Patent ID: 7025185

Claim:
A torque releasing device comprising: a first member in the form of a shaft; a second member disposed on an outer circumferential face of the first member and frictionally engageable with the first member to permit torque transmission from the first member but designed to be released from the frictional engagement with the first member in the event of an abnormal torque thereby to inhibit the torque transmission; and the second member comprising an outside cylinder portion including a hydraulic oil path which is operated by a pressure oil supplied thereto to produce a pressurizing force for bringing the first member and the second member into the frictional engagement; and a joint cylinder member formed in a thickness to permit the pressure oil in the hydraulic oil path to reduce the diameter thereof, and possessing an inner circumferential face on which the joint cylinder member reduced in the diameter frictionally engages an outer circumferential face of the first member, the outside cylinder portion fitted on the joint cylinder member for unitary rotation with the joint cylinder member; a first bearing disposed at one of the opposite axial-outside regions with respect to the hydraulic oil path in order to permit both of the members to rotate relative to each other when the members are released from the frictional engagement; and a second bearing disposed at the other of the opposite axial-outside regions with respect to the hydraulic oil path in order to permit both of the members to rotate relative to each other when the members are released from the frictional engagement, the second bearing comprises an angular contact ball bearing which includes an outer ring and an inner ring, raceway surfaces of which are applied with a pre-load, and which has its outer ring mounted to the joint cylinder member and its inner ring mounted to the first member, and wherein the joint cylinder member includes a segment of substantially the same thickness as that of its segment extended in correspondence to the hydraulic oil path, the former segment defined between the extent of the hydraulic oil path and the region where the second bearing is disposed.