Cam-Driven Hydraulic Lost-Motion Mechanisms for Overhead Cam and Overhead Valve Valvetrains

摘要

A valve operating system includes a cam and a roller follower. An input piston is spring-biased to follow motion of the roller follower. A hydraulic chamber filled with fluid selectively transfers motion from the input piston to an output piston operatively engaged with a poppet valve. A variable-bleed valve is in fluid communication with the hydraulic chamber and an outlet channel and configured to selectively vary a bleed rate between the hydraulic chamber and outlet channel. Displacement of the input piston into the hydraulic chamber causes movement of the output piston, depending on the bleed rate. A pushrod may transfer motion from the roller follower to the input piston. A hydraulic damping shoulder may restrict the closing velocity of the output piston. The system may be further characterized by an absence of a rocker arm. An auxiliary piston may replace the variable-bleed orifice in the lost-motion hydraulic linkage.