Abstract:
A fixing device includes a pair of fixing members that contact each other and that rotate or circulate, and that heat and press a sheet to fix the toner image to the sheet, the pair of fixing members being such that at least one of the pair of fixing members is to be cleaned; and a first cleaning device that cleans the at least one of the pair of fixing members to be cleaned by removing any residual toner on the at least one of the pair of fixing members to be cleaned therefrom. The at least one of the pair of fixing members to be cleaned includes a fixing belt and a supporting member. The first cleaning device includes a cleaning roller. The at least one of the pair of fixing members to be cleaned further includes a first contact member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2012-203340 filed Sep. 14, 2012. 
       BACKGROUND 
     Technical Field 
       [0002]    The present invention relates to a fixing device and an image forming apparatus. 
       SUMMARY 
       [0003]    According to an aspect of the invention, there is provided a fixing device including a pair of fixing members that contact each other and that rotate or circulate, and that heat and press a sheet that is transported with a toner image being carried thereby and that is interposed between the pair of fixing members, to fix the toner image to the sheet, the pair of fixing members being such that at least one of the pair of fixing members is to be cleaned; and a first cleaning device that is disposed in correspondence with the at least one of the pair of fixing members to be cleaned, the first cleaning device cleaning the at least one of the pair of fixing members to be cleaned by removing any residual toner on the at least one of the pair of fixing members to be cleaned from the at least one of the pair of fixing members to be cleaned. The at least one of the pair of fixing members to be cleaned includes a fixing belt that circulates, and a supporting member that extends at an inner side of the fixing belt in a widthwise direction that crosses a direction in which the fixing belt circulates, the supporting member rotatably supporting the fixing belt at both end portions thereof in the widthwise direction. The first cleaning device includes a cleaning roller that contacts an outer surface of the fixing belt and that rotates, separates any residual toner that is stuck on the fixing belt from the fixing belt, and causes the residual toner to adhere to the cleaning roller. The at least one of the pair of fixing members to be cleaned further includes a first contact member that is disposed at an area at the inner side of the fixing belt, the area being where the first contact member opposes the cleaning roller with the fixing belt being interposed therebetween, the first contact member contacting an inner surface of the fixing belt while the first contact member is disposed between the supporting member and the inner surface of the fixing belt, the first contact member being softer than the supporting member. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    An exemplary embodiment of the present invention will be described in detail based on the following figures, wherein: 
           [0005]      FIG. 1  is a schematic view of the structure of a printer according to an exemplary embodiment of the present invention; 
           [0006]      FIG. 2  is a perspective view of a fixing unit as seen from obliquely above the fixing unit; 
           [0007]      FIG. 3  is a perspective view of the fixing unit as seen from obliquely above the fixing unit and from an observing point differing from that from which the fixing unit in  FIG. 2  is seen; 
           [0008]      FIG. 4  is a perspective view of the fixing unit as seen from obliquely below the fixing unit; 
           [0009]      FIG. 5  is a perspective view of the fixing unit as seen from obliquely below the fixing unit and from an observing point differing from that from which the fixing unit in  FIG. 4  is seen; 
           [0010]      FIG. 6  is a rear view of the fixing unit as seen from the back (left in  FIG. 1 ) of the fixing unit; 
           [0011]      FIG. 7  is a sectional view of the fixing unit taken along arrows VII-VII shown in  FIG. 6 ; 
           [0012]      FIG. 8  is a perspective view of an assembly including a fixing belt and a heat roller of the fixing unit; 
           [0013]      FIG. 9  is a perspective view of the assembly including the fixing belt and the heat roller of the fixing unit as seen from an observing point differing from that from which the assembly in  FIG. 8  is seen; 
           [0014]      FIG. 10  is a perspective view of the assembly including the fixing belt and the heat roller of the fixing unit as seen from an observing point differing from those from which the assemblies in  FIGS. 8 and 9  are seen; 
           [0015]      FIG. 11  is a perspective view of the assembly including the fixing belt after removal of the heat roller; 
           [0016]      FIG. 12  is a perspective view of the assembly including the heat roller after removal of the fixing belt with the heat roller being unremoved; 
           [0017]      FIG. 13  is a schematic view of a first cleaning roller and a second cleaning roller of each cleaning device; 
           [0018]      FIG. 14  is a sectional schematic view showing a state in which the first cleaning roller contacts the heat roller and the second cleaning roller contacts its associated first cleaning roller; 
           [0019]      FIG. 15  is a front view of the cleaning device for the heat roller; 
           [0020]      FIG. 16  is a front view of an end portion of the first cleaning roller and an end portion of the second cleaning roller; 
           [0021]      FIG. 17  is an exploded perspective view of a portion of a supporting frame, a first bearing member (serving as a bearing of the first cleaning roller), and a second bearing member (serving as a bearing of the second cleaning roller); 
           [0022]      FIG. 18  is an exploded side view of the first bearing member and the second bearing member as seen from a direction of a rotation axis; 
           [0023]      FIG. 19  is a side view showing a state in which the first bearing member and the second bearing member are assembled as seen from the direction of the rotation axis; 
           [0024]      FIG. 20  shows the state in which the first bearing member and the second bearing member are assembled as seen from a direction of a portion where the first bearing member and the second bearing member are fitted to each other; 
           [0025]      FIG. 21  is a sectional view taken along arrows XXI-XXI in  FIG. 15 ; 
           [0026]      FIG. 22  is a sectional view taken along arrows XXII-XXII in  FIG. 15 ; 
           [0027]      FIG. 23  is a perspective view of a bearing section of the cleaning device for the fixing belt; 
           [0028]      FIG. 24  is an exploded perspective view of a portion of the supporting frame, a first bearing member (serving as a bearing of the first cleaning roller), and a second bearing member (serving as a bearing of the second cleaning roller) after further removal of, for example, the first cleaning roller and the second cleaning roller from the state shown in  FIG. 23 ; 
           [0029]      FIG. 25  is an exploded side view of the first bearing member and the second bearing member as seen from the direction of the rotation axis; 
           [0030]      FIG. 26  is a side view showing a state in which the first bearing member and the second bearing member are assembled as seen from the direction of the rotation axis; 
           [0031]      FIG. 27  is a front view of a portion that is the same as that shown in  FIG. 23 ; 
           [0032]      FIG. 28  is a sectional view taken along arrows XXVIII-XXVIII shown in  FIG. 27 ; 
           [0033]      FIG. 29  is a sectional view taken along arrows XXIX-XXIX shown in  FIG. 27 ; 
           [0034]      FIG. 30  is an external perspective view of a pressing device shown in cross section in  FIG. 7 ; 
           [0035]      FIG. 31  is a perspective view of an internal portion of the pressing device after leaving only both side portions of the fixing belt of the pressing device as they are and cutting away the remaining portion; 
           [0036]      FIG. 32  shows a portion of the pressing device at an inner side of the fixing belt after removal of the fixing belt including both of the side portions of the fixing belt; 
           [0037]      FIG. 33  is a front view of a guide member; 
           [0038]      FIG. 34  is a sectional view taken along arrows XXXIV-XXXIV shown in  FIG. 33 ; 
           [0039]      FIG. 35  is a front view of only a plate member after removal of sheet receiving members from the guide member as seen from an observing point that is the same as that from which the guide member in  FIG. 33  is seen; 
           [0040]      FIG. 36  is a front view of a sheet receiving member; 
           [0041]      FIG. 37  is a side view of the sheet receiving member; 
           [0042]      FIG. 38  is a perspective view of the sheet receiving member; 
           [0043]      FIG. 39  is a perspective view showing a first stage when a portion of the plate member is cut away and when the guide member is seen from a back side of a guide surface, the first stage being a stage during mounting of the sheet receiving members to the plate member, which is a stage after inserting insertion portions of the sheet receiving members into holes of the plate member and prior to moving the insertion portions along the guide surface; 
           [0044]      FIG. 40  is a side view of the guide member in the first stage shown in  FIG. 39 ; 
           [0045]      FIG. 41  shows a portion of the guide member when the guide member in the first stage is seen in a direction along arrows XLI-XLI shown in  FIG. 40 ; 
           [0046]      FIG. 42  is a perspective view showing a second stage when the portion of the plate member is cut away and when the guide member is seen from the back side of the guide surface, the second stage being a stage after the insertion portions of the sheet receiving members are inserted into the holes of the plate member and the insertion portions are moved along the guide surface, that is, a stage when the mounting is completed; 
           [0047]      FIG. 43  is a side view of the guide member in the second stage shown in  FIG. 42 ; and 
           [0048]      FIG. 44  shows a portion of the guide member when the guide member in the second stage is seen in a direction along arrows XLIV-XLIV shown in  FIG. 43 . 
