US3194162A

US3194162A - Piezoelectric fuel injector

Info

Publication number: US3194162A
Application number: US237815A
Authority: US
Inventors: Alfred L W Williams
Original assignee: Clevite Corp
Current assignee: Clevite Corp
Priority date: 1962-11-15
Filing date: 1962-11-15
Publication date: 1965-07-13
Anticipated expiration: 1982-07-13

Description

July 13, 1965 A. L. w. WILLIAMS PIEZOELECTRIC FUEL INJECTOR Filed NOV. 15, 1962 3 m 3 8 6 6 2 3 2 2 x I r I I I X x x x x 2 s 2 8 x x x INVENTOR.

ALFRED L.W.WlLLIAMS ATTORNEY 3,194,162 PEEZOELECTREC FUEL lNlECTUR Alfred L. W. Williams, Cleveland, (lhio, assignor to Clevite Corporation, a corporation of {thin Filed Nov. 15, 1962, Ser. No. 237,815 8 Claims. (til. 103-1) This invention relates generally to a fuel injector and,

more particularly, concerns an injector utilizing a piezoficulties arefrequently encountered in the form of clogging and erosion of and within the conduits, which in turn, has madeit diflicult to precisely meter and control small quantities of fluid. Aside from the metering consideration, the erosion and clogging of the conduits also necessitates a very high degree of maintenance to prevent and/or to reduce breakdowns of the system which occur quite frequently.

It is the primary object of this invention to provide a piezoelectrically operated fuel injector constructed in a manner to obviate the need for high pressure liquid fuel delivery to the injector and, to enable a precise metering and control of small quantities of fluid for delivery and/or injection into an internal combustion engine and to facilitate the employment of subjectinvention also in connection with gasoline engines.

It isanother object of this invention to provide a fuel injector in which the fuel is shockexcited momentarily before injection into the internal combustion engine; the shock excitation being effected without shock exciting the primary fluid supply conduits which are maintained at relatively low pressure at all times. This construction in accordance with this feature of the invention avoids the need for tight friction seals, check valves, small conduits and similar requirements.

One aspect of this invention is embodied in a fuel pump suitable for injecting fuel into an internal combustion engine which includes a housing with a fuel inlet connected to a fuel source, and a fuel outlet with a fluid chamber between the fuel inlet and outlet. The piezoelectric drive arrangement is disposed in operative relation to the housing and more particularly to the fluid chamber, the drive arrangement is piezoelectrically responsive to expand and contract along a predetermined axis upon excitation of the piezoelectric element so as to be effective to pressurize the liquid fuel within the chamber. A valve means is affixed to the fuel outlet for normally closing the outlet and to effect fluid passage through the outlet only when the fluid within the chamber is subjected to a predetermined pressure.

Another aspect of this invention resides in the provision of a piezoelectric fuel injector, which includes an injector body with a fluid chamber which has at one end a fuel inlet connected to a source of fuel. A piezoelectric drive arrangement is disposed in operative relation to the housing and more particularly to the fluid chamber,

the drive arrangement and more particularly a piezoelectric element, is piezoelectrically responsive to expand and contract along a predetermined axis upon excitation of the element so as to pressurize the liquid fuel within the chamber. An exponential horn forms part of the injector body or is connected thereto, and in either case is in fluid flow communication with the chamber and the narrow end of the exponential horn is open to provide a fluid outlet. And a valve member is affixed to the outlet to effect fluid passage through the outlet only when the fluid within the exponential horn is subjected to a predetermined pressure.

United States Patent extending portions throughslot 11.

3,194,152 Patented any 13, 1965 For a better understanding of the present invention,

is had to the following description taken in connection with theaccompanying drawings, and its scope will be pointed out in the appended claims.

The single figure in the drawing is a sectional view illustrating this invention.

