Cooling system of in-wheel motor

Abstract

To provide a cooling system of an in-wheel motor which can improve cooling performance of a motor.SOLUTION: A cooling system of an in-wheel motor includes: a first flow channel for circulating a liquid medium between the inside of a case where a motor is stored and a flow channel for cooling formed inside of a brake disk; and a second flow channel for circulating the liquid medium between the inside of the case and a cooling device. The cooling system of the in-wheel motor includes a control device for controlling opening / closing operation each of a first valve provided in the first flow channel and a second valve provided in the second flow channel, on the basis of the temperature of the motor and the temperature of the brake disk. Thereby, cooling of the motor by the cooling device through the liquid medium is enabled. Heat exchange between the motor and the brake disk through the liquid medium is enabled, which enables cooling and warming using a mutual temperature difference. Thereby, cooling performance of the motor can be improved.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a cooling system for an in-wheel motor having an electric motor arranged in a space on the inner periphery of a wheel. [Background technology]

[0002] A cooling system for an in-wheel motor is well known, which includes a wheel on which a tire is mounted, an electric motor connected to the wheel so as to be capable of transmitting power and at least a portion of which is disposed in a space on the inner periphery of the wheel, and a brake device having a brake disc disposed in the space on the inner periphery of the wheel and applying a braking torque to the wheel. Patent Document 1 discloses an in-wheel motor that includes a brake tube through which brake fluid supplied to the brake device flows and a brake tube through which brake fluid discharged from the brake device flows, and the electric motor is cooled by the brake fluid flowing through at least one of the brake tubes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-113722 Summary of the Invention [Problem to be solved by the invention]

[0004] In an in-wheel motor configuration, the electric motor and the brake disc are close to each other in the space around the wheel, and if the brake disc becomes hot due to heat generated during braking, the heat from the brake disc is easily transferred to the electric motor, which can reduce the cooling performance of the electric motor.

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a cooling system for an in-wheel motor that can improve the cooling performance of the electric motor. [Means for solving the problem]

[0006] The gist of a first invention is a cooling system for an in-wheel motor, comprising: (a) a wheel on which a tire is mounted; an electric motor connected to the wheel so as to be capable of transmitting power, at least a portion of which is disposed in a space on the inner periphery of the wheel; and a brake device having a brake disc disposed in the space on the inner periphery of the wheel and applying a braking torque to the wheel, (b) a case that houses the electric motor and immerses at least a portion of the electric motor in a liquid medium; (c) a cooling flow path formed inside the brake disc that cools the liquid medium by performing heat exchange between the liquid medium and outside air; (d) a cooling device that cools the liquid medium; and (e) a cooling device that cools the liquid medium between the inside of the case and the cooling flow path. The cooling system further comprises: (a) a first flow path for circulating a liquid medium; (f) a second flow path for circulating the liquid medium between the inside of the case and the cooling device; (g) a first valve provided in the first flow path that can be opened and closed alternatively between an open state that allows the liquid medium to flow in the first flow path and a closed state that blocks the flow of the liquid medium in the first flow path; (h) a second valve provided in the second flow path that can be opened and closed alternatively between an open state that allows the liquid medium to flow in the second flow path and a closed state that blocks the flow of the liquid medium in the second flow path; and (i) a control device that controls the opening and closing of each of the first valve and the second valve based on the temperature of the electric motor and the temperature of the brake disc. [Effects of the Invention]

[0007] According to the first aspect of the present invention, a first flow path for circulating a liquid medium between a case housing an electric motor and a cooling flow path formed inside the brake disc, and a second flow path for circulating a liquid medium between the case and a cooling device are provided. A control device is also provided for controlling the opening and closing of a first valve provided in the first flow path and a second valve provided in the second flow path based on the temperatures of the electric motor and the brake disc. This allows the cooling device to cool the electric motor via the liquid medium. Heat exchange between the electric motor and the brake disc is also possible via the liquid medium, enabling cooling and warming by utilizing the temperature difference between them. The flow of liquid medium through the first flow path and the second flow path is permitted or blocked based on the temperatures of the electric motor and the brake disc, allowing the electric motor to be appropriately cooled or warmed. This improves the cooling performance of the electric motor. Maintaining the temperature of the electric motor within an appropriate range leads to improved operating efficiency of the electric motor.

