Abstract:
There is provided a transfer device that is used for transferring a developer image hold on a surface of an image supporting body to a first face of a transfer member transported and includes a transfer member that includes a conductive surface layer that is rotatable around a first rotation axis and be elastically transformed, forms a second contact area, which differs from the first contact area in a transporting direction of the transfer member, by contacting with a second face of the transfer member, and is supplied with a transfer voltage used for transferring the developer image onto the first face of the transfer member, a transformation unit that elastically transforms the transfer member, and an adjustment unit that adjusts a shape of the second contact area by adjusting the degree of elastic transformation of the transfer member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2011-194029 filed Sep. 6, 2011. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a transfer device and an image forming apparatus. 
     SUMMARY 
     According to an aspect of the invention, there is provided a transfer device that is used for transferring a developer image hold on a surface of an image supporting body to a first face of a transfer member transported from an upstream side toward a downstream side, and the surface of the image supporting body and the transfer member are brought into contact with each other in a first contact area located on the first face, the transfer device including: a transfer member that includes a conductive surface layer that is rotatable around a first rotation axis and is elastically transformed, the transfer member having a second contact area that contacts with a second face of the transfer member, the second face being an opposite side of the transfer member to the first face, a transfer voltage which is used for transferring the developer image onto the first face of the transfer member being applied to the conductive surface layer, wherein the first contact area and the second contact area are located at different positions in a transporting direction of the transfer member; a transformation unit that transforms the transfer member elastically; and an adjustment unit that adjusts a shape of the second contact area by adjusting the degree of elastic transformation of the transfer 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 configuration diagram illustrating the entire configuration of an image forming apparatus according to a first exemplary embodiment of the present invention; 
         FIG. 2  is a configuration diagram of an image forming section and a primary transfer unit according to the first exemplary embodiment of the present invention; 
         FIG. 3A  is a configuration diagram of a pressing section according to the first exemplary embodiment of the present invention; 
         FIG. 3B  is a schematic diagram illustrating a contact position between a primary transfer roll and a shape adjusting roll according to the first exemplary embodiment of the present invention; 
         FIGS. 4A and 4B  are a plan view and a cross-sectional view of the primary transfer unit according to the first exemplary embodiment of the present invention, viewed in a direction perpendicular to the pressing direction of the shape adjusting roll; 
         FIG. 5A  is a schematic diagram illustrating a state in which the shape adjusting roll according to the first exemplary embodiment of the present invention is pressed in a direction opposite to the Y direction; 
         FIG. 5B  is a schematic diagram illustrating a distance between a first contact part and a second contact part when the shape adjusting roll according to the first exemplary embodiment of the present invention is pressed in the direction opposite to the Y direction; 
         FIG. 6A  is a schematic diagram illustrating a state in which the shape adjusting roll according to the first exemplary embodiment of the present invention is pressed in the Z direction; 
         FIG. 6B  is a schematic diagram illustrating a distance between the first contact part and the second contact part when the shape adjusting roll according to the first exemplary embodiment of the present invention is pressed in the Z direction. 
         FIG. 7A  is a schematic diagram illustrating a cylinder-shaped primary transfer roll according to the first exemplary embodiment of the present invention; 
         FIG. 7B  is a schematic diagram illustrating a distance between the first contact part and the second contact part when the shape adjusting roll according to the first exemplary embodiment of the present invention is pressed; 
         FIG. 8A  is a schematic diagram illustrating a hand drum-shaped primary transfer roll according to the first exemplary embodiment of the present invention; 
         FIG. 8B  is a schematic diagram illustrating a distance between the first contact part and the second contact part when the shape adjusting roll according to the first exemplary embodiment of the present invention is pressed; 
         FIG. 9A  is a schematic diagram illustrating a reverse hand drum-shaped primary transfer roll according to the first exemplary embodiment of the present invention; 
         FIG. 9B  is a schematic diagram illustrating a distance between the first contact part and the second contact part when the shape adjusting roll according to the first exemplary embodiment of the present invention is pressed; 
         FIG. 10A  is a schematic diagram illustrating an asymmetric-shaped primary transfer roll according to the first exemplary embodiment of the present invention; 
         FIG. 10B  is a schematic diagram illustrating a distance between the first contact part and the second contact part when the shape adjusting roll according to the first exemplary embodiment of the present invention is pressed; 
         FIG. 11A  is a schematic diagram illustrating a current flowing from the first contact part to the second contact part according to the first exemplary embodiment of the present invention; 
         FIG. 11B  is a graph illustrating a change in the transfer efficiency with respect to the current; 
         FIG. 12  is a configuration diagram of a pressing section according to a second exemplary embodiment of the present invention; 
         FIG. 13  is a configuration diagram of a pressing section according to a modified example of the first and second exemplary embodiments of the present invention; 
         FIG. 14  is a configuration diagram of an image forming section and a primary transfer unit according to a third exemplary embodiment of the present invention; and 
         FIGS. 15A and 15B  are schematic diagrams illustrating a state in which a transfer current flows when primary transfer is performed by applying a voltage to the shape adjusting roll according to the third exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Examples of a transfer device and an image forming apparatus according to a first exemplary embodiment of the present invention will be described. 
       FIG. 1  illustrates an image forming apparatus  10  as the first exemplary embodiment. The image forming apparatus  10  includes an enclosure housing  12  as an apparatus main body. Inside the enclosure housing  12 , an intermediate transfer belt  14  as an example of a cylinder-shaped transfer member that revolves and moves in the direction of arrow A (the counterclockwise direction illustrated in the figure), plural image forming sections  20 Y,  20 M,  20 C, and  20 K arranged along the rotation direction of the intermediate transfer belt  14 , primary transfer units  40 Y,  40 M,  40 C, and  40 K as examples of a transfer device, which will be described later, disposed on the inner side of the intermediate transfer belt  14  in correspondence with the image forming sections  20 Y,  20 M,  20 C, and  20 K, and a main control section  16  that controls each section of the image forming apparatus  10  are included. 
     The image forming section  20 Y is configured to include: a photoreceptor  22 Y that has a cylinder shape, rotates in the direction (the clockwise direction illustrated in the figure) of arrow R, and supports a developer image (toner image) on the outer circumferential face thereof as an example of an image supporting member; a charging roll  24 Y that charges the outer circumferential face of the photoreceptor  22 Y; an exposure unit  26 Y that forms an electrostatic latent image on the photoreceptor  22 Y by exposing the charged outer circumferential face of the photoreceptor  22 Y by using exposure light LY modulated based on image information of a Y color (yellow color); an image forming control section  27 Y that controls the operation of the exposure unit  26 Y; and a developer unit  32 Y as an example of a developer image forming unit that includes a developing roll  28 Y supporting Y color developer (toner) and forms a toner image (Y color) by developing the electrostatic latent image formed on the photoreceptor  22 Y by using Y-color toner. In addition, at a position facing the outer circumferential face of the photoreceptor  22 Y, a charge remover that removes electric charge remaining on the surface of the photoreceptor  22 Y after the primary transfer of the toner image is disposed, which is not illustrated in the figure. 
     Here, the image forming sections  20 M,  20 C, and  20 K are different from the image forming section  20 Y only in the color of toner, and the other configurations thereof are the same as those of the image forming section  20 Y. Thus subscripts M (magenta), C (cyan), and K (black) representing the toner colors are assigned to the ends of reference numerals of the members so as to be distinguishable from one another, and the description thereof will not be presented. In addition, in the description presented below, when the members do not need to be distinguished by the toner colors (Y, M, C, and K), a reference numeral not having each one of the subscript Y, M, C, or K may be used in description. 
     Print data including image data of an image to be formed on recording paper P is input to the main control section  16  through an input/output section (not illustrated in the figure). Then, after being decomposed into image information of each color (Y, M, C, and K) by the main control section  16 , the print data is output to the image forming control sections  27 Y,  27 M,  27 C, and  27 K corresponding to each color. In addition, under the control of the image forming control section  27 , the exposure unit  26  of each image forming section  20  is controlled so as to modulate the exposure light L. Furthermore, the units and sections disposed in the image forming apparatus  10  are electrically connected to the main control section  16 . 
