WO2016008055A1

WO2016008055A1 - Gaseous fuel injector

Info

Publication number: WO2016008055A1
Application number: PCT/CA2015/050668
Authority: WO
Inventors: Mark E. Dunn; David R. Wager; Ashish Singh
Original assignee: Westport Power Inc.
Priority date: 2014-07-18
Filing date: 2015-07-17
Publication date: 2016-01-21
Also published as: CA2857396A1

Abstract

It is difficult for a gaseous fuel direct injector to deliver a comparable mass of fuel on an energy equivalent basis as a liquid fuel direct injector, during an injection cycle, when the liquid fuel is pressurized above storage pressure and the gaseous fuel is not. A gaseous fuel direct injector comprises an elongated nozzle having a proximal end upstream from a distal end. There is an elongated valve member having a first end operatively connected with an actuator and extending through a longitudinal bore within the elongated nozzle, and having a second end opposite the first end. A valve member guide is disposed within the longitudinal bore between the elongated nozzle and the elongated valve member for aligning the elongated valve member along the longitudinal axis of the elongated nozzle. There is a valve seat in one of the distal end of the elongated nozzle and the valve member guide. The second end of the valve member cooperates with the valve seat to form a valve. The elongated valve member is moveable by the actuator to actuate the valve between a closed position and an open position. An outer diameter of a portion of the nozzle in the combustion chamber is less than 8 mm, and the nozzle, the elongated valve member and the valve member guide cooperate to choke the flow area at the valve seat.

Description

GASEOUS FUEL INJECTOR

Field of the Invention

[0001] The present application relates to a fuel injector for a gaseous fuel, and more particularly to a fuel injector that introduces a gaseous fuel directly into a combustion chamber of an internal combustion engine.

Background of the Invention

[0002] Gaseous fuels, such as natural gas, have been consumed along with conventional liquid fuels, such as gasoline, as a fuel for so called bi-fuel, dual fuel and other fuel internal combustion engines modified to be fuelled with some combination of liquid fuel and gaseous fuel. In this disclosure "bi-fuel" describes engines that can be fueled with either one fuel or another fuel, and "dual fuel" describes engines that are fueled with two different fuels at the same time. Some engines have also been made to be fueled with just a gaseous fuel in so-called "mono-fuel" or "dedicated ¹ natural gas" engines. However, the base engine that is used as the starting point for making a gaseous fuelled engine, no matter which type, has normally been an engine that was originally designed and manufactured for liquid fuel, with this base engine requiring modifications to operate with a gaseous fuel. This means that the base engine is optimized for operation with gasoline or diesel, and gaseous fuels like natural gas are considered a secondary fuel. As an example, recent technology improvements for gasoline engines include the adoption of direct injection for injecting the gasoline directly into the combustion chamber instead of injecting the gasoline somewhere in the intake air system. Current product offerings for bi-fuel engines employ direct injection for the gasoline and port injection into the intake air ports for the gaseous fuel. Direct injection provides fuel economy savings when operating on gasoline, and when operating on CNG such engines operate at reduced power due to displacement of oxygen by injecting the gaseous fuel into the intake air system. That is, when gaseous fuel is injected into the intake air port, a corresponding volume of air is displaced from entering the combustion chamber, which reduces the amount of oxygen available to burn with fuel during each combustion event, thereby reducing peak combustion pressure and power output. Due to reduced power, these internal combustion engines are typically limited to a narrower range of engine operating conditions when operating with natural gas alone, compared to when it is fueled with gasoline.

[0003] More recently, there is a growing desire to replace conventional liquid fuels with a gaseous fuel as the primary fuel, and even to employ the gaseous fuel as the only fuel available to the internal combustion engine in so called mono-fuel or dedicated CNG engines. All things being the same, to generate power comparable to a conventional liquid-fuelled engine, the gaseous fuel must be introduced after the intake valve closes so intake air is not displaced by gaseous fuel. There are fuel injection timing constraints when injecting during the compression stroke because as the piston moves towards the cylinder head, that is, when it is moving towards top dead center (TDC), the in-cylinder pressure increases. When the fuel is pressurized above maximum in-cylinder compression pressure it can be introduced generally at any time during the compression stroke. Liquid fuels can be pressurized with relative economy and efficiency compared to gaseous fuels, since liquid fuels are incompressible fluids compared to gaseous fuels, which are compressible. In light duty applications, there are budget constraints that preclude the use of gas compressors, which can adjust the pressure of the gaseous fuel as a function of engine operating conditions, since the economic and efficiency costs of pressurizing a gaseous fuel is considerably more than pressurizing a liquid fuel. In this circumstance, the gaseous fuel is compressed beforehand and stored in high pressure storage tanks, and as the gaseous fuel is consumed by the engine the pressure of the gaseous fuel in the storage tank continues to decrease until the pressure is below a predetermined minimum pressure required by the gaseous fuel injector to introduce a predetermined quantity of fuel within a predetermined injection window that allows the engine to operate at full load without being derated. Preferably, the predetermined minimum pressure of gaseous fuel is as low as possible to increase the useable amount of fuel in the storage tank for which the engine can operate at full load. As gaseous fuel is consumed and gaseous fuel pressure (tank pressure) decreases, the available injection 8

- 3 - timing window after the intake valve closes also decreases since the gaseous fuel pressure must be greater than in-cylinder pressure by a predetermined margin to be able to inject fuel. It is desirable for a gaseous fuel injector to be able to introduce the predetermined quantity of fuel within the predetermined injection window with a reduced gaseous fuel pressure such that the useable amount of fuel in the tank increases.

