JP5028101B2 - Belt conveying device and image heating device - Google Patents

Description

  The present invention relates to a belt conveyance device and an image heating device for rotating an endless belt.

  Examples of the image heating device include a fixing device that fixes an unfixed image on a recording material, and a gloss increasing device that increases the gloss of the image by heating the image fixed on the recording material. it can. Such an image heating apparatus is used in an image forming apparatus such as an electrophotographic copying machine, a printer, or a FAX.

  In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, an unfixed toner image is formed on a sheet-like recording material, and the toner image is heated and pressed by a fixing device to be fixed on the recording material. is doing.

  As such a fixing device, conventionally, a roller fixing type or a belt fixing type is adopted.

  A roller fixing type fixing device forms a fixing nip by pressing a pressure roller against a fixing roller having a heater inside, and fixes a toner image on a recording material at the fixing nip.

  By the way, in order to increase the gloss of the image and speed up the image formation, it is preferable to sufficiently melt the toner by lengthening the fixing nip. However, in the case of the roller fixing method, the apparatus becomes large. There is a tendency.

  Therefore, there is a demand for a belt-fixing type fixing device capable of extending the fixing nip while reducing the size of the device as compared with the roller fixing method (see Patent Documents 1 and 2). Specifically, the fixing nip is lengthened by forming a fixing nip with the fixing roller and the pressure belt in the apparatus of Patent Document 1, and forming the fixing nip with the fixing belt and the pressure belt in the apparatus of Patent Document 2.

  By the way, in the belt fixing type fixing device, there is a tendency that the belt moves toward one end side or the other end side in the width direction (hereinafter referred to as meandering) during the belt rotation process. Therefore, in such a fixing device, the meandering of the belt is corrected in order to prevent the belt from dropping off from the roller around which the belt is suspended or the end of the belt being damaged due to the meandering of the belt. It is an important technical issue.

  Therefore, in the apparatus described in Patent Document 1, in order to correct the meandering of the belt, the belt is positively swung in the width direction by inclining one of the rollers that suspend the belt. Hereinafter, such control is referred to as “swing type control”. In addition, the inclined roller is referred to as a “steering roller”.

Specifically, when the belt is offset to one side, the steering roller is tilted so that the belt is offset to the other side. On the other hand, when the belt is shifted to the other side, the belt is shifted to the other side by tilting the steering roller in the opposite direction. By repeating such control, the belt can be swung within a certain range.
Japanese Patent Application Laid-Open No. 11-194647 JP 2004-341346 A

  By the way, in the case of the above-mentioned “swing type control”, the belt always moves in the width direction, and with this movement, there is a possibility that the belt slides with the suspension roller and the fixing roller and deteriorates.

  Further, when the above-described “swing type control” is employed in a fixing device using a fixing belt and a pressure belt as described in Patent Document 2, one belt gives an extra meandering force to the other belt. There is a risk that.

  In other words, when “swing-type control” is adopted for both belts, if the direction of the meandering force applied from the other belt is opposite to the meandering correction direction by its own deviation control, meandering correction The power may be offset. As a result, there is a possibility that the meandering is not sufficiently solved, and there is a possibility that the belt is dragged by the other belt and the belt slips.

  An object of the present invention is to provide a belt conveyance device capable of stably conveying a belt while suppressing deterioration of the endless belt.

  Another object of the present invention is to provide an image heating apparatus that can stably convey a belt while suppressing deterioration of the belt.

In order to achieve the above object, a typical configuration of the belt conveyance device according to the present invention includes an endless belt, a support member that rotatably supports the belt, and the belt deviated from a central zone in the width direction. The tilt angle of the support member is set to a return angle so that the belt returns into the zone when in the position, and the belt does not come out of the zone when a set time has elapsed after the belt returns to the zone. setting means for setting the tilt angle of the support member to the balance angle, and have a, the setting means and the means changes the return angle of the support member according to the distance the belt is out of the zone To do.

In order to achieve the above object, a typical configuration of an image heating apparatus according to the present invention includes an endless belt for heating an image on a recording material at a nip portion, and the nip portion between the belt and the nip portion. A nip forming member to be formed, a support member that rotatably supports the belt, and the belt so that the belt returns into the zone when the belt is at a position outside the central zone in the width direction. A setting means for setting an inclination angle to a return angle, and setting an inclination angle of the support member to an equilibrium angle so that the belt does not come out of the zone when a set time has elapsed after the belt returns into the zone; and have a, the setting means and changing the return angle of the support member according to the distance the belt is out of the zone.

  ADVANTAGE OF THE INVENTION According to this invention, the belt conveying apparatus which can convey a belt stably, suppressing deterioration of an endless belt can be provided.

  Moreover, according to this invention, the image heating apparatus which can convey a belt stably, suppressing deterioration of a belt can be provided.

  First, an image forming unit of an image forming apparatus employing the belt conveying device (image heating device) according to the present invention will be specifically described.

(1) Image Forming Unit FIG. 2 is a longitudinal sectional view showing a schematic configuration of an electrophotographic full-color copying machine which is an example of an image forming apparatus equipped with a belt conveyance device (image heating device). First, an outline of the image forming unit will be described.

  Reference numeral 1 denotes a digital color image reader unit that photoelectrically reads an image of a color image document placed on the platen glass 2 as a color separation image signal by a full color sensor (CCD) 3. The color separation image signal is subjected to signal processing by the image processing unit 4 and then sent to a control circuit unit (hereinafter referred to as CPU) 100 of the digital color image printer unit 5. In this example, the CPU 100 functions as setting means, control means, and changing means, which will be described later.

  In the printer unit 5, UY, UM, UC, and UK are first to fourth image forming units arranged in tandem. Each image forming unit is a laser exposure type electrophotographic process mechanism. Based on the color separation image signal sent from the image processing unit 4 to the CPU 100, each image forming unit forms a color toner image on the surface of the rotating electrophotographic photosensitive drum at a predetermined control timing. That is, a yellow toner image is formed in the first image forming unit UY, a magenta toner image is formed in the second image forming unit UM, a cyan toner image is formed in the third image forming unit UC, and a black toner is formed in the fourth image forming unit UK. A toner image is formed.

  Since the configuration of the electrophotographic process mechanism and the image forming operation of each image forming unit are known, further description is omitted.

  Each color toner image formed in each image forming unit is sequentially superimposed and transferred by the primary transfer unit 6 onto the intermediate transfer belt 7 rotating in the clockwise direction of the arrow. As a result, an unfixed full-color toner image is formed on the belt 7.

  Thereafter, in the secondary transfer unit 8, a full color toner image is collectively applied to the recording material P fed from the cassette paper feeding mechanism unit 9, the deck paper feeding unit 10, or the manual paper feeding unit 11 at a predetermined control timing. Second transfer is performed.

  The recording material P is separated from the belt 7 and introduced into a belt fixing device 12 as an image heating device, and is nipped and conveyed at a fixing nip portion. In the nipping and conveying process, an unfixed full-color toner image is melted and mixed by heat and pressure and fixed on the surface of the recording material P as a full-color fixed image. The recording material P exiting the belt fixing device 12 is switched by a flapper 13 and discharged to a FU (face-up) discharge tray 14 or an FD (face-down) discharge tray 15 to complete a series of image forming operations. To do.

  When the double-sided printing mode is selected, the recording material P that has passed through the belt fixing device 12 is sent to the sheet path that leads to the paper discharge tray 15 by the flapper 13. The recording material P is switched back and conveyed, introduced into the re-conveying sheet path 16, turned upside down, and introduced into the secondary transfer unit 8 again. As a result, the toner image is secondarily transferred onto the two surfaces of the recording material P. Thereafter, the recording material P is introduced into the belt fixing device 12 and the fixing operation on the second side is performed, and the recording material on which double-sided printing has been performed is discharged to the FU discharge tray 14 or the FD discharge tray 15.

(2) Belt fixing device 12
FIG. 1 is a cross-sectional view showing a schematic configuration of a fixing device (also referred to as an image heating device) 12 having a belt conveying device. The fixing device 12 includes a twin belt type belt conveying device having an endless first belt and a second belt that rotate in pressure contact with each other.

