Control method and control device for hybrid vehicle

Abstract

To provide a control method of a hybrid vehicle capable of reducing a sense of incongruity felt by a driver due to an increase in the number of revolutions of an engine caused by a delay of a decrease in output of the engine with respect to a decrease in output of a power generation motor.SOLUTION: The control device (the power generation motor control unit 21 or the integrated control unit 60) acquires the temperature of the battery 30. When the temperature of the battery is equal to or higher than the input / output 0 limitation temperature, the control device gently changes a power generation torque change rate for reducing power generation torque generated by power generation by receiving excessive torque generated by the engine 10 with the lapse of time as the temperature of the battery 30 becomes lower and steeply changes the power generation torque change rate as the temperature of the battery 30 becomes higher during deceleration when an accelerator is turned off.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control method and a control device for a hybrid vehicle. [Background technology]

[0002] Patent Document 1 describes that when the temperature of a battery mounted on an electric vehicle becomes high, the input and output of the battery are limited to prevent the temperature from rising further. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-221885 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, series hybrid vehicles have become popular. Series hybrid vehicles use the engine to drive a generator motor, and charge the battery with the electricity generated by the generator motor. Series hybrid vehicles run by driving a drive motor that drives the drive wheels with electricity generated by the generator motor or electricity stored in the battery. When the driver releases the accelerator, not only is the output of the generator motor reduced, but the engine speed is also lowered to reduce output.

[0005] However, because the reduction in engine output is delayed relative to the reduction in generator motor output, when power generation is limited due to a high battery temperature or the like, the generator motor may not be able to absorb the excess torque caused by the engine's surplus energy. If the generator motor is unable to absorb the excess torque, the engine speed may rise sharply, causing the driver to feel uncomfortable. The present invention aims to provide a control method and control device for a hybrid vehicle that can alleviate the discomfort felt by the driver due to the increase in engine speed caused by the delay in the reduction in engine output relative to the reduction in generator motor output. [Means for solving the problem]

[0006] According to one aspect of the present invention, when the battery temperature is equal to or higher than the input / output zero limit temperature, the rate of change of the power generation torque, which reduces the power generation torque generated by the power generation motor over time when the hybrid vehicle is decelerating with the accelerator released, is changed more gradually as the battery temperature decreases and more rapidly as the battery temperature increases. [Effects of the Invention]

[0007] According to the hybrid vehicle control method and control device of the present invention, it is possible to reduce the discomfort felt by the driver due to an increase in engine speed caused by a delay in the reduction in engine output relative to the reduction in output of the generator motor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a series hybrid vehicle. [Figure 2] FIG. 2 is a time chart for explaining a control method and a control device for a hybrid vehicle according to one embodiment. [Figure 3] FIG. 3 is a block diagram showing a power generation torque change rate calculation unit included in the control device for a hybrid vehicle according to one embodiment. [Figure 4]FIG. 4 is a diagram showing a map that determines the rate of change of power generation torque based on the battery temperature and engine output when the hybrid vehicle starts to decelerate. [Figure 5] FIG. 5 is a characteristic diagram showing the rate of change of the power generation torque that is reduced over time after the hybrid vehicle starts to decelerate. [Figure 6] FIG. 6 is a flowchart showing a control method for a hybrid vehicle according to an embodiment and the operation of a control device for a hybrid vehicle according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A control method and control device for a hybrid vehicle according to one embodiment will be described below with reference to the accompanying drawings. First, a schematic configuration of a series hybrid vehicle will be described with reference to FIG. 1. In FIG. 1, a generator motor 20 is driven by an engine 10 to generate electricity. The engine 10 is used to drive the generator motor 20. A battery 30 is charged with the electric power generated by the generator motor 20. A drive motor 40 drives a pair of drive wheels 50 using the electric power generated by the generator motor or the electric power stored in the battery 30. In FIG. 1, thick solid arrows indicate the transmission of physical energy, and dashed dotted arrows indicate the transmission of electrical energy.

[0010] The engine 10 is controlled by an engine control unit 11, and the generator motor 20 is controlled by a generator motor control unit 21. The engine control unit 11 may be a computer called an ECM (Engine Control Module). The generator motor control unit 21 may be a computer called a VCM (Vehicle Control Module). The temperature of the battery 30 measured by a temperature sensor (not shown) is input to the battery control unit 31. The battery control unit 31 calculates the SOC (state of charge) based on measurements from a voltage sensor (not shown) and other devices to manage the state of the battery 30. The battery control unit 31 is made up of a computer. The integrated control unit 60 controls the hybrid vehicle by integrally controlling the engine control unit 11, generator motor control unit 21, and battery control unit 31. The integrated control unit 60 is made up of a computer.

