Electric vehicle control device

Abstract

To provide an electric vehicle control device that ensures that there is enough time from warning to a driver to restriction of a motor torque.SOLUTION: An electric vehicle control device comprises: an acquisition part which acquires a temperature of a motor as a travel power source of an electric vehicle and an index value indicating ease of temperature rise of the motor; an execution part which executes notification processing for notifying a driver of the electric vehicle of a warning when the temperature of the motor is a first temperature or higher and lower than a second temperature; a restriction part which restricts torque of the motor when the temperature of the motor is the second temperature or higher; and a setting part which sets the first temperature to a lower temperature in the case where the index value is a threshold or more than the case where the index value is less than the threshold.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control device for an electric vehicle.

Background Art

[0002] There is a technique for suppressing overheating of a motor that is a driving power source of an electric vehicle. For example, when the temperature of the motor becomes equal to or higher than a first temperature, a warning is notified to the driver, and when the temperature of the motor becomes equal to or higher than a second temperature that is higher than the first temperature, the torque of the motor is restricted. By restricting the torque of the motor, a further increase in temperature is suppressed (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a state where the motor is likely to heat up, there is a possibility that the temperature of the motor will become equal to or higher than the second temperature from the first temperature in a short time. In this case, there is a possibility that the torque of the motor will be restricted before the driver takes appropriate measures after receiving the warning.

[0005] Therefore, an object of the present invention is to provide a control device for an electric vehicle that secures a time from when a warning is given to the driver until the torque of the motor is restricted.

Means for Solving the Problems

[0006] The above object can be achieved by a control device for an electric vehicle, comprising: an acquisition unit that acquires the temperature of a motor which is a driving power source of the electric vehicle and an index value indicating the ease of temperature rise of the motor; an execution unit that executes a notification process of notifying a warning to a driver of the electric vehicle when the temperature of the motor is equal to or higher than a first temperature and lower than a second temperature; a restriction unit that restricts the torque of the motor when the temperature of the motor is equal to or higher than the second temperature; and a setting unit that sets the first temperature to a lower temperature when the index value is equal to or higher than a threshold value than when the index value is lower than the threshold value.

[0007] The index value may be the ascending gradient of the driving road surface on which the electric vehicle travels.

[0008] The index value may be the temperature of cooling water that cools the motor.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a control device for an electric vehicle that secures the time from warning the driver to restricting the torque of the motor.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0011] [Schematic Configuration of Electric Vehicle] FIG. 1 is a schematic configuration diagram of the electric vehicle 1. The electric vehicle 1 is an electric car equipped with a motor 2 as a driving power source. The electric vehicle 1 includes a motor 2, a propeller shaft 3, a differential gear 4, a drive shaft 5, drive wheels 6, a PCU (Power Control Unit) 7, a battery 8, and an ECU (Electric Control Unit) 10.

[0012] The motor 2 functions as an electric motor that outputs torque by power supply. The motor 2 further has a function as a generator that generates electricity when the electric vehicle 1 brakes. The stored electric power of the battery 8 is supplied to the motor 2 via the PCU 7. The generated electric power of the motor 2 is supplied to the battery 8 via the PCU 7. The ECU 10 adjusts the electric power exchanged between the motor 2 and the battery 8 by controlling the PCU 7.

[0013] The motor 2 is connected to the drive wheels 6 via the propeller shaft 3, the differential gear 4, and the drive shaft 5. When the torque of the motor 2 is transmitted to the drive wheels 6, the electric vehicle 1 travels.

[0014] The ECU 10 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a storage device, etc., and performs various controls by executing programs stored in the ROM and the storage device. The ECU 10 is an example of a control device for an electric vehicle, and specifically, functionally realizes an acquisition unit, an execution unit, a limitation unit, and a setting unit, which will be described later.

[0015] The ECU 10 is electrically connected to an ignition switch 20, a temperature sensor 21, a water temperature sensor 22, and a gradient sensor 23. The ignition switch 20 detects the on / off state of the ignition. The temperature sensor 21 detects the temperature of the motor 2 (hereinafter referred to as the motor temperature MT). The water temperature sensor 22 detects the temperature of the cooling water that cools the motor 2 (hereinafter referred to as the water temperature WT). The gradient sensor 23 detects the uphill gradient UG [%] of the traveling road surface. The ECU 10 is electrically connected to a display unit 24. The display unit 24 is controlled by the ECU 10 and is provided on the instrument panel of the vehicle.

[0016] [Motor Protection Control] Figure 2 is a flowchart illustrating motor protection control. This control is repeatedly executed while the ignition is on. The ECU 10 acquires the motor temperature MT and the uphill gradient UG by the temperature sensor 21 and the gradient sensor 23 (step S1). The uphill gradient UG is an example of an index value indicating the ease of temperature rise of the motor 2. This is because the larger the uphill gradient UG, the greater the torque of the motor 2, the greater the power supplied to the motor 2, and the easier it is for the motor 2 to heat up. Step S1 is an example of the process executed by the acquisition unit.

