US3539157A

US3539157A - Fuel metering system

Info

Publication number: US3539157A
Authority: US
Inventors: Edward F Fort
Original assignee: International Harverster Corp
Current assignee: Navistar International Corp
Priority date: 1969-05-14
Filing date: 1969-05-14
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10

Description

O United States Patent 1 3,539,157

[72] Inventor Edward F. Fort 3,326,539 6/1967 Phipps 26l/76X Napervllle, Illinois 3,386,710 6/1968 York 261/36 [211 Appl. No. 824,435 3,389,894 6/1968 Binder 26l/69X [22] May 1969 Primary Examiner-Tim R. Miles [45] Patented Nov. 10, 1970 AHOmey NOeI Arman [73] Assignee International Harvester Company Chicago, Illinois a corporation of Delaware [54] FUEL METERING SYSTEM Cl 1 5 D Fl 8 8 rawmg gs ABSTRACT: A carburetor construction for metering liquid [52] US. Cl. 261/34, f l f delivery upstream f the throttle valve to a Spark igni 261/69 137/815 123/119 tion engine having but one fuel delivery system for all engine [51] Illl. Clo operating conditions including as we as load condi [50] Field of Search 26l/34.l, tions. The system features a unique fuel discharge member 76; 137/815; 123/119 positioned centrally in the airflow conduit, having two sets of discharge orifices connected to the outlet lines of a propor- [56] References cued tional type fluid amplifier. Recycling of fuel in excess of en- UNITED STATES PATENTS gine demand to the fuel supply reservoir is avoided as well as 2,991,052 7/1961 Carlson et al. any necessity for a secondary source of fluid pressure.

- FUEL METERING SYSTEM BACKGROUND OF THE INVENTION spark ignition internal combustion engine. More in particular this invention relates to a carburetor construction employing a proportional fluid amplifier in combination with a fuel discharge member having two distinctly different sets of fuel discharge orifices wherein the entire combination is positioned within the airflow conduit adjacent the venturi portion thereof in a manner wherein the resulting system singularly is capable of supplying fuel to the engine at a substantially constant air-fuel ratio for all loads imposed upon the engine and still permit the engine to idle without a second idling fuel system.

It will be noted from the description herein that in the present invention the control of fuel flow to the engine is basically accomplished by a proportional type fluid amplifier which proportions the flow of fuel into two different sets of fuel delivery orifices and the amount of fuel thus delivered is metered in accordance with engine demand without the need for applying an external source of auxiliary pressure.

The prior art carburetor constructions usually provide two fuel metering systems of which the first is employed to deliver fuel upstream of the throttle valve during operating conditions imposing a load upon the engine and the second system delivers fuel downstream of the throttle valve for idling engine operating condition. Thus transition from one system to the other system during operation is required whereas in the present invention such transition is avoided.

US. Pat. No. 3,386,710 describes a fuel'metering system employing a fluid amplifier wherein the flow of liquid fuel is split into two streams, one of which discharges through a nozzle into the airflow conduit to the engine and the other stream discharges its liquid. fuel presumably to a fuel reservoir for recycling. The principal difference is that in the present invention a fuel discharge body of unique construction is employed which is provided with two distinctly differently positioned fuel discharge orifice means, one being connected to a first outlet of a proportional fluidic amplifier and the other connected to a second outlet whereby fuel flow to the two sets of discharge orifice means is proportioned in accordance with engine demand instead of recycling some of the fuel back to the fuel reservoir. Further departures from'that described in the aforementioned patent will also be noted such as, for examples, the position of the fluid amplifier with respect to the fuel float chamber; the ventu ri portion of the air inlet conduit,

and the fuel discharge orifice means.

SUMMARY OF THE INVENTION The principal object of the present invention is to provide a carburetor for a spark-ignition internal combustion engine having a fluidic fuel metering system which'system is singularly capable of delivering all metered fuel through a discharge body having a compound orifice means and a fluid amplifier.

Another important object of the invention is to provide a carburetor according to the preceding object wherein no portion of liquid fuel is directed back to the fuel reservoir for recycling.

A further important object of the invention is to provide a carburetor according to any of the preceding objects wherein no external or auxiliary secondary source of pressure is required.

Yet another important object of the invention-is toprovide a carburetor according to any of the precedingobjects wherein the fuel metering requirements are met according to engine demand and accomplished without requiring moving parts for metering.

Still another important object of the invention is to provide a carburetor according to any of the preceding objects which is capable of operating an internal combustion engine employing substantially constant predetermined fuel-air ratios throughout all or nearly all of the range of engine load.

