US2362879A - Carburetor - Google Patents

Description

N v.14,1944. G. M. Emma... 2,362,879

CARBURETOR Filed Feb. 5, 1945 v I l FIG.1.

INVENTOR. GEORGE MBICKNELL I j ATTORNEY.

Patented Nov. 14, 1944 cmmms'ron George M. Bicknell, St. Louis, Mo., assignor to Carter Carburetor Corporation, St. Louis; Mo.,

a corporation of Delaware Application February 3, 1943, Serial No. 474,583

12 Claims.

This invention relates to improvements in internal combustion engines and more particularly to improvements in carburetors and methods of controlling the supply of fuel to obtain the greatest operating efliciency from the engine. The invention is particularly designed for multicylinder engines of the type in which two or more cylinders or groups of cylinders are supplied by separate intake conduits and the most impor-v tant advantages of the invention are obtainable with engines designed to be used under varying conditions of speed and load, such as automotive engines. V

Most automotive engines in use at the present time are operated at speeds and loads substantially below the maximum capacity and this results in loss of efliciency because, the best point on the specific fuel curve of an automotive engine is usually found at speeds and loads above the normal operating speed and load of the engine. Even in truck engines which are normally operated at high speeds and loads, driving con-' ditions make it necessary to frequently operate the engine at speeds and loadsfar below those at which the best efliciency is obtainable,

Another cause of loss of efficiency at low speeds is the poor distribution and vaporization of fuel which results from the use of a Venturi size in the carburetor which has a capacity sufflcient to deliver the amount of fuel mixture required for operation at full power.

In theusual form of automotive carburetors now in use, liquid fuel is discharged into a venturi located anterior to the throttle valve where the suction available for drawing fuel from the. nozzle is substantially directly proportional to the degree of opening of the throttle valve and to the engine speed. It is desirable that the main fuel nozzle discharge into a restricted zone, preferably of Venturi shape,'sothat under the least favorable suction conditions, that is, when the throttle is fully opened, but the engine is operating slowly, quantities of fuel are discharged from the main nozzle. Accordingly, the size of the mixture conduit is necessarily a compromise between the relatively small size which is advantageous at low speeds, and the larger size which has maximum capacity for high speed operation. v

In order to overcome the disadvantages of this compromise, I have proyided two separate main venturis supplied by separate fu'e], nozzles together with a manual throttle valve to control the mixture discharged from one of the venturis and an automatically operated throttle valve to control the supply of additional fuel when required. The automatically operated throttle valve is controlled by a piston or diaphragm, one side of which is exposed to the suction in the venturi of the mixing conduit which is controlled by the manual throttle.

The above described arrangement would result in the operation of only one-half of the cylinders of the engine when the engine is operating at low speeds, except for the provision of a by-pass which-allows fuel from the manually controlled throttle barrel to flow to the mixing conduit operated by the automatically controlled throttle. Ithus obtain two main advantages; first, the fuel supply for all of the cylinders may be taken at low speeds through'a'venturi which is only large enough to supply one-half of the cylinders at high speeds. This results in better vaporization and distribution. The second advantage is that four cylinders operated directly through the manually controlled throttle barrel received mixture much more freely than the other four cylinders which results in operating the first four cylinders much nearer their efllciency peak than would be possible if the power was taken equally from all eight cylinders.

Restriction in the by-pass or barrel passage is sufficient to cause the most of the mixture to be supplied directly to the manually controlled manifold while just suflicient mixture will be supplied to the other passage during low power operation to carry the load of this part of the motor and prevent it being a drag onthe cylinders which are in full operation. At the same time, the by pass is not so small as to prevent motor when the manual throttle is wide open and the automatic throttle is closed as it would be when climbing or accelerating with wide open throttle at a low rate of speed.

