Abstract:
An improved device, system and/or method for modulating fuel injection rate through fast magnetostrictive actuation is provided. A fluidomechanical coupler uses fluid to operably couple a magnetostrictive element and a needle element. The fluidomechanical coupler permits the needle element to move from a closed position to an open position when the magnetostrictive element is actuated from a default length to an expanded length. The fluidomechanical coupler is configured to translate an input force into an output response in a direction opposite the input force. The fluidomechanical coupler includes input shafts each within an input bore and positioned adjacent to the magnetostrictive element, a movable output shaft within an output bore and positioned adjacent to the needle element, and fluid passageways connecting input bores and the output bore. Displacement of the fluid between the input bore and the output bore applies or removes a force on the output shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Appl. No. 62/184,115, filed on Jun. 24, 2015, which is incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates generally to fuel injection in internal combustion engines. More particularly, but not exclusively, the present disclosure relates to an improved device, system and/or method for continuously modulating fuel injection rate through fast and continuously controllable magnetostrictive actuation and a fluidomechanical coupler. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    Most contemporary internal combustion engines, including nearly all diesel fuel engines, use fuel injectors to mix fuel and air prior to combustion. Spark ignition engines generally mix the fuel and air prior to compression. By contrast, diesel fuel engines compress the air first, after which fuel is injected directly into the engine cylinder. Diesel engines do not use spark plugs, but rather rely on the increased temperature associated with the highly compressed air to ignite the air-fuel mixture. As a result, the characteristics associated with the air-fuel mixture (e.g., fuel metering, fuel atomization, etc.) define the performance of the diesel engine, making the fuel injector of paramount importance. Further, the high injection pressures require system component designs and materials capable of withstanding higher stresses in order to perform for extended durations and match the engine&#39;s durability targets. There is a need in the art for an improved fuel injector that more precisely controls the flow rate, dispersion, and timing of fuel injection within the cylinder without sacrificing durability. 
         [0004]    Over the years, much innovation has gone into improving the control of direct fuel injection. Two technologies have occupied the primary areas of research and development—electromagnetic solenoids and piezoelectric ceramics. Electromagnetic solenoids consist of an electromagnetically inductive coil wound around an armature. The coil is shaped such that the armature can be moved in and out of the center to provide a mechanical force to open and close the fuel injector. Solenoids offer enhanced durability and reliability, but are unsuitable for continuous control. In particular, the mechanical motion generated by the solenoid can never be proportional to the electrical input. Therefore, the solenoids are unable to effectively produce ideal fuel rate shapes or quick jets with minimal delay. Rather, by its operating principle, when a magnetic flux above a threshold value crosses an air gap, the two poles of the solenoid accelerate towards one another. The two poles close the gap and impact each other and often bounce back. The electromagnetic force that accelerates the two poles is inversely proportional to the square of the gap distance between the two poles, making velocity and position control difficult. Thus, the solenoid is either open, closed, bouncing, or transitioning between these states at a more or less uncontrollable rate. 
         [0005]    In contrast to electromagnetic solenoids, piezoelectric ceramics utilize the principle of internal generation of a mechanical strain from an applied electrical field. Certain crystalline materials generate changes from their static dimension when an external electric field is applied to the material. The key feature to this technology is that mechanical expansion is generally proportional to the applied voltage. As a result, piezoelectric ceramics offer speed and infinitely adjustable displacement within their expansion range, permitting continuous control over fuel injection. In particular, piezoelectric ceramics can provide for faster and smaller pulse injections to reduce in-cylinder formation of diesel emissions. However, an inherent defect of piezoelectric ceramics is susceptibility to performance degradation and limited working life. This is of less concern when lightly loaded, yet the demands associated with diesel fuel injection (i.e., heightened temperatures and pressures) render piezoelectric ceramics less than ideal for rate shaping fuel injection. Further, piezoelectric ceramics can disadvantageously become inoperable by depoling if a voltage applied is reverse to the original polarity. 
