Method and apparatus for engine control

Claims

Based upon the foregoing description of the invention, what is claimed is:

1. A method for controlling a combustion engine used in a process of converting heat energy, released by the combustion of a fuel, into mechanical energy, said engine having an output shaft which rotates while it is in operation and including at least one means for controlling said energy conversion process, said method comprising the steps of:

generating an electrical signal in the form of a binary number, said signal being indicative of a condition of said engine as of a selected instant in time during which said engine is operative in effecting said energy conversion process; then

arithmetically calculating a value corresponding to a setting of said means for controlling said energy conversion process, said calculating being performed using said binary number electrical signal, by a digital computer programmed to calculate said value from an algebraic function or functions describing a desired relationship between said engine condition and said means for controlling said energy conversion process; then

with an electrical circuit coupled between said digital computer and said means for controlling said energy conversion process, converting said calculated value into a setting of said means for controllng said energy conversion process; and thereafter

while said engine is in operation, continuously repeating the above sequence of steps at uniform angular intervals of rotation of said engine output shaft to effect changes in the settings of said means for controlling said energy conversion process in response to changes in said binary number electrical signal indicative of said engine condition.

2. A method for controlling a combustion engine in accordance with claim 1, wherein said step of generating a binary number electrical signal indicative of a condition of said engine includes the step of generating a binary number electrical signal indicative of the load on said engine, and wherein said step of arithmetically calculating a value corresponding to a setting of said means for controlling said energy conversion process includes arithmetically calculating a value corresponding to a setting of an adjustable means for controlling the amount of fuel metered to said engine, said algebraic function or functions describing a desired relationship between the load on said engine and settings of said means for controlling the amount of fuel metered to said engine.

3. A method for controlling a combustion engine in accordance with claim 1, wherein said engine includes throttle means for controlling the amount of air supplied to said engine, wherein the step of generating a binary number electrical signal indicative of a condition of said engine includes generating a binary number electrical signal indicative of the position of said throttle, and wherein said step of arithmetically calculating a value corresponding to a setting of said means for controlling said energy conversion process includes arithmetically calculating a value corresponding to a setting of an adjutable means for controlling the amount of fuel metered to said engine, said algebraic function or functions describing a desired relationship between positions of said throttle and settings of said means for controlling the amount of fuel metered to said engine.

4. A method for controlling a combustion engine in accordance with claim 1, wherein said engine has a rotatable output shaft, wherein the step of generating a binary number electrical signal indicative of a condition of said engine includes generating a binary number electrical signal indicative of the angular velocity of said engine output shaft, and wherein the step of arithmetically calculating a value corresponding to a setting of said means for controlling said energy conversion process includes arithmetically calculating a value corresponding to a setting of an adjustable means for controlling the amount of fuel metered to said engine, said algebraic function or functions describing a desired relationship between the angular velocity of said engine output shaft and settings of said means for controlling the amount of fuel metered to said engine.

5. A method for controlling a combustion engine in accordance with claim 1, wherein said engine has a rotatable output shaft and is of the spark-ignition type, wherein the step of generating a binary number electrical signal indicative of a conduction of said engine includes generating a binary number electrical signal indicative of the angular velocity of said engine output shaft, and wherein the step of arithmetically calculating a value corresponding to a setting of said means for controlling said energy conversion process includes calculating a value corresponding to a setting of an adjustable means for controlling the timing of the sparks supplied to said engine, said algebraic function or functions describing a desired relationship between the angular velocity of said engine and settings of said adjustable means for controlling the timing of the sparks supplied to said engine.

6. A method for controlling a combustion engine in accordance with claim 1, wherein said engine is of the spark-ignition type, wherein the step of generating a binary number electrical signal indicative of a condition of said engine includes generating a binary number electrical signal indicative of the load on said engine, and wherein the step of arithmetically calculating a value correspondng to a setting of said means for controlling said energy conversion process includes arithmetically calculating a value corresponding to a setting of an adjustable means for controlling the timing of the sparks supplied to said engine, said algebraic function or functions describing a desired relationship between the load on said engine and settings of said adjustable means for controlling the timing of the sparks supplied to said engine.

