Accumulator and vehicle drive device

Abstract

To provide a vehicle drive device which is formed in a shape more compact than conventional vehicle drive devices, and to provide an accumulator used in the vehicle drive device.SOLUTION: In an accumulator 25 which separates a liquid refrigerant from a gas refrigerant used for cooling and heating in a passenger compartment of a vehicle, heat is exchanged between a coolant which cools one of a motor 1 for driving the vehicle and an electric power conversion module 5 for allowing the motor 1 to operate and at least one of the gas refrigerant G and the liquid refrigerant M stored.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to Accumulator and This relates to a vehicle drive system. [Background technology]

[0002] Generally, the refrigeration cycle for an air conditioner used in a vehicle has a compressor, a condenser, an expansion valve, and an evaporator as basic components. Based on this refrigeration cycle, there is an accumulator type refrigeration cycle in which an accumulator is placed between the evaporator and the compressor to prevent liquid from returning to the compressor.

[0003] Patent Document 1 discloses an accumulator-type heat exchanger in which refrigerants exchange heat with each other to increase the heat absorption capacity by supercooling in order to enhance the cooling effect. The heat exchanger disclosed in Patent Document 1 includes a cylindrical outer casing, a cylindrical inner tank arranged coaxially within the casing, and a heat exchange passage provided in a spiral shape in the cylindrical space between the outer casing and the inner tank. In this heat exchanger, heat is exchanged between the forward refrigerant flowing in a spiral shape through the heat exchange passage and the return refrigerant in the inner tank, so that the forward refrigerant is supercooled and the return refrigerant is superheated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-66022 A Summary of the Invention [Problem to be solved by the invention]

[0005] Accumulators need to be installed in a small space in the engine room where many devices are intertwined. For example, in automobiles equipped with a motor as a driving source (such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), and fuel cell electric vehicles (FCEVs)), accumulators are often attached to and integrated with a vehicle drive device such as an e-axle. In addition, the motor and the gear that reduces the motor rotation integrated with the vehicle drive device are cooled with oil, and an oil cooler that exchanges heat with cooling water is installed. The oil cooler is also often attached to and integrated with the vehicle drive device. If both the accumulator and the oil cooler are attached and integrated, the vehicle drive device becomes larger, which may reduce the ease of mounting on the vehicle.

[0006] Therefore, a vehicle drive device having a more compact structure than the conventional device is provided. And an accumulator used in the vehicle drive device is desired. [Means for solving the problem]

[0007] The present invention accumulator One embodiment of the present invention is ,car Accumulators that separate liquid refrigerant from gas refrigerant used to heat and cool the passenger compartment And , Driving the vehicle Motor and Activating the motor A cooling fluid for cooling one of the power conversion modules; , savings Heat exchange occurs between at least one of the gaseous refrigerant and the liquid refrigerant that is stored.

[0008] This embodiment Accumulator According to the present invention, the cooling liquid flowing through either the motor or the power conversion module is , savingsSince heat exchange can be performed between the cooling liquid and at least one of the gas refrigerant and the liquid refrigerant stored in the accumulator, there is no need to provide a dedicated cooling device for cooling the cooling liquid. Or, even if a cooling device is provided, the cooling liquid is cooled by heat exchange with at least one of the gas refrigerant and the liquid refrigerant stored in the accumulator, so that the cooling liquid can be sufficiently cooled using a cooling device smaller than conventional devices. 。

[0009] One embodiment of the vehicle drive device of the present invention comprises the motor, the power conversion module, a housing that accommodates at least the motor and the power conversion module, and the above-described actuator attached to the housing.

[0010] Since the vehicle drive device of the present embodiment includes the actuator described above, it is not necessary to provide a cooling device in the vehicle drive device, or a small cooling device can be used, so the vehicle drive device can be made more compact than before. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an exploded perspective view illustrating a vehicle drive device according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram showing a circuit configuration of a vehicle drive device and a heating module. [Diagram 3] FIG. [Figure 4] FIG. 4 is a cross-sectional view of an accumulator according to a modified example of the first embodiment. [Diagram 5] FIG. 11 is an exploded perspective view illustrating a vehicle drive device according to a second embodiment. [Figure 6] FIG. 2 is a block diagram showing a circuit configuration of a vehicle drive device and a heating module. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention relates to Accumulator and An embodiment of a vehicle drive device will be described in detail with reference to the drawings. Accumulator andVehicle drive devices are used in automobiles (such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), and fuel cell electric vehicles (FCEVs)) that are equipped with a motor as a drive source for traveling. Hereinafter, these automobiles will be collectively referred to as "electric vehicles." Note that the embodiments described below are examples for explaining the present invention, and the present invention is not limited to only these embodiments. Therefore, the present invention can be embodied in various forms without departing from the gist of the present invention.

