US3652065A

US3652065A - Fluidic controlled carburetor

Info

Publication number: US3652065A
Application number: US742A
Authority: US
Inventors: Edward H Casey; James T Bickhaus
Original assignee: ACF Industries Inc
Current assignee: Carter Automotive Co Inc
Priority date: 1970-01-05
Filing date: 1970-01-05
Publication date: 1972-03-28
Anticipated expiration: 1989-03-28

Abstract

A carburetor having a mixing chamber, fuel bowl and fuel circuits is provided with fluidic control elements to control fuel flow for all normal driving conditions as well as for transient conditions such as cranking, warm-up, acceleration and deceleration. The fluidic elements control the fuel flow to compensate for altitude variations, and also control the air supply for cranking and warm-up. Pneumatically operated pure fluid amplifiers respond to vacuum signals from the engine manifold and mixing chamber and produce output signals for controlling valves located in the fuel circuits.

Description

limited States Patent (Iasey et a1.

[4 1 Mar. 28, 1972 [54] FLUIDIIC (:ONTROLLED CARBURETOR [72] Inventors: Edward H. Casey; James T. Bickhaus,

both of St. Louis, Mo.

ACF Industries, Incorporated, New York, NY.

[22] Filed: Jan. 5, 1970 [21] Appl.No.: 742

[73] Assignee:

[52] U.S.Cl. ..261/39 R, 261/39 D, 261/69 R,

3,556,488 l/l97l Arikawa et al ..26l/DIG. 69 3,388,898 6/1968 Wyczalek ..26l/DlG. 69 3,499,460 3/1970 Rainer ..l37/8 1.5 3,548,795 l2/l970 Howland ..26l/DIG. 69 3,577,964 5/1971 Lazar ..26l/DIG. 69

Primary Examiner-Tim R. Miles Attorney-Griffin, Branigan and Kindness [.57] ABSTRACT A carburetor having a mixing chamber, fuel bowl and fuel circuits is provided with fluidic control elements to control fuel flow for all normal driving conditions as well as for transient conditions such as cranking, warm-up, acceleration and deceleration. The fluidic elements control the fuel flow to compensate for altitude variations, and also control the air supply for cranking and warm-up. Pneumatically operated pure fluid amplifiers respond to vacuum signals from the engine manifold and mixing chamber and produce output signals for controlling valves located in the fuel circuits.

14 Claims, 2 Drawing Figures 3,313,531 4/1967 Winkleyctal.... ..26l/39B PATENTEDMAR281972 3,652,065

ama

FIG.I.

INVENTORS JAMES T. BICKHAUS EDWARD H. CASEY ATTORNEY PATENTinuARzs m2 sum 2 BF 2 FlG.2.

INVENTORS JAMES T. BICKHAUS EDWARD H. CASE g m'b mm'qlm an) ATTORNEY FLUIDIC CONTROLLED CARBURETOR BRIEF DESCRIPTION OF THE INVENTION The present invention relates to carburetors of the type employing fluidic control elements for controlling fuel flow from a fuel bowl to a mixing chamber.

An object of this invention is to provide a carburetor including fluidic control elements for controlling the flow of fuel from a bowl to a mixing chamber, said fluidic control elements providing control of fuel flow during cranking, warm-up, acceleration deceleration, and normal driving.

Another object of the invention is to provide a carburetor having fluidic control elements responsive to vacuum signals from a mixing chamber and an engine manifold for providing a rich air-fuel mixture during cranking, a leaner air-fuel mixture during idling, and a rich air-fuel mixture during periods of heavy engine load.

Another object of the invention is to provide a carburetor including fluidic control elements for performing the function heretofore performed by a fast idle cam.

Still another object of the invention is to provide a carburetor including fluidic control elements for performing the function ofa choke.

A further object of the invention is to provide a carburetor including fluidic control elements responsive to atmospheric pressure for adjusting fuel flow rate in accordance with altitude.

Yet another object of the invention is to provide a carburetor including a mixing chamber and fluidic controls responsive to the fuel temperature for controlling the flow of fuel to the mixing chamber.

A further object of the invention is to provide a carburetor including an air intake bore, a throttle valve in said bore, a fuel bowl, a plurality of fluidic control elements, means for sensing the pressure in the manifold of an engine, means for sensing the pressure in the air intake bore upstream of the throttle valve, and fuel lines connected between the fuel bowl and the air intake bore, one of the fuel lines connecting with the bore upstream of the throttle valve and the other connecting with the air intake bore downstream of the throttle valve, said fluidic control elements responding to the pressures in the air intake bore and the engine manifold for metering fuel to the fuel lines.

A further object of the invention is to provide a carburetor as defined in the preceding paragraph and including further means for mixing air with the fuel entering the air intake bore downstream of the throttle valve, said further means being controlled by said fluidic control means to provide a rich mixture during engine cranking and a lean mixture during engine idling. The fluidic control means may be controlled by a temperature sensing means such that the air-fuel mixture is enriched as the engine temperature increases.

Yet another object of the invention is to provide a carburetor including an air intake bore connecting with the intake manifold of an engine, a fuel bowl, means for sensing the pressure in said manifold, means for sensing pressure in said intake bore, and fluidic control means responsive to said pressure sensing means for metering the flow of fuel from said bowl to said intake bore. 1

Another object of the invention is to provide a carburetor as described in the preceeding paragraph wherein said fluidic control means includes means responsive to fuel temperature for controlling the rate at which fuel is metered.

