Battery pack

Abstract

To provide a more effective technology for uniformly cooling multiple battery cells. [Solution] The battery pack comprises a battery stack containing multiple battery cells and a chamber for distributing a coolant to the multiple battery cells. The chamber is equipped with a partition plate having multiple vents. The partition plate separates the chamber into a side with an inlet and a side with a battery stack. The shape of the partition plate is convex toward the inlet of the chamber.

Description

Technical Field

[0001] The present disclosure relates to a battery pack having a mechanism for uniformly cooling a plurality of battery cells.

Background Art

[0002] Patent Document 1 discloses a battery pack having a cooling structure capable of uniformly cooling an entire battery module. The battery pack includes a mechanism for equalizing the flow rate of a refrigerant. By equalizing the flow rate of the refrigerant, the entire battery module is uniformly cooled.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the cooling of a plurality of battery cells included in a battery pack is uneven, deterioration of the battery cells due to heat generation, overcharging, etc. is likely to occur.

[0005] One object of the present disclosure is to provide a more effective technique for uniformly cooling a plurality of battery cells.

Means for Solving the Problems

[0006] A first aspect relates to a battery pack mounted on a vehicle. The battery pack includes a battery stack including a plurality of battery cells, a chamber for distributing a refrigerant to the plurality of battery cells, and is provided with. The chamber includes a partition plate having a plurality of ventilation holes. The partition plate separates the chamber into a side of the inlet of the chamber and a side of the battery stack. The partition plate is convex towards the chamber inlet. [Effects of the Invention]

[0007] As the refrigerant passes through the vents in the partition plate, it loses pressure and its flow velocity decreases. The decrease in flow velocity is more pronounced where the original flow velocity was high. This means that the amount of refrigerant distributed to each battery cell becomes more uniform. As a result, the battery cells are cooled uniformly. Furthermore, by making the shape of the partition plate convex toward the chamber inlet, the refrigerant flows more smoothly to the surrounding areas, resulting in a more pronounced effect of uniformizing the flow velocity. In other words, the effect of uniformly cooling multiple battery cells is more pronounced. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of the battery pack installed in the vehicle. [Figure 2] This is a schematic diagram showing an example of a battery pack cooling mechanism. [Figure 3] This is a schematic diagram showing another example of a battery pack cooling mechanism. [Figure 4] This is a schematic diagram showing an example of a ventilation opening configuration. [Figure 5] This is a schematic diagram showing further examples of ventilation configurations. [Figure 6] This is a schematic diagram showing the relationship between the position of the chamber inlet and the shape of the partition plate. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described with reference to the attached drawings.

[0010] 1. Battery pack for vehicles Figure 1 is a schematic diagram of a battery pack 10 mounted on a vehicle 1. The battery pack 10 is used as a power source for electric vehicles such as BEVs, PEVs, and HEVs. In the drawing, the X direction indicates the direction in which the vehicle 1 moves forward. The Y direction indicates the left direction when viewing the vehicle 1 from above. The Z direction indicates the upward direction of the vehicle 1. These directions are set for the convenience of explanation and do not necessarily limit the embodiment. For example, in Figure 1, the battery cells 30, which will be described later, are stacked along the Y direction. However, the actual loading direction is not limited to the Y direction and may be, for example, the X direction.

[0011] The battery pack 10 comprises one or more battery stacks 20 (hereinafter simply referred to as battery stacks 20). Each battery stack 20 is composed of multiple battery cells 30 (also called single cells) stacked on top of each other. The battery cells 30 are rechargeable secondary batteries, such as lithium-ion secondary batteries. The battery pack 10 also typically includes a case (a so-called battery case) that covers the battery stacks 20. The battery case (not shown in the figure) is made of aluminum alloy or steel and serves to protect the battery cells 30 from external loads. The vehicle 1 is driven by the rotation of a motor powered by electricity stored in the battery pack 10 (more specifically, the battery cells 30).

