Patent ID: 8419575

Claim:
A ball-type tensioner, comprising: a reciprocable plunger for maintaining tension in a traveling timing chain, said plunger having an outer peripheral surface in which a plurality of annular rack teeth is formed; a housing having a plunger-accommodating hole, said plunger protruding from said plunger-accommodating hole and being reciprocably slidable therein in protruding and retracting directions; a plunger-biasing spring biasing said plunger in the protruding direction; an annular ball seat fitting around said plunger and displaceable along the directions of protrusion and retraction of the plunger, said ball seat being located within an annular groove formed in the wall of the plunger-accommodating hole, and having a plurality of ball-guiding grooves in which balls can move radially outward relative to the plunger; a ball seat-biasing spring engaged with a surface of said annular ball seat and biasing the ball seat in the direction of protrusion of said plunger; a set of balls in contact with the outer peripheral surface of the plunger and sequentially engageable with successive rack teeth of the plunger by moving radially outward in said ball-guiding grooves of the annular ball seat; and a sealing plate surrounding, and in fitting relationship with, the plunger, the sealing plate engaging said balls and limiting axial displacement of said balls, the annular ball seat and the ball seat-biasing spring in the direction of protrusion of the plunger within said annular groove; wherein each rack tooth has a forward surface facing in said protruding direction and a rearward surface facing in said retracting direction, the forward surfaces of said rack teeth having a diameter that decreases proceeding the protruding direction, and the rearward surfaces having a diameter that decreases proceeding in the rearward direction, the slope of the rearward surfaces relative to the protruding and retracting directions being greater than the slope of the forward surfaces relative to said protruding and retracting directions; wherein the ball-guiding grooves of the annular ball seat has an inclined bottom surface that faces a rearward face of a rack tooth; and wherein each of said balls simultaneously contacts the inclined bottom surface of a ball-guiding groove, said plunger and said sealing plate.