Gas injector with nozzle portion
By improving the sealing contact geometry of the valve seat and pivot head of the hydrogen injector nozzle, the fuel leakage problem caused by valve seat wear is solved, and efficient hydrogen sealing and durability are achieved.
Patent Information
- Application Number
- CN202380093581.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-02-10
- Filing Date
- 2023-12-27
- Publication Date
- 2025-09-05
AI Technical Summary
In existing hydrogen injector nozzle designs, the valve seat is prone to wear, leading to fuel leakage, especially when the hydrogen molecule size is small, the sealing is insufficient.
Design a nozzle section with improved sealing contact geometry including the valve seat and pivot head to increase valve seat durability and sealing performance by controlling the annular gap and taper angle.
The wear resistance and sealing performance of the injector nozzle are improved, ensuring effective sealing of hydrogen under high pressure and reducing the risk of leakage.
Smart Images
Figure CN120604031A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates generally to injection systems for internal combustion engines operating with gaseous fuels, and more particularly to injector nozzle arrangements for gas / hydrogen injectors. Background Art
[0002] As is well known, fuel injectors are associated with internal combustion engines. They are used to inject fuel into the engine's combustion chamber. Such fuel injectors typically include a nozzle body connected to an injector body. A fuel delivery passage extends from a fuel pump through the injector body to a nozzle chamber arranged in the nozzle body. The nozzle body has at least one nozzle orifice, allowing fuel to be injected from the nozzle chamber into the combustion chamber. A pivot is slidable within an axial center hole arranged in the nozzle body. The pivot includes a pivot head configured to engage a valve seat surrounding the nozzle orifice to prevent fuel from flowing through the nozzle orifice. The pivot is spring-biased in a closing direction. A solenoid actuator generates a magnetic field that allows the valve pivot to be actuated to open or close the nozzle orifice to allow or prevent fuel from flowing into the combustion chamber. The nozzle body has an upper contact surface that presses against a lower contact surface of the injector body.
[0003] In the context of developing hydrogen combustion engines, conventional fuel injector technology (gasoline or diesel) was adapted for gaseous fuel injection. A common problem with prior art nozzle designs is the susceptibility of valve seats to wear, particularly due to the lack of hydraulic damping compared to liquid fuels. In fact, failure mode analysis has revealed the presence of scratches on the valve seats, primarily around their inner perimeter. These scratches, in turn, can cause fuel leakage through them, which is naturally to be avoided.
[0004] This is particularly relevant for hydrogen injectors because hydrogen molecules are much smaller than conventional fuel molecules. Therefore, hydrogen fuel can flow through much narrower gaps, and as a result, hydrogen injector nozzles must seal more tightly and securely than conventional fuel injector nozzles. Furthermore, hydrogen injector components, such as valve seats, must be durable enough to prevent scratches from forming, through which hydrogen could leak.
[0005] The difficulty in designing a high-performance hydrogen injector lies in balancing the properties of its components in a way that meets all design requirements. In fact, while modifying a specific characteristic of a component can improve the performance of a design in one way, it can also significantly degrade performance in another way. For example, an increase in sealing pressure results in a tighter seal for hydrogen, but is also associated with increased stress under shock loads, which can reduce the durability of the valve seat or pivot head and cause leakage.
[0006] Technical issues
[0007] It is therefore an object of the present invention to provide an injector nozzle design having an improved pivot head to valve seat sealing contact geometry that increases valve seat durability. Summary of the Invention
[0008] The present invention relates to a nozzle portion for a gas injector, the nozzle portion comprising:
[0009] a nozzle body extending along a central axis, the nozzle body having a central passage along the central axis, the central passage extending between a proximal gas inlet and an opposing nozzle tip having a gas outlet;
[0010] a valve seat located at the nozzle tip and surrounding the central passage, the valve seat having an edge engaging portion engaging the central passage and a tapered annular valve seat surface extending outwardly from the edge engaging portion, the central passage having a diameter Di at the edge engaging portion, the annular valve seat surface being tapered with an aperture angle Av;
[0011] a pivot shaft having a pivot shaft and a pivot shaft head, the pivot shaft being reciprocally movable in the central passage between a closed position and an open position, wherein the closed position the pivot shaft rests on the valve seat to close gas flow through the valve seat, and the open position the pivot shaft is lifted from the valve seat to allow gas to be discharged from the nozzle tip;
[0012] wherein the pivot head has a valve seat facing side, the valve seat facing side having an annular sealing surface comprised between an inner annular surface and an outer annular surface, the annular sealing surface defining a sealing diameter Ds with the valve seat surface in the closed position of the pivot;
[0013] wherein the annular sealing surface of the pivot has a predetermined curvature radius Rs;
[0014] wherein the valve seat surface and the valve seat-facing side of the pivot head are configured to form an annular gap that tapers from the edge joint toward the sealing diameter Ds in the closed position;
[0015] Therein, the annular gap is such that a distance, referred to as the gap opening (g), which corresponds to the axial length between the edge joint and its axial projection on the side of the pivot shaft facing the valve seat, is at least 5 μm.
