MANUFACTURE OF COMMON RAIL

摘要

PROBLEM TO BE SOLVED: To increase an internal pressure fatigue strength by pressing a spherical body or a piece body to the main pipe rail flow passage opening end part of a branch hole so as to generate compression residual stress in the periphery of the main pipe rail flow passage opening end part. SOLUTION: A steel ball 5 and a bar-like steel ball receiver 7 are inserted into the inner part of a main pipe rail, and the steel ball 7 is arranged so as to bring the spherical surface of the steel ball 5 into contact with the main pipe rail flow passage opening end part of a branch hole 1-2. A punch 6 whose tip part is formed into a wedge shape is inserted form another main pipe rail end part. The force in the branch hole direction is applied to the steel ball 5 by the wedge action of the tip part of the punch 6, and thus the steel ball 5 is pressed to the main pipe rail flow passage opening end part of the branch hole 1-2. By this method, compression residual stress can be effectively generated and made to remain in the periphery of the main pipe rail flow passage end part of the branch hole 1-2. Thus, an inner pressure fatigue strength in a pipe connecting part can be increased.