EP0789504A2 - Temperature measuring device for the control circuit of an electric radiant heater - Google Patents
Temperature measuring device for the control circuit of an electric radiant heater Download PDFInfo
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- EP0789504A2 EP0789504A2 EP97101687A EP97101687A EP0789504A2 EP 0789504 A2 EP0789504 A2 EP 0789504A2 EP 97101687 A EP97101687 A EP 97101687A EP 97101687 A EP97101687 A EP 97101687A EP 0789504 A2 EP0789504 A2 EP 0789504A2
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- Prior art keywords
- heating conductor
- temperature
- measuring device
- resistance
- control circuit
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
- H05B3/74—Non-metallic plates, e.g. vitroceramic, ceramic or glassceramic hobs, also including power or control circuits
- H05B3/746—Protection, e.g. overheat cutoff, hot plate indicator
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B2213/00—Aspects relating both to resistive heating and to induction heating, covered by H05B3/00 and H05B6/00
- H05B2213/07—Heating plates with temperature control means
Definitions
- the invention relates to a temperature measuring device for a control circuit, in particular an electric radiant heater with a heating conductor arranged below a glass ceramic cooktop.
- DE 31 00 758 A1 describes a switching device for cooking appliances with a glass ceramic plate, a mechanical expansion element being arranged as a temperature sensor between the glass ceramic plate and a heating conductor.
- a switching contact coupled to the expansion element, the heating conductor is switched off when a target temperature is reached and switched on again with a certain hysteresis.
- a temperature controller for electric hot plates with a hydraulic temperature sensor is known from DE 28 50 389 B2.
- a temperature control for electrical surface heating is known.
- a heat-sensitive element is arranged between the heating element and a temperature sensor electrode.
- additional elements namely the temperature sensor electrode and the heat-sensitive element, are also required for temperature detection.
- the object of the invention is to propose a temperature measuring device of the type mentioned, in which the heating conductor itself is sufficient for the temperature detection.
- the above object is achieved in a temperature measuring device of the type mentioned at the outset in that a changeover switch is provided, which connects the heating conductor cyclically to a resistance measuring circuit, which detects the respective temperature-dependent ohmic resistance value of the heating conductor and generates a temperature-proportional control signal for the control circuit.
- heating conductor wires that can be used for radiant heating systems have known resistance characteristics or temperature coefficients. According to the invention, the respective resistance value of the heating conductor is recorded during operation and evaluated to regulate the heating power. This eliminates the need for a separate temperature sensor.
- the heating conductor therefore has a double function, in that it heats the hob and detects its temperature on the one hand, so that the control circuit regulates the temperature of the hob to an adjustable setpoint.
- the resistance measuring circuit only evaluates the ohmic resistance value of the heating conductor after a cooling time as a control signal for the control circuit, the cooling time being dimensioned such that the temperature of the heating conductor reflects the temperature of the Cooktop is.
- the resistance measuring circuit generates a switch-off signal for the control circuit in the event of a heating conductor resistance value which occurs when the heating conductor is overheated. It is achieved in that the heating conductor can be operated up to very close to its limit temperature. This has the advantage that for the calculation of the life span of the heating conductor to be guaranteed, at most small safety reserves have to be considered. The dimensioning of the heating conductor can thus be fully utilized in operation. This switch-off signal is only effective for a short time until the temperature of the heating conductor has dropped below the excess temperature.
- the resistance measuring circuit In order to detect faults in the heating conductor, such as a short circuit and / or an interruption in the heating conductor, the resistance measuring circuit generates a switch-off signal for the control circuit and an alarm signal if the resistance value is outside the normal operating range.
- the temperature measuring device described can be used not only with a radiant heater, but also with other heaters in which the heating wire is in close proximity to the measuring point. Since the heating wire must be separated from the energy supply circuit to determine the ambient temperature, use is particularly possible where a large thermal mass is to be heated, as is the case, for example, with night storage heaters.
- a heating conductor (2) is arranged at a distance in the usual manner below a hob (1) of a glass ceramic plate.
- the heating conductor (2) forms a spiral heating coil.
- the heating conductor (2) consists of a resistance wire with a positive temperature coefficient.
- the heating conductor (2) is connected to an energy regulator (3) which is connected to the electrical network (4).
- the energy regulator (3) works with an electronic load switch (5) on which the heating conductor (2) is connected via a two-pole switch (6).
- the switch (6) is preferably formed by electronic components.
- a resistance measuring circuit (7) is connected to the changeover switch (6), which has measuring electronics (8) and evaluation electronics (9).
- the resistance measuring circuit (7) generates a control signal for a control circuit (10) which controls the electronic load switch (5) and the changeover switch (6).
- a setpoint adjuster (11) is connected to the control circuit (10).
