Method for operating a heating device with an electronic gas / air connection, and heating device

Abstract

A method for operating a heating appliance (1) with an electronic gas-air mixture is proposed, comprising at least the following steps to be performed during heating operation: a) determining the opening position of a gas stepper motor valve (31) via an ignition ramp function; b) detecting the ionization current of a flame (4) of the heating appliance (1); c) detecting the opening position of the gas stepper motor valve (31) upon reaching a defined limit value of the ionization current; d) adjusting the ignition ramp function to open the gas stepper motor valve (31) by taking into account the position of the gas stepper motor valve (31) detected in step c). The method allows the ignition ramp function of a heating appliance (1) to be adapted to the tolerances of the gas stepper motor valve (31) and environmental variables, thereby ensuring increased operational reliability during ignition of the heating appliance (1).

Description

[0001] The invention relates to a method for adjusting an ignition ramp function of a heating device with electronic gas-air compound, a computer program, a control unit, a heating device and a use of a heating device.

[0002] Conventional gas burners typically control the gas-air ratio via a pneumatic gas-air regulator. Changing the fan speed simultaneously alters the gas flow and thus the output. In contrast, an electronic gas-air regulator eliminates the pneumatic coupling between gas and air. The output requested by the heating appliance's modulation controller is converted in the burner control unit into a speed signal for the fan and simultaneously into a command for the stepper motor on the gas valve. Since this method lacks a reference for the actual airflow, the exhaust gas quality must be monitored.

[0003] Electronic gas-air mixtures mean that gas and air are supplied separately. This means the gas flow follows the air flow via a stepper motor gas valve. In electronic gas-air mixtures, combustion is monitored by an ionization electrode. By measuring the electrical conductivity of the flame, the combustion quality can be assessed. This is used to control the gas supply, usually by means of an actuator designed as a gas stepper motor. One advantage over pneumatic gas-air mixtures is their adaptability to fluctuations in gas composition.

[0004] During the ignition process of an electronic gas-air mixture, a gas stepper motor valve is moved via a ramp control, simultaneously actuating an ignition device. The ionization current is measured via the ionization electrode as a signal from the flame. If no flame signal is present after a defined ignition safety time has elapsed, the ignition process is aborted.

[0005] However, it has been shown that various factors, such as component tolerances of the gas stepper motor valve, its wear condition, or even the gas composition during the ignition process, can lead to ignitions at the limit. These are often accompanied by strong backfires, which, in addition to unpleasant noises, can also cause damage to the heating unit.

[0006] EP 3 301 365 A1 discloses a method for controlling the ignition operation of a heating system, whereby an operating characteristic value recorded before the ignition operation can be taken into account. The operating characteristic value is suitable for determining the quality of a fuel used in the heating system, or its calorific value, or a fuel type and / or a power requirement of the heating system. A fluid supply parameter can be increased until an ignition value is reached and a flame ignites in the heating system. The method is carried out during the commissioning or ignition process of a heating appliance, and thus the problem of possible ignition at the limit, with the associated potential for damage to the heating appliance, remains. Furthermore, the method does not take into account possible component tolerances and / or the wear condition of connected components, such as, in particular, the gas stepper motor.

[0007] DE 20 2018 101271 U1 relates to a gas-fired heating appliance with an electronic gas-air mixture, in which a gas mass sensor determines the mass of the fuel gas and its associated physical properties, transmitting this information to a control unit. The control unit regulates and increases the initial gas mass flow based on these measured properties. The presence and integration of a gas mass sensor significantly increases the complexity of the heating appliance.

[0008] EP 3 228 936 A1 relates to a method for operating a gas burner. The gas burner has a pneumatic gas-air system in which a reference pressure in an air supply is used to adjust the mixing ratio of air and fuel gas. The method is therefore not suitable for adjusting the ignition ramp of a heating appliance with an electronic gas-air system.

[0009] The object of the invention is to provide a method for adapting the ignition ramp function of a heat generator with electronic gas-air compound, which overcomes the aforementioned problems of the prior art and enables a safe and trouble-free ignition process.

[0010] Furthermore, the process should be feasible without additional components, so that the robustness of a proposed heating device is not reduced compared to the state of the art.

[0011] These problems are solved by the features of the independent claims. Further advantageous embodiments of the solution proposed here are specified in the dependent claims. In addition, the features specified in the claims are further detailed and explained in the description, which also presents further preferred embodiments of the invention.

[0012] The proposed method for adjusting an ignition ramp function, which specifies an opening position of a gas stepper motor valve for a defined period during an ignition process, of a heating appliance with an electronic gas-air compound comprises at least the following steps to be carried out during heating operation: a) Determining the opening position of a gas stepper motor valve via an ignition ramp function; b) Determining the ionization current of the heater flame during step a); c) Determining the opening position of the gas stepper motor valve when a defined limit value of the ionization current detected in step b) is reached; d) Adapting the ignition ramp function to open the gas stepper motor valve, taking into account the opening position of the gas stepper motor valve detected in step c).

[0013] Steps a) - c) are performed simultaneously at least once. The procedure can also be carried out using a heating device, which is also described here.

