Gas injector for an internal combustion engine

Abstract

The present invention provides a gas injector (10) for an internal combustion engine, extending along an injector axis (A) from a proximal side (P) to a distal side (D) and comprising an injector body (12) defining a channel (20) extending from a proximal inlet portion (14) to a distal outlet portion (18) having an outlet opening (22) surrounded by a valve seat (24), an outwardly-opening pintle (26), a magnetic armature mechanically coupled to said pintle shaft in the direction of the injector axis and a spring arranged to bias said pintle towards its closed position. According to the invention, the pintle shaft (28) comprises a hollow length (28.1) extending along the injector axis, and the pintle comprises a proximal aperture (26.1) and a distal aperture (26.2), thereby defining an axial gas passage between the inlet portion (14) and the outlet portion (18), at least two flexible sealing membranes (40, 40') extend between the injector body (12) and the pintle shaft (28), the sealing membranes (40, 40') being axially spaced and configured to sealingly isolate the axial gas passage from an intermediate portion (44) of the gas injector (10), the intermediate portion (44) at least partially surrounding the pintle shaft (28) and being adapted to contain lubricating fluid, and at least one of said armature (32) and said spring (34) is arranged in said intermediate portion.

Description

[0001] GAS INJECTOR FOR AN INTERNAL COMBUSTION ENGINE

[0002] Technical field

[0003] The present invention generally relates to a gas injector for injection of gaseous fuel in an internal combustion engine.

[0004] Background Art

[0005] For automotive applications, hydrogen engines are considered as a promising alternative to gasoline or diesel engines. Indeed, emissions from hydrogen internal combustion engines consist mainly of water and do not comprise nearly as much pollutants as those from traditional engines. When designing hydrogen engine components, inspiration is naturally drawn from those of currently available thermal engines, which are typically powered by liquid fuel such as gasoline or diesel.

[0006] In their simplest form, the fuel delivery systems of such liquid fueled combustion engines typically comprise a liquid fuel tank with a low-pressure pump, a high- pressure pump connected thereto, a fuel rail and a plurality of fuel injectors.

[0007] However, the components of liquid fueled engines cannot be carelessly used in gaseous fueled internal combustion engines and must instead be adapted to meet specific technical requirements. In particular, when designing gaseous fuel delivery systems, care must be taken to anticipate possible fuel leaks and / or excessive pressure drops, which occur much more frequently with gaseous fuels than with their liquid counterparts. Moreover, gaseous fuels may lack some advantageous properties of liquid fuels such as self-lubrication or squeeze damping properties. Finally, some gaseous fuel such as hydrogen may cause embrittlement of some components, in particular components made from martensitic stainless steels.

[0008] Technical problem

[0009] It is an object of the present invention to provide a gas injector suitable for injection of gaseous fuel, which overcomes the aforementioned drawbacks.

[0010] This object is achieved by a gas injector as claimed in claim 1 . General Description of the Invention

[0011] In order to overcome the above-mentioned drawbacks, the present invention provides a gas injector for an internal combustion engine, the gas injector extending along an injector axis from a proximal side to a distal side and comprising: an injector body defining a channel extending from a proximal inlet portion to a distal outlet portion having an outlet opening surrounded by a valve seat, an outwardly-opening pintle having a pintle shaft and pintle head, wherein the pintle is movable along the injector axis between a closed position, in which the pintle head engages said outlet valve seat to prevent gas flow through the outlet opening, and an open position, in which the pintle head is distally spaced from the valve seat to enable flow of gas through the outlet opening, a magnetic armature mechanically coupled to said pintle shaft in the direction of the injector axis; and a spring arranged to bias said pintle towards its closed position.

[0012] According to the invention, the pintle shaft comprises a hollow length extending along the injector axis, and the pintle comprises a proximal aperture and a distal aperture, thereby defining an axial gas passage between the inlet portion and the outlet portion. At least two flexible sealing membranes extend between the injector body and the pintle shaft, the sealing membranes being axially spaced and configured to sealingly isolate the axial gas passage from an intermediate portion of the gas injector, the intermediate portion at least partially surrounding the pintle shaft and being adapted to contain lubricating fluid. Furthermore, at least one of the magnetic armature and the spring is arranged in said intermediate portion.

