US3556067A - High air velocity carburetor - Google Patents

Abstract

A carburetor utilizing high air velocities, and having primary and secondary venturi circuits. The secondary circuit begins to function in response to the primary throttle position, with both circuits fully operating to supply fuel from the ''''pickup point'''' to wide open throttle. The primary circuit is designed to provide maximum manifold depressions of a high order at certain engine speeds.

Description

United States Patent [72) Inventor Stephen Woods Harper Woods, Mich. (14155 Shadywood Drive, Apt. 63, Plymouth, Mich. 48170) [21) Appl. No. 822,828 [22] Filed Apr. 9, 1969 [45] Patented Jan. 19, 1971 Continuation-impart of application Ser. No. 629,488, Apr. 10, 1967, now abandoned.

[54] HIGH AIR VELOCITY CARBURETOR 5 Claims, 3 Drawing Figs.

[52] U.S.Cl 123/127, 261/23, 261/39, 261/41, 261/43, 261/64 [51] Int. Cl UFOZm 13/06 [50] Field ofSearch 261/43, 41.3,64,23, 50.1, 39.2DP; 123/127 [56] References Cited UNITED STATES PATENTS 1,676,827 7/1928 Howard et a1. 123/127 1,904,634 4/1933 Teeter.

Prentiss.

Farrell.

Olson Gretz.

Manning, Jr Bartholomew Martin.

Cook et a1. Kalert, .lr.

Smith Bickhaus et al.

Primary Examiner-Wendell E. Burns Atl0rneyWhittemore, I-Iulbert & Belknap PATENTEB JAN-1 9 I9" INVENTOR STEPHEN Woops av 4 iulilliuliil.

HIGH AIR VELOCITY CARBURETOR This application is a continuation-in-part of my copending application Ser. No. 629,488 filed Apr. 10, I967. SUMMA- RY OFTHEINVENTION I j The invention relates to a high'air velocity carburetor and more particularly to a carburetor evidencing substantially increased performance characteristics.

I-Ieretofore. carburetors for high speed internal combustion engines capable of about 2,800 rpm. or more at wide open throttle have required the use of an accelerator pump and/or economizer to obtain full power from the engine at above about 550 rpm. When the throttle was suddenly opened full from a closed position at about 500 rpm. the depression usually dropped to about .Sinches'of Mercury'or less, which is practically O depression, with a resultant temporary loss of fuel flow. This has cre'atedehgine power loss problems which werecircumvented by the use of an accelerator pump.

The present invention substantially eliminates the problems incident to use of an accelerator pump and provides improved engine acceleration performance percent little fuel waste and hydrocarbon emission. In accordance with the inventive concept, a primary venturi system is utilized in intimate conjunction with a secondary venturi system whereby a substantially high air velocity is maintained in the carburetor at all loads and engine speeds, from idle "and off idle road load through mid range road load and wide open throttle. The primary ven turi system supplies about percent to 50 percent of the engines total air requirements, while the secondary venturi system supplies about 50 percent to90 percent of the requirements. i

The concept of the invention eliminates completely the need for the accelerator pump andjeconomizer, and instead relies upon the secondary venturi system which is added to a primary venturi system and wherein the primary venturi is respectively which form vertically extending primary and secondary chambers 13 and 14 respectively. Chambers 13 and 14 are separate, but converge below wall 15 into a common 7 throttle bore 16 formed in an annular throttle body 17 which has a entrance throat l8. Bore 16 thus connects with and serves both the primary and secondary systems, and is provided with a suitably actuated throttle plate I9 therein pivoted on pin 19'.

The wall of primary chamber 13 is provided intermediate its ends with-a restriction forming a main venturi 20 for the air flow. A booster venturi 21 of greater restriction than main venturi 20 is disposed in the throat ofthe latter. At the top or intake of chamber 13, a suitable choke plate 22 is pivotally mounted on pin 22' and is actuated in any well-known way.

