Cooling system

Abstract

Provided is a cooling system that circulates a CO2-containing refrigerant and cools a battery or the like in a vehicle, wherein the cooling capacity of the battery is ensured while suppressing a decrease in the overall efficiency of the system. A cooling system (100) is provided with: a compressor (1) that compresses a refrigerant; a heat exchanger (2) for cooling the refrigerant from the compressor (1); heat exchangers (5a, 6a) that use the refrigerant cooled by the heat exchanger (2); a refrigerant passage (17) for supplying the refrigerant from the heat exchanger (2) to the battery (6) and returning the refrigerant to the compressor (1); an expansion valve (E2) provided in the refrigerant passage (17) on the upstream side of the battery (6); the control device (80) maintains the opening degree of the expansion valve (E2) constant when the battery temperature is within the first region (R1), increases the opening degree of the expansion valve (E2) as the battery temperature increases when the battery temperature is within the second region (R2), and maintains the opening degree of the expansion valve (E2) at a large opening degree when the battery temperature is within the third region (R3).

Description

TECHNICAL FIELD

[0001] The present application relates to a cooling system that circulates a refrigerant containing CO2 and cools the inside of a vehicle. BACKGROUND

[0002] Conventionally, in a refrigeration cycle used for air conditioning, a system that circulates a refrigerant by a compressor, a heat exchanger, and the like is used. In recent years, such a system that circulates a refrigerant is also used to cool constituent elements in the inside of a vehicle, for example, to cool a battery of an electric vehicle or a hybrid vehicle. As one example, in Patent Literature 1, a system is described in which a compressor, a first heat exchanger, and a second heat exchanger are connected by a refrigerant flow path, and the second heat exchanger is used to exchange heat between a refrigerant and an electric core, thereby cooling or heating the electric core.

[0003]

Prior Art Literature

Patent Literature

Patent Literature 1

[0004]

Problem to be Solved by the Invention

[0005] In a cooling system that cools a battery with a refrigerant, to improve the cooling capacity of the refrigerant to the battery, it is preferable to secure the amount of refrigerant supplied to the battery. For example, when the battery is externally charged, particularly when the charging rate is high, it is necessary to firmly secure the cooling capacity of the battery to suppress heating of the battery. However, if the amount of refrigerant supplied to the battery is increased, the efficiency of the entire system (i.e., the refrigeration cycle efficiency) will decrease.

[0006] The present application is to solve the problems of the above-described prior art, and aims to suppress a decrease in the efficiency of the entire system while securing the cooling capacity of a refrigerant to a battery in a cooling system that circulates a refrigerant containing CO2 and cools a battery or the like in the inside of a vehicle.

[0007]

Means of Solving the Problem

[0008] According to the above-described aspect of the present application, the air conditioning of the vehicle and the cooling of the battery can be appropriately achieved using one system (cooling system) that circulates the refrigerant. Furthermore, according to the present application, when the battery is externally charged, the expansion valve is maintained at a small opening degree when the battery temperature is in the first region, that is, when the battery temperature is low, and the efficiency of the entire system in the cooling system can be ensured by suppressing the flow rate of the refrigerant supplied from the refrigerant passage to the battery. When the battery temperature is in the second region, that is, when the battery temperature is high, according to the present application, the opening degree of the expansion valve is increased in accordance with the battery temperature, and the cooling capacity for the battery can be ensured by increasing the flow rate of the refrigerant supplied from the refrigerant passage to the battery. Furthermore, when the battery temperature is in the third region, that is, when the battery temperature is higher (when the battery temperature is high at a high charging rate), according to the present application, the opening degree of the expansion valve is maintained at a large opening degree, and thus the cooling capacity for the battery can be effectively ensured. Therefore, the present application can ensure the cooling capacity of the refrigerant for the battery while suppressing a decrease in the efficiency of the entire system when the battery is externally charged.

[0009] In the present application, it is preferable that the larger the C rate of the charging of the battery, the more the control device reduces the first region and increases the third region, and the more the control device increases the rate of change of the opening degree of the expansion valve with respect to the battery temperature in the second region.

[0010] According to the above-described aspect of the present application, when the battery temperature tends to increase and the C rate is large, the flow rate of the refrigerant supplied from the refrigerant passage to the battery can be increased, and thus the cooling capacity of the battery can be effectively ensured.

[0011] In the present application, when the refrigerant passage is the first refrigerant passage and the expansion valve is the first expansion valve, it is preferable that the cooling system further include: a second refrigerant passage for supplying refrigerant, which has been cooled at a second heat exchanger, to the compressor without passing through the first refrigerant passage; and a second expansion valve provided in the second refrigerant passage for expanding the refrigerant, wherein the control device increases the opening degree of the second expansion valve as the opening degree of the first expansion valve increases.

[0012] According to the above-described aspect of the present application, the flow rate of the refrigerant supplied from the second refrigerant passage to the compressor via the second expansion valve increases as the flow rate of the refrigerant supplied from the first refrigerant passage to the compressor via the first expansion valve increases, thereby suppressing the increase in the temperature of the refrigerant discharged from the compressor. As a result, it is possible to, for example, prevent the oil in the refrigerant from deteriorating in function or degrading.

[0013] In the present application, it is preferable that the control device limit the opening degree of the expansion valve to be below a prescribed limit opening degree so that the temperature of the refrigerant discharged from the compressor is below a prescribed temperature.

[0014] According to the above-described aspect of the present application, it is possible to limit the opening degree of the expansion valve to be below the limit opening degree, thereby suppressing the opening degree of the expansion valve from becoming excessively large and causing the temperature of the refrigerant discharged from the compressor to be high.

[0015] In the present application, it is preferable that the control device control the expansion valve in accordance with the temperature of the battery when the battery is charged at a C rate of a prescribed C rate or more.

[0016] According to the above-described aspect of the present application, it is possible to perform the above-described control of the expansion valve when the temperature of the battery tends to increase and the C rate is large.