         [0006]    In the 1970s, the United States Navy developed Terfenol-D, an intermetallic alloy of iron and the rare earth elements terbium and dysprosium. The material is one of the best known exhibitors of the property of magnetostriction. The property results from ferromagnetic materials changing their shape or dimensions during the process of magnetization. In other words, magnetostrictive materials couple a magnetic input to a mechanical output. The mechanical expansion is proportional to the magnitude of the current sheath circulating around the magnetostrictive element, regardless of direction of the circulating current. The behavior of magnetostrictive materials combines the advantages of both electromagnetic solenoids and piezoelectric ceramics without the shortcomings of either. In particular, magnetostrictive materials offer speed and infinitely adjustable displacement within their operating range, as well as the durability to survive the demands of the diesel fuel injection environment. The expansion associated with magnetostriction does not fatigue the material and any temperature effects do not permanently degrade the alloy. 
         [0007]    Precision fuel injection requires precision control of a needle position throughout the entire fuel injection event. Fuel injectors using magnetostrictive actuators are typically limited to a narrow range of operating conditions. Therefore, a need exists in the art for a fuel injector that can precisely control the needle position throughout the entire fuel injection event at any combination of load and speed of any internal combustion engine. 
       SUMMARY OF THE DISCLOSURE 
       [0008]    A primary object, feature, and/or advantage of the present disclosure is to improve on or overcome the deficiencies in the art. 
         [0009]    Another object, feature, and/or advantage of the present disclosure is to provide a fuel injector that can precisely control the needle position throughout the entire fuel injection event at any combination of load and speed of any internal combustion engine. A magnetostrictive actuator and fluidomechanical coupler replace the solenoid actuator and hydromechanical valve components on a production fuel injector. The magnetostrictive actuator converts voltage and current input into displacement and force output that can be finely controlled. 
         [0010]    Still another object, feature, and/or advantage of the present disclosure is a component that couples the magnetostrictive actuator and the needle via fluid, preferably fuel. The fluidomechanical coupler converts the expansion of the magnetostrictive actuator into a retraction of the needle, which can require translating an input force in one direction to an output response in an opposite direction. The forces on the fluidomechanical coupler from fuel pressure are substantially balanced with the forces associated with the magnetostrictive actuator, thus providing precise control the rate of fuel injection through minimal change in a ratio of forces. 
         [0011]    Still yet another object, feature, and/or advantage of the present disclosure is to continuously and variably control the electrical input to the magnetostrictive actuator such that the fluidomechanical coupler permits the needle to open and close quickly or slowly, thereby injecting small amounts or large amounts, at any desired and variable rate during an injection event. 
         [0012]    Another object, feature, and/or advantage of the present disclosure is to preload the magnetostrictive element with the fluidomechanical adapter to prevent tensile stress failure during operation. The fluidomechanical adapter can use fuel as its medium to supply the necessary compressive preload for the magnetostrictive element within the actuator assembly. 
         [0013]    These and/or other objects, features, and advantages of the present disclosure will be apparent to those skilled in the art. The present disclosure is not to be limited to or by these objects, features and advantages. No single embodiment need provide each and every object, feature, or advantage. 
         [0014]    According to an aspect of the disclosure, an improved fuel injector is provided. The fuel injector includes a magnetostrictive element operably connected to a solenoid coil. The magnetostrictive element has a default length, an expanded length, and any number of lengths between the two. A nozzle is disposed at a terminal end of the fuel injector. A needle element is disposed proximate to the terminal end of the fuel injector and movable between a closed position and an open position. A fluidomechanical coupler is provided. The fluidomechanical coupler uses fluid to operably couple the magnetostrictive element and the needle element. The fluidomechanical coupler is configured to permit the needle element to move from the closed position to the open position when the magnetostrictive element is actuated from the default length to the expanded length. 
         [0015]    The needle element can be moved from the closed position to the open position, at least in part, by forces on the needle element generated by high pressure fuel. The fluidomechanical coupler is configured to translate an input force into an output response in a direction opposite the input force. The fluid within the fluidomechanical coupler can be fuel. The fluid pressurized within the fluidomechanical coupler can preload the magnetostrictive element. The length of the magnetostrictive element is selectively variable between the default length and expanded length to selectively position the needle element at any point between the closed position and the open position. 
         [0016]    According to another aspect of the present disclosure a fuel injector includes a magnetostrictive element electromagnetically coupled to a solenoid coil, a needle element configured to selectively open a nozzle, and a fluidomechanical coupler using fluid to operably couple the magnetostrictive element and the needle element. The fluidomechanical coupler includes an input shaft slidably disposed within an input bore. The input shaft is positioned adjacent to the magnetostrictive element. The fluidomechanical coupler includes an output shaft slidably disposed within an output bore and positioned adjacent to the needle element. A fluid passageway connects to the input bore and the output bore. 
