Fuel Injector Assembly and Sleeve Insert

Abstract

 A fuel injector assembly for use in an internal combustion engine, and a sleeve insert for such a fuel injector assembly, are disclosed. The injector assembly has first and second components, each component associated with an intended common axis for the injector assembly. A sleeve insert is disposed between the first and second components, the sleeve insert being arranged in contact with at least one of the first and second components to align the at least one component towards the intended common axis.

Description

Technical Field

[0001] This invention is directed to a fuel injector assembly for an internal combustion engine, and a sleeve insert for such an assembly. In particular, but not exclusively, the invention relates to a fuel injector assembly for use in a compression ignition internal combustion engine.

Background to the invention

[0002] Various types of fuel injection system are known. For example, common rail fuel systems have a common rail pump for supplying fuel to a common rail, which in turn supplies fuel to a plurality of injectors of the fuel system. In unit injector fuel systems, each injector has a dedicated pump. Other types of injection system are known.

[0003] In many such fuel systems, fuel is supplied at high pressure to one or more injectors, each arranged to inject fuel into an associated engine cylinder. For example, in some systems fuel pressure is applied and reduced in order to close and open a valve, by which means fuel is intermittently injected into the cylinder. In certain systems, solenoids or piezoelectric actuators open and close the valve.

[0004] In such (and other) systems, high and variable pressures are present between various components of the injector. For example, high pressures are commonly present around the tips of such injectors, along the injector nozzle needle and between this and surrounding components such as the nozzle body and barrel.

[0005] For these reasons, the arrangement and alignment of components making up the injector assembly can be important in maintaining pressure and avoiding malfunctions. Precise machining of these components is commonly required.

[0006] For example, on current fuel injector design a very precise concentricity level between inner components is usually required. The axes or bores of the components must match or be aligned as closely as possible. This usually requires grinding machining of contact faces between the components, for example to remove surface inconsistencies which might result in misalignment of components and thus lack of concentricity between the components. Such components are generally located in high pressure areas of the system, and some participate in sealing functions.

[0007] Concentricity of and between such components has previously been addressed using special geometries for the contact faces of the components. However, such geometries typically make grinding/machining more difficult.

[0008] Fig. 1 shows an example of two such inner components (barrel 106 and nozzle body 108) which have a high pressure sealing function, but this could be applicable to other inner components within the fuel injector. The barrel and nozzle body surround the nozzle needle 104, and are themselves enclosed by the cap nut 102. The nozzle body and nozzle needle protrude from the end of the cap nut.

[0009] A raised annular lip or ring has been formed on the nozzle body, for insertion into an annular cavity on the barrel. This is intended to aid alignment, but features and shapes such as this annular ring make machining the components much more difficult, and obtaining sufficient grinding finishes on these components, particularly on the contact faces between them, more problematic.

[0010] The present invention aims to address these problems and provide improvements upon the known devices and methods.

Summary of invention

[0011] Aspects and embodiments of the invention are set out in the accompanying claims.

[0012] In general terms, one embodiment of a first aspect of the invention can provide a fuel injector assembly for use in an internal combustion engine, the injector assembly comprising: first and second components of the injector assembly, each component associated with an intended common axis for the injector assembly; and a sleeve insert, disposed between the first and second components, the sleeve insert being arranged in contact with at least one of the first and second components to align the at least one component towards the intended common axis.

[0013] The use of a sleeve insert provides a simpler system for improving concentricity between components, which is also more simple to assemble. The sleeve insert is separate from the first and second components, and can therefore be inserted between components during assembly. These features in turn allow straightforward grinding of contact surfaces between the components.

[0014] The sleeve insert can act as a centering device between two components, aligning at least one component more closely with a central axis, or an axis of the other.

[0015] Preferably, the first and second components are inner components of the injector assembly, arranged in series in the direction of the intended common axis. More preferably, the assembly further comprises an outer housing for inner components of the injector assembly.

