Fuel injector for gaseous fuel

Abstract

A fuel injector (1) for gaseous fuel is provided with: an injection nozzle (3); a tubular support body (4); an injection valve (7) configured to regulate the flow of gaseous fuel through the injection nozzle (3) and provided with a movable gate (9) and a valve seat (10) arranged outside the support body (4); an actuator (6) configured to move the shutter (9) between a closed position of the injection valve (7) and an open position of the injection valve (7); a gasket (13) made of an elastic material, which is arranged at the injection valve (7) to obtain a valve seat (10); and an end-of-stroke system (14) that determines the closed position and is separate from and independent of the gasket (13).

Description

[0001] Cross - reference to related applications

[0002] This patent application claims the priority of Italian Patent Application No. 102023000026607 filed on December 13, 2023, the entire disclosure of which is incorporated herein by reference. Technical field

[0003] The present invention relates to a fuel injector for gaseous fuels.

[0004] The present invention is advantageously applied to electromagnetic hydrogen injectors, and without loss of generality, the following discussion will specifically refer to electromagnetic hydrogen injectors. Background art

[0005] An electromagnetic hydrogen injector includes a cylindrical tubular support body equipped with a central feed channel that serves as a fuel conduit and terminates at an injection nozzle, and the injection nozzle is regulated by an injection valve controlled by an electromagnetic actuator. The injection valve is provided with a needle that, by the action of the electromagnetic actuator, overcomes the action of a closing spring that pushes the needle towards the closed position, and the needle moves between the closed position and the open position of the injection nozzle. The needle terminates at a gate that is adapted to seal against the valve seat of the injection valve.

[0006] The most suitable configuration of a hydrogen injector is to provide an outward - opening gate so that the closed position of the gate is not negatively affected by the pressure generated in the combustion chamber; that is, when the gate opens outward, the pressure generated in the combustion chamber pushes the gate towards the closed position, thus always ensuring that the fuel injector does not have an unwanted opening caused by pressure peaks in the combustion chamber.

[0007] When both the gate and the valve seat are made of metal, the long - term (i.e., after several operating cycles of the injector) sealing of the injection valve can be problematic because even a very small wear in the contact area between the gate and the valve seat can cause hydrogen leakage. In this regard, it is important to note that hydrogen has very small molecules, so even the smallest crack is sufficient to cause an unwanted outflow of hydrogen. In addition, it is important to note that hydrogen (unlike hydrocarbon liquid fuels) has neither lubricating properties nor hydraulic braking ability to mitigate the impact of the gate on the valve seat; therefore, in a hydrogen injector, the wear at the valve seat and / or the gate is definitely high (and thus the risk of forming cracks in the valve seat and / or the gate is high).

[0008] To address the above drawbacks, it has been proposed to cover the valve seat with a washer made of an elastic material (i.e., a washer made of an elastomer), which has the function of ensuring a seal (due to the ability of the washer to elastically deform and thus adapt to the shape of the gate). However, it has been noted that the washer made of an elastic material of the hydrogen injector wears out very quickly, thus significantly limiting the service life of the injector.

[0009] Patent applications DE102014224340A1 and DE102015201392A1 describe injectors for directly injecting gaseous fuel into the combustion chamber of an internal combustion engine; the injector includes a closing element for a valve that opens and closes a passage opening, a first metal or ceramic sealing seat (thus a non-elastic sealing seat), and a second sealing seat having at least one elastic sealing element.

[0010] Patent US9810179B2 describes an injector for directly injecting gaseous fuel into the combustion chamber of an internal combustion engine; the injector uses two different regions controlled by a valve needle to optimize the quantity and characteristics of injecting gaseous fuel into the internal combustion engine, providing more effective control of combustion and improved performance of the internal combustion engine. Summary of the Invention

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

[0012] According to the present invention, the fuel injector for gaseous fuel is manufactured according to what is described in the appended claims.

