Abstract:
An ultrasonic fuel injector for injecting a pressurized liquid fuel into the combustion chamber of an internal combustion engine that uses an overhead cam for actuating the injector includes a valve body having an injector needle disposed therein forming a needle valve to meter the flow of fuel through the injector. The valve body is formed of ceramic material that is transparent to magnetic fields changing at ultrasonic frequencies. The injector needle includes a magnetostrictive portion disposed in the region of the valve body that is surrounded by a wire coil wound around the outside surface of the ceramic valve body. The wire coil is connected to a source of electric power that oscillates at ultrasonic frequencies. A sensor is configured to signal when the overhead cam is actuating the injector to inject fuel into the combustion chamber of the engine. The sensor is connected to a control that is connected to the power source and is configured to operate same only when the overhead cam is actuating the injector to inject fuel into the combustion chamber of the engine. When the power source activates the oscillating magnetic field in the coil and applies same to the magnetostrictive portion of the needle, ultrasonic energy is applied to the pressurized liquid. The method involves retrofitting a conventional injector with a needle having a magnetostrictive portion and with a ceramic valve body surrounded by wound wire coils configured and disposed to subject the magnetostrictive portion of the needle to ultrasonically oscillating magnetic fields.

Description:
PRIORITY CLAIM 
     The present application hereby claims priority based on provisional application Ser. No. 60/254,737, which was filed on Dec. 11, 2000. 
    
    
     RELATED APPLICATIONS 
     This application is one of a group of commonly assigned patent applications which include application Ser. No. 08/576,543 entitled “An Apparatus and Method for Emulsifying A Pressurized Multi-Component Liquid”, in the name of L. K. Jameson et al.; and application Ser. No. 08/576,522 entitled “Ultrasonic Liquid Fuel Injection Apparatus and Method”, in the name of L. H. Gipson et al. The subject matter of each of these applications is hereby incorporated herein by this reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for injecting fuel into a combustion chamber and in particular to a unitized fuel injector for engines that use overhead cams to actuate the injectors. 
     Diesel engines for locomotives use unitized fuel injectors that are actuated by overhead cams. One such typical conventional unitized injector is schematically represented in FIG.  1  and is generally designated by the numeral  10 . This unitized injector  10  includes a steel valve body  11  that is disposed in an injector nut  29 . The steel valve body  11  houses a needle valve that can be biased in the valve&#39;s closed position to prevent the injector from injecting fuel into one of the engine&#39;s combustion chambers, which is generally designated by the numeral  20 . 
     As shown in FIG. 1B, which depicts an expanded cross-sectional view of a portion of the steel valve body  11  of FIG. 1, the needle valve includes a conically shaped valve seat  12  that is defined in the hollowed interior of the valve body  11  and can be mated with and against a conically shaped tip  13  at one end of a needle  14 . The hollowed interior of the valve body  11  further defines a fuel pathway  15  connecting to a fuel reservoir  16  and a discharge plenum  17 , which is disposed downstream of the needle valve. Each of several exit channels  18  typically is connected to the discharge plenum  17  by an entrance orifice  19  and to the combustion chamber  20  by an exit orifice  21  at each opposite end of each exit channel  18 . The needle valve controls whether fuel is permitted to flow from the storage reservoir  16  into the discharge plenum  17  and through the exit channels  18  into the combustion chamber  20 . 
     The conically shaped tip  13  at one end of needle  14 , which is housed in the hollowed interior of the valve body  11 , is biased into sealing contact with valve seat  12  by a spring  22 , which is housed in a cage  28  so as to be disposed to apply its biasing force against the opposite end of the needle  14  as shown in FIG. 1. A fuel pump  23  is disposed above the spring-biased end of the needle  14  and in axial alignment with the needle  14 . Another spring  24  biases a cam follower  25  that is disposed above and in axial alignment with each of the fuel pump  23  and the spring-biased end of the needle  14 . The cam follower  25  engages the plunger  26  that produces the pump&#39;s pumping action that forces pressurized fuel into the valve body  11  of the injector. An overhead cam  27  cyclically actuates the cam follower  25  to overcome the biasing force of spring  24  and press down on the plunger  26 , which accordingly actuates the fuel pump  23 . The fuel that is pumped into the valve body  11  via actuation of the pump  23  hydraulically lifts the conically shaped tip  13  of the needle  14  away from contact with the valve seat  12  and so opens the needle valve and forces a charge of fuel out of the exit orifices  21  of the injector  10  and into the combustion chamber  20  that is served by the injector. 
