Patent Publication Number: US-8126365-B2

Title: Belt rotating apparatus and recording apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2008-031151 filed on Feb. 12, 2008. 
     BACKGROUND OF THE INVENTION 
     Technical Field 
     The present invention relates to a belt rotating apparatus and a recording apparatus. 
     SUMMARY 
     In accordance with a first aspect of the invention, a belt rotating apparatus includes a circular belt; plural rollers about which the belt is entrained, the plural rollers including a drive roller which rotates the belt and an inclination change roller which is configured to change its own inclination; a belt side edge sensor which measures a position of a belt side edge in a belt width direction of the belt; and a cutter which is configured to trim the belt side edge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing an entire configuration of a recording apparatus according to an exemplary embodiment of the invention; 
         FIG. 2  is a schematic diagram showing a configuration of an edge sensor of the exemplary embodiment; 
         FIG. 3  is a perspective view showing a configuration in which an inclination of a steering roller of the exemplary embodiment is changed; 
         FIGS. 4A and 4B  are schematic diagrams showing a configuration of a belt edge cutter of the embodiment; 
         FIG. 5  is a schematic diagram showing a configuration of a modification of the belt edge cutter of the exemplary embodiment; 
         FIG. 6  is a flowchart showing a procedure for trimming a belt side edge in a belt rotating apparatus of the exemplary embodiment; 
         FIGS. 7A ,  7 B, and  7 C show measurement information on the edge sensor of the exemplary embodiment; 
         FIGS. 8A ,  8 B, and  8 C show measurement information on the edge sensor of the exemplary embodiment; 
         FIG. 9  is a schematic diagram showing plural examples of a shape error of an intermediate transfer belt of the exemplary embodiment; 
         FIG. 10  is a flowchart showing a modification example of the procedure for trimming the belt side edge in the belt rotating apparatus of the exemplary embodiment; 
         FIGS. 11A and 11B  are schematic diagrams showing a state in which the belt side edge is trimmed in the modification example of the procedure for trimming the belt side edge; 
         FIGS. 12A and 12B  show measurement information on the edge sensor of the exemplary embodiment; 
         FIG. 13  shows measurement information on the edge sensor of the exemplary embodiment; and 
         FIGS. 14A to 14D  are schematic diagrams showing a configuration in which a measurement range of the edge sensor of the exemplary embodiment is enlarged. 
     
    
    
     DESCRIPTION 
     An exemplary embodiment of the invention will be described below with reference to the drawings. 
     (Entire Configuration of Recording Apparatus) 
     An entire configuration of a recording apparatus according to an exemplary embodiment of the invention will be described.  FIG. 1  is a schematic diagram showing an entire configuration of a recording apparatus of the exemplary embodiment. 
     A recording apparatus  10  of the exemplary embodiment includes a recording medium storage unit (not shown) in which a recording medium P such as a sheet is accommodated, an image recording unit  14  which records an image in the recording medium P, a conveyance unit  16  which conveys the recording medium P from the recording medium storage unit to the image recording unit  14 , and a recording medium discharge unit (not shown) to which the recording medium P on which the image is recorded by the image recording unit  14  is discharged. 
     The image recording unit  14  includes inkjet recording heads  20 C,  20 M,  20 Y, and  20 K (hereinafter referred to be  20 C to  20 K) which eject ink droplets to record the image and a transfer belt rotating apparatus  50  having a circular intermediate transfer belt  12 . 
     The inkjet recording heads  20 C to  20 K are arranged in the color order of Cyan (C), Magenta (M), Yellow (Y), and Black (K) from an upstream side in a rotating direction of the intermediate transfer belt  12 . In the inkjet recording heads  20 C to  20 K, the ink droplet corresponding to each color is ejected to an intermediate transfer belt  12  from plural nozzles formed in a nozzle surface by a piezoelectric system, and the image is formed on a surface of the intermediate transfer belt  12 . In the inkjet recording heads  20 C to  20 K, another configuration in which the ink droplet is ejected by, for example, a thermal system may be adopted. 
     The inkjet recording heads  20 C to  20 K are formed such that a width direction (main-scanning directions of the inkjet recording heads  20 C to  20 K) is longer than the rotating direction (sub-scanning directions of the inkjet recording heads  20 C to  20 K) of the intermediate transfer belt  12 . Each of the inkjet recording heads  20 C to  20 K may form one line in the main-scanning direction without being moved in the main-scanning direction relative to the intermediate transfer belt  12 , and each of the inkjet recording heads  20 C to  20 K is moved in the sub-scanning direction relative to the intermediate transfer belt  12  to record a color image on the surface of the intermediate transfer belt  12 . The width direction of the intermediate transfer belt  12  shall mean a direction intersecting a rotating direction of the intermediate transfer belt  12 . 
