Abstract: The synthetic resin guide in accordance with the invention comprises an elongated synthetic resin shoe having a front surface for sliding contact with the transmission medium and a back surface opposite from the front surface and a plurality of engaging members disposed in longitudinally spaced relationship to one another. The guide also comprises an elongated synthetic resin base in contact with the back surface of the shoe and supporting the shoe, the base having a plurality of longitudinally spaced engaged portions each of which engages with one of the engaging members. One engaging member is fixed to the engaged portion with which it is engaged. The other engaging members are longitudinally movable relative to the engaged portions with which they are engaged. Thus, the guide allows longitudinal thermal expansion and contraction of the shoe relative to the base.

Abstract: In a ring-type tensioner, an expansible elastic ring disposed in a groove formed in the wall of a plunger-accommodating hole cooperates with teeth formed on the plunger to restrict axial movement of the plunger. The ring and the groove in the wall of the plunger-accommodating hole have flat radial surfaces for mutual engagement. However the ring also has oblique plunger-tooth engaging surfaces. The ring has manipulable end parts that can be locked in fixed relation to each other by a tool to secure the plunger against axial movement. The tool can also be inserted into a gap between the manipulable end parts to expand the ring and thereby release the plunger.

Abstract: In a chain tensioner, an expansible ring is disposed in an internal groove formed in the inner wall of a plunger-accommodating hole near an open end thereof. The ring cooperates with grooves formed on the plunger to exert a ratchet action. The relationship between the angles of the surfaces of the internal groove and the grooves on the plunger allows the plunger to protrude, restricts retraction of the plunger on start-up of a chain transmission, but allows retraction when chain tension becomes excessive. In one embodiment, in which the ring is a C-ring, the tensioner housing can be formed with external threads for mounting in a threaded hole on a timing chain cover or other engine part. In other embodiments, the ring can have externally protruding levers for manipulation of the ring.

Abstract: A ratchet mechanism of the ratchet tensioner comprises a toothed ratchet element slidable in a housing and movable in a sliding direction, a plunger movable in an advance/setback direction and having rack teeth engageable by the teeth of the ratchet element, and a ratchet-biasing spring for biasing the ratchet element so that its teeth engage the rack teeth. The rack teeth have stop surfaces facing in the setback direction and sliding surfaces facing the advancing direction. The sliding surfaces are curved surfaces bulging in the advancing direction and in the direction of disengagement of the ratchet element from the rack teeth, the bulge being in an area extending from an entry starting location to an entry ending location.

Abstract: A ratchet-type tensioner capable of restricting setback of a plunger includes a ratchet mechanism that allows setback of the plunger by sliding a ratchet element in a disengaging direction to disengage ratchet teeth from rack teeth when a reaction force acts on the plunger as a result of excessive chain tension. The ratchet element is slidable in a ratchet-receiving hole, and an inclination suppressing structure that prevents the ratchet element from becoming skewed in the ratchet receiving hole to an extent such that its forward end contacts one side of the hole while its rearward end contacts the opposite sides of the hole.

Abstract: There is provided a ratchet-type tensioner whose spring stopping washer for seating a ratchet biasing spring is rigidly and readily assembled to a ratchet-receiving hole so as not to fall out of the ratchet-receiving hole and which reduces flapping noise and prevents seizure of the plunger by securely and stably operating a ratchet mechanism in operating an engine. The ratchet-type tensioner 100 is arranged so that the spring stopping washer has a C-ring anchored in the rear-end area of the ratchet-receiving hole by fitting in a diameter-reduced state and by enlarging its diameter within an anchoring circumferential groove of the ratchet-receiving hole and a spring stopping piece extended from the C-ring to a ring center area to seat the ratchet biasing spring.

Abstract: In a ratchet tensioner, rack teeth on a plunger are engaged by ratchet teeth on one end of a movable plug that slides in a hole in the tensioner housing along a direction orthogonal of the direction of movement of the plunger. The movable plug is prevented from rotating in the hole in which it slides so that the ratchet teeth engage the rack teeth on the plunger smoothly and reliably.

Abstract: A sprocket for a chain drive using a roller or bushing chain has a plurality of different pitch angles, including both pitch angles larger than the standard pitch angle, and pitch angles smaller than the standard pitch angle. The number of pitch angles in the sprocket larger than the standard pitch angle is greater than the number of pitch angles in the sprocket smaller than the standard pitch angle. The sprocket teeth are integrally molded with the sprocket by sintering.

Abstract: In a sprocket comprising a sprocket hub, sprocket teeth and a cushion plate for contacting link plates of a transmission chain, the cushion plate is formed with concave portions at angular positions corresponding to the angular positions of the tips of the sprocket teeth, thereby avoiding contact, or reducing contact pressure, between the cushion plate and the middle parts of link plates of the chain.

Abstract: In a tensioner having a ratchet mechanism composed of annular teeth on a plunger and an expansible resilient ring disposed in a groove formed in the inner peripheral surface of a plunger-accommodating hole in a tensioner housing, the rear surfaces of the annular teeth have a steep slope, and the front surfaces of the annular teeth have a gradual slope with a convex curvature such that the rate of change of the slope decreases proceeding in the direction of retraction of the plunger.

