EP3690318B1 - Method for regulating a fuel-air mixture in a heating device - Google Patents

Method for regulating a fuel-air mixture in a heating device Download PDF

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Publication number
EP3690318B1
EP3690318B1 EP20150310.9A EP20150310A EP3690318B1 EP 3690318 B1 EP3690318 B1 EP 3690318B1 EP 20150310 A EP20150310 A EP 20150310A EP 3690318 B1 EP3690318 B1 EP 3690318B1
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EP
European Patent Office
Prior art keywords
ionisation
fuel gas
combustion
speed
signal
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Application number
EP20150310.9A
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German (de)
French (fr)
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EP3690318A3 (en
EP3690318A2 (en
Inventor
Heinz-Jörg Tomczak
Christian Schwarz
Stefan Hucke
Jochen Grabe
Tobias Funke
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Vaillant GmbH
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Vaillant GmbH
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Priority claimed from DE102019119186.6A external-priority patent/DE102019119186A1/en
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Publication of EP3690318A3 publication Critical patent/EP3690318A3/en
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Classifications

    • 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
    • F23D—BURNERS
    • F23D14/00—Burners for combustion of a gas, e.g. of a gas stored under pressure as a liquid
    • F23D14/02—Premix gas burners, i.e. in which gaseous fuel is mixed with combustion air upstream of the combustion zone
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N1/00—Regulating fuel supply
    • F23N1/02—Regulating fuel supply conjointly with air supply
    • F23N1/022—Regulating fuel supply conjointly with air supply using electronic means
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q3/00—Igniters using electrically-produced sparks
    • F23Q3/008—Structurally associated with fluid-fuel burners
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2227/00—Ignition or checking
    • F23N2227/20—Calibrating devices
    • 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
    • F23N2231/00—Fail safe
    • F23N2231/10—Fail safe for component failures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2231/00—Fail safe
    • F23N2231/12—Fail safe for ignition failures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2233/00—Ventilators
    • F23N2233/06—Ventilators at the air intake
    • F23N2233/08—Ventilators at the air intake with variable speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2237/00—Controlling
    • F23N2237/24—Controlling height of burner
    • F23N2237/26—Controlling height of burner oxygen-air ratio

Definitions

  • the invention is in the field of regulating a fuel gas-air mixture for a combustion process in a heating device, in particular for preparing hot water or heating a building.
  • a heating device in particular for preparing hot water or heating a building.
  • an ionization measurement is carried out in a flame area, especially in many heating devices. Such measurements should enable stable regulation over long periods of time. If the control fails, in most cases the heater has to be switched off, which of course should happen as rarely as possible.
  • flame monitoring is typically also carried out in heating devices, the main task of which is to ensure that no fuel gas is supplied after the heating device has been started if there is no flame. This prevents the formation of a potentially explosive mixture and the escape of unburned fuel gas. This can be accomplished in a number of different ways. There are optical, thermal and electronic systems. An electronic flame monitor that is often used uses an ignition electrode that is already present, which is otherwise not otherwise required after a flame has been ignited, to generate an ionization signal which, in the prior art, is not used for regulating but for monitoring the flame.
  • the specially prepared ionization signal can not only reliably detect the presence of a flame or its extinction, but also, for example, the physical lifting of the flame from the burner due to excessively high temperatures Measure the combustion air supply in good time. This means that it can be switched off at an early stage if the flame becomes unstable.
  • the regulation has so far often been carried out during operation by means of a separate ionization electrode.
  • the respective actual value of the ionization in the flame area is determined, which is proportional to the currently present lambda value, so that this can be derived from the ionization measurement.
  • An alternating voltage is applied to the ionization electrode, the flame area ionized in the presence of flames having a rectifying effect, so that an ionization current mainly only flows during one half-cycle of the alternating current.
  • This current or a proportional voltage signal derived therefrom, referred to below as an ionization signal, are measured and, if necessary, after digitization, further processed as an ionization signal in an analog / digital converter.
  • the lambda value can be measured and regulated to a target value by means of a control circuit.
  • the supply of air and / or fuel gas is changed by suitable actuators until the desired target value for lambda is reached.
  • a lambda value> 1 (1 corresponds to a stoichiometric ratio) is aimed for, e.g. B.
  • Lambda 1.3 to ensure that enough air is supplied for clean combustion with essentially no carbon monoxide generation.
  • lambda must remain so small that stable combustion is guaranteed.
  • the regulation can in particular take place via a valve for the supply of fuel gas and / or a fan for the supply of ambient air.
  • combustion controls which regulate the desired combustion quality (lambda value) via stored ionization current control curves.
  • the electrodes used are subject to a time-dependent drift, which essentially results from a growing oxide layer on the electrode surface, which has a negative influence on the measured signal.
  • calibration sequences are triggered cyclically (e.g. after a specifiable number of operating hours).
  • the basic structure of such heating devices, of measuring systems for ionization measurement and their use for regulation are, for example, also from the EP 0 770 824 B1 and the EP 2 466 204 B1 known.
  • the control accuracy can change in the course of time due to various influences, in particular due to influences on the state or the shape of the ionization electrode.
  • Various methods for recalibrating if necessary are specified, but all of them require a relatively high level of effort and / or, above all, can have the disadvantage that during recalibration the heater has to be operated at lambda values of 1 or even below at times, which leads to temporary generation of undesirable carbon monoxide.
  • the present invention aims to provide a remedy here in order to enable safe and reliable operation of a heater, stable control or, if necessary, emergency control in the event of malfunctions in a primary control system.
  • a heating device can be reliably regulated with these method steps, the time span t being able to be very long compared to the duration of the other method steps, for example several hours or even longer.
  • the control remains in the desired control range for the lambda value, and even when all process steps are repeated, there are no excessively high flame temperatures.
  • a method is preferred in which, if the fan speed stored in step 1.6 deviates from the value set in step 1.1 greater than a predeterminable deviation value, the setting of the fuel gas valve is corrected accordingly and steps 1.3 to 1.7 are repeated until the deviation is smaller than the deviation value, which corresponds to the achievement of a desired output of the heater.
  • the fan speed is the most accurate value to be measured in a heater, which is why it is preferred to set a desired output.
  • a method is particularly preferred in which the predeterminable amount in step 1.4 is selected so small that a distance between the lambda value and a range in which an impermissible amount or concentration of carbon monoxide can be generated is maintained. This embodiment ensures that when the method is carried out, regardless of the duration of the period t, only very little carbon monoxide is generated, even if the calibration of the system is checked again and again.
  • the method is carried out in the same way for fan speeds corresponding to different powers and associated settings of the fuel gas valve, which results in a calibration of the control that is updated again and again at time intervals of the length of the time span (t) all changes in the system are taken into account.
  • a calibration curve which is corrected again and again, is created for different outputs of the heater, so that the regulation described can be used in particular as a primary regulation.
  • a particularly preferred embodiment of the method is its use as a so-called emergency control.
  • a method according to one of claims 1 to 1 is used in the event of failure of the first ionization measurement or the control based on it 4, in particular using existing monitoring electronics. This option increases the availability of heating devices significantly, since in the event of a malfunction in the primary control system, the system cannot be switched off, but only switched over to the emergency system.
  • a heater which is particularly suitable for switching from a primary control to an emergency system, has the following components: an air supply and a fuel gas supply, which are controlled by a first control unit, and with a first measuring system, comprising an ionization electrode, a counter electrode, a first alternating current source and a first electronic evaluation system for determining a first ionization signal, which can be fed to the control unit, a second measuring system being present for measuring a second ionization signal, which can be generated between an ignition electrode for igniting a combustion and the counter electrode of the second measuring system, and where the first and the second system are each set up to determine a lambda value.
  • this also enables switching at Malfunctions of a primary control on an emergency system that can take over the control.
  • the heater preferably has a switchover unit which, if at least one component of the first measurement system fails, switches over to control with the second measurement system.
  • the ionization measurement according to the invention which can be used in this way for flame monitoring and control, works according to the following principle:
  • An alternating voltage without a direct voltage component from a voltage source with a high output impedance is applied between an ionization electrode and a counter electrode (ground). Due to a rectifying effect of a flame plasma when the flame is burning, an ionization current flows off to ground during each positive half-wave of the alternating voltage. The voltage amplitude of each positive half-wave is reduced because of the high output impedance of the voltage source, while the negative half-wave remains unchanged. As a result, a negative direct voltage component is impressed on the alternating voltage. The amplitude of this negative DC voltage component is converted as a mean value by means of an amplifier circuit into a voltage signal which, due to its characteristic curve, can be used for the purposes described here with a constant gas supply and increasing air supply. Typically, this signal is digitized by means of an analog / digital converter (eg into values between 0 and 1023) so that it can be further processed in a microprocessor.
  • an analog / digital converter eg into values between 0 and 1023
  • the characteristic curve of the signal results from a combination of different effects.
  • the ionization in the flame area is strongest when the combustion is operated in a stoichiometric ratio of combustion gas and combustion air
  • the flames move away (physical lift-off of the flames) with increasing gas mixture speed (larger combustion air volume per unit of time) from the outlet openings in the burner, which electronically form the mass in the system, which reduces the ion flow.
  • the temperature of the ionization electrode or the flame may also play a role in the rectifying effect.
  • the result is a curve with an easily reproducible minimum, which is close to a lambda value that is typical for continuous operation.
  • the invention also relates to a computer program product, comprising instructions which cause the described device to carry out the method proposed here.
  • Modern heating devices typically contain an electronic control which contains at least one programmable microprocessor which can be controlled by such a computer program product.
  • existing devices with ionization measurement and flame monitoring can be retrofitted for the method according to the invention using such a computer program product.
  • the invention also relates to an emergency running system for gas-operated heating devices, in particular in the case of combustion control based on ionization current.
  • ionization current is usually measured with an ionization current electrode to which a voltage is applied.
  • ionization current electrode to which a voltage is applied.
  • These electrodes are subject to a time-dependent drift, which essentially results from a growing oxide layer on the electrode surface, which has a negative influence on the measured signal.
  • calibration sequences are initiated cyclically (e.g. after x burner operating hours).
  • DE 195 39 568 C1 includes a calibration at the operating point with maximum ionization current (SCOT) or in the vicinity of this point (Sitherm).
  • the mixture that emerges from the burner is via an ignition voltage that is applied to the ignition electrode and forms sparks there ignited.
  • the respective minimum value of the signal is stored and the air volume flow through the fan is increased until a threshold value of the increase in the ionization current relative to the minimum value (point 3) is reached (point 2). Finally, the minimum value (point 3) is approached, which at the same time represents the operating point of the device. At this point, the device runs by regulating the fan until a period of time t has expired. After the time period t has elapsed, the system starts again from point 1.
  • the procedure for controlling combustion in a gas-powered heater is characterized by the following steps - the fan runs to a specified speed - the gas valve follows the fan speed via a specially designed characteristic ( Gas valve stepper position via fan speed) - the position of the gas valve stepper motor is now "frozen” and the fan speed is reduced in a defined manner, - the fan speed is now continuously increased, with the measured ionization signal following the characteristic curve - the respective minimum value of the signal is saved and the air volume flow is increased the fan is increased until a threshold value of the increase in the ionization current relative to the minimum value is reached, - lastly the minimum value is approached, which also represents the operating point of the device, - at this point the device runs through a control of the fan until a period of time t aba is called, - after the period t has elapsed, the system moves again starting from point 1.
  • FIG. 1 shows schematically an embodiment of a device proposed here.
  • a flame area 2 is formed during operation. Air enters the heater 1 via an air supply 3 and a fan 5. Combustion gas is mixed with the air via a combustion gas supply 4 and a combustion gas valve 6. An ignition electrode 7 ignites the mixture at the start of the combustion process and is then z. B. used as part of a flame monitor. A first ionization signal is measured in the flame region 2 by means of an ionization electrode 8.
  • a first measuring system S1 is used for this, from which the ionization electrode 8 is subjected to an alternating voltage from a first alternating voltage source, a first evaluation electronics 13 measuring the resulting ionization signal and converting it into a lambda value, i.e. a lambda value, according to calibration data (control curve) stored in a calibration data memory 15 Mixing ratio of air to fuel converted.
  • a control unit 17 can control the fan 5 and / or the fuel gas valve 6 in such a way that a sets the desired target value for lambda.
  • a flame monitor 16 can also be present.
  • a second measuring system S2 is put into operation by means of a switching unit 10, which connects a second AC voltage source 12 instead of ignition electronics to the ignition electrode 7 (if this has not already been done for flame monitoring), with a second Evaluation electronics 14 a second ionization signal is measured and evaluated, which also supplies an actual value for lambda and enables the lambda value to be regulated by means of the method according to the invention.
  • this type of control can also be used as a primary control, specifically in parallel to flame monitoring by means of an ignition electrode as the only ionization electrode or by means of a dedicated ionization electrode only for control.
  • only the second measuring system S2 needs to be present and can be used as the primary control system by means of its own calibration data.
  • the heater initially works in normal operation with a certain supply of fuel gas and an associated speed of the fan 5, with the ionization signal I1 being adjusted to a value of z. B. 100 ⁇ A [microAmpere] is controlled by adjusting the speed of the fan and / or the fuel supply. With valid calibration data (map, control curve), this type of control ensures that a desired lambda value is maintained over a large load range.
  • a switch to an emergency system can be triggered instead of a shutdown. In this case, a switch is made from the first measuring system S1 to the second measuring system S2.
  • a defined speed is set by the fan 5 approached and the associated fuel quantity is set using the stored characteristic curves.
  • the measuring system S2 determines a second ionization signal I2 determined by means of the ignition electrode 7. Then the gas supply is left unchanged, while the fan speed is reduced in a defined manner until a value below the desired lambda value is definitely reached, which is still well above a stoichiometric ratio of air to fuel gas, so that hardly any carbon monoxide is generated during this process and the flame temperature is not excessively high (see point "1" in Fig. 3 ). Starting from this lambda value, the speed of the fan 5 is increased until the second ionization signal detects a lifting of the flame from the burner 9 due to a sharp rise (see point "2" in FIG Fig. 3 ).
  • the heater can be operated (further) with this type of control as the primary control. If it is only used as an emergency control, when the heater is restarted it can be checked whether the primary control is working again and only switched to the emergency control if this is not the case.
  • Fig. 2 shows schematically a circuit as it can be used for the measuring system S2.
  • a second AC voltage source 12 with a high output resistance 18 initially supplies an AC voltage without a DC voltage component to the ignition electrode 7 and the counter electrode 9 (ground).
  • the voltage only drops in a half-wave due to the rectifying effect of the flame (shown as a diode in the equivalent circuit diagram), so that an alternating voltage is present at the input of the second evaluation electronics 14 (amplifier and converter) with a negative DC voltage component is present, which becomes the second ionization signal in the evaluation electronics 14 and can be converted in an analog / digital converter 20 and then processed further.
  • Fig. 3 illustrates qualitatively what happens in the process of regulating according to the invention by means of the second measuring system S2.
  • the second ionization signal I2 is plotted on the Y axis (in digitized form as a number between 0 and 1023) against the fan speed [rpm] on the X axis with a constant gas supply.
  • the resulting characteristic diagram shows an almost constant initial range, a decrease to a minimum (point "3") and then an increase.
  • the flame begins to detach, which can then become unstable as the air supply increases. Between points "1" and “2", however, the air supply can be varied without producing inadmissible amounts of carbon monoxide or instabilities in order to find the minimum at point "3" and use it for regulation.
  • the X-axis could also be provided with the lambda value as a scale because of the relationship described between the fan speed and the lambda value.
  • the present invention makes it possible, without significant changes to a heater itself, to set up a reliable emergency control system using only additional electronics, or even to use a method as the primary control system which does not generate any inadmissible amounts of carbon monoxide even during (re) calibration.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Combustion (AREA)
  • Regulation And Control Of Combustion (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)

