Thermal management system and solenoid valve control device

Abstract

The purpose of the present invention is to provide a thermal management system which, by controlling the opening degree of a solenoid valve, suppresses a sudden change in the degree of superheat of a refrigerant when the solenoid valve is opened and closed, and simultaneously achieves efficient cooling and stable temperature control of a cooling object. To this end, the heat management system is provided with: a compressor (1) that compresses a refrigerant; first heat exchangers (2, 3) for dissipating heat from the compressed refrigerant; a first solenoid valve (4C) and a second solenoid valve (4A, 4B) that expand the refrigerant after heat dissipation; a second heat exchanger (5) that causes the refrigerant expanded by the first solenoid valve (4C) to absorb heat; cooling objects (9, 10) cooled by the refrigerant expanded by the second solenoid valves (4A, 4B); and a solenoid valve control device (15) for controlling the opening and closing of the first solenoid valve (4C) and the second solenoid valves (4A, 4B), the solenoid valve control device (15) changing the opening degree of the second solenoid valves (4A, 4B) according to a predetermined time constant (Tc) when the second solenoid valves (4A, 4B) are opened or closed.

Description

Technical Field

[0001] The present invention relates to a thermal management system and a solenoid valve control device for cooling an air conditioner and an electric powertrain of a vehicle. Background Art

[0002] Electric vehicles require cooling of electric powertrain systems such as batteries and motors. For example, Patent Document 1 describes a vehicle air conditioning system that, in addition to providing stable cooling of the cooling target (battery) within the vehicle interior, includes a battery heat exchanger within the air conditioning refrigerant circuit for heat exchange between the air conditioning refrigerant and the heat medium used to cool the battery. Battery cooling is controlled by opening and closing a valve within the air conditioning refrigerant circuit based on the heat medium temperature (battery temperature).

[0003] In the above-mentioned vehicle air conditioning device, the refrigerant flow path will change when the above-mentioned valve device is opened and closed, and the refrigerant flow rate flowing in the heat exchanger will change sharply, thereby causing the battery temperature and the air temperature of the air conditioner to fluctuate greatly. To address this issue, Patent Document 1 proposes a technology that can perform stable temperature control by changing the compressor speed in accordance with the opening and closing of the solenoid valve.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-69929 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] As a means of using air-conditioning refrigerant to efficiently cool multiple cooling objects (batteries, motors, etc.), a thermal management system is being considered in which the air-conditioning refrigerant circuit is branched according to the number of cooling objects and an electromagnetic valve for expansion and flow control of the refrigerant is provided on each branched pipeline.

[0009] As a specific example, there is a thermal management system that uses air-conditioning refrigerant to cool batteries and motors. Downstream of a receiver, in addition to the refrigerant piping conventionally connected to the air-conditioning heat exchanger, refrigerant piping for battery cooling and refrigerant piping for motor cooling are branched out. Solenoid valves are provided upstream of the cooling objects (or heat exchangers used for cooling) of each piping, and the cooling objects are cooled by the refrigerant that has been expanded and decompressed by the solenoid valves.

[0010] When the prior art described in Patent Document 1 is applied to the aforementioned thermal management system, the compressor speed changes in response to the opening and closing of a solenoid valve for a specific cooling target, such as the battery cooling solenoid valve in the example above, causing the refrigerant flow rate in the motor cooling refrigerant piping to fluctuate simultaneously. This affects the refrigerant superheat of the cooling target. This can result in reduced cooling efficiency and difficulty controlling the temperature of the other cooling target (the motor in the example above). To maximize cooling efficiency, a constant refrigerant superheat is desirable.

[0011] The present invention is made in view of the above-mentioned problems, and its purpose is to provide a thermal management system that suppresses the rapid change of refrigerant superheat when the solenoid valve is opened and closed by controlling the opening of the solenoid valve, while achieving efficient cooling and stable temperature control of the cooling object.

[0012] Means for solving problems

[0013] In order to achieve the above-mentioned purpose, the present invention provides a thermal management system, which comprises: a compressor for compressing refrigerant; a first heat exchanger for dissipating heat from the compressed refrigerant; a first solenoid valve and a second solenoid valve for expanding the refrigerant after dissipating heat; a second heat exchanger for absorbing heat from the refrigerant expanded by means of the first solenoid valve; a cooling object cooled by the refrigerant expanded by means of the second solenoid valve; and a solenoid valve control device for controlling the opening and closing of the first solenoid valve and the second solenoid valve. In the thermal management system, the solenoid valve control device causes the opening degree of the second solenoid valve to change according to a specified time constant when opening or closing the second solenoid valve.

