Valve operating system for internal combustion engine

Abstract

In a valve operating system for an internal combustion engine that includes a valve operation mode changing mechanism capable of changing at least one of either the lift amount of opening of an engine valve openably and closably carried in an engine body or the opening or closing timing in accordance with a variation in hydraulic pressure supplied to the changing mechanism. A selector valve is provided and includes a valve element slidably received in a housing attached to the engine body to change the supply of hydraulic pressure to the valve operation mode changing mechanism. The housing of the selector valve is provided with a working oil chamber which receives an oil pressure for driving, toward a position to supply a higher hydraulic pressure to the valve operation mode changing mechanism, a valve element biased toward a position to supply a lower hydraulic pressure to the valve operation mode changing mechanism. The working oil chamber is connected through a leak jet to a drain chamber provided in the engine body. The leak jet permits the hydraulic pressure to be quickly released from the working oil chamber when the valve element of the selector valve is driven to block the communication between the hydraulic pressure supply source and the valve operation mode changing mechanism, thereby leading to a quick changing operation of the valve operation mode changing mechanism.