Injector and rail assembly

Abstract

An injector and rail assembly (10,fig.1) comprising a fuel injector 22 provided with a ring flange 48 and an injector head 20 for receiving fuel. The rail assembly comprises a common rail housing (12,fig.1) defining a reservoir volume 14. The rail housing comprises at least one socket 16 having a bore 18 for delivering fuel from the reservoir volume to the injector head. The injector and rail assembly further comprises a mechanical connector 26 for sealingly mounting the fuel injector to the socket. The connector has an upper portion 50 to threadedly engage an outer surface 28 of the socket and a lower portion 54 having a first face 66 to interface with a second face 62 of the ring flange. At least one of the first and second surfaces define a curved surface. The first face may be convexly curved and the second surface may be concavely curved.

Description

TECHNICAL FIELD 5 The invention relates to an injector and rail assembly for use in a common rail fuel injection system In particular, the invention relates to an injector and a rail connection assembly for use in a common rail fuel injection system for an internal combustion engine. 10 BACKGROUND In a gasoline direct injection fuel system, the fuel from a rail conduit is supplied to a plurality of injectors via a plurality of corresponding rail sockets, with each pair of injectors and the rail sockets being connected using a mechanical connector assembly. 15 The respective position of each rail socket and corresponding injector in a pair is constrained by how the rail conduit is mounted onto the engine head and how the respective injector pockets in the engine head are located relative to the rail assembly. Due to these positional constraints and also potential variations in the dimensions of the rail sockets, injectors, and the injector pockets, each rai! socket and its corresponding 20 injector may be axially and / or angularly misaligned. In addition to this, the amount of axial and / or angular misalignment of each socket and injector pair may be different from that of the other pairs, leading to variation in the amount of misalignment along the rail conduit. 25 While metallic connector interfaces between a rail socket and injector are robust, using a rigid mechanical connection to force a correction to any of the above mentioned misalignments may result in undesirable stresses and strains on the rail and the injector. Furthermore, if a misalignment is large, it could affect the sealing capabilities of the connector, which could in turn lead to fuel leakage between the rail socket and the 30 injector. The mechanical connector assembly must therefore be structurally strong, easy to mount, and prevent fuel leakage while allowing fuel to flow from the rail to the injector. Additionally, the mechanical connector assembly must be able to accommodate both unintended misalignment of the injector and rail socket central axes as well as an unintended separation between the socket and the top head of the injector. Existing mechanical connector assemblies rely on elastomer O-rings at the injector-5 socket interface. However, there is an increasing demand to improve fuel efficiency and reduce exhaust emissions which means injection is required at high fuel pressures, preferably in excess of 500bar. This creates a challenge for the sealing requirements as the elastomer seals are prone to performance degradation and failure over a long service life. The wide temperature range to which the seals are subjected over their 10 service life are also prejudicial to seal performance. In addition, these elastomeric seals may not be reliable in injection systems using gaseous fuel such as hydrogen which can gradually diffuse into the elastomer and degrade the material and the sealing function. This degradation may aggravate in 15 injection systems using hydrogen at very high pressure. It is against this background that the invention has been devised. SUMMARY OF THE INVENTION 20 According to one aspect of the present invention, there is provided an injector and rail assembly for a common rail fuel injection system, the injector and rail assembly comprising a fuel injector comprising an injector body provided with a ring flange arrangement and an injector head end for receiving fuel, a common rail housing defining 25 a reservoir volume for storing fuel at high pressure, the common rail housing comprising at least one socket having a bore for delivering high pressure fuel from the reservoir volume to the head end of the fuel injector; and a mechanical connector assembly for sealingly mounting the fuel injector to the socket of the common rail housing. The mechanical connector assembly comprises an upper portion configured to threadably 3C engage an outer surface of the socket a lower portion having a first surface configured to interface with a second surface of the ring flange arrangement; and an internal channel configured to receive at least a portion of the head end of the fuel injector. At least one of the first or second surfaces defines a curved surface. The invention advantageously allows for corrections to be made to axial and / or angular misalignments 35 which may occur between the injector and the socket. According to another aspect of the invention, there is provided an injector and rail assembly for a common rail fuel injection system, the injector and rail assembly comprising a fuel injector comprising an injector body provided with a ring flange 5 arrangement and an injector head end for receiving fuel, a common rail housing defining a reservoir volume for storing fuel at high pressure, the common rail housing comprising