Fuel-rail assembly

Abstract

A fuel-rail assembly 1 comprising a fuel rail 10 having an outlet portion 12 which defines an outlet channel 13. The assembly comprises a fuel injector 20 for injecting gaseous fuel into an engine 50.

Description

Technical Field

[0001] The invention generally relates fuel delivery systems in internal combustion engines and more particularly to a fuel-rail assembly and to a fuel injector. Background Art

[0002] Fuel injectors are used in combustion engines to inject fuel e.g. into a runner of an air intake manifold ahead of a cylinder intake valve or directly into the combustion chamber of an engine cylinder. For direct injection of fuel (e.g. diesel, gasoline, methane, hydrogen, or the like), the injectors are installed in the cylinder head of the internal combustion engine. A bracket or clip is used to secure each injector on the cylinder head and keep it in sealing contact against the pressure in the combustion chamber. The connection between the injector and the fuel rail is usually either a rigid fuel pipe (e.g., for high pressure diesel fuel systems) or direct coupling via an O-ring sealed interface (e.g. for the medium pressure gasoline and gaseous fuel systems).

[0003] Fuel injectors should only be mechanically loaded in the axial direction. However, parasitic lateral loads may occur, e.g., resulting from a poor design or installation of the fuel rail connection. Such lateral loads may damage the injector and compromise its integrity. This problem is especially relevant for direct-injection hydrogen injectors. Maintaining a gas-tight containment for pressurized hydrogen gas is extremely difficult due to its small molecular size. Thus, when the injector is subjected to bending by a lateral load, the seal may be disrupted, and hydrogen gas may start leaking. Excessive leakage of hydrogen at the injector tip is undesirable as it may lead to combustion instability (e.g., due to preignition) and an increase of tailpipe emissions. Lateral loads may be promoted by geometrical deviations in the cylinder head, the fuel injector and / or fuel rail components. Assembly tolerances also have an impact, as well as different thermal expansions that occur during engine operation. Also, a larger engine size with a high number of cylinders can further increase the risk. Technical Problem

[0004] It is thus an object of the present invention to provide an improved connection between a fuel rail and an injector for hydrogen fuel.

[0005] This problem is solved by a fuel-rail system according to claim 1. General Description of the Invention

[0006] The invention provides a fuel-rail assembly, more specifically a fuel-rail assembly for an internal combustion engine. The assembly is part of a fuel supply system of the combustion engine, e.g., as in a powertrain unitofan automotive vehicle. It comprises a fuel rail having an outlet portion made of metal and defining at least one outlet channel. Generally, the fuel rail is designed to contain fuel and deliver the fuel to at least one injector, normally a plurality of injectors (e.g. 3, 4 or 6). It comprises (for each injector) an outlet portion that defines an outlet channel. In other words, the outlet channel is disposed inside the outlet portion. The outlet channel(s) may branch off a main channel of the fuel rail (typically itself defined by a tubular body). The outlet portion - and normally the entire fuel rail - is made of metal, e.g., stainless steel. The fuel supply system is designed to provide a gaseous fuel to the engine, in particular hydrogen fuel. Within the fuel rail, the gaseous fuel may have a pressure of, e.g., of several dozen bars, e.g. in a range varying from 40 to 60 bar(a).

[0007] The fuel-rail assembly also comprises a fuel injector for injecting gaseous fuel into the engine. The injector extends along an axial direction from a proximal side to a distal side. At least some components of the fuel injector may be symmetric with respect to the axial direction. In assembled state, the distal side of the fuel injector faces the engine, while the proximal side faces away from the engine. The terms “proximal” and “distal” are used in the following to describe positions of various components. Typically, one fuel injector is provided per engine cylinder.

[0008] The injector comprises an injector body which defines the axial direction. In other words, the axial direction is fixed with respect to the injector body. It may correspond to a symmetry axis of at least some parts of the injector body. As a rule, the injector body comprises a plurality of components, some of which may be made of metal, typically all of them. Furthermore, the injector comprises a proximally disposed inlet portion made of metal, e.g. stainless steel. The inlet portion is proximally disposed, i.e., on the proximal side of the injector. At least a major part of the inlet portion may be disposed on the proximal side with respect to the injector body.

