EP2520862B1 - Monitoring the presence of two flames in a fuel combustion device - Google Patents

Description

The present invention generally relates to the technical field of fuel combustion devices which are used, for example, in heating and / or hot water technology and which are often referred to as burner control or burner. In particular, the present invention relates to a monitoring device and a method for independently monitoring the presence of a first flame and the presence of a second flame in such a fuel combustion device.

Fuel combustion devices are used, inter alia, in heating and / or hot water technology and in industrial thermal processing systems, which are used for example for metal melting or for the firing of ceramics. In the heating and / or hot water technology used fuel combustion devices, which are included for example in boilers or water heaters, usually work not only with a main flame, which provides the actual heat generation, but also with a so-called. Pilot flame, which also as ignition flame is called. Fuel combustion devices, which are referred to in this document as Feuerungsautomat, as a fuel burner or shortly as a burner may be, for example, gas burners or oil burners.

In some types of burners, the pilot flame will not fire even if no heating power is required. The pilot flame then serves only to open a fuel valve, which is the main flame is assigned to ensure rapid ignition of the main flame. In other types of burners, the pilot flame is temporarily deleted and only shortly before the ignition of the main flame, for example by means of an electric ignition, ignited again. When the main flame is activated, the burning pilot flame then ensures that the ignition of the main flame can take place in a controlled manner without any major "ignition".

For reasons of operational safety, it is prescribed by appropriate standards to be able to detect the presence of main and / or pilot flame independently.

From the basic technical documentation " Flame monitoring on oil and gas burners ", Siemens Building Technologies, CC1Z7302en, HVAC Products, 16.02.2005 It is known to use a UV detector for monitoring the presence of pilot flame and main flame. Such a UV detector, which is also referred to as UV flame sensor, consists of a series circuit of an ohmic resistor, a UV cell and a diode.

The UV cell of the UV detector has a glass bulb of a UV-transparent quartz glass, which is filled with inert gas. There are two electrodes in the glass bulb. When a voltage is applied between the two electrodes and this voltage is increased, a glow discharge (ignition) occurs when a critical voltage is reached. In this case, electrons emerge at the negative electrode, are accelerated to the positive electrode and ionize the noble gas. This leads to a flow of current through the UV cell. The UV cells used for flame monitoring typically show this behavior of autoignition only from voltages of more than 700 V. The situation is different when the UV cell of the flame to be monitored is irradiated with UV light of approximately 190 to 260 nm wavelength In this case, the Ignition effect depending on the intensity of UV radiation already at effective voltages of about 200 V on.

The diode of the UV detector is used for half-wave rectification, so that when operating the UV detector with an AC voltage in the case of the presence of a flame, a pulsed DC voltage occurs. In the case of a short circuit of the connection lines of the UV detector, the UV detector and thus the diode is bridged, so that when operating with an AC voltage also at the input of the UV detector downstream amplifier circuit instead of the pulsed DC voltage, an AC voltage occurs. Thus, the presence of a flame is indicated by a pulsed DC voltage and a line short is indicated by an AC voltage.

In addition, publication discloses US 3548395 A1 the preamble of the claim.

The independent monitoring of main and pilot flame by means of a respective UV detector has the disadvantage that for each of the two UV detectors each (a) a connecting line (each with two connecting wires) and (b) an amplifier circuit is required. Thus, a relatively high expenditure on equipment is required for the monitoring of main and pilot flame by means of a respective UV detector.

The invention has for its object to simplify independent monitoring of two spatially separated flames by means of a respective flame detector in view of the necessary apparatus required.

This object is solved by the subject matters of the independent claims. Advantageous embodiments of the present invention are described in the dependent claims.

According to a first aspect of the invention, a monitoring device for independently monitoring the presence of a first flame and the presence of a second flame in a fuel combustion device is described. The monitoring device comprises (a) a first flame detector arranged and arranged to receive first radiation emitted by the first flame, (b) a second flame detector arranged and arranged to receive second radiation which emits from the second flame is, (c) a voltage supply device, which is connected to the two flame detectors and which is adapted to apply an AC voltage having a first half-wave and a second half-wave to the two flame detectors, and (d) an evaluation circuit, which with the two flame detectors via a common signal input is connected. The two flame detectors are set up and switched in relation to the voltage supply device and to the evaluation circuit such that a first measurement signal present during the first half-wave is indicative at the common signal input for the intensity of the first radiation and a second measurement signal present during the second half-wave indicative of the common signal input for the intensity of the second radiation. Furthermore, the evaluation circuit is set up to evaluate the first measurement signal and the second measurement signal independently of each other.

The described monitoring device is based on the finding that, in the case of a suitable circuit of the two flame detectors, despite the use of a common signal input, both flame detectors can be read out independently of each other, provided that the first measurement signal is exclusively assigned to the first flame detector and the second measurement signal is exclusively assigned to the second flame detector. In this case, the first measurement signal can only during the first half-wave of the applied to both flame detectors AC voltage occur. Accordingly, the second measuring signal can occur only during the second half cycle of the alternating voltage.

Expressed in clear terms, this means that an assignment of the measurement signals of the two flame detectors to the first (pilot) flame or to the second (main) flame in the evaluation circuit is effected by a signal separation taking into account the positive and the negative half-wave. As a result, a separate flame intensity evaluation is possible in a simple yet effective manner.

