JP2010107659A - Image forming apparatus and image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which achieves further prolongation of mechanical service life of a belt member, subjected to steering control, without spoiling service life in terms of surface property of the belt member. <P>SOLUTION: A deviation control mechanism 21M controls a deviation moving direction of a fixing belt 27 by setting a tilt angle to a fixing steering roller 26 in accordance with pulse input of a stepping motor 60. In a first half period of the life in which the fixing belt 27 is new, a swing type steering control for moving the fixing belt 27 back and forth between both ends of the fixing steering roller 26 is performed. However, when a time difference between one-way moving time in one direction and one-way moving time in the other direction exceeds a prescribed threshold, the steering control of equilibrium point control for stopping the one-way moving of the fixing belt 27 in the center of the fixing steering roller 26 is performed thereafter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steering mechanism for a belt member mounted on an image forming apparatus, and more particularly to control for extending the life of a belt member that is steering-controlled by so-called swing type control.

  Steering control for dynamically controlling the tilt of the support rotator so that the belt member is mounted on a plurality of support rotators and rotates endlessly, so that the belt members are not offset and fall off the support rotator. An image forming apparatus to be executed has been put into practical use.

  Examples of the belt member that is controlled by steering include a recording material conveyance belt that adsorbs and conveys a recording material, and an intermediate transfer belt that primarily transfers a toner image and conveys the toner image to a secondary transfer unit. Further, as a belt member mounted on a fixing device, a gloss processing device, or the like of an image forming apparatus, a heating belt that contacts and heats the toner carrying surface of the recording material, and is disposed opposite to the heating belt so that the recording material is used as a heating belt. There is a pressure belt that is pressed and conveyed.

  In the steering control, usually, the steering mechanism that changes the inclination of the support rotator is controlled based on the output of the detection means that detects the position of the belt member in the axial direction of the support rotator. As steering control, so-called swing type control and so-called equilibrium point control have been put into practical use.

  In the swing type control, the steering mechanism is controlled based on the output of the detection means so as to reciprocate the belt member between predetermined limit positions determined in the axial direction of the support rotating body.

  In the equilibrium point control, the steering mechanism is controlled based on the output of the detection means so that the one-way movement of the belt member is stopped at a predetermined intermediate position determined in the axial direction of the support rotating body.

  Patent Document 1 discloses a fixing device that fixes a non-fixed toner image while sandwiching and conveying a recording material by pressing a heating belt and a pressure belt together.

  Patent Document 2 discloses an image forming apparatus that performs steering control on a rotating intermediate transfer belt to position it in the width direction. Here, two support rotating bodies for steering are arranged at a distance in the rotational direction of the belt member, and the inclination angle is changed in conjunction with the two steering support rotating bodies.

JP 2004-341346 A JP 2000-233843 A

  When the equilibrium point control is adopted as the steering control, in principle, since the steering mechanism is controlled so that the belt member continues to rotate at the intermediate position of the moving width, the edge of the recording material should continue to pass through a substantially constant position of the belt member. become. For this reason, rubbing scratches due to the edge of the recording material are concentrated at a certain position in the width direction of the belt member, and the performance (surface property) durable life of the belt member is shortened. This is because rubbing scratches on the surface of the belt member deteriorate the surface state, causing transfer unevenness in the case of an intermediate transfer belt and causing gloss unevenness in an image surface in the case of a heating belt.

  On the other hand, when the swing type control is adopted as the steering control, since the edge of the recording material passes through the random position of the belt member, the rubbing scratches due to the edge of the recording material is dispersed in the width direction of the belt member, The performance (surface property) durability life of the belt member becomes long. However, as compared with the equilibrium point control, the axial rubbing with respect to the support rotating body increases, and the number of times of reversal movement in which a large load is applied to the belt member increases. Therefore, the mechanical (strength) durability life of the belt member Becomes shorter.

  In particular, in an image heating apparatus, when a nip is formed by press-contacting each belt member controlled by a steering by a pressure mechanism, the movement of the belt member along the support rotating body interferes with each other, resulting in a large stress on the belt member. Works frequently. As a result, idling with the support rotator occurs, and the frictional state of the inner peripheral surface varies, thereby shortening the mechanical durability and hindering normal steering control.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of further extending the mechanical durability of a belt member without impairing the performance (surface property) durability of the belt member that is controlled by steering. Yes.

  An image forming apparatus according to the present invention includes a belt member that is stretched over a plurality of support rotating bodies and rotates endlessly, and the inclination of the support rotating body so as to move the belt member in the axial direction of the support rotating body. A steering mechanism to be changed; and a detecting means for detecting the position of the belt member in the axial direction, wherein the detecting means is configured to reciprocate the belt member between predetermined limit positions determined in the axial direction. A first control mode for controlling the steering mechanism based on the output is executed. Then, after the belt member reaches a predetermined limit state with accumulative use, based on the output of the detection means so as to stop the one-way movement of the belt member at a predetermined intermediate position determined in the axial direction. A second control mode for controlling the steering mechanism.

  In the image forming apparatus of the present invention, when the belt member reaches a predetermined limit state associated with accumulation of use as a result of continuing the swing type control, the equilibrium point control is executed thereafter.

  If the belt member whose contact surface with respect to the support rotating body and the uniformity of the tension distribution are deteriorated with the accumulation of use is continued and the swing type control with a large mechanical and strength load is continued, the progress of the deterioration is accelerated. For this reason, when the progress of the deterioration reaches a predetermined limit state, the control is switched to the equilibrium point control with a relatively small mechanical and strength burden to delay the progress of the deterioration. As a result, the mechanical and strength life of the belt member is extended more than when the swing type control is continued.

  Further, while the swing type control is continued, the sliding scratches due to the edge of the recording material are dispersed in the width direction of the belt member, and therefore, the belt member on the side in contact with the recording material when the equilibrium point control is started. The performance (surface property) durability life is still sufficient. For this reason, the remainder of the performance (surface property) durability life can be effectively utilized in the equilibrium point control.

  For this reason, compared to the case where the equilibrium point control is performed from the beginning to the end, the performance (surface property) durable life of the belt member becomes longer. In addition, compared to the case where swing type control is performed from the beginning to the end, the mechanical and strength durability life is extended.

  Therefore, the mechanical durability life of the belt member can be further extended without impairing the performance (surface property) durability life of the belt member subjected to steering control.

  Hereinafter, some embodiments of the present invention will be described in detail with reference to the drawings. In the image forming apparatus of the present invention, as long as the swing type control is switched to the equilibrium point control in the middle of the mechanical durability of the belt member, a part or all of the configuration of each embodiment is replaced with the alternative configuration. Other embodiments can also be realized.

  Accordingly, not only the steering control of the fixing belt and the pressure belt but also the steering control of the intermediate transfer belt, the recording material conveyance belt, the photosensitive belt, the transfer belt, the secondary transfer belt, and the like can be performed.

