Burner having a controller and an ignition and ionisation electrode and method for monitoring and igniting the flame of a burner

Abstract

The invention relates to a burner having a controller (40) and an ignition and ionisation electrode (20) for igniting and monitoring the burner flame, wherein the ignition and ionisation electrode (20) is arranged in the flame region of the burner, is electrically coupled to a discharge circuit (50) and supplies an ionisation signal when the flame of the burner is switched on, wherein the controller (40) supplies, on the basis of the ionisation signal, an output signal for controlling the burner, and wherein the discharge circuit (50) is connected to a DC voltage source (70). The invention also relates to a method for monitoring and igniting the flame of a burner and to a circuit arrangement for a burner.

Description

[0001] The invention relates to a burner with a control system and an ignition and ionization electrode for monitoring and igniting the burner flame, particularly in the manner of gaseous fuel burners used in heating systems for heating liquids (e.g., domestic hot water) and / or air, and installed in mobile spaces such as mobile homes and caravans. Furthermore, the invention relates to a circuit arrangement of a burner. The invention also relates to a method for monitoring and igniting the flame of a burner.

[0002] For the safe operation of burners, it is essential that the flame ignites reliably and that the flame can be reliably monitored.

[0003] To ignite the flame, an ignition electrode located in the flame area is typically used. This is usually coupled to a discharge circuit. When the flame is to be ignited at the burner, the fuel is released and flows out of a burner nozzle as a mixture with air. At the same time, the discharge circuit discharges via the ignition electrode, creating an ignition spark that ignites the fuel flowing out of the burner nozzle.

[0004] Once the burner flame is ignited, the flame must be continuously monitored to ensure that the fuel supply is stopped if the flame goes out. An ionization electrode is typically used to continuously monitor the flame. When the flame is burning, an ionization current develops between the ionization electrode and an electrical ground, which is typically formed by the burner. The ionization current is continuously monitored. If the flame goes out, this can be detected by a drop and eventually a cessation of the ionization current. The device can then be countered by shutting off the fuel supply. Alternatively, an attempt can be made to reignite the burner flame by discharging the ignition electrode again. If this is unsuccessful, the fuel supply must be shut off.

[0005] Solutions are also known in the prior art in which the ignition electrode and the ionization electrode are combined into a single electrode. This uses an alternating voltage source, and the rectifying effect of the ionization electrode is utilized to realize flame monitoring.

[0006] The disadvantage of this solution is that an AC voltage source is required. This is usually only the case if the device in which the burner is used is connected to an electrical supply. This is rarely the case for mobile applications such as motorhomes or camping trailers.

[0007] Other solutions, which use a common ignition and ionization electrode, operate without applying an external voltage to the ionization circuit and use the flame exclusively as a voltage source. The ionization current present is monitored.

[0008] If only the ionization current is monitored without applying an external voltage, the flame detection signal provided by the ionization electrode becomes very sensitive to deposits or contamination on the ionization electrode. Therefore, the ionization electrode must be cleaned or even replaced frequently.

[0009] EP 3 333 482 A1 discloses a gas burner comprising an adapter with four connectors, a DC / DC converter, and an igniter with a transmission coil and an ignition coil. Such an adapter allows the use of a single electrode serving as both a flame ionization electrode and an ignition electrode in conjunction with a gas burner control unit capable of operating with two separate electrodes.

[0010] The object of the invention is to create a burner in which the flame can be reliably ignited with little effort and without an alternating voltage source and then monitored to determine whether the flame has been ignited and whether it is burning.

[0011] To achieve this object, the invention provides a burner with a controller and an ignition and ionization electrode for igniting and monitoring the burner flame. The ignition and ionization electrode is arranged in the flame region of the burner, is electrically coupled to a discharge circuit, and delivers an ionization signal when the burner flame is switched on. The controller delivers an output signal for controlling the burner based on the ionization signal. The discharge circuit is connected to a DC voltage source, and the discharge energy of the discharge circuit can be adjusted by the controller by changing the frequency of a pulse width modulation. The invention is based on the fundamental idea of ​​combining the functions of the ignition electrode and the ionization electrode in a single electrode.This results in lower manufacturing costs, as only one electrode needs to be manufactured and installed. Furthermore, a single electrode simplifies burner maintenance, as only this one electrode needs to be checked and, if necessary, cleaned and aligned. Furthermore, the burner can be operated with a direct current source, eliminating the need for a complex alternating current supply. Furthermore, pulse-width modulation allows the discharge energy used during ignition to be adjusted to external influences that affect the ignition. This ensures that the flame is ignited reliably even under varying conditions.

