US3655170A

US3655170A - Fluidic carburetor

Info

Publication number: US3655170A
Application number: US17227A
Authority: US
Inventors: Jeffrey Michael Lazar
Original assignee: ACF Industries Inc
Current assignee: Carter Automotive Co Inc
Priority date: 1970-03-06
Filing date: 1970-03-06
Publication date: 1972-04-11
Anticipated expiration: 1989-04-11

Abstract

A fluidic carburetor having two fluid pure fluid amplifiers for controlling the rate of fuel flow to the carburetor bore. One fluid amplifier controls fuel flow during cranking and normal running conditions by sensing the vacuum at one point in a Venturi throat and at a second point upstream therefrom, the rate of fuel flow being dependent upon the difference in pressure at the two points. The rate of fuel flow is further controlled by an air temperature sensor and an engine temperature sensor. A second fluid amplifier is provided for feeding additional fuel to the bore during periods of acceleration.

Description

United States Patent Lazar [58] FieldofSearch ..26l/39 A, 39 B,36 A, 69 R, 26l/DIG. 69, 39 D; 123/119 R; 137/815 [56] References Cited UNITED STATES PATENTS 3,547,414 12/1970 Nardi ..261/DIG. 69 3,574,346 4/1971 Sulich ..26l/DIG. 69

AIR TEMP.

[15] 3,655,170 [4 1 Apr.11, 1972 3,548,795 12/1970 Howland ..26l/DlG. 69 3,556,488 l/l971 Arikawa et al ..26 l/DIG. 69 3,389,894 6/1968 Binder ..26l/DlG. 69

Primary Examiner-Tim R. Miles Attorney-Griffin, Branigan and Kindness [57] ABSTRACT A fluidic carburetor having two fluid pure fluid amplifiers for controlling the rate of fuel flow to the carburetor bore. One fluid amplifier controls fuel fiow during cranking and normal running conditions by sensing the vacuum at one point in a Venturi throat and at a second point upstream therefrom, the rate of fuel flow being dependent upon the difference in pressure at the two points. The rate of fuel flow is further controlled by an air temperature sensor and an engine temperature sensor. A second fluid amplifier is provided for feeding additional fuel to the bore during periods of acceleration.

6 Claims, 2 Drawing Figures MANIEQLQ VACUUM LOW PRESSURE RETURN Patented A ril 11, 1972 3,655,170

F I6 I FUEL PREssuR 1 AIR TEMP 0 I I 5e 62 32 34 as f {54 ENGINE TEMP. LOWRIZQIEJSEQSBEJRE MA I Q VAQLJLJM K |'i'| 1 F l G. 2.

LU D Z MA I Q 15;; m C 2 LESS THAN Io HG. O! 'i' 0 COLD ENGINE 3 o d MANIFOLD VACU M I GREATER THAN IdHG. L:1)J U.

AIR FLOW l PER MINUTE INvENToR I BY JEFFREY M. LAZAR ATTORNEYS FLUIDIC CARBURETOR OBJECTS OF THE INVENTION The present invention relates to a carburetor including fluid amplifiers for controlling the rate of fuel flow to the carburetor bore.

An object of the invention is to provide a carburetor employing a single pure fluid amplifier for controlling the rate of fuel flow to the carburetor bore during cranking, idling, and normal driving conditions.

An object of this invention is to provide a carburetor employing a fluid amplifier having first and second opposing control inputs responsive to the vacuum sensed at two points in a carburetor bore, said amplifier controlling the rate of fuel flow to the carburetor bore during cranking, idling, and normal driving conditions.

Another object of the invention is to provide a carburetor including means defining a carburetor bore having a Venturi throat therein, a fluid amplifier having two opposing control inputs, means for sensing the vacuum in the throat and upstream therefrom and applying said vacuum to said control inputs, and temperature sensing means for modifying the sensed vacuum applied to one of said control inputs.

A further object of the invention is to provide a carburetor including a fluid amplifier, and means controlling the amplifier so that it performs the function of an accelerating pump.

Still another object of the invention is to provide a carburetor comprising a pure fluid amplifier, a fluid signal delay means connected between opposing control inputs of the amplifier, and means for applying manifold vacuum signals to said control inputs, said manifold vacuum signals being applied to one of said control inputs through said delay means,

whereby the power stream of the amplifier is deflected from one output to a second for a predetermined interval of time when said manifold vacuum decreases. Fuel is supplied to the power stream input and is directed into the carburetor bore through the second output at a rate dependent upon the rate of change of manifold vacuum.

