Injector and rail assembly

Abstract

A common rail housing 102 has at least one socket 110 having a bore 112 for delivering high pressure fuel from a reservoir volume 104 to a head end 156 of a fuel injector 150. A connector arrangement 120 for sealingly mounting the fuel injector to the socket of the common rail housing has a radially outer portion 122 that threadably engages an outer surface 114 of the socket, a radially inner portion 124 extending inside the socket, and an internal channel 130 that receives at an injector end 132 of the connector arrangement the head end of the fuel injector. The radially inner portion may accommodate an annular sealing element 128 between the inner portion and an inner surface 116 of the socket. A secondary sealing element 152 may be disposed between the injector and the internal channel and retained by a radial flange element 151.

Description

FIELD OF THE INVENTION This invention relates to an injector and rail assembly and a connector arrangement for a common rail fuel injection system, for example for an internal combustion engine. BACKGROUND In a gasoline direct injection fuel system, the fuel from a rail is supplied to a plurality of injectors via a respective rail socket. One type of configuration of an injector mounting in a fuel injection system is the ‘seated’ injector type, in which a seat ring of the fuel injector rests on a ledge inside the pocket of the engine head. In such systems, a hold-down force is required to keep the fue! injector in place against the combustion pressure inside the cylinder during the engine operation. A connector arrangement is generally used to establish a reliable fuel supply path between the socket and injector. The connector should allow fue! supply along the intended fuel path and seal the path to avoid undesirable fuel leakage. In addition, the connector is designed to provide the hold-down force on the injector to keep the injector seated on the ledge. In seated injector arrangements, due to small variations in manufacturing tolerances an unintended gap or separation distance in either direction (along the centra! axis of the injector / socket) may be present between the injector and the part of the connector that provides the hold-down force. Furthermore, in addition to such axial variation, angular misalignment of the injector(s) and the common rail sockets can arise due to small variations in manufacturing tolerances of the precise positions of the rail (and its mounting), the sockets, and the engine head seatings, leading to, for example, a non-coaxiality of this arrangement. Axial and / or angular misalignments can contribute to non-optimal orientation and position of the injector spray tip and therefore result in non-optimal fuel injection spray directions and profiles, and further, inefficient fuel combustion. Previously considered assemblies rely on a resilient or spring clip connecting an injector to its respective socket and / or elastomeric o-rings at the injector-socket interface which may accommodate such angular and axial misalignments, and help hold the injector(s) in place on their respective ledge seatings inside the pockets of the engine head. However, such accommodation to unintended misalignments can result in an additional or undesirable stressing and straining of the rail conduit, socket, injector and other connecting components. This can lower the structural integrity and durable life of the components. Further, there is an increasing demand to improve fuel efficiency and reduce exhaust emissions which means injection is required at high fuel pressures, preferably 500 bar and above. This creates a challenge for the sealing requirements as the elastomer seals are prone to performance degradation and failure over a long service life. Along with harsh pressure conditions, the wide temperature range to which the seals are subjected over their 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 be aggravated in injection systems using hydrogen at very high pressure. Further, although using metallic sealing rings instead of elastomeric rings can provide a robust performance under high pressure and wide temperature conditions, using metallic sealing rings with an improperly designed connection arrangement may make the arrangement rigid or inflexible, for example then not optimally accommodating any angular or linear misalignments between the injectors and the rail sockets. It is against this background that the invention has been devised. SUMMARY OF THE INVENTION According to 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 a 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 connector arrangement for sealingly mounting the fuel injector to the socket of the common rail housing, the connector arrangement comprising: a radially outer portion configured to threadably engage an outer surface of the socket; a radially inner portion configured to extend inside the socket; and an internal channel configured to receive at an injector end of the connector arrangement the head end of the fuel injector. It is one advantage of the invention that provision of an inner portion of the connector arrangement internally to the socket, with threading of the connector outside the socket, can prevent leakage more efficiently than previously considered arrangements. For example, fuel delivered through the socket can be passed via the inner portion of the connector arrangement directly to the