BRIEF DESCRIPTION OF DRAWING FIG. 1 shows a first embodiment of a carburetor including fluidic controls; and,

FIG. 2 shows a second embodiment of a carburetor including fluidic controls.

DETAILED DESCRIPTION OF THE INVENTION (FIG. 1)

The embodiment of the invention shown in FIG. I includes a member 10 having a bore or air intake and mixing chamber 12 connecting with the manifold 14 of an internal combustion engine. The carburetor is of conventional design in that it includes a Venturi throat with a throttle valve 16 located downstream from the throat. Fuel from constant level fuel bowl 18 is supplied to the bore through a first fuel line 20 which terminates at an opening in the region of the Venturi throat, and through a second fuel line 22 which terminates at an opening located between the throttle valve and the engine manifold. Fuel line 20 connects with a chamber 24 located at the bottom of the fuel bowl and fuel line 22 is connected by means of a fuel line 22a to a second chamber 26 which is also located at the bottom of the fuel bowl.

The flow of fuel from the fuel bowl 18 to the bore 12 is controlled by a fluidic control circuit which, generally speaking, comprises a plurality of

pure fluid amplifiers

28, 30, 32 and 34, a plurality of spring

biased diaphragm valves

36, 38, 40 and 42, a variable flow restrictor 44, and a capillary sensor 46.

The fluid amplifiers are proportional fluid amplifiers of conventional design and each includes a power stream inlet connected to an air pump symbolically represented by triangles 48. Each amplifier includes two output lines and two or more control input lines.

Fluid amplifier 28 has four

control inputs

50, 52, 54 and 56. Control input 50 is connected through the capillary sensor 46 to the air pump 48. Control input 54 is connected through the variable flow restrictor 44 to the air pump. Control input 56 is connected to the chamber of check valve 36 whereas the control input 52 is vented to the atmosphere.

Fluid amplifier 30 has two

control inputs

62 and 64 which are connected to the

outputs

58 and 60, respectively of amplifier 28. The

outputs

66 and 68 of amplifier 30 are connected to the upper and lower chambers, respectively, of diaphragm valve 38.

Fluid amplifier 32 has four

control inputs

70, 72, 74 and 76. Control inputs 74 and 76 are connected to the

outputs

58 and 60, respectively, of amplifier 28. Control input 70 is vented to the atmosphere. Control input 72 is connected to a fluid passage 78 which terminates at an opening 80 in the Venturi throat. The

outputs

82 and 84 are connected to the upper and lower chambers, respectively, of diaphragm valve 40.

Fluid amplifier 34 has only two

control inputs

86 and 88. Control input 86 is vented to the atmosphere while control input 88 is connected to the fluid passage 78. The

outputs

90 and 92 of amplifier 34 are connected to the upper and lower chambers, respectively, of diaphragm valve 42. The amplifier is biased by any conventional biasing means so that the power stream is normally directed toward output 92 and is deflected to flow into output 90 only after the vacuum signal on control input 88 exceeds a predetermined value.

A manifold pressure sensing line 94 is connected between the engine manifold 14 and check valve 36. The valve includes a disc 96 that is normally biased away from the end of line 94 by a spring 98 when the engine is stopped or being cranked. As subsequently explained, the manifold vacuum sensed by line 94 is transmitted through valve 36 to control amplifier 28 during cranking. At idling or running speeds the manifold vacuum overcomes the bias of spring 98 and draws disc 96 against the end of line 94 so that no vacuum signal is applied to the control input 56 of amplifier 58.

Diaphragm valve 40 comprises an enclosed volume that is divided into upper and lower chambers by a diaphragm 40a. The diaphragm is connected by a spindle 40b to a poppet 400. A bias spring 40d acts against the diaphragm to seat the poppet in its closed position when the fluid pressures on opposite sides of diaphragm 40a are equal.

Diaphragm valve 42 is similar to valve 40 in construction and functions in the same manner. Valve 42 has a poppet 42c that is normally seated so as to prevent the flow of fuel from bowl 18 into chamber 24.

Valve 38 is similar to

valves

40 and 42 but differs in that a piston 380 is connected to its spindle. The piston has two seating surfaces and extends through the wall of a chamber 99. The chamber is connected by line 22b to the fuel line 22. As subsequently explained, the piston 38c replaces the functions of the fast idle cam heretofore used in carburetor controls. During cranking the piston is raised to close the opening in chamber 99 and thus prevent air from entering fuel line 22 through chamber 99. This provides a rich fuel mixture during cranking. During running, piston 38c is moved to its middle position so that sufficient air for cold idle may enter chamber 99 and mix with the fuel in line 22 to provide a fuel mixture adequate for warm-up. After the engine has warmed up, the piston 38c is moved downwardly sufficiently to reduce the air flow to that required for normal idle operation.

The capillary 46 provides for fuel enrichment during warmup and thus serves the same function as a choke. It is a temperature sensor and may be located in the water system, the exhaust manifold, or the air intake chamber 12. The flow restrictor 44 is adjusted so that at some atmospheric temperature such as 70 equal volumes of air from pump 48 flow through restrictor 44 and capillary 46 so as to apply equal but opposing control signals to amplifier 28. As the engine heats up, air flow through capillary 46 decreases and relatively more air flows through restrictor 44 than through the capillary, thus providing an unbalanced input to amplifier 28 that is dependent upon engine temperature.

