Method for manufacturing a battery pack

Abstract

To reduce the used amount of a heat transfer material interposed between a battery and a heat sink.SOLUTION: Batteries 12 are arrayed on a bottom plate (heat sink) 18 of a case 16 that accommodates the batteries 12, via a heat transfer material 20. There is formed a ventilation path where cooling air flows in a direction of arrow Y, on the side of the bottom plate 18 opposite to the side on which the batteries 12 are arrayed. The contact area between the heat transfer material 20 and each battery 12 is small in a battery 12 of the uppermost stream in a Y direction of the cooling air, gradually increases toward downstream, then gradually decreases, and is larger than that of a battery of the uppermost stream in a battery 12 of the lowermost stream.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery pack containing a plurality of batteries and a method for manufacturing the battery pack. [Background technology]

[0002] Battery packs, which are configured by housing multiple batteries in a case, are known as power sources for vehicle drive motors in electric vehicles and hybrid vehicles. Battery packs may have a cooler for cooling the housed batteries. Patent Document 1 listed below shows a cooler (40) that contacts multiple batteries (21) via a viscous layer (50) and has a cooling fluid flowing inside. Heat transfer is improved by filling the space between the batteries (21) and the cooler (40) with the viscous layer (50). Note that the reference characters in parentheses are the reference characters used in the patent document listed below, and are not related to the reference characters used in the description of the embodiments of the present application. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-67737 A Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for reducing the amount of filler material used between the battery and the cooler. An object of the present invention is to reduce the amount of filler material used. [Means for solving the problem]

[0005] The battery pack according to the present invention includes a heat sink, a plurality of batteries arranged on the heat sink along a surface of the heat sink, a heat transfer material interposed between the plurality of batteries and the heat sink, and a cooling flow path formed on the side of the heat sink opposite to the side on which the plurality of batteries are arranged, through which a cooling fluid for cooling the heat sink flows along the arrangement direction of the plurality of batteries. The contact area between the heat transfer material and each battery is small in the most upstream battery in the flow direction of the cooling fluid, gradually increases toward the downstream, and then gradually decreases, until the contact area of ​​the most downstream battery is larger than that of the most upstream battery.

[0006] The battery pack may also include a case that houses a plurality of batteries, and the bottom plate of the case may serve as a heat sink.

[0007] A method for manufacturing a battery pack according to the present invention is a method for manufacturing a battery pack including a heat sink plate on which a plurality of batteries are mounted, and a cooling flow path formed on the side of the heat sink opposite to the side on which the plurality of batteries are mounted, through which a cooling fluid flows to cool the heat sink, the method including the steps of providing a heat transfer material on the heat sink plate, and mounting the plurality of batteries on the heat sink plate via the heat transfer material in an array along the direction in which the cooling fluid flows. In the step of providing the heat transfer material, the heat transfer material is provided such that, when the plurality of batteries are mounted, the contact area between the heat transfer material and each battery is small in the most upstream battery in the direction in which the cooling fluid flows, gradually increases toward the downstream, and then gradually decreases, so that the contact area in the most downstream battery is larger than that of the most upstream battery.

[0008] The method for manufacturing a battery pack may further include the steps of arranging the multiple batteries in the same arrangement as when they were placed on the heat sink to form a battery stack before placing them on the heat sink, and measuring the temperature of the battery stack by passing current through the multiple batteries; and determining an amount of heat transfer material to be provided for each battery based on the measured temperature of the battery stack, which is an increase or decrease from a predetermined standard amount of heat transfer material to be provided, and the step of providing the heat transfer material includes providing the heat transfer material in the determined amount. Effect of the Invention

[0009] The upstream side, where the cooling fluid temperature is low, and the downstream side, where the exposed surface area of ​​the batteries is large, have good cooling properties, and by reducing the heat transfer area for the batteries located here, the amount of heat transfer material can be reduced. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic structure of a battery pack according to the present invention; [Diagram 2] FIG. 2 is a diagram showing a schematic structure of a battery pack according to the present invention, as viewed from above in FIG. 1 with the battery and part of the case removed. [Diagram 3] FIG. 13 is a diagram showing the amount of heat transfer material provided for each battery. [Figure 4] FIG. 4 is a diagram showing the temperature of each battery when the battery pack is in use. [Diagram 5] 3 is a flowchart showing a manufacturing method of a battery pack according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 and FIG. 2 are schematic diagrams showing the configuration of a battery pack 10. The battery pack 10 includes a battery stack 14 formed by arranging a plurality of batteries 12 in a row so as to be in close contact with each other, and a case 16 for accommodating the battery stack 14. FIG. 2 shows the state seen from above in FIG. 1 with the battery stack 14 removed. The battery stack 14 is composed of 13 batteries 12, but the number of batteries is not limited to this. The batteries 12 are placed on a bottom plate 18 that defines the bottom surface of the case 16 via a heat transfer material 20. The heat transfer material 20 may be a fluid such as clay, that is, a fluid that does not normally deform but deforms when a force of a certain degree or more is applied. By deforming, the heat transfer material 20 adheres to both the batteries 12 and the bottom plate 18, improving the heat transfer between the batteries 12 and the bottom plate 18. The amount of the heat transfer material 20 is determined for each battery 12.

