EP2027753A1 - Electric heating device with temperature detection through dielectric layer - Google Patents
Electric heating device with temperature detection through dielectric layerInfo
- Publication number
- EP2027753A1 EP2027753A1 EP07747463A EP07747463A EP2027753A1 EP 2027753 A1 EP2027753 A1 EP 2027753A1 EP 07747463 A EP07747463 A EP 07747463A EP 07747463 A EP07747463 A EP 07747463A EP 2027753 A1 EP2027753 A1 EP 2027753A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- detector
- detector electrode
- heating device
- electric heating
- dielectric layer
- Prior art date
- Legal status (The legal status 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 status listed.)
- Withdrawn
Links
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
- H05B3/00—Ohmic-resistance heating
- H05B3/20—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater
- H05B3/22—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible
- H05B3/26—Heating elements having extended surface area substantially in a two-dimensional plane, e.g. plate-heater non-flexible heating conductor mounted on insulating base
-
- 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
-
- 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
- H05B1/0288—Applications for non specified applications
- H05B1/0294—Planar elements
-
- 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
- H05B3/78—Heating arrangements specially adapted for immersion heating
- H05B3/82—Fixedly-mounted immersion heaters
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47J—KITCHEN EQUIPMENT; COFFEE MILLS; SPICE MILLS; APPARATUS FOR MAKING BEVERAGES
- A47J27/00—Cooking-vessels
- A47J27/21—Water-boiling vessels, e.g. kettles
- A47J27/21008—Water-boiling vessels, e.g. kettles electrically heated
- A47J27/21058—Control devices to avoid overheating, i.e. "dry" boiling, or to detect boiling of the water
- A47J27/21066—Details concerning the mounting thereof in or on the water boiling vessel
- A47J27/21075—Details concerning the mounting thereof in or on the water boiling vessel relating to the boiling sensor or to the channels conducting the steam thereto
-
- 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
- H05B2203/00—Aspects relating to Ohmic resistive heating covered by group H05B3/00
- H05B2203/021—Heaters specially adapted for heating liquids
Definitions
- the present invention relates to an electric heating device which is provided with a substantially flat carrier of material with good thermal conduction, on a first side of which material for heating can be arranged, an electrically insulating layer arranged on the second side of the carrier, heating conductors arranged on the thermally insulating layer, connecting means for connecting the heating conductors to a source of electrical energy, and a control circuit connected between the connecting means and the heating conductors.
- Such heating devices are generally known. They are used for instance as heating element in household appliances for heating water, such as kettles, coffee-making machines and washing machines.
- such heating devices are generally provided with temperature-dependent switches, such as switches provided with a bimetal, or with detection means for measuring the ohmic resistance of heating conductors for the purpose of determining the temperature therefrom.
- the present invention provides for this purpose such a heating device which is provided with at least one detector electrode, which is in contact with the electrically insulating layer and connected to the control circuit, wherein the control circuit is adapted to measure the detector current flowing through the detector electrode and wherein the control circuit is adapted to give a signal when the detector current exceeds a predetermined value.
- a heating device which is provided with at least one detector electrode, which is in contact with the electrically insulating layer and connected to the control circuit, wherein the control circuit is adapted to measure the detector current flowing through the detector electrode and wherein the control circuit is adapted to give a signal when the detector current exceeds a predetermined value.
- the electrically insulating layer is formed at least partly by a dielectric layer, and the detector electrode is separated from the heating conductor by the dielectric layer.
- the dielectric layer Use is made here of the dielectric properties of the layer.
- Such dielectric materials display this temperature-dependent behaviour, making them particularly suitable for this application. They moreover have the advantage that the relevant currents flowing through the dielectric, and thus through the detector electrode, are small compared to the current flowing through the heating conductor, but not so small that they are difficult to measure.
- the electrically insulating layer comprises a first partial layer
- the detector electrode is arranged on the first part layer
- the electrically insulating layer comprises a second partial layer in which the detector electrode is embedded.
- the first partial layer serves for the thermal conduction to the carrier and for electrical insulation
- the second partial layer can be optimized for an optimal temperature-dependent behaviour.
- the dielectric layer is preferably manufactured from a material, the characteristic of which has an inflection point between temperature and relative dielectric constant. This inflection point results in an easily detectable change in the detector current.
- a subsequent preferred embodiment provides the measure that the control device is adapted to reduce the power supplied to the heating conductor when the detector current flowing through the detector electrode exceeds a predetermined value. This prevents an early response of a thermal switch-off safety assumed to be present in application of this measure.
- the control according to this measure will after all already respond at a lower temperature, whereby the temperature at which the thermal switch-off safety responds is only reached later and a better temperature control takes place.
- the control can moreover be set such that the power is increased to the original value when the thus reduced power is insufficient to maintain the temperature at which this control responds, and a better temperature control is thus obtained.