- the heating conductor (2) is connected to the network (4) via the load switch (5) and a corresponding load current flows through it.
- the heating conductor (2) glows and heats the cooktop (1) or a vessel standing on it by means of radiant heat.
- the control circuit (10) switches the changeover switch (6) so that the glowing heating conductor (2) is connected to the measuring electronics (8).
- the evaluation electronics (9) generate a corresponding temperature-proportional control signal for the control circuit (10) from the measured resistance value.
- the resistance value is evaluated which is available immediately after the switch (6) has been switched over (cf. t1 in FIG. 2), then this corresponds to the annealing temperature (approximately 1100 ° C.) of the heating conductor (2). Evaluating this inherent resistance of the heating conductor (2) is advantageous if the circuit described is intended to prevent a maximum annealing temperature of the heating conductor (2) from being exceeded. When the maximum annealing temperature has been reached, the heating conductor (2) remains switched off from the mains (4) for a certain time.
- the temperature of the hob (1) is to be detected.
- the previously switched on, glowing heating conductor (2) remains switched off for a certain cooling time (t2-t1, for example about 1s) until it no longer glows or only glows dark. This is the case in the temperature range of around 750 ° C. Goes into the temperature prevailing on the heating conductor (2) now the temperature of the hob (1). Its resistance is therefore an image of the temperature of the hob (1) (cf. t2, t3 in FIG. 2).
- the cooling time can have a fixed value.
- the measuring time (t3-t2) is, for example, about 0.3 s. It is also possible to carry out the measurement in some points of the e-function immediately after the time (t1) and to extrapolate the further curve profile from the measured value profile and then to calculate the ambient temperature.
- the total measuring time can be shorter than the cooling time (t2-t1). Depending on the desired accuracy, the measurement can be stopped at an earlier or later time (before t2).
- the total cooling time (t3-t1) is significantly shorter than the cycle time specified above, after which the measurement described takes place again and again, so that the actual heating time is longer than the measuring time.
- the control circuit (10) switches off the load switch (5) before the changeover switch (6) switches from the load switch (5) to the resistance measuring circuit (7) is switched, and only switches on the load switch (5) when after the measuring process the changeover switch (6) is switched back from the resistance measuring circuit (7) to the load switch (5).
- the resistance measuring circuit (7) it is also possible to detect a resistance value that lies outside the normal operating range and to generate a switch-off signal for the control circuit (10) and an alarm signal.
- a resistance value outside the normal operating range is, for example, a short circuit and / or an interruption in the heating conductor (2).
- a resistance value which is not customary in operation is also one which is substantially smaller than the resistance value occurring at room temperature and / or which is significantly greater than the resistance value occurring at the maximum annealing temperature.
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- Ceramic Engineering (AREA)
- Electric Stoves And Ranges (AREA)
- Control Of Resistance Heating (AREA)
Abstract
Description
Die Erfindung betrifft eine Temperaturmeßeinrichtung für eine Regelschaltung insbesondere eines elektrischen Strahlungsheizgeräts mit einem unterhalb eines Glaskeramik-Kochfeldes angeordneten Heizleiter.The invention relates to a temperature measuring device for a control circuit, in particular an electric radiant heater with a heating conductor arranged below a glass ceramic cooktop.
In der DE 31 00 758 A1 ist eine Schalteinrichtung für Kochgeräte mit Glaskeramikplatte beschrieben, wobei zwischen der Glaskeramikplatte und einem Heizleiter ein mechanisches Ausdehnungselement als Temperaturfühler angeordnet ist. Mittels eines mit dem Ausdehnungselement gekoppelten Schaltkontakts wird der Heizleiter bei Erreichen einer Solltemperatur abgeschaltet und mit einer gewissen Hysterese wieder eingeschaltet.DE 31 00 758 A1 describes a switching device for cooking appliances with a glass ceramic plate, a mechanical expansion element being arranged as a temperature sensor between the glass ceramic plate and a heating conductor. By means of a switching contact coupled to the expansion element, the heating conductor is switched off when a target temperature is reached and switched on again with a certain hysteresis.
Ein Temperaturregler für Elektrokochplatten mit einem hydraulischen Temperaturfühler ist aus der DE 28 50 389 B2 bekannt.A temperature controller for electric hot plates with a hydraulic temperature sensor is known from DE 28 50 389 B2.
In der älteren Deutschen Patentanmeldung 195 22 748 ist eine Regeleinrichtung für eine Kochplatten-Strahlungsbeheizung beschrieben. Der auch hier vorgesehene mechanische Ausdehnungsfühler ist mittels eines Zusatzheizkörpers, dessen Leistung mittels eines Stellgliedes einstellbar ist, zusätzlich beheizbar.In the older German patent application 195 22 748 a control device for a hot plate radiant heating is described. The mechanical expansion sensor also provided here can be additionally heated by means of an additional heating element, the output of which can be adjusted by means of an actuator.