     However, the injector&#39;s exit orifices can become fouled and thereby adversely affect the amount of fuel that is able to enter the combustion chamber. Moreover, improving the fuel efficiency of these engines is desirable as is reducing unwanted emissions from the combustion process performed by such engines. 
     The goal of achieving more efficient combustion, which increases power and reduces pollution from the combustion process, thereby improving the performance of injectors, has largely been sought to be accomplished by decreasing the size of the injector&#39;s exit orifices and/or increasing the pressure of the liquid fuel supplied to the exit orifice. Each of these types of solutions aims to increase the velocity of the fuel that exits the orifices of the injector. 
     However, these solutions introduce problems of their own such as: the need to use exotic metals; lubricity problems; the need to micro inch finish moving parts; the need to contour internal fuel passages; high cost; and direct injection. For example, the reliance on smaller orifices means that the orifices are more easily fouled. The reliance on higher pressures in the range of 1500 bar to 2000 bar means that exotic metals must be used that are strong enough to withstand these pressures without contorting in a manner that changes the characteristics of the injector, if not destroying it altogether. Such exotic metals increase the cost of the injector. The higher pressures also create lubricity problems that cannot be solved by relying on additives in the fuel for lubrication of the injector&#39;s moving parts. Other means of lubricity such as applying a micro inch finish on the moving metal parts is required at great expense. Such higher pressures also create wear problems in the internal passages of the injector that must be counteracted by contouring the passages, which requires machining that is costly to perform. These wear problems also erode the exit orifices, and such erosion changes the character of the injector&#39;s plume over time and affects performance. Moreover, to achieve the higher pressures, the fuel pump must be localized with the injector for direct injection rather than disposed remotely from the injector. 
     Using ultrasonic energy to improve atomization of fuel injected into a combustion chamber is known, and advances in this field have been made as is evidenced by commonly owned U.S. Pat. Nos. 5,803,106; 5,868,153 and 6,053,424, which are hereby incorporated herein by this reference. These typically involve attaching an ultrasonic transducer on one end of an ultrasonic horn while the opposite end of the horn is immersed in the fuel in the vicinity of the injector&#39;s exit orifices and caused to vibrate at ultrasonic frequencies. However, unitized fuel injectors cannot be fitted with such ultrasonic transducers because of the disposition of the fuel pump, cam follower and overhead cam in axial alignment with the needle. 
     SUMMARY 
     Objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In a presently preferred embodiment of the present invention, the standard unitized injector actuated by overhead cams is retrofitted by replacing the steel valve body with a valve body that is composed of ceramic material that is transparent to magnetic fields oscillating at ultrasonic frequencies. The ceramic material is harder and more wear resistant than the steel at the pressures involved. 
     The retrofitting of the valve body also includes replacing the steel needle with a needle that has an elongated portion that is composed of magnetostrictive material that is capable of responding mechanically to magnetic fields oscillating at ultrasonic frequencies. The portion of the ceramic valve body surrounding the magnetostrictive portion of the retrofitted needle is itself surrounded by a wire coil that is capable of inducing in the region occupied by the magnetostrictive portion of the needle a magnetic field that is oscillating at ultrasonic frequencies and thus causes the magnetostrictive portion to vibrate at ultrasonic frequencies. This vibration causes the tip of the needle, which is disposed in the liquid fuel near the entrance to the discharge plenum and the channels leading to the injector&#39;s exit orifices, to vibrate at ultrasonic frequencies and therefore subjects the fuel to these ultrasonic vibrations. The ultrasonic stimulation of the fuel as it leaves the exit orifices permits the injector to achieve the desired performance while operating at lower pressures and using larger exit orifices than the conventional solutions that are aimed at increasing the velocity of the fuel exiting the injector. 