[0011] The engine control unit 11, the generator motor control unit 21, the battery control unit 31, and the integrated control unit 60 constitute a control device for the hybrid vehicle. At least the generator motor control unit 21 and the integrated control unit 60 may constitute the control device. As shown in FIG. 1, the control device may be constituted by multiple computers, or may be constituted by a single computer. The control device may be configured in any manner. An accelerator pedal operation signal is input to the integrated control unit 60.

[0012] When the battery 30 reaches a temperature higher than a predetermined temperature, the input and output of electric power must be set to zero. This is called the input / output zero limit. First, we will explain the normal operation of a hybrid vehicle when the temperature of the battery 30 is at a temperature at which the input / output zero limit is not required.

[0013] The engine control unit 11 (integrated control unit 60) instructs the engine 10 to set a target torque. The generator motor control unit 21 (integrated control unit 60) instructs the generator motor 20 to set a target rotation speed. The generator motor 20 receives torque generated by the engine 10, rotates at the target rotation speed, and generates electricity. The engine 10 may generate torque greater than the instructed target torque. The generator motor 20 receives torque greater than the target torque from the engine 10, rotates at a rotation speed greater than the target rotation speed, and generates more electricity. The upper limit of power generation by the generator motor 20 is the sum of the power required to drive the drive wheels 50 in response to accelerator pedal operation and the allowable input power amount of the battery 30.

[0014] During normal operation, the battery 30 has a predetermined input allowable power amount, so even if the engine 10 generates torque greater than the specified target torque, the generator motor 20 can absorb the excess torque of the engine 10. However, as the temperature of the battery 30 increases, the input allowable power amount approaches zero, so the upper limit of power generation by the generator motor 20 is only the power required to drive the drive wheels 50, and the generator motor 20 cannot absorb the excess torque of the engine 10. This causes the rotation speed of the engine 10 to increase by the amount of the excess torque.

[0015] Therefore, the engine control unit 11 (integrated control unit 60) instructs the engine 10 to a target rotation speed instead of a target torque. As a result, the engine 10 rotates at the instructed target rotation speed and generates torque. The generator motor 20 adjusts the absorption torque so that the amount of power generated is within the input allowable power amount of the battery 30.

[0016] Next, the operation of the hybrid vehicle when the temperature of the battery 30 is equal to or higher than the input / output zero limit temperature at which the input / output zero limit must be implemented will be described with reference to Figures 2 to 5. The operation of the hybrid vehicle when the temperature is equal to or higher than the input / output zero limit temperature is an operation according to a control method for a hybrid vehicle according to one embodiment, and is an operation based on control by a control device for a hybrid vehicle according to one embodiment.

[0017] In FIG. 2, (a) shows the temperature of the battery 30 (hereinafter referred to as battery temperature). Before time t1, the battery temperature is below the input / output zero limit temperature, and the battery temperature rises as time passes. At time t3, the battery temperature approaches the upper limit temperature that ensures battery functionality. In FIG. 2, (b), the dashed line shows the accelerator pedal operation signal, and the solid line shows the power generation torque by the generator motor 20. In FIG. 2, (c) shows the rotation speed of the engine 10.

[0018] The up and down direction of the accelerator pedal operation signal shown in Figure 2(b) indicates the amount of depression of the accelerator pedal. At time t1, the driver instantly releases his foot from the accelerator pedal to decelerate the hybrid vehicle. As described above, the decrease in output of the engine 10 is delayed relative to the decrease in output of the generator motor 20, causing the engine 10 to generate excessive torque. The battery temperature T1 at time t1 is above the input / output zero limit temperature, but there is still a considerable margin of error before the upper temperature limit for battery functionality.

[0019] Therefore, the generator motor control unit 21 controls the generator motor 20 to generate electricity by receiving the excess torque generated by the engine 10. At this time, the generator motor control unit 21 reduces the target generation torque to be generated by the generator motor 20 at a generation torque change rate Rt1 over time. Because the battery temperature T1 has a considerable margin up to the upper temperature limit for battery function assurance, the generator motor control unit 21 reduces the generation torque at a generation torque change rate Rt1 that has a gentle negative slope.

