US2893711A - Charge forming means - Google Patents

Description

July 7, 1959 A. D. MCDUFFIE 2,893,7.

CHARGE FORMING.' MEANS Filed Jan. 18, 1957 4 SheVets-Sheet i July 7, 1.959 A. D. MCDUFFIE 2,893,711

v CHARGE FORMING MEANS Filed Jan. 18, 1957 4 Sheets-Sheet 2 IN VEN TOR.

AWORNEY July 7, 1959 A. p. MQDUFFH; 2,893,711

CHARGE FORMING MEANSv Filed Jan. 18, 1957 4 Sheets-Sheet 3 ATVOQNEY July 7, 1959 A D MoDUFFlE 2,893,711

CHARGE F ORMING MEANS Filed Jan. 18, 1957 4 Sheets-Sheet 4 255 ffii fig# l ATTORNEY' United States Patent O 2,893,711 CHARGE FoRMiNG Archie D. McDullie, Berkley, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application January 18, 1957, Serial No. 634,915 s Claims. ((31.261-23) The present invention relates to internal combustion engines and more therefor.

In an engine of the so-called spark ignited variety, a combustible charge of atomizedV air and fuel is compressed and ignited in the various engine cylinders. In order to obtain themaximum fuel economy as well as lmaximum'performance from such an engine,it is essential lthat the air and fuel therein be properly mixed with each other in some predeterminedproportions. One means of metering the fuel is to employ a venturi or similar device 'in the induction system through which induction air flows andproduces a vacuum signal the magnitude of which is indicative of the mass or'quantity of air entering the engine.` Metering means responsive to the amount of `this 'vauum are thenemployed Vfor metering the fuel in terms thereof. In order tol insure a positive and accurate action of the metering means, due to hysteresis, friction, etc the vacuum transmitted tothe metering means'must be in excess of some minimum' amount. In order to 'obtain a vacuum in excessof the minimum amount during the periods of low air ow occurringin the idle range, the venturi must have a small throat. Although a vacuum of adequate magnitude c an be obtained at idle in this manner, such a'venturi presents a serious restriction to the flow of airtherethrough during full throttle' operation. As a` practical matter this restriction normally -lowers the volumetric efficiency vof the vengine and therefore materially limitsthe maximum power-output of the engine. Accordingly,"'heretofore ithas been the' practice, particularlyin CarburetOrs, to employ a plurality o f venturis for meteringithe fuel. Normally each of these venturis have separate throttle 'valves which areinterconnected with each e other. During light'loads only the primary throttle valve is open. However, when -the opening'of the primary throttle valve exceeds somepredetermined amount, the secondary throttle valve will commence to open along with the primary throttle. Thus the percentageof airow throughthe secondary passage will progressively increase with vthe load until .bothk of 'theth'r'ottles reach the vfully opened position at approximately the same time.` It may thus b e seen that the proportions by which the air how divides between hthe` two venturis will vary as the throttleA valve settings vary. In a'carburetor vof this typea separate fuel jet may be disposed in each' of the venturis and thus the fuel will beimetered -by separate means for each venturi. As a 'result the separate metering meanswill always meter the fuelon the basis `of the air vflowing therepast and the proportions by which the fuel divides will not atfe'ct the air-fuel ratio. Inotherv words the use of two independent metering means will eliminate any disruption Vor variations Aof the chargingcharacteristics as particularly to the fuel 'supply systems the air flow gradually changes from ljust-one venturi to a multiplicity of venturis.

Althoughfsuch arrangements have performed satisfactorily on present day carburetors, there are times `when the use of a compound `inletis desirable but the use 0f a separate metering` means'for each ofthe inlets is 2 impractical. For example, in one form of fuel injection system a pressure differential representing the mass of air entering the engine and 'a pressure differential representingy 'the' quantity of'f'fuel beingconsumed are balanced against each other`in order to 'maintain the desired airfuel'ratio'. 'The mechanisms -for-balancing the pressures are sensitive and -fa'irly expensiver As a result practical considerations preclude theA use'` of two such units in one fuel systemv eveii'if it' is necessary to employ a compound intake. Accordingly, Yfuel injection -gs'y`stems in general andthe mass'air ow type particular have employed only'a'single in'letthat is operative over Vthe entire engine operating range'. Asa result the design of the Venturi is a compromise usually resolved by making the venturi vas large as possible while still providing the'required minimum Vacuum at idle. Thus the operation of the engine has normally been impairedat either light load operation and/ or heavy load operation.