     The intermediate transfer belt  14 , for example, is a cylinder-shaped member formed from a polyimide resin as its main ingredient and includes carbon black as a conducting agent, and the surface resistivity thereof is adjusted to 9 to 12 log Ω/□. On the inner side of the intermediate transfer belt  14 , sequentially from the upstream side toward the downstream side in the direction of arrow A, a driving roll  34 , primary transfer rolls  42 Y,  42 M,  42 C, and  42 K to be described later, a tensile strength applying roll  36  that applies tensile strength to the intermediate transfer belt  14 , a support roll  35  that supports the intermediate transfer belt  14  from the inner side, and a backup roll  38  that is arranged at a secondary transfer position are disposed so as to be rotatable. The intermediate transfer belt  14  is supported by being wound around the driving roll  34 , the primary transfer rolls  42 Y,  42 M,  42 C, and  42 K, the tensile strength applying roll  36 , the support roll  35 , and the backup roll  38  and is revolved and moved in the direction of arrow A by driving the driving roll  34  so as to rotate by using a driving unit (not illustrated in the figure). 
     In addition, on the outer side of the intermediate transfer belt  14 , a belt cleaner  15  that is brought into contact with the intermediate transfer belt  14  so as to clean the surface thereof is disposed. Furthermore, on a side opposite to the backup roll  38  from the intermediate transfer belt  14 , a secondary transfer roll  41  that transfers the toner image formed on the intermediate transfer belt  14  to the recording paper P is disposed. The secondary transfer roll  41  is connected to a voltage applying unit (not illustrated in the figure) and is applied with a voltage of the polarity that is opposite to that of the toner and transfers the toner image to the recording paper P in accordance with an electric potential difference between the backup roll  38  and the secondary transfer roll  41 . 
     On the lower side of the intermediate transfer belt  14  in the lower portion of the inside of the enclosure housing  12 , a box-shaped storage section  17  in which the recording paper P is stored is disposed. In the storage section  17 , a feed roll  17 A that feeds out the recording paper P one sheet at a time is disposed to be rotatable on the upper side near the secondary transfer roll  41 . In addition, inside the enclosure housing  12 , a sheet transport path  19  that is connected from the feed roll  17 A to the upper face of the enclosure housing through the secondary transfer roll  41  is disposed. Furthermore, on the downstream side of the secondary transfer roll  41  in the transporting direction of the recording paper P in the sheet transport path  19 , a fixing section  30  that fixes the toner image transferred to the recording sheet P is disposed. 
     The fixing section  30  includes a fixing roll  31 A that is arranged on the toner-image face side of the recording paper P and includes an internal heat source and a pressing roll  31 B that presses the recording paper P toward the fixing roll  31 A. As the recording paper P enters a contact part (nip part) between the fixing roll  31 A and the pressing roll  31 B and is heated and pressed, the toner image is fixed to the recording paper P. 
     Next, the primary transfer unit  40  will be described. 
     As illustrated in  FIG. 2 , the primary transfer unit  40  is configured to include: a primary transfer roll  42  as an example of a transfer member that is supported to be rotatable by a bearing  54  (see  FIG. 3A ) to be described later and has an outer circumferential face being brought into contact with an inner circumferential face of the intermediate transfer belt  14 ; and a shape adjusting section  44  as an example of a shape adjusting unit that adjusts the shape of the primary transfer roll  42 . 
     In the description presented below, the axial direction of the primary transfer roll  42  will be described as the X direction, a direction that is perpendicular to the X direction and is parallel to the moving direction (the direction of arrow A) of the intermediate transfer belt  14  will be described as the Y direction, and a direction that is perpendicular to the X direction and the Y direction will be described as the Z direction. In addition, a first contact part between the photoreceptor  22  and the intermediate transfer belt  14  in the Y-Z plane is denoted by PA, and a second contact part between the intermediate transfer belt  14  and the primary transfer belt  42  is denoted by PB. Furthermore, the contact width of the contact part PB between the intermediate transfer belt  14  and the primary transfer roll  42  in the Y direction is denoted by N. In this exemplary embodiment, to be described later, since the surface of the photoreceptor is a rigid body, the contact width of the first contact part PA is commonly narrower than that of the contact part PB between the primary transfer roll  42  having an elastic surface layer and the intermediate transfer belt  14 . Accordingly, the contact width of the contact part PA is not illustrated in the figure. However, as long as the photoreceptor and the intermediate transfer belt are brought into contact with each other, it is apparent that there is a contact width to some extent. 
     The primary transfer roll  42 , for example, is a roll member in which the outer circumferential face of a core  42 A made of stainless steel (SUS) is coated with a urethane foam  42 B containing an ion conducting agent. In addition, the primary transfer roll  42  is disposed to be rotatable on the downstream side of the first contact part PA in the transporting direction (the direction of arrow A) of the intermediate transfer belt  14  and is brought into contact with a face of the intermediate transfer belt  14  that is on the opposite side of the photoreceptor  22  so as to form the second contact part PB. 
     In addition, the core  42 A of the primary transfer roll  42  is electrically connected to the photoreceptor  22  through a voltage applying section  48  as an example of a voltage applying unit. For example, the inner side of the photoreceptor  22  is grounded, and a voltage having a positive polarity that is opposite to the polarity (for example, the negative polarity) of the toner is applied to the core  42 A by the voltage applying section  48 . Accordingly, there is a difference of an electric potential between the electric potential of the photoreceptor  22  and the electric potential of the primary transfer roll  42 . Then, in accordance with the action of an electric field formed based on the electric potential difference, the toner (toner image) hold in the photoreceptor  22  is transferred to the intermediate transfer belt  14 . 
     Furthermore, the shape adjusting section  44  includes a shape adjusting roll  46  as an example of a shape adjusting member that is disposed to be rotatable with having the X direction as its axial direction and is brought into contact with the outer circumferential face of the primary transfer roll  42  and pressing parts  50 A and  50 B (see  FIG. 3A ) as examples of pressing units that independently press the one end and the other end of the shape adjusting roll  46  in the X direction toward the primary transfer roll  42 . 
     The shape adjusting roll  46  is formed from a cylinder-shaped stainless steel (SUS) having the same cross-section in the X-Z plane in the X direction and has the length in the X direction to be in the level similar to the length of the core  42 A of the primary transfer roll  42 . In addition, one end (the front side in the figure) and the other end (the rear side in the figure) of the shape adjusting roll  46  in the X direction are supported to be rotatable by one set of bearings  56  (see  FIG. 3A ) to be described later. 
     As illustrated in  FIG. 4A , the pressing part  50 A is disposed at one end of each of the primary transfer roll  42  and the shape adjusting roll  46 , and the pressing part  50 B is disposed at the other end of each of the primary transfer roll  42  and the shape adjusting roll  46 . In addition, since the members that configure the pressing part  50 A and the members that configure the pressing part  50 B have similar configurations, in the description below, while the pressing part  50 A will be described, the description of the pressing part  50 B will not be presented. 
     As illustrated in  FIG. 3A , the pressing part  50 A is configured to include: a holder  52  as an example of a support member that integrally supports one end of the primary transfer roll  42  and one end of the shape adjusting roll  46 ; a first bearing  54  into which one end of the primary transfer roll  42  is inserted; a second bearing  56  into which one end of the shape adjusting roll  46  is inserted; and a position adjusting screw  58  that urges the second bearing  56  toward the first bearing  54 . 
     The holder  52  is a plate having the X direction as its thickness direction and has a circular through hole  52 A that passes through it in the X direction at one end in the longitudinal direction, a rectangular opening portion  52 B that passes through it in the X direction at the other end in the longitudinal direction, and a screw hole  52 C that passes through it from the other end side in the longitudinal direction toward the inside of the opening portion  52 B formed therein. The first bearing  54  is fitted into the through hole  52 A so as to be fixed. 
     In the opening portion  52 B, the outer circumferential face of the second bearing  56  is brought into contact with one set of inner walls  52 D corresponding to the longer side of the rectangle. In addition, on the front side and the rear side of the inner wall  52 D in the X direction, a plate-shaped stopper member (not illustrated in the figure) is disposed so as to bypass the shape adjusting roll  46 , thereby preventing the second bearing  56  from being disengaged from the opening portion  52 B. 
     In addition, the position adjusting screw  58  is screwed into the screw hole  52 C of the holder  52 , and the lead edge portion of the position adjusting screw  58  is brought into contact with the outer circumferential face of the second bearing  56 . Accordingly, when the position adjusting screw  58  is turned in an advancing direction, the second bearing  56  is slid along the inner wall  52 D in the direction (a direction in which the second bearing  56  approaches the first bearing  54 ) of arrow +G. On the other hand, when the position adjusting screw  58  is turned in a retreating direction, the second bearing  56  is slid along the inner wall  52 D in the direction (a direction in which the second bearing  56  is separated away from the first bearing  54 ) of arrow −G. Here, since the pressing parts  50 A and  50 B are independent from each other, an inter-axial distance (corresponding to a segment OQ illustrated in  FIG. 3B ) between the primary transfer roll  42  and the shape adjusting roll  46  is configured to be independently adjusted. 
     In  FIG. 3B , a schematic diagram is shown which illustrates a contact position of the shape adjusting roll  46  in the primary transfer roll  42 . In  FIG. 3B , the position of the rotation center of the primary transfer roll  42  is denoted by a point O, and the position of the rotation center of the shape adjusting roll  46  is denoted by a point Q. In addition, a straight line that passes though the point O and is parallel to the Z direction is denoted by L 1 , and a straight line that passes through the point O and the point Q is denoted by L 2 . The extending direction of the straight line L 2  coincides with the direction of arrow +G and the direction of arrow −G. 