[0013] [First embodiment] As shown in Fig. 1 and Fig. 2, the vehicle drive device A according to the first embodiment includes an electric motor 1 (one example of a motor), a gear unit 2, a power conversion module 5, an oil pump 6, a switching valve 8, a compressor 21, and an accumulator 25. In the vehicle drive device A, the electric motor 1, the gear unit 2, the power conversion module 5, the oil pump 6, and the switching valve 8 are housed and integrated in a housing 4. The compressor 21 and the accumulator 25 are attached to a side wall of the housing 4 and integrated. "Integrated" includes a state in which they are fastened to the outer surface of the housing 4 by bolts or the like (the same applies below).

[0014] The electric motor 1 is a drive source for driving the electric vehicle. The gear unit 2 reduces the rotational drive force of the electric motor 1 and outputs it. The power conversion module 5 has an inverter and controls the drive current that drives the electric motor 1. In other words, the vehicle drive device A reduces the rotational drive force of the electric motor 1, which is driven by the drive current controlled by the power conversion module 5, by the gear unit 2 and then outputs it to the outside. The output from the vehicle drive device A is transmitted to the left and right wheels W via the differential gear 3. The compressor 21 and the accumulator 25 are used in a heating module B, which will be described later. In addition, a part of the accumulator 25 constitutes a heat exchanger D, which will be described later.

[0015] Inside the vehicle drive device A, a first coolant flow passage L1 is arranged through which oil (an example of a coolant) for cooling the electric motor 1 and the gear unit 2 flows. An example of the oil is insulating oil such as paraffin-based oil. The oil pump 6 is arranged in the middle of the first coolant flow passage L1 and pumps the oil flowing through the first coolant flow passage L1. The switching valve 8 is configured to be able to switch the flow passage of the oil pumped by the oil pump 6 between a cooling position and a non-cooling position. Specifically, in the cooling position, the oil flowing through the first coolant flow passage L1 is supplied to the heat exchanger D and cooled, and then supplied to the electric motor 1 and the gear unit 2. In the non-cooling position, the oil flowing through the cooling flow passage L is supplied to the electric motor 1 and the gear unit 2 without being cooled.

[0016] The heating module B includes an electric compressor 21, a condenser 22, an expansion valve 23, an evaporator 24, an accumulator 25, and a refrigerant flow path R that circulates gaseous refrigerant G among these. As described above, the compressor 21 and the accumulator 25 of the heating module B are attached to the housing 4 of the vehicle drive device A. The heating module B is configured as a heat pump, and as the gaseous refrigerant G, hydrofluorocarbon (HFC), hydrofluoroolefin (HFO), or the like is used.

[0017] The condenser 22 is disposed in the vehicle interior. The condenser 22 has an electric blower 22a that sends heated air into the vehicle interior. The heating module B compresses the gas refrigerant G to a high temperature and high pressure in the compressor 21, and liquefies the gas refrigerant G in the condenser 22, and releases the thermal energy (condensation heat) of the gas refrigerant G into the vehicle interior by the blower 22a. This increases the temperature in the vehicle interior. The gas refrigerant G becomes a liquid refrigerant M in the condenser 22.

[0018] The liquid refrigerant M that has passed through the condenser 22 is expanded in the expansion valve 23 to a low pressure and sent to the evaporator 24. In the evaporator 24, the liquid refrigerant M absorbs heat and evaporates. The evaporator 24 is equipped with an electric evaporation fan 24a to obtain thermal energy to evaporate the liquid refrigerant M. Most of the refrigerant vaporized by passing through this evaporator 24 is gaseous refrigerant G, but it also contains some liquid refrigerant M that is a mist liquid. The gaseous refrigerant G that contains the liquid refrigerant M is sent to the accumulator 25.

