CA1107376A

CA1107376A - Fuel demand engine control system

Info

Publication number: CA1107376A
Application number: CA308,061A
Authority: CA
Inventors: Lael B. Taplin
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1977-09-29
Filing date: 1978-07-25
Publication date: 1981-08-18
Also published as: ES473829A1; GB2009458B; DE2836067A1; IT7828161A0; IT1099198B; JPS5458136A; FR2404742A1; US4138979A; GB2009458A

Abstract

816.008 FUEL DEMAND ENGINE CONTROL SYSTEM

ABSTRACT OF THE DISCLOSURE

An electrically controlled closed loop system for maintaining a desired air-fuel ratio within an internal combustion engine. An operator-positioned accelerator commands a given fuel flow into the engine and the flow of air is controlled by means of a servo-actuated throttle plate. The commanded fuel flow and present position at the throttle plate are used to generate a basic command signal for controlling the servo motor to adjusting the position of the throttle plate. A gas detector or roughness sensor positioned in the engine is responsive to the actual air-fuel mixture in the engine which may be greater than or less than the desired air-fuel mixture and an error signal is generated which can be used to modify or correct the basic control signal in a closed loop manner for selectively adjusting throttle plate position to more precisely maintain a desired air-fuel ratio. While the present type of system has inherent acceleration enrichment since the fuel enters before the air flow increases, an undesirable condition of excessive enrichment may occur. The rate of change of commanded fuel flow is monitored to anticipate an impending undesirable condition of excessive enrichment and a transient control signal adjustment spike is generated to momentarily increase air flow to minimize the undesirable condition even before the gas detector or roughness sensor actually detects the existence of same. A closed loop governing system for metering the fuel flow may also be provided, if desired.

Description

816.008 BACKGROUNC) OF THE INVENTION
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Field of the Invention .

This invention relates to an electronic system for controlling the air-fuel mixture in an internal combustion engine and more particularly to a closed loop system for maintaining a desired air-fuel mixture in an internal combustion engine wherein the operator commands a given fuel flow and the control system adjusts air flow to maintain the desired air-fuel ratio.

Description of the Prior Art In recent years, the importance of maintaining a desired or optimal air-fuel ratio in an internal combustion engine has been increasingly emphasized. Recent health and safety concerns aimed at lowering or eliminating pollution and the like have been enacted into federal, state and local laws regulating emission standards. Today's internal combustion engines, such as those used in automobiles and the like, must conform to those standards and must, under substantially all operating conditions, generate and emit no more ~: :
than a predetermined amount of air pollutants such as carbon monoxide, non-combustible hydrocarbons, and various oxides of nitrogen.

Experience has shown that for each internal combustion engine, and for each set of conditions under which ~hat engine operates3 there exists certain deslred air-fuel ratlos which must be maintained for insuring optimal control over the generation and~ emission ~of pollutants~ Similarly, it has been found that there also exists, for a given engine and for a given set of englne operating conditions, optimal air-fuel ratios which produce optimal drivability.
Recent fuel~shortages and the ever-increasing cost of fuel has caused lncreased concern, and more recently ~legislation has been enacted se~ting various miles per gallon standards~for automobiles. ~ f~

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816.008 Therefore, -the number of miles per gallon is one irnportant aspect of drivability and another aspect relates to how responsive the internal combustion engine is to operator commands without stalling, sputtering, or producing engine roughness and the like.

Unhappily, there is, in many cases, a direct conflict between the optimal air-fuel ratio required for maintaining the minimal generation and emission of pollutants and the air-fuel ratio requlred for maintaining optimal drivability. Therefore, modern engines are usually required to select an air-fuel ratio which conforms to all regulations governing th~ generation and emission ofpollutants while providing the optimal drivability possible under such circumstances.

In most internal combustion engines, an accelerator is provided which can be selectively positionable by the operator to command a given air flow by selectively positioning a throttle valve and then fuel is metered into ~he engine by any of several methods, as by carburators or fuel injectors or the like.
In most systems designed for maintaining a predetermined air-fuel ratio1 for example in U.S. Patent 1~1O. 3,7~0,~32 for an "Electronic Control for the Air-Fuel Mixture and for the Ignition of an Internal Combustion Engine", the quantity of metered or injected fuel is varied to maintain the desired air-fuel ratio. Such systems have many inherent problems including the need for some syst~m of providing acceleration enrichment when the internal combustion engine is accelerating or some type of fuel enrichment during initial start and engine warm-up.

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816.008 Relatively few systems, such as that shown in U.S. Patent No.
3,983,848 for a "Fuel Injection System" allow the operator to command a given fuel flow and then control the flow of air to maintain a predetermined air-fuel ratio and most such systems require rather expensive and complex means for sensing the actual air flow~in the engine intake and do no,t use so?me form of negative feed-back for correcting air flow to obtain a more precise control overthe desired or optimal air-fuel ratio.

Still other systems~ such as that illustrated in U.S. Patent No.
3,738,341 for a "Device for Controlling the Air-Fuel Ratio in a Combustion Engine" are able to more accurately control air-fuel ratio by varying the quantity of injected fuel in accordance with a feed-back signal indicative of the level of carbon dioxide present in the exhaust system. While this is a relatively crude pollution control means, it does not possess the degree of sensitivity required for maintaining optimal drivability and the system must still provide some type of acceleration enrichment or the like.

The present invention does not require a separate acceleration enrichment system slnce it has inherent or automatic acceleration enrichment because the fuel flow commanded by the operator enters first and then the air flow increases.

The present invention avoids the problems and disadvantages of the prior art by providing a control system for selectively varying air flow in response to operator commanded fuel flow. Basic control is determined by various engine operating parameters including fuel flow and a closed loop system :
IS provided for sensing a parameter indicative of the actual air-fuel mixture existing In the enp,ine for adjustlng or correcting the control ~o maintain the desired or optimal air-fuel ratio.

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~16.008 SUMMARY OF THE INVENTION
__ The closed loop system of the present invention controls the air-fuel mixture in an internal combustion engine so as to maintain a desired ~r optimal air-fuel ratio under most engine operating conditions. An accelerator means is responsive to operator command for supplying a predetermined quantity of fuel to the engine and means are provided for controlling the air flow into the engine. Means responsive to the accelerator means are provided for genera-ting a first signal indicative of the quantity of supplied fuel and means responsive to the air flow control means generate a second signal indicative of the present actual air flow into the engine. Computing means are provided which is responsive to at least the first and second signals for generating a basic control signal for regulat;ng the air flow control means. Means responsive to the actual air-fuel mixture existing in the engine are provided for generating the feed-back signal and means responsive to the feed-back signal are provided for correcting ~:
the basic control signal so that the air flow control means may be responsiv2 thereto for selectively increasing and decreasing air flow into the engine to maintain a desired or optimal air-fuel ratio.

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The system of the presen~ invention possesses inherent or `~ ~ automatic acceleration enrichment, but if the accelerator means commands too rapid an lncrease in the fuel flow,~an undeslrable condltion of excesslve fuel enrichment may occur. In the preferred embodiment, means are provided for anticlpatlng an; irnpending conditlon of excesslve fuel enrichment and for generating a transient correction signal to temporarily increase air flow into the engine even be~ore~ the air-fuel mixture respohsive means can generate the feed-back signal indicative~of the actual existence of ~said candltion so as ~to m~lnim~ze said undeslrable co~ndition.

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816.008 In the present invention, the means responsive to the ac-tual air-fuel mixture existing in the engine for generating a feed-back sigrIal includes a gas sensor (in the preferred embodiment9 an oxygen sensor) but engine roughness sensing means or any similar means for providing a measure of the actual air-fuel mixture are also contemplated as being within the scope of the inventilon.

The invention also teaches an alternate embocliment which includes a fuel flow governing system wherein the accelerator means commands a given fuel flow and hence, a given engine speed, and maintains the desired engine speed by means of another closed loop control system.

