EP0614046A1 - Control device for gas burner automats of heating installations - Google Patents

Abstract

In order to simplify the design of an automatic gas firing unit of heating installations which are intended to have a high efficiency and operate with a low degree of pollution even in part-load ranges, the adjusting member for the air is a fan of variable speed which can be driven by a DC motor which can be controlled by, in particular, digital pulse-width-modulated control signals of a control unit to which the regulator is applied. The gas valve is re-adjusted as a function of the air pressure in the line leading from the fan to the burner. <IMAGE>

Description

The invention relates to a control or regulating device for automatic gas firing systems of heating systems of the type mentioned in the preamble of claim 1.

Such devices are already known. The heating power depends on the amount of combustible fluid supplied to the burner and the ratio of this amount to the combustion air supplied to the burner. It is advisable to set a ratio between fluid and air that is determined for optimum efficiency. In known control devices, the air is driven by a fan at a constant speed in a connecting line to the burner, while a throttle valve in the connecting line which can be controlled by the controller serves to control the air pressure in the connecting line. The setting element for the pressure of the combustible fluid supplied to the burner is then controlled as a function of this air pressure.

The invention has for its object to simplify such a control or regulating device above all constructively. The saving in energy is desirable and the burner should enable high efficiency and low-pollutant operation even in burners of relatively low output up to around 30 kW even in partial load ranges.

The invention is characterized in claim 1. Further embodiments of the invention are claimed or described in subclaims and in the description of the figures.

In the invention, the use of a throttle valve for controlling the air pressure can be dispensed with. Instead, the air pressure is varied by controlling the speed of the fan. This not only avoids the effort of an additional throttle valve with the corresponding mechanically moving parts and their susceptibility to malfunction, but can also save drive energy since the blower is in contrast to the prior art, in which it is always at maximum speed regardless of the size of the required air pressure must run in the connecting line, the required air pressure can be adjusted accordingly in the speed. A DC motor is used to drive the continuously modulating blower, which can be controlled by, in particular, pulse-width-modulated, that is to say digital, control signals from a control unit which is acted upon by the controller.

As such, it is already known (DE-OS 29 20 343) to use drive elements in the form of motors for valves in the fuel and air supply lines in burners and to control them as a function of measured variables; however, these are servomotors that regulate the position of valves.

While the dependency of the fluid pressure on the air pressure can be established in accordance with known control devices in that the fluid pressure is regulated as a function of the air pressure or is tracked in order to supply the desired fluid / air ratio to the burner, the air pressure is controlled as a function of the heat requirement or parameters decisive for the heating via the speed control of the DC motor and therefore of the fan.

Such control and regulating devices can be used for example for small gas heaters (wall or floor models) with gas fan burners, with which both the heating water of a heating system and the process water of single-family houses or apartments can be regulated, in particular in the power range up to 30 kW. The control device can also be used for fan burners in intermittent operation with devices for complete premixing of the fluid / air mixture and with closed combustion chambers. As already explained above, it is also recommended to use the air pressure as a reference variable for the gas pressure regulator of the compact gas control system. A modulation range of at least about 1: 3, for example 10-30 kW, but preferably over 1: 5, enables optimum efficiency and low-pollution operation even in the low-load range.

It is advisable to sense the speed of the blower or DC motor, in particular with the aid of Hall sensors, and to compare it with corresponding speed setpoints in order to generate output signals depending on the type or size of the difference, which in turn are used to control the pulse-width-modulated signals for the DC motor of the Blower serve. The actual speed values are used in particular for plausibility tests in automatic firing systems; a certain actual speed value would have to be exceeded during the pre-rinse time.

If gas is used as the combustible fluid, a control valve is used as an adjusting element for the fluid.

The motor that drives the blower is, in particular, a DC motor with a supply voltage of about 35-40 V. It takes up little space and also causes relatively low costs.

