Valve Mechanism for Internal Combustion Engine

A valve mechanism for an internal combustion engine, comprising:

• a first rocker arm (4) linked and connected on a free end side thereof to one of an intake valve and an exhaust valve and supported for rocking motion on a rocker shaft (3a);
• a second rocker arm (5) supported for rocking motion on said rocker shaft (3a) and disposed adjacent said first rocker arm (4) for being rotationally driven by a cam (2L);
• a cylinder (10) formed on one of said first and second rocker arms (4, 5) and a first piston (11) mounted for sliding motion in said cylinder (10);
• a contacting projection (4a) provided in a projecting manner on the other one of said first and second rocker arms (4, 5) for contacting with said first piston (11);
• a return spring (12) for biasing said first piston (11) toward a contacting position at which said first piston (11) contacts with said contacting projection (4a);
• and
• a second piston (14) disposed so to extend in parallel to said first piston (11) at least when said first piston (11) is at a non-contacting position and configured to displace, when hydraulic pressure is supplied thereto, said first piston (11) to a non-contacting position, at which said first piston (11) does not contact with said contacting projection (4a), against the biasing force of said return spring (12).