Fuel rail for high-pressure direct-injection internal combustion engines and method for manufacturing thereof
A fuel rail for high-pressure direct-injection internal combustion engines has an injector holder and a fastening bracket directly attached to a main body of the fuel rail. Thermal deformation may occur at the time of temporary fitting or brazing when assembling the rail. However, positional accuracy of the injector holder can be assured, which results in having an excellent sealing property. Components of the fuel rail for direct-injection internal combustion engines are made of steel or stainless steel, and the components are joined reciprocally by brazing. The components joined by brazing are finished by cutting work and/or burnishing processing after the brazing step.
1. A method for manufacturing a fuel rail for high-pressure direct-injection internal combustion engines, comprising the steps of:
providing a main rail made of steel or stainless steel having a flow passage therein and through holes communicating with the flow passage,
providing injector connecting structures made of steel or stainless steel,
reciprocally brazing the injector connecting structures and the main rail so that the injector connecting structures substantially align with the through holes, and
performing cutting work to the injector connecting structures that have been brazed to the main rail to form finish processed holes that communicate respectively with the through holes in the main rail, and
burnishing the injector connecting structures of the fuel rail that have been assembled to the main rail by brazing.
2. The method for manufacturing a fuel rail for high-pressure direct-injection internal combustion engines according to claim 1 , wherein a preliminary processing is performed on the injector connecting structures before brazing, and a finish processing is performed after brazing.
3. The method for manufacturing a fuel rail for high-pressure direct-injection internal combustion engines according to claim 2 , wherein the method is comprised of steps of firstly coating at least a contact portion with fuel of the components with a chemical nickel plating film, and secondly coating an outer surface of the components with a zinc plating film or a zinc-nickel plating film.
4. The method for manufacturing a fuel rail for high-pressure direct-injection internal combustion engines according to claim 1 , wherein the injector connecting structure are injector holders and wherein the method further comprises brazing fastening brackets made of steel or stainless steel to the main rail so that the injector holders and the fastening brackets are disposed in pairs on the main rail and performing cutting work to the fastening brackets that have been brazed to the main rail to form finish processed holes.
5. The method for manufacturing a fuel rail for high-pressure direct-injection internal combustion engines according to claim 4 , wherein the injector holders and the fastening brackets are brazed in pairs on one side of the main rail so as to be eccentric to a shaft core of the main rail.
6. The method for manufacturing a fuel rail for high-pressure direct-injection internal combustion engines according to claim 1 , wherein when the components of the fuel rail for direct-injection internal combustion engines are made of steel, and the method further comprising coating at least a contact region with fuel between the injector connecting structures and the main rail with a plating film.
7. The method for manufacturing a fuel rail for high-pressure direct-injection internal combustion engines according to claim 6 , wherein the plating film is a chemical nickel plating film.
8. The method for manufacturing a fuel rail for high-pressure direct-injection internal combustion engines according to claim 1 , wherein the step of providing injector connecting structures made of steel or stainless steel comprises providing injector connecting structures with no holes formed therein and wherein the step of performing cutting work to the injector connecting structures comprises forming the finish processed holes.
9. The method for manufacturing a fuel rail for high-pressure direct-injection internal combustion engines according to claim 1 , wherein the step of providing injector connecting structures made of steel or stainless steel comprises providing injector connecting structures with at least one pilot hole therein and wherein the step of performing cutting work to the injector connecting structures comprises forming the finish processed holes at the pilot hole.