[0019] In the accumulator 25, gas-liquid separation is performed on the gas refrigerant G containing the liquid refrigerant M supplied from the evaporator 24. That is, the liquid refrigerant M is separated from the gas refrigerant G containing the liquid refrigerant M. The accumulator 25 has a vertically long cylindrical structure for storing the gas-liquid separated liquid refrigerant M, and the gas-liquid separated liquid refrigerant M is stored in the bottom. In this accumulator 25, the position of the end of the refrigerant flow path R is set so that the gas refrigerant G can be supplied to the compressor 21 from above the liquid level of the liquid refrigerant M.

[0020] 3, the accumulator 25 includes therein a regulating plate 26 that reduces the pressure of the gaseous refrigerant G supplied from the evaporator 24. The regulating plate 26 is provided to achieve gas-liquid separation by collision of the gaseous refrigerant G containing the mist-like liquid refrigerant M, and to prevent the liquid refrigerant M from being blown up due to the pressure of the gaseous refrigerant G supplied from the evaporator 24.

[0021] The heat exchange section D is configured to have a heat exchange passage 27 (one example of a piping unit) in which a metal pipe with high thermal conductivity is formed into a spiral shape and arranged to pass through the inside (inside) of the accumulator 25. This heat exchange passage 27 is arranged to be immersed in the liquid refrigerant M stored inside the accumulator 25. The upstream end of the heat exchange passage 27 is connected to the switching valve 8, and the downstream end merges with the first coolant passage L1 downstream of the switching valve 8. Inside the heat exchange passage 27, oil flows through the first coolant passage L1 when the switching valve 8 is switched to the cooling position.

[0022] Next, the flow of oil in the first coolant flow passage L1 will be described. The oil is circulated in the first coolant flow passage L1 by the oil pump 6. That is, the first coolant flow passage L1 is arranged to circulate the oil through the electric motor 1, the gear unit 2, the oil pump 6, the switching valve 8, and the heat exchanger D. Specifically, the oil flowing through the first coolant flow passage L1 is heated by absorbing heat from the electric motor 1 and the gear unit 2 that are generated by driving. The heated oil is pressurized by the oil pump 6 and sent to the switching valve 8. When the switching valve 8 is switched to the cooling position, the oil is supplied to the inside of the accumulator 25 and flows through the heat exchange flow passage 27. The oil flowing through the heat exchange flow passage 27 is cooled by exchanging heat with the liquid refrigerant M. This heat exchange flow passage 27 is arranged to be immersed in the liquid refrigerant M inside the accumulator 25 and is composed of a metal pipe with high thermal conductivity, so that efficient heat exchange can be performed between the oil and the liquid refrigerant M. The oil cooled to the liquid refrigerant M flows out of the accumulator 25 and merges with the first coolant flow path L1 downstream of the switching valve 8. The oil cooled in the heat exchange section D is returned to the electric motor 1 and the gear unit 2, and absorbs heat from the electric motor 1 and the gear unit 2 to be heated again.

[0023] When the amount of heat generated in the electric motor 1 and the gear unit 2 is small and the oil is not heated to the extent that heat exchange (cooling) in the heat exchange section D is required, the switching valve 8 is switched to the non-cooling position. As a result, the oil flowing through the first coolant flow path L1 is returned to the electric motor 1 and the gear unit 2 again without being supplied to the heat exchange section D and cooled. The switching of the switching valve 8 is performed based on the temperature of the oil detected by a temperature sensor (not shown).

[0024] In this way, in the vehicle drive device A of the present embodiment, the oil heated by the heat generated by the electric motor 1 and the gear unit 2 is cooled not by an oil cooler but by a heat exchange section D having a heat exchange passage 27 configured to be able to exchange heat with the liquid refrigerant M of the accumulator 25. This eliminates the need for an oil cooler for cooling the oil, and allows the vehicle drive device A to be configured more compactly than before.

