A FUEL RAIL

Abstract: A fuel rail for a fuel injected engine is located directly above the engine and is formed by passages (17) in spacers (10, 12, 14) which space an air plenum (24) from the intake manifold (26). The rail has at least one main fuel passage (17) which is straight and on which fuel injector cups (28) are directly mounted with direct communication from the cups to the passage.

Description: This invention relates to a fuel rail for conveying fuel to the injectors of a fuel injected engine, in particular on a V-configuration engine. Fuel integrity i.e. a complete absence of any fuel leakages between the fuel rail and the injectors is of the utmost importance. Conventionally fuel rails have been made by fabrication of sheet metal components. It will be appreciated that in a V-configuration engine, the injectors for one bank of cylinders will be at an angle to the injectors in the other bank, and that the cups which form part of the rail and receive the ends of the injectors must therefore be correspondingly positioned at individually determined angles. In order to ensure fuel integrity, the angle of the cups where they are mounted on the rail must be accurately determined, and this is difficult when the rail is fabricated. For in-line engines it is known (see European Patent Specification 0 132 418) to construct a fuel rail as a single-piece aluminium stamping which is subsequently machined in order to provide the necessary mating surfaces for the injectors and for the fuel inlets and other connections. However it would not be possible, for manufacturing reasons, to construct a stamped rail to duplicate the fuel paths currently provided in a fabricated rail for a V-configuration engine with centrally located air inlet tracts. GB-A-2 142 089 discloses a fuel supply arrangement where a light-metal casting housing is positioned between a cover and an intake pipe. The housing contains passages for fuel and air. The fuel passages lead into fuel supply chambers and a holding element is fitted in each of these chambers. The fuel injectors are then connected to the holding elements. In this arrangement there are two seals between the holding element and the housing and one seal between the housing and the injector. All of these seals have to be carefully controlled for fuel tightness. EP-A-0 233 697, which forms part of the state of the art according to Art 54(3) EPC describes another design of fuel rail for an in-line engine. According to the invention, there is provided a fuel rail for a V-configuration engine which has two angularly offset banks of cylinders, the rail having a spacer body adapted to be located between an air plenum and the inlet manifold of the engine and with air passages therethrough to connect the plenum and the manifold, at least one longitudinal bore which defines a fuel passage extending through the spacer body, and a plurality of fuel injector cups with some of the cups being directed in one direction to receive fuel injectors located in one bank of the engine and others of the cups being directed in a different direction to receive injectors located in the other bank of the engine, characterised in that the spacer body comprises a number of separate spacer members joined together by a rail member or members through which the fuel passage runs, and in that the cups are manufactured in one piece with the spacer body, project from the spacer body and communicate directly with the fuel passage. Where the engine has centrally located air inlet tracts, a single longitudinal bore positioned centrally above the engine can provide the fuel passage so that it is possible to use a single, straight passage to serve the cups for the injectors on both banks of the engine. The rail can be manufactured as an aluminium stamping with subsequent machining to define the internal contours of the cups. This allows the cup positions to be defined much more accurately than was possible with the fabricated manifold. Additionally, the location of the rail member in spacer members which will be bolted between the plenum and the inlet manifold means that the position of the rail is very accurately defined, and there is no possibility of misalignment occurring either during assembly or during servicing. When there is a single, central longitudinal passage and a plurality of spacer members, the rail member preferably forms a dividing wall in the air passage through each spacer member, so that separation between the air passages from the plenum is maintained. The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an isometric view of a fuel rail in accordance with the invention, but showing only two out of the six cups which are actually needed; Figure 2 is a plan view of the fuel rail; Figure 3 is a side view; and Figure 4 is a section through the rail shown in juxtaposition with a plenum chamber and an inlet manifold, and indicating the positions which will be taken up by the fuel injectors. Figure 1 shows a rail 2 for a V6 engine, the rail having three spacer members 10, 12 and 14 connected to one another by a tubular rail member 16 defining a fuel passage extending through and between the spacers. The member 16 will have a continuous bore 17 right through its length, and the usual fuel inlet and fuel return connections will be made to the tube. These connections are not shown in the figures. The right hand end of the tube 16 is shown open to illustrate the bore 17. However in practice the bore 17 will stop short of one end of the tube and will be closed by a sealing plug at the other end. Each spacer has an upper surface 18 and a lower surface 20, and these surfaces are flat, and may be machined if necessary to achieve a truly flat face. The spacers have bores 22 through which fastening bolts can extend. In use, and referring now to Figure 4, the rail 2 is shown mounted between an air plenum 24 and an inlet manifold 26. The plenum 24 has an upper chamber region 25 from which air channels 27 extend downwardly to convey air for engine combustion to inlet passages 29 in the manifold 26. Conventionally the channels 27 lead directly into the passages 29, with a gasket between the respective metal surfaces. The fuel rail is then of a generally E-shape with the limbs of the E carrying the injector cups at the tips of the limbs and projecting into the spaces between the air channels 27 to connect to the injectors. With the construction in accordance with the invention, the downwardly extending channels 27 are shortened by the thickness of the spacer members, for example 14mm, and the parts of the channels which have been removed are replaced by the spacers 10, 12 and 14. Gaskets (not shown) will be provided both above and below the rail to close and seal the air passages between the plenum and the manifold. For connection with fuel injectors mounted in sockets in the manifold 26, injector cups 28 are formed on the portions of the member 16, which extend between the spacer members. In Figure 1 only two of these cups are shown, but in practice, there will be additional cups, two between the spacer members 12 and 14, and two to the right of the spacer member 14, and all six cups are shown in Figure 2 and in Figure 3. Each spacer member has two through passages 30 and 32. These passages are air passages which allow air to pass from the plenum 24 into the respective inlet passages 29 of the inlet manifold. The passages 30 and 32 are separated by a wall 38. The wall 38 can have any suitable cross-sectional shape provided that it has sufficient material to be able to form continuous walls for the bore 17. It will be preferable for the wall to be shaped with reference to the shape of the passages 30 and 32 so that no unnecessary restriction to air flow occurs and so that an effective seal can be provided between the passage 27, 30 and 29 and the passage 27,32 and 29. The whole rail can be formed in one piece by an aluminium stamping process which is in itself known. After stamping, a machining step will occur which involves a boring operation to form a continuous passage the length of the rail down the centre of the member 16, and subsidiary boring operations to form the injector seats in the cups 28. This machining, together with the formation of the necessary inlet and outlet connections, is described in EP-PS 0 132 418. It may also be necessary to machine the faces 18 and 20 of each spacer member so that the associated gaskets can provide and maintain a good seal between the adjacent components. In Figure 4 the location of two of the injectors is indicated by their centre-lines 38. To assemble this rail to an engine, the injectors are first mounted in their respective cups 28 in the fuel rail, the rail is then lowered onto the manifold, with the bores 22 locating on studs or registering with corresponding tapped bores in the manifold, the rail is lowered and the injectors are manipulated into place in the inlet manifold sockets. A gasket is placed on the top of the rail (there is also a gasket between the rail and the manifold) and the plenum 24 is then lowered on top and the plenum is fastened down to the manifold thus trapping and sealing the spacer members and the rail in place on the head.