[0017] Next, the ECU 10 determines whether the uphill gradient UG is equal to or greater than the gradient threshold value A (step S2). The gradient threshold value A is a positive value. Here, when the uphill gradient UG is equal to or greater than the gradient threshold value A, the torque of the motor 2 increases and the motor temperature MT is more likely to rise than when the uphill gradient UG is less than the gradient threshold value A. If the result in step S2 is No, the ECU 10 sets the first temperature T1 described later to the high temperature HT (step S3). If the result in step S2 is Yes, the ECU 10 sets the first temperature T1 to the low temperature LT (step S4). The low temperature LT is lower than the high temperature HT. That is, when the uphill gradient UG is equal to or greater than the gradient threshold value A, the first temperature T1 is set to a lower temperature than when the uphill gradient UG is less than the gradient threshold value A. Steps S2 to S4 are examples of the processes executed by the setting unit.

[0018] After the execution of step S3 or S4, the ECU 10 determines whether the motor temperature MT is equal to or higher than the first temperature T1 (step S5). If the result in step S5 is No, this control ends. If the result in step S5 is Yes, the ECU 10 executes a notification process to notify the driver of a warning (step S6). For example, the ECU 10 causes the display unit 24 to display a warning that there is a possibility that the torque of the motor 2 is restricted and prompts the driver to stop the vehicle. By stopping the electric vehicle 1 according to the warning, further temperature rise of the motor 2 is suppressed and the restriction of the torque of the motor 2 described later is avoided. Note that the method of notification is not limited to this. For example, the above warning may be notified by sound through a speaker of an audio system or a navigation system of the vehicle. Step S6 is an example of a process executed by the execution unit.

[0019] Next, the ECU 10 determines whether the motor temperature MT is equal to or higher than the second temperature T2 (step S7). The second temperature T2 is a temperature higher than the first temperature T1, that is, a temperature higher than the high temperature HT and the low temperature LT. If the result in step S7 is No, this control ends. If the result in step S7 is Yes, the ECU 10 restricts the torque of the motor 2 (step S8). The restriction of the torque may be realized by changing the upper limit torque that the motor 2 can output to a smaller value. Also, the restriction of the torque may be realized by multiplying the required torque to the motor 2 by a coefficient less than 1 and changing the required torque to a smaller value. Other than that, the restriction of the torque may be realized by restricting the value of the current applied to the motor 2 to a predetermined value or less, or by restricting the rotational speed of the motor 2. Thereby, the temperature rise of the motor 2 is suppressed. Step S2 is an example of a process executed by the restriction unit.

[0020] In FIGS. 3A and 3B, there are timing charts illustrating the transition of the motor temperature MT. FIG. 3A illustrates the transition of the motor temperature MT when the uphill gradient UG is less than the gradient threshold A and the first temperature T1 is set to the high temperature HT. As shown in FIG. 3A, when the motor temperature MT becomes equal to or higher than the low temperature LT (time t1), a warning is notified to the driver when the motor temperature MT becomes equal to or higher than the high temperature HT (time t2). After that, when the motor temperature MT becomes equal to or higher than the second temperature T2, the torque of the motor 2 is limited (time t3).

[0021] FIG. 3B illustrates the transition of the motor temperature MT when the uphill gradient UG is equal to or higher than the gradient threshold A and the first temperature T1 is set to the low temperature LT. As shown in FIG. 3B, a warning is notified to the driver when the motor temperature MT becomes equal to or higher than the low temperature LT (time t1) before the motor temperature MT becomes equal to or higher than the high temperature HT (time t2). After that, when the motor temperature MT becomes equal to or higher than the second temperature T2, the torque of the motor 2 is limited (time t3). In this way, the time from the warning (time t1) to the torque limit (time t3) is ensured. Thereby, the driver can take appropriate measures such as stopping before the torque limit.

[0022] In addition, the ECU 10 may execute a process of increasing the braking force of the electric vehicle 1 together with the warning. The increase in the braking force may be realized, for example, by performing a correction to increase the target braking force. By increasing the braking force of the electric vehicle 1 before the torque limit, it is suppressed that the electric vehicle 1 retreats on the uphill gradient at the time of torque limit. Also, when traveling in the automatic driving mode, the electric vehicle 1 may be decelerated or stopped together with the warning.