Fuel from bowl 5 passes into chamber 13 and is mixed with air passing downwardly therethrough. Assume that the engine is at curb idle and that choke plate 22 is at the substantially open position shown in full lines in FlG. 2, with throttle plate 19 also at substantially closed curb idle position shown in full lines. Fuel from bowl 5 will be drawn up through a main jet member 23 in the lower portion of primary well chamber 9, and hence upwardly through a tubular idle channel 24 having an idle feed restriction at its lower end. Channel 24 extends inwardly from chamber 9 and across primary chamber 13 slightly upstream of venturis 20 and 21, as at 25, and hence downwardly through the carburetor wall and connects to a restricted in sucha way as to provide substantially higher air velocities than have been used heretofore. For the concept to operate, it has been found that the manifold depression must be substantially higher than a mere few tenths of an inch of Mercury. i

The secondary throttle plate is fully responsive to the position of the primary throttle plate, and in turn controls a secondary air valve. The rate ofopening of the latter valve may be controlled to produce the desired acceleration rate, and various types of such valvesare contemplated.

The accompanying drawing illustrates the best mode presently contemplated by the inventor for carrying out the invention. I

In the drawing:

FIG. 1 is a top plan view of a carburetor constructed in accordance with the invention.

FIG. 2 is a section taken on line 2-2 of FIG. 1, with the fuel wells repositioned about 90 and the fuel bowl bisected and also repositioned for purposes of clarity.

FIG. 3 is a sectional view of a second embodiment of secondary venturi air valve control means.

The carburetor illustratedin the drawings is of the single barrel type. However, any multibarrel construction may be used without departing from the spirit of the invention.

As shown in FIGS. I and 2 of the drawing, the carburetor is of the down draft type and comprises a housing 1 which includes a fuel-receiving portion 2, a primary system portion 3 and a secondary system portion 4.

Fuel-receiving portion 2 comprises a chamber in housing 1 which forms a fuel bowl 5 adapted to contain fuel which enters the chamber through a suitable fuel inlet 6 having a control valve 7 therein. Valve 7 is automatically actuated by a float 8 which operates in the conventional manner to fuel fuel to flow into the bowl.

During operation of the carburetor, fuel from bowl 5 passes through a pair of separate well chambers 9 and 10 and into primary and secondary portions 3 and 4 respectively, as will be described.

Primary and secondary portions 3 and 4 comprise a pair of closely adjacent generally cylindrical members 11 and I2 passageway 26 in throttle body 17.,Passageway 26 is provided with a lower curb idle port 27 andan upper idle transfer port 28 for passage of fuel at idle into the engine intake manifold. Ports 27 and 28 straddle throttle plate 19 when the latter is in its curb idle position.

In the curb idle position, fuel will flow through curb idle port 27, which is adjustable as to size by an idle adjustment screw 29 to provide .the proper idle fuel mixture. As throttle plate 19 opens, upper idle transfer port 28 is also exposed, adding additional fuel as the engine requires it. Further opening of throttle plate 19 gradually reduces the manifold depression, but also increases the air flow velocity past portion 25 of channel 24. A small downwardly extending idle bleed opening 30 is disposed in portion 25, and as the air velocity increases past the opening, an increasing depression is created at the opening. Finally, when throttle plate, 19 has reached a certain open position, the depression at idle bleed opening 30 will reach equilibrium with the manifold depression. Fuel will then no longer flow through idle channel 24 to ports 27 and 28, but will instead fall through opening 30 past venturis 21 and 20 and through throttle bore 16 into the engine manifold. At the same time, fuel in bowl 5 will pass upwardly through a cylindrical well housing 31 which surrounds channel 24 in the well and hence discharges from a tube 3.2 in the area of booster venturi 21 and is drawn downwardly through throttle bore 16.

It is at this pickup point" that the secondary venturi system takes over.

Throttle plate 19, which is common to both venturi systems at the throttle bore 16, is connected, as by pivotal links 33, 34 and 35 to a secondary throttle plate 36 pivotally'mountedon pin 36' which is disposed in secondary chamber 14 adjacent the lower end of wall 15. In addition, an air valve which may take the form of a pivotal plate 37 mounted on pivot pin 37', is

disposed at the top or air intake of chamber 14. Fuel from fuel bowl 5 is supplied to secondary chamber 14 through a system of supply passages which are substantiallysimilar to those in the primary venturi system, and which supply fuel to the secondary venturi 38. The idle channel 24 and associated ports are not duplicated in the secondary system.

