A tensioner which adjusts the mean tensioner force to keep the chain tension as low as possible without sacrificing chain control, significantly improving drive efficiency as the chain wears and is subject to low dynamic loads.

A position of a reservoir hole of a hollow piston of a hydraulic tensioner is downside of a centerline or center plane of the piston to increase the oil retention within the internal reservoir during engine shutdown, reduce start up noise and decrease air from accumulating within the internal reservoir.

To provide a simple-structured tensioner that generates less knocking noise at the start-up of the engine and that prevents an excessive chain tension, severe friction, noise or vibration during the running of the engine, while also reducing production costs. The tensioner includes a ring control mechanism that controls the position of a resilient ring. The ring control mechanism includes a front-side restricting part having a front-side restricting surface and capable of restricting forward movement of the resilient ring, and a rear-side restriction member having a rear-side restricting surface and capable of restricting rearward movement of the resilient ring. The front-side restricting part is fixed to or formed integrally with the housing. The rear-side restriction member is disposed movable in a front to back direction relative to the housing and the plunger.

A tensioner which adjusts the mean tensioner force to keep the chain tension as low as possible without sacrificing chain control, significantly improving drive efficiency as the chain wears and is subject to low dynamic loads.

A filter assembled in front of oil inlet hole of a pressure relief valve prevents contamination of the pressure relief valve. A pressure relief valve and filter assembly for a tensioner includes a pressure relief valve comprising a hollow pressure relief valve body defining a chamber, the pressure relief valve body having a first end with an aperture, a second end, and a length extending from the first end to the second end and a filter comprising a filter body and mesh connected to the filter body. The mesh is positioned relative to the aperture such that the mesh prevents contaminants from entering the pressure relief valve through the aperture.

A chain tensioner includes an oil supply passage for supplying hydraulic oil into a pressure chamber defined by a cylinder and a plunger, and a check valve provided at the end of the oil supply passage. A leak gap is defined between the sliding surfaces of the cylinder and the plunger. The plunger is biased by a return spring in the direction in which the plunger protrudes out of the cylinder. A plug is press-fitted in a cylindrical inner periphery of a through hole formed in the plunger to extend from a protruding end surface of the plunger to the pressure chamber to define an air vent passage. It is possible to change the hydraulic damper force simply by replacing the plug with another different type of plug to define a different air vent passage.

To provide a simple-structured tensioner that generates less knocking noise at the start-up of the engine and that prevents an excessive chain tension, severe friction, noise or vibration during the running of the engine, while also reducing production costs. The tensioner includes a ring control mechanism that controls the position of a resilient ring. The ring control mechanism includes a front-side restricting part having a front-side restricting surface and capable of restricting forward movement of the resilient ring, and a rear-side restriction member having a rear-side restricting surface and capable of restricting rearward movement of the resilient ring. The front-side restricting part is fixed to or formed integrally with the housing. The rear-side restriction member is disposed movable in a front to back direction relative to the housing and the plunger.

A tensioner which adjusts the mean tensioner force to keep the chain tension as low as possible without sacrificing chain control, significantly improving drive efficiency as the chain wears and is subject to low dynamic loads.

A tensioner which adjusts the mean tensioner force to keep the chain tension as low as possible without sacrificing chain control, significantly improving drive efficiency as the chain wears and is subject to low dynamic loads.

A chain tensioner is provided which is configured such that the air remaining in a pressure chamber can be discharged to the outside through a helical gap defined between a screw and a threaded hole, and through between circumferentially separate radial ends of a spring washer mounted between the screw and a housing. The chain tensioner includes an air discharge groove or grooves formed in the seat surface of the head of the screw such that an annular space defined between the neck of the screw and the inner diameter surface of the spring washer communicates with the outside through the air discharge groove or grooves. Even if foreign objects clog the space between the separate radial ends so as to hinder air from being discharged through between the separate radial ends, the air remaining in the pressure chamber can be discharged to the outside through the air discharge groove or grooves.