Patent ID: 7618339

Claim:
A hydraulic tensioner comprising: a tensioner housing, having a circular, cylindrical plunger-receiving hole symmetrical about a central axis; a hollow plunger slidable, in the direction of said axis, in said plunger-receiving hole, and protruding, in a protruding direction, from the housing, said plunger having a circumferential inner surface, a protruding end, an end wall at its protruding end, and an oil discharge opening in said end wall, the plunger and the housing forming a high pressure oil chamber; a check valve for introducing oil under pressure into the high pressure oil chamber; a plunger-biasing spring urging the plunger in said protruding direction; and a relief valve within said plunger, said relief valve comprising a valve seat having an exterior, said valve seat being press-fit into said hollow plunger, a valve body movable into and out of engagement with said valve seat, a valve body-biasing spring for urging the valve body into engagement with the valve seat, and a hollow spring-receiving plug, also press-fit into said hollow plunger, said plug having an exterior surface, an interior space for receiving the valve body-biasing spring, and a bottom in engagement with an end of the valve body-biasing spring; wherein said relief valve seat includes a plurality of axial passages on its exterior, the axial passages cooperating with the circumferential inner surface of the plunger to provide axial oil passages, and a plurality of radial holes in the relief valve seat, communicating with said axial passages for allowing flow of oil from the relief valve to said axial passages; wherein axial oil passages are formed between the circumferential inner surface of the plunger and the spring-receiving plug when the spring receiving plug is press-fit into the hollow plunger, and plural radial oil grooves are formed in the end wall of the plunger, said radial oil grooves cooperating with said end wall of the plunger to provide radial oil passages, each of said radial oil passages communicating with one of said axial oil passages and with said discharge opening formed in the end wall of the plunger; wherein said spring-receiving plug has an outer surface comprising a plurality of flat surfaces disposed in planes parallel to and spaced from said axis and having opposite side edges meeting the circumferential inner surface of the plunger, and said axial oil passages are formed between the circumferential inner surface of the plunger and said axial flat portions on the outer surface of said plug; and wherein the exterior surface of said spring-receiving plug includes outer portions disposed between said flat surfaces and in press-fit relationship with said circumferential inner surface of the plunger, and another portion extending axially beyond said flat surfaces and said outer portions, said another portion having an outer peripheral surface all of which is spaced radially inward from said circumferential inner surface of the plunger.