Electronic Control For The Air-fuel Mixture And For The Ignition Of An Internal Combustion Engine

Abstract

A function generator is fed input signals corresponding to at least two different engine operating parameters, such as the position of the accelerator pedal and the engine rpm, the function generator, in dependence on these input signals, controlling the amount of fuel supplied to the cylinder so as to maintain a desired excess air coefficient .lambda. for each operating condition of the engine. In one form of the invention, the function generator controls the fuel and air supplied, as well as the ignition timing.

Description

BACKGROUND OF THE INVENTION

The invention relates to an electronic system for controlling the air-fuel mixture for Otto engines.

The major requirement placed on these systems is to reduce the concentration of partly burned or unburned components in the exhaust of internal combustion engines. Some known system completely cut off the fuel supply when the vehicle is coasting so that the engine is driven by the wheels. However, there are other operating conditions of the internal combustion engine for which exhaust purification is both possible and necessary.

After burning is one known method for purifying the exhaust. This method increases the consumption of fuel, and requires an expensive after burner.

SUMMARY OF THE INVENTION

An object of the invention is an electronic system for controlling the excess air coefficient .lambda. throughout as many operating conditions of the engine as possible so as to obtain an exhaust with a greatly reduced concentration of harmful components.

The excess air coefficient .lambda. expresses the ratio between air and fuel. By definition, .lambda. has a value of 1 for a stoichiometric mixture.

Among the poisonous components, particularly unburned hydrocarbons, carbon monoxide, and nitrogen oxide should be removed from the exhaust.

Briefly, the invention consists of first means for providing a respective electrical signal for each of at least two different engine operating parameters, the electrical signals corresponding to the parameters taken into account, and second means connected to receive these signals as input for controlling, in dependence on these signals, at least the amount for fuel supplied to the cylinder so as to obtain a desired excess air coefficient .lambda. for each operating condition of the engine.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the dependence of unburned hydrocarbons and nitrogen oxide concentration on .lambda. and on the ignition timing;

FIG. 2 is a graph showing the dependence on unburned hydrocarbons and carbon monoxide concentration on the sparking time;

FIGS. 3, 4, and 5 are block diagrams of three different embodiments of the invention;

FIGS. 3a, 3b, 4a, and 6 are wiring diagrams of four different embodiments of the electronic function generator of the invention; and

FIGS. 4d, 4c, 7, 8, and 9 are graphs used in explaining the operation of the function generators shown in FIGS. 4a and 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows graphically the discharge of poisonous exhaust fumes in dependence on the excess air coefficient .lambda.. The curves 40,41, and 42 pertain to nitgrogen oxide, with the respective ignition points of 25.degree.,35.degree. , and 50.degree. of topdead center. The curves 43,44, and 45 pertain to unburned hydrocarbon at the respective ignition points of 25.degree.,35.degree. , and 50.degree. of top-dead center. The concentration of carbon monoxide is not shown, the concentration falling with increasing .lambda. until .lambda. exceeds 1.2 whereupon the concentration does not further decline.

Accordingly, it is most advantageous to operate the internal combustion engine with a .lambda. of about 1.2. With still greater values of .lambda., combustion slips can occur, so that the concentration of unburned hydrocarbons increases sharply, as shown in FIG. 1. The fact that the greatest output of the engine occurs at .lambda.=0.9 must also be taken into account.

In accordance with the invention, a sensible compromise between engine output and clean exhaust is obtained in the following manner. A lean mixture is used during those driving conditions that prevail in the city, when maximum engine output is not required, thereby obtaining as clean an exhaust as possible; and a rich mixture is used during those driving conditions that prevail when driving across country, when a clean exhaust is not required.

In accordance with the invention, the speed of the vehicle is used to distinguish between these two groups of driving conditions.

FIG. 3 shows a first embodiment for use with an internal combustion engine having fuel injection. In accordance with the invention, this embodiment can, with slight modifications, also be used with carburetor engines.