at least one socket having a bore for delivering high pressure fuel from the reservoir volume to the head end of the fuel injector; and a mechanical connector assembly for sealingly mounting the fuel injector to the socket of the common rail housing. The 10 mechanical connector assembly comprises an upper portion configured to threadably engage an outer surface of the socket: a lower portion having a first surface configured to interface with a second surface of the ring flange arrangement; and an internal channel configured to receive at least a portion of the head end of the fuel injector. The lower portion of the mechanical connector assembly is not integral to the mechanical 15 connector assembly. By having the lower connector portion be a separate non-integral component to the rest of the connector, the inner diameter of the lower connector portion is not restricted by needing to be large enough to accommodate the top flange of the injector. For example, if the lower connector portion is a split ring or the like then it is able to be installed onto the injector body at right angles to the injector, and the inner 20 diameter of the lower connector portion need not be sized to accommodate the top flange of the injector. This in turn can allow for the ring flange arrangement of the injector to be smaller in diameter, which again can allow for the overall size of the stock used to machine the injector to be smaller and result in less wastage during the machining process of the injector. 25 The common rail housing may be defined by a conduit which defines the reservoir volume. The first surface may be a convexly curved surface and the second surface may be a 30 concavely curved surface. Alternatively, the first surface may be concavely curved while the second surface may be convexly curved. In other embodiments, the first and second surfaces may be configured in a complementary way to produce a rolling interface between the first and 35 second surfaces. The upper portion of the mechanical connector assembly may comprise an internal surface having a threaded arrangement for cooperating with a threaded arrangement on the outer surface of the socket. 5 The ring flange arrangement may comprise a ring and a flange, the flange being integral to the fuel injector, the ring being removably coupled to the fuel injector, the ring defining the second surface. 10 The lower portion of the mechanical connector assembly may not be integral to the mechanical connector assembly. The head end of the fuel injector may comprise an upper flange. The radial diameter of the upper flange may be less than the radial inner diameter of the socket bore. 15 Inner surfaces of the socket and the upper flange may cooperate to define a sealing ring cavity. The upper flange, a sloping portion of the socket, and a lower internal wail of the socket may cooperate to define a sealing ring cavity. An annular sealing element may be housed in the sealing ring cavity. The annular sealing element may be formed of one 20 of: a metal; and a composite material. Although using metallic sealing rings instead of elastomeric rings is known and can provide a robust performance under high pressure and wide temperature conditions, using metallic sealing rings with an improperly designed connection arrangement may 25 make the arrangement rigid or inflexible, for example then not optimally accommodating any angular or linear misalignments between the injectors and the rail sockets. The present invention overcomes this limitation using an advantageous mechanical connector assembly. 3C The common rail housing may comprise a housing for a doser. The doser may be provided between the reservoir volume and the socket. According to another aspect of the invention, there is provided an injector and rail 35 assembly for a common rail fuel injection system, the injector and rail assembly 4 comprising a fuel injector comprising an injector body provided with a ring flange arrangement and an injector head end for receiving fuel, a common rail housing defining a reservoir volume for storing fuel at high pressure, the common rail housing comprising at least one socket having a bore for delivering high pressure fuel from the reservoir 5 volume to the head end of the fuel injector; and a mechanical connector assembly for sealingly mounting the fuel injector to the socket of the common rail housing. The mechanical connector assembly comprises an upper portion configured to threadably engage with an outer surface of the socket; a lower portion having a first surface configured to interface with a second surface of the ring flange arrangement; and an 10 internal channel configured to receive at least a portion of the head end of the fuel injector. At least one of the first or second surfaces defines a curved surface. BRIEF DESCRIPTION OF THE DRAWINGS 15 Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front view of an injector and rail assembly, with the injector and rail socket connected via a mechanical connector according to an embodiment of the invention; 20 Figures 2a and 2b show non-limiting examples of axial and angular misalignments of between an injector and its corresponding socket; Figure 3 is a cross-sectional view of the injector and rail assembly of Figure 1; 25 Figure 4 is a cross-sectional view of an injector and rail assembly according to another embodiment of the invention; Figure 5 is a cross-sectional view of an injector and rail assembly according to another 3C embodiment of the invention; Figure 6 is a cross-sectional view of an injector and rail assembly according to another embodiment of the invention; Figures 7a, / b, and 7c each show different