Battery cooling system

Abstract

To uniformly cool a battery.SOLUTION: A battery cooling system 1 for cooling a battery 2 with a coolant flowing in a cooling path 3, which is provided along the battery 2, comprises a first port 31, a second port 32 and a switching device 20. The first port 31 is functioned as any one of an inlet and an outlet for the coolant with respect to the cooling path 3, and the second port 32 is functioned as the other of the inlet and the outlet for the coolant with respect to the cooling path 3. The switching device 20 switches a reference state, where the coolant flows in the cooling path 3 from the first port 31 toward the second port 32, and an inverse state where the coolant flows in the cooling path 3 from the second port 32 toward the first port 31.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery cooling system that cools a battery with a refrigerant flowing through a cooling path, and more particularly to a battery cooling system suitable for cooling a drive battery mounted on an electric vehicle.

Background Art

[0002] Conventionally, various methods for cooling a battery that generates heat during charging and discharging have been known. For example, Patent Document 1 discloses a method for cooling a plurality of battery cells (batteries) arranged in a stacked state with a refrigerant flowing in one direction along a cooling pipe (cooling path) in a vehicle battery system.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a cooling path in which the refrigerant flows in one direction as described in Patent Document 1, the temperature of the refrigerant tends to increase due to heat exchange with the battery as it progresses downstream. For this reason, at the outlet side (downstream side) of the cooling path, the temperature of the refrigerant is likely to be higher than that at the inlet side (upstream side) of the cooling path, and there is a risk that the cooling efficiency will decrease. If there is a large variation in the temperature of the refrigerant in the cooling path, the battery cannot be cooled uniformly, which may accelerate battery deterioration and reduce performance.

[0005] The present invention was devised in view of the above problems, and one of its objectives is to cool the battery uniformly.

Means for Solving the Problems

[0006] This invention is made to solve at least part of the above problems and can be realized as the following aspects or application examples.

[0007] (1) The battery cooling system according to this aspect is a battery cooling system that cools the battery with a refrigerant flowing through a cooling passage provided along the battery, and includes a first port that functions as either the inlet or the outlet of the refrigerant for the cooling passage, a second port that functions as the other of the inlet and the outlet, and a switching device that switches between a reference state in which the refrigerant flows through the cooling passage from the first port toward the second port and a reverse state in which the refrigerant flows through the cooling passage from the second port toward the first port. According to this aspect, since the flow direction of the refrigerant in the cooling passage is switched between the reference state and the reverse state, the upstream and downstream of the refrigerant in the cooling passage can be reversed. As a result, the temperature of the refrigerant is equalized between the upstream side and the downstream side in the flow direction of the cooling passage, so that the cooling efficiency can be equalized throughout the cooling passage. Therefore, the battery can be uniformly cooled by the refrigerant flowing through the cooling passage. As a result, high durability (deterioration suppression) and high performance of the battery can be realized. Here, the term "uniform" includes not only being strictly uniform but also meaning "substantially uniform".

[0008] (2) The battery cooling system according to this aspect further includes a first supply passage connected to the first port and capable of supplying the refrigerant to the cooling passage through the first port, a second supply passage connected to the second port and capable of supplying the refrigerant to the cooling passage through the second port, a first discharge passage connected to the first port and capable of discharging the refrigerant from the cooling passage through the first port, and a second discharge passage connected to the second port and capable of discharging the refrigerant from the cooling passage through the second port, and the switching device may switch the flow direction of the refrigerant so that the refrigerant flows through the first supply passage and the second discharge passage in the reference state and through the second supply passage and the first discharge passage in the reverse state. According to such a configuration, in the reference state, the refrigerant flows through the first supply path and the second discharge path, and in the reverse state, the refrigerant flows through the second supply path and the first discharge path, so that the flow direction of the refrigerant can be switched. In this way, if the flow path through which the refrigerant flows is selectively switched between the reference state and the reverse state, compared with the case of reversing the flow direction throughout the flow path of the refrigerant, the resistance received by the refrigerant immediately after the switching between the reference state and the reverse state can be reduced, and the responsiveness of the switching can be enhanced. Therefore, the battery can be cooled more appropriately.

[0009] (3) In the battery cooling system according to this aspect, a part of the first supply path and the first discharge path that is connected to the first port may be integrated with each other, and a part of the second supply path and the second discharge path that is connected to the second port may be integrated with each other. According to such a configuration, simplification and compactification of the refrigerant flow path can be achieved, and the inflow and outflow of the refrigerant to and from the first port and the second port can be smoothed. Therefore, the structure of the battery cooling system can be simplified and the cooling efficiency can be enhanced.

[0010] (4) The battery cooling system according to this aspect may further include a common supply path that is connected to both the first supply path and the second supply path and through which the refrigerant is supplied from the refrigerant supply source, and a common discharge path that is connected to both the first discharge path and the second discharge path and through which the refrigerant is discharged to the refrigerant discharge destination. According to such a configuration, in both the reference state and the reverse state, the refrigerant can be supplied to the common supply path and discharged from the common discharge path. Therefore, the flow direction of the refrigerant in the flow path from the refrigerant supply source and discharge destination to the battery cooling system can be made constant between the reference state and the reverse state. Thus, both the structure for supplying the refrigerant to the battery cooling system and the structure for discharging the refrigerant from the battery cooling system can be simplified.