The fluidic control circuit of FIG. 1 functions as follows. As the engine is cranked, the air pump 48 is driven so that air is applied to the power stream inputs of each of the

fluid amplifiers

28, 30, 32 and 34. As previously explained, amplifier 34 is geometrically biased so that its power stream is directed through output 92 to the lower chamber of valve 42. This blocks the flow of fuel from the fuel bowl into chamber 24 and fuel line 20.

Assuming that the engine is colder than the temperature setpoint of restrictor 44, more air from air pump 48 will pass through capillary 46 than will pass through the restrictor. Thus, the signal on control input 50 of amplifier 28 will be larger than the signal on control input 54 so that more of the power stream is directed toward output 60 than is directed toward output 58.

When the engine is cranked, the manifold pressure drops. This vacuum signal is transmitted through line 94 to valve 36. The vacuum signal is insufficient to overcome the bias of spring 98 so the valve does not close. Therefore, the vacuum signal passes through valve 36 to control input 56 of amplifier 28. The vacuum signal on control input 56 also tends to deflect the power stream of amplifier 28 so that more of the power stream is directed toward output 60 than is directed toward output 58.

The

outputs

58 and 60 are applied to control inputs 74 and 76, respectively, of amplifier 32. This amplifier has a balanced internal configuration such that its power stream divides equally between

outputs

82 and 84 in the absence of signals at any of its control inputs. Since the signal applied to control input 76 is greater than the signal applied to control input 74, the power stream is deflected so that more of is flows toward output 82 than flows toward output 84.

There is a further small signal which aids in deflecting the power stream of amplifier 32 during cranking. The throttle valve 16 is at least partially open so that a negative pressure exists in the air intake chamber 12. This pressure is sensed at opening 80 and conveyed through line 78 to control input 72 where it tends to draw the power stream of amplifier 32 toward output 82.

The

unbalanced outputs

82 and 84 create a greater pressure above diaphragm 40a than exists below it. The diaphragm moves downwardly to unseat poppet 40c. Fuel from bowl 18 may then pass through chamber 26, fuel line 22a, and fuel line 22 to the carburetor bore. The inverted U-shaped segment of line 22a prevents gravity feed of fuel from the bowl to the carburetor bore. Fuel is drawn from the bowl by the manifold vacuum present at the end of fuel line 22 during cranking. An air bleed permits mixing of air with the fuel to provide a better spray of fuel into the carburetor bore while a heater 97 heats the fuel to provide better vaporization at low speeds. This reduces exhaust emissions.

During the cranking period it is desirable to have a rich fuel mixture hence the piston 38c is positioned to prevent air from entering fuel line 22 through the port in chamber 99. The fluid amplifier 30 is normally balanced so that in the absence of signals at any of its control inputs the power stream divides and flows equally into

outputs

66 and 68. With equal pressures on both sides of diaphragm 38a, piston 38c is positioned as shown in the drawing so that air may enter chamber 99. However, during cranking the

outputs

58 and 60 of amplifier 28 are applied to the

control inputs

62 and 64, respectively of amplifier 30. Since the signal from output 60 is greater than the signal from output 58, the power stream of amplifier 30 is deflected so that a major portion of it flows toward output 68. This increases the pressure on the lower side of diaphragm 3811 thus raising the diaphragm and piston 38c to block the opening in chamber 99.

At the end of the cranking period, when the engine is running at fast idle speed, it is desirable to provide a rich fuel mixture to the carburetor. The manifold vacuum at idle speed is sufficient to overcome the bias of spring 98 so that the vacuum in line 94 draws disc 96 against the end of the line. This terminates the vacuum signal on control input 56 of amplifier 28 so that more of the power stream of the amplifier is directed toward output 58. However, assuming the engine is still cold, the signal on control input 50 is greater than the signal on control input 54 so that the major portion of the power stream is still directed toward output 60.

The reduced output 60 and the increased output 58 control amplifier 30 so that output 68 decreases and the output 66 increases. The diaphragm 38a shifts downwardly so that the piston 38c is in the position shown in the drawing. This permits air to enter chamber 99 from whence it passes through line 22b to line 22 where it mixes with the fuel.

In the transition from the cranking to the idle condition two opposing conditions affect the power stream of amplifier 32 and thus affect the positioning of poppet 40c. First, the change in magnitude of the signals at

outputs

58 and 60 produces corresponding changes in the magnitude of the signals at control inputs 74 and 76. The signal at control input 76 decreases as the signal at control input 74 increases thus tending to deflect more of the power stream toward output 84. On the other hand, the vacuum in intake bore 12 increases during idling over what it was during cranking and this change is transmitted over line 78 to control input 72 where it tends to direct more of the power stream toward output 82. Therefore, the relative magnitude of

outputs

82 and 84, and thus the position of poppet 400, is determined by the engine temperature sensed by capillary 46 and by the degree of vacuum in bore 12.

As the engine warms up, the idle speed may be reduced hence less fuel flow to the carburetor is required. As the engine warms up, the temperature is sensed by capillary 46 which cuts down on the rate of air flow to control input 50 of amplifier 28. Therefore, during the warming up period more and more of the power stream of amplifier 28 is directed toward output 58 while less and less is directed toward output 60. When the engine reaches a predetermined operating temperature there is equal air flow through restrictor 44 and capillary 46 to the

control inputs

50 and 54 so that the power stream divides equally between

outputs

58 and 60.

