electric vehicles

Abstract

To provide a technology which can reduce components constituting an electric vehicle.SOLUTION: An electric vehicle comprises a first motor for driving a first wheel, a second motor for driving a second wheel different from the first wheel, a temperature sensor disposed on the first motor, and a control device. The control device estimates the temperature of the first motor on the basis of a detection signal by the temperature sensor, corrects the temperature of the first motor on the basis of information indicating a relative relation between operation of the first motor and operation of the second motor, thereby estimates the temperature of the second motor, controls the operation of the first motor on the basis of the estimated temperature of the first motor, and controls the operation of the second motor on the basis of the estimated temperature of the second motor.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an electric vehicle. [Background technology]

[0002] Patent Document 1 discloses an electric vehicle including a first motor that drives a first wheel, a second motor that drives a second wheel, a first temperature sensor provided for the first motor, a second temperature sensor provided for the second motor, and a control device. The control device estimates the temperature of the first motor based on a detection signal from the first temperature sensor, estimates the temperature of the second motor based on a detection signal from the second temperature sensor, controls the operation of the first motor based on the first motor temperature, and controls the operation of the second motor based on the second motor temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-268644 Summary of the Invention [Problem to be solved by the invention]

[0004] The electric vehicle of Patent Document 1 requires motor sensors for estimating the temperatures of the first and second motors in order to control their operation. It is desirable to reduce the number of components constituting an electric vehicle.

[0005] This specification provides a technology that can reduce the number of parts that make up an electric vehicle. [Means for solving the problem]

[0006] In a first aspect of the present technology, an electric vehicle may include a first motor that drives a first wheel, a second motor that drives a second wheel different from the first wheel, a temperature sensor provided for the first motor, and a control device. The control device may estimate a temperature of the first motor based on a detection signal from the temperature sensor, estimate a temperature of the second motor by correcting the temperature of the first motor based on information indicating a relative relationship between an operation of the first motor and an operation of the second motor, control the operation of the first motor based on the estimated temperature of the first motor, and control the operation of the second motor based on the estimated temperature of the second motor.

[0007] With the above configuration, the control device can control the operation of the first motor based on the first motor temperature estimated based on the detection signal from the temperature sensor, and can control the operation of the second motor based on the second motor temperature estimated using the temperature of the first motor. Therefore, the electric vehicle does not need to have a temperature sensor provided for the second motor to estimate the second motor temperature. This allows the number of components constituting the electric vehicle to be reduced.

[0008] In a second aspect, in the first aspect, the information indicating the relative relationship may be information indicating a ratio of the required driving force of the second motor to the required driving force of the first motor.

[0009] Since there is a correlation between the required driving force and the motor temperature, the temperature of the second motor can be appropriately estimated by correcting the temperature of the first motor based on information indicating the ratio of the required driving force of the second motor to the required driving force of the first motor.

[0010] In a third aspect, in the first or second aspect, the information indicating the relative relationship may be information indicating a ratio of the rotation speed of the second motor to the rotation speed of the first motor.

[0011] There is a correlation between the rotation speed of the motor and the motor temperature. Therefore, by correcting the temperature of the first motor based on information indicating the ratio of the rotation speed of the second motor to the rotation speed of the first motor, the temperature of the second motor can be estimated appropriately.

[0012] In a fourth aspect, in any one of the first to third aspects, the information indicating the relative relationship may be information indicating the ratio of the motor load of the second motor to the motor load of the first motor.

