JP2015059963A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can suppress, when a rubbing rotating body contacts an endless belt to perform rubbing, the influence on the skew of the endless belt.SOLUTION: A fixing device includes: first and second rotating bodies that fix a toner image on a recording medium at a nip part, at least one of which being an endless belt; a rubbing rotating body that rubs the surface of the endless belt; and selection means for selecting whether or not to perform rubbing processing by the rubbing rotating body according to the position in the width direction of the endless belt.

Description

  The present invention relates to a fixing device that fixes a toner image on a sheet (on a recording material). This fixing device can be used in, for example, an image forming apparatus such as a copying machine, a printer, a FAX, and a multifunction machine having a plurality of these functions.

  Conventionally, as a fixing device mounted on an electrophotographic image forming apparatus, an endless fixing belt that rotates while being pressed against each other and a belt that fixes an unfixed toner image while sandwiching and conveying a recording material with a pressure belt A nip type fixing device has been proposed (Patent Document 1).

  By the way, in the belt nip type fixing device, a phenomenon in which the belt moves toward one end or the other end in the width direction (longitudinal direction) orthogonal to the recording material conveyance direction (hereinafter referred to as a shift movement) in the belt rotation process. Will occur. If this belt shift occurs and the belt moves all the way, the belt may fall off from the roller that stretches the belt, or the end of the belt may be damaged. For this reason, belt shift control for periodically moving the belt from one end to the other end is used to correct the belt shift.

  In addition, the fixing device partially deteriorates the surface shape of the fixing member each time the fixing process or the heating process is repeated, and the deteriorated surface shape is copied as it is onto the surface of the fixed image and appears as a scratch-like image. Alternatively, there is a problem that a uniform glossy state on the image surface cannot be obtained. Therefore, in the normal fixing state, the surface roughness of the fixing member surface layer is brought into contact with the surface layer of the fixing member by a roughening member (refreshing roller) as a rubbing rotary member disposed away from the fixing member. Has been proposed (Patent Document 2).

JP 2004-341346 A JP 2005-266785 A

  However, when the refresh roller as the rubbing rotator is brought into contact with the fixing belt, which is an endless belt, during the refresh operation, the shifting behavior of the belt changes. In particular, immediately after the fixing belt changes to move in the opposite direction from one end to the other, the shifting behavior changes. Then, there is a problem that the belt does not return from the shifted position, or conversely, the belt behavior changes in the shifted direction and the fixing belt may be shifted all the way.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that can suppress the influence on the endless belt when the rubbing rotator is in contact with the endless belt.

  In order to achieve the above object, a fixing device according to the present invention includes first and second rotating bodies in which at least one of fixing a toner image on a recording material at a nip portion is an endless belt, and the endless belt. A rubbing rotator that rubs the surface, and a selection unit that selects whether or not to perform the rubbing process by the rubbing rotator according to the position in the width direction of the endless belt. To do.

  According to the present invention, when rubbing is executed by the contact of the rubbing rotary member with the endless belt, the influence on the endless belt can be suppressed.

6 is a flowchart of belt refresh control of the fixing device according to the embodiment of the present invention. 1 is an overall view of an image forming apparatus equipped with a fixing device according to an embodiment of the present invention. 1 is a block diagram of an image forming apparatus equipped with a fixing device according to an embodiment of the present invention. 1 is a configuration diagram of a fixing device according to an embodiment of the present invention. FIG. 4 is a configuration diagram of a belt shift control mechanism of the fixing device according to the embodiment of the present invention. 1 is an overall view of a belt shift control mechanism of a fixing device according to an embodiment of the present invention. (A) thru | or (f) is an image figure of belt shift control of the fixing device which concerns on embodiment of this invention. FIG. 6 is a timing diagram of belt shift control of the fixing device according to the embodiment of the present invention. (A) thru | or (d) is an image figure of the belt refresh control of the fixing device which concerns on embodiment of this invention. FIG. 4 is a relationship diagram of belt shift control and belt refresh control of the fixing device according to the embodiment of the present invention. 10 is a flowchart of belt refresh control of a fixing device according to another embodiment that detects a normal range of an endless belt shift from a displacement amount of a steering roller. FIG. 9 is a configuration diagram of belt center position detection of a fixing device according to another embodiment that detects the position of the center portion in the width direction. It is a flowchart of the belt refresh control of embodiment which detects a position of the center part of the width direction.

