US3577964A

US3577964A - Control apparatus

Info

Publication number: US3577964A
Application number: US721994A
Authority: US
Inventors: Jeffrey M Lazar
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1968-04-17
Filing date: 1968-04-17
Publication date: 1971-05-11
Anticipated expiration: 1988-05-11
Also published as: GB1217801A; FR2006330A1; DE1919254A1; SE347790B

Abstract

A fluidic fuel control system wherein mass fuel flow into a mixing chamber is controlled in response to volumetric flow rate, temperature and pressure of air entering the chamber.

Description

United States Patent Inventor Jefirey M. Lazar Rosemount, Minn. 721.994

Apr. 17, 1968 May 11, 1971 Honeywell Inc. Minneapolis, Minn.

Appl. No. Filed Patented Assignee CONTROL APPARATUS 8 Claims, 2 Drawing Figs.

Primary Examiner-Laurence M. Goodridge Attorneys-Roger W. Jensen, Charles J. Ungemach and Ronald T. Reiling ABSTRACT: A fluidic fuel control system wherein mass fuel flow into a mixing chamber is controlled in response to volumetric flow rate, temperature and pressure of air entering the chamber.

VPATENIEDHYAYI 1 l9?! 3577,9641

" sum 1 0F 2 INVENTOR. JEFFREY M. LAZAR ATTORNEY PATENTEU HAY! 1 197i SHEET 2 BF 2 m A a TM X. N NL 5 m E. T VM T E m H 6 J 4 Y B CONTROL APPARATUS BACKGROUND OF THE INVENTION This invention pertains generally to fuel control systems and more particularly to fluidic fuel control systems wherein close control over the fuel-to-air ratio is maintained by controlling mass fuel flow into a mixing region in response to mass air flow thereinto.

The operation of an internal combustion engine requires that the air and fuel be mixed in certain proportions before being supplied to the engine. In a reciprocating engine, the fuel-to-air ratio is normally controlled by means of a conventional carburetion system which supplies the fuel mixture to the cylinders of the engine through an intake manifold or manifolds. A conventional carburetor basically comprises a mixing chamber and means for allowing the entry of fuel and air thereinto. A throttle valve is located between the mixing chamber and the intake manifold. A choke valve, for controlling the starting fuel mixture, is normally included at the air intake entranceto the mixing chamber. In addition, other devices for controlling the fuel mixture under various transient operating conditions of the engine may be included.

In normal operation, both fuel and air are drawn into the mixing chamber by means of a partial vacuum which is transmitted thereinto from the intake manifold through the throttle valve. For a given set of conditions, including air and fuel characteristics, carburetor settings and engine operation, an optimum fuel-to-air mixture can be closely approximated with a conventional carburetor. However, a conventional carburetor controls primarily the volumetric fuel and air flows into the mixing chamber, whereas a proper fuel-to-air mixture requires control of the fuel and air mass flows into the mixing chamber. Air mass flow is a function of volumetric airflow rate, air temperature and air pressure. Fuel mass flow is a function of volumetric flow rate and fuel temperature. Accordingly, since a conventional carburetor does not compensate for air tempera-' ture, air pressure or fuel temperature, it cannot provide an optimum fuel-to-air mixture under most operating conditions.

One of the increasingly serious problems of an improper fuel to air mixture, particularly in automobile engines, is that noxious exhaust gases including excessive unburned combustion products are produced. These exhaust gases contribute substantially to atmospheric pollution. In addition, optimum engine operation and efficiency cannot be provided unless the engine is supplied with a proper fuel-to-air mixture.

As previously noted, most conventional carburetors are provided with a number of accessory devices for controlling fuel mixture under engine starting, accelerating and other transient operating conditions. These accessory devices include butterfly and needle valves, fuel chambers, floats, mechanical temperature sensors and complicated interconnecting linkages. The fact that all of these parts must be manufactured and assembled increases the cost and complexity of production. In addition, the working interrelationships of these mechanical parts, many of which are moving elements, is critical. Accordingly, the initial adjustments must be carefully performed. Further, since moving mechanical parts are included, they are subject to wear and the carburetor must be periodically readjusted.

As has been discussed, conventional carburetion systems cannot generally provide an optimum fuel mixture for all operating conditions. In addition, since they 'contain a number of intricate moving mechanical parts and adjustments. they are complicated to manufacture, assemble and adjust. Further, they are subject to wear and are therefore unreliable. For these reasons, it is apparent that prior art carburetion systems are not generally satisfactory for use with modern internal combustion engines.

SUMMARY OF THE INVENTION The applicants fuel control system comprises a mixing chamber in combination with an air intake passage and a fuel nozzle. Means is provided for sensing volumetric flow rate,

temperature and pressure of the air entering the mixing chamber through the air intake passage. The signals indicative of the volumetric airflow rate, air temperature and air pressure are combined to form a signal indicative of mass airflow into the mixing chamber. This signal is supplied to a fuel metering valve which controls the flow of fuel into the mixing chamber through the fuel nozzle. In addition, fuel temperature and differential fuel pressure across the fuel metering valve are sensed and signals indicative thereof are provided. These signals are further utilized to control the mass fuel flow through the fuel metering valve such that a predetermined fuel-to-air mass ratio in the mixing chamber is maintained. In addition, means may be provided for sensing engine acceleration or loading and providing a signal indicative thereof. This signal may also be supplied to thefuel metering valve so as to provide improved transient engine operation.

In accordance with the teachings of this invention, the applicants unique fluidic fuel control system provides close control over the fuel-to-air mixture supplied to the engine, thus improving engine efiiciency and decreasing unburned combustion products in the engine exhaust gases. Automatic compensation is provided for variations in volumetric airflow into the mixing chamber due to such factors as clogging of an air cleaner in the air intake passage. In addition, the applicants invention makes maximum use of fluidic components in which there are no moving parts. Accordingly, wear is minimized and maximum reliability is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a preferred embodiment of the applicants fluidic fuel control systemshowing a mixing chamber, an air intake passage and a fuel metering valve partially broken away, and showing the fluidic sensors and logic circuit schematically; and

FIG. 2 shows a block diagram of the applicants fluidic fuel control system applied to a multicylinder reciprocating engine wherein fuel and air are individually mixed for each cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, reference numeral 10 generally refers to fuel supply apparatus for a reciprocating internal combustion engine. Apparatus I0 includes a carburetor 11 which supplies a fuel mixture to an intake manifold 12. Carburetor 11 is much simplified from a conventional carburetor in that it includes practically no moving parts or accessory devices. Carburetor 11 is mounted on manifold 12 by means of a plurality of bolts 13. Manifold l2 distributes the fuel mixture to the cylinders of a conventional reciprocating engine (not shown).

