Improvements relating to fuel injectors for gaseous fuels and related production methods

Abstract

Injection moulding apparatus 60 for moulding a fuel injector valve needle 8, the apparatus comprising a first mould plate 62 provided with a first mould cavity section 64, a second mould plate 66 prov

Description

Technical Field This disclosure relates generally to a configuration of a fuel injector suitable for injecting a gaseous fuel such as hydrogen, methane or natural gas into a combustion chamber of an internal combustion engine. The injector may be suitable for injection of other fuels and for use in other applications such as fuel cells. In addition to the configuration of a fuel injector, this disclosure relates to approaches for manufacturing such an injector. Background In the context of gaseous fuels, a typical fuel injector comprises an injector body which houses a fuel injector valve needle. The injector valve needle is slidable within the injector body to control the flow of gaseous fuel from one or more outlet openings in dependence on the lift position of the injector valve needle. Conventionally, injector valve needles have a metallic construction, and are typically formed from a milled stainless-steel component. This has benefits because stainless steel is a very durable material so that a valve needle formed in this way has a robust structure suitable for lasting over 1 billion injection cycles. However, a metallic construction has some associated disadvantages. For example, due to the density of stainless steel, a metal valve needle has a comparatively high mass which increases the response time for the valve needle to move between open and closed positions. Further, because the position of the valve needle is controlled by an electromagnetic actuator, there is a higher energy requirement to energize the valve needle due to its comparative high mass and the higher inertia of the valve needle can lead to increased impact loads on the sealing surfaces of the valve needle. One approach to addressing these issues is to manufacture the valve needle out of a plastics material which provides a mass advantage. However, there are technical challenges associated with this approach. It is against this background that the invention has been devised. Summary of the invention Against this background, the invention provides a fuel injector valve needle for use in a gaseous fuel injector, the fuel injector valve needle being of polymeric construction formed in an injection moulding process, and comprising: an elongated valve stem; optionally, a valve head; wherein the elongated valve stem comprises a first valve guide portion; wherein the first valve guide portion comprises a flow passage. A split line is defined in the flow passage of the first valve guide portion, the split line being an artefact from a moulding process from which the injector valve needle was produced. As well as being expressed as an injector valve needle, the examples of the invention also provide, from a second aspect, a moulding apparatus for moulding a fuel injector valve needle, the apparatus comprising: a first mould plate provided with a first mould cavity section, a second mould plate provided with a second mould cavity section, wherein the first mould plate and the second mould plate are configured to be united such that the first mould cavity section and the second mould cavity section create a complete mould cavity. The complete mould cavity is shaped to define external features of a fuel injector valve needle comprising: a valve head and a valve stem, wherein the valve stem comprises a first valve guide portion, wherein the first valve guide portion comprises a first fuel flow passage, wherein the first mould cavity section and the second mould cavity section are configured such that: the first mould cavity section and the second mould cavity section define together a first fuel flow passage mould feature that corresponds to the first fuel flow passage of the fuel injector valve needle such that a parting line between the first and second mould cavity sections is defined at the first flow passage of the fuel injector valve when it is ejected from the first and second mould plates after a moulding operation. The formation of split lines is inevitable on polymeric products that are produced by moulding processes such as injection moulding and compression moulding. This is because the polymer that is injected into the mould apparatus to form the product tends to penetrate a small distance into the very small interstice between mould cavity plates. It is possible for such split lines to be machined off by separate finished processes, such as by grinding. However, such finishing processes tend not to be as successful in creating fine surface finishes as they are on metal products, so it is preferable to avoid using them. Beneficially, injection mould cavities can be configured to provide very fine surface finishes so postprocessing of surface finishes is not required. Therefore, removal of split lines is not desirable. The examples of the invention address this issue by configuring the mould plates such that the split lines are formed on the valve needle in regions where their presence does not impact the function of the valve needle. In this case therefore, the split lines are formed on a flow passage in the valve guide portion. The valve guide portion is the part which slides in the fuel injector, in use, and therefore must have a very fine surface finish for frictional reasons. However, the fuel flow passage provides a route for fuel to flow past the valve guide portion and so will define a clearance with the corresponding