     In accordance with the present invention, a control is provided for actuation of the ultrasonically oscillating signal. The control is configured so that the actuation of the ultrasonically oscillating signal that is provided to the coil only occurs when the overhead cams are actuating the injector so as to allow fuel to flow through the injector and into the combustion chamber from the injector&#39;s exit orifices. Thus, the control operates so that the ultrasonic vibration of the fuel only occurs when fuel is flowing through the injector and into the combustion chamber from the injector&#39;s exit orifices. This control can include a sensor such as a pressure transducer that is disposed on the cam follower and includes a piezoelectric transducer that detects the pressure change indicating actuation of the follower by the cam. 
     Moreover, injectors can be made in accordance with the present invention as original equipment rather than as retrofits. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a cross-sectional view of a conventional unitized fuel injector actuated by overhead cams. 
     FIG. 1B is an expanded cross-sectional view of a portion of the steel valve body of the conventional unitized fuel injector of FIG.  1 A. 
     FIG. 2 is a diagrammatic representation of a partial perspective view with portions shown in phantom (dashed line) of a presently preferred embodiment of the apparatus of the present invention. 
     FIG. 3 is a partial perspective view of a presently preferred embodiment of the ceramic valve body of the apparatus of the present invention with portions cut away and portions shown in cross-section and environmental structures shown in phantom (chain dashed line). 
     FIG. 4 is a cross-sectional view of the ceramic valve body shown in FIG.  3 . 
     FIG. 5 is an expanded perspective view of one portion of a presently preferred embodiment of the valve body of the apparatus of the present invention with portions cut away and portions shown in cross-section and environmental components shown schematically. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference now will be made in detail to the presently preferred embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. The same numerals are assigned to the same components throughout the drawings and description. 
     As used herein, the term “liquid” refers to an amorphous (noncrystalline) from of matter intermediate between gases and solids, in which the molecules are much more highly concentrated than in gases, but much less concentrated than in solids. A liquid may have a single component or may be made of multiple components. The components may be other liquids, solid and/or gases. For example, a characteristic of liquids is their ability to flow as a result of an applied force. Liquids that flow immediately upon application of force and for which the rate of flow is directly proportional to the force applied are generally referred to as Newtonian liquids. Some liquids have abnormal flow response when force is applied and exhibit non-Newtonian flow properties. 
     In accordance with the present invention, as schematically shown in FIG. 2, not necessarily to scale, an internal combustion engine  30  with unitized fuel injectors  31  (only one being shown in FIG. 2) actuated by an overhead cam  27  forms the power plant of an exemplary apparatus, a broken away portion of which is shown generally and designated by the numeral  32 . Such apparatus  32  could be almost any device that requires a power plant and would include but not be limited to an on site electric power generator, a land vehicle such as a railroad locomotive for example, an air vehicle such as an airplane, or a marine craft powered by diesel such as an ocean going vessel. 
     The ultrasonic fuel injector apparatus of the present invention is indicated generally in FIG. 2 by the designating numeral  31 . Unitized injector  31  differs from the conventional unitized injector  10  described above primarily in the configuration and composition of the valve body  33  and the needle  36  and in the addition of a sensor, a control and an ultrasonic power source, and these differences are described below. The remaining features and operation of the injector  31  of the present invention are the same as for the conventional unitized injector. 
     A presently preferred embodiment of the valve body  33  of injector  31  is shown in FIG. 3 in a perspective view that is partially cut away and in FIG. 4 in a cross-sectional view. External dimensions of the valve body  33  matched those of the conventional valve body  11  for the conventional injector  10  and likewise fit within the injector nut  29 . In accordance with the present invention, the valve body  33  is composed of ceramic material, which is transparent to magnetic fields changing at ultrasonic frequencies. As embodied herein and shown in FIGS. 3 and 4 for example, this valve body  33  can be composed of ceramic material such as partially stabilized zirconia, which is available from Coors Ceramic Company of Golden, Colo. 