Carburetor 11 includes an air intake passage 14 through which air is drawn from the atmosphere into a mixing chamber 15. A conventional air cleaner 16 is provided at the inlet to air intake passage 14 to filter the air drawn therethrough. Air ina take passage 14 includes a venturi section 17 of smaller crosssectional area than the cross-sectional area of the remainder of the intake passage.

Carburetor 11 also includes a fuel nozzle 18 for injecting fuel into mixing chamber 15 wherein a turbulence generator 19 is provided for thoroughly mixing fuel and air drawn thereinto. Turbulence generator 19 may comprise any device suitable for mixing fuel and air. It may, for example, comprise fixed vanes at the exit of mixing chamber 15 or it may be a moving element. A throttle valve 20 is provided at the base of carburetor 11 so as to control the amount of fuel mixture entering manifold 12 from carburetor ll. Throttle valve 20 is a butterfly valve which rotates about an offcenter pivot axis 21 such that the partial vacuum normally existing within manifold I2 tends to maintain it in a closed position.

Reference numeral 25 generally refers to a fuel metering valve which controls the fuel flow to fuel nozzle 18. Metering valve 25 is connected to be supplied with fuel from a fuel source (not shown) by means of a fuel line 26, a fuel pump 27, a shutoff valve 28 and a fuel line 29. Fuel is supplied from fuel line 29 to metering valve 25 through a fuel inlet 30 and a pressure compensation port 31. Fuel valve 25 also includes a fuel outlet 32 which is connected to fuel nozzle 18 by means of a fuel line 33.

Metering valve 25 comprises a housing 35 which encloses a pneumatic chamber 36, a fuel inlet chamber 37, a fuel outlet chamber 38 and a fuel pressure compensation chamber 39. lnlet chamber 37 and outlet chamber 38 are separated by a wall 40 which contains a valve seat 41. Valve seat 41 in combination with a cone-shaped armature 42 comprise a valve which controls fuel flow between inlet chamber 37 and outlet chamber 38.

Armature 42 is connected to an actuating diaphragm 43 by means of a first connecting shaft 44. Shaft 44 extends through a wall 45 which separates pneumatic chamber 36 from inlet chamber 37. Diaphragm 43 divides pneumatic chamber 36 into a first pressure chamber 48 and a second pressure chamber 49.

Armature 42 is also connected to a compensation diaphragm 46 by means of a second connecting shaft 47. Diaphragm 46 separates outlet chamber 38 from compensation chamber 39. Pressure compensation port 31, diaphragm 46, connecting shaft 47, and pressure chambers 38 and 39 comprise fuel pressure responsive apparatus 52.

Diaphragms 43 and 46 are each flexible such that a pressure differential across either of the diaphragms will cause deflection thereof. Any deflection of diaphragms 43 or 46 is transmitted to armature 42 by means of shafts 44 and 47, thus causing movement of armature 42 relative to valve seat 41. Relative movement between armature 42 and valve seat 41 results in variation of the cross-sectional area of the passage through which fuel flows from inlet chamber 37 to outlet chamber 38, thus controlling the fuel flow rate therebetween.

Pressure chambers 48 and 49 communicate with

pressure ports

50 and 51 whereby a pneumatic pressure differential control signal can be applied across diaphragm 43. lnlet chamber 37 and compensation chamber 39 communicate with fuel line 29 through fuel inlet 30 and compensation port 31. Outlet chamber 37 communicates with fuel line 33 through outlet 32.

Reference numeral 55 generally refers to fluidic control apparatus for controlling metering valve 25. Control apparatus 55 includes an air mass flow sensor 56, a fluidic control circuit 60, an engine demand sensor 110 and a fuel temperature sensor 120. Air mass flow sensor 56 includes an airflow velocity sensor 80, a temperature sensor 90 and an air pressure sensor 100.

Control circuit 60 comprises a cascade of four proportional fluid amplifiers designated by reference numerals 61, 66, 71 and 76. Each of these amplifiers includes a power nozzle a, a first pair of opposing control ports 11 and c, a second pair of opposing control ports d and e, a first outlet passage f and a second outlet passage g. Reference hereinafter to a particular element of a fluid amplifier will be made by amplifier identification number and reference character of the particular element. For example, control port I; of amplifier 61 will be indicated by control port 611).

Reference numeral 130 refers to a source of filtered air under pressure which is connected to supply air to a conduit 131 through a valve 132. Power nozzles 61a, 66a, 71a and 76a are connected to conduit 131 by means of

conduits

62, 67, 72 and 77. Outlet passages 61f and 613 are connected to control ports 66b and 660 by means of

conduits

63 and 64. Outlet passages 66f and 663 are connected to control ports 71b and 710 by means of

conduits

68 and 69. Outlet passages 71f and 713 are connected to control ports 76b and 76c by means of conduits 73 and 74. Outlet passages 76f and 76g are connected to pressure

ports

50 and 51 of metering valve 25 by means of conduits 78 and 79.

Air velocity sensor 80 comprises a pair of static pressure taps 81 and 82 in communication with air intake passage 14 of carburetor 11. Pressure tap 81 is located just upstream from venturi section 17 of passage 14. Pressure tap 82 is located at venturi section 17 of passage 14. Pressure tap 81 is connected to control port 61b by means of a conduit 83, a static pressure chamber 101 and a conduit Chamber 101 comprises a portion of air pressure sensor 100 as will hereinafter be discussed. Pressure tap 82 is connected to control port 61c by means of a conduit 85.

