US 3855974 A
The composition of the exhaust gases is sensed, and the mass-ratio of air and fuel components of the mixture applied to the engine is controlled by controlling the flow of fuel to the carburetor, for example by adjusting a nozzle opening of fuel flow to the carburetor mixing chamber, or the pressure within the carburetor mixing chamber, under control of a sensed exhaust gas composition signal.
Description (OCR text may contain errors)
United States Patent Mayer Dec. 24, 1974 APPARATUS TO CONTROL THE AIR-FUEL  References Cited MIXTURE SUPPLIED TO INTERNAL UNITED STATES PATENTS COMBUSTION ENGINES 3,086,353 4/1963 Ridgeway 123/32 EA 5 Inventor: Hartmut Mayer, Aidlingen 3,548,792 12/1970 Palmer 123/32 EA Germany 3,738,341 6/1973 Loos 123/32 EA 3,759,232 9/1973 Wahl .1 123/32 EA  Assignee: Robert Bosch GmbH, Stuttgart,
Germany Primary Examiner-Charles J. Myhre Assistant ExaminerRonald B. Cox  hled' 1973 Attorney, Agent, or FirmFlynn & Frishauf I21 Appl. No.1 322,568
 ABSTRACT  Foreign Application priority Data The composition of the exhaust gases is sensed, and Apr 22 1972 Germany 2219768 the mass-ratio of air and fuel components of the mixture applied to the engine is controlled by controlling 52 US. 01...... 123/32 EA, 123/119 R 123/119 E F fuel carburemr for example by 60/285 ust ng a nozzle opening of fuel flow to the carburetor 51 1m. (:1. F02b 3/00 F02d 1/04 l l chamber or the Pressure the carburetor  Field of Search 03/119 R, g E, 32 AE, mlxmg chamber, under control of a sensed exhaust gas composition signal. I
22 Claims, 8 Drawing Figures PATENTED DEC24 I974 saw 3 or 7 PATENTED DEC 24 I974 SHEET U 0F PATENTED DEC 24 I974 saw 6 or 7 APPARATUS TO CONTROL THE AIR-FUEL MIXTURE SUPPLIED TO INTERNAL COMBUSTION ENGINES Cross reference to related application: U.S. Ser. No. 314,921, filed Dec. 14, 1972.
The present invention relates to apparatus to control the mass ratio of the air and fuel components of the airfuel mixture applied to internal combustion engines, and more particularly to control the fuel flow through a carburetor in dependence on the sensed composition of exhaust gases from the internal combustion engine, specifically an electrical control signal derived from an oxygen sensor subjected to the exhaust gases.
Optimum operation of internal combustion engines requires careful control of the composition of the airfuel mixture supplied to the engine. Particularly, when it is desired to keep noxious components in the exhaust gases at a minimum, the fuel-air mixture applied to the engine should have an air number of A l, in which the air number A is representative of the composition of the air-fuel mixture. When a stoichiometric mixture is present, then the air number will be 1.0. Constantly changing operating conditions of the engine, particularly when installed in an automotive vehicle, require controlof the air number A under command of composition of the exhaust gases. The composition of the exhaust gases itself can be sensed, as known, by means of an oxygen sensor.
It is an object of the present invention to provide a system in which the composition of the air-fuel mixture applied to the engine can be controlled simply and easily, and which is applicable to be used with carburetors, and particularly with constant pressure, or pressure equalized carburetors. The control system should be additionally suitable for installation in the demanding surroundings of automotive vehicles, and should be simple, reliable, and of low cost.
Subject matter of the present invention: Briefly, the flow of at least one of the components of the mixture, preferably the fuel component, is controlled by an electrical signal derived from a sensor, sensing the composition of the exhaust gases. Flow control can be obtained, in accordance ,with a feature of the invention, by adjusting the nozzle opening ofa fuel nozzle extending into the mixing chamber of the carburetor; in accordance with another feature of the invention, the
pressure in the mixing chamber is controlled under command of the electrical signal derived from the sensor.
