US2345168A - Charge forming device - Google Patents

Description

CHARGE FORMING DEVICE Filed July 20, 1940 1-"- cold? 3 Sheets- Sheet 1 INVENTORS P. LUM

GEORGE EMIL 0. WI 2TH I a 9ZIZTOHNEY March 2 1944- E. o. WIRTH ETAL ,3 ,1

' CHARGE FORMING DEVICE Filed July 20, 1940 Sheets-Sheet 2 I ENTORS 65mm: LUM

y EMIL. O. WIRTH a U'TORNE 5 March 28, 1944- E. o. WlRTH EIAL 2,345,168

CHARGE FORMING DEVICE Filed July 20, 1940 :5 Shets-Sheet s I "IIIIIIIIIIIII/ INVEWTORS 650265 P. LUM BY E MILO.WI2TH Patented Mar. 28, 1944 CHARGE FORMING DEVICE Emil 0. Wirth and George P. Lum, South Bend,

Ind.,assignors to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application July 20, 1940, Serial No. 346,510

6 Claims.

This invention relates generally to charge forming devices and particularly to horizontal twin barrel carburetors. Certain of the subject matter disclosed herein is being claimed in our copending continuation in part application Serial No. 437,345, filed April 2, 1942.

Many present day automobiles have extremely low hoods so that little vertical space exists thereunder for the downdraft type, of carburetor and its air filter which stand upwardly a considerable distance above the top of the engine. It has become a particularly diflicult Problem to use a downdraft carburetor on engines having overhead valves where the hood level has been lowered to an extreme degree, engines of this type generally having a greater overall vertical dimension than those of the L-head type.

Another factor that must be taken into consideration in solving the problem of a suitable charge forming device for such present day automdbiles is that certain types of engines used therein require a dual type of intake manifold each main conduit of which has its own inlet. The in-line or straight eight-cylinder internal combustion engine is one example of a motor generally using a dual intake manifold though other types of engines also use such a manifold.

In solving the present problem, it is, however,

undesirable for many reasons to revert to the updraft type of carburetor. One important reasage and will not run contrary to the direction of said stream even at low air velocities.

Another object of the invention is to provide a device of this character having means for thoroughly atomizing fuel discharged into the mixture passages by the acceleration pump so that said fuel will also be readily carried along by the air stream therein.

Still another object is to provide a device of this character having means for checking back flow of idling'fuel in the passages of the idling system.

It is a further object of the invention to provide a device of this character having a pluralby highly sensitive means for maintaining a sub stantially uniform fuel level in the fuel supply chamber; and by means for stabilizing the fuel son is that at low engine speeds the velocity of the upwardly moving air current in an updraft carburetor is often insufllcient to carry all the fuel particles along with it and as a. consequence a substantial portion of the fuel rims backward in the induction passages and escapes from the carburetor. This loss of fuel results in an inadequate fuel mixture particularly at low engine speeds. It is also diflicult to obtain satisfactory acceleration from a low speed since it is very nearly impossible to deliver an acceleration pump charge to the carburetor induction passage and have the slow moving stream of air pick up this concentrated fuel discharge and quickly carry it upwardly and into the engine cylinders.

The present invention provides a highly efficient charge forming device for engines of low hooded automobiles which will be within the restricted vertical limits imposed by such automobiles and which is so constructed that fuel particles from the main nozzle will be readily car supply between a plurality of main nozzles deriving economizer fuel from a common economize source.

Still further objects are the provision in a device of thi character of an internal vent for the acceleration jet air break chamber; of an acceleration pump disposed within the fuel reservoir and variable capacity means to compensate for various fuel movements occurring during operative movements of the accelerationpump piston; of means rendering the acceleration pump readily accessible; and stabilizing means for the movable wall member controlling the fuel level.