[0014] Furthermore, in the solenoid valve control device of the present invention for controlling the opening and closing of a solenoid valve for expanding refrigerant, the opening degree of the solenoid valve is changed in accordance with a predetermined time constant when the solenoid valve is opened or closed.

[0015] Effects of the Invention

[0016] According to the present invention, when a solenoid valve used to expand the refrigerant cooling the cooling object is opened and closed, the solenoid valve opening is controlled in a manner that has a time constant. This results in a smoother change in the refrigerant flow rate associated with the opening and closing of the solenoid valve. Furthermore, because rapid changes in the refrigerant flow rate are suppressed for each refrigerant pipe, the impact of flow rate changes on other refrigerant pipes can be reduced. As a result, rapid changes in the refrigerant superheat in the air conditioner heat exchanger and the cooling object can be suppressed. This allows for efficient cooling and stable temperature control of the air conditioner heat exchanger and the cooling object. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a diagram showing the configuration of a thermal management system and the flow of data and solenoid valve control signals in the first embodiment of the present invention.

[0018] Figure 2 This is a flowchart showing data processing in the solenoid valve control device in the first embodiment of the present invention.

[0019] Figure 3 This is a flowchart showing the calculation process of the electromagnetic valve opening and closing value in the first embodiment of the present invention.

[0020] Figure 4 This is a diagram showing a correction function for correcting the opening and closing value of the solenoid valve in the first embodiment of the present invention.

[0021] Figure 5 This is a flowchart showing a calculation process of the solenoid valve opening and closing value in a conventional example.

[0022] Figure 6 This is a diagram showing changes in the solenoid valve opening / closing value and the refrigerant superheat degree in a conventional example.

[0023] Figure 7 This is a diagram showing changes in the electromagnetic valve opening / closing value and the refrigerant superheat degree in the first embodiment of the present invention.

[0024] Figure 8 This is a diagram showing the relationship between the time constant of the correction function and the maximum value of the refrigerant superheat degree in the first embodiment of the present invention.

[0025] Figure 9 This is a diagram showing the configuration of a thermal management system and the flow of data and solenoid valve control signals in a second embodiment of the present invention.

[0026] Figure 10 This is a flowchart showing data processing in the solenoid valve control device in the second embodiment of the present invention. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described using the accompanying drawings. In the drawings, identical elements are denoted by the same reference numerals, and duplicate descriptions are omitted as appropriate.

[0028] Example 1

[0029] use Figures 1 to 8 A thermal management system and a solenoid valve control device according to a first embodiment of the present invention will be described below.

[0030] Figure 1This diagram shows the structure of the thermal management system in this embodiment, as well as the flow of data and solenoid valve control signals. The thermal management system includes: a compressor 1; an outdoor heat exchanger 2; an indoor heat exchanger 3; air conditioning solenoid valves 4C and 4D; an indoor heat exchanger 5; a refrigerant pipe 11 through which refrigerant flows; a receiver 7 for temporarily storing refrigerant; refrigerant pipes 11A and 11B branching from receiver 7; a motor 9 connected to refrigerant pipe 11A as a cooling target; a battery 10 connected to refrigerant pipe 11A as a cooling target; solenoid valves 4A through 4D; and a solenoid valve control device 13 that controls the opening and closing of solenoid valves 4A through 4D.

[0031] The refrigerant is compressed in compressor 1. Fan 8 draws in air outside the vehicle into outdoor heat exchanger 2, promoting heat exchange with the refrigerant. Indoor heat exchangers 3 and 5 exchange heat between the refrigerant and the air inside the vehicle. Switching four-way valve 6 reverses the flow of refrigerant through outdoor heat exchanger 2 and indoor heat exchangers 3 and 5, switching between cooling and heating modes in the air conditioner. Figure 1 In the cooling circuit, the outdoor heat exchanger 2 and the indoor heat exchanger 3 are condensers, the indoor heat exchanger 5 is an evaporator, and the refrigerant is decompressed by the solenoid valve 4C. In the heating circuit, the refrigerant is decompressed by the solenoid valve 4D.