[0023] [Modification Example of Motor Protection Control] Next, a modified example of motor protection control will be described. In this modified example, the water temperature WT of the cooling water for cooling the motor 2 is used. Therefore, the cooling circuit for cooling the motor 2 will be described. FIG. 4 is an exemplary diagram of the cooling circuit 100. The cooling circuit 100 includes paths 101, 102, 103, and 104. Path 101 flows cooling water from the five-way valve 30 through the radiator 31 to the reservoir tank 32. Path 102 flows cooling water from the five-way valve 30 through the ESU (Electricity Supply Unit) 33, the PCU 7, and the motor 2 and back to the five-way valve 30. A water pump P1 is disposed between the PCU 7 and the motor 2 on path 102. Also, a water temperature sensor 22 is provided between the water pump P1 and the motor 2 on path 102. The position of the water temperature sensor 22 is not limited to this and may be on path 102. A path 102a branches from upstream of the ESU 33 of path 102. Path 102a flows cooling water to the reservoir tank 32. Path 103 flows cooling water to the reservoir tank 32 through the heater 34 and the battery 8. Path 104 flows cooling water to the five-way valve 30 through the chiller 35. A water pump P2 is disposed between the reservoir tank 32 and the chiller 35 on path 104.

[0024] The radiator 31 promotes heat dissipation of the cooling water. The reservoir tank 32 removes bubbles in the cooling water. The ESU 33 controls charging of the battery 8 by the power of an external power source. The heater 34 raises the temperature of the battery 8 by heating the cooling water as necessary. The chiller 35 thermally connects the cooling circuit 100 and the heat pump circuit 200.

[0025] FIG. 5 is a flowchart illustrating a modified example of motor protection control. The ECU 10 acquires the motor temperature MT and the water temperature WT by the temperature sensor 21 and the water temperature sensor 22 (step S1a). The water temperature WT is an example of an index value indicating the ease of temperature rise of the motor 2. This is because the higher the water temperature WT, the lower the cooling effect by the cooling water and the easier it is for the motor 2 to heat up. Step S1a is an example of a process executed by the acquisition unit.

[0026] Next, the ECU 10 determines whether the water temperature WT is equal to or higher than the water temperature threshold B (step S2a). Here, when the water temperature WT is equal to or higher than the water temperature threshold B, the cooling effect by the cooling water is lower and the motor temperature MT is more likely to rise than when the water temperature WT is less than the water temperature threshold B. If the answer in step S2a is No, the ECU 10 sets the first temperature T1 to the high temperature HT (step S3). If the answer in step S2a is Yes, the ECU 10 sets the first temperature T1 to the low temperature LT (step S4). That is, when the water temperature WT is equal to or higher than the water temperature threshold B, the first temperature T1 is set to a lower temperature than when the water temperature WT is less than the water temperature threshold B. Steps S2a, S3, and S4 are an example of the processing executed by the setting unit. After that, the processing from step S5 and later is executed. Thereby, when the water temperature WT is high, it is possible to secure the time from warning to torque limitation, and the driver can take appropriate measures such as stopping before the torque of the motor 2 is limited.

[0027] In the above embodiment, the climbing gradient UG has been described as an example of the index value indicating the ease of temperature rise of the motor 2. In the above modification, the water temperature WT has been described as the index value. For example, both the climbing gradient UG and the water temperature WT may be used as the index value. For example, when the climbing gradient UG is less than the gradient threshold A and the water temperature WT is less than the water temperature threshold B, the first temperature T1 may be set to the high temperature HT, and in other cases, the first temperature T1 may be set to the low temperature LT. Further, when the climbing gradient UG is less than the gradient threshold A and the water temperature WT is less than the water temperature threshold B, the first temperature T1 may be set to the high temperature HT, when the climbing gradient UG is equal to or higher than the gradient threshold A or the water temperature WT is equal to or higher than the water temperature threshold B, the first temperature T1 may be set to the low temperature LT, and when the climbing gradient UG is equal to or higher than the gradient threshold A and the water temperature WT is equal to or higher than the water temperature threshold B, the first temperature T1 may be set to an even lower low temperature.

[0028] In the above embodiment, the electric vehicle 1 which is an electric vehicle has been described as an example, but it is not limited thereto. For example, the electric vehicle may be a hybrid vehicle equipped with an engine and a motor as a driving power source.

[0029] As described above in detail with reference to the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0030] 1 Electric vehicle 2 Motor 10 ECU (control device, acquisition unit, execution unit, restriction unit, setting unit of electric vehicle) 24 Display unit

Claims

1. An acquisition unit that acquires the temperature of a motor that is a driving power source of an electric vehicle and an index value indicating the ease of temperature rise of the motor; An execution unit that executes a notification process for notifying a warning to a driver of the electric vehicle when the temperature of the motor is equal to or higher than a first temperature and lower than a second temperature; A limiting unit that limits the torque of the motor when the temperature of the motor is equal to or higher than the second temperature; A setting unit that sets the first temperature to a lower temperature when the index value is equal to or higher than a threshold value than when the index value is lower than the threshold value, a control device for an electric vehicle.

2. The control device for an electric vehicle according to claim 1, wherein the index value is a climbing gradient of a traveling road surface on which the electric vehicle travels.

3. The control device for an electric vehicle according to claim 1 or 2, wherein the index value is the temperature of cooling water that cools the motor.

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