The invention will be described by way of example with reference to the accompanying drawings, wherein: FIG. I is a highly schematic diagram of a control loop to adjust the mass ratio of the air-fuel components of the mixture applied to an internal combustion engine;
FIG. 2 is a cross-sectional view through an equalized pressure carburetor having a fuel nozzle opening which is controllable by an electro-magnet having two windings;
FIG. 3 is a transverse cross-sectional view of a carburetor having a single control winding;
FIG. 4 is a transverse cross-sectional view of another embodiment in which an electrical control winding is connected to an air idler;
FIG. 5 is an enlarged fragmentary longitudinal view through a fuel nozzle, illustrating a control pin;
FIG. 6 is a longitudinal cross-section of an equalized pressure carburetor in which an air slider can be adjusted by means of an electro-magnet;
FIG. 7 is a longitudinal cross-sectional view of a carburetor in which air slider is arranged to change the pressure in the carburetor chamber;
and FIG. 8 is a longitudinal, schematic crosssectional view showing a valve to change the pressure in the pressure chamber of the carburetor of FIG. 7.
Internal combustion engines in general, and particularly internal combustion engines in which catalytic or thermal reactors (or both) are located in the exhaust systems should have the mass ratio of fuel and air supplied to the engine carefully controlled. Noxious components in the exhaust of the engine can then be effectively eliminated, or reduced to a negligible value. The air-fuel mixture is controlled by controlling the air number A, which may briefly be referred to as )t-control, under command of signals representative of the composition of the exhaust gases from the internal combustion engine.
A control loop suitable in the present invention is illustrated in FIG. 1, in which an internal combustion engine, schematically shown at 10, has an air-fuel mixture applied thereto by means of an equalized pressure, or constant pressure carburetor l1. Carburetor 11, the construction of which will be referred to in detail below, controls the relative application of air and fuel, in dependence on engine load, the loading itself being essentially derived from the position of the throttle 12 located in the intake 13 to the internal combustion engine 10. The air mass, or quantity, applied to the engine is controlled within the carburetor 11 by means of a control element 14, as schematically indicated, and having a non-linear position-air flow transfer curve, as schematically shown inFIG. 1. Fuel, likewise, is supplied within the carburetor by means of a fuel adjustment system 15, which likewise has non-linear characteristics. The internal combustion engine 10 has an exhaust system; an exhaust gas sensor 16 is located in sensing relationship to the exhaust gases from the engine 10 (as schematically indicated) to provide an electrical output signal from which'the composition of the exhaust gases can be determined. The output signalof the sensor 16 is applied to an element 17, at which it is compared with a predetermined reference derived from a reference generator 17a. Element 17, acting as a comparator, thus will provide an error output if the exhaust gas sensor provides a signal which deviates beyond a predetermined level indicative of deviation of the air number A from a pre-setvalue, for example k 1 (or another, predetermined value). The resulting error is applied to a control circuit 18 which preferably is an integral controller, that is, a circuit having integrating characteristics. In order to control the air number rapidly to a desired value, the integrating characteristics of controller 18 can be variable, with respect to time, that is, the time constant, that is the integration time constant of the controller may be variable. If, for example, sensor 16 provides an output signal for a predetermined period of time indicating that the air number k deviates from k 1, then the time constant of integral controller 18 is changed to provide for more rapid control action of the control loop and to regulate the input to the internal combustion engine more quickly so that the air number A will have the desired value of unity. A system of this type is described in US.
application Ser. No. 314,922, filed Dec. 14, 1972 and cross reference there listed, to which reference may be made. Controller 18 is connected to a control amplifier 19 which, in turn, connects to an electrical signalposition transducer 20 to convert the signals derived from amplifier 19 into mechanical output positions. Transducer 20 controls the positioning of a controlled element in the system, for example the needle of a needle valve through which fuel is supplied to the fuel supply system 15 and then to the engine.
The control loop of FIG. 1 controls the air number A of the air-fuel mixture being supplied to the engine 10 by changing the nozzle opening of the fuel nozzle of carburetor 11. It is equally possible to otherwise control the supply of fuel to the carburetor 1 1, for example by controlling the pressure in the mixing chamber of the carburetor 11 in dependence on the output signal derived from sensor 16 and connected over a control circuit, for example a circuit similar to that including elements 17, 18, 19, 20.
