Heat dissipation structure

Abstract

To provide a heat dissipation structure capable of changing an amount of a heat dissipation depending on a temperature of a heat source body.SOLUTION: A heat dissipation structure 10A is configured by combining a first member 14 and a second member 16 having a different volume change rate with a temperature, and a front surface area of the heat dissipation structure 10A changes with the temperature. Since the heat radiation amount by the heat radiation structure 10A can be changed by changing the front surface area of the heat radiation structure 10A in accordance with a level of the temperature of a heat source body 12, it is advantageous in maintaining the temperature of the heat source body 12 in an appropriate range. When the temperature of the heat source body 12 becomes high, the front surface area of the heat dissipation structure 10A becomes large, so that the heat dissipation of the heat source body 12 can be efficiently performed, and when the temperature of the heat source body 12 becomes low, the front surface area of the heat dissipation structure 10A becomes small, so that an excessive heat dissipation of the heat source body 12 can be suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat dissipation structure. [Background technology]

[0002] 2. Description of the Related Art Heat sinks have been known as heat dissipation structures for dissipating heat from a heat source. A heat sink generally includes a plate-shaped base plate that contacts a heat source, and a plurality of fins that are provided on the base plate and release heat into the air (see Patent Document 1). The heat dissipation performance of a heat sink, that is, the amount of heat dissipation, is a fixed value determined by the material and surface area of the heat sink, and the amount of heat dissipation cannot be adjusted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-220539 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the battery cells that make up the batteries installed in electric vehicles generate heat when they are charged and discharged, it is necessary to control their temperature within an appropriate range to maintain their performance. Therefore, it is conceivable to regard the battery cells as heat sources and use a heat sink to dissipate the heat from the battery cells. However, in a low-temperature environment, there is a concern that the heat sink with a fixed heat dissipation capacity may dissipate excessive heat from the battery cell, causing the temperature of the battery cell to fall below an appropriate range. Therefore, when a conventional heat sink with a fixed heat dissipation capacity is used, it is difficult to control the temperature of the battery cells within an appropriate range. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heat dissipation structure that can change the amount of heat dissipation depending on the temperature of a heat source. [Means for solving the problem]

[0005] In order to achieve the above object, one embodiment of the present invention is a heat dissipation structure that is placed in contact with a heat source and dissipates heat from the heat source, and is characterized in that the heat dissipation structure is composed of a first member and a second member that have different volume change rates with temperature, and the first member and second member are joined together, and the surface area of the heat dissipation structure changes with temperature. Furthermore, one embodiment of the present invention is characterized in that the first member is composed of a shaft, the second member is composed of a member having a cross-sectional area larger than that of the shaft and having a hole extending in a direction perpendicular to this cross-sectional area, the heat dissipation structure is formed by connecting the shaft to the hole, at a first temperature the total length of the first member is equal to the height of the second member along the axial direction of the hole, and the volume change rates of the first member and the second member are different such that at a second temperature higher than the first temperature, a longitudinal portion of the first member protrudes outside the hole. Furthermore, one embodiment of the present invention is characterized in that the first member is composed of a shaft, the second member is composed of a member having a cross-sectional area larger than that of the shaft and having a hole extending in a direction perpendicular to this cross-sectional area, the heat dissipation structure is formed by connecting the shaft to the hole, at a first temperature the total length of the first member is equal to the height of the second member along the axial direction of the hole, and there is a difference between the volume change rate of the first member and the volume change rate of the second member such that at a second temperature higher than the first temperature, the first member is immersed inside the hole. Furthermore, one embodiment of the present invention is characterized in that the first member is provided in plurality, the second member has a plurality of holes, and the heat dissipation structure is configured by connecting the plurality of first members to the plurality of holes. In addition, one embodiment of the present invention is characterized in that the first member is composed of a shaft, the second member is composed of a member having a cross-sectional area larger than that of the shaft and having a hole extending in a direction perpendicular to this cross-sectional area, the heat dissipation structure is formed by connecting the shaft to the hole, and the volume change rates of the first member and the second member are different such that at a second temperature higher than the first temperature, the second member experiences a larger volume increase than the volume increase of the first member. In one embodiment of the present invention, the surface area of the heat dissipation structure changes so as to increase as the temperature increases. In addition, one embodiment of the present invention is characterized in that the heat dissipation structure has an attachment surface that is placed in contact with the heat source, and the end of the first member and the end of the second member are located on the attachment surface. In one embodiment of the present invention, the heat source is a battery cell, and the attachment surface is disposed in contact with a surface of the battery cell. In addition, one embodiment of the present invention is characterized in that the heat source is a columnar positive terminal provided on the end surface of the battery cell, and the mounting surface is arranged in contact with the surface of the positive terminal. [Effects of the Invention]