[0017] In the present application, it is preferable that the cooling system further include a battery heat exchanger for causing the refrigerant in the refrigerant passage to flow around a plurality of battery cells in the battery, directly cooling the plurality of battery cells with the refrigerant, and that the refrigerant reduced in pressure by the expansion valve be supplied to the battery heat exchanger.

[0018] According to the above-described aspect of the present application, since the refrigerant directly cools the plurality of battery cells at the battery heat exchanger, it is possible to efficiently cool the plurality of battery cells. At this time, since the pressure resistance of the battery pack and the like is low, it is not desirable to directly supply high-pressure refrigerant from the compressor to the battery heat exchanger, and therefore, in the present application, the refrigerant from the compressor is reduced in pressure by the expansion valve and then supplied to the battery heat exchanger. This makes it possible to reliably protect the inside of the battery (the plurality of battery cells and the like).

[0019] In the present application, it is preferable that the second heat exchanger include an air conditioning heat exchanger for air conditioning of the vehicle, and further include a battery heat exchanger for supplying refrigerant outside a battery pack containing a plurality of battery cells at the battery and indirectly cooling the plurality of battery cells with the refrigerant.

[0020] According to the aspect of the present application described above, the battery can be appropriately cooled by using, for example, a battery heat exchanger that supplies refrigerant outside a battery pack, and a large heat exchange with the refrigerant can be achieved.

[0021] In the present application, it is preferable that the first heat exchanger be a cascade heat exchanger that performs heat exchange between a first heat cycle circuit and a second heat cycle circuit, wherein the first heat cycle circuit includes at least a compressor, a second heat exchanger, a refrigerant passage, and an expansion valve, and the second heat cycle circuit separately from the first heat cycle circuit includes an ambient air heat exchanger that performs heat exchange with ambient air.

[0022] According to the aspect of the present application described above, the second heat cycle circuit that performs heat exchange with ambient air performs heat exchange (cascade heat exchange) with the first heat cycle circuit, and thus the efficiency of the system as a whole of the first heat cycle circuit can be improved, in other words, the work of the compressor in the first heat cycle circuit can be reduced.

[0023] Further, in the present application, it is preferable that the cooling system further cool an electric motor of a vehicle driven by the electric power of the battery using the refrigerant cooled by the first heat exchanger.

[0024] According to the aspect of the present application described above, various constituent elements in the vehicle such as an electric motor and the like can be appropriately cooled using one system (cooling system) of circulating refrigerant.

[0025]

Effects of Invention

[0026] Figure 1 A schematic configuration view of a vehicle to which a cooling system according to an embodiment of the present application is applied; Figure 2 A schematic configuration view of a cooling system according to an embodiment of the present application; Figure 3 Figure 3 (a) and Figure 3 (b) are schematic configuration views of a first battery heat exchanger and a second battery heat exchanger, respectively, according to an embodiment of the present application; Figure 4 ​This is a block diagram of the electrical configuration of the cooling system according to an embodiment of the present invention; Figure 5 of Figure 5 (a) and Figure 5 (b) are the control of E2 opening degree and E3 opening degree respectively during stable driving or low-speed charging in the embodiments of the present invention; Figure 6 of Figure 6 (a) and Figure 6 (b) are the controls on E2 opening degree and E3 opening degree respectively performed during fast charging in the embodiments of the present invention; Figure 7 of Figure 7 (a) and Figure 7 (b) These are the controls on the E2 and E3 opening degrees respectively, performed when the battery overheats abnormally in an embodiment of the present invention. Detailed Implementation

[0027] The cooling system according to the embodiments of the present invention will be described below with reference to the accompanying drawings.

[0028] [Overall Structure] First refer to Figure 1 This describes the overall structure of the cooling system involved in this embodiment. Figure 1 This is a general structural diagram of a vehicle that utilizes the cooling system described in this embodiment.

[0029] like Figure 1 As shown, vehicle 200 is, for example, an electric vehicle with a cooling system 100 that circulates refrigerant through a refrigeration cycle. The cooling system 100 mainly includes: a compressor 1 for compressing the refrigerant; a heat exchanger 2 for cooling the refrigerant compressed by the compressor 1; a motor 4 for generating power to drive vehicle 200; an air conditioner 5 for conditioning the air inside vehicle 200; and a battery 6 for supplying power to drive motor 4.

[0030] Cooling system 100 circulates CO2 refrigerant (hereinafter sometimes simply referred to as "refrigerant") as a natural refrigerant. Typically, CO2 refrigerant is a CO2 containing refrigeration oils (oils) or additives such as PAG. Using this CO2 refrigerant allows compressor 1 to compress the refrigerant to very high pressures. The refrigerant compressed in this way by compressor 1 (liquid refrigerant, typically in supercritical states) is used by motor 4 for cooling the rotor and stator. Furthermore, motor 4 also uses refrigerant 1 to lubricate the sliding bearings supporting the rotating shaft. In addition, the refrigerant compressed by compressor 1 is used for air conditioning 5 and cooling of battery 6. For example, cooling system 100 supplies high-temperature, high-pressure gaseous refrigerant from compressor 1 to heat exchanger 2, low-temperature, high-pressure liquid refrigerant from heat exchanger 2 to motor 4, etc., and room-temperature, low-pressure gaseous refrigerant from motor 4, etc., to compressor 1.

[0031] [Structure of the cooling system] Next, refer to Figure 2 This embodiment describes the cooling system 100 in detail. Figure 2 This is a general structural diagram of the cooling system 100 involved in this embodiment.

[0032] like Figure 2 As shown, the cooling system 100 implements a cascade refrigeration cycle, which includes: a first thermal cycle loop (low-temperature loop) 100a, which circulates the aforementioned CO2 refrigerant; and a second thermal cycle loop (high-temperature loop) 100b, which includes an outside air heat exchanger 30 for heat exchange with the outside air, and circulates refrigerants such as propane and fluorinated refrigerants. Specifically, the first thermal cycle loop 100a and the second thermal cycle loop 100b perform cascade heat exchange at the heat exchanger 2 (hereinafter referred to as "cascade heat exchanger 2" as appropriate). This cascade heat exchanger 2 is equivalent to the "first heat exchanger" in this invention.