The fuel combustion device may be any burner, which is used in particular in the heating and / or hot water technology. The fuel to be combusted may be a solid, liquid or gaseous fuel under normal conditions. The described monitoring device currently seems to be particularly suitable for burners which burn gas or possibly even oil.

The described monitoring device has the advantage over known flame monitoring devices that when using only one flame detector, to which the two flame detectors are connected and which besides a display device has the described voltage supply device and the described evaluation circuit, the two flames can be independently monitored for their presence , Thus, an efficient monitoring of a main flame and a pilot flame in a fuel combustion device can be realized without great equipment expense. An additional terminal on the flame detector for the connection of the second flame detector is not required and to bridge the distance between the actual fuel combustion device in which burn the two flames, and a cabinet in which typically the Flame detector is arranged, only a two-wire flame detector connection cable is required.

It should be noted that the two mentioned flames can also be two partial flames of a so-called surface burner, which typically has a multiplicity of partial flames, wherein one partial flame is assigned to at least one opening of a fuel line. When igniting surface burners, a partial flame is usually ignited first, which then ignites the fuel which emerges from adjacent openings. In this way, all partial flames are ignited successively. For example, the fuel line can meander over a predetermined area.

According to an embodiment of the invention, the monitoring device further comprises (a) a common power supply line connecting the power supply to both the first flame detector and the second flame detector and / or (b) a common sense signal line connecting both the first flame detector and the first second flame detector connects to the common signal input of the evaluation circuit.

The use of a common in particular single-core (connection) line for the voltage supply of the two flame detectors and / or a common, in particular single-core (connection) line for the transmission of measurement signals, which were generated by the two flame detectors, to the evaluation circuit has the advantage that in each case a single connecting wire is sufficient to connect the two flame detectors to the power supply and / or to the evaluation circuit. This advantageously reduces the cabling effort between the voltage supply device and the two flame detectors and / or the cabling effort between the two flame detectors and the common signal input.

It should be noted that the common voltage supply line in each case connects one terminal of the two flame detectors to the voltage supply device, whereas the common measurement signal line connects the respective other terminals of the two flame detectors with the common signal input of the evaluation circuit.

According to a further exemplary embodiment of the invention, the first flame detector has a first electrically rectifying element and the second flame detector has a second electrically rectifying element, wherein the two rectifying elements are connected in anti-parallel with respect to the voltage supply device and to the common signal input. This has the advantage that the two half-waves of the alternating voltage, both of which are applied to the two flame detectors, can be separated in a simple and effective manner between the two flame detectors. In both flame detectors so that in each case only one half-wave of the AC power supply generates a measurement signal which can be detected and evaluated as a positive or negative half-wave signal from the evaluation independently of the respective other half-wave signal.

A separate evaluation of the two (half-wave) measurement signals can be achieved by a slight adaptation of a known evaluation circuit, such as e.g. the flame signal amplifier LME7 or the flame signal amplifier LMV Fa. Siemens. In this case, for example, a further amplifier circuit can be provided so that a separate amplifier circuit is used for each of the two (half-wave) measurement signals.

The rectifying element may for example be a tube. Preferably, the rectifying element is a diode made, for example, from a semiconductor material.

According to a further embodiment of the invention, the first flame detector further comprises a first radiation detector and the second flame detector further comprises a second radiation detector, wherein at least one of the two radiation detectors for electromagnetic radiation in the region of the ultraviolet spectral range is sensitive. This has the advantage that the presence of at least one flame is detected on the basis of the UV component in the electromagnetic emission spectrum of the flame. In this way disturbances in the range of the visible or the infrared spectral range can be effectively eliminated.

The ultraviolet spectral sensitive radiation detector may, for example, the o.g. UV cell, which has a glass bulb made of a UV-transparent quartz glass, in which there are two electrodes. In the glass bulb is also a noble gas, which is ionized by incident UV radiation, so that the UV cell is at least partially electrically conductive. Such a UV cell is particularly sensitive to radiation in the electromagnetic spectral range between 200 nm and 260 nm.

It should be noted that preferably both radiation detectors are sensitive to electromagnetic radiation in the ultraviolet spectral range. It is further noted that although currently the same types of radiation detectors are preferably used, a combination of different types of radiation detectors and in particular ultraviolet spectral sensitive radiation detectors may also be used.

According to a further exemplary embodiment of the invention, the evaluation circuit has a filter circuit. This has the advantage that the (half-wave) measurement signals of the two flame detectors are smoothed such that instead of in each case a pulsed DC voltage signal, a smoothed DC voltage signal in the evaluation circuit can be further processed. The filter circuit may preferably be connected directly downstream of the common signal input.

The filter circuit may, for example, be a so-called RC filter circuit which has one or more so-called RC elements, each having a resistor and a capacitor.

According to a further exemplary embodiment of the invention, the evaluation circuit has (a) a first amplifier circuit which is set up for amplifying exclusively the first measuring signal, and (b) a second amplifier circuit which is set up for amplifying exclusively the second measuring signal. This has the advantage that the two measurement signals can not only be detected independently of each other but also amplified and evaluated independently of each other. Preferably, each of the two amplifier circuits has its own output, at which a signal, in particular a DC signal, is output, which is indicative of the presence of the respective flame.