[0032] The motor 9 connected to the refrigerant piping 11A is cooled by the refrigerant after the pressure is reduced by the solenoid valve 4A. At this time, there are cases where the motor 9 is cooled by directly contacting the refrigerant piping, and cases where the motor 9 is cooled by the heat medium after exchanging heat with a heat medium different from the air-conditioning refrigerant via a heat exchanger (condenser). Detailed descriptions are omitted here. Similarly, the battery 10 connected to the refrigerant piping 11B is cooled by the refrigerant after the pressure is reduced by the solenoid valve 4B. At this time, as with the case of the motor 9, there are cases where the motor 9 is cooled directly by contacting the refrigerant piping, and there are cases where the motor 9 is cooled separately via a heat exchanger and a heat medium.

[0033] Figure 1The dotted arrows in the figure represent the flow of data or solenoid valve control signals. The refrigerant pressures Pref_mot and Pref_bat (hereinafter referred to as Pref for simplicity) are obtained by pressure sensors 12A and 12B, and the refrigerant temperatures Tref_mot and Tref_bat (hereinafter referred to as Tref for simplicity) are obtained by temperature sensors 13A and 13B. In addition, the cooling target temperatures Tpt_mot and Tpt_bat (hereinafter referred to as Tpt for simplicity) are obtained by temperature sensors 14A and 14B provided in the motor 9 and the battery 10. The obtained refrigerant pressure Pref, refrigerant temperature Tref, and cooling target temperature Tpt are input to the solenoid valve control device 15, and after being processed, they are output as solenoid valve control signals s3_mot and s3_bat (hereinafter referred to as s3 for simplicity) to the solenoid valves 4A and 4B. In addition, although the solenoid valves 4C and 4D are also controlled by the solenoid valve control device 15, since they are not related to this embodiment, the description of the solenoid valve control signals is omitted.

[0034] Figure 2 This is a flowchart showing the data processing in the solenoid valve control device 13. In step S10, the refrigerant pressure Pref and the refrigerant temperature Tref obtained from the pressure sensors 12A and 12B are input. In step S20, the refrigerant superheat Tsh downstream of the cooling objects 9 and 10 is calculated. In step S30, the target refrigerant superheat, that is, the target superheat Ttsh, is obtained as a pre-set value. Considering the cooling efficiency, it is desirable that the target superheat Ttsh be set to 15°C or less. In step S40, the difference between the refrigerant superheat Tsh and the target superheat Ttsh is calculated. In step S50, the solenoid valve target opening s2 is calculated by PID control based on the difference so that the refrigerant superheat Tsh and the target superheat Ttsh are consistent. And in step S60, the product of the solenoid valve opening and closing value s1 described later and the solenoid valve target opening s2 is calculated as the solenoid valve control signal s3. Finally, in step S70 , the solenoid valve control signal s3 is output to the solenoid valves 4A and 4B.

[0035] Figure 3This is a flowchart showing the calculation process for the solenoid valve opening / closing value s1. In step S110, the cooling target temperature Tpt obtained from the temperature sensors 14A and 14B installed on the cooling targets 9 and 10 is input. If multiple temperature sensors are installed on each of the cooling targets 9 and 10, multiple cooling target temperatures Tpt corresponding to the number of temperature sensors are input. In step S120, if multiple cooling target temperatures Tpt are input, processing is performed to calculate the cooling target temperature Tapt, which is a representative value of these cooling target temperatures (taking the maximum / minimum value, taking the average, etc.). In step S130, a threshold value T1, which is the target temperature for the cooling targets 9 and 10, is obtained. Threshold T1 is set for each cooling target 9 and 10. In step S140, the cooling target temperature Tapt is compared with the threshold value T1. If Tapt>T1, the process proceeds to step S160; otherwise, the process proceeds to step S170. In step S160, the solenoid valve opening / closing value s1(t) is set to 1 (indicating valve open). Here, t is a time variable within the system required for data processing. In step S170, the solenoid valve opening and closing value s1(t) is set to 0 (indicating valve closed). In steps S180 and S190, the value of s1(t-Δt) is confirmed. Figure 2 When processing data in the flowchart, s1(t-Δt) represents the solenoid valve opening and closing value s1 at the time of processing. When the value of s1(t) is inconsistent with the value of s1(t-Δt), the time t is reset to 0 in steps S200 and S210, and then the time elapsed is counted again. In step S220, the time constant Tc as a parameter for correcting the solenoid valve opening and closing value s1(t) is obtained. And when s1(t)=1, the value of the correction function G1(t) is set to the corrected solenoid valve opening and closing value s1 in step S230. Similarly, when s1(t)=0, the value of the correction function G2(t) is set to the corrected solenoid valve opening and closing value s1 in step S240. The corrected solenoid valve opening and closing value s1 is sent to Figure 2 The described step S60.

