GB2571932A

GB2571932A - Common fuel rail port assembly

Info

Publication number: GB2571932A
Application number: GB1803874.5A
Authority: GB
Inventors: Akin Levent; Sert Nihat
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-03-12
Filing date: 2018-03-12
Publication date: 2019-09-18
Also published as: GB201803874D0

Abstract

A fuel rail assembly, eg for a Diesel engine, comprises a common rail with a port 2, eg an outlet port, having a recess 10 accommodating an insert 8 which has a flow bore 9, a first end face 15 for forming a first sealing interface with a corresponding connection surface/seat 16 in the port recess 10, and a second end face 14 to connect or receive a connector end of fuel inlet or outlet component, eg a HP pipe 13. Both surfaces of the insert 8 may be tapered or conical; alternatively the first surface 15 may be flat with a biting surface (figs.4,5). The micro-drill 6 between the rail gundrill 7 and the connected component may be included in the insert 8 (figs.5,6). The flow bore through the insert 8 may have two different diameters, including the micro-drill bore 6 (fig.6). The insert 8 may be provided in a recess 10 in an axial port at an end of the rail 1

Description

Fig. 7b

COMMON FUEL RAIL PORT ASSEMBLY

TECHNICAL FIELD

This invention relates to fuel rails for fuel injected engines and has particular but not exclusive application to high pressure fuel rails for Diesel engines. Such fuel rails are typically referred to as “common rails”.

BACKGROUND OF THE INVENTION

In modern fuel injected engines high pressure fuel from a high pressure pump is provided to a high pressure fuel rail, before fuel is distributed to one or usually a plurality of fuel injectors via ports distributed along the fuel rail. At present such rails are created by machining of all features on one solid material. Only certain add-on components are assembled on to the machined rail body. All other functional features, for instance; inlet and outlet ports, LP piping interface, are created by machining.

Since the rail body is a full solid component, there is no flexibility in adapting machined fuel rails (e.g. outlet and inlet ports) for particular customer requirements where there can be different material selection allowing for example, optimization of hardness level with respect to rail body. Therefore, the problem with current art is that rail as a solid part does not have flexibility in customer interface especially for increasing sealing surface hardness or changing the surface texture at the sealing interface.

SUMMARY OF THE INVENTION

In one aspect is provided A fuel rail assembly comprising a fuel rail, including at least one port, said port including a recess, said port being fluidly connected to the common volume of the fuel rail, said recess accommodating an insert component, said insert component including a first end face adapted to form a first sealing interface with a corresponding connection surface/seat in the port recess, a second end face is adapted to connect or receive a connector end of fuel inlet or outlet component to form a second sealing interface, said insert component including a flow bore from said first face to a second face, such that fuel can flow to or from said common volume and said fuel inlet or outlet component via the bore of said insert component.

Said port may be an outlet port and said outlet component may be a fuel pipe connection pipe for a fuel injector.

Said first surface of said insert and/ or said corresponding connection surface/seat may have tapered or conical surfaces.

Said second surface of said insert and/or said connector end of said fuel inlet/outlet component may have tapered or conical surfaces.

Said port may be fluidly connected to the common volume of the fuel rail via a port bore, said port bore having an opening in said connection surface/seat in the port recess.

Said port bore may have a different diameter to said insert flow bore.

Said insert flow bore may comprise at least two bore portions each portion having different diameters.

The common volume of the fuel rail may be substantially formed from a gundrill.

Said port may include screw means adapted to be used with nut means to tighten the end of the fuel inlet or outlet component onto the second face of the insert and/or to tighten the first face of the insert onto the connection surface of port recess.

The (central) axis of the port may be generally aligned to be perpendicular and or coincident with the axis of the gundrill.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

- Figure 1 shows a partial schematic cross sectional view of a prior art common rail;

- Figure 2 and 3 shows examples of the invention showing a fuel rail port assembly according to embodiments;

- Figure 4 and 5 show further alternative designs according to embodiments of the inventions;

- Figure 6 shows a prior art recess hole design for a port located axially e.g. at the end of the common rail/gundrill;

- Figure 7a shows a recess hole design for a port located axially e.g. at the end of the common rail/gundrill according to one embodiment and figure 7b shows this with an insert.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure 1 shows a partial schematic cross sectional view of a prior art common rail 1 with high pressure outlet (port) 2. The common rail body at the outlet port includes a screw 3 for tightening e.g. by using a nut (not shown) machined into port protrusion 4. Through the protrusion is machined a cone seat 6, with “microdrill” 6 which is a fine bore, and designed to suit customer or application flow requirement. This is machined to the gundrill 7 to provide a flow conduit from the gundrill to the port.

In aspects of the invention an assembly component (insert) which is formed for particular customer application requirement is provided and assembled into the inlet or outlet ports. Such an insert component may be used for each inlet and or outlet ports, and the use of such an insert allows flexibility for the particular application, requirement or customer interface.