[0009] The injector body defines an injector cavity that communicates with a distally disposed injector nozzle, and the inlet portion defines an inlet channel which communicates with the injector cavity and is connected to the fuel rail outlet channel. The injector cavity is disposed within the injector body. On the distal side, the injector cavity communicates with the injector nozzle, through which gaseous fuel can be injected into the engine. It will be understood that fuel injection through the nozzle can be controlled by a movable valve element that engages a valve seat in a closed position. The valve element may be part of an elongate pintle that is axially movable within the injector body. The design of the nozzle or the actuating principle of the valve element are not important for the invention. By way of example, the pintle may be biased towards a closed position by a spring element and may be movable to an open position by an armature. The armature, in turn, may be movable by a magnetic field. A solenoid that that may be disposed partly around the armature is adapted (configured) to generate the magnetic field. Solenoid may be arranged around the injector body, preferably in a plastic body, e.g. by overmolding. The inlet portion defines an inlet channel, i.e. the inlet channel is disposed within the inlet portion. Although this is not essential for the invention, the inlet portion and the inlet channel are preferably straight and symmetric with respect to an axis that may be referred to as an inlet axis. The inlet channel communicates with the injector cavity, i.e., gaseous fuel may enter the fuel injector through the inlet channel and flow into the injector cavity, from where it may be ejected through the injector nozzle. The inner channel is connected to the outlet channel so that it can receive gaseous fuel from the fuel rail. Accordingly, the inlet portion is at least indirectly connected to the outlet portion (of the fuel rail).

[0010] According to the invention, the inlet portion is connected to the injector body through an articulation portion that is adapted (configured) so that the inlet portion is tiltable relative to the injector body while maintaining a gas-tight connection between the inlet channel and the injector cavity. In other words, although the inlet portion is part of the injector, it is not rigidly connected to the injector body. Rather, the connection through the articulation portion allows for the inlet portion to be tilted with respect to the injector body. For instance, in an “aligned position” or “ideal position”, the above-mentioned inlet axis may be parallel to the axial direction. However, it is possible to tilt the inlet portion so that the inlet axis is at a nonzero angle with respect to the axial direction. This angle may be referred to as a “tilt angle”. For most applications, the required tilt angle remains small, e.g. of a few degrees. The articulation portion is so adapted / configured that the inlet portion can be tilted while maintaining a gas-tight connection between the inlet channel and the injector cavity. Therefore, even in a tilted position, the fuel supply through the inlet portion to the injector body can be maintained without any (significant) fuel leakage. It will be understood that the term “gas-tight” refers to a situation in which gas leakage is negligible, although it may not be possible to guarantee a 100% tight connection, especially when hydrogen fuel is used. While the inlet portion and the injector body can be considered as rigid, the articulation portion can be considered as flexible.

[0011] Since the inlet portion is tiltable with respect to the injector body, misalignments between the injector body and the fuel rail can be compensated for at least to a certain extent. In contrast to prior art, in which the fuel injector can be considered as a rigid body extending from an inlet portion to the injector nozzle, the fuel injector of the inventive fuel rail has a certain degree of flexibility that is made possible by the articulation portion. This flexibility may in particular prevent damage to the injector resulting from lateral, i.e., radial loads.

[0012] In embodiments, the articulation portion is a flexible portion made of metal and is rigidly connected (in a fluid tight manner) to the inlet portion and the injector body. Although it is flexible, the articulation portion may preferably be made of the same metal as the inlet portion, usually stainless steel. The flexibility is achieved through the geometry of the articulation portion and / or its wall thickness, which may be lower than the wall thickness of the inlet portion. Further, the articulation portion is rigidly connected to both the inlet portion and the injector body, which usually refers to a non-removable connection (e.g. metallurgical connection). In other words, the articulation portion cannot be disconnected from the inlet portion of the injector body in a non-destructive way.

[0013] One embodiment provides that the articulation portion and the inlet portion are made of a single piece of metal. It is conceivable that the shape of the piece of metal is defined by casting / molding or additive manufacturing, but preferably the shape is at least to some extent defined by machining. On the one hand, the assembly process of the injector may be simplified if the two portions are made of a single piece, which may be referred to as an “inlet piece”. On the other hand, gas-tightness can best be guaranteed if both portions are seamlessly connected. The articulation portion may then be bonded to the injector body e.g. by welding or brazing. It should be noted that in this embodiment, there may not be a clear distinction between the inlet portion and the articulation portion. It is also conceivable that a part of the injector body and the articulation portion are made of a single piece of metal, possibly together with the inlet portion. In other embodiments, the articulation portion and the inlet portion may be joined, e.g. by welding or brazing, to form a single unit, before assembly to the fuel injector body.

