A power transmission device includes: a first pulley; a second pulley having a diameter equal to or larger than a diameter of the first pulley; a belt wound around the first pulley and the second pulley; and a detection unit configured to detect a displacement of the belt in a direction intersecting the surface of the belt. The detection unit is configured to detect the displacement of the belt at a predetermined measuring point. The distance from the border between a portion where the belt and the first pulley are in contact with each other and a portion where the belt and the first pulley are not in contact with each other, to the measuring point is equal to or smaller than the diameter of the first pulley.

A belt slip monitor system and method configured to determine whether a belt coupled to a motor-generator is slipping based on operational states of first and second movable portions of the belt slip monitor, wherein the operational states of the first and second movable portions are dependent upon the tension in the belt.

A transmission belt arrangement includes at least one transmission belt, at least one sensor configured to measure a parameter indicative of a distance between the at least one sensor and the at least one transmission belt, and processing circuitry configured to determine a state of the at least one transmission belt based on the parameter and/or based on the distance.

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.

In one aspect the invention relates to a tensioner that is capable of precognitively anticipating when it is desirable to increase the tension in a belt or other endless drive element so as to prevent belt slip prior to events that would raise the risk of it.

Systems and methods are provided for determining the length of a traction mechanism that is part of a traction drive of an engine. In one example, a method includes determining a position of a movable tensioning device relative to a traction mechanism drive using measuring technology, determining an actual length L.sub.AS of a traction mechanism computationally using the position of the tensioning device, determining a length change L with respect to a predefinable setpoint length L.sub.AS computationally using the computationally determined actual length L.sub.AS, and adjusting one or more operating parameters based on the length change.

A belt slip monitor system and method configured to determine whether a belt coupled to a motor-generator is slipping based on operational states of first and second movable portions of the belt slip monitor, wherein the operational states of the first and second movable portions are dependent upon the tension in the belt.

A belt drive for a work machine is disclosed. The belt drive has a drive belt that is wound around an input pulley and an out put pulley. The input pulley is rotated by a motor, and when rotated, transfers rotational motion to the output pulley by the drive belt. A controller is in communication with an input speed sensor that measures the input pulley and an output speed sensor that measures the output pulley. The controller calculates an input speed from the measurement of the input pulley, and an output speed from the measurement of the output pulley. The controller also sends a damaged belt signal to an operator control of the work machine when the output speed is lower by a predetermined threshold than the input speed.

An auto tensioner is supported on one side surface of a cylinder block (the outer surface of a front wall part) via a bracket. The auto tensioner includes: a tension pulley that is pressed against a belt; an arm that rotatably supports the tension pulley and is swingably supported to the bracket; and a hydraulic actuator that is supported by the arm and bracket to adjust the pressing force of the tension pulley to the belt using a predetermined position of the arm as a supporting point. The hydraulic actuator is disposed outside the water pump on the front wall part of the cylinder block.