     An angle θ (the acute angle side) of the straight line L 2  with respect to the straight line L 1  is set as 0°≦θ≦90°, and θ=75° in this exemplary embodiment. In other words, the shape adjusting roll  46  is arranged on the side lower than the point O that is the position of the rotation center of the primary transfer roll  42  and at a position that allows the second contact part PB to approach the first contact part PA (see  FIG. 2 ) when it is pressed by the pressing parts  50 A and  50 B (see  FIG. 3A ). 
     Next, an image forming process of the image forming apparatus  10  will be described. 
     In the image forming apparatus  10 , when print data including image data of an image to be formed on recording paper P is input to the main control section  16 , the print data is decomposed into image information of each color (Y, M, C, and K) by the main control section  16  and is output to the image forming control sections  27  corresponding to each color. Then, under the control of the image forming control sections  27 , the exposure unit  26  of each image forming section  20  is controlled so as to modulate exposure light L corresponding to each color. Then, the modulated exposure light L is emitted to the surface of the photoreceptor  22  that is charged by the charging roll  24 . By emitting the exposure light L to the surface of each photoreceptor  22  as above, an electrostatic latent image corresponding to the image information of a corresponding color is formed on each photoreceptor  22 . 
     Subsequently, the electrostatic latent image formed on each photoreceptor  22  is developed using toner by each developer  32 , whereby a toner image is formed on each photoreceptor  22 . Then, the toner images formed on the photoreceptors  22  are sequentially primary transferred on the outer circumferential face of the intermediate transfer belt  14  by the primary transfer unit  40 . In addition, attached materials such as residual toner attached to the surface of each photoreceptor  22  for which the primary transfer has been completed are removed by a cleaning unit (not illustrated in the figure), and the residual charge is removed, and residual electric charge is removed, for example, by the charge remover (not illustrated in the figure) that emits light to the photoreceptor  22 . 
     The toner images overlapped with one another on the outer circumferential face of the intermediate transfer belt  14  through the primary transfer are transported to the secondary transfer roll  41  in accordance with the movement of the intermediate transfer belt  14 . Then, the toner images are secondarily transferred to the recording paper P transported from the storage section  17  by the secondary transfer roll  41 . In addition, the toner images that have been secondarily transferred to the recording paper P are fixed on the recording sheet  9  by the fixing section  30 . The recording paper P on which the toner images are fixed as above is discharged to the upper face of the enclosure housing  12 . 
     Next, the operation of the first exemplary embodiment will be described. 
     First, a distance between the first contact part PA and the second contact part PB when the shape adjusting roll  46  is pressed to the primary transfer roll  42  by the pressing parts  50 A and  50 B and a difference between the width of the center portion of the second contact part PB in the axial direction and the widths of both end portions thereof will be described. 
     When the angle θ that represents the arrangement of the shape adjusting roll  46  is 90°, as illustrated in  FIG. 5A , the shape adjusting roll  46  presses the primary transfer roll  42  in a direction (the direction approaching the photoreceptor  22  side) opposite to the Y direction. Here, the core  42 A (see  FIG. 3A ) of the primary transfer roll  42  is supported on both end portions in the axial direction (the X direction) but is not supported at the center portion. Accordingly, when an external force is applied to the outer circumferential face of the primary transfer roll  42 , the center portion is deformed in the applying direction of the external force more than the both end portions. 
     Accordingly, as illustrated in  FIG. 5B , the center portion of the second contact part is moved in a direction (the first contact part PA side) opposite to the Y direction. Thus, a difference between a separation distance Δd 1  between the downstream-side end portion PAb (denoted by a straight line) of the first contact part PA and the upstream-side end portion PBa (denoted by a curve) of the second contact part PB in the center portion of the primary transfer roll  42  (see  FIG. 5A ) in the axial direction and separation distances Δd 2  and Δd 3  between the downstream-side end portion PAb of the first contact part PA and the upstream-side end portion PBa of the second contact part PB in both end portions in the axial direction decreases. 
     In this manner, when the angle θ is 90°, the shape adjusting roll  46  moves the center portion of the upstream-side end portion PBa of the second contact part PB in the axial direction to be close to the downstream-side end portion PAb of the first contact part PA, so that a separation distance between the downstream-side end portion PAb of the first contact part PA and the upstream-side end portion PBa of the second contact part PB is at the same level in the axial direction. Here, the reason for forming the contact area of the second contact part PB in the intermediate transfer belt  14  in a hand drum shape as illustrated in  FIG. 5B  is that the center portion of the primary transfer roll  42  is not supported as described above, and the contact pressure between the intermediate transfer belt  14  and the primary transfer roll  42  in the center portion in the axial direction is lower than the contact pressure between the intermediate transfer belt  14  and the primary transfer roll  42  in each end portion in the axial direction. 
     On the other hand, when the angle θ illustrating the arrangement of the shape adjusting roll  46  is 0°, as illustrated in  FIG. 6A , the shape adjusting roll  46  presses the primary transfer roll  42  in the Z direction (the direction approaching the intermediate transfer belt  14 ). 
     Accordingly, as illustrated in  FIG. 6B , as the width N of the second contact part PB in the Y direction, all the width N 1  of the center portion in the axial direction and the widths N 2  and N 3  of both end portions increase. In addition, the external force applied to the primary transfer roll  42  by the shape adjusting roll  46  is only in the Z direction, but there is no component in a direction opposite to the Y direction, whereby there is no change in the above-described difference between the separation distance Δd 1  and the separation distances Δd 2  and Δd 3 . As above, when the angle θ is 0°, the shape adjusting roll  46  increases the width of the second contact part PB in the Y direction in the center portion and both end portions in the axial direction. 
     On the other hand, as illustrated in  FIG. 3B , when the angle θ=75°, an external force F in the direction of arrow +G direction acts on the primary transfer roll  42  from the shape adjusting roll  46 , and the external force F is decomposed into a component force F 1  in a direction opposite to the Y direction and a component force F 2  in the Z direction. In other words, when the angle θ is more than 0° and less than 90°, the component force F 1  in the direction opposite to the Y direction and the component force F 2  in the Z direction act on the primary transfer roll  42 . Accordingly, the above-described difference between the separation distance Δd 1  and the separation distances Δd 2  and Δd 3  is decreased, and the width of the second contact part PB in the Y direction increases in the center portion and both end portions in the axial direction. 
     As illustrated in  FIG. 7A , in the case of the primary transfer roll  42  having the same external form in the X direction, as illustrated in  FIG. 7B , the separation distance Δd 1  between the downstream-side end portion PAb of the first contact part PA and the upstream-side end portion PBa of the second contact part PB in the center portion of the primary transfer roll  42  (see  FIG. 7A ) in the axial direction and separation distances Δd 2  and Δd 3  between the downstream-side end portion PAb of the first contact part PA and the upstream-side end portion PBa of the second contact part PB in both end portions in the axial direction are at the same level. In addition, as illustrated in  FIG. 4A , the amount of intrusion of the shape adjusting roll  46  into the primary transfer roll  42  according to the pressing part  50 A and the amount of intrusion of the shape adjusting roll  46  into the primary transfer roll  42  according to the pressing part  50 B are assumed to be the same. 
     In addition, as the width N of the second contact part PB in the Y direction, the width N 1  of the center portion and the widths N 2  and N 3  of both end portions in the axial direction are at the same level. Here, broken lines represent the shape of the second contact part PB in a case where the shape adjusting roll  46  (see  FIG. 3A ) is not used. As above, by using the shape adjusting roll  46 , compared to a case where the shape adjusting roll  46  is not used, the difference between the separation distance Δd 1  and the separation distances Δd 2  and Δd 3  is decreased, and the difference between the width N 1  of the center portion and the widths N 2  and N 3  of both end portions of the second contact part PB is decreased. 
     As illustrated in  FIG. 8A , in the case of the primary transfer roll  43  having an external form of a hand drum shape in which the center portion is thinner than both end portions, as illustrated in  FIG. 8B , the separation distance Δd 1  at the center portion of the primary transfer roll  43  (see  FIG. 8A ) in the axial direction is slightly shorter than the separation distances Δd 2  and Δd 3  at both end portions in the axial direction. In addition, as the width N of the second contact part PB in the Y direction, the width N 1  of the center portion in the axial direction is slightly shorter than the widths N 2  and N 3  of both end portions. 