According to a further exemplary embodiment of the invention, the evaluation circuit has a data processing unit which is set up to detect the presence of a fault of an electronic component of the evaluation circuit and, in particular, the faulty component based on a first output signal of the first amplifier circuit and on a second output signal of the second amplifier circuit identify. This has the advantage that an automatic error diagnosis of the evaluation circuit can be carried out in a simple manner. As a result, the reliability of the entire monitoring device can be significantly improved.

According to a further exemplary embodiment of the invention, the first amplifier circuit has a first diode on the input side, and the second amplifier circuit has a second diode on the input side. In this case, one of the two diodes is connected on the anode side to the common signal input and the other of the two diodes is connected on the cathode side to the common signal input.

By using two oppositely connected diodes, a separation of the two measuring signals associated with different half-waves can be achieved in a simple and efficient manner, so that the first measuring signal is supplied exclusively to the first amplifier circuit and the second measuring signal is supplied exclusively to the second amplifier circuit.

It should be noted that the described connection of the anode or the cathode with the common signal input can be a direct or an indirect connection. In the case of an indirect connection, at least one further electronic component is located between the anode or the cathode and the common signal input. In particular, the filter circuit described above can be located between the anode or the cathode and the common signal input.

According to a further exemplary embodiment of the invention, the first diode is a first zener diode and / or the second diode is a second zener diode.

A Zener diode behaves in a known manner in the forward direction as a normal diode. In the described monitoring device, the usual diode behavior ensures that the two measuring signals are separated from each other and supplied to one of the two amplifier circuits. However, in the reverse direction is a voltage which is greater than a specific breakdown voltage for the respective zener diode, Then the zener diode becomes low in the reverse direction. This behavior can be used in the described monitoring device by a suitable dimensioning of the zener diode, in particular by a suitable choice of the breakdown voltage, to detect a short circuit in the connection line, in particular a short circuit between the above-described voltage supply line and the common measurement signal line described above ,

According to a further exemplary embodiment of the invention, the breakdown voltage of at least one of the two zener diodes is dimensioned such that the at least one zener diode (a) is operated in a voltage range which is smaller in the case of a fault-free connection of the two flame detectors to the voltage supply device and to the common signal input is operated as the breakdown voltage, and (b) in the event of a short circuit between the voltage supply device and the common signal input in a voltage range which is greater than the breakdown voltage.

Said voltage range, which is greater than the blocking voltage, is also typically referred to as a passband. In this passband, the zener diode has lost its rectifying effect.

In the case of a short circuit, in particular between the above-described common voltage supply line and the above-described common measurement signal line at the zener diode, the alternating voltage provided by the voltage supply device, possibly after a smoothing by the filter circuit also described above, will be present. In the case of a short circuit, in contrast to a faultless operating state of the monitoring device, in which the relevant flame detector itself is in the event of detection of radiation ensures at least a certain voltage drop at the zener diode is applied to a higher AC voltage, this short circuit can be detected by an optionally modified by the Zener diode characteristic AC voltage which is fed into the relevant amplifier circuit and output at an output of the amplifier circuit. The presence of an output AC voltage can thus be regarded as a reliable indication that there is a short circuit in particular between the above-described common voltage supply line and the common measurement signal line described above. A short circuit can thus be reliably detected in a simple yet effective manner and thus the reliability of the entire monitoring device can be significantly increased.

It should be noted that the magnitude of the voltage drop across the flame detector is critically dependent on the type of radiation detector used in the particular flame detector. In the case of a currently considered particularly suitable UV cell, the voltage drop across the UV cell, even if just a comparatively high intensity of UV radiation is detected, on the order of 100 volts. In the case of a short circuit, therefore, there is a voltage of about 100 volts higher at the common signal input of the evaluation circuit. This increased voltage then leads, possibly after a certain attenuation by the above-described filter circuit, to the fact that the relevant zener diode is in its breakdown region at least during one of the two half-cycles of the alternating voltage. Of course, in order to detect the above-described functionality of the short-circuit detection on the basis of an AC output signal of the relevant amplifier circuit, one must select a Zener diode with a suitable characteristic breakdown voltage. In accordance with another aspect of the invention, a method for independently monitoring the presence of a first flame and the presence of a second flame in a fuel combustion apparatus is described. The described method comprises (a) applying an AC voltage provided by a voltage supply means having a first half-wave and a second half-wave to a first flame detector and to a second flame detector, (b) receiving a first radiation emitted from the first flame by means of the first flame detector, (c) receiving a second radiation emitted by the second flame by means of the second flame detector, (d) applying a first measurement signal present during the first half wave from the first flame detector to a common signal input of one Evaluation circuit, wherein the first measurement signal for the intensity of the first radiation is indicative, (e) supplying a second measurement signal present during the second half wave from the second flame detector to the common signal input of the evaluation circuit, wherein the second measurement signal for the intensity of the zw radiation is indicative, and (f) monitoring the presence of the first flame and the presence of the second flame by means of the evaluation circuit based on the first measurement signal and the second measurement signal.

The described method is also based on the finding that, in the case of a suitable circuit of the two flame detectors, despite the use of a common signal input, both flame detectors can be read out independently of each other, provided that the first measurement signal can be exclusively assigned to the first flame detector and the second measurement signal can be assigned exclusively to the second flame detector , This assignment is made according to the invention with reference to the two half-waves of the alternating voltage, which is provided by the voltage supply device for both flame detectors together. In this case, the first measurement signal only during the first half cycle the alternating voltage applied to both flame detectors occurs. Accordingly, the second measuring signal can occur only during the second half cycle of the alternating voltage.

