WO2008149334A2

WO2008149334A2 - Nebulizer and driver circuity therefor particularly useful for converting liquids to fine sprays at extremely low rates

Info

Publication number: WO2008149334A2
Application number: PCT/IL2008/000567
Authority: WO
Inventors: Amiram Keshet; Andrei Lavrentiev
Original assignee: Shira Inc-P.D. Ltd.
Priority date: 2007-06-04
Filing date: 2008-04-29
Publication date: 2008-12-11
Also published as: WO2008149334A3; IL183643A0

Abstract

A nebulizer for nebulizing a liquid into a fine spray and for introducing said fine spray into a gas flowing through a conduit, said nebulizer includes a housing including a lower section for receiving a piezoelectric device and driver circuitry therefor, an intermediate section including an inlet for inletting the liquid to be nebulized, and an upper section for receiving the nebulized liquid; a piezoelectric device in the upper part of the lower section of the housing for nebulizing said liquid when received in said intermediate section of the housing and when the piezoelectric device is driven by said driver circuitry; and a restrictor at the upper end of said upper section of the housing communicating with said conduit for restricting the flow of nebulized liquid into the as flowing through said conduit. The embodiments described are capable of nebulizing a liquid at a rate of less than 5 ml/hr, and are therefore particularly useful for nebulizing a fuel combustion catalyst in a vehicle internal combustion engine.

Description

NEBULIZER AJVD DRIVER CIRCUITY THEREFOR

PARTICULARLY USEFUL FOR CONVERTING LIQUIDS TO FINE SPRAYS AT EXTREMELY LOW RATES

FIELD AND BACKGROUND OF THE INVENTION The present invention relates to nebulizers, namely to devices which convert a liquid to a fine spray and to driver circuitry for nebulizers. Such devices are used in a wide variety of applications, including horticulture for growing plants aeroponically or conventionally, humidification control, medicated sprays, and the like.

A particularly important application of such nebulizers is in the delivery of a fuel combustion catalyst to vehicle internal combustion engines, such as described for example in International Patent Application Nos. PCT/US2005/040333 (WO 2006/052909), and PCT/US2005/043947 (WO 2006/062904). In such applications, the fuel combustion catalyst is to be delivered in finely— atomized form, and at extremely low rate, to the air intake of the combustion zone. The present invention is particularly useful in such catalyst delivery devices, and is therefore described below with respect to such an application.

For an efficient catalyst delivery device of this type, it is critical that the liquid containing the catalyst be atomized into extremely small and uniform droplets, that the rate of delivery of such nebulized liquid be controllable up to a very small rate, that the rate of delivery of such nebulized liquid be easily changeable as desired for any particular application, and that there be a minimum of sloshing of the liquid in the nebulizer caused by engine and/or road vibrations or angular changes in the vehicle.

OBJECT AND BRIEF SUMMARY OF THE PRESENT INVENTION

An object of the present invention is to provide a nebulizer for converting a liquid to a fine spray having advantages in one or more of the above respects making it particularly useful for the above application, but also useful in many other applications. Another object of the invention is to provide novel driver circuitry for driving nebulizers in an efficient manner.

According to one aspect of the present invention, there is provided a nebulizer for nebulizing a liquid into a fine spray and for introducing said fine spray into a gas flowing through a conduit, said nebulizer comprising: a housing including a lower section for receiving a piezoelectric device and driver circuitry therefor, an intermediate section including an inlet for inletting the liquid to be nebulized, and an upper section for receiving the nebulized liquid; a piezoelectric device in the upper part of the lower section of the housing for nebulizing said liquid when received in said intermediate section of the housing and when the piezoelectric device is driven by said driver circuitry; and a restrictor at the upper end of said upper section of the housing communicating with said conduit for restricting the flow of nebulized liquid into the as flowing through said conduit.

Several preferred embodiments are described for purposes of example. In one described preferred embodiment, the restrictor includes a cap closing the upper end of the upper section of the housing and formed with one or more small passageways defined by one or more small openings in the cap. In a second described preferred embodiment, the restrictor includes a small diameter nozzle for further nebulizing the liquid and for restricting the flow of the nebulized liquid into the gas flowing through the conduit. Preferably, the nozzle has a diameter of less than 10 microns.

Further, in one described preferred embodiment, the upper section of the housing includes a splash chamber of funnel shape having a small-diameter lower end, and a large diameter upper end facing the restrictor. In another described embodiment, the liquid to be nebulized is corrosive to the piezoelectric device, and the piezoelectric device is separated from the liquid by an inert material in the form of a separator having a bottom wall of elastomeric material overlying the piezoelectric device, and configured to receive the liquid to be nebulized.

According to another aspect of the present invention, there is provided a driver circuitry for driving the piezoelectric device, the driver circuitry comprising a power supply a power supply for supplying AC power to the piezoelectric driver; a voltage sensor for sensing the AC voltage supplied to the piezoelectric device and for producing an output signal corresponding thereto; a current sensor for sensing AC current through the piezoelectric device and for producing an output signal corresponding thereto; a phased loop discriminator for receiving the output signals of the voltage and current sensors and for outputting a signal corresponding to the difference in phase between the voltage and current sensor outputs; and a controller receiving the output signal of the phase loop discriminator and controlling the power supply to reduce the difference in phases to substantially zero.