During initial opening of throttle plate 19, secondary throttle plate 36 remains substantially closed due to the lost motion built into the linkage system by reason of the fact that the upper end of link 34 has a slidable connection with slot 39 in link 35. At the so-called pickup point," plate 19 is in the predetermined dotted position shown as A in FIG. 2. As throttle plate 19 is opened further, the linkage causes throttle plate 19 is opened further, the linkage causes throttle plate 36 to begin to open. By varying the linkage construction. the rate of opening of plate 36 relative to plate 19 can be changed to provide different fuel-air mixtures at different loads and engine speeds to suit performance requirements.

As secondary throttle plate 36 opens, air valve plate 37 is subjected to increased downward air pressure tending to open it from its generally closed position shown in full lines in FIG. 2. As this occurs, additional air flow is generated through secondary chamber 14 and through bore 16. Depending upon the particular engine requirements, the responsiveness of plate 37 to air pressure, and thus the plate opening rate, can be controlled.

In addition, it is preferable to prevent sudden snaplike opening of the valve 37. For this purpose, control means are provided to govern or dampen the opening rate of the valve.

One embodiment of control means is shown in FIGS. 1 and 2, wherein a plurality of pressure relief openings 40 are formed in plate 37, which allow air to filtrate through the valve at a predetermined calibrated rate. This reduces the initial force exerted on plate 37 when secondary throttle plate 36 is opened, and also provides a controlled initial rate of opening. Openings 40 are properly calibrated and disposed in the positions shown on an arc at progressively increasing distances from the pivot pin 37 for plate 37.

A second embodiment is shown in FIG. 3, wherein valve plate 37 is secured through suitable pivotally connected links 41, 42 to pneumatic dashpot which includes a plunger 43 movable within a cylinder 44. Plunger 43 is preloaded, as by a compression spring 45 which can be changed to provide the desired rate of dashpot operation. A bleed opening 46 in the wall of cylinder 44 controls the flow of air out of the dashpot chamber and may connect to primary chamber 13, wherein increased air flow through the chamber puts a vacuum on plunger 43 to assist in overcoming the force of spring 45.

The embodiments of openings 40 shown in FIGS. 1 and 2 and the dashpot shown in FIG. 3 provide controlled initial restraint to the movement of valve plate 37. Other resistance means may be provided without departing from the spirit of the invention. I

It has been found that the combined primary and secondary systems will only function in a manner which eliminates the requirement for an accelerator pump and economizer if very high air flow velocities are utilized. These velocities must be reflected in the following manifold depressions for the concept of the invention to operate:

1. To eliminate accelerator pump:

At Wide Secondary Throttle Plate lnoperative:

A. Manifold depression must be not less than 3 inches of Mercury 3,600 1,200 engine r.p.m.

B. Manifold depression must be not less than 7 inches of Mercury 0 3,600 engine r.p.m.

II. To eliminate economizer:

At pickup point" with Secondary Throttle Plate 36 Beginning to Open:

A. Manifold depression must be not less than inches of Mercury 0 700 engine r.p.m.

B. Manifold depression must be not less than 9 inches of Mercury 0 3,000 engine r.p.m.

It will be understood that there may be small reductions at times in these stated minimum depressions. within the scope of the invention. While I have determined that reduction of depression below the stated minimums by as much as .25 inches Hg, at wide open primary throttle may be unacceptable, reductions of depression below the stated minimums by as much as .5 inches Hg. at the "pickup point" may still produce satisfactory results.

If the depression values are permitted to fall below those given above, it is been found that major problems of engine hesitation, stumbling and stalling develop. This has been found to be true, regardless of the displacement of the particular engine.

In accordance with the invention, the area of main venturi will have to be restricted to a given maximum, which in turn will depend on the displacement of the particular engine or engines with which the carburetor is to be used. If the venturi area is smaller than the determined maximum. no harm will result. since this will increase the depression above the minimum values given above. and the smooth performance of the carburetor will be maintained.