[0012] 2. Cooling the battery The battery cell 30 generates heat when it is charged or discharged. If this heat is not properly dissipated, the temperature of the battery cell 30 will rise. When the battery cell 30 is charged or discharged at high temperatures, its degradation is accelerated. Specifically, the rise in temperature activates unwanted chemical reactions within the battery cell 30, which reduces the amount of energy that can be stored and lowers the charging efficiency.

[0013] To prevent the temperature of the battery cells 30 from rising, the battery pack 10 has a cooling mechanism. The cooling mechanism removes heat from the battery cells 30 by circulating a refrigerant to cool them. As a result, the temperature of the battery cells 30 is kept low. Air refrigerant or liquid refrigerant can be used as the refrigerant. To ensure that the refrigerant is supplied accurately to the battery cells 30, passages for the refrigerant are provided between each battery cell 30.

[0014] If there is a difference in the amount of refrigerant flowing between the battery cells 30, the degree of cooling of each battery cell 30 is different. As a result, variations occur in the temperatures of the battery cells 30. The variations in the temperatures of the battery cells 30 cause variations in the charging efficiency. That is, while a sufficiently cooled battery cell 30 has a high charging speed, a battery cell 30 that is not sufficiently cooled has a slow charging speed.

[0015] Consider the case of charging a battery stack 20 including battery cells 30 with different charging speeds. Fully charging a battery cell 30 with a slow charging speed means overcharging a battery cell 30 with a fast charging speed. The deterioration of the battery cell 30 is accelerated with overcharging. On the other hand, in order to prevent overcharging, if the battery cell 30 with a fast charging speed is not charged beyond the fully charged state, the battery cell 30 with a slow charging speed is used in a state where it does not reach full charge. That is, the storage capacity of the entire battery stack 20 is not efficiently used.

[0016] In order to keep the temperature of each battery cell 30 within the allowable temperature, it is necessary to enhance cooling. In order to cool the battery cell 30 with the highest temperature to the allowable temperature, measures such as increasing the rotation speed of the blower through which the refrigerant flows are required. However, high-speed rotation of the blower may cause noise and vibration, and there is a risk of impairing the comfort of the vehicle 1. Also, using sound-absorbing materials and vibration-absorbing materials as noise and vibration countermeasures leads to an increase in cost and weight. Further, when enhancing the cooling of the entire battery stack 20, it leads to overcooling the battery cells 30 that are already sufficiently cooled. This is not preferable from the perspective of energy efficiency.

[0017] Thus, differences in the temperatures of the battery cells 30 within the battery stack 20 cause various problems. Therefore, uniformly cooling each battery cell 30 is an essential aspect for the efficient utilization and long life of the battery pack 10. For that purpose, it is required to make the amount of refrigerant distributed to each battery cell 30 uniform.

[0018] 2-1. Partition plate One of the factors determining the amount of refrigerant distributed to each battery cell 30 is the pressure (static pressure) difference between the inlet and outlet of the passage between the battery cells 30. If the pressure distribution at the inlet of the inter-cell passage is not uniform, the cooling to each battery cell 30 will also be uneven. Therefore, by making the pressure distribution at the inlet of the inter-cell passage closer to uniform, the amount of refrigerant distributed to each battery cell 30 will also be made uniform. Here, since the flow velocity of the refrigerant corresponds to the pressure, making the pressure distribution of the refrigerant uniform corresponds to making the flow velocity of the refrigerant uniform.

[0019] Figure 2 is a schematic diagram showing an example of the cooling mechanism of the battery pack 10. To eliminate the uneven flow velocity distribution at the passage inlet, the battery pack 10 has a chamber 40 positioned to connect to the inter-cell passage inlet. The chamber 40 is a space provided for distributing refrigerant to each battery cell 30, and its shape is narrow at the chamber inlet 41 and wider on the side facing the battery stack 20. The refrigerant flows into the chamber 40 via a duct. The refrigerant flows towards the battery stack 20, spreading out within the chamber 40. In this process, the flow velocity of the refrigerant in the chamber 40 is high in front of the chamber inlet 41 and decreases as you move away from the front of the chamber inlet 41. In other words, the uneven flow velocity distribution cannot be eliminated by the chamber 40 alone.

