Valve for a fuel injector

Abstract

A fuel injector 200 for injecting hydrogen fuel into a manifold 232, the fuel injector comprising a body 226 defining a bore along a longitudinal axis of the body. The bore has an upper section and a

Description

11 07 25 Technical field

[0001] The present invention relates generally to a valve for a fuel injector and more specifically to a valve for a fuel injector used on an internal combustion engine. Background

[0002] Internal combustion (IC) engines are typically powered by combusting a fuel, such as petrol (gasoline) or diesel, in a combustion chamber. Hydraulic injectors in such IC engines benefit to varying degrees from lubrication at sliding interfaces from the working fluid (the fuel) that passes through clearances between components.

[0003] There is a recent trend in the automotive industry for cleaner fuel, in the form of hydrogen or natural gas, to be used in internal combustion engines. As well as reducing emissions, such new technologies can also increase fuel efficiency.

[0004] The use of such cleaner fuels, in particular hydrogen which is a dry gas with trace oils removed during processing, requires adaptation of the different parts of the combustion engine, to make them suitable for the different working conditions provided by these alternative fuels, such as operating pressures and flow variations.

[0005] The use of gas as a working fluid provides a particular challenge for fuel injectors, since these fuels do not provide the lubrication obtained with petrol and diesel fuels and the shift to such fuels results in a reduction in the lubrication that is available to aid sliding wear between components (since such working fluids do not form a film in the same way as petrol or diesel at the sliding interface between the components of the injector) As a result, injectors operating with gas suffer with problems related to wear generated by the friction of their internal parts.

[0006] An additional challenge provided by the use of gas as a working fluid is that the benefit of squeeze film damping provided by standard fuels used in internal combustion engines is greatly reduced. As such, problems resulting from noise generated by the valve moving between its closed and open positions also arise. The impact forces within the injector, as components come into contact with one another at the end of movements, are also greater. 11 07 25

[0007] It would be desirable to provide a fuel injector that could better adapt to the working conditions resulting from the use of these alternative fuels, without making fundamental changes that would prevent the fuel injectors to be used on existing combustion engines. It is against this background that the invention has been devised. Statement of the invention

[0008] In a first aspect herein, there is a fuel injector for injecting hydrogen fuel into a manifold. The fuel injector comprises a body defining a bore along a longitudinal axis of the body, the bore having an upper section and a lower section; a solenoid located in the upper section of the bore; a valve member located in the lower section of the bore and moveable between a closed position in which a fuel path to the manifold is closed and an open position in which a fuel path to the manifold is open; an integrated guide component located in the bore and positioned between the valve member and the solenoid, wherein the integrated guide component is made of a polymer material. The integrated guide component provides an armature seat for an armature of the solenoid when the valve member is in the closed position and provides a valve stop for the valve member when the valve member is at a full lift position in the open position. The armature is decoupled from the valve member.

[0009] Hydrogen gas that is used in fuel injector systems is processed to remove traces of oil, resulting in a dry gas. However, known hydraulic injectors rely on lubrication provided by the liquid working fluid passing through the clearance between the components. Where hydrogen is used as the working fluid in known injectors this tends to result in an increase in the levels of friction between the components due to a reduction in the lubrication available to assist the operation of the injector. In addition, known injectors using liquid working fluids, benefit from hydraulic damping provided by the working fluid that limits the impact of the moving parts, reducing the noise output during an injector’s operation. However, the compressible nature of hydrogen as working fluid means that, if it is used as the working fluid in a known injector, the benefit of squeeze film damping obtained with conventional fuels is greatly reduced, increasing the noise output during the injector’s operation.

[0010] The disclosure herein addresses the above problems related to the dryness of the hydrogen as working fluid, by providing an integrated valve component made of a polymer material and positioned within the injector’s body. The integrated valve component operates as a damping element, reducing the wear of the injector’s moveable parts, as well as the noise output resulting from the injector’s operation. 11 07 25

[0011] In some examples, an upper surface of the integrated guide component may define an armature seat for the armature, such that the armature is seated on the upper surface of the integrated guide component when the valve member is in its closed position. Optionally, a first portion of a lower surface of the integrated guide component may define the valve stop for the valve member when the valve member is at full lift.