[0006] According to one embodiment of the present invention, a first member and a second member having different rates of volume change with temperature are joined together, and the surface area of the heat dissipation structure changes with temperature. Therefore, when the heat of the heat source is transferred to the first and second members, the surface area of the heat dissipation structure can be changed depending on the temperature of the heat source, thereby changing the amount of heat dissipation by the heat dissipation structure, which is advantageous in maintaining the temperature of the heat source within an appropriate range. Furthermore, if the first member is a shaft and the second member is a member having a hole, and at a first temperature, the total length of the first member is equal to the height of the second member along the axial direction of the hole, and the volume change rates of the first member and the second member are such that at a second temperature higher than the first temperature, there is a difference in the amount by which the longitudinal portion of the first member protrudes outside the hole, the higher the temperature of the heat dissipation structure, the greater the amount by which the shaft of the first member protrudes outside the hole, thereby expanding the surface area of the heat dissipation structure. This increases the amount of heat dissipation by the heat dissipation structure, thereby enabling effective heat dissipation from the heat source, which is more advantageous for maintaining the temperature of the heat source within an appropriate range. Furthermore, as the temperature of the heat dissipation structure decreases, the amount by which the shaft of the first member protrudes outside the hole decreases, thereby reducing the surface area of the heat dissipation structure. This reduces the amount of heat dissipation by the heat dissipation structure, thereby suppressing excessive heat dissipation from the heat source, which is more advantageous for maintaining the temperature of the heat source within an appropriate range. Furthermore, the first member may be a shaft, and the second member may be a member having a cross-sectional area larger than that of the shaft and having a hole extending perpendicular to the cross-sectional area, wherein at a first temperature, the total length of the first member is equal to the height of the second member along the axial direction of the hole, and the volumetric change rates of the first member and the second member are different from each other at a second temperature higher than the first temperature. As the temperature of the heat dissipation structure increases, the exposed area of the inner circumferential surface of the hole increases, thereby expanding the surface area of the heat dissipation structure and increasing the amount of heat dissipation by the heat dissipation structure. This effectively dissipates heat from the heat source, which is advantageous for maintaining the temperature of the heat source within an appropriate range. Furthermore, as the temperature of the heat dissipation structure decreases, the amount of immersion of the shaft of the first member into the hole decreases, thereby reducing the surface area of the heat dissipation structure and reducing the amount of heat dissipation by the heat dissipation structure. This suppresses excessive heat dissipation from the heat source, which is advantageous for maintaining the temperature of the heat source within an appropriate range. Furthermore, by providing multiple first members, providing multiple holes in the second member, and constructing the heat dissipation structure by connecting multiple first members to the multiple holes, a large surface area of the heat dissipation structure can be secured, which is advantageous for further increasing the amount of heat dissipation by the heat dissipation structure, allowing the heat source to dissipate heat effectively, and is more advantageous for maintaining the temperature of the heat source within an appropriate range. Furthermore, if the first member is a shaft and the second member is a member having a cross-sectional area larger than that of the shaft and having holes extending in a direction perpendicular to this cross-sectional area, and the volume change rates of the first member and the second member are different such that at a second temperature higher than the first temperature, the volume increase of the second member is greater than the volume increase of the first member, the surface area of the second member increases as the temperature of the heat dissipation structure increases, and the surface area of the heat dissipation structure expands, thereby increasing the amount of heat dissipation by the heat dissipation structure, thereby enabling effective heat dissipation from the heat source, which is more advantageous for maintaining the temperature of the heat source within an appropriate range. Also, as the temperature of the heat dissipation structure decreases, the surface area of the heat dissipation structure decreases, thereby reducing the amount of heat dissipation by the heat dissipation structure, which prevents excessive heat dissipation from the heat source, which is more advantageous for maintaining the temperature of the heat source within an appropriate range. Furthermore, if the surface area of the heat dissipation structure increases as the temperature increases, the amount of heat dissipated by the heat dissipation structure increases as the temperature increases, allowing the heat source to be dissipated effectively, which is more advantageous for maintaining the temperature of the heat source within an appropriate range.Furthermore, as the temperature decreases, the surface area of the heat dissipation structure decreases and the amount of heat dissipation decreases, which can suppress excessive heat dissipation from the heat source, which is more advantageous for maintaining the temperature of the heat source within an appropriate range. Furthermore, by positioning the end of the first member and the end of the second member on the mounting surface, both the first member and the second member can be in stable contact with the heat source, which is advantageous for efficiently conducting heat from the heat source to the heat dissipation structure, allowing the heat source to be effectively dissipated, and is more advantageous for maintaining the temperature of the heat source within an appropriate range. Furthermore, if the heat source is a battery cell and the mounting surface is placed in contact with the surface of the battery cell, the heat dissipation structure can be placed in a location or area on the surface of the battery cell that becomes hot. This allows the heat dissipation amount of the heat dissipation structure to be appropriately adjusted depending on the temperature of the location or area of the battery cell that becomes hot, which is advantageous for maintaining the temperature of the battery cell within an appropriate temperature range that ensures the performance of the battery cell. Furthermore, when the heat source is a columnar positive terminal provided on the end face of the battery cell and the mounting surface is arranged in contact with the surface of the positive terminal, in the case of a battery cell in which the temperature of the positive terminal is likely to become high, the amount of heat dissipation from the heat dissipation structure can be changed depending on the temperature of the positive terminal, which is advantageous in maintaining the temperature of the battery cell within an appropriate temperature range that ensures the performance of the battery cell by appropriately dissipating heat from the battery cell. [Brief explanation of the drawings]

