Battery pack

Abstract

To provide a battery pack capable of reducing the temperature of gas to be discharged to the outside.SOLUTION: A battery pack comprises: a case 3 that houses a battery cell; and a pressure releasing valve 6 that opens when the inner pressure of the case 3 becomes equal to or higher than a predetermined pressure, and discharges gas inside the case 3 to reduce the inner pressure of the case. The pressure releasing valve 6 comprises: a passage 7 that communicates with the inside of the case 3 and the outside of the case 3; a valve body 8 that makes the passage 7 be in a communication state when the inner pressure of the case 3 becomes equal to or higher than the predetermined pressure; and a cooling device 11 for cooling gas flowing through the passage 7.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery pack that houses battery cells. [Background technology]

[0002] Patent Document 1 describes a battery pack that contains a plurality of unit cells arranged vertically and a refrigerant for cooling the unit cells. The refrigerant is stored in the battery pack, and a part of the unit cell arranged at the bottom of the plurality of unit cells is immersed in the refrigerant. In addition, a guide member protruding inward is provided on the inner surface of the upper wall of the battery pack so that the refrigerant vaporized by absorbing heat from the unit cells drips from the upper side of the unit cells. Note that the battery pack described in Patent Document 1 has heat dissipation fins on the outer wall surface of the case to improve heat dissipation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-218853 A Summary of the Invention [Problem to be solved by the invention]

[0004] The battery pack described in Patent Document 1 absorbs heat from the battery cells by vaporizing the refrigerant, and transfers the heat from the vaporized refrigerant to the case. The refrigerant is cooled by transferring heat from the refrigerant to the case, and changes phase to a liquid, and is dripped onto the battery cells to absorb heat from the battery cells again. That is, the battery pack is configured to cool the battery cells by changing phase of the refrigerant as a heat transport medium in the battery pack. However, when the amount of heat generated by the battery cells is equal to or greater than the amount of heat that can be dissipated from the case, heat cannot be transferred sufficiently from the vaporized refrigerant to the case. In other words, the refrigerant cannot be cooled to a degree that causes the refrigerant to change phase to a liquid, and the internal pressure of the battery pack may gradually increase.

[0005] On the other hand, in conventional battery packs, gas may be generated when the battery cells are discharged or charged, and in order to prevent the internal pressure from rising above a predetermined pressure due to the generation of gas, a pressure release valve is provided to open when the internal pressure rises to a predetermined pressure and release the gas to the outside. Therefore, as described above, even if the amount of heat generated by the battery cells exceeds the amount of heat that can be dissipated from the case, the pressure release valve opens, thereby preventing the internal pressure of the battery pack from rising excessively.

[0006] However, as described above, when the pressure release valve is opened and high-temperature refrigerant and high-temperature gas generated from the battery cells are discharged outside the battery pack, there is a possibility that other devices installed outside the battery pack may be heated, resulting in some effect on the other devices. Furthermore, if a separate device is provided to take in the high-temperature refrigerant and high-temperature gas discharged from the battery pack and cool them, this may reduce the mountability of the power storage device including the battery pack.

[0007] The present invention has been made in view of the above technical problems, and has an object to provide a battery pack capable of lowering the temperature of gas discharged to the outside. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a battery pack comprising a case for accommodating battery cells, and a pressure release valve that opens when the internal pressure of the case reaches or exceeds a predetermined pressure to discharge gas inside the case to the outside and reduce the internal pressure of the case, the pressure release valve comprising a flow path communicating between the inside of the case and the outside of the case, a valve body that opens the flow path when the internal pressure of the case reaches or exceeds the predetermined pressure, and a cooling device that cools the gas flowing through the flow path. The cooling device includes a refrigerant flow path formed in an outer wall of the flow path, a gas refrigerant flowing through the refrigerant flow path, and a heat exchanger that cools the gas refrigerant. The present invention is characterized in that

[0009] In the present invention, the cooling device may include a heat storage material provided on an outer wall of the flow path.