<< First Embodiment >>
(Image forming device)
FIG. 2 is an overall view of an image forming apparatus equipped with the fixing device according to the embodiment of the present invention. The image forming apparatus 100 is an image forming apparatus of a tandem type intermediate transfer system in which image forming units 1Y, 1M, 1C, and 1K are arranged in series on the horizontal portion of the intermediate transfer belt 40. Then, a full-color image is formed on the sheet material (recording material) S by electrophotography in accordance with the image signal transmitted from the external device. The image forming units 1Y, 1M, 1C, and 1K form toner images of yellow, magenta, cyan, and black on the photosensitive drums 11Y, 11M, 11C, and 11K, respectively, and primarily at the same image position on the intermediate transfer belt 40. Transcript.

  The intermediate transfer belt 40 is stretched and rotated by a driving roller 33, a tension roller 34, and a transfer counter roller 32 for performing secondary transfer. On the inner peripheral surface side of the intermediate transfer belt 40, primary transfer rollers 35Y, 35M, 35C, and 35K for performing primary transfer are disposed at positions facing the photosensitive drums 11Y, 11M, 11C, and 11K.

  The following members are provided around the photosensitive drum 11Y that forms a yellow toner image. That is, the charging roller 12Y that uniformly charges the surface of the photosensitive drum 11Y, the exposure device 13Y that irradiates the photosensitive drum 11Y with image light to form a latent image on the surface, and transfers the toner to the latent image on the photosensitive drum 11Y. The developing device 14Y forms a toner image. Further, a cleaning member 15Y is provided for removing toner remaining on the photosensitive drum 11Y after the primary transfer of the toner image. The configuration for forming magenta, cyan, and black toner images can be understood by replacing the subscript Y with M, C, and K in the above description.

  On the other hand, the sheet material (recording material) S stored in the paper feed cassettes 61, 62, 63, 64 is transported to the paper feed transport path 81 as one of the paper feed rollers 71, 72, 73, 74 rotates. Is done. Then, the registration roller 75 feeds the sheet material S to the secondary transfer portion formed by the contact between the secondary transfer roller 41 and the transfer counter roller 32 in synchronization with the toner image on the intermediate transfer belt 40. The sheet material S to which the toner image has been transferred is conveyed to the belt fixing device 50 by the conveyance belt 42, and the toner image is fixed on the surface (on the recording material) of the sheet material S by thermocompression, and the full-color image is fixed. The paper is sent to the paper discharge tray 65 through the paper conveyance path 82.

  FIG. 3 shows a control block of the image forming apparatus equipped with the fixing device according to the embodiment of the present invention. The entire control is performed by the CPU 200, to which an operation unit 201 configured by a liquid crystal touch panel, buttons, and the like is connected. In response to a user input from the operation unit 201, the image forming apparatus starts operation. Elements constituting the belt fixing device 50 are connected to the CPU 200. That is, the fixing belt attaching / detaching mechanism 202, the fixing belt driving mechanism 203, the pressure belt driving mechanism 204, the heater power supply circuit unit 205, the belt deviation control mechanism 206, the refresh roller attachment / detachment control mechanism 207, and the deviation detection sensors SL1, SL2, SR1, SR2 etc. are connected.

  The CPU 200 comprehensively controls each of the control mechanism units described above while controlling the RAM 252 as a calculation processing work area in accordance with a program stored in the ROM 251.

(Belt fixing device)
FIG. 4 is a cross-sectional view showing a schematic configuration of a belt fixing device 50 as a fixing device according to the present embodiment. The belt fixing device 50 is an assembly of a fixing belt unit 321 disposed on the upper side and a pressure belt unit 331 disposed on the lower side. The fixing belt unit 321 is an assembly including the following members.

