Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
  • B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
  • B41J2/01—Ink jet
  • B41J2/015—Ink jet characterised by the jet generation process
  • B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
  • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
  • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
  • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers
  • B05B17/0638—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers spray being produced by discharging the liquid or other fluent material through a plate comprising a plurality of orifices
  • B05B17/0646—Vibrating plates, i.e. plates being directly subjected to the vibrations, e.g. having a piezoelectric transducer attached thereto
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M2205/00—General characteristics of the apparatus
  • A61M2205/33—Controlling, regulating or measuring
  • A61M2205/3306—Optical measuring means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
  • B41J2202/00—Embodiments of or processes related to ink-jet or thermal heads
  • B41J2202/01—Embodiments of or processes related to ink-jet heads
  • B41J2202/15—Moving nozzle or nozzle plate

Definitions

• the present invention relates generally to the filed of fluid injection and more specifically to fuel injection, fluid dispensing, and non-aerosol spray.
• the invention provides a means for metering flow rate by electronic control of oscillations of a membrane.
• the fluid injection system is particularly advantageous in vehicle engines for fuel injection, and for liquid dispensing in medical and chemical laboratories.
• a means for injecting fuel into the cylinder of an engine and the proper time in the cycle of operation is a necessary component for operation of a compression ignition engine.
• Injection of fuel into either the manifold or into the cylinder on the intake stroke can be employed in spark ignition engines.
• the fuel injection system must do the following: 1) Inject the quantity of fuel demanded by the load on the engine and maintain this metered quantity constant from cycle to cycle and from cylinder to cylinder;
• the present invention provides an entirely new and innovative fluid injection device that is especially advantageous in applications that require precise metering of ejection of fluid droplets.
• a particularly important application is the automotive fuel injection system.
• the injector generates microscopic droplets of fuel that are readily atomized.
• the ejection flow rate may be controlled by electronic means such as a microprocessor.
• the manufacturing cost of this injection device is only a fraction of the cost of a mechanical injector.
• the present invention may also be advantageous in laboratory and medical applications for fluid dispensing and fluid metering.
• the principal innovative feature of the present invention is that it is capable of ejecting droplets of fluid and provide a simple means for controlling the ejection rate without kinematic or acoustic elements or a pump and therefore reduces the manufacturing cost and improves the accuracy of the ejection system.
• the control over the ejection rate may be provided directly by a microprocessor which further increases the accuracy and reduces the cost of the system.
• a membrane of a selected shape is mounted at its perimeter to a base.
• the base in the preferred embodiment is a piezoelectric device.
• the membrane is shaped so that its cross-section is reduced toward its center.
• the piezoelectric device is activated by an oscillating electrical signal the frequency of which is preferably equal to or close to the natural frequency of the membrane.
• a second or higher modal frequency is utilized. Because of the selected frequency of oscillation thereof, the center area of the membrane oscillates over a distance which is significantly greater than the oscillation of the base.
• this oscillation distance or amplitude at the base is one ten-thousandth of an inch.
• the amplitude of oscillation at the center of the membrane is fifteen to twenty times greater than that at the base.
• the actual ratio of center oscillation amplitude to base oscillation amplitude is also a function of the structural damping of the membrane.
• the membrane is highly damped so that the amplitude in its center area is extremely responsive to variations in the base amplitude.
• the center area of the membrane is provided with one or more apertures which, in the preferred embodiment of the invention described herein, are tapered in cross-section. One opening of each tapered aperture is in fluid communication with a reservoir of fuel or other liquid.
• the other opening of the aperture is positioned at an appropriate distance from the target which could be a combustion chamber towards which microscopic droplets of fluid from the reservoir are to be propelled.
• the amplitude of the center area of the membrane is above a predetermined threshold, the interaction between each tapered aperture and the fluid reservoir, will cause the fluid inside the aperture to compress in the first half of the oscillation cycle and decompress in the second half of the oscillation cycle. The decompression creates cavitation that tears away a droplet of fluid upon each excursion of the membrane. It has been found that by reducing the amplitude of the oscillations below the aforementioned preselected threshold, fluid droplets will not be ejected.
• It is still an additional object of the present invention to provide a droplet injection device comprising a membrane provided with tapered apertures that oscillate with frequency and amplitude that produce compression and cavitation of a fluid inside the aperture during each cycle of oscillation.
• Fig. 1 is a schematic illustration of the fluid ejecting device of the present invention shown configured for use for fuel injection;
• Fig. 2 is a schematic illustration of the present invention shown in its oscillating configuration
• Fig. 3 is a top view of the membrane of the present invention
• Fig. 4 is a bottom view of the membrane of the present invention.
• Fig. 5 is an enlarged cross-sectional view of the center area of the membrane illustrating that portion of the membrane shown in Fig. 2 in the circle labeled "see Fig. 5";
• Fig. 6 is an enlarged elevational view of the center area of the membrane of the present invention showing a preferred aperture shape
