Fuel injector and valve assembly for providing fuel to prime mover

Abstract

The present disclosure provides a fuel injector including a valve assembly located in a passage of an injector body. The valve assembly includes a plunger and a valve seat sealingly engageable by the plunger. The plunger is located longitudinally in the injector body, partially opening an inlet in the injector body upstream of the valve seat, while the plunger is sealingly engaged to the valve seat. The plunger is longitudinally displaced in the passage to open a flow path through the valve seat while gradually increasing the opening size of the flow path and the inlet.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Indian Provisional Application No. 202441006691 filed on February 1, 2024, which is incorporated herein by reference. Technical Field

[0003] The present disclosure generally relates to a fuel injector for injecting fuel to a prime mover, and more particularly to a valve assembly for a fuel injector configured to reduce non-linearity in fuel flow during opening of the valve assembly. Background Art

[0004] Fuel injectors for internal combustion engines use one or more valves to control the injection of fuel into the engine's combustion chamber or intake port in precisely controlled amounts, rates, and timing. Some fuel injectors include a plunger that displaces axially to unblock one or more sidewall inlets that allow fuel to flow into the fuel injector passage.

[0005] and exit the fuel injector. As the plunger displaces, particularly under low plunger lift and low fuel flow conditions, and under high plunger lift and high fuel flow conditions, there is a substantially nonlinear relationship between plunger displacement and the flow area created by one or more sidewall inlets. Consequently, the fuel flow rate into the fuel injector passageway during the initial and final stages of plunger displacement is also nonlinear.

[0006] Fuel flow control logic within an engine controller attempts to account for the nonlinearities of fuel flow at low and high plunger lifts in order to provide the precise fuel delivery control required. Consequently, the control logic must be able to accurately predict and / or simulate the nonlinear behavior that will occur as the plunger lifts, which increases complexity and can lead to reduced accuracy in determining the amount, rate, and timing of fuel injection, as well as performance fluctuations. Therefore, a need remains for the unique devices, systems, and techniques disclosed herein.

[0007] Disclosure of Illustrative Embodiments

[0008] For the purpose of clearly, concisely, and accurately describing the illustrative embodiments of the present disclosure, the manner and process of making and using the same, and to enable the practice, making, and using of the same, reference will now be made to certain exemplary embodiments, including those shown in the drawings, and specific language will be used to describe the same. It will be understood, however, that no limitation of the scope of the invention is thereby incurred, and that the present invention encompasses and protects such changes, modifications, and further applications of the exemplary embodiments as will occur to those skilled in the art. SUMMARY OF THE INVENTION

[0009] The present disclosure includes a fuel injector for supplying fuel to a prime mover, which includes a hydrogen fuel cell and other applications using gaseous fuel. In one embodiment, the fuel injector includes an elongated injector body defining a longitudinally extending passage therein. The passage extends from a first end of the injector body in a distal direction to a fuel outlet end. The fuel injector further includes a valve assembly mounted in the injector body. The valve assembly includes an actuator, a plunger, and a valve seat. The plunger is controllably displaced by the actuator to control the fuel flow into and out of the fuel injector to the prime mover.

[0010] Embodiments of the present invention include a valve assembly for a fuel injector for selectively providing a fuel flow through an injector body of the fuel injector. The valve assembly includes an actuator, a valve seat positionable in a passage of the injector body, and a plunger at least partially located within the valve seat and sealingly engaged with the valve seat in a closed position of the valve assembly. The plunger extends from the valve seat in the passage in a proximal direction and is coupled to the actuator. The plunger is longitudinally movable by the actuator to gradually increase a flow area of an inlet of the injector body into the passage, thereby providing a fuel flow into the passage. When the plunger is longitudinally moved by the actuator to open the valve assembly and provide a fuel flow through an opening of the valve seat, the plunger disengages from the valve seat.

