Gas injector for an internal combustion engine

Abstract

The present invention provides a gas injector (10) for injection of gaseous fuel in 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), and an outwardly-opening pintle (26) having a pintle shaft (28) and pintle head (30). 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. The pintle shaft (28) comprises a hollow length (28.1) extending from the proximal side to the distal side 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 and the outlet portion. At least one of the armature (32), the pole piece (38) and the spring (34) is arranged so as to surround the pintle (26) at points along the injector axis (A) located strictly between the proximal aperture (26.1) and the distal aperture (26.2).

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.

[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 .

[0011] General Description of the Invention

[0012] The present invention provides a gas injector for injection of gaseous fuel in an internal combustion engine. The gas injector extends along an injector axis from a proximal side to a distal side and comprises: 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.

[0013] Remarkably, the pintle shaft comprises a hollow length extending from the proximal side to the distal side and the pintle comprises a proximal and a distal aperture, thereby defining an axial gas passage between the inlet portion and the outlet portion.

[0014] Furthermore, at least one of the armature, the pole piece and the spring is arranged so as to surround the pintle at points along the injector axis located strictly between the proximal aperture and the distal aperture. This minimizes flow obstruction.

[0015] The present invention thus proposes an injector design for gaseous fuel which uses a hollow pintle shaft extending along the injector axis to convey fluid from the inlet portion to the outlet portion. The gas exits the pintle, respectively pintle shaft, at or near its distal end, typically via a lateral aperture upstream of the valve seat. Fuel can thus be forwarded through the injector in a straight channel (provided by the hollow shaft), avoiding flow through components such as armature or springs, hence avoiding pressure drops due to meandering flow paths.

[0016] Typically, the pintle shaft is fixedly connected to the pintle head. That is, the pintle is designed as a single component, although may be built from different parts (which are thus fixedly assembled).

[0017] Typically, the valve seat is part of the injector body, which is adapted to be mounted to the engine.

[0018] In embodiments, the fuel injector comprises a magnetic armature mechanically coupled to the pintle shaft to be axially moveable therewith, and a solenoid configured to selectively generate a magnetic field, thereby displacing the magnetic armature and forcing the pintle into its open position. The magnetic armature may be fixedly attached to the pintle shaft, preferably by welding, although other fixation means may be employed; form combination to axially lock armature and pintle together is also possible. The fuel injector may further comprise a pole piece arranged distally from the armature and / or a spring configured to bias the pintle towards its closed position, the spring being preferably arranged distally from the armature.

[0019] In embodiments, at least the armature, pole piece and spring are arranged within the injector channel so as to surround the pintle at points along the injector axis located strictly between the proximal aperture and the distal aperture. By isolating these three components from the gas flow path, the total pressure drop is further reduced.

[0020] In embodiments, an inlet member is arranged in the inlet portion and defines an axial gas inlet channel, in which the pintle shaft is clearance fitted. The gas inlet channel preferably comprises a proximal section connecting a distal cylindrical section of smaller cross-sectional area, more preferably via a tapered section, and the pintle shaft is clearance fitted inside the distal cylindrical section. A radial clearance gap between the hollow pintle shaft and the inlet member may be comprised between 5 pm and 15 pm. The inlet member and its distal cylindrical section thus serve as a proximal guide for the motion of the pintle, i.e. by constraining motion of the pintle to the injector axis.

[0021] In embodiments, the pintle shaft is clearance fitted in the outlet portion. A radial clearance gap between the hollow pintle shaft and the outlet portion may be comprised between 5 pm and 15 pm. The outlet portion thus serves as a distal guide for the motion of the pintle, i.e. by constraining motion of the pintle to the injector axis.

[0022] In embodiments, the channel includes a distal outlet chamber ending with the outlet opening, and the distal aperture of the pintle is arranged, at least in the closed position, into the outlet chamber. The distal outlet chamber essentially defines a plenum chamber for the gas directly upstream of the valve seat.

[0023] In embodiments, the injector body comprises a lower body and a seat member, which is affixed to the lower body and comprises the outlet opening and the valve seat. The seat member may be a tubular element mounted in axial continuity of the lower body and having an inwardly protruding proximal edge defining a lower guide for said pintle shaft and inwardly protruding distal edge defining said outlet opening and valve seat. The seat member may define said outlet chamber, the latter having a cross-section greater than the cross-section of the channel in the lower body.

[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. The pintle head may comprise a tubular attachment portion and the distal end of the pintle shaft may be engaged inside or around said tubular attachment portion. The distal aperture may further be arranged in the pintle shaft upstream of the tubular attachment portion; or the distal aperture may be arranged at the level of the tubular attachment and extends through the pintle shaft and tubular attachment.