[0013] There is a correlation between the motor load and the motor temperature. Therefore, by correcting the temperature of the first motor based on information indicating the ratio of the motor load of the second motor to the motor load of the first motor, the temperature of the second motor can be appropriately estimated. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating an outline of an electric vehicle. [Figure 2] 10 is a flowchart of a temperature estimation process. [Figure 3] 10 is a flowchart of a front torque limit value determination process. [Figure 4] 10 is a flowchart of a rear torque limit value determination process. DETAILED DESCRIPTION OF THE INVENTION

[0015] (First Example) (Electric vehicle 2 configuration) As shown in Fig. 1, the electric vehicle 2 includes a front motor 10, a rear motor 12, front wheels 14, rear wheels 16, a main ECU (Electronic Control Unit) 18, and a motor ECU 20. The electric vehicle 2 is an electric four-wheel drive vehicle. Note that the term "electric vehicle" in this specification broadly refers to a vehicle having a motor that drives the wheels. For example, electric vehicles include hybrid vehicles, battery-electric vehicles, fuel cell vehicles, plug-in hybrid vehicles, etc.

[0016] The front motor 10 is connected to the front wheels 14 via a front wheel drive shaft 22. The front motor 10 drives the front wheels 14 via the front wheel drive shaft 22. The front motor 10 is provided with a rotation speed sensor 10a that detects the rotation speed of the front motor 10 (hereinafter referred to as "front motor rotation speed"), and a resolver 10b that detects the motor rotation angle of a rotor (not shown) of the front motor 10.

[0017] The rear motor 12 is connected to the rear wheels 16 via a rear wheel drive shaft 24. The rear motor 12 drives the rear wheels 16 via the rear wheel drive shaft 24. The rear motor 12 is provided with a rotation speed sensor 12a that detects the rotation speed of the rear motor 12 (hereinafter referred to as "rear motor rotation speed"), a resolver 12b that detects the rotation angle of a rotor (not shown) of the rear motor 12, and a temperature sensor 12c that is provided for the rear motor 12. In this embodiment, the temperature sensor 12c is a sensor that detects the coil temperature TR1 of the coil (not shown) of the rear motor 12. It should be noted that the front motor 10 is not provided with a temperature sensor for the front motor 10.

[0018] The main ECU 18 is configured using a computer equipped with a CPU, ROM, and RAM. The main ECU 18 is electrically connected to an outside air temperature sensor 30 that detects the outside air temperature, a gradient sensor 32 that detects the gradient of the road surface on which the electric vehicle 2 is located, a vehicle speed sensor 34 that detects the vehicle speed of the electric vehicle 2, and the like. The main ECU 18 determines the required driving force in response to, for example, the accelerator operation by the user. Then, the main ECU 18 distributes the required driving force between the front wheel required driving force and the rear wheel required driving force based on the outside air temperature, gradient, vehicle speed, and the like. The main ECU 18 then supplies the motor ECU 20 with driving force distribution information D that indicates the ratio of the rear wheel required driving force to the front wheel required driving force.

[0019] The motor ECU 20 is configured using a computer including a CPU, ROM, and RAM. The motor ECU 20 is electrically connected to the rotation speed sensors 10a, 12a, the resolvers 10b, 12b, and the temperature sensor 10c. The motor ECU 20 is configured to be able to communicate with the main ECU 18. The motor ECU 20 calculates the front wheel required torque and the rear wheel required torque using driving force distribution information D supplied from the main ECU 18. The motor ECU 20 then controls the output current of a front inverter (not shown) connected to the front motor 10 so that the output torque of the front motor 10 becomes the front wheel required torque. The motor ECU 20 controls the output current of the front inverter so that the output torque of the front motor 10 does not exceed a front torque limit value, which will be described later. The motor ECU 20 also controls the output current of a rear inverter (not shown) connected to the rear motor 12 so that the output torque of the rear motor 12 becomes the rear wheel required torque. The motor ECU 20 controls the output current of the rear inverter so that the output torque of the rear motor 12 does not exceed a rear torque limit value, which will be described later.

[0020] (Temperature estimation process; Figure 2) The temperature estimation process executed by the motor ECU 20 will be described with reference to Figure 2. The temperature estimation process is a process for estimating a magnet temperature TF2 of the front motor 10 used in a front motor process (see Figure 3) described later, and a magnet temperature TR2 of the rear motor 12 used in a rear motor process (see Figure 4).

