US3898962A

US3898962A - Control system and devices for internal combustion engines

Info

Publication number: US3898962A
Application number: US365729A
Authority: US
Inventors: Gunther Honig; Uwe Kiencke
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1972-06-02
Filing date: 1973-05-31
Publication date: 1975-08-12
Anticipated expiration: 1992-08-12
Also published as: JPS4956033A; IT988897B; GB1395457A; JPS6014184B2; FR2189635A1; DE2226949C3; DE2226949A1; DE2226949B2; FR2189635B1

Abstract

To control at least one solenoid operated fuel injection valve in dependence upon the rate of air flow, and particularly to avoid interference with stray signals generated in the electrical system associated with an internal combustion engine, an air flow meter is arranged in the induction pipe of the engine which has an output providing signals in digital form, for example by controlling the frequency of an osciallator which is then converted into digital signals by a frequency/digital converter. The digital signals are applied to a computing circuit which includes a digital differential analyzer and an interpolator, or function generator which is connected therein and so set that it simulates the operating characteristics of the internal combustion engine to modify the digital signal and provide an output which can be converted by a frequency/time converter to a timing signal to control the solenoid of the fuel injection valve and open the fuel injection valve for a predetermined period of time, depending on rate of air flow, or other engine parameters, and as adjusted for the operating characteristics of the engine over its operating range.

Description

United States Patent [1 1 Honig et a1.

[ Aug. 12, 1975 CONTROL SYSTEM AND DEVICES FOR INTERNAL COMBUSTION ENGINES [75] Inventors: Gunther Honig, Braunschweigi Uwe Kiencke, Moglingen, both of Germany [73] Assignee: Robert Bosch G.m.b.H.,

Gerlingen-Schillerhohe, Germany 22 Filed: May 31,1973

[21] Appl. No.: 365,729

[30] Foreign Application Priority Data June 2, 1972 Germany 2226949 [52] US. Cl. 123/32 EA; 123/148 E [51] Int. Cl. F02D 5/00 [58] Field of Search 123/32 EA, 148 E [56] References Cited UNITED STATES PATENTS 3,689,755 9/1972 l-lodgson et a1. 123/32 EA 3,720,193 3/1973 Monpetit 123/32 EA 3,738,339 6/1973 Huntzinger et a1. 123/117 R 3,752,139 8/1973 Asplund 123/117 R 3,780,711 12/1973 Lindberg 123/32 EA 3,786,788 1 1974 Suda et a1 123/32 EA 3,816,717 6/1974 Yoshida et a]. 123/32 EA L C OSCILLATOR DECODER COMPUTER Primary ExaminerCharles .1 Myhre Assistant Examiner-Joseph Cangelosi Attorney, Agent, or FirmFlynn & Frishauf [5 7] ABSTRACT To control at least one solenoid operated fuel injection valve in dependence upon the rate of air flow, and particularly to avoid interference with stray signals generated in the electrical system associated with an internal combustion engine, an air flow meter is arranged in the induction pipe of the engine which has an output providing signals in digital form, for example by controlling the frequency of an osciallator which is then converted into digital signals by a frequency/digital converter. The digital signals are applied to a computing circuit which includes a digital differential analyzer and an interpolator, or function generator which is connected therein and so set that it simulates the operating characteristics of the internal combustion engine to modify the digital signal and provide an output which can be converted by a frequency/time converter to a timing signal to control the solenoid of the fuel injection valve and open the fuel injection valve for a predetermined period of time, depending on rate of air flow, or other engine parameters, and as adjusted for the operating characteristics of the engine over its operating range.

115 Claims, 29 Drawing Figures VOLTAGE/ VOLTAGE/ FREQUENCY FREQUENCY CONVERTER CONVERTER PATENTED 1 2W5 3, 898.962

SHEET 1 L C OSCILLATOR VOLTAGE/ FREQUENCY CONVERTER VOLTAGE/ FREQUENCY CONVERTER 1 COMPUTER 9 2 FIGS. 30, 3b; FlGS.8o8c

Fig.2b

PATENTEB mi 21975 SHEET PATENTED 3,898,962

SHEET 5 f1] Af 13+B Fig.5b

PATENTEM 3,898,962

SHEET 7 132 r H l f7 1 STROBIN OSCILLATION F A 0 STAGE SUPPRESSOR sL KmA iw I I d COUNTER We 140d I J 7 133 I f0! 142a STROBING FREQUENCY D|V|DER- I I GATE DIVIDER GATE l f02 i I w 137- I L 139 mg I CENTRAL a i DIVIDER- 1 I 106, COUNTER I o 150 151 T I f03 MS I c l I WJ PATENTEU mi 2 ms SHEET SZMDSE mm mm:

PATENTE mm 2 L975 SHEET fOS COUNTER CONTROL SYSTEM AND DEVICES FOR INTERNAL COMBUSTION ENGINES The invention relates to a control device for a fuel injection system of an internal combustion engine, having a computing circuit.

ln a fuel injection system as described in US. Ser. 798,650, a computing circuit is provided for controlling at least one injection valve in dependence upon the rate of air flow as measured by an air flow meter arranged in the engine induction pipe. Direct voltage signals are formed in the computing circuit and are proportional to the rate of air flow and the rotational speed of the crankshaft. These signals are further processed as analog signals in direct voltage amplifier stages. Such direct voltage amplifier stages serving as analog computers have to be adjusted very accurately and cause considerable difficulties with respect to their long-term stability. Furthermore, analog computing circuits are very sensitive to interference pulses which are produced in motor vehicles by, for example, the ignition system or the direction indicators.

It is an object of the invention to provide a control device for an internal combustion engine, for controlling at least one solenoid operated fuel injection valve in dependence upon the rate of air flow, which is reliable and essentially immune to disturbing influence.

SUBJECT MATTER OF THE INVENTION:

An air flow meter is arranged in the induction pipe of the engine and provides digital air flow output signals. A computing circuit has an input connected to receive the digital output signals. The computing circuit output controls the solenoid of the fuel injection valve. The computing circuit comprises a digital differential analyzer and at least one interpolator serving as a store for simulating the operating characteristics of the internal combustion engine.

