Fuel injector rail assembly for direct injection of fuel

A fuel rail assembly includes a fuel injector socket having a cylindrical end for receiving an injector and a boxed end for orienting and positioning the injector relative to the engine cylinder. A boxed shape end cap is fitted over the boxed end of the socket thereby supporting the socket. Planar saddle members are disposed on each side of the end cap and radiused edges are fitted to the cylindrical surface of the fuel distribution tube. A jump tube communicates fuel from the fuel distribution tube to the fuel injector socket. A bracket defines a sole plate for the assembly, for attachment to an engine head, and includes a generally planar surface for locating against the planar surface of the saddle members. Components of the fuel rail assembly are first assembled loosely on a fixture, then joined together as the fuel rail assembly.

TECHNICAL FIELD

The present invention relates to fuel rail assemblies for supplying fuel to fuel injectors of internal combustion engines; more particularly, to fuel rail assemblies for supplying fuel for direct injection of gasoline (DIG) or diesel fuel (DID) into engine cylinders; and most particularly, to an improved injector socket and socket bracketry used in the assembly.

BACKGROUND OF THE INVENTION

Fuel rails for supplying fuel to fuel injectors of internal combustion engines are well known. A fuel rail assembly, also referred to herein simply as a fuel rail, is essentially an elongate fuel manifold connected at an inlet end to a fuel supply system and having a plurality of ports for mating in any of various arrangements with a plurality of fuel injectors to be supplied. Typically, a fuel rail assembly includes a plurality of fuel injector sockets in communication with a manifold supply tube, the injectors being inserted into the sockets and held in place in an engine head by bolts securing the fuel rail assembly to the head.

Gasoline fuel injection arrangements may be divided generally into multi-port fuel injection (MPFI), wherein fuel is injected into a runner of an air intake manifold ahead of a cylinder intake valve, and direct injection (DIG), wherein fuel is injected directly into an engine cylinder, typically during or at the end of the compression stroke of the piston. Diesel fuel injection is also a direct injection type.

For purposes of clarity and brevity, wherever DIG is used herein it should be taken to mean both DIG and DID, and fuel rail assemblies in accordance with the invention as described below are useful in both DIG and DID engines.

DIG fuel rails require high precision in the placement of the injector sockets in the supply tube because the spacing and orientation of the sockets along the fuel rail assembly must exactly match the three-dimensional spacing and orientation of the fuel injectors as installed in cylinder ports in the engine. Further, a DIG fuel rail must sustain much higher fuel pressures than a MPFI fuel rail to assure proper injection of fuel into a cylinder having a compressed charge. DIG fuel rails may be pressurized to 100 atmospheres or more, for example, whereas MPFI fuel rails must sustain pressures of only about 4 atmospheres. The DIG injector is mounted directly into the cylinder head. Thus, the precision positioning of the each injector socket relative to its mounting hardware and particularly its respective cylinder port, and the integrity of the weld and braze joints that serve to accurately position the socket along the fuel tube are critical to the performance of the fuel delivery system.

Efforts to form satisfactory DIG fuel rails by metal forming the sockets and welding them to the fuel tube have resulted in limited success. The fabricating processes can produce significant stresses in the formed parts, and even slight misalignments of components such as sockets mounted into the distribution tube can create even further stresses when the assembly is bolted to an engine head.

To address these issues, DIG fuel rails have been formed with integrated sockets by precision casting followed by boring of various passages, or by precision/high cost machining of stainless steel. However, prior art cast fuel rails suffer from at least three serious shortcomings. First, they are expensive to manufacture, requiring multiple steps in casting, boring, and finishing. Second, they are typically an aluminum alloy, which is known to be subject to attack by some fuels. Desirable resistant alloys such as stainless steel are more costly to cast. Third, because the integrated fuel rail and sockets have been formed as one piece, tolerances that may exist between the one piece assembly, the cylinder head and the cylinder itself can still cause misalignment of the injectors, after assembly. This can result in unacceptable stresses placed on the rail, sockets and the injectors.

