Patent Grant
7819335
This invention relates generally to ultrasonic liquid delivery devices for delivering an atomized spray of liquid, and more particularly to a control system for controlling operation of such an ultrasonic liquid delivery device.
Ultrasonic liquid delivery devices are used in various fields to energize liquid for the purpose of atomizing the liquid to provide a fine mist or spray of the liquid. For example, such devices are used as nebulizers and other drug delivery devices, molding equipment, humidifiers, fuel injection systems for engines, paint spray systems, ink delivery systems, mixing systems, homogenization systems, and the like. Such delivery devices typically comprise a housing that has a flow path through which the liquid flows in a pressurized state to at least one and sometimes a plurality of exhaust ports or orifices of the housing. The pressurized liquid is forced to exit the housing at the exhaust port(s). In some constructions, the device may include a valve member to control the flow of liquid from the device.
In some conventional ultrasonic liquid delivery devices, an ultrasonic excitation member is typically incorporated in the device, and more particularly forms the portion of the housing that defines the exhaust port(s). The excitation member is vibrated ultrasonically as liquid exits the exhaust port(s) to energize impart ultrasonic energy to the exiting liquid. The ultrasonic energy tends to atomize the liquid so that a spray of liquid droplets is delivered from the exhaust port(s). As an example, U.S. Pat. No. 5,330,100 (Malinowski) discloses a fuel injection system in which a nozzle (e.g., part of the housing) of the fuel injector is itself constructed to vibrate ultrasonically so that ultrasonic energy is imparted to the fuel as the fuel flows out through an exit orifice of the injector. In such a configuration, there is a risk that vibrating the nozzle itself will result in cavitation erosion (e.g., due to cavitation of the fuel within the exit orifice) of the nozzle at the exit orifice.
In other ultrasonic liquid delivery devices the ultrasonic excitation member may be disposed in the flow path through which liquid flows within the housing upstream of the exhaust port(s). Examples of such a device are disclosed in related U.S. Pat. Nos. 5,803,106 (Cohen et al.); 5,868,153 (Cohen et al.); 6,053,424 (Gipson et al.) and 6,380,264 (Jameson et al.), the disclosure of each of which is incorporated herein by reference. These references generally disclose a device for increasing the flow rate of a pressurized liquid through an orifice by applying ultrasonic energy to the pressurized liquid. In particular, pressurized liquid is delivered into the chamber of a housing having a die tip that includes an exit orifice (or exit orifices) through which the pressurized liquid exits the chamber.
An ultrasonic horn extends longitudinally in part within the chamber and in part outward of the chamber and has a diameter that decreases toward a tip disposed adjacent the exit orifice to amplify the ultrasonic vibration of the horn at its tip. A transducer is attached to the outer end of the horn to vibrate the horn ultrasonically. One potential disadvantage of such a device is that exposure of the various components to a high-pressure environment imparts substantial stress on the components. In particular, because part of the ultrasonic horn is immersed in the chamber and another part is not, there is a substantial pressure differential imparted to the different segments of the horn, resulting in additional stress on the horn. Moreover, such apparatus cannot readily accommodate an operating valve member, which is common in some ultrasonic liquid delivery devices to control the delivery of liquid from the device.
In still other liquid delivery devices, and in particular those that include an operating valve member to control liquid flow from the device, it is known to ultrasonically excite the valve member itself as liquid exits the device. For example, U.S. Pat. No. 6,543,700 (Jameson et al.), the disclosure of which is incorporated herein by reference, discloses a fuel injector in which a valve needle of the injector is formed at least in part of a magnetostrictive material responsive to magnetic fields changing at ultrasonic frequencies. When the valve needle is positioned to permit fuel to be exhausted from the valve body (i.e., the housing), a magnetic field changing at ultrasonic frequencies is applied to the magnetostrictive portion of the valve needle. Accordingly, the valve needle is ultrasonically excited to impart ultrasonic energy to the fuel as it exits the injector via the exit orifices.
An ultrasonic liquid delivery device will typically operate most efficiently when the ultrasonic excitation member is excited at its natural frequency. However, in some liquid delivery devices, such as ultrasonic fuel injectors, the ultrasonic excitation member experiences a wide range of environmental conditions that can cause the natural frequency of the excitation member to drift. For example, ultrasonic fuel injectors experience substantial temperature changes between start-up and subsequent operation of the engine, resulting in thermal expansion and material property changes in the ultrasonic horn which in turn can shift the natural frequency of the horn. In addition, contact loading conditions, such as metal to metal contact between the horn and other elements of the injector such as the valve needle can also shift the natural frequency (e.g., because the valve needle would have its own resonant frequency that would cause some shift in that of the ultrasonic horn).
Accordingly, there is a need for a control system for an ultrasonic liquid delivery device, and in particular an open loop or feedback control system, that controls the excitation frequency of the device so as to operate at or near the natural frequency of the ultrasonic waveguide of the delivery device.
In one embodiment, an ultrasonic liquid delivery device generally comprises a housing having an internal chamber, at least one inlet in fluid communication with the internal chamber for receiving liquid into the internal chamber and at least one exhaust port in fluid communication with the internal chamber whereby liquid within the chamber exits the housing at said at least one exhaust port. An ultrasonic waveguide, separate from the housing, is disposed at least in part within the internal chamber of the housing to ultrasonically energize liquid within the internal chamber prior to the liquid being exhausted from the housing through the at least one exhaust port. An excitation device is operable to ultrasonically excite the ultrasonic waveguide and a control system is controls operation of the liquid delivery device between an excitation mode in which the excitation device is operated at an ultrasonic excitation frequency to ultrasonically excite the ultrasonic waveguide and a ring down mode in which the excitation device is inoperable to excite the ultrasonic waveguide such that the ultrasonic waveguide is allowed to ring down. The control system is operable to monitor the ring down and is responsive to the ring down of the ultrasonic waveguide to adjust the excitation frequency of the excitation device in the excitation mode thereof.
In another embodiment, an ultrasonic liquid delivery device generally comprises a housing having an internal chamber and at least one exhaust port in fluid communication with the internal chamber of the housing whereby liquid within the chamber exits the housing at said at least one exhaust port. A valve member is moveable relative to the housing between a closed position in which liquid within the internal chamber is inhibited against exhaustion from the housing via the at least one exhaust port, and an open position in which liquid is exhaustible from the housing via the at least one exhaust port. An ultrasonic waveguide ultrasonically energizes liquid within the internal chamber prior to the liquid being exhausted from the housing through the at least one exhaust port in the open position of the valve member. An excitation device is operable to ultrasonically excite the ultrasonic waveguide and a control system controls operation of the valve member to position the valve member from its closed to its open position to thereby exhaust liquid from the housing. The control system further controls operation of the excitation device to ultrasonically excite the ultrasonic waveguide. In the closed position of the valve member the control system initiates operation of the excitation device to ultrasonically excite the ultrasonic waveguide prior to controlling the valve member to move to its open position.