  That is, the fixing belt 327 which is a heating rotator formed of an endless belt, the fixing driving roller 324 which is inside the fixing belt 327 and serves as a belt suspension means, the fixing steering roller 326, and the heating belt 327 are opposed to each other. The pressure pad 328 is disposed in a manner. Here, the fixing belt 327 is suspended by a fixing driving roller 324 and a fixing steering roller 326, which are a plurality of belt suspension means, but is suspended by three or more belt suspension means instead of two. May be.

  The fixing belt 327 is caused to generate heat by an induction heating coil 329 disposed in the upper part. 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 silicon rubber having a thickness of 300 μm. Then, by driving the fixing motor 330, the fixing driving roller 324 and the pressure driving roller 333 are driven, and the fixing belt 327 is always rotated. By this rotation, a part of the fixing belt 327 heated by the induction heating coil 329 is sequentially replaced, and the entire fixing belt 327 is warmed.

  The pressure belt unit 331 is an assembly including the following members. That is, an endless pressure belt 332 as a pressure body, and a pressure driving roller 333, a pressure steering roller 334, and a heating belt which are inside the pressure belt 332 and serve as a belt stretching member are opposed to each other. The pressure pad 338 is disposed.

  The fixing belt unit 321 and the pressure belt unit 331 forming the nip portion can be attached / detached by a belt attaching / detaching mechanism 202 (not shown). When the sheet material S is nipped and conveyed, it is switched to the wearing state as shown in FIG. 4 and to the detached state otherwise, preventing unnecessary pressure from being applied between the fixing belt unit 321 and the pressure belt unit 331. It has a function of preventing the wear of the brazing member.

  A refreshing roller 322 as a rubbing rotating body shown in FIG. 4 is in contact with the surface of the fixing belt 327 and is rotated in contact (rotated by the rotation of the belt). By this rubbing treatment, the surface shape of the fixing belt 327 ( Improve surface condition). The refresh roller attachment / detachment drive motor 323 can switch whether the refresh roller 322 is brought into contact with the surface of the fixing belt 327 or not.

(Fixing belt shift control mechanism)
Next, the belt shift control mechanism of the belt fixing device 50 in this embodiment will be described with reference to FIG. Here, position detecting means for controlling the endless belt to move within the range from one end to the other end in the width direction (longitudinal direction) is provided at the end of the endless belt in the width direction. Since the configuration of the fixing belt unit 321 and the pressure belt unit 331 are substantially the same, the fixing belt unit 321 will be described as a representative here.

  The belt shift control mechanism includes belt steering means that controls the amount of movement of the endless belt in the width direction (direction perpendicular to the recording material conveyance direction) by changing the alignment of at least one belt suspension means. This belt steering means includes a steering control motor 360, a worm gear 361, a fan gear 362, a steering roller bearing 363, and a side plate 364 that supports them.

  The steering roller bearing 363 supports the shaft of the fixing steering roller 326. Reference numeral 365 denotes a left belt-side sensor unit that houses photosensors SL1 and SL2 as position detecting means for performing belt-level detection in two stages. Details will be described later. There are similar sensors SR1 and SR2 on the right side, but they are omitted in this figure.

  Here, the belt steering means controls to return the endless belt to the center in the width direction when it is determined that the endless belt is at the end in the width direction (longitudinal direction) based on the detection result of the position detection means. For a first steering state. In addition, a second steering state is provided for controlling the endless belt to remain at the center in the width direction when it is determined that the endless belt is not at the end in the width direction.

  When the steering control motor 360 is driven in the CW direction (clockwise), the worm gear 361 rotates and the direction of the sector gear 362 changes downward about the axis. Accordingly, since the steering roller bearing 363 moves downward, the fixing steering roller 326 slightly tilts in the back direction (leftward with respect to the belt rotation direction when viewed from directly above), and the entire fixing belt unit 321 is in the back direction. It becomes a shape inclined to. Accordingly, as the fixing belt 327 rotates, the fixing belt 327 moves toward the front (right).

