Simulator For Electronic Control Circuit In A Diesel Engine

Abstract

Signals corresponding to motor operating parameters are converted to electrical signals and normalized. Operational amplifier circuits accept normalized signals and have transfer functions simulating characteristic motor curves. Adjustment means are provided for changing the transfer function. Motor has control element which changes fuel injection for operating cycle as a function of output of operational amplifier circuits.

Description

BACKGROUND OF THE INVENTION

This invention relates to a simulator for Diesel motors which have electronically controlled fuel injection arrangements. Specifically, it relates to such Diesel motors which comprise circuit means for generating the characteristic curves of the engines and whose output determines the amount of fuel to be injected under different operating conditions.

Electronic control of the fuel injected in a Diesel motor makes it possible to drive the motor over its whole operating range in an optimum manner. It is possible to extract maximum efficiency from the motor and to maintain it very exactly below that point at which unburnt fuel reaches the exhaust. This of course greatly decreases pollution. It is however a very tedious job to adjust these control systems to the characteristic values for the particular motor with which they are to be used, since these adjustments require a long test procedure. This results from the fact that all auxiliary measured values enter into the various measurements and a change in one characteristic value can bring about a change in the behavior of the overall system. For example, if the characteristic of a speed sensor changes, this change must be taken into account in the adjustment of the overall regulating system.

SUMMARY OF THE INVENTION

It is an object of the present invention to furnish a simulator for a Diesel control system which permits a simple matching of a particular type of regulator to a Diesel motor, by facilitating the measurement of the parameters determining the operational characteristics of the motor.

The invention comprises sensing means sensing operating parameters of the engine and furnishing sensed signals in correspondence thereto. Converter means convert the sensed signals into corresponding electrical signals. The electrical signals are then normalized in a normalizing circuit. The output of the normalizing circuit is connected to the input of said second circuit means which furnish control signals varying in dependence on said normalized electrical signals. Said second circuit means have a transfer function which simulates the characteristic curves of the system and further have adjustment means for changing said transfer function. The engine comprises a control element which is responsive to the control signals furnished by the second circuit means and control the quantity of fuel injected per operating cycle in dependence on said control signals furnished by said second circuit means.

The adjustment means within said second circuit means comprise precision potentiometers so connected that adjustment of one does not affect the circuit associated with the other of said adjustment means. Further, the precision potentiometer is so constructed that the values to which they are set may be read. In a preferred embodiment of the invention, the simulator may be used both as electronic regulator when the engine is on a test stand, and when the engine is actually operating in a vehicle. Since the sensed signals are converted into normalized signals, such a simulator may be used for simulating a wide range of regulating systems and engines. It is merely necessary to normlize the operating parameters and then use the normalized signals (voltages) in conjunction with a single circuit arrangement which can be readily adjusted to simulate the characteristic curves of different regulator types in conjunction with the different types of motors to be used. The normalization of the input signals makes it possible to adjust the second circuit means furnishing the characteristic curves to normalized values also. Therefore the precision potentiometers which are used for setting the characteristic values determining the outputs of the second circuit means may be calibrated. The calibration curves of these potentiometers then picture the functional relationship between the values set on said poteniometers and the corresponding motor operating values. Thus it is possible to adjust a simulator to the exact values of a main regulator characteristic or to use the simulator to determine the characteristic data exactly, thus permitting an optimum matching of the regulator to the motor. The characteristic values determined by use of the simulator may then be set into the electronic regulator by trimming various adjustable resistors. This also facilitates the exchange of electronic regulators without changing the injection pump.

The second circuit means which have a transfer function simulating the characteristic curves of the system comprise first, second and third function generating means respectively furnishing outputs corresponding to the low speed idling characteristic, the full load limiting characteristic, and a variable speed governing characteristic. Switching means are provided which connect the output of the second function generator means alternatively to the output of the first or the third function generator means.

In a further embodiment of the present invention, a speed signal furnished by speed sensing means is used as the input to excess speed prevention circuit means which interrupt the fuel supply when the engine speed exceeds a predetermined maximum engine speed. Further, an additional circuit may be provided for increasing the fuel supply during the starting operation. If a regulator must be simulated which takes into account the temperature and pressure of the atmosphere surrounding the motor, or the motor temperature then corresponding signals derived from temperature and pressure sensors may be applied to the second circuit means. Further, in an another embodiment of the present invention, the injection time during the operating cycle at which the fuel injection commences, can be made dependent upon the speed or the load of the engine by connecting a suitable circuit to the output of the second circuit means or to the output of the sensors.

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 DRAWING

FIG. 1 is a block diagram of a simulator in accordance with this invention;

FIG. 2 is a circuit diagram showing converter means furnishing a speed voltage proportional to engine speed;

FIG. 3 shows an inductive sensor with associated oscillators;

FIG. 4 is a circuit diagram showing the function generator furnishing the idling characteristic;

FIG. 5 shows the transfer characteristics of the circuit in FIG. 4;

FIG. 6 is a function generator for the full load limiting characteristic;

FIG. 7 shows the transfer characteristic generated by the circuit of FIG. 6;

FIG. 8 shows a function generator for generating the variable speed characteristic;

FIG. 9 shows the characteristic curve generated by the circuit of FIG. 8; and

FIG. 10 is a block diagram of a normalizing stage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will now be described with reference to the drawing.

