tilt angle in the separated state.

[0142] First, in step S30, the sensor unit 390 detects the position of the fixing belt 310.

[0143] In step S31, if the fixing belt 310 is at the complete deviation position ("Yes" in step S31), the process proceeds to step S35. In step S35, the control unit 600 issues a complete deviation error.

[0144] If the fixing belt 310 is not in the complete deviation position ("No" in step S31), the process proceeds to step S32.

[0145] In step S32, the control unit 600 determines the difference B.Pdif between the sensor unit 390 and the "center" position or target position based on the detection result (B.Pnow) of the sensor unit 390.

[0146] B.Pdif = 4 - B.Pnow. Equation 1

[0147] The possible values ​​for B.Pnow are 1 to 7. Figure 17The relationship between the position of the fixing belt 310 and the value to be substituted into B.Pnow is shown. For example, if the fixing belt 310 is in the "near 3" position (first predetermined position), the control unit 600 substitutes 1 into B.Pnow. If the fixing belt 310 is in the "far 3" position, the control unit 600 substitutes 7 into B.Pnow.

[0148] In step S33, the control unit 600 adds the product of the difference B.Pdif and the integral gain I to the previously accumulated integral value Itotal:

[0149] Itotal(n)=I×B.Pdif+Itotal(n-1). Equation 2

[0150] Here, the initial value of Itotal is 0.

[0151] In step S34, the control unit 600 determines the sum of the product of the difference B.Pdif and the proportional gain P and the cumulative integral value Itotal(n) as the steering angle:

[0152] Steering angle = P × B.Pdif + Itotal(n). Equation 3

[0153] In this exemplary embodiment, the proportional gain P is 100, the integral gain I is 1, and a calculation is performed every 0.2 seconds. For example, if the sensor unit 390 detects a "far 1" position, the control unit 600 substitutes 5 into B.Pnow. In this case, the steering angle is given by the following equation:

[0154] Steering angle = 100×(4-5)+1×(4-5)+Itotal(n-1)=-101+Itotal(n-1).

[0155] The tilt angle of the steering roller 350 is determined by the value of the steering angle calculated above.

[0156] The tilt angle relative to the guide roller 350a can be positive or negative. If the value determined by equations 1 to 3 is positive, the guide roller 350 is tilted to move the fixing belt 310 to the other end of the guide roller 350. In this case, the guide roller 350 is... Figure 10 The tilt is counterclockwise. Similarly, if the tilt angle is negative, the tilting roller 350 is tilted to move the fixing belt 310 toward one end of the tilting roller 350. In this case, the tilting roller 350 is... Figure 10 Inclined clockwise.

[0157] Figure 10The diagram shows the case where the steering roller 350a has a steering angle of 0 and is parallel to the heating roller 340. However, this is not limiting. Due to variations in assembly precision, the steering roller 350a may not be parallel to the heating roller 340, thus allowing for some offset.

[0158] The larger the absolute value of the determined steering angle, the greater the clockwise or counterclockwise movement of the steering roller 350.

[0159] In other words, the farther the position of the fixing belt 310 in the width direction is from the "center" position or the target position, the greater the tilt angle of the guide roller 350. According to Equations 1, 2, and 3, if the fixing belt 310 is located at the "center" position or the target position, the steering angle according to this exemplary embodiment is 0. The guide roller 350 is tilted to maintain the fixing belt 310 at the "center" position. If the fixing belt 310 is located at the "center" position or the target position, this prevents the fixing belt 310 from moving from the target position to one end or the other end of the guide roller 350.

[0160] The aforementioned steering control is achieved by operating the tilting steering roller 350 based on the position of the fixing belt 310 in the width direction. In other words, the tilting steering roller 350 is operated to maintain the fixing belt 310 in a "center" position in the width direction.

[0161] The aforementioned steering control is characterized in that, compared to the contact state, in the width direction, the position of the fixing belt 310 performing the tilting steering roller 350 operation in the separated state falls on the "center" position side of those positions in the contact state, or even falls on the "center" position. Therefore, when the pressure rotating member 330 is in the separated state, the number of positions of the fixing belt 310 performing the tilting steering roller 350 operation in the width direction is greater than the number when the pressure rotating member 330 is in the contact state. (Refer to...) Figure 11 Provide its description.

