A work machine having a belt tensioning system is described. A belt is engaged with an engine drive sheave and a driven sheave of a rotor having a plurality of cutting tools configured for reducing wood infeed material. An idler pulley is mounted to an idler arm that is hinged to the machine frame. An actuator is hinged to the idler arm and the frame. The actuator may be extended and retracted in order to press the idler pulley into stronger and weaker engagement with the belt in order to set the desired amount of tension in the belt. One or more sensors may be used to sense the amount of tension in the belt, and the one or more sensors may be in communication with a control system that controls the actuator to monitor and adjust the belt tension so that it is maintained within desired limits.

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.

The derailleur has a damper that breaks the angular movements of a chain guide. Variable volume chambers in the damper are filled with a damping fluid and connected through a controlled fluid passage system so that fluid flows between chambers in response to angular movement of the chain guide. The damper comprises a dividing body in a mobile body coaxial to the axis X, mechanically constrained so that each rotation of the dividing body about the axis X is accompanied by a translation of the dividing body along the axis X. The dividing body is mechanically constrained to the chain guide and moves with it in the angular direction about the axis X. The chambers are formed in the mobile body on opposite sides of the dividing body and change volume in opposite directions when the dividing body moves along the axis X.

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.

An autonomous hydraulic expansion and contraction apparatus comprises a fixing unit, a cylinder unit, a support unit, a piston unit, a valve unit and oil supply parts. By controlling the expansion and contraction length of the support part by a simple manipulation of the valve part by moving the lever, the autonomous hydraulic expansion and contraction apparatus can be easily expanded and contracted to the combined length of the expansion and contraction equipment, and additionally, the convenience of use can be enhanced.

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.

A fixing tool of an auto-tensioner includes inwardly inclined engaging pieces inclined inwardly so as to be opposed to respective tapered surfaces of a spring seat and a cylinder of the auto-tensioner. The engaging pieces have concave surfaces that contact the tapered surfaces over a circumferentially extending area. This minimizes the deformation of the engaging pieces such that the diametrical distances therebetween increase due to contact with the tapered surfaces when sandwiching the spring seat and the cylinder with the engaging pieces from the axially opposite directions, thereby preventing the fixing tool from coming off.

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 system providing a drive belt with optimal tension to reduce flapping and other displacement movements relative to the pulley wheels. Included is a coil spring biasing the idler arm and its idler pulley wheel) in alignment to maintain the desired amount of tautness in the belt. Also included is a fluid spring mechanism that resists movement of the idler arm until such resistance is overcome by the coil spring.

A chain tensioner includes an oil supply passage for supplying hydraulic oil into a pressure chamber defined by a cylinder and a plunger, and a check valve provided at the end of the oil supply passage. A leak gap is defined between the sliding surfaces of the cylinder and the plunger. The plunger is biased by a return spring in the direction in which the plunger protrudes out of the cylinder. A plug is press-fitted in a cylindrical inner periphery of a through hole formed in the plunger to extend from a protruding end surface of the plunger to the pressure chamber to define an air vent passage. It is possible to change the hydraulic damper force simply by replacing the plug with another different type of plug to define a different air vent passage.