[0007] [Figure 1] 1A and 1B are perspective views schematically showing a heat dissipation structure according to a first embodiment, where (A) corresponds to a first temperature T1 and (B) corresponds to a second temperature T2. [Figure 2] (A) is a cross-sectional view taken along line AA in FIG. 1, which corresponds to a first temperature T1, and (B) is a cross-sectional view taken along line BB in FIG. 1(B), which corresponds to a second temperature T2. [Figure 3] FIG. 10 is a perspective view showing a second embodiment in which the heat dissipation structure of the first embodiment is provided in a battery cell. [Figure 4] 1A and 1B are explanatory diagrams showing a schematic view of battery cells housed in a module case, where (A) is a side cross-sectional view and (B) is a plan view. [Figure 5] 10A and 10B are perspective views schematically showing a heat dissipation structure according to a third embodiment, where (A) corresponds to a first temperature T1 and (B) corresponds to a second temperature T2. [Figure 6] (A) is a cross-sectional view taken along line AA in FIG. 5, which corresponds to a first temperature T1, and (B) is a cross-sectional view taken along line BB in FIG. 5(B), which corresponds to a second temperature T2. [Figure 7] 10A and 10B are explanatory diagrams showing a schematic diagram of a heat dissipation structure according to a fourth embodiment, in which (A) is a perspective view corresponding to a first temperature T1, (B) is a longitudinal cross-sectional view of (A), (C) is a perspective view corresponding to a second temperature T2, and (D) is a longitudinal cross-sectional view of (C). DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1(A) and 2(A), a heat dissipation structure 10A of this embodiment is disposed in contact with a heat source 12 that generates heat, and dissipates the heat from the heat source 12. The heat dissipation structure 10A is configured by joining a first member 14 and a second member 16 that have different rates of volume change due to temperature. In this embodiment, the first member 14 is made up of a plurality of shafts 1402 each having a rectangular cross section. The second member 16 is composed of a rectangular plate-shaped member having a cross-sectional area larger than that of the shaft 1402, a thickness the same as the length of the shaft 1402, and a flat upper surface 1601, and the rectangular plate-shaped member is provided with a plurality of holes 1602 that penetrate in the thickness direction. The cross section of the holes 1602 is rectangular so that the first member 14 can be coupled thereto, and the shafts 1402 are coupled to the holes 1602 . In the heat dissipation structure 10A, on one surface in the thickness direction of the second member 16, the lower end portion 1404 of the first member 14 and the lower end portion 1604 of the second member 16 are both located on the same plane, and this surface is formed as the mounting surface 18 of the heat dissipation structure 10A. It should be noted that the cross-sectional shapes of shaft 1402 and hole 1602 are not limited to rectangular, and the cross-sectional shapes of shaft 1402 and hole 1602 may of course be any of various shapes known in the art, such as a perfect circle, an ellipse, a triangle, a polygon with five or more sides, or an irregular shape.

[0009] As shown in FIG. 2(A), the heat dissipation structure 10A is attached to the heat source 12 by placing the attachment surface 18 of the heat dissipation structure 10A in contact with the surface 1202 of the heat source 12. The heat dissipation structure 10A can be attached to the heat source 12 using a bracket (not shown), or by adhering the mounting surface 18 to the surface 1202 of the heat source 12 with an adhesive having heat dissipation properties, and various conventionally known mounting structures can be used. In the embodiment, the heat source body 12 is described as having a rectangular plate shape and its flat upper surface (surface) 1202 is in contact with the mounting surface 18 of the heat dissipation structure 10A, but if the heat source body 12 has a flat side surface, the mounting surface 18 may be attached to that side surface, and the mounting location of the heat dissipation structure 10A is not limited.

[0010] 1(A) and 2(A), at the first temperature T1, the total length of the first member 14 is equal to the height of the second member 16 along the axial direction of the hole 1602 (the thickness of the second member 16). In other words, the upper surface 1601 of the second member 16 and the upper end surfaces of the plurality of first members 14 are located on the same plane. 1(B) and 2(B), there is a difference between the volume change rates of the first member 14 and the second member 16 such that at a second temperature T2 higher than the first temperature T1, a longitudinal portion of the first member 14 protrudes out of the hole 1602, in other words, a portion of the first member 14 near the upper end surface thereof protrudes above the upper surface 1601 of the second member 16. That is, in this embodiment, the second member 16 functions as a support member that supports a plurality of first members 14. In this embodiment, the first member 14 and the second member 16 are both formed from a material that exhibits positive thermal expansion, that is, a material whose volume increases as the temperature rises, and the thermal expansion coefficient of the first member 14 is greater than the thermal expansion coefficient of the second member 16. In this embodiment, the first member 14 and the second member 16 are used as the heat dissipation structure 10A, and therefore, it is preferable that the materials forming the first member 14 and the second member 16 both have high thermal conductivity. As the material for such a first member 14, for example, a metal material such as aluminum, duralumin, or zinc can be used. As the material of the second member 16, for example, a metal material such as tungsten or chromium steel can be used. Therefore, the surface area of heat dissipation structure 10A at second temperature T2 changes to be larger than the surface area of heat dissipation structure 10A at first temperature T1 by the area of the circumferential surface of shaft 1402 of first member 14 protruding from hole 1602 of second member 16. In other words, the surface area of heat dissipation structure 10A changes to be larger as the temperature increases.