[0004] The energy density of liquid fuels is greater than gaseous fuels. For a given volume of liquid fuel, the volume of gaseous fuel that provides an equivalent amount of energy is considerably larger. As the pressure of the gaseous fuel decreases, for example when the gaseous fuel is consumed by an engine in a system without a gas compressor to increase gaseous fuel pressure, the energy equivalent volume of the gaseous fuel, compared to the liquid fuel volume, increases. In this circumstance, a gaseous fuel injector that injects a gaseous fuel directly into the combustion chamber must provide a considerably greater flow area compared to a liquid fuel injector when the injection periods for both fuel injectors are the same. Normally the liquid fuel is pressurized, which can be accomplished both efficiently and economically, unlike the gaseous fuel where in a low cost system is not pressurized due to the greater economic and efficiency costs associated with pressurizing a gas. As a result, it is advantageous if the gaseous fuel injector injects an energy equivalent amount of fuel at lower minimum injection pressures compared to the liquid fuel injector; to accomplish this a higher volumetric flow rate is needed for gaseous fuels. Accordingly, gaseous fuel injectors are normally much larger than liquid fuel injectors for injecting the same amount of fuel on an energy basis. When modifying an engine that was designed for liquid fuel injectors, for example, in some engines which have attempted direct injection of gaseous fuels, when replacing gasoline direct injectors with CNG direct injectors in the same location, a fuel injector bore in the cylinder head or the cylinder wall is enlarged to accommodate a larger gaseous fuel injector. This type of modification to the cylinder head or engine block increases the cost of production and changes the thermal behavior of the engine as a result of the removal of material that acted as a structural member, which also increases thermal stress to the engine, which can reduce engine durability and shorten it's useful lifetime. [0005] The state of the art is lacking in a gaseous fuel injector that injects gaseous fuel directly into a combustion chamber that can supply enough fuel for engine performance comparable to that of liquid fuel internal combustion engines, and that can increase the useable amount of fuel in the storage tank, for an engine fuel system that does not pressurize the gaseous fuel above storage pressure.

Summary of the Invention

[0006] An improved fuel injector for injecting gaseous fuel directly into a combustion chamber of an internal combustion engine comprises an elongated nozzle having a proximal end upstream from a distal end. There is an elongated valve member having a first end operatively connected with an actuator and extending through a longitudinal bore within the elongated nozzle, and having a second end opposite the first end. A valve member guide is disposed within the longitudinal bore between the elongated nozzle and the elongated valve member for aligning the elongated valve member along the longitudinal axis of the elongated nozzle. There is a valve seat in one of the distal end of the elongated nozzle and the valve member guide. The second end of the valve member cooperates with the valve seat to form a valve. The elongated valve member is moveable by the actuator to actuate the valve between a closed position and an open position. An outer diameter of a portion of the elongated nozzle in the combustion chamber is less than 8 mm, for light duty engines, and 10 mm for medium duty engines, and the elongated nozzle, the elongated valve member and the valve member guide cooperate to choke the flow area at the valve seat. In a preferred embodiment, the elongated valve member moves into the combustion chamber when the valve is actuated from the closed position to the open position. [0007] The actuator can be one of a solenoid actuator, a solenoid actuator comprising a permanent magnet, a piezoelectric actuator and a magnetostrictive actuator. The actuator can provide a closing force when the valve is in the closed position. And when the fuel injector further comprises a spring that urges the valve closed, the actuator can provide at least 80% of the closing force and the spring at 8

- 5 - most 20% of the closing force when the valve is in the closed position. The valve member can be moved between the closed position and the open position in less than 700 μβ, and between the open position and the closed position in less than 700 β. The maximum velocity of the valve member is between 1 m/s and 1.5 m/s, when the distance between the open position and the closed position is at least 400 μηι.

[0008] In a preferred embodiment, a ratio between a diameter of the valve seat and the outer diameter of the portion of the elongated nozzle in the combustion chamber is between a range of 0.375 (3/8) to 0.625 (5/8). A flow area upstream from the valve seat is at least 1.5 times, and preferably at least 2 times, the flow area at the valve seat. A distance between the open position and the closed position is at least 400 μιη, and preferably in a range of 400 μηι and 600 μηι. An outer diameter of the valve member in the elongated nozzle is at most 2.5 mm and an inner diameter of the elongated nozzle is at least 4 mm. An outer diameter of a portion of the elongated nozzle in a bore in one of a cylinder head and a cylinder wall of the internal combustion engine is less than 8 mm. The outer diameter of the portion of the elongated nozzle in the combustion chamber is between a range of 7.5 mm and 7.7 mm.

[0009] The gaseous fuel is introduced into the combustion chamber at an injection pressure of at most 30 bar, and with an injection timing after an intake valve associated with the combustion chamber closes and before 90° TDC. In a preferred embodiment, the gaseous fuel is natural gas and the gaseous fuel injector provides a mass flow of 16 g/s of natural gas into the combustion chamber when the valve is in the open position.

[0010] In a preferred embodiment, the elongated nozzle further comprises an inner shelf, and the valve member guide further comprises a sleeve extending along the longitudinal axis of the gaseous fuel injector; and an annular collar extends around the sleeve. The annular collar abuts the inner shelf in the elongated nozzle and is secured thereto. The valve member guide further comprises two or more elongated protrusions extending radially outwardly from the sleeve and abutting an inner surface of the elongated nozzle.

[0011] In another preferred embodiment, the valve member guide comprises at least two semi-annular segments extending around different portions of an outer circumference of the valve member and spaced apart from each other along the longitudinal axis of the fuel injector. The different portions of the outer circumference can be partially overlapping. The at least two semi-annular segments can be connected to the valve member, or alternatively to the nozzle.

[0012] In yet another preferred embodiment, the valve guide is a valve guide and seat member comprising an annular portion having a valve seat and a conical section on an inner radial surface; a sleeve spaced apart from the annular portion; and at least two elongate protrusions extending from the sleeve towards an inner surface of the elongated nozzle and to the annular portion. The valve member is guided by the sleeve. In preferred embodiments, the valve member can comprise a needle and an annular abutment member extending around the needle and secured thereto, and spaced apart from the valve guide and seat member. When the actuator is activated to move the valve member to the open position, the valve member is stopped when the abutment member abuts the valve guide and seat member.

[0013] In still another preferred embodiment, the valve member comprises a needle and a spring retainer secured thereto, and the elongated nozzle further comprises a spring and a retaining and abutment member comprising an annular disc; an elongated cylindrical portion extending from the disc; and an annular protrusion extending radially outwards from the elongated cylindrical portion at an end opposite the annular disc. The spring is retained between the spring retainer and the annular disc, and the annular protrusion operates as a positive stop for the spring retainer when the valve member is made to move by the actuator. A compression spring extending between the elongated nozzle and the spring retainer urges the valve to the closed position. A fuel injector body has opposing ends and defines an interior space. One end of the fuel injector body is connected with an end of the elongated nozzle opposite the valve seat. In a preferred embodiment, the fuel injector body is a metallic tube.

