EP0209201A1 - Procédé pour chauffer dans un four et four à micro-ondes appliquant le procédé - Google Patents

Procédé pour chauffer dans un four et four à micro-ondes appliquant le procédé Download PDF

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Publication number
EP0209201A1
EP0209201A1 EP19860201243 EP86201243A EP0209201A1 EP 0209201 A1 EP0209201 A1 EP 0209201A1 EP 19860201243 EP19860201243 EP 19860201243 EP 86201243 A EP86201243 A EP 86201243A EP 0209201 A1 EP0209201 A1 EP 0209201A1
Authority
EP
European Patent Office
Prior art keywords
weight
heating
weight decrease
food
oven
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.)
Granted
Application number
EP19860201243
Other languages
German (de)
English (en)
Other versions
EP0209201B1 (fr
Inventor
Per Olov Gustav Risman
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.)
Whirlpool Europe BV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
Philips Norden AB
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 Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV, Philips Norden AB filed Critical Philips Gloeilampenfabrieken NV
Publication of EP0209201A1 publication Critical patent/EP0209201A1/fr
Application granted granted Critical
Publication of EP0209201B1 publication Critical patent/EP0209201B1/fr
Expired legal-status Critical Current

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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
    • H05B6/00—Heating by electric, magnetic or electromagnetic fields
    • H05B6/64—Heating using microwaves
    • H05B6/6447—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors
    • H05B6/6464—Method of operation or details of the microwave heating apparatus related to the use of detectors or sensors using weight sensors