injector head received by the connector, helping to prevent leakage which could otherwise occur at the interface between the injector and the socket. In addition, this arrangement accommodates axial and angular misalignment of the fuel injector, with minimal stress / strain, for example even if the sealing rings are metallic. In addition, arrangements according to embodiments of the invention can accommodate sealing rings of various geometrical and material types suitable to fuel injection applications, whilst still providing the sealing required and also accommodating axial and angular misalignments of the injector. In embodiments, the connector arrangement may sealingly retain or hold the injector to the socket. The common rail housing may be a common rail conduit. Suitably, the radially inner portion is configured to accommodate an annular sealing element between the inner portion and an inner surface of the socket, for example between an outer surface of the inner portion and the inner surface of the socket. This can further prevent leakage especially that which may affect the threadings, by sealing the inner portion of the connector inside the socket, whilst the threadings are outside the socket. In embodiments, the radially outer portion comprises an internal surface having a threaded arrangement for cooperating with a threaded arrangement on the outer surface of the socket. Suitably, the radially inner portion comprises a central region extended in the direction of a rail end of the connector arrangement for defining a sealing element channel between said central region and the inner surface of the socket. The annular sealing element may be disposed in the sealing element channel. In embodiments, the annular sealing element is formed of one of: a metal; or a composite material or polymer or elastomer. Suitably, the internal channel is configured to deliver fuel from inside the socket to the injector end of the connector arrangement. This can further minimize leakage, by delivering the fuel from inside the socket, rather than at the end of the socket or stem, and further by providing a single component through which the fuel travels from the socket to the injector head. In embodiments the internal channel comprises at the injector end a widened region for engaging the head end of the fuel injector. Optionally, the widened region has a frustoconical shape, narrowed in the direction of the rail end of the connector arrangement. Suitably, the head end of the fuel injector comprises a substantially part-spherical surface for engagement with the widened region internal channel of the connector arrangement within which it is received. In embodiments the internal channel widened region and / or the injector may have a different shape, such as a frustospherical shape and a bevelled or rounded head respectively. In embodiments, the fuel injector comprises a secondary sealing element disposed between the injector and the internal channel. This provides an arrangement in which the contact interface between the injector head and the internal channel of the connector arrangement is not required to provide the (or a substantial part of) sealing for the junction between the connector (and / or socket) and the injector head. Instead, the injector head / connector contact interface can be allowed to provide the relative movement or alignment of these components to accommodate slight angular misalignment of components of the assembly, while also applying the hold-down force to the injector head. Optionally, the fuel injector comprises a radial flange element for retaining the secondary sealing element. In embodiments, the radial flange element extends radially towards the interna! channel of the connector arrangement as far as a clearing distance between the flange element and the internal channel, which clearing distance being for accommodation of angular misalignment of the assembly. In embodiments, the seal for the injector is between the injector and the connector arrangement (here, the inner surface of the internal channel), rather than between the injector and the socket directly as in some previously considered arrangements. According to another aspect of the present invention, there is provided a connector arrangement for an injector and rail assembly for a common rail fuel injection system, the system having a fuel injector comprising a head end for receiving fuel and a common rail housing defining a reservoir volume for storing fuel at high pressure, the common rail housing having at least one socket having a bore for delivering high pressure fuel from the reservoir volume to the head end of the fuel injector, wherein the connector arrangement is configured to sealingly mount the fuel injector to the socket of the common rail housing, and wherein the connector arrangement comprises: a radially outer portion configured to threadabiy engage an outer surface of the socket a radially inner portion configured to extend inside the socket; and an internal channel configured to receive at an injector end of the connector arrangement the head end of the fuel injector. According to another 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 a 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 connector arrangement for sealingly mounting the fuel injector to the socket of the common rail housing, the connector arrangement configured to threadabiy engage an outer surface of the socket, the