[0011] (5) In the battery cooling system according to this aspect, the switching device includes a supply valve that opens one of the first supply path and the second supply path, and a discharge valve that opens one of the first discharge path and the second discharge path, and the reference state and the reverse state may be switched by controlling the supply valve and the discharge valve. According to such a configuration, the reference state and the reverse state can be switched by controlling the supply valve and the discharge valve. Therefore, for example, it is possible to switch between the reference state and the reverse state using a general-purpose switching valve. Thus, it contributes to reducing the product cost of the battery cooling system.

[0012] (6) In the battery cooling system according to this aspect, the battery has a cell stack in which a plurality of battery cells are stacked, and the switching device may switch the reference state and the reverse state when the temperature difference between the battery cells is greater than a preset threshold value. According to such a configuration, it is possible to make the cooling efficiency in the cooling path uniform at an appropriate timing as needed. As a result, each battery cell can be cooled more appropriately, so that the temperature can be made uniform among the battery cells. As a result, further extended life (deterioration suppression) and higher performance of the entire battery can be achieved.

[0013] (7) In the battery cooling system according to this aspect, the switching device may switch the reference state and the reverse state when the variation in the temperature of the refrigerant in the cooling path is greater than a predetermined value. According to such a configuration, it is possible to make the cooling efficiency in the cooling path uniform at an appropriate timing as needed. Thereby, the battery can be cooled more appropriately.

[0014] (8) The battery cooling system according to this aspect may further include a determination device that determines leakage of the refrigerant from the cooling path when the frequency of switching between the reference state and the reverse state by the switching device is higher than a preset frequency threshold. According to such a configuration, it is possible to detect the presence or absence of the possibility of refrigerant leakage by using the information on the frequency of switching between the reference state and the reverse state by the switching device, without separately providing a sensor or the like for detecting refrigerant leakage from the cooling passage. Therefore, while suppressing an increase in cost, the protection performance of the battery can be enhanced.

[0015] (9) In the battery cooling system according to this aspect, the battery may be a drive battery of an electric vehicle. According to such a configuration, as described above, by realizing high durability and high performance of the battery, it is possible to realize an extended cruising range and high performance of the electric vehicle.

Effects of the Invention

[0016] According to the present case, the battery can be cooled uniformly.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0018] With reference to the drawings, embodiments (aspects, application examples) of the present invention will be described. The following embodiments are merely illustrative, and are not intended to exclude various modifications and applications of technologies not explicitly shown in these embodiments. Each configuration of the following embodiments can be implemented with various modifications without departing from their gist. Also, they can be selectively adopted as necessary, or combined as appropriate.

[0019] [1. Device Configuration] [1-1. Overall Configuration] As shown in FIG. 1, a battery cooling system 1 according to this embodiment (hereinafter, also simply referred to as "cooling system 1") cools a battery 2 with a refrigerant (cooling medium) flowing through a cooling passage 3 provided along the battery 2. Here, the cooling system 1 and the battery 2 mounted on an electric vehicle 10 are exemplified.

[0020] The battery 2 is a high-voltage drive battery that stores electric power for driving the electric vehicle 10. In this embodiment, the battery 2 formed as a so-called battery pack is exemplified. As shown in FIG. 2, the battery 2 includes a cell stack 5 in which a plurality of battery cells 4 are stacked, and a casing 6 that houses components such as the cell stack 5 and cables (not shown). In this embodiment, the battery 2 having four (a plurality of) cell stacks 5 (battery modules) configured similarly to each other is exemplified. Note that in FIG. 2, only one of the battery cells 4 is labeled, and the casing 6 is shown in a simplified manner (with the lid removed).

[0021] In each cell stack 5, a plurality of battery cells 4 are arranged in the width direction DW. Also, in the battery 2, a plurality of cell stacks 5 are arranged in the length direction DL orthogonal to the width direction DW. Therefore, in the battery 2, a large number of battery cells 4 are arranged along both the width direction DW and the length direction DL. The battery 2 is mounted on the electric vehicle 10 in a posture such that both the width direction DW and the length direction DL are along the horizontal direction. The width direction DW can also be said to be the direction (stacking direction) in which a plurality of battery cells 4 are stacked in the cell stack 5.

[0022] Below, for example, the casing 6 of the battery 2 is provided with a cooling channel 3 along the battery 2 as shown in FIG. 3. The cooling channel 3 is a flow path for a refrigerant that cools each cell stack 5 (i.e., each battery cell 4, battery 2). Specifically, the cooling channel 3 is an elongated space through which the refrigerant can flow, and is formed, for example, as a hollow portion (pipe shape) formed between panels 30 stacked in the vertical direction (up and down direction). The cooling channel 3 extends on a plane (horizontal plane) along both the width direction DW and the length direction DL. Note that the cooling channel 3 may be provided along the battery 2, and may be provided, for example, above or inside the casing 6. In FIGS. 3 and FIGS. 4 to 5 described later, the refrigerant is shown colored with dots.