These and other'desirable objects inherent in and encompassed by the invention will become more apparent from the ensuing description of a preferred embodiment, the appended claims, and the annexed drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side view, partly broken away, of the carburetor construction of the present invention showing the position of the fuel discharge body in the air inlet conduit;

Flg. 2 is a plan view of the carburetor of the present invention.

FIG. 3 is an underside view of the fuel discharge body taken as indicated on line 33 ;of FIG. 1 showing the lower .fuel discharge orifices;-

FIG. 4 is a horizontal sectional view taken on line 4-4 of FIG. 1 illustrating the position of the fluid amplifier in the fuel discharge body; and

FIG. Sis a vertical sectional view taken on line 5-5 of FIG. 2 illustrating the various components of the carburetor more in detail.

' DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing the carburetor of this invention is indicated generally by the numeral 10. The carburetor 10 includes an inlet airflow conduit 11 having its upper end in communication with the atmosphere, usually through a conventional air filter (not shown) and its lower end in communication with the cylinders, through an intake manifold, of an internal combustion engine (not shown).Air flowing through the conduit 11 is controlled by a conventional throttle valve generally indicated at 12 which is varied by a rotational movement of the throttle valve shaft 13 in a conventional manner as indicated by the arrows in FIG. 1.

The conduit 11 includes a restriction or primary venturi portion 14 which reduces the static pressure of air flowing therethrough to create control signal pressure values related to the rate of air flowing through the conduit 11 as will be evident hereinafter. I

g The carburetor 10 is provided with a conventional fuel float bowl or float chamber indicated generally at 15. The chamber l5 includes a float 16 connected to an arm 17 pivotally connected at 18 to a sidewall 19 of the carburetor 10. The arm 17 is provided with a valve element 20 in cooperative alignment with valve seat 21 in a conventionalmanner as best illustrated in FIG. 5. A source of liquid fuel under pressure above atmospheric is connected to pipe'22 whereby liquid fuel is conventionally admitted into the float chamber 15 via pipe 22 and

valve

20, 21 until the amount of fuel 23 in the float chamber 15 reaches a predetermined fuel level 24 as indicated best in FIG. 5.

Referring again to FIG. 5 it will be observed that the upper portion of the float chamber 15 above the fuel level 24 is in communication with the inlet airflow conduit through passage 25 having a scoop 26 positioned to impose a pressure upon the surface of fuel 23 proportional to the total pressure of the air flowing through the conduit 11 at signal pressure region X. Thus the pressure value imposed upon the fuel 23 in float chamber 15 is approximately constant and essentially independent of the rate of airflow passing through pressure region X in the conduit 11. 4

The carburetor 10 includes a fuel discharge hody indicated generally by the numeral 27. As will be evident from FIG. 5 the discharge body 27 includes a hollow frustoconical shaped element 28'positioned concentrically within the airflow conduit 11 having an upper opening 29 in the pressure region X. The discharge body27 also includes a lower opening 30 which opens into signal pressure region Y in the conduit 11. At this point it will be observed that pressure region Y is the region of lowest pressure generated by the air flowing through the restriction 14 (primary venturi portion) of the conduit 11.

Referring again to FIG. 5 it will be seen that the upper opening 2? of the fuel discharge body 27 communicates with the lower opening 30 through a hollow portion 31 in the discharge body 27 which hollow portion 31 includes a restriction or secondary venturi portion 32. Thus it will be apparent that some of the air entering the pressure region X will pass through the upper opening 29 of the discharge body 27 through the hollow portion 31 and discharge through the lower opening 30 into the pressure region Y of the conduit 11. Movement of air through the hollow portion 31 of the discharge body 27 generates a signal pressure region Z of the secondary venturi portion 32 which region has pressure values lower than the corresponding pressure values in the pressure region Y for a given rate of air flowing through the conduit 11.

It will also be apparent from FIGS. 4 and that of the total amount of air passing through pressure region X of the conduit 11 only a minor percentage of such air passes through the hollow portion 31 of the fuel discharge body 27. The relationship of the pressure values in pressure regions X, Y, and Z for various engine operating conditions will be discussed later herein.

Referring again to FIG. 5 it will be seen that the fuel discharge body 27 includes a support member indicated generally at 33 which projects laterally into an aperture 34 disposed in sidewall 35 of the carburetor in supporting relation. Thus the hollow conical-shaped element 28 of the fuel discharge body 27 is supported concentrically within the conduit 11 as is evident from FIGS. I, 2, 4, and 5.