[0011] Heat dissipation structure 10A of the present embodiment is configured by joining first member 14 and second member 16, which have different rates of volume change with temperature, and the surface area of heat dissipation structure 10A changes with temperature. Therefore, when the heat from the heat source 12 is transferred from the mounting surface 18 to the first member 14 and the second member 16, the surface area of the heat dissipation structure 10A can be changed depending on the temperature of the heat source 12, thereby changing the amount of heat dissipation by the heat dissipation structure 10A, which is advantageous in maintaining the temperature of the heat source 12 within an appropriate range. For example, when the temperature of the heat source 12 becomes high, the surface area of the heat dissipation structure 10A becomes large, allowing the heat source 12 to dissipate heat efficiently, and when the temperature of the heat source 12 becomes low, the surface area of the heat dissipation structure 10A becomes small, preventing excessive heat dissipation from the heat source 12. Therefore, even if the temperature of the heat source 12 is within the appropriate temperature range, this is advantageous in preventing the heat source 12 from being excessively dissipated by the heat dissipation structure 10A, causing the temperature of the heat source 12 to fall below the appropriate temperature. In addition, in this embodiment, the first member 14 and the second member 16 are joined so that the joined state does not come loose even if their volumes change; in other words, they are joined so that even if their volumes change, the volume changes can be tolerated. However, a third member may be used to maintain the joined state of first member 14 and second member 16. However, if configured as in the embodiment, first member 14 and second member 16 can be joined without the third member, which is advantageous in terms of reducing the number of parts and weight.

[0012] In addition, in this embodiment, the first member 14 is composed of an axis 1402, the second member 16 is composed of a member having a hole 1602, and the heat dissipation structure 10A is composed by connecting the axis 1402 to the hole 1602 in a manner that allows for volume change.At a first temperature T1, the total length of the first member 14 is equal to the height of the second member 16 along the axial direction of the hole 1602, and the volume change rates of the first member 14 and the second member 16 are different in that at a second temperature T2 that is higher than the first temperature T1, the longitudinal portion of the first member 14 protrudes outside the hole 1602. Therefore, the higher the temperature of the heat source 12, i.e., the temperature of the heat dissipation structure 10A, the more the axis 1402 of the first member 14 protrudes outside the hole 1602, thereby expanding the surface area of the heat dissipation structure 10A, and therefore the amount of heat dissipation by the heat dissipation structure 10A increases, allowing the heat source 12 to dissipate heat more effectively, which is more advantageous in maintaining the temperature of the heat source 12 within an appropriate range. Furthermore, as the temperature of the heat dissipation structure 10A decreases, the amount by which the axis 1402 of the first member 14 protrudes outside the hole 1602 decreases, thereby reducing the surface area of the heat dissipation structure 10A. As a result, the amount of heat dissipation by the heat dissipation structure 10A decreases, which makes it possible to suppress excessive heat dissipation from the heat source 12 and is more advantageous in maintaining the temperature of the heat source 12 within an appropriate range.

[0013] Furthermore, multiple first members 14 are provided, multiple holes 1602 are provided in the second member 16, and the heat dissipation structure 10A is constructed by connecting multiple first members 14 to multiple holes 1602 so that the volume can change. This allows the heat dissipation structure 10A to have a large surface area, which is advantageous for further increasing the amount of heat dissipation by the heat dissipation structure 10A, allowing the heat source 12 to dissipate heat effectively, and is more advantageous for maintaining the temperature of the heat source 12 within an appropriate range.

[0014] Furthermore, the surface area of heat dissipation structure 10A increases as the temperature increases, and therefore the higher the temperature, the greater the amount of heat dissipation by heat dissipation structure 10A, allowing for effective heat dissipation from heat source 12, which is advantageous for maintaining the temperature of heat source 12 within an appropriate range. Furthermore, the lower the temperature, the smaller the surface area of heat dissipation structure 10A, and the lower the amount of heat dissipation, which prevents excessive heat dissipation from heat source 12, which is advantageous for maintaining the temperature of heat source 12 within an appropriate range.

[0015] In addition, in this embodiment, the heat dissipation structure 10A is described as being arranged with both the first member 14 and the second member 16 in contact with the heat source 12, but it is also possible to arrange one of the first member 14 and the second member 16 in contact with the heat source 12. In this case, the first member 14 or the second member 16 that has a larger rate of volume change due to heat may be placed in contact with the heat source 12 . It is also possible to arrange the first member 14 or the second member 16, whichever has a smaller rate of volume change due to heat, in contact with the heat source 12. However, if arranged in this manner, the heat from the heat source 12 will be transferred to the member with a larger rate of volume change via the member with a smaller rate of volume change, which will result in a slower increase in the volume of the member with a larger rate of volume change, which is disadvantageous in terms of effectively dissipating heat from the heat source 12. Furthermore, as in the embodiment, when the heat dissipation structure 10A is positioned with both the first member 14 and the second member 16 in contact with the heat source 12, that is, when an attachment surface 18 is provided where the end of the first member 14 and the end of the second member 16 are located on the same plane, and this attachment surface 18 is attached to the heat source 12, both the first member 14 and the second member 16 are supported by the heat source 12, which is advantageous in maintaining a stable bond between the first member 14 and the second member 16.

