mounted on bolts B1 and B2, and a movable chain guide G1, pivoted on a bolt B, and pressed against the chain by the plunger of a tensioner 500 in order to maintain tension in the chain.
An example of a known chain tensioner is described in United States Patent Application publication No. 2002/0052259, published May 2, 2002. As shown in FIG. 7, the known chain tensioner 500 comprises a tensioner housing 510 having a cylindrical plunger-accommodating hole 511 in which a plunger slides. The plunger has a cylindrical exterior surface through part of its length, which fits closely the cylindrical interior surface of the plunger-accommodating hole. The plunger protrudes through an opening at one end of the plunger-accommodating hole. A coil spring 540 extends into a hole 521in the plunger 520, and is compressed between the bottom of the plunger-accommodating hole 511 and the end of hole 521 in the plunger. The coil spring serves as a biasing means, continuously urging the plunger 520 in its protruding direction.
Oil is supplied under pressure to the plunger-accommodating hole 511 through an oil inflow channel 512 provided in the housing, and fills a high pressure oil chamber 513 formed by the plunger-accommodating hole 511 and the plunger 520. As illustrated in FIG. 5, slow leakage of oil from the high pressure oil chamber 513 through a small gap between the exterior of the cylindrical part of the plunger and the cylindrical internal wall of the plunger-accommodating hole 511 causes damping of the reciprocating movement of the plunger 520.