Gas burner controller adapter, gas burner appliance having such a gas burner controller adapter and method for operating such a gas burner appliance

A gas burner controller adapter for use in adapting a gas burner control device, which is configured to be connected to a flame ionization electrode and a separate ignition electrode, to operate in a gas burner that only includes a single electrode serving as both the flame ionization electrode and the ignition electrode.

This application claims priority to European Patent Application No. 16 202 335.2, filed Dec. 6, 2016 and entitled, “GAS BURNER CONTROLLER ADAPTER, GAS BURNER APPLIANCE HAVING SUCH A GAS BURNER CONTROLLER ADAPTER AND METHOD FOR OPERATING SUCH A GAS BURNER APPLIANCE,” which is incorporated herein by reference.

TECHNICAL FIELD

The present patent application relates to a gas burner controller adapter. Further on, the invention relates to a gas burner appliance having such a gas burner controller adapter and to a method for operating such a gas burner appliance.

BACKGROUND

Gas burner appliances comprise a burner chamber. A gas/air mixture can be combusted or burned within said burner chamber when the gas burner and thereby the gas/air mixture is ignited. Gas burner appliances further usually comprise a heat exchanger being positioned within the burner chamber for heating water by combusting or burning said gas/air mixture within said burner chamber. The water entering into the heat exchanger is often called return-flow water and the water exiting the heat exchanger is often called forward-flow water. Gas burner appliances further comprise an air pipe or air duct for providing the air of the gas/air mixture, a gas pipe or gas duct for providing the gas of the gas/air mixture and an exhaust pipe or exhaust duct through which exhaust flowing out of the burner chamber can emerge into the ambient of the gas burner. Gas burner appliances also comprise a fan being assigned to the exhaust pipe or the air pipe and a gas valve being assigned to the gas pipe. Gas burner appliances further comprise an ignition electrode for igniting the gas/air mixture and a flame ionization electrode for providing a measurement signal. Gas burner appliances also comprise a gas burner control device for controlling the operation the gas burner appliance, preferably for controlling the fan and/or the igniter on basis of a signal provided by the flame ionization electrode.

Such gas burner appliances are differentiated between gas burner appliances making use of an ignition electrode and a flame ionization electrode provided as separate electrodes, and gas burner appliances making use of a single electrode serving as flame ionization electrode and as ignition electrode. Both types of gas burner appliances use special gas burner control devices acting together with the single electrode or with the two separate electrodes. A key advantage of gas burner appliances making use of two separate electrodes, namely of one ignition electrode and of one flame ionization, is the more accurate flame ionization measurement during ignition phases of the gas burner appliance. However, gas burner appliances making use a single electrode are more cost effective.

SUMMARY

Against this background, a novel gas burner controller adapter is provided that allows the use of a single electrode serving as flame ionization electrode and as ignition electrode in connection with a gas burner control device that is adapted to act together with two separate electrodes. Further on, a gas burner appliance having such a gas burner controller adapter and method for operating such a gas burner appliance are provided.

The gas burner controller adapter comprises a first connection terminal through which the same is connectable to a gas burner control device, namely to an input/output terminal of the gas burner control device that is adapted to receive a voltage signal of a flame ionization electrode.

The gas burner controller adapter further comprises a second connection terminal through which the same is connectable to the gas burner control device, namely to an output terminal of the gas burner control device that is adapted to provide a first electrical voltage signal.

The gas burner controller adapter further comprises a third connection terminal through which the same is connectable to the gas burner control device, namely to another output terminal of the gas burner control device that is adapted to provide a second electrical voltage signal.

The gas burner controller adapter further comprises a fourth connection terminal through which the same is connectable to a single electrode which is used as ignition electrode and in addition as flame ionization electrode.

The gas burner controller adapter further comprises a DC/DC converter and an igniter having a transfer coil and an ignition coil.

Input terminals of DC/DC converter are connected to the second connection terminal and to the third connection terminal. Output terminals of the DC/DC converter are connected to the transfer coil of the igniter through a capacitor and through a thyristor. The ignition coil of the igniter is connected to the fourth connection terminal and to the first connection terminal.

Such a gas burner controller adapter allows to make use of a single electrode serving as flame ionization electrode and as ignition electrode in connection with a gas burner control device that is adapted to act together with two separate electrodes.