[0014] A particularly preferred way to provide a flexible metal portion is that the articulation portion is at least partially bellows-shaped and has a corrugated wall. The wall of the articulation portion has a plurality of corrugations, i.e., the wall alternatingly protrudes and recedes in the radial direction. This shape can be referred to as a bellows-shape or gaiter-shape. Such a shape can be also realized if the articulated portion and the inlet portion are made of a single piece. It will be understood that the corrugations, when combined with a sufficiently small wall thickness, provide excellent flexibility. Various numbers of corrugations may be chosen, e.g., between two and five. While a higher number of corrugations improves the flexibility, a lower number may facilitate the manufacturing process.

[0015] Apart from providing the articulation portion as a flexible metal portion, there are other possibilities. According to one option, the articulation portion comprises an inletconnector portion rigidly connected to the inlet portion and a body-connector portion rigidly connected to the injector body, wherein one of inlet-connector portion and the bodyconnector portion is disposed circumferentially around the other and is connected to the other by a form-fit connection with respect to the axial direction. The inlet-connector portion is rigidly connected to the inlet portion and is preferably made of a single piece therewith, which again may be referred to as an inlet piece. The inlet-connector portion may also be considered as part of the inlet portion. The body-connector portion is rigidly connected to the injector body and may be made of a single piece with at least a part of the injector body, or could be connected (joined / welded) thereto. It could also be considered as a part of the injector body. The inlet-connector portion may be disposed circumferentially around the body-connector portion, but it could also be the other way around. Both connector portions are connected by a form-fit connection with respect to the axial direction. This connection at least limits, and possibly prevents axial movement of the connector portions relative to each other. Specifically, the form-fit connection prevents the inlet portion from being removed from the injector body. However, it does not prevent the tilting of the inlet portion. In order to realize the tilting, the connector portions need to be movable with respect to each other.

[0016] In one embodiment, one connector portion could directly engage the other connector portion to establish the form-fit connection. For instance, an inward-facing flange of the radially outer portion could engage an outward-facing flange or a shoulder of the radially inner portion. The inward-facing flange could be produced by a bending process, e.g., after the two connector portions have been assembled. Another embodiment provides that the form-fit connection is established via an intermediate element made of metal which is radially interposed between the inlet-connector portion and the body connector portion. The intermediate element engages both connector portions to provide a form-fit connection. One reason for this configuration may be that the assembly process is facilitated. Preferably, the intermediate element is a snap ring made of metal. The snap ring may be made of spring steel, i.e., a steel that facilitates a certain amount of elastic deformation. The snap ring may be circular, but not fully annular, i.e. it is not closed, but comprises a gap, which allows for an adaption to different diameters. In particular, the snap ring may be expanded during assembly to be passed over a wider part of the radially inner connector portion, or it may be compressed to be passed over a narrow part of the radially outer connector portion. At least one of the connector portions may comprise a recess in which the snap ring is partially disposed.

[0017] At least in an aligned position of the inlet portion with respect to the axial direction, the inlet-connector portion and the body-connector portion may be separated by a radial gap. The aligned position is one position of the tiltable inlet portion with respect to the injector body. Specifically, this may be a position in which the abovementioned inlet axis is parallel to the axial direction. However, it could be a different position. In this aligned position, the inlet-connector portion and the body-connector portion are radially separated, namely by said radial gap. Preferably -in the aligned position- the gap is annular and substantially constant over the entire circumference. Due to the radial gap, the inlet portion can be tilted with respect to the injector body. Depending on the tilt angle, the inlet-connector portion and the body-connector portion may get into contact with each other when the inlet portion is in a “tilt position" that differs from the aligned position. The radial gap may have a different size in different axial positions. Preferably, it is at least 0.5 mm, at least 0.75mm, or at least 1.0 mm wide when the inlet portion is in the aligned position.