         [0017]    A biasing element can be operably connected to the needle element and configured to bias the needle element to a closed position. The fluid within the output bore moves the output shaft to permit high pressure fuel to overcome the biasing element (and high pressure fuel adjacent to the output shaft) and force the needle element to an open position. Displacement of the fluid between the input bore and the output bore applies or removes a force on the output shaft. 
         [0018]    According to yet another aspect of the present disclosure, a method for injecting high pressure fuel is provided. A fuel injector is provided having a magnetostrictive element electromagnetically connected to a solenoid coil, a fluidomechanical coupler, a needle element, and a nozzle. The solenoid coil is energized to cause expansion of the magnetostrictive element or deenergized to cause contraction (from an expanded length) of the magnetostrictive element. Fluid is displaced within the fluidomechanical coupler by the expansion or contraction of the magnetostrictive element. The displaced fluid causes an output response by the fluidomechanical coupler in a direction opposite the expansion or contraction of the magnetostrictive element. 
         [0019]    The output response of the fluidomechanical coupler can be in the direction opposite the expansion of the magnetostrictive element and permits the high pressure fuel to move the needle element to open the nozzle. The expansion or the contraction of the magnetostrictive element can be selectively controlled to variably control magnitude of fluid displacement and the output response of the fluidomechanical coupler, thereby controlling rate of fuel injection. The fuel injector can be installed on a diesel fuel engine. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Illustrated embodiments of the disclosure are described in detail below with reference to the attached drawing figures, which are incorporated by reference herein, and where: 
           [0021]      FIG. 1  is a perspective view of a fuel injector in accordance with an illustrative embodiment of the present disclosure; 
           [0022]      FIG. 2  is a cross-sectional view of the fuel injector of  FIG. 1  taken along section lines  2 - 2 ; 
           [0023]      FIG. 3  is a perspective view of a magnetostrictive element, end caps, and a fluidomechanical coupler in accordance with an illustrative embodiment of the present disclosure; 
           [0024]      FIG. 4  is a perspective view of a fluidomechanical coupler in accordance with an illustrative embodiment of the present disclosure; 
           [0025]      FIG. 5  is a detailed view of the fluidomechanical coupler of  FIG. 3  within circle  5 - 5 ; and 
           [0026]      FIG. 6  is a drivetrain of a fuel injector in accordance with an illustrative embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  shows a fuel injector  10  in accordance with an illustrative embodiment of the present disclosure. The fuel injector  10  includes an actuator assembly  12 , a retention housing  14 , a fluidomechanical coupler  16 , and an injector housing  18 . At least the actuator assembly  12 , the retention housing  14 , and/or the injector housing  18  can be threadably connected to one another, as illustrated in  FIG. 1 , or secured via other means commonly known in the art. Further, the actuator assembly  12 , the retention housing  14 , the fluidomechanical coupler  16 , and the injector housing  18  can be generally disposed coaxial to one another along a major axis  20  of the fuel injector  10  between a nozzle end  24  and a connection end  26 . The retention housing  14  is generally positioned between the actuator assembly  12  and the injector housing  18 , and includes one or more alignment surfaces  22  to ensure proper installation and prevent rotation of the fuel injector  10  within an internal combustion engine (not shown), preferably a diesel engine. 
         [0028]    Referring to  FIGS. 1 and 2 , the actuator assembly  12  is positioned proximate to the connection end  26  of the fuel injector  10 . The actuator assembly  12  generally includes the components required to receive an electrical input to actuate the magnetostrictive element  28  of the actuator assembly  12 . To that end, the actuator assembly  12  includes a fitting  30  threadably connected to a tail  32 . The tail  32  is configured to secure one or more wire leads (not shown) to the solenoid coil  34 . As commonly known in the art, the solenoid  34  coil is energized via the wire leads. A tail retainer  38  can secure the tail  32  to an actuator assembly housing  40 . 
         [0029]    The solenoid coil  34  can include one or more windings of conductive wire. In the exemplary embodiment illustrated in  FIG. 2 , the solenoid coil  34  has two windings. The solenoid coil  34  can be wound about a bobbin  36  comprised of non-conductive material. Thus, the bobbin  36  is coaxially disposed between the solenoid coil  34  and the magnetostrictive element  28 . 