[0013] The above design confers a plurality of technical advantages. Indeed, first of all, the present injector defines a straight gas passage extending throughout its length. Gas entering the gas passage at the inlet portion exits through the distal aperture near the outlet opening and upstream of the valve seat. A straight gas passage is thus provided, thereby avoiding significant pressure drops as undergone in conventional designs with solid pintle shafts, where the fuel has to flow around the pintle and through the armature and spring. Moreover, the magnetic armature may be arranged in the intermediate portion and submerged in lubricating fluid. In such a case, the closing motion of pintle generates a pressure increase of lubricating fluid on the proximal side of the armature, thereby reducing its speed towards the proximal side. This so called “squeeze damping” reduces the impact speed of the pintle against the valve seat, thereby improving the durability of the pintle head-valve seat contact interface. Furthermore, by submerging the armature and / or the spring in lubricating fluid, unwanted oscillations of moving components are better dampened, thereby preventing resonance from leading to inconsistent injections. Finally, components arranged in the intermediate portion are not in contact with hydrogen and are thus not susceptible to hydrogen embrittlement.

[0014] It may be noted that whereas the present injector has been developed for injection of gaseous fuel such as hydrogen, it can also be used for injection of pressurized / compressed air, e.g. in an engine combustion chamber.

[0015] The membranes are said to be “flexible” as they are able to deform according to the movement of the pintle in axial direction. The membranes are also, per design, fluid- tight. They can be made of metal or other appropriate material. The membranes are connected to the body or injector shaft in a fluid-tight manner. The connection of the membranes to the injector body or injector shaft may be direct or via an interposed element, in the latter case the interposed element is also connected in a fluid-tight manner to the body or shaft.

[0016] In embodiments, each sealing membrane is sealingly connected to an outer surface of the pintle shaft and to an inner surface of the injector body, thereby preventing flow of fluid between the inlet, outlet and intermediate portions, and each sealing membrane is expandable and / or elastically deformable in the direction of the injector axis. Preferably, each sealing membrane has an inner surface and an outer surface, and said inner surface is sealingly connected to the outer surface of the pintle shaft and to the inner surface of the injector body.

[0017] In embodiments, the sealing membranes are corrugated bellows. The sealing membranes may be made of metal, preferably austenitic stainless steel, copper, copper alloy, nickel or nickel alloy. In embodiments, the gas injector further comprises, one, preferably two guides configured to constrain motion of the pintle to the injector axis. Preferably at least one, more preferably two, sealing membrane is sealingly connected to the inner surface of the injector body by means of one respective guide. Alternatively or additionally, the armature may be clearance fitted in the injector body, thereby constraining motion of the pintle to the injector axis.

[0018] In embodiments, the armature is arranged in said intermediate portion, thereby dividing the intermediate portion in a proximal sub-portion and a distal sub-portion, and the armature comprises at least one through-hole, configured to promote flow of lubricating fluid between said proximal sub-portion and said distal sub-portion.

[0019] Preferably, the armature and / or the inlet member define a plenum chamber when the pintle is in its closed position, and the volume of said plenum chamber decreases during the closing motion of the pintle, thereby resulting in a pressure increase on the proximal side of the armature.

[0020] This increase in pressure on the proximal side of the armature results in a hydraulic braking force which slows down the closing motion of the pintle, thereby reducing the impact speed of the pintle head against the valve seat and improving their durability.

[0021] Preferably, in closed position, the inlet member at least partially covers the at least one through-hole of the armature, or the armature or the inlet member comprises a protruding shoulder whilst the other comprises an opposite, correspondingly shaped recess.

[0022] In embodiments, the gas injector further comprises a pole piece arranged in the intermediate volume.

[0023] In embodiments, a sealable orifice is formed in the injector body, the sealable orifice being configured to enable filling of the intermediate portion with lubricant fluid.

