Patent Publication Number: US-11048193-B1

Title: Pressure device and pressure processing device using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2020-058622 filed Mar. 27, 2020. 
     BACKGROUND 
     (i) Technical Field 
     The present disclosure relates to a pressure device and a pressure processing device using the same. 
     (ii) Related Art 
     A known pressure device is disclosed in Japanese Unexamined Patent Application Publication No. 2013-186304 (Detailed Description and  FIG. 4 ). 
     Japanese Unexamined Patent Application Publication No. 2013-186304 discloses a fixing device including: a heating part having an endless belt, a heating source for heating the endless belt, and an applying member to be applied to the inner surface of the endless belt; and a pressure part having a roller member disposed so as to oppose the endless belt to allow a medium to pass between the roller member and the endless belt, a pressure mechanism that applies pressure to the roller member, and a moving mechanism that moves the roller member to change the pressing force distribution in a nip area where the medium is nipped. 
     SUMMARY 
     Aspects of non-limiting embodiments of the present disclosure relate to providing a pressure device having a pair of pressure elements that can move toward and away from each other, in which contact-pressure-distribution variation is reduced in a contact area between the pair of pressure elements even if a reaction force is generated in the pressure elements when the pressure elements are driven in a contact manner, and providing a pressure processing device using the same. 
     Aspects of certain non-limiting embodiments of the present disclosure address the above advantages and/or other advantages not described above. However, aspects of the non-limiting embodiments are not required to address the advantages described above, and aspects of the non-limiting embodiments of the present disclosure may not address advantages described above. 
     According to an aspect of the present disclosure, there is provided a pressure device including: a first pressure element; a second pressure element that is disposed so as to oppose the first pressure element and that applies pressure to a medium nipped between the first pressure element and the second pressure element; a moving device that moves the second pressure element toward and away from the first pressure element, between a contact position and a retracted position; an urging member that urges the first pressure element toward the second pressure element when the second pressure element is located at the contact position; and a driving device that applies a driving force to the second pressure element, thus allowing the first pressure element to rotate in a driven manner when the second pressure element is located at the contact position. The moving device has a moving element that is provided on a side of the second pressure element opposite from a contact area between the first pressure element and the second pressure element and that moves the second pressure element toward the first pressure element. The driving device applies a driving force in a direction in which the second pressure element is urged toward the moving element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1A  shows the outline of an exemplary embodiment of a pressure processing device of the present disclosure, and 
         FIG. 1B  shows the relevant part of a pressure device used in the pressure processing device in  FIG. 1A ; 
         FIG. 2  shows an example of an image forming apparatus serving as the pressure processing device according to a first exemplary embodiment; 
         FIG. 3  shows an example of a fixing device serving as the pressure device used in the first exemplary embodiment; 
         FIG. 4  is a sectional view taken along line IV-IV in  FIG. 3 ; 
         FIG. 5  shows the relevant part of a moving mechanism of the fixing device according to the first exemplary embodiment; 
         FIG. 6  shows an example of a driving mechanism of the fixing device according to the first exemplary embodiment; 
         FIG. 7  shows a first modification of the fixing device according to the first exemplary embodiment; 
         FIG. 8  shows a second modification of the fixing device according to the first exemplary embodiment; 
         FIG. 9  shows the relevant part of a fixing device according to a first comparison example; 
         FIG. 10A  shows an example of a driving mechanism of the fixing device according to the first comparison example, and  FIG. 10B  shows an example of the nip pressure distribution in the longitudinal direction in a contact area in the fixing device; 
         FIG. 11  shows the relevant part of a fixing device according to a second comparison example; and 
         FIG. 12  shows an example of an ink jet apparatus, serving as the pressure processing device according to a second exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Outline of Exemplary Embodiment 
       FIG. 1A  shows the outline of an exemplary embodiment of a pressure processing device of the present disclosure. 
     In  FIG. 1A , the pressure processing device includes a processing unit  8  that applies a pressure-receiving object  9  onto a medium S, and a pressure device  1  that applies pressure to the pressure-receiving object  9  on the medium S. 
     As shown in  FIG. 1B , the pressure device  1  includes: a first pressure element  2 ; a second pressure element  3  that is disposed so as to oppose the first pressure element  2  and applies pressure to the medium S nipped between the first pressure element  2  and the second pressure element  3 ; a moving device  4  that moves the second pressure element  3  toward and away from the first pressure element  2 , between a contact position and a retracted position; an urging member  6  that urges the first pressure element  2  toward the second pressure element  3  when the second pressure element  3  is located at the contact position; and a driving device  7  that applies a driving force to the second pressure element  3  to allow the first pressure element  2  to rotate in a driven manner when the second pressure element  3  is located at the contact position. The moving device  4  includes a moving element  5  that is provided on a side of the second pressure element  3  opposite from a contact area CN between the first pressure element  2  and the second pressure element  3  and that moves the second pressure element  3  toward the first pressure element  2 . The driving device  7  applies a driving force in a direction in which the second pressure element  3  is urged toward the moving element  5 . 
     The pair of pressure elements  2  and  3  does not necessarily have to be a combination of an endless belt member and a roller member, and may be a combination of roller members. 
