| 摘要 |
PROBLEM TO BE SOLVED: To improve internal pressure fatigue strength by providing a branched hole having a complete round cross section in the direction of axial line of a short diameter of a flow passage of a main pipe rail on the main pipe rail of a common rail which is a high pressure fuel multi-branched pipe by using a metallic pipe having a flow passage constituted by an inner peripheral face having an elliptical cross section and an outer peripheral face having a complete round cross section. SOLUTION: A branched hole 1-2 having a complete round cross section is provide at a position where it agrees with the center in the direction of a long diameter of a flow passage of a main pipe rail 1 on the main pipe rail 1 which is a metallic pipe having a flow passage 1-1 constituted by an inner peripheral face having an elliptical cross section and an outer peripheral face 1' having a complete round cross section. Moreover, a branch pipe 2 is constituted by providing a flow passage 2-1 communicated with the flow passage 1-1 therein and a pressing seat face 2-3 constituted by a connection head part 2-2 in an end part thereof and is attached by screwing a nut 4 assembled in a branch pipe 2 side into a sleeve nipple 3a welded on the outer peripheral face 1' of the main pipe rail 1. Consequently, it is possible to suppress the generation of stress in a branched hole part effectively and increase the durability due to the improvement of internal pressure fatigue strength of the branched hole part in a root part of each branch pipe. |
