US2996051A

US2996051A - Carburetor

Info

Publication number: US2996051A
Application number: US2189A
Authority: US
Inventors: Stanley H Mick
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1960-01-13
Filing date: 1960-01-13
Publication date: 1961-08-15
Anticipated expiration: 1978-08-15

Description

Aug. 15, 1961 s. H. MICK 2,996,051

CARBURETOR Original Filed Aug, 27, 1959 5 Sheets-Sheet 1 IN VEN T OR.

71% BY j/zwz /mg/z/i AT TORNE Y 1961 s. H. MICK 2,996,051

CARBURETOR Original Filed Aug. 27, 1959 5 Sheets-Sheet 3 W4 if r 1 141 .94 i w g/QM ATTORNEY| 1961 s. H. MICK 2,996,051

CARBURETOR Original Filed Rug. 2'7, 1959 5 Sheets-Sheet 4 IN VEN T OR.

ATTORNEY S. H. MICK CARBURETOR Aug. 15, 1961 5 Sheets-Sheet 5 Original Filed Aug. 27, 1959 2,996,051 CARBURETOR Stanley H. Mick, St. Clair Shores, Mich, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Continuation of abandoned application Ser. No. 836,423,

Aug. 27, 1959. This application Jan. 13, 1960, Ser.

15 filaiins. (Cl. 123-119) The present invention relates to a charge forming device for an internal combustion engine in which an air valve is disposed in an induction passage and positioned by a diaphragm responsive to the pressure drop across the valve to maintain a fixed depression for fuel metering. The air valve position in turn controls the position of fuel metering rods to render fuel flow proportional to air flow. The present application is a continuation of Serial No. 836,423, Stanley H. Mick, filed August 27, 1959, and now abandoned.

In a normal fixed throat carburetor, a fuel metering signal is obtained proportional to the square of air flow through the induction passage. Due to the small quantity of air flow at idle, the signal is extremely small and slight variations in fuel level at the fuel jets will cause a considerable change or variation in idle fuel flow rate. In an automobile, it is virtually impossible to control the fuel level in the carburetor accurately. Fuel pressure variations, accelerations, decelerations, cornering and driving on various inclines cause relatively large variations in fuel level. From this standpoint, it is desirable to have a strong fuel metering signal or force available, even at idle, so that the fuel level variations will have an insignificant effect on the quantity of fuel metered.

The subject air valve carburetor provides such a strong metering force under idling conditions. The air valve is normally adjusted to maintain a constant pressure drop thereacross and accordingly a constant metering signal over the normal engine operating range. As the air valve opens and closes in response to variations in air fiow, a fuel metering rod operatively connected thereto opens and closes a fuel jet to maintain the proper mixture ratio. Under normal operating conditions, a constant fuel-air ratio is desired. Accordingly, in the present device as air flow increases the air valve is positioned so as to move the metering rod to correspondingly increase the fiow of fuel.

In the present invention the air valve is of the butterfly type and its position is controlled by a diaphragm which senses a depression across the air valve and opposes a spring tending to pull the air valve closed. The spring force is set so that when the depression across the air valve reaches a certain value, the diaphragm overcomes the spring and begins opening the air valve. In the preferred form, the spring acts on a lever mounted on the air valve shaft. As the air valve opens, the springs lever arm effectively decreases. By this method the depression across the air valve can be held constant over the air flow range, or can be made to decrease at higher air flow.

The present invention also includes unique cold starting and cold running devices which eliminates a choke valve and instead provides means for increasing the fuel flow in accordance with ambient temperatures as Well as manifold depression.

The details as well as other objects and advantages of the present invention will be apparent from a perusal of the detailed description which follows.