FIG. 1 is a block diagram of a simulator system receiving inputs n as a function of engine speed, .alpha. as the position of the accelerator pedal, and y as a function of the position of the control element regulating the amount of fuel injected per operating cycle, relative to a null position wherein zero fuel is injected. Converter means include a speed converter 10 which concorts the sensed signal n to a voltage U.sub.n which is a D.C. voltage proportional to engine speed. Further converters 11 and 12 generate voltages U.sub..alpha. and U.sub.y which are proportional to the pedal and control element positions as discussed above. The voltages U.sub.n U.sub..alpha., and U.sub.y are applied to a normalizing stage 13 at whose outputs the normalized voltages U.sub.n U.sub..alpha., and U.sub.y appear with both positive and negative polarity. Thus the normalizing stage 13 serves to convert the electrical voltages supplied by any kind of motor into normalized signals which always remain within a predetermined amplitude range. The normalized signals U.sub.n and U.sub..alpha. are applied to the input of second circuit means 14. Second circuit means 14 contain three function generator circuits 15,16 and 17, the first of which furnishes characteristic curves simulating motor characteristics under no load or idling conditions, the second, furnishes these characteristics under full load conditions, while the third has a transfer function simulating characteristic curves for operation as a variable speed governor. The outputs of the function generators are connected to the input of a control amplifier 19 via first switching means 18. Control amplifier 19 further receives the signals +U.sub.y at a feedback input. The output of control amplifier 19 is connected to the control element determining the quantity of fuel injected by operating cycle, numbered 21, via normally closed switching contacts 20. The contacts 20 are opened by means of an excess speed prevention circuit 22 when the speed of the engine exceeds a predetermined maximum speed. The input to the excess speed prevention circuit may either be the sensed signal n, or the electrical signal U.sub.n furnished by converter 10.

The arrangement described above operates as follows: The core of the simulator is the second circuit means 14 which simulates the characteristic curve of a Diesel regulator. It comprises function generators 15,16 and 17 which may be adjusted to furnish those characteristic curves under which the Diesel motor is to be operated. In order that this plurality of function generator circuits may be universallly applied, the inputs thereto are normalized voltages. These normalized voltages are generated in normalizing stage 13. To facilitate the signal processing, it is advantageous that each normalized voltage is available with both positive and negative polarity. If a simulator is used for a particular motor or any particular vehicle, the sensed signal signifying the various operating parameters must merely be transformed into normalized voltages in order that the function generators may be adjusted to yield the desired characteristic curves. For the maximum speed or the maximum excursion of the control element from its null position, the output of the normalizing stage is always a maximum. The inputs to the function generators are thus kept within a defined range independent of the excursion of the actual signals corresponding to the operating parameters. The simulator is thus universally applicable. In order to allow simulation of operating characteristics both under idling conditions and under intermediate load conditions as a variable speed governor, the outputs of function generator 15 and 17 are alternatively connected with the function generator 16 by means of a switch 18. Control amplifier 19 amplifies the signals supplied from circuit 14 so that the control element 21 which is associated with the injection pump will be operable in response thereto. The control element is shown as a magnetic valve in the Figures, but other types of control elements are also possible, for example control elements using a solenoid or a rotary magnet. In order that the positioning of the control element be both highly accurate and reproducable, the voltage U.sub.y,namely the normalized voltage signifying the position of the fuel control element is applied to a feedback input of control amplifier 19. Thus a feedback circuit results whose inputs are provided by the outputs of circuits 15 through 17 whose output positions the control element and whose feedback signal is the signal signifying the position of said control element. The feedback in this loop also results in a rapid setting of the reference inputs, since this setting is not affected by the time constants of the complete circuit including the Diesel motor. The excess speed prevention circuit 22 is provided so that any malfunction will not result in a motor speed exceeding a predetermined maximum speed. If such an increase in speed occurs, contact 20 is opened so that the operating coil of control element 21 becomes deenergized, interrupting the fuel injection process.

FIG. 2 shows one embodiment of the speed converter 10. A gear wheel rotates at engine speed and forms part of a magnetic circuit with a yoke, on which is mounted an induction coil 30, FIG. 2. Due to the periodic changes in the magnetic flux in this magnetic circuit in synchronism with the engine speed, pulses are induced in coil 30 which the converter circuit shown in FIG. 2 converts into a D.C. voltage proportional to engine speed. One end of induction coil 30 is connected to line 31 which is connected to ground potential. The other end of induction coil 30 is connected via a terminal 32 and a resistance R33 to line 34 which is the positive supply line furnishing a voltage +U.sub.b. Further connected to terminal 32 is one end of a capacitor C35, whose other terminal is connected to the base of a transistor T37 via a resistance R36. the emitter of transistor T37 is connected to ground, while its collector is connected to line 34 via a terminal 38 and a resistance R39. Terminal 40 is connected to terminal 38 via a resistance R41 and is further connected to the base of transistor T37 via a resistance R42. Terminal 40 is further connected to ground via capacitor C43. Terminal 38 is also connected to the base of transistor T45 via resistance R44. The collector of transistor 45 is connected to line 34 via a resistance R46. Furthermore, the base of a transistor T47 is connected to the collector of transistor T45. The collector of transistor T47 is connected to line 34 via a resistance R48. The emitter connections of transistors T45 and T47 are connected together and jointly connected to ground via a resistance R49. A voltage divider comprising resistors R51 and R52 and having a tap 53 is connected from line 34 to line 31 (ground potential). A capacitor C50 connects the collector of transistor T47 to tap 53. Tap 53 is further connected to the cathode of the diode 54 whose anode is connected to the base of a transistor T55. The base of transistor T55 is further connected to ground via the parallel combination of a resistance R56 and capacitor C57. The emitter of transistor 55 is directly connected to line 31, while its collector is connected via a series circuit of a diode 58, a diode 59 and a resistance R60 to line 34. Diodes 58 and 59 are connected in the direction allowing current flow through transistor T55. The common point of resistor R60 and diode D59 is connected to the base of a transistor T61 via a capacitor C62 whose first terminal is connected to ground via a resistance R63 and whose second (base side) terminal is connected to ground via a resistance R64. Capacitor C62 and resistors R63 and R64 form a .pi. filter. The emitter of transistor T61 is connected to line 34 while its collector is connected to ground via a resistance R65. Further, a resistance R66 is connected between the collector of transistor T61 and the base of transistor T55. A three-stage RC filter is connected to the collector of transistor T61. This three-stage filter comprises a resistor R68 having one terminal connected to the collector of transistor T61 and a second terminal connected to ground via a capacitance C71; a second stage comprising a resistor R69 having its first terminal connected to the common point of resistor R68 and capacitor C71 and its second terminal connected to ground via capacitor C72; and a third-stage comprising a resistance R70 having a terminal connected to the common point of resistance R69 and capacitor C72, and a second terminal connected to ground via a capacitance C73. Transistor T67 has a collector connected to line 34 and an emitter connected to ground via a resistance R74. The emitter of transistor T67 is further connected to the base of a transistor T75 whose emitter is connected to line 34 via an output terminal furnishing the voltage U.sub.n and a resistance R76, while its emitter is connected to ground. Transistors T67 and T75 are of opposite conductivity, transistor T67 being an npn transistor, while transistor T75 is a pnp transistor. The above-described arrangement operates as follows:

