Electric vehicle

Abstract

To provide an electric vehicle capable of smoothly going over a step.SOLUTION: This electric vehicle comprises: a motor that drives wheels; and a control device that executes lock protection control for reducing output torque of the motor in a lock state where current concentrates in a specific phase of the motor to flow. The control device determines whether an accelerator opening steeply increases after the end of the lock protection control when the lock protection control is executed at the time of going over a step from the start of the wheels to go over the step to the completion of going over the step, and sets an upper limit value of output torque of the motor to a torque size enough for the wheels to be able to go over the step when it is determined that the accelerator opening has steeply increased after the end of the lock protection control at the time of going over the step.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an electric vehicle.

Background Art

[0002] Patent Document 1 discloses that, in order to suppress a sudden acceleration of an electric vehicle after crossing a step, when it is determined that the wheel has crossed a step, the upper limit value of the output torque of the motor is limited to a predetermined value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an electric vehicle using a motor as a driving power source, lock protection control for limiting the output torque of the motor may be executed when the motor is in a locked state where current concentrates and flows in a specific phase of the motor. In this case, if the lock protection control is executed when the electric vehicle attempts to cross a step, a decrease in the output torque of the motor due to the lock protection control may occur in a situation where torque is required, and there is a risk that the step cannot be crossed smoothly.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide an electric vehicle that can smoothly cross a step.

Means for Solving the Problems

[0006] The present invention relates to an electric vehicle comprising a motor for driving wheels and a control device that executes lock protection control for reducing the output torque of the motor when in a locked state where current concentrates and flows in a specific phase of the motor. When the control device executes the lock protection control during a step climb from when the wheels attempt to cross a step until the crossing is completed, the control device determines whether the accelerator opening has suddenly increased after the lock protection control ends. If it is determined that the accelerator opening has suddenly increased after the lock protection control during the step climb ends, the upper limit value of the output torque of the motor is set to a magnitude of torque that allows the wheels to cross the step.

Advantages of the Invention

[0007] In the present invention, the vehicle can smoothly cross a step.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0009] Hereinafter, an electric vehicle according to an embodiment of the present invention will be specifically described. Note that the present invention is not limited to the embodiments described below.

[0010] FIG. 1 is a schematic diagram showing an electric vehicle according to an embodiment. The electric vehicle 1 includes a motor 2, wheels 3, and a control device 4. The electric vehicle 1 is composed of a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), an electric vehicle (BEV), or the like.

[0011] The motor 2 is a three-phase AC motor that functions as a power source for running, and is a motor generator having the functions of an electric motor and a generator. In the electric vehicle 1, the wheels 3 are driven by the power output from the motor 2. The motor 2 is connected to the wheels 3 so as to be able to transmit power. The power (torque) output from the motor 2 is transmitted to the wheels 3 via a power transmission device such as a gear. The motor 2 is a synchronous motor including a rotor in which permanent magnets are embedded and a stator around which a three-phase coil is wound. The three-phase coils (U-phase, V-phase, W-phase) wound around the stator of the motor 2 are electrically connected to an inverter. The motor 2 is electrically connected to a battery via the inverter. The motor 2 outputs torque using the electric power supplied from the battery. When a three-phase voltage is applied to the motor 2 by the inverter, a three-phase current flows through the coils of the motor 2, and torque is generated in the motor 2.

[0012] The control device 4 is a control device that controls the motor 2. The control device 4 includes a processor and a memory. The control device 4 loads a program stored in the storage unit into the working area of the memory and executes it, and realizes a function that matches a predetermined purpose by controlling each component through the execution of the program. Signals from various sensors mounted on the electric vehicle 1 are input to the control device 4. Signals from a vehicle speed sensor that detects the vehicle speed of the electric vehicle 1, an accelerator opening sensor that detects the depression amount (accelerator opening) of the accelerator pedal, and the like are input to the control device 4. The control device 4 executes various controls based on the signals input from the various sensors.

[0013] When the motor 2 is in a locked state, the control device 4 executes lock protection control to limit the output torque of the motor 2. When the electric vehicle 1 travels by the output torque of the motor 2, if it enters a locked state (a state where current is flowing but the motor 2 has stopped rotating) in which current concentrates and flows in a specific phase of the motor 2, in order to suppress the temperature of the motor 2 from rising due to the concentrated flow of current in the specific phase, lock protection control is executed to gradually reduce the torque command value of the motor 2. In the electric vehicle 1, lock protection control is executed to protect electrical equipment including the motor 2 and the inverter from thermal load.

[0014] The control device 4 determines whether to execute lock protection control (lock determination), and starts or ends lock protection control according to the result. The control device 4 determines whether the start condition of the lock protection control is satisfied. If it is determined that the start condition is satisfied, the lock determination is switched from OFF to ON and the lock protection control is started. During the execution of the lock protection control, the control device 4 determines whether the end condition of the lock protection control is satisfied. If it is determined that the end condition is satisfied, the lock determination is switched from ON to OFF and the lock protection control is ended.