As will be described more particularly below, a liquid nebulizer constructed according to one or more of the foregoing features is capable of producing a uniform spray of extremely small droplets, at an extremely low rate which rate can be conveniently changed as and when desired, and which avoids sloshing of the liquid within the nebulizer caused by engine and/or road vibrations or changes in vehicle angle. By including the separator, as set forth above, the nebulizer may also be used with respect to liquids which would otherwise be corrosive to the piezoelectric device. The foregoing features make the nebulizer particularly useful for delivering a catalyst to a vehicle fuel combustion zone in order to permit more efficient combustion of the fuel, but it will be appreciated that the invention, or various aspects to be described below, may be used in many other applications.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

Fig. 1 is a diagrammatical view illustrating one form of nebulizer system constructed in accordance with the present invention;

Fig. 2 is a perspective view illustrating the nebulizer device in the system of Fig. 1;

Fig. 3 is a side elevational view illustrating the nebulizer device of Fig. 2; Fig. 4 is an end elevational view of the nebulizer device of Fig. 2; Fig. 5 is a longitudinal sectional view along lines A — A of Fig. 4; Fig. 6 illustrates the lower section of the housing in the nebulizer device of Fig. 2;

Figs. 7 and 8 are perspective and end views, respectively, of the intermediate housing section in the nebulizer device of Fig. 2;

Fig. 9 illustrates the upper housing section of the nebulizer device of Fig. 2; Fig. 10 illustrates the coupling connector between the intermediate and upper housing sections of the nebulizer device of Fig. 2;

Fig. 11 illustrates a funnel-shaped splash chamber in the upper housing section; Fig. 12 illustrates a restrictor in the upper part of the upper housing section;

Fig. 13 illustrates a T-fitting outlet in the upper housing section of the nebulizer;

Fig. 14 diagrammatically illustrates another nebulizer system constructed in accordance with the present invention for delivering a catalyst to a vehicle engine to permit more efficient combustion of the fuel;

Fig. 15 is a diagrammatic sectional view illustrating the nebulizer in the system of Fig. 14;

Fig. 16 is a three-dimensional view, from the top, of the nebulizer of Fig. 15; Figs. 17 and 18 are top and bottom views, respectively, illustrating the separator in the nebulizer of Fig. 15;

Fig. 19 is a sectional view of the separator of Figs. 17 and 18;

Fig. 20 is an enlarged fragmentary view of the encircled portion of Fig. 19;

Fig. 21 is a diagrammatic view illustrating a nebulizer including both a funnel-shaped splash chamber is shown in Fig. 11 and the separator as shown in Figs. 15-20;

Fig. 22 illustrates a driver circuitry particularly useful for driving the piezoelectric device in the above-described embodiments.

It is to be understood that the foregoing drawings, and the description below, are provided primarily for purposes of facilitating understanding the conceptual aspects of the invention and possible embodiments thereof, including what is presently considered to be a preferred embodiment. In the interest of clarity and brevity, no attempt is made to provide more details than necessary to enable one skilled in the art, using routine skill and design, to understand and practice the described invention. It is to be further understood that the embodiments described are for purposes of example only, and that the invention is capable of being embodied in other forms and applications than described herein.

DESCRIPTION OF PREFERRED EMBODIMENTS

Overall Construction of the Nebulizer System of Figs. 1—13 With reference to Fig. 1, there is illustrated a nebulizer device, generally designated 2, constructed in accordance with the present invention for use in a system for the delivery of a combustion catalyst in the form of a spray of finely divided droplets to the air intake of a vehicle internal combustion engine, such as described in the above-cited PCT Patent Applications. The system illustrated in Fig. 1 includes, besides nebulizer device 2, a liquid catalyst reservoir 3 containing a liquid including finely-divided particles of the combustion catalyst. The catalyst liquid is to be delivered, via a solenoid control valve 4 and a feed line into the inlet 5 of nebulizer device 2. Valve 4 is controlled by a liquid-level sensor 6 within nebulizer device 2, for maintaining a predetermined level of the liquid therein. A piezoelectric device 7, such a piezoelectric crystal, is disposed within nebulizer device 2 to atomize the catalyst liquid therein and to discharge it into the air intake of the vehicle engine. Piezoelectric device 7 is driven by driver circuitry 7a within the nebulizer device energized by inlet power supply line 8, and controlled by the computerized controller 9.

As will be described more particularly below, and as shown particularly in Figs. 2—5, nebulizer device 2 includes a housing having a lower section, generally designated 10, containing the piezoelectric device 7 and its driver circuitry 7a; an intermediate housing section, generally designated 20 for receiving and maintaining the liquid to be nebulized at a predetermined level above the piezoelectric device 7; an upper housing section, generally designated 30 for receiving the finely atomized catalyst liquid (catalyst fog) produced by the piezoelectric device 7; and a coupling connector, generally designated 40, for coupling the intermediate housing section 20 to the upper housing section 30. Nebulizer device 2 further includes a funnel-shaped splash chamber 50 in the upper housing section 30 for directing the nebulated liquid to the upper end of the upper housing section while, at the same time, reducing splashing or sloshing of the liquid within the intermediate housing section 20 caused by the engine or road vibrations; a restrictor, generally designated 60 for restricting the outflow of the nebulized liquid to a desired low rate; and a T-fitting 70 attached to the upper end of the upper housing section 30 for discharging the nebulized fluid into the air intake of a combustion engine.

