Attachment of metal components by thermal drilling

A method of securing a metal component to a body having a metal wall includes placing the component against the body such that a wall of the component is in external surface contact with the wall of the body. An opening is then thermal drilled through the abutting walls causing thermal flow of material on opposite sides of the abutting walls that, when hardened, joins the component to the body.

The present invention relates to a method of attaching metal components to each other by means of thermal drilling, and more particularly to a fuel rail and method of assembly in which component holders are externally attached to a tubular fuel rail by use of thermal drilling techniques.

BACKGROUND AND SUMMARY OF THE INVENTION

It has been proposed to form openings in metal bodies, including tubular metal bodies, by used of thermal drilling techniques, also known as flow drilling techniques. See, for example, U.S. Pat. Nos. 3,939,683, 4,132,097, 4,185,486, 4,428,214 and 4,454,741. In general, a rapidly rotating piercing tool of hard material is brought into contact with an external surface of the wall of the body. Frictional heat and pressure of the piercing tool against the body cause material to flow axially and radially forming an opening through the wall of the body. The opening is surrounded by an annular collar formed by thermal flow of material along from the tool. That is, the material that is removed to form the opening flows along the surface of the tool to form the annular collar, as distinguished from forming chips or shavings as in typical drilling operations. A general object of the present invention is to utilize thermal drilling techniques of this type to secure two metal components to each other. An illustrative, but non-limiting, exemplary embodiment of the invention employs thermal drilling techniques to join a component holder to the external surface of a tubular fuel rail for an internal combustion engine.

A method of securing a metal component to a body having a metal wall, in accordance with a first aspect of the present invention, includes placing the component against the body such that a wall of the component is in external surface contact with the wall of the body. An opening is then thermally drilled through the abutting walls of the component and the body, causing thermal flow of material on opposite sides of the abutting walls that, when hardened, joins the component to the body.

A method of securing a metal cup-shaped component holder to an external surface of a hollow tubular fuel rail for an internal combustion engine, in accordance with an exemplary embodiment of the invention, includes locating the component holder such that a base wall of the holder is in external tangential surface contact with the fuel rail, and forming an opening through the base wall and through the fuel rail where the base wall is in contact with the fuel rail, by a thermal drilling process, to secure the holder to the fuel rail by thermal flow of material into the holder and the fuel rail surrounding the opening. A fuel rail assembly in accordance with another aspect of the invention includes a hollow tubular metal fuel rail having an external surface and at least one metal component holder externally attached to the fuel rail. The component holder has a flat wall with a first portion in external tangential contact with a second portion of the external surface. The component holder is attached to the fuel rail by means of an annular collar formed by flow of metal from the wall and the tube around an opening that extends through the first and second portions.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1-2illustrate a fuel rail assembly10, in accordance with an exemplary but presently preferred implementation of the invention, as comprising a tubular metal fuel rail12having a plurality of metal component holders14externally secured thereto. Fuel rail12is illustrated as a hollow cylindrical tubular fuel rail, although non-cylindrical geometries could be employed without departing from the scope of the invention. Component holders14are cup-shaped holders having a generally cylindrical side wall15open at its upper end and integrally joined at its lower end to a flat base wall16that is initially imperforate and the major dimension of which extends generally radially of the central axis of wall15. Holders14may be employed, for example, for mounting fuel injectors, dampers, inlet or outlet tubes or the like to the fuel rail assembly. Holder base wall16is in tangential contact with the external surface of the body of tubular fuel rail12. Holders14and fuel rail12may be of any suitable metal construction, such as low carbon steel or stainless steel. A hollow collar18surrounds an opening that extends through the abutting surfaces of fuel rail12and holder14. Collar18has a flange20disposed within the interior of holder14against base wall16firmly holding holder16against the external surface of fuel rail tube12. Thus, as clearly shown inFIGS. 2,5,6and6A, flange20likewise is formed such that its major dimension extends generally radially of the central axis of wall15so that flange20extends parallel to base wall16in snug overlapping clamping relation therewith. A ring22of brazing material preferably externally extends around the abutting surface portions of holder18and fuel rail12additionally securing the holder to the fuel rail.

FIGS. 4 and 5schematically illustrate the method of attaching holder14to tubular fuel rail12in accordance with the present invention. Base wall16of holder14is brought into tangential external surface contact with fuel rail12, and may be temporarily fixtured in this position by suitable means not shown. The abutting portions of the holder and rail are initially imperforate. A rapidly rotating piercing tool24is then brought into contact with base wall16of holder14in alignment with the line of surface contact between holder14and fuel rail12. The speed of rotation of the tool will depend upon the manufacturer, the number of holders simultaneously assembled to the fuel rail, and other factors. In one exemplary implementation of the invention, a 6.35 mm Flowdrill Thermal Drill was used with a Bridgeport Mill operating at about 3000 rpm. Thus, as clearly shown inFIGS. 4 and 5, tool24has a conically shaped pointed tip portion25that merges smoothly at its upper end with a constant diameter cylindrical shank portion27. Shank portion27terminates at its upper end at a radially extending flat abutment undersurface28of a diametrically enlarged follower shoulder portion26of tool24. As tool24is advanced into holder14, a hole is formed through the abutting walls of holder14and fuel rail12by thermal flow of material around the surface of the piercing tool. This material flows radially and axially along tool24into fuel rail12and into holder14where flange20is formed by abutment of the diametrically enlarged follower shoulder portion26of tool24. As illustrated schematically inFIG. 6a, the flow material from holder14generally forms flange20by metal flow radially outwardly between abutment undersurface28and base wall16so as to cause flange20to radially overlap base wall16in clamping relation therewith. This flow of material also forms the inner portion of collar18, and the flow material from rail12generally forms the outer portion of the collar, although these materials flow together so that there (preferably) is no sharp line of demarcation. The material flows weld the parts to each other. Tool24is then withdrawn, leaving holder14attached to fuel rail12by means of the physical structure of collar18after the material has hardened, which effectively welds cup-shaped holder14to the external surface of fuel rail tube12. This securement of holder14to fuel rail tube12by thermal drilling preferably is enhanced by placement of a brazing ring22externally around the portions of the joined surfaces, and subjecting the fuel rail assembly to an otherwise conventional brazing operation.

There have thus been provided a metal component assembly, preferably a fuel rail assembly, and a method of manufacture that fully achieve all of the objects and aims previously set forth. The assembly method of the present invention eliminates any need for separately piercing or drilling the opening in the fuel rail tube, with the consequent formation of shavings or slugs that must be removed from the assembly. The method of assembly in accordance with the present invention also eliminates any need to align preformed openings in the holder and tube, such as by press fit or other alignment techniques. The method of the present invention reduces assembly cost and complexity, and improves the quality of the resulting assembly. The thermal flow weld-like joint holds the components to each other at brazing temperatures (around 2000° F.). The invention has been disclosed in conjunction with an exemplary but presently preferred implementation thereof, and a number of modifications and variations have been discussed. Other modifications and variations will readily suggest themselves to persons of ordinary skill in the art. The invention is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.