     As above, even in a case where the primary transfer roll  43  has a hand drum shape, by using the shape adjusting roll  46 , compared to the configuration in which the shape adjusting roll  46  is not used, the difference between the separation distances Δd 1  and the separation distances Δd 2  and Δd 3  is decreased, and the difference between the width N 1  of the center portion and the widths N 2  and N 3  of both end portions of the second contact part PB is decreased. In  FIG. 8B , broken lines represent the shape of the second contact part PB in a case where the shape adjusting roll  46  (see  FIG. 3A ) is not used. In addition, as illustrated in  FIG. 8A , the primary transfer roll  43  is a roll member in which the outer circumferential face of the core  42 A is coated with a urethane foam  43 A containing an ion conducting agent. Furthermore, the amount of intrusion of the shape adjusting roll  46  into the primary transfer roll  43  according to the pressing part  50 A (see  FIG. 4A ) and the amount of protrusion of the shape adjusting roll  46  into the primary transfer roll  43  according to the pressing part  50 B (see  FIG. 4A ) are assumed to be the same. 
     As illustrated in  FIG. 9A , in the case of the primary transfer roll  45  having an external form of a reverse hand drum shape in which the center portion is thicker than both end portions, as illustrated in  FIG. 9B , the separation distance Δd 1  at the center portion of the primary transfer roll  45  (see  FIG. 8A ) in the axial direction is slightly longer than the separation distances Δd 2  and Δd 3  at both end portions in the axis direction. In addition, as the width N of the second contact part PB in the Y direction, the width N 1  of the center portion in the axial direction is slightly longer than the widths N 2  and N 3  of both end portions. 
     As above, even in a case where the primary transfer roll  45  has a reverse hand drum shape, by using the shape adjusting roll  46 , compared to the configuration in which the shape adjusting roll  46  is not used, the difference between the separation distances Δd 1  and the separation distances Δd 2  and Δd 3  is decreased, and the difference between the width N 1  of the center portion and the widths N 2  and N 3  of both end portions of the second contact part PB is decreased. In  FIG. 9B , broken lines represent the shape of the second contact part PB in a case where the shape adjusting roll  46  (see  FIG. 3A ) is not used. In addition, as illustrated in  FIG. 9A , the primary transfer roll  45  is a roll member in which the outer circumferential face of the core  42 A is coated with a urethane foam  45 A containing an ion conducting agent. Furthermore, the amount of intrusion of the shape adjusting roll  46  into the primary transfer roll  45  according to the pressing part  50 A (see  FIG. 4A ) and the amount of intrusion of the shape adjusting roll  46  into the primary transfer roll  45  according to the pressing part  50 B (see  FIG. 4A ) are assumed to be the same. 
     On the other hand, as illustrated in  FIG. 10A , in the case of a primary transfer roll  47  having different external forms on the pressing part  50 A side and the pressing part  50 B side in the axial direction (the X direction), the pressing part  50 A or the pressing part  50 B is independently adjusted, and the amount of intrusion of any one of the shape adjusting roll  46  into the primary transfer roll  47  is increased or decreased. Accordingly, as illustrated in  FIG. 10B , a difference between the separation distance Δd 1  at the center portion of the primary transfer roll  47  (see  FIG. 10A ) in the axial direction and the separation distances Δd 2  and Δd 3  at both end portions in the axial direction is decreased. In addition, regarding the width N of the second contact part PB in the Y direction, a difference between the width N 1  of the center portion in the axial direction and the widths N 2  and N 3  of both end portions is decreased. Furthermore, as illustrated in  FIG. 10A , the primary transfer roll  47  is a roll member in which the outer circumferential face of the core  42 A is coated with a urethane foam  47 A containing an ion conducting agent. 
     Next, a difference in the transfer current flowing from the primary transfer roll  42  to the photoreceptor  22  through the intermediate transfer belt  14  depending on the presence of the shape adjusting roll  46  will be described. 
     As a comparative example, in a case where the shape adjusting roll  46  is not used, as denoted by broken lines in  FIG. 11A , the width of the center portion of the second contact part PB in the Y direction is shorter than the width of both end portions in the Y direction. In other words, a distance between the upstream-side end portion PBa of the second contact part PB in the Y direction and the downstream-side end portion PAb of the first contact part PA at the center portion is longer than that at both end portions. 
     The electrical resistance of the intermediate transfer belt  14  is not zero, and thus, as the length of the path of a current (transfer current) flowing through the intermediate transfer belt  14  is increased, a current arriving at the photoreceptor  22  (see  FIG. 2 ) decreases. Accordingly, in the comparative example, when a current I applied to the core  42 A (see  FIG. 3A ) of the primary transfer roll  42  flows as a current i 4  at the center portion of the second contact part PB and flows as currents i 5  and i 6  at both end portions, i 4 &lt;i 5  and i 4 &lt;i 6 . 
     In  FIG. 11B , as an example, the relation between the current I applied to the primary transfer roll  42  when a solid image is formed and the transfer efficiency K of toner (the ratio of the amount of toner transferred to the intermediate transfer belt  14  with respect to the amount of toner disposed on the photoreceptor  22  as 100%) is represented as a graph. In the graph illustrated in  FIG. 11B , assuming that an excessive current I does not flow (a current over the apex of the graph is not applied), when the transfer efficiency at a current I 1  is denoted by K 1 , and the transfer efficiency at a current I 2  is denoted by K 2 , if I 1 &lt;I 2 , K 1 &lt;K 2 . In other words, as the current I is decreased, the transfer efficiency K decreases. 
     As illustrated in  FIG. 11B , in the case of not a solid image but a halftone image, the current at which the transfer efficiency in the graph of the halftone image is the maximum is lower than the current at which the transfer efficiency in the graph of the solid image is the maximum. However, in  FIG. 11B , the relation between the current and the transfer efficiency (the relation in the case of a solid image) that is also applicable to a halftone image is represented. 
     Here, as illustrated in  FIG. 11A , in the comparative example, since the current i 4  flowing through the center portion of the second contact part PB is lower than the currents i 5  and i 6  flowing through both end portions thereof, the transfer efficiency K at the center portion is lower than that at both end portions, whereby transfer unevenness (a difference between image densities) occurs. 
     On the other hand, according to this exemplary embodiment, as represented by rectangle-shaped solid lines in  FIG. 11A , a difference between the width of the center portion of the second contact part PB in the Y direction and the width of both end portions in the Y direction is decreased. In other words, the distance between the upstream-side end portion PBa of the second contact part PB in the Y direction and the downstream-side end portion PAb of the first contact part PA is at the same level at the center portion and both end portions. Accordingly, as currents flowing from the second contact part PB to the first contact part PA, the current i 1  flowing through the center portion and the currents i 2  and i 3  flowing through both end portions are at the same level, whereby the transfer unevenness is suppressed. In addition, by suppressing the transfer unevenness, a difference between image densities in the widthwise direction (the X direction) that occurs in accordance with the assembly state of each set decreases. 
     Next, results of measuring differences in the image density depending on the presence/no-presence of the shape adjusting roll  46  will be described. 
     In the measurement described below, as an example, the diameter of the photoreceptor  22  illustrated in  FIG. 2  is set to 84 mm, the outer diameter of the primary transfer roll  42  is set to 28 mm, the outer diameter of the core  42 A is set to 8 mm, and the outer diameter of the shape adjusting roll  46  is set to 10 mm. In addition, the separation distance between the first contact part PA and the center of the second contact part PB is set to 3 mm. As the primary transfer unit  40 , for example, the primary transfer units  40 C and  40 K (see  FIG. 1 ) corresponding to cyan (c) and black (K) are used. 
     In addition, three standards for the primary transfer roll  42  are used which include that there is hardly a difference (the amount of crown) between the outer diameter of a 10 mm end portion from the end-section of the urethane foam  42 B in the X direction and the outer diameter of the center portion (represented as 0.00 mm), the outer diameter of the center portion is smaller than the outer diameter of the end portion by 0.05 mm (represented as −0.05 mm), and the outer diameter of the center portion is larger than the outer diameter of the end portion by 0.05 mm (represented as +0.05 mm). In addition, the contact pressure at the first contact part PA between the photoreceptor  22  and the intermediate transfer belt  14  is set to 280 gf/300 mm. 
     For the evaluation of the image density, a transfer current (a current applied to the primary transfer roll  42 ) is acquired for which each image is output without any problem by outputting test patterns including a line image, a solid image, and a halftone image in advance. Then, in the condition of the transfer current, a pattern is output (printed) in which a monochrome halftone image of 20 mm×20 mm having the input coverage (area ratio) of 30% (entirely exposure halftone image is set as 100%) is arranged on the entire A4-size face of recording paper P (see  FIG. 1 ). 
     In addition, the measurement of the image density was performed by using X-Rite938 manufactured by X-Rite Inc. at a total of three positions including the position of the center portion of the recording paper P and the positions located 20 mm away from both end portions of the recording paper P. Then, an image density difference between the center portion and the right end portion and an image density difference between the center portion and the left end portion are acquired with the image density of the center portion used as a reference and are evaluated as three levels of o, Δ, and x. In the table, o indicates that there is no image density difference (|density difference Δ|≦0.01), Δ indicates that a slight image density difference is checkable (0.01&lt;|density difference Δ|0.025), and x indicates that an image density difference is checkable (0.025&lt;|image density Δ|). Here, the image density is a dimensionless amount. 
     First, results of measuring the image density for a configuration in which the shape adjusting roll  46  is not disposed as a comparative example are presented in Table 1. In the comparative example, for the primary transfer roll  42  having three kinds of the amount of crown, an image density difference is checked in one color of cyan and black. 
     