[0014] The actuator can comprise a lower flux guide within the fuel injector body; an upper flux guide within the fuel injector body spaced apart from the lower flux guide along the longitudinal axis, and an armature secured to the valve member and moveable between the lower and upper flux guides. The valve member can extend through the lower and upper flux guides and the armature. The lower and upper flux guides and the armature each comprise passageways dimensioned to provide a flow area at least 1.5 times the flow area at the valve seat. An upper valve member guide, in the form of a sleeve, is received in a bore in the lower flux guide, and guides the valve member. A preload spring extends into the upper flux guide and biases the valve member open. One end of the preload spring abuts the armature. A preload adjuster is secured with the fuel injector body and abuts an end opposite the one end of the preload spring to adjust the tension thereof. [0015] An annular retainer is connected with an end of the fuel injector body opposite the elongated nozzle. A gaseous fuel fitting is connected with an end of the annular retainer opposite the fuel injector body. A fluid communication channel extends from the gaseous fuel fitting through the annular retainer, the fuel injector body and the elongated nozzle to the valve. The annular retainer comprises a first annular portion connected to the body, and a second annular portion threadedly received in the first annular portion and threadedly receiving the preload adjuster and the gaseous fuel fitting.

[0016] An improved fuel injector for injecting gaseous fuel directly into a combustion chamber of an internal combustion engine comprises an elongated nozzle having a proximal end upstream from a distal end. There is an elongated valve member having a first end operatively connected with an actuator and extending through a longitudinal bore within the elongated nozzle, and having a second end opposite the first end. A valve member guide is disposed within the longitudinal bore between the elongated nozzle and the elongated valve member for aligning the elongated valve member along the longitudinal axis of the elongated nozzle. There is a valve seat in one of the distal end of the elongated nozzle and the valve member guide. The second end of the valve member cooperates with the valve seat to form a valve. The elongated valve member is moveable by the actuator to actuate the valve between a closed position and an open position. There is a compression spring urging the valve to the closed position. When the valve is in the closed position, both the actuator and the compression provide a closing force.

[0017] An improved fuel injector for injecting gaseous fuel directly into a combustion chamber of an internal combustion engine comprises an elongated nozzle having a proximal end upstream from a distal end. There is an elongated valve member having a first end operatively connected with an actuator and extending through a longitudinal bore within the elongated nozzle, and having a second end opposite the first end. A valve member guide is disposed within the longitudinal bore between the elongated nozzle and the elongated valve member for aligmng the elongated valve member along the longitudinal axis of the elongated nozzle. There is a valve seat in one of the distal end of the elongated nozzle and the valve member guide. The second end of the valve member cooperates with the valve seat to form a valve. The elongated valve member is moveable by the actuator to actuate the valve between a closed position and an open position. The displacement of the elongated valve member between the closed position and the open position is at least 400 um.

[0018] An improved fuel injector for injecting gaseous fuel directly into a combustion chamber of an internal combustion engine comprises an elongated nozzle having a proximal end upstream from a distal end. There is an elongated valve member having a first end operatively connected with an actuator and extending through a longitudinal bore within the elongated nozzle, and having a second end opposite the first end. A valve member guide is disposed within the longitudinal bore between the elongated nozzle and the elongated valve member for aligning the elongated valve member along the longitudinal axis of the elongated nozzle. There is a valve seat in one of the distal end of the elongated nozzle and the valve member guide. The second end of the valve member cooperates with the valve seat to form a valve. The elongated valve member is moveable by the actuator to actuate the valve between a closed position and an open position. The actuator moves the elongated valve member between the closed position and the open position in at most 700 μβ, and the actuator moves the elongated valve member between the open position and the closed position in at most 700 β.

Brief Description of the Drawings

[0019] FIG. 1 is a cross-sectional view of a gaseous fuel injector according to a first embodiment.

[0020] FIG. 2 is a cross-sectional view of a nozzle of the gaseous fuel injector of FIG. 1.

[0021] FIG. 3 is cross-sectional view of a valve member of the gaseous fuel injector of FIG. 1.

[0022] FIG. 4 is a perspective view of a valve member guide of the gaseous fuel injector of FIG. 1 according to a first embodiment. [0023] FIG. 5 is a cross-sectional view of a sleeve of the valve member guide of FIG. 4.

[0024] FIG. 6 is a perspective view of a collar of the valve member guide of FIG. 4.

[0025] FIG. 7 is a perspective view of a lower flux guide of an actuator assembly of the gaseous fuel injector of FIG. 1.

[0026] FIG. 8 is a perspective view of an upper flux guide of an actuator assembly of the gaseous fuel injector of FIG. 1.

[0027] FIG. 9 is a perspective view of an armature of an actuator assembly of the gaseous fuel injector of FIG. 1. [0028] FIG. 10 is a partial cross-sectional view of a nozzle assembly for the gaseous fuel injector of FIG. 1 according to a second embodiment.

[0029] FIG. 11 is a partial perspective view of an assembly of a valve member guide and a valve member of the nozzle assembly of FIG. 10. [0030] FIG. 12 is a partial cross-sectional view of a nozzle assembly comprising a valve member guide for the gaseous fuel injector of FIG. 1 according to a third embodiment.

[0031] FIG. 13 is a perspective view of a valve guide and seat member of the nozzle assembly of FIG. 12. [0032] FIG. 14 is a cross-sectional view of the valve guide and seat member of FIG. 13.

[0033] FIG. 15 is a perspective view of an abutment member of the nozzle assembly of FIG. 12.

[0034] FIG. 16 is a partial, cross-sectional view of a nozzle assembly for the gaseous fuel injector of FIG. 1 according to a fourth embodiment.

Detailed Description of Preferred Embodiment^)

[0035] Referring to FIGS. 1 through 6, there is shown fuel injector 100 according to one embodiment that injects gaseous fuel directly into a combustion chamber of an internal combustion engine. A gaseous fuel is any fuel that is in a gas state at standard temperature and pressure, which in the context of this application is 20 degrees Celsius (°C) and 1 atmosphere (atm). By way of example, typical gaseous fuels include, without limitation, natural gas, propane, hydrogen, methane, butane, ethane, other known fuels with similar energy content, and mixtures including at least one of these fuels. Natural gas itself is a mixture, and it is a popular gaseous fuel for internal combustion engines because it is abundant, less expensive and cleaner burning than oil-based liquid fuels, and the sources are broadly dispersed geographically around the world. Fuel injector 100 comprises nozzle assembly 110, actuator assembly 120 and fuel inlet assembly 130. Each of the assemblies comprises a collection of components that cooperate to provide functionality intended by the respective assembly, as will become apparent in the course of this application. Certain components span one or more assemblies and when describing these sections these components will at least be described with respect to the purpose the component serves in the respective assembly.

