EP0790409A2 - Measuring circuit for an ionic current in ignition devices for internal combustion engines - Google Patents

Measuring circuit for an ionic current in ignition devices for internal combustion engines Download PDF

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Publication number
EP0790409A2
EP0790409A2 EP97101843A EP97101843A EP0790409A2 EP 0790409 A2 EP0790409 A2 EP 0790409A2 EP 97101843 A EP97101843 A EP 97101843A EP 97101843 A EP97101843 A EP 97101843A EP 0790409 A2 EP0790409 A2 EP 0790409A2
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EP
European Patent Office
Prior art keywords
voltage
ignition
circuit
circuit arrangement
electrical system
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Granted
Application number
EP97101843A
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German (de)
French (fr)
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EP0790409A3 (en
EP0790409B1 (en
Inventor
Ulrich Dr. Bahr
Michael Daetz
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Volkswagen AG
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Deutsche Automobil GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P17/00—Testing of ignition installations, e.g. in combination with adjusting; Testing of ignition timing in compression-ignition engines
    • F02P17/12—Testing characteristics of the spark, ignition voltage or current
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P15/00—Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 and combined with layout of ignition circuits
    • F02P15/10—Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 and combined with layout of ignition circuits having continuous electric sparks
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P3/00—Other installations
    • F02P3/02—Other installations having inductive energy storage, e.g. arrangements of induction coils
    • F02P3/04—Layout of circuits
    • F02P3/045—Layout of circuits for control of the dwell or anti dwell time
    • F02P3/0453—Opening or closing the primary coil circuit with semiconductor devices
    • F02P3/0456—Opening or closing the primary coil circuit with semiconductor devices using digital techniques
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P17/00—Testing of ignition installations, e.g. in combination with adjusting; Testing of ignition timing in compression-ignition engines
    • F02P17/12—Testing characteristics of the spark, ignition voltage or current
    • F02P2017/125—Measuring ionisation of combustion gas, e.g. by using ignition circuits

