JP2009063861A - Belt feed device and image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out a favorable movement correction control for a shift movement correction of each belt even while endless shape belts which are in pressure contact with each other and rotate form a nip part. <P>SOLUTION: A belt fixing device 12 pinches and feeds a recording material by a pressing belt 32 and a fixing belt 27, and it has a detection sensor 66 to detect the position of the widthwise direction of the pressing belt 32, a detection sensor 65 to detect the position of the widthwise direction of the fixing belt 27, a roller 34 to correct the movement in the widthwise direction of the pressing belt 32 and a roller 26 to correct the movement in the widthwise direction of the fixing belt 27. When the detection sensor 66 detects that the pressing belt 32 has moved into the outside of the widthwise direction from the predetermined range, the roller 34 makes the pressing belt 32 move back in the direction of the predetermined range and the roller 26 makes the fixing belt 27 move in the same direction as the pressing belt 32 as well. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a belt conveyance device and an image heating device configured to rotate endless belts in pressure contact with each other, such as a belt nip belt fixing device mounted on an image forming apparatus.

  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. .

  Conventionally, as a fixing device mounted on an electrophotographic image forming apparatus, an unfixed toner image is fixed while a recording material is nipped and conveyed by an endless fixing belt and a pressure belt which are rotated in pressure contact with each other. A configured fixing device has been proposed (Patent Document 1). This belt fixing type fixing device achieves a sufficient fixing nip width (length in the recording material conveyance direction) while achieving a reduction in size and speed of the apparatus as compared with a roller fixing type fixing device mainly composed of a roller pair. )).

  By the way, in a belt nip type fixing device using an endless fixing belt or a pressure belt, the belt moves so as to be shifted to one side or the other side in the width direction orthogonal to the recording material conveyance direction during the rotation of the belt. Phenomenon (hereinafter referred to as shift movement) occurs. If the belt shifts, the belt may fall off from the roller that stretches the belt, or the end of the belt may be damaged. Therefore, in order to prevent this, it is necessary to correct the shift of the belt.

  Therefore, conventionally, in order to correct the shift of the belt, a technique for correcting the shift of the belt by tilting one of the plurality of rollers that stretch the belt is used as a steering roller. Has been proposed (Patent Documents 2 and 3). Specifically, when it is detected that the belt has moved a predetermined amount or more in the width direction, the steering roller is tilted so that the belt moves in a direction opposite to the moving direction, thereby correcting the shift of the belt. is doing.

JP 2004-341346 A Japanese Patent Application Laid-Open No. 11-194647 JP-A-5-27622

  By the way, in the twin belt fixing type fixing device having the fixing belt and the pressure belt rotating in pressure contact with each other as in the above-mentioned Patent Document 1, it is necessary to independently correct the shift of each belt. is there.

  However, since the fixing belt and the pressure belt are pressed against each other to form a nip portion (clamping portion), the force that corrects the shift of one belt (the force that moves the belt in the width direction) is pressed against this. There is a risk of affecting the other belt.

  For example, in order to suppress the occurrence of wrinkles on the recording material, the tension of the pressure belt is set slightly weaker than that of the fixing belt. The pressure belt is provided with a roller for applying oil to prevent friction on the inner surface of the belt. For this reason, the pressure belt is more susceptible to the force of correcting the above-described shift movement than the fixing belt.

  In such a case, even if control for correcting the displacement of the pressure belt is performed, the movement of the pressure belt may not be sufficiently corrected due to the influence of the fixing belt that is pressed to form the nip portion. . In particular, when the fixing belt is corrected for movement in the direction opposite to the direction of movement of the pressure belt, even if correction for movement of the pressure belt in pressure contact is made, sufficient correction of movement of the pressure belt is possible. There was a situation that could not be performed.

  Therefore, an object of the present invention is to implement good movement correction control for correcting the shift of each belt even when endless belts rotating in pressure contact with each other form a nip portion. Is to be done.

  In order to achieve the above object, the present invention provides a belt conveying apparatus for nipping and conveying a recording material between an endless first belt and a second belt that rotate in pressure contact with each other. First belt position detection means for detecting the position of the belt in the width direction orthogonal to the recording material conveyance direction, and second belt position detection for detecting the position of the second belt in the width direction orthogonal to the recording material conveyance direction Means, first movement correction means for correcting movement of the first belt in the width direction, and second movement correction means for correcting movement of the second belt in the width direction, When the first belt position detecting means detects that the first belt has moved to the outside in the width direction from the predetermined range, the first movement correcting means moves the first belt in the direction to return to the predetermined range. The second belt is also moved by the second movement correcting means. Wherein the moving in the same direction as one of the belt.

  According to the present invention, even in a state where endless belts that are pressed against each other and rotate to form a nip portion, good movement correction control is performed to correct the shift of each belt. Can do.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.

[First Embodiment]
An image heating apparatus as a belt conveying apparatus and an image forming apparatus having the image heating apparatus will be described. Here, as the image heating apparatus, a belt fixing apparatus that fixes an unfixed image on a recording material is illustrated, but the present invention is not limited to this. For example, other image heating apparatuses such as a gloss increasing apparatus that increases the gloss of an image by heating an image fixed on a recording material may be used.

(Image forming device)
First, a basic configuration of an image forming apparatus having a belt fixing device will be described with reference to FIG. 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 fixing device.

  In FIG. 2, reference numeral 1 denotes a digital color image reader unit, which 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 image 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 (see FIG. 6).