7. A method for controlling a combustion engine in accordance with claim 1, wherein said engine has a rotatable output shaft and includes means for recirculating engine exhaust gases through said engine, wherein the step of generating a binary number electrical signal indicative of a condition of said engine includes generating a binary number electrical signal indicative of the angular velocity of said engine output shaft, and wherein the step of arithmetically calculating a value corresponding to a setting of said means for controlling said energy conversion process includes arithmetically calculating a value corresponding to a setting of an adjustable means for controlling the amount of engine exhaust gases recirculated through said engine, said algebraic function or functions describing a desired relationship between the angular velocity of said engine and settings of said exhaust gas recirculation controlling means.

8. A method for controlling a combustion engine in accordance with claim 1, wherein said engine includes throttle means for controlling the amount of air supplied to said engine and means for recirculating engine exhaust gases through said engine, wherein the step of generating a binary number electrical signal indicative of a condition of said engine includes generating a binary electrical signal indicative of the position of said throttle means, and wherein the step of arithmetically calculating a value corresponding to a setting of said means for controlling said energy conversion process includes arithmetically calculating a value corresponding to a setting of an adjustable means for controlling the amount of engine exhaust gases recirculated through said engine, said algebraic function or functions describing a desired relationship between the position of said throttle means and said exhaust gas recirculation controlling means.

9. A method for controllng a combustion engine in accordance with claim 1, wherein said engine has a rotatable output shaft, said method further including the steps of generating electrical pulses at uniform time intervals, generating electrical pulses at uniform intervals of angular rotation of said engine output shaft, and using the first of the uniform time and angular rotation electrical pulses to occur after the completion of said sequence of steps to cause their repetition.

10. A method for controlling a combustion engine in accordance with claim 6, wherein said engine includes throttle meaans for controlling the amount of air supplied to said engine, said algebraic function or functions used to calculate a value corresponding to a setting of said means for controlling the timing of the sparks being different for positions of said throttle means above a predetermined value than the algebraic function used for calculating said spark timing where the position of said throttling means is below said predetermined value.

11. A method for controlling a combustion engine used in a process of converting heat energy, released by the combustion of a fuel, into mechanical energy, said engine including at least first and second means for controlling said energy conversion process, said method comprising the steps of:

generating an electrical signal in the form of a binary number, said signal being indicative of a condition of said engine as of a selected instant in time during which said engine is operative in effecting said energy conversion process; then

arithmetically calculating a first value corresponding to a setting of said first means for controlling said energy conversion process, said calculating being performed, using said binary number electrical signal, by a digital computer programmed to calculate said first value from an algebraic function or functions describing a desired relationship between said engine condition and said first means for controlling said energy conversion process;

arithmetically calculating a second value corresponding to a setting of said second means for controlling said energy conversion process, said calculating being performed, using said calculated value corresponding to a setting of said first means for controlling said energy conversion process, by said digital computer programmed to calculate said second value from an algebraic function or functions describing a desired relationship between settings of said first and second means for controlling said energy conversion process;

with a first electrical circuit coupled between said digital computer and said first means for controlling said energy conversion process, converting said calculated first value into a setting of said first means for controlling said energy conversion process;

with a second electrical circuit coupled between said digital computer and said second means for controlling said energy conversion process, converting said calculated second value into a setting of said second means for controlling said energy conversion process; and thereafter

while said engine is in operation, continuously repeating the above sequence of steps to effect changes in the settings of said first and second means for controlling said energy conversion process in response, respectively, to changes in said binary number electrical signal indicative of said engine condition and in said calculated first value.

12. A method for controlling a combustion engine in accordance with claim 11 wherein said engine has a rotatable output shaft, wherein said calculated first value corresponds to a setting of means of controlling the length of time fuel is metered to said engine, and wherein said calculated second value corresponds to a setting of means for controlling the angular positions of said engine output shaft at which the metering of fuel to said engine is initiated, whereby, the instants of initiation of fuel metering are determined by said calculated second value and the length of time of fuel metering following such initiations is determined by said calculated first value.

