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.

Systems are provided for a belt tensioner. In one example, the belt tensioner comprises a fluid chamber divided into a first portion and a second portion via a dividing wall. An eccentric housing, which defines the fluid chamber, rotates relative to the dividing wall based on a spring force and a belt force.

To provide a tensioner unit, a rocking lever, and a tensioner, which, prevent breakage of the tensioner in use for a prolonged period of time. A protruding part is provided to a rocking lever near an abutment surface for abutment with a plunger to make contact with a tensioner body. h and H satisfy the relationship of h<H, where h denotes a protruding amount of a lead part of the plunger, where the lead part means a part protruding from the plunger bore, from a tip end surface on an opened side of the tensioner body in a state where the plunger sits on a bottom of the plunger bore, and H denotes an interval between the abutment surface of the rocking lever and the tip end surface of the tensioner body when the protruding part is brought into contact with the tensioner body.

A hydraulic tensioner (10) and method of assembly can include a housing (12) having an aperture and a piston (16) received within the aperture for movement between an extended position and a retracted position. A tensioner spring (36) positioned within the aperture for bias the piston (16) toward the extended position. The piston (16) and the aperture of the housing (12) defining an expandable fluid chamber (18). The hydraulic tensioner (10) can include a cantilever spring (20) having a first end (22) attachable to the housing (12) and a second end (24) releasably engageable with the piston (16) for retaining the piston (16) in the retracted position against urging of the tensioner spring (36) during storage, shipment, installation, and service. The second end (24) can be disengageable from the piston (16) allowing movement of the piston (16) outwardly toward the extended position during operation in a working environment.

A hydraulic tensioner (10) and method of manufacture can include a housing (12), a piston (16) moveable from a retracted position toward an extended position with respect to the housing (12) in response to fluid pressure, and a tensioner spring (36) biasing the piston (16) toward the extended position. The hydraulic tensioner (10) can include a modular sleeve (14) supported by the housing (12) and defining an aperture (15) for slidably receiving the piston (16) and defining an expandable fluid chamber (18). The housing (12) can provide a fluid passage (39) for fluid communication between the expandable fluid chamber (18) and a source of pressurized fluid. The housing (12) can have a seat (25) in fluid communication with the aperture (15). An end (38) of the modular sleeve (14) can be seated with respect to a seat (25) of the housing (12) to seal the fluid passage (39).

A hydraulic tensioning device for a chain device, having a housing and having a clamping piston guided displaceably in a housing bore of the housing, the clamping piston having a piston cavity with a hardened inner circumferential surface, and also having a pressure relief valve unit arranged in the piston cavity. The pressure relief valve unit (12) is a preassemblable unit and includes a spring (18), a closing body (17) and a valve seat (16) and also a receptacle (15, 26) at least partially enclosing the valve seat (16), wherein the valve seat (16) is made of a metal material, has an at least partially hardened surface and wherein the receptacle (15, 26) forms a press-fit with the inner circumferential surface of the clamping piston (3).

A variable force tensioning assembly creates and maintains a tension force on an endless loop used to transmit power. The variable force tensioning assembly includes a body having a cylinder defining a cylinder inner diameter. An outer piston is disposed substantially within the cylinder and slidable therewithin. The outer piston includes an outer piston tube and a chamber divider extending through the outer piston tube. The outer piston and the body define a low rate portion. An inner piston is disposed at least partially within the outer piston tube and is slidable therewithin. The inner piston defines a high rate portion and acts with the outer piston against the body to create a variable force to push against the endless loop to maintain a constant tension in the endless loop.

A product for applying tension is disclosed. The product may include a block with a first bore opening into to the block. A body may be provided having a second bore substantially larger in diameter than the first bore. The body may be positioned against the block so that the first bore is open to the second bore. The body may have a passage for providing fluid to a pressure chamber from the second bore. The passage may be arranged to open to the second bore and form a tangent to the second bore. Fluid may flow from the first bore to the pressure chamber through the second bore and the passage substantially unimpeded. Fluid flow is impeded from the passage to the first bore as a result of the configuration of the first bore, second bore and passage.

A belt tensioner for an accessory drive of an internal combustion engine having a lever arm rotatably assembled to a hydraulic strut assembly. The hydraulic strut assembly including a fixing eye for rotatably mounting to a mounting boss of an engine, the fixing eye having a cupped portion at a first end to seat onto the mounting boss and a travel limiter at a second end extending along an axis of the hydraulic strut to limit travel of the lever arm toward the fixing eye.