     The moving device  4  has the moving element  5  that moves the second pressure element  3  toward and away from the first pressure element  2 . 
     The urging member  6  is necessary in maintaining the contact pressure at the contact area CN between the first pressure element  2  and the second pressure element  3 . The urging member  6  urges the first pressure element  2 , not the second pressure element  3 . 
     The driving device  7  applies a driving force to the second pressure element  3  such that the second pressure element  3  is pressed against the moving element  5 . As a result, it is possible to prevent a reaction force from acting on the contact area CN between the first pressure element  2  and the second pressure element  3 . 
     Next, typical and desirable aspects of the pressure device according to this exemplary embodiment will be described. 
     The first pressure element  2  is heated by a heating source  2   b . In this example, the device applies pressure while applying heat. The heating source  2   b  does not necessarily have to be provided in the first pressure element  2  and may be provided in the second pressure element  3 . 
     Furthermore, when the first pressure element  2  has a large number of attachments and has the heating source  2   b , an endless belt member  2   a  is heated by the heating source  2   b , and an opposing member  2   c  is disposed on the back of the belt member  2   a  opposed to the second pressure element  3 . 
     Furthermore, from the standpoint of reducing the installation space for the urging member  6 , it is desirable that the urging member  6  apply an elastic urging force produced by compressive deformation to the first pressure element  2 . 
     Furthermore, to reduce the urging force applied by the urging member  6 , it is desirable to make the first pressure element  2  retractable by an amount smaller than the amount by which the second pressure element  3  is moved. 
     In the moving device  4 , the moving element  5  includes: a pivot member  5   a  that is pivotable about a pivot support and acts on a supported portion of the second pressure element  3  to move the second pressure element  3  toward and away from the first pressure element  2 ; and a displacement member  5   b  that displaces the pivot member  5   a  so as to pivot within a predetermined area. 
     In this example, the pivot member  5   a  may be formed of one functional member or may be formed by connecting, via a spring member, two functional members that are pivotable about a common pivot support or different pivot supports; that is, the design may be changed as appropriate. The displacement member  5   b  is typically an eccentric rotation member (cam member). It is desirable that the pivot member  5   a  have a cam follower at a contact portion with respect to the eccentric rotation member (cam member), from the standpoint of reducing the contact resistance with respect to the pivot member  5   a.    
     The point at which the driving force from the driving device  7  is applied to the second pressure element  3  (the driving-force application point) is located upstream of the support point at which the second pressure element  3  is supported by the moving element  5  of the moving device  4  in the rotation direction of the second pressure element  3  and downstream of the contact area CN between the first pressure element  2  and the second pressure element  3  in the rotation direction of the second pressure element  3 . 
     It is desirable that the driving device  7  have a drive transmission system  7   a  (for example, a drive transmission gear train) that applies a driving force in the direction in which the second pressure element  3  moves away from the contact area CN at the driving-force application point to the second pressure element  3 . 
     It is more desirable that the moving element  5  have the pivot member  5   a  that is pivotable about the pivot support and acts on the supported portion of the second pressure element  3  to move the second pressure element  3  toward and away from the first pressure element  2 , and that the pivot support of the pivot member  5   a  be coaxial with a drive support of the driving device  7 . This configuration is desirable because the installation spaces for the moving device  4  and the driving device  7  can be partially shared. 
     The present disclosure will be described in more detail below based on the exemplary embodiments illustrated in the attached drawings. 
     First Exemplary Embodiment 
     Overall Configuration of Image Forming Apparatus 
       FIG. 2  shows the overall configuration of an image forming apparatus, serving as a pressure processing device according to the first exemplary embodiment. 
     In  FIG. 2 , an image forming apparatus  20  includes: an apparatus housing  21 ; an image-forming engine  22  for forming, for example, multiple color component images; and a sheet supply container  23  (in this example, a single-drawer structure) provided below the image-forming engine  22  to supply sheets, serving as media. A sheet supplied from the sheet supply container  23  is transported along a sheet transport path  24  extending substantially in the vertical direction, and images formed in the image-forming engine  22  are transferred by a simultaneous transfer device  25 . The image transferred to the sheet is fixed by a fixing device  26 , serving as an example of the pressure device, and the sheet having the image fixed thereto is discharged on a sheet output tray  27  provided, for example, at the top of the apparatus housing  21 . 
     Image-Forming Engine 
     In this example, the image-forming engine  22  includes multiple image forming units  30  ( 30   a  to  30   d ) that form color component images with toners (in this example, yellow (Y), magenta (M), cyan (C), and black (K)) using an electrophotographic system. The color component images formed by the image forming units  30  are first-transferred to an intermediate transfer body  40 , and the images on the intermediate transfer body  40  are simultaneously transferred (second-transferred) to a sheet by the simultaneous transfer device  25 . 