Description

Die Erfindung liegt auf dem Gebiet der Regelung eines Brenngas-Luftgemisches für einen Verbrennungsprozess in einem Heizgerät, insbesondere zur Warmwasserbereitung oder Beheizung eines Gebäudes. Zur Messung einer Qualität der Verbrennung, die hauptsächlich von dem während der Verbrennung vorliegenden Verhältnis von Luft zu Brenngas (Lambda-Wert, auch Luftzahl genannt) abhängt, wird insbesondere bei vielen Heizgeräten eine lonisationsmessung in einem Flammenbereich durchgeführt. Solche Messungen sollen eine stabile Regelung über lange Zeiträume ermöglichen. Fällt die Regelung aus, so muss in den meisten Fällen das Heizgerät abgeschaltet werden, was natürlich möglichst selten vorkommen sollte.The invention is in the field of regulating a fuel gas-air mixture for a combustion process in a heating device, in particular for preparing hot water or heating a building. To measure the quality of the combustion, which mainly depends on the ratio of air to fuel gas (lambda value, also known as the air ratio) that is present during the combustion, an ionization measurement is carried out in a flame area, especially in many heating devices. Such measurements should enable stable regulation over long periods of time. If the control fails, in most cases the heater has to be switched off, which of course should happen as rarely as possible.

Außerdem wird in Heizgeräten typischerweise auch eine Flammenüberwachung durchgeführt, deren wesentliche Aufgabe darin besteht, sicherzustellen, dass nach dem Start des Heizgerätes keine Zufuhr von Brenngas erfolgt, wenn keine Flamme vorliegt. Damit werden die Entstehung eines eventuell explosiven Gemisches und das Austreten von unverbranntem Brenngas verhindert. Dies kann auf viele verschiedene Weisen erreicht werden. Es gibt optische, thermische und elektronische Systeme. Ein oft eingesetzter elektronischer Flammenwächter nutzt eine ohnehin vorhandene Zündelektrode, die ansonsten nach der Zündung einer Flamme nicht anderweitig benötigt wird, zur Erzeugung eines lonisationssignals, welches im Stand der Technik nicht zur Regelung, sondern zur Überwachung der Flamme dient. Das speziell aufbereitete lonisationssignal kann nicht nur das Vorhandensein einer Flamme bzw. deren Erlöschen sicher detektieren, sondern beispielsweise auch das physische Abheben der Flamme vom Brenner durch zu hohe Verbrennungsluftzufuhr frühzeitig messen. So kann bei Instabilitäten der Flamme frühzeitig eine Abschaltung erfolgen.In addition, flame monitoring is typically also carried out in heating devices, the main task of which is to ensure that no fuel gas is supplied after the heating device has been started if there is no flame. This prevents the formation of a potentially explosive mixture and the escape of unburned fuel gas. This can be accomplished in a number of different ways. There are optical, thermal and electronic systems. An electronic flame monitor that is often used uses an ignition electrode that is already present, which is otherwise not otherwise required after a flame has been ignited, to generate an ionization signal which, in the prior art, is not used for regulating but for monitoring the flame. The specially prepared ionization signal can not only reliably detect the presence of a flame or its extinction, but also, for example, the physical lifting of the flame from the burner due to excessively high temperatures Measure the combustion air supply in good time. This means that it can be switched off at an early stage if the flame becomes unstable.