     The valve body  33  is hollowed about most of the length of its central longitudinal axis and configured to receive therein an injector needle  36 . As in the conventional needle, a forward portion of the injector needle  36  defines the conically shaped tip  13 . The hollowed portion of the valve body defines the same fuel reservoir  16  as in the conventional valve body  11 . Reservoir  16  is configured to receive and store an accumulation of pressurized fuel in addition to accommodating the passage therethrough of a portion of the injector needle  36 . The hollowed portion of the valve body  33  further defines the same discharge plenum  17  as in the conventional valve body  11 . Plenum  17  communicates with the fuel reservoir  16  and is configured for receiving pressurized liquid fuel. The shape of the hollowed portion is generally cylindrically symmetrical to accommodate the external shape of the needle, but varies from the shape of the needle at different portions along the central axis of the valve body to accommodate the fuel reservoir  16  and the discharge plenum  17 . The differently shaped hollowed portions that are disposed along the central axis of the valve body  33  generally communicate with one another and interact with the needle  36  in the same manner as these same features would in the conventional valve body  11  of the conventional injector  10 . 
     The hollowed portion of the valve body  33  also defines a valve seat  12  that is configured as a truncated conical section that connects at one end to the opening of the discharge plenum  17  and at the opposite end is configured in communication with the fuel reservoir  16 . Thus, the discharge plenum  17  is connected to the fuel reservoir via the valve seat  12  in the same manner as in the conventional valve body  11 . 
     In valve body  33 , as in the conventional valve body  11 , at least one and desirably more than one nozzle exit orifice  21  is defined through the lower extremity of the valve body  34  of the injector  31 . Each nozzle exit orifice  21  connects to the discharge plenum  17  via an exit channel  18  defined through the lower extremity of the injector&#39;s valve body and an entrance orifice  19  defined through the inner surface that defines the discharge plenum  17 . Each channel  18  and its orifices  19 ,  21  may have a diameter of less than about 0.1 inches (2.54 mm). For example, the channel  18  and its orifices  19 ,  21  may have a diameter of from about 0.0001 to about 0.1 inch (0.00254 to 2.54 mm). As a further example, the channel  18  and its orifices  19 ,  21  may have a diameter of from about 0.001 to about 0.01 inch (0.0254 to 0.254 mm). The beneficial effects from the ultrasonic vibration of the fuel before the fuel leaves the exit orifice  21  of the injector  31  has been found to occur regardless of the size, shape, location and number of channels  18  and the orifices  19 ,  21  of same. 
     As shown in FIG. 4, the valve body  33  of the injector  31  also defines a fuel pathway  115  that is configured and disposed off-axis within the injector&#39;s valve body. The fuel pathway  115  is configured to supply pressurized liquid fuel to the fuel reservoir  16  and is connected to the fuel reservoir  16  and communicates with the discharge plenum  17 . 
     As shown in FIG. 3, one end of the valve body  33  is configured to be mated to the spring cage  28  (shown in dashed line in FIG. 3) that holds the spring  22  that biases the position of the needle  36  as in the conventional injector  10 . Design considerations for the valve body  33  included maintaining adequate surface area for sealing and to minimize stress concentrations and prevent high-pressure fuel leakage between mating parts. Sealing of high-pressure fuel is accomplished in this particular injector by mating surfaces between parts which are clamped together by the injector nut  29 . The sealing, or contact, surfaces should be sized such that the contact pressure is significantly greater than the peak injection pressure that must be contained. The static pressure within the valve body  33  is also the sealing pressure between the valve body  33  and the mating cage  28 . The sealing pressure included a sealing safety factor of 1.62 for an estimated peak injection pressure of 15,000 psi. 