methods of assembling the different embodiments of the injector and rail assemblies described above; and Figure 8 is a cross-sectional view of an injector and rail assembly according to another embodiment of the invention. DETAILED DESCRIPTION In general, embodiments of the invention provide arrangements for common rail fuel injection systems which provide improved management of axial and / or angular misalignments of the fuel injector with the socket, while providing more secure and adaptable means for preventing leakage of fuel from the interface between the injector and the socket. Embodiments of the invention are applicable to any such fuel injection systems, for example those used by vehicles such as automobiles, submersibles, and the like. The fuel used may be any liquid or gaseous fuel for use in such systems, such as hydrocarbon-based fuels, synthetic fuels such as eiectrofuels, hydrogen or other alternative fuels, and the like. The embodiments of the invention are also applicable to fuel injection systems that employ auxiliary systems such as lubrication dosing systems as is described below with respect to Figure 8, or other auxiliary systems and the like. Embodiments of the invention are described in relation to a seated arrangement of the injector, in which the injector seat ring rests on a ledge inside the pocket of the engine, as opposed to a hanging arrangement, in which the injector is retained against the socket and / or rail by a clip or pin. In the following description, directional or relative references such as ‘upper’, lower’, ‘above’ and ‘below’, relate to the orientation of the features as illustrated in the drawings, but such references are not to be considered limiting. The skilled reader will appreciate that injector and rail assemblies in accordance with embodiments of the invention may be oriented differently to the manner depicted in the drawings in practice. Figures 1 and 2 show an injector and rail assembly 10 for a fuel system of a gasoline direct injection engine which includes a common rail housing 12 including a conduit defining a reservoir or rail volume 14 for storing fuel at high pressure. The injector and rail assembly 10 also includes a socket 16 having a central axis L and a bore 18 defining a passage for delivering high pressure fuel from the reservoir volume 14 to the head end 20 of a fuel injector 22. An outlet 24 of the rail conduit allows fuel to enter the socket 16 from the rail volume 14. The fuel injector 22 is mounted onto the engine head (not shown), and the socket 16 is typically forged or brazed onto the rail housing 12. A 5 mechanical connector assembly or connector 26 connects the head end 20 of the fuel injector 22 to the socket 16. The connector 26 may be made from, for example, metal, polymer, overmolded material, or fibre-reinforced polymer. In practice, several injectors 22 may be clamped along the length of the rail housing 12 depending on the number of cylinders in the engine. A lock nut (not shown) may also be included on the socket 16 10 between the connector 26 and the rail housing 12 to counteract possible loosening of the connector 26 by engine vibrations. In many rail systems which use a seated injector arrangement, the position of the rail socket central axis is typically constrained by the mounting of the rail to the mounting 15 boss on the engine, while the injector position is constrained by the position of the seating ledge on the engine head. Due to variance in manufacturing tolerances, the differences in these positions may result in axial misalignment of the fuel injector with the socket, where when the injector is mounted inside the pocket of the engine head there can be an axial gap / distance between the injector and the socket or its connecting 20 part on the socket; such misalignment can result in fuel leakage. Forced correction of such misalignment or gapping by an intervening resilient / 'tensile or springy C-clip (between the socket and the injector) or other inflexible mechanical connections can lead to undesirable load on the rail and injector. Also, variance in 25 manufacturing tolerances can lead to tilting of the injectors relative to the socket axis, and the correction of this misalignment using inflexible metallic connections can lead to fuel leakage and undesirable stressing / straining of the fuel rail and injector as well as the connector itself. 30 In this embodiment, as will be described below, if such a gap is present then the threading 58, 30 on the connector 26 and the socket 16 allows the connector 26 to be moved gradually closer to the engine head, until it bridges the gap, at which point the connector 26 can be tightened to the extent required to provide a secure downward force on the injector 22. This adjusts for axial misalignment without over-loading the fuel rail 35 assembly 10, including the injector 22 and connector 26, which helps in improving the 7 fatigue life and structural integrity of the associated components. The same mechanism can be used to accommodate differing operating pressure conditions. In embodiments, in addition to bridging a gap in this manner, the same mechanism 5 allows the connector 26 to address any axial misalignment in the opposite direction, for example excessive compression or overlapping of the associated parts, by moving the connector 26 doser to the rail (rather than the engine head) by turning. Figure 2a shows an example of such an axial misalignment of the injector 22 and the 10 socket 16 which embodiments of the invention can accommodate. Figure 2b shows an example of angular misalignment of the injector 22 and the socket 16, as will be described in more detail below, which the invention can also advantageously accommodate. 