Nach dem Stand der Technik wird bisher im Betrieb die Regelung oft mittels einer gesonderten lonisationselektrode durchgeführt. Unabhängig von der Art der Elektrode wird der jeweilige Ist-Wert der Ionisation im Flammenbereich ermittelt, der proportional dem gerade vorliegenden Lambda-Wert ist, so dass dieser aus der lonisationsmessung abgeleitet werden kann. Dabei wird an die lonisationselektrode eine Wechselspannung angelegt, wobei der bei Vorhandensein von Flammen ionisierte Flammenbereich eine gleichrichtende Wirkung hat, so dass ein lonisationsstrom hauptsächlich jeweils nur während einer Halbwelle des Wechselstromes fließt. Dieser Strom oder ein daraus abgeleitetes proportionales Spannungssignal, im Folgenden lonisationssignal genannt, werden gemessen und gegebenenfalls nach einer Digitalisierung in einem Analog/Digital-Wandler als lonisationssignal weiterverarbeitet. So kann der Lambda-Wert gemessen und mittels eines Regelkreises auf einen Sollwert geregelt werden. Dabei wird die Zufuhr von Luft und/oder Brenngas durch geeignete Stellglieder verändert, bis der gewünschte Sollwert für Lambda erreicht ist. Im Allgemeinen wird ein Lambda-Wert > 1 (1 entspricht einem stöchiometrischen Verhältnis) angestrebt, z. B. Lambda = 1,3, um sicherzustellen, dass genug Luft für eine saubere Verbrennung im Wesentlichen ohne Erzeugung von Kohlenmonoxid zugeführt wird. Dabei muss Lambda aber so klein bleiben, dass eine stabile Verbrennung gewährleistet ist. Die Regelung kann insbesondere über ein Ventil für die Zufuhr von Brenngas und/oder ein Gebläse für die Zufuhr von Umgebungsluft erfolgen.According to the prior art, the regulation has so far often been carried out during operation by means of a separate ionization electrode. Regardless of the type of electrode, the respective actual value of the ionization in the flame area is determined, which is proportional to the currently present lambda value, so that this can be derived from the ionization measurement. An alternating voltage is applied to the ionization electrode, the flame area ionized in the presence of flames having a rectifying effect, so that an ionization current mainly only flows during one half-cycle of the alternating current. This current or a proportional voltage signal derived therefrom, referred to below as an ionization signal, are measured and, if necessary, after digitization, further processed as an ionization signal in an analog / digital converter. In this way, the lambda value can be measured and regulated to a target value by means of a control circuit. The supply of air and / or fuel gas is changed by suitable actuators until the desired target value for lambda is reached. In general, a lambda value> 1 (1 corresponds to a stoichiometric ratio) is aimed for, e.g. B. Lambda = 1.3 to ensure that enough air is supplied for clean combustion with essentially no carbon monoxide generation. However, lambda must remain so small that stable combustion is guaranteed. The regulation can in particular take place via a valve for the supply of fuel gas and / or a fan for the supply of ambient air.

Aus der DE 196 18 573 C1 und der DE 195 02 901 C1 sind beispielsweise solche Verbrennungsregelungen bekannt, die über hinterlegte lonisationsstrom-Regelkurven die gewünschte Verbrennungsqualität (Lambda-Wert) einregeln. Die verwendeten Elektroden unterliegen einer zeitabhängigen Drift, die im Wesentlichen aus einer anwachsenden Oxidschicht auf der Elektrodenoberfläche resultiert, die einen negativen Einfluss auf das gemessene Signal hat. Um den störenden Einfluss dieser Drift zu kompensieren, werden zyklisch Kalibriersequenzen angestoßen (z. B. nach einer vorgebbaren Anzahl von Betriebsstunden).From the DE 196 18 573 C1 and the DE 195 02 901 C1 For example, such combustion controls are known which regulate the desired combustion quality (lambda value) via stored ionization current control curves. The electrodes used are subject to a time-dependent drift, which essentially results from a growing oxide layer on the electrode surface, which has a negative influence on the measured signal. In order to compensate for the disruptive influence of this drift, calibration sequences are triggered cyclically (e.g. after a specifiable number of operating hours).

Aus der DE 195 39 568 C1 ist beispielsweise das Vorgehen bei einer Kalibrierung bekannt, wobei zeitweise eine Verbrennung im Bereich von Lambda = 1 durchgeführt wird, was aber mit der Erzeugung einer gewissen Menge an Kohlenmonoxid verbunden sein kann. Auch entstehen bei Lambda-Werten im Bereich von 1 sehr hohe Flammtemperaturen, die wiederum die lonisationselektrode schädigen, so dass ein Kalibriervorgang die Lebensdauer der lonisationselektrode verringern kann.From the DE 195 39 568 C1 For example, the procedure for a calibration is known, with combustion in the range of lambda = 1 being carried out at times, but this can be associated with the generation of a certain amount of carbon monoxide. Lambda values in the range of 1 also result in very high flame temperatures, which in turn damage the ionization electrode, so that a calibration process can reduce the service life of the ionization electrode.

Der grundsätzliche Aufbau solcher Heizgeräte, von Messystemen zur lonisationsmessung und zu deren Benutzung zur Regelung sind beispielsweise auch aus der EP 0 770 824 B1 und der EP 2 466 204 B1 bekannt. Dort ist auch beschrieben, dass sich die Regelgenauigkeit im Laufe der Zeit durch verschiedene Einflüsse verändern kann, insbesondere durch Einflüsse auf den Zustand oder die Form der lonisationselektrode. Verschiedene Verfahren zu einer Nachkalibrierung bei Bedarf sind angegeben, die aber alle einen relativ hohen Aufwand erfordern und/oder vor allem den Nachteil haben können, dass bei der Nachkalibrierung das Heizgerät zeitweise bei Lambda-Werten von 1 oder sogar darunter betrieben werden muss, was zu einer vorübergehenden Erzeugung von unerwünschtem Kohlenmonoxid führen kann.The basic structure of such heating devices, of measuring systems for ionization measurement and their use for regulation are, for example, also from the EP 0 770 824 B1 and the EP 2 466 204 B1 known. There it is also described that the control accuracy can change in the course of time due to various influences, in particular due to influences on the state or the shape of the ionization electrode. Various methods for recalibrating if necessary are specified, but all of them require a relatively high level of effort and / or, above all, can have the disadvantage that during recalibration the heater has to be operated at lambda values of 1 or even below at times, which leads to temporary generation of undesirable carbon monoxide.

Aus der EP 2 014 985 B1 ist auch schon eine Regelung bekannt, die betrieben und kalibriert werden kann, ohne die Verbrennung in einen Bereich nahe Lambda = 1 zu verlegen, so dass auch bei einer Kalibrierung wenig Kohlenmonoxid entsteht. Allerdings ist es damit nicht immer möglich, einen optimalen Lambda-Wert einzuhalten.From the EP 2 014 985 B1 a regulation is already known that can be operated and calibrated without the combustion going into a range close to lambda = 1 relocated so that little carbon monoxide is produced even during calibration. However, it is not always possible to maintain an optimal lambda value.

Hier will die vorliegende Erfindung Abhilfe schaffen, um einen sicheren und zuverlässigen Betrieb eines Heizgerätes, eine stabile Regelung oder bei Bedarf eine Notlaufregelung bei Störungen in einem primären Regelsystem zu ermöglichen.The present invention aims to provide a remedy here in order to enable safe and reliable operation of a heater, stable control or, if necessary, emergency control in the event of malfunctions in a primary control system.

Zur Lösung dieser Aufgabe dienen ein Verfahren sowie ein Computerprogrammprodukt gemäß den unabhängigen Ansprüchen. Vorteilhafte Ausgestaltungen und Weiterbildungen der Erfindung sind in den jeweiligen abhängigen Ansprüchen angegeben. Die Beschreibung, insbesondere im Zusammenhang mit den Figuren, veranschaulicht die Erfindung und gibt weitere Ausführungsbeispiele an.A method and a computer program product according to the independent claims serve to solve this problem. Advantageous refinements and developments of the invention are specified in the respective dependent claims. The description, in particular in connection with the figures, illustrates the invention and specifies further exemplary embodiments.