     As shown in FIGS. 2-4, the dome portion  34  of the valve body  33  constitutes the exterior bearing surface that is received within the injector nut  29 , and is the portion of the valve body  33  that is configured to bear the compressive force applied to hold the unitized injector  31  together. An objective of this design of the valve body  33  was to minimize stress concentrations on the lower shoulder portion  35  of the valve body  33  when mating surfaces between parts in this injector  31  are clamped together by the injector nut  29 . 
     In accordance with the present invention, the compression load was diverted from the shoulder portion  35  to the dome portion  34  by means of an annular metal collar  40  disposed between the dome portion  34  of the valve body  33  and the interior surface of the injector nut  29 . The annular collar  40  is configured to receive and absorb part of the compressive load applied to the valve body  33  within the injector nut  29 . Desirably, the annular collar is composed of a metal such as aluminum which is softer than the ceramic material and softer than the metal forming the injector nut  29 . In this way the annular collar  40  compensates for the more brittle composition of the ceramic valve body that might otherwise crack in areas such as shoulder portion  35  that otherwise might bear some of this compressive force. 
     Another critical location where high pressure fuel leakage is to be avoided is the annular area between the external surface of the needle  36  and the internal surface  37  that defines the axial bore within the valve body  33 . The internal bore  37  of the valve body  33  and the needle  36  disposed therein are selectively fitted to maintain minimal clearances and leakage. A value of 0.0002 inch is a typical maximum clearance between the external diameter of the needle  36  and the diameter of the bore  37  disposed immediately upstream of reservoir  16  in the nozzle  34 . 
     The configuration and operation of the needle valve in the injector  31  of the present invention is the same as in the conventional injector  10  described above. As shown in FIG.  4 . for example, the second end of the injector needle  36  defines a tip shaped with a conical surface  13  that is configured to mate with and seal against a portion of the conically shaped valve seat  12  defined in the hollowed portion of the injector&#39;s valve body  33 . The opposite end of the injector needle  36  is connected so as to be biased into a position that disposes the conical surface  13  of the injector needle  36  into sealing contact with the conical surface of the valve seat  12  so as to prevent the fuel from flowing out of the fuel passageway  115 , into the storage reservoir  16 , into the discharge plenum  17 , through the exit channels  18 , out of the nozzle exit orifices  21  and into the combustion chamber  20 . As shown schematically in FIG. 3, as in the conventional injector  11 , a spring  22  provides one example of a means of biasing the conical surface  13  of the injector needle  36  into sealing contact with the conical surface  12  of the valve seat. Thus, when the injector needle  36  is disposed in its biased orientation, fuel cannot flow under the force of gravity alone from the fuel passageway  115  out of the nozzle exit orifices  21  and into the combustion chamber  20  into which the lower extremity of the fuel injector  31  is disposed. 
     As is conventional and schematically shown in FIG. 2 for example, the actuation of the cam  25  operates to overcome the biasing force of spring  24  and force the conical end of the injector needle and the conically shaped valve seat apart so as to permit the flow of fuel into the discharge plenum and out of the nozzle exit orifices  21  of the fuel injector  31  into the combustion chamber  20  of the engine  30  of the apparatus  32 . This is accomplished as in the conventional unitized injectors  10  described above, i.e., by actuation of a pump  23  that forces pressurized fuel to hydraulically lift the needle  36  against the biasing force of the spring  22 . 
     As used herein, the term “magnetostrictive” refers to the property of a sample of ferromagnetic material that results in changes in the dimensions of the sample depending on the direction and extent of the magnetization of the sample. Magnetostrictive material that is responsive to magnetic fields changing at ultrasonic frequencies means that a sample of such magnetostrictive material can change its dimensions at ultrasonic frequencies. 