[0008] Furthermore, according to the first aspect of the present invention, the secondary effect of appropriately cooling and warming up the brake discs can be achieved, thereby improving the cooling performance of the brake discs. Maintaining the temperature of the brake discs within an appropriate range leads to maintaining appropriate braking performance.

[0009] The first invention is a technology that leads to suppression of temperature rise in the electric motor and the brake disc, improvement of cooling efficiency, and thermal management. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a schematic configuration of a vehicle equipped with an in-wheel motor cooling system to which the present invention is applied; [Figure 2] FIG. 1 is a cross-sectional view illustrating a schematic configuration of a power transmission device for an in-wheel motor. [Figure 3] FIG. 1 is a schematic diagram illustrating a general configuration of a cooling system for an in-wheel motor. [Figure 4]10 is a table showing an example of the opening and closing operations of the first valve and the second valve according to the MG temperature and the disk temperature. [Figure 5] 1 is a flowchart illustrating a main part of the control operation of the electronic control device, and is a flowchart illustrating the control operation for improving the cooling performance of the motor. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0012] FIG. 1 is a diagram illustrating a schematic configuration of a vehicle 10 equipped with an in-wheel motor cooling system 200 (see FIG. 3 ) to which the present invention is applied. In FIG. 1 , the vehicle 10 includes four drive wheels 20 (front, rear, left, and right), four motors 30 provided for each drive wheel 20, a brake control device 40, four brake devices 50 provided for each drive wheel 20, and an electronic control device 60. The drive wheels 20 include a right front wheel 22, a left front wheel 24, a right rear wheel 26, and a left rear wheel 28. The motors 30 include a right front motor 32, a left front motor 34, a right rear motor 36, and a left rear motor 38. The brake device 50 includes a right front brake 52, a left front brake 54, a right rear brake 56, and a left rear brake 58. The vehicle 10 is a four-wheel drive vehicle (= all-wheel drive vehicle) capable of adjusting the torque distribution of the drive wheels 20. Note that the above “left and right” refer to the left and right relative to the forward direction of the vehicle 10.

[0013] The motor 30 is a power source that generates power that serves as drive torque. The motor 30 is a known rotating electric machine, a so-called motor generator. The motor 30 is connected to a battery 80 provided in the vehicle 10 via an inverter 70 provided in the vehicle 10. The inverter 70 is controlled by an electronic control device 60, thereby controlling the MG torque Tm, which is the output torque of the motor 30. The power also has the same meaning as torque or force unless otherwise specified.

[0014] The brake control device 40 includes a brake master cylinder and a brake actuator (not shown) that generate a brake hydraulic pressure Pbra. The brake control device 40 controls the braking torque Tbra applied to the drive wheels 20 by the brake device 50 in accordance with commands from the electronic control device 60. The brake control device 40 supplies the brake hydraulic pressure Pbra to a cylinder of a caliper 50c (see FIG. 2) of the brake device 50. When the brake hydraulic pressure Pbra is supplied to the cylinder of the caliper 50c, a pad 50p (see FIG. 2) of the brake device 50 is pressed against a brake disc 50d (see FIG. 2) of the brake device 50, and braking torque Tbra is applied by frictional force. In the brake control device 40, under normal conditions, a master cylinder hydraulic pressure generated from the brake master cylinder and having a magnitude corresponding to the amount of brake operation by the driver is supplied to the cylinder of the caliper 50c as the brake hydraulic pressure Pbra. On the other hand, in the brake control device 40, for example, when an automatic brake control is activated, a brake oil pressure Pbra corresponding to the braking torque Tbra required for each control is supplied to the cylinder of the caliper 50c. The brake disc 50d is also called a brake rotor or a disc rotor.