[0162] In the contact state according to this exemplary embodiment, the tilting guide roller 350 is not operated at the "near 1" position (second predetermined position). In contrast, in the separated state, it is operated at the second tilt angle at the "near 1" position (second predetermined position). Figure 11 At angle B), the tilting roller 350 is operated.

[0163] exist Figure 11In this context, the second tilt angle refers to the angle at which the guide roller 350 tilts relative to the guide roller 350a to move the fixing belt 310 toward the other end of the guide roller 350. If the guide roller 350 tilts in the first direction (i.e., counterclockwise in the figure), the fixing belt 310 moves toward the other end of the guide roller 350. If the sensor unit 390 detects that the fixing belt 310 is at a "near 1" position (second predetermined position), the control unit 600 tilts the guide roller 350 to the position of the guide roller 350d, which is the position of the guide roller 350b on the guide roller 350a side. This tilt angle is called the second tilt angle (angle B). In other words, the first tilt angle > the second tilt angle.

[0164] Similarly, if sensor unit 390 detects that fixing belt 310 is in the "far 1" position, control unit 600 tilts guide roller 350 in the second direction (i.e., clockwise in the figure). Fixing belt 310 thus moves toward one end of guide roller 350. Here, compared to the case where guide roller 350 is tilted at angle -A, guide roller 350 is tilted to position guide roller 350e (angle -B), which is the position tilted toward guide roller 350a.

[0165] In the separated state, at the "near 2" position (third predetermined position), the operation of tilting the steering roller 350 at the third tilt angle is further performed.

[0166] exist Figure 12 In this diagram, the third tilt angle refers to the angle at which the guide roller 350 tilts from guide roller 350a to move the fixing belt 310 toward the other end of the guide roller 350. If the guide roller 350 tilts counterclockwise in the diagram, the fixing belt 310 moves toward the other end of the guide roller 350. If the sensor unit 390 detects that the fixing belt 310 is at the "near 2" position (third predetermined position), the control unit 600 tilts the guide roller 350 to the position of guide roller 350f, which is tilted toward guide roller 350b, compared to the case where the guide roller 350 is tilted at the second tilt angle. This tilt angle is called the third tilt angle (angle C). In other words, the third tilt angle > the second tilt angle.

[0167] Similarly, if sensor unit 390 detects that the fixing belt 310 is in the "far 2" position, control unit 600 tilts the guide roller 350 in the second direction (i.e., clockwise in the figure). The fixing belt 310 thus moves toward one end of the guide roller 350. In this case, compared to the case where the guide roller 350 is tilted at angle -B, the guide roller 350 tilts to the position of guide roller 350g (angle -C), which is the position tilted toward guide roller 350c.

[0168] The guide roller 350 is tilted at angles B, -B, C, or -C. In the contact state, the change in tilt angle of the guide roller 350 caused by a single tilting operation is from angle A to angle -A, while in the separation state, the maximum change in tilt angle is from angle C to angle -C. Therefore, the change in tilt angle of the guide roller 350 caused by a single tilting operation in the separation state is less than that in the contact state. This helps to maintain the fixing belt 310 at the center of the guide roller 350.

[0169] If the pressure rotating member 330 is in the contact state, the operation of the tilting roller 350 will not be performed in the "near 1", "near 2", "far 1" or "far 2" positions. Conversely, if the pressure rotating member 330 is in the disengaged state, the operation of the tilting roller 350 will be performed in the "near 1", "near 2", "far 1" and "far 2" positions.

[0170] like Figure 14 As shown, by performing the above-mentioned steering control, the fixing belt 310 can reciprocate within a narrower range than when the pressure rotating member 330 is in contact.

[0171] Specifically, in this exemplary embodiment, if the pressure rotating member 330 is in a separated state, the fixing belt 310 moves within a range in the width direction between a "near 1" position and a "far 1" position. Conversely, if the pressure rotating member 330 is in a contact state, the fixing belt 310 moves within a range in the width direction between a "near 3" position and a "far 3" position.

[0172] As the fixing belt 310 moves from the "far 1" position to the "far 3" position, 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 in the width direction. Similarly, the distance increases as the fixing belt 310 moves from the "near 1" position to the "near 3" position. In the separated state, when the fixing belt 310 is in the "near 1" or "far 1" position, the first operation of tilting the guide roller 350 after the fixing belt 310 moves from the "center" position is performed. In contrast, in the contact state, the first operation is performed when the fixing belt 310 is in the "near 3" or "far 3" position. Therefore, it can be said that when the pressure rotating member 330 is in the separated state, in the width direction, the distance between the center position of the fixing belt 310 and the center position of the moving range of the fixing belt 310 after the center position of the fixing belt 310 separates from the center position of the moving range of the fixing belt 310 is smaller than the distance when the pressure rotating member 330 is in the contact state.