       
         
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Amount of Crown 
                 0.00 mm 
                 −0.05 mm 
                 +0.05 mm 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Result of Measurement 
                 Difference 
                 Difference 
                 Difference 
               
               
                 of Difference in Image 
                 in Image 
                 in Image 
                 in Image 
               
               
                 Density 
                 Density 
                 Density 
                 Density 
               
             
          
           
               
                 Cyan 
                 Center 
                 X 
                 X 
                 X 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 X 
                 X 
                 X 
               
               
                   
                 Left 
               
               
                 Black 
                 Center 
                 X 
                 X 
                 Δ 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 X 
                 X 
                 X 
               
               
                   
                 left 
               
               
                   
               
             
          
         
       
     
     Next, in the image forming apparatus  10  of this exemplary embodiment illustrated in  FIG. 1 , results of measuring the image density is represented in Table 2. The results represented in Table 2 are results after the amount of intrusion of the shape adjusting roll  46  into the primary transfer roll  42  is adjusted in advance by the pressing parts  50 A and  50 B (see  FIG. 3A ) while the image density is measured in advance. In addition, the contact position of the shape adjusting roll  46  in the primary transfer roll  42  is a position at an angle θ of 75° illustrated in  FIG. 3B . 
     
       
         
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Amount of Crown 
                 0.00 mm 
                 −0.05 mm 
                 +0.05 mm 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Result of Measurement 
                 Difference 
                 Difference 
                 Difference 
               
               
                 of Difference in Image 
                 in Image 
                 in Image 
                 in Image 
               
               
                 Density 
                 Density 
                 Density 
                 Density 
               
             
          
           
               
                 Cyan 
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 Left 
               
               
                 Black 
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 left 
               
               
                   
               
             
          
         
       
     
     As illustrated in Table 2, in the image forming apparatus  10  according to this exemplary embodiment, an image having no image density difference is acquired. The reason for this is thought to be as below. As illustrated in  FIGS. 2 ,  7 B,  8 B, and  9 B, by pressing the shape adjusting roll  46  to the primary transfer roll  42  so as to be intruded therein, the bending due to the weight of the primary transfer roll  42  or a contact of the primary transfer roll  42  with the intermediate transfer belt  14  is corrected, and accordingly, a difference in the separation distance between the downstream end portion PAb of the first contact part PA and the upstream-side end portion PBa of the second contact part PB between the center portion (Δd 1 ) and both end portions (Δd 2  and Δd 3 ) is decreased, and a difference between the width N 1  of the center portion of the second contact part PB and the widths N 2  and N 3  of both end portions is decreased. 
     In addition, as a modified example of this exemplary embodiment, the measurement results of image densities when the contact position of the shape adjusting roll  46  with respect to the primary transfer roll  42  is at a position (see  FIG. 6A ) at which the angle θ is 0° are represented in Table 3. 
     
