A pressure regulator is in fluid communication with a supply inlet of a hydraulic tensioner to actively control fluid to the inlet of the hydraulic tensioner. By actively controlling the pressure regulator based on engine conditions and thus the oil pressure being fed to the hydraulic tensioner, the oil pressure to the hydraulic tensioner may be reduced at low engine speeds, increasing the efficiency of the timing system, or allowing full oil pressure at high engine speeds and low engine temperature.

A tensioner moves the flow restriction controlling the tensioner tuning to the nose of the piston through a hole ranging in cross sectional area from 0.01 mm.sup.2 to 1.1 mm.sup.2. It also eliminates a component from the design of the tensioner. The piston hole geometry is one or a plurality of holes.

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 with a simple structure is provided, which is capable of keeping oil pressure in a first high oil-pressure chamber stable and holding a chain favorably. The tensioner includes a plunger, a housing, a check valve, an inner sleeve, and a biasing member. In the housing, a second high oil-pressure chamber and a unit setting part are formed. In the unit setting part, a relief valve unit is set. A gap between an inner circumferential surface of a plunger hole and an outer circumferential surface of the inner sleeve functions as part of an oil flow passage that connects the first high oil-pressure chamber and the second high oil-pressure chamber.

Endless track system tensioning system comprising: Tensioner having a cylinder and a piston within the cylinder forming a variable volume chamber containing liquid. Reservoir containing liquid and gas fluidly connected to the cylinder chamber. Conduit fluidly connected between the chamber and the reservoir allowing liquid to flow therebetween to move a position of the piston. The gas applying hydrostatic pressure to liquid biasing the piston toward an extended position, biasing an idler wheel assembly against an endless track. Valve disposed along the conduit for controlling liquid flow through the conduit, movable between: Open position in which liquid is allowed to flow, rendering piston movable, allowing for relative movement between a frame and an idler wheel assembly. Closed position in which liquid is prevented from flowing rendering piston effectively immovable within the chamber, effectively preventing relative movement between frame and idler wheel assembly.

A track system comprising a dynamic tensioning device located between an idler wheel and the support frame as to apply proper tension in the track. The dynamic tensioning device is adapted to block at its current length upon the occurrence of a determined condition. The dynamic tensioner is adapted to substantially maintain its length when an acceleration and or deceleration of the track system reaches a predetermined value. For instance, such characteristic is relevant in an event of emergency braking. A dynamic tensioner would become contracted and the tension in the endless track would become too low. A low tension could cause the endless track to ratchet.

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 hydraulic traction mechanism tensioner for a traction mechanism drive of a motor vehicle, having a housing, and a valve which has an actuating element and is inserted in a fluid supply channel of the housing, wherein the valve hydraulically connects a first channel section of the fluid supply channel which opens into the pressure chamber to a hydraulic supply in a first position of the actuating element, and disconnects the first channel section from the hydraulic supply in a second position of the actuating element, wherein the valve is configured as a pressure regulating valve, wherein the actuating element can be moved beyond the second position into at least one further, third position, with the result that a volume of the first channel section is increased in comparison with the second position.

A traction mechanism tensioning unit (1) for a traction mechanism drive of a motor vehicle is provided. The traction mechanism tensioning unit (1) includes a housing (2) in which a hydraulic tensioner (3) is arranged, the hydraulic tensioner (3) has a cylinder element (4) connected rigidly to the housing (2), in which an axially moving piston (5) is arranged, a compression spring (18) is arranged for generating an axial tensioning force on the piston (5) in a compression chamber (6) formed between the cylinder element (4) and the piston (5), and the hydraulic tensioner (3) is fluidly connected to a pressurized medium supply line (8) via a pressure control valve (7) arranged in the housing (2) for realizing a constant pressurized medium pressure in the compression chamber (6).

A hydraulic tensioner includes a tensioner housing having a bore extending a length, with a slot along the length of the bore. A hollow piston is slidably received within the bore and has an outer circumference with a chamfer adjacent a formed edge. An expandable circlip is received by the outer circumference of the piston. The circlip includes a substantially clover shaped body with a plurality of lobes connected to a first leg and a second leg through connecting portions. The expandable circlip has a free state, in which the lobes of the circlip are engaged with at least the chamfer of the piston, and an expanded state, in which the first leg and the second leg are moved away from each other, disengaged from the chamfer. When the expandable circlip is in the free state, the piston is prevented from being ejected from the bore of the housing.