[0011] Embodiments of the present disclosure include a fuel injector for supplying fuel to a prime mover. The fuel injector includes an elongate injector body defining a longitudinally extending passage therein. The passage extends in a distal direction from a first end of the injector body toward an outlet end of the injector body. The injector body includes at least one inlet extending radially through the injector body and in fluid communication with the passage. The fuel injector body further includes a valve assembly including an actuator, a valve seat in the passage downstream of the at least one inlet, and a plunger that is longitudinally displaceable in the passage by the actuator to control the fuel flow from the fuel injector to the prime mover. The plunger includes a first flow control portion that is longitudinally movable along the at least one inlet to control the fuel flow through the at least one inlet into the passage. The plunger further includes a second flow control portion operatively associated with the first flow control portion. The second flow control portion sealingly engages the valve seat in a closed position of the valve assembly, wherein no fuel flow passes through the valve seat, while the first flow control portion of the plunger is positioned to permit fuel to pass through the at least one inlet into the passage. The plunger is longitudinally movable in the passage to disengage the second flow control portion from the valve seat, thereby providing fuel flow through the valve seat, while increasing a first flow area through the at least one inlet and increasing a second flow area through the valve seat as the plunger is longitudinally displaced in the passage to a fully open position.

[0012] This summary is not intended to identify key or essential features of the claimed subject matter nor is it intended to be used to limit the scope of the claimed subject matter. Additional embodiments, forms, objects, features, advantages, aspects, and benefits will become apparent from the following description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The description herein refers to the accompanying drawings, where like reference numerals refer to like parts throughout the several views, and in which:

[0014] Figure 1 is a schematic view of a fuel injection system.

[0015] Figure 2 is a longitudinal cross-sectional view of an exemplary valve assembly of a fuel injector for a system according to an embodiment of the present disclosure Figure 1 of.

[0016] Figure 3 is Figure 2 a partial longitudinal cross-sectional view of the valve assembly of, wherein the valve seat is in a closed position by engaging the plunger.

[0017] Figure 4 isFigure 2 Partial longitudinal sectional view of the valve assembly in the initial stage when the valve seat is opened by the displacement of the plunger.

[0018] Figure 5 is Figure 2 Partial longitudinal sectional view of the valve assembly in the intermediate stage when the valve seat is opened.

[0019] Figure 6 is Figure 2 Partial longitudinal sectional view of the valve assembly in the final stage from the opening to the fully open position of the valve seat.

[0020] Figure 7 is a graph showing the plunger lift versus the flow rate during the opening of the valve assembly in Figure 2 the valve assembly. Detailed Description

[0021] Referring to Figure 1 , there is shown a fuel injection system 10 that includes at least one fuel injector 100a, 100b, 100c,......, 100n for a fuel supply system 22 of a prime mover 12 (such as an internal combustion engine or a fuel cell). The fuel supply system 22 may include, for example, a combustion chamber, an intake manifold, an intake duct, a compressor, a fuel mixer, or any other fuel supply system. The at least one fuel injector 100a, 100b, 100c, ……, 100n is in fluid communication with a fuel source 16 containing fuel 18 and a fuel tank / regulator 20 to distribute fuel 18 to the injectors 100a, 100b, 100c, ……, 100n. Although Figure 1 a plurality of fuel injectors are schematically shown in, the system 10 may include any number of fuel injectors, including one fuel injector. Pressurized fuel 18 is supplied from the fuel tank / regulator 20 to each of the fuel injectors 100a, 100b, 100c, ……, 100n. The fuel 18 may be, for example, a gaseous fuel such as hydrogen, propane, natural gas, etc. The fuel 18 may also be a liquid fuel such as diesel or gasoline. In the following discussion, the fuel injectors 100a, 100b, 100c, ……, 100n are described with reference to a fuel injector 100 as shown in Figures 2 to 6 .

[0022] In one embodiment, the fuel injector 100 supplies fuel to the prime mover 12. The fuel injector 100 includes an elongated injector body 102 that defines a longitudinally extending channel 104 therein. The channel 104 extends from a first end 106 of the injector body 102 in a distal direction toward an outlet end 108. The injector body 102 includes at least one inlet 114 that extends radially through the injector body 102 and is in fluid communication with the channel 104.

