Fuel injector for gaseous fuel

Abstract

To provide a fuel injector for a gaseous fuel.SOLUTION: A fuel injector 1 is for a gaseous fuel, and the fuel injector 1 has: an injection nozzle; a support body 4 that ends in the injection nozzle; an injection valve configured to adjust a gaseous fuel flow through the injection nozzle, the injection valve being constituted of a movable shutter 9 and a valve seat 10; and an actuator configured to move the shutter 9 between a closed position of the injection valve in which the shutter 9 is pressed against the valve seat 10, and an open position of the injection valve in which the shutter 9 is separate from the valve seat 10. The shutter 9 and the valve seat 10 are shaped to have a main contact area 17, in which the shutter 9 comes into contact with the valve seat 10 when the shutter 9 is in the closed position, and a secondary contact area 18, which is separate and spaced apart from the main contact area 17 and in which the shutter 9 comes or could come into contact with the valve seat 10 when the shutter 9 is in the closed position.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This patent application claims priority to Italian Patent Application No. 102024000011164, filed May 16, 2024, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a fuel injector for gaseous fuels.

[0003] The invention is advantageously applied to electromagnetic hydrogen injectors, to which, due to lack of generality, explicit reference is made in the following description. [Background technology]

[0004] The electromagnetic hydrogen injector comprises a cylindrical tubular support provided with a central supply channel, which serves as a fuel duct and terminates in an injection nozzle controlled by an injection valve operated by an electromagnetic actuator. The injection valve is provided with a plunger which is moved between the closed and open positions of the injection nozzle by the action of the electromagnetic actuator against the action of a closing spring which pushes the plunger towards the closed position. The plunger terminates in a shutter designed to abut in a sealing manner against the valve seat of the injection valve.

[0005] The most preferred configuration of the hydrogen injector requires the shutter to open outwards so that its closed position is not adversely affected by pressures generated in the combustion chamber, i.e., as the shutter opens outwards, pressures generated in the combustion chamber push the shutter towards the closed position, thus ensuring that the fuel injector is not unnecessarily opened by pressure peaks in the combustion chamber at all times.

[0006] If both the shutter and the valve seat are made of metal, sealing of the injection valve over the long term (i.e., after several operating cycles of the injector) can be problematic, since even slight wear in the contact area between the shutter and the valve seat can cause hydrogen leakage. In this regard, it is important to point out that hydrogen has very small molecules, and therefore even a tiny crack can be sufficient for unwanted hydrogen leakage. Furthermore, it should be pointed out that hydrogen (unlike hydrocarbon-based liquid fuels) does not have lubricating properties or hydraulic damping capabilities to cushion the impact of the shutter against the valve seat, and as a result, the wear experienced by the valve seat and shutter can be significantly higher in hydrogen injectors (and therefore there is a higher risk of cracks in the valve seat and / or shutter).

[0007] To overcome the above drawbacks, the valve seat can be covered with a sealing gasket (made of a non-metallic material) that serves to ensure a tight seal (thanks to the seal's ability to elastically deform to fit the shape of the shutter). However, it has been observed that the gaskets in hydrogen injectors wear out quickly, thus significantly limiting the service life of the injector.

[0008] German Patent Application Nos. 102014224340(A1) and 102015201392(A1) disclose a gas injector for injecting gas fuel directly into the combustion chamber of an internal combustion engine, which injector comprises a valve closing element for opening and closing a passage opening, a first sealing seat, in particular a metallic or ceramic sealing seat, which is arranged closer to the combustion chamber and has no elastomer, and a second sealing seat, which is arranged further away from the combustion chamber and has at least one elastomer sealing element.

[0009] German Patent Application No. 102014224345 (A1) discloses a gas injector for injecting gaseous fuel directly into the combustion chamber of an internal combustion engine, the injector comprising a valve closing element for opening and closing a passage opening, a first sealing seat with two metallic sealing elements, a second sealing seat with an elastomeric sealing element and a third sealing seat with a further elastomeric sealing element. Summary of the Invention

[0010] The object of the present invention is to provide a fuel injector for gaseous fuels which does not have the above-mentioned drawbacks (i.e. ensures perfect sealing even over a long period of time) and which is in particular easy and economical to manufacture.

