Patent Publication Number: US-11662161-B2

Title: Heat conduction device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation application of International Patent Application No. PCT/JP2017/042492 filed on Nov. 28, 2017, which designated the U.S. and claims the benefit of priority from Japanese Patent Application No. 2016-245478 filed on Dec. 19, 2016, and Japanese Patent Application No. 2017-186657 filed on Sep. 27, 2017. The entire disclosures of all of the above applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a heat conduction device that transfers heat of a heat source. 
     BACKGROUND 
     A heat conduction device is known, which takes heat of a human body or supplies heat to the human body by heat conduction by using, as a heat source (hot heat source or cold heat source), a peltier device or a metal pipe through which a heat medium whose temperature is controlled. 
     SUMMARY 
     A heat conduction device according to an aspect of the present disclosure includes a heat source portion, a temperature control surface, and a heat transfer portion. The heat source portion generates at least hot heat or cold heat. The temperature control surface is sectioned into multiple temperature control sections, and at least some of the multiple temperature control sections are distance away from the heat source portion. The heat transfer portions connect the heat source portion and the temperature control sections so as to transfer heat therebetween. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view illustrating a heat conduction device according to at least one embodiment of the present disclosure. 
         FIG.  2    is a cross-sectional diagram illustrating a flow of heat in the heat conduction device of at least one embodiment of the present disclosure. 
         FIG.  3    is a graph illustrating a relationship between a surface temperature of a temperature control surface and a distance between the temperature control surface and a heat source portion. 
         FIG.  4    is a graph illustrating a relationship between a surface temperature of a temperature control surface and a distance between the temperature control surface and a heat source portion. 
         FIG.  5    is a cross-sectional diagram illustrating a heat conduction device according to at least one embodiment of the present disclosure. 
         FIG.  6    is a cross-sectional diagram illustrating a heat conduction device according to at least one embodiment of the present disclosure. 
         FIG.  7    is a cross-sectional diagram illustrating a heat conduction device according to at least one embodiment of the present disclosure. 
         FIG.  8    is a block diagram illustrating a configuration of a heat conduction device including a thermal switch, according to at least one embodiment of the present disclosure. 
         FIG.  9    is a block diagram illustrating a configuration of the heat conduction device including thermal switches, according to at least one embodiment of the present disclosure. 
         FIG.  10    is a perspective view illustrating a heat conduction device according to at least one embodiment of the present disclosure. 
         FIG.  11    is a cross-sectional view of the heat conduction device of at least one embodiment of the present disclosure. 
         FIG.  12    is a perspective view illustrating a heat conduction device according to at least one embodiment of the present disclosure. 
         FIG.  13    is a plan view illustrating a heat transfer sheet according to at least one embodiment of the present disclosure. 
         FIG.  14    is a cross-sectional diagram illustrating a heat conduction device according to at least one embodiment of the present disclosure. 
     
    
    