An equalized pressure carburetor 11 is shown in FIG. 2. This carburetor has a cross bore 21, which may also be termed the mixing chamber, in which an air pressure responsive slider or piston 22 is slidably located. A fuel nozzle arrangement 23 extends into the mixing chamber. Throttle 12 is likewise located in the cross bore 21. Slider 22 is generally hollow and cylindrical, closed off at the end, to form a cup-shaped piston Slider 22 is formed with a bore 24 extending from the interior through one end surface extending into the cross bore 21. Bore 24 connects to a pressure chamber 25, so that any vacuum within mixing chamber 21 is transferred, to the chamber 25. Chamber 25 is defined on the one hand by the cover 26 of the carburetor, and on the other by a membrane 27 connected to slider 22 as well as with the cover 26, Membrane 27, at its other side, defines a second pressure chamber 28 in which a reference pressure is maintained. The air slider is guided in a central opening or bore formed in the structural unit 29, which also defines and forms the mixing chamber and may be part of the inlet to the internal combustion engine. A spring 30 is interposed between theinside of the carburetor cover 26 and the air slider, which can move against the compressive force of the spring. A bushing 31 is secured to the" inside of the air slider 22, within which an armature 32 of a solenoid is located. Armature 32 has a valve needle 33 secured thereto. Needle 33 extends into a fuel nozzle opening 34. Armature 32 is held by two compression springs 35, 36, likewise contained within bushing 31. Compression spring 35 bears against one end'surface of armature 32, and further on the inner surface 37 of bushing 31. The other spring bears against the other end surface of the armature 36 and against a cover or end piece 38 closing off bushing 31. End piece 38 of bushing 31 is additionally connected by means of rod 39 to a piston 40 which is slidable within a chamber 41 filled with a damping fluid. Piston 40 is so dimensioned that a slight amount of fluid 41 can leak along the sides thereof, so that-piston 40 in chamber 41 will act as a dashpot, to dampen movement of the slider22. A solenoid coil 43, formed of two separate windings, is located in the part of the carburetor 26 which extends interiorly of chamber 25, to influence movement of the armature 32.
Fuel supply nozzle opening 34 is located at the other side of air slider 22. Needle 33 is slidably located within the nozzle opening 34. The opening 34 is formed by a hole in the end surface of a sleeve 44, retained within the guide tube 45. Guide tube 45 is secured to the central unit 29 of the carburetor, and sleeve 44 is adjustable by means of a set screw 46. Adjustment of set screw 46 controls the idling fuel supply of the carburetor. Screw 46 is guided in the holding plug 47 which is screwed into the central unit 29 of the carburetor.
The central unit 29 is hollow, and includes a float chamber 49 therein. A cover 48 is secured to the central unit 29, to close off the float chamber. A float 50, operating a float valve 51 is located within the float chamber in order to control the flow of fluid to the carburetor chamber 49.
Operation: The operation of an equalized pressure carburetor in general is known. Upon opening of throttle 12, from the position shown in FIG. 2, more air flow will pass through the bore, or mixing chamber 21. Due to the increased air requirements of the internal combustion engine 10, not shown in FIG. 2, the air speed around the slider 22, and guide tube 45, will increase. The increased air, speed'increases the vacuum within the mixing chamber. The vacuum is transferred over bore 24 to the interior of the cup-shaped air slider 22, that is, to first chamber 25. As the vacuum in first chamber 25 increases (that is, as the pressure decreases), the air slider is pushed upwardly against the force of the helical spring 30, and the weight of the slider itself. This increases the space between slider 22 and guide tube or sleeve 45. The slider will move upwardly until a balance will arise between the weight of the slider, the force of the spring 30, and the vacuum in chamber 25. The slider thus responds to pneumatic pressure (in the particular application to negative pressure with respect to ambient air, i.e., to vacuum) and thus is used as a pressure responsive element, or piston. The arrangement isso taken that under balance conditions, and for any operating condition of the internal combustion engine, the air-fuel mixture will be set to have an air number ofX 1. In order to accurately adjust the air number to the value of unity however, the electromagnet can be energized so that armature 32 will be moved under influence of energization of current supplied to coil 43. The two windings of coil 43 are I so selected that the forces derived from the two windings are opposite to each other. Thus, when the error signal is zero, that is, when the air number is as desired,
for example A 1, both windings have current flowing therein which is equal so that the sum of the magnetic fields will be zero. If one. of the two windings has more current than the other one, upwardly or downwardly directed forces will act on armature 32 which is formed as a permanent magnet. Thus, the needle 33 connected to the armature 32 will be moved within the fuel nozzle opening 34 to change the fuel flow to the engine, regardless of the position of the air slider 22, with respect to the opening (34); as determined by air demand, or vacuum within the mixing chamber 21. Changes in the position of the air slider 22, due to changes in loading on the engine (as determined, for example, by operating conditions of an automotive vehicle) will not have any effect on the position of the armature 32 with respect to the slider 22, since the position of the armature 32 within its guide bushing 31 is entirely independent of position of the air slider 22 with respect to the nozzle opening 34. Rapid oscillations of armature 32 are prevented by the dashpot 40, 41.