  In the present embodiment, only main parts related to toner image formation / transfer will be described. However, the present invention includes a printer, various printing machines, a copier, a fax machine, a composite machine, in addition to necessary equipment, equipment, and a housing structure. It can be implemented in various applications such as a machine.

  In addition, about the general matter of the image forming apparatus shown in patent document 1, 2, and a fixing device, illustration is abbreviate | omitted and the overlapping description is abbreviate | omitted.

<First Embodiment>
FIG. 1 is an explanatory diagram of a configuration of the image forming apparatus according to the first embodiment.

  As shown in FIG. 1, in the image forming apparatus 100 of the first embodiment, four image forming units UY, UM, UC, and UK are arranged in a linear section of the intermediate transfer belt 7 supported by a plurality of support rotating bodies. This is a tandem intermediate transfer type full-color copier.

  In the image forming unit UY, a yellow toner image is formed on the photosensitive drum 1 </ b> Y and is primarily transferred to the intermediate transfer belt 7. In the image forming unit UM, a magenta toner image is formed on the photosensitive drum 1M, and is primarily transferred onto the yellow toner image on the intermediate transfer belt 7. In the image forming portions UC and UK, a cyan toner image and a black toner image are formed on the photosensitive drums 1C and 1K, respectively, and are similarly primarily transferred to the intermediate transfer belt 7.

  The four-color toner images primarily transferred to the intermediate transfer belt 7 are conveyed to the secondary transfer portion T2 and collectively transferred to the recording material P. The recording material P is curvature-separated from the intermediate transfer belt 7 on the downstream side of the secondary transfer portion T2 and introduced into the fixing device (fixing unit) 12. The fixing device 12 fixes the full-color permanently fixed image on the surface of the recording material P by sandwiching and conveying the recording material P at the fixing nip portion and applying heat and pressure to the mixed color by applying heat and pressure to the unfixed full-color toner image. To do.

  When the single-sided printing mode is selected, the recording material P that has exited the fixing device 12 passes through the flapper 13 and is discharged to the paper discharge tray 14 or the paper discharge tray 15.

  When the double-sided printing mode is selected, the printed recording material P that has exited the fixing device 12 is once sent by the flapper 13 into a sheet path that leads to the paper discharge lay 15 and is conveyed in a switchback manner. Thereafter, the sheet is introduced into the re-conveying sheet path 16 and is again introduced into the secondary transfer portion T2 in a state where the front and back sides are reversed. As a result, the toner image is also secondarily transferred to the back side of the recording material P, and thereafter, the recording material P is discharged to the paper discharge tray 14 or the paper discharge tray 15 via the fixing device 12.

  The recording material P drawn from the paper feed cassette 9 is separated one by one by the separating device 10 and fed toward the registration roller 11. The registration roller 11 sandwiches and conveys the recording material P in synchronization with the toner image on the intermediate transfer belt 7 and feeds it to the secondary transfer portion T2. It is also possible to send the recording material P from the deck 9A to the registration roller 11.

  The intermediate transfer belt 7 is supported around a driving roller 7a, a tension roller 7b, and a counter roller 7c, is driven by the driving roller 7a, and rotates in a direction indicated by an arrow R2 at a predetermined process speed. The intermediate transfer belt 7 is formed endlessly with a polyimide resin (PI) having a thickness of 100 μm containing carbon black and imparting resistance.

  The image forming units UY, UM, UC, and UK have the same configuration except that the color of toner used in the attached developing device is different from yellow, magenta, cyan, and black. Hereinafter, the yellow image forming unit UY will be described, and the redundant description of the other image forming units UM, UC, and UK will be omitted.

  A charging device 2Y, an exposure device 3Y, a developing device 4Y, a primary transfer roller 5Y, and a cleaning device 6Y are disposed around the photosensitive drum 1Y. The photosensitive drum 1Y has a negatively charged photosensitive layer formed on the outer peripheral surface of an aluminum cylinder and rotates in the direction of arrow R1.

  The charging device 2Y charges the surface of the photosensitive drum 1Y to a uniform negative potential, and the exposure device 3Y applies a laser beam obtained by ON-OFF modulation of scanning line image data obtained by developing a yellow separated color image to a polyhedral mirror. To form an electrostatic image of the image on the surface of the photosensitive drum 1Y. The developing device 4Y supplies the negatively charged toner to the photosensitive drum 1Y to reversely develop the electrostatic image.

  The primary transfer roller 5 </ b> Y is pressed against the photosensitive drum 1 </ b> Y via the intermediate transfer belt 7 to form a primary transfer portion between the photosensitive drum 1 </ b> Y and the intermediate transfer belt 7. The toner image is primarily transferred to the intermediate transfer belt 7 by applying a positive DC voltage to the primary transfer roller 5Y while the toner image carried on the photosensitive drum 1Y passes through the primary transfer portion. The cleaning device 6Y removes the transfer residual toner that passes through the primary transfer portion and remains on the surface of the photosensitive drum 1Y.

  The secondary transfer roller 8 is pressed against the opposing roller 7 c via the intermediate transfer belt 7 to form a secondary transfer portion T <b> 2 between the intermediate transfer belt 7 and the secondary transfer roller 8. The toner image is recorded by applying a positive voltage to the secondary transfer roller 8 while the recording material P is sandwiched and conveyed by the secondary transfer portion T2 over the toner image carried on the intermediate transfer belt 7. Secondary transfer to the material P is performed.

  The counter roller 7c is connected to the ground potential, and bends the intermediate transfer belt 7 on the downstream side of the secondary transfer portion T2 to separate the recording material P attached to the intermediate transfer belt 7 from the intermediate transfer belt 7 with a curvature. .

<Fixing device>
FIG. 2 is a cross-sectional view showing a schematic configuration of the fixing device 12.

  As shown in FIG. 2A, the fixing device 12 as an example of the image heating means is an assembly of a fixing belt unit 21 disposed on the upper side and a pressure belt unit 31 disposed on the lower side. .

  The fixing belt unit 21 is an assembly in which an endless fixing belt 27 is supported around a fixing driving roller 24 and a fixing steering roller 26, and a pressure pad 28 is disposed inside the fixing belt 27.

  The fixing belt 27 is heated by induction by an induction heating coil 29 disposed in the upper part, and generates heat. For the fixing belt 27, for example, a magnetic metal layer such as a nickel metal layer or a stainless steel layer having a thickness of 75 μm, a width of 380 mm, and a circumferential length of 200 mm is coated with a silicon rubber having a thickness of 300 μm.

  The pressure belt unit 31 is an assembly in which an endless pressure belt 32 is supported around a pressure driving roller 33 and a pressure steering roller 34, and a pressure pad 38 is disposed inside the pressure belt 32. is there.

