Lower tray for battery case

Abstract

To prevent a reduction in cooling efficiency.SOLUTION: A lower tray for a battery case 20 comprises: a tray body 21 that is formed of a single member in a form in which a peripheral wall part 23 is erected from an outer peripheral edge of a bottom wall part 22, and is arranged with a battery cell 12 on a top face of the bottom wall part 22; and a cooling member 31 that is attached to a lower face of the bottom wall part 22, and forms coolant paths 42 with the bottom wall part 22 for causing coolant to flow. The cooling member 31 is a member made of synthetic resin having a thermal conductivity lower than the bottom wall part 22.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a lower tray for a battery case.

Background Art

[0002] Patent Document 1 discloses a battery pack structure having a plate-like cooling member and a plurality of wall-like frames attached to the outer peripheral edge of the cooling member. The cooling member is integrated by welding an upper cooling layer and a lower cooling layer stacked one on top of the other. A cooling flow path for flowing cooling water is formed between the upper cooling layer and the lower cooling layer. The battery pack is attached in a state of being placed on the upper surface of the cooling member. By the cooling member taking away the heat generated in the battery pack, overheating of the battery pack is prevented.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When this type of battery pack structure is attached to the lower surface of an automobile body, in a situation where the outside air temperature is high, the lower cooling layer is heated by radiant heat from the high-temperature road surface, and the temperature of the cooling water rises. When this occurs, since the cooling efficiency decreases, improvement is desired.

[0005] The present invention has been completed based on the above circumstances, and an object thereof is to suppress a decrease in cooling efficiency.

Means for Solving the Problems

[0006] The lower tray for a battery case of the present disclosure is It is composed of a single member in a form where the peripheral wall portion is raised from the outer peripheral edge of the bottom wall portion, and includes a tray body on which a battery cell is disposed on the upper surface of the bottom wall portion, a cooling member attached to the lower surface of the bottom wall portion and configured to form a refrigerant flow path for flowing refrigerant between the bottom wall portion and the bottom wall portion. The cooling member is a member made of a synthetic resin having a lower thermal conductivity than the bottom wall portion.

Effect of the Invention

[0007] According to the present disclosure, it is possible to suppress a decrease in cooling efficiency when provided in an exposed state on the lower surface of the vehicle body.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. Combinations of the following plurality of form examples arbitrarily combined within a range that does not cause contradictions are also included in the mode for carrying out the invention. The lower tray for the battery case of the present disclosure is (1) It is composed of a single member in a form where the peripheral wall part is raised from the outer peripheral edge of the bottom wall part, and includes a tray body on which a battery cell is arranged on the upper surface of the bottom wall part, and a cooling member attached to the lower surface of the bottom wall part and constituting a refrigerant flow path for flowing refrigerant between the bottom wall part and the cooling member. The cooling member is a member made of synthetic resin with a lower thermal conductivity than the bottom wall part. When the lower tray for the battery case of the present disclosure is arranged on the lower surface of the vehicle body, the lower surface of the cooling member is exposed so as to face the road surface. The thermal resistance between the lower surface (outer surface) and the upper surface (inner surface facing the refrigerant flow path) of the cooling member is larger than the thermal resistance between the lower surface and the upper surface of the bottom wall part. The cooling member can suppress the temperature rise of the refrigerant caused by radiant heat from the road surface, and the bottom wall part can efficiently transfer the heat of the battery cell to the refrigerant. Even if the cooling member is provided so as to be exposed facing the road surface, a decrease in cooling efficiency can be suppressed. Since the cooling member is made of synthetic resin, weight reduction can be achieved compared to a metal cooling member.

[0010] (2) In (1), it is preferable that the space between the lower surface of the bottom wall part and the flange-shaped joint part along the outer peripheral edge of the cooling member is joined in an airtight or liquid-tight manner by a liquid sealant. According to this configuration, in the process of joining the cooling member and the bottom wall part, it is not necessary to apply pressure. Even if the surface roughness of the lower surface of the bottom wall part or the upper surface of the cooling member is large, reliable sealing can be achieved.