Induction coil 30 constantly has a direct current flowing through it whose amplitude is determined by its internal resistance and the value of resistance R33. The A.C. voltage, speed voltage, induced in the coil is decoupled by capacitor C35 and is applied to the base of transistor T37 via a resistance R36. Transistor T37 forms a single stage input amplifier which has a feedback resistance comprising resistors R41 and R42 which, because of capacitor C43, form a filter whose output depends upon frequency. The filter is so designed that little feedback exists for the desired operating voltage, but that low frequency amplitude modulated noise voltages which result from inaccuracies in the mechanical portion of the sensor, are filtered out. Furthermore, the feedback tends to stabilize the D.C. operating point. Transistor T45 and T47 together constitute a Schmitt trigger circuit which transforms the amplified speed signal into a voltage with rectangular pulses. The negative pulses serve as trigger pulses for switching the monostable multivibrator formed by transistors T55 and T61 to the unstable state. The trigger pulses are derived from the rectangular pulses furnished by the Schmitt trigger circuit by means of a differentiating circuit comprising resistors R51 and R52 and capacitor 50, as well as diode 54. The three-stage RC filter connected to the output of the monostable multivibrator serves to furnish a voltage at its output which corresponds to the arithmetic mean of the monostable multivibrator output. This voltage is also available at the emitter of transistor T75, since stages T67 and T75 operate as emitter follower stages, thereby preventing any coupling between the speed converter circuit and circuits to which the speed voltage is to be furnished. The reason that the emitter follower stages contain two transistors of different conductivity is to obtain a high temperature stability. Temperature dependent variations in the two base emitter circuits tend to cancel each other.

FIG. 3 shows one embodiment of converter means converting the movement of either the gas pedal or the control element away from a null position into a voltage proportional to such an excursion. The converter comprises a transistor T83 and T84, which together constitute a Clapp oscillator. The sensor comprises a differential coil 85 having a movable core 106. The differential choke 85 also serves as an inductivity in the oscillator circuit. The osciallating circuit of the Clapp oscillator is formed by the series connection of inductivity 85 with capacitors C86,C87 and C88. The base of transistor T83 is connected to the common point of capacitors C86 and C87, while its collector is connected to line 34 furnishing the positive supply voltage, and its emitter is connected to line 31 (ground potential) via the series combination of resistances R89 and R90. The base of transistor T83 is connected to the emitter of transistor T84 via a resistance R91. Transistor T84 has an emitter connected to line 34. The oscillator output voltage is derived from one terminal of the choke 85 via a diode 92 and connected to ground from the cathode of diode 92 via a parallel circuit comprising a capacitor C94 and a variable resistor R93. Resistance R93 has a movable arm 95 which is connected on the one hand to the base of transistor T84, and on the other hand to the emitter of transistor T84 via a series circuit comprising a capacitor C96 and a resistance R97. The second terminal of choke 85 is connected to ground. Choke 85 further has a center tap which is connected to a diode 99 to the base of a transistor T100. Center tap 98 of choke 85 is further connected to ground via a series circuit comprising a capacitor C101 and a resistance R102. The base of transistor T100 is connected to ground via a filter comprising the parallel circuit of a resistance R103 and a capacitance C104. The collector of transistor T100 is connected to ground, while its emitter is connected to line 34 via a resistance R105. The voltage U.sub.y, which is a D.C. voltage proportional to the excursion of the pedal or control element from its null position, is derived from the emitter of transistor T100 and is the voltage existing at this emitter relative to ground potential. The voltage U.sub.y is generated since the metallic core 106 of inductivity 85 is moved so that the impedance of the two halves of the inductance changes while the overall impedance of the coil remains constant.

The above-described arrangement operates as follows: The capacity of the Clapp oscillator is distributed among several components. A voltage is generated across capacitor C87 which drives transistor T83. Since this transistor operates as an emitter follower, energy is transferred from the output of the emitter follower, which is in phase with its input, via the line connecting the common point of resistors R89 and R90 to the common point of capacitor C87 and C88, so that capacitor C88 is charged by current which has been amplified by transistor T83. So that the output of the oscillator is a voltage of constant amplitude, a control voltage is derived via diode D92, is rectified, and is applied to the filter comprising capacitor C94 and resistance R93. A part of the control voltage determined by the variable arm of resistance R93 is applied to transistor T84 which is a part of a voltage divider furnishing the base voltage to transistor T83. Transistor T84 thus has an output circuit which serves as a variable resistance. The operating point of transistor T83 thus varies in dependence on the amplitude of the output voltage of the oscillator. The voltage relative to ground derived from the center tap 98 of choke 85 is rectified by diode D99 and filtered by the filter comprising resistor R103 and capacitance C104. This voltage is also furnished at the emitter of emitter follower transistor T100. A Clapp oscillator is preferred to other types of oscillators for this application, since the amplitude of its output voltage is not limited by the amplitude of the supply voltage, but may be appreciably larger than said supply voltage. A high oscillator output voltage is desirable, since the accuracy of the inductive sensor increases with increasing amplitude of oscillator voltage applied to choke 85.