[0016] In the first embodiment, both the first member 14 and the second member 16 are formed from a material that exhibits positive thermal expansion, that is, the volume increases as the temperature rises, and the thermal expansion coefficients of the first member 14 and the second member 16 are positive values. However, as long as there is a difference between the volume change rate of the first member 14 and the volume change rate of the second member 16 such that the longitudinal portion of the first member 14 protrudes outside the hole 1602 at a second temperature T2 higher than the first temperature T1, as shown in Figures 1(B) and 2(B), the relationship between the thermal expansion coefficients of the first member 14 and the second member 16 is not limited. For example, the following relationships of thermal expansion coefficients are possible: 1) The thermal expansion coefficient of the first member 14 is a positive value, and the thermal expansion coefficient of the second member 16 is zero. 2) The first member 14 has a positive thermal expansion coefficient, and the second member 16 has a negative thermal expansion coefficient. 3) The thermal expansion coefficient of the first member 14 and the thermal expansion coefficient of the second member 16 are both negative values, and the absolute value of the thermal expansion coefficient of the first member 14 is smaller than the absolute value of the thermal expansion coefficient of the second member 16.

[0017] (Second embodiment) Next, a second embodiment in which the heat dissipation structure 10A of the first embodiment is applied to a cooling structure for a battery cell 20 will be described with reference to FIGS. As will be described later, a plurality of battery cells 20 are electrically connected to form a battery module 22, and the plurality of battery modules 22 form a battery pack. The battery pack is mounted on an electric vehicle powered by a motor alone, a hybrid vehicle, or an electric vehicle powered by a motor, such as a plug-in hybrid vehicle that can be externally charged or externally powered, and forms a battery pack that supplies power to the motor. In the second embodiment, the battery cell 20 is a secondary battery made of a lithium ion battery.

[0018] As shown in FIG. 3, the battery cell 20 has a rectangular plate shape, and has a height, a width, and a thickness that is smaller than the height and the width. A pair of electrode terminals 24, 26 are provided on both ends of the upper end surface 2002 of the battery cell 20 in the width direction. One of the pair of electrode terminals 24, 26 is a positive electrode terminal 24, and the other is a negative electrode terminal 26. In the second embodiment, the positive electrode terminal 24 and the negative electrode terminal 26 are columnar with a rectangular cross section. As shown in Figures 4(A) and (B), multiple battery cells 20 are arranged opposite each other in the thickness direction with their upper end surfaces 2002 facing upward and housed in a module case 28 to form a battery module 22. The module case 28 comprises a bottom wall 2802 on which the lower end surface 2004 of each battery cell 20 is placed, four side walls 2804 standing from the periphery of the bottom wall 2802, and an upper wall 2806 connecting the upper ends of the four side walls 2804, and a cooling air flow path 30 through which cooling air circulates is formed between the upper wall 2806 and the upper end surface 2002 of each battery cell 20 (a pair of electrode terminals 22, 24). In the drawing, reference numeral 32 denotes an inlet provided on the side wall 2804 through which cooling air is introduced, and reference numeral 34 denotes an outlet provided on the side wall 2804 through which the cooling air is discharged. It should be noted that the heat dissipation structure 10A is illustrated in a simplified manner in FIGS.

[0019] As shown in FIGS. 4(A) and 4(B), the positive electrode terminals 24 and negative electrode terminals 26 of adjacent battery cells 20 are electrically connected by a bus bar (wiring member) 36. The bus bar and each electrode terminal are attached, for example, by inserting male screws (not shown) protruding from each electrode terminal 22, 24 into holes (not shown) formed on both ends of the bus bar 36, and then attaching nuts (not shown) to the male screws to fasten the bus bar 36 to the electrode terminals 22, 24. Note that various conventionally known structures can be used as the structure for attaching the bus bar 36 to each electrode terminal 22, 24.

[0020] As shown in FIG. 3, the positive electrode terminal 24 has four side surfaces 2402 and an upper surface (surface) 2404 made of a rectangular flat surface connecting the side surfaces 2402, and the heat dissipation structure 10A is provided on the upper surface 2404. That is, the heat dissipation structure 10A has an attachment surface 18 formed with the same contour as the upper surface 2402 of the positive terminal 24, and the attachment surface 18 is disposed in contact with the upper surface 2402 of the positive terminal 24 as the heat source 12. Therefore, as shown in FIG. 4(A), the cooling air flowing through the cooling airflow passages 30 of the module case 28 promotes heat dissipation from the heat dissipation structure 10A, and the battery cells 20 dissipate heat efficiently. It should be noted that the shape of the heat dissipation structure 10A is depicted in a simplified manner in FIGS.

