Battery pack

Abstract

To improve a cooling efficiency of a battery pack while suppressing an increase in a weight of a battery pack.SOLUTION: A battery pack comprises: a plurality of battery cells; a cooling path in which a coolant formed of a gas for cooling the plurality of battery cells flows; and a passage constituting member that is thermally connected to the plurality of battery cells while constituting at least one part of the coolant passage. The passage constituting member includes: a heat radiation surface to be exposed toward the coolant passage; and a plurality of projections 6 projecting into the coolant passage from the heat radiation surface. Each projection 6 includes: a base end 6A coupled to the heat radiation surface; a tip end 6B on a side opposite to the base end 6A; an upstream side surface 6C facing an upstream side of the coolant passage; and a downstream side surface 6D facing a downstream side of the coolant passage. The upstream side surface 6C includes an inclination surface that is inclined toward the downstream side of the coolant passage as being separated from the base end 6A of each projection 6. The upstream side surface 6C includes a concave 6E that generates a vortex of the coolant.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to a battery pack. [Background technology]

[0002] Electric vehicles and hybrid vehicles are equipped with a battery pack that contains multiple battery cells that supply power to a motor. When such a vehicle runs, the multiple battery cells contained in the battery pack generate heat, particularly when the vehicle accelerates rapidly, performs regenerative control, or quickly charges the multiple battery cells. Patent Document 1 discloses a battery pack that includes a heat dissipation structure that cools the multiple battery cells. The heat dissipation structure disclosed in Patent Document 1 includes a passage component that constitutes a cooling air passage through which cooling air flows. A protrusion including a first protrusion and a second protrusion that protrude into the cooling air passage is provided on the inner surface of the cooling air passage. The first protrusion and the second protrusion extend in different directions along the inner surface of the cooling air passage and are continuous with each other in the width direction of the cooling air passage. The heat dissipation structure disclosed in Patent Document 1 enhances cooling efficiency by generating turbulence near the inner surface of the cooling air passage using the first protrusion and the second protrusion of the protrusion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-162527 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the heat dissipation structure disclosed in Patent Document 1, the first and second protrusions of the protrusion are continuous with each other in the width direction of the cooling air passage. This increases the surface area of ​​the protrusion and improves the cooling efficiency, but increases the mass of the protrusion. Therefore, the heat dissipation structure disclosed in Patent Document 1 has a problem in that the mass of the battery pack increases significantly.

[0005] An object of the present disclosure is to improve the cooling efficiency of a battery pack while suppressing an increase in the mass of the battery pack. [Means for solving the problem]

[0006] A battery pack according to one embodiment of the present disclosure comprises a plurality of battery cells, a refrigerant passage through which a refrigerant consisting of a gas flows for cooling the plurality of battery cells, and a passage component member constituting at least a portion of the refrigerant passage and thermally connecting to at least one of the plurality of battery cells, the passage component member including a heat dissipation surface exposed to the refrigerant passage and a plurality of protrusions protruding from the heat dissipation surface into the refrigerant passage, each of the plurality of protrusions including a base end coupled to the heat dissipation surface, a tip end opposite the base end, an upstream side facing the upstream of the refrigerant passage, and a downstream side facing the downstream of the refrigerant passage, the entirety or a portion of the upstream side of each of the plurality of protrusions including an inclined surface that slopes toward the downstream of the refrigerant passage as it moves away from the base end of a protrusion among the plurality of protrusions corresponding to the upstream side, and the upstream side of each of the plurality of protrusions has at least one depression that generates a vortex of the refrigerant.

[0007] In the above battery pack, the at least one recess may include a plurality of recesses formed on the upstream side surface that generate a vortex of the coolant, and the inclined surface and the plurality of recesses may be located over the entire upstream side surface.

[0008] In the above battery pack, the inclined surface is located over the entire upstream side surface, and the upstream side surface includes a base end region located at the base end of the protrusion, a tip region located at the tip of the protrusion, and an intermediate region located between the base end region and the tip region, and the at least one recess may not be present in the base end region of the upstream side surface, but may be present in at least one of the tip region and the intermediate region of the upstream side surface.

[0009] In the above battery pack, the at least one recess may include a plurality of recesses formed in the upstream side surface that generate a vortex of the refrigerant, and the plurality of recesses may include a first recess located in the tip region of the upstream side surface and a second recess located in the intermediate region of the upstream side surface and having a larger opening area than the first recess.

[0010] In the battery pack, the at least one depression may be a circular dimple having a circular concave surface. In the battery pack, the at least one depression may be an elliptical dimple having an elliptical concave surface.

[0011] In the battery pack, the upstream side surface may have an arc shape that is convex toward the upstream of the refrigerant passage in a plan view of the projection. In the above battery pack, the at least one recess may include a plurality of recesses formed on the upstream side surface that generate a vortex of the refrigerant, and the plurality of recesses may be located only at the center of the upstream side surface in the width direction of the refrigerant passage along the height direction of the protrusion.

[0012] In the above battery pack, the passage forming member may include a heat conduction member provided between the plurality of battery cells and the refrigerant passage, the heat conduction member may include the heat dissipation surface exposed to the refrigerant passage, and the plurality of protrusions may protrude from the heat dissipation surface of the heat conduction member into the refrigerant passage. Effect of the Invention

[0013] A battery pack according to an aspect of the present disclosure can improve the cooling efficiency of the battery pack while suppressing an increase in the mass of the battery pack. [Brief description of the drawings]

[0014] [Figure 1] 1 is a perspective view showing the appearance of an exemplary battery pack according to a first embodiment; [Diagram 2]2 is a cross-sectional view of the battery pack shown in FIG. 1 taken along line AA when viewed from the side. [Diagram 3] FIG. 2 is a perspective view showing an exemplary frame according to the first embodiment. [Figure 4] 2 is a partial cross-sectional view of a portion BB of the battery pack of FIG. 1 as viewed from the front. [Diagram 5] FIG. 2 is a bottom view of an exemplary case body according to the first embodiment. [Figure 6] FIG. 2 is a perspective view illustrating exemplary protrusions according to a first embodiment. [Figure 7] FIG. 2 is a perspective view showing a basic configuration of an exemplary protrusion according to the first embodiment. [Figure 8] 6 is a simulation result showing the flow velocity of the refrigerant in the refrigerant passage. [Figure 9] FIG. 13 is a perspective view of another exemplary protrusion; [Figure 10] FIG. 8 is a side cross-sectional view of the protrusion shown in FIG. 7. [Figure 11] 6 is a simulation result showing a flow of a refrigerant in a refrigerant passage in the first comparative example. [Figure 12] 5 is a simulation result showing a flow of a refrigerant in a refrigerant passage in the first embodiment. [Figure 13] FIG. 13 is a partially enlarged view of the simulation results shown in FIG. 12. [Figure 14] FIG. 13 is a perspective view illustrating an exemplary protrusion according to a second embodiment. [Figure 15] 11 is a simulation result showing a flow of a refrigerant in a refrigerant passage in the second embodiment. [Figure 16] FIG. 13 is a perspective view illustrating an exemplary protrusion according to a third embodiment. [Figure 17] FIG. 11 is a perspective view showing a protrusion of a second comparative example. [Figure 18] 1 is a table showing simulation results for examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of a battery pack according to the present disclosure will be described with reference to the accompanying drawings. For simplicity and clarity of description, the components shown in the drawings are not necessarily drawn to scale. The accompanying drawings are merely illustrative of embodiments of the present disclosure and should not be considered as limiting the present disclosure. Throughout the drawings, the same reference numerals and descriptions refer to similar, but not necessarily identical, components.

