Abstract
Provided is an end seal structure of a fuel rail for a gasoline direct injection engine, the end seal structure being characterized in that: a pressure receiving surface is formed on an inner wall surface of the end cap having the cap-nut shape, the pressure receiving surface defining a seat surface; a pressing surface is formed at an end of the rail body, the pressing surface defining a seat surface facing the pressure receiving surface; the end cap having the cap-nut shape and including the pressure receiving surface is screwed and fixed to the rail body; and the pressure receiving surface of the end cap is brought into pressure contact with the pressing surface of the rail body by an axial force created by tightening of the end cap having the cap-nut shape so as to seal the end of the rail body.
Claims
1. An end seal structure of a fuel rail for a gasoline direct injection engine, comprising: a rail body composed of a pipe having a pressing surface formed at least at one end of the rail body and defining a spherical seat surface, and external threads formed on the rail body; and an end cap that has a cap-nut shape with a closed end, an open end and an inner wall surface extending from the open end to the closed end, internal threads formed in the inner wall surface, and a pressure receiving surface formed on the inner wall surface of the end cap, the pressure receiving surface defining a concave tapered seat surface and being disposed so that the internal threads are between pressure receiving surface and the open end of the end cap; wherein the end cap is screwed and fixed to the rail body so that the concave tapered pressure receiving surface of the end cap is brought into pressure contact with the spherical pressing surface of the rail body by an axial force created by tightening the internal threads of the end cap to the external threads of the rail body to seal the end of an opening of the rail body.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 is a cross-sectional view illustrating an end seal structure of a fuel rail for a gasoline direct injection engine in accordance with a first embodiment of the present invention.
(2) FIG. 2 is a cross-sectional view illustrating an end seal structure in accordance with a second embodiment of the present invention.
(3) FIG. 3 is a cross-sectional view illustrating an example of a conventional end seal structure of a fuel rail for a gasoline direct injection engine.
(4) FIG. 4 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
(5) A main pipe rail in accordance with the present invention is a main body of a fuel rail for gasoline direct injection engines, in which a fuel inlet pipe (not shown) is connected to one end or a wall surface of the main pipe rail, the fuel inlet pipe is connected by a piping (not shown) to a fuel tank (not shown), fuel of the fuel tank is transferred to the fuel inlet pipe through the piping and a fuel pump, made to flow from the fuel inlet pipe to the main pipe rail, and then injected from an injector (not shown) into a cylinder (not shown). The main pipe rail 1 includes a plurality of sockets (not shown) or the like in its circumferential wall portion, the socket being adapted to allow the injector to be connected thereto. By way of example, a four-cylinder engine and an in-line six-cylinder engine will be equipped with four sockets and six sockets, respectively, which are provided at desired intervals.
(6) In FIG. 1, a reference sign 1 denotes a rail body 1 and a reference sign 2 denotes an end cap 2 with a cap-nut shape. More specifically, in an end seal structure of a fuel rail for a gasoline direct injection engine in accordance with a first embodiment illustrated in FIG. 1, an external thread 1-2 is formed on an outer circumferential surface of an end of the pipe of the rail body 1 that has a cylindrical inner circumferential wall surface 1-1a defining a flow passage 1-1 therein, a tapered section 1-4 is provided at an end of the rail body continuing to the external thread 1-2 and a pressing surface 1-3 defining a spherical seat surface is positioned adjacent to the tapered section. Meanwhile, the end cap 2 having the cap-nut shape and fastened to the outer circumference of the end of the pipe of the rail body 1 includes a pressure receiving surface 2-1 defining a tapered seat surface on an inner wall surface which is a surface facing the pressing surface 1-3 of the rail body 1, the end cap 2 is screwed and attached to the external thread 1-2 formed at the end of the pipe of the rail body 1, and the pressing surface 1-3 provided on the rail body 1 is brought into pressure contact with the pressure receiving surface 2-1 of the end cap 2 having the cap-nut shape by the axial force created by tightening of the end cap 2 having the cap-nut shape and thereby the end of the rail body 1 is sealed.