In one embodiment of a method for controlling an ultrasonic liquid delivery device, an ultrasonic waveguide is ultrasonically excited an excitation frequency. The excitation subsequently ceases to excite the ultrasonic waveguide to allow the ultrasonic waveguide to ring down. A ring down frequency of the ultrasonic waveguide is determined as the waveguide rings down. The excitation frequency is then adjusted in response to the ring down frequency being different from the excitation frequency of the ultrasonic waveguide.
In another method of operating an ultrasonic liquid delivery device, a valve member of the device is positioned in its closed position. Liquid is delivered into the internal chamber of the housing and is ultrasonically energized with the valve member in its closed position. The valve member is repositioned toward its open position to permit liquid to be exhausted from the housing via the at least one exhaust port, wherein the step of ultrasonically energizing the liquid within the internal chamber of the housing with the valve member in its closed position is initiated prior to repositioning the valve member toward its open position.
a is an expanded view of a central portion of the cross-section of
Corresponding reference characters indicate corresponding parts throughout the drawings.
With reference now to the drawings and in particular to
The term liquid, as used herein, refers to an amorphous (noncrystalline) form 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. The liquid may comprise a single component or may be comprised of multiple components. For example, 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. Other suitable liquids have abnormal flow response when force is applied and exhibit non-Newtonian flow properties.
As examples, the ultrasonic liquid delivery device of the present invention may be used to deliver liquids such as, without limitation, molten bitumens, viscous paints, hot melt adhesives, thermoplastic materials that soften to a flowable form when exposed to heat and return to a relatively set or hardened condition upon cooling (e.g., crude rubber, wax, polyolefins and the like), syrups, heavy oils, inks, fuels, liquid medication, emulsions, slurries, suspensions and combinations thereof.
The fuel injector 21 illustrated in
The fuel injector 21 comprises a housing, indicated generally at 23, for receiving pressurized fuel from a source (not shown) of fuel and delivering an atomized spray of fuel droplets to the engine, such as to a combustion chamber of the engine. In the illustrated embodiment, the housing 23 comprises an elongate main body 25, a nozzle 27 (sometimes also referred to as a valve body) and a retaining member 29 (e.g., a nut) holding the main body, nozzle and nut in assembly with each other. In particular, a lower end 31 of the main body 25 seats against an upper end 33 of the nozzle 27. The retaining member 29 suitably fastens (e.g., threadably fastens) to the outer surface of the main body 25 to urge the mating ends 31, 33 of the main body and nozzle 27 together.
The terms “upper” and “lower” are used herein in accordance with the vertical orientation of the fuel injector 21 illustrated in the various drawings and are not intended to describe a necessary orientation of the fuel injector in use. That is, it is understood that the fuel injector 21 may be oriented other than in the vertical orientation illustrated in the drawings and remain within the scope of this invention. The terms axial and longitudinal refer directionally herein to the lengthwise direction of the fuel injector (e.g., the vertical direction in the illustrated embodiments). The terms transverse, lateral and radial refer herein to a direction normal to the axial (e.g., longitudinal) direction. The terms inner and outer are also used in reference to a direction transverse to the axial direction of the fuel injector, with the term inner referring to a direction toward the interior of the fuel injector and the term outer referring to a direction toward the exterior of the injector.
The main body 25 has an axial bore 35 extending longitudinally along its length. The transverse, or cross-sectional dimension of the bore 35 (e.g., the diameter of the circular bore illustrated in
The cross-sectional dimension of the central bore 35 is stepped further inward as it extends below the solenoid valve seat to define a shoulder 45 which seats a pin holder 47 that extends longitudinally (and coaxially in the illustrated embodiment) within the central bore. As illustrated in
Longitudinally below the low pressure chamber 49, the central bore 35 of the main body 25 narrows even further to define a guide channel (and high pressure sealing) segment 51 (
A fuel inlet 57 (
The main body 25 also has an outlet 69 (
With particular reference now to
Intermediate its tip 81 and upper end 33 the cross-sectional dimension (e.g. the diameter in the illustrated embodiment) of the nozzle bore 75 is generally uniform along the length of the nozzle as illustrated in
Referring now to
The head 87 of the pin holder 47 has a generally concave, or dish-shaped recess 95 formed centrally in its upper surface, and a bore 97 that extends longitudinally from the center of this recess to the internal channel 91 of the pin holder. As illustrated in
The pin 93 is elongate and suitably extends coaxially within the pin holder channel 91 and axial bore 35 of the main body 25. An upper segment of the pin 93 is slidably received within the internal channel 91 of the pin holder 47 in closely spaced relationship therewith while the remainder of the pin extends longitudinally outward from the pin holder down into the low pressure chamber 49 of the bore 35 of the main body 25. As illustrated in
Also disposed within the low pressure chamber 49 of the main body bore 35 are a tubular sleeve 107 (
The valve needle 53 (broadly, the valve member) is elongate and extends coaxially within the bore 35 of the main body 25 from an upper end 113 (
Referring particularly to
In general, the spacing between the closure surface 117 of the valve needle terminal end 115 and the opposed surface of nozzle tip 81 in the open position of the valve needle is suitably in the range of about 0.002 inches (0.051 mm) to about 0.025 inches (0.64 mm). However, it is understood that the spacing may be greater or less than the range specified above without departing from the scope of this invention.
It is contemplated that the nozzle 27, and more particularly the tip 81, may be alternatively configured such that the exhaust ports 83 are disposed other than on the nozzle inner surface that seats the closure surface 117 of the valve needle 53 in the closed position of the valve needle. For example, the exhaust ports 83 may be disposed downstream (in the direction in which fuel flows toward the exhaust ports) of the nozzle surface that seats the closure surface 117 of the valve needle 53 and remain within the scope of this invention. One suitable example of such a valve needle, nozzle tip and exhaust port arrangement is described in U.S. Pat. No. 6,543,700, the disclosure of which is incorporated herein by reference to the extent it is consistent herewith.
It will be understood that the pin 93, the hammer 109 and the valve needle 53 are thus conjointly moveable longitudinally on a common axis within the fuel injector housing 23 between the closed position and the open position of the valve needle. The spring 111 disposed between the sleeve 107 and the hammer 109 suitably biases the hammer, and thus the valve needle 53, toward the closed position of the valve needle. It is understood that other suitable valve configurations are possible for controlling the flow of fuel from the injector for delivery to the engine without departing from the scope of this invention. For example, the nozzle 27 (broadly, the housing 23) may have an opening through which the valve needle 53 extends outward of the nozzle and through which fuel exits the nozzle for delivery to the engine. In such an embodiment the terminal end 115 of the valve needle 53 would seal against the nozzle 27 exterior thereof in the closed position of the valve needle. It is also understood that operation of the valve needle 53 may be controlled other than by a solenoid valve and remain within the scope of this invention. It is further understood that the valve needle 53 or other valve arrangement may be omitted altogether from the fuel injector 21 without departing from the scope of this invention.