     In accordance with the present invention, the injector needle defines at least a first portion  38  that is configured to be disposed in the central axial bore  37  defined within the valve body  33 . As shown in FIGS. 3 and 4 for example, this first portion  38  of the injector needle  36  is indicated by the stippling and is formed of magnetostrictive material that is responsive to magnetic fields changing at ultrasonic frequencies. The length of the first portion  38  composed of magnetostrictive material can be about one third of the overall length of needle  36 . However, the entire needle  36  can be formed of the magnetostrictive material if desired. A suitable magnetostrictive material is provided by an ETREMA TERFENOL-D7 magnetostrictive alloy, which can be bonded to steel to form the needle of the injector. The ETREMA TERFENOL-D7 magnetostrictive alloy is available from ETREMA Products, Inc. of Ames, Iowa 50010. Nickel and permalloy are two other suitable magnetostrictive materials. 
     Upon application of a magnetic field that is aligned along the longitudinal axis of the injector needle  36 , the length of this first portion  38  of the injector needle  36  increases or decreases slightly in the axial direction. Upon removal of the aforementioned magnetic field, the length of this first portion  38  of the injector needle  36  is restored to its unmagnetized length. Moreover, the time during which the expansion and contraction occur is short enough so that the injector needle  36  can expand and contract at a rate that falls within ultrasonic frequencies, namely, 15 kilohertz to 500 kilohertz. The overall length of needle  36  in the needle&#39;s unmagnetized state is the same as the overall length of the conventional needle  14 . 
     In further accordance with the present invention, the axial bore  37  of the injector&#39;s valve body  33  is defined by a wall that is composed of material that is transparent to magnetic fields changing at ultrasonic frequencies. As embodied herein and shown in FIGS. 3 and 4 for example, this wall that defines the axial bore  37  is composed of ceramic material such as partially stabilized zirconia. The partially stabilized zirconia ceramic material has excellent material properties and satisfies the requirement for an electrically non-conductive material between the winding (described below) and needle  36 . Partially stabilized zirconia has relatively high compressive strength and fracture toughness compared to all other available technical ceramics. 
     The inner surface  39  of the cavity within the valve body  33  is disposed so as to coincide with the first portion  38  of the injector needle  36  that is disposed within the axial bore  37  of the valve body  33  of the injector  31 . As shown in FIG. 4 for example, the internally hollowed portion  39  of the valve body  33  defines a cylindrical cavity that is configured to receive therein at least a first portion  38  of the injector needle  36 . As shown in FIG. 4 for example, the length of the inner surface  39  of the cavity comprised a majority of the axial bore  37  of the valve body  33  and had a diameter that was sized 0.001 inch larger than the diameter of axial bore  37  in order to prevent binding of the needle  36  due to potential non-concentricity of the assembly. 
     In yet further accordance with the present invention, a means is provided for applying within the cavity of the axial bore of the injector body, a magnetic field that can be changed at ultrasonic frequencies. The magnetic field can change from on to off or from a first magnitude to a second magnitude or the direction of the magnetic field can change. This means for applying a magnetic field changing at ultrasonic frequencies desirably is carried at least in part by the injector&#39;s valve body  33 . As embodied herein and shown in FIG. 3 for example, the means for applying within the cavity of the axial bore  37  a magnetic field changing at ultrasonic frequencies can include an electric power source  46  and a wire coil  42  that is wrapped around the outermost surface  43  of the portion of the valve body  33  that surrounds the portion of the valve body&#39;s cavity that receives the portion  38  of the needle  36  that is formed of magnetostrictive material. 
     The electrical winding  42  was wound directly around the valve body  33  and potted to prevent shorting of the coil&#39;s turns to the injector nut  29 . As shown in FIGS. 3 and 4 for example, the wire coil  42  can be imbedded in potting material, which is generally represented by the stippled shading that is designated by the numeral  48 . As shown in FIGS. 3 and 4 for example, electrical grounding of one end of the winding  42  was accomplished through contact with one side of a copper washer  49 . The opposite side of washer  49 , which could be formed of another conductive material besides copper, desirably features dimples (not shown) that would compress against the interior surface of the injector nut  29  when the valve body  33  is assembled in the metallic injector nut  29  and assure good electrical contact with injector nut  29 . 
