GB2027488A - Fuel atomization system - Google Patents

Abstract

An intermittently actuated fuel injector 10, 11 is mounted on the throttle body 20 of an internal combustion engine 15 so as to spray atomized fuel into the throttle bores 26, 27 of a twin-choke carburettor against throttle blades 30, 31. The atomized fuel is mixed in, and further atomized by, the turbulent high velocity air flowing in the gap between the walls of the throttle bores 26, 27 and the edges of the throttle blades 30, 31. At wide open throttle position, part of the fuel plates on surface 29. It is then mixed and further atomized by the air which shears the plated fuel off a discontinuous edge of surface 29. Differences in the air/fuel ratio between cylinders are reduced by achieving injections at a predetermined advance before top dead center of the cylinders. The injectors may be co-axial with the throttle bores 26, 27 and inject into secondary venturis upstream of the throttle blades 30, 31. The injectors may provide all the fuel required by the engine or may function as power jets in a conventional float-chamber fed carburettor. <IMAGE>

Description

SPECIFICATION Fuel atomization system The invention relates generally to air/fuel management systems for internal combustion engines, and more particularly, to fuel atomization systems for intermittently injected engines.

In a conventionally-carbureted internal combustion engine, fuel is drawn into a throttle bore from a float bowl as the result of a pressure drop created by the increased velocity of air through a conventional venturi. The incoming air atomizes or breaks up the fuel into variable-sized droplets, and, after the engine has warmed up, these droplets are vaporized in the air flow or on the intake manifold by previously released heat of combustion conducted thereto.

In a conventional multi-point fuel-injected internal combustion engine, the injectors are located in close proximity to the intake valve of each cylinder and are actuated once, twice, or sequentially each cycle when all the intake valves are closed. The injectors break up the fuel into a fine mist in the intake manifold side of each intake valve and the fuel is thereafter vaporized as the result of the previously released heat of combustion.

To reduce the cost of a fuel management system for an injected engine, it has been proposed to reduce the number of injectors by using just one injector for each throttle bore instead of one for each cylinder. In such systems, the fuel would be injected at a single point rather than at each cylinder and hence the term "single point" injection as compared to "multi-point" injection.

In some such single-point systems, the injector would be located at some point on the intake manifold downstream of the throttle plate and upstream of the intake valves. One of the limitations of some single-point belowthrottle-plate systems hindering, if not preventing, their commercial adoption is that for various reasons they produce unacceptable levels of driveability and emissions. For example, the contours of the intake manifold increase the difficulty of transporting a uniform air/fuel mixture to each cylinder resulting in cylinder-to-cylinder differences in the air/fuel ratios.Also, lower manifold vacuum at high engine load results in a lower differential pressure that hinders complete mixing and further atomization and results in a greater proportion of undesirable incomplete combustion, either because large fuel droplets are insufficiently conducted to some cylinders making them run too lean for complete combustion or because the large droplets are conducted to other cylinders causing them to run too rich.

In an attempt to avoid some of the abovenoted limitations, the US patents to Eversole et al 3 778 038 and Knapp et al 3953548 each disclose the use of a continuous injector mounted above a complexly-shaped throttle valve that is axially movable in a speciallyshaped throttle bore. The US patent to Sellers 2714501 discloses a continuous injector mounted above a conventional butterfly throttle valve. And the US patent to Goodrich et al 2 877 003 discloses specially-shaped fuel discharge means for continuously discharging fuel into a zone of high velocity air created in cooperation with specially-shaped throttle valve means. However, in such continuous injection systems, the quantity of fuel delivered is varied by varying the continuous flow rate in accordance with one or more engine operating conditions.Such continuous injection systems lose some of the precision otherwise obtainable by intermittently injecting fuel in pulses having each width precisely tailored to instantaneous engine conditions. Moreover, such continuous injection systems therefore incur the cost of additional mechanical and electrical apparatus to vary the continuous flow rates. Thus, while they theoretically might improve atomization, such continuous injection systems probably will not be adopted for large scale mass production, not only because of their additional costs and operational complexity, but also because it is not clear that their precision can be improved to meet all present legal emission requirements, much less future requirements.