With particular reference now to
In general, the waveguide may be constructed of a metal having suitable acoustical and mechanical properties. Examples of suitable metals for construction of the waveguide include, without limitation, aluminum, monel, titanium, and some alloy steels. It is also contemplated that all or part of the waveguide may be coated with another metal. The ultrasonic waveguide 121 is secured within the fuel injector housing 23, and more suitably in the high pressure chamber 55 as in the illustrated embodiment, by the mounting member 79. The mounting member 79, located longitudinally between the ends 123, 129 of the waveguide 121, generally defines an upper segment 131 of the waveguide that extends longitudinally up (in the illustrated embodiment) from the mounting member 79 to the upper end 129 of the waveguide and a lower segment 133 that extends longitudinally down from the mounting member to the terminal end 123 of the waveguide.
While in the illustrated embodiment the waveguide 121 (i.e., both the upper and lower segments thereof) is disposed entirely within the high pressure chamber 55 of the housing, it is contemplated that only a portion of the waveguide may be disposed within the high pressure chamber without departing from the scope of this invention. For example, only the lower segment 133 of the waveguide 121, including the terminal end 123 thereof, may be disposed within the high pressure chamber 55 while the upper segment 131 of the waveguide is disposed exterior of the high pressure chamber, and may or may not be subjected to high pressure fuel within the injector housing 23.
The inner cross-sectional dimension (e.g., inner diameter in the illustrated embodiment) of the waveguide 121 (e.g., the cross-sectional dimension of the interior passage 127 thereof) is generally uniform along the length of the waveguide and is suitably sized to accommodate the valve needle 53, which extends coaxially within the interior passage of the waveguide along the full length of the waveguide (and above the waveguide into abutment with the hammer 109 in the illustrated embodiment). It is understood, however, that the valve needle 53 may extend only along a portion of the interior passage 127 of the waveguide 121 without departing from the scope of this invention. It is also understood that the inner cross-sectional dimension of the waveguide 121 may be other than uniform along the length of the waveguide. In the illustrated embodiment, the terminal end 115 of the valve needle 53, and more suitably the closure surface 117 of the valve needle, is disposed longitudinally outward of the terminal end 123 of the waveguide 121 in both the open and closed positions of the valve needle. It is understood, however, that the closure surface 117 of the terminal end 115 of the valve needle 53 need only extend outward of the terminal end 123 of the waveguide 121 in the closed position of the valve needle and may be disposed fully or partially within the interior passage 127 of the waveguide in the open position of the valve needle.
As illustrated best in
Along a pair of longitudinally spaced segments (e.g., one segment 137 (
With particular reference to
The outer cross-sectional dimension of the portion 195 of the lower segment 133 of the waveguide 121 suitably increases, and more suitably tapers or flares transversely outward adjacent to or more suitably at the terminal end 123 of the waveguide. For example, the cross-sectional dimension of this enlarged portion 195 of the lower segment 133 of the waveguide 121 is sized for closely spaced or even sliding contact relationship with the nozzle 27 within the central bore 75 thereof to maintain proper axial alignment of the waveguide (and hence the valve needle 53) within the high pressure chamber 55.
As a result, the portion of the flow path between the waveguide 121 and the nozzle 27 is generally narrower adjacent to or at the terminal end 123 of the waveguide relative to the flow path immediately upstream of the terminal end of the waveguide to generally restrict the flow of fuel past the terminal end of the waveguide to the exhaust ports 83. The enlarged portion 195 of the lower segment 133 of the waveguide 121 also provides increased ultrasonically excited surface area to which the fuel flowing past the terminal end 123 of the waveguide is exposed. One or more flats 197 (
In one example, the enlarged portion 195 of the waveguide lower segment 133, e.g., at and/or adjacent the terminal end 123 of the waveguide, has a maximum outer cross-sectional dimension (e.g., outer diameter in the illustrated embodiment) of about 0.2105 inches (5.35 mm), whereas the maximum outer cross-sectional dimension of the waveguide immediately upstream of this enlarged portion may be in the range of about 0.16 inches (4.06 mm) to slightly less than about 0.2105 inches (5.35 mm).
The transverse spacing between the terminal end 123 of the waveguide 121 and the nozzle 27 defines an open area through which fuel flows along the flow path past the terminal end of the waveguide. The one or more exhaust ports 83 define an open area through which fuel exits the housing 23. For example, where one exhaust port is provided the open area through which fuel exits the housing 23 is defined as the cross-sectional area of the exhaust port (e.g., where fuel enters into the exhaust port) and where multiple exhaust ports 83 are present the open area through which fuel exits the housing is defined as the sum of the cross-sectional area of each exhaust port. In one embodiment, a ratio of the open area at the terminal end 123 of the waveguide 121 and the nozzle 27 to the open area through which fuel exits the housing 23 (e.g. at exhaust ports 83) is suitably in the range of about 4:1 to about 20:1.
It is understood that in other suitable embodiments the lower segment 133 of the waveguide 121 may have a generally uniform outer cross-sectional dimension along its entire length (e.g. such that no enlarged portion 195 is formed), or may decrease in outer cross-sectional dimension (e.g., substantially narrow towards its terminal end 123) without departing from the scope of the invention.
Referring again to
In the illustrated embodiment the excitation device 145 comprises a piezoelectric device, and more suitably a plurality of stacked piezoelectric rings 147 (e.g., at least two and in the illustrated embodiment four) surrounding the upper segment 131 of the waveguide 121 and seated on a shoulder 149 formed by the mounting member 79. An annular collar 151 surrounds the upper segment 131 of the waveguide 121 above the piezoelectric rings 147 and bears down against the uppermost ring. Suitably, the collar 151 is constructed of a high density material. For example, one suitable material from which the collar 151 may be constructed is tungsten. It is understood, however, that the collar 151 may be constructed of other suitable materials and remain within the scope of this invention. The enlarged portion 153 adjacent the upper end 129 of the waveguide 121 has an increased outer cross-sectional dimension (e.g., an increased outer diameter in the illustrated embodiment) and is threaded along this segment. The collar 151 is internally threaded to threadably fasten the collar on the waveguide 121. The collar 151 is suitably tightened down against the stack of piezoelectric rings 147 to compress the rings between the collar and the shoulder 149 of the mounting member 79.