[0020] The generator motor 20 generates electricity at the rate of change of power generation torque Rt1 in response to the excess torque generated by the engine 10, so that the excess torque generated by the engine 10 is absorbed by the generator motor 20. Therefore, as shown in Figure 2(c) , there is no spike in the rotation speed of the engine 10 when deceleration begins at time t1. The battery temperature rises slightly as a result of the generator motor 20 generating electricity, but this does not pose a problem because there is a considerable margin of error before the upper temperature limit for battery functionality is reached.

[0021] At time t2, the driver releases the accelerator to decelerate the hybrid vehicle. The battery temperature T2 at time t2 is equal to or higher than the input / output zero limit temperature, and has a small margin of error before the upper temperature limit for battery function assurance. The generator motor control unit 21 controls the generator motor 20 to generate electricity by receiving the excess torque generated by the engine 10. However, because the battery temperature T2 does not have a sufficient margin of error before the upper temperature limit for battery function assurance, the generator motor control unit 21 reduces the power generation torque generated by the generator motor 20 at a power generation torque change rate Rt2 that has a steeper negative slope than the power generation torque change rate Rt1.

[0022] The generator motor 20 generates electricity at the rate of change of power generation torque Rt2 in response to the excess torque generated by the engine 10, and thus some of the excess torque generated by the engine 10 is absorbed by the generator motor 20. Therefore, as shown in FIG. 2(c), the engine 10 speed increases slightly in a spike-like manner when deceleration begins at time t2. Because the engine 10 speed increases only slightly, the driver does not feel much discomfort. Even if the driver does feel discomfort, it is only slight. The battery temperature increases slightly as the generator motor 20 generates electricity slightly, but this does not pose a problem because there is a small margin of error before the upper temperature limit for battery function assurance.

[0023] At time t3, the driver releases the accelerator to decelerate the hybrid vehicle. At time t3, the battery temperature T3 is close to the upper temperature limit for battery function assurance. The generator motor control unit 21 controls the generator motor 20 so that it generates almost no electricity due to the excessive torque generated by the engine 10. The generator motor control unit 21 reduces the power generation torque generated by the generator motor 20 at a power generation torque change rate Rt3 that has an even steeper negative slope than the power generation torque change rate Rt2.

[0024] By setting the rate of change of power generation torque when the generator motor 20 generates power in response to the excess torque generated by the engine 10 to a steep rate of change of power generation torque Rt3, the generator motor 20 practically generates almost no power and the excess torque generated by the engine 10 is not absorbed by the generator motor 20. Therefore, as shown in FIG. 2(c), the rotation speed of the engine 10 increases in a spike-like manner when deceleration begins at time t3. Although the driver may feel uncomfortable, the battery temperature hardly increases, so it is possible to prevent the battery temperature from reaching or exceeding the upper limit temperature.

[0025] In this way, the control device acquires the temperature of the battery 30, which is charged with electric power generated by the generator motor 20 driven by the engine 10. When the hybrid vehicle is decelerating with the accelerator released, the generator motor 20 receives excess torque generated by the engine 10 due to a delay in the reduction in output of the engine 10 compared to the reduction in output of the generator motor 20. When the temperature of the battery 30 is equal to or higher than the input / output zero limit temperature, the control device controls the generator motor 20 as follows. The control device changes the generation torque change rate, which reduces over time the generation torque generated by the generator motor 20 receiving excess torque to generate electricity, more gradually as the temperature of the battery 30 decreases and more steeply as the temperature of the battery 30 increases.

[0026] According to one embodiment of the control method and control device for a hybrid vehicle, it is possible to reduce the discomfort felt by the driver due to an increase in the rotation speed of the engine 10 caused by a delay in the reduction in the output of the engine 10 relative to the reduction in the output of the generator motor 20.

[0027] In Figure 2, the rate of change of the power generation torque is changed only in response to the battery temperature. In Figure 2(b), the accelerator pedal depression amounts before deceleration begins at times t1, t2, and t3 are the same. The excess torque generated by the engine 10 increases as the output of the engine 10 (hereinafter referred to as engine output), which is determined by the accelerator pedal depression amount, increases. Therefore, it is preferable to change the rate of change of the power generation torque in response to the battery temperature and the engine output.

[0028] Fig. 3 shows the power generation torque change rate calculation unit 210 provided in the generator motor control unit 21. A map, as shown in Fig. 4, is set in the power generation torque change rate calculation unit 210 to determine the power generation torque change rate in accordance with the battery temperature before deceleration begins and the engine output before deceleration begins. When a deceleration determination signal indicating the start of deceleration is input from the integrated control unit 60, the power generation torque change rate calculation unit 210 determines and outputs the power generation torque change rate in accordance with the battery temperature before deceleration begins and the engine output before deceleration begins, based on the map shown in Fig. 4. Determining the power generation torque change rate in accordance with the battery temperature and the engine output makes it possible to obtain a more appropriate power generation torque change rate that takes into account not only the battery temperature but also the engine output.