Referring now to the drawing, there is shown an injector body 10 adapted to be mounted in operable proximity to a cylinder of an internal combustion engine by means of a threaded extension 12. i

The injector body is hollow and comprisesa fluid path including a fuel inlet 14 whichis connectable to a source of combustible fuel, a passageway 16, a fuel chamber 16a and a bleed-line 16b connecting into the chamber to permit liquid fuel to be discharged to eliminate air from the fluid path. Mounted in a fiuid-tight fashion, and either constructed as an integral part of the injector body or as a separate component, is an exponential horn 18. The hollow horn defines the fuel. chamber 16a. The large cross-sectional area of the horn is constructed to receive a stationary bar 19 extending radially across this opening; the narrow and small cross-sectional area is disposed opposite to the cylinder of the internal combustion engine (not shown). Aflixed to the narrow opening of the horn 18 is a smallpintle valve 20. A spring 22 secured to the bar 19 and connected with the .valve 29, holds the pintle valve against the end opening of the exponential horn 18, with a force sufficient to preventfuel leakage from the horn when the injector device is not operated.

Disposed within the injector body and facing the large cross-sectional area of the exponential horn 18 is a piezoelectric drive unit 24 comprising two tubular piezoelectrically responsive elementsZd, suitably polarized and electroded so that the application of an. electric charge will cause the elements to expand and contract along the longitudinal axis of the device. The driveunit 24 is inserted into the injector body by gliding the outwardly Preferably, these piezoelectric elements are made of barium. titanate, lead titanate zirconate or other such polycrystalline ceramic materials. It should be noted that a single ceramic may be used with equal facility.

As is shown in the drawing, the piezoelectric elements 26 are mounted end to end within an insulating. casing 28 and interposed between the two elements are a plurality of aluminum discs 29 effective to apply the electric charge to the electroded surfaces of the piezoelectric elements. These discs are, in turn, electrically connected to a voltage source by means of conductor 31. One outer end of the elements bears against the injector body which is constructed to be rigid against longitudinal displacement. The opposite end of the stack of elements 26 is in bearing relationship with a piston head 30. The casing member 28 is suitablyconstructed to avoid any interference with the engagement between the elements 26 and the piston 33. The piston head bears quite heavily against the piezoelectric elements and forces the elements against the injector body by means of anelongated piston stern member 32 extending concentrically through the elements and being coaxially aligned with the exponential horn. The stem is rigidly. connected to thepiston head and adjustably secured to the injector body by means of an adjustment member 34 aflixed to and between the injector body 14 and the pistonstem member 32 and effective to vary the amount of force that is exercised by the piston head against the elements to precompress them. The stem member 32 is surrounded with an insulating cover 33 to avoid shorting the electric circuit. The contact of the outer end faces of the ceramic elements 26 with the piston head 30 and the injector body 10 defines in eflect .by applying an electric charge to the conductor 31., and

more particularly to the aluminum disc 29, the charge causing an axial movement of the piezoelectric elements relative to the exponential horn 18 thereby narrowing or expanding, as the case may be, the fluid chamber 16a, or cavity, between the piston and the exponential horn. However, the application of the charge may, selectively, cause either a contraction or an elongation of the piezoelectric elements depending upon the polarity applied.

Thus, the application of a voltage having a given polarity will cause the piston to be moved axially toward the exponential horn, whereas the application of voltage ofopposite polarity will cause the piston to be retracted.

Inasmuch as the ceramic elements 26 are incapable of exerting a suitable tension force, the piston is designed to act as a spring to provide compressive stress on the stack of elements under all conditions of charge. The stem member 32 is constructed of a material sufliciently resilient to stretch the stem member in the magnitude of the pump stroke desired. Where fuel injection is to be accomplished by application of a voltage causing axial expansion of the piezoelectric stack, initial tension can be relatively small. On the other hand if injection is to be produced by discharging the stack from a reverse voltage, the initial tension applied to the stem member must produce a stretch exceeding the normal pump stroke, e.g., the normalpiston stroke may be in the order of .002. In this case, a reverse voltage may be applied producing a contraction of the stack in the amount of .002" and to assure compression under the charge condition, the stem member may be given an initial stretch of .004 allowing .002" left in the charged condition.

