Variable duration valve lifter improvements

Details Variable duration valve lifter improvements Variable duration valve lifter improvements

1989-08-28

1990-04-03

Myhre, Charles J.

Internal-combustion engines

Poppet valve operating mechanism

Tappet

123 9055, 123 9035, F01L 116, F01L 124

Patent

active

049131060

ABSTRACT:
Improvements are provided to the variable duration lifter, and the valve train of which the lifter is a part, which have the effect of reducing the tapping noise of the valves at low RPM, which is characteristic of effective variable duration lifters. This is achieved by utilizing an effective length of the valve train which produces a reduced volume of the oil reservoir defined between the outer cylinder of the lifter and the internal plunger, such that when the engine operates at low RPM, the internal plunger "bottoms out" before the valve seats. This is coupled with a modified cam having a closing ramp which seats the valve more smoothly and quietly than does the conventional ramp. To further insure the quiet seating of the valve at the appropriate point of cam rotation, the bleed passageway of the lifter plunger is enlarged in cross-section in the preferred embodiment, and to reduce trauma on the underside of the lifter, a groove or flat is ground down the entire length of the external cylinder of the lifter which, by virtue of being in communication with the oil gallery, provides lubrication for the cam-following bottom of the lifter body.

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