  Conversely, when the steering control motor 360 is driven in the CCW direction (counterclockwise), the worm gear 361 rotates and the direction of the sector gear 362 changes upward about the axis. Accordingly, since the steering roller bearing 363 moves upward, the fixing steering roller 326 slightly tilts toward the front (right with respect to the belt rotation direction when viewed from directly above), and the entire fixing belt unit 321 also moves toward the front. It becomes an inclined shape. Thus, as the fixing belt 27 rotates, the fixing belt 27 moves in the back (left) direction.

  FIG. 6 is a diagram illustrating a case where the steering roller 326 is tilted in order to return the fixing belt 327 of the fixing belt unit 321 to the front (right) side with respect to the belt rotation direction when viewed from directly above. . Since the driving for inclining the steering roller 326 is on the back side as described above, the end of the steering roller 326 is raised by the steering control motor 360. The amount of displacement of the height of the end portion is hereinafter referred to as the amount of displacement D of the end portion. The + direction of the displacement amount D is on the upper side, the direction returning to the back (left) side with respect to the belt rotation direction, and the − direction is the lower side, and is on the near side (right) with respect to the belt rotation direction. It is the direction to return.

  Since the position in the width direction of the belt tends to move according to the change in the displacement amount D at the end, ideally, the displacement has a substantially horizontal inclination angle so that the belt position does not move left and right as much as possible from the current position. The quantity is expressed as a reference quantity ± 0 state. Ideally, if the displacement amount D is set to the reference amount ± 0, the belt does not move left and right from that position, but in reality, the belt is shifted due to various factors, and the belt moves left and right with respect to the stretching roller. To do. Although the fixing belt unit 321 has been described in FIG. 6, the basic configuration is the same for the pressure belt 332 and the pressure belt unit 331.

(Fixing belt shift control)
Next, the belt deviation detecting means will be described in detail with reference to FIG. Since detection of the belt deviation of the fixing belt 327 and the pressure belt 332 is basically the same, in this embodiment, the fixing belt 327 will be described as a representative. FIG. 7A is a view of the fixing belt portion between the belt driving roller 324 and the steering roller 326 as viewed from above. SL1 and SL2 and SR1 and SR2 are first belt deviation detection means disposed at predetermined intervals on both the left and right ends in the width direction (longitudinal direction) of the fixing belt 327, and the outer side of the first belt deviation detection means. 2 belt deviation detecting means.

  Each sensor is a light detection type sensor (photo sensor) in which a light transmitting element a and a light receiving element b are combined as shown in FIG. When the fixing belt 327 moves more than a predetermined amount to the left or right in the width direction during the fixing belt rotation driving process, the belt edge on the side of the movement moves between the light transmitting element a and the light receiving element b. They are arranged in a relational configuration that blocks the optical path between them. Each sensor is turned on when the light path is open, and turned off when the light path is cut off.

  FIG. 7B shows a state in which the fixing belt 327 is rotationally driven within an allowable shift range between the left first sensor SL1 and the right first sensor SR1. Both right first sensors SR1 are on. The CPU 200 determines that the fixing belt 327 is rotationally driven within an allowable shift range when both the sensors SL1 and SR2 are turned on. The allowable shift range of the fixing belt 327 at this time is represented as a shift normal range 601.

  When the fixing belt 327 moves to the left and the left first sensor SL1 is turned off at the left belt edge as shown in FIG. 7C, the CPU 200 determines that the fixing belt 327 has moved too far to the left. Then, the belt shift control mechanism 206 (steering roller displacement mechanism) is operated to displace the end portion of the steering roller 326 in the direction in which the fixing belt 327 is moved back to the opposite right side, and the roller is inclined. Thereafter, when the steering roller 326 is displaced, the fixing belt 327 moves toward the right side and the left first sensor SL1 is turned on. When the state returns to the state of FIG. Reduce the amount D.