[0036] Nozzle assembly 110 comprises nozzle 140, shown in FIG. 2, which is hollow and open ended in construction, having valve seat 150 at distal end 160, interior shelf 170 near proximal end 180, and interior space 190 therebetween. Fuel injector 100 is installed in a bore, for example in a cylinder head or cylinder wall in an engine block, such that portion 200 of nozzle 140 resides inside a combustion chamber. Annular groove 210 receives a seal (not shown), such as a polymer ring or the like, that seals nozzle 140 against the bore in the cylinder head or the engine block, depending upon where the fuel injector is installed. Elongated valve member 220, shown in FIG. 3, comprises needle 222 that extends into the opening at distal end 160 of the nozzle and through interior space 190 into actuator assembly 120, and head 224 that in cooperation with valve seat 150 forms injection valve 230. In the illustrated embodiment fuel injector 100 is an outwardly opening fuel injector, meaning injection valve 230 opens when head 224 of the elongated valve member moves away from contact with valve seat 150, and remains open so long as head 224 is spaced from valve seat 150. Nozzle valve member guide 240, shown in FIG. 4, is rigidly connected with nozzle 140 by annular collar 310, which is fixedly attached, for example, by welding, to outer surface 320 of sleeve 250 and to nozzle 140 where it abuts shelf 170. In assembled fuel injector 100, installed needle 222 extends through hollow sleeve 250, which guides the movement of needle 222 along longitudinal axis 260 so that head 224 remains aligned with valve seat 150 to improve sealing and for more consistently distributed fluid flow through nozzle 110, when needle 222 is actuated by actuator assembly 120, as will be discussed in more detail below. In the embodiment shown in FIG. 4, elongated protrusions 280 extend radially outwardly from sleeve 250 and abut inner surface 290 of nozzle 140 and serve to align end 300 of valve member guide 240 with longitudinal axis 260. Valve bias means 330 comprises spring retainer 340, which is fixedly attached, for example by a welded connection, to valve member 220, and helical compression spring 3 0 retained between proximal end 180 of nozzle 140 and the retainer, which urges head 224 towards valve seat 150 such that valve 230 is biased to the closed position. The location of spring retainer 340 along valve member 220 is selected in combination with the spring constant and other characteristics of helical compression spring 350 to provide a predetermined biased closing force for valve 230. Annular protrusion 270 of valve member guide 240 extends radially outwardly from sleeve 250, and serves to act as a positive stop (an abutment) to constrain movement of valve member 220. That is, with respect to the illustrated embodiment, when actuator assembly 120 activates valve 230 to open, the distance that valve member 220 can travel is limited by spring retainer 340 coming into contact with annular protrusion 270. In the shown embodiment fuel injector body 360 is in the form of a thin- walled metallic tube, with an L-shaped end that abuts annular shelf 370 on nozzle 140. Injector body 360 is removably attached to nozzle 140, by locknut 380 which engages nozzle 140 by means of threaded assembly 375, but in other embodiments it can be welded to nozzle 140. Injector body 360 extends from nozzle assembly 110, through actuator assembly 120, to fuel inlet assembly 130. Annular seal 390 extends around longitudinal axis 260 of nozzle 140 and fluidly seals the nozzle with fuel injector body 360.

[0037] When the base engine is a gasoline-fueled direct injection light duty engine, a gaseous fuel injector with the features described herein is enabled to be manufactured with the outer diameters of portions 200 and 205 of nozzle 140 being less than 8 millimeters (mm), and preferably between 7.5 mm and 7.7 mm, such that gaseous fuel injector 100 can be installed into standard sized fuel injector bores employed for gasoline direct injectors. When gaseous fuel injector 100 is to be installed into a standard sized fuel injector bore in a medium duty engine, the described features enable the outer diameters of portions 200 and 205 to be less than 10 mm. In this application light duty engines are defined to be engines that have swept volumes of less than 900 cubic centimeters (cc) per cylinder, and that typically have cylinder bore diameters less than 105 mm, and medium duty engines are defined to be engines that have swept volumes between 900 cc and 1700 cc per cylinder, and that typically have cylinder bore diameters between 105 mm and 140 mm. By installing gaseous fuel injector 100 into standard sized fuel injector bores, the conversion of an engine that employs gasoline direct injectors to one that employs natural gas direct injectors, such as gaseous fuel injector 100, is simplified. The cooperation of the components in nozzle assembly 110, where the outer diameter is reduced compared to that of actuator assembly 120 and fuel inlet assembly 130, provides a fuel flow area (described in more detail below) that enables direct replacement of gasoline direct injectors without requiring modification to fuel injector bores.

[0038] With reference to FIG. 1, actuator assembly 120 is now described in more detail. In the illustrated and preferred embodiment, actuator 400 is a solenoid-type actuator that employs at least one permanent magnet and has a constant overall air gap length in the flux paths of the actuator to generate a force that acts on an armature connected to valve member 220. In other embodiments solenoid actuators that do not comprise a permanent magnet and/or have a constant overall air gap length can be employed, as well as strain-type actuators such as piezoelectric actuators and magnetostrictive actuators. Actuator 400 is spaced apart, along the longitudinal axis, from nozzle assembly 110. Annular support 410 abuts annular shelf 420 (seen in FIG. 2) around nozzle 140 and extends away from proximal end 180 inside fuel injector body 360 and supports annular spacer 430. Components of actuator 400 inside fuel injector body 360 are supported by spacer 430. Lower flux guide 440, in the form of an annulus in the illustrated embodiment, abuts annular spacer 430 and is radially and axially constrained, with respect to longitudinal axis 260, by fuel injector body 360. The lower flux guide provides a path for magnetic flux associated with actuator 400. In this application the term lower refers to items further downstream, with respect to fuel flow, in fuel injector 100, and the term upper refers to items further upstream, where fuel flows into fuel inlet assembly 130 and out of nozzle assembly 110. Actuator valve member guide 450 extends into a bore of lower flux guide 440 and serves to align the axial movement of valve member 220 through the lower flux guide in actuator assembly 120. Upper flux guide 470, in the form of an annulus in the illustrated embodiment, is spaced apart from lower flux guide 440, and is radially and axially constrained, with respect to longitudinal axis 260, by fuel injector body 360. Armature 480, also in the form of an annulus in the illustrated embodiment, is positioned between lower and upper flux guides 440 and 470 respectively, and is fixedly attached to valve member 220, for example by a weld, such that air gap 490 is a predetermined distance. When actuator 400 is activated it operates to move armature 480 and valve member 220, such that valve 230 either opens or closes depending on the direction of movement of the valve member. Lower and upper flux guides 440 and 470 have passageways 620 and 630 respectively, and armature 480 has passageways 640, seen in FIGS.7, 8 and 9 respectively, that are dimensioned to provide a predetermined flow area for gaseous fuel therethrough, which is at least 1.5 times the flow area through valve 230 when opened. In the illustrated embodiment, the passageways 620, 630 and 640 are in the form of slots. The slots forming passageways 620 in flux guide 440 of FIG. 7 extend radially from the bore of the annulus and from end to end of the flux guide, and for a portion of the longitudinal extent to the outer radial surface of the flux guide. In addition to fuel passage, the passageways also reduce eddy current losses that result when actuator 400 is activated causing a varying magnetic field in the lower and upper flux guides and the armature.