Bei dem genannten Stand der Technik ist in allen Fällen ein eigenes Fühlerelement zur Erfassung der Temperatur des Kochfeldes erforderlich.In the prior art mentioned, a separate sensor element for detecting the temperature of the hob is required in all cases.
Aus der DE 29 36 890 C2 ist eine Temperaturregelung für eine elektrische Oberflächenbeheizung bekannt. Zwischen dem Heizelement und einer Temperaturfühlerelektrode ist ein wärmeempfindliches Element angeordnet. Das Heizelement selbst ist zwar Teil der Temperaturfühleranordnung, jedoch sind auch hier zusätzliche Elemente, nämlich die Temperaturfühlerelektrode und das wärmeempfindliche Element, zur Temperaturerfassung nötig.From DE 29 36 890 C2 a temperature control for electrical surface heating is known. A heat-sensitive element is arranged between the heating element and a temperature sensor electrode. Although the heating element itself is part of the temperature sensor arrangement, additional elements, namely the temperature sensor electrode and the heat-sensitive element, are also required for temperature detection.
Aufgabe der Erfindung ist es, eine Temperaturmeßeinrichtung der eingangs genannten Art vorzuschlagen, bei der für die Temperaturerfassung der Heizleiter selbst genügt.The object of the invention is to propose a temperature measuring device of the type mentioned, in which the heating conductor itself is sufficient for the temperature detection.
Erfindungsgemäß ist obige Aufgabe bei einer Temperaturmeßeinrichtung der eingangs genannten Art dadurch gelöst, daß ein Umschalter vorgesehen ist, der den Heizleiter zyklisch an eine Widerstandsmeßschaltung legt, die den jeweiligen temperaturabhängigen ohmschen Widerstandswert des Heizleiters erfaßt und ein temperaturproportionales Steuersignal für die Regelschaltung erzeugt.According to the invention, the above object is achieved in a temperature measuring device of the type mentioned at the outset in that a changeover switch is provided, which connects the heating conductor cyclically to a resistance measuring circuit, which detects the respective temperature-dependent ohmic resistance value of the heating conductor and generates a temperature-proportional control signal for the control circuit.
Handelsübliche, für Strahlungsbeheizungen verwendbare Heizleiterdrähte weisen bekannte Widerstandskennlinien bzw. Temperaturkoeffizienten auf. Erfindungsgemäß wird im Betrieb der jeweilige Widerstandswert des Heizleiters erfaßt und zur Regelung der Heizleistung ausgewertet. Dadurch erübrigt sich ein eigener Temperaturfühler. Der Heizleiter hat also eine Doppelfunktion, indem er einerseits das Kochfeld beheizt und andererseits dessen Temperatur erfaßt, so daß die Regelschaltung die Temperatur des Kochfeldes auf einen einstellbaren Sollwert regelt.Commercially available heating conductor wires that can be used for radiant heating systems have known resistance characteristics or temperature coefficients. According to the invention, the respective resistance value of the heating conductor is recorded during operation and evaluated to regulate the heating power. This eliminates the need for a separate temperature sensor. The heating conductor therefore has a double function, in that it heats the hob and detects its temperature on the one hand, so that the control circuit regulates the temperature of the hob to an adjustable setpoint.
Um sicherzustellen, daß die Widerstandsmeßschaltung die am Kochfeld herrschende Temperatur und nicht nur die Eigentemperatur des glühenden Heizleiters erfaßt, wertet die Widerstandsmeßschaltung den ohmschen Widerstandswert des Heizleiters erst nach einer Abkühlzeit als Steuersignal für die Regelschaltung aus, wobei die Abkühlzeit so bemessen ist, daß die Temperatur des Heizleiters ein Abbild der Temperatur des Kochfeldes ist.To ensure that the resistance measuring circuit the temperature prevailing on the hob and not only the intrinsic temperature of the glowing heating conductor, the resistance measuring circuit only evaluates the ohmic resistance value of the heating conductor after a cooling time as a control signal for the control circuit, the cooling time being dimensioned such that the temperature of the heating conductor reflects the temperature of the Cooktop is.