For instance, many applications/requirements require an increase in hardness in the sealing interface(s). As the “prior art” full solid rail body, there is a maximum limit due to mechanical properties of the rail (body) itself. Consequently, while hardness increase is limited by rail functional requirements, the use of an insert as in embodiments is advantageous (e.g. to customers) because it will enable to improve HP fuel sealing performance and lead less risk for the rail sealing surface wear during its service life in the field.

The insert may be selectable from varying designs having varying shapes and configurations (e.g. dimensions and angles) as well as different materials such that the insert can provide material and hardness selection flexibility, machining optimization availability. Outlet/inlet ports do not have to be adapted or manufactured specially for the inserts. In other words, a single design of common rail can be used and the flexibility provided by providing different designs of inserts / insert design options. The insert which may be preferably cone shaped at one or both ends and can be used for existing rails. Therefore there is no need to provide bespoke common rails for different requirements. In one example, final rail product after “insert” assembly can be exactly the same from dimensional point of view, as current designs. On the other hand, it is also available to implement any change in customer interface as per customer request.

Figure 2 shows an example of the invention showing a (e.g. cone) insert 8 implementation for an e.g. high pressure port on a fuel rail. Here the insert 8 may be referred to as a cone insert as in examples the inner and/or outer faces of the insert may be formed partially or completely in the shape of a cone or tapered. Sealing between “cone insert” and rail body (Second sealing) may be provided by two different angle oriented cone interface - where the recess in the port of the common rail includes also a conical surface of preferably a different angle to the conical surface of the respective insert end with which it forms an interfaces, to produce a good seal when the screw/nut means is applied to tighten the cone insert and high pressure pipe on the common rail (port).

The figure shows a cross section through a common rail at an outlet port location as before, and similar components have like reference numerals to that in figure 1. Any type of assembly method to fit the insert into the outlet port may be used such as screw means, interference fit, tight fit, clearance fit as before the port include a M14/M16/M20 Screw for tightening (Customer Interface) machined onto the outlet. The port 2 (protrusion 4) is machined to provide a screw for tightening 3 as before and formed or machined to provide a recess 10 with (e.g. tapered/conical) seat 16 so as to receive an insert 8. The insert 8 has a bore 9 (transition hole) located through its central axis allowing flow from the gundrill 7 via a micro hole /bore 12 machined in the rail to the outlet port. In assembly a high pressure oulet pipe 13 (which connects e.g. to the fuel injectors) is connected to the outer surface of the insert, so as to form a seal allowing flow of fuel from the gundrill through the bore in the insert to the outlet pipe. The upper surface of the insert 14 may have a cone shaped (i.e. tapered) recess (which can be regarded as a cone seat) adapted to receive the high pressure connector pipe. The cone narrows towards its proximal end i.e. towards the gundrill.

The lower surface 15 of the insert may be also a further conical surface again narrowing towards the proximal end so as to form a good fit with an appropriately formed seat 16 in the common rail (i.e.such a seat may also include a conical surface).

The invention is not limited to conical surfaces at either or both ends of the insert. Any sealing feature in between “cone insert” and rail can be implemented (or indeed between the cone upper surface and the end of the fuel pipe) such as conical, biting edge, etc. A micro-hole 6 (bore) is machined into the end of the recess to the gundrill allow fuel flow therefrom.

Figure 3 shows an alternative design according to another example of the invention and shows a cone insert implementation in a high pressure port. Like components have the same reference numerals as figure 2. Sealing in between “cone insert” and rail body (Second sealing) is provided by two different angle oriented cone interface. Thus the upper surface of the cone insert may have a cone angle which is somewhat different than the chamfer/taper cone angle of the end of the high pressure pipe to provide enhanced sealing. Similarly the lower surface of the insert may have a somewhat different angle than the tapered/conical recess seat 16 in the outlet port. In this design, there is provided a transition hole/bore 17 machined into the outlet port which connects to the micro-hole 6

Both designs in the examples have two sealing surface. One is between the HP pipe and an upper surface of the insert and the other one is in between the lower surface “cone insert” and rail body. In the figures shown, cone sealing diameters are preferably the same. This means that there is no hydraulic force increase. Furthermore, design options enable lower sealing diameter for the second sealing (in between “cone insert” and rail body) which allows lower hydraulic force.

It would be understood by the skilled person the invention may include various design alternatives. The first or second (upper and lower) sealing surfaces can use as biting edge instead of cone sealing surface. Any form of sealing design or mechanism may be utilized.

In a particular advantageous embodiment, the micro-drill/bore may be provided (i.e. located/formed) within the insert. The insert can be designed to have a bore allowing flow from the common rail to the HP pipe, and which may have any diameter or indeed may have different diameters along the length of the bore, This allows design flexibility.

