US3674245A - Carburetor for internal-combustion engine - Google Patents

Abstract

A carburetor for an internal-combustion engine, equipped with an accelerator-controlled butterfly valve in a mixing channel, has a first fuel-injection nozzle downstream and a second fuelinjection nozzle upstream of that valve, each of these nozzles opening into the channel in the immediate vicinity of a respective high-pressure duct serving to atomize the injected fuel. The atomizer duct for the first nozzle is unblocked under low-load conditions (idling) by a diaphragm-controlled valve responsive to the suction prevailing in the channel beyond the closed butterfly valve. The second nozzle, supplied by an ancillary fuel pump under the control of the accelerator under high-load conditions (kickdown), may have its atomizer duct connected to an air-pressure accumulator which is charged at low load by the pressure differential developed across the butterfly valve.

Description

United States Patent Massarotti 1 July 4, 1972 54] CARBURETOR FOR INTERNAL- 2,012,564 3/1935 Holmes ..261/D1G. 51 COMBUSTION ENGINE 1,932,188 10/1933 Roth ..261/D1G. 51 3,295,839 1/1967 Mitchell... .....261/41 D 1 1 Inventor! Lulgl Massarfltll, Mflano, Italy 2,027,263 1/1936 Bashor 261/34 A [73] Assignee: Atomjuboll S.r.l., Milano, Italy 2,345,168 3/1944 wmh et A 1,289,300 12/1918 Stokes ..261/41 D [22] Filed: March 25,1970

Primary Examiner-Tim R. Miles [2]] Appl' 23l64 Attorney-Karl F. Ross [30] Foreign Application Priority Data ABSTRACT March 26, 1969 Italy ..14626 A/69 A carburetor for an internal-combustion g q pp with an accelerator-controlled butterfly valve in a mixing s21 u.s.c1 ..26l/28, 261 34 A, 261/41 D, channel, has a first fuel-injection nozzle downstream and a 26l/DlG. 51, 123/33 E Second fuel-injection nozzle upstream of that valve, each of 51 1111.01 ..F02m 3/08, F02m 7/06 theSe nozzles opening into the channel in the immediate [58] Field of Search ..261 I28, 30, DIG. 51, 41 D, vicinity of a respective high-Pressure duct serving awmize 261/34 A 78 123/33 E the injected fuel. The atomizer duct for the first nozzle is unblocked under low-load conditions (idling) by a diaphragm- [56] References Cited controlled valve responsive to the suction prevailing in the channel beyond the closed butterfly valve. The second nozzle, UNITED STATES PATENTS supplied by an ancillary fuel pump under the control of the accelerator under high-load conditions (kickdown), may have 1,947,919 2/1934 Prennss ..26l/34 A its atomizer duct connected to an aippressure accumulator 3,437,320 4/1969 Walker et al ..26l/4l D which is charged at low load by the pressure iff im 3 531094 9/1970 1 1 developed across the butterfly valve. 1,460,667 7/1923 2,100,205 1 1/1937 Spohr ..261/34 A 8 Claims, 4 Drawing Figures PNENTEDJUL 41972 3574245 SHEET 1 Bf 2 Luigi M 0 ss arohi INVENTOR.

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Luigi Mass 0 rotfi INVENTOR.

Attorney CARBURETOR FOR INTERNAL-COMBUSTION ENGINE My present invention relates to a carburetor for an intemalcombustion engine, e.g., as used in automotive vehicles.

Such carburetors generally comprise a mixing channel including flow-control means, such as a butterfly valve, for selectively throttling an air/fuel mixture streaming toward a combustion chamber or, via a manifold, to a plurality of combustion chambers in which the mixture ignites to develop a thrust. Where the combustion chamber is the interior of a piston cylinder, the suction stroke of the cylinder aspirates the air/fuel mixture at a rate determined in part by the position of the throttle valve and in part by the speed of the engine. In an automotive vehicle, the throttle valve is linked with the accelerator pedal so as to be substantially closed when the driver takes his foot off the pedal, i.e., under conditions of minimum load such as idling or downhill travel. Under high load, as during acceleration, the throttle valve is wide open to increase the rate of fuel admission; in some engines an ancillary fuel pump responds to a stepping upon the pedal beyond the normal operating range (kickdown) to inject additional fuel into the mixture fed to the cylinders.