According to an embodiment of the invention, the method further comprises (g) erasing the first flame, (h) evaluating the first measurement signal, and (i) viewing the monitoring device as faulty if the evaluation of the first measurement signal erroneously indicates a presence of the first Flame indicates.

The at least temporary extinction of the first flame has the advantage that the functionality of the monitoring device can be checked in a simple manner. In particular, a short circuit between the o.g. common power supply line and the o.g. common measurement signal line are detected, because only in such a short circuit even when an AC signal is applied to the common signal input when the first flame detector does not receive radiation.

The extinction of the first flame can be done, for example, by closing a valve for the fuel supply to the first flame. In this case, however, at least a certain delay time should be waited with the evaluation of the first measurement signal, which corresponds to the expected time difference between the closing of the valve and the actual extinction of the first flame. Depending on the design of the fuel combustion device concerned, this delay time may be, for example, between 1 second and 10 seconds.

The deletion of the first flame can be carried out in an advantageous manner in the context of a so-called intermittent operation of the fuel combustion device. A special turn off the first flame just for the purpose of checking the Functioning of the monitoring device is thus not required in an advantageous manner.

By intermittent operation, in accordance with relevant product standards for fuel combustion devices, also referred to as automatic firing devices, an operating mode is to be understood in which the flames are turned off at least once (1x) in the course of 24 hours. In the area of normal heating applications for residential areas, this requirement is usually met. This is often the case with several burner starts per hour. The fuel combustion device described can thus use the commissioning process to check its functionality and in particular to test the flame monitoring system. Thus, the flame monitoring system is tested relatively often in intermittent operation.

It should be noted that the described method can be carried out in the same way with the second flame.

It is further pointed out that even with fuel combustion devices or burners in which at least one flame (the pilot flame) always remains on, detection of a fault, in particular a short circuit, may be possible. Thus, for example, in the embodiment described above, the monitoring device, in which suitably dimensioned Zener diodes are used, in the case of a voltage breakdown at a half-wave (at the other half-wave, the zener diode is already conductive) and thus at an AC voltage to the relevant amplifier circuit of the Evaluation circuit to be closed on a short circuit between the common voltage supply line and the common measuring signal line.

It should be noted that embodiments of the invention have been described with reference to different subject matters. In particular, some embodiments of the invention are described with apparatus claims and other embodiments of the invention with method claims. However, it will be readily apparent to those skilled in the art upon reading this document that, unless explicitly stated otherwise, in addition to a combination of features associated with a type of subject matter, any combination of features that may result in different types of features are also possible Subject matters belong.

• Figur 1 zeigt eine Überwachungsvorrichtung gemäß einem ersten Ausführungsbeispiel der Erfindung, bei dem zur Separation der von zwei Flammendetektoren bereitgestellten Messsignale gleichrichtende Dioden verwendet werden.
• Figur 2 zeigt eine Überwachungsvorrichtung gemäß einem zweiten Ausführungsbeispiel der Erfindung, bei dem zur Separation der beiden Messsignale Zenerdioden verwendet werden, so dass auch ein Fühlerkurzschluss erkannt werden kann.
• Figur 3 zeigt für unterschiedliche Flammenkonstellationen die logischen Ausgangssignale, welche an den beiden Ausgängen der in Figur 2 dargestellten Verstärkerschaltung anliegen.
• Figur 4 zeigt für unterschiedliche Flammenkonstellationen und für den Fall eines Fühlerkurzschlusses zwischen der in Figur 2 dargestellten gemeinsamen Spannungsversorgungsleitung und der gemeinsamen Messsignalleitung die Ausgangssignale, welche an den beiden Ausgängen der Auswerteschaltung anliegen.
• Figur 5 zeigt ein Zeitdiagramm, wie im Rahmen eines intermittierenden Betriebs einer Brennstoff-Verbrennungsvorrichtung, welche eine Haupt- und eine Pilotflamme aufweist, ein Fühlerkurzschluss zwischen der in Figur 2 dargestellten gemeinsamen Spannungsversorgungsleitung und der gemeinsamen Messsignalleitung erkannt werden kann.

Further advantages and features of the present invention will become apparent from the following exemplary description of presently preferred embodiments.

• FIG. 1 shows a monitoring device according to a first embodiment of the invention, in which rectifying diodes are used to separate the measurement signals provided by two flame detectors.
• FIG. 2 shows a monitoring device according to a second embodiment of the invention, in which Zener diodes are used for the separation of the two measurement signals, so that a sensor short circuit can be detected.
• FIG. 3 shows for different flame constellations the logical output signals, which at the two outputs of the in FIG. 2 abut illustrated amplifier circuit.
• FIG. 4 shows for different flame constellations and for the case of a sensor short circuit between the in FIG. 2 represented common voltage supply line and the common measuring signal line, the output signals which are applied to the two outputs of the evaluation circuit.
• FIG. 5 FIG. 10 is a timing diagram showing, as part of an intermittent operation of a fuel combustion apparatus having a main and a pilot flame, a sensor short between the in. FIG FIG. 2 shown common power supply line and the common measurement signal line can be detected.

