Battery system

Abstract

To provide a cell system that can reduce power consumption due to cooling.SOLUTION: A cell system includes a battery pack, a ventilation unit bringing the battery pack into contact with outside air, a battery temperature acquisition unit that acquires the temperature inside the battery pack, a pressure reducing unit that reduces the pressure inside the battery pack, and a control unit that controls the pressure reducing unit on the basis of the acquired temperature. The control unit controls the pressure reducing unit to reduce the pressure inside the battery pack, and executes pressure reduction control to take the outside air into the battery pack through the ventilation unit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a battery system.

Background Art

[0002] Conventionally, a battery system mounted on a vehicle has been known (see, for example, Patent Document 1). The battery system of Patent Document 1 discloses a system for reducing the pressure inside a battery cell in order to vent the gas generated inside the battery cell.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a battery system, it is preferable to keep the temperature inside a battery pack in which a plurality of battery cells are grouped together constant. For this reason, it is necessary to provide a cooling device for cooling the battery cells inside the battery pack. However, since such a cooling device consumes power, there is a problem that, for example, in a high-temperature and high-humidity region, the power consumption for cooling increases.

[0005] An object of the present disclosure is to provide a battery system capable of suppressing the power consumption due to cooling.

Means for Solving the Problems

[0006] The battery system according to this disclosure comprises a battery pack, a ventilation section connecting the battery pack to the outside air, a battery temperature acquisition section for acquiring the temperature inside the battery pack, a pressure reduction section for reducing the pressure inside the battery pack, and a control section for controlling the pressure reduction section based on the acquired temperature. The control section controls the pressure reduction section to reduce the pressure inside the battery pack and performs pressure reduction control to take in outside air into the battery pack through the ventilation section.

[0007] This configuration allows outside air to be drawn into the depressurized battery pack. This enables the use of the latent heat of vaporization from the outside air to lower the temperature inside the battery pack. As a result, the battery pack can be cooled efficiently while suppressing power consumption. [Effects of the Invention]

[0008] According to this disclosure, a battery system can be provided that can suppress power consumption due to cooling. [Brief explanation of the drawing]

[0009] [Figure 1] A system diagram of a battery system according to one embodiment of the present disclosure. [Figure 2] A schematic diagram of a battery pack according to one embodiment of the present disclosure. [Figure 3] A flowchart illustrating a control procedure performed by a control unit according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0010] Hereinafter, an embodiment of this disclosure will be described with reference to the drawings. In Figures 1 and 2, the longitudinal direction of vehicle C is denoted as Q, and the front of the longitudinal direction Q is denoted as F. The lateral direction of vehicle C is denoted as P, and the right side of the lateral direction P is denoted as R. In some specifications, the lateral direction may also be referred to as the vehicle width direction.

[0011] As shown in Figure 1, the battery system 1 comprises a battery pack 2, a ventilation section 4 connecting the battery pack 2 to the outside air, a battery temperature acquisition section 6 for acquiring the temperature inside the battery pack 2, a pressure reduction section 8 for reducing the pressure inside the battery pack 2, a control section 10 for controlling the pressure reduction section 8, a cooling device 12, a humidity acquisition section 14 for acquiring the humidity of the outside air, and an outside air temperature acquisition section 16 for acquiring the temperature of the outside air.

[0012] The battery system 1 of this embodiment is a battery system mounted on a vehicle C. The vehicle C is an electric vehicle equipped with a motor generator 20 (MG in Figure 1) connected to the wheels 22 and capable of traction and regeneration. The electric vehicle may be, for example, a plug-in hybrid vehicle (PHEV) capable of external charging or external power supply. The battery system 1 is a system for supplying power from a battery pack 2 to the motor generator 20 via an inverter (not shown).

[0013] The battery pack 2 has a battery module 2b which is composed of multiple battery cells 2a. In this embodiment, the battery cells 2a are lithium-ion secondary batteries. The battery pack 2 is a housing made of resin or metal for holding and housing multiple such battery modules 2b. In addition, such battery cells 2a generate heat in accordance with the input and output of power from the battery cells 2a. For this reason, the battery pack 2 requires a cooling device 12. Furthermore, the battery pack 2 may have a heater or the like to warm the battery cells 2a when the battery pack 2 is at a low temperature. As shown in Figures 1 and 2, PN lines 2c extend from the battery pack 2 to supply power from each battery module 2b to an inverter (not shown).