In the drawings:

FIGURE 1 is an elevational view of the subject carburetor;

atent Patented Aug. 15, 1961 FIGURE 2 is a plan view of the carburetor;

FIGURE 3 is a view along line 3-3 of FIGURE 2;

FIGURE 4 is an elevational view with a cover plate removed to view the fuel reservoir;

FIGURE 5 is a fragmentary view showing the fuel reservoir inlet valve;

FIGURE 6 is an enlarged sectional view of the starting enrichment device;

FIGURE 7 is a bottom view of the carburetor;

FIGURE 8 is an elevational view of the carburetor showing the side opposite that shown in FIGURE 1; v

FIGURES 9-11 are fragmentary sectional views showing the cold running enrichment device;

FIGURE 12 is a view showing the accelerator pump and cold starting enrichment device;

FIGURE 13 is a view along line 13-13 of FIGURE FIGURE 14 is a fragmentary enlargement of the fuel metering orifices and nozzles; and

FIGURE 15 is a diagrammatic representation of the carburetor.

FIGURES 1 through 14 show the actual construction of the subject air valve carburetor indicated generally at 10. FIGURE 15 is a diagrammatic representation of the carburetor and is the figure which mainly will be used to describe the invention.

As best seen in FIGURES 3 and 15 main casing 12 includes a common air intake portion 14 which includes a wall 16 dividing the intake opening into a pair of openings or

passages

18 and 20. Flow through

passages

18 and 20 is controlled by a pair of throttle valves 22 and '23 mounted on a common operating shaft 24. Throttle shaft 24 includes a lever 26 fixed thereto and which lever is adapted to be suitably articulated to an accelerator pedal, not shown.

A butterfly type air valve 28 is fixed for rotation with a shaft 30 extending through the induction passage 14 anteriorly of the

throttle valves

22 and 23. A lever 32 is fixed to air valve shaft 30 and has one end of a link 34 articulated thereto. The other end of link 34 is articulated to arm 36 of a multi-armed lever 38 which in turn is pivotally mounted on a shaft 44 fixedly disposed within casing 12. The multi-armed lever 38 includes another arm 42 articulated through a link 44 to a diaphragm 46. A tension spring 43 is secured at one end to arm 42 and grounded to casing 12 at the other end. Spring 43 biases air valve 28 toward a closed position. Diaphragm 46 is peripherally clamped between casing 12 and a cover casing 48. The underneath side of diaphragm 46 is openly communicated with the fuel reservoir 50. Hence the underside of diaphragm 46 is exposed to substantially atmospheric pressure.

Diaphragm 46 and cover casing 48 define a chamber- 52 which communicates through a passage 54 drilled through cover casing 48 and main casing 12 with inducposed to substantially atmospheric pressure through a vent tube 56, extending anteriorly of air valve 28, and the upper side of the diaphragm being exposed to the pressure posteriorly of valve 28, the pressure drop existing across the air valve will likewise exist across the di aphragm. Diaphragm 46 will be positioned, and through the linkage system 44, 36, 34 and 32 position air valve 28 to maintain a substantially constant pressure drop across the air val-ve. As air flow increases through induction passage 14 air valve 28 will be proportionally opened by diaphragm 46.

In order to maintain a predetermined fuel-air ratio, it is apparent that as air valve 28 opens in response to increased air flow, it is also necessary to increase the quantity of fuel supplied. The means whereby fuel is increased or varied in accordance with the position of the air valve will now be considered.

Before referring to the fuel metering means, per se, the fuel source will be described in greater detail. As already noted, the fuel reservoir is indicated generally at 50 and is formed within casing 12. Fuel is supplied to reservoir 50 from any suitable transfer pump, not shown, and enters casing 12 through a passage 60. A float controlled valve mechanism 62 is pivotally mounted within reservoir 50 and in the normal manner controls the quantity of fuel admitted to the reservoir in accordance with the fuel level within the reservoir.

As best seen in FIGURES 13-15, a pair of fuel metering orifices 64--65 are formed in casing 12 and disposed within reservoir 50. Orifices 64-65 communicate through casing passage 66 with

fuel nozzles

68 and 70 extending within the individual throttle intake passages 18 and intermediate the air valve and throttle valves 28 and 22-23.

A U-shaped member 72 is formed to provide a pair of metering rods 74 and 76 which respectively coact with the fuel metering orifices 64 and 65 to regulate the quantity of fuel flow through the orifices. Each of the metering rods terminates in a tapered end portion which is formed by forming the rod ends with a pair of fiat tapered sides. Thus the metering rods are not contoured as has been the practice with metering rods in the past and rather than replacing the rods to provide proper fuel flow rates for a particular engine, an appropriate adjustment may be made Within the linkage system controlling the rods.

