Patent Publication Number: US-2017357194-A1

Title: Transport device, fixing device, and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-114531 filed Jun. 8, 2016. 
     BACKGROUND 
     Technical Field 
     The present invention relates to transport devices, fixing devices, and image forming apparatuses. 
     SUMMARY 
     According to an aspect of the invention, there is provided a transport device including: a first rotational member; a second rotational member that forms a nip with the first rotational member and transports a medium by nipping the medium therebetween; a guide member that is disposed so as to leave a gap with respect to the first rotational member and that comes into contact with the medium having passed through the nip to guide the medium in a predetermined direction; a changing part that supports the second rotational member so as to be rotatable and that moves the second rotational member to change a nip state between the second rotational member and the first rotational member; and an interposed member supported by the changing part and nipped between the first rotational member and the guide member, the interposed member including, in an intersecting direction intersecting a direction in which the interposed member is nipped, multiple portions having different thicknesses, the interposed member being nipped at any one of the multiple portions, while being moved in the intersecting direction in accordance with the movement of the second rotational member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a front view showing the configuration of an image forming apparatus according to a first exemplary embodiment; 
         FIG. 2  is a front view of a fixing device constituting the image forming apparatus according to the first exemplary embodiment, showing the case where the pressure state of the nip is a full-latch state; 
         FIG. 3  is a perspective view of a first lever member and a second lever member constituting the fixing device according to the first exemplary embodiment; 
         FIG. 4A  is a front view of the fixing device according to the first exemplary embodiment, showing the case where the pressure state of the nip is a half-latch state; 
         FIG. 4B  is a front view of the fixing device according to the first exemplary embodiment, showing an unlatched state in which the nip is not formed; 
         FIG. 5A  shows a contact state between a fixing roller and a pressure belt in the fixing device according to the first exemplary embodiment, in the case where the pressure state of the nip is a full-latch state; 
         FIG. 5B  shows the contact state between the fixing roller and the pressure belt in the fixing device according to the first exemplary embodiment, in the case where the pressure state of the nip is a half-latch state; 
         FIG. 6  shows the position of a separating baffle constituting the fixing device according to the first exemplary embodiment; 
         FIG. 7  is a front view of a fixing device constituting an image forming apparatus according to a second exemplary embodiment; 
         FIG. 8  is a front view of a fixing device constituting an image forming apparatus according to a modification; 
         FIG. 9  is front view of a fixing device constituting an image forming apparatus according to another modification; and 
         FIG. 10  is a front view of a fixing device constituting an image forming apparatus according to a fourth comparison example (another modification), showing the case where the pressure state of the nip is a full-latch state. 
     
    
    
     DETAILED DESCRIPTION 
     Outline 
     Two exemplary embodiments, namely, a first exemplary embodiment and a second exemplary embodiment, will be described below. 
     First Exemplary Embodiment 
     The first exemplary embodiment will be described. First, the overall configuration of an image forming apparatus according to this exemplary embodiment and an image forming operation will be described. Then, the configuration of a fixing device, serving as a relevant part in this exemplary embodiment, and a fixing operation will be described. Finally, advantages of this exemplary embodiment will be described. 
     Overall Configuration of Image Forming Apparatus 
     As shown in  FIG. 1 , an image forming apparatus  10  according to this exemplary embodiment includes: a transport section  12 , which includes a roller pair  13  for transporting a sheet P; an image forming section  14 , which form, with toner T, a toner image G on the sheet P transported by the transport section  12 ; a fixing device  30 , which heats the toner image G to fix the toner image G to the sheet P; and a controller  20 . The image forming section  14  is an example of a forming section. The sheet P is an example of a medium. The fixing device  30  is an example of a transport device. 
     The image forming section  14  performs steps including charging, exposure, development, and transfer, which are the steps performed in a known electrophotographic system. The controller  20  controls the respective sections of the image forming apparatus  10 , except for the controller  20  itself. 
     In the description below, a direction indicated by arrows Y and −Y in  FIG. 1  is referred to as a height direction of the image forming apparatus  10 , a direction indicated by arrows X and −X is referred to as a width direction of the image forming apparatus  10 , and a direction perpendicular to the height and width directions of the image forming apparatus  10  is referred to as a depth direction (denoted by Z) of the image forming apparatus  10 . In a front view of the image forming apparatus  10 , the height, width, and depth directions of the image forming apparatus  10  are referred to as Y, X and Z directions, respectively. When one side and the other side of the X, Y, and Z directions need to be distinguished from each other, in a front view of the image forming apparatus  10 , an upper side is referred to as a Y-direction side, a lower side is referred to as a −Y-direction side, a right side is referred to as an X-direction side, a left side is referred to as a −X-direction side, a far side is referred to as a Z-direction side, and a near side is referred to as a −Z-direction side. 
     Thus, the description of the overall configuration of the image forming apparatus  10  according to this exemplary embodiment has been completed. 
     Image Forming Operation 
     Next, an image forming operation according to this exemplary embodiment will be described with reference to  FIG. 1 . 
     When the controller  20  receives image data from an external device (not shown), the controller  20  actuates the respective sections of the image forming apparatus  10 , except for the controller  20  itself. More specifically, the controller  20  causes the transport section  12  to transport a sheet P, causes the image forming section  14  to form a toner image G, and causes the fixing device  30  to fix the toner image G to the sheet P. The sheet P to which the toner image G has been fixed is discharged outside the image forming apparatus  10 . Thus, an image forming operation is completed. 
     Thus, the description of the image forming operation according to this exemplary embodiment has been completed. 
     Configuration of Relevant Part 
     Next, the configuration of the relevant part (the fixing device  30 ) according to this exemplary embodiment will be described. 