[0024] In embodiments, the pintle head comprises a pin-shaped attachment portion that is fitted inside a distal axial open end of said pintle shaft, thereby closing the latter. Preferably, the pintle head comprises a comprises a tubular attachment portion and the distal end of the pintle shaft is engaged inside or around said tubular attachment portion. Preferably, the distal aperture is arranged in the pintle shaft upstream of the tubular attachment portion, and / or the distal aperture is arranged at the level of the tubular attachment and extends through the pintle shaft and tubular attachment.

[0025] In embodiments, the gas injector further comprises a solenoid arranged to generate, when energized, a magnetic field that distally attracts said magnetic armature.

[0026] The present invention further provides a fuel delivery system comprising a gaseous fuel tank configured to store pressurized gaseous fuel, and a fuel rail fluidly coupled to at least one gas injector as described above.

[0027] In embodiments, the fuel delivery system further comprises pressure regulating means configured to decrease the pressure of fuel flow therethrough, wherein the pressure regulating means is serially connected between the fuel tank and the fuel rail.

[0028] Brief Description of the Drawings

[0029] A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

[0030] Fig. 1 is a cross sectional view of an embodiment of the inventive gas injector;

[0031] Fig. 2 is a cross sectional view of another embodiment of the inventive gas injector;

[0032] Fig. 3 is an enlarged view of the embodiment of figure 1 ;

[0033] Fig. 4 is an enlarged view of another embodiment;

[0034] Fig. 5 is a schematic view of a gaseous fuel delivery system comprising the inventive gas injector; and

[0035] Figs. 6a-d are principle views of alternative configurations of the pintle.

[0036] Description of Preferred Embodiments

[0037] Figure 1 shows a first embodiment of the gas injector 10 according to the present invention. The gas injector 10 is adapted to inject a gaseous fuel, in particular hydrogen (H2) or natural gas (CH4), into a combustion chamber of an internal combustion engine (not shown). The term “gaseous fuel” generally includes combustible fluids which are in their gaseous state when exposed to nominal operating conditions of the injector and the engine, e.g. pressure and temperature. Regarding more specifically hydrogen as gaseous fuel for an ICE, it typically consists of a gas with at least 90% hydrogen (H2), preferably pure hydrogen with no more than 2% impurities. In other applications, such as in engines with a precombustion chamber, the present gas injector 10 can also be used to inject pressurized (dry) air into the combustion chamber.

[0038] The gas injector 10 is mostly symmetrical about an injector axis A and comprises an injector body 12, which may be made of one or several pieces. The injector body 12 comprises a main body 12a and a lower body 12b, which are here separate parts fixed together, but could alternatively be integral.

[0039] The injector 10 includes an inlet portion 14 on a proximal side P and an outlet portion 18 on a distal side D, where an outlet opening 22 is surrounded by a valve seat 24. The inlet portion 14 is typically fluidly coupled to a fuel rail 106 at the proximal side P for supply of pressurized gaseous fuel to the gas injector 10. When installed on the engine, the injector body portion with the outlet portion 18, i.e. lower body 12.b, is arranged in a bore in the cylinder head, which opens into a combustion chamber (not shown) of the engine.

[0040] The injector body 12 defines a channel 20, which extends along injector axis A from the inlet portion 14 to the outlet portion 18. The channel 20 forms an internal, elongate passageway (or cavity) that extends throughout the injector body 12, from an inlet opening 21 to the outlet opening 22. Depending on the design, the channel 20 may comprise sections of different shapes or cross-sections along its length. Where the body is made of several pieces, they are assembled together in a fluid- tight manner.

