Engine start systems and technique for hybrid electric vehicles

摘要

An engine starting system and technique for transitioning from an electric drive mode to a hybrid drive made in a hybrid electric vehicle is disclosed. In an electric drive mode the torque demand of the hybrid electric vehicle is met by an electromechanical device. The starting technique includes slipping a clutch between the engine and electromechanical device with the vehicle in the electric drive mode to rotate the engine, disengaging the clutch so that the engine is fueled to obtain a speed that approximates a speed of the electromechanical device, and engaging the clutch to couple the engine and the electromechanical device to the drive shaft to meet driver torque demand.

主权项

1. A method, comprising:
operating a hybrid electric vehicle in an electric drive mode wherein a driver torque demand is satisfied by a torque output from an electromechanical device to a drive shaft and the electromechanical device is engaged to a transmission through the drive shaft; increasing the torque output of the electromechanical device by an engine starting torque prior to transitioning from the electric drive mode to the hybrid drive mode while the electromechanical device remains fully engaged to the transmission to meet driver torque demand with the electromechanical device during starting of the internal combustion engine; transitioning from the electric drive mode to a hybrid drive mode by slippingly engaging a friction clutch connecting the electromechanical device to the internal combustion engine to rotate the internal combustion engine while the electromechanical device remains fully engaged with the transmission to satisfy the driver torque demand; disengaging the friction clutch when a speed of the internal combustion engine reaches a first threshold; fueling the internal combustion engine after disengaging the friction clutch to increase the speed of the internal combustion engine to a second threshold; and when the speed of the internal combustion engine reaches the second threshold, operating the hybrid electric vehicle in a hybrid drive mode by engaging the friction clutch to couple a torque output of the internal combustion engine and the torque output of the electromechanical device to the drive shaft.