Gas fuel injector

Abstract

A fuel injector for controlling delivery of gaseous fuel into an intake passage of an internal combustion engine defines a fuel flow passage extending from an inlet to an outlet in a fuel flow direction. An actuator moves the normally closed valve member from a closed position to an open position. The annular valve seat is inclined with respect to the fuel flow direction such that the gaseous fuel flows against the fuel flow direction and acts on the valve member in the opening direction when the actuator is energized to move the valve member to the open position. The valve member includes an extension including a helical rib defining a helical channel, the helical rib supported on an inner surface of the outflow channel to direct axial movement of the valve member, and the helical channel imparting centripetal acceleration to the gaseous fuel as it flows through the outflow channel.

Description

Technical Field

[0001] In current state-of-the-art propulsion systems, high-flow gas valves are required to supply the fuel needed for the engine to operate. The present invention describes a novel method of delivering fluid to an engine in a very efficient and low-restriction manner. The design incorporates a "flow balance" function that greatly reduces the flow forces acting on the valve. The present invention also incorporates novel vortex features that will increase and enhance mixing and flow in the engine. Background Art

[0002] Utilizing gaseous fuels such as hydrogen or methane as homogeneous charge fuels instead of gasoline poses a challenge for delivering a sufficient amount of gaseous fuel and air to an internal combustion engine to produce an equivalent energy output as achieved with existing gasoline and diesel fuels. The volumetric energy density of gasoline and diesel fuels is much greater than that of gaseous fuels such as hydrogen and methane, which allows a smaller amount of fuel to produce acceptable engine power and torque. Replacing liquid fuels such as gasoline and diesel with such cleaner-burning and potentially more abundant gaseous fuels requires the supply of a large amount of gaseous fuel in a short period of time. Previous attempts to design fuel injection valves to supply gaseous fuel have encountered problems of turbulence and "choking" at high gas flow rates, making it impossible to deliver a sufficient amount of gaseous fuel during the short time of the engine intake stroke.

[0003] Although gaseous fuels have the potential for clean combustion, in order to control the generation of nitrogen oxides (NOX), it is necessary to ensure that combustion occurs in the presence of excess oxygen. Operating at an excess oxygen equivalence ratio requires more air to enter, and the combustion chamber head typically has two or three intake valves and two or three exhaust valves. This leaves very little space in the head area for a direct injection cylinder fuel injector or spark plug. Operating high-speed valves via an overhead camshaft further complicates and reduces the available space for the direct injection cylinder fuel injector and spark plug.

[0004] Therefore, it is extremely difficult to deliver an equivalent amount of energy through any conduit with a cross-section larger than a gasoline engine spark plug or a diesel engine fuel injector for alternative fuels such as hydrogen, methane, propane, butane, ethanol, or methanol, all of which have a lower energy value per unit volume than gasoline or diesel fuels. Summary of the Invention

[0005] Disclosed is a gas fuel injector valve for delivering gas fuel to the intake port of an internal combustion engine. Delivering fuel to the intake port of an internal combustion engine may also be described as port fuel injection (PFI), and the disclosed fuel injector may be used as a port fuel injector. The components of the fuel injector are configured to perform multiple functions, such that the fuel injector has a reduced number of parts and simplified assembly. The valve structure is pressure balanced such that the gas fuel pressure is used to help keep the valve closed and, when the valve is opened, to help complete the opening movement of the valve. The pressure balanced valve design reduces the force required to close and open the valve, thereby reducing the actuation force from the solenoid and other actuators. The disclosed fuel injector includes a feature downstream of the valve seat that imparts a swirling motion to the gas fuel passing through the valve, which enhances the mixing of the gas fuel with air in the intake path.