[0015] The electronic control unit 60 is a controller including a control device for the vehicle 10. The electronic control unit 60 is configured to include a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, an input / output interface, etc. The CPU executes various controls of the vehicle 10 by performing signal processing according to a program stored in advance in the ROM while utilizing the temporary storage function of the RAM.

[0016] The electronic control device 60 is supplied with various signals based on detection values ​​from various sensors provided on the vehicle 10. The various sensors include, for example, an MG temperature sensor 90, a wheel speed sensor 92, and a brake oil pressure sensor 94. The various signals include, for example, an MG temperature THm, a wheel speed Nw, and a brake oil pressure Pbra. The MG temperature sensor 90 includes a temperature sensor provided in each of the four motors 30. The wheel speed sensor 92 includes a wheel speed sensor provided in each of the four drive wheels 20. The brake oil pressure sensor 94 includes an oil pressure sensor provided in each of the four brake devices 50. The MG temperature THm includes the temperature of each of the four motors 30. The wheel speed Nw includes the rotational speed of each of the four drive wheels 20. The brake oil pressure Pbra includes the brake oil pressure Pbra in each of the four brake devices 50.

[0017] The electronic control device 60 outputs various command signals to each device provided in the vehicle 10. These devices are, for example, the brake control device 40, the inverter 70, etc. The various command signals are, for example, a brake control command signal Sbra, an MG control command signal Sm, etc. The brake control command signal Sbra is a command signal for controlling the braking torque Tbra of each of the four drive wheels 20. The MG control command signal Sm is a torque command value for controlling the MG torque Tm of each of the four motors 30.

[0018] 2 is a cross-sectional view illustrating the schematic configuration of an in-wheel motor power transmission device 100. The vehicle 10 is equipped with a power transmission device 100 provided for each of the four drive wheels 20 and the motor 30. The power transmission device 100 transmits the power of the motor 30 to the drive wheels 20.

[0019] 2, the drive wheel 20 includes a tire 20t and a wheel 20w to which the tire is attached. The power transmission device 100 is provided in a space A on the inner circumferential side of the wheel 20w. The power transmission device 100 includes a rotor shaft 102, an intermediate shaft 104, a gear 106, an output shaft 108, a wheel hub 110, and the like. The vehicle 10 includes a case 120, which is a non-rotating member, that houses the motor 30, the rotor shaft 102, the intermediate shaft 104, the gear 106, and the like. The stator 30s of the motor 30 is fixed to the case 120.

[0020] The rotor shaft 102 is a rotating member that rotates integrally with the rotor 30r of the motor 30. The intermediate shaft 104 is disposed coaxially with the rotor shaft 102, and its outer peripheral surface is spline-fitted with the inner peripheral surface of the rotor shaft 102, for example.

[0021] The gear 106 is disposed coaxially with the output shaft 108 and is integrally connected to the outer peripheral surface of the output shaft 108 by, for example, press fitting. Gear teeth formed on the outer peripheral surface of the gear 106 mesh with gear teeth formed on the outer peripheral surface of the intermediate shaft 104 on the side opposite to the rotor shaft 102. At this meshing location, the gear 106 has a larger diameter than the intermediate shaft 104. Therefore, a parallel-axis gear reducer 112 is configured by the gear teeth formed on the outer peripheral surface of the intermediate shaft 104 on the side opposite to the rotor shaft 102, the gear 106, and the output shaft 108.