[0023] The schematic top view shape of the cooling channel 3 of the present embodiment is U-shaped with both the starting point and the ending point facing one side (the right side in FIG. 3) of the width direction DW. Further, the cooling channel 3 has a shape in which the portion from the starting point (the first port 31 described later) to the ending point (the second port 32 described later) of this U shape branches into a plurality of parts and then merges. Thereby, the cooling efficiency of the cooling channel 3 is improved. Furthermore, the cooling channel 3 of the present embodiment has a shape in which the half portion close to the starting point of the U shape and the half portion close to the ending point of the U shape are symmetric to each other. However, the specific shape of the cooling channel 3 may be appropriately set so as to be able to cool all the battery cells 4, and is not limited to the example of the present embodiment.

[0024] [1-2. Main component configuration] The cooling system 1 includes a first port 31 that functions as either the inlet or the outlet of the refrigerant for the cooling channel 3, and a second port 32 that functions as the other. Here, the refrigerant inlet refers to the portion (inlet port) where the refrigerant flows into the cooling channel 3, and the refrigerant outlet here refers to the portion (outlet port) where the refrigerant flows out of the cooling channel 3.

[0025] In this embodiment, an example is shown in which both the first port 31 and the second port 32 are provided on one side (the right side in FIG. 3) in the width direction DW of the battery 2. However, the arrangement of the first port 31 and the second port 32 is not limited to this. The first port 31 and the second port 32 may be provided, for example, on both sides (the left side and the right side in FIG. 3) in the width direction DW of the battery 2, may be provided on one side (the upper side or the lower side in FIG. 3) in the length direction DL of the battery 2, or may be provided on both sides (the upper side and the lower side in FIG. 3) in the length direction DL of the battery 2, respectively.

[0026] Hereinafter, a state in which the refrigerant flows through the cooling path 3 from the first port 31 toward the second port 32 is referred to as a reference state (see FIG. 4). Conversely, a state in which the refrigerant flows through the cooling path 3 from the second port 32 toward the first port 31 is referred to as a reverse state (see FIG. 5). In the reference state, the first port 31 functions as an inlet of the cooling path 3, and the second port 32 functions as an outlet of the cooling path 3. Conversely, in the reverse state, the second port 32 functions as an inlet of the cooling path 3, and the first port 31 functions as an outlet of the cooling path 3.

[0027] As shown in FIG. 1, the cooling system 1 includes a switching device 20 that switches between the reference state and the reverse state. Further, the cooling system 1 according to this embodiment further includes refrigerant passages 11 to 16 for flowing the refrigerant through the cooling path 3, and a determination device 7 that determines leakage of the refrigerant from the cooling path 3. Further, the switching device 20 of this embodiment includes a plurality of valves 21 to 24 for switching the flow state of the refrigerant in the refrigerant passages 11 to 16, and a control device 25 that controls the open / closed states of the valves 21 to 24.

[0028] The refrigerant passages 11 to 16 are provided outside the cooling passage 3 and the battery 2. The refrigerant passages 11 to 16 are roughly classified into supply passages 11 to 13 for supplying refrigerant to the cooling passage 3 and discharge passages 14 to 16 for discharging refrigerant from the cooling passage 3. The supply passages 11 to 13 are further classified into a first supply passage 11 connected to the first port 31, a second supply passage 12 connected to the second port 32, and a common supply passage 13 connected to both the first supply passage 11 and the second supply passage 12. Similarly, the discharge passages 14 to 16 are further classified into a first discharge passage 14 connected to the first port 31, a second discharge passage 15 connected to the second port 32, and a common discharge passage 16 connected to both the first discharge passage 14 and the second discharge passage 15.

[0029] Here, the refrigerant passages 11 to 16 will be described with reference to the flow direction of the refrigerant. Refrigerant is supplied to the common supply passage 13 from a refrigerant supply source (e.g., a radiator on the upstream side) not shown in the figure. Then, from the common supply passage 13, the first supply passage 11 and the second supply passage 12 branch off in a T-shape or a Y-shape. Therefore, the refrigerant supplied to the common supply passage 13 can be supplied to the first supply passage 11 and the second supply passage 12. Also, the first supply passage 11 can supply refrigerant to the cooling passage 3 through the first port 31, and the second supply passage 12 can supply refrigerant to the cooling passage 3 through the second port 32.

[0030] On the other hand, the first discharge passage 14 can discharge refrigerant from the cooling passage 3 through the first port 31, and the second discharge passage 15 can discharge refrigerant from the cooling passage 3 through the second port 32. The first discharge passage 14 and the second discharge passage 15 merge into the common discharge passage 16 in a T-shape or a Y-shape. Therefore, both the refrigerant discharged from the first port 31 to the first discharge passage 14 and the refrigerant discharged from the second port 32 to the second discharge passage 15 can flow out into the common discharge passage 16. The common discharge passage 16 discharges the refrigerant to a discharge destination (e.g., a radiator on the downstream side) not shown in the figure. Note that a cooling circuit in which the refrigerant circulates may be formed by connecting the upstream side of the common supply passage 13 and the downstream side of the common discharge passage 16 to each other.

[0031] In this embodiment, the downstream side of the first supply path 11 (a part connected to the first port 31) and the upstream side of the first discharge path 14 (a part connected to the first port 31) are made common and then connected to the first port 31. That is, a part of the first supply path 11 and the first discharge path 14 that is connected to the first port 31 is integrated with each other. Similarly, in this embodiment, the downstream side of the second supply path 12 (a part connected to the second port 32) and the upstream side of the second discharge path 15 (a part connected to the second port 32) are made common and then connected to the second port 32. That is, a part of the second supply path 12 and the second discharge path 15 that is connected to the second port 32 is integrated with each other. However, the refrigerant passages 11 to 16 are not limited to such a partially common configuration, and may be formed independently (individually) of each other entirely.