     The intermediate transfer belt  12  conveys the color image recorded on the intermediate transfer belt  12  to a nip portion  26  formed between a transfer roller  22  and a facing roller  24  which faces the transfer roller  22 . 
     Plural conveyance roller pairs  28  convey a recording medium P stored in the recording medium storage unit (not shown) to the nip portion  26 . The transfer roller  22  transfers the color image conveyed by the intermediate transfer belt  12  to the recording medium P conveyed to the nip portion  26 , thereby forming the color image on the recording medium P. 
     After the color image is fixed to the recording medium P, the recording medium P is discharged to the recording medium discharge unit (not shown). 
     In an inner periphery of the intermediate transfer belt  12 , a flat plate  32  is provided to keep the intermediate transfer belt  12  smooth in an image recording area where the ink ejected from each of the inkjet recording heads  20 C to  20 K lands on the intermediate transfer belt  12 . 
     (Configuration of Transfer Belt Rotating Apparatus  50 ) 
     A configuration of the transfer belt rotating apparatus  50  of the exemplary embodiment will be described below. 
     In the exemplary embodiment, the transfer belt rotating apparatus  50  having the intermediate transfer belt  12  is cited as an example of the belt rotating apparatus having the belt. However, the belt rotating apparatus having the belt is not limited to the transfer belt rotating apparatus. 
     The belt rotating apparatus may be a photosensitive belt rotating apparatus which rotates a photosensitive belt or a conveyance belt rotating apparatus which rotates a conveyance belt for conveying the recording medium. 
     The transfer belt rotating apparatus  50  of the exemplary embodiment is used in the inkjet recording apparatus. However, the belt rotating apparatus may be used in an electrophotographic recording apparatus. The belt rotating apparatus may be used in applications except for the recording apparatus which records the image. 
     As described above, the transfer belt rotating apparatus  50  includes the circular intermediate transfer belt  12 . The intermediate transfer belt  12  is formed into an endless shape. The intermediate transfer belt  12  may be a belt having a seam in which end portions are joined to each other. 
     The intermediate transfer belt  12  is entrained about plural rollers (in the exemplary embodiment, five rollers)  22 ,  52 ,  54 ,  56 , and  58 . The plural rollers  22 ,  52 ,  54 ,  56 , and  58  include the transfer roller  22 , a drive roller  52  which rotates the intermediate transfer belt  12 , a steering roller  54  which is of an example of the inclination change roller which may change the inclination thereof, a driven roller  56  which is driven by the intermediate transfer belt  12 , and an adjustment roller  58  which may manually change the inclination. 
     It is only necessary to entrain the intermediate transfer belt  12  about at least two rollers. It is only necessary that the two rollers include at least the drive roller  52  and the steering roller  54 . The steering roller  54  may also be used as the drive roller  52  or other rollers. 
     A drive unit imparts a drive force to the drive roller  52  to rotate the drive roller  52  in a predetermined direction (A direction in  FIG. 1 ), and the drive roller  52  imparts a torque to the intermediate transfer belt  12  to rotate the intermediate transfer belt  12  in a predetermined direction (B direction in  FIG. 1 ). The drive unit of the drive roller  52  is connected to a control unit  80 , and the drive roller  52  is rotated based on a drive instruction by the control unit  80 . 
     The transfer belt rotating apparatus  50  includes an edge sensor  60  which is of an example of the belt side edge sensor which measures a position of a belt side edge in the belt width direction of the intermediate transfer belt  12 . 
     As shown in  FIG. 2 , the edge sensor  60  includes an arm  64  which is rotatable about a pivot  62  which is of the rotating axis, a tension spring  66  which is of an example of the biasing member, and a displacement sensor  68 . 
     The tension spring  66  biases the arm  64  such that one of end portions of the arm  64  (upper-side portion of the arm  64  with respect to the pivot  62  in  FIG. 2 ) is pulled toward the belt side edge of the intermediate transfer belt  12 . Therefore, the arm  64  is maintained while one of the end portions abuts on the belt side edge of the intermediate transfer belt  12 . 
     When the intermediate transfer belt  12  is moved in the width direction thereof, the one of the end portions of the arm  64  which abuts on the belt side edge of the intermediate transfer belt  12  is rotated about the pivot  62 , which displaces the other end portion (lower-side portion of the arm  64  with respect to the pivot  62  in  FIG. 2 ) of the arm  64 . 
     A measuring portion  68 A of the displacement sensor  68  abuts on the other end portion of the arm  64 , and the measuring portion  68 A measures a displacement amount of the other end portion of the arm  64 . Therefore, a movement amount of the belt side edge of the intermediate transfer belt  12  is measured, and the belt side edge position is measured in the belt width direction. 