       
    
    
     DETAILED DESCRIPTION 
       [0049]    An exemplary embodiment of the present invention will hereunder be described. 
         [0050]      FIG. 1  is a schematic view of the structure of a printer  100  according to an exemplary embodiment of the present invention. 
         [0051]    A sheet tray  120  in which sheets P are placed upon each other is disposed at a lower portion of the printer  100 . As shown in  FIG. 1 , the sheet tray  120  is set at the printer  100  while protruding towards a back surface side (R side) of the printer  100  beyond a housing  110 . 
         [0052]    For replenishing the sheet tray  120  with sheets P, the sheet tray  120  is drawable towards a front surface side (F side). 
         [0053]    When the sheets P that are placed upon each other in the sheet tray P are taken out by a pickup roller  131 , and two or more of the sheets remain placed upon each other, flip rollers  132  separate only one sheet. The separated sheet P is transported until a leading edge of the sheet P reaches adjustment rollers  133 . The adjustment rollers  133  adjust the orientation of the transported sheet P, and further transports the transported sheet P downstream in accordance with an image formation timing (described later). 
         [0054]    A sheet transport belt  140  is disposed above the adjustment rollers  133 . The sheet transport belt  140  is placed around rollers  141 , circulates in the direction of arrow A, and transports upward the sheet P that has been transported further downstream (upward in  FIG. 1 ) from the adjustment rollers  133 . 
         [0055]    Each of four drum-like photoconductor members  150  that rotates in the direction of arrow B is disposed so as to oppose the sheet transport belt  140 . A charging unit  151 , a developing unit  152 , and a cleaner  153  are disposed around each of the photoconductor members  150 . Each transfer unit  154  is disposed at a position where the sheet transport belt  140  is interposed between each transfer unit  154  and its associated photoconductor member  150 . Further, an exposure unit  160  is disposed behind the photoconductor members  150  (that is, on the left of the photoconductor members  150  in  FIG. 1 ). 
         [0056]    The photoconductor members  150  are charged by the associated charging units  151 , and are exposed by being irradiated with exposure light beams  160   a  that are emitted from the exposure unit  160  and that are modulated on the basis of an image signal, so that electrostatic latent images are formed on the associated photoconductor members  150 . The electrostatic latent images on the associated photoconductor members  150  are developed by the associated developing units  152  using toners of corresponding colors, so that toner images of the corresponding colors are formed on the photoconductor members  150 . 
         [0057]    Here, the size of each photoconductor member  150  in a direction of a rotation axis of each photoconductor member  150  (that is, in a direction perpendicular to the plane of  FIG. 1 ) is larger than a size of a sheet in the same direction (widthwise direction), and the toner images are formed almost to both edges of the sheet in the widthwise direction thereof. This also applies in a vertical direction (transport direction) of the sheet, and the toner images are formed from a location that is very close to a front edge to a location that is very close to a rear edge of the sheet at the photoconductor members  150 . 
         [0058]    The aforementioned toner image formation cycle is executed in synchronism with a transport timing in which the sheet is sent out by the adjustment rollers  133  and is transported by the sheet transport belt  140 . By the transfer units  154 , the toner images of the corresponding colors that are formed on the associated photoconductor members  150  are transferred so as to be successively placed upon each other on the sheet. 
         [0059]    The sheet to which the toner images have been transferred is transported further upward, and is subjected to heat and pressure by a fixing unit  170 , so that the toner images on the sheet are fixed to the sheet, as a result of which an image formed by the fixed toner images is formed on the sheet. The sheet is discharged to a paper exit tray  111  by a paper exit roller assembly  180 . 
         [0060]    The paper exit roller assembly  180  includes a paper exit roller  173  and a paper exit roller  181 . The paper exit roller  173 , a fixing belt  171  (described below), and a heat roller  172  (described below) constitute the fixing unit  170 . The paper exit roller  181  is provided at a printer body. The paper exit roller  181 , which is provided at the printer body, is a driven roller that rotates by being driven by the rotation of the paper exit roller  173  of the fixing unit  170 . The printer  100  is such that a portion of the housing  110  above the fixing unit  170  and a portion of a front surface side of the printer  100  open in the direction of arrow C around a rotation shaft  112 , so that a sheet that is jammed during transport thereof is capable of being manually taken out. 
         [0061]    The fixing unit  170  according to the exemplary embodiment includes the endless fixing belt  171  that circulates and the heat roller  172  that drives the fixing belt  171  and that heats toner images on a sheet. A leading edge of the sheet that has been transported upward by the sheet transport belt  140  strikes a guide member  174 . Thereafter, the guide member  174  guides the sheet to a fixing area that is interposed between the fixing belt  171  and the heat roller  172 . The guide member  174  is a part that also constitutes a portion of the fixing unit  170 . 
         [0062]    In the printer  100 , as mentioned above, an image is formed almost to the front edge, the rear edge, and both side edges of the sheet. Therefore, the toner may flow onto the sheet transport belt  140  from the edges of the sheet. If the toner that has overflowed onto the sheet transport belt  140  is left as it is, the overflowed toner may stain the sheet by adhering to, for example, the back surface of the sheet. Therefore, a cleaning blade  142  that scrapes off the toner that has overflowed onto the sheet transport belt  140  is provided at this location. The toner that has been scraped off by the cleaning blade  142  is collected in a collecting case (not shown). 
         [0063]    When images are to be formed on both surfaces of the sheet, an image is formed on a first surface of the sheet as described above, and the paper exit roller assembly  180  discharges the sheet onto the paper exit tray  111  up to a location where the rear edge of the sheet is interposed between the paper exit rollers of the paper exit roller assembly  180 . At a timing thereof, the paper exit roller assembly  180  reverses its rotation. As a result, the sheet is pulled in again, and is transported downward along a sheet transport path  191 , so that a leading edge of the sheet (that is, a trailing edge of the sheet in the sheet transport direction when an image is formed on the first surface) reaches the adjustment rollers  133 . At this time, when the image has been formed on the first surface, the front and back are reversed. Thereafter, the sheet is transported by the adjustment rollers  133  again, and an image is formed on a second surface of the sheet similarly to when the image is formed on the first surface. The sheet on whose second surface the image has been formed is discharged onto the paper exit tray  111  by the paper exit roller assembly  180 . 
         [0064]      FIGS. 2 and 3  are each a perspective view of the fixing unit of the printer shown in  FIG. 1  as seen from obliquely above the fixing unit from different observing points.  FIGS. 4 and 5  are each a perspective view of the fixing unit shown in  FIGS. 2 and 3  as seen from obliquely below the fixing unit from different observing points. 
         [0065]    The leading edge of the sheet that has been transported upward by the sheet transport belt  140  shown in  FIG. 1  strikes the guide member  174  shown in  FIGS. 4 and 5  (also refer to  FIG. 1 ). Then, the sheet is guided to the fixing area that is interposed between the fixing belt  171  and the heat roller  172  shown in  FIG. 1 . The heat roller  172  is also shown in  FIG. 5 . 
         [0066]    The sheet that has passed the fixing area pushes up a sheet path switching member  175 , passes between the paper exit roller  173  and the paper exit roller  181  at the printer body (see  FIG. 1 ), and is discharged onto the paper exit tray  111 . 
         [0067]    In a mode in which images are formed on both surfaces of the sheet, when the rear edge of the sheet passes the sheet path switching member  175  while being transported onto the paper exit tray  111  by the paper exit roller assembly, and the sheet path switching member  175  that has been pushed upward until this time returns to its original position, the paper exit roller  173  reverses its rotation. As a result, the sheet passes the sheet path switching member  175  this time, and is transported along the sheet transport path  191  shown in  FIG. 1 . The path that is subsequently taken by the sheet is as described above. 
         [0068]    Levers  176  are shown in  FIGS. 2 to 5 . Each lever  176  is a lever for facilitating removal of a sheet that is jammed between the fixing belt  171  and the heat roller  172  by loosening the sheet at an area where the sheet is jammed. 
         [0069]    A gear  177  is shown in  FIG. 4 . The gear  177  receives driving force from a drive source (not shown), provided at the printer body, and transmits the driving force to the heat roller  172  and the paper exit roller  173 . A clutch (not shown) is provided between the gear  177  and the paper exit roller  173 . When the paper exit roller  173  reverses its rotation, the driving force received by the gear  177  is not transmitted to the paper exit roller  173 . 