Das erfindungsgemäße Verfahren zur Regelung einer Verbrennung in einem Heizgerät mittels eines in einem Flammenbereich des mit Verbrennungsluft und Brenngas betriebenen Heizgerätes gemessenen lonisationssignals, welches aus einem von einer lonisationselektrode zu einer Gegenelektrode durch den Flammenbereich fließenden lonenstrom abgeleitet wird, wobei das Verhältnis (Lambda-Wert) von Verbrennungsluft zu Brenngas bei der Verbrennung in dem Heizgerät anhand von Kalibrierdaten aus dem lonisationssignal bestimmt und mittels Einstellung der Zufuhr an Brenngas und/oder der Zufuhr an Verbrennungsluft geregelt wird, weist zumindest folgende Schritte auf:

  • 1.1 ein Gebläse zur Zufuhr von Verbrennungsluft wird auf eine vorgebbare Drehzahl gebracht,
  • 1.2 ein Brenngasventil wird mittels einer vorgebbaren Kennlinie auf eine dieser Drehzahl zugeordnete Stellung gebracht,
  • 1.3 in dieser Stellung wird das Brenngasventil festgehalten,
  • 1.4 die Drehzahl wird um einen vorgebbaren Betrag reduziert,
  • 1.5 anschließend wird die Drehzahl kontinuierlich oder schrittweise erhöht und das jeweilige lonisationssignal gemessen,
  • 1.6 dabei wird ein Minimum des lonisationssignals festgestellt und mit der zugehörigen Gebläsedrehzahl gespeichert,
  • 1.7 die Gebläsedrehzahl wird weiter erhöht, bis ein vorgebbarer Schwellwert des lonisationssignals relativ zum Minimum erreicht wird,
  • 1.8 danach wird die Gebläsedrehzahl auf die zu dem Minimum gehörige Gebläsedrehzahl reduziert und dort für eine vorgebbare Zeitspanne t gehalten oder zur Regelung des lonisationssignals auf den aktuellen konstanten Wert genutzt,
  • 1.9 nach Ablauf der Zeitspanne t werden die Schritte ab 1.4 wiederholt.
The method according to the invention for regulating combustion in a heating device by means of an ionization signal measured in a flame area of the heating device operated with combustion air and fuel gas, which is derived from an ion current flowing from an ionization electrode to a counter electrode through the flame area, the ratio (lambda value) from combustion air to combustion gas during combustion in the heating device is determined on the basis of calibration data from the ionization signal and is regulated by adjusting the supply of combustion gas and / or the supply of combustion air, has at least the following steps:
  • 1.1 a fan for supplying combustion air is brought to a predefinable speed,
  • 1.2 a fuel gas valve is brought to a position assigned to this speed by means of a predeterminable characteristic curve,
  • 1.3 the fuel gas valve is held in this position,
  • 1.4 the speed is reduced by a specifiable amount,
  • 1.5 then the speed is increased continuously or step by step and the respective ionization signal is measured,
  • 1.6 a minimum of the ionization signal is determined and stored with the associated fan speed,
  • 1.7 the fan speed is increased further until a predeterminable threshold value of the ionization signal is reached relative to the minimum,
  • 1.8 then the fan speed is reduced to the fan speed associated with the minimum and held there for a predeterminable period of time t or used to control the ionization signal to the current constant value,
  • 1.9 after the time period t has elapsed, steps from 1.4 are repeated.

Mit diesen Verfahrensschritten lässt sich ein Heizgerät zuverlässig regeln, wobei die Zeitspanne t sehr lang im Vergleich zu der Dauer der anderen Verfahrensschritte sein kann, beispielsweise mehrere Stunden oder noch länger. Andererseits entsteht bei der Wiederholung der Schritte ab 1.4 vernachlässigbar wenig Kohlenmonoxid, so dass es auf die Länge der Zeitspanne in dieser Hinsicht nicht ankommt und auch sonst keine wesentlichen Nachteile gegen eine Wiederholung sprechen. Die Regelung bleibt dadurch in dem gewünschten Regelbereich für den Lambda-Wert und auch bei der Wiederholung aller Verfahrensschritte entstehen keine übermäßig hohen Flammtemperaturen.A heating device can be reliably regulated with these method steps, the time span t being able to be very long compared to the duration of the other method steps, for example several hours or even longer. On the other hand, if you repeat steps from 1.4 onwards, negligibly little carbon monoxide is produced, so that it affects the The length of the time span does not matter in this regard and there are no other significant disadvantages against a repetition. As a result, the control remains in the desired control range for the lambda value, and even when all process steps are repeated, there are no excessively high flame temperatures.

Bevorzugt wird ein Verfahren, bei dem bei einer Abweichung der in Schritt 1.6 gespeicherten Gebläsedrehzahl von der in Schritt 1.1 eingestellten größer als ein vorgebbarer Abweichungswert eine entsprechende Korrektur der Einstellung des Brenngasventils vorgenommen und die Schritte 1.3 bis 1.7 so oft wiederholt werden, bis die Abweichung kleiner als der Abweichungswert ist, was dem Erreichen einer gewünschten Leistung des Heizgerätes entspricht. Dies führt dazu, dass nicht nur ein gewünschter Lambda-Wert eingehalten, sondern auch eine bestimmte vorgebbare Leistung eingeregelt werden kann. Im Allgemeinen ist die Gebläsedrehzahl der am genauesten zu messende Wert in einem Heizgerät, weshalb diese zur Einstellung einer gewünschten Leistung bevorzugt eingesetzt wird.A method is preferred in which, if the fan speed stored in step 1.6 deviates from the value set in step 1.1 greater than a predeterminable deviation value, the setting of the fuel gas valve is corrected accordingly and steps 1.3 to 1.7 are repeated until the deviation is smaller than the deviation value, which corresponds to the achievement of a desired output of the heater. This leads to the fact that not only a desired lambda value is maintained, but also that a certain specifiable power can be regulated. In general, the fan speed is the most accurate value to be measured in a heater, which is why it is preferred to set a desired output.

Besonders bevorzugt ist ein Verfahren, bei dem der vorgebbare Betrag in Schritt 1.4 so gering gewählt wird, dass ein Abstand des Lambda-Wertes zu einem Bereich, in dem eine unzulässige Menge oder Konzentration an Kohlenmonoxid erzeugt werden kann, eingehalten wird. Diese Ausführung stellt sicher, dass bei der Durchführung des Verfahrens unabhängig von der Dauer der Zeitspanne t nur sehr wenig Kohlenmonoxid erzeugt wird, auch wenn die Kalibrierung des Systems immer wieder geprüft wird.A method is particularly preferred in which the predeterminable amount in step 1.4 is selected so small that a distance between the lambda value and a range in which an impermissible amount or concentration of carbon monoxide can be generated is maintained. This embodiment ensures that when the method is carried out, regardless of the duration of the period t, only very little carbon monoxide is generated, even if the calibration of the system is checked again and again.

In einer Ausführungsform der Erfindung wird das Verfahren für unterschiedlichen Leistungen entsprechende Gebläsedrehzahlen und zugehörigen Einstellungen des Brenngasventils in gleicher Weise durchgeführt, woraus sich eine immer wieder in Zeitabständen der Länge der Zeitspanne (t) aktualisierte Kalibrierung der Regelung ergibt, die alle Änderungen im System berücksichtigt. Auf diese Weise entsteht eine immer wieder korrigierte Kalibrierkurve für unterschiedliche Leistungen des Heizgerätes, wodurch die beschriebene Regelung insbesondere als primäre Regelung eingesetzt werden kann.In one embodiment of the invention, the method is carried out in the same way for fan speeds corresponding to different powers and associated settings of the fuel gas valve, which results in a calibration of the control that is updated again and again at time intervals of the length of the time span (t) all changes in the system are taken into account. In this way, a calibration curve, which is corrected again and again, is created for different outputs of the heater, so that the regulation described can be used in particular as a primary regulation.

Eine besonders bevorzugte Ausführungsform des Verfahrens ist aber die Verwendung als sogenannte Notlaufregelung. Für Heizgeräte, die eine Regelung mittels eines ersten Messsystems mit einer ersten lonisationsmessung und eine separate von einer Überwachungs-Elektronik durchgeführte Flammenüberwachung mittels einer zweiten lonisationsmessung aufweisen, wird bei Ausfall der ersten lonisationsmessung oder der darauf basierenden Regelung auf ein Verfahren gemäß einem der Ansprüche 1 bis 4, insbesondere unter Nutzung einer vorhandenen Überwachungs-Elektronik umgeschaltet. Diese Möglichkeit erhöht die Verfügbarkeit von Heizgeräten signifikant, da bei einer Störung der primären Regelung nicht abgeschaltet, sondern nur auf das Notlaufsystem umgeschaltet werden kann.A particularly preferred embodiment of the method, however, is its use as a so-called emergency control. For heating devices that have a control by means of a first measurement system with a first ionization measurement and a separate flame monitoring carried out by monitoring electronics by means of a second ionization measurement, a method according to one of claims 1 to 1 is used in the event of failure of the first ionization measurement or the control based on it 4, in particular using existing monitoring electronics. This option increases the availability of heating devices significantly, since in the event of a malfunction in the primary control system, the system cannot be switched off, but only switched over to the emergency system.

Ein Heizgerät, das insbesondere für die Umschaltung von einer primären Regelung auf ein Notlaufsystem geeignet ist, hat folgende Komponenten: eine Luftzufuhr und eine Brenngaszufuhr, die von einer ersten Regeleinheit geregelt werden, und mit einem ersten Messsystem, umfassend eine lonisationselektrode, eine Gegenelektrode, eine erste Wechselstromquelle und eine erste Auswertelektronik zur Ermittlung eines ersten Ionisationssignales, das der Regeleinheit zuführbar ist, wobei ein zweites Messsystem zur Messung eines zweiten lonisationssignales vorhanden ist, welches zwischen einer zur Zündung einer Verbrennung vorhandenen Zündelektrode und der Gegenelektrode vom zweiten Messsystem erzeugbar ist und wobei das erste und das zweite System jeweils zur Bestimmung eines Lambda-Wertes eingerichtet sind. Dies ermöglicht neben den bekannten Funktionen der Regelung und Flammenüberwachung auch noch eine Umschaltung bei Störungen einer primären Regelung auf ein Notlaufsystem, welches die Regelung übernehmen kann.A heater, which is particularly suitable for switching from a primary control to an emergency system, has the following components: an air supply and a fuel gas supply, which are controlled by a first control unit, and with a first measuring system, comprising an ionization electrode, a counter electrode, a first alternating current source and a first electronic evaluation system for determining a first ionization signal, which can be fed to the control unit, a second measuring system being present for measuring a second ionization signal, which can be generated between an ignition electrode for igniting a combustion and the counter electrode of the second measuring system, and where the the first and the second system are each set up to determine a lambda value. In addition to the known functions of control and flame monitoring, this also enables switching at Malfunctions of a primary control on an emergency system that can take over the control.

