Patent ID: 7168515

Claim:
A hybrid drive system for an automotive vehicle, comprising: (a) an engine operable by combustion of a fuel to generate a drive force; (b) an electric motor; (c) an output member operatively connected to a drive wheel of the vehicle for driving the vehicle; (d) a planetary gear device having a first rotary element connected to said engine, a second rotary element connected to said electric motor; and a third rotary element; (e) a first clutch through which said second rotary element is connected to said output member; (f) a second clutch through which said third rotary element is connected to said output member; (g) forward-motor-drive control means for engaging said first clutch and releasing said second clutch, to thereby establish a forward motor drive mode in which the automotive vehicle is driven in a forward direction by operation of said electric motor while said engine is at rest; (h) forward-engine-drive control means for releasing said first clutch and engaging said second clutch, to thereby establish an engine-and-motor drive mode in which the automotive vehicle is driven in the forward direction by operation of both of said engine and said electric motor; (i) said first clutch being a frictionally coupling clutch; and (j) first-clutch-releasing stand-by means operable upon switching of a vehicle drive mode from said forward motor drive mode to said engine-and-motor drive mode, said first-clutch-releasing stand-by means reducing an engaging torque of said first clutch to a value not causing slipping of said first clutch, before said first clutch is released.