The air pressure in the connecting line between the fan and burner can also be used for other control tasks. A switch-off can be carried out if the air pressure falls below a limit. While the actual speed values of the blower or its DC motor sensed via the Hall sensors also represent a measure of the air pressure in the connecting line, a slipping of the fan from the blower shaft or the adjustment of fan blades could lead to a reduction in air pressure even if the blower speed remains the same. However, if the air pressure in the connecting line is sensed and it is found that it has fallen below a limit value, this is an indication of a malfunction. During the "start-up phase" - during pre-rinsing - there must be a certain air pressure before the burner control unit initiates further steps so that there is always an air pressure determination. In "burner mode" - after the "start-up phase" - on the other hand, it is sufficient if the air pressure is only checked occasionally and in particular whenever the actual speed value is greater than a certain setpoint; if there is insufficient air pressure, the burner control unit initiates a repetition.

Depending on a speed limit value, an ignition signal can also be generated for the ignition unit in order to start the burner operation by means of an automatic burner control. The control device then acts simultaneously as part of an automatic burner control.

Likewise, the control can be done so that a timer for a predetermined pre-purge time for a high fan speed and a high air pressure, i.e. a large air flow through the burner and boiler room, but at the same time prevents the supply of flammable fluid to the burner

Correspondingly, a signal can also be generated when the supply of combustible fluid is shut off, as a result of which the control unit continues to apply a control signal to the blower's direct current motor for a certain time, while the fuel supply is shut off in order to flush the burner and boiler room and the chimney with air and combustion gases to free.

The effect of this pre-rinsing or post-rinsing is optimal if the control signals drive the speed of the DC motor up to full load, since the greatest amount of air per unit time is then enforced.

During the ignition time, the fan can be set to an adjustable value, e.g. between 50 and 70% of its maximum speed, i.e. its full load, can be reduced in order to achieve optimal ignition when used as an automatic burner control.

Figur 1

ein schematisches Schaubild einer erfindungsgemäßen Steuereinrichtung;

Figur 2

ein zeitabhängiges Ablaufdiagramm von Funktionen von Aggregaten der Steuerungseinrichtung;

Figur 3

Drehzahlbereiche während verschiedener Zeitabschnitte der Steuereinrichtung beim Anfahren des Brennerbetriebs (als Feuerungsautomat) und während des Heizungsbetriebs (als Temperaturregler) und

Figur 4

eine schematische Darstellung einer elektronischen Steuereinrichtung, mit der die beiden Aufgaben sowohl eines Feuerungsautomaten als auch eines Temperaturreglers in integrierter Bauweise nach einer besonderen Ausbildung der Erfindung lösbar sind.

Exemplary embodiments of the invention will now be explained in more detail with reference to the drawing. Show:

Figure 1

a schematic diagram of a control device according to the invention;

Figure 2

a time-dependent flow chart of functions of Units of the control device;

Figure 3

Speed ranges during different periods of the control device when starting the burner operation (as a burner control) and during heating operation (as a temperature controller) and

Figure 4

is a schematic representation of an electronic control device with which the two tasks of both a burner control and a temperature controller can be solved in an integrated design according to a special embodiment of the invention.

According to FIG. 1, gas flows as a combustible fluid F via a feed line ZL to the burner B of a heating boiler HK. The gas pressure P _{F of} the fluid F is regulated by a pneumatic constant or ratio pressure regulator valve V as a function of the air pressure P _A , which is led from the outlet of the blower G to the control valve V. The temperature controller R adjusts the speed n _{IST of} the motor M _G and thereby also the air pressure P _A in the connecting line VL. The constant pressure control valve V adjusts the gas pressure P _{F in} accordance with the actual value of the air pressure P _A , so that the optimum amount of gas is always adjusted to the current amount of air. The DC motor M _G can be set at speeds between approximately 200 and 6000 rpm with a power of up to 22 VA. The air A is conducted to the burner B via the connecting line VL. The air pressure P _A in the connecting line VL is determined by the air pressure sensor F _A according to a special embodiment of the invention. The fan G is driven by a 39 V DC motor M, the speed of which can be sensed as the actual speed value n _ACT using a speed sensor F _n , in particular a Hall sensor.

