WO2002096155A1 - Appareil de chauffage dote d'une protection contre la surchauffe - Google Patents

Appareil de chauffage dote d'une protection contre la surchauffe Download PDF

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Publication number
WO2002096155A1
WO2002096155A1 PCT/IB2002/001864 IB0201864W WO02096155A1 WO 2002096155 A1 WO2002096155 A1 WO 2002096155A1 IB 0201864 W IB0201864 W IB 0201864W WO 02096155 A1 WO02096155 A1 WO 02096155A1
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WO
WIPO (PCT)
Prior art keywords
heater
temperature
heating element
conductive layer
control circuit
Prior art date
Application number
PCT/IB2002/001864
Other languages
English (en)
Inventor
Rene H. Van Der Woude
Thijs De Haan
Tang P. Har
Original Assignee
Koninklijke Philips Electronics N.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2002096155A1 publication Critical patent/WO2002096155A1/fr

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Classifications

    • 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
    • H05B1/00—Details of electric heating devices
    • H05B1/02—Automatic switching arrangements specially adapted to apparatus ; Control of heating devices
    • H05B1/0227—Applications
    • H05B1/0252—Domestic applications
    • H05B1/0258—For cooking
    • H05B1/0269—For heating of fluids

Definitions

  • the present invention relates to an overheating-protected heater for an appliance.
  • an appliance may be an electric iron, a water cooker, a hot-plate, etc.
  • the heater comprises a heating element which is selectively connectable to a power supply and a temperature control circuit having a temperature sensor in thermal contact with the heating element, which control circuit is arranged so as to control the heating element in response to temperature measurement signals from the temperature sensor.
  • Such an overheating-protected heater is known, for example, from US-A-6,046,438, where tracks of a heating resistor are arranged on a surface of a substrate and a thermal sensor is located in or surrounded by a thinner portion of the substrate.
  • the present invention has for its object to provide a simplified configuration of an overheating-protected heater in which the substrate, which belongs to an appliance, does not require further processing for implementing the overheating-protected heater in the appliance.
  • Another object of the present invention is to provide an overheating-protected heater with an improved degree of reliability and transient response.
  • a further object of the present invention is to provide an overheating-protected heater with which the required temperatures can be reliably reached, but are not exceeded.
  • an overheating-protected heater which is characterized in that the temperature sensor comprises in that order a first conductive layer having a resistance, an insulator layer having temperature-dependent dielectric characteristics, and a second conductive layer so as to form the equivalent of a parallel configuration of a resistor and a capacitor, wherein the temperature-dependent leakage current through the parallel configuration provides the temperature measurement signal for the temperature control circuit.
  • the present invention thus utilizes leakage currents. Leakage currents used in the above-mentioned way were found to increase exponentially at high temperatures, i.e. in dependence upon the actual temperature, the temperature-dependent resistivity properties of the conductive layers, and/or the temperature-dependent dielectric properties of the insulating layer.
  • the temperature control circuit can reliably respond to the temperature measurement signal and control the power supply to the heating element so as to achieve the desired temperature.
  • the heating element comprises a heating resistor
  • the first conductive layer forms the heating resistor.
  • the number of components is reduced and the configuration is further simplified.
  • the insulating layer of the temperature sensor may be made to extend as a protective layer over the heating element. The robustness and reliability of the heater can be increased thereby in that the heating element is protected by the insulating layer.