[0014] The ventilation section 4 is a membrane that allows gases such as air to pass through in one direction while suppressing the penetration of liquids such as water. The ventilation section 4 is, for example, a foamed resin membrane formed with a predetermined cell diameter. An example of such a membrane is a membrane filter. In this embodiment, the predetermined cell diameter is, for example, a cell diameter that can suppress the penetration of liquid water while allowing water vapor in the air to pass through. In this embodiment, the ventilation section 4 is provided on the side of the battery pack 2 and connects the air outside the battery pack 2 (outside air) to the inside of the battery pack 2. More specifically, as shown in Figure 2, it is provided on one side of the battery pack 2 in the vehicle width direction (the left side in this embodiment). By providing the ventilation section 4 in such a position, even if the vehicle C travels on a flooded road, it is possible to suppress the intrusion of water from the ventilation section 4. In addition, in this embodiment, the ventilation section 4 is provided on one side of the battery pack in the vehicle width direction, but the ventilation section 4 may be provided on both sides, or on any of the top, bottom, front, or rear surfaces of the battery pack, or a combination of these surfaces.

[0015] As shown in Figure 1, the battery temperature acquisition unit 6 is a device for acquiring the temperature of the battery cells 2a and monitoring the temperature state of the battery. In this embodiment, it is a temperature sensor that detects the temperature of the battery cells 2a. However, the battery temperature acquisition unit 6 may also be a system that estimates the temperature of the battery cells 2a by, for example, acquiring the temperature inside the battery pack 2.

[0016] The pressure reduction unit 8 is a device for reducing the pressure inside the battery pack 2. In this embodiment, the pressure reduction unit 8 includes a vacuum pump 8a (VP in Figure 1) and a vacuum pipe 8b connected from the vacuum pump 8a to the inside of the battery pack 2. The vacuum pump 8a sucks air from inside the battery pack 2 via the vacuum pipe 8b, thereby reducing the pressure inside the battery pack 2. The vacuum pump 8a may be used, for example, as a pump to reduce the pressure of a brake master cylinder. Alternatively, it may be a vacuum pump 8a used in an air conditioning system that supplies conditioned air to the interior of a vehicle C. Furthermore, the pressure reduction unit 8 is not limited to such a system as long as it can reduce the pressure inside the battery pack 2. For example, the pressure reduction unit 8 may be equipped with a discharge device in the housing of the battery pack 2 that forcibly discharges air from inside the battery pack 2, thereby reducing the pressure inside the battery pack 2. Alternatively, the pressure reduction unit 8 may reduce the pressure of the battery pack 2 by utilizing the negative pressure of a master cylinder or air conditioning system without operating the vacuum pump 8a.

[0017] The control unit 10 is electrically connected to at least the battery temperature acquisition unit 6, the pressure reduction unit 8, the humidity acquisition unit 14, and the cooling device 12, and controls these devices. In addition, the control unit 10 may be electrically connected to each battery cell 2a, each battery module 2b, and an accelerator position sensor 24a that detects the opening degree of the accelerator 24, and may perform control of the motor generator 20, acquire the state of charge (SOC) of each battery cell 2a and battery module 2b, and control the input and output of power.

[0018] The control unit 10 is actually an ECU (Electronic Control Unit) composed of a microcomputer including an arithmetic unit, a memory, an input / output buffer, etc. Based on the maps and programs stored in the memory, the control unit 10 controls the vacuum pump 8a to execute a pressure reduction control for reducing the pressure of the battery pack 2. Also, based on the maps and programs stored in the memory, the control unit 10 controls the water pump 12a described later to execute a liquid cooling control for flowing a refrigerant through the refrigerant passage 12b to cool the battery pack 2. Further, the control unit 10 may execute control of the motor generator 20 and control of power input / output of each battery cell 2a and battery module 2b based on the maps and programs stored in the memory. Note that various controls are not limited to software processing, and can also be processed by dedicated hardware (electronic circuits).