     As shown in  FIG. 2 , the fixing device  30  according to this exemplary embodiment includes: a housing  31 , serving as a principal unit of the fixing device; a fixing roller  32 ; a pressure belt  34 ; a separating member  40 ; a pressure member  48 ; and interposed members  100 . The fixing roller  32  is an example of a first rotational member and a heating part. The pressure belt  34  is an example of a second rotational member and a pressure part. The separating member  40  is an example of a guide member. The pressure member  48  is an example of a changing part. 
     Housing 
     As shown in  FIG. 2 , the housing  31  is formed in a box shape having a longitudinal direction extending in the Z direction and is provided with openings, through which a sheet P can pass, in walls (not shown) on the Y- and −Y-direction sides. The housing  31  also has a pair of side walls  33  facing each other in the Z direction. The side walls  33  are disposed parallel to an X-Y plane. A cylindrical shaft  36  extending in the Z direction is provided on the X-direction side of the side walls  33 , and a cylindrical shaft  38  extending in the Z direction is provided on the −X-direction side of the side walls  33 . 
     The shaft  36  projects from the inside to the outside (i.e., toward the Z- and −Z-direction sides) of the side walls  33 . The shaft  36  is disposed on the radially outside (i.e., on the X-direction side) of the fixing roller  32  (described below), so as to extend in the axial direction of the fixing roller  32  (Z direction). In  FIG. 2 , the axis of the shaft  36  is denoted by reference sign C 1 . 
     The shaft  38  projects from the inside to the outside (i.e., toward the Z- and −Z-direction sides) of the side walls  33 . The shaft  38  is disposed on the outside (i.e., on the −X-direction side) of the pressure belt  34 , so as to extend in the axial direction of the pressure belt  34  (Z direction). In  FIG. 2 , the axis of the shaft  38  is denoted by reference sign C 2 . 
     Fixing Roller 
     As shown in  FIG. 2 , the fixing roller  32  is formed of a cylindrical core  32 A and a rubber layer  32 B formed on an outer circumferential surface  32 A 1  thereof. Although illustration is omitted, the rubber layer  32 B is cylindrical and covers the outer circumferential surface  32 A 1  of the core  32 A in such a state that end portions of the core  32 A project from ends of the rubber layer  32 B. The fixing roller  32  is disposed on a toner image G side (i.e., X-direction side) of a sheet transport path A (see  FIG. 1 ), so as to be rotatable about a shaft extending in the Z direction. A halogen heater  39  is provided inside the core  32 A 1 . The halogen heater  39  is an example of a heat source. 
     The halogen heater  39  generates heat by receiving power from a power supply (not shown) to heat the core  32 A and, thus, the rubber layer  32 B. A gear (not shown) is provided on the Z-direction side of the core  32 A. The gear is rotated by a motor (not shown). In this manner, the fixing roller  32  is heated by the halogen heater  39  and, in turn, heats a sheet P and a toner image G (toner T) formed thereon while rotating, thus fixing the toner image G to the sheet P. 
     Pressure Belt 
     As shown in  FIG. 2 , the pressure belt  34  is disposed on the other side (−X-direction side) of the sheet transport path A (see  FIG. 1 ) from the fixing roller  32 , so as to be rotatable (revolve) about a shaft extending in the Z direction. The pressure belt  34  is an endless belt. 
     A pressure pad  62  (described below) is provided inside the pressure belt  34 . The pressure belt  34 , due to the friction between the pressure belt  34  and the fixing roller  32 , follows the rotation of the fixing roller  32  and revolves. The pressure belt  34  forms a nip N with the fixing roller  32  and transports the sheet P while nipping the sheet P at the nip N. In this exemplary embodiment, for example, the sheet is transported in the Y direction in the fixing device  30 , and the width direction perpendicular to the sheet-transport direction is the Z direction. 
     Separating Member 
     The separating member  40  is disposed at a distance (gap G) from the fixing roller  32 . The separating member  40  comes into contact with the sheet P that has passed through the nip N to guide the sheet P in a predetermined direction. Herein, the predetermined direction is a direction in which the sheet transport path A (see  FIG. 1 ) extends. As viewed in the Z direction, the transport path A is located on the −X-direction side of a separating baffle  46  (described below). The gap G will be described below. 
     The separating member  40  includes: a pair of brackets  42  facing each other in the Z direction; an attaching member  44  with the Z-direction ends supported by the brackets  42 ; the separating baffle  46  attached to the attaching member  44 ; and securing members  47  fixed to the attaching member  44  (see  FIG. 2 ). Because the bracket  42  on the Z-direction side and the bracket  42  on the −Z-direction side have the same configuration and are disposed symmetrically with respect to the middle part, in the Z direction, of the fixing roller  32 , the bracket  42  on the −Z-direction side will be described herein, and the description of the bracket  42  on the Z-direction side will be omitted. 
     Bracket 
     As shown in  FIG. 2 , as viewed in the Z direction, the bracket  42  is formed in an arch shape and is disposed parallel to the X-Y plane. More specifically, the bracket  42  is formed in a quarter-circle shape, which is obtained by dividing a ring-shaped plate into four segments in the circumferential direction. One end (the −Y-direction end) of the bracket  42  in the circumferential direction is rotatably joined to the shaft  36 . In other words, the bracket  42  is movable about the shaft  36  (axis C 1 ) in an arch shape around an axis C 1 , on the radially outer side of the fixing roller  32 . As viewed in the Z direction, the bracket  42  is constantly urged in a counterclockwise direction about the axis C 1  by a spring (not shown). 
     Attaching Member 
     The attaching member  44  is an elongated member having a longitudinal direction extending in the Z direction (see  FIG. 2 ). As viewed in the Z direction, the Z-direction ends of the attaching member  44  are fixed to the other end of the bracket  42  in the circumferential direction. As viewed in the Z direction, a portion of the attaching member  44  is disposed so as to be inclined with respect to the Y direction, such that the Y-direction end is located on a further X-direction side than the −Y-direction end. The −Y-direction end of the attaching member  44  is bent toward the −X-direction side. 