The present invention also contemplates a closed loop method of maintaining a desired air-fuel ratio in an internal combustion engine comprisingthe steps of supplying a quantity of fuel to the engine under operator command, measuring a first parameter indicative of the actual air flow into the engine, controlling the air flow into the engine as. a function of the quantity of fuel supplied to the engine mder~ op.erator command and said measured parameter indica~ive oE actual air flow into the engine, measuring an engine operating parameter indicative of the actual air-fuel mixture existing in the engine and selectively increasing and decreasing the controlled air flow in response to themeasured engine operated parameter in a closed loop manner so as to maintain a desired or optimal air-fuel ratio under substantially all engine operating conditions. Again, the step of anticipating an impending undesirable condition of excessive fuel enrichment and increasing air flow to minimize same is contemplated in tlle preferred embodiment~.

Since the system of the present invention has inherent :~ acceleration enrichment, it is inherently more simple than many of the systems i: ~ used today. Th~erefore, it avoids the problems associated: with generating acceleration enrichment and the problems inherent in maintaining a desired air-f uel ratio during periods of acceleratlon enrichment.

~ ~, ~16.008 Unlike those few systems of the prior art which cornmanded fuel flow and then electrically controlled air flow to maintain a desired air-fuel ratio, the present invention is not nearly as susceptible to undesirable conditions of excessive enrichment which occur whenever the commanded fuel flow is caused to increase too quickly or the like since means are provided for anticipating such an undesirable condition and for minimizing same.

The system of the present inven-tion is able to more accurately and precisely control and maintain a predetermined optimal or desired air-fuel mixture since the feed-back signal, which in the preferred embocliment of the present invention is taken from an oxygen sensor in the exhaust system of the engine, it is used to adjust a basic or scheduled control signal in order to "fine tune" or correct or adjust the air flow to more accurately maintain and control the desired air-fuel ratio under substantially all engine operating conditions.

The method and apparatus contemplated by the preferred embodiment of the present invention provides a means for operating an internal combustion engine in a closed loop mode based upon various sensed engine operating parameters so as to accurately permit the engine to maintain a predetermined optimal or desired air-fuel mixture which can be selected to meet all pollution standards while pPoviding the best~possible drivability under suchcircumstances. The system of the present invention is relatively inexpensive9 simple, easy to maintain, and provides a high degree of adherence to a desired or programmed air-fuel ratio, together with the superior engine smoothness and drivability inherent therein, heretofore unattainable or commercially unfeasable` ` ~ in the systems of the prior art.

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816.008 Other advantages and meritorious features of the present invention will be more fully understood from the following detailed description of the drawings and the preferred embodiment, the appended claims and the drawings, which are briefly described hereinbelow.

BRIEF DESCRIPTION O]F THE DRAWINGS

Figure I is a block diagram illustrating the closed loop control system of the present invention;

Figure 2 is a schematic diagram of the anticipation circui try, closed loop control circuitry and error correction circuitry of Figure l;
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Figure 3 is a block diagram illustrating an alternate analog implementation of the electronic control unit of block 35 of Figure l;

Figure 4 is a block diagram illustrating the closed loop f uel control governing system which may be used with the system of the present invention; and :: ~ Figure 5 is a block diagram illustrating an alternate embodiment of the circuitry of block 188 of Figure 4.

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816.008 DESCRIPTION OF TH~ PREFERRE~D EMBODIME11~1T

~ igure l shows an internal combustion engine 10 havin~ an intake system 11, an exhaust system 12 and an output shaft 13 which is operatively rotated by the combustion of fuel and air within the engine 10, as conventionally known.

The intake system ll includes an intake manifold 14, an air inlet apparatus lS, and a throat or conduit 16 communicating the air inlet apparatus 15 with the intake manifold 14. A throttle valve 17, SUCtl as a conventional butterfly valve or the like, is operatively disposed within the throat 16 to control the flow of air between the air inlet apparatus 15 and the intake manifolcl 14 and therefore to the individual, conventionally known cylinders~ not shown, but known in the art, for varying or controlling the air-fuel ratio or mixture within the intake system ll, or alternatively within the individual cylinders of the engine 10, as conventionally known.

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A conventional fuel pump or fuel supply system 18 supplies fuel to an inlet means 19 in a fuel port assembly 20 via fuel conduit 21. A fuel metering rod 22 is at least partially disposed within the inlet l9 of the fuel inlet port 20 for controlling or metering via its position within the inlet l9 the quantity of fuel supplied from the conduit 21 through the inlet l~ and into the intake sy~tem 11.

An accelerator ~pedal 23 is provided which can be selectively positioned by the operator of the vehicle to command or positively control a prede~ermined ~fuel; flow as hereinafter described. ~ A linkage assembly~ 2~ is operatively connected between the accelerator pedal 23 and a control end of the 9_ .~ . ~ . . . ..

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fuel meteriny ro~ 22 so as to selectively vary or adjus-t-the position of the fuel metering rod wlthin -the Euel port 20 so as to control the quantity of fuel supplied by the fuel pump 18 and the conduit 21 through the inle-t 19 and into the intake system 11 of the engine 10. Therefore, in -the system of the present inven-tion, the operator positively commands the quantity of fuel to be supplied to the internal combustion engine 10 by selectively positioning the accelerator 23 and thereby positively con-trolling the position of the fuel metering rod 22 via the linkage assembly 24.
A conventional positional tran.~i~ucing rneans 25 is opera-tively associated with a portion oE the linkage assembly 24, or alterna-tively with the fuel metering rod 22, in order to sense the relative positi~n thereof and generate a first electrical signal on lead 26 which is indicative of the relative position o-E one of the accelerator 23, the linkage assembly 24 or the fuel metering rod 22 and which is also, therefore, propor-tional to and indicative of the quantity of fuel commanded to be supplied to the intake system 11 through the inlet 19.
A means ~or sensing the n~nifold absolute pressure within the in-take manifold 14 is represented by the block 27 which is opera-tively connect-ed to the intake manifold 14 via conduit 28. me contents of the manifold absolute pressure detection syste~ of block 27 is conventional and may be, for examlple, that shown in co-pending Canadian Patent Application Serial No. 308,503 for a "Closed Loop Exhaust Gas Recirculation Control System"
which was filed on July 31, 1978 and which is assigned -to the assignee of the present invention. It will, of course, be understood -that, sinae the preferred embodLment of the present invention discloses a system which is prim~rily analog in nature, only the analog portion o~ the system disclosed in said ao-pending case would be used although the system of -the presen-t invention could also be converted to digital form by following the teach-ings shown in said co-pending application and by similar conversion techni-ques known in the art.

-pg/ i - 10 -816.008 Similarly, an engine speed sensing system or shaft position transducer is represented by block 31 which may be operatively associated with the output shaft 13 as indicated by the dotted line 32 so as to measure engine speed, RPM, shaft position, or any similar engille operating parameter, as knownin the art~ The block could, for example, contain the circuitry disclosed in theabove referenced co-pending application or any type of conventional shaft position transducer capable of outputting an analog or digital signal indicative of engine speed or the like. Conventional D/A conversion techniques could be used if required.

A temperature transducer 33 is operatively associated with the engine 10 for measuring the engine temperature or alternatively, the temperature of the engine coolant, as conventionally known. Any type of temperature transducer capable of sensing the temperature in its immediate area and outputting a signal proportional to and indicative of said temperature may be employed.