In vorteilhafter Weiterbildung der Erfindung erzeugt die Widerstandsmeßschaltung bei einem Heizleiter-Widerstandswert, der bei einer Übertemperatur des Heizleiters auftritt, ein Abschaltsignal für die Regelschaltung. Es ist dadurch erreicht, daß der Heizleiter bis sehr nahe an seine Grenztemperatur betrieben werden kann. Dies hat den Vorteil, daß für die Berechnung der zu gewährleistenden Lebensdauer des Heizleiters höchstens geringe Sicherheitsreserven berücksichtigt werden müssen. Die Dimensionierung des Heizleiters kann damit im Betrieb voll ausgenutzt werden. Dieses Abschaltsignal wirkt nur kurzzeitig, bis die Temperatur des Heizleiters unter die Übertemperatur abgesunken ist.In an advantageous development of the invention, the resistance measuring circuit generates a switch-off signal for the control circuit in the event of a heating conductor resistance value which occurs when the heating conductor is overheated. It is achieved in that the heating conductor can be operated up to very close to its limit temperature. This has the advantage that for the calculation of the life span of the heating conductor to be guaranteed, at most small safety reserves have to be considered. The dimensioning of the heating conductor can thus be fully utilized in operation. This switch-off signal is only effective for a short time until the temperature of the heating conductor has dropped below the excess temperature.
Um Störungen des Heizleiters, wie beispielsweise einen Kurzschluß und/oder eine Unterbrechung des Heizleiters, zu erfassen, erzeugt die Widerstandsmeßschaltung bei einem Widerstandswert außerhalb des betriebsüblichen Bereichs ein Abschaltsignal für die Regelschaltung und ein Alarmsignal.In order to detect faults in the heating conductor, such as a short circuit and / or an interruption in the heating conductor, the resistance measuring circuit generates a switch-off signal for the control circuit and an alarm signal if the resistance value is outside the normal operating range.
Die beschriebene Temperaturmeßeinrichtung läßt sich nicht nur bei einem Strahlungsheizgerät, sondern auch bei anderen Heizgeräten verwenden, bei denen der Heizleiterdraht in unmittelbarer Nähe zur Meßstelle liegt. Da der Heizleiterdraht für die Ermittlung der Umgebungstemperatur vom Energie-Speisekreis getrennt werden muß, ist ein Einsatz besonders dort möglich, wo eine große thermische Masse erhitzt werden soll, wie dies beispielsweise bei Nachtspeicheröfen der Fall ist.The temperature measuring device described can be used not only with a radiant heater, but also with other heaters in which the heating wire is in close proximity to the measuring point. Since the heating wire must be separated from the energy supply circuit to determine the ambient temperature, use is particularly possible where a large thermal mass is to be heated, as is the case, for example, with night storage heaters.
Weitere vorteilhafte Ausgestaltungen der Erfindung ergeben sich aus den Unteransprüchen und der folgenden Beschreibung eines Ausführungsbeispiels. In der Zeichnung zeigen:
- Figur 1 ein Blockschaltbild einer Strahlungsbeheizung eines Kochfeldes eines Strahlungsheizgerätes und
- Figur 2 ein Widerstands/Temperatur-Zeitdiagramm des Heizleiters.
- Figure 1 is a block diagram of a radiant heating of a hob of a radiant heater and
- Figure 2 is a resistance / temperature time diagram of the heating conductor.
Unterhalb eines Kochfeldes(1) einer Glaskeramikplatte ist ein Heizleiter(2) mit Abstand in üblicher Weise angeordnet. Der Heizleiter(2) bildet eine spiralförmig verlegte Heizwendel. Der Heizleiter(2) besteht aus einem Widerstandsdraht mit positivem Temperaturkoeffizienten. Der Heizleiter(2) ist mit einem Energieregler(3) verbunden, der an das elektrische Netz(4) angeschlossen ist.A heating conductor (2) is arranged at a distance in the usual manner below a hob (1) of a glass ceramic plate. The heating conductor (2) forms a spiral heating coil. The heating conductor (2) consists of a resistance wire with a positive temperature coefficient. The heating conductor (2) is connected to an energy regulator (3) which is connected to the electrical network (4).
Der Energieregler(3) arbeitet mit einem elektronischen Lastschalter(5), an dem der Heizleiter(2) über einen zweipoligen Umschalter(6) liegt. Der Umschalter(6) ist vorzugsweise von elektronischen Bauteilen gebildet. An den Umschalter(6) ist eine Widerstandsmeßschaltung(7) angeschlossen, die eine Meßelektronik(8) und eine Auswerteelektronik(9) aufweist. Die Widerstandsmeßschaltung(7) erzeugt ein Steuersignal für eine Regelschaltung(10), welche den elektronischen Lastschalter(5) und den Umschalter(6) steuert. Mit der Regelschaltung(10) ist ein Sollwertsteller(11) verbunden.The energy regulator (3) works with an electronic load switch (5) on which the heating conductor (2) is connected via a two-pole switch (6). The switch (6) is preferably formed by electronic components. A resistance measuring circuit (7) is connected to the changeover switch (6), which has measuring electronics (8) and evaluation electronics (9). The resistance measuring circuit (7) generates a control signal for a control circuit (10) which controls the electronic load switch (5) and the changeover switch (6). A setpoint adjuster (11) is connected to the control circuit (10).
