Motor cooling system

Abstract

In a motor cooling system that uses a refrigerant containing oil in CO2 to cool the motor, the oil inside the motor is reliably drained. [Solution] The motor cooling system 100 mounted on the vehicle 200 includes a compressor 3 for compressing a refrigerant containing oil in CO2, a heat exchanger 5 for cooling the refrigerant compressed by the compressor 3, a motor 1 for driving the vehicle 200, refrigerant passages 23 and 24 for supplying the refrigerant cooled by the heat exchanger 5 into the motor 1, and a control device 80 configured to control the compressor 3. The control device 80 is configured to control the compressor 3 to generate a supercritical refrigerant in order to supply the supercritical refrigerant from the refrigerant passage 24 into the motor 1 when the conditions for supplying a supercritical refrigerant are met.

Description

Technical Field

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[0001] The present invention relates to a motor cooling system for cooling a motor of a vehicle.

Background Art

[0002] In recent years, with the practical application of electric vehicles, small and high-performance motors have been developed. As for this high-performance motor, improvement in output and torque per unit volume is particularly required. Further, with the improvement in the output and torque of the motor, it is required to cool the motor with high efficiency. In response to this requirement, technologies such as air cooling, water cooling, and oil cooling of the motor have been developed.

[0003] As one method of cooling a motor, a method of directly supplying a refrigerant to the motor can be considered. For example, Patent Document 1 describes a motor cooling structure that cools a magnet embedded in a rotor of a motor using a refrigerant (such as ATF (Automatic Transmission Fluid)). This motor cooling structure forms a refrigerant passage extending from the shaft of the motor toward the magnet in the rotor, and cools the magnet by supplying the refrigerant from this passage.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When cooling a motor using a refrigerant, one possible method is to supply the refrigerant between the motor's rotor and stator. In this case, the stirring resistance caused by the refrigerant between the rotor and stator changes quadratically with respect to the motor speed. That is, as the motor speed increases, the stirring resistance becomes very large. Therefore, motors in electric vehicles and other applications that operate at extremely high rotational speeds tend to generate significant resistance. In particular, using a high-viscosity refrigerant results in extremely high resistance.

[0006] Therefore, the inventors of this invention considered using a refrigerant consisting of low-viscosity CO2 (hereinafter referred to as "CO2 refrigerant," or sometimes simply "refrigerant") to achieve both a reduction in stirring resistance and an improvement in cooling performance. Such a CO2 refrigerant has high insulating properties and, as a so-called natural refrigerant, takes into consideration its impact on the environment and human health.

[0007] However, the refrigerants mentioned above usually contain a small amount of oil (such as PAG). This is because a compressor is used to bring the refrigerant supplied to the motor to the desired state, and oil is needed for lubrication within this compressor. On the other hand, lubricating oil is also used in the bearings that support the motor's rotating shaft. As a result, when oil enters the motor, not just CO2, that is, when oil enters the gap between the rotor and stator, an oil film (in other words, an oil reservoir) forms in this gap, which increases the stirring resistance.

[0008] The present invention was made to solve the problems of the prior art described above, and aims to reliably discharge oil from inside a motor in a motor cooling system that uses a refrigerant containing oil in CO2 to cool the motor. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides a motor cooling system mounted on a vehicle, comprising: a compressor for compressing a refrigerant containing oil in CO2; a heat exchanger for cooling the refrigerant compressed by the compressor; a motor for driving the vehicle; a refrigerant passage for supplying the refrigerant cooled by the heat exchanger into the motor to cool the motor; and a control device configured to control at least the compressor, wherein the control device is configured to control the compressor to generate a supercritical refrigerant in order to supply the supercritical refrigerant from the refrigerant passage into the motor when predetermined conditions are met.

[0010] According to the present invention configured in this way, by supplying a supercritical refrigerant into the motor, the compatibility of this supercritical refrigerant can be utilized to draw in oil from within the motor, and the oil can be effectively discharged together with the refrigerant. This removes the oil film (in other words, oil reservoir) formed inside the motor and suppresses the increase in stirring resistance caused by the oil inside the motor.

[0011] In the present invention, preferably, the control device is configured to control the compressor to generate a supercritical refrigerant when predetermined conditions are met, and to control the compressor to generate a liquid-phase refrigerant when predetermined conditions are not met. In the present invention configured as described above, the control device supplies liquid-phase refrigerant into the motor when predetermined conditions are not met, thereby limiting the supply of supercritical refrigerant, that is, preventing the unnecessary supply of supercritical refrigerant. This reduces the load on the compressor required to generate supercritical refrigerant and suppresses the increase in resistance caused by supplying supercritical refrigerant into the motor.

[0012] In the present invention, preferably, the control device is configured to control the compressor to generate a liquid-phase refrigerant in order to supply a liquid-phase refrigerant to the motor after a predetermined time has elapsed since the supply of a supercritical refrigerant to the motor began after predetermined conditions have been met. With the present invention configured in this way, by supplying a supercritical refrigerant for a certain period of time, it is possible to terminate the supply of the supercritical refrigerant when the oil in the motor has been completely drained. As a result, the load on the compressor required to generate the supercritical refrigerant can be reduced. In other words, power consumption by the compressor can be reduced.

[0013] In the present invention, preferably, the refrigerant passage has a first passage for supplying a supercritical refrigerant into the motor and a second passage for supplying a liquid-phase refrigerant into the motor, the motor cooling system further has valves provided in the first passage and / or the second passage, and the control device is configured to control the valves to supply a supercritical refrigerant into the motor from the first passage when predetermined conditions are met, and to control the valves to supply a liquid-phase refrigerant into the motor from the second passage when the predetermined conditions are not met. With the present invention configured in this way, by controlling the valve and switching the passages through which the refrigerant flows (first passage, second passage), the refrigerant supplied to the motor can be easily switched between a supercritical refrigerant and a liquid-phase refrigerant.

[0014] In the present invention, preferably, the motor cooling system further includes a motor rotation speed sensor for detecting the rotation speed of the motor, and the control device is configured to determine that a predetermined condition has been met when the rotation speed (motor rotation speed) detected by the motor rotation speed sensor is less than a predetermined rotation speed. According to the present invention configured in this manner, a supercritical refrigerant can be supplied when the motor is rotating at low speeds, and the increase in resistance caused by supplying a supercritical refrigerant into the motor can be effectively suppressed.