It should be noted that features of different embodiments, which are the same or at least functionally identical to the corresponding features or components of the embodiment, are provided with the same reference numerals or with a reference numeral, which is only in its first digit of the reference number of a (functionally) corresponding feature or a (functional) corresponding component. In order to avoid unnecessary repetitions, features or components already explained on the basis of a previously described embodiment will not be explained in detail later.

It should also be noted that the embodiments described below represent only a limited selection of possible embodiments of the invention. In particular, it is possible to suitably combine the features of individual embodiments with one another, so that a multiplicity of different embodiments are to be regarded as obviously disclosed to the person skilled in the art with the embodiment variants explicitly illustrated here.

FIG. 1 shows a monitoring device 100 according to a first embodiment of the invention. The monitoring device 100 has two flame detectors, a first flame detector 110 and a second flame detector 120, on. According to the embodiment shown here is used the first flame detector 110 monitors the presence of a main flame of a fuel combustion device, and the second flame detector 120 monitors the presence of a pilot flame of the fuel combustion device. How out FIG. 1 it can be seen, each of the two flame detectors 110, 120 each have a resistor 112 or 122, a UV cell 114 or 124 and a rectifying diode 116 and 126, respectively. The two diodes 116 and 126 are connected in anti-parallel with respect to each other to a common measuring signal line 134.

The two UV cells 114 and 124 each have a glass bulb of a UV-transparent quartz glass, which is filled with inert gas. There are two electrodes in the glass bulb. If a voltage is applied between the two electrodes and, in addition, the noble gas is irradiated with UV light which is emitted by the main flame or by the pilot flame, then the UV cell in question becomes at least partially electrically conductive and a current can flow through it corresponding flame detector 110, 120 flow.

The monitoring device 100 further comprises, arranged in a housing, not shown, designed as a transformer power supply device 130, which is connected via a resistor R, a common voltage output 131 and a common power supply line 132 with the two flame detectors 110 and 120. The common voltage output is formed as a terminal contact 131 in the housing (not shown) of the monitoring device 100. According to the exemplary embodiment illustrated here, the transformer 130 performs a transformation in which a 50 Hz input signal with a mains voltage Unetz is transformed from 230V to a 50 Hz output signal with a sensor voltage Usensor of approximately 300V. It should be noted that of course also voltage transformations with other frequencies and / or with other values for the primary voltage and / or the secondary voltage possible are. For example, in the US, an input signal with an effective voltage of 120V and a frequency of 60 Hz is usually used.

The monitoring device 100 further has an evaluation circuit 150, which in turn comprises a first amplifier circuit 152 and a second amplifier circuit 154. The first amplifier circuit 152 has on the input side a diode D10, which is connected to a common signal input 138. The second amplifier circuit 154 has on the input side a diode D20, which is likewise connected to the common signal input 138. According to the exemplary embodiment shown here, the common signal input is designed as a connection contact 138 in the above-mentioned housing (not shown).

How out FIG. 1 As can be seen, in relation to the common measuring signal line 134, the two diodes 116 and D10 have the same "polarity". That is, a current flowing through the first flame detector 110 is exclusively processed by the first amplifier circuit 152. Similarly, with respect to the common sense signal line 134, the two diodes 126 and D20 are connected to the same "polarity". That is, a current flowing through the second flame detector 120 is exclusively processed by the second amplifier circuit 154.

Since the two flame detectors 110 and 120 are supplied with an alternating voltage via the common voltage supply line 132, the first flame detector 110 can only become conductive during the positive half-cycle of the alternating voltage (with the main flame burning), whereas the second flame detector 120 (during burning pilot flame) only during the negative half-wave of the AC voltage can become conductive. The transmitted via the common measurement signal line 134 to the evaluation circuit 150 measurement signal of both Flame detectors 110 and 120 are then separated from the two diodes D10 and D20, so that, as already described above, the first amplifier circuit 152 is associated with a first output A1 to the first flame detector 110 and the second amplifier circuit 154 with a second output A2 to the second Flame detector 120 is assigned.

How out FIG. 1 As can be seen, the first amplifier circuit 152 has a first low-pass filter, which is formed by a resistor R10 and a capacitor C10. In a corresponding manner, the second amplifier circuit 154 has a second low-pass filter, which is formed by a resistor R20 and a capacitor C20. These two filter circuits 152 and 154 have the effect that the pulsed DC voltage applied to the filter input is smoothed, so that a DC signal is output to a good approximation at the respective filter output. This DC signal is then amplified by the respective amplifier circuit 152 or 154. How out FIG. 1 As can be seen, the first amplifier circuit 152 has three resistors R11, R12 and R13 and a bipolar transistor T10. The second amplifier circuit 154 has four resistors R21, R22, R23 and R24 and a bipolar transistor T20. According to the embodiment illustrated here, the two amplifier circuits 152 and 154 operate as shown FIG. 1 apparent, with two voltage levels of 5 volts and 0 volts (GND).