     In this example, the image forming units  30  ( 30   a  to  30   d ) each include, for example: a drum-shaped photoconductor  31 ; a charging device  32  that charges the photoconductor  31 ; a latent-image writing device  33  that forms an electrostatic latent image on the charged photoconductor  31 ; a developing device  34  that develops the electrostatic latent image formed on the photoconductor  31  with the corresponding color component toner; a first transfer device  35  disposed on the back surface of the intermediate transfer body  40  so as to oppose the photoconductor  31  to first-transfer the image on the photoconductor  31  to the intermediate transfer body  40 ; and a cleaning device  36  that removes the toner remaining on the photoconductor  31  after the first transfer. 
     Although the latent-image writing device  33  in this example individually writes a latent image on the corresponding image forming unit  30  by using, for example, an LED array, it is also possible to provide a common laser scanning device that writes the respective color-component electrostatic latent images on the respective image forming units  30  using the corresponding laser light or to provide separate laser scanning devices. Toner cartridges  37  ( 37   a  to  37   d ) supply color component toners to the developing devices  34  of the respective image forming units  30  ( 30   a  to  30   d ). 
     Furthermore, the intermediate transfer body  40  in this example is formed of a belt-like member stretched over multiple belt rollers  41  to  44  and is rotationally driven in a predetermined direction by the belt roller  41 , serving as a driving roller. The belt roller  43  serves as a tension roller that applies desired tension to the intermediate transfer body  40 . 
     An intermediate-transfer-body cleaning device  47  removes residue (toner, paper dust, etc.) on the intermediate transfer body  40 . 
     Furthermore, in this example, the simultaneous transfer device  25  includes a transfer roller  25   a  that is in contact with the surface of the intermediate transfer body  40  so as to be rotated in a driven manner. By forming a desired transfer electric field between the transfer roller  25   a  and the belt roller  42  supporting the intermediate transfer body  40 , the images on the intermediate transfer body  40  are simultaneously transferred to the sheet. 
     A registration roller  28  for positioning the sheet to be fed to the simultaneous transfer device  25  is provided upstream of the simultaneous transfer device  25  in the sheet transport path  24 , and a discharging roller  29  is provided immediately before the sheet output tray  27  in the sheet transport path  24 . 
     Overall Configuration of Fixing Device 
     In the fixing device  26  according to this exemplary embodiment, the first pressure element  2  has a heating function. A sheet with an unfixed image is nipped between the first pressure element  2  and the second pressure element  3 , and heat and pressure are applied to the unfixed image to fix the image. 
     As shown in  FIGS. 2 and 3 , the first pressure element  2  in this example operates on, for example, a so-called induction heating system and includes: a heat-fixing belt  61  having a heat-generating layer that generates heat by the effect of a magnetic field; a magnetic-field generator  63  that is disposed at a predetermined distance from the outer circumferential surface of the heat-fixing belt  61  and that generates a magnetic field to cause the heat-fixing belt  61  to generate heat; and a pressing pad  65  that is disposed on the back of the heat-fixing belt  61 , at a portion opposed to the second pressure element  3 , and that presses the heat-fixing belt  61  toward the second pressure element  3 . 
     As shown in  FIGS. 2 and 3 , the second pressure element  3  includes a pressure-fixing roller  62  that is disposed so as to oppose a portion of the heat-fixing belt  61  corresponding to the pressing pad  65  and that transports the sheet nipped between the pressure-fixing roller  62  and the heat-fixing belt  61 . 
     Fixing Heating Belt and Fixing Pressure Roller 
     In this example, the heat-fixing belt  61  includes an endless belt member having a larger width than at least the width of the sheet. The belt member has multiple layers including, for example: a base layer; a conducting layer (functioning as a heat-generating layer) made of, for example, a non-magnetic metal; an elastic layer; a surface layer; and the like. 
     The pressure-fixing roller  62  includes a rotary shaft  621  and an elastic roller body  622  provided around the rotary shaft  621 . 
     Magnetic-Field Generator 
     In this example, the magnetic-field generator  63  includes a base  631  surrounding substantially a half of the outer circumferential surface of the heat-fixing belt  61 , the half being located opposite from the pressure-fixing roller  62 . The base  631  extends in the width direction of the heat-fixing belt  61  and has an arc-shaped section. The base  631  has a coil receiving portion  632  extending in the width direction of the heat-fixing belt  61 , and a magnetizing coil  633  having a winding structure is held in the coil receiving portion  632 . 
     Furthermore, in this example, magnetic-field trapping members  64  ( 64   a  and  64   b ) are provided on the outside of the magnetic-field generator  63  (more specifically, at a portion of the base  631  on the back of the magnetizing coil  633 , the portion being opposite from the heat-fixing belt  61 ) and on the inside of the heat-fixing belt  61 , at a portion facing the magnetic-field generator  63 , respectively. The magnetic-field trapping members  64  ( 64   a  and  64   b ) are made of a magnetic material (for example, ferrite) and have a substantially arc-shaped section conforming to the shape of the base  631 . By sandwiching the heat-fixing belt  61  from the outside and the inside with the magnetic-field trapping members  64 , the magnetic field generated by the magnetizing coil  633  is trapped, thus forming a desired magnetic path and improving the heating efficiency of the electromagnetic induction. 