Preferably, a cathode of the thyristor is connected to one of the output terminals of the DC/DC converter and to a capacitor which is connected between the two output terminals of the DC/DC converter as well as between the cathode of the thyristor and the transfer coil. An anode of the thyristor is connected to the transfer coil of the igniter. A gate of the thyristor is connected to a fifth connection terminal of the adapter through which the adapter is connectable to the gas burner control device, namely to another output terminal of the gas burner control device that is adapted to provide a third electrical voltage signal. Such a gas burner controller adapter allows to use a single electrode serving as flame ionization electrode and as ignition electrode in connection with a gas burner control device that is adapted to act together with two separate electrodes. The fifth connection terminal is either directly connected to a gate of the thyristor or indirectly connected to a gate of the thyristor through a synchronization circuit.

During ignition phases the ignition coil is also connected to ground through an overvoltage limiter. The overvoltage limiter is connected between the first connection terminal and the output terminal of the DC/DC converter to which the cathode of the thyristor is connected.

DESCRIPTION

FIG. 1shows a schematic view of an exemplary gas burner appliance10. The gas burner appliance10comprises a gas burner chamber11with a gas burner surface17in which combustion of a gas/air mixture having a defined mixing ratio of gas and air takes place during burner-on phases of the gas burner. The combustion of the gas/air mixture results into flames12monitored by a flame ionization electrode13. The electrode13serves also as ignition electrode to ignite the gas/air mixture. So, the gas burner appliance10uses a single electrode13serving as ignition electrode and as flame ionization electrode.

The defined gas/air mixture is provided to the burner chamber11of the gas burner by mixing an air flow with a gas flow. A fan14sucks in air provided by an air duct15and further sucks in gas provides by a gas duct16. A gas regulating valve18for adjusting the gas flow through the gas duct16and a gas safety valve19are assigned to the gas duct16. Exhaust resulting from the combustion of the gas/air mixture flows out of the burner chamber through an exhaust pipe21.

Thermal energy resulting from the combustion may be used to heat water flowing through a heat exchanger50of the gas burner appliance10. The defined gas/air mixture having the defined mixing ratio of gas and air is provided to the burner chamber11of the gas burner. The defined gas/air mixture is provided by mixing the air flow provided by an air duct15with a gas flow provided by a gas duct16. The air flow and the gas flow become preferably mixed by a mixing device23. Such a mixing device can be designed as a so-called Venturi nozzle. The quantity of the air flow and thereby the quantity of the gas/air mixture flow is adjusted by the fan14, namely by the speed of the fan14. The fan speed can be adjusted by an actuator22of the fan14. The fan speed of the fan14is controlled by a gas burner control device20generating a control variable for the actuator22of the fan14.

The defined mixing ratio of the defined gas/air mixture is controlled by the gas regulating valve18, namely by a pneumatic controller24of the same. The pneumatic controller24of the gas regulating valve18controls the opening/closing position of the gas valve18. The position of the gas valve18is adjusted by the pneumatic controller24on basis of a pressure difference between the gas pressure of the gas flow in the gas pipe16and a reference pressure. The gas regulating valve18is controlled by the pneumatic controller24in such a way that the pressure at the outlet of the gas valve18is equal to the reference pressure.

InFIG. 1, the ambient pressure serves as reference pressure. However, it is also possible to use the air pressure of the air flow in the air duct15as the reference pressure. The pressure difference between the gas pressure and the reference pressure is determined pneumatically by a pneumatic sensor of the pneumatic controller24.

Alternatively, it is possible to determine the pressure difference between the gas pressure of the gas flow in the gas pipe and the reference pressure electronically by an electric sensor (not shown). In this case, the gas valve18would be controlled by an electronic controller, e.g. by the gas burner control device20.

In any case, the mixing ratio of the defined gas/air mixture is controlled in such a way that over the entire modulation range of the gas burner the defined mixing ratio of the defined gas/air mixture is kept constant. A modulation of “1” means that the fan14is operated at maximum fan speed and thereby at full-load of the gas burner. A modulation of “5” means that the fan14is operated at 20% of the maximum fan speed and a modulation of “10” means that the fan14is operated at 10% of the maximum fan speed. By changing the fan speed of the fan14the load of the gas burner can be adjusted. Over the entire modulation range of the gas burner the defined mixing ratio of the defined gas/air mixture is kept constant.

The invention is not limited to the exemplary gas burner appliance shown inFIG. 1.

As described above, the gas burner appliance10uses a single electrode13serving as ignition electrode and as flame ionization electrode. The gas burner control device20of the gas burner appliance10however is as such adapted to act together with two separate electrodes, namely with an ignition electrode and flame ionization electrode provided by separate electrodes.

A gas burner controller adapter25allows to make use of such a combination of a single electrode13together with a gas burner control device20that is adapted to act together with two separate electrodes.

The gas burner controller adapter25comprises a first connection terminal26through which the same is connectable to a gas burner control device20, namely to an input/output terminal27of the gas burner control device20that is adapted to receive a measurement signal of the electrode13.

