EP0456245A2 - Ignition system for a heater using a fuel - Google Patents

Ignition system for a heater using a fuel Download PDF

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Publication number
EP0456245A2
EP0456245A2 EP91107574A EP91107574A EP0456245A2 EP 0456245 A2 EP0456245 A2 EP 0456245A2 EP 91107574 A EP91107574 A EP 91107574A EP 91107574 A EP91107574 A EP 91107574A EP 0456245 A2 EP0456245 A2 EP 0456245A2
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EP
European Patent Office
Prior art keywords
ignition device
glow
flame
glow element
heater
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP91107574A
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German (de)
French (fr)
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EP0456245B1 (en
EP0456245A3 (en
Inventor
Thomas Ganz
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Webasto SE
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Webasto SE
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Publication of EP0456245A3 publication Critical patent/EP0456245A3/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23D—BURNERS
    • F23D3/00—Burners using capillary action
    • F23D3/40—Burners using capillary action the capillary action taking place in one or more rigid porous bodies
    • 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
    • F23N5/14—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermo-sensitive resistors
    • F23N5/143—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using thermo-sensitive resistors using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/001—Glowing plugs for internal-combustion engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2227/00—Ignition or checking
    • F23N2227/38—Electrical resistance ignition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2229/00—Flame sensors

