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 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).

An object of the present invention is to provide a tensioner that has a reduced number of components and lighter weight and is easy to assemble. The tensioner according to the present invention is configured such that a base member is detachably and mechanically joined to a rear end opening of a cylindrical plunger with a closed front end against the resilience of biasing means that is accommodated inside the plunger such as to be freely extend and contract. The joint between the plunger and the base member is a mechanical connection that is one of a thread engagement, a press-fit, and a pin connection.

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).

The present invention generally relates to vehicle and machinery in agriculture, construction, forestry, mining and powersport. It further generally relates to track systems and traction assemblies used with such vehicles. The track assembly includes components having particular features that, alone or in combination, participate in decreasing the vibrations 5 undergone by the vehicle. According to embodiments, split frames are used with suspension, tandem subassemblies, “tridem subassemblies”, adjustable damping components, drive shaft openings, lowering of resulting the track band tension and rosta assemblies.

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.

To provide a tensioner capable of keeping oil pressure in an oil pressure chamber stable with a simple structure. The tensioner is equipped with a pressure adjusting mechanism that adjusts oil pressure in the oil pressure chamber and includes an adjustment space formed in a housing and communicating with the oil pressure chamber, a movable member disposed such as to be movable to and from the oil pressure chamber, and a pressure adjusting biasing unit that biases the movable member toward the oil pressure chamber. A liquid tight seal is maintained between the movable member and an inner wall of the adjustment space, between a position where the movable member has moved closest to the oil pressure chamber and a position where the movable member is farthest from the oil pressure chamber.

To provide a tensioner that can keep the oil pressure in an oil pressure chamber stable and consistently generate suitable reaction force and damping force to impact loads to reduce looseness in the chain and noise. A piston is set such as to partition an inner space of a plunger into an adjustment space on the front side and the oil pressure chamber on the rear side, a piston restricting member restricting the movement of the piston toward the adjustment space. An oil relief mechanism is configured to cause the piston to move forward when oil pressure in the oil pressure chamber rises so as to discharge oil inside the oil pressure chamber to the outside. The piston restricting member has an orifice function that can control the amount of discharged oil.

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.

Provided is a tensioner capable of stabilizing an oil pressure in an oil pressurizing chamber. The tensioner includes a pressure adjustment unit. The pressure adjustment unit includes a unit case attached to the housing or the plunger, a moving member disposed in the case inner space to be capable of moving closer to and farther away from the oil pressurizing chamber, and a pressure adjustment biasing unit which biases the moving member toward the oil pressurizing chamber. A gap between an inner wall of the case inner space and the moving member is configured to be held in a liquid tight state at any position between a position where the moving member is closest to the oil pressurizing chamber as a result of moving and a position where the moving member is most distant from the oil pressurizing chamber.