  In the printer unit 5, UY, UM, UC, and UK are the 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, the yellow toner image is formed on the drum surface in the first image forming unit UY, the magenta toner image is formed on the drum surface in the second image forming unit UM, and the cyan toner is formed on the drum surface in the third image forming unit UC. In the fourth image forming unit UK, a black toner image is formed on the drum surface.

  The color toner images formed on the drum surface of each image forming unit are sequentially superimposed and transferred by the primary transfer unit 6 on the surface of the intermediate transfer belt 7 rotating in the clockwise direction of the arrow. As a result, an unfixed full-color toner image is synthesized and formed on the surface of the belt 7 by superimposing the four color toner images. The combined full-color toner image is secondarily transferred collectively onto the surface of the recording material P by the secondary transfer unit 8. The recording material P is fed from the cassette paper feeding mechanism 9, the deck paper feeding unit 10, or the manual paper feeding unit 11 to the secondary transfer unit 8 at a predetermined control timing.

  The recording material P onto which the toner image has been transferred is separated from the surface of the belt 7 and is introduced into the belt fixing device 12, and is nipped and conveyed at the 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 that has exited 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.

  When the double-sided printing mode is selected, the recording material P printed on the first side from the belt fixing device 12 is sent by the flapper 13 to a sheet path that once leads to the FD paper discharge layout 15. 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, a toner image is secondarily transferred and formed on the second surface side of the recording material P. Thereafter, the recording material P is introduced into the belt fixing device 12 as in the case of the first side printing. As a result, the double-side printed recording material is discharged to the FU discharge tray 14 or the FD discharge tray 15.

(Belt fixing device)
Next, the configuration of the belt fixing device 12 will be described with reference to FIG. FIG. 1 is a cross-sectional view showing a schematic configuration of the belt fixing device 12. The fixing device 12 is a twin-belt type belt conveyance device having an endless first belt and a second belt which are rotated in pressure contact with each other.

  Here, in the following description, with respect to the fixing device 12, the front surface is a device surface viewed from the front side of the device as shown in FIGS. 1 and 2. Left and right are, as shown in FIG. 4 and the like, when the fixing device 12 is viewed from the front, the front side is right and the back side is left. 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 orthogonal to the recording material conveyance direction on the recording material conveyance path surface and a length in that direction.

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

  The fixing belt unit 21 is an assembly in which a fixing belt 27 as an endless (endless) second belt, a driving roller 24, a steering roller 26, a pressure pad 28, an induction heating coil 29, and the like are incorporated inside a casing 22. It is.

  The drive roller 24 is a belt support member (belt suspension member) that rotationally drives 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 is a belt support member that constitutes a second movement correction unit that corrects the movement of the fixing belt 27 in the width direction. The roller 26 is disposed substantially in parallel with the driving roller 24 on the upstream side of the driving roller 24, with the left and right end shafts thereof rotatably supported via bearings between the left and right side plates of the casing 22. It is. The roller 26 corrects the movement of the fixing belt 27 by switching the inclination (position) of the roller 26 based on detection information from a detection sensor unit 65 described later.

  The fixing belt 27 is wound around the two rollers 24 and 26. The fixing belt 27 is heated by an induction heating coil 29 as a heating means disposed in the upper part. As the fixing belt 27, for example, a magnetic metal layer such as a nickel metal layer or a stainless steel layer having a thickness of 75 μm, a width of 380 mm, and a circumferential length of 200 mm is coated with silicon rubber having a thickness of 300 μm.

  The pressure pad 28 is disposed inside 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 pressure pad 28 contacts the lower inner surface of the fixing belt 27 at a position close to the driving roller 24.

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

  The pressure belt unit 31 is an assembly in which a pressure belt 32 as an endless first belt, a driving roller 33, a steering roller 34, a pressure pad 38, and the like are incorporated inside a casing 35.

  The drive roller 33 is a belt support member (belt suspension member) that rotationally drives 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 is a belt support member that constitutes a first movement correction unit that corrects the movement of the pressure belt 27 in the width direction. The roller 34 is disposed substantially parallel to the drive roller 33 on the upstream side of the drive roller 33, with the left and right end shafts rotatably supported via bearings between the left and right side plates of the casing 35. It is. The roller 34 corrects the movement of the pressure belt 32 by switching the inclination (position) of the roller 34 based on detection information from a detection sensor unit 66 described later.

  The pressure belt 32 is suspended between the two rollers 33 and 34.

  The pressure pad 38 is disposed inside the pressure belt 32, and both left and right ends thereof are supported between the left and right side plates of the casing 35. The pressure pad 38 contacts the upper inner surface of the pressure belt 32 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 biasing the left and right bearings in a direction away from the drive roller 33 by spring members.

  The pressure belt unit 31 can swing up and down around the attaching / detaching 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 rotationally controlled by the belt attaching / detaching mechanism 102, and a belt pressure contact position (see FIG. 1) where the large diameter cam portion contacts the lower surface of the casing 35 and a belt separation where the small diameter cam portion contacts the lower surface of the casing 35. The position is switched (see FIG. 3). That is, the fixing belt unit 21 and the pressure belt unit 31 are in the press contact state shown in FIG. 1 when the recording material P is nipped and conveyed by the rotation control of the eccentric cam 44 by the belt attaching / detaching mechanism 102, and in the other cases The separated state shown in FIG. As a result, unnecessary pressure is prevented from being applied between the fixing belt unit and the pressure belt unit, and wear of the members is prevented.

  An oil application roller 45 is provided on the inner surface of the pressure belt 32 to reduce the frictional force. The oil application roller 45 follows the rotation of the pressure belt 32 and uniformly applies oil to the inner surface of the belt. As a result, friction on the inner surface of the pressure belt is prevented.