[0033] In addition to the compressor 1 and motor 4, the first thermal circulation loop 100a of the cooling system 100 mainly includes an air conditioning heat exchanger 5a (specifically, an evaporator that generates and supplies cold air to the vehicle interior) for heat exchange at the air conditioning 5; a first battery heat exchanger 6a and a second battery heat exchanger 6b for heat exchange to cool the battery 6; refrigerant passages 11-20 for refrigerant flow; a pump 23 for pumping refrigerant; flow regulating valves V1, V2, and V3 for regulating the refrigerant flow rate; and expansion valves E1, E2, and E3 for expanding and depressurizing the refrigerant.

[0034] In this embodiment, the compressor 1 has a first compressor 1a on the upstream side and a second compressor 1b on the downstream side, and the compressor 1 performs two-stage compression on the refrigerant. The first compressor 1a increases the pressure of the refrigerant P3 to pressure P2 (pressure P2 > pressure P3), and the second compressor 1b increases the pressure of the refrigerant P2 to pressure P1 (pressure P1 > pressure P2). As an example, pressure P1 is about 3 MPa, pressure P2 is about 1.5 MPa, and pressure P3 is about 0.1 MPa.

[0035] Furthermore, in this embodiment, the battery 6 is cooled by two heat exchangers, namely the first battery heat exchanger 6a and the second battery heat exchanger 6b. (Refer to the following...) Figure 3 (a) and Figure 3 (b) The structure of the first battery heat exchanger 6a and the second battery heat exchanger 6b is described. Figure 3 (a) and Figure 3 (b) Examples of the first battery heat exchanger 6a and the second battery heat exchanger 6b are shown in general terms. More specifically, Figure 3 (a) is a top view of the battery pack 61 of battery 6 from the outside. Figure 3 (b) is a top view obtained by looking through the inside of the battery pack 61.

[0036] like Figure 3 As shown in (a), the first battery heat exchanger 6a supplies refrigerant at the battery 6 to the outside of the battery pack 61 containing several battery cells 62 (typically to the surface of the casing), and more specifically, causes the refrigerant to flow in a serpentine flow path 63, thereby indirectly cooling the several battery cells 62 inside the battery 6 with refrigerant. Various known methods for indirectly cooling the battery cells 62 inside the battery 6 with refrigerant can also be used here, and are not limited to these methods. Figure 3 The scheme shown in (a). Conversely, as... Figure 3 As shown in (b), the second battery heat exchanger 6b allows refrigerant to flow around the plurality of cells 62 within the battery 6, so that even if the refrigerant flows into the interior of the battery pack 61, the plurality of cells 62 are directly cooled by the refrigerant. Furthermore, the aforementioned first battery heat exchanger 6a and the aforementioned air conditioning heat exchanger 5a are equivalent to the "second heat exchanger" in this invention. In the above case, the air conditioning heat exchanger 5a cools the evaporator (the object being cooled) of the air conditioner 5 with refrigerant, and the first battery heat exchanger 6a cools the battery 6 (the object being cooled) with refrigerant.

[0037] Return below Figure 2The flow of refrigerant within the first thermal cycle loop 100a will be explained in detail below. The refrigerant, compressed by the compressor 1, is supplied from refrigerant channel 11 to the cascade heat exchanger 2. After being cooled by the cascade heat exchanger 2, the refrigerant is supplied from refrigerant channel 12 (connected to refrigerant channel 11) to the air conditioning heat exchanger 5a, from refrigerant channel 13 (connected to refrigerant channel 11) to the first battery heat exchanger 6a, and from refrigerant channel 15 (connected to refrigerant channel 11) to the motor 4. Refrigerant channels 12 and 13 converge at point C1 and connect to refrigerant channel 16, thereby supplying the refrigerant that has undergone heat exchange in the air conditioning heat exchanger 5a and the first battery heat exchanger 6a to refrigerant channel 16. Furthermore, the refrigerant cooled by the cascade heat exchanger 2 can be directly supplied to the refrigerant channel 16 via the refrigerant channel 14 connected to the refrigerant channel 11, bypassing the air conditioning heat exchanger 5a and the first battery heat exchanger 6a (i.e., bypassing refrigerant channels 12, 13, and 15). At this time, the refrigerant channel 14 and the refrigerant channel 16 merge at a point C2 downstream of the aforementioned confluence point C1. In addition, refrigerant channels 12, 13, and 14 are respectively equipped with flow regulating valves V1, V2, and V3 for regulating the flow rate of the refrigerant through each channel, and refrigerant channel 15 is equipped with an expansion valve E1 for expanding the refrigerant supplied to the motor 4. The function of the expansion valve E1 is to reduce the pressure of the refrigerant from P1 to P2.

[0038] Furthermore, refrigerant passage 16 is connected to refrigerant passage 17, and the refrigerant in refrigerant passage 16 is supplied to the second battery heat exchanger 6b through refrigerant passage 17. In refrigerant passage 17, an expansion valve E2 for expanding the refrigerant is provided upstream of the second battery heat exchanger 6b, thereby supplying the refrigerant to the second battery heat exchanger 6b after pressure reduction via expansion valve E2. The function of expansion valve E2 is to reduce the pressure of the refrigerant from P1 to P3. Furthermore, in refrigerant passage 17, an internal heat exchanger (IHX: Internal Heat Exchanger) 6c with a known double-tube structure is provided downstream of the second battery heat exchanger 6b, and a first compressor 1a of compressor 1 is connected further downstream of the second battery heat exchanger 6b. The refrigerant at pressure P3 after pressure reduction via expansion valve E2 is supplied to the first compressor 1a.