Other types of single-point systems that purport to improve atomization are represented by those disclosed in the US patents to Rivere 3931814 and 3 868 936, Boltz 3 782 639 and Byrne 3 943 904. While each of these patents discloses the use of a conventional intermittent injector, each also requires injection into some special structure responsive to manifold vacuum to draw in atmospheric air to assist in the mixing of the fuel.

The Rivere patents thus disclose injection into double-venturi chokes located upsteam of the throttle plates; the Boltz patent discloses injection into a nozzle located preferably downstream of the throttle plates, and the Byrne patent discloses injection into a sonic mixer located centrally between two throttle plates.

By requiring the use of a sonic nozzle, each of the above-mentioned single-point intermittent systems optimize the mixing and atomization of fuel at just those load conditions at which the flow through the nozzle is sonic. In each case, additional structure is required to effect atomization at other conditions. For example, the system disclosed in the Rivere patent 3 868936 requires the use of one injector with the double venturi chokes for heavy loads and a second injector below the throttle blades for low loads and idling speeds. Similarly, the system disclosed in the patent to Boltz 3 782 639 effects optimum atomization at only the sonic conditions deter mined by the diameter of the orifice and the differential pressure there across.The system disclosed in the patent to Byrne 3 943 904 effects sonic mixing only during idle and high intake manifold vacuum conditions. At other conditions, the Byrne injector produces a spray pattern which passes without restriction through the orifice into a diverging outlet nozzle.

It is, of course, desirable to improve the atomization and mixing of fuel at all load conditions with the same simple structure while at the same time retaining the precision of intermittent fuel injection.

Therefore, the present invention proposes a fuel atomization system for an internal combustion engine having an intake manifold which distributes a combustible air/fuel charge to at least one cylinder of the engine, characterized in that it comprises: a throttle body, mounted intermediate said intake manifold and a source of air, for regulating the amount of air ingested into the intake manifold and for mixing at least part of said ingested air with fuel to form said air/fuel charge, said throttle body including a throttle bore having a plate shaped throttle valve means rotatably mounted to present a variable restriction to the air flowing through said bore to said intake manifold, said throttle valve means being rotatable from a closed position where said throttle valve presents a maximum restriction to air flow in said throttle bore to an open position where said throttle valve means presents a minimum restriction to air flow in said throttle bore, said throttle bore and said throttle valve means creating a mixing zone therebetween caused by the turbulent high velocity air flow around the periphery of the throttle valve means; and an electronically-actuated intermittent fuel injection valve mounted proximate said throttle bore for injecting at timed intervals an atomized spray of fuel into the air flow of said throttle bore to become entrained therein and to create said air/fuel charge, said injection occurring before the air/fuel charge passes from said mixing zone such that said zone acts to further atomize said intermittently injected fuel.

The invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a plan view of one embodiment of the invention wherein each of a pair of intermittently actuated fuel injectors is sidemounted on a throttle body so that the spray axis of each injector is substantially perpendicular to the axis of the throttle bore and is directed at the throttle shaft; Figure 2 is a partially fragmentary side-view taken along view 2-2 of the throttle body and injectors of Fig. 1; Figure 3 is an elevation view of a second embodiment of the invention wherein each of a pair of intermittently-actuated injectors is top-mounted over the top of a respective boost venturi of a conventional four-barrel internal combustion engine carburetor so that the spray axis of each injector is coaxial with the axis of the throttle bore and intersects the throttle shaft;; Figure 4 is a partially fragmentary side-view taken along view 4-4 of the top-mounted injectors and conventional carburetor of Fig.

3; and Figure 5 is a fragmented side view of the second embodiment of the invention wherein the discontinuous edge between the throttle bore and the intake manifold is shown.

Turning now to Figs. 1 and 2, there is shown therein a side-mounted embodiment of the invention wherein a pair of intermittently electro-magnetically actuated fuel injectors 10 and 11 are side-mounted on the left side (or front with respect to the engine) of a twobarrel throttle body 20 that in turn is suitable secured to the intake manifold 14 of an internal combustion engine 1 5.

