Electric vehicle

Abstract

To provide a technique that can increase such a possibility that an electric vehicle can travel in a four-wheel drive mode under a low-temperature environment.SOLUTION: An electric vehicle includes: a front motor; a rear motor; a first temperature sensor that detects the outside air temperature; a second temperature sensor that detects the rear motor temperature; and a control device that can selectively execute a four-wheel drive mode in which both the front motor and rear motor are operated, and a two-wheel drive mode in which only the former of the front motor and rear motor is operated. The control device has a memory that stores a rear torque distribution ratio and a rear torque upper limit value. When the outside air temperature is below a first predetermined temperature, the control device executes the four-wheel drive mode using the rear torque distribution ratio and the rear torque upper limit value. When the rear motor temperature exceeds a second predetermined temperature while the four-wheel drive mode is being executed, the control device corrects the rear torque distribution ratio and the rear torque upper limit value stored in the memory to the lower side and executes the two-wheel drive mode.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Patent Document 1 discloses an electric vehicle equipped with a front motor for driving the front wheels, a rear motor for driving the rear wheels, and a control device for controlling the operation of the front motor and the rear motor. The control device can selectively execute a four-wheel drive mode in which both the front motor and the rear motor are operated, and a two-wheel drive mode in which only the front motor or the rear motor is operated. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-126128 A Summary of the Invention [Problem to be solved by the invention]

[0004] In low-temperature environments, it is desirable to run an electric vehicle in four-wheel drive to ensure the running stability of the electric vehicle. However, if the temperature of the rear motor exceeds a predetermined temperature while the electric vehicle is running in four-wheel drive, the electric vehicle will switch from four-wheel drive to two-wheel drive to protect the rear motor.

[0005] This specification provides a technique that can extend the time that an electric vehicle can run in four-wheel drive mode in a low-temperature environment. [Means for solving the problem]

[0006] In a first aspect of the present technology, a vehicle includes a front motor for driving front wheels, a rear motor for driving rear wheels, a first temperature sensor for detecting an outside air temperature, a second temperature sensor for detecting a rear motor temperature, and a control device capable of selectively executing a four-wheel drive mode in which both the front motor and the rear motor are operated and a two-wheel drive mode in which only the former of the front motor and the rear motor is operated. The control device has a memory for storing a rear torque distribution ratio indicating a distribution ratio of torque distributed to the rear motor and a rear torque upper limit value of the rear motor, and executes the four-wheel drive mode using the rear torque distribution ratio and the rear torque upper limit value stored in the memory when the outside air temperature is lower than a first predetermined temperature, and executes the two-wheel drive mode by correcting the rear torque distribution ratio and the rear torque upper limit value stored in the memory to lower values ​​when the rear motor temperature exceeds a second predetermined temperature during execution of the four-wheel drive mode.

[0007] According to the above configuration, when the rear motor temperature exceeds the second predetermined temperature while the four-wheel drive mode is being executed, the control device corrects the rear torque distribution ratio and the rear torque upper limit value stored in the memory to the lower side. In this case, the rear torque distribution ratio and the rear torque upper limit value corrected to the lower side are used the next time the four-wheel drive mode is executed. This reduces the thermal load on the rear motor. Therefore, even when the four-wheel drive mode is executed, it is possible to prevent the rear motor temperature from exceeding the second predetermined temperature. Therefore, it is possible to extend the time during which the four-wheel drive mode can be executed in a low-temperature environment, i.e., the time during which the electric vehicle runs in four-wheel drive. As a result, it is possible to improve the running stability of the electric vehicle in a low-temperature environment. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing an outline of an electric vehicle 2. [Diagram 2] 4 is a flowchart of a correction process executed by the control device 24. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (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 battery 18, inverters 20, 22, a control device 24, and a temperature sensor 26 that detects the outside air temperature. The electric vehicle 2 is an electric four-wheel drive vehicle. In this specification, the electric vehicle broadly means a vehicle having a motor that drives the wheels. For example, electric vehicles include battery electric vehicles, fuel cell vehicles, plug-in hybrid vehicles, etc. in addition to hybrid vehicles.