[0019] The cooling device 12 is a device for cooling the battery pack 2. In the present embodiment, the cooling device 12 is a liquid cooling type cooling device 12 having a water pump 12a, a refrigerant passage 12b, and a radiator 12c. As shown in FIGS. 1 and 2, the refrigerant passage 12b enters the inside of the battery pack 2 and passes near each battery module 2b to cool each battery module 2b. The water pump 12a is a device that is connected to the refrigerant passage 12b, sucks up the refrigerant flowing inside the refrigerant passage 12b, and sends it back to the refrigerant passage 12b to cause the refrigerant in the refrigerant passage 12b to flow back. The radiator 12c includes a heat exchanger, a fan, etc., and is a device that cools the refrigerant by exchanging heat between the refrigerant and the outside air.

[0020] The humidity acquisition unit 14 is a device for acquiring the humidity of the outside air. In the present embodiment, the humidity acquisition unit 14 is a humidity sensor that measures the humidity in the air. However, the humidity acquisition unit 14 only needs to be able to acquire the humidity of the outside air. That is, the humidity acquisition unit 14 may be a program that acquires the temperature of the outside air using, for example, an outside air temperature sensor described later and estimates the humidity from the acquired outside air temperature.

[0021] The outside air temperature acquisition unit 16 is a device for acquiring the temperature of the outside air. In the present embodiment, the outside air temperature acquisition unit 16 is an outside air temperature sensor that measures the temperature in the air.

[0022] Next, the control procedure executed by the control unit 10 will be described using the flowchart of FIG. 3. Note that the control unit 10 starts the control procedure when an ignition switch (not shown) is turned on.

[0023] In step S1, the control unit 10 acquires the battery temperature TB from the battery temperature acquisition unit 6. When the control unit 10 acquires the battery temperature TB, it proceeds to step S2.

[0024] In step S2, the control unit 10 determines whether the outside air temperature TO is lower than the battery temperature TB. Here, the outside air temperature TO may be a value within a predetermined temperature range with respect to the temperature actually acquired by the outside air temperature acquisition unit 16. The predetermined temperature range is, for example, plus or minus 2 degrees. When the outside air temperature TO is significantly higher than the battery temperature, the inside of the battery pack 2 cannot be cooled. Therefore, when the control unit 10 determines that the battery temperature TB is the outside air temperature TO That's all. (step S2 YES), it proceeds to step S3.

[0025] In step S3, the control unit 10 obtains the required power (an example of a required output) BQ, which is the power required by each battery module 2b, and determines whether the required power BQ is equal to or greater than a predetermined power (an example of a predetermined required output) BQt. The larger the accelerator opening Th obtained from the accelerator position sensor 24a, the more power the motor generator 20 requires. Therefore, the required power BQ also increases. Thus, the required power BQ can be calculated by the control unit 10 from, for example, the accelerator opening Th obtained from the accelerator position sensor 24a. Each battery module 2b is more likely to generate heat as the required power BQ increases. Therefore, the predetermined power BQt can be, for example, a value at which the battery temperature TB is expected to rise above a predetermined temperature. If the control unit 10 determines that the required power BQ is less than the predetermined power BQt (step S3 NO), it proceeds to step S4.

[0026] In step S3, if the control unit 10 determines that the requested power BQ is equal to or greater than a predetermined power BQt (step S3 YES), it proceeds to step S11, changes the first predetermined temperature TB1 to a second predetermined temperature TB2 which is lower than the first predetermined temperature TB1, and proceeds to step S4.

[0027] In step S4, the control unit 10 determines whether the battery temperature TB obtained in step S1 is equal to or greater than the first predetermined temperature TB1 or the second predetermined temperature TB2. That is, the control unit 10 determines whether the battery temperature TB is high, equal to or greater than the first predetermined temperature TB1 or the second predetermined temperature TB2. In this case, since the second predetermined temperature TB2 is lower than the first predetermined temperature TB1, when the required power BQ is high and the battery module 2b is more likely to become hotter, the control from step S3 onward can be executed from a lower battery temperature TB stage. As a result, when the required power BQ is high, the temperature of the battery module 2b can be reduced more quickly.