[0012] A cooling flow path 22 through which a cooling fluid flows is formed on the bottom plate 18 of the case 16 on the side opposite to the side on which the batteries 12 are arranged. In this battery pack 10, the cooling fluid is air, and the cooling flow path 22 is a ventilation path through which an airflow (cooling air) for cooling generated by a ventilation fan 24 passes (hereinafter, the cooling flow path will be referred to as the ventilation path). The direction of the airflow flowing through the ventilation path 22 is indicated by an arrow Y in Figs. 1 and 2, and the airflow flows from left to right in Figs. 1 and 2 along the arrangement direction of the batteries 12. Heat generated by the batteries 12 is dissipated from the bottom plate 18 of the case 16 via the heat transfer material 20 to the cooling air flowing through the ventilation path 22. Thus, the bottom plate 18 functions as a heat sink that dissipates heat from the batteries 12.

[0013] The batteries 12 arranged at the ends of the battery stack 14 have a larger surface area in contact with the surrounding air than the batteries 12 arranged in the center, and the heat generated in the batteries 12 is more likely to escape. Therefore, the temperature rise of the batteries 12 arranged at the ends of the battery stack 14 is more suppressed than that of the batteries 12 arranged in the center.

[0014] As the cooling air flows through the ventilation passage 22, its temperature increases due to heat from the bottom plate 18. Therefore, the temperature difference between the batteries 12 and the cooling air is greater upstream than downstream, and the cooling capacity of the cooling air is greater. Therefore, the temperature rise of the batteries 12 on the upstream side is suppressed compared to the downstream side.

[0015] The batteries 12 at both ends of the battery stack 14 are favorable for heat dissipation and have a lower temperature. Also, on the upstream side where the temperature of the cooling air is lower, the batteries 12 are cooled more. Therefore, at both ends of the battery stack 14, the temperature rise of the upstream batteries 12 is suppressed. For the batteries 12 with a lower temperature due to the suppressed temperature rise, the amount of the heat transfer material 20 provided on the bottom plate 18 is determined so that the contact area between the corresponding heat transfer material 20 and the batteries 12 and the bottom plate 18 is small, and for the batteries 12 with a higher temperature, the contact area is large. Specifically, with respect to the direction of the flow of the cooling air, the contact area of ​​the heat transfer material 20 corresponding to the upstream battery 12 is small, gradually increases toward the downstream, becomes maximum at the center slightly downstream, and then gradually decreases toward the downstream. The contact area of ​​the heat transfer material 20 at the most downstream is larger than that at the most upstream.

[0016] FIG. 3 is a diagram showing the amount of heat transfer material 20 provided on the bottom plate 18 corresponding to each battery 12. The contact area between the heat transfer material 20, the battery 12, and the bottom plate 18 increases or decreases according to the increase or decrease in the amount of the heat transfer material 20. In FIG. 3, the horizontal axis shows the position of each battery 12 arranged as a battery stack 14, with the left side being the upstream side of the cooling air and the right side being the downstream side. In FIG. 3, the dashed line C shows a case where the heat transfer material 20 is provided uniformly to each battery 12, and the solid line S shows a case where the amount of the heat transfer material 20 provided for each battery 12 is changed as described above. The amount of the heat transfer material 20 provided shown by the dashed line C is referred to as the uniform amount C, and the amount provided shown by the solid line S is referred to as the standard amount S. In this example, the standard amount S is set so that the maximum amount of the amount provided for one battery 12 is equal to the uniform amount C. As shown in FIG. 2, the difference in the amount provided for one battery 12 corresponds to the length of the heat transfer material 20 in the longitudinal direction of each battery 12.

[0017] FIG. 4 shows the temperature of each battery 12 when the battery pack 10 is used. The dashed line Tc shows the temperature distribution when the heat transfer material 20 is provided at a uniform amount C, and the solid line Ts shows the temperature distribution when the heat transfer material 20 is provided at a standard amount S. The thin line Tu shows the upper limit of the operating temperature range of the battery 12. If the amount of the heat transfer material 20 provided is changed from the uniform amount C to the standard amount S, the amount of the heat transfer material 20 can be reduced by an amount corresponding to the area between the dashed line C and the solid line S in FIG. 3. However, even in this case, the battery temperature does not exceed the upper limit Tu of the operating temperature range of the battery. It can also be seen that the temperature of each battery 12 is more uniform in the case of the standard amount S provided than in the case of the uniform amount C provided.

[0018] The amount of heat generated by the batteries 12 may vary depending on the production lot. For a battery stack 14 made of batteries 12 from a production lot that generates a small amount of heat, there is room to reduce the amount of heat transfer material 20. Also, when the amount of heat generated is large, the amount of heat transfer material 20 may be increased to suppress the temperature of the batteries 12.