15 Figures 3 to 6 show an injector 22 and a connector 26, etc according to different embodiments of the invention. For each embodiment, the injector 22 has a longitudinal axis which is preferably aligned with the central longitudinal axis L of the socket 16. The socket 16 has a radially outer surface 28 which comprises threads 30 that spiral 20 around and along the central axis L, along the radially outer surface 28 of the socket 16. The threads 30 extend along the majority of the length of the socket 16 along its central axis L. In other embodiments, the threads 30 may extend along the entire length of the socket 16 along central axis L. The provision of a threaded socket can allow for the height of the connector 26 to be adjusted in relation to the socket 16 without providing 25 an unnecessarily high preload to the rail 14 or compressing other components, as is explained above. The bore 18 of the socket 16 is circular and extends vertically along the central axis L, defining an upper internal wall 32, a sloping section 38, and a lower internal wall 34. The 30 upper internal wall 32 protrudes slightly into the bore 18 towards the central axis L such that the upper internal wall 32 has a diameter Duw which is smaller than the diameter Dlw of the lower internal wall 34. The sloping section 38 joins the upper internal wall 32 to the lower internal wall 34 and thus has a diameter which varies along the central axis L. The upper internal wall 32 and sloping section 38 therefore together define an internal 35 protrusion 36. In other embodiments, the protrusion 36 may instead have a horizontal 8 ledge or similar, such that the sloping section instead extends substantially perpendicularly to the central axis L. The head end 20 of the fuel injector 22 is substantially cylindrical with a diameter which 5 is smaller than the diameter Duw of the bore upper internal wall 32 and has an annular top (upper) flange 40 with a diameter Dtf. Diameter Dtf is smaller than the diameter Diw of the socket bore 18 such that there is a small gap 42 between the bore 18 lower internal wall 34 and the outer side wall of the top flange 40 when the head end 20 of the injector 22 is inserted into the socket bore 18. The small gap 42 allows for the injector and rail 10 assembly 10 to accommodate some tilt of the injector when it is assembled into the socket, without loading the injector or the socket. The size of the gap 42 depends on the angle of inclination of the injector 22 that can be accommodated, which also depends on the rolling interface range between the connector 26 and the contoured surface of the ring flange arrangement 48. The angle of inclination also depends on different 15 factors, for example, control of manufacturing tolerance, constraints between the injector top flange 40 and internal protrusion 36, etc. The top flange 40 is situated a distance below the top of the head end 20 of the fuel injector 22, such that the top surface of the top flange 40, a portion of the lower internal 20 wall 34 of the bore 18, the sloping section 38, and a portion of the head end 20 of the fuel injector 22 together define a sealing ring cavity 44. The sealing ring cavity 44 houses an annular sealing element 46 and prevents the sealing element 46 from being easily dislodged. The internal protrusion 36 is especially advantageous in securing the sealing element 46 within this sealing ring cavity 44. However, in some embodiments it is 25 possible for there to be no internal protrusion in the socket, in which case the sealing element 46 rests on top of the top flange 40. One or more of these surfaces which interact to form the sealing ring cavity 44 may be curved or rounded to align more closely with the shape of the sealing element 46. In 30 embodiments, the annular sealing element 46 is flexible and may be an elastomeric or metallic O-ring, alternatively it may be a C-ring, E-ring, Y-ring or other similar element. This sealing element could be an energized ring that employs within their construction a resilient media or a structural member such as springs. The sealing element could be plain or heat-treated or surface coated based on the application needs. The seal between the injector 22 and the engine environment, which prevents leakage from the interface between the injector and the socket / connector, is provided by this sealing element 46. Thus, the seal does not have to be provided by an interface between the injector head 20 and an inner surface of the socket 16 as in previously considered 5 arrangements. The injector 22 also comprises a ring flange arrangement 48, 148, etc which is situated below the head end 20 of the injector 22. As is shown in the Figures, the body of the injector 22 which extends below the ring flange arrangement 48,148, etc has a diameter 10 which is larger than the diameter of the head end 20 of the fuel injector 22. As the configuration of the ring flange arrangement 48, 148, etc may differ between the embodiments, it will be described in more detail below with respect to each different embodiment. 