connector arrangement comprising an internal channel configured to receive at an injector end of the connector arrangement the head end of the fuel injector, wherein the fuel injector comprises a secondary sealing element disposed between the injector and the internal channel. Optionally, the fuel injector comprises a radial flange element for retaining the secondary sealing element. According to another aspect of the present invention there is provided an injector and rail assembiy for a common rail fuel injection system; the injector and rail assembly comprising: a fuel injector comprising a head end for receiving fuel; a common rail housing comprising at least one socket having a bore for delivering fuel from the housing to the fuel injector; and a connector arrangement for mounting the fuel injector to the socket of the common rail housing, the connector arrangement comprising: a radially outer portion configured to threadably engage an outer surface of the socket: a radially inner portion configured to extend inside the socket; and an internal channel configured to receive the fuel injector. It will be appreciated that preferred and / or optional features of the first aspect of the invention may be incorporated alone or in appropriate combination in other aspects of the invention also. BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more readily understood, preferred non-limiting embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an injector and rail assembiy of an embodiment of the invention; Figure 2 is a cross-sectional view of the injector and rail assembly in Figure 1; Figures 3a to 3d are perspective views to show the installation steps for the injector and rail assembly in Figure 1 when applied to an injector installation; Figure 4 is a perspective view of an injector and rail assembly according to another embodiment of the invention. In the drawings, as well as in the following description, like features are assigned like reference signs. SPECIFIC DESCRIPTION In general embodiments of the invention provide arrangements for common rail fuel injection systems which provide improved management of axial and / or angular misalignment 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 fluid fuel for use in such systems, such as hydrocarbon-based fuels, synthetic fuels such as efuels, hydrogen or other alternative fuels, 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. However, embodiments of the invention are also applicable to a hanging arrangement, as will be described later below. Referring to Figures 1 and 2, an injector and rail assembly according to one embodiment of the invention, referred to generally as 100, for a fuel system of a gasoline direct injection engine includes a common rail housing 102 defining a reservoir or rail volume 104 for storing fuel at high pressure and comprising a socket 110 having a bore 112 for delivering high pressure fuel from the reservoir volume 104 to the head end 156 of a fuel injector, referred to generally as 150, which is coupled to the rail housing 102. An outlet 106 in the rail reservoir aliows fuel to enter the socket from the reservoir. The injector has a longitudinal axis which is aligned with the longitudinal axis of the socket 110. The socket 110 is preferably forged or may be brazed onto the main rail housing 102. An interface between the socket and the fuel injector is provided by a connector arrangement, identified generally as item 120. In embodiments, several injectors may be coupled to the common rail housing along the length of the housing, depending on the number of cylinders in the engine; Figures 3c and 3d illustrate an embodiment of such a multi-injector system. A connector arrangement 120 is provided for mounting or retaining the fuel injector to the socket. In contrast to previously considered systems in which the fuel injector is received and secured inside the bore of the socket, or alternatively in which a mounting arrangement is provided outside the socket to secure the fuel injector, here the connector arrangement comprises an outer eiement, for exampie for securing the mounting, and an inner element, for example for completing the seal of the interface between the components. In embodiments, the nut 120 and components of the arrangement are formed of metal, providing a robust mounting which has increased durability in comparison to previously considered systems. In embodiments, the connector is shaped in the form of a hexagonal nut, to allow an appropriate tool to turn the connector on the threadings described below. In this embodiment, a radially outer portion 122 of the connector nut 120 is configured to threadably engage an outer surface 114 of the socket. The socket’s outer surface 114 is threaded and cooperates with corresponding threading 123 on an inner surface of the outer portion 122 of the connector. In common rail systems using a seated injector arrangement, the position of the rail socket central axis is typically constrained by the mounting of the rail to the mounting boss on the engine head, while the injector position is constrained by the position of the seating ledge inside of the pocket of 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 engine head, where when the injector is mounted inside the pocket of the engine head there can be an additional gap / distance between the injector and the socket; such misalignment can result in fuel leakage. Forced correction of such