Driving torque control method for electric four-wheel drive automobile

Abstract

The embodiment of the invention discloses a torque control method for an electric four-wheel drive automobile, which comprises the following steps: judging whether a brake pedal is opened or not whendetermining that the driving torque demand of the electric four-wheel drive automobile is a negative value; if not, determining the recovery torque demand value to be a first recovery torque demand value, determining the front wheel end recovery torque coefficient to be a first front wheel end recovery torque coefficient, and determining the rear wheel end recovery torque coefficient to be a firstrear wheel end recovery torque coefficient; determining a front wheel end recovery torque demand value and a rear wheel end recovery torque demand value according to the first recovery torque demandvalue, the first front wheel end recovery torque coefficient and the first rear wheel end recovery torque coefficient, wherein the recovery torque coefficient of the wheel end of the first front wheelis 1, and the recovery torque coefficient of the wheel end of the first rear wheel is 0. Therefore, the effects of optimizing the impact in the torque zero-crossing stage and improving the driving response are achieved.

Description

technical field [0001] The embodiments of the present invention relate to the technical field of automobiles, in particular to a driving torque control method of an electric four-wheel drive automobile. Background technique [0002] For traditional vehicles with internal combustion engines and transmissions, there are torque buffer devices such as torsion springs, hydraulic torque converters or clutches, which can absorb and weaken most of the impact problems caused by sudden torque changes. For pure electric vehicles, there is no torque buffer device on the transmission path of the power system (motor, reduction gear, differential, wheel). Considering the gear structure and drive shaft structure, the driving force and recovery force will be reduced during the transmission process. Affected by the gear gap and the torsional stiffness of the drive shaft, when the torque is switched between the driving torque and the recovery torque during the driving of the electric vehicle, ...

AI Technical Summary

Problems solved by technology

For pure electric vehicles, there is no torque buffer device on the transmission path of the power system (motor, reduction gear, differential, wheel). Considering the gear structure and drive shaft structure, the driving force and recovery force will be reduced during the transmission process. Affected by the gear gap and the torsional stiffness of the drive shaft, when the torque is switched between the driving torque and the recovery torque during the driving of the electric vehicle, the meshing surfaces of the two meshing gears in the drive train are constantly changing due to the rapid change of the torque direction. Switching, accompanied by the continuous change of the torsion direction of the transmission shaft, due to the short response time of the motor torque and no buffering of the torque transmission, the meshing of the gears will cause meshing shocks, which will affect the drivability of the vehicle

The existing torque over 0 strategy, aiming at the existence of meshing impact, limits the torque change rate before and after the motor torque exceeds 0 according to the vehicle speed and actual motor torque. Although the NVH performance of the whole vehicle is improved, it leads to Tipin working condition (with 0% When the accelerator coasting energy recovery or braking energy recovery state is driving, the working condition of stepping on a certain accelerator quickly) the longitudinal acceleration response of the vehicle slows down, and the drivability of the vehicle deteriorates

If the torque change rate before and after the motor torque exceeds 0 is not limited, the motor torque will cause gear meshing impact when the motor torque changes direction, which will affect the NVH performance of the vehicle

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