These shortcomings of the integrated rail and sockets design have been addressed in U.S. Pat. No. 7,159,569 to Keegan et al. (hereinafter the '569 patent), issued on Jan. 9, 2007 and entitled FABRICATED FUEL RAIL ASSEMBLY FOR DIRECT INJECTION OF FUEL, of which relevant portions are hereby incorporated by reference. Disclosed therein is a fuel rail assembly wherein the rail and sockets are provided with saddle members and flanges and a jump tube fluidly connecting each socket to the fuel rail through a hole pierced in the side of the socket. The pieces are first loosely assembled in a jig to achieve a precise orientation and location for each of the sockets. Then, once the precise orientation and location is achieved, the sockets, jump tubes and rail are permanently jointed together as by welding or brazing. Thus, a precise positioning of the sockets relative to the cylinder itself can be attained in the X, Y and Z directions, independent of the tolerance stack up that heretofore has been found to exist. Also, the individual components can be fabricated less expensively as compared to the machined integrated tube/socket design. For example, the sockets may be deep drawn or formed from sheet steel instead of being cast and machined. However, this design suffers from a drawback in that the sockets are generally cylindrical making it difficult to fabricate a hole in the side of each socket to sealably receive a jump tube. Further, the saddle members and flanges that serve to precisely position the sockets must depend on the end flange of the socket as a locating reference point and cannot utilize the rounded portion of the cylindrical sockets to locate the positioning joints with the necessary accuracy.

What is needed in the art is a fuel rail assembly for DIG engine fuel systems, whose components can be fabricated inexpensively.

What is further needed in the art is a DIG fuel rail assembly that can precisely position each fuel injector socket relative to its respective cylinder independent of the tolerance stack-up of the combined components.

What is further needed in the art is a DIG fuel rail assembly wherein the jump tubes can be reliably positioned and sealed to the fuel injector sockets.

It is a principal object of the present invention to provide an inexpensive, high-precision fuel rail assembly for use with a DIG or DID internal combustion engine.

SUMMARY OF THE INVENTION

Briefly described, a fuel rail assembly, in accordance with the invention, includes a fuel injector socket having a cylindrical end for receiving a fuel injector and a boxed end for accurately orienting and positioning the injector relative to the engine cylinder. An end cap member, similarly boxed shape, is fitted over the boxed end of the socket supporting the socket on one or more sides. Planar saddle members are disposed on each side of the end cap member and include radiused edges for fitting to the outside contour of the cylindrical surface of the fuel distribution tube. A jump tube communicates fuel from the fuel distribution tube to the boxed shape end of the fuel injector socket. A bracket defines a sole plate for the assembly, for attachment to an engine head, and a generally planar surface for locating against the planar surface of one of the saddle members. Preferably, all components are formed of a non-reactive, brazable alloy such as stainless steel, for example, 304 stainless steel.

Components of a fuel rail assembly in accordance with the invention may be first assembled loosely on a precision fixture, then joined to fix relationships and brazed and fired in a brazing oven to produce a precision, fuel rail assembly.

The fuel injector socket, including its cylindrical portion and its boxed end portion, may be formed as one piece from sheet steel or its boxed end portion and cylindrical portion may be formed separately and joined together. The bracket and one saddle may also be formed in one piece. On one aspect of the invention, the planar surface of the saddle members may be located directly against the boxed end surfaces of the fuel injector socket. Thereby eliminating the end cap member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIG. 1, prior art fuel rail assemblies110, as generally disclosed in the '569 patent, are shown exemplarily arranged as for use on a V-8 engine112(left assembly110L, right assembly110R). For simplicity, the following description of the prior art assembly deals solely with left assembly110L (referred to herein below as “110”) but should be taken as applying equally to right assembly11OR.