[0012] In some examples, the integrated guide component may define a radially inner surface and the valve member defines a radially outer surface, the inner and outer surfaces being in contact with one another and wherein the inner surface of the integrated guide component is configured to act as a guide for the valve member as the valve member moves between the open and closed positions.

[0013] Optionally, at a closed position the valve member may sit on top of the valve seat such that a first gap is defined between the valve member and the integrated guide component, and the armature sits on top of an upper surface of the integrated guide component forming a second gap between the armature and an upper pole piece of the solenoid. In some examples, the first gap may be smaller than the second gap.

[0014] In some examples, when the solenoid is at a de-energised state a valve spring may be configured to seat the valve member on the valve seat, closing an injector outlet, and an armature spring is configured to seat the armature on a top surface of the integrated guide component. Alternatively, when the valve member is at full lift, the valve member may be placed against a first portion of a lower surface of the integrated guide component. Optionally, the solenoid may comprise an armature and an upper pole piece and, when the valve member is at full lift, the armature and upper pole piece are separated by a small gap ( / .e., the armature and upper pole piece do not touch).

[0015] In some examples, the fuel injector may comprise a valve stem, wherein the stem may comprise a bore that allows fuel to flow between the lower section and the upper section of the injector.

[0016] In some examples, the valve stem may include an insert made of a polymer material. Optionally, the insert may be made of PTFE or PEEK.

[0017] In some examples, the integrated guide component may be made of PTFE or PEEK. 11 07 25

[0018] In summary the disclosure herein relates to a high-flow hydrogen (H2) port fuel injection (PFI) injector with an integrated valve guide. The integrated valve guide is made of a polymer material and is positioned within the injector’s body, between the valve member and the armature, and acts as a seat for the armature when the valve is at a closed position and as a valve stop for the valve member when the valve is at an open position. As such, the integrated valve guide may operate as a damping element, both damping the impact of the valve member as it reaches the valve stop and damping the impact of the armature during the valve closing operation. Brief description of the drawings

[0019] Figure 1A is a schematic cross-sectional view of a known fuel injector, with the valve at a closed position.

[0020] Figure 1B is a schematic cross-sectional view of a known fuel injector, with the valve at a full lift position.

[0021] Figure 2 is a schematic cross-sectional view of a fuel injector according to an embodiment of the disclosure.

[0022] Figure 3A is a schematic cross-sectional view of a fuel injector according to an embodiment of the disclosure, with the valve in its closed position.

[0023] Figure 3B is a schematic cross-sectional view of a fuel injector according to an embodiment of the disclosure, with the valve in its open position. Detailed description

[0024] Technology to adjust combustion engines to new cleaner fuels is continuously being developed. Currently, fuel injectors used for hydrogen (H2) combustion engines generally use injectors developed for use with fuels such as petrol and diesel. One example of these injectors is a low flow Port Fuel Injection (PFI) injector, that works with H2 and can operate with natural gas as well. However, there is an increasing demand for H2 injectors that can operate at higher flow and at low pressure. Gas flow rates required to achieve comparable power outputs to gasoline or diesel vehicles is higher for H2 combustion engines than for gasoline / diesel engines. Known fuel injectors carried over from gasoline technologies are limited on their flow capacity so cannot meet the demand of more powerful H2 combustion 11 07 25 engines in larger applications. Operating at low pressure offers benefits in being able to utilise more of the stored gas.

[0025] Known fuel injectors, which were developed for use with liquid working fluids, present several issues when used with gas as working fluids. One of these issues is variation in the injector’s flow performance. A major cause of injector flow performance variation and drift when using hydrogen as fuel is injector valve axial guidance wear, which is mainly related to excessive friction between an axial guide and the injector’s valve stem. Hydraulic injectors, which rely on lubrication provided by the working fluid passing through the clearance between the components, experience a drastic reduction in the lubrication available to aid sliding wear when used with fuels in gas phase. This is specially the case with hydrogen injection, where the gas is dry, and trace oils are removed during processing, resulting in high levels of friction between the components of the injector.

