Fuel injector for gaseous fuel

Abstract

To provide a fuel injector for a gaseous fuel, which ensures a perfect seal in a long term and, in particular, is easy and inexpensive to produce.SOLUTION: There is provided a fuel injector (1) for gaseous fuel, The fuel injector (1) has: an injection nozzle (3); a support body (4) with a tubular shape; an injection valve (7) that is configured to adjust a gaseous fuel flow through the injection nozzle (3), the injection valve (7) being provided with a movable shutter (9) arranged outside the support body (4) and with a valve seat (10); an actuator (6) that is configured to move the shutter (9) between the closed position of the injection valve (7) and the open position of the injection valve (7); a gasket (13) of an elastomeric material, which is arranged at the injection valve (7) to obtain the valve seat (10); and an end-of-stroke system (14), the end-of-stroke system (14) determining the closed position and being separate from and independent of the gasket (13).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] (Cross - reference to related applications) This application claims priority to Italian Patent Application No. 102023000026607, filed on December 13, 2023. The entire disclosure of that application is incorporated herein by reference.

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

[0003] The present invention is advantageously applied to electromagnetic hydrogen injectors. In the following discussion, an explicit reference to electromagnetic hydrogen injectors will be made, without loss of generality thereby.

Background Art

[0004] An electromagnetic hydrogen injector comprises a cylindrical tube - shaped support with a central supply channel. The central supply channel serves as a fuel duct and ends at an injection nozzle which is regulated by an injection valve controlled by an electromagnetic actuator. The injection valve comprises a needle which is moved between a closed position and an open position of the injection nozzle against the action of a closing spring which, under the action of the electromagnetic actuator, pushes the needle towards the closed position. The needle ends with a shutter which is adapted to seat sealingly against the valve seat of the injection valve.

[0005] The most suitable configuration of a hydrogen injector provides an outward - opening shutter so that the closed position of the shutter is not negatively affected by the pressure increased in the combustion chamber. That is, when the shutter opens outward, the pressure increased in the combustion chamber pushes the shutter towards the closed position, and in this way, it is always ensured that the fuel injector does not have an unwanted opening caused by the pressure peak in the combustion chamber.

[0006] When both the shutter and the valve seat are made of metal, the long-term sealing of the injection valve (i.e., after several operating cycles of the injector) can be problematic because even minor wear in the contact zone between the shutter and the valve seat can cause hydrogen leakage. In this regard, it is important to note that since hydrogen has very small molecules, even the smallest crack can be sufficient for the undesired outflow of hydrogen. Furthermore, hydrogen (unlike hydrocarbon-based liquid fuels) does not have lubricating properties nor hydraulic braking capabilities to cushion the impact of the shutter against the valve seat. As a result, it is also important to note that in a hydrogen injector, wear in the valve seat and / or shutter can become very significant (and thus the risk of cracks being created in the valve seat and / or shutter is high).

[0007] To address the above drawbacks, it has been proposed to cover the valve seat with a gasket made of an elastic material (i.e., a gasket made of an elastomer) that has a function of ensuring a hermetic seal (the hermetic seal is due to the ability of the gasket to elastically deform and self-adapt to the shape of the shutter). However, it has been pointed out that gaskets made of elastic materials in hydrogen injectors wear rapidly, and thus the service life of the injector is greatly limited.

[0008] German Patent Application Publication No. 102014224340 (Patent Document 1) and German Patent Application Publication No. 102015201392 (Patent Document 2) describe an injector for directly injecting gaseous fuel into the combustion chamber of an internal combustion engine. The injector comprises a closing element of a valve for opening and closing a passage port, a first sealing sheet made of metal or ceramic and thus without using an elastomer, and a second sealing sheet having at least one elastomeric sealing element.

[0009] U.S. Patent No. 09810179 (Patent Document 3) describes an injector for directly injecting gaseous fuel into the combustion chamber of an internal combustion engine. The injector utilizes two different regions controlled by a valve needle to optimize the amount and characteristics of the gaseous fuel injection into the internal combustion engine, providing more efficient combustion control and improved performance of the internal combustion engine.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0011] An object of the present invention is to provide a fuel injector for gaseous fuel that does not have the above-mentioned drawbacks (i.e., ensures complete sealing even in the long term), and is particularly easy and inexpensive to manufacture.

