Patent ID: 8287428

Claim:
A power transmission apparatus disposed at a driving path between an engine for generating driving force resulting from combustion of fuel and driving wheels driven by the driving force of the engine, the power transmission apparatus comprising: a motor that is provided at the driving path, and drives the driving wheels through the driving path by generating driving force resulting from electrical energy, and transforms kinetic energy at the driving path to electrical energy; a normal close type clutch that is provided at the driving path and disposed between the engine and the motor, includes an input communicated with the engine and an output communicated with the driving wheels, and is selectively set in an engaging state in which the input is engaged with the output and a released state in which the input is released from the output, wherein the clutch is normally set in the engaging state by biasing force of a biasing member and is set in the released state when hydraulic pressure is applied; a hydraulic-pressure feeding device configured to adjust the hydraulic pressure and supply the adjusted hydraulic pressure to the clutch; and a control device configured to control the hydraulic-pressure feeding device so that the hydraulic pressure applied to the clutch has a desired level, wherein in a case of changing the clutch from the engaged state to the released state, if a difference between rotation number of the input and that of the output is smaller than a predetermined value, the control device controls the hydraulic-pressure feeding device so that the hydraulic pressure applied to the clutch has a first level to bring the clutch to a fully released state; and, wherein if the difference becomes equal to or larger than the predetermined value, the control device controls the hydraulic-pressure feeding device so that the hydraulic pressure applied to the clutch has a second level lower than the first level to bring and keep the clutch to a state just before the engaged state.