Temperature sensor 90 comprises a capillary passage 91 located within air intake passage .14 of carburetor 11. One end of capillary passage 91 is connected to conduit 131 by means of a conduit 92. The other end of capillary passage 91 is connected to control port 61d by means of a conduit 93. Control port 61e is connected to conduit 131 through an orifice 94 which also comprises a portion of air temperature sensor 90.

Air pressure sensor comprises static pressure chamber 101 which includes a pressure tap 102. Pressure tap 102 communicates with the interior of chamber 101 through an orifice 103. Pressure tap 102 is connected to control port 66s by means of conduits 104 and 105. Conduits 104 and 105 are connected to conduit 131 through an orifice 106. Control port 66d is connected to conduit 131 through an orifice 107 and conduit 67. Orifices 106 and 107 also comprise portions of air pressure sensor 100. I

Engine demand sensor 110 comprises a pressure port 111 in communication with the interior of manifold 12. Pressure port 111 is connected to control port 7111 through a conduit 112 and an orifice 113. Pressure port 111 is also connected to control port 71e through conduit 112, an orifice 114 and a pres sure tank 115.

Orifices

113 and 114 are of the same size.

Fuel temperature sensor comprises a capillary passage 121 located within inlet chamber 37 of metering valve 25. One end of capillary passage 121 is connected to conduit 131. The other end of capillary passage 121 is connected to control port 760! by means of a conduit 122. Control port 76a is connected to conduit 131 through an orifice 123 which also comprises a portion of fuel temperature sensor 120.

In normal operation of the engine with which fuel supply ap paratus 10 is associated, the action of the pistons and valves within the engine cause a partial vacuum in intake manifold 12. The reduced pressure within manifold 12 functions to draw fuel mixture from mixing chamber 15 at a rate dependent upon the position of throttle valve 20 and the pressure differential thereacross. The removal of fuel mixture from mixing chamber 15, in turn, results in airflow through air intake passage 14. In order to maintain the proper fuel-to-air mass ratio in mixing chamber 15, mass fuel flow into chamber 15 is controlled in response to mass airflow thereinto. The applicants fluidic fuel control system functions to control the mass fuel flow into mixing chamber 15 in response to mass airflow thereinto as follows.

As a prerequisite to operation of the applicant's fuel control system, filtered air under pressure must be provided to power the fluid amplifiers and certain of the sensors. in addition, fuel under pressure must be supplied to fuel metering valve 25. When the engine is running, air under pressure may be supplied by means of a compressor operating as an engine accessory. Likewise, fuel under pressure may be provided by means of a fuel pump operating from engine power.

However, during engine startup, engine power is not available. Nevertheless, cranking the engine during the starting process will cause sufiicient operation of the fuel pump to supply the necessary starting fuel to the engine. In addition, metering valve 25 may be constructed such that in the absence of any control signals supplied thereto, it will allow a predeter mined flow of fuel therethrough sufficient for starting the engine. Further, a manual or temperature controlled mechanical choke may be provided for limiting the airflow through the air intake passage so as to enrich the fuel mixture and provide for easy engine starting.

Alte'rnately, auxiliary means may be provided for supplying air and fuel under pressure. Accordingly, source may include an air storage tank or the compressor may be electrically driven from battery power. Similarly, fuel pump 27 may be electrically driven, thus eliminating the need for engine power. Valve 132 on the discharge side of source 130 provides means for shutting off airflow therefrom and conserving air pressure in the storage tank, if one is provided; when the engine is not operating. Valve 28 on the discharge side of pump 27 provides means for shutting off fuel flow to metering valve 25 when this is so desired.

With source 130 in operation and valve 132 open, air under pressure is supplied to power nozzles 61a, 66a, 71a and 76a, thereby causing fluid streams to issue therefrom. The operation of amplifiers 61, 66, 71 and 76 is identical, therefore only the operation of amplifier 61 will be discussed in detail. In the absence of pressure differential signals supplied to the control ports of amplifier 61, the fluid stream issuing from power nozzle 61a will be substantially equally divided between outlet passages 61f and 613. Accordingly, in the absence of pressure differential input signals to amplifier 61, no pressure differential output signal will be produced thereby. However, if a pressure differential input signal is supplied to either or both sets of opposing control ports, a pressure difierential output signal will generally be produced between outlet passages 61f and 61g. If a pressure differential signal is supplied to the first pair of opposing control ports such that the pressure at control port 61b is greater than the pressure at control port 61c, the pressure produced in outlet passage 613 will be greater than the pressure produced in outlet passage 61f. Similarly, if a pressure differential signal is supplied to the second pair of opposing control ports such that the pressure at control port 61d is greater than the pressure at control port 616, the pressure produced in outlet passage 613 will be greater than the pressure produced in'outlet passage 61f. This discussion of the operation of amplifier 61 applies equally well to amplifiers 66, 71 and 76..

Venturi section 17 of air intake passage 14 and static pressure ports 81 and 82 operate as a venturi meter wherein static pressure varies inversely with flow velocity. Since the crosssectional area of venturisection 17 is smaller than the crosssectional area of the upstream portion of intake passage 14 and the same air is flowing through both portions of the passage, the flow velocity through venturi section 17 is greater than the flow velocity through the portions of intake passage 14 upstream therefrom. The static pressure produced in static pressure port 81 is a function of the ambient pressure of the air surrounding the engine, the condition of air cleaner 16 and the airflow velocity through passage 14. The static pressure produced in static pressure port 82 will be less than the pressure produced in static pressure port 81 an amount dependent on the difference in velocities of airflow through passage 14 and venturi section 17. Since the cross-sectional areas of passage 14 and venturi section 17 are fixed, the pressure differential between static pressure ports 81 and 82 is also indicative of the volumetric airflow rate into mixing chamber 15.

lt will be apparent to those skilled in the art that other means for sensing airflow velocity can equally as well be used. For example, a dynamic pressure tap can be provided within passage 14 or venturi section 17 and oriented upstream to the airflow therethrough. The pressure thus sensed can then be utilized in conjunction with a fixed reference pressure to obtain a pressure differential signal indicative of the airflow velocity through passage 14 or venturi section 17 The pressure produced at static pressure port 81 is transmitted to control port 61b by means of conduit 83, static pressure chamber 101 and conduit 84. As will hereinafter be noted, orifice 103 and the pressure in conduit 104 are of such a magnitude that a negligible change in pressure within static pressure chamber 101 is produced. The pressure produced in static pressure port 82 is transmitted to control port 61c by means of conduit 85. Accordingly, the pressure differential signal supplied to control ports 61b and 61c is indicative of the volumetric rate of airflow into mixing chamber 15. As airflow through intake passage 14 increases, the pressure at control port 61c decreases relative to the pressure at control port 61b. Conversely, as airflow through intake passage 14 decreases, the pressure at control port 61c increases relative to the pressure at control port 61b.