  • a highly preferable embodiment of the present invention is one in which separate components of the heater are formed from a similar material as a basic material, and the separate components are formed by the provision of a specific filler material in the basic material so as to provide the desired properties corresponding to the actual component being formed therefrom.
  • a specific, non-limiting example polyimide resin and silicone are mentioned as basic materials.
  • the insulating layer having the desired temperature-dependent dielectric properties may be chosen from a group of suitable materials such as SiO 2 , Al 2 O 3 , A1N, SiN, Bn, TiO, BaTiO 3 , semiconductors, glass materials, or polymer resins such as poly-imide and silicones.
  • a filler material such as graphite or carbon may be added in a predetermined amount to polyimide as a binder material for the heating resistor and/or the conductive layer so as to provide the desired conductive properties.
  • Contact elements may also be made from polyimide as a basic material, to which a filler material such as silver may be added to obtain the desired contacting and power-distributing properties for contact elements.
  • Fig. 1 shows a water cooker having a heater according to the present invention
  • Fig. 2 diagrammatically shows an electric iron having a heater according to the present invention
  • Fig. 3 shows a heater according to the present invention on a substrate, partly broken away, in more detail than in Figs. 1 and 2;
  • Fig. 4 is a graph of leakage currents plotted against temperature in an overheating-protected heater according to the present invention.
  • Fig. 5 shows an electrical circuit which is equivalent to the configuration of Fig. 3.
  • Figs. 6 and 7 show embodiments of control circuits, to be used for overheating protection in a heater according to the present invention.
  • Fig. 1 schematically shows a water cooker 1 having a heater 2 according to the present invention incorporated therein.
  • the novel and inventive heater 2 is arranged in a conventional manner on a substrate 6, of which the face opposite the heater 2 is directed toward an inner space 7 of the water cooker 1 for transferring heat from the heater 2 to water in the interior space 7 so as to heat this water.
  • the heater 2 comprises a control circuit 5 which analyzes temperature measurement signals from the heater 2 and controls a relay 8 in response thereto.
  • the relay 8 is arranged between a power supply 4 and connectors 9 leading to the heater 2.
  • the heater 2 comprises a heating resistor 10 and a temperature sensor 11 which extends over a considerable portion of the surface of the heating resistor 10.
  • the sensor 11 will be described in more detail below.
  • Fig. 2 shows another embodiment of an appliance according to the present invention.
  • the appliance in Fig. 2 is an electric iron 3 of which the ironing sole may be considered the substrate 6.
  • the heater 2 according to the present invention is arranged on the surface of the substrate 6, opposite the actual sole of the iron 3, which can be brought into functional contact with garments to be ironed.
  • Fig. 3 shows a heater 2 according to the present invention arranged on a substrate 6 of an appliance, where two insulating layers 12, 13 are arranged between the substrate 6 and the heater 2.
  • the first insulating layer 13, closest to the substrate may be made, for example, from sol-gel, and the second layer 12 may be made, for example, from polyimide.
  • the first insulating layer 13 provides a bonding for the polyimide second insulating layer 12.
  • the second insulating layer 12 may provide a good bonding for the heater 2.
  • the heater 2 itself comprises, according to the present invention, a heating resistor 10 having contacts 15 at opposite sides of the heating resistor 10.
  • the heating resistor 10 is made, for example, from polyimide as a basic material, to which a filler material is added so as to provide the desired heating resistor properties, i.e. to generate heat when a voltage is applied across the contacts 15.
  • the contacts themselves may also be made, for example, from polyimide as a basic material, to which silver may be added as a filler material so as to obtain the desired contacting and power-distributing properties for the contacts 15.
  • An insulating layer 14 having temperature-dependent dielectric properties is arranged over the heating resistor 10. The insulating layer 14 is partly broken away in Fig. 3, but it may extend over a large surface area.