[0025] [Modification of the first embodiment] Next, the configuration of the vehicle drive device A according to a modified example of the first embodiment will be described with reference to FIG. 4. In this modified example, the configuration of the heat exchanger D is different from that of the first embodiment. In this modified example, the heat exchange passage 27 constituting the heat exchanger D is not disposed so as to be immersed in the liquid refrigerant M stored inside the accumulator 25, but is disposed so as to wind around the outer periphery (outside) of the accumulator 25 where the liquid refrigerant M is stored inside. Even with the heat exchanger D configured in this way, heat exchange can be performed between the oil flowing through the heat exchange passage 27 and the liquid refrigerant M inside the accumulator 25, and the oil can be cooled.

[0026] Second Embodiment Next, the configuration of a vehicle drive device A according to the second embodiment will be described with reference to Figs. 5 and 6. In this embodiment, unlike the first embodiment, the vehicle drive device A is equipped with an oil cooler 7. Also, the coolant flowing through the heat exchange passage 27 is not oil but cooling water (one example of a coolant). Therefore, the vehicle drive device A of this embodiment does not have a switching valve 8 that switches the first coolant passage L1. Other than that, it has the same configuration as the first embodiment. Therefore, in the description of this embodiment, parts of the configuration that are the same as those in the first embodiment are given the same reference numerals, and detailed description of the similar configuration will be omitted.

[0027] In this embodiment, the oil cooler 7 is attached to and integrated with the power conversion module 5, and is housed in the housing 4 (see FIG. 5). Therefore, the housing 4 of this embodiment is slightly larger than that of the first embodiment.

[0028] The first coolant flow path L1 of this embodiment is arranged to circulate oil through the electric motor 1, the gear unit 2, the oil pump 6, and the oil cooler 7. The oil cooler 7 is configured to exchange heat between the oil flowing through the first coolant flow path L1 and the coolant flowing through the second coolant flow path L2. Note that the coolant used is a long-life coolant (LLC) containing ethylene glycol, propylene glycol, or the like.

[0029] As shown in FIG. 6, in this embodiment, a radiator 9 and an electric water pump 11 are provided outside the housing 4. The radiator 9 and the water pump 11 are provided in the middle of the second coolant flow path L2. In the second coolant flow path L2, the water pump 11, the radiator 9, the power conversion module 5, and the heat exchange flow path 27 are provided in this order on the downstream side as viewed from the oil cooler 7. That is, the coolant flowing through the second coolant flow path L2 flows through the oil cooler 7, the water pump 11, the radiator 9, the power conversion module 5, and the heat exchange flow path 27, and returns to the oil cooler 7. The heat exchange flow path 27 is a part of the second coolant flow path L2. The radiator 9 is provided with an electric radiator fan 9a. In FIG. 6, the heat exchange flow path 27 is illustrated as being immersed in the liquid refrigerant M inside the accumulator 25 as shown in FIG. 3. However, the heat exchange passage 27 is not limited to the configuration in FIG. 3, and may be configured to wind around the outer periphery of the accumulator 25 where the liquid refrigerant M is stored inside, as shown in FIG.

[0030] In this embodiment, the oil that has absorbed heat from the electric motor 1 and the gear unit 2 flows through the first coolant flow path L1 and is pressurized by the oil pump 6. The oil then flows into the oil cooler 7, where it is cooled by heat exchange with the cooling water flowing through the second coolant flow path L2, and is then returned to the electric motor 1 and the gear unit 2. The oil then absorbs heat again from the electric motor 1 and the gear unit 2 and is heated.

[0031] The cooling water heated by heat exchange with the oil in the oil cooler 7 flows through the second coolant flow path L2, is pressurized by the water pump 11, and is then supplied to the radiator 9. The cooling water cooled in the radiator 9 is then supplied to the power conversion module 5, where it is heated by absorbing heat generated by the inverter of the power conversion module 5. The heated cooling water is then supplied to the inside of the accumulator 25, and flows through the heat exchange flow path 27 of the heat exchanger D. The cooling water flowing through the heat exchange flow path 27 is cooled by heat exchange with the liquid refrigerant M. The cooled cooling water flows out of the accumulator 25 and is returned to the oil cooler 7. Then, it is heated again by heat exchange with the oil.