Definitions

  • the invention relates to an ignition device for a fuel-operated heating device, in particular a vehicle auxiliary heating device, with at least one glow element, the ignition device also serving as a flame monitoring device.
  • an ignition device for a fuel-operated heater of the aforementioned type is known.
  • a bar glow plug is provided as the ignition device, in which the glow bar serving as the glow electrode also forms an ionization electrode, which is used for flame monitoring.
  • This provides a flame monitoring device which is thermally insensitive, responds quickly and is inexpensive to manufacture.
  • a protective tube is provided in the case of a glow plug, which forms the ionization electrode. If the rod glow plug is used for flame monitoring using the ionization principle, additional devices must be provided on the rod glow plug which act as an ionization electrode for flame monitoring. Therefore, the usual design of a rod glow plug must be changed and a rod glow plug especially suitable for ionization flame monitoring must be manufactured.
  • a glow plug for internal combustion engines which is designed as a rod glow plug.
  • This glow plug has a ceramic carrier on which a heating element similar to a conductor track is applied.
  • the embodiment of a glow plug described there is also suitable for arranging an overheating protection (PTC resistor) and / or a voltage limiter (varistor) in the connecting leads of the heating element. There is no flame monitoring.
  • a flame sensor as a flame sensor device, which projects into the combustion chamber of the heating device.
  • Such flame monitors not only interfere with the flame formation in the combustion chamber, but are also very sensitive to faults, since they must always be in the flame zone during combustion.
  • DE-OS'en 28 02 625 and 26 41 274 are glow ignition devices specified, in which PTC resistors are used as protection against overheating, the operating state in the second-mentioned publication being able to be detected via the optical glow pattern in a filament ignition device with a PTC resistor.
  • the invention has for its object to provide an ignition device for a fuel-operated heater of the generic type, in which a reliable flame monitoring without additional flame detector component is made possible to simplify the design of such a fuel-operated heater.
  • an ignition device for a fuel-operated heating device in particular a vehicle auxiliary heater, with at least one glow element, the ignition device also serving as a flame monitoring device, is characterized in that the flame monitoring device is formed by the glow element with a PTC behavior, the resistance of which is additionally increased of flame formation increased.
  • the PTC behavior of the glow element such as, for example, a tungsten glow element, is thus used to carry out flame monitoring during the glow process and also later.
  • the resistance increases with increasing temperature of the material.
  • This temperature range is in the invention laying the ignition device essentially only to take circuitry measures with regard to the implementation of flame monitoring, which can be integrated into the control device of the heater. This reduces the amount of components involved in the manufacture of such a heater.
  • the ignition device can preferably be designed such that when an additional resistance increase of the glow element occurs, i.e. during flame monitoring by means of the ignition device, a shutdown of the glow operation of the glow ignition device is triggered, since a flame is now present in the combustion chamber for starting the burner operation of the heater.
  • an additional resistance increase of the glow element occurs, i.e. during flame monitoring by means of the ignition device, a shutdown of the glow operation of the glow ignition device is triggered, since a flame is now present in the combustion chamber for starting the burner operation of the heater.
  • the design of the ignition device according to the invention also permits constant monitoring of the combustion operation if the current signal to the ignition device is applied in a constant or clocked manner, so that continuous flame monitoring can also be carried out while the heater is in operation.
  • the current signal can preferably be significantly smaller than that required for the actual glow operation.
  • the flame monitoring can thus be used both in the glow phase of the glow ignition device, if it is used for its intended purpose as an ignition device, and in the combustion mode, so that the combustion behavior can be detected and monitored by means of appropriate evaluations.
  • the energy supplied to the ignition device can be reduced if the ignition device is heated by the flame formation and therefore the electrical energy requirement for keeping the temperature of the ignition device constant is lower.
  • the respective sizes are component-specific.
  • the ignition device is switched off when the decrease in energy requirement determined on the basis of the PTC behavior of the glow element falls below a predetermined preset value.
  • a bar glow plug can be used as the ignition device, which has a glow element, such as a filament, embedded in a ceramic mass. Tungsten, which has a pronounced PTC behavior, is particularly suitable as the material for the glow element or the filament.
  • the burner is formed by an evaporation burner 1, which has an absorbent body 2, such as a fleece, on a carrier, which is arranged in a combustion tube 3, which delimits a combustion chamber 4.
  • Liquid fuel is supplied to the evaporative burner 1 via a fuel feed line 5.
  • a rod glow plug 7 is provided as an ignition device designated overall by 6, which goes through the carrier and the absorbent body 2 of the vaporization burner 1 and projects into the combustion chamber 4.
  • the rod glow plug 7 has, for example, a filament 8 as the glow element, which is preferably made of tungsten and which is embedded in a ceramic mass 9.
  • the glow plug 7 is operated in the glow phase by means of a glow clock relay or transistor in such a way that the glow element 8 embedded in the ceramic mass 9, like the incandescent filament, serves as a glow element, so that the glow plug 7 is connected to an air / fuel prepared for the ignition of the evaporative burner 1 - Mixture is heated to a suitable temperature.
  • This suitable temperature or target temperature is approximately in the order of 1100 ° C.
  • a constant current I is applied to the glow element 8 of the glow plug 7 during the glow pauses, ie the clock breaks of a glow clock relay 10.
  • the rod glow plug 7 and thus the glow element or the filament 8 thereof are additionally heated by the flame temperature, and the resistance of the glow element 8 increases due to the PTC behavior.
  • This additional increase in resistance generates a voltage drop in the line section with constant current, which is used for flame monitoring.
  • This voltage drop can then be used via an evaluation device (not shown) in order to trigger corresponding switching operations via a control device (not shown) of the heater. Even if this voltage drop does not occur and therefore no flame has formed in the combustion chamber 4, corresponding switching operations can be triggered as in the case of a conventional additional flame monitor.
  • a control circuit 11 of the glow plug 7 in the example shown can be designed so that in the event of flame detection and a steep increase in the resistance of the glow element or the filament 8 of the glow plug due to the PTC behavior, the glow operation of the glow plug 7 can be stopped by others To save energy for heating the glow element 8, since the ignition device 6 has already ignited the fuel mixture prepared on the evaporation burner 1. Even if the glow plug 7 is then switched off, the flame monitoring, based on the PTC behavior of the glow element 8, can also be continued during the firing operation of the heater, in which the current signal to be applied to the glow plug 7 is maintained continuously or in a clocked manner. Thus, the flame formation in the combustion chamber 4 can also be detected during the combustion operation via the control circuit and a downstream evaluation device.
  • FIG. 2 As an essential difference from FIG. 1, an ignition device 6 is shown, which has an open glow element, such as a glow filament 8 ', which is not embedded in a ceramic mass, but is exposed in the combustion chamber 4.
  • an open glow element such as a glow filament 8 '
  • the control functions explained above are also carried out here.
  • the electrical energy to be kept constant at the ignition device 6 can also be changed and controlled if the change in resistance of the glow element or the glow filament 8 'is evaluated in a corresponding manner due to the PTC behavior.
  • a corresponding control can of course also be carried out in the embodiment shown in FIG.
  • the invention is not limited to the example shown, but the ignition device 6 and the flame monitoring implemented with it in the invention can also be used in other designs of burners of a fuel-operated heating device.
  • a burner design other than the evaporation burner 1 shown can also be used in such a heater.
  • the glow element need not be designed in the form of an incandescent filament 8, 8 ', but the glow element can have any shape that is suitable for the respective application, such as band-shaped, serpentine or the like.

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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)

Abstract

An ignition system for a heater using a fuel is indicated, which has at least one glow element, preferably in the form of a glow coil. This glow element is at the same time used as a flame-monitoring device, the PTC action of the same being used, in which an additional resistance increase arises as a result of the flame temperature during flame formation. If a constant current is applied to the glow element during flame monitoring, the additional resistance increase during flame formation brings about a voltage drop which indicates that a flame has formed in the combustion chamber of the heater. Depending upon this, corresponding switching processes can then be triggered in the heater. For example, the ignition system can be switched off. Moreover, even with the ignition system switched off, the current signal can be applied constantly or in a clocked manner during the combustion operation of the heater, so that constant flame monitoring is possible for monitoring the flame formation even during combustion operation. Preferably, the ignition system is in the form of a rod glow plug and has a glow element which is embedded in a ceramic mass. In this connection, the glow element of the rod glow plug preferably consists of tungsten which has a PTC action. <IMAGE>

Description

Die Erfindung befaßt sich mit einer Zündeinrichtung für ein brennstoffbetriebenes Heizgerät, insbesondere Fahrzeugzusatzheizgerät, mit wenigstens einem Glühelement, wobei die Zündeinrichtung zugleich als Flammüberwachungsrichtung dient.The invention relates to an ignition device for a fuel-operated heating device, in particular a vehicle auxiliary heating device, with at least one glow element, the ignition device also serving as a flame monitoring device.