[0016] In an embodiment, the second component is an inner component of the injector assembly, and the first component is an outer housing for inner components of the injector assembly. Such an arrangement can provide a simple centering effect to align the second component inside the first.

[0017] Suitably, the intended common axis is an axis of the first component, and the sleeve insert is arranged to align the second component towards the axis of the first component.

[0018] In an embodiment, the intended common axis is an axis of an injector nozzle to be contained by the first and second components. The sleeve insert may be arranged to align at least the second component towards the axis of the injector nozzle.

[0019] Suitably, the sleeve insert is disposed around an outer side of the at least one component.

[0020] In an alternative embodiment, the sleeve insert is disposed around an inner side of the at least one component. Preferably, the sleeve insert is disposed around an outer side of a further inner component, such as an injector nozzle.

[0021] In an embodiment, the sleeve insert is arranged in contact with both of the first and second components, to align the second component towards the axis of the first component.

[0022] Preferably, the sleeve insert is elongated in the direction of the intended common axis. The sleeve insert may be configured to span a junction of the first and second components, and may overlap a portion of each of the first and second components. More preferably, the sleeve insert is configured to contact the overlapped portions of the first and second components to maintain an alignment of the first and second components in the direction of the axis of the first component.

[0023] Suitably, the sleeve insert is accommodated by a notch in the at least one component. Preferably, the accommodation of the sleeve insert by the notch provides a flush surface between an outer or inner perimeter of the at least one component and an outer or inner perimeter of the sleeve insert. In one embodiment, the sleeve insert is accommodated by a pair of notches, one in each of the first and second components.

[0024] Suitably, the sleeve insert is arranged to provide a seal against a high pressure environment at a core of the fuel injector assembly. The sleeve insert may be configured to span the junction of the first and second components, and may overlap a portion of each of the first and second components. The sleeve insert may be configured to contact the overlapped portions of the first and second components to maintain an alignment of the first and second components in the direction of the axis of the first component.

[0025] Such features allow the high pressure environment around such components to be maintained. For example, where the sleeve insert spans a junction on an inner side between components, leakage between the components at the junction can be limited. In addition, as the sleeve insert may be machinable to a higher tolerance than other components, a seal around enclosed components, such as a nozzle needle, can be improved.

[0026] In an embodiment in which the sleeve insert is arranged to provide a seal against a high pressure environment at a core of the fuel injector assembly, the first and second components arranged in series each may, but need not, surround the core of the fuel injector assembly, the core extending in the direction of the intended common axis.

[0027] Suitably, the fuel injector assembly further comprises a third component of the injector assembly, the sleeve insert disposed between the first and third components, and in contact with each of the first, second and third components.

[0028] The first and second components may have similar diameters. The first and second components may be cylindrical, or each comprise at least one portion having a circumference. The first and second components may be a barrel or upper housing, and a nozzle body, respectively, of a fuel injector assembly, and the outer housing may comprise a cap nut.

[0029] One embodiment of a second aspect of the invention can provide a sleeve insert for a fuel injector assembly according to any of the above embodiments.

[0030] The above aspects and embodiments may be combined to provide further aspects and embodiments of the invention.

Brief description of the drawings

[0031] The invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a diagram illustrating a previously considered fuel injector assembly; and

Figures 2 and 3 are diagrams illustrating fuel injector assemblies according to embodiments of the invention.

Detailed description of preferred embodiments

[0032] The following embodiments generally provide a fuel injector assembly in which a sleeve insert is used to centre or align components of the injector assembly. These are generally more simple than previously considered methods for addressing alignment, concentricity and machining issues.

[0033] The benefits of these embodiments are:

• improving the concentricity level between two (or more) inner components
• simplifying the design of the contact faces between the two (or more) inner components
• simplifying the machining operations of those two (or more) inner components
• possibly removing the grinding operation on contact faces of the two (or more) inner components
• simplifying the assembly process of the two (or more) inner components
• improving (in the case of the inner centering sleeve) the inner sealing function

[0034] One such embodiment is outlined below. In order to overcome geometric constraints on inner components that need to be resistant to high pressure (such as requiring an annular lip as in Figure 1) and complex assembly processes, the embodiment provides a centering or alignment sleeve between the two (or more) inner components.