The signals at control inputs 74 and 76 of amplifier 32 vary in proportion to the signals at

outputs

58 and 60, respectively, so that more of the power stream of this amplifier is directed toward output 84 as the engine temperature approaches normal running temperature. This tends to lift poppet 40c and cut down on the fuel supplied to the carburetor bore through line 22. However, because of the vacuum signal derived from the intake chamber 12 and transmitted to control input 72 over line 78, a major portion of the power stream continues to be directed into output 82 so that diaphragm 40a is at least partially deflected downwardly to unseat poppet 400.

The change in magnitude of the signals at

outputs

58 and 60 during engine warm-up are transmitted to control

inputs

62 and 64 of amplifier 30 so that the

outputs

66 and 68 approach equality as the normal engine operating temperature is reached. The pressures on each side of diaphragm 38a ap proach equality and the diaphragm is moved downwardly by spring 38d so that piston 380 is fully seated when the normal operating temperature is reached. This cuts off the intake of air into chamber 99.

During periods of low engine load all fuel is supplied to the intake bore 12 through fuel line 22. As previously stated, fluid amplifier 34 is biased so that its power stream flows to output 92 unless a vacuum signal of predetermined magnitude is applied to its control input 88. The fluid pressure at output 92 operates diaphragm valve 42 so as to seat poppet 420. Thus, no fuel can be drawn into the intake bore even though throttle valve 16 is partially opened and a vacuum exists at the end of fuel line 20.

As the engine load is increased and throttle valve 16 is moved toward a more open position, the vacuum at the Venturi increases. This vacuum signal is transmitted over line 78 to

fluid amplifiers

32 and 34. The vacuum signal controls amplifier 32 so that more of its power stream is deflected toward output 82 thus tending to move poppet 400 to a more open position. Thus, poppet 400 is moved toward the fully opened position as engine load increases to thereby supply more fuel to the engine.

Just before poppet 40c reaches the fully opened position, the vacuum at the Venturi becomes great enough to overcome the bias of amplifier 34. The vacuum signal directs more and more of the power stream of the amplifier toward output 90 as the vacuum signal becomes greater. This moves poppet 42c downwardly to admit more and more fuel to the fuel line 20. The vacuum at the Venturi withdraws the fuel from line 20 and it is mixed with the air flowing downwardly through chamber 12 before flowing past the throttle valve to the engine manifold.

The carburetor of FIG. 1 is admirably suited for controlling fuel flow during transient conditions such as acceleration and deceleration. During acceleration, the throttle valve 16 is opened to admit more fuel to the engine. When the throttle valve is opened, the manifold vacuum causes an increase in vacuum at the Venturi throat that has two immediate effects. First, the vacuum signal is transmitted over line 78 to control the power streams of

amplifiers

32 and 34 thereby opening poppets 40c and 42c and admitting more fuel to lines 20 and 22. Secondly, the increased vacuum at the Venturi throat draws fuel from line 20 at a faster rate.

The operation of the carburetor during deceleration is the reverse of its operation during acceleration. During deceleration the throttle valve is closed thus reducing the vacuum at the Venturi throat. The reduced vacuum tends to withdraw less fuel from line 20. At the same time, the reduced vacuum signal is sensed at orifice 80 and transmitted over line 78 to

amplifiers

40 and 42, controlling the outputs from these amplifiers so as to close poppets 40c and 420.

The quantity of air entering intake chamber 12 with each engine stroke decreases with altitude. Therefore, for maximum fuel economy, the amount of fuel mixed with the air should be reduced to an amount that is just sufficient to consume the available oxygen. The embodiment of FIG. 1 automatically compensates for altitude by reducing fuel flow.

The altitude compensation is accomplished by the

control inputs

52, 70, and 86 of the

amplifiers

28, 32 and 34, respectively. These inputs are vented to the atmosphere. Thus, there is a continuous pressure signal applied to these inputs that varies as the altitude varies.

Consider the case of a vehicle at some altitude above sea level. The pressure at

inputs

52, 70 and 86 is at some value below that at sea level. The decreased pressure at input 52 (as compared to that at sea level) causes the power stream of amplifier 28 to be deflected so that the signal at output 58 increases and the signal at output 60 decreases. The output 58 is applied to input 74 of amplifier 74 thus deflecting the power stream of the amplifier toward output 84. This deflection is aided by the decreased pressure at input 70. The combined effect of inputs 70 and 74 is to deflect more of the power stream toward output 84 than would be deflected thereto at sea level. This raises poppet 400 thus reducing the rate at which fuel is admitted to fuel line 22a from the fuel bowl to some rate which is less than the rate at which it would be admitted at sea level.

The poppet 420 is also controlled so as to provide less fuel flow than would otherwise be the case at sea level. The lower atmospheric pressure at control input 86 of amplifier 88 acts against any vacuum signal at input 88 thus reducing the proportion of the power stream that would otherwise flow toward output 90 and increasing the proportion that would otherwise flow toward output 92. This produces a greater pressure below diaphragm 92 than above it thus tending to raise poppet 42c thereby reducing the rate of fuel flow to the air intake chamber through fuel line 20.

EMBODIMENT OF FIGURE 2 The carburetor of FIG. 2 is similar to that of FIG. 1 in that it comprises a member 10 having a bore or air intake chamber 10 connecting with the intake manifold 14 of an internal combustion engine. Fuel from a constant level fuel bowl 18 is supplied to the bore through a fuel line 20 that terminates at an opening in the Venturi throat formed within member 10. A throttle valve 16 is located downstream of the Venturi throat.