. In order to understand the operation of air temperature sensor 9.0 and fuel temperature sensor 120, it is necessary to know the effects of temperature on airflow through a simple orifice and through a capillary passage. The airflow through a simple orifice is substantially independent of temperature over the range of temperatures to which a fuel control system for an engine would normally be exposed. However, over the same range of temperatures, impedance to airflow through a capillary passage is directly dependent upon the viscosity of the air which, in turn, is directly dependent upon the air temperature. Accordingly, as the temperature of air flowing through a capillary passage increases, pressure drop across the passage increases and airflow through the passage decreases. These characteristics of airflow through an orifice and the capillary passage are utilized in the applicants fuel control system as follows Control port 61d is supplied with a fluid pressure signal from conduit 131 through conduit 92, capillary passage 91 and conduit 93. Capillary passage 91 is exposed to the air fuel mixture within mixing chamber 15. Accordingly, heat is transferred from the air fuel mixture within mixing chamber 15 to the air within capillary passage 91 such that the temperature of the air within capillary passage 91 approximates the temperature'of the mixture. Thus, 'as the temperature of the air entering mixing chamber 15 increases, the pressure drop across capillary passage 91 increases and the pressure signal supplied to control port 61d decreases.

A pressure signal is also supplied to control port 61e, which opposes control port 61b, from conduit 131 through orifice 94. Since the impedance produced by orifice 94 to airflow therethrough is substantially independent of temperature, the pressure signal supplied to control port 61a varies primarily only with changes in pressure supplied thereto from conduit 131. The pressure supplied to capillary passage 91 from conduit 131 varies in the same manner as the pressure supplied to orifice 94. Accordingly, the pressure differential signal supplied to control ports 61d and 6le is indicative of the temperature of the mixture within chamber 15. Further, as the temperature of the mixture within chamber 15 increases, the pressure signal supplied to control port 61d decreases. Conversely, as the temperature of the mixture within chamber 15 decreases, the pressure signal supplied to control port 61d increases. Capillary passage 81 and orifice 94 are sized such that for a predetermined normal air temperature, the pressure signals supplied to control ports 61d and 61e are substantially equal.

It will be noted by those skilled in the art that other means for sensing air temperature can also be used. For example, a temperature sensing bulb containing a fluid having a high coefficient of thermal expansion can be located within passage 14 or mixing chamber 15. Expansion of the fluid within the bulb can be transmitted by means of a tube to a flow controller whereby a temperature dependent pressure is produced. This pressure can be utilized in conjunction with a fixed reference pressure to obtain a pressure differential signal indicative of the temperature of the air within passage 14 or mixing chamber 15.

Amplifier 61 functions to sum the pressure signals supplied to control ports 61b through 61e and produce a pressure differential signal indicative thereof between outlet passages 61f and 61g. From the previous discussion of amplifier 61, it can be seen that as the volumetric rate of airflow into mixing chamber 15 increases, the pressure signal produced in outlet passage 613 will increase relative to the pressure signal produced in outlet passage 61f. Similarly, as the temperature of the air entering mixing chamber 15 decreases, the pressure signal produced in outlet passage 613 will increase relative to the pressure signal produced in outlet passage 61f.

The pressure signals produced in outlet passages 61f and 613 are transmitted to control ports 66b and 66c through

conduits

63 and 64. Control port 66d is supplied with a pressure signal from conduit 131 through conduit 67 and orifice 107. In addition, control port 66e is supplied with a pressure signal from conduit 131 through orifice 106. However, the pressure signal supplied to control port 66e is modified by the air flowing into static pressure chamber 101 through conduit 104 and orifice 103. The airflow rate through orifice 103 varies with the pressure differential thereacross. The pressure in conduit 104 is greater than the pressure within chamber 101 which is substantially the same as the pressure of the air within intake passage 14. The pressure of the air within mixing chamber is the pressure of the air within passage 14, modified only by a pressure recovery factor across venturi section 17. The pressure recovery factor remains substantially constant over the range of flow velocities normally present through venturi section 17. Accordingly, the pressure within chamber 101 is indicative of the pressure of the air entering mixing chamber 15. it should be noted that this means of sensing air pressure automatically compensates for variations in air pressure due to variations in pressure drop across air cleaner 16. Thus, as air cleaner 16 becomes clogged through use, means is provided for automatically compensating the fuel flow into mixing chamber 15 such that the predetermined fuel-to-air ratio is maintained.

Assuming that the pressure in conduit 104 remains constant, airflow through orifice 103 will increase as the pressure decreases and decrease as the air pressure increases. However, since the pressure in conduit 104 which is supplied thereto from conduit 131 through orifice 106 cannot be assumed to remain constant, compensation for any variation thereof must be provided. This compensation is provided by means of the pressure signal supplied to control port 66d from conduit 131 through orifice 107. Since any variation and pressure in conduit 131is applied to both control ports 66d and 66e, any such pressure variations are self-cancelling. Accordingly, the pressure differential signal applied to control ports 66:! and 66a is indicative of the pressure of the air entering mixing chamber 15. As the pressure of the air entering mixing chamber 15 increases, the pressure at control port 66a will increase relative to the pressure at control port 660i. Conversely, as the pressure of the air entering mixing chamber 15 decreases, the pressure at control port 66e will decrease relative to the pressure at control port 66d.