(7) According to the end seal structure of the fuel rail for the gasoline direct injection engine shown in FIG. 1, when the end cap 2 having the cap-nut shape threadedly attached to the end of the pipe of the rail body 1 is tightened, then the pressing surface 1-3 provided on the rail body 1 brings into pressure contact with the pressure receiving surface 2-1 provided on the end cap by the axial force created by the tightening of the end cap 2 having the cap-nut shape, the end of an opening of the rail body 1 is thus sealed as described above, and as a result, the thread fastening section of the end cap 2 having the cap-nut shape and the rail body 1 and the flow passage 1-1 of the rail body 1 are completely closed. Accordingly, according to this end seal structure of the fuel rail for the gasoline direct injection engine, the thread fastening section of the end cap 2 having the cap-nut shape acts as a compressive stress against deformation in the radial direction of the rail body 1 (swelling toward the outside of the pipe) which is created when an internal pressure acts upon the flow passage 1-1 of the rail body 1. As a result, the thread fastening section exhibits excellent characteristics in terms of resistance to fatigue failure and has the capability of accommodating itself to a higher internal pressure applied to the flow passage 1-1 of the rail body 1. Also, the thread fastening section of the end cap 2 having the cap-nut shape is constructed and arranged such that it does not contact the fuel (pressure medium) in the rail body 1. Accordingly, even if the shape of the thread fastening section has any unevenness, it never acts as a factor that leads to breakage due to concentration of stress. Moreover, the stability and reliability of the seal at the end of the rail body 1 are ensured thanks to the metal seal mechanism that the pressing surface 1-3 provided on the rail body 1 brings into pressure contact with the pressure receiving surface 2-1 provided on the end cap by the axial force created by tightening of the end cap 2 having the cap-nut shape and thereby the end of the rail body 1 is sealed.
(8) An end seal structure of a fuel rail for a gasoline direct injection engine in accordance with a second embodiment shown in FIG. 2 has the same structure as the end seal structure of the fuel rail for the gasoline direct injection engine in accordance with the first embodiment shown in FIG. 1 except that the pressing surface provided on the rail body takes a large spherical shape without the tapered section. Specifically, a pressing surface 11-3 having a spherical seat surface is formed at an end of the rail body continuing to the external thread 11-2 formed on the outer circumference of the pipe of the rail body 11 that has a cylindrical inner circumferential wall surface 11-1a defining a flow passage 11-1 therein, a pressure receiving surface 12-1 having a tapered seat surface is formed on an inner wall surface which is a surface facing the pressing surface 11-3 of the end cap 12 having the cap-nut shape screwed and fixed to an outer circumference of the end of the pipe of this rail body 11, so that the pressing surface 11-3 provided on the rail body 11 brings into pressure contact with the pressure receiving surface 12-1 provided on the end cap 12 having the cap-nut shape by the axial force created by tightening of the end cap 12 having the cap-nut shape, which is screwed and fixed to the external thread 11-2 formed at the end of the pipe of the rail body 11, and thereby the end of the rail body 11 is sealed.
(9) Also in the end seal structure of the fuel rail for the gasoline direct injection engine illustrated in FIG. 2, similarly to the end seal structure shown in FIG. 1, when the end cap 12 having the cap-nut shape threadedly attached to the end of the rail body 11 is tightened, the pressing surface 11-3 provided on the rail body 11 brings into pressure contact with the pressure receiving surface 12-1 provided on the end cap by the axial force created by the tightening of the end cap 12 having the cap-nut shape, thereby the end of the opening of the rail body 11 is sealed as described above, and as a result, the thread fastening section of the end cap 12 having the cap-nut shape and the rail body 11, and the flow passage 11-1 of the rail body 11 are completely closed. Accordingly, also in the case of this end seal structure of the fuel rail for the gasoline direct injection engine, the thread fastening section of the end cap 12 having the cap-nut shape acts as a compressive stress against deformation in the radial direction of the rail body 11 (swelling toward the outside of the pipe) which is created when an internal pressure acts upon the flow passage 11-1 of the rail body 11. As a result, the thread fastening section exhibits excellent characteristics in terms of resistance to fatigue failure and has the capability of accommodating itself to a higher internal pressure applied to the flow passage 11-1 of the rail body 11. Also, the thread fastening section of the end cap 12 having the cap-nut shape is constructed and arranged such that it does not contact the fuel (pressure medium) in the rail body 11. Accordingly, in this embodiment as well, even if the shape of the thread fastening section of the end cap 12 having the cap-nut shape has any unevenness, it never acts as a factor that leads to breakage due to concentration of stress. Moreover, the stability and reliability of the seal at the end of the rail body 11 are ensured thanks to the metal seal mechanism that the pressing surface 11-3 provided on the rail body 11 brings into pressure contact with the pressure receiving surface 12-1 provided on the end cap by the axial force created by tightening of the end cap 12 having the cap-nut shape and thereby the end of the rail body 11 is sealed.
REFERENCE SIGNS LIST
(10) 1, 11 Rail body 1-1, 11-1 Flow passage 1-1a, 11-1a Inner circumferential wall surface 1-2, 11-2 External thread 1-3, 11-3: Pressing surface 1-4: Tapered section 2, 12: End cap having a cap-nut shape 2-1, 12-1 Pressure receiving surface