[0015] In the present invention, preferably, the control device is configured to control the compressor to generate a liquid-phase refrigerant in order to supply a liquid-phase refrigerant to the motor when the rotational speed exceeds a predetermined rotational speed while a predetermined condition is met and a supercritical refrigerant is being supplied to the motor. With the present invention configured in this way, when the motor speed increases (typically during acceleration), the operation of the compressor for generating a supercritical refrigerant can be terminated, thereby reducing power consumption by the compressor. As a result, more power can be allocated to the motor, making it possible to accurately meet the vehicle's acceleration requirements.

[0016] In the present invention, preferably, the motor cooling system further includes at least one of the following: an acceleration sensor for detecting the acceleration of the vehicle, a camera for photographing the area around the vehicle, a distance sensor for detecting the distance between the vehicle and objects present in its surroundings, and a GPS sensor for detecting the current position of the vehicle. The control device is configured to predict when the vehicle will stop based on signals obtained from at least one of the acceleration sensor, camera, distance sensor, and GPS sensor, and to determine that a predetermined condition has been met when a vehicle stop is predicted. In the present invention configured as described above, taking into consideration that it takes some time for the compressor to generate a supercritical refrigerant, the compressor is started in advance at the timing when the vehicle is expected to stop, before the motor actually reaches a low rotation speed. This ensures that a supercritical refrigerant is reliably supplied when the motor is running at low speed, and effectively balances the suppression of increased resistance caused by supplying a supercritical refrigerant into the motor with ensuring the discharge of oil from the motor by the supercritical refrigerant.

[0017] In the present invention, preferably, the motor cooling system further includes a pedal sensor that detects pedal operation by a driver to apply braking force to the vehicle, and the control device is configured to determine that a predetermined condition has been met when pedal operation is detected by the pedal sensor. Even in the present invention configured as described above, considering that it takes some time for the compressor to generate a supercritical refrigerant, the compressor operation for generating the supercritical refrigerant is started in advance at the timing when the pedal operation for braking the vehicle is detected by the pedal sensor, before the motor actually reaches a low rotation speed. This ensures that a supercritical refrigerant is reliably supplied when the motor is running at low rotation speeds, and accurately achieves both the suppression of increased resistance due to supplying a supercritical refrigerant into the motor and the assurance of oil discharge from the motor by the supercritical refrigerant.

[0018] In the present invention, preferably, the motor cooling system further includes an oil tank for storing oil and an oil level sensor for detecting the level of oil stored in the oil tank, and the control device is configured to determine that a predetermined condition has been met when the level detected by the oil level sensor is greater than or equal to a first predetermined value and less than a second predetermined value that is greater than the first predetermined value. According to the present invention configured in this way, by controlling the supply of supercritical refrigerant based on the oil level determination result using a first predetermined value and a second predetermined value, it is possible to reliably drain the oil from the motor while preventing compressor seizure due to insufficient oil in the refrigerant, even when there is a relatively large amount of oil in the motor.

[0019] In a preferred example of the present invention, the motor comprises a rotor and a stator, a rotating shaft connected to the rotor, and a sliding bearing supporting the rotating shaft, wherein a coolant is supplied between the rotor and the stator from a coolant passage, and the motor cooling system has a coolant passage for supplying coolant to the sliding bearing, separate from the coolant passage, and an oil passage for supplying oil to the sliding bearing.

Advantages of the Invention

[0020] According to the present invention, in a motor cooling system that cools a motor using a refrigerant containing oil in CO2, the oil in the motor can be reliably discharged.

Brief Description of the Drawings

[0021] [Figure 1] It is a schematic configuration diagram of a vehicle to which a motor cooling system according to an embodiment of the present invention is applied. [Figure 2] It is a schematic configuration diagram of a motor cooling system according to an embodiment of the present invention. [Figure 3] It is a schematic configuration diagram showing an enlarged view of the periphery of a motor of a motor cooling system according to an embodiment of the present invention. [Figure 4] It is a block diagram showing the electrical configuration of a motor cooling system according to an embodiment of the present invention. [Figure 5] It is a time chart showing the control according to an embodiment of the present invention. [Figure 6] It is a flowchart showing the control according to an embodiment of the present invention. [Figure 7] It is a time chart showing the control according to a modification of an embodiment of the present invention. [Figure 8] It is a flowchart showing the control according to a modification of an embodiment of the present invention.

Modes for Carrying Out the Invention

[0022] Hereinafter, a motor cooling system according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0023] [Overall Configuration] First, referring to FIG. 1, it is a schematic configuration diagram of a vehicle to which a motor cooling system according to the present embodiment is applied.

[0024] As shown in Figure 1, the vehicle 200 is, for example, an electric vehicle and has a motor cooling system 100. This motor cooling system 100 mainly includes a motor 1 that generates power to drive the vehicle 200, a compressor 3 that compresses the refrigerant supplied to the motor 1, and a heat exchanger (condenser) 5 that includes a condenser and a fan, etc., and cools the refrigerant compressed by the compressor 3.

[0025] The motor cooling system 100 circulates a refrigerant in a refrigeration cycle, specifically a CO2 refrigerant (hereinafter sometimes simply referred to as "refrigerant") as a natural refrigerant. This CO2 refrigerant contains not only CO2 but also oils such as PAG (refrigerant oil) (and may also contain additives). Because such a CO2 refrigerant is used, the compressor 3 is configured to compress the refrigerant to a very high pressure. The motor 1 uses the refrigerant (typically liquid refrigerant) compressed by the compressor 3 to cool the rotor and stator, and to lubricate the sliding bearings that support the rotating shaft. In this case, the motor 1 is configured to function as an expansion valve or evaporator in the refrigeration cycle. For example, in the motor cooling system 100, high-temperature liquid refrigerant is supplied from the compressor 3 to the heat exchanger 5, low-temperature liquid refrigerant is supplied from the heat exchanger 5 to the motor 1, and high-temperature gaseous refrigerant is supplied from the motor 1 to the compressor 3. The refrigerant compressed by the compressor 3 may also be used for air conditioning in air conditioners or for cooling batteries.

[0026] [Motor Cooling System Configuration] Next, the motor cooling system 100 according to this embodiment will be described in detail with reference to Figures 2 to 4.

[0027] First, Figure 2 is a schematic diagram of the motor cooling system 100 according to this embodiment. As shown in Figure 2, the motor cooling system 100 mainly includes, in addition to the motor 1, compressor 3 and heat exchanger 5 described above, an oil tank 6 for storing oil, refrigerant passages 21-24 and 26 through which refrigerant (CO2 refrigerant) flows, a mixed fluid passage 25 through which a mixed fluid of refrigerant and oil flows, and an oil passage 27 through which oil flows. Also, as shown in Figure 2, the motor 1 has a rotating shaft 13 and a pair of sliding bearings 15 that support the rotating shaft 13.