The signal outputted from the MAP block 27 is a voltage proportional to and indicative of the actual absolute manifold pressure existingwithin the intake manifold 14 of the engine 10 and this signal is transmitted via lead 34 back to a conventional electronic control unit (ECU) 35 which senses various predetermined engine operating parameters and outputs a basic control signal in accordance with the sensed parameters for maintaining a desired schedule or program of air-fuel ratios.
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The basic ~ontrol uni-t or cc~pu-tirlg me~ls 35 of the present invention is preferably of -the type disclosed in U.S. Paten-t No. 3,734,068 which issued -to J.N. Reddy on May 22, 1973 Eor a "Fuel Injection Control System" and which is assigned to the assignee of the present invention, but any type of commemially available, con~entional means, preferably analog, but even digital, for computing or scheduling a control signal in accordance with various measured engine operating parameters may be used such as those disclosed in U.S. Patent No. 3,750,632 entitlecl "Electronic Control for the Air-E'uel Mixture arid for the Ignition of an Internal Cc~bustion Engine";
U.S. Patent No. 3,763,720 for a "Shift Shock Preventive Device for Motor Vehicle E`uel Injection System"; U.S. Patent No. 3,969,614 for a "Method and Apparatus for Engine Control"; and U.S. Patent No. 3,986,006 for a "Fuel Injection Controlling for an Internal Combust.ion Engine". All of these patents utilize some form of analog or digital control unit or computing means which could be readily ada~tecl for performi~ng ~he functions recluired of the ECU 35 for implemenkation of the present invention. Still further, the relatively simple analog implementation of the circuit of Figure 3 could also be used ko implement the necessary control function of the present invention, A signal indicative of the engine speed is supplied from block 31 : to another input of the ECU 35 via leacl 36 and the output of the temperature transducer 33 is suppliecl to yet another input to the ECU 35 via lead 37.
e ECU 35 may also be prDvided with a signal proportional to and indicative of ambient atm~spheric pressure, as measured by a conventional pressure transducer 38 whose outpu~ is supplied via the ambient pressure measurement circuitry of block 39 to yet another input of the ECU 35, if required.
A~ditionally, information regardin~ ambient temperature may be supplied to the E W 35 via c~lother temperature transducer ~1 which measures:ambient ~ ~temperature and supp:lies a signal or voltage proportional to and indicative of the e~bient temperature to yet ano~her input of the ~CU 35 via the : circuitry of block ~2. -~ ~ -~ ~ sd~ 12-.. . . . . . . .

816.008 Still another input oE the ECU 35 recei~es the ~irst signal outputted from the position sensing transducer 25 which is indicative of the commanded fuel flow via lead 26, node 4:3 and lead 44. Lastly, the ECU 35 receives information concerning the present or current actual air flow into the engine 10 from a conventional positional transducer 45 which is operatively associated with the actuator means 47 through which a conventional DC servo motor 48 selectively adjusts the position of the throttle valve 17 or directly with the throttle valve 17 or moîor 48 itself so as to output a voltage proportional to and indicative of the present position of the throttle valve 17 and hence indirectly of the present actual air flow into the intake manifold 14. This signal indicative of present air flow is transmitted from the positional sensor 45 back to the yet another input of the ECU 35 via lead 49.
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In the preferred embodiment of the present invention, the ECU 35 receives at least the input information concerning the commanded fuel flow from transducer 25 and ~he information indicative of the present position of the throttle valve 17 and hence of the present air flow, and any of the other engineoperating parameters MAP, RPMj engine temperature, coolant temperature and the like and various other parameters such as atmospheric pressure and ambient temperature and the like which may be required, and computes or determines a basic control signal which it generates and outpu~s via lead 51. The basic control signal is indicative of the desired or scheduled position of the throttle valve to adjust the alr flow so as to maintain a predetermined scheduled or pre-, programmed air-fu~el mixture. The basic control slgnal is supplied through an error correction or summing network 52 wherein lt may be adjusted or corrected and then the corrected control signal is supplied via lead 53 to control the operation of a conventional DC servo motor 48 which ~adjusts the position of the~
throttle valve 17 via servo motor actuator means 47, as known in the art.
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-816.008 As presently described, the operator of the vehicle or the person controlling the operation oE the internal combustion engine 10 commands a predetermined fuel flow by manually positioning the accelerator pedal 23 to position the fuel metering rod 22 so as to aclmit a predetermined quantity of fuel into the intake manifold 14. A signal indicative of the quanti ty of fuel commanded is supplied back to the ECU 35 via lead 26, node 43 and lead 44 and ECU 35 also receives information indicative of the present position of the throttle valve 17 and hence of current air flow into the system via lead 49. E(~U
35 may also receive information relating to other engine operating pararneters as heretofore described, if desired. The ECU 35 responds to the current engine operating parameters and to the signal indicative of the fuel supply currently being commanded and generates a basic control signal via lead 51, circuit 52 andlead 53 which causes the servo motor 48 to adjust the position of the throttle valve 17 so as to selectively open or close the valve to increase or decrease air flow so as to main~ain a predetermin~ed scheduled pre-programmed or desired air-fuel ratio as determined by the circuitry or programming of the ECU 35, as conventionally known.

The system of the present invention, however, further provides a closed loop for fine tuning or correcting the basic control signal so as to insure ~ that the servo motor 48 more accurately positions the throttle valve 17 to .
continuously supfply the required air flow for maintaining the desired or optimal air-fuel mixture within the engine 10. The closed loop feed-back system of the present invention includes sensing means 54 responsive to the actual air-fuel mixture existing within the engine 10 for supplying a feed-back signal indicative thereof back to the correction circuitry of block 52 ;~or correcting or ad'justing the basic control signal to more accurately position the throttle yalve and more` ~ ~ precisely control air flow.

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In -the preferred enbodiment of the present in~ention, the sensing means is a conventional gas sensor such as tha-t disclosed iII U.S. Patent No.
4,005,689 for a "Fuel Injection System Con-trolling Air-Fuel Ratio by Intake Manifold Gas Sensor" which is assigned to the assignee of the present invention. In the preferred embodiment, the gas sensor is an oxygen sensing transducer 54 which transmits an analog signal or voltage via lead 55 back to a summing network 56. At the sum~ing net~ork 56, which is a conventional analog adder/subtraetor, the value of the signal on lead 55 is sub-trae~ed frcm a first referenee signal supFlied to the adder/subtraetor 56 via lead 57, where the value of the reference voltage is selected so that the output of the adder/subtractor 56 is proportional to the væiation of the quantity of oxygen sensed in the exhaust system 12 frcm stoichiometric. ~his difference signal indicative of the væ iation frcm stoichicmetric is supplied via lead 58 to one input of a compæ ator 59 whose other output is eoupled via lead 61 with a seeoIld reference voltage whieh is established so that the output of the ecmpæ ator 5g has a first sign whenever the oxygen sensing means 54 determines that the engine 10 is operating belcw the stoiehicmetrie air-fuel ratio and another polarity signal when the oxygen sensor 54 deteets that the engine is o~erating above the stoichicmetric air-fuel ratio. The output of the eo~Farator 59 may be supplied via lead 62 to the input of an integrating eircuit represented by block 63. The integrator output is eonnected via lead 64 to a summing input of the eireuitry of block 52 so that the feed~
baek signal frcm the integrator 63 may be algebraieally added to the basie eontrol signal on lead 51 so as to fine tune or eorreet the basie eontrol signal to more aeeurately control the operation of the servo motor 48 and therefore the positioning of the throttle valve l7 for more aeeurately eontrolling air flow and therefore more preeisely maintaining a desir~d or optimal air-fuel ratio within the engine 10.

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Theref~e r ~he system o~ -the present invention responds to a commanded fuel ~low determlned by the position of the accelerator 23 and to various other actual engine operating parameters and the ECU 35 computes a basic control signal ~or controlling the operation of a DC servo motor 48 which control-ably posi-tions the thro-ttle valve 17 for controlling air flow.
The actual air-fuel mixture existing in the engine 10 is measured, via the oxygen sensor 54, to supply a feed-back signal Eor correcting the basic con-trol signal in a closed loop manner so that the corrected con-trol signal supplied via lead 53 to the servo motor 48 allows a more precise or accurate positioning of the throttle valve and enables the system o:E the present invention to more accurately maintain a predetermined desired or optimal air-~uel ratio under substantially all engine operating conditions.
As previously described, the sensing means 54 is, in the preferred embodiment of the present invention, a gas sensor ~or sensing the content of oxygen or the relative content of oxygen in the exhaust system 12 of the engine 10 as a measure of the actual air-fuel mixture existing within the engine 10, Alternatively, the sensing means 54 could be a means for sensing engine roughness, since engine roughness is generated by excessively high or low air-fuel ratios. Therefore, the invention also contemplates that the sensing means 5~ or means associated with RPM block 31 could alternatively be a means for . .
sensing engine roughness and generating a signal proportional ~-to and indicative of engine roughness as an indicator of the actual air-~uel ratio or mixture existing in the engine 10.
For example, the roughness sensing means disclosed in the commonly assignecl U.S. Patent Nos. 3,789,~16 and 3,872,8~6 could :~ : be used for generating the required signal indicative of engine . .
~ roughness.