[0025] The 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 fuel injector as described above.

[0026] 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.

[0027] Brief Description of the Drawings

[0028] A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which:

[0029] Fig. 1 is a cross sectional view of an embodiment of the inventive gas injector, in closed position;

[0030] Fig.2 is a detail view of the outlet portion of the gas injector of Fig.1 , in open position;

[0031] Figs. 3a-d are principle views of alternative configurations of the pintle; and

[0032] Fig. 4 is a schematic view of a gaseous fuel delivery system comprising the inventive gas injector;

[0033] Description of Preferred Embodiments

[0034] 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. As used herein, the terms fuel, fuel gas and gaseous fuel are used as synonyms. Likewise, the injector may be referred to as gas injector or fuel injector.

[0035] The fuel 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 integral but could alternatively be separate parts fixed together.

[0036] 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 fuel injector 10. When installed on the engine, the injector body portion with the outlet portion 18, i.e. the lower body 12b, is arranged in a bore in the cylinder head, which opens into a combustion chamber (not shown) of the engine.

[0037] 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 gastight manner, such that the channel 20 defines a gas-tight passage.

[0038] 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 (Fig.2), 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 fuel injector 10 is said to open outwardly.

[0039] It may further be noted that the valve seat is part of the injector body, i.e. the part that forms the outer wall of the injector and by which the injector is mounted to the engine.

[0040] 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 is 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, 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 armature 32 towards the proximal side P, thereby biasing the pintle 26 towards its closed position. In the embodiment of Fig. 1 , the coil spring 34 is arranged distally from the armature 32, with its proximal end engaging the latter and its distal end engaging a shoulder 12.1 formed in the injector body 12. Other spring configurations can be envisaged.

[0041] 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, partially surrounding the coil spring 34. To guide the magnetic field, a magnetic ring 40 is incorporated in the main body; alternatively, the wall thickness of the main body 12a can be locally reduced to form a so-called magnetic shunt. It will be appreciated that 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.

[0042] 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 , whereas the opposite tube end is closed by the pintle head 30, which is partially inserted in the pintle shaft 28 (a pin-like attachment portion 31 of the pintle head is inserted in pintle shaft 28). Therefore, 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 one hole, or typically a number of holes, in the peripheral wall of the pintle shaft 28 proximal to the pintle head 30. The size and number of the holes depend on the desired flow rate.

[0043] The open position of the pintle 26 is shown in Fig.2. The pintle 26 has moved distally, whereby a flow passage is opened between the pintle head 30 and valve seat through which gaseous fuel is discharged (as indicated by the arrows in Fig.2).

[0044] 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.

[0045] 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 with a tapering distal section 15.2 ending with a narrow section 15.3, which serves as upper guide for the pintle shaft 28. Here a small operating clearance exists for guiding the pintle 26 during its reciprocating motions, offering only a small passage for gas. The central passage and narrow section are centered on the injector axis A. A rail adapter 17 is mounted on the inlet member 15, which is an application dependent element for coupling to the rail.

[0046] The closing stroke of the pintle 26 (i.e. movement in proximal direction) under the action of spring 34 is limited by the valve seat 24. Reference sign 42 indicates a resilient member, e.g. of annular shape, that is compressed by the upwardly moving armature 32, thereby reducing the impact speed of the pintle head 30 as it reaches the valve seat 24. This resilient member 42 (e.g. a polymer ring, in particular an elastomer), which can be fixed to the armature 32 or the inlet member 14, reduces shocks and seat wear.

[0047] In this embodiment, on the distal side D, the gas injector 10 comprises a seat member 23 which is arranged at the distal end of the lower body, partially received in a front recess 19. The seat member 23 has a generally cylindrical shape (coaxial with injector axis A), with a proximal opening 23.2 defined by an inwardly protruding annular edge (or lip) and a distal opening 23.3, likewise defined by the an inwardly protruding annular edge (or lip).

[0048] The pintle shaft 28 is clearance fitted in the proximal opening 23.2 of the seat member 18 such that the latter is able to axially guide motion of the former along injector axis A, hence forming a lower guide.

[0049] The distal opening 23.3 of the seat member 23 corresponds to the outlet opening 22 of the injector 10. The valve seat 24 is thus defined by the lower edge so as to surround the distal opening 23.3 1 the outlet opening 22. Hence, when the pintle 26 is in the closed position, flow through the distal opening 18.3 is prevented, and the inner volume 18.1 of the outlet portion 18 defines a plenum chamber, also denoted 23.1 , 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 23.1 is open and pressurized gaseous fuel is discharged in the engine’s combustion chamber.

