EP0991299A2 - Système de cuisson électrique par transfert de chaleur par contact ainsi que le procédé de commande associé à un tel système - Google Patents

Système de cuisson électrique par transfert de chaleur par contact ainsi que le procédé de commande associé à un tel système Download PDF

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Publication number
EP0991299A2
EP0991299A2 EP99119462A EP99119462A EP0991299A2 EP 0991299 A2 EP0991299 A2 EP 0991299A2 EP 99119462 A EP99119462 A EP 99119462A EP 99119462 A EP99119462 A EP 99119462A EP 0991299 A2 EP0991299 A2 EP 0991299A2
Authority
EP
European Patent Office
Prior art keywords
hotplate body
cooking system
heating
cooking
hotplate
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Withdrawn
Application number
EP99119462A
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German (de)
English (en)
Other versions
EP0991299A3 (fr
Inventor
Gerhard Schmidmayer
Lars Schubert
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BSH Hausgeraete GmbH
Original Assignee
BSH Bosch und Siemens Hausgeraete GmbH
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 BSH Bosch und Siemens Hausgeraete GmbH filed Critical BSH Bosch und Siemens Hausgeraete GmbH
Publication of EP0991299A2 publication Critical patent/EP0991299A2/fr
Publication of EP0991299A3 publication Critical patent/EP0991299A3/fr
Withdrawn legal-status Critical Current