     In the neighborhood of the belt side edge of the intermediate transfer belt  12 , the outside shall mean an outside in the belt width direction and the outside is indicated by an arrow direction of  FIG. 4B , and the inside shall mean an inside in the belt width direction and the inside is indicated by the opposite direction to the arrow direction of  FIG. 4B . 
     As shown in  FIG. 1 , the edge sensor  60  is connected to the control unit  80 , and positional information on the belt side edge in the belt width direction is transmitted to the control unit  80 . The edge sensor  60  supplies a positive value to the control unit  80  when the intermediate transfer belt  12  is moved outer side in the belt width direction, and the edge sensor  60  supplies a negative value to the control unit  80  when the intermediate transfer belt  12  is moved inner side in the belt width direction. 
     The edge sensor  60  is not limited to the contact type sensor, but the edge sensor  60  may be a non-contact type sensor in which a laser beam is utilized. 
     In the steering roller  54 , as shown in  FIGS. 1 and 3 , while a position of a first end portion  54 A in the axial direction is fixed, a second end portion  54 B in the axial direction of the steering roller  54  is fixed to a first end portion  74 A of an arm  74  which is rotatable about a rotating axis  72 , and the second end portion  54 B may be swung about the rotating axis  72 . 
     A cam  76  and a tension spring  78  are provided in a second end portion  74 B of the arm  74 . The cam  76  is rotatably supported, and the tension spring  78  is of the biasing member which biases the second end portion  74 B of the arm  74  against the cam  76 . 
     The tension spring  78  pulls the second end portion  74 B of the arm  74  upward. Therefore, the second end portion  74 B of the arm  74  is kept abutted on the cam  76 . 
     In the cam  76 , a circumferential surface whose distance from a rotating axis is not kept constant abuts on the second end portion  74 B of the arm  74 . A drive unit of the cam  76  is connected to the control unit  80 , and the cam  76  is rotated to displace the second end portion  74 B of the arm  74  based on a drive instruction of the control unit  80 . The displacement of the second end portion  74 B of the arm  74  displaces the first end portion  74 A of the arm  74  to change the inclination of the steering roller  54 . The change of the inclination of the steering roller  54  moves the intermediate transfer belt  12  along the steering roller  54 . 
     Specifically, the edge sensor  60  transmits the positional information on the belt side edge in the belt width direction, the control unit  80  computes a correction amount of meandering of the intermediate transfer belt  12  based on the positional information, and the control unit  80  performs a predetermined amount of rotation to the cam  76  in a direction A 1  or B 1  of  FIG. 3  according to the correction amount. 
     When the cam  76  is rotated in the direction A 1  of  FIG. 3  to press down the second end portion  74 B of the arm  74 , the second end portion  54 B of the steering roller  54  is lifted in a direction A 2  of  FIG. 3  through the first end portion  74 A of the arm  74 , and the intermediate transfer belt  12  is moved in a direction A 3  of  FIG. 3 . 
     On the other hand, when the cam  76  is rotated in the direction B 1  of  FIG. 3  to cause the tension spring  78  to lift the second end portion  74 B of the arm  74 , the second end portion  54 B of the steering roller  54  is pressed down in a direction B 2  of  FIG. 3  through the first end portion  74 A of the arm  74 , and the intermediate transfer belt  12  is moved in a direction B 3  of  FIG. 3 . 
     As shown in  FIGS. 1 and 4 , the transfer belt rotating apparatus  50  includes a belt edge cutter  82  which may trim the belt side edge. As shown in  FIG. 4 , the belt edge cutter  82  is a circle cutter, and a facing roller  84  which becomes a pad is disposed to face the belt edge cutter  82  while the intermediate transfer belt  12  is provided between the belt edge cutter  82  and the facing roller  84 . The facing roller  84  is driven by the intermediate transfer belt  12 . 
     The belt edge cutter  82  is disposed on the side on which the edge sensor  60  is provided, and the belt edge cutter  82  trims the belt side edge measured by the edge sensor  60 . 
     The belt edge cutter  82  may be brought into contact with and separated from the intermediate transfer belt  12 . A drive unit of the belt edge cutter  82  is connected to the control unit  80 , the belt edge cutter  82  is brought into contact with the intermediate transfer belt  12  based on a contact instruction of the control unit  80 , and the belt edge cutter  82  is separated from the intermediate transfer belt  12  based on a separation instruction of the control unit  80 . 
     The control unit  80  drives the drive roller  52  to rotate the intermediate transfer belt  12  while bringing the belt edge cutter  82  into contact with the intermediate transfer belt  12 , thereby trimming the belt side edge of the intermediate transfer belt  12 . 
     The belt edge cutter  82  is disposed inner side the belt side edge rather than an envisioned displacement amount of the belt side edge so as not to be located on the outer side of the belt side edge in the belt width direction even if the belt side edge is displaced at the envisioned amount. 
