Hybrid power drive system

A hybrid drive power system comprising:

• a first gear-shift mechanism assembled with a first input shaft to be applied with the drive power of an engine through a first friction clutch,
• a second gear-shift mechanism assembled with a second input shaft to be applied with the drive power of the engine through a second friction clutch,
• a motor-generator in drive connection with the first input shaft or the second input shaft, and a driven mechanism to be driven by the drive power transmitted from an output shaft of the first gear-shift mechanism or from an output shaft of the second gear-shift mechanism,
• a rotation speed sensor provided to detect a rotation speed of the engine, and
• control means for comparing a deceleration in the rotation speed of the engine detected by the rotation speed sensor with a preset upper limit when a change-speed stage selected at either one of the first and second gear-shift mechanisms is switched over to another change-speed stage of the other one of the first and second gear-shift mechanisms, for activating the motor-generator as an electric motor to cause load torque counteracting against input torque applied to the input shaft of the other one of the first and second gear-shift mechanisms from the engine when the deceleration in the rotation speed of the engine exceeds the upper limit and for releasing engagement of the change-speed stage selected at the other one of the first and second gear-shift mechanisms after the input torque is counteracted by the load torque.