  The fixing belt unit 21 and the pressure belt unit 31 can be attached and detached by a belt attaching / detaching mechanism 102 which is an example of a pressure mechanism. Specifically, a belt attaching / detaching mechanism 102 composed of an electromagnetic solenoid-plunger mechanism, a cam mechanism, a lever mechanism, and the like is connected to the pressure belt unit 31 so that a pressure contact state and a separation state with an appropriate pressure force can be achieved. Is set. The control circuit unit 110 switches between two states (a wearing state and a detached state by the pressurizing mechanism) according to the operation state of the image forming apparatus (100: FIG. 1).

  As shown in FIG. 2A, when the recording material P is nipped and conveyed and the toner image is heated and fixed, the fixing belt unit 21 and the pressure belt unit 31 are in the attached state. In the wearing state, the belt attaching / detaching mechanism 102 rotates and presses the pressure belt unit 31 with respect to the fixing belt unit 21 with the attaching / detaching shaft portion 43 as an axis to press-contact the pressure belt unit 31.

  In other cases, as shown in FIG. 2B, the fixing belt unit 21 and the pressure belt unit 31 are switched to the detached state to prevent unnecessary pressure and friction from being applied between them. To prevent wear of the belt member. In the detached state, the belt attaching / detaching mechanism 102 releases the pressure by rotating the pressure belt unit 31 with respect to the fixing belt unit 21 with the attaching / detaching shaft portion 43 as an axis.

<First steering mechanism, second steering mechanism>
FIG. 3 is an explanatory diagram of the steering mechanism of the fixing belt and the pressure belt, and FIG. 4 is an explanatory diagram of the steering control.

  As shown in FIG. 3, the fixing belt unit 21 includes a shift control mechanism 21M, and the fixing belt 27 is individually controlled in the axial direction by the shift control mechanism 21M. The pressure belt unit 31 includes a shift control mechanism 31M, and the pressure belt 32 is individually controlled in the axial direction by the shift control mechanism 31M. Since the configuration and control related to the steering control in the fixing belt unit 21 and the pressure belt unit 31 are the same, only the fixing belt unit 21 will be described here, and redundant description regarding the pressure belt unit 31 will be omitted.

  The shift control mechanism 21M fixes a stepping motor 60 for steering control to the side plate 64, and supports a sector gear 62 so as to be rotatable by a shaft 70. A worm gear 61 is fixed to the output shaft of the stepping motor 60, and a steering roller bearing 63 that supports the shaft of the fixing steering roller 26 is fixed to the sector gear 62.

  The left belt-side sensor unit 65 disposed on the side plate 64 so as to correspond to the edge of the fixing belt 27 contains the photosensors SL1 and SL2 for detecting the belt-side detection in two stages. Details will be described later. There is a similar right belt-side sensor unit (66: FIG. 5) on the front (right) side, but it is omitted in FIG.

  When the stepping motor 60 is driven in the CW direction (clockwise), the worm gear 61 rotates in the forward feed direction, and the direction of the sector gear 62 changes downward about the shaft 70. Accordingly, since the steering roller bearing 63 moves downward, the back (left) side of the fixing steering roller 26 tilts downward, and the entire fixing belt unit 21 tilts downward toward the back (left) direction. It becomes a shape. Accordingly, as the fixing belt 27 rotates, the fixing belt 27 moves along the fixing steering roller 26 in the front (right) direction.

  Conversely, when the stepping motor 60 is driven in the CCW direction (counterclockwise), the worm gear 61 rotates in the pull-back direction and the direction of the sector gear 62 changes upward about the shaft 70. Accordingly, since the steering roller bearing 63 moves upward, the back (left) side of the fixing steering roller 26 tilts upward, and the entire fixing belt unit 21 tilts obliquely downward toward the front (right). Become a shape. Accordingly, as the fixing belt 27 rotates, the fixing belt 27 moves in the back (left) direction along the fixing steering roller 26.

  As shown in FIG. 4, when the fixing belt 27 approaches the front (right) side, the back (left) side of the fixing steering roller 26 is moved upward by a displacement amount D in order to return to the back (left) side. Be inclined. At this time, as shown in FIG. 3, the shift control mechanism 21 </ b> M for inclining the fixing steering roller 26 is on the back (left) side of the fixing device 12. ) Side end is raised.

  The amount of displacement of the height of the end portion of the fixing steering roller 26 is hereinafter referred to as the amount of displacement D of the end portion. The + direction of the displacement amount D is the upward direction, and is a direction in which the displacement amount D returns to the back (left) side with respect to the belt rotation direction. The minus direction of the displacement amount D is a downward direction, and is a direction in which the displacement amount D returns toward the front (right) side with respect to the belt rotation direction.

  When the displacement amount D at the end of the fixing steering roller 26 changes, the position in the width direction of the fixing belt 27 tends to move accordingly. For this reason, ideally, the amount of displacement with a substantially horizontal inclination angle is expressed as a reference amount ± 0 state so that the belt position does not move left and right as much as possible from the current position.

  Ideally, if the displacement amount D is set to the reference amount ± 0, the belt should not move left and right from that position, but in reality, the deviation occurs due to various factors, and the fixing belt 27 The belt moves along the fixing steering roller 26 in the belt width direction (left and right).

  4 describes the configuration and control related to the fixing belt unit 21, but the basic configuration and control are the same for the pressure belt unit 31 as well.

<First detection means, second detection means, control means>
FIG. 5 is a block diagram of control of the fixing device, and FIG. 6 is an explanatory diagram of the arrangement of the shift detection sensor.

  As shown in FIG. 5, a control system of the image forming apparatus 100 including the fixing device 12 is configured. The entire control is performed by the control circuit unit 110, to which an operation unit 101 configured by a liquid crystal touch panel, buttons, and the like is connected. The control circuit unit 110 starts the operation of the image forming apparatus 100 in response to a user input from the operation unit 101. The control circuit unit 110 controls the following mechanisms and circuits of the fixing device 12.

  The belt attaching / detaching mechanism 102 is a mechanism for performing an attaching / detaching operation between the fixing belt unit 21 and the pressure belt unit 31 shown in FIG.

  The fixing belt driving roller driving mechanism 103 drives the driving roller 24 of the fixing belt unit 21 shown in FIG. 2A to rotate the stretched fixing belt 27.

  The pressure belt drive roller drive mechanism 104 drives the drive roller 33 of the pressure belt unit 31 shown in FIG. 2A to rotate the stretched pressure belt 32.

  The heater power supply circuit unit 105 is a circuit that controls power supply to the induction heating coil 35, and turns on and off power supply to the induction heating coil 35 according to a signal from the control circuit unit 110.

  The deviation control mechanisms 21M and 31M drive the stepping motor 60 shown in FIG. 3 in accordance with a signal from the control circuit unit 110, and perform control to correct the deviation of the fixing belt 27 and the pressure belt 32.

  The deviation detection sensors SL1 and SL2 are sensors that are disposed in the left belt deviation sensor unit (65: FIG. 3) and detect the belt deviation amount of the fixing belt 27.