Die Arbeitsweise der beschriebenen Schaltung ist im wesentlichen folgende:The operation of the circuit described is essentially as follows:
Bei der in Figur 1 dargestellten Stellung des Umschalters (6) liegt der Heizleiter(2) über den Lastschalter(5) am Netz(4) und ist von einem entsprechenden Laststrom durchflossen. Der Heizleiter(2) glüht und beheizt durch Strahlungswärme das Kochfeld(1) bzw. ein auf diesem stehendes Gefäß.In the position of the switch (6) shown in FIG. 1, the heating conductor (2) is connected to the network (4) via the load switch (5) and a corresponding load current flows through it. The heating conductor (2) glows and heats the cooktop (1) or a vessel standing on it by means of radiant heat.
Zyklisch, beispielsweise alle 5 bis 10 s, wird von der Regelschaltung(10) der Umschalter(6) umgeschaltet, so daß der glühende Heizleiter(2) an der Meßelektronik(8) liegt. Dabei erfaßt diese den jeweiligen temperaturabhängigen ohmschen Widerstandswert des Heizleiters(2), beispielsweise indem sie eine Gleichspannung an den Heizleiter(2) legt und den fließenden Strom mißt. Die Auswerteelektronik (9) erzeugt aus dem gemessenen Widerstandswert ein entsprechendes temperaturproportionales Steuersignal für die Regelschaltung(10).Cyclically, for example every 5 to 10 s, the control circuit (10) switches the changeover switch (6) so that the glowing heating conductor (2) is connected to the measuring electronics (8). This detects the respective temperature-dependent ohmic resistance value of the heating conductor (2), for example by applying a DC voltage to the heating conductor (2) and measuring the flowing current. The evaluation electronics (9) generate a corresponding temperature-proportional control signal for the control circuit (10) from the measured resistance value.
Wird der Widerstandswert ausgewertet, der gleich nach dem Umschalten des Umschalters(6) vorliegt (vgl. t1 in Figur 2), dann entspricht dieser der Glühtemperatur (etwa 1100°C) des Heizleiters(2). Diesen Eigenwiderstand des Heizleiters(2) auszuwerten, ist günstig, wenn durch die beschriebene Schaltung vermieden werden soll, daß eine maximale Glühtemperatur des Heizleiters(2) überschritten wird. Ist die maximale Glühtemperatur erreicht, dann bleibt der Heizleiter(2) für eine gewisse Zeit vom Netz(4) abgeschaltet.If the resistance value is evaluated which is available immediately after the switch (6) has been switched over (cf. t1 in FIG. 2), then this corresponds to the annealing temperature (approximately 1100 ° C.) of the heating conductor (2). Evaluating this inherent resistance of the heating conductor (2) is advantageous if the circuit described is intended to prevent a maximum annealing temperature of the heating conductor (2) from being exceeded. When the maximum annealing temperature has been reached, the heating conductor (2) remains switched off from the mains (4) for a certain time.
Mit der beschriebenen Schaltung soll vor allem die Temperatur des Kochfeldes(1) erfaßt werden. Hierfür bleibt der zuvor eingeschaltete, glühende Heizleiter(2) für eine gewisse Abkühlzeit (t2-t1, beispielsweise etwa 1s) abgeschaltet, bis er nicht mehr oder nur noch dunkel glüht. Dies ist im Temperaturbereich von etwa 750°C der Fall. In die am Heizleiter(2) herrschende Temperatur geht jetzt die Temperatur des Kochfeldes(1) ein. Sein Widerstand ist somit ein Abbild der Temperatur des Kochfeldes(1) (vgl. t2, t3 in Figur 2). Die Abkühlzeit kann einen festen Wert haben Es ist jedoch auch möglich, nach dem Umschalten des Umschalters(6) (Zeitpunkt t1) den Widerstand des Heizleiters(2) wiederholt zu messen und den Meßwert erst dann auszuwerten, wenn sich der in einer e-Funktion abfallende Widerstand nur noch wenig ändert (vgl. t2,t3 in Figur 2). Dies ist der Fall, wenn der Heizleiter(2) praktisch nicht mehr glüht und sein Widerstand ein Abbild der Kochfeldtemperatur ist, was beispielsweise im Temperaturbereich um 750°C gegeben ist. Aus dem in der Zeit(t3-t2) gemessenen Widerstandswert wird ein temperaturproportionales Steuersignal für die Regelschaltung(10) erzeugt, welche dadurch in Abhängigkeit vom eingestellten Sollwert beim nachfolgenden Umschalten des Heizleiters(2) auf den Lastschalter(5) den Lastschalter(5) entsprechend steuert. Die Meßzeit(t3-t2) beträgt beispielsweise etwa 0,3s. Es ist auch möglich, bei einem Meßbeginn gleich nach dem Zeitpunkt(t1) in einigen Punkten der e-Funktion die Messung vorzunehmen und aus dem Meßwertverlauf den weiteren Kurvenverlauf zu extrapolieren und danach die Umgebungstemperatur zu errechnen. Die Gesamtmeßzeit kann dabei kleiner als die Abkühlzeit(t2-t1) sein. Je