The lower housing section 10 of nebulizer device 2 is more particularly illustrated in Fig. 6. As mentioned above, it houses the piezoelectric device 7, as well as its driver circuitry 7a, and it is therefore preferably made of metal (such as aluminum) for good heat dissipation. In addition, it is formed with external radiating ribs 11 to increase the dissipation of the heat generated by the drive circuitry 7a within it. One end of the lower housing section 10 is closed by an end wall 12 through which the power supply 8 (Fig. 1) passes for the driver circuitry 7a within it. The opposite end of the lower housing section 10 is formed with a threaded outer cylindrical surface 13 for receiving the intermediate housing section 20, and is further formed with an annular inner shoulder 14 for receiving the piezoelectric device 7

(Fig. 1). As shown particularly in Fig. 5, the inner shoulder 14 first receives a sealing ring 15 for sealing the driver circuitry 7a from the liquid within the intermediate housing section 20. It then receives the piezoelectric device 7 which is immersed in the liquid within the intermediate housing section 20 when the latter section is attached to the lower housing section 10.

As seen particularly in Fig. 7, the intermediate housing section 20 includes a cylindrical part 21 formed with internal thread 22 at one end for threading onto the external threads 13 of the lower housing section 10 so as to firmly grip the seal 15 sealing the liquid within the intermediate housing section 20 from the interior of the lower section 10. Intermediate section 20 further includes a side compartment 23 having an inlet 24 at one end for receiving the inlet feed line 5 from the liquid reservoir 3 via valve 4 (Fig. 1).

Side compartment 23 further includes liquid-level sensor 6, schematically shown in Fig. 1, in the form a permanent magnet 25 presettable within a channel 26 in a wall of the side compartment to the desired height of the liquid above the piezoelectric device 7. Permanent magnet 25 cooperates with another magnet 27 which floats on top of the liquid within the side compartment to sense the level of the liquid therein, and thereby the level of the liquid within the cylindrical part 21 defining the column of the liquid above the piezoelectric device 7. As shown in Fig. 8, side compartment 23 further includes a pair of outlet connectors 28 connected to control valve 4 (Fig. 1) to control the supply of the liquid from reservoir 3 to the side compartment via the inlet 5.

Preferably, side compartment 22 is made of transparent material, so that the liquid level within that compartment can also be visually seen from the outside. The upper housing section 30, as illustrated in Fig. 9, is of cylindrical configuration and is used to contain finely atomized catalyst liquid or fog generated by the piezoelectric device 7. Upper section 30 is also preferably transparent so that the nebulized liquid can also be visually seen, and is formed with a series of openings 31, 32 in its opposite ends for coupling to the intermediate housing section 20 and the T-fitting 70, respectively.

Coupling connector 40, as seen particularly in Fig. 10, is used for coupling the intermediate housing section 20 to the upper housing section 30. It includes a cylindrical part 41 adapted to receive, at its opposite ends, the intermediate housing section 20 and the upper housing section 30. It further includes a rectangular side extension 42 for receiving the side compartment 23 of the intermediate housing section 20. Rectangular side extension is formed with a pin 43 adapted to be received within opening (not shown) at the upper end of the side compartment 23 (Fig. 7), to reinforce or brace the connection between the intermediate housing section 20 and the upper housing section 30.

The funnel— shaped splash chamber 50, as illustrated in Fig. 11, is disposed primarily within the upper housing section 30 of nebulizer device 2. It includes a small diameter lower end 51 of cylindrical configuration, and an upper end 52 of conical configuration increasing uniformly in diameter towards its outer end. The small diameter lower end 51 is open so as to enclose the piezoelectric device 7, and is formed with three feet 53 spaced around its circumference to stably support the splash chamber over the piezoelectric device 7. Its upper conical end 52 is formed with a pair of openings 54 defining free-flow passageways for the liquid between its inner face and its outer face.

Splash chamber 50 is introduced into the housing of nebulizer device 2 such that the lower small-diameter end 51 of the splash chamber is located within the intermediate housing section 20, whereas its upper conical end 52 is located within the lower part of the upper housing section 30. Thus, as shown in Fig. 1, the lower end 51 of the splash chamber encloses the piezoelectric device 7 and defines a column of the liquid over the piezoelectric device, arriving to about the juncture line 54 of the two ends 51 and 52, whereas the upper conical end 52 of the baffle, located within the lower end of the upper housing section 30, is spaced from the upper end of the upper section 30, and directs the nebulized liquid to the upper end of housing section 30. As will be described more particularly below, the lower cylindrical end 51 of splash chamber 50 maintains a constant column of the liquid above the piezoelectric device 7, and thus reduces splashing and sloshing in the nebulizer device caused by the engine or road vibrations or by changes in the angular position of the vehicle, S while the openings 55 in conical end 52 permit the liquid to freely pass from one face to the other of the splash chamber and thereby to maintain the constant level even under extreme sloshing conditions.