[0020] To ensure a uniform flow velocity distribution at the inter-cell passage inlet, the chamber 40 is equipped with a partition plate 50. The partition plate 50 separates the chamber 40 into the chamber inlet 41 side and the battery stack 20 side. The partition plate 50 is equipped with a plurality of vents 51. The partition plate 50 is made of, for example, metal. Examples of the shapes of the multiple vents 51 include slit shapes, circular shapes, etc. For example, perforated metal (steel or aluminum plate with many holes) which is an industrial product, functions as a partition plate 50 equipped with vents 51.

[0021] The refrigerant flows through the vents 51 of the partition plate 50 to the battery cells 30. When passing through the vents 51, the proportion of refrigerant pressure loss is large in the high-velocity region, and the flow velocity drops significantly after passing through. On the other hand, in the low-velocity region, the proportion of refrigerant pressure loss is relatively small, and the flow velocity does not drop significantly after passing through. As a result, after passing through the vents 51, the refrigerant flow velocity (pressure) distribution becomes more uniform.

[0022] In the example shown in Figure 2, the partition plate 50 extends linearly from one wall surface of the chamber 40 to the other. To further enhance the effect of homogenizing the flow velocity distribution, it is effective to make the partition plate 50 the shape shown in Figure 3. In the example shown in Figure 3, the partition plate 50 is convex toward the chamber inlet 41. Alternatively, it can be said that the partition plate 50 is curved so as to bulge toward the chamber inlet 41. When the partition plate 50 has a curved shape as shown in Figure 3, the refrigerant flows more smoothly along the partition plate 50 toward the surrounding area (the wall side of the chamber 40) than when it has a linear shape as shown in Figure 2. Therefore, the flow velocity is homogenized more smoothly when the partition plate 50 has a curved shape than when it has a linear shape.

[0023] 2-2. Effects By installing a partition plate 50 equipped with vents 51 inside the chamber 40, the flow velocity distribution of the refrigerant flowing to the battery cells 30 becomes more uniform. This means that the amount of refrigerant distributed to each battery cell 30 becomes more uniform. As a result, the battery cells 30 are cooled uniformly. Furthermore, by making the shape of the partition plate 50 convex toward the chamber inlet 41, the refrigerant flows more smoothly to the surrounding area, resulting in a more pronounced effect of uniformizing the flow velocity.

[0024] 3. Example Configuration 3-1. Ventilation Insulation Configuration Figures 4 and 5 are schematic diagrams showing examples of the configuration of the vents 51. In Figure 4, the shape and distribution of the vents 51 are all the same. Alternatively, as shown in Figure 5, the shape of the vents 51 may differ from place to place. For example, the shape and distribution of the vents 51 may change depending on the distance from the chamber inlet 41 of the chamber 40. In this disclosure, the partition plate 50 has an i-th portion and an i+1-th portion which is further from the chamber inlet 41 than the i-th portion. The multiple vents 51 include an i-th vent included in the i-th portion and an i+1-th vent included in the i+1-th portion. In Figures 4 and 5, the first portion 50a is located in front of the chamber inlet 41. The second portions 50b are located on both sides of the first portion 50a. In this case, the second portions 50b on the left and right of the first portion 50a are assumed to be at equal distances from the chamber inlet 41. The chamber inlet 41 is located in the center in the width direction of the chamber 40.

[0025] In Figures 5(A) to (C), the shape and distribution of the vents 51 differ between the first section 50a and the second section 50b.