[0012] According to the present invention, a fuel injector for gaseous fuel is manufactured in accordance with the content described in the appended claims.

[0013] The claims illustrate preferred embodiments of the present invention, which are an essential part of this specification.

[0014] Hereinafter, the present invention will be described with reference to the accompanying drawings. The accompanying drawings show non-limiting and exemplary embodiments of the present invention.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

DETAILED DESCRIPTION OF THE INVENTION

[0016] In FIG. 1, reference numeral 1 generally indicates an injector for gaseous fuel (in particular, hydrogen). The injector extends about the longitudinal axis 2 and is adapted to be controlled to inject hydrogen through an injection nozzle 3 that leads directly to the combustion chamber of a cylinder of an internal combustion engine E (schematically shown in FIG. 4). That is, the internal combustion engine E is supplied with hydrogen and includes an injection system that uses the corresponding hydrogen injector 1 to directly inject hydrogen into a plurality of cylinders. Thus, the internal combustion engine E includes at least one cylinder and an injection system that uses a fuel (hydrogen) injector 1 to directly inject hydrogen into the cylinder.

[0017] As shown in FIG. 1, the fuel injector 1 includes a support 4. The support 4 has a cylindrical tube shape with a cross-section that varies along the longitudinal axis 2 and has a supply channel 5 that extends along the entire length of the support 4 for supplying pressurized hydrogen toward the injection nozzle 3.

[0018] The support 4 houses an electromagnetic actuator 6 in its upper portion and an injection valve 7 (shown in FIG. 2) in its lower portion. In use, the injection valve 7 is actuated by the electromagnetic actuator 6 to regulate the flow of hydrogen through the injection nozzle 3 obtained at the injection valve 7. According to different embodiments not shown, the actuator 6 is of the piezoelectric type rather than the electromagnetic type.

[0019] The electromagnetic actuator 6 is configured to axially move (i.e., along the longitudinal axis 2) a movable unit comprising a needle 8 ending with a shutter 9 having a bulb-like shape (shown in FIG. 2). The shutter 9 cooperates with a valve seat 10 (shown in FIG. 2) of the injection valve 7 to regulate the flow of hydrogen through the injection nozzle 3. In other words, the support 4 ends with a through-hole in which the valve seat 10 is defined and which is engaged by the shutter 9. In particular, the electromagnetic actuator 6 is configured to move the shutter 9 between a closed position (shown in FIG. 2) and an open position (shown in FIG. 3) of the injection valve 7. Further, the electromagnetic actuator 6 comprises a closing spring 11 that normally maintains the fuel injector 1 in a closed state. That is, the closing spring 11 pushes the shutter 9 towards the closed position of the injection valve 7. In other words, the injection valve 7 is normally closed by a closing spring 11 that pushes the needle 8 into the closed position, in which the shutter 9 of the needle 8 is pressed against the valve seat 10 of the injection valve 7.

[0020] As shown in FIGS. 2 and 3, the shutter 9 is arranged outside the support 4 and is pressed against the support 4 by the closing spring 11 of the electromagnetic actuator 6. As a result, in order to move from the closed position to the open position of the injection valve 7, the shutter 9 moves along the longitudinal axis 2 towards the outside of the support 4, i.e., in the same direction of movement as the hydrogen supply direction. In the open position of the injection valve 7 (shown in FIG. 3), the shutter 9 is separated from the valve seat 10 and a passage opening 12 having a crown-shaped cross-section is generated. As a result, the hydrogen injected to pass through the injection nozzle 3 has an internally hollow conical shape at the outlet. In other words, the electromagnetic actuator 6 is configured to move the shutter 9 between a closed position of the injection valve 7 (shown in FIG. 2) in which the shutter 9 is pressed against the valve seat 10 and an open position of the injection valve 7 (shown in FIG. 3) in which the shutter 9 is separated from the valve seat 10 to form the passage opening 12 through which the hydrogen flows.