Further objects and advantages of the invention will be apparent from the following description, taken in connection with the accompanying drawings, in which: V

Figure 1 is a vertical section through a charge forming device embodying the invention taken' longitudinally ofthe induction passages on line l-l of Figure 2;

Figure 2 is a vertical section through the device taken on line 2-2 ofFlgure 1;

' Figure 3 is a side elevation of the accelerator pump actuating lever taken on line 3-3 of Id:- ure 1' ried along by the air streamin the induction pasg5 4 is a partial vertical section through theair and mixture passages taken on line 4-8 of Figure 2;

Figure 5 is an elevational view of the flange end of the air passages; and

Figure 6 is a partial vertical section through the cover of the fuel supply chamber showing a modification of the vent for said chamber.

The embodiment of the invention illustrated in the drawings and hereinafter described is a preferred embodiment thereof which may be used with a dual horizontal intake manifold such as the one of special construction disclosed in copending application of Emil 0. Wirth for 8, Fuel supply system, filed July 20, 1940, and bearing Serial No. 346,483. It is to be distinctly understood however that the present invention is not to be limited to the embodiment herein disclosed nor to the type of manifold with which it is'preferably used, nor otherwise, except by the appended claims. Referring more particularly to the drawings, the carburetor disclosed therein is of the horizontal draft, double-barrel type. It includes abody section l within which is a fuel supply chamber orreservoir II, and air horn section l2, and a throttle body section It.

Section l2 forms a horizontal air inlet H which is controlled by a choke valve l of any suitable construction, manipulated either manually or automatically in the known manner. Posterior to the choke valve the walls of the passage are flared as indicated at I6 and the passage then branches into two horizontal mixture passages |I controlled by throttle valves I8 mounted on a common shaft l8 which is connected with an accelerator pedal and/or hand control in any well known manner. are positioned in close proximity to each other and their axes including the centers of the outlets Ila are in the same horizontal plane, the outlets 'of said passages being adapted for registration with corresponding inlets of an intake manifold.

Each passage comprises a small venturi 20 supplied with fuel from a main fuel nozzle 2| and discharging into a larger venturi 22. Each nozzle 2| is received within a bore and secured therein by a threaded plug 28 having a calibrated fuel metering orifice 24, said oriflce being below the fuel level L-L in said chamber. Each nozzle 2| is also provided with an air bleed 2 la from the air inlet passage l4. Fuel discharged by the main nozzles is readily carried along by the air stream in the mixture passages due to the horizontal position of said passages and horizontal movement of air therein and air at even low velocities will cause the fuel to flow toward the intake manifold and be delivered thereto. It should be noted that the air passages I4 and H are at the top of the carburetor and that when attached to an internal combustion engine the device will not extend above the top thereof.

Fuel is supplied to both main nozzles 21 at constant head by means of the constant-level fuel reservoir or chamber II which includes a lower portion Ila and upper portion ||b connected by vertical portion 0. The portion Ho and lower part of He constitute the fuel accommodating space. Constant level in the chamber II is maintained through hydrostatic pressure acting on a flexible diaphragm 25 which closes the lower end of said chamber. The diaphragm is marginally clamped between a flange 26 on the lower end of the body l0 and a flange 21 about the rim of The mixture passages H by screws 29. The diaphragm provides a movable wall or member which becomes the effective capacity limiting bottom of the fuel chamber, the capacity of said chamber consequently being variable.

At its underside, the diaphragm 25 has a metal disk 30 with a downturned rounded flange 30a. The disk reinforces or supports the diaphragm over a relatively large central circular portion of its area so that the fiexure of the diaphragm occurs primarily in the annular area 3| outside the supported central area. Beneath the diaphragm is a coil spring 32, the upper end of which isreceived in a shallow recessed washer 33 and the/lower end in a similar washer 34.- The upper .washeris secured between the disk 30 and a lock nut 35, of -well known character, received on the threaded depending end of screw 36, a hat disk 3'! being interposed between the hexagonal head 38 of screw 38 and the upper surface of the diaphragm The lower washer 34 is received on a reduced end'portion 39 of adjustment screw 40, the washer abutting on a shoulder formed at the base of said reduced portion 39. The spring is centered by the washers 33 and 34 relative to the axis of the diaphragm and reacts between said washers, thereby providing a yielding support for the diaphragm.