Since such amplifier circuits are familiar to the person skilled in the art, their mode of operation will not be explained in detail here. The skilled person will, however, from the two in FIG. 1 Amplifier circuits 152 and 154 shown immediately clear that if the first flame detector 110 is at least partially conductive (the main flame is on), at the first output A1, a logic level of about 0 volts (Low) is output. If the first flame detector 110 does not receive UV radiation (the main flame is off), the first flame detector 110 and at the output A1 is a logic level of about 5 volts (high) on. Due to the presence of the resistor R24, if the second flame detector 120 at least partially becomes conductive upon receiving UV radiation (the pilot flame is on), a logic level of approximately 5 volts (High) is output at the second output A2. If the second flame detector 120 does not receive UV radiation (the pilot flame is off), the second flame detector 120 locks and the output A2 has a logic level of about 0 volts (low). By evaluating the two voltage levels, it is thus possible to monitor the presence of the main flame associated with the first flame detector 110 and the presence of the pilot flame associated with the second flame detector 120. Despite the use of a common voltage supply line 132 and a common measurement signal line 134, the measurement signals can be unambiguously assigned to the two flames due to the anti-parallel arrangement of the two flame detectors and an independent monitoring of the two flames is possible.

FIG. 2 shows a monitoring device 200 according to a second embodiment of the invention. The monitoring device 200 has a voltage supply device 230 designed as an AC voltage source and a DC voltage source 260. Like a comparison between the two FIGS. 1 and 2 can be seen, an evaluation circuit 250 of the monitoring device 200 differs from the in FIG. 1 evaluation circuit 150 shown only in that (a) instead of the ordinary diodes D10 and D20 each Zener diode ZD10 or ZD20 is used and that (b) in addition a two-stage low-pass filter circuit 240 is provided which two resistors R1 and R2 and two capacitors C1 and C2. The separation between (a) the measurement signal from the first flame detector 110 and (b) the measurement signal from the second flame detector 120 is performed in the same manner as in FIG FIG. 1 therefore, will not be explained again in detail.

In the monitoring device 200, the two-stage low-pass filter circuit 240 ensures that the measurement signals from both flame detectors 110 and 120 are smoothed immediately after the common signal input 138.

The two Zener diodes ZD10 and ZD20 contribute to the fact that compared to the monitoring device 100 in the monitoring device 200 additionally a sensor short circuit between the common voltage supply line 132 and the common measurement signal line 134 can be detected. For this purpose, the breakdown or zener voltages of the two Zener diodes ZD10 and ZD20 are dimensioned such that, in the event of a sensor short circuit, the input voltage applied to the common signal input 138 is greater than the Zener voltage of the two Zener diodes ZD10 and ZD20. It should be noted that, in the event of a sensor short circuit, the full AC voltage applied to the common signal input 138 is provided by the voltage supply device 130. In contrast, in the usual operation of the monitoring device 200 at burning flames over the UV cells of the two flame detectors 110 and 120, not shown, at least a certain voltage drops, so that the voltage applied to the common signal input 138 voltage is smaller than that at a sensor short circuit applied AC voltage. Thus, the two transistors T10 and T20, an AC signal is supplied at a sensor short circuit. This results in the following output signals: Exit A1: low → Skin flame on High → Skin Flame off Wechselsp. → Sensor short circuit Exit A1: low → Pilot flame on High → Pilot flame off Wechselsp. → Sensor short circuit

It should be noted that in FIG. 2 a circuit diagram of the monitoring device 200 suitable for a simulation program is shown, with which the following operating states can be simulated: (A) The main flame is burning → Switch S1 is closed (B) The pilot flame is burning → Switch S2 is closed (C) Sensor short circuit before → Switch S3 is closed

At the evaluation unit 270, shown schematically as an oscilloscope, the voltage signals applied to the two outputs A1 and A2 can be displayed for all possible operating states.

FIG. 3 shows for different flame constellations the logical output signals, which at the two outputs of the in FIG. 2 abut illustrated amplifier circuit. The reference symbol AA1 denotes the output signal which corresponds to the in FIG. 2 assigned output A1 is assigned. The reference character AA2 denotes the output signal which corresponds to the in FIG. 2 assigned output A2 is assigned. For reasons of clarity, the output signal AA1 is shown shifted by -2 volts.

As already explained above, the level of the output signal AA2 is "low" when the pilot flame is off. If the level of the output signal is "High", then the pilot flame is burning. Further, the level of the output signal AA1 is "High" when the main flame is off. When the level of the output signal AA1 is "Low", the main flame is burning.

FIG. 4 shows for different flame constellations and for the case of a sensor short circuit between the in FIG. 2 represented common voltage supply line 132 and the common measuring signal line 134, the output signals AA1 and AA2, which abut the two outputs A1 and A2 of the evaluation circuit 150. If there is no sensor short circuit, the levels of the output signals AA1 and AA2 assume the values "Low" and "High" which have already been described above (AA1 is also in FIG. 3 shown shifted by -2 volts).

At the in FIG. 4 illustrated exemplary scenario is in two windows a sensor short circuit before. The first sensor short circuit starts at ta and ends at tb, the second sensor short circuit starts at tc and ends at td = 12.8 seconds. As already described above, in both of these sensor short-circuit time windows, both the output signal AA1 and the output signal AA2 are an AC signal which has the same frequency as the AC voltage source 230 (see FIG. FIG. 2 ) having.

FIG. 5 FIG. 10 is a timing diagram showing, as part of an intermittent operation of a fuel combustion apparatus having a main and a pilot flame, a sensor short between the in. FIG FIG. 2 shown common power supply line and the common measurement signal line can be detected. This is not necessarily the in FIG. 2 shown monitoring device 200 with the two zener diodes ZD10 and ZD20 required. Rather, as explained below, a sensor short circuit with the in FIG. 1 monitoring device 100 are detected on the basis of a temporal correlation between a switching cycle of switched fuel supply valves and the resulting output at the outputs A1 and A2 (flame) signals.