[0021] With the above configuration, it goes without saying that the same effects as those of the first embodiment can be achieved, and the higher the temperature of the heat source 12, that is, the battery cell 20, the larger the surface area of the heat dissipation structure 10A becomes, thereby increasing the amount of heat dissipation, thereby enabling the battery cell 20 to effectively dissipate heat; and the lower the temperature of the battery cell 20, the smaller the surface area of the heat dissipation structure 10A becomes, thereby decreasing the amount of heat dissipation, thereby suppressing excessive heat dissipation from the battery cell 20. Therefore, by appropriately dissipating heat from the battery cell 20, it is advantageous to maintain the temperature of the battery cell 20 within an appropriate temperature range that ensures the performance of the battery cell 20. In particular, since the heat dissipation structure 10A is located in the cooling air flow path 30 of the module case 28, the expanded surface area of the heat dissipation structure 10A is dissipated by the cooling air, which is advantageous for efficiently dissipating heat from the battery cells 20.

[0022] Although the heat dissipation structure 10A may be provided on both the positive electrode terminal 24 and the negative electrode terminal 26, for example, in the case of a lithium ion battery in which the temperature of the positive electrode terminal 24 is likely to become higher than that of the negative electrode terminal 26, providing the heat dissipation structure 10A only on the positive electrode terminal 24 as in this embodiment provides the following effects. That is, the amount of heat dissipation by the heat dissipation structure 10A can be changed depending on the temperature of the positive terminal 24, which tends to become high, and this is advantageous in maintaining the temperature of the battery cells 20 within an appropriate temperature range that ensures the performance of the battery cells 20 by appropriately dissipating heat from the battery cells 20. Furthermore, the effect of promoting heat dissipation from the battery cells 20 can be sufficiently obtained while limiting the number of heat dissipation structures 10A, which is also advantageous in reducing the cost of the heat dissipation structure 10A.

[0023] In the second embodiment, the heat dissipation structure 10A is arranged in contact with the upper surface 2402 of the positive terminal 24, but the heat dissipation structure 10A may also be arranged in contact with the side surface 2402 of the positive terminal 24. Furthermore, the shape of the positive electrode terminal 24 (electrode terminal) is not limited to a rectangular column, and it goes without saying that the heat dissipation structure 10A can be provided on electrode terminals of various conventionally known shapes, such as a cylindrical shape.

[0024] In the second embodiment, the heat source 12 is a columnar positive terminal 24 provided on the upper end surface 2002 of the battery cell 20, and the mounting surface 18 of the heat dissipation structure 10A is arranged in contact with the upper surface 2404 of the positive terminal 24. However, it goes without saying that the mounting surface 18 of the heat dissipation structure 10A may be arranged in contact with a portion of the surface of the battery cell 20 other than the electrode terminal 24 serving as the heat source 12. That is, depending on the type and shape of the battery cell 20, it is conceivable that the parts and areas of the surface of the battery cell 20 that are likely to become hot will differ. In this case, the heat dissipation structure 10A can be arranged in contact with the parts or areas of the surface of the battery cell 20 that tend to become hot. This is advantageous in that the amount of heat dissipation by the heat dissipation structure 10A can be appropriately adjusted according to the temperature of the parts or areas of the battery cell 20 that tend to become hot, and therefore, it is advantageous in that the temperature of the battery cell 20 can be maintained within an appropriate temperature range that ensures the performance of the battery cell 20.

[0025] (Third embodiment) Next, a heat dissipation structure 10B according to a third embodiment will be described with reference to FIGS. In the following embodiments, the same parts and members as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be simplified, with the focus being on the differences. As shown in Figures 5(A) and 6(A), the third embodiment is similar to the first embodiment in that the first member 14 is composed of a plurality of shafts 1402, the second member 16 is composed of a member having a cross-sectional area larger than that of the shafts 1402 and having a plurality of holes 1602 extending in a direction perpendicular to this cross-sectional area, and the heat dissipation structure 10B is composed of the shafts 1402 coupled to the holes 1602 in a manner that allows volume change, and at a first temperature T1, the total length of the first member 14 is equal to the height of the second member 16 along the axial direction of the holes 1602. On the other hand, the third embodiment differs from the first embodiment in that the volume change rates of the first member 14 and the second member 16 are such that at a second temperature T2 higher than the first temperature T1, the first member 14 sinks into the hole 1602, as shown in Figures 5(B) and 6(B), in other words, the upper end surface of the first member 14 sinks from the upper surface 1601 of the second member 16. In the third embodiment, the first member 14 is made of a material that exhibits negative thermal expansion, meaning that its volume decreases as the temperature increases, and the second member 16 is made of a material that exhibits positive thermal expansion, meaning that its volume increases as the temperature increases. In other words, the thermal expansion coefficient of the first member 14 is negative, and the thermal expansion coefficient of the second member 16 is positive. As the material of such a first member 14, for example, ceramic materials such as β-eucryptite (LiAlSiO4), zirconium tungstate (ZrW2O8), BiNi1-xFexO3 (BNFO: bismuth nickel iron oxide) can be used. The second member 16 may be made of a metal material such as aluminum, duralumin, or zinc.