Restrictor 60 (Fig. 12) at the upper end of the upper housing section 30 is in the form of a cap closing that section of the housing, except for a plurality of small openings spaced circumferentially around the cap. Thus, as shown in Fig. 12, restrictor 60 includes a disk 61 with a plurality of spacers 62 spaced around its periphery, such that the spaces 63 between spacers 62 define small passageways for the nebulized liquid. Preferably, the upper surface 61a of the restrictor increases slightly in thickness to a central region 61b, which is of uniform thickness, for strengthening purposes.

Restrictor 60 is firmly secured to the upper end of the upper housing section 30 by T-connector 70, as illustrated in Fig. 13. Thus, T-connector 70 includes: a middle leg 71 attachable to the upper end of the upper housing section 30, securely holding the restrictor 60 therein; a second leg 72 at one end for coupling to the air supply duct; and a third leg 73 at the opposite end for connection to the combustion zone to receive the air with the finely atomized catalyst and its liquid carrier mixed within the air applied to the combustion zone. Operation of the Nebulizer System of Figs. 1-13 The operation of the nebulizer system illustrated in Figs. 1-13 of the drawings will be apparent from the description above.

Thus, the nebulizer device 2 is assembled as shown in Figs. 1—5 such that the piezoelectric device 7 is mounted at the upper end of the lower housing section 10 and is exposed to the open end of the intermediate housing section 20. The small- diameter end 51 of the funnel-shaped splash chamber 50 encloses the piezoelectric device 7, and the upper conical end 52 of splash chamber 50 is located within the upper housing section 30. Connector coupling 40 connects the two housing sections 20, 30 together, with the side extension 42 of the coupling connector securely engaging the side compartment 23 of the intermediate housing section 20. Restrictor 60 is placed over the upper end of the upper housing section 30 and is secured in place by T-fitting 70.

Liquid reservoir 3, containing the catalyst particles in a liquid carrier, is connected via valve 4 to inlet 5 received in inlet opening 24 (Fig. 8) in the side compartment 23 of the intermediate housing section 20. In addition, the outlet terminals 28 of the intermediate housing section 20 are connected via line 6 to valve 4 so as to control the valve by the liquid level sensor 6 in order to maintain a uniform liquid level within side compartment 23, and thereby within the main cylindrical chamber 21 of the intermediate housing section 20. As indicated earlier, the liquid level sensor within side compartment 23 includes the fixed magnet 25 fixed at the desired liquid level height, cooperable with the floating magnet 27 floating on top of the liquid level within that compartment. Thus, if the liquid level within that compartment drops below the desired liquid level, valve 4 would be actuated to feed more liquid via inlet 5 into compartment 23; and if the actual level of the liquid within that compartment rises higher than desired, valve 4 would be closed until the level recedes to the desired height.

The level of the liquid within compartment 23 determines the height of the column of liquid above the piezoelectric device 7 within the intermediate housing section 20. This is done, as described above, by the lower cylindrical end of splash chamber 50 which is maintained relatively constant despite engine vibration, road vibration, changes in angle or direction of the vehicle, etc. The openings 54 at the lower part of the conical end 52 of splash chamber 50 permit the free flow of the liquid in either direction, and thereby maintain the level of the liquid over the piezoelectric device substantially constant.

When piezoelectric device 7 is driven via its driver circuitry 8 as powered by the power supply line 9, the mechanical vibrations of the piezoelectric device produce a spray (or fog) of finely divided droplets of the liquid carrier with the catalyst material therein, which spray is directed upwardly through the spaces 63 defined by the spacer elements 62 of restrictor device 60. Restrictor device 60 thus controls the rate of dispensing of the spray to the outlet end of the upper housing section 30 via middle leg 71 of T-fitting 70. The atomized spray of the catalyst material is drawn, by the Venturi effect, into the air inletted via leg 72 of T-connector 70 and outletted to the combustion zone via leg 73 of the connector. The delivery rate of the nebulized catalyst liquid is largely controlled by controller 9, which controls the periods, the frequency and the intensity of operation of the piezoelectric device 7, according to the demands of the vehicle engine. However, the range of delivery rates of the atomized spray (or fog) of catalyst material is determined largely by the spaced small passageways 63 defined by the spacer element 62 around the periphery of restrictor device 60. Since the restrictor device 60 is in the form of a cap applied to the upper end of the upper housing section 30 of the nebulizer device, a plurality of such caps or restrictor devices can be provided for any delivery rate that may be desirable for each particular application. In the embodiment of the invention described above, the desired rate is usually about 1-4 ml/hour, but if any other rate is desired, this may be accomplished by merely substituting the appropriate restrictor cap for the desired rate.

The combustion catalyst used, as well as the liquid carrier therefor, may be any of the known formulations, such as described with respect to the two above-cited PCT Applications. The Nebulizer Systems of Figs. 14-21

Fig. 14 illustrates another nebulizer system constructed in accordance with the present invention, and generally designated 100, including a nebulizer 102 for the delivery of a combustion catalyst in the form of a spray of finely divided droplets to the air intake of a vehicle combustion engine. In this case, however, the catalyst is highly corrosive to the piezoelectric device, and therefore nebulizer 102 includes a separator, to be described more particularly below with respect to Figs. 15 and 17—20, which protects the piezoelectric device from the catalyst liquid. In Fig. 14, the catalyst liquid is contained within a reservoir 103 in the form of a replacement bag supported by a frame 104 mounted to the vehicle by fastener elements 105. Frame 104 further supports a pump and electronics unit 106 for controlling the flow of the catalyst liquid to the nebulizer 102 by a feed tube 107. The system further includes a gravity overflow return tube 108 for returning excess catalyst liquid back to the reservoir 103.