Definitions

  • the invention relates to a circuit arrangement for ion current measurement according to the preamble of patent claim 1.
  • an element zener diode or varistor
  • the spark plug to which a constant voltage drops and to which a capacitor is assigned, to which the voltage dropping at the element is assigned builds up so that this voltage can be used as a measuring voltage source.
  • the capacitor can be connected in parallel to the zener diode or the varistor via further diodes connected in the charging direction.
  • This known generation of the measuring voltage is relatively simple, but requires a large storage capacitor.
  • the measuring voltage is not constant, particularly in the case of longer measuring phases, such as occur at low speeds, since the storage capacitor is discharged by the measuring current.
  • a current is therefore superimposed on the measuring current which is caused by the discharge of stray capacitances in the spark plug, ignition coil and supply lines.
  • a leakage current through the Zener diode used for voltage limitation is superimposed on the measuring current.
  • Another disadvantage of this known circuit arrangement is that the current measuring resistor is connected in series with the storage capacitor. This causes a non-linearity, since the voltage across the ion measuring section is a function of the measured value.
  • a voltage of positive polarity is applied to the spark plug in order to sample an ion current with negative polarity, which is caused by the combustion.
  • a capacitor is connected to the low potential side of the secondary winding of the ignition coil, which is charged by means of the electrical ignition current supplied via a diode in order to obtain the voltage with positive polarity.
  • a zener diode ensures the voltage limitation on the capacitor.
  • the capacitor current is supplied to a current / voltage converter unit in order to convert the ion current flowing from the capacitor into a voltage. The o. G. Disadvantage of a non-linearity does not arise, since in the current / voltage converter the negative connection of the capacitor is kept at a virtual ground potential.
  • the two known circuit arrangements have the disadvantage in common that a voltage between 70 V and 400 V is required to measure the ion current. H. is to be applied to the spark plug of an internal combustion engine.
  • a circuit arrangement for ion current measurement in which a measuring voltage is generated by an AC voltage applied to the primary side of the ignition coil.
  • the AC voltage applied on the primary side is transformed to a higher voltage level via the ignition coil, frequencies in the range from 10 kHz to 100 kHz being used.
  • the ion current signal effects an amplitude modulation of the alternating current generated on the secondary side.
  • Disadvantages of this known circuit arrangement are on the one hand the use of filters which separate the ion current signal, whose useful frequency range is between 100 Hz and 20 kHz, from the carrier signal and, on the other hand, the nonlinear distortions which occur in the case of AC excitation due to the asymmetry of the ion current characteristic.
  • US Pat. No. 5,483,818 describes a circuit arrangement for the detection of an ion current, in which the low potential side of the secondary circuit of the ignition coil is led via a resistor to the inverting input of an operational amplifier, while a reference voltage of approx. 40 V is supplied to its non-inverting input.
  • This operational amplifier is connected by means of a resistor as an inverting amplifier, so that the reference voltage for the purpose of measuring the ion current is present as a measuring voltage on the secondary circuit.
  • the measurement voltage generated as an ion current measurement signal at the output of this operational amplifier is fed to a threshold value circuit for evaluation.
  • Zener diodes To derive the ignition current generated during the ignition, two series-connected Zener diodes are connected to the secondary circuit. To compensate for the leakage current occurring in these Zener diodes - which falsifies the ion current measurement - a control circuit is provided which is also controlled by the output of the operational amplifier. This control circuit is made up of a further operational amplifier with a corresponding circuit consisting of resistors and capacitors.
  • the object of the present invention is to provide a circuit arrangement of the type mentioned, which the above. Avoids disadvantages, leads to a high measurement quality of the ion current in the combustion chamber of an internal combustion engine and can be implemented with little effort.
  • circuit means are provided with which one constant measuring voltage is applied to the secondary circuit of the ignition coil, which has a voltage value that is equal to or less than the value of the voltage of the vehicle electrical system and a rectifier element is also provided that derives the ignition current generated during the ignition of the spark plug to the vehicle electrical system.
  • a measuring voltage according to the invention avoids the disadvantages which occur when using a measuring voltage of the order of 40 V to 400 V.
  • the circuitry required for this is very low, although a constant measuring voltage is supplied simultaneously with this circuit arrangement according to the invention over the entire measuring phase.
  • shunt resistances such as those caused by sooting of the spark plugs during a cold start, do not have as great an effect since the specific conductance of soot increases proportionally with the applied voltage.
  • the measuring sections of the spark plugs of an internal combustion engine serving as ion current probes are connected in parallel, so that the circuit complexity remains extremely low.
  • a differential amplifier is provided as the preferred circuit means for applying the measurement voltage to the secondary circuit of the ignition coil.
  • a reference voltage is fed to an input thereof, the value of which corresponds to the measuring voltage and the differential amplifier is connected as an inverting amplifier. so that the desired measuring voltage is present at the other input.
  • the ion current is converted into a voltage serving as a measurement signal, which voltage is then fed to an evaluation.
  • FIG. 1 shows a transistor ignition system, for the sake of simplicity only one ignition output stage with a spark plug Zk for an internal combustion engine is shown.
  • the ignition output stage comprises an ignition coil Tr with primary and secondary circuit, consisting of a primary and secondary winding, the aforementioned spark plug Zk being connected to the secondary winding.
  • the primary winding is connected with its one connection to an on-board battery voltage U B of 12 V, for example, and is connected with its other connection to an ignition transistor 1.
  • This ignition transistor 1 is controlled via its control electrode by a control circuit 2, in that ignition trigger pulses are supplied to this ignition transistor 1 via its connecting line.
  • the secondary winding is connected with its high voltage side to the spark plug Zk, while its low potential side is led to the inverting input of a differential amplifier 3.
  • a constant reference voltage U ref preferably 5 V, is applied to the non-inverting input of this differential amplifier 3, this constant reference voltage being generated by a constant voltage source 6.
  • This constant reference voltage U ref is the via this differential amplifier 3 Secondary circuit of the ignition coil Zk fed and passes via this as the measurement voltage U measure to the spark plug Zk working as an ion current measuring section.
  • the differential amplifier 3 is constructed as an inverting amplifier in that its inverting input is connected to its output via a resistor R.
  • diodes D1 and D2 are provided, which derive the ignition current to ground or vehicle electrical system potential.
  • the diode D1 is connected between the inverting input of the differential amplifier 3 and the vehicle electrical system U B in such a way that the ignition current can flow off to the vehicle electrical system.
  • the second diode D2 has its anode at ground potential and its cathode is also connected to the inverting input of the differential amplifier 3.
  • a resistor (not shown in FIG. 1) can be provided in the feed line to the inverting input of the differential amplifier 3, which additionally limits the current flowing into the differential amplifier 3.
  • the inverting differential amplifier 3 converts the ion current into a voltage U ion , which is fed as a measurement signal to an evaluation unit 5.
  • the measuring voltage U meas preferably 5 V, supplied to the secondary circuit of the ignition coil Tr is constant during the entire measuring period. Since the ion measurement current is in the ⁇ A range, a differential amplifier 3 with a low input current is used, which is available inexpensively today. Due to the low-impedance provision of this measuring voltage U meß reloading of stray capacities, as they occur in other known systems with AC load , such as. B. knocking combustion can occur. This advantage of the invention is particularly noticeable when several ion current measuring sections are operated in parallel are, as will be explained further below with reference to FIG. 2, because the effective stray capacity can be multiplied.
  • FIG. 1 also shows a control unit 4, which takes over the function of an engine management system and in turn controls the control circuit 2.
  • engine parameters such as load, speed and temperature are fed to this control unit 4 via an input E.
  • Corresponding actuators are controlled via outputs A.
  • the ion current signal generated by the evaluation circuit 5 is also fed to the control unit 4.
  • the ion current signal can be used to detect the knocking of the internal combustion engine and to set up a corresponding knock control by controlling the ignition timing.
  • Another application is to use the ion current signal to detect misfires.
  • the cylinder can be in the crank position at which the ignition is to take place, both in the compression and in the exhaust stroke. Normal combustion with the associated ion current signal only occurs if the ignition process is carried out in the compression cycle. When ignited in the exhaust cycle, the ion current signal is almost zero. This allows the phase relationship between the crankshaft and camshaft to be recognized.
  • FIG. 2 shows a transistor ignition system of a 4-cylinder internal combustion engine with ignition output stages each assigned to a cylinder, each ignition output stage comprising an ignition coil Tr 1 ... Tr 4 , an ignition transistor 1a ... 1d and associated spark plug Zk 1 ... Zk 4 is constructed.
  • the ignition transistors 1a ... 1d are controlled via their control electrodes by a circuit 2a for cylinder selection, which in turn is connected to a control circuit 2 which supplies the corresponding ignition trigger pulses for the individual cylinders of this circuit 2a.
  • a control device 4 which controls the control circuit 2.
  • each ignition coil Tr 1 ... Tr 4 is routed to a circuit node S which is connected to the inverting input of a differential amplifier 3.
  • This differential amplifier 3 is also constructed as an inverting amplifier by means of a resistor R connecting the inverting input to the output.
  • a constant reference voltage U ref which is generated by a constant voltage source 6, is fed to the non-inverting input of this differential amplifier 3.
  • This constant reference voltage U ref is less than the vehicle electrical system voltage and is 5 V and leads to the desired measuring voltage U meas at the circuit node S and thus also at the ion current paths of the spark plugs Zk 1 ... Zk 4 connected in parallel.
  • two diodes D1 and D2 are provided for deriving the ignition current to ground or the electrical system.
  • the measurement signal U ion obtained at the output of the differential amplifier 3 is fed to an evaluation circuit 5, which in turn is controlled by a control unit 4, the function of which corresponds to that of the control unit from FIG. 1.
  • an additional resistor (likewise not shown) can be provided in the feed line to the inverting input of the differential amplifier 3, which additionally limits the current flowing into the differential amplifier 3.
  • the circuit arrangement according to the invention for ion current measurement can be used not only in transistor ignition systems, as shown in the two exemplary embodiments, but also in alternating current ignitions or high-voltage capacitor ignitions.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Ignition Installations For Internal Combustion Engines (AREA)