In accordance with a feature of the invention, and particularly for use in automotive vehicles, the air flow meter comprises an air flow sensitive element which controls the frequency of an oscillator such that its output frequency is dependent upon the rate of air flow. A frequency/digital converter then'provides the digital output. The frequency/digital converter then preferably is the input circuit for thedigital differential analyzer. H

A frequency/digital converter converts an input frequency (whose value may be an analog of an operating parameter of the engine, such as the rate of air flow) into a digital output. An interpolator processes a digital input (in this case the output of the frequency/digital converter) in accordance with predetermined functions to produce a digital output dependent upon the interpolator input in accordance with said functions (which may represent one or more known operating characteristics of the' engine). The frequency/digital converter and the interpolator contain counters which require no adjustment. Interference pulses may possibly cause slight errors in counting but such errors can be made negligible if sufficiently high frequencies are chosen.

The digital differential analyzer is in the particular description with reference to the drawings referred to as an incremental computing circuit since, in the same manner as in an analog computer, the function value is stored in a counter once it has been calculated,

and only the variation or the increment of the function is added to the stored function value in a subsequent interval of time. Therefore, the digital differential analyzer operates to a large extent like an analog computer and, nevertheless, can achieve the same accuracy as a conventional digital computing circuit, since the calculated function value is present in the counter in the form of a binary number having a plurality of digits. The accuracy can be increased by increasing the number of digits of the binary numbers. Of course, the number of digits is limited by the required rate of computing.

The functions or characteristics, according to which the injected quantity of fuel have to depend upon operating parameters, such as the engine speed or the rate of air flow in order to obtain optimum combustion of the air/fuel mixture, can be ascertained experimentally in an internal combustion engine. These functions are to be simulated by the computing circuit and, for this reason, have to be stored therein. In the digital differential analyzer, the interpolator serves as a store for the functional interrelationships designated fields of characteristics, and converts an input frequency into an output frequency which is generally non-linearly dependent upon the input frequency. Thus, the functions or fields of characteristics ascertained experimentally can be adapted to any desired internal combustion engine.

There are two different types of fuel injection systems. In one type, the injection valves are operated intermittently and are opened for a specific injection period at each stroke of the associated cylinder of the internal combustion engine. The quantity of fuel injected is at least approximately proportional to the injection period, since the valves are fully opened during this period. In the other type, the injection valves are open continuously. The flow cross section, and thus the quantity of fuel injected into the induction pipe per unit of time, is proportional to a control current which is fed to the solenoids of the injection valves.

The control device in accordance with the invention can be adapted to the first type of fuel injection system in which intermittently operating injection valves are provided for metering the fuel, by feeding the output frequency of at least one interpolator to a frequency/- time converter for the purpose of controlling the injection valves. The frequency/time converter serves to convert the output frequency of the interpolator into an injection period proportional thereto.

The control device of the present invention can be adapted to the second type of fuel injection system in which continuously operating injection valves are provided for metering the fuel, by feeding the output frequency of at least one interpolator at least indirectly to the electrical inputs of the injection valves. If it is ensured that the output frequency of the interpolator consists of pulses of constant length, the average current strength fed to the injection valves is proportional to this output frequency of the interpolator. The inductance of the solenoid serving to open an injection valve serves to form the average value of the current.

When the digital differential analyzer is used to control the fuel injection system, it is preferable for it to also effect the so-called warming-up enrichment of the fuel/air mixture, since'an internal combustion engine requires a richer mixture when in the cold state. The mixture can be enriched during the warming-up phase if the electrical output of a temperature sensor in thermal contact with the engine block of the internal combustion engine is connected to the input of a voltage/- frequency converter, the output of the oscillator is connectedto a first frequency/digital converter, and the output of the voltage/frequency converter is connected to a second frequency/digital converter.

A plurality of non-linear fields of characteristics of the internal-combustion engine can be superimposed by connecting a respective interpolator to the output of each frequency/digital converter.

The air flow meter fitted in the induction pipe measures a quantity of air which flows through the induction pipe per unit of time. A specific quantity of fuel is likewise injected into the induction pipe per unit of time in the case of continuously operating injection valves. Therefore, a'further correction circuit is not required and the output frequencies of the interpolators can be fed without further processing to the solenoids of the injection valves. On the other hand, in the first type of fuel injection system which includes intermittently operating injection valves, a further correction circuit is required to take into account the speed of the internal combustion engine.

The open periods of the inlet valves are shorter at higher speeds of the internal combustion engine, so that the internal combustion engine draws in a smaller quantity of air per stroke with the same measured rate of air flow per unit of time. Thus, the speed of the internal combustion engine also has to be taken into account for accurately calculating the quantity of fuel to be injected. This can be achieved if the second interpolator and the pulse tachogenerator are connected to two inputs of a divider, the outputs of the first interpolator and the divider are connected to two inputs of a multiplier, and the output of the multiplier is connected to the input of the frequency/time converter whose output serves for controlling the injection valves.

The frequency/time converter converts the output frequency of the computing circuit into an injection period proportional thereto.

The above-described features of the control device in accordance with the invention at the same time enable the exhaust gases to be relatively uncontaminated with obnoxious substances, since the above-mentioned simulation of the fields of characteristics of the internal combustion engine leads to optimum combustion of the air/fuel mixture. The cleanliness of the exhaust gases can be still further improved however if an oxygen measuring sensor is arranged in an exhaust gas collecting manifold of the internal combustion engine, the output of the oxygen measuring sensor being connected to a further input of the computing circuit by way of a voltage/frequency converter. The oxygen measuring senser ascertains the accuracy with which the optimum fuel/air mixture has been calculated.

The injection period calculated by the computing circuit in dependence upon the operating parameters of the internal combustion engine can be corrected in a particularly accurate manner in dependence upon the output signal of the oxygen measuring sensor if a servoloop having a subtractor for comparing the desired value with the actual value is provided for the air number of the air/fuel mixture fed to the internal combustion engine, and if the voltage/frequency converter is connected to a first input of the subtractor and a desiredvalue setter is connected'to'the second input of the subtractor. (The air number A represents the mass ratio of air to fuel and is chosen to be 1.0 for a stoichiometric mixture).