         [0070]    The other gear  178  is shown in  FIG. 5 . The gear  178  is a gear that receives driving force from the other driving source (not shown), provided at the printer body, when the paper exit roller  173  reverses its rotation. The gear  178  receives the driving force, and transmits the driving force to a gear  179  that is shown in  FIGS. 2 to 4  and that is directly connected to the paper exit roller  173 , so that the paper exit roller  173  reverses its rotation. 
         [0071]      FIG. 6  is a rear view of the fixing unit as seen from the back (left in  FIG. 1 ) of the fixing unit.  FIG. 7  is a sectional view of the fixing unit taken along arrows VII-VII shown in  FIG. 6 . 
         [0072]    As mentioned above, the fixing unit  170  includes, for example, the fixing belt  171 , the heat roller  172 , the paper exit roller  173 , the guide member  174 , the sheet path switching member  175 , the levers  176 , and the gear  179 . The heat roller  172  includes a circular cylindrical body  172   a  that rotates and a heating source  172   b  that is disposed in the circular cylindrical body and that heats the circular cylindrical body. The fixing belt  171  constitutes a pressing device  400  that presses against the heat roller  172  a sheet that has been transported towards the fixing area where the fixing belt  171  and the heat roller  172  contact each other. Although described in detail below, metallic inner frames  410 , pressing members  420  and  430 , and felt members  440  and  441  are disposed at an inner side of the fixing belt  171  at the pressing device  400 . 
         [0073]    The fixing unit  170  further includes a cleaning device  200  that cleans the fixing belt  171  and a cleaning device  300  that cleans the heat roller  172 . 
         [0074]    As mentioned above, the printer  100  is a printer that forms images that spread almost to the edges of a sheet, and toner may overflow from the edges of the sheet. Therefore, even the fixing unit  170  includes the cleaning device  200  that cleans the fixing belt  171  and the cleaning device  300  that cleans the heat roller  172 . 
         [0075]    The cleaning device  200  includes a first cleaning roller  210  that contacts the fixing belt  171  and a second cleaning roller  220  that contacts the first cleaning roller  210 . The cleaning device  300  includes a first cleaning roller  310  that contacts the heat roller  172  and a second cleaning roller  320  that contacts the first cleaning roller  310 . 
         [0076]    Although described in detail below, the first cleaning rollers  210  and  310  are urged by springs towards the fixing belt  171  and the heat roller  172 , respectively, and the second cleaning rollers  220  and  320  are urged by springs towards the first cleaning rollers  210  and  310 , respectively. Here, the vectors of spring urging forces on the first cleaning rollers  210  and  310  are superimposed upon the vectors of spring urging forces on the second cleaning rollers  220  and  320 . In this way, by pushing the cleaning rollers in a direction in which the vectors of the two urging forces are superimposed upon each other, the overall urging force is small, so that it is possible to obtain a sufficient urging force using small springs. This contributes to size reduction. 
         [0077]      FIGS. 8 to 10  are each a perspective view of an assembly including the fixing belt and the heat roller of the fixing unit as seen from different observing points.  FIG. 11  is a perspective view of the assembly including the fixing belt after removal of the heat roller.  FIG. 12  is a perspective view of the assembly including the heat roller after removal of the fixing belt with the heat roller being unremoved. 
         [0078]      FIG. 8  shows metallic supporting frames  510 , the fixing belt  171 , and the heat roller  172 . The fixing belt  171  is rotatably supported by the supporting frames  510  at both end portions in a direction of a rotation axis thereof. The heat roller  172  is also rotatably supported by the supporting frames  510 . The first cleaning roller  210  of the cleaning device  200  that cleans the fixing belt  171  is shown in  FIG. 8 . The first cleaning roller  210  extends so as to be long in a direction of a rotation axis over an entire area of the fixing belt  171  where it contacts a sheet.  FIG. 11  shows the second cleaning roller  220  of the cleaning device  200  in addition to the fixing belt  171  and the first cleaning roller  210  of the cleaning device  200 . 
         [0079]    The length of the second cleaning roller  220  is substantially the same as the length of the first cleaning roller  210 . The second cleaning roller  220  contacts the first cleaning roller  210  over the entire area of the first cleaning roller  210  in the direction of the rotation axis of the first cleaning roller  210 . 
         [0080]    Here, the first cleaning roller  210  is a member that contacts an outer surface of the fixing belt  171 , is driven and rotated as the fixing belt  171  circulates, separates any residual toner stuck on the fixing belt  171  from the fixing belt  171 , and causes the residual toner to adhere to itself. 
         [0081]    The second cleaning roller  220  is a member that contacts the first cleaning roller  210  at a position where the first cleaning roller  210  is interposed between the second cleaning roller  220  and the fixing belt  171 , is driven and rotated as the first cleaning roller  210  rotates, separates the residual toner stuck on the first cleaning roller  210  from the first cleaning roller  210 , and causes the residual toner to adhere to itself. The residual toner stuck on the second cleaning roller  220  remains stuck on the second cleaning roller  220  while the printer  100  (see  FIG. 1 ) is capable of being used, that is, until the life of the printer  100  ends. 
         [0082]      FIGS. 9 and 10  each show the first cleaning roller  310  and the second cleaning roller  320  of the cleaning device  300  that cleans the heat roller  172 , in addition to the fixing belt  171  and the heat roller  172 .  FIG. 12  shows a state in which the heat roller  172  is supported by the supporting frames  510  after removal of the fixing belt  171 . The first cleaning roller  310  and the second cleaning roller  320  of the cleaning device  300  that cleans the heat roller  172  are also shown in  FIG. 12 . 
         [0083]    The material and the dimensions of the first cleaning roller  310  and the material and the dimensions of the second cleaning roller  320  are the same as those of the first cleaning roller  210  and the second cleaning roller  220  of the cleaning device  200  that cleans the fixing belt  171 . 
         [0084]    The first cleaning roller  310  of the cleaning device  300  that cleans the heat roller  172  contacts the heat roller  172  and extends over substantially the entire area of the heat roller  172  in a direction of a rotation axis of the heat roller  172 . The second cleaning roller  320  contacts the first cleaning roller  310 , and extends over substantially the entire area of the first cleaning roller in a direction of a rotation axis of the first cleaning roller. 
         [0085]    The roles of the first cleaning roller  310  and the second cleaning roller  320  of the cleaning device  310  that cleans the heat roller  172  are, respectively, the same as those of the first cleaning roller  210  and the second cleaning roller  220  of the cleaning device  200  that cleans the fixing belt. That is, the first cleaning roller  310  that contacts the heat roller  172  is a member that contacts the heat roller  172 , is driven and rotated as the heat roller  172  rotates, separates any residual toner stuck on the heat roller  172  from the heat roller  172 , and causes the residual toner to adhere to itself. The second cleaning roller  320  is a member that contacts the first cleaning roller  310  at a position where the first cleaning roller  310  is interposed between the second cleaning roller  320  and the heat roller  172 , is driven and rotated as the first cleaning roller  310  rotates, separates the residual toner stuck on the first cleaning roller  310  from the first cleaning roller  310 , and causes the residual toner to adhere to itself. The residual toner stuck on the second cleaning roller  320  remains stuck on the second cleaning roller  320  until the life of the printer  100  ends. 
       Shapes and Hardnesses of Cleaning Rollers 
       [0086]      FIG. 13  is a schematic view of the first cleaning roller and the second cleaning roller of each cleaning device.  FIG. 14  is a sectional schematic view showing a state in which the first cleaning roller contacts the heat roller and the second cleaning roller contacts the first cleaning roller.  FIGS. 13 and 14  schematically clarify the points regarding each cleaning device that are unclear in the figures that have been described up to now. 
         [0087]      FIG. 13  shows a state in which the first cleaning rollers  210  and  310  and the associated second cleaning rollers  220  and  320  are disposed apart from and beside each other. 
         [0088]    As clarified in  FIG. 13 , each of the first cleaning rollers  210  and  310  is what is called a crown roller whose diameter decreases continuously from the center thereof towards both ends thereof along the rotation axis. In contrast, each of the second cleaning rollers  220  and  320  in the exemplary embodiment is a straight roller having the same diameter at any location in a direction of a rotation axis thereof. 
         [0089]    However, as illustrated in detail with reference to  FIG. 14 , the first cleaning rollers  210  and  310  are formed of materials that are relatively soft, so that the second cleaning rollers  220  and  320  contact the entire areas of the associated first cleaning rollers  210  and  310  in the directions of the rotation axes thereof. 