Claims: A fuel rail (2) for a V-configuration engine which has two angularly offset banks of cylinders, the rail having a spacer body (10,12,14) adapted to be located between an air plenum (24) and the inlet manifold (26) of the engine and with air passages (30, 32) therethrough to connect the plenum and the manifold, at least one longitudinal bore (17) which defines a fuel passage extending through the spacer body (10,12,14), and a plurality of fuel injector cups (28) with some of the cups (28) being directed in one direction to receive fuel injectors located in one bank of the engine and others of the cups being directed in a different direction to receive injectors located in the other bank of the engine, characterised in that the spacer body comprises a number of separate spacer members (10,12,14) joined together by a rail member or members through which the fuel passage runs, and in that the cups (28) are manufactured in one piece with the spacer body, project from the spacer body and communicate directly with the fuel passage. A fuel rail as claimed in any Claim 1, wherein the rail member forms a dividing wall in the air passage through each spacer member, so that the separation between the air passages from the plenum is maintained. A fuel rail as claimed in Claim 1 or Claim 2 for an engine which has centrally located air inlet tracts, wherein a single longitudinal bore is positioned centrally above the engine to provide the fuel passage so that it is possible to use a single, straight passage to serve the cups for the injectors on both banks of the engine. A fuel rail as claimed in any preceding claim, which is manufactured as an aluminium stamping with subsequent machining to define the internal contours of the cups.

Inventors: HAIGH, MATTHEW, HERBERT, MARTIN JOHN DONALD, O'LEARY, WILLIAM JOSEPH JAMES 10 VINCENT LODGE
Applicants: FORD FRANCE SOCIETE ANONYME, FORD MOTOR COMPANY LIMITED, FORD-WERKE AKTIENGESELLSCHAFT
Application year: 1987
Main classification: F02M55
IPC codes: F02M37, F02M55, F02M69