Valve operating system for internal combustion engines

Abstract

A drive cam follower operatively connected to an engine valve and a free cam follower capable of becoming free relative to the engine valve are adjacently disposed and adapted to impart in mutually different modes of operation in response to said engine valve rotation of a cam shaft. A connection change-over mechanism is provided between the cam followers and is capable of changing-over the interconnection and disconnection thereof, and resilient biasing means is provided between the free cam follower and the engine body for resiliently urging the free cam follower toward the cam shaft. The resilient biasing means comprises an urging piston slidably received in the engine body for abutment against the free cam follower, and a spring arrangement interposed between the urging piston and the engine body to resiliently bias the urging piston in a direction to abut against the free cam follower. The spring arrangement may comprise series-related springs having different spring constant with one of the springs having a non-linear load characteristic. A vent opening and a lubrication arrangement are provided to facilitate operation of the piston. The urging piston is provided, at its end closer to the free cam follower, with an abutment formed with a smaller diameter to abut against the free cam follower. This facilitates assembly of the resilient biasing means to the engine body, and makes it possible to dispose the resilient biasing means in proximity to a pivoting point of the free cam follower.