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816.00S As previously stated, most of the systems of the prior art wherein the air flow is controlled by operator command and the fuel flow is controllablyadjusted for maintaining a desired air-fuel ratio suffer from the problem that additional circuitry is usually required to provide for acceleration enrichment.This problem never exists wi~h the system of the !present invention since it hasthe advantage of automatic or inherent acceleratibn enrichment since the fuel enters the intake system 11 first and then the air flow is adjusted in response thereto.

However, a problem can occur when the accelerator 23 is rapidly depressed to command a rapid increase in the quan-tity of fuel supplied to the intake system 11. In this case, too great a quantity of fuel ~rill be supplied to the intake system 11 before the oxygen sensing means 54 is able to feed back a correction signal to the servo mo~or 48 for supplying additional air with ~he result that an undesirable condition OI excessive fuel enrichment will exist in the engine 10.

The present invention provides a differentiator network 65 for eliminating or at least minimizing this problem. In operation, the input to the differentiator circuit of block 65 is connected via leacl 66 to node 43 for monitoring or receiving the flrst signal indicative oE commanded fuel flow therefrom. The output of the differentiator is connected via lead 67 to another summing input of the circuit of block 52 for correcting or supplementing ~he basic control signal supplied thereto via lead 51 as described later in detail.
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16.00S In brief, tIle differentiator of block 65 monitors the rate of change of the signal indicative of the commanded fuel flo~v and responds to a rapid increase in commanded Iuel flow to output a transient voltage spike correction signal which is added to the basic control signal in summing network 52 and supplied via lead 53 to adjust operation of the servo motor 48 to o?en the throttle valve 17 to immediately and momentarily increase the air flo~v to the engine 10 even be~ore the oxygen sensor 54 is able to detect the actual existence of the excessive enrichment condition so as to eliminate or at least minimi~e the extent and duration of the undesirable condition of excessive enrichment. Since the voJtage spike is a transien~ signal, it quickly dissipates to restore control of the servo-actuated throttle to the basic control signal and feed-back signal so that correction for any actual excessive enrichment can be made in the normal manner. However, the differentiator enables the system to anticipate or predict an impending undesirable condition of excessive fuel enrichment and generate a correcive signal for minimizing the effects thereof.

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Figure Z is a schematic diagram of the feed back loop comprising the gas sensing means 54, adder/su~tractor 56, comparator 59 and integrator 63;
the differentiator of block 65; and the summing network of block 52 of Figure 1.
The summing network 52 includes an operational amplifier 71 having its non-~ .
inverting input directly connected to ground via lead 72 and its inverting input .
connected via lead 73 to a common summing node or junction 74. The output of ~j; the operational amplifier 71 is connected via lead 75 to an output node 76 and the output node 76 is connected via lead 53 to the input of the servo motor of block 48 to control the operation thereof. A` feed-back resistor 77 has one end connected to sumrning node 74 ànd its opposite end connected to the output node 76 so as to establish a conventional analog ~adder or summing circuit wherein ` ~ each of the signals supplied to the summing node 74 are algebraically added to :
the other and then amplified or scaled to produce an output signal proportional ~` thereto which is supplied via lead 53 to the servo motor 48.

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816.008 The basic control signal from the ECU 35 is connected via lead 51 to the common summing node 74 and pro~ides the basic or prirnary input to the operational amplifier 71. Th;s basic control signal is used to operate or control the operation of the DC servo motor 48 to selectiYely vary the position of ~he throttle valve 17, as conventionally known. As previously described, the basic control si~nal on lead 51 can be corrected or adjusted via the feed-back signal or voltage spike transient correction signal so as to provide a finely tuned or correc~ed control signal at the output which is supplied to the control input ofthe DC servo motor 48 via lead 53, as previously described. ~1 The feed-back loop of the present invention includes the gas sensor 54 or, alternatively, the roughness sensor of block 5~4'. The output of the oxygen sensor 5lf or roughness sensor 54' is a signal generally representative of the actual air-fuel mixture existing within the internal combustion engine 10 and this signal is supplied through a resistor 78 to the non-inverting input of an operational amplifier 79. lhe inverting input of the operational amplifier 79 isconnected via lead 81 to a node 82. Node 82 is a tap of a voltage divider network and ia connected to ground through a first voltage divider resistor 83 and through a resistor 84 to output node B5. The output of the operational amplifier 79 is taken from output node 85 and the configuration of the operational amplifier 79 together with resistors 7B,83 and 84 establishes a buffer stage or scaling circuit for adjusting the level of the output signal as required Eor the signal level needs of the present system.
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816.008 Output node 25 is connected through a resistor 86 to a summln~
node 37. Summing node 87 is connected via lead 88 to the invertin~ input of an operational amplifier 89. The summing node 87 is also connected to a source of positive poten~ial ~hrough a resistor 91 and to the output 92 of the ampllfier 89 via resistor 93. The non-inverting input of the o,oerational amplifier 89 is connected dir~ctly to ground throu~h lead 94O The amplifier 89 together with resistors 86, 91 and 93 are configured to form a conventional analog adder-subtractor or summing circuit wherein a reference si~nal indicative of a stoichiometric air-fuel mixture is summed with the negative of a scaled signal indicative of the actually existing air-fuel mixture in the engine 10 so that the signal appearing at the output node 92 represents the variation of the actual air-fuel mixture existing in the engine from stoichiometricO

Output node 92 is connected via leacl 95 to the non~inverting input of an operational amplifier 96 whose inverting input is connected vla leacl 97 to voltage divider node 98. Node 98 is connected to ground through a resistor 99 and through a voltage divider resistor 101 to a second node 102. Node 102 Is connected directly to a source of positive potential through lead 103 and throu~h another voltage dividing resistor 104 to voltage diYider node lOS. Noe~e 105 is connected to ground through a resistor 106 and to the non-inverting input OI an operational amplifier 107 via lead 108. The output of the operational amplifiet 96 is supplied through a resistor 108 to a node 109 which is also connected to ground through a resistor 111. The operational amplifier 96 together wi~h resistors 99 and 101 form an analog comparator. The reference voltage is provided to the non-inverting input via the lead 97 from ~he voltage divider comprising resistors 99, 101 and node 98. This reference vol~age is established so that a first polarity output will be supplied at the output of operational amplifier 96 if the input signal on lead 95 indicates an air-fuel mixture which is less than stoichiometric and oE an opposite polarity when the signal on lead 9S indicates an , air-fuel mixture which is more than stoichiometric.

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No~e .L09 is a1so c:onnecte(.l through a resi.stor 113 to voltage input node 102 an~ via lecld l.l~ l:o input no~e 115. Node 115 :is connected to -the inverting input oE the operati.onal ampliEier :1.07 via ]ead 11.6 and to an inte~ra~ing capacitor 117 which is connected between the input nocle - llS and the Olltput node ].18 of the operat:ional. arnplifier 107 so as to Eorm a standard analog integrator. The integrator 63, comprising the operati.onal amplifier 107, i.ntegrating capacitor 117, and the various resistors 108, 109, 104 and 105 will i.ntegrate the comparator output signal and transmit a feed-back signal via lead 119 resistor 12() and lead 64 back to the common ~10 summing node 74 so as to enable the output of the integrator 63 to con-trollably adjust or correct the value of the basic control s:ignal to Eine tune the signal commanding the operation of the servo mo-tor 48 as previously described.
The system for anticipating an impending undesirable condition of excessive fuel enrichmen-t will now be described. The positional sensor 25 of : Figure 1 is represented as a voltage divider configuration wherein a first voltage divider resistor 121 has one end connected to a source of positive potential and its opposite end connected to a voltage divider node 122.
: ~ Node 122 is connected to ground through a variable resistor 123 whose value is changed in a conventional potentiometer fashion as the position of the accelerator 23, linkage 24, andjor fuel metering rod 22 is changed by the ; ~ operator's command.
. The voltage signal present at node 22 is indicative of the commanded fuel flow and is supplled via lead 124 to one plate of a differentiating capacitor 125 whose opposite plate is connected via lead 126 to input node 127. Node 127 is c,onnected via lead 128 to the iliverting input~of an operational amplifler 129 whose non-inverting lnput is connected directly to ground through lead 131. The output of operational amplifier :'~ 129 lS connected vla lead 132 to an output node 133 and~a feed-back resistor 134 has one end connected to the input node 12i and its opposite end connected to the output node 133 so that the combination:or configuration of the sd~ 21-.

