Common rail for diesel engines

Abstract

A common rail for a diesel engine has a main pipe rail with an axial flow passage. Branch holes are made in the main pipe rail and communicate with the axial flow passage. The main pipe rail is worked to decrease stress concentration near the branch holes. The whole inner peripheral surface of the main pipe rail and the branch holes then is subjected to autofrettage processing to generate a compressive residual stress on the entire inner peripheral surface of the main pipe rail and the branch holes for increasing fatigue strength.

Description

[0001] This application is a divisional U.S. patent application Ser. No. 10 / 653,477, filed Sep. 2, 2003.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a common rail, such as high-pressure fuel manifolds, block rails, or the like, in a fuel injection system for diesel engines, and more particularly, to a common rail for diesel engines, in which portions of a branch hole or holes on a main pipe rail and a whole inner peripheral surface of the main pipe rail are enhanced in fatigue strength for inner pressures. [0004] 2. Description of the Related Art [0005] A common rail in a fuel injection system for diesel engines is shown in FIG. 7, and has a circular main pipe 11. The main pipe 11 has an internal flow passage 11-1. A branch hole 11-2 is provided in a peripheral wall of the main pipe 11 and communicates to the internal flow passage 11-1. The branch hole 11-2 leads to an outwardly opened pressure-receiving seat surface 11-3. A cy...

AI Technical Summary

Benefits of technology

[0020] As described above, stress concentration at the peripheral edge of the branch hole is relaxed and autofrettage is then applied according to the invention. Thus, high compressive residual stresses can be made present in the whole common rail due to the synergistic effect of a decrease of stress concentration applied at the peripheral edge of the branch hole and autofrettage applied on the whole flow passage in the main pipe rail and the flow passage in the branch hole. Accordingly excellent durability can be expected also for the flow passage in the main pipe rail and the opening peripheral edge of the branch hole while fatigue strength for inner pressures is increased at the inner peripheral edge of the lower end of the branch hole.

Problems solved by technology

In common rails for diesel engines, however, disadvantages are caused when autofrettage is applied without application of further processings in the stock pipe as described herein.

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