  On the other hand, when the fixing belt 327 moves further to the left side in spite of the displacement of the steering roller 326 in the state of FIG. 7C, the second left side belt edge at the left belt edge as shown in FIG. The sensor SL2 is also turned off. In this state, in order to prevent the fixing belt 327 from being damaged, the operation of the fixing roller 324 that drives the fixing belt 327 is stopped, and the image forming operation of the entire apparatus is stopped, and then an error is displayed on the operation unit 201. I do. The movement range of the left end of the fixing belt 327 at this time is referred to as a left-side abnormal range 602.

  Further, in the state of FIG. 7C, the following cases are determined to be abnormal. That is, even if the steering roller 326 is displaced, the left first sensor SL1 does not turn on even after a predetermined time has elapsed, or the left first sensor SL1 remains off, but the right first sensor This is a case where SR1 is turned off. In this case, the shift movement control of the fixing belt 327 cannot be performed normally, and the fixing belt 327 may be damaged. Therefore, the operation of the fixing roller 324 that drives the fixing belt 327 is stopped, and the image of the entire apparatus is further stopped. After the forming operation is stopped, an error is displayed on the operation unit 201.

  Similarly, when the fixing belt 327 moves to the right and the right first sensor SR1 is turned off at the right belt edge as shown in FIG. 7E, the CPU 200 indicates that the fixing belt 327 is too close to the right. to decide. Then, the belt shift control mechanism 206 is operated to displace the steering roller 326 in a direction in which the fixing belt 327 is moved back to the opposite left side. When the steering roller 326 is displaced and the fixing belt 327 moves to the left side and the right first sensor SR1 is turned on and the state returns to the state of FIG. 7B, the displacement amount D of the steering roller 326 is obtained. Reduce.

  On the other hand, although the steering roller 326 is displaced in the state shown in FIG. 7E, the fixing belt 327 further moves to the right side, and the second right side belt edge portion as shown in FIG. If the sensor SR2 is also turned off, it is determined that the fixing belt 327 has moved to the right. Then, the operation of the entire apparatus is stopped and error display is performed in the same way as when moving to the left side. The movement range of the right end of the fixing belt at this time is referred to as a right-side abnormal range 603.

  Here, FIG. 8 shows the relationship between the belt deviation detection means SL1, SR1, the displacement D of the steering control motor 360, the steering roller 326, and the position of the fixing belt 327 in the main scanning direction. When detecting that the left first sensor SL1 is off, the CPU 200 rotates the steering control motor 360 in the CW direction, and greatly changes the displacement amount D of the steering roller 326 in the-direction.

  In this embodiment, the displacement amount at this time is set to −10 mm. As a result, when the fixing belt 327 moves toward the right side and detects that the left first sensor SL1 is turned back on, the CPU 200 rotates the steering control motor 360 in the CCW direction, and changes the displacement amount D of the steering roller 326. -Reduce to 1mm.

  Since the displacement amount D is small but has a negative displacement amount, the displacement amount D is gradually moved to the right in a normal case. Thereafter, when detecting that the right first sensor SR1 is turned off, the CPU 200 rotates the steering control motor 360 in the CCW direction, and greatly changes the displacement amount D of the steering roller 326 in the + direction. In this embodiment, the amount of displacement at this time is +10 mm. As a result, when the fixing belt 327 moves to the right side and detects that the left first sensor SL1 is turned back on, the CPU 200 rotates the steering control motor 360 in the CW direction and sets the displacement amount D of the steering roller 326. Reduce to + 1mm.

  By repeating the control as described above, the fixing belt 327 can be driven stably within the normal shift range 601 without being shifted to the left and right ends.

(Fixing belt refresh control)
Next, fixing belt refresh control will be described. FIGS. 9A to 9D show the position of the refresh roller 322 which is a rubbing rotary member during the image forming operation and the refresh operation. FIG. 9A is a diagram showing the positional relationship of each component when the unfixed toner 801 is carried on the recording paper 800 during the image forming operation. At this time, the refresh roller 322 is in a state of being separated from the fixing belt 327.