[0010] The front motor 10 is connected to the front wheels 14 via a front wheel drive shaft 28. The front motor 10 drives the front wheels 14 via the front wheel drive shaft 28. The rear motor 12 is connected to the rear wheels 16 via a rear wheel drive shaft 30. The rear motor 12 drives the rear wheels 16 via the rear wheel drive shaft 30. The rear motor 12 is provided with a temperature sensor 12a that detects the rear motor temperature, which is the temperature of the rear motor 12. The temperature sensor 12a detects, for example, the temperature of a coil (not shown) of the rear motor 12.

[0011] The battery 18 is a rechargeable secondary battery, and includes, as an example, a plurality of lithium-ion cells. The inverters 20, 22 convert the DC power supplied from the battery 18 into AC power and supply it to the front motor 10 and the rear motor 12, respectively.

[0012] The control device 24 is a controller including a memory 24a. The control device 24 can selectively execute a four-wheel drive mode in which both the front motor 10 and the rear motor 12 are operated, and a two-wheel drive mode in which only the front motor 10 and the rear motor 12 are operated. The control device 24 calculates a required torque while the electric vehicle 2 is traveling, based on the accelerator pedal opening, the vehicle speed, and the like. When the two-wheel drive mode is being executed, the control device 24 controls the operation of the battery 18, the inverter 20, and the front motor 10 so that the front torque of the front motor 10 becomes the required torque. When the four-wheel drive mode is being executed, the control device 24 controls the operation of the battery 18, the inverter 20, the front motor 10, the inverter 22, and the rear motor 12 so that the total torque of the front torque and the rear torque of the rear motor 12 becomes the required torque. The memory 24a stores a rear torque distribution ratio indicating a distribution ratio (e.g., 30%) of the torque required to be distributed to the rear motor 12, and a rear torque upper limit value that is an upper limit value of the rear motor 12. The rear torque distribution ratio and the rear torque upper limit value are information used when the four-wheel drive mode is executed in a low temperature environment. The memory 24a stores combinations of the rear torque distribution ratio and the rear torque upper limit value corresponding to each of a plurality of outside temperature ranges. The plurality of outside temperature ranges are, for example, below -10°C, -10°C to 0°C, 0°C to 5°C, etc.

[0013] (Correction process; Figure 2) The correction process executed by the control device 24 will be described with reference to Fig. 2. The correction process is a process for correcting the rear torque distribution ratio and the rear torque upper limit value in the memory 24a. The control device 24 starts the process in Fig. 2, for example, when the ignition switch is turned on.

[0014] In S10, the control device 24 determines whether the outside air temperature detected by the temperature sensor 26 is less than a first predetermined temperature (e.g., 5°C). The first predetermined temperature is a threshold value for determining that the vehicle is in a low-temperature environment. If the outside air temperature is less than the first predetermined temperature (YES in S10), the control device 24 proceeds to S12. On the other hand, if the outside air temperature is not less than the first predetermined temperature (NO in S10), the control device 24 ends the processing of FIG. 2.

[0015] In S12, the control device 24 identifies a combination of a rear torque distribution ratio and a rear torque upper limit value corresponding to the outside air temperature from the memory 24a. After that, when the electric vehicle 2 starts traveling, the control device 24 identifies the required torque, and determines the front torque and the rear torque using the rear torque distribution ratio and the rear torque upper limit value identified in S12. Then, the control device 24 controls the operations of the battery 18, the inverter 20, the front motor 10, the inverter 22, and the rear motor 12 based on the determined front torque and rear torque. In this way, the four-wheel drive mode is executed in a low-temperature environment, and the electric vehicle 2 travels in four-wheel drive.