     EMBODIMENTS 
     Hereinafter, embodiments for implementing the present disclosure will be described referring to drawings. In each embodiment, portions corresponding to the elements described in the preceding embodiments are denoted by the same reference numerals, and redundant explanation may be omitted. In each of the embodiments, when only a part of the configuration is described, the other parts of the configuration can be applied to the other embodiments described above. The present disclosure is not limited to combinations of embodiments which combine parts that are explicitly described as being combinable. As long as no problems are present, the various embodiments may be partially combined with each other even if not explicitly described. 
     First Embodiment 
     A first embodiment of the present disclosure will be described below with reference to the drawings. A heat conduction device  1  of the present embodiment is a cooling-heating device having a panel shape and can be used in a temperature control sheet for a vehicle, for example. 
     As shown in  FIG.  1   , the heat conduction device  1  of the present embodiment includes a heat source portion  10 . The heat source portion  10  functions as a hot heat source supplying hot heat or a cold heat source supplying cold heat. 
     The heat source portion  10  of the present embodiment is a cooling water passage through which cooling water whose temperature is adjusted flows. In an example shown in  FIG.  1   , the cooling water flows inside the heat source portion  10  in a direction perpendicular to the drawing sheet. 
     The cooling water is a heat medium receiving hot heat of a heat generating device (not shown) or cold heat of a cooling device (not shown). The heat generating device is a device generating hot heat during its operation such as an internal combustion engine, a cooling water intercooler, and an inverter. The cooling device is a device generating cold heat during its operation such as a chiller of a refrigeration cycle. 
     The heat conduction device  1  includes a temperature control surface  11 . At least a part of the temperature control surface  11  is distance away from the heat source portion  10 . The temperature control surface  11  is a contact surface that contacts with a human body. 
     The temperature control surface  11  is sectioned into multiple temperature control sections  11   a , and each of the temperature control sections is thermally connected with the heat source portion  10  by a heat transfer sheet  12  through a thermal resistance adjuster  14 . One end of the heat transfer sheet  12  is connected to the above-described temperature control section  11   a . The heat transfer sheet  12  corresponds to a heat transfer portion of the present disclosure. Since each of the temperature control sections  11   a  is connected to the heat source portion  10 , each of the temperature control sections  11   a  can directly transfer heat of the heat source portion  10 , and accordingly the temperature can be uniformed. Since the temperature control sections  11   a  are separated from each other based on a distance from the heat source portion  10 , uniform temperature control can be performed. The uniform temperature control means adjusting to a temperature at which the user can feel warm or cold without feeling discomfort when the human body is in contact. The uniform temperature control provides a temperature distribution on the temperature control surface  11  in which a temperature difference between sections having high temperature and sections having low temperature is at or below 20 degrees Celsius, more preferably 10 degrees Celsius or 5 degrees Celsius, and accordingly the user can feel comfortable without feeling unpleasant. 
     In the present embodiment, the heat transfer sheet  12  and the temperature control sections  11   a  are integrated with each other, and a part of the heat transfer sheet  12  is the temperature control sections  11   a . Accordingly, the heat transfer sheet  12  and the temperature control sections  11   a  are made of the same material. However, the material of the heat transfer sheet  12  may be different from that of the temperature control sections  11   a . The temperature control surface  11  may be covered with fabric to improve comfort when the human body contacts as long as the human body senses warm and cold sufficiently when the heat is exchanged between the temperature control surface  11  and the human body. The surface of the temperature control surface  11  may be covered with a sheet member for protection. 
     Since the temperature control sections  11   a  are separated from each other based on a distance from the heat source portion  10 , uniform temperature control can be performed. In an example shown in  FIG.  1   , the temperature control sections  11   a  are sectioned into five sections based on a distance from the heat source portion  10  (that is, in a left-right direction). The heat transfer sheets  12  are provided so as to correspond to the temperature control sections  11   a  sectioned based on the distance from the heat source portion  10 . Since the heat transfer sheet  12  corresponding to the temperature control sections  11   a  farther from the heat source portion  10  is longer, the thermal resistance caused by the heat transfer sheet  12  is larger, and accordingly the heat from the heat source portion  10  is less likely to be transferred to the temperature control section  11   a . Since the temperature control sections  11   a  are sectioned based on the distance from the heat source portion  10 , the heat transfer from the heat source portion  10  to close temperature control sections  11   a , to which the heat is easily transferred, and the heat transfer from the heat source portion  10  to distant temperature control sections  11   a , to which the heat is hard to be transferred, can be adjusted, and accordingly uniform temperature control can be performed over the entire part of the temperature control surface  11 . In the example shown in  FIG.  1   , the temperature control sections  11   a  separated from each other based on the distance from the heat source portion  10  are further sectioned into three sections along a direction perpendicular to a direction along which the temperature control surface  11  is sectioned based on the distance from the heat source portion  10 . However, the temperature control sections  11   a  are not necessarily sectioned in the direction perpendicular to the direction along which the temperature control surface  11  is sectioned based on the distance from the heat source portion  10 . 
     The lengths of the heat transfer sheets  12  are different from each other based on the distance between the temperature control section  11   a  and the heat source portion  10 . In the example shown in  FIG.  1   , the heat transfer sheet  12  located on the upper side is short, and the heat transfer sheet  12  located on the lower side is long. If each of the temperature control sections  11   a  are made of the same material having the same properties, the same width, and the same thickness, the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  varies based on the length of the heat transfer sheet  12 . The uniform temperature control can be performed in the entire part of the temperature control surface  11  by adjusting the difference in the thermal resistance caused by the heat transfer sheet  12  to uniform the thermal resistance between the temperature control sections  11   a  and the heat source portion  10 . 
     In the present embodiment, a thermal resistance adjuster  14  is provided between the heat source portion  10  and the heat transfer sheet  12  to adjust the difference of the thermal resistance caused by the difference of the lengths of the heat transfer sheets  12 . The thermal resistance adjuster  14  is configured to adjust the thermal resistance between the heat source portion  10  and the temperature control sections  11   a.    
     The thermal resistance adjuster  14  adjusts the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  based on the distance between the heat source portion  10  and the temperature control section  11   a , i.e. based on the length of the heat transfer sheet  12 . The longer the heat transfer sheet  12  is, the larger the thermal resistance caused by the heat transfer sheet  12  is. The shorter the heat transfer sheet  12  is, the smaller the thermal resistance caused by the heat transfer sheet  12  is. The thermal resistance adjuster  14  adjusts the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  connected by the short heat transfer sheet  12  to be large while the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  connected by the long heat transfer sheet  12  does not increase. Specifically, the thermal resistance between the heat source portion  10  and the heat transfer sheet  12  can be adjusted by changing the length of the thermal resistance adjuster  14  between the heat source portion  10  and the heat transfer sheet  12 . Here, as the heat transfer sheet  12  is longer, the length of the thermal resistance adjuster  14  in the left-right direction between the heat transfer sheet  12  and the heat source portion  10  is shortened. As the heat transfer sheet  12  is shorter, the length of the thermal resistance adjuster  14  in the left-right direction between the heat transfer sheet  12  and the heat source portion  10  is elongated. 
     Thereby, the thermal resistance between the heat source portion  10  and each temperature control section  11   a  can be uniformed, and the temperature distribution generated on the temperature control surface  11  can be uniformed. 
     In the present embodiment, the thermal resistance adjuster  14  is provided between the heat source portion  10  and the heat transfer sheet  12 . However, the thermal resistance adjuster  14  may be provided inside the heat transfer sheet  12  or in the temperature control section  11   a  that is a contact part contacting with the human body. 