[0035] This sleeve may be located at two different positions:

• on a direct high pressured fuel side - an inner centering sleeve (Figure 2)
• on an outer, cap nut side - an outer centering sleeve (Figure 3).

[0036] Figure 2 illustrates the first type of centering or alignment sleeve insert, in a fuel injector assembly. This diagram shows the tip of a fuel injector assembly; embodiments of the invention are similarly applicable to other parts of such an assembly, where two or more components can usefully be better aligned than they otherwise might be, or be more simply aligned compared to previous attempts.

[0037] In similar fashion to Figure 1, the assembly comprises a cap nut 202, nozzle needle 204, barrel 206 and nozzle body 208. The cap nut encloses the inner components of the assembly, although the nozzle needle and nozzle body protrude slightly from the end of the nut. The cap nut is generally cylindrical, with an inner annular shoulder abutting internal components, preventing their egress from the assembly.

[0038] The barrel 206 and nozzle body 208 are arranged in series along the axis of the assembly, and are enclosed within the cap nut, both abutting an inner side of the cap nut. The barrel and nozzle body are also generally cylindrical. A junction between the contact faces of the barrel and the nozzle body extends around a plane perpendicular to the injector axis.

[0039] A bore through the barrel 206 and nozzle body 208, along the axis of the assembly, houses the nozzle needle. This bore and the nozzle needle are a particular focus of the high pressures acting on the injector. Therefore it is important that this inner, high pressure fuel side of the components is adequately sealed.

[0040] The sleeve insert (210) is positioned at the junction between the barrel and nozzle body, spanning the junction between the components. In this embodiment, the sleeve is on an inner side of these components, in the bore defined through them. The sleeve is recessed into both the barrel and the nozzle body, thereby presenting a continuous flush surface along the inner side of the barrel, then along the inner side of the sleeve, then along the inner side of the nozzle body. This surface houses the nozzle needle in the bore along the assembly.

[0041] The recession is achieved by means of an annular notch or cavity in each of the barrel and nozzle body, the cavities or notches opposing each other across the junction. The sleeve insert is generally ring-shaped, with a rectangular cross section extending in the direction of the injector axis. Each cavity is generally as deep as half the length of this rectangular cross section, so that around half of the sleeve is accommodated on either side.

[0042] The sleeve insert therefore provides a centering or concentricity improving role; the two components, here the barrel and nozzle body, are essentially prevented from moving with respect to each other in the plane perpendicular to the injector axis, as the sleeve contacts an inner face of both of the components. Any difference or misalignment of the axes or bores of the two components in the injector assembly is largely corrected, as the opposing cavities are brought into alignment by the sleeve spanning the junction. Therefore any lack of concentricity between the two components is minimised.

[0043] In similar fashion the inner sleeve (as opposed to the outer sleeve later described) can help to correct a slightly eccentric bore in one or both of the components; the bores of the components will be aligned by the sleeve, preserving as far as possible the trueness of the inner bore housing the needle, to maintain the high pressures involved.

[0044] The sleeve spans the junction between the barrel and nozzle body, helping to seal the high pressure environment on the inner side in the bore of the injector. Leakages along the junction, between the contact faces of the components, are minimised. The effect is compounded by the higher pressure on the inner side of the injector, in the bore housing the needle; this additional pressure is applied radially against the inner side of the sleeve, helping the sleeve to plug against the cavities and the junction.

[0045] The sealing effect may also be improved by the sleeve, due to the likely greater tolerances available for machining such a simple ring component, as compared to the more complex barrel and nozzle body. The inner surface of the sleeve may therefore provide an improved surface as compared to the inner surface of the barrel and nozzle body. The inner surface of the sleeve may be smoother, and/or have better circularity than the barrel/nozzle body, thereby providing a better seal against the nozzle needle.