The flow of fuel from the fuel bowl 18 to the bore 12 is controlled by a fluidic control circuit comprising a plurality of pure

fluid amplifiers

100, 102, and 104, a diaphragm operated valve 106, a variable flow restriction 108, a capillary sensor 1 l0, and a valve 1 12. Each of the fluid amplifiers has a power stream inlet that is connected to a pump 114 or other suitable means for supplying air under pressure.

Fluid amplifier includes a control input 116 and first and

second outputs

118 and 120. Control input 116 is connected through needle valve 112 to a line 122 that terminates at an opening in engine manifold 14. Output 118 is connected to a control input 124 of amplifier 104.

Fluid amplifier 104 has three

additional control inputs

126, 128 and 130, and first and

second outputs

132 and 134. Control input 126 is connected to an air line 136 that terminates at an opening 138 in the Venturi region of bore 12.

Outputs

132 and 134 are connected to the lower and upper chambers, respectively, of diaphragm operated valve 106. This valve includes a diaphragm 106a connected by a spindle 1061) to a metering piston 106:: which meters fuel flow from the bowl to fuel line 20 through chamber 24.

The control elements described thus far function as follows. The air pump is started to supply air to the power stream inlet of each amplifier. The internal configuration of amplifier 104 is such that its power stream tends to divide equally between

outputs

132 and 134. However, the internal configuration of amplifier 100 is such that its power stream is normally directed toward output 118 from whence it is conveyed to control input 124 of amplifier 104. This partially deflects the power stream of amplifier 104 so that more of the power stream is directed toward output 132 than is directed toward output 134. The resulting unbalanced pressures on diaphragm 106a raise the diaphragm thereby raising piston 1060 from its fully seated position. Because the output end of fuel line 20 is higher than the level of fuel in bowl 18, fuel does not enter chamber 12 at this time.

When the engine is cranked, a small vacuum or slightly negative pressure is developed in the intake manifold 14. This vacuum signal is further limited by the needle valve 112 so that the resulting signal reaching the control input of amplifier 100 has substantially no effect on amplifier 100.

The throttle valve is partially open during cranking so air flowing downwardly through air intake bore 12 as a result of the manifold vacuum creates a negative pressure that sucks fuel into the bore where it mixes with the air. The negative pressure in the Venturi throat is sensed at orifice 138 and transmitted by way of line 136 to the control input 126 of amplifier 104 where it aids the signal being applied to control input 124. Thus, more of the power stream of amplifier 104 is directed toward output 132 thereby raising piston 1060. This permits more fuel to flow past the piston to fuel line during the cranking interval when a rich fuel mixture is desired.

When the cranking interval terminates and the engine begins to idle, it is desirable to lean out the air-fuel mixture. As the engine begins to idle, the vacuum in the manifold 14 increses to a point where the vacuum signal at control input 116 of amplifier 100 is sufficient to direct a major portion of the power stream of the amplifier toward output 120 where it is exhausted to the atmosphere. As the power stream is directed toward output 120, the magnitude of the signal at output 118 drops causing a corresponding decrease in the signal at input 124 of amplifier 104. The power stream ofamplifier 104 shifts so that more of it is directed toward output 134 than was directed thereto during the cranking interval. Therefore, valve 106 is operated to shift piston 1060 downwardly to reduce the rate of fuel flow to bore 112.

Control input 126 is the primary control of the position of piston 1060 during normal running. The vacuum in the Venturi throat increases as the speed is increased and this vacuum acts through control input 126 to draw more and more of the power stream toward output 132. This raises piston 106v to admit fuel to line 20 at a faster rate. At the same time, the greater vacuum at the Venturi throat sucks fuel into bore 12 from fuel line 20 at a faster rate.

Cold fuel does not vaporize as readily as a warm fuel. Furthermore, the heat of an engine aids in vaporizing the fuel. When an engine and its fuel are cold it is desirable to provide additional fuel to insure that sufficient fuel is supplied to all cylinders of the engine. The embodiment of FIG. 2 provides an automatic control that allows additional fuel to be supplied to an engine when it and/or its fuel is cold. This automatic control includes the amplifier 102, the restrictor 108, and the capillary sensor 110.

Capillary sensor 110 serves as a temperature sensing element and is located in fuel bowl 18 below the normal fuel level. Since the fuel bowl is located over the engine and is thus heated thereby, the capillary 110 directly senses the temperature of the fuel and indirectly senses the temperature of the engine.

Fluid amplifier 102 has first and

second control inputs

140 and 142, and first and

second outputs

144 and 146. The air pump 114 is connected through the variable flow restrictor 108 to control input 140. Control input 142 is connected through capillary sensor 110 to a point in the air line intermediate the air pump and the flow restrictor. The flow restrictor is adjusted so that at some predetermined temperature such at 70, there is an equal flow of air through the flow restrictor and the capillary sensor to control

inputs

140 and 142. Thus, at the predetermined temperature the power stream of amplifier 102 divides equally between

outputs

144 and 146. These outputs are connected to control

inputs

128 and 130 of amplifier 104 so as to apply opposing control signals to amplifier 104.