  • a suitable filler material or materials such as SiO 2 , Al 2 O 3 , A1N, SiN, BN, TiO 2 , BaTiO 3 , semiconductor materials etc. in order to provide the desired temperature-dependent dielectric properties.
  • the added amount of the filler materials can be used to determine the actually achieved temperature-dependent dielectric properties of the insulating layer 14. It is shown clearly in Fig. 3 that the insulating layer 14 extends over a considerable portion, if not all, of the heating resistor 10, thus forming a protective layer over the heating resistor.
  • a conductive layer 16 is arranged over a considerable portion of the surface of the insulating layer 14.
  • the conductive layer 16 may be made, for example, from polyimide as a basic material, to which a filler material is added, such as graphite or carbon, to provide the desired conductive properties to the conductive layer 16.
  • Fig. 4 is a graph of leakage currents LC plotted on the vertical axis against temperature T plotted on the horizontal axis. Curve 17 shows the AC leakage current, and curve 18 shows the DC leakage current. Both leakage currents increase exponentially at temperatures above 250° C. Any appropriate choice of the material for the insulating layer 14 having the temperature-dependent dielectric characteristics renders it possible to define the temperature at which this insulating layer 14 begins to exhibit its exponential increase. In a configuration in which a basic material is used such as the one described above with reference to Fig. 3 together with a filler material to achieve the desired properties, the amounts of this filler material may be varied in order to obtain a adesired temperature- dependent characteristic, such as the one shown in Fig. 4.
  • Fig. 5 shows an electrical circuit which is equivalent to the configuration of Fig. 3. It is apparent from Fig. 5 that the control circuit 5 shown is connected to the conductive layer 16 in Fig. 3, whereby a parallel configuration of a capacitor 21 and a resistor 22 is formed between the control circuit and the electrical path between the contacts 15 in Fig. 3.
  • a similar configuration 19 of a capacitor and a resistor in parallel is formed between the electrical paths from one of the contacts 15 to the other and the substrate.
  • This parallel configuration 19 is of less importance to the present invention than the parallel configuration of the capacitor 21 and the resistor 22.
  • the control circuit 5 is connected to the power supply 4.
  • the control circuit 5 is further connected to the parallel configuration of the capacitor 21 and the resistor 22 to obtain therefrom leakage currents from which the ambient temperature of the heating resistor 10 can be derived.
  • the control circuit 5 is further connected to the relay 8 to open the switch 20 whenever the received leakage currents indicate an excess of temperature.
  • the leakage current through the latter parallel configuration is thus used as the temperature measurement signal for the control circuit 5.
  • the relay 8 is shown to be connected to the control circuit 5, so that the relay 8 can open the switch 20 in the electrical path for power supply to the heating resistor in response to a higher than desired temperature.
  • the switch 20 forms the switch means in the sense of the present invention.
  • FIG. 6 shows a capacitive sensor and the control circuit 5 in accordance with the invention.
  • a first inverting amplifier 23, in the form of a Schmitt trigger, has its input connected to its output via a feedback resistor 24.
  • Two capacitors are situated between the input and a reference terminal 25, which functions as signal ground for the sensor circuit.
  • a first capacitor is formed by a parasitic input capacitor 26 having a value C p ⁇ and a second capacitor is formed by the capacitance of value C s of a sensing capacitor 21 in Fig. 5, having a first plate formed by the conductive layer 16 forming a sensor electrode connected to the input.
  • the second plate is formed by the heating resistor 10.
  • the temperature measurement signal is diagrammatically shown as an AC source 27.
  • the inverting amplifier 23, the feedback resistor 24 and the two capacitors 26 and 21 (the latter capacitor being shown in Fig. 5) form an oscillator whose oscillation frequency F s decreases as the overall summed capacitance C p] + Cs of the capacitors 26 and 21 increases.
