Cooling system for electric vehicles

Abstract

We provide cooling systems for electric vehicles. [Solution] A cooling system used in an electric vehicle equipped with a motor for driving includes a cooling circuit that cools the motor by circulating a heat transfer medium. The cooling system includes an electric pump that circulates the heat transfer medium in the cooling circuit. The cooling system includes a first temperature acquisition means for acquiring the motor temperature. The cooling system includes a torque acquisition means for acquiring the motor torque. The cooling system includes a pump control device for controlling the operation of the pump. When the motor temperature acquired by the first temperature acquisition means is less than a predetermined temperature threshold, the pump control device operates the pump at a first output, and when the motor temperature acquired by the first temperature acquisition means is greater than the temperature threshold, the pump control device operates the pump at a second output greater than the first output. The pump control device changes the temperature threshold according to the acquired torque acquired by the torque acquisition means.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a cooling system for electric vehicles. Here, an electric vehicle broadly refers to a vehicle having a driving motor for driving wheels, and includes, for example, battery electric vehicles (BEV), hybrid electric vehicles (HEV), fuel cell electric vehicles (FCEV), etc.

Background Art

[0002] The cooling system for electric vehicles described in Patent Document 1 includes an electric pump for circulating a heat medium that cools the motor. When the output of the motor becomes equal to or greater than a predetermined threshold output, the output of the pump is increased.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the technology of Patent Document 1, regardless of the temperature of the motor, when the output of the motor is equal to or greater than the threshold output, the output of the pump is increased. Since the output of the pump may be increased more than necessary, there is a risk that the power consumption of the pump will increase unnecessarily.

Means for Solving the Problems

[0005] The cooling system for electric vehicles disclosed herein is used in electric vehicles equipped with a motor for driving. The cooling system includes a cooling circuit that cools the motor by circulating a heat transfer medium. The cooling system includes an electric pump that circulates the heat transfer medium in the cooling circuit. The cooling system includes a first temperature acquisition means for acquiring the temperature of the motor. The cooling system includes a torque acquisition means for acquiring the torque of the motor. The cooling system includes a pump control device that controls the operation of the pump. When the motor temperature acquired by the first temperature acquisition means is less than a predetermined temperature threshold, the pump control device operates the pump at a first output, and when the motor temperature acquired by the first temperature acquisition means is greater than the temperature threshold, the pump control device operates the pump at a second output greater than the first output. The pump control device changes the temperature threshold according to the acquired torque acquired by the torque acquisition means.

[0006] With the above configuration, the temperature threshold for switching the motor output can be changed according to the acquired torque. For example, the temperature threshold can be changed to be higher when the acquired torque is low (i.e., when the motor generates little heat). This expands the range in which the pump operates at the first output (low output) when the motor's required cooling amount is relatively small. This makes it possible to reduce the pump's power consumption while adequately cooling the motor. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram shows the schematic configuration of electric vehicle 1. [Figure 2] This figure shows an example of a control map M1. [Figure 3] This is a flowchart illustrating the operation of the pump control device 44. [Figure 4] This figure shows an example of a control map M2. [Modes for carrying out the invention]

[0008] The pump control device may set the temperature threshold as a first temperature threshold when the acquired torque is less than a predetermined torque threshold, and as a second temperature threshold that is less than the first temperature threshold when the acquired torque is greater than the torque threshold.

[0009] According to the above configuration, the range in which the pump operates at a first output (low output) when the acquired torque is lower than a predetermined torque threshold can be extended. This makes it possible to reduce the power consumption of the pump.

[0010] The system may further include a second temperature acquisition means for acquiring the temperature of the heat transfer medium. The pump control device may change at least one of the first temperature threshold and the second temperature threshold in at least two steps such that the value becomes higher when the temperature of the heat transfer medium acquired by the second temperature acquisition means is low.

[0011] The lower the temperature of the heat transfer medium, the greater the amount of heat absorbed. Therefore, the pump output can be reduced while maintaining the same cooling capacity. With the above configuration, the lower the temperature of the heat transfer medium, the wider the range in which the pump operates at the first output (low output). This makes it possible to reduce the power consumption of the pump.

[0012] The system may further include a second temperature acquisition means for acquiring the temperature of the heat transfer medium. The pump control device may change the torque threshold in at least two stages such that it becomes a higher value when the temperature of the heat transfer medium acquired by the second temperature acquisition means is low.