         [0090]    As mentioned above, the residual toner stuck on the second cleaning rollers  220  and  320  remains stuck on the second cleaning rollers  220  and  320  until the life of the printer  100  (see  FIG. 1 ) ends. 
         [0091]    Since, in the printer  100 , images are formed over the entire area of a sheet in a widthwise direction thereof, any toner that has overflowed in the widthwise direction of the sheet may adhere to the fixing belt  171  and the heat roller  172 . The printer  100  is capable of using sheets of multiple sizes instead of sheets of one size. As shown schematically in  FIG. 13 , residual toner ST that ultimately remains stuck on the second cleaning rollers  220  and  320  tends to accumulate on both end portions of the second cleaning rollers  220  and  320  in the directions of the rotation axes thereof. That is, when the residual toner is included, the diameter towards both ends of each of the second cleaning rollers  220  and  320  along the rotation axis tends to be larger than the diameter at the center of each of the second cleaning rollers  220  and  320  along the rotation axis. With the first cleaning rollers  210  and  310  being crown rollers, it is possible to reliably move the residual toner stuck on the first cleaning rollers  210  and  310  to the second cleaning rollers  220  and  320 , respectively, over a long period of time from when the printer  100  is a new printer to which the residual toner ST is not stuck yet to when the printer  100  is a new printer to which the residual toner ST is not stuck yet to when the printer  100  is one having a considerable amount of residual toner ST accumulated thereon and being very near the end of its life. 
         [0092]    Since the first cleaning rollers  210  and  310  are crown rollers, the following actions are be expected due to their relationships with the heat roller  172 . 
         [0093]    As described with reference to  FIG. 7 , the heat roller  172  includes the circular cylindrical body  172   a  that rotates and the heating source  172   b  that is disposed in the circular cylindrical body and that heats the circular cylindrical body. The heating source  172   b  is a long heating source extending in a direction of a rotation axis thereof so that the entire area of the heat roller  172  in the direction of the rotation axis thereof is substantially uniformly heated. As mentioned above, multiple types of sheets are usable in the printer  100 , with sheets that are small and that use only a central area of the heat roller  172  in the direction of the rotation axis thereof (that is, does not use the entire area of the heat roller  172  in the direction of the rotation axis thereof) being among the multiple types of sheets. In this case, when the sheet passes the heat roller  172 , heat at the central portion of the heat roller tends to be taken away by the sheet, as a result of which the temperature of the central portion of the heat roller  172  tends to be relatively low, and the temperatures at both ends of the heat roller  172  tend to be relatively high. When a temperature distribution in which the temperature of the central portion of the heat roller  172  is low and the temperatures of both ends of the heat roller  172  are high occurs, the diameter of the central portion of the heat roller  172  tends to be small and the diameters of both of the ends of the heat roller  172  tend to be large due to thermal expansion. That is, these tendencies of the heat roller  172  are the reverse of the tendencies of a crown roller. Therefore, when the first cleaning roller  310  that contacts the heat roller  172  is a crown roller, a contact width of the first cleaning roller  310  with the heat roller  172  is maintained at a normal contact width over the entire area thereof in the direction of the rotation axis thereof, so that any residual toner stuck on the heat roller  172  is further reliably moved to the first cleaning roller  310 . 
         [0094]    Each of the first cleaning rollers  210  and  310  is a roller having an elastic peripheral surface. More specifically, each of the first cleaning rollers  210  and  310  in the exemplary embodiment is a rubber roller including a shaft core that is surrounded by a heat-resistant rubber. As the heat-resistant rubber, for example, silicone rubber or fluorocarbon rubber may be used, with rubber having a hardness degree (JIS A) of approximately 15 being suitable for the heat-resistant rubber. 
         [0095]    If a heat-resistant rubber that is relatively soft is used in each of the first cleaning rollers  210  and  310 , it is possible to ensure contact area between the first cleaning roller  210  and the fixing belt  171 , contact area between the first cleaning roller  310  and the heat roller  172 , contact area between the first cleaning roller  210  and the second cleaning roller  220 , and contact area between the first cleaning roller  310  and second cleaning roller  320 . 
         [0096]    The second cleaning roller  220  is a roller having a peripheral surface having a hardness that is higher than that of the first cleaning roller  210 . The second cleaning roller  320  is a roller having a peripheral surface having a hardness that is higher than that of the first cleaning roller  310 . More specifically, in the exemplary embodiment, each of the second cleaning rollers  220  and  320  is a metallic roller whose peripheral surface is subjected to blasting. Each of the first cleaning rollers  210  and  310  is a rubber roller. Since the second cleaning rollers  220  and  320  are metallic rollers, if the second cleaning rollers  220  and  320  are pushed against the first cleaning rollers  210  and  310 , respectively, as shown in  FIG. 14 , the first cleaning rollers  210  and  310  are recessed, and the recessed areas become a contact area between the first cleaning roller  210  and the second cleaning roller  220  and a contact area between the first cleaning roller  310  and the second cleaning roller  320 . Since the first cleaning rollers  210  and  310  are recessed suddenly at the areas where they contact the second cleaning rollers  220  and  320 , respectively, the separation of the residual toners stuck on the first cleaning rollers  210  and  310  is facilitated. Since the second cleaning rollers  220  and  320  have rough surfaces because they are subjected to blasting, the residual toners stuck on the first cleaning rollers  210  and  310  are reliably removed. Due to the blasting, the second cleaning rollers  220  and  320  have surface properties that tend to hold the removed residual toners. 
         [0097]    The hardness of the first cleaning roller  210  is lower than the hardness of the fixing belt  171 , and the hardness of the first cleaning roller  310  is lower than the hardness of the heat roller  172 . Therefore, as shown by its relationship with the heat roller  172  in  FIG. 14 , the first cleaning roller  310  is flexed even at its area of contact with the heat roller  172 , so that a contact area having a wide width is provided in the direction of rotation, and residual toner stuck on the heat roller  172  is reliably moved to the first cleaning roller  310 . Here, if the purpose is to only provide a contact area having a wide width between the heat roller  172  and the first cleaning roller  310 , the hardness of either one of the heat roller  172  and the first cleaning roller  310  may be set low. Here, the hardness of the first cleaning roller  310  is made low to reduce the possibility of scratching of the surface of the heat roller  172  caused when the heat roller  172  contacts the first cleaning roller  310 . 
         [0098]    If rubber rollers having a hardness degree of approximately 15 are used as the first cleaning rollers  210  and  310 , the peripheral surfaces of the rubber rollers have proper adhesiveness. Therefore, even from this viewpoint, residual toners stuck on the fixing belt  171  and the heat roller  172  are more reliably moved to the first cleaning rollers  210  and  310 , respectively. 
       Cleaning Roller Bearings and Spring Urging 
       [0099]      FIG. 15  is a front view of the cleaning device for the heat roller. 
         [0100]      FIG. 15  shows the supporting frames  510 , the heat roller  172  that is rotatably supported by the supporting frames  510 , and the first cleaning roller  310  and the second cleaning roller  320  of the cleaning device  300  for the heat roller  172 . Arrows XXI-XXI and arrows XXII-XXII indicate positions in cross section (described later). The sectional views along the arrows XXI-XXI and the arrows XXII-XXII are described below. 
         [0101]      FIG. 16  is a front view of an end portion of the first cleaning roller and an end portion of the second cleaning roller (that is, the end portion at a side indicated by the arrows XXI-XXI and the end portion at a side indicated by the arrows XXII-XXII in  FIG. 15 ). 
         [0102]      FIG. 17  is an exploded perspective view of a portion of the supporting frame, a first bearing member (serving as a bearing of the first cleaning roller), and a second bearing member (serving as a bearing of the second cleaning roller). 
         [0103]      FIG. 18  is an exploded side view of the first bearing member and the second bearing member as seen from a direction of a rotation axis.  FIG. 19  is a side view showing a state in which the first bearing member and the second bearing member are assembled as seen from the direction of the rotation axis.  FIG. 20  shows the state in which the first bearing member and the second bearing member are assembled as seen from a direction of a portion where the first bearing member and the second bearing member are fitted to each other (that is, as seen from an observing point that differs by 90 degrees from that from which the first bearing member and the second bearing member are seen in  FIG. 19  and as seen from the direction of arrow XX in  FIG. 19 ). 
         [0104]    Here, although only a bearing section at one end portion is described, the description also applies to a bearing section at the other end portion. 
         [0105]    The first bearing member  330  has a semicircular groove  331 . A shaft of the first cleaning roller  310  is inserted into the semicircular groove  331 , so that the first cleaning roller  310  is rotatably supported by the first bearing member  330 . 