     Structure around Pressing Pad 
     A pad support member  66  that supports the pressing pad  65  is disposed inside the heat-fixing belt  61  opposed to the pressure-fixing roller  62 . The pad support member  66  has the shape of a rod extending in the width direction of the heat-fixing belt  61  and supports the pressing pad  65  at a portion facing the pressure-fixing roller  62 . By pressing the heat-fixing belt  61  against the pressure-fixing roller  62 , the sheet S is nipped at a predetermined contact area CN between the pressure-fixing roller  62  and the heat-fixing belt  61  and is transported, and the image on the sheet S is fixed. 
     In this example, a support bracket  67  is provided on the pad support member  66  to support the magnetic-field trapping member  64  ( 64   b ) located inside the heat-fixing belt  61 . 
     Support Structure in Fixing Device 
     Support Structure for Heat-Fixing Belt 
     In this exemplary embodiment, as shown in  FIG. 4 , in the support structure for the heat-fixing belt  61 , the pad support member  66  and the magnetic-field generator  63  are held by a pair of holders  68  at both ends in the width direction intersecting the moving direction of the heat-fixing belt  61  and are integrated as the first pressure element  2 . 
     In this example, as shown in  FIGS. 4 and 5 , the holders  68  have holder arms  681  that are pivotable about predetermined supports P 1 , serving as pivot supports. The heat-fixing belt  61  is urged toward the pressure-fixing roller  62  by urging springs  69  and can be retracted from a predetermined initial position. 
     The respective components of the fixing device  26  are accommodated in a fixing housing  261 . Retention pins  262  are fixed to, for example, portions of the fixing housing  261 . The urging springs  69  are positioned with respect to the retention pins  262 . First ends of the urging springs  69  are engaged with the base ends of the retention pins  262 , and second ends of the compressed urging springs  69  are engaged with hook portions  682  formed on the holder arms  681 . With this structure, the holder arms  681  are urged in the counterclockwise direction in  FIG. 5  about the supports P 1 , serving as the pivot supports, by the elastic restoring force of the urging springs  69 , and stopper projections  683  formed on the holder arms  681  are brought into contact with stopper walls  263  formed on the fixing housing  261 . In this way, the initial position of the heat-fixing belt  61  is set. 
     In this example, as shown in  FIG. 5 , the supports P 1  are located in an area between the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62  and the axis of the rotary shaft  621  of the pressure-fixing roller  62 , the area being on a sheet-entering side. 
     Support Structure for Pressure-Fixing Roller 
     As shown in  FIG. 4 , in the pressure-fixing roller  62 , both ends of the rotary shaft  621  of the roller body  622  are rotatably supported by bearing members  71  and  72 . 
     In this example, the bearing member  71  on the rear side (denoted by “Rr” in  FIG. 4 ) of the apparatus housing  21  is provided at a predetermined position, and the bearing member  72  on the front side (denoted by “Ft” in  FIG. 4 ) of the apparatus housing  21  is movably supported by a moving mechanism  80 . 
     Herein, the moving mechanism  80  moves a portion of the pressure-fixing roller  62  supported by the other bearing member  72  in a direction (in the arrow Z direction corresponding to the vertical direction in  FIG. 4 ) intersecting the rotary shaft direction about a pivot support P 0 , where the pressure-fixing roller  62  is supported by one bearing member  71 , thus moving the pressure-fixing roller  62  toward and away from the heat-fixing belt  61 , between the contact position, where the pressure-fixing roller  62  is in contact with the heat-fixing belt  61  located at the initial position, and the retracted position, where the pressure-fixing roller  62  is retracted from the contact position. 
     In this example, when, for example, a paper jam occurs at the contact area CN in the fixing device  26 , the moving mechanism  80  may release the contact state between the heat-fixing belt  61  and the pressure-fixing roller  62  to enable a jam eliminating operation. In addition, for example, when the fixing device  26  is started, the moving mechanism  80  temporarily retracts the pressure-fixing roller  62  to the retracted position from the heat-fixing belt  61  to eliminate heat conduction to the pressure-fixing roller  62  so that the heat-fixing belt  61  alone is efficiently heated. 
     Details of the moving mechanism  80  will be described below. 
     Driving System in Fixing Device 
     As shown in  FIG. 4 , in the fixing device  26  in this example, a driving mechanism  90  is connected to the rear end of the rotary shaft  621  of the pressure-fixing roller  62 . 
     Herein, in the driving mechanism  90 , a driven transmission gear  93  is coaxially connected to the end of the rotary shaft  621  of the pressure-fixing roller  62 , and the driving force from the driving motor  91  is transmitted to the driven transmission gear  93  via a drive transmission mechanism  92  including a predetermined drive transmission gear train. 
     In this example, the driving mechanism  90  rotationally drives the pressure-fixing roller  62  and allows the heat-fixing belt  61 , which is in contact with the pressure-fixing roller  62  in a state in which the pressure-fixing roller  62  is disposed at the contact position by the moving mechanism  80 , to be rotated in a driven manner. 
