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.

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 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.

An object of the present invention is to provide a chain tensioner which enables operations on an elastic ring member during assembly and maintenance work to be readily performed and which is capable of eliminating protrusion of an operating portion of the elastic ring member in a direction opposite to a mounting surface, with a simple configuration. A ring holding portion 112 provided on an open side of a plunger housing hole 111 includes a pressing projection 113 and a restricting portion 114 which restrict rotation of the elastic ring member 130 and which oppose both outer sides of a pair of operating portions 132 of the elastic ring member 130 in a circumferential direction, and the pressing projection 113 is arranged at a position closer to a mounting surface 115 than the restricting portion 114.

A pressure relief valve (10) in a hydraulic tensioner for an endless loop power transmission member and method of assembly can include a check valve member (18) positioned within a fluid passage (14) defined by a housing (12) for movement toward and away from a valve seat (16) defined by the housing (12), a spring (20) normally biasing the check valve member (18) toward the valve seat (16), and a spring retainer (22) assembled within the fluid passage (14) to a variable depth in response to feedback pressure for automatically adjusting a biasing force of the assembled spring (20) to compensate for tolerances effecting a relief pressure value of an assembled pressure relief valve and allowing control of the relief pressure value to be within a predetermined range with respect to a predetermined target relief pressure value for driving the check valve member (18) away from the valve seat (16).

A hydraulic auto-tensioner for an engine accessory is provided where a sleeve fit-in hole is formed at an upper surface of a bottom portion of a cylinder accommodating a hydraulic oil, a lower end portion of a sleeve is press-fitted in the sleeve fit-in hole, and a lower end portion of a rod is slidably inserted in the sleeve to define a pressure chamber inside the sleeve. A lower end face of the sleeve is in abutment with a divided bottom surface of the sleeve fit-in hole to trap burrs produced when the lower end portion of the sleeve is press-fitted into the sleeve fit-in hole between the divided bottom surface of the sleeve fit-in hole and the lower end face of the sleeve, so that burrs are prevented from mixing into the hydraulic oil.