- the above stated switch-off safety can be formed by a separate control, but it can also be obtained by making use of the same- configuration as used for the temperature control which responds at a lower temperature.
- a subsequent embodiment provides the measure that the device comprises a first and a second detector electrode which are each embedded in a different dielectric. This measure can be implemented by selecting the dielectrics such that the detector current comprises a discontinuity at a different temperature.
- control device is adapted to reduce the power supplied to the heating conductor when the detector current through the first detector electrode exceeds a predetermined value, and to interrupt the power supplied to the heating conductor when the detector current through the second detector electrode exceeds a predetermined value.
- the detector electrode is adapted to conduct electric current in the vicinity of a region in which a part of the heating conductor with a high potential is located close to a heating conductor with a low potential.
- the primary object of the detector electrode is to conduct leakage current from the heating conductor to the control circuit.
- the detector electrode can however also have a second function, i.e. to provide a type of temperature- dependent leakage current between two parts of the heating conductor having a preferably greatly differing potential.
- a leakage current from a part of the heating conductor with a low potential, through the dielectric and to the detector electrode, through the detector electrode and from the detector electrode to a part of the heating conductor with a high potential can reach considerable values when the distances through the dielectric are not too great and when the temperature reaches high values. This current can become so great that the parts of the heating conductor through which this combined current passes reach a temperature such that the conductor melts or burns there.
- the current is hereby interrupted so that an intrinsic safety is obtained.
- This effect can be reinforced by arranging a layer of material with good conduction parallel to the detector electrode or incorporated in the detector electrode at those locations where a great potential difference prevails or can prevail between nearby parts of the heating conductor.
- More than two electrodes may be applied; this allows to obtain more switch points at different temperatures.
- the variation in switch points may be obtained through adequate choice of materials, that is such that each of the electrodes is surrounded by material having its inflection points at different temperatures. Other possibilities, like combinations of layers of different materials are not excluded.
- Figure 1 is a schematic cross-sectional view of a first embodiment
- Figure 2 is a schematic cross-sectional view of a second embodiment
- Figure 3 shows a graph for elucidation of the invention.
- Figure 1 shows a carrier 1 which functions for instance as bottom of a container which can be filled with liquid for heating.
- the top side of carrier 1 is adapted to come into contact with the liquid for heating.
- the carrier is manufactured from material with good thermal conduction, such as steel.
- An electrically insulating layer 2 is arranged on the underside of carrier 1. Because the thermal energy must be propagated through this insulating layer 2, a material is preferably selected for this layer which combines a high electrical resistance with a low thermal resistance.
- a detector electrode 3 is formed on this layer 2. This detector electrode 3 is for instance circular.
- a dielectric layer 4 is placed on insulating layer 2 and over detector electrode 3. This dielectric layer 4 of course has electrically insulating properties and preferably thermally conducting properties.
- this dielectric layer 4 fulfils a function in the detection system according to the invention, the layer has dielectric properties.
- a heating conductor 5 Arranged on this dielectric layer is a heating conductor 5 with a resistance value such that it can convert the required power from electrical energy to thermal energy.
- a leakage current will start to flow through the dielectric layer, which will necessarily also flow through the detector electrode, in the case of a potential difference between the detector electrode and the heating conductor.
- the heating device further comprises a thermal safety circuit 6 which is for instance provided with a bimetal. Other principles can also be applied.
- a control circuit 7 Arranged between safety circuit 6 and the heating conductor is a control circuit 7 which is connected to detector electrode 3.
- Control circuit 7 is adapted to measure the current flowing through detector electrode 3 and to give a warning signal when the current flowing through the detector electrode exceeds a predetermined value.
- This warning signal can be used to warn the user of the heating device, but can also be used to initiate a function in the appliance of which the heating device forms part. In the present case the signal is used to reduce the power supplied to the heating conductor.
- Figure 3 shows a graph of the relation between temperature and leakage current of a layer of dielectric material at a determined potential difference between the electrodes arranged on either side of the layer. This shows that, when a dielectric material of a determined composition is used, the layer has the behaviour that at a determined temperature the leakage current through the material layer suddenly increases strongly in the manner of a discontinuity. This phenomenon is used in the present invention.
- a continuous line here shows the behaviour of a first composition of the dielectric layer, and a broken line shows the behaviour of a second composition.
- the discontinuity in question in the form of an inflection point, occurs at different temperatures.
- figure 2 shows a cross-section of a second embodiment of the invention. This embodiment differs from the first embodiment due to the presence of two detector electrodes and two different dielectric layers manufactured from different materials.
- first dielectric layer 4a with a first dielectric material, which extends over only a part of the surface of the carrier and covers a first detector electrode 3a
- second dielectric layer 4b with a second dielectric material, which extends over another part of the surface of the carrier and covers a second detector electrode 3b.