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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
    • 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 present invention relates to a contact heat-transferring electric cooking system with a hotplate body for heating a cooking vessel which can be placed on the upper side thereof, with a centrally arranged first heating element held on the underside and at least one second heating element arranged peripherally thereto, to which at least one temperature sensor is assigned, and with a control unit, which is connected to the heating elements and the temperature sensors for controlling the heating power of the cooking system, and a method for operating the cooking system.
  • Such a cooking system is known from the publication DE 197 01 640 A1, the electric hotplate transmitting the contact heat consisting of a non-oxide ceramic, in particular of silicon nitride.
  • Its very thin hotplate body is self-supporting in the form of a disc in a built-in plate, for example a glass ceramic plate, and has an extremely flat surface or the surface contour of a special cooking vessel base. This results in such a small gap to the bottom of the cooking vessel that thermal coupling is possible even with greater power densities with only a small K temperature difference.
  • the cooking surface of the hotplate body is convexly curved upwards in the form of a spherical cap. In such an embodiment, it is necessary that the lower surface of the The bottom of the saucepan has the appropriate shape, ie in this case it is concavely curved in the same way.
  • the object of the present invention is to provide a cooking system according to the preamble of claim 1, the high efficiency of which is essentially independent of the contour of the underside of the pan base.
  • this is achieved in a cooking system according to the preamble of claim 1 in that the control unit sets a temperature or linear expansion gradient in the hotplate body from the central area to the peripheral area thereof through the predefined heating outputs of the heating elements and thereby a defined curvature of the hotplate body for minimization of the distance between the top of the hotplate body and the bottom of the cooking vessel.
  • the method according to the invention for operating the cooking system is characterized in that, at least in a certain phase of the heating process, the temperature in the central area of the hotplate body is kept higher than in the peripheral area by a control unit in order to achieve a defined curvature of the hotplate body in the direction of the cooking vessel base located above it .
  • the defined temperature gradients in the hotplate body cause corresponding stresses in the hotplate body, which cause its defined curvature.
  • the cooking system according to the invention is suitable for setting the degree of curvature or the flatness of the top of the hotplate body in a defined manner. This makes it possible, irrespective of the contour of the bottom of the cooking vessel, to make the distance or air gap suitably small. Regardless of the cooking vessel used, a good thermal coupling of the hotplate body to the cooking vessel is always ensured.
  • a surface protective layer using the sol-gel technique is advantageously applied to the top of the hotplate body.
  • this prevents protection against the tarnishing of stainless steel hotplate bodies or scratching or other soiling.
  • extremely thin protective layers can be easily implemented using sol-gel technology.
  • the sol-gel layer can be applied to the hotplate body, for example, in a simple immersion process.
  • the low baking temperatures compared to the enamelling technique are particularly favorable in the sol-gel technique.
  • the applied sol-gel layers are also suitable for the temperatures typical in such cooking systems.
  • the layer thicknesses are only a few ⁇ m. Due to the sol-gel technique the layers applied, despite their low thickness, both in the case of a multi-layer technique on one another and on the substrate material itself, in particular metal, have great stability and great adhesion.
  • the hotplate body is formed in a dome-shaped manner at approximately 20 ° C.
  • This curvature away from the underside of the pot bottom can be realized in particular by a crowning of a metal plate serving as a hotplate body or another suitable material. This ensures that pots with cup bases that curve downward in the form of a dome can be placed on the cooking system in a stable manner and at the same time a large-area thermal contact between the hotplate body and the pot base is possible.
  • the material of the hotplate body is advantageously metal, in particular stainless steel or aluminum. Compared to, for example, silicon nitride, metal in particular has the better thermal conductivity properties and also cost advantages. On the one hand for reasons of stability and on the other hand for reasons of cost, the thickness of the metal plate advantageously ranges between approximately 2 and 5 mm.
  • an expansion plate is held essentially in the central region of the hotplate body, the coefficient of thermal expansion of which differs from that of the hotplate body.
  • the hotplate body has a flat recess on its underside in the central area. In terms of production technology, this is easier than holding the insert in the hotplate body.
  • the central recess for example in the form of a spherical cap, on the underside of the hotplate body in its central region, the heating process leads to tangential and radial tensile stresses. These cause the hotplate body to bend upwards or towards the underside of the cooking vessel base.
  • a sensor system is preferably provided to detect the large-area contact between the bottom of the cooking vessel and the top of the hotplate body.
  • This can be implemented, for example, by a capacitive sensor arrangement.
  • the changing capacitance between the two plates with changing distance between the top of the hotplate body and the underside of the pan base is used in a manner known per se as a measurement signal.
  • the control unit evaluates the rate of change in the temperature of the hotplate body over time during the heating process. This takes advantage of the fact that, with a known heating power supplied, the temperature rise of the hotplate body is significantly reduced if there is sufficient thermal power contact between the pan base and the hotplate body.
  • the cooking vessel manufacturers could announce the flatness or the degree of curvature of the base of the pan, and for the operator to be able to predefine the cooking system via an input unit at the start of the respective cooking process.
  • the control unit then calculates the corresponding heating outputs or heating output profiles of the first and second radiators from the specified curvature and the desired or set heating output.
  • control unit keeps the temperature difference between the central area and the peripheral area of the hotplate body and thus its curvature essentially constant from the detection of sufficient thermal contact between the two. Furthermore, the control unit guarantees, by means of a correspondingly adapted heating output of the two heating elements, that the heating output specified by an operator via the operating unit is reached.
  • control unit first controls the second heating element arranged in the peripheral region of the hotplate body for a certain time.
  • the peripheral area is heated relative to the central area of the hotplate body. Tangential and radial tensile stresses are created in the peripheral area of the hotplate body. As a result of these tensile stresses increases the size of the radiator and excellent flatness of the surface of the hotplate body is achieved.
  • a hob has a glass ceramic plate 1, in or below which a cooking system 3 is held.
  • a circular hotplate body 5 made of stainless steel is placed in a circular opening of the glass ceramic plate 1 from above.
  • a pot 6 known per se is placed with an underside of the pot bottom (shown in broken lines).