The gas burner controller adapter25further comprises a second connection terminal28through which the same is connectable to the gas burner control device20, namely to an output terminal29of the gas burner control device20that is adapted to provide a first electrical voltage signal.

The gas burner controller adapter25further comprises a third connection terminal30through which the same is connectable to the gas burner control device20, namely to another output terminal31of the gas burner control device20that is adapted to provide a second electrical voltage signal.

The first electrical voltage signal is higher than the second electrical voltage signal. The first electrical voltage signal may be in the range of 24V and the second electrical voltage signal may be at ground voltage level GND.

The first electrical voltage signal and the second electrical voltage signal are constant voltage level signals.

The gas burner controller adapter25further comprises a fourth connection terminal32through which the same is connectable to the single electrode13which is used as ignition electrode and in addition as flame ionization electrode. Another connection terminal33of the gas burner controller adapter25is connected to ground GND.

The gas burner controller adapter25further comprises a DC/DC converter34and an igniter35having a transfer coil35aand an ignition coil35b. Input terminals of DC/DC converter34are connected to the second connection terminal28and to the third connection terminal30. Output terminals of the DC/DC converter34are connected to the transfer coil35aof the igniter35through a capacitor36and through a thyristor37. The ignition coil35bof the igniter35is connected to the fourth connection terminal32and to the first connection terminal26.

The cathode of the thyristor37is connected to one of the output terminals of the DC/DC converter34. The anode of the thyristor37is connected to the transfer coil35aof the igniter35. The capacitor36in connected between the two output terminals of the DC/DC converter34. Further on, the capacitor36is connected as well between the cathode of the thyristor37and the transfer coil35aof the igniter35.

The gas burner controller adapter25further comprises a fifth connection terminal38through which the same is connectable to the gas burner control device20, namely to another output terminal39of the gas burner control device20that is adapted to provide a third electrical voltage signal. The third electrical voltage signal is preferably non constant but variable. The third electrical voltage signal is preferably alternating between the voltage level of the first electrical voltage signal and the voltage level of the second electrical voltage signal.

In the embodiment show inFIG. 2, the fifth connection terminal38and the first connection terminal26are both connected to a synchronization circuit40through which the fifth connection terminal38is directly connected to a gate of the thyristor37. The synchronization circuit40of the gas burner controller adapter25provides an output signal at the gate of the thyristor37in such a way that ignition pulses of the igniter35synchronizes to the zero-crossing of the flame ionization signal provided by single electrode13. The synchronization circuit40may comprise a comparator and a monostable flip-flop.

In the embodiment show inFIG. 3, the fifth connection terminal38of gas burner controller adapter25is directly connected to a gate of the thyristor37. In the embodiment show inFIG. 3, the gas burner control device20comprises a microcontroller41that provides the synchronization signal for synchronizing the ignition pulses of the igniter35with the zero-crossing of the flame ionization signal provided by single electrode13. The gas burner controller adapter25ofFIG. 3does therefore not comprise the synchronization circuit40.

Preferably, the gas burner controller adapter25further comprises an overvoltage limiter42connected between the first connection terminal26and the output terminal of the DC/DC converter34to which the cathode of the thyristor37is connected. Said output terminal of the DC/DC converter34to which the cathode of the thyristor37is connected to ground GND. During ignition phases, the ignition coil35bis connected to ground through an overvoltage limiter42, namely when the ignition voltage is above a defined threshold. The overvoltage limiter42provides overvoltage protection at the input/output terminal27of the gas burner control device20, namely for an amplifier/comparator circuit51of the gas burner control device20connected to the input/output terminal27of the gas burner control device20. The input/output terminal27acts as output for a voltage provided by the amplifier/comparator circuit51and as input for the flame signal.

Such a gas burner controller adapter25allows use of a single electrode13to serve as a flame ionization electrode and as an ignition electrode in connection with a gas burner control device20that is adapted to act together with two separate electrodes.

With the gas burner controller adapter25, a gas burner appliance installed in the field making use of two separate electrodes can be converted to a gas burner appliance making use of a single electrode13serving as a flame ionization electrode and as an ignition electrode.

The polarity of the mains voltage provided at the terminals29,31or at the terminals28,30has no effect on proper function. Further on, the energy of the ignition spark is completely independent from mains voltage and frequency, while it is generated from the DC/DC converter34with a constant output voltage.

FIG. 4shows details of the gas burner control device20ofFIG. 3, namely details of the amplifier/comparator circuit51.

The amplifier/comparator circuit51of the gas burner control device20is connected between the input/output terminal27of the gas burner control device20and the microcontroller41of the gas burner control device20.