When the temperature of the fuel in bowl 18 is below the predetermined temperature capillary tube 110 permits a greater flow of air to control input 142 than flow restrictor 108 permits to flow toward control input 140. The power stream of amplifier 102 is thus deflected so that a major portion of the stream is directed toward output 144 and a lesser portion is directed toward output 146. Therefore, the signal at control input 130 of amplifier 104 is greater than that at control input 128 thus deflecting the power stream of this amplifier further toward output 132. This raises diaphragm 106a and piston 106c so that more fuel may flow to fuel line 20.

As the fuel in bowl 18 warms up, the mass flow of air through the capillary 110 is reduced thus reducing the magnitude of the signal at control 142. From the foregoing description, it is obvious that as the control signal at 142 is reduced the piston 106C will be lowered to reduce the rate of fuel flow. When the temperature of the fuel reaches the predetermined temperature as determined by the setting of flow restrictor 108, the signals at

control inputs

140 and 142 become equal. The power stream of amplifier 102 divides equally into

outputs

144 and 146 so that equal and opposing signals are applied to control inputs 128 and of amplifier 104. Thus, when the temperature of the fuel is at the predetermined temperature, amplifier 102 exerts no control and the position of piston 106c is determined only by the magnitudes of the control signals applied to control

inputs

124 and 126 of amplifier 104.

For purposes of clarity and ease of illustration, the embodiments described above do not show certain details which may easily be supplied by those skilled in the art. For example, it will be appreciated that the output channels of the fluid amplifiers, particularly

amplifiers

30, 32, 34 and 104 should be vented to prevent a condition of static flow from developing. The venting may preferably be at the amplifiers but may also be accomplished by vents at the diaphragm controlled valves.

In summary, the present invention provides a novel carburetor including fluidic control circuits capable of controlling fuel flow under all normal driving conditions, during cranking, warm-up, acceleration, and deceleration. Furthermore, it provides automatic compensation for altitude and performs the functions normally performed by the choke and fast idle cam in more conventional fuel control systems. It offers a further advantage over known carburetors employing fluidic control elements in that all control functions are performed by air rather than by the liquid fuel, yet the air and fuel are not mixed.

While preferred embodiments of the invention have been shown and described, various modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. For example, single outputs from the fluid amplifiers may be used for control purposes rather than using two opposing outputs.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising:

first means defining an air intake bore for communicating with the intake manifold of an engine;

second means for holding a supply of fuel;

a fuel line connected with said second means and terminating at an opening in said bore for supplying fuel to said bore, the negative pressure in said bore drawing fuel from said line;

fuel metering means for metering the flow of fuel from said second means to said bore through said fuel line;

means for sensing the pressure in said intake manifold;

fluid amplifier means for controlling said metering means;

and,

control means responsive to said pressure sensing means for controlling said fluid amplifier means,

said control means applying the negative pressure in said manifold to said fluid amplifier means during cranking of said engine and blocking the negative pressure in said manifold from said fluid amplifier means once said engine begins to idle,

said fluid amplifier means controlling said metering means to meter more fuel through said fuel line during cranking than it meters therethrough during idling.

2. A carburetor as claimed in claim 1 and further comprising means for heating fuel flowing through said fuel line.

3. A carburetor as claimed in claim 1 and further comprismg:

an air line connected at one end with said fuel line intermediate said second means and said opening; said air line terminating at a second opening; and,

air metering means responsive to said fluid amplifier means for metering the flow of air into said air line, said fluid amplifier means controlling said air metering means to admit no air to said line during cranking but controlling said air metering means to admit air once said engine begins to idle.

4. A carburetor as claimed in claim 3 and further comprising:

A throttle valve located in said air intake bore upstream from said fuel line opening;

a Venturi throat in said air intake bore upstream from said throttle valve;

a second fuel line connected with said second means and terminating at a further opening in the region of said Venturi throat;

a second fuel metering means for metering the flow of fuel from said second means to said air intake bore;

further fluid amplifier means for controlling said second fuel metering means whereby fuel is admitted to said second fuel line only when said further fluid amplifier means receives a signal exceeding a predetermined magnitude;

further means for sensing the negative pressure at said Venturi throat; and,

means responsive to said further sensing means for applying the negative pressure at said throat to said fluid amplifier means and said further fluid amplifier means.

5. A carburetor as claimed in claim 41 and further comprising:

temperature responsive means responsive to engine temperature for controlling said fluid amplifier means, said fluid amplifier means responding to said temperature responsive means to control said fuel metering means and said air metering means whereby a rich air-fuel mixture is fed to said fuel line when said engine is cold and a leaner air-fuel mixture is fed thereto when said engine is hot.

6. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising:

means defining an air intake bore for communicating with the intake manifold of an engine;

a throttle valve for controlling air flow through said intake bore to said manifold;

a fuel supply;

a first fuel line connected between said fuel supply and said air intake bore, said first fuel line terminating at an opening downstream of said throttle valve;

a second fuel line connected between said fuel supply and said air intake bore, said second fuel line terminating at an opening upstream of said throttle valve;

first sensing means for sensing the pressure in said engine manifold;

second sensing means for sensing the pressure in said air intake bore;

first fluidic control means responsive to said first and second sensing means for metering the flow of fuel through said first fuel line;

second fluidic control means responsive to said second sensing means for metering the flow of fuel through said second fuel line; and,

means responsive to said first sensing means for admitting air to said first fuel line during idling, but blocking the admission of air thereto during cranking,

7. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising:

a fuel supply;

first sensing means for sensing the pressure in said engine manifold;

second sensing means for sensing the pressure in said air intake bore;

said first fluidic control means comprising:

a control valve;

a first pure fluid amplifier, having a control input, a power stream input, and an output;

said first sensing means being connected through said control valve to a control input of said first fluid amplifier;

said control valve including means for blocking the connection between said sensing means and said control input when said manifold pressure exceeds the negative pressure therein during cranking of said engine;

a fuel metering valve metering means in said first fuel line;

and,

a second fluid amplifier having a control input connected to the output of said first fluid amplifier and an output connected to said fuel metering valve.