[0032] Conventionally, the cooling water was heated by the power conversion module 5 and then directly supplied to the oil cooler 7. Therefore, in order to perform sufficient heat exchange between the high-temperature cooling water and the oil in the oil cooler 7, it is necessary to increase the length of the flow path in which the cooling water and the oil face each other, and the oil cooler 7 is made large. However, in this embodiment, the cooling water heated in the power conversion module 5 is supplied to the heat exchange section D formed in the accumulator 25, and is cooled by heat exchange with the liquid refrigerant M. Therefore, the temperature of the cooling water supplied to the oil cooler 7 is lower than in the past, and necessary heat exchange with the oil can be performed even if the flow path in which the cooling water and the oil face each other is not long. In other words, since a smaller oil cooler 7 than in the past can be used, the vehicle drive device A can be configured compactly.

[0033] [Another embodiment] In addition to the above-described embodiment and its modified examples, the present invention may be configured as follows (common numbers and symbols as in the embodiment are used to designate parts having the same functions as in the embodiment).

[0034] <1> The heat exchange section D is configured so that the cross section of the heat exchange passage 27 is formed into a non-circular shape such as an ellipse or a rectangle to increase the area of ​​contact between the heat exchange passage 27 and the liquid refrigerant M. Furthermore, the heat exchange section D may be configured by providing fins for heat exchange on the outer surface of the heat exchange passage 27.

[0035] <2> In the above embodiment and its modified examples, the cooling liquid (oil or cooling water) flowing through the heat exchange passage 27 exchanges heat with the liquid refrigerant M stored in the accumulator 25, but heat exchange may also be performed with a gas refrigerant G instead of or together with the liquid refrigerant M.

[0036] <3> In the second embodiment, the accumulator 25 (heat exchange flow path 27) is disposed downstream of the power conversion module 5, but this is not limited thereto. The accumulator 25 may be configured to be disposed upstream of the power conversion module 5, that is, between the radiator 9 and the power conversion module 5. By adding a function of cooling the coolant with the accumulator 25 to the circuit, the original cooling capacity is improved and the temperature of the coolant flowing into the oil cooler 7 is reduced. Therefore, even if the accumulator 25 is disposed upstream of the power conversion module 5, the cooling performance is improved compared to a circuit to which the accumulator 25 is not added.

[0037] As mentioned above Accumulator 25 and In an embodiment of the vehicle drive device A, the following configuration is envisaged.

[0038] (1) Accumulator 25 One aspect of ,car An accumulator 25 for separating liquid refrigerant M from gaseous refrigerant G used for heating and cooling the passenger compartments of both vehicles. And , Driving a vehicle Motor (electric motor 1) and Start the motor A cooling liquid for cooling one of the power conversion modules 5; , savings Heat exchange takes place between the gas refrigerant G and / or the liquid refrigerant M stored therein.

[0039] This aspect Accumulator 25 Now, the cooling fluid (oil or cooling water) flowing through either the motor (electric motor 1) or the power conversion module 5 is , savingsSince heat exchange can be performed between the accumulator 25 and at least one of the gas refrigerant G and the liquid refrigerant M, there is no need to provide a dedicated cooling device for cooling the cooling liquid. Alternatively, even if a cooling device is provided, the cooling liquid is cooled by heat exchange with at least one of the gas refrigerant G and the liquid refrigerant M stored in the accumulator 25, so that the cooling liquid can be sufficiently cooled using a cooling device smaller than in the past. 。

[0040] (2)(1) The accumulator 25 according to In this case, the oil used as the coolant for the motor (electric motor 1) is ,heat It is preferable that the cooling is performed by exchange.

[0041] According to this, the oil ,a The refrigerant is cooled by exchanging heat with at least one of the gas refrigerant G and the liquid refrigerant M stored in the accumulator 25. Therefore, the oil cooler 7 is not required. Become .

[0042] (3)(1) or (2) an accumulator 25 In It is preferable that the coolant flows through the inside of a piping unit (heat exchange flow path 27) arranged on the inside or outside.

[0043] As a result, the cooling liquid flows inside the piping unit (heat exchange passage 27) that performs heat exchange inside or outside the accumulator 25, and is cooled by heat exchange with at least one of the gas refrigerant G and liquid refrigerant M stored in the accumulator 25.

