Patent ID: 7918754

Claim:
A hydraulic tensioner comprising: a housing having a plunger-accommodating hole; a plunger slidable in the plunger-accommodating hole and protruding therefrom in a protruding direction from a position of minimum protrusion to a position of maximum protrusion, for applying tension to an endless, flexible, traveling, timing transmission chain, said plunger having a hollow bore extending from a rear end of the plunger to an internal location adjacent an opposite end of the plunger, and forming an internal oil storage space within the plunger; a plunger-biasing spring accommodated in a high pressure oil chamber formed between said plunger-accommodating hole and a rear end of said plunger, said spring biasing the plunger in said protruding direction; a check valve unit, press-fit in the rear end of said plunger and closing said internal oil storage space, the check valve unit being arranged to allow flow of oil from said internal oil storage space to said high pressure oil chamber while blocking reverse flow of oil from the high pressure oil chamber to the oil storage space; and an oil supply hole connecting the internal oil storage chamber to the exterior of the plunger, for supplying oil to said internal oil storage chamber; in which the housing has an outer surface, an oil introduction recess formed in said outer surface and having a bottom, and an oil supply bore extending from said bottom of the oil introduction recess to the interior of the plunger-accommodating hole and providing a path for flow of oil from the exterior of the housing to the interior of the plunger-accommodating hole; in which the plunger has an outer peripheral surface and a recess formed in said outer peripheral surface; in which said oil supply hole in the plunger has an opening within said recess; in which the recess formed in the outer peripheral surface of the plunger, extends in the direction of protrusion of the plunger, at least from a location at which it is in register with the oil supply bore when the plunger is in said position of minimum protrusion to a location at which it is also in register with the oil supply bore when the plunger is in said position of maximum protrusion, whereby oil is allowed to flow from the oil supply bore to the oil supply hole throughout the stroke of the plunger; in which the length of the recess formed in the outer peripheral surface of the plunger, in the direction of protrusion of the plunger, is equal to the maximum stroke of said plunger; and in which the oil supply bore extends from said bottom of the oil-introduction recess to the interior of the plunger-accommodating hole diagonally both downward and in the protruding direction of the plunger.