[0039] Furthermore, refrigerant passage 16 branches into refrigerant passage 18 and refrigerant passage 20 downstream of its connection with refrigerant passage 17. Refrigerant passage 18 is equipped with an expansion valve E3 for expanding the refrigerant. The function of expansion valve E3 is to reduce the pressure of the refrigerant from P1 to P2. Additionally, refrigerant passage 18 merges with refrigerant passage 15, which is equipped with the aforementioned motor 4, at a junction C3 located downstream of expansion valve E3. Refrigerant passages 15 and 18 connect to refrigerant passage 19. Refrigerant passage 19 connects between the first compressor 1a and the second compressor 1b of compressor 1, supplying refrigerant at pressure P2 after being reduced by expansion valves E1 and E3 to the second compressor 1b. Refrigerant passage 20 connects with refrigerant passage 11 between compressor 1 and cascade heat exchanger 2 at a junction C4 downstream of refrigerant passage 20. Refrigerant passage 20 is equipped with a pump 23 and an internal heat exchanger (IHX) 24 having a known double-tube structure. Such a refrigerant passage 20 allows refrigerant from the aforementioned refrigerant passage 16 to be supplied to the cascade heat exchanger 2 via pump 23 without passing through compressor 1 (i.e. bypassing compressor 1).

[0040] Furthermore, refrigerant passage 17 corresponds to the "first refrigerant passage" in this invention, and refrigerant passages 18 and 19 correspond to the "second refrigerant passage" in this invention. Additionally, expansion valve E2 corresponds to the "first expansion valve" in this invention, and expansion valve E3 corresponds to the "second expansion valve" in this invention.

[0041] Next, the second thermal circulation loop 100b of the cooling system 100 is a high-temperature loop that circulates refrigerants such as propane and fluorinated refrigerants, as described above. In addition to an outside air heat exchanger 30 for heat exchange with the outside air, it also includes a refrigerant passage 31 for refrigerant flow, a pump 32 for pumping refrigerant, and an expansion valve 33 for expanding the refrigerant. In the cooling system 100 of this embodiment, this second thermal circulation loop 100b is provided separately from the first thermal circulation loop 100a, thereby improving the overall system efficiency of the first thermal circulation loop 100a, in other words, reducing the work done by the compressor 1.

[0042] The following will refer to Figure 2 as well as Figure 4 The electrical configuration of the cooling system 100 involved in this embodiment is described. Figure 4 This is a block diagram of the electrical configuration of the cooling system 100 according to this embodiment.

[0043] like Figure 4As shown, the cooling system 100 has a control device 80, which performs various controls within the system. The control device 80 is composed of a computer, which has one or more processors 80a (typically a CPU), and memory 80b that stores various programs interpreted and executed by the processor 80a (including basic control programs such as the OS, and application programs that start on the OS and implement specific functions) and various data such as ROM and RAM.

[0044] The cooling system 100 includes refrigerant temperature sensors 41, 42, 43, and 44 for detecting refrigerant temperature and refrigerant pressure sensors 51, 52, and 53 for detecting refrigerant pressure (see reference). Figure 2 ), a cabin temperature sensor 71 for detecting the cabin temperature, a battery temperature sensor 72 for detecting the temperature of the battery 6 (hereinafter referred to as "battery temperature"), and a motor temperature sensor 73 for detecting the temperature of the motor 4. Specifically, such as Figure 2 As shown, refrigerant temperature sensor 41 is located on refrigerant channel 11 between compressor 1 and cascade heat exchanger 2 (specifically, upstream of the junction point C4 of refrigerant channel 11 and refrigerant channel 20). Refrigerant temperature sensor 42 is located at the junction point C2 of refrigerant channel 14 and refrigerant channel 16. Refrigerant temperature sensor 43 is located at the junction point C3 of refrigerant channel 15 and refrigerant channel 18. Refrigerant temperature sensor 44 is located on refrigerant channel 17 downstream of the second battery heat exchanger 6b and IHX6c. Furthermore, refrigerant pressure sensor 51 is located on refrigerant channel 11 downstream of cascade heat exchanger 2, refrigerant pressure sensor 52 is located on refrigerant channel 15 downstream of motor 4, and refrigerant pressure sensor 53 is located on refrigerant channel 17 downstream of the second battery heat exchanger 6b and IHX6c.

[0045] The control device 80 provides control signals to and controls the compressor 1, flow regulating valves V1, V2, V3, and expansion valves E1, E2, and E3 based on the detection signals from the aforementioned sensors 41-44, 51-53, and 71-73. Specifically, in this embodiment, when the battery 6 is externally charged, the control device 80 controls the opening degree of expansion valves E2 and E3 (hereinafter referred to as "E2 opening degree" and "E3 opening degree") based on the battery temperature detected by the battery temperature sensor 72, in order to ensure the cooling capacity of the refrigerant for the battery 6 while suppressing the decrease in efficiency of the cooling system 100 (especially the first thermal cycle loop 100a) (details described later).

[0046] [Control Methods] The following describes the control performed by the control device 80 in this embodiment. First, the basic concepts of control involved in this embodiment will be explained.

[0047] The balance between the efficiency (COP) and cooling capacity of the cooling system 100 varies depending on various factors, such as the driving conditions of the vehicle 200, whether cooling is used while the vehicle 200 is in motion, and the charging speed of the battery 6 (low-speed charging, fast charging). Therefore, to improve the driving range of the vehicle 200 and shorten the charging time of the battery 6, it is preferable to adjust the balance between cooling capacity and efficiency by considering factors such as those described above.

[0048] In the cooling system 100 of this embodiment, the temperature of the refrigerant discharged from the compressor 1 (hereinafter appropriately referred to as "compressor discharge temperature"), the overall cooling capacity of the system, and the overall efficiency of the system vary depending on the balance between the proportion of refrigerant supplied to the compressor 1 (first compressor 1a) from the junction point C2 via the refrigerant passage 17, expansion valve E2, and the second battery heat exchanger 6b (hereinafter referred to as "first refrigerant proportion") and the proportion of refrigerant supplied to the compressor 1 (second compressor 1b) from the junction point C2 via the refrigerant passage 18, expansion valve E3, junction point C3, and refrigerant passage 19 (hereinafter referred to as "second refrigerant proportion"). In this case, the first and second refrigerant proportions are adjusted by the expansion valve E2 on the refrigerant passage 17 and the expansion valve E3 on the refrigerant passage 18, respectively. Basically, the following tendencies exist: a higher proportion of refrigerant 1 results in a higher compressor discharge temperature, while a higher proportion of refrigerant 2 results in a lower compressor discharge temperature; a higher proportion of refrigerant 1 results in a higher overall cooling capacity of the system; a higher proportion of refrigerant 1 results in a lower overall system efficiency, and a higher proportion of refrigerant 2 results in a lower overall system efficiency.