[0021] According to the preferred embodiment shown in the attached drawings, the shutter 9 has an initial portion that is coupled to the valve seat 10 and has an outer diameter that gradually increases along the longitudinal axis 2, an intermediate portion having a substantially constant outer diameter along the longitudinal axis 2, and a terminal portion that is close to the injection nozzle 3 and has an outer diameter that gradually decreases along the longitudinal axis 2.

[0022] As shown in FIGS. 2 and 3, the fuel injector 1 includes a gasket 13 made of an elastomeric material (i.e., a natural or synthetic polymer having the behavior of an elastic rubber), which is attached to the support 4 and is disposed in the injection valve 7 so as to obtain the valve seat 10. That is, in the closed position (shown in FIG. 2), the shutter 9 seats against the outer surface of the gasket 13 to effect sealing and prevent the outflow of hydrogen.

[0023] As shown in FIGS. 2 and 3, the fuel injector 1 includes a stroke end system 14, which is remote from and independent of the gasket 13 and stops the stroke of the shutter 8 pushed by the closing spring 11 to define the closed position (shown in FIG. 2). In other words, the stroke of the needle 8 that moves by the thrust exerted by the closing spring 11 does not stop by the contact between the shutter 9 and the gasket 13 (defining the valve seat 10), but rather it stops by the contact occurring within the stroke end system 14. The stroke end system 14 is calibrated such that in the closed position (shown in FIG. 2), i.e., the position where the stroke end system 14 stops the movement of the needle 8, the shutter 9 is in contact with the gasket 13 (defining the valve seat 10) and elastically compresses the gasket 13 to ensure the necessary sealing.

[0024] The stroke end system 14 includes an abutting member 15 integral with the needle 8 and an abutting member 16 that is integral with the support 4, faces the abutting member 15, and contacts the abutting member 15 to stop the movement of the needle 8.

[0025] According to the preferred embodiment shown in the accompanying drawings, the stroke end system 14 is not adjacent to the gasket 13. In other words, the stroke end system 14 is arranged such that there is a non-zero axial distance (i.e., measured along the longitudinal axis 2) from the gasket 13 and is axially spaced from the gasket 13. Since the stroke end system 14 is not adjacent to the gasket 13, the portion of the support 4 within the zone of the gasket 13 (i.e., within the zone of the valve seat 10 of the injection valve 7) can be designed (optimized) to ensure the best flow of hydrogen through, and the sealing diameter of the valve seat 10 can be increased. In other words, at the valve seat 10 defined by the gasket 13, there are no shape or size constraints due to the stroke end system 14 (because the stroke end system 14 is away from the gasket 13), so there is greater design freedom to create the zone of the gasket 13 (i.e., the zone of the valve seat 10 of the injection valve 7) to ensure the best flow of hydrogen through and increase the sealing diameter of the valve seat 10.

[0026] In the above embodiment, mention was made of the injection of hydrogen, but the fuel injector 1 can also be used to inject any other type of gaseous fuel, such as methane.

[0027] The embodiments described herein can be combined with each other.

[0028] The above fuel injector 1 has many advantages.

[0029] First, the above fuel injector 1 guarantees a perfect seal even in the long term. This result is obtained thanks to the presence of the gasket 13. The gasket 13 is elastically compressed by the shutter 9 in the closed position (shown in Figure 2) and self - adapts to the shape of the shutter 9 to hermetically seal the entire contact area.

[0030] Furthermore, the above fuel injector 1 has a very long service life. This result is obtained by the fact that the stroke of the needle 8 towards the closed position (shown in Figure 2) is stopped by the stroke - end system 14, and the gasket 13 is not excessively compressed (and thus worn). In other words, thanks to the presence of the stroke - end system 14, all the kinetic energy of the moving unit (of which the needle 8 and the shutter 9 are part) is dissipated onto the gasket 13, thus avoiding excessive compression of the gasket 13.

[0031] Finally, the above electromagnetic fuel injector 1 has few design differences that make it easy to manufacture compared to similar known hydrogen (fuel) injectors, so production is simple and inexpensive.