[0032] A first supply valve 21 and a second supply valve 22 that are selectively opened and closed are respectively arranged in the first supply path 11 and the second supply path 12. Similarly, a first discharge valve 23 and a second discharge valve 24 that are selectively opened and closed are respectively arranged in the first discharge path 14 and the second discharge path 15. These valves 21 to 24 allow the flow of refrigerant in the corresponding refrigerant passages 11, 12, 14, 15 in the open state and prohibit it in the closed state.

[0033] The first supply valve 21 and the second supply valve 22 are examples of supply valves that open either the first supply path 11 or the second supply path 12. The first supply valve 21 and the second supply valve 22 of this embodiment are controlled such that when one is open, the other is closed. Similarly, the first discharge valve 23 and the second discharge valve 24 are examples of discharge valves that open either the first discharge path 14 or the second discharge path 15. The first discharge valve 23 and the second discharge valve 24 of this embodiment are controlled such that when one is open, the other is closed.

[0034] Valves 21 to 24 (supply valve and discharge valve) are opened and closed in relation to each other. Specifically, as shown in FIG. 4, in the reference state, the first supply valve 21 and the second discharge valve 24 are opened, and the second supply valve 22 and the first discharge valve 23 are closed. Thereby, in the reference state, the refrigerant flows through the first supply passage 11 and the second discharge passage 15, and the flow direction of the refrigerant in the cooling passage 3 becomes the reference direction D1 from the first port 31 toward the second port 32.

[0035] On the other hand, as shown in FIG. 5, in the reverse state, the first supply valve 21 and the second discharge valve 24 are closed, and the second supply valve 22 and the first discharge valve 23 are opened. Thereby, in the reverse state, the refrigerant flows through the second supply passage 12 and the first discharge passage 14, and the flow direction of the refrigerant in the cooling passage 3 becomes the reverse direction D2 from the second port 32 toward the first port 31, which is opposite to the reference state.

[0036] Note that in both the reference state and the reverse state, the refrigerant is supplied through the common supply passage 13 and discharged from the common discharge passage 16. Thus, although the flow direction of the refrigerant in the cooling passage 3 is reversed between the reference state and the reverse state, the flow direction of the refrigerant in the common supply passage 13 and the common discharge passage 16 is made constant (unchanged).

[0037] As shown in FIG. 1, each of the control device 25 and the determination device 7 is, for example, an electronic control device configured as an LSI device or an embedded electronic device integrating a microprocessor, ROM, RAM, etc., and is mounted on the electric vehicle 10. Here, the control device 25 and the determination device 7 formed separately from each other are illustrated, but the functions of the control device 25 and the determination device 7 may be integrated in one electronic control device.

[0038] On the input side of the control device 25, a BMU8 (Battery Management Unit) that manages the battery 2 is connected. The BMU8 is connected to, for example, a temperature sensor that detects the temperature of each battery cell 4 and has information on the temperature of each battery cell 4. The information on the temperature of each battery cell 4 is transmitted from the BMU8 to the control device 25. Also, valves 21 to 24 are connected to the output side of the control device 25. On the other hand, the control device 25 is connected to the input side of the determination device 7. Also, an output device 9 such as a display or a speaker provided near the driver's seat of the electric vehicle 10 is connected to the output side of the determination device 7.

[0039] [2. Control Configuration] [2-1. Switching Device] The switching device 20 of the present embodiment switches between the reference state and the reverse state by controlling the valves 21 to 24 with the control device 25. The control device 25 controls the opening and closing states of the valves 21 to 24 based on the information transmitted from the BMU8. Specifically, when a predetermined switching condition is satisfied, the control device 25 switches the opening and closing states of each of the valves 21 to 24.

[0040] The switching condition is that the temperature difference Td between the battery cells 4 is greater than a preset threshold value Tt (Tt < Td). The temperature difference Td here refers to the maximum temperature difference Td for all the battery cells 4. The control device 25 determines whether the switching condition is met (whether Tt < Td) based on the information transmitted from the BMU8. Specifically, the control device 25 refers to the temperature information of each battery cell 4 transmitted from the BMU8, extracts the highest temperature T1 and the lowest temperature T2 from the temperatures of all the battery cells 4 included in the battery 2, and calculates their difference |T1 - T2| as the temperature difference Td. Then, the control device 25 determines whether the switching condition is met by comparing the calculated temperature difference Td with the preset and stored threshold value Tt.

[0041] The threshold value Tt is, for example, the upper limit value of the temperature difference Td allowed for the battery cell 4, and is set to a value slightly smaller than the temperature difference Td that accelerates the deterioration of the battery cell 4. The establishment of the switching condition Tt < Td means that the temperature difference between the two battery cells 4 included in the battery 2 is large enough for the deterioration of the battery cell 4 to accelerate. In the battery 2, the larger the number of the built-in battery cells 4, the greater the tendency for the temperature difference Td between the battery cells 4 to become larger. For this reason, the threshold value Tt may be set to a larger value as the number of the battery cells 4 included in the battery 2 (all the cell stacks 5) is larger, for example.