[0023] The fuel injector 100 includes a valve assembly 120 in a passage 104. The valve assembly 120 includes an actuator 130, a valve seat 150 in the passage 104 downstream of at least one inlet 114, and a plunger 170 that is longitudinally displaceable in the passage 104 by the actuator 130 to control the fuel flow from the fuel injector 100 to the prime mover 12. The plunger 170 includes a first flow control portion 172 that is longitudinally movable along at least one inlet 114 to control the fuel flow through at least one inlet 114 into the passage 104. The plunger 170 further includes a second flow control portion 174 operatively associated with the first flow control portion 172. The second flow control portion 174 sealingly engages the valve seat 150 in a closed position of the valve assembly 120, in which no fuel flow passes through the valve seat 150, while the first flow control portion 172 of the plunger 170 is positioned to permit fuel to enter the passage 104 through at least one inlet 114. The plunger 170 is longitudinally movable in the passage 104 to disengage the second flow control portion 174 from the valve seat 150, thereby providing a fuel flow through the valve seat 150 while increasing the first flow area through at least one inlet 114 and increasing the second flow area through the valve seat 150 as the plunger 170 is longitudinally displaced in the passage 104 to a fully open position.

[0024] In one embodiment, a valve assembly 120 for a fuel injector 100 is provided for selectively providing a fuel flow through an injector body 102 of the fuel injector 100. The valve assembly 120 includes an actuator 130, a valve seat 150 that is positionable in a passage 104 of the injector body 102, and a plunger 170 that is at least partially within the valve seat 150 and sealingly engaged therewith in a closed position of the valve assembly 120. The plunger 170 extends from the valve seat 150 in the passage 104 in a proximal direction and is coupled to the actuator 130. The plunger 170 is longitudinally movable by the actuator 130 to progressively increase the flow area of an inlet 114 of the injector body 102 into the passage 104, thereby providing a fuel flow into the passage 104. When the plunger 170 is longitudinally moved by the actuator 130 to open the valve assembly 120 and provide a fuel flow through an opening 152 in the valve seat 150, the plunger 170 disengages from the valve seat 150.

[0025] Figure 2An exemplary injector body 102 for an embodiment of a fuel injector 100 extends longitudinally along a central longitudinal axis A and includes a passage 104 defined by the injector body 102 extending from a first end 106 to or toward a gas outlet end 108. The longitudinally extending passage 104 receives a valve assembly 120. The valve assembly 120 includes a valve seat 150, a plunger 170, and an actuator 130 for controlling fuel flow through a laterally extending inlet 114 into the passage 104 and through an opening 152 of the valve seat 150. In the discussion herein, "proximal" or "proximally" refers to an axial position or upstream direction toward the first end 106 and / or the actuator 130, and "distal" or "distally" refers to an axial position or downstream direction toward the outlet end 108. The injector body 102 may be composed of a plurality of parts coupled to each other to form the injector body 102, or may be composed of a single sleeve or component forming the injector body 102.

[0026] In one embodiment, the plunger 170 includes a first plunger portion 180 and a second plunger portion 182 operably associated with the first plunger portion 180. A first flow control portion 172 is provided on the first plunger portion 180, and a second flow control portion 174 is provided on the second plunger portion 182. The first plunger portion 180 is located proximal to the valve seat 150. The second plunger portion 182 is at least partially located within the valve seat 150 and extends proximally through the opening 152 of the valve seat 150.

[0027] In one embodiment, the first plunger portion 180 is positioned to abut and engage the second plunger portion 182 end to end. A longitudinal displacement of the first plunger portion 180 with the actuator 130 causes a longitudinal displacement of the second plunger portion 182 within the passage 104. Other embodiments contemplate other configurations of the first plunger portion 180 and the second plunger portion 182, such as an integral body of the plunger 170, or more than two plunger portions operably associated with each other.