[0039] Referring again to FIG. 1, annular flux guides 500 and 510, also called stator segments, extend around the outer surface of fuel injector body 360 and form magnetic flux paths with lower flux guide 440 and upper flux guide 470 respectively. Permanent magnet 520 extends annularly around fuel injector body 360 and forms a magnetic flux path with armature 480 and flux guides 510 and 530. Flux guide 530 extends annularly around the permanent magnet and forms additional magnetic flux paths with flux guides 500 and 510. Stator housing 540 retains flux guides 500, 510, 530 and permanent magnet 520 to fuel injector body 360, and is fixedly attached thereto, such as by a weld. Coil 570 extends annularly around the outer surface of fuel injector body 360 and is electrically connected with an electrical connection (not shown), which in turn is electrically connected with an actuator driver (not shown) for activating actuator 400 to open and close valve 230. Actuator assembly 120 further comprises preload spring 550 extending into a bore of upper flux guide 470 and abutting armature 480. By positioning preload spring 550 in this way, the overall length of fuel injector 100 along longitudinal axis 260 is reduced. Positional adjustment of inner preload adjuster 560, to set the tension of preload spring 550 on armature 480, is allowed by a threaded connection with retainer 600, which is described in more detail when discussing fuel inlet assembly 130 below. Generally, preload spring 550 is at least loaded by an amount that when valve 230 is fully opened the preload spring does not reach its free length (fully extended). A shim can be employed between preload spring 550 and armature 480, depending upon the material of the armature, to avoid fretting.

[0040] When valve 230 is closed, there is an opening force acting on the valve from preload spring 550 and fuel pressure within fuel injector 100, which is balanced by a closing force provided by permanent magnet 520 and spring 350. Magnetic flux from permanent magnet 520 flows through armature 480, upper flux guide 470 and flux guides 510 and 530, thereby latching the armature to the upper flux guide when the valve is closed. In other embodiments that do not employ an actuator comprising a permanent magnet, the actuator can be activated to apply a portion of the closing force when valve 230 is closed, for example by energizing an electromagnet of a solenoid actuator. Alternatively, or additionally, actuator 400 can provide the closing force using other known techniques. In a preferred embodiment, permanent magnet 520 provides approximately 90% of the closing force when head 224 of valve member 220 is seated on valve seat 150, and spring 350 provides approximately 10% of the closing force. In this circumstance, when valve 230 is opened, spring 350 compresses, and the closing force provided by the spring increases according to the spring rate. When the valve is biased in this manner, spring 350 and permanent magnet 520 can both be made smaller, thereby reducing the size of fuel injector 100 in the corresponding regions where these components are located. In other preferred embodiments, spring 350 can provide up to 20% of the closing force and permanent magnet 520 can provide at least 80% of the closing force, when head 224 is seated on valve seat 150.

[0041] In a preferred embodiment actuator 400 moves head 224 of valve member 220 from the closed position, in fluidly sealed contact with valve seat 150, to the open position a distance of at least 400 micrometers (μηι) away from the closed position, and preferably between 400 μηι and 600 μπι. By moving head 224 at least 400 μπι the flow area through valve 230 is increased, compared to previously known gaseous fuel injectors that move valve members no more than 300 μιη, which increases the rate at which gaseous fuel is introduced into the combustion chamber, thereby allowing a predetermined quantity of gaseous fuel to be introduced at a lower gaseous fuel pressure, compared to previous gaseous fuel injectors employing an equivalent injection window, which increases the useable fuel in a gaseous fuel storage tank, and accommodates decreasing the outer diameters of portions 200 and 205 of nozzle 140 to and below 8 mm for light duty engines, and below 10 mm for medium duty engines, without sacrificing engine performance. Actuator 400 in cooperation with valve member 220, valve member guide 140 and spring 350, opens valve 230 from the closed position to the open position in less than 700 microseconds (μβ), and similarly closes the valve from the open position to the closed position in less than 700 μβ. In a preferred embodiment, the opening and closing time for valve 230 is less than 500 μβ. The maximum velocity of valve member 220 is between 1 meters/second (m/s) and 1.5 m/s during flight, either opening or closing, and when the valve member nears the end of its stroke, actuator 400 can be activated with debounce or parachute pulses to decelerate the valve member before impact. [0042] With reference to FIG. 1, fuel inlet assembly 130 is described in more detail. Annular retainer 590 is fixedly attached to fuel injector body 360, for example by welding, and removably joined to spigot retainer 600, for example, by a threaded connection as shown. Annular seals 605 and 606 fluidly seal inlet assembly 130. The threaded connections allow greater serviceability of fuel injector 100 because it allows easier access for repair and replacement of internal components, or modular servicing that permits the retention of the fuel inlet assembly and replacement of just the internal components of the actuator assembly or just the internal components of the nozzle assembly. However, in other embodiments retainers 590 and 600 can be rigidly connected such as by a weld, or can be manufactured as a unitary component. The threaded connection between preload adjuster 560 and retainer 600 allows the force applied to valve member 220 by preload spring 550 to be adjusted by screwing the preload adjuster toward or away from the valve member, which compresses and decompresses the preload spring respectively. In other embodiments preload adjuster 560 can be replaced by a preload spring spacer, which can be fixed into position relative to retainer 600 to permanently set the preload force. Gas fitting 610 fluidly connects with a source of gaseous fuel, such as a fuel rail (not shown). In alternative embodiments, gas fitting 610 can be fixedly attached to retainer 600, for example by welding, or formed as a unitary component, with preload adjuster 560 inserted and threaded into the retainer portion from the lower side. [0043] The fluid passages through which the gaseous fuel flows from gas fitting 610 to valve seat 150 are designed to increase volumetric flow capacity compared to previously known designs by a unique combination of known techniques and novel features. For example, in the actuator assembly, as shown in FIGS. 7 to 9, slotted openings 620, 630 and 640 are provided in respective lower flux guide 440, upper flux guide 470 and armature 480 to increase the flow area through such components. Gaseous fuel flows out of actuator 400 through annular spacer 430, around spring retainer 340 and spring 350, and through openings 650 and 655 formed between collar 310 and sleeve 250 (seen in FIG. 4). Within nozzle 140, gaseous fuel flows between sleeve 250 and inner surface 290 of the nozzle, around elongated protrusions 280 and through valve 230, when opened.