Also seen in Fig. 14 are the following connections from or to the pump unit 106 and the electronics sub-assembly therein: electrical line 109 for electrically driving the piezoelectric device within nebulizer 102; electrical connection 110 from the engine ignition switch 111, or a sensor sensing the running of the engine; and a power-supply cable 112 for supplying 12 or 25 volts to the pump unit 106.

Nebulizer 102 includes a housing, generally designated 120, having a lower section 121 receiving the piezoelectric device and its driver circuit driven via electrical line 109; an intermediate section 122 for receiving the liquid to be nebulized via feed tube 107; and an upper section 123 for directing the nebulized liquid or spray into the air intake of the vehicle engine via a T-fitting 124. Fitting 124 has a middle leg 124a connected to housing section 123, an inlet leg 124b for inletting the air to be directed to the engine, and an outlet leg 124c for outletting the inletted air mixed with the atomized catalyst. As will be described more particularly below, the connection between housing section 123 and T— fitting 124 includes a restrictor device 125, in the form of a small-diameter nozzle, which further nebulizes the catalyst liquid into a very fine spray, and restricts the flow of the catalyst spray into the air intake at a desired slow rate. Upper housing section 123 further includes a transparent wall 126 to permit viewing the atomized catalyst liquid outputted from the intermediate housing section 122.

The nebulizer 102 is more particularly illustrated in Figs. 15 and 16. As shown in Fig. 15, the lower housing section 121 houses the piezoelectric device 130 and its driver circuit 131, as in the embodiment of Figs. 1-13. Accordingly, lower housing section 121 is also made of metal, such as aluminum, for good heat dissipation, and is also formed with external radiating ribs 132 to increase the dissipation of the heat generated by the driver circuitry 131.

As also shown in Fig. 15, the upper end of the lower housing section 121 includes an internally-threaded socket 121a receiving an externally-threaded extension 122a in the intermediate housing section 122. The piezoelectric device 130 is clamped between them when the intermediate section 122 is threaded into the lower section 121. As also seen in Fig. 15, the separator 132 is fixed within the intermediate housing section 122 and is spaced above the bottom of that housing section to define a compartment 133. As will be described below, compartment 133 receives a liquid, such as water, for isolating the piezoelectric device 130 from the catalyst liquid introduced into the intermediate housing section 122 above the separator 132.

Separator 132 is more particularly illustrated in Figs. 17-20 of the drawings. It is preferably made as a single unit of elastomeric material which is inert to the catalyst liquid, and thereby protects the piezoelectric device from the catalyst liquid. As shown in Figs. 17-20, separator 132 is of a circular disc configuration, formed in a central region with a depending, circular cup-shaped configuration 133 having a conical side wall 134 and a bottom wall 135. As shown particularly in Figs. 19 and 20, bottom wall 135 is formed with a central circular region 135a of reduced thickness as compared to the thickness of the remainder of bottom wall 135. Preferably, central region 135a of bottom wall 135 is thinner by at least one order of magnitude. For example, the reduced area 135a may have a thickness of 0.1 mm, while the remainder of the bottom wall 135 could have a thickness of 1.0 mm or greater. The peripheral region 136 around the center cup 133 is of decreasing thickness towards the central cup, e.g. at an angle about 2° (Fig. 19), and is formed with an opening 137 laterally of the cup. As shown particularly in Fig. 18, the under surface of separator 132 is integrally formed with a plurality of ribs 138 which radiate outwardly towards the outer rim of the separator and decrease in height towards the outer rim. The outer rim of separator 133 is formed with a downwardly-extending flange 139 (Fig. 19) to facilitate fixing the separator within the intermediate housing section 122.

Elastomeric separator 132 serves to protect the piezoelectric device 130 from the highly corrosive catalyst liquid introduced into the intermediate housing section 122 above the separator, whereas the liquid (e.g. water) in compartment 133 is effective not only to further protect the piezoelectric device from the corrosive catalyst liquid, but also to transmit the ultrasonic vibrations of the piezoelectric device to the catalyst liquid within cup 133 of separator 132. In addition, the specific construction of the separator, particularly the very thin region 135a in the bottom wall 135 of the cup 133, efficiently transmits the ultrasonic vibrations of the piezoelectric device to a column of the catalyst liquid within cup 133 of the separator 132.

As indicated earlier, restrictor device 125 is a small-diameter nozzle which further nebulizes the liquid catalyst and introduces it as a very fine spray into the inlet gas passing through the T— fitting to the combustion chamber of the internal combustion engine. Nozzle 125 has a diameter of not more than 5 microns, preferably 2-3 microns, so as to produce droplets preponderantly (e.g., about 80 per cent( in the 3 micron range. Such an arrangement using nozzle 125 was found effective not only to produce such small-diameter droplets, but also to discharge those droplets at an extremely low rate, e.g., at the rate of less than 5 ml/hr, preferably at a rate 1-4 ml/hr.