FIG. 4 is a block diagram showing a function generator furnishing characteristic curves under idling conditions. These lines are shown in FIG. 5 and will be referred to in discussing FIG. 4. The input voltages to the circuit are normalized speed voltages of both positive and negative polarity, namely the voltages +U.sub.n and -U.sub.n, as well as the acceleration signals +U.sub..alpha. -U.sub..alpha.. Stage 15, which is shown in FIG. 4, comprises a first, second and third operational amplifier which are constructed similarly as those used in analog computers. Operational amplifiers 110 and 111, herein referred to as first and second operational amplifier means, have inputs receiving the normalized speed voltage-U.sub.n as well as a constant bias voltage. The constant bias voltage in both cases is derived from a positive reference voltage source furnishing a positive reference voltage U.sub.ref, a determined portion of which is applied to the input of operational amplifier 110 and 111, respectively, by precision potentiometers 112 and 113. The output of operational amplifier 110 is connected to the cathode of a diode D114, whose anode is connected via a potentiometer 123 and a resistance R.sub.e to the input of operational amplifier 110. The circuit comprising diode 114, potentiometer 123 and resistance R.sub.e is a feedback circuit. Analogously, the output of operational amplifier 111 is connected to the anode of diode 115 whose cathode is connected to a potentiometer 116 which in turn is connected to a resistance R.sub.e whose other terminal is connected to the input of operational amplifier 111. A further feedback loop of operational amplifier 110 comprises a Zener diode Z117, whose anode is connected to the output of operational amplifier 110 (herein referred to as the first operational amplifier output), and whose cathode is connected to the input (first operational amplifier input) of operational amplifier 110. Similarly, operational amplifier 111 has a feedback loop comprising Zener diode Z118 whose cathode is connected to the output and anode is connected to the input of operational amplifier 111. For purposes of simplification, all input resistances are shown as equally valued resistors R.sub.e. The output voltage of operational amplifier 110 is derived from the anode of diode D114 and is applied to the input of third operational amplifier means, 119, via a resistance R.sub.e. Similarly, the output voltage of operational amplifier 111 is derived from the cathode of diode D115 and is connected to the third operational amplifier input via a resistance R.sub.e. Furthermore, the normalized voltage representing the accelerator pedal position, -U.sub..alpha. is connected to an input of operational amplifier 119 via a resistance R.sub.e, as is a percentage of speed voltage +U.sub.n as derived from a potentiometer 120. A further potentiometer 121 serves to couple an adjustable portion of a negative reference voltage -U.sub.ref to the input of operational amplifier 119 via a resistance R.sub.e. Operational amplifier 119 has a feedback loop containing Zener diode Z122 whose anode is connected to the operational amplifier input, while its cathode is connected to operational amplifier output. A further feedback loop comprises the series resistance of a diode D123 and a resistance R.sub.e. Diode 123 has a cathod connected to the operational amplifier output, while the output voltage U.sub.R is derived from the anode of diode D123.

The above-described arrangement operates as follows: Since each operational amplifier causes a reversal in sign, it is advantageous to have the normalized signals or voltages available with both positive and negative polarity to avoid having to use an additional operational amplifier. A voltage excursion from the null value takes place at the output of operational amplifier 110 when diode 114 is in the conductive direction. For this to occur, the output voltage of the operational amplifier 110 must be negative. If it is positive, it is short-circuited by Zener diode 117. Since the gain of an operational amplifier is equal to the negative quotient of the feedback resistance to the input resistance, this quotient, for a positive output voltage, is zero because of the low resistance offered by Zener diode Z117. In order to have a negative output voltage for operational amplifier 110, its input voltage must be positive. This input voltage is always positive as long as the bias voltage UL.sub.2 set on potentiometer 112 exceeds the negative normalized speed voltage -U.sub.n. For a standstill motor, the speed voltage -U.sub.n is zero therefore permitting the full potentiometer voltage to be applied to the input of amplifier 110. The gain of amplifier 110 is adjusted by adjusting potentiometer 123. Even if the operational amplifier is overdriven for full input voltage, its output voltage cannot exceed the value set by Zener diode Z117. If the normalized voltage -U.sub.n increases, the output voltage of amplifier 110 slowly decreases since its positive input voltage is becoming smaller. As soon as -U.sub.n reaches the value set on potentiometer 112, namely the voltage UL.sub.2, the output voltage of amplifier 110 becomes zero. If U.sub.n increases further, the polarity of the output voltage of operational amplifier 110 changes, since -U.sub.n now exceeds +UL.sub.2. however diode 114 is now blocked so that no voltage appears at its anode. The output voltage (characteristic curve generated by operational amplifier 110) therefore has the following shape: The output voltage first has a maximum negative value set by Zener voltage of Zener diode Z117 or by overdriving amplifier 110. The output voltage then remains constant until the input voltage has a value for which Zener diode Z117 blocks or amplifier 110 is no longer overdriven. The output voltage then decreases with a positive slope to zero. The output voltage reaches zero when the voltage -U.sub.n is equal UL.sub.2. Further increases of the voltage -U.sub.2 cause no further increase in output voltage. The slope of the increasing portion of the characteristic curve changes with changes in the gain of amplifier 110 which in turn is adjusted with the help of potentiometer 123.

