End seal structure of fuel rail for gasoline direct injection engine

Abstract

Provided is an end seal structure of a fuel rail for a gasoline direct injection engine that has a simple structure and allows an end cap part to meet higher pressure requirements in a fuel rail having the structure in which one end or both ends of a rail body composed of a tubular member, such as a pipe, is/are closed by an end cap or end caps. The end seal structure employs a thread fastening method using the end cap and a collar brazed at the opening end of the fuel rail body and a gasket sealing method as a sealing method, wherein a gasket interposed between the end cap and the fuel rail body is tightened by an axial force generated due to tightening of the end cap that is screwed and fastened to the fuel rail body so as to be sealed.

Claims

1. An end seal structure of a fuel rail for a gasoline direct injection engine, the fuel rail having a structure in which one end or both ends of a fuel rail body composed of a tubular member is/are closed by an end cap or end caps with a thread fastening method, the end seal structure comprising: a collar brazed at an outer circumference of an opening end of the fuel rail body in such a manner that a thread fastening part provided in a part of an inner wall surface of the collar projects from the opening end; a convex end cap to be screwed together with the thread fastening part of the collar; and a gasket that is made of metal and interposed between the convex end cap and the fuel rail body, wherein the gasket is tightened by an axial force generated due to tightening of the convex end cap so as to seal the opening end of the fuel rail body.

2. The end seal structure of the fuel rail for the gasoline direct injection engine according to claim 1, wherein the fuel rail body and the convex end cap are made of stainless steel, or a surface treatment material obtained by performing a surface treatment using Ni or a Ni-based alloy on various steel products.

3. The end seal structure of the fuel rail for the gasoline direct injection engine according to claim 2, wherein the gasket is made of copper or brass, or a surface treatment material obtained by performing a surface treatment, such as plating, on these materials.

4. The end seal structure of the fuel rail for the gasoline direct injection engine according to claim 1, wherein the gasket is made of copper or brass, or a surface treatment material obtained by performing a surface treatment, such as plating, on these materials.

5. An end seal structure of a fuel rail for a gasoline direct injection engine, comprising: a fuel rail body having an axial end with an opening and an outer circumferential surface extending from the end; a collar having opposite first and second longitudinal ends and an inner circumferential surface extending between the first and second longitudinal ends, areas of the inner circumferential surface adjacent the first longitudinal end being unthreaded and in surface contact with the outer circumferential surface of the fuel rail body adjacent the end of the fuel rail body, areas of the inner circumferential surface of the collar adjacent the second end of the collar having internal threads projecting axially beyond the end of the fuel rail body, the collar being brazed at the outer circumferential surface of the fuel rail body; a convex end cap having an axial end and external threads extending from the axial end, the external threads of the end cap being threaded to the internal threads of the collar; and a metal gasket interposed between the axial end of end cap and the axial end of the fuel rail body, the gasket being sealed to the inner circumferential surface of the collar, the axial end of the fuel rail body and the axial end of the end cap by an axial force generated by tightening of the convex end cap to the collar.

6. The end seal structure of the fuel rail for the gasoline direct injection engine of claim 5, wherein the fuel rail body and the convex end cap are made of stainless steel, or a surface treatment material obtained by performing a surface treatment using Ni or a Ni-based alloy on various steel products.

7. The end seal structure of the fuel rail for the gasoline direct injection engine of claim 6, wherein the gasket is made of copper or brass, or a surface treatment material obtained by performing a surface treatment on these materials.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a cross-sectional view illustrating an embodiment of an end seal structure of a fuel rail for a gasoline direct injection engine according to the present invention.

(2) FIG. 2 is a cross-sectional view illustrating an example of a conventional end seal structure of a fuel rail for a gasoline direct injection engine.

(3) FIG. 3 is a cross-sectional view illustrating another example of a conventional end seal structure of a fuel rail for a gasoline direct injection engine.

DETAILED DESCRIPTION

(4) An end seal structure of a fuel rail for a gasoline direct injection engine according to the present invention will be described with reference to the drawings.

(5) In the fuel rail for the gasoline direct injection engine according to the present invention, a fuel inlet pipe (not illustrated) is connected to one end or a pipe wall surface of the fuel rail. The fuel inlet pipe is connected to a fuel tank (not illustrated) via a piping (not illustrated), and a fuel in the fuel tank is transferred to the fuel inlet pipe through the piping and the fuel pump, made to flow from the fuel inlet pipe to the main pipe rail, and is then injected from an injector (not illustrated) into a cylinder (not illustrated).

(6) The main pipe rail is a rail body for a gasoline direct injection engine and includes a plurality of sockets (not illustrated) and the like that are formed at its circumferential wall part and allow the injector to be connected thereto. For example, a four-cylinder engine and an in-line six-cylinder engine are provided with four sockets and six sockets, respectively, which are provided at desired intervals.

(7) FIG. 1 shows the cross-sectional view illustrating the embodiment of the end seal structure of the fuel rail for the gasoline direct injection engine according to the present invention. Referring to FIG. 1, reference numeral 1 denotes a fuel rail body; 1-1, a flow passage; 1-1a, an inner peripheral wall surface; 1-1b, an end-cap-side opening end face (pressure receiving surface); 2, a collar; 2-1, a thread fastening part; 3, a brazed part that couples the fuel rail body 1 and the collar 2; 4, a convex end cap; 4-1, a thread fastening part to be screwed together with the thread fastening part 2-1 provided on the collar 2; 4-2, a pressing surface provided on a surface of the convex end cap, facing the opening end face of the fuel rail body; and 5, a gasket.