[0042] The switching condition may be that, instead of or in addition to the above Tt < Td, the variation in the temperature of the refrigerant in the cooling passage 3 is larger than a predetermined value X. The "variation in the temperature of the refrigerant in the cooling passage 3" here refers to the temperature difference Tc of the refrigerant at a plurality of locations in the cooling passage 3. For example, the control device 25 may refer to the temperatures of the refrigerant at two locations, near the first port 31 and near the second port 32 in the cooling passage 3, and determine that the switching condition is satisfied when the temperature difference Tc, which is the difference between these temperatures, is larger than the predetermined value X (X < Tc).

[0043] The predetermined value X is, for example, the upper limit value of the temperature difference Tc allowed for the refrigerant in the cooling passage 3, and is set to a value slightly smaller than the temperature difference that accelerates the deterioration of the battery cell 4. The establishment of the switching condition X < Tc means that the variation in the temperature of the refrigerant in the cooling passage 3 is large enough for the deterioration of the battery cell 4 to accelerate. Similar to the threshold value Tt, the predetermined value X may be set to a larger value as the number of the battery cells 4 included in the battery 2 (all the cell stacks 5) is larger.

[0044] When the switching condition is satisfied, the control device 25 switches between the reference state and the reverse state. The control device 25 of the present embodiment switches between the reference state and the reverse state by switching the opening / closing states of the valves 21 to 24. For example, when the switching condition is satisfied in the reference state shown in FIG. 4, the control device 25 closes the first supply valve 21 and the second discharge valve 24 and opens the second supply valve 22 and the first discharge valve 23. As a result, the opening / closing states of the valves 21 to 24 are switched from the reference state shown in FIG. 4 to the reverse state shown in FIG. 5. That is, the flow direction of the refrigerant in the cooling passage 3 is switched from the reference direction D1 to the reverse direction D2 (opposite direction).

[0045] Conversely, when the switching condition is satisfied in the reverse state shown in FIG. 5, the control device 25 opens the first supply valve 21 and the second discharge valve 24 and closes the second supply valve 22 and the first discharge valve 23. As a result, the opening / closing states of the valves 21 to 24 are switched from the reverse state shown in FIG. 5 to the reference state shown in FIG. 4. That is, the flow direction of the refrigerant in the cooling passage 3 is switched from the reverse direction D2 to the reference direction D1 (opposite direction).

[0046] [2-2. Determination device] When a predetermined warning condition is satisfied, the determination device 7 determines a refrigerant leak from the cooling passage 3 (hereinafter, also simply referred to as "refrigerant leak"). The determination device 7 determines whether the warning condition is satisfied based on the information transmitted from the control device 25. Further, when the determination device 7 of the present embodiment determines a refrigerant leak, it warns the user (for example, the driver of the electric vehicle 10) through the output device 9.

[0047] The warning condition is that the switching frequency F of the switching device 20 between the reference state and the reverse state (hereinafter, also simply referred to as "switching frequency F") is higher than a preset frequency threshold Ft (Ft < F). Here, the switching frequency F corresponds to the number of times the switching condition is satisfied per unit time. The determination device 7 of the present embodiment determines whether the warning condition is satisfied (whether Ft < F) based on the control status by the control device 25. Specifically, the determination device 7 calculates the switching frequency F by counting the number of times it is determined that the switching condition is satisfied by the control device 25 per unit time. Then, the determination device 7 determines whether the warning condition is satisfied by comparing the calculated switching frequency F with the preset and stored frequency threshold Ft.

[0048] The frequency threshold Ft is, for example, the upper limit value that the switching frequency F can take during normal times when there is no refrigerant leakage, and is set to a value slightly lower than the switching frequency F that is so high as to be considered abnormal. The establishment of the warning condition means that the temperature difference Td between the battery cells 4 is likely to increase, or the temperature of the refrigerant in the cooling path 3 is likely to vary, which means that the switching frequency F is extremely high. As a cause of this, a decrease in cooling efficiency due to refrigerant leakage (a decrease in the refrigerant flow rate in the cooling path 3) can be considered. Therefore, the establishment of the warning condition means that there is a possibility of refrigerant leakage.

[0049] When the warning condition is satisfied (Ft < F), the determination device 7 determines that there is refrigerant leakage and warns the driver of the electric vehicle 10, who is the user, that there is a possibility of refrigerant leakage. The warning by the determination device 7 may be, for example, outputting a warning display to the output device 9 which is a display, or outputting a warning sound from the output device 9 which is a speaker. By such a warning, the determination device 7 prompts the user to confirm the refrigerant leakage.

[0050] [3. Flowchart] FIG. 6 is a flowchart illustrating a control procedure implemented by the cooling system 1 (control device 25 and determination device 7). This flow is repeatedly executed, for example, while the power supply of the electric vehicle 10 is on. At the start of this flow, it is assumed that the refrigerant is flowing in the reference direction D1 in the cooling passage 3 (in the reference state). Also, during the execution of this flow, it is assumed that information on the temperature of each battery cell 4 is transmitted from the BMU 8 to the control device 25 at any time, and information on the control status by the control device 25 is transmitted to the determination device 7 at any time.

[0051] In step S1, based on the information transmitted from the BMU 8, the control device 25 determines whether the switching condition (Tt < Td) is satisfied. If the switching condition is not satisfied here, the flow returns in the reference state. Therefore, in this case, the flow direction of the refrigerant in the cooling passage 3 remains in the reference direction D1.