[0026] One consequence of the lack of lubrication within the injectors using H2 as fuel, is the flow variation resulting when the valve member reaches its lift stop. The lift stop and valve member are both typically metallic components and the use of hydrogen gas as the working fluid provides limited damping between these components which means that the valve member tends to bounce off the valve stop. Although, electronic control methods can be implemented to limit the velocity of the valve member at full lift and when reaching the valve stop, the primary means, when using liquid working fluids, of limiting the impact of the valve member and the noise output during an injector’s operation is through hydraulic damping or squeeze film damping. Simulations have shown that when using gas as the working fluid, the compressible nature of the working fluid means that the benefit of squeeze film damping obtained with conventional fuels is greatly reduced, with no notable reduction in velocity of the valve member until the gap between the components is at a micron level.

[0027] The present disclosure solves the above drawbacks by providing a single component, an integrated guide component, which provides radial guidance for the valve member during use; a valve stop for the valve member including damping of the valve member as it reaches its maximum lift during valve opening and damping of an armature assembly as the valve is closed. These functions will be described in more detail in the following paragraphs.

[0028] General and specific embodiments of the disclosure will be described below with reference to the Figures. 11 07 25

[0029] Figures 1A and 1B show a cross-sectional view of a known fuel injector 100 with the valve at its closed position and at its open (full lift) position, respectively. As shown in Figure 1A, the injector 100 has a body 110 comprising a valve assembly and defining a bore 102 that houses a valve stem 112. The valve stem 112 is configured to move along the longitudinal axis of the injector’s body 110. The valve body 110 defines a valve seat 118 for a valve member 116 in the closed position. The injector 100 also includes a solenoid 104, including an armature component (which forms a single unit together with the valve member 116) and is formed from a magnetic material for actuating the valve, and a spring 108 which has a preload that is set through an iterative process. The fuel flow path of the injector 100 is through the centre of the valve stem 112 and, in use, fuel flows from the top of the stem 112 towards the valve seat 118, exiting the valve through an outlet 120 on the valve seat 118.

[0030] The valve is operated through energisation / de-energisation of the solenoid 104. In a de-energised state, the valve is shut (as shown in of Figure 1A), and the spring 108 holds the stem 112 and the valve member 116 seated on the valve seat 118, closing the injector’s outlet 120. In the injector 100 of Figures 1A / 1B, the armature and the valve member 116 are a single unit and therefore, when the solenoid 104 is energised, the armature component and valve member 116 move upwards towards the lift stop 106 and away from the valve seat 118, opening the valve outlet 120. The valve’s open position, in which the valve member 116 has been lifted from the valve seat 118, is shown in Figure 1B.

[0031] The known injector has several drawbacks when used with a working fluid that is a gas. Typically, magnetic materials are softer and more susceptible to wear which produces debris that compromise the sealing performance of the valve. In addition, the injector 100 of Figures 1A and 1B includes metal-on-metal contact at the top of travel when the armature component and valve member 116 strike the lift stop 106 of the upper pole piece 114 at full lift, and when the armature component and valve member 116 strike the valve seat 118 during closing of the valve. These two points of contact during the valve operation also generate a high level of noise. In particular, during the closing operation the valve, the armature component and valve member 116 may bounce off the valve seat 118 due to the impact and the lack of damping in the valve operation, which also contribute to the high level of noise generated.

[0032] Figure 2 shows a cross-sectional view of a fuel injector 200 according to an embodiment of the present disclosure. The injector 200 comprises a body 226 that defines a bore along the longitudinal axis of the body 226. An upper section of the bore houses a solenoid 210 comprising a stator, an armature assembly having an armature 214, an upper 11 07 25 pole piece 208, an armature spring 204, an armature spring seat 206 and a collar 202. The lower section of the bore houses a valve assembly comprising a valve member 220 and a valve spring 222. The upper and lower sections of the bore are separated by an integrated guide component 216.

