To prevent errors from arising in the retreating clearance of a torque pin in positioning the torque adjusting bolt of a torque increasing device into place.

A torque pin 7 and a torque spring 10 are enclosed in a case main body 5, a torque adjusting bolt 8 is screwed into the case main body 5, a transmission pin 11 behind the torque pin 7 is opposed to the torque adjusting bolt 8 via a retreating clearance (t), a bolt fixing tool 14 is pressed against the receiving surface 12 of the torque adjusting bolt 8 form the side wall 13 of the case main body 5, and the torque adjusting bolt 8 is positioned into place by the bolt fixing tool 14 from a direction perpendicular to its longitudinal direction.