Expandable hydraulic tappet with a variable exit valve

摘要

An expandable hydraulic tappet with a variable exit valve is supplied for use in an internal combustion engine to selectively vary timing by altering the effective profile of a camshaft. The tappet expands to extend the drive train between the camshaft and a camshaft operated mechanism by enlarging and filling an internal hydraulic chamber with a noncompressible hydraulic fluid via an inlet port and inlet valve. The fluid is retained in the tappet chamber until a predetermined pressure is attained, when an exit valve opens to exit the pressurized fluid from the chamber at a predetermined rate. The exit valve includes a bore having a predetermined configuration to provide one or more exit flow rates and also dampen valve operation. An exit valve control means responds to the pressure within the hydraulic chamber to open and close the exit valve and vary the flow rates as desired.