Patent ID: 7803079

Claim:
A method fabricating a power transmission apparatus, the apparatus comprising: a bearing support portion arranged on a driven unit; an input shaft arranged inside the bearing support portion; a wheel journalled on the outer periphery of the bearing support portion through a rolling bearing and rotationally driven by a drive source; and a power transmission device interposed between the wheel and the input shaft for coupling the wheel and the input shaft to each other; wherein a cylindrical metal ring is fitted on the inner periphery of the wheel, the method fabricating the power transmission apparatus comprising the steps of: press-fitting an outer ring of the rolling bearing into the inner periphery of the metal ring; pushing a distal end of a punch, which has a progressively increasing cross-sectional area from the distal end of the punch to a proximal end of the punch, into a front-side end surface of the metal ring in a rearward direction of the power transmission apparatus to form punched holes, while at the same time the parts of the metal ring nearer to the inner periphery than the punch are pushed radially inward by the punch to form caulked portions, to fixedly caulk the outer ring, wherein, the punch has: a conical surface, which is on a side of the punch that is near to the rolling bearing, along a longitudinal axis of the punch, when the punch is in a position to form the punched holes, wherein the conical surface is defined such that a radius extending from the longitudinal axis of the punch progressively increases from the distal end of the punch to the proximal end of the punch, and wherein the conical surface is part of a circular conical surface; and a flat surface along the longitudinal axis of the punch on a side of the punch near to the wheel, when the punch is in the position to form the punched holes, and wherein each punched hole has: a conical surface, which is on a side of the punched hole that is near to the rolling bearing, along a longitudinal axis of the punched hole, wherein the conical surface is defined such that a radius extending from the longitudinal axis of each punched hole progressively increases from a rear end to a front end of the punched hole, and wherein the conical surface is part of a circular conical surface; and a flat surface along the longitudinal axis of the punched hole on a side of the punched hole near to the wheel.