Assembly method for cross shaft universal joint

A method for assembling a cross shaft universal joint wherein the universal joint comprises:

• a yoke comprising a pair of joining-arm sections, and a pair of circular holes formed in tip-end sections of the pair of joining-arm sections;
• a cross shaft comprising a shaft section;
• and a pair of cup bearings for supporting both end sections of the shaft section on an inside of the pair of circular holes so the shaft may rotate freely;
• and
• the pair of cup bearings is assembled in portions between the pair of circular holes of the pair of joining arm sections and the both end sections of the shaft section that is inserted inside the pair of circular holes from an inside-surface side of the pair of joining-arm sections, by press-fitting the cup bearings inside the pair of circular holes from an outside-surface side of the pair of joining-arm sections using a pair of press-fitting punches;
• wherein
• the method comprises a step of adjusting an amount of movement of the pair of press-fitting punches according to dimensions of the yoke or cross shaft, or size of elastic deformation of the pair of joining-arm sections during the press-fitting of the pair of cup bearings inside the pair of circular holes,
• in a state of the pair of joining-arm sections being backed up, and the shaft section being inserted into the pair of circular holes from the inside-surface side of the pair of joining-arm sections,
• one of the pair of cup bearings is press-fitted to a preset position where press-fitting is complete using one of the pair of press-fitting punches based on a feed amount of the one of the pair of press-fitting punches, then the one of the pair of press-fitting punches is moved back and the other of the pair of cup bearings is press-fitted to a preset reference position using the other of the pair of press-fitting punches based on a feed amount of the other of the pair of press-fitting punches;
• and
• the other of the pair of cup bearings is then pressed together with the shaft section of the cross shaft using the other of the pair of press-fitting punches, and the preset reference position where the size of the pressure that is applied to the other of the pair of press-fitting punches becomes a specified size is determined to be the preset reference position where press-fitting is complete, then press-fitting of the other of the pair of cup bearings is stopped and the other of the pair of press-fitting punches is moved back.

A method for assembling a cross shaft universal joint wherein the universal joint comprises:

• a yoke comprising a pair of joining-arm sections, and a pair of circular holes formed in tip-end sections of the pair of joining-arm sections;
• a cross shaft comprising a shaft section;
• and a pair of cup bearings for supporting both end sections of the shaft section on an inside of the pair of circular holes so the shaft may rotate freely;
• and
• the pair of cup bearings is assembled in portions between the pair of circular holes of the pair of joining arm sections and the both end sections of the shaft section that is inserted inside the pair of circular holes from an inside-surface side of the pair of joining-arm sections, by press-fitting the cup bearings inside the pair of circular holes from an outside-surface side of the pair of joining-arm sections using a pair of press-fitting punches;
• wherein
• the method comprises a step of adjusting an amount of movement of the pair of press-fitting punches according to dimensions of the yoke or cross shaft, or size of elastic deformation of the pair of joining-arm sections during the press-fitting of the pair of cup bearings inside the pair of circular holes,
• when the inside surfaces of the tip-end sections of the pair of joining-arm sections are backed up by a pair of supporting members that moves by being driven by servo motors, the pair of supporting members is moved by being driven by the servo motors in directions parallel to a center axis of the pair of circular holes and in directions away from each other so that the pair of supporting member approach the inside surfaces of the tip-end sections of the pair of joining-arm sections, and at the instant when specified torques occur in the servo motors, the pair of supporting members is stopped and the inside surfaces of the tip-end sections of the pair of joining-arm sections are supported by the pair of supporting members;
• next, amounts of shifting from a center position in a direction of the center axis of the circular holes of the pair of supporting members to the center position in the direction of the center axis of the circular holes of the pair of supporting members in a state in which the pair of joining-arm sections are supported are found by using a number of pulses of the servo motors;
• and
• when press-fitting the pair of cup bearings using the pair of press-fitting punches, amounts of movement in a forward direction of the pair of press-fitting punches are respectively corrected based on the amounts of shifting.