[0173] Reference Figure 15 The flowchart describes a variant example (second exemplary embodiment).

[0174] Figure 15 It's a flowchart, specifically for... Figure 8 In the flowchart of the contact state, step S007, "Is the fixing belt located at the 'near 3' position?", is modified to "Is the fixing belt located at the 'near 1' position?", and step S004, "Is the fixing belt located at the 'far 3' position?", is modified to "Is the fixing belt located at the 'far 1' position?".

[0175] Descriptions that are redundant with the description of the first exemplary embodiment will be omitted.

[0176] Since the guide roller 350 tilts at a first tilt angle in step S003, the fixing belt 310 moves past the "center" position toward the other end. As the fixing belt 310 moves toward the other end, the sensor unit 390 detects the position of the fixing belt 310 and performs control to change the tilt angle of the guide roller 350 via steering control, instead of performing control at the "center" position. The guide roller 350 remains at the first tilt angle. In step S014, if the fixing belt 310 moves toward the other end of the guide roller 350 and the sensor unit 390 detects that the fixing belt 310 is at the "far 1" position ("Yes" in step S014), the process proceeds to step S006. If the sensor unit 390 does not detect that the fixing belt 310 is at the "far 1" position ("No" in step S014), the process proceeds to step S005.

[0177] In step S017, if the fixing belt 310 moves toward one end of the guide roller 350 and the sensor unit 390 detects that the fixing belt 310 is in the "near 1" position (yes in step S017), the process proceeds to step S003. If the sensor unit 390 does not detect that the fixing belt 310 is in the "near 1" position (no in step S017), the process proceeds to step S008.

[0178] Changing the tilt angle of the steering roller 350 takes approximately 1.5 seconds. Therefore, if the steering control is too late, "overshoot" may occur, in which the fixing belt 310 moves upward to the fully offset position. However, performing steering control at the "near 1" and "far 1" positions can prevent the fixing belt 310 from moving upward to the fully offset position.

[0179] like Figure 16 As shown, by performing the above-mentioned steering control, the fixing belt 310 can reciprocate within a narrower range than when steering control is performed at the "near 3" and "far 3" positions.

[0180] Other embodiments

[0181] The embodiments of the present invention can also be implemented by providing software (programs) that perform the functions of the above embodiments to a system or device via a network or various storage media, and the computer or central processing unit (CPU) or microprocessor unit (MPU) of the system or device reads out and executes the program.

[0182] While the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be interpreted in the broadest possible sense to cover all such modifications and equivalent structures and functions.

Claims

1. A fixing device, comprising: The fixing belt is rotatable and circular; A heating roller is configured to contact the inner circumferential surface of the fixing belt and apply heat to the fixing belt; The steering roller is configured to contact the inner circumferential surface of the fixing belt together with the heating roller; A pressure rotating member is configured to press the fixing belt, wherein the pressure rotating member and the fixing belt form a clamping portion and, in order to fix the unfixed toner image to the recording material, the recording material carrying the unfixed toner image is conveyed to the clamping portion and clamped between the pressure rotating member and the fixing belt. A contact-separation mechanism is configured to move the pressure rotating member to a position where the pressure rotating member is in contact with the fixing belt and to a position where the pressure rotating member is separated from the fixing belt. It includes a position detection unit configured to detect the position of the fixing belt in the fixing belt width direction; as well as The control unit is configured to control the oscillation of the guide roller based on the detection results of the position detection unit, so that the fixing belt moves to a predetermined position in the width direction. Specifically, in the separated state, the distance between the center position of the fixing belt and the center position of the fixing belt's movement range when the tilting guide roller is first operated after the fixing belt separates from the center position of the fixing belt's movement range in the width direction is less than the distance in the contact state.

2. The fixing device according to claim 1, wherein, In the predetermined operation, the rotation speed of the fixing belt is the same when the pressure rotating member is in the separated state as when the pressure rotating member is in the contact state.

3. The fixing device according to claim 1 or 2, wherein, In the separated state, the change in the tilt angle of the steering roller caused by a single tilting operation of the rotating steering roller based on the detection results of the position detection unit is less than the change in the contact state.

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