It is now` proposed to provide a fuel injection system having a fuelmetering mechanism and an'inductiori inlet which has a restrictionthat will develop a large pressure differential atidle or light `load operation but will not materially impede the flow of air into the engine at high speed'. This is tobe accomplishedby-providing an induction intake having a'primaiyinlet and a-se'condary inlet that are disposedfiri4 parallel with each other and joined together'so that a single throttle valve will retain complete control over *the'volume of air entering the engine.t Ihe-primaryinl'e't may comprise a venturi havin'gi-a throat area-sufficiently small to produce an adequate vacuum yeven 1at idle for 'operating the metering mechanism.` During light loads, i.e., below some predetermined amount, a secondary valve in the secondary inlet will'rem'ain' completely closed and prevent the flow of any air therethrough. The vacuum drop in the venturi throat v`may then be employed to meter the fuel flow by being balanced against thefuel pressuredrop across an orifice in the fuel'line. However when the air ow through the `engine approaches an amount where the restriction of the venturi begins to limit the air flow, the valve in the secondary inlet may open and allow air to `flow through 'both the primary and secondary'inlets. Since the amount of airflow through `the secondary'inlet has f no direct 'effect on the metering mechanism, it may be free of any metering restrictions and have alarge enough cross section to present a'minimum air iiow therethrough.

At should be noted that when the metering of the `fuel is dependent upon the proportions between a'fu'el pressure amount of restriction to vfthe 'differential across a flow restrietion such as 'an orice action `and the charge in balance at all times; Although the transition from theventuri to the secondary inlet may be gradual, in order to simplify the controls, it has been found preferable that both lthe secondary inlet valve and the secondary metering orifice" be either `totally `inoperative or totally operative. Thus the secondary inlet v alve and orifice notonly become operativ@ simultaneously but will also move from the fully closed position to vthe fully open position .substantially vsystem embodying the present invention.

Figure 2 is a diagrammaticview of a fuel injection system embodying a modified form of the invention.

Figure 3 is a diagrammatic view of a portion of the embodiment in Figure 2 with the parts being broken away and in section.

Figure 4 is a fragmentary diagrammatic view of a portion of another embodiment of the present invention. Referring to the drawings in more detail, the present invention may be incorporated in a charge forming means adapted to be employed on any type of engine 12. however, in the present instance, the means 10 is particularly adapted for use on an engine 12 of the so-called spark ignited variety wherein a combustible charge of air and atomized fuel is formed in the induction system 14 and compressed in the engine cylinders and then ignited by means of an electrical discharge across a spark gap or similar element located in the engine cyliners. The engine 12 includes a pair of 'angularly disposed banks of .cylinders A cylinder head is secured to each bank with intake passages 16 extending therethrough to communicate with the combustion chambers.

This induction system 14 for the engine 12 includes an air manifold 17 having an intake l18 communicating with .the atmosphere and a plurality of branch passages 20 which are interconnected with the various intake passages 16 for supplying the induction air to the cylinders. A

.throttle valve 22 may be provided at any suitable location such as in the intake 18 for controlling the llow of air through the manifold 17. The intake 18 includes a primary venturi passage 24 having a restricted throat 26 and a secondary inlet passage 28 which is disposed in parallel to the primary venturi passage 24. The inner ends of these two passages are interconnected with each other so as to discharge into the induction manifold 17 through a common passage 30. In order to control the total amount of air flow through the induction system 14, the throttle valve 22 may berdisposed inthe passage 30 downstream of the junction of the two passages 24 Yand 28. Although the primary venturi passage 24 remains open all of 4the time a secondary valve 32 may be provided in the secondary inlet passage 28 for controlling the flow of air therethrough without directly affecting the air flow in the primary venturi passage 24.