  Here, in the following description, with respect to the fixing device 12, the front is the device surface viewed from the recording material inlet side. Left and right are left or right when the fixing device 12 is viewed from the front. The upstream side and the downstream side are the upstream side and the downstream side in the recording material conveyance direction. The width direction and the width are a direction parallel to a direction orthogonal to the recording material conveyance direction on the recording material conveyance path surface and a dimension in that direction.

  The fixing device 12 includes a fixing unit 21 and a pressure unit 31 that are arranged vertically.

  The unit 21 includes a fixing belt 27 as an endless (endless) first belt, a driving roller 24, a steering roller 26 as a support member, a pressure pad 28, an induction heating coil 29, and the like inside the casing 22. It is an assembly.

  The driving roller 24 (belt suspension member) has a function of suspending and fixing the fixing belt 27. The roller 24 is disposed such that the left and right end shaft portions thereof are rotatably supported between the left and right side plates of the casing 22 via bearings.

  The steering roller 26 (support member) has a function of rotatably supporting the fixing belt 27 and controlling its position in the width direction. The roller 26 is disposed such that the left and right end shaft portions thereof are rotatably supported between the left and right side plates of the casing 22 via bearings. Further, the roller 26 is configured to be able to change its inclination (posture) by displacing the other end side around the one end side in the longitudinal direction as will be described later.

  The fixing belt 27 is wound around the two rollers 24 and 26. In this embodiment, the fixing belt 27 is heated by electromagnetic induction by an induction heating coil 29 as a heating source. 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 used as a belt base layer, and a silicon rubber layer having a thickness of 300 μm is coated on the outer surface.

  The pressure pad 28 is disposed in contact with the inner surface of the fixing belt 27, and both left and right ends thereof are supported between the left and right side plates of the casing 22, respectively. The pad 28 has a function of pressing the fixing belt 27 from the inside toward the pressure belt at a position close to the driving roller 24.

  The induction heating coil 29 is a combination of a litz wire coil that is flattened in an oval shape and a plate-like magnetic core, and is opposed to the outer surface of the fixing belt 27 with a gap between the casing 22 and the casing 22. It is supported and arranged.

  The steering roller 26 also functions as a tension roller that applies tension to the fixing belt 27 by urging the left and right bearings away from the drive roller 24 by spring members.

  The pressure unit 31 includes a pressure belt 32 as a second endless belt (another endless belt), a driving roller 33, a steering roller 34 as a support member, a pressure pad 38, and the like inside the casing 35. It is an assembled assembly.

  The drive roller 33 (belt suspension member) has a function of suspending and rotating the pressure belt 33. The roller 33 is disposed such that the left and right end shaft portions thereof are rotatably supported between the left and right side plates of the casing 35 via bearings.

The steering roller 34 as a support member has a function of rotatably supporting the pressure belt 27 and controlling its position in the width direction. The roller 34 is disposed with its left and right end shaft portions rotatably supported between the left and right side plates of the casing 35 via bearings. Further, as described later, the roller 34 is configured to be able to change its inclination (posture) by displacing the other end side around the one end side in the longitudinal direction.
The pressure belt 32 is wound around the two rollers 33 and 34.

  The pressure pad 38 is disposed in contact with the inner surface of the pressure belt 32, and both left and right ends thereof are supported between the left and right side plates of the casing 35, respectively. The pressure pad 38 has a function of applying pressure from the inside of the pressure belt 32 toward the fixing belt at a position close to the drive roller 33.

  The steering roller 34 also functions as a tension roller that applies tension to the pressure belt 32 by urging the left and right bearings away from the drive roller 33 by spring members.

  The pressurizing unit 31 can swing in the vertical direction around the detachable shaft portion 43, and the lower surface of the casing 35 is received and supported by the eccentric cam 44. The eccentric cam 44 is half-rotation driven and controlled by the belt attaching / detaching drive mechanism 102 to switch between a first rotation angle posture in which the large-diameter cam portion faces upward and a second rotation angle posture in which the small-diameter cam portion faces upward. It is done.

  By switching the eccentric cam 44 to the first rotation angle posture, the unit 31 moves upward about the attachment / detachment shaft portion 43. As a result, as shown in FIG. 1, the driving roller 33 is in a state in which the pressure belt 32 and the fixing belt 27 are sandwiched between the driving roller 24 on the unit 21 side. In addition, the pressure pad 38 and the pressure pad 28 on the unit 21 side sandwich the pressure belt 32 and the fixing belt 27.

  Thus, the state of FIG. 1 is a wearing state of the unit 21 and the unit 31. In this wearing state, the fixing belt 27 and the pressure belt 32 are pressed against each other at the portions of the driving roller 24, the pressure pad 28, the driving roller 33, and the pressure pad 38, and the fixing is wide in the recording material conveyance direction. A nip portion N is formed. That is, such a state is a state where a fixing operation is possible.

  In the above, the fixing belt 27 of the fixing unit 21 is an endless belt for heating the image on the recording material at the nip portion. The pressure unit 21 is a nip forming member that forms a nip portion with the fixing belt 27. Further, the pressure belt 32 is another endless belt that is rotatable by being pressed against the fixing belt 27.

  On the other hand, when the eccentric cam 44 is switched to the second rotation angle posture, the unit 31 moves downward about the detachable shaft portion 43. As a result, the pressure applied to the drive roller 24 and the pressure pad 28 by the drive roller 33 and the pressure pad 38 is released, and the pressure belt 32 is separated from the fixing belt 27 as shown in FIG. The state of FIG. 3 is a detached state of the unit 21 and the unit 31. In such a state, the fixing operation cannot be performed and a standby state is entered.

  In the operation control of the image forming apparatus, when the fixing device 12 is in operation (when the recording material is nipped and conveyed by the fixing nip portion), the CPU 100 causes the drive mechanism 102 to move the eccentric cam 44 to the first rotation angle as shown in FIG. By switching to the posture, the units 21 and 31 are held in the wearing state.

  Further, the CPU 100 switches the eccentric cam 44 to the second rotation angle posture as shown in FIG. 3 by the drive mechanism 102 when the fixing device 12 is not in operation (except when the recording material is nipped and conveyed by the fixing nip portion). Control unit 21 and 31 in a detached state. Thereby, it is possible to prevent unnecessary pressure from being applied between the units 21 and 31, thereby preventing wear of the members.

  The belt attaching / detaching mechanism can be configured by an electromagnetic solenoid plunger mechanism, a lever mechanism, or the like in addition to the cam mechanism.

  Further, the CPU 100 turns on the fixing driving roller driving mechanism 103 and the pressure driving roller driving mechanism 104 when the fixing device 12 is in operation. When the drive mechanism 103 is turned on, the drive roller 24 is rotationally driven at a predetermined speed in the clockwise direction of the arrow in FIG. As the roller 24 rotates, the fixing belt 27 rotates in the clockwise direction indicated by the arrow. At this time, the steering roller 26 rotates following the rotation of the fixing belt 27.

  Further, when the drive mechanism 104 is turned on, the drive roller 33 is rotationally driven in the counterclockwise direction indicated by the arrow at a predetermined speed. As the roller 33 rotates, the pressure belt 32 rotates counterclockwise as indicated by the arrow. The steering roller 34 rotates following the rotation of the pressure belt 32. The peripheral speeds of both drive rollers are set so that the rotational speed of the fixing belt 27 and the rotational speed of the pressure belt 32 are substantially the same.

  Further, the CPU 100 turns on the excitation circuit 105 and applies a high frequency current to the induction heating coil 29. As a result, the metal layer of the fixing belt 27 is inductively heated to heat the fixing belt. The surface temperature of the fixing belt 27 is detected by a temperature detection element TH such as a thermistor, and electrical information regarding the temperature of the fixing belt 27 is input to the CPU 100. The CPU 100 controls the power supplied from the excitation circuit 105 to the induction heating coil 29 so that the fixing belt reaches a predetermined fixing temperature based on the temperature information input from the temperature detection element TH.

  Thus, the recording material P carrying the unfixed toner image is introduced into the fixing device 12 from the side of the secondary transfer unit 8 in a state where the fixing belt 27 rises to a predetermined fixing temperature and is adjusted in temperature. The recording material P is introduced with the surface having an unfixed toner image facing the fixing belt. Then, the recording material P is nipped and conveyed by a fixing nip portion N which is a pressure contact portion between the fixing belt 27 and the pressure belt 32, whereby the unfixed toner image is fixed to the recording material by heat and pressure.