The accelerator 13 controls the position of the throttle valve in the intake manifold 11 of an internal combustion engine so as to control the amount of air flowing through the cylinders. This air flow is measured either by a heated temperature sensor 15, which is cooled by the air stream, or by a static plate 15a. The measured values are converted into electrical signals of suitable amplitude by a respective transducer 16 or 16a, the output of which is connected to a first input of an electronic function generator 19. A transducer 14 measures the angular position of the throttle valve 12, the output of this transducer being connected to the second input of the function generator 19. Connected to the third input of the function generator is a multivibrator 18, which delivers pulses at a frequency proportional to the engine rpm. The input of the multivibrator is connected to the primary winding 17 of the ignition coil, not shown. The output of the function generator 19 is connected to a first input of a differential amplifier 20. This differential amplifier 20 is part of a servo control that also comprises a dosing valve 22, an electromagnetic control 21 for the valve, and a transducer 23 for providing the signal voltage corresponding to the actual setting of the valve 22 for controlling the latter.

The function generator 19 delivers a signal corresponding to the desired amount of fuel that is to be supplied to the injection valves. The signal from the function generator, which represents a desired value, is compared by the differential amplifier 20 with the signal from the transducer 23, which represents the actual value. If the signal of the desired value is larger than that of the actual value, the dosing valve 22 is opened more by the electromagnetic control 21.

The function generator 19 is designed so that its output signal is dependent upon the amount of air passing through the intake manifold 11. The engine rpm and the angular position of the throttle valve are obtained from the transducers 16 (or 16a) and 18 as correction signals, and delivered to the other two inputs of the function generator.

Consequently, the fuel supplied to the cylinders is so measured that in all operating conditions of the engine a suitable excess air coefficient .lambda. is obtained.

FIG. 3a shows a first embodiment of the function generator 19. Positioned in the intake manifold 11 are two resistors 150 and 152, which together with two other resistors 151 and 153 constitute a Wheatstone bridge. The voltage across the diagonal of the bridge is conducted by respective resistors 193 and 199 to the two inputs of an operational amplifier 198. The output of the operational amplifier 198 is connected to the base of a voltage amplification transistor 194 and by a resistor 197 to the positive line 40. The collector of the transistor 194 is connected to the base of a power transistor 195, the emitter of the transistor 194 being connected to the collector of the transistor 195 and to the junction between the resistors 150 and 152. The emitter of the transistor 195 is connected by a resistor 196 to the positive line 40.

The junction between the resistors 150, 151, and 199 is connected to an input resistor 192 of a non-linear amplifier 190, the output of which is connected by a resistor 191 to the input of the differential amplifier 20. The position of the accelerator 13 is obtained by means of a potentiometer 24, the wiper of which moves with the accelerator and is connected by a resistor 241 to the input of the differential amplifier 20. The multivibrator 18 is connected by a rectification stage 181 and a resistor 182 to the input of the differential amplifier 20.

The Wheatsone bridge consists of a low ohmage branch 150,151 and of a high ohmage branch 152,153, so that most of the current flowing through the bridge and through the power transistor 195 flows through the low ohmage branch. The value of the resistor 150 in the intake manifold 11 is such that the current through it heats the resistor to a temperature of about 200.degree.C. The current control circuit, which includes the operational amplifier 198 and transistors 194 and 195, serves to keep the current at such a value that the resistor 150 remains at a temperature of about 200.degree.C. no matter what amount of air streams through the intake manifold.

Since the resistor 150 has a positive temperature coefficient, the voltage drop across it will become smaller if the air stream in the intake manifold cools the resistor. Consequently, the voltage at the junction between the resistors 150 and 151 becomes more positive. The voltage at the output of the operational amplifier 198 falls, the transistors 194 and 195 thereby becoming more conductive so as to increase the amount of current flowing through the bridge and to maintain the resistor 150 at its original temperature.

Thus, the current through the bridge is a measure of the amount of air flowing through the intake manifold 11, since the higher the rate at which air streams past the resistor 150 the more the resistor is cooled. Since the bridge current is not a linear function of the air flow per unit time, the voltage drop across the resistor 151 is not proportional to this air flow. The non-linear amplifier 190 serves to make linear the voltage drop across resistor 151. This amplifier can comprise, for example, a resistor-diode network, such as is shown in FIG. 4a(components 252 to 259).

These signal voltages --proportional to the air flow per unit time, to the position of the accelerator 13, and to the engine rpm-- are conducted by the adding resistors 191, 241, and 182 to the input of the differential amplifier 20. Accordingly, the dosing valve 22 is opened wider the greater the air flow, the higher the engine rpm, and the more the accelerator is depressed.