- the first dielectric material is herein chosen so that it has a characteristic as according to the continuous line in figure 3 and the second dielectric material is chosen so that it has a characteristic corresponding to the broken line in figure 3.
- Both detector electrodes are connected to a control circuit 8 which is adapted to reduce the power supplied to the heating conductor when the leakage current carried through the first detector electrode exceeds a predetermined value, and to switch off the heating conductor when the leakage current carried through the second detector electrode exceeds another predetermined value.
- a particularly suitable enamel composition for application in a dielectric layer of the heating element, preferably the first dielectric layer comprises between 0 and 10% by mass OfV 2 O 5 , between 0 and 10% by mass of PbO, between 5 and 13% by mass of B2O 3 , between 33 and 53% by mass of Sid, between 5 and 15% by mass of AI 2 O 3 , between 0-10% by mass of ZrO 2 and between 20 and 30% by mass of CaO.
- the preferred composition also comprises between 0 and 10% by mass OfBi 2 O 3 .
- Such a composition results in an enamel layer with an improved durability when used in heating elements.
- the enamel composition can be melted relatively easily and herein has a favourable viscosity, whereby it can be applied easily to different types of surface.
- the enamel composition adheres particularly well to metals, in particular to steel, more particularly to ferritic chromium steel, and still more particularly to ferritic chromium steel with numbers 444 and/or 436 according to the American AISI norm.
- the maximum compressive stress of the enamel layer which can be obtained from the enamel composition lies in the range between 200 - 250 MPa for the new composition.
- the maximum compressive stress generally lies in the range of 70 - 170 MPa.
- the preferred enamel composition furthermore has a high temperature resistance so that prolonged exposure to temperatures up to about 53O°C, with peak loads up to 700 0 C, does not cause problems.
- a first dielectric layer on the basis of the preferred enamel composition therefore has little risk of breakdown, in other words is less susceptible to degeneration owing to prolonged load at a high voltage than known enamel compositions.
- the properties of the enamel composition are furthermore such that the chance of crack formation in a dielectric layer manufactured therefrom is reduced in the case of temperature changes.
- the preferred enamel composition has the additional advantage that dielectric layers with the desired properties can be applied to the surface for heating in small layer thicknesses. This enhances the heat conduction.
- a particular preferred embodiment comprises a dielectric in which at least the lithium and/or sodium and/or potassium content of the first and the second dielectric layers differ from each other. It is advantageous herein if the enamel composition of the first dielectric layer is substantially free of lithium and/or sodium ions.
- the second dielectric layer comprises at least lithium and/or sodium ions.
- the enamel composition comprises between 0.1 and 6% by weight of potassium.
- the load-bearing capacity of the adhesion of the enamel composition to a substrate surface is less critical.
- the enamel composition is burnt into a heating element.
- the compressive stress is reduced but is still high enough to prevent the undesired formation of hair cracks.
- the chance of hair crack formation has however been found to increase.
- a low leakage current at increased temperatures also remains ensured.
- the surface for heating, on which the dielectric is arranged can be manufactured from any heat-conducting material.
- the surface for heating is preferably manufactured substantially from metal, for instance steel and/or aluminium. Particularly advantageous is ferritic chromium steel, preferably with a chromium content of at least 10% by weight
- the coefficient of expansion of the material from which the surface for heating is manufactured does not differ too much from the coefficient of expansion of the first dielectric layer, for instance no more than 20 to 45%, for instance relative to steel, more preferably no more than 20 to 35%.
- the coefficient of expansion of the second layer preferably does not differ any more than 0 to 25% relative to that of the first layer.