oder

in Relation gesetzt werden. Bei diesem Beispiel erzeugt der Regler R ein Ausgangssignal, das dem Drehzahl-Sollwert n entspricht und im Vergleicher mit dem Drehzahl-Istwert n_IST verglichen wird. In Abhängigkeit von der Art (plus oder minus) und/oder der Größe der Differenz dieser beiden Drehzahlwerte kann das Steueraggregat St_G beeinflußt werden, das seinerseits entsprechende Steuersignale S_ST zur Steuerung bzw. Regelung der Drehzahl des Gleichstrommotors M erzeugen könnte.The temperature is regulated via the controller R as a function of actual temperature values, for example the room temperature T _R , the boiler temperature T _K , the outside temperature T _A and / or the flow temperature T _V , which is sent to the controller via an analog / digital converter A / D R supplied and there with setpoint values, eg

or

be put in relation. In this example, the controller R generates an output signal that corresponds to the speed setpoint n and is compared in the comparator with the speed actual value n _ACTUAL . Depending on the type (plus or minus) and / or the size of the difference between these two speed values, the control unit St _G can be influenced, which in turn could generate corresponding control signals S _ST for controlling or regulating the speed of the DC motor M.

WA:

der Wärmebedarf bzw. die Wärmeanforderung durch den Regler

FS:

Flammensignal

LP:

Luftdruckmeldung des externen Luftdruckprüfers (Kontakt) F_A

STB:

Sicherheitstemperaturbegrenzer

V:

Gasventil in der Zuleitung ZL

Z:

Zündsignal zum Zündaggregat

S_ST:

Steuersignal zum Gleichstrommotor des Gebläses

n_IST:

Drehzahl-Istwert abgeleitet vom Halldrehzahlfühler F_n

thl:

Zeit zum Hochlaufen des Gebläses

tv:

Vorspülzeit

tbre:

Bremszeit für das Gebläse

tz:

Zündzeit

ts:

Sicherheitszeit

tb:

Betriebszeit der Brennerregelung

tn:

Nachspülzeit

t:

Zeit

A:

Startbefehl (Reglereinschaltung)

B:

Beginn des Brennerbetriebs

C:

Beginn der Außerbetriebsetzung

D:

Ende der Außerbetriebsetzung und Übergang in die Heimlaufzeit

In the flow chart according to FIG. 2, the necessary signals are denoted in the rows WA to Z with thick lines and impermissible signals with thin lines. Here mean:

WA:

the heat requirement or the heat requirement by the controller

FS:

Flame signal

LP:

Air pressure message from the external air pressure tester (contact) F _A

STB:

Safety temperature limiter

V:

Gas valve in the ZL supply line

Z:

Ignition signal to the ignition unit

S _ST :

Control signal to the fan DC motor

n _IS :

Actual speed value derived from Hall speed sensor F _n

thl:

Time to start up the fan

tv:

Pre-rinse time

tbre:

Braking time for the blower

tz:

Ignition time

ts:

Security time

tb:

Operating time of the burner control

tn:

Rinse time

t:

time

A:

Start command (controller activation)

B:

Start of burner operation

C:

Start of decommissioning

D:

End of decommissioning and transition to home life

At time A, the controller gives the control device a start command to the automatic firing device, which happens, for example, when the temperature T in the process water circuit or in the heating circuit has dropped below a minimum value. During the run-up time thl, the DC motor M _{G of} the blower G is subjected to control signals S _ST , in particular pulse-width-modulated, so that its speed n _{ACT increases} to a maximum value as soon as an (adjustable) setpoint (speed setpoint n _SET ) is reached and the external one Air pressure detector LP closes its contact. The pre-rinse time tv begins. At this time, a certain air pressure P _{A is} reached in the connecting line VL. In order to keep the pre-purge time short, it is advisable to run the fan G at full load during the pre-purge time tv. Via the feedback of the _actual speed value n ACTUAL and the air pressure actual value (LP contact closed), the burner control can continue its function program when the required minimum values are reached. If the speed and / or the air pressure have not reached the predetermined limit value before the start of the pre-purge time tv, a lockout occurs.