The second resistor positioned in the intake manifold, the resistor 152, is part of the high ohmage branch and therefore does not heat up as a consequence of the current. The value of its resistance does, however, depend on the temperature of the streaming air. The resistor 152 thus compensates for the ambient temperature. With the aid of the operational amplifier 198 and transistors 194 and 195, the difference in temperature between the resistors 150 and 152 is therefore held constant.

FIG. 3b shows a second, simplified, embodiment of the function generator 19. In this embodiment, the amount of air per unit time is measured by means of a static plate 15a, which is mechanically connected to the wiper 165 of a potentiometer 160. A spring 166 holds the wiper in its position of rest. The potentiometer 160 has a series of fixed taps, respective resistors 161,162,163, and 164 being connected between neighboring taps. The potentiometer 160 is connected between the positive rail 40 and ground. A resistor 167 connects the wiper 165 to the input of the differential amplifier 20. In other respects, this embodiment is the same as the embodiment shown in FIG. 3a.

The purpose of the resistors 160 to 164 is to provide on the wiper 165 a voltage that is linearly related to the air flow per unit time. In this embodiment, it is not necessary to compensate for the ambient temperature, since the movement of the static plate 15a depends on the air density and therefore on the temperature. Otherwise, the operation of this embodiment is the same as that of the first embodiment shown in FIG. 3a.

In the second embodiment of the invention, shown in FIG. 4, the function generator controls both the amount of fuel and the amount of combustion air.

The electronic function generator 25 has two outputs. The first output is connected to the input of the differential amplifier 20, which, as in the embodiment shown in FIG. 3, controls the dosing valve 22. The second output of the function generator is connected to the input of a second differential amplifier 26, which by means of a second electromagnetic control 27 controls the throttle valve 12. The three inputs of the function generator 25 are respectively connected to the transducer 13, the transducer 24, and to the multivibrator 18. The functions of these three components have already been described.

The function generator 25 can have one or two other inputs to which, if required, transducers 28 and 29 for respectively refurnishing signals corresponding to air temperature and/or the air pressure can be connected.

In this embodiment, the function generator 25 controls both the dosing valve 22 and the throttle valve 12, the latter being controlled by means of a servo loop.

The signal inputs to the function generator 25 are obtained from the transducers 24,18, and 14. In a refinement of this embodiment, additional inputs of the function generator 25 can be connected to the aforesaid transducers 28 and 29, which furnish corrections signals in dependence on the air temperature and the air pressure.

FIG. 4a is a wiring diagram of one form of the function generator 25. The heart of the generator is an electronic multiplier 48 having two multiplying inputs 481 and 482 and two correction inputs 483 and 484. The output of the multiplier is connected to the input of the differential amplifier 20. The first multiplying input is connected to a diode-resistor network (components 252 to 259) and is connected by a resistor 251 to the output of the transducer 24. The diode-resistor network contains two voltage dividers 252,254 and 253,255, which are connected between the positive line 40 and ground. The tap of each of these voltage dividers is connected by a diode and a resistor connected in series (256 and 257, or 258 and 259) to the first multiplying input 481.

A resistor 43 connects the output of the transducer 24 to the input of the differential amplifier 26. A Zener diode 45 is connected between this input and ground. The rectification stage 181 is connected between the second multiplying input 482 of the multiplier 48 and the multivibrator 18.

The first correction input 483 is connected by a resistor 282 to the tap of the voltage divider consisting of a resistor 281 and of a negative temperature coefficient resistor 280. The NTC resistor 280 measures the ambient temperature. A resistor 291 connects the second correction input 484 to the wiper of a potentiometer 290. This wiper is mechanically connected to a bellows for measuring the air pressure.

FIGS. 4b and 4c show the two families of curves that can be obtained with the function generator shown in FIG. 4a. FIG. 4b illustrates how the amount of fuel Q is dependent on the engine rpm n. Q and n are given in percent of their maximum values. The fixed parameter is the position .alpha..sub.P of the accelerator, which is also given in percent of the maximum possible value. FIG. 4c illustrates the dependence of the amount of fuel Q on the accelerator position .alpha..sub.P for different fixed values of the parameter n. Practical tests have shown these two families of curves to be best.