  • the oscillation frequency F s will be comparatively low if the heater is cool and it will be comparatively high if the heater is hot.
  • the detected voltage of voltage source 27 is very high there will no longer be a free oscillation and the oscillation frequency F s will be pulled to the mains frequency.
  • the output of the first inverting amplifier 23 is connected to the input of a second inverting amplifier 28, also formed by a Schmitt trigger, via a series resistor 29 having a value R 2 .
  • This input is connected to the reference terminal 25 via a parasitic capacitor 30 having a value C p2 and a reference capacitor 31 having a value C r .
  • V(t) across the overall capacitance at the input of the first inverting amplifier 23 will vary between the low threshold voltage Vj and the high threshold voltage V h within one period T.
  • the voltage across the overall capacitance will vary in accordance with:
  • N 0 is the initial voltage
  • ⁇ * (C s +C pl )
  • Ri is the value of the feedback resistor 24.
  • equation (3) can be reduced to the following approximation:
  • V pp V cc / ⁇ 4 * F s * R 2 * (C r + C p2 ) ⁇ (6)
  • resistor 29 is now selected to be equal to resistor 24, and equation (5) is substituted in equation (6), it follows that:
  • V pp V n * (C s + C pl ) / (C r + C p2 ) (7)
  • V pp is smaller than V n if C s is smaller than C r , so that the two trigger thresholds V n and V h of the second inverting amplifier 28 are not exceeded and a DC level appears at the output of this amplifier 28.
  • V pp is greater than V n if C s is greater than C r , so that the two trigger thresholds V n and V h are exceeded periodically and an AC signal with the oscillation frequency F s appears at the output of amplifier 28.
  • the voltage difference V n is substantially equal for the inverting amplifiers 23 and 28 if the amplifiers are identical and are integrated on one semiconductor body.
  • the resistors 24 and 29 have equal values. A parasitic capacitance parallel to these resistors will then have no effect on the ripple voltage V pp either because a strictly symmetrical load is seen from the output of the first amplifier 23 to the reference terminal 25.
  • a comparator 32 which is also formed by an inverting Schmitt trigger and which has an input and an output, can detect whether this output carries an AC or a DC signal said input receiving a signal from the output of the second inverting amplifier 28 via a charge pump 33.
  • the charge pump 33 comprises a first capacitor 34 connected between the output of the second amplifier 28 and a node 35, a first diode 36 having its cathode connected to the node 35 and its anode to the reference terminal 25, a second diode 37 having its anode connected to the node 35 and its cathode to the input of comparator 32, and a resistor 38 and a capacitor 39, which are connected between the input of the comparator 32 and the reference terminal 25.
  • the charging current i through the capacitor 34 per oscillation period 1/F is approximately equal to:
  • Ci is the value of the capacitor 34
  • V j is the junction voltage of the diodes 36 and 37
  • V 2 is the voltage across the capacitor 39
  • R 3 is the value of the resistor 38. If the threshold voltages of the comparator 32 lie approximately at half the supply voltage V cc> the voltage V 2 must be equal to V cc /2 at the minimum frequency Fi , and the following equation is valid:
  • Fig. 7 shows the capacitive sensor circuit of Figure 6 used in an electrical apparatus.
  • the inverters 23, 28 and 32 are implemented by means of dual-input Schmitt trigger NANDs.
  • the output of the inverter 32 drives the base of an NPN switching transistor 40 via a fourth dual-input Schmitt trigger NAND 41 and a current-limiting resistor 42, the emitter of said switching transistor being connected to the reference terminal 25 via a light- emitting diode (LED) 43 and the collector of this transistor driving the energizing coil 44 of a relay 8 via an interrupter switch 46.
  • the relay and the NANDs receive their supply voltage from a supply voltage source (not shown), which may comprise a rectifier circuit (not shown). The relay actuates a switch 20. At comparatively low oscillation frequencies, i.e.
  • the relay 8 is energized in response to the AC/DC signal at the output of the second inverting amplifier 28.