[0019] FIG. 5 is a flow chart showing a part of the manufacturing process of the battery pack 10. Prior to manufacturing the battery pack 10, the standard provided amount S, the increased provided amount I, and the decreased provided amount D of the heat transfer material 20 are determined as shown in FIG. 3. The standard provided amount S is an amount at which the battery temperature during use falls within a temperature range with a predetermined margin from the upper limit value of the battery use temperature range when the battery stack 14 is formed from the batteries 12 with an average heat generation amount. The increased provided amount I is an amount increased from the standard provided amount S, and the increase amount is common to each battery 12. The decreased provided amount D is an amount decreased from the standard provided amount S, and the decrease amount is common to each battery 12. In addition, the temperature of the battery stack 14 formed from the batteries 12 with an average heat generation amount is associated with the standard provided amount S when each battery 12 is energized individually without being housed in the case 16. A temperature in a predetermined range including this temperature is referred to as a standard temperature. If the temperature measured of the battery stack 14 alone is within the standard temperature range, the heat transfer material 20 is provided in a standard amount S, and if it exceeds the standard temperature range, an increased amount I is provided, and if it is below the standard temperature range, a decreased amount D is provided.

[0020] First, a plurality of batteries 12 are closely arranged to form a battery stack 14 (S100). Before the battery stack 14 is housed in the case 16, current is applied to each battery 12, and the temperature is measured after a predetermined time has elapsed (S102). The temperature of the battery stack 14 may be determined by obtaining the temperature distribution of the entire surface of the battery stack 14 that faces the bottom plate 18 of the case 16 when the battery stack 14 is housed in the case 16, that is, the bottom surface of the battery stack 14, using thermography, and calculating the average temperature of the bottom surface. Alternatively, the temperature may be measured at one or more representative points.

[0021] The measured temperature of the battery stack 14 is compared with a standard temperature range (S104). If it is within the standard temperature range, the amount of heat transfer material 20 to be provided is set to a standard provided amount S (S106). If it is outside the standard temperature range, the amount of heat transfer material 20 to be provided is set to an increased increased provided amount I (S108). If it is below the standard temperature range, the amount of heat transfer material 20 to be provided is set to a reduced reduced provided amount D (S110).

[0022] Then, a determined amount of heat transfer material 20 is provided on the bottom surface of the case 16 (S112). The heat transfer material 20 is provided for each battery 12 in a direction perpendicular to the battery arrangement direction, and is preferably disposed in the center of each battery 12 in this perpendicular direction. The battery stack 14 is then placed on the heat transfer material 20. At this time, the battery stack 14 is pressed toward the bottom plate 18 of the case 16. This pressing force causes the heat transfer material 20 to spread and to come into close contact with each battery 12 and the bottom plate 18. The amount of heat transfer material 20 provided is determined so that the contact area between the heat transfer material 20, the battery 12, and the bottom plate 18 at this time is a predetermined area.

[0023] For battery stacks 14 with higher temperatures, the amount of heat transfer material 20, i.e., the contact area between the batteries 12 and the bottom plate 18, is increased to allow more heat generated in the batteries 12 to be transferred to the bottom plate 18, accelerating the cooling of the batteries 12. For battery stacks 14 with lower temperatures, the amount of heat transfer material 20 can be further reduced.

[0024] The relationship between the temperature of the battery stack 14 and the amount provided may be updated as appropriate. For example, for a battery pack 10 provided with the standard amount S of heat transfer material 20, the battery temperature in an actual usage state is measured to confirm whether it is the expected temperature. If the temperature is higher than the expected temperature, the standard amount S is increased and updated, or the standard temperature for the battery stack 14 corresponding to the standard amount S is decreased and updated. [Explanation of symbols]

[0025] 10 battery pack, 12 battery, 14 battery stack, 16 case, 18 bottom plate (heat sink), 20 heat transfer material, 22 ventilation path (cooling flow path), 24 ventilation fan.

Claims

1. A method for manufacturing a battery pack including a heat sink plate on which a plurality of batteries are mounted, and a cooling flow path formed on an opposite side of the heat sink plate from the side on which the plurality of batteries are mounted, through which a cooling fluid flows along the heat sink plate to cool the heat sink, comprising: providing a heat transfer material on the heat sink; placing the plurality of batteries on the heat sink via the heat transfer material in an array along a direction in which the cooling fluid flows; Including, in the step of providing the heat transfer material, the heat transfer material is provided such that, when the plurality of batteries are placed, a contact area between the heat transfer material and each of the batteries is small in the most upstream battery in the flow direction of the cooling fluid, gradually increases toward the downstream, and then gradually decreases, so that the contact area in the most downstream battery is larger than that in the most upstream battery; Furthermore, the method for manufacturing the battery pack includes: forming a battery stack by arranging the plurality of batteries in the same arrangement as when the batteries were placed on the heat sink before placing the batteries on the heat sink, and measuring the temperature of the battery stack by passing current through the plurality of batteries; determining a supply amount of the heat transfer material for each of the batteries, the supply amount being increased or decreased based on the measured temperature of the battery stack; Including, The step of providing the heat transfer material includes providing the heat transfer material at the determined amount. A method for manufacturing a battery pack.

2. 2. The method for manufacturing a battery pack according to claim 1, wherein the battery pack includes a case that houses the plurality of batteries, and a bottom plate of the case is the heat sink.

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