[0022] The wheel hub 110 is disposed coaxially with the output shaft 108 and transmits the rotation output from the parallel-shaft gear reducer 112 to the drive wheels 20. The wheel hub 110 is, for example, press-fitted onto the output shaft 108 from the side opposite the parallel-shaft gear reducer 112 and fastened with a nut 114 attached to the output shaft 108. A wheel 20w and a brake disc 50d are each fastened to the wheel hub 110 with bolts (not shown). The brake disc 50d is disposed in a space A on the inner circumferential side of the wheel 20w.

[0023] In the power transmission device 100, power from the motor 30 is transmitted to the drive wheels 20 via a rotor shaft 102, an intermediate shaft 104, a gear 106, an output shaft 108, and a wheel hub 110 in this order.

[0024] The motor 30 is an electric motor that is coupled to the wheel 20w so as to be capable of transmitting power, and at least a portion of which is disposed in the space A on the inner periphery side of the wheel 20w, and functions as an in-wheel motor.

[0025] The brake device 50 includes a caliper 50c, a brake disc 50d, and a pad 50p, and applies a braking torque Tbra to the wheel 20w.

[0026] In the in-wheel motor configuration, the brake disc 50d is close to the motor 30. Therefore, heat generated in the brake disc 50d during braking is transferred to the motor 30, making it easier for the MG temperature THm to rise.

[0027] The case 120 housing the motor 30 is oil-tight, and the internal space B of the case 120 contains oil FLD for lubricating the motor 30. The case 120 immerses at least a portion of the motor 30 in the oil FLD as a liquid medium. In this embodiment, the oil FLD is used to improve the cooling performance of the motor 30.

[0028] 3 is a schematic diagram illustrating the general configuration of an in-wheel motor cooling system 200. The in-wheel motor cooling system 200 is provided for each of the four drive wheels 20 and the motor 30. The cooling system 200 will be described below with reference to FIG. 2 as well.

[0029] 3 , the cooling system 200 includes a wheel 20w, a motor 30, and a brake device 50. The cooling system 200 further includes a case 120, a cooling flow path 50dr, a first flow path 210, a second flow path 220, a first valve 230, a second valve 240, and an electronic control device 60.

[0030] The wheel 20w has a second cooling passage 20wr formed therein that cools the oil FLD by exchanging heat between the oil FLD and the outside air. In the cooling system 200, the wheel 20w functions as a cooling device that cools the oil FLD.

[0031] The cooling passage 50dr is formed inside the brake disc 50d. The cooling passage 50dr is a cooling passage that cools the oil FLD by exchanging heat between the oil FLD and the outside air.

[0032] The first flow path 210 is a flow path that circulates the oil FLD between the inside of the case 120 and the brake disc 50d (particularly, the cooling flow path 50dr). The second flow path 220 is a flow path that circulates the oil FLD between the inside of the case 120 and the wheel 20w (particularly, the second cooling flow path 20wr). The inside of the case 120 is synonymous with the internal space B of the case 120. The first flow path 210 and the second flow path 220 are formed inside the output shaft 108 and inside the wheel hub 110, respectively.

[0033] The first valve 230 is provided in the first flow path 210. The first valve 230 is a solenoid valve that can be selectively opened and closed between an open state that allows the flow of oil FLD in the first flow path 210 and a closed state that blocks the flow of oil FLD in the first flow path 210. The second valve 240 is provided in the second flow path 220. The second valve 240 is a solenoid valve that can be selectively opened and closed between an open state that allows the flow of oil FLD in the second flow path 220 and a closed state that blocks the flow of oil FLD in the second flow path 220.

[0034] The electronic control device 60 functionally includes a valve opening / closing control section 62 that controls the opening / closing operation of each of the first valve 230 and the second valve 240 based on the MG temperature THm and the disc temperature THd. The disc temperature THd is the temperature of the brake disc 50d. The electronic control device 60 outputs a first opening / closing control command signal Sv1 to the first valve 230 and a second opening / closing control command signal Sv2 to the second valve 240.

