EP0525345B1 - Device and method for monitoring a flame - Google Patents

Device and method for monitoring a flame Download PDF

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Publication number
EP0525345B1
EP0525345B1 EP92109976A EP92109976A EP0525345B1 EP 0525345 B1 EP0525345 B1 EP 0525345B1 EP 92109976 A EP92109976 A EP 92109976A EP 92109976 A EP92109976 A EP 92109976A EP 0525345 B1 EP0525345 B1 EP 0525345B1
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EP
European Patent Office
Prior art keywords
signal
flame
voltage
frequency
processing arrangement
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EP92109976A
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German (de)
French (fr)
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EP0525345B2 (en
EP0525345A1 (en
Inventor
Klaus Krieger
Markus Dipl.-Ing. Koenig (Fh)
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Robert Bosch GmbH
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Robert Bosch GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/12—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods
    • F23N5/123—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2223/00—Signal processing; Details thereof
    • F23N2223/08—Microprocessor; Microcomputer
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2223/00—Signal processing; Details thereof
    • F23N2223/20—Opto-coupler
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2229/00—Flame sensors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2229/00—Flame sensors
    • F23N2229/12—Flame sensors with flame rectification current detecting means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2231/00—Fail safe
    • F23N2231/06—Fail safe for flame failures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/20—Systems for controlling combustion with a time programme acting through electrical means, e.g. using time-delay relays
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements

Definitions

  • the invention relates to a device and a method for monitoring a flame according to the preamble of the independent claims.
  • a circuit is known from Patent Abstracts of Japan Vol. 12, no. 134 (to JP-A-62 255 729), in which a pulse is generated by a sensor arranged in the flame and by a capacitor which is discharged via a circuit device is generated, the duration of which is used as a signal for the presence of a flame. The detected pulse duration is forwarded to a signal processing arrangement and evaluated accordingly.
  • EP 0 388 065 provides means for potential isolation between the sensor circuit and the signal processing arrangement; the signal processing takes place in that the discharge of a capacitor is provided via an optocoupler. This is an analog signal transmission in which a voltage / frequency converter is not provided.
  • the device according to the invention with the characterizing features of claim 1 has the advantage that the signal emitted by the sensor is fed to a voltage / frequency converter, the output signal of which is passed on to a signal processing arrangement.
  • the signal emitted by the sensor is thus converted into a dynamic signal, which is passed on to the signal processing arrangement via a potential separation.
  • each component failure that prevents the dynamic behavior leads to the same information as the signal behavior when the flame is extinguished. Depending on the design of the signal processing arrangement, this can lead to the fuel-heated device being switched off and / or to an alarm.
  • the conversion of the sensor signal into a variable independent of the potential of the sensor circuit ensures simple and safe transmission of the sensor signal to the signal processing arrangement. This conversion takes place by means of a voltage / frequency converter, which can also be designed as a current / frequency converter.
  • the voltage / frequency converter is constructed in the form of a pulse width modulator or a frequency modulator
  • dynamic characteristic variables are assigned to the sensor signal, such as, for. B. the duty cycle or the frequency or the phase of an oscillating signal, which are easy to manufacture and detectable again. It is also possible to assign several parameters to the sensor signal and thus generate redundancy.
  • the sensor signal can be converted particularly simply into a pulse-width-modulated signal if a comparator is provided which compares the sensor signal with a triangular voltage.
  • the basic frequency of the triangular voltage which can also be changed over time, gives a frame time before and the level of the sensor signal determines the relationship between pulse and pause within the frame time.
  • the senor can be designed as a simple electrode extending into the flame area, for example in the form of a wire. If a voltage is applied between the torch and the electrode, a current flows when the flame is present. This current or the resulting voltage drop across an electrical component can be used to evaluate whether a flame is present or not. In this way, expensive optical sensors can be avoided.
  • the parallel processing of the output signal of the voltage / frequency converter in the signal processing arrangement which can also be used to control the fuel supply, and in a safety circuit generates redundancy and thus reduces malfunction in the event of errors.
  • the safety circuit can be constructed by the simplest means, which only checks the characteristic values containing the flame information for upper or lower limit values. The safety circuit can then act directly on the valve in the fuel supply line, or z. B. on the energy supply of this valve.
  • a circuit operating according to the inventive method according to claim 9 for monitoring a flame of a fuel-heated device converts the signal emitted by the sensor into an oscillating signal with predeterminable characteristic values, the signal advantageously being supplied to a signal processing arrangement by means of potential isolation.
  • the characteristic values containing the information regarding the flame e.g. B. the pulse pause ratio of a square wave signal or the frequency and / or phase of the oscillating signal can be selected so that Influences, such as interference in the circuit contained in the sensor, have no influence on the characteristic values.
  • a safety circuit which checks the characteristic values of the oscillating signal for specific limit values and emits an alarm signal when the values are exceeded or fallen below. This provides a redundant circuit with a high level of error protection in a simple manner.
  • FIG. 1 shows a schematic overview of assemblies
  • FIG. 2 shows a schematic circuit diagram of a possible embodiment
  • FIG. 3 shows two voltage / time diagrams which correspond to one another and which explain the generation of a pulse-width-modulated signal after the embodiment according to FIG. 2.
  • 10 denotes a burner of a fuel-heated device, not shown, and 12 the fuel supply line to the burner 10.
  • Two valves 14 act on the fuel supply line 12, which valves can advantageously be designed as solenoid valves. These valves are generally known and are not described in detail here.
  • the flame area 16 of the burner 10 is scanned by a sensor 18 which is connected via a line 20 to a signal processing arrangement 22.
  • the line 20 is interrupted by a potential separation 24, which is constructed in the form of an optocoupler.
  • the opto-coupler 24 is a common component, so that its functionality will not be discussed.
  • a microcomputer circuit is used as the signal processing arrangement 22, which also controls the entire device. This is connected to the valves 14 and can act on and off as well as continuously regulating them.
  • a voltage / frequency converter 26 is also provided in line 20, which is shown in the embodiment of FIG. 2 in the form of a pulse width modulator and is described in more detail here.
  • the pulse width modulator contains a comparator 28, to the first input of which line 20 is connected.
  • the further line 20 is connected to the output of the comparator 28.
  • a triangle generator 30 is provided, the output of which is led to the second input of the comparator.
  • a frequency modulator can also be used, which emits an output signal of a specific frequency or a specific phase depending on the sensor signal coupled into it by means of the line 20.
  • a pulse width modulator on which frequency modulation is superimposed in such a way that the pulse repetition frequency or the predetermined frame time of the pulse train changes.
  • the circuit required for this can be constructed, for example, in the form of a multivibrator.
  • the sensor 18 is in the form of an electrode extending into the flame region 16, in particular through a wire end, and is connected to a voltage source 34 via a voltage divider 32.
  • the other side of the voltage source 34 is connected to a device ground via the burner 10.
  • the circuit electrode 18, voltage divider 32, voltage source 34 and burner 10 is open and no current flows. If there is a flame, the path between the burner 10 and the electrode 18 is ionized, a current flows and partial voltages drop across the partial resistors of the voltage divider 32.
  • the line 20 is connected between the partial resistors on the voltage divider 32, whereby a partial voltage is used as a signal. The information results from the fact that a voltage drops across the partial resistance in the case of a flame, while there is no voltage without a flame.
  • the voltage source 34 is designed as an AC voltage source.
  • the flame has a rectifying effect, so that a uniform voltage drops across the resistors 32.
  • a diode 38 in the form of a Zener diode limits the maximum input voltage at the comparator 28 and a capacitor 40 also smoothes this voltage.
  • a line 42 branches off from the line 20 between the potential separation 24 and the signal processing arrangement 22 and leads to a safety circuit 44 which acts directly (FIG. 1) or indirectly (FIG. 2) on the solenoid valves 14.
  • the safety circuit 44 contains a frequency / voltage converter 46, the negated output of which is led to the input of an AND gate 48.
  • the second input of the AND gate 48 is connected to the solenoid valves 14.
  • the output of the AND gate 48 leads to a bimetallic switch 50, which is in the power supply to the solenoid valves 14, not shown. This arrangement creates a simple redundant safety circuit which closes the solenoid valves 14 independently and reliably in the event of errors.
  • the circuit described above works as follows: If the burner 10 shown in FIG. 2 is in operation, a voltage drops across the partial resistors of the voltage divider 32. This voltage is rectified and smoothed, then compared in comparator 28 with a triangular voltage and thus a pulse width modulated signal of uniform amplitude is generated. This is supplied to the signal processing arrangement 22 and the frequency / voltage converter 46 to the safety circuit 44 via the potential separation 24. When operating correctly, the frequency of the transmitted signal is within certain limits. For example, as Microprocessor-designed signal processing arrangement 22 controls or regulates the normal operation of the fuel-heated device.
  • the voltage across the partial resistors of the voltage divider 32 is omitted and thus influences the frequency of the signal transmitted to the signal processing arrangement 22.
  • the microcomputer detects that there is no flame and outputs a signal to close the valves 14 if this has not already been done.
  • the safety circuit 44 also operates in a corresponding manner if, instead of the pulse-width modulated, a frequency-modulated or a mixed form of pulse-width and frequency-modulated signal is used. It is only important for this that the frequency / voltage converter 46 checks the output signal of the voltage / frequency converter 26 for predetermined limit values and, when these limits are exceeded or undershot, can be identified by a signal change at its output.
  • assemblies 36, 26, 24, 22, 44 shown in FIG. 1 are implemented in whole or in part as program sequences in a microcomputer.
  • the method according to the invention for monitoring a flame provides that any sensor 18, for example an optical sensor or an electrode, emits a signal to a signal processing arrangement 22.
  • This signal which can be uniform or alternating, is converted into an oscillating signal with certain characteristic values, such that the characteristic values contain the information as to whether a flame is present or not.
  • the characteristic values are, for example, a pulse width ratio, a frequency or a phase position or combinations thereof. If these characteristic values exceed or fall below certain limits, it can thereby be recognized whether the flame is present or not or whether there is an error.
  • the signal processing arrangement 22 can be connected in parallel with a safety circuit 44, the task of which is merely to check whether the characteristic values lie within predefinable limit values and to generate an output signal as a function thereof.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Regulation And Control Of Combustion (AREA)
  • Control Of Combustion (AREA)

Description

Stand der TechnikState of the art

Die Erfindung betrifft eine Vorrichtung und ein Verfahren zum Überwachen einer Flamme nach der Gattung der unabhängigen Ansprüche. Durch Patent Abstracts of Japan Vol. 12, no. 134 (zu JP-A-62 255 729) ist eine Schaltung bekannt geworden, bei der durch einen in der Flamme angeordneten Sensor und durch einen Kondensator der über eine Schaltungseinrichtung entladen wird, ein Impuls erzeugt wird, dessen Dauer als Signal für das Vorhandensein einer Flamme genutzt wird. Dabei wird die erfaßte Impulsdauer an eine signalverarbeitende Anordnung weitergeleitet und entsprechend ausgewertet.The invention relates to a device and a method for monitoring a flame according to the preamble of the independent claims. A circuit is known from Patent Abstracts of Japan Vol. 12, no. 134 (to JP-A-62 255 729), in which a pulse is generated by a sensor arranged in the flame and by a capacitor which is discharged via a circuit device is generated, the duration of which is used as a signal for the presence of a flame. The detected pulse duration is forwarded to a signal processing arrangement and evaluated accordingly.