An example of determining the theoretical main venturi size to satisfy the requirements for an engine of given displacement is as follows:

It will be assumed that the engine is four-cycle with 290 cubic inches. It is first necessary to calculate the engine air requirements. It can be shown that:

(A) (1) 100.6 c.f.m. at 1,200 r.p.m. (A) (2)==1.666 c.f.s. at 1,200 r.p.m. (B)(1)=302.0 c.f.m. at 3,600 r.p.m. (B) (2)=5.033 c.f.s. at 3,600 r.p.m.

displacement X air flow, cu. ft./min.=

A. 3 inches Hg. .25 ft. Hg.

B. 7 inches Hg. .5833 ft. Hg.

It is now necessary to convert feet of Mercury to feet of air. Using the formula:

B. -y,, specific weight of Hg. 845.3 lb./cu.ft.

C. h ft. of flowing air 7 Specific weight of air .073 lb./cu.ft. it is possible to show the following:

A. At 3 in. or .25 ft. of Hg., flowing air= 2894.7 cu. ft.

B. At 7 in. or .5833 ft. of Hg, flowing air 6754.3 cu. ft.

The law of continuity of flow is: Q AV, where 1. Q Quantity offluid air flowing in c.f.s.

2. A Cross-sectional area of the restriction at point of velocity pressure in sq. ft.

3. V Fluid air velocity in f.p.s.

=v v where:

(A) g= Gravitational acceleration in ft./sec./sec. (B) h =Vel0city head in feet of fluid flowing air= h (from above) Since h =h and Q=AV,

and

it is possible to show that A. A .84 in. diameter venturi at 1,200 r.p.m.

B. A 1.047 in. diameter venturi at 3,600 r.p.m.

Thus, a venturi of .84 in. diameter would satisfy the above specified requirements as to minimum manifold depression. It would be suitable for both 1,200 r.p.m. and 3,600 r.p.m. since it would give a value above the minimum at 3,600 r.p.m. The venturi of 1.047 in. diameter would not satisfy the requirements, since it would give a value below the minimum at 1,200 r.p.m.

The above example is based on a theoretical engine of 100 percent efficiency, rather than the normal 80 percent -85 percent of most high compression engines. in addition, frictional losses in the airflow, as well as temperature and barometric variations have not been considered.

Perhaps the biggest source of friction in a carburetor is in the venturi restriction itself and in the size of the throttle bore 16 and air chamber 13. It can be shown that, with a given manifold depression, as the difference between venturi area and throttle bore area increases, the airflow capacity of the carburetor increases. Thus, to remain above the minimum manifold depression values given above, the size of venturi 20 should be determined, and the throttle bore adjusted in size to give the desired airflow characteristics. in addition to, or in place of throttle bore size variations. the airflow characteristics may also be changed by changing the distance between throttle bore 16 and venturi 20. Also, the size and positioning of booster venturi 21 and other components within chamber 13 will have some bearing on the air flow. But, the proper interrelationship of size and position between throttle bore 16 and venturi 20 will produce most if not all desired air velocities. Properair box studies will provide the information necessary to obtain these interrelationships.

The size of main venturi 20 needed to maintain the desired high manifold depression is substantially smaller than in conventional carburetor systems. However, there is no power loss when going into midrange and high range carburetor operation because of secondary venturi portion 4, which provides increased air flow and fuel availability automatically in response to the position of throttle plate 19. At the pickup point" described above, portion 3 is functional and portion 4 begins to operate. And both portions operate at wide open throttle. There is thus sufficient depression to provide fuel to the primary portion 3 at all ranges of carburetor operation, as well as to the secondary portion 4 above the pickup point."

The concept of the invention provides high air velocity through the carburetor at all engine speeds and load with little if any loss of engine power output. Fuel evaporation within the carburetor is at a maximum. with fuel dumping being substantially eliminated. A carburetor embodying the inventive concept has fewer parts than heretofore without sacrificing fuel delivery characteristics. In addition. a carburetor designed in accordance with the invention can be effectively used on a variety of high speed engines with differentdisplacements, regardless of the type of fuel used.

While the embodiment described and shown utilizes only a single primary and single secondary system, any suitable multiples of primary and/or secondary may be used without departing from the spirit of the invention.