Landscapes
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Control Of Resistance Heating (AREA)
- Resistance Heating (AREA)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NL2000081A NL2000081C2 (nl) | 2006-05-23 | 2006-05-23 | Elektrische verwarmingsinrichting met temperatuurdetectie door dielektrische laag. |
PCT/NL2007/050240 WO2007136268A1 (en) | 2006-05-23 | 2007-05-23 | Electric heating device with temperature detection through dielectric layer |
Publications (1)
Publication Number | Publication Date |
---|---|
EP2027753A1 true EP2027753A1 (en) | 2009-02-25 |
Family
ID=37757093
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP07747463A Withdrawn EP2027753A1 (en) | 2006-05-23 | 2007-05-23 | Electric heating device with temperature detection through dielectric layer |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP2027753A1 (nl) |
CN (1) | CN200950672Y (nl) |
NL (1) | NL2000081C2 (nl) |
WO (1) | WO2007136268A1 (nl) |
Families Citing this family (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NL2001283C2 (nl) * | 2008-02-13 | 2009-08-14 | Otter Controls Ltd | Verwarmingselement en vloeistofhouder voorzien van een dergelijk verwarmingselement. |
CN101754498A (zh) * | 2009-12-25 | 2010-06-23 | 康盛樵 | 一种双层绝缘并防止漏电的电加热器 |
US10076000B2 (en) | 2012-12-20 | 2018-09-11 | The Middleby Corporation | Control of cooking appliance in response to control-compartment, cooling fan failure |
DE102013200277A1 (de) | 2013-01-10 | 2014-01-30 | E.G.O. Elektro-Gerätebau GmbH | Heizeinrichtung und Verfahren zur Temperaturmessung an der Heizeinrichtung |
DE102015207253A1 (de) | 2015-04-21 | 2016-10-27 | E.G.O. Elektro-Gerätebau GmbH | Heizeinrichtung zum Erhitzen von Flüssigkeiten, Verdampfer für ein Elektrogargerät und Verfahren zum Betrieb einer Heizeinrichtung |
PL3096585T3 (pl) | 2015-05-18 | 2018-06-29 | E.G.O. Elektro-Gerätebau GmbH | Urządzenie grzejne do ogrzewania płynów i sposób eksploatacji takiego urządzenia grzejnego |
EP3145273B1 (de) * | 2015-09-21 | 2019-08-07 | E.G.O. ELEKTRO-GERÄTEBAU GmbH | Heizeinrichtung zum erhitzen von wasser und verfahren zum betrieb einer solchen heizeinrichtung |
DE102016214283A1 (de) | 2016-08-02 | 2018-02-08 | E.G.O. Elektro-Gerätebau GmbH | Verdampfereinrichtung für Wasser und Gargerät mit einer solchen Verdampfeinrichtung |
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 |
DE102018203609B4 (de) | 2018-03-09 | 2022-01-05 | E.G.O. Elektro-Gerätebau GmbH | Verfahren und Vorrichtung zur Erfassung einer Temperatur an einem Heizelement |
DE102018213869B4 (de) * | 2018-08-17 | 2020-03-05 | E.G.O. Elektro-Gerätebau GmbH | Heizeinrichtung und Verfahren zum Betrieb einer Heizeinrichtung |
US11614497B2 (en) | 2019-12-03 | 2023-03-28 | International Business Machines Corporation | Leakage characterization for electronic circuit temperature monitoring |
EP3835654A1 (en) | 2019-12-13 | 2021-06-16 | E.G.O. Elektro-Gerätebau GmbH | Method of operating a steam generator, steam generator and cooking device |
EP3840528B1 (en) | 2019-12-16 | 2022-10-12 | E.G.O. Elektro-Gerätebau GmbH | Method of operating a steam generator, steam generator and cooking device with a steam generator |
DE102020207784A1 (de) * | 2020-06-23 | 2021-12-23 | E.G.O. Elektro-Gerätebau GmbH | Heizeinrichtung mit einer Temperaturmesseinrichtung und Verfahren zur Temperaturmessung an der Heizeinrichtung und zur Herstellung |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2272619A (en) * | 1992-11-11 | 1994-05-18 | Central Research Lab Ltd | Temperature control in a heater assembly |
NL1014601C2 (nl) * | 2000-03-10 | 2001-09-11 | Ferro Techniek Bv | Verwarmingselement, vloeistofhouder en werkwijze voor het waarnemen van temperatuurwisselingen. |
WO2002096155A1 (en) * | 2001-05-23 | 2002-11-28 | Koninklijke Philips Electronics N.V. | Heater with overheating protection |
US8680443B2 (en) * | 2004-01-06 | 2014-03-25 | Watlow Electric Manufacturing Company | Combined material layering technologies for electric heaters |
EP1831120B1 (en) * | 2004-11-23 | 2015-08-19 | Ferro Techniek Holding B.V. | Enamel composition, assembly and use thereof on a substrate surface |
-
2006
- 2006-05-23 NL NL2000081A patent/NL2000081C2/nl not_active IP Right Cessation
- 2006-08-18 CN CNU2006201312251U patent/CN200950672Y/zh not_active Expired - Fee Related
-
2007
- 2007-05-23 EP EP07747463A patent/EP2027753A1/en not_active Withdrawn
- 2007-05-23 WO PCT/NL2007/050240 patent/WO2007136268A1/en active Application Filing
Non-Patent Citations (1)
Title |
---|
See references of WO2007136268A1 * |
Also Published As
Publication number | Publication date |
---|---|
NL2000081C2 (nl) | 2007-11-26 |
CN200950672Y (zh) | 2007-09-19 |
WO2007136268A1 (en) | 2007-11-29 |
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Legal Events
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Effective date: 20121031 |
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STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
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18D | Application deemed to be withdrawn |
Effective date: 20130311 |