  • an undesirable air gap is formed at room temperature between the top of the hotplate body 5 and the underside of the pan base 6, which affects the heat transfer from the hotplate body 5 to the pan base 6.
  • the hotplate body 5 is designed as a 4 mm thick disc, the upper side of which is provided with an approximately 5 ⁇ m thick transparent protective layer 13 applied using the sol-gel technique.
  • the protective layer is also possible to color and / or make opaque.
  • the protective layer 13 protects the stainless steel during operation, in particular from tarnishing and scratching.
  • the hotplate body 5 On the top of the hotplate body 5 facing the pot 6, the hotplate body 5 has a circumferentially extending shoulder 7 with which the hotplate body 5 lies on the edge region of the opening of the glass ceramic plate 1.
  • a sufficient gap 9 is formed on the circumferential side between the side wall of the hotplate body 5 and the wall of the opening of the glass ceramic plate 1 in order to allow the hotplate body 5 to expand radially when it is heated in the heating process in accordance with the operating procedure.
  • at least the gap 9 is partially filled with silicone adhesive 11.
  • the hotplate body 5 can be held in the opening of the glass ceramic plate 1 by holding devices (not shown).
  • a dome-shaped recess 15 is formed on the underside of the stainless steel plate 5 in the central area. This extends approximately over half the diameter of the hotplate body 5 and reaches its maximum depth in the center or center of the circular disk 5.
  • an electrical insulation layer (not shown in more detail), for example using the sol-gel technique or an enamelling technique upset.
  • a large area of a first heating element 17 is printed on this insulation layer in the region of the recess 15, that is to say in the central region of the hotplate body 5, in particular using thick-film technology with a suitable paste.
  • the first heating element 17 can, for example, run in a spiral and have a plurality of sub-heating circuits connected in series and / or in parallel (not shown).
  • a second heating element 21 and a second temperature sensor 23 are printed over a large area outside the recess 15 in the annular peripheral region of the hotplate body 5.
  • the heating elements 17, 21 and sensors 19, 23 can in turn be covered with a protective layer (not shown).
  • a thermal insulation layer is provided below the heating elements 17, 21 in order to reduce the energy losses of the cooking system 3 below the glass ceramic plate 1 (not shown).
  • the cooking system 3 has an electronic control unit 25, which connects to the first and second heating elements 17, 21 and the first via connecting lines 27 and second temperature sensor 19, 23 is connected. Furthermore, the control unit 25 is connected via control lines 29 to circuit breakers (not shown in more detail) which serve to control the heating power of the heating elements 17, 21. In order to make the power control particularly sensitive, it can be implemented by an oscillation or pulse packet control or a suitable phase control. The appropriate switching or control of mains half-waves ensures that the prescribed flicker rates are observed.
  • An input unit 31 is also connected to the control unit 25. The operator can use this to specify, for example, the desired heating output and, if appropriate, also the nature, in particular the curvature, of the base of the pot.
  • the functioning of the cooking system according to the first exemplary embodiment shown in FIG. 1 can be, for example, the following:
  • the operator specifies a desired output and at the same time the degree of curvature of the pan base used, which is known to him, in the input unit 31.
  • the heating process can also take place fully automatically according to FIG. 2 if the curvature of the pot base 6 is unknown.
  • the control unit 25 switches a limited heating output to the second heating element 21, which is arranged in the peripheral region of the hotplate body 5. This causes tangential and radial tensile stress in the peripheral area, which results in an increase in the circumference or an extension of the hotplate body 5.
  • a complete flatness of the top of the hotplate body 5 can be achieved.
  • This first phase can be completed after a few seconds, for example 15 to 30 seconds. If a pot 6 is placed on the hotplate body 5 with a completely flat bottom of the pot bottom, the actual heating process can be started immediately afterwards.
  • the heating power of the first heating element 17 is increased at time t2 according to FIG. 2.
  • the plate deformation takes place on account of the mechanical effects caused by the heating of the central area Tensions continue towards the bottom of the pot 6, ie the stainless steel plate 5 bulges upwards.
  • the control unit 25 recognizes that the thermal contact between the bottom of the pot 6 and the top of the hotplate body 5 is sufficiently large, ie that the air gap originally present between them is reduced to a minimum.
  • This contact detection is based on the fact that from the time of sufficient thermal contact between the bottom of the pot and the top of the hotplate body 5, the temperature rise per unit of time decreases significantly in the central and peripheral areas. This is caused by the fact that as a result of the good heat-conducting contact between the pot 6 and the hotplate body 5, significantly more heat is removed from the overall system.
  • Typical values for the time interval from time t2 to time t3 can be 30 to 60 seconds.
  • the desired heating output is then set and, at the same time, the required degree of curvature of the hotplate body 5 for establishing a heat-conducting contact to the underside of the pan base 6 is ensured. If it is determined when the desired heating power is reached that the distance between the top of the hotplate body 5 and the bottom of the pan base 6 has increased undesirably, the said temperature gradient is reset by the control unit 25.
  • the hotplate body 5 is in each case slightly modified from that of the first exemplary embodiment.
  • the hotplate body is 5 each with a crown of about 0.1 mm.
  • the hotplate body 5 is designed as a dome that is curved downward in the central region away from the base of the pot.
  • a round plate-shaped insert part 43 can also be inserted into a correspondingly shaped circular recess in the underside of the hotplate body 5. This has a larger coefficient of thermal expansion than the hotplate body 5.
  • the function of the hotplate body 5 according to the third exemplary embodiment corresponds to that of the first and second exemplary embodiment, the mechanical stresses in the hotplate body 5 being caused in particular by the different material properties or coefficients.
  • phase a the hotplate body 5 has a dome-shaped contour that curves downward. To change this, heat is supplied to the peripheral region of the hotplate body 5 via the second heating element 21. In phase b, this leads to complete flatness of the hotplate body 5 due to the mechanical stresses that arise, as explained above.
  • phase c the first heating element 17 in the region of the recess 15 is first subjected to heating power in order to prevent the hotplate body 5 from arching To reach the bottom of the pot 6. Due to the temperature gradient present in the hotplate body 5, the hotplate body 5 bulges into the upwardly curved pot base 6 until there is sufficient thermal contact between the pot base 6 and the hotplate body 5.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Cookers (AREA)
  • Control Of Resistance Heating (AREA)
EP99119462A 1998-09-30 1999-09-30 Système de cuisson électrique par transfert de chaleur par contact ainsi que le procédé de commande associé à un tel système Withdrawn EP0991299A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE1998145103 DE19845103A1 (de) 1998-09-30 1998-09-30 Kontaktwärmeübertragendes elektrisches Kochsystem und Verfahren zum Betreiben eines entsprechenden Kochsystems
DE19845103 1998-09-30