[0010] In addition, in this invention, the cooling device may include a refrigerant flow path formed in an outer wall of the flow path, a gas refrigerant flowing through the refrigerant flow path, and a heat exchanger that cools the gas refrigerant.

[0011] In the present invention, the gas refrigerant may include an insulating refrigerant.

[0012] In addition, in the present invention, a battery cell refrigerant that cools the battery cells may be provided inside the case, and the battery cell refrigerant and the gas refrigerant may be refrigerants of the same substance.

[0013] In the present invention, a lower end of the case may be in communication with the coolant flow path.

[0014] In the present invention, the case may have a side wall formed in a vertical direction, and the pressure release valve may be connected to the side wall.

[0015] In this invention, the case may be provided with a partition that divides the internal space into a battery cell side and a pressure release valve side, and the upper end of the partition in the vertical direction may be formed with a predetermined gap between it and a lid that seals the upper side of the case in the vertical direction. Effect of the Invention

[0016] According to this invention, a case that houses battery cells is provided with a pressure release valve that opens to reduce the internal pressure of the case when the internal pressure of the case reaches or exceeds a predetermined pressure. The pressure release valve includes a flow path that communicates between the inside and outside of the case, a valve body that opens the flow path when the internal pressure of the case reaches or exceeds the predetermined pressure, and a cooling device that cools the gas flowing through the flow path. Therefore, as the gas inside the battery pack flows through the flow path, the gas is cooled by the cooling device, making it possible to prevent high-temperature gas from being discharged to the outside of the battery pack. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a schematic diagram for explaining an example of a battery pack according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing a schematic example of a pressure relief valve. [Diagram 3] 13 is a schematic diagram for explaining an example in which a pressure release valve is provided in a side wall of a case main body. FIG. [Figure 4] 10A and 10B are schematic diagrams for explaining an example in which a partition wall is provided, in which FIG. 10A shows a battery pack in a horizontal state, and FIG. 10B shows a battery pack in an inclined state. [Diagram 5] FIG. 11 is a cross-sectional view showing a schematic diagram of another example of a pressure relief valve. [Figure 6] FIG. 11 is a cross-sectional view showing a schematic example of a flow channel provided with fins. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A schematic diagram for explaining an example of a battery pack according to an embodiment of the present invention is shown in Fig. 1. The battery pack 1 shown in Fig. 1 is configured to supply power to a motor (not shown) of a hybrid vehicle, an electric vehicle, or the like, and to house a battery that is charged with the power generated by the motor. Specifically, the battery pack 1 includes a cylindrical case body 2 with a bottom and a lid 3 that seals the opening (top), and is configured as a case that seals the internal space by fixing the case body 2 and the lid 3 together by bolting, welding, or the like.

[0019] A plurality of battery cells 4, each of which is made up of a secondary battery such as a lithium-ion battery or a nickel-metal hydride battery, are arranged side by side inside the case body 2. The case body 2 may also house electrical devices (not shown) such as wiring that connects the battery cells 4 and electrical circuits for controlling the power output from or input to the battery cells 4.

[0020] The battery cells 4 configured in this manner generate heat as they are discharged and charged. For this reason, cooling oil 5 for cooling the battery cells 4 is stored in the case body 2. Specifically, the cooling oil 5 is stored so that at least a portion of the lower side of the battery cells 4 is immersed in the cooling oil 5. For this cooling oil 5, insulating oil such as perfluorocarbon or a fluorine-based inert liquid can be used to suppress the occurrence of short circuits or leakage current through the cooling oil 5 within the battery pack 1. This cooling oil 5 corresponds to the "battery cell refrigerant" in this embodiment of the present invention.