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  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Control Of Resistance Heating (AREA)

Abstract

L'invention concerne un appareil de chauffage doté d'une protection contre la surchauffe (2) destiné à un appareil comportant un substrat (6) à chauffer. Cet appareil de chauffage comprend un élément chauffant (10), un capteur de température (11) en contact thermique avec l'élément chauffant, et un circuit de commande destiné à commander l'élément chauffant en réponse à des signaux de mesure de température provenant du capteur de température. Cette invention concerne plus particulièrement, une configuration dans laquelle le capteur de température comprend, dans cet ordre, une première couche conductrice (10) possédant une résistance, une couche isolante (14) présentant des caractéristiques diélectriques dépendantes de la température, et une seconde couche conductrice (16) de manière à former l'équivalent d'une configuration parallèle d'une résistance et d'un condensateur. Le courant de fuite dépendant de la température à travers la configuration parallèle fournit le signal de mesure de température destiné au circuit de commande de température.
PCT/IB2002/001864 2001-05-23 2002-05-21 Appareil de chauffage dote d'une protection contre la surchauffe WO2002096155A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SGPCT/SG01/00155 2001-05-23
SG0100155 2001-05-23

Publications (1)

Publication Number Publication Date
WO2002096155A1 true WO2002096155A1 (fr) 2002-11-28

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6919540B2 (en) * 2000-03-10 2005-07-19 Ferro Techniek Holding B. V. Heating element, liquid container and method for detecting temperature changes
WO2006083162A1 (fr) * 2004-11-23 2006-08-10 Ferro Techniek Holding B.V. Element chauffant et procede de detection de variations de temperature
NL2000081C2 (nl) * 2006-05-23 2007-11-26 Ferro Techniek Holding Bv Elektrische verwarmingsinrichting met temperatuurdetectie door dielektrische laag.
NL2001283C2 (nl) * 2008-02-13 2009-08-14 Otter Controls Ltd Verwarmingselement en vloeistofhouder voorzien van een dergelijk verwarmingselement.
CN106793205A (zh) * 2016-12-05 2017-05-31 东莞佐佑电子科技有限公司 一种厚膜发热管防局部干烧结构及其方法
EP3177104A1 (fr) * 2015-12-02 2017-06-07 Whirlpool Corporation Procédé de diagnostic pour un chauffage électrique
WO2021111254A1 (fr) * 2019-12-03 2021-06-10 International Business Machines Corporation Caractérisation de fuite pour surveillance de température de circuit électronique

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3359525A (en) * 1964-10-14 1967-12-19 Du Pont Electric heating element
GB2272619A (en) * 1992-11-11 1994-05-18 Central Research Lab Ltd Temperature control in a heater assembly
EP0848209A2 (fr) * 1996-12-11 1998-06-17 Isuzu Ceramics Research Institute Co., Ltd. Elément chauffant céramique et son procédé de fabrication
US6063463A (en) * 1998-01-08 2000-05-16 Xerox Corporation Mixed carbon black fuser member coatings

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3359525A (en) * 1964-10-14 1967-12-19 Du Pont Electric heating element
GB2272619A (en) * 1992-11-11 1994-05-18 Central Research Lab Ltd Temperature control in a heater assembly
EP0848209A2 (fr) * 1996-12-11 1998-06-17 Isuzu Ceramics Research Institute Co., Ltd. Elément chauffant céramique et son procédé de fabrication
US6063463A (en) * 1998-01-08 2000-05-16 Xerox Corporation Mixed carbon black fuser member coatings

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6919540B2 (en) * 2000-03-10 2005-07-19 Ferro Techniek Holding B. V. Heating element, liquid container and method for detecting temperature changes
WO2006083162A1 (fr) * 2004-11-23 2006-08-10 Ferro Techniek Holding B.V. Element chauffant et procede de detection de variations de temperature
NL2000081C2 (nl) * 2006-05-23 2007-11-26 Ferro Techniek Holding Bv Elektrische verwarmingsinrichting met temperatuurdetectie door dielektrische laag.
WO2007136268A1 (fr) * 2006-05-23 2007-11-29 Ferro Techniek Holding B.V. Dispositif de chauffage électrique de détection de température par couche diélectrique
NL2001283C2 (nl) * 2008-02-13 2009-08-14 Otter Controls Ltd Verwarmingselement en vloeistofhouder voorzien van een dergelijk verwarmingselement.
EP3177104A1 (fr) * 2015-12-02 2017-06-07 Whirlpool Corporation Procédé de diagnostic pour un chauffage électrique
CN106793205A (zh) * 2016-12-05 2017-05-31 东莞佐佑电子科技有限公司 一种厚膜发热管防局部干烧结构及其方法
WO2021111254A1 (fr) * 2019-12-03 2021-06-10 International Business Machines Corporation Caractérisation de fuite pour surveillance de température de circuit électronique
CN114761901A (zh) * 2019-12-03 2022-07-15 国际商业机器公司 用于电子电路温度监视的漏电特征化
US11614497B2 (en) 2019-12-03 2023-03-28 International Business Machines Corporation Leakage characterization for electronic circuit temperature monitoring

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