US Patent 7870801 Rotational power transfer device and related manufacturing method

A rotational power transfer device and a method of manufacturing the same are provided. The rotational power transfer device includes a first rotary member and a second rotary member. The first rotary member has an inner periphery formed with a solid lubricating layer composed of a chemical film and molybdenum disulfide. The second rotary member has an outer cylindrical periphery applied with a layer of grease including a mixture of oil with a higher frictional coefficient than that of lubricating oil and molybdenum disulfide. The second rotary member is press fitted to the first rotary member to allow the outer cylindrical periphery thereof to be placed in face-to-face relation to the inner cylindrical periphery of the first rotary member, enabling a rotational power in excess to be stably absorbed without causing any increase in the rotational power at which the slippage occurs.