  FIG. 9B is a diagram showing the positional relationship of each component when the recording paper 800 passes through the fixing nip during the image forming operation. Most of the toner that has passed through the fixing nip is the fixed toner 802 fixed and fixed on the recording paper 800. However, a very small amount of toner may remain as residual toner 803 on the fixing belt. If the refresh roller 322 remains in contact with the fixing belt 327 in this state, the residual toner 803 adheres to the refresh roller 322, and the relationship of contact with the fixing belt 327 and rubbing is lost. become.

  Therefore, the refresh roller 322 is separated from the fixing belt 327 during an image forming operation in which the residual toner 803 may be carried. In the meantime, the residual toner 803 on the fixing belt 327 is recovered using a residual toner recovery member (not shown).

  FIG. 9C is a diagram showing the positional relationship between the components at the start of the refresh operation. By issuing a command to the refresh roller attachment / detachment control mechanism 207 from the CPU 200, the refresh roller attachment / detachment motor 323 is driven to bring the refresh roller 322 into contact with the fixing belt 327. Further, the fixing motor 330 is rotated at a predetermined speed by giving a command to the fixing belt driving roller driving mechanism 203 and the pressure belt driving roller driving mechanism 204. Thereby, the surface roughness of the fixing belt 327 can be made uniform.

  Here, as shown in FIG. 3, the CPU 200 is a selection unit that selects whether or not to perform the rubbing process by the rubbing rotary body in accordance with the position of the endless belt in the width direction orthogonal to the conveyance direction of the recording material. It is functioning. That is, the attachment / detachment of the refresh roller attachment / detachment control mechanism 207 to the endless belt is selected based on the output of the deviation sensor (SL1, SL2, SR1, SR2) 208.

  Here, how to determine the time for which the refresh roller 322 is in contact with the fixing belt 327 will be described. In order to make the surface of the fixing belt 327 uniform, it is determined how many times the refresh roller 322 contacts the same portion of the fixing belt 327 and does not depend on the speed relationship at the time of contact. Therefore, a time obtained by dividing the circumference of the fixing belt by the rotation speed of the fixing belt may be set as the minimum contact time.

  FIG. 9D is a diagram showing the positional relationship between the components at the end of the refresh operation. By issuing a command from the CPU 200 to the refresh roller attachment / detachment control unit 207, the refresh roller attachment / detachment motor 323 is driven, and the refresh roller 322 is separated from the fixing belt 327. Further, the fixing motor 330 is rotated at a predetermined speed by giving a command to the fixing belt driving roller driving mechanism 203 and the pressure belt driving roller driving mechanism 204.

(Effect of refresh roller wearing on belt shift control)
10 shows a change in the main scanning direction position of the fixing belt 327 in the normal belt shift control described with reference to FIG. 8, and a change in the main scanning direction position of the fixing belt 327 when the refresh roller 322 is attached to the fixing belt 327. It is a figure for comparing with. FIG. 10A shows a change in the position in the main scanning direction of the fixing belt 327 in the normal state where the refresh roller 322 is separated. On the other hand, FIG. 10C shows a change in the position in the main scanning direction of the fixing belt 327 when the refresh roller 322 contacts the fixing belt 327 at the timing shown in FIG.

  When the refresh roller 322 is brought into contact with the belt, resistance of the belt shift control is generated, so that the shift amount of the fixing belt shift is smaller than in the normal case. For this reason, the position of the fixing belt 327 tends to stay near the end, and the possibility of the fixing belt 327 being cut off becomes high. Further, when the refresh operation is finished in this state and the refresh roller 322 is separated from the fixing belt 327 (FIG. 10D), there is a possibility that the fixing belt 327 may approach by reaction that the resistance of the fixing belt 327 decreases. is there.

  For this reason, in this embodiment, it is confirmed that the fixing belt 327 is in the normal range 601 (FIG. 7B), and the refreshing roller 322 is contacted to prevent the fixing belt 327 from being incomplete. .