[0006] The fuel injector includes a sealed injector body that defines a fuel flow passage extending from an inlet to an outlet in a fuel flow direction. A valve member is disposed within the injector body and is moved between a closed position and an open position by an actuator. The valve member includes an annular valve member surface that mates with an annular valve seat surface in the closed position. The annular valve seat is located in a valve chamber and has a valve seat surface that is inclined at an acute angle relative to the fuel flow direction and the longitudinal axis of the fuel injector. The valve member defines a fuel flow passage between the inlet of the fuel injector and the valve chamber that allows pressurized gas fuel in the valve chamber to act on the valve member to bias the valve member toward the valve seat when the valve member is in the closed position. When the valve member is in the open position, the inclination angle of the valve seat surface causes the gas fuel to flow against the fuel flow direction and act on the valve member in an opening direction. The valve member includes an extension that projects into an outflow passage downstream of the valve seat, the extension having an outer surface that includes a plurality of helical ribs defining a plurality of helical channels. The helical ribs are supported on the inner surface of the outflow passage to guide the movement of the valve member, and the helical channels impart a centripetal acceleration to the gas fuel as the gas fuel flows through the outflow passage. The outflow passage has a first diameter D1 immediately downstream of the valve seat surface and a second diameter D2 downstream of the first diameter D1 that is less than the first diameter D1.

[0007] In some embodiments, the valve seat surface is a conical surface and the valve member surface is a conical surface concentric with the valve seat surface. The conical valve seat surface may be oriented at an acute angle with respect to the longitudinal axis of the fuel injector, the acute angle being measured along the fuel flow direction. In another embodiment, the valve member surface is a conical surface oriented at a first acute angle with respect to the longitudinal axis of the fuel injector, the valve seat surface is a conical surface oriented at a second acute angle with respect to the longitudinal axis of the fuel injector, the first acute angle being greater than the second acute angle, and the valve member surface contacts the valve seat surface at the seal line. In an alternative configuration, the valve member surface is an annular surface having a large radius of curvature in a plane parallel to the longitudinal axis of the fuel injector, and the valve member surface contacts the valve seat surface at the seal line.

[0008] The fuel injector includes an actuator in the form of a solenoid, the actuator including a coil and a flux washer surrounding the fuel injector inlet, and the valve member includes an upper portion configured as an armature on which the magnetic field generated when current is applied to the coil acts. In one embodiment, the fuel injector body includes an inlet for receiving pressurized gaseous fuel, the inlet also serving as a magnetic pole of the solenoid. When the valve member is in the closed position, the coil surrounds the axial gap between the end of the inlet facing the armature and the armature, and the flux washer includes a cup-shaped magnetic upper flux washer surrounding the coil and a cylindrical non-magnetic wear bushing radially located between the coil and the inlet and the armature. The bushing spans the axial gap and guides the axial movement of the upper portion of the valve member between the closed and open positions. The non-magnetic wear bushing also guides the magnetic flux generated by the coil through the magnetic pole and the upper end of the valve member.

[0009] The upper portion of the valve member may define a fuel flow passage upstream of the valve surface, allowing pressurized gaseous fuel to flow from the inlet when the valve member is in the closed position to fill the valve chamber upstream of the valve seat surface. The fuel flow passage may be concentric with the axial passage defined by the inlet and include a radial opening that allows gaseous fuel to flow radially outward from the axial passage into the valve chamber. In one embodiment, the valve seat is attached to the fuel injector body by a separable airtight connection, allowing the valve seat surface to be disassembled, repaired or replaced and reattached to the fuel injector body. The separable airtight connection may be a threaded connection. The valve seat surface may be the surface of an annular insert received in a recess defined by the valve seat, the annular insert being made of a flexible material selected to deform and absorb the closing shock when the valve member contacts the valve seat surface in the closing direction of the valve. The annular insert may be made of a material selected from polytetrafluoroethylene (PTFE), rubber, silicone, nitrile and plastic.