         [0106]    The second bearing member  340  also has a semicircular groove  341 . A shaft of the second cleaning roller  320  is inserted into the groove  341  of the second bearing member  340 , so that the second cleaning roller  320  is rotatably supported by the second bearing member  340 . 
         [0107]    As shown in  FIGS. 17 and 18 , a groove  511  that is provided between two sides  511   a  extending in the directions of a double-headed arrow D-D is formed in the metallic supporting frame  510 . Grooves  332  into which the sides  511   a  of the supporting frame  510  are inserted are formed in corresponding sides of the first bearing member  330 . The first bearing member  330  is disposed so as to be movable in the directions of the double-headed arrow D-D along the groove  511  of the supporting frame  510  while the sides  511   a  of the supporting frame  510  are fitted to the grooves  332  of the first bearing member  330 . A first spring member  350  (described later; see  FIG. 21 ) pushes the first bearing member  330  in the direction in which the first cleaning roller  310 , supported by the first bearing member  330 , is pushed against the heat roller  172 . 
         [0108]    Two grooves  333  that are fitted to the second bearing member  340  are further formed in the first bearing member  330 . These grooves  333  extend in the same direction as the grooves  332  for being fitted to the supporting frame  510 . Two protrusions  342  that enter the two grooves  333  of the first bearing member  330  are provided on the second bearing member  340 . 
         [0109]    The second bearing member  340  is supported so as to be movable in the directions of the double-headed arrow D-D with respect to the first bearing member  330  while the two protrusions  342  are inserted in the two grooves  333  of the first bearing member  330  (see  FIG. 20 ). 
         [0110]    The second bearing member  340  is supported by the first bearing member  330  that is supported by each supporting frame  510 . A second spring member  360  (described later; see  FIG. 22 ) pushes the second bearing member  340  in the direction in which the second cleaning roller  320 , supported by the second bearing member  340 , is pushed against the first cleaning roller  310 , supported by the first bearing member  330 . 
         [0111]    Further, as shown in  FIG. 19 , the groove  331  for the bearing of the first cleaning roller, provided in the first bearing member  330 , and the groove  341  for the bearing of the second cleaning roller, provided in the second bearing member  340 , are also disposed side by side in the directions of the double-headed arrow D-D. 
         [0112]    Accordingly, since the second bearing member  340  is supported by the first bearing member  330 , the printer is smaller than that having a structure in which the first bearing member  330  and the second bearing member  340  are separately supported by the supporting frames  510 . 
         [0113]    Since the first bearing member  330  is supported by the supporting frames  510  that support the heat roller  172 , the direction in which the first cleaning roller  310 , supported by the first bearing member  330 , is pushed against the heat roller  172  is precisely controlled. Similarly, since the second bearing member  340  is supported by the first bearing member  330  that supports the first cleaning roller  310 , the direction in which the second cleaning roller  320 , supported by the second bearing member  340 , is pushed against the first cleaning roller  310 , supported by the first bearing member  330 , is precisely controlled. 
         [0114]      FIG. 21  is a sectional view taken along arrows XXI-XXI in  FIG. 15 .  FIG. 22  is a sectional view taken along arrows XXII-XXII in  FIG. 15 . 
         [0115]    As shown in  FIG. 21 , the first spring member  350 , which includes a compression spring, applies a force to the first bearing member  330  in the direction in which the first cleaning roller  310 , supported by the first bearing member  330 , is pushed against the heat roller  172 . 
         [0116]    As shown in  FIG. 22 , the second spring member  360 , which includes a torsion spring, applies a force to the second bearing member  340  in the direction in which the second cleaning roller  320 , supported by the second bearing member  340 , is pushed against the first cleaning roller  320 , supported by the first bearing member  330 . 
         [0117]    Here, the first bearing member  330  is supported by the supporting frames  510  so as to be movable in the directions of the double-headed arrow D-D (see  FIGS. 17 and 18 ). The second bearing member  340  is supported so as to be movable in the same directions (the directions of the double-headed arrow D-D) with respect to the first bearing member  330 . Further, the rotation axis of the first cleaning roller  310 , supported by the first bearing member  330 , and the rotation axis of the second cleaning roller  320 , supported by the second bearing member  340 , are also disposed side by side in the directions of the double-headed arrow D-D. 
         [0118]    Therefore, when the second spring member  360  shown in  FIG. 22  applies a force to the second bearing member  340 , the second spring member  360  pushes the second cleaning roller  320 , supported by the second bearing member  340 , against the first cleaning roller  310 , supported by the first bearing member  330 . In addition, in cooperation with the first spring member  350  that applies a force to the first bearing member  330  shown in  FIG. 21 , the second spring member  360  pushes the first cleaning roller  310  against the heat roller  172 . In contrast, the second cleaning roller  320  is pushed against the first cleaning roller  310  by only the second spring member  360  that applies a force to the second bearing member  340 . Therefore, a push force on the heat roller  172  by the first cleaning roller  310  is a reliably stronger push force than that on the first cleaning roller  310  by the second cleaning roller  320 . 
         [0119]    If the relationship between the strengths of these push forces is reversed, the second cleaning roller  320  is strongly pushed against the first cleaning roller  310 , as a result of which the resistance of the second cleaning roller  320  with respect to the rotation of the first cleaning roller  310  becomes large. This makes it difficult for the first cleaning roller  310  to receive driving force from the heat roller  172  and to be driven and rotated. Therefore, such a relationship may hinder the first cleaning roller  310  from being driven and rotated. Here, the push force of the first cleaning roller  310  on the heat roller  172  is kept reliably larger than the push force of the second cleaning roller  320  on the first cleaning roller  310 . Therefore, the first cleaning roller  310  is reliably driven and rotated as the heat roller  172  rotates, and the second cleaning roller  320  is reliably driven and rotated as the first cleaning roller  310  rotates. This causes residual toner to be reliably transferred. 
         [0120]    As described above, the directions of movement of the first bearing member  330  and the directions of movement of the second bearing member  340  are in the directions of the double-headed arrow D-D (see  FIGS. 17 and 18 ). In addition, the rotation axis of the first cleaning roller  310 , supported by the first bearing member  330 , and the rotation axis of the second cleaning roller  320 , supported by the second bearing member  340 , are also disposed side by side in the directions of the double-headed arrow D-D. Therefore, the direction of the vector of the push force by the second spring member  360  coincides with the direction of the vector of the push force by the first spring member  350 . Consequently, when the first cleaning roller  310  is pushed against the heat roller  172 , it is possible to obtain a required push force using a minimum spring force. 
         [0121]      FIG. 23  is a perspective view of a bearing section of the cleaning device for the fixing belt. 
         [0122]      FIG. 23  shows one of the end portions of each of the first cleaning roller  210  and the second cleaning roller  220  of the cleaning device  200 , provided for the fixing belt, in an axial direction thereof, the first cleaning roller  210  and the second cleaning roller  220  being disposed so as to be hidden by the guide member  174  (also see  FIG. 1 ). Although the bearing structure of only one end portion of the cleaning device for the fixing belt is shown and illustrated, the bearing structure of the other end portion is also the same. 
         [0123]    A first bearing member  230 , which is a bearing of the first cleaning roller  210 , is further shown in  FIG. 23 . 
         [0124]    The first bearing member  230  is movably supported by the supporting frames  510 . Although not shown in  FIG. 23 , a second bearing member  240 , which is a bearing of the second cleaning roller  230 , (see  FIGS. 24 to 26 ) is also provided, and is movably supported by the first bearing member  230 . Further, a first spring member  250  that pushes the first bearing member  230  and a second spring member  260  that pushes the second bearing member  240  are also provided. 
         [0125]      FIG. 24  is an exploded perspective view of a portion of the supporting frame, the first bearing member, and the second bearing member after further removal of, for example, the first cleaning roller and the second cleaning roller from the state shown in  FIG. 23 . 
         [0126]      FIG. 25  is an exploded side view of the first bearing member and the second bearing member as seen from a direction of a rotation axis.  FIG. 26  is a side view showing a state in which the first bearing member and the second bearing member are assembled as seen from the direction of the rotation axis. 
         [0127]    The first bearing member  230  has a semicircular groove  231 . A shaft of the first cleaning roller  210  is inserted into the semicircular groove  231 , so that the first cleaning roller  210  is rotatably supported by the first bearing member  230 . 