[0016] The present invention provides a nozzle section with an improved design at the pivot / seat interface. The inventors' research has determined that an annular gap with controlled geometry is desirable to avoid severe wear. In fact, the inventors have found that, despite the desire for a conical / spherical geometry, the distance between the pivot sealing surface and the opposing edge at the valve seat periphery (referred to herein as the gap opening, g) is the relevant parameter. Increasing the gap opening also means increasing the length of the valve seat surface between the edge joint and the sealing diameter. This has two main benefits: the larger sealing surface ensures that the pivot is always closed in a defined area away from the edge joint; and the controlled taper angle creates some separation between the pivot sealing surface and the edge joint, which avoids contact between the pivot and the edge, thereby avoiding overstress and wear.
[0017] Advantageously, the injector nozzle portion according to the present invention is less susceptible to wear and fatigue, ensures sufficient contact pressure between the pintle head and the valve seat to seal hydrogen in the injector nozzle, and keeps head losses in the conical gap within acceptable limits.
[0018] Hereinafter, embodiments of the present invention are disclosed which are believed to be particularly effective in achieving the above-mentioned benefits.
[0019] In an embodiment, the difference between the sealing diameter Ds and the diameter Di at the edge joint is greater than 0.20 times the sine of Av / 2, preferably greater than 0.32 times the sine of Av / 2, and less than 1.67 times the sine of Av / 2, preferably less than 1.44 times the sine of Av / 2, more preferably less than 0.84 times the sine of Av / 2, and even more preferably less than 0.72 times the sine of Av / 2. These designs provide a choice of two diameters of interest that controls the length of the surface on which the pivot head lands, thereby improving the contact interface between the pivot head and the valve seat.
[0020] In an embodiment, the radius of curvature Rs of the annular sealing surface of the pivot shaft facing the valve seat is between 1 mm and 2 mm, preferably between 1 mm and 1.8 mm.
[0021] In an embodiment, the annular sealing surface of the valve seat facing side of the pivot extends beyond an axial projection of the edge engagement portion on the valve seat facing side of the pivot.
[0022] In an embodiment, the annular sealing surface of the pivot shaft facing the valve seat side has a tapered hole Ai of more than 132° at its junction with the inner annular surface, preferably at least 140°.
[0023] In an embodiment, the annular sealing surface of the pivot shaft facing the valve seat side has a tapered bore Ao at its junction with the outer annular surface of less than 108°, preferably not more than 100°.
[0024] In an embodiment, the valve seat is configured such that a tapered annular valve seat surface faces distally and the pivot head presses proximally against the annular valve seat surface in the closed position.
[0025] In an embodiment, the seal diameter Ds is between 3.88 mm and 5.97 mm.
[0026] In an embodiment, the distance between the sealing diameter Ds and the edge joint along the valve seat surface is greater than 0.104 mm, preferably greater than 0.162 mm, and less than 0.831 mm, preferably less than 0.716 mm, more preferably less than 0.416 mm, and even more preferably less than 0.358 mm.
[0027] In an embodiment, the diameter Di at the edge junction is greater than 3.6 mm and less than 5.35 mm.
[0028] In an embodiment, the difference between the sealing diameter Ds and the diameter Di at the edge joint is greater than 0.18 mm, preferably greater than 0.28 mm, and less than 1.44 mm, preferably less than 1.24 mm, more preferably less than 0.72 mm, and even more preferably less than 0.62 mm. For example, the difference between Ds and Di can be equal to 0.28 mm, 0.62 mm, 0.72 mm, or 1.24 mm.