15 In embodiments, the connector 26 is shaped in the form of a hexagonal nut, to allow an appropriate tool to turn the connector 26 on the threads 58 described below. The connector 26 has an upper connector portion 50, a middle connector portion 52, 252, etc, and a lower connector portion 54, 254, etc. The upper connector portion 50, 20 middle connector portion 52, 252, etc, and at least a part of the lower connector portion 54, 254, etc are all formed integrally. The upper connector portion 50 has a radially inner surface 56 that is configured to threadably engage with the outer threads 30 of the socket 16, i.e. with an outer surface of the socket 16. The radially inner surface 56 therefore comprises threads 58 that spiral around and along the length of the radially inner surface 25 56 of the upper connector portion 50. To enable the injector 22 to remain well seated on the ledge of the pocket inside the engine head (not shown) against combustion gas pressure, a downward (seating) force on the injector 22 is required. This is achieved by turning the connector 26 on the socket 30 16 such that it engages with the flange ring arrangement 48, 148, etc on the injector 22. Tightening of the connector 26 provides the seating force on the injector 22 and locks the connector 26 with the socket 16. The threaded connection of the connector 26 with the socket 16 helps to adjust for any axial gaps caused by misalignment, without inducing extraneous stresses and / or strains on the injector and rail assembly 10. The upper connector portion 50 transitions to the middle connector portion 52, 252, etc, which then transitions to the lower connector portion 54, 254, etc. The iower connector portion 54,254, etc has a lower surface 66, 266, etc (or first surface) which is configured to interface with an upper surface 62, 162, etc (or second surface) of the ring flange 5 arrangement 48, 148, etc. As the configuration of the lower connector portion 54, 254, etc may differ between the embodiments, the iower connector portion 54, 254, etc and its interface with the ring flange arrangement 48, 148, etc wiil be described in more detail below with respect to each different embodiment. 10 The connector 26 also defines an internal channel 60 which is configured to receive at least a portion of the head end 20 of the fuel injector 22, as well as at least a portion of the socket 16 when the socket 16 and connector 26 are threadably engaged. Now, each of the embodiments of Figures 3 to 6 will be described in turn. 15 Figure 3 shows a first embodiment according to the invention. The ring flange arrangement 48 (or ring flange) is situated below the top flange 40 of the injector 22, and in this embodiment the ring flange 48 is integral to the body of the fuel injector 22. The ring flange 48 has a diameter which in this example, is substantially the same as 20 the external diameter of the socket 16. However, other diameters of the ring flange 48 are envisaged. For example, the diameter of the ring flange 48 should be sufficient enough to accommodate the tilting of the injector 22 due to misalignment with the socket 16 and therefore the connector 26, such that when the injector 22 is tilted, the upper surface 62 of the ring flange 48 is still in contact with at least a portion of the lower 25 surface 66 of the lower connector portion 54. The lower surface of the ring flange 48 extends perpendicularly from the main axis of the body of the fuel injector 22. In contrast, the upper surface 62 of the ring flange 48 is concave and curved such that the upper surface 62 of the ring flange 48 extends 30 outwards from the body of the fuel injector 22 through a rounded chamfer, as the upper surface 62 tapers away from the body of the fuel injector 22 and upwards to terminate in a substantially pointed rim 64, ultimately defining a curved surface. In this embodiment, the upper surface 62 of the ring flange 48 is curved in a part-spherical shape, however alternatively, the upper surface 62 may be contoured to have a 35 spheroidal, ellipsoidal, conical shape or the like. In this embodiment, the lower connector portion 54 is integral to the rest of the connector 26. The lower connector portion 54 extends radially inwards from the middle connector portion 52 to create a “lip” for the connector 26, such that the inner diameter of the lower 5 portion 54 is smaller than the inner diameter of the middle portion 52 or the upper portion 50. In fact, in this embodiment the inner diameter of the lower portion 54 is substantially the same as the diameter Dlw of the lower internal wall 34 of the socket 16 However, other inner diameters of the lower portion 54 are envisaged. For example, the inner diameter of the lower portion 54 should be sufficient to accommodate the top flange 40 10 during assembly, such as when using an assembly method which is described below with respect to Figures 7a, 7b, and 7c. It is possible then that the inner diameter of the lower portion 54 is smaller than the diameter Dlw of the lower internal wall 34 of the socket 16, for example, when a greater tilt of the injector 22 needs to be accommodated and so the gap 42 needs to be increased and therefore the top flange 40 can have a 15 smaller diameter. The lower surface 66 of the lower connector portion 54 is convex and curved to substantially complement the shape of the upper surface 62 of the ring flange 48. More specifically, in this embodiment the lower surface 66 of the Sower connector portion 54 20 extends radially inwards and downwards to define a curved surface extending from the lower connector portion 54, to terminate in a rounded end 68. In this embodiment, the lower surface 66 of the lower connector portion 54 is curved in a part-spherical shape, however alternately, the lower surface 66 may be contoured to have a spheroidal, ellipsoidal, conical shape or the like. 25 As mentioned briefly above, the lower surface 66 of the lower connector portion 54 is configured to interface with the upper surface 62 of the ring flange arrangement 48. This is primarily enabled by the complementary curved surfaces. This allows for a rolling interface between the connector 26 and the ring flange 48 that can accommodate 3C angular tilt and a degree of rolling interaction between said connector 26 and the injector 22. The second embodiment as shown in Figure 4 is the same as the first embodiment of Figure 3, except that the ring flange arrangement 148 comprises a first ring 170 which 35 is integral to the injector 22, and a second ring 172 which is machined separately and 12 mounted onto the first integral ring 170, either by push-fitting, cooperating threading, or the like. The upper surface 162 of the ring flange 148 is therefore a part of this separate second ring 172. 