[0028] In the illustrated embodiment, the valve seat 150 is located within the passage 104 and is joined to the injector body 102. The valve seat 150 includes a cylindrical housing 154. The housing 154 includes an end wall 156 defining the opening 152. The opening 152 is opened and closed by the plunger 170. In the illustrated embodiment, the plunger 170 and specifically the second plunger portion 182 extends through the opening 152 of the end wall 156 of the housing 154. The second plunger portion 182 of the plunger 170 includes a radially protruding flange 176 located within the housing 154. A seal 178 is fixed to and supported on the flange 176 and / or the end wall 156 of the valve seat 150. When the valve assembly 120 is in a closed position, the seal 178 sealingly engages the end wall 156 of the housing 154 around the opening 152.

[0029] In one embodiment, the second flow control portion 174 of the plunger 170 is formed by a flange 176 and a seal 178. In one embodiment, the seal 178 is an elastomeric seal at the sealing interface of the flange 176 and the end wall 156 surrounding the opening 152. The seal 178 provides a fluid-tight seal to prevent fuel flow (such as gaseous fuel flow or liquid fuel flow) through the opening 152, unless the plunger 170 is longitudinally displaced distally.

[0030] The first plunger portion 180 includes a stem portion 184 and a radially protruding portion 186 extending radially outward from the stem portion 184. In one embodiment, the first flow control portion 172 is formed by a sealing engagement of the radially protruding portion 186 along the inlet 114 with the inner surface 105 of the injector body 102. The first plunger portion 180 is longitudinally movable along the inlet 114 to control fuel flow through the inlet 114 into the passage 104 via the first flow control portion 172, thereby gradually increasing the open flow area of the inlet 114 into the passage 104, as Figures 3 to 6 shown. The radially protruding portion 186 includes at least one longitudinal hole 190 therethrough, which is configured to allow fuel flow in the distal direction towards the valve seat 150.

[0031] In one embodiment, the first plunger portion 180 includes a second radially protruding portion 187 extending radially outward from the stem portion 184. The second radially protruding portion 187 is located proximal to the inlet 114 and contacts the inner surface 105 of the injector body 102 to guide the longitudinal movement of the first plunger portion 180 along the injector body 102. The second radially protruding portion 187 may include longitudinal channels to allow fuel flow therethrough.

[0032] In one embodiment, the first plunger portion 180 includes a tapered nose 192 extending distally from the radially protruding portion 186 to contact the second plunger portion 182. The second plunger portion 182 includes a second tapered nose 194, which extends proximally through the opening 152 in the valve seat 150 to contact the tapered nose 192 of the first plunger portion 180. The second plunger portion 182 includes a flange 176 extending radially outward from the second tapered nose 194 in the valve seat 150.

[0033] In one embodiment, the second plunger portion 182 includes a shaft portion 196 received within the housing 154, where a second tapered nose 194 extends from the shaft portion 196 and projects from the housing 154 through the hole 152. A flange 176 extends radially outward from the shaft portion 196 to contact the valve seat 150 in the closed position of the valve assembly 120. A spring 198 may be positioned about the shaft portion 196 of the second plunger portion 182. The spring 198 contacts the radially extending flange 176 to bias the seal 178 of the radially extending flange 176 into contact with the end wall 156 of the valve seat 150.

[0034] Reference Figure 3 , the valve assembly 120 is shown in the closed position such that no fuel flow is permitted through the valve seat 150. However, the inlet 114 is partially open due to the longitudinal position of the plunger 170. Specifically, the first flow control portion 172 is positioned along the inlet 114 such that the proximal side of the inlet 114 is open to permit fuel flow through the flow area A1 into the passage 104. The longitudinal hole 190 permits fuel flow through the radially projecting portion 186 to occupy the volume in the passage 104 on the proximal side of the valve seat 150. As Figure 7 shown, no fuel flow passes through the valve seat 150 in the closed position of the valve assembly 120.