[0029] Preferably, the central passage comprises at its distal end a cylindrical end section connected to said valve seat at said edge junction.
[0030] In an embodiment, the gap opening is at least 8 μm, preferably more than 10 μm.
[0031] The conical annular valve seat may have a cone angle Av between 5 and 175°, preferably between 90 and 150°, more preferably between 110 and 130°.
[0032] The present invention also provides an injector for gaseous fuel comprising a nozzle portion according to any of the above designs and a solenoid actuator configured to selectively actuate the pintle. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Further details and advantages of the present invention will be apparent from the following detailed description of several non-limiting embodiments with reference to the accompanying drawings, in which:
[0034] Figure 1 is a longitudinal sectional view of a gas fuel injector according to an embodiment of the present invention;
[0035] Figure 2 yes Figure 1 an enlarged view of detail X shown;
[0036] Figure 3 for Figure 2 Enlarged view of the Y position in the middle;
[0037] Figure 4 yes Figure 3 Schematic diagram of the pivot head and valve seat interface;
[0038] Figure 5 is a schematic diagram of a pivot head and valve seat interface according to a comparative design which does not form a part of the present invention;
[0039] Figure 6 Yes Figure 4 and Figure 5 A graph showing the theoretical sealing contact pressure of the interface design;
[0040] Figure 7 Yes Figure 4 and Figure 5 Graph of the theoretical stress of the interface design under impact load. DETAILED DESCRIPTION
[0041] Figure 1 A gas injector 10 comprising an embodiment of the present nozzle portion is schematically shown. The gas injector 10 is designed for injecting a gaseous fuel, in particular hydrogen.
[0042] The injector 10 comprises an injector housing 12 extending along a longitudinal axis A. The injector housing 12 has an axial cavity defining a central passage 14 for gaseous fuel extending from a proximal end (inlet side of the injector) to an opposite distal end D (discharge end).
[0043] At the proximal side P, only partially shown, a fitting (not shown) is provided for fluid connection to a gas supply tube (not shown). The fitting is connected to the central passage 14, and a filter (not shown) may be arranged in the inlet section. The injector 10 includes an actuator portion 16 located at the proximal side P. The actuator portion 16 includes a slidably arranged actuator shaft 18. The actuator shaft 18 is hollow and open-ended so that gas can flow through the actuator shaft 18. The actuator shaft 18 is integral with a magnetic armature 20 extending radially therefrom. Reference numeral 22 denotes a solenoid coil which, when energized, generates a magnetic field that attracts the armature 20 in the direction of the distal side D (i.e., downward in the figure) and thereby moves the actuator shaft 18 in an opening direction, as will be discussed below.
[0044] Below the actuation shaft 18 is the nozzle portion 24, with a nozzle body 26 forming the distal section of the injector housing 12. The nozzle body 26 includes, at its end or distal tip, a valve seat 28 surrounding the central passage 14. The open end of the central passage 14 at the valve seat is referred to as the nozzle orifice 29 and forms the gas outlet of the nozzle / injector.
[0045] The pivot 30 is slidably disposed in the central passage 14 relative to the nozzle body 26. The pivot 22 includes a pivot head 32 configured to cooperate with the valve seat 28 to stop or allow gas to escape at the injector tip. The pivot 30 also includes a pivot rod 34 and a pivot seat 36 (a protruding annular collar). A compression spring 38 is disposed between the nozzle body 26 and the pivot seat 36 to bias the pivot head 32 toward the proximal end P: this is the closed position (in the closed position). Figure 1 ), wherein the pivot head 32 rests on the valve seat 28, thereby blocking flow through the central passage 14 downstream of the valve seat 28. Conversely, the actuation shaft 18 is configured to transmit a force to the pivot 30 toward the distal end D so as to lift the pivot head 32 from the valve seat 28 and thereby allow gas to exit at the nozzle tip.
[0046] Thus, when an injection event is triggered by an engine control unit connected to the injector 10, the solenoid 22 is energized, and the actuating shaft 18 and the pivot 30 are moved toward the distal end D, thereby moving the pivot head 32 away from the valve seat 28, thereby opening the nozzle hole 29 and exhausting the gas in the engine. Then, when the solenoid is de-energized, the pivot 30 is urged toward the proximal end P by the spring 38, and the pivot head 32 rebounds against the valve seat 28, thereby sealing the nozzle hole 29.