Operational amplifier 111 operates in similar fashion. However, the diodes D115 and Z118 have a polarity opposite to the corresponding diodes of operational amplifier 110, that is the anode rather than the cathode of diode D115 is connected to the output of amplifier 111. An output voltage appears at the cathode of diode D115 only when the output voltage of amplifier 111 is positive. Since operational amplifiers cause a sign reversal, the input voltage must be negative in order to achieve a positive output voltage. The input voltage to operational amplifier 111 becomes negative, when the speed voltage -U.sub.n exceeds the constant voltage +UL.sub.1 set on potentiometer 113. If the speed voltage is zero, the input of the amplifier receives the full voltage set on potentiometer 113. Since this voltage is positive, the output voltage of the operational amplifier is negative; diode 115 is blocked and the gain is zero, since diode Z118 is now in a conductive condition. If the speed voltage -U.sub.n exceeds +UL.sub.1, the output voltage of operational amplifier 111 becomes positive, diode 115 conducts and a voltage different from zero may be derived from its cathode. The characteristic lines furnished by operational amplifier 111 therefore are as follows: As long as the speed voltage -U.sub.n is smaller than the voltage +UL.sub.1, the voltage furnished at the cathode of diode 115 is zero. As soon as the speed voltage exceeds the voltage +UL.sub.1, the output voltage begins to rise with a positive slope to a maximum value at which maximum values Zener diode Z118 becomes conductive. The slope of this positively increasing voltage is set on potentiometer 116 since this potentiometer varies the gain of amplifier 111.

The above-described output voltages are added to a constant voltage set on potentiometer 121 as well as to the speed voltage +U.sub.n and the acceleration signal or pedal position signal -U.sub..alpha. in operational amplifier 119. Since this amplifier again causes a reversal in sign, the characteristic curves furnished by amplifier 110 and 111 furnish characteristic curves at the output of amplifier 119 which have a negative slope. The polarity of diodes 123 and Zener diode Z122 in the feedback loops of amplifier 119 have a polarity such that only if the sum of all input voltages furnished to amplifier 119 is positive, does a negative characteristic voltage U.sub.R appear at the output, namely at the anode of diode 123. This voltage is herein referred to as the control signal. Thus potentiometer 121 must be so adjusted that even low speed voltages +U.sub.n cause a characteristic curve in accordance with FIG. 5 to appear at the output of operational amplifier 119. The characteristic curves furnished by amplifiers 110 and 111 are added to the other operating parameter voltages at amplifier 119 so that the characteristic curve as shown in FIG. 5 results. Since the output voltages of operational amplifiers 110 and 111 are zero in the region between UL.sub.1 and UL.sub.2, this part of the characteristic is determined solely by the speed and pedal position signals. The pedal position signals U.sub..alpha. causes a horizontal translation of the second of the characteristic curve in the total region. The slope of the line, designated Vn in the region between UL.sub.2 and UL.sub.1, is divided as shown in the Figure.

FIG. 6 is a block diagram for the circuit generating the characteristic curve at full load. The corresponding curve is shown in FIG. 7. For full load limiting, only the normalized voltages representing the speed signal are required. Operational amplifier 127 receives as input a constant negative bias voltage derived from source -U.sub.ref, via potentiometer 139 and further receives the speed signal +U.sub.n. Operational amplifier 127 is the fourth operational amplifier, while the other operational amplifier shown in FIG. 6, amplifier 128, is the fifth operational amplifier. Amplifier 137 also shown in FIG. 6 is herein referred to as the summing amplifier. Operational amplifier 128 receives a positive bias voltage U.sub.n2 via potentiometer 140 and the negative speed signal -U.sub.n. The feedback loops of amplifiers 127 and 128 are similar to those previously described for amplifiers 110 and 111 in FIG. 4. The slope of the generated curves may be adjusted by adjusting the gains of the amplifiers by potentiometers 129 and 130, respectively. The operational amplifiers have diodes 131 and 132, as well as Zener diodes Z133 and Z134 in their feedback loops. The output voltages of the two amplifiers are again derived from the other terminals of diodes and are applied to the summing amplifier, amplifier 137, which operates in analogous fashion to summing amplifier 119 in FIG. 4. It will be noted that no Zener diode appears in the feedback loop of operational amplifier 137. This is to indicate that the limiting of the output voltage of these operational amplifiers may be achieved simply by overdriving the amplifiers, rather than by use of a Zener diode. Operational amplifier 137 has a further input receiving a constant voltage derived from a negative reference source via a potentiometer 138.

The above-described arrangement operates as follows: The output voltage derived from the second function generator means as described above (FIG. 6) can only be a negative voltage since it is derived from the anode of the diode having a cathode directly connected to the output of amplifier. Thus, for an output voltage to appear, the amplifier must receive a positive input voltage. This is the case when the positive speed signal exceeds the voltage U.sub.n1. The slope of the curves is adjustable by means of potentiometer 129. The portion of the output voltage of amplifier 127, which is applied to the input of the summing amplifier, is adjustable by potentiometer 135. The slope of the curve generated by amplifier 127 is negative; this slope is reversed by operational amplifier 137, so that operational amplifier 127 working jointly with amplifier 137 generates the portion of the full load time shown in FIG. 7 as having a positive slope. The voltage URo, which marks the beginning of the full load line for a speed voltage of zero, is adjustable at potentiometer 138. The portion of the characteristic curve with a negative slope is similarly derived from operational amplifier 128. The voltage at the cathode of diode 132 only exceeds zero, when the amplifier has a negative input signal. This causes a positive output voltage and causes diode 132 to be in the conductive condition. This condition of course obtains as soon as the negative normalized speed voltage is larger than the voltage U.sub.n2 set on potentiometer 140. A characteristic line of positive slope first appears at the cathode of diode 132. This is inverted by operational amplifier 137, thus furnishing the portion of the characteristic curve having a negative slope (FIG. 7). The gain of operational amplifier 128 is adjustable by adjusting the potentiometer 130, while the portion of the output voltage of amplifier 128, which is to be applied to the input of amplifier 137, is determined by the setting of potentiometer 136. Zener diodes 133 and 134 serve the same portion as the Zener diode shown in FIG. 4. Since the characteristic curves generated by amplifiers 127 and 128 must extend over the total speed range, the potentiometers 135 and 136 determine which part of the range is supplied by which of the operational amplifiers 127 and 128.