Referring now to FIGS. 4 and 5 it will be seen that within the fuel discharge body 27 there is a proportional fluid amplificr, indicated generally by the numeral 36, having an interaction zone 37. Liquid fuel 23 from the float chamber 15 enters the interaction zone 37 through fuel inlet tube 38 and nozzle 39 as indicated. The fluid amplifier 36 includes an upper outlet 40, which discharges fuel into the hollow portion 31 of the discharge body '27 through port 41 and also a lower outlet 42 which discharges fuel from the interaction zone 37 to discharge orifices 43 disposed in the lower end portion of the discharge body 27.

In FIGS. 3 and 5 it will be seen that in the lower portion of the discharge body 27 there is an annular passage 44 which is communicatively connected to the lower outlet 42 of the fluid amplifier 36 through passage 45. The bottom surface of the discharge body 27 is provided with a plurality of peripherally disposed vertical discharge orifices 43which communicate the annular passage 44 with pressure region Y. Thus fuel from the interaction zone 37 of the fluid amplifier 36 passing sure region Y of the conduit 11 through passage 45, annular passage 44, and discharge orifices 43 whereby the airstream passing through pressure region X is converted to an air-fuel mixture stream for delivery to the cylinders of the associated engine.

Referring to FIG. 4 it will be seen that the fluid amplifier 36 includes a splitter 46 which is positioned to divide the stream of liquid fuel entering the interaction zone 37 from the inlet nozzle 39. The proportioning of the liquid fuel emanating from the inlet; nozzle 39 into the interaction zone 37'to the upper and lower outlets 40, 42 of the fluid amplifier 36 is governed by a system of signal pressures which will now be described.

Referring to FIG. 4 it will be seen that the fluid amphfier 36 includes a lower signal pressure passage 47 and an upper signal pressure passage 48 both of which communicate with the interaction zone 37. The lower signal pressure passage 47 communicates with the pressure region Y of the conduit 11 through a downwardly extending pipe 47a projecting thereto as will be evident from FIGS. 1, 4 and 5. Likewise the upper signal pressure passage 48 communicates with the pressure region X of the conduit 11 through an upwardly extending pipe 48a projecting thereto as will be evident from FIGS. 1, 3 and 4. The operation of the carburetor 10 will now be described.

In explaining the operation of the carburetor 10 it is pointed out that the term pressure" as used herein is intended to mean absolute pressure thus avoiding any confusion which might arise if the term vacuum was used.

The static pressure value in signal pressure region X during engine operation will always be slightly below atmospheric pressure and will vary but slightly throughout all engine operating conditions. However, these very slight static pressure changes are augmented somewhat by the action of the scoop 26. Thus the static'pressure existing above the fuel level 1 24 in the float chamber 15 will be equal to or perhaps slightly higher than the static pressure value existing in signal pressure region X. I

For a given engine operating condition the static pressure value in the signal pressure region Z will always be lower than the corresponding pressurevalue in the signal pressure regions X and Y. Further, the corresponding pressure value; in the signal pressure region Y will always be less than the corresponding static pressure value in signal pressure region X but greater than the corresponding pressure value' in signal pressure region 2. In short the static pressure value in pressure region Y will always be a value between the corresponding pressure values of pressure regions X and Z. From this it will be apparent that the motivating force for moving the fuel 23 fuel level 24 is always just slightlybelow the horizontal plane of the inlet nozzle 39 of the fluid amplifier 36. If the fuel level 24 is above the horizontal plane of the inlet nozzle 39 fuel would drain into the inlet airflow conduit 11 when the engine is stopped which, of course, is undesirable. On the other hand if the fuel level 24 is considerably below the horizontal plane of inlet nozzle 39 anunnecessarily high pressure differential between pressure region X with respect to pressure regions Y and Z would be required to move the fuel 23 through the inlet nozzle 39 which of course undesirably reduces sensitivity to fuel flow. From this it will be apparent that by proper sizing of the inlet nozzle 39 the fuel 23 is metered into the interaction zone 37 of the fluid amplifier 36 as a function of the integrated static pressure values existing in the signal pressure regions X, Y and Z for any given condition of engine operation. Thus the size of the restriction in the inlet nozzle 39 controls the fuelto-air ratio. A

The metered liquid fuel 23 entering the interaction zone 37 of the fluid amplifier 36 as above described is now directed proportionately to the

spill ports

41 and 43 through upper outlet 40 and lower outlet 42, respectively, as a function not only of the pressure differential existing between signal pressure regions X and Y acting through signal pressure passages 48 and 47, respectively, but also the static pressure value existing in pressure region Z which is reflected in the upper outlet 40 of the fluid amplifier 36. Hence the proportioning of liquid fuel from the interaction zone 37 through the spill or

discharge ports

41 and 43 is also a function of the integral static pressure values existing in the signal pressure regions X, Y, and Z for any given condition of engine operation.