[0016] The following detailed description includes a battery pack embodying an exemplary embodiment of the present disclosure. This detailed description is merely explanatory in nature and is not intended to limit the embodiments of the present disclosure or the application and uses of such embodiments.

[0017] [Battery pack configuration] First, a schematic configuration of a battery pack will be described. The battery pack is mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and supplies power to an electric motor or the like. The battery pack includes a plurality of battery cells, a refrigerant passage through which a refrigerant made of a gas for cooling the plurality of battery cells flows, and a passage component that forms at least a part of the refrigerant passage and is thermally connected to at least one of the plurality of battery cells. The plurality of battery cells are secondary batteries such as lithium ion secondary batteries and nickel hydrogen secondary batteries. The refrigerant is made of air, nitrogen, or any appropriate gas for cooling the plurality of battery cells. The battery pack may further include a case having an internal space that accommodates the plurality of battery cells. The refrigerant passage is provided in the case. The case may include an air inlet for introducing the refrigerant into the case and an exhaust port for discharging the refrigerant outside the case. The refrigerant passage communicates with the air inlet and the exhaust port. The plurality of battery cells may be included in one or more assembled batteries. The coolant passage can be provided adjacent to one or more battery cells, through one or more battery cells, or between two battery cells in the battery pack. The passage component includes a heat dissipation surface exposed to the coolant passage and a plurality of protrusions protruding from the heat dissipation surface into the coolant passage. Each of the plurality of protrusions includes a base end bonded to the heat dissipation surface, a tip end opposite to the base end, an upstream side surface facing the upstream of the coolant passage, and a downstream side surface facing the downstream of the coolant passage. The entire or part of the upstream side surface of each of the plurality of protrusions includes an inclined surface that slopes toward the downstream of the coolant passage as it moves away from the base end of the protrusion corresponding to the upstream side of the plurality of protrusions. The upstream side surface of each of the plurality of protrusions has at least one depression that generates a vortex flow of the coolant. In general, if the flow speed of the coolant is not too high, the flow of the coolant flowing over the upstream side surface of the protrusion is a laminar flow in which the coolant flows regularly. When the flow of the coolant flowing over the upstream side surface is a laminar flow, a relatively thick temperature boundary layer is formed on the upstream side surface, and sufficient heat transferability of the protrusion cannot be obtained. According to the above-mentioned configuration, by generating a vortex in at least one recess on the upstream side, the development of a thermal boundary layer formed on the upstream side can be suppressed, and therefore the heat transfer coefficient between the protrusions and the refrigerant can be improved without increasing the volume (mass) of the protrusions.As a result, the cooling efficiency of the battery pack can be improved while suppressing an increase in the mass of the battery pack.

[0018] [First embodiment] [Specific configuration of the battery pack] FIG. 1 is a perspective view showing the appearance of an exemplary battery pack 1 according to the first embodiment. FIG. 2 is a cross-sectional view of part AA of the battery pack 1 shown in FIG. 1 as viewed from the side. A specific configuration of the battery pack 1 will be described with reference to FIGS. 1 and 2. In the first embodiment, the battery pack 1 has a substantially rectangular parallelepiped shape. In the following description, the X direction is the longitudinal direction of the battery pack 1, the Y direction is the transverse direction perpendicular to the longitudinal direction of the battery pack 1, and the Z direction is the height direction of the battery pack 1.

[0019] 1 and 2, the battery pack 1 includes a plurality of assembled batteries 10 and a refrigerant passage 44 through which a refrigerant made of a gas flows to cool the assembled batteries 10. Each assembled battery 10 includes a plurality of battery cells 10A, which will be described later.

[0020] The battery pack 1 further includes a case 2 having an internal space for accommodating a plurality of assembled batteries 10. The case 2 includes an air inlet 33 for introducing a refrigerant into the case 2 and an exhaust port 34 for discharging the refrigerant to the outside of the case 2. A refrigerant passage 44 communicates with the air inlet 33 and the exhaust port 34. Thus, the refrigerant flows from the air inlet 33 to the exhaust port 34 along the refrigerant passage 44 in the case 2. That is, the air inlet 33 is upstream of the refrigerant passage 44, and the exhaust port 34 is downstream of the refrigerant passage 44. In the example of FIG. 1, the air inlet 33 is located on the front side of the case 2 in the longitudinal direction of the battery pack 1, and the exhaust port 34 is located on the rear side opposite to the front side of the case 2. In FIG. 1, in the X direction, which is the longitudinal direction of the battery pack 1, the right front direction of FIG. 1 is the upstream direction of the refrigerant passage 44, and the direction opposite to the upstream direction is the downstream direction of the refrigerant passage 44. In the first embodiment, the case 2 may include a case body 2A and a frame 3 attached to the case body 2A. The case body 2A is fixed to a vehicle (not shown) via the frame 3. The frame 3 is a framework for fixing the case body 2A to the vehicle. For example, the frame 3 is fixed to the vehicle with a plurality of fasteners 11. In the first embodiment, the case body 2A has a substantially rectangular parallelepiped shape, and the frame 3 has a rectangular shape in a plan view.

[0021] As shown in FIG. 2, the case body 2A according to the first embodiment includes an upper case 21 and a lower case 22. The upper case 21 and the lower case 22 define an internal space of the case 2 (case body 2A) that houses a plurality of assembled batteries 10 (four in FIG. 2). The upper case 21 may include a flange portion 21A that protrudes horizontally from the periphery of the lower end of the upper case 21. The upper case 21 may be, for example, a substantially rectangular box-shaped member that is open downward. The upper case 21 may have a tapered shape that tapers from the lower end to the upper end. The corners of the upper case 21 may also be rounded. In the example of FIG. 2, the lower case 22 has a shape obtained by turning the upper case 21 upside down. The lower case 22 may include a bottom wall 23 that has a mounting surface 23A on which the plurality of assembled batteries 10 are mounted and a bottom surface 23B on the opposite side to the mounting surface 23A. The flange portion 21A of the upper case 21 and the flange portion 22A of the lower case 22 can be sealed so that the flange portions 21A, 22A are in close contact with each other. In the first embodiment, the frame 3 is attached to the lower end of the case main body 2A. In one example, the frame 3 may be attached to the upper end, side, or any appropriate portion of the case main body 2A.

[0022] FIG. 3 is a perspective view showing an exemplary frame 3 according to the first embodiment. As shown in FIG. 3, the frame 3 may include a substrate 31 and an outer frame 32 erected from the periphery of the substrate 31. The substrate 31 has, for example, a rectangular shape in a plan view. A recess 35 of the frame 3 is defined by the substrate 31 and the outer frame 32. The outer frame 32 of the frame 3 may be composed of, for example, a hollow square pipe of a metal such as iron. The outer frame 32 may include an upstream frame wall 32U and a downstream frame wall 32D that face each other in the longitudinal direction (x direction) of the battery pack 1. The upstream frame wall 32U and the downstream frame wall 32D have, for example, an elongated shape. In the first embodiment, the air supply port 33 is formed in the upstream frame wall 32U of the frame 3. In the example of FIG. 3, the air supply port 33 is located at the center of the upstream frame wall 32U in the longitudinal direction of the upstream frame wall 32U. In the first embodiment, the exhaust port 34 is formed in the downstream frame wall 32D of the frame 3. 3, the two exhaust ports 34 are located at equal intervals on the downstream frame wall 32D in the longitudinal direction of the downstream frame wall 32D. In another example, the air supply port 33 and the exhaust port 34 may be formed at any appropriate position on the case body 2A or the case 2.