[0028] The refrigerant passage 21 is a passage for supplying refrigerant from the compressor 3 to the motor 1, etc., via the heat exchanger 5, and branches into refrigerant passages 22, 23, and 24 downstream of the heat exchanger 5. The refrigerant passage 21 is equipped with a refrigerant pressure sensor 51 for detecting the pressure of the refrigerant.

[0029] Refrigerant passage 22 is a passage for supplying refrigerant into the sliding bearing 15, and refrigerant passages 23 and 24 are passages for supplying refrigerant into the motor 1. In particular, refrigerant passage 23 is a passage for supplying liquid-phase refrigerant into the motor 1 (corresponding to the "second passage" in this invention), and refrigerant passage 24 is a passage for supplying supercritical refrigerant into the motor 1 (corresponding to the "first passage" in this invention). The refrigerant supplied to the sliding bearing 15 from refrigerant passage 22 is used for lubrication of the sliding bearing 15, the refrigerant supplied to the motor 1 from refrigerant passage 23 is used for cooling the motor 1, and the refrigerant supplied to the motor 1 from refrigerant passage 24 is used for draining oil from the motor 1.

[0030] Furthermore, a check valve 35 is provided in the refrigerant passage 22. In addition, a cooling valve 30 is provided in the refrigerant passage 23, which can be opened and closed to switch between supplying and shutting off refrigerant through the passage, and a discharge valve 31 is provided in the refrigerant passage 24, which can be opened and closed to switch between supplying and shutting off refrigerant through the passage. It should be noted that the system is not limited to providing valves (cooling valve 30 and discharge valve 31) in each of the refrigerant passages 23 and 24; in other words, it is not limited to using two valves. In other examples, a valve may be provided in either one of the refrigerant passages 23 or 24, or a three-way valve may be provided at the branching point of the refrigerant passages 23 and 24, and such a single valve may be used to allow refrigerant to flow in either one of the refrigerant passages 23 or 24.

[0031] The mixed fluid passage 25 is a passage for supplying the mixed fluid of refrigerant and oil discharged from the motor 1 to the oil tank 6. The oil tank 6 is configured to separate the oil from the mixed fluid supplied from the mixed fluid passage 25 (gas-liquid separation), store the separated oil, and supply the remaining refrigerant (which also contains a small amount of oil) to the compressor 3 through the refrigerant passage 26. The oil tank 6 is also equipped with an oil level sensor 52 for detecting the level of the stored oil (oil level).

[0032] The oil passage 27 is a passage for supplying oil stored in the oil tank 6 to the sliding bearing 15. The oil supplied to the sliding bearing 15, along with the refrigerant mentioned above, is used for lubrication of the sliding bearing 15. The oil passage 27 is equipped with an oil pump 33 for pressurizing the oil, a hydraulic pressure sensor 53 for detecting the oil pressure (hydraulic pressure), and a check valve 36.

[0033] In the motor cooling system 100 described above, the refrigerant is supplied (specifically ejected) into the motor 1 from the refrigerant passages 23 and 24, causing a pressure reduction, so the motor 1 functions as an expansion valve for the refrigeration cycle. Furthermore, the supplied refrigerant exchanges heat within the motor 1 (at which time the refrigerant absorbs heat and evaporates), so the motor 1 functions as an evaporator for the refrigeration cycle.

[0034] Next, Figure 3 is a schematic diagram showing an enlarged view of the area around the motor 1 of the motor cooling system 100 according to this embodiment. Specifically, Figure 3 is a cross-sectional view of the motor 1 along the axial direction. In Figure 3, the state in which supercritical refrigerant is supplied into the motor 1 from the refrigerant passage 24 is schematically shown.

[0035] As shown in Figure 3, the motor 1 of the motor cooling system 100 includes a rotor 11 and a stator 12, a rotating shaft 13 connected to the rotor 11 and one end of which is connected to the transaxle (not shown) of the vehicle 200, a pair of sliding bearings 15 that support the rotating shaft 13 of the motor 1, and a housing 14 that houses the rotor 11, stator 12, rotating shaft 13, and sliding bearings 15.

[0036] Furthermore, the housing 14 of the motor 1 is provided with a sealing member 18 to seal the side of the rotating shaft 13 that is connected to the transaxle, etc. (the side where the sliding bearing 15 shown on the left in Figure 3 is provided). This sealing member 18 is provided to prevent fluid leakage from the gap between the portion of the rotating shaft 13 that extends from the housing 14 to the outside and the housing 14. The sealing member 18 is configured as a mechanical seal that uses oil supplied from the oil passage 27 to prevent fluid leakage.

[0037] Furthermore, as shown in Figure 3, in the motor cooling system 100, the refrigerant passage 22 is configured to supply refrigerant to each of the pair of sliding bearings 15 in the motor 1, and the refrigerant passage 23 is configured to supply refrigerant (refrigerant in liquid phase) to the gap between the rotor 11 and the stator 12 in the motor 1. In particular, the refrigerant passage 23 branches into two passages downstream of the cooling valve 30, and refrigerant is supplied from these two passages to the gap between the rotor 11 and the stator 12.

[0038] Furthermore, the refrigerant passage 24 branches into four refrigerant passages 24a to 24d at the branching section 24x located downstream of the discharge valve 31, and each of these refrigerant passages 24a to 24d is configured to supply refrigerant (supercritical refrigerant) into the motor 1. Specifically, refrigerant passages 24a and 24b are configured to supply refrigerant to the gap between the rotor 11 and the stator 12, particularly to the central portion in the axial direction of the rotor 11 and stator 12, while refrigerant passages 24c and 24d are configured to supply refrigerant from the sides of the rotor 11 and stator 12.

[0039] As mentioned above in the "Problems the Invention Aims to Solve," since the refrigerant (CO2 refrigerant) contains oil, and since oil is used in the sliding bearing 15, not only CO2 but also oil enters the gap between the rotor 11 and the stator 12, forming an oil film (in other words, an oil reservoir) in this gap (see arrow A1 in Figure 3). As a result, the stirring resistance in the motor 1 increases.

