Control method for hybrid vehicles, and control system for hybrid vehicles

Abstract

According to the present invention: when inputtable power to a battery 2 is set to decrease as the charging rate of the battery 2 approaches a predetermined upper limit and the charging rate of the battery 2 reaches the vicinity of the upper limit due to regenerative power received from a drive motor 1 and generated power received from a generator 4, and the inputtable power becomes less than the sum of the regenerative power and the generated power, the supply of fuel to an engine 3 stops and power generation of the generator 4 is stopped, the power from the battery 2 is supplied to the generator 4, and the engine 3 is subjected to a power operation, whereby the regenerative power is consumed; when the temperature of a catalyst while a power generation request is stopped exceeds a predetermined temperature for inhibiting degradation of the catalyst, the supply of fuel to the engine 3 is continued whereby the output of the engine 3 is maintained; and, thereafter, when the moving average of a current pertaining to said sum exceeds a predetermined standard value, or when the negative electrode potential of the battery 2 becomes less than a predetermined standard potential, the output of the engine 3 is reduced.

Claims

1. In a control method for a hybrid vehicle in which power is exchanged between the drive motor and the battery, a generator driven by a power generation engine charges the battery in response to power generation requests from the driver, and exhaust gas emitted from the engine is treated by a catalyst, The system is configured such that the available power input to the battery decreases as the battery's charge level approaches a predetermined upper limit. When the power generation request for the drive is stopped, if the temperature of the catalyst is below a predetermined temperature for suppressing the deterioration of the catalyst, the fuel supply to the engine is stopped. If the temperature of the catalyst exceeds the predetermined temperature when the power generation request for the drive is stopped, the power generation request for the catalyst is started. When the power generation request for the drive is stopped, the engine is driven at the fuel-efficient operating point where the engine's output efficiency is maximized in a coordinate space with the engine's rotational speed and torque as axes, and when the power generation request for the catalyst is started, the engine is driven at the fuel-efficient operating point. If the input power is lower than the power obtained by driving the engine at the fuel-efficient operating point, the operating point is moved from the fuel-efficient operating point to a position at a predetermined lower limit rotational speed along an efficiency operating line that includes the fuel-efficient operating point in the coordinate space and is represented as the trajectory of the efficient operating point where the engine's fuel consumption is minimized when the engine is driven at an operating point where the output is lower than the fuel-efficient operating point. A control method for a hybrid vehicle that, if the input power becomes even lower thereafter, reduces the torque while maintaining the rotational speed at the lower limit rotational speed.

2. A control method for a hybrid vehicle according to claim 1, wherein the output of the engine is stopped when the charge level of the battery exceeds the upper limit.

3. The output of the engine is controlled based on the rotational speed command value and the torque command value. A control method for a hybrid vehicle according to claim 1, wherein the engine output is stopped if, during the process of reducing the engine output, the response to the rotational speed command value and the torque command value becomes slower than the delay time of the engine control system for a predetermined period of time or longer.

4. A control method for a hybrid vehicle according to claim 1, wherein the torque becomes zero when the rotational speed is at the lower limit rotational speed and the temperature of the catalyst falls below the predetermined temperature, and the fuel supply to the engine is stopped.

5. The drive motor and A battery that exchanges power with the aforementioned drive motor, A generator that is driven by an engine for power generation and also generates power in response to power generation requests for driving associated with driver operation, thereby charging the battery, A catalyst for processing exhaust gas emitted from the aforementioned engine, The system includes a control unit that controls the battery, the engine, and the generator, In a control system for a hybrid vehicle, the amount of power that can be input to the battery decreases as the battery's charge level approaches a predetermined upper limit, The control unit, When the power generation request for the drive is stopped, if the temperature of the catalyst is below a predetermined temperature for suppressing the deterioration of the catalyst, the fuel supply to the engine is stopped. If the temperature of the catalyst exceeds the predetermined temperature when the power generation request for the drive is stopped, the power generation request for the catalyst is started. When the power generation request for the drive is stopped, the engine is driven at the fuel-efficient operating point where the engine's output efficiency is maximized in a coordinate space with the engine's rotational speed and torque as axes, and when the power generation request for the catalyst is started, the engine is driven at the fuel-efficient operating point. If the input power is lower than the power obtained by driving the engine at the fuel-efficient operating point, the operating point is moved from the fuel-efficient operating point to a position at a predetermined lower limit rotational speed along an efficiency operating line that includes the fuel-efficient operating point in the coordinate space and is represented as the trajectory of the efficient operating point where the engine's fuel consumption is minimized when the engine is driven at an operating point where the output is lower than the fuel-efficient operating point. A control system for a hybrid vehicle that, if the input power becomes even lower thereafter, reduces the torque while maintaining the rotational speed at the lower limit rotational speed.

6. The control system for a hybrid vehicle according to claim 5, wherein the control unit stops supplying fuel to the engine when the rotational speed is at the lower limit rotational speed, the torque becomes zero, and the temperature of the catalyst falls below the predetermined temperature.

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