. .

operational. alllplifier :129, capacltor 125 arld re~s.istor 13~ forms d conventional ana:Loc3 difEerent:iator circuit capable of differen-tiating -~he si~nal ind:icati.ve o:E the commanded fuel flow for monitorin~ -the rate of change -thereof. The ou-tput node 133 is connccted -through a resistor 135 to lead 67 which supplies the second correc-tion signal or d.ifferentia-ted signal to the common summing node 74.
In operation, the anticipation or prediction of an impending undesirable condition oE excessive fuel enrichment occurs as follows. Whenever the operator commands a rapid increase in the quanti-ty of fuel to be metered into the intake system 11 of the engine 10, as by rapidly depressing the accelerator pedal 23, the voltage signal outputted from the position sensor 25 will rapidly increase. The differentiator :: circuit 65 difEerentiates this signal and monitors the rate of change or rapid increase therein for outputting a voltage spike or transient signal which quickly rises and then falls. This ` transient voltage spike is supplied to the summing node 74 and immediately modifies the basic control signal to be transmitted ~`20 via lead 53 to the DC servo motor of block 48 to momentarily and immediately adjust the position of the throttle valve 17 ~
; : so as to temporarily increase the air flow into the intake system 11. As soon as the voltage spike dissipates, the control of the servo motor is restored to the basic control signal on lead 51 and the feed-back signal coming from lead 64 so that even if the impending undesirable condltion is not entirely avoided, the gas-sensing feed-back means will enable the :~ appropriate correction to be made so as to enable the system to quickly restore and accurately maintain the desired air-~30 fuel ratio.
., .
,~, , ~ ~J~

. ~ ~
~ sd~ -22- . .

Fig~lre 3 shows a block di.agram o-f a relativel~ sir~].is-tic im-plemen-tation oE the basic control function of the ECU 35 of Figure 1 as used in the sys-tem of the presen-t invention. The air flcw control signal "A" may be obtalnecl from the equation f f ~-~atT-To~ ~
~ = A
2C Cd ~m ~
where Wf.represen~s the fuel flGw; Kf is a constant approxima-tely equal to the desired air-fuel ratio; T represents the actual engi.ne -t~mperature; To represen-ts a constant reEerence temperature such as a "cold start" thresh-hold; TA represents the ambient air temperature; C represen-ts a gas-Elcw constant; Cd represents the discharge co-efficient for ~he par-ticular throttle valve; Pm equals the absolute manifold press~re of -the engine; Pa represents ambient atmospheric pressure; and A rep.resents the area of the throttle opening which is a measure of air flcw into the engine. Appropriate . scaling can ~e used to appropriately m~dify the control parameter "A" to enable it to be used for directly controlling the op~ration of the DC servo motor 48 to position the throttle valve as required to satisfy the equation for a pre- -determined desired or optimal air-fuel muxture within the engine.
In the block diagram of Figure 3, the signal Wf which represents fuel flow can be t~ken as a measure of the fuel fl~w commanded by the acceler-ator 23 and, measured via sensor 25. This signal is supplied via input 141 to ; a block 142 which implements the~consta~,t Kf/2CCd and the resultung value WfKf/2oCd whlch is itself a constant is supplied via lead 143 into one input of the analog mul-tiplier of block 144. The ambient air temperature, as measured by the sensor 41 is supplied via lead 145 to the analog-implemented square root circuit of block 146 so that the~sq~làre root of the ambient temF~
erature is supplied via lead 147 to the other input o~ the analog multiplier 144. m e product . , .
. ' ~ - 2~3 -, "i ., . ,., ~ " ~ ",: ,:,,:, , , : " ~ ",:

WfK

2CCd is supplied via lead 148 to the first input of the analog multiplier of block 149.
The engine temperature, as measuxed by the temperature sensor 33, is supplied via lead 151 to the plus input of an analog summing circuit 152 and the ~erperat~re constant To is supplied via lead 153 to a subtrac-ti~e input thereto so that-the difference T-'~ is provided at the output of the summlng circuit 152 and is supplied via lead 154 to the first input oE the analog multiplier of block 155. The other input of the analog multiplier of block 155 is supplied with a constant "a" via lead 156.and the product a(T-T0) is presented to one input of an analog summing cixcuit 157 via le.ad 158. Another input.of the summ m g circuit 151 is provided with a volt~ge represen~ing the'number "1" via lec~d 159 and the ou-tput l+a(T-T0). is.supplied ~-via lead 161 to the second input of the analog multiplier 149 so that the product WfKf. (l~a(~-T0~ is supplied via - .. .
2CCd , . . ...... .
lead 163 to the divldent input of a conventional analog divider circuit 164.
The absolute manifold pressure Pm is sensed by the sensing means of block 27 of Figure 1 and is provided via lea1 165 bo the analog-implemenbed square root circuitry of block 166 so tha-t the square root.of Pm is supplied via lead 167 to one input of the analog multiplier ~E block 168. S~multaneous-:::
;- ly, the signal Pm is supplied via lead 169 to the subtractive input of an ana.-log summing circuit 171 which also receives the posi-tive signal Pa from the a~bient pressure sensor 38 of Figure l via lead 172 Hence, the output of the' summQng circuit 171 is the difference Pa ~ Pm and thi~ quantit~ is suppliedvia~lead 173 to the input of a~square root circuit 170. The output of bloc~
: ~ 170 is supplied via lead :
~ :

p~r ~ ~

3~
1~0 to ~ S~CO~ input oJ tile ana].og multi.plier of hlock l.68. rrhe ~nalog multiplicr 16~ rnllltiplies the signals present at its i.nputs and produc~s the L~roduct P P P at i.ts ~utput and this product is m a m supplied via lead 17~ to the diviso~ input of the analog div:ider of block 164 so that the si.gnal A is outputted from the divisor circuitry of block 164 via lead 175 and can be used or scaled and then used to drive the DC servo motor 48 Eor accurately positioning the thrott].e valve 17 in accordance with the given parameters to maintain a scheduled or pre-programmed air-fuel mixture in the engine in accordance with a schedule determined by the various constants utilized in establishi.ng the analog network of Figure 3.
Each of the blocks used in Figure 3 is a conventional analog circui-t and may be purchased as "off the shelf" items from any number of sources such as from any Burr-Brown catalog. A standard scaling circuit using operational amplifiers and resistors can be used to implement the function present at the output of block 142; conventional ana].og summlng circuits using operational amplifiers can be used to construct the adder/
subtractor circuits 152, 157 and 171; conventional analog square root circuits can be used to perform the functions of blocks 146, 166 and 170; conventional analog multipliers can be used to implement blocks 144, 149 and 168 and a conventional analog.dlvider can be used to implement the function of block 164. Alternatively, a conventional multifunction converter for implementing all required analog circuit functions, such as the Burr-Brown 4301 and 4302 circuits which implement the transfer function Eo = V (V /V ) can be used to implement all of the circuits ,, ;~ required for building the system of Figure 3. Alternatively, the circuits required for lmplementlng the system of Figure 3 can be found in any ~ :
standard text book on operational amplifiers such as "An Introduction to ,: . . , : ~ :
. ~ Operational Amplifier" by Lucas M. Faulkenberry, which is published by ~30 : John Wiley & Sons, New York, New York , 1977, or "Modern Operational Ci.rcuit .: -Designs", by John I. Smith, published by Wiley-Interscience, New York, New :~: Yorh,:1971.