[0021] In addition, since the battery cells 4 discharge and charge by chemical reactions between the electrolyte contained therein and the positive and negative electrode materials, gas (hereinafter referred to as "ejected gas") Gs may be ejected from the battery cells 4 into the battery pack 1. Furthermore, at least a part of the cooling oil 5 is vaporized by absorbing heat from the battery cells 4. As a result of the gas being ejected into the battery pack 1 and the cooling oil 5 being vaporized in this manner, the internal pressure of the battery pack 1 gradually increases. Therefore, in the example shown in FIG. 1, a pressure release valve 6 is provided on the upper surface of the battery pack 1, i.e., on the lid portion 3, in order to prevent the internal pressure of the battery pack 1 from increasing to a predetermined pressure or higher. In the following description, the vaporized cooling oil 5 is referred to as refrigerant gas Gr.

[0022] Fig. 2 is an enlarged view for explaining an example of the pressure release valve 6. The pressure release valve 6 shown in Fig. 2 has a flow path 7 that communicates with the inside and outside of the battery pack 1. A valve body 8 that switches the flow path 7 between a communicating state and a cutoff state is provided inside the pressure release valve 6. The pressure release valve 6 is switched from a cutoff state to a communicating state by being pressed by the internal pressure of the battery pack 1. For example, the pressure release valve 6 can be configured to switch from the cutoff state to the communicating state by breaking when the internal pressure of the battery pack 1 increases to a predetermined pressure, or as shown in Fig. 2, the valve body 8 is brought into contact with a valve seat 10 by the elastic force of an elastic member 9, and when the internal pressure of the battery pack 1 increases to a predetermined pressure, the valve body 8 is separated from the valve seat 10 to switch from the cutoff state to the communicating state.

[0023] A cooling device 11 is provided in a portion of the flow path 7 closer to the inside of the battery pack 1 than the valve body 8, for cooling the ejected gas Gs and the refrigerant gas Gr flowing through the flow path 7. The cooling device 11 may cool the outer wall surface of the flow path 7 to cool the ejected gas Gs and the refrigerant gas Gr by the temperature difference between the ejected gas Gs and the refrigerant gas Gr and the outer wall surface of the flow path 7, or may cool the ejected gas Gs and the refrigerant gas Gr by arranging a pipe inside the outer wall surface of the flow path 7 and exchanging heat between the pipe and the ejected gas Gs and the refrigerant gas Gr.

[0024] The cooling device 11 shown in FIG. 2 is configured to form an annular refrigerant flow passage 12 inside the pressure release valve 6, and to cool the outer wall surface of the flow passage 7 by flowing a refrigerant (gas refrigerant) through the refrigerant flow passage 12. Specifically, the refrigerant flow passage 12 for the refrigerant to flow is formed in a portion upstream (inside the battery pack 1) of the outer wall portion 7a of the flow passage 7 from a portion where the valve body 8 is provided. This refrigerant flow passage 12 is connected to a heat exchanger 13, and heat is transferred from the ejected gas Gs and the refrigerant gas Gr flowing through the flow passage 7 to the outer wall portion 7a of the flow passage 7, and the refrigerant absorbs the heat. After that, the refrigerant that has flowed into the heat exchanger 13 is cooled. Then, the cooled refrigerant is configured to flow again into the pressure release valve 6 (specifically, the refrigerant flow passage 12).

[0025] The above-mentioned refrigerant flow path 12 may be damaged when an excessive external force acts on the battery pack 1, and in such a case, the refrigerant flowing through the refrigerant flow path 12 may leak into the battery pack 1. In order to prevent such leakage of the refrigerant from causing a short circuit or electric leakage in the battery pack 1, it is preferable to use an insulating oil such as perfluorocarbon or a fluorine-based inert liquid as the refrigerant. In other words, it is preferable to use an insulating refrigerant for the refrigerant flow path 12.

[0026] By forming the refrigerant flow path 12 in the pressure release valve 6 and cooling the pressure release valve 6 in this way, when the high-temperature ejected gas Gs and the high-temperature refrigerant gas Gr generated in the battery pack 1 flow through the flow path 7, heat is transferred from the ejected gas Gs and the refrigerant gas Gr to the pressure release valve 6 due to the temperature difference between the pressure release valve 6 and the gases Gs and Gr. In other words, by cooling the pressure release valve 6, the ejected gas Gs and the refrigerant gas Gr can be efficiently cooled. As a result, it is possible to suppress the high-temperature gas from being discharged to the outside of the battery pack 1.