The waveguide 121 and excitation device 145 of the illustrated embodiment together broadly define a waveguide assembly, indicated generally at 150, for ultrasonically energizing the fuel in the high pressure chamber 55. Accordingly, the entire waveguide assembly 150 is disposed entirely within the high pressure fuel chamber 55 of the fuel injector 21 and is thus generally uniformly exposed to the high pressure environment within the fuel injector. As an example, the illustrated waveguide assembly is particularly constructed to act as both an ultrasonic horn and a transducer to ultrasonically vibrate the ultrasonic horn. In particular, the lower segment 133 of the waveguide 121 as illustrated in
Upon delivering electrical current (e.g., alternating current delivered at an ultrasonic frequency) to the piezoelectric rings 147 of the illustrated embodiment the piezoelectric rings expand and contract (particularly in the longitudinal direction of the fuel injector 21) at the ultrasonic frequency at which current is delivered to the rings. Because the rings 147 are compressed between the collar 151 (which is fastened to the upper segment 131 of the waveguide 21) and the mounting member 79, expansion and contraction of the rings causes the upper segment of the waveguide to elongate and contract ultrasonically (e.g., generally at the frequency that the piezoelectric rings expand and contract), such as in the manner of a transducer. Elongation and contraction of the upper segment 131 of the waveguide 121 in this manner excites the resonant frequency of the waveguide, and in particular along the lower segment 133 of the waveguide, resulting in ultrasonic vibration of the waveguide along the lower segment, e.g., in the manner of an ultrasonic horn.
As an example, in one embodiment the displacement of the lower segment 133 of the waveguide 121 resulting from ultrasonic excitation thereof may be up to about six times the displacement of the piezoelectric rings and upper segment of the waveguide. It is understood, though, that the displacement of the lower segment 133 may be amplified more than six times, or it may not be amplified at all, and remain within the scope of this invention.
It is contemplated that a portion of the waveguide 121 (e.g., a portion of the upper segment 131 of the waveguide) may alternatively be constructed of a magnetostrictive material that is responsive to magnetic fields changing at ultrasonic frequencies. In such an embodiment (not shown) the excitation device may comprise a magnetic field generator disposed in whole or in part within the housing 23 and operable in response to receiving electrical current to apply a magnetic field to the magnetostrictive material wherein the magnetic field changes at ultrasonic frequencies (e.g., from on to off, from one magnitude to another, and/or a change in direction).
For example a suitable generator may comprise an electrical coil connected to the generating system which delivers current to the coil at ultrasonic frequencies. The magnetostrictive portion of the waveguide and the magnetic field generator of such an embodiment thus together act as a transducer while the lower segment 133 of the waveguide 121 again acts as an ultrasonic horn. One example of a suitable magnetostrictive material and magnetic field generator is disclosed in U.S. Pat. No. 6,543,700, the disclosure of which is incorporated herein by reference to the extent it is consistent herewith.
While the entire waveguide assembly 150 is illustrated as being disposed within the high pressure chamber 55 of the fuel injector housing 23, it is understood that one or more components of the waveguide assembly may be wholly or partially disposed exterior of the high pressure chamber, and may even be disposed exterior of the housing, without departing from the scope of this invention. For example, where a magnetostrictive material is used, the magnetic field generator (broadly, the excitation device) may be disposed in the main body 25 or other component of the fuel injector housing 23 and be only partially exposed to or completely sealed off from the high pressure chamber 55. In another embodiment, the upper segment 131 of the waveguide 121 and the piezoelectric rings 147 (and collar 151) may together be located exterior of the high pressure chamber 55 without departing from the scope of this invention, as long as the terminal end 123 of the waveguide is disposed within the high pressure chamber.
By placing the piezoelectric rings 147 and collar 151 about the upper segment 131 of the waveguide 121, the entire waveguide assembly 150 need be no longer than the waveguide itself (e.g., as opposed to the length of an assembly in which a transducer and ultrasonic horn are arranged in a conventional end-to-end, or “stacked” arrangement). As one example, the overall waveguide assembly 150 may suitably have a length equal to about one-half of the resonating wavelength (otherwise commonly referred to as one-half wavelength) of the waveguide. In particular, the waveguide assembly 150 is suitably configured to resonate at an ultrasonic frequency in the range of about 15 kHz to about 100 kHz, more suitably in the range of about 15 kHz to about 60 kHz, and even more suitably in the range of about 20 kHz to about 40 kHz. The one-half wavelength waveguide assembly 150 operating at such frequencies has a respective overall length (corresponding to a one-half wavelength) in the range of about 133 mm to about 20 mm, more suitably in the range of about 133 mm to about 37.5 mm and even more suitably in the range of about 100 mm to about 50 mm. As a more particular example, the waveguide assembly 150 illustrated in
An electrically non-conductive sleeve 155 (which is cylindrical in the illustrated embodiment but may be shaped otherwise) is seated on the upper end of the collar 151 and extends up from the collar to the upper end of the high pressure chamber 55. The sleeve 155 is also suitably constructed of a generally flexible material. As an example, one suitable material from which the sleeve 155 may be constructed is an amorphous thermoplastic polyetherimide material available from General Electric Company, U.S.A., under the tradename ULTEM. However, other suitable electrically non-conductive materials, such as ceramic materials, may be used to construct the sleeve 155 and remain within the scope of this invention. The upper end of the sleeve 155 has an integrally formed annular flange 157 extending radially outward therefrom, and a set of four longitudinally extending slots 159 defining four generally flexible tabs 161 at the upper end of the sleeve. A second annular flange 163 is formed integrally with the sleeve 155 and extends radially outward from the sleeve just below the longitudinally extending slots 159, i.e., in longitudinally spaced relationship with the annular flange 157 disposed at the upper end of the sleeve.
A contact ring 165 constructed of an electrically conductive material circumscribes the sleeve 155 intermediate the longitudinally spaced annular flanges 157, 163 of the sleeve. In one embodiment, the contact ring 165 is suitably constructed of brass. It is understood, however, that the contact ring 165 may be constructed of other suitable electrically conductive materials without departing from the scope of this invention. It also understood that a contact device other than a ring, such as a single point contact device, flexible and/or spring-loaded tab or other suitable electrically conductive device, may be used without departing from the scope of the invention. In the illustrated embodiment, the inner cross-sectional dimension (e.g., the diameter) of the contact ring 165 is sized slightly smaller than the outer cross-sectional dimension of the longitudinal segment of the sleeve 155 extending between the annular flanges 157, 163.
The contact ring 165 is inserted onto the sleeve 155 by urging the contact ring telescopically down over the upper end of the sleeve. The force of the ring 165 against the annular flange 157 at the upper end of the sleeve 155 urges the tabs 161 to flex (e.g. bend) radially inward to allow the ring to slide down past the annular flange formed at the upper end of the sleeve and to seat the ring on the second annular flange 163. The tabs 161 resiliently move back out toward their initial position, providing frictional engagement between the contact ring 165 and the sleeve 155 and retaining the contact ring between the annular flanges 157, 163 of the sleeve.