  In other words, the fixing belt 27 is installed so as to be in contact with the image carrying surface of the recording material P and heated from the image carrying surface side, and heats the image on the recording material at the nip portion.

(3) Belt Shift Control Mechanism The belt shift control mechanism is a mechanism that controls the shift in the width direction that occurs when the fixing belt 27 and the pressure belt 32 are rotated in each of the fixing unit 21 and the pressure unit 31. is there.

  In this embodiment, in each of the units 21 and 31, the CPU 100 as the setting means controls (steering control) the inclination (inclination angle and attitude) of the steering rollers 26 and 34. That is, by adjusting the alignment (arrangement posture or parallelism, etc.) of the steering rollers 26 and 34 with respect to the driving rollers 24 and 33 which are other belt suspension members, the position in the width direction of each belt is controlled. .

  More specifically, the CPU 100 sets the tilt angle of the steering roller 26 to the return angle so that the belt 27 returns into the zone when the fixing belt 27 is out of the center zone in the width direction with respect to the fixing unit 21. Set. Then, the tilt angle of the steering roller 26 is set to an equilibrium angle so that the belt 27 does not move out of the zone when the set time has elapsed after the belt 27 returns to the zone.

  Further, the CPU 100 sets the tilt angle of the steering roller 34 to the return angle so that the pressure belt 32 returns to the zone when the pressure belt 32 is out of the center zone in the width direction with respect to the pressure unit 31. Set. Then, the inclination angle of the steering roller 34 is set to an equilibrium angle so that the pressure belt 32 does not move out of the zone when the set time has elapsed after the pressure belt 32 returns to the zone.

  FIG. 4 is a perspective view of the belt deviation control mechanism portion of the unit 21 and the unit 31. A belt shift control mechanism of the fixing belt 27 is disposed on the right side of the unit 21. A belt shift control mechanism for the pressure belt 32 is also provided on the right side of the unit 31. FIG. 5 is a right side view of the unit 21, and FIG. 6 is a right side view of the unit 31.

  First, the belt shift control mechanism of the fixing belt 27 will be described with reference to FIGS.

  22 R is a right side plate of the housing 22 of the unit 21. Reference numeral 62 denotes a sector gear disposed so as to be rotatable in the vertical direction about the support shaft 62a with respect to the right side plate 22R. Reference numeral 62 b denotes an elongated hole provided in the sector gear 62. The right bearing 63 of the steering roller 26 is fitted into the elongated hole 62b so as to be slidable along the elongated hole. The right end shaft portion 26aR of the steering roller 26 is rotatably supported by the right bearing 63. 62c is a right bearing biasing spring that is contracted in the elongated hole portion 62b. The spring 62c constantly urges the right bearing 63 to move along the long hole portion in a direction away from the drive roller 24. A stepping motor 60 for steering control of the steering roller 26 is disposed on the right side plate 22R of the housing 22. A worm gear 61 is fixed to the rotating shaft of the motor 60. The worm gear 61 is meshed with the sector gear 62. The fan-shaped gear 62 moves up and down around the support shaft 62a in conjunction with forward / reverse rotation driving of the worm gear 61 by the motor 60, whereby the steering roller 26 is steering-controlled. Details thereof will be described later. Reference numerals 65 and 66 denote belt shift sensor units as detection means disposed on the right and left sides of the fixing belt 27 in the width direction. That is, it is a detecting means for detecting that the fixing belt 27 has deviated from the center zone in the width direction to the outside in the width direction. Each of them contains a photo sensor for detecting belt misalignment (position detection) in two stages. Details thereof will be described later. The above is the belt shift control mechanism of the fixing belt 27.

  Reference numeral 24 a R denotes a right end shaft portion of the driving roller 24. The right end shaft portion 24aR is rotatably supported by a right bearing 67 fixedly disposed on the right side plate 22R of the housing 22. Reference numeral 24 aL denotes a left end shaft portion of the driving roller 24. The left end shaft portion 24aL is rotatably supported by a left bearing fixedly disposed on the left side plate (not shown) of the housing 22. Reference numeral 26 aL denotes a left end shaft portion of the steering roller 26. The left end shaft portion 26aL is rotatably supported by a long bearing provided in the left side plate of the housing 22 and a left bearing fitted in a slidable manner along the long hole. Similarly to the right bearing 63, the left bearing is constantly urged to move in the direction away from the drive roller 24 along the elongated hole portion by a left bearing biasing spring that is contracted in the elongated hole portion. In this manner, the steering roller 26 is a belt tension roller that applies tension to the fixing belt 27 by biasing the bearings of the left and right end shaft portions 26aL and 26aR away from the drive roller 24 by the biasing springs. Also works. Reference numerals 26L and 26R denote flanges disposed at the left and right ends of the steering roller 26, which serve as a safety mechanism that receives the end of the belt when the fixing belt 27 moves excessively.

  Next, the belt shift control mechanism of the pressure belt 32 will be described with reference to FIGS. Reference numeral 35R denotes a right side plate of the housing 35 of the unit 31. Reference numeral 72 denotes a sector gear disposed so as to be rotatable in the vertical direction about the support shaft 72a with respect to the right side plate 35R. Reference numeral 72 b denotes an elongated hole provided in the sector gear 72. A right bearing 73 of the steering roller 34 is fitted into the elongated hole portion 72b so as to be slidable along the elongated hole. The right end shaft portion 34aR of the steering roller 34 is rotatably supported by the right bearing 73. Reference numeral 72c denotes a right bearing biasing spring that is contracted in the elongated hole portion 72b. The spring 72c constantly urges the right bearing 73 to move away from the drive roller 33 along the elongated hole portion. A stepping motor 80 for steering control of the steering roller 34 is disposed on the right side plate 35R of the housing 35. A worm gear 81 is fixed to the rotating shaft of the motor 80. The worm gear 81 is meshed with the sector gear 72. The fan-shaped gear 72 moves up and down around the support shaft 72a in conjunction with forward / reverse rotation driving of the worm gear 81 by the motor 80, whereby the steering roller 34 is steering-controlled. On the right side and the left side of the pressure belt 32, as in the case of the fixing belt 27, belt shift sensor units (reference numerals 85 and 86 in FIG. 8) are arranged as detection means. That is, it is a detecting means for detecting that the pressure belt 32 has moved out of the center zone in the width direction outward in the width direction. Each of them contains a photo sensor that performs belt deviation detection (position detection) in two stages. The above is the belt shift control mechanism of the pressure belt 32.

  Reference numeral 33aR denotes a right end shaft portion of the driving roller 33. The right end shaft portion 33aR is rotatably supported by a right bearing 87 fixedly disposed on the right side plate 35R of the housing 35. The left end shaft portion of the drive roller 33 is rotatably supported by a left bearing fixedly disposed on a left side plate (not shown) of the housing 35. Reference numeral 34aL denotes a left end shaft portion of the steering roller 34. This left end shaft portion 34aL is rotatably supported by a long bearing provided in the left side plate of the housing 35, and a left bearing fitted in a slidable manner along the long hole. As with the right bearing 73, the left bearing is constantly urged to move in a direction away from the drive roller 33 along the elongated hole portion by a left bearing biasing spring that is contracted in the elongated hole portion. As described above, the steering roller 34 is a belt tension that applies tension to the pressure belt 32 by urging the bearings of the left and right end shaft portions 34aL and 34aR away from the drive roller 33 by the urging springs. Also functions as a roller. Reference numerals 34L and 34R denote flanges disposed at the left and right ends of the steering roller 34, which serve as a safety mechanism that receives the end of the belt when the pressure belt 32 moves excessively.

(4) Belt Shift Control Operation In order to solve the above-described problem, the twin belt type fixing device in this embodiment has the following two control modes: control mode A and control mode B.

  Here, an angle when the above-described steering roller (support member) for suspending the belt is tilted from the reference posture state (arbitrarily set) is defined as a tilt angle. In this example, the longitudinal direction and the horizontal direction of the steering roller are parallel to each other in the reference posture state, but this is not the only example. That is, the reference posture state of the steering roller may be a state inclined by a predetermined angle with respect to the horizontal.