[0049] As an example, when vehicle 200 is in motion, to extend the driving range, control device 80 controls expansion valves E2 and E3 to keep the proportions of the first and second refrigerants relatively low, thereby suppressing cooling capacity and ensuring efficiency. As another example, when battery 6 is externally charged, to complete charging in a short time, control device 80 controls expansion valves E2 and E3 to set the proportions of the first and second refrigerants to a moderate level, thereby improving cooling capacity, limiting the compressor discharge temperature below a specified temperature (e.g., below 180°C), and limiting efficiency above a specified value (e.g., above 1).

[0050] The following will explain the specific control performed by the control device 80 on the expansion valves E2 and E3 in this embodiment.

[0051] (Control during stable driving or low-speed charging) First refer toFigure 5 (a) and (b) illustrate the control performed in this embodiment during stable driving or during low-speed charging. Figure 5 (a) illustrates the control of the E2 opening (vertical axis) based on battery temperature (horizontal axis). Figure 5 (b) illustrates the control of the E3 opening (vertical axis) based on the E2 opening (horizontal axis). The above... Figure 5 (a) and (b) are equivalent to control diagrams for E2 opening and E3 opening when driving steadily or charging at low speed.

[0052] In this embodiment, the control device 80 will perform the following actions when the vehicle 200 is driving stably or when the battery 6 is undergoing low-speed charging (referring to external charging, the same below): Figure 5 The control is shown in (a) and (b). Stable driving refers, for example, when the vehicle's acceleration / deceleration (absolute value) is less than the specified value, while low-speed charging refers, for example, when the battery 6 is charged at a rate less than the specified C-rate (e.g., 1C). During stable driving or low-speed charging as described above, the battery 6 will generate heat steadily (approximately 0.4kW). Furthermore, the C-rate refers to the charging speed of the battery 6, which is basically defined as the ratio of the charging current value to the battery capacity.

[0053] Specifically, such as Figure 5 As shown in (a), during stable driving or low-speed charging, the control device 80 maintains the E2 opening at 0 (fully closed) when the battery temperature is in the first region R1 on the low-temperature side. Therefore, when the battery temperature is relatively low, the overall system efficiency can be ensured by suppressing the proportion of the first refrigerant. Furthermore, the first region R1 is equivalent to a range where the battery temperature of the battery 6 (cell 62) can be sufficiently cooled by using the first battery heat exchanger 6a to indirectly cool the cell 62 without directly cooling it with the second battery heat exchanger 6b. In addition, when the control device 80 sets the E2 opening to 0 (fully closed) as described above, it also sets the E3 opening to 0 (fully closed). Figure 5 (b) Therefore, the overall system efficiency can be effectively ensured by also suppressing the proportion of the second refrigerant.

[0054] On the other hand, such as Figure 5As shown in (a), when the battery temperature is in the second region R2, which is higher than the temperature of the first region R1, the control device 80 linearly increases the E2 opening degree as the battery temperature rises. This increases the proportion of the first refrigerant, thereby ensuring the refrigerant's cooling capacity for the battery 6. More specifically, when the control device 80 increases the E2 opening degree according to the battery temperature as described above, it limits the E2 opening degree to below a predetermined limit opening degree Lim1. That is, it increases the E2 opening degree within a range below the limit opening degree Lim1 to keep the compressor discharge temperature below a predetermined temperature (e.g., 180°C). Here, the predetermined compressor discharge temperature is set based on the following condition: when the refrigerant temperature exceeds this predetermined temperature, the oil in the refrigerant will not function, the sliding surface will seizure, the sealing performance will decrease, and the oil will degrade. Furthermore, the limit opening degree Lim1 is set in advance based on a predetermined temperature similar to this.

[0055] Furthermore, when the control device 80 controls the E2 opening as described above during stable driving or low-speed charging, such as... Figure 5 As shown in (b), as the E2 opening increases, the control device 80 also linearly increases the E3 opening. Therefore, as the proportion of the first refrigerant increases, the proportion of the second refrigerant also increases, thereby suppressing the rise in compressor discharge temperature.

[0056] Furthermore, the reason why increasing the proportion of the second refrigerant (i.e., increasing the amount of refrigerant supplied to compressor 1 via refrigerant channels 18 and 19) as described above can suppress the rise in compressor discharge temperature is as follows. In this embodiment, compressor 1 pressurizes the refrigerant in two stages through the first and second compressors 1a and 1b. The upstream first compressor 1a is supplied with refrigerant that has been depressurized by expansion valve E2, and the mixed refrigerant discharged to the first compressor 1a, combined with a refrigerant in a relatively low enthalpy state (i.e., a refrigerant with a lower enthalpy than the refrigerant pressurized by the first compressor) after being depressurized by expansion valve E3, is supplied to the downstream second compressor 1b. This suppresses the refrigerant pressurized by the second compressor 1b from being at a high temperature, thereby suppressing the rise in compressor discharge temperature.

[0057] (Control during fast charging) The following will refer to Figure 6 (a) and (b) illustrate the control performed during fast charging in this embodiment. Figure 6 (a) illustrates the control of the E2 opening (vertical axis) based on battery temperature (horizontal axis). Figure 6 (b) illustrates the control of the E3 opening (vertical axis) based on the E2 opening (horizontal axis). Figure 6 (a) and Figure 6(b) Control diagrams for E2 and E3 openings applicable during fast charging.

[0058] In this embodiment, the control device 80 performs [operation] during the fast charging of the battery 6. Figure 6 The controls shown in (a) and (b) refer to the control methods used during fast charging, for example, when battery 6 is charged at a rate greater than a specified C rate (e.g., 2C, 3C, 4C). During fast charging, the heat generated inside the cell 62 of battery 6 is greater than the heat dissipated from the end face of cell 62. Therefore, during fast charging, in order to suppress the local temperature rise of battery 6, it is more necessary to directly cool cell 62 than during slow charging.