Fig. 16 illustrates a modification wherein the upper end of housing section 123 includes a cover plate 126 acting as a restrictor, similar to the restrictor plate 60 of Fig. 12. Plate 126 includes one or more openings 126a, for restricting the outflow of nebulized liquid catalyst from housing section 123. A further cover plate 127 overlies, and is spaced from, plate 126, and is formed with an outlet opening 128 for directing the outflow of the nebulized liquid catalyst into leg 124a of the T— fitting 124. The column of the liquid catalyst in cup 133 above the piezoelectric device

130 is controlled by a liquid— level sensor of a different type from that described with respect to the Figs. 1-13 embodiment. As shown in Fig. 15, the liquid level sensor is in the form of a float 140 overlying a vertical tube 141 received within opening 137 in separator 132. Vertical tube 141 serves as the inlet of the catalyst liquid into housing section 122 above the separator cup 132; and float 141, which floats on the surface of the liquid catalyst, closes the upper end of the vertical tube when the liquid catalyst reaches the desired level. Thus, vertical tube 141 may be moved to the appropriate vertical position according to the desired liquid level of the liquid catalyst.

As further shown in Fig. 15, float 140 includes a depending stem 142 of smaller outer diameter than the inner diameter of vertical tube 141 , for guiding the vertical movements of the float with respect to the vertical tube.

As further seen in Fig. 15, housing section 122 includes a heating coil 143 which may, for example, be controlled by the ignition switch in order to preheat the water within chamber 133 from a cold starting condition. Since housing section 10 is made of a metal (e.g., aluminum), it also acts as a shield preventing RFI (radio frequency interference) with other electronic devices. Operation of the Nebulizer System of Figs. 14-20

It will be appreciated that the nebulizer system 100 illustrated in Figs. 14-20 operates in substantially the same manner as described above with respect to the nebulizer system of Fig. 1-13, with the following main exceptions:

First, the elastomeric separator 132 in the intermediate housing section 122 above the piezoelectric device 130, isolates the piezoelectric device from the liquid catalyst introduced into housing section 122 for nebulization. Thus, such an arrangement is particularly useful where a corrosive material, such as a liquid catalyst, is to be nebulized, thereby extending the working life of the piezoelectric device. The structure of the elastomeric separator 132 as described above, and as illustrated more particularly in Figs. 17-20, and especially the very thin central region 135a of the bottom wall 135 of cup 134, in effect provides a thin membrane for receiving the catalyst liquid to be nebulized. This thin membrane, together with the liquid (e.g. water), in compartment 133, enhances the vibration of the catalyst liquid by the piezoelectric device.

Secondly, the provision of the very small diameter nozzle 125 at the outlet of the nebulizer chamber further nebulizes the liquid catalyst into a very fine spray, wherein the particles are predominantly (e.g. at least about 80 per cent) of 3 microns or less.

Thirdly, the height of the liquid column above the piezoelectric device 130 is controlled by a float 140 rather than an electromagnetic switch, which also automatically closes the inlet (upper end of vertical tube 141) into the nebulizer chamber so as to produce the desired height of the catalyst column over the piezoelectric device.

Fourthly, the nebulizer illustrated in the system of Figs. 14-20 includes a heating coil 143 which can be controlled, e.g. by the ignition switch, to preheat the nebulizer, and particularly the liquid (e.g. water) within chamber 133 separating, with elastomeric separator 132, the liquid catalyst from the underlying piezoelectric device 130.

In all other respects, the nebulizer system 100, illustrated in Figs. 14-20, operates in substantially the same manner as described above with respect to the nebulizer system of Figs. 1—13. The Nebulizer of Fig. 21

Fig. 21 illustrates a nebulizer, generally designated 202, which is of a similar construction as nebulizer 102 in Fig. 15, and therefore corresponding parts have been identified by the same reference numerals to facilitate understanding. The main difference is that nebulizer 202 illustrated in Fig. 21 also includes a funnel-shaped splash chamber 250 in the intermediate and upper housing sections 132 and 133, similar to the funnel-shaped splash chamber 50 illustrated in Fig. 11.

Thus, the funnel-shaped splash chamber 250 illustrated in Fig. 21 includes a small diameter lower end 251 of cylindrical configuration, and an upper end 252 of conical configuration increasing uniformly in diameter towards its outer end. The small diameter lower end 251 is open and overlies cup 133 formed in the separator plate 132. Splash chamber 250 may be otherwise constructed and positioned as splash chamber 50 in Fig. 11 to maintain a constant column of the liquid catalyst above the piezoelectric device 131, and thus reduce splashing and sloshing in the nebulizer device caused by the engine or road vibrations, or by changes in the angular position of the vehicle.