The knees in the curves shown in FIG. 4c are obtained by the diode of the resistor network 252 to 259. The diode 256 or the diode 258 is conductive as long as its cathode potential is lower than the precisely set voltage at the respective tap of the voltage divider. When one or both of these diodes is conductive, an additional current flows through one or both of the voltage dividers to the first multiplying input 41. The Zener diode 45 ensures that the throttle valve 12 is completely opened at some intermediate position, such as 70 percent of maximum position, of the accelerator 13, as shown in FIG. 7.

In this second embodiment of the invention (FIG. 4), as in the first embodiment (FIG. 3), the dosing valve 22 is opened wider in measure as the accelerator 13 approaches its maximum position and as the engine rpm is raised. The volume of air is not taken into account, since the function generator 25 also controls the throttle valve 12.

FIG. 1 shows that the nitrogen oxide concentration is still quite large at .lambda.=1.2, and that it can be reduced both by increasing the value of .lambda., and by delaying the ignition point. Misfirings, which cause a pronounced increase in hydrocarbon concentration at large values of .lambda., can be reduced by prolonging the sparking time. FIG. 2 shows the dependence of hydrocarbon concentration on the sparking time.

The third embodiment of the invention, shown in FIG. 5, has all of the features of the first two embodiments in addition to having means for prolonging the sparking time to at least 2 milliseconds and means for adjusting the ignition timing. The devices for metering the air and fuel are so designed that the internal combustion engine at partial load is fed a very lean mixture with a .lambda. as large as 1.4. By prolonging the sparking time to above 2 milliseconds, there are obtained the curves 43a, 44a, and 45a (see FIG. 1) for hydrocarbon concentration. These curves show that the exhaust is very clean.

The third embodiment of the invention incorporates a function generator 32 having 4 inputs and 3 outputs. Aside from the two transducers 24 and 18, previously described, there are connected to respective ones of the inputs two additional transducers 33 and 34, respectively providing a signal corresponding to the temperature of the cooling water and to the pressure of the air. The first output of the function generator is connected to the fuel regulating system 35, which controls the amount of fuel supplied to the fuel injection valves 30. A second output of the function generator is connected to a throttle valve control amplifier 36, which regulates the throttle valve 12 by means of a control device 37. A third output of the function generator is connected to an ignition timer setting device 38, the output of which is connected to an ignition device 39, to which is connected a plurality of spark plugs 31.

Unnecessary complication of FIG. 5 is avoided by showing feedback circuit 37a for only the throttle valve control amplifier 36. The feedback circuit enables comparison between the actual setting of the throttle valve 12 and the desired setting. Similar feedback circuits for comparing actual and desired settings can also be provided for the fuel regulating system 35 and the ignition timer setting device 38.

FIG. 6 shows the wiring diagram of the function generator 32, the transducers 33 and 34 being omitted.

The output signals of the function generator 32 are shown in FIGS. 7, 8, and 9. FIG. 7 shows the dependence of the position .alpha..sub.D of the throttle valve 12 on the position .alpha..sub.P of the accelerator 13. FIG. 8 shows the dependence of the required amount q of fuel for each piston stroke on the engine rpm n and on the accelerator position .alpha..sub.P. The value of .lambda. and the accelerator position of .alpha..sub.p are given for each of the curves in FIG. 8. FIG. 9 shows the dependence of the spark advance .alpha..sub.Z on the engine rpm n and on the accelerator position .alpha..sub.P.

The families of curves shown respectively in FIGS. 4b and 8 are different, because, along the ordinate, the amount of fuel is plotted for continuous metering in FIG. 4d, whereas in FIG. 8 the amount is plotted per injection. Experiments have shown that both families of curves are ideal for the particular operating conditions.

The most important parts of the function generator shown in FIG. 6 are the multiplier 48, the first control amplifier 55, the second control amplifier 61, and the three Zener diodes 45,47, and 57.

The transducer 24, which provides a signal corresponding to the position of the accelerator 13, is a potentiometer or an inductive voltage divider of which the upper terminal is connected to a positive direct current voltage 40. In the following description it will be assumed that the transducer 24 is a potentiometer.

A resistor 43 connects the wiper of the potentiometer 24 to an output terminal 44, which is connected to the input of the throttle valve control amplifier 36. The positive direct current potential on the potentiometer wiper is also connected by a resistor 46 to a first input of the multiplier 48, by a resistor 53 to the input of the first control amplifier 55, and by a resistor 59 to the input of the second control amplifier 61.

The Zener diode 45 limits the amplitude of the output signal of the potentiometer 24, causing the knee in the curve shown in FIG. 7.