Abstract: A tensioner for a chain or similar power transmission medium comprises a spring-biased plunger having annular rack teeth with gradually sloping forward surfaces and steeper rearward surfaces. The teeth are engaged by radially movable balls received in inclined grooves in an axially movable annular ball seat disposed in an annular groove formed in the wall of a plunger-accommodating hole in a tensioner housing. The bottoms of the inclined grooves face a steep rearward surface of a rack tooth, and the annular ball seat is axially movable in the annular groove and biased in the plunger protruding direction by a spring that exerts a biasing force greater than the biasing force exerted on the plunger. The balls and the movable annular ball seat block retraction of the plunger on engine start-up, but permit retraction when excessive force is imparted to the plunger while the plunger is in a protruding condition.

Abstract: In a hydraulic tensioner, at least a part of a bar is located within a coil spring that biases a plunger in the protruding direction. The bar reduces the volume of the high pressure oil chamber of the tensioner.

Abstract: In a hydraulic tensioner having a coiled plunger-biasing spring, the volume of the high pressure oil chamber is reduced by incorporating a bar inside the spring. One of both ends of the spring are formed to block passage of the bar, so that the bar and spring can be installed as a pre-assembled unit, and dropping of the bar out of the spring can be avoided.

Abstract: In a ratchet-type tensioner having a toothed ratchet piston biased toward a rack of teeth formed on a protruding plunger in a direction transverse to the direction of plunger movement, the rack teeth and the ratchet teeth are mutually engageable and inclined at angles such that the biasing force urging the teeth of the ratchet piston into engagement with the rack teeth is sufficient to block retraction of the plunger during engine start-up but can be overcome when chain tension becomes excessive during engine operation following engine start-up.

Abstract: In a chain guide mechanism, fixed and movable guides are attached to a guide bridge by cooperation of bosses on the guides with boss-receiving holes formed in spaced-apart elements of arms of the bridge. A fixed guide is held against rotation by cooperation of a projection on its mounting boss with a notch in a boss-receiving hole in a guide bridge arm element. A base, extending from an intermediate location at which the arms come together has a pressing structure that engages bosses on a driving sprocket, and a groove for receiving teeth of the driving sprocket.

Abstract: In a chain tensioner, an expansible ring is disposed in an internal groove formed in the inner wall of a plunger-accommodating hole near an open end thereof. The ring cooperates with grooves formed on the plunger to exert a ratchet action. The relationship between the angles of the surfaces of the internal groove and the grooves on the plunger allows the plunger to protrude, restricts retraction of the plunger on start-up of a chain transmission, but allows retraction when chain tension becomes excessive. In one embodiment, in which the ring is a C-ring, the tensioner housing can be formed with external threads for mounting in a threaded hole on a timing chain cover or other engine part. In other embodiments, the ring can have externally protruding levers for manipulation of the ring.

Abstract: In a ratchet tensioner, a linearly moving ratchet for engagement with rack teeth on a plunger is operated a piston that is spring-biased in a direction to engage the ratchet teeth with the rack, and movable by oil pressure in a direction to disengage the ratchet teeth from the rack. The piston is located within a hole in the housing and, with that hole, forms a second high pressure oil chamber that can receive oil through an oil supply path independent of the oil supply path that carries oil to a first high pressure oil chamber formed by the plunger and the tensioner housing.

Abstract: In a ratchet-type tensioner, a rocking ratchet pawl is released from a rack of teeth on a tensioner plunger following engine start-up by a hydraulically operated pin slidable in a pin hole and caused to protrude therefrom by oil under pressure received directly from an external oil supply, or alternatively from the tensioner's high pressure oil chamber through a passage in the tensioner housing. Optionally, an orifice can be provided within the pin hole to control flow of oil when the supply is excessive and to avoid leakage when the supply is insufficient.

Abstract: A sprocket for a chain drive using a roller or bushing chain has a plurality of different pitch angles, including both pitch angles larger than the standard pitch angle, and pitch angles smaller than the standard pitch angle. The number of pitch angles in the sprocket larger than the standard pitch angle is greater than the number of pitch angles in the sprocket smaller than the standard pitch angle. The sprocket teeth are integrally molded with the sprocket by sintering.

Abstract: The hollow plunger of a hydraulic tensioner, slidably receives a sleeve that divides the high pressure oil chamber into two parts. The first part is formed by the plunger and a plunger-accommodating hole of the tensioner housing. The second part is formed by the plunger and the sleeve. Two springs, one being in the first part, and the other being in the second part, urge the plunger in the protruding direction. When the second part is filled with oil during ordinary engine operation, a negative pressure in the second part exerts a force opposing protruding movement of the plunger. Therefore, the springs can be made strong enough to prevent excessive chain vibration and noise during engine start-up when the parts of the high pressure oil chamber are not filled with oil, without causing the tensioner to exert excessive force on the chain during ordinary engine operation.