In order to charge the air flowing through the induction system 14 with fuel to thereby form a combustible charge, a pressurized fuel system 34 is provided that positively injects the fuel into the branch passages 20 immediately adjacent the intake Valves 36. In the present instance this fuel system 34 includes a storage tank 38,

pressure boosting means 40, a metering mechanism 42 and means 44 for distributing the fuel to the cylinders. The pressure means 4l! includes one or more fuel pumps 4S capable of delivering the fuel in sufficient quantities and pressures to actuate the system 34. The discharge line 46 from the pump 45 includes a filter 48 and is connected to a pressure relief valve 50 effective to regulate the fuel pressure by by-passing any surplus fuel for return to the storage tank 38.

In order to meter the fuel in proportion to the air flow,

the fuel metering mechanism 42 includes a fuel metering v valve 52 therein. The upstream side of this valve 52 is interconnected with the pressure relief valve 50 by a fuel line 54 and' the downstream side of the valve 52 is interconnected with the fuel distributor 44 by means of a.

` metered fuel line 56 having a pair of parallel branches 58 and 60 each of which Vhas a metering restriction 62 -and 64 therein.l Although these restrictions 62 and 64 insure the proper operation of the engine. In other words may be of any suitable type, they are preferably orifices that create a pressure differential thereacross similar to` the pressure differential in aventuri. The primary braucht 58 is preferably open at all times whereas the secondary' branch 60 includes a secondary fuel valve 66.

Although the distributor 44 may be any suitable flow-- divider, in the present instance it includes a rotor 68 driven. by the engine camshaft for delivering the fuel to the noz-- zles 70 in timed relation with the opening of the intake:

valves 36.

The metering mechanism 42 includes a housing having: an air diaphragm 72 and a fuel diaphragm 74 therein: which are operatively interconnected with each otherand with the metering valve 52 by a reciprocable shaft 76. The air diaphragm 72 has one side 78 thereof exposed to atmospheric air pressure while the opposite side forms a movable wall of a vacuum chamber interconnected with the venturi throat 26 by a vacuum or control signal line.-82. Thus there will be a pressure differential across the air diaphragm 72 that will create a force on the shaft 76 indicative of the volume of air entering the engine and .tending to open the metering valve.

The fuel diaphragm 74 separates' a pair of fuel chambers 84 and 86. The high pressure chamber 84 is connected tothe metered fuel line 56 anterior to the metering restrictions 62 and 64 by a tube 88 while the low pressure chamber -86 on the opposite side of the diaphragm 74 is connected to the' fuel line 5 6 posterior to the metering restrictions 62 and 64 by another tube 90. Since the hydraulic resistances of the restrictions 62 and 64 will create a pressure differential thereacross proportional to the fuel flow, thediaphragm 74 will create a second force on theshaft 76 proportional to the fuel flow and tending to close the valve 52 in opposition to the rst force. It may thus bevseen that as the air flows through the venturi 24 it will create a vacuum in the throat 26 of the venturi. This vacuum will produce a force on the diaphragm 72 that will tend to move the shaft 7 6 to the right (Figure l) and open theA metering valve 52, thereby increasing the fuel flow. At the same time the fuel distributed to the cylinders, i.e., the metered fuel, will flow through the metering orifices `62 and/0r 64 and produce a pressure diiferentialthereacross that will tend to move the valve 52 to the left and close the valve 52 to thereby decrease the .fuel flow. It will lthus be seen that the fuel ow and air flow will produce opposed pressure forcesbnjthe dia- .phragms 72 and 74 that will move the shaft 76 axially and adjust the valve 52 until the forces are balanced.

When a stable condition is thus established the air and fuel flows are in some predetermined proportions.

When the engine is idling or driving a light load the -A secondary valve 32 in the secondary passage 28 is prefthe primary venturi 24 may have a sufficiently small throat 26 to develop an adequate vacuum even at light loads to overcome any friction, etc., and positively operate the diaphragms, fuel metering valve, etc. If the size of the metering restriction 62 is properly chosen the air and the fuel pressure differentials will actuate the fuel valve 52 to maintain the air-fuel ratio at the desired amount to the primary metering orifice 62 is matched with the small venturi 24.