Referring now to FIGURES 3, 13 and 15, multi-armed lever 38 includes an arm 78 having an outwardly opening slot 80 which is adapted to slidably engage with the upper or closed end 82 of the metering rod member 72. As diaphragm 46 is moved upwardly in response to increased air flow through induction passage 14 lever 38 will be rotated in a counterclockwise direction opening air valve 28 and also moving the metering rods out of the fuel metering orifices thereby permitting increased fuel flow through the latter. Accordingly, through the interconnection of diaphragm 46, air valve 28 and metering rod member 72 a substantially constant fuel-air ratio may be maintained under all air flow conditions.

While a constant fuel-air ratio is desirable under normal operating conditions, there are certain operating conditions during which it is desired to enrichen the fuel-air ratio. The conditions under which an enriched fuel-air ratio is desired are cold start, cold running, high power demand including acceleration. The means whereby these various operating conditions are accommodated to achieve an enriched fuel-air ratio will now be considered.

The means for achieving acceleration enrichment will be considered first. An accelerator pump 90 and starting enrichment device 92 are respectively formed in the bottom of casing 12 and enclosed by a common cover casing 94.

Accelerator pump 90 includes a diaphragm member 96 peripherally clamped between casings 12 and 94. A rod 98 is centrally fixed to diaphragm 96 and extends through cover casing 94. Rod 98 is adapted to engage with and in turn be actuated by a lever 100 operatively connected to throttle valve shaft 24. Accelerator pump actuating lever 100 is connected to throttle shaft lever 26 through a spring member 104.

A spring 106 is disposed intermediate casing 12 and diaphragm 96 and normally biases the latter in a fuel charging direction. Chamber 108 defined by diaphragm 96 and casing 12 is communicated with fuel reservoir 50 through a conduit 110. A ball check valve 112 is formed within a cavity 114 formed in casing 12. Valve 112 is adapted to seat against fingers 116 when spring 106 biases the diaphragm 96 in a charging direction permitting fuel to be drawn from fuel reservoir 50 into chamber 108. A,

4 fuel outlet passage 118 leads from the accelerator pump chamber 108. I

Upon a sudden opening of throttles 22-23 as would occur during acceleration conditions, lever 26 tensions spring 104 and in turn causes lever to rotate urging the diaphragm 96 in a discharging direction. This movement of diaphragm 96 will cause the ball check valve 112 to come to rest against seat 120 thereby preventing fuel from being forced back into reservoir 50. Instead, the fuel from chamber 108 will be discharged through passage 118 and into chamber 122 formed by casing 12 and a diaphragm 124. The pressurized acceleration charge will then cause a spring biased ball check valve 126 to be unseated permitting the acceleration charge to flow out of a conduit 128 which communicates with pump shooters or nozzles 130 disposed in the induction passage posteriorly of the air valve 28.

The spring 132 biasing ball check valve 126 into a seating position is normally strong enough to prevent the vacuum forces acting on the pump shooters from drawing fuel from the accelerator pump under normal operating conditions. Referring once again to the accelerator pump, a stud 134 is centrally mounted on diaphragm 96 and is adapted to retain the ball check valve 112 against its seat 1211 during the final movement of the pump diaphragm. In the event the engine is warm, flooding is prevented during cranking by fully opening throttle 22 which through lever 26, spring 104 and lever 100 moves rod 98 upwardly to seat ball valve 112 against seat 120. This blocks flow from fuel reservoir 50 and thereby prevents excess fuel from being drawn into induction passage 14.

As already noted, during engine starting operation it is necessary to momentarily enrich the fuel-air ratio. For this purpose the starting enrichment device 92 is provided. It has already been stated that under normal operating conditions, spring 132 is strong enough to maintain ball check valve 126 in a seated position to prevent the vacuum forces within induction passage 14 from drawing fuel through the accelerator pump shooter or nozzle 130. However, means is provided for unseating valve 126 during starting conditions to provide the fuel-air ratio enrichment required for this purpose.