In der EP 0 388 065 sind Mittel zur Potentialtrennung zwischen Sensorkreis und signalverarbeitender Anordnung vorgesehen; die Signalverarbeitung erfolgt dadurch, daß die Entladung eines Kondensators über einen Opto-Koppler vorgesehen ist. Hierbei handelt es sich um eine analoge Signalübertragung, bei der ein Spannungs-/Frequenzumsetzer nicht vorgesehen ist.EP 0 388 065 provides means for potential isolation between the sensor circuit and the signal processing arrangement; the signal processing takes place in that the discharge of a capacitor is provided via an optocoupler. This is an analog signal transmission in which a voltage / frequency converter is not provided.

Vorteile der ErfindungAdvantages of the invention

Die erfindungsgemäße Vorrichtung mit den kennzeichnenden Merkmalen des Anspruchs 1 hat den Vorteil, daß das vom Sensor abgegebene Signal einem Spannungs-/Frequenzumsetzer zugeführt wird, dessen Ausgangssignal an eine signalverarbeitende Anordnung weitergeleitet wird. Das vom Sensor abgegebene Signal wird so in ein dynamisches Signal überführt, das über eine Potentialtrennung an die signalverarbeitende Anordnung weitergeleitet wird. Durch die Trennung der Potentiale des Sensorkreises und des Kreises der signalverarbeitenden Anordnung lassen sich Einstreuungen in die empfindlichen Sensorschaltung in vorteilhafter Weise weitgehend vermeiden.The device according to the invention with the characterizing features of claim 1 has the advantage that the signal emitted by the sensor is fed to a voltage / frequency converter, the output signal of which is passed on to a signal processing arrangement. The signal emitted by the sensor is thus converted into a dynamic signal, which is passed on to the signal processing arrangement via a potential separation. By separating the potentials of the Interference in the sensitive sensor circuit and the circuit of the signal processing arrangement can be largely avoided in an advantageous manner.

Durch die dynamische Signalübertragung führt jeder Bauteilausfall, der das dynamische Verhalten unterbindet, zur gleichen Information wie das Signalverhalten bei erloschener Flamme. Je nach Auslegung der signalverarbeitenden Anordnung kann dies zur Abschaltung des brennstoffbeheizten Gerätes und/oder zu einem Alarm führen.Due to the dynamic signal transmission, each component failure that prevents the dynamic behavior leads to the same information as the signal behavior when the flame is extinguished. Depending on the design of the signal processing arrangement, this can lead to the fuel-heated device being switched off and / or to an alarm.

Die Umsetzung des Sensorsignals in eine vom Potential des Sensorkreises unabhängige Größe gewährleistet ein einfaches und sicheres Übertragen des Sensorsignals auf die signalverarbeitenden Anordnung. Diese Umsetzung erfolgt mittels eines Spannungs-/Frequenzumsetzers, der auch als Strom/Frequenzumsetzer ausgeführt sein kann.The conversion of the sensor signal into a variable independent of the potential of the sensor circuit ensures simple and safe transmission of the sensor signal to the signal processing arrangement. This conversion takes place by means of a voltage / frequency converter, which can also be designed as a current / frequency converter.

Durch die in den Unteransprüchen aufgeführten Maßnahmen sind vorteilhafte Weiterbildungen der in den übergeordneten Ansprüchen angegebenen Maßnahmen möglich.The measures listed in the subclaims permit advantageous developments of the measures specified in the superordinate claims.

Wird der Spannungs-/Frequenzumsetzer in der Form eines Pulsweitenmodulators oder eines Frequenzmodulators aufgebaut, werden dem Sensorsignal dadurch dynamische Kenngrößen zugeordnet, wie z. B. das Tastverhältnis oder die Frequenz bzw. die Phase eines oszillierenden Signals, die auf einfache Weise herstellbar und wieder detektierbar sind. Es ist auch möglich, dem Sensorsignal mehrere Kenngrößen zuzuordnen und so eine Redundanz zu erzeugen.If the voltage / frequency converter is constructed in the form of a pulse width modulator or a frequency modulator, dynamic characteristic variables are assigned to the sensor signal, such as, for. B. the duty cycle or the frequency or the phase of an oscillating signal, which are easy to manufacture and detectable again. It is also possible to assign several parameters to the sensor signal and thus generate redundancy.

Besonders einfach kann das Sensorsignal in ein pulsweitenmodeliertes Signal überführt werden, wenn ein Komparator vorgesehen ist, der das Sensorsignal mit einer Dreiecksspannung vergleicht. Die Grundfrequenz der Dreieckspannung, die auch zeitlich veränderbar sein kann, gibt eine Rahmenzeit vor und die Höhe des Sensorsignals bestimmt das Verhältnis zwischen Impuls und Pause innerhalb der Rahmenzeit.The sensor signal can be converted particularly simply into a pulse-width-modulated signal if a comparator is provided which compares the sensor signal with a triangular voltage. The basic frequency of the triangular voltage, which can also be changed over time, gives a frame time before and the level of the sensor signal determines the relationship between pulse and pause within the frame time.