Since the venturiy throat 26 is sufficiently restricted to produce a large vacuum at the limited air liow occurring during engine idling and light loads, at heavier loads with Athe increased air ilow the venturi 24 will present a large L resistance .tothe induction-air ow and as a result will A decrease the volumetric efficiency of the induction system 7a: r4. accordingly. the Secondaryjnletlimey lis PfQYiFd in parallel to the primary inlet 24 so as to supply additional air during heavy loads. It has been found preferable for the's'econdary inlet to comprise a cylindrical passage 'free' from any ow restricting obstructions therein.

The secondary throttle valve 32 in the secondary passage 28 controls the air ow therethrough and is actua-ted by a trigger unit 92`that will retain the valve 32 closed when necessary to insure a large enough air flow through -the venturi 24 to always create aY strong vsignal and will open the valve 32 when necessary to prevent a decrease in the volumetric eiciency of fthe'engine. Although the trigger unit 92 may be responsive to any suitable type of signal Since the volume of air owing through lthe Vinduc- {tion'sys'tem 14 is the primary consideration, the triggering signal is preferably indicative of such a flow. Accordingly, in the present instance the trigger unit 92 includes a spring biased diaphragm 94 that has one side exposed to atmosphere and the other `side exposed to the VKyacuum ina chamber96 .connected to the intake manifold posterior to the throttle valve 22. The diaphragm 94 is connected to a booster vacuum valve 9S by a lost motion linkage 100 that will allow the valve to remain closed unless the intake vacuumV is less than some predetermined amount. The booster valve 98 isconnected to -the'diajphragm 102 inthe secondary fuel valve 6.6 by a line 103 vandto the chamber 104 for the diaphragm 105 in the control'for the secondary throttle valve 32 by a line 106 having' arestric'tion 108 therein. It may thus be seen that -Wherever the induction vacuum is less than some predetermined amount the diaphragm 94 Will open the valve permitting booster vacuum in a conduit 109 to act in lline 103 to open the secondary throttle valve 32 and the secondary fuel valve 66. The lost motion linkage 100 permits the diaphragm 94 to move considerably before yit 4opens'or closes thevalve 98. The vacuum required to close the valve 93 is considerably below that required to :open the valve 98 to thereby prevent hunting in the zsystem.

The operation of this system may be summarized as :follows:

' When the engine is lightly loaded and the air flow is small, the 'throttle valve 22 is closed or nearly closed and there will be a'high vacuum in the intake manifold. This high vacuum will be transmitted to the chamber 196 by the line 110 and will cause the diaphragm 94 to compress the spring 112. Under these circumstances there will be sufficient slack in the lost motion linkage 100 to allow booster vacuum valve 98 to remain closed. Thus the springs 114 and 116 lwill bias the secondary inlet valve '32"and the secondary fuel valve 66 closed'.` Conse- -quently, all of the air and fuel will ow through the primary venturi 24 and the primary orifice 62 respectively. 4If the primary fuel orifice 62 is matched to the primary venturil 24 the motion of the fuel metering valve tobalance the forces on the air and fuel diaphragms 72 land 74 'will insure the air and fuel ow inv thedesired proportions`.` As the throttle valve 22 opens the intake vacuum ydecreases until all of the slack disappears from the lo'st `rnotion 'linkage 1700 and the booster vacuum valve 98 opens. As soon as this occurs the source of booster vacuum will be interconnected with the secondary'throttle` diaphragm chamber and the diaphragm chamber inthe 'secondary fuel valve 66. This will substantially instantly open the secondary fuel valve 66 and allow the fuel to How through both the primary and secondary fuel rnetering ,orifices 6 2 vand 64. Simultaneously therewith, the air tin Vthe secondary inlet actuator will be exhausted therefrom and cause the secondary inlet valve 32 to open. It 'may ybe seen that if the combined resistances of the two .orifices 62 and 64 are matched tothe divided air flow through the primary venturi 26 and the secondary Vinlet 2S' ,the diaphragme 72 and 74 and metering valve 52`wil1 'insure the desiredair-fuel ratio as before.