Bevorzugt weist das Heizgerät dazu eine Umschalteinheit auf, die bei Ausfall mindestens einer Komponente des ersten Messsystems auf eine Regelung mit dem zweiten Messsystem umschaltet.For this purpose, the heater preferably has a switchover unit which, if at least one component of the first measurement system fails, switches over to control with the second measurement system.

Die erfindungsgemäße Ionisationsmessung, die in dieser Art zur Flammenüberwachung und Regelung eingesetzt werden kann, arbeitet nach folgendem Prinzip:The ionization measurement according to the invention, which can be used in this way for flame monitoring and control, works according to the following principle:

Zwischen einer lonisationselektrode und einer Gegenelektrode (Masse) wird eine Wechselspannung ohne Gleichspannungsanteil aus einer Spannungsquelle mit hoher Ausgangsimpedanz angelegt. Durch einen gleichrichtenden Effekt eines Flammenplasmas bei brennender Flamme fließt ein lonisationsstrom während jeder positiven Halbwelle der Wechselspannung gegen Masse ab. Die Spannungsamplitude jeder positiven Halbwelle wird wegen der hohen Ausgangsimpedanz der Spannungsquelle reduziert, während die negative Halbwelle unverändert erhalten bleibt. Hierdurch wird der Wechselspannung ein negativer Gleichspannungsanteil aufgeprägt. Die Amplitude dieses negativen Gleichspannungsanteils wird als Mittelwert mittels einer Verstärkerschaltung in ein Spannungssignal umgewandelt, das aufgrund seines charakteristischen Verlaufs bei gleichbleibender Gaszufuhr und steigender Luftzufuhr für die hier beschriebenen Zwecke verwendet werden kann. Typischerweise wird dieses Signal mittels eines Analog/Digitalwandlers (z.B. in Werte zwischen 0 und 1023) digitalisiert, so dass es in einem Mikroprozessor weiterverarbeitet werden kann.An alternating voltage without a direct voltage component from a voltage source with a high output impedance is applied between an ionization electrode and a counter electrode (ground). Due to a rectifying effect of a flame plasma when the flame is burning, an ionization current flows off to ground during each positive half-wave of the alternating voltage. The voltage amplitude of each positive half-wave is reduced because of the high output impedance of the voltage source, while the negative half-wave remains unchanged. As a result, a negative direct voltage component is impressed on the alternating voltage. The amplitude of this negative DC voltage component is converted as a mean value by means of an amplifier circuit into a voltage signal which, due to its characteristic curve, can be used for the purposes described here with a constant gas supply and increasing air supply. Typically, this signal is digitized by means of an analog / digital converter (eg into values between 0 and 1023) so that it can be further processed in a microprocessor.

Der charakteristische Verlauf des Signals ergibt sich aus einer Kombination verschiedener Effekte. Einerseits ist die Ionisation im Flammenbereich am stärksten, wenn die Verbrennung in einem stöchiometrischen Verhältnis von Verbrennungsgas und Verbrennungsluft betrieben wird, andererseits entfernen sich die Flammen (physisches Abheben der Flammen) bei steigender Gasgemischgeschwindigkeit (größerer Verbrennungsluftmenge pro Zeiteinheit) von den Austrittsöffnungen im Brenner, die elektronisch die Masse in dem System bilden, was den lonenstrom verringert. Unter Umständen spielt auch die Temperatur der lonisationselektrode bzw. der Flamme für den gleichrichtenden Effekt eine Rolle. Im Ergebnis ergibt sich ein Verlauf mit einem gut reproduzierbaren Minimum, welches in der Nähe eines für einen Dauerbetrieb typischen Lambda-Wertes liegt.The characteristic curve of the signal results from a combination of different effects. On the one hand, the ionization in the flame area is strongest when the combustion is operated in a stoichiometric ratio of combustion gas and combustion air, on the other hand, the flames move away (physical lift-off of the flames) with increasing gas mixture speed (larger combustion air volume per unit of time) from the outlet openings in the burner, which electronically form the mass in the system, which reduces the ion flow. The temperature of the ionization electrode or the flame may also play a role in the rectifying effect. The result is a curve with an easily reproducible minimum, which is close to a lambda value that is typical for continuous operation.

Die Erfindung betrifft auch ein Computerprogrammprodukt, umfassend Befehle, die bewirken, dass die beschriebene Vorrichtung das hier vorgeschlagene Verfahren ausführt. Moderne Heizgeräte enthalten typischerweise eine elektronische Steuerung, die mindestens einen programmierbaren Mikroprozessor enthält, der durch ein solches Computerprogrammprodukt gesteuert werden kann. Insbesondere können vorhandene Geräte mit einer lonisationsmessung und einer Flammenüberwachung durch ein solches Computerprogrammprodukt für das erfindungsgemäße Verfahren nachgerüstet werden.The invention also relates to a computer program product, comprising instructions which cause the described device to carry out the method proposed here. Modern heating devices typically contain an electronic control which contains at least one programmable microprocessor which can be controlled by such a computer program product. In particular, existing devices with ionization measurement and flame monitoring can be retrofitted for the method according to the invention using such a computer program product.

