PISTON MANUFACTURING METHOD OF HYDRAULIC MASTER CYLINDER OF CENTER VALVE TYPE FOR VEHICLE, AND PISTON

摘要

PROBLEM TO BE SOLVED: To secure rigidity in the axial direction of the piston by preventing cold shut from being generated when a piston used for a hydraulic master cylinder of a center valve type for a vehicle is molded.

SOLUTION: A cavity 55 is arranged to lay the piston central axis CL horizontally, and the piston 40 is molded in a horizontally laid posture. Runners 56 and 57 are formed on guide hole cores 51a and 52a for forming the guide hole 42 on an intermediate shaft part 40a of the piston 40. On the external surfaces of the guide hole cores 51a and 52a, injection gates G1, G1 and G2 are provided. The injection gate G2 is arranged on the piston central axis CL. On the cores 51a and 52a in the cavity 55, the distal end of a valve housing hole core 53 is projected.

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