[0011] According to the present invention there is provided a fuel injector for gaseous fuels as claimed in the accompanying claims.

[0012] The appended claims describe preferred embodiments of the invention and form an integral part of this specification. [Brief explanation of the drawings]

[0013] The present invention will now be described with reference to the accompanying drawings, which show some non-limiting embodiments thereof.

[0014] [Figure 1] FIG. 2 is a partial cross-sectional side view of the fuel injector. [Figure 2] 2A-2C are two longitudinal cross-sectional views of the end of the fuel injector of FIG. 1 in a closed position and an open position, respectively; [Figure 3] 2A-2C are two longitudinal cross-sectional views of the end of the fuel injector of FIG. 1 in a closed position and an open position, respectively; [Figure 4] FIG. 4 is an enlarged view of a detail of FIGS. 2 and 3. [Figure 5] FIG. 5 is an enlarged view of a variant of the detail of FIG. 4. [Figure 6] 2 is a schematic diagram of an internal combustion engine using the fuel injector of FIG. 1; DETAILED DESCRIPTION OF THE INVENTION

[0015] In Figure 1, the number 1 indicates as a whole a gaseous fuel (in particular hydrogen) injector which extends about a longitudinal axis 2 and is designed to operate to inject hydrogen through an injection nozzle 3 which is in direct communication with the combustion chamber of a cylinder of an internal combustion engine E (schematically shown in Figure 6), i.e. the internal combustion engine E is fuelled by hydrogen and is provided with an injection system which injects hydrogen directly into a number of cylinders using corresponding hydrogen injectors 1, so that the internal combustion engine E comprises at least one cylinder and an injection system which injects hydrogen directly into the cylinder using fuel (hydrogen) injectors 1.

[0016] According to FIG. 1 , the fuel injector 1 comprises a support 4 having a cylindrical tubular shape with a variable cross section along its longitudinal axis 2, the support 4 having a feed channel 5 extending along its entire length for feeding pressurized hydrogen to an injection nozzle 3.

[0017] The support 4 houses in its upper region an electromagnetic actuator 6 and in its lower region an injector 7 (shown in Figure 2), which, in use, is operated by the electromagnetic actuator 6 so as to regulate the flow of hydrogen through the injection nozzle 3, which is obtained in the region of the injector 7. According to a different embodiment, not shown, the actuator 6 is a piezoelectric actuator instead of being an electromagnetic actuator.

[0018] The electromagnetic actuator 6 is configured to axially (i.e., along the longitudinal axis 2) move a movable device provided with a plunger 8 terminating in a bulb-shaped shutter 9 (shown in FIG. 2). The shutter 9 cooperates with a valve seat 10 (shown in FIG. 2) of the injector 7 to regulate the flow of hydrogen through the injection nozzle 3. The valve seat 10 constitutes a sealing area, i.e., an area where the shutter 9 of the injector 7 comes into contact with the support 4 to form a seal. In other words, the support 4 terminates in a through opening, in which the valve seat 10 is defined and engaged by the shutter 9. In particular, the electromagnetic actuator 6 is configured to move the shutter 9 between a stable, fully closed position (shown in FIG. 2), in which the shutter 9 is stationary and immobile, and an open position of the injector 7 (shown in FIG. 3). In other words, in the closed position (shown in FIG. 2), the shutter 9 is stationary and stable because it has reached a limit stop that prohibits further closing. Furthermore, the electromagnetic actuator 6 is provided with a closing spring which keeps the fuel injector 1 normally closed, i.e. which pushes the shutter 9 towards the closed position of the injector 7. In other words, the injector 7 is normally closed by a closing spring 11 which pushes the plunger 8 towards the closed position, in which the shutter 9 of the plunger 8 presses against the valve seat 10 of the injector 7.