Adjustment screw 40 is threaded into a stud 4| depending from the bottom of cap 28, said screw being in axial alignment with the diaphragm 25 and provided with an axial bore 42 therethro gh in which is slidably received a depending stem 43 of screw 35, whereby the diaphragm is permitted freevertical operative movement but is supported against axial tilting. A lock nut 44 locks the screw 40 in adjusted position. However, other suitable mechanism may be employed to support and adjust the diaphragm.

About the depending end of screw 40 is an inte gral annular flange 45 depending from the cup 28. A removable plug 46, pressed into and frictionally held in an annular notch in the free end of flange 45, completes enclosure of a chamber 41. This plug prevents tampering with the adjustment of screw 4| once said adjustment has been made establishing the proper fuel level in the fuel chamber. However, should it become necessary to alter the addustment of screw 40, the plug 46 may be removed to provide access to said screw 4|. The passage 48 provides an air vent between chamber 4'! and compartment 15 so that the respective pressures therein will at all times be equalized with respect to each other, thereby preventing establishment of undesirable pressures that might otherwise occur in chamber 41, such as would restrict operative movements of stem 43 in bore 42. It should be noted that the stem 43 fits loosely enough in the bore 42 to substantially eliminate friction with the walls thereof so as to ensure free operative movements of the diaphragm which must necessarily be highly sensitive to even slight variations of hydrostatic pressure within "the fuel chamber The top wall or cover 49 of the fuel chamber has a hollow boss 50 for a pipe connection with I a fuel source and within said boss a fuel strainer 5| is disposed for straining out foreign particles a cup-shaped bottom cap 28 secured to the body fuel reservoir II.

member 83 having a seat 84 with which a valve II cooperates.

'A bracket 38 is received on the lower end of the valve member 83 and is secured between the enlarged" head 81 of the valve member and the free end of the stud l2. Bracket 50 has an upturned end 58 which is associated with a flattened side 58 of stud 52 to retain the bracket in proper position. Depending arms 68 of the bracket,

spaced apart from each other, support a pin 8I on which a valve actuating lever i2 is hinged-and downturned end portion" of the bracket provides a stop for limiting the valve opening movement of lever 82 by engagement with a projecting end portion 64 of said lever, the valve actuatingtrated and includes in upstanding boss on the lever I! being eonnected to the valve 88 by a wire '5.

Means operably connecting lever 62 with the diaphragm includes a link 68 pivotally connected at $1 to the lever 82 and .at 88 to a actuated lever 8.

The lever 88 is pivotally' mounted on a shaft I0 having its ends fixed in op posite walls of the body II. The end of lever 88 adjacent the axis of the diaphragm is bifurcated, and the free end of each fork 'II is turned about a pin I2 operably received in an annular groove 18 in an extension I4 of thehead 88 of screw- 86. Through this connecting means vertical movements of the diaphragm eflect opposite vertical movements of the valve 88 for controlling the flow of fuel into the fuel chamber. The link 6 is weighted at "a to diminish or eliminate the unbalance in mass acting on lever 88,

the inertia eifects of which, resulting from vertical accelerations, might otherwise interfere with the maintenance of the proper fuel level. It will be readily apparent that the right hand half of lever 68 or the lever 02 could be weighted instead of link 66.