[0013] In the range where the acquired torque is lower than the torque threshold, the range in which the pump operates at the first output (low output) is wider than in the range where the acquired torque is higher than the torque threshold. With the above configuration, the lower the temperature of the heat transfer medium (i.e., the higher the cooling capacity), the wider the range in which the pump operates at the first output (low output) can be extended by increasing the torque threshold. This makes it possible to reduce the power consumption of the pump.

[0014] The pump control device may further include a rotation speed acquisition means for acquiring the rotation speed of the motor. The pump control device may change at least one of the first temperature threshold and the second temperature threshold in at least two stages such that the value becomes higher when the motor rotation speed acquired by the rotation speed acquisition means is small.

[0015] With the above configuration, the temperature threshold can be modified so that it is higher when the motor speed is low (i.e., when the amount of heat generated by the motor is low). The range in which the pump operates at the first output (low output) can be extended. The power consumption of the pump can be reduced. [Examples]

[0016] (Configuration of electric vehicle 1) Figure 1 shows a schematic configuration of the electric vehicle 1 of this embodiment. In Figure 1, signal lines are shown as dotted lines. The electric vehicle 1 mainly comprises a battery pack 12, a power control circuit 14, a motor 16, a gear unit 18, a motor control device 20, and a cooling system 30.

[0017] The motor 16 is mechanically connected to the gear unit 18. The gear unit 18 drives the wheels (not shown) of the electric vehicle 10. The battery pack 12 is a power source that supplies power to the motor 16. The battery pack 12 is connected to the motor 16 via a power control circuit 14. The power control circuit 14 converts the DC power supplied from the battery pack 12 into AC power supplied to the motor 16. The operation of the power control circuit 14 is controlled by the motor control device 20. The motor control device 20 controls the torque output by the motor 16 by controlling the operation of the power control circuit 14 in response to torque commands from a higher-level control device (not shown).

[0018] The cooling system 30 is configured to cool the motor 16. Note that the cooling system 30 is not limited to the motor 16 and may be configured to cool other devices such as the power control circuit 14 and the gear unit 18. The cooling system 30 mainly includes a cooling circuit 32, a heat medium cooler 34, a pump 40, and a pump control device 44. The pump 40 and the heat medium cooler 34 are arranged on the cooling circuit 32. The pump control device 44 controls the operation of the pump 40. The cooling circuit 32 is configured such that the heat medium circulates by the pump 40. In this embodiment, the heat medium is oil. The heat medium circulating in the cooling circuit 32 recovers heat from the motor 16 and releases the heat in the heat medium cooler 34. Thereby, the motor 16 is cooled.

[0019] The cooling system 30 further includes a first temperature sensor 51, a second temperature sensor 52, a torque sensor 53, and a rotation speed sensor 54. The first temperature sensor 51 is arranged on the motor 16, acquires the temperature of the motor 16, and outputs the motor temperature Tm. The second temperature sensor 52 is arranged on the cooling circuit 32, acquires the temperature of the heat medium, and outputs the heat medium temperature Tw. The torque sensor 53 is arranged on the motor 16, acquires the torque output from the motor 16, and outputs the acquired torque Tq. The rotation speed sensor 54 is arranged on the motor 16, acquires the rotation speed of the motor 16, and outputs the rotation speed Rm. The motor temperature Tm, the heat medium temperature Tw, the acquired torque Tq, and the rotation speed Rm are input to the pump control device 44. Note that the first temperature sensor 51 is an example of the first temperature acquisition means. The second temperature sensor 52 is an example of the second temperature acquisition means. The torque sensor 53 is an example of the torque acquisition means. The rotation speed sensor 54 is an example of the rotation speed acquisition means.

[0020] (Control content by the pump control device 44) The pump control device 44 controls the pump 40 based on a control map M1 stored in advance. FIG. 2 shows an example of the control map M1. The horizontal axis is the acquired torque Tq, and the vertical axis is the motor temperature Tm. The control map M1 includes a normal threshold NTh (solid line) and a low-temperature threshold LTh (dotted line). The normal threshold N_Th is a threshold used when the heat medium temperature Tw is higher than the heat medium threshold Tw_Th. The low-temperature threshold L_Th is a threshold used when the heat medium temperature Tw is lower than the heat medium threshold Tw_Th. Note that the heat medium threshold Tw_Th, the normal threshold N_Th, and the low-temperature threshold L_Th can be determined in advance according to the capacity of the pump 40, the motor 16, etc.