[0011] (3) In (2), it is preferable that a plurality of protrusions protruding upward are formed on the cooling member, and the lower surface of the bottom wall part and the upper surfaces of the plurality of protrusions are joined by the liquid sealant. According to this configuration, since the cooling member is a plate-shaped member made of synthetic resin, there is a concern that its rigidity is low and deformation may occur. However, since the cooling member is joined to the bottom wall part at a plurality of protrusions, deformation of the cooling member can be prevented.

[0012] (4)(3) In this case, it is preferable that the plurality of protrusions have an elongated shape extending in parallel, and the refrigerant flow path is partitioned into a plurality of parallel flow paths by the plurality of protrusions. According to this configuration, the refrigerant can be caused to flow in a laminar flow in the refrigerant flow path by utilizing the protrusions.

[0013] (5)(2) to (4) In this case, it is preferable that the bottom wall portion is made of a material having higher rigidity than the cooling member. According to this configuration, since the bottom wall portion is less likely to deform than the cooling member, even if the cooling member is in a thin plate shape, peeling between the bottom wall portion and the cooling member due to deformation of the bottom wall portion can be prevented.

[0014] (6)(1) or (2) In this case, it is preferable that a heat transfer layer that directly contacts the battery cell is formed on the upper surface of the bottom wall portion. According to this configuration, the thermal resistance between the battery cell and the bottom wall portion is smaller than when an air layer is interposed between the battery cell and the bottom wall portion.

[0015] [Details of Embodiments of the Present Disclosure] <Example 1> Hereinafter, Example 1 embodying the present invention will be described with reference to FIGS. 1 to 6. In the following description, regarding the front-rear direction, the F direction in FIGS. 1 to 6 is defined as the front. Regarding the up-down direction, the H direction in FIGS. 1 to 6 is defined as the up. Regarding the left-right direction, the R direction in FIGS. 1 to 4 is defined as the right.

[0016] The lower tray 20 for the battery case of the first embodiment (hereinafter referred to as "lower tray 20") is a member that constitutes the battery case 10 by being attached from below to the upper case 11. The interior of the battery case 10 functions as a battery accommodation space 13 for accommodating the battery cells 12. The battery case 10 is attached to an electric vehicle, a hybrid vehicle, etc. (not shown). The attachment position of the battery case 10 is the lower surface of the vehicle body (not shown), that is, a position exposed to the outside of the vehicle body. The lower surface of the battery case 10 faces the road surface (not shown) without any other objects (such as components of the automobile) intervening therebetween.

[0017] The lower tray 20 includes a tray body 21 made of a single member, a plurality of reinforcing members 26 for reinforcing the tray body 21, and a plurality of coolers 30 for cooling the battery cells 12. The single member is not one formed by integrating a plurality of parts by welding, adhesion, etc., but is one part formed in a form having no joints or joining parts.

[0018] The tray body 21 is a part formed into a shallow square dish shape by pressing a single metal plate material. As the material of the tray body 21, an alloy containing iron (steel plate), etc. is used. The entire surface of the tray body 21 is subjected to cationic ED coating. The tray body 21 has a bottom wall portion 22 forming a horizontal flat plate shape, a peripheral wall portion 23 rising upward from the outer peripheral edge of the bottom wall portion 22 over the entire circumference, and a flange portion 24 projecting horizontally outward from the upper end edge of the peripheral wall portion 23 over the entire circumference.

[0019] In a plan view of the tray body 21 seen from above, the bottom wall portion 22 forms a rectangle with its long side oriented in the front-rear direction. On the upper surface of the bottom wall portion 22, a heat transfer layer 25 that directly contacts the bottom wall portion 22 and the battery cell 12 is disposed. The peripheral wall portion 23 has a front wall portion 23F, a rear wall portion 23R, and a pair of left and right side wall portions 23S. The front wall portion 23F and the rear wall portion 23R are disposed along the short side of the bottom wall portion 22. The left and right side wall portions 23S are disposed along the long side of the bottom wall portion 22. The flange portion 24 projects horizontally outward from the upper end edge of the peripheral wall portion 23.