From the above it will be apparent that when the engine is idling (low rate of airflow through conduit 11) most if not all of the fuel metered into the interaction zone 37 will bt discharged through the spill port 4I.'Conversely, when the engine is operating at or near full load condition (high rate of airflow through conduit 11) substantially all of the fuel metered into the interaction zone 37 will be discharged through the ports 43. During intermediate engine operating conditions fuel emanates from ports 43 as well as that of port 41. Of course it is apparent that the discharge body 27 may have other configurations for the discharge orifices'4l and 43 depending somewhat on space limitations.

smoothly for a good cylinder-to-cylinder distribution of substantially constant air-fuel ratio mixture is achieved. During engine operating conditions of part load or full load the velocity of the air flowing into the conduit 11 is much greater and hence the turbulence existing in pressure region Y at orifices 43 is quite high thus again resulting in good vaporization of fuel in substantially constant air-fuel ratio. However, it is pointed out that the fluid amplifier 36 preferably should be positioned in close proximity to the hollow conical-shaped element 28 as otherwise the sensitivity of this fuel system is lessened with reference to the pressure changes occurring in the pressure regions X, Y, and Z.

Having thus described a preferred embodiment of the invention, it can now be seen that the objects of the invention have been fully achieved and it must be understood that changes and modifications may be made which do not depart from the spirit of the invention as disclosed nor'from the scope thereof as defined in the appended claims.

lclaim:

I. An internal combustion engine fuel metering system comprising:

a. an inletairflow conduit having a primary venturi portion disposed therein capable of generating a first signal pressure region in said primary venturi portion and a second signal pressure region upstream of said primary venturi portion in an airstream flowing therethrough;

b. said conduit having a throttle valve means for controlling and an upper opening extending into said second signal pressure region;

. said discharge body having a secondary venturi portion in said hollow portion capable of generating a third signal pressure region in said airstream;

a proportional fluid amplifier having an interaction zone positioned in adjunctive relation to said secondary venturi portion of said discharge body;

g. said fluid amplifier having an upper outlet communicatively connecting said interaction zone to a first fuel discharge means in said discharge body;

h. said fluid amplifier having a lower outlet communicatively connecting said interaction ,zone to a second fuel discharge means in said discharge body;

. signal pressure passage means communicatively connecting said interaction zone with at least one of said pressure regions;

j. a source of liquid fuel under pressure proportional to the pressure in said second signal pressure region; and k. fuel inlet means communicatively' connecting said interaction zone with said source of liquid fuel whereby the integrated pressure values of said signal pressure regions regulate the rate of flow of fuel through said fuel inlet means into said interaction zone and said fluid amplifier proportions the flow of said fuel through said first and second fuel discharge means into said airstream for converting said airstream to an air-fuel mixture of substantially constant air-to-fuel ratio.

2. An internal combustion engine fuel metering system according to claim 1 wherein said first fuel discharge means comprises at leastone spill port positioned adjacent said secondaryventuri portion in said hollow portion of said fuel discharge body for discharging fuel into said third signal pres sure region of said airstream.

3. An internal combustion engine fuel metering system according to claim 1 wherein said second fuel discharge means comprises a plurality of fuel discharge orifices positioned in said fuel discharge body for discharging fuel into said first signal pressure region of said airstream. 1

4. An internal combustion engine fuel metering system according to claim 1 wherein said signal pressure passage means includes a first signal pressure passage communicatively conmeeting in signal relation said interaction zone with said first signal pressure region in said airstream and a second signal passage communicatively connecting in signal relation said interaction zone with said second signal pressure region in said airstream.

5. An internal combustion engine fuel metering system according to claim I wherein said source of liquid fuel comprises a chamber positioned adjacent said primary venturi portion of said inlet airflow conduit, the lower portion being filled with liquid fuel to a' predetermined level, and the upper portion of said chamber communicatively connected to said second signal pressure region. r

6. An internal combustion engine fuel metering system according to claim Swherein the communicative connection a between the upper portion of said chamber and said second signal pressure region includes a scoop disposed in said region of said conduit positioned to augment changes in static pressure values existing in said region for correspondingly imposing said augmented pressure values in said upper portion of said chamber.

7. An internal combustion engine fuel metering system according to claim 5 wherein means are provided in said chamber for limiting the entry of liquid fuel therein to a predetermined fuel level, said fuel level being slightly below said interaction zone of said fluid amplifier. 8. An internal combustion engine fuel metering system according to claim 1 wherein said fuel discharge body is positioned concentrically in said airflow conduit between said first and second signal pressure regions, said body being supported by a support member fixed to a sidewall of said conduit.