[0018] In order to provide the gas-tight connection between the inlet channel and the injector cavity, a sealing element made of polymer material may be interposed between the inlet-connector portion and the body connector portion. It will be understood that the sealing element sealingly engages both connector portions. It may have an annular shape so that it extends circumferentially in the tangential direction. It is elastically deformed by the interaction with the connector portions. Possible polymer materials for the sealing element include e.g. elastomers, elastomer material, in particular fluoroelastomer materials (e.g. FKM), or flurosilicone materials, or similar and other appropriate materials (e.g. HNBR). Preferably, the sealing element is preferably disposed proximal of the intermediate element. This may protect the sealing element from excessive temperatures, while the metallic intermediate element, which is thermally more robust, can provide a shielding effect.

[0019] In order to provide further options for compensating for any misalignment between components of the fuel-rail assembly, it is preferred that the inlet portion is connected to the rail outlet portion so that it is tiltable relative to the outlet portion while maintaining a gas-tight connection between the outlet channel and the inlet channel. The connection between the inlet portion and the outlet portion may be similar to the one between the inlet portion and the injector body, or it may be different. It may allow for a similar tilt angle as the articulation portion. This is usually reasonable because in many cases, the outlet portion is aligned in parallel with the injector body but is radially offset thereto. In order to compensate for this radial offset, the inlet portion has to be tilted about the same angle relative to the outlet portion and the injector body.

[0020] There are various options how the outlet portion and the inlet portion can be connected to one another. According to a preferred option, one of the inlet portion and the outlet portion is partially inserted into the other, with at least one elastic sealing element being radially interposed between the inlet portion and the outlet portion to provide a gastight seal. One could say that one portion forms a sleeve around the other portion. Specifically, the inlet portion may be partially inserted into the outlet portion, so that the outlet portion is circumferentially disposed around a proximal part of the inlet portion. The inlet portion and the outlet portion may be separated by a radial gap, which enables the abovementioned tilting of the inlet portion. In some locations, the radial gap may have a width of up to 1.5 mm or 1.0 mm, while it may be larger in other locations. It will be understood that in order to provide a gas-tight connection, some sealing element has to be disposed in the radial gap. [0021 ] According to one embodiment, an annular sealing element and a backup ring are radially interposed between the inlet portion and the outlet portion. The backup ring and sealing element are adjacent one another, the function of the backup ring being to support the sealing element, namely to limit extrusion of the seal ring. Typically, the sealing element may be disposed proximally from the backup ring. The sealing element may be made of elastomer material, like fluoroelastomer materials or flurosilicone material, and particularly FKM or HNBR. The backup ring may be made of more rigid material, e.g.. PTFE, thus having a lower elasticity but a higher temperature resistance than the first sealing element.

[0022] In embodiments, the articulation portion is configured such that the inlet portion is tiltable relative to the injector body about a tilt angle of at least 1°, typically about 1° to 3°, or possibly more, in any direction. The tilt angle may be measured with respect to an “ideal position”, which could e.g. be the aligned position in which the inlet axis of the inlet portion is aligned with the axial direction. It will be understood that since the tilt angle can be assumed in any direction, the total angular range possible for the inlet portion is twice the tilt angle.

[0023] Preferably, the inlet portion is tiltable to compensate for a radial deviation of the injector body relative to the outlet portion of at least 1 mm in any direction. “Radial deviation” refers to a deviation from an “ideal position” (e.g., the aligned position) with respect to the radial direction. It will be understood that the maximum possible deviation depends on the possible tilt angle, which may be in the range specified above, and on the length of the inlet portion. In some embodiments, the length of the inlet portion may be between 10 mm and 100 mm.

[0024] In a preferred embodiment the injector body is rigidly connected, preferably by clamping, to a cylinder head of the engine. A clamping bracket may be interposed between the cylinder head and the injector body, which exerts an axial force on the injector, thereby securing it to the cylinder head. The radial position of the injector body can be secured by frictional forces between the injector body and the clamping bracket, by a formfit with the clamping device and / or by a form-fit with the cylinder head. At the same time, the fuel rail may be directly or indirectly mounted on the cylinder head. Thus, the relative position of the injector body and the fuel rail can be assumed to remain the same.