A guide ring 167 constructed of an electrically non-conductive material circumscribes and electrically insulates the contact ring 165. As an example, the guide ring 167 may (but need not necessarily) be constructed of the same material as the sleeve 163. In one embodiment, the guide ring 167 is suitably retained on the sleeve, and more suitably on the contact ring 165, by a clamping, or frictional fit of the guide ring on the contact ring. For example, the guide ring 167 may be a discontinuous ring broken along a slot as illustrated in
In one particularly suitable embodiment, an annular locating nub 169 extends radially inward from the guide ring 167 and is receivable in an annular groove 171 formed in the contact ring 165 to properly locate the guide ring on the contact ring. It is understood, however, that the contact ring 165 and guide ring 167 may be mounted on the sleeve 155 other than as illustrated in
As seen best in
Additional electrical wiring 183 extends from the contact ring 165 down along the outside of the sleeve 155 within the high pressure chamber 55 and into electrical communication with an electrode (not shown) disposed between the uppermost piezoelectric ring 147 and the next lower piezoelectric ring. A separate wire 184 electrically connects the electrode to another electrode (not shown) disposed between the lowermost piezoelectric ring 147 and the ring just above it. The mounting member 79 and/or the waveguide 121 provide the ground for the current delivered to the piezoelectric rings 147. In particular, a ground wire 185 is connected to the mounting member 79 and extends up to between the middle two piezoelectric rings 147 into contact with an electrode (not shown) disposed therebetween. Optionally, a second ground wire (not shown) may extend from between the middle two piezoelectric rings 147 into contact with another electrode (not shown) between the uppermost piezoelectric ring and the collar 151.
With particular reference now to
In the illustrated embodiment, the configuration of the waveguide 121 is such that a nodal plane (i.e., a plane transverse to the waveguide at which no longitudinal displacement occurs while transverse displacement is generally maximized) is not present. Rather, the nodal region of the illustrated waveguide 121 is generally dome-shaped such that at any given longitudinal location within the nodal region some longitudinal displacement may still be present while the primary displacement of the waveguide is transverse displacement.
It is understood, however, that the waveguide 121 may be suitably configured to have a nodal plane (or nodal point as it is sometimes referred to) and that the nodal plane of such a waveguide is considered to be within the meaning of nodal region as defined herein. It is also contemplated that the mounting member 79 may be disposed longitudinally above or below the nodal region of the waveguide 121 without departing from the scope of the invention.
The mounting member 79 is suitably configured and arranged in the fuel injector 21 to vibrationally isolate the waveguide 121 from the fuel injector housing 23. That is, the mounting member 25 inhibits the transfer of longitudinal and transverse (e.g., radial) mechanical vibration of the waveguide 121 to the fuel injector housing 23 while maintaining the desired transverse position of the waveguide within the high pressure chamber 55 and allowing longitudinal displacement of the waveguide within the fuel injector housing. As one example, the mounting member 79 of the illustrated embodiment generally comprises an annular inner segment 187 extending transversely (e.g., radially in the illustrated embodiment) outward from the waveguide 121, an annular outer segment 189 extending transverse to the waveguide in transversely spaced relationship with the inner segment, and an annular interconnecting web 191 extending transversely between and interconnecting the inner and outer segments. While the inner and outer segments 187, 189 and interconnecting web 191 extend continuously about the circumference of the waveguide 121, it is understood that one or more of these elements may be discontinuous about the waveguide such as in the manner of wheel spokes, without departing from the scope of this invention.
In the embodiment illustrated in
The outer segment 189 of the mounting member 79 is configured to seat down against a shoulder formed by the nozzle 27 generally adjacent the upper end 33 of the nozzle. As seen best in
The interconnecting web 191 is constructed to be relatively thinner than the inner and outer segments 187, 189 of the mounting member 79 to facilitate flexing and/or bending of the web in response to ultrasonic vibration of the waveguide 121. As an example, in one embodiment the thickness of the interconnecting web 191 of the mounting member 79 may be in the range of about 0.2 mm to about 1 mm, and more suitably about 0.4 mm. The interconnecting web 191 of the mounting member 79 suitably comprises at least one axial component 192 and at least one transverse (e.g., radial in the illustrated embodiment) component 194. In the illustrated embodiment, the interconnecting web 191 has a pair of transversely spaced axial components 192 connected by the transverse component 194 such that the web is generally U-shaped in cross-section.
It is understood, however, that other configurations that have at least one axial component 192 and at least one transverse component 194 are suitable, such as L-shaped, H-shaped, I-shaped, inverted U-shaped, inverted L-shaped, and the like, without departing from the scope of this invention. Additional examples of suitable interconnecting web 191 configurations are illustrated and described in U.S. Pat. No. 6,676,003, the disclosure of which is incorporated herein by reference to the extent it is consistent herewith.
The axial components 192 of the web 191 depend from the respective inner and outer segments 187, 189 of the mounting member and are generally cantilevered to the transverse component 194. Accordingly, the axial component 192 is capable of dynamically bending and/or flexing relative to the outer segment 189 of the mounting member in response to transverse vibratory displacement of the inner segment 187 of the mounting member to thereby isolate the housing 23 from transverse displacement of the waveguide. The transverse component 194 of the web 191 is cantilevered to the axial components 192 such that the transverse component is capable of dynamically bending and flexing relative to the axial components (and hence relative to the outer segment 189 of the mounting member) in response to axial vibratory displacement of the inner segment 187 to thereby isolate the housing 23 from axial displacement of the waveguide.
In the illustrated embodiment, the waveguide 121 expands radially as well as displaces slightly axially at the nodal region (e.g., where the mounting member 79 is connected to the waveguide) upon ultrasonic excitation of the waveguide. In response, the U-shaped interconnecting member 191 (e.g., the axial and transverse components 192, 194 thereof) generally bends and flexes, and more particularly rolls relative to the fixed outer segment 189 of the mounting member 79, e.g., similar to the manner in which a toilet plunger head rolls upon axial displacement of the plunger handle. Accordingly, the interconnecting web 79 isolates the fuel injector housing 23 from ultrasonic vibration of the waveguide 121, and in the illustrated embodiment it more particularly isolates the outer segment 189 of the mounting member from vibratory displacement of the inner segment 187 thereof. Such a mounting member 79 configuration also provides sufficient bandwidth to compensate for nodal region shifts that can occur during ordinary operation. In particular, the mounting member 79 can compensate for changes in the real time location of the nodal region that arise during the actual transfer of ultrasonic energy through the waveguide 121. Such changes or shifts can occur, for example, due to changes in temperature and/or other environmental conditions within the high pressure chamber 55.