[0021] In S10, the motor ECU 20 estimates the coil temperature TR1 of the rear motor 12 using the detection signal from the temperature sensor 12c.

[0022] In S12, the motor ECU 20 estimates the magnet temperature TR2 of the rear motor 12 using the coil temperature TR1 of the rear motor 12 estimated in S10. The motor ECU 20 calculates the magnet temperature TR2 using a temperature model or the like that indicates the correlation between the coil temperature TR1 and the magnet temperature TR2. That is, the motor ECU 20 estimates the magnet temperature TR2 using a detection signal from the temperature sensor 12c.

[0023] In S20, the motor ECU 20 determines the driving force distribution information D. The driving force distribution information D indicates the ratio of the front wheel required driving force to the rear wheel required driving force. As described above, the driving force distribution information D is supplied from the main ECU 18 to the motor ECU 20.

[0024] In S22, the motor ECU 20 estimates the magnet temperature TF2 of the front motor 10 by correcting the magnet temperature TR2 of the rear motor 12 estimated in S10 based on the driving force distribution information D identified in S20. Specifically, the motor ECU 20 calculates the magnet temperature TF2 by multiplying the magnet temperature TR2 by the driving force distribution information D.

[0025] In S30, the motor ECU 20 monitors whether a predetermined time (for example, 1 second) has elapsed since the end of S22. If the predetermined time has elapsed, the motor ECU 20 determines YES in S30 and returns to S10. That is, the motor ECU 20 executes S10 to S22 every time the predetermined time has elapsed.

[0026] (Front torque limit value determination process; Figure 3) Referring to FIG. 3, a front torque limit value determination process for determining the front torque limit value will be described.

[0027] In S50, the motor ECU 20 determines whether the magnet temperature TF2 of the front motor 10 estimated in S22 of Fig. 2 is higher than a first predetermined temperature. If the magnet temperature TF2 is equal to or lower than the first predetermined temperature (NO in S50), the motor ECU 20 proceeds to S52, and if the magnet temperature TF2 is higher than the first predetermined temperature (YES in S50), the motor ECU 20 proceeds to S54.

[0028] In S52, the motor ECU 20 determines the first torque limit value as the front torque limit value. After completing S52, the motor ECU 20 proceeds to S56.

[0029] In S54, the motor ECU 20 determines a second torque limit value that is smaller than the first torque limit value as the front torque limit value. After completing S52, the motor ECU 20 proceeds to S56. S56 is the same as S30 in FIG. 2. That is, the motor ECU 20 executes the processes of S50 to S54 every time a predetermined time elapses. With this configuration, when the magnet temperature TF2 of the front motor 10 is relatively high, the front torque limit value can be reduced. That is, the motor load of the front motor 10 can be limited. This prevents the magnet temperature TF2 from becoming too high, thereby improving the durability of the front motor 10.

[0030] (Rear torque limit value determination process; Fig. 4) Referring to FIG. 4, a rear torque limit value determination process for determining the rear torque limit value will be described.

[0031] In S70, the motor ECU 20 determines whether the magnet temperature TR2 of the rear motor 12 estimated in S12 of Fig. 2 is higher than a second predetermined temperature. If the magnet temperature TR2 is equal to or lower than the second predetermined temperature (NO in S70), the motor ECU 20 proceeds to S72, and if the magnet temperature TR2 is higher than the second predetermined temperature (YES in S70), the motor ECU 20 proceeds to S74. The second predetermined temperature may be the same as or different from the first predetermined temperature.

[0032] In S72, the motor ECU 20 determines the third torque limit value as the rear torque limit value. After completing S72, the motor ECU 20 proceeds to S76.

[0033] In S74, the motor ECU 20 determines a fourth torque limit value that is smaller than the third torque limit value as the rear torque limit value. After completing S72, the motor ECU 20 proceeds to S76. S76 is the same as S30 in FIG. 2. That is, the motor ECU 20 executes the processes of S70 to S74 every time a predetermined time elapses. With this configuration, when the magnet temperature TR2 of the rear motor 12 is relatively high, the rear torque limit value can be reduced. That is, the motor load of the rear motor 12 can be limited. This makes it possible to prevent the magnet temperature TR2 from becoming too high, thereby improving the durability of the rear motor 12.