  Control mode A: When the belt is in the normal zone in the center of the width direction (see FIG. 9) (when it is within the range), the inclination angle of the steering roller is adjusted so that the belt stays in this zone. Equilibrium mode set to. In this example, even when the longitudinal direction of the steering roller is parallel to the horizontal direction, it is referred to as “setting the steering roller inclination angle to an equilibrium angle”.

  In other words, this balanced mode is a mode in which the steering roller inclination angle is set to the balanced angle so that the shifting toward the one side and the other side in the width direction of the belt is balanced. It can also be said to be a mode in which the posture of the steering roller is set to the equilibrium posture state when the belt is in the zone that is in the normal range (when it is within the zone).

  The equilibrium angle (equilibrium state) is set in advance by measurement after assembly of the apparatus, and is stored in a nonvolatile memory as storage means. That is, the control mode A is executed when the CPU 100 as the setting means reads data corresponding to the equilibrium angle in the memory.

  In this example, as described above, this equilibrium angle coincides with a horizontal angle orthogonal to the direction of gravity.

  Control mode B: A return mode in which the tilt angle of the steering roller is set to the return angle so that the belt returns into the zone when the belt (a part of the belt) is out of the normal zone.

  In other words, the return mode is a mode in which the attitude of the steering roller is set to the inclined state when the belt (a part of the belt) is out of the zone in the normal range in the width direction.

  Note that this return angle (inclined state) is also set in advance by measurement after assembly of the device, and is stored in the memory described above. That is, the control mode B is executed when the CPU as the setting means reads the data corresponding to the return angle in the memory.

  The return angle is prepared for both the case where the belt is disengaged to one end in the width direction and the case where the belt is disengaged to the other end. In this example, as will be described later, the return angle when the belt is disengaged to one end side in the width direction and when the belt is disengaged to the other end side has the same absolute value and different directions.

  Furthermore, in this example, it is intended to realize stable belt conveyance by making the state of the control mode A as long as possible.

  More specifically, the control mode A is an equilibrium point maintenance mode in which the steering roller is returned to an equilibrium angle at which the balance of the left and right meandering of the belt is not substantially lost when the meandering of the belt is eliminated.

  More specifically, the control mode B is meandering when the belt meandering is confirmed by the endurance status of the apparatus or the deviation control of the other belt in spite of executing the control mode A. This is a meander-removal mode in which the steering roller is tilted at an angle sufficient to return to the opposite direction.

  In short, while the control mode B is provided to prevent the belt crossing error, the control mode A is provided to allow the belt to stay in the normal zone in the center in the width direction for as long as possible. Is.

  In the configuration in which both belts independently correct the deviation in the twin belt method, the belts are difficult to meander while both belts are in contact with each other, thereby realizing stable belt deviation control. Therefore, with the configuration of the present example, it is possible to suppress a decrease in the life due to the movement of the belt while preventing the belt from being damaged due to the deviation of the belt.

  Therefore, basically, control (control mode A) is performed so that the belt stays in a zone that is a normal range in the center in the width direction. While this control is being performed, when the belt is moved toward the end in the width direction due to the movement of the other belt, the control is returned to the center normal range zone (control mode B). ) Is also included. In short, both the mode for eliminating the meandering by moving the belt and the mode for minimizing the movement of the belt are provided. As will be described later, there is also a mode for finely adjusting the equilibrium angle (posture) of the steering roller for minimizing the movement of the belt.

  The belt shift control mechanisms of the fixing belt 27 and the pressure belt 32 have the same structure as described in the above section (3), and the mechanism operation and control sequence are also the same. Therefore, here, the belt shift control of the fixing belt 27 will be described as a representative.

  This will be described with reference to FIGS. When the motor 60 is driven in the CW direction (clockwise) in response to an instruction from the CPU 100 as setting means (control means), the worm gear 61 rotates and the sector gear 62 rotates downward about the support shaft 62a. To do. Along with this, the right bearing 63 of the steering roller 26 also moves downward, so that the steering roller 26 is inclined to the lower right as shown by the broken line in FIG. become. As a result, the fixing belt 27 is in a state where the tension on the right side is lower than that on the left side in the width direction. Therefore, as the fixing belt 27 rotates, the fixing belt 27 gradually decreases in the right direction along the length of the roller (roller axial direction). Moving.

  Conversely, when the motor 60 is driven in the CCW direction (counterclockwise) according to an instruction from the CPU 100, the worm gear 61 rotates and the sector gear 62 rotates upward about the support shaft 62a. Along with this, the right bearing 63 of the steering roller 26 also moves upward, so that the steering roller 26 rises on the right end side with respect to the left end side, and tilts downward to the left as shown by the one-dot chain line in FIG. Become a shape. As a result, the fixing belt 27 is in a state where the tension on the left side is lower than that on the right side in the width direction. Therefore, as the fixing belt 27 rotates, the fixing belt 27 gradually moves in the left direction along the length of the roller.

  In FIG. 7, D is a displacement amount for raising and lowering the right end portion of the steering roller 26. That is, this is the amount of inclination (inclination angle) of the steering roller 26. The + direction of the displacement amount D is an upward displacement, and is a direction in which the fixing belt 27 is returned to the left side. The − direction is a downward displacement, and is a direction in which the fixing belt 27 is returned to the right side.

  When the displacement amount D of the end portion of the steering roller 26 changes, that is, when the inclination amount (inclination angle) of the steering roller 26 changes, the position in the width direction of the fixing belt 27 tends to move to the left or right side accordingly. . Therefore, ideally, the displacement amount of the end portion at which the steering roller 26 as the belt shift control member has a substantially horizontal inclination angle is expressed as a reference amount ± 0 state so that the belt position does not move from the current position to the left and right as much as possible. To do. The angular state of the steering roller 26 is the reference posture 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 displaced due to various factors. It may move.

  The above is the fixing belt control of the fixing unit 21, but the pressing belt control of the pressing unit 31 is basically the same.

  FIG. 8 is a block diagram of a control system of the image forming apparatus including the belt type fixing device of this embodiment. The entire control is performed by a CPU 100 as setting means (control means), and an operation unit 101 configured by a liquid crystal touch panel, buttons, and the like is connected to the CPU 100. In response to a user input from the operation unit 101, the image forming apparatus starts operation.

  The CPU 100 includes a belt attaching / detaching mechanism 102, a fixing belt driving roller driving mechanism 103, a pressure belt driving roller driving mechanism 104, an excitation circuit 105, a fixing steering control mechanism (motor driver) 106, a pressure steering control mechanism (motor driver) 107, and the like. To control. In addition, electrical temperature information from the temperature detection element TH is input to the CPU 100. Further, the CPU 100 receives electrical information about the belt deviation from the left and right belt deviation sensor units 66 and 65 on the fixing unit 21 side and the left and right belt deviation sensor units 86 and 85 on the pressure unit 31 side. input. The sensor units 66, 65 and 86, 85 are sensors that detect the positions (belt deviation amounts) of the fixing belt 27 and the pressure belt 32.

  The belt attaching / detaching mechanism 102 is a mechanism for performing the attaching / detaching operation of the fixing unit 21 and the pressure unit 31 described above. The fixing belt driving roller driving mechanism 103 drives the driving roller 31 of the fixing unit 21 and rotates the stretched fixing belt 27. Similarly, the pressure belt drive roller drive mechanism 104 drives the pressure belt drive roller 33 of the pressure unit 31 to rotate the stretched pressure belt 32. The excitation circuit 105 is a circuit that controls power supply to the induction heating coil 29, and the control circuit unit 100 supplies power from the excitation circuit 105 to the induction heating coil 29 based on electrical temperature information input from the temperature detection element TH. On-off control.

  The fixing steering control mechanism 106 performs control to drive the motor 60 and correct the deviation of the fixing belt 27 in accordance with a signal from the CPU 100.

  The pressure steering control mechanism 107 performs control to drive the motor 80 in accordance with a signal from the CPU 100 and correct the shift of the pressure belt 32.