• Figs. 7 and 8 are schematic illustrations of the fluid characteristic within a tapered aperture during each half of an oscillation cycle.
• Figs. 9 and 10 are schematic illustrations of an alterative embodiment which employs a different structure for producing mechanical oscillations.
• the fluid ejection device 10 of the present invention comprises a membrane 12 having a perimeter area 14 and a center area 16.
• the perimeter 14 of membrane 12 is affixed to an oscillator 18 which may for example be piezo-ceramic.
• the center area 16 of membrane 12 is provided with a planar surface 15 through which there are apertures 22.
• the portion of center 15 having the apertures is in contact with a source of fluid 17 which supplies fluid 19 to produce an ejection of fluid droplets 20.
• the oscillatory motion of the membrane 12 is shown in Fig. 2. It will be seen therein, that the perimeter 14 of the membrane 12, by virtue of its contact with the oscillator 18, oscillates in a vertical direction as viewed in Fig.
• One is the shape of the membrane 12 and the other is the frequency of oscillation that is selected for activation of the oscillator 18. More specifically, membrane 12 is configured so that its cross-section is reduced toward the center.
• the membrane configuration may be understood best by referring to Figs. 2, 3 and 4 which illustrate a preferred embodiment thereof.
• the apertures 22 in membrane 12 may be understood best by referring to Fig. 5 and 6.
• the center portion 15 of the membrane 12 is provided with apertures 22, each characterized by a tapered wall 24, forming a large opening 26 on one side thereof.
• the thickness of the center 15 of the membrane 12 in the preferred embodiment shown herein is 0.003 inches.
• Each aperture 22 is positioned at or near the center of the membrane and is circular in shape with large opening 26 having a radius of 0.005 inches and the small opening 28 thereof having a radius of 0.0015 inches.
• the shape of membrane 12 and, in particular, the reduction in cross-section of the membrane between its perimeter 14 and its center 16, is selected to provide a significant increase in amplitude of oscillation between the perimeter and the center of membrane 12. This increase in oscillation amplitude has been found to occur at particular frequencies of oscillation of the membrane 12 such as at the second harmonic of the natural oscillating frequency of the membrane.
• the oscillation amplitude is 0.0001 inches at the perimeter.
• the frequency of oscillation is approximately 60,000 Hz., which corresponds to the second modal frequency of the membrane 12.
• the fuel droplet ejection level that is the level above which the amplitude of oscillation of the center 15 of the membrane 12 causes fuel droplets to be ejected therefrom, is approximately 0.0016 inches.
• the perimeter oscillation is adjusted so that the center oscillation varies in amplitude from cycle to cycle, so that it is just above the ejection level and below the ejection level upon alternate cycles.
• the actual ejection level threshold that is the actual oscillation amplitude of the center of the membrane which causes the ejection of fuel droplets, depends upon the characteristics of the fluid selected, as well as the shape and dimensions of the aperture 22. In the particular refereed embodiment shown herein, the ejection level is achieved using gasoline fuel. As shown in Figs.
• the fluid 19 continuously adheres through solid/fluid surface interaction to the large opening 26 of aperture 22.
• the fluid is compressed in the first half of the oscillation (Fig. 7) when the membrane strokes toward the fluid the decompresses in the second half of the oscillation cycle (Fig. 8) .
• the decompression occurs simultaneously when the membrane strokes away from the fluid reservoir.
• One droplet is ejected each time the amplitude of oscillation of the aperture element 15 exceeds the ejection level threshold.
• the number of droplets and spacing therebetween, are a function of the frequency of oscillation. In the preferred embodiment hereof, at a 60,000 Hz.
• FIGs. 9 and 10 An alternative embodiment of the invention is illustrated in Figs. 9 and 10.
• This alternative embodiment is merely one example of the numerous additional implementations that may be employed to produce oscillating action with at least one tapered aperture.
• this embodiment is similar to an acoustic tone generator, in that it comprises a membrane 30 having a piezoelectric layer 31.
• the membrane which is provided with tapered apertures 28 near its center, encloses a container 32 which comprises a fluid supply line 33. Terminals 35 permit the application of an alternating voltage to the piezoelectric layer 31 which then responds by alternating expansion and contraction membrane 30 bows in and out in response to the alternative voltage thereby producing the fluid-droplet ejection described for the preferred embodiment.
• the invention comprises a membrane having a perimeter and center area, the center area having a thinner cross-section than the perimeter for amplification of the oscillation amplitude.
• the perimeter is affixed to a mechanical oscillator for imparting oscillatory motion to the perimeter at a selected frequency and of a selected amplitude.
• a fuel supply or supply of other fluid is in fluid communication with a tapered hole of the membrane thereby supplying fluid to be ejected from the tapered hole upon each oscillation thereof toward a target each time the oscillation amplitude exceeds a predetermined threshold amplitude.
• the selected frequency of operation is at least a second harmonic of the natural frequency of the oscillation of the membrane, the perimeter of the membrane is oscillated by a piezoelectric element or other mechanical oscillator which oscillates in response to an applied electric voltage.
• the center oscillation amplitude of the membrane is at least 10 times greater than the perimeter oscillation amplitude when the average structural damping of the membrane is at least 10 percent.
• a damping ratio of 10 percent or greater is preferred to use in the present invention in order to make the center of the membrane extremely responsive to variations of the oscillating amplitude at the perimeter of the membrane.

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Cited By (22)

Citations (4)

• 1992
  • 1992-06-18 WO PCT/US1992/005275 patent/WO1993001404A1/en active Application Filing

Patent Citations (4)

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