As best seen in FIGURES 6 and 15, diaphragm 124 includes a piston valve 136 centrally fixed thereto and adapted to be slidably mounted within a boss portion 137 of cover casing 94. Piston valve 136 has two relieved portions 138 and 140. Casing boss 137 includes a first passage 142 communicating with atmosphere and a second passage 144 communicating with a conduit 146 in turn communicating with the diaphragm vacuum passage 54. A port 148 is also provided in boss 137 and communicates the bottom of piston valve 136 through a conduit 149 with induction passage 14 posteriorly of throttle valves 22-23. Thus manifold vacuum acts on the bottom of the piston valve. A stud 150 is also centrally mounted on diaphragm 124 and is adapted to engage with ball check valve 126. A spring 152 is disposed between diaphragm 124 and cover casing 94 and is of sufficient strength to move the diaphragm upwardly causing the stud to unseat ball check valve 126.

Under normal operating conditions manifold vacuum acting on the bottom of piston valve 136 will normally maintain the piston and diaphragm 124 in a downward position in which stud 150 is out of engagement with ball check valve 126 preventing induction passage vacuum from drawing fuel through the accelerator pump. However, during starting conditions, FIGURE 15, the cranking vacuum acting on the bottom of piston valve 136 is of too low a value to overcome spring 152 the latter which, therefore, moves the diaphragm upwardly unseating ball check valve 126 permitting induction passage vacuum to draw additional fuel through the accelerator pump and discharge the same through pump shooters 130. In the extended or cranking position, relieved portion 138 of piston valve 136 communicates chamber 154- with the atmosphere through passage 142. On the other hand, during normal operating conditions, FIGURE 6, manifold vacuum retracts piston valve 136 cutting off atmospheric vent 142 and permitting relieved portion 136 to admit vacuum from diaphragm vacuum passages 146 and 54 to chamber 154 to retain the diaphragm 124 in a retracted position. It is apparent that starting enrichment device 92 will only be operative to enrich the fuelair ratio during cranking conditions and as soon as the engine becomes operative ball check valve 126 is seated by spring 132 to block induction passage induced flow to the pump shooters 130.

Until the engine warms suificiently, it is desirable to maintain at least a slightly enriched fuel-air ratio which is achieved in the subject device through control of the fuel metering rod member 72. Referring again to FIG- URES 3 and 15, it will once again be noted that the upper end 82 of the fuel metering rod is disposed in slot 80 of arm 78. It will further be apparent that as metering rod member 72 is moved radially inwardly or outwardly within slot 86 the effective length of arm 78 is varied. To illustrate, for a given amount of rotative movement of lever 38, the movement of the metering rod member radially outwardly within slot 80 will increase the opening movement of the metering rods 74 and 76 relative to the metering orifices 64 and 65. On the other hand, a radially inward movement of the metering rod member within slot 81) will decrease the movement of the metering rods relatively to the metering orifices. This type of movement of metering rod member 72 vw'thin slot 80 of arm 78 is utilized to provide cold running as well as power enrichment as will now be considered in greater detail.

A lever 168 is fixed to a shaft 162 pivotally supported in casing 12. Lever 169 includes an end having an outwardly open slotted portion 164 which is adapted to engage with upper end 82 of-metering rod member 72 to move the latter inwardly and outwardly relative to slot 80 of arm 78 as lever 160 is rotated. The rotation of lever 16!) is controlled by two forces, one responsive to ambient temperature and the other manifold vacuum. Lever shaft 162 extends through casing 12 and has a U-shaped bracket 166 fixed thereto. U-shaped bracket or lever 166 includes a pair of adjustable stops 168 and 170 adapted to coact with a rotatable cam member 172 disposed intermediate these stops. Lever 166 is articulated through a link 174 with a piston member 176 disposed within casing 12 and defining a chamber 178 with said casing. Chamber 178 communicates with manifold vacuum through a passage 180. A spring 182 is disposed within chamber 178 and is adapted to bias piston 176 in a direction urging stop 168 into engage- Inent with cam member 172. Stop 168 is the power or enrichment stop whereas stop 170 is the economy stop. Assuming an increase in engine load it is apparent that manifold vacumm will drop under which condition spring 182 will bias the piston 176 in a direction moving the power stop 168 into engagement with cam 172. This movement of bracket lever 166 imparts a counterclockwise rotation to lever 160 causing the metering rod member 72 to slide radially outwardly within arm slot 80 increasing the effective length of arm 78 and in turn increasing the opening between the metering rods and the fuel metering orifices to increase the flow of fuel. During normal engine load conditions piston 178 is moved by manifold vacuum until the economy stop 17b engages cam 172 shortening the effective length of arm 78 and correspondingly decreasing the fuel flow through the metering orifices 64 and 65.