     The attaching member  44  has female screw portions (not shown) provided at a distance from each other in the Z direction. These female screw portions receive screws  57 . The screws  57  are used to attach a proximal end portion  46 A of the separating baffle  46  (described below, and see  FIGS. 4A and 4B ) to the attaching member  44 . Compression coil springs  56  are fitted onto the screws  57 . As a result of male threads on the screws  57  being screwed into the female screw portions in the attaching member  44 , the compression coil springs  56  urge the proximal end portion  46 A of the separating baffle  46  away from the attaching member  44 . 
     Separating Baffle 
     The separating baffle  46  is formed of a rectangular plate having a longitudinal direction extending in the Z direction (see  FIGS. 2, 4A, and 4B ). The separating baffle  46  has the proximal end portion  46 A and a distal end portion  46 B. The proximal end portion  46 A is fixed to (held by) a rectangular-plate-shaped holder  58  having a longitudinal direction extending in the Z direction. The holder  58  is attached to a −X-direction side of the attaching member  44  with the screws  57  and is urged toward the −X-direction side by the compression coil springs  56 . In this manner, as a result of the proximal end portion  46 A being fixed to the bracket  42  via the holder  58 , the separating baffle  46  is attached to the bracket  42 . 
     As shown in  FIG. 6 , the distal end portion  46 B of the separating baffle  46  is a free end projecting from the holder  58 . The distal end portion  46 B is disposed downstream of the nip N in the sheet-transport direction, at a position a distance d away from the outer circumferential surface of the fixing roller  32  (i.e., the outer circumferential surface of the rubber layer  32 B). The transported sheet P comes into contact with the distal end portion  46 B. The gap G described above is a gap between the distal end portion  46 B and the outer circumferential surface of the fixing roller  32 . The width of the gap G between the distal end portion  46 B and the outer circumferential surface of the fixing roller  32  is the distance d. The distal end portion  46 B is disposed so as to project from the holder  58  in a direction opposite to the rotation direction of the fixing roller  32 . Herein, the distance between the downstream end of the nip N and the distal end portion  46 B in the sheet-transport direction is referred to as a distance Lb. When the leading end of the transported sheet P in the transport direction comes into contact with the distal end portion  46 B of the separating baffle  46 , the separating baffle  46  guides (separates) the sheet P in a direction away from the outer circumferential surface of the fixing roller  32 . 
     Securing Member 
     The securing members  47  are a pair of cylindrical columns that are fixed to the end portions of the attaching member  44  in the longitudinal direction with screws (not shown) (see  FIG. 2 ). The securing members  47  are formed of, for example, metal. The securing members  47  extend in the longitudinal direction of the attaching member  44  and symmetrically project from the ends of the attaching member  44  in the Z and −Z directions. Furthermore, as viewed in the Y direction, the securing members  47  overlap the core  32 A projecting from the ends of the rubber layer  32 B of the fixing roller  32 . The securing members  47  nip the interposed members  100  with the core  32 A of the fixing roller  32 . As has been described above, as a result of the securing members  47  and the core  32 A of the fixing roller  32  nipping the interposed members  100  therebetween, in other words, as a result of the securing members  47  being in contact with the interposed members  100 , the brackets  42  (separating member  40 ) constantly urged by the spring (not shown) are positioned. As a result, the distance d between the distal end portion  46 B of the separating baffle  46  and the outer circumferential surface of the fixing roller  32  is determined. 
     Pressure Member 
     The pressure member  48  supports the pressure belt  34  so as to be rotatable and moves the pressure belt  34  toward the fixing roller  32  side to change the nip state between the pressure belt  34  and the fixing roller  32 . Herein, “to change the nip state” is to switch between two nip states, namely, a state in which the nip N is formed and a state in which the nip N is not formed, and is to change the level of the pressure at the nip N in the state in which the nip N is formed. 
     As shown in  FIGS. 2 and 3 , the pressure member  48  includes the pressure pad  62 , a holder  64  that holds the pressure pad  62 , first lever members  66  that support the holder  64 , and second lever members  68  to which the first lever members  66  are mounted in a movable manner. Furthermore, as viewed in the Z direction, the pressure member  48  can be moved in an arc about the axis C 2  by the cam unit  80 . 
     Pressure Pad 
     As shown in  FIGS. 5A and 5B , the pressure pad  62  is disposed inside the pressure belt  34 . The pressure pad  62  includes, for example, a pad member  62 A and a pad member  62 B. 
     The pad member  62 A is formed of, for example, a rectangular-plate-shaped silicon rubber member having a longitudinal direction extending in the Z direction and a transverse direction extending in the sheet-transport direction. The pad member  62 A is in contact with the pressure belt  34  over an area between the upstream end and a part before (upstream of) the downstream end of the nip N in the sheet-transport direction and applies pressure to the pressure belt  34  with an urging force exerted by a compression coil spring  63  (described below). 
     The pad member  62 B is formed of, for example, a rectangular-parallelepiped-shaped silicon rubber member elongated in the Z direction. The pad member  62 B is fixed to the holder  64  (described below) and is in contact with the pressure belt  34 , at a downstream end part of the nip N in the sheet-transport direction, thus applying pressure to the pressure belt  34 . 
     Holder 
     As shown in  FIGS. 5A and 5B , the holder  64  is, for example, an elongated member elongated in the Z direction and is disposed inside the pressure belt  34 . The holder  64  has a recess  64 A recessed in the −X-direction, as viewed in the Z direction. The recess  64 A accommodates the compression coil spring  63 , which is deformed in the X direction. The compression coil spring  63  urges the pad member  62 A against the pressure belt  34 . The −X-direction end of the pad member  62 B is fixed to the Y-direction end of the holder  64  with a screw (not shown). In addition, the Z-direction-ends of the holder  64  are fixed to the first lever members  66  (see  FIG. 3 ) with screws (not shown). 