[0050] The clearances between the pintle shaft 28 and the narrow section 15.3 of the inlet portion 14, and between the pintle shaft 28 and the proximal opening 23.2 of the seat member 23 are such that the vast majority of the fuel flowing through the injector 10 flows through the inner volume 28.1 of the pintle shaft 28, the distal aperture 26.2, and the inner volume 23.1 of the seat member 23. These clearances may be of about 5 to 15 pm in radius. Hence only a small fraction of the fuel 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.

[0051] The injector body 12 and pintle 26 are typically made of metallic material, in particular steel or stainless steel; however, this should not be construed as limiting and other appropriate materials may be employed. 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 an air-tight manner, e.g. by welding. 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. That is the pintle is typically a single component, although it may be built from different parts.

[0052] Figure 4 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.

[0053] Turning to Figs 3a-3d, 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 3a-c. The distal aperture 26.2 may be formed through both the pintle shaft 28 and the pintle head 30, as shown on figure 3b, the recess may be formed exclusively through the pintle head 30, as shown on figure 3c, 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 injection of gaseous fuel in 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 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); characterized in that the pintle shaft (28) comprises a hollow length (28.1 ) extending from the proximal side (P) to the distal side (D) and the pintle (26) 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); and at least one of the armature (32), the pole piece (38) and the spring (34) is arranged so as to surround the pintle (26) at points along the injector axis (A) located strictly between the proximal aperture (26.1 ) and the distal aperture (26.2).

2. The gas injector (10) according to claim 1 , further comprising a magnetic armature (32) mechanically coupled to the pintle shaft (28) to be axially moveable therewith, and a solenoid (36) configured to selectively generate a magnetic field, thereby displacing the magnetic armature (32) and forcing the pintle (26) into its open position.

3. The gas injector (10) according to claim 2, wherein the magnetic armature (32) is fixedly attached to the pintle shaft (28), preferably by welding.

4. The gas injector (10) according to claims 2 or 3, further comprising a pole piece (38) arranged distally from the armature (32).

5. The gas injector (10) according to any of claims 2 to 4, wherein a spring (34) is configured to bias the pintle (26) towards its closed position, the spring (34) being preferably arranged distally from the armature (32).

6. The gas injector (10) according to claim 2 to 5, wherein at least one of the armature (32), pole piece (38) and spring (34) are arranged within the injector channel (20), preferably all of them.

7. The gas injector (10) according to any of the preceding claims, wherein an inlet member (15) is arranged in the inlet portion (14) and defines an axial gas inlet channel, in which the pintle shaft (28) is clearance fitted.

8. The gas injector (10) according to claim 7, wherein the gas inlet channel comprises a proximal section (15.1 ) connecting a distal cylindrical section (15.3) of smaller cross-sectional area, preferably via a tapered section (15.2), and wherein the pintle shaft (28) is clearance fitted inside the distal cylindrical section (15.3).

9. The gas injector (10) according to claim 7 or 8, wherein a radial clearance gap between the hollow pintle shaft (28) and the inlet member (14) is comprised between 5 pm and 15 pm.

10. The gas injector (10) according to any of the preceding claims, wherein the pintle shaft (28) is clearance fitted in the outlet portion (18).

11. The gas injector (10) according to claim 10, wherein a radial clearance gap between the hollow pintle shaft (28) and the outlet portion (18) is comprised between 5 pm and 15 pm.

12. The gas injector (10) according to any of the preceding claims, wherein the channel includes a distal outlet chamber (23.1 ) ending with the outlet opening (22), and wherein the distal aperture (26.2) of the pintle (26) is arranged, at least in the closed position, into said outlet chamber (23.1 ).

13. The gas injector (10) according to any of the preceding claims, wherein the injector body (12) comprises a lower body (12b) and a seat member (23), whichis affixed to the lower body (12) and comprises the outlet opening (22) and the valve seat (24).

14. The gas injector (10) according to any of the preceding claims, wherein the seat member (23) is a tubular element mounted in axial continuity of the lower body (12b) and having an inwardly protruding proximal edge (23.2) defining a lower guide for said pintle shaft and inwardly protruding distal edge (23.3) defining said outlet opening (22) and valve seat (24).

15. The gas injector (10) according to the preceding claim, wherein the seat member (23) defines said outlet chamber (23.1 ), the latter having a cross-section greater than the cross-section of the channel (20) in the lower body (12b).

16. 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.

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

18. The gas injector (10) according to the preceding claim, 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.

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 the preceding claim, 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).

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