  Next, a belt shift control mechanism of the belt fixing device 12 will be described with reference to FIG. The belt shift control mechanism is a mechanism that controls movement of the fixing belt unit 21 and the pressure belt unit 31 so as to return the shift in the lateral direction that occurs when the fixing belt 27 and the pressure belt 32 are rotated. Since the belt shift control mechanisms of the fixing belt unit 21 and the pressure belt unit 31 have substantially the same configuration, the belt shift control mechanism of the fixing belt unit 21 will be described as an example here.

  The belt shift control mechanism includes a steering control stepping motor 60, a worm gear 61, a fan gear 62, a steering roller bearing 63, and a side plate 64 that supports them. The steering roller bearing 63 supports the shaft of the fixing steering roller 26.

  Reference numeral 65 denotes a fixing belt shift detection sensor unit, which is a second belt position detecting means for detecting the position of the fixing belt 27 in the width direction. The fixing belt deviation detection sensor unit 65 is disposed at the left and right ends of the fixing belt 27 in the width direction, and includes upper photosensor SL1 and upper SL2 that detect left belt deviation, and upper photosensor SR1 that detects right belt deviation. , And upper SR2. Details thereof will be described later. Note that a similar pressure belt shift detection sensor unit 66 (see FIG. 1) is also disposed on the left and right ends of the pressure belt 32 in the width direction on the pressure belt unit 31 side. The pressure belt shift detection sensor unit 66 is a first belt position detection unit that detects the position of the pressure belt 32 in the width direction. In order to distinguish from the fixing belt deviation detection sensor unit 65, the photo sensors on the pressure belt deviation detection sensor unit 66 side are described as lower SL1, lower SL2, upper SR1, and upper SR2.

  When the stepping motor 60 is driven in the CW direction (clockwise), the worm gear 61 rotates, and the sector gear 62 swings downward about the shaft. Accordingly, since the steering roller bearing 63 moves downward, the fixing steering roller 26 is slightly inclined to the back side (left side), and the entire fixing belt unit 21 is inclined to the back side. Accordingly, the fixing belt 27 is in a state where the tension on the back side is lower than that on the near side, so that the fixing belt 27 gradually moves to the back side (left side) where the tension is low as the fixing belt 27 rotates.

  Conversely, when the stepping motor 60 is driven in the CCW direction (counterclockwise), the worm gear 61 rotates and the sector gear 62 swings upward about the axis. Accordingly, the steering roller bearing 63 moves upward, so that the fixing steering roller 26 is slightly inclined toward the front side (right side), and the entire fixing belt unit 21 is also inclined toward the front side. As a result, the fixing belt 27 is in a state where the tension on the near side is lower than that on the far side, so that the fixing belt 27 gradually moves to the near side (right side) where the tension is low as the fixing belt 27 rotates.

  FIG. 5 is a view of the case where the steering roller 26 is tilted to return the fixing belt 27 of the fixing belt unit 21 to the left side when viewed from the front. Since the control mechanism for inclining the steering roller 26 is on the back side as described above, the end portion of the steering roller 26 is raised by the stepping motor 60. 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 the upper side and is a direction that returns toward the front side (right side) of the apparatus, and the − direction is the lower side and is a direction that returns toward the back side (left side) of the apparatus.

  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 amount becomes a substantially horizontal inclination angle so that the belt position does not move from side to side as much as possible from the current position. Is expressed as a reference amount ± 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 21 is described in FIG. 5, the basic configuration is the same for the pressure belt unit 31.

  However, since the fixing belt and the pressure belt are rotating toward the abutment surface that is inside, the direction in which the deviation occurs with respect to the inclination of the steering roller is reversed.

  For example, when the fixing steering roller 26 is displaced upward by 400 pulses in the vertical direction, the tension on the back side of the belt increases, so that the fixing belt 27 moves to the near side.

  On the other hand, when the pressure steering roller 34 is displaced upward by 400 pulses in the vertical direction, the tension on the back side of the belt decreases, so that the pressure belt 32 moves to the back side.

  Therefore, when the fixing belt 27 and the pressure belt 32 are moved in the same direction in the width direction, the inclination angles of the fixing steering roller 26 and the pressure steering roller 34 are displaced in the opposite directions.

  FIG. 6 is a block diagram showing a control system of an image forming apparatus including a belt fixing device. The entire control is performed by the CPU 100 which is a control circuit unit, and an operation unit 101 composed of a liquid crystal touch panel, buttons, and the like is connected thereto. In response to a user input from the operation unit 101, the image forming apparatus starts operation.

  The CPU 100 is connected to the belt attaching / detaching mechanism 102, the belt deviation control mechanism 106, the fixing belt deviation detection sensor unit 65, and the pressure belt deviation detection sensor unit 66, and performs control and state detection from the CPU 100. Further, a fixing belt driving roller driving mechanism 103, a pressure belt driving roller driving mechanism 104, a heater power supply circuit unit 105, and the like are connected to the CPU 100, and control and state detection are performed from the CPU 100.

  The belt attaching / detaching mechanism 102 is a mechanism for performing a pressure contact and separation operation between the fixing belt unit 21 and the pressure belt unit 31 described above. The fixing belt driving roller driving mechanism 103 drives the fixing driving roller 24 of the fixing belt unit 31 and rotates the stretched fixing belt 27. Similarly, the pressure belt drive roller drive mechanism 104 drives the pressure drive roller 33 of the pressure belt unit 31 to rotate the stretched pressure belt 32. The heater power supply circuit unit 105 is a circuit that controls power supply to the induction heating coil 29, and turns the power supply on and off in response to a signal from the CPU 100.