Intermittent fuel injectors 10 and 11 are of the type emitting a narrow conical spray of uniformly-small fuel droplets about an injector spray axis A-A defined as the center of the conical spray. The electrical connectors 8 and 9 of injectors 10 and 11 are electrically connected to the output of an injector drive circuit 12, the input to which is connected to a pulse width computer 13. Injectors 10 and 11 may be of any type that is electromagnetically actuated such as by an injector drive circuit 1 2 for intermittent durations corresponding to the widths of pulses computed by suitable pulse width computing means 1 3 in response to one or more engine operating conditions including engine speed, manifold air pressure, temperature, etc.Preferably, however, injectors 10 and 11 are of the type disclosed in the commonly-assigned patents to Kiwior 4040 688 and Kiwior et al 4057 190.

A suitable injector drive circuit 12 is preferably of the type shown in the commonlyassigned patent to Reddy 3 725 678, or the patent to Davis et al 3 783 344, each of which are based on the invention disclosed in the commonly-assigned co-pending patent application to Reddy 370140. A suitable pulse width computing unit 1 3 preferably is of the analog type disclosed in the commonly-assigned reissue patent to Reddy RE 29 060 or of the digital type disclosed in the commonlyassigned patent to Hartford 3 964443. The disclosures of each of the specifically-identified cases are hereby expressly incorporated herein by reference.

Each of the injectors 10 and 11 comprise an inlet end 1 6 and an outlet end 1 8 suitably secured to the side of throttle body 20 by a suitable injector fuel rail and mounting means in the form of a tubular injector mounting bushing 40, an L-shaped fuel delivery mounting bracket 50, a fuel delivery mounting block 60, a pair of injector-to-fuel rail fittings 70 and 72, a fitting retaining plate 80, and a fuel rail means 90.

Injector mounting bushing 40 comprises a peripheral external shoulder 42 seated in a counterbore 43 machined in the front-facing side of throttle body 20 and further comprises a pair of internal counterbores 44 and 45, counterbore 44 seating an O-ring 46 against the external cylindrical periphery of the outlet end 1 8 of the injector 10. Injector mounting bushing 40 is fitted into the counterbore 43 in the throttle body 20 and has an outlet opening 48 forming a suitable aperture in a throttle bore wall 24 of the throttle body 20 so as to permit any spray emitted from the outlet end 1 8 of injector 10 to pass unrestricted and unimpeded therefrom into a throttle bore 26 of throttle body 20.

The inlet end 1 6 of injector 10 is fitted into a suitable channel counterbored in fitting 70 and sealingly engaged therein by another 0ring. Fitting 70 comprises a hub 76 protruding through an aperture in retaining plate 80 and encircled by a resilient grommet 78 biased between the retaining plate 80 and suitable shoulder on the fitting 70. To bias retaining plate 80 towards the throttle body 20, the inboard end of L-shaped bracket 50 is suitably fastened to the front side of throttle body 20 by a nut 52 on a stud 54 threadedly secured in throttle body 20 intermediate throttle bores 26 and 27. The outboard end of L-shaped bracket 50 is secured to the inboard end of retainer mounting block 60 by a first pair of socket head screws 64 and 66 and the mounting block 60 is secured to the fitting retainer plate 80 by a second set of socket head screws 68 and 69.The injector mounting means thus cooperate to secure the injectors 10 and 11 relative to the side of throttle body 20 in a manner whereby each end 1 6 and 1 8 of each injector is permitted to move in one direction but is captured from moving in the other direction.

Each injector-to-fuel rail fitting 70 and 72 comprises a second set of passages communicated with a common fuel rail means 90.

Such common fuel rail means may comprise individual metallic sections 92 and 94 protruding from the opposite side of fittings 70 and 72 and joined by resilient connecting tubes 96 and 98 or may preferably be a single metallic fuel rail of the type disclosed in the commonly-assigned patent to Peterson et al 3 776 209, hereby incorporated herein by reference.