Other objects of the invention and its mode of operation will become apparent upon consideration of the following description and the accompanying drawing.

BRIEF DESCRIPTION OF DRAWING FIG. 1 schematically illustrates a preferred embodiment of the invention; and,

FIG. 2 is a diagram illustrating variations in the fuel to air ratio for various operating conditions.

DETAILED DESCRIPTION As shown in FIG. 1, a preferred embodiment of the invention comprises means defining a carburetor bore CB adapted to pass air downwardly therethrough to the intake manifold M of an internal combustion engine. The carburetor bore has a Venturi section formed therein and a throttle valve 10 is located downstream from the Venturi section.

The illustrated embodiment of the invention further comprises a fluidic control circuit for supplying fuel to the carburetor bore. The fluidic control circuit includes a first pure fluid amplifier 12, a second pure fluid amplifier 14, an engine temperature sensor 16, and an air temperature sensor 18.

Fluid amplifier 12 comprises a power stream input 20, first and second

control signal inputs

22 and 24, and first and

second outputs

26 and 28. The power stream input is connected by way of a fuel supply line 30 to the high pressure side of a fuel pump (not shown). Output 26 is connected by way of a fuel line 32 to a noule 33, and output 28 is connected to a fuel return line 34.

The control input 24 of amplifier 12 is connected to a line 36 which terminates at an orifice 38 located upstream of the Venturi throat in the carburetor bore. The control input 22 is connected through

temperature sensors

16 and 18 to an orifice 40 located in a recess in the wall of the Venturi throat. The temperature sensors may be capillary tubes having an opening therethrough that tends to restrict fluid flow.

Fluid amplifier 12 is a proportional fluid amplifier of conventional design. Fluid amplifier 12 has an internal configuration such that fuel applied to power stream input 20 normally flows to output 28 in the absence of any control signals at

control inputs

22 and 24. However, a part or all of the power stream may be directed toward output 26 by applying a vacuum signal to control input 22 that is greater than a vacuum signal applied to control input 24.

Fluid amplifier 12 comprises the primary fuel flow control during cranking, idling, and normal running conditions and functions in the following manner. Fuel is supplied to the power stream input 20 through line 30 and the internal configuration of the amplifier causes the power stream to flow through output 28 to the fuel return line 34. A major portion of this power stream returns to the fuel supply through line 34. However, because of an adjustable flow restrictor 68, a portion of the power stream is directed to a control input of amplifier 14 for reasons which are subsequently described.

When the engine is cranked, a portion of the power stream of amplifier 12 is supplied to the carburetor bore. The throttle valve 10 is partially opened so that air is drawn downwardly through the carburetor bore by the vacuum created in the intake manifold as the engine is cranked. The air flowing downwardly through the carburetor bore creates a vacuum in the Venturi throat. This vacuum signal is sensed at orifice 40 and transmitted through

temperature sensors

16 and 18 to control input 22 of amplifier 12. The orifice 38 also senses a vacuum signal that is transmitted over line 36 to control input 24 of the amplifier. Since the vacuum at orifice 40 is much greater than the vacuum at orifice 38, the signal at control input 22 draws the power stream of amplifier 12 toward output 26 so that a small portion of the fuel comprising the power stream flows from output 26 through fuel line 32 to orifice 33. At the orifice, the fuel is mixed with the air and moves downwardly past the throttle valve to the engine manifold.

At the end of the cranking interval, as the engine begins to idle, the manifold vacuum increases thereby drawing air through the carburetor bore at a' faster rate. The negative pressures sensed at

orifices

40 and 38 are applied to the control inputs of amplifier 12 thereby deflecting more of the power stream of the amplifier toward output 26. This supplies sufficient fuel for idling through output 26 and line 32 to nozzle 33.