     The thermal resistance between the heat source portion  10  and the temperature control section  11   a  can be adjusted finely by using the thermal resistance adjuster  14  made of a low-thermal resistance material. If the thermal resistance is adjusted by the member having high thermal resistance, the thermal resistance is likely to be large even if the size of the member is small, and accordingly processing with very high dimensional accuracy is required. In contrast, when the member having low thermal resistance is used, it is possible to use the member having a large size when correcting the same amount of thermal resistance, and it is possible to reduce the required processing accuracy. Examples of the member having low thermal resistance include materials having high thermal conductivity such as graphite and various metal materials such as aluminum, copper, silver, gold, and titanium. When titanium is used, corrosion resistance can be improved. In contrast, materials having low thermal conductivity such as resin can be used as the member having low thermal resistance as long as the dimensions such as thickness of the material can be controlled with high accuracy, such as a film and a tape. In this case, it is also possible to give the heat resistance adjusting portion  14   a  function as a bonding member by using one having adhesiveness or stickiness. 
     As a method of adjusting the thermal resistance between the heat source portion  10  and each temperature control section  11   a , not only the method providing the above-described thermal resistance adjuster  14  but also a method adjusting the thickness, shape, and thermal conductivity of the heat transfer sheet can be used. Specifically, in order to adjust the thermal resistance between the heat transfer sheet  12  connecting the heat source portion  10  and the temperature control section  11   a  close to the heat source portion  10 , the thermal resistance can be adjusted by using a material with a low thermal conductivity for the heat transfer sheet, reducing the thickness or the width of the heat transfer sheet, or changing the shape of the heat transfer sheet in two dimensions or three dimensions. 
     Since the heat transfer sheets  12  are stacked with each other, the heat transfer sheets  12  can be formed in a compact shape and installed in a narrow place. 
     The heat transfer sheet  12  is made of a sheet-shaped material having high thermal conductivity. As a high thermal conductivity material, metallic materials other than a carbon material can be used. As a carbon material, it is possible to use a sheet made of carbon fiber, carbon nanotube, graphene, diamond or the like in addition to a graphite sheet. As the metal, it is possible to use a single metal such as gold, silver, aluminum, copper or an alloy of these metals. 
     When an anisotropic heat conductive material, which is likely to transfer heat in a direction parallel to the sheet surface (a left-right direction and a thickness direction of the drawing paper) compared to in a direction perpendicular to the sheet surface (an up-down direction in the drawing), is used as the material of the heat transfer sheet  12 , the effects in the up-down direction can be reduced, and accordingly the heat can be effectively transferred between the temperature control surface  11   a  and the heat source portion  10 . As the degree of anisotropy of the thermal conductivity, the thermal conductivity in the direction parallel to the sheet surface is 10 times or more, more preferably 100 or more times larger than the thermal conductivity in the direction orthogonal to the sheet surface. The heat conductivity of the heat transfer sheet  12  is higher in the direction parallel to the sheet surface, that is, in the direction connecting the heat source portion  10  and the temperature control section  11   a  than the heat conductivity in at least one other direction. 
     Examples of such high thermal conductivity materials include graphite sheets such as Graphinity (manufactured by Kaneka), PGS graphite sheets (manufactured by Panasonic), and GD-AGS (manufactured by Guardneck). In the present embodiment, Graphinity (40 μm in thickness) manufactured by Kaneka is used as the high thermal conductivity material. The thermal conductivity of the Kaneka Graphinity of the present embodiment in the direction parallel to the sheet surface is 1500 W/mK, the thermal conductivity in the direction perpendicular to the sheet surface is 5 W/mK. The thermal conductivity in the direction parallel to the sheet surface is 300 times larger than the thermal conductivity in the direction perpendicular to the sheet surface. 
     One graphite sheet may be used as one heat transfer sheet  12 , and some graphite sheets may be stacked to be used as one heat transfer sheet  12 . When some graphite sheets are stacked and used as one heat transfer sheet  12 , the heat conductivity of the heat transfer sheet  12  can be increased. 
     The heat transfer sheets  12  are stacked with each other. Thermal insulation sheets  13  are disposed between the adjacent heat transfer sheets  12 , and the thermal insulation sheets  13  and the heat transfer sheet  12  are alternately stacked with each other. The heat insulation sheet  13  covers the heat transfer sheet  12 . The heat insulation sheet  13  is a sheet-shaped heat insulating material, and for example, foamed urethane, foamed olefin, foamed resin such as foamed acrylic, glass wool, or ceramic fiber such as silica wool can be used as the heat insulation sheet  13 . In the present embodiment, Marinetex Cross (thickness: 0.18 mm) manufactured by Nichias or LZ-2000 (thickness: 0.9 mm) manufactured by Inoac is used as the heat insulation sheet  13 . The heat insulation sheet  13  corresponds to the heat insulation portion of the present disclosure. 
     The heat insulation sheet  13  makes it difficult to transfer heat between the respective heat transfer sheets  12 . In addition to the effect that it is possible to directly transfer hot heat or cold heat of the heat source portion  10  to the temperature control section  11   a  by the heat transfer sheet  12  as described above, desired temperature control can be performed without being affected by the temperature change of another temperature control section  11   a  even when the temperature of an object (for example, a human body) in contact is different in each temperature control section  11   a.    
     As shown to  FIG.  1    and  FIG.  2   , the heat transfer sheet  12  and the heat insulation sheet  13  are bent in one part or several parts according to these thicknesses. Thus, in the present embodiment, the temperature control sections  11   a  are located on the same plane. 
     By using a flexible material as a constituent material of the heat transfer sheet  12  and the heat insulation sheet  13 , it is possible to form a curved surface as well as bending and twisting. As a flexible material of the heat transfer sheet  12 , thin metal plate can be used as well as carbon materials such as graphite sheet. Moreover, foamed resin, glass wool, or ceramic fibers such as silica wool may be used as a flexible material of the heat insulation sheet  13 . 
     The heat source portion  10  and the thermal resistance adjuster  14  are accommodated in a casing  15 . The casing  15  is covered with a heat source heat insulation portion  16 . The casing  15  may be made of the material that is the same as the thermal resistance adjuster  14 , for example. When the casing  15  and the thermal resistance adjuster  14  are made of the same material, the casing  15  and the thermal resistance adjuster  14  may be provided as a single component. 
     The material of the heat source heat insulation portion  16  may be the same as that of the heat insulation sheet  13 . Since the heat source heat insulation portion  16  suppress the heat dissipation from the heat source portion  10  and the thermal resistance adjuster  14  to the outside, the amount of heat that is transferred from the heat source portion  10  to the temperature control sections  11   a  can be increased. The heat source heat insulation portion  16  is not necessarily required when the heat of the heat source portion  10  can be transferred to the temperature control surface  11  sufficiently. 
     The heat transfer sheets  12  and the heat insulation sheets  13  may be bonded with each other by adhesive to laminate the heat transfer sheets  12  and the heat insulation sheets  13 . In this case, the sheets  12 ,  13  may be bonded over the entire surface, or the sheets  12 ,  13  may be partially bonded. 
     When the sheets  12  and  13  are partially adhered, for example, the portions of the sheets  12  and  13  accommodated in the casing  15  are adhered to each other, and the portions of the sheets  12  and  13  outside the casing  15  are not adhered to each other. When the sheets  12 ,  13  are partially adhered to each other, the laminate formed of the heat transfer sheets  12  and the heat insulation sheets  13  is more flexible than in the case where the respective sheets  12 ,  13  are adhered over the entire surface. 
     In  FIG.  2   , flows of the heat in a case where the heat source portion  10  supplies cold heat to cool the human body in contact with the temperature control surface  11  are illustrated. In the example shown in  FIG.  2   , the temperature control surface  11  are sectioned into three temperature control sections  11   a  based on the distance from the heat source portion  10 . As shown in  FIG.  2   , the heat of the human body moves from the temperature control sections  11   a  to the heat source portion  10  through the heat transfer sheets  12 . Thereby, the human body in contact with the temperature control sections  11   a  is cooled by the cold heat of the heat source portion  10 . 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Distance (cm) 
                 1 
                 3 
                 5 
                 7 
                 9 
                 11 
                 13 
                 15 
                 17 
                 19 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Embodiment (° C.) 
                 16.3 
                 16.7 
                 16.9 
                 17.6 
                 18.0 
                 18.7 
                 19.6 
                 20.7 
                 21.7 
                 23.0 
               