misalignment or gapping by an intervening resilient or springy C-clip (between the socket and the injector) or other inflexible mechanical connections using metallic sealing rings can lead to undesirable load on the rail and injector. Also, variance in manufacturing tolerances can lead to tilting of the injectors relative to the socket axis and correction or accommodation of this misalignment using metallic sealing rings with inflexible connectors can lead to fuel leakage and undesirable stressing / straining of the fuel rail and injector as well as the connector itself. Instead, in this embodiment if a gap is present the threading 114 / 123 on the connector arrangement 120 and the socket 110 allows the connector to be moved gradually closer to the engine head, until it bridges the gap (for example, between a rounded surface 156 of the head of the injector with a conical interface in the lower cavity 130 / 132 of the connector 120 in the embodiments described below), at which point the connector can be tightened to the extent required to provide a secure downward force on the injector. This adjusts for axial misalignment without over-loading the fuel rail assembly, including the injector and connector, which helps in improving the 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 allows the connector to address any axial misalignment in the opposite direction, for example excessive compression or overlapping of the associated parts, by moving the nut closed to the rail (rather than the engine head) by suitably turning (for example, so that the head of the injector rests against the conical interface, which components described with reference to embodiments below). In addition, in this embodiment a radially inner portion 124 is configured to extend inside the socket, so that there is an operable portion of the connector both outside the socket (providing threading adjustment as above) and inside the socket. This for instance allows a conduit or channel (for example channel 130 described below) to extend from inside the socket to the injector head; this can help prevent leakage by bringing the high pressure initial delivery interface inside the socket, rather than at the end of the socket (or at the end of a stem) as in previously considered arrangements having a connector element. In this embodiment, the rail end of the connector arrangement 120 is formed into inner 124 and outer 122 annular portions which extend from the body of the connector towards the rail. These features can also be seen in Figure 3a. Thus the outer portion as described above extends along an outer surface of the socket 114, engaging with threadings thereon, and the inner portion extends into the centre of the socket, forming a raised central region (raised in the direction of the rail) or pedestal. An outer edge of this inner portion thus extends partly along an inner surface 116 of the socket. Here, the inner portion is also configured to accommodate an annular sealing element 128 between the inner portion and the inner surface 116 of the socket. This is in contrast to previously considered systems having threading on an outer surface of an interface between the rail and the injector, in which sealing elements are incorporated also on the outside surface. In such embodiments, any fuel leakage which could still occur at the interface between the injector head and the socket and / or mounting arrangement may be allowed to enter the threadings, which may be adversely affected by the fuel. Here, the sealing arrangement is inside the socket (and at the connector / mjector junction, as described below), whereas the threading is outside the socket, thus minimizing the possibility that any leakage will affect the threadings. In this embodiment, the connector arrangement 120 has on the inner portion 124 the raised region or section 125 in the centre of the nut (extending in the direction of the rail), defining a sealing element channel 126 between the outer side of the raised section 125 and the inner surface 116 of the socket. The centre of the nut 120 as noted above defines a fuel channel 130 between the socket and the fuel injector, and therefore this fuel channel also passes through the raised section 125. The sealing element channel 126 is occupied by a sealing element 128. The raised section 125 incorporates a sliding, lubricated or otherwise friction-reduced interface 127 with the inside cylindrical surface of the socket wall, so that when the threading on the outer portion 122 of the connector 120 is operated, the inner portion is also allowed to move within the socket. In an embodiment, the internal wall 116 of the socket also incorporates an internal chamfer, ledge or similar (not shown), arranged over the channel 126 to help keep the sealing element 128 in place in the channel. The sealing element 128 prevents fuel leakage from the socket around the outside of the inner portion 124. As can be seen, the sealing element can be of any type sufficient to prevent such leakage; for example, the sealing element can be a sealing ring, such as an O-ring, C-ring, E-ring or Y-ring, any other type of sealing rings that establish a sealing connection with adjacent and interacting surfaces, in an embodiment, these sealing rings comprise energized rings that employ within their construction a resilient media or a structural member such as a spring. In embodiments, the sealing element may be configured to be deformable