Aus DE-OS 37 06 555 ist eine Zündeinrichtung für ein brennstoffbetriebenes Heizgerät der vorstehend genannten Art bekannt. Bei einer dort gezeigten Ausführungsform ist als Zündeinrichtung eine Stabglühkerze vorgesehen, bei der der als Glühelektrode dienende Glühstab zugleich eine Ionisationselektrode bildet, die zur Flammüberwachung dient.From DE-OS 37 06 555 an ignition device for a fuel-operated heater of the aforementioned type is known. In one embodiment shown there, a bar glow plug is provided as the ignition device, in which the glow bar serving as the glow electrode also forms an ionization electrode, which is used for flame monitoring.

Hierdurch erhält man eine Flammüberwachungseinrichtung, welche thermisch unempfindlich ist, schnell anspricht und kostengünstig hinsichtlich der Herstellung ist. Hierzu ist bei einer Stabglühkerze ein Schutzrohr vorgesehen, welches die Ionisationselektrode bildet. Wenn man die Stabglühkerze zur Flammüberwachung unter Ausnutzung des Ionisationsprinzips nutzt, müssen zusätzliche Einrichtungen an der Stabglühkerze vorgesehen werden, welche als Ionisationselektrode zur Flammüberwachung wirken. Daher muß die sonst übliche Auslegungsform einer Stabglühkerze abgeändert werden und es muß eine speziell für die Ionisationsflammüberwachung geeignete Stabglühkerze hergestellt werden.This provides a flame monitoring device which is thermally insensitive, responds quickly and is inexpensive to manufacture. For this purpose, a protective tube is provided in the case of a glow plug, which forms the ionization electrode. If the rod glow plug is used for flame monitoring using the ionization principle, additional devices must be provided on the rod glow plug which act as an ionization electrode for flame monitoring. Therefore, the usual design of a rod glow plug must be changed and a rod glow plug especially suitable for ionization flame monitoring must be manufactured.

Aus DE-OS 32 31 781 ist eine Glühkerze für Brennkraftmaschinen bekannt, welche als Stabglühkerze ausgebildet ist. Diese Glühkerze besitzt einen Keramikträger, auf welchem ein leiterbahnähnliches Heizelement aufgebracht ist. Die dort beschriebene Ausführungsform einer Glühkerze eignet sich auch für ein Anordnen eines Überhitzungsschutzes (PTC-Widerstand) und/oder eines Spannungsbegrenzers (Varistors) in den Anschlußleitern des Heizelements. Eine Flammüberwachung erfolgt hierbei nicht.From DE-OS 32 31 781 a glow plug for internal combustion engines is known, which is designed as a rod glow plug. This glow plug has a ceramic carrier on which a heating element similar to a conductor track is applied. The embodiment of a glow plug described there is also suitable for arranging an overheating protection (PTC resistor) and / or a voltage limiter (varistor) in the connecting leads of the heating element. There is no flame monitoring.

Ferner ist es bei brennstoffbetriebenen Heizgeräten, insbesondere Fahrzeugzusatzheizgeräten, üblich, zusätzlich zu einer Zündeinrichtung, wie einer Stabglühkerze, einen Flammwächter als Flammwächtereinrichtung vorzusehen, welcher in die Brennkammer des Heizgerätes ragt. Derartige Flammwächter stören nicht nur die Flammenbildung in der Brennkammer, sondern sind auch sehr störungsempfindlich, da sie im Brennbetrieb sich immer in der Flammenzone befinden müssen.Furthermore, in the case of fuel-operated heating devices, in particular vehicle auxiliary heating devices, it is customary to provide, in addition to an ignition device, such as a bar glow plug, a flame sensor as a flame sensor device, which projects into the combustion chamber of the heating device. Such flame monitors not only interfere with the flame formation in the combustion chamber, but are also very sensitive to faults, since they must always be in the flame zone during combustion.