[0059] Specifically, in Figure 6 In (a), number G1 indicates the graph used during stable driving as described above or during low-speed charging (as opposed to...). Figure 5 (a) are the same), while G2 and G3 indicate the charts used during fast charging. Specifically, chart G3 is used when charging at a C-rate greater than chart G2. For example, chart G2 is used when the C-rate is 3C, while chart G3 is used when the C-rate is 4C.

[0060] As shown in Figures G2 and G3, during fast charging, when the battery temperature is in the first region R1 (low temperature side), the control device 80 maintains the E2 opening at 0 (fully closed). When the battery temperature is in the second region R2 (higher than the first region R1), the control device 80 linearly increases the E2 opening as the battery temperature rises. When the battery temperature is in the third region R3 (higher than the second region R2), the control device 80 maintains the E2 opening at its maximum opening, Lim1. Specifically, the higher the C-rate during charging, the smaller the first region R1 (R13 < R12 < R11) and the larger the third region R3 (R33 > R32) the control device 80 becomes, and the greater the rate of change (increase rate) of the E2 opening relative to the battery temperature in the second region R2. Therefore, when the C-rate during charging of battery 6 is high, increasing the proportion of the first refrigerant can improve the cooling capacity of the refrigerant on battery 6, specifically, it can effectively cool the battery cell 62.

[0061] Furthermore, when the control device 80 controls the E2 opening degree as described above during fast charging, such as... Figure 6 As shown in (b), as the E2 opening increases, the control device 80 also linearly increases the E3 opening. Therefore, by increasing the proportion of the second refrigerant in accordance with the increase in the proportion of the first refrigerant, the rise in compressor discharge temperature can be suppressed. The reason for suppressing the rise in compressor discharge temperature in this way is explained above.

[0062] (Control when the battery overheats abnormally) Next refer to Figure 7 (a) and (b) illustrate the control measures taken when the battery 6 overheats abnormally in this embodiment. Figure 7 (a) illustrates the control of E2 opening degree (vertical axis) based on battery temperature (horizontal axis). Figure 7 (b) shows the control of E3 opening (vertical axis) based on E2 opening (horizontal axis).

[0063] In this embodiment, the control device 80 performs the following actions when the battery 6 abnormally heats up: Figure 7 The control shown in (a) and (b) refers to the situation where abnormal heating of battery 6 occurs due to thermal runaway caused by internal short circuits or other reasons (this thermal runaway occurs due to various reactions and pyrolysis within battery 6). In this case, control device 80 detects an internal short circuit in battery 6 by measuring current and voltage values, or determines the occurrence of abnormal heating as described above by detecting gases generated within battery 6. Alternatively, control device 80 may also determine the occurrence of abnormal heating by observing changes in battery temperature over time.

[0064] Specifically, such as Figure 7 As shown in (a), when the battery 6 does not overheat abnormally, the control device 80 operates as described above (refer to...). Figure 5 (a) When the battery temperature is in the first region R1 (low temperature side), the E2 opening is maintained at 0 (fully closed). When the battery temperature is in the second region R2 (higher temperature side than the first region R1), the E2 opening increases linearly with the increase of battery temperature. However, when the control device 80 detects abnormal heating of the battery 6 (arrow A1), for example, when an internal short circuit is detected in the battery 6, as shown by arrow A2, the control device 80 first rapidly (stepwise) increases the E2 opening to the limit opening Lim1. This suppresses abnormal heating of the battery 6 by rapidly increasing the cooling capacity of the refrigerant for the battery 6.

[0065] Furthermore, as indicated by arrow A3, if the battery temperature continues to rise after the control device 80 sets the E2 opening to the maximum opening Lim1 as described above, the control device 80 will quickly (in a stepwise manner) increase the E2 opening to a maximum opening Lim2, which is larger than the maximum opening Lim1. Regarding the maximum opening Lim2, when the E2 opening is at this large opening, the compressor discharge temperature may exceed the aforementioned specified temperature (i.e., oil function degradation or oil deterioration may occur). Therefore, by setting the E2 opening to such a maximum opening Lim2, the compressor discharge temperature is allowed to exceed the specified temperature, maximizing the refrigerant's cooling capacity for the battery 6, thereby prioritizing the cooling of the battery 6. This suppresses abnormal heating of the battery 6 and avoids the worst-case scenario of battery fire.

[0066] like Figure 7 As shown in (b), when the control device 80 controls the E2 opening degree as described above when the battery 6 is abnormally overheating, the control device 80 will control the E3 opening degree based on the E2 opening degree. When the E2 opening degree is not less than the aforementioned limit opening degree Lim1 (at which point the battery 6 basically does not generate abnormal heat), the same Figure 5 (b) Figure 6 (b) Similarly, the control device 80 initially increases the opening degree of E3 linearly as the opening degree of E2 increases. Furthermore, when the opening degree of E2 reaches or exceeds the limit opening degree of Lim1, i.e., when the battery 6 abnormally heats up and the opening degree of E2 is increased to or above the limit opening degree of Lim1 to address this situation ( Figure 7 (a) The control device 80 linearly decreases the opening of E3 as the opening of E2 increases. This allows the compressor discharge temperature to rise, prioritizing the cooling battery 6.

