Common rail for diesel engine

Abstract

There is provided a common rail for a diesel engine in which fatigue strength against inner pressure is increased by reducing the difference in hardness or elongation between a steel surface and a nonmetal inclusion on the inner surface of, or in the surface layer of, a rail and lowering the degree of concentration of fatigue stress. The common rail includes a main pipe rail having a circulating passage extending in its inside in the axial direction thereof, branch holes formed in an axial peripheral wall portion of the main pipe rail, and branch connectors connected to the respective branch holes integrally or via separate connecting members, and a Ni-diffused fatigue strength reinforcing layer which is formed by heating a Ni layer plated in advance is formed on at least a portion of an inner circumferential surface of the common rail. The increased strength and the action of the fatigue strength reinforcing layer lowers the degree of fatigue concentration to increase fatigue strength against inner pressure. Consequently, the common rail serves the superior advantage of being capable of performing reliable and stable functions with superior durability and without leakage of fuel due to occurrence of cracks.

Dependencies are inferred from the claim text.