[0046] Figure 3 illustrates the second type of centering or alignment sleeve insert, in the fuel injector assembly. In similar fashion to Figures 1 and 2, the assembly comprises a cap nut 302, nozzle needle 304, barrel 306 and nozzle body 308.

[0047] In this embodiment, the sleeve insert (310) is on an outer side of the components, between the components and the cap nut. Again the sleeve is recessed into both the barrel and the nozzle body, thereby presenting a continuous flush surface, this time along the outer side of the components and sleeve. This surface abuts the inner side of the cap nut.

[0048] The recession is again achieved by means of an annular cavity in each of the barrel and nozzle body, the cavities opposing each other across the junction. This time the cavities are cut into the outer side of the components, rather than the inner side as in Figure 2.

[0049] The sleeve insert therefore again provides a centering or concentricity improving role; the two components, are again prevented from moving with respect to each other in the plane perpendicular to the injector axis, as the sleeve contacts an outer face of both of the components. Any difference or misalignment of the axes of the two components in the injector assembly is largely corrected, as the opposing cavities are brought into alignment by the sleeve spanning the junction. An outer sleeve insert of this type could be used for its centering function alone. For example, the sleeve could be introduced around an inner component, such as either the barrel or nozzle body, simply to centre that component in the bore of the cap nut, to align the axis of the component with that of the cap nut. In such a use, the sleeve would likely not be recessed into the component, in order to provide the centering function. Such a centering function could be used instead of or in addition to embodiments in which the sleeve spans two or more components.

[0050] The use of the sleeve insert in either the inner or outer sleeve configuration may reduce or remove completely the need for the grinding operation on contact faces of the two (or more) inner components, with grinding finishing only on the centering sleeve.

[0051] Surface inconsistencies which might otherwise result in misalignment of components, and thus lack of concentricity between the components, should no longer affect concentricity due to the sleeve's aligning/centering effect. The sleeve can be made long enough in the axial direction so that such irregularities project no further from either contact face than the span of the sleeve across the junction. In such a case, the grinding on these contact faces may no longer be used. Grinding of certain surfaces may nevertheless be needed, particularly on the inner side or surface of the sleeve which aims to help provide a sealing function.

[0052] This simplifies the overall manufacture of the injector; it is easier to obtain a pair of flat (or near flat) contact surfaces, and form or carve a notch or cavity of the same size and shape in each opposing surface, than to obtain one such surface and cavity, and then a raised lip, next to a flat surface, to fit into the cavity, as in Figure 1.

[0053] The manufacture or assembly of the injector will also be simplified by use of either type of sleeve insert. For example, the inner components, such as the barrel and nozzle body, can be assembled consecutively into the injector as before, but now with the sleeve inserted as an intervening step. As a smaller, lighter and simpler component, the sleeve will likely be far easier to slot into the cavity or cavities than a lip raised on one component, as in Figure 1.

[0054] In alternative embodiments, the first and second components, whether barrel and nozzle body or others, may have differing diameters. Where a second component has a smaller diameter than the first, the recession on the second may be smaller, or the housing may also change diameter to accommodate the change in size. The sleeve insert may be shaped to compensate, for example the sleeve may be angled or stepped towards the narrower component.

[0055] The components and sleeve may have shapes other than cylindrical. For example, either or both components may be frusto-conical, which may require a different sleeve shape, employing the same principal. For example, if one is differently shaped, the sleeve may be recessed into a similar cavity on both components, or alternatively a slightly different shaped cavity on one side. In embodiments, the sleeve may take a different form at one end to facilitate this.

[0056] The components and sleeve may have cross sections overall or in certain portions which are not circular - for example, elliptical or hexagonal.

[0057] In some embodiments, the sleeve insert may be used to span more than two components. For example an inner or outer sleeve may be positioned between first and third components, and traverse a second component between the first and third. In such an embodiment, a notch may be present on each of the first and third components, but the intermediate component may simply be reduced in diameter by the width of the sleeve to accommodate it.