FIG. 8 shows an embodiment of a circuit generating the variable speed governor curves indicated in FIG. 9. In order to generate these curves, both the normalized speed voltages U.sub.n and -U.sub.n, as well as the normalized pedal position voltage U.sub..alpha. are required. The seventh operational amplifier, amplifier 145, is connected to the positive speed voltage +U.sub.n via a potentiometer 146. Its feedback path comprises a diode Z147 in parallel with a feedback resistance R.sub.v. The sixth operational amplifier, amplifier 148, has a Zener diode Z149 in one feedback loop, and a potentiometer 150 in series with a diode 151 in another feedback loop. This operational amplifier has a first input of the negative normalized speed voltage -U.sub.n, a second input connected to the positive normalized pedal position voltage +U.sub..alpha.. The outputs of operational amplifiers 145 and 148 are connected together via a series circuit having resistors R152 and R153. The common point of the resistors is denoted by reference numeral 154. From this common point, a diode D155 and a potentiometer 156 make a connection via an input resistance Re to the input of amplifier 148. The anode of diode D155 is connected to point 154. The output voltage of the stage is derived from the cathode of diode D151 and is applied to the input of the eighth operational amplifier, amplifier 157. Amplifier 157 has a first feedback loop comprising a Zener diode Z158 and a second feedback loop having a diode D159 in series with an input resistance Re. The output of the third function generator means (FIG. 8) is derived from the anode of diode 159.

The above-described arrangement operates as follows: As is well known, in operational amplifiers of this type, the voltage at the input of the amplifier remains substantially at zero throughout. This point must be kept in mind in the following discussion. It is noted that the outputs of amplifiers 145 and 148 are summed at point 154. Diode D155, whose cathode for the reasons set forth, is substantially at zero, becomes conductive when the voltage at point 154 becomes positive, and the diode D155 becomes conductive, operational amplifier 148 has an additional feedback path, namely the path comprising diode D155 and potentiometer 156. Since this path is in parallel with the previous feedback path, the gain of amplifier 148 decreases. This change in gain of amplifier 148 causes a breakpoint in the output characteristic. Reference to FIG. 9 shows that these breakpoints take place along the line marked G. The portions of the curve over line G result from amplifier 148 operating without the additional feedback path and have a slope adjustable by adjustment of potentiometer 150. The gain of the portion of the lines G is determined by the setting of both potentiometers 150 and 156. Amplifier 157 operates only to effect sign reversal. First let it be assumed that a voltage U.sub..alpha. is applied which, since it is a positive voltage at the input of amplifier 148, causes a negative voltage at its output. For a speed voltage U.sub.n of zero, diode 155 is blocked. For increasing voltage -U.sub.n and constant voltage U.sub..alpha., the positive potential at the output of amplifier 148 increases and the negative potential at the output of amplifier 145 also increases. However, the input at the amplifier 145 is only a portion of the voltage +U.sub.n determined by the setting of potentiometer 146. Therefore for each value of U.sub..alpha., a voltage value results from the setting of potentiometer 146 for which diode D155 becomes conductive and the second feedback loop of amplifier 148 becomes effective.

It will be noted that the output of operational amplifiers of the first, second and third function generator (summing amplifiers) each have a diode connected in a feedback loop from whose anode the desired characteristic curve is derived. In this connection, the non-linearity of the diode has only a negligible influence on the derived output voltage. Furthermore, when the three function generators are interconnected, each diode becomes conductive only when its anode receives the maximum of the three potentials. Thus the diodes act as an OR circuit which transmits only the highest voltage applied thereto. Thus the overall characteristic (control signal) which effects the control element, is always derived from that function generator whose output voltage has the highest value.

FIG. 10 shows an embodiment of a normalizing stage. The normalizing stage has operational amplifiers 167 and 168. operational amplifier has an input connected to receive one of the electrical signals signifying an operating parameter, for example voltage U.sub..alpha.. It has a further input voltage which is a fixed biasing voltage derived from a reference source U.sub.ref, or to be more exact, a portion of said reference voltage as set on a potentiometer P169. The gain of amplifier 167 is adjustable by means of a feedback potentiometer P170. Operational amplifier 168 merely serves for sign reversal. The stage operates as follows: The amplification of amplifier 167 is adjusted via potentiometer P170 and the reference voltage applied to the stage is adjusted by means of potentiometer P169 in such a manner that when the gas pedal is in the null position, that is .alpha.=o, the voltage -U.sub..alpha. is also zero, and that for a maximum pedal position .alpha. , the voltage -U.sub..alpha. assumes the maximum permissible value.

While the invention has been illustrated and described as embodied in a system embodying operational amplifiers, it is not intended to be limited to the details shown, since various modifications, structural, and circuit 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: I claim:

1. For internal combustion engines having injection means and fuel regulator means, a simulator system, comprising, in combination, sensing means cooperating with any given one of said engines for furnishing sensed signals each corresponding to an operating parameter of said given one of said engines; converter means operatively associated with said sensing means for converting said sensed signals into corresponding electrical signals; normalizing circuit means furnishing normalized electrical signals, in response to said electrical signals, said normalizing circuit means comprising normalizing operational amplifier means having adjustable input circuit means connected to said converter means for receiving said corresponding electrical signals and adjustable feedback circuit means, said normalizing circuit means furnishing normalized electrical signals in response to said corresponding electrical signals received by said adjustable input circuit means; second circuit means operatively associated with said normalizing circuit means for furnishing control signals varying in dependence on said normalized electrical signals, said second circuit means having a transfer function simulating the characteristic curves of said regulator means, and adjustment means for changing said transfer function to correspond to said fuel regulator means associated with said given one of said engines; and a control element responsive to said control signals for controlling the quantity of fuel injected per operating cycle.