While in the illustrated embodiment the inner and outer segments 187, 189 of the mounting member 79 are disposed generally at the same longitudinal location relative to the waveguide, it is understood that the inner and outer segments may be longitudinally offset from each other without departing from the scope of this invention. It is also contemplated that the interconnecting web 191 may comprise only one or more axial components 192 (e.g., the transverse component 194 may be omitted) and remain within the scope of this invention. For example where the waveguide 121 has a nodal plane and the mounting member 79 is located on the nodal plane, the mounting member need only be configured to isolate the transverse displacement of the waveguide. In an alternative embodiment (not shown), it is contemplated that the mounting member may be disposed at or adjacent an anti-nodal region of the waveguide, such as at one of the opposite ends 123, 129 of the waveguide. In such an embodiment, the interconnecting web 191 may comprise only one or more transverse components 194 to isolate axial displacement of the waveguide (i.e., little or no transverse displacement occurs at the anti-nodal region).
In one particularly suitable embodiment the mounting member 79 is of single piece construction. Even more suitably the mounting member 79 may be formed integrally with the waveguide 121 as illustrated in
In one suitable embodiment the mounting member 79 is further constructed to be generally rigid (e.g., resistant to static displacement under load) so as to hold the waveguide 121 (and hence the valve needle 53) in proper alignment within the high pressure chamber 55. For example, the rigid mounting member in one embodiment may be constructed of a non-elastomeric material, more suitably metal, and even more suitably the same metal from which the waveguide is constructed. The term rigid is not, however, intended to mean that the mounting member is incapable of dynamic flexing and/or bending in response to ultrasonic vibration of the waveguide. In other embodiments, the rigid mounting member may be constructed of an elastomeric material that is sufficiently resistant to static displacement under load but is otherwise capable of dynamic flexing and/or bending in response to ultrasonic vibration of the waveguide. While the mounting member 79 illustrated in
With reference back to
Because the mounting member 79 extends transverse to the waveguide 121 within the high pressure chamber 55, the lower end 31 of the main body 25 and the upper end 33 of the nozzle 27 are suitably configured to allow the fuel flow path to divert generally around the mounting member as fuel flows within the high pressure chamber. For example, as best illustrated in
In one embodiment, the fuel injector is operated by a suitable control system (not shown) to control operation of the solenoid valve and operation of the excitation device 145. Such control systems are known to those skilled in the art and need not be described further herein except to the extent necessary. Unless an injection operation is occurring, the valve needle 53 is biased by the spring 111 in the bore 35 of the main body 25 to its closed position with the terminal end 115 of the valve needle in sealing contact with the nozzle tip 81 to close the exhaust ports 83. The solenoid valve provides a closure at the recess 95 formed in the head 87 of the pin holder 47 to close the bore 97 that extends longitudinally through the pin holder. No current is supplied by the control system to the waveguide assembly in the closed position of the valve needle 53.
High pressure fuel flows from a source of fuel (not shown) into the fuel injector 21 at the fuel inlet 57 of the housing 23. Suitable fuel delivery systems for delivering pressurized fuel from the fuel source to the fuel injector 21 are known in the art and need not be further described herein. In one embodiment, the high pressure fuel may be delivered to the fuel injector 21 at a pressure in the range of about 5,000 psi (340 bar) to about 30,000 psi (2070 bar). The high pressure fuel flows through the upper distribution channel 59 of the main body 25 to the annular gap 99 between the main body and the pin holder 47, and through the feed channel 101 of the pin holder into the internal channel 91 of the pin holder above the pin 93 and up through the bore 97 in the pin holder. High pressure fuel also flows through the high pressure flow path, i.e., through the lower distribution channel 61 of the main body 25 to the high pressure chamber 55 to fill the high pressure chamber, both outward of the waveguide 121 and within the interior passage 127 of the waveguide. In this condition the high pressure fuel above the pin 93, together with the bias of the spring 111, inhibits the high pressure fuel in the high pressure chamber 55 against urging the valve needle 53 to its open position.
When the injector control system determines that an injection of fuel to the combustion engine is needed, the solenoid valve is energized by the control system to open the pin holder bore 97 so that high pressure fuel flows out from the pin holder to the fuel return channel 71 at the upper end 37 of the main body 25 as lower pressure fuel, thereby decreasing the fuel pressure behind (e.g., above) the pin 93 within the pin holder. Accordingly, the high pressure fuel in the high pressure chamber 55 is now capable of urging the valve needle 53 against the bias of the spring 111 to the open position of the valve needle. In the open position of the valve needle 53, the terminal end 115 of the valve needle is sufficiently spaced from the nozzle tip 81 at the exhaust ports 83 to permit fuel in the high pressure chamber 55 to be exhausted through the exhaust ports.
Upon energizing the solenoid valve to allow the valve needle 53 to move to its open position, such as approximately concurrently therewith, the control system also directs the high frequency electrical current generator to deliver current to the excitation device 145, i.e., the piezoelectric rings 147 in the illustrated embodiment, via the contact ring 165 and suitable wiring 183 that electrically connects the contact ring to the piezoelectric rings. As described previously, the piezoelectric rings 147 are caused to expand and contract (particularly in the longitudinal direction of the fuel injector 21) generally at the ultrasonic frequency at which current is delivered to the excitation device 145.
Expansion and contraction of the rings 147 causes the upper segment 131 of the waveguide 121 to elongate and contract ultrasonically (e.g., generally at the same frequency that the piezoelectric rings expand and contract). Elongation and contraction of the upper segment 131 of the waveguide 121 in this manner excites the waveguide (e.g., suitably at the resonant frequency of the waveguide), and in particular along the lower segment 133 of the waveguide, resulting in ultrasonic vibration of the waveguide along the lower segment and in particular at the expanded portion 195 of the lower segment at the terminal end 123 thereof.
With the valve needle 53 in its open position, high pressure fuel in the high pressure chamber 55 flows along the flow path, and in particular past the ultrasonically vibrating terminal end 123 of the waveguide 121, to the exhaust ports 83 of the nozzle tip 81. Ultrasonic energy is applied by the terminal end 123 of the waveguide 121 to the high pressure fuel just upstream (along the flow path) of the exhaust ports 83 to generally atomize the fuel (e.g., to decrease droplet size and narrow the droplet size distribution of the fuel exiting the injector 21). Ultrasonic energization of the fuel before it exits the exhaust ports 83 produces a pulsating, generally cone-shaped spray of atomized liquid fuel delivered into the combustion chamber served by the fuel injector 21.