[0041] The valve seat 24 defines an annular surface 25 that faces outwardly, i.e. away from the channel 20, and which may typically be a conical surface. A pintle 26 is axially movable between closed and open positions to control flow of gaseous fuel through the outlet opening 22. The pintle 26 comprises a pintle shaft 28, which extends along the injector axis A and is moveably received inside channel 20, and a pintle head 30, which radially protrudes from the pintle shaft 28 at the distal end thereof. Pintle head 30 forms a valve member (or plug) that is adapted to cooperate with the valve seat 24. When the pintle 26 is in its closed position (as shown in Fig.1 ), the pintle head 30 engages the valve seat 24, thereby preventing gas flow through the outlet opening 22. Conversely, when the pintle 26 is in its open position (not shown), the pintle head 30 is distally spaced from the valve seat 24, thereby enabling fuel flow through the outlet opening 22. It may be noted that the pintle head 30 is located downstream (in gas flow direction) of the valve seat 24 and the pintle 26 opens in flow direction; hence the gas injector 10 is said to open outwardly.

[0042] Reference sign 36 designates a solenoid coil that cooperates with a magnetic armature 32 to actuate the pintle 26. The armature 32 is mechanically coupled to the pintle shaft 28, such that it moves therewith in the direction of the injector axis A. In embodiments, the armature 32 is fixedly attached to the pintle shaft 28, e.g. by welding (as is the case here), press-fit, or screwing, or through form combination. Hence, the pintle shaft 28 extends from the pintle head 30 up to the armature 32, and in the presented embodiment extends proximally beyond the armature 32. A coil spring 34 surrounding the pintle shaft 28 is arranged to bias the pintle 26 towards its closed position. In the embodiment of Fig. 1 , the coil spring 34 is arranged distally from a pintle perch 29, with its proximal end engaging the latter and its distal end engaging a distal annular guide ring 42. Other spring configurations can be envisaged.

[0043] In use, to perform an injection event where gas is discharged through the outlet opening 22, the solenoid 36 is energized to create a magnetic field that attracts the armature 32 in the distal direction and causes the pintle 26 to move distally in an open position, when the force due to the magnetic field overcomes the spring force. Reference sign 38 designates a pole piece arranged distally from the armature 32 to enhance and shape the magnetic field. More specifically, the pole piece 38 is arranged between the armature 32 and the lower body 12b. To guide the magnetic field, a non-magnetic ring 39 is incorporated in the main body; alternatively, the wall thickness of the main body 12a can be locally reduced to form a so-called shunt.

[0044] The pintle shaft 28 comprises a hollow length 28.1 extending from proximal side P to the distal side D. The pintle 26 further comprises a proximal aperture 26.1 and a distal aperture 26.2. As will be understood, the pintle shaft 28 defines an axial gas passage that enables to convey gas from the inlet portion 14 to the outlet portion 18.

[0045] In this embodiment, the pintle shaft 28 is realized as a straight tube having a proximal axial open end which forms the proximal aperture 26.1 , and an opposite distal axial closed end. The distal aperture 26.2 is laterally or radially arranged, here about the distal end of the pintle shaft 28. In the embodiment of Fig.1 , the distal aperture 26.2 is formed by a plurality of holes in the peripheral wall of the pintle shaft 28 proximal to the pintle head 30. The size and number of the holes may depend on the desired flow rate.

[0046] When the pintle 26 is moved distally, a flow passage is opened between the pintle head 30 and valve seat, through which gaseous fuel is discharged.

[0047] The present injector 10 thus provides a design with a straight gas passage extending throughout the injector length. Gas entering the gas passage at the inlet portion 14 exits through the distal aperture 26.2 near the outlet opening 22 and upstream of the valve seat 24. A straight gas passage is thus provided, thereby avoiding significant pressure drops as undergone in conventional designs with solid pintle shafts, where the fuel has to flow around the pintle and through the armature and spring.

[0048] At the top of the pintle shaft 28, i.e. at the proximal side P, gaseous fuel enters through the axially located proximal aperture 26.1 . As can be seen, an inlet member 15 is arranged to close the injector cavity 20 on the proximal side (inserted through opening 21 ) and is sealingly fixed to the injector body 12 by a continuous, gas-tight weld. The inlet member 15 is a globally tubular element defining a central passage 15.1 centered on the injector axis A. A rail adapter (not shown) may be mounted on the inlet member 15, which is an application dependent element for coupling to the rail.

