METHOD OF MANUFACTURING BOOT FOR CONSTANT-VELOCITY UNIVERSAL JOINT AND MANUFACTURING APPARATUS FOR USE IN THE METHOD, AND BOOT FOR CONSTANT-VELOCITY UNIVERSAL JOINT

摘要

There is disclosed a boot for a constant-velocity universal joint, in which a secondary molded portion including a thick portion is formed on an inner peripheral portion of a large-diameter side end portion formed as a primary molded member and in which a material in secondary molding is prevented from leaking. A manufacturing method includes: a step of forming a secondary molding space between a large-diameter side end portion inner peripheral surface of the primary molded member and an outer peripheral surface of a core mold; and a step of injecting a molten material into the secondary molding space to mold the secondary molded portion. The step of molding the secondary molded portion includes the steps of: applying a pressure of the molten material injected into the secondary molding space to a tapered surface 27 extending toward the large-diameter side end portion from a small-diameter portion 7b just in the vicinity of a large-diameter side end portion 3, expanding the tapered surface toward the small-diameter portion, and pressure-contacting the small-diameter portion 7b held between the inner peripheral surface of a divided mold 51 and the outer peripheral surface of a core mold 69 onto the core mold outer peripheral surface.