Abstract

Die Erfindung betrifft eine Schaltungsanordnung zur lonenstrommessung im Verbrennungsraum einer Brennkraftmaschine mit einer aus Primär- und Sekundärkreis bestehenden Zündspule (TR), die von einem Bordnetz (UB) gespeist wird, und einer im Sekundärkreis angeordneten Zündkerze (ZK), die gleichzeitig als lonenstromsonde dient. Erfindungsgemäß sind Schaltungsmittel vorgesehen, mit denen eine lonenmeßspannung an den Sekundärkreis der Zündspule (TT) abgelegt wird, wobei diese lonenmeßspannung einen Wert aufweist, der dem Wert des Bordnetzes (UB) entspricht oder unter diesem Wert liegt und ferner ein Gleichrichterelement (D1) in den Sekundärkreis geschaltet wird, das den während der Zündung der Zündkerze erzeugten Zündstrom auf das Bordnetz ableitet.The invention relates to a circuit arrangement for ion current measurement in the combustion chamber of an internal combustion engine with an ignition coil (TR) consisting of primary and secondary circuit, which is fed by an electrical system (UB), and a spark plug (ZK) arranged in the secondary circuit, which also serves as an ion current probe. According to the invention, switching means are provided with which an ion measurement voltage is applied to the secondary circuit of the ignition coil (TT), this ion measurement voltage having a value that corresponds to or is below the value of the vehicle electrical system (UB) and also a rectifier element (D1) in the Secondary circuit is switched, which derives the ignition current generated during the ignition of the spark plug on the electrical system.

Description

Die Erfindung betrifft eine Schaltungsanordnung zur Ionenstrommessung gemäß dem Oberbegriff des Patentanspruches 1.The invention relates to a circuit arrangement for ion current measurement according to the preamble of patent claim 1.

Eine solche Schaltungsanordnung ist aus den Druckschriften DE-OS 30 06 665 und DE 19 50 24 02 A1 bekannt.Such a circuit arrangement is known from the documents DE-OS 30 06 665 and DE 19 50 24 02 A1.

So wird bei der Schaltungsanordnung nach der DE-OS 30 06 665 zwischen der Hochspannungsquelle und der Zündkerze ein Element (Zenerdiode oder Varistor) geschaltet, an dem eine konstante Spannung abfällt und dem ein Kondensator zugeordnet ist, an dem sich die an dem Element abfallende Spannung aufbaut, so daß diese Spannung als Meßspannungsquelle verwendbar ist. Der Kondensator kann dabei parallel zur Zenerdiode bzw. dem Varistor über weitere in Laderichtung geschaltete Dioden verbunden werden.Thus, in the circuit arrangement according to DE-OS 30 06 665, an element (zener diode or varistor) is connected between the high-voltage source and the spark plug, to which a constant voltage drops and to which a capacitor is assigned, to which the voltage dropping at the element is assigned builds up so that this voltage can be used as a measuring voltage source. The capacitor can be connected in parallel to the zener diode or the varistor via further diodes connected in the charging direction.

Diese bekannte Erzeugung der Meßspannung ist relativ einfach, erfordert jedoch einen großen Speicherkondensator. Die Meßspannung ist besonders bei längeren Meßphasen, wie sie bei niedrigen Drehzahlen vorkommen, nicht konstant, da der Speicherkondensator durch den Meßstrom entladen wird. Dem Meßstrom ist daher ein Strom überlagert, der durch die Entladung von Streukapazitäten in Zündkerze, Zündspule und Zuleitungen hervorgerufen wird. Weiterhin ist dem Meßstrom ein Leckstrom durch die zur Spannungsbegrenzung verwendete Zenerdiode überlagert. Ein weiterer Nachteil dieser bekannten Schaltungsanordnung besteht darin, daß der Strommeßwiderstand in Reihe zum Speicherkondensator geschaltet ist. Dieses bewirkt eine Nichtlinearität, da die an der Ionenmeßstrecke anliegende Spannung eine Funktion des Meßwertes ist.This known generation of the measuring voltage is relatively simple, but requires a large storage capacitor. The measuring voltage is not constant, particularly in the case of longer measuring phases, such as occur at low speeds, since the storage capacitor is discharged by the measuring current. A current is therefore superimposed on the measuring current which is caused by the discharge of stray capacitances in the spark plug, ignition coil and supply lines. Furthermore, a leakage current through the Zener diode used for voltage limitation is superimposed on the measuring current. Another disadvantage of this known circuit arrangement is that the current measuring resistor is connected in series with the storage capacitor. This causes a non-linearity, since the voltage across the ion measuring section is a function of the measured value.

Bei der Schaltungsanordnung gemäß der DE 19 50 24 02 A1 wird eine Spannung positiver Polarität an die Zündkerze angelegt, um einen Ionenstrom mit negativer Polarität abzutasten, der durch die Verbrennung hervorgerufen wird. Zur Erzeugung dieser Spannung wird ein Kondensator mit der Niedrigpotentialseite der Sekundärwicklung der Zündspule verbunden, der mittels dem über eine Diode zugeführten elektrischen Zündstrom geladen wird, um die Spannung mit positiver Polarität zu erhalten. Eine Zenerdiode sorgt für die Spannungsbegrenzung an dem Kondensator. Der Kondensatorstrom wird einer Strom/Spannungs-Wandlereinheit zugeführt, um den aus dem Kondensator fließenden Ionenstrom in eine Spannung umzuwandeln. Dabei tritt der o. g. Nachteil einer Nichtlinearität nicht auf, da bei dem Strom/Spannungs-Wandler der negative Anschluß des Kondensators auf einem virtuellen Massepotential gehalten wird.In the circuit arrangement according to DE 19 50 24 02 A1, a voltage of positive polarity is applied to the spark plug in order to sample an ion current with negative polarity, which is caused by the combustion. To generate this voltage, a capacitor is connected to the low potential side of the secondary winding of the ignition coil, which is charged by means of the electrical ignition current supplied via a diode in order to obtain the voltage with positive polarity. A zener diode ensures the voltage limitation on the capacitor. The capacitor current is supplied to a current / voltage converter unit in order to convert the ion current flowing from the capacitor into a voltage. The o. G. Disadvantage of a non-linearity does not arise, since in the current / voltage converter the negative connection of the capacitor is kept at a virtual ground potential.

Den beiden bekannten Schaltungsanordnungen ist der Nachteil gemeinsam, daß zur Messung des Ionenstromes eine Spannung zwischen 70 V und 400 V erforderlich ist, die an die Ionenmeßstrecke, d. h. an die Zündkerze einer Brennkraftmaschine anzulegen ist.The two known circuit arrangements have the disadvantage in common that a voltage between 70 V and 400 V is required to measure the ion current. H. is to be applied to the spark plug of an internal combustion engine.