Due to the fact that the by-pass or cross passage is not in the direct line of fuel flow, the mixture supplied to the cross passage and to the automatically controlled cylinder group is leaner than that which'is supplied to the manually controlled cylinder group. This results in better economy, and also in maintaining better heating of the automatically controlled cylinders because of the slow combustion of the leaner mixture.

' In order to realize the advantages of my invention more completely, I provide a fuel cut-,oi'l for the main nozzle on the automatic side of the carburetor and this fuelcut-off is controlled by the automatic throttle in such a manner as to prevent the supply of fuel through this main nozzle when the automatic throttle is closed. I also provide an independent idling system for the automatically controlled side of the carburetor although this feature is not necessarily required.

The invention will be better understood upon reference to the accompanying drawing in which:

Fig; l is a diagrammatic perspective of an intake manifold with a sectionalized carburetor mounted thereon.

Fig. 2 is a diagram of the dual manifold ar rangement for application of my invention to a typical eight cylinder engine.

The carburetor shown is of the downdraft type having a divided mixture conduit, the lower portion thereof forming a pair of mixing conduits l and 2 including venturis 3 and 4 and having a common air inlet horn 5. Butterfly throttle valves 6 and I are mounted, respectively, in the lower or discharge portions of the mixture conduits and a choke valve 8 is similarly mounted in air born 5. The choke valve may be operated by any suitable manual or automatic control device (not shown and conveniently of the type shown in CoifeyPatent No. 2,085,351). The air horn is provided with an annular rib 9 to facilitate the mounting of the usual air cleaner and silencer device (not shown).

Throttle valve 6 has an arm l2 rigidly secured, to its shaft l3 and to this arm there is connected a link [4 extending to the usual throttle pedal for manual control of the valve. Throttle I has a lever l rigid with its shaft I6 and to the outer end of this lever there is pinned a rod ll which is secured to the lower, movable end I8 of a bellows I9. The bellows is supported at its upper end by a bracket 20, secured to the body of the carburetor, and an apertured lug 2| slidably receives and guides'throttle operating rod H. A tube 22 extends to a port 23 opening into mixture conduit controlled by manual throttle 6 so that the suction conditions in this conduit are transmitted to bellows 19.

It will be understood that the bellows may be a cylinder and piston or flexible diaphragm, and spring means may be provided if desired to assist the inherent resiliency of the bellows to hold the throttle valve 1 in closed position until the desirable amount of suction has been built up as hereinafter described.

A constant level fuel reservoir 26 is formed on the carburetor in which fuel is maintained at a substantially uniform level by the usual float and needle valve mechanism, the float being shown at 21. A main fuel passage or nozzle 28 communicates with the fuel reservoir through a calibrated stant level fuel reservoir whenever throttle l is metering orifice 28 and discharges into the smallest or primary venturi 3 in mixture conduit l. A second main nozzle 30 communicates with the fuel reservoir through a. calibrated metering restriction 3| and communicates with the smallest or primary venturi 4 in second mixture conduit 2. Metering orifice or restriction 29 is controlled by a metering rod 32 pinned at its upper end to a lever 33 which is pivotally mounted at 34 and connected at its opposite end by mean of a link 35 to an arm 36 rigid with manual throttle shaft [3. Metering pin 32 and its control linkage are arranged so that as manual throttle 6 is opened, the metering pin will be raised so as to progressively move smaller portions thereof into me tering orifice 29 and thus enrich the mixture being discharged through mixture conduit I.

The second metering orifice 3i is controlled by a metering pin 40 yieldingly connected at its substantially closed.

When both throttle valves 6 and 1 are substantially closed, fuel is supplied to mixture-conduits i and 2 through the usual idling ports 48 and d9 communicating with the constant level reservoir through passages 50 and 5| having restrictions 52 and 63 and air bleeds 54 and 55. Idling passage supplying mixture conduit i communicates with the enlarged lower portion 56 of main fuel passage 28 posterior to metering restriction 29 so as to form an interconnected idle in which all fuel for supplying both the main and idling passages flows through a single metering restriction. Idling passage 5| supplying secondary mixture conduit 2, communicateswith the fuel reservoir by means of a port 58 which is independent of secondary main nozzle 30 so that fuel will be discharged from idling ports 49 whenever throttle 1 is substantially closed, regardless of the position of meteringpin 40.