  The deviation detection sensors SR1 and SR2 are sensors that are arranged in the right belt deviation sensor unit 66 and detect the belt deviation amount of the fixing belt 27.

  The control circuit unit 110 detects the belt shift of the fixing belt 27 using the shift detection sensors SL1, SL2, SR1, and SR2, and executes belt position correction control using the shift control mechanism 21M.

  That is, while the heating belt member (27) is in a new state, the first steering mechanism (21M) is used by swing type control so as to reciprocate between the deviation detection sensors SL1 and SR1 as an example of the first detection means. To control. When a sign of abnormality appears in the reciprocating movement of the heating belt member (27) and a predetermined judgment criterion is applied, the first steering mechanism (using the equilibrium point control is stopped so as to stop the one-way movement at an intermediate position of the reciprocating movement. 21M).

  In addition, a pair of belt shift sensor units (not shown) in which a shift detection sensor is similarly disposed are installed on the pressure belt member (32) that presses against the heating belt member (27) to form a heating nip. Yes. The control circuit unit 110 detects the position in the width direction of the pressure belt member (32) using these deviation detection sensors, which are examples of second detection means, and is an example of a second steering mechanism. The shift control mechanism 31M is controlled. However, since belt deviation detection and correction control in the fixing belt 27 and the pressure belt 32 are basically the same, the fixing belt unit 21 will be described below as a representative.

  Further, the shift detection sensor is not limited to the form in which two left and right sensors are arranged. The number and arrangement of the deviation detection sensors can be arbitrarily determined, and the belt position detection method need not be limited to the method using the optical sensor.

  As shown in FIG. 6A, the shift detection sensors SL1 and SL2 detect the rear (left) edge of the fixing belt 27, and the shift detection sensors SR1 and SR2 are in front of the fixing belt 27 (right). Detect side edges. The fixing belt 27 spans between the fixing driving roller 24 and the fixing steering roller 26 and rotates in the direction of the arrow.

  The deviation detection sensors SL1 and SL2 are first and second detection means arranged at predetermined intervals corresponding to the inner side and the outer side of the limit range set on the back (left) side in the width direction of the fixing belt 27. It is.

  The deviation detection sensors SR1 and SR2 are first and second detection means arranged at predetermined intervals corresponding to the inside and outside of the limit range set on the front (right) side in the width direction of the fixing belt 27. It is.

  As shown in FIG. 6B, the shift detection sensors SL1, SL2, SR1, and SR2 are transmitted light detection sensors (photointerrupters) each including a light transmitting element a and a light receiving element b. When the rotating fixing belt 27 moves more than a predetermined amount to the left or right in the width direction, the belt edge on the moving side enters between the light transmitting element a and the light receiving element b, and the optical path of the detection light Shut off. The deviation detection sensors SL1, SL2, SR1, and SR2 are turned on when the optical path is open and turned off when the optical path is blocked.

  FIG. 6B shows a state in which the fixing belt 27 rotates within an allowable shift range between the left first shift detection sensor SL1 and the right first shift detection sensor SR1. At this time, both the first left side detection sensor SL1 and the first right side detection sensor SR1 are on.

  The control circuit unit 110 determines that the fixing belt 27 is rotating within an allowable shift range by turning on both the left and right shift detection sensors SL1 and SR2. The allowable shift range of the fixing belt 27 at this time is expressed as a normal shift range 51. The outer movement range beyond the left end of the normal range 51 is denoted as a left-side abnormal range 52, and the outer movement range beyond the right end of the normal range 51 is denoted as a right-side abnormality range 53.

<First control mode>
FIG. 7 is an explanatory diagram of the fixing belt detection operation by the deviation detection sensor, and FIG. 8 is a flowchart of the swing type control.

  During the first half of the life until the fixing belt 27 reaches a predetermined mechanical limit state, the control circuit unit 110 swings the fixing belt member (pressure belt member) back and forth like a pendulum between predetermined limit positions. Perform type control. In the swing type control, the first steering mechanism (second steering mechanism) is controlled so as to reverse the movement of the fixing belt member (pressure belt member) in accordance with the output state of the first detection means (second detection means). .

  As shown in FIG. 7A with reference to FIG. 5, when the fixing belt 27 moves to the left side and the belt edge turns off the detection sensor SL1, the control circuit unit 110 causes the fixing belt 27 to Judge that it is too close to the back (left) side. For this reason, the control circuit unit 110 operates the shift control mechanism 21M to incline the fixing steering roller 26 in a direction in which the fixing belt 27 is moved back to the opposite (right) side.

  In spite of this, if the fixing belt 27 continues to move further to the left side and the belt edge turns off the outer deviation detection sensor SL2 as shown in FIG. It is determined that the inclination of the fixing steering roller 26 is insufficient. For this reason, the control circuit unit 110 further increases the displacement amount of the end portion of the fixing steering roller 26 to increase the inclination amount of the fixing steering roller 26.

  If the outside shift detection sensor SL2 remains off for 10 seconds even under such control, the control circuit unit 110 determines that the return movement by the fixing steering roller 26 is impossible. The control circuit unit 110 stops the driving of the fixing belt 27 and stops the image forming operation in order to prevent the fixing belt 27 from being damaged. After that, an error is displayed on the operation unit 101 to indicate that it is necessary to contact the service person.

  As shown in FIG. 7 (c) with reference to FIG. 5, when the fixing belt 27 is moved toward the front (right) side and the belt edge is turned off, the control circuit unit 110 is turned off. Determines that the fixing belt 27 is too close to the front (right) side. For this reason, the control circuit unit 110 operates the shift control mechanism 21M to incline the fixing steering roller 26 in a direction in which the fixing belt 27 is moved back to the opposite back (left) side.

  In spite of this, when the fixing belt 27 moves further toward the near side (right side) and the belt edge turns off the outer side deviation detection sensor SR2 as shown in FIG. 110 further increases the amount of displacement of the end of the fixing steering roller 26.

  If the deviation detection sensor SR2 remains off for 10 seconds even under such control, the control circuit unit 110 stops driving the fixing belt 27, stops the image forming operation, and displays an error display on the operation unit 101. Do.

  As shown in FIG. 8 with reference to FIG. 5, the control circuit unit 110 periodically reviews the shift control every 100 msec. The control circuit unit 110 periodically reads the output states of the shift detection sensors SL1, SL2, SR1, and SR2, and checks whether or not they are the same as the previous time (S101).

  If the output states of the slip detection sensors SL1, SL2, SR1, SR2 are unchanged between the previous time and the current time (YES in S101), the current steering amount is maintained and the process is terminated.

  However, if the output states of the deviation detection sensors SL1, SL2, SR1, SR2 are different between the previous time and the current time (NO in S101), the steering amount is changed as shown in Table 1 according to the changed pattern (S102). .