[0013] The claims illustrate preferred embodiments of the present invention, which are an integral part of this description. Brief Description of the Drawings

[0014] The present invention will now be described with reference to the accompanying drawings, which illustrate non-limiting exemplary embodiments of the present invention, wherein:

[0015] Figure 1 is a partial cross-sectional side view of the fuel injector; and

[0016] Figure 2 and 3 is the corresponding Figure 1 two longitudinal cross-sectional views of the end of the fuel injector in the closed position and the open position; and

[0017] Figure 4 schematically shows an internal combustion engine using the Figure 1 fuel injector. Detailed Description of the Invention

[0018] InFigure 1 1, in the figure, generally denotes a gaseous fuel (in particular hydrogen) injector, which is developed about a longitudinal axis 2 and is suitable for being controlled for injecting hydrogen through an injection nozzle 3, which leads directly to an internal combustion engine E (in Figure 4 That is, the internal combustion engine E is fed with hydrogen and is provided with an injection system which directly injects hydrogen into a plurality of cylinders using corresponding hydrogen injectors 1; therefore, the internal combustion engine E includes at least one cylinder and an injection system which directly injects hydrogen into the cylinder using the fuel (hydrogen) injector 1.

[0019] according to Figure 1 As shown, the fuel injector 1 comprises a support body 4 having a cylindrical tubular shape with a variable cross section along the longitudinal axis 2 and a feed channel 5 extending along the entire length of the support body 4 for feeding pressurized hydrogen to the injection nozzle 3.

[0020] The support body 4 accommodates the electromagnetic actuator 6 in its upper part and the injection valve 7 (such as Figure 2 in use, the injection valve 7 is actuated by an electromagnetic actuator 6 for regulating the hydrogen flow through the injection nozzle 3, which is obtained at the injection valve 7. According to a different embodiment not shown, the actuator 6 is of piezoelectric type instead of electromagnetic type.

[0021] The electromagnetic actuator 6 is configured to move the movable unit axially (ie along the longitudinal axis 2), the movable unit being provided with a needle 8 terminating in a bulb-shaped gate 9 (eg Figure 2 The gate 9 and the valve seat 10 of the injection valve 7 (as shown in FIG. Figure 2 ) for regulating the flow of hydrogen through the injection nozzle 3. In other words, the support body 4 terminates in a through hole, the valve seat 10 is defined in the through hole, and the through hole is engaged by the gate 9. In particular, the electromagnetic actuator 6 is configured to close the injection valve 7 in the closed position (as shown in FIG. Figure 2 ) and the open position (as Figure 3 1 and 1 ). In addition, the electromagnetic actuator 6 is provided with a closing spring 11, which normally keeps the fuel injector 1 closed, i.e. the closing spring 11 pushes the gate 9 towards the closed position of the injection valve 7. In other words, the injection valve 7 is normally closed due to the closing spring 11, which pushes the needle 8 into the closed position, in which the gate 9 of the needle 8 is pressed against the valve seat 10 of the injection valve 7.

[0022] according to Figure 2 and Figure 3As shown, the gate 9 is arranged outside with respect to the support body 4 and is pushed against the support body 4 by the closing spring 11 of the electromagnetic actuator 6; thus, in order to switch from the closed position of the injection valve 7 to the open position, the gate 9 moves along the longitudinal axis 2 towards the outside of the support body 4, that is, in the moving direction identical to the hydrogen feed direction. In the open position of the injection valve 7 (as Figure 3 shown), the gate 9 is separated from the valve seat 10, forming a channel opening 12 with a crown-shaped cross-section; thus, the hydrogen gas ejected 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 gate 9 between the closed position of the injection valve 7 (as Figure 2 shown) and the open position of the injection valve 7 (as Figure 3 shown), in the closed position, the gate 9 presses against the valve seat 10, and in the open position, the gate 9 is separated from the valve seat 10 to form a channel opening 12 through which the hydrogen gas flows.