Unter Ausnutzung der ionisierenden Eigenschaften der Flamme kann der Sensor als einfache, sich in den Flammenbereich erstreckende Elektrode, beispielsweise in Form eines Drahtes, ausgebildet sein. Wird zwischen Brenner und Elektrode eine Spannung angelegt, so fließt, wenn die Flamme vorhanden ist, ein Strom. Dieser Strom oder auch der dadurch bedingte Spannungsabfall an einem elektrischem Bauteil kann zur Auswertung, ob eine Flamme vorhanden ist oder nicht, herangezogen werden. Auf diese Weise lassen sich teure optische Sensoren vermeiden.Taking advantage of the ionizing properties of the flame, the sensor can be designed as a simple electrode extending into the flame area, for example in the form of a wire. If a voltage is applied between the torch and the electrode, a current flows when the flame is present. This current or the resulting voltage drop across an electrical component can be used to evaluate whether a flame is present or not. In this way, expensive optical sensors can be avoided.

Das parallele Verarbeiten des Ausgangssignals des Spannungs-/Frequenzumsetzers in der signalverarbeitenden Anordnung, die auch zur Steuerung der Brennstoffzufuhr Verwendung finden kann, und in einer Sicherheitsschaltung erzeugt eine Redundanz und vermindert so ein Fehlverhalten bei auftretenden Fehlern. Die Sicherheitsschaltung kann durch einfachste Mittel aufgebaut sein, die lediglich die die Flammeninformation enthaltenen Kennwerte auf obere oder untere Grenzwerte überprüft. Die Sicherheitsschaltung kann dann direkt auf das Ventil in der Brennstoffzufuhrleitung wirken, oder z. B. auf die Energieversorgung dieses Ventils.The parallel processing of the output signal of the voltage / frequency converter in the signal processing arrangement, which can also be used to control the fuel supply, and in a safety circuit generates redundancy and thus reduces malfunction in the event of errors. The safety circuit can be constructed by the simplest means, which only checks the characteristic values containing the flame information for upper or lower limit values. The safety circuit can then act directly on the valve in the fuel supply line, or z. B. on the energy supply of this valve.

Eine nach dem erfindungsgemäßen Verfahren gemäß Anspruch 9 zum Überwachen einer Flamme eines brennstoffbeheizten Gerätes arbeitende Schaltung überführt das vom Sensor abgegebene Signal in ein oszillierendes Signal mit vorgebbaren Kennwerten, wobei das Signal in vorteilhafter Weise über Mittel zur Potentialtrennung einer signalverarbeitenden Anordnung zugeführt wird. Die die Information bezüglich der Flamme enthaltenen Kennwerte, z. B. das Impulspausenverhältnis eines Rechtecksignals oder die Frequenz und/oder Phasenlage des oszillierenden Signals können so ausgewählt werden, daß Einflüsse, wie Einstreuungen in die den Sensor enthaltene Schaltung, keinen Einfluß auf die Kennwerte ausüben. Weiterhin ist es möglich, solche Kennwerte auszuwählen, die bei auftretenden Fehlern, wie z. B. einem Bauteilausfall, bestimmte Extremwerte annehmen, die sich leicht detektieren lassen.A circuit operating according to the inventive method according to claim 9 for monitoring a flame of a fuel-heated device converts the signal emitted by the sensor into an oscillating signal with predeterminable characteristic values, the signal advantageously being supplied to a signal processing arrangement by means of potential isolation. The characteristic values containing the information regarding the flame, e.g. B. the pulse pause ratio of a square wave signal or the frequency and / or phase of the oscillating signal can be selected so that Influences, such as interference in the circuit contained in the sensor, have no influence on the characteristic values. Furthermore, it is possible to select such characteristic values that are used when errors occur, such as. B. a component failure, certain extreme values that can be easily detected.

Ferner kann vorgesehen werden, daß unabhängig von der signalverarbeitenden Anordnung eine Sicherheitsschaltung vorgesehen wird, die die Kennwerte des oszillierenden Signals auf bestimmte Grenzwerte überprüft und bei Über- oder Unterschreiten ein Alarmsignal abgibt. Dadurch erhält man auf einfache Weise eine redundante Schaltung mit hoher Fehlersicherheit.Furthermore, it can be provided that, regardless of the signal processing arrangement, a safety circuit is provided which checks the characteristic values of the oscillating signal for specific limit values and emits an alarm signal when the values are exceeded or fallen below. This provides a redundant circuit with a high level of error protection in a simple manner.

Zeichnungdrawing

Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt und in der nachfolgenden Beschreibung unter Angabe weiterer Vorteile näher erläutert. Es zeigen Figur 1 eine schematische Übersicht von Baugruppen, Figur 2 ein schematisches Schaltbild einer möglichen Ausführung und Figur 3 zwei miteinander korrespondierende Spannungs-/Zeitdiagramme, die das Erzeugen eines pulsweitenmodulierten Signals nach der Ausführung gemäß Figur 2 erläutert.An embodiment of the invention is shown in the drawing and explained in more detail in the following description with further advantages. FIG. 1 shows a schematic overview of assemblies, FIG. 2 shows a schematic circuit diagram of a possible embodiment, and FIG. 3 shows two voltage / time diagrams which correspond to one another and which explain the generation of a pulse-width-modulated signal after the embodiment according to FIG. 2.

Beschreibung des AusführungsbeispielsDescription of the embodiment

In Figur 1 ist mit 10 ein Brenner eines nicht dargestellten brennstoffbeheizten Gerätes und mit 12 die Brennstoffzufuhrleitung zum Brenner 10 bezeichnet. Auf die Brennstoffzufuhrleitung 12 wirken zwei Ventile 14, die vorteilhaft als Magnetventile ausgebildet sein können. Diese Ventile sind allgemein bekannt und werden hier nicht näher beschrieben.In Figure 1, 10 denotes a burner of a fuel-heated device, not shown, and 12 the fuel supply line to the burner 10. Two valves 14 act on the fuel supply line 12, which valves can advantageously be designed as solenoid valves. These valves are generally known and are not described in detail here.

