US Patent 7753818 Controller of drive device for vehicle

A control apparatus for a vehicular drive system including a differential mechanism operable to distribute an output of an engine to a first electric motor and a power transmitting member, and a second electric motor connected to the power transmitting member. The control apparatus, which permits size reduction of the vehicular drive system, or improvements of fuel economy and vehicle drivability, includes a switching clutch or switching brake for switching a the differential mechanism between a continuously-variable shifting state and a step-variable shifting state, to enable the drive system to have both of an advantage of a fuel economy improvement of a transmission the speed ratio of which is electrically variable, and an advantage of high power transmitting efficiency of a gear type power transmitting device. The control apparatus includes an engine-torque-variation restriction control operable in the continuously-variable shifting state of the differential mechanism, to control an electric path torque, for restricting a variation of the torque to be transmitted to the power transmitting member, irrespective of a variation of the engine torque, so that the engine torque variation to be transmitted to drive wheels is restricted to improve the vehicle drivability.