POWER TRANSMISSION SYSTEM FOR HYBRID VEHICLE

A power transmission system for a hybrid vehicle includes planetary gear mechanisms that couple an internal combustion engine, an electric motor, and a transmission, and has a brake that engages and disengages the internal combustion engine with and from a housing. The planetary gear mechanisms have a first rotary element, a second rotary element, a third rotary element, and a fourth rotary element. Any one of the internal combustion engine, the electric motor, and the transmission is connected to a respective one of the first rotary element, the second rotary element, and the third rotary element. The fourth rotary element is configured as an inertial member for suppressing transmission of a torque fluctuation of the internal combustion engine to the transmission side.