     From the viewpoint of cutting edge protection of the belt edge cutter  82 , preferably an elastic material such as rubber and a resin is used as a material for the surface of the facing roller  84 . The facing roller  84  may not be driven by the intermediate transfer belt  12 , but the facing roller  84  may be a facing platen which is slid on and brought into contact with the intermediate transfer belt  12 . In the case of the facing platen, desirably the elastic material such as the rubber and the resin is also used as the material for the surface. 
     In order to reduce a sliding load on the belt, preferably the facing roller  84  and the facing platen are brought into contact with the intermediate transfer belt  12  when the belt side edge is trimmed, and the facing roller  84  and the facing platen are separated from the intermediate transfer belt  12  in other cases. 
     The belt edge cutter  82  and the facing roller  84  may be formed into an integral unit, or the belt edge cutter  82  and the facing roller  84  may separately be formed. Alternatively, the belt edge cutter  82  and the facing roller  84  may be detachably attached to the transfer belt rotating apparatus  50  and, in a case that the trimming of the belt side edge is necessary, for example, the intermediate transfer belt  12  is replaced for new one, an operator attaches the belt edge cutter  82  and the facing roller  84  to perform the work for trimming the belt side edge, and the belt edge cutter  82  and the facing roller  84  may be detached after the work is completed. 
     The belt edge cutter  82  is not limited to a circle cutter, but the belt edge cutter  82  may be a usual knife cutter, laser cutter, and ultrasonic cutter. 
     As shown in  FIG. 5 , a rotating file  85  may be used instead of the belt edge cutter  82 . The rotating file  85  removes a part of the belt side edge by filing away the belt side edge. 
     In the exemplary embodiment, as shown in  FIG. 1 , a home mark  86  for detecting a home position of the intermediate transfer belt  12  is provided at an inner circumferential surface of the intermediate transfer belt  12 , and the transfer belt rotating apparatus  50  includes a sensor  88  which detects the home mark  86 . The sensor  88  detects the home mark  86  every one rotation of the intermediate transfer belt  12 , thereby detecting timing of one rotation of the intermediate transfer belt  12 . The sensor  88  is connected to the control unit  80 , and detection information on the detected home mark  86  is transmitted to the control unit  80 . 
     (Procedure for Trimming Belt Side Edge of Intermediate Transfer Belt  12 ) 
     A procedure for trimming the belt side edge of the intermediate transfer belt  12  will be described with reference to a flowchart of  FIG. 6 . 
     In Step  100 , the sensor  88  detects the home mark  86  provided at the rotating intermediate transfer belt  12  when the transfer belt rotating apparatus  50  starts the operation of trimming the belt side edge. The detection information in which the sensor  88  detects the home mark  86  is transmitted to the control unit  80 . 
     In Step  102 , based on the instruction of the control unit  80 , the edge sensor  60  starts the measurement of the belt side edge in the belt width direction of the intermediate transfer belt  12 . The positional information on the belt side edge measured by the edge sensor  60  is transmitted to the control unit  80 . 
     The sensor  88  detects the home mark  86  provided at the rotating intermediate transfer belt  12  again, and the detection information is transmitted to the control unit  80 , whereby the control unit  80  detects the one rotation of the intermediate transfer belt  12 . 
     At this point, in the information measured by the edge sensor  60 , as shown in  FIG. 8A , the belt side edge position is displaced in a waveform manner, and the belt side edge position is displaced toward one direction as the number of belt rotations is increased. 
     The reason why the belt side edge position is displaced toward one direction as the number of rotations is increased while the belt side edge position is displaced in the waveform manner in the measurement information is attributed to the fact that both sets of measurement information (see  FIGS. 8B and 8C ) overlap each other to indicate the information shown in  FIG. 8A . Information shown in  FIG. 8B  indicates a walk component (meandering component) of the intermediate transfer belt  12  caused by the position shift or inclination of each of the rollers  22 ,  52 ,  54 ,  56 , and  58  about which the intermediate transfer belt  12  is entrained. Information shown in  FIG. 8C  indicates a profile component of the belt side edge caused by a shape variation of the intermediate transfer belt  12 .  FIG. 9  shows plural examples of the shape variation of the intermediate transfer belt  12 , and a portion indicated by dotted lines in  FIG. 9  shows the shape-variation-free belt shape. 
     As shown in  FIG. 8B , the information indicating the walk component becomes the linear inclination component which indicates that the belt side edge of the intermediate transfer belt  12  is displaced toward one direction in the belt width direction. As shown in  FIG. 8C , the information indicating the profile component of the belt side edge becomes the waveform component which indicates that the belt side edge of the intermediate transfer belt  12  is periodically displaced in both directions in the belt width direction. 
     The items of measurement information of  FIGS. 7A through 8C  indicate a transition of the position in the belt width direction of the belt side edge according to the rotation of the intermediate transfer belt  12 , and a vertical axis relatively indicates the belt side edge position in the belt width direction of the intermediate transfer belt  12 . 