[0040] To address these problems, in this embodiment, a supercritical refrigerant is supplied into the motor 1 from the refrigerant passage 24. Since the supercritical refrigerant has high compatibility with oil, it can effectively incorporate oil. Therefore, by supplying the supercritical refrigerant to the gap between the rotor 11 and the stator 12, the oil in this gap can be accurately incorporated by the refrigerant, and the incorporated oil can be discharged together with the refrigerant from the mixed fluid passage 25. As a result, the oil film formed in the gap between the rotor 11 and the stator 12 can be removed, preventing an increase in stirring resistance. In this embodiment, four refrigerant passages 24a to 24d are used to supply refrigerant to locations in the motor 1 where stirring resistance is likely to occur (see the refrigerant supply state shown in Figure 3).

[0041] Next, the electrical configuration of the motor cooling system 100 according to this embodiment will be described with reference to Figure 4. Figure 4 is a block diagram showing the electrical configuration of the motor cooling system 100 according to this embodiment.

[0042] As shown in Figure 4, the motor cooling system 100 has a control device 80 configured to perform various controls in the system. The control device 80 is composed of a computer comprising one or more processors 80a (typically a CPU) and memory 80b such as ROM or RAM that stores various programs (including basic control programs such as an OS and application programs launched on the OS to realize specific functions) and various data that are interpreted and executed on the processors 80a.

[0043] In addition to the sensors 51-53 described above (see Figure 2), the motor cooling system 100 also includes a motor speed sensor 54 for detecting the motor speed of motor 1 (the rotational speed of the rotor 11 and rotating shaft 13, which is synonymous with rotational speed), a vehicle speed sensor 55 for detecting the speed of vehicle 200, an acceleration sensor 56 for detecting the acceleration of vehicle 200, an accelerator sensor 57 for detecting the operation of the accelerator pedal in vehicle 200 (especially the accelerator pedal opening), a brake sensor 58 for detecting the operation of the brake pedal in vehicle 200, a camera 59 for photographing the area around vehicle 200 (typically in front), a distance sensor 60 for detecting the distance between vehicle 200 and objects in its vicinity (typically a vehicle in front), and a GPS (Global Positioning System) sensor 61 for detecting the current position of vehicle 200.

[0044] For example, the distance sensor 60 could be a millimeter-wave radar, laser radar, or ultrasonic sensor, and a typical example would be LiDAR (Light Detection And Ranging). The GPS sensor 61 includes a GPS receiver and a gyro sensor. The accelerator sensor 57 and brake sensor 58 are examples of "pedal sensors" in this invention.

[0045] Based on the detection signals from these sensors 51 to 61, the control device 80 supplies control signals to the motor 1, compressor 3, cooling valve 30, discharge valve 31, oil pump 33, and oil level warning light 34. The oil level warning light 34 is a lamp that warns when the level of oil stored in the oil tank 6 (detected by the oil level sensor 52) is below a predetermined value.

[0046] In this embodiment, the control device 80 primarily controls the compressor 3 to generate a liquid-phase refrigerant or a supercritical refrigerant, and also controls the opening and closing of the cooling valve 30 and the discharge valve 31, respectively, to supply the liquid-phase refrigerant or supercritical refrigerant into the motor 1 from the refrigerant passage 23 or the refrigerant passage 24.

[0047] [Control Method] Next, the control performed by the control device 80 of the motor cooling system 100 in this embodiment will be described in detail.

[0048] In this embodiment, the control device 80 determines whether or not to supply supercritical refrigerant into the motor 1 (this determines whether or not the "predetermined conditions" in the present invention are met), and if it determines that supercritical refrigerant should be supplied into the motor 1, it controls the compressor 3 to generate supercritical refrigerant, and also controls the cooling valve 30 to close and the discharge valve 31 to supply this supercritical refrigerant into the motor 1 from the refrigerant passage 24. In this way, the supercritical refrigerant supplied into the motor 1 draws in the oil in the gap between the rotor 11 and the stator 12 and discharges it together with the refrigerant. This removes the oil film (in other words, oil reservoir) formed in the gap between the rotor 11 and the stator 12, thereby preventing an increase in stirring resistance.

[0049] In response to this, if the control device 80 does not determine that supercritical refrigerant should be supplied into the motor 1, that is, if liquid-phase refrigerant should be supplied into the motor 1, it controls the compressor 3 to generate liquid-phase refrigerant and controls the cooling valve 30 to open and the discharge valve 31 to supply this liquid-phase refrigerant into the motor 1 from the refrigerant passage 23. This prevents the unnecessary supply of supercritical refrigerant into the motor 1. This reduces the load on the compressor 3 for generating supercritical refrigerant and suppresses the increase in resistance caused by supplying supercritical refrigerant into the motor 1. It should be noted that supplying liquid-phase refrigerant into the motor 1 tends to result in less stirring resistance due to the refrigerant than supplying supercritical refrigerant into the motor 1. This is because when liquid-phase refrigerant is supplied into the motor 1, the refrigerant changes from a liquid state to a gaseous state (including gas-liquid mixed phase) within the motor 1.

[0050] Furthermore, the control device 80 controls the compressor 3 and switches the opening and closing of the cooling valve 30 and the discharge valve 31, respectively, to terminate the supply of supercritical refrigerant and supply liquid-phase refrigerant to the motor 1 when a predetermined time has elapsed since the start of supplying supercritical refrigerant to the motor 1 as described above. In this way, by supplying supercritical refrigerant for a certain period of time, the supply of supercritical refrigerant is terminated when the oil discharge from the motor 1 is complete. This reduces the load on the compressor 3 for generating supercritical refrigerant. From this perspective, the predetermined time is determined based on the time required to supply supercritical refrigerant until the oil discharge from the motor 1 is complete.

[0051] Furthermore, the control device 80 performs control to supply the supercritical refrigerant described above into the motor 1 when the following determination conditions (corresponding to an example of the "predetermined conditions" in the present invention, and hereinafter referred to as "supercritical refrigerant supply conditions") are met. When these supercritical refrigerant supply conditions are not met, the control device 80 performs control to supply the liquid phase refrigerant into the motor 1. When supplying supercritical refrigerant, the control device 80 sets the "discharge rate increase request flag" to ON in order to increase the discharge rate of the compressor 3.

[0052] As a first example, the control device 80 determines that the conditions for supplying supercritical refrigerant have been met when the motor rotation speed detected by the motor rotation speed sensor 54 is below a predetermined rotation speed. This is done to supply supercritical refrigerant when the motor 1 is rotating at low speeds in order to suppress the increase in resistance caused by supplying supercritical refrigerant into the motor 1. This is because the stirring resistance caused by the refrigerant is smaller at low rotation speeds compared to high rotation speeds. Furthermore, from this perspective, the control device 80 controls the compressor 3 and switches the opening and closing of the cooling valve 30 and the discharge valve 31, respectively, when the motor rotation speed rises above the predetermined rotation speed while the motor rotation speed is being supplied with supercritical refrigerant after the motor rotation speed has fallen below the predetermined rotation speed, in order to terminate the supply of supercritical refrigerant and supply liquid-phase refrigerant into the motor 1. The predetermined rotation speed mentioned above is set based on the motor rotation speed at which the stirring resistance caused by the refrigerant (especially the supercritical refrigerant) is below a predetermined level.