     Electrically connected to the other end of the winding  42  is a contact ring  44  that is embedded in a channel  41  formed between shoulder  35  and the outermost buildup of potting material  48  as shown in FIGS. 3,  4  and  5  for example. Electrically connecting winding  42  to the ultrasonic power source  46  was accomplished through a spring loaded electrical probe  54  that was kept in electrical contact with contact ring  44 . As shown in FIGS. 4 (schematically) and  5  (enlarged, cut-away perspective) for example, the back end of probe  54  is threaded through the injector nut  29 , and an electrically insulating sleeve  55  surrounds the section of probe  54  that extends through injector nut  29  and into channel  41  in valve body  33 . 
     As shown schematically in FIGS. 2 and 5 for example, the probe  54  in turn can be connected to an electrical lead  45  that electrically connects to a source of electric power  46  that can be activated by a control  47  to oscillate at ultrasonic frequencies. From one perspective, the combination of the needle  36  composed of magnetostrictive material and the coil  42  function as a magnetostrictive transducer that converts the electrical energy provided to the coil  42  into the mechanical energy of the expanding and contracting needle  36 . A suitable example of a control  47  for such a magnetostrictive transducer is disclosed in commonly owned U.S. Pat. Nos. 5,900,690 and 5,892,315, which are hereby incorporated herein in their entirety by this reference. Note in particular FIG. 5 in U.S. Pat. Nos. 5,900,690 and 5,892,315 and the explanatory text of same. 
     In further accordance with the present invention, electrification of the coil  42  at ultrasonic frequencies is governed by the control  47  so that it occurs only when the injector needle  36  is positioned so that fuel flows from the storage reservoir  16  into the discharge plenum  17 . In other words, the control  47  ensures that the ultrasonic vibration of the fuel only occurs when the injector  31  is open and injecting fuel into the combustion chamber  20 . As schematically shown in FIG. 2, control  47  can receive a signal from a pressure sensor  51  that is disposed on the cam follower  25  and detects when the cam  27  engages the follower  25 . When the cam  27  depresses the follower  25 , the pump  23  is actuated and pumps fuel into the valve body  33 , thereby increasing the pressure in the fuel within the valve body  33  so as to hydraulically open the needle valve and cause fuel to be injected out of the exit orifices  21  of the injector  31 . The pressure sensor  51  can include a pressure transducer such as a piezoelectric transducer that generates an electrical signal when subjected to pressure. Accordingly, the pressure sensor  51  sends an electric signal to the control  47 , which can include an amplifier to amplify the electrical signal that is received from the sensor  51 . Control  47  is configured to then provide this amplified electrical signal to activate the oscillating power source  46  that powers the coil  42  via lead  45  and induces the desired oscillating magnetic field in the magnetostrictive portion  38  of the needle  36 . Control  47  also governs the magnitude and frequency of the ultrasonic vibrations through its control of power source  46 . Other forms of control can be used to achieve the synchronization of the application of ultrasonic vibrations and the injection of fuel by the injector, as desired. 
     During the injection of fuel, the conically-shaped end  13  of the injector needle  36  is disposed so as to protrude into the discharge plenum  17 . The expansion and contraction of the length of the injector needle  36  caused by the elongation and retraction of the magnetostrictive portion  38  of the injector needle  36  is believed to cause the conically-shaped end  13  of the injector needle  36  to move respectively a small distance into and out of the discharge plenum  17  as would a sort of plunger. This in and out reciprocating motion is believed to cause a commensurate mechanical perturbation of the liquid fuel within the discharge plenum  17  at the same ultrasonic frequency as the changes in the magnetic field in the magnetostrictive portion  38  of the injector needle  36 . This ultrasonic perturbation of the fuel that is leaving the injector  31  through the nozzle exit orifices  21  results in improved atomization of the fuel that is injected into the combustion chamber  20 . Such improved atomization results in more efficient combustion, which increases power and reduces pollution from the combustion process. The ultrasonic vibration of the fuel before the fuel exits the injector&#39;s orifices produces a plume that is an uniform, cone-shaped spray of liquid fuel into the combustion chamber  20  that is served by the injector  31 . 