Der Flammenbereich 16 des Brenners 10 wird mit einem Sensor 18 abgetastet, der über eine Leitung 20 mit einer signalverarbeitenden Anordnung 22 verbunden ist. Die Leitung 20 wird unterbrochen durch eine Potentialtrennung 24, die in Form eines Opto-Kopplers aufgebaut ist. Der Opto-Koppler 24 ist ein gängiges Bauteil, so daß auch auf dessen Funktionsweise nicht eingegangen wird.The flame area 16 of the burner 10 is scanned by a sensor 18 which is connected via a line 20 to a signal processing arrangement 22. The line 20 is interrupted by a potential separation 24, which is constructed in the form of an optocoupler. The opto-coupler 24 is a common component, so that its functionality will not be discussed.

Als signalverarbeitende Anordnung 22 findet eine Mikrocomputerschaltung Anwendung, die auch die Steuerung des gesamten Gerätes wahrnimmt. Diese ist mit den Ventilen 14 verbunden und kann sowohl an- und abschaltend als auch stetigregelnd auf diese einwirken.A microcomputer circuit is used as the signal processing arrangement 22, which also controls the entire device. This is connected to the valves 14 and can act on and off as well as continuously regulating them.

In der Leitung 20 ist ferner ein Spannungs-/Frequenzumsetzer 26 vorgesehen, der im Ausführungsbeispiel gemäß der Figur 2 in der Form eines Pulsweitenmodulators dargestellt und hier näher beschrieben ist.A voltage / frequency converter 26 is also provided in line 20, which is shown in the embodiment of FIG. 2 in the form of a pulse width modulator and is described in more detail here.

Der Pulsweitenmodulator enthält einen Komparator 28, an dessen erstem Eingang die Leitung 20 angeschlossen ist. An dem Ausgang des Komparators 28 ist die weiterführende Leitung 20 angeschlossen. Weiterhin ist ein Dreiecksgenerator 30 vorgesehen, dessen Ausgang auf den zweiten Eingang des Komparators geführt ist. Durch das Vergleichen der Dreieckspannung Ud (Figur 3) mit der auf Leitung 20 liegenden Signalspannung Ue entsteht am Ausgang des Komperators 28 eine Rechteckspannung, deren Amplitude Ua einen voreinstellbaren Wert besitzt und deren Impulspausenverhältnis bei festvorgegebener Dreieckspannung von der Signalspannung Ue auf der Leitung 20 abhängt (siehe Figur 3).The pulse width modulator contains a comparator 28, to the first input of which line 20 is connected. The further line 20 is connected to the output of the comparator 28. Furthermore, a triangle generator 30 is provided, the output of which is led to the second input of the comparator. By comparing the triangular voltage Ud (FIG. 3) with the signal voltage Ue on line 20, a square-wave voltage is produced at the output of the comparator 28, the amplitude Ua of which is a preset value Has value and whose pulse pause ratio depends on the signal voltage Ue on the line 20 for a predetermined triangular voltage (see FIG. 3).

Anstatt des Impulsweitenmodulators kann auch ein Frequenzmodulator eingesetzt werden, der ein Ausgangssignal bestimmter Frequenz oder bestimmter Phase in Abhängigkeit des mittels der Leitung 20 in ihn eingekoppelten Sensorsignals abgibt.Instead of the pulse width modulator, a frequency modulator can also be used, which emits an output signal of a specific frequency or a specific phase depending on the sensor signal coupled into it by means of the line 20.

Es ist auch denkbar, einen Pulsweitenmodulator einzusetzen, dem eine Frequenzmodulation in der Form überlagert ist, daß sich die Impulsfolgefrequenz beziehungsweise die vorgegebene Rahmenzeit der Impulsfolge ändert. Die hierzu erforderliche Schaltung kann zum Beispiel in Form eines Multivibrators aufgebaut sein.It is also conceivable to use a pulse width modulator on which frequency modulation is superimposed in such a way that the pulse repetition frequency or the predetermined frame time of the pulse train changes. The circuit required for this can be constructed, for example, in the form of a multivibrator.

Der Sensor 18 ist in Form einer sich in den Flammenbereich 16 erstreckenden Elektrode, insbesondere durch ein Drahtende, ausgebildet und über einen Spannungsteiler 32 mit einer Spannungsquelle 34 verbunden. Die andere Seite der Spannungsquelle 34 ist über den Brenner 10 mit einer Gerätemasse verbunden.The sensor 18 is in the form of an electrode extending into the flame region 16, in particular through a wire end, and is connected to a voltage source 34 via a voltage divider 32. The other side of the voltage source 34 is connected to a device ground via the burner 10.

Steht über dem Brenner 10 keine Flamme, so ist der Kreis Elektrode 18, Spannungsteiler 32, Spannungsquelle 34 und Brenner 10 offen und es fließt kein Strom. Bei vorhandener Flamme wird die Strecke zwischen Brenner 10 und Elektrode 18 ionisiert, ein Strom fließt und über den Teilwiderständen des Spannungsteilers 32 fallen Teilspannungen ab. Die Leitung 20 ist zwischen den Teilwiderständen am Spannungsteiler 32 angeschlossen, wodurch eine Teilspannung als Signal verwendet wird. Die Information ergibt sich daraus, daß bei einer Flamme eine Spannung am Teilwiderstand abfällt, während ohne Flamme keine Spannung vorhanden ist.If there is no flame above the burner 10, the circuit electrode 18, voltage divider 32, voltage source 34 and burner 10 is open and no current flows. If there is a flame, the path between the burner 10 and the electrode 18 is ionized, a current flows and partial voltages drop across the partial resistors of the voltage divider 32. The line 20 is connected between the partial resistors on the voltage divider 32, whereby a partial voltage is used as a signal. The information results from the fact that a voltage drops across the partial resistance in the case of a flame, while there is no voltage without a flame.