Stops 168 and 170 are respectively adjustable relative to lever 166 through threaded studs 184 and 186. In this manner the basic power and economy positions may be adjusted for any particular engine.

In order to vary the amount of movement of lever 160 in accordance with engine temperature, cam 172 is 6 fixed to a shaft 188 the other end of which is connected to one end of a thermostatic coil 190'. As engine temperature increases coil 190 will cause cam 172 to move in a clockwise direction, as viewed in FIGURE 15, to thereby limit the enrichment movement of levers and 166.

Through a lever 192 fixed to shaft 188 and link 194 the thermostatic coil 1% controls a fast idle cam 196 which functions in the normal manner to determine the idle positions of the throttle valves 22-23.

To provide for idle air flow through induction passage 14 and throttle passages 1820, a first idle air passage 197-498-201] is provided for bypassing air around air valve 28 and a second idle air bypassage 200202204 whereby air is bypassed around the throttle valves. The air flow through the respective bypass passages is regulated through adjustable valve elements 286 and 208 by screwing the valve elements into or out of the respective passages 198 and 202. The idle fuel-air mixture may be leaned by backing screw 286 out of passage 198 thereby increasing the air bypassing valve 28. Thus air valve 28 tends to close in turn causing fuel metering rods 74 and 76 to close fuel metering orifices 6465 and thereby leaning the idle mixture.

In order to externally vent fuel reservoir 50 when the engine is inoperative, a throttle controlled vent device of the type disclosed in Patent 2,771,282 is provided. Briefly, this device includes a valve indicated generally at 210 and mounted in casing 12 in communication with reservoir 5' Valve 2111 is normally biased closed but is adapted to be opened by a link member 212. When the throttle valves are closed, link 212 is engaged by an arm 214 on throttle lever 26 moving the link downwardly and opening valve 210 and thereby venting reservoir 50.

Referring to FIGURES 8 and 15, throttle lever 26 includes an arcuate slot 216 in which one end of a link 2118 is loosely articulated. The other end of link 218 is pivotally connected to fast idle cam 196. Lever 26 includes adjustable screw 221) which coacts with the steps of the cam to determine the cold idle position of throttle 22. When the engine is cold the throttle stop is on the high step of the cam as shown in FIGURE 8. Under this condition, enrichment cam 172 controlled by coil 192 biases lever 160 in a counterclockwise direction to increase fuel flow through metering orifices 6465, supra. Under these conditions, if the operator fully opens the throttle the fuel-air ratio will normally be too rich for proper engine operation. However, the end of slot 216 will engage link 218 rotating the fast idle cam in a counterclockwise direction which through link 194 will move cam 172, fixed to shaft 188, and lever 160 to temporarily decrease fuel flow through the fuel metering orifices.

The subject carburetor has been purposely constructed so that the same depression that causes air flow past air valve 28 also causes fuel flow through the metering orifices 64 and 65. For this reason and because air valve 28 and metering rods 72 are mechanically connected, signal variations do not change the air-fuel ratio. Accordingly, the subject carburetor is reasonably insensitive to friction. In the past, many so called air valve type carburetors were commercially rejected because they were too sensitive to friction.