Embodiment of FIG. 3: The basic construction of the equalized pressured carburetor of FIG. 3 is similar to that of FIG. 2; similar parts have been given the same reference numerals and will not be explained again.
The essential elements, air slider 22 slidable in the central element 29 and supported against the pressure of a spring 30 in the housing of the carburetor are present. Likewise, a needle to control a needle valve is secured to the armature 32 of a solenoid to control the size of the opening of fuel nozzle 34. The armature 32 is guided in a sleeve 52. Armature 32 is secured in central position by a pair of compression springs 53, 54, bearing against opposite sides of the armature 32. The other ends of the springs bear against the inner surface 55 of sleeve 52, on the one hand, and the second spring 54 bears against a cover plug 56 of the carburetor. The air slider 22 changes position under differential pressure .in chambers 25, 28, the vacuum within the mixing chamber being transferred into chamber 25 through bore 24, as in the embodiment of FIG. 2. The second chamber 28 carries reference (atmospheric) pressure,
and motion of the slider 22 essentially dependson the vacuum in the mixing chamber of the carburetor. The
lower part of the carburetor has a float chamber with a float, as known, which controls the supply of fuel to the carburetor. The armature 32 is moved under influence of current flowing in coil 57 surrounding sleeve 52. The difference in the construction according to FIG. 3 lies in the coil 57, which carries a single winding. The springs, and the normal current through the winding are so arranged that, if the control current is derived from amplifier 19 (FIG. 1) an average excitation current normally flowing through winding 57 is either increased or decreased. The armature then can be a soft iron core. Theneedle 33 of needle valve 34 is moved upwardly or downwardly, that is, enters the nozzle 34 more or less, in dependence on the magnitude of the control current flowing through winding 57. This increases or decreases the attractive force acting on the armature 32, and as a result of movement of armature 32, needle 33 moves upwardly or downwardly, until a new equilibrium position between magnetic attractive force acting on the armature. and the relative forces due to spring 54, and spring 53 is established. The displacement-force characteristics of spring 54 can be matched to the displacement-magnetic force characteristics of the electromagnetic position transducer system formed by coil 57 and armature 32, so that feedback on the armature upon movement of the air slider 22, due to change in loading on the engine, can be compensated.
Embodiment of FIG. 4: The construction is similar to that described in connection with FIGS. 2 and 3 and similar elements have been given similar reference numerals and will not be described again. The air slider 22, in this embodiment, is moved in the mixing chamber in dependence on vacuum therein. The reference chamber determines the position of slider 22. If a pressure differential is sensed between the pressures in chamber 25 and chamber 28, membrane 27 which is secured to the slider will be deflected. thus adjusting the position of slider 22. Slider 22 is secured to the housing of the carburetor by means of spring 30. Opposite the slider is the fuel supply nozzle which includes a guide sleeve'45 within which a sleeve 44 is placed. Nozzle opening 34 is formed in the inner end surface of sleeve 44, the effective flow diameter of which is determined by the depth of penetration of the needle 33.
The position of needle 33 is determined on the one hand by the position of the slider 22. Additionally, needle 33 can be moved by the action of current flowing through coil 61. Air slider 22 is formed with a central bore 58. A shaft-shaped extension is slidable in bore 58, extension 60 hearing against a spring 59 within the bore 58. Shaft 60 functions as the armature for coil 61. As coil 61 is energized with currents of different magnitude, shaft 60 and the attached needle 33 slidable. in opening 34 is pulled into the central bore 58 more, 0r less, so that an additional change in effective opening size of the nozzle 34 is obtained, independently of the position of the air slider 22, and depending on the current flowing in coil 61.