In the illustrated embodiment of
The illustrated device 421 comprises a housing, designated generally at 423, having an inlet 457 for receiving liquid into the housing. The liquid is suitably pressurized in the range of slightly above 0.0 psi (0.0 bar) to about 50,000 psi (3,450 bar). In the illustrated embodiment, the housing 423 is comprised at least in part of an upper (with respect to the vertical orientation of the device 421 illustrated in
While the insert 482 illustrated in
The liquid inlet 457 extends transversely through the sidewall 552 of the lower housing member 427 into fluid communication with the internal chamber 455 of the housing 423. It is contemplated, however, that the liquid inlet 457 may be disposed substantially anywhere along the side of the lower housing member 427, or along the side of the upper housing member 425, or even extend axially through the top of the upper housing member and remain within the scope of this invention. Thus, the internal chamber 455 illustrated in
The device 423 illustrated in
An elongate ultrasonic waveguide assembly, generally indicated at 550, extends axially of the housing 423 (e.g., in the longitudinal or vertical direction of the housing illustrated in
As illustrated in
It is understood, however, that the terminal end 523 of the waveguide 521 (or other segment thereof) need not be in closely spaced relationship with the sidewall 552 of the lower housing member 427 to remain within the scope of this invention. For example, the outer cross-sectional dimension of the waveguide 521 may be substantially uniform along its length instead of having the enlarged portion 695, or it may narrow toward the terminal end 523 of the waveguide. Alternatively, or additionally, the inner cross-sectional dimension of the sidewall 552 of the lower housing member 427 may not decrease toward the lower end 481 of the lower housing member.
The waveguide 521 is suitably interconnected to the housing 423 within the internal chamber 455 by a transversely extending mounting member 479 constructed substantially similar to the mounting member 79 of the embodiment of
The waveguide assembly 550 also comprises the excitation device 545 (e.g., the piezoelectric rings 547 in the illustrated embodiment), which is compressed against the mounting member 479 by the collar 551 threadably fastened to the upper segment 531 of the waveguide 521. Electrical current is supplied to the excitation device 545 by suitably wiring (not shown but similar to the wiring 181, 183 of the embodiment of
In operation, liquid is delivered to the liquid inlet 457 of the housing 423 for flow along the flow path, e.g., within the internal chamber 455, to the exhaust port 483. As pressurized liquid flows past the terminal end 523 of the waveguide 521 to the exhaust port 483, the waveguide assembly 450 is operated in substantially the same manner as the waveguide assembly 150 of the fuel injector 21 of
In the embodiment illustrated in
The control system 2001 comprises a suitable controller 2003 such as, without limitation, a control circuit, a computer that executes control software, a programmable logic controller and/or other suitable control device. The controller 2003 is capable of sending signals (not shown) to the solenoid 2004 (or other suitable device) to control positioning of the valve needle 53 between its closed and open positions. The controller 2003 is also capable of sending data and/or other signals (such as an excitation frequency 2005, an operating signal or other suitable signal) to an ultrasonic frequency drive signal generator 2007, as discussed previously, to turn on and off the drive signal 2007 that operates the excitation device 145.
In an excitation mode of the fuel injector 21, e.g., when a fuel injection event is to occur to deliver fuel to the combustion chamber, the controller 2003 signals the solenoid 2004 to reposition the valve needle 53 from its closed to its open position. The controller 2003 also signals the drive signal generator 2007 to generate an ultrasonic frequency drive signal 2009 that drives the excitation device at an excitation frequency, which in turn excites the ultrasonic waveguide to energize fuel before it is exhausted from the housing. As an example, in one suitable embodiment the drive signal 2009 is an ultrasonic frequency alternating current analog sine wave. In another suitable example the drive signal 2009 is a digitally stepped sine wave to increase the rate at which the waveguide 121 rings up to its intended motion.
In one embodiment the controller 2003 sends the signal to the drive signal generator 2007 at the same time as or shortly after sending the signal to the solenoid 2004 as described previously. Alternatively, the controller 2003 may send the signal to the drive signal generator 2007 shortly before sending the signal to the solenoid 2004. For example, when the control system 2001 determines that an injection of fuel to the combustion engine is needed, the control system initiates ultrasonic energization of liquid in the high pressure chamber 55 by directing the drive signal generator 2007 to deliver current (i.e., the drive signal 2009) to the excitation device 145, i.e., the piezoelectric rings 147 in the illustrated embodiment, via the contact ring 165 and suitable wiring 183 that electrically connects the contact ring to the piezoelectric rings. The piezoelectric rings 147 are caused to expand and contract (particularly in the longitudinal direction of the fuel injector 21) generally at the ultrasonic frequency at which current is delivered to the excitation device 145.
Expansion and contraction of the rings 147 causes the upper segment 131 of the waveguide 121 to elongate and contract ultrasonically (e.g., generally at the same frequency that the piezoelectric rings expand and contract) as described above. In particular, elongation and contraction of the upper segment 131 of the waveguide 121 in this manner excites the waveguide (e.g., suitably at the resonant frequency of the waveguide), and in particular along the lower segment 133 of the waveguide, resulting in ultrasonic vibration of the waveguide along the lower segment and in particular at the expanded portion 195 of the lower segment at the terminal end 123 thereof.
Shortly after directing the drive signal generator 2007 to deliver the drive signal 2009 to the excitation device 145 (i.e., after initiating ultrasonic energizing of the fuel in the high pressure chamber 55) the solenoid is energized by the control system 2001 to reposition the valve needle 53 toward its open position. Specifically, as discussed previously, the pin holder bore 97 is opened so that high pressure fuel flows out from the pin holder to the fuel return channel 71 at the upper end 37 of the main body 25 as lower pressure fuel, thereby decreasing the fuel pressure behind (e.g., above) the pin 93 within the pin holder. Accordingly, the high pressure fuel in the high pressure chamber 55 is now capable of urging the valve needle 53 against the bias of the spring 111 to the open position of the valve needle.
Ultrasonically energizing fuel in the high pressure chamber 55 just prior to repositioning the valve needle 53 toward its open position facilitates more rapid movement of the valve needle to its open position. As one example, in one suitable embodiment the drive signal generator 2007 initiates delivery of the drive signal 2009 to the excitation device 145 in the range of about 0.1 milliseconds to about 5 milliseconds, and more suitably about 1 millisecond to about 5 milliseconds, prior to the control system 2001 energizing the solenoid valve to reposition the valve needle 53 toward its open position.
Once fuel is ejected from the fuel injector 21, the valve needle 53 is allowed to close and the controller 2003 sends a signal to the drive signal generator 2007 to stop driving the excitation device 145, thereby ceasing to actively drive the ultrasonic waveguide 121. In a particularly suitable embodiment, a single injection event may comprise a series of short pulses during which the valve needle 53 opens and closes repeatedly, with the ultrasonic excitation device 145 (and hence the waveguide assembly 150) being driven and subsequently free from being driven by the drive signal generator 2007 (i.e., the drive signal 2009 is turned on and off) at each opening and subsequent closing of the valve needle. The valve needle 53 then remains closed (and the excitation device 145 remains unexcited by the drive signal generator 2007) for a relatively longer period of time such as the rest of the engine cycle before the next injection event occurs.
