Automatic Tensioner

An auto-tensioner comprising:

• a base having a cylindrical part;
• an arm supported so as to be rotatable with respect to the base;
• a pulley which is rotatably provided at the arm and around which a belt is to be wound;
• a friction member sandwiched between an inner circumferential surface of the cylindrical part and the arm in a radial direction of the cylindrical part;
• and
• a coil spring which has one end locked to the friction member and the other end locked to the base and is disposed in a state of being compressed in an axial direction of the cylindrical part, thereby pressing the friction member against the arm in the axial direction and rotationally biasing the arm in one direction with respect to the base through the friction member, wherein
• the friction member comprises:
• an arcuate surface capable of sliding along the inner circumferential surface of the cylindrical part,
• a first locking part located further toward the one direction side than the arcuate surface in a circumferential direction of the cylindrical part, locked to the arm, and inclined with respect to the radial direction so as to face the one direction side as the first locking part goes toward an outside in the radial direction, and
• a second locking part locked to the one end of the coil spring further on the outside in the radial direction than the first locking part, and
• the friction member and the arm comprise a restricting unit which restricts the friction member from moving toward the one direction side with respect to the arm.