A throttle shaft 28 passes through the center of throttle body 20 and each of the throttle bores 26 and 27 thereof and perpendicularly intersects the injector spray axes A-A. Throttle shaft 28 has a pair of butterfly throttle plates or blades 30 and 31 secured thereto to rotate therewith respectively in each throttle bore 26 and 27. The top outboard end of throttle shaft 28 is drivingly secured to a throttle shaft position signalling means 32 which preferably is of the type disclosed in the commonly-assigned patent to Reddy 3 926 153, hereby incorporated herein by reference.The bottom outboard end of throttle shaft 28 is driveably attached to a throttle lever 34 that is biased by a throttle lever return spring 35 in a counter-clockwise closing direction towards a fully-closed position established when an idle tab 36 of throttle lever 34 abuts against one end of an idle set screw 37 threadedly engaged in a hub 38 directly over the throttle shaft 28.

Idle set screw 37 is adjusted so that, when idle tab 36 of throttle lever 34 abuts thereagainst, throttle plates 30 and 31 establish a position wherein the peripheral edges of the butterfly throttle plates establish leading and trailing idle air gaps 24a and 24b and 25a and 25b relative to the cylindrical walls of the respective throttle bores 26 and 27. The width of these idle air gaps is set by the adjustment of the idle set screw 37 so as to allow the engine manifold vacuum to suck in a quantity of turbulent high-velocity air past the leading and trailing edges 30a and 30b of the throttle blades sufficient to properly mix the narrow conical spray of fuel intermittently emitted by injectors 10 and 11 so as to sustain satisfactory idling operations of the engine while at the same time producing minimum undesirable exhaust gas emissions.

When in their closed positions, butterfly throttle blades 30 and 31 are slanted with respect to the spray axes A-A so that the leading edge 30a of the throttle blade 30 is both closest to the injector 10 and above the spray axes A-A and the trailing edge 30b is farthest away from the injector 10 and below the spray axes A-A.

Also connected to throttle lever 34 is a throttle cable 39 connected to an operatorcontrolled throttle pedal (not shown) in the vehicle passenger compartment. When the throttle pedal is depressed, the throttle cable 39 is pulled rearwardly of the engine (to the right in Figs. 1 and 2) causing the throttle blades to be rotated clockwise in an opening direction to establish a desired position intermediate the above-described closed position and a wide-open-throttle (WOT) position wherein the throttle blades coincide with the vertical axes B-B of each throttle bore.

Since injector 10 emits atomized conical sprays of uniformly small droplets, most of the emitted spray is mixed with the air passing ..

turbulently about the leading edge 30a of throttle blade 30 when in its idle or off-idle positions. Another much smaller part impinges on the downstream side of the throttle blade, flows therealong to the downstream side 30b, and is there mixed in the air vortices created by the turbulent air flowing past the downstream side of each throttle blade.

In vehicle tests of the embodiment shown and described with respect to Figs. 1 and 2, satisfactory driveability and emission results were obtained at even cold temperatures except that the maximum cylinder-to-cylinder differences in the air/fuel ratios delivered to different cylinders were observed to increase over that experienced with conventional multipoint systems. A part of this increase in the maximum cylinder-to-cylinder difference in air/fuel ratios was reduced by inserting the injectors 10 and 11 so that their tips protruded into their respective throttle bores 26 and 27 along their spray axes A-A by an amount sufficient to pass through the laminar boundary layer of air adhering to the walls 24 of the throttle bores 26 and 27.In this manner, rather than being unevenly deflected toward certain cylinders by the more viscous laminar air flow, the conical spray of fuel droplets was emitted directly into the turbulent high-velocity air to be further atomized and mixed therein.

Another part of the increase in the cylinderto-cylinder difference in air/fuel ratios was observed to occur in the 'six-inch crowd' condition wherein the manifold pressure was six inches of mercury below atmospheric. This crowd condition is normally associated with up-shifts in the demanded load which in turn requires opening the throttle blades to near their WOT position. This part of the increase in the cylinder-to-cylinder difference in air/ fuel ratios was reduced by securing a baffle plate 29 transversely across each throttle bore 26 and 27 immediately downstream of throttle shaft 28 and coincident with throttle bore axes B-B.The baffle plate 29 deflects the lower half of the conical spray of fuel droplets that would otherwise impinge on and run along the downstream side of the throttle plates 30 and 31 and is thereby delivered to the cylinders from the center of each throttle bore 26 and 27.