5 From Figure 4, it can be seen that the first integral ring 170 has a diameter which is smaller than the diameter of the ring flange arrangement 48 of the embodiment shown in Figure 3. The diameter of the second ring 172 therefore substantially matches the diameter of the ring flange arrangement 48 of the embodiment of Figure 3, such that overall, the ring flange arrangements 48, 148 of the embodiments of Figures 3 and 4 10 have substantially equal outer diameters. Advantageously, as the first ring 170 is integral to the injector 22 while the second ring 172 is not, the comparatively smaller diameter of the integral first ring 170 allows for a smaller stock to be used when machining the body of the injector 22. This can simplify 15 the machining process of the body of the injector 22 while also reducing the amount of material wastage from this machining process. Having a separate ring 172 which hosts the contoured upper surface 162 allows for the possibility of more complicated surfaces to be machined to interface with the connector 26; if defects occur during the machining of the contoured upper surface 162, then it is more efficient and less wasteful to discard 20 the second ring 172 as opposed to an entire body of the injector 22. It is therefore also advantageous to be able to simply replace the second ring 172 during maintenance of the injector 22 if the upper surface 162 has undergone detrimental wear or damage. The third embodiment as shown in Figure 5 is the same as the first embodiment of Figure 25 3, except that in this embodiment, the lower connector portion 254 (and therefore the lower surface 266 which interfaces with the ring flange 248) is not integral to the upper portion 50 and is in fact a separate component. The connector 26 is therefore formed of at least two parts 254, 50. This provides similar advantages to the multiple part flange described above with respect to the embodiment of Figure 4, wherein it is advantageous 30 to be able to simply replace the lower connector portion 254 during maintenance of the injector 22 assembly if the lower surface 266 has undergone detrimental wear or damage. The lower connector portion 254 is a discontinuous ring with a slot cut-out radially through the ring. This cut-out is better seen in Figure 7c. The cut-out slot is large enough to accommodate the diameter of the main body of the head end 20 of the injector 35 22 during assembly, such as in an assembly method shown in Figure 7c. During assembly with the connector 26, the tower connector portion 254 is inserted radially onto the body of the injector 22 to engage with the undercut on the connector 274. In all embodiments, the diameter of the opening at the base of the connector 26 which 5 leads into the internal channel 60 needs to be large enough to accommodate the top flange 40 of the injector 22. However, when the injector and rail assembly 10 is assembled, the tower connector portion 54, 254, etc must extend sufficiently towards the central axis L of the socket 16 such that there is adequate contact between the lower surface 66, 266, etc of the lower connector portion 54, 254, etc and the upper surface 10 62, 162, etc of the ring flange arrangement 48, 148, etc. By having the lower connector portion 254 be a separate non-integral component to the rest of the connector 26, if the lower connector portion 254 is a split ring or the like then it is able to be installed onto the body of the injector 22 at right angles to the injector 22, and the inner diameter of the lower connector portion 254 is not restricted by needing to be large enough to 15 accommodate the top flange 40 of the injector 22. This in turn can allow for the ring flange arrangement 248 of the injector 22 to be smaller in diameter, which again can allow for the overall size of the stock used to machine the injector 22 to be smaller and result in less wastage during the machining process of the injector 22. 20 The middle connector portion 252 in this instance comprises an undercut 274 which interfaces with a complementary mating notch 276 on the lower connector portion 254. The complementary shapes of the undercut 274 and the notch 276 advantageously secure the lower connector portion 254 against the middle connector portion 252 such that the lower connector portion 254 is not dislodged if there is angular tilt of the injector 25 22. The upper surface 262 of the ring flange 248 and the lower surface 266 of the lower connector portion 254 in this embodiment each have a different curvature to the embodiment shown in Figures 3 and 4. The curvature of these surfaces varies across 3C different embodiments, The fourth embodiment as shown in Figure 6 is the same as the third embodiment of Figure 5, except that the lower connector portion 354 takes the form of a split O-ring or a full O-ring with a circular cross section. The lower surface 366 of the lower connector 35 portion 354 is therefore a portion of the circumference of the O-ring 354. 