         [0030]    The magnetostrictive element  28  can be comprised of an alloy including one or more rare earth and/or transition elements. More specifically, the alloy can be formed of grain-oriented polycrystalline rare earth and/or transition metal materials of the formula Tb x Dy x-1 Fe 2-w , wherein 0.20≦x≦1.00 and 0≦w≦0.20. The grains of the material have their common principal axes substantially along the growth axis of the material. As the alloy has its grain oriented in the axial direction, the favored direction of magnetostrictive response of the magnetostrictive element  28  is formed into a shape with ends that are substantially parallel to each other and substantially perpendicular to the favored direction of magnetostrictive response. The magnetostrictive element  28  can have a transverse dimension perpendicular to the direction of magnetostrictive response substantially smaller than one-quarter wavelength at the electromechanical resonant frequency of the apparatus. The magnetostrictive element  28  can have a length in the direction of magnetostrictive response of no greater than one-quarter wavelength at the electromechanical resonant frequency of the apparatus. The magnetostrictive element  28  has a default length and is configured to expand to an expanded length, and/or selectively expandable to any length between the default length and the expanded length to selectively control the rate of fuel injection. 
         [0031]    In an exemplary embodiment, the magnetostrictive element  28  is elongated or rod-shaped. In a preferred embodiment, the magnetostrictive element  28  is cylindrical, but the present disclosure contemplates the shape can be an ellipsoid, parallelepiped, prismatic, or other similar or suitable shapes. To guard against fracture of the magnetostrictive element  28 , an end cap  42  can be secured to each end of the magnetostrictive element  28 . Preferably, the end caps  42  are made of a hardened, ferromagnetic material to minimize flux divergence at the rod ends. Epoxy can bond the outside diameter edge of the end caps  32  to prevent chipping. The end caps  42  distribute the load across the face of the magnetostrictive element  28  through the compliant epoxy used for bonding. 
         [0032]    To minimize the energy required to generate a field strength sufficient to excite the magnetostrictive element  28 , a return flux path  44 , preferably of ferromagnetic material, is provided to guide the lines of magnetic force around the outside of the solenoid coil  34  from one end of the magnetostrictive element  28  to the other. 
         [0033]    The technical operation of the magnetostrictive element  28  is described in co-pending, co-owned U.S. patent application Ser. No. 14/174,560, filed on Feb. 6, 2014, and Ser. No. 14/577,240, filed on Dec. 14, 2014, both of which are incorporated herein by reference in their entireties. In short, a voltage waveform of one polarity is applied, inducing a current waveform of matching polarity to flow through solenoid coil  34 . The current within solenoid coil  34  establishes a magnetic field of matching polarity. This magnetic field generates magnetic lines of force that cross into the magnetostrictive element  28  with corresponding magnetic flux density of matching polarity. Lines of magnetic flux close back on themselves through the flux return path  44  which, together with the magnetostrictive element  28 , forms a complete magnetic circuit. The magnetic flux waveform within the magnetostrictive element  28 , regardless of polarity, causes a corresponding axial expansion. The continuous control of the current into solenoid coil  34  continuously controls the axial expansion or contraction of the magnetostrictive element  28 . The rate at which current increases or decreases and its maximum magnitude are both converted by the magnetostrictive element  28  into corresponding mechanical displacement. As used herein, “contract” or “contraction” refer to the shortening of the magnetostrictive element  28  from a length greater than the default length. 
         [0034]    To achieve the advantages of magnetostrictive actuation of a fuel injector, the expansion and contraction of the magnetostrictive element  28  must be translated into a corresponding output that provides for precise and variable control over fuel injection. To that end, the fluidomechanical coupler  16  is provided. The fluidomechanical coupler  16  can be disposed at least partially within the retainer housing  14  and/or the injector housing  18  proximate to an end of actuator assembly  12 , as illustrated in  FIG. 2 . More particularly, the fluidomechanical coupler  16  is positioned adjacent to an end cap  42  associated with one end of the magnetostrictive element  28 , as illustrated in  FIG. 3 . As disclosed in detail herein, the expansion and contraction of the magnetostrictive element  28  results in an input force and/or an output response from the fluidomechanical coupler  16 . 