[0025] The invention also provides a fuel injector for injecting gaseous fuel into an engine, the injector extending along an axial direction from a proximal side to a distal side and comprising an injector body which defines the axial direction and a proximally disposed inlet portion made of metal, the injector body defining an injector cavity that communicates with a distally disposed injector nozzle, and the inlet portion defining an inlet channel which communicates with the injector cavity and is adapted for connection to an outlet channel of a fuel rail. According to the invention, the inlet portion is connected to the injector body through an articulation portion that is adapted so that the inlet portion is tiltable relative to the injector body while maintaining a gas-tight connection between the inlet channel and the injector cavity.

[0026] All these terms have been explained above with respect to the inventive fuelrail assembly and will therefore not be explained again. Preferred embodiments of the inventive fuel injector correspond to those of the inventive fuel-rail assembly. Brief Description of the Drawings

[0027] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a sectional view of a first embodiment of an inventive fuel-rail assembly; Fig.2 is a sectional view of a portion of a fuel injector of the fuel-rail assembly from fig.1; Fig.3 is a sectional view of a second embodiment of an inventive fuel-rail assembly; and Fig.4 is a detail view Fig.3. Description of Preferred Embodiments

[0028] Fig. 1 shows a fuel-rail assembly 1 according to a first embodiment of the invention, which can be used for a hydrogen internal combustion engine 50, e.g., in a powertrain unit of an automotive vehicle. The fuel-rail assembly 1 comprises a fuel rail 10 that conveys and distributes fuel to a plurality of injectors 20, one of which being shown in fig. 1 and in fig.2. The fuel rail 10 is conventionally made of metal, e.g., stainless steel, and shaped as a tubular body that defines a main channel 11 (extending in the longitudinal direction of the fuel rail body), from which a plurality of outlet channels 13 branch off. The outlet channel 13 is disposed in an outlet portion 12. It extends parallel to an axial direction A (typically transversely to the axis of the main channel 11). The fuel rail 10 typically has at least one inlet port (not shown) for the gaseous fuel, and may have a port for a pressure sensor (not shown) adapted to sense the pressure in the main channel 11.

[0029] The injector 20 has an injector body 21 that is inserted into a receptacle 52 (through bore) of a cylinder head 51 which is part of the engine 50. It is rigidly mounted to the cylinder head 51 by a clamping bracket 53 that is secured to the cylinder head 51 by a screw 54. Specifically, the clamping bracket 53 engages a shoulder 33 of the injector body 21. The injector body 21, which is shown in more detail in fig.2, defines the axial direction A and is partially symmetric thereto. The side of the injector 20 that faces the engine 50 is referred to as a distal side D, while the side facing away from the engine 50 is referred to as a proximal side P. On the proximal side P, the injector body 21 is connected to an inlet portion 40 via an articulation portion 45, both of which will be described further below. The injector 20 is directly coupled to the fuel rail though said inlet portion 40.