     Herein, as shown in  FIGS. 2 and 5A , a pressure state in which the pad member  62 A is pressed further toward the holder  64  than the pad member  62 B (a state in which the pad member  62 A and the pad member  62 B are in contact with the pressure belt  34 ) is referred to as a full-latch state. Furthermore, as shown in  FIGS. 4A and 5B , a pressure state in which the pad member  62 A is in contact with the pressure belt  34  and in which the pad member  62 B is not in contact with the pressure belt  34  is referred to as a half-latch state. In other words, when the fixing roller  32  and the pressure belt  34  are in contact with each other or nip a sheet P therebetween, a state in which the pressure belt  34  applies a higher pressure is the full-latch state, and a state in which the pressure belt  34  applies a lower pressure than that in the full-latch state is the half-latch state. As shown in  FIG. 4B , a state in which the pressure applied by the pressure belt  34  is lower than that in the half-latch state (i.e., a non-contact state, in which the nip N is not formed) is referred to as an unlatched state. 
       FIG. 3  shows the first lever member  66  and the second lever member  68  on the −Z-direction side. The first lever member  66  and the second lever member  68  on the Z-direction side have the same configuration as those on the −Z-direction side, and the first lever members  66 , as well as the second lever members  68 , are disposed symmetrically with respect to the middle part of the holder  64  (see  FIG. 2 ) in the Z direction. Hence, only the first lever member  66  and the second lever member  68  on the −Z-direction side will be described, and the description of the first lever member  66  and the second lever member  68  on the Z-direction side will be omitted. The Z-direction-ends of the holder  64  are fixed to U-shaped recessed portions in the first lever members  66  with screws (not shown). 
     First Lever Member 
     As shown in  FIG. 3 , the first lever member  66  includes an outer wall  66 A and an inner wall  66 B, which are disposed at a distance from each other in the Z direction, and a front wall  66 C. The outer wall  66 A is disposed on the −Z-direction side of the inner wall  66 B. As viewed in the Z direction, the outer wall  66 A and the inner wall  66 B are formed in a U shape that opens toward the X-direction side. The front wall  66 C connects the X-direction end, on the Y-direction side, of the outer wall  66 A and the X-direction end, on the Y-direction side, of the inner wall  66 B. Furthermore, a through-hole  66 D extending in the Z direction is provided in the −Y-direction end of the outer wall  66 A and the −Y-direction end of the inner wall  66 B. The shaft  38  is inserted through the through-hole  66 D. Thus, the first lever member  66  is mounted to the shaft  38  so as to be movable in an arc about the axis C 2 . 
     A plate-shaped press part  66 E is provided in the first lever member  66 , at a position on the −X-direction side of the front wall  66 C. The press part  66 E has a female screw part (not shown) penetrating in the X direction. The X-direction end of the compression coil spring  67  is in contact with the surface of the press part  66 E facing the −X-direction side. The −X-direction end of the compression coil spring  67  is in contact with the second lever member  68  (described below). Hence, the Y-direction end of the first lever member  66  is urged in the direction away from the second lever member  68  by an urging force of the compression coil spring  67 . 
     Second Lever Member 
     As shown in  FIG. 3 , the second lever member  68  includes an outer wall  68 A and an inner wall  68 B, which are disposed at a distance from each other in the Z direction, and a rear wall  68 C. The outer wall  68 A is disposed on the −Z-direction side of the inner wall  68 B. The first lever member  66  is disposed between the outer wall  68 A and the inner wall  68 B. 
     As viewed in the Z direction, the outer wall  68 A is formed in a U shape that opens toward the X-direction side. A shaft part  68 D extending in the Z direction and projecting toward the −Z-direction side is provided at the X-direction end, on the Y-direction side, of the outer wall  68 A. A cam follower  72 , which has a cylindrical shape as viewed in the Z direction, is provided on the shaft part  68 D so as to be rotatable about a shaft part  68 D. 
     One end of a shaft  74  extending in the Z direction is attached to a middle part of the outer wall  68 A, in the in the Y direction, on the −X-direction side. The other end of the shaft  74  is attached to a middle part of the inner wall  68 B in the Y direction, on the −X-direction side. A cam follower  75  (see  FIG. 2 ), which has a cylindrical shape as viewed in the Z direction, is provided on the shaft  74  so as to be rotatable about the shaft  74 . Furthermore, a through-hole  68 E extending in the Z direction is provided in the X-direction end, on the −Y-direction side, of the outer wall  68 A. The shaft  38  is inserted into the through-hole  68 E. 
     The inner wall  68 B is formed in an L shape, as viewed in the Z direction. As described above, the other end of the shaft  74  in the Z direction is attached to a middle part of the inner wall  68 B, in the Y direction, on the −X-direction side. A through-hole (not shown) extending in the Z direction is provided in the X-direction end, on the −Y-direction side, of the inner wall  68 B. The shaft  38  is inserted into this through-hole. Specifically, the −Y-direction end of the outer wall  68 A and the −Y-direction end of the inner wall  68 B are coupled to each other so as to be rotatable about the axis C 2  of the shaft  38 . In other words, the second lever member  68  is provided on the shaft  38  so as to be movable in an arc about the axis C 2 , on the Z- and −Z-direction sides of the first lever member  66 . 
     The rear wall  68 C connects the −X-direction end, on the Y-direction side, of the outer wall  68 A and the −X-direction end, on the Y-direction side, of the inner wall  68 B. Furthermore, the rear wall  68 C has a through-hole (not shown) extending in the X direction. An adjustment screw  76  is inserted into this through-hole so as to extend toward the X-direction side. 
