Method and system for starting engine of parallel hybrid electric vehicle

Abstract

The invention discloses a parallel hybrid automobile engine starting method and system. The parallel hybrid automobile engine starting method comprises the steps of determining engine torque expectedvalue and engine rotation speed expected value according to automobile speed, gear and accelerator pedal state, which are obtained in real time under a sliding condition; when the engine torque expected value is larger than or equal to a preset torque threshold, controlling a driving motor to drive a transmission system and tow an engine; when the engine torque expected value is less than a presettorque threshold, obtaining the current SOC value; according to the relation between the SOC value and a preset electric quantity threshold, controlling the driving motor to tow the engine to different rotation speed values; after detecting that the engine is towed to a stable working condition, controlling the engine to ignite; and controlling output torques of the driving motor and the engine to alternate with each other so as to finish the starting of the engine. According to the parallel hybrid automobile engine starting method and system, the requirement of a hybrid automobile on accuracy control of the engine starting in the process from sliding to accelerating is satisfied and model selections of the motor and a battery are comparatively flexible so that lower development cost is realized.

Description

technical field [0001] The invention relates to the field of hybrid electric vehicles, in particular to a method and system for starting an engine of a parallel hybrid electric vehicle. Background technique [0002] Parallel hybrid electric vehicles have received more attention because of their minor changes to the traditional vehicle transmission system and obvious fuel-saving effects. Parallel hybrid power includes a driving motor and a C0 clutch. In order to maximize the vehicle's fuel-saving capability, the engine will be turned off when the vehicle speed is higher than a predetermined speed and is in a coasting state, so as to save fuel consumption; but This brings about a problem. If the driver's driving intention at this time is to want the vehicle to enter the acceleration state, it is difficult to meet the driver's speed requirements only by relying on the drive motor of the hybrid vehicle. Therefore, the parallel hybrid system must be activated at this time. Start...

AI Technical Summary

Problems solved by technology

During this process, on the one hand, the engine switches from the flameout state to the ignition state, and the drive motor must directly drag the engine to a higher speed point (target speed) to start the engine while driving, so that the speed overshoot may be too large , the control is relatively rough; on the other hand, the torque of the drive motor to drive the engine is relatively large, and the remaining power of the battery is a key indicator to meet the output of the drive motor. The control strategy lacks comprehensive consideration of the battery power. Usually, a larger drive motor and a battery with a larger capacity are used to avoid this problem, which leads to an increase in the cost of hybrid vehicles.

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