Even with the addition of such an ancillary fuel pump, it is difficult to dimension the mixing channel of the carburetor and the associated throttle valve in a manner providing an optirnum air/fuel ration under all load conditions. Conventional carburetors, therefore, are generally designed for best performance, i.e., substantially full combustion without residue, atintermediate loads and are considerably less efficient under extreme operating conditions. Even the use of an ancillary fuel pump does not completely remedy this drawback for high loads, owing to the inertia of the pump which delays the attainment of an operating speed high enough for effective injection.

The general object of my present invention, therefore, is to provide an improved carburetor avoiding the aforestated disadvantages.

A more specific object is to provide means in such carburetor for improving the effectiveness of fuel injection under certain operating conditions, as during incipient acceleration.

A carburetor embodying my invention comprises a first injection nozzle opening into the mixing channels downstream of the throttle valve, in order to supply fuel in a position of substantial closure of that valve, and a second injection nozzle opening into the channel upstream of the throttle valve, designed to deliver additional fuel in a wide-open valve position; a first and a second atomizer are respectively juxtaposed with these nozzles for dispersing the droplets of liquid fuel injected by one or the other nozzle under the conditions specified.

The two atomizers are basically constituted by ducts having outlets near the respective injection noules and receiving compressed air from a common supply or from individual supplies of air pressure. In the case of the first (downstream) nozzle, which may be simply connected to a fuel reservoir under nonnal atmospheric pressure, the air escaping into the mixing channel creates a Venturi effect which promotes the discharge of liquid fuel from the nozzle. In the case of the second (up stream) nozzle, which advantageously is connected to an ancillary fuel pump, the air stream intensifies the injection especially at the beginning of a pumping operation.

According to a more specific feature of my invention, either or both atomizers are provided with pressure-sensitive control means communicating with the mixing channel to ascertain the need for fuel injection. Thus, the supply duct of the downstream atomizer may contain a control valve normally blocking the flow of compressed air to its outlet, this valve being provided with unblocking means responsive to low pressures on the suction side of the mixing channel such as those occurring with the engine idling and with the accelerator retracted to close the throttle valve.On the upstream side, where in the presence of an ancillary fuel pump the injectionpromoting atomizer is needed only during the initial stages of acceleration under high load, the compressed-air supply may be of the intermittently operable type, such as a limitedcapacity air-pressure accumulator which is charged under low-load conditions by a feedback connection to the suction side of the channel whereby the development of a pressure differential across throttle valve causes the aspiration of atmospheric air into the accumulator for storage until needed.

The above and other features of my invention will be described in greater detail hereinafter with reference to the accompanying drawing in which:

FIG. 1 is an axial sectional view of a carburetor according to the invention, shown in idling position;

FIG. 2 is a view similar to FIG. 1, showing the carburetor in kickdown position;

FIG. 3 is a view similar to FIG. 1, illustrating a modified carburetor according to the invention in idling position;

and FIG. 4 is a view similar to FIG. 3, showing the carburetor thereof in kickdown position.

The carburetor 1 shown in FIGS. 1 and 2 comprises a housing 2 with a mixing channel having an. upstream section 3 and a downstream section 3' separated from each other by a butterfiy-type throttle valve 10; channel section 3 is constricted at 4 to form a diffuser just ahead of valve 10.

From a conventional fuel injector, not shown, an air/fuel mixture entering the channel section 3 is drawn past the valve 10 into a junction 11 with a manifold 12 leading to a set of nonillustrated piston cylinders equipped with the usual spark plugs or equivalent igniters. An ancillary fuel pump 7 and a fuel reservoir 5-are fed via a conduit 6 from a reservoir of hydrocarbon fuel such as gasoline or Diesel oil; a lever 8, pivoted to the pump housing at 8', controls the operation of pump 7 and is displaceable against the: force of a spring 9 by a rod 9 mechanically linked, like the butterfly valve 10, with the accelerator pedal of a vehicle containing the carburetor 1. In the low-load position of FIG. 1, valve 10 is closed and pump 7 is inoperative; in the high-load position of FIG. 2, valve 10 is wide open and pump 7 is actuated to deliver fuel from reservoir 5 to a nozzle 13by way of a duct 13' containing a springloaded check valve 14.

Another nozzle 15 communicates with the fuel reservoir 5 by way of a duct 15" whose effective cross-section is manually adjustable by a setscrew 15'.

