Abstract: A tensioner comprises shaft members that mate with each other by way of thread portions. A first shaft member is rotatable with respect to a casing and is restrained from moving in its axial direction. A second shaft member, which is restrained from rotating with respect to the casing, is movable in its axial direction. A torsion spring applies torque in a first direction to the first shaft member. A torque switching member, which can switch frictional torque in association with the rotation of the first shaft member, is provided between the first shaft member and the casing.

Abstract: A tensioner comprises shaft members that mate with each other by means of thread portions. A first shaft member is rotatable with respect to a casing and is restrained from moving in its axial direction. A second shaft member, which is restrained from rotating with respect to the casing, is movable in its axial direction. A torsion spring applies torque in a first direction to the first shaft member. A torque switching member, which can switch frictional torque in association with the rotation of the first shaft member, is provided between the first shaft member and the casing.

Abstract: A compression coil spring is used as a return spring which is stored in the housing of a clutch to urge the clutch piston in its returning direction. The effective number of turns of the compression coil spring is two or less, and the number of turns at an end-turn portion thereof is more than 0.45 and not more than 0.7. The compression coil spring is used in the compressed state throughout the operating stroke of the clutch piston. The number of turns at the end-turn portion is desirably within the range of 0.5 to 0.65, more desirably within the range of 0.55 to 0.62.