  In the example described later, the amount of movement of the steering roller is set to 0.0046 (mm / pulse) every time the motor 60 (80) is driven by one pulse.

  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 27 and the pressure belt 32 is basically the same, detection of the deviation of the fixing belt 27 will be described as a representative.

  FIG. 9A is a plan view of a fixing belt portion between the driving roller 24 and the steering roller 26. The left and right belt deviation sensor units 66 and 65 are respectively provided with sensors SL1 and SL2, SR1 serving as belt deviation detection means each having a first and a second belt deviation detection means arranged at predetermined intervals. -It has SR2. Each of these sensors is a light detection sensor (photo sensor) in which a light transmitting element a and a light receiving element b are combined. Then, in the fixing belt rotation driving process, when the fixing belt 27 moves more than a predetermined amount to the left or right in the width direction, the belt edge on the side of the movement is between the light transmitting element a and the light receiving element b. It is arranged in a relational structure that enters and 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.

  (A) and (b) are the states when the fixing belt 27 is rotationally driven within an allowable shift range between the left first sensor SL1 and the right first sensor SR1. Both the sensor SL1 and the first right sensor SR1 are on. The CPU 100 determines that the fixing belt 27 is rotationally driven within an allowable deviation movement range when both the sensors SL1 and SR1 are turned on. The allowable shift range of the fixing belt 27 at this time is represented as a shift normal range (central zone) 51.

  When the fixing belt 27 moves to the left and the left first sensor SL1 is turned off at the left belt edge as shown in (c), the CPU 100 determines that the fixing belt 27 has moved too far to the left. In order to move the fixing belt 27 back to the opposite right side, the motor 60 is driven in the CW direction by the fixing steering control mechanism 106 to displace the right end portion of the steering roller 26 downward (shown by a broken line in FIG. 7). ).

  Nevertheless, when the fixing belt 27 further moves to the left side and the left second sensor SL2 is also turned off at the left belt edge as shown in (d), the displacement of the fixing steering roller 26 is further increased. The roller 27 is increased in inclination to the right.

  Even in this state, if the left second sensor SL2 is kept off for 10 seconds, the control circuit unit of the CPU 100 stops the rotation of the fixing belt driving roller 24 in order to prevent the fixing belt 27 from being damaged. . The CPU 100 further stops the image forming operation of the entire image forming apparatus, displays an error on the operation unit 101, and displays that the customer is contacted by a service person (service person call display). The leftward movement range of the fixing belt 27 is represented as a left-side abnormal range 52 in FIG.

  When the fixing belt 27 moves to the right and the right first sensor SR1 is turned off at the edge of the right belt as shown in (e), the CPU 100 determines that the fixing belt 27 has moved too far to the right. . Then, in order to move the fixing belt 27 back to the opposite left side, the motor 60 is driven in the CCW direction by the fixing steering control mechanism 106 to displace the right end portion of the steering roller 26 upward (the chain line in FIG. 7). Shown).

  Nevertheless, the displacement of the steering roller 26 is further increased when the right belt second sensor SR2 is also turned off at the right belt edge as shown in (f) by the fixing belt 27 moving further to the right. And the inclination of the roller 27 to the left is increased.

  Even in this state, when the right-side second sensor SR2 is kept off for 10 seconds, the CPU 100 fixes the fixing belt 27 in order to prevent the fixing belt 27 from being damaged, as in the case where the fixing belt 27 is moved to the left side. The rotation of the belt driving roller 24 is stopped. Further, the CPU 100 stops the image forming operation of the entire image forming apparatus, displays an error on the operation unit 101, and displays a service man call. This rightward movement range of the fixing belt 27 is represented as a left-side abnormal range 53 in FIG.

(5) Control Determination Flow Next, the control determination flow of the CPU 100 as the setting means (control means) will be described in detail with reference to FIG. 10 regarding the belt deviation detection and deviation correction control described in FIG. The “steering amount” described below means an angle (or an amount by which the steering roller is tilted). Further, the “steering position” means that the steering roller is in a state inclined (including horizontal) at a predetermined angle.

  In this embodiment, when determining the timing for performing the steering control for correcting the shift of the fixing belt 27, when the detected shift amount of the fixing belt reaches a predetermined range (± 2), the steering amount of the steering roller 26 is set. A predetermined inclination is set. Further, when the fixing belt is positioned at the center of the central zone that is in the normal range, control is performed to return the steering roller inclination angle to the equilibrium angle. At this time, when the set time elapses after the belt returns to the central zone, the tilt angle of the steering roller is returned to the equilibrium angle. Thus, in this example, control is performed based on “time”. Further, the “set time” is changed by the CPU 100 (changing means) in accordance with the peripheral speed of the belt, that is, the rotational speed of the driving roller. The CPU (setting means) 100 also changes the return angle of the steering roller 26 according to the distance that the belt is out of the zone. The CPU (setting means) 100 also changes the set time according to the changed return angle. This will be described below.

  Step S201 in FIG. 10 is a processing procedure executed by the CPU 100 every 100 ms by the interval timer 1000 (FIG. 8) as a measuring means.

  In the initial state, the first and second sensors SL1 and SL2 of the left sensor unit 66 and the first and second sensors SR1 and SR2 of the right sensor unit 65 are both ON, and detect a belt shift. It is not in the state. At this time, the displacement amount D of the end portion of the steering roller 26 is a reference amount ± 0 (equilibrium angle of the steering roller 26).

  When step S201 is started, it is first detected in step S202 whether the left first sensor SL1 is ON. If not ON, the process proceeds to step S203, and the motor 60 is driven by 400 pulses in the CW direction so that the displacement amount D of the steering roller 26 becomes a predetermined value DL1 (the return angle of the steering roller 26).

  Subsequently, a loop is performed until the left first sensor SL1 is turned ON again by the belt deviation correction control in step S203 (S204). If the left second sensor SL2 is turned OFF during this loop, the displacement is changed again to perform further correction, which will be described later (FIGS. 12 and 13).

  In this example, the timer 1000 measures the elapsed time from the time when the belt entered the zone. This will be specifically described below.

  When the left first sensor SL1 returns to the ON state again, the position of the belt is just past the left first sensor SL1, and is still at the center position of the central zone that is the normal range in FIG. 9B. It cannot be said that it has fully returned. Therefore, a timer Tref that reversely drives the motor 60 is set so that the displacement amount D of the steering roller 26 is returned to the reference amount ± 0 when a predetermined time has passed in step S205, and the sequence is ended in step S206.

  If the left first sensor SL1 is ON in step S202, it is detected in step S207 whether the right first sensor SR1 is ON. If it is not ON as in the case of the left side, the process proceeds to step S208, and the motor 60 is driven by 400 pulses in the CCW direction so that the displacement amount D of the steering roller 26 becomes a predetermined value DR1 (return angle). Subsequently, a loop is performed until the right first sensor SR1 is turned ON again by the belt deviation correction control in step S208 (S209). When the right first sensor SR1 returns to the ON state again, the belt position is just past the right first sensor SR1, and is still at the center position of the central zone that is the normal range in FIG. 9B. It cannot be said that it has fully returned. Therefore, a timer Tref that reversely drives the motor 60 is set so that the displacement amount D of the steering roller 26 is returned to ± 0 (equilibrium angle) when a predetermined time has elapsed in step S210, and the sequence is ended in S206.

  If the left first sensor SL1 is ON in step S202 and the right first sensor SR1 is also ON in step S207, it is determined that the fixing belt 27 is stable in the central zone as shown in FIG. 9B. However, no particular control is performed. In step S206, the sequence ends.

  The timer Tref set in step S205 or step S210 activates the timer handler in step S251 when a predetermined time has elapsed.

  Subsequently, when the timer is set from step S205 so that the displacement amount D = ± 0 in step S252, the motor 60 is rotated backward by 400 pulses in the CCW direction. When the timer is set from step S210, the motor is rotated backward by 400 pulses in the CW direction. In step S253, the timer handler is terminated.