     In Step  104 , the control unit  80  determines whether or not the belt side edge position (measured value of edge sensor  60 ) is matched with that of the belt side edge at the start when one rotation of the intermediate transfer belt  12  is completed. The timing at which the edge sensor  60  detects the belt side edge position may be identical to the timing at which the sensor  88  detects the home mark  86 , or the edge sensor  60  may detect the belt side edge position at the timing at which the belt is conveyed to a predetermined distance after the home mark  86  is detected. 
     When the belt side edge position is not matched with that of the belt side edge at the start time, the process goes to Step  106 , and the control unit  80  controls the inclination of the steering roller  54  such that the belt side edge position is matched with that of the belt side edge at the start time. As shown in  FIG. 7B , the position of the steering roller  54  where the walk (meandering) of the intermediate transfer belt  12  becomes zero is obtained, and the inclination of the steering roller  54  is aligned with the obtained position. After the inclination of the steering roller  54  is controlled in Step  106 , the process returns to Step  100 . The steering adjustment in Steps  100 ,  102 ,  104 , and  106  are performed once or repeatedly performed until the belt side edge position is matched with that of the belt side edge at the start time. 
     Noted that, in the example of  FIG. 7A , because the belt side edge is not matched with that of the belt side edge at the start time, the process goes to Step  106 . When the belt is long, a meandering width is increased and sometimes the belt side edge position is partially out of a measurement range (measurable range) of the edge sensor  60  as shown in  FIG. 7A . However, it is only necessary that the belt side edge position fall within the measurement range at the start timing and the timing after one rotation, and no trouble occurs even if the belt side edge position exceeds the measurement range in mid-course. 
     The invention is not limited to the configuration in which the control unit  80  controls the steering roller  54  to automatically control the meandering of the intermediate transfer belt  12 , but the operator may manually change the inclination of the adjustment roller  58  to adjust the meandering of the intermediate transfer belt  12  based on the measurement result of the edge sensor  60 . 
     On the other hand, when the belt side edge position is matched with that of the belt side edge at the start time in Step  104 , the process goes to Step  108 , the belt edge cutter  82  is brought into contact with the intermediate transfer belt  12  based on the contact instruction of the control unit  80 . 
     In Step  110 , one turn of the intermediate transfer belt  12  is performed to trim the belt side edge of the intermediate transfer belt  12  along the rotating direction of the intermediate transfer belt  12 , and the trimmed belt side edge is removed to end the operation of trimming the belt side edge. 
     In the exemplary embodiment, the control unit  80  controls the belt edge cutter  82  and the cutter is automatically brought into contact with the intermediate transfer belt  12  to trim the belt side edge thereof. The cutter is not manually manipulated. The operator may manually manipulate the belt edge cutter  82 , instead. 
     As described above, the belt side edge is trimmed without generating a step in the belt side edge, the shape variation of the belt side edge is eliminated, and the profile component of the belt side edge substantially becomes zero. By this, in the information measured by the edge sensor  60 , both the walk component and the profile component become zero as shown in  FIG. 7C . At this point, the belt side edge position of the intermediate transfer belt  12  does not exceed the measurement range of the edge sensor  60 . 
     (Alternative Example of Procedure for Trimming Belt Side Edge of Intermediate Transfer Belt  12 ) 
     An alternative example of the procedure for trimming the belt side edge of the intermediate transfer belt  12  will be described below with reference to the flowchart of  FIG. 10 . 
     In Step  200 , the sensor  88  detects the home mark  86  provided at the rotating intermediate transfer belt  12  when the transfer belt rotating apparatus  50  starts the operation of trimming the belt side edge. Detection information to the effect that the sensor  88  has detected the home mark  86  is transmitted to the control unit  80 . 
     In Step  202 , based on the instruction of the control unit  80 , the edge sensor  60  starts the measurement of the belt side edge in the belt width direction of the intermediate transfer belt  12 . The positional information on the belt side edge measured by the edge sensor  60  is transmitted to the control unit  80 . 
     The sensor  88  detects the home mark  86  provided at the rotating intermediate transfer belt  12  again, and the detection information is transmitted to the control unit  80 , whereby the control unit  80  detects one rotation of the intermediate transfer belt  12 . 
     At this point, in the information measured by the edge sensor  60 , as shown in  FIG. 12A , the belt side edge position is displaced in the waveform manner, and the belt side edge position is displaced toward one direction as the number of turns is increased. 
     The items of measurement information of  FIGS. 12A and 12B  indicate a transition of the position in the belt width direction of the belt side edge according to the rotation of the intermediate transfer belt  12 , and the vertical axis relatively indicates the belt side edge position in the belt width direction of the intermediate transfer belt  12 . 