Ferner ist es auch bekannt, daß die Verwendung einer Meßspannung von ca. 400 V die Verrußungsgeschwindigkeit beim Kaltstart einer Brennkraftmaschine erhöht, wie dies beispielsweise in der EP 0 30 53 47 B1 beschrieben ist.Furthermore, it is also known that the use of a measuring voltage of approximately 400 V increases the sooting speed when cold starting an internal combustion engine, as is described, for example, in EP 0 30 53 47 B1.

Weiterhin ist aus der DE-OS 33 27 766 eine Schaltungsanordnung zur Ionenstrommessung bekannt, bei der eine Meßspannung durch eine auf der Primärseite der Zündspule angelegten Wechselspannung erzeugt wird. Dabei wird die auf der Primärseite angelegte Wechselspannung über die Zündspule auf ein höheres Spannungsniveau transformiert, wobei Frequenzen im Bereich von 10 kHz bis 100 kHz verwendet werden. Das Ionenstromsignal bewirkt eine Amplitudenmodulation des sekundärseitig entstehenden Wechselstromes. Nachteilig bei dieser bekannten Schaltungsanordnung ist einerseits die Verwendung von Filtern, die das Ionenstromsignal, dessen Nutzfrequenzbereich zwischen 100 Hz und 20 kHz beträgt, vom Trägersignal trennen und andererseits die bei Wechselstromanregung durch die Unsymmetrie der Ionenstromkennlinie entstehenden nichtlinearen Verzerrungen. Diese Unsymmetrie ergibt sich aufgrund der höheren Beweglichkeit der negativen Ladungsträger gegenüber der positiven Ionen. Bei unsymmetrischen Elektroden, wie sie bei einer Zündkerte vorliegen, entsteht dann ein größerer Strom, wenn sich die unbeweglicheren positiven Ladungsträger auf die größere Elektrode hin bewegen.Furthermore, from DE-OS 33 27 766 a circuit arrangement for ion current measurement is known, in which a measuring voltage is generated by an AC voltage applied to the primary side of the ignition coil. The AC voltage applied on the primary side is transformed to a higher voltage level via the ignition coil, frequencies in the range from 10 kHz to 100 kHz being used. The ion current signal effects an amplitude modulation of the alternating current generated on the secondary side. Disadvantages of this known circuit arrangement are on the one hand the use of filters which separate the ion current signal, whose useful frequency range is between 100 Hz and 20 kHz, from the carrier signal and, on the other hand, the nonlinear distortions which occur in the case of AC excitation due to the asymmetry of the ion current characteristic. This asymmetry results from the higher mobility of the negative ones Charge carriers compared to the positive ions. In the case of asymmetrical electrodes, such as are present in the case of a spark plug, a larger current is generated when the more immobile positive charge carriers move towards the larger electrode.

Schließlich ist in der US 5,483,818 eine Schaltungsanordnung zur Detektion eines Ionenstromes beschrieben, bei der die Niedrigpotentialseite des Sekundärkreises der Zündspule über einen Widerstand auf den invertierenden Eingang eines Operationsverstärkers geführt ist, während dessem nichtinvertierenden Eingang eine Referenzspannung von ca. 40 V zugeführt wird. Dieser Operationsverstärker ist mittels eines Widerstandes als invertierender Verstärker geschaltet, so daß die Referenzspannung zum Zwecke der Ionenstrommessung als Meßspannung an dem Sekundärkreis anliegt. Die am Ausgang dieses Operationsverstärkers als Ionenstrommeßsignal erzeugte Meßspannung wird zur Auswertung einer Schwellwertschaltung zugeführt.Finally, US Pat. No. 5,483,818 describes a circuit arrangement for the detection of an ion current, in which the low potential side of the secondary circuit of the ignition coil is led via a resistor to the inverting input of an operational amplifier, while a reference voltage of approx. 40 V is supplied to its non-inverting input. This operational amplifier is connected by means of a resistor as an inverting amplifier, so that the reference voltage for the purpose of measuring the ion current is present as a measuring voltage on the secondary circuit. The measurement voltage generated as an ion current measurement signal at the output of this operational amplifier is fed to a threshold value circuit for evaluation.

Zur Ableitung des während der Zündung erzeugten Zündstromes sind zwei in Serie geschaltete Zenerdioden an den Sekundärkreis angeschlossen. Zur Kompensation des in diesen Zenerdioden auftretenden Leckstromes - der die Ionenstrommessung verfälscht - ist ein Regelkreis vorgesehen, der ebenfalls von dem Ausgang des Operationsverstärkers gesteuert wird. Dieser Regelkreis ist aus einem weiteren Operationsverstärker mit entsprechender aus Widerständen und Kondensator bestehender Beschaltung aufgebaut.To derive the ignition current generated during the ignition, two series-connected Zener diodes are connected to the secondary circuit. To compensate for the leakage current occurring in these Zener diodes - which falsifies the ion current measurement - a control circuit is provided which is also controlled by the output of the operational amplifier. This control circuit is made up of a further operational amplifier with a corresponding circuit consisting of resistors and capacitors.

Der Nachteil dieser bekannten Schaltungsanordnung liegt in deren aufwendigem Schaltungsaufbau und der damit verbundenen hohen Herstellungskosten.The disadvantage of this known circuit arrangement lies in its complex circuit structure and the associated high manufacturing costs.

Daher besteht die Aufgabe der vorliegenden Erfindung darin, eine Schaltungsanordnung der eingangs genannten Art anzugeben, die die o.g. Nachteile vermeidet, zu einer hohen Meßqualität des Ionenstromes im Brennraum einer Brennkraftmaschine führt und mit geringem Aufwand realisierbar ist.Therefore, the object of the present invention is to provide a circuit arrangement of the type mentioned, which the above. Avoids disadvantages, leads to a high measurement quality of the ion current in the combustion chamber of an internal combustion engine and can be implemented with little effort.