13. A method for controlling a combustion engine in accordance with claim 11 wherein:

said engine is of the spark ignition type;

said first means for controlling said energy conversion process comprises means for controlling the timing of sparks supplied to said engine and said calculated first value corresponds to a setting of said means for controlling spark timing; and

said second means for controlling said energy conversion process comprises means for controlling the amount of fuel supplied to said engine and said calculated second value corresponds to a setting of said means for controlling the amount of fuel supplied to said engine.

14. A method for controlling a combustion engine in accordance with claim 11 wherein:

said engine is of the spark ignition type;

said first means for controlling said energy conversion process comprises means for controlling the amount of fuel supplied to said engine and said calculated first value corresponds to a setting of said means for controlling the amount of fuel supplied to said engine; and

said second means for controlling said energy conversion process comprises means for controlling the timing of sparks supplied to said engine and said calculated second value corresponds to a setting of said means for controlling spark timing.

15. A method for controlling a combustion engine in accordance with claim 11 wherein:

said engine is of the spark ignition type;

said first means for controlling said energy conversion process comprises means for controlling the timing of sparks supplied to said engine and said calculated first value corresponds to a setting of said means for controlling spark timing; and

said second means for controlling said energy conversion process comprises means for controlling the amount of exhaust gases recirculated through said engine and said calculated second value corresponds to a setting of said means for controlling the amount of exhaust gases recirculated through said engine.

16. A method for controlling a combustion engine in accordance with claim 11 wherein:

said engine is of the spark ignition type;

said first means for controlling said energy conversion process comprises means for controlling the amount of exhaust gases recirculated through said engine and said calculated first value corresponds to a setting of said means for controlling the amount of exhaust gases recirculated through said engine; and

said second means for controlling said energy conversion process comprises means for controlling the timing of sparks supplied to said engine and said calculated second value corresponds to a setting of said means for controlling spark timing.

17. A method for controlling a combustion engine in accordance with claim 11 wherein:

said first means for controlling said energy conversion process comprises means for controlling the amount of fuel supplied to said engine and said calculated first value corresponds to a setting of said means for controlling the amount of fuel supplied to said engine; and

said second means for controlling said energy conversion process comprises means for controlling the amount of exhaust gases recirculated through said engine and said calculated second value corresponds to a setting of said means for controlling the amount of exhaust gases recirculated through said engine.

18. A method for controlling a combustion engine in accordance with claim 11 wherein:

said first means for controlling said energy conversion process comprises means for controlling the amount of exhaust gases recirculated through said engine and said calculated first value corresponds to a setting of said means for controlling the amount of exhaust gases recirculated through said engine; and

said second means for controlling said energy conversion process comprises means for controlling the amount of fuel supplied to said engine and said calculated second value corresponds to a setting of said means for controlling the amount of fuel supplied to said engine.

BACKGROUND OF THE INVENTION

This invention relates to a method and apparatus for the control of a combustion engine. While the general principles and teachings hereinafter disclosed are applicable to all combustion engines, the invention is hereinafter described in detail in connection with its application to a reciprocating, fuel-injected, spark-ignition internal combustion engine.

As used herein, the term "engine" refers to a device which converts heat energy, released by combustion of a fuel, into mechanical energy in a rotating output shaft of the engine. Also, the term "combustion" is defined as the rapid chemical union of a fuel with oxygen, accompanied by the liberation of useful heat energy. Also, as used herein, the term "binary number" means a number represented by a plurality of bits of information having either of two states.

In an engine, the energy conversion process takes place in a combustion chamber. Various means may be provided for controlling the characteristics of this energy conversion process. For example, means may be provided for controlling the amount of fuel metered into the combustion chamber, for controlling the amount of air supplied to the combustion chamber, for controlling the ratio of fuel to air, and, in a spark-ignition engine, for controlling the timing of sparks supplied to the engine. Also, a recent development used in connection with spark-ignition internal combustion engines for the purpose of effecting a reduction in undesirable exhaust emissions is exhaust gas recirculation (EGR). Where EGR is employed, it is very desirable to provide means for controlling the amount of exhaust gas recirculated to the engine combustion chamber.

A common feature of all engine control systems is that they employ means for sensing at least one condition of the engine while it is operative in effecting the energy conversion process. As a result of sensing this condition, one or more of the means for controlling the energy conversion process are adjusted to the extent required to obtain a desired result.