Publications (2)

Publication Number Publication Date
EP0991299A2 true EP0991299A2 (fr) 2000-04-05
EP0991299A3 EP0991299A3 (fr) 2002-01-16

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Application Number Title Priority Date Filing Date
EP99119462A Withdrawn EP0991299A3 (fr) 1998-09-30 1999-09-30 Système de cuisson électrique par transfert de chaleur par contact ainsi que le procédé de commande associé à un tel système

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EP (1) EP0991299A3 (fr)
DE (1) DE19845103A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102007012379A1 (de) * 2007-03-14 2008-09-18 BSH Bosch und Siemens Hausgeräte GmbH Kochfeldvorrichtung

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4394564A (en) * 1981-12-21 1983-07-19 General Electric Company Solid plate heating unit
US4410793A (en) * 1980-09-09 1983-10-18 Karl Fischer Electric hotplate
EP0162620A2 (fr) * 1984-05-11 1985-11-27 THORN EMI Patents Limited Dispositif pour cuire
DE8702883U1 (de) * 1987-02-25 1987-05-07 Rowenta-Werke Gmbh, 6050 Offenbach Vorrichtung zum Warmhalten von Speisen, Getränken, Geschirr o. dgl.
US5352864A (en) * 1990-07-18 1994-10-04 Schott Glaswerke Process and device for output control and limitation in a heating surface made from glass ceramic or a comparable material
DE19701640A1 (de) * 1997-01-10 1998-07-16 Ego Elektro Geraetebau Gmbh Kontaktwärmeübertragendes Kochsystem mit einer Elektro-Kochplatte

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE632822C (de) * 1933-04-12 1936-07-14 Johannes Juul Unmittelbar vom Strom durchflossener Heizkoerper zur Heizung von Bratpfannen, Kochgefaessen u. dgl.
DE757176C (de) * 1939-06-10 1953-02-23 Entpr S Electr Fribourgeoises Elektrische Heizplatte mit Formaenderung in einem bestimmten Sinne
NO135390C (no) * 1975-09-02 1977-03-30 Rdal Og Sunndal Verk A S Elektrisk kokeplate med termostat.
DE19617319A1 (de) * 1996-04-19 1997-10-23 Inter Control Koehler Hermann Verfahren sowie Einrichtung zur Regelung der Heizenergie einer Heizeinheit
DE19643698C2 (de) * 1996-05-11 2000-04-13 Aeg Hausgeraete Gmbh Vorrichtung zur Abschirmung von für kapazitive Messungen verwendeten Leiterbahnen eines Kochfeldes

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4410793A (en) * 1980-09-09 1983-10-18 Karl Fischer Electric hotplate
US4394564A (en) * 1981-12-21 1983-07-19 General Electric Company Solid plate heating unit
EP0162620A2 (fr) * 1984-05-11 1985-11-27 THORN EMI Patents Limited Dispositif pour cuire
DE8702883U1 (de) * 1987-02-25 1987-05-07 Rowenta-Werke Gmbh, 6050 Offenbach Vorrichtung zum Warmhalten von Speisen, Getränken, Geschirr o. dgl.
US5352864A (en) * 1990-07-18 1994-10-04 Schott Glaswerke Process and device for output control and limitation in a heating surface made from glass ceramic or a comparable material
DE19701640A1 (de) * 1997-01-10 1998-07-16 Ego Elektro Geraetebau Gmbh Kontaktwärmeübertragendes Kochsystem mit einer Elektro-Kochplatte

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Publication number Publication date
DE19845103A1 (de) 2000-04-06
EP0991299A3 (fr) 2002-01-16

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