Oil pump for internal combustion engine and method of operating the same

摘要

An oil pump for an internal combustion engine is provided with an intake port and a discharge port, each formed in a pump housing. The oil pump has a power pump serving as a first main pump and an electric pump serving as a second auxiliary pump, both of which may be contained in a same pump housing. The power pump is rotated by a driving force of a crankshaft, and the electric pump is rotated by the driving force of an electric motor. This makes it possible to reduce the maximum capacity of the power pump serving as the main pump. In a vehicle operating range where the oil discharging pressure generated by the power pump becomes insufficient, the electric pump serving as the auxiliary pump is operated together with the power pump such that appropriate oil discharging pressure or appropriate oil discharging quantity can be achieved. The electric pump may also be allowed to operate for a period of time after shutting off of the engine.