Timing belt tensioner with stops controlled by frictional brake

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 operably engaging said pivot arm to provide a predetermined, limited amount of rotational play therebetween and to prevent 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 comprising a one-way clutch member and a frictional brake member, said frictional brake member being a frictional clamp member relatively fixed to said pivot shaft by means of frictional engagement therewith, said frictional engagement being overcome manually during installation to rotationally position said backstop device to engage the pivot arm when in the minimum belt take-up position, said one-way clutch member including a pair of axially aligned rotational members disposed around said pivot shaft, one of said rotational members engaging said pivot arm and the other of said rotational members is a clamp holder which engages said frictional clamp member, at least one of said rotational members having a cylindrical surface, wherein said one-way clutch member further includes a clutch spring, one end of said clutch spring overlapping said cylindrical section of said at least one of said rotational members and the opposite end of said clutch spring being attached to the other of said rotational members, said clutch spring thereby permitting said rotational members to rotate in one direction relative to each other to permit said pivot arm to pivot substantially freely in said belt take-up direction but substantially preventing said rotational members from rotating in an opposite direction relative to each other to resist pivoting of said pivot arm in said direction opposite to said belt take-up direction.