[0067] [Functions and Effects] Next, the function and effect of the cooling system 100 involved in this embodiment will be explained. In this embodiment, a cooling system that circulates a refrigerant containing CO2 (CO2 refrigerant) and cools the interior of a vehicle 200 includes: a compressor 1 for compressing the refrigerant; a cascade heat exchanger 2 for cooling the refrigerant compressed by the compressor 1; an air conditioning heat exchanger 5a and a first battery heat exchanger 6a for using the refrigerant cooled by the cascade heat exchanger 2; a refrigerant passage 17 for supplying refrigerant to the battery 6 inside the vehicle 200 to cool it with the refrigerant cooled by the cascade heat exchanger 2, and supplying the refrigerant used for cooling the battery 6 to the compressor 1; and an expansion valve E2 located upstream of the refrigerant passage 17. The expansion valve E2 is used to expand the refrigerant. The control device 80 acquires the battery temperature and controls the expansion valve E2 based on the battery temperature. When the battery 6 is externally charged, the control device 80 performs the following processing: when the battery temperature is in the first region R1, the opening of the expansion valve E2 is kept constant; when the battery temperature is in the second region R2, which is higher than the temperature of the first region R1, the opening of the expansion valve E2 is set to be larger than the opening of the first region R1, and the opening of the expansion valve E2 increases as the battery temperature rises; when the battery temperature is in the third region R3, which is higher than the temperature of the second region R2, the opening of the expansion valve E2 is maintained at a larger opening than the opening of the second region R2.

[0068] According to this embodiment as described above, the refrigerant circulating in the cooling system 100 can be used to properly achieve both air conditioning of the vehicle 200 and cooling of the battery 6. Furthermore, according to this embodiment, when the battery 6 is externally charged, if the battery temperature is in the first region R1 (i.e., the battery temperature is low), the expansion valve E2 will maintain a small opening, ensuring the overall system efficiency of the cooling system 100 (especially the first thermal cycle loop 100a) by suppressing the flow rate of refrigerant supplied from the refrigerant passage 17 to the battery 6. However, if the battery temperature is in the second region R2 (i.e., the battery temperature is high), according to this embodiment, the opening of the expansion valve E2 will increase according to the battery temperature, ensuring the cooling capacity of the battery 6 by increasing the flow rate of refrigerant supplied from the refrigerant passage 17 to the battery 6. Furthermore, according to this embodiment, if the battery temperature is in the third region R3 (i.e., the battery temperature is even higher) (higher charging rates often result in higher battery temperatures), the opening of the expansion valve E2 will be maintained at a large opening, thereby effectively ensuring the cooling capacity of the battery 6. Therefore, this embodiment can ensure the cooling capacity of the refrigerant for the battery 6 while suppressing the overall system efficiency decline when the battery 6 is externally charged.

[0069] Furthermore, according to this embodiment, the higher the C-rate of charging the battery 6, the smaller the first region R1 and the larger the third region R3 of the control device 80, and the higher the rate of change of the opening of the expansion valve E2 in the second region R2 relative to the battery temperature. Therefore, when the battery temperature tends to increase and the C-rate of charging the battery 6 is high, the flow rate of refrigerant supplied from the refrigerant channel 17 to the battery 6 can be increased, thereby effectively ensuring the cooling capacity of the battery 6.

[0070] Furthermore, according to this embodiment, the cooling system 100 also includes: refrigerant passages 18 and 19 for supplying refrigerant to the compressor 1 after cooling at the air conditioning heat exchanger 5a and the first battery heat exchanger 6a without passing through the refrigerant passage 17; and an expansion valve E3 provided on the refrigerant passage 18 for expanding the refrigerant. The control device 80 increases the opening of the expansion valve E3 as the opening of the expansion valve E2 increases. Therefore, the flow rate of refrigerant supplied to the compressor 1 from the refrigerant passages 18 and 19 via the expansion valve E3 increases with the increase in the flow rate of refrigerant supplied to the compressor 1 from the refrigerant passage 17 via the expansion valve E2, thereby suppressing the rise in compressor discharge temperature. As a result, functional degradation or deterioration of the oil in the refrigerant can be suppressed.

[0071] Furthermore, according to this embodiment, the control device 80 limits the opening degree of the expansion valve E2 to below the limit opening degree Lim1, so that the compressor discharge temperature is below the specified temperature. This prevents the expansion valve E2 from opening too large, which could lead to a high compressor discharge temperature. As a result, it effectively suppresses functional degradation or deterioration of the oil in the refrigerant.

[0072] Furthermore, according to this embodiment, the control device 80 can control the expansion valves E2 and E3 as described above when the battery 6 is charged at a C-rate higher than a predetermined value. Therefore, when the battery temperature tends to increase and the C-rate is high, the aforementioned control of the expansion valves E2 and E3 can be performed.

[0073] Furthermore, according to this embodiment, the cooling system 100 also includes a second battery heat exchanger 6b, which is used to direct the refrigerant in the refrigerant passage 17 to the vicinity of several battery cells 62 within the battery 6, thereby directly cooling the several battery cells 62; wherein, the refrigerant, after being depressurized by the expansion valve E2, is supplied to the second battery heat exchanger 6b. According to this embodiment, since the refrigerant directly cools the several battery cells 62 at the second battery heat exchanger, the several battery cells 62 of the battery 6 can be effectively cooled. At this time, since the battery pack 61, etc., has low pressure resistance, it is not desirable to directly supply high-pressure refrigerant from the compressor 1 to the second battery heat exchanger 6b; therefore, in this embodiment, the refrigerant from the compressor 1 is depressurized by the expansion valve E2 and then supplied to the second battery heat exchanger 6b. This reliably protects the interior of the battery 6 (several battery cells 62, etc.).

[0074] According to this embodiment, as heat exchangers using refrigerant cooled by the cascade heat exchanger 2, there is an air conditioning heat exchanger 5a for air conditioning the vehicle 200, and a first battery heat exchanger 6a for supplying refrigerant to the outside of the battery pack 61 containing several cells 62 at the battery 6 and indirectly cooling the several cells 62 with the refrigerant. Therefore, by using the first battery heat exchanger 6a to supply refrigerant to the outside of the battery pack 61 and indirectly cool the several cells 62, the battery 6 can be properly cooled, and a large heat exchange with the refrigerant can be achieved.