Referring toFIGS. 1 through 3, fuel rail assembly110comprises a metal bracket118having a foot portion120, defining a sole plate for mating with an engine head via bolts152through bracket bolt holes150, and a flange portion122(FIG. 2) formed generally orthogonal to foot portion120for structural rigidity. Foot portion120is provided with a plurality of openings124for receiving a plurality of formed sockets126, each having a flange128at the open end of the socket for mating with the underside surface130of portion120. Openings124are oversize to allow lateral positioning adjustment of sockets126during assembly of the fuel rail. Bracket118further comprises a flange132at each end for supporting a saddle134. Supported by saddles134is a fuel distribution tube136. Fuel supply tube and fittings138at a first end and a cap140at a second end of fuel distribution tube136are shown, a known in the art. Each socket126is provided with an opening142through a side of rounded cylindrical portion143, and distribution tube is provided with a plurality of matching openings144, wherein jump tubes146are received for supplying fuel from tube136to each socket126.

Note that it is an important feature of the fuel rail assembly disclosed in the '569 patent that the assembly fit precisely onto an engine head wherein the fuel injectors have been inserted and are extending from their respective precision bores. Accordingly, the components of the fuel rail are first assembled loosely onto a fixture simulating such an engine head, to assure proper orientations and positions of the components in the X, Y and Z directions, then are secured to each other to prohibit further relative movement.

Referring now toFIG. 4, a second embodiment210of a fuel rail assembly of the prior art, as disclosed in the '569 patent, is similar to first embodiment110except that single bracket118is replaced by a plurality of individual brackets218, one for each fuel injector position. Each bracket218comprises a sole plate220and a generally orthogonal first flange222for structural rigidity. A second flange232on bracket218is supportive of a saddle234, one for each bracket218. Saddles234are supportive of fuel distribution tube236. Brackets218are provided with oversize slotted openings224for receiving sockets226which are retained by retaining plates290. Jump tubes246are connected between distribution tube236and sockets226. Brackets218are provided with elongated bolt holes250for bolting assembly210to an engine head.

Referring toFIGS. 5,6and7, fuel rail assembly310in accordance with the invention is shown. Fuel rail assembly310includes, as its main components, fuel distribution tube336, jump tube346, fuel injector sockets326, and various saddles and flanges to assure precise orientation and positioning of the sockets. Referring toFIG. 5in which the surrounding components of the third from left injector socket have been left out for clarity of description, andFIG. 5a, socket326includes central axis358and elongate body portion360, generally cup-shaped and closed at a first end362. Second end364is open and defines flange366. Elongate body portion includes cylindrical section368adjacent flange366for sealably receiving an end of a fuel injector assembly (not shown) as known in the art. Cylindrical section368and flange366are similar to the open end of injector sockets known in the art.

In accordance with the invention, elongate body portion360of socket326also defines boxed section370. The boxed section includes first planar opposing sides372a,band seconded planar opposing sides374a,b. Sides372a,band374a,bare formed in planes generally parallel to socket central axis358. In one aspect of the invention, one of said first and second set of planar opposing sides is longer than the other, such as sides372a,bare longer than sides374a,bas shown inFIG. 7. Boxed section370is closed at first end362, opposite flange366, thereby forming a generally cup shaped fuel injector socket as known in the art, the primary difference being boxed section370. Socket326may be readily formed or drawn from sheet steel. An opening342is formed in one of the sides372a,372b,374a,374bto receive jump tube346during assembly of fuel rail assembly310. In one aspect of the invention, opening342is formed in one of the longer sides372afor receiving jump tube346to add rigidity to the longer planar side for opposing the high pressures of the DIG system. Jump tube346may include collar348. A corresponding opening343is formed in fuel distribution tube for receiving the other end of jump tube346.