: ~ ~
~ sd~ -25-~

:~ : , ... . . , " . ., FLyure ~ repres~llts an alternate embodiment of the means for commal~dillcJ f.uel flow and represe:nts a gov~rniny s~stem wherein -the ~ositioning of the accelerator pedal 23 positively controls the posi-ti.oning oE a linkage sys-tem 24 for directly controlling the posi-tioning of a fuel metering rod 22 within the inle-t 19 of a fuel inlet port 20 as previously described -to control the flow of fuel from the conduit 21 -through the inle-t 19 and into -the intake system 11 of the engine 10. As represented by the break 181 in the linkage assembly 24, the accelerator pedal 23 may be used to directly and positively control the positioning of the fuel me-tering rod 22.or, as herein-after described, it can be used to allow positive control plus indirect closed loop control of the fuel metering rod 22 or the positive control may be eliminated and a closed loop fuel control system established without positive control.
To establish the closed loop control, a linkage member 182 having one end operatively coupled to the linkage 24, has its opposite end operatively connected to a rod-like element or member 183 which is movably disposed within the hollow central core of electromagnetic coil means 184. The electromagnetic coil means 184 is configured such that the vertical positioning of the element 183 within its hollow .: central core determines -the level or magnitude of the voltage signal present on i-ts output leads 185. The output voltage is, therefore, proportional to the accelerator commanded fuel flow desired by the operator and is supplied to the inputs of a ~ :
:~ :
conventional voltage controlled:oscillator 186 which produces : -an oscillating signal or waveform having a predetermined ~ frequency controlled by the magnitude of the voltage present ~ 30 on input leads 185 and there~ore a frequency which is ~ ~ ~ indicative of the operator commanded fuel flow.

, : : .:

~ sd/~ : 26-816.008 1h0 output waveform whose frequency i~ indicative of commanded fuel flow is supplied via lead 187 to one input oE a conventional frequency comparator 188 whose other input is supplied with a second signal waveEorm via lead 189. The second s;gnal waveform has a frequency which is indicative of the engine speed such as may be produced by $he conventional RPM circuitry of block 31 of Figure 1 previously described. The frequency comparator 188 outputs a signal which is indicative of the difference between the actual engine speed and the commanded or desired engine speed, since from the standpolnt of the operator, commanded fuel flow is proportional to desired engine speed, and this signal is supplied either directly or through a conventional integrator circuit via lead 191 to control the operation of a conventional DC servo motor 192.

The servo motor 192 operates an actuator member 193 which may be used to control the positioning of the fuel metering rod 22 within the inlet 19 to control the quantity of fuel supplied to the intake system 11 either alone or in conjunction with the positive control of linkage 24. The closed loop systern of Figure 4 is closed on en~ine speed since a signal whose frequency is indicative of actual engine operating speed is supplied or fed back to the control circuitry of block 18~ to drive the DC servo motor 192 which makes a desired correction in the positioning of the fuel metering rod 22 until the operator commanded fuel flow, and hence engine speed, is attained.
;

As indicated by the dotted line 194, the fuel flow measuring means or position transducer 25 may be operatively coupled to the actuator 193 to obtain a positional measurement indicative of the commanded fuel flow instead of to the linkage system 24 or the fuel metering rod 22 as previously described. In all other respects, the system of Figure 4 could be used to supplement the system of Figure 1 if a go~rerning system were desired or if it .
were desired to provide operator commanded fuel flow without a direct positive control linkage between the accelerator 23 and the fuel metering rod 22.

;

'`' ':` ,'' . ' , - .. ~ :

7~

B16.008 Figure 5 illustrates an alternate embodiment to the means for controlling the operation of the servo operated actuator 193 for positioning the fuel metering element 22 of Figure 4 to maintain the operator commanded fuel flow or engine speed. In Figure 5, a conventional RPM measuring system, such as one geared to count timing pulses located on a movable element, such as a pulleyattached to the output shaft 13 of the en8ine 10, and these pulses are supplied via lead 201 to a conventional bina~y counter 202. At predetermined intervals, the digital number stored in the counter 202 may be transferred in paralleJ via data path 203 to the "A" input of an arithmlatic logic unit 204. The voltage controlled oscillator 186 supplies a series of pulses to a second binary counter205 via lead 206 and at said predetermined periodic interval9 the binary number stored within the counter 205 may be transferred via data path 207 to the "B"
input of the ALU 204.

The arithmatic logic unit 204 is a conventionally available unit which outputs a digital number indicative of the magnitude of the difference between the numbers present at the "A" and "B" inputs via data path 208 to a digital to analog conver-ter 209. The output of the D/A converter 209 is supplied via lead 211 to a node 212 and from node 212 directly to a f.irst input of a first logical AND gate 213 and via lead 214 to the first input o a second logical ANDgate 215. Therefore, the pulse width or duration of the signal presert at the first input of the AND gates 213, 215 is indicative of the magnitude of the difference between the actual and desired engine speeds and hence reprPsentative of the magnitude of the correction to be mado.

: ~

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:; , ' ' ~ ' ~' '~, , ' 73~

816.008 The carry output of the ALU 204 is supplied via lead 216 to a node 217. Node 217 is connected via lead 218 to the second input of Jogical A~JD gate213 and directly to the input of an inverter 219 whose output is connected directly to ~he second input of the second logical AND gate 215. Since the signal present at the carry output indicates whe~her the signal present at the "A" input is greater than or less than the signal present at the "B" input, ANI:) gate 213 will be enabled whenever the desired engine speed is greater than the actual engine speed while the second AND gate 2I5 will be enabled whenever the actual engine speed is greater than the desired engine speed. The output of AND gate 213 is connected via lead 221 to the forward drive input of a conventional forward-reverse servo motor 222 while the reverse input is connected to the output of the second AND gate 215 via leacl 223. Therefore9 the servo actuator member 193 which controls the position of the fuel metering rod 22 will be driven in the forward direction whenever AND gate 213 is enabled and in the reverse direction whenever AND gate 215 is enabled and in either case7 the amount which the actuator member 193 is turned will be determined by the pulse width or duration of the pulse outputted from the D/A converter 209. It will, of course, be realized that any suitable type of comparator means could also be used to implement the closed loop fuel metering system of Figure 4.

As described herein, the method and apparatus of the present invention enables the air flow to be controlled in response to operator commanded fuel flow. Various engine operating parameters are measured to generate a control signal designed to maintain a predetermined scheduled or pre-programmed air-fuel mixture within the engine and a feed-back s;gnal generally indicative of the actual air-fuel mixture existing within the engine, such as from an oxygen sensor disposed in the exhaust manifold, can be used to correct the basic control signal to provide an extremely açcurate means for maintaining a desired or optimal air-:Euel schedule under substantially all engine operating ' .

, 816.008 conditions. Anticpation circuitry may be employed to anticipate an impending undesirable condition oE excessive enrichment and for generating a transient corrective signal which can be used to provide addi tional air flow into thi~
system even before the feed-back system can sense the actual existence of the undesirable condition within the engine to minimize the undesirable condition ofexcessive enrichment.

With this detailed description of a specific circuit used to illustrate the preferred embodiment of the present invention ancl the operation thereof, it will be obvious to those skilled in the ar~ that various modifications can be made in the circuitry and means for implementing the method and apparatus of the present invention without departing from the spirit and scope of my invention which is limited only by the appended claims.