     In Step  204 , the control unit  80  compares the position (measured value of the edge sensor  60 ) of the belt side edge after one rotation of the intermediate transfer belt  12  to the position (measured value of the edge sensor  60 ) of the belt side edge at the start time. 
     As a result of the comparison in Step  204 , when the belt side edge position after one rotation of the intermediate transfer belt  12  is located at the same position (measured value of the edge sensor  60  is zero) as the belt side edge at the start time, or when the belt side edge position after one rotation of the intermediate transfer belt  12  is located at the outer side (positive side of the measured value of the edge sensor  60 ) of the belt side edge position at the start time in the belt width direction, the process goes to Step  206 , and the control unit  80  controls the inclination of the steering roller  54  such that the belt side edge position is located at the inner side (negative side of the measured value of the edge sensor  60 ) of the belt side edge position in the belt width direction at the start time. Then the process returns to Step  200 . The steering adjustments in Steps  200 ,  202 ,  204 , and  206  are performed or repeatedly performed until the belt side edge position is located at the inner side (negative side of the measured value of the edge sensor  60 ) of the belt side edge in the belt width direction at the start time. 
     As a result of the comparison in Step  204 , when the belt side edge position after one rotation of the intermediate transfer belt  12  is located at the inner side (negative side of the measured value of the edge sensor  60 ) of the belt side edge position in the belt width direction at the start time, the process goes to Step  208 , and the control unit  80  stores a steering position of the steering roller  54 , that is, a steering angle at which the steering roller  54  was inclined, in the steering position storage memory. Then the process goes to Step  210 . 
     In Step  210 , the control unit  80  controls the inclination of the steering roller  54  such that the belt side edge position which was previously set at the inner side of the belt side edge position in the belt width direction at the start time in the preceding Steps is located slightly at the outer side of the belt side edge position at the start time. That is, as shown in  FIG. 12B , the position (steering angle at which the steering roller  54  is inclined) of the steering roller  54  at which the walk (meandering) of the intermediate transfer belt  12  becomes positive (the belt side edge of the intermediate transfer belt  12  is displaced toward the outer side in the width direction according to the rotation) is found and the steering roller  54  is inclined accordingly. Then the process goes to Step  212 . 
     In Step  212 , the sensor  88  detects the home mark  86  provided at the rotating intermediate transfer belt  12 . The detection information to the effect that the sensor  88  has detected the home mark  86  is transmitted to the control unit  80 . 
     In Step  214 , based on the instruction of the control unit  80 , the edge sensor  60  starts the measurement of the belt side edge in the belt width direction of the intermediate transfer belt  12 . The positional information on the belt side edge position in the belt width direction measured by the edge sensor  60  is transmitted to the control unit  80 . 
     The sensor  88  again detects the home mark  86  provided at the rotating intermediate transfer belt  12 , and the detection information is transmitted to the control unit  80 , whereby the control unit  80  detects one rotation of the intermediate transfer belt  12 . 
     In Step  216 , the control unit  80  compares the position (measured value of the edge sensor  60 ) of the belt side edge after one rotation of the intermediate transfer belt  12  to the position (measured value of the edge sensor  60 ) of the belt side edge at the start time of the one rotation. 
     As a result of the comparison in Step  216 , when the belt side edge position is located at the same position (measured value of the edge sensor  60  is zero) as the belt side edge at the start time of the one rotation, or when the belt side edge position is located at the inner side (negative side of the measured value of the edge sensor  60 ) of the belt side edge position at the start time of the one rotation, the process returns to Step  208 . 
     As a result of the comparison in Step  216 , when the belt side edge position after one rotation of the intermediate transfer belt  12  is located at the outer side (positive side of the measured value of the edge sensor  60 ) of the belt side edge position at the start time of the one rotation, the process goes to Step  218 . 
     In Step  218 , the control unit  80  determines whether or not the displacement amount of the belt side edge in the belt width direction from the belt side edge position at the start time of the one rotation is a half or less of the measurement range of the edge sensor  60 . 
     As a result of the comparison in Step  218 , when the displacement amount is greater than a half or less of the measurement range of the edge sensor  60 , the process goes to Step  220 , and the inclination of the steering roller  54  is returned to the state of one step before. That is, the inclination of the steering roller  54  is adjusted such that the adjustment amount performed in the immediately preceding Step  210  is canceled, and the inclination of the steering roller  54  is returned to the state in Step  208 . Then the process goes to Step  222 . 
     In Step  222 , the inclination of the steering roller  54  is adjusted by a half of the adjustment amount of the steering roller  54  which was performed in Step  210  such that the belt side edge position is located at the outer side of the belt side edge position at the start time of the rotation. This is referred to as “halving the steering angle of the steering roller  54 ”. Then the process returns to Step  212 . 