FIG. 5 illustrates, in greater detail, the arrangement of the needle valve and the opening for fuel supply. The remainder of the carburetor may be constructed in connection with any one of the embodiments FIGS. 2-4, for example. Needle 33 is guided in a sleeve 62 having an upper end surface 63 in which the fuel opening 64 is formed. The effective clear cross section of the opening 64 will depend on the depth of-penetration of the tapering needle 33 within sleeve 62. Sleeve 62 itself isretained in a guide tube 65. A fuel duct 66 is formed in guide tube 65, extending in a direction axially parallel to the longitudinal axis of the needle 33. Duct 66 terminates in the mixing chamber of the carburetor; the other end matches a cross bore formed in the wall 67 of sleeve 62. Duct 66, together with the cross bore, provides a bypass for fuel, with respect to the fuel nozzle 64 in sleeve 62. The effective flow through the bypass can be changed by rotating sleeve 62 with re spect to the guide element 65, so that the cross bore will match more, or less, with the end of the duct 66, and thus change the effective flow diameter of the connection between the interior of sleeve 62 and duct 66. This rotation of the duct can be effected electromagnetically, under control of an electromagnet which has current flowing therethrough depending on the output signal of the oxygen sensor 16 (FIG. 1) in the exhaust system of the internal combustion engine. The needle 33 is then secured to the slider 22 of the carburetor. The needle 33 may be of uniformly tapering outline, or may be formed with a taper which follows a curve to provide nonlinear relationship of deflection of the slider, and hence needle 33, with respect to cross section diameter of the opening 64. Likewise, the cross bore 67a, which matches duct 66, may have a suitably shaped configuration so that rotation of sleeve 62, and hence wall 67 in which opening 67a is formed, with respect to resulting constriction of the matching opening with duct 66 in nonlinear, and in accordance with design criteria matching current flow through a coil 167,. energized for example from amplifier 19 (FIG.'1) to re- 7 v sulting control of fuel flow from duct 66. To effect rotation, a pancake, or flat coil 167 can be located beneath the lower end of sleeve 67 which is closed off by a small disc-magnet 168, having semicircular poles as schematically indicated by S and N in FIG. 5.
Various other systems to change the effective cross sectional flow opening of the fuel nozzle 35 can be uti- Iized. For example, a slider can be used to change the air opening between sleeve 44 and needle 33 of the carburetor, the slider being in form of a push element, a
. lamella, or the like. The slider, or control lamella can be controlled, as in the other examples, by means of an electromagnet which has control current applied thereto, the intensity of which depends on the output control signal representative of composition of the exhaust gases, as sensed by the sensing element 16 ('FIG. 1). Depending on the magnitude of the control current, and if desired, also on its direction, a slider is introduced more or less, in longitudinal direction, in sleeve 62, to increase or decrease an otherwise constant flow opening of fuel. Control by means of a lamella may also be obtained by changing the opening of a lamella closure, which may be constructed similar to the diaphragm of a blade-type photographic shutter.
In the embodiments heretofore described, the massratio of the air component and fuel component of airfuel mixture was controlled by controlling the flow rate of fuel to the mixing chamber as a function of the control signal from the output of the oxygen sensor, and additional to (and independently of) control of the fuel opening as commanded by the fuel demand of the engine. The correction of the mass-ratio of the air and fuel components can also be obtained by other systems. For example, pressure within the mixing chamber of the, carburetor can be changed as a function of the sensed exhaust signal.
Changing the air slider 22, under the influence of extraneous forces, changes the pressure within the mixing chamber by changing the air flow immediately adjacent the fuel nozzle 34, and thus changes the conditions under which fuel is sucked out of the fuel supply opening. If the cross sectional area of the air path decreases, by movement of air slider 22 into the mixing chamber, a simultaneous decrease of the cross sectional area of the nozzle opening will result since the conical needle 32 penetrates further into the nozzle 34. Due to the increased air velocity, however, at the edge of the nozzle opening 34, and the resulting increased vacuum, the air-fuel mixture will become somewhat richer since more fuel will be removed due to the increased vacuum.