[0033] The valve member 220 is moveable between a closed position in which a fuel path from a fuel inlet 224 to a manifold 232 is closed and an open position in which the fuel path via an outlet 233 to the manifold 232 is open. In its closed position the valve member 220 is seated against a valve seat 228 such that the outlet is closed.

[0034] The solenoid 210, which is housed within the bore of the body 226, in turn defines a solenoid bore along the longitudinal axis of the injector body. A stem 218 and a guide tube 212, located between the stem 218 and the armature 214, extend through the solenoid bore. The valve stem 218 includes an insert made of a polymer material such as, for example but not limited to PTFE or PEEK.

[0035] The integrated guide component 216 is made of a polymer material, such as, but not limited to PTFE or PEEK, and is placed within the injector 200 between the valve member 220 and the armature 214. The guide tube 212 is press fitted to the armature 214 and then machined within the armature 214, and the stem 218 is press fitted with the valve and machined within the valve in a single operation. This assembly process results in a high level of concentricity between the armature 214, the guide tube 212 and the stem 218, which improves the radial guidance provided by the guide tube 212 to the armature 214 and the stem 218, and the precision in the fit between these elements.

[0036] The armature 214 is mechanically coupled to the guide tube 212 and the valve member 220 is mechanically coupled to the stem 218 through a press fit operation, which may optionally include a welding operation.

[0037] The valve member 220 comprises a base portion 221 upon which are disposed an outer circular wall 223 and inner circular wall 225 which extend parallel to the longitudinal axis of the injector 200. The inner and outer walls (225, 223) are separated by an annular recess 227 and the inner wall defines a central recess 229 which is dimensioned to receive an end of the valve stem 218. The valve spring 222 is located in the annular recess 227 such that one end of the valve spring 222 acts against the base portion 221 of the valve member 220 and a second end of the valve spring 222 acts against the integrated guide component 216. In the valve’s closed position, the top surface of the outer circular wall 223 is separated by a gap 11 07 25 from a lower surface of the integrated guide component. This gap, which is around 0.52mm (in the injector shown in Figures 2, 3A and 3B) defines the valve lift 236. When seated against the valve seat 228 in its closed position, the base portion 221 of the valve member 220 closes the outlet 233 such that there is no fuel path from the fuel inlet 224 to the manifold 232.

[0038] The injector 200 shown in Figure 2 is approximately 32 mm wide and approximately 64 mm long (It is noted that the length, width, and gap separations described herein for Figures 2, 3A and 3B may vary for different injectors in other engine systems). The integrated guide component 216 is formed by introducing a polymer unit within the valve assembly through a press fitting operation and machining the polymer unit to form the integrated guide component 216 within the valve assembly, to achieve the desired profile with the required level of concentricity. This results in a more precise coupling of the components forming the injector. In addition, the preload setting on the valve spring 222 is controlled during machining of the integrated guide component 216. The valve spring preload is managed through parameters such as, machining tolerances of the guide tube 212, the tolerance on the machining of the valve member 220, and the final assembly of valve seat 228 into the injector body 226. Accordingly, the above assembly process eliminates the trial-and-error process often used to set the valve spring preload in known injectors. Therefore, in embodiments of the present invention, several assembly stages are incorporated into the machining operation, requiring less assembly steps than the ones required in known injectors.

[0039] Fuel entering the injector 200 via the fuel inlet 224 will, in addition to the direct fuel path from the inlet 224 to the outlet, enter other parts of the injector 200. For example, the working fluid will run through a bore in the centre of the stem 218 in the longitudinal direction along the body 226 of the injector 200 and enter the upper section of the injector bore where the armature spring 204 and collar 202 are located. The working fluid in these parts of the injector acts as a pressure equaliser between within the upper and lower sections of the injector 200, enabling the injector 200 to operate at varying rail pressures and different levels of injection, while providing injection stability.