[0036] Here, use Figure 4 To illustrate Figure 3 The correction functions G1(t) and G2(t) described in steps S230 and S240 are used. Figure 4 (a) is the correction function G1(t), Figure 4(b) is the correction function G2(t). As time t increases, the correction function G1(t) converges from 0 to 1 according to the time constant Tc, and the correction function G2(t) converges from 1 to 0 according to the time constant Tc. It should be noted that while this embodiment shows an example of a correction function using an exponential function, this is not limited to the example shown here. Any function that converges to 1 or 0 according to the time constant Tc can be used as a correction function.

[0037] Next, the effects of this embodiment will be described in comparison with a case where the solenoid valve opening / closing value s1 is not corrected (conventional example). Figure 5 Flowchart showing the calculation process of the electromagnetic valve opening / closing value s1 in the conventional example. Figure 5 In, not executed Figure 3 Steps S180 to S240, in step S250, the solenoid valve opening and closing value s1(t) is directly set to the solenoid valve opening and closing value s1, and delivered to Figure 2 Flowchart of Figure 6 Shown in the use Figure 5 The flow chart of the compressor 1 ( Figure 1 The target superheat is set to 5°C. Figure 6 (a) shows the change in the solenoid valve opening / closing value s1 in a conventional example. When the opening / closing value s1 of solenoid valve 4A (shown by a solid line) changes from 1 to 0, solenoid valve 4A closes. Furthermore, when the opening / closing value s1 of solenoid valve 4B (shown by a dotted line) changes from 0 to 1, solenoid valve 4B opens. When the opening / closing value s1 of solenoid valve 4B changes from 1 to 0, solenoid valve 4B closes. Figure 6 (b) shows the change in the refrigerant superheat at this time, and it can be confirmed that the refrigerant superheat fluctuates greatly when the electromagnetic valves 4A and 4B are opened and closed. This is caused by the rapid change in the refrigerant flow rate accompanying the opening and closing of the electromagnetic valves.

[0038] As described above, conventional examples have a problem in that the refrigerant superheat also fluctuates significantly due to the rapid change in refrigerant flow rate when the solenoid valves 4A and 4B are opened and closed. Therefore, as in this embodiment, this problem can be solved by independently controlling the solenoid valves 4A and 4B provided on the refrigerant pipes 11A and 11B of the cooling objects 9 and 10. Figure 7 The figure shows the corrected electromagnetic valve opening / closing value s1 and the refrigerant superheat at the inlet of the compressor 1 when this embodiment is applied. Figure 6 Comparing the results with those obtained above, the corrected solenoid valve opening / closing value s1 converges to 1 or 0 after a period of time, and accordingly, the variation in the refrigerant superheat is suppressed.

[0039] The influence of the time constant Tc of the correction functions G1(t) and G2(t) on the fluctuation of the refrigerant superheat will be further described. Figure 8 The relationship between the time constant Tc and the maximum refrigerant superheat is shown. It can be seen that the larger the time constant Tc, the smaller the maximum refrigerant superheat. Generally, in the indoor heat exchanger 5 for air conditioning, the refrigerant superheat is preferably kept below 15°C. In this embodiment, it was confirmed that by setting the time constant Tc to 20 seconds or longer, the refrigerant superheat can be suppressed to approximately 15°C or less. In other words, a time constant Tc of 20 seconds or longer is recommended.

[0040] (Summary)

[0041] In the first embodiment, the thermal management system includes: a compressor 1 for compressing refrigerant; a first heat exchanger 2, 3 for dissipating heat from the compressed refrigerant; a first solenoid valve 4C and a second solenoid valve 4A, 4B for expanding the refrigerant after dissipating heat; a second heat exchanger 5 for absorbing heat from the refrigerant expanded by means of the first solenoid valve 4C; cooling objects 9, 10 that are cooled by the refrigerant expanded by means of the second solenoid valve 4A, 4B; and a solenoid valve control device 15 for controlling the opening and closing of the first solenoid valve 4C and the solenoid valves 4A, 4B. In the above-mentioned thermal management system, the solenoid valve control device 15 changes the opening degree of the second solenoid valve 4A, 4B in accordance with a prescribed time constant Tc when opening or closing the second solenoid valve 4A, 4B.

[0042] In addition, in the first embodiment, in the solenoid valve control device 15 that controls the opening and closing of the solenoid valves 4A and 4B that expand the refrigerant, when the second solenoid valves 4A and 4B are opened or closed, the opening degree of the second solenoid valves 4A and 4B is changed in accordance with the prescribed time constant Tc.