[0053] As a second example, the control device 80 predicts the stopping of the vehicle 200 based on signals acquired from at least one of the acceleration sensor 56, camera 59, distance sensor 60, and GPS sensor 61, and determines that the conditions for supplying supercritical refrigerant have been met when the stopping of the vehicle 200 is predicted. In this second example as well, the basic principle is to supply supercritical refrigerant when the motor 1 is rotating at a low speed in order to suppress the increase in resistance caused by supplying supercritical refrigerant into the motor 1. In particular, in this second example, considering that it takes some time for the compressor 3 to generate supercritical refrigerant, the operation of the compressor 3 to generate supercritical refrigerant is started in advance at the timing when the stopping of the vehicle 200 is predicted, before the motor 1 actually rotates at a low speed (i.e., before the vehicle 200 has almost come to a complete stop). The control device 80 sets the "stop prediction flag" to ON when the stopping of the vehicle 200 is predicted in this way.

[0054] As a third example, the control device 80 determines that the conditions for supplying supercritical refrigerant have been met when it detects a pedal operation by the driver to apply braking force to the vehicle 200, specifically when the brake sensor 58 detects a depressing operation of the brake pedal. In this third example as well, the basic principle is to supply supercritical refrigerant when the motor 1 is rotating at a low speed in order to suppress the increase in resistance caused by supplying supercritical refrigerant into the motor 1. In particular, in this third example, considering that it takes some time for the compressor 3 to generate supercritical refrigerant, the operation of the compressor 3 to generate supercritical refrigerant is started in advance at the timing when the brake pedal is pressed, before the motor 1 actually starts rotating at a low speed (i.e., before the vehicle 200 has almost come to a stop).

[0055] As a fourth example, the control device 80 determines that the conditions for supplying supercritical refrigerant are met when the oil level detected by the oil level sensor 52 is equal to or greater than the first level (first predetermined value) and less than the second level (second predetermined value) which is greater than the first level. Here, first, when the oil level is less than the second level, it means that the oil level in the oil tank 6 is relatively low, which can be said to mean that there is a relatively large amount of oil in the motor 1. In this case, the oil in the motor 1 should be discharged with supercritical refrigerant. Furthermore, when the oil level is equal to or greater than the first level, it means that the refrigerant contains a sufficient amount of oil to properly operate the compressor 3. In other words, when the compressor 3 is operated to generate supercritical refrigerant, the compressor 3 can be properly lubricated with the oil contained in the refrigerant so that seizure or other problems do not occur in the compressor 3. In this way, by controlling the supply of supercritical refrigerant based on the oil level determination results using the first and second levels, it becomes possible to reliably drain the oil from the motor 1 while preventing the compressor 3 from seizing due to insufficient oil in the refrigerant, even when there is a relatively large amount of oil in the motor 1.

[0056] While the above examples show four criteria for determining the supercritical refrigerant supply conditions, it is not necessary to use only one of these four criteria; it is preferable to use a combination of two or more of these four criteria.

[0057] Next, with reference to Figure 5, the control flow performed by the control device 80 in this embodiment will be described. Figure 5 is a time chart showing the control according to this embodiment. From top to bottom, Figure 5 shows the time changes of the stop prediction flag (on / off), motor speed, brake pedal (on / off), discharge volume increase request flag (on / off), discharge valve 31 (opening / closing), and cooling valve 32 (opening / closing). Here, we illustrate the case where the first to third examples described above are used as the supercritical refrigerant supply conditions.

[0058] First, at time t11, the control device 80 predicts that the vehicle 200 will stop based on signals obtained from at least one of the acceleration sensor 56, camera 59, distance sensor 60, and GPS sensor 61, and sets the stop prediction flag to ON. Subsequently, at time t12, the motor rotation speed falls below a predetermined rotation speed N1, and the brake pedal is turned ON (i.e., the brake pedal is pressed). At this time t12, the control device 80 turns on the discharge volume increase request flag and controls the compressor 3 to generate a supercritical refrigerant, and also controls the discharge valve 31 and the cooling valve 30 to supply this supercritical refrigerant into the motor 1 from the refrigerant passage 24.

[0059] Subsequently, at time t13, a predetermined time T1 has elapsed since the supply of supercritical refrigerant to the motor 1 began. Therefore, at this time t13, the control device 80 terminates the supply of supercritical refrigerant and supplies liquid-phase refrigerant to the motor 1. Specifically, the control device 80 turns off the discharge volume increase request flag and controls the compressor 3 to generate liquid-phase refrigerant, and also controls the discharge valve 31 to close and the cooling valve 30 to supply liquid-phase refrigerant to the motor 1 from the refrigerant passage 23.

[0060] Furthermore, as described above, when the brake pedal is pressed, motor 1 generates heat due to regenerative braking. At this time, the discharge rate of compressor 3 is increased, and the amount of refrigerant supplied to motor 1 increases, so that the heat generated by regeneration can be dealt with effectively. In addition, the regenerative power from motor 1 can be used to increase the workload of compressor 3.

[0061] Next, with reference to Figure 6, a flowchart illustrating the specific control according to this embodiment will be described. This flow is repeatedly executed by the control device 80 at a predetermined cycle. Specifically, the processor 80a within the control device 80 reads a program stored in memory 80b and executes the program, thereby realizing the control related to this flow. Here, we will illustrate the case where the first to fourth examples described above are used as the supercritical refrigerant supply conditions.

[0062] First, in step S10, the control device 80 acquires various information, such as the detected values, from the sensors 51 to 61 (Figure 4) described above. Then, the control device 80 proceeds to step S11 and determines whether the oil level detected by the oil level sensor 52 is at or above the first level and below the second level. If the control device 80 determines that the oil level is at or above the first level and below the second level (step S11: Yes), it proceeds to step S12. On the other hand, if the control device 80 does not determine that the oil level is at or above the first level and below the second level (step S11: No), that is, if the oil level is below the first level or at or above the second level, it terminates the control related to this flow. In this case, the control device 80 does not perform the control to supply the supercritical refrigerant into the motor 1 (the same applies hereinafter).