by the pressure of the fuel within the socket, so that during operation this pressure bears down on the sealing element so that contact with the channel and the inner surface 116 of the socket are increased, providing a more secure seal. It is also notable that, in part because the sealing element in this embodiment is not required to provide any additional structural capability or provide resilience against moving parts it is in contact with, the sealing element can be of any suitabie material, rather than being limited to only metallic sealing rings. The sealing element may be of metal or polymer or composite, and can if needed be heat-treated or surface coated, depending on the application needs. This provides a more adaptable sealing arrangement, which can accommodate different temperature ranges and pressure / durability requirements, different types of fuels, and different specification or cost profiles, for example in different types of engine / vehide; in some previously considered arrangements, using metallic sealing elements may be too rigid or inflexible to accommodate any angular or linear misalignments between the injectors and the rail sockets, as described herein. The connector arrangement 120 also comprises an internal channel 130 which is (at the injector end of the connector) configured to receive the head end of the fuel injector 150. In the embodiment illustrated, the connector 120 has a widened region or recess 130 / 132 at the lower, injector end for engaging the head of the injector. This widened region has a frustoconical-walied portion 132, the narrowed end of the frustoconical shape towards the rail end of the connector. The injector 150 has an injector head 156 of part-spherical form which is received within the conical-walled portion of the internal channel and engages with this conical-walled portion to form a meta!-to-metal interface. This contact interface does not necessarily constitute a sealing interface; the sealing element 152 described below performs the main part of this function. However, the shapes of the conical wall and the spherical injector head permit angular tilting of the injector axis with respect to the socket axis, while the metal-to-metal interface is still capable of exerting (via tightening of the nut, as described above) the necessary downward force to seat the injector on the ledge inside the engine head. This allows the connector arrangement to accommodate angular misalignment, as well as axial misalignment as described in the preceding paragraphs. In this embodiment, the fuel injector 150 has its own, secondary sealing element or injector sealing element 152. This means that the seal between the injector and the engine environment, which prevents leakage from the interface between the injector and the socket / connector, is provided by this secondary sealing element 152, rather than by the head end of the injector itself, the interface between the head end and the inner wall 132 of the connector (or socket) as in previously considered arrangements. Thus the injector head / connector interface can be used largely just to ensure the right amount of accommodation of misalignments, rather than also having to provide the sealing function. A ring flange 151 on the injector upper housing supports the injector sealing element 152. This sealing element thus forms a sealing contact interface with the internal surface of the channel 130 of the connector 120 and the injector head. This is also in contrast to some previously considered arrangements in which a seal for an injector head inside a socket (without a connector or adjustable arrangements as described herein) would be provided between the injector and the socket directly. This sealing element 152 may be an O-ring or C-ring, or similar element, and may have the options as above as the sealing element 128. In embodiments, the specific shapes of the injector head 156 and internal surface 132 of the connector cavity 130 may differ; for example the internal surface of the connector may be arcuate or spheroid or the like, while the injector head may be bevelled or rounded. In each embodiment, the interface between the injector head and the connector internal surface is such that an amount of movement of the injector head inside the connector channel 130 (away from the axis of the injector) is permitted, with the injector surface camming along the internal wall 132, so that angular misalignments can be accommodated. it may also be noted that the advantages of the invention of providing more secure and efficient sealing for the socket / injector interface by providing threading outside the socket and sealing inside, can be achieved in embodiments without necessarily providing angular misalignment accommodation as well. In embodiments, if for some reason the means described herein relating to the channel 130 and injector head 156 are unable to be implemented, elastomeric means can be provided in a manner consistent with previously considered arrangements, to accommodate angular misalignment. The flange also allows a U-pin 172 to be incorporated in the arrangement, via holes in the lower portion of the connector 120 (as shown in Figure 1 and Figure 3d). As in previously considered systems, the U-pin helps hold the injector with the nut during transportation to the customer site before assembling the unit onto the engine head. One way of packaging the unit for transportation is to have the