valve guide of the injector body. This means that a split line formed here does not impact the function of the injector valve needle and does not require post processing. Therefore, configuring the cavity sections of the mould so that the flow passage feature is split between the cavity sections means that the split line on the resulting injection valve, when moulded, is defined on the flow passage rather than on the fuel guide. This means that no surface finish operation needs to be performed. This is particularly useful since surface finishing processes on plastic parts can give inconsistent results. Preferred and / or optional features of the examples of the invention as defined in the dependent claims. In particular, the complete mould cavity may be shaped to further define external features of a fuel injector valve needle comprising a second valve guide portion comprising a second fuel flow passage, wherein: the first mould cavity section and the second mould cavity section define together a second fuel flow passage mould feature that corresponds to the second fuel flow passage of the fuel injector valve needle such that a parting line is defined also at the second flow passage of the fuel injector valve needle when it is ejected from the first and second mould plates after a moulding operation. The first fuel flow passage and the second fuel flow passage, and therefore the mould cavity features that define them, may be substantially flat zones of the respective valve guides and associated valve guide mould cavity features. The valve guides may be cylindrical parts of the valve needle that have external surfaces with a very fine surface finished suitable for guiding axial linear movement of the injector. The fuel injector valve needle is of polymeric construction, as it is formed from an injection moulding process and apparatus. The valve stem may be formed of a first polymeric material whilst there may be additional features formed thereon from a second polymeric material. Brief Description of the Drawings Figure 1 is a view of a fuel injector suitable for gaseous fuels such as hydrogen, wherein the fuel injector incorporates a fuel injector valve needle of plastics construction; Figure 2 is a view of the fuel injector valve needle in isolation from the fuel injector, Figures 3 and 4 are view of the fuel injector valve needle of Figures 1 and 2 being arranged with an injection moulding apparatus for producing the fuel injector valve needle, Figure 5 is an enlarged view of part of the injector valve needle illustrating the presence of the split line in more detail. Detailed description With reference to Figure 1, a fuel injector 2 is shown. The fuel injector 2 is suitable for use with a gaseous fuel such as natural gas or hydrogen. The fuel injector 2 includes an injector body 4 or ‘nozzle body’ that comprises an actuator arrangement 6 that is configured to act on an injector valve needle or ‘pintle’ 8 which is contained in an elongated internal passage or cavity 3 of the injector body 4. The injector body 4 and the actuator arrangement 6 are shown as separate parts in Figure 1, but it should be appreciated that this is a possible implementation but that the two parts may be a single component. In this example the actuator arrangement 6 is received over the injector body 4 and rests on a shoulder 10 of the injector body 4. The actuator arrangement 6 comprises a solenoid 12 that is electrically coupled to a connector 14 that extends away from the injector body 4 at an oblique angle. Internal electrical connections are included (but not shown in Figure 1) that couple the electrical connector 142 to the solenoid 12 so that it can be supplied with electrical energy in use. The injector body 4 and actuator arrangement 6 are provided with seals 16, which in this case are O-rings, so that the fuel injector 2 can be received in an engine block of an associated internal combustion engine (not shown) in order to inject gaseous fuel into a combustion chamber of the engine. In this respect, therefore, the fuel injector 2 in Figure 1 is suitable for use as a direct injection fuel injector. However, the skilled person would understand that suitable modifications that are within the ambit of the skilled person would permit the fuel injector to be used within a port fuel injection variant. It should also be noted at this point that the injector body 4 may instead be configured to be received in another component or assembly such as a fuel cell housing. Such changes are not discussed here as they are not the focus of the invention, as defined in the claims. The injector valve needle 8 is housed within the injector body 4 and is configured to move axially towards and away from a valve seat 20 to control the delivery of gaseous fuel through an injector outlet 22. The injector outlet 22 is shown here as including a downwardly depending annular wall 23 which is shaped to form a cup-like surround for the outlet 22. Other injector outlet forms are possible, and this is just one formation by way of example. As will be appreciated from Figure 1. and also from Figure 2 which shows the injector valve needle 8 isolated from the surrounding components, the injector valve needle 8 has an elongated shape and, as such, is configured to define a valve stem 24 which terminates at its lower end at a valve head 26. The fuel injector 2 is of a type known as an ‘inward opening’ injector and, as such, the injector valve needle 8 is shaped so that the valve head 26 is relatively large and disc-shaped in form. The valve head 26 has a generally flat underside surface that is configured to seat against the valve seat 20 of the injector