       
         
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Amount of Crown 
                 0.00 mm 
                 −0.05 mm 
                 +0.05 mm 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Result of Measurement 
                 Difference 
                 Difference 
                 Difference 
               
               
                 of Difference in Image 
                 in Image 
                 in Image 
                 in Image 
               
               
                 Density 
                 Density 
                 Density 
                 Density 
               
             
          
           
               
                 Cyan 
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 Left 
               
               
                 Black 
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 ◯ 
                 Δ 
                 ◯ 
               
               
                   
                 left 
               
               
                   
               
             
          
         
       
     
     As illustrated in Table 3 and  FIG. 6A , it is understood that the difference between the image densities of the center portion and both end portions is decreased by only arranging the shape adjusting roll  46  right below the primary transfer roll  42 . 
     As described above, according to the primary transfer unit  40  of this exemplary embodiment, by adjusting the shape of the primary transfer roll  42  by using the shape adjusting section  44 , regarding a separation distance between the first contact part PA (or the downstream-side end portion PAb of the first contact part PA) and the upstream-side end portion PBa of the second contact part PB, the difference between the separation distance Δd 1  at the center portion of the primary transfer roll  42  in the axial direction (the X direction) and the separation distances Δd 2  and Δd 3  at both end portions is decreased. 
     Accordingly, in the axial direction of the primary transfer roll  42 , a difference between transfer currents flowing from the primary transfer roll  42  to the photoreceptor  22  through the intermediate transfer belt  14  is decreased. Therefore, compared to a configuration in which the primary transfer roll  42  is brought into contact with the intermediate transfer belt  14  without having bending deformation, the difference in the image densities in the center portion and both end portions in the widthwise direction (the X direction) intersecting the transporting direction of the intermediate transfer belt  14  is decreased. 
     In addition, in the primary transfer unit  40 , the width N of the second contact part PB in the Y direction is increased, and the difference between the width N 1  of the center portion and the widths N 2  and N 3  of both end portions in the axial direction is decreased. Accordingly, the contact pressure between the intermediate transfer belt  14  and the primary transfer roll  42  is uniform in the widthwise direction (the axial direction), whereby the bending of the intermediate transfer belt  14  is suppressed. 
     Furthermore, in the primary transfer unit  40 , since the shape adjusting roll  46  is disposed so to be rotatable, the shape adjusting roll  46  rotates in accordance with the rotation of the primary transfer roll  42 . Accordingly, compared to a case where the shape adjusting roll is fixed, the load acting on the primary transfer roll  42  at the time of rotating the primary transfer roll  42  is decreased. 
     In addition, in the primary transfer unit  40 , since the position adjusting screw  58  is capable to directly adjust the axial distance between the shape adjusting roll  46  and the primary transfer roll  42 , compared to a configuration in which the axial distance between the primary transfer roll  42  and the shape adjusting roll  46  is not adjusted, the number of components of the shape adjusting section  44  is decreased. 
     Furthermore, in the primary transfer unit  40 , as illustrated in  FIG. 3B , since the shape adjusting roll  46  is arranged on the side lower than the position (point O) of the rotation center of the primary transfer roll  42  and at a position allowing the primary transfer roll  42  to approach the photoreceptor  22  when it is pressed by the pressing parts  50 A and  50 B, a component force F 1  in the direction opposite to the direction and the component force F 2  in the Z direction act on the primary transfer roll  42 . In addition, the difference between the separation distance Δd 1  of the center portion and the separation distances Δd 2  and Δd 3  of both end portions is decreased, and the width of the second contact part PB in the Y direction increases at the center portion and both end portions in the axial direction. Accordingly, the adjustment of the position of the second contact part PB in the transporting direction of the intermediate transfer belt  14  and the adjustment of the width N of the second contact part PB are simultaneously performed. 
     In addition, in the primary transfer unit  40 , as illustrated in  FIG. 3A , since the holder  52  is included at which the pressing part  50 A ( 50 B) integrally supports the primary transfer roll  42  and the shape adjusting roll  46 , even in a case where the position adjusting screw  58  is turned so as to press the shape adjusting roll  46  to the primary transfer roll  42 , the installation position of the primary transfer roll  42  with respect to the intermediate transfer belt  14  is not displaced. Accordingly, compared to a configuration in which the primary transfer roll  42  and the shape adjusting roll  46  are supported in a separated manner, the misregistration of the reference position (the position at which the shape adjusting roll  46  is pressed toward the rotation center of the primary transfer roll  42 ) at which the intermediate transfer belt  14  and the primary transfer roll  42  are brought into contact with each other due to the positional adjustment of the shape adjusting roll  46  is suppressed. 
     In addition, according to the image forming apparatus  10 , since the primary transfer of the toner image from the photoreceptor  22  to the intermediate transfer belt  14  is performed by each primary transfer unit  40  that includes the shape adjusting section  44 , compared to a configuration in which the primary transfer roll  42  is brought into contact with the intermediate transfer belt  14  without performing bending deformation of the primary transfer roll  42  by using the shape adjusting section  44 , a difference in the image density in the widthwise direction that occurs due to the attachment state of each member decreases. 
     Next, an example of a transfer device and an image forming apparatus according to a second exemplary embodiment of the present invention will be described. The same reference numerals as those of the first exemplary embodiment are assigned to components that are basically the same as those of the first exemplary embodiment, and the description thereof will not be presented. 
       FIG. 12  illustrates a primary transfer unit  70  according to the second exemplary embodiment. The primary transfer unit  70  has a configuration that is acquired by replacing the shape adjusting section  44  with a shape adjusting section  71  as an example of a shape adjusting unit in the primary transfer unit  40  (see  FIG. 3A ) of the image forming apparatus  10  according to the first exemplary embodiment. In addition, the shape adjusting section  71  has a configuration that includes pressing parts  72 A and  72 B, which replaces the pressing parts  50 A and  50 B, as examples of pressing units that press a shape adjusting roll  46  to the primary transfer roll  42  and the shape adjusting roll  46 . The other configurations are similar to those of the first exemplary embodiment. 
     The pressing part  72 A is disposed at one end of the primary transfer roll  42  and the shape adjusting roll  46 , and the pressing part  72 B is disposed at the other end of the primary transfer roll  42  and the shape adjusting roll  46 . In addition, since the members configuring the pressing part  72 A and the members configuring the pressing part  72 B have similar configurations, in the description below, the pressing part  72 A will be described, but the description of the pressing part  72 B will not be presented. 
     The pressing part  72 A is configured to include: a holder  74  as an example of a support member that integrally supports one end of the primary transfer roll  42  and one end of the shape adjusting roll  46 ; a first bearing  54 ; a second bearing  56 ; a plate-shaped bearing holder  76  in which the second bearing  56  is fixed; and an urging spring  77  that urges the bearing holder  76  to the primary transfer roll  42  side; a plate member  78  to which the urging spring  77  is attached; and a pressure adjusting screw  79  that urges the plate member  78 . 
     The holder  74  includes a holder main body  74 A that is a plate member having the X direction as its thickness direction. At one end of the holder main body  74 A in the longitudinal direction, a circular through hole  74 B that passes through in the X direction is formed, and, in the through hole  74 B, the first bearing  54  is fitted so as to be fixed. In addition, in the center portion of the holder main body  74 A, plate-shaped guide rails  74 C and  74 D that are arranged in a direction intersecting the direction of an arrow +G and the direction of an arrow −G with a space interposed therebetween, have the direction of the arrow +G and the direction of the arrow −G as the longitudinal direction thereof, and protrude in the direction of an arrow X are integrally formed. Furthermore, at the other end of the holder main body  74 A, a plate-shaped support part  74 E protruding in the direction of the arrow X is integrally formed. 
     The guide rails  74 C and  74 D are arranged to be parallel to each other, and, on the inner side of the guide rails  74 C and  74 D, the bearing holder  76  and the plate member  78  are fitted so as to be slidable in the direction of the arrow +G or the direction of the arrow −G. In addition, one end of the urging spring  77  is fixed to the bearing holder  76 , and the other end thereof is fixed to the plate member  78 . 
     In addition, in the support part  74 E, a screw hole  74 F passing through the direction of the arrow +G is formed, and, in the screw hole  74 F, the pressure adjusting screw  79  is screwed. Furthermore, the lead edge of the pressure adjusting screw  79  is brought into contact with the other face (the lower side in the figure) of the plate member  78 . 
     Next, the operation of the second exemplary embodiment will be described. 