[0021] The normal threshold N_Th will be described. The normal threshold N_Th includes a first temperature threshold N_Th1 and a second temperature threshold N_Th2. The first temperature threshold N_Th1 is a threshold used in a region (region N_R1) where the acquired torque Tq is smaller than the normal torque threshold N_Tq_Th. The second temperature threshold N_Th2 is a threshold used in a region (region N_R2) where the acquired torque Tq is larger than the normal torque threshold N_Tq_Th. The second temperature threshold N_Th2 is a lower temperature threshold than the first temperature threshold N_Th1.

[0022] A region (region N_R1) where the acquired torque Tq is smaller than the normal torque threshold N_Tq_Th will be described. In region N_R1, when the motor temperature Tm is smaller than the first temperature threshold N_Th1, the pump 40 is operated at the first output OT1. On the other hand, when the motor temperature Tm is larger than the first temperature threshold N_Th1, the pump 40 is operated at the second output OT2. The second output OT2 is a larger output than the first output OT1. The values of the first output OT1 and the second output OT2 can be various. In this embodiment, the first output OT1 is set to a value small enough to turn off the cooling of the motor 16. Also, the second output OT2 is set to a value large enough to turn on the cooling of the motor 16.

[0023] Furthermore, we will explain the region (region N_R2) where the acquired torque Tq is greater than the normal torque threshold N_Tq_Th. In region N_R2, when the motor temperature Tm is less than the second temperature threshold N_Th2, the pump 40 is operated at the first output OT1. On the other hand, when the motor temperature Tm is greater than the second temperature threshold N_Th2, the pump 40 is operated at the second output OT2.

[0024] The low-temperature threshold L_Th is explained below. The low-temperature threshold L_Th comprises a first temperature threshold L_Th1 and a second temperature threshold L_Th2. The first temperature threshold L_Th1 is the threshold used in the region where the acquired torque Tq is smaller than the low-temperature torque threshold L_Tq_Th. The second temperature threshold L_Th2 is the threshold used in the region where the acquired torque Tq is larger than the low-temperature torque threshold L_Tq_Th. Here, the low-temperature torque threshold L_Tq_Th is a torque value higher than the normal torque threshold N_Tq_Th. Also, the second temperature threshold L_Th2 is a temperature threshold lower than the first temperature threshold L_Th1.

[0025] This section describes the region (region L_R1) where the acquired torque Tq is smaller than the low-temperature torque threshold L_Tq_Th. In region L_R1, when the motor temperature Tm is smaller than the first temperature threshold L_Th1, the pump 40 operates at the first output OT1. On the other hand, when the motor temperature Tm is larger than the first temperature threshold L_Th1, the pump 40 operates at the second output OT2.

[0026] Furthermore, we will explain the region (region L_R2) where the acquired torque Tq is greater than the low-temperature torque threshold L_Tq_Th. In region L_R2, when the motor temperature Tm is less than the second temperature threshold L_Th2, the pump 40 is operated at the first output OT1. On the other hand, when the motor temperature Tm is greater than the second temperature threshold L_Th2, the pump 40 is operated at the second output OT2.

[0027] (Operation flow of the pump control device 44) The operation of the pump control device 44 will be explained using the flowchart in Figure 3. Hereafter, "Step 10" will be abbreviated as "S10". The flow in Figure 3 starts when the ignition switch of the electric vehicle 1 is turned on. The flow in Figure 3 is also executed repeatedly at a predetermined cycle.

[0028] In S10, the pump control device 44 determines whether the heat transfer medium temperature Tw obtained by the second temperature sensor 52 is higher than the heat transfer medium threshold Tw_Th. If the determination is positive (S10: YES), the process proceeds to S20, and the pump control device 44 performs normal operation (S20~S50). Normal operation is the operation that uses the normal threshold N_Th (see Figure 2). On the other hand, if the determination in S10 is negative (S10: NO), the process proceeds to S120, and the pump control device 44 performs low-temperature operation (S120~S150). Low-temperature operation is the operation that uses the low-temperature threshold L_Th (see Figure 2). This will be explained below.

[0029] The normal operation (S20-S50) is described below. In S20, the pump control device 44 selects the normal threshold N_Th. In S30, the pump control device 44 determines whether the acquired torque Tq obtained by the torque sensor 53 is greater than the normal torque threshold N_Tq_Th. If the determination is negative (S30: NO), it is determined that the first temperature threshold N_Th1 is to be used, and the process proceeds to S40 (see Figure 2, region N_R1).

