A method for controlling engine torque

摘要

A system and method of controlling engine torque in a motor vehicle having an internal combustion engine and multi-ratio transmission when launched from a neutral idle rest condition is disclosed.

At neutral idle, the transmission is controlled such that the input and output members 100 and 32,72 are decoupled. During vehicle launch engine torque is controlled based upon a comparison of an engine brake torque limit with a corresponding engine torque amount that is requested by the vehicle operator. Two methods are used to determine the engine brake torque limit, the first does this as a function of time and the second method determines the engine brake torque limit by estimating the torque capacity of the forward clutch 106 at any given time using a mathematical model and a calibrated offset of turbine torque. As a result, the actual engine torque output is optimized at all times to provide approximately the maximum amount of requested torque without exceeding the capacity of the transmission's forward clutch 106.