Method of operating a transmission

Abstract

A method of controlling a launch clutch during an engine restart event commands a positive torque capacity before the engine reaches idle speed. Early application of the launch clutch reduces the time delay between brake pedal release and vehicle acceleration. To avoid excessive drag on the engine during the restart event, the torque capacity is adjusted using closed loop control. A controller calculates a maximum rate of change of torque capacity based on measured engine speed and an engine acceleration and does not increase the commanded torque capacity faster than the calculated rate. In some circumstances the maximum rate of change may be negative, resulting in a reduction in commanded torque capacity.

Description

TECHNICAL FIELD[0001]This disclosure relates to the field of automatic transmissions for motor vehicles. More particularly, this disclosure relates to the control of controlling a launch clutch during an engine restart.BACKGROUND[0002]Internal combustion engines are operable over a limited range of engine speeds. Engines typically must be rotating at least a few hundred revolutions per minute (rpm) to produce power. Since an engine cannot produce power at very low speeds, the engine has traditionally been operated at a predetermined idle speed even while the vehicle is stationary and no power is required. To reduce fuel consumption, it is desirable not to operate the internal combustion engine while the vehicle is stationary such as while waiting at a traffic light. If the engine is stopped when the vehicle is stationary, then the engine must be restarted when the driver indicates a desire to move, generally by releasing the brake pedal and pressing the accelerator pedal. The time r...

AI Technical Summary

Benefits of technology

The patent describes a method for starting a vehicle quickly using a dual clutch transmission. It involves measuring the speed of the engine when it is first starting, and adjusting the capacity of a launch clutch based on this speed to prevent excessive delay in acceleration. The adjustment can also consider the engine's acceleration during acceleration. This method helps to make the vehicle start more quickly and smoothly.

Problems solved by technology

Commanding the launch clutch to transmit torque prior to the engine reaching idle speed results in earlier vehicle acceleration.

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