(Fixing belt refresh control execution timing)
Next, how the fixing belt refresh control is executed during printing will be described according to the flow of FIG. When a print job input via the operation unit 201 (FIG. 3) is started, the CPU 200 executes an image forming operation as described in the schematic configuration diagram of the image forming apparatus in FIG. 2 (S1001). Next, the CPU 200 counts up an execution sheet counter indicating that the image forming operation has been executed (S1002). Next, the CPU 200 determines whether or not the image forming operation continues for the second and subsequent sheets (S1003). If the image forming operation continues, the CPU 200 determines whether or not the execution sheet counter exceeds the refresh operation execution threshold (S1004).

  Here, the refresh operation execution threshold is a threshold for determining whether or not the fixing belt refresh control is to be executed. When the execution sheet counter exceeds the refresh operation execution threshold, the print job is interrupted and the fixing belt refresh control is executed. Run. In this embodiment, the refresh operation execution threshold is 4000 sheets. Thereafter, when the print job is repeated and the execution sheet counter reaches 4001, the CPU 200 determines that the condition for executing the refresh operation in the job is satisfied (S1004). In order to enter the refresh operation during the job from here, the speed S of the fixing motor 330 at the time before entering the refresh operation is stored (S1005).

  Next, the CPU 200 interrupts the image forming operation (S1006). As a result, the recording paper 800, which is a recording material (sheet material) on which the unfixed toner 801 is placed, is not conveyed, and there is no problem even if the refresh roller 322 contacts the fixing belt 327. Next, the CPU 200 sets the speed of the fixing motor 330 to the highest speed (S1007). This is to shorten the time required for the refresh operation as much as possible.

  Next, the CPU 200 determines whether or not the fixing belt 327 is in the normal range 601 (S1008). Here, whether or not the fixing belt 327 is in the normal deviation range 601 is determined based on the fact that both the left first sensor SL1 and the right first sensor SR1 are on as shown in FIG. If the fixing belt 327 is not in the normal deviation range 601, the control waits until the fixing belt 327 returns to the normal deviation range 601 by the fixing belt deviation control described above.

  When the fixing belt 327 is in the normal deviation range 601, the CPU 200 as the selection unit causes the refresh roller 322 to contact the fixing belt 327 (S1009). Then, the refresh operation start time T1 is stored (S1010).

  Thereafter, the CPU 200 determines whether or not the difference between the current times T2 and T1 exceeds the refresh operation end threshold, and holds the refresh operation state until it exceeds the refresh operation end threshold. Here, the refresh operation end threshold is a threshold for determining the time for executing the fixing belt refresh control. As described above, the minimum time is calculated from the time obtained by dividing the fixing belt circumference by the fixing belt rotation speed. The In the present embodiment, the refresh operation end threshold is 30 seconds.

  When the refresh operation is continued and the difference between T2 and T1 exceeds the refresh operation end threshold (S1011), the refresh operation is terminated and the execution number counter is cleared to 0 (S1012). Thereafter, the CPU 200 moves the refresh roller 322 away from the fixing belt 327 (S1013). In order to resume the job, the fixing motor speed is set to the speed S stored in S1005 (S1014). Thereafter, the operation returns to the image forming operation again (S1001), and the above operation is repeated until the last page is reached (S1003).

(Other embodiments)
In the above embodiment, the determination whether the fixing belt 327 is shifted and in the normal range 601 in S1008 is performed using the left first sensor SL1 and the right first sensor SR1. However, the same effect can be obtained by adopting a configuration in which it is determined that the fixing belt 327 is shifted and in the normal range 601 by other means.

  For example, it can be determined from the displacement amount D of the steering roller 326. In the above embodiment, the displacement amount D of the steering roller 326 is controlled in four stages of +10 mm, +1 mm, −1 mm, and −10 mm. Among these, when the displacement amount D of the steering roller 326 is +1 mm and −1 mm, it can be determined that the fixing belt 327 is shifted and stably driven within the normal range 601.