               
                 Comparative 
                 17.9 
                 19.9 
                 22.5 
                 23.3 
                 24.2 
                 24.6 
                 25.0 
                 25.2 
                 25.3 
                 25.3 
               
               
                 example (° C.) 
               
               
                   
               
            
           
         
       
     
       FIG.  3    and Table 1 show relationships between a surface temperature of the temperature control surface  11  and the distance between the temperature control surface  11  and the heat source portion  10 . In the example shown in  FIG.  3    and Table 1, the temperature of the heat source portion  10  is 5 degrees Celsius, and the outside air temperature is 26 degrees Celsius. In  FIG.  3    and Table 1, a configuration in which the temperature control surface  11  is not sectioned is shown as a comparative example. In  FIGS.  3 ,  4   , 26 degrees Celsius is indicated by a dotted line. 
     As shown in  FIG.  3    and Table 1, in the comparative example in which the temperature control surface  11  is formed as single surface, the increase rate of the surface temperature of the temperature control surface  11  is high, and accordingly the surface temperature rapidly approaches the outside air temperature with the distance from the heat source portion  10 . In contrast, in the present embodiment in which the temperature control surface  11  is divided into the temperature control sections  11   a , the surface temperature of the temperature control surface  11  gradually increases. For this reason, in the present embodiment, the surface temperature of the temperature control surface  11  is maintained at a low level even at a part disposed away from the heat source portion  10  to some extent. That is, in the present embodiment, it is possible to effectively transfer the cold heat of the heat source portion  10  to a place away from the heat source portion  10 . 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Distance (cm) 
                 1 
                 3 
                 5 
                 7 
                 9 
                 11 
                 13 
                 15 
                 17 
                 19 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Embodiment (° C.) 
                 16.3 
                 — 
                 16.9 
                 17.6 
                 18.0 
                 18.7 
                 19.6 
                 20.7 
                 21.7 
                 23.0 
               
               
                 Comparative 
                 17.9 
                 — 
                 24.5 
                 24.8 
                 25.0 
                 25.2 
                 25.2 
                 25.3 
                 25.3 
                 25.5 
               
               
                 example (° C.) 
               
               
                   
               
            
           
         
       
     