14 The middle connector portion 252 also has an undercut 274 similar to that of the embodiment shown in Figure 5. The interface between the lower connector portion 354 and the middle connector portion 252 therefore comprises two distinct points of contact 5 between the middle connector portion 252 and the lower connector portion 354, as opposed to one substantially continuous line of contact as shown in the third embodiment of Figure 5. However, it is envisaged that the undercut 274 of the middle connector portion 252 may 10 be curved to complement the shape of the O-ring 354 and therefore also have a continuous line of contact, preventing any slippage of the O-ring 354 relative to the undercut 274 during assembly and regular service life operation The upper surface 362 of the ring flange arrangement 48 is also similar to that of the 15 embodiment shown in Figure 3. It shall be appreciated that the injector and rail assembly 10 may have other configurations, such as having an injector ring flange arrangement which has an additional non-integral ring, such as is shown in Figure 4, as well as also having a 20 connector with a non-integral lower connector portion, such as is shown in Figures 5 and 6. Figures 7a, 7b, and 7c each show different methods of assembling the different embodiments of the injector and rail assemblies described above. 25 Figure 7a shows a method for assembling the first embodiment as shown in Figure 3 wherein the ring flange 48 is fully integral to the fuel injector 22, and the connector 26 comprises only one component. The sealing element 46 is placed onto the injector head 20 before the injector 22 is inserted into the engine head. Separately, the connector 26 30 is mounted onto the socket 16. The rail housing 12 and socket 16 which now includes the connector 26 can then be mounted over the injector head 20. The method of assembly as shown in Figure 7b corresponds to an embodiment similar to the fourth embodiment as shown in Figure 6 wherein the lower connector portion 354 35 is not integral to the rest of the connector 26. This method is therefore the same as the 15 method as shown in Figure 7a, except that the lower connector portion 354 is preloaded into the undercut 274 on the connector 26. In this instance, the inner diameter of the lower connector portion 254 is large enough to accommodate the top flange 40 of the injector 22. 5 The method of assembly as shown in Figure 7c corresponds to an embodiment similar to the third embodiment as shown in Figure 5, wherein the Sower connector portion 254 is not integral to the rest of the connector 26. This method is therefore the same as the method as shown in Figure 7b, except that the lower connector portion 354 is a split ring 10 and so is preloaded onto the body of the injector 22 before the rail housing 12, the socket 16, and connector 26 are mounted onto the injector 22. In this instance, the inner diameter of the lower connector portion 254 does not need to be large enough to accommodate the top flange 40 of the injector 22, unlike the other embodiments. 15 The skilled person will appreciate that there is more than one suitable way of assembling and mounting the fuel injector and rail assembly on the engine head. This depends on the configuration of the ring flange 48, 148, etc and the connector 26, as well as preference for packaging and transporting the components, and the suitability of mounting on the engine head at the customer plant. 20 Figure 8 shows an alternative configuration of an injector and rail assembly 110, preferably for use with gaseous fuels such as hydrogen gas, wherein the common rail housing 12 has a housing 78 for an oil lubrication doser, the housing 78 being provided between the reservoir volume 14 and the socket 16. The doser is directly connected to 25 an oil pump (not shown) which provides a small amount of oil into the housing 78 which is interspersed with the hydrogen gas such that droplets of oil can lubricate the walls of the injector 22. While Figure 8 does not show a connector or a lower flange of the fuel injector 22, it is 3C envisaged that any of the connectors 26 or lower flanges 48, 148, etc of the embodiments described above can be used with this assembly 110. Other modifications and variations will be apparent to the skilled person without deviating from the scope of the appended claims. List of parts 10 - injector and rail assembly 12 - rail housing in the form of a conduit 5 14 - reservoir / rail volume for fuel 16 - socket L - socket central axis 18 - socket bore 20 - head end of fuel injector (this also includes the lower flange) 10 22 - fuel injector 24 - outlet in rail conduit 26 •••• mechanical connector assembly or connector 28 - socket radially outer surface 30 - socket outer threads 15 32 - upper internal wall (of bore section) 34 - lower internal wall (of bore section) 36 - internal protrusion Duw - lower internal wall (of bore section) diameter Dlw - lower internal wall (of bore section) diameter 20 38 - sloping portion (of bore section) 40 - injector top flange Dtf - injector top flange diameter 42 - gap between injector top flange 40 and lower internal wall 36 44 ~ sealing ring cavity 25 46 - annular sealing element 48, 148, etc-fuel injector ring flange arrangement 50 - upper connector portion 52, 252, etc - middle connector portion 54, 254, etc - lower connector portion 30 56 ~ radially inner surface of upper connector portion 58 - connector threads 60 - connector internal channel 62, 162, etc - upper surface of ring flange arrangement 64 - pointed rim of ring flange upper surface 35 66, 266, etc - lower surface of the lower connector portion 17 68 - rounded edge of lower connector portion 170 - flange first integral ring 172 - flange second non-integral ring 274 - undercut on connector 5 276 - notch on connector 78 ~ housing for an oil lubrication doser