[0035] Reference Figure 4 , the valve assembly 120 is shown in the initial stage of opening such that fuel flow is permitted through the opening 152 of the valve seat 150. By the longitudinal distal displacement of the plunger 170, the inlet 114 is opened slightly further. Specifically, the first flow control portion 172 is located further distally along the inlet 114 than in the closed position, and the second flow control portion 174 of the plunger 170 disengages from the valve seat 150 to provide a flow area A2 greater than the flow area A1. The flow area into the passage 104 provided by the inlet 114 is greater than the flow area provided by the opening 152 of the valve seat 150. Thus, the fuel flow rate through the opening 152 is controlled at the valve seat 150 by the position of the second flow control portion 174 of the plunger 170. As Figure 7 shown, in this initial stage of opening of the valve assembly 150, as the second flow control portion 174 of the plunger 170 is displaced away from engagement with the valve seat 150 in the closed position of the valve assembly 120, the fuel flow rate increases linearly.

[0036] Reference Figure 5, the valve assembly 120 is shown in an open intermediate stage such that an increasing amount of fuel flow is allowed through the valve seat 150 by forming an increasing flow area through the valve seat opening 152. The inlet 114 is further opened by the displacement of the first flow control portion 172 of the plunger 170 along the longitudinal distal end of the inlet 114 to provide a flow area A3 that is greater than the flow area A2. However, the flow area in the inlet passage 104 provided by the inlet 114 is smaller than the flow area provided by the opening 152 through the valve seat 150. Thus, during the open intermediate stage, the fuel flow through the valve seat 150 is controlled by the first fuel flow control portion 172 at the inlet 114. As Figure 7 shown, as the second flow control portion 174 of the plunger 170 is displaced away from the valve seat 150 from the closed position of the valve assembly 120, the fuel flow rate continues to increase linearly during the initial stage of opening of the valve assembly 150.

[0037] Reference Figure 6 , the valve assembly 120 is shown in a fully open stage of opening such that a maximum amount of fuel flow is allowed through the opening 152 of the valve seat 150 by the longitudinal displacement of the second flow control portion 174 of the plunger 170. The inlet 114 is further opened by the longitudinal distal displacement of the plunger 170 to provide a flow area A4 that is greater than the flow area A3. However, the inlet 114 is not fully opened and remains at least partially blocked by the first flow control portion 172 of the plunger 170 to maintain the linear increase of the fuel flow rate to the fully open position, as Figure 7 shown.

[0038] Additional written descriptions of several exemplary embodiments should now be provided. In one exemplary embodiment, a fuel injector for supplying fuel to a prime mover is provided. The fuel injector includes an elongated injector body defining a longitudinally extending passage therein. The passage extends in a distal direction from a first end of the injector body toward an outlet end of the injector body. The injector body includes at least one inlet extending radially through the injector body and in fluid communication with the passage. The fuel injector body includes a valve assembly including an actuator, a valve seat in the passage downstream of the at least one inlet, and a plunger that is longitudinally displaceable in the passage by the actuator to control the fuel flow from the fuel injector to the prime mover. The plunger includes a first flow control portion that is longitudinally movable along the at least one inlet to control the fuel flow through the at least one inlet into the passage. The plunger further includes a second flow control portion operatively associated with the first flow control portion. The second flow control portion sealingly engages the valve seat in a closed position of the valve assembly, wherein no fuel flow passes through the valve seat, wherein the first flow control portion of the plunger is positioned to permit fuel to pass through the at least one inlet into the passage. The plunger is longitudinally movable in the passage to disengage the second flow control portion from the valve seat, thereby providing fuel flow through the valve seat, while increasing a first flow area through the at least one inlet and increasing a second flow area through the valve seat as the plunger is longitudinally displaced in the passage to a fully open position.

[0039] In one embodiment, the plunger includes a first plunger portion in the passage and a second plunger portion at least partially within the valve seat. The first plunger portion includes the first flow control portion, and the first plunger portion abuts and engages the second plunger portion such that the first plunger portion longitudinally displaces the second plunger portion as the actuator longitudinally displaces.