[0020] The reinforcing member 26 is a metal member parallel to the short side of the tray body 21. The reinforcing member 26 is joined to the upper surface of the bottom wall portion 22 and the inner surfaces of the pair of left and right side wall portions 23S by arc spot welding. The attachment positions of the reinforcing member 26 on the bottom wall portion 22 are regions of the battery cells 12 adjacent to each other in the front-rear direction. The reinforcing member 26 has a function of enhancing the rigidity of the tray body 21 and suppressing relative displacement between the bottom wall portion 22 and the side wall portion 23S.

[0021] One cooler 30 is composed of a part of the bottom wall portion 22 and one cooling member 31 which is a component separate from the tray body 21. The cooling member 31 is a dish-shaped member made of a material having a lower thermal conductivity and a smaller specific gravity than the tray body 21. As the material of the cooling member 31, synthetic resins such as PE, PA66, and PA610 are used. The cooling member 31 has a bottom plate portion 32, a wall-shaped peripheral edge portion 33 that rises from the outer peripheral edge of the bottom plate portion 32 over the entire circumference, and a flange-shaped joint portion 34 that extends from the upper end edge of the peripheral edge portion 33. In a plan view of the cooling member 31 seen from above, the cooling member 31 has an elongated shape in the left-right direction. The cooling member 31 has a flat dish shape with a small height dimension (thickness dimension) with respect to the width dimension in the front-rear direction and the length dimension in the left-right direction.

[0022] A rectangular area of the bottom plate portion 32 excluding the left and right end portions functions as a horizontal flat rectifying portion 35. A plurality of protrusions 36 extending linearly and elongated in the left - right direction are formed on the upper surface of the rectifying portion 35. The plurality of protrusions 36 are arranged in parallel at intervals in the front - rear direction (the width direction of the cooling member 31). A pair of recesses 37 are formed at the left and right end portions of the bottom plate portion 32 in a recessed form so as to be lower than the upper surface of the rectifying portion 35. A cylindrical inflow port 38 protruding leftward is provided at the left end portion of the peripheral portion 33. A cylindrical outflow port 39 protruding rightward is provided at the right end portion of the peripheral portion 33. The inflow port 38 and the outflow port 39 communicate with the recess 37. The flange - like joint portion 34 horizontally projects outward from the upper end edge of the peripheral portion 33 to the outside of the cooling member 31.

[0023] One cooler 30 is configured by joining one cooling member 31 to the outer surface of the tray body 21. The joining of the cooling member 31 and the tray body 21 is performed using a liquid sealant 40 called FIPG (Formed In Place Gasket). By the liquid sealant 40, the upper surface of the flange - like joint portion 34 and the lower surface of the bottom wall portion 22 are joined in a liquid - tight manner, and the upper surfaces of the plurality of protrusions 36 and the lower surface of the bottom wall portion 22 are joined in a liquid - tight manner. The joint portion between the cooling member 31 and the bottom wall portion 22 is located outside (below the tray body 21) of the tray body 21 (battery accommodation space 13).

[0024] By joining the cooling member 31 to the bottom wall portion 22, a pair of left - right chambers 41 and one refrigerant flow path 42 communicating with both chambers 41 are formed inside the cooler 30. The chamber 41 is a space partitioned by the lower surface of the bottom wall portion 22, the upper surface of the recess 37, and the inner peripheral surface of the peripheral portion 33, and communicates with the inflow port 38 or the outflow port 39. One refrigerant flow path 42 is a flat space partitioned by the upper surface of the rectifying portion 35, the lower surface of the bottom wall portion 22, and the inner peripheral surface of the peripheral portion 33. One refrigerant flow path 42 is partitioned into a plurality of parallel flow paths 43 by a plurality of protrusions 36. Each parallel flow path 43 extends linearly in the left - right direction with a constant width dimension. The left and right end portions of each parallel flow path 43 communicate with the chamber 41.