[0023] According to the preferred embodiment shown in the drawings, the gate 9 has: an initial portion that is connected to the valve seat 10 and has a gradually increasing outer diameter 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 a gradually decreasing outer diameter along the longitudinal axis 2.

[0024] According to Figure 2 and Figure 3 shown, the fuel injector 1 includes a gasket 13 made of an elastic material (i.e., a natural or synthetic polymer having elastic rubber properties), the gasket 13 being attached to the support body 4 and arranged at the injection valve 7 to obtain the valve seat 10; that is, in the closed position (as Figure 2 shown), the gate 9 abuts against the outer surface of the gasket 13 so as to form a seal, thereby preventing the hydrogen gas from flowing out.

[0025] According to Figure 2 and Figure 3 shown, the fuel injector 1 includes a stroke end system 14 that is separated from and independent of the gasket 13 and determines the closed position (as Figure 2 shown), stopping the stroke of the gate 8 pushed by the closing spring 11; in other words, the stroke of the needle 8 that moves due to the thrust applied by the closing spring 11 does not stop because of the contact between the gate 9 and the gasket 13 (which defines the valve seat 10), but because of the contact that occurs in the stroke end system 14. The stroke end system 14 is calibrated such that in the closed position (as Figure 2 shown), that is, at the position where the stroke end system 14 stops the movement of the needle 8, the gate 9 contacts the gasket 13 (the gasket 13 defines the valve seat 10) and elastically compresses the gasket 13 to ensure the necessary seal.

[0026] The stroke end system 14 includes an abutting member 15 integral with the needle 8, and an abutting member 16 integral with the support body 4, facing the abutting member 15 and contacting the abutting member 15 to stop the movement of the needle 8.

[0027] According to the preferred embodiment shown in the drawings, the stroke end system 14 is not adjacent to the gasket 13; in other words, the stroke end system 14 is arranged at a non-zero axial (i.e., measured along the longitudinal axis 2) distance from the gasket 13, so as to be axially spaced from the gasket 13. Since the stroke end system 14 is not adjacent to the gasket 13, the portion of the support body 4 in the region of the gasket 13 (i.e., in the region of the valve seat 10 of the injection valve 7) can be designed (optimized) to ensure the best flow of hydrogen, and the sealing diameter of the valve seat 10 can be larger; in other words, because at the valve seat 10 defined by the gasket 13, due to the stroke end system 14, there are no shape or size constraints (because the stroke end system 14 is far from the gasket 13), so there is more design freedom to manufacture the region of the gasket 13 (i.e., the region of the valve seat 10 of the injection valve 7) to ensure the best flow of hydrogen and to increase the sealing diameter of the valve seat 10.

[0028] In the above embodiment, the injection of hydrogen is referred to, but the injector 1 can be used to inject any other type of gaseous fuel, such as methane.

[0029] The embodiments described herein can be combined with each other.

[0030] The fuel injector 1 described above has many advantages.

[0031] First of all, even in the long term, the fuel injector 1 described above ensures perfect sealing. This result is obtained due to the presence of the gasket 13, which is elastically compressed by the gate 9 in the closed position (as Figure 2 shown), adapts to the shape of the gate 9, and hermetically seals the entire contact area.

[0032] In addition, the fuel injector 1 described above has a very long service life. This result is obtained because the stroke of the needle 8 towards the closed position (as Figure 2 shown) is stopped by the stroke end system 14 without overpressing (and thus wearing) the gasket 13. In other words, by releasing all the kinetic energy possessed by the movable unit (of which the needle 8 and the gate 9 are a part) onto the gasket 13, the presence of the stroke end system 14 avoids overpressing the gasket 13.

[0033] Finally, since the fuel injector 1 described above has few and easily manufacturable structural differences compared to similar known hydrogen (fuel) injectors, its manufacture is simple and inexpensive.