By virtue of the described circuit arrangement, the computing circuit becomes a component part of the servo-loop which controls the injection period in dependence upon the actual measured composition of the air/fuel mixture.

The construction of the control device, as a servoloop has'a further advantage that the computing accuracy does not have to be' so high. That is to say, a small error in the calculated injection period is immediately corrected by the servo-loop. Therefore, in the embodiment having a servo-loop, the total expenditure on circ'uitry is only slightly greater than in the embodiment without such a feedback loop.

The invention is further described hereinafter, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an internal combustion engine having various measuring transducers;

FIG. 2a is a sectional view of an oxygen mearuing sensor; I

FIG. 2b is a graph of the output voltage of the oxygen measuring sensor; I

FIG. 3a is a block circuit diagram of a first embodiment of control device in accordance with the invention; v

FIG. 3b is a block circuit diagram of a second embodiment of control device;

FIG. 4a is a circuit diagram of a series multiplier;

FIG. 4b is a pulse diagram for explaining the mode of operation of the series multiplier illustrated in FIG. 4a;

FIG. 5a is a block circuit diagram :of a frequency/digital converter and an interpolator of the control devices of FIGS. 3a and 3b,

FIGS. 5b and 5c are graphs for explaining the mode of operation of the.circuit illustrated in FIG. 5a;

FIG. 6 is a block circuit diagram of a divider and a plurality of multipliers of the control devices of FIGS. 3a and 3b;

FIG. 7 is a circuit diagram of a frequency/time converter of the control device of FIG. 3a; I

FIGS. 8a to are block circuit diagrams of parts of further embodiments of control devices in accordance with the invention (third to fifth embodiments); I

FIG. 9a is a circuit diagram of thefrequency/digital converter of FIG. 5a;

FIG. 9b shows pulse graphs for explaining the operation of the frequency/digital converter of FIG. 5a;

FIG. 9c is a circuit diagram of a modification of the frequency/digital converter illustrated in FIG. 9a;

FIG. 10 is a circuit diagram of a central divider counter appearing in FIG. 5a and subsequent Figures;

FIG. 11a is a circuit diagram of a pulse generator of FIG. 5a; 1

FIG. 1 1b is a pulse diagram for explaining the mode of operation of the pulse generator illustrated in FIG. 1 la; f 1

FIG. 12a is a circuit diagram of a range decoder of Fio.sa,--

FIG. 12b is a table for explaining the switching functions of the range decoder illustrated-in FIG. 12a;

FIG. 13 is a circuit diagram of a divider-gate of the kind appearing in FIG. 5a and subsequent Figures;

FIG. 14a is a circuit diagram of a divider of FIG. 3a,"

Claims

1. In combination with an internal combustion engine having an induction pipe, a control device for controlling at least one solenoid (32, 33) operated fuel injection valve (29, 30) in dependence upon the rate of air flow to the engine through the induction pipe, comprising an air flow meter (25, 26) to be arranged in the induction pipe of the engine; an oscillator (28), the frequency of which is controlled by the air flow meter (25, 26) to provide an oscillator output signal whose frequency is a function of the rate of air flow; a frequency digital converter connected to receive the oscillator output signals and providing digital signals representative of the frequency of the oscillator, and hence of the rate of air flow; and a digital computing circuit having an input connected to receive the digital signals and having an output connected to and controlling the solenoid (32, 33) of the fuel injection valve (29, 30), said computing circuit comprising a digital differential analyzer whose input is responsive to said digital signals derived as a function of frequency of the oscillator. and at least one interpolator (58, 61) having stored therein simulated operating characteristics of the internal combustion engine over its operating range to modify the digital signals passing through said computing circuit in accordance with said simulated operating characteristics of the combustion engine.

2. A control device as claimed in claim 1, for an engine having at least one intermittently operating fuel injection valve (29, 30) for metering the fuel, in which the computing circuit includes a frequency/time converter (70) connected to and controlling the solenoid (32, 33) of the fuel injection valve and being responsive to the output frequency (f11, f21) of the interpolator (58, 61).

3. A control device as claimed in claim 2, in which said frequency/time converter (FIG. 7: 70) comprises a frequency/digital converter (132), a backward counter (141) and a transfer gate (140) connecting the output of the frequency/digital converter (132) to the input of the backward counter (141).

4. A control device as claimed in claim 3, in which the backward counter (141) comprises a series combination of a plurality of JK flip-flops (142-144) to whose triggering inputs a stepping pulse train (f03) is applied.

5. A control device as claimed in claim 4, comprising a first AND gate (150); wherein the Q2 outputs of the JK flip-flops (142-144) are connected to inputs of the AND gate (150) whose output is connected by way of an inverter (151) stage to one input of another AND gate (145) to whose other input is applied the strobing pulse train (f03), and whose output is connected to the triggering inputs of the JK flip-flops (142-144).

6. A control device as claimed in claim 3, comprising a power amplifier (153) having its output connected to the inputs of the solenoids (32, 33) serving to actuate the fuel injection valves (29, 30); a JK flip-flop, (152) the input of the power amplifier (153) being connected to the output of the JK flip-flop (152), said JK flip-flop (152) being controlled by the backward counter.

7. A control device as claimed in claim 4, in which the transfer gate (140) comprises a group of AND gates (147-149) of equal number to the number of steps of the backward counter, one input of each of the AND gates of the group being connected to a signal representative of engine speed; and means (150) operable in synchronism with the rotational speed of the crankshaft of the internal combustion engine generating said speed signal.

8. A control device as claimed in claim 7, comprising a JK flip-flop (152) having its J input connected to the speed signal, its K input connected to the output of the AND gate (150), and the strobing pulse train (f 03) is applied to the triggering input thereof of the JK flip-flop.

9. A control device as claimed in claim 2, in which the frequency/time converter (FIG. 7: 70) comprises a frequency/digital converter (132) which includes a forward/backward counter (133) and a feedback loop containing a digital/frequency converter (140, 141, 142) arranged between the binary number output and the counting input (z) of the forward/backward counter (133) (FIG. 7).

