Battery pack structure

Abstract

The present invention provides a battery pack structure that enables uniform temperature distribution of battery cells while minimizing cost reduction, power efficiency degradation, and increased size. [Solution] The structure of a battery pack 11 is provided in which a plurality of battery cells 10 are arranged and housed in a battery case 20, and comprises a cooling member 22 provided in the battery case 20 and a heat transfer member 24 interposed between the cooling surface 23 of the cooling member 22 and the battery cells 10, wherein the distribution of the heat transfer area A between the battery cells 10 and the cooling member 22 is adjusted based on the heat transfer coefficient λ of the cooling surface 23 and the thickness of the heat transfer member 24, and the heat transfer area A is larger at both ends of the battery cell 10 than in the center of the arrangement of battery cells 10, and / or is smaller at the ends of the arrangement of battery cells 10 than in the center of the arrangement of battery cells 10.

Description

Technical Field

[0001] The present invention relates to a battery pack structure.

Background Art

[0002] Patent Document 1 discloses a battery pack including a plurality of Peltier elements, a plurality of control circuits for controlling the plurality of Peltier elements respectively, a plurality of battery cells each connected to at least one end of the plurality of Peltier elements, and a heat transfer member connected to the other ends of the plurality of Peltier elements. In this battery pack, the heat transfer directions of the plurality of Peltier elements are controlled by driving the plurality of control circuits individually, and heat transfer between the battery cells connected to the Peltier elements is performed through the heat transfer member to equalize the temperatures of the plurality of battery cells.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the above battery pack, a Peltier element and a control circuit are required for each battery cell, and moreover, a heat exchange mechanism on the exhaust heat side of the Peltier element is required, which leads to an increase in cost and size. Also, power is required to drive the Peltier element, resulting in an increase in electricity costs. Thus, in the above battery pack, having a heat exchanger using a Peltier element for each battery cell is disadvantageous in terms of cost, power efficiency, and size.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a battery pack structure capable of equalizing the temperatures of battery cells while suppressing an increase in cost, a decrease in power efficiency, and an increase in size.

Means for Solving the Problems

[0006] To achieve the above objective, the battery pack structure of the present invention is: A battery pack structure in which multiple battery cells are arranged and housed in a battery case, A cooling member provided in the aforementioned battery case, A heat transfer member interposed between the cooling surface of the cooling member and the battery cell, Equipped with, Based on the heat transfer coefficient of the cooling surface and the thickness of the heat transfer member, the distribution of the heat transfer area between the battery cell and the cooling member is adjusted. The heat transfer area is larger at both ends of the battery cell than at the center, and / or smaller at the ends of the battery cell array than at the center of the array.

[0007] In this battery pack structure, the heat transfer area between the battery cell and the cooling material is larger at both ends of the battery cell than in the center, and / or smaller at the ends of the battery cell array than in the center. This allows for reduced and equalization of temperature variations between individual battery cells and / or arrayed battery cells housed in the battery case, while minimizing cost, power efficiency degradation, and size increases. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a battery pack structure that can equalize the temperature of battery cells while suppressing cost, power efficiency reduction, and size increase. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a perspective view of a part of the battery pack illustrating the battery pack structure according to this embodiment. [Figure 2] Figure 2 is a schematic diagram illustrating the temperature distribution of the cooling material in the battery loading section of the battery case. [Figure 3] Figure 3 is a schematic diagram illustrating the temperature distribution of battery cells placed in the battery mounting section of a battery case. [Figure 4]Figure 4 shows the distribution of heat transfer area between the battery cell and the cooling material. [Figure 5] Figure 5 is a graph showing the relationship between heat transfer area, heat transfer coefficient, and temperature in a single battery cell. [Figure 6] Figure 6 is a graph showing the relationship between heat transfer area, heat transfer coefficient, and temperature in an array of battery cells. [Figure 7] Figure 7 is a graph showing the results of temperature evaluation for a battery pack containing multiple battery cells. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the drawings. Figure 1 is a perspective view of a part of a battery pack 11 illustrating the battery pack structure according to this embodiment. Figure 2 is a schematic diagram illustrating the temperature distribution of the cooling member 22 in the battery loading section 21 of the battery case 20. Figure 3 is a schematic diagram illustrating the temperature distribution of the battery cells 10 placed on the battery loading section 21 of the battery case 20. In Figures 2 and 3, the temperature distribution is represented by the intensity of the color, with darker colors indicating lower temperatures.