According to the embodiment shown here, a valve for supplying fuel to the main flame is opened at a time t1. The opened main flame valve is in FIG. 5 represented by the bar 581. If the monitoring device operates correctly and then addresses the main flame, which is assumed below, the presence of the main flame is displayed at the time A1 at a time t2. The corresponding flame signal is in FIG. 5 represented by the bar 581a.

The time delay t2-t1 depends i.a. from the time required for fuel transport from the valve exit to the location of the main flame. Accordingly, a maximum delay time TSA1 dependent on its design can be determined for each fuel combustion device within which the main flame must start at the latest. This delay time TSA1 may be between 1 second and 10 seconds, depending on the design of the fuel combustion device concerned. If, however, within this time period TSA1 from t1 the first flame signal is not addressed, then it can be assumed that the flame monitoring device is defective.

If the main flame valve is closed at a time t5, then with a properly functioning monitor, the main flame flame signal 581a is expected to go out within a certain time delay at a time t6. If this is not the case, then it can be assumed that there is a sensor short circuit.

The same applies to the opening (at a time t3) and closing (at a time t7) of the valve for the fuel supply to the pilot flame. In FIG. 5 the open pilot flame valve is represented by the bar 582. In a properly functioning monitoring device, the pilot flame signal 582a becomes the pilot flame appear at a time t4 and disappear again at a time t8. If the flame signal 582a is still present for a longer time even after the pilot flame valve has been closed, then it can also be assumed that there is a sensor short circuit. In this case also, in the case of a correctly functioning monitoring device, the time difference between t3 and t4 must not be greater than a characteristic delay time TSA2 for starting the pilot flame.

In the FIG. 2 Because of its basically three different output signals ("Low", "High" and "AC voltage"), which can be present at each of the two outputs A1 and A2, monitoring device 200 shown permits extensive error consideration. In this case, component errors of the evaluation circuit 150 can be reliably detected and the affected components even identified. Thus, for example, the requirements of the standards EN230 / EN298 regarding the behavior in case of component defects are met.

The following Table 1 shows various component errors of the monitoring device 200 and the associated output signals at the outputs A1 and A2. The following abbreviations are used in Table 1: C: collector B: Base e: emitter L / H / W: Condition remains unchanged despite "component fault" when "Low", "High" or "AC signal" AC: AC signal FCS: Sensor short circuit FS: flame signal

At the output A1, "high" means that there is no flame signal from the skin flame, and "low" means that there is a flame signal from the skin flame.

At output A2, "high" means that there is a flame signal from the skin flame, and "low" means that there is no flame signal from the skin's flame. Table 1: Error type Exit A1 Output A2 R1 interruption "High" "Low" R2 interruption "High" "Low" R10 interruption "High" L / H / W R11 interruption "High" L / H / W R12 interruption L / H / W L / H / W R13 interruption "Low" L / H / W R20 interruption L / H / W "Low" R21 interruption L / H / W "Low" R22 interruption L / H / W L / H / W R23 interruption L / H / W "Low" R24 interruption L / H / W "High" C1 interruption AC (FCS) AC (FCS) short circuit "High" "Low" C2 interruption AC (FCS) AC (FCS) short circuit "High" "Low" C10 interruption L / H / W L / H / W no FS if A2 active short circuit "High" L / H / W C20 interruption L / H / W L / H / W no FS if A1 is active short circuit L / H / W "Low" D10 interruption "High" L / H / W short circuit L / H / W L / H / W D20 interruption L / H / W "Low" short circuit L / H / W L / H / W T10 Interruption C "High" L / H / W Interruption B "High" L / H / W Interruption E "High" L / H / W Short circuit CE "Low" L / H / W Short circuit EB "High" L / H / W Short circuit CB "Low" L / H / W T20 Interruption C L / H / W "Low" Interruption B L / H / W "High" Interruption E L / H / W "High" Short circuit CE L / H / W "Low" Short circuit EB L / H / W "High" Short circuit CB L / H / W "Low"

LIST OF REFERENCE NUMBERS

100

monitoring device

110

first flame detector

112

resistance

114

Radiation sensitive sensor element (e.g., UV cell, photo element, ...)

116

diode

120

second flame detector

122

resistance

124

Radiation sensitive sensor element (e.g., UV cell, photo element, ...)

126

diode

130

Voltage supply device / transformer

131

common voltage output / connection contact

132

common power supply line

134

common measuring signal line

138

common signal input / connection contact

150

evaluation

152

first amplifier circuit

154

second amplifier circuit

R

resistance

D10, D20

diode

R10, R20

resistance

R11, R21

resistance

C10, C20

capacitor

R12, R22

resistance

T10, T20

bipolar transistor

R13, R23

resistance

R24

resistance

GND

Dimensions

A1

first exit

A2

second exit

Unetwork

mains voltage

Usensor

sensor voltage

200

monitoring device

230

Power supply / AC source

240

Low-pass filter circuit (two-stage)

250

evaluation

260

DC voltage source

270

oscilloscope

S1, S2, S3

switch

R1, R2

resistance

C1, C2

capacitor

ZD10, ZD20

Zener diode

AA1

Output signal A1

AA2

Output signal A2

581

Valve for pilot flame (flame 1) opened

581a

Flame signal for main flame (AA1 = "Low")