10. A control device as claimed in claim 9, in which the digital/frequency converter is a series multiplier and includes a divider-counter (106) and a divider-gate (140) connected to the outputs of the divider-counter (106).

11. A control device as claimed in claim 10, further comprising a subtractor (135) having its output connected to the counting input (z) of the forward/backward counter (133) and its input connected to the input signal (f7) to the frequency/digital converter (132), and the output frequency of the divider-gate (140).

12. A control device as claimed in claim 11, in which a frequency divider (141) is arranged between the output of the divider-gate (140) and the subtractor (135).

13. A control device as claimed in claim 11, in which an oscillation suppressor (136) is arranged between the subtractor (135) and the counting input (z) of the forward/backward counter (133) the oscillation-suppressor also being connected to and controlling the counting direction input (d) of the forward/backward counter (133).

14. A control device as claimed in claim 11, comprising first and second strobing circuits (134, 142), wherein said input signal (f7) and said output frequency of the divider gate (140) are applied via the respective first and second strobing stage (134, 142) to the inputs of the subtractor (135).

15. A control device as claimed in claim 7, wherein the frequency/digital converter (132) comprises a forward/backward counter (133), in which the binary output of the forward/backward counter (133) is connected to the second inputs of the group of AND gates (147-149).

16. A control device as claimed in claim 1, for an engine having a continuously operating fuel injection valve (29, 30) for metering the fuel, in which the output of said interpolator (58, 611) at least in part determines energization of the solenoid (32, 33) which controls the position of the fuel injection valve.

17. A control device as claimed in claim 1, further comprising a temperature sensor (38) placed in thermal contact with the internal combustion engine (20) and a voltage/frequency converter (39) whose input is connected to the electrical output of the temperature sensor (38), and wherein the computing circuit includes a second frequency/digital converter (60) whose input is connected to the output of the voltage/frequency converter (39).

18. A control device as claimed in claim 17, comprising a second interpolator (61) connected to the output of the second frequency/digital converter (60).

19. A control device as claimed in claim 2, comprising a pulse tachogenerator (41) driven by the crankshaft (40) of the internal combustion engine (20) and providing a speed signal (f3); wherein the computing circuit is connected to process the output of the interpolator (58) and the output (f3) of the tachogenerator (41) to obtain a derived signal dependent upon both the air quantity and the engine speed, said derived signal being fed at least indirectly to said frequency/time converter (70).

20. A control device as claimed in claim 19, in which the computing circuit comprises a divider (63), one of whose inputs is connected to the tachogenerator (f3) so that the output frequency of the divider is dependent upon the reciprocal of the engine speed, and a multiplier (64), having two inputs to which the outputs of the interpolator (58) and the divider (63) are respectively connected so that said deRived signal appears at the output of said multiplier (64).

21. A control device as claimed in claim 18, wherein the computing circuit includes a frequency/time converter (70) responsive to the output frequency (f11, f21) of the interpolator, and connected to and controlling the solenoid of the fuel injection valve, further comprising a pulse tachogenerator (41) adapted to be driven by the crankshaft (40) of the internal combustion engine (20), and providing a speed signal (f3); wherein the computing circuit comprises a divider (63) having two inputs to which the second interpolator (61) and the tachogenerator (41) are respectively connected, and a multiplier (64) having two inputs to which the outputs of the first interpolator (58) and the divider (63) are respectively connected, the output of said multiplier (64) being connected at least indirectly to the input of the frequency/time converter (70) whose output controls the solenoid (32, 33) of the fuel injection valve (29, 30).

22. A control device as claimed in claim 21, in which the divider (63) comprises (FIG. 14a) a forward counter (122), a ''''final reading'''' store (123) whose inputs are connected to the binary number output of the forward counter (122); and a synchronizing gate (120), a first output of which is connected to a reset input (R) of the forward counter (122) and a second output of which is connected to a ''''transfer command'''' input (H) of the final reading store (123), the output frequency (f21) of the second interpolator (61) being applied to the counting input (z) of the forward counter (122) and the output frequency of the pulse tachogenerator (41) being applied to the input of said synchronizing gate (120).

23. A control device as claimed in claim 22, in which the synchronizing gate (120) has a synchronizing input (121) to which a strobing pulse train (f03) is applied.

24. A control device as claimed in claim 22, in which said synchronizing gate (120) comprises first and second JK flip-flops (263, 265), the output frequency (f3) of the tachogenerator (41) being applied directly to the J input of each first flip-flop (263) and to the K input thereof by way of an inverter stage (264), the J of the second flip-flop (265) being connected to the Q1 output and the K inputs of both the first flip-flop (263) and the second flip-flop (265) being connected together.

25. A control device as claimed in claim 24, in which the triggering inputs of the first and second JK flip-flops (263, 265) form the synchronizing input of the synchronizing gate (121), the gate (121) further comprising a first AND gate (266) having inputs connected respectively to the synchronizing input (121) and the Q1 output of the first JK flip-flop (263) and a second AND gate (267) having inputs connected respectively to the Q1 output of the second JK flip-flop (265) and to said synchronizing input (121).

26. A control device as claimed in claim 25, in which the output of the first AND gate (266) is connected to the transfer command input (H) of the final reading store (123) and the output of the second AND gate (267) is connected to the reset input of the forward counter (122).

27. A control device as claimed in claim 22, in which the forward counter (122) comprises a plurality of interconnected JK flip-flops (256-259) whose triggering inputs are interconnected to form the counting input (z), the reset input (R) being common to the plurality of JK flip-flops (256-259).

28. A control device as claimed in claim 22, in which the final reading store (123) comprises a plurality of D flip-flops (260-262) whose triggering inputs are interconnected to form the transfer command input (H) and whose D inputs are connected to the binary number output of the forward counter (122).

29. A control device as claimed in claim 18, in which the computing circuit Comprises a first multiplier (64) having two inputs to which the outputs of the two interpolators (58, 61) are connected, the output frequency of said multiplier being fed at least indirectly to said solenoid (32, 33) of the fuel injection valve (29, 30).