[0010] In one embodiment, the valve member surface is disposed on the downstream side of a radially protruding flange. The flange may be configured to deflect from an unloaded position to a loaded position when the valve member contacts the valve seat surface in the closing direction to absorb the closing shock. The deflection of the flange from the unloaded position to the loaded position is caused by the bias of the valve closing spring and the accumulation of pressurized gaseous fuel in the valve chamber acting on the valve member, and the valve closing spring is arranged to bias the valve member to the closed position. The deflection of the flange from the unloaded position to the loaded position may cause the sealing line between the valve member surface and the valve seat surface to move radially inwards relative to the longitudinal axis of the fuel injector.

[0011] In one embodiment, the valve member is made of a ferromagnetic material and extends as a single integral part from the upper end configured as an armature to the lower end, and the lower end includes the valve member which defines the valve member surface and includes an extension protruding in the direction of the fuel inflow and outflow passage. In other embodiments, the upper end of the valve member is made of a ferromagnetic material and is configured as an armature, while the lower end including the valve member is made of a different material, the valve member defines the valve member surface and includes an extension protruding in the direction of the fuel inflow and outflow passage, and the lower end is connected to the top end of the valve member to move therewith.

[0012] The object of the present invention is to reduce the number of parts in a fuel injector valve for gaseous fuel, thereby reducing the manufacturing cost.

[0013] Another object of the present invention is to provide a compact fuel injector valve with reduced flow resistance to facilitate the delivery of a large amount of gaseous fuel to the intake path of an internal combustion engine in a short time.

[0014] Another object of the present invention is to provide a fuel injector valve which generates a gaseous fuel flow and enhances the mixing of the gaseous fuel with the air present in the intake path of an internal combustion engine. Description of the Drawings

[0015] Figure 1 is a longitudinal cross-sectional view of an embodiment of an injector for gaseous fuel according to aspects of the present disclosure;

[0016] Figure 2 is a sectional perspective view of an embodiment of an injector for gaseous fuel according to aspects of the present disclosure;

[0017] Figure 3 is an enlarged cross-sectional view through a part of the valve seat and the valve member, showing a flexible valve member according to aspects of the present disclosure;

[0018] Figure 4 is an enlarged cross-sectional view through a part of the valve seat and the valve member, showing the valve member and the valve seat surface according to aspects of the present disclosure; and

[0019] Figure 5 is an enlarged cross-sectional view of a portion of a valve seat and an adjacent portion of a valve chamber, showing a serviceable valve seat in accordance with aspects of the present disclosure. DETAILED DESCRIPTION

[0020] An example of a fuel injector for gaseous fuel is Figures 1 to 5 shown. The disclosed fuel injector 10 includes an injector body 12 that includes an inlet 14, a coil assembly 16, a valve chamber 18, and a valve seat 20. In accordance with aspects of the present disclosure, the inlet 14 serves as a structural component of the fuel injector 10 to which a fuel delivery conduit is connected, and the inlet 14 also serves as a fixed magnetic pole of a solenoid that generates an actuating force for the fuel injector 10. A valve member 22 is disposed in the valve chamber 18 and is located on top of the valve seat 20. The valve member 22 extends from the valve seat 20 toward the inlet 14 and includes an armature (upper) end 24 that serves as a solenoid armature. As Figure 1 shown, a biasing spring 26 biases the valve member 22 toward a closed position against the valve seat 20, forming a normally closed valve. The valve member 22 also includes a lower extension 28 that is received in an outflow passage 30 defined by the valve seat 20. The axial movement of the valve member 22 between the closed and open positions is guided at the armature end 24 within the coil assembly and by the lower extension 28 within the outflow passage 30 downstream of the valve seat.