[0025] The heat generated in the battery cell 12 is transmitted to the bottom wall portion 22 of the tray body 21 through the heat transfer layer 25. The bottom wall portion 22 constitutes a heat transfer path for transferring the heat of the battery cell 12 to the refrigerant. Since the bottom wall portion 22 is made of metal, it has a small thermal resistance and exhibits a good heat transfer function. A refrigerant (coolant) is supplied to the cooler 30, and the refrigerant supplied to the cooler 30 takes away the heat of the battery cell 12 in the process of passing through the cooler 30. Specifically, the refrigerant flows into the left chamber 41 from the inflow port 38, flows in a laminar flow in a plurality of parallel flow paths 43 constituting the refrigerant flow path 42, passes through the right chamber 41, and flows out of the cooler 30 from the outflow port 39. Since the refrigerant in the cooler 30 is in direct contact with the bottom wall portion 22, it takes away the heat of the bottom wall portion 22 and the battery cell 12 in the process of passing through the cooler 30 (the chamber 41 and the refrigerant flow path 42). In addition, since the surface of the bottom wall portion 22 is coated with cationic ED, even if the refrigerant is water, rusting of the bottom wall portion 22 is prevented.

[0026] Since the cooling member 31 constituting the cooler 30 faces the road surface, it receives radiant heat from the road surface. However, since the cooling member 31 is made of a synthetic resin having a lower thermal conductivity than metal, it has a larger thermal resistance compared to the case where it is made of metal and functions as a heat insulating member. Therefore, even if the outer surface (lower surface) of the cooling member 31 receives radiant heat, the heat is difficult to be transmitted to the inner surface (upper surface) of the cooling member 31. Since the heat transfer from the cooling member 31 to the refrigerant is suppressed, the temperature rise of the refrigerant due to the heat transfer from the cooling member 31 is also suppressed. The bottom wall portion 22 constituting the heat transfer path between the battery cell 12 and the refrigerant has a small thermal resistance. Therefore, the lower tray 20 of the first embodiment is excellent in the cooling efficiency by the refrigerant.

[0027] The lower tray 20 for the battery case of the first embodiment includes a tray body 21 and a cooling member 31. The tray body 21 is formed of a single member in a form in which a peripheral wall portion 23 is raised from the outer peripheral edge of a bottom wall portion 22. A battery cell 12 is arranged on the upper surface of the bottom wall portion 22. The cooling member 31 is attached to the lower surface of the bottom wall portion 22. The cooling member 31 forms a refrigerant flow path 42 for flowing a refrigerant between the bottom wall portion 22. The cooling member 31 is a member made of a synthetic resin having a lower thermal conductivity than the bottom wall portion 22.

[0028] When the lower tray 20 is arranged on the lower surface of the vehicle body, the lower surface of the cooling member 31 is exposed so as to face the road surface. The thermal resistance between the lower surface (outer surface) of the cooling member 31 and the upper surface (inner surface facing the refrigerant flow path 42) of the cooling member 31 is larger than the thermal resistance between the lower surface and the upper surface of the bottom wall portion 22. Therefore, the cooling member 31 can suppress the temperature rise of the refrigerant caused by the radiant heat from the road surface, and the bottom wall portion 22 can efficiently transfer the heat of the battery cell 12 to the refrigerant. Even if the cooling member 31 is provided so as to be exposed to face the road surface, a decrease in cooling efficiency can be suppressed. Since the cooling member 31 is made of synthetic resin, weight reduction can be achieved as compared with a metal cooling member 31.

[0029] The space between the lower surface of the bottom wall portion 22 and a flange-shaped joint portion 34 along the outer peripheral edge of the cooling member 31 is joined in an airtight or liquidtight manner by a liquid sealant 40. According to this configuration, it is not necessary to apply pressure in the process of joining the cooling member 31 and the bottom wall portion 22. Even if the surface roughness of the lower surface of the bottom wall portion 22 or the upper surface of the cooling member 31 is large, the liquid sealant 40 absorbs the surface roughness, so that sealing can be surely performed.