     Control System in Fixing Device 
     As shown in  FIG. 4 , in this example, a control unit  100  is connected to the fixing device  26 . The control unit  100  is formed of a microcomputer including, for example: a processor, such as a CPU; a read-only memory (ROM); a random-access memory (RAM); and an input/output (I/O) port and transmits a control signal to the moving mechanism  80  and the driving mechanism  90  according to an image-forming program preliminarily installed in the processor to control the moving operation of the moving mechanism  80  and the driving operation of the driving mechanism  90 . 
     The timing when the driving mechanism  90  starts to drive the pressure-fixing roller  62  may be selected as appropriate; it may be either after the pressure-fixing roller  62  is moved to the contact position by the moving mechanism  80  or before the pressure-fixing roller  62  reaches the contact position. 
     A temperature sensor (not shown), serving as a temperature control system in the fixing device  26 , is disposed at an appropriate position on the inner circumferential surface of the heat-fixing belt  61  in a contact or non-contact manner. The temperature sensor detects the temperature of the heat-fixing belt  61 , and the control unit  100  controls generation of a magnetic field by the magnetic-field generator  63  on the basis of the information obtained by the temperature sensor to control the temperature of the heat-fixing belt  61 . 
     Configuration Example of Moving Mechanism 
       FIG. 5  shows a configuration example of the moving mechanism  80  assembled in the fixing device  26 . 
     In  FIG. 5 , the moving mechanism  80  includes a first support arm  81  that pivots about a predetermined support P 2  (in this example, the support P 2  is coaxial with the supports P 1  of the holder arms  681 ) and a second support arm  82  that also pivots about the support P 2 . 
     In this example, the first support arm  81  includes an arm member  811  extending from the support P 2  and surrounding, in a substantially L shape, a circumferential portion of the bearing member  72  for the pressure-fixing roller  62 , the circumferential portion being located opposite from the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62 . A cam member  83 , serving as an eccentric rotation member, is disposed on a portion of the arm member  811  opposite from the bearing member  72 , and a cam follower  84 , which is, for example, a roller, is provided on a portion of the arm member  811  corresponding to the cam member  83 . 
     The second support arm  82  includes an arm member  821  extending from the support P 2  toward the opposite side of the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62  so as to surround, in a substantially C shape, a circumferential portion of the bearing member  72  for the pressure-fixing roller  62 . The arm member  821  has a recess  822  surrounding the bearing member  72 , on the side closer to the bearing member  72 . A compressed nip spring  85  is disposed between a bent end of the arm member  821  and a bent end of the arm member  811  of the first support arm  81 . The bent ends of the arm members  811  and  821  are connected to each other by a nip screw  86  to hold the nip spring  85  in place and to restrict the maximum span between the bent ends of the arm members  811  and  821 . 
     Setting of Driving-Force Application Point by Driving Mechanism 
     As shown in  FIG. 6 , in the driving mechanism  90  in this example, the driving force of the driving motor  91  is transmitted to the driven transmission gear  93  of the pressure-fixing roller  62  via the drive transmission mechanism  92 . A mesh position Q between a drive transmission gear  92   a , which is located at the final stage of the drive transmission mechanism  92 , and the driven transmission gear  93  is set at a position downstream of the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62  in the rotation direction of the pressure-fixing roller  62  and upstream of the contact portion between the bearing member  72  and the recess  822  in the second support arm  82  of the moving mechanism  80  in the rotation direction of the pressure-fixing roller  62 . 
       FIG. 6  schematically shows the relevant part of the moving mechanism  80  shown in  FIG. 5 . 
     Operation of Fixing Device 
     Moving Operation in Fixing Device 
     First, the moving operation in the fixing device  26  will be described. 
     When the fixing device  26  is to be driven, the pressure-fixing roller  62  has to be moved to the contact position, where the pressure-fixing roller  62  is in contact with the heat-fixing belt  61 , to form the contact area CN having a predetermined contact pressure between the heat-fixing belt  61  and the pressure-fixing roller  62 . 
     At this time, as shown in  FIGS. 5 and 6 , in the moving mechanism  80 , the cam member  83  is rotated by a driving motor (not shown) in a direction in which the distance between the center of the cam member  83  and the cam follower  84  increases and is stopped when a predetermined distance is reached. In this state, the first support arm  81  is pivoted by the cam member  83 , via the cam follower  84 , about the support P 2  toward the heat-fixing belt  61 . As a result, the pivot end of the first support arm  81  presses the nip spring  85  in a direction in which the nip spring  85  is compressed, and the nip spring  85  presses the pivot end of the second support arm  82 . In this case, because the second support arm  82  presses the bearing member  72  toward the heat-fixing belt  61  with the arm member  821  fitted in the recess  822 , the end of the pressure-fixing roller  62  supported by the bearing member  72  is pivoted about the end supported by the bearing member  71  and is disposed at the contact position, forming the contact area CN between the pressure-fixing roller  62  and the heat-fixing belt  61 . At this time, the pressure-fixing roller  62  is disposed at the predetermined contact position and is in contact with the heat-fixing belt  61  urged by the urging springs  69 . Hence, the nip load produced by the urging force of the urging springs  69  acts in the contact area CN. 