[0040] In yet another embodiment, the first plunger portion includes a main body portion and a radially protruding portion extending radially outward from the main body portion. The radially protruding portion contacts an inner surface of the injector body and overlaps the at least one inlet in the closed position and the fully open position.

[0041] In yet another embodiment, the radially protruding portion includes at least one longitudinal hole that permits fuel to flow from the inlet through the radially protruding portion.

[0042] In yet another embodiment, the first plunger portion includes a second radially protruding portion extending radially outward from the main body portion. The second radially protruding portion is located proximal to the at least one inlet and contacts the inner surface of the injection body to guide longitudinal movement of the first plunger portion along the injector body.

[0043] In yet another embodiment, the second plunger portion includes a shaft portion and a radially extending flange extending radially outward from the shaft portion. The radially extending flange contacts the valve seat in the closed position.

[0044] In yet another embodiment, the second plunger portion includes a seal on the radially extending flange that sealingly engages the valve seat in the closed position.

[0045] In yet another embodiment, a spring surrounding the shaft portion of the second plunger portion contacts the radially extending flange. The spring biases the radially extending flange into contact with the valve seat.

[0046] In yet another embodiment, the valve seat includes a cylindrical housing in the passage of the injector body. The housing at least partially houses the second plunger portion. The housing includes an end wall defining an opening that is opened and closed by the second plunger portion.

[0047] In yet another embodiment, the second plunger portion projects through the opening in the end wall of the housing.

[0048] According to yet another aspect of the present disclosure, there is provided a valve assembly for a fuel injector for selectively providing a fuel flow through the fuel injector. The valve assembly includes an actuator and a valve seat that can be located in a passage of the injector body. The valve assembly further includes a plunger that is at least partially located within the valve seat and sealingly engages the valve seat in the closed position of the valve assembly. The plunger extends in a proximal direction from the valve seat in the passage. The plunger is coupled to the actuator and is longitudinally movable by the actuator to gradually increase the flow area of the inlet of the injector body into the passage, thereby providing a fuel flow into the passage. When the plunger is longitudinally moved by the actuator to open the valve assembly and provide a fuel flow through the opening of the valve seat, the plunger disengages from the valve seat.

[0049] In one embodiment, the plunger includes a first flow control portion that is longitudinally movable along the inlet to control the fuel flow through the inlet into the passage. The plunger further includes a second flow control portion operatively associated with the first flow control portion. The second flow control portion sealingly engages the valve seat in the closed position.

[0050] In yet another embodiment, the plunger may longitudinally move in the distal direction in the passage to disengage the second flow control portion from the valve seat, thereby providing a fuel flow through the opening of the valve seat while increasing the flow area through the inlet and increasing the second flow area through the opening of the valve seat.

[0051] In one embodiment, the valve seat includes a cylindrical housing. The housing includes an end wall that defines the opening that is opened and closed by the plunger.

[0052] In yet another embodiment, the plunger extends through an opening in the end wall of the housing. The plunger includes a flange located within the housing. A seal on the flange sealingly engages the housing around the opening in the closed position.

[0053] In one embodiment, the plunger includes a first plunger portion proximal to the valve seat and a second plunger portion that extends proximally through the opening of the valve seat in the valve seat. The first plunger portion and the second plunger portion are adjacently engaged end to end.

[0054] In yet another embodiment, the first plunger portion includes a radially protruding portion configured to sealingly engage the injector body along the inlet. The radially protruding portion includes at least one longitudinal hole therethrough.

[0055] In yet another embodiment, the first plunger portion includes a tapered nose that extends distally from the radially protruding portion to contact the second plunger portion.

[0056] In yet another embodiment, the second plunger portion includes a second tapered nose that extends proximally through the opening in the valve seat to contact the tapered nose of the first plunger portion.

[0057] In yet another embodiment, the second plunger portion includes a flange that extends radially outward from the second tapered nose in the valve seat.