The amplifier/comparator circuit51comprises an amplifier43. The amplifier43is connected in such a way between the input/output terminal27of the gas burner control device20and the microcontroller41of the gas burner control device20that a first capacitor44is connected between the input/output terminal27of the gas burner control device20and the amplifier43while a second capacitor45and a resistor46are connected between the amplifier43and an output terminal of the microcontroller41, The microcontroller41provides at the output terminal of the same a rectangular voltage signal VR.

The second capacitor45and the resistor46transform that rectangular voltage signal VRsignal into a triangular voltage signal VT. The amplifier43provides the amplified triangular voltage signal VTAat the first capacitor44at which also the flame ionization voltage from electrode13is provided. The amplified triangular voltage signal VTAand the voltage from electrode13provided at the input/output terminal27influence together the voltage VCacross the first capacitor44.

The amplifier/comparator circuit51further comprises a comparator47, wherein the output of the comparator47is connected to an input terminal of the microcontroller41. The voltage VCacross the capacitor44is provided as first input voltage to the a first input terminal of the comparator47and the ground voltage level GND is provided as second input voltage to a second input terminal of the comparator47. Resistors48and49are connected to the input terminals of the comparator47, namely the resistor48between the first input terminal of the comparator47and the input/output terminal27of the gas burner control device20and the resistor49between the two input terminals of the comparator47. The comparator47provides the PWM voltage signal VPWMto the input terminal of the microcontroller41.

FIGS. 5, 6both show the voltage VCacross the capacitor44as well as the PWM output voltage signal VPWMof the comparator47over the time t.FIG. 6shows in addition the amplified triangular voltage signal VTAprovided by the microcontroller41and by the amplifier43.

FIG. 5shows the voltage signals VCand VPWMwithout disturbance effects from an ignition. In the time interval Δt1ofFIG. 5no flame12is present. The voltage signal VCcorresponds to the amplified triangular voltage signal VTAand the duty cycle of the PWM voltage signal VPWMis 50%.

In the time interval Δt2ofFIG. 5a flame12is present, the duty cycle of the PWM voltage signal VPWMis 60% corresponding to a relative small burner load of the gas burner appliance.

In the time interval Δt3ofFIG. 5a flame12is present, the duty cycle of the PWM voltage signal VPWMis 80% corresponding to a relative high burner load of the gas burner appliance10.

So, from the duty cycle of the PWM voltage signal VPWMthe microcontroller41can detect if a flame12is present and can further detect the burner load of the gas burner appliance10.

FIG. 6shows the voltage signals VCand VPWMwith disturbance effects from an ignition of the gas/air mixture caused by the igniter35. At points of time t1, t3and t5ofFIG. 6ignition pulses are provided by the igniter35, wherein said ignition pulses influence the voltage signals VCacross the capacitor44. InFIG. 6, the voltage signal VCacross the capacitor44depend only from the amplified triangular voltage signal VTAprovided by the microcontroller41and by the amplifier43and from the ignition pulsed provided by the igniter. InFIG. 6, the ignition pulses do not result into flames12and into a combustion. As can be seen fromFIG. 6, after the time intervals Δtx the disturbance effects from the ignition are no longer present and the voltage signals VCacross the capacitor44corresponds to the amplified triangular voltage signal VTAbecause no flame12is present.

Considering the above, the present application provides a method for operating the gas burner appliance10.

During ignition phases of the gas burner appliance10, the single electrode13is used as ignition electrode for igniting the gas/air mixture and as flame ionization electrode.

After each ignition spark which is provided by the electrode13a defined stabilization time in monitored, wherein the single electrode13is only used as flame ionization electrode during ignition phases after expiration of the stabilization time and before a next ignition spark occurs. Said stabilization time corresponds to the time intervals Δtx after which the disturbance effects from the ignition are no longer present in the voltage signal VCacross the capacitor44.

The duration of said defined stabilization time Δtx depends from the capacity of the capacitor44and from the resistance of the resistors48,49connected between input/output terminal27of the gas burner control device20and the amplifier43and comparator47of the gas burner control device20. The stabilization time Δtx is a fixed time interval stored within the microcontroller41.

The output PWM signal VPWMof the comparator47is used to determine if a flame12is present and to determine burner load of the gas burner appliance10. If the duty cycle of the output PWM signal VPWMof the comparator47after expiration of the stabilization time Δtx is 50%, no flame is present. If the duty cycle of the output PWM signal VPWMof the comparator47after expiration of the stabilization time Δtx is greater than 50%, a flame is present. The duty cycle of the output PWM signal VPWMof the comparator is indicative about the burner load.

LIST OF REFERENCE SIGNS