Thus; yilow of induction air Will be relatively unrestrictedlas` the air may'divide itsflow and enter through Aboth' 'the secondary inlet 28a`nd the primary venturi 24.

If the `secondary throttle valve :3 2 gradually opens with increasing airflow, itis necessary to increase the fuel ow through the secondary orifice in the identical manner in order to maintain vthe desired airfuel ratio. In .other words the ratio o f lthe division of the vair ow through primary venturi and secondary inlet and the division of fuel flow through the primary and secondary metering orifices must be similar. kHowevenit has been found that byin- Vst antaneously completely .opening the second inlet valve and the transfervalve, there will be no blending problems which might otherwise occur vin gradually opening these two valves.

It maybe found desirable to place the restriction 108 in the vacuum line to the diaphragmchamber 104'to 'slightly retard the flow of air therefrom. This will cause a slight time delay inthe opening of the secondary throttle valve 32, thus insuring the secondary fuel valve 6 6 opening slightly `ahead of the secondary throttle valve 32. -As a result there may 'be short'intervals Aduring which lthe charge is excessively rich, a condition desirable during acceleration, but more important it will also .eliminate Iany `lean condition that' might .cause'a misfiring .of the engine.

lBy maintaining the valves 32 and 66 either completely opened or completely closed, the .air will either flow entirely through the primary venturi v24 or divide its flow between the venturi `24 and secondary inlet 28 in some predetermined ratio. Thus if the' primary orifice .62 is matched -to the primary venturi 2.4 and the primary .and

secondary orifices A62 and 64 are matched to the primary be maintained constant at all times. 1

As an alternative, the .embodiment of the charge forming means 120 'disclosed in Figures 2 and 3 may .be ernployed. This embodiment includes an induction system 122 having an intake manifold 124with aninlet riser 126 in the center thereof and a plurality of branch passages 128 arranged to communicate with the cylinders in a V-type engine. An intake assembly 130 may be mounted on the riser 126 for drawing the induction air from the atmosphere and Supplying it to the manifold 12.4. The present intake 13 0 includes a primary venturi passage'132 having Aa restricted throat 134 and a secondary inlet passage 136 in parallel thereto. The secondary inlet passage 136 includes a throttle valve 13.8 normally biasedclosed by a spring 140 but adapted to be opened by the vacuum in a chamber 142 behind lthe diaphragm 144. A pair of throttle valves 146 may be provided on a common shaft 148 passing through the lower Vends of the primary and secondary passages 132 and 13.6 -for 'controlling 4the How of induction air into ythe engine while a choke valve '150 is disposed upstream thereof for temporarily increasing the vacuum inthe throat 134 ofthe venturi Y13:2.V

In order vto form a' combustible charge Aof air and fuel, a fuel injection system 152 is provided which includes'a fuel storage tank 154, fuel pumping means 156, Aa pressure relief valve 15S, a metering mechanism 16.0 and'a distributing mechanism 162 which will distribute the'fuel to various nozzles 164 located in the various cylinderspor branch passages of the manifold 124. The vpumping means 156 may include a' single fuel pumpor as'inithe present embodiment it includes a'transfer pump 165 and `a booster pump 166.

The pressure relief valve 153 is of the by-pass type and includes a .diaphgram 168-responsive to the-fuel pressure and a spring 17.0 biasing the valve closed. The ,ten-

lsionof .the spring 170 maybe a fixed ,amount or if `desired 'diaphragms 186 and 188 oppose each other.

in position. .The air diaphragm 186 forms an inner chamor high pressure fuel chamber 196 and an outer or low pressure fuel chamber 198. These two chambers 196 'and 198 are interconnected with each other by a pair of primary metering orifices 200 and 202 so that the fuel flowing therebetween will create a pressure differential across the fuel diaphragm 188. A yoke 204 pivoted at the pin 206 in the upper portion of the center wall 208 has one arm 210 attached to the center of the air diaphragm 186 and the other arm 212 attached to the center of the fuel diaphragm 188 so that the forces on the two A fuel metering valve 214 in the inlet 176 includes a plunger 216 `that engages the lower end 218 of the other arm 212 to be actuated thereby. It may thus be seen that the forces on the two diaphragms 186 and 188 will be effective to move the yoke 204 and actuate the metering valve 214.