       FIG.  4    and Table 2 show the relationships between the surface temperature of the temperature control surface  11  and the distance from the heat source portion  10  of the temperature control surface  11  when a human body is in contact with a part of the temperature control surface  11 . In the example shown in  FIG.  4    and Table 2, the human body is in contact with a part of the temperature control surface  11  3 cm away from the heat source portion  10 . Also in the example shown in  FIG.  4    and Table 2, the temperature of the heat source portion  10  is 5 degrees Celsius, and the outside temperature is 26 degrees Celsius. A configuration in which the temperature control surface  11  is not divided is shown as a comparative example. 
     As shown in  FIG.  4    and Table 2, in the comparative example where the temperature control surface  11  is formed as single surface, the surface temperature rapidly increases at a part father from the heat source portion  10  than the part where the human body is in contact. That is, in the comparative example, although the cold heat of the heat source portion  10  can be transferred to the human body in contact with the temperature control surface  11 , the cold heat of the heat source portion  10  is unlikely to be transferred to a part farther from the part in contact with the human body due to the heat of the human body. When a portion of the human body whose area is larger than a certain area is in contact with the temperature control surface  11 , the user feels the hot heat or cold heat at a part close to the heat source. However, the user may not sufficiently feel the hot heat or the cold heat at the other part farther from the heat source due to the heat transfer at the part close to the heat source. 
     In contrast, in the present embodiment, each temperature control section  11   a  of the temperature control surface  11  is independently connected to the heat source portion  10  through the heat transfer sheet  12 . Accordingly, even when the human body is in contact with a part of the temperature control surface  11 , the other part of the temperature control surface  11  is unlikely to be affected. For this reason, in the present embodiment, the surface temperature of the temperature control surface  11  is maintained at a low level even at a part farther from the heat source portion  10  than the part in contact with the human body. That is, according to the present embodiment, the cold heat can be transferred to the human body in contact with a part of the temperature control surface  11 . In addition, the cold heat of the heat source portion  10  can be effectively transferred to the other part farther from the heat source portion  10  than the part at which the human body is in contact with the temperature control surface  11 . As a result, the temperature of the temperature control surface  11  can be uniformed without being influenced by the disturbance factor generated on the temperature control surface  11 . 
     According to the present embodiment described above, the temperature control surface  11  is divided into temperature control sections  11   a  based on the distance from the heat source portion  10 , and the respective temperature control section  11   a  and the heat source portion  10  are connected through heat transfer sheet  12 . Thus, regardless of the distance from the heat source portion  10 , the temperature control sections  11   a  can be directly heated or cooled by the heat of the heat source portion  10 . Therefore, the temperature control section  11   a  disposed away from the heat source portion  10  can also be heated or cooled in the same manner as the temperature control section  11   a  disposed near the heat source portion  10 , and the entire temperature control surface  11  can be adjusted to a uniform temperature. 
     Further, according to the configuration of the present embodiment, even when a thermal disturbance, such as a contact of a human body with the temperature control surface  11 , that occurs heat exchange between the temperature control surface  11  and the outside is occurred, the temperature of the temperature control surface  11  can be uniformed. 
     Moreover, in the present embodiment, as described above, since the flex material is used for the heat transfer sheet  12 , it is possible to form an appropriate curved surface even in contact with the human body, and accordingly the comfort is not impaired. 
     Second Embodiment 
     Next, a second embodiment of the present disclosure will be described. In the first embodiment described above, the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  is adjusted by the thermal resistance adjuster  14 . In the second embodiment, the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  is adjusted by changing the shape or the material of the heat transfer sheets  12 . 
     In  FIG.  5   , an example where the thicknesses of the heat transfer sheets  12  are varied is shown. When the thicknesses of the heat transfer sheets  12  are varied as shown in  FIG.  5   , the thermal resistance of the heat transfer sheet  12  can be decreased by making the heat transfer sheet  12  thick, and the thermal resistance of the heat transfer sheet  12  can be increased by making the heat transfer sheet  12  thin. 
     Moreover, although illustration is omitted, the widths of the heat transfer sheets  12  may be varied, and the material of the heat transfer sheet  12  may be varied. When the widths of the heat transfer sheets  12  are varied, the thermal resistance can be decreased by increasing the width of the heat transfer sheet  12 , and the thermal resistance can be increased by decreasing the width of the heat transfer sheet  12 . When the materials of the heat transfer sheets  12  are varied, the thermal resistance can be reduced by using a material having a large thermal conductivity, and the thermal resistance can be increased by using a material having a small thermal conductivity. 
     Since the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  is uniformed by the heat transfer sheet  12  itself in the second embodiment, the adjustment of the thermal resistance by the thermal resistance adjuster  14  is not necessary, and accordingly the thermal resistance adjuster  14  is not needed. Therefore, direct heat exchange can be performed between the heat source portion  10  and the heat transfer sheet  12 . 
     When the heat transfer sheet  12  uniforms the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  as in the second embodiment, the heat transfer sheet  12  has the same function as the thermal resistance adjuster  14 . The adjustment of the thermal resistance by the heat transfer sheet  12  and the adjustment of the thermal resistance by the thermal resistance adjuster  14  may be used together to mutually complement the function of adjusting the temperature control surface  11  to a uniform temperature. 
     Third Embodiment 
     Next, a third embodiment of the present disclosure will be described. In the first embodiment described above, the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  is adjusted by the thermal resistance adjuster  14 . In the third embodiment, the temperature control sections  11   a  are provided based on the thermal resistance between the heat source portion  10  and the temperature control section  11   a . For example, the area of the temperature control section  11   a  may be varied based on the thermal resistance between the heat source portion  10  and the temperature control section  11   a.    
     In  FIG.  6   , an example where the area of the temperature control section  11   a  is varied based on the thermal resistance between the heat source portion  10  and the temperature control section  11   a . As shown in  FIG.  6   , when the thermal resistance between the heat source portion  10  and the temperature control section  11   a  is large, the area of the temperature control section  11   a  is small. When the thermal resistance between the heat source portion  10  and the temperature control section  11   a  is small, the area of the temperature control section  11   a  is large. Specifically, the area of the temperature control section  11   a  far from the heat source portion  10  is small, and the area of the temperature control section  11   a  close to the heat source portion  10  is large. 