[0023] As shown in FIG. 2, the refrigerant passage 44 according to the first embodiment is formed between the frame 3 and the case main body 2A. In the example of FIG. 2, the lower end of the lower case 22 is fitted into the recess 35 of the frame 3 so that the refrigerant passage 44 is formed between the recess 35 of the frame 3 and the bottom wall 23 of the lower case 22. The refrigerant passage 44 is defined by the bottom surface of the recess 35 of the frame 3 and the bottom surface 23B of the lower case 22. That is, the frame 3 and the bottom wall 23 of the lower case 22 function as a duct that constitutes the refrigerant passage 44 and are used as a passage-constituting member. The bottom wall 23 is also used as a partition wall that separates the internal space that accommodates the multiple assembled batteries 10 from the refrigerant passage 44. Therefore, the battery pack 1 includes a duct formed adjacent to the multiple assembled batteries 10 at the bottom of the case 2. In one example, the battery pack 1 may include a duct formed adjacent to the multiple assembled batteries 10 at the side or upper part of the case 2.

[0024] As shown in Figs. 1 and 2, the battery pack 1 according to the first embodiment further includes a blower 4 attached to the air inlet 33 of the case 2. The blower 4 may include a housing 40 and a fan 43 provided in the housing 40. The housing 40 may be, for example, box-shaped and may have an intake section 41 that takes in a refrigerant and an air outlet 42 that communicates with the air inlet 33 of the frame 3. The fan 43 is driven, for example, by an electric motor (not shown). The blower 4 is configured to supply the refrigerant to the refrigerant passage 44 via the intake section 41, the air outlet 42, and the air inlet 33 by driving the fan 43. This allows the refrigerant to flow from the air inlet 33 to the exhaust outlet 34 along the refrigerant passage 44 in the case.

[0025] FIG. 4 is a partial cross-sectional view of the BB portion of the battery pack 1 according to the first embodiment of FIG. 1 as seen from the front. As shown in FIG. 4, the battery pack 10 may include a plurality of battery cells 10A stacked in the thickness direction of the battery cells 10A, a pair of end plates 10B, 10B abutting both ends of the stacked battery cells 10A, and a restraining device (not shown) that restrains the end plates 10B, 10B with a certain pressure. The stacked battery cells 10A are electrically connected by a bus bar (not shown) or the like. In this manner, the battery pack 10 is configured. In the example of FIG. 2, the plurality of battery packs 10 are arranged on the mounting surface 23A at equal intervals along the direction in which the refrigerant flows (the plurality of arrows shown in FIG. 2). In another example, the plurality of battery packs 10 may be arranged on the mounting surface 23A in the width direction of the refrigerant passage 44, or in any appropriate manner in the path direction and width direction of the refrigerant passage 44.

[0026] As shown in FIG. 2, the bottom wall 23 of the case 2 (lower case 22) according to the first embodiment may include one or more heat conductive members 5. The one or more heat conductive members 5 are arranged between the battery packs 10 and the refrigerant passage 44. In the example of FIG. 2, the bottom wall 23 of the case 2 (lower case 22) includes a plurality of (four in FIG. 2) heat conductive members 5 arranged between the battery packs 10 and the refrigerant passage 44. This can improve the thermal conductivity of the path of the bottom wall 23 from the battery packs 10 to the refrigerant passage 44. The heat conductive member 5 has, for example, a plate shape having the same thickness as the bottom wall 23. In the example of FIG. 2, the positions and shapes of the heat conductive members 5 correspond to the positions and shapes of the battery packs 10.

[0027] 4, each of the multiple thermally conductive members 5 may include a mounting surface 5A on which the battery pack 10 is mounted and a heat dissipation surface 5B opposite to the mounting surface 5A. The heat dissipation surface 5B is exposed to the refrigerant passage 44. In some embodiments, the bottom wall 23 does not need to include a thermally conductive member 5. Therefore, the mounting surfaces 5A and 23A have a function of absorbing heat generated from the battery pack 10. The heat dissipation surface 5B (bottom surface 23B) has a function of dissipating heat absorbed from the mounting surfaces 5A and 23A to the refrigerant passage 44.

[0028] FIG. 5 is a bottom view of an exemplary case body 2A (bottom wall 23) according to the first embodiment. For ease of explanation, FIG. 5 does not show the substrate 31 of the frame 3. In FIG. 5, the arrows indicate the direction in which the refrigerant flows. As shown in FIG. 5, the bottom wall 23 of the case body 2A (lower case 22) has a plurality of through holes 23C (four in FIG. 5) penetrating the bottom wall 23. A plurality of heat conductive members 5 are fitted into the plurality of through holes 23C of the bottom wall 23, respectively. The plurality of heat conductive members 5 are fixed airtightly to a plurality of inner circumferential surfaces that define the plurality of through holes 23C of the bottom wall 23, respectively.

[0029] As the material of the heat conductive member 5, metals with high thermal conductivity such as aluminum alloys and copper alloys can be used as long as the insulation with the assembled battery 10 is not an issue. In addition, in order to ensure insulation, a resin with inorganic filler with high thermal conductivity added can be used as the resin of the heat conductive member 5. For example, a resin obtained by adding inorganic filler to silicone resin (polyalkylsiloxane) used as the main body can be exemplified. A resin obtained by adding inorganic filler to liquid crystal polymer used as the main body may be used. Furthermore, a resin obtained by adding inorganic filler to acrylic resin used as the main body may be used. These materials of the heat conductive member 5 are selected or combined in consideration of thermal conductivity, strength, insulation, and the like. When a metal heat conductive member 5 is used, a resin with high thermal conductivity such as silicone grease may be filled so as to fill the gap between the heat conductive member 5 and the assembled battery 10.

[0030] [Protrusion configuration] As shown in FIG. 2, the duct formed by the frame 3 and the bottom wall 23 of the lower case 22 used as a passage component includes a plurality of protrusions 6 protruding from the inner surface of the duct into the refrigerant passage 44. The plurality of protrusions 6 are members that dissipate heat transferred from the plurality of assembled batteries 10 to the duct (the frame 3 and the bottom wall 23 of the lower case 22) to the refrigerant flowing in the refrigerant passage 44. By using the plurality of protrusions 6, it is possible to improve the heat transfer coefficient between the duct and the refrigerant. For example, a metal with high thermal conductivity such as an aluminum alloy or a copper alloy is used as the material of the protrusions 6. In the first embodiment, the bottom wall 23 of the lower case 22 includes a plurality of protrusions 6 protruding from the bottom surface 23B of the bottom wall 23 into the refrigerant passage 44. In the example of FIG. 2, the plurality of protrusions 6 protrude into the refrigerant passage 44 from the heat dissipation surface 5B of the heat conduction member 5 of the bottom wall 23. The frame 3 and the bottom wall 23 of the lower case 22 are thermally connected to the plurality of assembled batteries 10. In particular, the bottom wall 23 of the lower case 22 is adjacent to the battery pack 10, and multiple battery packs 10 are placed on the bottom wall 23 of the lower case 22. Therefore, the heat from the multiple battery packs 10 that is transferred to the bottom wall 23 of the lower case 22 has a higher temperature than the frame 3. By arranging the multiple protrusions 6 on the bottom wall 23 of the lower case 22, the heat transferred from the multiple battery packs 10 can be efficiently dissipated.

[0031] Fig. 6 is a perspective view showing exemplary multiple protrusions 6 according to the first embodiment. In Fig. 6, the arrows indicate the direction in which the coolant flows. As shown in Fig. 6, the multiple protrusions 6 are located on the entire heat dissipation surface 5B of the heat conduction member 5. In one example, the multiple protrusions 6 may be located only on a part of the heat dissipation surface 5B of the heat conduction member 5, for example, only in the center of the heat dissipation surface 5B.