[0035] The valve opening / closing control unit 62 acquires the MG temperature THm and the disk temperature THd. The valve opening / closing control unit 62 acquires the MG temperature THm based on, for example, a signal from the MG temperature sensor 90. The valve opening / closing control unit 62 acquires the disk temperature THd by, for example, calculating an estimated value of the disk temperature THd. The valve opening / closing control unit 62 calculates the estimated value of the disk temperature THd by applying the wheel speed Nw, the brake hydraulic pressure Pbra, the operating time of the brake device 50, etc. to, for example, a predetermined map or relational expression that has been obtained in advance experimentally or by design and stored, that is, a predetermined map or relational expression.

[0036] The valve opening / closing control unit 62 determines whether the MG temperature THm and the disk temperature THd are in a predetermined high temperature state requiring cooling, a predetermined low temperature state requiring warming, or an optimum temperature state between the predetermined high temperature state and the predetermined low temperature state.

[0037] The valve opening / closing control unit 62 controls the opening / closing operation of each of the first valve 230 and the second valve 240 based on the determination results of each of the MG temperature THm and the disk temperature THd. The valve opening / closing control unit 62 outputs a first opening / closing control command signal Sv1 to control the opening / closing operation of the first valve 230. The valve opening / closing control unit 62 outputs a second opening / closing control command signal Sv2 to control the opening / closing operation of the second valve 240.

[0038] 4 is a table showing an example of the opening and closing operations of the first valve 230 and the second valve 240 in response to the MG temperature THm and the disk temperature THd. Note that in the figure, "motor temperature" is synonymous with the MG temperature THm, and "brake temperature" is synonymous with the disk temperature THd.

[0039] 4, when both the MG temperature THm and the disc temperature THd are in a high temperature state, it is determined that the motor 30 is at a high temperature, and that heat from the brake disc 50d is being transferred to the motor 30 via the oil FLD. In this case, cooling the motor 30 is given priority. When the valve opening / closing control unit 62 determines that both the MG temperature THm and the disc temperature THd are in a high temperature state, it closes the first valve 230 and opens the second valve 240. This prevents heat from being transferred from the brake disc 50d to the motor 30 via the oil FLD, and also allows the motor 30 to be cooled by the wheel 20w.

[0040] If the MG temperature THm is in a high temperature state and the disc temperature THd is in an appropriate temperature state, the problem is that the motor 30 is too high. In this case, the flow of oil FLD through the first flow path 210 and the second flow path 220 keeps the motor 30 at an appropriate temperature. If the valve opening / closing control unit 62 determines that the MG temperature THm is in a high temperature state and the disc temperature THd is in an appropriate temperature state, it opens both the first valve 230 and the second valve 240. This allows the heat of the motor 30 to be released from both the brake disc 50d and the wheel 20w.

[0041] When the MG temperature THm is in a high temperature state and the disc temperature THd is in a low temperature state, the problem is that the motor 30 is high in temperature and the brake disc 50d is low in temperature. In this case, the flow of oil FLD through the first flow path 210 maintains the motor 30 and the brake disc 50d at an appropriate temperature. If the second valve 240 is opened, the heat of the motor 30 can be released by the wheel 20w, but the flow rate of oil FLD through the first flow path 210 decreases, which may require time to maintain the brake disc 50d at an appropriate temperature. Therefore, the second valve 240 is closed to increase the flow rate of oil FLD through the first flow path 210 and speed up heat exchange between the motor 30 and the brake disc 50d. When the valve opening / closing control unit 62 determines that the MG temperature THm is in a high temperature state and the disc temperature THd is in a low temperature state, the valve opening / closing control unit 62 opens the first valve 230 and closes the second valve 240. This allows the heat of the motor 30 to be released by the brake disc 50d.