         [0128]    The second bearing member  240  also has a semicircular groove  241 . A shaft of the second cleaning roller  220  is inserted into the groove  241  of the second bearing member  240 , so that the second cleaning roller  220  is rotatably supported by the second bearing member  240 . 
         [0129]    As shown in  FIGS. 24 and 25 , a groove  512  that is provided between two sides  512   a  extending in the directions of a double-headed arrow E-E is formed in the metallic supporting frame  510 . Grooves  232  into which the sides  512   a  of the supporting frame  510  are inserted are formed in corresponding sides of the first bearing member  230 . The first bearing member  230  is disposed so as to be movable in the directions of the double-headed arrow E-E along the groove  512  of the supporting frame  510  while the sides  512   a  of the supporting frame  510  are fitted to the grooves  232  of the first bearing member  230 . A first spring member  250  (see  FIGS. 23 and 28 ) pushes the first bearing member  230  in the direction in which the first cleaning roller  210 , supported by the first bearing member  230 , is pushed against the fixing belt  171 . 
         [0130]    Two grooves  233  that are fitted to the second bearing member  240  are further formed in the first bearing member  230 . These grooves  233  extend in the same direction as the grooves  232  for being fitted to the supporting frame  510 . Two protrusions  242  that enter the two grooves  233  of the first bearing member  230  are provided on the second bearing member  240 . 
         [0131]    The second bearing member  240  is supported so as to be movable in the directions of the double-headed arrow E-E with respect to the first bearing member  230  while the two protrusions  242  are inserted in the two grooves  233  of the first bearing member  230 . 
         [0132]    The second bearing member  240  is supported by the first bearing member  230  that is supported by each supporting frame  510 . A second spring member  260  (see  FIGS. 23 and 29 ) pushes the second bearing member  240  in the direction in which the second cleaning roller  220 , supported by the second bearing member  240 , is pushed against the first cleaning roller  210 , supported by the first bearing member  230 . 
         [0133]    Further, as shown in  FIG. 26 , the groove  231  for the bearing of the first cleaning roller, provided in the first bearing member  230 , and the groove  241  for the bearing of the second cleaning roller, provided in the second bearing member  240 , are also disposed side by side in the directions of the double-headed arrow E-E. 
         [0134]    Accordingly, since the second bearing member  240  is supported by the first bearing member  230 , the printer is smaller than that having a structure in which the first bearing member  230  and the second bearing member  240  are separately supported by the supporting frames  510 . 
         [0135]    Since the first bearing member  230  is supported by the supporting frames  510 , the direction in which the first cleaning roller  210 , supported by the first bearing member  230 , is pushed against the fixing belt  171  is precisely controlled. Similarly, since the second bearing member  240  is supported by the first bearing member  230 , the direction in which the second cleaning roller  220 , supported by the second bearing member  240 , is pushed against the first cleaning roller  210 , supported by the first bearing member  230 , is precisely controlled. 
         [0136]      FIG. 27  is a front view of a portion that is the same as that shown in  FIG. 23 .  FIG. 28  is a sectional view taken along arrows XXVIII-XXVIII shown in  FIG. 27 .  FIG. 29  is a sectional view taken along arrows XXIX-XXIX shown in  FIG. 27 . 
         [0137]    As shown in  FIG. 28 , the first spring member  250 , which includes a compression spring, applies a force to the first bearing member  230  in the direction in which the first cleaning roller  210 , supported by the first bearing member  230 , is pushed against the fixing belt  171 . 
         [0138]    As shown in  FIG. 29 , the second spring member  260 , which similarly includes a compression spring, applies a force to the second bearing member  240  in the direction in which the second cleaning roller  220 , supported by the second bearing member  240 , is pushed against the first cleaning roller  220 , supported by the first bearing member  230 . 
         [0139]    Here, the first bearing member  230  is supported by the supporting frames  510  so as to be movable in the directions of the double-headed arrow E-E (see  FIGS. 24 and 25 ). The second bearing member  240  is supported so as to be movable in the same directions (the directions of the double-headed arrow E-E) with respect to the first bearing member  230 . Further, the rotation axis of the first cleaning roller  210 , supported by the first bearing member  230 , and the rotation axis of the second cleaning roller  220 , supported by the second bearing member  240 , are also disposed side by side in the directions of the double-headed arrow E-E. 
         [0140]    Therefore, when the second spring member  260  shown in  FIG. 29  applies a force to the second bearing member  240 , the second spring member  260  pushes the second cleaning roller  220 , supported by the second bearing member  240 , against the first cleaning roller  210 , supported by the first bearing member  230 . In addition, in cooperation with the first spring member  250  that applies a force to the first bearing member  230  shown in  FIG. 28 , the second spring member  260  pushes the first cleaning roller  210  against the fixing belt  171 . Therefore, a push force on the fixing belt  171  by the first cleaning roller  210  is a reliably stronger push force than that on the first cleaning roller  210  by the second cleaning roller  220 . 
         [0141]    The action that is based on the relationship between the strengths of the push forces is the same as that based on the relationship between the strengths of the push forces of the first cleaning roller  310  and the second cleaning roller  320  of the cleaning device  300  that cleans the heat roller  172 . Therefore, the same description thereof will not be repeated. 
         [0142]    As described above, the directions of movement of the first bearing member  230  and the directions of movement of the second bearing member  240  are in the directions of the double-headed arrow E-E (see  FIGS. 24 and 25 ). In addition, the rotation axis of the first cleaning roller  210 , supported by the first bearing member  230 , and the rotation axis of the second cleaning roller  220 , supported by the second bearing member  240 , are also disposed side by side in the directions of the double-headed arrow E-E. Therefore, as in the cleaning device  300  for the heat roller  172 , the direction of the vector of the push force by the second spring member  260  coincides with the direction of the vector of the push force by the first spring member  250 . Consequently, when the first cleaning roller  210  is pushed against the fixing belt  171 , it is possible to obtain a required push force using a minimum spring force. 
       Structure of Pressing Device 
       [0143]      FIG. 30  is an external perspective view of the pressing device  400  shown in cross section in  FIG. 7 .  FIG. 31  is a perspective view of an internal portion of the pressing device  400  after leaving only both side portions of the fixing belt of the pressing device  400  as they are and cutting away the remaining portion.  FIG. 32  shows a portion of the pressing device at an inner side of the fixing belt after removal of the fixing belt including both of the side portions of the fixing belt. 
         [0144]    The periphery of the pressing device  400  is covered by the fixing belt  171 . The metallic inner frames  410  extend in an axial direction in the interior of the pressing device  400 . Ends of the respective inner frames  410  are secured to the respective supporting frames  510  shown in, for example,  FIG. 8 . Each side portion of the fixing belt  171  is supported by a supporting portion  411  at the side of its corresponding inner frame  410 . The fixing belt  171  receives rotational driving force of the heat roller  172  (see  FIG. 7 ) and circulates in the direction of arrow F. 
         [0145]    The pressing member  420 , formed of resin and extending in an axial direction, is secured to the inner frames  410 . A pressing member  430 , formed of rubber and similarly extending in an axial direction, is secured to the pressing member  420 , formed of resin. 
         [0146]    The heat roller  172  (see, for example,  FIGS. 8 and 9 ) is disposed in an area where it opposes the pressing members  420  and  430  with the fixing belt  171  being disposed between the heat roller  172  and the pressing members  420  and  430 . The pressing members  420  and  430  push the fixing belt  171  towards the heat roller  172  from an inner side thereof. The fixing area where an outer surface of the fixing belt  171  and the heat roller  172  contact each other is formed between the outer surface of the fixing belt  171  and the heat roller  172 . 
         [0147]    The rubber pressing member  430  pushes the fixing belt  171  towards the heat roller  172  with a suitable elasticity. The resin pressing member  420  increases separability of a sheet when the sheet passes the pressing member  420 . The pressing members  420  and  430  are exemplary second contact members. 
         [0148]    The felt member  440 , serving as an exemplary first contact member extending in an axial direction, is further secured to the inner frames  410  of the pressing device  400 . The felt member  440  is a member that is softer than the inner frames  410  and is disposed in an area where it opposes the first cleaning roller  210  (see  FIGS. 7 ,  8 , and  11 ) with the fixing belt  171  being interposed therebetween. In the exemplary embodiment, since the soft felt member  440  is disposed between the inner frames  410  and an inner surface of the fixing belt  171 , a contact area having sufficient width is provided between the outer surface of the fixing belt  171  and the first cleaning roller  210 . This contributes to reliable removal of residual toner on the fixing belt. 
