To provide a tensioner capable of preventing slipping between a rack portion and ratchet pawls and securing a large backlash with a simple structure. The tensioner includes a ratchet rotatably mounted on a housing and having a front pawl and a rear pawl spaced apart in a front and rear direction on a side face positioned opposite the rack portion. The ratchet includes an additional pawl formed between the front pawl and the rear pawl in the front and rear direction on the side face positioned opposite the rack portion.

A stack of disk springs are placed between a second piston of a dual hydraulic variable force tensioner system and a hydraulic tensioner arm to allow much higher spring rates if desired. The springs may be stacked in multiple configurations to provide different spring rates. Package space can be reduced depending on the number of springs and orientations of said springs within the tensioner arm.

To provide a tensioner capable of preventing slipping between a rack portion and ratchet pawls and securing a large backlash with a simple structure. The tensioner includes a ratchet rotatably mounted on a housing and having a front pawl and a rear pawl spaced apart in a front and rear direction on a side face positioned opposite the rack portion. The ratchet includes an additional pawl formed between the front pawl and the rear pawl in the front and rear direction on the side face positioned opposite the rack portion.

A tensioning device, more particularly a hydraulically actuated chain tensioner, for a chain drive of an internal combustion engine, having a tensioner housing, a tensioning piston which is displaceably guided in a piston bore of the tensioner housing and has a piston skirt, a transport securing means for fastening the tensioning piston in the tensioner housing, a adjustment apparatus for incrementally adjusting and limiting the working range of the tensioning piston, and a final position securing means for the captive arrangement of the tensioning piston in the piston bore. The transport securing means, the adjustment apparatus and the final position securing means together have a single securing ring for fastening the tensioning piston in the tensioner housing, the incremental adjustment and limiting of the working range of the tensioning piston and the captive arrangement of the tensioning piston. A chain drive, more particularly a control chain drive, of an internal combustion engine, having such a tensioning device is also provided.

A variable force tensioner (VFT) system that includes a primary piston split into two chambers disposed within a primary bore. The two chambers including a first low pressure chamber having a primary reservoir therein that feeds fluid through a check valve into a second high pressure chamber to control a biasing force on the primary piston. A piston bore clearance path can extend along a groove in the primary bore to feed oil back to the primary reservoir from the high pressure chamber.

A tensioner includes a movable section, a fixed section, a flat spiral spring, and a back-up spring. The movable section receives load from an entrained transmission body through a tension member. The fixed section supports the movable section so as to be capable of displacing. The flat spiral spring biases the movable section so as to resist the tension member. The flat spiral spring unwinds in a state in which there is a small inter-plate friction force in cases in which there is a large biasing force applied to the tension member to counter load acting from the tension member. The flat spiral spring winds-up in a state in which there is a large inter-plate friction force in cases in which there is a small biasing force applied to the tension member to counter load acting from the tension member. The back-up spring limits wind-up of the flat spiral spring.

To provide a tensioner and a relief valve unit that enable a reduction in the number of parts to be processed and the number of assembling steps, reduce the amount of oil flowing out to the outside, prevent damage to the check valve, and improve the oil recovery rate. The relief valve unit that releases oil when pressure inside an oil pressure chamber reaches or exceeds a predetermined high pressure includes a check valve unit that stops reverse flow of oil flowing into the oil pressure chamber as a valve element, the check valve unit being slidably inserted in the relief valve unit. The relief valve unit includes a unit pressing spring that presses the check valve unit toward a relief valve seat. The check valve unit includes an oil passage for allowing oil to flow between an inner side and an outer side of the check valve unit.

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 stack of disk springs are placed between a second piston of a dual hydraulic variable force tensioner system and a hydraulic tensioner arm to allow much higher spring rates if desired. The springs may be stacked in multiple configurations to provide different spring rates. Package space can be reduced depending on the number of springs and orientations of said springs within the tensioner arm.

A hydraulic tensioner can include a valve retainer and valve member within a housing including a cavity, passageway, and boss. The passageway provides fluid communication with the cavity through an end face of the cavity. The boss is disposed about the passageway and extends axially outward from the end face. The valve retainer can include a first plate. The first plate can be fixedly coupled to the housing. The valve member can include a second plate that can be axially between the first plate and the boss. The second plate can extend in a radial direction beyond an outermost edge of the boss. The second plate can move axially between a closed position wherein the second plate is in sealing contact with the boss and an open position wherein the second plate is axially spaced apart from the boss. The valve spring biases the second plate toward the closed position.