A third arm 60 is formed rigidly on manual throttle shaft l3 and connected by a link 6i to a lever 62 pivotally mounted at 63, the lever being connected at its other end to a piston rod 6t and piston 65 forming an accelerating pump. Piston 65 operates in cylinder 66 so as to discharge a shot of fuel in the mixture conduit I when throttle 6 is open. Any suitable type of accelerating pump and valving may be provided, but I prefer to use the type shown in my Patent No. 2,252,958 having a discharge outlet as diagrammatically indicated at 12. The mixture outlet 61 on the normally controlled side discharges into manifold portion 68 which has one or more outlet branches 69 and HI. These outlets supply fuel to the inner group of cylinders H of the associated internal combustion engine 82. The outer groups of cylinders T2 are supplied from th mixin conduit l3 controlled by the automatically operated throttle l which discharges into the manifold 14 having discharge outlets l5 and 16. Since different engines have different distribution, it may be expedient to mount the carburetor on the manifold structure in such a manner as to have the manually controlled mixture conduit supply outer cylinder groups 12 instead of the inner cylinders, as shown.

In order to provide for the supply of fuel to the outer cylinder groups 12 under part throttle conditions and to assist in damping undesirable pressure pulsations in the manifold, I provide a restricted balance passage Ti which permits the flow of a limited amount of mixture to the manifold portion 14 when the valve 1 is closed. One of the reasons for supplying some fuel to the cylinder groups 12 even when sufficient power could be obtained by operation of the cylinder group II, is to maintain the temperature of these cylinders so that full operation can be instantly resumed and other reasons which will be apparent to those skilled in the art. This requirement, is well satisfied by the delivery of a leaner mixture than might be desirable otherwise, particularly because maximum economy and also greater heating effect are obtainable from a leaner mixture. The position of the passage Tl with respect to the fuel discharge is such that only fuel aseasre V 3 which has been substantially gasified enters this passage from the discharge outlet 61, the unvapo rized fuel being discharged downwardly through the manifold 68 therebycausing the mixture delivered to the cylinder group H to be richer than that delivered to the groups 12.

' In the operation of the carburetor, the-carbureting elements shownat the left side of" "Fig. l, includingmixture conduit I, main noz- 21 ,28, idling system 48, 50, metering pin 32, and the accelerating pump function to provide properly metered fuel for all low speed operating conditions. The elements shown at the right side When the engine is operated under part throttle conditions at comparatively low speeds, for

' instance 15 to 40 miles per hour in a car which is capable of a maximum speed of approximately 85 miles per hour, most of the power will be delivered by the inner cylinder group II so that these cylinders will be operating more efliciently than that would be the case if abalanced amount of power were taken from all 8 cylinders. Cylinder groups 12 will deliver a comparatively small amount of power and operate on a rather lean mixture so as to consume very little fuel. During acceleration substantially all of the fuel will be supplied through the mixing conduit 61 but enough mixture will flow through the by-pass and manifold 15 and 16 to cause cylinder groups I2 to carry substantially their full load. At higher speeds, when throttle 'l is open, the fuel supply from mixing conduit 61 will be delivered entirely to cylinder group H and cylinder groups 12 will be supplied from mixing conduit 13.

Various modifications may be made as will occur to those skilled in the art and the exclusive use of all modifications as come within the scope of the appended claims is contemplated.

I claim:

1. In an internal combustion engine having a plurality of cylinder groups, separate intake conduits for supplying fuel mixture to said groups, a manually operated throttle valve for controlling one ofsaid conduits, a throttle valve for another of said conduits, means responsive to the velocity of flow through the manually controlled conduit for controlling the throttle in the otherconduit, and a cross passage connecting said conduits posterior to said throttle valves.