I Claim:

Claims

816.008 1. A closed loop system for controlling the air-fuel mixture in an internal combustion engine comprising:
accelerator means for supplying a quantity of fuel to said internal combustion engine;
means responsive to said accelerator means for generating a first signal indicative of said quantity of supplied fuel;
means for controlling the flow of air into said internal combustion engine;
means responsive to said air flow control means for generating a second signal indicative of the actual air flow into said engine;
control signal-computing means responsive to at least said first and second signals for generating a basic control signal for regulating said airflow control means, said basic control signal commanding a desired air flow as afunction of the quantity of fuel supplied to the engine;
means responsive to the actual air-fuel mixture existing in said engine for generating a feed-back signal indicative thereof; and means responsive to said feed-back signal for correcting said basic control signal, said air flow control means being responsive to said corrected control signal for selectively increasing and decreasing the air flow into said engine to maintain a desired optimal air-fuel ratio under substantially all engine operating conditions.
31 316.008 2. The closed loop system of Claim l further including means responsive to said first signal for anticipating an impending undesirable condition of excessive fuel enrichment and for generating a second correction signal, saidmeans responsive to said feed-back signal also being responsive to said second correction signal for modifying said basic control signal to temporarily increase the air flow to said engine even before said air-fuel mixture responsive means can generate said feed-back signal indicative of the existence of said undesirable condition so as to minimize the extent of said undesirable condition.
3. The closed loop system of Claim 1 further including means responsive to said first signal for monitoring the rate of change thereof and for generating a second correction signal indicative of a rapid increase therein which corresponds to a prediction of an impending excessive enrichment condition, saidcorrecting means being responsive to said second correction signal for modifyingsaid basic control signal even before receiving said feed-back signal indicative of the existence of said undesirable condition, said air flow control means being responsive to said modified control signal for temporarily increasing the air flow into said engine for minimizing the degree and duration of said predicted excessive enrichment condition.
4. The closed loop system of Claim 3 wherein said means for monitoring the rate of change of said first signal and for generating said second correction signal includes means for computing the first derivative of said first signal, said derivative appearing as a voltage spike waveform whenever a rapid increase in said first signal is detected, said rapid increase in said first signal being indicative of: an impending excessive enrichment condition within said engine, said correcting means and said air flow control means being responsive to 816.008 said spike waveform for immediately and temporarily increasing air flow and then restoring control of said air flow control means to said basic control signal as corrected by said feed-back signal when said voltage spike waveform dissipates.
5. The closed loop system of Claim 1 wherein said means for controlling the flow of air into said internal combustion engine includes a throttle valve disposed in the intake system of said engine and servo motor means responsive to said control signals for varying the position of said throttle valve to selectively increase and decrease said air flow into said internal combustion engine.
6. The closed loop system of Claim 5 wherein said means for generating said second signal includes transducer means operatively associated with one of said servo motor means and said throttle valve for generating an electrical signal indicative of the relative position thereif, said electrical signal corresponding to said second signal and being proportional to and indicative of the actual air flow into said internal combustion engine.
7. The closed loop system of Claim 1 wherein said acceleration means includes:
a manually positionable accelerator for positively commanding the quantity of fuel to be supplied to said internal combustion engine;
a fuel inlet into said internal combustion engine;
means for supplying fuel to said fuel inlet;
a fuel metering rod disposed at least partially within said inlet for regulating the passage of fuel therethrough; and 16.008 linkage means operatively coupled between said accelerator and said fuel metering rod for selectively varying the position thereof so as to positively regulate the quantity of fuel supplied to said engine.
8. The closed loop system of Claim 7 wherein said means for generating said first signal includes transducer means operatively associated with one of said fuel metering rod and said linkage means for generating an electrical signal indicative of the relative position thereof, said electrical signal corresponding to said first signal and being proportional to and indicative of the quantity of fuel which the operator has commanded to be supplied to said engine.
9. The closed loop system of Claim 1 wherein said means responsive to the actual air-fuel mixture within said internal combustion engine includes gas sensing means.
10. The closed loop system of Claim 9 wherein said gas sensing - means includes an oxygen sensing element disposed within the intake system of said internal combustion engine.
11. The closed loop system of Claim 9 wherein said gas sensing means includes an oxygen sensing element disposed within the exhaust system of said internal combustion engine.
12. The closed loop system of Claim 1 wherein said means responsive to the actual air-fuel mixture existing within said internal combustion engine includes means for sensing engine roughness.
34 316.008 13. The closed loop system of Claim 1 wherein said accelerator means includes a closed loop fuel governing means for controllably maintaining the desired quantity of fuel supplied to said internal combustion engine.
14. The closed loop system of Claim 13 wherein said accelerator means includes:
a manually positionable accelerator for commanding the quantity of fuel to be supplied to said engine and hence the engine speed desired by the operator;
a fuel inlet into said internal combustion engine;
means for supplying fuel into said fuel inlet;
a fuel metering rod disposed at least partially within said inlet for regulating the passage of fuel therethrough;
linkage means operatively coupled to said accelerator for moving in proportion to the operator commands transmitted thereto by said accelerator;
and wherein said closed loop governor means includes;
electrical coil means having a hollow central portion;
a rod-like member disposed for relative movement within said hollow central portion, said electrical coil means being responsive to the relative : position of said rod-like member: within said hollow central portion for generating a voltage indicative thereof;
one of said electrical coil means and said rod-like member being operatively connected to said linkage means for relative movement therewith such that said relative position indicative voltage is also indicative of the desired engine speed commanded by the operator's positioning of said accelerator;
means responsive to said position indicative voltage for generating a first waveform whose frequency is determined by the value of said generated voltage;
means for generating a second waveform whose frequency is indicative of the actual engine speed;

16.008 means for comparing said first and second waveforms and generating an error signal indicative of the difference therebetween; and means closing a feed-back loop and responsive to said error signal for selectively positioning said fuel metering rod to control the quantity of fuel supplied to said internal combustion engine so as to maintain the desired enginespeed commanded by the positioning of said accelerator.
16.008 15. An electrical system for controlling the air-fuel mixture in an internal combustion engine system having an intake system, at least one cylinder, a throttle valve disposed within said intake system for regulating the flow of air to said cylinder, means for metering a quantity of fuel into said cylinder, and manually operable accelerator means for positively controlling said fuel metering means, said electrical system comprising:
means responsive to one of said accelerator means and said fuel metering means for generating a first signal indicative of the quantity of fuel to be metered into said cylinder;
throttle valve positioning means responsive to a control signal for regulating the position of said throttle valve to selectively vary the flow of air into said cylinder;
means responsive to one of said throttle valve and said throttle valve positioning means for generating a second signal indicative of the actual air flow into said cylinder;
electronic control unit means responsive to at least said first and second signals for generating a base control signal commanding a predetermined desired air flow as a function of metered fuel and the like for controlling saidthrottle valve positioning means;
gas sensing means disposed in said engine for generating a feed-back signal indicative of the actual air-fuel mixture existing therein;
loop-closing means responsive to said feed-back signal for correcting said base control signal such that said throttle valve positioning means is responsive to said corrected control signal for more accurately maintaining adesired air-fuel ratio in said internal combustion engine; and means responsive to said first signal for anticipating an undesirable condition of excessive enrichment and for generating a transient correction signal indicative thereof even before said gas sensing means detects the actual existence of same for immediately correcting said base control signaland temporarily increasing the air flow into said cylinder for minimizing said undesirable condition.
16.008 16. The system for controlling the air-fuel mixture in an internal combustion engine of Claim 15 wherein said means for anticipating an undesirable condition of excessive enrichment includes means operatively coupled to said means for generating said first signal for computing the first derivative thereof and for generating a transient voltage spike correction signal whenever a rapid increase in said first signal occurs which indicates that an undesirable condition of excessive fuel enrichment is imminent.
17. The system for controlling the air-fuel mixture of an internal combustion engine of Claim 15 wherein said throttle valve positioning means includes a DC servo motor responsive to said basic control signal, said corrected control signal and said transient correction signal for selectively positioning said throttle valve to vary the flow of air into said cylinder.
18. The system for controlling the air-fuel mixture in an internal combustion engine of Claim 15 wherein said system further includes a closed loop governor means for controlling the metering of fuel into said cylinder.
19. The system for controlling the air-fuel mixture in an internal combustion engine of Claim 18 wherein said governor means includes:
a linkage operatively coupled to said accelerator means for movement therewith;
electromagnetic means responsive to the relative movement of said linkage for generating an output voltage indicative thereof;

voltage controlled oscillator means for generating a first waveform having a frequency dictated by the value of said generated voltage and indicative of the desired engine speed commanded by the positioning of said accelerator means;