[0044] The flow area through fuel injector 100 is choked at valve 230, and when the valve is in the open position, the flow area through the valve is at least 4.5 mm², and preferably 5 mm². In portion 200 of nozzle 140, the inner diameter of the nozzle is at least 4.2 mm and the outer diameter of needle 222 is at most 2.4mm, and preferably 2.2mm, thereby defining a flow area of around 10 mm². In portion 205 of nozzle 140, the inner diameter of nozzle 140 is at least 6 mm, and the outer diameter of sleeve 230 in this region is at most 3.6 mm, except around elongate protrusions 280 which extend to inner surface 290 of the nozzle, thereby defining a flow area at most of around 18 mm². The inner diameter of nozzle 140 is reduced in portion 200, compared to portion 205, as a consequence of annular groove 210, which is required for retaining a sealing member that seals the combustion chamber, and as a result the outer diameter of needle 222 is constrained such that a predetermined flow area is maintained in this region. Nozzle 140, valve member 220 and valve member guide 240 cooperate to provide a flow area that is at least 1.5 times the flow area through valve 230 when opened, and preferably at least between 2 and 3 times the flow area. Since the respective outer diameters of actuator assembly 120 and fuel inlet assembly 130 are much larger than nozzle assembly 110, for example around 25 mm, the challenge of achieving a flow area of at least 1.5 times that through valve 230 is reduced compared to the nozzle assembly. By choking the flow at valve seat 150, and providing an upstream flow area to valve seat flow area ratio of between 1.5 and 3, the pressure drop between the gaseous fuel rail (not shown) and valve seat 150 is reduced and preferably minimized, which improves the mass flow rate of the fuel injection spray cone into the combustion chamber, for an outwardly opening injector, and the mass flow rates of fuel jets, for an inwardly opening injector. For light duty engines, when valve 230 is opened fuel injector 100 can provide a fuel flow rate of 16 grams/second (g/s) of natural gas, for example, when natural gas pressure is 30 bar and injection timing is before 90° before TDC during the compression stroke, and for medium duty engines the fuel injector can provide a flow rate of 30 g/s under similar constraints. When natural gas pressure is 15 bar, fuel injector 100 can provide a fuel flow rate of 8 g/s for a light duty engine, and 15 g/s for a medium duty engine.

[0045] When valve 230 is closed, the opening force provided by fuel pressure inside fuel injector 100 and preload spring 550, which acts on head 224, increases as the size of the valve seat diameter Dvs (seen in FIG. 2) increases. In preferred embodiments, to hold valve 230 in a closed position, actuator 400, or a combination of the actuator and spring 350, provides a closing force greater than the opening force. As diameter Dvs increases typically actuator 400, or spring 350, or both, increase in size. It is desirable for the overall outer diameter of fuel injector 100 be less than 30mm, such that installation into a variety of engines can be accommodated. The outer diameter of fuel injector 100 can be constrained to less than 30 mm when a ratio between the valve seat diameter Dvs and the diameter DN,₂OO of portion 200 of the nozzle (seen in FIG. 2) in the combustion chamber is between a range of 0.375 (3/8) to 0.625 (5/8). In addition to constraining the overall outer diameter of fuel injector 100, it is desirable to maintain a minimal wall thickness of portion 200 of the nozzle, in the combustion chamber, where combustion forces acting on the nozzle may cause reduced lifetime of the fuel injector when the wall thickness in this region becomes too thin. When the D_Vs to D_N,2oo ratio is between 0.375 and 0.625, and when the diameter of portion 200 is between 7 and 10 mm, the wall thickness of portion 200 of the nozzle has a desirable margin of safety for durability.

[0046] Referring now to FIGS. 10 and 11, nozzle assembly 112 is a second embodiment that comprises valve member guide 242 instead of a sleeve-style, like valve member guide 240 shown in FIG. 4. Stepped and staggered semi-annular guide segments 282a, 282b and 282c (282a-c) each extend around a portion of the outer circumference of needle 222, such that the flow area around each segment is at least 1.5 times the flow area at the valve seat when valve 231 is open. Semi-annular guide segments 282a-c are each located at a different axial location along longitudinal axis 260 (stepped), and each supports needle 222 at a different circumferential location around the needle (staggered), however the guide segments can be overlapping around the circumference. In the illustrated embodiment guide segments 282a-c resemble a staircase. In other embodiments, at least two semi-annular guide segments are employed to guide valve member 220. Semi-annular guide segments 282a-c can be connected with needle 222, or can be connected to an inner surface of nozzle 141; the former technique simplifies manufacturing of the nozzle and the latter technique decreases needle mass.