2. A system as set forth in claim 1 wherein said adjustable input circuit means comprise a first and second input respectively receiving said electrical signals and a reference signal; and varying means for varying the amplitude of said reference signal.

3. A system as set forth in claim 2 wherein said varying means comprise a potentiometer.

4. A system as set forth in claim 1 wherein said adjustable feedback circuit means comprise feedback potentiometer means.

5. A system as set forth in claim 1, further comprising control amplifier means interconnected between the output of said second circuit means and said control element.

6. a system as set forth in claim 1, wherein said simulator system serves as an electronic control for said engine under test.

7. A system as set forth in claim 1, wherein said simulator system serves as an electronic control for said engine in a vehicle.

8. A system as set forth in claim 5, wherein said second circuit means comprise first function generator means furnishing an idling characteristic; a second function generator means connected in parallel with said first function generator means and furnishing a full load limiting characteristic; and third function generator means connected in parallel with said first function generator means and furnishing a variable speed governing characteristic.

9. A system as set forth in claim 8, further comprising first switching means interposed between the output of said first, second and third function generator means in such a manner that the output of said second function generator means is alternatively combined with said first or said third function generator means.

10. A system as set forth in claim 5, wherein said sensing means comprise speed sensor means furnishing a speed signal as a function of engine speed; and further comprising excess speed prevention means connected to said speed sensor means for terminating fuel injection in response to speed signals indicating engine speeds exceeding a predetermined maximum engine speed.

11. A system as set forth in claim 10, further comprising starting circuit means operatively associated with said speed sensor means for furnishing excess fuel during starting of said engine.

12. A system as set forth in claim 9, further comprising temperature sensing means furnishing temperature signal indicative of engine temperature connected to said second circuit means.

13. A system as set forth in claim 9, further comprising additional temperature sensing means furnishing an additional temperature signal indicative of atmospheric temperature to said second circuit means.

14. A system as set forth in claim 5, further comprising additional circuit means connected to the output of said second circuit means for changing the injection starting time during each operating cycle in dependence on engine speed and load.

15. A system as set forth in claim 5, further comprising further circuit means connected to the output of said sensing means for changing the injection starting time during each operating cycle in dependence on engine speed and load.

16. For internal combustion engines having injection means and regulator means, a simulator system, comprising, in combination, sensing means cooperating with any given one of said engines for furnishing sensed signals signals each corresponding to an operating parameter of said given one of said engines, said sensing means comprising speed sensor means having a gear wheel rotating at engine speed, a yoke operatively associated with said gear wheel, and an induction coil mounted on said yoke, the rotation of said gear wheel inducing an alternating voltage in said induction coil; converter means operatively associated with said sensing means for converting said sensed signals into corresponding electrical signals, said converter means comprising speed converter means having input amplifier means amplifying said alternating voltage, trigger circuit means connected to the output of said input amplifier means and furnishing a trigger signal for each cycle of said alternating voltage, monostable multivibrator means connected to the output of said trigger circuit means, and low-pass filter means connected to the output of said monostable multivibrator means; normalizing circuit means operatively associated with said converter means for furnishing normalized electrical signals corresponding to said electrical signals; second circuit means operatively associated with said normalizing circuit means for furnishing control signals varying in dependence on said normalized electrical signals, said second circuit means having a transfer function simulating the characteristic curves of said regulator means, and adjustment means for changing said transfer function to correspond to said regulator means associated with said given one of said engines; control amplifier means connected to the output of said second circuit means; and a control element responsive to said control signals for controlling the quantity of fuel injected per operating cycle.

17. For internal combustion engines having injection means, regulator means, and an accelerator pedal, a simulator system, comprising, in combination, sensing means cooperating with any given one of said engines for furnishing sensed signals each corresponding to an operating parameter of said given one of said engines, said sensing means comprising a core mechanically coupled to said accelerator pedal for movement therewith; converter means operatively associated with said sensing means for converting said sensed signals into corresponding electrical signals, said converter means comprising differential coil means operatively associated with said core for furnishing an electrical pedal position signal at a center tap of said differential coil, and oscillator means furnishing a constant alternating voltage to said differential coil; normalizing circuit means operatively associated with said converter means for furnishing normalized electrical signals corresponding to said electrical signals; second circuit means operatively associated with said normalizing circuit means for furnishing control signals varying in dependence on said normalized electrical signals, said second circuit means having a transfer function simulating the characteristic curves of said regulator means, and adjustment means for changing said transfer function to correspond to said regulator means associated with said given one of said engines; control amplifier means connected to the output of said second circuit means; and a control element responsive to said control signals for controlling the quantity of fuel injected per operating cycle.

18. For internal combustion engines having regulator means and injection means including a control element, the quantity of fuel injected per operating cycle varying in dependence of the position of said control element relative to a null position, a simulator system, comprising, in combination, sensing means cooperating with any given one of said engines for furnishing sensed signals each corresponding to an operating parameter of said given one of said engines, said sensing means comprising a second core, mechanically coupled to said control element for movement therewith, and a second differential coil operatively associated with said second core and having a center tap; converter means operatively associated with said sensing means for converting said sensed signals into corresponding electrical signals, said converter means comprising oscillator means for furnishing a constant alternating voltage to said second differential coil, thereby creating an electrical control element positioned signal at said center tap of said second coil; normalizing circuit means operatively associated with said converter means for furnishing normalized electrical signals corresponding to said electrical signals; second circuit means operatively associated with said normalizing circuit means for furnishing control signals varying in dependence on said normalized electrical signals, said second circuit means having a transfer function simulating the characteristic curves of said regulator means, and adjustment means for changing said transfer function to correspond to said regulator means associated with said given one of said engines; and control amplifier means connected to the output of said second circuit means for furnishing amplified control signals to said control element.