Um einen Materialtransport innerhalb der Flamme zu vermeiden, wird die Spannungsquelle 34 als Wechselspannungsquelle ausgelegt. Die Flamme besitzt eine gleichrichtende Wirkung, so daß über den Widerständen 32 eine gleichförmige Spannung abfällt. Eine Diode 38 in der Form einer Zenerdiode begrenzt die maximale Eingangsspannung am Komparator 28 und ein Kondensator 40 glättet diese Spannung zusätzlich.In order to avoid material being transported within the flame, the voltage source 34 is designed as an AC voltage source. The flame has a rectifying effect, so that a uniform voltage drops across the resistors 32. A diode 38 in the form of a Zener diode limits the maximum input voltage at the comparator 28 and a capacitor 40 also smoothes this voltage.

Von der Leitung 20 zweigt zwischen der Potentialtrennung 24 und der signalverarbeitenden Anordnung 22 eine Leitung 42 ab, die zu einer Sicherheitsschaltung 44 führt, die direkt (Figur 1) oder indirekt (Figur 2) auf die Magnetventile 14 wirkt.A line 42 branches off from the line 20 between the potential separation 24 and the signal processing arrangement 22 and leads to a safety circuit 44 which acts directly (FIG. 1) or indirectly (FIG. 2) on the solenoid valves 14.

In Figur 2 enthält die Sicherheitsschaltung 44 einen Frequenz-/Spannungsumsetzer 46 dessen Ausgang negiert auf den Eingang eines UND-Glieds 48 geführt ist. Der zweite Eingang des UND-Glieds 48 ist mit den Magnetventilen 14 verbunden. Der Ausgang des UND-Glieds 48 führt zu einem Bimetallschalter 50, der sich in der nicht dargestellten Stromzufuhr zu den Magnetventilen 14 befindet. Durch diese Anordnung ist eine einfache redundante Sicherheitsschaltung geschaffen, die bei auftretenden Fehlern die Magnetventile 14 selbständig und zuverlässig schließt.In FIG. 2, the safety circuit 44 contains a frequency / voltage converter 46, the negated output of which is led to the input of an AND gate 48. The second input of the AND gate 48 is connected to the solenoid valves 14. The output of the AND gate 48 leads to a bimetallic switch 50, which is in the power supply to the solenoid valves 14, not shown. This arrangement creates a simple redundant safety circuit which closes the solenoid valves 14 independently and reliably in the event of errors.

Die vorbeschriebene Schaltung arbeitet wie folgt: Ist der in Figur 2 abgebildete Brenner 10 in Betrieb, so fällt über den Teilwiderständen des Spannungsteilers 32 eine Spannung ab. Diese Spannung wird gleichgerichtet und geglättet, anschließend im Komparator 28 mit einer Dreieckspannung verglichen und so ein Pulsweiten moduliertes Signal einheitlicher Amplitude erzeugt. Dieses wird über die Potentialtrennung 24 der signalverarbeitenden Anordnung 22 und dem Frequenz-/Spannungsumsetzer 46 der Sicherheitsschaltung 44 zugeführt. Bei fehlerfreiem Betrieb liegt die Frequenz des übertragenen Signals innerhalb bestimmter Grenzwerte. Die beispielsweise als Mikrocomputer ausgelegte signalverarbeitende Anordnung 22 steuert oder regelt den normalen Betrieb des brennstoffbeheizten Gerätes.The circuit described above works as follows: If the burner 10 shown in FIG. 2 is in operation, a voltage drops across the partial resistors of the voltage divider 32. This voltage is rectified and smoothed, then compared in comparator 28 with a triangular voltage and thus a pulse width modulated signal of uniform amplitude is generated. This is supplied to the signal processing arrangement 22 and the frequency / voltage converter 46 to the safety circuit 44 via the potential separation 24. When operating correctly, the frequency of the transmitted signal is within certain limits. For example, as Microprocessor-designed signal processing arrangement 22 controls or regulates the normal operation of the fuel-heated device.

Am Ausgang des Frequenz-/Spannungsumsetzers 46 liegt ein Signal an, das über eine Negierung dem UND-Glied 48 zugeführt ist. Die Ventile 14 sind geöffnet, wodurch ein Signal am zweiten Eingang des UND-Glieds 48 anliegt. In diesem Zustand erzeugt das UND-Glied kein Ausgangssignal, der Bimetallschalter 50 bleibt geschlossen und die Stromzufuhr zu den Magnetventilen 14 bleibt erhalten.At the output of the frequency / voltage converter 46 there is a signal which is fed to the AND gate 48 via a negation. The valves 14 are open, as a result of which a signal is present at the second input of the AND gate 48. In this state, the AND gate generates no output signal, the bimetal switch 50 remains closed and the current supply to the solenoid valves 14 is maintained.

Erlischt die Flamme, zum Beispiel durch eine normale Abschaltung oder durch einen auftretenden Fehler, so entfällt die Spannung an den Teilwiderständen des Spannungsteilers 32 und beeinflußt damit die Frequenz des zur signalverarbeitenden Anordnung 22 übertragenen Signals. Der Mikrocomputer detektiert, daß keine Flamme mehr vorhanden ist und gibt ein Signal zum Schließen der Ventile 14 aus, wenn dies nicht bereits geschehen ist.If the flame goes out, for example due to a normal shutdown or due to an error that occurs, the voltage across the partial resistors of the voltage divider 32 is omitted and thus influences the frequency of the signal transmitted to the signal processing arrangement 22. The microcomputer detects that there is no flame and outputs a signal to close the valves 14 if this has not already been done.