nach der gewünschten Genauigkeit kann die Meßwertaufnahme zu einem früheren oder späteren Zeitpunkt (vor t2) abgebrochen werden.With the circuit described above, the temperature of the hob (1) is to be detected. For this purpose, the previously switched on, glowing heating conductor (2) remains switched off for a certain cooling time (t2-t1, for example about 1s) until it no longer glows or only glows dark. This is the case in the temperature range of around 750 ° C. Goes into the temperature prevailing on the heating conductor (2) now the temperature of the hob (1). Its resistance is therefore an image of the temperature of the hob (1) (cf. t2, t3 in FIG. 2). The cooling time can have a fixed value. However, it is also possible to measure the resistance of the heating conductor (2) repeatedly after switching the switch (6) (time t1) and to evaluate the measured value only when it has an e-function falling resistance changes only a little (cf. t2, t3 in FIG. 2). This is the case when the heating conductor (2) practically no longer glows and its resistance is an image of the hob temperature, which is the case, for example, in the temperature range around 750 ° C. A temperature-proportional control signal for the control circuit (10) is generated from the resistance value measured in time (t3-t2), which, depending on the set value, subsequently switches the load switch (5) when the heating conductor (2) is subsequently switched to the load switch (5). controls accordingly. The measuring time (t3-t2) is, for example, about 0.3 s. It is also possible to carry out the measurement in some points of the e-function immediately after the time (t1) and to extrapolate the further curve profile from the measured value profile and then to calculate the ambient temperature. The total measuring time can be shorter than the cooling time (t2-t1). Depending on the desired accuracy, the measurement can be stopped at an earlier or later time (before t2).
Die gesamte Abkühlzeit(t3-t1) ist wesentlich kleiner als die oben angegebene Zykluszeit, nach der die beschriebene Messung immer wieder stattfindet, damit die eigentliche Heizzeit länger als die Meßzeit ist.The total cooling time (t3-t1) is significantly shorter than the cycle time specified above, after which the measurement described takes place again and again, so that the actual heating time is longer than the measuring time.
Um zu vermeiden, daß der Umschalter(6) den Laststrom schaltet, schaltet die Regelschaltung(10) den Lastschalter(5) ab, bevor der Umschalter(6) vom Lastschalter(5) auf die Widerstandsmeßschaltung(7) geschaltet wird, und schaltet den Lastschalter(5) erst ein, wenn nach dem Meßvorgang der Umschalter(6) von der Widerstandsmeßschaltung(7) auf den Lastschalter(5) zurückgeschaltet ist.In order to prevent the changeover switch (6) from switching the load current, the control circuit (10) switches off the load switch (5) before the changeover switch (6) switches from the load switch (5) to the resistance measuring circuit (7) is switched, and only switches on the load switch (5) when after the measuring process the changeover switch (6) is switched back from the resistance measuring circuit (7) to the load switch (5).
Mittels der Widerstandsmeßschaltung(7) ist es auch möglich, einen Widerstandswert, der außerhalb des betriebsüblichen Bereichs liegt, zu erfassen und ein Abschaltsignal für die Regelschaltung(10) sowie ein Alarmsignal zu erzeugen. Ein solcher Widerstandswert außerhalb des betriebsüblichen Bereichs ist beispielsweise ein Kurzschluß und/oder eine Unterbrechung des Heizleiters(2). Bei einem Heizleiter mit positiven Temperaturkoeffizienten ist ein betriebsunüblicher Widerstandswert auch ein solcher, der wesentlich kleiner ist als der bei Raumtemperatur auftretende Widerstandswert und/oder der wesentlich größer ist als der bei maximaler Glühtemperatur auftretende Widerstandswert.By means of the resistance measuring circuit (7), it is also possible to detect a resistance value that lies outside the normal operating range and to generate a switch-off signal for the control circuit (10) and an alarm signal. Such a resistance value outside the normal operating range is, for example, a short circuit and / or an interruption in the heating conductor (2). In the case of a heating conductor with positive temperature coefficients, a resistance value which is not customary in operation is also one which is substantially smaller than the resistance value occurring at room temperature and / or which is significantly greater than the resistance value occurring at the maximum annealing temperature.