[0019] 2 and 3, the shutter 9 is arranged outside the support 4 and is pressed against it by the closing spring 11 of the electromagnetic shutter 6, so that to shift the injector 7 from its closed position to its open position, the shutter 9 moves towards the outside of the support 4, i.e., along the longitudinal axis 2, in the same direction of movement as the hydrogen supply direction. In the open position of the injector 7 (shown in FIG. 3), the shutter 9 is away from the valve seat 10 and thus forms a passage opening 12 with a crown-shaped cross section, so that the hydrogen injected through the injection nozzle 3 has, at the outlet, the shape of a hollow cone. In other words, the electromagnetic actuator 6 is configured to move the shutter 9 between the closed position of the injector 7 (shown in FIG. 2), in which the shutter 9 is pressed against the valve seat 10, and the open position of the injector 7 (shown in FIG. 3), in which the shutter 9 is away from the valve seat 10, so as to form the passage opening 12 through which the hydrogen flows.

[0020] According to the embodiment shown in the accompanying drawings, the shutter 9 has an initial portion that is connected to the valve seat 10 and has an outer diameter that gradually increases along the longitudinal axis 2, an intermediate portion that has a substantially constant outer diameter along the longitudinal axis 2, and an end portion that is closer to the injection nozzle 3 and has an outer diameter that gradually decreases along the longitudinal axis 2. According to other embodiments not shown, the shutter 9 may have a different shape and may, for example, lack an end portion (i.e. it may terminate in a bottom portion with a flat wall that is located immediately after the intermediate portion or that is located immediately after the initial portion).

[0021] 2 and 3, the fuel injector 1 comprises a sealing gasket 13 made of a non-metallic material, which is connected to the support 4 and arranged in the region of the injection valve 7 to form the valve seat 10, i.e. in the closed position (shown in FIG. 2), the shutter 9 abuts against the outer surface of the gasket 13 to obtain a seal and thus prevent hydrogen leakage. The gasket 13 is made of a non-metallic material (unlike the other components of the fuel injector 1, which are made of a metallic material), which has an elasticity greater than that of the shutter 9 and the support 4. By way of example, the gasket 13 can be made of an elastomeric material (i.e. a natural or synthetic polymer with elastic rubber behavior) or a plastic material (e.g. PTFE).

[0022] 2 and 3, the fuel injector 1 comprises a limit stop system 14, which is separate and independent from the gasket 13, and which establishes the closed position (shown in FIG. 2) by stopping the movement of the plunger 8 pushed by the closing spring 11; in other words, the movement of the plunger 8, which is moved by the thrust applied by the closing spring 11, is not stopped by contact between the shutter 9 and the gasket 13 (which defines the valve seat 10), but by contact occurring within the limit stop system 14. The limit stop system 14 is configured (designed) so that in the closed position (shown in FIG. 2), i.e., the position where the limit stop system 14 stops the movement of the plunger 8, the shutter 9 comes into contact with the gasket 13 (which defines the valve seat 10) and presses the gasket 13 with a force sufficient to ensure the required sealing, i.e., elastically compresses the gasket 13 to ensure the required sealing.

[0023] The limit stop system 14 comprises a striker element (15) integral with the plunger 8 and a striker element 16 integral with the support (4), facing the striker element 15 and contacting the striker element 15 to stop the movement of the plunger 8.

[0024] According to a preferred embodiment shown in the accompanying drawings, the limit stop system 14 is not adjacent to the gasket 13; in other words, the limit stop system 14 is axially spaced from the gasket 13 and is therefore located at a non-zero axial distance (i.e., measured along the longitudinal axis 2) from the gasket 13. Because the limit stop system 14 is not adjacent to the gasket 13, the portion of the support 4 in the area of ​​the gasket 13 (i.e., in the area of ​​the valve seat 10 of the injector 7) can be designed (optimized) to ensure the best hydrogen flow and the sealing diameter of the valve seat 10 can be larger. In other words, because the area of ​​the valve seat 10 defined by the gasket 13 is not restricted in shape or size by the limit stop system 14 (because the limit stop system 14 is far from the gasket 13), there is more freedom in the design to make the area of ​​the gasket 13 (i.e., in the area of ​​the valve seat 10 of the injector 7) to ensure the best hydrogen flow and to increase the sealing diameter of the valve seat 10.