[0028] If the control unit 10 determines that the battery temperature TB is equal to or greater than the first predetermined temperature TB1 or the second predetermined temperature TB2 (step S4 YES), it proceeds to step S5.

[0029] In step S5, the control unit 10 obtains the state of charge (SOC) of each battery cell 2a or each battery module and determines whether the SOC is lower than a predetermined SOCt. If the control unit 10 determines that the SOC is not lower than the predetermined SOCt (i.e., the SOC is equal to or greater than the predetermined SOCt) (step S5 NO), the process proceeds to step S6.

[0030] In step S6, the control unit 10 obtains the humidity H of the outside air and determines whether the humidity H of the outside air is equal to or greater than a predetermined humidity H1. The predetermined humidity H1 should be, for example, a humidity level such that latent heat of vaporization occurs when outside air is mixed into the inside of the battery pack 2. That is, if the outside air is dry, there is little moisture in the air and the amount of moisture that vaporizes is small. Therefore, a decrease in the temperature inside the battery pack 2 due to latent heat of vaporization cannot be expected. On the other hand, if the humidity H is equal to or greater than the predetermined humidity H1, latent heat of vaporization can be expected. If the control unit 10 determines that the humidity H is equal to or greater than the predetermined humidity H1, it proceeds to step S7.

[0031] In step S7, the control unit 10 performs pressure reduction control to reduce the pressure inside the battery pack 2 and sends outside air into the battery pack 2 through the ventilation section 4. At this time, the temperature inside the battery pack 2 decreases due to the latent heat of vaporization. After performing pressure reduction control, the control unit 10 proceeds to step S8.

[0032] In step S8, the control unit 10 determines whether the battery temperature TB has decreased. That is, even if the temperature inside the battery pack 2 decreases due to latent heat of vaporization, the battery temperature TB may not decrease. For this reason, if the battery temperature TB has decreased (step S8 YES), the control unit 10 proceeds to step S9.

[0033] In step S9, the control unit 10 determines whether the battery temperature TB is below the third predetermined temperature TB3. The third predetermined temperature TB3 is the temperature at which each battery cell 2a has been sufficiently cooled. If the control unit 10 determines that the battery temperature TB is below the third predetermined temperature TB3 (step S9 YES), it determines that cooling is complete and proceeds to step S10.

[0034] In step S10, the control unit 10 terminates the pressure reduction control and returns the process to step S1.

[0035] In step S2, if the control unit 10 determines that the battery temperature TB is greater than the ambient temperature TO (step S2 NO), it proceeds to step S14 and performs normal liquid cooling control using only the cooling device 12 without executing the control from step S3 onwards. Normal liquid cooling control is a control that operates the cooling device 12 according to the battery temperature TB to lower the battery temperature TB. After performing normal liquid cooling control, the control unit 10 returns to step S1.

[0036] If the control unit 10 determines in step S4 that the battery temperature TB is lower than the first predetermined temperature TB1 or the second predetermined temperature TB2 (step S4 NO), it does not perform either depressurization control or liquid cooling control and returns to step S1. In other words, the control unit 10 determines that cooling of the battery cell 2a is not necessary.

[0037] If the control unit 10 determines in step S5 that the charge level (SOC) is less than a predetermined charge level (SOCt), it proceeds to step S14 to prohibit pressure reduction control. This suppresses power consumption, for example, when the vacuum pump 8a is operating.

[0038] If the control unit 10 determines in step S6 that the humidity H is less than the predetermined humidity H1 (step S6 NO), it proceeds to step S12. In other words, the control unit 10 determines that the outside air is dry.

[0039] In step S12, the control unit 10 prioritizes liquid cooling control over pressure reduction control. After executing liquid cooling control, the control unit 10 proceeds to step S13 to determine whether the battery temperature TB has decreased. If the control unit 10 determines that the battery temperature TB has decreased (step S13 YES), it proceeds to step S9. On the other hand, if the control unit 10 determines that the battery temperature TB has not decreased (step S13 NO), it proceeds to step S7 to execute pressure reduction control.