The operation of the mechanism for controlling the fuel supply to chamber II is as follows:

When the-chamber is empty spring 82 yieldingly maintains the. diaphragmat its upward limit of movement at which position valve is wide open. As fuel, supplied by gravity or pressure or otherwise, enters through the duct in the boss I8 it is discharged past the valve 08 and into the As the fuel accumulates in the chamber, the hydrostatic pressure of the liquid chamber II are vented to the air horn passage I4. Venting of compartment lito the air horn passage is effected through the respective compiston.

cover plate or top wall 48 of the fuel chamber. The upper portion of the fuel chamber is vented to atmosphere through passages 88. A raised.

central portion 84 of the boss 82 supports a dust cap 85 in spaced relation thereto to permit free movement of air through passages 83, the cap 85 being secured to the raised portion 84 by a screw 88. Should an external vent of this type be used for the fuel chamber the compartment Ii should be similarly vented and a vent to atmosphere (not shown) should be provided in cap 28. While certain types of venting to both sides of the diaphragm have been illustrated and described herein it is to be understood that any other suitable method of venting may be employed.

An annular accelerating well 81 isprovided about each nozzle II by reduction of a portion of the nomle at 88 and openings 88 in the nozzle permit fuel to pass from the well into the passage 88 or said nozzle in the well known manner.

Idling fuel for each mixture passage I1, is'

drawn from the lower end of the acceleration well 81 of the respective nozzles through a lateral passage 8|, thence upwardly through an idling tube82 threaded into the body as at 88, to a point above the normal fuel level L-L (Figure 2) in the carburetor. From the tube 82, the fuel flows inwardly and upwardly through inclined passages 84 and horizontally through passages 85' to idling nozzle 81 (Figure 4) ,of known construction, discharging adjacent the throttle. A limited quantity ofair is bled into the idling fuel for the idling nozzles of the respective mixture passages through orifices 88a communicating with the air hom entrance. Additional air is .bled to the idling fuel, through continuations 88 of passages 84 which 'gcommunicate with a cyl-- 'inder I80 through respective restricted orifices I 0| in passages 88 adjacent one end of said cylinder. Air from the air inlet passage I4 reaches the said end of the cylinder through a passage I02 and an opening I08 in end wall I04 of said cylinder. A screen I00 covers opening I03" to filter out foreign matter from air entering the cylinder through opening I08. A piston I06 is reciprocatingly disposedin cylinder I00 and functions as an air valve to control ports I01 ofpassages 88. Actuation of the piston in a direction to close ports I" is efiected by a compression spring I08 received within a bore I08 in said Opening movement of the piston is effected by suctionposterior to. the throttle valves communicated by means of duct I I2, which communicates with both mixture passages I1,

and respective'ducts III, H4, H8, Ilia and open-' ing II Ia, the latter being through end wall III of cylinder I00. During engine idling and low municating ducts I8, ll, I8, I8 and 80. The upper portion III) of the fuel chamber, above the fuel level L-L, vents to duct." through vent 8| in the-top wall.48, so-that the air pressure within the fuel chamber II and in compartment I5 is equal to the pressure of the air entering the inlet Ipassage I4. This type of venting above and below the diaphragm is preferred as it tends to balance out the effect of any restriction of the air .entering the carburetor: such as occurs with file use of an air cleaner particularly as it becomes clogged with dirt, and produces a more nearly uniform fuel mixture. p 1

InFigureB,amodifledtype of ventingis pressure posterior to the throttle valves the piston is moved by manifoldv suction to .the extreme right against the force of spring I08, as shown in Figure 1,'at.which limit of movement ports" I01. are open to permit air to be bled into the idling fuel through said ports, as well as through orifices 8841. Upon a rise of pressure posterior to the throttle, as whensald throttle valves are opened to accelerate the engine, the spring urges the piston to the opposite limit of movement and closes said ports I" thereby cutting of! atmospheric pressure through said ports and preventing the back flow of idling fuel through the idlin fuel passages that such pressure would otherwise eflect in connection with gravity. There will be some suction on the idling male 81 which will tend to draw the idling fuel in the idling passages toward the idling nozzle against back flow due to gravity and suction of the main fuel nozzles. Thus, when the throttle valves are again closed and the idling nozzles come into normal opera-- tion, idling fuel is immediately available at said nozzles and a lag in the delivery of idling fuel is prevented such as would occur if the idling fuel passages had been drained or partially drained of fuel. However, other suitable means to reduce or eliminate back flow of fuel in the idle fuel passages may be employed. 5

The carburetor is providedwith an economizer system for supplying supplementary fuel from the reservoir II to the main fuel nozzles 2I,

which includes a spring pressed economizer valve I I8, of known construction, vertical passage I26,

' horizontal passage m and branches m.