     The actual distance between the tip  13  of the needle  36  and the entrance orifice  19  or the exit orifice  21  when the needle valve is opened in the absence of the oscillating magnetic field was not changed from what it was in the conventional valve body  11 . In general, the minimum distance between the tip  13  of the needle  36  and the entrance orifice  19  of the channels  18  leading to the exit orifices  21  of the injector  31  in a given situation may be determined readily by one having ordinary skill in the art without undue experimentation. In practice, such distance will be in the range of from about 0.002 inches (about 0.05 mm) to about 1.3 inches (about 33 mm), although greater distances can be employed. Such distance determines the extent to which ultrasonic energy is applied to the pressurized liquid other than that which is about to enter the exit orifice. In other words, the greater the distance, the greater the amount of pressurized liquid which is subjected to ultrasonic energy. Consequently, shorter distances generally are desired in order to minimize degradation of the pressurized liquid and other adverse effects which may result from exposure of the liquid to the ultrasonic energy. 
     Immediately before the liquid fuel enters the entrance orifice  19 , the vibrating tip  13  that contacts the liquid fuel applies ultrasonic energy to the fuel. The vibrations appear to change the apparent viscosity and flow characteristics of the high viscosity liquid fuels. The vibrations also appear to improve the flow rate and/or improve atomization of the fuel stream as it enters the combustion chamber  20 . Application of ultrasonic energy appears to improve (e.g., decrease) the size of liquid fuel droplets and narrow the droplet size distribution of the liquid fuel plume. Moreover, application of ultrasonic energy appears to increase the velocity of liquid fuel droplets exiting the injector&#39;s orifice  21  into the combustion chamber  20 . The vibrations also cause breakdown and flushing out of clogging contaminants at the injector&#39;s exit orifice  21 . The vibrations can also cause emulsification of the liquid fuel with other components (e.g., liquid components) or additives that may be present in the fuel stream. 
     The injector  31  of the present invention may be used to emulsify multi-component liquid fuels as well as liquid fuel additives and contaminants at the point where the liquid fuels are introduced into the internal combustion engine  30 . For example, water entrained in certain fuels may be emulsified by the ultrasonic vibrations so that fuel/water mixture may be used in the combustion chamber  20 . Mixed fuels and/or fuel blends including components such as, for example, methanol, water, ethanol, diesel, liquid propane gas, bio-diesel or the like can also be emulsified. The present invention can have advantages in multi-fueled engines in that it may be used so as to render compatible the flow rate characteristics (e.g., apparent viscosities) of the different fuels that may be used in the multi-fueled engine. Alternatively and/or additionally, it may be desirable to add water to one or more liquid fuels and emulsify the components immediately before combustion as a way of controlling combustion and/or reducing exhaust emissions. It may also be desirable to add a gas (e.g., air, N 2 O, etc.) to one or more liquid fuels and ultrasonically blend or emulsify the components immediately before combustion as a way of controlling combustion and/or reducing exhaust emissions. 
     One advantage of the injector  31  of the present invention is that it is selfcleaning. Because of the ultrasonic vibration of the fuel before the fuel exits the injector&#39;s orifices  21 , the vibrations dislodge any particulates that might otherwise. clog the channel  18  and its entrance and exit orifices  19 ,  21 , respectively. That is, the combination of supplied pressure and forces generated by ultrasonically exciting the needle  36  amidst the pressurized fuel directly before the fuel leaves the nozzle  34  can remove obstructions that might otherwise block the exit orifice  21 . According to the invention, the channel  18  and its entrance orifice  19  and exit orifice  21  are thus adapted to be self-cleaning when the injector&#39;s needle  36  is excited with ultrasonic energy (without applying ultrasonic energy directly to the channel  18  and its orifices  19 ,  21 ) while the exit orifice  21  receives pressurized liquid from the discharge chamber  17  and passes the liquid out of the injector  31 . 
     While the specification has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. Accordingly, the scope of the present invention should be assessed as that of the appended claims and any equivalents thereto.