In this manner, the baffle plate 29 appears to duplicate one function of the throttle blades when in their full wide-open-throttle position to the extent that, in such position of the throttle blades, the conical spray of fuel droplets impinges or "plates" on the throttle blades 30 and 31, runs downward along the downstream sides thereof under the influence of the engine vacuum and the air stream and into the center of the bore. The fuel is subsequently sheared off the discontinuous trailing edge 30b of the throttle blade 30 into droplets sufficiently small so that, when mixed with air, they provide a combustible mixture having a satisfactory cylinder-to-cylinder difference in air/fuel ratios.To the extent that WOT conditions do not provide a vertical throttle blade position the small portion of the fuel which plates on the blades will be deflected unevenly to the different cylinders causing cylinder-to-cylinder differences. Under high load conditions, the amount of fuel plated in such a manner will increase and, it is believed, so will the cylinder-to-cylinder difference. The situation may be ameliorated with the baffle plate 29 by directing the plated fuel into the center of the bore.

When intermittently actuated by injector drive circuit 1 2 for periods corresponding to pulse widths provided by pulse width computer 13, side-mounted intermittent injectors 10 and 11 inject fuel in a manner that was found to result in stable engine operations at all engine speeds and especially at the critical idle and off-idle conditions. Moreover, while the cylinder-to-cylinder differences in air/fuel ratios were found to produce acceptable emission results, the maximum cylinder-to-cylinder differences were further reduced, and the emission results accordingly improved, by advancing the commencement of injection by a predetermined advance before an engineevent.For example, when the embodiment shown in Figs. 1 and 2 was dynamometer tested at 30 MPH road load conditions on a 1 977 Cadillac Seville 350 CID engine having a single plane intake manifold, the maximum cylinder-to-cylinder difference in air/fuel ratios measured at each cylinder was minimized when injection was commenced between 30 and 60 degrees before top dead center (BTDC) of each stroke before the intake of the next cylinder. When the same embodiment was tested at 55 MPH 6" Hg road load conditions on a 1 977 Cadillac Seville 350 CID engine having a two-plane intake manifold, the maximum difference was minimized at about + 90 BTDC.In any event, the advance of single point injection with respect to an engine event such as TDC is selected to minimize the maximum cylinder-to-cylinder difference in air/fuel ratios for each engine family by running a "timing sweep" of the air/fuel ratios measured at each cylinder for different injection timing advances and load conditions. Further, disclosure of such timing advance is provided in commonly-assigned copending now allowed application SN 778 822 filed March 17, 1977 on a "Single Point Intermittent Flow Fuel Injection System", such disclosure being hereby expressly incorporated herein by reference.

Shown in Figs. 3 and 4 is an alternative embodiment of the invention that is shown in Figs. 1 and 2. As will be described in further detail below, the embodiment of Figs. 3 and 4 comprises a pair of narrow-cone-angle intermittent injectors 100 and 1 01, each mounted to have its spray axis A-A coaxial with the axis B-B of a respective boost venturi 11 2 and 11 3 in two different barrels or throttle bores 114 and 11 5 of a conventional fourbarrel carburetor 11 6 that may be a conventional 350 Rochester four-barrel carburetor except for the removal of the choke plate and shaft over the boost venturis.In this embodi ment, a conventional float-bowl-to-metering-jet fuel path (not shown) conventionally supplies fuel for idling and off-idle conditions, and such conventionally supplied fuel is then mixed with air having its velocity conventionally increased by the primary venturi system 11 8 and 11 9 of the conventional carburetor.

However, at or near full load conditions where the slower air flow results in poorer atomization and mixing, the conventionally supplied fuel is augmented by an intermittently injected atomized spray into the boost venturis, thereby effecting better fuel mixing and atomization.

