Abstract:
Hydraulic engine valve lifter (10) includes a pair of pistons (Pcf, Pvd) defining a pressure chamber (Cp) therebetween and a separate lash adjusting piston (Pla) which defines a lash adjustment chamber (Cla) with one of the pistons in the pair. One-way valve structures (V) permit fluid to flow from the pressure chamber (Cp) into the lash adjustment chamber (Cla) thereby displacing the lash adjusting piston (Pla) to, in turn, adjust valve lash. Motion damping functions during a downstroke of the lifter pistons (Pcf, Pvd, Pla) are also provided by a valve damper chamber (Cd) and fluid passageways (90b, 112) between the pressure and damper chambers (Cp and Cd, respectively). Structure (126 and 90c/120) is provided which opens communication between the pressure and damper chambers (Cp and Cd, respectively) during upstroke of the lifter pistons (Pcf, Pvd, Pla) (thereby precluding motion damping) and then closes communication at a predetermined location during downstroke (thereby providing motion damping).
Abstract:
A control arrangement for, and a method for controlling the closing movement of, a valve operating assembly in a piston engine adapted between a cam device (5) of a camshaft (4) of the engine (1 ) and an inlet valve mechanism (6) arranged to open and close the inlet valve (3) in association with a cylinder of the engine. The control arrangement (7) comprises a body part (8), in which a piston de¬ vice (9) is movably arranged to be in force transmission connection with the camshaft (4) and the valve mechanism (6), the body part (8) and the piston device (9) together defining a first chamber (13), into which hydraulic medium can be selectively fed for providing a delay in the closing of the inlet valve (3). The body part (8) is provided with a first duct (16) for releasing of pressure in the first chamber (13) under control of a gu ide member (10) movably arranged in the body part (8) between the cam device (5) and the piston device (9). The guide member (10) includes a third chamber (18), which is arranged to be in communication with the first duct (16) and a control piston (20) located in said third chamber (18) and movably arranged with regard to the guide member (10) for controlling pressure medium flow through said third chamber (18).