Assuming that the engine is cold when started, the point A in FIG. 2 represents the fuel to air ratio at curb idle speed. It is well known that a warm engine aids in vaporizing fuel. Therefore, when an engine is cold, more fuel must be supplied to the engine than if it were warm, to insure that sufficient fuel is distributed to each of the cylinders. For the same reason, the fuel to air ratio must be varied in accordance with the temperature of the air flowing into the carburetor bore. The

capillary sensors

16 and 18 serve the function of controlling the fuel flow so that more fuel is supplied to the carburetor bore when the engine and/or air is cold than when warm, all other operating conditions being constant. Assume that the intake air is at some fixed temperature and that the engine is cold and idling at curb idle speed. The vacuum in the Venturi throat draws air into the carburetor bore from orifice 40. This air is drawn from amplifier 12 in the region where power stream input 20 and control input 22 intersect. It travels through air line 44, capillary 16, air line 46, and capillary 18 to the orifice 40. When capillary 16 is cold, it forms a fluid passage that offers little resistance to fluid flow. Assume for the moment that the same is true of capillary 18. Therefore, the vacuum sensed at orifice 40 is manifested at control input 22 as a vacuum signal of substantially the same magnitude.

As the engine warms up, the temperature of the engine is sensed by capillary 16 which may be disposed in the engine cooling system. As the capillary warms up, it offers increased resistance to the flow of fluid therethrough. Thus, the vacuum sensed at orifice 40 is manifested at control input 22 as a vacuum signal of smaller magnitude. This smaller magnitude vacuum signal cannot deflect as much of the power stream of amplifier 12 toward output 26 as the larger magnitude signal could. Therefore, as the engine warms up, less fuel flows through output 26 and line 32 to the nozzle 33. In FIG. 2, the point B represents the fuel to air ratio at curb idle speed once the engine has reached its operating temperature.

In view of the foregoing explanation, the operation of the air temperature capillary sensor 18 is believed obvious. The effect of capillary 18 may be visualized by reference to FIG. 2. As the air temperature of the intake air rises, the line AB shifts to the right. Conversely, as the temperature decreases, the line AB shifts to the left.

As previously stated, amplifier 12 provides the fuel to the carburetor bore during normal driving conditions. As throttle is opened, more air is drawn through the carburetor bore thereby increasing the vacuum at

orifices

40 and 38. However, the vacuum at the Venturi throat increases at a faster rate than does the vacuum in the region of orifice 38 upstream of the throat. Therefore, as throttle 10 is opened the vacuum signal at control input 22 of amplifier 12 increases in comparison with the vacuum signal at control input 24. This draws the power stream more toward output 26 from whence it is injected into the carburetor bore through nozzle 33.

In FIG. 2, the line AC is a plot of the fuel to air ratio for a cold engine at various running speeds from curb idle (point A) to full throttle (point C). The line BD is a plot of the fuel to air ratio for a warm engine at various running speeds from curb idle (point B) to full throttle (point D). It will be understood that the line AC approaches and then merges into or becomes the line BD as the engine approaches its normal operating temperature.

In a conventional carburetor, a device known as an accelerating pump is provided for the purpose of supplying additional fuel to the carburetor bore during periods of acceleration. Fluid amplifier l4 performs the function of such a pump and comprises a power stream input 50, first and second outputs 52 and 54, and four

control signal inputs

56, 58, 60 and 62.

Power stream input 50 is connected to the fuel supply line 30 so that it receives fuel at its power stream input whenever the fuel pump is operating. Output 54 and control input 58 are connected to the fuel return line 34. Output 52 is connected to the fuel line 32 which terminates at orifice 33 in the carburetor bore.

A manifold vacuum sensing means comprising a line 63 terminating at an orifice 64 in the engine intake manifold is directly connected to control

inputs

60 and 62 of amplifier 14. The line 63 is further connected through a fluid capacitance or signal delay means 66 to the control input 56.

Fluid amplifier 14 may be a proportional fluid amplifier of conventional design. It has an internal configuration such that in the absence of any signals at the control inputs, the power stream is normally divided at the splitter formed at the junction of outputs 52 and 54 so that part flows toward output 52 and part flows toward output 54. However, as will now be explained, the power stream is controlled so that it only flows toward output 52 for a short interval of time following an acceleration or opening of throttle valve 10.

During cranking, fuel from supply line 30 is applied to both the

power stream inputs

20 and 50. As previously explained, during cranking a major portion of the power stream of amplifier l2 flows through output 28 to the fuel return line 34. By

proper design of the connecting lines, or by placing a flow restrictor 68 in line 34 downstream of its junction with control input 58, a portion of the output from amplifier 12 may be directed to control input 58. This deflects the power stream of amplifier 14 toward output 54 from whence it flows through line 34 to the return side of the fuel source.