[0021] The coil assembly 16 includes a solenoid coil 32, a cup-shaped upper flux washer 34, a lower flux washer 36, and a cylindrical non-magnetic bushing 38. Applying a current to the solenoid coil 32 generates a magnetic flux in a magnetic circuit defined by the upper flux washer 34, the lower flux washer 36, the inlet 14, and the armature end 24 of the valve member 22. The non-magnetic bushing 38 guides the magnetic flux radially inward into the lower end of the inlet 14 and the armature end 24 of the valve member 22, maximizing the attractive force of the armature end 24 of the valve member 22 toward the inlet 14. The coil assembly 16 is configured to generate sufficient force to move the valve member 22 from Figure 1 the closed position shown to an open position where the upper end 24 of the valve member 22 abuts the bottom of the inlet 14 and the valve member surface 40 of the valve member 22 is separated from the valve seat surface 42. The opening stroke of the valve member 22 is defined by the axial distance between the lower end of the inlet 14 and the valve seat surface 42. In the disclosed embodiment, the stroke (opening distance) of the valve member is between 500 microns and 1 millimeter. The non-magnetic bushing 38 may be made of non-magnetic stainless steel. The non-magnetic bushing and / or adjacent surfaces of the armature end 24 of the valve member 22 may be coated to enhance wear resistance and reduce friction at the surface interface.

[0022] An embodiment of the disclosed fuel injector 10 may be assembled as follows: The valve seat 20, valve chamber 18, and coil assembly 16 are interconnected by an annular laser weld. The valve seat 20, valve chamber 18, and coil assembly are fixed to maintain the concentricity of these components until they are permanently joined by welding. The valve member 22 and biasing spring 26 are inserted into the valve chamber 18, with the valve member surface 40 abutting the valve seat surface 42, and the armature end 24 of the valve member is surrounded by the non-magnetic bushing 38 of the solenoid assembly 16. Finally, the inlet 14 is pressed through the upper flux washer 34 and non-magnetic bushing 38 to an axial position corresponding to the desired opening stroke of the valve member 22. The inlet 14 is then welded to the upper flux washer 34. The inlet 14, upper flux washer 34, lower flux washer 36, valve chamber 18, and valve seat 20 are joined by an annular laser weld, and the injector body 12 is hermetically sealed to contain gaseous fuel.

[0023] The disclosed fuel injector 10 employs a pressure balanced valve configuration in which gaseous fuel pressure helps to hold the valve member 22 closed, and when the valve member 22 moves to its open position, the gaseous fuel flow helps to move the valve member 22 in the opening direction. The pressure balanced valve configuration reduces the force required to actuate the valve and allows for the selection of a smaller solenoid coil that requires less electrical power. As Figure 1 shown, the armature end 24 of the valve member 22 defines a fuel flow passage 44 that is concentric with the axial passage in the inlet 14. The biasing spring 26 is compressed between the inlet 14 and a radially inwardly projecting shoulder of the valve member 22. The axial intermediate portion 46 of the valve member 22 defines a plurality of openings 48 that allow gaseous fuel to flow into the valve chamber 18. The intermediate portion 46 of the valve member 22 has a reduced diameter to reduce the total mass of the valve member and lower the material cost of the valve member 22. When the valve member 22 is in Figure 1 the closed position shown, the gaseous pressure in the valve chamber 18 acts on the upper surface of the valve flange 50 to bias the valve member surface 40 against the valve seat surface 42. The gaseous pressure in the valve chamber 18 acts in combination with the force of the biasing spring to produce a closing force on the valve member 22, ensuring a tight seal between the valve member surface 40 and the valve seat surface 42. The biasing force of the biasing spring 26 can be reduced because the gaseous pressure in the valve chamber 18 also acts on the valve member 22 in the closing direction.

[0024] As Figure 4As shown, in one embodiment, the valve seat surface 42 and the valve member surface 40 are concentric conical surfaces that are inclined relative to the central longitudinal axis of the fuel injector 10. The inclination of the conical valve seat surface 42 and the valve surface 40 results in a partially reversed flow of gaseous fuel through the fuel injector 10. The gaseous fuel flow between the valve seat surface 42 and the valve surface 40 has a radial component toward the central axis of the fuel injector 10 and an axial component toward the inlet 14 of the fuel injector 10. The axial component of the gaseous fuel flowing toward the inlet 14 acts on the valve member 22 to assist in the movement of the valve member 22 in the opening direction. The surface areas and inclination angles of the valve surface 40 and the valve seat surface 42 can be selected to provide the desired lift for the valve member 22 at a predetermined gaseous fuel pressure and flow rate.