[0042] When the MG temperature THm is in an appropriate temperature state and the disc temperature THd is in a high temperature state, the problem is that the brake disc 50d is too high. In this case, the brake disc 50d is brought to an appropriate temperature by the flow of oil FLD through the first flow path 210. At this time, the second valve 240 is closed to increase the flow rate of oil FLD through the first flow path 210 and speed up heat exchange between the motor 30 and the brake disc 50d. When the valve opening / closing control unit 62 determines that the MG temperature THm is in an appropriate temperature state and the disc temperature THd is in a high temperature state, the valve opening / closing control unit 62 opens the first valve 230 and closes the second valve 240. This allows the brake disc 50d to be cooled as quickly as possible.

[0043] If the MG temperature THm and the disk temperature THd are both in the optimum temperature state, opening the first valve 230 and / or the second valve 240 may result in poor lubrication of the motor 30. In this case, priority is given to lubrication of the motor 30. If the valve opening / closing control unit 62 determines that the MG temperature THm and the disk temperature THd are both in the optimum temperature state, it closes both the first valve 230 and the second valve 240. This allows the motor 30 to be quickly lubricated and kept warm.

[0044] If the MG temperature THm is at an appropriate temperature and the disc temperature THd is at a low temperature, the problem is that the brake disc 50d is at a low temperature. In this case, the brake disc 50d is kept at an appropriate temperature by the flow of oil FLD through the first flow path 210. At this time, cooling by the wheel 20w is not performed. If the valve opening / closing control unit 62 determines that the MG temperature THm is at an appropriate temperature and the disc temperature THd is at a low temperature, it opens the first valve 230 and closes the second valve 240. This makes it possible to block heat release from the wheel 20w and warm up the brake disc 50d using the heat of the motor 30.

[0045] When the MG temperature THm is in a low temperature state and the disc temperature THd is in an appropriate temperature state, the problem is that the motor 30 is low in temperature. In this case, the flow of oil FLD through the first flow path 210 brings the motor 30 to an appropriate temperature. At this time, the second valve 240 is closed to increase the flow rate of oil FLD through the first flow path 210 and speed up heat exchange between the motor 30 and the brake disc 50d. When the valve opening / closing control unit 62 determines that the MG temperature THm is in a low temperature state and the disc temperature THd is in an appropriate temperature state, the valve opening / closing control unit 62 opens the first valve 230 and closes the second valve 240. This makes it possible to block heat release from the wheel 20w and quickly warm up the motor 30.

[0046] When both the MG temperature THm and the disc temperature THd are in a low state, it is considered that the motor 30 and the brake disc 50d are both at low temperatures. In this case, cooling by the flow of oil FLD through the first flow path 210 and the second flow path 220 is not performed. When the valve opening / closing control unit 62 determines that both the MG temperature THm and the disc temperature THd are in a low state, it closes both the first valve 230 and the second valve 240. This makes it possible to block heat release from the wheel 20w and the brake disc 50d and to quickly lubricate and warm up the motor 30.

[0047] When the MG temperature THm is in a low temperature state and the disc temperature THd is in a high temperature state, the problem is that the motor 30 is low in temperature and the brake disc 50d is high in temperature. In this case, the flow of oil FLD through the first flow path 210 maintains the motor 30 and the brake disc 50d at an appropriate temperature. At this time, the second valve 240 is closed to increase the flow rate of oil FLD through the first flow path 210 and speed up heat exchange between the motor 30 and the brake disc 50d. Furthermore, cooling by the wheel 20w is not performed. When the valve opening / closing control unit 62 determines that the MG temperature THm is in a low temperature state and the disc temperature THd is in a high temperature state, the valve opening / closing control unit 62 opens the first valve 230 and closes the second valve 240. This allows heat from the brake disc 50d to be transferred to the motor 30, allowing the motor 30 to warm up quickly.

[0048] FIG. 5 is a flowchart illustrating the main control operations of the electronic control device 60, which are performed to improve the cooling performance of the motor 30, and which are executed repeatedly, for example.