[0044] (4) In the accumulator 25 described in (3), it is preferable that the piping unit (heat exchange passage 27) is arranged so that the inside is immersed in the liquid refrigerant M.

[0045] When the piping unit (heat exchange passage 27) is arranged so as to be immersed in the liquid refrigerant M inside the accumulator 25, the cooling liquid directly exchanges heat with the liquid refrigerant M via the piping unit (heat exchange passage 27), thereby enabling efficient heat exchange.

[0046] (5) In the accumulator 25 described in (4), it is preferable that the piping unit (heat exchange passage 27) is formed in a spiral shape.

[0047] (6) In the accumulator 25 described in (3), it is preferable that the piping unit (heat exchange passage 27) is arranged so as to be wound around the portion where the liquid refrigerant M is stored on the outside.

[0048] When the piping unit (heat exchange passage 27) is arranged so as to be wound around the location where the liquid refrigerant M is stored outside the accumulator 25, there is no need to arrange the piping unit (heat exchange passage 27) inside the accumulator 25, so a configuration for performing heat exchange with the liquid refrigerant M can be easily obtained.

[0049] (7) One embodiment of a vehicle drive device A includes a motor (electric motor 1), a power conversion module 5, a housing 4 that accommodates at least the motor (electric motor 1) and the power conversion module 5, and an accumulator 25 described in any one of (1) to (6) above attached to the housing 4.

[0050] According to the vehicle drive device A of this embodiment, since the actuator 25 described in any one of (1) to (6) above is included, it is not necessary to provide a cooling device in the vehicle drive device A, or a small cooling device can be used. Therefore, the vehicle drive device A can be configured more compactly than before.

[0051] (8) Vehicle drive device A according to (7) In Power Conversion Module 5 The engine is further provided with an oil cooler 7 for exchanging heat between cooling water as a coolant for cooling the engine and oil as a coolant for cooling the motor (electric motor 1), and it is preferable that the cooling water is cooled by heat exchange in the accumulator 25, and then heat exchange is performed between the cooling water and the oil in the oil cooler 7.

[0052] Conventionally, in order to perform sufficient heat exchange between the cooling water and the oil in the oil cooler 7, it is necessary to increase the length of the flow path in which the cooling water and the oil face each other, and the oil cooler 7 is made larger. However, in this configuration, the cooling water heated in the power conversion module 5 is cooled by exchanging heat with at least one of the gas refrigerant G and the liquid refrigerant M stored in the accumulator 25. Therefore, the temperature of the cooling water supplied to the oil cooler 7 is lower than in the past, and necessary heat exchange with the oil can be performed even if the length of the flow path in which the cooling water and the oil face each other is not long. In other words, a smaller oil cooler 7 can be used than in the past, and the vehicle drive device A can be configured more compactly than in the past. [Industrial Applicability]

[0053] The present invention relates to Accumulator and It can be used in vehicle drive systems. [Explanation of symbols]

[0054] 1: electric motor (motor), 4: housing, 5: power conversion module, 7: oil cooler, 25: accumulator, 27: heat exchange flow path (piping unit), A: vehicle drive device, G: gas refrigerant, M: liquid refrigerant

Claims

1. A vehicle drive device comprising: a motor that drives a vehicle, a power conversion module that operates the motor, a housing that accommodates at least the motor and the power conversion module, and an accumulator attached to the housing that separates liquid refrigerant from a gas refrigerant used for heating and cooling the interior of the vehicle, wherein heat exchange is performed between a cooling liquid that cools either the motor or the power conversion module and at least one of the gas refrigerant and the liquid refrigerant stored in the accumulator.

2. 2. The vehicle drive device according to claim 1, wherein the oil as the cooling liquid for cooling the motor is cooled by heat exchange in the accumulator instead of an oil cooler that exchanges heat between the oil and cooling water that cools the power conversion module.

3. 2. The vehicle drive device according to claim 1, further comprising an oil cooler that exchanges heat between cooling water as the coolant that cools the motor and oil as the coolant that cools the motor, wherein the cooling water is cooled by heat exchange in the accumulator, and then exchanges heat with the oil in the oil cooler.

4. The vehicle drive device according to claim 1 , wherein the coolant flows through an interior of a piping unit that performs heat exchange inside or outside the accumulator.

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