[0047] Referring now to FIGS. 12, 13, 14 and 15, nozzle assembly 113 is shown according to a third embodiment. Valve guide and seat member 660 comprises annular portion 670 having valve seat 150 on an inner surface of the annulus, sleeve 253 spaced apart from the annular portion, and elongated protrusions 283 that extend from sleeve 253 to the annular portion and to the inner surface of portion 200 of nozzle 143 to assist with centering of sleeve 253 during assembly. Needle 222 (seen in FIG. 12) extends through and is guided by sleeve 253. In the illustrated embodiment there are four protrusions 283, preferably equally spaced around longitudinal axis 260. In other embodiments there can be at least two elongated protrusions, and possibly more than four, providing the flow area past elongated protrusions 283 in the nozzle is at least 1.5 times the flow area through valve 230 when in the open position. Edge 675 is at the intersection of two transverse surfaces in the illustrated embodiment. In other preferred embodiments edge 675 can be replaced by a conical surface, or a chamfered or rounded corner to improve the flow of gaseous fuel through annular portion 670 by reducing turbulence as the fuel flows past protrusions 283 towards valve 230. In the illustrated embodiment, the lower end of nozzle 143 receives valve guide and seat member 660 such that annular portion 670 abuts with nozzle 143 and is fixed thereto, such as by welding. Retaining and abutment member 700 abuts shelf 170 and comprises disc portion 710 extending from bore 720 radially outwardly towards inner surface 730 of nozzle 143. Protrusions 715 extend radially outwardly from disc portion 710 to inner surface 730 of the nozzle and axially below disc portion 710 such that passageways 760 for fuel are formed between member 700 and nozzle 143. Compression spring 350 (shown in FIG. 1) is retained between disc portion 710 and spring retainer 340 (shown in FIG. 1). Elongated cylindrical portion 690 extends from disc portion 710 and annular protrusion 273 extends radially outwardly from cylindrical portion 690, and serves to act as a positive stop (an abutment) to constrain movement of valve member 220. In this embodiment, cylindrical portion 690 does not act as a guide for needle 222. While guidance for needle 222 is not needed in the illustrated embodiment, in other embodiments it could, for example for configurations that have a longer and/or thinner needle. When actuator assembly 120 (shown in FIG. 1) activates valve 230 to open, the distance valve member 220 can travel is limited by spring retainer 340 abutting annular protrusion 273. [0048] Referring now to FIG. 16, nozzle assembly 114 is shown according to a fourth embodiment. Annular abutment member 701 extends around needle 222 of the valve member and is fixedly attached thereto. Coil spring 350 (shown in FIG. 1) is retained between spring retainer 340 (shown FIG. 1) and shelf 170 of nozzle 144. When actuator assembly 120 (shown in FIG. 1) is activated to move valve member 220 such that valve 230 opens, the travel of the valve member is stopped when abutment member 701 abuts valve guide and seat member 660. Fuel flows around an outer periphery of abutment member 701 between the inner surface of nozzle 144 and the outer periphery. Compared to the embodiment of FIGS. 12 to 15, this embodiment simplifies the nozzle assembly by replacing retaining and abutment member 700 with abutment member 701, which is less complicated to manufacture. However, this embodiment increases the moving mass of the valve member which can delay opening and closing times.

[0049] While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings. By way of example, it will be understood by persons familiar with injector technology that certain variations, such as integration of components like the integration of sleeve 250, with one or more of annular protrusion 270, annular collar 310 and/or elongated protrusions 280 by casting, to obviate welded joints, can be employed without departing from the spirit of the disclosed invention as claimed.

Claims

What is claimed is:

1. A fuel injector for injecting gaseous fuel directly into a combustion chamber of an internal combustion engine, the fuel injector comprising: an actuator; an elongated nozzle having a proximal end upstream from a distal end; an elongated valve member having a first end operatively connected with the actuator and extending through a longitudinal bore within the elongated nozzle, and having a second end opposite the first end; a valve member guide disposed within the longitudinal bore between the elongated nozzle and the elongated valve member for aligning the elongated valve member along the longitudinal axis of the elongated nozzle; a valve seat in one of the distal end of the elongated nozzle and the valve member guide, the second end of the valve member cooperating with the valve seat to form a valve, the elongated valve member moveable by the actuator to actuate the valve between a closed position and an open position; wherein an outer diameter of a portion of the elongated nozzle in the combustion chamber is less than 8 mm, and the elongated nozzle, the elongated valve member and the valve member guide cooperate to choke the flow area at the valve seat.

2. The fuel injector of claim 1, wherein the actuator is one of a solenoid actuator, a solenoid actuator comprising a permanent magnet, a piezoelectric actuator and a magnetostrictive actuator.

3. The fuel injector of claim 1, wherein when the internal combustion engine has a swept volume of 900 cc and 1700 cc per cylinder, the outer diameter of the portion of the elongated nozzle in the combustion chamber is less than 10 mm.

4. The fuel injector of claim 1, wherein a ratio between a diameter of the valve seat and the outer diameter of the portion of the elongated nozzle in the combustion chamber is between a range of 0.375 (3/8) to 0.625 (5/8).

5. The fuel injector of claim 1 , further comprising a spring urging the valve toward the closed position when in the open position, and when the valve is in the closed position the actuator providing at least 80% of the closing force and the spring at most 20% of the closing force.

6. The fuel injector of claim 1 , wherein a flow area upstream from the valve seat is at least 2 times the flow area at the valve seat.

7. The fuel injector of claim 6, wherein the flow area upstream from the valve seat is at least 1.5 times the flow area at the valve seat.

8. The fuel injector of claim 1, wherein a distance between the open position and the closed position is at least 400 um.

9. The fuel injector of claim 1 , wherein the distance is in a range of 400 um and 600 μιη.

10. The fuel injector of claim 1, wherein the valve member is moved between the closed position and the open position in less than 700 μβ, and between the open position and the closed position in less than 700 us.

1 1. The fuel injector of claim 1 , wherein the maximum velocity of the valve member is between 1 m/s and 1.5 m/s, and a distance between the open position and the closed position is at least 400 μηι.

12. The fuel injector of claim 1, wherein an outer diameter of the valve member in the elongated nozzle is at most 2.5 mm and an inner diameter of the elongated nozzle is at least 4 mm.

13. The fuel injector of claim 1, wherein gaseous fuel is introduced at a pressure of at most 30 bar.

14. The fuel injector of claim 1 , wherein gaseous fuel is introduced after an intake valve associated with the combustion chamber closes and before 90° TDC.

15. The fuel injector of claim 1, wherein gaseous fuel is introduced at a pressure of at most 30 bar and at a timing between after an intake valve associated with the combustion chamber closes and before 90° TDC; and wherein the gaseous fuel is natural gas and the gaseous fuel injector provides a mass flow of 16 g s of natural gas into the combustion chamber when the valve is in the open position.

16. The fuel injector of claim 1, wherein an outer diameter of a portion of the elongated nozzle in a bore in one of a cylinder head and a cylinder wall of the internal combustion engine is less than 8 mm.

17. The fuel injector of claim 1, wherein the outer diameter of the portion of the elongated nozzle in the combustion chamber is between a range of 7.5 mm and 7.7 mm.