[0049] 5, each step in the flowchart corresponds to a function of the valve opening / closing control unit 62. First, in step (hereinafter, "step" will be omitted) S10, the MG temperature THm and the disk temperature THd are acquired. Next, in S20, it is determined whether the MG temperature THm and the disk temperature THd are in a high temperature state, a low temperature state, or an optimum temperature state. Next, in S30, the opening / closing operation of each of the first valve 230 and the second valve 240 is controlled based on the determination results of the MG temperature THm and the disk temperature THd in S20.

[0050] As described above, this embodiment includes a first flow path 210 for circulating oil FLD between the inside of the case 120 housing the motor 30 and the cooling flow path 50dr, and a second flow path 220 for circulating oil FLD between the inside of the case 120 and the wheel 20w. The electronic control device 60 controls the opening and closing of the first valve 230 provided in the first flow path 210 and the second valve 240 provided in the second flow path 220 based on the MG temperature THm and the disc temperature THd. This allows the motor 30 to be cooled by the wheel 20w via the oil FLD. Heat exchange between the motor 30 and the brake disc 50d is also possible via the oil FLD, enabling cooling and warming by utilizing the temperature difference between them. The flow of oil FLD through the first flow path 210 and the second flow path 220 is permitted or blocked based on the MG temperature THm and the disc temperature THd, allowing the motor 30 to be appropriately cooled or warmed. This improves the cooling performance of the motor 30. Maintaining the MG temperature THm in an appropriate range leads to improved operation efficiency of the motor 30.

[0051] Furthermore, according to this embodiment, a secondary effect is obtained in that the brake disc 50d is appropriately cooled and warmed up. Therefore, the cooling performance of the brake disc 50d can be improved. Maintaining the disc temperature THd within an appropriate range leads to maintaining an appropriate braking effect.

[0052] Furthermore, according to this embodiment, the MG temperature THm and the disk temperature THd are acquired, and it is determined whether the MG temperature THm and the disk temperature THd are in a high temperature state, a low temperature state, or an optimum temperature state, and the opening and closing operations of the first valve 230 and the second valve 240 are controlled based on the determination results. This allows the motor 30 to be cooled and warmed up appropriately, thereby appropriately improving the operating efficiency of the motor 30.

[0053] Furthermore, according to this embodiment, when it is determined that both the MG temperature THm and the disk temperature THd are in a high temperature state, the first valve 230 is closed and the second valve 240 is opened. When it is determined that both the MG temperature THm and the disk temperature THd are in a low temperature state, the first valve 230 and the second valve 240 are closed. This allows the motor 30 to be maintained at an appropriate temperature, thereby appropriately improving the operating efficiency of the motor 30.

[0054] Furthermore, according to this embodiment, the wheel 20w, which has the second cooling passage 20wr formed therein for cooling the oil FLD, functions as a cooling device for cooling the oil FLD, eliminating the need for a dedicated cooling device for cooling the oil FLD.

[0055] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0056] For example, in the above-described embodiment, oil FLD is used as the liquid medium for heat exchange, but this is not limiting. For example, cooling water or the like may be used as the liquid medium. In other words, the present invention can be applied not only to oil-cooled cooling systems but also to water-cooled cooling systems.

[0057] In the above-described embodiment, the wheel 20w is used as an example of a cooling device for cooling the liquid medium, but the present invention is not limited to this. For example, the cooling device may be a dedicated cooler for cooling the liquid medium.

[0058] In the above-described embodiment, an all-wheel drive vehicle in which all of the driving wheels 20 are in-wheel motors has been exemplified as a vehicle employing an in-wheel motor system, but the present invention is not limited to this. For example, a vehicle may have in-wheel motor driving wheels only on the front wheels or only on the rear wheels. In this case, the wheels other than the driving wheels of the in-wheel motor may be driven wheels, or may be driving wheels to which power distributed by a differential gear is transmitted.