[0047] Figure 2 Shown Figure 1 Magnified view of detail X. In particular, the pivot head 32 of the nozzle orifice 29 and the valve seat 28 are visible. Figure 3 Also shown Figure 2 A magnified view of the detail Y.
[0048] As can be seen, the end of the central channel 14 connects to the outwardly extending valve seat 28 at the nozzle orifice 29 via an edge joint 40. The valve seat 28 is a conical surface that defines an aperture angle Av of a corresponding annular valve seat surface (hence also designated 28). Angle Av can typically be comprised between 5 and 175 degrees. The injector 10 is designed as an outwardly opening injector, whereby the valve seat 28 faces away from the proximal end in the direction of gas discharge.
[0049] In contrast, pivot head 32 has a valve seat-facing side 42 with an annular sealing surface 44 having a predetermined radius of curvature Rs and an arc length Ls. Annular sealing surface 44 is comprised between an inner annular surface 46 and an outer annular surface 48. Inner annular surface 46 is tangent to the inner end of annular sealing surface 44 and defines a tapered surface having an aperture angle Ai. Outer annular surface 48 is tangent to the outer end of annular sealing surface 44 and defines a tapered surface having an aperture angle Ao. The tapered angles of valve seat 28, inner annular surface 46, and outer annular surface 48 are indicated relative to central axis A and are therefore labeled Av / 2, Ai / 2, and Ao / 2, respectively.
[0050] In the closed position, the annular sealing surface 44 of the pivot head presses against the valve seat surface 28; they contact each other in a gas-tight manner along a circular contact line. This circular contact line has a predetermined diameter, referred to as Ds - the sealing diameter. It should be noted that the pivot and nozzle body are typically made of metal (e.g., stainless steel). The sealing line is thus achieved through a metal-to-metal seal. A high contact pressure is required to provide a hydrogen seal, which is achieved by the return spring and the value of Rs.
[0051] In the case of hydrogen injection, at operating pressures up to 50 bar, it is desirable that the sealing diameter Ds be positioned at a controlled distance from the central passage, taking into account hydraulic and spring forces. In particular, it is desirable that the difference between the sealing diameter Ds and the diameter Di at the edge joint 40 be greater than 0.20*sin(Av / 2) and less than 1.67*sin(Av / 2).
[0052] Figure 4 is a schematic diagram showing the interface between the pivot head 32 and the valve seat 28 in the closed position. Figures 1 to 3 The same reference numerals are used in the figures. The diameters Di and Ds are indicated relative to the longitudinal axis A and are therefore designated Di / 2 and Ds / 2. The cone angle of the valve seat 28 is indicated relative to the central axis A and is therefore designated Av / 2. One will recognize the end section of the central channel 14, which is cylindrical here. The central channel 14 ends at its distal end in a nozzle orifice 29, where it is surrounded by the valve seat 28. The cylindrical central channel 14 and the conical valve seat 28 are discontinuous and form an edge joint 40. The pivot head 32 is represented here only by the arc of the annular sealing surface 44 corresponding to the radius of curvature Rs.
[0053] It can be seen that the valve seat surface 28 and the valve seat facing side 42 of the pivot head 32 are configured to form a tapered annular gap 50 that decreases from the edge joint 40 toward the sealing diameter Ds in the closed position.
[0054] Reference symbol g denotes the gap opening, ie the distance corresponding to the axial length between the edge joint 40 and its axial projection on the valve seat-facing side of the pivot. To improve interface durability, the gap is preferably at least 5 μm, more preferably at least 8 μm or more than 10 μm.
[0055] The dependency of this parameter is explained below: The distance Lv between the edge joint 40 and the sealing diameter Ds along the outer peripheral wall of the valve seat 28 depends on the valve seat angle, the sealing diameter Ds, and the diameter Di at the edge joint 40 .
[0056] The gap g between the pivot head 32 and the edge joint 40 along line A′ (parallel to axis A and therefore the axis of motion of the pivot X) can be determined based on the distance Lv along the outer peripheral wall of the valve seat 28, the valve seat angle Av and the curvature radius Rs of the pivot annular sealing surface 44.