[0058] According to another aspect of the present disclosure, there is provided a valve assembly for a fuel injector for selectively providing a fuel flow through the fuel injector. The valve assembly includes an actuator, a valve seat positionable in a passage of the injector body, and a plunger at least partially located within the valve seat. The plunger extends from the valve seat in the passage in a proximal direction. The valve assembly includes an elastomeric seal located between the valve seat and the plunger to sealingly close the valve assembly in a closed position of the valve assembly. The plunger is coupled to the actuator and the plunger is longitudinally movable by the actuator to progressively increase a flow area of an inlet of the injector body into the passage, thereby providing a fuel flow into the passage. When the plunger is longitudinally moved by the actuator to unseal the valve assembly and provide a fuel flow through an opening of the valve seat, the plunger disengages from the valve seat.

[0059] Although the illustrative embodiments of the present disclosure have been described in detail in the drawings and the foregoing description, it is to be considered as illustrative rather than restrictive in nature. It should be understood that only certain exemplary embodiments have been shown and described, and all changes and modifications falling within the spirit of the invention claimed are desired to be protected. It should be understood that although the use of words such as preferably, preferably, preferred or more preferred as utilized in the foregoing description indicate that such described features may be more desirable, they are not necessarily so and embodiments without such words are contemplated to be within the scope of the invention, which is defined by the appended claims. When reading the claims, it is intended that when words such as "a", "an", "at least one" or "at least a portion" are used, the claims are not to be limited to only one item unless there is an express contrary statement in the claim. When the language "at least a portion" and / or "a portion" is used, the item may include a portion and / or the whole item unless there is an express contrary statement.

Claims

1. A fuel injector for supplying fuel to a prime mover, the fuel injector comprising: An elongate injector body defining therein a longitudinally extending passageway that extends in a distal direction from a first end of the injector body toward an outlet end of the injector body, the injector body including at least one inlet extending radially through the injector body and in fluid communication with the passageway; And A valve assembly including an actuator, a valve seat in the passageway downstream of the at least one inlet, and a plunger, the plunger being longitudinally displaceable in the passageway by the actuator to control the fuel flow from the fuel injector to the prime mover, wherein: The plunger includes a first flow control portion that is longitudinally movable along the at least one inlet to control the fuel flow through the at least one inlet into the passageway; The plunger includes a second flow control portion operatively associated with the first flow control portion, the second flow control portion sealingly engaging the valve seat in a closed position of the valve assembly, in which no fuel flow passes through the valve seat, wherein the first flow control portion of the plunger is positioned to permit fuel to pass through the at least one inlet into the passageway; and The plunger is longitudinally movable in the passageway to disengage the second flow control portion from the valve seat, thereby providing fuel flow through the valve seat, while increasing a first flow area through the at least one inlet and increasing a second flow area through the valve seat as the plunger is longitudinally displaced in the passageway to a fully open position.

2. The fuel injector according to claim 1, wherein the plunger includes: A first plunger portion in the passageway, the first plunger portion including the first flow control portion; And A second plunger portion at least partially located within the valve seat, the second plunger portion including the second flow control portion, wherein the first plunger portion abuts and engages the second plunger portion such that the first plunger portion longitudinally displaces the second plunger portion as the actuator is longitudinally displaced.

3. The fuel injector according to claim 2, wherein the first plunger portion includes: A main body portion; And A radially protruding portion extending radially outward from the main body portion, wherein the radially protruding portion contacts an inner surface of the injector body and overlaps the at least one inlet in the closed position and the fully open position.

4. The fuel injector according to claim 3, wherein the radially protruding portion includes at least one longitudinal hole allowing fuel to flow from the inlet through the radially protruding portion.

5. The fuel injector according to claim 3, wherein the first plunger portion includes a second radially protruding portion extending radially outward from the main body portion, wherein the second radially protruding portion is located proximal to the at least one inlet and contacts the inner surface of the injector body to guide longitudinal movement of the first plunger portion along the injector body.

6. The fuel injector according to any one of claims 2 to 5, wherein the second plunger portion comprises: a shaft portion; and a radially extending flange that extends radially outward from the shaft portion, wherein the radially extending flange contacts the valve seat in the closed position.