19. For internal combustion engines having injection means and regulator means, a simulator means, comprising, in combination, sensing means cooperating with any given one of said engines for furnishing sensed signals including a speed signal, each corresponding to an operating parameter of said given one of said engines; converter means operatively associated with said sensing means for converting said sensed signals into corresponding electrical signals; normalizing circuit means operatively associated with said converter means for furnishing normalized electrical signals in response to said electrical signals, said normalized electrical signals including a normalized speed signal; second circuit means operatively associated with said normalizing circuit means for furnishing control signals varying in dependence on said normalized electrical signals, said second circuit means comprising first function generator means furnishing an idling characteristic, second function generator means connected in parallel with said first function generator means and furnishing a full load limiting characteristic, and third function generator means connected in parallel with said first function generator means and furnishing a variable speed governing characteristic, said first function generator means comprising first, second and third operational amplifier means respectively having a first, second and third input and a first, second and third output, first, second and third adjustable biasing voltage furnishing means respectively connected to said first, second and third operational amplifier inputs, means connecting said first and second operational amplifier outputs to said third operational amplifier input, and first, second and third operational amplifier feedback circuits, respectively connected from the output to the input of said first, second and third operational amplifier means, each of said operational amplifier feedback circuits comprising a diode and resistance means series connected with said diode, and means connecting said normalized speed signal to said first, second and third operational amplifier inputs.

20. A system as set forth in claim 16, wherein said speed converter means further comprise temperature compensated emitter follower means connected to the output of said low-pass filter means.

21. A system as set forth in claim 16, wherein said input amplifier means comprise feedback means connected from the output to the input of said input amplifier means.

22. A system as set forth in claim 17, wherein said oscillator means comprise a Clapp oscillator.

23. A system as set forth in claim 18, wherein said oscillator means comprise a Clapp oscillator having a constant output voltage.

24. A system as set forth in claim 8, wherein said first,second and third function generator means each comprise operational amplifier means.

25. A system as set forth in claim 24, wherein said operational amplifier means each comprise a feedback circuit having a diode.

26. A system as set forth in claim 25, wherein said operational amplifier means comprise at least one feedback loop having a Zener diode for limiting the maximum output voltage of the associated operational amplifier means.

27. A system as set forth in claim 8, wherein said normalizing circuit means furnish a normalized speed signal in response to said electrical speed signal; and wherein said first function generator means comprises first, second and third operational amplifier means respectively having a first, second and third input and a first, second and third output, first, second and third adjustable biasing voltage furnishing means respectively connected to said first, second and third operational amplifier inputs, means connecting said first and second operational amplifier outputs to said third operational amplifier input, and first, second and third operational amplifier feedback circuits, respectively connected from the output to the input of said first, second and third operational amplifier means, each of said operational amplifier feedback circuits comprising a diode and resistance means series connected with said diode, and means connecting said normalized speed signal to said first, second and third operational amplifier inputs.

28. A system as set forth in claim 19, wherein said normalized speed signal comprises a positive normalized speed signal and a negative normalized speed signal; and wherein said means connected to said normalized speed signal to said first, second and third operational amplifier inputs comprise means connecting said negative normalized speed signal to said first and second operational amplifier inputs, and means connecting said positive normalized speed signal to said third operational amplifier input.

29. A system as set forth in claim 28, wherein said first, second and third adjustable biasing voltage furnishing means comprise a positive reference voltage source; first potentiometer means connecting said positive voltage source to said first operational amplifier input; second potentiometer means connecting said positive voltage source to said second operational amplifier input; a negative reference voltage source; and third potentiometer means connecting said negative reference voltage source to said third operational amplifier input.

30. A system as set forth in claim 19, wherein said second function generator means comprise fourth operational amplifier means furnishing characteristic lines of positive slope and having at least one break point; fifth operational amplifier means furnishing characteristic lines of negative slope and having at least one break point; and summing amplifier means connected to the outputs of said fourth and fifth operational amplifier means and furnishing a summing amplifier output signal corresponding to the sum thereof.

31. A system as set forth in claim 30, wherein said normalizing circuit means furnishes a positive and a negative normalized speed signal in response to said electrical speed signal; and wherein said third function generator means comprise sixth, seventh and eighth operational amplifier means respectively having sixth, seventh and eighth operational amplifier inputs and outputs; wherein said sixth operational amplifier means furnishes a characteristic line having at least one break point; further comprising a first and second series connected resistor connected between said sixth and seventh operational amplifier output terminals and having a common point; a series circuit comprising a diode and a potentiometer connected between said common point and said sixth operational amplifier input; means connecting said sixth operational amplifier output to said eight operational amplifier input; and means furnishing an adjustable reference voltage to said eighth operational amplifier input.

32. A system as set forth in claim 8, wherein said first, second and third function generator means re-spectively comprise a first, second and third function gen-erator output stage comprising respectively a third oper-ational amplifier means, summing amplifier means, and eighth operational amplifier means; and wherein each of said function generator output stages comprises feedback circuit means, each of said feedback circuit means comprising a diode having a first and second terminal, and means connecting said first terminals to the respective ones of said operational amplifier outputs; and wherein said control signals are derived from said second terminals of said diodes.

33. A system as set forth in claim 26, wherein said first function generator means comprise first and second operational amplifier means, said first and second operational amplifier means each having a feedback circuit comprising feedback potentiometer means; wherein said first function generator means further comprise third operational amplifier means, said third operational amplifier means having a feedback circuit comprising a resistor.