Patent ID: 7165638

Claim:
A hybrid drive system for an automotive vehicle comprising: (a) a vehicle drive power source including an engine operable by combustion of a fuel to generate a drive force, and an electric motor; (b) a transmission; (c) a clutch of a frictional coupling type disposed between said engine and said transmission, said clutch being engaged to switch a vehicle drive mode from a motor drive mode in which the automotive vehicle is driven by operation of said electric motor only, to an engine drive mode in which the automotive vehicle is driven by operation of said engine; (d) clutch-slip control means for effecting a slipping engagement of said clutch upon switching of the vehicle drive mode from said motor drive to said engine drive mode; and (e) transition-input-torque estimating means for estimating an input torque of said transmission on the basis of an engaging torque of said clutch during said slipping engagement of said clutch while the vehicle drive mode is switched from said motor drive mode to said engine drive mode.