In DE-OS'en 28 02 625 und 26 41 274 sind Glühzündeinrichtungen angegeben, bei denen PTC-Widerstände als Überhitzungsschutz eingesetzt werden, wobei in der zweitgenannten Druckschrift der Betriebszustand über das optische Glühbild bei einer Glühdrahtzündeinrichtung mit PTC-Widerstand erfaßt werden kann.In DE-OS'en 28 02 625 and 26 41 274 are glow ignition devices specified, in which PTC resistors are used as protection against overheating, the operating state in the second-mentioned publication being able to be detected via the optical glow pattern in a filament ignition device with a PTC resistor.

Aus DE-OS 27 43 325 läßt sich ein Kanalheizer entnehmen, der eine Temperatursteuerung bzw. Temperaturbegrenzung unter Verwendung von Heißleitern hat.From DE-OS 27 43 325 a duct heater can be seen which has a temperature control or temperature limitation using thermistors.

Der Erfindung liegt die Aufgabe zugrunde, eine Zündeinrichtung für ein brennstoffbetriebenes Heizgerät der gattungsgemäßen Art bereitzustellen, bei welchem eine zuverlässige Flammüberwachung ohne zusätzliches Flammwächterbauteil zur Vereinfachung der Auslegung eines derartigen brennstoffbetriebenen Heizgeräts ermöglicht wird.The invention has for its object to provide an ignition device for a fuel-operated heater of the generic type, in which a reliable flame monitoring without additional flame detector component is made possible to simplify the design of such a fuel-operated heater.

Nach der Erfindung zeichnet sich eine Zündeinrichtung für ein brennstoffbetriebenes Heizgerät, insbesondere Fahrzeugzusatzheizgerät, mit wenigstens einem Glühelement, wobei die Zündeinrichtung zugleich als Flammüberwachungseinrichtung dient, dadurch aus, daß die Flammüberwachungseinrichtung von dem Glühelement mit einem PTC-Verhalten gebildet wird, deren Widerstand sich zusätzlich bei der Flammenbildung erhöht.According to the invention, an ignition device for a fuel-operated heating device, in particular a vehicle auxiliary heater, with at least one glow element, the ignition device also serving as a flame monitoring device, is characterized in that the flame monitoring device is formed by the glow element with a PTC behavior, the resistance of which is additionally increased of flame formation increased.

Bei der erfindungsgemäßen Zündeinrichtung für ein brennstoffbetriebenes Heizgerät wird somit das PTC-Verhalten des Glühelements, wie beispielsweise eines Wolframglühelements, genutzt, um eine Flammüberwachung während des Glühvorgangs und auch später vorzunehmen. Bei einem Material mit PTC-Verhalten nimmt der Widerstand mit steigender Temperatur des Materials zu.In the ignition device according to the invention for a fuel-operated heating device, the PTC behavior of the glow element, such as, for example, a tungsten glow element, is thus used to carry out flame monitoring during the glow process and also later. With a material with PTC behavior, the resistance increases with increasing temperature of the material.

Dieser Temperaturbereich ist bei der erfindungsgemäßen legung der Zündeinrichtung im wesentlichen nur schaltungstechnische Maßnahmen im Hinblick auf die Verwirklichung einer Flammüberwachung zu treffen, welche sich in die Steuereinrichtung des Heizgerätes integrieren lassen. Hierdurch verringert sich der Bauteilaufwand bei der Herstellung eines solchen Heizgerätes.This temperature range is in the invention laying the ignition device essentially only to take circuitry measures with regard to the implementation of flame monitoring, which can be integrated into the control device of the heater. This reduces the amount of components involved in the manufacture of such a heater.

Vorzugsweise kann nach der Erfindung die Zündeinrichtung so ausgelegt werden, daß beim Auftreten eines zusätzlichen Widerstandsanstieges des Glühelements, d.h. während der Flammüberwachung mittels der Zündeinrichtung, eine Abschaltung des Glühbetriebes der Glühzündeinrichtung ausgelöst wird, da nunmehr eine Flamme in der Brennkammer zur Aufnahme des Brennbetriebes des Heizgerätes vorhanden ist. Somit kann man unter Ausnutzung des PTC-Verhaltens des Glühelements auch die Zündeinrichtung selbsttätig abschalten.According to the invention, the ignition device can preferably be designed such that when an additional resistance increase of the glow element occurs, i.e. during flame monitoring by means of the ignition device, a shutdown of the glow operation of the glow ignition device is triggered, since a flame is now present in the combustion chamber for starting the burner operation of the heater. Thus, one can also switch off the ignition device automatically using the PTC behavior of the glow element.

Auch gestattet die erfindungsgemäße Auslegung der Zündeinrichtung eine ständige Überwachung des Brennbetriebes, wenn man das Stromsignal an die Zündeinrichtung konstant oder getaktet anlegt, so daß man eine ständige Flammüberwachung auch während des Betriebes des Heizgerätes vornehmen kann. Das Stromsignal kann vorzugsweise wesentlich kleiner als das für den eigentlichen Glühbetrieb erforderliche sein.The design of the ignition device according to the invention also permits constant monitoring of the combustion operation if the current signal to the ignition device is applied in a constant or clocked manner, so that continuous flame monitoring can also be carried out while the heater is in operation. The current signal can preferably be significantly smaller than that required for the actual glow operation.