         [0149]    The felt member  440  is impregnated with lubricating oil. When the fixing belt  171  circulates, the lubricating oil with which the felt member  440  is impregnated is applied to the inner surface of the fixing belt  171 . This reduces friction resistance between the pressing member  420  and the inner surface of the fixing belt  171  and the pressing member  430  and the inner surface of the fixing belt  171 , so that the fixing belt  171  circulates smoothly. Although not shown in  FIGS. 30 to 32 , the pressing device  400  includes another felt member  441  (see  FIG. 7 ). The felt member  441  is also impregnated with lubricating oil. The lubricating oil with which the two felt members  440  and  441  are impregnated is applied to the inner surface of the fixing belt  171 . 
         [0150]    If the felt member  440  shown in  FIGS. 31 and 32  and the first cleaning roller  210  opposing the felt member  440  with the fixing belt being disposed therebetween are traced along the fixing belt  171  from the fixing area where the fixing belt  171  is pushed against the heat roller  172  by the pressing members  420  and  430 , the felt member  440  and the first cleaning roller  210  are disposed at a closer distance when the felt member  440  and the first cleaning roller  210  are traced towards an upstream side of the fixing belt  171  in the direction in which the fixing belt  171  circulates (in a direction opposite to the direction of arrow F shown in  FIGS. 30 and 31 ) than when the felt member  440  and the first cleaning roller  210  are traced towards a downstream side of the fixing belt  171  in the direction in which the fixing belt  171  circulates (in the direction of arrow F shown in  FIGS. 30 and 31 ). That is, the felt member  440  and the first cleaning roller  210  are disposed upstream of the fixing area in the direction in which the fixing belt  171  circulates. 
         [0151]    As described above, the fixing belt  171  circulates by being driven by the rotation of the heat roller  172  that contacts the fixing belt  171  at the fixing area. The first cleaning roller  210  rotates by being driven by the circulation of the fixing belt  171 . Therefore, if, for example, the first cleaning roller  210  is disposed downstream of the fixing area, the first cleaning roller  210  is pushed against an area of the fixing belt  171  where it is pushed out by the heat roller  172 , and is rotated. As a result, the behavior of the fixing belt  171  and the rotation of the first cleaning roller  210  may become unstable. In contrast, in the exemplary embodiment, since, for example, the first cleaning roller  210  is disposed upstream of the fixing area, an area of the fixing belt  171  where the first cleaning roller  210  is disposed corresponds to an area where the fixing belt  171  is pulled in by the heat roller  172  and the orientation of the fixing belt  171  is stable. Accordingly, the first cleaning roller  210  that is disposed in this area is also stably driven, so that any residual toner on the fixing belt  171  is reliably stably transferred to the first cleaning roller  210 . 
       Guide Member 
       [0152]      FIG. 33  is a front view of the guide member.  FIG. 34  is a sectional view taken along arrows XXXIV-XXXIV shown in  FIG. 33 . 
         [0153]    As described with reference to  FIG. 1 , a leading edge of a sheet that has been transported upward by the sheet transport belt  140  strikes the guide member  174 , is further transported, and is guided to the fixing area that is interposed between the fixing belt  171  and the heat roller  172 . 
         [0154]    The guide member  174  includes a plate member  610  having a guide surface  611  and sheet receiving members  620  arranged on the guide surface  611  of the plate member  610 . As shown in, for example,  FIG. 12 , the plate member  610  is secured to the supporting frames  510 . The guide surface  611  of the plate member  610  is a surface that faces a sheet that is transported towards the guide member  174 . As shown in  FIGS. 1 and 34 , the guide member  174  is disposed so that its guide surface  611  faces obliquely downward. The plate member  610  is formed of a metallic plate in the exemplary embodiment. 
         [0155]    The sheet receiving members  620  are formed of resin (such as fluorocarbon resin), and are disposed at the guide surface  611  of the plate member  610  so as to be spaced apart from each other in widthwise directions (that is, in the directions of a double-headed arrow G-G in  FIG. 33 ) that cross the transport direction of a sheet. The sheet receiving members  620  protrude from the guide surface  611 . A transport-direction front edge of a sheet that is transported directly strikes these sheet receiving members  620 . In the widthwise directions of the sheet (that is, in the directions of the double-headed arrow G-G in  FIG. 33 ), the sheet receiving members  620  are closely arranged at an interval that does not allow the sheet to contact areas of the guide surface  611  situated between adjacent sheet receiving members  620 . 
         [0156]    The transport-direction front edge of the sheet that has been transported towards the guide member  174  from below the guide member  174  strikes the sheet receiving members  620  that are disposed so as to protrude from the guide surface  611 . As mentioned above, in the printer  100  (see  FIG. 1 ), an image that spreads from a front edge portion to a rear edge portion of the sheet is formed. Therefore, toner may be stuck up to the front edge of the sheet that has been transported towards the guide member  174 . When the sheet is guided to the fixing area with the toner stuck on its front edge, it is possible for the toner stuck on the front edge to adhere to the fixing belt  171  and the heat roller  172  in the fixing area, and, thus, to a location of the sheet that is situated downward from the front edge of the sheet by a distance corresponding to a distance of one rotation of the fixing belt  171  and the heat roller  172 . This may stain an image on the sheet or the back surface of the sheet. 
         [0157]    In the exemplary embodiment, the transport-direction front edge of the sheet that has been transported towards the guide member  174  strikes the sheet receiving members  620 ; and the toner stuck on the front edge of the sheet separates from the front edge of the sheet by shock generated when the front edge strikes the sheet receiving members  620 , and lands on the guide surface  611 . The plate member  610  having the guide surface  611  is disposed near the heat roller  172 , and the plate member  610  according to the exemplary embodiment has high thermal conductivity because the plate member  610  is formed of a metallic plate. Therefore, the temperature of the plate member  610  becomes high enough to fuse the toner, as a result of which the toner that has landed on the guide surface  611  adheres to the guide surface  611 . Consequently, although the guide surface  611  is disposed so as to face obliquely downward, the percentage by which the toner that has been separated from the front edge of the sheet falls is very slight. This prevents the interior of the printer from being inadvertently stained by the toner. 
         [0158]    The sheet receiving members  620  are formed of resin materials, and, thus, have low thermal conductivity. As a result, the toner is prevented from sticking onto the sheet receiving members  620 . 
         [0159]    The plate member  610  that is formed of a metallic plate is grounded with respect to the housing  110  (see  FIG. 1 ) of the printer  100  through the supporting frames  510  that support the plate member  610  (see  FIG. 12 ), so that the plate member  610  electrically has zero potential. The sheet receiving members  620  arranged at the guide surface  620  are arranged at the guide surface  611  in the widthwise directions (the directions of the double-headed arrow G-G) at locations that are upstream in the transport direction of a front-edge area  611   a  at the side of the fixing area so as not to be disposed in the front-edge area  611   a.    
         [0160]    Therefore, after the front edge of the sheet that has been transported upward towards the guide member  174  strikes the sheet receiving members  620  of the guide member  174 , the sheet is guided to the fixing area while the sheet contacts the front-edge area  611   a  of the guide surface  611 . When the sheet contacts the guide surface  611 , the sheet that has been charged up to this time undergoes discharge through the plate member  610 . Accordingly, after the discharge, the sheet is guided to the fixing area, so that an image defect or sheet staining that may occur when the charged sheet enters the fixing area is prevented from occurring. 
         [0161]    Next, the structure of the sheet receiving members  620  at the guide member  174  and the method of mounting the sheet receiving members  620  to the plate member  610  will be described. 
         [0162]      FIG. 35  is a front view of only the plate member  610  after removal of the sheet receiving members  620  from the guide member  174  as seen from an observing point that is the same as that from which the guide member  174  is seen in  FIG. 33 . 
         [0163]    The plate member  610  is provided with the guide surface  611  and holes  630  that pass through the back surface of the plate member  610  defined as such when the guide surface  611  is the front surface and that are used for mounting the sheet receiving members  620  thereto. These holes  630  are holes for mounting thereto the sheet receiving members  620  one at a time. The holes  630  are formed so as to be spaced apart in the widthwise directions of the sheet (that is, the directions of the double-headed arrow G-G). 
         [0164]      FIGS. 36 ,  37 , and  38  are, respectively, a front view, a side view, and a perspective view of a sheet receiving member. 
         [0165]    Each sheet receiving member  620  has a body  621  and an insertion portion  622 . Each body  621  is a portion that protrudes from the guide surface  611  when the associated sheet receiving member  620  is mounted to the plate member  610 . Each insertion portion  622  is a portion that protrudes from the associated body portion  621  towards the plate member  610  and is inserted into the associated hole  630  shown in  FIG. 35 . 
