Valve operation control system in internal combustion engine.

摘要

A valve operation control system in an internal combustion engine comprises an engine valve (5) openably and closably supported on an engine body (E), at least one valve spring (11,12) for biasing said engine valve in a valve-closing direction, and valve driving means (16) interposed between a valve-operating cam (15) and the engine valve (5) to transmit a force in the valve-opening direction provided by the valve-operating cam (15) to the engine valve. The valve driving means includes a valve-opening resilient member (20) for exhibiting a repulsive force in a direction to open the engine valve, and closed-position retaining means (A1) is interposed between the engine valve (5) and the valve operating cam (15) for retaining the engine valve (5) at its closed position, with a valve-opening force provided by the valve-operating cam (15) being accumulated by the valve-opening resilient member (20). The closed-position retaining means (A1) is arranged to be switchable between a retaining state and a releasing state to control the timing of opening the engine valve (5) depending upon the operational condition of the engine.