[0063] Next, in step S12, the control device 80 determines whether the stop prediction flag is on or off. Here, the control device 80 predicts that the vehicle 200 will stop based on signals obtained from at least one of the acceleration sensor 56, camera 59, distance sensor 60, and GPS sensor 61. If the control device 80 predicts that the vehicle 200 will stop, it sets the stop prediction flag to on.

[0064] In one example, the control device 80 predicts that vehicle 200 will stop if the acceleration detected by the acceleration sensor 56 decreases to below a predetermined value (i.e., if vehicle 200 decelerates relatively significantly). In another example, the control device 80 predicts that vehicle 200 will stop if the brake lights of the vehicle ahead, as captured by the camera 59, are illuminated, or if the traffic light ahead, as captured by the camera 59, is red, or if the road sign ahead, as captured by the camera 59, indicates a stop sign or the like. In yet another example, the control device 80 predicts that vehicle 200 will stop if the distance to the vehicle ahead, as detected by the distance sensor 60, decreases to below a predetermined value (corresponding to the vehicle ahead decelerating relatively significantly and the distance between vehicles becoming shorter). In yet another example, the control device 80 predicts that vehicle 200 will stop if, in addition to the current position of vehicle 200 detected by the GPS sensor 61, the control device 80 refers to map data from the navigation system installed in vehicle 200 and determines that the current position of vehicle 200 is a point where stopping or decelerating is necessary (intersection, traffic light, or downhill road). It is advisable to combine the various examples given here as appropriate.

[0065] If the control device 80 determines that the stop prediction flag is on as a result of step S12 (step S12: Yes), it proceeds to step S13. If it does not determine that the stop prediction flag is on (step S12: No), that is, if the stop prediction flag is off, it terminates the control related to this flow.

[0066] Next, in step S13, the control device 80 determines whether the motor rotation speed detected by the motor rotation speed sensor 54 is less than a predetermined rotation speed N1. If the control device 80 determines that the motor rotation speed is less than the predetermined rotation speed N1 (step S13: Yes), it proceeds to step S14. If it does not determine that the motor rotation speed is less than the predetermined rotation speed N1 (step S13: No), that is, if the motor rotation speed is N1 or greater, it terminates the control related to this flow.

[0067] Next, in step S14, the control device 80 determines whether the brake pedal is pressed or not. In this case, the control device 80 determines whether the brake pedal has been pressed or not by the brake sensor 58. If the control device 80 determines that the brake pedal is pressed (step S14: Yes), that is, the brake pedal is pressed, it proceeds to step S15. On the other hand, if the control device 80 does not determine that the brake pedal is pressed (step S14: No), that is, the brake pedal is not pressed, it terminates the control related to this flow.

[0068] Next, in step S15, the control device 80, having found that all the conditions in steps S11 to S14 are met, that is, the conditions for supplying supercritical refrigerant are met, turns on the discharge volume increase request flag and controls the compressor 3 to generate supercritical refrigerant. Then, in step S16, the control device 80 controls the system to open the discharge valve 31 and close the cooling valve 30 so that supercritical refrigerant is supplied from the refrigerant passage 24 into the motor 1.

[0069] Next, in step S17, the control device 80 determines whether the motor rotation speed detected by the motor rotation speed sensor 54 is less than a predetermined rotation speed N1. If the control device 80 does not determine that the motor rotation speed is less than the predetermined rotation speed N1 (step S17: No), that is, if the motor rotation speed is N1 or greater, the process proceeds to step S19. In step S19, the control device 80 controls the discharge valve 31 to close and the cooling valve 30 to terminate the supply of supercritical refrigerant and supply liquid-phase refrigerant into the motor 1 from the refrigerant passage 23. At this time, the control device 80 also controls the compressor 3 to generate liquid-phase refrigerant by turning off the discharge volume increase request flag. Finally, the control device 80 terminates the control related to this flow.

[0070] In response, if the control device 80 determines that the motor rotation speed is less than a predetermined rotation speed N1 (step S17: Yes), it proceeds to step S18 and determines whether a predetermined time T1 has elapsed since it began supplying the supercritical refrigerant into the motor 1. If the control device 80 determines that the predetermined time T1 has elapsed (step S18: Yes), it proceeds to step S19 and performs the same control as described above, ending the control related to this flow. On the other hand, if the control device 80 does not determine that the predetermined time T1 has elapsed (step S18: No), it returns to step S16. In this case, the control device 80 continues to supply the supercritical refrigerant.

[0071] In the above-described flow, four determination processes (steps S11 to S14) were performed to determine the supercritical refrigerant supply conditions. However, it is not necessary to perform all four of these determination processes; at least one of these four processes is sufficient.

[0072] [Mechanism of Action and Effects] Next, the operation and effects of the motor cooling system 100 according to this embodiment will be described.

[0073] In this embodiment, the motor cooling system 100 mounted on the vehicle 200 includes a compressor 3 for compressing a refrigerant containing oil in CO2, a heat exchanger 5 for cooling the refrigerant compressed by the compressor 3, a motor 1 for driving the vehicle 200, refrigerant passages 23 and 24 for supplying the refrigerant cooled by the heat exchanger 5 into the motor 1, and a control device 80 configured to control the compressor 3. The control device 80 is configured to control the compressor 3 to generate a supercritical refrigerant in order to supply the supercritical refrigerant from the refrigerant passage 24 into the motor 1 when the conditions for supplying a supercritical refrigerant are met.

[0074] According to this embodiment, by supplying a supercritical refrigerant into the motor 1, the compatibility of this supercritical refrigerant can be utilized to draw in oil from within the motor 1, and the oil can be effectively discharged together with the refrigerant. This removes the oil film (in other words, oil reservoir) formed inside the motor 1 (especially in the gap between the rotor 11 and the stator 12), thereby suppressing the increase in stirring resistance caused by the oil inside the motor 1.

[0075] Furthermore, in this embodiment, the control device 80 is configured to control the compressor 3 to generate supercritical refrigerant when the supercritical refrigerant supply conditions are met, and to control the compressor 3 to generate liquid-phase refrigerant when the supercritical refrigerant supply conditions are not met. In this embodiment, the control device 80 limits the circumstances under which supercritical refrigerant is supplied, that is, it prevents the unnecessary supply of supercritical refrigerant. This reduces the load on the compressor 3 for generating supercritical refrigerant and suppresses the increase in resistance caused by supplying supercritical refrigerant into the motor 1.