When the engine beings to idle, a smaller portion of the power stream of amplifier 12 is directed toward output 28 hence the magnitude of the positive pressure signal at control input 58 is reduced. However, the manifold vacuum increases as the engine begins to idle and this vacuum signal is applied to control inputs and 62 where it tends to draw the power stream of the amplifier toward output 54. Thus, the power stream continues its flow toward output 54 even though the positive pressure signal at control input 58 is reduced in magnitude.

Amplifier 14 functions to supply additional fuel to the carburetor bore during acceleration or when the engine load is increased, the amount of fuel supplied being dependent upon the rate of change of manifold pressure. This is accomplished by differentiating the manifold vacuum signal by means of fluid capacitance 66, and applying the differentiated signal to control input 56 so as to oppose the vacuum signal applied to control

inputs

60 and 62.

Consider the case of an acceleration resulting from suddenly opening throttle valve 10 to its fully opened position. Air flows past the throttle valve into the manifold thereby suddenly raising the manifold pressure from the first value (E in FIG. 2) to a less negative value F. The manifold vacuum is sensed at orifice 64 and applied over line 63 to control

inputs

60 and 62 of amplifier 14. With less negative pressure at

control inputs

60 and 62, the internal configuration of the amplifier directs more of its power stream toward output 52. From output 52 the power stream flows through fuel line 32 and is injected into the carburetor bore through orifice 33.

The less negative manifold vacuum signal is applied to fluid capacitance 66 at the same time it is applied to control

inputs

60 and 62. The capacitance 66 functions in a manner similar to that of an electrical capacitor in an electrical circuit. Thus, assuming an instantaneous change from P, to P, at the input of the capacitance, the output pressure waveform has a sloping front that increases (or decreases) from P, to P Therefore, at the instant the reduced manifold vacuum signal is applied to control

inputs

60 and 62, the pressure at control input 56 is the same as before the throttle valve was opened. However, the pressure at control input 56 begins to increase at a rate dependent upon the volume of capacitance 66. As the pressure at control input 56 increases, the net force resulting from the pressures on opposite sides of the power stream tends to direct the power stream back toward output 54. When the pressure at control input 56 reaches the value of the manifold vacuum at

control inputs

60 and 62, the power stream of the amplifier is fully deflected so as to flow through output 54 to the fuel return line.

It should be noted that even though the throttle valve may be held in the fully opened position, the power stream of amplifier 14 is directed toward output 52 only for the interval of time that it takes the pressure at control input 56 to become equal to the pressure at

control inputs

60 and 62.

On the other hand, if the throttle is controlled so as to raise the manifold pressure at a constant rate at least a portion of the power stream will be directed toward output 52 as long as the manifold pressure is increasing. This should be obvious since, if the manifold pressure is steadily increasing, the pressure at

control inputs

60 and 62 is always greater than the pressure at control input 56 by a constant amount. The portion of the power stream directed toward output 52 is determined by the differential pressures at inputs 56 and

inputs

60 and 62, and thus is determined by the rate at which the manifold pressure increases. Of course a limit must be reached where the throttle valve can be opened no further, at which time the manifold pressure stops increasing, and the power stream of amplifier 14 is again directed toward output 54.

With respect to amplifier 14, it should be noted that fuel under pressure is applied to control input 58 whereas a vacuum signal is applied to control

inputs

60 and 62. This may result in some fuel, either liquid or vapor, being drawn into the manifold through line 63 and

control inputs

60 and 62. However, the amount of fuel entering the manifold in this manner is less than that required for idling.

Since pneumatic signals are employed to deflect the fuel comprising the power streams of the amplifiers, there is a mixing of the air and fuel. This promotes vaporization and aids in obtaining a good spray pattern at orifice 33. However, the air should be removed from that portion of the fuel that is recirculated before the fuel is returned to the fuel pump. This may be accomplished by connecting return line 34 to the fuel tank. Alternatively, the return line 34 may be connected through a vapor-liquid vessel to the low pressure side of the fuel pump.

While a preferred illustrative embodiment has been shown and described, various modifications in the form and detail thereof may be made without departing from the spirit and scope of the invention as defined by the appended claims. For example, for purpose of explanation it has been assumed that the power stream of amplifier would divide equally between outputs 52 and 54 in the absence of any control input signals. By proper limitation of control signals an amplifier may be employed having an internal configuration such that its power stream is fully or partially directed toward output 52 in the absence of any control signals. Furthermore, adjustable flow restrictors such as flow restrictor 68 may be located in any or all inputs and outputs from the fluid amplifiers to provide manual adjustment of signal magnitudes.