[0034] As described above, the electric vehicle 2 includes the rear motor 12 (an example of a "first motor") that drives the rear wheels 16 (an example of a "first wheel"), the front motor 10 (an example of a "second motor") that drives the front wheels 14 (an example of a "second wheel"), a temperature sensor 12c provided for the rear motor 12, and a motor ECU 20 (an example of a "control device"). The motor ECU 20 estimates a magnet temperature TR2 of the rear motor 12 based on a detection signal from the temperature sensor 12c, corrects the magnet temperature TR2 based on information indicating the relative relationship between the operation of the rear motor 12 and the operation of the front motor 10, and estimates a magnet temperature TF2 of the front motor 10, controls the operation of the rear motor 12 based on the magnet temperature TR2, and controls the operation of the front motor 10 based on the magnet temperature TF2.

[0035] With the above configuration, the motor ECU 20 can control the operation of the rear motor 12 based on the magnet temperature TR2 estimated based on the detection signal from the temperature sensor 12c, and can also control the operation of the front motor 10 based on the magnet temperature TF2 estimated using the magnet temperature TR2. Therefore, the electric vehicle 2 does not need to be equipped with a temperature sensor provided for the front motor 10 to estimate the magnet temperature TF2. This allows the number of parts that make up the electric vehicle 2 to be reduced.

[0036] Furthermore, the information indicating the relative relationship is driving force distribution information D, which indicates the ratio of the driving force required by the front motor 10 to the driving force required by the rear motor 12 to the driving force required by the front wheels. There is a correlation between the required driving force and the magnet temperature. Therefore, by correcting the magnet temperature TR2 based on the information indicating the ratio of the driving force required by the front motor 10 to the driving force required by the rear motor 12 to the driving force required by the front wheels, it is possible to appropriately estimate the magnet temperature TF2.

[0037] (Second Example) The electric vehicle 2 of this embodiment differs from the electric vehicle 2 of the first embodiment in the content of the processes executed in S20 and S22 of FIG.

[0038] In S20 of FIG. 2, the motor ECU 20 acquires the front motor rotation speed and the rear motor rotation speed.

[0039] In S22, the motor ECU 20 estimates the magnet temperature TF2 of the front motor 10 using the magnet temperature TR2 of the rear motor 12 estimated in S10, the front motor rotation speed acquired in S20, and the rear motor rotation speed acquired in S20. The motor ECU 20 calculates information indicating the ratio of the front motor rotation speed to the rear motor rotation speed, and corrects the magnet temperature TR2 based on that information to estimate the magnet temperature TF2. Specifically, the magnet temperature TF2 is calculated by multiplying the magnet temperature TR2 by that information.

[0040] As described above, in this embodiment, the information indicating the relative relationship is information indicating the ratio of the front motor rotation speed of the front motor 10 to the rear motor rotation speed of the rear motor 12. There is a correlation between the motor rotation speed and the magnet temperature. Therefore, by correcting the magnet temperature TR2 based on the information indicating the ratio of the front motor rotation speed to the rear motor rotation speed, it is possible to appropriately estimate the magnet temperature TF2.

[0041] (Third Example) The electric vehicle 2 of this embodiment differs from the electric vehicle 2 of the first embodiment in the content of the processes executed in S20 and S22 of FIG.

[0042] 3, the motor ECU 20 identifies a motor load of the rear motor 12 (hereinafter referred to as "rear motor load") and a motor load of the front motor 10 (hereinafter referred to as "front motor load"). The motor ECU 20 identifies the rear motor load based on, for example, the output power of the front inverter, and identifies the rear motor load based on the output current of the rear inverter.