8. A carburetor as claimed in claim 7 and further comprising:

air metering means for metering air into said first fuel line;

and,

A third fluid amplifier having a power stream, a control input connected with an output of said first fluid amplifier, and an output connected with said air metering means,

said sensed manifold pressure controlling said first amplifier to thereby control said third fluid amplifier to position said air metering means whereby no air is admitted during engine cranking but air is admitted during idling.

9. A carburetor as claimed in claim 8 and further comprising:

a source of pressurized air;

an adjustable flow restrictor;

a capillary tube engine temperature sensor;

said first fluid amplifier having a second control input connected through said flow restrictor and a third opposing control input connected through said capillary tube to said source of pressurized air;

whereby the output of said first fluid amplifier varies with engine temperature, said output controlling said second fluid amplifier and said fuel metering valve to admit less fuel to said first fuel line as engine temperature increases, and controlling said third fluid amplifier and said air metering means to admit less air to said first fuel line as engine temperature increases.

10. A carburetor as claimed in claim 9 wherein:

said second fluid amplifier has a further control input responsive to said second sensing means.

111. A carburetor as claimed in claim 10 wherein said intake bore has a Venturi throat formed therein, said second fuel line terminating at an opening in the region of said throat, and said second sensing means comprising an air line which also terminates at an opening in said throat.

12. A carburetor as claimed in claim 11 wherein said second fluidic control means comprises:

a second fuel metering valve having metering means in said second fuel line;

a fourth pure fluid amplifier having a control input connected to said second sensing means, a power stream input, and an output connected to said fuel metering valve.

13. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising:

means defining an air intake bore for communicating with the intake manifold of an engine, said bore having a Venturi throat formed therein;

a constant level fuel bowl;

a fuel line connected with said fuel bowl and terminating at an opening in the region of said throat;

a valve including a metering piston for metering fuel flow through said line;

first pressure sensing means for sensing manifold pressure;

first fluidic control means responsive to said first sensing means for controlling said valve to meter fuel through said line during engine cranking;

second pressure sensing means for sensing pressure in the region of said throat; and,

second fluidic control means responsive to said second sensing means for controlling said valve to meter fuel through said line once the engine has reached idle speed.

14. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising;

means defining an air intake bore for communicating with the intake manifold of an engine, said bore having an Venturi throat formed therein;

a constant level fuel bowl;

a valve including a metering piston for metering fuel flow through said line;

first pressure sensing means for sensing manifold pressure;

second pressure sensing means for sensing pressure in the region of said throat;

second fluidic control means responsive to said second sensing means for controlling said valve to meter fuel through said line once the engine has reached idle speed;

temperature sensing means disposed in said fuel bowl; and,

means responsive to said temperature sensing means for controlling said first and second fluidic control means whereby said valve is positioned to meter more fuel through said line when said fuel is cold than when it is warm.

Claims

1. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising: first means defining an air intake bore for communicating with the intake manifold of an engine; second means for holding a supply of fuel; a fuel line connected with said second means and terminating at an opening in said bore for supplying fuel to said bore, the negative pressure in said bore drawing fuel from said line; fuel metering means for metering the flow of fuel from said second means to said bore through said fuel line; means for sensing the pressure in said intake manifold; fluid amplifier means for controlling said metering means; and, control means responsive to said pressure sensing means for controlling said fluid amplifier means, said control means applying the negative pressure in said manifold to said fluid amplifier means during cranking of said engine and blocking the negative pressure in said manifold from said fluid amplifier means once said engine begins to idle, said fluid amplifier means controlling said metering means to meter more fuel through said fuel line during cranking than it meters therethrough during idling.

3. A carburetor as claimed in claim 1 and further comprising: an air line connected at one end with said fuel line intermediate said second means and said opening; said air line terminating at a second opening;and, air metering means responsive to said fluid amplifier means for metering the flow of air into said air line, said fluid amplifier means controlling said air metering means to admit no air to said line during cranking but controlling said air metering means to admit air once said engine begins to idle.

4. A carburetor as claimed in claim 3 and further comprising: a throttle valve located in said air intake bore upstream from said fuel line opening; a Venturi throat in said air intake bore upstream from said throttle valve; a second fuel line connected with said second means and terminating at a further opening in the region of said Venturi throat; a second fuel metering means for metering the flow of fuel from said second means to said air intake bore; further fluid amplifier means for controlling said second fuel metering means whereby fuel is admitted to said second fuel line only when said further fluid amplifier means receives a signal exceeding a predetermined magnitude; further means for sensing the negative pressure at said Venturi throat; and, means responsive to said further sensing means for applying the negative pressure at said throat to said fluid amplifier means and said further fluid amplifier means.