[0040] The magnetic armature 214 is coupled to the non-magnetic guide tube 212 component through a press fit, and, as described in relation to Figures 3A and 3B below, the integrated guide component 216 provides radial guidance and damping for both the armature 214 and the valve member 220 during the opening and closing operations of the valve assembly. The lower surface of the integrated guide component 216 comprises a valve stop portion 240 that stops the upward motion of the valve member 220 during valve opening. The integrated guide component 216 also defines an upper surface 242, perpendicular to the longitudinal axis of 11 07 25 the injector 200, which defines an armature seating surface when the solenoid 210 is in a deenergised state. The integrated guide component 216 defines an inner surface, a portion of which is in contact with the outer surface of the outer wall of the valve member 220. The outer surface of the valve member 220 is configured to slide relative to the inner surface portion of the integrated guide component 216 such that the integrated guide component 216 acts as a guide to the valve member 220, reducing lateral movement of the valve member 220 when the valve member 220 moves during actuation of the valve, both during closing and opening operation of the valve. The use of a polymer material to form the integrated guide component 216 allows a lower friction coefficient to be achieved in the dry gas environment.

[0041] Figures 3A and 3B show the injector 200 of Figure 2 at closed and open (full lift) positions, respectively.

[0042] In Figure 3A, the solenoid 210 is in a de-energised state and the valve member 220 is seated against the valve seat 228, closing the injector’s outlet such that the valve is closed.

[0043] As shown in Figure 3A, when the valve is closed, the armature 214 is seated on the top surface 242 of the integrated guide component 216 and there is a gap 234 between the top end of the armature 214 and the bottom end of the upper pole piece 208. This gap is hereafter referred as the “armature lift” 234. When the solenoid 210 is switched to its deenergised state, the armature spring 204 acts to push the guide tube 212 towards the manifold 232 end of the injector 300A. As noted above, the armature 214 is coupled to the guide tube 212 and so the armature spring 204 pushes the guide tube 212 towards the manifold end of the injector 200 until the armature 214 sits on the upper surface 242 of the integrated guide component 216.

[0044] Within the injector body 226, there are parts that are static, in other words that do not move with respect to the injector body during valve operation. The upper pole piece 208, the solenoid stator, the valve seat 228, the filter 230 and the integrated guide component 216 remain static in relation to the injector body 226 when the solenoid 210 goes from a deenergised state to an energised state.

[0045] When the solenoid 210 is energised, the magnetic armature 214 is attracted under the influence of the magnetic field towards the upper pole piece 208. The guide tube 212 which is mechanically coupled to the armature 214, and the armature spring seat 206, move upwards with the armature 214 towards the top end of the injector 200. This upwards movement closes a small gap between the collar 202 and the armature spring seat 206 such that the upwardly 11 07 25 moving armature 214 / guide tube 212 / armature spring seat 206 also carries the collar 202 in an upwards direction. The collar 202 is coupled to the stem 218 and so upwards movement of the collar 202 lifts the stem which lifts the valve member 220 from its valve seat 228. The stem 218 and the collar 202 move upwards together with the valve member 220 until the valve member 220 reaches the valve stop portion 240 on the lower surface of the integrated guide component 216. This is the valve’s fully open / full lift position in which fuel can flow from the fuel inlet 224 to the outlet 233 and into the manifold 232. As described above, it is noted that the armature 214 initially moves under the influence of the magnetic field and travels a distance before the guide tube 212 interacts with the collar 202. The armature 214 therefore builds up momentum before “picking” up the collar 202 (which is coupled through the stem 218 to the valve member 220). This enables a faster injector opening response than if the valve member 220 was moved at the same time as the armature 214.

