Torque distribution method for engine and motor of energy-efficient hybrid electric vehicle

摘要

A torque distribution method for an engine and a motor of an energy-efficient hybrid electric vehicle comprises the following steps: providing an offline specific fuel consumption map of the engine in all operating states; enabling the engine and motor to respond to the required torque T during travelling together, the motor and the engine working in cooperation at the same rotational speed so as to achieve the optimal working efficiency; acquiring a current state of charge (SOC) of the vehicle battery, and distributing the engine torque T and the motor torque T according to the following situation: if the SOC is greater than a first preset value, entering a first distribution mode; if the SOC is less than a second preset value, enter a second distribution mode; and otherwise, maintaining the current working state. The method can fully utilize the performance advantage of the engine and that of the motor, so that the system works at high efficiency all the time, thereby decreasing the energy consumption of the vehicle, greatly reducing harmful emission, and facilitating energy conservation and environmental protection.

主权项

1. A method for distributing torque between an engine and an electric motor for an energy efficiency improvement of hybrid electric vehicles, comprising:
A. providing an offline Brake Specific Fuel Consumption (BSFC) map of the engine in all operating states, wherein the offline BSFC map illustrates contours of BSFC values of the engine with a horizontal axis thereof representing rotational speed of the engine and a vertical axis thereof representing torque of the engine, and the all operating states include operating states in which the rotational speed of the engine ranges from 0 to nEng, and for each rotational speed the torque of the engine ranges from 0 to TEng_max, where nEng represents a maximum rotational speed the engine can reach, and TEng_max represents a torque of external characteristic for each corresponding rotational speed, where the torque of external characteristic TEng_max is a net torque obtained by subtracting a frictional torque from an indicated torque of the engine; B. enabling the engine and the electric motor to collaboratively respond to a demanding torque TD during traveling, wherein the engine and the electric motor work in cooperation at a same rotational speed so as to achieve an improved working efficiency; and C. acquiring a current State Of Charge (SOC) of a power battery mounted on the vehicles, and distributing a torque generated by the engine TEng_pre and a torque generated by the electric motor TMac_pre as follows:
c1. if the SOC is greater than a first preset value, entering a first distribution mode, which means: if TDTMac_maxCAN, setting TMac_pre=TMac_maxCAN and TEng_pre=−TMac_maxCAN, where TMac_maxCAN is a maximum torque constraint value of the electric motor acquired in real time via an in-vehicle network; if the SOC is not greater than the first preset value, maintaining a current working state; orc2. if the SOC is less than a second preset value, entering a second distribution mode, which means: setting TEng_pre=TBSFC and TMac_pre=TD−TBSFC, where TBSFC represents a torque of the engine corresponding to a lowest specific fuel consumption value in a current rotational speed of the engine, and TBSFC is acquired from the offline BSFC map; and if the SOC is not less than a second preset value, maintaining the current working state.