[0032] FIG. 7 is a perspective view showing a basic configuration of an exemplary protrusion 6 according to the first embodiment. Each of the multiple protrusions 6 includes a base end 6A coupled to the heat dissipation surface 5B, a tip end 6B opposite to the base end 6A, an upstream side surface 6C facing the upstream side of the refrigerant passage 44, and a downstream side surface 6D facing the downstream side of the refrigerant passage 44. The heat conductive member 5 having the multiple protrusions 6 may be, for example, a one-piece metal product. As shown in FIG. 7, the protrusion 6 according to the first embodiment has a semi-frustum shape like a truncated cone. In one example, the protrusion 6 may have a columnar, rectangular columnar, cylindrical, truncated cone, semi-frustum, truncated cone, or any other suitable shape that dissipates heat. In the example of FIG. 7, the protrusion 6 tapers from the base end 6A of the protrusion 6 toward the tip 6B. In addition, the tip 6B of the protrusion 6 is rounded. This can reduce the flow path resistance caused by the protrusion 6. The upstream side 6C includes a base region located at the base end 6A of the projection 6, a tip region located at the tip 6B of the projection 6, and an intermediate region located between the base region and the tip region.

[0033] FIG. 8 is a simulation result showing the flow velocity of the refrigerant in the refrigerant passage 44. As a simulation condition, one protrusion 6 is arranged in the refrigerant passage 44, and the flow velocity of the refrigerant supplied into the refrigerant passage 44 is set to 7 m / s. In FIG. 8, the refrigerant passage 44 is divided into five regions R1 to R5 showing different flow velocities of the refrigerant. In FIG. 8, the flow velocity of the refrigerant is shown by the darkness of the color. Specifically, the darker the color of the region, the faster the flow velocity of the refrigerant in the region. The flow velocity of the refrigerant is fastest in the order of the first region R1, the second region R2, the third region R3, the fourth region R4, and the fifth region R5. In FIG. 8, the fifth region R5, in which the flow velocity of the refrigerant is the slowest, is located near the base end 6A of the protrusion 6, particularly near the base end region of the upstream side surface 6C. This shows that the flow velocity of the refrigerant is the slowest at the base end 6A of the protrusion 6, and the refrigerant is likely to stagnate near the base end 6A of the protrusion 6. In FIG. 8, the first region R1 where the flow rate of the refrigerant is the fastest is located near the tip 6B of the protrusion 6, particularly the tip region of the upstream side surface 6C. In addition, the second to fifth regions R2 to R5 are located in order on both sides of the first region R1 near the tip 6B of the protrusion 6. This shows that the flow rate of the refrigerant is the fastest at the tip 6B of the protrusion 6, and the main stream of the refrigerant hits the tip 6B of the protrusion 6 and flows behind the protrusion 6. In this specification, the base end region of the upstream side surface 6C is a region where the refrigerant is likely to stagnate and the flow rate of the refrigerant is relatively slow. On the other hand, the tip region of the upstream side surface 6C is a region where the main stream of the refrigerant hits and the flow rate of the refrigerant is relatively fast. For example, the base end region, intermediate region, and tip region of the upstream side surface 6C are divided by dividing the upstream side surface 6C into thirds in the height direction of the protrusion 6. The division ratio of the base end region, intermediate region, and tip region is not limited to thirds and may be appropriately determined according to the above-mentioned state of the refrigerant.

[0034] As shown in FIG. 7, the entire upstream side surface 6C of the protrusion 6 includes an inclined surface that inclines toward the downstream of the refrigerant passage 44 from the base end 6A to the tip 6B of the protrusion 6. In one example, the inclined surface of the upstream side surface 6C may be provided only on a part of the upstream side surface 6C. For example, the inclined surface of the upstream side surface 6C may be provided on at least a part of the base end region, the intermediate region, and the tip region. In this case, the inclined surface of the upstream side surface 6C inclines toward the downstream of the refrigerant passage 44 as it moves away from the base end 6A of the protrusion 6. In the example of FIG. 7, the downstream side surface 6D is approximately perpendicular to the heat dissipation surface 5B of the heat conduction member 5. This allows a relatively large vortex to be generated in the vicinity of the downstream side surface 6D. In another example, the downstream side surface 6D may have an inclined surface, for example, an inclined surface that inclines toward the upstream of the refrigerant passage 44 from the base end 6A to the tip 6B of the protrusion 6. In the example of FIG. 7, the upstream side surface 6C has a circular arc shape that is convex toward the upstream of the refrigerant passage 44 in a plan view of the protrusion 6. This can reduce the flow path resistance caused by the protrusion 6. In the example of FIG. 7, the upstream side surface 6C having such an arc shape is connected to the downstream side surface 6D. In another example, the upstream side surface 6C may be a flat surface. The protrusion 6 may also include two lateral side surfaces opposed to each other in the width direction of the refrigerant passage 44. In this case, each lateral side surface is connected to the upstream side surface 6C and the downstream side surface 6D.

[0035] [Pot configuration] As shown in FIG. 7, the upstream side surface 6C of the protrusion 6 has a plurality of (three in FIG. 7) recesses 6E that generate a vortex flow of the refrigerant. The number of recesses 6E may be one, two, or four or more. The number of recesses 6E may be appropriately determined in consideration of parameters such as the size of the protrusion 6 and the recesses 6E, and the flow rate of the refrigerant. The shape of the plurality of recesses 6E may be a shape for generating a vortex flow, for example, a cube, a rectangular parallelepiped, a hemisphere, a cone, a cylinder, a triangular prism, or any suitable shape for generating a vortex flow. In the first embodiment, the recess 6E is a circular dimple having a circular concave surface. In this specification, the circular dimple is a part of a recess having a hemispherical shape, and refers to a circular dimple that is thinner than a recess having a hemispherical shape. A series of refrigerant flows in the circular dimple 6E are smoother than a series of refrigerant flows in a recess having a hemispherical shape. In this specification, the series of refrigerant flows in the circular dimple 6E refers to a series of refrigerant flows when the refrigerant flows into the circular dimple 6E, a vortex of the refrigerant is generated in the circular dimple 6E, and the refrigerant is discharged outside the circular dimple 6E. The series of refrigerant flows in other parts have the same meaning as the series of refrigerant flows in the circular dimple 6E. In addition, in the depressions 6E having shapes that are difficult to generate vortex flows, such as triangular prisms and rectangular parallelepipeds, vortex flows are generated, but compared to the circular dimples 6E, the flow rate of the refrigerant is slower and the refrigerant is more likely to stagnate. The series of refrigerant flows in the circular dimples 6E are less turbulent than the depressions 6E having shapes that are difficult to generate vortex flows. Therefore, by using circular dimples as the depressions 6E, the heat transfer coefficient between the protrusions 6 and the refrigerant (hereinafter also referred to as the heat transfer coefficient of the protrusions 6) can be improved.

[0036] In another example, as shown in Fig. 9, the plurality of recesses 6E may be elliptical dimples having an elliptical concave surface. As with circular dimples, the flow of the refrigerant in the elliptical dimples is less disturbed than the recesses 6E having shapes that are less likely to generate vortex flows, such as triangular prisms and rectangular parallelepipeds. By forming elliptical dimples instead of circular dimples, the number of recesses can be reduced, improving the manufacturing efficiency of the battery pack 1.