According to Figure 3, the speed must _IS n G of the fan during the pre-purge time tv a minimum value of, for example, 2400 rev / min exceed.

During the braking time tbre, the speed of the fan G is reduced in accordance with lower control signals S _ST .

An ignition signal Z is then applied to an ignition unit of the burner B during the ignition time tz, for example to ignition electrodes thereof, while the fan G continues to run at the same speed, for example 40% of the maximum speed, but the maximum value of 2900 rpm in this example according to FIG 3 may not exceed. In the course of the ignition time tz, the valve in the supply line ZL opens, i.e. the pneumatic pressure regulator V for the combustible fluid F, which serves as an adjusting unit, whereby the safety time ts begins, within which a flame signal must be detected by a flame sensor, otherwise the lockout occurs. This safety time ts is, for example, up to 10 s, while the pre-rinsing time tv can be, for example, up to 50 s and the maximum braking time tbre is also of this order of magnitude.

If the flame message is present at the end of the safety time ts, the transition to the operating position takes place and the burner operating time tb begins, during which the fan speed n _{ACT is} dependent on the pulse-width-modulated control signals S _ST and this in turn is dependent on the output signals specified by controller R in a speed range (adjustable), which, according to FIG. 3, moves between approximately 600 and 6000 rpm, as the maximum value specification and plausibility limit, while the highest speed is typically 4000 rpm. It is not necessary to monitor the air pressure during the burner operating time tb, since the speed sensor Fn with its output signals offers sufficient security.

If the flow temperature T _{V is} higher than the switch-off threshold, the burner operation is set by the controller R at time C by stopping the supply of combustible fluid F to the burner B by the adjusting member V. However, the fan G can remain in operation in order to blow off combustion residues. During this blocking time is tsp the fan speed N _is ramped up (programmed) to full load, then the home run whereupon as a regular transition in the standby phase followed.

According to the special embodiment of the invention according to FIG. 4, the device is equipped with a microcomputer MC; it takes on both the tasks of the temperature controller and the tasks of the burner control. A further microcomputer MC 1 can be in data exchange relationship with the microcomputer MC, which takes over a monitoring function in order to ensure the safety of the burner control. The flame sensor F _F emits output signals both to the microcomputer MC and to the other microcomputers MC 1 serving for monitoring purposes. Both microcomputers MC, MC1 can independently close or open two switching elements for the control terminals of the gas valve. The two computers also monitor each other for correct functioning.

A setting device allows the programming of the microcomputer MC by entering data into the memory SP. The microcomputer MC initiates the initiation of control signals S _ST in the signal generator SG. The comparator Ve compares the actual speed value n _ACTUAL with the programmed speed setpoint values n _TARGET , in order to initiate corresponding functions in the event of deviations or exceeding or falling short of the speeds shown in FIG. The two microcomputers MC, MC1 act on two switches S1, S2 connected in series in the 24 V AC voltage line WL; the line WL supplies the drive unit AA for the fuel gas valve V with electrical alternating current.

An advantage of this integration of the electronic control device, which is arranged in particular on, for example, only two printed circuit boards, is that it is unnecessary to use a separate control device with the associated components on the one hand for the burner control and on the other hand for the temperature controller. Thus, a single signal generator SG is sufficient to generate and deliver the pulse-width-modulated control signals S _ST , which perform their task both for controlling the start-up program (in the function as an automatic burner control unit) and for regulating the temperature during burner operation (in the function as a controller). Which are the Hall speed sensor F _n sensed actual rpm values n _IS not only during the start-up program (function as automatic firing), but also during the regular burner operation to control and regulate evaluated.