In either case, the device may be operated on the basis of a mechanical pump or on a shock wave principle which will be hereafter further described. The operation of the device as a mechanical pump requires confinement of liquid trapped between the exponential horn 18 and the piston 30. This is accomplished by providing relatively close clearances between the piston circumference and v the injector body wall, a small cross-sectional fluid inlet line and a check valve 36. When voltage is repeatedly applied to the ceramic elements and upon expansion and contraction of the elements with corresponding movements of the piston face, the fuel is forced through the exponential horn forcing the pintle valve to give way immediately upon an initial pressure rise resulting from the movement of the piston 30.

In the alternate operation of this device, a shock wave is imparted to the liquid fuel stored within the exponential horn either by means of a sudden application of an electric potential of suitable polarity to cause forward movement of the piston or by sudden discharge of the piezoelectric stack while the stack is charged in opposite polarity. A voltage source for supplying a sudden charge is illustrated in United States application Serial No. 231,891 for Piezoelectric Voltage Generator and a voltage source describing a device for releasing a sudden potential in a piezoelectric ceramic is shown and described in co-pending application Serial No. 150,808,

now Patent No. 3,138,174, entitled A Cyclicly Operating Piezoelectric Voltage Source, both cases being assigned to the same assignee as the instant invention. As the shock wave advances into the exponential horn 1.8, its

. pressure is increased and the pintle valve 20 is caused to open permitting small quantities of liquid fuel to be injected into the cylinder of the internal combustion engine. Since the fluid pressure behind the shock wave is relatively low, high pressure is confined to the narrow end of the exponential horn and relatively low pressure prevails within the fluid passageway 16, the fluid inlet 14 and the predominant area of the exponential horn 18.

Those skilled in the art will appreciate that the successful operation of the device on the basis of the shock wave principle will depend upon adequate matching of signal frequency in the ceramic elements with dimensions of the exponential horn. Since dimensions of the horn are necessarily small, the pulse period must necessarily be relatively short. In instances where the pulse duration exceeds requirements for the shock wave operation, the

device will act as a mechanical pump.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that 7 various changes and modifications may be made therein without departing from the invention, and it is aimed, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A fuel pump suitable for use as a fuel injector for an internal combustion engine comprising, in combination:

a housing having a fuel inlet connectable to a fluid fuel source and a fuel outlet and a-chamber therebetween; piezoelectric means disposed in operative relation to said housing and more particularly to said chamber, said means being piezoelectrically responsive to expand and contract along a predetermined axis upon excitation thereof;

means, including a check Vale, and a piston in operative relation with said piezoelectric means and disposed proximate to said chamber, said means being effective to sequentially interrupt fluid communication between said fluid inlet and fluid outlet and pressurize fluid within the chamber;

and valve means aflixed to said fuel outlet for normally closing said outlet, but to permit fluid Passage therethrough in response to a predetermined pressure within said chamber.

2. A piezoelectric fuel injector comprising, in combination:

an injector body having a fluid passageway therethrough and providing at one end of said passageway a fuel inlet connected to a source of fuel;

piezoelectric drive means disposed in operative relation to said injector body and more particularly to said passageway and piezoelectricallyresponsive to expand and contract along a predetermined axis upon excitation thereof;

a horn disposed in fluid flow communication with said passageway and the large end thereof in operative proximity to said means, said horn providing at the narrow end a fluid outlet; means, including a check valve, and a piston associated with said drive, said means being effective to sequentially interrupt fluid communication between said fluid inlet and fluid outlet and pressurize fluid fuel within said horn;

and valve means in said outlet to effect fluid passage therethrough in response to a predetermined fluid pressure within said horn.

3. A piezoelectric fuel injector comprising, in combination:

an injector body having a fluid passageway therethrough and providing at one end thereof a fluid inlet connected to a source of fuel;

an exponential horn disposed in fluid flow communication with said passageway and providing at the narrow end of said horn a substantially restricted fluid outlet; and a piezoelectric drive means including a piezoelectrically responsive element, said means being constructed and arranged proximate to the large end of the exponential horn to drive fluid into and through said horn upon excitation of said element of a predetermined magnitude to establish a shock wave and a substantial fluid pressure differential between the fluid inlet and the narrow portion of said horn, While the pressure differential between a predominant portion of the horn and the fluid inlet remains substantially the same.