Mit anderen Worten betrifft die Erfindung auch ein Notlaufsystem für gasbetriebene Heizgeräte, insbesondere bei lonisationsstrom-basierter Verbrennungsregelung. Aus der DE 196 18 573 C1 und DE 195 02 901 C1 sind Verbrennungsregelungen bekannt, die über hinterlegte lonisationsstrom-Regelkurven die gewünschte Verbrennungsqualität (Luftzahl lambda) einregeln. Der lonisationsstrom wird in der Regel mit einer lonisationsstrom-Elektrode, an der eine Spannung angelegt wird, gemessen. Diese Elektroden unterliegen einer zeitabhängigen Drift, die im Wesentlichen aus einer anwachsenden Oxidschicht auf der Elektrodenoberfläche resultiert, die einen negativen Einfluss auf das gemessene Signal hat. Um den störenden Einfluss dieser Drift zu kompensieren werden zyklisch (z.B: nach x Brennerbetriebsstunden) Kalibriersequenzen angestoßen. DE 195 39 568 C1 beinhaltet eine Kalibrierung beim Betriebspunkt mit maximalem lonisationsstrom (SCOT) oder in der Nähe dieses Punktes (Sitherm). Der maximale lonisationsstromstrom ist näherungsweise bei lambda=1 zu messen. Aus EP 2 014 985 B1 ist bekannt, dass ein Kalibrierpunkt im Gegensatz zu lambda=1 auch bei dem Punkt genutzt werden kann, an dem die Flamme physisch vom Brenner abzuheben beginnt. Konventionelle Regelungssysteme, die auf einer Messung und Auswertung des lonisationsstroms basieren, nutzen einen Kalibrierpunkt bei lambda=1 oder nahe an 2 lambda=1. Somit fahren die Systeme zyklisch im stöchiometrischen bzw. kurzzeitig im unterstöchiometrischen Bereich mit dort auftretenden sehr hohen CO Emissionen und sehr hohen Flammentemperaturen. Die hohen CO Werte gilt es zu vermeiden, da Kohlenmonoxid bekanntermaßen ein gefährliches Atemgift ist. Die hohen Temperaturen die besonders bei nah-stöchiometrischer Verbrennung auftreten wirken sich stark auf die Lebensdauer der verwendeten lonisationsstromelektroden aus, so dass diese verhältnismäßig häufig ausgetauscht werden müssen. Die genannten Probleme werden erfindungsgemäß dadurch gelöst, dass über eine geeignete Elektronik-Hardwareschaltung ein Kalibrierpunkt nahe dem gewünschten Arbeitspunkt des Heizgerätes genutzt wird, der zyklisch angefahren wird. Dieser Punkt liegt im Bereich von lambda -1,5 und liefert hier zum einen verhältnismäßig kalte Flammentemperaturen bei gleichzeitig sehr niedrigen CO Emissionen. Nachfolgend werden Ausführungsbeispiele der Erfindung erläutert und deren Funktionen beschrieben. Figur 1 stellt eine Vorrichtung zum Durchführen des erfindungsgemäßen Verfahrens dar. Nachdem ein gewünschtes Gas-Luft-Verhältnis über die Gasarmatur und das Gebläse eingestellt worden ist, wird das Gemisch, das aus dem Brenner austritt über eine Zündspannung, die an der Zündelektrode anliegt und dort Funken bildet gezündet. Sobald eine stabile Flamme erkannt ist funktioniert die Erfindung wie folgt: Das Gebläse fährt auf eine festgelegte Drehzahl (z.B. n=6000 rpm) - das Gasventil folgt der Gebläsedrehzahl über eine ausgelegte Kennlinie (Gasarmatur-Stepperposition über Gebläsedrehzahl). Die Position des Gasarmatur-Steppermotors wird jetzt "eingefroren" und die Gebläsedrehzahl definiert reduziert (Punkt "1", Figur 2). Die Gebläsedrehzahl wird nun stetig hochgefahren wobei das gemessene lonisationssignal von Punkt 1 (Figur 2) kommend der Kennlinie folgt. Der jeweilige Minimalwert des Signals wird gespeichert und der Luftvolumenstrom über das Gebläse soweit erhöht, bis ein Schwellwert vom Anstieg des lonisationsstroms relativ zum Minimalwert (Punkt 3) erreicht ist (Punkt 2). Zuletzt wird der Minimalwert (Punkt 3) angefahren, der gleichzeitig den Arbeitspunkt des Gerätes darstellt. In diesem Punkt läuft das Gerät über eine Regelung des Gebläses bis eine Zeitspanne t abgelaufen ist. Nach Ablauf der Zeitspanne t verfährt das System wieder beginnend von Punkt 1. Das Verfahren zur Regelung einer Verbrennung bei einem gasbetriebenen Heizgerät, ist gekennzeichnet, durch folgende Schritte - das Gebläse fährt auf eine festgelegte Drehzahl - das Gasventil folgt der Gebläsedrehzahl über eine ausgelegte Kennlinie (Gasarmatur-Stepperposition über Gebläsedrehzahl) - die Position des Gasarmatur-Steppermotors wird jetzt "eingefroren" und die Gebläsedrehzahl definiert reduziert, - die Gebläsedrehzahl wird nun stetig hochgefahren wobei das gemessene lonisationssignal der Kennlinie folgt - der jeweilige Minimalwert des Signals wird gespeichert und der Luftvolumenstrom über das Gebläse soweit erhöht, bis ein Schwellwert vom Anstieg des lonisationsstroms relativ zum Minimalwert erreicht ist, - zuletzt wird der Minimalwert angefahren, der gleichzeitig den Arbeitspunkt des Gerätes darstellt, - in diesem Punkt läuft das Gerät über eine Regelung des Gebläses bis eine Zeitspanne t abgelaufen ist, - nach Ablauf der Zeitspanne t verfährt das System wieder beginnend von Punkt 1.In other words, the invention also relates to an emergency running system for gas-operated heating devices, in particular in the case of combustion control based on ionization current. From the DE 196 18 573 C1 and DE 195 02 901 C1 Combustion controls are known which regulate the desired combustion quality (air ratio lambda) via stored ionization flow control curves. The ionization current is usually measured with an ionization current electrode to which a voltage is applied. These electrodes are subject to a time-dependent drift, which essentially results from a growing oxide layer on the electrode surface, which has a negative influence on the measured signal. In order to compensate for the disruptive influence of this drift, calibration sequences are initiated cyclically (e.g. after x burner operating hours). DE 195 39 568 C1 includes a calibration at the operating point with maximum ionization current (SCOT) or in the vicinity of this point (Sitherm). The maximum ionization current is to be measured approximately at lambda = 1. the end EP 2 014 985 B1 it is known that, in contrast to lambda = 1, a calibration point can also be used at the point at which the flame begins to physically lift off the burner. Conventional control systems based on a measurement and evaluation of the ionization current use a calibration point at lambda = 1 or close to 2 lambda = 1. The systems therefore run cyclically in the stoichiometric or briefly in the sub-stoichiometric range with very high CO emissions and very high flame temperatures occurring there. The high CO levels should be avoided, as carbon monoxide is known to be a dangerous breath poison. The high temperatures that occur particularly with near-stoichiometric combustion have a strong effect on the service life of the ionization current electrodes used, so that they have to be replaced relatively frequently. The problems mentioned are solved according to the invention in that a calibration point close to the desired operating point of the heater, which is approached cyclically, is used via a suitable electronic hardware circuit. This point is in the range of lambda -1.5 and on the one hand provides relatively cold flame temperatures with very low CO emissions at the same time. In the following, exemplary embodiments of the invention are explained and their functions are described. Figure 1 represents a device for carrying out the method according to the invention. After a desired gas-air ratio has been set via the gas valve and the fan, the mixture that emerges from the burner is via an ignition voltage that is applied to the ignition electrode and forms sparks there ignited. As soon as a stable flame is detected The invention works as follows: The fan runs to a fixed speed (e.g. n = 6000 rpm) - the gas valve follows the fan speed via a designed characteristic (gas valve stepper position via fan speed). The position of the gas valve stepper motor is now "frozen" and the fan speed is reduced in a defined manner (point "1", Figure 2 ). The fan speed is now increased steadily, whereby the measured ionization signal from point 1 ( Figure 2 ) coming follows the characteristic. The respective minimum value of the signal is stored and the air volume flow through the fan is increased until a threshold value of the increase in the ionization current relative to the minimum value (point 3) is reached (point 2). Finally, the minimum value (point 3) is approached, which at the same time represents the operating point of the device. At this point, the device runs by regulating the fan until a period of time t has expired. After the time period t has elapsed, the system starts again from point 1. The procedure for controlling combustion in a gas-powered heater is characterized by the following steps - the fan runs to a specified speed - the gas valve follows the fan speed via a specially designed characteristic ( Gas valve stepper position via fan speed) - the position of the gas valve stepper motor is now "frozen" and the fan speed is reduced in a defined manner, - the fan speed is now continuously increased, with the measured ionization signal following the characteristic curve - the respective minimum value of the signal is saved and the air volume flow is increased the fan is increased until a threshold value of the increase in the ionization current relative to the minimum value is reached, - lastly the minimum value is approached, which also represents the operating point of the device, - at this point the device runs through a control of the fan until a period of time t aba is called, - after the period t has elapsed, the system moves again starting from point 1.

Ein schematisches Ausführungsbeispiel der Erfindung, auf das diese jedoch nicht beschränkt ist, und die Funktionsweise des erfindungsgemäßen Verfahrens werden nun anhand der Zeichnung detailliert erläutert. Es stellen dar:

Fig. 1:
schematisch ein erfindungsgemäßes Heizgerät,
Fig. 2:
eine schematische Schaltung zur Erzeugung eines lonisationssignals gemäß der Erfindung und
Fig. 3:
ein Diagramm zur Veranschaulichung eines Mess- und Regelvorganges mit dem erfindungsgemäßen Verfahren.
A schematic embodiment of the invention, to which it is not limited, and the mode of operation of the method according to the invention will now be explained in detail with reference to the drawing. They represent:
Fig. 1:
schematically a heater according to the invention,
Fig. 2:
a schematic circuit for generating an ionization signal according to the invention and
Fig. 3:
a diagram to illustrate a measurement and control process with the method according to the invention.

Figur 1 zeigt schematisch ein Ausführungsbeispiel einer hier vorgeschlagenen Vorrichtung. In einem Heizgerät 1 zur Verbrennung eines Brenngases mit Luft bildet sich beim Betrieb ein Flammenbereich 2 aus. Luft gelangt über eine Luftzufuhr 3 und ein Gebläse 5 in das Heizgerät 1. Brenngas wird der Luft über eine Brenngaszufuhr 4 und ein Brenngasventil 6 beigemischt. Eine Zündelektrode 7 zündet beim Start des Verbrennungsprozesses das Gemisch und wird danach z. B. als Teil eines Flammenwächters verwendet. Mittels einer lonisationselektrode 8 wird ein erstes lonisationssignal im Flammenbereich 2 gemessen. Dazu dient ein erstes Messsystem S1, von dem die lonisationselektrode 8 mit einer Wechselspannung aus einer ersten Wechselspannungsquelle beaufschlagt wird, wobei eine erste Auswerteelektronik 13 das entstehende lonisationssignal misst und nach in einem Kalibrierdatenspeicher 15 gespeicherten Kalibrierdaten (Regelkurve) in einen Lambda-Wert, also ein Mischungsverhältnis von Luft zu Brennstoff umrechnet. Mit diesem Wert als Ist-Wert kann eine Regeleinheit 17 das Gebläse 5 und/oder das Brenngasventil 6 so regeln, dass sich ein gewünschter Sollwert für Lambda einstellt. Eine Flammenüberwachung 16 kann ebenfalls vorhanden sein. Figure 1 shows schematically an embodiment of a device proposed here. In a heater 1 for burning a fuel gas with air, a flame area 2 is formed during operation. Air enters the heater 1 via an air supply 3 and a fan 5. Combustion gas is mixed with the air via a combustion gas supply 4 and a combustion gas valve 6. An ignition electrode 7 ignites the mixture at the start of the combustion process and is then z. B. used as part of a flame monitor. A first ionization signal is measured in the flame region 2 by means of an ionization electrode 8. A first measuring system S1 is used for this, from which the ionization electrode 8 is subjected to an alternating voltage from a first alternating voltage source, a first evaluation electronics 13 measuring the resulting ionization signal and converting it into a lambda value, i.e. a lambda value, according to calibration data (control curve) stored in a calibration data memory 15 Mixing ratio of air to fuel converted. With this value as the actual value, a control unit 17 can control the fan 5 and / or the fuel gas valve 6 in such a way that a sets the desired target value for lambda. A flame monitor 16 can also be present.