body 4, as is shown in Figure 1. When the injector is energised, the injector valve needle 8 is lifted away from the valve seat 20 which permits a flow of gaseous fuel to flow out of the injector outlet 22 from a fuel chamber 29 that is housed by the injector body 4. It should be noted at this point that the valve head 26 may be structured differently in different injector and the relatively large disc-shaped valve head 26 shown in Figure 2 is simply by way of example, as would be appreciated by a skilled person, equipped with knowledge of fuel injector designs for gas applications. The injector valve needle 8 is biased into engagement with the valve seat 20 by way of a biasing means in the form of a valve spring 30 that is housed in the injector body 4 at the end of the injector valve needle 8 opposite to the valve head 26. The valve spring 30 is received over a spring retaining rod 32 at the upper end of the injector vaive needle 8. Movement of the injector valve needle 8 towards and away from the valve seat 20 is controlled by the actuator arrangement 6 as has been mentioned above. The actuator arrangement 6 acts on an armature 33 of the fuel injector vaive needle 8. The armature 33 in this case is an annular component made of a ferromagnetic material, such as a magnetic steel, so that it is susceptible to the magnetic field generated by the solenoid 12. The armature 33 may be received over a part of the injector valve needle 8 and held in place by a suitable surface feature of the injector valve needle 8. To control the sliding movement of the injector valve needle 8 within the injector body 4, the injector valve needle 8 is provided with at least one valve guide. In this example, the injector valve needle 8 has two valve guides: a first valve guide portion 34 and a second valve guide portion 36. As illustrated, the first valve guide portion 34 and the second valve guide portion 36 are portions of the valve stem 24 that have an enlarged outer diameter compared to neighbouring portions of the valve stem 24. In this example, the first valve guide portion 34 has a larger diameter than the second valve guide portion 36. The first valve guide portion 34 is positioned at a lower point on the injector valve needle 8 compared to the second valve guide portion 36, in the orientation of the drawings. Therefore, the first valve guide portion 34 and the second valve guide portion 36 are spaced along the injector valve needle 8 in the direction of the axis X. In this example, the first and second valve guides portions 34,36 are cylindrical parts of the injector valve needle 8 that are dimensioned precisely to correspond with corresponding guiding surfaces of the injector body 4. The guiding surfaces are labelled as 38 and 40 in Figure 1. In this way, the injector valve needle 8 can move axially without any sideways movement as it is guided closely within the injector body 4. Notably, the valve guide surfaces 38,40 are provided by guide inserts 42,43 that are received within the injector body 4 but it should be noted that these are not essential and the guide surfaces 38,40 may instead by provided as integral surfaces of the injector body 4. So that gaseous fuel can flow past the first and second valve guide portions 34,36, each of them is shaped to include or define a respective at least one fuel flow passage. In this example the first valve guide portion 34 is provided with a pair of fuel flow passages 44,45. Also the second valve guide portion 36 is provided with a respective pair of fuel flow passages 46,48. The passages may be provided by suitable surfaces such as flats, recesses or grooves, for example. The fuel flow passages 44,45,46,48 may therefore also be considered to be fuel flow passage surfaces. The fuel low passages 42-48 are diametrically opposed about the valve stem 24 in this example. The fuel flow passages 42,44 are apparent in Figure 1 as a small gap that is present between the valve stem 24 and the adjacent valve guide surface 38,40 of the injector body 4. In use, gaseous fuel is delivered to the elongated internal passage 3 of the injector body 4 by a suitable fuel delivery system at an inlet section 50 of the injector body 4. The inlet section 50 is defined at the lower end of the injector body 4, in the orientation of the drawings. The inlet section 50 is shaped like a collar (e.g. as an annulus) so that it would receive gaseous fuel when the injector body 4 is installed in an engine block, for example, or an equivalent component. The inlet collar 50 provides one or more fuel inlet apertures 51 that penetrate the thickness of the injector body 4 at the region of the inlet collar 50 to provide a path for fuel to flow from the inlet collar 50 to the fuel delivery chamber 29. Other ways of delivering gas to the internal cavity 3 of the injector body 4 are known and would be acceptable. Such a delivery system is not within the scope of this discussion so will not be described further. However, it would be within the understanding of the skilled person. The gaseous fuel travels radially inwards through the fuel inlet apertures 51 of the injector body 4 and fills the fuel delivery chamber 29 that is positioned upstream of the valve head 26. As has been mentioned, movement of the injector valve needle 8 in the upwards direction so that the valve head 26 lifts away from the valve seat 20 causes gaseous to be ejected from the fuel delivery chamber 52 past the valve seat 20 and through the injector outlet(s) 22. To ensure that the pressure of gas on the injector valve needle 8 is balanced, gas is allowed to travel from the fuel delivery chamber 29 to other parts of the internal cavity 3 of the