     To vary the area of the temperature control sections  11   a , the length of the temperature control section  11   a  in a left-right direction in  FIG.  6    may be adjusted as shown in  FIG.  6   , or the length of the temperature control section  11   a  in a direction perpendicular to the drawing sheet of  FIG.  6    may be adjusted. 
     In these cases, similarly to the second embodiment, since the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  is uniformed by the temperature control section  11   a  itself, the adjustment of the thermal resistance by the thermal resistance adjuster  14  is not necessary, and accordingly the thermal resistance adjuster  14  is not needed. Therefore, direct heat exchange can be performed between the heat source portion  10  and the heat transfer sheet  12 . 
     When the temperature control section  11   a  uniforms the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  as in the third embodiment, the heat transfer sheet  12  has the same function as the thermal resistance adjuster  14 . Similarly to the second embodiment, the adjustment of the thermal resistance by the temperature control section  11   a  and the adjustment of the thermal resistance by the thermal resistance adjuster  14  may be used together to mutually complement the function of adjusting the temperature control surface  11  to a uniform temperature. 
     Fourth Embodiment 
     Next, a fourth embodiment of the present disclosure will be described. In the above-described first embodiment, the temperature control sections  11   a  adjacent to each other are located on one plane by bending the heat transfer sheets  12  and the heat insulation sheets  13 . In the fourth embodiment, the heat transfer sheets  12  and the heat insulation sheets  13  extend straight to have a flat shape. 
     As shown in  FIG.  7   , when the heat transfer sheets  12  and the heat insulation sheets  13  have a flat shape, steps are provided between the temperature control sections  11   a  adjacent to each other. The steps are formed between the temperature control sections  11   a  adjacent to each other in the fourth embodiment. However, when the heat transfer sheets  11   a  and the heat insulation sheets  13  are sufficiently thin, the user senses the temperature control surface  11  as a flat surface or a curved surface without sensing the steps even when the steps are formed between the temperature control sections  11   a . In addition, depending on the application of the heat conduction device  1 , there may be no problem even if the user senses the steps provided between the temperature control sections  11   a.    
     Fifth Embodiment 
     Next, a fifth embodiment of the present disclosure will be described. In the fifth embodiment, a heat transfer path between the heat source portion  10  and the temperature control sections  11   a  can be switched between a connected state and a disconnected state in the configurations of the above-described embodiments. For example, the heat transfer path is configured to be able to be separated, and thus the heat transfer path between the heat source portion  10  and the temperature control section  11   a  can be connected and disconnected by mechanically switching the heat transfer sheet  12  between the connected state and disconnected state. Thereby, on/off control of heat transfer between the heat source portion  10  and the temperature control sections  11   a  can be performed. 
     Specifically, as shown in  FIGS.  8 ,  9   , a thermal switch  17  configured to control the heat transfer is inserted between the heat source portion  10  and the heat transfer sheet  12 . The thermal switch  17  is a switch configured to switch between the heat conductive state and the heat insulated state between the heat source portion  10  and the heat transfer sheet  12 . By using the thermal switch  17 , unnecessary heat transfer from the heat source portion  10  to the heat transfer sheet  12  can be suppressed, or the heat transferred from the heat source portion  10  to the heat transfer sheet  12  can be increased drastically. 
     A well-known structure can be used as the heat switch  17  such as thermal switches described in WO 2014/156991 A1 or JP 2015-092101 A. 
     An example where the thermal switch  17  is provided between the heat source portion  10  and the heat transfer sheet  12  is shown in  FIG.  8   . When the heat transfer from the heat source portion  10  to the heat transfer sheet  12  is not necessary, the unnecessary heat transfer can be suppressed by shutting off the heat transfer path by the thermal switch  17 . 
     An example where two heat source portions  10   a ,  10   b  are provided is shown in  FIG.  9   . For example, a first heat source portion  10   a  is used as a hot heat source, and a second heat source portion  10   b  is used as a cold heat source. A first thermal switch  17   a  is provided between the first heat source portion  10   a  and the heat transfer sheet  12 , and a second thermal switch  17   b  is provided between the second heat source portion  10   b  and the heat transfer sheet  12 . According to the configuration shown in  FIG.  9   , the heat source portions  10   a ,  10   b  connected to the heat transfer sheet  12  can be switched by using two thermal switches  17   a ,  17   b , and accordingly the temperature of the temperature control surface  11  can be changed quickly. 
     Bonding between the respective components shown in  FIGS.  8 ,  9    can be performed by a method providing a good thermal connection such as brazing, soldering, and screwing. Further, the respective components may be connected by heat pipes. Furthermore, the first heat source portion  10   a  (hot heat source) in  FIG.  9    can also be configured by a Peltier device. In that case, the first heat source portion  10   a  is electrically controlled, and the first heat switch  17   a  is not necessary. 
     Sixth Embodiment 
     Next, a sixth embodiment of the present disclosure will be described. The sixth embodiment is different from the first embodiment in the configurations of the heat transfer sheet  12  and the thermal resistance adjuster  14 . 
     In the above-described first embodiment, the thermal resistance adjuster  14  is provided between the heat source portion  10  and the heat transfer sheet  12 . However, in the sixth embodiment, the heat transfer sheet  12  is separated, and the thermal resistance adjuster  14  is provided between the separated heat transfer sheets  12 . For this reason, in the sixth embodiment, the heat source portion  10  and the heat transfer sheet  12  are in direct contact with each other, and direct heat exchange can be performed between the heat source portion  10  and the heat transfer sheet  12 . 
     As shown in  FIG.  10   , in the sixth embodiment, multiple thermal resistance adjusters  14  are provided to correspond to multiple heat transfer sheets  12 . In an example shown in  FIG.  10   , the heat transfer sheet  12  is separated into two pieces, and the thermal resistance adjuster  14  is provided between the separated heat transfer sheets  12 . The heat is transferred between the separated heat transfer sheets  12  through the thermal resistance adjuster  14 . The material of the thermal resistance adjuster  14  has a thermal conductivity lower than the heat transfer sheet  12 . In the sixth embodiment, the size of each of the thermal resistance adjusters  14  is the same. 
       FIG.  11    is an upper view of a cross section of the heat conduction device  1  taken at the position of the heat transfer sheet  12 . As shown in  FIG.  11   , the thermal resistance adjuster  14  of the sixth embodiment includes multiple adjusters  14   a ,  14   b . The adjusters  14   a ,  14   b  are made of different materials having different thermal conductivities. 
     In the sixth embodiment, the first adjuster  14   a  is made of TIM (Thermal Interface Material), and the second adjuster  14   b  is made of PET resin. The thermal conductivity of the TIM is about 10 W/mK, and the thermal conductivity of the PET resin is about 0.1 W/mK. 