         [0166]    In mounting the sheet receiving members  620  to the plate member  610 , the insertion portions  622  of the sheet receiving members  620  are inserted into the holes of the plate member  610 , and are moved along the guide surface  611 . This causes the sheet receiving members  620  to be mounted to the plate member  610  while the bodies  621  thereof protrude from the guide surface  611 . 
         [0167]    Accordingly, the structure for mounting the sheet receiving members  620  to the plate member  610  is one in which, after the insertion portions  622  of the sheet receiving members  620  are inserted into the holes  630  of the plate member  611 , the sheet receiving members  620  are moved along the guide surface  611  of the plate member  610  thereof, to mount the sheet receiving members  620  to the plate member  610 . Therefore, compared to a structure in which sheet receiving members are mounted to a plate member by only inserting insertion portions into holes, this structure allows the sheet receiving members  620  to be firmly mounted to the plate member  610  while reducing the amount by which the sheet receiving members  620  protrude towards the back side. The cleaning device  200  for cleaning the fixing belt  171  is disposed very close to a back surface of the guide surface  611  of the plate member  610  (see  FIG. 7 ). When the amount by which the sheet receiving members  620  protrude to the back side of the guide surface  611  is made small, the size of the printer  100  is reduced. 
         [0168]    Here, in the exemplary embodiment, the sheet receiving members  620  are mounted to the plate member  610  by inserting the insertion portions  622  into the holes  630  in the plate member  610  and moving the insertion portions  622  along the guide surface  611  in a direction in which they approach the fixing area (in the direction of arrow H shown in  FIG. 35 ). 
         [0169]    The direction of arrow H corresponds to a direction in which a sheet that is transported pushes the sheet receiving members  620 . Therefore, the sheet receiving members  620  are more firmly secured to the plate member  610  during use of the printer  100 , so that the possibility with which the sheet receiving members  620  are removed from the plate member  610  during the use of the printer  100  is further reduced. 
         [0170]    The insertion portion  622  of each sheet receiving member  620  includes a first wing-like protrusion  641  and a second wing-like protrusion  642 . Each first wing-like protrusion  641  is disposed at the back in a direction in which the associated insertion portion  622  moves along the guide surface  611  after the associated insertion portion  622  is inserted into the hole  630  in the plate member  610 . Each second wing-like protrusion  642  is disposed at the front in the direction in which the associated insertion portion  622  moves along the guide surface  611  after the associated insertion portion  622  is inserted into the hole  630  in the plate member  610 . 
         [0171]    As shown in  FIG. 37 , each first wing-like protrusion  641  includes a first protruding portion  641   a  and lugs  641   b . Each first protruding portion  641   a  protrudes in a direction in which its associated insertion portion  622  is inserted into the hole  630 . The lugs  641   b  are spaced apart from the associated body  621  by an amount allowing the plate member  610  to be interposed therebetween, and extend from the associated first protruding portion  641   a  to respective sides in the widthwise direction that crosses both the insertion direction and the movement direction. 
         [0172]    Similarly to each first wing-like protrusion  641 , each second wing-like protrusion  642  includes a first protruding portion  642   a  and lugs  642   b . Each first protruding portion  642   a  protrudes in a direction in which its associated insertion portion  622  is inserted into the hole  630 . The lugs  642   b  are spaced apart from the associated body  621  by an amount allowing the plate member  610  to be interposed therebetween, and extend from the associated first protruding portion  642   a  to respective sides in the widthwise direction that crosses both the insertion direction and the movement direction. 
         [0173]    The insertion portion  622  of each sheet receiving member  620  includes a second protruding portion  643  that is positioned between the first wing-like protrusion  641  and the second wing-like protrusion  642 , and that protrudes in the direction in which the insertion portion  622  is inserted into its associated hole  630  (see also  FIGS. 41 and 44  (described later)). 
         [0174]      FIG. 39  is a perspective view showing a first stage when a portion of the plate member  610  is cut away and when the guide member is seen from a back side of the guide surface, the first stage being a stage during mounting of the sheet receiving members to the plate member, that is, a stage after the insertion portions  622  of the sheet receiving members  620  are inserted into the holes of the plate member  610  and prior to moving the insertion portions  622  along the guide surface. 
         [0175]      FIG. 40  is a side view of the guide member in the first stage shown in  FIG. 39 .  FIG. 41  shows the guide member in the first stage as seen from a direction along arrows XLI-XLI shown in  FIG. 40 . 
         [0176]      FIG. 42  is a perspective view showing a second stage when the portion of the plate member  610  is cut away and when the guide member is seen from the back side of the guide surface, the second stage being a stage after the insertion portions  622  of the sheet receiving members  620  are inserted into the holes of the plate member  610  and the insertion portions  622  are moved along the guide surface, that is, a stage after completion of the mounting. 
         [0177]      FIG. 43  is a side view of the guide member in the second stage shown in  FIG. 42 .  FIG. 44  shows a portion of the guide member when the guide member in the second stage is seen from a direction along arrows XLIV-XLIV shown in  FIG. 43 . 
         [0178]    As shown in  FIGS. 41 and 44 , the holes  630  in the plate member  610  are each defined by a first portion  631 , a second portion  632 , a third portion  633 , and a fourth portion  634 . 
         [0179]    Each first portion  631  is a portion that is wide enough to receive its associated first wing-like protrusion  641  of the insertion portion  622  of its associated sheet receiving member  620 , and each second portion  632  is a portion that is wide enough to receive its associated second wing-like protrusion  642  of the insertion portion  622  of its associated sheet receiving member  620 . 
         [0180]    Each third portion  633  is a portion that extends in the direction in which the insertion portion  622  of its associated sheet receiving member  620  moves along the guide surface  611  after being inserted into its associated hole  630  and that connects its associated first portion  631  and its associated second portion  632 . In the first stage in which each first portion  631  and each second portion  632  receive its associated first wing-like protrusion  641  and its associated second wing-like protrusion  642 , each third portion  633  receives its associated second protruding portion  643 . In the second stage in which the sheet receiving members  620  are moved in the aforementioned movement direction, each third portion  633  receives the first protruding portion  641   a  of its associated first wing-like protrusion  641  (see  FIG. 37 ), and sandwiches its associated first wing-like protrusion  641   a  in the widthwise direction. At this time, the plate member  610  is interposed between the bodies  621  and the lugs  641   b  of each of the first wing-like protrusions  641  (see  FIGS. 36 to 38 ) in a plate thickness direction. 
         [0181]    As indicated by the positional relationship shown in  FIG. 41 , each third portion  633  defining its associated hole  630  has a narrow width portion  633   a  towards a front side thereof in a direction of movement of its associated second protruding portion  643  in the first stage, each narrow width portion  633   a  having a width that is narrower than that of its corresponding second protruding portion  643 . Each narrow width portion  633   a  has a width that allows passage of its associated second protruding portion  643  towards the front in the direction of movement thereof only when a force acting towards the front in the direction of movement thereof is applied to its associated sheet receiving member  620  in the first stage. 
         [0182]    As shown in  FIG. 44 , in the second stage, each second protruding portion  643  is positioned at a location where it reaches after passing a front side of its associated narrow width portion  633   a  in the movement direction thereof. Each narrow width portion  633   a  provides resistance, so that each sheet receiving member  620  does not easily move backward in the movement direction thereof. As a result, each sheet receiving member  620  is prevented from being removed from the plate member  610 . 
         [0183]    Each fourth portion  634  defining its associated hole  630  receives the first protruding portion  642   a  of its associated second wing-like protrusion  642  in the second stage (see  FIG. 37 ), and sandwiches and supports its associated first protruding portion  642   a  in the widthwise direction. In this second stage, similarly to the lugs  641   b  of each first wing-like protrusion  641 , the lugs  642   b  of each second wing-like protrusion  642  (see  FIGS. 36 to 38 ) and the body  621  of its associated sheet receiving member  620  sandwich the plate member  610 . 
         [0184]    Each sheet receiving member  620  according to the exemplary embodiment includes the insertion portion  622  having the above-described structure. The holes  630  of the plate member  610  each have the above-described form. The insertion portions  622  and the holes  630  allow the sheet receiving members  620  to be simply and firmly mounted to the plate member  610 . 
         [0185]    Here, although the present invention is applied to the printer  100  having the structure shown in  FIG. 1 , the present invention is widely applicable to image forming apparatuses of a type that forms images using toner. 
         [0186]    The foregoing description of the exemplary embodiment 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 embodiment was 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.