[0052] On the other hand, if the switching condition is satisfied in step S1, the process proceeds to step S2, and the control device 25 switches the flow direction of the refrigerant in the cooling passage 3 to the opposite direction. Specifically, in step S2, the flow direction of the refrigerant in the cooling passage 3 is switched from the reference direction D1 to the reverse direction D2 (from the reference state to the reverse state). Thus, in step S2, the reference state and the reverse state are switched. These steps S1 and S2 are processes implemented by the control device 25.

[0053] Subsequently, in step S3, the determination device 7 determines whether the warning condition (Ft < F) is satisfied. If the warning condition is not satisfied here, the flow returns in the reverse state. On the other hand, if the warning condition is satisfied in step S3, the process proceeds to step S4, the determination device 7 detects refrigerant leakage and warns the user of the possibility of refrigerant leakage, and then the flow returns in the reverse state. These steps S3 and S4 are processes implemented by the determination device 7.

[0054] Note that after the switching between the reference state and the reverse state in step S2, the flow returns through the determination process in step S3. Therefore, based on the result of the determination process in the next step S1 (determination of the success or failure of the switching condition), the switching between the reference state and the reverse state is repeated as necessary. For example, if the flow returns while in the reverse state as described above and the switching condition is satisfied again in the next step S1, the flow direction of the refrigerant in the cooling passage 3 is switched from the reverse direction D2 to the reference direction D1 (from the reverse state to the reference state) in the subsequent step S2.

[0055] However, depending on the flow rate of the refrigerant and the heat generation amount of the battery 2, it may take time for the switching between the reference state and the reverse state to affect the temperature of the refrigerant (low responsiveness of the switching). Therefore, even if there is no refrigerant leakage, the temperature difference Td between the battery cells 4 and the variation in the temperature of the refrigerant in the cooling passage 3 may not be reduced immediately after the switching between the reference state and the reverse state. For this reason, after the switching between the reference state and the reverse state in step S2, considering the above responsiveness, the re-switching between the reference state and the reverse state may not be performed for a certain period.

[0056] [4. Operations and Effects] (1) In the above cooling system 1, since the flow direction of the refrigerant in the cooling passage 3 is switched in the opposite direction between the reference state and the reverse state, the upstream and downstream of the refrigerant in the cooling passage 3 can be reversed. As a result, since the temperature of the refrigerant is equalized between the upstream side and the downstream side in the flow direction in the cooling passage 3, the cooling efficiency can be equalized throughout the cooling passage 3. Therefore, the battery 2 can be uniformly cooled by the refrigerant flowing through the cooling passage 3. As a result, it is possible to achieve an extended life (deterioration suppression) and high performance of the battery 2. Here, the term "uniform" includes not only the strict meaning of being exactly the same but also the meaning of "substantially uniform".

[0057] (2) If the above-described refrigerant passages 11 to 16 are provided, in the reference state, refrigerant flows through the first supply passage 11 and the second discharge passage 15, and in the reverse state, refrigerant flows through the second supply passage 12 and the first discharge passage 14, so that the flow direction of the refrigerant can be switched. In this way, if the flow passages through which the refrigerant flows are selectively switched between the reference state and the reverse state, compared with the case of reversing the flow direction throughout the refrigerant flow passage, the resistance that the refrigerant receives immediately after the switching between the reference state and the reverse state can be reduced, and the responsiveness of the switching can be enhanced. For this reason, the battery 2 can be cooled more appropriately.

[0058] (3) If the first supply passage 11 and the first discharge passage 14 are integrated with each other in a part where they are connected to the first port 31, the refrigerant flow passage can be simplified and made compact, and the inflow and outflow of the refrigerant to and from the first port 31 can be smoothed. Similarly, if the second supply passage 12 and the second discharge passage 15 are integrated with each other in a part where they are connected to the second port 32, the refrigerant flow passage can be simplified and made compact, and the inflow and outflow of the refrigerant to and from the second port 32 can be smoothed. Therefore, the structure of the cooling system 1 can be simplified and the cooling efficiency can be enhanced.

[0059] (4) If a common supply passage 13 connected to both the first supply passage 11 and the second supply passage 12 and a common discharge passage 16 connected to both the first discharge passage 14 and the second discharge passage 15 are provided, in both the reference state and the reverse state, the refrigerant can be supplied to the common supply passage 13 while discharging the refrigerant from the common discharge passage 16. For this reason, the flow direction of the refrigerant in the flow passage from the refrigerant supply source and discharge destination to the cooling system 1 can be made constant between the reference state and the reverse state. Therefore, both the structure for supplying the refrigerant to the cooling system 1 and the structure for discharging the refrigerant from the cooling system 1 can be simplified.

[0060] (5) If supply valves 21 and 22 that open either one of the first supply path 11 and the second supply path 12, and discharge valves 23 and 24 that open either one of the first discharge path 14 and the second discharge path 15 are provided, the reference state and the reverse state can be switched by controlling these valves 21 to 24. Therefore, for example, it is possible to switch between the reference state and the reverse state using a general-purpose switching valve. Thus, it contributes to the reduction of the product cost of the cooling system 1.