Diese Aufgabe wird durch die kennzeichnenden Merkmale des Patentanspruches 1 gelöst, wonach Schaltungsmittel vorgesehen sind, mit denen eine konstante Meßspannung an den Sekundärkreis der Zündspule angelegt wird, die einen Spannungswert aufweist, die gleich oder kleiner als der Wert der Spannung des Bordnetzes ist und ferner ein Gleichrichterelement vorgesehen ist, das den während der Zündung der Zündkerze erzeugten Zündstrom auf das Bordnetz ableitet.This object is achieved by the characterizing features of claim 1, according to which circuit means are provided with which one constant measuring voltage is applied to the secondary circuit of the ignition coil, which has a voltage value that is equal to or less than the value of the voltage of the vehicle electrical system and a rectifier element is also provided that derives the ignition current generated during the ignition of the spark plug to the vehicle electrical system.

Durch die erfindungsgemäße Verwendung einer Meßspannung, deren Wert der Bordnetzspannung des Fahrzeuges bzw. kleiner als dieselbe ist, werden die bei Verwendung einer Meßspannung in der Größenordnung von 40 V bis 400 V auftretenden Nachteile vermieden. Außerdem ist der hierfür erforderliche Schaltungsaufwand sehr gering, obwohl gleichzeitig mit dieser erfindungsgemäßen Schaltungsanordnung über die gesamte Meßphase eine konstante Meßspannung geliefert wird.The use of a measuring voltage according to the invention, the value of which is less than or equal to the vehicle electrical system voltage, avoids the disadvantages which occur when using a measuring voltage of the order of 40 V to 400 V. In addition, the circuitry required for this is very low, although a constant measuring voltage is supplied simultaneously with this circuit arrangement according to the invention over the entire measuring phase.

Da die Größe des Ionenstromes direkt proportional zur angelegten Meßspannung ist und eine Sättigung, wie dies z. B. vom Flammenionisationsdetektor her bekannt ist, wegen der hohen Ionenkonzentration und den geringen freien Weglängen der Ionen nicht auftritt, führt eine konstante Meßspannung zu dem Vorteil, daß deren Genauigkeit direkt in das Ionenstromsignal eingeht.Since the size of the ion current is directly proportional to the applied measuring voltage and a saturation, as z. B. is known from the flame ionization detector, does not occur because of the high ion concentration and the small free path lengths of the ions, a constant measuring voltage leads to the advantage that its accuracy is directly involved in the ion current signal.

Ferner führt die Verwendung einer niedrigen Meßspannung auch dazu, daß sich Nebenschlußwiderstände, wie sie beim Kaltstart durch Verrußung der Zündkerzen entstehen, nicht so stark auswirken, da der spezifische Leitwert von Ruß proportional mit der anliegenden Spannung ansteigt.Furthermore, the use of a low measuring voltage also means that shunt resistances, such as those caused by sooting of the spark plugs during a cold start, do not have as great an effect since the specific conductance of soot increases proportionally with the applied voltage.

Gemäß einer weiteren, besonders bevorzugten Ausführungsform der Erfindung werden die Meßstrecken der als Ionenstromsonden dienenden Zündkerzen einer Brennkraftmaschine parallelgeschaltet, so daß hierdurch der Schaltungsaufwand äußerst gering bleibt.According to a further, particularly preferred embodiment of the invention, the measuring sections of the spark plugs of an internal combustion engine serving as ion current probes are connected in parallel, so that the circuit complexity remains extremely low.

Als bevorzugtes Schaltungsmittel zum Anlegen der Meßspannung an den Sekundärkreis der Zündspule ist ein Differenzverstärker vorgesehen. Dabei wird gemäß einer weiteren Ausführungsform der Erfindung dessen einem Eingang eine Referenzspannung zugeführt, deren Wert der Meßspannung entspricht und der Differenzverstärker als invertierender Verstärker geschaltet, so daß am anderen Eingang die gewünschte Meßspannung anliegt. Damit wird der Ionenstrom mit einfachsten Schaltungsmitteln in eine als Meßsignal dienende Spannung umgewandelt, die anschließend einer Auswertung zugeführt wird.A differential amplifier is provided as the preferred circuit means for applying the measurement voltage to the secondary circuit of the ignition coil. According to a further embodiment of the invention, a reference voltage is fed to an input thereof, the value of which corresponds to the measuring voltage and the differential amplifier is connected as an inverting amplifier. so that the desired measuring voltage is present at the other input. With the simplest circuit means, the ion current is converted into a voltage serving as a measurement signal, which voltage is then fed to an evaluation.

Im folgenden soll die Erfindung anhand von Ausführungsbeispielen im Zusammenhang mit den Zeichnungen dargestellt und erläutert werden. Es zeigen:

Figur 1
ein erstes Ausführungsbeispiel der erfindungsgemäßen Schaltungsanordnung und
Figur 2
ein zweites Ausführungsbeispiel der erfindungsgemäßen Schaltungsanordnung.
The invention is to be illustrated and explained below using exemplary embodiments in conjunction with the drawings. Show it:
Figure 1
a first embodiment of the circuit arrangement according to the invention and
Figure 2
a second embodiment of the circuit arrangement according to the invention.

Die Figur 1 zeigt eine Transistorzündanlage, wobei der Einfachheit halber lediglich eine Zündendstufe mit einer Zündkerze Zk für eine Brennkraftmaschine dargestellt ist.FIG. 1 shows a transistor ignition system, for the sake of simplicity only one ignition output stage with a spark plug Zk for an internal combustion engine is shown.

Die Zündendstufe umfaßt eine Zündspule Tr mit Primär- und Sekundärkreis, bestehend aus einer Primär- und Sekundärwicklung, wobei an die Sekundärwicklung die schon genannte Zündkerze Zk angeschlossen ist. Die Primärwicklung ist mit ihrem einen Anschluß an eine von einer Bordbatterie gelieferten Bordnetzspannung UB von beispielsweise 12 V angeschlossen und mit ihrem anderen Anschluß mit einem Zündtransistor 1 verbunden. Dieser Zündtransistor 1 wird über dessen Steuerelektrode von einer Regelschaltung 2 angesteuert, indem über deren Verbindungsleitung Zündauslöseimpulse diesem Zündtransistor 1 zugeführt werden.The ignition output stage comprises an ignition coil Tr with primary and secondary circuit, consisting of a primary and secondary winding, the aforementioned spark plug Zk being connected to the secondary winding. The primary winding is connected with its one connection to an on-board battery voltage U B of 12 V, for example, and is connected with its other connection to an ignition transistor 1. This ignition transistor 1 is controlled via its control electrode by a control circuit 2, in that ignition trigger pulses are supplied to this ignition transistor 1 via its connecting line.