Further, such top mounted injectors can be utilized to deliver the total fuel flow requirements to the throttle bores instead of a "trim" adjustment at the power operating regions as described above. This embodiment is similar in operation to the side-mounted implementation and can be accomplished by proper fuel pulse timing and sizing after disablement of the fuel passages of the conventional carburetor shown.

Accordingly, atomization of the fuel by the injectors would be aided by a further breakup and mixing with the air/flow by the high velocity turbulent flow at the throttle blade and bore interface during idle and partial throttle conditions with or without the boost venturi. Thereafter, the boost venturi is combined with the structure to provide an additional atomizing assist in these regions and a greater secondary assist to atomization at wide-open-throttle conditions. To provide a fairly constant atomizing assist for the air/fuel mixtures, the venturi can be of the variable cross-section type with a substantially constant air flow velocity therethrough.

The primary atomization and the fuel injection path is controlled by the injector and it therefore should be positioned to reduce wall wetting and miximize air/fuel mixing near the injector tips. The coaxial or concentric positioning of the injectors with respect to the throttle bores aides in producing these effects and is further thought to reduce cylinder-tocylinder differences in air/fuel ratio as fuel is not initially entrained asymmetrically in the air flow.

Turning now to the details of the embodiment shown in Figs. 3 and 4, the injectors 100 and 101 are mounted in an injector mounting assembly 1 20 comprising a pair of injector location pockets 1 22 and 1 23 welded to a mounting plate 1 24 supported by support members 1 26 and 1 27 relative to the air horn 128 of the carburetor 116.To position each injector 100 and 101 at a coaxial space over the top of each respective boost venturi 11 2 and 113, an external shoulder, for example, 102 on the valve body of each injector intermediate its inlet end 106 and outlet end 108 is seated on a bottom lip of each pocket 122 and 123, and the spray tip of each injector protrudes downwardly through a central opening through each bottom lip. To secure each injector 100 and 101 in the radial direction, a respective socket head set screw 121a and 121b is inserted through respective pocket 1 22 and 1 23 to bear against a relieved shoulder on the outer periphery of each injector valve body.

The lower end of each support member 126 and 127 is secured to the side of air horn 1 28 of the carburetor 11 6 by a respective nut 1 29 and 1 30 fastened from the outboard side on a bolt 131 and 132 inserted through the off-center outboard openings in the sides of air horn 128, such off-center openings being those in which the outboard ends of the choke plate shaft are otherwise supported.) To further support the injector mounting asembly 1 20 relative to the air horn 128, the lower end of a third support member 1 34 is inserted over a dowel upstandingly fixed to the top of the air horn 1 28. Injector mounting plate 1 24 is secured relative to support member 1 34 by a nut 136 on a stud 1 37 threadedly engaged in support member 1 34 and protruding upwardly through a suitable aperture in mounting plate 1 24.

A fourth support member 1 40 is threadedly positioned on a stud 142, which in turn is threadedly engaged in the hole previously tapped for the air cleaner support stud. An extended air cleaner support stud 1 44 is axially positioned in support member 1 40 and is locked in position thereon by a nut 1 46 threaded down on air cleaner shaft 144 so as to secure injector mounting plate 1 24 relative to support member 140 and stud 142.

The top or inlet end 106 and 107 of each injector 100 and 101 is slip-fitted into a respective counterbore 1 50 and 1 51 provided in an injector-to-fuel rail fitting 1 52 and 1 53 and is sealingly engaged therein by a respective O-ring 1 54 and 1 55. Connecting each of the fittings 1 52 and 1 53 is a one portion 1 56 of a metallic fuel rail, and extending outwardly from each fitting 1 52 and 1 53 are other portions 1 58 and 159, the outboard ends of which are suitably communicated with a pressure regulated source (not shown) of pressurized fuel.The top of each injector-to-fuel rail fitting 1 52 and 1 53 is retained by a retainer plate 1 60 that is suitably spaced above injector mounting plate 1 24 by a pair of spacers 162 and 163, the bottom end of each of which terminates in a respective location dowel 164 and 165 extending through a suitable aperture in injector mounting plate 1 24. The upper end of each spacer 1 62 and 163 terminates in a stud 166 and 167 onto which a nut 1 68 and 1 69 is respectively threaded down against retainer plate 1 60.