By way of a resistor 50 and of the first output terminal 51, the electronic multiplier 48 delivers the control signal for the fuel regulating system 35. The family of curves shown in FIG. 8 graphs this signal. In order to ensure that the curves, as n .fwdarw. 0, do not converge towards the origin but instead towards point A, a negative direct current voltage is applied to the first input terminal 41 of the multiplier 48. A resistor 49 connects this input terminal to the multiplier 48. The other input of the multiplier is connected to the output of the multivibrator 18, the multivibrator, as previously explained, providing a voltage signal corresponding to the engine rpm n.

For angular positions of the accelerator that approach the maximum position, the curves of FIG. 8 should have a knee, as shown. This knee is provided by the Zener diode 47.

Whereas the signals corresponding to the engine rpm and to the position of the accelerator are multiplied together to determine the amount of fuel per system stroke, these two signals are added together at the input of the first control amplifier 55 to adjust the ignition timing. There results the family of parallel straight lines, shown in FIG. 9. A resistor 52 conducts the rpm dependent signal, and a resistor 53 conducts the accelerator position dependent signal, to the input of amplifier 55.

The first control amplifier 55 has a negative feedback circuit, composed of a resistor 56 and of a Zener diode 57. This amplifier causes advance of the sparking in measure as the engine rpm rises and the accelerator is depressed, but only until the accelerator pedal reaches one-half of its maximum position. The Zener diode 57 causes the knees in the curves at high engine rpm, as shown in FIG. 9. When the accelerator pedal is pushed to beyond one-half of its maximum position, the spark must be retarded, as shown in FIG. 9. For this purpose, the second control amplifier 61 is provided. The input of this amplifier is connected by a resistor 59 to the output of the transducer 24, which provides a signal corresponding to the angular position of the accelerator, and by a resistor 60 to a negative direct current voltage at the terminal 42. Because of the negative feedback circuit, composed of the resistor 62, and of the diode 63, no signal appears at the output of the amplifier 61, so long as the summation signal at the input has a negative value for small angular positions of the accelerator pedal. As soon as the input signal to the amplifier 61 is positive, the output of the amplifier provides a negative signal that is proportional to the angular position of the accelerator pedal. By suitably choosing the value of the resistor 54, the voltage output of the amplifier 61, when it exceeds a certain value, has a negative effect at the input of the amplifier 55. In this way, the ignition is retarded for larger and larger values of the angular position of the accelerator.

In the second and third embodiments of the invention (FIGS. 4 and 5), the multiplier can be, for example, a Hall effect multiplier. In this case, for example, the current in the Hall probe is equal to the input current of the first multiplier input 481, and the magnetic field is proportional to the current of the second input 482. The correction voltages can be conducted by summing resistors, thereby enabling omission of additional correction inputs.

The advantageous features of the third embodiment of the invention will now be briefly described. Two fundamental steps reduce the concentration of harmful components in the exhaust. First, the internal combustion engine is operated with excess air in order to reduce the concentration of carbon monoxide and of hydrocarbons. Second, the concentration of nitrogen oxide is reduced by lowering the maximum combustion temperature. This is done by making the excess air coefficient .lambda. very large (.lambda. =1.4). Combustion slips, or misfirings, are avoided by prolonging the sparking time to several milliseconds and by advancing the spark. Means are provided for eliminating the steps to cleanse the exhaust when a large output is required from the internal combustion engine. In the third embodiment, the criterion for the elimination of these steps is the speed of the vehicle. These steps can also be eliminated by providing, as with automatic drive, a kick down switch; the steps are bypassed when the accelerator is pushed all the way down to the floorboard.

The third embodiment is a very advantageous compromise solution. It provides good cleaning of the exhaust and yet can be manufactured at a price that is substantially below that of exhaust purifiers that have after burners.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of circuits differing from the types described above.

While the invention has been illustrated and described as embodied in an electronic control for the air-fuel mixture and for the ignition of an internal combustion engine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

Claims

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. An electronic system for controlling the air-fuel mixture in an internal combustion engine having an accelerator, at least one cylinder and a throttle valve, first means for providing a first signal corresponding to the position of the accelerator and a second signal corresponding to the engine rpm; second means including an electronic function generator having input means connected to receive said first and second signals for controlling the amount of fuel supplied to the cylinder so as to obtain a desired excess air coefficient alpha for each operating condition of the engine, and said second means further including means for controlling the position of the throttle valve comprising an amplifier having an input connected to receive said first signal, and a Zener diode connected between ground and said input of said amplifier to become conductive when said accelerator is greatly depressed so that the throttle valve is completely opened before the accelerator is moved to its maximum position.

