Patent ID: 6383103
Filing Date: 2002-05-07
Classification: F01L,F15B,F16F,F16H

Abstract:
A hydraulic tensioner comprising:a tensioner housing having a plunger accommodation bore formed therein, said bore having an open top and a bottom wall; a single plunger slidably fitted into said plunger accommodation bore of said tensioner housing and urged by a spring such that a tip portion of said plunger is projected to the exterior of said plunger accommodation bore through said open top, said plunger having a hollow portion opening to an end face of said plunger which faces said bottom wall of said plunger accommodation bore, there being a high-pressure oil chamber defined between said housing and said hollow portion of said plunger and filled with oil; a check valve mechanism disposed at the bottom of said plunger accommodation bore equipped with a check ball for permitting the passage therethrough of the oil in only one direction from the exterior of said housing into said high-pressure oil chamber; and a relief mechanism arranged in fluid communication with said high-pressure oil chamber, wherein said relief valve mechanism includes a separate generally cup-shaped orifice member having a peripheral helical groove having one end in fluid communication with said high-pressure oil chamber, said groove being formed in an outer circumferential surface of said orifice member providing a peripheral orifice having said one end open to said high-pressure oil chamber and the other end open for allowing the oil and air to leak out from said high-pressure oil chamber, and a relief valve integrally assembled with said orifice member and solely operable to release the oil from said high-pressure oil chamber when the pressure in said high-pressure oil chamber exceeds a predetermined limit, and wherein said relief valve includes a cup-shaped sleeve slidably mounted in the interior of said cup-shaped orifice member, a sleeve spring urging said sleeve in a direction toward said high-pressure oil chamber, and a discharge port formed in a sidewall of said orifice member, said discharge port being normally closed by said sleeve and adapted to be opened when said sleeve is displaced in a direction away from said high-pressure oil chamber against the force of said sleeve spring.