Battery cooling unit

Abstract

To reduce the temperature difference among cells in a battery cell.SOLUTION: A battery cooling unit has a coolant flow passage 1 for a coolant to flow inside and cools a battery 2 by heat conduction in such a manner that the battery 2 contacts with a coolant flow passage 1 directly or indirectly. In an inner wall surface 111 of the coolant flow passage 1, irregularities 13 are provided to be more densely present in positions closer to the downstream side of the flow of the coolant and to be less densely present in positions closer to the upstream side of the flow of the coolant.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a battery cooler that cools a battery by heat exchange between a refrigerant flowing through a refrigerant passage and the battery. [Background technology]

[0002] Patent Document 1 discloses a battery cooler in which a plurality of island-shaped protrusions are arranged at equal distance intervals in the direction of refrigerant flow on the inner wall surface of a refrigerant flow path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-026228 A Summary of the Invention [Problem to be solved by the invention]

[0004] A battery cooler is known that cools a battery stack by arranging a battery stack in a row of multiple cells in the direction of the refrigerant flow on a refrigerant flow path through which the refrigerant flows in one direction. In such a battery cooler, the refrigerant flowing through the refrigerant flow path becomes hotter as it moves from the upstream side to the downstream side due to heat received from the battery stack. Therefore, in such a battery cooler, the cells arranged downstream become hotter than the cells arranged upstream, resulting in a temperature difference between the cells.

[0005] However, for safe and proper operation of batteries such as lithium-ion batteries, it is necessary to keep all of the individual cells in the battery stack below a specified temperature and to keep the temperature difference between cells in the battery stack below a specified temperature difference.

[0006] Furthermore, in recent years, battery packs have become larger and have higher energy densities, which has resulted in an increase in the amount of heat generated by the cells, and this has led to a tendency for the temperature of the coolant to rise more significantly.

[0007] Therefore, an object of the present invention is to provide a battery cooler that can reduce the temperature difference between cells in a battery stack. [Means for solving the problem]

[0008] The battery cooler of the present invention is a battery cooler that has a refrigerant flow path through which a refrigerant flows, and cools the battery through thermal conduction by the battery coming into direct or indirect contact with the refrigerant flow path, and is characterized in that the inner wall surface of the refrigerant flow path is provided with irregularities that become denser from the upstream side to the downstream side of the flow of the refrigerant. Effect of the Invention

[0009] The present invention can reduce the temperature difference between cells in a battery stack. [Brief description of the drawings]

[0010] [Figure 1] 1 is a perspective view of a refrigerant passage and a battery stack of a battery cooler according to a first embodiment, and a bottom view of an upper plate of the refrigerant passage. [Diagram 2] 13 is a perspective view of a refrigerant passage and a battery stack of a battery cooler of a second embodiment, and a bottom view of an upper plate of the refrigerant passage. FIG. [Diagram 3] 13 is a perspective view of a refrigerant passage and a battery stack of a battery cooler of a third embodiment, and a bottom view of an upper plate of the refrigerant passage. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] <First embodiment> Hereinafter, a battery cooler 10 according to a first embodiment will be described with reference to Fig. 1. The battery cooler 10 is disposed under a battery pack mounted on a vehicle such as an electric vehicle or a hybrid vehicle. The battery cooler 10 can cool the battery pack by a refrigerant flowing inside. The refrigerant flowing inside the battery cooler 10 may be, for example, engine cooling water, or a liquid such as cooling oil or an air conditioner refrigerant.

[0012] 1 is a perspective view of a refrigerant flow path 1 and a battery stack 2 of a battery cooler 10, and a bottom view of an upper plate 11 of the refrigerant flow path 1. A battery pack mounted on a vehicle has a configuration in which battery stacks 2, each having a plurality of cells 21 arranged in a row, are arranged in parallel in multiple rows as shown in FIG. 1. The refrigerant flow path in the battery cooler 10 branches into refrigerant flow paths 1 in the same number as the battery stacks 2, and each of these refrigerant flow paths 1 is disposed one below each of the battery stacks 2. There are multiple combinations of the refrigerant flow paths 1 and the battery stacks 2, but FIG. 1 shows only one combination of the refrigerant flow path 1 and the battery stacks 2.