[0076] Furthermore, in this embodiment, the control device 80 is configured to control the compressor 3 to generate liquid-phase refrigerant in order to supply liquid-phase refrigerant to the motor 1 after a predetermined time T1 has elapsed since the supercritical refrigerant supply conditions were met and the supply of supercritical refrigerant to the motor 1 began. This allows the supply of supercritical refrigerant to be terminated when the oil in the motor 1 has been completely drained by supplying supercritical refrigerant for a certain period of time, thereby reducing the load on the compressor 3 required to generate supercritical refrigerant. In other words, power consumption by the compressor 3 can be reduced.

[0077] Furthermore, in this embodiment, the motor cooling system 100 includes a refrigerant passage 23 for supplying liquid-phase refrigerant into the motor 1, a refrigerant passage 24 for supplying supercritical refrigerant into the motor 1, a cooling valve 30 provided in the refrigerant passage 23, and a discharge valve 31 provided in the refrigerant passage 24. The control device 80 is configured to control the discharge valve 31 to supply supercritical refrigerant into the motor 1 from the refrigerant passage 24 when the supercritical refrigerant supply conditions are met, and to control the cooling valve 30 to supply liquid-phase refrigerant into the motor 1 from the refrigerant passage 24 when the supercritical refrigerant supply conditions are not met. As a result, by controlling the cooling valve 30 and the discharge valve 31 and switching the passages through which the refrigerant flows (refrigerant passages 23 and 24), the refrigerant supplied to the motor 1 can be easily switched between supercritical refrigerant and liquid-phase refrigerant.

[0078] Furthermore, in this embodiment, the motor cooling system 100 further includes a motor rotation speed sensor 54 for detecting the motor rotation speed, and the control device 80 is configured to determine that the supercritical refrigerant supply condition is met when the motor rotation speed is less than a predetermined rotation speed N1. This makes it possible to supply supercritical refrigerant when the motor 1 is rotating at low speeds, and effectively suppresses the increase in resistance caused by supplying supercritical refrigerant into the motor 1.

[0079] Furthermore, in this embodiment, the control device 80 is configured to control the compressor 3 to generate liquid-phase refrigerant in order to supply liquid-phase refrigerant to the motor 1 when the motor speed reaches a predetermined rotational speed N1 or higher while the supercritical refrigerant supply conditions are met and supercritical refrigerant is being supplied to the motor 1. This allows the operation of the compressor 3 to generate supercritical refrigerant to be terminated when the motor speed increases (typically during acceleration), thereby reducing power consumption by the compressor 3. As a result, more power can be allocated to the motor 1, making it possible to accurately meet the acceleration requirements of the vehicle 200.

[0080] Furthermore, in this embodiment, the motor cooling system 100 further includes at least one of the following: an acceleration sensor 56 for detecting the acceleration of the vehicle 200, a camera 59 for photographing the area around the vehicle 200, a distance sensor 60 for detecting the distance between the vehicle 200 and objects in its vicinity, and a GPS sensor 61 for detecting the current position of the vehicle 200. The control device 80 is configured to predict when the vehicle 200 will stop based on signals obtained from at least one of the acceleration sensor 56, camera 59, distance sensor 60, and GPS sensor 61, and to determine that the conditions for supplying supercritical refrigerant have been met when the vehicle 200 is predicted to stop. In this embodiment, considering that it takes some time for the compressor 3 to generate supercritical refrigerant, the operation of the compressor 3 to generate supercritical refrigerant is started in advance at the timing when the vehicle 200 is predicted to stop, before the motor 1 actually starts rotating at a low speed. This ensures a reliable supply of supercritical refrigerant when the motor 1 is rotating at low speeds, and effectively balances the suppression of increased resistance caused by supplying supercritical refrigerant into the motor 1 with ensuring oil discharge from the motor 1 using the supercritical refrigerant.

[0081] Furthermore, in this embodiment, the motor cooling system 100 further includes a brake sensor 58 that detects the driver's brake pedal operation to apply braking force to the vehicle 200, and the control device 80 is configured to determine that the conditions for supplying supercritical refrigerant have been met when the brake pedal operation is detected by the brake sensor 58. In this embodiment as well, considering that it takes some time for the compressor 3 to generate supercritical refrigerant, the operation of the compressor 3 to generate supercritical refrigerant is started in advance at the timing when the brake pedal is pressed, before the motor 1 actually starts rotating at a low speed. This also ensures that supercritical refrigerant is reliably supplied when the motor 1 is rotating at a low speed, and accurately achieves both the suppression of increased resistance due to supplying supercritical refrigerant into the motor 1 and the assurance of oil discharge from the motor 1 by the supercritical refrigerant.

[0082] Furthermore, in this embodiment, the motor cooling system 100 further includes an oil tank 6 for storing oil and an oil level sensor 52 for detecting the oil level stored in the oil tank 6. The control device 80 is configured to determine that the conditions for supplying supercritical refrigerant have been met when the oil level detected by the oil level sensor 52 is at or above the first level and below the second level (> first level). By controlling the supply of supercritical refrigerant based on the oil level determination results using these first and second levels, it is possible to reliably discharge the oil from the motor 1 while preventing the compressor 3 from seizing due to insufficient oil in the refrigerant, even when there is a relatively large amount of oil in the motor 1.

[0083] [Differentiation] In the embodiments described above, a third example of the supercritical refrigerant supply conditions was the condition of whether or not a driver performed a pedal operation to apply braking force to the vehicle 200. In particular, in the third example, the brake pedal depression operation detected by the brake sensor 58 was used as the driver's pedal operation to apply braking force to the vehicle 200. This third example assumed the application of the present invention to a vehicle that performs so-called two-pedal operation, where driving force is applied to the vehicle by depressing the accelerator pedal and braking force is applied to the vehicle by depressing the brake pedal. In contrast, the modified version applies the present invention to a vehicle that performs so-called one-pedal operation, where driving force is applied to the vehicle by depressing the accelerator pedal and braking force is applied to the vehicle by releasing the accelerator pedal. In this modified version, the control device 80 determines the supercritical refrigerant supply conditions by using the accelerator pedal release operation detected by the accelerator sensor 57 as the driver's pedal operation to apply braking force to the vehicle 200.

[0084] The control method related to this modified example will be specifically explained with reference to Figures 7 and 8. First, Figure 7 is a time chart showing the control according to the modified example. From top to bottom, Figure 7 shows the time changes of the stop prediction flag (on / off), motor speed, differential value of accelerator pedal opening, discharge volume increase request flag (on / off), opening and closing of the discharge valve 31, and opening and closing of the cooling valve 32. Here, only the differences from the control method according to the above embodiment (Figure 5) will be explained.