An air compressor or other source of high-pressure air, not shown, is connected to the inlet end 25 of a duct 23 tenninating at an outlet 23 in the immediate vicinity of nozzle 13 just upstream of butterfly valve 10. Another duct 21 branches off the duct 23 at 24 and terminates at an outlet 22 next to noule l5, downstream from valve 10. Duct 21 contains a control valve 20 that is linked by a stem 19 with a flexible diaphragm l7 interposed, as a vertically movable piston, between an upper compartment 16 and a lower compartment 16" of a suction chamber 16; compartment 16" communicates with the low-pressure section 3 of the carburetor channel, in the vicinity of outlet 22, by way of a conduit 18. Compartment 16' may be open toward the atmosphere or may be sealed to contain a constant quantity of gas.

With the throttle valve 10 closed, as shown in FIG. 1, and with the engine operating, suction generated in manifold 12 is communicated to channel section 3" and via conduit 18 to compartment 16" of pressure sensor 16 whereby valve 20 is opened to admit high-pressure air to outlet 22. The resulting air stream entrains fuel from reservoir 5 through nozzle 15 into the channel at a limited rate designed for substantially complete combustion in the piston cylinders of the idling engine; the injected fuel is instantly atomized by the air issuing from outlet 22.

Under high-load conditions, as illustrated in FIG. 2, valve 10 is opened and pump 7 is set in motion to inject additional fuel into the channel by way of nozzle: 13. The air stream continuously issuing from outlet 23 of duct 23' instantly vaporizes and atornizes the injected fuel for effective combustion with delivery of the needed additional thrust.

In FIGS. 3 and 4 the downstream nozzle 15 and its atomizer 22 have not been illustrated but nevertheless are presumed to be present in order to operate in the aforedescribed manner during idling (FIG. 3). The carburetor l of FIGS. 3 and 4 differs from the carburetor 1 of FIGS. 1 and 2 in that its highpressure duct 23; terminating at the upstream outlet 23, has been separated from the supply duct (21) of the downstream atomizer and is connected instead to a pressure accumulator 27 of limited capacity. Accumulator 27 comprises a bellows 31 divided by a rigid internal partition 32 into a low-pressure compartment 33 and a high-pressure compartment 34 bounded by an upper header 28 and a lower header 29; the two headers are rigidly interconnected by a yoke 30. Compartment 33 is vented to the atmosphere through an orifice 36 in header 28 and communicates via a conduit 26 with the downstream section 3' of the mixing channel; this compartment also contains a compression spring 35 bearing upon header 28 and partition 32. Compartment 34 communicates with duct 23' via a port normally blocked by a check valve 40 under pressure of a spring 41; another check valve 37, loaded by a spring 38, normally blocks an intake port covered by an air filter 39.

In the operation of the carburetor 1', the pressure differential developed between channel section 3 and 3 during idling conditions (FIG. 3) generator suction in duct 26 whereby partition 32 is drawn upwardly to compress the biasing spring 35. With check valve 40 obstructing the connection to duct 23', ambient air enters the compartment 34 via check valve 37 so as to charge the pressure accumulator 27. When the butterfly valve is then partly opened under normal driving conditions, the suction in duct 26 is reduced so that spring 35 compresses the air in compartment 34. In a certain position of butterfly valve 10, established by suitable selection of the forces of springs 35 and 41, check valve 40 yields so that air from compartment 34 enters the channel section 3 to disperse the fuel droplets delivered to nozzle 23 by the simultaneously actuated pump 7.

Naturally, the carburetors l and 1' may work into any number of engine cylinders or other combustion chambers connected to outlet 11 of channel 3, 3; though the system has been described with particular reference to an automotive vehicle, the engine served by the carburetor could also be used to drive other types of load.

lclaim:

l. A carburetor for an internal-combustion engine, comprising a housing with a channel for an air/fuel mixture aspirated into a combustion chamber; throttle means in said channel movable between a wide-open position and a substantially closed position; a first injection nozzle connected to a first supplemental supply of liquid fuel and opening into said channel downstream of said throttle means; a second injection nozzle connected to a second supplemental supply of liquid fuel and opening into said channel upstream of said throttle means; first atomizing means juxtaposed with said first nozzle and effective in said substantially closed position for dispersing droplets of fuel injected into said channel via said first nozzle; second atomizing means juxtaposed with said second nozzle and effective in said wide-open position for dispersing droplets of fuel injected into said channel via said second nozzle; and pressure-sensitive control means for at least one of said atomizing means communicating with said channel; said first atomizing means comprising a source of high-pressure air having an outlet near said first nozzle, said control means including a valve normally blocking the passage of high-pressure air from said source to said outlet and unblocking means for said valve responsive to low pressure in said channel beyond said throttle means.