[0025] In other words, the limit stop system 14 is coupled to the plunger 8 and is arranged at a non-zero axial distance from the gasket 13 so as to be further from the injection nozzle 3 than the gasket 13, and furthermore, the limit stop system 14 does not block the supply channel 5 in any position and therefore does not prevent gaseous fuel from flowing along the supply channel 5 past the limit stop system 14 towards the injection nozzle 3. In other words, the two elements 15 and 16 of the limit stop system 14 are arranged inside the supply channel 5 and only partially occupy it, so that in any position fuel can flow freely along the supply channel 5 past the limit stop system 14 towards the injection nozzle 3.

[0026] 4, the shutter 9 and the valve seat 10 are shaped to have a main contact area 17 of the non-metallic material gasket 13 having an annular shape (axisymmetric about the longitudinal axis 2), and the shutter 9 is always in contact with the valve seat 10 (i.e., the sealing area of ​​the support 4) formed by the non-metallic material gasket 13 when in a stable, fully closed position. Furthermore, the shutter 9 and the valve seat 10 are shaped to have a secondary contact area 18 of the non-metallic material gasket 13 having an annular shape (axisymmetric about the longitudinal axis 2), which is separated and spaced apart from the main contact area 17, and the shutter 9 is in contact (or can be in contact with) the valve seat 10 when in the closed position.

[0027] The shutter 9 and the valve seat 10 are shaped to have a separation region 19, which is part of the non-metallic material gasket 13 and is interposed between the primary contact region 17 and the secondary contact region 18, separating the primary contact region 17 from the secondary contact region 18, and the shutter 9 never comes into contact with the valve seat 10 formed by the non-metallic material gasket 13. In particular, when the shutter 9 is in the closed position, the shutter 9 is at a distance from the valve seat 10 in the region of the separation region 19, which distance is greater than the distance separating the shutter 9 from the valve seat 10 in the region of the primary contact region 17 and greater than the distance separating the shutter 9 from the valve seat 10 in the region of the secondary contact region 18. That is, when the shutter 9 is in the closed position, the separation region 19 of the valve seat 10 is farther away from the shutter 9 than the primary contact region 17 of the valve seat 10 and the secondary contact region 18 of the valve seat 10.

[0028] In other words, the non-metallic gasket 13 defines both a primary contact area 17 and a secondary contact area 18 that is separate and spaced from the primary contact area 17 .

[0029] 4, when the shutter 9 is in the closed position, the shutter 9 is at a constant distance from the valve seat 10 over the entire area of ​​the primary contact area 17, i.e., when the shutter 9 is in the closed position, the shutter 9 is at the same distance from the valve seat 10 over the entire area of ​​the primary contact area 17. Similarly, when the shutter 9 is in the closed position, the shutter 9 is at a constant distance from the valve seat 10 over the entire area of ​​the secondary contact area 18, i.e., when the shutter 9 is in the closed position, the shutter 9 is at the same distance from the valve seat 10 over the entire area of ​​the secondary contact area 18.

[0030] 4, the shutter 9 and the valve seat 10 are shaped to contact each other at both the primary contact area 17 and the secondary contact area 18 when the shutter 9 is in the closed position. In other words, even if the valve seat 10 has an initial size and a nominal size, the shutter 9 and the valve seat 10 are shaped to contact each other at both the primary contact area 17 and the secondary contact area 18 when the shutter 9 is in the closed position. Therefore, when the shutter 9 is in the closed position, the shutter 9 contacts the valve seat 10 (i.e., the sealing area) at both the primary contact area 17 and the secondary contact area 18.

[0031] In the embodiment shown in Figure 4, the two contact areas 17 and 18 are configured to always cooperate and therefore constitute two separate and distinct sealing points which act simultaneously when the shutter 9 is in the closed position.