In the embodiment of FIG. 6, the vacuum in the mixing chamber of a carburetor is determined, in part at least, by the output signal derived from the oxygen sensor 16 (FIG. 1) in the exhaust system of the internal combustion engine. Parts similar to those previously described in connections with FIGS. 1-5 have been given the same reference numerals and will not be described again. The cross bore 21 in the central element 29 of the carburetor has slider 22 located therein. Slider 22 is suspended by a membrane 27 which forms, at opposite sides, a limit for the vacuum chamber 25 and the reference or pressure chamber 28. As before, the position of the slider 22 will be determined by the equilibrium which will obtain in view of the vacuum arising in the mixing chamber 21 due tothe operation of the engine and position of throttle 12, spring pressure and weight of the slider 22. A sleeve 68 is located within the slider which is formed with a relief at its lower side, shown at 69, in which a shaft-shaped extension 70 of needle 71 is secured, and locked in place by means of a set screw 72. Needle 71- is slidable in the fuel nozzle opening 73, formed in a sleeve 74. Sleeve 74 is retained in a guide tube or sleeve 75, in turn secured to a screw 76. The free opening of nozzle 73 is determined by the depth of penetration of needle 71, and thus changes the fuel flow through the nozzle. The carburetor has a float 77 to control the amount of fuel flow to the carburetor. A soft iron core 97 is located within sleeve 68, and thus secured to the slider 22. Sleeve 68 extends at least partially within the interior of a winding 78, which acts on the soft iron core 97, so that core 97 in effect will be an armature for winding 78, to attract, or repel the armature 97. Coil 78 is secured to the housing of the carburetor. The coil 78 can be so wound that it has two windings with resultant magnetic forces which, if there is zero control current, the magnetic forces will be in balance, to cancel each other. It is also possible to form the coil with a single winding, as explained in connection with FIG. 3, ,in which an average current flows which, depending on error signals, increases or decreases from a median value as commanded by the oxygen sensor in the exhaust system.
- Embodiment of FIG. 7: The shifting of the air slider, and thus the change in the pressure relationships within the mixing chamber are determined by the chambers 25 and 28. Chamber 25 has the pressure (or rather, vacuum) present in the mixing chamber of the carburetor applied thereto, duct or bore 24 within the slider 22 forming a direct connection to chamber 25. Chamber 28 has a reference pressure, usually ambient air pressure applied thereto, the position of the slider being determined by the differential pressure in chambers 25 and 28. Shifting of the slider can thus be obtained by changing the pressure'in either one of the chambers 25 or 28. This can be done simply by controlling pressure equalization between the two chambers 25, 28. Slider 22, which is suspended on membrane 27 is thus changed in position, so that control of the air-fuel ratio of the mixture applied to the engine can be effected by changing the pressure in the mixing chamber. In general, the construction is similar to that explained in connections with FIGS. 2-6. Change in pressure is best obtained by controlling the pressure in chamber 28 and then controlling equalization of pressures between the chambers 25 and 28. The two chambers have connecting elements 78,79'secured thereto, connector 78 connecting over a bore 80 with chamber 25, and connector 79 connecting over a bore 81 with chamber 28 The two connectors 78, 79 are connected to a control valve, seen in detail in FIG. 8. The two connections, 78, 79 are connected, respectively, to connectors 82, 83 of the valve shown in FIG. 8. The valve has a valve body 84 with a slidable piston 85 which is formed with an armature 86 extending into the interior of a helical compression spring 87. Spring 87 bears on one side to the facing surface 88 of piston 85 and on the other to the interior of the valve housing 89. The upper part of the valve body 84 supports a coil 90 which, upon excitation, attracts or repels the armature and thus changes the position of the control piston 85. Control piston 85 is formed as a double-cone, arranged such that the smaller cross sectional surfaces of the cones are facing each other. The narrowest portion of the double-cone 85 has a cross bore 91 therein which extends or connects to a longitudinal bore 92, connecting with the interior 93 of the valve body 84 and, in turn, to the connector 83 which leads to the second pressure chamber 28 over connector 29. A cross bore 94 further extends to the space formed by the constriction of the piston 85, at the junction of the tip part of thecones, to vent which additional bore duct 95 is connected to the connector 82 which leads to chamber 25.
Operation: Let it be assumed that, over the entire operating region, the carburetor should provide a mixture which is on the lean side. If no current is supplied through the winding 90, piston 85 will seat against the lower part of the housing, since compression spring 87 will force the piston downwardly. Cross bore 94 has outside air applied, so that pressure existing in bore 91, and longitudinal bore 92 will. be at ambient outside pressure, and chamber 28 will likewise have'ambient outside pressure. The first pressure chamber 25 will be closed off and disconnected from the valve.
