Hydraulic lifter

Claim 1

A hydraulic clearance adjuster for a valve gear of an internal combustion engine, comprising: a casing having a bore formed therein with a blind bottom end and a fluid passage for receiving hydraulic fluid; plunger means slidably received in said bore of said casing, said plunger means comprising: a hollow upper plunger member defining a first interior cavity therein and having a top end projecting from said casing, an open bottom end, a fluid inlet hole communicating said fluid passage of said casing with the interior cavity of said upper plunger member and at least one air vent hole in said upper plunger member in fluid communication with said first interior cavity which at least one air vent hole is located above said fluid inlet hole and which opens into a clearance space formed between said casing and said upper plunger member, and a hollow lower plunger member defining a second interior cavity therein and having an open top end abutting against the open bottom end of said upper plunger member thereby defining a reservoir chamber formed by said first and second interior cavities of said upper and lower plunger members for receiving hydraulic fluid introduced through said fluid passage of said casing and said fluid inlet hole of said upper plunger member, and a bottom end defining a pressure chamber formed between the blind bottom end of said bore of said casing and the bottom end of said lower plunger member and being formed with a feed hole communicating said reservoir chamber with said pressure chamber; a check valve provided in said feed hole for permitting fluid flow from said reservoir chamber to said pressure chamber and preventing return flow; and means for biasing said plunger means outwardly of said cavity.