     When a sheet S having an unfixed image passes through the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62  under the condition in which the heat-fixing belt  61  has been heated to a necessary temperature for fixing processing, the unfixed image on the sheet S is heated and pressed and thus is fixed to the sheet S. 
     When, for example, a paper jam occurs at the contact area CN in the fixing device  26 , the contact state (nip state) between the heat-fixing belt  61  and the pressure-fixing roller  62  needs to be released. 
     At this time, in the moving mechanism  80 , a driving motor (not shown) rotates the cam member  83  in a direction in which the distance between the center of the cam member  83  and the cam follower  84  decreases and stops when a predetermined distance is reached. In this state, the first support arm  81  is pressed toward the cam member  83  by the elastic restoring force of the nip spring  85  disposed between the first support arm  81  and the second support arm  82 . As a result, the second support arm  82  is also pulled toward the cam member  83 , moving the bearing member  72  surrounded by the second support arm  82  in a direction away from the heat-fixing belt  61 , and moving the pressure-fixing roller  62  to the predetermined retracted position. Because the maximum length of the nip spring  85  is restricted by the nip screw  86 , the nip spring  85  does not extend beyond a predetermined length. 
     Driving Operation in Fixing Device 
     In this exemplary embodiment, as shown in  FIG. 6 , the driving-force application point (corresponding to the mesh position Q) by the driving mechanism  90  is set at a position downstream of the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62  in the rotation direction of the pressure-fixing roller  62  and upstream of the contact portion between the bearing member  72  and the recess  822  in the second support arm  82  of the moving mechanism  80  in the rotation direction of the pressure-fixing roller  62 . In this state, a reaction force F caused by the application of driving force by the driving mechanism  90  acts on the moving mechanism  80 . In this example, the cam member  83  receives the reaction force F. Therefore, in this example, not the reaction force F, but the nip load produced by the urging springs  69  alone, is applied to the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62 . Hence, the nip load at the contact area CN is balanced between the driven side and the opposite side of the pressure-fixing roller  62  and is stable over the entire contact area CN in the longitudinal direction. 
     In this exemplary embodiment, the moving mechanism  80  moves the pressure-fixing roller  62  toward and away from the heat-fixing belt  61 . Hence, compared with a system in which the heat-fixing belt  61  is moved toward and away from the pressure-fixing roller  62  (first comparison example), a large moving distance can be easily ensured. 
     In this exemplary embodiment, because the urging springs  69  are compressed only by an amount allowing the heat-fixing belt  61  to move from the initial position to the nip position, the nip load at the contact area CN can be controlled to a certain low level, and thus, the torque when the pressure-fixing roller  62  is driven can be controlled to a low level. 
     Although the heat-fixing belt  61  has a large number of attachments in this exemplary embodiment, because the heat-fixing belt  61  is not moved toward and away from the pressure-fixing roller  62 , the risk of applying large impacts on the attachments of the heat-fixing belt  61  by moving the heat-fixing belt  61  is small. 
     First Modification 
       FIG. 7  shows the relevant part of the fixing device  26  according to a first modification. 
     The basic structure of the fixing device  26  in  FIG. 7  is substantially the same as that according to the first exemplary embodiment, except for the position of the pivot support of the first support arm  81  and the second support arm  82 . The same components as those in the first exemplary embodiment will be denoted by the same reference signs, and detailed descriptions thereof will be omitted. 
     In this example, the basic structure of the driving mechanism  90  is substantially the same as that according to the first exemplary embodiment, and the mesh position Q between the drive transmission gear  92   a , which is located at the final stage of the drive transmission mechanism  92 , and the driven transmission gear  93  is set at a position downstream of the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62  in the rotation direction of the pressure-fixing roller  62  and upstream of the contact portion between the bearing member  72  and the recess  822  in the second support arm  82  of the moving mechanism  80  in the rotation direction of the pressure-fixing roller  62 . 
     Herein, the drive transmission gear  92   a  rotates about a pinned support P 3 , and the pivot support of the first support arm  81  and the second support arm  82  is coaxial with the pinned support P 3  of the drive transmission gear  92   a.    
     In this example, by making the pivot support of the first support arm  81  and the second support arm  82  of the moving mechanism  80  coaxial with the pinned support P 3  of the drive transmission gear  92   a  of the driving mechanism  90 , the components of the moving mechanism  80  and the driving mechanism  90  are arranged in a small space, compared with a configuration in which the components are provided at different positions. 
     Although omitted from the illustration, it is also possible to make the supports P 1  of the holder arms  681  of the heat-fixing belt  61  coaxial with the pinned support P 3  of the drive transmission gear  92   a.    
     Second Modification 
       FIG. 8  shows the relevant part of the fixing device  26  according to a second modification. 
     In  FIG. 8 , the basic structure of the fixing device  26  is substantially the same as that according to the first exemplary embodiment, except for the moving mechanism  80 . The same components as those in the first exemplary embodiment will be denoted by the same reference signs, and detailed descriptions thereof will be omitted. 
     In  FIG. 8 , the moving mechanism  80  has one support arm  88 , instead of the two support arms (the first support arm  81  and the second support arm  82 ). 
