Patent Publication Number: US-9841712-B2

Title: Fixing device, heating member, 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. 2016-018049 filed Feb. 2, 2016. 
     BACKGROUND 
     Technical Field 
     The present invention relates to a fixing device, a heating member, and an image forming apparatus. 
     SUMMARY 
     According to an aspect of the invention, a fixing device includes a belt member that moves in a circulating manner, a pressure member that is disposed to be in contact with an outer circumferential surface of the belt member, and pressurizes a recording material on which an image is formed, and a heating member. The heating member includes a curved portion that is curved along an inner circumferential surface of the belt member and is in contact with the inner circumferential surface, a bent portion that is bent from an upstream side end portion of the curved portion in a moving direction of the belt member and is separated from the inner circumferential surface, and a heat generation portion that is provided in the curved portion, generates heat upon energization, and heats the belt member. A generated heat amount in the curved portion on the upstream side in the moving direction is larger than a generated heat amount in the curved portion on a downstream side in the moving direction. 
    
    
     
       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 view illustrating a configuration of an image forming apparatus according to an exemplary embodiment; 
         FIG. 2  is a view illustrating a configuration of a fixing device according to the exemplary embodiment; 
         FIG. 3  is a view illustrating a heating member according to the exemplary embodiment, and is a view when the heating member is viewed in the width direction of a belt member; 
         FIG. 4  is a view when the heating member is viewed from the IV direction in  FIG. 3 ; 
         FIG. 5  is a graph illustrating an example of the temperature of the heating member in the moving direction; and 
         FIG. 6  is a view illustrating an example of a configuration of a heating member in the related art, and is a view when the heating member is viewed in the width direction of a belt member. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the exemplary embodiment of the invention will be described in detail with reference to the attached drawings. 
       FIG. 1  is a view illustrating a configuration of an image forming apparatus  10  according to the exemplary embodiment. 
     A housing  11  is provided in the image forming apparatus  10 . On the inside of the housing  11 , an accommodating container  12  which accommodates a sheet which is an example of a recording material, and an image forming portion  14  which is an example of an image forming unit that performs image-forming on the sheet, are provided. 
     In addition, on the inside of the housing  11 , a sheet transporting mechanism  16  which transports the sheet to the image forming portion  14  from the accommodating container  12 , and a controller  20  which controls operations of each portion of the image forming apparatus  10 , are provided. 
     In addition, above the housing  11 , a sheet loading portion (not illustrated) which loads the sheet on which the image is formed, is provided. 
     A photoconductor drum  32  which rotates in the clockwise direction in the drawing is provided in the image forming portion  14 . Furthermore, in the image forming portion  14 , a transfer roll  26  which rotates in the counterclockwise direction in the drawing and transfers a toner image held by the photoconductor drum  32  to the sheet, is provided. In addition, in the exemplary embodiment, the image forming apparatus  10  in which one photoconductor drum  32  is installed is illustrated as an example, but the image forming apparatus  10  may be a so-called tandem type in which plural photoconductor drums  32  are installed. 
     In addition, in the image forming portion  14 , a charging roll  23  which is disposed around the photoconductor drum  32  and charges the photoconductor drum  32  is provided. Furthermore, in the image forming portion  14 , based on the image data from the controller  20 , an exposure device  36  which exposes the photoconductor drum  32  and forms an electrostatic latent image in the photoconductor drum  32 , is provided. 
     Furthermore, in the image forming portion  14 , a developing device  38  which develops the electrostatic latent image formed by the exposure device  36  and forms the toner image on the photoconductor drum  32 , is provided. 
     In the sheet transporting mechanism  16 , a sheet passing path  48  which is a path through which the sheet passes, is provided. Furthermore, in the sheet transporting mechanism  16 , a transport roller  50  which transports the sheet is provided beside the sheet passing path  48 . In addition, in  FIG. 1 , only one group of transport rollers  50  is illustrated, but plural groups of transport rollers  50  are provided. 
     In addition, at an upper part (on the downstream side of a transfer portion  35 T in the transporting direction of the sheet) of the drawing from the transfer portion  35 T formed by the photoconductor drum  32  and the transfer roll  26 , a fixing device  60  which fixes the transferred toner image on the sheet to the sheet, is provided. 
     Furthermore, at the upper part of the drawing of the fixing device  60 , a transport roller  52  which transports the sheet to which the toner image is fixed to the sheet loading portion (not illustrated), is provided. 
     In the image forming apparatus  10  of the exemplary embodiment, first, the uppermost sheet among the sheets accommodated in the accommodating container  12  is sent out onto the sheet passing path  48  by a sending roll  13 . 
     Next, the sheet is transported to the transfer portion  35 T by the transport roller  50  provided on the sheet passing path  48 . 
     Meanwhile, in the image forming portion  14 , the charging of the photoconductor drum  32  by the charging roll  23 , and the exposure of the photoconductor drum  32  by the exposure device  36  are performed, and the electrostatic latent image is formed on the photoconductor drum  32 . Next, the electrostatic latent image is developed by the developing device  38 , and the toner image is formed on the photoconductor drum  32 . 
     In addition, the toner image is transferred to the sheet in the transfer portion  35 T by the transfer roll  26 . After this, the sheet is transported to the fixing device  60 , and heating processing and pressurizing processing are performed on the sheet by the fixing device  60 . In addition, the sheet which passes through the fixing device  60  is loaded on the sheet loading portion which is not illustrated. 
     Next, a configuration of the fixing device  60  will be described.  FIG. 2  is a view illustrating a configuration of the fixing device  60  in which the exemplary embodiment is employed. 
     As illustrated in  FIG. 2 , in the fixing device  60  of the exemplary embodiment, as illustrated in  FIGS. 1 and 2 , a fixing belt module  64  which is used in fixing the toner image to the sheet, is provided. In addition, in the fixing device  60 , a pressure roll  65  which abuts against the fixing belt module  64  is provided. 
     In the fixing belt module  64 , a belt member  64 A formed in an annular (endless) shape is provided. The belt member  64 A rotates in the direction illustrated by an arrow  1 A in  FIG. 1 , and circulates and moves. Furthermore, in the fixing device  60  of the exemplary embodiment, an inner circumferential surface  64 N of the belt member  64 A is coated with oil, to thereby reduce sliding resistances between the belt member  64 A and other members which are in contact with the inner circumferential surface  64 N of the belt member  64 A. 
     In addition, in the exemplary embodiment, oil (for example, silicone oil) is used as an example of lubricant for reducing the sliding resistance between the belt member  64 A and other members, but other types of lubricant may be used. Examples of other types of lubricant include a solid material (for example, zinc stearate), or synthetic lubricating oil grease (for example, silicone grease or fluorine grease) into which a solid material and liquid are mixed. 
     In addition, in the fixing belt module  64 , a pressing pad  64 B which presses against the pressure roll  65  via the belt member  64 A is provided. In the fixing device  60  of the exemplary embodiment, a nip portion N is formed between the pressing pad  64 B and the pressure roll  65 . 
     Furthermore, in the fixing belt module  64 , a support frame  64 C which supports the pressing pad  64 B is provided. 
     Furthermore, a heating member  70  is provided in the fixing belt module  64 . The heating member  70  is in contact with the inner circumferential surface  64 N of the belt member  64 A and heats the belt member  64 A. 
     Although will be described later in detail, the heating member  70  of the exemplary embodiment is configured of a flexible heat generating member having a thin plate shape. 
     In the fixing belt module  64  of the exemplary embodiment, the heating member  70  is installed at a position different from the nip portion N. Accordingly, compared to a case where the heating member  70  is installed at the nip portion N, the strength of the heating member  70  decreases, and according to this, it is possible to reduce heat capacity of the heating member  70 . 
     In this case, the heat is prevented from being deprived by the heating member  70 , and warmup time of the fixing device  60  is further shortened. 
     In addition, in a configuration in which the heating member  70  is installed in the nip portion N, since a relatively large load acts on the heating member  70  from the nip portion N, it is necessary that the rigidity of the heating member  70  increases. In this case, the heat capacity of the heating member  70  increases, and the warmup time of the fixing device  60  increases. 
     The pressure roll  65  abuts against the outer circumferential surface of the belt member  64 A provided in the fixing belt module  64 , and pressurizes the sheet on which the image is formed. 
     In the pressure roll  65 , a cylindrical member  65 A formed of a metal material is provided. Furthermore, in the pressure roll  65 , an elastic layer  65 B which is stacked on the outer circumference of the cylindrical member  65 A and formed of a material having elasticity, is provided. 
     In the fixing device  60  of the exemplary embodiment, the sheet is supplied to the nip portion N which is a part at which the fixing belt module  64  and the pressure roll  65  are in contact with each other, and the sheet is pressed by the fixing belt module  64  and the pressure roll  65  at the nip portion N. Accordingly, the toner image on the sheet is pressurized and heated, and the toner image is fixed to the sheet. 
     In addition, in the fixing device  60  of the exemplary embodiment, the pressure roll  65  rotates in the direction illustrated by an arrow  1 B by a motor which is not illustrated, and the belt member  64 A of the fixing belt module  64  is driven by the pressure roll  65  and rotates in the direction illustrated by the arrow  1 A. 
     Next, a configuration of the heating member  70  in which the exemplary embodiment is employed will be described in detail.  FIG. 3  is a view illustrating the heating member  70  in which the exemplary embodiment is employed, and is a view when the heating member  70  is viewed in the width direction of the belt member  64 A (refer to  FIG. 2 ). In addition,  FIG. 4  is a view when the heating member  70  is viewed from the IV direction in  FIG. 3 . 
     In addition, there is a case where the width direction of the belt member  64 A in the following description is simply referred to as “width direction”. In addition, in the description above, there is a case where the moving direction (the direction illustrated by the arrow  1 A in  FIG. 2 ) of the belt member  64 A is simply referred to as “moving direction”. 
     As described above, the heating member  70  of the exemplary embodiment is configured of the heat generating member having a thin plate shape that extends along the width direction of the belt member  64 A. A heat generation pattern  71  is provided in the heating member  70 . As illustrated in  FIGS. 3 and 4 , the heat generation pattern  71  extends along the width direction and generates the heat upon energization. 
     The heating member  70  of the exemplary embodiment is obtained, for example, by stacking an insulating member made of glass or the like on a plate-shaped base material made of SUS or the like, and by further stacking the insulating member on the heat generation pattern  71  after printing the heat generation pattern  71  made of AgPd or the like on the stacked insulating member. 
     A curved portion  70 B is provided in the heating member  70  of the exemplary embodiment. As illustrated in  FIGS. 3 and 4 , the curved portion  70 B is curved to follow the inner circumferential surface  64 N (refer to  FIG. 2 ) of the belt member  64 A (refer to  FIG. 2 ). The curved portion  70 B is provided to face the inner circumferential surface  64 N of the belt member  64 A in a state where the heating member  70  is installed on the inner circumference of the belt member  64 A. In addition, the curved portion  70 B is formed in a state where the outer circumferential surface has a curvature to be swollen toward the inner circumferential surface  64 N side of the belt member  64 A. 
     Furthermore, a bent portion  70 A is provided in the heating member  70 . The bent portion  70 A is bent toward the inner circumferential side of the belt member  64 A via a folding portion  70 C that extends in the width direction on the upstream side in the moving direction of the belt member  64 A on the curved portion  70 B, is provided. The bent portion  70 A is bent in the direction of being separated from the inner circumferential surface  64 N of the belt member  64 A in a state where the heating member  70  is installed on the inner circumference of the belt member  64 A. 
     In addition, the heating member  70  includes an upstream side end portion  70 D which is located on the upstream side in the moving direction of the belt member  64 A, and a downstream side end portion  70 E which is located on the downstream side in the moving direction of the belt member  64 A. In this example, the upstream side end portion  70 D is provided in the end portion of the bent portion  70 A on the upstream side in the moving direction, and the downstream side end portion  70 E is provided in the end portion of the curved portion  70 B on the downstream side in the moving direction. 
     In the exemplary embodiment, the above-described heat generation pattern  71  is formed in the curved portion  70 B of the heating member  70 . 
     As illustrated in  FIG. 4 , the heat generation pattern  71  includes a heat generation portion  711  which generates the heat upon energization. In addition, the heat generation pattern  71  includes a power feeding portion  712  which feeds the electricity to the heat generation portion  711  connected to the heat generation portion  711 . In addition, in the heating member  70 , the heat generation portion  711  in the heat generation pattern  71  mainly generates the heat, and the power feeding portion  712  rarely generates the heat. 
     In the heating member  70  illustrated in  FIG. 4 , the heat generation portion  711  is divided into three regions, that is a first heat generation portion  711 A, a second heat generation portion  711 B, and a third heat generation portion  711 C, across from one end to the other end (from the left side to the right side in  FIG. 4 ) in the width direction. 
     In addition, the power feeding portion  712  is provided on the downstream side in the moving direction in the curved portion  70 B, and includes a first heat generation portion  711 A, a second heat generation portion  711 B, and a third heat generation portion  712 C which are respectively connected to the first power feeding portion  712 A, the second power feeding portion  712 B, and the third heat generation portion  711 C. Furthermore, the power feeding portion  712  includes a common power feeding portion  712 D which is provided on the upstream side in the moving direction in the curved portion  70 B, and is connected to the first heat generation portion  711 A, the second heat generation portion  711 B, and the third heat generation portion  711 C. 
     In the exemplary embodiment, by employing such a configuration, the first heat generation portion  711 A, the second heat generation portion  711 B, and the third heat generation portion  711 C can be energized separately, to generate the heat. 
     In addition, in the fixing device  60  of the exemplary embodiment, for example, in a case where the toner image is fixed to a sheet having a narrow width, only the second heat generation portion  711 B is energized which is located at the center portion in the width direction. Accordingly, for example, compared to a case where the entire heat generation portion  711  is energized, excessive heat generating is prevented in the heating member  70 , and the power consumption is reduced. 
     Here, in the heating member  70  of the exemplary embodiment, the heat generation pattern  71  is formed only in the curved portion  70 B, and the heat generation pattern  71  is not provided in the bent portion  70 A. By employing such a configuration, in the folding portion  70 C which is a boundary between the bent portion  70 A and the curved portion  70 B, the heat generation pattern  71  is prevented from being folded in the thickness direction of the heating member  70 . Accordingly, disconnection of the heat generation pattern  71  or generation of temperature unevenness or the like in the heat generation pattern  71 , is prevented. 
     In addition, in the heating member  70  of the exemplary embodiment, as illustrated in  FIG. 4 , a gap (region in which the heat generation pattern  71  is not formed) is formed between the heat generation pattern  71  and the folding portion  70 C. More specifically, the gap is formed between the common power feeding portion  712 D of the heat generation pattern  71  and the folding portion  70 C. Similarly, in the heating member  70 , a gap is formed between the heat generation pattern  71  and the downstream side end portion  70 E. More specifically, the gap is formed between the first power feeding portion  712 A of the heat generation pattern  71  and the downstream side end portion  70 E. 
     In addition, the bent portion  70 A on the upstream side in the moving direction is provided in the heating member  70  of the exemplary embodiment. Thereby, in a case where the heating member  70  is installed on the inner circumference of the belt member  64 A, the upstream side end portion  70 D of the heating member  70  is in a state of being separated from the inner circumferential surface  64 N of the belt member  64 A. 
     As being separated, the oil which adheres to the inner circumferential surface  64 N of the belt member  64 A is prevented from being scraped by the upstream side end portion  70 D of the heating member  70 . As a result, the oil enters between the heating member  70  and the inner circumferential surface  64 N of the belt member  64 A. 
     Here, when the upstream side end portion  70 D of the heating member  70  comes into contact with the inner circumferential surface  64 N of the belt member  64 A, the oil is likely to be blocked by the upstream side end portion  70 D, and the oil is unlikely to enter between the heating member  70  and the inner circumferential surface  64 N of the belt member  64 A. In addition, in this case, the oil is unlikely to reach the contact portion between the pressing pad  64 B and the inner circumferential surface  64 N of the belt member  64 A. 
     In addition, in this case, the wear of the belt member  64 A, the heating member  70 , and the pressing pad  64 B is accelerated. In this case, the belt member  64 A is unlikely to rotate, and transporting failure of the sheet or wrinkle of the sheet is likely to be generated. 
     However, in the heating member  70  having the heat generation pattern  71 , in a case where the bent portion  70 A is provided for preventing the oil from being scraped, there is a case where a warpage is generated in the heating member  70  due to thermal expansion according to the disposition or the like of the heat generation pattern  71 . 
       FIG. 6  is a view illustrating an example of a configuration of the heating member  70  in the related art, and is a view when the heating member  70  is viewed in the width direction of the belt member  64 A (refer to  FIG. 2 ). In addition, in  FIG. 6 , configuration elements similar to those of  FIGS. 1 to 4  will be given the same reference numerals. 
     In the heating member  70  in the related art illustrated in  FIG. 6 , in the curved portion  70 B, the heat generation pattern  71  is disposed in the center portion in the moving direction. More specifically, in the curved portion  70 B, the heat generation pattern  71  is disposed to make a generated heat amounts by the heat generation portion  711  equal to each other in an upstream portion  70 B 1  which is located on the upstream side of a center line  70 X in the moving direction and in a downstream portion  70 B 2  which is located on the downstream side of the center line  70 X in the moving direction. 
     In other words, in the heating member  70  in the related art illustrated in  FIG. 6 , the heat generation pattern  71  is disposed so that the center line in the moving direction in the heat generation portion  711  of the heat generation pattern  71  matches the center line  70 X of the heating member  70 . 
     In other words, in the heating member  70  illustrated in  FIG. 6 , the distance from the folding portion  70 C which is a boundary between the curved portion  70 B and the bent portion  70 A to the heat generation portion  711 , and the distance from the downstream side end portion  70 E to the heat generation portion  711 , is equal to each other. Accordingly, in a case where the entire heating member  70  is viewed, the distance from the upstream side end portion  70 D to the heat generation portion  711  becomes longer than the distance from the downstream side end portion  70 E to the heat generation portion  711 . In other words, in the heating member  70  of  FIG. 6 , an area of a region in which the heat generation portion  711  is not provided is larger than that on the upstream side in the moving direction than that on the downstream side in the moving direction. 
     In a case where the heat generation pattern  71  is disposed in the heating member  70  in this manner, when the heat generation portion  711  generates the heat by energizing the heat generation pattern  71 , warpage toward the width direction may occur in the heating member  70 . 
     Specifically, in a case where the heat generation pattern  71  generates the heat, in the heating member  70 , the temperature of the center portion in the moving direction in the curved portion  70 B provided with the heat generation pattern  71  (heat generation portion  711 ) becomes high. 
     Meanwhile, near the bent portion  70 A, or the folding portion  70 C and the downstream side end portion  70 E, which are not provided with the heat generation pattern  71 , the temperature increases by the conduction of the heat generated by the heat generation pattern  71 , and the temperature becomes lower than that of the center portion in the moving direction in the curved portion  70 B. 
     Here, as described above, in the heating member  70  of  FIG. 6 , an area of a region, in which the heat generation portion  711  is not provided, on the upstream side in the moving direction is larger than that of the region on the downstream side in the moving direction. Therefore, when the heat generation pattern  71  generates the heat, in a case where the entire heating member  70  is viewed, the temperature on the upstream side in the moving direction in the heating member  70  is lower than the temperature on the downstream side in the moving direction in the heating member  70 . In other words, when the entire heating member  70  is viewed, the temperature on the downstream side in the moving direction in the heating member  70  is higher than the temperature on the upstream side in the moving direction in the heating member  70 . 
     The heating member  70  has a thin plate shape having flexibility as described above, and is deformed by thermal expansion due to the increase in the temperature. In addition, in a case where the heat generation pattern  71  generates the heat, the heating member  70  illustrated in  FIG. 6  is more largely deformed on the downstream side in the moving direction in the heating member  70  than on the upstream side in the moving direction in the heating member  70  due to a temperature difference. 
     Therefore, as illustrated by an arrow P in  FIG. 6 , there is a concern that a warpage from the upstream side toward the downstream side in the moving direction is generated in the heating member  70 . Here, the heating member  70  has a thin plate shape, and the length thereof along the moving direction is greater than the thickness thereof. Therefore, the rigidity in the moving direction of the heating member  70  is larger than the rigidity in the thickness direction of the heating member  70 , and a warpage in the moving direction generated in the heating member  70  is unlikely to be corrected by an external force. 
     In the heating member  70 , in addition to the warpage from the upstream side toward the downstream side in the moving direction, a warpage in the thickness direction of the heating member  70  is generated in the curved portion  70 B as illustrated by a dashed arrow Q of  FIG. 6 . However, since the rigidity of the thickness direction of the heating member  70  is small, the curved portion  70 B of the heating member  70  can correct warpage of the heating member  70  in the thickness direction by stress or the like applied from the belt member  64 A by the inner circumferential surface  64 N (refer to  FIG. 2 ) of the belt member  64 A (refer to  FIG. 2 ). Therefore, the warpage in the thickness direction of the heating member  70  is unlikely to become a problem. 
     Regarding the problem, in the exemplary embodiment, by making the disposition of the heat generation pattern  71  (heat generation portion  711 ) in the heating member  70  different from that of  FIG. 6 , the warpage of the above-described heating member  70  in the moving direction is prevented. Hereinafter, by using the above-described  FIGS. 2 to 4 , a configuration of the heating member  70  of the exemplary embodiment will be described in detail. 
     In the heating member  70  of the exemplary embodiment, the heat generation pattern  71  is arranged in the following manner. That is, a generated heat amount by the heat generation portion  711  of the upstream portion  70 B 1  of the curved portion  70 B which is located on the upstream side of the center line  70 X in the moving direction is equal to that of the heat generation portion  711  of the downstream portion  70 B 2  of the curved portion  70 B which is located on the downstream side of the center line  70 X in the moving direction. 
     In other words, in the heating member  70  of the exemplary embodiment, compared to the heating member  70  illustrated in  FIG. 6 , the position of the heat generation pattern  71  is shifted to the upstream side in the moving direction. 
     In other words, in the heating member  70  of the exemplary embodiment, the distance from the folding portion  70 C which is the boundary between the curved portion  70 B and the bent portion  70 A to the heat generation portion  711 , becomes shorter than the distance from the downstream side end portion  70 E to the heat generation portion  711 . Accordingly, in the heating member  70  of the exemplary embodiment, the difference between the distance from the upstream side end portion  70 D to the heat generation portion  711  and the distance from the downstream side end portion  70 E to the heat generation portion  711  is smaller than that of the heating member  70  illustrated in  FIG. 6 . 
     In addition, in the heating member  70  of the exemplary embodiment, it is preferable that the heat generation pattern  71  is disposed so that the distance from the upstream side end portion  70 D to the heat generation portion  711  is equal to the distance from the downstream side end portion  70 E to the heat generation portion  711 . 
       FIG. 5  is a graph illustrating an example of the temperature of the heating member  70  in the moving direction. In  FIG. 5 , the solid line illustrates the temperature of the heating member  70  of the exemplary embodiment, and one-dot chain line illustrates the temperature of the heating member  70  in the related art illustrated in  FIG. 6 . In addition, in  FIG. 5 , the dashed line illustrates the temperature of the heating member  70  in which the other configuration which will be described later is employed. 
     As illustrated by the solid line in  FIG. 5 , in the heating member  70  of the exemplary embodiment, the region (in  FIG. 5 , a region which is flat along the horizontal axis) in which the heat generation portion  711  generates the heat is shifted to the upstream side of the center line  70 X of the curved portion  70 B in the moving direction compared to the heating member  70  in the related art illustrated in  FIG. 6 . 
     As a result, in the heating member  70  of the exemplary embodiment, the temperature of the heating member  70  near the bent portion  70 A and the upstream side end portion  70 D is higher than that of the heating member  70  in the related art illustrated in  FIG. 6 . In addition, in the heating member  70  of the exemplary embodiment, the temperature difference between the upstream side and the downstream side in the moving direction is smaller than that of the heating member  70  in the related art illustrated in  FIG. 6 . 
     Accordingly, in the heating member  70  of the exemplary embodiment, compared to the heating member  70  in the related art illustrated in  FIG. 6 , the difference in a modification amount due to the thermal expansion between the upstream side and the downstream side in the moving direction is reduced. Therefore, in the exemplary embodiment, the warpage of the heating member  70  in the moving direction is reduced. 
     Here, as described above, in the heating member  70  of the exemplary embodiment illustrated in  FIGS. 2 to 4 , the position of the heat generation pattern  71  (heat generation portion  711 ) in the curved portion  70 B is shifted to the upstream side in the moving direction compared to the heating member  70  in the related art illustrated in  FIG. 6 . Accordingly, in the curved portion  70 B, the generated heat amount of the upstream portion  70 B 1  located on the upstream side of the center line  70 X in the moving direction is larger than that of the downstream portion  70 B 2  located on the upstream side of the center line  70 X in the moving direction. Thereby, the warpage of the heating member  70  in the moving direction is reduced. However, a configuration for making the generated heat amount of the upstream portion  70 B 1  larger than that of the downstream portion  70 B 2  is not limited thereto. 
     For example, the heat generation pattern  71  (heat generation portion  711 ) may be disposed in the center portion in the moving direction in the curved portion  70 B similar to the heating member  70  in the related art illustrated in  FIG. 6 , and density (area) of the heat generation portion  711  in the upstream portion  70 B 1  with respect to the center line  70 X in the moving direction may be made larger than that of the downstream portion  70 B 2 . Accordingly, in the curved portion  70 B, the generated heat amount of the upstream portion  70 B 1  can be made larger than that of the downstream portion  70 B 2 . 
     In addition, in a case where such a configuration is employed, as illustrated by the dashed line in  FIG. 5 , the temperature in the upstream portion  70 B 1  is higher than that in the heating member  70  in the related art illustrated in  FIG. 6 . As a result, the temperature of the heating member  70  near the bent portion  70 A and the upstream side end portion  70 D is higher than that of the related art illustrated in  FIG. 6 . Further, the temperature difference between the upstream side and the downstream side in the moving direction of the heating member  70  is smaller than that of the related art illustrated in  FIG. 6 . 
     Accordingly, compared to the heating member  70  in the related art illustrated in  FIG. 6 , the difference in the modification amount due to the heat expansion between the upstream side and the downstream side in the moving direction is reduced, and the warpage of the heating member  70  in the moving direction is reduced. 
     In addition, as illustrated in  FIGS. 2 to 4 , the density of the heat generation portion  711  in the upstream portion  70 B 1  may be made larger than that in the downstream portion  70 B 2 , in addition to the configuration in which the disposition of the heat generation pattern  71  (heat generation portion  711 ) in the curved portion  70 B is shifted to the upstream side in the moving direction. Even in this case, similarly, compared to the heating member  70  in the related art illustrated in  FIG. 6 , the difference in deformation amount due to the heat expansion between the upstream side and the downstream side in the moving direction is reduced, and the warpage in the moving direction of the heating member  70  is reduced. 
     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.