[0026] According to the third embodiment, not only can the same effects as those of the first embodiment be achieved, but in the third embodiment, as shown in Figures 5(B) and 6(B), the higher the temperature of the heat dissipation structure 10B, the more the axis 1402 of the first member 14 is immersed inside the hole 1602. Therefore, the higher the temperature of the heat source 12, i.e., the temperature of the heat dissipation structure 10B, the larger the exposed area of the inner surface of the hole 1602 becomes, which increases the surface area of the heat dissipation structure 10B and increases the amount of heat dissipation by the heat dissipation structure 10B, allowing the heat source 12 to dissipate heat effectively, which is more advantageous in maintaining the temperature of the heat source 12 within an appropriate range. Furthermore, as the temperature of the heat dissipation structure 10B decreases, the amount by which the axis 1402 of the first member 14 is immersed inside the hole 1602 decreases, thereby reducing the surface area of the heat dissipation structure 10B. As a result, the amount of heat dissipation by the heat dissipation structure 10B decreases, which makes it possible to suppress excessive heat dissipation from the heat source 12, which is more advantageous in maintaining the temperature of the heat source 12 within an appropriate range.

[0027] Furthermore, when the heat dissipation structure 10B of the third embodiment is provided on the positive terminal 24 of the battery cell 20 as in the second embodiment, the axis 1402 of the first member 14 is immersed inside the hole 1602, and therefore, unlike the second embodiment, the first member 14 does not protrude from the upper end of the second member 16. Therefore, as shown in FIG. 4(A), a wide cooling air flow path 30 through which cooling air flows can be secured without increasing the height of the module case 28, which is advantageous in reducing the size of the module case 28 and, in turn, in reducing the size and space of the battery pack.

[0028] In the third embodiment, the first member 14 is formed from a material that exhibits negative thermal expansion, meaning that its volume decreases as the temperature increases, and the second member 16 is formed from a material that exhibits positive thermal expansion, meaning that its volume increases as the temperature increases, and the thermal expansion coefficient of the first member 14 is a negative value, while the thermal expansion coefficient of the second member 16 is a positive value. However, the relationship between the thermal expansion coefficients of the first member 14 and the second member 16 is not limited as long as there is a difference between the volume change rates of the first member 14 and the second member 16 such that the first member 14 is immersed inside the hole 1602 at a second temperature T2 higher than the first temperature T1, as shown in Figures 5(B) and 6(B). For example, the following relationships of thermal expansion coefficients are possible: 1) The first member 14 has a coefficient of thermal expansion of zero and the second member 16 has a coefficient of thermal expansion of a positive value. 2) The thermal expansion coefficient of the first member 14 and the thermal expansion coefficient of the second member 16 are both positive values, and the thermal expansion coefficient of the first member 14 is smaller than the thermal expansion coefficient of the second member 16. 3) The thermal expansion coefficient of the first member 14 and the thermal expansion coefficient of the second member 16 are both negative values, and the absolute value of the thermal expansion coefficient of the first member 14 is greater than the absolute value of the thermal expansion coefficient of the second member 16.

[0029] (Fourth embodiment) Next, a heat dissipation structure 10C according to a fourth embodiment will be described with reference to FIG. In the heat dissipation structure 10C of the fourth embodiment, the first member 14 is composed of an axis 1410, and the second member 16 is composed of a member having a cross-sectional area larger than that of the axis 1410 and having a hole 1610 extending in a direction perpendicular to this cross-sectional area. More specifically, the first member 14 is composed of the cylindrical axis 1410, and the second member 16 is formed in a cylindrical shape with a hole 1610 having a circular cross-section running through it along the central axis. A flange 1412 having an outer diameter larger than the outer diameter of the shaft 1410 is provided at the end of the shaft 1410, and in the fourth embodiment, the end surface of this flange 1412 is formed as a flat mounting surface 18, and the mounting surface 18 is attached to the heat source body 12. The heat dissipation structure 10C is configured such that the shaft 1410 cannot fall out of the hole 1610 and the shaft 1410 is connected to the hole 1610 by a fitting (interference fit) that allows the volume to change when the hole 1610 and the shaft 1410 are connected. In the heat dissipation structure 10C of the fourth embodiment, the heat of the heat source 12 is transferred from the flange 1412 of the first member 14 to the shaft 1410, and also transferred from the shaft 1410 and flange 1412 of the first member 14 to the second member 16. The volume change rate of the first member 14 and the volume change rate of the second member 16 are different in that at a second temperature T2 higher than the first temperature T1, the volume of the second member 16 increases more significantly than the volume increase of the first member 14. In the fourth embodiment, both the first member 14 and the second member 16 are formed of a material that exhibits positive thermal expansion, meaning that the volume increases as the temperature rises, and the thermal expansion coefficients of the first member 14 and the second member 16 are positive values, with the thermal expansion coefficient of the second member 16 being larger than the thermal expansion coefficient of the first member 14. As the material for such a first member 14, for example, a metal material such as tungsten or chromium steel can be used. The second member 16 may be made of a metal material such as aluminum, duralumin, or zinc. In the fourth embodiment, as shown in FIGS. 7(A) and 7(B), the upper end surface of the first member 14 and the upper surface 1601 of the second member 16 are located on the same plane at the first temperature T1. Furthermore, as shown in Figures 7(C) and (D), at a second temperature T2 higher than the first temperature T1, the volume of the second member 16 increases significantly, the area of the outer surface 1612 of the second member 16 and the areas of the upper surface 1601 and lower surface of the second member 16 increase, and a large area of the inner surface of the hole 1610 of the second member 16 is exposed, expanding the surface area of the heat dissipation structure 10C. As a result, the amount of heat dissipation by the heat dissipation structure 10C increases, allowing the heat source 12 to dissipate heat effectively, which is more advantageous in maintaining the temperature of the heat source 12 within an appropriate range. Furthermore, as the temperature of the heat dissipation structure 10C decreases, the surface area of the heat dissipation structure 10C decreases, and therefore the amount of heat dissipated by the heat dissipation structure 10C decreases, thereby suppressing excessive heat dissipation from the heat source 12, which is more advantageous in maintaining the temperature of the heat source 12 within an appropriate range.