injector body 4 by flowing past fuel flow passages 42-48 and through some internal passages (if appropriate; not shown in the figures). It is important that gas is permitted to fill the internal cavity 3 quickly so that the gas pressure on the various external surfaces of the injector valve needle 8 is equalised so as to avoid any adverse effect on the valve opening times and the fuel flow passages 42--48 assist with this objective. The fuel flow passages therefore provide a pressure equalisation function within the internal cavity 3 from the delivery chamber 29 to the upper end of the internal cavity 3 near the valve spring 30. In the above discussion, and from observing Figures 1 and 2, it should be appreciated that the fuel flow passages 42-48 defined at the first and second valve guide portions 34,36 are in the form of ‘flats’, as the term is commonly known in the art. That is, a ‘flat’ is a substantially flat or planar region or zone of an otherwise curved or non-flat surface. In this context, the guide portions 34,36 are cylindrical parts (optionally or preferably with a circular cross section) with an outside surface dimensioned to be a sliding fit with an adjacent surface within the injector body 4, whereas the fuel flow passages 42-48 are flattened zones, regions or parts of the otherwise cylindrical surface which defines a clearance with the injector body 4 in use so that fuel can flow past the cylindrical guide portions 34,36. The fuel flow passages 42-48 may also be designed as channels or grooves instead of flats. in the above discussion, it will be appreciated that the injector valve needle 8 undergoes reciprocating movement within the injector body 8 and is expected to endure many millions of cycles over its lifetime. Such an injector valve needle 8 must therefore be very robust, so is typically made from a metal material, such as steel. However, recent developments have suggested that plastics or polymeric materials have much to offer in terms of taking advantage of the lower unit mass compared to metals. In general, it is known to manufacture injector valve needles from polymeric material such as PEEK (Polyether-ether-ketone) and polyimides, polyamides, and polyimide-amides The formation of split lines is inevitable on polymeric products that are produced by injection moulding processes. This is because the polymer that is injected into the mould apparatus to form the product tends to penetrate a small distance into the very small interstice between mould cavity plates. It is possible for such split lines to be machined off by separate finished processes, such as by grinding. However, such finishing processes tend not to be as successful in creating fine surface finishes as they are on metal products, so it is preferable not to use them. Beneficially, injection mould cavities can be configured to provide very fine surface finishes so post-processing of surface finishes is not required. Therefore, removal of split lines is not desirable. The examples of the invention address this issue by configuring the mould plates such that the split lines are formed on the valve needle in regions where their presence does not impact the function of the valve needle. Figures 3 and 4 provide a further explanation. In these Figures, a moulding apparatus 60 is shown for moulding the fuel injector valve needle 8. The moulding apparatus 60 comprises a first mould plate 62 and a second mould plate 66. The first mould plate 62 is provided with a first mould cavity section 64, and the second mould plate 66 is provided with a second mould cavity section 68. The moulding apparatus 60 may be suitable for different moulding systems, such as injection moulding or compression moulding. As such, it will be appreciated that various components of the moulding apparatus 60 are not shown here for ease of understanding, such as sprues, guides, flow passages, support frame, hydraulic presses and so on. Such aspects of moulding apparatus are conventional and are not central to the invention and so no discussion will be provided here. The first mould plate 62 and the second mould plate 66 are configured to be united such that the first mould cavity section 64 and the second mould cavity section 68 create a complete mould cavity. The complete mould cavity is shaped to define external features of a fuel injector valve needle 8. The injector valve needle 8 is shown being positioned between spaced-apart mould plates 62,66 in Figures 3 and 4. As can be seen from Figures 3 and 4, the first and second mould cavity sections 64,68 are shaped to define a 'blank’ or void that defines the final moulded product’s shape, size, and surface details. It is the part of the mould where the molten material is injected (or is captive, in a compression moulding approach) and solidified to form the desired object which in this case is the injector valve needle 8. The shape of the mould cavity sections 64,66 are seen to be the inverse of the outer shape of the injector valve needle 8. It is apparent from the Figures that the mould cavity sections 64,66 are dimensioned to define approximately half of the injector valve needle 8, although this proportionality between the cavity halves is not essential. It has been discussed above that the injector valve needle 8 comprises the first valve guide portion 34 and the second valve guide portion 36 and the functions of these parts. It will be appreciated therefore that each of the first mould cavity section 64 and the second mould cavity section 68 define together first valve guide mould features 70a,70b that correspond to the first valve guide portion 34 defined on the injector valve needle 8. In this