Die Sekundärwicklung ist mit ihrer Hochspannungsseite mit der Zündkerze Zk verbunden, während deren Niedrigpotentialseite auf den invertierenden Eingang eines Differenzverstärkers 3 geführt ist. An den nicht-invertierenden Eingang dieses Differenzverstärkers 3 wird eine konstante Referenzspannung Uref, vorzugsweise 5 V angelegt, wobei diese konstante Referenzspannung von einer Konstantspannungsquelle 6 erzeugt wird. Diese konstante Referenzspannung Uref wird über diesen Differenzverstärker 3 dem Sekundärkreis der Zündspule Zk zugeführt und gelangt über diese als Meßspannung Umeß an die als Ionenstrommeßstrecke arbeitende Zündkerze Zk.The secondary winding is connected with its high voltage side to the spark plug Zk, while its low potential side is led to the inverting input of a differential amplifier 3. A constant reference voltage U ref , preferably 5 V, is applied to the non-inverting input of this differential amplifier 3, this constant reference voltage being generated by a constant voltage source 6. This constant reference voltage U ref is the via this differential amplifier 3 Secondary circuit of the ignition coil Zk fed and passes via this as the measurement voltage U measure to the spark plug Zk working as an ion current measuring section.

Der Differenzverstärker 3 ist als invertierender Verstärker aufgebaut, indem dessen invertierender Eingang über einen Widerstand R mit dessen Ausgang verbunden ist.The differential amplifier 3 is constructed as an inverting amplifier in that its inverting input is connected to its output via a resistor R.

Um während des Zündvorganges an der Zündkerze Zk einen niederohmigen Pfad für den Sekundärstrom zur Verfügung zu stellen, sind Dioden D1 und D2 vorhanden, die den Zündstrom auf Masse bzw. Bordnetzpotential ableiten. Hierzu ist die Diode D1 derart zwischen dem invertierenden Eingang des Differenzverstärkers 3 und dem Bordnetz UB geschaltet, daß der Zündstrom auf das Bordnetz abfließen kann. Die zweite Diode D2 liegt dagegen mit ihrer Anode auf dem Massepotential und ist mit ihrer Kathode ebenfalls mit dem invertierenden Eingang des Differenzverstärkers 3 verbunden. Die Verwendung einer Diode zur Ableitung von positiven Spannungen auf das Bordnetzpotential hat gegenüber der Verwendung von Zenerdioden den Vorteil, daß die Leckströme von Dioden deutlich niedriger sind als diejenigen der Zenerdioden.In order to provide a low-resistance path for the secondary current at the spark plug Zk during the ignition process, diodes D1 and D2 are provided, which derive the ignition current to ground or vehicle electrical system potential. For this purpose, the diode D1 is connected between the inverting input of the differential amplifier 3 and the vehicle electrical system U B in such a way that the ignition current can flow off to the vehicle electrical system. By contrast, the second diode D2 has its anode at ground potential and its cathode is also connected to the inverting input of the differential amplifier 3. The use of a diode to derive positive voltages from the vehicle electrical system potential has the advantage over the use of Zener diodes that the leakage currents of diodes are significantly lower than those of the Zener diodes.

Ferner kann ein Widerstand (in der Figur 1 nicht dargestellt) in der Zuleitung zum invertierenden Eingang des Differenzverstärkers 3 vorgesehen werden, der den in den Differenzverstärker 3 fließenden Strom zusätzlich begrenzt.Furthermore, a resistor (not shown in FIG. 1) can be provided in the feed line to the inverting input of the differential amplifier 3, which additionally limits the current flowing into the differential amplifier 3.

Der invertierende Differenzverstärker 3 wandelt den Ionenstrom in eine Spannung Uion um, die als Meßsignal einer Auswerteeinheit 5 zugeführt wird. Die dem Sekundärkreis der Zündspule Tr zugeführte Meßspannung Umeß, hier vorzugsweise 5 V, ist während der gesamten Meßdauer konstant. Da der Ionenmeßstrom im µA-Bereich liegt, wird ein Differenzverstärker 3 mit einem niedrigen Eingangsstrom verwendet, der heutzutage kostengünstig verfügbar ist. Durch die niederohmige Bereitstellung dieser Meßspannung Umeß entfallen Umladungen von Streukapazitäten, wie sie in anderen bekannten Systemen bei Wechselstrombelastung, wie sie z. B. bei klopfender Verbrennung, auftreten können. Dieser Vorteil der Erfindung macht sich besonders dann bemerkbar, wenn mehrere Ionenstrommeßstrecken parallel betrieben werden, wie dies weiter unten anhand von Figur 2 erläutert wird, weil sich dabei die wirksame Streukapazität vervielfachen kann.The inverting differential amplifier 3 converts the ion current into a voltage U ion , which is fed as a measurement signal to an evaluation unit 5. The measuring voltage U meas , preferably 5 V, supplied to the secondary circuit of the ignition coil Tr is constant during the entire measuring period. Since the ion measurement current is in the µA range, a differential amplifier 3 with a low input current is used, which is available inexpensively today. Due to the low-impedance provision of this measuring voltage U meß reloading of stray capacities, as they occur in other known systems with AC load , such as. B. knocking combustion can occur. This advantage of the invention is particularly noticeable when several ion current measuring sections are operated in parallel are, as will be explained further below with reference to FIG. 2, because the effective stray capacity can be multiplied.

Die Figur 1 zeigt ferner ein Steuergerät 4, das die Funktion eines Motormanagements übernimmt und seinerseits die Regelschaltung 2 ansteuert. Hierzu werden dieser Steuereinheit 4 über einen Eingang E Motorparameter, wie Last, Drehzahl und Temperatur zugeführt. Entsprechende Aktuatoren werden über Ausgänge A gesteuert. Das von der Auswerteschaltung 5 erzeugte Ionenstromsignal wird gleichfalls dem Steuergerät 4 zugeführt.FIG. 1 also shows a control unit 4, which takes over the function of an engine management system and in turn controls the control circuit 2. For this purpose, engine parameters such as load, speed and temperature are fed to this control unit 4 via an input E. Corresponding actuators are controlled via outputs A. The ion current signal generated by the evaluation circuit 5 is also fed to the control unit 4.