Bei der erfindungsgemäßen Zündeinrichtung kann somit die Flammüberwachung sowohl in der Glühphase der Glüzündeinrichtung, wenn sie ihren bestimmungsgemäßen Zweck als Zündeinrichtung verfolgt, als auch beim Brennbetrieb genutzt werden, so daß das Brennverhalten mittels entsprechenden Auswertungen erfaßt und überwacht werden kann.In the ignition device according to the invention, the flame monitoring can thus be used both in the glow phase of the glow ignition device, if it is used for its intended purpose as an ignition device, and in the combustion mode, so that the combustion behavior can be detected and monitored by means of appropriate evaluations.

Um einen energiesparenden Betrieb der Zündeinrichtung zu ermöglichen, kann die der Zündeinrichtung zugeführte Energie herabgesetzt werden, wenn durch die Flammenbildung die Zündeinrichtung erwärmt wird und daher der elektrische Energiebedarf zur Konstanthaltung der Temperatur der Zündeinrichtung geringer ist. Die jeweiligen Größen sind hierbei bauteilspezifisch.To ensure energy-saving operation of the ignition device enable, the energy supplied to the ignition device can be reduced if the ignition device is heated by the flame formation and therefore the electrical energy requirement for keeping the temperature of the ignition device constant is lower. The respective sizes are component-specific.

Gemäß einer weiteren Ausgestaltungsform wird die Zündeinrichtung abgeschaltet, wenn die aufgrund des PTC-Verhaltens des Glühelements ermittelte Energiebedarfsabnahme einen vorbestimmten Vorgabewert unterschreitet. Als bevorzugte Ausführungsform läßt sich als Zündeinrichtung eine Stabglühkerze einsetzen, welche ein in eine Keramikmasse eingebettetes Glühelement, wie eine Glühwendel, hat. Für das Glühelement oder die Glühwendel kommt als Material insbesondere Wolfram in Betracht, das ein ausgeprägtes PTC-Verhalten hat.According to a further embodiment, the ignition device is switched off when the decrease in energy requirement determined on the basis of the PTC behavior of the glow element falls below a predetermined preset value. As a preferred embodiment, a bar glow plug can be used as the ignition device, which has a glow element, such as a filament, embedded in a ceramic mass. Tungsten, which has a pronounced PTC behavior, is particularly suitable as the material for the glow element or the filament.

Die Erfindung wird nachstehend anhand von bevorzugten Ausführungsformen unter Bezugnahme auf die Zeichnung näher erläutert. Darin zeigt:

Fig. 1
eine schematische Ansicht einer bevorzugten Ausführungsform einer Zündeinrichtung für ein brennstoffbetriebenes Heizgerät, und
Fig. 2
eine Ausführungsvariante mit einer anderen Zündeinrichtung.
The invention is explained below with reference to preferred embodiments with reference to the drawing. It shows:
Fig. 1
a schematic view of a preferred embodiment of an ignition device for a fuel-operated heater, and
Fig. 2
an embodiment variant with another ignition device.