[0040] In other words, when the outside air is dry, the latent heat of vaporization obtained by reduced pressure control cannot be expected to be significant. For this reason, the control unit 10 first performs liquid cooling control. However, if the battery temperature TB does not decrease even after performing liquid cooling control, continuing liquid cooling control will only consume power. Therefore, if the battery temperature TB does not decrease by liquid cooling control, the control unit 10 performs reduced pressure control. This allows the battery cell 2a to be cooled efficiently while suppressing power consumption.

[0041] If the control unit 10 determines in step S8 that the battery temperature TB has not decreased, it proceeds to step S12. In other words, if the control unit 10 prioritizes the depressurization control but the battery temperature TB does not decrease, it uses liquid cooling control in combination to cool the battery cell 2a. This allows for efficient cooling of the battery cell 2a while suppressing power consumption due to liquid cooling control.

[0042] If the battery temperature TB is higher than the third predetermined temperature TB3 in step S9, the control unit 10 proceeds to step S5 and continues cooling the battery cell 2a until it falls below the third predetermined temperature TB3, prioritizing either depressurization control or liquid cooling control.

[0043] As explained above, this disclosure provides a battery system 1 that can suppress power consumption due to cooling.

[0044] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. In particular, the various modifications described herein can be combined as needed.

[0045] (a) In the above embodiment, the cooling device 12 is exemplified as a liquid-cooled type, but the disclosure is not limited thereto. The cooling device 12 may be an air-cooled type cooling device 12 that blows cooling air onto the battery pack 2 to cool each battery module 2b.

[0046] (b) In the above embodiments, the required power was used as an example of the required output, but the disclosure is not limited thereto. The required output may be any value that indicates the load required for each battery cell 2a and each battery module 2b. For example, the required output may be a value calculated based on the output exerted by the motor generator 20. [Explanation of Symbols]

[0047] 1: Battery System 2: Battery pack 2a: Battery cell 4: Ventilation section 6:Battery temperature acquisition section 8: Depressurization section 10: Control Unit 12: Cooling device 12b: Refrigerant passage 14: Humidity acquisition section H: Humidity H1: Predetermined humidity SOC: Charging rate SOCt: Predetermined charging rate TB:Battery temperature TB1: 1st predetermined temperature TB2: 2nd predetermined temperature

Claims

1. A battery pack, The aforementioned battery pack and a ventilation section that connects to the outside air, A battery temperature acquisition unit that acquires the temperature inside the battery pack, A pressure reducing unit for reducing the pressure inside the battery pack, Based on the acquired temperature, a control unit controls the depressurization unit, A refrigerant passage through which the refrigerant flows, passing through the aforementioned battery pack, A humidity acquisition unit that acquires the humidity of the outside air, Equipped with, The control unit has a pressure reduction control that controls the pressure reduction unit to reduce the pressure inside the battery pack and takes in outside air into the battery pack through the ventilation unit. The control unit further includes a liquid cooling control that cools the battery pack by flowing a refrigerant through the refrigerant passage. If the humidity is above a predetermined level, the pressure reduction control is executed in priority over the liquid cooling control. If the humidity is below the predetermined humidity, the liquid cooling control is executed in priority over the pressure reduction control. Battery system.

2. An outside air temperature acquisition unit that acquires the temperature of the outside air, Equipped with, The control unit, when the temperature is equal to or higher than the ambient temperature, controls the depressurization unit to reduce the pressure inside the battery pack and performs depressurization control to draw outside air into the battery pack through the ventilation unit. The battery system according to claim 1.

3. The control unit executes the pressure reduction control when the temperature exceeds a first predetermined temperature. The battery system according to claim 1.

4. The control unit changes the first predetermined temperature to a second predetermined temperature lower than the first predetermined temperature if the requested output, which is the output required by the battery pack, is equal to or greater than a predetermined requested output. The battery system according to claim 3.

5. The control unit prohibits the pressure reduction control when the battery's charge level is lower than a predetermined charge level. The battery system according to any one of claims 1 to 4.

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