rail and injector together with the U-pin on the nut. An alternative is having the rail and the injector (along with the nut and sealing rings) as two separate entities, without using the U-pin as shown here. The outermost edge of the flange 151 defines a clearing distance or gap 157 with the internal surface of the connector channel 130. This gap permits the tilt of the injector axis relative to the longitudinal axis of the mounting assembly as described above in relation to the injector head / conical surface interface, but is sized to limit this tilt to a certain extent. Embodiments of the invention thus have the advantages described above in relation to secure and adaptable sealing, whilst accommodating axial and angular misalignment. In addition, embodiments of the invention can be composed of all metallic materials, including sealing elements, to withstand high pressure and temperature ranges and maintain good sealing interfaces in such conditions, and to help in minimizing gas diffusion and embrittlement issues, for example as in hydrogen fuel applications. In an embodiment as shown in Figure 4, a check or Socking nut 174 can also be used along with the connector 120. This is disposed above the connector arrangement 120, between it and the rail assembly. The check nut provides additional security of locking tightness and stability for the connector arrangement, for example to withstand extreme vibrating conditions. In an alternative embodiment, features of the embodiments illustrated herein can be used with a hanging arrangement fuel injector system. In this arrangement, a U-pin 172 performs the function of holding the injector 150 inside the cavity of the main nut 120 during the transportation, and when the unit is mounted on the engine head, the U-pin is retained. The U-pin only needs to be strong enough to withstand / bear the downward force on the injector due to the high pressure of the fuel inside the cavity of the socket and the cavity inside the connector upstream of the injector head, and vibration from the engine operation. This is in part permitted by embodiments of the invention having the secondary sealing element 152 which does the job of sealing this part of the assembly rather than the injector 150 and channel 130 / 132 interface; since the sealing element 152 is performing the sealing function, there is less need to provide high resilience in the U-pin to bias the head of the injector 156 up towards the channel surface 132. A further advantage of the threading arrangement on the nut 120 with reference to a hanging arrangement is that the spray tip of the injector needs to be accurately positioned inside the engine pocket to get a good spray of fuel inside the engine cylinder and hence promote an efficient combustion of the fuel; the connector arrangements of embodiments of the invention allow fine adjustment of the vertical position of the injector to enable spray optimisation. With reference to Figures 3a to 3d, steps for assembly of a fuel injector and rail assembly and / or connector arrangement according to an embodiment of the invention are described below. Initially, the sealing element 128 is inserted into the connector 120, into the channel 126 of the inner portion 124 of the nut. Each of the series of connector arrangements 120 is then attached to each respective socket 110 of the rail assembly 102, by screwing the connector onto the threaded section on the outer surface of the socket. For assembly onto the engine head, the injectors are assembled with the injector sealing elements 152 on the respective flanges 151. Each injector is then seated into the respective connector arrangement, so that the conical surface 132 contacts the head 156 of the injector. In an embodiment, injectors can be pre-assembled with a U-pin, for ease of assembly. The assembled rail and injectors are then mounted on the engine head, so that inside each pocket the seating ring 170 of each injector 150 is aimed towards the ledge inside the pocket. Typically, the rail is bolted to the top of the engine head on its mounting boss. Each connector 120 is then turned on the threaded section of the socket until the respective injector and connector arrangement together have moved downwards sufficiently that the seating ring of the respective injector engages and rests on the ledge inside the engine head. Recall that there may be different tolerances and different alignments for different injectors; the respective connectors can be adjusted to accommodate different axial gaps or overlaps, and the heads of the injectors will move inside the connector channels 130 away from the injector axis if necessary to accommodate angular misalignment. The connector 120 can be tightened with a calibrated wrench so that the injector is held onto the ledge with a sufficient force to withstand the cylinder pressure. During nut tightening, the conical wails 132 of the internal channel 130 of the nut establish a contact interaction with the spherically contoured head of the injector 5 and transmit the necessary force to hold the head adapter ring against the ledge inside the engine head. The U-pin can be retained or removed after mounting the rail and injector onto the engine head as described above. It will be appreciated by a person skilled in the art that the invention could be modified to take many alternative forms to that described herein, without departing 10 from the scope of the appended claims.