Amplifier 66 functions to sum the pressure signals supplied to control ports 66b through 66c and produce a pressure signal indicative thereof between outlet passage 66f and 66g. From the foregoing discussion of the operation of amplifier 61, which is identical to the operation of amplifier 66, it can be seen that the pressure differential output signals produced between outlet passages 66f and 663 are indicative of volumetric flow rate, temperature and pressure of the air entering mixing chamber 15. Further, it can be seen that the pressure signal produced in outlet passage 66f increases relative to the pressure signal produced in outlet passage 66g as the volumetric rate of flow of air into mixing chamber 15 increases, as the air temperature decreases and/or as the air pressure increases.

Conversely, the pressure signal produced in outlet passage 66f decreases as the volumetric rate of flow of air into mixing chamber 15 decreases, as the air temperature increases and/or as the air pressure decreases. It is pointed out that the mass rate of airflow into mixing chamber 15 varies directly with volumetric rate of flow of air thereinto. Further, it varies directly with the pressure and inversely with the temperature of the air entering mixing chamber 15. Accordingly proper sizing of the various elements which comprise airflow velocity sensor 80, temperature sensor 90 and air pressure sensor 100 results in production of a pressure differential output signal between outlet passages 66f and 663 which is indicative of the mass rate of airflow into mixing chamber 15.

The pressure signals produced in outlet passages 66f and 663 are supplied to control ports 71b and 710 through

conduits

68 and 69. Control port 71d is supplied with a pressure signal from pressure port 111 in intake manifold 12 through conduit 112 and orifice 113. Further, control port 71a is supplied with the pressure signal from pressure port 111 through conduit 112, orifice 114 and pressure tank 115. Pressure port 111, conduit 112,

orifices

113 and 114 and pressure tank 115,

which comprise engine demand sensor 110, operate as follows to provide improved transient engine operation.

As previously pointed out, operation of the engine with which intake manifold 12 is associated results in a partial vacuum within the manifold. For steady state engine operation, the pressure within manifold 12 remains constant at some value dependent on the operating conditions of the en gine. However, if an increased load is placed on the engine, the engine will decelerate. Slowing down of engine operation results in a decrease in the partial vacuum within manifold 12 or an increase in pressure therein. Similarly, if it is desired to accelerate the engine, throttle valve 20 is opened. Opening of throttle valve 20 results in a decrease in the partial vacuum within manifold 12 or an increase in pressure therein. Conversely, either a decrease in the load on the engine or closing of throttle valve 20 results in a decrease in pressure within manifold 12. Accordingly, any change in the setting of throttle valve 20 or in the loading conditions of the engine, which will hereinafter be referred to as engine demand, results in a change in pressure within manifold 12. Changes in engine demand are thus reflected as pressure changes in pressure port 1 l 1.

For improved transient engine operation, it has been found advantageous to increase the fuel-to-air ratio when engine acceleration is desired or an increased load is placed on the engine. Conversely, it is advantageous to decrease the fuel-to-air ratio, thereby decreasing combustion byproducts, when engine deceleration is desired.

Orifices

113 and 114 and pres sure tank 115 comprise a high pass fluid circuit by which this result is achieved.

During steady state engine operation the pressure within manifold 12 remains constant. Thus, pressure tank 115 is allowed to charge to a pressure equal to the pressure within manifold 12 less the pressure drop across orifice 114 due to the small amount of flow through control port 712. Since orifices 113 and .114 are of the same size, the pressure drops thereacross are equal and equal pressure signals are supplied to control ports 71d and 71e. However, if the pressure within manifold 12 increases, indicating increased engine demand, this increased pressure signal is immediately transmitted to control port 71d. Due to the capacity of pressure tank 115, there is a delay in the transmission of the increased pressure signal to control port 7le. Conversely, if the pressure within manifold decreases, indicating decreased engine demand, the decreased pressure signal is immediately transmitted to control port 71d. Due to the capacity of pressure tank 115, there is a delay in the transmission of the decreased pressure signal to control port 71e. Accordingly, a pressure differential signal is supplied to control ports 71d and 712 only during transient engine operation. Further, as engine demand increases, the pressure signal at control port 71d will increase relative to the pressure signal at control port 71e. As engine demand decreases, the pressure signal at control port 71d decreases relative to the pressure signal at control port 71s. This results in an increased fuel-to-air ratio for increased engine demand and a decreased fuel-to-air ratio for decreased engine demand as will hereinafter be shown.

Amplifier 71 functions to sum the pressure signals supplied to control ports 71b through 71c and produce a pressure signal indicative thereof between outlet passages 71f and 71g. From the foregoing discussion of the operation of amplifier 61, which is identical to the operation of amplifier 71, it can be seen that the pressure differential output signal produced between outlet passages 7 If and 713 is indicative of mass rate of airflow into mixing chamber 15 and engine demand. Further, it can be seen that the pressure signal produced in outlet passage 71g increases relative to the pressure signal produced in outlet passage 71f as the mass rate of airflow into mixing chamber 15 and/or engine demand increases. Conversely, the pressure signal produced in outlet passage 71g decreases as the mass rate of airflow into mixing chamber 15 and/or engine demand decreases.

The pressure signals produced in outlet passages 71]" and 71g are transmitted to control ports 76b and 76c through conduits 73 and 74. Control port 76d is connected to receive a pressure signal from conduit 131 through capillary passage 121 and conduit 122. Control port 76e is supplied with the pressure signal from conduit 131 through orifice 123. Capillary passage 121 is located within fuel inlet chamber 37 of metering valve 25 and operates to sense the temperature of the fuel therein. The operation of capillary passage 121 and orifice 123 in sensing temperature is the same as that described for capillary passage 91 and orifice 94 and need not be further discussed. It should, however, be noted that various other means for sensing fuel temperature can also be used. For example, a temperature sensor similar to the previously discussed alternate air temperature sensor can be used for sensing fuel temperature.