[0027] Furthermore, by using an insulating refrigerant as the refrigerant for cooling the pressure release valve 6, even if the refrigerant flow path 12 is damaged and the refrigerant leaks into the battery pack 1, the occurrence of a short circuit or leakage of electricity within the battery pack 1 can be suppressed, in other words, the insulation within the battery pack 1 can be maintained.

[0028] The pressure release valve 6 in the embodiment of the present invention is not limited to being provided in the lid 3 as in the example shown in FIG. 1, but may be provided in a side wall 2a of the case body 2 that is formed facing the vertical direction. FIG. 3 shows an example of a configuration in which the pressure release valve 6 is attached to the side wall 2a of the case body 2. In the example shown in FIG. 3, the pressure release valve 6 is configured to cool the ejected gas Gs and the refrigerant gas Gr by flowing a refrigerant through the pressure release valve 6, and the same refrigerant as that for cooling the battery cells 4 is used as the refrigerant. In addition, the lower end of the battery pack 1 is in communication with the refrigerant flow path 12. That is, the refrigerant is configured to flow through the refrigerant flow path 12 and the battery pack 1.

[0029] In this manner, by attaching the pressure release valve 6 to the side wall 2a of the case main body 2, and by using the same refrigerant to cool the battery cells 4 and the pressure release valve 6, and by connecting the battery pack 1 to the refrigerant flow path 12, the refrigerant in the battery pack 1 can be cooled to suppress a rise in temperature of the battery pack 1, and the piping can be prevented from becoming complex in shape and large in size.

[0030] Furthermore, when the pressure release valve 6 is attached to the side wall 2a of the case body 2, if the battery pack 1 tilts, such as when the vehicle is traveling uphill or on a banked road, the liquid phase refrigerant in the battery pack 1 may flow into the flow path 7 of the pressure release valve 6. A configuration for preventing the refrigerant from flowing into the flow path 7 of the pressure release valve 6 and further leaking from the flow path 7 to the outside is shown in FIG.

[0031] In the example shown in FIG. 4, a partition wall 14 is provided opposite the opening of the flow path 7 of the pressure release valve 6 facing the inside of the battery pack 1. That is, the partition wall 14 divides the internal space of the case body 2 into the battery cell 4 side and the pressure release valve 6 side. The partition wall 14 has its lower end and side end fixed to the case body 2. Meanwhile, a predetermined gap is provided between the upper end of the partition wall 14 and the lid 3 in the vertical direction. Specifically, as shown in FIG. 4(b), the partition wall 14 is formed up to a position at the same height as the oil level of the cooling oil 5 when the battery pack 1 is tilted at a predetermined angle. That is, the space on the battery cell 4 side and the space on the pressure release valve 6 side are connected to each other only at the upper end in the vertical direction across the partition wall 14.

[0032] By providing the partition 14 in this manner, even if the battery pack 1 is tilted at a certain angle as shown in Fig. 4(b), the oil level of the cooling oil 5 does not exceed the partition 14, and the cooling oil 5 can be prevented from flowing toward the pressure release valve 6. As a result, the cooling oil 5 can be prevented from leaking to the outside of the battery pack 1.

[0033] In addition, the above-mentioned cooling device 11 may be configured to exchange heat with the ejected gas Gs and the refrigerant gas Gr as long as it is capable of exchanging heat with the ejected gas Gs and the refrigerant gas Gr, and is not limited to being configured using a refrigerant. In addition to or instead of being configured using a refrigerant, the cooling device 11 may be configured to exchange heat with the ejected gas Gs and the refrigerant gas Gr.