[0029] FIG. 5 shows the rate of change in torque generated by the generator motor 20 during deceleration. If the rate of change in torque generated by Rt1 has the gentlest slope and the rate of change in torque generated by Rt3 has the steepest slope, the rate of change in torque generated by Rt1 changes between Rt3 and Rt3 depending on at least the battery temperature, and preferably on the battery temperature and engine output. The rate of change in torque generated by Rt1 changes more steeply as the engine output increases. This allows the rate of change in torque generated by Rt1 to be adjusted appropriately for the engine output.

[0030] A control method for a hybrid vehicle according to one embodiment and the operation of a control device for a hybrid vehicle according to one embodiment will be described using the flowchart shown in Fig. 6. In Fig. 6, when the power of the hybrid vehicle is turned on and the control device starts processing, the control device determines in step S1 whether deceleration has started. If deceleration has not started (NO), the control device shifts the processing to step S7.

[0031] If deceleration is started in step S1 (YES), the control device determines in step S2 whether the battery temperature is below the upper limit temperature for battery function assurance. If the battery temperature is below the upper limit temperature (YES), the control device acquires the battery temperature and engine output at the start of deceleration in step S3. In step S4, the control device determines the rate of change of power generation torque according to the battery temperature and engine output. In step S5, the control device controls the power generation torque of the power generation motor 20 using the determined rate of change of power generation torque, and then proceeds to step S7.

[0032] If the battery temperature is not below the upper limit temperature in step S2 (NO), the control device controls the power generation torque of the generator motor 20 at the steepest rate of change in power generation torque in step S6, and then proceeds to step S7. In this way, if the battery temperature is above the upper limit temperature, the rate of change in power generation torque is fixed to the steepest rate of change. This allows power generation by the generator motor 20 to be stopped, so the battery temperature can be gradually lowered to below the upper limit temperature.

[0033] In step S7, the control device determines whether the power of the hybrid vehicle has been turned off. If the power has not been turned off (NO), the control device repeats the processing from step S1 onwards. If the power has been turned off (YES), the control device ends the processing.

[0034] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention. [Explanation of symbols]

[0035] 10 Engine 11 Engine control unit 20 Generator motor 21 Generator motor control unit 30 Battery 31 Battery control unit 40 Drive motor 50 drive wheels 60 Integrated control unit 210 Power generation torque change rate calculation unit

Claims

1. A control device for controlling a hybrid vehicle, The temperature of a battery that charges the electric power generated by the generator motor driven by the engine is acquired. When the temperature of the battery is equal to or higher than a zero input / output limit temperature that limits the input / output of the battery to zero, the rate of change of the power generation torque that reduces the power generation torque generated by the power generation motor over time during deceleration of the hybrid vehicle with the accelerator released is changed more gradually as the temperature of the battery decreases and more abruptly as the temperature of the battery increases. A method for controlling a hybrid vehicle.

2. 2. The method for controlling a hybrid vehicle according to claim 1, wherein the control device determines the rate of change of the power generation torque based on the temperature of the battery and the output of the engine at the time when the hybrid vehicle starts to decelerate.

3. 3. The method for controlling a hybrid vehicle according to claim 2, wherein the control device changes the rate of change of the power generation torque more sharply as the output of the engine at the start of deceleration of the hybrid vehicle increases.

4. 4. The hybrid vehicle control method according to claim 1, wherein the control device stops power generation by the generator motor when the temperature of the battery is equal to or higher than an upper limit temperature that ensures the function of the battery.

5. The engine and a generator motor driven by the engine to generate electricity; a battery that charges the electric power generated by the power generating motor; a drive motor that drives drive wheels using the electric power generated by the generator motor or the electric power stored in the battery; A control device for controlling a hybrid vehicle including: When the temperature of the battery is equal to or higher than a zero input / output limit temperature that limits the input / output of the battery to zero, the rate of change of the power generation torque that reduces the power generation torque generated by the power generation motor over time during deceleration of the hybrid vehicle with the accelerator released is changed more gradually as the temperature of the battery decreases and more abruptly as the temperature of the battery increases. A control device for a hybrid vehicle.

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