[0030] In S40, the pump control device 44 determines whether the motor temperature Tm obtained by the first temperature sensor 51 is higher than the first temperature threshold N_Th1. If the determination is negative (S40: NO), the process proceeds to S200, the output of the pump 40 is set to the first output OT1 (low output), and the process returns to S10. On the other hand, if the determination is positive (S40: YES), the process proceeds to S210, the output of the pump 40 is set to the second output OT2 (high output), and the process returns to S10.

[0031] Furthermore, if the judgment in S30 is affirmative (S30:YES), it is determined that the second temperature threshold N_Th2 will be used, and the process proceeds to S50 (see Figure 2, region N_R2). In S50, the pump control device 44 determines whether the motor temperature Tm obtained by the first temperature sensor 51 is higher than the second temperature threshold N_Th2. If the judgment is negative (S50:NO), the process proceeds to S200, where the output of the pump 40 is set to the first output OT1 (low output), and the process returns to S10. On the other hand, if the judgment is affirmative (S50:YES), the process proceeds to S210, where the output of the pump 40 is set to the second output OT2 (high output), and the process returns to S10.

[0032] The low-temperature operation (S120-S150) is described below. In S120, the pump control device 44 selects a low-temperature threshold L_Th. In S130, the pump control device 44 determines whether the acquired torque Tq obtained by the torque sensor 53 is greater than the low-temperature torque threshold L_Tq_Th. If the determination is negative (S130: NO), it is determined that the first temperature threshold L_Th1 is to be used, and the process proceeds to S140 (see Figure 2, region L_R1).

[0033] In S140, the pump control device 44 determines whether the motor temperature Tm obtained by the first temperature sensor 51 is higher than the first temperature threshold L_Th1. If the determination is negative (S140: NO), the process proceeds to S200, where the output of the pump 40 is set to the first output OT1 (low output), and the process returns to S10. On the other hand, if the determination is positive (S140: YES), the process proceeds to S210, where the output of the pump 40 is set to the second output OT2 (high output), and the process returns to S10.

[0034] Furthermore, if the judgment in S130 is affirmative (S130:YES), it is determined that the second temperature threshold L_Th2 will be used, and the process proceeds to S150 (see Figure 2, region L_R2). In S150, the pump control device 44 determines whether the motor temperature Tm obtained by the first temperature sensor 51 is higher than the second temperature threshold L_Th2. If the judgment is negative (S150:NO), the process proceeds to S200, where the output of the pump 40 is set to the first output OT1 (low output), and the process returns to S10. On the other hand, if the judgment is affirmative (S150:YES), the process proceeds to S210, where the output of the pump 40 is set to the second output OT2 (high output), and the process returns to S10.

[0035] (effect) The effects of normal operation (S20~S50) will be explained. As shown in Figure 2, in the technology of this embodiment, the first output OT1 (low output) is used when the motor temperature Tm is lower than the temperature threshold, and the second output OT2 (high output) is used when the motor temperature Tm is higher than the temperature threshold. The higher the temperature threshold, the wider the range in which the pump 40 operates with the first output OT1, and thus it is possible to reduce power consumption. However, the higher the temperature threshold, the higher the motor temperature at which the pump 40 starts operating with the second output OT2, so the cooling margin decreases and it becomes difficult to cope with a rapid rise in motor temperature Tm. Therefore, the technology of this embodiment is equipped with a configuration that changes the temperature threshold according to the acquired torque Tq. Specifically, in the region N_R1 where the acquired torque Tq is smaller than the normal torque threshold N_Tq_Th, the first temperature threshold N_Th1 (low temperature) is used, and in the region N_R2 where the acquired torque Tq is larger than the normal torque threshold N_Tq_Th, the second temperature threshold N_Th2 (high temperature) is used. Region N_R1 is a region with a larger cooling margin than region N_R2. This is because the lower the acquired torque Tq, the less heat is generated by the motor 16. Therefore, by using the first temperature threshold N_Th1 (low temperature) in region N_R1, the range in which the pump 40 operates at the first output OT1 (low output) can be expanded while ensuring a cooling margin. In other words, the range in which the pump operates at the first output OT1 (the range shown by hatching in Figure 2) can be expanded to the higher temperature side of the motor temperature Tm in region N_R1 than in region N_R2 (see expanded region EA). This makes it possible to reduce the power consumption of the pump 40.