[0085] In the modified example, at time t22, the derivative of the accelerator pedal opening detected by the accelerator sensor 57 becomes less than 0. This means that in the vehicle 200, which is operated using so-called one-pedal operation, braking force has begun to be applied to the vehicle 200 as the accelerator pedal is released. At this time t22, the stop prediction flag is set to ON, and the motor rotation speed is less than the predetermined rotation speed N1. Therefore, at time t22, the control device 80 turns on the discharge volume increase request flag to control the compressor 3 to generate a supercritical refrigerant, and also controls the device to open the discharge valve 31 and close the cooling valve 30 so that this supercritical refrigerant is supplied to the motor 1 from the refrigerant passage 24.

[0086] Next, Figure 8 is a flowchart showing control according to a modified embodiment of the present invention. This flow is also repeatedly executed by the control device 80 at a predetermined period. Specifically, the processor 80a in the control device 80 reads a program stored in the memory 80b and executes the program, thereby realizing the control related to this flow.

[0087] Steps S20-S23 and S25-S29 in Figure 8 are identical to steps S10-S13 and S15-S19 in Figure 6, respectively, so their explanations will be omitted, and step S24 will be explained here. In step S24, the control device 80 calculates the derivative of the accelerator pedal opening detected by the accelerator sensor 57 and determines whether this derivative is less than 0. Here, the control device 80 determines whether the accelerator pedal has been released in a vehicle 200 that performs so-called one-pedal operation. As a result of step S24, if the control device 80 determines that the derivative of the accelerator pedal opening is less than 0 (step S24: Yes), it proceeds to step S25. If it does not determine that the derivative of the accelerator pedal opening is less than 0 (step S24: No), that is, if the accelerator pedal has not been released, the control related to this flow is terminated.

[0088] Even with these modifications, considering that it takes some time for the compressor 3 to generate supercritical refrigerant, the operation of the compressor 3 to generate supercritical refrigerant can be started in advance at the moment the accelerator pedal is released, before the motor 1 actually reaches low rotation speed. As a result, supercritical refrigerant can be reliably supplied when the motor 1 is at low rotation speed, and both the suppression of increased resistance due to supplying supercritical refrigerant into the motor 1 and the assurance of oil discharge from the motor 1 by the supercritical refrigerant can be accurately achieved. [Explanation of symbols]

[0089] 1 motor 3 Compressors 5 Heat exchanger 6 Oil tank 11 rotors 12 staters 13 Rotation axis 15 Plain bearings 21-24, 26 Refrigerant passages 25 Mixed fluid passage 27 Oil passage 30 Cooling valves 31 Discharge valve 80 Control device 100 Motor Cooling System 200 vehicles

Claims

1. A motor cooling system installed in a vehicle, CO 2 A compressor for compressing a refrigerant containing oil, A heat exchanger for cooling the refrigerant compressed by the compressor, A motor for driving the aforementioned vehicle, To cool the motor, a refrigerant passage is provided for supplying the refrigerant cooled by the heat exchanger into the motor, A control device configured to control at least the compressor, It has, A motor cooling system characterized in that the control device is configured to control the compressor to generate the supercritical refrigerant in order to supply the supercritical refrigerant into the motor from the refrigerant passage when predetermined conditions are met.

2. The motor cooling system according to claim 1, wherein the control device is configured to control the compressor to generate the refrigerant in a supercritical state when the predetermined conditions are met, and to control the compressor to generate the refrigerant in a liquid phase state when the predetermined conditions are not met.

3. The motor cooling system according to claim 1, wherein the control device is configured to control the compressor to generate the refrigerant in a liquid phase state in order to supply the refrigerant in a liquid phase state to the motor after a predetermined time has elapsed since the supply of the refrigerant in a supercritical state began after the predetermined conditions have been met.

4. The refrigerant passage comprises a first passage for supplying the refrigerant in a supercritical state into the motor, and a second passage for supplying the refrigerant in a liquid phase state into the motor. The motor cooling system further includes valves provided in the first passage and / or the second passage. The control device is configured to control the valve to supply the refrigerant in a supercritical state to the motor through the first passage when the predetermined conditions are met, and to control the valve to supply the refrigerant in a liquid phase state to the motor through the second passage when the predetermined conditions are not met. The motor cooling system according to claim 1.

5. The motor cooling system further includes a motor speed sensor for detecting the rotational speed of the motor. The motor cooling system according to claim 1, wherein the control device is configured to determine that the predetermined condition has been met when the rotational speed detected by the motor rotational speed sensor is less than a predetermined rotational speed.

6. The motor cooling system according to claim 5, wherein the control device is configured to control the compressor to generate the liquid-phase refrigerant in order to supply the liquid-phase refrigerant to the motor when the rotational speed becomes equal to or greater than the predetermined rotational speed while the predetermined conditions are met and the supercritical refrigerant is being supplied to the motor.

7. The motor cooling system further comprises at least one of the following: an acceleration sensor for detecting the acceleration of the vehicle; a camera for photographing the area around the vehicle; a distance sensor for detecting the distance between the vehicle and objects in its vicinity; and a GPS sensor for detecting the current position of the vehicle. The motor cooling system according to claim 1, wherein the control device is configured to predict the stopping of the vehicle based on signals obtained from at least one of the acceleration sensor, the camera, the distance sensor, and the GPS sensor, and to determine that the predetermined condition has been met when the stopping of the vehicle is predicted.

8. The motor cooling system further includes a pedal sensor that detects pedal operation by a driver to apply braking force to the vehicle. The motor cooling system according to claim 1, wherein the control device is configured to determine that the predetermined condition has been met when the pedal operation is detected by the pedal sensor.

9. The motor cooling system further comprises an oil tank for storing the oil and an oil level sensor for detecting the level of the oil stored in the oil tank. The motor cooling system according to claim 1, wherein the control device is configured to determine that the predetermined condition is met when the level detected by the oil level sensor is greater than or equal to a first predetermined value and less than a second predetermined value greater than the first predetermined value.

10. The motor comprises a rotor and a stator, a rotating shaft connected to the rotor, and a sliding bearing supporting the rotating shaft, and is configured such that the refrigerant is supplied between the rotor and the stator from the refrigerant passage. The motor cooling system according to claim 1, wherein the motor cooling system has, separately from the refrigerant passage, a refrigerant passage for supplying the refrigerant to the sliding bearing, and an oil passage for supplying the oil to the sliding bearing.

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