In all other respects, nebulizer 202 illustrated in Fig. 21 is constructed and operates in substantially the same manner as described above with respect to nebulizer 202 of Fig. 15. The Driver Circuitry of Fig. 22

Fig. 22 illustrates a preferred driver circuitry which may be used for driving the piezoelectric device in any of the above-described embodiments. Normally, a driver circuit would have to be tailor— made to produce the maximum output, depending on environmental conditions, such as the liquid to be atomized, its viscosity, the ambient temperature, etc. The driver circuitry illustrated in Fig. 22 enables a maximum output to be produced under any of such environmental conditions. Briefly, the driver circuitry illustrated in Fig. 22 and therein generally designated 300, includes a power supply for supplying AC powder to the piezoelectric device, generally designated 302. As will be described more particularly below, such circuitry further includes a voltage sensor for sensing the AC voltage supplied to the piezoelectric device and for producing an output corresponding thereto, and a current sensor for sensing the AC current through the piezoelectric device and for producing an output corresponding thereto. Both outputs are inputted to a phased loop discriminator 304 which outputs a signal corresponding to the difference in phase between the outputs of the voltage and current sensors. Such phase difference is shown by curves 306 in Fig. 22 The phase difference output of the phased loop discriminator is applied to a controller, in the form of a microprocessor 308, which produces an output signal applied, via a voltage-control oscillator 310 and a signal forming logic 312, to reduce the phase difference to zero, such that the current and voltage curves shown at 306 in Fig. 22 have the same "zero" cross-over point.

As further shown in Fig. 22, the power supply includes a voltage source 314 for supplying power to all the electric components shown in Fig. 22, and a half-bridge rectifier 316 converting the DC voltage to a rectangular AC voltage. The output of rectifier 316 is passed through a band filter 318 before applied to the piezoelectric device 302. Fig. 22 further illustrates the voltage sensor 320, which senses the voltage applied to the piezoelectric device, and the current sensor in the form of a comparator 322 having one input coupled to the piezoelectric device 302, and another input coupled to ground. As shown in Fig. 22, the sensed voltage and current are applied as inputs to the phased loop discriminator 304 which outputs a signal corresponding to the difference in phases.

Fig. 22 further illustrates sensors 324, for sensing various environmental conditions, such as certain parameters of the liquid to be atomized, its viscosity and ambient temperature, etc., and inputs this information to microprocessor 308. Microprocessor 308 may further include inputs from a computer, such as a personal computer 326, to enable manual control of the microprocessor according to particular conditions for the particular application.

While the invention has been described above with respect to several preferred embodiments, it will be appreciated that these are set forth merely for purposes of example, and that many other variations and applications of the invention may be made. For example, the invention could be also used for atomizing water alone (without the catalyst) and mixing the atomized water with air before mixed with fuel in a combustion chamber, e.g., as described in U.S. Patent 7,143,582. In addition, the invention could be used for atomizing medical sprays, or for producing water fogs for growing plants, as described, for example, in U.S. Patents 5,300,260 and 5,136,804.

Many other variations and applications of the invention will be apparent.

Claims

What is claimed is:

1. A nebulizer for nebulizing a liquid into a fine spray and for introducing said fine spray into a gas flowing through a conduit, said nebulizer comprising: a housing including a lower section for receiving a piezoelectric device and driver circuitry therefor, an intermediate section including an inlet for inletting the liquid to be nebulized, and an upper section for receiving the nebulized liquid; a piezoelectric device in the upper part of the lower section of the housing for nebulizing said liquid when received in said intermediate section of the housing and when the piezoelectric device is driven by said driver circuitry; and a restrictor at the upper end of said upper section of the housing communicating with said conduit for restricting the flow of nebulized liquid into the gas flowing through said conduit.

2. The nebulizer according to Claim 1, wherein said restrictor includes a cap closing the upper end of said upper section of the housing and formed with one or more small passageways defined by one or more small openings in said cap.

3. The nebulizer according to Claim 1, wherein said restrictor includes a small diameter nozzle for further nebulizing the liquid and for restricting the flow of the nebulized liquid into the gas flowing through said conduit.

4. The nebulizer according to Claim 3, wherein said nozzle has a diameter of less than 10 microns.

5. The nebulizer according to Claim 1, wherein said restrictor restricts the flow of the nebulized liquid into said conduit to a rate of less than 5 ml/hour.

6. The nebulizer according to Claim 1, wherein said upper section of the housing includes a splash chamber of funnel shape having a small-diameter lower end, and a large diameter upper end facing said restrictor.

7. The nebulizer according to Claim 1, wherein said intermediate section of the housing includes a liquid level sensor for sensing the level of the liquid, and a valve controlled by said liquid level sensor for controlling the level of the liquid therein so as to be at a predetermined height above the piezoelectric device in said lower section of the housing.

8. The nebulizer according to Claim 7, wherein said liquid level sensor maintains a column of the liquid of 30-50 mm above the piezoelectric device.

9. The nebulizer according to Claim 7, wherein said liquid level sensor comprises a first magnet presettable in said intermediate section of the housing to the desired level of the liquid therein above the piezoelectric device, a second magnet floatable on the liquid in said intermediate section of the housing, and an electrical switch actuated by said first magnet when aligned with said second magnet.

10. The nebulizer according to Claim 7, wherein said liquid sensor includes a float, and said valve includes a vertical tube constituting said inlet into the intermediate section of the housing and extending therein for a height determining said predetermined height above the piezoelectric device; said float including a depending stem received in the upper end of said vertical tube for guiding the vertical movement of the float until it seats on the upper end of said vertical tube to close the inletting of the liquid into said intermediate section of the housing.