     Since the TIM constituting the first adjustment portion  14   a  is a paste-like material having adhesiveness, it is easy to fill the gaps between the separated heat transfer sheets  12 , and accordingly it is possible to suppress the formation of gaps between the heat transfer sheet  12  and the thermal resistance adjuster  14 . In addition, since the TIM material has flexibility, it can form an appropriate curved surface even in contact with the human body in combination with the heat transfer sheet  12  having flexibility, and accordingly comfort is not impaired. 
     The thermal conductivity can be adjusted by adjusting the ratio between the first adjuster  14   a  and the second adjuster  14   b . Specifically, the thermal conductivity can be increased by increasing the proportion of the first adjuster  14   a , and the thermal conductivity can be decreased by increasing the proportion of the second adjuster  14   b . In the sixth embodiment, as the heat transfer sheet  12  is longer, the proportion of the first adjuster  14   a  in the thermal resistance adjuster  14  is increased to increase the thermal conductivity. Moreover, as the heat transfer sheet  12  is shorter, the proportion of the second adjuster  14   b  in the thermal resistance adjuster  14  is increased to decrease the thermal conductivity. 
     In the sixth embodiment, the casing  15  is made of an acrylic resin which is a nonmetal material. The casing  15  has an inlet  18  through which the cooling water flows into the heat source portion  10  from the outside, and an outlet  19  through which the cooling water flows out of the heat source portion  10  to the outside. Moreover, the casing  15  and the heat transfer sheet  12  are joined by the adhesive or the adhesive agent. 
     As indicated by a dashed line in  FIG.  11   , the heat insulation sheet  13  is provided with a groove  13   a . The groove  13   a  of the heat insulation sheet  13  and the heat transfer sheets  12  located on both sides of the heat insulation sheet  13  define a hollow space. The groove  13   a  has a U-shape and communicates with the heat source portion  10 . For this reason, the cooling water of the heat source portion  10  flows through the groove  13   a . Thereby, the contact area of the heat source portion  10  and the heat transfer sheet  12  can be increased. 
     According to the sixth embodiment described above, the heat transfer sheet  12  is divided into multiple parts, and the thermal resistance adjuster  14  is disposed between the separated heat transfer sheets  12 . Also by such a configuration, differences of the thermal resistance due to the difference of the lengths of the heat transfer sheets  12  can be adjusted. Thereby, the thermal resistance between the heat source portion  10  and each temperature control section  11   a  can be uniformed, and the temperature distribution generated on the temperature control surface  11  can be uniformed. 
     In the sixth embodiment, the thermal resistance of the thermal resistance adjuster  14  can be adjusted by using the adjusters  14   a ,  14   b  made of different materials and by adjusting the ratio between the adjusters  14   a ,  14   b . In the configuration of the sixth embodiment, the thermal resistance adjuster  14  may be made of single material. When the thermal resistance adjuster  14  is made of single material, the thermal resistance of the thermal resistance adjuster  14  can be adjusted by adjusting the size or the shape of the thermal resistance adjuster  14 . For example, the thermal resistance of the thermal resistance adjuster  14  can be adjusted by varying the widths of the thermal resistance adjuster  14  sandwiched between the separated heat transfer sheets  12 . 
     In the sixth embodiment, the heat source portion  10  is directly in contact with the heat transfer sheet  12 . Accordingly, the heat can be directly exchanged between the heat source portion  10  and the heat transfer sheet  12 , and the heat of the heat source portion  10  can be efficiently transferred to the heat transfer sheet  12 . 
     In the sixth embodiment, the groove  13   a  communicating with the heat source portion  10  is provided in the heat insulation sheet  13 . Accordingly, the contact area of the heat source portion  10  and the heat transfer sheet  12  can be increased, and the heat can be efficiently exchanged between the heat source portion  10  and the heat transfer sheet  12 . 
     The amount of heat transferred from the heat source portion  10  to the heat transfer sheet  12  may be adjusted by adjusting the contact area of the heat source portion  10  with the heat transfer sheet  12  by varying the size of the groove  13   a  of the heat insulation sheet  13 . Specifically, the amount of the heat transferred from the heat source portion  10  to the heat transfer sheet  12  can be increased by increasing the size of the groove  13   a  of the heat insulation sheet  13 , and the amount of the heat transferred from the heat source portion  10  to the heat transfer sheet  12  can be decreased by decreasing the size of the groove  13   a  of the heat insulation sheet  13 . Therefore, the groove  13   a  of the heat insulation sheet  13  is enlarged as the heat transfer sheet  12  is longer, and the groove  13   a  of the heat insulation sheet  13  is smaller as the heat transfer sheet  12  is shorter. 
     Further, in the sixth embodiment, the casing  15  is made of a nonmetal material. Thereby, the following effects can be obtained. 
     When the thermal resistance adjuster  14  and the casing  15  are integrally formed of a metal material in the first embodiment, the thermal resistance adjuster  14 , the casing  15 , and the heat transfer sheet  12  are bonded by using silver paste having a high thermal conductivity. In this case, a heating process is required for bonding, and the thermal resistance adjuster  14  and the casing  15  made of a metal material and the heat transfer sheet  12  made of a graphite sheet are easily peeled off. 
     In contrast, in the sixth embodiment, the heat source portion  10  and the heat transfer sheet  12  are directly in contact with the heat transfer sheet  12 . Accordingly, the silver paste for bonding of the casing  15  and the heat transfer sheet  12  are not needed, and the casing  15  and the heat transfer sheet  12  can be bonded by using an adhesive. For this reason, a heating process is unnecessary for joining of the casing  15  and the heat transfer sheet  12 , and the casing  15  and the heat transfer sheet  12  are unlikely to peel off. 
     Further, the weight of the heat conduction device  1  can be reduced by using the acrylic resin which is a nonmetallic material as a material of the casing  15 . 
     Seventh Embodiment 
     Next, a seventh embodiment of the present disclosure will be described. In the seventh embodiment, the thermal resistance between the heat source portion  10  and the temperature control section  11   a  is adjusted by varying the shapes of the heat transfer sheets  12 . 
     As shown in  FIGS.  12 ,  13   , in the seventh embodiment, at least some of the heat transfer sheets  12  include a notch  12   a . In the seventh embodiment, the thermal resistance of the heat transfer sheet  12  is adjusted by the notch  12   a  of the heat transfer sheet  12 . In the seventh embodiment, the thermal resistance adjuster  14  is not provided. 
     As shown in  FIG.  13   , four heat transfer sheets  12  include the notch  12   a , excepting one heat transfer sheet  12  that is the longest in the longitudinal direction in five heat transfer sheets  12  of the heat conduction device  1 . At a portion of the heat transfer sheet  12  where the notch  12   a  is provided, the length in the width direction of the heat transfer sheet  12  is short. The longitudinal direction of the heat transfer sheet  12  is a direction in which the heat transfer sheet  12  connects the heat source portion  10  and the temperature control surface  11  (a left-right direction of  FIG.  13   ). The width direction of the heat transfer sheet  12  is a direction perpendicular to the direction in which the heat transfer sheet  12  connects the heat source portion  10  and the temperature control surface  11  (an up-down direction of  FIG.  13   ). 
     The thermal resistance R of the heat transfer sheet  12  having the notch  12   a  can be calculated by the following equation 1. 
     