Figure 4 and 5 shows alternative designs according to embodiments of the inventions where the micro-drill bore 6 is provided within the insert. Like components again have similar reference numerals. Again the insert has a cone formed recess 14 in the upper surface to receive the high pressure connector pipe. The lower surface 15 is generally flat and may include a biting surface to form a seal interface with the lower (generally flat) surfacS 16 in the recess of the main bore in the outlet. A transition bore 17 may be provided from the gundrill to the lower surface of the recess in the outlet, i.e. connected to a bore (microdrill in the insert) to provide a flow conduit for fuel. The skilled person would be aware that such a transition bore may be of any diameter suitable for the application or specification. Again similar components are designated with like reference numerals to previous figures

In addition to example mentioned above (designed for radially connected outlet/inlet ports on to the rail), embodiments also provide design flexibility for HP rail inlet/outlet ports which are arranged in the axial direction, that is at the end(s) of the gundrill where the (central) axis of the port is generally aligned to be perpendicular and or coincident with the axis of the gundrill. The use of inserts allows problems with gundrill position discrepancies (inaccuracies/faults) to be overcome. So for example, where it is required to have one of outlet/inlet ports arranged in the axial direction, it can be almost impossible to design a transition hole or microdrill and gundrill transition interface due to gundrill position discrepancies which are frequent especially for the rails with longer gundrill lengths (for high capacity), the intersection i.e. conjunction of the outlet/inlet port with gundrill is troublesome. To solve such problems conventionally, a recess (hole) design 10 is created to the end of gundrill as can be shown in figure 6 which shows an inlet/ outlet port located/connected with the end of the gundrill e.g. at the end of the rail . However in this case, there may be limited opportunity to machine outlet/inlet port.

Figure 7a shows how according to one embodiment, an extended recess 10 or a “recess hole”/ gundrill with an insert 8 can be used to provide a robust axial inlet/outlet port which does not need to be machined to high tolerances. Figure 7b shows the final assembled outlet/inlet port axially arranged similar to figure 7a with a suitable insert 8. Here the insert has one flat face 20 which rests on a flat rim 21 in the recess, and a distal conical face 22which receives the high pressure pipe (to the injector). The insert includes the micro bore /hole 6 which may have any diameter or have a plurality of diameters along its length.

As a summary, the invention is implemented using an insert component which may include conical tapered or chamfered surfaces to provide sealing between appropriately formed or machined surfaces in the recess of the outlet port and/or the end of the fuel pipe. The invention provides flexibility on customer HP pipe 5 interface. It allows an increase of cone surface hardness, which is the main advantage, as well as overcomes some machining limits and provides an opportunity to better optimize surface texture and geometry discrepancies, in order to improve sealing performance and more service life for customer satisfaction.

The invention can be used for both axial inlet or outlet port implementation on the rail.

Claims

1. A fuel rail assembly comprising a fuel rail, including at least one port, said port including a recess, said port being fluidly connected to the common volume of the fuel rail, said recess accommodating an insert component, said insert component including a first end face adapted to form a first sealing interface with a corresponding connection surf ace/seat in the port recess, a second end face is adapted to connect or receive a connector end of fuel inlet or outlet component to form a second sealing interface, said insert component including a flow bore from said first face to a second face, such that fuel can flow to or from said common volume and said fuel inlet or outlet component via the bore of said insert component.

2. A fuel rail assembly as claimed in claim 1 where said port is an outlet port and said outlet component is a fuel pipe connection pipe for a fuel injector.

3. A fuel rail assembly as claimed in claims 1 or 2 wherein said first surface of said insert and/ or said corresponding connection surface/seat have tapered or conical surfaces.

4. A fuel rail assembly as claimed in claims 1 to 3 wherein said second surface of said insert and/or said connector end of said fuel inlet/outlet component have tapered or conical surfaces.

5. A fuel rail assembly as claimed in claim 1 to 4 where said port is fluidly connected to the common volume of the fuel rail via a port bore, said port bore having an opening in said connection surface/seat in the port recess.

6. A fuel rail assembly as claimed in claim 5 where said port bore has a different diameter to said insert flow bore.

7. A fuel rail assembly as claimed in claims 1 to 6 wherein said insert flow bore comprises at least two bore portions each portion having different diameters.

8. A fuel rail assembly as claimed in claim 1 to 7 where said the common volume of the fuel rail is substantially formed from a gundrill.

9. A fuel rail assembly as claimed in claims 1 to 8 where said port includes screw means adapted to be used with nut means to tighten the end of the fuel inlet or outlet component onto the second face of the insert and/or to tighten the first face of the insert onto the connection surface of port recess.

10. A fuel rail assembly as claimed in claims 1 to 9 where the (central) axis of the port is generally aligned to be perpendicular and or coincident with the axis of the gundrill.