Fastened down onto the carburetor 11 4 by a wing nut 1 71 coacting with extended air cleaner stud 1 44 is an air cleaner assembly 1 70 having a lower peripheral lip 1 72 biased down against an outboard shoulder or air horn 128. Upstanding about a central annular opening 1 74 on an annular gasket 1 76 mounted on the top of an air cleaner a cover 1 78 is the annular bottom lip of a thin cylinder 180, the annular upper lip of which is sealingly engaged in annular gasket 1 82 secured to the bottom of a central top cover 184.A pair of grommets 1 86 and 1 88 secured in suitable openings through thin cylinder 180 sealingly engage the portions 1 58 and 1 59 of the metallic fuel rail so as to prevent dirty air from leaking into the carburetor 11 6 around the fuel rail.

With respect to Fig. 5, a pair of intermittently-actuated fuel injectors 108 and 109 are secured in the throttle body above respective butterfly throttle plates 223 and 222. Throttle plates 222 and 223 are commonly mounted on a throttle shaft 224 to be pivoted in a respective throttle bore 226 and 227. The injectors 108 and 109 are mounted so that each injector spray axis A-A intersects throttle shaft 224 and is coaxial with the bore axis B-B of each respective throttle bore 226 and 227.

Also as with the embodiments of Figs. 1, 2 in Fig. 5 throttle shaft 224 is fixedly connected to an operator-controllable throttle lever and responds to an opening force applied to a throttle cable pin by a throttle cable (not.shown) connected to the vehicle's throttle pedal against the bias of at least one return spring connected between a return spring pin and the engine. The throttle lever also comprises an idle tab (not shown) similar to idle tab 36 of the embodiments shown in Figs. 1 and 2, such idle tab being biased by the return spring to normally abut against an idle set screw (not shown) similar to idle set screw 37 of the embodiment shown in Figs. 1 and 2.As also described with respect to the embodiments shown in Figs. 1 and 2, the idle set screw is adjusted so that, when the idle tab of the throttle lever abuts thereagainst, throttle plates 222 and 223 establish a closed position thereof wherein the peripheral edges of the butterfly throttle plates 222 and 223 establish an idle air gap relative to the cylindrical walls 226 and 227 of the throttle bores. The width of this idle air gap is set so as to allow the engine manifold vacuum to suck in a sufficient quantity of turbulent high velocity air past the edges of the throttle blades to properly mix the conical spray of fuel intermittently emitted by injectors 108 and 109 so as to sustain satisfactorily idling operations of the engine while at the same time producing a minimum of undesirable exhaust gas emissions.

The throttle body is mounted on the intake manifold 240 of the engine 1 5 so as to establish downstream of throttle shaft 224 a discontinuous edge 242 and 243 at which the fuel plated onto the walls 226 and 227 of the throttle bores is mixed and further atomized by being sheared off by the air flowing over such discontinuous edges. Such discontinuous edge may be effected as shown in Fig. 5 by causing the outlets of the throttle bores 226 and 227 to be of smaller diameter than the peripheral openings 244 and 245 of the intake manifold 240.

The discontinuous edge is necessitated more at high fuel flow rates where wall wetting of the inner side of the throttle bore is unavoidable. These high fuel rates are simultaneously accompanied by high air flow rates and, if a shear edge can be formed at some position on the bore to create a discontinuity, then these plated fuel droplets will sufficiently atomize as they are torn from the edge.

While the two most advantageous positionings of the injectors with respect to the throttle blade have been shown and described, it is understood further refinements as to angular and linear displacement can be accomplished without departing from the primary objects of the invention.

Having described several embodiments of the invention, it is undestood that the specific terms and examples are employed herein in a descriptive sense only and not for the purpose of any limitation. Other embodiments of the invention, modifications thereof, and alternatives thereto will be obvious to those skilled in the art and may be made without departing from the spirit of the invention. The appended claims aim to cover the modification and changes as are within the true scope and spirit of the invention.