The outlet of the low pressure chamber 198 is Connected to a metered fuel line 220 that is connected to a pressure check valve 222 for maintaining the pressure in the system anterior thereto, in excess of some predetermined vamount and to the fuel distributor 162.

In addition to the primary metering orifices 200 and 202, a secondary metering orice 224 and an enrichment orifice 226 are provided in parallel thereto. Thus any fuel ow through these orifices will also be eective to contribute to the pressure differential across the diaphragms 186 and 188. The rich orifice 226 is controlled by a valve 228 actuated in response to the intake vacuum.

During the normal operating range the valve 228 will be closed but when the induction vacuum is low, as occurs during full throttle operation, the valve 228 Will open and as a result the charge will be enriched to provide maximum power.

The secondary orifice 224 is controlled by a valve 230 normally retained closed by a spring 232 and opened by a diaphragm 234 responsive to the pressure in the chamber 236 therebehind. The pressures in the diaphragm chambers 142 and 236 are controlled by a booster vacuum valve 238 in a trigger unit 240. The valve includes a ball 242 that is positioned by an over center snap spring 244 to block either the vent 246 or the booster vacuum line 247. The spring 244 is engaged by an arm 248 on thev throttle shaft and when the throttle valves 138 are closed or in the light load range, the spring 244 will retain the booster valve 238 closed as shown. At some point during the opening of the throttle, the arm 248 will cause -the spring 244 to pass over center and open the booster valve 238. When this occurs the booster vacuum will appear in both the secondary fuel valve diaphragm chamvber 236 and the secondary throttle diaphragm chamber 142. As a result the secondary metering orice 224 and -the secondary inlet 176 will completely open substan- .Y tially simultaneously.

The operation of this embodiment may be summarized as follows:

During idle and part throttle operation the arm 248 on the throttle shaft Will deflect the spring 244 so as to close the booster vacuum valve 238. -Thus the springs 140 and 232 acting on the diaphragms 144 and 234 will insure the valves 138 and 230 being retained in the closed positions. primary orifices 200 and 202 and all of the air flows As a result all of the fuel flows through the through the primary venturi 132. These forces tend to swing the yoke 204 for opening or closing the fuel metering valve 214 and regulating the fuel ow. Since the fuel forces and air forces are iny opposition to each other and they will position the fuel valve 214 to cause the two pressure differentials and therefore the air and fuel flows l to be maintained ink some predetermined proportions. If the resistances of the venturi 132 and the primary orifices 200 and 202 'are properly matched, the resultant chargel ployed.

secondary fuel metering orifices 200, 202 and 224. At

the same time the diaphragm 144 will open the secondary throttle valve 138 and thus allow air to enter through both the venturi 132 and the secondary inlet passage 136. If the primary and secondary fuel orifices are matched against the divided air flow, the desired air-fuel ratio will be maintained. This ratio is normally suitable for maximum economy; however, if the intake vacuum drops sufliciently the power enrichment orifice 226 will open for a rich charge suitable for maximum power. When the throttle valve 146 closes the spring 244 will again pass over center and close the booster vacuum valve 238. This will open the vent 246 and allow the springs 140 and 232 to move the valves 138 and 230 and close the secondary inlet 136 and the secondary fuel orice 224.

As a further modification, the embodiment of the charge forming means disclosed in Figure 4 may be em- In this embodiment the induction system is similar to that in the previous embodiments. The intake assembly 250 includes a housing 252 having a primary venturi passage 254 and a secondary inlet passage 256. The lower ends of these passages 254 and 256 are joined together so as to discharge into a common passage 270 vhaving a single throttle valve 272 disposed therein for controlling the amount of air flowing through the engine. The secondary passage 256 is substantially cylindrical and free from any flow restricting means therein except for a secondary throttle 260. This valve 260 is normally retained closed by a spring member 262 but a diaphragm 264 responsive to the vacuum in the chamber 266 therebehind is effective to open the Valve 260.

