When a hybrid vehicle picks up speed, the torque of a first motor is gradually reduced based on a vehicle speed before the vehicle speed reaches a vehicle speed threshold. When the vehicle speed is equal to or greater than the vehicle speed threshold, the torque of the first motor is reduced to zero....http://www.google.com.au/patents/US6932738?utm_source=gb-gplus-sharePatent US6932738 - Drive control apparatus for hybrid vehicle