[0049] In this embodiment, on the distal side D, the gas injector 10 comprises a seat member 23 which is arranged at the distal end. The seat member 23 has a generally annular shape (coaxial with injector axis A), with an inward annular protrusion (or lip) surrounding the outlet opening 22 so as to define the valve seat 24.

[0050] Hence, when the pintle 26 is in the closed position, flow through the outlet opening 22 is prevented, and an inner volume 18.1 of the outlet portion 18 defines a plenum chamber in fluid communication with the inner volume 28.1 of the hollow pintle shaft 28. Conversely, when the pintle 26 is in the open position, the chamber 18.1 is open and pressurized gaseous fuel is discharged in the engine’s combustion chamber.

[0051] It will be appreciated that the gas injector 10 further comprises a proximal and a distal sealing membrane 40, 40’, which are elastically deformable along the injector axis A. The sealing membranes 40, 40’ have a generally tubular shape, with one end sealingly connected to an outer surface of the pintle shaft 28 and the opposite end sealingly connected to an inner surface of the injector body 12. The membranes have fluid-tight walls and connected in a fluid-tight manner at both ends.

[0052] The sealing membranes 40, 40’ may be sealingly connected to the injector body 12 by means of guide rings 42 arranged within the injector body 12 so as the surround the pintle shaft 28 with a small clearance, thereby constraining its motion to the injector axis A. In the embodiment of figure 1 , each sealing membrane 40, 40’ has the form of a bellow sealingly welded at one end 40.1 , 40’.1 to the pintle shaft 28 and at the other end 40.2, 40’.2 to a respective guide ring 42, with each guide ring 42 being itself sealingly welded to the injector body 12. The guide rings 42 thus both constrain motion of the pintle 26 to the injector axis A and ensure fluid-tight sealing between their respective sealing membrane 40 and the injector body 12, whilst each sealing membrane 40, 40’ ensures low-friction, fluid-tight sealing between their respective guide ring 42 and the pintle shaft 28.

[0053] The proximal and distal sealing membranes 40, 40’ thus sealingly isolate the inlet portion 14 and the outlet portion 18 from an intermediate portion 44, within which the coil spring 34, pintle perch 29, armature 32 and pole piece 38 are advantageously arranged. In other words, gaseous fuel flowing through the injector 10 never enters the intermediate portion 44, and instead flows along the axial gas passage from the inlet portion 14 through the inner volume 28.1 of the pintle shaft 28 and the distal aperture 26.2, to the inner volume 18.1 of the outlet portion 18. Hence, none of the gas flowing through the injector 10 flows around the armature 32, pole piece 38 and coil spring 34, which are normally regions of the flow where high pressure drops tend to occur.

[0054] As the intermediate portion 44 is sealingly isolated from the axial gas passage, its volume may be filled with a lubricating fluid via a sealable aperture 46, which may subsequently be plugged by press-fitting of a spherical ball made from stainless steel . Said lubricating fluid is typically a liquid having advantageous lubricating and squeeze damping properties, such as a low viscosity synthetic oil with appropriate doping additives.

[0055] Figure 2 shows a second embodiment of the gas injector 10 according to the present invention. The embodiment of figure 2 mainly differs from the embodiment of figure 1 in that it does not have a guide ring 42 on the proximal side P. Instead, the proximal sealing membrane 40 is welded at one end 40.1 to the pintle shaft, extends proximally from the proximal aperture 26.1 of the pintle shaft 28 along the injector axis A, and is welded at the other end 40.2 to the injector body 12 near the inlet (via a fixing ring 41 ). Hence the axial gas passage between the inlet portion 14 and the outlet portion 18 is defined by both the proximal sealing membrane 40 and the hollow pintle shaft 28. This configuration enables a reduction of the pintle shaft 28 length of about 30% when compared to the embodiment of figure 1 , thereby saving costs. The axial guiding of the pintle 26 on the proximal side is here achieved by the controlled annular clearance between armature 32 and injector body 12. Meanwhile, the axial guiding of the pintle 26 on the distal side is achieved by the distal guide 42’. Contrary to the embodiment of figure 1 , the guide 42’ is not submerged in lubricating fluid. The guide 42’ should thus be made of a material able to resist the sliding motion of the pintle without lubrication, such as e.g. a copper-alloy or a high- temperature resistant technical polymer compound, e.g. carbon filled PEEK. It is noted that these axial guiding configurations in the embodiments of figure 1 and 2 are not mutually exclusive, e.g. the gas injector of figure 2 could have the distal guide configuration of figure 1 . The distal guide 42’ is held in place between a shoulder in the injector body 12 and a fixing ring 4T welded to the distal end 40.2’ of bellow 40’ and to the injector body.