1 claim: 1. In a carburetor for a high speed compression engine having a known displacement, a main discharge throttle bore, separate primary and secondary air passages leading to said throttle bore, a main throttle valve in said throttle bore, a normally closed secondary throttle valve: in said secondary air passage, means responsive to movement of said throttle valve past a predetermined partially open position to open said secondary throttle valve, means for maintaining said seconda ry throttle valve, means for maintaining relatively high velocity air flow through the carburetor at all engine speeds and for providing the following manifold depressions during engine operation:

1. depression not less than 3 in. Hg. at 1.200 engine r.p.mv 2. depression not less than 7 in. Hg. at 3,600 engine r.p.m. said second mentioned means comprising air restrictive venturi means of predetermined] cross section in ac cordance with said known engine displacement disposed in said primary air passage, an air valve in said secondary air passage upstream from said secondary throttle valve for controlling the flow of air into said secondary air passage upon opening of said secondary throttle valve. damper means for retarding the initial rate of opening of said air valve, and fuel inlets in said primary air passage and in said secondary air passage between said secondary throttle valve and said air valve. 2. The structure defined in claim 1, wherein said damper means includes aperture means formed in said air valve.

3. The structure defined in claim 1, wherein said damper means comprises a spring-biased pneumatic dashpot connected to said air valve, the spring-biasing force of said dashpot resisting opening of said air valve, and air discharge means connecting said dashpot with said primary air passage so that increasing air flow through said primary air passage places a vacuum on said dashpot tending to overcome the spring-biasing force.

4. The structure defined in claim ll, wherein said second mentioned means provides the following manifold depressions during engine operation: 7 l

l. depressionsnot less than 5 in. Hg. at 700 engine r.p.m.

2. depressions not less than 9 in. Hg. at 3,000 engine r.p.m.

5. The structure defined in claim ll, wherein said second mentioned means provides the following manifold depressions during engine operation:

1 With said second air passage closed to air flow:

a. depression not less than 3 in. Hg. at 1,200 engine r.p.m. b. depression not less than 7 in. Hg. at 3,600 engine r.p.m. 2. with said throttle valve moving just beyond said partially open position: a. depression not less than 5 in. Hg. at 700 engine r.p.m. b. depression not less than 9 in Hg. in. Hg at 3,000 engine r.p.m.

Claims (8)

1. In a carburetor for a high speed compression engine having a known displacement, a main discharge throttle bore, separate primary and secondary air passages leading to said throttle bore, a main throttle valve in said throttle bore, a normally closed secondary throttle valve in said secondary air passage, means responsive to movement of said throttle valve past a predetermined partially open position to open said secondary throttle valve, means for maintaining said secondary throttle valve, means for maintaining relatively high velocity air flow through the carburetor at all engine speeds and for providing the following manifold depressions during engine operation: 1. depression not less than 3 in. Hg. at 1,200 engine r.p.m. 2. depression not less than 7 in. Hg. at 3,600 engine r.p.m. said second mentioned means comprising air restrictive venturi means of predetermined cross section in accordance with said known engine displacement disposed in said primary air passage, an air valve in said secondary air passage upstream from said secondary throttle valve for controlling the flow of air into said secondary air passage upon opening of said secondary throttle valve, damper means for retarding the initial rate of opening of said air valve, and fuel inlets in said primary air passage and in said secondary air passage between said secondary throttle valve and said air valve.

2. with said throttle valve moving just beyond said partially open position: a. depression not less than 5 in. Hg. at 700 engine r.p.m. b. depression not less than 9 in Hg. in. Hg at 3,000 engine r.p.m.

2. depressions not less than 9 in. Hg. at 3,000 engine r.p.m.

2. The structure defined in claim 1, wherein said damper means includes aperture means formed in said air valve.

2. depression not less than 7 in. Hg. at 3,600 engine r.p.m. said second mentioned means comprising air restrictive venturi means of predetermined cross section in accordance with said known engine displacement disposed in said primary air passage, an air valve in said secondary air passage upstream from said secondary throttle valve for controlling the flow of air into said secondary air passage upon opening of said secondary throttle valve, damper means for retarding the initial rate of opening of said air valve, and fuel inlets in said primary air passage and in said secondary air passage between said secondary throttle valve and said air valve.

3. The structure defined in claim 1, wherein said damper means comprises a spring-biased pneumatic dashpot connected to said air valve, the spring-biasing force of said dashpot resisting opening of said air valve, and air discharge means connecting said dashpot with said primary air passage so that increasing air flow through said primary air passage places a vacuum on said dashpot tending to overcome the spring-biasing force.

4. The structure defined in claim 1, wherein said second mentioned means provides the following manifold depressions during engine operation:

5. The structure defined in claim 1, wherein said second mentioned means provides the following manifold depressions during engine operation:

Images