     In this example, the support arm  88  includes an arm member  881  extending from the support P 2  toward the opposite side of the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62  so as to surround, in a substantially C shape, a circumferential portion of the bearing member  72  for the pressure-fixing roller  62 . The cam member  83  is disposed on a portion of the arm member  881  opposite from the bearing member  72 , and the cam follower  84 , which is, for example, a roller, is provided on a portion of the arm member  881  corresponding to the cam member  83 . 
     Furthermore, the arm member  881  has a recess  882 , which surrounds the bearing member  72 , on the side closer to the bearing member  72 . A compressed nip spring  85  is disposed between the bent end of the arm member  881  and a portion  264  of the fixing housing  261 . The bent end of the arm member  881  and the portion  264  of the fixing housing  261  are connected by a nip screw  86 , thus holding the nip spring  85  in place and restricting the maximum span between the bent end of the arm member  881  and the portion  264  of the fixing housing  261 . 
     In this example, the urging force of the nip spring  85  applied to the support arm  88  is greater than that in the moving mechanism  80  according to the first exemplary embodiment. Other basic effects are substantially the same as those according to the first exemplary embodiment. 
     To evaluate the performance of the fixing device  26  according to the first exemplary embodiment, the fixing device  26  according to the first exemplary embodiment will be compared with fixing devices according to first and second comparison examples. 
     First Comparison Example 
       FIG. 9  shows the relevant part of the fixing device  26  according to the first comparison example. 
     In  FIG. 9 , the basic structure of the fixing device  26  is substantially the same as that according to the first exemplary embodiment, except that the fixing device  26  includes a pair of moving mechanisms  80 ′, which are different from the moving mechanism according to the first exemplary embodiment. The driving-force application point (corresponding to a mesh position Q′ described below) by a driving mechanism  90 ′ is also different from the driving-force application point according to the first exemplary embodiment. 
     In  FIG. 9 , the pressure-fixing roller  62  is provided at a predetermined position in a fixed manner. 
     In this example, the pair of moving mechanisms  80 ′ are provided on the heat-fixing belt  61  side. 
     In the moving mechanisms  80 ′, support arms  181  project from the holders  68  for the heat-fixing belt  61  and are supported so as to be pivotable relative to the fixing housing  261 . Furthermore, the retention pins  262  are fixed to portions of the fixing housing  261 , and nip springs  182  are positioned with respect to the retention pins  262 . First ends of the nip springs  182  are engaged with the base ends of the retention pins  262 , and second ends of the compressed nip springs  182  are engaged with the hook portions  682  formed on the holders  68 . With this structure, the support arms  181  are urged in the counterclockwise direction in  FIG. 9  about pivot supports of the support arms  181  by the elastic restoring force of the nip springs  182 . 
     Furthermore, in the moving mechanisms  80 ′, cam members  183 , which are eccentric rotary members, are provided in an area on the sheet-output side of the holders  68  in the fixing housing  261 , and cam followers  184 , which are, for example, rollers, are provided on portions of the holders  68  facing the cam members  183 . 
     As shown in  FIG. 10A , in the driving mechanism  90 ′, the driving force of a driving motor  91 ′ is transmitted to a driven transmission gear  93 ′ of the pressure-fixing roller  62  via a drive transmission mechanism  92 ′. The mesh position Q′ between the drive transmission gear  92   a ′, which is located at the final stage of the drive transmission mechanism  92 ′, and the driven transmission gear  93 ′ is set at a position upstream of the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62  in the rotation direction of the pressure-fixing roller  62  and at a position where the driving-force transmission direction is oriented toward the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62 . 
     In this example, when the distance between the circumferential surfaces of the cam members  183  and the cam followers  184  is a predetermined small distance, the holders  68  are pivoted about the support arms  181  by the urging force of the nip springs  182 , bringing the heat-fixing belt  61  to the contact position where the heat-fixing belt  61  is in contact with the pressure-fixing roller  62 . Meanwhile, when the distance between the circumferential surfaces of the cam members  183  and the cam followers  184  is a predetermined large distance, the cam members  183  cause the holders  68  to pivot in the clockwise direction while further compressing the nip springs  182 , bringing the heat-fixing belt  61  to the retracted position where the heat-fixing belt  61  is retracted from the pressure-fixing roller  62 . 
     However, in this example, because the distance by which the heat-fixing belt  61  is moved toward and away from the pressure-fixing roller  62  by the cam mechanism (the cam members  183  and the cam followers  184 ) is small, it is difficult to stably move the heat-fixing belt  61  toward and away from the pressure-fixing roller  62 . 
     Increasing the moving distance of the heat-fixing belt  61  will increase the nip load produced by the nip springs  182 , which not only makes it difficult to reduce the torque when the pressure-fixing roller  62  is driven, but also makes it difficult to suppress impacts, caused by the movement, on the heat-fixing belt  61  having a large number of attachments. 
     Furthermore, in this comparison example, the reaction force F′ caused by the application of driving force by the driving mechanism  90 ′ acts on the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62 . Hence, in this example, the reaction force F′ acts on the driving mechanism  90 ′ side, in addition to the nip load applied to the contact area CN by the nip springs  182 , which makes the nip load in the contact area CN unbalanced between the driven side and the non-driven side of the pressure-fixing roller  62 , as shown in  FIG. 10B . 