[0013] The refrigerant flow path 1 is a tube with a rectangular cross section formed by an upper plate 11, a lower plate 12, and a side plate (not shown). The side plate constitutes the side wall of the refrigerant flow path 1 and is connected to the upper plate 11 and the lower plate 12. The upper plate 11 and the lower plate 12 are both arranged so as to be horizontal. A space with a height of 3 mm is formed between the upper plate 11 and the lower plate 12. The refrigerant flows through the space between the upper plate 11 and the lower plate 12 in the same direction as the direction in which the cells 21 are arranged in a row. The lower surface 111 of the upper plate 11 and the upper surface 121 of the lower plate 12 constitute a part of the inner wall surface of the refrigerant flow path 1. The upper surface 112 of the upper plate 11 is bonded via a thermally conductive material to the lower surface of the battery pack case 3 on which the battery stack 2 is placed. Since the cells 21 are in contact with the refrigerant flow path 1 via the battery pack case 3 and the thermally conductive material in this way, the refrigerant flow path 1 can cool the cells 21 by thermal conduction.

[0014] 1, a plurality of hemispherical protrusions 13 each having a height of 1 mm that protrude downward are provided on the lower surface 111 of the upper plate 11 so that the density increases from the upstream side to the downstream side of the refrigerant flow. Therefore, the heat transfer area between the refrigerant and the lower surface 111 of the upper plate 11 is larger on the downstream side where the protrusions 13 are densely arranged than on the upstream side. Furthermore, as an additional effect of providing the protrusions 13, the downstream side where the protrusions 13 are densely arranged promotes turbulent flow of the refrigerant more than the upstream side, so that the heat transfer coefficient between the refrigerant and the lower surface 111 of the upper plate 11 can be improved.

[0015] With regard to the amount of heat Q transferred to the refrigerant via the lower surface 111 of the upper plate 11, the relationship of the following formula 1 holds.

[0016] Q = heat transfer area × heat transfer coefficient × (wall temperature – coolant temperature) Equation 1

[0017] The temperature of the refrigerant flowing through the refrigerant flow path 1 is higher on the downstream side than on the upstream side of the refrigerant flow path 1. Therefore, (wall temperature - refrigerant temperature) in formula 1 is higher on the upstream side of the refrigerant flow path 1 than on the downstream side. However, by providing a convex portion 13 on the lower surface 111 of the upper plate 11 so that the downstream side is denser than the upstream side, the heat transfer area and heat transfer coefficient in formula 1 are larger on the downstream side of the refrigerant flow path 1 than on the upstream side. Therefore, the battery cooler 10 can make the amount of heat exchange on the downstream side of the refrigerant flow path 1 closer to the amount of heat exchange on the upstream side. Since the battery cooler 10 can make the amount of heat exchange on the downstream side of the refrigerant flow path 1 closer to the amount of heat exchange on the upstream side in this way, the temperature difference between the cells 21 in the battery stack 2 can be reduced.

[0018] <Second embodiment> Next, a battery cooler 20 of a second embodiment will be described with reference to Fig. 2. The battery cooler 20 of the second embodiment has the same configuration as the battery cooler 10 of the first embodiment, except that a rib 13a is provided on the upper plate 11a of the refrigerant flow path 1a instead of the protrusion 13. Therefore, for the battery cooler 20 of the second embodiment, the same components as those of the battery cooler 10 of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0019] FIG. 2 is a perspective view of the refrigerant flow path 1a of the battery cooler 20 and the battery stack 2, and a bottom view of the upper plate 11a of the refrigerant flow path 1a of the battery cooler 20. As shown in FIG. 2, the upper plate 11a of the refrigerant flow path 1a of the battery cooler 20 is provided with a plurality of ribs 13a with a height of 1 mm that protrude downward so as to become denser from the upstream side to the downstream side of the refrigerant flow. All of the ribs 13a extend in a direction perpendicular to the direction in which the refrigerant flows. The ribs 13a are provided so that the intervals between the ribs 13a are narrower on the downstream side than on the upstream side of the refrigerant flow path 1a. Therefore, the heat transfer area between the refrigerant and the lower surface 111a of the upper plate 11a is larger on the downstream side where the ribs 13a are densely provided than on the upstream side. Furthermore, as an added effect of providing the ribs 13a, the turbulent flow of the refrigerant is promoted more on the downstream side, where the ribs 13a are densely arranged, than on the upstream side, thereby improving the heat transfer coefficient between the refrigerant and the lower surface 111a of the upper plate 11a.