316.008 means for generating a second waveform whose frequency is indicative of the actual engine speed;
means for comparing said first and second waveforms and for outputting an error signal indicative of the difference therebetween; and means closing said feed-back loop and responsive to said error signal for selectively increasing and decreasing the quantity of fuel metered into said cylinder for maintaining the desired engine speed commanded by the operator's positioning of said accelerator means.
20. The system for controlling the air-fuel mixture in an internal combustion engine of Claim 15 wherein said gas sensing means includes an oxygen sensing element.
39 316.008 21. An electrical system for controlling the air-fuel mixture in an internal combustion engine system having an intake system, at least one cylinder, a throttle valve disposed within said intake system for regulating the flow of air into said cylinder, means for metering a quantity of fuel into said cylinder, and manually operable accelerator means for positively controlling said fuel metering means, said electrical system comprising:
means responsive to one of said accelerator means in said fuel metering means for generating a first signal indicative of the quantity of fuel to be metered into said cylinder;
throttle valve positioning means responsive to a control signal for regulating the position of said throttle valve to selectively vary the flow of air into said cylinder;
means responsive to one of said throttle valve and said throttle valve positioning means for generating a second signal indicative of the actual air flow into said cylinder;
electronic control unit means responsive to at least said first and second signals for generating a base control signal commanding a predetermined desired air flow as a function of metered fuel and the like for controlling saidthrottle valve positioning means;
means for sensing engine roughness which is indicative of the actual existence of an improper air-fuel mixture within said engine and for generating a feed-back signal indicative thereof;
loop-closing means responsive to said feed-back signal for correcting said basic control signal such that said throttle valve positioning means is responsive to said corrected control signal for more accurately maintaining a desired air-fuel ratio in said internal combustion engine system;
and 16.008 means responsive to said first signal for anticipating an undesirable condition of excessive enrichment and for generating a transient correction signal indicative thereof even before said engine roughness sensing means detects the actual existence of other than the desired air-fuel mixture within said engine for immediately correcting said base control signal and temporarily increasing the air flow into said cylinder for minimizing said undesirable condition.
41 ?16.008 22. The system for controlling the air-fuel mixture in an internal combustion engine of Claim 21 wherein said means for anticipating an undesirable condition of excessive enrichment includes means operatively coupled to said means for generating said first signal for computing the first derivative thereof and for generating a transient voltage spike correction signal whenever a rapid increase in said first signal occurs which indicates that an undesirable condition of excessive fuel enrichment is imminent.
23. The system for controlling the air-fuel mixture of an internal combustion engine of Claim 21 wherein said throttle valve positioning means includes a DC servo motor responsive to said basic control signal, said corrected control signal or said transient correction signal for selectively positioning said throttle valve to vary the flow of air to said cylinder.
24. The system for controlling the air-fuel mixture in an internal combustion engine of Claim 21 wherein said system further includes a closed loopgovernor means for controlling the metering of fuel into said cylinder.
25. The system for controlling the air-fuel mixture in an internal combustion engine of Claim 24 wherein said governor means includes:
a linkage operatively coupled to said accelerator means for movement therewith;
electromagnetic means responsive to the relative movement of said linkage for generating an output voltage indicative thereof;
voltage controlled oscillator means for generating a first waveform having a frequency dictated by the value of said generated voltage and indicative of the desired engine speed commanded by the positioning of said accelerator means;

816.008 means for generating a second waveform whose frequency is indicative of the actual engine speed;
means for comparing said first and second waveforms and for outputting an error signal indicative of the difference therebetween; and means closing said feed-back loop and responsive to said error signal for selectively increasing and decreasing the quantity of fuel metered into said cylinder for maintaining the desired engine speed commanded by the operator's positioning of said accelerator means.
43 816.008 26. A closed loop method of maintaining a desired air-fuel ratio in an internal combustion engine comprising the steps of:
supplying a quantity of fuel to said engine under operator command;
measuring a first parameter indicative of the actual air flow into said engine;
controlling the air flow into said engine as a function of said quantity of fuel supplied to said engine under operator command and said first measured parameter indicative of actual air flow into said engine;
measuring another engine operating parameter indicative of the actual air-fuel mixture existing in said engine; and selectively increasing and decreasing said controlled air flow in response to said measured engine operating parameter indicative of the actual air-fuel mixture existing in said engine in a closed loop manner so as to maintain a desired optimal air-fuel ratio under substantially all engine operating conditions.
44 816.008 27. The closed loop method of maintaining a desired air-fuel ratio of Claim 26 further including the additional step of anticipating an impending undesirable condition of excessive fuel enrichment and increasing air flow to minimize said undesirable condition.
28. The closed loop method of maintaining a desired air-fuel ratio of Claim 26 further including the steps of monitoring the rate at which said quantity of fuel is supplied to said engine, predicting an undesirable condition of excessive fuel enrichment whenever said monitored rate of fuel supply increases,and temporarily and immediately increasing said controlled air flow to minimize said undesirable condition of excessive fuel enrichment.
29. The closed loop method of maintaining a desired air-fuel ratio of Claim 26 wherein said step of measuring an engine operating parameter indicative of the actual air-fuel mixture existing within said engine includes the step of sensing the oxygen content of the gases existing within said engine.
30, The closed loop method of maintaining a desired air-fuel ratio of Claim 26 wherein said step of measuring an engine operating parameter indicative of the actual air-fuel mixture existing within said engine includes the step of sensing engine roughness as a measure of an actually existing but undesirable air-fuel mixture.

816.008 31. The closed loop method of maintaining a desired air-fuel ratio of Claim 26 wherein said step of supplying a quantity of fuel to said engine under operator command includes generating a first signal waveform indicative of the desired engine speed as a function of the operator commanded supply of fuel, generating a second signal waveform indicative of the actual engine speed, comparing said first and second signal waveforms and generating an error signal indicative of the difference therebetween, and increasing and decreasing said quantity of fuel supplied to said engine in a closed loop manner in response -tosaid error signal until said operator commanded desired engine speed is attained.

816.008 32. In a system for controlling the air-fuel mixture in an internal combustion engine having at least one engine cylinder, a closed loop method of maintaining a desired optimal air-fuel ratio under various operating conditions comprising the steps of:
feeding an operator-commanded quantity of fuel into said cylinder;
generating a first signal indicative of the quantity of fuel fed into said cylinder;
generating a second signal indicative of the actual air flow into said cylinder;
computing a basic control signal indicative of the desired air flow as a function of said first and second signals;
sensing the oxygen present in the air-fuel mixture actually existing in said engine;
generating a third signal indicative of the actual air-fuel mixture as a function of the quantity of sensed oxygen present therein;
adjusting said basic control signal in a closed loop manner to increase and decrease computed air flow to more precisely maintain said desired air-fuel ratio;
monitoring the rate of change of said quantity of fuel commanded to be fed into said cylinder to anticipate an impending undesirable condition of excessive fuel enrichment; and generating a transient signal for adjusting said basic control signal even before said oxygen-sensing step is able to detect the actual existence of said undesirable condition to temporarily increase the air flow into said cylinder so as to minimize said undesirable condition of excessive enrichment.
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816.008 33. In a system for controlling the air-fuel mixture in an internal combustion engine having at least one engine cylinder, a closed loop method of maintaining a desired optimal air-fuel ratio under various operating conditions comprising the steps of:
feeding an operator-commanded quantity of fuel into said cylinder;
generating a first signal indicative of the quantity of fuel fed into said cylinder;
generating a second signal indicative of the actual air flow into said cylinder;
computing a basic control signal indicative of desired air flow as a function of said first and second signals;
monitoring engine roughness as a measure of undesirably high and undesirably low actual air-fuel mixtures existing within said engine;
generating a third signal from said monitored engine roughness, said third signal being indicative of the magnitude of said undesirably high or low air fuel mixture actually existing within said engine;
adjusting said basic control signal in a closed loop manner to increase and decrease computed air flow to more precisely maintain said desired air-fuel ratio;
monitoring the rate of change of said quantity of fuel commanded to be fed into said cylinder to anticipate an impending undesirable condition of excessive fuel enrichment; and generating a transient signal for adjusting said basic control signal even before said engine roughness monitoring means is able to detect said undesirably high or low air-fuel mixture within said engine to temporarily increase the air flow into said cylinder in order to minimize said undesirable condition of excessive enrichment.