The air pressure switch or sensor F _A ensures that when the burner controls are operated, ie in the "start-up phase", sufficient air pressure is always built up for purging the burner chamber and fireplace. During the operation of the temperature controller R, uz in modulating operation, the speed n of the fan G can drop so low that the air pressure sensor F _A no longer responds if the heat demand WA is low.

In this case, the use of an additional air pressure sensor is recommended, which responds to lower air pressure corresponding to a lower fan speed. Depending on the speed range, one or the other air pressure sensor can then be used. In order to save such a second air pressure sensor, it is advantageous to switch the switching state each time a high heat requirement occurs, which results in such a high speed n of the fan G that the air pressure sensor F _A must respond of the air pressure sensor F _A. If the air pressure sensor F _A does not respond, the system is switched off and the starting procedure is repeated.

The air pressure sensor F _{A also} responds to the safety test, according to which there is a brief switch-off and restart at least once every 24 hours using the automatic burner control.

Claims (10)

Control device for gas burner controls for heating systems, in which the burner for the boiler is gas as a combustible fluid, the pressure of which can be adjusted by an adjusting element, and air can be supplied via a blower and a connecting line, in which the air pressure in the connecting line is also possible is adjustable by an adjusting element and a constant or ratio pressure controller controls or regulates or adjusts the optimal gas quantity as a manipulated variable depending on the air pressure or the conveyed air quantity in the connecting line,
characterized by
that a blower (G) with variable speed serves as an adjusting element for the air, which can be driven by a direct current motor (M _G ), which can be controlled by control signals (S _ST ) of a control unit (St _G ) which the controller (R) acts on . Device according to claim 1,
characterized,
that the control unit (St _G ) acts on the DC motor (M _G ) with digital pulse-width-modulated control signals (S _ST ). Device according to claim 1 or 2,
characterized,
that the control unit (St _G ) can be controlled as a function of output signals from a comparator which compares the actual speed value (n _ACTUAL ) of the blower (G) with a speed setpoint value (n _SET ), which the controller (R) considers Output signal and thereby regulates the speed. Device according to one of the preceding claims,
characterized,
that an air pressure sensor (F _A ) senses the air pressure in the connecting line (VL) between the fan (G) and the burner (B) when the actual speed value (n _ACTUAL ) is greater than a speed setpoint value (n _SET ) and that the burner control unit carries out repetition, ie switching off and on again, if the air pressure is insufficient. Device according to one of the preceding claims,
characterized,
that Hall sensors (F _n), digital sound signals produce than actual rotational speed values (n _IST). Device according to one of claims 3-5,
characterized,
that the adjusting element for the air pressure is designed as a purely pneumatic constant pressure control valve (V) with two series-connected shut-off valves which can be controlled by the air pressure (P _A ) in the connecting line (VL). Device according to one of the preceding claims,
marked by
the use of a direct current motor (M _G ) for the fan (G), with which a modulation range of at least 1: 3 of the burner (B) can be operated. Device according to claim 7,
marked by
the use of a DC motor (M _G ) for the fan (G), with which a modulation range of about 1:10 of the burner (B) can be operated. Device according to one of the preceding claims,
marked by
the combination with a temperature controller (R), which controls the air volume depending on the heat requirement (WA), e.g. on the outside temperature (T _A ), the room temperature (T _R ) of the room to be heated, the boiler temperature and / or the flow temperature (T _V ), changed as a manipulated variable. Use of a device according to one of the preceding claims in connection with a temperature controller ( _R ) which controls the boiler temperature and / or the flow temperature (T _V ) as a function of the heat requirement (WA), for example the room temperature (T _R ) and / or the outside temperature , regulates.

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