A lean mixture means that the air number is 1. The oxygen sensor 16 (FIG. 1) will sense an excess of oxygen, and a control current will be supplied from amplifier 19 to coil 90. The amplitude of the control current will depend on the controller 18, and amplifier l9, and, in dependence on the amplitude of the control current, armature 86 and with it control piston will be pulled upwardly, more or less, against the force of spring 87. Upward motion of piston 85 provides a connection between the first carburetor chamber 25 and the second chamber 28 (longitudinal bore 92, cross bore 91, cross bore 95). The cross bore 94 which is connected to ambient outside pressure is gradually closed off. As the current through winding 90 increases, the pressure differential between the first chamber 25 and the second chamber 28 will become less and less until the two chambers 25, 28 will have equal pressure arising therein. As the pressure difference decreases, slider 22 will be moved downwardly, causing an increase of fuel component of the fuel-air mixture (a richer mixture). If the current through coil 90 drops, the effect will reverse, and the piston will move downwardly. The system is preferably so set that an average excitation current will flow through winding 90 when there is no control signal from sensor 16 (indicative of air number A l The control piston 85, as well as the air slider 22 will slightly oscillate or vibrate about an average value at which A is approximately equal to unity.
The contruction illustration in FIGS. 7 and 8 has the particular advantage that a carburetor of the type of F IG. 7, that is, a standard carburetor can be used and the air slider thereof can be additionally controlled as a function of the composition of exhaust gases, that is, the mass-ratio or mass relationship of the air component and fuel component of the mixture applied to the engine can be influenced without changes of the con struction of the carburetor beyond tapping the vacuum chamber, and, the air reference chamber thereof, and connecting the taps to a control valve as shown in FIG. 8 and described in connection therewith.
Variou schanges and modifications may be made and features discussed and described in connection with the drawing of any embodiment may be used with other embodiments, within the scope of the inventive concept.
1. Apparatus to control the air component and fuel component of the air-fuel mixture supplied to an internal combustion engine (10) having sensing means (16) sensing the composition of the exhaust gases and providing an electrical control signal, and a carburetor (11) having control means (22, 23) supplying fuel to the mixing chamber in dependence on commanded fuel requirements of the engine for mixture of a mixing chamber (21) the fuel component and the air component and for application to the engine wherein the carburetor comprises means forming a fuel nozzle opening (34, 73), and a needle (33, 71) movable within the fuel nozzle, the nozzle opening, upon relative selective positioning of said nozzle and needle being electrically controllable and arranged to additionally control supply of fuel to the mixing chamber, and being connected to and controlled by said electrical control signal and operatively connected to the carburetor fuel supply means to additionally regulate the relative flow of the fuel component of the mixture with respect to the air component, independently of demand of fuel-air mixture by the engine, under control of said electrical control signal provided by the sensing means to adjust the mass ratio of the air and fuel components of the mixture being applied to the engine in dependence on the composition of the exhaust gases;
and wherein the fuel supply means includes an air pressure responsive piston (22) movably located in the path of the air stream supplied to the engine upon engine operation, the needle (33, 71) being slidably located in the piston (22) and movable under control of said control signal.
2. Apparatus according to claim 1 further comprising an electrical network connected to receive the control signal from said sensing means and comprising a control circuit having non-linear amplification (l8) and a control amplifier (19), the controllable means being positioned by said amplifier.
3. Apparatus according to claim 2 wherein the control circuit is an integrating circuit.
4. Apparatus according to claim 1 wherein the'electrically controllable fuel nozzle includes a solenoid coil system (43), and an armature (36) therefor, the armature being connected to the needle (33, 71 movement of the armature with respect to the coil changing the position of the needle with respect to the nozzle opening (34, 73). 4
5. Apparatus according to claim 4 wherein the armature is a permanent magnet.
6. Apparatus according to claim 5 wherein the solenoid coil system includes a pair of excitation windings (43), connected to provide mutually opposing magnetic forces acting on the permanent magnet upon excitation of the respective windings.
7. Apparatus according'to claim 5 wherein a pair of spring means (35, 36) are provided, the armature (32) being located between the spring;
one of the springs bearing against the air idler and the other spring bearing against the housing of the carburetor.