2. In an internal combustion engine having a plurality of cylinder groups, separate intake conduits for supplying fuel mixture to said groups, a manually operated throttle valve for controlling a first one of said conduits, a second throttle valve for ,a second of said conduits means for controlling said throttles, and means for supplying a limited amount'of fuel mixture from said first conduit to said secondconduit when said second throttle is closed.

the supply of fuel mixture to a first one of said groups, asecond throttle valve controlling the supply of fuel to another of said groups, idling systems discharging adjacent said throttle'when closed, means normally closing said second throttle when the power required from the engine is comparatively small, means responsive to increased power demand for opening said second throttle, and means to bypass a reduced supply of fuel to said second group from the conduit supplying said first group when said second throttle is closed.

4. In an internal combustion engine having a plurality of cylinder. groups, separate intake conduits for supplying fuelmixture to said groups, a manually operatedthrottle valvefor normally controlling the supply of fuel mixture to one of said groups, a second throttle valve controlling thesupply of fuel to another of said groups, means normally closing said second throttle when the power required from the engine is compara tivelysmall, means responsive to increased power demand for opening said second throttle, and means for partially relieving the suction in said second intake conduit when said manual throttle is moved towards open position.

.5. The method of operating an internal combustion engine of the type having a plurality of cylinder groups which comprises supplying idling fuel to all of said groups, increasing the fuel supply to different groups at different rates in response to increased power demands until one of said groups is receiving all the fuel it requires for full power operationat a predetermined intermediate speed, while restricting the fuel supply,

to another group, and increasing the fuel supply to the other of said groups in response to a further increase in .power demand.

6. The method of operating an internal combustion engine of the type having a plurality of cylinder groups which comprises supplying idlin fuel to all of said. groups, increasing the fuel 7 supply to different groups at different rates in response to increased power demand until one of 1 said groups is receiving all the fuel it requires for full power operation at a predetermined intermediate speed, while restricting the fuel supply to another group, and increasing the fuel supply to the other of said groups in response to an increase in engine speed.

c 7. The method of operating an lntemal combustion engine which comprises operating all cylinders of the engine during idling, increasing the ficient fuel to a part of the cylinders to developa the necessary power for operation at normal loads, supplying only suflicient fuel to the remaining'cylinders to keep them in operation atnormai loads and supplying maximum fuel to all cylinders when the engine is operating under full load.

9. The method of operating an internal combustion engine of the type having a plurality of cylindergroups which comprises supplying sufflcient fuel to one group of said cylinders for developing the power required to operate under normal loads, supplying a smaller amount of fuel of leaner quality to another group of cylinders to keep them in operation while the power is being developed by the first group of cylinders, supplying maximum quantities of fuel of substantially equal quality to all cylinders during full load operation.

10. The method of operatin an internal combustion engine of the type having a plurality of cylinder groups which comprises supplying sufduits and carburetors for supplying fuel mixture to said groups, a manually operated throttle for controlling a first one of said carburetors, a second throttle and a liquid fuel valve controlling the supply of fuel by said second carburetor, means normally closing said second throttle and said fuel valve to cut off the supply of fuel by said second carburetor when the power required from the engine is comparatively small, means responslve to increased power demands for opening said second throttle and fuel valve, and means for supplying a limited amount of fuel to said conduit when said second throttle and said fuel valve are closed.

12. In an internal combustion engine having a plurality of cylinder groups, separate intake conduits and carburetors for supplying fuel mixture to said groups, throttle valves for said conduits, idling systems discharging adjacent said throttle valves when closed, a fuel valve controlling the supply of liquid fuel to said second conduit, and a bypass between said conduits for supp ying fuel from said first conduit to said second conduit when said liquid fuel valve is closed.

GEORGE M. BICKNELL.

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