When the drive signal 2009 from the drive signal generator 2007 is turned off, the ultrasonic waveguide 121, and more particularly the waveguide assembly 150 in the illustrated embodiment, transitions to what is referred to herein as a ring down mode of the fuel injector 21. In this ring down mode, the waveguide assembly 150 is undriven by the signal generator 2007 but is otherwise free to continue vibrating as its motion decays (i.e., rings down) at a rate corresponding to the amount of damping present in the waveguide assembly. More particularly, once the driving force is removed from the waveguide assembly 150 the assembly will ring down at its natural frequency. In the waveguide assembly 150 of the illustrated embodiment, the ultrasonic waveguide 121 rings down and thus drives vibration of the excitation device 145, and more particularly the piezoelectric rings 147 that are clamped against the mounting member 79. The stress on the piezoelectric rings 147 generates an electrical signal indicative of a ring down frequency 2013 of the waveguide assembly 150.
The control system 2001 further comprises a feedback sensor 2011 that is connected to the excitation device and in the illustrated embodiment is capable of sensing the electric signal (e.g., voltage) generated by the piezoelectric rings during ring down of the waveguide assembly. As one example, the feedback sensor 2011 may comprise a conventional motionally equivalent circuit, and in one suitable embodiment a motionally equivalent circuit having a clamped capacity of approximately 1,000 picofarad. The feedback sensor 2011 is capable of transmitting a signal to the controller 2003 indicative of the ring down frequency of the waveguide assembly 150 and the controller is capable of receiving such a signal. In one particularly suitable embodiment the ring down frequency 2013 determined by the feedback sensor 2011 is an average ring down frequency determined over a predetermined number of periods following termination of the drive signal 2009 to the excitation device 145, such as in the range of about 5-10 cycles. It is understood, though, that the ring down frequency 2013 may be averaged over more than 10 periods, or less than 5 periods within the scope of this invention. It is also understood that the ring down frequency may be determined from a single period, such as the first period after termination of the drive signal or a particular period after such termination of the drive signal 2009.
While in the illustrated embodiment of
It is also contemplated that the feedback sensor 2011 may be connected to and/or monitor ring down of the waveguide assembly 150 other than at the excitation device 145. For example, the feedback sensor may monitor motion of the waveguide 121 component of the waveguide assembly 150 substantially at any location along the length of the waveguide, and then convert the motion to an electrical signal that is sent to the controller 2003.
In accordance with one method for controlling operation of the fuel injector 21 (i.e., broadly, the ultrasonic liquid delivery device), the controller 2003 adjusts the excitation frequency of the drive signal 2009 sent to the excitation device 145 in response to the ring down frequency 2013 determined by the feedback sensor 2011 during the previous ring down mode. More suitably, as illustrated in
To facilitate a sufficiently powerful ring down signal of the waveguide assembly 150 (e.g., to be sensed by the feedback sensor 2011), it is contemplated in one embodiment that the drive signal 2009 generated by the drive signal generator 2007 is turned off at its peak (as opposed to the zero-crossing or elsewhere between peaks). In this manner the excitation device 145 (and hence the waveguide 121) is displaced as much as possible (and thus has more energy that must be damped out during ring down) when the signal is terminated. It is understood, however, that the drive signal 2009 may be turned off other than at its peak and remain within the scope of this invention.
In one suitable embodiment, the controller 2003 operates according to an ignition (or cold start) sequence upon start-up of the engine in which the fuel injector 21 is incorporated. The purpose of the ignition sequence is to approximate an initial excitation frequency 2005 that is close to or at the natural frequency of the waveguide assembly 150 achieve an efficient start-up of the engine. For example, in one such ignition sequence the controller 2003 signals the drive signal generator 2007 to generate a short drive signal 2009 (e.g., a pulse) in the form of a wave, and more suitably a square wave in a range close to an operating frequency for which the waveguide assembly 150 was originally designed, such as within about 1,000 kHz. For the fuel injector 21 of the illustrated embodiment, which is intended to operate at approximately 40 kHz, such a square wave may be at a frequency in the range of about 39 to about 41 kHz. This short wave signal is suitably conducted with the valve needle 53 in its closed position but may also be conducted in combination with opening the valve needle without departing from the scope of this invention. Alternatively, a short impulse wave that is a fraction of the expected wave period, such as about one-tenth of the expected period, may be used. It also contemplated that other impulses or signals may be used to initiate ring down of the waveguide assembly 150 without departing from the scope of this invention.
When the short wave signal terminates, the ring down response of the waveguide assembly 150 is initiated. After a fixed delay period following termination of the wave signal to permit noise in the system to dissipate, a ring down signal is determined by the feedback sensor 2011 and the controller 2003 subsequently operates as discussed above and illustrated in
In the method described above, the difference between the ring down frequency 2013 and the excitation frequency 2005 is determined for each pulse of a multiple pulse injection event. It is understood, however, that the ring down frequency 2013 may be determined only once during each multiple pulse injection event, such as on the first pulse or the last pulse of such an event. In such an embodiment the excitation frequency 2005 would be adjusted by the controller 2003, if necessary, on the first pulse of each multiple pulse injection event. It is also contemplated that the ring down frequency 2013 may be monitored more infrequently than discussed above without departing from the scope of this invention.
It is also contemplated that in some embodiments the valve needle 53 may be opened and closed during the multiple pulses of a single engine cycle while leaving the waveguide assembly 150 excited (i.e., instead of turning it on and off with each opening and closing of the valve needle. In such an embodiment, the waveguide assembly 150 is excited during the first pulse of a multiple pulse engine cycle, along with opening of the valve needle 53—and the excitation signal is not turned off until the valve needle is to be closed following the last pulse of the engine cycle. The excitation frequency 2005 is then adjusted before the next engine cycle and remains fixed during the multiple pulses of the next cycle.
It is understood that in some liquid delivery devices, the waveguide assembly 150 may not fully ring down before the next excitation mode (or injection event) is to occur. To this end, in one embodiment the control system 2001 monitors the ring down during the ring down mode and, if ring down is still present when the next pulse is to occur the controller 2003 signals the drive signal generator 2007 to generate a signal 2009 in phase with the ring down signal. In another embodiment a resistive load may be applied to the waveguide assembly 150 to artificially damp out the ring down.
While in the control system 2001 operation described above adjustment of the excitation frequency 2005 is based on a determined difference between the excitation frequency and the ring down frequency 2013, it is contemplated that other methods may be used to determine a needed excitation frequency adjustment. For example, in one alternative embodiment the controller 2003 may determine a phase error between the drive signal 2009 and the ring down signal obtained by the feedback sensor 2011. The controller then determines a needed frequency shift, if necessary, for the excitation drive signal 2009 to be in phase with the ring down signal. To determine such a phase error, the drive signal 2009 is suitably terminated (i.e., to initiate ring down) when the signal is at its peak.
When introducing elements of the present invention or preferred embodiments thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
This patent application is a continuation-in-part patent application of U.S. patent application Ser. No. 11/337,634 filed on Jan. 23, 2006, the entire disclosure of which is incorporated herein by reference.
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