[0012] Advantageously, the supply voltage provided by the DC power source is between 8 and 50 V. Thus, an on-board electrical system voltage of 12 V, which is common in motorhomes and camping trailers, is perfectly sufficient to serve as the supply voltage. Furthermore, on-board electrical systems with 24 or even 48 V, such as those found in trucks or, in some cases, motorhomes and caravans, could also be used as the supply voltage.

[0013] Preferably, a voltage converter is provided, which the controller uses to vary the supply voltage of the DC voltage source before feeding it to the discharge circuit. Increasing the voltage is advantageous because reliability is improved when operating the ignition and ionization electrode at voltages above the usual vehicle electrical system voltages. With a higher voltage, the flame can be monitored in a manner that is little or not at all affected by the degree of contamination or deposits on the electrode.

[0014] Advantageously, the voltage converter can vary the voltage of the DC voltage source between 100 and 300 V. These values ​​represent a good compromise between the ignition and monitoring advantages described above and an acceptable cost for the voltage converter.

[0015] The DC voltage source can be a battery or accumulator. This allows the burner to operate independently of the on-site infrastructure. Furthermore, no additional power source is required, as the vehicle's on-board battery or auxiliary battery can serve as the DC voltage source.

[0016] The discharge circuit may include a capacitor and an ignition transformer. These components are inexpensive and allow the discharge circuit to be easily designed to ensure a long service life.

[0017] Preferably, an operational amplifier is provided that amplifies the ionization signal applied to the control system when the burner flame is switched on. The operational amplifier can be used, in particular, to amplify the DC voltage component of the ionization signal, which indicates the presence and indirectly the quality of the flame, and to make it available to the control system.

[0018] The aforementioned object is also achieved by a circuit arrangement comprising a controller and an ignition and ionization electrode for igniting and monitoring the burner flame of a burner. The ignition and ionization electrode is arranged in the flame region of the burner, is electrically coupled to a discharge circuit, and delivers an ionization signal when the burner flame is switched on. The controller delivers an output signal for controlling the burner based on the ionization signal. The discharge circuit is connected to a DC voltage source. The circuit arrangement can alternatively be referred to as an "ignition and ionization circuit arrangement" of a burner, in particular a gas burner with an electrode. The circuit arrangement is assigned to a burner as in the preceding and following embodiments and versions. Therefore, the circuit arrangement can also be designed according to these aspects.To avoid repetition, reference is made to the preceding and following explanations.

[0019] The above-mentioned task is also solved by a method for monitoring and igniting the flame of a burner, with the following steps: a) a discharge circuit is fed by a DC voltage source, b) a flame is ignited by a controller releasing the gas flow in the burner and causing a discharge of the discharge circuit via an ignition and ionization electrode, whereby the discharge energy of the discharge circuit can be adjusted by the controller by changing the frequency of a pulse width modulation, c) an ionization signal generated and amplified by the ignition and ionization electrode is detected and monitored by the controller, d) the controller outputs an output signal based on the amplified ionization signal, depending on which the air supply and / or the gas supply to the burner is controlled.

[0020] Regarding the resulting advantages, please refer to the above explanations regarding the burner.

[0021] Advantageously, the supply voltage of the DC electrode in step a) can be varied by controlling it using a voltage converter depending on one or more of the following influencing factors: the burner, the burner temperature, and the degree of contamination or deposits on the ignition and ionization electrode, which can be estimated based on the service life or the resistance of a protective circuit. As already explained, taking these external factors into account has a positive impact on successful flame ignition and reliable flame monitoring.

[0022] Preferably, the discharge energy during flame ignition in step b) can be varied by the controller depending on the ambient temperature and / or humidity. Adjusting the discharge energy ensures that a clean ignition spark is generated between the electrode and the burner, and that the burner flame is reliably ignited in a wide variety of situations.