[0034] Fig. 5 is a cross-sectional view for explaining another configuration of the cooling device 11. In the cooling device 11 shown in Fig. 5, a portion of the outer wall of the flow passage 7 that is closer to the inside of the battery pack 1 than the valve body 8 is made of a heat storage material 15 such as paraffin.

[0035] By forming the outer wall portion 7a of the flow path 7 with the heat storage material 15 in this manner, heat can be transferred from the ejected gas Gs and the refrigerant gas Gr to the heat storage material 15 within the range of the heat capacity of the heat storage material 15, and the ejected gas Gs and the refrigerant gas Gr can be efficiently cooled, as in the above example. As a result, it is possible to suppress the emission of high-temperature gas to the outside of the battery pack 1.

[0036] In addition, the cooling efficiency of the cooling device 11 can be improved as the contact area with the ejected gas Gs and the refrigerant gas Gr increases. Therefore, the flow path 12 may further include a heat exchanger such as a fin or labyrinth for increasing the contact area with the ejected gas Gs and the refrigerant gas Gr. FIG. 6 is a cross-sectional view for explaining an example of a pressure release valve 6 having fins 16 provided in the flow path 12. The pressure release valve 6 shown in FIG. 6 has a plurality of fins 16 provided on the outer wall of the flow path 7, which is closer to the inside of the battery pack 1 than the valve body 8. The means for cooling the pressure release valve 6 may be a refrigerant flow as shown in FIG. 2, or a heat storage material 15 as shown in FIG. 5.

[0037] By providing the fins 16 in the flow passage 7 in this way, the contact area with the ejected gas Gs and the refrigerant gas Gr is increased, thereby improving the efficiency of heat transfer between the ejected gas Gs and the refrigerant gas Gr, and the ejected gas Gs and the refrigerant gas Gr can be efficiently cooled, as in the above example. As a result, it is possible to suppress the discharge of high-temperature gas to the outside of the battery pack 1. [Explanation of symbols]

[0038] 1 Battery pack 2 Case body 2a side wall 3 Lid 4 Battery Cells 5 Cooling oil 6 Pressure Relief Valve 7 Flow Path 7a Exterior wall 8 Valve body 11 Cooling device 12 Coolant flow path 13 Heat exchanger 14 Bulkhead 15 Heat storage material 16 Finn Gr refrigerant gas Gs Ejected gas

Claims

1. A battery pack comprising a case for accommodating battery cells, and a pressure release valve that opens when the internal pressure of the case reaches or exceeds a predetermined pressure to release gas inside the case to the outside and reduce the internal pressure of the case, the pressure release valve includes a flow path communicating between the inside of the case and the outside of the case, a valve body that opens the flow path when the internal pressure of the case becomes equal to or higher than the predetermined pressure, and a cooling device that cools the gas flowing through the flow path, The cooling device includes a refrigerant flow path formed in an outer wall of the flow path, a gas refrigerant flowing through the refrigerant flow path, and a heat exchanger that cools the gas refrigerant. A battery pack characterized by:

2. 2. The battery pack according to claim 1, The cooling device includes a heat storage material provided on an outer wall of the flow path. A battery pack characterized by:

3. 3. The battery pack according to claim 1, The gas refrigerant includes an insulating refrigerant. A battery pack characterized by:

4. 4. The battery pack according to claim 1, a battery cell refrigerant that cools the battery cells is provided inside the case; The battery cell refrigerant and the gas refrigerant are made of the same material. A battery pack characterized by:

5. 5. The battery pack according to claim 4, The lower end of the case is in communication with the refrigerant flow path. A battery pack characterized by:

6. 6. The battery pack according to claim 1, The case has a side wall formed in a vertical direction, The pressure relief valve is coupled to the side wall. A battery pack characterized by:

7. 7. The battery pack according to claim 6, a partition wall that divides the internal space of the case into a battery cell side and a pressure release valve side; The upper end of the partition wall in the vertical direction is formed with a predetermined gap between it and a lid portion that seals the upper side of the case in the vertical direction. A battery pack characterized by:

Images