2. A carburetor as defined in claim 1 wherein said unblocking means comprises a suction chamber provided with a duct temiinating at said channel downstream of said throttle means, said control means further including piston means in said suction chamber connected with said valve.

3. A carburetor as defined in claim 4 wherein said piston means comprises a flexible diaphragm.

4. A carburetor as defined in claim 1 wherein said control means further comprises an air-pressure accumulator of limited storage capacity having an outlet near said second nozzle and charging means for said accumulator responsive to low pressure in said channel beyond said throttle means during periods of substantial closure of the latter.

5. A carburetor as defined in claim 4 wherein said accumulator comprises a bellows with a movable partition dividing its interior into a first and a second compartment, said charging means including a suction line extending from a downstream location of said channel to said first compartment, said second compartment communicating with said outlet.

6. A carburetor as defined in claim 5, further comprising biasing means in said bellows bearing upon said partition in a sense tending to discharge air from said second compartment through said outlet.

7. A carburetor as defined in claim 6, further comprising a first check valve between said second compartment and said outlet for preventing the flow of air from said channel to said second compartment, and a second check valve between said second compartment and the atmosphere for enabling the aspiration of ambient air into said second compartment upon displacement of said partition against the force of said biasing means by low pressure in said suction line.

8. A carburetor as defined in claim 1 wherein said second supplemental supply comprises a fuel pump mechanically linked with said throttle means.

Claims (8)

1. A carburetor for an internal-combustion engine, comprising a housing with a channel for an air/fuel mixture aspirated into a combustion chamber; throttle means in said channel movable between a wide-open position and a substantially closed position; a first injection nozzle connected to a first supplemental supply of liquid fuel and opening into said channel downstream of said throttle means; a second injection nozzle connected to a second supplemental supply of liquid fuel and opening into said channel upstream of said throttle means; first atomizing means juxtaposed with said first nozzle and effective in said substantially closed position for dispersing droplets of fuel injected into said channel via said first nozzle; second atomizing means juxtaposed with said second nozzle and effective in said wide-open position for dispersing droplets of fuel injected into said channel via said second nozzle; and pressure-sensitive control means for at least one of said atomizing means communicating with said channel; said first atomizing means comprising a source of highpressure air having an outlet near said first nozzle, said control means including a valve normally blocking the passage of high-pressure air from said source to said outlet and unblocking means for said valve responsive to low pressure in said channel beyond said throttle means.

2. A carburetor as defined in claim 1 wherein said unblocking means comprises a suction chamber provided with a duct terminating at said channel downstream of said throttle means, said control means further including piston means in said suction chamber connected with said valve.

3. A carburetor as defined in claim 4 wherein said piston means comprises a flexible diaphragm.

4. A carburetor as defined in claim 1 wherein said control means further comprises an air-pressure accumulator of limited storage capacity having an outlet near said second nozzle and charging means for said accumulator responsive to low pressure in said channel beyond said throttle means during periods of substantial closure of the latter.

5. A carburetor as defined in claim 4 wherein said accumulator comprises a bellows with a movable partition dividing its interior into a first and a second compartment, said charging means including a suction line extending from a downstream location of said channel to said first compartment, said second compartment communicating with said outlet.

6. A carburetor as defined in claim 5, further comprising biasing means in said bellows bearing upon said partition in a sense tending to discharge air from said second compartment through said outlet.

7. A carburetor as defined in claim 6, further comprising a first check valve between said second compartment and said outlet for preventing the flow of air from said channel to said second compartment, and a second check valve between said second compartment and the atmosphere for enabling the aspiration of ambient air into said second compartment upon displacement of said partition against the force of said biasing means by low pressure in said suction line.

8. A carburetor as defined in claim 1 wherein said second supplemental supply comprises a fuel pump mechanically linked with said throttle means.

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