         [0035]      FIG. 4  illustrates a fluidomechanical coupler  16  in accordance with an exemplary embodiment of the present disclosure. The fluidomechanical coupler  16  includes a plumbing block  46  or housing within which the components of the fluidomechanical coupler  16  are disposed. While  FIG. 4  shows the plumbing block  46  as transparent, this is for illustrative purposes only. The plumbing block  46  is constructed of a metal and/or other suitable material capable of handling the temperatures and/or pressures associated with the operation of the fluidomechanical coupler  16  and the fuel injector  10  generally. 
         [0036]    At least one input shaft  48  is movably disposed within input bores  49  of the plumbing block  46  and configured to receive an input force from the actuator assembly  12 , particularly the magnetostrictive element  28 . In a preferred embodiment, the fluidomechanical coupler  16  has two input shafts  48 . The input shafts  48  can be elongated cylinders, as illustrated in  FIG. 4 , or of any suitable size and/or shape without deviating from the objects of the present disclosure. Input needle stops  53  can be associated with ends of the input shafts  48  to ensure proper axial positioning of the input shafts  48  within the plumbing block  46 . Similarly, an output shaft  50  is movably disposed within output bores  51  of the plumbing block  46  and configured to provide an output response based, at least in part, on the input force to the input shafts  48 . The output shaft  50  can be a staged elongated cylinder, as illustrated in  FIG. 4 , or of any suitable size and/or shape without deviating from the objects of the present disclosure. The output shaft  50  can be generally coaxial to the quill  52  and/or needle element  54  (see  FIG. 6 ), and substantially positioned along the major axis  20  of the injector  10 . An output needle stop  56  can be connected to an end  57  of the output shaft  50  to provide for proper interfacing between the output shaft  50  and the quill  52  as well as to ensure proper axial positioning of the output shaft  50  within the plumbing block  46 . As illustrated in  FIG. 3 , the input shafts  48  can be oriented parallel to the output shaft  50  and positioned radially within the plumbing block  46  from the major axis  20  relative to the output shaft  50 . 
         [0037]    The fluidomechanical coupler  16  includes a cap  58  disposed within the plumbing block  46 . The cap  58  can be threadably engaged to an interior of the plumbing block  46  and positioned proximate to an end  59  of the output shaft  50  opposite the needle stop  56 , as illustrated in  FIG. 4 . The cap  58  is dimensioned and positioned so as to provide a void  60  between the cap  58  and the end  59  of the output shaft  50 . The void  60  is in fluid communication with a high pressure fuel supply (not shown) via the main fuel rail  62 . As a result, the void  60  is generally filled with high pressure fuel, which places a force on the output shaft  50  in a direction generally represented by arrow  64 . A seal  66 , such as a brass ring or the like, can be associated with the cap  58  to prevent leakage of the high pressure fuel from the plumbing block  46 . The forces on the output shaft  50  (in the direction of arrow  64 ) are substantially counteracted by the force on the output shaft  50  by the quill  52  and needle  54  in a direction generally represented by arrow  68 , which will be discussed in detail below. 
         [0038]    Referring to  FIGS. 4 and 5 , the fluidomechanical coupler  16  is designed such that fluid is disposed within a portion of the input bores  49  and/or the output bores  51 . In particular, fluid is disposed within a gap  70  within the input bores  49  adjacent the end of the input shafts  48  and/or a gap  72  within the output bore  51  adjacent to a flanged surface  74  extending around the output shaft  50 . The input shafts  48  and the output shaft  50  are operably connected by channels  76  or fluid passageways extending between the input bores  49  and the output bore  51 . The channels  76  are configured to permit displacement of fluid between the input bores  49  and the output bore  51  during operation of the fluidomechanical coupler  16 . In a preferred embodiment, the fluid is a portion of the high pressure fuel in the void  60  that effectively leaks into the gaps  70 ,  72  based on the pressure and/or tolerances between the input shafts  48  and the input bores  49  and/or the output shaft  50  and the output bore  51 . 