[0023] Preferably, as soon as the controller detects in step d) that the amplified ionization signal is below a predetermined limit, the fuel supply can be shut off, or after a further discharge of the discharge circuit, a check can be carried out to determine whether the controller detects an ionization signal above the limit. This ensures that if the flame goes out, which can be detected by a drop in the ionization signal, no unburned fuel escapes from the burner. As an alternative to shutting off the fuel supply, an attempt can be made to reignite the escaping fuel by automatic re-ignition in order to continue operation without any loss of comfort. Alternatively, the aim can be to stabilize the combustion behavior or, for example, to achieve a specific calorific value (so-called lambda value) by controlling the supply of air and / or fuel.

[0024] The invention is described below with reference to an embodiment illustrated in the accompanying drawing, in which: Figure 1 schematic of a burner with an assembly for igniting and monitoring the burner flame.

[0025] Figure 1 shows a burner with a burner nozzle 10 and with an ignition and ionization electrode 20.

[0026] The burner is used to heat air and / or water and can be installed in mobile homes and caravans, for example.

[0027] The ignition and ionization electrode 20 is arranged in the flame area of ​​the burner nozzle 10 and, when the flame is switched on, generates an ionization signal, which is transmitted to a controller 40 via a protection circuit 22 and an operational amplifier 30. The ignition and ionization electrode 20 and the protection circuit 22 are electrically coupled to a discharge circuit 50.

[0028] The discharge circuit 50 includes a capacitor 52 and an ignition transformer 54.

[0029] The discharge circuit 50 and the protection circuit 22 are fed by a supply voltage of a DC voltage source 70 converted by a voltage converter 60.

[0030] The supply voltage of the DC voltage source 70 can be between 8 and 50 V. It is conceivable to use a battery 72 or an accumulator 74 as the DC voltage source 70. Alternatively, a power supply unit can be used.

[0031] In the illustrated embodiment, the supply voltage of the DC voltage source 70 is variably converted by the controller 40 with the aid of the voltage converter 60. This can be achieved using pulse width modulation, the frequency of which ranges from a few kHz to 1 MHz. It is conceivable that the voltage can be varied between 100 and 300 V, although it is typically 180 V.

[0032] The supply voltage of the DC voltage source 70 can be varied by the voltage converter 60 depending on various influencing factors, such as the burner type, the burner temperature and the degree of contamination or deposits on the ignition and ionization electrode 20. The degree of contamination and deposits on the electrode are estimated based on the service life or on the resistance present in the protection circuit 22.

[0033] In addition, it is conceivable to introduce a voltage divider and a low-pass filter in order to be able to measure the voltage converted by the voltage converter 60 by means of the controller 40.

[0034] In addition, the controller 40 may include a proportional-integral-derivative controller or a proportional-integral controller by means of which the converted voltage can be regulated to a setpoint.

[0035] To ignite the burner flame, the controller 40 releases the fuel supply, causing the fuel-air mixture to flow out of the burner nozzle 10. At the same time, ignition occurs by discharging the discharge circuit 50 via the ignition and ionization electrode 20.

[0036] The discharge energy released by the discharge circuit 50 upon ignition can be variably adjusted by the controller 40. The discharge energy can be varied by changing the number of discharges per second. The discharge frequency typically ranges from 8 to 50 Hz.

[0037] In this embodiment, it is conceivable to control the discharge energy of the discharge circuit 50 by the controller 40 depending on external influencing factors such as the ambient temperature and / or the air temperature.

[0038] When the burner flame is lit, an ionization signal is generated at the ignition and ionization electrode 20. At the same time, the converted supply voltage of the DC voltage source 70 is applied as an external voltage to the protection circuit 22. The operational amplifier 30 amplifies the DC voltage component of the ionization signal, which is present at the ignition and ionization electrode 20 due to the rectifying properties of the flame.

[0039] The controller 40 detects the amplified ionization signal present at the burner nozzle 10 due to the burner flame and, depending on the ionization signal, emits an output signal that controls the gas supply to the burner nozzle 10. If no ionization signal is present at the controller 40 when the fuel supply is enabled, or if the ionization signal is below a predetermined limit, the controller 40 stops the further fuel supply. This prevents further fuel from flowing out of the burner nozzle, which would then not be combusted.