Claims (9)
daß ein Umschalter(6) vorgesehen ist, der den Heizleiter (2) zyklisch an eine Widerstandsmeßschaltung(7) legt, die den jeweiligen temperaturabhängigen ohmschen Widerstandswert des Heizleiters(2) erfaßt und ein temperaturproportionales Steuersignal für die Regelschaltung(10) erzeugt.Temperature measuring device for a control circuit, in particular of an electric radiant heater, with a heating conductor arranged below a glass ceramic cooktop, characterized in that
that a changeover switch (6) is provided, which connects the heating conductor (2) cyclically to a resistance measuring circuit (7), which detects the respective temperature-dependent ohmic resistance value of the heating conductor (2) and generates a temperature-proportional control signal for the control circuit (10).
dadurch gekennzeichnet,
daß die Widerstandsmeßschaltung(7) den ohmschen Widerstand des Heizleiters(2) erst nach einer Abkühlzeit (t3-t1) als Steuersignal für die Regelschaltung(10) auswertet, wobei die Abkühlzeit so bemessen ist, daß die Temperatur des Heizleiters(2) ein Abbild der Temperatur des Kochfeldes(1) ist.Temperature measuring device according to claim 1,
characterized,
that the resistance measuring circuit (7) evaluates the ohmic resistance of the heating conductor (2) only after a cooling time (t3-t1) as a control signal for the control circuit (10), the cooling time being dimensioned such that the temperature of the heating conductor (2) is an image the temperature of the hob (1).
dadurch gekennzeichnet,
daß die Abkühlzeit einen festen Wert hat.Temperature measuring device according to claim 2,
characterized,
that the cooling time has a fixed value.
dadurch gekennzeichnet,
daß der Widerstand des Heizleiters(2) erst ausgewertet wird, wenn sich seine Temperatur höchstens noch wenig ändert.Temperature measuring device according to claim 2,
characterized,
that the resistance of the heating conductor (2) is only evaluated when its temperature changes little at most.
dadurch gekennzeichnet,
daß die Regelschaltung(10) den Umschalter(6) zyklisch, etwa alle 5 bis 10 s, demgegenüber kurzzeitig auf die Widerstandsmeßschaltung(7) schaltet.Temperature measuring device according to one of the preceding claims,
characterized,
that the control circuit (10) switches the changeover switch (6) cyclically, approximately every 5 to 10 s, in contrast, briefly to the resistance measuring circuit (7).
dadurch gekennzeichnet,
daß ein zur Steuerung des Heizleiters(2) vorgesehener Lastschalter(5) vor dem Umschalten des Heizleiters(2) auf die Widerstandsmeßschaltung(7) abschaltet und/oder nach dem Zurückschalten des Heizleiters(2) auf den Lastschalter(5) einschaltet.Temperature measuring device according to one of the preceding claims,
characterized,
that a load switch (5) provided for controlling the heating conductor (2) switches off before the heating conductor (2) is switched to the resistance measuring circuit (7) and / or switches on after the heating conductor (2) is switched back to the load switch (5).
dadurch gekennzeichnet,
daß der Umschalter(6) zweipolig ist.Temperature measuring device according to one of the preceding claims,
characterized,
that the changeover switch (6) has two poles.
dadurch gekennzeichnet,
daß die Widerstandsmeßschaltung(7) nach einem Heizleiter-Widerstandswert, der bei einer Übertemperatur des Heizleiters(2) auftritt, ein Abschaltsignal für die Regelschaltung(10) erzeugt.Temperature measuring device according to one of the preceding claims,
characterized,
that the resistance measuring circuit (7) generates a switch-off signal for the control circuit (10) after a heating conductor resistance value which occurs when the heating conductor (2) is overheated.