  That is, it is detected by the belt deviation sensor units (detecting means) 65 and 66 that the fixing belt 27 has deviated from the center in the width direction to the outside in the width direction. Then, a timer (measuring unit) 1000 measures the time elapsed since the fixing belt 27 returned to the zone. The CPU (setting means) 100 switches the inclination angle of the steering roller 26 from the equilibrium angle to the return angle when the fixing belt 27 is detected by the belt deviation sensor units 65 and 66. Further, the CPU 100 switches the tilt angle of the steering roller 26 from the return angle to the equilibrium angle when the measurement time of the timer 1000 reaches the set time.

  Next, the timing and control amount of the belt deviation detection and deviation correction control described in FIG. 9 will be described in detail with reference to FIG.

  FIG. 11A is a timing chart of correction control when the fixing belt 27 moves to the left and the left first sensor SL1 is turned off. In this description, FIG. ) From the state (c) to the state (b) again.

  In FIG. 11A, 301 indicates ON (non-detection) / OFF (detection) of the left first sensor SL <b> 1, and is a signal input to the CPU 100. Similarly, 303 indicates the rotational speed of the drive roller 24 controlled by the output signal of the CPU 100, and is set to 200 mm / sec. Reference numeral 304 denotes a displacement amount of the steering roller 26 controlled by an output signal from the CPU 100.

  First, when the left first sensor SL1 is turned OFF at the point 305, the CPU 100 rotates the motor 60 by a predetermined pulse in the CW direction, and the displacement amount D of the steering roller 26 is set to a predetermined value DL1 (in a negative direction from the reference amount ± 0). Return angle). As a result, the steering roller 26 is tilted to the right, so that the left side of the belt is gradually returned and corrected, and at the point 306, the left first sensor SL1 is turned on.

  At this time, the left end of the fixing belt 27 is still located near the left first sensor SL1. Therefore, the displacement DL1 is maintained until a time 308 has elapsed in which the fixing belt 27 is likely to be positioned approximately at the center of the central zone, which is an area between the sensors SL1 and SR1. When the point 307 at which the time 308 has elapsed is reached, the motor 60 is rotated by a predetermined pulse in the CCW direction so as to return the displacement D of the steering roller 26 to the reference amount ± 0 (equilibrium angle). The time 308 until the displacement D of the steering roller 26 is returned to the reference amount ± 0 is calculated from the rotational speed of the fixing belt 27 and the displacement D until the reference amount ± 0 is returned. For example, when DL1 = 2.0 mm and the belt rotation speed is 200 mm / sec, it is 10 sec.

  FIG. 11B is a timing chart of the correction control when the fixing belt 27 is moved leftward and the left first sensor SL1 is turned off. The difference from the above (a) is that the rotational speed of the drive roller 24 shown at 303 is set to 100 mm / sec.

  Also in the case of FIG. 11B, as in the case of FIG. 11A, when the left first sensor SL1 is turned OFF at the point 311, the CPU 100 turns the motor 60 to CW so that the displacement amount D of the steering roller 26 becomes DL1. Rotate in the direction by a predetermined number of pulses. As a result, the steering roller 26 tilts to the right, so that the belt shift is gradually corrected and the left side first sensor SL1 is turned on at a point 312.

  At this time, the left end of the fixing belt 27 is still located near the left first sensor SL1. Therefore, this displacement amount DL1 is maintained until a time 314 when the fixing belt 27 is likely to be positioned substantially in the center of the central zone has elapsed, and when this time has elapsed, the displacement amount D of the steering roller 26 is returned to the reference amount ± 0.

  The time 314 until the displacement amount D is returned to the reference amount ± 0 is longer in the case of FIG. 11A because the time required for the belt to return to the center of the central zone becomes longer when the rotation speed of the fixing belt 27 is slow. Longer than (200 mm / sec). Specifically, the time 314 is about twice as short as the time 308, 18 seconds when DL1 = 2.0 mm and the belt rotation speed is 100 mm / sec.

  Here, an example will be described where the displacement amount D of the steering roller 26 is set to DL1, and the deviation of the fixing belt 27 is not sufficiently returned despite the predetermined inclination angle.

  That is, since the belt has moved to the left side until the left first sensor SL1 is turned off, the displacement amount of the steering roller 26 is set to DL1, and if the fixing belt 27 rotates normally in this state, the belt The shift is eliminated. However, in the case of a belt that is highly endured and severely worn, there may be cases where the correction is not sufficiently effective.

  FIG. 12 is a control flow in the case where the belt has not moved back and the belt has moved to the second left sensor SL2 in such a case.

  Steps S211 to S216 in FIG. 12 are the parts as described above when the belt shift is restored by setting the displacement amount of the steering roller 26 to DL1 when the first left side sensor SL1 of the belt is turned off. It is. Since this part is the same as steps 201 to 205 in the flow of FIG.

  Step S214 is a part waiting for the left first sensor SL1 to be turned on after changing the displacement amount of the steering roller 26 to DL1. In this state, there is a possibility that the shift of the belt does not return and the shift of the left second sensor SL2 may proceed, so in step S217, it is confirmed whether the left second sensor SL2 is ON.

  If the detection value of the left second sensor SL2 is ON, the left end of the belt is considered to be between the left first sensor SL1 and the left second sensor SL2, so that the left first sensor SL1 is turned off as it is. Keep waiting.

  When the detection value of the second left sensor SL2 is OFF, it is considered that the fixing belt 27 is further shifted to the left. Therefore, the motor 60 is driven by a difference amount from the displacement amount DL1 so that the end portion displacement amount D of the steering roller 26 becomes DL2 = 4.0 mm. Here, since the number of pulses of the motor 60 required for the displacement from the displacement amount ± 0 state to the displacement amount DL2 is 110 pulses, the motor 60 is equivalent to 50 pulses, which is a difference when the displacement amount DL1 is moved. Is further driven in the CW direction.

  Thus, when the left first sensor SL1 returns to the ON state again, the position of the belt is just past the left first sensor SL1, and it cannot be said that the belt has sufficiently returned to the central position of the central zone. Therefore, a timer Tref that reversely drives the motor 60 is set so that the displacement amount D of the steering roller 26 returns to ± 0 after a predetermined time has elapsed in step S216, and the sequence ends in step S213.

  In FIG. 13, after the fixing belt 27 moves to the left and performs the shift control according to the OFF signal of the left first sensor SL1, the OFF signal of the left second sensor sensor SL2 is detected and further shift control is performed. It is the figure which showed the timing chart at the time of performing.

  In the initial state of FIG. 13, both the left first sensor SL1 and the left second sensor SL2 are in the ON state. When the belt shifts to the left as shown in FIG. 9C in accordance with the rotation of the fixing belt 27 from this state, the motor 60 is rotated by a predetermined pulse in the CW direction. That is, as indicated by point 321, the motor 60 is rotated by a predetermined pulse in the CW direction so that the displacement amount D of the steering roller 26 becomes a predetermined value DL1 in the minus direction from the reference amount ± 0.

  However, there is a case where the belt further moves toward the left side, and the second left sensor SL2 is turned OFF as shown in FIG. 9D (point 322). In such a case, the motor 60 is rotated by a difference of a predetermined pulse so that the displacement D of the steering roller 26 is set to a predetermined value DL2 larger than the predetermined value DL1 in order to more strongly correct the belt shift (backward movement). .

  When the belt finally starts to return in this state, the left second sensor SL2 is first turned ON (point 323). However, if the displacement amount D of the steering roller 26 is returned to DL1, it may start again. Therefore, the displacement amount is maintained as DL2. When the belt shift returns sufficiently, the left first sensor SL1 also returns to ON, but the displacement D of the steering roller 26 is still maintained at DL2. Then, when the sensor SL1 is in the ON state (point 324) and the belt 27 reaches a time 326 that is located approximately in the center of the central zone that is an area between the sensors SL1 and SR1 (point 325). ), The motor 60 is reversely rotated by a predetermined pulse. That is, the motor 60 is rotated in the reverse direction by a predetermined pulse to return the displacement amount D of the steering roller 26 to the reference amount ± 0.

  Since the displacement amount DL2 is larger than DL1, when the displacement amount of the steering roller 26 is displaced to DL2, the amount of movement of the belt in the width direction per unit time is larger than when the displacement amount is DL1. For this reason, the time from when the left first sensor SL1 is also turned ON to when the fixing belt 27 is substantially returned to the center is shorter than when the displacement is DL1. Therefore, the time 326 is preferably set shorter than the case of FIG. 11A in the case of the displacement DL1 (time 308: 10 sec). In this example, when DL2 = 4.0 mm and the belt rotation speed is 200 mm / sec, the time 326 is 7 sec.