         [0039]    Upon an input force to the input shafts  48  (in the direction of arrow  64 ), the input shafts  48  move within the input bore  49  in the same direction. The fluid within the gap  70  is displaced through the channels  76  into the gap  72  within the output bore  51  proximate to the flanged surface  74  of the output shaft  50 . The fluid generates a force on the flanged surface  74 , and thus on the output shaft  50  generally, in a direction of arrow  68 . Based on the unique force balance of the fuel injector  10 , discussed in detail below, the force moves the output shaft  50  in the direction of arrow  68 . Conversely, when the input force is removed from the input shafts  48 , the unique force balance of the fuel injector  10  results in the output shaft  50  moving in the direction of arrow  66 . The flanged surface  74  of the output shaft  50  displaces fluid from gap  72 , through the channels  76 , into the gap  70  of the input bore  49 . The input shafts  48  are forced in a direction of arrow  68 . Taken together, the fluidomechanical coupler  16  is configured to translate an input force into an output response in a direction opposite the input force. 
         [0040]    With the advantageous structure of function of the fluidomechanical coupler  16  developed, reference is made to  FIG. 6 .  FIG. 6  illustrates the so-called drivetrain  77  of the fuel injector  10 . The drivetrain  77  can include the magnetostrictive actuator  28  (with or without end caps  42 ), input shafts  48 , output shaft  50 , needle stop  56 , quill  52 , biasing element  78 , and needle element  54 . The drivetrain  77  is disposed within the various housings of the fuel injector  10  as disclosed herein and as partially illustrated in  FIGS. 1 and 2 . Referring to  FIGS. 1 and 2 , the quill  52 , biasing element  78 , and needle element  74  are not shown, but it can be appreciated that the quill  52  is positioned adjacent to the output shaft  50 . The quill  52 , biasing element  78 , and needle element  54  are disposed within the injector housing  18 . A nozzle  80  is associated with the fuel injector  10  at the nozzle end  24 . The needle element  54  is positioned proximate to the nozzle end  24  and moveable between a closed position and an open position. In the closed position, the needle element  54  obstructs the nozzle  80  such that no fuel is permitted to be ejected from the fuel injector  10 . In the open position, the needle element  54  is moved (in the direction of arrow  68 ) such that high pressure fuel is injected from the fuel injector  10  into the internal combustion engine (not shown). 
         [0041]    The biasing element  78  is operably connected to the needle element  54  and configured to bias the needle element  54  in the closed position. The biasing element  78  can include a compression spring and/or shim. In the illustrated embodiment of  FIG. 6 , the biasing element  78  is disposed between the needle element  54  and the quill  52 . 
         [0042]    As illustrated in  FIG. 6 , the needle element  54  has a neck portion  82  and a head portion  84 . When installed within the injector housing  18 , the neck portion  82  is positioned proximate to the main fuel rail inlet  86  (see  FIG. 1 ) fluidly connected to the main fuel supply. Based on the difference in outer diameters between the neck portion  82  and the head portion  84 , the high pressure fuel entering the fuel injector through the main fuel rail inlet  86  imposes a force on the needle element  54  in the direction of arrow  68 . Grooves  85  generally keep the needle element  54  and/or the quill  52  (and/or other moving structure) centered within their respective bores. More particularly, the grooves  85  permit pressure associated with the high pressure fuel to redistribute itself evenly around the circumference(s) of the needle element  54  and/or the quill  52 , thereby preventing friction between the structure(s) and their bores. To a lesser extent, the high pressure fuel within the grooves  85  can further provide force urging a portion of the drivetrain  77  (i.e., the needle element  54 , the quill  52 , and output shaft  50 ) in a direction of arrow  68  to move the needle element  54  to the open position. 
         [0043]    The unique force balance mentioned herein is described as follows. The following structures generally urge the needle element  54  to the closed position (“closing forces”)(i.e., in the direction of arrow  64 ): (a) fuel rail pressure from the fuel within the void  60  impose a force on the output shaft  50 ; and (b) the biasing element  78 . The fuel rail pressure acting on the needle element  54  and/or the quill  52  generally urge the needle element to the open position (“opening forces”)(i.e., in the direction of arrow  68 ). The forces are substantially balanced, but the closing forces slightly exceed the opening forces such that the fuel injector  10  is closed by default, and more particularly, when the magnetostrictive element  28  is at a default length. 