[0046] When the solenoid 210 is de-energised the magnetic field begins to decay and the armature spring 204 and the valve spring overcome the residual magnetic force to return the valve to its closed position. The valve member 220 moves downwards, towards the valve seat 228, under the force of the valve spring 222. The stem 218 and collar 202, which are mechanically coupled to the valve member 220, also move downwards together with the valve member 220. The armature spring 204 seat moves downwards, under the force of the armature spring 204. The guide tube 212 and armature 214, which are mechanically coupled to the armature spring seat 206 also move downwards, returning to their initial positions. During this de-energising step, the valve member 220 sits on the valve seat 228 before the armature 214 reaches the integrated guide component 216, such that the armature 214 continues to move downwards after the valve member 220 reaches the valve seat 228. Therefore, the mass of the armature 214 is decoupled from the valve member 220 seating on the valve seat 228 and so effectively the moving mass within the injector 200 is divided into two, one mass corresponding to the armature 214, and the other to the valve member 220. This decoupling of the armature mass from the valve member mass enables a faster valve closing response. As noted above, the integrated guide component 216 is formed from a polymer material. This enables the integrated guide component 216 to operate as a damping element, both damping the impact of the valve member 220 as it reaches the valve stop 240 during valve opening and damping the impact of the armature 214 during the valve closing operation.

[0047] The injector 200 of Figures 3A and 3B may be connected to a manifold 232. When the valve is closed and the solenoid 210 is de-energised, the internal part of the injector 200 is flooded with H2 gas. When the solenoid 210 is energised, the armature 214 is attracted 11 07 25 towards the upper pole piece 208 above it, puling the guide tube 212 and the armature spring seat 206, such that the gap between the armature spring seat 206 and the collar 202 is closed. At the point in which the gap between the armature spring seat and the collar 202 is closed, the armature 214 is still moving upwards towards the upper pole piece 208, and the valve member 220, the stem 218 and the collar 202 are also moving upwards within the injector’s body 226, such that there is a momentum formed by the magnetic pull of the solenoid 210 that acts on the armature 214 and the valve member 220 the stem 218 and the collar 202. Therefore, the movement of the valve when the solenoid 210 is actuated does not require the build-up of force to overcome the pressure of the H2 gas accumulated at the top of the injector’s body 226 when the valve was at a closed position.

[0048] When the valve is at full lift, the valve member 220 reaches the valve stop 240 of the integrated guide component 216 and the armature 214 stops at a position close to the upper pole piece 208, but without touching the upper pole piece 208, such that a small gap of about 0.05 mm (for the injector shown in Figures 2, 3A and 3B) remains between the armature 214 and the upper pole piece 208. Therefore, the armature lift 234 is greater than the valve lift 236 and the armature’s movement is stopped by the valve member 220 reaching the integrated guide component 216 (since at this point there is coupling between the valve member 220 and the armature 214 via the stem 218, collar 202, armature spring seat 206 and guide tube 212). Consequently, metal-to-metal impact / contact within the injector is reduced since the armature 214 does not seat against the upper pole piece 208. Additionally, the valve member 220 (metal) stops against the integrated guide component 216 (polymer material) which acts as a damping element during the valve operation. In addition, the decoupling of the mass of the valve member 220 and the armature 214 as described above, results in a reduction in the inertia of the elements that are displaced within the injector 200 during the valve operation, which contributes to the reduction of the impact and, consequently, the noise generated within the injector 200 when the valve member 220 reaches full lift, and when the valve member 220 reaches the valve seat 228.

[0049] Because the armature 214 does not touch the upper pole piece 208 at full lift, when the solenoid 210 is de-energised, the armature 214 does not experience a magnetic lag caused by the valve spring 222 having to overcome a magnetic force that may form between abutting metallic elements while the electromagnetic force is still decaying within the injector 200. Accordingly, the air gap formed between the armature 214 and the upper pole piece 208 facilitates the valve operation, by enabling a smoother release of the valve at full lift, resulting in an improved closing response time. 11 07 25

[0050] The magnetic field produced by injector solenoids is not uniform and, in injectors 100 known in the art the stem 112 may be pulled slightly to one side when the solenoid 104 goes from a de-energised state to an energised state. This causes friction between the stem 112 and the central bore wall which may result in wear between the components that produces debris that compromises the sealing performance of the valve. In the known injector configurations for liquid fuels (e.g., gasoline, diesel engines), the friction between the stem 112 and the central bore wall is reduced by using a metal ring placed at the bottom end of the stem, which acts as a guide. In embodiments of the present invention, the stem 218 and the guide tube 212 move relative to each other under the action of the solenoid 210 energisation or the valve spring 222 / armature spring 204. As such, the guide tube 212 provides radial guidance to the stem 218, reducing the effect of the solenoid’s asymmetrical magnetic field. In addition, the valve stem 218 features an insert made of a polymer material such as, for example but not limited to PTFE or PEEK, which reduces the friction between the stem and the guide tube, improving the valve operation and reducing the debris formation.