  In Table 1, the output states of the shift detection sensors SL1, SL2, SR1, SR2 are indicated by ON (light-shielding): 1 and OFF (transmission): 0. The steering amount is the number of pulses input to the stepping motor (60: FIG. 3) in order to set the displacement amount D on the back (left) side of the fixing steering roller 26 shown in FIG. The + direction of the steering amount is the upward direction, and is the direction in which the fixing belt 27 is returned to the back (left) side. The minus direction of the steering amount is a downward direction, and is a direction in which the fixing belt 27 is returned to the front (right) side.

  The steering amount is based on the position (home position) of the fixing steering roller 26 in which the balance between the left and right belts is balanced in terms of unit design. Home position sensors (not shown) that turn on when the fixing steering roller 26 is at the home position are mounted on the upper and lower belts of the fixing device 12 shown in FIG. The steering amount indicates the number of steps for driving the stepping motor 60 from the home position on. When the number of steps is positive, the fixing steering roller 26 moves in the direction in which the belt moves to the right. When the number of steps is negative, the fixing steering roller 26 moves in the direction in which the belt moves to the left. Moving.

  As shown in Table 1, when the shift detection sensors SL1, SL2, SR1, SR2 are 0, 1, 0, 0, the fixing belt 27 is in the left shift abnormal range 52 as shown in FIG. You are in the first stage. The steering amount at this time is 100 pulses, and the belt position is L1. The 100 pulses incline the fixing steering roller 26 by an angle that can correct the meandering to the right when the fixing belt 27 is in the first stage of the left-side abnormal range 52.

  When the shift detection sensors SL1, SL2, SR1, SR2 are 1, 1, 0, 0, the fixing belt 27 is in the second stage of the left shift abnormal range 52 as shown in FIG. The steering amount at this time is 200 pulses, and the belt position is L2. The 200 pulses tilt the fixing steering roller 26 by an angle that can correct the meandering to the right when the fixing belt 27 is in the second stage of the left-side abnormal range 52.

  When the shift detection sensors SL1, SL2, SR1, SR2 are 0, 0, 1, 0, the fixing belt 27 is in the first stage of the right shift abnormal range 53 as shown in FIG. The steering amount at this time is 100 pulses, and the belt position is R1. The 100 pulses tilt the fixing steering roller 26 by an angle that can correct the meandering to the left when the fixing belt 27 is in the first stage of the right-side abnormal range 53.

  When the deviation detection sensors SL1, SL2, SR1, SR2 are 0, 0, 1, 1, the fixing belt 27 is in the second stage of the right deviation abnormal range 53 as shown in FIG. The steering amount at this time is 200 pulses, and the belt position is R2. The 200 pulses tilt the fixing steering roller 26 by an angle that can correct the meandering to the left when the fixing belt 27 is in the second stage of the left-side abnormal range 52.

<Second control mode>
FIG. 9 is a flowchart of the equilibrium point control, and FIG. 10 is a flowchart of the control to return to the equilibrium steering amount after the belt movement is reversed. FIG. 11 is a flowchart of control for setting the time to return to the balanced steering amount, and FIG. 12 is a flowchart of control for setting the balanced steering amount.

  During the latter half of the life after the fixing belt 27 reaches a predetermined mechanical limit state, the control circuit unit 110 moves the fixing belt member (pressure belt member) at the center position after reversing the movement at the predetermined limit position. Execute the equilibrium point control to stop.

  In the equilibrium point control, when the first detection means (second detection means) detects the fixing belt member (pressure belt member), the reversal movement is started and moved at the center of the first support rotary body (second support rotary body). The first steering mechanism (second steering mechanism) is controlled to stop.

  Specifically, after waiting for the elapse of the return time Tret set to ½ of the one-way movement time along the first support rotator (second support rotator), the steering of the equilibrium steering amount α (β) is performed. Do. The equilibrium steering amount α (β) is input to a stepping motor (60: FIG. 3) set so that the fixing belt member (pressure belt member) does not move along the first support rotator (second support rotator). The number of pulses to be performed. When the belt member reaches the limit positions set at both ends of the support rotator, the support rotator is inclined so as to move the belt member back toward the limit position on the opposite side, as in the swing type control. However, without waiting for the belt member to reach the limit position on the opposite side as in swing type control, when the half of the one-way movement time between the limit positions has elapsed, the inclination amount of the support rotating body is set to the default angle (α , Β) to stop the return movement.

  In the equilibrium point control, the stepping motor (60: FIG. 3) is controlled as shown in Table 2 according to the output states of the shift detection sensors SL1, SL2, SR1, SR2. In Table 2, since the positions other than the belt position CT are the same as those in Table 1, redundant description is omitted.

  As shown in Table 2, when the deviation detection sensors SL1, SL2, SR1, SR2 are 0, the fixing belt 27 is in the normal range 51 as shown in FIG. The steering amount at this time is an α pulse, and the belt position is CT (central zone). In the equilibrium point control, the steering amount of the stepping motor (60: FIG. 3) is changed to the equilibrium steering amount α at the timing when the fixing belt 27 is reversely moved to the center of the normal range 51. As a result, the fixing belt 27 that has been reversely moved stops moving at the center of the belt position CT.

  As shown in FIG. 9 with reference to FIG. 5, the control circuit unit 110 executes a balance point control processing procedure every 100 ms by an interval timer.

  The control circuit unit 110 retracts the stored current position PosNow to the previous position PosOld (S202).

  Next, the states of the deviation detection sensors SL1, SL2, SR1, SR2 are detected, the corresponding belt position is obtained from Table 2, and is substituted into the current position PosNow. At the same time, the steering amount Pstair corresponding to the current position PosNow is obtained from Table 2 (S203).

  Next, the current position PosNow and the previous position PosOld are compared. If they are the same (YES in S204), the current steering amount is maintained because the belt position has not changed (S209).

  If it has changed (NO in S204), it is compared whether or not the previous position PosOld is the belt position L2 or the belt belt position R2 (S205).

  When the previous position PosOld was the belt position L2 or the belt position R2 (YES in S205), it means that the normal deviation correction control performed between the belt position L1 and the belt position R1 has been deviated. Therefore, the steering is maintained at the belt position L2 or the belt position R2 until the belt position becomes the label CT.

  If the previous position PosOld is not the belt position L2 or the belt position R2 (NO in S205), it is compared whether or not the current position PosNow is the position CT (S206).

  If the current position PosNow is the position CT (YES in S206), the counting of the return time Tret until the steering amount is returned to the equilibrium steering amount α is started (S207).

  If the current position PosNow is not the position CT (NO in S206), the belt position meanders from the center side toward the outside. That is, either the belt position has moved from the position CT to the belt position L1 or the belt position R1, the belt position L1 has moved to the belt position L2, or the belt position R1 has moved to the belt position R2.

  Accordingly, the meandering correction of the belt position is necessary, and as shown in Table 2, the stepping motor 60 of the shift control mechanism 21M is driven to the steering amount corresponding to the current position PosNow (S208).