Amplifier 76 operates in the same manner as amplifier 61 to sum the pressure signals supplied to control ports 76b through 76e and to produce a pressure differential signal indicative thereof between outlet passages 76f and 76g. It should be noted that an increase in mass rate of airflow into mixing chamber 15, an increase in engine demand and/or an increase in fuel temperature results in an increase in the pressure signal produced in outlet passage 76g. Conversely, a decrease in mass rate of airflow into mixing chamber 15, a decrease in en gine demand and/or a decrease in fuel temperature results in an increase in the pressure signal produced in outlet passage 763 relative to the pressure signal produced in outlet passage 76f. it is pointed out that for a given mass rate of fuel flow, the volumetric flow rate varies directly with fuel temperature. Accordingly, by properly sizing capillary passage 121 and orifice 123, the pressure differential signals produced between outlet passages 76f and 76g include compensation for variations in fuel temperature.

The pressure signals produced in outlet passages 76f and 763 are transmitted to pressure chambers 48 and 49 through conduits 78 and 79. The pressure differential between pressure chambers 48 and 49 functions to deflect actuating diaphragm 43 thereby moving armature 42 relative to valve seat 41. Accordingly, the cross-sectional area of the fuel passage between inlet chamber 37 and outlet chamber 38 is varied and fuel flow therebetween is controlled. It should be noted that only the cross-sectional area of the fuel passage between inlet chamber 37 and outlet chamber 38 is varied in response to the mass rate of airflow into mixing chamber 15, engine demand and fuel temperature. The mass rate of fuel flow between inlet chamber 37 and outlet chamber 38 is dependent on the fuel pressure across the passage between the two chambers in addition to the cross-sectional area of the passage. For a given cross-sectional area, the fuel flow through the passage varies directly with fuel pressure thereacross. .Pressure compensation chamber 39 andpressure compensation diaphragm 46 operate to compensate for variations in fuel flow between inlet chamber 37 and outlet chamber 38 due to variations in fuel pressure differential betweenthe two chambers. The same fuel pressure is supplied to inlet chamber 37 and compensation chamber 39. Accordingly, the same differential fuel pressure present between inlet chamber 37 and outlet chamber 38 is also present across compensation diaphragm 46. As this differential fuel pressure increases, diaphragm 46 deflects so as to decrease the cross-sectional area of the passage between inlet chamber 37 and outlet chamber 38. Conversely, as the fuel pressure differential between inlet chamber 37 and outlet chamber 38 decreases, compensation diaphragm 46 deflects so as to increase the cross-sectional area of the fuel passage between the two chambers.

The fuel which flows from inlet chamber 37 to outlet chamber 38 through the fuel passage between the two chambers is supplied to fuel nozzle 18 through fuel line 33. From the foregoing discussion it can be seen that the rate at which fuel is supplied to fuel nozzle 18 is controlled in response to the mass rate of airflow into mixing chamber 15. In addition,

compensation is provided for variations in fuel temperature and variations in fuel pressure across metering valve 25. Positive control is thus maintained over the ratio of fuel and air mass flow rates into the mixing chamber. Accordingly, it is possible to maintain a predetermined fuel-to-air mixture under a wide range of operating conditions. Thus, optimum engine efficiency under a wide range of operating conditions can be achieved and the emission of unburned combustion products in the engine exhaust gases can be minimized. Means for enriching the fuel mixture under increased engine demand conditions and reducing the fuel-to-air ratio under decreased engine demand conditions is also provided so that improved transient engine operation is achieved. Further, the applicants fluidic fuel control system utilizes a minimum number of moving mechanical elements, thus simplifying assembly and adjustment and increasing reliability.

Reference is now made to FIG. 2 which shows the applicants fluidic fuel control system applied to a multicylinder reciprocating engine wherein fuel and air are individually mixed for each cylinder. Since the essential elements of the systems shown in both FIGS. 1 and 2 are the same, the same reference numerals will be used therein to designate corresponding elements.

Reference numeral refers to a multicylinder reciprocating engine (shown in cross section) having a plurality of cylinders 151. Each cylinder 151 contains a piston 152 which is connected to a crank shaft 153 by means of a connecting rod 154. Crank shaft 153 is carried in suitable bearings (not shown) whereby it is adapted to rotate about an axis 155. Each cylinder 151 is capped by a cylinder head 156 which includes an intake valve 157. Each intake valve 157 is slideably mounted in cylinder head 156 by means of a valve stem and valve guide 158. Intake valves 157 are adapted to be driven from crank shaft 153 by means of suitable gears, cams, springs and linkages (not shown).

Cylinders 151, pistons 152 and cylinder heads 156 define a plurality of combustion chambers 160. Each combustion chamber 160 communicates with a fuel mixing chamber 161 through a valve 157. Each mixing chamber 161 is adapted to be supplied with fuel by means of a fuel nozzle 162. Fuel nozzles 162 are of equal size and are designed so as to atomize fuel passing therethrough. Mixing chambers 161 are also adapted to be supplied with air from the atmosphere through an air cleaner 165, an air horn 166, a throttle valve 167 and an intake manifold 168. Air horn 166 is substantially the same as previously described carburetor 11 except that it is not provided with a fuel'nozzle or a turbulence generator. Air cleaner 165, throttle valve 167 and manifold 168 are substantially the same as air cleaner 16, throttle valve 20, and intake manifold 12 and need not be further described.

Reference numeral 25 in FIG. 2 refers to a fuel metering valve which is identical to fuel metering valve 25 in H6. 1. Metering valve 25 in H6. 2 is connected to be supplied with fuel from a fuel source (not shown) by means of a fuel pump 27 and is connected to fuel nozzles 162 by means of a fuel line 170. Fuel line l70differs from fuel line 33 in FIG. 1 only in that it includes a plurality of branches 171, one branch leading to each fuel noule 162. Fuel pump 25 also includes fuel pressure responsive apparatus 52 which functions to compensate for the effects of variations in fuel source pressure.