[0030] The injector body 21 is at least partially made of metal, preferably entirely. It defines an injector cavity 23 that extends from a so-called upper housing region on the proximal side down to an injector nozzle 24 on the distal side D. The injector body may typically be made of two or more components that are assembled by joining / welding, to have a fixed and gas-tight body structure. The injector nozzle 24 is shown in a closed state in fig. 1. In this state, a pintle head 25.2 of a pintle 25 engages a valve seat 22.1 formed in the injector nozzle 24 portion, the valve seat 22.1 surrounding an outlet orifice 22.2 at the distal portion. In the closed position the injector nozzle 24 is thus closed as the pintle head 25.2 rests on the valve seat 22.1 and obstructs flow through the outlet orifice 22.2. The pintle 25 has an elongate pintle shaft 25.1 and a pintle perch 25.3 (or collar) that radially protrudes from the pintle shaft 25.1. A pintle spring 11 engages the pintle perch 25.3, thus biasing the pintle 25 towards the closed position. From the proximal side P, an armature shaft 28 engages the pintle shaft 25.1. The armature shaft 28 is coupled -here welded- to an armature 27 so that both can move together in the axial direction A within the injector cavity 23. An armature spring 29 acts on the armature 27 and biases it towards the distal side D. A plurality of guide elements 26 of the injector body 21 are disposed in the injector cavity 23 to axially guide the pintle 25 and the armature shaft 28, respectively. Furthermore, a solenoid 30 is disposed around the injector body 21. Typically, the solenoid 30 is overmolded by plastic material. When the solenoid 30 is activated (i.e. energized), it generates a magnetic field that is enhanced by a pole piece 31 (not shown) arranged distally from the armature. Accordingly, the armature 27 is pulled towards the distal side D by the generated magnetic field. The magnetic attraction, together with the force of the armature spring 29, overcomes the force of the pintle spring 11 so that the nozzle 24 is opened. [0031 ] As can be seen in fig. 1, the inlet portion 40 defines an inlet channel 41 that communicates with the outlet channel 13 of the fuel rail 10 and with the injector cavity 23. The inlet portion 40 and the inlet channel 41 are symmetric to an inlet axis B, which in fig. 1 is parallel to the axial direction A. The inlet portion 40 and the articulation portion 45 are provided as a single unit made of stainless steel, of globally tubular shape, which is herein referred to as an inlet piece 42. The inlet piece 42 is connected to a proximal portion 32 of the injector body 21 by metal joining (e.g. welding or brazing). While the inlet portion 40 has a comparatively thick and rigid wall that is parallel to the inlet axis B, the articulation portion 45 is bellows-shaped with a corrugated wall 46. In this embodiment, the corrugated wall 46 has a total of two corrugations, but it could be more or possibly less. The corrugated wall 46 has a smaller thickness than the wall of the inlet portion 40. This, together with the bellows-like shape, gives the articulation portion 45 a certain degree of flexibility. As noted above, the inlet portion 40 and the articulation portion 45 are preferably provided as a single unit: it can be manufactured in one piece; or the inlet portion 40 and the articulation portion 45 may be welded / joined together.

[0032] Fig. 1 shows the fuel rail 10 and the injector body 21 perfectly aligned, wherefore the flexibility of the articulation portion 45 is not relevant. This changes, however, if the fuel rail 10 and the injector body 21 are radially offset, i.e. perpendicular to the axial direction A. In this case, the inlet portion 40 can be tilted (i.e. is tiltable) with respect to the injector body 21 in order to compensate for the misalignment. That is the inlet portion can be inclined, to some extent, relative to the axial direction of the injector, respectively relative to the body. The tiltability is also facilitated by the connection between the inlet portion 40 and the fuel rail outlet portion 12. As can be seen in fig. 1, the inlet portion 40 is partially inserted into the outlet portion 12, while being separated therefrom by a first radial gap 14. In order to provide a gas-tight connection, a sealing element 16 and a backup ring 15 (both being annular) are radially interposed between the inlet portion 40 and the outlet portion 12. By way of example, the backup ring 15 can be made of PTFE and the sealing element 16 can be made of elastomer material, in particular a fluoroelastomer material (e.g. FKM), or a flurosilicone material, or similar and other appropriate materials (e.g. HNBR). Due to the elasticity of these elements 15, 16 and the presence of the first radial gap 14, the inlet portion 40 is tiltable relative to the outlet portion 12. This configuration also avoids metal to metal contacts, that could lead to wear and be a cause of leakage.

[0033] Fig. 3 shows a second embodiment of a fuel rail assembly 1 according to the present invention, which largely corresponds to the first embodiment and insofar will not be explained again. In this case, however, the articulation portion 45 comprises a bodyconnector portion 34 (i.e. cylindrical, proximal end portion) of the injector body 21 and an inlet-connector portion 43 that is part of the inlet piece 42. The inlet-connector portion 43 circumferentially surrounds the body-connector portion 34 in a sleeve-like manner (forming a slip-fit like connection). The connector portions 34, 43 are formed-fittingly connected through an intermediate element 48, in this case a snap ring made of spring steel. Due to the form-fit connection, the inlet piece 42 cannot be removed from the injector body 21.

[0034] More specifically, the body-connector portion 34 is formed by a straight tubular portion axially continuing the injector cavity 23 on the proximal side. The bodyconnector portion 34 can be in one piece with the body upper housing or joined / welded thereto. The inlet piece 42 has a straight pipe section 42.1, which connects the rail, here with an inner diameter corresponding to the inner diameter of the body-connector portion 34. The inlet-connector portion 43 fits over the body-connector portion 34. It comprises a sleeve portion 43.1 that connects the pipe section 42.1 through a base portion 43.2. In embodiments, the length of pipe section 42.1 can range from 10 to 100 mm, in particular the apparent length extending from the inlet-connector portion 43 to the entrance of the outlet portion 12.