[0025] The surface area of the valve seat surface 42 is determined in part by the radial extent 43 of the valve seat surface 42 and the inclination angle B of the valve seat surface 42. In Figure 1 the embodiment, the inclination angle B of the valve surface is an acute angle of approximately 60° measured along the fuel flow direction relative to the longitudinal axis A-A of the fuel injector 10. An acute angle inclination between 30° and 80° can be used in the disclosed fuel injector 10. A smaller angle and a larger radial extent 43 of the valve seat surface 42 will tend to impart more axial momentum to the gaseous fuel flow to provide a greater lift force to the valve member 22, while a larger angle and a smaller radial extent 43 of the valve seat surface 42 will tend to impart less axial momentum to the gaseous fuel flow and a smaller lift force to the valve member 22. The greater lift force on the valve member 42 is obtained at the expense of the resistance to the fuel flow through the fuel injector, and thus the inclination angle B and the radial extent 43 of the valve seat surface 42 are selected to provide the desired lift without significantly increasing the resistance to the fuel flow through the fuel injector 10.

[0026] The disclosed fuel injector 10 includes a lower valve extension 28 that extends into an outflow passage 30 downstream of a valve seat surface 42. The lower extension 28 has an outer surface that defines a plurality of parallel helical channels 52 between helical ribs 54. Outer ends of the helical ribs 54 are configured to be received within the outflow passage 30 and assist in centering the valve member 22 within the valve seat 20 and guiding axial movement of the valve member 22 between a closed position and an open position. The outer end and / or adjacent surfaces of the outflow passage 30 may be hard coated to reduce wear and friction at this sliding interface. The helical configuration of the ribs 54 and channels 52 causes the gaseous fuel to swirl as it exits the fuel injector 10. Organizing the flow of the gaseous fuel into a swirling motion avoids the disordered turbulence that would increase back pressure and promotes rapid mixing of the gaseous fuel when it is combined with an air stream in an intake passage. The outflow passage 30 has a first diameter D1 and a smaller downstream second diameter D2, at the first diameter, the outflow passage 30 surrounds the lower extension of the valve member 22. The smaller diameter D2 accelerates the rotation and velocity of the swirling gaseous fuel, and the difference between the diameters D1 and D2 can be selected to provide a desired degree of acceleration.

[0027] The channels 52 on the lower extension 28 are oriented at an acute angle D with respect to the longitudinal axis A-A of the fuel injector. The flow area and angular orientation of the channels 52 are selected to impart a predetermined centripetal acceleration to the gaseous fuel as it passes through the outflow passage 30 immediately downstream of the valve surface 42. The acute angle D of the channels 52 with respect to the longitudinal axis A-A of the fuel injector 10 can range from 10° to 45°. Around the circumference of the lower extension 28, the number of channels 52 can range from 10 to 30. The size of each channel 52 is selected such that the combined flow area allows a predetermined mass flow rate of gaseous fuel per second at a predetermined pressure. The gradual narrowing of the fuel along the outflow passage 30 from diameter D1 to diameter D2 at the outlet end of the fuel injector 10 further accelerates the fuel. In combination, the configuration of the channels 52 and the outflow passage 30 imparts a predetermined centripetal acceleration and flow velocity to the gaseous fuel, which enhances the mixing of the gaseous fuel with the air entering the internal combustion engine combustion chamber. Sufficient mixing of the gaseous fuel and air promotes complete and clean combustion of the fuel / air charge in the cylinder.

