Patent Application
20240295324
The invention relates to a device for electronic control for a low-emission log wood stove with two combustion chambers positioned one above the other in the optimized underfire principle according to the generic term of the first patent claim.
There are now various types of devices for regulating the air supply to optimize the combustion of solid fuels.
DE 20200311 U1 reveals a low-emission log wood-burning stove with an optimised underfire principle. This chimney has two superimposed combustion chambers which are separated by a combustion carrier/grate as a support for the solid fuel, whereby the lower combustion chamber serves as an afterburner chamber and ash box. To regulate the combustion, a handle is used, which operates a sealing device for the smoke exhaust in order to direct the combustion gases, produced during the combustion of the solid fuel in the first, upper combustion chamber, into the second, lower combustion chamber and to enable a low-emission and effective combustion.
The smoke is then extracted through an opening located in the lower combustion chamber.
This type of control has the disadvantage that all actuations of the closure device are carried out at the subjective discretion of the operator, on the basis of experience and feeling. The control by hand is very time-consuming, since depending on the state of the combustion again and again Corrections must be made. The actuation of the shutter cannot be carried out optimally, since the operator has no possibility to detect the temperature in the smoke extractor. A temperature detection is necessary to open or close the closure device at the optimal time or to determine the optimal time for refilling the solid fuel.
Furthermore, a control of a low-emission log wood fireplace with optimized underfire principle using a thermobimetal for actuating the closure device is known. Depending on the temperature surrounding the thermobimetal, the supply of fresh air is regulated. Here it is disadvantageous that if the thermobimetal closes the closure device and in the further course of the temperature drop is too large, for example by different conditions at the installation site and or the nature of the solid fuel (piece size, moisture content, etc.), the opening of the closure device can only take place after cooling of the thermobimetal. During the cooling period, a bad burn-up with increased pollutant emissions takes place. Optimal low-emission combustion cannot be achieved with this.
The skilled person is further aware of a regulation of the combustion air supply with the aid of a lambda probe. This principle is usually used for boilers for central heating and wood gasifiers. Here, the oxygen content in the combustion chamber or the residual oxygen content of the exhaust gas is permanently measured by the lambda probe and compared with the oxygen content of the air surrounding the boiler. The signal from the lambda probe can then be used to determine the necessary speed of a blower that regulates the supply of combustion air.
The disadvantage here is the need for a power connection, high acquisition costs and time-consuming installation.
It is becoming increasingly important to adapt the combustion process with solid fuel to ecological requirements and to continue to optimize it.
The invention is based on the problem to create a simple solution in design and manufacture for a device for electronic control for a low-emission log wood stove with two combustion chambers positioned one above the other in the optimized underfire principle, which regulates reliably, precisely, without mains connection, independently, without intervention of the operator, is adapted to the individual characteristics of the stove by a freely parameterizable program of the control unit and thus meet the latest requirements of the Combustion Ordinance for the reduction of pollutant emissions and other provisions for obtaining the Blue Angel quality seal and eliminate the disadvantages of the state of the art.
According to the invention, the problem is solved in that the device for electronic control for a low-emission log wood stove from two superimposed combustion chambers, separated by a support for solid fuel with an output to the lower combustion chamber, a smoke extractor, an output in the upper combustion chamber for smoke exhaust with a closable flap, an exit in the lower combustion chamber to the smoke extractor, a combustion chamber door with a door lock/handle and a door contact switch exist and are characterized therein that a control unit (controller), electrically connected with at least two temperature sensors and a door contact switch, an electric motor which actuates at least one actuator (flap) via transmission elements, controls, wherein the temperature detection in the smoke exhaust behind the output of the respective combustion chamber takes place at least one temperature sensor each, the temperature sensors the Detecting temperature change over time and the speed of the temperature change, the temperature target-actual evaluation by the control unit (controller) over parameterizable time periods serves as an evaluation criterion for the combustion state of the solid fuel, the degree of the outgassing process (size and/or moisture content of the solid fuel) is detected by the recording and evaluation of the temperature rise and the temperature drop over time, the target actual Temperature over time in comparison with the comparative values stored in the program for combustion optimization as an adaptive system takes place so that the respective nature of the solid fuel (moisture, type of wood, piece size . . . ) is taken into account for the optimal combustion process and the necessity of the new feed with solid fuel is determined via the program and displayed via a visual signaling device that is clearly visible to the user.
Thus, a solution was found with which the above-mentioned disadvantages of the prior art are eliminated.
Advantageous embodiments of the invention emerge from the dependent claims.
Thus, it proves to be a favorable design of the device that the opening or closing process initiated by the control unit of the actuator flap, due to the use of an electric drive (electric motor), can be carried out almost instantaneously.