[0037] As shown in FIG. 7, the multiple recesses 6E according to the first embodiment are located on the entire upstream side surface 6C. Specifically, the multiple recesses 6E on the upstream side surface 6C include a tip recess 6E1 located in the tip region of the upstream side surface 6C, a middle recess 6E2 located in the middle region of the upstream side surface 6C, and a base recess 6E3 located in the base region of the upstream side surface 6C. The multiple recesses 6E1, 6E2, and 6E3 are located on the entire upstream side surface 6C (tip region, middle region, and base region). In one example, the multiple recesses 6E may be located only in the center of the upstream side surface 6C in the width direction of the refrigerant passage 44 along the height direction of the protrusion 6. For example, when the upstream side surface 6C has a circular arc shape as shown in FIG. 7, the refrigerant hits the center of the upstream side surface 6C first, so that the flow speed of the refrigerant flowing over the center of the upstream side surface 6C is faster than that of other parts of the upstream side surface 6C. In such a configuration, the recess 6E in the center of the upstream side surface 6C has higher heat dissipation characteristics than the recesses 6E in other regions. Therefore, the heat transfer coefficient of the protrusion 6 can be improved by a smaller number of recesses 6E. In another example, the multiple recesses 6E may be located side by side on the upstream side surface 6C in the width direction (Y direction) of the refrigerant passage 44. In the first embodiment, the downstream side surface 6D does not have the recesses 6E. In one example, the downstream side surface 6D, for example, the tip region of the downstream side surface 6D where no vortex is generated, may have the recesses 6E formed thereon. In the example of FIG. 7, the inclined surface is located on the entire upstream side surface 6C (the tip region, the middle region, and the base region). The multiple recesses 6E are located on the entire upstream side surface 6C, which is an inclined surface. Since the refrigerant flows relatively fast on the inclined surface, the vortex of the refrigerant can be efficiently generated in the multiple recesses 6E. In another example, at least one of the multiple recesses 6E may be located on the inclined surface of the upstream side surface 6C of the protrusion 6.

[0038] FIG. 10 is a side cross-sectional view of an exemplary protrusion 6 according to the first embodiment shown in FIG. 7. The height H of the protrusion 6 can be, for example, 10 mm or more and 15 mm or less. The inclination angle θ of the upstream side surface 6C of the protrusion 6 can be, for example, 10 degrees or more and 15 degrees or less. Here, the inclination angle θ is an inclination angle with respect to a direction perpendicular to the installation surface of the protrusion 6. In the first embodiment, the recess 6E is a circular dimple. The radius R of the circular dimple 6E can be, for example, 1.0 mm or more and 1.5 mm or less. Here, the radius R is the radius of curvature that defines the surface of the recess in the dimple cross section. The depth D of the circular dimple 6E can be, for example, 0.6 mm or more and 1.1 mm or less. Therefore, the depth D of the circular dimple 6E is smaller than the radius R of the circular dimple 6E. That is, the circular dimple 6E has a shallower depth D than a recess having a hemispherical shape. The height H of the protrusion 6 and the inclination angle θ of the upstream side surface 6C are not limited to the above ranges, and may be appropriately determined in consideration of various parameters such as the height and width of the refrigerant passage 44 and the flow speed of the refrigerant. The radius R and depth D (opening area and depth) of the circular dimple 6E are not limited to the above ranges, and may be appropriately determined so as to generate a vortex flow of the refrigerant. Furthermore, when the recess 6E is a recess other than a circular dimple, the opening area and depth of the recess 6E may be appropriately determined so as to generate a vortex flow of the refrigerant.

[0039] [Function of battery pack 1 according to the first embodiment] In the first embodiment, a plurality of recesses 6E are formed on the entire upstream side 6C of the plurality of protrusions 6. As described above, generally, if the flow rate of the refrigerant is not too fast, the flow of the refrigerant flowing on the upstream side 6C of the protrusion 6 is a laminar flow in which the refrigerant flows regularly. If the flow of the refrigerant flowing on the upstream side 6C is a laminar flow, a relatively thick temperature boundary layer is formed on the surface of the upstream side 6C, and sufficient heat transferability of the protrusion 6 cannot be obtained. By generating vortexes in the plurality of recesses 6E formed on the entire upstream side 6C, the development of the temperature boundary layer formed on the upstream side 6C can be suppressed. This improves the heat transfer rate of the protrusion 6, and thus improves the cooling efficiency of the battery pack 1.

[0040] [Simulation results] A computer was used to simulate the flow of the refrigerant in the refrigerant passage 44, and the heat transfer coefficient and temperature of the heat dissipation surface 5B and the protrusions 6. The simulation results showing the flow of the refrigerant in the refrigerant passage 44 will be described with reference to Figures 11 to 13. The simulation results showing the heat transfer coefficient and temperature of the heat dissipation surface 5B and the protrusions 6 will also be described.

[0041] FIG. 11 shows a simulation result showing the flow of the refrigerant in the refrigerant passage 44 for the first comparative example, which is a conventional technique. In the simulation conditions for the first comparative example, one protrusion 6 was arranged on the heat dissipation surface 5B in the refrigerant passage 44, and a heating element (not shown) was arranged below the protrusion 6. In the simulation conditions for the first comparative example, a protrusion 6 without a recess was used, the height H of the protrusion 6 was set to 10 mm, the inclination angle θ of the upstream side surface 6C of the protrusion 6 was set to 10 degrees, and the flow speed of the refrigerant supplied to the refrigerant passage 44 was set to 7 m / s. In the simulation conditions for the first comparative example, the distance G between the protrusion 6 and the ceiling of the refrigerant passage 44 was set to 10 mm, the heat generation amount of the heating element was set to 2 W, the temperature in the refrigerant passage was set to 26.85 degrees, and the temperature of the refrigerant was set to 26.85 degrees. 11, it can be seen that vortex flows are generated at an upstream corner portion C1 between the heat dissipation surface 5B and the base end region of the upstream side surface 6C of the projection 6, and at a downstream corner portion C2 between the heat dissipation surface 5B and the downstream side surface 6D of the projection 6. In addition, a simulation result of the heat transfer coefficient shows that the heat transfer coefficient of the projection 6 is 113 W / m 2 K, and the heat transfer coefficient for the heat dissipation surface 5B is 239 W / m 2 K. In addition, the temperature simulation results showed that the temperatures of the heat dissipation surface 5B and the protrusions 6 were 28.034 degrees.

[0042] FIG. 12 is a simulation result showing the flow of the refrigerant in the refrigerant passage 44 for the first example, which is an example of the first embodiment. FIG. 13 is a partially enlarged view of the simulation result shown in FIG. 12. In the simulation conditions for the first example, a protrusion 6 having three recesses 6E1, 6E2, and 6E3, which are circular dimples, is used, the depth D of the circular dimples 6E1, 6E2, and 6E3 is set to 0.6 mm, and the radius R of the circular dimples 6E1, 6E2, and 6E3 is set to 1.0 mm. The other simulation conditions are the same as those for the first comparative example. Referring to FIGS. 12 and 13, it can be seen that vortex flows are generated in the recesses 6E1 to 6E3 in addition to the corner portions C1 and C2. In addition, in the simulation results for the heat transfer coefficient, the heat transfer coefficient for the protrusion 6 is 238 W / m 2 K, and the heat transfer coefficient for the heat dissipation surface 5B is 320 W / m 2 K. Furthermore, a temperature simulation result showed that the temperature of the heat dissipation surface 5B and the protrusions 6 was 28.029 degrees. A heat transfer coefficient simulation result showed that the heat transfer coefficient for the protrusions 6 of the first embodiment was higher than that for the protrusions 6 of the first comparative example. Furthermore, the temperature for the heat dissipation surface 5B and the protrusions 6 of the first embodiment was lower than that for the heat dissipation surface 5B and the protrusions 6 of the first comparative example. Therefore, it was demonstrated that the cooling efficiency is improved by the protrusions 6 of the first embodiment.