[0014] In step a), the opening position of a gas stepper motor valve is determined via an ignition ramp function. The gas stepper motor valve controls the gas supply and thus the composition of the gas mixture (gas-air mixture) supplied to the heat generator via its opening position. The ignition ramp function is preferably a linear function and defines the opening position of the gas stepper motor valve for a defined period, in particular the ignition safety time.

[0015] Simultaneously, step b) is performed, which involves capturing the ionization current during the process of determining the opening position of the gas stepper motor valve.

[0016] Furthermore, according to step c), the measured ionization current is compared with a defined limit value. Upon reaching the defined limit value, the opening position of the gas stepper motor valve is detected. The heater can then return to normal heating operation. It should be noted that the ignition safety time is irrelevant for the implementation of the procedure proposed here; instead, the opening position of the gas stepper motor valve is adjusted according to the ignition ramp function until the defined limit value is reached.

[0017] In step d), the ignition ramp function is adjusted. The ignition ramp function can be characterized by a minimum opening position of the gas stepper motor valve, resulting in a lean combustion mixture, for example with a lambda value of approximately 1.6, and a maximum opening position of the gas stepper motor valve, resulting in a higher fuel-to-fuel ratio in the combustion mixture, for example with a lambda value of approximately 1.1. Often, the gas stepper motor valve is in its minimum opening position at the start of a defined period and in its maximum opening position at the end of a defined period, the ignition safety time.

[0018] The maximum opening position of the adapted ignition ramp function can be proportional to, or preferably equal to, the opening position of the gas stepper motor valve detected in step c) when the defined limit value is reached.

[0019] The minimum opening position of the firing ramp function can be changed by the same amount in the opposite direction as the maximum opening position. Thus, if the maximum opening position of the adapted firing ramp function is lowered by Δx, the minimum opening position of the adapted firing ramp function can be raised by the same value Δx. In this implementation, the opening position at the midpoint of the defined period is the same for both the original and adapted firing ramp functions.

[0020] The defined limit value in step c) can be a value determined in advance that ensures safe ignition without deflagrations.

[0021] In one embodiment of the method, it can be determined, at least during the execution of steps a) to c), that the flame goes out or begins to go out. Based on this, processes for ending the heating operation and subsequently restarting it (automatically) can be initiated.

[0022] In a preferred embodiment, the method proposed here is repeated regularly. An advantage is that the ignition ramp function can thus be continuously adapted to changing boundary conditions, such as wear of the gas stepper motor valve and / or changes in the fuel composition.

[0023] According to a further preferred embodiment, steps a) - c) are repeated several times, and an average value of the opening position of the gas stepper motor valve detected in step c) is calculated. The ignition ramp function can then be adjusted according to step d) using the average of the detected opening positions. An advantage of this embodiment is seen in increased process reliability due to a larger database.

[0024] Another aspect is also proposed: a computer program comprising commands that cause a heating device proposed here to execute a procedure proposed here.

[0025] Another aspect that is proposed is a machine-readable storage medium on which the computer program is stored. This machine-readable storage medium can be a computer-readable data carrier.

[0026] A control unit for a heating device is also proposed, configured to carry out a procedure presented here. For this purpose, the control unit can, for example, include or have a processor. In this context, the processor can, for example, execute the procedure stored in a memory (of the control unit). Preferably, at least the ignition ramp function and / or the defined limit value are stored in the same memory.

[0027] Another aspect is the proposal for a heating appliance with a control unit as presented here. This heating appliance is a gas-fired unit with a gas burner and a gas supply system that can deliver a mixture of gas and combustion air (electronic gas-air mixture) to the gas burner.

[0028] This document presents a method for operating a heating appliance with an electronic gas-air mixture, a computer program, and a heating appliance for carrying out the method, which at least partially solve the problems described with reference to the prior art. In particular, the method, the computer program, and the heating appliance each contribute to ensuring a reliable ignition process for the heating appliance. Furthermore, the proposed method is technically easy to implement, as no additional technical equipment is required.

[0029] In particular, the proposed method involves adjusting the ignition ramp function during heating operation, enabling permanent (continuous or intermittent) adaptation of the ignition ramp function to changes in the gas mixture (or its calorific value) and potential changes in components involved in mixture formation, especially the gas stepper motor valve. The ignition ramp function can be limited to a predefined threshold value for the flame ionization current, where this predefined threshold value can represent a limiting combustion air ratio (lambda value) that should not be undercut during ignition to avoid critical ignition events.

[0030] The invention and its technical context will now be explained in detail with reference to the figures. It should be noted that the figures are schematic and are not intended to limit the invention.

[0031] They represent: Fig. 1 : a sequence of a procedure proposed here, Fig. 2 : a control curve of a heating device, Fig. 3 : a representation of an adjustment of the ignition ramp function according to the proposed method, and Fig. 4 : a heating device suggested here.

[0032] Fig. 1 Figure 1 shows an exemplary and schematic representation of the sequence of a procedure proposed here. The procedure allows for the adjustment of an ignition ramp function of a heating device in operation. Procedure steps a) to d) are shown as blocks 110, 120, 130, and 140.