  As shown in FIG. 10 with reference to FIG. 5, when the return time Tret is up, the steering amount is returned to the balanced steering amount α.

  When the return time Tret is up (YES in S220), it is compared whether or not the current position PosNow is the position CT (S221).

  If the current position PosNow is the position CT (YES in S221), the equilibrium steering amount α is set to the steering amount Pstair (S222). Then, the stepping motor (60: FIG. 3) is driven by α pulses from the reference position, and the fixing steering roller 26 is tilted (S223).

  If the current position PosNow is not the position CT (YES in S221), the fixing belt 27 shown in FIG. 6B has left the normal range 51 during the return time Tret. Therefore, without returning the steering amount to the equilibrium steering amount α, the steering amount is set as shown in Table 2 by returning to the equilibrium point control flow shown in FIG.

  As shown in FIG. 11 with reference to FIGS. 3 and 6B, a return time Tret is set. This sequence is executed when the fixing device 12 is attached to the image forming apparatus 100.

  First, while the fixing belt 27 is in the normal range 51, the stepping motor 60 is driven by DL1 pulses from the reference position to tilt the fixing steering roller 26 (S302).

  As a result, when the fixing belt 27 moves and the shift detection sensor SL1 is turned on (YES in S303), the fixing steering roller 26 is tilted in the opposite direction by driving the stepping motor 60 from the reference position by DR1 pulses. At the same time, measurement of the one-way travel time Tret1 from when the fixing belt 27 turns off the deviation detection sensor SL1 to when the opposite deviation detection sensor SR1 turns on is started (S304).

  Next, when the opposite side detection sensor SR1 is turned on (YES in S305), the measurement of the one-way travel time Tret1 is finished, and the stepping motor 60 is driven again by DL1 pulses from the reference position to tilt the fixing steering roller 26. At the same time, measurement of the one-way movement time Tret2 from when the fixing belt 27 turns off the deviation detection sensor SR1 to when the opposite deviation detection sensor SL1 turns on is started (S306).

  Next, when the opposite side detection sensor SL1 is turned on (YES in S307), the measurement of the one-way movement time Tret2 is ended (S308).

  Next, a value ½ of the average value of the one-way travel time Tret1 and the one-way travel time Tret2 measured in this way is obtained and set as a time-up value of the return time Tret (S309).

  Note that the method of obtaining the time-up value of the return time Tret is not limited to the method of FIG. In addition, one-way movement time Tret1 and one-way movement time are calculated based on the belt position before the start of one-way movement time measurement, by substituting 1/2 of the shorter one of one-way movement time Tret1 and one-way movement time Tret2. Any one half of Tret2 may be adopted.

  As shown in FIG. 9, when the steering amount is not changed, the balanced steering amount α is finely adjusted (S209).

  The equilibrium steering amount α is the number of pulses when the belt is maintained at the center position of the fixing steering roller 26 with a twin belt. By finely adjusting the balanced steering amount α, the optimal balanced steering position can always be maintained.

  The equilibrium steering amount α always varies due to variations in parallelism between the fixing belt 27 and the pressure belt 32 at the time of assembling the fixing device 12, changes in part dimensions due to thermal expansion, parts wear state, and the like. In addition, it is difficult to find a true equilibrium position where the fixing belt 27 does not actually move to the left or right, and the gentle meandering of the fixing belt 27 to the left or right always occurs due to the balance of the fixing device 12.

  In such a situation, detecting the steering amount at which the meandering speed of the fixing belt 27 is minimized is to finely adjust the balanced steering amount. The balance point angle of the fixing steering roller 26 is finely adjusted optimally so that the optimum balance steering amount can always be set.

  The equilibrium steering amount α is initialized after the image forming apparatus is powered on or after the fixing device 12 is detached and attached by maintenance or the like. Thereafter, after the temperature of the fixing device 12 is stabilized, the equilibrium steering amount α is set, and the change in the alignment characteristic due to the temporal change of the fixing device 12 is canceled.

  As shown in FIG. 12 with reference to FIGS. 3 and 6B, thereafter, the balanced steering amount α is finely adjusted during image formation.

  In other words, if α is 2 or more and the current position PosNow is the belt position L1 (YES in S502), it is determined that the equilibrium steering amount α so far tends to be closer to the belt position L1 than the belt position R1. it can. Therefore, the balance steering amount α is not finely adjusted on the assumption that the balance is achieved.

  Next, if α is −2 or less and the current position PosNow is the belt position R1 (YES in S502), the previous equilibrium steering amount α tends to be closer to the belt position R1 than the belt position L1. Can be judged. Therefore, the balance steering amount α is not finely adjusted on the assumption that the balance is achieved.

  Next, if the previous position PosOld is the belt position CT (YES in S504) and the current position PosNow is the belt position L1 (YES in S506), it can be determined that the previous equilibrium steering amount α tends to be closer to the belt position L1. . Therefore, the steering control is corrected to a tendency toward the belt position R1 by subtracting one balance steering amount α (S508).

  Next, if the previous position PosOld is the belt position CT (YES in S504) and the current position PosNow is the belt position R1 (YES in S505), it can be determined that the previous equilibrium steering amount α tends to be closer to the belt position R1. . Therefore, the steering control is corrected to a tendency toward the belt position L1 by adding one balanced steering amount α (S507).

  The fine adjustment method of the equilibrium steering amount α is not limited to this method. For example, the number of times of meandering from the belt position CT to the belt position L1 and the number of times of meandering from the belt position CT to the belt position R1 while the fixing belt 27 is steered to the equilibrium steering amount α at the belt position CT are counted. May be. Further, when the fixing belt 27 is controlled to the equilibrium steering amount α, the equilibrium steering amount α may be finely adjusted so that the fixing belt 27 moves to the lower side.

  By the way, in a belt nip type fixing device using a twin belt, a phenomenon (shifting movement) occurs in which the belt member moves so as to be shifted toward one side or the other side in the width direction during the rotation of the belt member. Then, when the shift movement occurs and the belt member approaches, there is a risk that the belt member may fall off from the roller that spans the belt member or the end of the belt member may be damaged. For this reason, it has been proposed to dynamically correct the shifting of the rotating belt member by incorporating steering control.

  Equilibrium point control and swing type control have been proposed as steering control. The equilibrium point control is a shift correction control that maintains the belt member at the center position of the steering roller, and the swing type control is a shift correction control that periodically moves the belt member from one end to the other end.

  However, in a twin belt fixing device in which a pair of belt members pressurize at least during printing, when the shift correction control is applied to one belt member, the shift force of one belt member is brought into pressure contact with the nip portion. This affects the shifting force of the other belt member. Therefore, the shift movement correction control of one belt member constituting the twin belt needs to be designed in consideration of the influence of the shift force of the other belt member.