  The above-described control in FIGS. 11 to 13 is the case of the reverse control when the fixing belt 27 moves to the left side, but the reverse control when the fixing belt 27 moves to the right side is the same.

  Further, the belt deviation detection and deviation correction control of the pressure belt (other endless belt) 32 on the pressure unit 31 side are the same as the belt deviation detection and deviation correction control of the fixing belt 27 on the fixing unit 21 side described above. .

  As described above, in the belt fixing device having the belt deviation detection sensor on both ends in the belt width direction, after the displacement amount (return angle) of the steering roller for correcting the belt deviation is displaced (return angle) at the deviation detection. Then, control is performed to return this again. In this case, the control is performed to return the displacement amount to the reference value (equilibrium angle) after a lapse of time from the end of the belt passing through the first stage detection sensor to the return to the center position (center zone). I do. Therefore, it is possible to suppress the deterioration caused by frequent movement of the belt in the width direction, which is a problem in the conventional “swing type control”. Furthermore, the belt shift control as described above can be appropriately performed without separately providing a detection mechanism for detecting that the belt is positioned (returned) in the center of the central zone.

  Further, the set time for switching the tilt angle of the steering roller from the return angle to the equilibrium angle is changed based on the rotational speed of the belt and the displacement amount of the steering roller (the tilt angle of the steering roller). Therefore, it is possible to cope with various operating conditions, and the belt can be stably conveyed.

  Specifically, in this example, when the peripheral speed of the belt (drive roller) is as follows, a set time is calculated and set by multiplying different coefficients depending on the steering amount and the peripheral speed of the belt.

200mm / sec ... Steering amount K x 1.0mm / sec
100mm / sec ... Steering amount K x 0.55mm / sec (when feeding thick paper)
70mm / sec ... Steering amount K x 0.3mm / sec (Standby)
In the above description, the timing of the timer is assumed to be the time when the belt enters the zone (the time when the belt disappears from the detection region of the first-stage deviation detection sensor SL1 (SR1)). A simple example is also acceptable.

  For example, when the belt is out of the center zone in the width direction, the elapsed time from the time when the steering roller 26 is tilted to return the belt into the zone may be measured by a timer. Since there is a possibility that the belt may not immediately return into the zone, the above example in which the time when the belt enters the zone is more preferable as the timer calculation timing.

  The attachment / detachment control of the belt fixing device 12 will be described with reference to the control system block diagram of FIG.

  As shown in FIG. 1, when the unit 21 and the unit 31 are switched to the wearing state, the fixing belt 27 and the pressure belt 32 are in pressure contact with each other, and a fixing nip portion that is wide in the recording material conveyance direction between the belts. N is formed.

  The CPU 100 controls the belt attaching / detaching mechanism 102 during the operation of thermally fixing the unfixed toner image on the recording material P to switch to the wearing state in which the fixing nip portion N is thus formed.

  Further, when the image forming apparatus is on standby, the CPU 100 controls the belt attaching / detaching mechanism 102 to hold the unit 21 and the unit 31 in the detached state as shown in FIG. Thereby, the pressure belt 32 and the fixing belt 27 are held in a non-contact state, and the heat loss of the fixing belt by the pressure belt 32 is reduced.

  Further, even during the image forming operation (print job operation), the CPU 100 also switches the fixing device 12 to the detached state when the time until the recording material P enters the fixing nip becomes long. .

  Based on the image formation start signal, the CPU 100 controls the belt attaching / detaching mechanism 102 to switch and hold the fixing device 12 in the wearing state, thereby bringing the outer surface of the pressure belt 32 into contact with the lower surface of the fixing belt 27. Further, the fixing belt driving roller driving mechanism 103 and the pressure belt driving roller driving mechanism 104 are controlled so that the fixing belt 27 and the pressure belt 32 are rotationally driven at a speed of 200 mm / s in accordance with the conveyance speed of the recording material P. To. Further, the exciting circuit 105 is controlled to supply electric power to the induction heating coil 29 to raise the temperature of the fixing belt 27. The surface temperature of the fixing belt 27 is detected by the temperature detection element TH, and the temperature detection signal is input to the CPU 100. The CPU 100 controls the excitation circuit 105 to vary the power supply to the induction heating coil 29 so that the temperature detection signal input from the temperature detection element TH is maintained at a detection amount corresponding to a predetermined fixing temperature, and the fixing belt. The surface of 21 is kept at a constant temperature.

  Subsequently, a recording material P carrying an unfixed toner image is introduced into the fixing nip N from the secondary transfer unit 8 side to the fixing device 12 and is nipped and conveyed to the fixing nip N. In this process, the unfixed toner image surface of the recording material P is brought into close contact with the surface of the fixing belt 27, and the toner image is heated by the heat of the fixing belt 27 and fixed to the surface of the recording material P by heating and pressure. It is discharged and conveyed.

  Next, the relationship between the attachment / detachment control of the fixing device 12 and the shift control of the fixing belt and the pressure belt described in FIG. 9 will be described with reference to FIG. FIG. 14 shows steps in which the CPU 100 determines the duration of displacement of the steering roller (corresponding to the set time described above) when the belt fixing device 12 is attached (FIG. 1) and detached (FIG. 3). .

  In this example, unlike Example 1, when the belt is out of the central zone in the width direction, the elapsed time from when the steering roller 26 (34) is tilted to return the belt into the zone is measured by a timer. It is configured to do. This will be specifically described below.

  The content of the control is almost the same between the fixing unit 21 and the pressure unit 31. For this reason, the fixing belt 27 and the pressure belt 32, and the fixing steering roller 26 and the pressure steering roller 34 are collectively described. However, the displacement of the fixing belt 27 and the pressure belt 32 occurs independently. Actual control is performed independently.

  First, in step S301, it is determined whether the belt 27 (32) is on the left side or the right side. That is, it is detected whether the left first sensor SL1 is in the OFF state and the right first sensor SR1 is in the OFF state, and the process proceeds to step S302. At this time, the steering roller 26 (34) has a reference amount ± 0 (equilibrium angle).

  In step S302, based on the determination in step S301, the steering roller 26 (34) is displaced by a predetermined displacement amount (return angle) so that the belt 27 (32) returns to the central zone. The displacement amount (= inclination amount) of the steering roller 26 (34) represents the amount of movement caused by driving the motor 60 (80) located at the end of the steering roller 26 (34). In this embodiment, it represents how many millimeters the steering end of the steering roller 26 (34) has moved vertically from the reference amount ± 0. The specific amount of displacement is DL3 = 3.0 mm when detecting a belt shift to the left, and DR3 = −3.0 mm (3.0 mm downward) when a belt shift to the right is detected. .

  Subsequently, in step S303, it is determined whether the fixing belt 27 and the pressure belt 32 are in the attached state (contact state) or the detached state (non-contact state). In step S304, a time (second) until the displacement (return angle) of the steering roller 26 (34) is returned to the reference state (equilibrium angle) is set depending on which state. The specific numerical value is 10 seconds in the wearing state and 5 seconds in the detached state.

  This is because, in the detached state, compared to the worn state, the belt is not affected by the pressure contact, so that the speed at which each of the fixing belt 27 and the pressure belt 32 returns is faster. Therefore, the time for returning the displacement when the fixing belt 27 and the pressure belt 32 are removed is set shorter than that when the fixing belt 27 and the pressure belt 32 are worn.

  As described above, the time for returning the displacement of the steering roller 26 (34) is switched depending on whether it is in the worn state or the detached state with respect to the other belt. That is, the CPU (changing unit) 100 changes the set time according to whether or not the belt is in contact with the nip forming member. As a result, the belt position can be more reliably returned to the center. Therefore, stable belt deviation control can be realized.

  In the above example, both the fixing unit and the pressure unit are configured to have endless belts. However, the configuration is not limited thereto. That is, it is only necessary that at least one of the fixing unit and the pressure unit has the above-described endless belt and a transport device that transports the endless belt.