[0020] In the battery cooler 20, similarly to the battery cooler 10 of the first embodiment, the temperature of the refrigerant flowing through the refrigerant flow path 1a is higher on the downstream side than on the upstream side of the refrigerant flow path 1a. Therefore, (wall surface temperature-refrigerant temperature) in formula 1 is higher on the upstream side of the refrigerant flow path 1a than on the downstream side. However, by providing ribs 13a on the lower surface 111a of the upper plate 11a so that the downstream side is denser than the upstream side, the heat transfer area and heat transfer coefficient in formula 1 are larger on the downstream side of the refrigerant flow path 1a than on the upstream side. Therefore, the battery cooler 20 can make the heat exchange amount on the downstream side of the refrigerant flow path 1a closer to the heat exchange amount on the upstream side. Since the battery cooler 20 can make the heat exchange amount on the downstream side of the refrigerant flow path 1a closer to the heat exchange amount on the upstream side in this way, the temperature difference between the cells 21 in the battery stack 2 can be reduced.

[0021] <Third embodiment> Next, a battery cooler 30 of a third embodiment will be described with reference to Fig. 3. The battery cooler 30 of the third embodiment has the same configuration as the battery cooler 10 of the first embodiment, except that a rib 13b is provided on the upper plate 11b of the refrigerant flow path 1b instead of the protrusion 13. Therefore, for the battery cooler 30 of the third embodiment, the same components as those of the battery cooler 10 of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0022] FIG. 3 is a perspective view of the refrigerant flow path 1b of the battery cooler 30 and the battery stack 2, and a bottom view of the upper plate 11b of the refrigerant flow path 1b of the battery cooler 30. As shown in FIG. 3, the upper plate 11b of the refrigerant flow path 1b of the battery cooler 30 is provided with a plurality of ribs 13b with a height of 1 mm that protrude downward so as to become denser from the upstream side to the downstream side of the refrigerant flow. All of the ribs 13b extend in a direction parallel to the direction in which the refrigerant flows. The ribs 13b are provided so that the intervals between the ribs 13b are narrower on the downstream side than on the upstream side of the refrigerant flow path 1b. Therefore, the heat transfer area between the refrigerant and the lower surface 111b of the upper plate 11b is larger on the downstream side where the ribs 13b are densely provided than on the upstream side. Furthermore, as an added effect of providing the ribs 13b, the turbulent flow of the refrigerant is promoted more on the downstream side, where the ribs 13b are densely arranged, than on the upstream side, thereby improving the heat transfer coefficient between the refrigerant and the lower surface 111b of the upper plate 11b.

[0023] In the battery cooler 30, similarly to the battery cooler 10 of the first embodiment, the temperature of the refrigerant flowing through the refrigerant flow path 1b is higher on the downstream side than on the upstream side of the refrigerant flow path 1b. Therefore, (wall surface temperature-refrigerant temperature) in formula 1 is higher on the upstream side of the refrigerant flow path 1b than on the downstream side. However, by providing ribs 13b on the lower surface 111b of the upper plate 11b so that the downstream side is denser than the upstream side, the heat transfer area and heat transfer coefficient in formula 1 are larger on the downstream side of the refrigerant flow path 1b than on the upstream side. Therefore, the battery cooler 30 can make the heat exchange amount on the downstream side of the refrigerant flow path 1b closer to the heat exchange amount on the upstream side. Since the battery cooler 30 can make the heat exchange amount on the downstream side of the refrigerant flow path 1b closer to the heat exchange amount on the upstream side in this way, the temperature difference between the cells 21 in the battery stack 2 can be reduced.

[0024] <Supplementary explanation of the embodiment> The battery cooler of the present disclosure is not limited to the above-mentioned embodiment, and may be implemented in various forms within the scope of the present disclosure. For example, the shape of the protrusions provided on the inner wall surface of the refrigerant flow path may be a shape other than a hemisphere. In addition, the height of the protrusions and ribs may be a height other than 1 millimeter. [Explanation of symbols]

[0025] 1, 1a, 1b refrigerant flow path; 2 battery stack; 3 battery pack case; 10, 20, 30 battery cooler; 11, 11a, 11b upper plate; 12 lower plate; 13 convex portion; 13a, 13b ribs; 21 cell; 111, 111a, 111b lower surface; 112 upper surface; 121 upper surface.

Claims

[Claim 1] A battery cooler comprising a refrigerant flow path through which a refrigerant flows, and a battery is in direct or indirect contact with the refrigerant flow path to cool the battery by thermal conduction, A battery cooler characterized in that an inner wall surface of the refrigerant flow path is provided with unevenness so that the density increases from the upstream side to the downstream side of the flow of the refrigerant.

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