Explanation of Reference Numerals

[0032] 1 Fuel injector 2 Longitudinal axis 3 Injection nozzle 4 Support 5 Supply channel 6 Electromagnetic actuator 7 Injection valve 8 Needle 9 Shutter 10 Valve seat 11 Closing spring 12 Passage 13 Gasket 14 Stroke - end system 15 Contact member 16 Contact member E Internal combustion engine

Claims

1. A fuel injector (1) for a gaseous fuel, said fuel injector (1) comprising: An injection nozzle (3); a support (4) having a tubular shape, said support (4) having a longitudinal axis (2) and having therein a feed channel (5) which terminates in said injection nozzle (3); an injection valve (7) configured to regulate the flow of the gaseous fuel through the injection nozzle (3) and comprising a movable shutter (9) arranged outside the support (4) and comprising a valve seat (10); an actuator (6) configured to move the shutter (9) between a closed position of the injector (7), in which the shutter (9) is pressed against the valve seat (10), and an open position of the injector (7), in which the shutter (9) is moved away from the valve seat (10) to create a passage port (12) through which the gaseous fuel flows; A needle (8) supporting the shutter (9); a gasket (13) of elastomeric material, said gasket (13) being arranged on said injector (7) so as to obtain said valve seat (10) and being in contact with said shutter (9) in said closed position of said injector (7); an end-of-stroke system (14) that defines the closed position and that is separate and independent of the gasket (13); A fuel injector (1) comprising: the end of stroke system (14) is coupled to the needle (8) and is positioned such that there is a non-zero axial distance from the gasket (13), i.e. a distance measured along the longitudinal axis (2), and is further from the injection nozzle (3) than the gasket (13); and The fuel injector (1), characterized in that in each position, the stroke end system (14) does not interrupt the supply channel (5) and therefore does not prevent the gas fuel from flowing past the side of the stroke end system (14) and along the supply channel (5) towards the injection nozzle (3).

2. 2. The fuel injector (1) of claim 1, wherein the end of stroke system (14) is calibrated such that in the closed position, the shutter is in contact with and elastically compresses the gasket (13).

3. 2. The fuel injector (1) of claim 1, wherein the stroke end system (14) is configured to stop movement of the shutter (9) despite contact of the shutter (9) against the gasket (13) that defines the valve seat (10).

4. 2. The fuel injector (1) according to claim 1, wherein the stroke end system (14) comprises a first abutment member (15) integral with the needle (8) and a second abutment member (16) integral with the support (4), facing the first abutment member (15) and coming into contact with the first abutment member (15) to stop the movement of the needle (8).

5. 5. A fuel injector (1) as claimed in claim 4, wherein the two members (15, 16) of the stroke end system (14) are arranged inside the supply channel (5) and only partially occupy the supply channel (5), and in each position the fuel flows freely past the sides of the stroke end system (14) and along the supply channel (5) towards the injection nozzle (3).

6. the actuator (6) comprises a closing spring (11) configured to push the shutter (8) towards the closed position; and 6. The fuel injector (1) according to any one of claims 1 to 5, wherein the stroke end system (14) is configured to stop a stroke of the needle (8) pushed by the closing spring (11).

7. 7. A fuel injector (1) as claimed in claim 6, wherein the stroke of the needle (8) moved by the thrust exerted by the closing spring (11) is not stopped by contact between the shutter (9) and the gasket (13), but it is stopped by contact occurring in the stroke end system (14).

8. The shutter (9) has a bulbous shape and an initial portion coupled to the valve seat (10) and having an outer diameter that increases along the longitudinal axis (2); an intermediate portion having a constant outer diameter along said longitudinal axis (2); 6. The fuel injector (1) according to claim 1, further comprising a terminal portion (2) which is closer to the injection nozzle (3) and has an outer diameter which gradually decreases along the longitudinal axis (2).

9. 6. A fuel injector (1) according to claim 1, wherein the shutter (9) is arranged outside the support (4) and, in order to move the injection valve (7) from the closed position to the open position, it moves towards the outside of the support (4) in the same movement direction as the fuel supply direction.

10. The fuel injector (1) of any one of the preceding claims, wherein the end of stroke system (14) is not adjacent to the gasket (13).

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