[0036] The effects of low-temperature operation (S120~S150) are explained below. The lower the temperature of the heat transfer medium, the greater the amount of heat absorbed. Therefore, the output of the pump 40 can be reduced while maintaining the same cooling capacity. In this embodiment, the normal threshold N_Th is used when the heat transfer medium temperature Tw is higher than the heat transfer medium threshold Tw_Th, and the low-temperature threshold L_Th is used when the heat transfer medium temperature Tw is lower than the heat transfer medium threshold Tw_Th. As a result, when the heat transfer medium temperature Tw is low, using the low-temperature threshold L_Th expands the range in which the pump 40 operates at the first output OT1 (low output) while maintaining the cooling capacity. In other words, using the low-temperature threshold L_Th expands the range in which the pump operates at the first output OT1 to the higher temperature side of the motor temperature Tm compared to using the normal threshold N_Th (see Figure 2, arrow Y1). This makes it possible to reduce the power consumption of the pump 40.

[0037] Furthermore, in low-temperature operation (S120~S150), the technology of this embodiment uses the normal torque threshold N_Tq_Th when the heat transfer medium temperature Tw is higher than the heat transfer medium threshold Tw_Th, and the low-temperature torque threshold L_Tq_Th when the heat transfer medium temperature Tw is lower than the heat transfer medium threshold Tw_Th. The low-temperature torque threshold L_Tq_Th is a higher torque than the normal torque threshold N_Tq_Th. As a result, when the heat transfer medium temperature Tw is low, using the low-temperature torque threshold L_Tq_Th allows the range in which the pump 40 operates at the first output OT1 to be extended to the high-torque side of the acquired torque Tq (see Figure 2, arrow Y2). This makes it possible to reduce the power consumption of the pump 40. [Examples]

[0038] In Example 2, another embodiment of the control content by the pump control device 44 will be described. Since the configuration of the electric vehicle 1 (Figure 1) is the same in Examples 1 and 2, its description will be omitted. Also, common parts in Examples 1 and 2 are given the same reference numerals, and their descriptions will be omitted. In the following, only matters specific to Example 2 will be described.

[0039] The pump control device 44 stores a control map M2 (Figure 4) in addition to the control map M1 (Figure 2) described above. The low-temperature threshold L_Th in control map M2 (Figure 4) is lower than the low-temperature threshold L_Th in control map M1 (Figure 2) by an offset value OF1. Therefore, the range in which the pump 40 operates at the first output OT1 (low output) during low-temperature operation is expanded by an offset value OF1 in control map M1 compared to control map M2. Similarly, the normal threshold N_Th in control map M2 (Figure 4) is lower than the normal threshold N_Th in control map M1 (Figure 2) by an offset value OF2. Therefore, the range in which the pump 40 operates at the first output OT1 (low output) during normal operation is expanded by an offset value OF2 in control map M1 compared to control map M2. In other words, the power consumption of the pump 40 is lower when using control map M1 than when using control map M2. Note that control maps M1 and M2 are identical in all other respects.

[0040] The operation of the pump control device 44 in Example 2 will now be explained. To achieve the operation in Example 2, S5 should be added before S10 in the flow chart of Figure 3. After executing S200 and S210, the process should return to S5.

[0041] In S5, the pump control device 44 determines whether the rotational speed Rm obtained by the rotational speed sensor 54 is higher than the rotational speed threshold Rm_Th. The rotational speed threshold Rm_Th can be predetermined according to the output characteristics of the motor 16, etc. If the rotational speed Rm is lower than the rotational speed threshold Rm_Th (S5:NO), the pump control device 44 selects control map M1 and executes the processes from S10 onwards. On the other hand, if the rotational speed Rm is higher than the rotational speed threshold Rm_Th (S5:NO), the pump control device 44 selects control map M2 and executes the processes from S10 onwards.

[0042] (effect) The smaller the rotational speed Rm of the motor 16, the less heat is generated by the motor 16. Therefore, the output of the pump 40 can be reduced while maintaining the same cooling capacity. In this embodiment, control map M1 (Figure 2) is used when the rotational speed Rm is lower than the rotational speed threshold Rm_Th, and control map M2 (Figure 4) is used when the rotational speed Rm is higher than the rotational speed threshold Rm_Th. As mentioned above, control map M1 has a wider range in which the pump 40 operates at the first output OT1 (low output) than control map M2. Therefore, by using control map M1 when the rotational speed Rm is low, it is possible to reduce the power consumption of the pump 40 while maintaining the cooling capacity.