[0040] According to an alternative, if the ionization signal falls below a predetermined limit, the controller 40 reactivates the discharge circuit 50. If a stable flame subsequently develops again at the burner nozzle 10, an ionization signal is again applied to the controller 40, and the burner can continue to operate. If no ionization signal is detected after an ignition attempt, the controller 40 stops the further supply of fuel.

Claims

1. A burner comprising a control unit (40) and an ignition and ionization electrode (20) for igniting and monitoring the burner flame, wherein the ignition and ionization electrode (20) is arranged in the flame area of the burner, is electrically coupled to a discharge circuit (50) and provides an ionization signal when the flame of the burner is switched on, wherein the control unit (40) provides an output signal for actuating (40) the burner on the basis of the ionization signal, wherein the discharge circuit (50) is connected to a DC voltage source (70), characterized in that the discharge energy of the discharge circuit (50) can be adjusted by the control unit (40) by means of frequency change of a pulse width modulation.

2. The burner according to claim 1, characterized in that the supply voltage provided by the DC voltage source (70) is between 8 and 50 V.

3. The burner according to claim 1 or 2, characterized in that a voltage transformer (60) is provided by means of which the control unit (40) varies the supply voltage of the DC voltage source (70) before the discharge circuit (50) is supplied therewith.

4. The burner according to any of the preceding claims, characterized in that the voltage transformer (60) varies the voltage of the DC voltage source (70) between 100 and 300 V.

5. The burner according to any of the preceding claims, characterized in that the DC voltage source (70) is a battery (72) or an accumulator (74).

6. The burner according to any of the preceding claims, characterized in that the discharge circuit (50) comprises a capacitor (52) and / or an ignition transformer (54).

7. The burner according to any of the preceding claims, characterized in that an operational amplifier (30) is provided which amplifies the ionization signal which is present when the burner flame is switched on.

8. A circuit arrangement comprising a control unit (40) and an ignition and ionization electrode (20) for igniting and monitoring the burner flame of a burner, in particular according to any of the preceding claims, wherein the ignition and ionization electrode (20) is arranged in the flame area of the burner, is electrically coupled to a discharge circuit (50) and provides an ionization signal when the flame of the burner is switched on, wherein the control unit (40) provides an output signal for actuating (40) the burner on the basis of the ionization signal, and wherein the discharge circuit (50) is connected to a DC voltage source (70), characterized in that the discharge energy of the discharge circuit (50) can be adjusted by the control unit (40) by means of frequency change of a pulse width modulation.

9. A method of monitoring and igniting the flame of a burner, comprising the following steps: a) a discharge circuit (50) is supplied by a DC voltage source (70); b) a flame is ignited by a control unit (40) releasing the fuel supply in the burner and causing a discharge of the discharge circuit (50) via an ignition and ionization electrode (20), wherein the discharge energy of the discharge circuit (50) can be adjusted by the control unit (40) by means of frequency change of a pulse width modulation; c) an ionization signal generated by the ignition and ionization electrode (20) and amplified is detected and monitored by the control unit (40); d) the control unit (40) outputs an output signal on the basis of the amplified ionization signal as a function of which the gas and / or air supply of the burner is controlled.

10. The method according to claim 9, characterized in that the supply voltage of the DC voltage source (70) in step a) is varied by the control unit (40) using a voltage transformer (60) as a function of one or more of the following influencing factors: the burner, the burner temperature and the degree of contamination or the deposits on the ignition and ionization electrode (20) which can be estimated on the basis of the service life or the resistance of a protective circuit (22).

11. The method according to claim 9 or 10, characterized in that the discharge energy upon ignition of the flame in step b) is varied by the control unit (40) as a function of the ambient temperature and / or the air humidity.

12. The method according to any of claims 9 to 11, characterized in that as soon as the control unit (40) detects in step d) that the amplified ionization signal is below a predetermined limit value, the fuel supply is stopped, or after a further discharge of the discharge circuit (50), it is checked whether an ionization signal above the limit value is detected by the control unit (40).

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