[0032] In an alternative embodiment shown in Figure 5, there is no limit stop system 14 and the closed position is established by the gasket 13 (defining the valve seat 10); in other words, the movement of the plunger 8, which is moved by the thrust applied by the closing spring 11, is stopped by contact between the shutter 9 and the gasket 13 (defining the valve seat 10). In the alternative embodiment shown in Figure 5, when the valve seat 10 has an initial size and a nominal size, the shutter 9 and the valve seat 10 are shaped so that they do not contact each other at the secondary contact area 18 when the shutter 9 is in the closed position; that is, when the valve seat 10 has an initial size and a nominal size and is in the closed position, the shutter 9 contacts the valve seat 10 (i.e., the sealing area) only at the primary contact area 17 and not at the secondary contact area 18. In other words, the shutter 9 and the valve seat 10 are shaped such that only when the valve seat 10 has a worn size (i.e., when the gasket 13 has worn thin on the primary contact area 17 and no longer ensures the desired seal) do the shutter 9 and the valve seat 10 contact each other at the secondary contact area 18 when the shutter 9 is in the closed position; i.e., only when the valve seat 10 has a worn size (i.e., when the gasket 13 has worn thin on the primary contact area 17 and no longer ensures the desired seal) does the shutter 9 contact the valve seat 10 (i.e., the sealing area) at both the primary contact area 17 and the secondary contact area 18 (or only at the secondary contact area 18) when the shutter 9 is in the closed position. Thus, in the embodiment shown in FIG. 5 , the secondary contact area 18 constitutes a “reserve” that only functions when the valve seat 10 has a worn size.

[0033] 5, the two contact areas 17 and 18 are not configured to always cooperate, since under nominal conditions (i.e. when the fuel injector 1 is new and therefore not worn), sealing is only obtained in the primary contact area 17, while the secondary contact area 18 does not perform any sealing function. On the other hand, when the fuel injector 1 wears and therefore undergoes a change in shape and / or size in the area of ​​the primary contact area 17 (i.e. when the gasket 13 wears thin on the primary contact area 17 and no longer ensures the desired sealing), sealing is also obtained in the secondary contact area 18 (or, if necessary, only in the secondary contact area 18), i.e. the secondary contact area 18 constitutes a backup solution that is only used when there is wear in the area of ​​the primary contact area 17.

[0034] When the shutter 9 is in the closed position, the shutter 9 is at a first constant distance from the valve seat 10 over the entire area of ​​the primary contact area 17 and at a second constant distance from the valve seat 10 over the entire area of ​​the secondary contact area 18. In the embodiment shown in FIG. 4, the first distance (zero because the shutter 9 is in contact with the valve seat 10 over the entire area of ​​the primary contact area 17) is the same as the second distance (zero because the shutter 9 is in contact with the valve seat 10 over the entire area of ​​the secondary contact area 18). In the embodiment shown in FIG. 5, the first distance (zero because the shutter 9 is in contact with the valve seat 10 over the entire area of ​​the primary contact area 17) is less than the second distance (non-zero because the shutter 9 is spaced from the valve seat 10 over the entire area of ​​the secondary contact area 18).

[0035] In the embodiment shown in the accompanying drawings, the shutter 9 and valve seat 10 are shaped to have two separate and independent contact areas 17 and 18, and according to other embodiments not shown, the shutter 9 and valve seat 10 are shaped to have three or more separate and independent contact areas 17 and 18 (for example, three, four or five separate and independent contact areas 17 and 18).

[0036] Although the above embodiments refer to the injection of hydrogen, the injector 1 can be used to inject any other type of gaseous fuel, such as methane, for example.

[0037] The embodiments described herein can for this reason be combined with one another without going beyond the scope of protection of the present invention.

[0038] The fuel injector 1 described above has many advantages.

[0039] First of all, the fuel injector 1 described above ensures perfect sealing even over time, a result achieved thanks to the presence of the gasket 13, which in the closed position (shown in Figure 2) is elastically compressed by the shutter 9, adapts to the shape of the shutter 9 and seals the entire contact area.