[0016] In S14, the control device 24 monitors whether the rear motor temperature detected by the temperature sensor 12a exceeds a second predetermined temperature. If the rear motor temperature exceeds the second predetermined temperature, the control device 24 judges YES in S14 and proceeds to S16. Note that, if the ignition switch is turned OFF while waiting in S14, the control device 24 ends the process of FIG. 2.

[0017] In S16, the control device 24 corrects the rear torque distribution ratio and rear torque upper limit value determined in S12 to the lower side and stores them in the memory 24a. That is, the control device 24 updates the rear torque distribution ratio and rear torque upper limit value in the memory 24a. When S16 ends, the control device 24 ends the processing of FIG. 2. Note that, when the control device 24 determines YES in S14, it executes the two-wheel drive mode instead of the four-wheel drive mode. This makes it possible to prevent the rear motor 12 from overheating, and to protect the rear motor 12.

[0018] As described above, the electric vehicle 2 includes the front motor 10 that drives the front wheels 14, the rear motor 12 that drives the rear wheels 16, a temperature sensor 26 (an example of a "first temperature sensor") that detects an outside air temperature, a temperature sensor 12a (an example of a "second temperature sensor") that detects a rear motor temperature, and a control device 24 that can selectively execute a four-wheel drive mode or a two-wheel drive mode. The control device 24 has a memory 24a that stores a rear torque distribution ratio and a rear torque upper limit value, and executes the four-wheel drive mode using the rear torque distribution ratio and the rear torque upper limit value stored in the memory 24a when the outside air temperature is lower than a first predetermined temperature (YES in S10 of FIG. 2), and corrects the rear torque distribution ratio and the rear torque upper limit value stored in the memory 24a to lower values ​​while executing the four-wheel drive mode when the rear motor temperature exceeds a second predetermined temperature (YES in S14).

[0019] According to the above configuration, when the rear motor temperature exceeds the second predetermined temperature while the four-wheel drive mode is being executed, the control device 24 corrects the rear torque distribution ratio and the rear torque upper limit value stored in the memory 24a to the lower side. In this case, the rear torque distribution ratio and the rear torque upper limit value corrected to the lower side are used the next time the four-wheel drive mode is executed. This reduces the thermal load on the rear motor 12. Therefore, even if the four-wheel drive mode is executed, it is possible to prevent the rear motor temperature from exceeding the second predetermined temperature. Therefore, it is possible to lengthen the time during which the four-wheel drive mode can be executed in a low-temperature environment, that is, the time during which the electric vehicle 2 runs in four-wheel drive. As a result, it is possible to improve the running stability of the electric vehicle 2 in a low-temperature environment. [Explanation of symbols]

[0020] 2: electric vehicle, 10: front motor, 12: rear motor, 12a: temperature sensor, 14: front wheels, 16: rear wheels, 18: battery, 20, 22: inverter, 24: control device, 24a: memory, 26: temperature sensor, 28: front wheel drive shaft, 30: rear wheel drive shaft

Claims

[Claim 1] An electric vehicle, A front motor that drives the front wheels; A rear motor that drives the rear wheels; A first temperature sensor that detects an outside air temperature; a second temperature sensor for detecting a rear motor temperature, the rear motor temperature being a temperature of the rear motor; a control device capable of selectively executing a four-wheel drive mode in which both the front motor and the rear motor are operated, and a two-wheel drive mode in which only the front motor and the rear motor are operated; Equipped with The control device includes: a memory that stores a rear torque distribution ratio indicating a distribution ratio of torque to be distributed to the rear motor and a rear torque upper limit value of the rear motor, When the outside air temperature is lower than a first predetermined temperature, the four-wheel drive mode is executed by utilizing the rear torque distribution ratio and the rear torque upper limit value stored in the memory; When the rear motor temperature exceeds a second predetermined temperature while the four-wheel drive mode is being executed, the rear torque distribution ratio and the rear torque upper limit value stored in the memory are corrected to the lower side, and the two-wheel drive mode is executed.

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