Reference numeral refers to fluidic control apparatus for controlling metering valve 25. Control apparatus 175 is similar to control apparatus 55 and includes an air mass flow sensor 56, a fuel temperature sensor 120 and a control circuit 180. Air'mass flow sensor 56 includes an air velocity sensor 80, a temperature sensor 90 and an air pressure sensor 100. Air velocity sensor 80, temperature sensor 90 and air pressure sensor 100 are adapted to sense air velocity, temperature and pressure within air horn 166 and supply signals indicative of air mass flow therethrough to control circuit 180. Fuel temperature sensor 120 is adapted to sense the fuel temperature within fuel valve 25 and supply a signal indicative thereof to control circuit 180. Control circuit is adapted to receive signals from air mass flow sensor 56 and fuel temperature sensor 120 and provide control signals to metering valve 25 in response to air mass flow through air horn 166 and fuel ternperature within fuel valve 25.

in normal operation of engine 150, crank shaft 153 rotates about axis 155, thus causing pistons 152 to move in a reciprocating manner along the axes of cylinders 151. At predetermined points in the operating cycle, when pistons 152 are moving away from cylinder heads 156, valves 157 are caused to open, thus allowing a fuel mixture present within mixing chambers 161 to be drawn thereinto. The act of drawing fuel mixture from mixing chambers 161 causes air to be drawn through air horn 166 and intake manifold 168. Manifold 168 is designed such that air from air horn 166 is equally distributed to all mixing chambers 161. in addition, valves 157 to all combustion chambers 160 open with equal frequency. Therefore, the rate at which air is drawn through air horn 166 is indicative of the average rate at which air enters each mixing chamber 161.

Air mass flow through air horn 166 is sensed by air mass flow sensor 56 in a manner identical to that described for the system of FIG. 1. In addition, fuel temperature is sensed in a manner identical to that described for the system of FIG. 1, Signals indicative of air mass flow and fuel temperature are supplied to control circuit 180. Control circuit 180 functions in a manner similar to that described for control circuit 60 to provide a control signal responsive to air mass flow and fuel temperature to fuel valve 25. Fuel pressure responsive apparatus 52 further provides compensation for variations in fuel pressure across metering valve 25. Metering valve 25 operates as previously described to control mass fuel flow through fuel line 170 in response to mass air flow through air horn 166.

Fuel nozzles 162 and branches 171 of fuel line 170 are designed to equally distribute the fuel carried by fuel line 170 among the mixing chambers 161. Accordingly, the mass rate at which fuel is supplied to each of mixing chambers 161 is dependent on the mass airflow through air horn 166, which is a function of the average mass airflow into each mixing region. Thus, close control is provided over the mass fuel-to-air ratio of the fuel mixture entering combustion chambers 160 from mixing regions 161. The result is that optimum engine efficiency under a wide range of operating conditions is achieved and the emission of objectionable exhaust products is minimized.

Although the applicant's invention has been described and illustrated in detail, it should be understood that the same is by way of illustration and example only and is not to be taken by way of limitation. The spirit and scope of this invention are limited only by the terms of the following claims.

lclaim:

1. Fuel mixing apparatus comprising:

a mixing chamber;

an air intake passage in communication with said mixing chamber for supplying air thereinto;

a fuel nozzle in communication with said mixing chamber for introducing fuel thereinto;

air velocity sensing means operable to provide a first fluid signal indicative of the velocity of airflow through said air intake passage;

first temperature sensing means operable to provide a second fluid signal indicative of the air-fuel mixture temperature within said mixing chamber;

air pressure sensing means operable to provide a third fluid signal continuously indicative of the air pressure within said air intake passage;

control means including a plurality of fluid amplifiers. said control means having control port means and signal output means;

first means connecting said air velocity sensing means, said first temperature sensing means and said air pressure sensing means to the control port means of said control means so as to convey the first, second and third fluid signals thereto, said control means being operable to provide a fourth signal at the signal output means indicative of the mass airflow into said mixing chamber in response to the first, second and third fluid signals;

fuel metering means including a control input, a fuel inlet and a fuel outlet, the fuel inlet being adapted to be connected to a source of fuel under pressure, said fuel metering means being operable to control fuel flow between the fuel inlet and the fuel outlet in response to a signal supplied to the control input;

second means connecting the signal output means of said control means to the control input of said fuel metering means so as to convey the fourth signal thereto; and

third means connecting the fuel outlet of said fuel metering means to said fuel nozzle, said fuel metering means being operable to control fuel flow into said mixing chamber in response to mass airflow into said mixing chamber.

2. The fuel mixing apparatus of claim 1 further including fuel temperature sensing means operable to provide a fifth fluid signal indicative of the fuel temperature within sad fuel metering means and means connecting said fuel temperature sensing means to said control means so as to convey the fifth fluid signal thereto, the fourth fluid signal provided by said control means being responsive to mass airflow into said mixing chamber and temperature of the fuel within said fuel metering means.

3. The fuel mixing apparatus of claim 2 further including fuel pressure responsive means associated with said fuel metering means, said fuel pressure responsive means being operable to control said fuel metering means in response to the fuel pressure thereacross, said fuel metering means being operable to control mass fuel flow into said mixing chamber in response to mass airflow into said mixing chamber.

4. The fuel mixing apparatus of claim 3 in combination with an internal combustion engine and further including demand sensing means operable to provide a sixth fluid signal indicative of engine acceleration and loading and means connecting said demand sensing means to said control means so as to convey the sixth fluid signal thereto, said fuel metering means being operable to control mass fuel flow into said mixing chamber in response to mass airflow into said mixing chamber and engine demand.

5. The fuel mixing apparatus of claim 1 wherein:

said air velocity sensing means comprises a venturi section in said air intake passage, said venturi section including a throat of smaller cross-sectional area than the cross-sectional area of the remainder of said air intake passage, said venturi section having a first static pressure port upstream from its throat and a second static pressure port at its throat;

said air temperature sensing means comprises a first orifice adapted to be supplied with fluid under pressure and a capillary passage adapted to be supplied with fluid under pressure, the capillary passage being located within said air intake passage;

said air pressure sensing means comprises a second orifice adapted to be supplied with fluid under pressure, a third orifice adapted to be supplied with fluid under pressure, a fourth orifice in communication with said air intake passage, and means connecting said third and said fourth orifices, last named means including a pressure tap;

said control means comprises a cascade of proportional fluid amplifiers, each amplifier having a pair of opposing control ports; and

said first means comprises means connecting the first and second static pressure ports of said air velocity sensing means to opposing control ports of an amplifier in said cascade of proportional fluid amplifiers, means connecting the first orifice and the capillary passage of said temperature sensing means to opposing control ports of an amplifier in said cascade of proportional fluid amplifiers and means connecting the second orifice and the pressure tap of said air pressure sensing means to opposing control ports of an amplifier in said cascade of proportional fluid amplifiers.