[0057] It will be noted that in this embodiment, annular sealing surface 44 extends beyond the projection of the edge joint along axis A' onto the pivot. In other words, annular sealing surface 44 extends inwardly beyond the projected axis A'. In other words, annular sealing surface 44 connects to inner annular surface 46 at a diameter less than D i .
[0058] <Preferred Parameters>
[0059] Preferably, the valve seat has an aperture angle Av between 110° and 130°, in particular 119°, 120° or 121°.The pivot sealing surface 44 may have a radius of curvature Rs comprised between 1 mm and 1.8 mm.
[0060] The nozzle hole diameter Di at the edge joint 40 may be comprised between 3.6 mm and 5.35 mm. The sealing diameter Ds may be comprised between 3.88 mm and 5.97 mm.
[0061] With these parameters, Lv can be comprised between 0.104 mm and 0.831 mm, with the gap opening g being greater than 5 μm and even 8 μm or 10 μm and above.
[0062] Furthermore, as will be apparent from the following discussion, the nozzle assembly having this configuration increases the contact pressure between the pintle head and the valve seat, thereby improving the hydrogen sealing capability of the injector having this nozzle assembly.
[0063] <Example A>
[0064] An exemplary embodiment is described below. The valve seat has an angle Av = 119°. The pivot sealing surface 44 has a radius of curvature Rs = 1 mm.
[0065] The nozzle hole diameter at the edge joint 40 is Di = 3.62 mm. The sealing diameter Ds = 3.9 mm
[0066] Using these parameters, Lv = 0.162 mm and the gap opening g = 14.1 μm.
[0067] Comparative Example B
[0068] In order to better illustrate the effect of the present invention, Figure 5 An alternative interface design is shown (not forming part of the present invention) in which the central channel terminates with a chamfer (tapered section) before the edge junction. For ease of description, with the addition of chamfer 52, the same Figure 4 The same reference numerals are used in the drawings.
[0069] The valve seat has an angle Av = 120°. The pivot sealing surface 44 has a radius of curvature Rs = 2 mm.
[0070] The nozzle hole diameter at the edge joint 40 is Di = 3.9 mm. The sealing diameter Ds = 4.0 mm
[0071] Using these parameters, Lv = 0.057 mm and the gap opening g = 0.9 μm.
[0072] Figure 6 Measured at 41 bar Figure 4 and Figure 5 The probability density (1: Figure 4 Creative design; 2: Figure 5 Comparison between the two curves shows that the minimum sealing pressure for Design A is 7% greater than the minimum sealing pressure for Comparative Design B. The difference in sealing pressure is most likely due to Figure 4 and Figure 5 The embodiment results from the difference between the radii of the quasi-spherical portion of the pivot head.
[0073] FIG8 shows Figure 4 and Figure 5 A comparison of the two curves shows that the stress under impact load for the design according to Example A of the present invention is 12% greater than that for the comparative design B, but remains below 50% of the elastic limit. This difference is likely due to Figure 4 and Figure 5 The embodiment results from the difference in radius of the quasi-spherical portion of the pivot head.
[0074] Another advantage of the design according to the invention is therefore that the sealing contact pressure, ie the tightness of the seal, is increased while the stress under shock loads is kept within a safe range.
Claims
1. A nozzle portion (24) for a gas injector (10), the nozzle portion comprising: a nozzle body (26) extending along a central axis (A), the nozzle body (26) having a central passage (14) along the central axis (A), the central passage extending between a proximal gas inlet and an opposing nozzle tip having a gas outlet; a valve seat (28) surrounding the central passage (14) at the nozzle end, the valve seat (28) having an edge joint (40) joined to the central passage (14) and a tapered annular valve seat surface (28) extending outwardly from the edge joint (40), the central passage (14) having a diameter Di at the edge joint (40), the annular valve seat surface (28) being tapered with an aperture angle Av; a pivot shaft (30) having a pivot shaft (34) and a pivot shaft head (32), the pivot shaft (30) being reciprocally movable in the central passage (14) between a closed position and an open position, wherein the pivot shaft (30) rests on the valve seat (28) to close the flow of gas through the valve seat, and the pivot shaft (30) is lifted from the valve seat (28) to allow gas to be discharged from the nozzle tip; wherein the pivot head (32) has a valve seat facing side (42), the valve seat facing side having an annular sealing surface (44) comprised between an inner annular surface (46) and an outer annular surface (48), the annular sealing surface (44) defining a sealing diameter Ds with the valve seat surface (28) in the closed position of the pivot (30); wherein the annular sealing surface (44) of the pivot head (32) has a predetermined curvature radius Rs; wherein the valve seat surface (28) and the valve seat-facing side (42) of the pivot head (32) are configured to form an annular gap (50) that tapers from the edge joint (40) toward the sealing diameter Ds in the closed position; The annular gap (50) is such that a distance, referred to as the gap opening (g), is at least 5 μm, which corresponds to the axial length between the edge joint (40) and its axial projection on the valve seat-facing side (42) of the pivot (30).