  The belt shift control mechanism 106 drives the steering control stepping motor 60 shown in FIG. 4 in accordance with a signal from the CPU 100, and performs control to correct the shift movement of the fixing belt 27 and the pressure belt 32 in the width direction.

  Next, the belt position detecting means for detecting the position in the width direction of the belt will be described in detail with reference to FIGS. Since the configuration for detecting the positions in the width direction of the fixing belt 27 and the pressure belt 32 (deviation in the width direction) is basically the same, the fixing belt unit 21 will be described as an example.

  FIG. 7A is a view of the fixing belt portion between the belt driving roller 24 and the steering roller 26. The photosensors SL1 and SL2 and the photosensors SR1 and SR2 are belt position detection means arranged at predetermined intervals on both the left and right sides of the fixing belt 27 in the width direction. The belt position detecting means includes photosensors SL1 and SR1 on the inner side in the width direction and photosensors SL2 and SR2 on the outer side in the width direction on the left side and the right side in the belt width direction, respectively. 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. In each sensor, when the fixing belt 27 moves more than a predetermined amount to the left or right in the width direction in the process of rotating the fixing belt, the belt edge on the side of the movement is between the light transmitting element a and the light receiving element b. It is configured to enter and block 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.

  FIGS. 7A and 7B show a state in which 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 first sensor SL1 and the right first sensor SR1 are on. The control circuit unit 100 determines that the fixing belt 27 is rotationally driven within an allowable shift range by turning on the sensors SL1 and SR1. The allowable shift range of the fixing belt 27 at this time is expressed as a shift normal range 51 (see FIG. 7B) as a predetermined range.

  As shown in FIG. 7B, the right and left shift detection sensors SL1, SL2, SR1, SR2 are not shielded, and the section where the left and right ends of the belt are shifted and within the normal range 51 is defined as a central zone (predetermined range). ).

  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 FIG. 8A, the control circuit unit 100 indicates that the fixing belt 27 has moved too far to the left. to decide. Then, a belt shift control mechanism 106 (steering roller displacement mechanism), which will be described later, is operated to displace the end portion of the fixing steering roller 26 so that the fixing belt 27 is moved back to the opposite right side, thereby tilting the roller. Nevertheless, when the fixing belt 27 moves further to the left side and the left second sensor SL2 is also turned off at the left belt edge as shown in FIG. 8B, the displacement of the fixing steering roller 26 is changed. Is further increased to increase the inclination of the roller. Even in this state, if the left-side second sensor SL2 remains off for a predetermined time (here, 10 seconds), it is determined that the fixing belt 27 has moved to the left, and the fixing belt 27 is prevented from being damaged. The operation of the fixing driving roller 24 that drives the motor 27 is stopped. Further, after the image forming operation of the entire apparatus is stopped, an error is displayed on the operation unit 101 to display that the customer is informed of the service person. The moving range of the left end of the fixing belt is referred to as a left-side abnormal range 52 (see FIG. 7B) outside the normal range 51 in the width direction.

  When the belt shields the left side detection sensors SL1 and SL2, it is described as a left second stage zone, and when the belt shields only the left side detection sensor SL1, it is described as a left first stage zone. The left second stage zone moves more in the belt width direction than the left first stage zone.

  When the fixing belt 27 moves to the right and the right first sensor SR1 is turned off at the right belt edge as shown in FIG. 8C, the control circuit unit 100 causes the fixing belt 27 to move to the right. Judge that it has passed. Then, a belt shift control mechanism 106 described later is operated to displace the end portion of the fixing steering roller 26 in a direction in which the fixing belt 27 is moved back to the opposite left side, and the roller is inclined. Nevertheless, when the fixing belt 27 further moves to the right side and the right second sensor SR2 is also turned off at the right belt edge as shown in FIG. 8D, the fixing steering roller 26 is displaced. To further increase the inclination of the roller. Even in this state, if the right-side second sensor SR2 remains off for a predetermined time (here, 10 seconds), it is determined that the fixing belt 27 has moved to the right and the fixing belt 27 is prevented from being damaged. The operation of the fixing driving roller 24 that drives the motor 27 is stopped. Further, after the image forming operation of the entire apparatus is stopped, an error is displayed on the operation unit 101 to display that the customer is informed of the service person. The moving range of the right end of the fixing belt is referred to as a right-side abnormal range 53 (see FIG. 7A) that is outside the normal range 51 in the width direction.

  When the belt shields only the right side detection sensor SR1, the right first stage zone is indicated. When the belt shields the right side detection sensors SR1 and SR2, the right side second stage zone is indicated. The right-side second stage zone has a greater shift in the belt width direction than the right-side first stage zone.

  The relationship between the position in the belt width direction and the detection by the belt deviation detection sensor described above is the same for both the fixing belt unit 21 and the pressure belt unit 31.

  7 and 8 is arranged as shown in the table of FIG. 9 when the belt shift state and the belt shift detection sensor state are arranged.

  Next, with respect to the belt deviation detection and deviation correction control described with reference to FIGS. 7 and 8, the control determination flow of the CPU 100 will be described in detail with reference to FIG.

  Step S201 in FIG. 10A is a processing procedure executed by the CPU 100 every 100 ms by the interval timer. In the initial state, the detection values of the belt deviation detection sensors 65 and 66 are ON at both the left and right sides, and no belt deviation is detected, and the displacement amount D of the end portion of the fixing steering roller 26 is the reference amount ± 0. It is. That is, the fixing steering roller 26 is in the first position for holding the fixing belt 27 in the central zone (predetermined range 51).