Das Ionenstromsignal kann dazu verwendet werden, um das Klopfen der Brennkraftmaschine zu detektieren und über eine Steuerung des Zündzeitpunktes eine entsprechende Klopfregelung aufzubauen.The ion current signal can be used to detect the knocking of the internal combustion engine and to set up a corresponding knock control by controlling the ignition timing.

Eine weitere Anwendung besteht darin, das Ionenstromsignal zur Erkennung von Entflammungsaussetzern zu verwenden.Another application is to use the ion current signal to detect misfires.

Bei 4-Takt-Motoren kann sich der Zylinder bei der Kurbelposition, bei der die Zündung erfolgen soll sowohl im Kompressions- als auch im Auspufftakt befinden. Nur wenn der Zündvorgang im Kompressionstakt durchgeführt wird, entsteht eine normale Verbrennung mit dem zugehörigen Ionenstromsignal. Bei Zündung im Auspufftakt ist das Ionenstromsignal nahezu Null. Hierdurch kann die Phasenbeziehung zwischen Kurbel- und Nockenwelle erkannt werden.With 4-stroke engines, the cylinder can be in the crank position at which the ignition is to take place, both in the compression and in the exhaust stroke. Normal combustion with the associated ion current signal only occurs if the ignition process is carried out in the compression cycle. When ignited in the exhaust cycle, the ion current signal is almost zero. This allows the phase relationship between the crankshaft and camshaft to be recognized.

Figur 2 zeigt eine Transistorzündanlage einer 4-Zylinder-Brennkraftmaschine mit jeweils einem Zylinder zugeordneten Zündendstufen, wobei jede Zündendstufe aus einer Zündspule Tr1 ... Tr4, jeweils einem Zündtransistor 1a ... 1d und zugehöriger Zündkerze Zk1 ... Zk4 aufgebaut ist.FIG. 2 shows a transistor ignition system of a 4-cylinder internal combustion engine with ignition output stages each assigned to a cylinder, each ignition output stage comprising an ignition coil Tr 1 ... Tr 4 , an ignition transistor 1a ... 1d and associated spark plug Zk 1 ... Zk 4 is constructed.

Die Zündtransistoren 1a ... 1d werden über deren Steuerelektroden von einer Schaltung 2a zur Zylinderselektion angesteuert, die ihrerseits mit einer Regelschaltung 2 verbunden ist, die die entsprechenden Zündauslöseimpulse für die einzelnen Zylinder dieser Schaltung 2a zuführt.The ignition transistors 1a ... 1d are controlled via their control electrodes by a circuit 2a for cylinder selection, which in turn is connected to a control circuit 2 which supplies the corresponding ignition trigger pulses for the individual cylinders of this circuit 2a.

Gleichfalls wie in dem Ausführungsbeispiel gemäß Figur 1 ist ein Steuergerät 4 vorgesehen, das die Regelschaltung 2 ansteuert.Likewise, as in the exemplary embodiment according to FIG. 1, a control device 4 is provided which controls the control circuit 2.

Zur Messung des Ionenstromes ist jeweils die Niedrigpotentialseite des Sekundärkreises jeder Zündspule Tr1 ... Tr4 auf einen Schaltungsknoten S geführt, der mit dem invertierenden Eingang eines Differenzverstärkers 3 verbunden ist. Dieser Differenzverstärker 3 ist ebenfalls als invertierender Verstärker mittels eines den invertierenden Eingang mit dem Ausgang verbindenden Widerstandes R aufgebaut. Dem nicht-invertierenden Eingang dieses Differenzverstärkers 3 wird eine konstante Referenzspannung Uref zugeführt, die von einer Konstantspannungsquelle 6 erzeugt wird. Diese konstante Referenzspannung Uref ist kleiner als die Bordnetzspannung und beträgt 5 V und führt zu der erwünschten Meßspannung Umeß am Schaltungsknoten S und somit auch an den parallelgeschalteten Ionenstromstrecken der Zündkerzen Zk1 ... Zk4.To measure the ion current, the low potential side of the secondary circuit of each ignition coil Tr 1 ... Tr 4 is routed to a circuit node S which is connected to the inverting input of a differential amplifier 3. This differential amplifier 3 is also constructed as an inverting amplifier by means of a resistor R connecting the inverting input to the output. A constant reference voltage U ref , which is generated by a constant voltage source 6, is fed to the non-inverting input of this differential amplifier 3. This constant reference voltage U ref is less than the vehicle electrical system voltage and is 5 V and leads to the desired measuring voltage U meas at the circuit node S and thus also at the ion current paths of the spark plugs Zk 1 ... Zk 4 connected in parallel.

Ferner sind ebenso wie in dem Ausführungsbeispiel gemäß Figur 1 zwei Dioden D1 und D2 zur Ableitung des Zündstromes auf Masse bzw. Bordnetz vorgesehen.Furthermore, as in the exemplary embodiment according to FIG. 1, two diodes D1 and D2 are provided for deriving the ignition current to ground or the electrical system.

Das am Ausgang des Differenzverstärkers 3 erhaltene Meßsignal Uion wird einer Auswerteschaltung 5 zugeführt, die ihrerseits von einem Steuergerät 4 angesteuert wird, dessen Funktion demjenigen Steuergerät aus Figur 1 entspricht.The measurement signal U ion obtained at the output of the differential amplifier 3 is fed to an evaluation circuit 5, which in turn is controlled by a control unit 4, the function of which corresponds to that of the control unit from FIG. 1.

Schließlich kann auch in diesem Ausführungsbeispiel gemäß Figur 2 ein zusätzlicher Widerstand (ebenfalls nicht dargestellt) in der Zuleitung zum invertierenden Eingang des Differenzverstärkers 3 vorgesehen werden, der den in den Differenzverstärker 3 fließenden Strom zusätzlich begrenzt.Finally, in this exemplary embodiment according to FIG. 2, an additional resistor (likewise not shown) can be provided in the feed line to the inverting input of the differential amplifier 3, which additionally limits the current flowing into the differential amplifier 3.

