Power transmission apparatus fabrication method and power transmission apparatus fabricated by the method

A power transmission 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,
• wherein an outer ring of the rolling bearing is press-fitted into the inner periphery of the metal ring;
• wherein punched holes, each having a progressively increasing cross-sectional area from a rear end to a front end, are formed by pushing a punch in a rearward direction of the power transmission apparatus into a front-side end surface of the metal ring, while parts of the metal ring nearer to the inner periphery than the punch are pushed radially inward to form caulked portions, to fixedly caulk the outer ring, 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.

A power transmission apparatus comprising:

• a bearing support portion arranged on a driven unit;
• an input shaft arranged inside the bearing support portion;
• a pulley journalled on an outer surface of the bearing support portion through a rolling bearing, wherein the pulley is adapted to by rotationally driven by a drive source;
• and
• a power transmission device located between the wheel and the input shaft for coupling the wheel and the input shaft to each other,
• a cylindrical metal ring fitted on an inner surface of the pulley, wherein an outer ring of the rolling bearing is press-fitted to an inner surface of the metal ring, wherein the cylindrical metal ring has a front end and a rear end, and the rear end of the metal ring faces the driven unit;
• punched holes formed in a front end surface of the metal ring, wherein each punched hole has:
• a progressively increasing cross-sectional area from a rear end to a front end of each punched hole in the axial direction of the metal ring, and parts of the metal ring that are located radially inward of each punched hole are deformed in a radially inward direction of the metal ring to form caulked portions for fixing the metal ring to the outer ring of the rolling bearing,
• a conical surface, which is on a side of the punched hole that faces radially inward toward the rolling bearing, wherein the conical surface extends along a longitudinal axis of the punched hole, and 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 further wherein the conical surface is defined as a part of a circular conical surface;
• and
• a flat surface that extends generally in the axial direction of the metal ring, is opposed to the conical surface and faces in a radially outward direction of the metal ring.