[0043] In S22, the motor ECU 20 estimates the magnet temperature TF2 of the front motor 10 using the magnet temperature TR2 of the rear motor 12 estimated in S10, the front motor load specified in S20, and the rear motor load specified in S20. The motor ECU 20 calculates information indicating the ratio of the front motor load to the rear motor load, and corrects the magnet temperature TR2 based on that information to estimate the magnet temperature TF2. Specifically, the magnet temperature TF2 is calculated by multiplying the magnet temperature TR2 by that information.

[0044] As described above, in this embodiment, the information indicating the relative relationship is information indicating the ratio of the motor load of the front motor 10 to the rear motor load of the rear motor 12. There is a correlation between the motor load and the magnet temperature. Therefore, by correcting the magnet temperature TR2 based on the information indicating the ratio of the front motor load to the rear motor load, it is possible to appropriately estimate the magnet temperature TF2.

[0045] While specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

[0046] (First Modification) In S20 of FIG. 2, the motor ECU 20 may identify the history of the rear wheel required driving force and the history of the front wheel required driving force over a predetermined period (for example, 5 seconds), and in S22, calculate the magnet temperature TF2 using the history of the rear wheel required driving force and the history of the front wheel required driving force. A similar configuration is also applicable to the second and third embodiments. In another modification, the motor ECU 20 may identify the average value of the rear wheel required driving force and the average value of the front wheel required driving force over a predetermined period in S20, and in S22, calculate the magnet temperature TF2 using the average value of the rear wheel required driving force and the average value of the front wheel required driving force. A similar configuration is also applicable to the second and third embodiments.

[0047] (Second Modification) In S20 of FIG. 2, the motor ECU 20 may acquire information from two or more of the first to third embodiments, and in S22, calculate the magnet temperature TF2 using the information from two or more of the first to third embodiments.

[0048] (Third Modification) A temperature sensor may be provided in the front motor 10, but not in the rear motor 12. Furthermore, if the electric vehicle 2 includes a left front wheel motor that drives the left front wheel and a right front wheel motor that drives the right front wheel, a temperature sensor may be provided in only one of the left front wheel motor and the right front wheel motor.

[0049] (Fourth Modification) The temperature sensor 12c may be a sensor that detects the magnet temperature TF2 of the rear motor 12, the temperature in the vicinity of the rear motor 12, or the temperature of the oil flowing through the reduction gear corresponding to the rear motor 12.

[0050] Furthermore, the technical elements described in this specification or drawings may exhibit technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings may achieve multiple objectives simultaneously, and achieving one of those objectives alone is technically useful. [Explanation of symbols]

[0051] 2: electric vehicle, 10: front motor, 10a: rotation speed sensor, 10b: resolver, 10c: temperature sensor, 12: rear motor, 12a: rotation speed sensor, 12b: resolver, 12c: temperature sensor, 14: front wheels, 16: rear wheels, 18: main ECU, 20: motor ECU, 22: front wheel drive shaft, 24: rear wheel drive shaft, 30: outside air temperature sensor, 32: gradient sensor, 34: vehicle speed sensor

Claims

1. a first motor that drives a first wheel; a second motor that drives a second wheel different from the first wheel; a temperature sensor provided for the first motor; a control device; Equipped with The control device estimating a temperature of the first motor based on a detection signal from the temperature sensor; correcting the temperature of the first motor based on information indicating a relative relationship between an operation of the first motor and an operation of the second motor, thereby estimating the temperature of the second motor; controlling operation of the first motor based on the estimated temperature of the first motor; and controlling operation of the second motor based on the estimated temperature of the second motor.

2. The electric vehicle according to claim 1 , wherein the information indicating the relative relationship is information indicating a ratio of the required driving force of the second motor to the required driving force of the first motor.

3. The electric vehicle according to claim 1 , wherein the information indicating the relative relationship is information indicating a ratio of the rotation speed of the second motor to the rotation speed of the first motor.

4. 2. The electric vehicle according to claim 1, wherein the information indicating the relative relationship is information indicating a ratio of the motor load of the second motor to the motor load of the first motor.

Images