[0011] As shown in Figure 1, the battery pack structure according to this embodiment is a battery pack 11 comprising a plurality of battery cells 10. The battery cells 10 are housed in an arranged state within the battery case 20.

[0012] The battery cells 10 are formed in a rectangular parallelepiped shape and are arranged in one direction (the Y direction in Figure 1) with their widths aligned in the same direction (the X direction in Figure 1).

[0013] The battery case 20 has multiple rows of battery mounting sections 21, and multiple battery cells 10 are arranged on top of these battery mounting sections 21.

[0014] The battery case 20 includes a cooling member 22. The cooling member 22 is provided in each battery mounting portion 21, and its upper surface is a cooling surface 23. The battery cells 10 are placed on the cooling surface 23 of the cooling member 22 via a heat transfer member 24.

[0015] The cooling member 22 has a flow path (not shown) inside, and a cooling medium such as a coolant is flowed through this flow path. For example, the flow path is provided at the center in the width direction of each battery mounting portion 21 in the cooling member 22. Then, by flowing the cooling medium through this flow path, the heat of the battery cells 10 is transmitted to the cooling member 22 via the heat transfer member 24, and the battery cells 10 are cooled.

[0016] [[ID=(8)]]By the way, in the assembled battery 11 provided with the cooling member 22, since the temperature of the battery cells 10 is directly related to the power efficiency, it is desirable to reduce the temperature variation in a single battery cell 10 and the temperature variation between the arranged battery cells 10.

[0017] However, as shown in FIG. 2, in the battery mounting portion 21 of the cooling member 22, since the cooling medium flowing through the flow path at the center in the width direction X cools the central side more than both ends in the width direction X, temperature variation occurs in a single battery cell 10. Further, as shown in FIG. 3, the battery cells 10 arranged in the battery mounting portion 21 have a higher temperature on the central side in the arrangement direction Y and a lower temperature toward both ends, so temperature variation also occurs between the battery cells 10.

[0018] Therefore, in the present embodiment, based on the heat transfer coefficient of the cooling surface 23 of the cooling member 22 and the thickness of the heat transfer member 24 interposed between the cooling surface 23 and the battery cells 10, the distribution of the heat transfer area between the battery cells 10 and the cooling member 22 is adjusted to suppress and equalize the temperature variation in a single battery cell 10 and the temperature variation between the arranged battery cells 10.

[0019] Specifically, based on the following formula (1), the distribution of the heat transfer area A is adjusted so that the product of the heat transfer coefficient λ and the heat transfer area A is constant.

[0020] Q = A·λ·ΔT / L …(1) however, Q: Heat flow [W] A: Heat transfer area [m²] 2 ] λ: Heat transfer coefficient [W / mK] ΔT: temperature difference [K] L: Thickness of the heat transfer component [m]

[0021] Furthermore, if the thickness of the heat transfer member 24 between the battery cell 10 and the cooling member 22 varies during the assembly process, the variation in the thickness of the heat transfer member 24 is determined in advance, and the distribution of the heat transfer area A between the battery cell 10 and the cooling member 22 is adjusted accordingly.

[0022] The following describes a specific example of temperature equalization of the battery cell 10 in this embodiment. Figure 4 shows the distribution of the heat transfer area A between the battery cell 10 and the cooling element 22. Figure 5 is a graph showing the relationship between the heat transfer area A, heat transfer coefficient λ, and temperature T in a single battery cell 10. Figure 6 is a graph showing the relationship between the heat transfer area A, heat transfer coefficient λ, and temperature T in an array of battery cells 10. In Figure 4, the heat transfer area A is shown by a dashed line, and a larger period of the dashed line indicates a larger heat transfer area A.

[0023] (Temperature equalization in individual battery cells) As shown in Figure 4, in the battery pack structure according to this embodiment, in the battery cell 10 located in the center of the array (the battery cell 10C on the left in Figure 4), the heat transfer area A is larger at both ends PE compared to the central PC in the width direction. Similarly, in the battery cell 10 located at the end of the array (the battery cell 10E on the right in Figure 4), the heat transfer area A is also larger at both ends PE compared to the central PC in the width direction.