[0015] As shown in FIG. 1, when the electric vehicle 1 attempts to cross the step 10, if the motor 2 enters a locked state, the control device 4 executes lock protection control. Therefore, a decrease in the output torque of the motor 2 due to the lock protection control occurs in a situation where torque is required to cross the step 10. When the electric vehicle 1 fails to gain speed when climbing the step, if the motor torque is gradually increased, the lock protection control may be executed when high torque is required. When the lock protection control is executed, since the motor torque is reduced for a certain period of time, it is difficult to cross the step 10 easily. Therefore, the electric vehicle 1 is configured to be able to smoothly cross the step 10 even when the lock protection control is executed when crossing the step 10.

[0016] Specifically, as shown in FIG. 2, when the wheel 3 of the electric vehicle 1 comes into contact with the step 10, the vehicle speed begins to decrease toward 0, the accelerator opening begins to increase, and the control device 4 increases the output torque (MG torque) of the motor 2 to the upper limit value, i.e., the MG upper limit torque, and starts to gradually increase the MG upper limit torque (time t1). When the electric vehicle 1 attempts to cross the step 10, the control device 4 limits the maximum value of the output torque of the motor 2 by the MG upper limit torque, and controls to gradually increase the MG upper limit torque as the time taken to cross the step 10 elapses.

[0017] After that, when the output torque of the motor 2 continues to increase along the MG upper limit torque with the vehicle speed being 0, the start condition for the lock protection control is satisfied, and the lock determination switches from OFF to ON (time t2). In response to the satisfaction of the start condition, the control device 4 executes the lock protection control and decreases the output torque of the motor 2 to a value smaller than the MG upper limit torque. Then, when the end condition for the lock protection control is satisfied during the execution of the lock protection control, the control device 4 terminates the lock protection control, and the lock determination switches from ON to OFF (time t3).

[0018] After the termination of the lock protection control, when the accelerator opening suddenly increases, the control device 4 sets the MG upper limit torque to a torque value that can cross the step 10 (time t4). After time t4, the control device 4 increases the output torque of the motor 2 in response to the suddenly increased accelerator opening.

[0019] Then, after the vehicle speed starts to increase from 0, it is determined that the ascent of the step 10 is completed (time t5). The determination that the ascent is completed is made based on the fact that the vehicle speed has increased and the accelerator opening has decreased. After the electric vehicle 1 has ascended the step 10, the control device 4 gradually decreases the increased MG upper limit torque.

[0020] In the electric vehicle 1 configured as described above, even when the lock protection control is executed during the process of crossing the step 10, when it is determined that the accelerator opening has rapidly increased after the lock determination has shifted from ON to OFF, the MG upper limit torque is rapidly increased to the required torque determined from the height of the step 10, enabling the wheel 3 to climb over the step 10. As a result, the time during which the rotational speed of the motor 2 is near 0 and the torque of the motor 2 is high torque is shortened, the second lock protection control is not executed, and the jerk during the climb over the step 10 can be avoided.

[0021] FIG. 3 is a flowchart showing a processing flow when crossing a step. The control shown in FIG. 3 is implemented by the control device 4.

[0022] The control device 4 determines whether it is the time of climbing over a step (step S1). In step S1, it is determined whether the electric vehicle 1 is attempting to cross the step 10.

[0023] If it is determined that it is the time of climbing over a step (step S1: Yes), the control device 4 determines whether there is a history of the lock determination shifting from ON to OFF (step S2). In step S2, it is determined whether there is history information indicating that the lock protection control was started and then ended while the electric vehicle 1 was attempting to cross the step 10.

[0024] If it is determined that there is a history of the lock determination shifting from ON to OFF (step S2: Yes), the control device 4 determines whether the accelerator opening has rapidly increased (step S3). In step S3, it is determined whether the accelerator opening has rapidly increased after the lock protection control is implemented.

[0025] If it is determined that the accelerator opening has not rapidly increased (step S3: No), this control routine proceeds to step S6.

[0026] When it is determined that the accelerator opening has increased rapidly (Step S3: Yes), the control device 4 calculates the necessary torque for crossing the step 10 based on the image of the step 10 captured by the camera 5 (Step S4). In Step S4, the height of the step 10 is estimated from the image data captured by the camera 5, and the necessary torque is calculated based on the step height.

[0027] The control device 4 corrects the MG upper limit torque (Step S5). In Step S5, the MG upper limit torque of the motor 2 is set to a value equal to or greater than the necessary torque calculated in Step S4.

[0028] The control device 4 increases the MG upper limit torque over time (Step S6). In Step S6, the MG upper limit torque is increased over time from the value set in Step S5.

[0029] The control device 4 determines whether the step climb is completed (Step S7). In Step S7, it is determined whether the vehicle speed has increased and the accelerator opening has decreased.

[0030] When it is determined that the step climb is completed (Step S7: Yes), the control device 4 gradually decreases the value of the MG upper limit torque toward the original value (Step S8). In Step S8, the MG upper limit torque increased by the process of Step S6 is decreased.