In order to form a combustible charge of air and fuel, a fuel injection system is provided for injecting metered fuel into the charge. This system may be substantially the same as that in the foregoing embodiments wherein a fuel metering valve is actuated by an air diaphragm responsive to the vacuum in the throat 268 of the venturi 254 and a fuel diaphragm is responsive to the pressure drop across a primary metering orifice 271 and a secondary metering orifice 273. The flow of fuel through the secondary orifice 273 is controlled by a valve 274 biased closed by a spring 276 and opened by a diaphragm 278 responsive to the pressure in the chamber 280.

In order to actuate the diaphragms 264 and 278 controlling the secondary throttle valve 260 and the secondary orifice 273, a trigger unit 282 is provided. This unit 282 includes a booster vacuum valve 284 controlled by a diaphragm 286 having the chamber 288 therebehind interconnected with the throat 268 of the venturi 254. The valve 284 is normally biased closed by a spring 290 and thus blocks the booster vacuum line 292 and opens the vent 294 to atmosphere. This will cause the the venturi 254 is adequate to produce a strong vacuum,

the diaphragm 286 will open the booster valve 284 and close the vent 294. This will cause booster vacuum to appear in the diaphragm chambers 266 and 280, thereby causing the diaphragms to open the secondary throttle valve 260 and the secondary fuel valve 274. When the g air flow again decreases, the booster valve 284 will close and open the vent 294 so that the secondary throttle 260 and fuel valve 274 will also close. It may thus be seen that the actuation of the secondary throttle valve 260 will be regulated directly in proportion to the quantity of air `flowing through the primary venturi 254. Consequently,

there will always be a vacuum signal of at least somepredetermined amount irrespective of the position of the primary throttlervalye272 orzthe amount'qf intake manifold vacuum.

' It isto he understood that, although the invention has been described with specific reference to particular embodimentsthereo it is not to he solimited since changes and alterations therein mayy he made which are within the full intended scope of this invention as defined by the appended claims.

I claim:

l. Charge forming means for an engine having an induction system with an intake comprising a first inlet having means for produci-ng a signal indicative of the quantity of air flowing therethrough, a second inlet in parallel with said first inlet and being free of any metering means therein, a secondary valve disposed in said secondary inlet to control the flow of air therethrough, a throttle valve disposed downstream of said inlets for simultaneously controlling the total amount of air flow through said inlets, fuel supply means responsive to said signal and effective to atomize metered fuel into said charge in proportion to said charge, means responsive to the vacuum in said induction system posterior to said throttle valve for simultaneously opening said secondary valve when said vacuum is less than some predetermined amount and to modify the responsiveness of said fuel means in proportion thereto.

2. Charge forming means for an engine comprising an induction system having an intake and a fuel system for injecting metered quantities of atomized fuel into the air in said induction system, said intake including a pair of parallel air inlets one of which includes means to produce a signal indicative of the quantity of air flow therethrough and the other of which is free of any signal producing means but includes a secondary valve therein, said fuel system including primary and secondary fuel orifices adapted to produce a signal indicative of the quantity of fuel flow, means for maintaining said signals in some predetermined proportions and means for simultaneously controlling the position of said secondary valve and the operation of said secondary orifice to maintain said air-fuel ratio in some predetermined proportion.

3. Charge forming means for an engine comprising an induction system having an intake and a fuel supply system for injecting metered quantities of atomized fuel into the air in said induction system, said intake including a pair of parallel air inlets, only one of which includes means to produce a signal indicative of the quantity of air iiow therethrough and the other of which is free of any signal producing means but includes a secondary valve therein, throttle means downstream of said inlets for controlling the fiow of air therethrough, said fuel system including primary and secondary fuel orifices adapted to produce a signal indicative of the quantity of fuel ow, metering means for maintaining said air and fuel signals in some predetermined proportions and means responsive to the load on said engine for simultaneously controlling the position of said secondary valve and the operation of said secondary orifice.