         [0044]    In operation, the fluidomechanical coupler  16  operably couples the magnetostrictive element  28  to the needle element  54 . The fluidomechanical coupler  16  is configured to permit the needle element  54  to move from the closed position to the open position when the magnetostrictive element  28  is actuated from the default length to the expanded length. As the solenoid  34  is energized and the magnetostrictive element  28  expands, the end cap  42  moves the input shafts  48  within the input bores  49  in the direction of arrow  64 . The fluid within the gap  70  of each of the input bores  49  (and/or the gap  72  of the output bore  51 ) is displaced into the output bore  51 . The increased fluid within the output bore  51  provides sufficient force to the flanged surfaces  74  of the output shaft  50  to overcome the forces associated with fuel rail pressure within the void  60  and the biasing element  78  (i.e., opening forces exceed closing forces). As a result, the output shaft  50  is urged in the direction of arrow  68 , including the end  57  of the output shaft  50 . The quill  52 , which is positioned adjacent to and held in direct contact with the end  57  of the output shaft  50 , is urged in the direction of arrow  68  due to the high pressure fuel within the main fuel rail  62  in fluid contact with the quill  52 , and more particularly the grooves of the quill  52 . Similarly, the needle element  54 , which is positioned adjacent to and held in direct contact with the quill  52 , is urged in the direction of arrow  68  due to the high pressure fuel within the main fuel rail  62  in fluid contact with the needle element  54 , and more particularly the head portion  84  and grooves of the needle element  54 . The needle element  54  moves from the closed position to the open position, after which high pressure fuel within the main fuel line  62  is injected through the nozzle  80  to the internal combustion engine. 
         [0045]    After the completion of the injection event, the solenoid  34  is deenergized, and the magnetostrictive element  28  contracts (i.e., from the expanded length) and/or returns to the default length. Due to the contraction of the magnetostrictive element  28 , the magnetostrictive element  28  no longer forces the input shafts  48  to displace the fluid through the channels  76  into the output bore  51 . Rather, the forces on the end  59  of the output shaft  51  from the high pressure fuel within the void  60  (together with the biasing element  78 ) overcome the forces associated with the high pressure fuel within the main fuel rail  62  in fluid contact with the needle element  54  and/or the quill  52  (i.e., closing forces exceed opening forces). As a result, the needle element  54  returns from the open position to the closed position. Further, the movement of the output shaft  50  in a direction of arrow  64  causes the flanged surface  74  to displace at least a portion of the fluid within the output bore  51  into the channels  76  and the input bores  49 . The pressure of the fluid within the input bores  49  forces the input shafts  48  in the direction of arrow  48  such that the input shafts  48  remain adjacent to and/or in direct contact with the end caps  42  of the magnetostrictive element  28 . Taken together, displacement of the fluid between the input bores  49  and the output bore  51  applies or removes a force on the output shaft  50 . 
         [0046]    The input shafts  48 , which remain adjacent to and/or in direct contact with the end caps  42  of the magnetostrictive element  28 , also provide a constant compressive force on the magnetostrictive element  28 . This advantageous feature of the fluidomechanical coupler  16  results in a compressive preload on the magnetostrictive element  28  and prevents tensile failure during operation. Further, the magnetostrictive element  28  has a default length and is configured to expand to an expanded length, and/or selectively expandable to any length between the default length and the expanded length to selectively control the rate of fuel injection. Selectively controlling the expansion or contraction of the magnetostrictive element  28  variably controls the magnitude of fluid displacement between the input bores  49  and the output bore  51 , thereby selectively controlling the rate of fuel injection. 
         [0047]    The disclosure is not to be limited to the particular embodiments described herein. In particular, the disclosure contemplates numerous variations in which the fluidomechanical coupler can translate an input force from a magnetostrictive actuator into an output response to provide precise control over fuel injection. The foregoing description has been presented for purposes of illustration and description. It is not intended to be an exhaustive list or limit any of the disclosure to the precise forms disclosed. It is contemplated that other alternatives or exemplary aspects are considered included in the disclosure. The description is merely examples of embodiments, processes or methods of the disclosure. It is understood that any other modifications, substitutions, and/or additions can be made, which are within the intended spirit and scope of the disclosure. For the foregoing, it can be seen that the disclosure accomplishes at least all that is intended. 
         [0048]    The previous detailed description is of a small number of embodiments for implementing the disclosure and is not intended to be limiting in scope. The following claims set forth a number of the embodiments of the disclosure with greater particularity.