[0028] Figure 3 An embodiment of a valve flange 50 is shown, which is configured to flex under a closing pressure applied by a biasing spring 26 and pressurized fuel in a valve chamber 18. In Figure 3In an embodiment, the valve member surface 42 is defined by an annular large-radius curved surface that contacts the valve seat surface at the seal line 41. When the valve member surface 40 at the bottom of the valve flange 50 first contacts the valve seat surface 42, there is no accumulated gas pressure in the valve chamber 18, and the valve flange 50 is in the position shown by the solid line. At the initial contact, the valve member surface 40 and the valve seat surface contact at the seal line 41a. When the valve flange 50 bends towards the position shown by the dashed line to absorb the closing shock and in response to the increased gas pressure in the valve chamber 18, the seal line moves radially inwards from 41a to 41b. By selecting the dimensions of the flange and the radius of the valve member surface 40, the valve flange 50 can be designed to have a predetermined degree of bendability.

[0029] Figure 4 An alternative configuration of the valve flange 50 including a conical valve member surface 40 is shown. The acute angle C of the valve member surface 40 with respect to the longitudinal axis A-A of the fuel injector 10 is greater than the acute angle B of the valve seat surface 42 with respect to the longitudinal axis A-A. The valve member surface 42 and the valve seat surface 40 contact at the seal line 41. Over time, the valve seat surface 42 may wear, causing the seal line 41 to move radially outwards.

[0030] Figure 5 An alternative fuel injector configuration is shown, in which the valve seat 20 has a threaded connection 35 to the valve chamber 18. This allows the valve seat 20 to be disassembled, repaired or replaced. Other forms of airtight, separable closures can also be used to connect the valve seat 20 to the valve chamber 18. In Figure 5 an embodiment, the valve seat surface 42 is defined by an insert 37 that is received in a recess or gland 39 defined by the valve seat 20. The insert 37 can be designed to be removed and replaced from the valve seat 20, or can be permanently attached to the valve seat 20 so as to be replaced with the valve seat 20. The insert 37 is annular and can be made of any durable, flexible material from which a seal can be formed, such as PTFE, silicone, rubber, nitrile, plastic, etc. The insert 37 can be a custom shape as shown in Figure 5 or a standard shape such as an O-ring, and the gland 30 is configured accordingly. This form of valve seat will absorb the closing shock and extend the service life of the fuel injector 10 by allowing the valve seat surface 42 to be updated regularly.

[0031] Among the benefits and improvements disclosed herein, other objects and advantages of the disclosed embodiments will become apparent to those skilled in the art. Detailed embodiments of a gas fuel injector are disclosed; however, it should be understood that the disclosed embodiments are merely illustrative of the invention, which can be implemented in various forms. Additionally, each example given in connection with the various embodiments of the invention is intended to be illustrative, not restrictive.

[0032] Throughout the specification and claims, the following terms have the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrase "in certain embodiments" as used herein does not necessarily refer to the same embodiments, although it may. The phrases "in another embodiment" and "in some other embodiments" as used herein do not necessarily refer to different embodiments, although they may. Thus, as described above, the various embodiments can be readily combined, as will be apparent to one of ordinary skill in the art.

[0033] Further, as used herein, the term "or" is synonymous with the term "and / or", unless the context clearly dictates otherwise. The term "based on" is not exclusive and allows for being based on additional factors not described, unless the context dictates otherwise. Also, throughout the specification, the meanings of "a", "an", and "the" include plural referents. The meaning of "in" includes "in" and "on".