7. The fuel injector according to claim 6, wherein the second plunger portion comprises a seal on the radially extending flange that sealingly engages the valve seat in the closed position.

8. The fuel injector according to claim 6, comprising a spring around the shaft portion of the second plunger portion that contacts the radially extending flange, the spring biasing the radially extending flange into contact with the valve seat.

9. The fuel injector according to claim 2, wherein the valve seat comprises a cylindrical housing in the passage of the injector body, the housing at least partially receiving the second plunger portion, the housing comprising an end wall that defines an opening that is opened and closed by the second plunger portion.

10. The fuel injector according to claim 9, wherein the second plunger portion projects through the opening in the end wall of the housing.

11. A valve assembly for a fuel injector for selectively providing a fuel flow through the fuel injector, the valve assembly comprising: an actuator; and a valve seat that is positionable in a passage of the injector body; a plunger that is at least partially located within the valve seat and sealingly engages the valve seat in the closed position of the valve assembly, the plunger extending in a proximal direction from the valve seat in the passage, wherein: the plunger is coupled to the actuator; the plunger is longitudinally movable by the actuator to progressively increase the flow area of the inlet of the injector body into the passage, thereby providing a fuel flow into the passage; and when the plunger is longitudinally moved by the actuator to open the valve assembly and provide a fuel flow through the opening of the valve seat, the plunger disengages from the valve seat.

12. The valve assembly according to claim 11, wherein: the plunger comprises a first flow control portion that is longitudinally movable along the inlet to control the fuel flow through the inlet into the passage; the plunger comprises a second flow control portion that is operably associated with the first flow control portion and that sealingly engages the valve seat in the closed position.

13. The valve assembly according to claim 12, wherein: the plunger is longitudinally movable in a distal direction in the passage to disengage the second flow control portion from the valve seat, thereby providing a fuel flow through the opening of the valve seat while increasing the flow area through the inlet and increasing a second flow area through the opening of the valve seat.

14. The valve assembly according to claim 11, wherein the valve seat comprises a cylindrical housing, the housing comprising an end wall that defines the opening that is opened and closed by the plunger.

15. The valve assembly according to claim 14, wherein: The plunger extends through an opening in the end wall of the housing; The plunger includes a flange located within the housing; and A seal on the flange sealingly engages the housing around the opening in the closed position.

16. The valve assembly according to claim 11, wherein the plunger includes: A first plunger portion located proximal to the valve seat; And A second plunger portion located within the valve seat, the second plunger portion extending proximally through the opening in the valve seat, the first plunger portion and the second plunger portion being adjacently engaged end-to-end.

17. The valve assembly according to claim 16, wherein the first plunger portion includes a radially protruding portion configured to sealingly engage the injector body along the inlet, the radially protruding portion including at least one longitudinal hole therethrough.

18. The valve assembly according to claim 17, wherein the first plunger portion includes a tapered nose extending distally from the radially protruding portion to contact the second plunger portion.

19. The valve assembly according to claim 18, wherein the second plunger portion includes a second tapered nose extending proximally through the opening in the valve seat to contact the tapered nose of the first plunger portion.

20. The valve assembly as claimed in claim 19, wherein the second plunger portion includes a flange radially outwardly extending from the second tapered nose in the valve seat.

21. A valve assembly for a fuel injector for selectively providing a fuel flow through the fuel injector, the valve assembly comprising: An actuator; A valve seat that can be positioned in a passage of the injector body; A plunger that is at least partially located within the valve seat, the plunger extending proximally from the valve seat in the passage; And An elastomeric seal located between the valve seat and the plunger to sealingly close the valve assembly in the closed position of the valve assembly, wherein: The plunger is coupled to the actuator; The plunger can be longitudinally moved by the actuator to gradually increase the flow area of the inlet of the injector body into the passage, thereby providing a fuel flow into the passage; and When the plunger is longitudinally moved by the actuator to unseal the valve assembly and provide a fuel flow through the opening in the valve seat, the plunger disengages from the valve seat.

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