[0033] In block 110, according to step a), a process is carried out to determine the opening position of a gas stepper motor valve via an original ignition ramp function Z 0 (t).

[0034] Simultaneously with block 110, the ionization current I lon is recorded in block 120 according to step b).

[0035] In block 130, analogous to blocks 110 and 120 according to step c), the opening position of the gas stepper motor valve is detected when a predefined limit value of the ionization current I lon is reached.

[0036] In block 140, according to step d), the ignition ramp function Z(t) is adjusted taking into account the opening position of the gas stepper motor valve recorded in block 130 when a predefined limit value of the ionization current I lon is reached and an adapted ignition ramp function Z is defined.

[0037] Fig. 2 Figure 1 shows a control curve Rλn as a function of the ionization current I ion as a function of a fan speed n G. The control curve Rλn represents a nominal λ-value of the burner operation, for example a lambda value λ=1.3. The fan speed n G is an example of an operating parameter of a gas supply system of the heating appliance.

[0038] At a blower ignition speed nz, points Pmin and Pmax can be defined. Point Pmin corresponds to an ionization current I ion at the minimum opening position of the gas stepper motor valve and thus a maximum lambda value, for example, λ=1.6 for the ignition ramp function Z(t). Point Pmax defines an ionization current I ion at the maximum opening position of the gas stepper motor valve and thus a minimum lambda value, for example, λ=1.1, for the ignition ramp function Z(t). In this context, the defined limit value of the ionization current can be determined.

[0039] Fig. 3 Figure 1 shows a diagram depicting the opening position of the gas stepper motor valve during an ignition process as a function of time t. Time tZ defines the end of the ignition process, the ignition safety time. The function Z0(t) represented an original ignition ramp function that had not yet been adapted to tolerances of the gas stepper motor valve and environmental variables. Point ZD represents the opening position of the gas stepper motor valve, as recorded in block 130, when a predefined limit value of the ionization current is reached at time tZ. An adaptation of the original ignition ramp function Z0(t) can now be achieved by having an adapted ignition ramp function ZA(t) assume the value ZD at time tZ.The change value Δx is defined as the difference between the original ignition ramp function Z 0 (t) at time t Z and the opening position of the gas stepper motor valve recorded in block 130 when the predefined limit value ZD of the ionization current I lon is reached. A further adjustment can consist of the adapted ignition function ZA (t) passing through a point Z 0 (0)+ Δx at t=0.

[0040] Fig. 4Figure 1 shows an example of a heating appliance 1 proposed here, comprising a heat generator 11. An air intake duct 2 leads to the heat generator 11, in which a gas supply device 21, designed here as a blower, is arranged. The speed of the blower is a measure of the heating output of the heating appliance 1. A gas stepper motor valve 31 is arranged in a gas supply 3. An ionization electrode 41 is positioned in the heat generator 11 in the area of ​​a flame 4, by means of which an ionization current I ion of the flame 4 can be measured. An ignition device 42 is also arranged in the area of ​​the flame 4, configured to ignite the flame 4 during an ignition process.

[0041] A control unit 5 is electrically connected at least to the ionization electrode 41, the gas stepper motor valve 31 and the blower.

[0042] To carry out the proposed procedure, at least one ignition ramp function Z 0 (t) and a defined limit value of the ionization current I lon are stored in a memory in the control unit 5.

[0043] The method allows the adaptation of an ignition ramp function of a heating device to the tolerances of the gas stepper motor valve and environmental variables, thereby ensuring increased operational reliability when igniting the heating device. Reference symbol list

[0044] 1Heating unit 11Heat generator 2Air intake duct 21Gas supply device 3Gas supply 31Gas stepper motor valve 4Flame 41Ionization electrode 42Ignition device 5Control unit

Claims

1. Method for adjusting an ignition ramp function, which, during an ignition process, specifies an opening position of a gas stepper motor valve (31) for a defined period of time , of a heating device (1) with an electronic gas-air composite, comprising at least the following steps to be performed during heating operation: a) Method of opening the gas stepper motor valve (31) via the ignition ramp function; b) Detecting the ionisation current of a flame (4) during the execution of step a); c) Detecting the opening position of the gas stepper motor valve (31) when a defined limit value of the ionisation current detected in step b) is reached; d) Adjusting the ignition ramp function, taking into account the opening position of the gas stepper motor valve (31) detected in step c) when the defined limit value of the ionisation current is reached.

2. Method according to the preceding claim, wherein, when adjusting the ignition ramp function in step d), the opening position of the gas stepper motor valve (31) detected in step c) defines the maximum opening position of the adjusted ignition ramp function.

3. Method according to one of the preceding claims, wherein the method is repeated at defined time intervals.

4. Heating device (1) with an electronic gas-air composite comprising an ionisation electrode (41), a gas stepper motor valve (31) and a control unit (5), wherein the control unit (5) is adapted to perform a method according to claim 1.

5. Computer programme comprising instructions that cause a heating device (1) according to claim 4 to execute a method according to claim 1.

6. Machine-readable storage medium on which the computer programme according to claim 5 is stored.

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