4. Charge forming means for an engine comprising an induction system having an intake and a fuel supply system for injecting metered quantities of atomized fuel into the air in said induction system, said intake including a pair of parallel air inlets, only o-ne of which includes means to produce a signal indicative of the quantity of air fiow therethrough and the other of which iS free of any signal producing means but includes a secondary valve therein, throttle means downstream of said inlets for controlling the fiow of air therethrough, said fuel system including primary and secondary fuel orifices adapted to produce a signal indicative of the quantity of fuel fiow, means for maintaining said air and fuel signals in some predetermined proportions and means responsive to the position of said throttle valves for retaining said 10 secondary valve and said secondary orifice closed when said throttle valve is closed more than ,some predetermined amount and effective to completely open said secondary valve and said secondary orifice when said throttle valve is open more than some predetermined amount.

`5'. .Charge formi-ng means for an enginecomprising an induction system having an intake and a Vfuel supply system for injecting metered quantities of atomized fuel into the air in said induction system, said intake includi-ng a pair of parallel air inlets, only one of which includes means to produce an air signal indicative of the quantity of air flow therethrough and the other of which is free of any signal producing means but includes a secondary valve therein, throttle means downstream of Said inlets for controlling the flow of air therethrough, said fuel system including primary and secondary fuel orifices adapted to produce fuel signal indicative of the quantity of fuel filow, means for maintaining said air and fuel signals in some predetermined proportions and means responsive to the strength of said air signal for retaining said secondary valve and said secondary orifice closed when said signal is less than some predetermined amount and for simultaneously completely opening said secondary valve and said secondary orifice when said signal is in excess of some predetermined amount.

6. Charge for-ming means for an engine comprising an induction system having an intake and a fuel supply system for injecting metered quantities of atomized fuel into the air in said induction system, said intake including a pair of parallel air inlets, only one of which includes means to produce a signal indicative of the quantity lof air flow therethrough and the other of which is free of any signal producing means but includes a secondary valve therein, throttle means downstream of said inlets for controlling the ow of air therethrough, said fuel system including primary and secondary fuel orifices adapted to produce a signal indicative of the quantity of fuel fiow, means for maintaining said air and fuel signals in some predetermined proportions and means responsive to the amount of vacuum downstream of said throttle valves for retaining said secondary valve and secondary orifice completely closed when said vacuum is in excess of said predetermined amount and for completely opening said secondary valve and said secondary orifice when said vacuum is less than some predetermined amount.

7. Charge forming means for an engine comprising an induction system having an intake and a fuel supply system for injecting metered quantities of atomized fuel into the air in said induction system, said intake includ'- ing a pair of parallel air inlets, only one of which includes means to produce a signal indicative of the quantity of air fio'w therethrough and the other of which is free of any signal producing means but includes a secondary valve therein, throttle means downstream of said inlets for controlling the flow of air therethrough, said fuel system including primary and secondary fuel orifices adapted to produce Ia signal indicative of the quantity of fuel flow, means for maintaining said air and fuel signals in some predetermined proportions, and means responsive to an operating condition of said engine for retaining said secondary valve and said secondary orifice closed and effective to completely open said secondary valve and said secondary orifice whenever said engine operating condition is exceeded.

8. An induction intake for an engine having an induction system and a fuel supply system for atomizing metered quantities of fuel into the air in said induction system, said induction intake comprising a pair of inlets disposed in parallel with each other, throttle means disposed downstream of said inlets for controlling the flow` through said inlets, one of said inlets including means for producing a signal indicative of the flow therethrough and effective to actuate said fuel supply system for controlling a quantity of metered fuel atomized in said` charge, the other of said inlets including a secondary valve for controlling the amount of air ow through said other inlet, means responsive to a predetermined engine operating condition for retaining said secondary valve closed and for completely opening said secondary valve whenever said predetermined engine operating condition is exceeded.

References Cited in the file of this patentv UNITED STATES PATENTS Strebinger Nov. 2, 1948 Stresen-Reuter Oct. 10, 1950 l Mock Jan. 27, 1953 Ronalet et al Aug. 6, 1957

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