[0030] The cooling member 31 is a plate-shaped member made of synthetic resin, and therefore has low rigidity, and there is concern that it may deform. A plurality of protrusions 36 that protrude upward like ribs are formed on the flow straightening portion 35 of the cooling member 31, and the rigidity of the flow straightening portion 35 is increased by the protrusions 36. Moreover, the lower surface of the bottom wall portion 22 and the upper surfaces of the plurality of protrusions 36 are joined by a liquid sealing material 40. This makes it possible to prevent the cooling member 31 from deforming.

[0031] The multiple protrusions 36 are elongated and arranged in parallel. The refrigerant flow path 42 is divided into multiple parallel flow paths 43 by the multiple protrusions 36. With this configuration, the refrigerant can flow in a laminar manner in the refrigerant flow path 42 by utilizing the protrusions 36.

[0032] The bottom wall portion 22 is made of a material having higher rigidity than the cooling member 31. Because the bottom wall portion 22 is less likely to deform than the cooling member 31, even if the cooling member 31 is in the form of a thin plate, separation between the bottom wall portion 22 and the cooling member 31 due to deformation of the bottom wall portion 22 can be prevented.

[0033] A heat transfer layer 25 that is in direct contact with the battery cell 12 is formed on the upper surface of the bottom wall portion 22. According to this configuration, the thermal resistance between the battery cell 12 and the bottom wall portion 22 is smaller than when an air layer is interposed between the battery cell 12 and the bottom wall portion 22.

[0034] <Other Examples> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments are also included within the technical scope of the present invention. The bottom wall and the cooling member may be joined by thermal welding. · The bottom wall portion may also be made of synthetic resin, similar to the cooling member. In this case, it is preferable to use a material for the synthetic resin of the bottom wall portion that has different physical properties and composition from that of the cooling member. Specifically, a material with higher rigidity than the cooling member can be used as the synthetic resin material of the bottom wall portion, or a material with higher heat conductivity than the cooling member can be used as the synthetic resin material of the bottom wall portion. Also, a synthetic resin without fillers can be used as the material of the cooling member, and a synthetic resin containing fillers can be used as the material of the bottom wall portion. · The cooling member is not limited to a plate shape and may be a block shape. · The protrusion may have a shape that does not form a plurality of parallel flow paths (for example, hemispherical or frustum-shaped). · The refrigerant flow path may be constituted by a single space that is not partitioned into a plurality of parallel flow paths.

Explanation of Reference Numerals

[0035] 10… Battery case 12… Battery cell 20… Lower tray 21… Tray body 22… Bottom wall portion 23… Peripheral wall portion 25… Heat transfer layer 31… Cooling member 34… Flange-shaped joint portion 36… Protrusion 40… Liquid sealant 42… Refrigerant flow path 43… Parallel flow path

Claims

1. A battery case lower tray comprising a single member in a form where a peripheral wall portion is raised from an outer peripheral edge of a bottom wall portion, and a battery cell is disposed on an upper surface of the bottom wall portion; a cooling member attached to a lower surface of the bottom wall portion and configured to form a refrigerant flow path for flowing a refrigerant between the bottom wall portion and the cooling member. The cooling member is a lower tray for a battery case made of a synthetic resin member having a lower thermal conductivity than the bottom wall portion.

2. The lower tray for a battery case according to claim 1, wherein a space between a lower surface of the bottom wall portion and a flange-shaped joint portion along an outer peripheral edge of the cooling member is joined in an airtight or liquidtight manner by a liquid sealant.

3. A plurality of protrusions protruding upward are formed on the cooling member; The lower tray for a battery case according to claim 2, wherein a lower surface of the bottom wall portion and upper surfaces of the plurality of protrusions are joined by the liquid sealant.

4. The plurality of protrusions are elongated and extend in parallel; The lower tray for a battery case according to claim 3, wherein the refrigerant flow path is partitioned into a plurality of parallel flow paths by the plurality of protrusions.

5. The lower tray for a battery case according to any one of claims 2 to 4, wherein the bottom wall portion is made of a material having higher rigidity than the cooling member.

6. The lower tray for a battery case according to claim 1 or claim 2, wherein a heat transfer layer that directly contacts the battery cell is formed on an upper surface of the bottom wall portion.

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