[0040] Furthermore, the fuel injector 1 described above has an extremely long service life. This result is achieved thanks to the presence of two separate and distinct contact areas 17 and 18 of the same non-metallic material gasket 13 between the shutter 9 and the valve seat 10, which allows for increased sealing capacity when the shutter 9 is in the closed position. In particular, the two separate and distinct contact areas 17 and 18 can be configured (designed) to always operate together (as shown in FIG. 4) or to operate alternately (as shown in FIG. 5), with the secondary contact area 18 serving as a backup / replacement / support for the main contact area 17 in the event of wear. Furthermore, this result is also achieved thanks to the limit stop system 14 halting movement of the plunger 8 toward the closed position (shown in FIG. 2) without excessively stressing (and therefore wearing) the gasket 13. In other words, the presence of the limit stop system 14 avoids overstressing the gasket 13 by dissipating all of the kinetic energy of the moving equipment (of which the plunger 8 and shutter 9 are part) onto the gasket 13.

[0041] Finally, the fuel injector 1 described above has only minor structural differences compared to known hydrogen (fuel) injectors that can be easily implemented, and is therefore simple and economical to manufacture. [Explanation of symbols]

[0042] 1 fuel injector 2 Longitudinal axis 3 spray nozzle 4 Support 5. Supply Channels 6 Electromagnetic Actuators 7 Injection valve 8 plunger 9 Shutter 10 Valve seat 11 Closing spring 12 Passage opening 13 Gasket 14 Limit Stop System 15 Striker Elements 16 Striker Elements 17 Main contact area 18 Secondary contact area 19 Separation area E. Internal combustion engine

Claims

1. A fuel injector (1) for gaseous fuel, comprising: an injection nozzle (3); a support (4) having a tubular shape, having a longitudinal axis (2) and provided therein with a feed channel (5) terminating in said injection nozzle (3); an injection valve (7) configured to regulate the gaseous fuel flow through the injection nozzle (3) and provided with a movable shutter (9) and a valve seat (10) arranged outside the support (4); a non-metallic gasket (13) arranged in the region of the injection valve (7) to obtain the valve seat (10); A plunger (8) supporting the shutter (9); an actuator (6) configured to move the shutter (9) between a stable fully closed position of the injector (7), in which the shutter (9) is stationary and unmoving and pressed against the valve seat (10), and an open position of the injector (7), in which the shutter (9) is spaced from the valve seat (10) to create a passage opening (12) through which the gaseous fuel flows; a fuel injector, wherein the shutter (9) and the valve seat (10) formed by the non-metallic material gasket (13) are shaped to have a main contact area (17) of the non-metallic material gasket (13), and when the shutter (9) is in the stable, fully closed position, the shutter (9) is always in contact with the valve seat (10) formed by the non-metallic material gasket (13); The fuel injector (1) is characterized in that the shutter (9) and the valve seat (10) formed by the non-metallic material gasket (13) are shaped so that a secondary contact area (18) of the non-metallic material gasket (13) is separated and spaced from the main contact area (17) of the non-metallic material gasket (13), and when the shutter (9) is in the stable, fully closed position, the shutter (9) is always in contact with the valve seat (10) formed by the non-metallic material gasket (13) at the secondary contact area (18) or only comes into contact when the main contact area (17) is worn.

2. 2. The fuel injector (1) of claim 1, wherein the shutter (9) and the valve seat (10) formed by the non-metallic material gasket (13) are shaped to have a separation area (19), the separation area (19) being part of the non-metallic material gasket (13) and being interposed between the primary contact area (17) and the secondary contact area (18), separating the primary contact area (17) from the secondary contact area (18), and the shutter (9) never coming into contact with the valve seat (10) formed by the non-metallic material gasket (13).

3. 3. The fuel injector (1) of claim 2, wherein when the shutter (9) is in the stable, fully closed position, the shutter (9) is at a third distance from the valve seat (10) formed by the non-metallic material gasket (13) in the region of the separation region (19), the third distance being greater than a first distance separating the shutter (9) from the valve seat (10) formed by the non-metallic material gasket (13) in the region of the primary contact region (17) and greater than a second distance separating the shutter (9) from the valve seat (10) formed by the non-metallic material gasket (13) in the region of the secondary contact region (18).