  When step S201 is started, the degree of belt deviation is detected from the state of the belt deviation detection sensors 65 and 66 in steps S202 and S207. First, if the belt has entered the first-stage zone on the left side in step S202, the process proceeds to step S203 to return the belt to the central zone. In step S203, the steering control stepping motor 60 is driven by 400 pulses in the CCW direction so that the displacement amount D of the fixing steering roller 26 becomes a predetermined value DL1. As a result, the fixing steering roller 26 is displaced from the first position for holding the fixing belt 27 in the central zone to the second position for correcting the shift movement of the fixing belt 27.

  Hereinafter, a displacement amount for returning the left side (the back side of the apparatus) of the belt of the belt fixing device 12 to the central zone is described as DL1.

  Subsequently, the process loops until it is detected by the belt deviation correction control in step S203 that the state of the belt deviation detection sensor is again located in the central zone (step S204). During this loop, if the left side second deviation detection sensor SL2 detects that the belt has entered the second stage zone on the left side, the amount of displacement is changed again for further correction, but this is omitted here.

  When returning from the left first stage zone to the central zone again, the position of the left end of the belt is just past the left first sensor SL1, and has not yet fully returned to the central position. Therefore, a timer Tret for reversely driving the steering control stepping motor 60 is set so that the displacement amount D of the fixing steering roller 26 is returned to the reference amount ± 0 after a predetermined time has elapsed in step S205, and the sequence is ended in S206. . That is, the fixing steering roller 26 is displaced to the second position, and after a predetermined time has elapsed, the fixing steering roller 26 is returned from the second position to the first position.

  If it is determined in step S202 that the belt has not entered the left side first stage zone, it is detected in step S207 whether the belt has entered the right side first stage zone. If the belt has entered the first zone on the right side in step S207, the process proceeds to step S208 to return the belt to the central zone. In step S208, the steering control stepping motor 60 is driven by 400 pulses in the CW direction so that the displacement amount D of the fixing steering roller 26 becomes a predetermined value DR1. As a result, the fixing steering roller 26 is displaced from the first position for holding the fixing belt 27 in the central zone to the second position for correcting the shift movement of the fixing belt 27.

  Hereinafter, a displacement amount for returning the right side (front side of the apparatus) of the belt of the belt fixing device 12 to the central zone is described as DR1.

  Subsequently, a loop is repeated until the state of the belt deviation detection sensor returns to the central zone by the belt deviation correction control in step S208 (step S209). When returning to the central zone again from the first stage zone toward the right side, the position of the right end of the belt is just past the right side first sensor SR1, and has not yet returned to the central position sufficiently. For this reason, a timer Tret for reversely driving the steering control stepping motor 60 is set so that the displacement amount D of the fixing steering roller 26 is returned to the reference amount ± 0 after a predetermined time has elapsed in step S210, and the sequence is ended in S206. . That is, the fixing steering roller 26 is displaced to the second position, and after a predetermined time has elapsed, the fixing steering roller 26 is returned from the second position to the first position.

  If it has not entered the first-stage zone on the left side in step S202 and has not entered the first-stage zone on the right side in step S207, the fixing belt 27 is in the center zone, and the center as shown in FIG. Judged to be stable. As described above, when it is determined in steps S202 and S207 that the fixing belt is stable in the central zone, no control is performed and the sequence is terminated in step S206.

  The timer Tret set in step S205 or step S210 activates the timer handler in step S221 in FIG. 10B when a predetermined time has elapsed. Subsequently, in step S222, the stepping motor 60 is reversely rotated so that the displacement amount D = ± 0. When the timer is set from step S205, the stepping motor 60 is rotated backward by 400 pulses in the CW direction, and the timer handler is terminated in step S223. If the timer is set from step S210, the stepping motor 60 is reversely rotated by 400 pulses in the CCW direction, and the timer handler is terminated in step S223.

  The belt deviation correction control described above is the same for the upper and lower fixing belt units and the pressure belt unit. Hereinafter, since the control is different between the upper fixing belt unit and the lower pressure belt unit, the description will be made separately.

  Next, control of the fixing belt when the pressure belt 32 moves in the width direction will be described. Here, the control for assisting the correction of the movement of the pressure belt by the fixing belt when the pressure belt moves to the left side (the rear side of the apparatus) will be described as an example.

  When the fixing belt 27 and the pressure belt 32 are in contact with each other and rotating, the pressure belt 32 may be displaced and may move to the left as shown in FIG.

  Step S231 and subsequent steps in FIG. 11 are sequences that are called only in the following states among the processing procedures executed by the CPU 100 every 100 ms by the interval timer, as in FIG. In this state, the pressure belt 32 moves to the left side and the photo sensor lower SL1 = OFF, is located at least in the first stage zone near the left side, and the pressure steering roller to return from the back side to the center zone. 34 is inclined by a displacement amount D = DL1. That is, the pressure steering roller 34 is displaced from the first position for holding the pressure belt 32 in the central zone to the second position for correcting the shift movement of the pressure belt 32. is there.

  In normal belt deviation correction control, the position of the pressure belt 32 returns to the central zone by inclining the end of the pressure steering roller 34 by the displacement amount D = DL1. However, the belt may not be sufficiently deviated due to wear due to deterioration with time of the belt, and may move further to the left side (the back side of the apparatus) as shown in FIG. 8B.

  In this state, when the position of the pressure belt 32 is acquired from the pressure belt shift detection sensor 66 in step S232 and the pressure belt 32 has entered the left second stage zone, it is shown in FIG. 8B. Thus, it can be said that the pressure belt 32 is in a large state. Therefore, the process proceeds to step S233 in which it is determined whether or not the correction of the pressure belt is supported by the fixing belt 27.

