TORQUE TRANSMISSION DEVICE

PROBLEM TO BE SOLVED: To stabilize torque at the initial stage of rotation of a torque limiter using a coil spring and to provide an increased lubrication life. SOLUTION: A coil spring 3 is incorporated between an inner ring 1 and an outer ring 2 rotatably arranged at the outside, and the coil spring 3 is provided with a small coil part 3a to fasten the outside diameter surface of the inner ring 1. One of bent pieces 4 and 5 formed at the two ends of the coil spring 3 is coupled to the outer ring 2, and the other bend piece 5 is coupled to a regulation ring 6 pressed in the opening end part of the outer ring 2. The inner ring 1 is formed of a sintered substance having sintering density of 5.4-6.4g/cm and the infinite number of small holes formed in an internal part are impregnated with a lubricant. Further, through sizing of the inner ring, the opening of the small hole is throttled, a contact part between the inner ring 1 and the small diameter coil part 3a is lubricated by a lubricant with which the surface of the inner ring 1 oozes and initial torque is stabilized. By throttling the opening of the small hole by sizing, an outflow amount of lubrication oil is limited to provide an increase lubrication life.