Zur Verdeutlichung der Erfindung ist in den Figuren nur ein Brennerbereich eines Heizgerätes jeweils gezeigt. Bei den dargestellten Beispielen wird der Brenner von einem Verdampfungsbrenner 1 gebildet, der einen saugfähigen Körper 2, wie ein Vlies, auf einem Träger hat, der in einem Brennrohr 3 angeordnet ist, das eine Brennkammer 4 begrenzt. Über eine Brennstoffzuleitung 5 wird dem Verdampfungsbrenner 1 flüssiger Brennstoff zugeführt. Als eine insgesamt mit 6 bezeichnete Zündeinrichtung ist in Figur 1 eine Stabglühkerze 7 vorgesehen, die durch den Träger und den saugfähigen Körper 2 des Verdampfungsbrenners 1 geht und in die Brennkammer 4 ragt. Die Stabglühkerze 7 hat als Glühelement beispielsweise eine Glühwendel 8, die vorzugsweise aus Wolfram besteht und die in eine Keramikmasse 9 eingebettet ist. Mittels eines Glühtaktrelais oder Transistors wird die Stabglühkerze 7 in der Glühphase so betrieben, daß das in die Keramikmasse 9 eingebettete Glühelement 8, wie die Glühwendel als Glühelement dient, so daß die Stabglühkerze 7 auf eine für die Zündung des am Verdampfungsbrenners 1 aufbereiteten Luft/Brennstoff-Gemisches geeignete Temperatur erwärmt wird. Diese geeignete Temperatur oder Soll-Temperatur liegt etwa in der Größenordnung von 1100°C. Während der Glühpausen, d.h. der Taktpausen eines Glühtaktrelais 10, wird ein konstanter Strom I an das Glühelement 8 der Stabglühkerze 7 angelegt. Wenn in der Brennkammer 4 sich ein Flamme ausgebildet hat, wird die Stabglühkerze 7 und somit das Glühelement bzw. die Glühwendel 8 derselben zusätzlich durch die Flammentemperatur erwärmt, und aufgrund des PTC-Verhaltens des Glühelements 8 steigt deren Widerstand zusätzlich an. Durch diesen zusätzlichen Widerstandsanstieg wird ein Spannungsabfall in dem Leitungsabschnitt mit konstantem Strom erzeugt, der zur Flammüberwachung genutzt wird. Über eine nicht näher dargestellte Auswerteeinrichtung kann dann dieser Spannungsabfall genutzt werden, um über eine nicht näher dargestellte Steuereinrichtung des Heizgerätes entsprechende Schaltvorgänge auszulösen. Auch wenn dieser Spannungsabfall nicht auftritt und sich daher keine Flamme in der Brennkammer 4 ausgebildet hat, können entsprechende Schaltvorgänge wie bei einem üblichen zusätzlichen Flammwächter ausgelöst werden.To illustrate the invention, only one burner area of a heater is shown in each case in the figures. In the examples shown, the burner is formed by an evaporation burner 1, which has an absorbent body 2, such as a fleece, on a carrier, which is arranged in a combustion tube 3, which delimits a combustion chamber 4. Liquid fuel is supplied to the evaporative burner 1 via a fuel feed line 5. In FIG. 1, a rod glow plug 7 is provided as an ignition device designated overall by 6, which goes through the carrier and the absorbent body 2 of the vaporization burner 1 and projects into the combustion chamber 4. The rod glow plug 7 has, for example, a filament 8 as the glow element, which is preferably made of tungsten and which is embedded in a ceramic mass 9. The glow plug 7 is operated in the glow phase by means of a glow clock relay or transistor in such a way that the glow element 8 embedded in the ceramic mass 9, like the incandescent filament, serves as a glow element, so that the glow plug 7 is connected to an air / fuel prepared for the ignition of the evaporative burner 1 - Mixture is heated to a suitable temperature. This suitable temperature or target temperature is approximately in the order of 1100 ° C. A constant current I is applied to the glow element 8 of the glow plug 7 during the glow pauses, ie the clock breaks of a glow clock relay 10. If a flame has formed in the combustion chamber 4, the rod glow plug 7 and thus the glow element or the filament 8 thereof are additionally heated by the flame temperature, and the resistance of the glow element 8 increases due to the PTC behavior. This additional increase in resistance generates a voltage drop in the line section with constant current, which is used for flame monitoring. This voltage drop can then be used via an evaluation device (not shown) in order to trigger corresponding switching operations via a control device (not shown) of the heater. Even if this voltage drop does not occur and therefore no flame has formed in the combustion chamber 4, corresponding switching operations can be triggered as in the case of a conventional additional flame monitor.

Eine Ansteuerschaltung 11 der Stabglühkerze 7 bei dem dargestellten Beispiel kann so ausgelegt werden, daß bei einer Flammerkennung und eines steilen Anstieges des Widerstandes des Glühelements bzw. der Glühwendel 8 der Stabglühkerze aufgrund des PTC-Verhaltens der Glühbetrieb der Stabglühkerze 7 gestoppt werden kann, um weitere Energie zum Aufheizen des Glühelements 8 einzusparen, da nämlich bereits die Zündeinrichtung 6 das am Verdampfungsbrenner 1 aufbereitete Brenngemisch gezündet hat. Selbst wenn die Stabglühkerze 7 dann abgeschaltet ist, kann die Flammüberwachung, basierend auf dem PTC-Verhalten des Glühelements 8 auch während des Brennbetriebes des Heizgerätes fortgesetzt werden, in dem das an die Stabglühkerze 7 anzulegende Stromsignal ständig oder getaktet aufrechterhalten wird. Somit kann man über die Ansteuerschaltung und einer nachgeordneten Auswerteinrichtung die Flammbildung in der Brennkammer 4 auch während des Brennbetriebes erfassen.A control circuit 11 of the glow plug 7 in the example shown can be designed so that in the event of flame detection and a steep increase in the resistance of the glow element or the filament 8 of the glow plug due to the PTC behavior, the glow operation of the glow plug 7 can be stopped by others To save energy for heating the glow element 8, since the ignition device 6 has already ignited the fuel mixture prepared on the evaporation burner 1. Even if the glow plug 7 is then switched off, the flame monitoring, based on the PTC behavior of the glow element 8, can also be continued during the firing operation of the heater, in which the current signal to be applied to the glow plug 7 is maintained continuously or in a clocked manner. Thus, the flame formation in the combustion chamber 4 can also be detected during the combustion operation via the control circuit and a downstream evaluation device.