     As a result of the comparison in Step  218 , when the displacement amount is a half or less of the measurement range of the edge sensor  60 , the process goes to Step  224 . 
     In Step  224 , the control unit  80  determines whether or not the displacement amount of the belt side edge in the belt width direction from the belt side edge position at the start time of the one rotation is 1/10 of the measurement range of the edge sensor  60  or more. 
     As a result of the comparison in Step  224 , when the displacement amount is less than 1/10 of the measurement range of the edge sensor  60 , the process returns to Step  210 . As a result of the comparison in Step  224 , when the displacement amount is 1/10 of the measurement range of the edge sensor  60  or more, the process goes to Step  226 . 
     In Step  226 , the belt edge cutter  82  is brought into contact with the intermediate transfer belt  12  based on a contact instruction from the control unit  80 . In Step  228 , one rotation of the intermediate transfer belt  12  is performed. 
     In Step  230 , the inclination of the steering roller  54  is changed to the steering position stored in the steering position storage memory in Step  208  such that the belt side edge position after one rotation of the intermediate transfer belt  12  is slightly moved to an inner side in the belt width direction (the negative side of the measured value of the edge sensor  60 ). 
     In Step  232 , the intermediate transfer belt  12  is rotated to trim the belt side edge of the intermediate transfer belt  12  along the rotating direction thereof.  FIG. 11B  shows this state. The trimmed belt side edge is removed to end the operation of trimming the belt side edge. 
     In this manner, the control unit  80  controls the belt edge cutter  82 , and the cutter is automatically brought into contact with the intermediate transfer belt  12  to trim the belt side edge of the intermediate transfer belt  12 . The operator may manually manipulate the belt edge cutter  82 . 
     In order that the belt is trimmed such that the smooth belt side edge is obtained with no step in the obtained belt side edge, it is necessary that the belt side edge be moved outer side (positive direction) once to perform the trimming. In the belt steering control during the actual image recording after the trimming of the belt, preferably the profile component indicating the belt shape variation is decreased as much as possible from the viewpoint of belt position accuracy. Therefore, in the adjustment amount in Step  210 , the belt side edge is adjusted so as to be located outer side in the belt width direction within the range of 1/10 to ½ of the measurement range of the edge sensor  60 . Because the walk component indicating the belt meandering is overlapped on the measured value in the actual control, the belt movement amount to the outer side is decreased as much as possible and, for example, it is necessary that the belt movement amount to the outer side be restricted to ½ or less of the measurement range. On the other hand, when the belt movement amount to the outer side is excessively small, the belt side edge may be cut inner side against the operator&#39;s intention due to unexpected disturbance such as impact or a belt conveyance variation. For this reason, it is more practicable to set the belt movement amount to the outer side at a predetermined value or more. For example, the belt movement amount to the outer side is set 1/10 or more of the measurement range. 
     When the belt is long, the meandering width is increased accordingly, and the belt side edge position is out of the measurement range of the edge sensor  60  as shown in  FIG. 12A . However, it is only necessary that the belt side edge position fall within the measurement range at the start timing and the timing after one rotation, and no trouble occurs even if the belt side edge position exceeds the measurement range in mid-course. 
     The invention is not limited to the configuration in which the control unit  80  controls the steering roller  54  to automatically control the meandering of the intermediate transfer belt  12 , but the operator may manually change the inclination of the adjustment roller  58  to adjust the meandering of the intermediate transfer belt  12  based on the measurement result of the edge sensor  60 . 
       FIG. 11A  shows the state in which the belt edge is located outer side in the width direction compared with the start point of the rotation when one rotation of the intermediate transfer belt  12  is performed. The line drawn inner side the intermediate transfer belt  12  indicates the cut line of the belt edge cutter  82  when the intermediate transfer belt  12  is rotated.  FIG. 11B  shows the state in which the inclination of the steering roller  54  is changed to rotate belt such that the belt edge is located inner side in the width direction compared with the start point of the rotation after one rotation of the intermediate transfer belt  12  is performed. The line drawn inner side the intermediate transfer belt  12  indicates the cut line of the belt edge cutter  82 , and the cut line after one rotation of the intermediate transfer belt  12  merges the cut line at the start point of the rotation. 
     In the exemplary embodiment, the inclination of the steering roller  54  is changed such that the belt side edge position is slightly moved inner side (measured value of the edge sensor  60  becomes the negative side) after one rotation of the intermediate transfer belt  12 . However, as long as the belt may be trimmed such that the step is not generated in the cut line, the inclination of the steering roller  54  may be changed such that the belt side edge position is slightly located inner side (measured value of the edge sensor  60  becomes the negative side) before one rotation of the intermediate transfer belt  12  is completed. 