[0059] In the above-described embodiment, the MG temperature THm is obtained based on a signal from the MG temperature sensor 90, and an estimated value of the disk temperature THd is calculated based on the wheel speed Nw, etc., to obtain the disk temperature THd. However, this is not a limitation. For example, the MG temperature THm may be estimated based on the operating load of the motor 30, or the temperature of the oil FLD in the case 120, and the MG temperature THm may be obtained. Alternatively, the disk temperature THd may be obtained based on a signal from a temperature sensor.

[0060] It should be noted that the above is merely one embodiment, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0061] 20t: Tire 20w: Wheel (cooling device) 20wr: Second cooling flow path 30: Motor (electric motor, in-wheel motor) 50: Brake device 50d: Brake disc 50dr: Cooling flow path 60: Electronic control unit (control device) 120: Case 200: Cooling system 210: First flow path 220: Second flow path 230: First valve 240: Second valve A: Space on the inner circumference of the wheel FLD: Oil (liquid medium)

Claims

1. A cooling system for an in-wheel motor, comprising: a wheel on which a tire is mounted; an electric motor connected to the wheel so as to be capable of transmitting power, the electric motor having at least a portion disposed in a space on an inner circumferential side of the wheel; and a brake device having a brake disc disposed in the space on the inner circumferential side of the wheel, and applying a braking torque to the wheel, a case in which the electric motor is housed and at least a portion of the electric motor is immersed in a liquid medium; a cooling flow path formed inside the brake disc for cooling the liquid medium by performing heat exchange between the liquid medium and outside air; a cooling device for cooling the liquid medium; a first flow path that allows the liquid medium to circulate between the inside of the case and the cooling flow path; a second flow path for circulating the liquid medium between the inside of the case and the cooling device; a first valve provided in the first flow path that is operable to open and close selectively between an open state that allows the liquid medium to flow through the first flow path and a closed state that blocks the liquid medium from flowing through the first flow path; a second valve provided in the second flow path, the second valve being operable to selectively open and close between an open state that allows the liquid medium to flow through the second flow path and a closed state that blocks the liquid medium from flowing through the second flow path; a control device that controls opening and closing of each of the first valve and the second valve based on a temperature of the electric motor and a temperature of the brake disc; 10. The cooling system for an in-wheel motor, comprising:

2. The control device acquiring a temperature of the electric motor and a temperature of the brake disc; determining whether the temperature of the electric motor and the temperature of the brake disc are in a predetermined high temperature state requiring cooling, a predetermined low temperature state requiring warming, or a predetermined optimum temperature state between the high temperature state and the low temperature state; 2. The in-wheel motor cooling system according to claim 1, wherein opening and closing operations of the first valve and the second valve are controlled based on the results of determining the temperature of the electric motor and the temperature of the brake disc.

3. The control device when it is determined that the temperature of the electric motor and the temperature of the brake disc are both in the high temperature state, the first valve is brought into the closed state and the second valve is brought into the open state, 3. The in-wheel motor cooling system according to claim 2, wherein when it is determined that the temperature of the electric motor and the temperature of the brake disc are both in the low temperature state, the first valve and the second valve are both closed.

4. The control device when it is determined that the temperature of the electric motor is in the high temperature state and the temperature of the brake disc is in the appropriate temperature state, both of the first valve and the second valve are brought into the open state, 3. The in-wheel motor cooling system according to claim 2, wherein when it is determined that the temperature of the electric motor is in the high temperature state and the temperature of the brake disc is in the low temperature state, or when it is determined that the temperature of the electric motor is in the optimum temperature state and the temperature of the brake disc is in the high temperature state, the first valve is set to the open state and the second valve is set to the closed state.

5. 5. The cooling system for an in-wheel motor according to claim 1, wherein the cooling device is the wheel, and a second cooling passage is formed therein, the second cooling passage cooling the liquid medium by performing heat exchange between the liquid medium and outside air.

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