RESINOUS GEAR AND MANUFACTURING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To greatly improve the strength and precision of a spur gear in comparison with those obtained by usual injection molding, on the occasion of molding the gear by injecting a resin material. SOLUTION: After a cylindrical primary molded body 5 smaller than the gear teeth of the spur gear is molded by primary injection of the resin material, the resin material is injected secondarily inside the primary molded body 5 so that a secondary injection pressure be applied to the molded body 5. Thereby the primary molded body is stretched to the circumferential direction of the gear so that it be along a gear form 4a and molecules of the resin material are oriented. According to this constitution, the strength and the precision in the circumferential direction can be improved remarkably.