     Second Comparison Example 
       FIG. 11  shows the relevant part of the fixing device  26  according to a second comparison example. 
     The basic structure of the fixing device  26  in  FIG. 11  is substantially the same as that according to the first exemplary embodiment, except that the fixing device  26  includes the moving mechanisms  80 ′ that are different from the moving mechanism in the first exemplary embodiment. The driving-force application point by the driving mechanism  90 ′ (see  FIG. 10 ) is substantially the same as that in the first comparison example. 
     In this example, the heat-fixing belt  61  is provided at a predetermined position in a fixed manner. 
     The moving mechanisms  80 ′ of the pressure-fixing roller  62  have substantially the same structure as the moving mechanism in, for example, the first exemplary embodiment. 
     In this comparison example, the heat-fixing belt  61  is provided in a fixed manner. Because the nip load at the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62  is determined by the urging force of the nip spring  85 , if a large moving distance is to be obtained with the moving mechanisms  80 ′, the nip load produced by the nip spring  85  is to be increased, making it difficult to reduce the torque when the pressure-fixing roller  62  is driven. 
     Also in this comparison example, the reaction force F′ caused by the application of driving force by the driving mechanism  90 ′ acts on the contact area CN between the heat-fixing belt  61  and the pressure-fixing roller  62 . Hence, in this example, the reaction force F′ acts on the driving mechanism  90 ′ side, in addition to the nip load applied to the contact area CN by the nip springs  85 , which makes the nip load in the contact area CN unbalanced between the driven side and the non-driven side of the pressure-fixing roller  62 , as shown in  FIG. 10B . 
     Second Exemplary Embodiment 
       FIG. 12  shows the relevant part of an ink jet printer, serving as a pressure processing device according to a second exemplary embodiment. 
     In  FIG. 12 , an ink jet printer  200  includes an ink cartridge  201  that stores printing ink, a printhead  202  having ink jet nozzles on the lower surface thereof, and a platen  203  facing the printhead  202 . The ink cartridge  201  and the platen  203  constitute a printing unit.  FIG. 12  also shows a pair of transport rollers  206  that transport a transfer material  210  and a discharge port  207  from which the transfer material  210  after thermal transfer is discharged. 
     A heat press device  220 , serving as a pressure device, includes a platen roller  222  and a hot roller  221  for transferring ink on hot-stamp foil to the transfer material  210 , together with a foil layer. 
     Hot-stamp foil  230  is wound on a roller  223 . The hot-stamp foil  230  paid out of the roller  223  is transported between the printhead  202  and the platen  203 , where a pattern is printed with ink. The hot-stamp foil  230  on which the pattern has been printed is guided to the heat press device  220 , where the ink and the foil layer are transferred to the transfer material  210  by means of heat pressing. After the transfer, the hot-stamp foil  230  is wound on a roller  224 . Guide rollers  225  and  226  guide the hot-stamp foil  230 . 
     Although the ink jet printer  200  further includes an ink carrier that reciprocates with the ink cartridge  201  held thereon, a driving mechanism for driving the ink carrier, and the like, the illustration thereof is omitted in this example. 
     When the thermal transfer is to be performed using this ink jet printer  200 , a lateral inversion pattern of a desired pattern to be printed on the transfer material  210  is formed by using a control unit (not shown). Then, the data of the pattern is transmitted to the ink jet printer  200 . The ink jet printer  200  prints the lateral inversion pattern on the hot-stamp foil  230  with the ink ejected from the printhead  202  according to the pattern. The hot-stamp foil  230  on which the pattern has been printed with ink is fed between the hot roller  221  and the platen roller  222  of the heat press device  220 . Meanwhile, a transfer material  210  is transported to the heat press device  220  by the transport roller  206  and is superimposed on the hot-stamp foil  230 . Heat pressing by the hot roller  221  and the platen roller  222  is performed on the superimposed portion. As a result, the ink printed on the hot-stamp foil  230  is softened and adhered to the transfer material  210 , and the foil layer of the hot-stamp foil  230  is transferred to the transfer material  210 , together with the ink. After the thermal transfer, the transfer material  210  is discharged from the discharge port  207 , and the hot-stamp foil  230  without the foil layer is wound on the roller  224 . 
     In this example, the first pressure element  2  and the second pressure element  3  of the present disclosure may be used as the hot roller  221  and the platen roller  222  of the heat press device  220 . 
     Although the transfer material  210  is fed to the heat press device  220  by the transport roller  206  in this example, the transfer material  210  may be set in the heat press device  220  by hand each time transfer is to be performed. The platen roller  222  may be vertically movable to adjust the distance between the hot roller  221  and the platen roller  222 , so that transfer materials  210  of various thicknesses can be used. Furthermore, although the hot-stamp foil  230  wound on the roller  223  is preliminarily stored in the ink jet printer  200  in this example, the hot-stamp foil  230  may be supplied from the outside of the ink jet printer  200 . 
     The foregoing description of the exemplary embodiments of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.