[0024] In other words, as shown in Figure 5, in the width direction X of the battery cell 10, the heat transfer coefficient λ of the cooling member 22 is smaller on the PE sides at both ends compared to the central PC, making cooling more difficult. Therefore, in this embodiment, the heat transfer area A with the cooling member 22 on the PE sides at both ends, which are difficult to cool, is made larger than that on the central PC, thereby suppressing and equalizing the temperature T of each battery cell 10.

[0025] (Equalizing the temperature of battery cells) As shown in Figure 4, in the battery pack structure according to this embodiment, the heat transfer area A of the battery cell 10 located at the end of the array (the battery cell 10E on the right in Figure 4) is smaller than that of the battery cell 10 located in the center of the array (the battery cell 10C on the left in Figure 4).

[0026] In other words, as shown in Figure 6, in the arrangement direction Y of the arranged battery cells 10, the heat transfer coefficient λ of the cooling member 22 is smaller towards the center of the arrangement compared to the ends, making cooling more difficult. Therefore, in this embodiment, the heat transfer area A of the cooling member 22 in the center of the arrangement, where cooling is more difficult, is made larger than at the ends of the arrangement, thereby suppressing and equalizing the temperature T of the arranged battery cells 10.

[0027] Thus, according to the battery pack structure of this embodiment, the heat transfer area A between the battery cell 10 and the cooling member 22 is larger at both ends compared to the center of the battery cell 10, and further, the area at the ends of the arrangement of battery cells 10 is smaller than the area at the center of the arrangement of battery cells 10. As a result, it is possible to suppress and equalize temperature variations between individual battery cells 10 housed in the battery case 20 and between arranged battery cells 10, while suppressing cost, power efficiency reduction, and size increase.

[0028] In the above embodiment, the heat transfer area A between the battery cell 10 and the cooling member 22 is made larger at both ends relative to the center of the battery cell 10, and smaller at the ends of the arrangement of battery cells 10 than at the center of the arrangement. However, the heat transfer area A between the battery cell 10 and the cooling member 22 may be made larger at both ends relative to the center of the battery cell 10, or it may be made smaller at the ends of the arrangement of battery cells 10 than at the center of the arrangement.

[0029] (Examples) Twenty-four heaters H1 to H24, each mimicking a battery cell 10, were arranged on a cooling element 22, and the temperature T in the battery cells 10 of the battery pack 11 was evaluated.

[0030] (1) Subject to evaluation The evaluation was performed using two methods: one in which the distribution of heat transfer area A between heaters H1-H24 and cooling element 22 was adjusted, and another in which the distribution of heat transfer area A between heaters H1-H24 and cooling element 22 was kept constant. In the example, the heat transfer area A of heaters H1-H24 at the ends of the array was made smaller than that of heaters H1-H24 in the center of the array.

[0031] (2) Evaluation results Figure 7 shows the evaluation results, displaying the temperatures of selected heaters H1, H3, H10, H16, H18, H22, and H24 from among heaters H1 to H24. In the example, the maximum temperature difference from the average temperature was 4.2°C for all 24 heaters H1 to H24, confirming that the temperature variation was reduced. In the comparative example, the maximum temperature difference from the average temperature for all 24 heaters H1 to H24 was 10.3°C.

[0032] From this, it was confirmed that in the comparative example where the distribution of the heat transfer area A between the battery cell 10 and the cooling member 22 was kept constant, the temperature of the heater at the ends became lower, and the temperature difference between the center and the ends of the arrangement became larger. In contrast, in the embodiment, it was found that by adjusting the distribution of the heat transfer area A between the heater and the cooling member 22, the temperature variation of the heater, which mimics the battery cell 10, could be equalized. [Explanation of symbols]

[0033] 10 battery cells 11 battery packs 20 Battery Cases 22 Cooling components 23 Cooling surface 24 Heat transfer components A Heat transfer area λ Heat transfer coefficient

Claims

[Claim 1] A battery pack structure in which multiple battery cells are arranged and housed in a battery case, A cooling member provided in the aforementioned battery case, A heat transfer member interposed between the cooling surface of the cooling member and the battery cell, Equipped with, Based on the heat transfer coefficient of the cooling surface and the thickness of the heat transfer member, the distribution of the heat transfer area between the battery cell and the cooling member is adjusted. The heat transfer area is larger at both ends of the battery cell than at the center, and / or smaller at the ends of the battery cell array than at the center of the array of battery cells. Assembled battery structure.

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