[0034] List of reference signs of the drawings

[0035] 1 Fuel injector

[0036] 2 Longitudinal axis

[0037] 3 Injection nozzle

[0038] 4 Support body

[0039] 5 Feed channel

[0040] 6 Electromagnetic actuator

[0041] 7 Injection valve

[0042] 8 Needle

[0043] 9 Gate

[0044] 10 Valve seat

[0045] 11 Closing spring

[0046] 12 Channel opening

[0047] 13 Washer

[0048] 14 End-of-stroke system

[0049] 15 Adjacent member

[0050] 16 Adjacent member

[0051] E Internal combustion engine

Claims

1. A fuel injector (1) for gaseous fuel, comprising: Spray nozzle (3); a support body (4) having a tubular shape, the support body (4) having a longitudinal axis (2) and in which a feed channel (5) terminating in a spray nozzle (3) is arranged; an injection valve (7), the injection valve (7) being configured to regulate the flow of gaseous fuel through the injection nozzle (3) and being provided with a movable gate (9) and a valve seat (10), the gate (9) being arranged outside the support body (4); an actuator (6) configured to move a gate (9) between a closed position of the injection valve (7), in which the gate (9) presses against a valve seat (10), and an open position of the injection valve (7), in which the gate (9) is separated from the valve seat (10) to produce a passage opening (12), through which the gaseous fuel flows; a needle (8), the needle (8) supporting a gate (9); a gasket (13) of elastic material, which is arranged at the injection valve (7) to obtain a valve seat (10) and which, in the closed position of the injection valve (7), is in contact with the gate (9); and an end-of-stroke system (14) which determines the closed position and is separate and independent from the gasket (13); The fuel injector (1) is characterized in that: an end-of-stroke system (14) coupled to the needle (8) and arranged at an axial distance from the gasket (13), i.e. measured along the longitudinal axis (2), which is not zero, so as to be further away from the injection nozzle (3) relative to the gasket (13); and The end-of-stroke system (14) does not interrupt the feed channel (5) in every position, and therefore does not prevent the gaseous fuel from flowing along the feed channel (5) to the injection nozzle (3), the gaseous fuel passing by the end-of-stroke system (14).

2. A fuel injector (1) according to claim 1, wherein the end-of-stroke system (14) is calibrated so that in the closed position the gate is in contact with the gasket (13) and elastically compresses the gasket (13).

3. A fuel injector (1) according to claim 1, wherein the end-of-stroke system (14) is configured to stop the movement of the gate (9) regardless of the contact of the gate (9) against a gasket (13) defining the valve seat (10).

4. A fuel injector (1) according to claim 1, wherein the end-of-stroke system (14) comprises a first abutment member (15) integral with the needle (8), and a second abutment member (16), which is integral with the support body (4), faces the first abutment member (15) and contacts the first abutment member (15) to stop the movement of the needle (8).

5. A fuel injector (1) according to claim 4, wherein the two components (15, 16) of the end-of-stroke system (14) are arranged inside the feed channel (5) and only partially occupy the feed channel (5), so that in each position the fuel flows freely along the feed channel (5) towards the injection nozzle (3), passing by the end-of-stroke system (14).

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

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

8. The fuel injector (1) according to any one of claims 1 to 5, wherein: The gate (9) has a bulb shape and comprises: an initial portion coupled to the valve seat (10) and having a gradually increasing outer diameter along the longitudinal axis (2); a middle portion having a constant outer diameter along the longitudinal axis (2); and An end portion, which is closer to the injection nozzle (3), has a gradually decreasing outer diameter along the longitudinal axis (2).

9. The fuel injector (1) according to any one of claims 1 to 5, wherein: The shutter (9) is arranged outside the support body (4) and is moved toward the outside of the support body (4) in the same movement direction as the fuel feed direction in order to switch from the closed position of the injection valve (7) to the open position.

10. The fuel injector (1) according to any one of claims 1 to 5, wherein: The end-of-stroke system (14) is not adjacent to the washer (13).

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