     The adjustment screw  76  is inserted through the compression coil spring  67 , between the rear wall  68 C and the press part  66 E. A male screw part (not shown) at the end of the adjustment screw  76  is screwed into the female screw part formed in the press part  66 E of the first lever member  66 . With this configuration, when the adjustment screw  76  is screwed in further, the compression coil spring  67  is compressed, increasing the urging force applied to the first lever member  66 . 
     When the brackets  42  and the pressure member  48  are viewed in the Z direction, as shown in  FIG. 2 , when the pressure member  48  is moved clockwise about the axis C 2 , the brackets  42  are moved counterclockwise about the axis C 1 . Furthermore, when the pressure member  48  is moved counterclockwise about the axis C 2 , the brackets  42  are moved clockwise about the axis C 1 . 
     Cam Unit 
     As shown in  FIG. 2 , a cam unit  80  includes a shaft  81  rotated by a motor (not shown), and a cam  82  attached to the shaft  81 . The shaft  81  is disposed in the housing  31  so as to extend in the Z direction. The Z-direction-ends of the shaft  81  are rotatably supported by the side walls  33  and bearings (not shown). The shaft  81  is disposed on the −X-direction side of the second lever members  68 , such that the cam  82  and the cam follower  75  are in contact with each other. 
     As viewed in the Z direction, the cam  82  has an elliptical shape having a large-diameter part (i.e., a part corresponding to the long axis) and a small-diameter part (i.e., a part corresponding to the short axis). A recessed portion  82 A is formed in the large-diameter part. A part between the large-diameter part and the small-diameter part is referred to as a middle-diameter part. A part of the cam  82  on the opposite side from the recessed portion  82 A is referred to as a projecting portion  82 B. When the cam  82  is rotated, moving, via the cam follower  75 , the first lever member  66  and the second lever member  68  (see  FIG. 3 ) in an arc about the axis C 2  of the shaft  38 , the pressure pad  62  presses the pressure belt  34 . In short, the pressure belt  34  is moved toward the fixing roller  32  by the pressure member  48  and the cam unit  80  and is urged against the fixing roller  32 . 
     When the projecting portion  82 B of the cam  82  is in contact with the cam follower  75 , the fixing roller  32  and the pressure belt  34  are in the full-latch state (see  FIG. 2 ). When the middle-diameter part of the cam  82  is in contact with the cam follower  75 , the fixing roller  32  and the pressure belt  34  are in the half-latch state (see  FIG. 4A ). When the recessed portion  82 A of the cam  82  is in contact with the cam follower  75 , the fixing roller  32  and the pressure belt  34  are in the unlatched state (see  FIG. 4B ). The unlatched state, the half-latch state, and the full-latch state are switched as a result of the controller  20  (see  FIG. 1 ) actuating the cam unit  80  according to the type of the sheet P. 
     For example, when a thick sheet, which has a greater thickness than a normal sheet, is used for an image forming operation, the cam unit  80  is driven and controlled such that the half-latch state is achieved. When a normal sheet or a thin sheet, which has a smaller thickness than the normal sheet, is used for an image forming operation, the cam unit  80  is driven and controlled such that the full-latch state is achieved. Furthermore, when the image forming apparatus  10  is in a stand-by state, or when a sheet P is jammed in the fixing device  30  (a so-called paper jam), the cam unit  80  is driven and controlled such that the unlatched state is achieved. The pressure member  48  moves according to the type of the sheet P in this manner. Interposed member 
     The interposed members  100  adjust the distance d, that is, the width of the gap G between the distal end portion  46 B and the outer circumferential surface of the fixing roller  32 . As shown in  FIG. 2 , the interposed members  100  are elongated rod-shaped members. The interposed members  100  are made of, for example, metal. 
     The interposed members  100  each have, at one end thereof in the longitudinal direction, a through-hole  102  extending in the Z direction. A pin PN, which is provided on the second lever member  68  of the pressure member  48 , is fitted into the through-hole  102 . The interposed members  100  are supported by the pressure member  48  so as to be rotatable about the pin PN. The interposed members  100  are supported by the pressure member  48  on the Z-direction side and on the −Z-direction side. 
     The thickness (the width in the Y direction) of each interposed member  100  is gradually changed from one end to the other end in the longitudinal direction. More specifically, the interposed member  100  includes multiple portions having different thicknesses, which are, in this order from one end of the interposed member  100  in the longitudinal direction: a first portion  100 A; a first inclined portion  100 B; a second portion  100 C; a second inclined portion  100 D; and a third portion  100 E. The first portion  100 A, the second portion  100 C, and the third portion  100 E each have a constant thickness in the longitudinal direction of the interposed member  100 , and their thicknesses increase in this order. The first inclined portion  100 B and the second inclined portion  100 D connect the longitudinally adjoining portions and are gradually increased in thicknesses from one end to the other end in the longitudinal direction. The heights (i.e., the lengths in the thickness direction of the interposed member  100 ) of the first inclined portion  100 B and the second inclined portion  100 D are smaller than the radius of the securing members  47 . The first inclined portion  100 B, the second portion  100 C, the second inclined portion  100 D, and the fourth portion  100 E are formed on the other end side (the side opposite from the side provided with the through-hole  102 ) of the interposed member  100  in the longitudinal direction. 
     As has been described above,  FIG. 2  shows the fixing device  30  in the full-latch state. In the full-latch state, the first portion  100 A of the interposed member  100  is nipped between the fixing roller  32  (the core  32 A) and the separating member  40  (the securing member  47 ), thus determining the distance d.  FIG. 4A  shows the fixing device  30  in the half-latch state. In the half-latch state, the second portion  100 C of the interposed member  100  is nipped between the fixing roller  32  (the core  32 A) and the separating member  40  (the securing member  47 ), thus determining the distance d.  FIG. 4B  shows the fixing device  30  in the unlatched state. In the unlatched state, the third portion  100 E of the interposed member  100  is nipped between the fixing roller  32  (the core  32 A) and the separating member  40  (the securing member  47 ), thus determining the distance d. The longitudinal direction of the interposed member  100  is an example of a direction intersecting the direction in which the interposed member  100  is nipped between the fixing roller  32  and the separating member  40 . 