Claims

1. An injector and rail assembly (100) for a common rail fuel injection system; the injector and rail assembly comprising:a fuel injector (150) comprising a head end (156) for receiving fuel;a common rail housing (102) defining a reservoir volume (104) for storing fuel at high pressure, the common rail housing comprising at least one socket (110) having a bore (112) for delivering high pressure fuel from the reservoir volume to the head end of the fuel injector; anda connector arrangement (120) for sealingly mounting the fuel injector to the socket of the common rail housing, the connector arrangement comprising:a radially outer portion (122) configured to threadably engage an outer surface (114) of the socket;a radially inner portion (124) configured to extend inside the socket; andan internal channel (130) configured to receive at an injector end (132) of the connector arrangement the head end of the fuel injector.

2. The injector and rail assembly (100) as claimed in claim 1, wherein the radially inner portion (124) is configured to accommodate an annular sealing element (128) between the inner portion and an inner surface (116) of the socket.

3. The injector and rail assembly (100) as claimed in claim 1 or claim 2, wherein the radially outer portion comprises an internal surface (123) having a threaded arrangement for cooperating with a threaded arrangement (114) on the outer surface of the socket.

4. The injector and rail assembly (100) as claimed in any of claims 1 to 3, wherein the radially inner portion comprises a central region (125) extended in the direction of a rail end of the connector arrangement for defining a sealing element channel (126) between said central region and the inner surface (116) of the socket.

5. The injector and rail assembly (100) as claimed in any of claims 1 to 4, wherein the annular sealing element is formed of one of: a metal; and a composite material.

6. The injector and rail assembly (100) as claimed in any of claims 1 to 5, wherein the internal channel (130) is configured to deliver fuel from inside the socket (110) to the injector end of the connector arrangement.

7. The injector and rail assembly (100) as claimed in any of claims 1 to 6, wherein the internal channel (130) comprises at the injector end a widened region (132) for engaging the head end of the fuel injector.

8. The injector and rail assembly (100) as claimed in claim 7, wherein the widened region (132) has a frustoconical shape, narrowed in the direction of the rail end (125) of the connector arrangement (120).

9. The injector and rail assembly (100) as claimed in claim 7 or claim 8, wherein the head end (156) of the fuel injector (150) comprises a substantially part-spherical surface for engagement with the widenedregion internal channel (132) of the connector arrangement (120) within which it is received.

10. The injector and rail assembly (100) as claimed in any of the claims 1 to 9, wherein the fuel injector (150) comprises a secondary sealing element (152) disposed between the injector and the internal channel (130).

11. The injector and rail assembly (100) as claimed in claim 10, wherein the fuel injector comprises a radial flange element (151) for retaining the secondary sealing element.

12. The injector and rail assembly (100) as claimed in claim 11, wherein the radial flange element extends radially towards the internal channel (130) of the connector arrangement (120) as far as a clearing distance (157) between the flange element and the internal channel, which clearing distance being for accommodation of angular misalignment of the assembly.

13. A connector arrangement (120) for an injector and rail assembly (100) for a common rail fuel injection system, the system having a fuel injector (150) comprising a head end (156) for receiving fuel and a common rail housing (102) defining a reservoir volume (104) for storing fuel at high pressure, the common rail housing having at least one socket (110) having a bore (112) for delivering high pressure fuel from the reservoir volume to the head end of the fuel injector,wherein the connector arrangement (120) is configured to sealingly mount the fuel injector (150) to the socket (110) of the common rail housing (102), and wherein the connector arrangement comprises:a radially outer portion (122) configured to threadably engage an outer surface (114) of the socket;a radially inner portion (124) configured to extend inside the socket; andan internal channel (130) configured to receive at an injector end (132) of the connector arrangement the head end of the fuel injector.

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