[0075] Furthermore, according to this embodiment, the cascade heat exchanger 2 performs heat exchange between the first heat cycle loop 100a and the second heat cycle loop 100b. The first heat cycle loop 100a includes at least a compressor 1, an air conditioning heat exchanger 5a, and a first battery heat exchanger 6a. The second heat cycle loop 100b, separate from the first heat cycle loop 100a, includes an outside air heat exchanger 30 for heat exchange with outside air. Thus, the heat exchange between the second heat cycle loop 100b and the first heat cycle loop 100a (cascade heat exchange) improves the overall system efficiency of the first heat cycle loop 100a, in other words, reduces the work done by the compressor 1.

[0076] Furthermore, according to this embodiment, the cooling system 100 uses refrigerant cooled by the cascade heat exchanger 2 to further cool the motor 4 of the vehicle 200 powered by the battery 6. Thus, the refrigerant circulating in the cooling system 100 can be used to properly cool various components within the vehicle 200, such as the motor 4.

[0077] [Variation Example] In the above embodiment, the cooling system 100 is composed of a first heat cycle loop 100a and a second heat cycle loop 100b. However, in other examples, the cooling system 100 can be composed of only the first heat cycle loop 100a. In this case, the cascade heat exchanger 2 can simply be used as an external air heat exchanger. Furthermore, if the cooling system 100 is composed of both the first heat cycle loop 100a and the second heat cycle loop 100b, although the system efficiency will be improved (i.e., the work done by the compressor 1 can be reduced), the structure will become more complex. Therefore, when simplifying the structure is a priority over system efficiency, the cooling system 100 can be composed of only the first heat cycle loop 100a.

[0078] Furthermore, in the above embodiment, the temperature of the battery 6 is detected by the battery temperature sensor 72. However, in other examples, the temperature of the battery 6 can be estimated based on the current value, voltage value, output requirements, or charging speed requirements of the battery 6. Also, in other examples, the temperature of the battery 6 can be estimated based on the temperature of the refrigerant detected by the refrigerant temperature sensor 44 installed on the refrigerant channel 17 downstream of the second battery heat exchanger 6b.

[0079] [Numbering Explanation] 1. Compressor 1a First compressor 1b Second compressor 2. Heat exchanger (cascade heat exchanger) 4 motors 5. Air conditioning 5a Air Conditioning Heat Exchanger 6 batteries 6a First Battery Heat Exchanger 6b Second Battery Heat Exchanger 11-20 Refrigerant Channels 41, 42, 43, 44 Refrigerant temperature sensors 51, 52, 53 Refrigerant pressure sensors 61 Battery Pack 62 cells 80 Control device 100 Cooling System 100a First thermal cycle loop 100b Second thermal cycle loop 200 vehicles E1, E2, E3 expansion valves V1, V2, V3 flow control valves

Claims

1. A cooling system that circulates a refrigerant containing CO2 to cool the interior of a vehicle, characterized in that... include: Compressor, for compressing the refrigerant; The first heat exchanger is used to cool the refrigerant after it has been compressed by the compressor; The second heat exchanger is used to at least perform air conditioning of the vehicle using the refrigerant cooled by the first heat exchanger; A refrigerant passage is used to supply the refrigerant to the battery and to supply the refrigerant cooled at the battery to the compressor for cooling the battery in the vehicle using the refrigerant cooled by the first heat exchanger. An expansion valve is provided on the refrigerant passage on the upstream side of the battery, and is used to expand the refrigerant; A control device acquires the temperature of the battery and controls the expansion valve based on the temperature of the battery; When the battery is externally charged, the control device performs the following processing: When the battery temperature is within the first region, the opening of the expansion valve is kept constant. When the battery temperature is in a second region, which is higher than the temperature of the first region, the opening of the expansion valve is set to a larger opening than that of the first region, and the opening of the expansion valve increases as the battery temperature rises. When the battery temperature is in the third region, which is on the side with a higher temperature than the second region, the opening of the expansion valve is maintained at a larger opening than that in the second region.

2. The cooling system according to claim 1, characterized in that: The higher the C-rate of the battery charging, the smaller the first region and the larger the third region of the control device, and the higher the rate of change of the opening of the expansion valve in the second region relative to the temperature of the battery.

3. The cooling system according to claim 1 or 2, characterized in that: When the refrigerant passage is used as the first refrigerant passage and the expansion valve is used as the first expansion valve, the cooling system further includes: a second refrigerant passage and a second expansion valve. The second refrigerant passage is used to supply the refrigerant, after being cooled at the second heat exchanger, to the compressor without passing through the first refrigerant passage. The second expansion valve is disposed on the second refrigerant passage and is used to expand the refrigerant. The control device causes the opening degree of the second expansion valve to increase as the opening degree of the first expansion valve increases.

4. The cooling system according to claim 1 or 2, characterized in that: The control device limits the opening of the expansion valve to below a specified limit, so that the temperature of the refrigerant discharged from the compressor is below a specified temperature.

5. The cooling system according to claim 1 or 2, characterized in that: When the battery is charged at a C-rate higher than a specified C-rate, the control device controls the expansion valve based on the temperature of the battery.

6. The cooling system according to claim 1 or 2, characterized in that: The cooling system also includes a battery heat exchanger, which is used to direct the refrigerant in the refrigerant channel to the area around several cells in the battery, thereby directly cooling the several cells. The refrigerant, after being depressurized by the expansion valve, is supplied to the battery heat exchanger.

7. The cooling system according to claim 1 or 2, characterized in that: The second heat exchanger includes an air conditioning heat exchanger for air conditioning the vehicle, and also includes a battery heat exchanger for supplying the refrigerant at the battery to the outside of a battery pack containing a plurality of cells and indirectly cooling the plurality of cells with the refrigerant.

8. The cooling system according to claim 1 or 2, characterized in that: The first heat exchanger is configured as a cascade heat exchanger that exchanges heat between a first heat cycle loop and a second heat cycle loop. The first heat cycle loop includes at least the compressor, the second heat exchanger, the refrigerant passage, and the expansion valve. The second heat cycle loop includes an outside air heat exchanger that exchanges heat with the outside air, separately from the first heat cycle loop.

9. The cooling system according to claim 1 or 2, characterized in that: The cooling system uses the refrigerant cooled by the first heat exchanger to further cool the motor that powers the vehicle with electricity from the battery.

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