  In step S233, the state of the fixing belt shift detection sensor 65 is acquired in order to obtain the shift movement state (fixing belt shift level) of the fixing belt. If the fixing belt 27 is not located in the first-stage zone or the second-stage zone on the right side, the fixing belt 27 is located in the central zone or the first-stage zone or the second-stage zone on the left side like the pressure belt 32. Yes. That is, the fixing belt 27 is in a state where there is room to move to the right side. Therefore, in step S233, it is determined that the correction correction of the pressure belt 32 can be assisted by the fixing belt 27, and the process proceeds to step S234.

  In step S234, the end of the fixing steering roller 26 is inclined by the displacement amount D = DL1 so as to move the fixing belt 27 in the right direction so as to be in the same direction as the moving direction (shift correction direction) of the pressure belt 32. . Accordingly, the pressure belt 32 is affected by the movement of the fixing belt 27 in the right direction, and gradually starts moving from the current position (left first stage zone) toward the central zone.

  If this state continues, the pressure belt 32 eventually returns to the center position as shown in FIG. 7B, but if it remains as it is, the fixing belt 27 now enters the right first stage zone and eventually the right second stage zone. It approaches to the right end as shown in FIG. 8 (d).

  Therefore, the inclination of the fixing steering roller 26 for assisting correction of the shift of the pressure belt 32 is restored to the displacement amount D = ± 0 under any of the following conditions. The condition is that a predetermined time has passed since the pressure belt 32 has passed the left side detection sensor SL1 (the time when the belt is expected to return to the center position) or the fixing belt 27 is in the first stage on the right side. Whether the right side detection sensor SR1 has detected the movement to the zone. This will be described in detail below.

  After the fixing steering roller 26 is tilted in step S234, whether or not the pressure belt 32 has returned to the central zone is monitored by the pressure belt deviation detection sensor 66 in step S235. When the pressure belt 32 returns to the central zone in step S235, the inclination of the fixing steering roller 26 is returned to the displacement amount D = ± 0 in step S236 after a predetermined time, and the interval timer sequence ends (step S237).

  During this time, the fixing belt 27 is continuously monitored by the fixing belt shift detection sensor 65 to determine whether it has reached the right first stage zone so that the fixing belt 27 does not shift to the right side (step S238). While the fixing belt 27 is located in the central zone, a loop is performed between step S235 in order to continue the control for assisting the correction of the pressure belt shift described above.

  When the output value of the deviation detection sensor 66 on the pressure belt unit side is originally in a state where the pressure belt 32 is located in the central zone, the sequence is immediately terminated (step S237).

  On the other hand, if it is detected in step S238 that the level of the fixing belt 27 has shifted to the first right zone, the process proceeds to step S239 because the fixing belt 27 is now approaching the right side. To do. First, the fixing steering roller 26 inclined in step S234 is returned to the displacement D = ± 0. Then, the fixing steering roller 26 is inclined by the amount of displacement D = DR1 in order to return the fixing belt 27 approaching the right side to the central zone (step S240). Further, a timer Tret is set so that the fixing steering roller 26 returns to the displacement amount D = ± 0 again after a predetermined time (step S241), and the sequence is ended (step S237).

  If the deviation level of the fixing belt 27 is already in the right first stage or the second stage zone at the time of step 233, the fixing belt 27 has a deviation in the opposite direction to the pressure belt 32. Therefore, it is determined that the fixing belt 27 has no room to move to the right side, and the fixing belt 27 cannot assist the correction of the shift of the pressure belt 32.

  Therefore, in step S242, the feeding of the subsequent recording material is stopped and the recording material in the apparatus is discharged. In step S243, the pressure belt 32 is separated from the fixing belt 27 and the fixing belt unit 21 and the pressure belt unit 31 are independently corrected for belt misalignment (step S244). The details of the control when the deviation correction of each belt is performed independently are as described above.

  After the fixing belt and the pressure belt are separated from each other, when the deviation of each belt is restored, the pressure belt 32 is again pressed against the fixing belt 27 (step S245), and the original sequence is restored (step S237).

  The above is the auxiliary control of the fixing belt 27 when the pressure belt 32 that has largely shifted to the left in the width direction is corrected toward the right. Similarly, when the pressure belt 32 that has largely shifted to the right in the width direction is corrected toward the left, the left-right relationship is reversed, but auxiliary control of the fixing belt 27 is performed.

  As described above, according to the present embodiment, even when both the belts 32 and 27 form a nip portion, it is possible to perform good shift correction control for correcting the shift of each belt. it can.

  However, contrary to the above-described state, when the fixing belt 27 is largely shifted to the left or right in the width direction and the pressure belt 32 is located in the central zone, the pressure belt 32 is close to the fixing belt 27. Control for assisting correction is not performed.

  This is because the pressure belt 32 has a lower belt tension than the fixing belt 27 in order to prevent the recording material from being wrinkled, and oil is applied to the inner surface of the belt. Therefore, the pressure belt 32 is easily dragged by the movement of the fixing belt 27 in the width direction when rotating in pressure contact with each other.

  Accordingly, when the deviation of the pressure belt 32 is large, the correction of the deviation by the fixing belt 27 is performed, but when the deviation of the fixing belt 27 is large, the correction of the deviation by the pressure belt 32 is not performed, and the job is temporarily stored. Suspend, and then separate the upper and lower belts to make individual corrections. This prevents the pressing belt 32 from being dragged by the movement of the fixing belt 27 in the width direction, which in turn has an adverse effect.

