Patent ID: 8267819

Claim:
A belt tensioner for a motor vehicle engine, comprising: a pivot shaft configured to be mounted stationary relative to the motor vehicle engine; a pivot arm pivotally mounted on said pivot shaft; a pulley rotationally supported on said pivot arm; a spring that biases said pivot arm in a belt take-up direction; and a backstop device installed about the pivot shaft and operably engaging said pivot arm providing a predetermined, limited amount of rotational play between said pivot arm and said backstop device and preventing rotational movement of said pivot arm from a minimum belt take-up position in a direction opposite said belt take-up direction, said backstop device including a frictional clamp member and a one-way clutch member including a pair of axially aligned, generally cylindrical members disposed around said pivot shaft, one of said generally cylindrical members having an arm-engaging portion engaging said pivot arm and the other of said generally cylindrical members is a clamp holder which supports said frictional clamp member, and wherein said one-way clutch member includes a clutch spring which overlaps said pair of generally cylindrical members and permits said generally cylindrical members to rotate in one direction relative to each other permitting said pivot arm to pivot substantially freely in said belt take-up direction, but substantially prevents said generally cylindrical members from rotating in an opposite direction relative to each other resisting said pivot arm from pivoting in a direction opposite to said belt take-up direction by engagement of said pivot arm by said arm-engaging portion, frictional engagement of said frictional clamp member with said pivot shaft, and interlocking action of said one-way clutch member between said frictional clamp member and said arm-engaging portion; wherein said clutch spring is connected to the generally cylindrical member which comprises the clamp holder.