8. Apparatus according to claim 4 wherein spring means are provided supporting the armature in predetermined position with respect to the solenoid coil system;
and dashpot means (40, 41, 42) are provided, connected to the armature and dampening oscillatory excursions of the armature. 9. Apparatus according to claim 4 wherein the armature (32) is a soft iron core, and the solenoid coil system comprises an excitation winding (57) and means (19) are provided to supply a holding current to the excitation winding to maintain the soft iron core armature (32) in a predetermined rest position.
10. Apparatus according to claim 9 further comprising spring means (53, 54) bearing on opposite sides of the armature, the spring means supporting the armature floatingly between the slider and the housing of the carburetor.
11. Apparatus according to claim 4 wherein the solenoid coil system is secured to the carburetor housing.
12. Apparatus according to claim 4 wherein the solenoid system is secured to the piston (22) of the carburetor (11).
13. Apparatus according to claim 1 including movable means located adjacent the gap between the needle (33, 71) and the nozzle opening (34, 73) to change the relative side of the opening of the gap between the needle and the nozzle;
the position of the movable means being controlled under command of said control signal.
14. Apparatus according to claim 1 wherein the carburetor includes means forming a fuel nozzle opening (34, 73) and a needle (33, 71) movable within the fuel nozzle; and
the electrically controllable fuel nozzle includes a lamella locatedin the gap between the fuel nozzle opening (34, 73) and the needle (33, 71) to change the relative opening of the gap between the nozzle and the needle, the position of the lamella being controlled under command of said control signal.
15. Apparatus according to claim 1 comprising a sleeve (62) having an end opening forming said fuel nozzle opening (34); i
a cross bore formed in the wall (67) of the sleeve;
a guide tube (65) surrounding the sleeve; and a duct (66) within the guide tube and terminating in the mixing chamber (21) of the carburetor at one end, and adjacent the cross bore of the sleeve (62) at the other end;
the sleeve (62) and a guide tube (65) being relatively movable to effect alignment, or misalignment of the cross bote and of the duct (66);
and electrical means (167) controlling relative movement of said sleeve and said guide tube to control the flow of fuel from said sleeve through said cross bore into said duct, under command of said control signal.
16. Apparatus according to claim 1 wherein the electrically controllable means comprises means controlling the pressure in the mixing chamber (21) of the carburetor (11) said means being connected to and controlled by said electrical control signal provided by said sensing means.
17'. Apparatus according to claim wherein the sleeve and guide tube are relatively rotatable, and said motion controlling means effect relative rotation of said sleeve and said duct to effect relative alignment, or misalignment of the cross bore and one end of said duct (65 and thus the flow of the fuel component from the carburetor to the mixing chamber.
18. Apparatus according to claim 16 wherein said pressure control means comprises electrically positionable means controlling the position of the pressure responsive piston (22) in the carburetor in dependence of the output signal from said sensing means.
19. Apparatus according toclaim 16 wherein said pressure control means comprises an armature (97) and an electromagnet, the armature being secured to the air slider (22) and the electromagnet being secured to the carburetor housing, relative excitation of the coil of the magnet shifting the position of the slider within the carburetor.
20. Apparatus according to claim 19 wherein a pair of pressure chambers (25, 28) are provided locating the piston (22) in the carburetor and adjusting the relative position, with respect to the carburetor housing of said slider in dependence on vacuum in the intake to the engine;
and said pressure control means (90) comprises electrically controllable valve means controlling the pressure in at least one of said chambers in dependence on the electrical control signals provided by said sensing means.
21. Apparatus according to claim 20 wherein one of said pressure chambers has ambient air pressure applied thereto, and the other of said pressure chambers has pressure within the mixing chamber of the carburetor applied thereto;
and the valve means are connected to controllable under command of said electrical signal provided by said sensing means (16), selectively equalize the pressures within said chambers (25, 28).
22. Apparatus according to claim 21 wherein said valve means comprises a control piston and means controlling the position of said piston within the valve means, connected to and controlled by said control signal from said sensing means (16);
and connecting ducts connecting the pressure chambers (25, 28) to said valve means, the position of the control piston, as commanded by said control signal, selectively and continuously adjusting the relative pressure in the pressure chamber (25) connected to the mixing chamber (21).