Hydraulic valve lash adjuster

摘要

A hydraulic lash adjuster mechanism (10) for an internal combustion engine, the adjuster having a body (12) having a bore (14) formed therein with a piston (18) slidingly received within the bore (14). The lash adjuster is in communication with one end of a cam follower (22) that is in communication at its other end with a valve stem. A rotating cam (20) contacts said cam follower (22) to apply force to the piston during a valve lift event. The lash adjuster has a low pressure chamber (28) formed in the piston (18) and a high pressure chamber (36) formed between the bottom (16) of the bore (14) and the bottom of the piston (18). Engine fluid that is passed to the low pressure chamber (28) is in communication with the high pressure chamber (36) through a valve opening (32). A mechanism (38) selectively opens or closes the valve opening (32) in response to pressure differences between the low pressure chamber (28) and the high pressure chamber (36). An actuating means (54) is included for allowing free leak down of engine fluid from the high pressure chamber (36) to the low pressure chamber (28) when the cam follower (22) is on the cam base circle.