(8) Specifically, the end seal structure of the fuel rail for the gasoline direct injection engine according to the embodiment illustrated in FIG. 1 includes: the collar 2 brazed at the outer circumference of the pipe end of the fuel rail body 1 including the flow passage 1-1 and the cylindrical inner peripheral wall surface 1-1a in such a manner that the thread fastening part projects from the pipe end; the convex end cap 4 to be screwed and attached to the thread fastening part of the collar 2; and the gasket 5 that is made of metal and interposed between the opening end of the fuel rail body 1 and the convex end cap 4. The collar 2 is provided with the thread fastening part 2-1 to be screwed together with the thread fastening part 4-1 of the convex end cap 4 in a part of the inner wall surface thereof. Areas other than the projecting part are brazed by the brazed part 3 at the outer circumference of the opening end of the fuel rail body 1 so that the part provided with the thread fastening part 2-1 projects from the opening end of the fuel rail body 1. Further, the gasket 5 is interposed between the opening end face 1-1b of the fuel rail body 1 and the pressing surface 4-2 of the convex end cap 4 that faces the opening end face 1-1b.

(9) In this regard, the fuel rail body 1 and the convex end cap 4 are preferably made of stainless steel or a surface treatment material that is obtained by performing a surface treatment using Ni or a Ni-based alloy on various steel products, such as low-carbon steel, in view of corrosion resistance and pressure resistance. Further, the gasket 5 is preferably made of copper or brass, or a surface treatment material that is obtained by performing a surface treatment, such as plating, on these materials, in view of sealing properties and corrosion resistance.

(10) In the end seal structure of the fuel rail for the gasoline direct injection engine having the structure described above, when an end of the fuel rail body 1 is sealed, the gasket 5 is fitted into the collar 2; the thread fastening part 4-1 of the convex end cap 4 is screwed into the thread fastening part 2-1 of the collar 2; and the convex end cap 4 is tightened in a state where the gasket 5 is brought into contact with the opening end face (pressure receiving surface) 1-1b of the fuel rail body 1. At this time, the gasket 5 is tightened and sealed by an axial force generate due to tightening of the convex end cap 4.

(11) Specifically, in the end seal structure of the fuel rail for the gasoline direct injection engine having the structure described above, the gasket 5 interposed between the opening end face (pressure receiving surface) 1-1b of the fuel rail body 1 and the pressing surface 4-2 located closer to the convex end cap 4 is tightened by an axial force generated due to tightening of the convex end cap 4, which is screwed and attached to the collar 2 fixed by brazing to the opening end of the fuel rail body 1. With this structure, the opening end of the fuel rail body 1 is sealed, and the flow passage 1-1 of the fuel rail body 1, the brazed part 3, and the thread fastening parts 2-1 and 4-1 are completely blocked.

(12) Accordingly, in the case of the end seal structure of the fuel rail for the gasoline direct injection engine, the brazed part 3 that couples the fuel rail body 1 and the collar 2 is the area on which a force (compressive stress) against deformation (swelling toward the outside of the tubular member) in the radial direction of the fuel rail body 1 that is generated under application of an internal pressure to the flow passage 1-1 of the fuel rail body 1 acts. Consequently, an excellent fatigue resistance characteristic can be provided and higher pressure requirements for the internal pressure to be applied to the flow passage 1-1 of the fuel rail body 1 can be met.

(13) Further, since the brazed part 3 that couples the fuel rail body 1 and the collar 2 is not in contact with the fuel (pressure medium) in the fuel rail body 1 due to the action of the gasket 5. Therefore, even when any unevenness exists in the shape of the brazed part, it does not act as a cause of breakage due to the concentration of stress. Furthermore, since a metal seal method is employed in which the gasket 5 is brought into pressure contact with the opening end face (pressure receiving surface) 1-1b of the fuel rail body 1 by an axial force generated due to tightening of the convex end cap 4, the stability and reliability of the seal at the end of the fuel rail body 1 can be ensured.

(14) Note that in the present invention, when the fuel rail body 1 and the convex end cap 4 are made of stainless steel, or a surface treatment material obtained by performing a surface treatment using Ni or a Ni-based alloy on various steel products, the corrosion resistance and pressure resistance are enhanced, which leads to an increase in lifetime. Further, when the gasket 5 is made of copper or brass, or a surface treatment material obtained by performing a surface treatment, such as plating, on these materials, the sealing properties and corrosion resistance are enhanced, thereby further ensuring the stability and reliability of the seal. While the above embodiments illustrate the metal seal method using a gasket as a sealing method, the seal material is not limited to one made of metal. Other materials can also be adopted, as a matter of course.

REFERENCE SIGNS LIST

(15) 1 Fuel rail body 1-1 Flow passage 1-1a Inner peripheral wall surface 1-1b Opening end face 2 Collar 2-1, 4-1 Thread fastening part 3 Brazed part 4 Convex end cap 4-2 Pressing surface 5 Gasket