2. The nozzle portion (24) according to claim 1, wherein The difference between the sealing diameter Ds and the diameter Di at the edge joint (40) is greater than 0.20 times the sine of Av / 2, preferably greater than 0.32 times the sine of Av / 2, and less than 1.67 times the sine of Av / 2, preferably less than 1.44 times the sine of Av / 2, more preferably less than 0.84 times the sine of Av / 2, and even more preferably less than 0.72 times the sine of Av / 2.
3. The nozzle portion (24) according to claim 1 or 2, wherein: The radius of curvature Rs of the annular sealing surface (44) of the pivot shaft (30) facing the valve seat side (42) is between 1 mm and 2 mm, preferably between 1 mm and 1.8 mm.
4. The nozzle portion (24) according to claim 1, 2 or 3, wherein The annular sealing surface (44) of the valve seat facing side (42) of the pivot shaft (30) extends beyond the axial projection of the edge joint (40) on the valve seat facing side (42) of the pivot shaft (30).
5. The nozzle portion (24) according to any one of the preceding claims, wherein The annular sealing surface (44) of the pivot shaft (30) facing the valve seat side (42) has a tapered bore Ai of greater than 132°, preferably at least 140°, at its junction with the inner annular surface (46).
6. The nozzle portion (24) according to any one of the preceding claims, wherein The annular sealing surface (44) of the pivot shaft (30) facing the valve seat side (42) has a tapered bore Ao of less than 108°, preferably not more than 100°, at its junction with the outer annular surface (48).
7. The nozzle portion (24) according to any one of the preceding claims, wherein The valve seat (28) is configured such that the tapered annular valve seat surface (28) faces distally and the pivot head (32) presses proximally against the annular valve seat surface (28) in the closed position.
8. The nozzle portion (24) according to any one of the preceding claims, wherein The sealing diameter Ds is between 3.88 mm and 5.97 mm.
9. The nozzle portion (24) according to any one of the preceding claims, wherein The distance between the sealing diameter Ds and the edge joint (40) along the valve seat surface (28) is greater than 0.104 mm, preferably greater than 0.162 mm, and less than 0.831 mm, preferably less than 0.716 mm, more preferably less than 0.416 mm, and even more preferably less than 0.358 mm.
10. The nozzle portion (24) according to any one of the preceding claims, wherein The diameter Di at the edge joint (40) is greater than 3.6 mm and less than 5.35 mm.
11. The nozzle portion (24) according to any one of the preceding claims, wherein The difference between the sealing diameter Ds and the diameter Di at the edge joint (40) is greater than 0.18 mm, preferably greater than 0.28 mm, and less than 1.44 mm, preferably less than 1.24 mm, more preferably less than 0.72 mm, and even more preferably less than 0.62 mm.
12. The nozzle portion (24) of any preceding claim, the central passage (14) comprising at its distal end a cylindrical end section connected to the valve seat (28) at the edge junction (40).
13. The nozzle portion (24) according to any one of the preceding claims, wherein The gap opening (g) is at least 8 μm, preferably greater than 10 μm.
14. The nozzle portion (24) according to any one of the preceding claims, wherein The conical annular valve seat (28) may have a cone angle Av between 5 and 175°, preferably between 90 and 150°, more preferably between 110 and 130°.
15. An injector (10) for gaseous fuel, comprising a nozzle portion (24) according to any one of the preceding claims and an electromagnetic actuator (22) configured to selectively drive the pintle (30).