     As described above, the shape variation of the belt side edge is reduced to decrease the profile component of the belt side edge and, as shown in  FIG. 13 , the belt side edge position of the intermediate transfer belt  12  does not exceed the measurement range of the edge sensor  60  in the information measured by the edge sensor  60 . 
     The procedure for trimming the belt side edge in the Modification of Procedure noted above may be performed twice. In such cases, after the first trimming of the belt side edge is ended in Step  232 , the flow returns to Step  200 . 
     In the case of the second trimming, in Step  204 , the control unit  80  performs the comparison to determine the adjustment amount of the inclination of the steering roller  54  using the positional information on the belt side edge. The positional information on the belt side edge is supplied from the edge sensor  60 , and the positional information on the belt side edge is larger amount than the time of the first trimming. Therefore, when the belt side edge position is moved outer side or inner side from the start point, the movement amount may be decreased compared with the first trimming, and the intermediate transfer belt  12  is trimmed with high accuracy. Accordingly, the shape error of the belt side edge is further reduced to decrease the profile component of the belt side edge. 
     The reason why the second trimming can be performed using the larger amount of positional information on the belt side edge than the time of the first trimming is that the outline of the belt side edge falls within the measurement range of the edge sensor  60  by the first trimming of the belt side edge. Desirably, the control unit  80  utilizes all the items of data of the positional information on the belt side edge sequentially supplied from the edge sensor  60 . 
     (Configuration in which Measurement Range of Edge Sensor  60  is Enlarged) 
     A configuration in which the measurement range of the edge sensor  60  is enlarged will be described below. 
     In the above-described procedures, when the belt side edge of the intermediate transfer belt  12  is trimmed, it is necessary that the belt side edge position at the start time and the belt side edge position after one rotation of the intermediate transfer belt  12  fall within the measurement range of the edge sensor  60 . Desirably, the measurement range of the edge sensor  60  is enlarged such that the belt side edge position surely falls within the positional information of the edge sensor  60 . 
     As shown in  FIG. 14A , the edge sensor  60  is a sensor in which a lever is utilized, and the edge sensor  60  has a relationship of a point (contact point)=power point at which the arm  64  abuts on the belt side edge, a pivot=fulcrum, and a point of action=a point (contact point) at which the measuring portion  68 A of the displacement sensor  68  abuts on the other end portion (lower side of the pivot in  FIG. 14A ) of the arm  64 . The displacement amount of the belt side edge of the intermediate transfer belt  12  is detected as the movement amount of the other end portion of the arm  64  relative to the displacement sensor  68 . 
     In the edge sensor  60  in which the lever is utilized, a distance between a power point and a fulcrum is increased, that is, a distance between the pivot  62  and a region of the arm  64  abutting on the belt side edge is increased, thereby decreasing the movement amount of the other end portion of the arm  64  relative to the displacement sensor  68 . That is, the displacement amount of the belt side edge of the intermediate transfer belt  12  is fed into the displacement sensor  68  while downscaled, thereby enlarging the measurement range of the edge sensor  60 . 
     In the edge sensor  60  in which the lever is utilized, a distance between the fulcrum and a point of action is decreased, that is, a distance between the pivot  62  and the other end portion (measurement point of the displacement sensor  68 ) of the arm  64  is decreased, thereby decreasing the movement amount of the other end portion of the arm  64  relative to the displacement sensor  68 . That is, the displacement amount of the belt side edge of the intermediate transfer belt  12  is fed into the displacement sensor  68  while downscaled, thereby enlarging the measurement range of the edge sensor  60 . 
     Specifically, as shown in  FIG. 14B , the arm  64 , the pivot  62 , and the displacement sensor  68  are shifted in a direction (X direction in  FIG. 14B ) in which the arm  64 , the pivot  62 , and the displacement sensor  68  are moved away from the intermediate transfer belt  12 . Therefore, the distance between the power point and the fulcrum is increased. The configuration of  FIG. 14B  becomes the effective method in the edge sensor  60  in which the positional relationship among the arm  64 , the pivot  62 , and the displacement sensor  68  cannot be changed because the arm  64 , the pivot  62 , and the displacement sensor  68  are integral with one another. 
     As shown in  FIG. 14C , the pivot  62  may be made closer to the side of the displacement sensor  68 . This can decrease the distance between the fulcrum and the point of action. Such a configuration becomes an effective method in the edge sensor  60  in which the displacement sensor  68  is separately attached. 
     As shown in  FIG. 14D , the pivot  62  may be close to the side of the displacement sensor  68 . Therefore, the distance between the fulcrum and the point of action is decreased while the distance between the power point and the fulcrum is increased. In the edge sensor  60  in which the arm is independently provided, plural attaching holes for the pivot  62  are made, and the attaching position of the pivot  62  may be changed to realize the configuration of  FIG. 14D . 
     The invention is not limited to the exemplary embodiment, but various modifications and changes can be made. The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The exemplary embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.