     As has been described above, the thicknesses of the first portion  100 A, the second portion  100 C, and the third portion  100 E increase in this order, and the separating member  40  is rotatable about the axis C 1 . Hence, the interposed member  100  is configured to increase the distance d in the order of the full-latch state (see  FIG. 2 ), the half-latch state (see  FIG. 4A ), and the unlatched state (see  FIG. 4B ). 
     With this configuration, the interposed members  100  serve to adjust the distance d according to the latch state, by being nipped between the fixing roller  32  and the separating member  40  at any of the portions having different thicknesses. 
     Thus, the description of the configuration of the relevant part according to this exemplary embodiment (the configuration of the fixing device  30 ) has been completed. 
     Fixing Operation 
     Next, the fixing operation with the fixing device  30  according to this exemplary embodiment will be described below with reference to the drawings. In the fixing operation in this exemplary embodiment, the controller  20  controls the fixing device  30  to heat, with the halogen heater  39 , and rotate the fixing roller  32 . However, in the fixing device  30  according to this exemplary embodiment, as has been described above, when a thick sheet, which has a greater thickness than the normal sheet, is used for an image forming operation, the cam unit  80  is driven and controlled such that the half-latch state is achieved, as shown in  FIGS. 4A and 5B ; when a normal sheet or a thin sheet, which has a smaller thickness than the normal sheet, is used for an image forming operation, the cam unit  80  is driven and controlled such that the full-latch state is achieved, as shown in  FIGS. 2 and 5A ; and when the image forming apparatus  10  is in a stand-by state, or when a paper jam occurs, the cam unit  80  is driven and controlled such that the unlatched state is achieved, as shown in  FIG. 4B . The latch state is changed from one to another (the cam unit  80  is driven and controlled) by the controller  20  before the sheet P is transported by the transport section  12 , as a result of, for example, an operator entering, via an input part (not shown), the type of the sheet P or the like used for the image forming operation, and the data about the type of the sheet P or the like being sent to the controller  20 . The sheet P on which a toner image G is formed by the image forming section  14  and which is transported by the transport section  12  enters the nip N, where the toner image G is fixed, and is guided through the transport path A by the separating baffle  46 . Thus, the fixing operation is completed. 
     Thus, the description of the fixing operation in this exemplary embodiment has been completed. 
     Advantage 
     Next, advantages (first, second, third, and fourth advantages) of this exemplary embodiment will be described below, by comparing this exemplary embodiment with comparison examples (first, second and third comparison examples). Note that, when components or the like mentioned in this exemplary embodiment will be mentioned in the comparison examples, the same reference signs and names will be used even when such components are not illustrated. 
     First Advantage 
     The first advantage is provided by a configuration in which the interposed member  100  is (rotatably) supported by the pressure member  48 , includes, in the longitudinal direction, multiple portions having different thicknesses and is nipped between the fixing roller  32  and the separating member  40  at any one of these portions having different thicknesses, while moving in accordance with the rotation of the pressure member  48 . The first advantage will be described by comparing this exemplary embodiment with a first comparison example (not shown). 
     The fixing device according to the first comparison example does not include the interposed members  100  and the securing members  47  (see  FIG. 2 ). In the fixing device according to the first comparison example, the separating member  40  is positioned (in a non-rotatable manner) with respect to the side walls  33  (see  FIG. 2 ). Other configurations of the first comparison example are the same as those of this exemplary embodiment. 
     Because of this configuration, in the first comparison example, the distance d (the width of the gap G between the distal end portion  46 B and the outer circumferential surface of the fixing roller  32 ) is not adjusted in accordance with the movement of the pressure member  48 . 
     In contrast, as shown in  FIGS. 2, 4A, and 4B , in the fixing device  30  according to this exemplary embodiment, the interposed member  100  is (rotatably) supported by the pressure member  48 . The interposed members  100  are nipped between the fixing roller  32  and the separating member  40  at any one of the portions having different thicknesses, while moving in accordance with the rotation of the pressure member  48 . 
     Hence, in the fixing device  30  according to this exemplary embodiment, it is possible to adjust the width of the gap G (distance d) between the fixing roller  32  and the separating member  40 , in accordance with the change in the nip state between the fixing roller  32  and the pressure belt  34 . In other words, in the fixing device  30  according to this exemplary embodiment, it is possible to adjust the distance d in accordance with the change in the nip state according to the thickness of the sheet P, that is, in accordance with the change in the latch state according to the thickness of the sheet P. Hence, in the image forming apparatus  10  according to this exemplary embodiment, when a medium having a specific thickness is used, a guide fault in the fixing device  30  (a so-called paper jam at the separating baffle  46 ) is suppressed, compared with a configuration in which the width of the gap G (distance d) between the fixing roller  32  and the separating member  40  cannot be changed in accordance with the change in the nip pressure between the fixing roller  32  and the pressure belt  34 . 
     Second Advantage 
     The second advantage is provided by a configuration in which the first inclined portion  100 B and the second inclined portion  100 D connect longitudinally adjoining portions and are gradually increased in thickness from one end to the other end in the longitudinal direction of the interposed members  100 . The second advantage will be described by comparing this exemplary embodiment with a second comparison example (not shown). 
     Interposed members (not shown) in the second comparison example each do not have the first inclined portion  100 B or the second inclined portion  100 D. Hence, in the interposed members in the second comparison example, surfaces perpendicular to the longitudinal direction of the interposed members are formed at the boundary between the first portion  100 A and the second portion  100 C and the boundary between the second portion  100 C and the third portion  100 E. Other configurations of the second comparison example are the same as those of this exemplary embodiment. Note that, because the second comparison example has a configuration that provides the first advantage, the second comparison example falls within the technical scope of the present invention. 