[0056] Figure 3 shows an enlarged view of region X of figure 1 . As it can be seen, the armature 32 divides the intermediate portion 44 into a proximal sub-portion 44a and a distal sub-portion 44b. The armature 32 may comprise a plurality of through-holes 48 to promote flow of fluid through the armature 32, i.e. between the proximal subportion 44a and the distal sub-portion 44b. During motion of the armature 32, the volume of each sub-portion 44a, 44b varies. More specifically, when the pintle 26 moves into its open position, the armature 32 moves distally, thereby increasing the volume of the proximal sub-portion 44a and decreasing the volume of the distal subportion 44b. Conversely, when the pintle 26 moves into its closed position, the armature 32 moves proximally, thereby increasing the volume of the distal subportion 44b and decreasing the volume of the proximal sub-portion 44a.

[0057] On the proximal side of the armature 32, in the embodiment of figures 1 and 3, the armature 32 and the inlet member 15 are arranged such that, when the pintle 26 is in its closed position, only an extremely narrow gap exist between the armature 32 and the inlet member 15. More specifically, each through-hole 48 of the armature 32 is essentially covered on the proximal side by a surface of the inlet member 15. Hence, when the pintle 26 moves towards its closed position, flow of lubricating fluid from the proximal sub-portion 44a to the distal sub-potion 44b is severely restricted, effectively closing off the volume of the proximal sub-portion 44a. The armature 32 and the inlet member 15 thus defines an annular plenum chamber 49 on the proximal side, within the proximal sub-portion 44a. The volume of this plenum chamber 49 decreases during the closing motion of the pintle 26, therefore leading to a pressure increase on the proximal side of the armature 32. This increase in pressure on the proximal side of the armature 32 results in a hydraulic braking force which slows down the closing motion of the pintle 26, thereby reducing the impact speed of the pintle head 30 against the valve seat 24 and improving their durability.

[0058] Figure 4 shows and additional or alternative configuration for region Y of figure 3. In this embodiment, the armature 32 has a snubber function, whereby the armature 32 or the inlet member 15 comprises a protruding shoulder 50 whilst the other comprises an opposite, correspondingly shaped recess 52 configured to cooperate with protruding shoulder 50. As the pintle 26 moves towards its closed position, the protruding shoulder 50 is at least partially inserted in the correspondingly shaped recess 52, thereby defining an annular plenum chamber 49 within which lubricating fluid is trapped. Again, during the closing motion of the pintle 26 the volume of the plenum chamber 49 decreases, resulting in a pressure increase on the proximal side of the armature 32. As previously mentioned, increasing the pressure on the proximal side of the armature 32 during the closing motion of the pintle 26 reduces the impact speed of the pintle head 30 against the valve seat 24 and improves their durability.

[0059] On the distal side of the armature 32, the pole piece 38 and / or the armature 32 may comprise a protruding shoulder 54 which defines the contact surface between the armature 32 and the pole piece 38 when the pintle 26 is in its open position. Said protruding shoulder(s) 54 is arranged to maintain a minimum separation gap between the distal end of each through hole 48 and the pole piece 38, thereby preventing excessive hydraulic braking force from occurring during the opening motion of the pintle 26. The injector body 12 is typically made of metallic material, in particular steel or stainless steel. As the annular guides 42 of the embodiment figure 1 and the coil spring 34 are immersed in lubricants, these components are not susceptible to hydrogen embrittlement and can thus be made of conventional martensitic stainless steels. In other words, only the valve seat 24 and the pintle 26 are in direct contact with hydrogen. These components could thus be made of austenitic stainless steels, thereby reducing the risk of hydrogen embrittlement. The sealing membranes 40 can be made of metal, preferably austenitic stainless steel, copper (alloy), nickel (alloy); however, these should not be construed as limiting and other appropriate materials may be employed.