Bei der in Figur 2 dargestellten Variante sind gleiche oder ähnliche Teile mit denselben Bezugszeichen wie in Figur 1 versehen und werden daher nicht nochmals erläutert. In Figur 2 ist als wesentlicher Unterschied zu Figur 1 eine Zündeinrichtung 6 gezeigt, die ein offenes Glühelement, wie eine Glühwendel 8' hat, die nicht in eine Keramikmasse eingebettet ist, sondern in der Brennkammer 4 freiliegt. Die voranstehend erläuterten Steuerfunktionen werden auch hierbei durchgeführt. Ferner kann auch die zur Temperaturkonstanthaltung an der Zündeinrichtung 6 aufzuwendende elektrische Energie geändert und gesteuert werden, wenn die Widerstandsänderung des Glühelements bzw. der Glühwendel 8' aufgrund des PTC-Verhaltens in entsprechender Weise ausgewertet wird. Eine entsprechende Steuerung läßt sich natürlich auch bei der in Figur 1 gezeigten Ausführungsform vornehmen.In the variant shown in FIG. 2, the same or similar parts are provided with the same reference numerals as in FIG. 1 and are therefore not explained again. In FIG. 2, as an essential difference from FIG. 1, an ignition device 6 is shown, which has an open glow element, such as a glow filament 8 ', which is not embedded in a ceramic mass, but is exposed in the combustion chamber 4. The control functions explained above are also carried out here. Furthermore, the electrical energy to be kept constant at the ignition device 6 can also be changed and controlled if the change in resistance of the glow element or the glow filament 8 'is evaluated in a corresponding manner due to the PTC behavior. A corresponding control can of course also be carried out in the embodiment shown in FIG.

Selbstverständlich ist die Erfindung nicht auf das dargestellte Beispiel beschränkt, sondern die Zündeinrichtung 6 und die bei der Erfindung hiermit verwirklichten Flammüberwachung können auch bei anderen Ausbildungsformen von Brennern eines brennstoffbetriebenen Heizgerätes eingesetzt werden. Auch kann eine andere Brennerbauform als ein dargestellter Verdampfungsbrenner 1 bei einem solchen Heizgerät verwendet werden. Insbesondere braucht das Glühelement nicht in Form einer Glühwendel 8, 8' ausgelegt zu sein, sondern das Glühelement kann irgendeine beliebige und für den jeweiligen Anwendungszweck geeignete Gestalt, wie bandförmig, schlangenförmig oder dergleichen, haben.Of course, the invention is not limited to the example shown, but the ignition device 6 and the flame monitoring implemented with it in the invention can also be used in other designs of burners of a fuel-operated heating device. A burner design other than the evaporation burner 1 shown can also be used in such a heater. In particular, the glow element need not be designed in the form of an incandescent filament 8, 8 ', but the glow element can have any shape that is suitable for the respective application, such as band-shaped, serpentine or the like.

BezugszeichenReference numerals

11
Verdampfungsbrenner insgesamtTotal evaporative burners
22nd
Saugfähiger KörperAbsorbent body
33rd
BrennrohrFuel tube
44th
BrennkammerCombustion chamber
55
BrennstoffzuleitungFuel supply
66
Zündeinrichtung insgesamtIgnition device overall
77
StabglühkerzeGlow plug
88th
Glühwendel als Glühelement in Figur 1Filament as a glow element in FIG. 1
8'8th'
Glühwendel als Glühelement in Figur 2Filament as glow element in Figure 2
99
KeramikmasseCeramic mass
1010th
GlühtaktrelaisGlow contact relay
1111
Ansteuerschaltung insgesamt der Stabglühkerze 7Control circuit in total of the glow plug 7

Claims (11)