       
         
           
             
               
                 
                   
                     [ 
                     
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                       ⁢ 
                       
                           
                       
                       ⁢ 
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                   R 
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                       1 
                       
                         λ 
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                       { 
                       
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                             ( 
                             
                               
                                 W 
                                 
                                   W 
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                               1 
                             
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                           L 
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                       } 
                     
                   
                 
               
               
                 
                   ( 
                   1 
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     Here, λ is the thermal conductivity of the heat transfer sheet  12 , d is the thickness of the heat transfer sheet  12 , W is the length of the heat transfer sheet  12  in the width direction, W 1  is the length of the part of the heat transfer sheet  12  at which the notch  12   a  is provided, L is the length of the heat transfer sheet  12  in the longitudinal direction, and L 1  is the length of the notch  12   a  in the longitudinal direction of the heat transfer sheet  12 . 
     From equation 1, the thermal resistance R of the heat transfer sheet  12  can be adjusted by adjusting at least one of the length of the notch  12   a  in the longitudinal direction of the heat transfer sheet  12  and the length of the notch  12   a  in the width direction of the heat transfer sheet  12 . 
     In the example shown in  FIG.  13   , the lengths of the notches  12   a  in the longitudinal direction of the heat transfer sheet  12  are uniformed, and the lengths of the notches in the width direction of the heat transfer sheet  12  are varied. Specifically, when the length of the heat transfer sheet  12  in the longitudinal direction is small, the length of the notch  12   a  in the width direction of the heat transfer sheet  12  is long. When the length of the heat transfer sheet  12  in the longitudinal direction is large, the length of the notch  12   a  in the width direction of the heat transfer sheet  12  is small, or the notch  12   a  is not provided. The thermal resistance can be uniformed among the heat transfer sheets  12  having different lengths. 
     In the seventh embodiment described above, the notches  12   a  are provided in the heat transfer sheets  12 , and the thermal resistance is adjusted by adjusting the size of the notch  12   a . Accordingly, the thermal resistance between the heat source portion  10  and the temperature control section  11   a  can be adjusted by varying the shape of the heat transfer sheets  12 . 
     In the configuration of the seventh embodiment, the length of the notch  12   a  in the width direction of the heat transfer sheet  12  is varied between the heat transfer sheets  12 . However, the length of the notch  12   a  in the longitudinal direction of the heat transfer sheet  12  may be varied. 
     In the seventh embodiment, the thermal resistance of the heat transfer sheet  12  is adjusted by providing the notch  12   a  in the heat transfer sheet  12 , but a cut-off portion formed by cutting off a part of the heat transfer sheet  12  may be provided in addition to or instead of the notch  12   a . The thermal resistance of the heat transfer sheet  12  can be adjusted by varying the length of the cut-off portion provided in the heat transfer sheet  12 . Specifically, the thermal resistance can be increased by increasing the size of the cut-off portion, and the thermal resistance can be decreased by decreasing the size of the cut-off portion. 
     Eighth Embodiment 
     Next, an eighth embodiment of the present disclosure will be described. In the above-described embodiments, all of the heat transfer sheets  12  are connected to the heat source portion  10  directly or through the thermal resistance adjuster  14 . In the eighth embodiment, some of the heat transfer sheets  12  are connected to the heat source portion  10 . 
     As shown in  FIG.  14   , in the eighth embodiment, the heat source portion  10  is in contact with some of the heat transfer sheets  12  stacked with each other. In the example shown in  FIG.  14   , the heat source portion  10  is in contact with the outermost one of the heat transfer sheets  12 . The heat source portion  10  is in contact with the heat transfer sheet  12  that is the longest in the heat transfer sheets  12 . The heat source portion  10  and the heat transfer sheet  12  in contact with the heat source portion  10  are covered with an outer heat insulation sheet  20 . 
     In the eighth embodiment, a peltier device that is a hot heat source is used as the heat source portion  10 . Accordingly, hot heat is supplied to the temperature control surface  11  through the heat transfer sheet  12 . 
     In the heat conduction device  1 , the heat transfer sheets  12  and the heat insulation sheets  13  are alternately stacked with each other as in the above-described first embodiment. In the eighth embodiment, heat conductive stacking members  21  are provided between the heat transfer sheets  12  at a part overlapping the heat source portion  10  when viewed in the sheet stacking direction, instead of the heat insulation sheets  13 . The heat is transferred in the sheet stacking direction between the heat transfer sheets  12  through the stacking members  21  at the part overlapping the heat source portion  10  in the sheet stacking direction. 
     The stacking member  21  of the eighth embodiment has adhesiveness. The heat transfer sheets  12  adjacent to each other can be bonded by using the adhesive stacking members  21 , and the heat transfer sheets  12  can be joined in a stacking state. An adhesive tape such as Kapton (registered trademark of DuPont) film can be suitably used as the stacking member  21 . 
     The thermal resistance of the stacking member  21  of the eighth embodiment in the sheet stacking direction can be adjusted. For example, the thermal resistance of the stacking members  21  can be adjusted by varying the shapes or the materials of the stacking members  21 . 
     According to the above-described eighth embodiment, the heat conductive stacking members  21  are provided at the part corresponding to the heat source portion  10  in the configuration in which some of the heat transfer sheets  12  stacked with each other are in contact with the heat source portion  10 . According to this, heat of the heat source portion  10  can be transferred in the sheet stacking direction, and the heat transfer sheets distant from the heat source portion  10 . 
     Since the thermal resistance of the stacking members  21  can be adjusted in the eighth embodiment, the thermal resistance between the heat transfer sheets  12  in the sheet stacking direction can be adjusted. Accordingly, the thermal resistance between the heat source portion  10  and the temperature control sections  11   a  can be uniformed, and the temperature control sections  11   a  can be uniformly controlled. 
     The present disclosure is not limited to the embodiments described above, and various modifications can be made as follows within a range not departing from the spirit of the present disclosure. 
     In the above-described embodiments, the heat conduction device of the present disclosure is used in the temperature control seat for a vehicle. However, the heat conduction device can be used for different purposes. For example, the heat conduction device of the present disclosure may be used in a device that directly transfers heat to a human body such as a wheel heater. The heat conduction device may be used in a device that uses heat radiation or heat convection such as an underfloor radiator that radiates heat inside the passenger compartment from a part of a vehicle under the floor during a side-panel air-conditioning or parking. 
     In the above-described embodiments, the heat source portion  10  is the cooling water passage through which the heat medium flows. However, hot heat or cold heat may be directly generated in the heat source portion  10  by directly contacting a heat generating device or a cooling device, or by providing a heater or a peltier device in the heat source portion  10 . 
     In the above-described embodiments, a part of the heat transfer sheet  12  constitutes the temperature control sections  11   a . However, the heat transfer sheet  12  and the temperature control sections  11   a  may be provided as separated members. 
     In the above-described first embodiment, one thermal resistance adjuster  14  is provided between the heat source portion  10  and the heat transfer sheets  12 . However, multiple thermal resistance adjusters  14  may be provided to correspond to multiple heat transfer sheets  12 , and each thermal resistance adjusters  14  may be provided between the heat source portion  10  and each heat transfer sheets  12 . In this case, the thermal resistance may be adjusted by each of the thermal resistance adjusters  14 . The thermal resistance of the thermal resistance adjusters  14  can be adjusted by varying the shapes or the materials of the thermal resistance adjusters  14 . The thermal resistance may be adjusted by making one thermal resistance adjuster  14  from multiple materials having different thermal conductivities. 
     Although the present disclosure has been described in accordance with the examples, it is understood that the present disclosure is not limited to the above examples or structures. To the contrary, the present disclosure is intended to cover various modification and equivalent arrangements. In addition, while the various elements are shown in various combinations and configurations, which are exemplary, other combinations and configurations, including more, less or only a single element, are also within the spirit and scope of the present disclosure. 
     Comparative Example 
     A heat conduction device is known, which takes heat of a human body or supplies heat to the human body by heat conduction by using, as a heat source (hot heat source or cold heat source), a peltier device or a metal pipe through which a heat medium whose temperature is controlled. 
     In such a heat conduction device, when a contact surface with the human body or clothes is formed directly on the surface of the heat source, the device tends to be large and rigid. For this reason, the heat conduction (heat transfer) member connected to the heat source may form a temperature control surface in contact with the human body. However, it may be difficult to adjust the temperature of a part distant from the heat source compared to a part close to the heat source, and uniform temperature adjustment over the entire temperature control surface may be difficult. 
     In a comparative example, to uniform the temperature of the entire temperature control surface, a pipe through which the heat medium flows is provided in the heat conduction device along the rim of the contact surface, and multiple heat conduction members are connected to the pipe. In the heat conduction device of, a metal plate such as an aluminum plate used as a heat spreader is inserted between the temperature control surface and the heat conduction member to control temperature of the temperature control surface more uniformly. 
     According to studies by the inventors of the present disclosure, in the heat conduction device of the comparative example, the thermal resistance may increase with the lengths of the heat conduction members from the heat source. Further, the heat transferred to a part of the heat conduction member close to the heat source may influence the heat transfer to a part distant from the heat source. Accordingly, temperature difference may occur between an end of the heat conduction member close to the heat source and another end, and it may be difficult to uniform the temperature of the entire temperature control surface. Further, when a metal plate is provided between the contact surface and the heat conduction member as a heat spreader, the metal plate is required to be thicker than a certain thickness to sufficiently spread heat in the contact surface, and accordingly the heat may not be sufficiently transferred from the heat source to the human body.