[0058] The junction and contact faces between components may not necessarily lie in a plane. For example, the faces may take complementary frusto-conical forms, which would still be easier to grind flat than a surface comprising a lip. In such cases, the sleeve insert can be either be recessed in the same way as above, or be formed to match, taking a similar shape to those described above, but with end portions of ring sloped to match the profile of the contact faces.

[0059] The sleeve insert may have a number of optional different design features. For example, the cross section may be square, rectangular or another appropriate geometry, depending on the requirements of the particular assembly. For example, if minimal grinding of the contact faces between the barrel and nozzle body is preferred, a rectangular cross section (or otherwise elongate in the axial direction) may be preferred, in order to span what may be a wider junction due to imperfections in the contact surfaces. The notch or cavity to accommodate the insert will take similar complementary forms.

[0060] The sleeve may be hollow, or have one or more inner cavities - these may provide ease of manufacture, or preferred mechanical properties such as flexibility or rigidity. The sleeve may be a discontinuous ring or cylinder, for example in cases where alignment is more important than sealing performance, and where manufacture of such a ring or cylinder is more convenient.

[0061] It will be appreciated by those skilled in the art that the invention has been described by way of example only, and that a variety of alternative approaches may be adopted without departing from the scope of the invention, as defined by the appended claims.

Claims

1. A fuel injector assembly for use in an internal combustion engine, the injector assembly comprising:

first (206) and second (208) components of the injector assembly, each component associated with an intended common axis for the injector assembly; and

a sleeve insert (210), disposed between the first and second components, the sleeve insert being arranged in contact with at least one of the first and second components to align the at least one component towards the intended common axis.

2. A fuel injector assembly according to Claim 1, wherein the first and second components are inner components of the injector assembly, arranged in series in the direction of the intended common axis.

3. A fuel injector assembly according to Claim 2, further comprising an outer housing (202) for inner components of the injector assembly.

4. A fuel injector assembly according to any preceding claim, wherein the intended common axis is an axis of the first component, and wherein the sleeve insert is arranged to align the second component towards the axis of the first component.

5. A fuel injector assembly according to any preceding claim, wherein the intended common axis is an axis of an injector nozzle (204) to be contained by the first and second components, and wherein the sleeve insert is arranged to align at least the second component towards the axis of the injector nozzle.

6. A fuel injector assembly according to any preceding claim, wherein the sleeve insert is disposed around an outer side of the at least one component.

7. A fuel injector assembly according to any of the Claims 1 to 5, wherein the sleeve insert (310) is disposed around an inner side of the at least one component.

8. A fuel injector assembly according to Claim 7, wherein the sleeve insert is disposed around an outer side of a further inner component.

9. A fuel injector assembly according to any preceding claim, wherein the sleeve insert is arranged in contact with both of the first and second components, to align the second component towards the axis of the first component.

10. A fuel injector assembly according to Claim 9, wherein the sleeve insert is elongated in the direction of the intended common axis, and wherein the sleeve insert is configured to span a junction of the first and second components, overlapping a portion of each of the first and second components.

11. A fuel injector assembly according to Claim 10, wherein the sleeve insert is configured to contact the overlapped portions of the first and second components to maintain an alignment of the first and second components in the direction of the axis of the first component.

12. A fuel injector assembly according to any preceding claim, wherein the sleeve insert is accommodated by a notch in the at least one component.

13. A fuel injector assembly according to Claim 12, wherein the accommodation of the sleeve insert by the notch provides a flush surface between an outer or inner perimeter of the at least one component and an outer or inner perimeter of the sleeve insert.

14. A fuel injector assembly according to any preceding claim, wherein the sleeve insert is arranged to provide a seal against a high pressure environment at a core of the fuel injector assembly and wherein the first and second components arranged in series each surround the core of the fuel injector assembly, the core extending in the direction of the intended common axis.

15. A fuel injector assembly according to any preceding claim, further comprising a third component of the injector assembly, the sleeve insert disposed between the first and third components, and in contact with each of the first, second and third components.

Drawing