[0061] (6) If the reference state and the reverse state are switched when the temperature difference Td between the battery cells 4 is larger than the threshold value Tt, the cooling efficiency in the cooling path 3 can be equalized at an appropriate timing as needed. As a result, each battery cell 4 is cooled more appropriately, so the temperature can be equalized among the battery cells 4. Consequently, further extended life (deterioration suppression) and high performance of the entire battery 2 can be realized.

[0062] Note that since the information on the temperature of each battery cell 4 is usually possessed by an existing electronic control device (for example, BMU8), in the cooling system 1, processes such as detection and calculation of the temperature of each battery cell 4 are not required. Therefore, according to the cooling system 1 where the switching condition is Tt < Td, it is possible to determine whether the switching condition is met using known information (information on the temperature of each battery cell 4). For this reason, just by providing a structure (for example, refrigerant passages 11 to 16 and valves 21 to 24) for switching between the reference state and the reverse state, the temperature can be equalized among the battery cells 4 as described above.

[0063] (7) If the reference state and the reverse state are switched when the variation in the temperature of the refrigerant in the cooling path 3 is larger than a predetermined value X, the cooling efficiency in the cooling path 3 can be equalized at an appropriate timing as needed. Thereby, the battery 2 can be cooled more appropriately.

[0064] If it is determined that there is a refrigerant leak when the switching frequency F is higher than the frequency threshold Ft, it is possible to detect the possibility of a refrigerant leak by using the information on the switching frequency F without separately providing a sensor or the like for detecting a refrigerant leak. Therefore, the protection performance of the battery 2 can be enhanced while suppressing an increase in cost. Further, if the user is warned when it is determined that there is a refrigerant leak, the user can be prompted to confirm the refrigerant leak. Therefore, it contributes to the early detection of a refrigerant leak.

[0065] (9) If the battery 2 is a drive battery of the electric vehicle 10, as described above, by realizing the longer life and higher performance of the battery 2, it is possible to realize an extended cruising range and higher performance of the electric vehicle 10.

[0066] [5. Others] The cooling system 1 only needs to include at least the first port 31, the second port 32, and the switching device 20. That is, in the cooling system 1, the determination device 7 may be omitted, or the structure for allowing the refrigerant to flow in and out of the cooling passage 3 may be a structure other than the refrigerant passages 11 to 16 described above. According to the cooling system 1 including at least the first port 31, the second port 32, and the switching device 20, the battery 2 can be cooled uniformly as described above.

[0067] The switching device 20 only needs to be able to switch between the reference state and the reverse state, and its specific configuration is not limited to the above example. The switching device 20 may, for example, reverse the flow direction of the refrigerant by switching the rotation direction of a pump that pumps the refrigerant in a cooling circuit in which cooling is circulated, and switch between the reference state and the reverse state. In this way, the switching device 20 may switch between the reference state and the reverse state by a method other than controlling the opening and closing states of the valves 21 to 24 described above.

[0068] Further, for example, instead of the first supply valve 21 and the second supply valve 22 described above, a single valve (for example, a three-way valve) that selectively opens either the first supply passage 11 or the second supply passage 12 may be applied. Similarly, a single valve that selectively opens either the first discharge passage 14 or the second discharge passage 15 may be substituted for the first discharge valve 23 and the second discharge valve 24 described above. In these cases, the structure of the switching device 20 can be simplified compared to the above-described embodiment.

[0069] The control configuration of the control device 25 is not limited to the above example. For example, when the control device 25 can acquire information on the temperature difference Td between the battery cells 4 from the BMU 8, the process of calculating the temperature difference Td from the temperature information of each battery cell 4 may be omitted. Further, the control device 25 may switch between the reference state and the reverse state based on conditions other than the above switching conditions (Tt < Td, X < Tc).

[0070] The battery 2 may be various batteries that require cooling. For example, it may not have a plurality of battery cells 4 and a cell stack 5, or it may not be a drive battery mounted on the electric vehicle 10. That is, the cooling system 1 is applicable not only to the drive battery of the electric vehicle 10 but also to the cooling of various batteries.

[0071] [6. Supplementary Note] Regarding the above embodiments, the following supplementary notes are disclosed.

[0072] (Supplementary Note 1) A battery cooling system that cools a battery with a refrigerant flowing through a cooling passage provided along the battery, a first port that functions as either an inlet or an outlet of the refrigerant for the cooling passage, a second port that functions as the other of the inlet and the outlet, and a switching device that switches between a reference state in which the refrigerant flows through the cooling passage from the first port toward the second port and a reverse state in which the refrigerant flows through the cooling passage from the second port toward the first port. A battery cooling system characterized by the above.

[0073] (Appendix 2) A first supply path connected to the first port and capable of supplying the refrigerant to the cooling path through the first port, A second supply path connected to the second port and capable of supplying the refrigerant to the cooling path through the second port, A first discharge path connected to the first port and capable of discharging the refrigerant from the cooling path through the first port, A second discharge path connected to the second port and capable of discharging the refrigerant from the cooling path through the second port, further comprising: The switching device switches the flow direction of the refrigerant so that the refrigerant flows through the first supply path and the second discharge path in the reference state, and the refrigerant flows through the second supply path and the first discharge path in the reverse state. The battery cooling system according to Appendix 1, characterized by the above.