It is generally knowrfthat an air bledmain fuel nozzle has an inherent pulsating flow characteristic of rather high frequency which under norf mal conditions is so rapid as to have no adverse We have total quantity of fuel discharged and results in In order to remedy this condition, fuel passages I22 are provided with restricted portions I23 which dampen the fluctuations of 'the fuel between the nozzles 2|.

The restricted portions I28 are adjacent each other atthe point where passage I2I branches in opposite directions in the accelerator wells of the respective main nozzles. Other suitable means may be employed to prevent fluctuation of fuel between I the nozzle, and the invention is not to be confined to the above described means.

Vacuum economizer valve actuating means I26, of well known construction and operation, is provided and is subjected to varying air pressures posterior to the throttle valves. Communication between the air passages i1 posterior to said throttle valves is effected through passages H2, H8, H4, I48, I41 and I46. Upon a rise in air pressure posterior to the throttle, a contact disk I22, secured to the spring pressed flexible diaphra'gm I84, impinges against valve stem-I26,

thereby opening the economizer valve.

The economizer valve actuating mechanism i comprises a chamber III! in a plug Ill threaded into a side wall of the fuel chamber, said chamber being subjected to varying air pressures posterior to the throttle valves as will be described hereinafter.

v An accelerator pump I36, of known construction, is incorporated in the carburetor, and includes a cylinder I58 formed integrally with the interior wall I80 and open-at I52 for communication with the chamber II, whereby removal of the pump piston may be made.- Within the cylinder is disposed, the piston comprising a plunger I5! having the usual facing material I51. The plunger is fixed to a piston rod I6I having an enlarged free end portion I62 longttudinally drilled from said free end. An annular flange I63 is provided on the enlarged end member I62 and a diaphragm I64 is secured to said flange and a washer I65 by turning over the free end of member I62. A marginal portion of the diaphragm I64 is clamped within a diaphragm chamber I61 adjacent the inner end thereof by a cup-shaped nut I68 screwed into said chamber I61, a retaining washer I68 being interposed between the diaphragm and adjacent rim of extension I10 is secured to piston rod I6I by comes so severe as to cause a deficiency in the pressing milled end III of rod I10 into the bore in the enlarged end I62 of said piston rod. The rod I18 extends through an opening I18 in the head of nut I68, the opening Illbeing of substantially greater diameter than rod I16 thereby permitting free operative movements thereof. However, any other suitable sealing means may be employed.

It should be noted that the capacity of the cylinderexteriorly of the piston and the capacity of the variable capacity chamber I61 vary inversely of each other. Consequently, the volume of fuel moved by reciprocating action of the piston is compensated for by inverse variation in the capacity of the chamber I61 so that the fuel level in the reservoir is substantially unaffected by the movements of the acceleration pump piston.