  Further, in the equilibrium point control, there is a problem in image quality as the belt member is used and accumulated. This is because minute scratches on the surface of the belt, which can be formed by the recording material passing through the same portion of the belt member, have become apparent.

  In recent years, output products have been sold, and in the future, demands for image quality will increase, so that the life of the fixing device is shorter than the current state in the method of controlling the belt at the same position.

  On the other hand, in the swing type control, there is no problem in the image quality as the belt member is used and accumulated, but there is a problem that the belt is broken. This is because uneven wear occurs on the inner surface portion of the belt member as usage accumulates, and the shifting force is partially weakened. As a result, the influence of the shifting force of the other belt member becomes too large, causing the belt member to slip all the way.

  On the other hand, a method of increasing the displacement amount of the steering roller is conceivable so as not to be affected by the shifting force of the other belt member. However, this method leads to an increase in the size of the apparatus. On the other hand, if the amount of displacement is too large, the amount of movement of the belt member becomes too large, leading to the occurrence of wrinkles on the recording material and image defects. For this reason, it is difficult for the swing type control method to extend the life of the fixing device beyond the current level.

  Therefore, in the first to third embodiments, the swing type control is performed when the belt member is new, and the control is switched to the equilibrium point control after the belt member reaches a predetermined limit state. As a result, it is not necessary to increase the amount of steering displacement, so the life of the fixing device can be extended without increasing the size of the fixing device and reducing the occurrence of wrinkles on the recording material and image defects. become. In the twin belt type fixing device, the service life can be extended. When the control is switched from the swing type control to the equilibrium point control, the service person can be notified of the replacement time of the fixing device, so that the downtime due to the replacement of the fixing device can be minimized. Therefore, usability is also useful.

<Example 1>
FIG. 13 is a flowchart of switching control according to the first embodiment.

  In the first embodiment, when the difference between the one-way movement time in the front (right) side direction and the one-way movement time in the back (left) direction of the belt member is equal to or greater than a predetermined value, the balance is controlled from the swing-type shift control. Switch to point control.

  In swing-type shift control, at the start of use, the time for the fixing belt 27 to move from the shift detection sensor SR1 to the shift detection sensor SL1 is substantially the same as the time for the shift belt 27 to move from the shift detection sensor SL1 to the shift detection sensor SR1. However, as the usage time accumulates, a difference occurs in the moving time. This is detected by using this determination, and a predetermined limit state accompanying use accumulation is determined.

  As shown in FIG. 13 with reference to FIG. 5, it is determined whether the shift detection sensor SR1 or the shift detection sensor SL1 is turned on (S602). When it is detected that either of them is turned on (YES in S602), the position of the fixing belt 27 is known from the sensor, and thus the steering movement for the belt position is started. After the steering movement is completed, measurement of the one-way movement time A of the fixing belt 27 is started (S603).

  Next, it is determined whether or not the sensor opposite to the first sensor turned on in S602 is turned on (S604). When the sensor on the opposite side is turned on (YES in S604), the measurement of the one-way movement time A is terminated and the steering movement for the belt position is started (S605). After the steering movement is completed, measurement of the one-way movement time B of the fixing belt 27 is started.

  Next, it is determined whether the first sensor on the opposite side to the sensor turned on in S604 is turned on (S606). When the first sensor is turned on (YES in S606), the measurement of the one-way travel time B is terminated and the steering movement for the belt position is started (S607).

  Next, the difference between the one-way travel time A and the one-way travel time B measured in S605 and S607 is calculated. If the calculation result is smaller than the threshold value (NO in S608), the swing-type shift control is continued and the shift control is performed. The switching determination is continued (S610).

  On the other hand, when the difference result is larger than the threshold value (YES in S608), it is determined that the limit is the swing-type shift control, and the control is switched to the equilibrium point control (S609).

  Since the difference time may temporarily exceed the threshold due to sensor reading timing, disturbance, etc., the swing-type shift control may be switched to the equilibrium point control when the threshold is continuously exceeded several times. .

  Here, the reason for switching to the equilibrium point control is that one of the twin belts becomes the equilibrium point control, so that the movement of the belt is reduced, and as a result, the influence of the shifting force of the one belt is reduced. This is because the consumption of the twin belt can be suppressed.

  When the steering control method is switched, a communication means (not shown) is used to notify that the replacement of the fixing device 12 is near. Once switched to the equilibrium point control, the determination of the shift control switching is no longer performed.

<Example 2>
FIG. 14 is a flowchart of switching control according to the second embodiment.

  In Example 2, when either the one-way movement time in the front (right) side direction or the one-way movement time in the back (left) direction of the belt member is equal to or greater than a predetermined value, Switch to equilibrium point control.

  In swing-type shift control, even if control is performed with the same steering amount, the one-way travel time for the fixing belt 27 to move from the shift detection sensor SR1 to the shift detection sensor SL1 is as follows: Change occurs. This is detected by using this determination, and a predetermined limit state accompanying use accumulation is determined. Since the one-way movement time for the fixing belt 27 to move from the deviation detection sensor SL1 to the deviation detection sensor SR1 is the same, this one-way movement time may be determined.

  As shown in FIG. 14 with reference to FIG. 5, when it is detected that either of the shift detection sensors SR1 and SL1 is turned on (YES in S702), the steering movement for the belt position is started. Then, after the steering movement is completed, measurement of the one-way movement time A of the fixing belt 27 is started (S703).

  Next, it is determined whether or not the sensor opposite to the first sensor turned on in S702 is turned on (S704). When the sensor on the opposite side is turned on (YES in S704), the measurement of the one-way travel time A is terminated (S705).

  Next, when the one-way movement time A is equal to or less than the threshold value (NO in S706), the swing-type shift control is continued, and the shift control switching determination is continued (S708).

  However, if the one-way movement time A is longer than the threshold (YES in S706), it is determined that the swing-type shift control limit is reached, and the control is switched to the equilibrium point control (S707).

  Note that the one-way travel time A may temporarily exceed the threshold value due to sensor reading timing, disturbance, etc., so if the threshold value is exceeded several times in succession, the swing type shift control is switched to the equilibrium point control. Also good.

  Here, the reason for switching to the equilibrium point control is that one of the twin belts becomes the equilibrium point control, so that the movement of the belt is reduced, and as a result, the influence of the shifting force of the one belt is reduced. This is because the consumption of the twin belt can be suppressed.

  When the steering control method is switched, a communication means (not shown) is used to notify that the replacement of the fixing device 12 is near. Once switched to the equilibrium point control, the determination of the shift control switching is no longer performed.

<Example 3>
FIG. 15 is a flowchart of switching control according to the third embodiment.

  In Example 3, one of the one-way movement time in the front (right) side direction and the one-way movement time in the back (left) side direction of the belt member is longer than the predetermined value by one or more times compared to the previously measured one-way movement time. If this happens, switch from swing-type shift control to equilibrium point control.