[0043] [Effects of the first embodiment] The battery pack 1 of the first embodiment has the following advantages. (1) The battery pack 1 includes a plurality of assembled batteries 10, a refrigerant passage 44 through which a refrigerant made of gas flows for cooling the plurality of assembled batteries 10, and a bottom wall 23 that constitutes a part of the refrigerant passage 44 and is thermally connected to the plurality of assembled batteries 10. The bottom wall 23 includes a bottom surface 23B exposed to the refrigerant passage 44, and a plurality of protrusions 6 protruding from the bottom surface 23B into the refrigerant passage 44. Each of the plurality of protrusions 6 includes a base end 6A connected to the bottom surface 23B, a tip end 6B opposite to the base end 6A, an upstream side surface 6C facing the upstream side of the refrigerant passage 44, and a downstream side surface 6D facing the downstream side of the refrigerant passage 44. The entire upstream side surface 6C of each of the plurality of protrusions 6 includes an inclined surface that is inclined toward the downstream of the refrigerant passage 44 from the base end 6A toward the tip end 6B of the protrusion 6. The upstream side surface 6C of each of the plurality of protrusions 6 has a plurality of recesses 6E that generate vortexes of the refrigerant. According to such a configuration, it is possible to improve the heat transfer coefficient of the protrusions 6 without increasing the volume (mass) of the protrusions 6. Therefore, it is possible to improve the cooling efficiency of the battery pack 1 while suppressing an increase in the mass of the battery pack 1.

[0044] (2) The plurality of recesses 6E are provided over the entire inclined upstream side surface 6C. With this configuration, a plurality of eddies of the refrigerant are generated over the entire inclined upstream side surface 6C, so that the heat transfer coefficient of the protrusions 6 can be further improved.

[0045] (3) Each of the recesses 6E is a circular dimple having a circular concave surface. With this configuration, the flow of the refrigerant through the circular dimples 6E is less turbulent than that through recesses 6E having shapes that are less likely to generate vortexes, such as triangular prisms and rectangular parallelepipeds. This further improves the heat transfer coefficient of the protrusions 6.

[0046] (4) The upstream side surface 6C of each of the multiple protrusions 6 has an arc shape that is convex toward the upstream of the refrigerant passage 44 in a plan view of the protrusion 6. With this configuration, the flow path resistance caused by the protrusion 6 can be reduced.

[0047] (5) The multiple recesses 6E are located along the height direction of the protrusion 6 only at the center of the upstream side surface 6C in the width direction of the refrigerant passage 44. When the upstream side surface 6C has the above-mentioned arc shape, the refrigerant hits the center of the upstream side surface 6C first, so the flow speed of the refrigerant flowing over the center of the upstream side surface 6C is faster than other parts of the upstream side surface 6C. With this configuration, the recess 6E at the center of the upstream side surface 6C has higher heat dissipation characteristics than the recesses 6E in other areas. Therefore, the heat transfer coefficient of the protrusion 6 can be improved with a smaller number of recesses 6E.

[0048] (6) Bottom wall 23 includes a heat conductive member 5 provided between the multiple battery packs 10 and refrigerant passage 44. Heat conductive member 5 includes a heat dissipation surface 5B exposed to refrigerant passage 44. The multiple protrusions 6 protrude from heat dissipation surface 5B of heat conductive member 5 into refrigerant passage 44. With this configuration, the thermal conductivity of the path from the multiple battery packs 10 to the multiple protrusions 6 can be improved.

[0049] [Second embodiment] Next, the battery pack 1 according to the second embodiment will be described. In the battery pack 1 according to the second embodiment, the arrangement of the plurality of recesses 16E in the protrusion 16 is different from that of the battery pack 1 according to the first embodiment. In the first embodiment, the plurality of recesses 6E are provided on the entire upstream side surface 6C of the protrusion 6, but in the second embodiment, the plurality of recesses 16E are not present in the base end region of the upstream side surface 6C. In other words, in the second embodiment, the plurality of recesses 16E are present in a non-base end region other than the base end region of the upstream side surface 6C. Hereinafter, the arrangement of the plurality of recesses 16E in the protrusion 16 according to the second embodiment, which is a difference from the first embodiment, will be mainly described, and the description of the contents overlapping with the first embodiment will be omitted.

[0050] FIG. 14 is a perspective view showing an exemplary protrusion 16 according to the second embodiment. In FIG. 14, elements of the protrusion 16 that are similar to those of the protrusion 6 according to the first embodiment are given the same reference numerals. The protrusion 16 shown in FIG. 14 differs from the protrusion 6 shown in FIG. 7 of the first embodiment in that the base recess 6E3 is not present. In the example of FIG. 14, the upstream side 6C of the protrusion 16 has a tip recess 16E1 and a middle recess 16E2. In another example, the upstream side 6C of the protrusion 16 may have the tip recess 16E1 or the middle recess 16E2. In other words, the multiple recesses 16E of the protrusion 16 may be provided in a part of the non-base end region of the upstream side 6C. Referring to the partially enlarged view of the simulation result for the first embodiment shown in FIG. 13, the vortex flow generated in the upstream corner portion C1 is combined with the vortex flow generated in the base recess 6E3. The vortex generated in the upstream corner portion C1 and the vortex generated in the base end recess 6E3 interact with each other, causing a series of refrigerant flows to be disturbed in the upstream corner portion C1. Similarly, the series of refrigerant flows in the base end recess 6E3 are also disturbed. In the second embodiment, since the protrusion 16 does not have a base end recess, it is possible to suppress the series of refrigerant flows in the upstream corner portion C1 from being disturbed. As a result, it is believed that the protrusion 16 of the second embodiment can improve the heat transfer coefficient of the protrusion 16 compared to the protrusion 6 of the first embodiment.

[0051] Using a computer, the flow of the refrigerant in the refrigerant passage 44 of the second example, which is an example of the second embodiment, and the heat transfer coefficient and temperature of the heat dissipation surface 5B and the protrusion 16 of the second example were simulated. FIG. 15 shows the simulation results showing the flow of the refrigerant in the refrigerant passage 44 of the second example. In the simulation conditions of the second example, the protrusion 16 having the tip recess 16E1 and the middle recess 16E2 was used. The other simulation conditions are the same as those of the first example. Referring to FIG. 15, it can be seen that the series of refrigerant flows in the upstream corner portion C1 are not disturbed, and a normal vortex flow is generated in the upstream corner portion C1. In the second example, it is preferable that the dimensions of the base end region of the upstream side surface 6C and the position of the recess 16E are set so that the vortex flow in the upstream corner portion C1 and the vortex flow in the recess 16E do not interact (or combine) with each other. For example, the dimensions of the base end region of the upstream side surface 6C in the height direction of the protrusion 16 are the same as or larger than the dimensions of the vortex flow in the upstream corner portion C1 in the height direction of the protrusion 16. 14 is the same as or higher than the maximum height position of the upstream corner portion C1. Similar to the dimension of the base end region of the upstream side surface 6C in the height direction of the protrusion 16, the dimension of the base end region of the upstream side surface 6C in the width direction of the protrusion 16 can be set according to the dimension of the vortex of the upstream corner portion C1 in the width direction of the protrusion 16. A simulation result of the heat transfer coefficient shows that the heat transfer coefficient for the protrusion 16 is 305 W / m 2 K, and the heat transfer coefficient for the heat dissipation surface 5B is 239 W / m 2K. In addition, the temperature simulation results showed that the temperature of the heat dissipation surface 5B and the protrusions 16 was 28.024 degrees. That is, the heat transfer coefficient of the protrusions 16 in the second embodiment is higher than that of the protrusions 6 in the first embodiment. The heat transfer coefficient of the heat dissipation surface 5B in the second embodiment is lower than that of the heat dissipation surface 5B in the first embodiment. The temperature of the heat dissipation surface 5B and the protrusions 16 in the second embodiment is lower than that of the heat dissipation surface 5B and the protrusions 6 in the first embodiment. Here, the refrigerant flowing through the refrigerant passage 44 is in contact with the heat dissipation surface 5B, but does not hit the heat dissipation surface 5B. The surface area where the refrigerant hits the protrusions 16 is larger than the surface area where the refrigerant hits the heat dissipation surface 5B. It is considered that the heat transfer coefficient of the protrusions 16 has a greater effect on the cooling efficiency and temperature of the heat dissipation surface 5B and the protrusions 16 than the heat transfer coefficient of the heat dissipation surface 5B. Therefore, it was demonstrated that the cooling efficiency is further improved by the protrusions 16 in the second embodiment.