     As illustrated in  FIG. 12 , when the pressure adjusting screw  79  is turned in the direction of the arrow +G, the plate member  78  is slid along the guide rails  74 C and  74 D in the direction of the arrow +G. Then, depending on the elastic force of the urging spring  77  that is compressed in accordance with the movement of the plate member  78 , the bearing holder  76  is slid in the direction of the arrow +G, and the shape adjusting roll  46  is pressed to the outer circumferential face of the primary transfer roll  42 . 
     On the other hand, when the pressure adjusting screw  79  is turned in a retreating direction toward the direction of the arrow −G, the plate member  78  is slid along the guide rails  74 C and  74 D in the direction of the arrow −G depending on the weight thereof and the elastic force of the urging spring  77 . Then, depending on the elastic force of the urging spring  77  that has been stretched in accordance with the movement of the plate member  78 , the bearing holder  76  is slid in the direction of the arrow −G, and the shape adjusting roll  46  retreats from the outer circumferential face of the primary transfer roll  42 . 
     As above, the primary transfer unit  70  is capable to adjust the pressure by bringing the pressure adjusting screw  79  into contact with the primary transfer roll  42  and the shape adjusting roll  46 . Accordingly, even in a case where the primary transfer roll  42  or the shape adjusting roll  46  is eccentric, the shape adjusting roll  46  is brought into contact with the primary transfer roll  42  in accordance with the elastic force of the urging spring  77 . 
     In addition, according to the primary transfer unit  70 , by adjusting the shape of the primary transfer roll  42  by using the shape adjusting section  71 , as illustrated in  FIG. 7B , regarding a separation distance between the first contact part PA (or the downstream-side end portion PAb of the first contact part PA) and the upstream-side end portion PBa of the second contact part PB, the difference between the separation distance Δd 1  at the center portion of the primary transfer roll  42  in the axial direction (the X direction) and the separation distances Δd 2  and Δd 3  at both end portions is decreased. 
     Accordingly, in the axial direction of the primary transfer roll  42 , a difference between transfer currents flowing from the primary transfer roll  42  and the photoreceptor  22  through the intermediate transfer belt  14  is decreased. Therefore, compared to a configuration in which the primary transfer roll  42  is brought into contact with the intermediate transfer belt  14  without having bending deformation, the difference in the image densities in the center portion and both end portions in the widthwise direction (the X direction) intersecting the transporting direction of the intermediate transfer belt  14  is decreased. 
     In addition, in the primary transfer unit  70 , as illustrated in  FIG. 7B , the width N (N 1 , N 2 , and N 3 ) of the second contact part PB in the Y direction is increased, and the difference between the width N 1  of the center portion and the widths N 2  and N 3  of both end portions in the axial direction is decreased. Accordingly, the contact pressure between the intermediate transfer belt  14  and the primary transfer roll  42  is uniform in the widthwise direction (the axial direction), whereby the bending of the intermediate transfer belt  14  is suppressed. 
     In addition, according to the image forming apparatus  10 , since the primary transfer of the toner image from the photoreceptor  22  to the intermediate transfer belt  14  is performed by each primary transfer unit  70  that includes the shape adjusting section  71 , compared to a configuration in which the primary transfer roll  42  is brought into contact with the intermediate transfer belt  14  without performing bending deformation of the primary transfer roll  42  by using the shape adjusting section  71 , a difference in the image density in the widthwise direction that occurs due to the attachment state of each member decreases. 
     Here,  FIG. 13  illustrates a primary transfer unit  80  as a modified example of the primary transfer unit  40  (see  FIG. 2 ) according to the first exemplary embodiment and the primary transfer unit  70  (see  FIG. 12 ) according to the second exemplary embodiment. 
     The primary transfer unit  80  has a configuration in which a sliding section  90  that slides the primary transfer roll  42  in the +Z direction or the −Z direction and a shape adjusting section  100  as examples of the shape adjusting unit are disposed. The shape adjusting section  100  has a configuration including pressing parts  102 A and  102 B as an example of pressing units that press the shape adjusting roll  46  to the primary transfer roll  42  and a shape adjusting roll  46 . The other configurations are similar to those of the first exemplary embodiment. 
     The sliding section  90  includes a holder  92  that is fixed inside the enclosure housing  12  (see  FIG. 1 ) of the image forming apparatus  10  by using a bracket (not illustrated in the figure). The holder  92  is a plate member having the X direction as its thickness direction, and, in the center portion of the holder  92 , a rectangle-shaped opening portion  92 A that passes through in the X direction is formed. In addition, in the holder  92 , a screw hole  92 B is formed which passes through from the other end side in the longitudinal direction of the holder  92  toward the inside of the opening portion  92 A. 
     In the opening portion  92 A, the outer circumferential face of the first bearing  54  is brought into contact with one set of the inner walls  92 C corresponding to the longer sides of the rectangle. In addition, on the front side and the rear side of the inner wall  92 C in the X direction, a plate shaped stopper member (not illustrated in the figure) is disposed by bypassing the core  42 A, whereby the first bearing  54  is prevented from being disengaged from the opening portion  92 A. 
     In addition, in the screw hole  92 B of the holder  92 , a position adjusting screw  94  is screwed. The lead edge portion of the position adjusting screw  94  is brought into contact with the outer circumferential face of the first bearing  54 . Furthermore, inside the opening portion  92 A, an urging spring  96  having one end attached to the inner wall (reference numeral is not illustrated) of the opening portion  92 A and the other end urging the first bearing  54  in the direction of the arrow −Z is disposed. 
     Accordingly, when the position adjusting screw  94  is turned in an advancing direction, the first bearing  54  is slid along the inner wall  92 C of the opening portion  92 A in the direction (a direction in which the primary transfer roll  42  approaches the intermediate transfer belt  14 ) of the arrow +Z. On the other hand, when the position adjusting screw  94  is turned in a retreating direction, the first bearing  54  is slid along the inner wall  92 C in the direction (a direction in which the primary transfer roll  42  is separated away from the intermediate transfer belt  14 ) of the arrow −Z. 
     The pressing parts  102 A and  102 B include a holder  104  that is supported so as to be rotatable in the direction of an arrow +r or the direction of an arrow −r within the Y-Z plane by using a bracket (not illustrated in the figure) inside the enclosure housing  12  (see  FIG. 1 ) of the image forming apparatus  10 . The holder  104  is a plate member having the X direction as its thickness direction, and, in the center portion of the holder  104 , a rectangle-shaped opening portion  104 A that passes through in the X direction is formed. In addition, in the holder  104 , a screw hole  104 B is formed which passes through from the other end side in the longitudinal direction of the holder  104  toward the inside of the opening portion  104 A. 
     In the opening portion  104 A, the outer circumferential face of the second bearing  56  is brought into contact with one set of the inner walls  104 C corresponding to the longer sides of the rectangle. In addition, on the front side and the rear side of the inner wall  104 C in the X direction, a plate-shaped stopper member (not illustrated in the figure) is disposed by bypassing the shape adjusting roll  46 , whereby the second bearing  56  is prevented from being disengaged from the opening portion  104 A. 
     In addition, in the screw hole  104 B of the holder  104 , the position adjusting screw  106  is screwed, and the lead edge portion of the position adjusting screw  106  is brought into contact with the outer circumferential face of the second bearing  56 . Furthermore, inside the opening portion  104 A, an urging spring  108  having one end attached to the inner wall (reference numeral is not illustrated) of the opening portion  104 A and the other end urging the second bearing  56  in the direction of the arrow −G is disposed. 
     Accordingly, when the position adjusting screw  106  is turned in an advancing direction, the second bearing  56  is slid along the inner wall  104 C of the opening portion  104 A in the direction (a direction in which the shape adjusting roll  46  approaches the primary transfer roll  42 ) of the arrow +G. On the other hand, when the position adjusting screw  106  is turned in a retreating direction, the second bearing  56  is slid along the inner wall  104 C in the direction (a direction in which the shape adjusting roll  46  is separated away from the primary transfer roll  42 ) of the arrow −G. 
     Here, for example, when the position of the primary transfer roll  42  is moved in the direction of the arrow +Z by turning the position adjusting screw  94 , the rotation center of the primary transfer roll  42  is not located on the axis of rotation (not illustrated in the figure) of the position adjusting screw  106 . Accordingly, after the holder  104  is moved in the direction of the arrow −r so as to locate the rotation center of the primary transfer roll  42  on the axis (not illustrated) of rotation of the position adjusting screw  106 , the position adjusting screw  106  is turned. Therefore, even in a case where the position of the primary transfer roll  42  in the direction of the arrow Z changes, the shape adjusting roll  46  is pressed toward the rotation center of the primary transfer roll  42 . 
     As illustrated in Table 4, it may be understood that the difference in the image densities of the center portion and both end portions is decreased even in a case where the primary transfer roll  42  and the shape adjusting roll  46  are configured to be independently supported by different holders  92  and  104 . 
     