[0060] The seat member 23 can be made integral with the injector lower body 12b or can be a pre-fabricated piece securely fixed thereon in a gas-tight manner, e.g. by welding, as shown on figure 1 . Likewise, the pintle head 30 can be made integral with the pintle shaft 28 or can be a pre-fabricated piece securely fixed thereon, e.g. by interference fit, welding, etc.

[0061] Figure 5 shows a schematic view of a gaseous fuel delivery system 100 comprising a gaseous fuel tank 102, a pressure regulator 104, and a fuel rail 106 coupled to a plurality of inventive gas injectors 10 as described above. The pressure regulator 104 is serially connected between the gaseous fuel tank 102 and the fuel rail 106 by means of piping 108. The pressure regulator is configured to decreases 104 the flow pressure upstream thereof to a nominal working pressure range, e.g. around 5 to 40 bar. The gaseous fuel tank 102 is configured to store pressurized gaseous fuel at pressures of up to 700 bars.

[0062] Turning to Figs 6a-6d, possible alternative embodiments of the pintle design are shown, with different configurations for the distal aperture 26.2. Specifically, the pintle shaft 28 may be inserted in a blind bore formed in the pintle head 30, as shown on figure 6a-c. The distal aperture 26.2 may be formed through both the pintle shaft 28 and the pintle head 30, as shown on figure 6b, the recess may be formed exclusively through the pintle head 30, as shown on figure 6c, and the pintle head 30 may comprise a through-hole surrounding a filled portion of the pintle shaft 28, the filled portion being distal to the distal opening 26.2 and preventing flow through the pintle head 30.

Claims

Claims1 . A gas injector (10) for an internal combustion engine, extending along an injector axis (A) from a proximal side (P) to a distal side (D) and comprising: an injector body (12) defining a channel (20) extending from a proximal inlet portion (14) to a distal outlet portion (18) having an outlet opening (22) surrounded by a valve seat (24); an outwardly-opening pintle (26) having a pintle shaft (28) and pintle head (30); wherein the pintle (26) is movable along the injector axis (A) between a closed position, in which the pintle head (30) engages said outlet valve seat (24) to prevent gas flow through the outlet opening (22), and an open position, in which the pintle head (30) is distally spaced from the valve seat (24) to enable flow of gas through the outlet opening (22); a magnetic armature (32) mechanically coupled to said pintle shaft (28) in the direction of the injector axis (A); a spring (34) arranged to bias said pintle (26) towards its closed position; characterized in that the pintle shaft (28) comprises a hollow length (28.1 ) extending along the injector axis, and the pintle comprises a proximal aperture (26.1 ) and a distal aperture (26.2), thereby defining an axial gas passage between the inlet portion (14) and the outlet portion (18) at least two flexible sealing membranes (40, 40’) extend between the injector body (12) and the pintle shaft (28), the sealing membranes (40, 40’) being axially spaced and configured to sealingly isolate the axial gas passage from an intermediate portion (44) of the gas injector(10), the intermediate portion (44) at least partially surrounding the pintle shaft (28) and being adapted to contain lubricating fluid, at least one of said armature (32) and said spring (34) is arranged in said intermediate portion.

2. The gas injector (10) according to any of the preceding claims, wherein each sealing membrane (40, 40’) is sealingly connected to an outer surface of the pintle shaft (28) and to an inner surface of the injector body (12), thereby preventing flow of fluid between axial gas passage and the intermediate portion (44); and wherein each sealing membrane (40, 40’) is expandable and / or elastically deformable in the direction of the injector axis (A).