Claims

1. A fuel injector for controlling the delivery of gaseous fuel into an intake passage of an internal combustion engine, the fuel injector comprising: a fuel injector body defining a fuel flow passage extending from an inlet to an outlet in a fuel flow direction; an actuator; an annular valve seat located in a valve chamber, the valve seat having a valve seat surface inclined with respect to the fuel flow direction; an outflow passage having a first diameter D1 immediately downstream of the valve seat surface and a second diameter D2 downstream of the first diameter D1, the second diameter D1 being smaller than the first diameter D1; a valve member having a valve member surface complementary to the valve seat surface, the valve member including an extension projecting into the outflow passage, the extension having an outer surface including a plurality of helical ribs defining a plurality of helical channels; wherein the valve member reciprocates between a closed position and an open position, in the closed position, the valve member surface mates with the valve seat surface, in the open position, the valve surface is separated from the valve seat surface, allowing gaseous fuel to flow past the valve seat surface and into the outflow passage, the valve member is moved from the closed position to the open position by the actuator, when the valve member is in the closed position, the gaseous fuel pressure in the valve chamber serves to bias the valve member towards the valve seat, and when the valve member is in the open position, the inclination of the valve seat surface causes gaseous fuel to flow against the fuel flow direction and act on the valve member in the opening direction, the helical ribs bear against an inner surface of the outflow passage to guide the movement of the valve member, and the helical channels impart a centripetal acceleration to the gaseous fuel as it flows through the outflow passage.

2. The fuel injector according to claim 1, wherein, The valve seat surface is a conical surface and the valve member surface is a conical surface concentric with the valve seat surface.

3. The fuel injector according to claim 1, wherein, The valve seat surface is a conical surface oriented at an acute angle with respect to a longitudinal axis of the fuel injector, the acute angle being measured in the fuel flow direction.

4. The fuel injector according to claim 1, wherein, The actuator is a solenoid including a coil and a flux washer surrounding the inlet of the fuel injector, and the valve member includes an upper portion configured as an armature, and when current is applied to the coil, the generated magnetic field acts on the armature.

5. The fuel injector according to claim 4, wherein, The upper portion of the valve member defines a fuel flow passage upstream of the valve surface, and when the valve member is in the closed position, the fuel flow passage allows pressurized gaseous fuel to flow from the inlet to fill the valve chamber upstream of the valve seat surface.

6. The fuel injector according to claim 4, comprising an inlet for receiving pressurized gaseous fuel, wherein, The inlet also serves as a magnetic pole of the solenoid.

7. The fuel injector according to claim 6, wherein, When the valve member is in the closed position, there is an axial gap between an end of the coil facing the armature around the inlet and the armature, the flux washer includes a cup-shaped magnetic upper flux washer surrounding the coil and a cylindrical non-magnetic wear-resistant bushing radially located between the coil and the inlet and the armature, the bushing spans the axial gap and guides the axial movement of the upper portion of the valve member between the closed position and the open position.

8. The fuel injector according to claim 2, wherein, The surface of the valve member is oriented at a first acute angle with respect to the longitudinal axis of the fuel injector, the seat surface is oriented at a second acute angle with respect to the longitudinal axis of the fuel injector, the first acute angle being greater than the second acute angle, and the surface of the valve member contacts the seat surface at the sealing line.

9. The fuel injector according to claim 1, wherein, The surface of the valve member is an annular surface having a large radius of curvature in a plane parallel to the longitudinal axis of the fuel injector, and the surface of the valve member contacts the seat surface at the sealing line.

10. The fuel injector according to claim 1, wherein, The valve seat is attached to the fuel injector body by a separable gas-tight connection, the seat surface is replaceable, and the valve seat can be reattached to the fuel injector body.

11. The fuel injector according to claim 1, wherein, The seat surface is the surface of an annular insert received in a recess defined by the valve seat, the annular insert being made of a flexible material selected to deform and absorb the closing impact when the valve member contacts the seat surface along the closing direction of the valve.

12. The fuel injector according to claim 11, wherein, The annular insert is made of a material selected from PTFE, rubber, silicone, nitrile, and plastic.

13. The fuel injector according to claim 1, wherein, The valve member defines a fuel flow passage concentric with the axial passage defined by the inlet, the fuel flow passage including a radial opening that permits gaseous fuel to flow radially outward from the axial passage into the valve chamber.

14. The fuel injector according to claim 10, wherein, The separable gas-tight connection is a threaded connection.

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