Claims (11)

1. A fuel atomization system for an internal combustion engine having an intake manifold which distributes a combustible air/fuel charge to at least one cylinder of the engine, characterized in that it comprises: a throttle body, mounted intermediate said intake manifold and a source of air, for regulating the amount of air ingested into the intake manifold and for mixing at least part of said ingested air with fuel to form said air/fuel charge, said throttle body including a throttle bore having a plate shaped throttle valve means rotatably mounted to present a variable restriction to the air flowing through said bore to said intake manifold, said throttle valve means being rotatable from a closed position where said throttle valve presents a maximum restriction to air flow in said throttle bore to an open position where said throttle valve means presents a minimum restriction to air flow in said throttle bore, said throttle bore and said throttle valve means creating a mixing zone therebetween caused by the turbulent high velocity air flow around the periphery of the throttle valve means; and an electronically actuated intermittent fuel injection valve mounted proximate said throttle bore for injecting at timed intervals an atomized spray of fuel into the air flow of said throttle bore to become entrained therein and to create said air/fuel charge, said injection occurring before the air/fuel charge passes from said mixing zone such that said zone acts to further atomize said intermittently injected fuel.

2. A fuel atomization system according to claim 1, characterized in that said injection valve is mounted relative to said throttle bore such that atomized spray is directed along a spray axis which is coaxial with the throttle bore.

3. A fuel atomization system according to claim 2, characterized in that a venturi means is located intermediate said atomized spray and the throttle valve means, said venturi means being operable to assist the mixing of said atomized spray with the air ingested into the manifold from said source.

4. A fuel atomization system according to claim 3, characterized in that said venturi means is variable to provide a substantially constant air velocity therethrough for consistently mixing the air and atomized fuel spray thoroughly.

5. A fuel atomization system according to anyone of claims 1 to 4, characterized in that it further comprises at least one engine parameter sensor means providing a parameter signal having a magnitude corresponding to at least one engine operating parameter, said engine comprising at least one cylinder to which a mixture of air from a source of air and fuel intermittently injected from a source of pressurized fuel is admitted from said intake manifold at respective first and second engine event times and is ignited at respective third and fourth engine event times, said fuel atomization system comprising: pulse width computing and injector drive means coupled to said engine parameter sensor means operative to generate a series of intermittent fuel injection actuation command pulses each having a width varying in accordance with said parameter signal and commencing at an injection time having a predetermined advance from one of said engine event times; said intermittent fuel injection valve means being coupled to said source of pressurized fuel and said pulse width computing and injector drive means, said intermittent fuel injection valve means mounted on said throttle body means so as to intermittently emit a partially-atomized spray of fuel droplets along a spray axis co-axial with said throttle bore axis.

6. A fuel atomization system according to claim 5 for an engine which comprises at least two cylinders, characterized in that said predetermined advance is selected to minimize the maximum difference in the air/fuel ratios of the mixture admitted to said at least two different cylinders.

7. A fuel atomization system according to claim 6, for an engine which comprises a single plane intake manifold characterized in that said predetermined advance is between 30 degrees and 60 degrees before top dead center of the compression stroke of one of said at least two different cylinders.

8. A fuel atomization system according to claim 6, for an engine which comprises a two plane intake manifold characterized in that said predetermined advance is between 90 degrees of either side of top dead center of a compression stroke of one of said cylinders.

9. A fuel atomization system according to anyone of the preceding claims, characterized in that said throttle body comprises a venturi means located intermediate said intermittent fuel injection valve and said throttle valve means, said injection valve and said venturi means being coaxial with said throttle bore.

1 0. A fuel atomization system according to claim 9, characterized in that said venturi means comprises fuel supply means for providing a first flow of fuel in accordance with the flow of air and that said intermittent fuel injection valve provides a second flow of fuel complementing said first flow in accordance with said engine operating parameter.

11. A fuel atomization system substantially as described and as shown in the accompanying drawings.