[Second Embodiment]
A belt fixing device according to a second embodiment will be described. The schematic configuration of an electrophotographic full-color copying machine, which is an example of an image forming apparatus equipped with a belt fixing device, and the basic form of shift correction control of the belt fixing device are the same as those in the first embodiment described above.

  In FIG. 12, when the fixing belt 27 and the pressure belt 32 are rotating in pressure contact, only the pressure belt 32 is deviated and moved to the left as shown in FIG. The correction control flow is the same, and the conditions at the beginning of the control are the same as those in FIG.

  Step S251 and subsequent steps in FIG. 12 are sequences that are called only in the following states among the processing procedures executed by the CPU 100 every 100 ms by the interval timer, as in FIG. In this state, the pressure belt 32 moves to the left side and the photo sensor lower SL1 = OFF, is located at least in the first stage zone near the left side, and the pressure steering roller to return from the back side to the center zone. 34 is inclined by a displacement amount D = DL1.

  In normal belt deviation correction control, the position of the pressure belt 32 returns to the central zone by inclining the end of the pressure steering roller 34 by the displacement amount D = DL1. However, the belt may not be sufficiently deviated due to wear due to deterioration with time of the belt, and may move further to the left side (the back side of the apparatus) as shown in FIG. 8B.

  In this state, when the position of the pressure belt 32 is acquired from the pressure belt shift detection sensor 66 in step S252 and the pressure belt 32 has entered the left second stage zone, it is shown in FIG. 8B. Thus, it can be said that the pressure belt 32 is in a large state. Therefore, the process proceeds to step S253 in which it is determined whether or not the correction of the pressure belt is supported by the fixing belt 27.

  Subsequently, in step S253, the fixing belt shift detection sensor 65 acquires the shift movement state (fixing belt shift level) of the fixing belt. If the fixing belt 27 is not located in the first stage zone or the second stage zone on the right side, the fixing belt 27 is located in the central zone or on the left side of the central zone. That is, the fixing belt 27 is in a state where there is room to move to the right side. Therefore, in step S253, it is determined that the correction correction of the pressure belt 32 can be assisted by the fixing belt 27, and the process proceeds to step S254.

  In step S254, the end of the fixing steering roller 26 is inclined by the displacement amount D = DL1 so as to move the fixing belt 27 in the right end direction so as to be in the same direction as the movement direction (shift correction direction) of the pressure belt 32. .

  After the fixing steering roller 26 is tilted in step S254, whether the pressure belt 32 has returned to the central zone in step S255 is monitored by the pressure belt shift detection sensor 66. When the pressure belt 32 returns to the central zone in step S255, the inclination of the fixing steering roller 26 is returned to the displacement amount D = ± 0 in step S256 after a predetermined time, and the interval timer sequence ends (step S257).

  During this time, the fixing belt 27 is continuously monitored by the fixing belt shift detection sensor 65 to determine whether it has entered the right first stage zone or the right second stage zone so that the fixing belt 27 does not move to the right side (step S258). ). Then, while the right side shift is not detected by the fixing belt 27, a loop is executed to step S255 in order to continue the control for assisting the pressure belt shift correction described above until the pressure belt 32 returns to the central zone.

  Originally, in step S252, when the pressure belt deviation detection sensor 66 detects that the pressure belt 32 is located in the central zone, no deviation correction is necessary, and the sequence is immediately terminated (step S257). .

  If it is detected in step S255 that the fixing belt 27 has entered the right first stage zone while the pressure belt 32 is being returned to the central zone in step S255, the fixing belt 27 is now moved to the right side. Since the state is going to approach, the process proceeds to step S259. Then, the fixing steering roller 26 inclined in step S254 is returned to the displacement amount D = ± 0. Then, the fixing steering roller 26 is inclined by the amount of displacement D = DR1 in order to return the fixing belt 27 approaching the right side to the central zone (step S260).

  This state is an unfavorable situation from the viewpoint of correcting the belt shift between the fixing belt and the pressure belt because the shift correction direction of the pressure belt 32 and the shift correction direction of the fixing belt 27 are opposite. Therefore, in step S261, the shift reverse correction timer Trekov is started, and the time during which the shift correction of the belts 32 and 27 is working in the reverse direction is measured.

  Subsequently, the fixing belt deviation detection sensor 65 detects the deviation of the fixing belt 27 (step S262), and monitors whether or not the state in which the fixing belt 27 enters the right first stage or second stage zone continues for a predetermined time. (Step S263). If the state where the fixing belt 27 is shifted to the right side continues for a predetermined time (20 seconds in this case), it is determined that the fixing belt 27 and the pressure belt 32 are not in a state where the correction of correction is not working effectively, and the job is temporarily executed. The process is interrupted (step S264). Then, the pressure belt 32 is separated from the fixing belt 27 (step S265), and the fixing belt unit 21 and the pressure belt unit 31 are independently corrected for belt deviation (step S266). The details of the control when the deviation correction of each belt is performed independently are as described above.

  After the fixing belt and the pressure belt are separated from each other, when the deviation of each belt is restored, the pressure belt 32 is again pressed against the fixing belt 27 (step S267), and the original sequence is restored (step S257).

  Therefore, when a deviation occurs in the fixing belt 27 that assists the correction of the deviation of the pressure belt 32, if the deviation of the belt cannot be corrected even if the deviation of each belt is corrected while being pressed, the belt is removed. The offset correction is performed independently at a distance. In this way, reliable belt deviation correction control is performed.

  As described above, even in the present embodiment, even when both the belts 32 and 27 form a nip portion, it is possible to perform good shift correction control for correcting the shift of each belt. . Therefore, it is possible to prevent unexpected belt slippage due to belt wear.

