Patent ID: 8689960

Claim:
A torque limiter comprising: a shaft member; and a tube member which is rotatably fitted over the shaft member; wherein said shaft member includes: an oil pressure expanding chamber for pressing an outer peripheral face of the shaft member against an inner peripheral face of the tube member; a circumferentially extending chamber communicated with the oil pressure expanding chamber, projected inward from the oil pressure expanding chamber in a radial direction of the shaft member, and extending in a circumferential direction of the shaft member; and an oil removing hole opened to the circumferentially extending chamber, and having a radially extending part which is extended inward in the radial direction from the circumferentially extending chamber, wherein said oil removing hole is so constructed that when a load less than a determined value is exerted on the shaft member or the tube member, an end of the oil removing hole at an opposite side to the circumferentially extending chamber is sealed, whereby the oil pressure expanding chamber is inflated with the oil which is sealed in the oil pressure expanding chamber thereby to frictionally engage the shaft member and the tube member with each other, and when a load more than the determined value is exerted on the shaft member or the tube member, the end of the oil removing hole at the opposite side to the circumferentially extending chamber is opened to the exterior due to a relative rotational movement of the tube member and the shaft member, whereby the oil in the oil pressure expanding chamber is removed thereby to release the frictional engagement between the shaft member and the tube member, and wherein, while the oil pressure expanding chamber is inflated, an area of a region where a face of the circumferentially extending chamber intersects the oil pressure expanding chamber in an extended plane extended toward the oil pressure expanding chamber is larger than a sectional area of an opening of the oil removing hole which is opened to the circumferentially extending chamber.