  As shown in FIG. 15 with reference to FIG. 5, when it is detected that one of the shift detection sensors SR1 and SL1 is turned on (YES in S802), the steering movement for the belt position is started. Then, after the steering movement is completed, measurement of the one-way movement time A of the fixing belt 27 is started (S803).

  Next, it is determined whether or not the sensor opposite to the first sensor turned on in S802 is turned on (S804). When the sensor on the opposite side is turned on (YES in S804), the measurement of the one-way travel time A is terminated (S805).

  Next, the difference between the one-way travel time A measured this time and the one-way travel time A 'measured last time is taken and compared with a threshold value (S806). If the difference time is smaller than the threshold (NO in S806), the swing-type shift control is continued and the shift control switching determination is continued (S808).

  However, if the difference time is larger than the threshold (YES in S806), it is determined that the limit is the swing-type shift control, and the control is switched to the equilibrium point control (S807).

  Note that the one-way travel time A may temporarily include noise due to sensor reading timing, disturbances, etc., so if the threshold is exceeded several times, the swing-type shift control is switched to the equilibrium point control. May be.

  Here, the reason for switching to the equilibrium point control is that one of the twin belts becomes the equilibrium point control, so that the movement of the belt is reduced, and as a result, the influence of the shifting force of the one belt is reduced. This is because the consumption of the twin belt can be suppressed.

  When the steering control method is switched, a communication means (not shown) is used to notify that the replacement of the fixing device 12 is near. Once switched to the equilibrium point control, the determination of the shift control switching is no longer performed.

<Example 4>
The criterion for detecting the predetermined limit state related to the reciprocating movement is not limited to the method of actually measuring the moving time. The control amount of the first steering mechanism so that the moving speed of the heating belt member along the first support rotator becomes a predetermined value, and the moving speed of the pressure belt member along the second support rotator becomes a predetermined value. It may be determined that the control amount of the second steering mechanism has reached a predetermined determination criterion.

  In the fourth embodiment, it is assumed that the degree of wear of the heating belt member and the pressure belt member progresses according to the number of image formations and the cumulative image formation time. That is, the swing type control is switched to the equilibrium point control when either the number of image formations or the accumulated time of image formation reaches a predetermined criterion (800,000 sheets, 50,000 hours) first.

It is explanatory drawing of a structure of the image forming apparatus of 1st Embodiment. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a fixing device. It is explanatory drawing of the steering mechanism of a fixing belt and a pressure belt. It is explanatory drawing of steering control. It is a block diagram of control of a fixing device. It is explanatory drawing of arrangement | positioning of a deviation detection sensor. FIG. 10 is an explanatory diagram of a fixing belt detection operation by a deviation detection sensor. It is a flowchart of swing type control. It is a flowchart of equilibrium point control. It is a flowchart of control which returns to an equilibrium steering amount after reversal of belt movement. It is a flowchart of control which sets time until it returns to the amount of balanced steering. It is a flowchart of control which sets the amount of equilibrium steering. 3 is a flowchart of switching control according to the first embodiment. 6 is a flowchart of switching control according to the second embodiment. 10 is a flowchart of switching control according to the third embodiment.

Explanation of symbols

1Y, 1M, 1C, 1K photosensitive drums 2Y, 2M, 2C, 2K charging devices 3Y, 3M, 3C, 3K exposure devices 4Y, 4M, 4C, 4K developing devices 5Y, 5M, 5C, 5K primary transfer rollers 6Y, 6M, 6C, 6K Cleaning device 7 Intermediate transfer belts 7a, 7b, 7c Support rotating body (drive roller, tension roller, counter roller)
8 Secondary transfer roller 12 Fixing device 21 Fixing belt unit 21M Steering mechanism (shift control mechanism)
24 Support Rotator (Fixing Drive Roller)
26 Support Rotating Body (Fixing Steering Roller)
27 Belt member, heating belt member (fixing belt)
28, 38 Pressure pad 29 Induction heating coil 31 Pressure belt unit 31M Steering mechanism (shift control mechanism)
32 Belt member (pressure belt)
33 Support Rotator (Pressure Drive Roller)
34 Support Rotating Body (Pressure Steering Roller)
60 Stepping Motor 61 Worm 62 Fan Gear 63 Steering Roller Bearing 64 Side Plate 65 Left Belt Shift Sensor Unit 66 Right Belt Shift Sensor Unit 67 Stepping Motor 80 Belt Shift Normal Range 81 Belt Shift Left Abnormal Range 82 Belt Shift Right Abnormal Range 110 Control Means Control circuit section)
SR1, SR2, SL1, SL2 detection means (shift detection sensor)

Claims (4)

A belt member that is wound around a plurality of support rotating bodies and rotates endlessly;
A steering mechanism that changes the inclination of the support rotator so as to move the belt member in the axial direction of the support rotator;
Detecting means for detecting the position of the belt member in the axial direction,
In the image forming apparatus for controlling the steering mechanism based on the output of the detection means so as to reciprocate the belt member between predetermined limit positions determined in the axial direction.
After the belt member reaches a predetermined limit state related to the reciprocating movement with accumulative use, the output of the detection means so as to stop the one-way movement of the belt member at a predetermined intermediate position determined in the axial direction. And controlling the steering mechanism on the basis of the image forming apparatus. A heating belt member that is wound around a plurality of first support rotating bodies and rotates endlessly;
A pressure mechanism that rotates in pressure contact with the heating belt member to form a heating nip of the recording material;
A first steering mechanism that changes an inclination of the first support rotator so as to move the heating belt member in an axial direction of the first support rotator;
First detecting means for detecting the position of the heating belt member in the axial direction,
In the image forming apparatus for controlling the first steering mechanism based on the output of the first detection means so as to reciprocate the heating belt member between predetermined limit positions determined in the axial direction.
After the heating belt member reaches a predetermined limit state related to reciprocating movement with accumulative use, the first movement of the heating belt member is stopped at a predetermined intermediate position determined in the axial direction. An image heating apparatus that controls the first steering mechanism based on an output of a detection means. The pressure mechanism includes a pressure belt member that is wound around a plurality of second support rotating bodies and rotates endlessly, and the pressure belt member is moved in the axial direction of the second support rotating body. A second steering mechanism for changing the inclination of the second support rotor, and a second detection means for detecting the position of the pressure belt member in the axial direction,
Based on the output of the second detection means, the second steering mechanism is controlled so as to reciprocate the pressure belt member between predetermined limit positions determined in the axial direction. After reaching the predetermined limit state related to the reciprocating movement with the accumulation of use, the output of the second detecting means so as to stop the one-way movement of the pressure belt member at a predetermined intermediate position determined in the axial direction. The image heating apparatus according to claim 2, wherein the second steering mechanism is controlled based on the control.   3. The predetermined limit state relating to the reciprocating movement is a state in which a moving time when the heating belt member moves between the predetermined limit positions exceeds a predetermined determination criterion. Or the image heating apparatus of 3.

Images