example, the injector valve needle 8 also comprises a second valve guide portion 36. Accordingly, therefore, the first mould cavity section 64 and the second mould cavity section 68 define together second valve guide mould features 72a,72b that correspond to the second valve guide portion 36 defined on the injector valve needle 8. In addition to the first and second valve guide mould features 70a,70b,72a,72b, the first and second mould cavity sections 64,68 also define further features of the injector valve needle 8. In overview, these are a spring retaining rod feature 80a,b that corresponds to the spring retaining rod 32 of the injector valve needle 8, an armature feature 82a,b that corresponds to the armature 33 of the valve needle, one or more intermediate valve stem features 84a,b that correspond to narrower parts of the injector valve stem 24, and a valve head feature 86a,b that corresponds to the valve head 26 of the injector valve needle 8. It will be appreciated particularly from Figures 3 and 4 that the two mould plates 62,66 form half each of the injector valve needle 8. When united, the two mould plates 62,66 joint together at a planar interface P that bisects the injector valve needle 8 along its longitudinal axis X. The axis X is marked in Figs 2-4. Since the joining faces of the two mould plates 62,66 are flat, as is the standard with injection moulding and compression moulding machines, it will be appreciated that a parting line is formed along the moulded component, that is, the injector valve needle 8, that extends along the injector valve needle 8 at a position demarked by the longitudinal axis X which is aligned with the planar interface P between the two mould plates 62,66. The way in which the mould features 70a,b;72a,b of the mould plates 62,66 are configured is to arrange the fuel flow passages 44-48 on the first and second valve guide portions 34,36 so that the fuel flow passages 44-48 are oriented on the planar interface P. This is because the first and second valve guide mouid features 70a,70b,72a,72b further comprise respective fuel flow passage features. More specifically, a first pair of fuel flow passage mouid features 90 is provided on the first valve guide mould features 70a,b whereas a second pair 92 of fuel flow passage mould features 92 are provided on the second valve guide mould features 72a,b. It should be noted that the fuel flow passage mould features 90,92 are most clearly apparent in Figure 4. The pairs of fuel flow passage mould features may also be single fuel flow passage mould features. It will be noticed that the fuel flow passage mould features 90,92 span the planar interface P. This means that when the injector valve needle 8 is moulded by the moulding apparatus 60, a parting line is formed on the injector valve needle 8 at the fuel flow passages 44-48. The position of the parting lines on each of the fuel flow passages 44-48 is shown in Figure 4, and labelled as 100 in respect of the parting line 100 formed on the first flow passage 44,45 and labelled 101 in respect of the second fuel flow passage 46,48. In addition, Figure 5 shows a representation of part of the injector valve needle 8 and, more specifically, just the second valve guide portion 34 of the valve needle 8. Here, adjoining part of the injector valve needle 8 with reduced diameters are shown in dotted lines. In Figure 5, it can be seen that the curved outer surface 102 of the second valve guide portion 34 is cylindrical and has a generally circular cross section apart from the first and second fuel flow passages 44,45. A first one 44 of the fuel flow passages 44,45 can be seen in full in Figure 5 due to the orientation of the Figure, but the second one 45 of the fuel flow passages is hidden. The parting line 100 can be seen extending axially along the fuel flow passage 44 and is represented by a small upstanding projection that extends up from the flat surrounding surface of the fuel flow passage 44. It should be noted that the relative dimensions of the parts in Figure 5 may not be true to scale. However, it can be appreciated that since the fuel flow-passage 44 is merely used for the passing of gaseous fuel and not used as a guiding surface, the presence of the parting line 100 does not cause a problem with this functionality. The skilled person would appreciate that various adaptations may be made to the illustrated examples without departing from the inventive concept, as defined by the claims. As an enhancement to the above-described approach for producing an injector valve needle 8, it should be appreciated that various features may be incorporated into the moulding process. For example, the armature 32 may form an insert in the mould cavity and thus may be at least partially embedded into the valve needle for a strong connection between the two components. Further, the valve needle 8 may be co-moulded with other parts, such as lift stops, and sealing surfaces. For example, the valve head and the valve stem may be moulded from a first plastics material such as PEEK, and wherein the fuel injector valve needle further comprises additional features moulded thereon which are formed from a second plastics material that is different to the first plastics material. The first plastics material may be selected from a group comprising: polyimides, polyamides, and polyimde-amides. The second plastics material may be selected from second plastics material is selected from a group comprising fluoroelastomer, synthetic rubber, natural rubber. Furthermore, other features such as flow ribs, internal passages and so on may also be moulded into the valve needle 8 as part of a more complex moulding system.