     Because of this configuration, in the second comparison example, when the interposed members are moved in accordance with a change in the latch state, the securing members may be caught by such boundaries between the portions having different thicknesses. 
     In contrast, in this exemplary embodiment, as shown in  FIGS. 2, 4A, and 4B , the first inclined portion  100 B and the second inclined portion  100 D connect longitudinally adjoining portions and are gradually increased in thickness from one end to the other end in the longitudinal direction of the interposed members  100 . 
     Hence, in the fixing device  30  according to this exemplary embodiment, compared with a case where surfaces perpendicular to the longitudinal direction of the interposed members  100  are formed at the boundary between first portion  100 A and the second portion  100 C and the boundary between the second portion  100 C and the third portion  100 E, the securing members  47  are less likely to be caught by the boundaries (i.e., the distance d can be smoothly adjusted). 
     Third Advantage 
     The third advantage is provided by a configuration in which the securing members  47  are cylindrical, and the radius of the securing members  47  is larger than the heights of the first inclined portion  100 B and the second inclined portion  100 D, that is, the heights of steps in the interposed members  100 . The third advantage will be described by comparing this exemplary embodiment with a third comparison example (not shown). 
     The radius of the securing members  47  in the third comparison example is smaller than the heights of the steps in the interposed members  100 . Other configurations of the third comparison example are the same as those of this exemplary embodiment. Note that, because the third comparison example has a configuration that provides the first and second advantages, the third comparison example falls within the technical scope of the present invention. 
     Because of this configuration, in the third comparison example, when the interposed members are moved in accordance with a change in the latch state, the securing members may be caught by such boundaries (steps) between the portions having different thicknesses. 
     In contrast, in this exemplary embodiment, as shown in  FIGS. 2, 4A, and 4B , the radius of the securing members  47  is larger than the heights of the first inclined portion  100 B and the second inclined portion  100 D, that is, the heights of the steps in the interposed members  100 . 
     Hence, in the fixing device  30  according to this exemplary embodiment, compared with a case where the radius of the securing members  47  is smaller than the heights of the steps in the interposed members  100 , the securing members  47  are less likely to be caught by the boundaries (i.e., the distance d can be smoothly adjusted). 
     Fourth Advantage 
     A fourth advantage is provided by a configuration in which the fixing roller  32  is in contact with the interposed members  100  at the outer circumferential surface  32 A 1  of the core  32 A. The fourth advantage will be described by comparing this exemplary embodiment with a fourth comparison example (see  FIG. 10 ). 
     In the fourth comparison example, as shown in  FIG. 10 , the fixing roller  32  is in contact with the interposed members  100  at the outer circumferential surface of the rubber layer  32 B (of the fixing roller  32 ). Other configurations of the fourth comparison example are the same as those of this exemplary embodiment. Note that, because the fourth comparison example has a configuration that provides the first, second, and third advantages, the fourth comparison example falls within the technical scope of the present invention. 
     In the fourth comparison example, because the interposed members  100  are in contact with the outer circumferential surface of the rubber layer  32 B, the rubber layer  32 B could be recessed, depending on the elastic modulus of the rubber layer  32 B, or the like factors. Due to the long-term use, the degree by which the rubber layer  32 B is recessed may change. As a result, the distance d changes in the fourth comparison example. 
     In contrast, in this exemplary embodiment, as shown in  FIGS. 2, 4A, and 4B , the fixing roller  32  is in contact with the interposed members  100  at the outer circumferential surface  32 A 1  of the core  32 A. 
     Hence, in the fixing device  30  according to this exemplary embodiment, compared with a configuration in which the fixing roller  32  is in contact with the interposed members  100  at the outer circumferential surface of the rubber layer  32 B (of the fixing roller  32 ), the distance d is less likely to change. 
     Thus, the description of the advantages of this exemplary embodiment, as well as the description of the first exemplary embodiment, has been completed. 
     Second Exemplary Embodiment 
     Next, a second exemplary embodiment will be described with reference to  FIG. 7 . Portions of this exemplary embodiment different from those of the first exemplary embodiment will be described below. Note that, when components or the like mentioned in the first exemplary embodiment will be mentioned in this exemplary embodiment, the same reference signs and names will be used even when such components are not illustrated. 
     Configuration 
     A fixing device  30 A according to this exemplary embodiment (see  FIG. 7 ) differs from the fixing device  30  according to the first exemplary embodiment (see  FIG. 2 ) only in the configuration of interposed members  200 . More specifically, the interposed members  200  according to this exemplary embodiment each include a support rod  210  and a rotation member  220 . The fixing device  30 A is an example of a transport device. 
     The support rod  200  is a rod having through-holes  212 A and  212 B at ends. The through-hole  212 A provided at one end of the support rod  200  receives the pin PN provided on the second lever member  68  of the pressure member  48 . Thus, the support rod  200  is supported by the second lever member  68  so as to be rotatable about the pin PN. The through-hole  212 B provided at the other end of the support rod  200  receives a pin  222  provided on a rotation member  220  (described below). 
     The rotation member  220  is a ring-shaped member, and the core  32 A of the fixing roller  32  is fitted to the inner circumference of the rotation member  220 . Thus, the rotation member  220  is supported by the core  32 A so as to be rotatable about the core  32 A. The rotation member  220  includes the pin  222 , a ring part  224 , and a projecting portion  226 . 