  For example, the fixing unit includes a known fixing roller instead of an endless belt, while the pressure unit includes an endless belt and a conveying device that conveys the endless belt. Even with such a configuration, it is possible to suppress deterioration of the belt due to sliding with the suspension roller and the fixing roller in accordance with the control for returning the belt to the central zone.

  Further, in the above-described example, the steering roller is inclined by displacing the other end side about the one end side in the longitudinal direction. However, the present invention is not limited to such a configuration.

  For example, the steering roller may be configured to be inclined by displacing one end side and the other end side in opposite directions with respect to the central portion in the longitudinal direction.

  Furthermore, in the above-described example, the roller is used as the support member that controls the position in the width direction of the belt, but the configuration is not limited to this.

  For example, instead of the steering roller, a fixing member such as a pad fixedly arranged so as not to rotate may be used.

  Further, the image heating apparatus may be configured such that a fixing belt that heats an image on a recording material at a nip portion is arranged to heat from the opposite side of the recording material carrying the image. it can.

  If the configuration of the belt conveyance device described above is employed, it is possible to stably convey the belt while suppressing deterioration of the belt. In addition, since the steering roller is inclined only when the belt deviates from the central zone, the driving frequency of the driving source for displacing the steering roller can be reduced, and the power consumption by the driving source can be reduced. Furthermore, it is advantageous in terms of usability, for example, the frequency with which operating noise is generated by the drive source is reduced.

  In addition, since the time for moving the belt in the width direction is remarkably reduced as compared with the conventional swing type control configuration, the influence of the meandering control of one belt on the meandering control of the other belt can be reduced. Can do.

  Such belt control can be realized without providing a separate mechanism for detecting that the belt has returned to the central position of the central zone. Therefore, it is possible to reduce the size and cost of the apparatus.

It is a cross-sectional view of the fixing device of the embodiment. 1 is a cross-sectional view illustrating a schematic configuration of an example of an image forming apparatus. FIG. 3 is a cross-sectional view of the fixing device in which the fixing unit and the pressure unit are removed. FIG. 3 is a schematic perspective view of a main part of the fixing device. FIG. 4 is a right side view of the fixing unit. It is a right view of a pressurization unit. It is explanatory drawing of the steering operation of a steering roller. 2 is a block diagram of a control system of a fixing device. FIG. It is explanatory drawing of a belt meandering position and a belt shift position detection sensor. It is a figure which shows the control judgment flow at the time of detecting the deviation | shift of a belt. It is a figure which shows the correction | amendment control timing when the shift | offset | difference of a belt is detected. It is a figure which shows the control judgment flow when the deviation further progresses although what started the belt deviation correction. 7 is a control timing chart in a case where the deviation of the belt started to be corrected further proceeds. FIG. 10 is a diagram illustrating determination steps of belt deviation correction control when belt attachment / detachment control is performed in the second embodiment.

Explanation of symbols

  12 .. Belt fixing device (belt conveying device), 21 .. Fixing belt unit, 31 .. Pressure belt unit, 27 .. Fixing belt, 32 .. Pressure belt, 24. 33 ... Belt drive roller, 26 .34..Steering roller, 100..Control circuit section, 106.107..Steering control mechanism, 60.80..Stepping motor, SL1, SL2, SR1, SR2,.

Claims (17)

Endless belt,
A support member for rotatably supporting the belt;
When the belt is out of the center zone in the width direction, the tilt angle of the support member is set to a return angle so that the belt returns into the zone, and a set time has elapsed after the belt returns to the zone. Setting means for setting the inclination angle of the support member to an equilibrium angle so that the belt does not deviate from the zone when
And have a, the setting means belt conveying apparatus characterized by changing the angle back of the support member according to the distance the belt is out of the zone.   Detection means for detecting that the belt has deviated from the zone in the width direction; and measuring means for measuring a time elapsed since the belt returned into the zone; and the setting means, When the belt is detected by the detection means, the inclination angle of the support member is switched from the equilibrium angle to the return angle, and when the measurement time of the measurement means reaches a set time, the inclination angle of the support member is returned to the return angle. The belt conveyance device according to claim 1, wherein the belt conveyance device is switched from an angle to the equilibrium angle. The belt conveying apparatus according to claim 1 , further comprising a changing unit that changes the set time according to a return angle after the change. The set further comprises a changing means for changing in accordance with the circumferential speed of the time the belt, it belt conveying device according to any one of claims 1 to 3, characterized in. The belt conveying device according to any one of claims 1 to 4 , further comprising another endless belt that is rotatable in pressure contact with the belt. A support member that supports the other belt, and a tilt angle of the support member so that the other belt returns into the zone when the other belt is out of the central zone in the width direction. Setting means for setting the inclination angle of the support member to an equilibrium angle so that the other belt does not come out of the zone when a set time has elapsed since the other belt returned into the zone. The belt conveyance device according to claim 5 , further comprising: An endless belt for heating the image on the recording material at the nip,
A nip forming member that forms the nip portion with the belt;
A support member for rotatably supporting the belt;
The tilt angle of the support member is set to a return angle so that the belt returns to the zone when the belt is out of the center zone in the width direction, and set after the belt returns to the zone. Setting means for setting an inclination angle of the support member to an equilibrium angle so that the belt does not deviate from the zone when time elapses;
And have a, the setting means image heating apparatus and changes the return angle of the support member according to the distance the belt is out of the zone. Detection means for detecting that the belt has deviated from the zone in the width direction; and measuring means for measuring a time elapsed since the belt returned into the zone; and the setting means, When the belt is detected by the detection means, the inclination angle of the support member is switched from the equilibrium angle to the return angle, and when the measurement time of the measurement means reaches a set time, the inclination angle of the support member is returned to the return angle. The image heating apparatus according to claim 7 , wherein the image heating apparatus is switched from an angle to the equilibrium angle. The image heating apparatus according to claim 7 , further comprising a changing unit that changes the set time according to a return angle after the change. Image heating apparatus according to any one of claims 7 to 9 wherein said set further comprising a changing means for changing in accordance with time peripheral speed of the belt, it is characterized. Image heating apparatus according to any one of claims 7 to 10, characterized in the setting time is the belt further comprises a changing means for changing, depending on whether contact with the nip forming member . The belt image heating apparatus according to any one of claims 7 to 11, wherein the installation is, that in contact with the image carrying surface of the recording material. The nip forming member is an image heating apparatus according to any one of claims 7 to 12, characterized in that, further comprising a rotatable another endless belt and the belt and press.   A support member that supports the other belt, and a tilt angle of the support member so that the other belt returns into the zone when the other belt is out of the central zone in the width direction. Setting means for setting the inclination angle of the support member to an equilibrium angle so that the other belt does not come out of the zone when a set time has elapsed since the other belt returned into the zone. The image heating apparatus according to claim 13, further comprising: Endless belt,
A support member for rotatably supporting the belt;
When the belt is out of the center zone in the width direction, the tilt angle of the support member is set to a return angle so that the belt returns into the zone, and a set time has elapsed after the belt returns to the zone. Setting means for setting the inclination angle of the support member to an equilibrium angle so that the belt does not deviate from the zone when
Changing means for changing the set time according to the peripheral speed of the belt;
A belt conveyance device comprising: An endless belt for heating the image on the recording material at the nip,
A nip forming member that forms the nip portion with the belt;
A support member for rotatably supporting the belt;
The tilt angle of the support member is set to a return angle so that the belt returns to the zone when the belt is out of the center zone in the width direction, and set after the belt returns to the zone. Setting means for setting an inclination angle of the support member to an equilibrium angle so that the belt does not deviate from the zone when time elapses;
Changing means for changing the set time according to the peripheral speed of the belt;
An image heating apparatus comprising: An endless belt for heating the image on the recording material at the nip,
A nip forming member that forms the nip portion with the belt;
A support member for rotatably supporting the belt;
The tilt angle of the support member is set to a return angle so that the belt returns to the zone when the belt is out of the center zone in the width direction, and set after the belt returns to the zone. Setting means for setting an inclination angle of the support member to an equilibrium angle so that the belt does not deviate from the zone when time elapses;
Changing means for changing the set time according to whether the belt is in contact with the nip forming member;
An image heating apparatus comprising: