Patent Publication Number: US-11378899-B1

Title: Thermally conductive pipe, thermal processing device, and processing system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2020-211953 filed Dec. 22, 2020. 
     BACKGROUND 
     (i) Technical Field 
     The present disclosure relates to a thermally conductive pipe, a thermal processing device, and a processing system. 
     (ii) Related Art 
     In related art, as a thermally conductive pipe referred to as a heat pipe or the like, for example, those described in Japanese Unexamined Patent Application Publication No. 11-337279 (claim 1 and so forth) and Japanese Unexamined Patent Application Publication No. 2017-83138 (claim 1, paragraph 0032, and so forth) are known. 
     Japanese Unexamined Patent Application Publication No. 11-337279 (claim 1 and so forth) describes a heat pipe including a pipe body having a hollow portion sealed at both ends, a working fluid being present in the hollow portion to perform heat exchange with the outside, and a wick mounted in the hollow portion of the pipe body to provide a capillary force to return the working fluid condensed in a condenser to an evaporator. The wick has a substantially cylindrical structure formed by braiding a large number of wires into a helical shape. 
     Japanese Unexamined Patent Application Publication No. 2017-83138 (claim 1, paragraph 0032, and so forth) describes a heat pipe including a container, a working fluid enclosed inside the container, and a wick provided on the inner surface of the container and made of sintered metal obtained by sintering metal powder. The occupancy rate of the wick in a heat absorber of the container is 65% to 90%, and the occupancy rate of the wick in a heat radiator of the container is 40% to 60%. 
     SUMMARY 
     Aspects of non-limiting embodiments of the present disclosure relate to a thermally conductive pipe, a thermal processing device, and a processing system capable of obtaining excellent thermal conductivity performance even when the cross-sectional area in the transverse direction intersecting the longitudinal direction of a pipe is reduced, compared with a case where the occupancy rate of the cross-sectional area of a liquid transfer member with respect to the cross-sectional area in the transverse direction of the inside of the pipe is not in a range of 20% or more and 50% or less. 
     Aspects of certain non-limiting embodiments of the present disclosure address the above advantages and/or other advantages not described above. However, aspects of the non-limiting embodiments are not required to address the advantages described above, and aspects of the non-limiting embodiments of the present disclosure may not address advantages described above. 
     According to an aspect of the present disclosure, there is provided a thermally conductive pipe including a pipe having closed both end portions; a working fluid that is enclosed in inside of the pipe and that is vaporized and liquefied; and a liquid transfer member that extends in a longitudinal direction of the inside of the pipe and that transfers the liquefied working fluid at least in the longitudinal direction. An occupancy rate of a cross-sectional area of the liquid transfer member to a cross-sectional area in a transverse direction of the inside of the pipe is in a range of 20% or more and 50% or less. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure will be described in detail based on the following figures, wherein: 
         FIG. 1A  is a schematic sectional view taken in the longitudinal direction of a thermally conductive pipe according to a first exemplary embodiment, and  FIG. 1B  is a schematic sectional view taken along line IB-IB of the thermally conductive pipe of  FIG. 1A ; 
         FIG. 2  is a schematic diagram illustrating a measurement apparatus used for an evaluation test in a state viewed from three directions; 
         FIG. 3  is a graph presenting results of the evaluation test; 
         FIG. 4A  is a schematic sectional view taken in the longitudinal direction of a thermally conductive pipe according to a modification of the first exemplary embodiment, and  FIG. 4B  is a schematic sectional view taken along line IVB-IVB of the thermally conductive pipe of  FIG. 4A ; 
         FIG. 5A  is a schematic sectional view taken in the longitudinal direction of a thermally conductive pipe according to a modification of the first exemplary embodiment, and  FIG. 5B  is a schematic sectional view taken along line VB-VB of the thermally conductive pipe of  FIG. 5A ; 
         FIG. 6  is a schematic diagram illustrating the inside of a processing system according to a second exemplary embodiment; 
         FIG. 7  is a schematic diagram illustrating the inside of a thermal processing device according to the second exemplary embodiment; 
         FIG. 8  is a schematic partly sectioned view illustrating the thermal processing device of  FIG. 7  in a state viewed from another direction; 
         FIG. 9A  is a schematic sectioned view illustrating a portion of a heating unit applied to the thermal processing device of  FIG. 7 , and  FIG. 9B  is an exploded view of the heating unit of  FIG. 9A ; 
         FIG. 10  is a schematic diagram illustrating a portion of the thermal processing device of  FIG. 7 ; 
         FIG. 11A  is a schematic diagram illustrating a portion of the heating unit, and  FIG. 11B  is a schematic diagram illustrating a thermally conductive pipe; 
         FIG. 12A  is a schematic diagram illustrating the inside of a cooling device according to a modification of the second exemplary embodiment, and  FIG. 12B  is a schematic partly sectioned view illustrating a portion of the cooling device of  FIG. 12A ; and 
         FIG. 13A  is a conceptual diagram illustrating a processing system according to a modification of the second exemplary embodiment, and  FIG. 13B  is a conceptual diagram illustrating another configuration example of the processing system according to the modification of the second exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments for implementing the present disclosure (merely referred to as exemplary embodiments in the specification) will be described below with reference to the drawings. 
     First Exemplary Embodiment 
       FIGS. 1A and 1B  illustrate a heat pipe  1  as an example of a thermally conductive pipe according to a first exemplary embodiment. In the drawings such as  FIGS. 1A and 1B , reference sign Ld indicates the longitudinal direction of the heat pipe  1 , and reference sign Sd indicates the transverse direction that is a direction intersecting (actually orthogonal to) the longitudinal direction Ld of the heat pipe  1 . 
     Thermally Conductive Pipe 
     The heat pipe  1 , which is an example of a thermally conductive pipe, includes a pipe  10  having closed both end portions  10   a  and  10   b , a working fluid  12  that is enclosed inside the pipe  10  and that is vaporized and liquefied, and a liquid transfer member  15  that extends in the longitudinal direction Ld inside the pipe  10  and that transfers the liquefied working fluid  12  in the longitudinal direction Ld. 
     The pipe  10  is a pipe having a hollow structure that is made of metal having a relatively high thermal conductivity, has a circular cross section, and is long in one direction. The shape of the circular cross section is not limited to a perfect circle, but includes a slightly distorted circle. The slightly distorted circle is, for example, a circle having a circularity of 200 μm or less. The closing form, structure, and the like of the end portions  10   a  and  10   b  of the pipe  10  are not particularly limited as long as the end portions  10   a  and  10   b  are sealed to such an extent that the working fluid  12  does not leak. One of the end portions  10   a  and  10   b  may have an end portion structure that is initially closed. 
     As such a pipe  10 , a pipe suitable for the purpose of use is used. For example, from the viewpoint of making the cross-sectional area of the entire heat pipe  1  relatively small in the transverse direction Sd, a reduced-diameter cylindrical pipe having a circular shape in cross section with an outer diameter of 3 mm or less is used as an example of the pipe  10 . The outer diameter of the pipe  10  may be, for example, 2 mm or more from the viewpoint of being able to be manufactured and securing the minimum strength. 
     The pipe  10  may be thinned such that the thickness thereof is in a range of 0.05 mm or more and 0.2 mm or less. 
     In the case where the diameter of the pipe  10  is reduced or the thickness of the pipe  10  is reduced as described above, the installation space and heat capacity of the pipe  10  are reduced, and the thermal conductivity of the pipe  10  is increased. 
     The pipe  10  may be formed of a metal material such as stainless steel or aluminum. For example, the pipe  10  may be made of oxygen-free copper (high purity copper of 99.96% or more containing almost no oxide) from the viewpoint of obtaining high thermal conductivity and ease of processing. 
     In a case where the surface of the pipe  10  may be oxidized, the surface may be subjected to an antioxidant treatment. Examples of the antioxidant treatment include plating, application of an antioxidant or the like, and coating. 
     The working fluid  12  is a medium that is vaporized (for example, evaporated) and liquefied (condensed) in accordance with a temperature distribution inside the pipe  10 . A required amount of the working fluid  12  is enclosed inside the pipe  10 . 
     In the first exemplary embodiment, for example, pure water is used as the working fluid  12 . In  FIGS. 1A, 1B , and the like, the working fluid  12  is illustrated in an exaggerated manner for the convenience of understanding. 
     The liquid transfer member  15  is a material capable of transferring the working fluid  12  liquefied inside the pipe  10  at least in the longitudinal direction Ld of the pipe  10 . The liquefied working fluid  12  is transferred by the liquid transfer member  15  using a capillary force generated from a low-temperature region toward a high-temperature region having a relatively higher temperature than that of the low-temperature region in the pipe  10 . 
     As the liquid transfer member  15 , plural wires made of metal, a bundle of plural metal wires, a metal net formed by crossing plural metal wires into a net shape, sintered metal obtained by sintering metal powder, or the like is used. Among these, a bundle of plural metal wires is, for example, a bundle of twisted metal wires. The sintered metal may be sintered and attached to, for example, an inner wall surface of the pipe  10 . 
     When the liquid transfer member  15  formed of plural wires is used, ultrafine wires each having an outer diameter of 0.06 mm or less may be used. The liquid transfer member  15  formed of the plural ultrafine wires has a larger surface area, thereby easily obtaining a capillary force. When a reduced-diameter pipe  10  having an outer diameter of 3 mm or less is used, the liquid transfer member  15  formed of extra-fine wires is effective because adjustment of the occupancy rate, which will be described later, is facilitated and the work for inserting the liquid transfer member  15  into the reduced-diameter pipe  10  is facilitated. 
     As illustrated in  FIG. 1A , the liquid transfer member  15  is disposed inside the pipe  10  so as to extend in the longitudinal direction Ld. 
     As illustrated in  FIG. 1B , the liquid transfer member  15  according to the first exemplary embodiment is disposed in contact with at least a portion of an inner wall surface  10   c  of the pipe  10  in the circumferential direction. As illustrated in  FIG. 1A , the liquid transfer member  15  according to the first exemplary embodiment is also disposed in contact with a portion of the inner wall surface  10   c  of the pipe  10  in the longitudinal direction Ld. 
     In order to dispose the liquid transfer member  15  in contact with a portion of the inner wall surface  10   c  of the pipe  10 , for example, it is possible to apply a method of fixing both end portions of the liquid transfer member  15  at positions at which both the end portions are maintained in contact with the inner wall surface  10   c  at the both end portions  10   a  and  10   b  of the pipe  10 , or a method of sintering the liquid transfer member  15  with respect to the inner wall surface  10   c.    
     In the heat pipe  1 , from the viewpoint of improving the efficiency of circulating the working fluid  12  to obtain excellent thermal conductivity performance, for example, the occupancy rate (=(S 2 /S 1 )×100)) of a cross-sectional area S 2  of the liquid transfer member  15  with respect to a cross-sectional area S 1  of the inside of the pipe  10  in the transverse direction Sd is set in a range of 20% or more and 50 or less. 
     When the liquid transfer member  15  is formed of plural wires, the cross-sectional area S 2  of the liquid transfer member  15  is the total area of the cross-sectional areas of the wires. When the liquid transfer member  15  is formed of sintered metal attached to the inner wall surface  10   c  of the pipe  10 , the cross-sectional area S 2  is the total area of the cross-sectional areas occupied by the sintered metal in the cross section of the pipe  10  in the transverse direction Sd of the pipe  10 . The range of the occupancy rate is also derived from test results which will be described later. 
     When the occupancy rate of the heat pipe  1  is less than 20%, the heat pipe  1  less likely obtains the ability to move the liquefied working fluid  12  from the low-temperature region to the high-temperature region in the pipe  10  using the capillary force of the liquid transfer member  15 . 
     In contrast, when the occupancy rate exceeds 50%, the heat pipe  1  no longer sufficiently secures a flow path (space) for moving the vaporized (for example, evaporated) working fluid  12  from the high-temperature region to the low-temperature region due to the atmospheric pressure difference in the pipe  10 , and it is difficult to efficiently move the working fluid  12 . When the occupancy rate exceeds 50%, as the diameter of the heat pipe  1  is reduced, it becomes difficult to insert the liquid transfer member  15  into the pipe  10  of the heat pipe  1  at that time. 
     The occupancy rate is more preferably in a range of, for example, 25% or more and 40% or less. 
     Next, a test performed to examine the thermal conductivity performance of the heat pipe  1  will be described. 
     In the test, plural heat pipes  1  having different occupancy rates are prepared, each heat pipe is installed in a measurement apparatus  200  illustrated in  FIG. 2 , and then the temperature difference between two points in the vicinity of the heat pipe when the measurement apparatus  200  is operated is measured as an evaluation index for the thermal conductivity performance. 
     As the heat pipes, heat pipes are prepared in which various liquid transfer members  15  are disposed in oxygen-free copper pipes  10  (lengths in the longitudinal direction Ld are 320 mm) having circular sections with outer diameters in a range of 2 to 3 mm and thicknesses in a range of 0.05 to 0.20 mm so as to have occupancy rates indicated along the horizontal axis in  FIG. 3 . 
     Specifically, as the heat pipes  1 , heat pipes having occupancy rates of the liquid transfer members  15  of 8%, 13%, 28%, 33%, and 100% are prepared. As illustrated in  FIGS. 1A and 1B , each of the liquid transfer members  15  is disposed in contact with a portion of the corresponding pipe  10  extending in the longitudinal direction Ld and in contact with a portion of the inner wall surface  10   c  of the pipe  10 . As the heat pipe having the occupancy rate of 100%, a copper wire having a solid structure having the same size as the pipe  10  is used. 
     As illustrated in  FIG. 2 , the measurement apparatus  200  includes a measurement table  201  made of a rectangular aluminum plate, a radiating plate  202  made of aluminum and disposed at a central portion of the lower surface of the measurement table  201 , heating plates  203 A and  203 B made of aluminum and disposed on both end sides in the longitudinal direction adjacent to the radiating plate  202  on the lower surface of the measurement table  201 , heaters (planar heaters)  205 A and  205 B disposed on the lower surfaces of the heating plates  203 A and  203 B, pressing members  206  that press the heat pipe  1  and the like against the measurement table  201  to hold the heat pipe  1 , and thermocouples  207   a  and  207   b  that measure temperature. The numerical values in parentheses in  FIG. 2  indicate the dimensions (mm) of the above-described components. 
     The radiating plate  202  and the heating plate  203  are the same aluminum plates except that the thickness (TBD: 100 mm) of the radiating plate  202  is larger than that of the heating plate  203 . 
     In this test, measurement is performed as follows. 
     First, as illustrated in  FIG. 2 , the heat pipe  1  to be measured is prepared by being installed on the measurement table  201  of the measurement apparatus  200  in a state of facing the measurement table  201  in a posture in which the liquid transfer member  15  is located at the lowermost portion of the pipe  10 . At this time, the heat pipe  1  is held on the measurement table  201  via grease  204  having thermal conductivity. As the grease  204 , for example, grease having a thermal conductivity of 1 to 10 W/m/K is used. 
     Next, the outputs of the heaters  205 A and  205 B are adjusted to obtain a first measurement temperature of the inner thermocouple  207   b  located inside an end portion of the measurement table  201  when the measurement temperature by the outer thermocouple  207   a  located on the end portion side of the measurement table  201  stabilizes at a first test temperature of 150° C. 
     The outputs of the heaters  205 A and  205 B are adjusted to obtain a second measurement temperature of the inner thermocouple  207   b  when the measurement temperature by the outer thermocouple  207   a  stabilizes at a second test temperature of 230° C. 
     The average of the temperature difference between the first test temperature and the first measurement temperature and the temperature difference between the second test temperature and the second measurement temperature in one heat pipe  1  is obtained as the temperature difference (characteristics) of the measured heat pipe  1 . 
       FIG. 3  illustrates measurement results of the heat pipes  1  having the above-described occupancy rates. The smaller the value of the temperature difference, the better the thermal conduction. A temperature difference T of an allowable level may be, for example, 60° C. or less. 
     From the results illustrated in  FIG. 3 , the heat pipes satisfying the temperature difference T of the allowable level of 60° C. or less are the heat pipes in which the occupancy rates of the liquid transfer members  15  are 28% and 33%. In contrast, in the case of the heat pipes in which the occupancy rates of the liquid transfer members  15  are 8%, 13%, and 100%, the temperatures do not become equal to or lower than 60° C. that is the temperature difference T of the allowable level. 
     In addition, as the temperature difference measured in this test decreases, the temperature difference between the portion heated by the heater  205 A or the like and the inner non-heated portion adjacent to the heated portion tends to decrease due to good heat transfer (heat transportation) by the heat pipe, which may indicate that the thermal conductivity performance is good. In contrast, as the measured temperature difference increases, the heat transfer by the heat pipe is not sufficiently performed, which may indicate that the thermal conductivity performance is relatively poor. That is, there may be a correlation that the magnitude of the temperature difference measured in this test indicates good or poor of the thermal conductivity performance. 
     Thus, it is found from this test that the heat pipe  1  in which the occupancy rate of the liquid transfer member  15  is 20% or more and 50% or less may obtain excellent thermal conductivity performance. 
     Modification of First Exemplary Embodiment 
     In the heat pipe  1  according to the first exemplary embodiment, as illustrated in  FIGS. 4A and 4B , the liquid transfer member  15  may be disposed in contact with the entire region of the inner wall surface  10   c  of the pipe  10 . The contact with the entire region of the inner wall surface  10   c  is not limited to a case where the liquid transfer member  15  is completely in contact with the entire region of the inner wall surface  10   c , but also includes a case where a portion of the liquid transfer member  15  is close to the inner wall surface  10   c  but is slightly separated to be in a non-contact state. 
     At this time, the liquid transfer member  15  is disposed so as to extend also in the longitudinal direction Ld inside the pipe  10 . As the liquid transfer member  15 , plural wires made of metal and disposed side by side, a metal net formed by crossing plural metal wires into a net shape, sintered metal obtained by sintering metal powder, or the like is used. 
     The heat pipe  1  according to this modification is also configured such that the occupancy rate of the cross-sectional area S 2  of the liquid transfer member  15  with respect to the cross-sectional area S 1  of the inside of the pipe  10  in the transverse direction Sd is in a range of 20% or more and 50% or less. 
     As illustrated in  FIGS. 5A and 5B , the heat pipe  1  according to first exemplary embodiment may be disposed such that the liquid transfer member  15  is substantially not in contact with the inner wall surface  10   c  of the pipe  10 . The state in which the liquid transfer member  15  is substantially not in contact with the inner wall surface  10   c  is not limited to a case where the liquid transfer member  15  is not in contact with the inner wall surface  10   c  at all, but also includes a case where a portion of the liquid transfer member  15  is in contact with a portion of the inner wall surface  10   c.    
     At this time, the liquid transfer member  15  is disposed so as to extend also in the longitudinal direction Ld inside the pipe  10 . As the liquid transfer member  15 , for example, plural wires made of metal and disposed side by side, a bundle of plural metal wires, a metal net formed by crossing plural metal wires into a net shape, or the like is used. 
     The heat pipe  1  according to this modification is also configured such that the occupancy rate of the cross-sectional area S 2  of the liquid transfer member  15  with respect to the cross-sectional area S 1  of the inside of the pipe  10  in the transverse direction Sd is in the range of 20% or more and 50% or less. 
     Second Exemplary Embodiment 
       FIGS. 6 and 7  illustrate a configuration example according to a second exemplary embodiment.  FIG. 6  illustrates a processing system  7  according to the second exemplary embodiment, and  FIG. 7  illustrates a thermal processing device  5  according to the second exemplary embodiment. 
     In the following description, the direction indicated by arrow X in the drawings is the width direction of the apparatus, the direction indicated by arrow Y is the height direction of the apparatus, and the direction indicated by arrow Z is the depth direction orthogonal to the width direction and the height direction. A circle attached to the intersection of arrows X and Y in the drawing indicates that the depth direction (arrow Z) of the apparatus is directed downward orthogonal to the drawing. 
     The processing system  7  includes a thermal processing device  5  having a thermal processor that performs thermal processing of heating or cooling a processing target object  9  passing in contact with the thermal processor, and another processing apparatus  2  that performs another processing other than the thermal processing on the processing target object  9  before or after passing through the thermal processing device  5 . 
     The thermal processing device  5  includes a thermal processor  5   h  that performs thermal processing of heating or cooling a processing target object  9  passing in contact with the thermal processor  5   h , and a thermally conductive pipe  1  installed in a portion of the thermal processor  5   h  where a temperature difference in a passage width direction Wd of the processing target object  9  is to be suppressed. 
     In the second exemplary embodiment, an image forming apparatus  7 A that performs processing of forming an image on a processing target object  9  is applied as an example of the processing system  7 . In the second exemplary embodiment, since the processing system  7  is the image forming apparatus  7 A, a heating device  5 A including a thermal processor that performs thermal processing of heating a processing target object  9 , as an example of the thermal processing device  5 , an imaging device  2 A that performs imaging on the processing target object  9  before passing through the heating device  5 A, as an example of the other processing device  2 , and a recording sheet  9 A on which an image is formed, as an example of the processing target object  9 , are applied. 
     Processing System 
     The image forming apparatus  7 A as an example of the processing system  7  is an apparatus that forms an image by forming an image formed of a developer as an example of powder on a recording sheet  9 A and then heating and fixing the image. 
     As illustrated in  FIG. 6 , the image forming apparatus  7 A includes a housing  70  having a certain external shape. The imaging device  2 A, a sheet feed device  4 , the heating device  5 A, and the like are disposed in an internal space of the housing  70 . A one-dot chain line in  FIG. 6  indicates a major transport path when a recording sheet  9 A is transported in the housing  70 . 
     The imaging device  2 A is a device that forms a toner image formed of a toner as a developer and transfers the toner image to a recording sheet  9 A. The imaging device  2 A includes a photoreceptor drum  21  that rotates in a direction indicated by arrow A. Devices such as a charging device  22 , an exposure device  23 , a developing device  24 , a transfer device  25 , and a cleaning device  26  are disposed around the photoreceptor drum  21 . 
     Among these, the photoreceptor drum  21  is an example of an image holder, and is a drum-shaped photoreceptor having a photosensitive layer serving as an image formation surface and an image holding surface. The charging device  22  is a device that charges the outer peripheral surface (image formation surface) of the photoreceptor drum  21  to a predetermined surface potential. The charging device  22  includes, for example, a charging member having a roll shape or the like which is brought into contact with the image formation surface on the outer peripheral surface of the photoreceptor drum  21  and to which a charging current is supplied. 
     The exposure device  23  is a device that forms an electrostatic latent image by performing exposure to light based on image information on the charged outer peripheral surface of the photoreceptor drum  21 . The exposure device  23  operates by receiving an image signal generated by an image processor (not illustrated) or the like performing predetermined processing on image information input from the outside. The image information is, for example, information on an image to be formed, such as a character, a figure, a photograph, or a pattern. The developing device  24  is a device that develops the electrostatic latent image formed on the outer peripheral surface of the photoreceptor drum  21  with a developer (toner) of a corresponding predetermined color (for example, black) to visualize the electrostatic latent image as a monochromatic toner image. 
     Next, the transfer device  25  is a device that electrostatically transfers the toner image formed on the outer peripheral surface of the photoreceptor drum  21  to a recording sheet  9 A. The transfer device  25  includes, for example, a transfer member having a roll shape or the like which is brought into contact with the outer peripheral surface of the photoreceptor drum  21  and to which a transfer current is supplied. The cleaning device  26  is a device that cleans the outer peripheral surface of the photoreceptor drum  21  by removing unnecessary substances such as unnecessary toner and paper dust adhering to the outer peripheral surface of the photoreceptor drum  21 . 
     In the imaging device  2 A, an area in which the photoreceptor drum  21  and the transfer device  25  face each other is a transfer position TP at which the toner image is transferred. 
     The sheet feed device  4  is a device that houses and sends a recording sheet  9 A to be fed to the transfer position TP in the imaging device  2 A. The sheet feed device  4  is configured by disposing one or plural housing bodies  41  that house recording sheets  9 A and devices such as one or plural sending devices  43  that send out the recording sheets  9 A. 
     The housing bodies  41  are each a housing member having a stack plate (not illustrated) on which plural recording sheets  9 A are stacked and housed in a predetermined direction. The sending devices  43  are each a device that feeds the recording sheets  9 A stacked on the stacking plate of the corresponding housing body  41  one by one by a device such as plural rolls. The sheet feed device  4  according to the second exemplary embodiment includes, for example, two housing bodies  41   a  and  41   b  capable of respectively housing recording sheets  9 Aa and recording sheets  9 Ab having different widths at the time of transport, and two sending devices  43   a  and  43   b  that respectively send out the recording sheets  9 Aa and the recording sheets  9 Ab housed in the housing bodies  41   a  and  41   b.    
     The sheet feed device  4  is connected to the transfer position TP in the imaging device  2 A by a feed transport path  45  as an example of a transporting section. The feed transport path  45  is a transport path along which a recording sheet  9 A ( 9 Aa or  9 Ab) sent out from the sheet feed device  4  is transported and fed to the transfer position TP, and is configured by disposing plural transport rollers  46   a  to  46   c  that sandwich and transport the recording sheet  9 A, and plural guide members (not illustrated) that secure a transport space for the recording sheet  9 A and guide the transport of the recording sheet  9 A. 
     The recording sheet  9 A may be any sheet-shaped recording medium that is able to be transported in the housing  70  and to which a toner image is able to be transferred and thermally fixed. The material, form, and the like of the recording sheet  9 A are not particularly limited. 
     The heating device  5 A is a device that performs processing of applying heat and pressure to thermally fix, to the recording sheet  9 A, the toner image of an unfixed image transferred at the transfer position TP of the imaging device  2 A. The heating device  5 A is configured such that devices such as a heating rotary body  51  and a pressing rotary body  52  are disposed in an internal space of a housing  50  having an inlet  50   a  and an outlet  50   b  for the recording sheet  9 A. 
     In the heating device  5 A, as illustrated in  FIGS. 6 and 7 , the heating rotary body  51  and the pressing rotary body  52  are disposed to rotate in contact with each other, and apply heat and pressure to a recording sheet  9 A or the like passing through a contact portion FN at which the heating rotary body  51  and the pressing rotary body  52  contact each other. In the heating device  5 A, a portion constituted by the heating rotary body  51  and the pressing rotary body  52  is the thermal processor  5   h.    
     Details of the heating device  5 A will be described later. 
     In the image forming apparatus  7 A, an image is formed, for example, as follows. 
     For example, in the image forming apparatus  7 A, when a controller (not illustrated) receives an instruction for an operation of forming an image, the imaging device  2 A executes a charging operation, an exposure operation, a developing operation, and a transfer operation, and the sheet feed device  4  executes an operation of sending out a predetermined recording sheet  9 A ( 9 Aa or  9 Ab) and transporting and feeding the recording sheet  9 A to the transfer position TP via the feed transport path  45 . 
     Thus, a toner image corresponding to image information is formed on the photoreceptor drum  21 , and the toner image is transferred to the recording sheet  9 A fed from the sheet feed device  4  to the transfer position TP. At this time, the recording sheet  9 A to which the toner image has been transferred is separated from the photoreceptor drum  21  in a state of being sandwiched between the rotating photoreceptor drum  21  and the transfer device  25 , and is sent out toward the heating device  5 A. 
     Subsequently, in the heating device  5 A of the image forming apparatus  7 A, as illustrated in  FIG. 7 , a fixing operation is executed in which heating and pressing are performed on the recording sheet  9 A when the recording sheet  9 A to which a toner image  92  has been transferred is introduced into and passes through the above-described contact portion FN. Thus, the unfixed toner image  92  is molten under pressure and fixed to the recording sheet  9 A. In this case, the heating rotary body  51  and the pressing rotary body  52  function as a transporting section that transports the recording sheet  9 A. 
     The recording sheet  9 A after the fixing is output from the housing  50  in a state of being sandwiched between the heating rotary body  51  and the pressing rotary body  52  in the heating device  5 A, then is transported to an outlet  72  via an output transport path, and finally is sent out and housed in a sheet housing portion  73  provided in a portion of the housing  70  by an output roll  48 . 
     Thus, a basic image forming operation of the image forming apparatus  7 A to form a monochromatic image on one side of a recording sheet  9 A is completed. 
     Thermal Processing Device 
     Next, the heating device  5 A as an example of the thermal processing device  5  will be described in detail. 
     As illustrated in  FIGS. 7, 8 , and the like, the heating device  5 A according to the second exemplary embodiment employs, as the heating rotary body  51 , a belt-nip-form heating unit  55  including a rotatable heating belt  53  and a heat generating body  54  as an example of a heating section that generates heat so as to form the contact portion (nip) FN at which the heating belt  53  is pressed against and contacts the pressing rotary body  52  from the inner peripheral surface thereof, and employs a pressure roll  56  in a roll shape as the pressing rotary body  52 . 
     The heating unit  55  performs thermal processing of heating a recording sheet  9 A at the contact portion FN at which the heating unit  55  is in contact in the passage width direction Wd ( FIG. 8  and the like) intersecting a transport direction C of the recording sheet  9 A. 
     The heating unit  55  holds the heat generating body  54  in contact with the inner peripheral surface of the heating belt  53  by a contact holder  61  and rotatably holds the heating belt  53  by a portion of the contact holder  61  and left and right end-portion holders  62 A and  62 B. The heating unit  55  supports the contact holder  61  and the left and right end-portion holders  62 A and  62 B by a support  63 . 
     The heating belt  53  is an endless belt for thermal conduction having flexibility and heat resistance. As the heating belt  53 , for example, a belt molded into, as an original shape thereof, a cylindrical shape with a material such as a synthetic resin which is polyimide, polyamide, or the like is applied. 
     As illustrated in  FIGS. 9A, 9B, 10 , and the like, the heat generating body  54  includes a substrate  541 , plural ( 3  in this example) heat generating portions  542 A,  542 B, and  542 C provided on one surface  541   a  of the substrate  541  which contacts the inner peripheral surface of the heating belt  53 , and a wiring portion  543  for supplying power to the heat generating portions  542 A,  542 B, and  542 C. 
     The substrate  541  is a plate-shaped member having a rectangular shape with a larger width size W in the passage width direction Wd intersecting the transport direction C of a recording sheet  9 A than a maximum width size W 1  of the recording sheet  9 A. The substrate  541  is made of an electrically insulating material. For example, a ceramic substrate is applied as the substrate  541 . The surface (one surface)  541   a  of the substrate  541  which contacts the inner peripheral surface of the heating belt  53  is coated with a coating layer formed thereon after the heat generating portions  542 A,  542 B, and  542 C are provided. 
     As illustrated in  FIG. 11A , the heat generating portions  542 A,  542 B, and  542 C are heating wire portions linearly provided on the one surface  541   a  of the substrate  541  to extend in the longitudinal direction (the direction extending in the passage width direction Wd of the recording sheet  9 A) and to be separate from each other in the passage width direction Wd of the recording sheet  9 A, thereby being in a parallel state. 
     Since  FIG. 11A  is a drawing illustrating a state viewed from a back surface (the other surface)  541   b  opposite to the one surface  541   a  of the substrate  541  of the heat generating body  54 , the heat generating portion  542  provided on the one surface  541   a  is not actually visible. However, for the convenience of describing the heat generating portion  542 ,  FIG. 11A  illustrates the heat generating portion  542  in a state seen through from the other surface  541   b.    
     The heat generating portions  542 A,  542 B, and  542 C have substantially the same length in the longitudinal direction of the substrate  541 , but are configured such that regions where relatively large amounts of heat are generated are present at positions different from each other so as to conform to the difference in width size W when a recording sheet  9 A is transported. 
     That is, for example, as illustrated in  FIG. 11A , the first heat generating portion  542 A is configured such that a central portion excluding end portions on both end sides in the longitudinal direction is a region where a large amount of heat is generated. The first heat generating portion  542 A is used when a recording sheet  9 A having a width size W of an intermediate width size W 2  (&lt;W 1 ) passes. The second heat generating portion  542 B is configured such that portions corresponding to end portions on both end sides of the first heat generating portion  542 A are regions where a large amount of heat is generated. The third heat generating portion  542 C is configured such that a central portion in the longitudinal direction (for example, a portion of about ⅓ of the total length) is a region where a large amount of heat is generated. The third heat generating portion  542 C is used when a recording sheet  9 A having a width size W of a minimum size W 3  (&lt;W 2 ) passes. 
     The configuration of the regions where the heat generating portions  542 A,  542 B, and  542 C generate relatively large amounts of heat in the second exemplary embodiment is a configuration in a case where a center reference transport method (center registration method) is employed. With the method, a recording sheet  9 A is guided and transported such that the center position in the passage width direction Wd when the recording sheet  9 A is transported passes through, for example, a reference center position of the passage region width of the recording sheet  9 A in the contact portion FN of the heating device  5 A. 
     The regions where the heat generating portions  542 A,  542 B, and  542 C generate relatively large amounts of heat are each provided, for example, by making at least one of the width and the thickness or both of the heating wire portion smaller than those of the other portion (portion where heat generation is suppressed) so that the electric resistance value becomes relatively high. 
     The temperature of the heat generating body  54  due to the heat generated by the heat generating portions  542 A,  542 B, and  542 C is measured by a temperature sensor (not illustrated) disposed in contact with a certain location on the other surface  541   b  of the substrate  541  of the heat generating body  54 , and the measurement information is fed back to a heating controller (not illustrated). 
     As illustrated in  FIG. 11A  and the like, the wiring portion  543  is provided such that a line concentration portion thereof is present at one end portion in the longitudinal direction of the heat generating body  54  and at a position outside one of the end-portion holders  62 A and  62 B. The wiring portion  543  according to the second exemplary embodiment is configured as an end portion obtained by extending one end portion of the substrate  541  to the outside of the right end-portion holder  62 B. 
     The wiring portion  543  includes an electrically insulating substrate  543   a , individual wiring portions  543   b ,  543   c , and  543   d  individually connected to one end portions of the heat generating portions  542 A,  542 B, and  542 C as indicated by broken lines in  FIG. 11A , and a common wiring portion  543   e  connected in a manner common to the other end portions of the heat generating portions  542 A,  542 B, and  542 C as indicated by dotted lines and broken lines in  FIG. 11A . 
     As illustrated in  FIG. 8  and the like, the heat generating body  54  is connected to a power supply connection portion  64  that supplies power to the wiring portion  543  and further to the heat generating portion  542 . 
     The power supply connection portion  64  according to the second exemplary embodiment includes a housing (connector body)  641  having an attachable and detachable shape for connection and plural contact terminals  642  provided on one side surface of the housing  641  in an exposed state while being connected to the connection end portions of wires of the wiring portion  543 . 
     For example, as illustrated in  FIG. 11A , the power supply connection portion  64  is connected to a power supply source connection portion  14 , which extends from a power supply (not illustrated) in the image forming apparatus  7 A and is wired, and is enabled to be energized. 
     As illustrated in  FIG. 9B  and the like, the contact holder  61  is a plate-shaped member long in one direction and provided with a housing recess  61   a  for housing and holding the heat generating body  54  on one surface on the side to be brought into contact with the inner peripheral surface of the heating belt  53 . 
     The contact holder  61  is provided with an attachment groove portion  61   b  and an attachment contact portion  61   c  that are used when being attached to the support  63 , on the other surface opposite to the one surface. 
     In the contact holder  61 , one long-side end portion on the one surface provided with the housing recess  61   a  is formed as an intake guide portion  61   d  including a bent surface that guides the heating belt  53  to be taken into the above-described contact portion FN, and the other long-side end portion on the one surface is formed as an ejection guide portion  61   e  including a curved surface that guides the heating belt  53  in a direction in which the heating belt  53  is ejected from the contact portion FN. 
     Each of the left and right end-portion holders  62 A and  62 B is a member in which a curved belt guiding and holding portion  622  that guides and holds both end portions of the heating belt  53  in the width direction so as to allow both the end portions to rotate from the inner peripheral surface thereof is provided on an inner surface of a disk-shaped body  621  in which a portion facing the pressing roll  56  is missing. The left and right end-portion holders  62 A and  62 B are provided with attachment recesses (not illustrated) for attaching the end portions of the support  63  on the inner side of the belt guiding and holding portion  622  of the body  621  thereof. 
     As illustrated in  FIG. 8  and the like, the support  63  is a member longer than the length of the heat generating body  54  in the longitudinal direction. As the support  63 , as illustrated in  FIG. 9A ,  FIG. 9B , and the like, for example, a member having a shape in which long-side end portions of a flat plate long in one direction are bent substantially at a right angle in the same direction so as to have a concave shape in cross section is applied. 
     When the contact holder  61  is attached, as illustrated in  FIG. 9B  and the like, one bent end portion  63   b  of the support  63  is fitted into the attachment groove portion  61   b  of the contact holder  61 , while the other bent end portion  63   c  is kept in contact with the attachment contact portion  61   c  of the contact holder  61 . Thus, the support  63  supports the contact holder  61  in a state in which a portion of the contact holder  61  in the longitudinal direction is sandwiched. 
     As the pressing roll  56  as the pressing rotary body  52 , for example, a roll is applied in which an elastic body layer, a release layer, and the like are provided on the outer peripheral surface of a columnar or cylindrical roll base body made of metal or the like. 
     As illustrated in  FIG. 8 , shaft portions  56   c  and  56   d  at both end portions in the axial direction of the pressing roll  56  are rotatably supported by a pressing mechanism (not illustrated) disposed in the housing  50 . The pressing roll  56  receives a pressure such as to be pressed against the heating unit  55  from the pressing mechanism. Consequently, as illustrated in  FIGS. 7 and 8 , the pressing roll  56  is maintained in a state in which the roll outer peripheral surface is in pressure contact with a predetermined pressure over the longitudinal direction of the one surface  541   a  of the heat generating body  54  via the heating belt  53  in the heating unit  55 . 
     A portion of the pressing roll  56  in pressure contact with the heating unit  55  serves as the above-described contact portion FN. 
     As illustrated in  FIG. 8 , a power passive gear  75  as an example of a driving input section is attached to one shaft portion  56   c  of the pressing roll  56 , and the power passive gear  75  meshes with a power transmission gear (not illustrated) in a driving transmission device  76  disposed on the housing  70  side of the image forming apparatus  7 A. Thus, when a required time for an image forming operation or the like comes, as illustrated in  FIG. 7 , the pressing roll  56  is driven to rotate at a predetermined speed in a direction indicated by arrow B 1  by receiving a rotational force transmitted from the driving transmission device  76 . 
     When the pressing roll  56  is driven to rotate, as illustrated in  FIG. 7 , the heating belt  53  in the heating unit  55  is driven to rotate in a direction indicated by arrow B 2 . 
     The heating device  5 A is configured such that, when an image forming operation is executed, a region in which the heat generating body  54  of the heating unit  55  generates heat is adjusted in accordance with the difference in width size W of the recording sheet  9 A passing through the contact portion FN. 
     For example, when a recording sheet  9 A of which the width size W at the time of transport is the maximum width size W 1  is to be passed, power is supplied to both the first heat generating portion  542 A and the second heat generating portion  542 B to cause a region corresponding to the maximum width size W 1  to generate heat. When a recording sheet  9 A having the minimum size W 3  is to be passed, power is supplied only to the third heat generating portion  542 C to cause a region corresponding to the minimum size W 3  to generate heat. When a recording sheet  9 A having the intermediate width size W 2  is to be passed, power is supplied only to the first heat generating portion  542 A to cause a region corresponding to the intermediate width size W 2  to generate heat. 
     Thus, the heating device  5 A efficiently generates heat by causing the heat generating body  54  of the heating unit  55  to conform to the difference in width size W of the recording sheet  9 A. 
     In contrast, also in the heating device  5 A, for example, when recording sheets  9 A having a width size W (a size including the intermediate width size W 2  and the minimum size W 3 ) smaller than the maximum width size W 1  are continuously passed and heated, a non-passage region E 2  which is a region through which the recording sheets  9 A do not pass is generated in the contact portion FN (actually, the heat generating body  54 ). Thus, since the non-passage region E 2  is continuously heated from the portion where the heat generation is suppressed in the heat generating portion  542  without the heat being taken by the passing recording sheet  9 A, the temperature tends to rise. 
     In this case, a portion of the heat generating body  54  corresponding to the non-passage region E 2  becomes relatively high in temperature as compared with a passage region E 1  through which the recording sheets  9 A pass, so that a temperature difference occurs. Consequently, when a recording sheet  9 A having a wide width is passed and heated thereafter, heating unevenness may be induced, or the contact holder  61  may be locally heated and may be adversely affected. 
     That is, when the thermal processing is performed in the heating device  5 A as described above, as illustrated in  FIGS. 8 and 10 , the heat generating body  54  in the thermal processor  5   h  of the heating device  5 A is in a state where an unwanted temperature difference occurs between the passage region E 1  through which the recording sheet  9 A passes and the non-passage region E 2  of the recording sheet  9 A. At this time, the portion of the heat generating body  54  corresponding to the non-passage region E 2  becomes a high-temperature portion that increases in temperature during the thermal processing and causes a temperature difference, while the portion of the heat generating body  54  corresponding to the passage region E 1  becomes a low-temperature portion that has a relatively lower temperature than the portion (high-temperature portion) corresponding to the non-passage region E 2  during the thermal processing and causes a temperature difference. 
     Thus, in the heating device  5 A, from the viewpoint of suppressing the occurrence of the temperature difference due to an unwanted increase in temperature in the portion (high-temperature portion) of the heat generating body  54  corresponding to the non-passage region E 2 , two heat pipes  1 A and  1 B are disposed in contact with the surface (back surface)  541   b  of the heat generating body  54  opposite to the surface  541   a  that contacts the heating belt  53  in the heating unit  55  as illustrated in  FIGS. 7 to 10 . Here, the high-temperature portion is a portion that generates a temperature at which the working fluid  12  enclosed in the heat pipes  1 A and  1 B is at least vaporizable, and is, for example, a portion having a temperature of 150° C. or higher. 
     Each of the heat pipes  1 A and  1 B employs the heat pipe  1  having the configuration according to the first exemplary embodiment. 
     As illustrated in  FIGS. 11A, 11B , and the like, the heat pipes  1 A and  1 B have substantially the same length as the length of the heat generating portion  542  of the heat generating body  54 . Since the two heat pipes  1 A and  1 B are disposed in parallel at positions at which an installation space is limited, heat pipes having a relatively small diameter (for example, an outer diameter in a range of 2 to 3 mm) are applied. 
     As illustrated in  FIGS. 8, 10 , and the like, the heat pipes  1 A and  1 B are disposed so as to be in contact with each other in the longitudinal direction (the direction extending in the passage width direction Wd of the recording sheet  9 A) on the other surface  541   b  of the heat generating body  54  and to be parallel to each other at a predetermined interval in a transport direction C of the recording sheet  9 A. 
     In the second exemplary embodiment, the configuration is disposed as follows. That is, as illustrated in  FIGS. 9A, 9B , and the like, mounting grooves  65 A and  65 B in which the heat pipes  1 A and  1 B are mounted are provided in the housing recess  61   a  of the contact holder  61 , and the heat pipes  1 A and  1 B are mounted to be housed in the mounting grooves  65 A and  65 B, respectively. Subsequently, when the heat generating body  54  is housed in the housing recess  61   a  of the contact holder  61 , the state is maintained in which the other surface  541   b  of the heat generating body  54  is in contact with the heat pipes  1 A and  1 B and the heat pipes  1 A and  1 B are pressed into the mounting grooves  65 A and  65 B. The heat pipes  1 A and  1 B may be partially bonded and fixed to the other surface  541   b  of the heat generating body  54  with a material such as an adhesive or grease having thermal conductivity. 
     In the heating device  5 A, as illustrated in  FIG. 8  and the like, the heat pipes  1 A and  1 B are disposed so as to be in contact with the portion (the low-temperature portion when there is the non-passage region E 2 ) corresponding to the passage region E 1  through which a recording sheet  9 A having the maximum width size W 1  passes, the portion including at least the portion (the high-temperature portion) of the heat generating body  54  in the thermal processor  5   h  corresponding to the non-passage region E 2 . At this time, the heat pipes  1 A and  1 B are each configured such that the occupancy rate of the liquid transfer member  15  is maintained in the range of 20% or more and 50% or less in the region in contact with the portion corresponding to the passage region E 1  through which the recording sheet  9 A having the maximum width size W 1  passes, the portion including the portion (high-temperature portion) corresponding to the non-passage region E 2 . 
     In the heating device  5 A, as illustrated in  FIGS. 8, 9A , and the like, the heat pipes  1 A and  1 B are disposed such that the liquid transfer member  15  is in contact with a portion of the inner wall surface  10   c  ( FIGS. 1A, 1B , and the like) inside the pipe  10  that faces the heat generating body  54 . 
     In the heating device  5 A in which the heat pipes  1 A and  1 B are disposed, even when the portion of the heat generating body  54  at the contact portion FN corresponding to the non-passage region E 2  through which the recording sheet  9 A does not pass is generated and the temperature rises, the heat of the portion of the heat generating body  54  corresponding to the non-passage region E 2  is moved to the portion (low-temperature portion) of the heat generating body  54  corresponding to the passage region E 1  of the recording sheet  9 A where the temperature becomes relatively lower than the temperature of the portion (high-temperature portion) of the heat generating body  54  corresponding to the non-passage region E 2  by the action of heat transfer of the heat pipes  1 A and  1 B. 
     At this time, the heat pipes  1 A and  1 B generally transfer heat as follows. 
     For example, in each of the heat pipes  1 A and  1 B, heat is conducted in a portion of the pipe  10  which is in contact with the portion (high-temperature portion) of the heat generating body  54  corresponding to the non-passage region E 2  of the recording sheet  9 A, and the working fluid  12  inside the portion of the pipe  10  is heated and vaporized. At this time, the corresponding portions of the heat pipes  1 A and  1 B take the heat required for vaporization and absorb the heat. Then, the vaporized working fluid  12  moves toward a portion where the temperature and the pressure inside the pipe  10  are relatively low due to increases in temperature and pressure caused by the vaporization (for example, evaporation). The portion where the temperature and the pressure of the pipe  10  are relatively low at this time is a portion located on the central side of the pipe  10  in contact with the portion (low-temperature portion) of the heat generating body  54  corresponding to the passage region E 1  of the recording sheet  9 A. 
     In contrast, in the portion of the pipe  10  which is in contact with the portion (low-temperature portion) of the heat generating body  54  corresponding to the passage region E 1  of the recording sheet  9 A, the vaporized working fluid  12  is cooled, thereby being aggregated and liquefied. At this time, heat of condensation generated by the liquefaction is released and radiated at the corresponding portions of the heat pipes  1 A and  1 B. Then, the liquefied working fluid  12  moves, due to the capillary force of the liquid transfer member  15 , substantially in the longitudinal direction Ld of the pipe  10  to the portion (high-temperature portion) in contact with the portion corresponding to the non-passage region E 2  of the recording sheet  9 A. 
     In the heat pipes  1 A and  1 B, by repeating the above-described operations, heat is transferred from a portion having a relatively high temperature to a portion having a relatively low temperature in the pipe  10  substantially in the longitudinal direction Ld of the pipe  10 . Thus, also in the heat generating body  54  with which the heat pipes  1 A and  1 B are in contact, heat in a portion (high-temperature portion) corresponding to the non-passage region E 2  is moved to a portion (low-temperature portion) corresponding to the passage region E 1  of the recording sheet  9 A. 
     Consequently, in the heating device  5 A, as compared with a case where the heat pipes  1 A and  1 B are not disposed, an increase in temperature in the non-passage region E 2  is suppressed, and occurrence of an unwanted temperature difference in the heat generating body  54  is also suppressed. 
     In the heating device  5 A, even when the cross-sectional area S 1  of the pipe  10  in the transverse direction Sd is reduced, excellent thermal conductivity performance may be obtained as compared with a case where a heat pipe in which the occupancy rate of the liquid transfer member  15  is not in the range of 20% or more and 50% or less is used. 
     At this time, since the occupancy rate of the liquid transfer member  15  in each the heat pipes  1 A and  1 B is maintained in the range of 20% or more and 50% or less, for example, a sufficient passage space for the movement of the vaporized working fluid  12  is secured inside the pipe  10  as described above, so that the movement to the low-temperature portion of the pipe  10  is smoothly performed. Furthermore, as described above, the capillary force of the liquid transfer member  15  having an occupancy rate of 20% or more of the liquefied working fluid  12  is obtained, so that the movement (transfer) to the high-temperature portion of the pipe  10  is smoothly performed. That is, for example, in the heat pipes  1 A and  1 B, the circulating movement of the working fluid  12  inside the pipe  10  is efficiently performed, and the heat transfer is also efficiently performed. 
     Thus, in the heating device  5 A, a temperature difference generated in the passage width direction Wd of the heat generating body  54  in the thermal processor  5   h , that is, an unwanted temperature difference generated between the high-temperature portion corresponding to the non-passage region E 2  and the low-temperature portion corresponding to the passage region E 1  in the heat generating body  54  is efficiently suppressed. In particular, in the heating device  5 A, in order to heat and melt an image formed of a toner and satisfactorily fix the image to a recording sheet  9 A, for example, heating is performed in a range of 150° C. to 230° C. by the heat generating body  54 ; however, an unwanted temperature difference generated in the heat generating component  54  is effectively suppressed although the heat pipes  1 A and  1 B having the relatively small diameters described above are applied. 
     Thus, in the heating device  5 A, even in a case where recording sheets  9 A having a width size W (a size including the intermediate width size W 2  and the minimum width size W 3 ) smaller than the maximum width size W 1  are continuously passed, and then a recording sheet  9 A having a width size W (W 1  or W 2 ) relatively larger than the small width size W (W 2  or W 3 ) is passed to perform the heating processing, heating with less variation in heating temperature caused by the unwanted temperature difference may be performed. 
     In the image forming apparatus  7 A, even when the recording sheets  9 A having the relatively small width size W (W 2 , W 3 ) are continuously used and the recording sheet  9 A having the width size W (W 1 , W 2 ) relatively larger than the width size W (W 2 , W 3 ) is used to perform image formation, the toner image formed by the imaging device  2 A is satisfactorily fixed by heating in the heating device  5 A with less variation in heating temperature caused by the unwanted temperature difference. Thus, in the image forming apparatus  7 A, it is possible to obtain a uniform image with less fixing unevenness (heating unevenness) caused by the unwanted temperature difference. 
     Modification of Second Exemplary Embodiment 
     Although the heating device  5 A is exemplified as the thermal processing device  5  in the second exemplary embodiment, the thermal processing device  5  may be, for example, a cooling device  5 B including a thermal processor  5   j  that performs thermal processing of cooling a processing target object  9  passing in contact as illustrated in  FIGS. 12A and 12B . 
     The cooling device  5 B is configured by disposing, in an internal space of a housing  50  having an inlet  50   a  and an outlet  50   b  for a processing target object  9 , devices such as a transport device  57  for the processing target object  9 , a cooler  58  as an example of the thermal processor  5   j  that cools the processing target object  9  transported by the transport device  57 , and a pressing rotary body  59  that presses the processing target object  9  against the cooler  58 . 
     As the processing target object  9  among these, for example, a sheet-shaped or plate-shaped object to be cooled is applied. In the cooling device  5 B, as the processing target object  9 , for example, those having a feed width W of the maximum width size W 1  and those having a feed width W of an intermediate width size W 2  narrower than the maximum width size W 1  are targeted. 
     As the transport device  57 , for example, a device using a belt transport method is used. Specifically, the transport device  57  includes an endless transport belt  57   a  having thermal conductivity, support rolls  57   b  and  57   c  around which the transport belt  57   a  is wound and supported so as to be rotatable in a direction indicated by arrows, a driving device (not illustrated) that transmits rotational power to one of the support rolls  57   b  and  57   c , and the like. 
     The pressing rotary body  59  having, for example, a roll shape is used. The pressing rotary body  59  is disposed so as to be driven to rotate by pressing the transport belt  57   a  of the transport device  57  against the cooler  58 . 
     The cooler  58  is disposed in contact with the inner surface of the transport belt  57   a  of the transport device  57  and constituted as a processor that performs cooling. Specifically, the cooler  58  includes a support  58   a  having thermal conductivity and a cooling body  58   b  that continuously feeds or circulates a cooling medium (gas or liquid) (not illustrated) to the support  58   a  through a pipe, a path, or the like in the passage width direction Wd of the processing target object  9 . A portion of the cooler  58  that contacts the inner surface of the transport belt  57   a  functions as a major cooler. 
     The support  58   a  is a long member having a size longer than the maximum width size W 1  of the processing target object  9  in the passage width direction Wd. The cooling body  58   b  is a cooler linearly provided to extend in the longitudinal direction of the support  58   a  (the direction extending in the passage width direction Wd of the recording sheet  9 A) and in a parallel state separated from each other in the passage width direction Wd of the processing target object  9 . The cooling body  58   b  is coupled to a device (not illustrated) that generates and feeds a cooling medium. 
     In the cooling device  5 B, the processing target object  9  is cooled when the processing target object  9  transported by the transport belt  57   a  of the transport device  57  passes through the cooler  58 . At this time, the processing target object  9  passes while being pressed against the cooler  58  by the pressing rotary body  59 . 
     Also in the cooling device  5 B, for example, when processing target objects  9  having a width size W (intermediate width size W 2 ) smaller than the maximum width size W 1  are continuously passed and cooled, a non-passage region E 2  that is a region through which the processing target objects  9  do not pass is generated in the cooler  58 . Thus, a portion of the cooler  58  corresponding to the passage region E 1  through which the processing target objects  9  pass absorbs heat by cooling during the thermal processing and the temperature thereof rises, whereas a portion of the cooler  58  corresponding to the non-passage region E 2  of the processing target objects  9  does not absorb heat by cooling during the thermal processing and thus tends to be in a low temperature state. 
     In this case, while the portion of the cooler  58  corresponding to the passage region E 1  is relatively high in temperature, the portion of the cooler  58  corresponding to the non-passage region E 2  is locally low in temperature, a temperature difference occurs in the entire cooler  58 , and consequently, cooling unevenness may be induced when a processing target object  9  having a large width size W (W 1 ) is passed and cooled thereafter. 
     That is, in the cooling device  5 B, when the thermal processing of cooling is performed as described above, the cooler  58  which is the thermal processor  5   j  is in a state in which an unwanted temperature difference occurs between the portion corresponding to the passage region E 1  of the processing target object  9  and the portion corresponding to the non-passage region E 2  of the processing target object  9 , as illustrated in  FIG. 12B . At this time, the portion of the cooler  58  corresponding to the passage region E 1  of the processing target object  9  becomes a high-temperature portion that increases in temperature and causes a temperature difference, while the portion of the cooler  58  corresponding to the non-passage region E 2  becomes a low-temperature portion that has a relatively lower temperature than the portion (high-temperature portion) corresponding to the passage region E 1  and causes a temperature difference. 
     In the cooling device  5 B, as illustrated in  FIGS. 12A and 12B , two heat pipes  1 A and  1 B are disposed in contact with a surface (back surface) of the cooler  58  opposite to a surface thereof that contacts the transport belt  57   a , from the viewpoint of suppressing occurrence of an unwanted temperature difference between the portion (high-temperature portion) of the cooler  58  corresponding to the passage region E 1  of the processing target object  9  and the portion (low-temperature portion) of the cooler  58  corresponding to the non-passage region E 2  of the processing target object  9 . Here, the high-temperature portion is a portion that generates a temperature at which the working fluid  12  enclosed in the heat pipes  1 A and  1 B is at least vaporizable, and is, for example, a portion having a temperature of 100° C. or higher. 
     Each of the heat pipes  1 A and  1 B employs the heat pipe  1  having the configuration according to the first exemplary embodiment. 
     In the cooling device  5 B, as illustrated in  FIG. 12B , the heat pipes  1 A and  1 B are disposed in a state in contact with the portion of the cooler  58  in the thermal processor  5   j  corresponding to the passage region E 1  through which the processing target object  9  having at least the maximum width size W 1  passes. At this time, the heat pipes  1 A and  1 B are configured such that the occupancy rate of the liquid transfer member  15  is maintained in a range of 20% or more and 50% or less in a region that contacts the portion corresponding to the passage region E 1  through which the processing target object  9  having the maximum width size W 1  passes. 
     In the cooling device  5 B, the heat pipes  1 A and  1 B are each disposed such that the liquid transfer member  15  is in contact with a portion of the inner wall surface  10   c  ( FIGS. 1A, 1B , and the like) inside the corresponding pipe  10  which faces the cooler  58 . 
     In the cooling device  5 B in which the heat pipes  1 A and  1 B are disposed, even when the portion of the cooler  58  that the processing target object  9  contacts (via the transport belt  57   a ) corresponding to the non-passage region E 2  of the processing target object  9  is generated and a temperature difference occurs, the heat of the portion of the cooler  58  corresponding to the passage region E 1  is moved to the portion (low-temperature portion) corresponding to the non-passage region E 2  of the processing target object  9  where the temperature is relatively lower than the temperature of the portion (high-temperature portion) corresponding to the passage region E 1  by the action of heat transfer of the heat pipes  1 A and  1 B. 
     Consequently, in the cooling device  5 B, as compared with a case where the heat pipes  1 A and  1 B are not disposed, when the portion corresponding to the non-passage region E 2  of the processing target object  9  is generated, a temperature rise in the passage region E 1  is suppressed, and occurrence of an unwanted temperature difference in the cooler  58  is suppressed. 
     In the cooling device  5 B, even when the cross-sectional area S 1  of the pipe  10  in the transverse direction Sd is reduced, excellent thermal conductivity performance is obtained as compared with the case where the heat pipe in which the occupancy rate of the liquid transfer member  15  is not in the range of 20% or more and 50% or less is used. 
     Another example of the thermal processing device  5  may be, for example, a drying device including a thermal processor  5   h  that performs thermal processing of drying a processing target object  9  and a thermally conductive pipe  1  such as a heat pipe disposed at a portion of the thermal processor  5   h  where a temperature difference occurring in the passage width direction Wd of the processing target object  9  is to be suppressed. The thermal processing of drying at this time is thermal processing of heating. 
     The thermally conductive pipe  1  represented by the heat pipe disposed in the thermal processing device  5  may be a thermally conductive pipe  1  ( FIGS. 4A, 4B, 5A, and 5B ) having the configuration described in the modification of the first exemplary embodiment. The number of the thermally conductive pipes  1  arranged in the thermal processing device  5  is not limited to two, and may be one, or three or more. The transport device  57  disposed in the thermal processing device  5  may be a transport device using a transport method other than the belt transport method. 
     Although the second exemplary embodiment exemplifies the image forming apparatus  7 A including the imaging device  2 A and the heating device  5 A as the processing system  7 , the processing system  7  may have another configuration. 
     Another example of the processing system  7  may be, for example, a processing system including a coating apparatus, a printer, another image forming apparatus, or the like, in which a processing apparatus  2  that performs another processing such as coating, printing, or image formation by another image forming method on a processing target object  9  is employed as another processing apparatus  2  that performs another processing other than the thermal processing, as illustrated in  FIG. 13A . In this case, as the thermal processing device  5 , a suitable device such as the heating device  5 A, the cooling device  5 B, or the drying device described above is used. 
     As illustrated in  FIG. 13B , the processing system  7  is also applicable to an apparatus in which the processing apparatus  2  performs another processing other than the thermal processing on a processing target object  9  after passing through the thermal processing device  5 . 
     The foregoing description of the exemplary embodiments of the present disclosure has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the disclosure and its practical applications, thereby enabling others skilled in the art to understand the disclosure for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.