11. The nebulizer according to Claim 1 , wherein said lower section of the housing is formed of metal and includes an outer surface defining radiating fins for radiating the heat generated by the driver circuitry for the piezoelectric device.

12. The nebulizer according to Claim 1, wherein said inlet of the intermediate section of the housing is formed in a side compartment communicating with the interior of the intermediate section of the housing.

13. The nebulizer according to Claim 1, wherein said upper section of the housing is at least partly of transparent material to permit viewing the nebulized liquid therein.

14. The nebulizer according to Claim 1, wherein said outlet in the upper section of the housing is connected to a middle leg of a T- fitting having one end leg connectable to the conduit through which said gas is introduced, and an opposite end leg for outputting said gas mixed with said fine spray of the nebulized liquid.

15. The nebulizer according to Claim 1, wherein said piezoelectric device is located so as to be immersed in said liquid to be nebulized.

16. The nebulizer according to Claim 1, wherein said liquid to be nebulized is corrosive to said piezoelectric device, and wherein said piezoelectric device is separated from said liquid by an inert material.

17. The nebulizer according to Claim 16, wherein said inert material separating said piezoelectric device from said liquid to be nebulized is a separator having a bottom wall of elastomeric material overlying said piezoelectric device and configured to receive said liquid.

18. The nebulizer according to Claim 17, wherein said elastomeric bottom wall of the separator is included in a cup formation in the central region of the separator to overlie said piezoelectric device.

19. The nebulizer according to Claim 18, wherein said bottom wall of the cup has a central region of elastomeric material to overlie said piezoelectric device, and of substantially smaller thickness than the remainder of the separator to enhance the vibration thereof by said piezoelectric device.

20. The nebulizer according to Claim 19, wherein said separator is an integral unit made of elastomeric material and formed with said cup formation depending from the central region of the separator; and wherein said separator is further formed with ribs radiating from said cup outwardly to the peripheral portion of the separator for enhancing vibrations of the elastomeric bottom wall of the cup.

21. The nebulizer according to Claim 20, wherein said separator is formed with a marginal region around said cup formation, which marginal region is of decreasing thickness from the outer edge of the separator towards said cup; and wherein the diameter of said cup decreases towards its bottom wall.

22. The nebulizer according to Claim 17, wherein the upper section of the housing includes a splash chamber of funnel shape having a small-diameter lower end, and a large-diameter upper end facing, but spaced from, the outlet of said upper section of the housing.

23. The nebulizer according to Claim 1, wherein said driver circuitry comprises: a power supply for supplying AC power to the piezoelectric driver; a voltage sensor for sensing the AC voltage supplied to the piezoelectric device and for producing an output signal corresponding thereto; a current sensor for sensing AC current through the piezoelectric device and for producing an output signal corresponding thereto; a phased loop discriminator for receiving the output signals of the voltage and current sensors and for outputting a signal corresponding to the difference in phase between said voltage and current sensor outputs; and a controller receiving the output signal of the phase loop discriminator and controlling said power supply to reduce the difference in phases to substantially zero.

24. The nebulizer according to Claim 23, wherein said controller includes a voltage controlled oscillator controlled by said output signal of the phased loop discriminator.

25. The nebulizer according to Claim 23, wherein said power supply includes a DC voltage source and an inverter converting the DC voltage to AC; and wherein said controller further includes a signal forming logic circuit controlled by said voltage control oscillator and controlling said inverter.

26. The nebulizer according to Claim 25, wherein said inverter includes a half-bridge rectifier converting the DC voltage to a rectangular AC voltage.

27. The nebulizer according to Claim 23, wherein said controller further includes an environmental sensor for sensing one or more parameters of the environment and for controlling the output of said controller in accordance with the sensed environment parameter or parameters.

28. The nebulizer according to Claim 23, wherein said controller further includes an input from a computer effective to control the output signal of the controller in accordance with the output from said computer.

29. A driver circuitry for a piezoelectric device, comprising: a power supply for supplying AC power to the piezoelectric driver; a voltage sensor for sensing the AC voltage supplied to the piezoelectric device and for producing an output signal corresponding thereto; a current sensor for sensing AC current through the piezoelectric device and for producing an output signal corresponding thereto; a phased loop discriminator for receiving the output signals of the voltage and current sensors and for outputting a signal corresponding to the difference in phase between said voltage and current sensor outputs; and a controller receiving the output signal of the phase loop discriminator and controlling said power supply to reduce the difference in phases to substantially zero.

30. The driver circuitry according to Claim 29, wherein said controller includes a voltage controlled oscillator controlled by said output signal of the phased loop discriminator.

31. The driver circuitry according to Claim 29, wherein said power supply includes a DC voltage source and an inverter converting the DC voltage to AC; and wherein said controller further includes a signal forming logic circuit controlled by said voltage control oscillator and controlling said inverter.

32. The driver circuitry according to Claim 31, wherein said inverter includes a half-bridge rectifier converting the DC voltage to a rectangular AC voltage.

33. The driver circuitry according to Claim 29, wherein said controller further includes an environmental sensor for sensing one or more parameters of the environment and for controlling the output of said controller in accordance with the sensed environment parameter or parameters.

34. The driver circuitry according to Claim 28, wherein said controller further includes an input from a computer effective to control the output signal of the controller in accordance with the output from said computer.