Means for actuating the acceleration pump is particularly shown in Figure 3 and comprises a lever I14 pivoted at I16, the free end of which is perforated to pivotally receive laterally turned end portion I11 of rod I10. A lever I18 floats on the pivotal axis I16 of lever I14 and is connectedto lever E14 by a spring I18 having its ends enlarged end by clamping same between the as attached to lateral arms 86 and I8I of levers I14 and I18, respectively. The levers are normally retained in the aligned position, as shown in Figure 3, by abutment of lug I82 on lever I18 against a laterally turned stopmember I88 of lever $14. A link I84, pivoted to the free end of lever I18, is operably connected to the throttle actuating mechanism, not shown, so that the acceleration pump is actuated with opening movement of the throttle valve. Rotation of lever I18. counterclockwise with reference to Figure 3, tensions spring I18, thereby pulling lever I14 in a manner to effect fuel discharging movement to the accelerator pump piston in the well known manner. The accelerator pump operating means herein illustrated and described is preferred although any other suitable means may be used. The pump receives fuel througha check valve I88 and discharges it upon discharge movement of the piston through vertical passage I88, lateral passage I80, vertical passage I81, and horizontal passage, I82, the latter forking into two downwardly inclined branches I83, each branch supplying fuel to respective pasages I84. Each passage I84 is inclined upwardly and is provided with a restricted orifice I86 from which accelerating fuel is discharged across air break chamber or bore I86 and through'the discharge opening I81, the latter being of somewhat larger diameter than the orifice I86 and in axial alignment therewith to permit free flow of the fuel stream thercthrough into the mixture passage velocities.

II. The accelerating fuel is discharged posterior to the throttle and the direction of discharge is such that slight initial opening of the throttle valve brings said valve into the path of the fuel being discharged, said path being the axial line of the orifice I95 and opening I96. Impingement of the fuel stream upon the valve causes the stream to be broken up and atomized so that same will be carried along by the air stream in the mixture passage I1, and will not settle and collect within said passage I! nor runcontrary to the direction of the air stream even at low air Passage I89 is provided with a ball check valve I89a in an enlarged portion |89b of said passage, the valve being above the fuel level of chamber I I. The air break I96, separating restricted orifice I95 and opening I91, is interiorly vented to the upper portion I l b of the fuel chamber by means of passages I98, I99 and 200.-

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the inventidn r sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

. We claim:

1. In a carburetor having an induction passage including an air inlet, means forming a fuel chamber having an air space above the fuel accommodating portion thereof, a yielding wall member forming a part of the fuel chamber and side of the wall member relative to the fuel chamber, and means whereby the upper portion of the fuel chamber and the compartment are vented to the air inlet.

2. In a carburetor having a pair of induction passages, a fuel reservoir, fuel nozzles adapted to discharge fuel into respective induction passages, means includingfuel metering means for supply- .ing fuel from the reservoir to the nozzles, means for supplying the nozzles with an auxiliary fuel supply from a common source including a fuel passage interconnecting said nozzles posterior to said metering means, and means in said passage for damping fluctuations of fuel flow between the nozzles.

3. In a carburetor foran internal combustion engine having a plurality of induction passages, a fuel reservoir, a fuel nozzle for each induction passage receiving fuel from the reservoir, and a conduit having a branch to each ofthe fuel nozzles for supplying same with an auxiliary supply of fuel, each of said branches having a restriction therein for damping fluctuations of fuel flow in said branches.

4. In a carburetor having a throttle controlled induction passage, means forming a fuel reservoir including a yielding member responsive to hydro-' static pressure of fuel therein, a fuel inlet, a valve for said inlet controlled by the yielding member, a wall forming a chamber on the side of the yielding member opposite the reservoir, a guide projecting outwardly through the wall of said chamber, a stabilizer attached to the yielding member and operably associated with the guide, resilient means reacting between the guide and the yielding member, said guide being adjustable to alter the effectiveness of the resilient means whereby the level of the fuel in the reservoir may be varied, and a second chamber enclosing the projecting end of the guide.

5. The invention defined in claim 4 and including a vent between the chambers.

6. In a charge forming device having an induction passage controlled by a throttle, means forming a fuel chamber including a yielding wall member responsive to hydrostatic pressure of fuel in said chamber, a valve controlled fuel inlet, means connecting the wall member and the valve,

means forming a closed chamber on the outer side of the wall member, and means for venting both chambers to the induction passage.

mm 0. WIRTH. GEORGE P. LUM.

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