Claims

1. Injection moulding apparatus for moulding a fuel injector valve needle, the apparatus comprising:a first mould plate provided with a first mould cavity section,a second mould plate provided with a second mould cavity section,wherein the first mould plate and the second mould plate are configured to be united such that the first mould cavity section and the second mould cavity section create a complete mould cavity;wherein the complete mould cavity is shaped to define external features of a fuel injector valve needle comprising:a valve head and a valve stem, wherein the valve stem comprises a first valve guide portion, wherein the first valve guide portion comprises a first fuel flow passage,wherein the first mould cavity section and the second mould cavity section are configured such that:the first mould cavity section and the second mould cavity section define together a first fuel flow passage mould feature that corresponds to the first fuel flow passage of the fuel injector valve needle such that a parting line between the first and second mould cavity sections is defined at the first flow passage of the fuel injector valve when it is ejected from the first and second mould plates after a moulding operation.

2. The injection moulding apparatus of Claim 1, wherein the complete mould cavity is shaped to further define external features of a fuel injector valve needle comprising a second valve guide portion comprising a second fuel flow passage, wherein:the first mould cavity section and the second mould cavity section define together a second fuel flow passage mould feature that corresponds to the second fuel flow passage of the fuel injector valve needle such that a parting line is defined also at the second flow passage of the fuel injector valve needle when it is ejected from the first and second mould plates after a moulding operation.

3. The injection moulding apparatus of Claim 2, wherein the second fuel flow passage mould feature corresponding to the second fuel flow passage is a substantially flat zone of the second valve guide mould feature.

4. The injection moulding apparatus of Claim 3, wherein one or more regions of the second valve guide mould feature adjacent the second fuel flow passage mould feature is a curved surface.

5. The injection moulding apparatus of any one of the preceding claims, wherein the first fuel flow passage mould feature corresponding to the first fuel flow passage is a substantially flat zone of the first valve guide mould feature.

6. The injection moulding apparatus of Claim 5, wherein one or more regions of the first valve guide mould feature adjacent the first fuel flow passage mould feature is a curved surface.

7. The injection moulding apparatus of any one of the preceding claims, wherein the complete mould cavity is shaped to define an armature insert feature which, when used in an injection moulding process for the injector valve needle, integrates a ferromagnetic armature component into the moulded fuel injection valve needle.

8. A fuel injector valve needle for use in a gaseous fuel injector, the fuel injector valve needle being of polymeric construction formed in a cavity moulding process, and comprising:an elongated valve stem;optionally, a valve head;wherein the elongated valve stem comprises a first valve guide portion;wherein the first valve guide portion comprises a flow passage; andwherein a split line is defined in the flow passage of the first valve guide portion, the split line being an artefact from the injection moulding process from which the injector valve needle was produced.

9. The fuel injector valve needle of Claim 8, further comprising a second valve guide portion comprising a second fuel flow passage, wherein a split line is also defined in the second fuel flow passage.

10. The fuel injector valve needle of Claims 8 and 9, wherein the second fuel flow-passage of the second valve guide portion is a substantially flat zone of the second valve guide portion.

11. The fuel injector valve needle of Claim 10, wherein one or more regions of the second valve guide portion adjacent the second fuel flow passage is a curved surface.

12. The fuel injector valve needle of any one of Claims 8 to 11, wherein the first fuel flow passage of the first vaive guide portion is a substantially flat zone of the first fuel valve guide portion.

13. The fuel injector valve needle of Claim 12, wherein one or more regions of the first valve guide portion adjacent the first fuel flow passage is a curved surface.

14. The fuel injector valve needle of any one of Claims 8 to 13, further comprising a magnetic armature component.

15. The fuel injector valve needle of Claim 14, wherein the magnetic armature component is at least partially embedded in the valve stem of the fuel injector valve needle.

16. The fuel injector valve needle of any one of Claims 8 to 15, wherein the valve head and the valve stem are of a first plastics material, and wherein the fuel injector valve needle further comprises additional features moulded thereon which are formed from a second plastics material that is different to the first plastics material.

17. The fuel injector valve needle of Claim 16, wherein the first plastics material is selected from a group comprising: polyimides, polyamides, and poiyimde-amides.

18. The fuel injector valve needle of Claim 17, wherein the second plastics material is selected from a group comprising fluoroelastomer, synthetic rubber, natural rubber.15

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