30. A control device as claimed in claim 29 for an engine having a throttle, or butterfly valve (23), which includes a decoder (FIG. 1: 48) responsive to the position of the throttle or butterfly valve (23) of the internal combustion engine (20) and in which the computing circuit comprises a second multiplier (65) having two inputs connected respectively to the output of the first multiplier (64) and to the decoder (48).

31. A control device as claimed in claim 30, wherein the decoder (48) comprises (FIG. 15) a logic network having logic gates (271-274), and two switches (45, 46) the first (45) of which is operable when the throttle or butterfly valve is in the idling position, and the second (46) of which is operable when the throttle or butterfly valve is in its full load position, the logic gates being controlled by said switches.

32. A control device as claimed in claim 1 further comprising a voltage/frequency converter (67) for producing a frequency which increases with increasing voltage of the power supply for the solenoid (32, 33), and in which said computing circuit comprises a frequency converter (68) whose input is connected to the output of the voltage/frequency converter (67) to provide a frequency which decreases with increasing power supply voltage, and an adder (69) having two inputs of which one is connected at least indirectly to the output of said at least one interpolator (58) and the other is connected to the output of the frequency converter (68), the output of the adder (69) being fed at least indirectly to said solenoid (32, 33).

33. A control device as claimed in claim 32, in which the frequency converter (68) comprises a divider to which a strobing pulse train (f02) is applied as a dividend and to which the output frequency (f4) of the voltage/frequency converter (67) is applied as a divider.

34. A control device as claimed incclaim 33, wherein the divider comprises (FIG. 6) a forward counter (127), a final reading store (128) whose inputs are connected to the binary number output of the forward counter (127), and a synchronizing gate (126), a first output of which is connected to a reset input (R) of the forward counter (127) and a second output of which is connected to a transfer command input (H) of the final reading store (128), the strobing pulse train (f02) being applied to the counting input of the forward counter (127) and the output (f4) of the voltage/frequency converter (67) being applied to the input of the last-mentioned synchronizing gate (126).

35. A control device as claimed in claim 34, in which the synchronizing gate (126) has a synchronizing input to which a strobing pulse train (f01) is applied.

36. A control device as claimed in claim 34, and further comprising at least one additional counter (122), final reading store (123) and gate (120); wherein the forward counter (127), the final reading store (128) and the synchronizing gate (126) are of the same construction as the additional forward counter (122), the final reading store (123) and the synchronizing gate (120).

37. A control device as claimed in claim 34, wherein the frequency converter (68) comprises (FIG. 6) a series multiplier comprising a divider-counter (106) and a divider-gate (129) connected to the outputs of the divider-counter (106), the divider-gate (129) being connected between the output of the final reading store (128) and said other input of the adder (69).

38. A control device as claimed in claim 1, in which the frequency/digital converter (57) comprises (FIG. 5a) a forward/backward counter (101) and a feedback loop including a digital/frequency converter (102, 106) arranged between the binary number oUtput (g1) and the counting input (z) of the forward/backward counter (101).

39. A control device as claimed in claim 38, in which the digital/frequency converter (102, 106) is a series multiplier and includes a central divider-counter (106) and a divider-gate (102) connected to the outputs of the central divider-counter (106).

40. A control device as claimed in claim 39, in which the central divider/counter (106) has a plurality of groups of outputs and one group being connected to said divider-gate being connected to effect division counting in other circuits of the device whereby said central divider/counter will be common to the device.

41. A control device as claimed in claim 40, in which the central divider/counter comprises the divider/counter (106) forms the divider counter of claims 10 and 37.

42. A control device as claimed in claim 39, comprising (FIG. 5a) subtractor (98) connected by its output to the counting input (z) of the forward/backward counter (101), the input signal (f1) to the frequency/digital converter (57) and the output frequency (f16) of the divider-gate (102) being applied to respective inputs of the subtractor (98).

43. A control device as claimed in claim 42, comprising a frequency divider (99) arranged between the output of the divider-gate (102) and the input to the subtractor (98).

44. A control device as claimed in claim 42, in which an oscillation suppressor (100) is arranged between the subtractor (98) and the counting input (z) of the forward/backward counter (101), the oscillation suppressor also controlling the counting direction input (d) of the forward/backward counter (101).

45. A control device as claimed in claim 44, in which the oscillation suppressor (100) comprises (FIG. 9a) a D flip-flop (175) whose D input is connected to the input of the subtractor (98) which receives the pulses to be counted negatively and whose triggering input is connected to the output of the subtractor (98), an EXCLUSIVE OR gate (176) whose two inputs are connected to the D input and the Q2 output of the D flip-flop (175), and a NAND gate (177) whose first input is connected to the triggering input of the D flip-flop (175) by way of an inverter (178) and whose second input is connected to the output of the EXCLUSIVE OR gate (176), the output of the NAND gate (177) being connected to the counting input (z) of the forward/backward counter (101) and the Q2 output of the D flip-flop (175) being connected to the counting direction input (d) of the forward/backward counter (101).

46. A control device as claimed in claim 42, comprising (FIG. 9a) respective first (97) and second (172) strobing stages connected to the inputs of the subtractor (98) to apply said input signal (f1) and said output frequency (f16), respectively therethrough to the subtractor (98).

47. A control device as claimed in claim 46, in which the first strobing stage comprises a series combination comprising first (167) and second (170) D flip-flops whose triggering inputs are controllable by a stepping pulse train (f01) inverted in an inverter stage (169), the input signal being applied as a frequency to the D input of said first D flip-flop (167), and a NAND gate (171) whose output forms the output of the first strobing stage (97) and whose two inputs are connected respectively to the Q1 output of said first D flip-flop (167) and the Q2 output (171) of said second D flip-flop.

48. A control device as claimed in claim 43, comprising (FIG. 9a) a strobing stage (172) connected between the output of the frequency divider (99) and the subtractor (98), and including a D flip-flop (172), whose triggering input is connected to an inverted stepping pulse train (-f01) and whose D input is connected to the output of the frequency divider (99), and a NAND gate (173) whose two inputs are connected respectively to the D input and The Q2 output of the D flip-flop (172) and whose output is connected to the subtractor (98).