[0031] The control device 4 erases the history that the lock determination has shifted from ON to OFF (Step S9). When the process of Step S9 is executed, this control routine ends.

[0032] When it is determined that it is not during the step climb (Step S1: No), when it is determined that there is no history that the lock determination has shifted from ON to OFF (Step S2: No), when it is determined that the step climb is not completed (Step S7: No), this control routine ends.

[0033] As described above, according to the embodiment, even when the lock protection control is executed when overcoming the step 10, by setting the MG upper limit torque to be equal to or greater than the required torque determined from the height of the step 10, the output torque of the motor 2 can increase rapidly, and it is possible to overcome the step 10. As a result, the time during which the motor rotation speed is near 0 and the motor torque is high torque is shortened, the second lock protection control can be avoided from being executed, and the jerk during step climbing can be avoided. As a result, the electric vehicle 1 can smoothly overcome the step 10.

[0034] In addition, when it is possible to climb over the step without executing the lock protection control, the control device 4 continues the running control as it is. Thereby, it is possible to suppress the deterioration of the riding comfort due to a sudden climb caused by a rapid increase in torque.

[0035] Further, the method for determining the completion of step climbing may be a known method such as a determination method based on the vehicle speed and torque. It may be a method such as determination by Lidar or the camera 5 or a method of determining the rear wheel climb from the front wheel climb information.

[0036] In addition, although the MG upper limit torque is changed by executing the lock protection control, the torque that is the execution condition of the lock protection control may be calculated based on the motor temperature or the inverter temperature. In this case, the torque that is the execution condition of the lock protection control is compared with the torque required to overcome the step 10. When the torque that is the execution condition of the lock protection control is smaller than the torque required to overcome the step 10, the torque required to overcome the step 10 may be set as the MG upper limit torque from the beginning.

[0037] In addition, the control device 4 can execute crawl control. The crawl control can be used in off-road driving control. The crawl control is a control aimed at making the electric vehicle 1 travel at a constant speed without operating the accelerator pedal. During the execution of the crawl control, in order for the electric vehicle 1 to travel at a constant vehicle speed, when the actual vehicle speed is lower than the target vehicle speed, the drive torque is gradually increased, and when the actual vehicle speed exceeds the target vehicle speed, the drive torque is gradually decreased. In the control device 4 of the modification, as shown in FIG. 4, during the execution of the lock protection control, the gradual increase in torque by the crawl control is stopped (time t12), and when the lock protection control ends (time t13), the crawl control is ended, and the motor torque is rapidly increased to the required torque determined from the height of the step 10 to climb over the step 10 (time t13 to t14).

[0038] FIG. 5 is a flowchart showing a processing flow when climbing over a step during crawl control. The control shown in FIG. 5 is executed by the control device 4.

[0039] The control device 4 determines whether or not the crawl control is being executed (step S21).

[0040] The control device 4 determines whether or not the electric vehicle 1 is at the time of climbing over a step (step S22).

[0041] When it is determined that the electric vehicle 1 is at the time of climbing over a step (step S22: Yes), the control device 4 determines whether or not there is a history that the lock determination has shifted from ON to OFF (step S23).

[0042] When it is determined that there is a history that the lock determination has shifted from ON to OFF (step S23: Yes), the control device 4 calculates the required torque for climbing over the step 10 based on the image of the step 10 captured by the camera 5 (step S24).

[0043] The control device 4 turns off the crawl control (step S25).

[0044] The control device 4 increases the output torque of the motor 2 to the required torque (step S26). In step S26, the output torque of the motor 2 is increased so as to satisfy the required torque calculated in step S24.

[0045] The control device 4 determines whether the step climb is completed (step S27).

[0046] When it is determined that the step climb is completed (step S27: Yes), the control device 4 decreases the MG torque (step S28).

[0047] The control device 4 erases the history that the lock determination has shifted from ON to OFF (step S29).

[0048] The control device 4 turns on the crawl control (step S30). In step S30, the crawl control is restarted. When the process of step S30 is performed, this control routine ends.

[0049] When it is determined that it is not during step climb (step S22: No), when it is determined that there is no history that the lock determination has changed from ON to OFF (step S23: No), and when it is determined that the step climb is not completed (step S27: No), this control routine ends.

Explanation of Signs

[0050] 1 Electric vehicle 2 Motor 3 Wheel 4 Control device 5 Camera 10 Step

Claims

【Claim 1】 A motor for driving a wheel, A control device that executes lock protection control for reducing the output torque of the motor when the motor is in a locked state in which current concentrates and flows in a specific phase of the motor, An electric vehicle comprising: The control device, When the lock protection control is executed during the step climb from when the wheel attempts to cross a step until the crossing is completed, determines whether the accelerator opening has suddenly increased after the lock protection control ends, When it is determined that the accelerator opening has suddenly increased after the lock protection control during the step climb ends, sets the upper limit value of the output torque of the motor to the magnitude of the torque that allows the wheel to cross the step. An electric vehicle characterized by the above.

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