4. When the shutter (9) is in the stable fully closed position, the shutter (9) is at a first constant distance from the valve seat (10) formed by the non-metallic material gasket (13) in the area of ​​the entire main contact area (17); 4. The fuel injector (1) according to claim 1, 2 or 3, wherein the shutter (9) is at a second constant distance from the valve seat (10) formed by the non-metallic material gasket (13) in the area of ​​the entire secondary contact area (18).

5. 5. The fuel injector (1) of claim 4, wherein the first distance is less than the second distance.

6. 5. The fuel injector (1) of claim 4, wherein the first distance is equal to the second distance.

7. 5. The fuel injector (1) according to claim 1, wherein the shutter (9) and the valve seat (10) formed by the non-metallic material gasket (13) are shaped to contact each other at both the primary contact area (17) of the non-metallic material gasket (13) and the secondary contact area (18) of the non-metallic material gasket (13) when the shutter (9) is in the stable, fully closed position.

8. 5. The fuel injector (1) according to claim 1, wherein even if the valve seat (10) formed by the non-metallic material gasket (13) has an initial size and a nominal size, the shutter (9) and the valve seat (10) formed by the non-metallic material gasket (13) are shaped so as to contact each other at both the primary contact area (17) of the non-metallic material gasket (13) and the secondary contact area (18) of the non-metallic material gasket (13) when the shutter (9) is in the stable, fully closed position.

9. 5. The fuel injector (1) according to claim 1, wherein when the valve seat (10) formed by the non-metallic material gasket (13) has an initial size and a nominal size, the shutter (9) and the valve seat (10) formed by the non-metallic material gasket (13) are shaped so as not to come into contact with each other at the secondary contact area (18) of the non-metallic material gasket (13) when the shutter (9) is in the stable, fully closed position.

10. 10. The fuel injector (1) of claim 9, wherein the shutter (9) and the valve seat (10) formed by the non-metallic material gasket (13) are shaped so that they come into contact with each other at the secondary contact area (18) of the non-metallic material gasket (13) when the shutter (9) is in the stable, fully closed position only when the valve seat (10) formed by the non-metallic material gasket (13) has a worn size.

11. 11. The fuel injector (1) according to claim 1, wherein the non-metallic material gasket (13) constituting the valve seat (10) is wide enough to define both the primary contact area (17) and the secondary contact area (18) that is separate and spaced from the primary contact area (17).

12. 12. The fuel injector (1) according to any one of claims 1 to 11, comprising a limit stop system (14) that establishes the closed position, is separate and independent from the gasket (13), and is configured such that in the closed position the shutter contacts the gasket (13) and elastically compresses the gasket (13).

13. 13. The fuel injector (1) according to claim 12, wherein the limit stop system (14) is configured to stop movement of the shutter (9) independently of contact of the shutter (9) with the gasket (13) forming the valve seat (10).

14. the limit stop system (14) is connected to the plunger (8) and is positioned at a non-zero axial distance, i.e., a distance measured along the longitudinal axis (2), from the gasket (13) so as to be further from the injection nozzle (3) than the gasket (13); the limit stop system (14) does not block the supply channel (5) in any position and therefore does not prevent the gaseous fuel from passing next to the limit stop system (14) and along the supply channel (5) towards the injection nozzle (3); A fuel injector (1) according to claim 12 or 13.

15. the limit stop system (14) comprises a first striker element (15) integral with the plunger (8) and a second striker element (16) integral with the support (4), facing the first striker element (15) and coming into contact with the first striker element (15) to stop the movement of the plunger (8); the two elements (15, 16) of the limit stop system (14) are arranged inside the supply channel (5) and only partially occupy the supply channel (5), so that in every position the fuel flows freely along the supply channel (5) past the limit stop system (14) towards the injection nozzle (3); A fuel injector (1) according to claim 13 or 14.

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