To illustrate what is meant by the phrase "means for controlling the energy conversion process of an engine", these being controlled variables, consideration may be given to a throttled, spark-ignition, fuel-injected internal combustion engine. In such case, the controlled variables are throttle angle, which controls the amounts of air supplied to the engine, fuel flow per cycle, fuel-injection timing, ignition timing, and, if EGR is used, the settings of the means used to control the amount of exhaust gases recirculated through the engine. To effect control of these variables that determine the characteristics of the energy conversion process, various engine conditions may be sensed while the engine is operative. Thus one or more of the following variable engine conditions may be sensed: crankshaft position, engine speed, mass air-flow into the engine, intake-manifold pressure, throttle angle, EGR-valve position, throttle-angle rate of change, engine-speed rate of change, fuel temperature, fuel pressure, EGR-valve rate of change, vehicle speed and acceleration, engine coolant temperature, engine torque, air-to-fuel ratio, exhaust emissions, etc. Other sensed conditions may include ambient temperature, ambient air pressure, humidity, transmission gear position, and perhaps others.

SUMMARY OF THE INVENTION

A main object of the invention is to employ a digital computer to calculate, on a real-time basis, that is, while the engine is operative, proper settings for one or more of the controlled variables from measurements made on one or more variable engine conditions. The method and apparatus of the invention provide a system which for the first time offers the possibility of a total system approach to engine control wherein account may be taken of the interactions of the various interdependent, variable conditions of engine operation. A very important feature of the invention is that it now is possible to eliminate the engine operating instabilities characteristic of prior art engine control systems and, by this elimination, to obtain equilibrium conditions of engine operation at all times.

The method and apparatus of the invention concerns the control of an engine used in the conversion of heat energy, released by the combustion of a fuel, into mechanical energy. The engine has at least one adjustable means for controlling the energy conversion process performed by it. While the engine is operative, an electrical signal is generated in the form of a binary number. This electical signal is indicative of a condition of the engine as of a selected instant in time. From this binary-number electrical signal indicative of a condition of the engine, a digital computer arithmetically calculates a value corresponding to a setting of the means for controlling the energy conversion process. The digital computer is programmed to calculate the control value from an algebraic function or functions describing a desired relationship between the sensed engine condition and settings of the means for controlling the energy conversion process. The resulting value, in the form of a binary number, is converted into a setting of the means for controlling the energy conversion process. The conversion of the binary number into a setting of the engine controlling means is accomplished with the aid of a suitable electrical circuit coupled between the digital computer and the engine controlling means.

The apparatus of the invention includes a digital computer having a central processing unit and a memory. The digital computer is connected, directly or indirectly, to the means for sensing the varying engine condition and is coupled to an electrical circuit used to adjust the settings of the energy-conversion-controlling means. The digital computer is programmed to calculate repetitively values corresponding to settings for the energy-conversion-controlling means from an algebraic function or functions describing a predetermined desired relationship between the sensed condition and the settings for the energy-conversion-controlling means. The results of the repetitive calculations are transformed by the electrical circuit into adjustments of the energy-conversion-controlling means.

The invention may be better understood by reference to the detailed description which follows and to the drawings. This detailed description of the invention is of an embodiment of the engine control system of the invention as it may be applied to a throttled, reciprocating, fuel-injected, spark-ignition internal combustion engine. It should be understood, however, that the principles and approaches taken in connection with this particular type of engine are applicable to other types as well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of an engine control system for a throttled, reciprocating, fuel-injected, spark-ignition internal combustion engine;

FIG. 2 contains four waveforms 2a, 2b, 2c and 2d obtained at various points in the schematic diagram of FIG. 1;

FIG. 3 is a flow diagram illustrative of the operation of the digital computer used to arithmetically calculate values for the adjustable engine energy-conversion-controlling devices, these devices being used to control fuel metering, EGR-valve position, and ignition-system spark-timing;

FIG. 4 is a detailed flow diagram illustrating the programming of the digital computer as it is used to control fuel metering in the engine;

FIG. 5 is a graph of engine speed versus wide-open-throttle fuel-injection pulse-width;

FIG. 6 is a graph of intake-manifold absolute pressure versus fuel-injection pulse-width;