[0035] In order to provide a gas-tight connection, a sealing element 49 is interposed between the connector portions 34, 43. Here, it rests on an annular shoulder towards facing the base portion 43.2. The sealing element of 49 is an annular element, .e.g an O-ring, and may be made of elastomer material, in particular a fluoroelastomer material (e.g. FKM), or a flurosilicone material, or similar and other appropriate materials (e.g. HNBR).

[0036] In the assembled configuration, the snap ring is partially received in an annular groove 34.1 in the connector portions 34 as well as in a radial recess 43.3 on the inner face of the sleeve portion. The annular groove 34.1 is designed as stowage recess, i.e. it is adapted so that the span ring can be elastically deformable to be received in the stowage recess during assembly of the connector portions 34, 43.

[0037] The connector portions 34, 43 are configured to be separated by a second radial gap 47 in the aligned position (in which the inlet axis B is parallel to the axial direction A), which allows the inlet portion 42 to be tilted relative to the injector body 21. For example, in the aligned position the second radial gap 47 may have a width of at least 1 mm, but a greater or smaller width is also possible. In the aligned configuration, the gap is annular with a substantially constant width. Fig. 3, however shows the inlet portion 40 in a tilted position in which the inlet axis B deviates from the axial direction a by a nonzero tilt angle. In this example, the tilt angle is about 2°, but it could be smaller or greater. Due to the tilting position, the second radial gap 47 is smaller than 1 mm in some locations. The tilting of the inlet portion 40 may allow to compensate for a radial deviation between the fuel rail outlet portion 12 and the injector body 21. Preferably, the radial deviation can be at least 1 mm in any direction.

[0038] As can be better seen in Fig.4, the connector portions 34, 43 are in axial abutment. The body-connector portion 34 has an end portion 34.2 in abutment against a frusto-conical surface 43.4 of the base portion 43.2, around the distal end of the channel 41. In Fig.4, the end portion 34.2 has a frusto-conical end surface, but in other embodiments it may be rather rounded to better assist the pivoting / rotation of the inlet piece 42 relative to the body.

[0039] Legend of Reference Numbers: 1 fuel-rail assembly 10 fuel rail 11 main channel 12 outlet portion 13 outlet channel 14, 47 radial gap 15, 16, 49 sealing element 20 injector 21 injector body 22 distal portion 22.1 valve seat 23 injector cavity 24 25 25.1 25.2 25.3 26 27 28 29 30 31 32 33 34 40 41 42 43 45 46 48 50 51 52 53 54 A B injector nozzle pintle pintle shaft pintle head pintle perch guide element armature armature shaft armature spring solenoid pole piece proximal portion shoulder body-connector portion inlet portion inlet channel inlet piece inlet-connector portion articulation portion corrugated wall intermediate element engine cylinder head receptacle clamping bracket screw axial direction inlet axis

Claims

1. A fuel-rail assembly (1) comprising:a fuel rail (10) having an outlet portion (12) made of metal and defining an outlet channel (13),a fuel injector (20) for injecting gaseous fuel into an engine (50), the injector (20) extending along an axial direction (A) from a proximal side (P) to a distal side (D) and comprising an injector body (21) which defines the axial direction (A), and a proximally disposed inlet portion (40) made of metal, the injector body (21) defining an injector cavity (23) that communicates with a distally disposed injector nozzle (24), and the inlet portion (40) defining an inlet channel (41) which communicates with the injector cavity (23) and is connected to the outlet channel (13),wherein the inlet portion (40) is connected to the injector body (21) through an articulation portion (45) that is adapted so that the inlet portion (40) is tiltable relative to the injector body (21) while maintaining a gas-tight connection between the inlet channel (41) and the injector cavity (23).

2. The fuel-rail assembly according to claim 1, wherein the articulation portion (45) is a flexible portion made of metal and is rigidly connected to the inlet portion (40) and the injector body (21).

3. The fuel-rail assembly according to any of the preceding claims, wherein the articulation portion (45) and the inlet portion (40) are made of a single piece (42) of metal, or made as a preassembled single unit.

4. The fuel-rail assembly according to any of the preceding claims, wherein the articulation portion (45) is at least partially bellows-shaped and has a corrugated wall (46).

