Patent ID: 6471611
Filing Date: 2002-10-29
Classification: F16H

Abstract:
A free piston auto-tensioner for providing a continual adequate tension to a belt-shaped power transmission member comprising:a cylindrical body; a rod fitted in the body so as to be moved back and forth along its axial direction, extending outside the body so as to urge the belt-shaped power transmission member via an idler pulley; a block placed in the body and having one end portion and the other end portion, one end portion of the block receiving the rod movably and defining therein a first fluid chamber together with the rod for storing a fluid, the other end portion defining a second fluid chamber together with a movable piston which is moved by a distance corresponding to a stroke of the rod; a first urging member formed into a hollow configuration and urging the rod to extend the same outside the body and disposed between an outer surface of the block and an inner surface of the body; a second urging member formed into a cylindrical configuration and making the piston pressurize the fluid in the second fluid chamber so as to compensate for the total inside volume defined by the first fluid chamber, the second fluid chamber and an inner space of the body which is in fluid communication with the first and second fluid chambers; and damping means for controlling a fluid communication between the first fluid chamber and the second fluid chamber so as to adjust an engagement of the idler pulley with the belt-shaped power transmission member in such a manner that when a tension thereof is decreased a quick propulsive movement of the idler pulley to the belt-shaped power transmission member is allowed by the first urging member, while when the tension is increased, the idler pulley is retracted gradually from the belt-shaped power transmission member by a registration of the belt-shaped power transmission member, the damping means includes one or more sliding gaps provided between the block and the rod so as to connect the first fluid chamber and the second fluid chamber via the inner space of the body.