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

1. A fluidic carburetor including means defining a carburetor bore through which air may flow to the intake manifold of an engine;

a fluid amplifier having a power stream input, first and second outputs, and first, second, third and fourth control inputs;

a fluid capacitance means connected between said first and second control inputs, said first and second control inputs being disposed on opposing sides of said power stream input;

means for applying a positive pressure signal to said third control input that reduces with engine speed, said third control input being disposed on the same side of said power stream input as said first control input;

means for applying fuel to said power stream input;

fuel return means connected to said first output;

means for conveying fuel from said second output to said bore; and,

means connected between said manifold and said second and fourth control inputs for applying a signal representing manifold vacuum to said capacitance means and said second and fourth control inputs,

said control inputs coacting to deflect said power stream to said second output for a predetermined interval of time when said manifold vacuum drops.

2. A fluidic carburetor as claimed in claim 1 wherein said bore has a Venturi throat formed therein, said carburetor further comprising:

a second fluid amplifier having a power stream input, first and second outputs, and first and second control inputs;

first means connected to said first control input and terminating at a first orifice in said throat for applying a first control signal to said second amplifier dependent upon the vacuum at said throat;

second means connected to said second control input and terminating at a second orifice in said bore upstream of said throat for applying a second control signal to said second amplifier dependent upon the vacuum at said second orifice;

means for supplying fuel to the power stream of said second said second output being connected to said fuel return means and to said means for applying a positive pressure signal to the third control input of said fluid amplifier; and,

means connected to said second output of said second fluid amplifier for injecting fuel into said bore,

said first and second control signals controlling said second fluid amplifier to direct more of its power stream to said second output and less to said first output as said first signal increases in magnitude with respect to said second signal.

3. A fluidic carburetor as claimed in claim 2 and further comprising:

temperature sensing means disposed to sense engine temperature,

said temperature sensing means including means for reducing the magnitude of said first control signal relative to the vacuum at said throat as said engine temperature approaches normal operating temperature.

4. A fluidic carburetor as claimed in claim 2 and further comprising a throttle valve in said bore downstream of said throat.

5. A fluidic carburetor as claimed in claim 2 wherein said first means comprise an air passage including a temperature sensitive capillary tube responsive to engine temperature.

6. A fluidic carburetor as claimed in claim 5 wherein said first means includes a further temperature sensitive capillary tube disposed in said bore for sensing the temperature of the air flowing therethrough.

Claims

1. A fluidic carburetor including means defining a carburetor bore through which air may flow to the intake manifold of an engine; a fluid amplifier having a power stream input, first and second outputs, and first, second, third and fourth control inputs; a fluid capacitance means connected between said first and second control inputs, said first and second control inputs being disposed on opposing sides of said power stream input; means for applying a positive pressure signal to said third control input that reduces with engine speed, said third control input being disposed on the same side of said power stream input as said first control input; meanS for applying fuel to said power stream input; fuel return means connected to said first output; means for conveying fuel from said second output to said bore; and, means connected between said manifold and said second and fourth control inputs for applying a signal representing manifold vacuum to said capacitance means and said second and fourth control inputs, said control inputs coacting to deflect said power stream to said second output for a predetermined interval of time when said manifold vacuum drops.

2. A fluidic carburetor as claimed in claim 1 wherein said bore has a Venturi throat formed therein, said carburetor further comprising: a second fluid amplifier having a power stream input, first and second outputs, and first and second control inputs; first means connected to said first control input and terminating at a first orifice in said throat for applying a first control signal to said second amplifier dependent upon the vacuum at said throat; second means connected to said second control input and terminating at a second orifice in said bore upstream of said throat for applying a second control signal to said second amplifier dependent upon the vacuum at said second orifice; means for supplying fuel to the power stream of said second amplifier; said second output being connected to said fuel return means and to said means for applying a positive pressure signal to the third control input of said fluid amplifier; and, means connected to said second output of said second fluid amplifier for injecting fuel into said bore, said first and second control signals controlling said second fluid amplifier to direct more of its power stream to said second output and less to said first output as said first signal increases in magnitude with respect to said second signal.

3. A fluidic carburetor as claimed in claim 2 and further comprising: temperature sensing means disposed to sense engine temperature, said temperature sensing means including means for reducing the magnitude of said first control signal relative to the vacuum at said throat as said engine temperature approaches normal operating temperature.