FIG. 7 is a graph of fuel-injection pulse-width correction-factor versus engine coolant temperature;

FIG. 8 is a detailed flow diagram for the digital computer as programmed for the arithmetic calculation of EGR-valve position;

FIG. 9 is a graph of a family of curves representing EGR-valve-angle .beta. versus throttle angle .theta., each curve being for a different engine speed;

FIG. 10 is a graph of engine-speed correction-factor K.sub.N versus engine speed, this correction factor K.sub.N being used in EGR-valve-position calculation;

FIG. 11 is a graph of EGR-angle-coefficient C.sub.A versus throttle angle .theta. for three values of engine-speed correction factor K.sub.N ;

FIG. 12 is a detailed flow diagram illustrating the programming of the digital compouter as it is used to calculate ignition-system spark-timing;

FIG. 13 is a graph of engine-speed spark-advance .alpha..sub.N versus engine speed N;

FIG. 14 is a graph of engine-load spark-advance .alpha..sub.p versus engine intake-manifold absolute pressure;

FIGS. 15a and 15b are, respectively, schematic diagrams for the engine control system clock-oscillator and time-interrupt circuits illustrated in block form in FIG. 1, FIG. 15c is a schematic diagram for the synchronizer circuit shown in block from in FIG. 1, and FIG. 15d is a schematic diagram for the P.sub.r -interrupt circuit shown in block form in FIG. 1;

FIG. 16 is a general schematic diagram of a programmable-interval-generator circit;

FIG. 17 is a block diagram of a fuel-injection-control logic circuit;

FIG. 18 is a circuit diagram of the fuel-injection start-delay control circuit illustrated in block form in FIG. 17;

FIG. 19 is a circuit diagram of the fuel-injection start-distributor illustrated in block form in FIG. 17;

FIG. 20 is a circuit diagram of a fuel-injector power-driver illustrated in block form in FIG. 16;

FIG. 21 is a circuit diagram for the EGR stepper-motor-control logic circuit illustrated in block form in FIG. 1;

FIG. 22 is a circuit diagram for a spark-timing logic circuit illustrated in block diagram form in FIG. 1; and

FIG. 23 is a schematic diagram of breakerless ignition system and engine-starter circuits illustrated in block form in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, the method and apparatus of the invention are embodied in an engine control system as applied to a Ford Motor Company 351 cubic inch, V-8, reciprocating, throttled, electronically fuel-injected, spark-ignition internal combustion engine. The controlled variables, that is, the adjustable variables selected to control or determine the characteristics of the engine's energy conversion process, are fuel-injection pulse-width, fuel-injection timing, EGR-valve position, and ignition-system spark-timing. Means are provided for adjusting, or setting, each of these controlled variables.

Adjustments of these controlled variables are made while the engine is operative in effecting the conversion of heat energy, released by the combustion of a fuel, into mechanical energy. A digital computer is employed to calculate arithmetically, repetitively and on a real-time basis, values corresponding to settings of the controlled variables. These values are calculated by the digital computer based upon a desired predetermined algebraic relationship established between the particular controlled variables involved and one or more conditions of the engine that are sensed during its operation.

In this embodiment of the invention, the controlled-variable fuel-injection pulse-width is algebraically related to the sensed conditions of engine load, as inferred from measurement of intake-manifold absolute pressure, and engine speed. Fuel-injection pulse width is also a function of ambient temperature and cylinder-head coolant temperature. With respect to the controlled-variable EGR-valve position, which determines the amount of engine exhaust gases recirculated to the combustion chambers of the engine, the sensed conditions to which it is algebraically related are throttle angle and engine speed. The remaining controlled variable determinative of the energy conversion process, that is, ignition-system spark-timing, is an algebraic function of engine load, as inferred from measurement of intake-manifold absolute pressure, and engine speed.

The desired algebraic relationships between the controlled variables and the sensed conditions are determined experimentally. At every instant in the operation of the engine, and over its entire range of operation, there exists optimum settings for the controlled variables. The definition of what is optimum is not fixed, but rather depends upon the use to which the engine is to be put and its state of operation at a particular instant. For example, where the engine and its control system are to be employed in a passenger car, the overall goal for the engine control system may be