dadurch gekennzeichnet,
daß die Widerstandsmeßschaltung(7) bei einem Heizleiter-Widerstandswert außerhalb des betriebsüblichen Bereichs ein Abschaltsignal für die Regelschaltung und ein Alarmsignal erzeugt.Temperature measuring device according to one of the preceding claims,
characterized,
that the resistance measuring circuit (7) generates a shutdown signal for the control circuit and an alarm signal at a heat conductor resistance value outside the normal range.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19604658 | 1996-02-09 | ||
| DE19604658A DE19604658A1 (en) | 1996-02-09 | 1996-02-09 | Temperature measuring device for a control circuit of an electric radiant heater |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0789504A2 true EP0789504A2 (en) | 1997-08-13 |
| EP0789504A3 EP0789504A3 (en) | 1998-01-14 |
Family
ID=7784903
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP97101687A Withdrawn EP0789504A3 (en) | 1996-02-09 | 1997-02-04 | Temperature measuring device for the control circuit of an electric radiant heater |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US5951897A (en) |
| EP (1) | EP0789504A3 (en) |
| DE (1) | DE19604658A1 (en) |
Cited By (1)
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|---|---|---|---|---|
| DE10104787A1 (en) * | 2001-01-29 | 2002-08-22 | Ego Elektro Geraetebau Gmbh | Method, for heating cooker plate, involves generating dynamic thermal convection of food in vessel by applying non-uniform and/or asymmetrical heat distribution in initial cooking stage |
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| DE19813996A1 (en) * | 1998-03-28 | 1999-10-07 | Aeg Hausgeraete Gmbh | Cooker with structure for heating both by induction and resistance |
| DE19835622A1 (en) * | 1998-08-06 | 2000-02-10 | Bsh Bosch Siemens Hausgeraete | Home appliance |
| IT1313951B1 (en) * | 1999-12-16 | 2002-09-26 | Whirlpool Co | METHOD AND DEVICE FOR DETECTING OVERHEATING OF A CONTAINER PLACED ON A GLASS-CERAMIC HOB DURING |
| TW552669B (en) * | 2000-06-19 | 2003-09-11 | Infineon Technologies Corp | Process for etching polysilicon gate stacks with raised shallow trench isolation structures |
| DE10048181B4 (en) * | 2000-09-28 | 2011-08-11 | Gustav Magenwirth GmbH & Co. KG, 72574 | Vehicle with a heated throttle grip |
| DE10120098B4 (en) * | 2001-04-25 | 2004-02-05 | Brose Fahrzeugteile Gmbh & Co. Kg | Heating and method for controlling the heating of a functional unit of a motor vehicle |
| GB0115831D0 (en) * | 2001-06-28 | 2001-08-22 | Ceramaspeed Ltd | Radiant electric heater |
| DE10156037A1 (en) * | 2001-11-15 | 2003-06-05 | Behr Hella Thermocontrol Gmbh | Method for monitoring operation of heater element of motor vehicle interior heater based on comparing actual resistance of heater elements against known resistance temperature characteristic |
| GB0206069D0 (en) * | 2002-03-15 | 2002-04-24 | Ceramaspeed Ltd | Electrical heating assembly |
| DE102004014024B4 (en) * | 2003-03-24 | 2006-01-26 | Stiebel Eltron Gmbh & Co. Kg | Method and device for calcification recognition of an electric radiator |
| DE102004059159A1 (en) * | 2004-12-08 | 2006-06-14 | BSH Bosch und Siemens Hausgeräte GmbH | Cooking surface comprises heating conductor and controller wherein controller has heating conductor-temperature sensor, which measures the temperature of heating conductor |
| DE102006022327A1 (en) * | 2006-05-12 | 2007-11-15 | BSH Bosch und Siemens Hausgeräte GmbH | Device and method for controlling and / or regulating a heating power of a heating element of a cooktop |
| DE102006032698A1 (en) * | 2006-07-14 | 2008-01-24 | Bleckmann Gmbh & Co. Kg | Electrical heating system controlling method for use in e.g. dish washer, involves controlling electrical heating system based on actual resistance values and change of resistance values of electrical resistor heating unit |
| DE102007040891A1 (en) * | 2007-08-24 | 2009-04-30 | E.G.O. Elektro-Gerätebau GmbH | Heating device, method for operating a heater and electric heater with such a heater |
| US20180051888A1 (en) * | 2016-08-22 | 2018-02-22 | Haier Us Appliance Solutions, Inc. | Oven appliance surface element with no onboard sensor |
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| DE2936890A1 (en) | 1978-09-15 | 1980-03-27 | Matsushita Electric Works Ltd | TEMPERATURE CONTROL FOR ELECTRIC SURFACE HEATING |
| DE2850389B2 (en) | 1978-11-21 | 1980-12-04 | E.G.O. Regeltechnik Gmbh, 6833 Waghaeusel | Temperature regulators for electric heating devices, in particular for electric hotplates |
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| DE10104787A1 (en) * | 2001-01-29 | 2002-08-22 | Ego Elektro Geraetebau Gmbh | Method, for heating cooker plate, involves generating dynamic thermal convection of food in vessel by applying non-uniform and/or asymmetrical heat distribution in initial cooking stage |
| DE10104787B4 (en) * | 2001-01-29 | 2006-01-26 | E.G.O. Elektro-Gerätebau GmbH | Method for heating a cooking plate |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0789504A3 (en) | 1998-01-14 |
| US5951897A (en) | 1999-09-14 |
| DE19604658A1 (en) | 1997-08-14 |
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