Da auch das Eingangssignal der Sicherheitsschaltung 44 beeinflußt ist, ändert sich ebenfalls das Ausgangssignal des Frequenzspannungsumsetzers 46. Durch die Negation des Eingangs des UND-Glieds 48 führt dies zu einem Ausgangssignal des UND-Glieds 48 wodurch der Bimetallschalter 50 geöffnet und die Stromzufuhr zu den Magnetventilen unterbrochen wird, wenn die Magnetventile 22 nicht bereits durch die Steuereinheit 22 abgeschaltet werden. Auf diese Weise wird - unabhängig von der signalverarbeitenden Anordnung 22 - das brennstoffbeheizte Gerät im Fehlerfall durch Schließen der Magnetventile 14 abgeschaltet. Bei einer normalen Abschaltung im fehlerfreien Betrieb, führt das Öffnen der Magnetventile 14 zum Erlöschen des auf den zweiten Eingang des UND-Gliedes 48 geführten Signals, so daß die Änderung des Ausgangssignals des Frequenzspannungsumsetzers 46 nicht zum Öffnen des Bimetallschalters 50 führt.Since the input signal of the safety circuit 44 is also influenced, the output signal of the frequency voltage converter 46 also changes. By negating the input of the AND gate 48, this leads to an output signal of the AND gate 48, whereby the bimetallic switch 50 opens and the current supply to the solenoid valves is interrupted if the solenoid valves 22 are not already switched off by the control unit 22. In this way, regardless of the signal processing arrangement 22, the fuel-heated device is switched off in the event of a fault by closing the solenoid valves 14. During a normal shutdown in error-free operation, the opening of the solenoid valves 14 leads to the extinction of the signal led to the second input of the AND gate 48, so that the change in the output signal of the frequency voltage converter 46 does not lead to the opening of the bimetal switch 50.

In entsprechender Weise arbeitet die Sicherheitsschaltung 44 auch dann, wenn statt des pulsweitenmodulierten ein frequenzmoduliertes oder eine Mischform aus pulsweiten- und frequenzmoduliertem Signal Verwendung findet. Wichtig ist hierfür nur, daß der Frequenz-/Spannungsumsetzer 46 das Ausgangssignals des Spannungs-/Frequenzumsetzers 26 auf vorgegebene Grenzwerte überprüft und bei Über- oder Unterschreiten dieser Grenzwerte durch eine Signaländerung an seinem Ausgang erkennbar macht.The safety circuit 44 also operates in a corresponding manner if, instead of the pulse-width modulated, a frequency-modulated or a mixed form of pulse-width and frequency-modulated signal is used. It is only important for this that the frequency / voltage converter 46 checks the output signal of the voltage / frequency converter 26 for predetermined limit values and, when these limits are exceeded or undershot, can be identified by a signal change at its output.

Es ist auch denkbar, daß die in Figur 1 aufgezeigten Baugruppen 36, 26, 24, 22, 44 ganz oder teilweise als Programmabläufe in einem Mikrocomputer realisiert sind.It is also conceivable that the assemblies 36, 26, 24, 22, 44 shown in FIG. 1 are implemented in whole or in part as program sequences in a microcomputer.

Das erfindungsgemäße Verfahren zum Überwachen einer Flamme sieht vor, daß ein beliebiger Sensor 18, zum Beispiel ein optischer Sensor oder eine Elektrode, ein Signal an eine signalverarbeitende Anordnung 22 abgibt. Dieses Signal, das gleichförmig oder wechselförmig sein kann, wird in ein oszillierendes Signal mit bestimmten Kennwerten überführt, derart, daß die Kennwerte die Information, ob eine Flamme vorhanden ist oder nicht, enthalten. Die Kennwerte sind beispielsweise ein Pulsweitenverhältnis, eine Frequenz oder eine Phaselage oder auch Kombinationen hiervon. Über- oder unterschreiten diese Kennwerte bestimmte Grenzen, so kann dadurch erkannt werden, ob die Flamme vorhanden ist oder nicht oder ob ein Fehler vorliegt.The method according to the invention for monitoring a flame provides that any sensor 18, for example an optical sensor or an electrode, emits a signal to a signal processing arrangement 22. This signal, which can be uniform or alternating, is converted into an oscillating signal with certain characteristic values, such that the characteristic values contain the information as to whether a flame is present or not. The characteristic values are, for example, a pulse width ratio, a frequency or a phase position or combinations thereof. If these characteristic values exceed or fall below certain limits, it can thereby be recognized whether the flame is present or not or whether there is an error.

Weiterhin kann der signalverarbeitenden Anordnung 22 eine Sicherheitsschaltung 44 parallelgeschaltet werden, deren Aufgabe lediglich darin besteht, zu überprüfen, ob die Kennwerte innerhalb vorgebbarer Grenzwerte liegen und in Abhängigkeit davon ein Ausgangssignal zu generieren.Furthermore, the signal processing arrangement 22 can be connected in parallel with a safety circuit 44, the task of which is merely to check whether the characteristic values lie within predefinable limit values and to generate an output signal as a function thereof.

Auf diese Weise kann eine Flamme einfach, fehlersicher und redundant überwacht werden. Auftretende Fehler, wie ein Bauteilausfall oder Einstreuungen in den Sensorkreis müssen nicht durch die signalverarbeitende Anordnung 22 erkennbar sein, sondern führen durch die Grenzwertüberwachung der Sicherheitsschaltung direkt zum Abschalten des brennstoffbeheizten Gerätes.In this way, a flame can be monitored easily, fail-safe and redundantly. Errors that occur, such as a component failure or interference in the sensor circuit, need not be recognizable by the signal processing arrangement 22, but instead lead directly to the fuel-heated device being switched off by the limit value monitoring of the safety circuit.