I claim:

1. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted in said induction passage, an air valve rotatably mounted in said induction passage anteriorly of said throttle valve, a servo device operatively connected to and adapted to control the position of said air valve in accordance with the pressure drop across the air valve, a source of fuel, conduit means communicating said fuel source with said induction passage intermediate said air and throttle valves, a metering orifice in said conduit means, a metering rod adapted to coact with said metering orifice to control the quantity of fuel fiow therethrough, said metering rod being adjustably connected to said servo device whereby fuel flow through the metering orifice is proportional to the degree of opening of said air valve, and means for varying the adjustable connection between the metering rod and said servo device to vary the fuel flow rate through said metering orifice in accordance with certain engine operating conditions.

2. A charge forming device as set forth in claim 1 in which the adjustable connection varying means comprises an engine temperature and load responsive device for increasing fuel flow through the metering orifice upon a decrease in said temperature or an increase in said load.

3. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted in said induction passage, an air valve rotatably mounted in said induction passage anteriorly of said throttle valve, a servo device operatively connected to and adapted to control the position of said air valve in accordance with the pressure drop across the air valve, a source of fuel, first and second conduit means communicating said fuel source with said induction passage intermediate said air and throttle valves, a metering orifice in said first conduit means, a metering rod adapted to coact with said metering orifice to control the quantity of fuel flow therethrough, said metering rod being adjustably connected to said servo device whereby fuel flow through the metering orifice is proportional to the degree of opening of said air valve, means for varying the adjustable connection between the metering rod and said servo device to vary the fuel flow rate through said metering orifice in accordance with certain engine operating conditions, a valve device adapted to prevent fuel flow through said second conduit during normal engine operating conditions, and means for opening said valve device to permit engine cranking vacuum to draw fuel through said second conduit means for starting enrichment.

4. A charge forming device as set forth in claim 3 in which the valve device includes a spring biased ball check valve, and further in which the valve device opening means includes a spring biased diaphragm adapted to engage and unseat the ball check valve, a piston valve connected to said diaphragm, engine vacuum normally acting on the piston valve to move the diaphragm out of engagement with the ball check valve.

5. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted in said induction passage, an air valve rotatably mounted in said induction passage anteriorly of said throttle valve, a servo device operatively connected to and adapted to control the position of said air valve in accordance with the pressure drop across the air valve, a source of fuel, first and second conduit means communicating said fuel source with said induction passage intermediate said air and throttle valves, a metering orifice in said first conduit means, a metering rod adapted to coact with said metering orifice to control the quantity of fuel flow therethrough, said metering rod being adjustably connected to said servo device whereby fuel fiow through the metering orifice is proportional to the degree of opening of said air valve, means for varying the adjustable connection between the metering rod and said servo device to vary the fuel flow rate through said metering orifice in accordance with certain engine operating conditions, a valve device adapted to prevent fuel flow through said second conduit during normal engine operating conditions, and means for opening said valve device to permit engine cranking vacuum to draw fuel through said second conduit means for starting enrichment, and a throttle valve actuated accelerator pump associated with the second conduit means, said pump being adapted to discharge fuel through said valve device upon rapid opening of the throttle valve.

6. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted in said induction passage, an air valve rotatably mounted in said induction passage anteriorly of said throttle valve, a servo device operatively connected to and adapted to control the position of said air valve in accordance with the pressure drop across the air valve, a source of fuel, first and second conduit means communicating said fuel source with said induction passage intermediate said air and throttle valves, a metering orifice in said first conduit means, a metering rod adapted to coact with said metering orifice to control the quantity of fuel flow therethrough, said metering rod being adjustably connected to said servo device whereby fuel flow through the metering orifice is proportional to the degree of opening of said air valve, and means for varying the adjustable connection between the metering rod and said servo device to vary the fuel flow rate through said metering orifice in accordance with certain engine operating conditions, a spring biased ball check valve disposed in and normally blocking fuel flow through said second conduit means, a spring biased diaphragm adapted to engage and unseat the ball check valve, a piston valve connected to said diaphragm, engine vacuum normally acting on the piston valve to move the diaphragm out of engagement with the ball check valve, and a throttle valve actuated accelerator pump associated with the second conduit means, said pump being adapted to unseat the ball check valve and discharge fuel through the second conduit means upon the rapid opening of the throttle valve.

7. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted in said induction passage, an air valve rotatably mounted in said induction passage anteriorly of said throttle valve, a control diaphragm one side of which is exposed to substantially atmospheric pressure, conduit means communicating the other side of said diaphragm with said induction passage intermediate said air and throttle valves, a first lever articulated to said diaphragm, a second lever fixed to said air valve, a linkage means interconnecting said levers to permit said diaphragm to position said air valve to maintain a substantially constant pressure drop across said valve under normal air flow conditions, a source of fuel, conduit means communicating said fuel source with said induction passage intermediate said air and throttle valves, a metering orifice in said conduit means, a metering rod adapted to coact with said metering orifice to control the quantity of fuel flow therethrough, said metering rod being adjustably articulated to said first lever causing fuel flow through the metering orifice to be proportional to the degree of opening of said air valve, and means for varying the adjustable connection between the metering rod and said first lever to vary the fuel fiow rate through said metering orifice in accordance with certain engine operating conditions.

8. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted in said induction passage, an air valve rotatably mounted in said induction passage anteriorly of said throttle valve, a control diaphragm one side of which is exposed to substantially atmospheric pressure, conduit means communicating the other side of said diaphragm with said induction passage intermediate said air and throttle valves, a first lever articulated to said diaphragm, a second lever fixed to said air valve, a linkage means interconnecting said levers to permit said diaphragm to position said air valve to maintain a substantially constant pressure drop across said valve under normal air flow conditions, a source of fuel, conduit means communicating said fuel source with said induction passage intermediate said air and throttle valves, a metering orifice in said conduit means, a metering rod adapted to coact with said metering orifice to control the quantity of fuel flow therethrough, saidtmetering rod being adjustably articulated to said first lever whereby fuel flow through the metering orifice is proportional to the degree of opening of said air valve, and temperature responsive means for varying the adjustable connection between the metering rod and said first lever to increase fuel flow when the engine temperature is below a predetermined value.

9. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted in said induction passage, an air valve rotatably mounted in said induction passage anteriorly of said throttle valve, a control diaphragm one side of Which is exposed to substantially atmospheric pressure, conduit means communicating the other side of said diaphragm with said induction passage intermediate said air valve and said throttle valve, a first lever articulated to said diaphragm, a second lever fixed to said air valve, a linkage means interconnecting said levers to permit said diaphragm to position said air valve to maintain a substantially constant pressure drop across said valve under normal air flow conditions, a source of fuel, conduit means communicating said fuel source with said induction passage intermediate said air and throttle valves, a metering orifice in said conduit means, a metering rod adapted to coact With said metering orifice to control the quantity of fuel flow therethrough, said metering rod being adjustably articulated to said first lever causing fuel flow through the metering orifice to be proportional to the degree of opening of said air valve, means for varying the adjustable connection between the metering rod and said first lever to vary the fuel flow rate through said metering orifice in accordance 'with certain engine operating conditions, an accelerator pump, a first passage connecting the fuel source with said pump, a second passage connecting said pump with said induction passage intermediate said air and throttle valves, said pump including a diaphragm, a casing coacting with said diaphragm to define a first chamber communicating with said first passage means, a valve means permitting flow from said fuel source to said chamber and preventing flow from the chamber back to the fuel source, spring means urging said diaphragm in a direction tending to draw fuel from said fuel source into said chamber, a discharge passage communicating said pump chamber with said second passage means, throttle control means for urging said diaphragm against the force of said spring to discharge fuel from the pump chamber to said induction passage.

10. A charge forming device as set forth in claim 9 in which the adjustable connection varying means comprises an engine temperature and load responsive device whereby fuel flow will be decreased upon an increase in said temperature or a decrease in said load.

11. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted in said induction passage, an air valve rotatably mounted in said induction passage anteriorly of said throttle valve, a control diaphragm one side of which is exposed to substantially atmospheric pressure, conduit means communicating the other side of said diaphragm with said induction passage intermediate said air valve and said throttle valve, a first lever articulated to said diaphragm, a second lever fixed to said air valve, a linkage means interconnecting said levers to permit said diaphragm to position said air valve to maintain a substantially constant pressure drop across said valve under normal air flow conditions, a source of fuel, conduit means communicating said fuel source with said induction passage intermediate said air and throttle valves, a metering orifice in said conduit means, a metering rod adapted to coact with said metering orifice to control the quantity of fuel flow therethrough, said metering rod being adjustably articulated to said first lever causing fuel flow through the metering orifice to be proportional to the degree of opening of said air valve, means for varying the adjustable connection between the metering rod and said first lever to vary the fuel flow rate through said metering orifice in accordance with certain engine operating conditions, an accelerator pump, a first passage connecting the fuel source with said pump, a second passage connecting said pump with said induction passage intermediate said air and throttle valves, said pump including a diaphragm, a casing coacting with said diaphragm to define a first chamber communicating with said first passage means, a valve means permitting flow from said fuel source to said chamber and preventing flow from the chamber back to the fuel source, spring means urging said diaphragm in a direction tending to draw fuel from said fuel source into said chamber, a discharge passage communicating said pump chamber with said second passage means, throttle control means for urging said diaphragm against the force of said spring to discharge fuel from the pump chamber to said induction passage, a spring biased valve disposed intermediate said pump chamber discharge and said second passage means, said spring biased valve means normally blocking fuel flow through said second passage means when the accelerator pump is inoperative, and means for unseating said spring biased valve during engine cranking conditions permitting engine cranking vacuum to draw fuel through said second passage means.

12. A charge forming device for an internal combustion engine comprising an induction passage, a throttle valve rotatably mounted in said induction passage, an air valve rotatably mounted in said induction passage anteriorly of said throttle valve, a control diaphragm, one side of said diaphragm being exposed to substantially atmospheric pressure, conduit means communicating the other side of said diaphragm with said induction passage intermediate said air valve and said throttle valve, a first lever articulated to said diaphragm, a lever fixed to said air valve, a linkage means interconnecting said air valve lever and said first lever permitting said diaphragm to position said air valve to maintain a constant pressure drop across said valve under all air flow conditions, a source of fuel, conduit means communicating said fuel source with said induction passage intermediate said air valve and throttle valve, a metering orifice in said conduit means, a metering rod adapted to coact with said metering orifice to control the quantity of fuel flow therethrough, said metering rod being adjustably connected to said first lever causing fuel flow through the metering orifice to be proportional to the degree of opening of said air valve, an engine temperature and load responsive device for varying the adjustable connection between the metering rod and said first lever to increase fuel flow through said metering orifice upon a decrease in said temperature or an increase in said load, an accelerator pump, a first passage connecting the fuel source with said pump, a second passage connecting said pump with said induction passage intermediate said air and throttle valves, said pump including a diaphragm, a casing coacting with said diaphragm to define a first chamber communicating with said first passage means, a valve means permitting flow from said fuel source of said chamber and preventing flow from the chamber back to the fuel source, spring means urging said diaphragm in a direction tending to draw fuel from said fuel source into said chamber, a discharge passage communicating said pump chamber 'with said second passage means, throttle control means for urging said diaphragm against the force of said spring to discharge fuel from the pump chamber to said induction passage, a spring biased valve disposed intermediate said pump chamber discharge and said second passage means, said spring biased valve means normally blocking fuel flow through said second passage means when the accelerator pump is inoperative, and means for unseating said spring biased valve during engine cranking conditions permitting en- 11 gine cranking vacuum .to draw fuel through said second passage means.

13. A change forming device'as set forth in claim 1 and including passage means for bypassing induction passage air flo'w around said air valve during engine idling operation, and adjustable valve means coacting with said passage means to vary the pressure drop across the air valve whereby the metering rod is adjusted to vary idle fuel flow.

12 14. A charge forming device as set forth in claim 1 and including means operable when said throttle is moved to wide open position to render the adjustable connection varying means inoperativeto increase the fuel flow rate. 15. A charge forming device as set forth in claim 3 and including means for blocking fuel flow through the valve device when the throttle is moved to Wide open position.

No references cited.