[0026] In Figure 5(A), the area of ​​the first vent 51a in the first section 50a is smaller than the area of ​​the second vent 51b in the second section 50b. This reduces the amount of refrigerant passing through the first section 50a, which has a higher flow velocity, and as a result contributes to uniform cooling of the battery cell 30. Generalizing the configuration in Figure 5(A), it can be expressed as the area of ​​the i-th vent being smaller than the area of ​​the (i+1)th vent.

[0027] In Figure 5(B), the first vent 51a in the first section 50a is more sparsely distributed than the second vent 51b in the second section 50b. This reduces the amount of coolant passing through the first section 50a, which has a higher flow velocity, and as a result contributes to uniform cooling of the battery cell 30. Generalizing the configuration in Figure 5(B), it can be said that the i-th vent is arranged to be more sparsely distributed than the i+1th vent.

[0028] In Figure 5 (C), the area of ​​the first vent 51a in the first section 50a is smaller than the area of ​​the second vent 51b in the second section 50b. Furthermore, the first vent 51a in the first section 50a is more sparsely distributed than the second vent 51b in the second section 50b. In other words, Figure 5 (C) can be considered a combination of (A) and (B). In this case as well, the amount of refrigerant passing through the first section 50a is reduced, contributing to the uniform cooling of the battery cell 30.

[0029] 3-2. Inlet location and partition plate shape Figure 6 is a schematic diagram showing the relationship between the position of the chamber inlet 41 and the shape of the partition plate 50. The position of the chamber inlet 41 does not need to be on the center line of the chamber 40. In Figure 6, the chamber inlet 41 is located to the right of the center of the chamber 40. Also, the shape of the partition plate 50 is convex (bulging on the right side) toward the chamber inlet 41. The partition plate 50 is divided into three parts, the first part 50a, the second part 50b, and the third part 50c, in order from the right side closest to the chamber inlet 41. The area of ​​the first vent 51a, the second vent 51b, and the third vent 51c corresponding to each part decreases as they get closer to the chamber inlet 41.

[0030] In the examples described so far, the vent 51 has an i-th vent corresponding to a discontinuous division, such as the i-th part of the partition plate 50. However, the configuration of the vent 51 may change continuously (gradually) regardless of the discontinuous division. That is, the vent 51 may be configured such that its area gradually decreases as it approaches the chamber inlet 41, or it may be configured such that the vents 51 are distributed more sparsely as they approach the chamber inlet 41. [Explanation of Symbols]

[0031] 1: Vehicle, 10: Battery pack, 20: Battery stack, 30: Battery cell, 40: Chamber, 41: Chamber inlet, 50: Partition plate, 51: Vent

Claims

1. A battery pack installed in a vehicle, A battery stack containing multiple battery cells, A chamber for distributing refrigerant to the plurality of battery cells Equipped with, The chamber is equipped with a partition plate having a plurality of ventilation holes, The partition plate separates the chamber into the side with the chamber's inlet and the side with the battery stack. The shape of the partition plate is convex toward the inlet of the chamber. Battery pack.

2. A battery pack according to claim 1, The partition plate comprises an i-th portion and an i+1-th portion that is further from the inlet of the chamber than the i-th portion. The plurality of vents include the i-th vent included in the i-th portion and the i+1-th vent included in the i+1-th portion. The area of ​​the i-th vent is smaller than the area of ​​the i+1-th vent. Battery pack.

3. A battery pack according to claim 1, The area of ​​each of the plurality of vents is configured to decrease as it approaches the inlet of the chamber. Battery pack.

4. A battery pack according to claim 1, The partition plate comprises an i-th portion and an i+1-th portion that is further from the inlet of the chamber than the i-th portion. The plurality of vents include the i-th vent included in the i-th portion and the i+1-th vent included in the i+1-th portion. The i-th vent is more sparsely distributed than the i+1 vent. Battery pack.

5. A battery pack according to claim 1, The plurality of vents are arranged so that they are more sparsely distributed as they approach the inlet of the chamber. Battery pack.

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