Claims (10)

  1. Device for monitoring a flame of a fuel-heated apparatus, having at least one sensor for detecting the flame, which transmits a signal to a signal-processing arrangement, the signal transmitted by the sensor (18) being fed to a voltage/frequency converter (26), characterized in that the dynamic output signal thereof is relayed to the signal-processing arrangement (22) via means (24), provided at least between the voltage/frequency converter (26) and the signal-processing arrangement (22), for electrical isolation.
  2. Device according to Claim 1, characterized in that the voltage/frequency converter (26) is realized as a pulse-width modulator (28, 30) whose output signal contains the information on the flame as pulse duty factor.
  3. Device according to Claim 1, characterized in that the voltage/frequency converter (26) is realized as a frequency modulator whose output signal contains the information on the flame as frequency or as phase.
  4. Device according to Claim 1, characterized in that the voltage/frequency converter (26) is realized in the form of a combination of pulse-width and frequency modulator whose output signal contains the information on the flame in the characteristic values of pulse duty factor and frequency or phase.
  5. Device according to one of the preceding claims, characterized in that the sensor (18) is constructed as an electrode which extends into a flame region (16) and is connected to a voltage source (34) and through which a current flows when a flame is present.
  6. Device according to one of the preceding claims, characterized in that the signal-processing arrangement (22) contains an evaluator which transmits control signals at least to a valve (14) acting on a fuel feed line (12) of the fuel-heated apparatus.
  7. Device according to one of the preceding claims, characterized in that a safety circuit (44) is provided which contains a frequency/voltage converter (46) to which an output signal of the voltage/frequency converter (26) is fed, and which transmits control signals at least to a valve acting on a fuel feed line (12) of the fuel-heated apparatus.
  8. Device according to Claim 1, characterized in that an optocoupler is provided as means (24) for electrical isolation.
  9. Method for monitoring a flame of a fuel-heated apparatus, having a sensor for detecting the flame which transmits a signal to a signal-processing arrangement, the signal transmitted by the sensor (18) being transformed into an oscillating signal having prescribable characteristic values, characterized in that the characteristic values contain the information of the sensor (18), and in that the dynamic output signal is relayed to the signal-processing arrangement (22) via means (24) for electrical isolation.
  10. Method according to Claim 9, characterized in that the oscillating signal is fed to a safety circuit (44) which, independently of the signal-processing arrangement (22), transmits a signal at least to a valve (14) acting on a fuel feed line (12) of the fuel-heated apparatus when the characteristic values overshoot or undershoot specific limiting values.
EP92109976A 1991-07-09 1992-06-13 Device and method for monitoring a flame Expired - Lifetime EP0525345B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4122636A DE4122636C2 (en) 1991-07-09 1991-07-09 Device and method for monitoring a flame
DE4122636 1991-07-09

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EP0525345A1 EP0525345A1 (en) 1993-02-03
EP0525345B1 true EP0525345B1 (en) 1996-09-04
EP0525345B2 EP0525345B2 (en) 2003-10-01

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DE19632983C2 (en) * 1996-08-16 1999-11-04 Stiebel Eltron Gmbh & Co Kg Control device for a gas burner
DE19712373A1 (en) 1997-03-25 1998-10-01 Bosch Gmbh Robert Device for monitoring a burner
US6084518A (en) * 1999-06-21 2000-07-04 Johnson Controls Technology Company Balanced charge flame characterization system and method
DE10023273A1 (en) * 2000-05-12 2001-11-15 Siemens Building Tech Ag Measuring device for a flame
DE10027846A1 (en) * 2000-05-25 2001-11-29 Siemens Building Tech Ag Signal generator
DE10125574A1 (en) * 2001-05-25 2002-11-28 Siemens Building Tech Ag Flame monitoring device with which an asymmetrical voltage is applied across burner and ionization electrode to detect presence of flame
DE10302232B3 (en) * 2003-01-20 2004-08-05 Dräger Safety AG & Co. KGaA Line section for self-regulating fire extinguishing training installation using thermo-bimetallic element for reversible opening and closing of fuel exit opening in line wall
DE10313120B3 (en) * 2003-03-24 2004-08-19 Dräger Safety AG & Co. KGaA Self-regulating fire extinguishing training unit for fire extinguishing training installation using switches with thermobimetallic elements for controlling fuel feed along fuel line
DE102008021164B4 (en) * 2008-04-28 2011-08-25 Mertik Maxitrol GmbH & Co. KG, 06502 Method and gas control fitting for monitoring the ignition of a gas appliance, in particular a gas-fired stove
ITTO20090019A1 (en) * 2009-01-14 2010-07-15 Bitron Spa CIRCUIT DEVICE FOR DETECTING THE FLAME IN A GAS BURNER
DE102009022056A1 (en) 2009-05-22 2010-11-25 Siemens Building Technologies Hvac Products Gmbh Method for detecting and monitoring electrical alternating voltage in furnace of heating system, involves determining level of voltage based on cycle of pulse-width modulated signal, and comparing level with limit value
DE102013221511A1 (en) * 2013-10-23 2015-04-23 Robert Bosch Gmbh Device for determining an ionization current of a flame

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NL8401173A (en) * 1984-04-12 1985-11-01 Philips Nv FLAME PROTECTION CIRCUIT.
GB8906235D0 (en) * 1989-03-17 1989-05-04 Cambridge Instr Ltd Flame detection apparatus and method

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EP0525345B2 (en) 2003-10-01
EP0525345A1 (en) 1993-02-03
DE59207035D1 (en) 1996-10-10
DE4122636C2 (en) 1999-08-12
DE4122636A1 (en) 1993-01-14

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