5. A carburetor as claimed in claim 4 and further comprising: temperature responsive means responsive to engine temperature for controlling said fluid amplifier means, said fluid amplifier means responding to said temperature responsive means to control said fuel metering means and said air metering means whereby a rich air-fuel mixture is fed to said fuel line when said engine is cold and a leaner air-fuel mixture is fed thereto when said engine is hot.

6. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising: means defining an air intake bore for communicating with the intake manifold of an engine; a throttle valve for controlling air flow through said intake bore to said manifold; a fuel supply; a first fuel line connected between said fuel supply and said air intake bore, said first fuel line terminating at an opening downstream of said throttle valve; a second fuel line connected between said fuel supply and said air intake bore, said second fuel line terminating at an opening upstream of said throttle valve; first sensing means for sensing the pressure in said engine manifold; second sensing means for sensing the pressure in said air intake bore; first fluidic control means responsive to said first and second sensing means for metering the flow of fuel through said first fuel line; second fluidic control means responsive to said second sensing means for metering the flow of fuel through said second fuel line; and, means responsive to said first sensing means for admitting air to said first fuel line during idling, but blocking the admission of air thereto during cranking.

7. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising: means defining an air intake bore for communicating with the intake manifold of an engine; a throttle valve for controlling air flow through said intake bore to said manifold; a fuel supply; a first fuel line connected between said fuel supply and said air intake bore, said first fuel line terminating at an opening downstream of said throttle valve; a second fuel line connected between said fuel supply and said air intake bore, said second fuel line terminating at an opening upstream of said throttle valve; first sensing means for sensing the pressure in said engine manifold; second sensing means for sensing the pressure in said air intake bore; first fluidic control means responsive to said first and second sensing means for metering the flow of fuel through said first fuel line; second fluidic control means responsive to said second sensing means for metering the flow of fuel through said second fuel line; and, said first fluidic control means comprising: a control valve; a first pure fluid amplifier, having a control input, a power stream input, and an output; said first sensing means being connected through said control valve to a control input of said first fluid amplifier; said control valve including means for blocking the connection between said sensing means and said control input when said manifold pressure exceeds the negative pressure therein during cranking of said engine; a fuel metering valve metering means in said first fuel line; and, a second fluid amplifier having a control input connected to the output of said first fluid amplifier and an output connected to said fuel metering valve.

8. A carburetor as claimed in claim 7 and further comprising: air metering means for metering air into said first fuel line; and, a third fluid amplifier having a power stream, a control input connected with an output of said first fluid amplifier, and an output connected with said air metering means, said sensed manifold pressure controlling said first amplifier to thereby control said third fluid amplifier to position said air metering means whereby no air is admitted during engine cranking but air is admitted during idling.

9. A carbUretor as claimed in claim 8 and further comprising: a source of pressurized air; an adjustable flow restrictor; a capillary tube engine temperature sensor; said first fluid amplifier having a second control input connected through said flow restrictor and a third opposing control input connected through said capillary tube to said source of pressurized air; whereby the output of said first fluid amplifier varies with engine temperature, said output controlling said second fluid amplifier and said fuel metering valve to admit less fuel to said first fuel line as engine temperature increases, and controlling said third fluid amplifier and said air metering means to admit less air to said first fuel line as engine temperature increases.

10. A carburetor as claimed in claim 9 wherein: said second fluid amplifier has a further control input responsive to said second sensing means.

11. A carburetor as claimed in claim 10 wherein said intake bore has a Venturi throat formed therein, said second fuel line terminating at an opening in the region of said throat, and said second sensing means comprising an air line which also terminates at an opening in said throat.

12. A carburetor as claimed in claim 11 wherein said second fluidic control means comprises: a second fuel metering valve having metering means in said second fuel line; a fourth pure fluid amplifier having a control input connected to said second sensing means, a power stream input, and an output connected to said fuel metering valve.

13. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising: means defining an air intake bore for communicating with the intake manifold of an engine, said bore having a Venturi throat formed therein; a throttle valve for controlling air flow through said intake bore to said manifold; a constant level fuel bowl; a fuel line connected with said fuel bowl and terminating at an opening in the region of said throat; a valve including a metering piston for metering fuel flow through said line; first pressure sensing means for sensing manifold pressure; first fluidic control means responsive to said first sensing means for controlling said valve to meter fuel through said line during engine cranking; second pressure sensing means for sensing pressure in the region of said throat; and, second fluidic control means responsive to said second sensing means for controlling said valve to meter fuel through said line once the engine has reached idle speed.

14. A carburetor for controlling fuel intake to an internal combustion engine, said carburetor comprising: means defining an air intake bore for communicating with the intake manifold of an engine, said bore having a Venturi throat formed therein; a throttle valve for controlling air flow through said intake bore to said manifold; a constant level fuel bowl; a fuel line connected with said fuel bowl and terminating at an opening in the region of said throat; a valve including a metering piston for metering fuel flow through said line; first pressure sensing means for sensing manifold pressure; first fluidic control means responsive to said first sensing means for controlling said valve to meter fuel through said line during engine cranking; second pressure sensing means for sensing pressure in the region of said throat; second fluidic control means responsive to said second sensing means for controlling said valve to meter fuel through said line once the engine has reached idle speed; temperature sensing means disposed in said fuel bowl; and, means responsive to said temperature sensing means for controlling said first and second fluidic control means whereby said valve is positioned to meter more fuel through said line when said fuel is cold than when it is warm.