[0074] (Appendix 3) A part of the first supply path and the first discharge path that leads to the first port is integrated with each other. A part of the second supply path and the second discharge path that leads to the second port is integrated with each other. The battery cooling system according to Appendix 2, characterized by the above.

[0075] (Appendix 4) A common supply path connected to both the first supply path and the second supply path, through which the refrigerant is supplied from the refrigerant supply source, A common discharge path connected to both the first discharge path and the second discharge path, through which the refrigerant is discharged to the refrigerant discharge destination, further comprising: The battery cooling system according to Appendix 2 or 3, characterized by the above.

[0076] (Appendix 5) The switching device has a supply valve that opens either the first supply path or the second supply path, and a discharge valve that opens either the first discharge path or the second discharge path, and switches between the reference state and the reverse state by controlling the supply valve and the discharge valve. The battery cooling system according to any one of Appendices 2 to 4, characterized by the above.

[0077] (Appendix 6) The battery has a cell stack in which a plurality of battery cells are stacked. The switching device switches between the reference state and the reverse state when the temperature difference between the battery cells is greater than a preset threshold value. The battery cooling system according to any one of Appendices 1 to 5, characterized by the above.

[0078] (Appendix 7) The switching device switches between the reference state and the reverse state when the variation in the temperature of the refrigerant in the cooling path is greater than a predetermined value. The battery cooling system according to any one of Appendices 1 to 6, characterized by the above.

[0079] (Appendix 8) When the frequency of switching between the reference state and the reverse state by the switching device is higher than a preset frequency threshold value, the battery cooling system further includes a determination device for determining leakage of the refrigerant from the cooling path. The battery cooling system according to any one of Appendices 1 to 7, characterized by the above.

[0080] (Appendix 9) The battery is a drive battery for an electric vehicle. The battery cooling system according to any one of Appendices 1 to 8, characterized by the above.

Explanation of Reference Numerals

[0081] 1 Cooling system (battery cooling system) 2 Battery 3 Cooling path 4 battery cells 5 cell stacks 6 casings 7 determination devices 8 BMU 9 output devices 10 electric vehicles 11 first supply path (refrigerant path) 12 second supply path (refrigerant path) 13 common supply path (refrigerant path) 14 first discharge path (refrigerant path) 15 second discharge path (refrigerant path) 16 common discharge path (refrigerant path) 20 switching devices 21 first supply valve (supply valve) 22 second supply valve (supply valve) 23 first discharge valve (discharge valve) 24 second discharge valve (discharge valve) 25 control devices 30 panels 31 first ports 32 second ports D1 reference direction D2 reverse direction DL length direction DW width direction F switching frequency Ft frequency threshold T1 maximum temperature T2 minimum temperature Tc temperature difference of refrigerant Td temperature difference between battery cells Tt threshold X predetermined value

Claims

1. A battery cooling system for cooling a battery with a refrigerant flowing through a cooling path provided along the battery, a first port that functions as either an inlet or an outlet of the refrigerant for the cooling path, a second port that functions as the other of the inlet and the outlet, and a switching device that switches between a reference state in which the refrigerant flows through the cooling path from the first port to the second port and a reverse state in which the refrigerant flows through the cooling path from the second port to the first port. A battery cooling system characterized by the above.

2. A first supply path connected to the first port and capable of supplying the refrigerant to the cooling path through the first port, A second supply path connected to the second port and capable of supplying the refrigerant to the cooling path through the second port, A first discharge path connected to the first port and capable of discharging the refrigerant from the cooling path through the first port, A second discharge path connected to the second port and capable of discharging the refrigerant from the cooling path through the second port, further comprising The switching device switches the flow direction of the refrigerant so that the refrigerant flows through the first supply path and the second discharge path in the reference state, and the refrigerant flows through the second supply path and the first discharge path in the reverse state. The battery cooling system according to claim 1, characterized by the above.

3. A part of the first supply path and the first discharge path that connect to the first port are integrated with each other, A part of the second supply path and the second discharge path that connect to the second port are integrated with each other. The battery cooling system according to claim 2, characterized by the above.

4. A common supply path connected to both the first supply path and the second supply path, through which the refrigerant is supplied from a refrigerant supply source, Further comprising a common discharge path connected to both the first discharge path and the second discharge path, and discharging the refrigerant to the discharge destination of the refrigerant. The battery cooling system according to claim 2, characterized in that.

5. The switching device has a supply valve that opens either one of the first supply path and the second supply path, and a discharge valve that opens either one of the first discharge path and the second discharge path, and switches between the reference state and the reverse state by controlling the supply valve and the discharge valve. The battery cooling system according to claim 2, characterized in that.

6. The battery has a cell stack in which a plurality of battery cells are stacked. The switching device switches between the reference state and the reverse state when the temperature difference between the battery cells is greater than a preset threshold value. The battery cooling system according to claim 1, characterized in that.

7. The switching device switches between the reference state and the reverse state when the variation in the temperature of the refrigerant in the cooling path is greater than a predetermined value. The battery cooling system according to claim 1, characterized in that.

8. Further comprising a determination device for determining leakage of the refrigerant from the cooling path when the frequency of switching between the reference state and the reverse state by the switching device is higher than a preset frequency threshold. The battery cooling system according to claim 1, characterized in that.

9. The battery is a drive battery for an electric vehicle. The battery cooling system according to claim 1, characterized in that.

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