6. A fluidic fuel control system for an internal combustion engine including a combustion chamber, and a fuel nozzle and an air intake passage for supplying fuel and air thereinto comprising:

volumetric airflow sensing means operable to provide a first fluid signal indicative of volumetricairflow into the combustion chamber;

air pressure sensing means operable to provide a second fluid signal indicative of the pressure of air flowing into the combustion chamber; fluidic summing means; first means connecting said volumetric airflow sensing means and said air pressure sensing means to said summing means so as to convey the first and second fluid signals thereto, said fluidic summing means being operable to produce a third fluid signal indicative of mass airflow into the combustion chamber;

fuel metering means including a control input, a fuel inlet and a fuel outlet, the fuel inlet being adapted to be connected to a source of fuel under pressure;

second means connecting said fluidic summing means to the control input of said fuel metering means so as to convey the third fluid signal thereto, said fuel metering means being operable to control fuel flow between the fuel inlet and the fuel outlet in response to the third fluid signal;

third means connecting the fuel outlet of said fuel metering means to the fuel noule;

fuel temperature sensing means; and

fourth means connecting said fuel temperature sensing means to the control input of said fuel metering means.

7. The fluidic fuel control system of claim 6 further including first temperature sensing means operable to provide a fourth fluid signal indicative of a temperature of air fuel flowing into the combustion chamber and fourth means connecting said first temperature sensing means to said fluidic summing means so as to convey the fourth fluid signal thereto, said third fluid signal produced by said summing means further being a function of the fourth fluid signal.

8. The fluidic fuel control system of claim 7 further including fuel pressure responsive means associated with said fuel metering means, said fuel pressure responsive means being operable to control said fuel metering means in response to fuel pressure thereacross, said fuel metering means being operable to control mass fuel flow into the combustion chamber in response to mass airflow thereinto.

Claims

1. Fuel mixing apparatus comprising: a mixing chamber; an air intake passage in communication with said mixing chamber for supplying air thereinto; a fuel nozzle in communication with said mixing chamber for introducing fuel thereinto; air velocity sensing means operable to provide a first fluid signal indicative of the velocity of airflow through said air intake passage; first temperature sensing means operable to provide a second fluid signal indicative of the air-fuel mixture temperature within said mixing chamber; air pressure sensing means operable to provide a third fluid signal continuously indicative of the air pressure within said air intake passage; control means including a plurality of fluid amplifiers, said control means having control port means and signal output means; first means connecting said air velocity sensing means, said first temperature sensing means and said air pressure sensing means to the control port means of saiD control means so as to convey the first, second and third fluid signals thereto, said control means being operable to provide a fourth signal at the signal output means indicative of the mass airflow into said mixing chamber in response to the first, second and third fluid signals; fuel metering means including a control input, a fuel inlet and a fuel outlet, the fuel inlet being adapted to be connected to a source of fuel under pressure, said fuel metering means being operable to control fuel flow between the fuel inlet and the fuel outlet in response to a signal supplied to the control input; second means connecting the signal output means of said control means to the control input of said fuel metering means so as to convey the fourth signal thereto; and third means connecting the fuel outlet of said fuel metering means to said fuel nozzle, said fuel metering means being operable to control fuel flow into said mixing chamber in response to mass airflow into said mixing chamber.

5. The fuel mixing apparatus of claim 1 wherein: said air velocity sensing means comprises a venturi section in said air intake passage, said venturi section including a throat of smaller cross-sectional area than the cross-sectional area of the remainder of said air intake passage, said venturi section having a first static pressure port upstream from its throat and a second static pressure port at its throat; said air temperature sensing means comprises a first orifice adapted to be supplied with fluid under pressure and a capillary passage adapted to be supplied with fluid under pressure, the capillary passage being located within said air intake passage; said air pressure sensing means comprises a second orifice adapted to be supplied with fluid under pressure, a third orifice adapted to be supplied with fluid under pressure, a fourth orifice in communication with said air intake passage, and means connecting said third and said fourth orifices, last named means including a pressure tap; said control means comprises a cascade of proportional fluid amplifiers, each amplifier having a pair of opposing control ports; and said first means comprises means connecting the first and second static pressure ports of said air velocity sensing means to opposing control ports of an amplifier in said cascade of proportional fluid amplifiers, means connecting the first orifice and the capillary passage of said temperature sensing means to opposing control ports of an amplifier in said cascade of proportional fluid amplifiers and means connecting the second orifice and thE pressure tap of said air pressure sensing means to opposing control ports of an amplifier in said cascade of proportional fluid amplifiers.

6. A fluidic fuel control system for an internal combustion engine including a combustion chamber, and a fuel nozzle and an air intake passage for supplying fuel and air thereinto comprising: volumetric airflow sensing means operable to provide a first fluid signal indicative of volumetric airflow into the combustion chamber; air pressure sensing means operable to provide a second fluid signal indicative of the pressure of air flowing into the combustion chamber; fluidic summing means; first means connecting said volumetric airflow sensing means and said air pressure sensing means to said summing means so as to convey the first and second fluid signals thereto, said fluidic summing means being operable to produce a third fluid signal indicative of mass airflow into the combustion chamber; fuel metering means including a control input, a fuel inlet and a fuel outlet, the fuel inlet being adapted to be connected to a source of fuel under pressure; second means connecting said fluidic summing means to the control input of said fuel metering means so as to convey the third fluid signal thereto, said fuel metering means being operable to control fuel flow between the fuel inlet and the fuel outlet in response to the third fluid signal; third means connecting the fuel outlet of said fuel metering means to the fuel nozzle; fuel temperature sensing means; and fourth means connecting said fuel temperature sensing means to the control input of said fuel metering means.