582

Valve for main flame (flame 2) open

582a

Flame signal for pilot flame (AA2 = "Low")

TSA 1

Delay time for ignition of the main flame

TSA2

Delay time for igniting the pilot flame

Claims (12)

1. Monitoring device for the independent monitoring of the presence of a first flame and of a second flame in a fuel combustion device, said monitoring device (100, 200) having
   a first flame detector (110), configured and arranged to receive first radiation, which is emitted by the first flame,
   a second flame detector (120), configured and arranged to receive second radiation, which is emitted by the second flame,
   a voltage supply device (130, 230) that is connected to the two flame detectors (110, 120) and is configured to apply an alternating voltage with a first half wave and a second half wave to the two flame detectors (110, 120), and
   an evaluation circuit (150, 250),
   characterised in that
   the evaluation circuit (150, 250) is connected to the two flame detectors (110, 120) via a common signal input (138),
   the two flame detectors (110, 120) are configured in such way, and are wired in such a way in relation to the voltage supplying device (130, 230) and to the evaluation circuit (150, 250), that

   - a first measurement signal that is present at the common signal input (138) during the first half wave is indicative of the intensity of the first radiation and

   - a second measurement signal that is present at the common signal input (138) during the second half wave is indicative of the intensity of the second radiation, and

   the evaluation circuit (150, 250) is configured to evaluate the first measurement signal and the second measurement signal independently of one another.
2. Monitoring device according to the previous claim having, in addition,
   a common voltage supply line (132) that connects the voltage supplying device (130, 230) to both the first flame detector (110) and the second flame detector (120) and/or
   a common measurement signal line (134) that connects both the first flame detector (110) and the second flame detector (120) to the common signal input (138) of the evaluation circuit (150, 250).
3. Monitoring device according to one of the previous claims, wherein
   the first flame detector (110) has a first electrically rectifying element (116) and
   the second flame detector (120) has a second electrically rectifying element (126), wherein
   the two rectifying elements (116, 126) are wired antiparallel to one another in relation to the voltage supplying device (130) and to the common signal input (138).
4. Monitoring device according to the previous claim, wherein
   the first flame detector (110) also has a first radiation detector (114) and
   the second flame detector (120) also has a second radiation detector (124),
   wherein at least one of the two radiation detectors (114, 124) is sensitive to electromagnetic radiation in the region of the ultraviolet spectral range.
5. Monitoring device according to one of the previous claims, wherein
   the evaluation circuit (150, 250) has a filter circuit (R20, C20; R10, C10; 240).
6. Monitoring device according to one of the previous claims, wherein
   the evaluation circuit (150, 250) has
   a first amplifier circuit (152) that is configured to amplify the first measurement signal exclusively and
   a second amplifier circuit (154) that is configured to amplify the second measurement signal exclusively.
7. Monitoring device according to the previous claim, wherein the evaluation circuit (250) has a data processing unit that is configured to detect the presence of a fault in an electronic component of the evaluation circuit (250) and, in particular, to identify the faulty component, on the basis of a first output signal (AA1) from the first amplifier circuit (152) and of a second output signal (AA2) from the second amplifier circuit (154).
8. Monitoring device according to the two previous claims, 6 and 7, wherein
   the first amplifier circuit (152) has a first diode (D10, ZD10) on the input side and
   the second amplifier circuit (154) has a second diode (D20, ZD20) on the input side, wherein
   one of the two diodes is connected to the common signal input (138) on the anode side and the other is connected to the common signal input (138) on the cathode side.
9. Monitoring device according to the previous claim, wherein the first diode is a first Zener diode (ZD10) and/or
   the second diode is a second Zener diode (ZD20).
10. Monitoring device according to claim 9, wherein
    the breakdown voltage of at least one of the two Zener diodes (ZD10, ZD20) is of such a magnitude that the at least one Zener diode

    (a) is operated within a voltage range that is lower than the breakdown voltage if the connection of the two flame detectors (110, 120) to the voltage supplying device (230) and to the common signal input (138) is fault-free and

    (b) is operated within a voltage range that is higher than the breakdown voltage if a short circuit occurs between the voltage supplying device (230) and the common signal input (138).
11. Method for the independent monitoring of the presence of a first flame and of a second flame in a fuel combustion device, said method consisting in
    applying an alternating voltage supplied by a voltage supplying device (130, 230) with a first half wave and a second half wave to a first flame detector (110) and a second flame detector (120),
    receiving first radiation, which is emitted by the first flame, by means of the first flame detector (110),
    receiving second radiation, which is emitted by the second flame, by means of the second flame detector (120),
    directing a first measurement signal present during the first half wave from the first flame detector (110) to a common signal input (138) of an evaluation circuit (150, 250), wherein the first measurement signal is indicative of the intensity of the first radiation,
    directing a second measurement signal present during the second half wave from the second flame detector (120) to the common signal input (138) of the evaluation circuit (150, 250), wherein the second measurement signal is indicative of the intensity of the second radiation, and
    monitoring the presence of the first flame and of the second flame by means of the evaluation circuit (150, 250), on the basis of the first measurement signal and the second measurement signal.
12. Method according to the previous claim, said method also consisting in
    extinguishing the first flame,
    evaluating the first measurement signal and
    considering the monitoring device (100, 200) to be faulty if the evaluation of the first measurement signal incorrectly indicates the presence of the first flame.

Images