Another favorable embodiment of the device is when the electric drive (electric motor) is optionally connected via transmission elements or directly to the actuator flap.
Another possible embodiment is that the control can be carried out either in battery or mains operation.
The signaling of the operating states “regular operation”, “recharging” or “disturbance” with its own coloring over a single optical signaling transmitter, leads to a further favorable design.
A supplementary embodiment is that a memory in the control unit that cannot be erased by the user records the operating hours, operating states, minimum and maximum temperatures for the purpose of traceability and, if necessary, can also serve to clarify warranty claims.
Exemplary embodiments of the device according to the invention is described in more detail below using an embodiment. It shows:
The stove 1 in this example consists of an upper combustion chamber 2 and a lower combustion chamber 3, separated by a shelf for the solid fuel 19. In this shelf is an outlet 4 to the lower combustion chamber 3. In the upper as well as in the lower combustion chamber 2 and 3 there are each an outlet 5 and 8 to the smoke outlet 7.
In the upper combustion chamber 2 is a valve 5 acting as an actuator which can close the output 6 to the smoke outlet 7 if necessary, as shown in
The mode of action of the low-emission log wood stove 1 with two superimposed combustion chambers 2 and 3 in the optimized underfire principle are known in the art. A more detailed presentation and explanation of the details is therefore omitted in this embodiment.
The description of the function of the device according to the invention follows the individual phases or modes of the combustion process. To illustrate the individual process steps, characterized by reference signs, the program flow chart shown in the drawings
The necessary power supply of the control unit 13 is provided by a battery-operated voltage source 15. As a voltage source 15 can also alternatively serve a mains connection. When applying the voltage to the control unit 13, either by inserting batteries into the voltage source or via the mains connection, a reference run is made by the electric motor 12 for determining the position of the actuator flap 5 and checking the function. The controller 13 is now ready for operation in stand-by mode (procedure step 14A). With the first opening of the firebox door 9 of the chimney 1 in the cold state, the control unit is activated from stand-by mode via the door contact switch 14 (method step 14B) and via the electric motor 12 and the transmission element 11, the actuator flap 5 is switched to the open position via the electric motor 2 and the transmission element 5 (
This process is repeated, controlled by the control unit 13, until a stable combustion has been established. The switch to the rule mode now takes place.
After a stable combustion has been achieved, by detecting the maximum temperature TAU max by the temperature sensor 18 (process step 18A) in the lower combustion chamber 3, the fall below the value of a specified temperature corridor (TAU ma tolerance) after evaluation in the Control unit 13 (method step 18B) activated a reload signal (method step 18C) and signaled by a visual display 16, which shows the operator the correct time for reloading (method step 16A). Due to different amounts of each recharged solid fuel 20, the temperature corridor (TAU max tolerance) is determined in its expansion, but not the temperature level (TN) this is detected and determined by the control unit 13 after each refilling
For refilling, the firebox door 10 is opened by actuating the door lock 9 and the door contact switch 14 is actuated, a signal to the control unit 13 is given (method step 14D), which in turn controls the electric motor 12 and opens the actuator flap 11 via the transmission element 5 (method step 5A). After closing the door (method step 14C), a parameterized waiting time tw3 (see) is activated (method step 13C) and the exhaust gas temperature is measured by the temperature sensor 17 in the smoke outlet 7 (method step 17D). After the expiry of the waiting period tw 3 (see) and exceeding the flue gas temperature TA (° C.) specified in the program, the actuator flap 5 is closed via the already known actuators 11 and 12 (method step 5B) and the combustion gases are led through the outlet 4 into the lower combustion chamber 3. After switching, it may happen that the temperature TAU (° C.), e.g. due to too large pieces of wood or too wet wood, etc., is not yet sufficient for the outgassing process. In this case, a strong temperature drop of the flue gas is measured by the temperature sensor 17 and detected by the control unit 13 (method step 17E) and actuator flap 5 (method step 5A) opened. As a result, a parameterized waiting time t«4 (see) is activated again (method step 13D) and the exhaust gas temperature in the smoke outlet 7 is measured by the temperature sensor 17 until a preset temperature Tsoii (° C.) is reached again. This process is repeated, controlled by the control unit 13, until a stable combustion has been established.
If the exhaust gas temperature TA (° C.), measured by the temperature sensor 17 falls below a specified value TA son (method step 17F) and is no longer refilled, the actuator flap 5 is opened (method step 5A). The remaining solid fuel 20 burns down and the chimney cools. If the temperature measured by temperature sensor 17 in smoke outlet 7 drops below 50° C., the control unit 13 deactivates and goes into stand-by mode.
The device according to the invention is of course not limited to the embodiment shown. Rather, changes and modifications are possible without leaving the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 005 202.9 | Aug 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2021/000135 | 8/25/2020 | WO |