2. An electronic system for controlling the air-fuel mixture in an internal combustion engine having a throttle valve, an accelerator and at least one cylinder comprising, in combination first means comprising a first transducer for providing a first signal corresponding to the position of the accelerator and a second transducer for providing a second signal corresponding to the engine rpm; second means connected to receive said signals as input for controlling, in dependence upon said signals, the amount of fuel supplied to an engine cylinder so as to obtain a desired excess air coefficient alpha for each operating condition of the engine, said second means including an electronic function generator for selecting the ignition timing in dependence upon said signals, said function generator including an electronic multiplier having first and second inputs respectively connected to receive said first and second signals, said second means further including ignition timing setting means for adjusting the ignition timing, a first control circuit having an input connected to receive said first and second signals and an output connected to said ignition timing setting means to control the latter in dependence upon said signals, and wherein said second means further includes throttle-valve setting means for adjusting the throttle-valve position and a second control circuit having an input connected to said transducers to receive said signals and having an output connected to said throttle-valve setting means to control the latter in dependence upon said signals.

3. A system as defined in claim 1, wherein said second means includes means for providing a rich mixture only at full load operation and at operation at low engine rpm and small load.

4. A system as defined in claim 1, wherein said first means provide a third signal corresponding to the amount of air passing through the intake manifold, and wherein said function generator input means is connected to receive said third signal.

5. A system as defined in claim 4, wherein said first means includes a static plate for measuring the amount of air passing through said intake manifold, and first transducer means for converting the movements of said static plate into said third electrical signal.

6. A system as defined in claim 4, wherein said first means includes temperature dependent resistance means located in the intake manifold air flow for providing a temperature dependent resistance, and transducer means connected to said resistance means for converting the temperature dependency thereof into said third signal.

7. A system as defined in claim 1, wherein said first means provides a third signal corresponding to the air temperature, a fourth signal corresponding to the air pressure, and a fifth signal corresponding to the engine temperature, and means for connecting said input means of said function generator to said third, fourth, and fifth signals.

8. A system as defined in claim 2, wherein said second means includes dosing valve means for controlling the amount of fuel fed to the cylinder, and an electronic function generator connected to said dosing valve means to regulate the latter in dependence on said engine operating parameters.

9. A system as defined in claim 2, wherein said second means includes fuel injection valve means for controlling the amount of fuel fed to the cylinder, and an electronic function generator connected to said fuel injection valve means to regulate the open time of the latter in dependence on said engine operating parameters.

10. A system as defined in claim 1, wherein said second means includes metering means for controlling the flow of fuel to the cylinder, and control means for setting said ignition timing, said metering means, and the throttle valve.

11. A system as defined in claim 10, wherein said control means includes servo loop means and feedback means for feeding back said operating parameters as an actual value in said servo loop means.

12. A system as defined in claim 1, including a further differential amplifier for controlling the amount of fuel supplied to the cylinder, said function generator including an electronic multiplier having first and second inputs and an output, said output being connected to the input of said further differential amplifier, said first input being connected to receive said first signal, and wherein said first means includes a further transducer for providing said second signal, and further including rectifying means having an input and an output, said input being connected to receive said second signal and said output being connected to said second input of said multiplier.

13. A system as defined in claim 12, further including resistance-diode network means connected to said first input of said multiplier for providing a non-linear function.

14. A system as defined in claim 2, further including a first resistor and a second control amplifier connected in parallel between the output of said first transducer and said input of said first control amplifier.

15. A system as defined in claim 14, including a negative feedback circuit connected between the input and output of said second control amplifier, said feedback circuit including a diode and a resistor connected in parallel.

16. A system as defined in claim 2, including a negative feedback circuit connected between said input and output of said first control amplifier, said feedback circuit including a Zener diode and a resistor connected in parallel.

17. A system as defined in claim 2, including a Zener diode connected between said output and said first input of said multiplier.

18. A system as defined in claim 14, wherein said first multiplier input is connected to a first constant bias voltage and the input of said second control amplifier is connected to a second constant bias voltage.