     The ring part  224  is a ring having, at the center thereof, a through-hole having an inside diameter equivalent to the outside diameter of the core  32 A. The projecting portion  226  is formed on the outer circumference of the ring part  224  and projects in the radial direction of the ring part  224 . The projecting portion  226  is formed over a predetermined area of the ring part  224  in the circumferential direction. The projecting portion  226  includes, for example, in this order in the clockwise direction as the fixing device  30 A viewed from the Z-direction side: a first projecting portion  226 A having a predetermined thickness; a first inclined portion  226 B; a second projecting portion  226 C having a larger thickness than the first projecting portion  226 A; a second inclined portion  226 D; and a third projecting portion  226 E having a larger thickness than the second projecting portion  226 C. The first inclined portion  226 B and the second inclined portion  226 D connect the portions adjoining each other in the circumferential direction of the ring part  224  and are gradually increased in thicknesses from one end to the other end in the circumferential direction. The rotation direction of (the ring part  224  of) the interposed member  200  is an example of a direction intersecting the direction in which the interposed member  200  is nipped between the fixing roller  32  and the separating member  40 . 
     With this configuration, in the fixing device  30 A according to this exemplary embodiment, the interposed members  200  is (rotatably) supported by the pressure member  48  and is nipped between the fixing roller  32  and the separating member  40  at one of the multiple portions having different thicknesses (any one of the first projecting portion  226 A, the second projecting portion  226 C, and the third projecting portion  226 E) and at another portion (any one of the first projecting portion  226 A, the second projecting portion  226 C, and the third projecting portion  226 E), in accordance with the rotation of the pressure member  48 .  FIG. 7  shows the fixing device  30 A in a full-latch state. 
     Thus, the description of the configuration of this exemplary embodiment has been completed. 
     Fixing Operation 
     Next, the fixing operation with the fixing device  30 A according to this exemplary embodiment will be described below, focusing on the difference to that of the first exemplary embodiment. In the fixing device  30 A according to this exemplary embodiment, when a thick sheet, which has a greater thickness than the normal sheet is used for an image forming operation, the cam unit  80  is driven and controlled such that the half-latch state is achieved. At this time, the second projecting portion  226 C of the interposed member  200  is nipped between the securing members  47  and the fixing roller  32 . When a normal sheet or a thin sheet, which has a smaller thickness than the normal sheet, is used for an image forming operation, the cam unit  80  is driven and controlled such that the full-latch state is achieved, as shown in  FIG. 7 . At this time, the first projecting portion  226 A of the interposed member  200  is nipped between the securing members  47  and the fixing roller  32  (not shown). Furthermore, when the image forming apparatus  10  is in a stand-by state, or when a paper jam occurs, the cam unit  80  is driven and controlled such that the unlatched state is achieved. At this time, the third projecting portion  226 E of the interposed member  200  is nipped between the securing members  47  and the fixing roller  32  (not shown). 
     Thus, the description of the fixing operation in this exemplary embodiment has been completed. 
     Advantage 
     The advantages of this exemplary embodiment advantage are the same as those (the first, second, and third advantages) of the first exemplary embodiment. 
     Thus, the description of the advantages of this exemplary embodiment, as well as the description of the second exemplary embodiment, has been completed. 
     Although the present invention has been described by taking specific exemplary embodiments as examples, the present invention is not limited to the exemplary embodiments described above. For example, the following embodiments are also included in the technical scope of the present invention. 
     For example, in the above-described exemplary embodiments, it has been described that the separating baffle  46  is disposed at the distance d from the outer circumferential surface of the fixing roller  32 . However, the fixing roller  32  and the pressure belt  34  may be exchanged, and the separating baffle  46  may be disposed at the distance d from the outer circumferential surface of the pressure belt  34 . In this modification (not shown), the fixing roller  32  is an example of the second rotational member, and the pressure belt  34  is an example of the second rotational member. 
     Furthermore, in the above-described exemplary embodiments, it has been described that the interposed members  100  and  200  are nipped, between the securing members  47  and the fixing roller  32  at any of the three portions having different thicknesses. Hence, in the above-described exemplary embodiments, it has been described that there are three latch states, namely, the full-latch state, the half-latch state, and the unlatched state. However, the configurations in which the interposed members  100  and  200  are nipped at any of the three portions having different thicknesses are merely examples, and the interposed members  100  and  200  may be nipped at two or four portions having different thicknesses. Furthermore, as shown in a modification illustrated in  FIG. 8 , the orientation of the interposed members  100  in the thickness direction may be reversed. Moreover, as shown in another modification illustrated in  FIG. 9 , the thickness of a portion of the interposed member  100  nipped between the securing member  47  and the fixing roller  32  may be gradually increased from one end to the other end. In this configuration, the portion to be nipped, which is gradually increased in thickness, may be regarded as being formed of multiple portions having different thicknesses. 
     In the above-described exemplary embodiments, the fixing devices  30  and  30 A have been described as examples of a transport device. However, the transport device may be applied to a device other than the fixing device, as long as the device has a configuration in which an interposed member is (rotatably) supported by a pressure member, includes multiple portions having different thicknesses, and is nipped between a first rotational member and a separating member at any one of the portions having different thicknesses, in accordance with the rotation (movement) of the pressure member. Examples of the transport device include a decurler for decurling the sheet P and a dryer constituting an ink jet recording apparatus. 
     In the description of the fourth advantage of the first exemplary embodiment, it has been described that the first exemplary embodiment has an advantage over, for example, the fourth comparison example in that the distance d is less likely to be changed. However, the configuration as in the fourth comparison example, in which the fixing roller  32  is in contact with the interposed members  100  at the outer circumferential surface of the rubber layer  32 B (see  FIG. 2 ), is superior to the configuration as in the first exemplary embodiment, in which the fixing roller  32  is in contact with the interposed members  100  at the outer circumferential surface  32 A 1  of the core  32 A (see  FIG. 10 ), in the following point: because, when the rubber layer  32 B is thermally expanded due to long-term use of the fixing device  30 , the position of the guide member  40  needs to be adjusted, taking into consideration the amount expanded; the fourth comparison example, unlike the first exemplary embodiment, enables the position of the guide member  40  to be adjusted, by taking into consideration the amount expanded. 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.