[0043] According to the first embodiment constructed as described above, when the solenoid valves 4A and 4B used to expand the refrigerant cooling the cooling targets 9 and 10 are opened and closed, the solenoid valve opening is controlled so that the solenoid valve opening has a time constant Tc. This results in a gentle change in the refrigerant flow rate associated with the opening and closing of the solenoid valves. Furthermore, since rapid changes in the refrigerant flow rate are suppressed for each refrigerant pipe 11A and 11B, the impact of flow rate changes on other refrigerant pipes can be reduced. As a result, rapid changes in the refrigerant superheat in the air conditioning heat exchanger 5 and the cooling targets 9 and 10 can be suppressed. As a result, efficient cooling and stable temperature control of the air conditioning heat exchanger 5 and the cooling targets 9 and 10 are possible.

[0044] Furthermore, the thermal management system of the first embodiment includes first temperature sensors 14A and 14B for detecting the temperatures of the cooling targets 9 and 10. A solenoid valve control device 15 opens second solenoid valves 4A and 4B when the output value Tapt from the first temperature sensors 14A and 14B is greater than a predetermined threshold value T1, and closes second solenoid valves 4A and 4B when the output value Tapt from the first temperature sensors 14A and 14B is below the predetermined threshold value T1. This allows the temperatures of the cooling targets 9 and 10 to be maintained at the target temperature T1.

[0045] The thermal management system in the first embodiment also includes second temperature sensors 13A and 13B for detecting the temperature Tref of the refrigerant after passing through the cooling targets 9 and 10, and pressure sensors 12A and 12B for detecting the pressure Pref of the refrigerant after passing through the cooling targets 9 and 10. The solenoid valve control device 15 calculates the refrigerant superheat Tsh based on the output values ​​of the first temperature sensors 14A and 14B, the second temperature sensors 13A and 13B, and the pressure sensors 12A and 12B. The solenoid valve control device 15 calculates the target opening s2 of the second solenoid valves 4A and 4B to match the superheat Tsh with a predetermined target superheat Ttsh. When the second solenoid valves 4A and 4B are opened, the openings of the second solenoid valves 4A and 4B are aligned with the target opening s2. This maintains the refrigerant superheat at the inlet of the compressor 1 at the target superheat Ttsh.

[0046] Example 2

[0047] use Figure 9 and Figure 10 A thermal management system and a solenoid valve control device according to a second embodiment of the present invention will be described.

[0048] Figure 9 This diagram illustrates the structure of the thermal management system in this embodiment, as well as the flow of data and solenoid valve control signals. The thermal management system in this embodiment includes a data storage unit 16 that stores time-series data, such as the cooling target temperature Tpt obtained from temperature sensors 14A and 14B installed in the motor 9 and battery 10, the refrigerant temperature Tref obtained from temperature sensors 13A and 13B installed in the refrigerant pipes 11A and 11B, and the refrigerant pressure Pref obtained from pressure sensors 12A and 12B installed in the refrigerant pipes 11A and 11B; and a calculation unit 17 that uses this stored time-series data to calculate the solenoid valve target opening s2. The calculation unit 17 uses, for example, machine learning or data assimilation to calculate the appropriate solenoid valve target opening s2 in accordance with the operating conditions. The solenoid valve target opening s2 calculated by the calculation unit 17 is input to the solenoid valve control device 15A.

[0049] Figure 10This is a flowchart illustrating data processing in the solenoid valve control device 15A. In step S1010, the solenoid valve target opening s2 outputted from the calculation unit 17 is inputted. In step S1020, the solenoid valve control signal s3 is calculated by multiplying the corrected solenoid valve opening value s1 described in the first embodiment by the solenoid valve target opening s2 calculated by the calculation unit 17. In step S1030, the solenoid valve control signal s3 is outputted to the solenoid valves 4A and 4B.

[0050] According to this embodiment, the appropriate solenoid valve target opening s2 can be calculated using data acquired for each vehicle. In other words, the solenoid valves 4A and 4B can be controlled based on individual differences in vehicles and characteristics of vehicle usage, which is expected to further improve heat utilization efficiency through thermal management.