Zündeinrichtung für ein brennstoffbetriebenes Heizgerät, insbesondere Fahrzeugzusatzheizgerät, mit wenigstens einem Glühelement (8), wobei die Zündeinrichtung (6) zugleich als Flammüberwachungseinrichtung dient, dadurch gekennzeichnet, daß die Flammüberwachungseinrichtung von dem Glühelement (8) mit einem PTC-Verhalten gebildet wird, deren Widerstand sich zusätzlich bei der Flammenbildung erhöht.Ignition device for a fuel-operated heating device, in particular vehicle auxiliary heating device, with at least one glow element (8), the ignition device (6) also serving as a flame monitoring device, characterized in that the flame monitoring device is formed by the glow element (8) with a PTC behavior, the resistance of which additionally increases with the flame formation. Zündeinrichtung nach Anspruch 1, dadurch gekennzeichnet, daß an der Zündeinrichtung (6) in ihren Glühpausen ein konstanter Strom zur Erfassung des Spannungsabfalls aufgrund der bei der Flammenbildung zusätzlich auftretenden Widerstandserhöhung des Glühelements (8) anliegt.Ignition device according to Claim 1, characterized in that a constant current for detecting the voltage drop is present at the ignition device (6) in its glowing pauses due to the additional increase in resistance of the glow element (8) which occurs during flame formation. Zündeinrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß eine Abschaltung des Glühbetriebes der Zündeinrichtung (6) nach Maßgabe des zusätzlichen Widerstandsanstiegs des Glühelements (8) erfolgt.Ignition device according to Claim 1 or 2, characterized in that the glow operation of the ignition device (6) is switched off in accordance with the additional increase in resistance of the glow element (8). Zündeinrichtung nach Anspruch 3, dadurch gekennzeichnet, daß zur weiteren Flammüberwachung während des Brennbetriebes das Stromsignal an der Zündeinrichtung (6) angelegt bleibt.Ignition device according to claim 3, characterized in that for further flame monitoring during the combustion operation, the current signal at the ignition device (6) remains in place. Zündeinrichtung nach Anspruch 4, dadurch gekennzeichnet, daß das Stromsignal wesentlich kleiner als für den eigentlichen Glühbetrieb erforderlich ist.Ignition device according to claim 4, characterized in that the current signal is substantially smaller than that required for the actual glow operation. Zündeinrichtung nach Anspruch 4 oder 5, dadurch gekennzeichnet, daß das Stromsignal periodisch kurzzeitig angelegt bleibt.Ignition device according to claim 4 or 5, characterized in that the current signal remains applied briefly periodically. Zündeinrichtung nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß die dem Glühelement (8) zuzuführende elektrische Energie nach Maßgabe des Energiebedarfs zur Temperaturkonstanthaltung bauteilspezifisch auf der Basis des PTC-Verhaltens der Zündeinrichtung (6) vermindert wird.Ignition device according to one of the preceding claims, characterized in that the electrical energy to be supplied to the glow element (8) is reduced in a component-specific manner on the basis of the PTC behavior of the ignition device (6) in accordance with the energy requirement for keeping the temperature constant. Zündeinrichtung nach Anspruch 7, dadurch gekennzeichnet, daß bei Abnahme der dem Glühelement (8) zuzuführenden elektrischen Energie unter einen vorbestimmten Vorgabewert die Zündeinrichtung (6) abgeschaltet wird.Ignition device according to claim 7, characterized in that when the electrical energy to be supplied to the glow element (8) is reduced below a predetermined preset value, the ignition device (6) is switched off. Zündeinrichtung nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß die Zündeinrichtung (6) in Form einer Stabglühkerze (7) mit einem in eine Keramikmasse (9) eingebetteten Glühelement (8) ausgebildet ist.Ignition device according to one of the preceding claims, characterized in that the ignition device (6) is designed in the form of a rod glow plug (7) with a glow element (8) embedded in a ceramic mass (9). Zündeinrichtung nach Anspruch 9, dadurch gekennzeichnet, daß das Glühelement (8) aus Wolfram besteht.Ignition device according to claim 9, characterized in that the glow element (8) consists of tungsten. Zündeinrichtung nach Anspruch 9 oder 10, dadurch gekennzeichnet, daß das Glühelement als Glühwendel (8) ausgebildet ist.Ignition device according to claim 9 or 10, characterized characterized in that the glow element is designed as a filament (8).
EP91107574A 1990-05-11 1991-05-10 Ignition system for a heater using a fuel Expired - Lifetime EP0456245B1 (en)

Applications Claiming Priority (2)

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DE4015097 1990-05-11
DE4015097A DE4015097C1 (en) 1990-05-11 1990-05-11

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EP0834652A1 (en) * 1996-04-10 1998-04-08 Denso Corporation Glow plug, its production process and ion current detector
US5893993A (en) * 1996-09-12 1999-04-13 Denso Corporation Glow plug with ion sensing electrode
US5922229A (en) * 1996-09-12 1999-07-13 Denso Corporation Glow plug with ion sensing electrode
WO2004082971A1 (en) * 2003-03-18 2004-09-30 Webasto Ag Heating device comprising an adjustable heater plug/flame monitor

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EP0834652A1 (en) * 1996-04-10 1998-04-08 Denso Corporation Glow plug, its production process and ion current detector
EP0834652B1 (en) * 1996-04-10 2004-10-13 Denso Corporation Glow plug, its production process and ion current detector
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WO2004082971A1 (en) * 2003-03-18 2004-09-30 Webasto Ag Heating device comprising an adjustable heater plug/flame monitor

Also Published As

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EP0456245B1 (en) 1995-01-18
DE4015097C1 (en) 1991-04-11
DE59104287D1 (en) 1995-03-02
EP0456245A3 (en) 1992-02-19

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