[0052] [Effects of the second embodiment] The battery pack 1 according to the second embodiment has the following new advantages in addition to the advantages (1) and (3) to (6) of the battery pack 1 according to the first embodiment.

[0053] An inclined surface is located over the entire upstream side surface 6C of each of the multiple protrusions 16. The upstream side surface 6C includes a base end region located at the base end 6A of the protrusion 16, a tip end region located at the tip 6B of the protrusion 16, and an intermediate region located between the base end region and the tip end region. The multiple recesses 16E are not present in the base end region of the upstream side surface 6C, but are present in at least one of the tip region and the intermediate region of the upstream side surface 6C. With this configuration, the heat transfer coefficient of the protrusions 16 can be further improved by suppressing the disturbance of the series of refrigerant flows in the upstream corner portion C1. Therefore, the battery pack 1 having the multiple protrusions 16 can further improve the cooling efficiency.

[0054] [Third embodiment] Next, the battery pack 1 according to the third embodiment will be described. In the battery pack 1 according to the third embodiment, the size of the multiple recesses 16E in the protrusion 26 is different from that of the battery packs 1 according to the first and second embodiments. In the first and second embodiments, the multiple recesses 6E, 16E have the same size, but in the third embodiment, the tip recess 26E1 of the protrusion 26 has a size smaller than the other recesses 26E located in the non-tip region other than the tip region of the upstream side surface 6C. Hereinafter, the size of the multiple recesses 26E in the protrusion 26 according to the third embodiment, which is a difference from the first and second embodiments, will be mainly described, and the description of the contents overlapping with the first and second embodiments will be omitted.

[0055] As described above with reference to the simulation results showing the flow velocity of the refrigerant in the refrigerant passage 44 shown in FIG. 8, the flow velocity of the refrigerant is the fastest at the tip 6B of the protrusion 6, and the main flow of the refrigerant hits the tip 6B of the protrusion 6 and flows to the rear of the protrusion 6. When the main flow of the refrigerant flows into the tip recess 6E1 located at the tip 6B of the protrusion 6, the flow velocity of the main flow of the refrigerant slows down. The decrease in the flow velocity of the main flow of the refrigerant greatly affects the heat transfer coefficient of the protrusion 6. Therefore, in order to further improve the heat transfer coefficient of the protrusion 26, it is effective to make the size of the tip recess 26E1 smaller or to make the size of the other recesses 26E located in the non-tip region larger. In the third embodiment, the tip recess 26E1 of the protrusion 26 has a smaller opening area than the other recesses 26E located in the non-tip region other than the tip region of the upstream side surface 6C. Alternatively, the tip recess 26E1 of the protrusion 26 may have a shallower depth than the other recesses 26E. This makes it possible to further improve the heat transfer coefficient at the protrusions 26 while suppressing a decrease in the velocity of the main flow of the coolant.

[0056] FIG. 16 is a perspective view showing an exemplary protrusion 26 according to the third embodiment. In FIG. 16, elements of the protrusion 26 that are similar to those of the protrusion 16 according to the second embodiment are given the same reference numerals. In the example of FIG. 16, the protrusion 26 differs from the protrusion 16 shown in FIG. 14 of the second embodiment in terms of the opening area and depth of the intermediate recess 26E2. The opening area of ​​the intermediate recess 26E2 is larger than the opening area of ​​the tip recess 26E1. The depth of the intermediate recess 26E2 is deeper than the depth of the tip recess 26E1. In the example of FIG. 16, the upstream side surface 6C of the protrusion 26 has the tip recess 26E1 and the intermediate recess 26E2. In another example, the upstream side surface 6C may be formed with the tip recess 6E1, the intermediate recess 6E2, and the base recess 6E3.

[0057] Fig. 17 is a perspective view showing a protrusion 36 of a second comparative example with respect to the protrusion 26 according to the third embodiment. In Fig. 17, the elements of the protrusion 36 that are similar to those of the protrusion 26 according to the third embodiment are given the same reference numerals. In the protrusion 36 of the second comparative example, the opening area of ​​the intermediate recess 36E2 is smaller than the opening area of ​​the tip recess 36E1, unlike the protrusion 26 according to the third embodiment. Also, in the protrusion 36 of the second comparative example, the depth of the intermediate recess 36E2 is shallower than the depth of the tip recess 36E1, unlike the protrusion 26 according to the third embodiment.

[0058] FIG. 18 is a list of simulation results for examples and comparative examples including the third example which is an example of the third embodiment and the second comparative example. In the simulation conditions for the second comparative example, the radius R of the tip recess 36E1 of the protrusion 36 was set to 1.5 mm, and the depth D of the tip recess 36E1 of the protrusion 36 was set to 1.1 mm. The other simulation conditions were the same as those for the second embodiment. The simulation results for the heat transfer coefficient showed that the heat transfer coefficient for the protrusion 36 was 300 W / m 2 K, and the heat transfer coefficient for the heat dissipation surface 5B is 239 W / m 2 K. In the temperature simulation results, the temperatures of the heat dissipation surface 5B and the protrusions 36 were 28.021 degrees.

[0059] In the simulation conditions for the third embodiment, the radius R of the intermediate depression 26E2 of the protrusion 26 was set to 1.5 mm, and the depth D of the intermediate depression 26E2 of the protrusion 26 was set to 1.1 mm. The other simulation conditions were the same as those for the second embodiment. The simulation results for the heat transfer coefficient showed that the heat transfer coefficient for the protrusion 26 was 301 W / m 2 K, and the heat transfer coefficient for the heat dissipation surface 5B is 237 W / m 2 K. In the temperature simulation results, the temperatures of the heat dissipation surface 5B and the protrusions 26 were 28.018 degrees.

[0060] Therefore, the heat transfer coefficient for the protrusions 26 of the third embodiment is slightly higher than that for the protrusions 36 of the second comparative example. The heat transfer coefficient for the heat dissipation surface 5B of the third embodiment is slightly lower than that for the heat dissipation surface 5B of the second comparative example. The temperature for the heat dissipation surface 5B and the protrusions 26 of the third embodiment is slightly lower than that for the heat dissipation surface 5B and the protrusions 36 of the second comparative example. As described above, it is considered that the heat transfer coefficient for the protrusions 26 has a greater effect on the cooling efficiency and temperature of the heat dissipation surface 5B and the protrusions 26 than the heat transfer coefficient for the heat dissipation surface 5B. This proves that the protrusions 26 of the third embodiment improve the cooling efficiency more than the protrusions 36 of the second comparative example.

[0061] Furthermore, from the list of simulation results for the examples and comparative examples, it can be seen that the heat transfer coefficient of the protrusions 6 is improved by providing the recesses 6E in the protrusions 6, that the heat transfer coefficient of the protrusions 6 is further improved by removing the base end recesses 6E3 of the protrusions 6, and that the heat transfer coefficient of the protrusions 6 is further improved by making the size of the tip recesses 6E1 of the protrusions 6 smaller than the size of the intermediate recesses 6E2 of the protrusions 6.