4. A fuel injector according to claim 3, and means for suddenly applying an electric potential of a given polarity to said piezoelectric element to suddenly elongate said element and to transmit a shock Wave to the fluid fuel in the large end of said exponential horn.

5. A fuel injector according to claim 3, and means for applying an electric potential of a given polarity to said piezoelectric element and for suddenly discharging the electric potential stored in said element to shock excite the latter to transmit a shock wave to the fluid fuel in the large end of said exponential horn.

6. A fuel injector according to claim 3, wherein the axial length of said horn is substantially greater than the wave length corresponding to the frequency induced in the piezoelectric drive means.

7. A fuel injector according to claim 4, and a pintle valve connected to said outlet and effective to prevent fluid passage therethrough except upon shock excitation of the fluid within said horn.

8. A piezoelectric fuel inejctor comprising, in combination:

an injector body having a fluid passageway therethrough and proviidng at one end thereof a fuel inlet connected to a source of fuel;

a tabular piezoelectric element electroded and polarized to expand and contract axially upon the application of an electric potential to said element, one end of the 6 element being disposed in fixed relation to the injector body;

piston means, at least portions thereof constructedof relatively resilient material and coaxial-1y extending through said tubular element and including an enlarged end facing the other end of said element, the opposite end of said piston means being adjustably secured to said body and effective to precornpress said element against said injector body;

an exponential horn having a large and a narrow opening, with the large opening disposed adjacent to the enlarged end of the piston means;

a voltage source for suddenly applying an electric potential of ;a given polarity to shock excite said piezoelectric element and to transmit a shock wave to the fluid fuel in the large end of said exponential horn;

the axial length of said horn being substantially greater than the wave length corresponding to the frequency induced in the piezoelectric drive means; and

a pint'le valve connected to said outlet effective to prevent fluid passage the-rethrough only upon shock ex citation of the fluid within said horn.

References Cited by the Examiner UNITED STATES PATENTS 2,317,166 4/43' Abrams 1031 2,453,595 11/48 Rosenthal. 2,512,743 6/50 Hansell 103-1 2,756,106 7/56- Schenk 239--453 2,756,107 7/56 Kor-da 2394-53 2,949,900 8/60 Bodine 123-498 FOREIGN PATENTS 508,582 7/ 39 Great Britain.

LAURENCE V. EFNER, Primary Examiner.

Claims

1. A FUEL PUMP SUITABLE FOR USE AS A FUEL INJECTOR FOR AN INTERNAL COMBUSTION ENGINE COMPRISING, IN COMBINATION: A HOSUING HAVING A FUEL INLET CONNECTABLE TO A FLUID FUEL SOURCE AND A FUEL OUTLET AND A CHAMBER THEREBETWEEN; PIZOELECTRIC MEANS DISPOSED IN OPERATIVE RELATION TO SAID HOUSING AND MORE PARTICULARLY TO SAID CHAMBER, SAID MEANS BEING PIEZOELECTRICALLY RESPONSIVE TO EXPAND AND CONTRACT ALONG A PREDETERMINED AXIS UPON EXCITATION THEREOF; MEANS, INCLUDING A CHECK VALE, AND A PISTON IN OPERATIVE RELATION WITH SAID PIEZOELECTRIC MEANS AND DISPOSED PROXIMATE TO SAID CHAMBER, SAID MEANS BEING EFFECTIVE TO SEQUENTIALLY INTERRUPT FLUID COMMUNICATION BETWEEN SAID FLUID INLET AND FLUID OUTLET AND PRESSURIZE FLUID WITHIN THE CHAMBER; AND VALVE MEANS AFFIXED TO SAID FUE OUTLET FOR NORMALLY CLOSING SAID OUTLET, BUT TO PERMIT FLUID PASSAGE THERETHROUGH IN RESPONSE TO A PREDETERMINED PRESSURE WITHIN SAID CHAMBER.