[0051] It will be appreciated that the description provided above serves to demonstrate possible examples of the present invention. Features described in relation to any of the examples above may be readily combined with any other features described with reference to different examples without departing from the scope of the invention as defined in the appended claims.

Claims

11 07 251. A fuel injector (200) for injecting hydrogen fuel into a manifold (232), the fuel injector (200) comprising:a body (226) defining a bore along a longitudinal axis of the body, the bore having an upper section and a lower section;a solenoid (210) located in the upper section of the bore;a valve member (220) located in the lower section of the bore and moveable between a closed position in which a fuel path to the manifold (232) is closed and an open position in which a fuel path to the manifold (232) is open;an integrated guide component (216) located in the bore and positioned between the valve member (220) and the solenoid (210), wherein the integrated guide component (216) is made of a polymer material,wherein the integrated guide component (216) provides an armature seat (242) for an armature (214) of the solenoid (210) when the valve member (220) is in the closed position and provides a valve stop (240) for the valve member (220) when the valve member (220) is at a full lift position in the open position, andwherein the armature (214) is decoupled from the valve member (220).

2. A fuel injector (200) as claimed in claim 1, wherein an upper surface of the integrated guide component (216) defines an armature seat (242) for the armature (208), such that the armature (214) is seated on the upper surface of the integrated guide component (216) when the valve member (220) is in its closed position.

3. A fuel injector (200) as claimed in claim 1, wherein a first portion of a lower surface of the integrated guide component (216) defines the valve stop (240) for the valve member (220) when the valve member (220) is at full lift.

4. A fuel injector (200) as claimed in claim 2, wherein the integrated guide component (216) defines a radially inner surface and the valve member (220) defines a radially outer surface, the inner and outer surfaces being in contact with one another and wherein the inner surface of the integrated guide component (216) is configured to act as a guide for the valve member (220) as the valve member (220) moves between the open and closed positions.

5. A fuel injector (200) as claimed in claim 1, wherein at a closed position the valve member (220) sits on top of a valve seat (228) such that a first gap (236) is defined between the valve member (220) and the integrated guide component (216), and the armature (214)11 07 25sits on top of an upper surface of the integrated guide component (216) forming a second gap (234) between the armature (214) and an upper pole piece (208) of the solenoid.

6. A fuel injector as claimed in claim 5, wherein the first gap (236) is smaller than the second gap (234).

7. A fuel injector (200) as claimed in any preceding claim, wherein, when the solenoid (210) is at a de-energised state a valve spring (222) is configured to seat the valve member (220) on the or a valve seat (228), closing an injector outlet (233), and an armature spring (204) is configured to seat the armature (214) on a top surface of the integrated guide component (216).

8. A fuel injector (200) as claimed in any preceding claim, wherein when the valve member (220) is at full lift, the valve member (220) is placed against a first portion of a lower surface of the integrated guide component (216).

9. A fuel injector (200) as claimed in claim 8, wherein the solenoid (210) comprises an armature (214) and an upper pole piece (208) and, when the valve member (220) is at full lift, the armature (214) and upper pole piece (208) are separated by a small gap (234).

10. A fuel injector (200) as claimed in any preceding claim, comprising a valve stem (218) wherein the stem (218) comprises a bore that allows fuel to flow between the lower section and the upper section of the injector (200).

11. A fuel injector (200) as claimed in claim 10, wherein the valve stem (218) includes an insert made of a polymer material.

12. A fuel injector (200) as claimed in claim 11, wherein the insert is made of PTFE or PEEK.

13. A fuel injector (200) as claimed in any preceding claim, wherein the integrated guide component (216) is made of PTFE or PEEK.

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