Die erfindungsgemäße Schaltungsanordnung zur Ionenstrommessung ist nicht nur bei Transistorzündanlagen, wie in den beiden Ausführungsbeispielen dargestellt, einsetzbar, sondern gleichfalls bei Wechselstromzündungen oder Hochspannungskondensatorzündungen.The circuit arrangement according to the invention for ion current measurement can be used not only in transistor ignition systems, as shown in the two exemplary embodiments, but also in alternating current ignitions or high-voltage capacitor ignitions.

Claims (7)

Schaltungsanordnung zur Ionenstrommessung im Verbrennungsraum einer Brennkraftmaschine, bestehend aus: a) einer Zündspule (Tr, Tr1 ... Tr4) mit Primär- und Sekundärkreis, die von einem eine Bordnetzspannung (UB) liefernden Bordnetz gespeist wird, b) einer im Sekundärkreis angeordneten Zündkerze (Zk, Zk1 ... Zk4), die gleichzeitig als Ionenstromsonde dient, gekennzeichnet durch folgendes Merkmal: c) es sind Schaltungsmittel (3, R) vorgesehen, mit denen eine konstante Meßspannung (Umeß) an die Niedrigpotentialseite des Sekundärkreises der Zündspule (Tr, Tr1 ... Tr4) angelegt wird, die einen Spannungswert aufweist, der gleich oder kleiner als der Wert der Bordnetzspannung (UB) ist und d) ferner ist ein Gleichrichterelement (D1) vorgesehen, das den während der Zündung der Zündkerze (Zk, Zk1 ... Zk4) erzeugten Zündstrom (IZünd) auf das Bordnetz ableitet. Circuit arrangement for ion current measurement in the combustion chamber of an internal combustion engine, consisting of: a) an ignition coil (Tr, Tr 1 ... Tr 4 ) with primary and secondary circuit, which is fed by an on-board electrical system supplying an on-board electrical system voltage (U B ), b) a spark plug (Zk, Zk 1 ... Zk 4 ) arranged in the secondary circuit, which also serves as an ion current probe, characterized by the following feature: c) there are circuit means (3, R) with which a constant measuring voltage (U meas ) is applied to the low potential side of the secondary circuit of the ignition coil (Tr, Tr 1 ... Tr 4 ), which has a voltage value which is equal to or is less than the value of the vehicle electrical system voltage (U B ) and d) a rectifier element (D1) is also provided, which leads the ignition current (I Zünd ) generated during the ignition of the spark plug (Zk, Zk 1 ... Zk 4 ) to the vehicle electrical system. Schaltungsanordnung nach Anspruch 1, dadurch gekennzeichnet, daß als Gleichrichterelement eine Halbleiterdiode (D1) vorgesehen ist.Circuit arrangement according to Claim 1, characterized in that a semiconductor diode (D1) is provided as the rectifier element. Schaltungsanordnung nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß bei mehreren Zündspulen (Tr1 ... Tr4) mit jeweils einer Zündkerze (Zk1 ... Zk4) als Ionenstromsonde die von den Ionenstromsonden gebildeten Meßstrecken parallelgeschaltet sind.Circuit arrangement according to one of the preceding claims, characterized in that in the case of a plurality of ignition coils (Tr 1 ... Tr 4 ), each with a spark plug (Zk 1 ... Zk 4 ) as the ion current probe, the measuring sections formed by the ion current probes are connected in parallel. Schaltungsanordnung nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß als Schaltungsmittel (3, R) ein als invertierender Verstärker geschalteter Differenzverstärker vorgesehen ist.Circuit arrangement according to one of the preceding claims, characterized in that a differential amplifier connected as an inverting amplifier is provided as the switching means (3, R). Schaltungsanordnung nach Anspruch 4, dadurch gekennzeichnet, daß der eine Eingang des Differenzverstärkers (3) mit der Niedrigpotentialseite des Sekundärkreises der Zündspule (Tr, Tr1 ... Tr4) verbunden ist und dem anderen Eingang eine Referenzspannung (Uref) zugeführt wird, deren Wert der Meßspannung (Umeß) entspricht, und der Ausgang des Differenzverstärkers (3) über einen Widerstand (R) mit dem einen Eingang verbunden ist.Circuit arrangement according to Claim 4, characterized in that one input of the differential amplifier (3) is connected to the low potential side of the secondary circuit of the ignition coil (Tr, Tr 1 ... Tr 4 ) and the other input is supplied with a reference voltage (U ref ), whose value corresponds to the measuring voltage (U meas ), and the output of the differential amplifier (3) is connected to the one input via a resistor (R). Schaltungsanordnung nach Anspruch 5, dadurch gekennzeichnet, daß die Referenzspannung (Uref) von einer Konstantspannungsquelle (6) erzeugt wird.Circuit arrangement according to Claim 5, characterized in that the reference voltage (U ref ) is generated by a constant voltage source (6). Schaltungsanordnung nach einem der Ansprüche 4 bis 6, dadurch gekennzeichnet, daß die am Eingang des Differenzverstärkers (3, R) anliegenden negativen Spannungsspitzen mit einer Diode (D2) auf Massepotential des Bordnetzes abgeleitet wird.Circuit arrangement according to one of claims 4 to 6, characterized in that the negative voltage peaks present at the input of the differential amplifier (3, R) are derived with a diode (D2) to the ground potential of the vehicle electrical system.
EP97101843A 1996-02-16 1997-02-06 Measuring circuit for an ionic current in ignition devices for internal combustion engines Expired - Lifetime EP0790409B1 (en)

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EP0790408A2 (en) 1997-08-20
US5914604A (en) 1999-06-22
DE59705316D1 (en) 2001-12-20
ES2166479T3 (en) 2002-04-16
EP0790406A2 (en) 1997-08-20
US5758629A (en) 1998-06-02
EP0790409A3 (en) 1999-01-20
US6043660A (en) 2000-03-28
EP0790406B1 (en) 2003-07-02
DE59710359D1 (en) 2003-08-07
EP0790409B1 (en) 2003-08-20
EP0790406A3 (en) 1999-01-27
DE19605803A1 (en) 1997-08-21
DE59710592D1 (en) 2003-09-25
EP0790408A3 (en) 1999-01-20
EP0790408B1 (en) 2001-11-14

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