[0043] Although embodiments have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself.

[0044] (modified version) Hysteresis characteristics may be set for the normal threshold N_Th and the low-temperature threshold L_Th. Specifically, the normal threshold N_Th used for switching from the first output OT1 to the second output OT2 should be set higher by a predetermined hysteresis temperature than the normal threshold N_Th used for switching from the second output OT2 to the first output OT1. Similarly, a hysteresis temperature can be set for the low-temperature threshold L_Th. This prevents the pump 40 from frequently switching outputs, thereby extending the lifespan of the pump 40.

[0045] The method for obtaining the temperature of the motor 16 is not limited to the method using the first temperature sensor 51, but may be various. For example, the temperature of the motor 16 may be obtained by calculation from the driving conditions of the motor 16, etc. The method for obtaining the temperature of the heat transfer medium is not limited to the method using the second temperature sensor 52, but may be various. For example, the temperature of the heat transfer medium may be obtained by calculation from the operating conditions of the cooling circuit 32, etc. The method for obtaining the torque output from the motor 16 is not limited to the method using the torque sensor 53, but may be various. For example, the torque may be obtained using control command values, etc. The method for obtaining the rotational speed of the motor 16 is not limited to the method using the rotational speed sensor 54, but may be various. For example, the rotational speed may be obtained using control command values, etc.

[0046] The example described here involves changing the first temperature threshold in two stages between the first temperature threshold N_Th1 and L_Th1, but this is not the only possible configuration. It may be changed in three or more stages, or continuously. Similarly, the second temperature threshold and torque threshold may also be changed in multiple stages or continuously.

[0047] Although an embodiment in which both the first and second temperature thresholds are changed according to the heat transfer medium temperature Tw has been described, the embodiment is not limited to this embodiment. An embodiment in which either the first or second temperature threshold is changed according to the heat transfer medium temperature Tw is also possible. [Explanation of symbols]

[0048] 1: Electric vehicle 16: Motor 30: Cooling system 32: Cooling circuit 40: Motor 44: Pump control device 51: First temperature sensor 53: Torque sensor Tm: Motor temperature Tq: Acquired torque N_Th: Normal threshold L_Th: Low temperature threshold OT1: First output OT2: Second output

Claims

1. A cooling system used in an electric vehicle equipped with a motor for driving, A cooling circuit that cools the motor by circulating a heat transfer medium, An electric pump for circulating the heat transfer medium within the cooling circuit, A first temperature acquisition means for acquiring the temperature of the motor, Torque acquisition means for acquiring the torque of the motor, A pump control device for controlling the operation of the pump, wherein when the motor temperature obtained by the first temperature acquisition means is less than a predetermined temperature threshold, the pump is operated at a first output, and when the motor temperature obtained by the first temperature acquisition means is greater than the temperature threshold, the pump is operated at a second output greater than the first output, Equipped with, The pump control device changes the temperature threshold according to the acquired torque obtained by the torque acquisition means. Cooling system.

2. The pump control device is When the acquired torque is less than a predetermined torque threshold, the temperature threshold is set as the first temperature threshold. The cooling system according to claim 1, wherein when the acquired torque is greater than the torque threshold, the temperature threshold is set to a second temperature threshold that is smaller than the first temperature threshold.

3. The system further comprises a second temperature acquisition means for acquiring the temperature of the heat transfer medium, The cooling system according to claim 2, wherein the pump control device changes at least one of the first temperature threshold and the second temperature threshold in at least two steps such that the value becomes higher when the temperature of the heat medium obtained by the second temperature acquisition means is lower.

4. The system further comprises a second temperature acquisition means for acquiring the temperature of the heat transfer medium, The cooling system according to claim 2 or 3, wherein the pump control device changes the torque threshold in at least two stages such that it becomes a higher value when the temperature of the heat transfer medium obtained by the second temperature acquisition means is low.

5. The system further includes a rotation speed acquisition means for acquiring the rotation speed of the motor, The cooling system according to claim 2 or 3, wherein the pump control device changes at least one of the first temperature threshold and the second temperature threshold in at least two stages such that the value becomes higher when the motor rotation speed acquired by the rotation speed acquisition means is small.

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