  Also, when the inclination of the fixing steering roller is displaced to assist the correction of the deviation of the pressure belt, if it is detected that the deviation of the fixing belt in the reverse direction is increased, this is stopped, and the upper and lower belts are moved. Separate. As a result, it is possible to prevent the upper and lower belts from returning and leaning in the opposite direction. As a result, it is possible to realize a belt fixing device that prevents belt cross-cutting and reduces downtime.

  INDUSTRIAL APPLICABILITY The present invention is applicable to an apparatus that needs to perform control to correct a belt shift that occurs in a width direction orthogonal to the rotation direction in all belt conveying apparatuses configured to rotate an endless belt.

It is sectional drawing of a belt fixing apparatus. 1 is a cross-sectional view showing an example of an image forming apparatus equipped with a belt fixing device. FIG. 3 is a cross-sectional view of a belt fixing device in which a fixing belt unit and a pressure belt unit are separated from each other. It is a perspective view of the principal part of a belt fixing device. It is operation | movement explanatory drawing of a steering roller. 2 is a block diagram illustrating a control system of an image forming apparatus including a belt-type fixing device. FIG. It is explanatory drawing of the position of a belt of a belt fixing device, and a belt shift | offset | difference detection sensor. It is explanatory drawing of the position of a belt of a belt fixing device, and a belt shift | offset | difference detection sensor. It is a table | surface figure which shows the relationship between the detection state of a belt shift | offset | difference detection sensor, and shift | offset | difference level. It is a flowchart figure which shows the flow of the operation | movement which correct | amends the shift | offset | difference of a belt. FIG. 10 is a flowchart illustrating an example of an operation flow including auxiliary control of a fixing belt during correction of a pressure belt shift. FIG. 10 is a flowchart illustrating an example of an operation flow including auxiliary control of a fixing belt during correction of a pressure belt shift.

Explanation of symbols

P: Recording material SL1, SL2, SR1, SR2 ... Photo sensor 12 ... Belt fixing device 21 ... Fixing belt unit 22 ... Casing 24 ... Drive roller 26 ... Steering roller 27 ... Fixing belt 28 ... Pressure pad 29 ... Induction heating coil 31 ... pressure belt unit 32 ... pressure belt 33 ... drive roller 34 ... steering roller 35 ... casing 38 ... pressure pad 43 ... detachable shaft 44 ... eccentric cam 45 ... oil application roller 50 ... belt deviation normal range 51 ... belt deviation Left side abnormal range 52 ... Belt side right side abnormal range 60 ... Steering control stepping motor 61 ... Worm gear 62 ... Fan gear 63 ... Steering roller bearing 64 ... Side plate 65 ... Fixing belt side detection sensor unit 66 ... Pressure belt side detection sensor unit 100 ... CP
DESCRIPTION OF SYMBOLS 101 ... Operation part 102 ... Belt attaching / detaching mechanism 103 ... Fixing belt drive roller drive mechanism 104 ... Pressure belt drive roller drive mechanism 105 ... Heater feeding circuit part 106 ... Belt shift control mechanism

Claims (6)

A belt conveyance device for nipping and conveying a recording material between an endless first belt and a second belt that rotate in pressure contact with each other,
First belt position detecting means for detecting a position in the width direction perpendicular to the recording material conveyance direction of the first belt;
Second belt position detection means for detecting a position in the width direction perpendicular to the recording material conveyance direction of the second belt;
First movement correction means for correcting movement of the first belt in the width direction;
Second movement correction means for correcting movement in the width direction of the second belt,
When the first belt position detecting means detects that the first belt has moved to the outside in the width direction from the predetermined range, the first belt is moved in a direction to return the first belt to the predetermined range by the first movement correcting means. In addition, a belt conveying device characterized in that the second belt is moved in the same direction as the first belt by the second movement correcting means.   When the first belt is moved in the direction to return the first belt to the predetermined range by the first movement correcting means, the second belt is moved in the direction opposite to the first belt by the second belt position detecting means. Is detected, the second belt is not moved in the same direction as the first belt, but the first belt and the second belt are separated from each other and then moved in a direction to return each belt to a predetermined range. The belt conveyance device according to claim 1, wherein:   While the second belt is moved in the same direction as the first belt by the second movement correcting means to return the first belt to the predetermined range, the second belt position detecting means 2. When detecting that the belt has moved outward in the width direction from the predetermined range, the second belt is moved in a direction to return the belt to the predetermined range by the second movement correcting means. The belt conveying apparatus as described.   While the first belt is moved in the direction to return the first belt to the predetermined range by the first movement correction means, the second belt is returned by the second movement correction means to return the second belt to the predetermined range. When the state where the belt is moved in the opposite direction to the first belt has elapsed for a predetermined time, the first belt and the second belt are separated from each other, and the respective belts are brought into a predetermined range by the respective movement correction means. The belt conveying device according to claim 3, wherein the belt conveying device is moved in a returning direction. Each of the first movement correction unit and the second movement correction unit has a belt support member that supports the belt, and moves the belt by displacing the belt support member based on information from the belt position detection unit. To correct,
When the belt position detection means detects that the belt has moved outward in the width direction from the predetermined range, the belt movement is corrected from the first position for holding the belt in the predetermined range. To the second position to
5. The belt support member is returned from the second position to the first position when a predetermined time has elapsed since the belt support member was displaced to the second position. 6. Belt conveyor.   An image on a recording material is heated at a nip portion formed by press-contacting the first belt and the second belt, comprising the belt conveyance device according to claim 1. An image heating apparatus.

Images