[0062] [Effects of the third embodiment] The battery pack 1 according to the third embodiment has the following new advantages in addition to the advantages (1), (3) to (6) of the battery pack 1 according to the first embodiment and the advantages of the battery pack 1 according to the second embodiment.

[0063] The opening area of ​​the middle recess 26E2 is larger than the opening area of ​​the tip recess 26E1. With this configuration, it is possible to further improve the heat transfer coefficient of the protrusions 26 while suppressing a decrease in the speed of the main flow of the refrigerant. Therefore, the battery pack 1 having the multiple protrusions 26 can further improve the cooling efficiency.

[0064] [Another example] Regardless of the first to third embodiments, the present invention can be carried out as follows. In the first to third embodiments, the coolant passage 44 is formed between the frame 3 and the case body 2A, but the coolant passage 44 may be provided inside the case body 2A. In that case, the coolant passage 44 can be provided inside the case body 2A adjacent to one or more assembled batteries 10, passing through one or more assembled batteries 10, or between two assembled batteries 10.

[0065] In the first to third embodiments, the frame 3 and the bottom wall 23 of the lower case 2, which are parts of the case 2, form the duct, but a duct, a pipe, or any appropriate flow path member for flowing a refrigerant, which is a member separate from the case 2, may be arranged in the battery pack 1 (case 2) as a path forming member for forming the refrigerant passage 44. The duct, pipe, or any appropriate flow path member for flowing a refrigerant is arranged in the battery pack 1 (case 2) adjacent to one or more assembled batteries 10, through one or more assembled batteries 10, or between two assembled batteries 10. The multiple protrusions 6, 16, 26 protrude into the refrigerant passage 44 from the inner surface of the duct, pipe, or any appropriate flow path member for flowing a refrigerant.

[0066] A plurality of battery pack components (e.g., the case body 2A, the battery cell 10A, the assembled battery 10, or the end plate 10B, etc.) of the battery pack 1 may be used as the passage component. That is, the refrigerant passage 44 is constituted by a plurality of battery pack components. For example, the refrigerant passage 44 may be constituted by the case body 2A and the end plate 10B at the side of the case body 2A. The refrigerant passage 44 may also be constituted by the mounting surface 23A of the case body 2A and the two assembled batteries 10 between the two assembled batteries 10. Furthermore, the refrigerant passage 44 may be constituted by the case body 2A and the plurality of assembled batteries 10 at the upper part of the case body 2A. The cross section of the refrigerant passage 44 in the width direction may have a shape in which a part of the refrigerant passage 44 is opened, for example, a substantially U-shaped shape. The plurality of protrusions 6, 16, 26 protrude into the refrigerant passage 44 from the surface or wall of the battery pack component that faces the refrigerant passage 44 and is thermally connected to at least one assembled battery 10.

[0067] The multiple protrusions 6, 16, 26 may be provided in a portion that constitutes at least a portion of the coolant passage 44 and that is thermally connected to a heat-generating component of the battery pack 1 other than the battery cells 10A (battery assembly 10) (for example, an inverter device).

[0068] A plurality of refrigerant passages 44 may be provided inside the battery pack 1 (case 2). The plurality of refrigerant passages 44 may use one or a combination of the above-mentioned types of refrigerant passages 44. The number of refrigerant passages 44 may be determined appropriately taking into consideration parameters such as the size of the battery pack 1, the available space within the battery pack 1, and the number of battery cells 10A (battery assembly 10).

[0069] Although the first to third embodiments have been described taking as an example a plurality of assembled batteries 10 each including a plurality of stacked battery cells 10A, the battery pack 1 may include a single assembled battery 10. Also, in the first to third embodiments, the plurality of battery cells 10A are stacked in the width direction of the refrigerant passage 44, but the plurality of battery cells 10A may be stacked in the direction in which the refrigerant flows or may be inverted upside down. The layout of the battery cells 10A and the assembled batteries 10 is not limited.

[0070] The numerical limitations in the first to third embodiments are merely examples and do not limit the present disclosure. Those skilled in the art can optimize the numerical limitations as appropriate depending on the configurations of the battery cell 10A, the battery pack 1, etc.

[0071] The first to third embodiments are directed to a battery pack 1 for in-vehicle use, but the use of the present disclosure is not limited thereto, and a stationary battery pack 1 for use in a home, a factory, etc. may also be assumed, and the size, etc. of such a battery pack 1 can be selected as appropriate.

[0072] It goes without saying that a person skilled in the art may add, delete, or modify the configuration of this disclosure without departing from the scope of the claims. [Explanation of symbols]

[0073] 1. Battery pack 3...Frame (passageway component) 5…Heat conductive material 5B…Heat radiation surface 6,16,26…Protrusion 6A…Proximal end 6B...Tip 6C…Upstream side 6D…Downstream side 6E, 16E, 26E…recess 10A…Battery cell 23...Bottom wall (passage component) 23B…Bottom surface (heat radiation surface) 44…Refrigerant passage

Claims

1. A battery pack comprising: A plurality of battery cells; a coolant passage through which a gas coolant for cooling the plurality of battery cells flows; a passage component member that configures at least a portion of the refrigerant passage and is thermally connected to at least one of the plurality of battery cells; the passage component includes a heat dissipation surface exposed to the refrigerant passage and a plurality of protrusions protruding from the heat dissipation surface into the refrigerant passage, each of the plurality of protrusions includes a base end coupled to the heat dissipation surface, a tip end opposite to the base end, an upstream side surface facing the upstream side of the refrigerant passage, and a downstream side surface facing the downstream side of the refrigerant passage; a part or the whole of the upstream side surface of each of the plurality of projections includes an inclined surface that is inclined toward the downstream of the refrigerant passage as it moves away from the base end of a projection corresponding to the upstream side surface of the plurality of projections, The battery pack, wherein the upstream side of each of the plurality of protrusions has at least one depression that generates a vortex of the coolant.

2. the at least one recess includes a plurality of recesses formed on the upstream side and configured to generate vortexes in the coolant; The battery pack according to claim 1 , wherein the inclined surface and the plurality of recesses are located on the entire upstream side surface.

3. The inclined surface is located on the entire upstream side surface, the upstream side surface includes a base end region located at the base end of the projection, a tip end region located at the tip end of the projection, and an intermediate region located between the base end region and the tip end region, The battery pack according to claim 1 , wherein the at least one recess is absent in the base end region of the upstream side surface, and is present in at least one of the tip end region and the intermediate region of the upstream side surface.

4. the at least one recess includes a plurality of recesses formed on the upstream side and configured to generate vortexes in the coolant; The plurality of recesses include a first recess located in the tip region of the upstream side; The battery pack according to claim 3 , further comprising: a second recess located in the intermediate region of the upstream side surface, the second recess having a larger opening area than the first recess.

5. The battery pack of claim 1 , wherein the at least one depression is a circular dimple having a circular concave surface.

6. The battery pack of claim 1 , wherein the at least one depression is an elliptical dimple having an elliptical concave surface.

7. The battery pack according to claim 1 , wherein the upstream side surface of the protrusion has an arc shape that is convex toward the upstream of the refrigerant passage in a plan view.

8. the at least one recess includes a plurality of recesses formed on the upstream side and configured to generate vortexes in the coolant; The battery pack according to claim 7 , wherein the plurality of recesses are located only at a center of the upstream side surface in a width direction of the refrigerant passage and along a height direction of the protrusion.

9. the passage component includes a heat conductive member provided between the plurality of battery cells and the refrigerant passage, the heat conducting member includes the heat dissipation surface exposed to the refrigerant passage, The battery pack according to claim 1 , wherein the plurality of protrusions protrude from the heat dissipation surface of the heat conduction member into the refrigerant passage.

Images