[0030] In the fourth embodiment, the thermal expansion coefficients of the first member 14 and the second member 16 are positive values, and the thermal expansion coefficient of the second member 16 is greater than the thermal expansion coefficient of the first member 14. However, the relationship between the thermal expansion coefficients of the first member 14 and the second member 16 is not limited as long as there is a difference between the volume change rates of the first member 14 and the second member 16 such that at a second temperature T2 higher than the first temperature T1, the volume increase of the second member 16 is greater than the volume increase of the first member 14. For example, the following relationships of thermal expansion coefficients are possible: 1) The thermal expansion coefficient of the first member 14 is zero and the thermal expansion coefficient of the second member 16 is a positive value. 2) The first member 14 has a negative thermal expansion coefficient and the second member 16 has a positive thermal expansion coefficient. In addition, it is optional to provide recesses or protrusions, or grooves or protrusions, on the outer surface 1612 or upper surface 1601 of the second member 16, for example, to increase the surface area of the second member 16 and thereby increase the heat dissipation amount of the heat dissipation structure 10C. Furthermore, it goes without saying that the fourth embodiment may be applied to the battery cell 20 in the same manner as the second embodiment. [Explanation of symbols]

[0031] 10A, 10B, 10C Heat dissipation structure 12 Heat source 1202 Surface (Top surface) 14 First member 1402 axes 1404 Lower end 1410 Axis 1412 flange 16 Second member 1601 Top surface 1602 holes 1604 Lower end 1610 hole 1612 Outer surface 18 Mounting surface 20 battery cells 2002 Top surface 2004 Lower end surface 22 Battery Module 24 Positive terminal (electrode terminal) 2402 Side 2404 Top surface (surface) 26 Negative terminal (electrode terminal) 28 Module Case 2802 Bottom wall 2804 Side wall 2806 Upper wall 30 Cooling air flow path 32 entrance 34 Outlet 36 Busbar

Claims

1. A heat dissipation structure that is arranged in contact with a heat source and dissipates heat from the heat source, the heat dissipation structure is configured by combining a first member and a second member having different rates of volume change due to temperature, The surface area of the heat dissipation structure varies with temperature. A heat dissipation structure characterized by:

2. the first member comprises a shaft; the second member is configured as a member having a cross-sectional area larger than the cross-sectional area of the shaft and provided with a hole extending in a direction perpendicular to this cross-sectional area, the heat dissipation structure is configured by coupling the shaft to the hole, At a first temperature, the overall length of the first member is equal to the height of the second member along the axial direction of the hole; a difference between a volume change rate of the first member and a volume change rate of the second member such that a longitudinal portion of the first member protrudes outside the hole at a second temperature higher than the first temperature; 2. The heat dissipation structure according to claim 1.

3. the first member comprises a shaft; the second member is configured as a member having a cross-sectional area larger than the cross-sectional area of the shaft and provided with a hole extending in a direction perpendicular to this cross-sectional area, the heat dissipation structure is configured by coupling the shaft to the hole, At a first temperature, the overall length of the first member is equal to the height of the second member along the axial direction of the hole; a difference between a volume change rate of the first member and a volume change rate of the second member such that the first member is immersed in the hole at a second temperature higher than the first temperature; 2. The heat dissipation structure according to claim 1.

4. The first member is provided in plurality, The second member has a plurality of holes, the heat dissipation structure is configured by coupling the plurality of first members to the plurality of holes.

4. The heat dissipation structure according to claim 2 or 3.

5. the first member comprises a shaft; the second member is configured as a member having a cross-sectional area larger than the cross-sectional area of the shaft and provided with a hole extending in a direction perpendicular to this cross-sectional area, the heat dissipation structure is configured by coupling the shaft to the hole, a difference between a volume change rate of the first member and a volume change rate of the second member such that, at a second temperature higher than the first temperature, the volume of the second member increases more significantly than the volume of the first member; 2. The heat dissipation structure according to claim 1.

6. The surface area of the heat dissipation structure changes so as to increase with increasing temperature.

2. The heat dissipation structure according to claim 1.

7. the heat dissipation structure has a mounting surface that is placed in contact with the heat source; an end of the first member and an end of the second member are located on the mounting surface; 2. The heat dissipation structure according to claim 1.

8. the heat source is a battery cell, the mounting surface is disposed in contact with a surface of the battery cell; 8. The heat dissipation structure according to claim 7.

9. the heat source is a columnar positive electrode terminal provided on an end surface of the battery cell, The mounting surface is disposed in contact with the surface of the positive electrode terminal.

8. The heat dissipation structure according to claim 7.

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