       
         
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
               
                   
                 Amount of Crown 
                 0.00 mm 
                 −0.05 mm 
                 +0.05 mm 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Result of Measurement 
                 Difference 
                 Difference 
                 Difference 
               
               
                 of Difference in Image 
                 in Image 
                 in Image 
                 in Image 
               
               
                 Density 
                 Density 
                 Density 
                 Density 
               
             
          
           
               
                 Cyan 
                 Center 
                 ◯ 
                 Δ 
                 ◯ 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 ◯ 
                 Δ 
                 ◯ 
               
               
                   
                 Left 
               
               
                 Black 
                 Center 
                 ◯ 
                 Δ 
                 ◯ 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 Δ 
                 Δ 
                 ◯ 
               
               
                   
                 left 
               
               
                   
               
             
          
         
       
     
     Next, an example of a transfer device and an image forming apparatus according to a third exemplary embodiment of the present invention will be described. The same reference numerals as those of the first and second exemplary embodiments are assigned to components that are basically the same as those of the first and second exemplary embodiments, and the description thereof will not be presented. 
       FIG. 14  illustrates a primary transfer unit  110  according to the third exemplary embodiment. The primary transfer unit  110  has a configuration that is acquired by changing the connection destination of the voltage applying section  48  that is located on a side opposite to the photoreceptor  22  side from the core  42 A of the primary transfer roll  42  to the shape adjusting roll  46  in the primary transfer unit  40  (see  FIG. 3A ) according to the first exemplary embodiment. In addition, the primary transfer roll  42  is in a floating state. The other configurations are similar to those of the first exemplary embodiment. 
     The electrical resistance of the shape adjusting roll  46  is lower than that of the primary transfer roll  42 . In addition, a voltage used for generating an electric potential difference between the photoreceptor  22  and the primary transfer roll  42  is applied to the shape adjusting roll  46  by the voltage applying section  48 . 
     Next, the operation of the third exemplary embodiment will be described. 
     By using the shape adjusting section  44 , as described above, in the axial direction of the primary transfer roll  42 , a difference between transfer currents flowing from the primary transfer roll  42  to the photoreceptor  22  through the intermediate transfer belt  14  is decreased. Therefore, compared to a configuration in which the primary transfer roll  42  is brought into contact with the intermediate transfer belt  14  without having bending deformation, the difference between the image densities of the center portion and both end portions in the widthwise direction (the X direction) intersecting the transporting direction of the intermediate transfer belt  14  is decreased. 
     In addition, according to the image forming apparatus  10 , since the primary transfer of the toner image from the photoreceptor  22  to the intermediate transfer belt  14  is performed by each primary transfer unit  110  that includes the shape adjusting section  44 , compared to a configuration in which the primary transfer roll  42  is brought into contact with the intermediate transfer belt  14  without having bending deformation, a difference in the image density in the widthwise direction that occurs due to the attachment state of each member decreases. 
     As illustrated in  FIG. 15A , in the primary transfer unit  110 , when a voltage is applied to the shape adjusting roll  46  by the voltage applying section  48  in a state in which the shape adjusting roll  46  is brought into contact with the primary transfer roll  42 , near a contact part PC between the shape adjusting roll  46  and the primary transfer roll  42 , a current Ia flows in a direction from the surface (the outer circumferential face) of the primary transfer roll  42  toward the core  42 A. In addition, near the second contact part PB, a current Ia flows from the core  42 A to the surface of the primary transfer roll  42 . At this time, apart of ions J (small circles illustrated in the figure) of the ion conducting agent is eccentrically located (polarized) on the outer circumferential side (the second contact portion PB side). 
     Subsequently, as illustrated in  FIG. 15B , when the primary transfer roll  42  rotates, a portion at which the ions J are eccentrically located inside the primary transfer roll  42  moves to the contact part PC between the shape adjusting roll  46  and the primary transfer roll  42 . Then, the ions J move again toward the core  42 A. As above, the direction of the electric filed is reversed every time the primary transfer roll  42  rotates, and the operation of alternately applying a positive voltage and a negative voltage may be thought to be acquired, whereby the polarization of the primary transfer roll  42  is thought to be suppressed. In addition, since the polarization of the primary transfer roll  42  is suppressed, the increase in the electrical resistance of the primary transfer roll  42  is suppressed. 
     Next, the results of measuring the image densities in the image forming apparatus  10  according to the third exemplary embodiment are illustrated in Table 5. The results of Table 5 are results after the amount of intrusion of the shape adjusting roll  46  into the primary transfer roll  42  is adjusted in advance by the pressing parts  50 A and  50 B (see  FIG. 3A ) when the image density is measured. In addition, the contact position of the shape adjusting roll  46  with respect to the primary transfer roll  42  is the position at which the angle θ illustrated in  FIG. 3B  is 75°. 
     
       
         
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                   
                 Amount of Crown 
                 0.00 mm 
                 −0.05 mm 
                 +0.05 mm 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Result of Measurement 
                 Difference 
                 Difference 
                 Difference 
               
               
                 of Difference in Image 
                 in Image 
                 in Image 
                 in Image 
               
               
                 Density 
                 Density 
                 Density 
                 Density 
               
             
          
           
               
                 Cyan 
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 Left 
               
               
                 Black 
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 Right 
               
               
                   
                 Center 
                 ◯ 
                 ◯ 
                 ◯ 
               
               
                   
                 left 
               
               
                   
               
             
          
         
       
     
     As illustrated in Table 5, also in the image forming apparatus  10  according to the third exemplary embodiment, an image having no image density difference may be acquired. 
     The present invention is not limited to the above-described exemplary embodiments. 
     The primary transfer roll  42  may be disposed on the upstream side of the first contact part PA in the transporting direction of the intermediate transfer belt  14 . In such a case, since the second contact part is located on the upstream side, inter-axis distances Δd 1 , Δd 2 , and Δd 3  are defined between the downstream-side end portion PBb (not illustrated in the figure) of the second contact part and the upstream-side end portion PAa (not illustrated in the figure) of the first contact part, but it is apparent to those skilled in the art that the present invention may be applied to the case similar to a case where the primary transfer roll  42  is located on the downstream side. In addition, in a configuration in which the backup roll  38  and the secondary transfer roll  41  are arranged so as to be deviated from the transporting direction of the intermediate transfer belt  14 , the shape adjusting section  44 ,  71 , or  100  may be used as the secondary transfer roll  41 . In such a case, the intermediate transfer belt  14  is an example of an image supporting member, and the recording paper P is an example of a transfer member. In addition, the shape adjusting section  44 ,  71 , or  100  may be used as the backup roll  38 . 
     In the image forming apparatus  10  according to the third exemplary embodiment, instead of the shape adjusting section  44 , the shape adjusting section  71  may be used. 
     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.