49. A control device as claimed in claim 46, in which the subtractor (98) comprises an EXCLUSIVE OR gate (98) whose two inputs are connected to the outputs of said first and second strobing stages (97, 172).

50. A control device as claimed in claim 49, comprising a NAND gate (174) connected by its first input to the input of the EXCLUSIVE OR gate (98) forming the subtraction stage by its second input to an inverted stepping pulse train (-f01) and having its output connected to the forward/backward counter (101).

51. A control device as claimed in claim 46, in which the first and second strobing stages (FIG. 9c: 97, 172) are similar.

52. A control device as claimed in claim 46, wherein the subtractor (98) comprises (FIG. 9c) two AND gates (291, 292) each connected by one input via a respective inverter stage (293, 294) to the output of a respective one of the first and second strobing stages (97, 172a, 172), and by another input to the other of the first and second strobing stages, and an OR gate (298), connected by its inputs at least indirectly to the outputs of the two AND gates (291, 292).

53. A control device as claimed in claim 52, wherein the oscillation suppressor (100) comprises a JK flip-flop (295) whose J, K inputs are connected to the outputs of the two AND gates (291, 292), and further first and second AND gates (296, 297), two inputs of said first of which (296) are connected respectively to the J input and the Q1 output of the JK flip-flop (295) and two inputs of said second of which (297) are connected respectively to the K input and the Q2 output of the JK flip-flop (295), the outputs of the first and second AND gates (296, 297) being connected to the inputs of the OR gate (298).

54. A control device as claimed in claim 53, in which the output of the OR gate (298) is connected to the counting input (z) of the forward/backward counter (101), and the output of one of the further first and second AND gates (296, 297) is connected to the counting direction input (d) of the forward/ backward counter (101).

55. A control device as claimed in claim 42, in which the divider-gate (102) has two frequency outputs (f12, f13), an adder (103), the two frequency outputs (f12, f13) being connected to inputs of the adder (103) whose output is connected to the input of the subtractor (98).

56. A control device as claimed in claim 55, in which the adder (103) comprises a NAND gate.

57. A control device as claimed in claim 55, comprising an adder circuit (107) whose inputs are connected to outputs of said central divider-counter (106) for producing a constant offset or shift frequency (f15) which is fed to an input of the subtractor (98).

58. A control device as claimed in claim 57, comprising an additional adder (105), having its output connected to the input of the frequency divider (99), its inputs connected to the outputs of the adders (103) and the adder circuit (107).

59. A control device as claimed in claim 58, comprising respective strobing stages (104, 108) connected to the input of the additional adder (105).

60. A control device as claimed in claim 59, in which the adder circuit (107) and the respective strobing stage (108) together comprise a NOR gate (107) which has an additional strobe input (197).

61. A control device as claimed in claim 17, in which the second frequency/digital converter (60) is of the same construction as the frequency/digital converter (57).

62. A control device as claimed in claim 1, in which the interpolator (58) comprises (FIG. 5a) a range or interval decoder (110); a forward/backward counter (101); the output (81) of the forward/backward counter being connected to the input of the range decoder (110); and a constant store (112) and a slope store (115) whOse inputs are connected to the digital output of the range decoder (119), the constant store (112) and the slope store (115) serving to store reference constants and slopes to simulate the operating characteristics of the engine and to modify the output signal of the interpolator in relation to the input signal to be interpolated over different ranges of the input signal as determined by the range decoder (110) whereby the output signal will be, at any level, a function of the input signal as modified by the transfer function of the interpolator at the respective signal level or range.

63. A control device as claimed in claim 62, in which the range decoder comprises (FIG. 12a) NAND gates (231-239) whose outputs provide the decoder binary output and whose inputs are connected at least indirectly to those outputs of the forward/backward counter (101) associated with the highest binary digits.

64. A control device as claimed in claim 63, comprising inverter stages (232, 235), some inputs of at least some of the NAND gates (231-239) being connected via the inverter stages to the respective counter (101) outputs.

65. A control device as claimed in claim 62, in which the constant store (112) and the slope store (115) are in the form of wired stores.

66. A control device as claimed in claim 62, in which the interpolator (57) further comprises a series multiplier connected to the constant store (112) for producing the reference constants of the interpolated function according to the decoded ranges.

67. A control device as claimed in claim 66, in which the series multiplier comprises a divider-counter (106) and a separate divider-gate (111), the constant store (112) having a binary number output connected to the binary number input of the divider-gate (111).

68. A control device as claimed in claim 62, in which the interpolator (57) further comprises a series multiplier connected to the output of the slope store (115) for producing portions of the interpolated function linearly dependently upon the input frequency in the individual decoded ranges.

69. A control device as claimed in claim 68, further comprising a strobing stage (114) connected to the input (z) to the series multiplier.

70. A control device as claimed in claim 69, wherein the strobing stage (114) comprises (FIG. 9a) an AND gate (114) of which a first input is connected to said divider-gate frequency output (f13) NOR gate (195), and a second input of the AND gate (114) being connected to the output of the NOR gate (195), which has two inputs to which respective strobing pulse trains (f 01, f 02) are applied.

71. A control device as claimed in claim 68, wherein the series multiplier of claim comprises (FIG. 5a) a divider-counter (113), and a divider-gate (102), the counting input of the counter (113) being connected to the frequency output of the divider-gate (102); and a second divider-gate (114), the slope store (115) having a binary number output connected to the binary number input of the second divider-gate (114).

72. A control device as claimed in claim 71, in which the interpolator further comprises (FIG. 5a) an adder (116) whose output forms the output of the interpolator (57), the frequency outputs of the second divider-gate (114) and the separate divider-gate (111) being applied to respective inputs of the adder (116).

73. A control device as claimed in claim 72, further comprising respective strobing stages (113a, 112a) connected between the inputs of the adder (116) and the outputs of the divider-gates (114, 111).

74. A control device as claimed in claim 73, the device comprises more than one interpolator, and at least two interpolators are similar.