[0051] (Summary)

[0052] The thermal management system in the second embodiment includes: second temperature sensors 13A, 13B for detecting the temperature of the refrigerant after passing through the cooling objects 9, 10; and pressure sensors 12A, 12B for detecting the pressure of the refrigerant after passing through the cooling objects 9, 10, and includes: a data storage unit 16, which stores the timing data of the output values ​​of the first temperature sensor 14A, 14B, the second temperature sensor 13A, 13B and the pressure sensor 12A, 12B; and a calculation unit 17, which calculates the target opening s2 of the second solenoid valve 4A, 4B based on the above-mentioned timing data stored in the data storage unit 16, and the solenoid valve control device 15A makes the opening of the second solenoid valve 4A, 4B consistent with the target opening s2 when opening the second solenoid valve 4A, 4B.

[0053] According to the second embodiment configured as described above, the second solenoid valves 4A and 4B can be controlled based on individual differences between vehicles and characteristics of vehicle usage patterns, and further improvement in heat utilization efficiency is expected through thermal management.

[0054] Furthermore, the present invention is not limited to the above-described embodiments and encompasses various variations. For example, the above-described embodiments are provided to facilitate understanding of the present invention and are not necessarily limited to embodiments having all of the described structures. Furthermore, a portion of the structure of one embodiment may be replaced with a structure of another embodiment, and a structure of another embodiment may be added to a structure of one embodiment. Furthermore, other structures may be added, deleted, or substituted for a portion of the structure of each embodiment.

[0055] Description of Reference Numerals

[0056] 1: Compressor, 2: Outdoor heat exchanger (1st heat exchanger), 3: Indoor heat exchanger (1st heat exchanger), 4A, 4B: Solenoid valve (2nd solenoid valve), 4C: Solenoid valve (1st solenoid valve), 4D: Solenoid valve, 5: Indoor heat exchanger (2nd heat exchanger), 6: Four-way valve, 7: Receiver, 8: Fan, 9: Motor (cooling target), 10: Battery (cooling target), 11, 11A, 11B: Refrigerant piping, 12A, 12B: Pressure sensor, 13A, 13B: Temperature sensor (2nd temperature sensor), 14: Data storage unit, 14A, 14B: Temperature sensor (1st temperature sensor), 15, 15A: Solenoid valve control device, 16: Data storage unit, 17: Calculation unit.

Claims

1. A thermal management system comprising: A compressor that compresses the refrigerant; a first heat exchanger for dissipating heat from the compressed refrigerant; A first solenoid valve and a second solenoid valve for expanding the refrigerant after heat dissipation; a second heat exchanger for absorbing heat from the refrigerant expanded by the first solenoid valve; a cooling object cooled by the refrigerant expanded by the second solenoid valve; and The solenoid valve control device for controlling the opening and closing of the first solenoid valve and the second solenoid valve, wherein the thermal management system is characterized in that: The solenoid valve control device changes the opening degree of the second solenoid valve in accordance with a predetermined time constant when opening or closing the second solenoid valve.

2. The thermal management system according to claim 1, wherein: A first temperature sensor is provided for detecting the temperature of the cooling object. The solenoid valve control device is composed of: When the output value of the first temperature sensor is greater than a predetermined threshold value, the second electromagnetic valve is opened. When the output value of the first temperature sensor is equal to or less than a predetermined threshold value, the second electromagnetic valve is closed.

3. The thermal management system according to claim 2, wherein: have: a second temperature sensor for detecting the temperature of the refrigerant after passing through the cooling object; and a pressure sensor for detecting the pressure of the refrigerant after passing through the cooling object; The solenoid valve control device is composed of: The superheat degree of the refrigerant is calculated based on the output values ​​of the second temperature sensor and the pressure sensor. calculating a target opening of the second electromagnetic valve so that the superheat degree matches a predetermined target superheat degree, When the second electromagnetic valve is opened, the opening degree of the second electromagnetic valve is made to coincide with the target opening degree.

4. The thermal management system according to claim 2, wherein: have: a second temperature sensor for detecting the temperature of the refrigerant after passing through the cooling object; and a pressure sensor for detecting the pressure of the refrigerant after passing through the cooling object; The thermal management system comprises: a data storage unit that stores time-series data of output values ​​of the first temperature sensor, the second temperature sensor, and the pressure sensor; and a calculation unit that calculates a target opening degree of the second electromagnetic valve based on the time series data stored in the data storage unit, The solenoid valve control device makes the opening degree of the second solenoid valve coincide with the target opening degree when opening the second solenoid valve.

5. A solenoid valve control device for controlling the opening and closing of a solenoid valve for expanding a refrigerant, wherein: When the solenoid valve is opened or closed, the opening degree of the solenoid valve is changed according to a predetermined time constant.

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