Bei einer wie auch immer gearteten Störung dieser Regelung wird mittels einer Umschalteinheit 10 ein zweites Messsystem S2 in Betrieb gesetzt, welches eine zweite Wechselspannungsquelle 12 statt einer Zündelektronik auf die Zündelektrode 7 aufschaltet (sofern dies nicht zur Flammenüberwachung bereits erfolgt ist), wobei in einer zweiten Auswerteelektronik 14 ein zweites lonisationssignal gemessen und ausgewertet wird, das ebenfalls einen Ist-Wert für Lambda liefert und mittels des erfindungsgemäßen Verfahrens eine Regelung des Lambda-Wertes ermöglicht. Grundsätzlich ist diese Art der Regelung auch als primäre Regelung einsetzbar, und zwar parallel zu einer Flammenüberwachung mittels einer Zündelektrode als einzige lonisationselektrode oder mittels einer eigenen lonisationselektrode nur für die Regelung. In diesem Fall muss nur das zweite Messsystem S2 vorhanden sein und kann mittels eigener Kalibrierdaten als primäres Regelungssystem eingesetzt werden.In the event of any kind of disturbance of this regulation, a second measuring system S2 is put into operation by means of a switching unit 10, which connects a second AC voltage source 12 instead of ignition electronics to the ignition electrode 7 (if this has not already been done for flame monitoring), with a second Evaluation electronics 14 a second ionization signal is measured and evaluated, which also supplies an actual value for lambda and enables the lambda value to be regulated by means of the method according to the invention. In principle, this type of control can also be used as a primary control, specifically in parallel to flame monitoring by means of an ignition electrode as the only ionization electrode or by means of a dedicated ionization electrode only for control. In this case, only the second measuring system S2 needs to be present and can be used as the primary control system by means of its own calibration data.

In dem hier gewählten Ausführungsbeispiel arbeitet das Heizgerät zunächst im Normalbetrieb bei einer bestimmten Zufuhr von Brenngas und einer zugehörigen Drehzahl des Gebläses 5, wobei mittels des ersten Messsystems S1 das lonisationssignal I1 auf einen für diesen Zustand als Soll-Wert vorgegebenen Wert von z. B. 100 µA [mikroAmpere] geregelt wird, indem die Drehzahl des Gebläses und/oder die Brennstoffzufuhr verstellt werden. Diese Art der Regelung bewirkt bei gültigen Kalibrierdaten (Kennfeld, Regelkurve), dass über einen großen Lastbereich ein gewünschter Lambda-Wert eingehalten wird. Bei einer Störung in diesem System, kann statt einer Abschaltung eine Umschaltung auf ein Notlaufsystem ausgelöst werden. In diesem Fall wird vom ersten Messsystem S1 auf das zweite Messsystem S2 umgeschaltet. Eine definierte Drehzahl wird über das Gebläse 5 angefahren und die über hinterlegte Kennlinien zugehörige Brennstoffmenge eingestellt. Das Messsystem S2 ermittelt zu Beginn des Notlaufes ein mittels der Zündelektrode 7 ermitteltes zweites lonisationssignal I2. Dann wird die Gaszufuhr unverändert gelassen, während die Gebläsedrehzahl definiert abgesenkt wird, bis sicher ein Wert unterhalb des gewünschten Lambda-Wertes erreicht ist, der aber immer noch deutlich oberhalb eines stöchiometrischen Verhältnisses von Luft zu Brenngas liegt, so dass kaum Kohlenmonoxid bei diesem Vorgang erzeugt wird und auch keine übermäßig erhöhte Flammtemperatur herrscht (siehe Punkt "1" in Fig. 3). Von diesem Lambda-Wert ausgehend wird die Drehzahl des Gebläses 5 erhöht, bis das zweite lonisationssignal durch einen starken Anstieg ein Abheben der Flamme vom Brenner 9 detektiert (siehe Punkt "2" in Fig. 3). Von diesem Punkt aus wird nun die Drehzahl des Gebläses 5 wieder abgesenkt, wobei das lonisationssignal beobachtet wird, um die genaue Lage des (absoluten) Minimums des lonisationssignals zu bestimmen und den Sollwert auf dem Minimum oder dessen Nähe einzuregeln (siehe Punkt "3" in Fig. 3).In the exemplary embodiment selected here, the heater initially works in normal operation with a certain supply of fuel gas and an associated speed of the fan 5, with the ionization signal I1 being adjusted to a value of z. B. 100 µA [microAmpere] is controlled by adjusting the speed of the fan and / or the fuel supply. With valid calibration data (map, control curve), this type of control ensures that a desired lambda value is maintained over a large load range. In the event of a fault in this system, a switch to an emergency system can be triggered instead of a shutdown. In this case, a switch is made from the first measuring system S1 to the second measuring system S2. A defined speed is set by the fan 5 approached and the associated fuel quantity is set using the stored characteristic curves. At the beginning of the emergency run, the measuring system S2 determines a second ionization signal I2 determined by means of the ignition electrode 7. Then the gas supply is left unchanged, while the fan speed is reduced in a defined manner until a value below the desired lambda value is definitely reached, which is still well above a stoichiometric ratio of air to fuel gas, so that hardly any carbon monoxide is generated during this process and the flame temperature is not excessively high (see point "1" in Fig. 3 ). Starting from this lambda value, the speed of the fan 5 is increased until the second ionization signal detects a lifting of the flame from the burner 9 due to a sharp rise (see point "2" in FIG Fig. 3 ). From this point, the speed of the fan 5 is now reduced again, the ionization signal being observed in order to determine the exact position of the (absolute) minimum of the ionization signal and to regulate the setpoint to the minimum or its vicinity (see point "3" in Fig. 3 ).

Regelungstechnisch ist es einfacher einen Wert in einer Flanke nahe eines Minimums als Sollwert zu nutzen (hier insbesondere in der Flanke hin zum fetteren Gemisch, also zwischen Punkt "1" und "3" in Fig. 3), weil dann bei einer (positiven oder negativen) Änderung des Istwertes klar ist, in welcher Richtung eine Korrektur erfolgen muss. In jedem Fall lässt sich so ein gewünschter Lambda-Wert nahe 1,4 einregeln und einhalten, ohne dass bei dem Vorgang in unzulässigem Maße Kohlenmonoxid erzeugt wird.In terms of control, it is easier to use a value in an edge close to a minimum as a setpoint (here in particular in the edge towards the richer mixture, i.e. between point "1" and "3" in Fig. 3 ), because if there is a (positive or negative) change in the actual value, it is clear in which direction a correction must be made. In any case, a desired lambda value close to 1.4 can be regulated and maintained without the process producing an inadmissible amount of carbon monoxide.

Es kann allerdings sein, dass nach Einstellung des gewünschten Lambda-Wertes (noch) nicht die gewünschte Leistung (gewünschte Drehzahl des Gebläses) exakt erreicht ist. Änderungen z. B. an der Gasarmatur, deren Stellmotor, den Umgebungsbedingungen oder den Strömungsverhältnissen in dem Heizgerät können dazu führen, dass nach Einstellung des gewünschten Lambda-Wertes eine andere als die zur gewünschten Leistung gehörige Gebläsedrehzahl (die am genauesten festlegbare Größe in dem System) anliegt. In diesem Fall wird die Öffnung der Gasarmatur in der erforderlichen Richtung geändert und der ganze Vorgang, falls erforderlich iterativ, wiederholt, bis Lambda-Wert und Leistung die gewünschten Sollwerte annehmen. In der Regel wird dies maximal drei Durchgänge des beschriebenen Verfahrens erfordern.However, it is possible that after setting the desired lambda value, the desired output (desired speed of the fan) has not (yet) been reached exactly. Changes z. B. on the gas valve, its servomotor, the ambient conditions or the flow conditions in the heater can lead to the fact that, after setting the desired lambda value, a different output than that of the desired output Corresponding fan speed (the most precisely definable variable in the system) is applied. In this case, the opening of the gas valve is changed in the required direction and the whole process, if necessary iteratively, is repeated until the lambda value and power take on the desired setpoints. As a rule, this will require a maximum of three rounds of the procedure described.

Mit den so gefundenen Einstellungen kann jetzt die weitere Regelung für eine vorgebbare Zeitspanne t durchgeführt werden, nach der der beschriebene Vorgang zur Kalibrierung oder Überprüfung dieser Regelung wiederholt wird. Grundsätzlich kann das Heizgerät allein mit dieser Art der Regelung als primäre Regelung (weiter) betrieben werden. Falls sie nur als Notlaufregelung dient, kann bei einem Neustart des Heizgerätes jeweils geprüft werden, ob die primäre Regelung wieder funktioniert und erst dann auf die Notlaufregelung umgeschaltet werden, wenn dies nicht der Fall ist.With the settings found in this way, the further control can now be carried out for a predeterminable period of time t, after which the described process for calibrating or checking this control is repeated. In principle, the heater can be operated (further) with this type of control as the primary control. If it is only used as an emergency control, when the heater is restarted it can be checked whether the primary control is working again and only switched to the emergency control if this is not the case.