75. A control device as claimed in claim 74, further comprising an oxygen measuring sensor (36) located to be responsible to exhaust gas from the internal combustion engine (20); and a voltage/frequEncy converter (37) whose input is connected to the oxygen measuring sensor (36) and whose output is connected to the computing circuit.

76. A control device as claimed in claim 75, wherein (FIG. 8a) the oxygen measuring sensor (36) and the voltage/frequency converter (37) connected thereto are connected in a servo-loop, said loop also comprising a subtractor or comparator (160) to compare a desired reference value with an actual value of the air number of the fuel/air mixture fed to the internal combustion engine, the voltage/frequency converter (37) being connected to a first input of the subtractor (150); and means to connect said reference value connected to the second input of the subtractor (160).

77. A control device as claimed in claim 76, in which said reference value connecting means comprises a multiplier (161).

78. A control device as claimed in claim 77, in which the multiplier (161) comprises (FIG. 8a) a series multiplier including a divider-counter (106) and a divider-gate (162) connected to the outputs of the divider-counter (106); a dividing factor store (163), the divider-gate (162) being connected between the dividing factor store (163) and the second input of the subtractor (160).

79. A control device as claimed in claim 78, wherein a central divider-counter (106) is provided in the device, and the divider-counter (106) comprises said central divider-counter.

80. A control device as claimed in claim 76, in which the servo-loop comprises an integrating controller (157) connected to the output of the subtractor or comparator (160).

81. A control device as claimed in claim 80, further comprising an oscillation suppressor (158) is arranged between the subtractor (160) of said integrating controller (157).

82. A control device as claimed in claim 80, wherein said integrating controller comprises a forward/backward counter (157).

83. A control device as claimed in claim 82, wherein the computing circuit further comprises (FIG. 8a) a further multiplier (156) which has two inputs of which a first is connected to the output of the integrating controller (157); second is connected to the output of the interpolator (58), the output of the last-mentioned further multiplier (156) controlling said solenoid (32, 33) of the fuel injection valve (29, 30).

84. A control device as claimed in claim 83, further comprising means (69) connecting a signal representative of supply voltage for the solenoid (32, 33) to the second input of the further multiplier (156).

85. A control device as claimed in claim 82, in which the computing circuit comprises (FIG. 8b) an adder (165) whose inputs are connected to the output of said integrating controller (157); and means (69) connecting a signal representative of operating parameters affecting the device to the input of said adder (165), the output of the adder (165) controlling the solenoid (32, 33) of the fuel injection valve (29, 30).

86. A control device as claimed in claim 85, wherein said connecting means comprises a signal adder (69) having engine operating parameter signals applied thereto, said signal adder (69) being connected to the second input of the adder (165).

87. A control device as claimed in claim 85, in which said servo-loop includes (FIG. 8b) a digital/frequency converter (106, 166) which arranged between the integrating controller (157) and the adder (165).

88. A control device as claimed in claim 83, further comprising a frequency/time converter (70), the output of the furhter multiplier (156) being connected to the input of said frequency/time converter (70).

89. A control device as claimed in claim 85, further comprising (FIG. 8b) a frequency/time converter (70) the output of the adder (165) being connected to the input of said frequency/time converter (70).

90. A control device as claimed in claim 82, further comprising a frequency/time converter (70) (FIG. 8c) having two inputs (f 7, f 9), said servo-loop comprises a digital/frequency converter (106, 166) connected between the forward/backward counter (157) and an input (f 9) of said frequency/time converter (70).

91. A control device as claimed in claim 90, wherein (FIG. 8c) the frequency/time converter comprises a backward counter (141) and the output of the digital/frequency converter (106, 166) is connected as a stepping input (f 9) to the backward counter (141).

92. A control device as claimed in claim 89, in which the digital/frequency converter (106, 166) comprises (FIG. 8b) a series multiplier comprising a divider-counter (106) and a divider-gate (166) connected to the outputs of the divider-counter (106), the divider-gate (166) being connected between the output of the forward/backward counter (157) and the frequency/time converter (70).

93. A control device as claimed inclaim 92, wherein a central divider-counter (106) is provided in the device and the divider-counter (106) comprises said central divider-counter.

94. A control device as claimed in claim 1, wherein the device has at least one multiplier 64, and said multiplier comprises (FIG. 4a) a series multiplier and comprises a divider-counter (71) and a divider-gate (72) connected to the divider-counter outputs.

95. A control device as claimed in claim 94, in which the divider-gate (72) comprises a decoding portion (87) for decoding the outputs of the divider-counter (71) and a pulse synthesis portion (88) to provide a pulse train from the decoded outputs.

96. A control device as claimed in claim 95, in which said synthesis portion (88) includes an output OR gate (95), and AND gates (92-94), equal in number to the number of stages of the divider-counter (71) connected to the inputs of the output OR gate (95).

97. A control device as claimed in claim 96, counting input (76) of the divider-counter (71) forms the first input of the respective multiplier, and the second input of the respective multiplier is in the form of a binary number input (84, 85, 86) whose individual binary digit inputs are each connected to an input (84-86) of a respective one of the AND gates (92 - 94).

98. A control device as claimed in claim 96, in which said decoding portion (87) includes a plurality of logic gates (89 -91) whose inputs (80 - 83) are connected to the outputs of the individual stages (73, 74, 75) of the respective divider-counter (71) and whose outputs are connected to respective inputs of the AND gates (92 - 94).

99. A control device as claimed in claim 1, further comprising (FIG. 11a) a common pulse generator (109) for supplying strobing pulse trains (f 01 - f 04) to strobing stages and means generating a clock pulse train (f 0) and controlling the common pulse generator (109).

100. A control device as claimed in claim 99, the common pulse train generator means comprises a crystal oscillator for producing said clock pulse train (f 0).

101. A control device as claimed in claim 99, wherein the device comprises synchronizing gates the flip-flops, and the strobing pulses for said gates and flip-flops are provided by said common pulse generator.

102. A control device as claimed in claim 1, wherein the device has a central divider-counter, which comprises (FIG. 10) a forward counter (198) to which a stepping pulse traian (f 05) is fed and a decoding portion (199); the device has divider-gates connected to the decoding portion of said central divider-counter.