Referring again toFIGS. 5,6and7, mounting assembly380is shown for precisely orienting and locating the sockets relative to their respective cylinders in accordance with the invention. Mounting assembly380includes, for each fuel injector socket, a mounting bracket382, a first saddle388a, a second saddle388band a socket end cap392. Each bracket382comprises a base plate384and a generally orthogonal first flange386. Base plate384is provided with a hole350for mounting the bracket and the rail assembly to the cylinder head (not shown) with a bolt (not shown). First saddle388aadjacent bracket382includes a generally planar surface389and further includes a radiused edge390supportive of fuel distribution tube336and shaped to closely fit the outer circumferential contour of fuel distribution tube336. First saddle388amay also include first saddle flange391generally orthogonal to planar surface389for structural rigidity. Socket end cap392, disposed adjacent first saddle388a, is generally box-shaped including opposing planar sides394aand394bdisposed in planes parallel to each other, third side396and top398. Side399is open to permit passage of jump tube346from fuel distribution tube336to fuel injector socket326. The box-shape of socket end cap392is sized to freely receive boxed section370of fuel injector socket326. Second saddle388b, adjacent end cap392, is generally planar and, similar to first saddle388a, includes planar surface389and a radiused edge390supportive of fuel distribution tube336and shaped to closely fit the outer circumferential contour of fuel distribution tube336.

To assure accurate positioning of the fuel injector socket, fuel rail assembly310may be sub-assembled in an assembly fixture having mandrels simulating fuel injectors in an engine and a first reference feature simulating the mounting points of brackets382to the cylinder head, and a second reference feature correctly positioning fuel distribution tube336, axially, relative to the cylinder head. In this manner, the fuel injector sockets have freedom of movement in the X, Y and Z directions (FIG. 5) to be first precisely located and oriented before being fixed in place by welding and brazing.

An exemplary method of assembling fuel rail assembly, in accordance with the invention, comprises the steps of:

a) installing a socket326onto each mandrel to a predetermined axial and rotational position;

b) inserting a first end of a jump tube346into each socket opening342of side372aof the socket;

c) positioning a fuel distribution tube against the second reference feature of the fixture while at the same time inserting a second end of each jump tube346into receiving holes343formed in the fuel distribution tube;

d) fitting socket end cap392over boxed section370of first end360of the fuel injector socket so that planar opposing side374aof section370is proximate opposing side394aof the socket end cap, planar opposing side374bof section370is proximate opposing side394bof the socket end cap, and planar side374bof section370is proximate third side396of the socket end cap;

e) engaging radiused edges390of saddles388a,bwith the circumferential outer surface of the fuel distribution tube336and the planar surfaces389of saddles388a,bwith sides394aand394bso that planar surfaces lie flat against sides394a,band generally perpendicular to the longitudinal axis of the fuel distribution tube;

f) locating a mounting bracket against the first reference in the assembly fixture and such that first flange386of the bracket is flatly in contact with saddle388a;

g) joining, as for example by tack welding, all components together;

h) applying a braze filler metal to all joints and seams to form a “green” fuel rail assembly; and

i) heating the green assembly, as in a brazing oven to seal and/or loin with braze all joints and seams.

As compared to the prior art, fuel rail assembly310, in accordance with the invention, beneficially provides flat mating surfaces between bracket382and saddle388a, between saddle388aand socket end cap392, and between socket end cap392and saddle388bfor improved weld/brazed joints and for more accurately orienting and positioning the fuel injector sockets within the assembly. Further, the close fit of socket end cap392over the top and three sides of boxed end section370of the fuel injector socket provides support to the planar walls of the socket under the higher fuel pressures of the DIG system. Rigidity is added to the fourth wall by the jump tube.

While the entire elongate body360of socket326, including boxed section370and the lower tubular cylindrical section of the body is shown as formed as one piece, it is understood that the lower section and boxed section may be formed separately and then joined and sealed together, and that the boxed section may then be machined instead of drawn from sheet stock.

While the first saddle and bracket are shown as separate components, it is understood the two could be formed as one piece, in accordance with the invention.

While a box-shaped socket end cap is shown fitting between the boxed section of the fuel injector socket and the first planar saddle to add structure rigidity to the boxed section of the socket, it is understood that the socket end cap may be eliminated and the first planar saddle be disposed directly against one of the planar sides of the boxed section of the fuel injector socket.