18. The fuel injector of claim 1 , wherein the elongated nozzle further comprises an inner shelf, the valve member guide further comprising: a sleeve extending along the longitudinal axis of the gaseous fuel injector; and an annular collar extending around the sleeve; wherein the annular collar abuts the inner shelf in the elongated nozzle and is secured thereto.

19. The fuel injector of claim 18, wherein the valve member guide further comprises two or more elongated protrusions extending radially outwardly from the sleeve and abutting an inner surface of the elongated nozzle.

20. The fuel injector of claim 1 , wherein the valve member guide comprises at least two semi-annular segments extending around different portions of an outer circumference of the valve member and spaced apart from each other along the longitudinal axis of the fuel injector.

21. The fuel injector of claim 20, wherein the different portions of the outer circumference are partially overlapping.

22. The fuel injector of claim 20, wherein the at least two semi-annular segments are connected to the valve member.

23. The fuel injector of claim 1 , wherein the valve guide is a valve guide and seat member comprising: an annular portion having the valve seat; a sleeve spaced apart from the annular portion; and at least two elongate protrusions extending from the sleeve towards an inner surface of the elongated nozzle and to the annular portion; wherein the valve member is guided by the sleeve.

24. The fuel injector of claim 23, wherein the valve member comprises a needle and an annular abutment member extending around the needle and secured thereto, and spaced apart from the valve guide and seat member, wherein when the actuator is activated to move the valve member to the open position, the valve member is stopped when the abutment member abuts the valve guide and seat member.

25. The fuel injector of claim 23, wherein the valve member comprises a needle and a spring retainer secured thereto, further comprising a spring and a retaining and abutment member comprising: an annular disc; an elongated cylindrical portion extending from the disc; and an annular protrusion extending radially outwards from the elongated cylindrical portion at an end opposite the annular disc; wherein the spring is retained between the spring retainer and the annular disc, and the annular protrusion operates as a positive stop for the spring retainer when the valve member is made to move by the actuator.

26. The fuel injector of claim 1, further comprising: a spring retainer fixed to the valve member; and a compression spring extending between the elongated nozzle and the spring retainer and urging the valve to the closed position.

27. The fuel injector of claim 1 , further comprising a fuel injector body having opposing ends defining an interior space, one end of the fuel injector body connected with an end of the elongated nozzle opposite the valve seat.

28. The fuel injector of claim 27, wherein the fuel injector body is a metallic tube.

29. The fuel injector of claim 27, wherein the actuator comprises: a lower flux guide within the fuel injector body; an upper flux guide within the fuel injector body spaced apart from the lower flux guide along the longitudinal axis, and an armature secured to the valve member and moveable between the lower and upper flux guides; wherein the valve member extends through the lower and upper flux guides and the armature.

30. The fuel injector of claim 29, the lower and upper flux guides and the armature each comprising passageways dimensioned to provide a flow area at least 1.5 times the flow area at the valve seat.

31. The fuel injector of claim 29, further comprising an upper valve member guide, in the form of a sleeve, received in the lower flux guide, the upper valve member guide receiving the valve member.

32. The fuel injector of claim 29, further comprising a preload spring extending into a bore in the upper flux guide and biasing the valve member open.

33. The fuel injector of claim 32, wherein one end of the preload spring abuts the armature, further comprising a preload adjuster secured with the fuel injector body and abutting an end opposite the one end of the preload spring to adjust the tension thereof.

34. The fuel injector of claim 29, further comprising: an annular retainer connected with an end of the fuel injector body opposite the elongated nozzle; a gaseous fuel fitting connected with an end of the annular retainer opposite the fuel injector body; wherein a fluid communication channel extends from the gaseous fuel fitting through the annular retainer, the fuel injector body and the elongated nozzle to the valve.

35. The fuel injector of claim 34, wherein the annular retainer comprises a first annular portion connected to the body, and a second annular portion threadedly received in the first annular portion and threadedly receiving the preload adjuster and the gaseous fuel fitting.

36. The fuel injector of claim 1 , wherein the elongated valve member moves into the combustion chamber when the valve is actuated from the closed position to the open position.

37. A fuel injector for directly injecting gaseous fuel into a combustion chamber of an internal combustion engine comprising: an actuator; an elongated nozzle having a proximal end upstream from a distal end; an elongated valve member having a first end operatively connected with the actuator and extending through a longitudinal bore within the elongated nozzle, and having a second end opposite the first end; a valve member guide disposed within the longitudinal bore between the elongated nozzle and the elongated valve member for aligning the elongated valve member along the longitudinal axis of the elongated nozzle; a valve seat in one of the distal end of the elongated nozzle and the valve member guide, the second end of the valve member cooperating with the valve seat to form a valve, the elongated valve member moveable by the actuator to actuate the valve between a closed position and an open position; a compression spring urging the valve to the closed position; wherein when the valve is in the closed position both the actuator and the compression spring provide a closing force.

38. A fuel injector for directly injecting gaseous fuel into a combustion chamber of an internal combustion engine comprising: an actuator; an elongated nozzle having a proximal end upstream from a distal end; an elongated valve member having a first end operatively connected with the actuator and extending through a longitudinal bore within the elongated nozzle, and having a second end opposite the first end; a valve member guide disposed within the longitudinal bore between the elongated nozzle and the elongated valve member for aligning the elongated valve member along the longitudinal axis of the elongated nozzle; a valve seat in one of the distal end of the elongated nozzle and the valve member guide, the second end of the valve member cooperating with the valve seat to form a valve, the elongated valve member moveable by the actuator to actuate the valve between a closed position and an open position; wherein the displacement of the elongated valve member between the closed position and the open position is at least 400 μιη.

39. A fuel injector for directly injecting gaseous fuel into a combustion chamber of an internal combustion engine comprising: an actuator; an elongated nozzle having a proximal end upstream from a distal end; an elongated valve member having a first end operatively connected with the actuator and extending through a longitudinal bore within the elongated nozzle, and having a second end opposite the first end; a valve member guide disposed within the longitudinal bore between the elongated nozzle and the elongated valve member for aligning the elongated valve member along the longitudinal axis of the elongated nozzle; a valve seat in one of the distal end of the elongated nozzle and the valve member guide, the second end of the valve member cooperating with the valve seat to form a valve, the elongated valve member moveable by the actuator to actuate the valve between a closed position and an open position; wherein the actuator moves the elongated valve member between the closed position and the open position in less than 700 us, and the actuator moves the elongated valve member between the open position and the closed position in less than 700 με.