Claims

1. An injector and rail assembly (10) for a common rail fuel injection system, the injector and rail assembly (10) comprising:5 a fuel injector (22) comprising an injector body provided with a ring flangearrangement (48; 148) and an injector head end (20) for receiving fuel:a common rail housing (12) defining a reservoir volume (14) for storing fuel at high pressure, the common rail housing (12) comprising at least one socket (16) having a bore (18) for delivering high pressure fuel from the reservoir volume (14) to 10 the injector head end (20); anda mechanical connector assembly (26) for sealingly mounting the fuel injector (22) to the socket (16) of the common rail housing (12), the mechanical connector assembly (26) comprising:an upper portion (50) configured to threadably engage an outer surface 15 (28) of the socket (16);a lower portion (54, 254) having a first surface (66, 266) configured to interface with a second surface (62, 162) of the ring flange arrangement (48, 148); andan internal channel (60) configured to receive at least a portion of the 20 head end (20) of the fuel injector (22);wherein at least one of the first or second surfaces (66, 266, 62, 162) defines a curved surface2. The injector and rail assembly (10) of Claim 1, wherein the first surface (66, 266) 25 is a convexly curved surface and the second surface (62, 162) is a concavelycurved surface.

3. The injector and rail assembly (10) of any preceding claim, wherein the upper portion (50) of the mechanical connector assembly (26) comprises an internal 30 surface (56) having a threaded arrangement (58) for cooperating with a threadedarrangement on the outer surface (30) of the socket (16).

4. The injector and rail assembly (10) of any preceding claim, wherein the ring flange arrangement (48) comprises a ring (172) and a flange (170), the flangebeing integral to the fuel injector (22) and the ring (172) being removably coupled to the fuel injector (22), the ring (172) defining the second surface (162).

5. The injector and rail assembly (10) of any preceding claim, wherein the lower portion (254) of the mechanical connector assembly (26) is a separate part from the upper portion (50) of the mechanical connector assembly (26).

6. The injector and rail assembly (10) of any preceding claim, wherein the head end (20) of the fuel injector (22) comprises an upper flange (40).

7. The injector and rail assembly (10) of any preceding claim, wherein the radial diameter of the upper flange (40) is less than the radial inner diameter of the socket bore (18).

8. The injector and rail assembly (10) of any preceding claim, wherein inner surfaces of the socket (16) and the upper flange (40) cooperate to define a sealing ring cavity (44).

9. The injector and rail assembly (10) of Claim 8, wherein the upper flange (40), a sloping portion (38) of the socket (16), and a lower internal wall (34) of the socket (16) cooperate to define the sealing ring cavity (44).

10. The injector and rail assembly (10) of Claim 8 or Claim 9, wherein an annular sealing element (46) is housed in the sealing ring cavity (44).

11. The injector and rail assembly of Claim 10, wherein the annular sealing element (46) is formed of one of: a metal; and a composite material.21

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