103. A control device as claimed in claim 99, wherein the device has a divider-counter operating in accordance with clock pulses, in which said stepping pulse train is provided by said common pulse generator as the clock pulse train.

104. A control device as claimed in claim 102, in which each divider-gate (111) connected to said central divider-counter (106) comprises (FIG. 13) a group of AND gates (241-248) Equal in number to the number of stages of the forward counter (198), and at least one output OR gate (249) connected by its inputs to the outputs of the AND gates of the group (241-248).

105. A control device as claimed in claim 104, in which the decoding portion (199) includes a plurality of logic gates (200-218) whose inputs are connected to the outputs of the individual stages of the forward counter (198) and whose outputs are connected to respective inputs of the AND gates of the group (241-248).

106. A control device as claimed in claim 1, wherein the device includes at least one voltage/frequency converter (39) which comprises (FIG. 16a) a voltage-controlled oscillator.

107. A control device as claimed in claim 106, in which said voltage-controlled oscillator comprises (FIG. 16a) a first operational amplifier (275) whose output is connected to its inverting input by an integrating capacitor (281), the input voltage (277) to be converted into a frequency being impressed upon one input (inverting) of the first operational amplifier whilst a reference voltage (289, 290; 279, 280) is applied to its other input; a second operational amplifier (283) connected by one input (inverting) to the output of the first operational amplifier (275) and by its other input to a reference voltage; and a semi-conductor switch (282) in parallel with said integrating capacitor (281), the output frequency of said voltage/frequency converter appearing at the output of the second operational amplifier (283), said second operational amplifier being connected to control said semi-conductor switch (282).

108. A control device as claimed in claim 1, in which the oscillator is in the form of an LC oscillator having a coil element (27) and a core element (26) movably arranged in the coil element; a baffle plate (25) is arranged in the flow of intake air to the engine (20); and one of the elements is secured to the baffle plate to move therewith.

109. In combination with an internal combustion engine having an air induction pipe, a central device for controlling at least one solenoid operated (32, 33) fuel injection means (29, 30) in dependence upon the rate of air flow, comprising an air flow sensing transducer means (25, 26, 28, 57) to be arranged in the induction pipe of the engine and including means responsive to air flow and providing a corresponding signal, an oscillator having its frequency of oscillation controlled by air flow through the air flow responsive means so that the output frequency of the oscillator will be dependent upon and a function of the rate of the air flow, and a frequency/digital converter connected to said oscillator and providing a digital air flow output signal in digital form as a function of the frequency of the oscillator; and a digital computing circuit having an input connected to be responsive to said air flow digital signals and having an output for controlling the fuel injection means (29, 30, 32, 33), said computing circuit comprising a digital differential analyzer whose input is responsive to signals in digital form, and at least one interpolator (58, 61) storing simulated engine operation characteristics to modify the signal from said air flow transducer means in accordance with the operating characteristics of the internal combustion engine.

110. In combination with an internal combustion engine, a control system, in which the engine (20) has an air induction pipe, at least one fuel injection valve (29, 30), a solenoid (32, 33) controlling the operation of the injection valve, said system comprising transducer means responsive to a respective engine operation, or operating parameter and providing a parameter output signal in digital form, said transducer means including means sensing an engine operation or operating parameter and having a corresponding variable output; a variable frequency oscillator having a frequency variation control element, said control element being operatively connected to said sensing means to vary the frequency of the oscillator in accordance with said variable output; and frequency/digital conversion means converting said variable frequency into a digital signal to provide a digital parameter output signal; a computer network having a digital differential analyzer; function storage means storing at least one transfer function of the engine fuel supply with respect to an operation, or operating parameter of the engine to simulate the operation and behavior of the engine upon variation of the respective parameter, the parameter output signal from said transducer means being connected to the computer network input to be processed therein and to develop a derived output signal, in digital form, as modified by said transfer function in the function storage means and simulating engine operation or behavior, with respect to the instantaneous value of said parameter signal; and digital-time conversion means connected to the solenoid of the injection valve having said computed output applied thereto and converting said output into a signal of such time duration that the injection valve is energized to open as determined to be appropriate to the engine with regard to the instantaneous engine operation, or operating state as sensed by said transducer means.

111. System according to claim 110, wherein a power supply is provided and wherein at least two transducer means are provided, each responsive to at least one parameter, said parameters comprising: air flow through the engine induction tube; engine temperature; engine exhaust gas composition; engine speed; power supply voltage; engine throttle position; each said transducer means providing a respective parameter output signal in digital form, as a function of frequency of the respective oscillator, to said computer network; a plurality of transfer function storage means, one for each of said at least two parameters, the respective digital parameter signal being applied to the respective transfer function storage means to develop respective developed output signals; and wherein said computer network further comprises combining circuit means logically combining the derived output signals and developing a composite, derived output signal, in digital form, said composite derived output signal being applied to said digital-time conversion means, whereby the energization time of the injection valve, or valves will be a function of at least two of said parameters.

112. System according to claim 111, wherein some of the transducer means comprises at least one other of the transducer means comprises means sensing an electrical output voltage representative of a respective parameter; a voltage controlled oscillator having a variable frequency output, the frequency variation depending on and being a function of the variable voltage; and frequency/digital conversion means converting said variable frequency, as controlled by said variable voltage, into a digital signal to provide one of said digital parameter output signals,

113. System according to claim 111, wherein said transducer means comprises means sensing the respective engine operation or operating parameter and providing an electrical output quantity, the level of which is representative of said respective parameter; a variable frequency, electrically controlled oscillator having its oscillation frequency controlled by said electrical quantity to provide an output signal, the frequency of which varies in accordance with said level, and hence said variable parameter; and frequency/digital conversion means converting said variable frequency into a respective digital signal to provide a respective one of said digital parameter output signals.

114. System according to claim 110, wherein said valve is a two-position valve of the ON-OFF, or OPEN-CLOSED typE; and said output signal has a time duration which controls the open time of the valve.

115. System according to claim 110, wherein said valve is of the continuously open type; and said output signal has an average energy which controls the extent of opening of the valve in accordance with said average energy.