  A control flowchart in this case is shown in FIG. The overall flow is the same as in FIG. 1, but whether or not the refresh operation can be started in S1108 is determined based on whether the displacement amount D of the steering roller 326 is within ± 1 mm. When the displacement amount D of the steering roller 326 is larger than ± 1 mm, it waits until the displacement amount D of the steering roller 326 returns to within ± 1 mm by the fixing belt shift control described above.

  The left first sensor SL1 and the right first sensor SR1 are sensors for detecting the position of the end portion of the fixing belt 327, but the fixing belt 327 is also provided by providing a sensor for detecting the position of the center portion of the fixing belt 327. It is possible to determine that the shift is in the normal range 601. For example, as shown in FIG. 12, a marker 1201 is attached to the inner central portion of the fixing belt 327, and a sensor 1202 for detecting the marker 1201 is provided. As a result, in the range where the sensor detects the marker 1201, it is possible to determine that the fixing belt 327 is in a stable state and is driven within the normal range 601.

  FIG. 13 shows a control flowchart in that case. The overall flow is the same as in FIG. 10, but whether or not the refresh operation can be started in S <b> 1308 is determined when the sensor 1202 detects the marker 1201. When the sensor 1202 does not detect the marker 1201, the process waits until the sensor 1202 detects the marker 1201 by the fixing belt shift control described above.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to this, It can be variously deformed within the range of the identity of this invention, such as combining the technical matter described in each embodiment. . For example, in the above-described embodiment, the fixing device that fixes an unfixed toner image on the sheet has been described as an example. However, the present invention is not limited to this, and the toner that is assumed on the sheet in order to improve the gloss of the image. The present invention can be similarly applied to a device for heating and pressing an image (also called a fixing device in this case).

200 ·· CPU, 208 ·· Shift sensor (SL1, SL2, SR1, SR2), 322 ·· Refresh roller, 327 ·· Fusing belt, 332 ·· Pressure belt

Claims (10)

First and second rotating bodies in which at least one of fixing a toner image on a recording material at the nip portion is an endless belt;
A rubbing rotator for rubbing the surface of the endless belt;
Selecting means for selecting whether or not to perform the rubbing process by the rubbing rotary body according to the position in the width direction of the endless belt;
A fixing device. Position detecting means for detecting the position of the endless belt in the width direction orthogonal to the conveying direction of the recording material;
Control means for controlling the endless belt to move within a range from one end to the other end in the width direction according to a detection result of the position detection means;
The fixing device according to claim 1, further comprising: The endless belt is suspended by a plurality of belt suspension means;
3. The fixing device according to claim 1, further comprising belt steering means for controlling an amount of movement of the endless belt in the width direction by changing an alignment of at least one of the belt suspension means.   4. The fixing device according to claim 1, wherein when the endless belt is at an end portion in the width direction, selection is made not to perform the rubbing process. 5.   4. The fixing device according to claim 1, wherein the rubbing process is selected when the endless belt is in a central portion in the width direction. 5. Position detecting means for detecting the position of the endless belt in the width direction perpendicular to the conveyance direction of the recording material;
The belt steering means controls to return the endless belt to the center in the width direction when it is determined that the endless belt is at the end in the width direction based on the detection result of the position detection means. A first steering state and a second steering state for controlling the endless belt to remain at the center in the width direction when it is determined that the endless belt is not at the end in the width direction. And comprising
4. The fixing device according to claim 3, wherein when the belt steering unit determines that the first steering state is set, a selection is made not to execute the rubbing process. 5.   The fixing device according to claim 2, wherein the position detection unit is provided at both ends in the width direction.   The fixing device according to claim 2, wherein the position detection unit is provided at a central portion in the width direction and detects a position of a marker provided at an inner central portion of the endless belt.   The rubbing rotary body rotates in contact with the surface of the endless belt when the rubbing process is performed, and is separated from the surface of the endless belt when the rubbing process is not performed. Item 9. The fixing device according to any one of Items 1 to 8.   The fixing device according to claim 1, wherein each of the first and second rotating bodies includes a pressure belt that is suspended by a plurality of belt suspension means.