Fig. 2 zeigt schematisch eine Schaltung, wie sie für das Messsystem S2 eingesetzt werden kann. Eine zweite Wechselspannungsquelle 12 mit einem hohen Ausgangswiderstand 18 liefert zunächst eine Wechselspannung ohne Gleichspannungsanteil an die Zündelektrode 7 und die Gegenelektrode 9 (Masse). Beim Auftreten einer Flamme zwischen den beiden (hier als Ersatzschaltbild 19 dargestellt) fällt die Spannung wegen der Gleichrichterwirkung der Flamme (im Ersatzschaltbild als Diode dargestellt) nur in einer Halbwelle ab, so dass am Eingang der zweiten Auswerteelektronik 14 (Verstärker und Umwandler) eine Wechselspannung mit einem negativen Gleichspannungsanteil anliegt, die in der Auswerteelektronik 14 zu dem zweiten lonisationssignal wird und in einem Analog/Digitalwandler 20 umgewandelt und dann weiter verarbeitet werden kann. Fig. 2 shows schematically a circuit as it can be used for the measuring system S2. A second AC voltage source 12 with a high output resistance 18 initially supplies an AC voltage without a DC voltage component to the ignition electrode 7 and the counter electrode 9 (ground). When a flame occurs between the two (shown here as equivalent circuit diagram 19), the voltage only drops in a half-wave due to the rectifying effect of the flame (shown as a diode in the equivalent circuit diagram), so that an alternating voltage is present at the input of the second evaluation electronics 14 (amplifier and converter) with a negative DC voltage component is present, which becomes the second ionization signal in the evaluation electronics 14 and can be converted in an analog / digital converter 20 and then processed further.

Fig. 3 veranschaulicht qualitativ, was bei dem Vorgang der erfindungsgemäßen Regelung mittels des zweiten Messsystems S2 geschieht. In dem gezeigten Diagramm ist das zweite lonisationssignal I2 auf der Y-Achse (in digitalisierter Form als Zahl zwischen 0 und 1023) gegen die Gebläsedrehzahl [rpm] auf der X-Achse bei konstanter Gaszufuhr aufgetragen. Das entstehende charakteristische Diagramm zeigt einen fast konstanten Anfangsbereich, einen Abfall zu einem Minimum (Punkt "3") und darauf folgend einen Anstieg. Erfahrungswerte haben gezeigt, dass das Minimum in etwa bei einem üblicherweise gewünschten Lambda-Wert von 1,3 bis 1,4 liegt, der konstante Bereich links davon, z. B. bei Punkt "1" aber noch weit von Lambda =1 entfernt ist. In dem Anstieg etwa bei Punkt "2" beginnt die Ablösung der Flamme, die dann mit steigender Luftzufuhr instabil werden kann. Zwischen den Punkten "1" und "2" kann jedoch die Luftzufuhr ohne Erzeugung von unzulässigen Mengen Kohlenmonoxid oder Instabilitäten variiert werden, um das Minimum bei Punkt "3" zu finden und zur Regelung zu nutzen. Die X-Achse könnte wegen des beschriebenen Zusammenhanges zwischen Gebläsedrehzahl und Lambda-Wert auch mit dem Lambda-Wert als Skala versehen sein. Fig. 3 illustrates qualitatively what happens in the process of regulating according to the invention by means of the second measuring system S2. In the diagram shown, the second ionization signal I2 is plotted on the Y axis (in digitized form as a number between 0 and 1023) against the fan speed [rpm] on the X axis with a constant gas supply. The resulting characteristic diagram shows an almost constant initial range, a decrease to a minimum (point "3") and then an increase. Experience has shown that the minimum lies roughly at a typically desired lambda value of 1.3 to 1.4, the constant range to the left, e.g. B. at point "1" but is still far from lambda = 1. In the rise approximately at point "2", the flame begins to detach, which can then become unstable as the air supply increases. Between points "1" and "2", however, the air supply can be varied without producing inadmissible amounts of carbon monoxide or instabilities in order to find the minimum at point "3" and use it for regulation. The X-axis could also be provided with the lambda value as a scale because of the relationship described between the fan speed and the lambda value.

Die vorliegende Erfindung erlaubt es, ohne wesentliche Veränderungen an einem Heizgerät selbst nur durch zusätzliche Elektronik eine zuverlässige Notlaufregelung einzurichten oder sogar als primäre Regelung ein Verfahren einzusetzen, welches auch bei einer (Nach-)Kalibrierung keine unzulässigen Mengen an Kohlenmonoxid erzeugt.The present invention makes it possible, without significant changes to a heater itself, to set up a reliable emergency control system using only additional electronics, or even to use a method as the primary control system which does not generate any inadmissible amounts of carbon monoxide even during (re) calibration.

BezugszeichenlisteList of reference symbols

11
Heizgerätheater
22
FlammenbereichFlame area
33
LuftzufuhrAir supply
44th
BrenngaszufuhrFuel gas supply
55
Gebläsefan
66th
BrenngasventilFuel gas valve
77th
ZündelektrodeIgnition electrode
88th
lonisationselektrodeionization electrode
99
Brenner / GegenelektrodeTorch / counter electrode
1010
UmschalteinheitSwitching unit
1111
erste Wechselspannungsquellefirst AC voltage source
1212th
zweite Wechselspannungsquellesecond AC voltage source
1313th
erste Auswerteelektronikfirst evaluation electronics
1414th
zweite Auswerteelektroniksecond evaluation electronics
1515th
KalibrierdatenspeicherCalibration data memory
1616
FlammenüberwachungFlame control
1717th
RegeleinheitControl unit
1818th
AusgangswiderstandOutput resistance
1919th
Ersatzschaltbild einer FlammeEquivalent circuit diagram of a flame
2020th
Analog/DigitalwandlerAnalog / digital converter
S1S1
erstes Messsystemfirst measuring system
S2S2
zweites Messsystemsecond measuring system
I1I1
erstes lonisationssignalfirst ionization signal
I2I2
zweites lonisationssignalsecond ionization signal

Claims (6)

  1. Method for regulating combustion in a heating device (1) by means of an ionisation signal (I2) measured in a flame region (2) of the heating device (1) operated with combustion air and fuel gas, which ionisation signal is derived from an ion current flowing from an ionisation electrode (7, 8) to a counter electrode (9) through the flame region (2), wherein the ratio (lambda value) of combustion air to fuel gas during combustion in the heating device (1) is determined by way of calibrating data from the ionisation signal (I2) and is regulated by adjusting the supply of combustion gas and/or the supply of combustion air, characterised by the following steps:
    1.1 a fan (5) for supplying combustion air is brought to a predeterminable speed,
    1.2 a fuel gas valve (6) is brought to a position associated with this speed by means of a predeterminable characteristic,
    1.3 the fuel gas valve (6) is held in this position,
    1.4 the speed is reduced by a predeterminable amount,
    1.5 afterwards the speed is increased continuously or stepwise and the respective ionisation signal (I2) is measured,
    1.6 a minimum of the ionisation signal (I2) is detected and stored with the corresponding fan speed,
    1.7 the fan speed is increased further until a predeterminable threshold value of the ionisation signal relative to the minimum is reached,
    1.8 the fan speed is then reduced to the minimum associated fan speed and held there for a preset time period (t) or is used to regulate the ionisation signal (I2) to the current constant value,
    1.9 after the time period (t) has elapsed the steps from 1.4 are repeated.
  2. Method according to claim 1, wherein if the fan speed saved in step 1.6 deviates from the fan speed set in 1.1 by more than a predefinable deviation valve, a corresponding correction is made to the setting of the fuel gas valve and steps 1.3 to 1.7 are repeated until the deviation is smaller than the deviation valve which corresponds to the heating device (1) achieving a desired output.
  3. Method according to claim 1 or 2, wherein the predefinable amount in step 1.4 is selected to be so low that a distance of the lambda value is maintained to a region in which an inadmissible amount or concentration of carbon monoxide can be produced.
  4. Method according to any of the preceding claims, wherein the method is carried out in the same way for fan speeds corresponding to different outputs and associated settings of the fuel gas valve (6), resulting in a calibration of the regulation which is updated repeatedly at intervals of the length of the time period (t) and which takes into account all changes in the system.
  5. Method according to any of the preceding claims, wherein for heating devices which have regulation by means of a first measuring system (S1) with a first ionisation measurement and a separate flame monitoring carried out by monitoring electronics by means of a second ionisation measurement, in the event of failure of the first ionisation measurement or the regulation based thereon, switching over to a method according to any of claims 1 to 4 using existing monitoring electronics.
  6. Computer program product, comprising commands which mean that a control unit (17) of a heating device (1),
    having an air supply (3) and a fuel gas supply (4), which can be regulated by a first control unit (17), and having a first measuring system (S1), comprising an ionisation electrode (8), a counter electrode (9), a first alternating current source (11) and a first evaluation electronics (13) for determining a first ionisation signal (I1), which can be supplied to the control unit (17), wherein a second measuring system (S2) for measuring a second ionisation signal (I2) is provided which can be generated by the second measuring system (S2) between an ignition electrode (7) provided for igniting combustion and the counter electrode (9) and wherein the first (S1) and the second (S2) system are set up respectively for determining a lambda value,
    performs the method according to any of claims 1 to 5.
EP20150310.9A 2019-01-29 2020-01-06 Method for regulating a fuel-air mixture in a heating device Active EP3690318B1 (en)

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EP0770824B1 (en) 1995-10-25 2000-01-26 STIEBEL ELTRON GmbH & Co. KG Method and circuit for controlling a gas burner
DE19539568C1 (en) 1995-10-25 1997-06-19 Stiebel Eltron Gmbh & Co Kg Gas burner regulation system
DE19618573C1 (en) 1996-05-09 1997-06-26 Stiebel Eltron Gmbh & Co Kg Gas burner regulating method controlled by ionisation electrode signal
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