3. The gas injector (10) according to any of the preceding claims, wherein the proximal sealing membrane (40) extends proximally from the proximal aperture (26.1 ) of the pintle shaft (28) along the injector axis (A).

4. The gas injector (10) according to any of the preceding claims wherein the sealing membranes (40, 40’) are corrugated bellows.

5. The gas injector (10) according to any of the preceding claims wherein the sealing membranes (40, 40’) are made of metal, preferably austenitic stainless steel, copper, copper alloy, nickel or nickel alloy.

6. The gas injector (10) according to any of the preceding claims, wherein each sealing membrane (40, 40’) has an inner surface and an outer surface, and wherein said inner surface is sealingly connected to the outer surface of the pintle shaft (28) and to the inner surface of the injector body (12).

7. The gas injector (10) according to any of the preceding claims, further comprising at least one, preferably two, guide (42) configured to constrain motion of the pintle to the injector axis (A).

8. The gas injector (10) according to claim 7, wherein at least one, preferably two, sealing membrane (40, 40’) is sealingly connected to the inner surface of the injector body (12) by means of one respective guide (42).

9. The gas injector (10) according to any of the preceding claims, wherein the armature (32) is arranged in said intermediate portion (44), thereby dividing the intermediate portion (44) in a proximal sub-portion (44a) and a distal sub-portion(44b), and wherein the armature (32) comprises at least one through-hole (48), configured to promote flow of lubricating fluid between said proximal sub-portion (44a) and said distal sub-portion (44b).

10. The gas injector (10) according to claim 9, wherein the armature (32) and / or the inlet member (15) define a plenum chamber (49) when the pintle (26) is in its closed position, and wherein the volume of said plenum chamber (49) decreases during the closing motion of the pintle (26), thereby resulting in a pressure increase on the proximal side of the armature (32).11 . The gas injector (10) according to claim 10, wherein, in closed position, the inlet member (15) at least partially covers the at least one through-hole (48) of the armature (32), or wherein the armature (32) or the inlet member (15) comprises a protruding shoulder (50) whilst the other comprises an opposite, correspondingly shaped recess (52).

12. The gas injector (10) according to any of the preceding claims, wherein the armature (32) is clearance fitted in the injector body (12), thereby constraining motion of the pintle (26) to the injector axis (A).

13. The gas injector (10) according to any of the preceding claims, further comprising a pole piece (38) arranged in the intermediate volume (44).

14. The gas injector (10) according to any of the preceding claims, wherein a sealable orifice (46) is formed in the injector body (12), the sealable orifice (46) being configured to enable filling of the intermediate portion (44) with lubricant fluid.

15. The gas injector (10) according to any of the preceding claims, wherein the pintle head (30) comprises a pin-shaped attachment portion that is fitted inside a distal axial open end of said pintle shaft (28), thereby closing the latter.

16. The gas injector (10) according to claim 15, wherein the pintle head (30) comprises a comprises a tubular attachment portion and the distal end of the pintle shaft (28) is engaged inside or around said tubular attachment portion.

17. The gas injector (10) according to claim 16, wherein the distal aperture (26.2) is arranged in the pintle shaft (28) upstream of the tubular attachment portion; or the distal aperture (26.2) is arranged at the level of the tubular attachment and extends through the pintle shaft (28) and tubular attachment.

18. The gas injector (10) according to any of the preceding claims, further comprising a solenoid arranged to generate, when energized, a magnetic field that distally attracts said magnetic armature.

19. Fuel delivery system (100) comprising a gaseous fuel tank (102) configured to store pressurized gaseous fuel, and a fuel rail (106) fluidly coupled to at least one gas injector (10) according to any of the preceding claims.

20. Fuel delivery system (100) according to claim 19, further comprising pressure regulating means (104) configured to decrease the pressure of fuel flow therethrough, wherein the pressure regulating means (104) is serially connected between the fuel tank (102) and the fuel rail (106). 21 . Use of the gas injector as claimed in any one of claims 1 to 18 for the injection of gaseous fuel or compressed air.

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