5. The fuel-rail assembly according to any of the preceding claims, wherein the articulation portion (45) comprises an inlet-connector portion (43) rigidly connected to the inlet portion (40) and a body-connector portion (34) rigidly connected to the injector body (21), whereinone of inlet-connector portion (43) and the body-connector portion (34) is disposed circumferentially around the other, and is connected to the other by a form-fit connection with respect to the axial direction (A).

6. The fuel-rail assembly according to claim 5, wherein the form-fit connection is established via an intermediate element (48) made of metal which is radially interposed between the inlet-connector portion (43) and the body connector portion (34).

7. The fuel-rail assembly according to claim 6, wherein the intermediate element is a snap ring which is partially received in an annular groove (34.1) in the body connector portion as well as in a radial recess (43.3) in the inlet-connector portion (43), one of the annular groove and radial recess being designed as stowage recess adapted so that the snap ring can be elastically deformed to be received in the stowage recess during assembly of the connector portions.

8. The fuel-rail assembly according to claim 6 or 7, whereinthe body-connector portion (34) is formed by a straight tubular portion axially continuing the injector cavity (23) on the proximal side;the inlet portion (40) comprises a pipe section (42.1) unitary with the inlet-connector portion (43);the inlet-connector portion (43) fits over the body-connector portion (34);the inlet-connector portion (43) comprises a sleeve portion (43.1) that connects the pipe section (42.1) through a base portion (43.2).

9. The fuel-rail assembly according to claim 8, wherein the body-connector portion (34) has a rounded end portion (34.2) in abutment against a frusto-conical surface (43.4) of the base portion 43.2, around the channel (41).

10. The fuel-rail assembly according to any of the preceding claims, wherein at least in an aligned position of the inlet portion (40) with respect to the axial direction (A), the inletconnector portion (43) and the body-connector portion (34) are separated by a radial gap (47).

11. The fuel-rail assembly according to any of the preceding claims, wherein an elastomeric sealing element (49) is interposed between the inlet-connector portion (43) and the body connector portion (34), which sealing element (49) is preferably disposed proximal of the intermediate element (48).

12. The fuel-rail assembly according to any of the preceding claims, wherein the inlet portion (40) is connected to the outlet portion (12) so that it is tiltable relative to the outlet portion (12) while maintaining a gas-tight connection between the outlet channel (13) and the inlet channel (41).

13. The fuel-rail assembly according to any of the preceding claims, wherein one of the inlet portion (40) and the outlet portion (12) is partially inserted into the other, with an elastic sealing element (16) being radially interposed between the inlet portion (40) and the outlet portion (12) to provide a gas-tight seal.

14. The fuel-rail assembly according to any of the preceding claims, wherein an annular sealing element (16) and backup ring (15) axially offset from the first sealing element (15) are radially interposed between the inlet portion (40) and the outlet portion (12).

15. The fuel-rail assembly according to any of the preceding claims, wherein the articulation portion (45) is adapted so that the inlet portion (40) is tiltable relative to the injector body (21) about a tilt angle of at least 1° , preferably between 1 and 3° , in any direction.

16. The fuel-rail assembly according to any of the preceding claims, wherein the inlet portion (40) is tiltable to compensate for a radial deviation of the injector body (21) relative to the outlet portion (12) of at least 1 mm in any direction.

17. The fuel-rail assembly according to any of the preceding claims, wherein the injector body (21) is rigidly connected, preferably by clamping, to a cylinder head (51) of the engine (50).

18. A fuel injector (20) for injecting gaseous fuel into an engine, the injector (20) extending 5 along an axial direction (A) from a proximal side (P) to a distal side (D) and comprising an injector body (21) which defines the axial direction (A), and a proximally disposed inlet portion (40) made of metal, the injector body (21) defining an injector cavity (23) that communicates with a distally disposed injector nozzle (24), and the inlet portion (40) defining an inlet channel (41) which communicates with the injector cavity (23) and is 10 adapted for connection to an outlet channel (13) of a fuel rail (10),wherein the inlet portion (40) is connected to the injector body (21) through an articulation portion (45) that is configured such that the inlet portion (40) is tiltable relative to the injector body (21) while maintaining a gas-tight connection between the inlet channel (41) and the injector cavity (23).

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