Definitions

  • the invention relates to a method for heating of food in oven, in which energy is fed into an oven space, where the food is placed, and at least one signal representing at least one parameter at the heating being fed back to a control device for the energy source for influencing the heating procedure, for example as regards power level and remaining processing time in an automatic heating process.
  • a common direct method is temperature measurement by means of insert transducers.
  • these transducers do only function reliably in liquid-shaped or relatively thich heating objects.
  • overheating can arise in the surface at the place of insertion.
  • Further drawbacks are due to difficulties in the handling and problems in case of rotating bottom place in the oven.
  • An essential and principle weakness is that the temperature is only measured in one point, which is not always representative.
  • Weight sensors of different types have come to increased use. Normally the heating pan is tared empty, whereafter the food is introduced and the whole is put into the oven. Usually it is also necessary to push a button for initial temperature (e.g. frozen, refrigirator temperature, room temperature) and another for desired process (e.g. defrosting, re-heating, cooking). In a newer type of automatic control humidity sensing and weight sensing have also been combined. In these knwon systems the weighing scale however only serves as an auxilliary device in order to decrease the requirement for judgement from the users side.
  • initial temperature e.g. frozen, refrigirator temperature, room temperature
  • desired process e.g. defrosting, re-heating, cooking.
  • the invention relates to an automatic heating procedure in oven, which is controlled thereby that a signal representing the instantaneous condition of the food during the heating procedure is fed back to the energy source and the object of the invention is to enable an improved and more optimal control of the automatic process than that obtained with use of previously known sensors, in particular humidity sensors.
  • the invention is based upon the idea that the weight decrease and the course of the same will give a better indication on the evaporation and its course, which in turn is a good indication on the instantaneous condition of the food, than that which can be obtained with use of humidity sensor.
  • the weight decrease will for example not be constant until a moment, when the food has been heated down to an appreciable depth below the surface, so that its cooling due to heat convention inwardly is small.
  • the surface temperature then does not need to be 100 0 C because the power balance due to convective and evaporative surface cooling can occur earlier.
  • the weight decrease and its course can be used for sensing the condition of the food far beyond the moment, when for example a humidity transducer according to know technic has ceased to produce signal variation.
  • Furthermore supplied power can easily be sensed by the electronic means which are included in the system: then a further possibility is obtained for comparison with the weight decrease rate for controlling the termination of the heating or cooking process.
  • the weight decrease as such does not always provide the best indication on how far the heating has advanced.
  • the initial weight and the variation rate of the weight are known an appreciably improved automatic control can be realized.
  • the initial weight of the food is measured and used in combination with the weight decrease for controlling the automatic process.
  • the instantaneous weight decrease rate i.e. the weight decrease per time unit, is determined and used in order to control the process.
  • a usable control parameter representing the weight decrease is the elapsed time until a given absolute or relative weight decrease has occured.
  • Another usable control parameter representing the weight decrease rate is the elapsed time until a given weight decrease rate has been reached.
  • the absolute or relative weight decrease can be used in combination with the instantaneous weight decrease rate for controlling the automatic heating process.
  • the intended process type (defrosing, re-heating, cooking) can be selected by the user, this selection being used in combination with measured weight decrease or weight decrease rate in a pre-programmed final processing algorithm with the initial weight as variable.
  • a microwave oven in which the method is used, comprising an oven cavity for accomodating the food to be heated and a microwave source for feeding microwave energy into the cavity, is according to the invention characterized thereby that it comprises a weighing device which consecutively (continously or intermittently) determines the weight of the food introduced into the oven cavity and delivers a signal representing this weight, an analogue-to-digital converter for converting the weight indicating signal to a digital magnitude and a control device for the microwave source, which is supplied with the signal from the analogue-to-digital converter and is adapted to influence the heating process as regards power level and/or remaining process time in dependence on parameters which are derived from the said weight indicating signal and which represent weight decrease or weight decrease rate and elapsed time and initial weight.
  • the microwave oven can furthermore comprise a keyboard for setting desired process type (defrosting, re-heating, cooking), the setting of the keyboard influencing the control device to produce desired final heating in combination with measured weight decrease or weight decrease rate and initial weight.
  • desired process type defrosting, re-heating, cooking
  • Fig. 1 showing the power balance during heating at a temperatur of ca. 40 0 C
  • P0 represents supplied power
  • P1 represents the evaporative losses
  • P2 represents the convective losses
  • P3 represents losses due to heating of vessel
  • P4 represents the utilized power, i.e. the power which is dissipated in the food and which causes temperature increase therein. It is evident that the main part of the supplied is utilized in the food, while the evaporative loss power as well as remaining loss powers are relatively small as compared with the utilized power.
  • Fig. 2 showing the power balance in case of cooking (ca. 100 o C)
  • PO again represents supplied power
  • P1' represents the evaporative losses
  • P2' the convective losses.
  • the utilized power in the food is zero as well as losses due to heating of the vessel. In this case all supplied power also must be removed, which usually takes place by evaporation. This will result in a constant weight decrease rate.
  • An evaporative loss power of 300 W for example corresponds to a weight decrease rate of ca. 8g/minute at a surface temperature of +80 0 C.
  • Fig. 3 shows some curves over the weight decrease S as function of the time t in some different heating cases: the curve 1a relates to ca. 400 g water or soup in an open pan, the curve 1b the same quantity in a covered pan, the curve 2 relates the same quantity of compact food, for example pudding, in a covered pan and the curve 3 relates to a larger quantity (1000 g) of compact food.
  • the initial temperature is in all cases normal room temperature and the oven is a microwave oven with ca. 600 W output power.
  • heating process can be interrupted immediately (the temperature is ca. 65 0 C).
  • the heating time can be elongated with ca. 30% which results in a final temperature of 75 0 C.
  • the heating continues with a relatively low power (this has not been done in the curve). After a while v/V will be > a given pre-programmed value (perhaps after 3 minutes). Then the heating continues further 30% of the total heating time until then, whereafter the food is ready.
  • FIG. 4 shows schematically a microwave oven with magnetron and a coarse diagram for a control circuit, by means of which the principles of the invention can be realized.
  • A designates an oven cavity
  • B is a magnetron which via a waveguide connection (not shown) feeds microwave energy into the cavity
  • C is a start-stop circuit for the magnetron.
  • C is included a timer and an intermittently operating switch arrangement, as a cam follower device, whereby the average power delivered by the magnetron can be set.
  • a weighing scale D is according to the invention placed in the bottom of the cavity and measures continously the weight of the introduced food.
  • the scale which may of strain gaugetype, delivers an electrical signal which represents the instantaneous value of the measured weight.
  • This signal is fed to an analogue-to-digital converter E, in which it is converted to a digital signal, and is thereafter applied to a control device F.
  • the control device F receives signals from a keyboard G and delivers its output signal to the start-stop circuit for the magnetron.
  • the keyboard G can also be directly connected to the start-stop circuit for pure manual setting.
  • the control device F comprises for this purpose memory means, in which the initial weight of the introduced food with reduction for the weight of the vessel is stored. Furthermore the control device F has calculating means which from the weight indicating signal derives magnitudes representing the weight decrease and/or the weight decrease rate. By means of these magnitudes: initial weight, weight decrease and/or weight decrease rate then the heating or cooking process is controlled such that optimal result is obtained in each individual heating case.
  • the control device F can suitably comprise a microprocessor or the like, which is pre-programmed to perform desired function.
  • a microprocessor or the like which is pre-programmed to perform desired function.
  • An example of a flow diagram for a program which is executed by a microprocessor included in the control device is given in Fig. 5.
  • the process is started by pushing an "on"-button, represented by the block 10 in Fig. 5, whereby the oven is made clear for use. Thereafter taring is effected by putting the empty vessel into the oven and pushing a button marked “tarinq" represented by the block 11 in Fig. 5, whereby the vessel is weighed and the weight of the vessel M T is stored. Then the vessel is filled with food to be heated and weighing of the food plus the vessel is initiated by pushing a corresponding button on the keyboard. This operation is represented by the block 12 in Fig. 5. The initial weight M of the food is then calculated by subtracting the weight M T of the vessel from the total weight determined in the block 12 and the value of M is stored in order to serve as a control parameter during the whole heating process.
  • the calculation and storing of the initial weight M is represented by the block 13 in Fig. 5.
  • the block 14 it is checked if M is smaller than 50 g. If the answer is "yes” then the process is interrupted, the block 15, and the oven assumes ready state for Automatic heating. This is because so small quantities are not heated automatically. If the answer is "no” then the process continues thereby that a parameter T1 representing the initial temperature of the food is set, the block 16.
  • T1 which is set by means of buttons on the keyboard can for example assume one of three values representing "freezing temperature”, "refrigirator temperature” and "room temperature”, respectively. Then desired process is selected, the block 17, also by means of buttons on the keyboard.
  • the heating process is then started by pushing a start button, the block 18, whereby the magnetron is connected to its operation voltage. Simultanously the timer is started for indicating the running time t from the start of the magnetron, the block 19.
  • the absolute decrease of weight M-Mp is determined and the following question "is M-Mp larger than 2 g ?" is made, Mp being the weight of the food during the heating. If the answer to the question in the block 20 is "no" then repeatedly new calculation of the absolute decrease of weight M-Mp and comparison with the absolute value 2 g is effected.
  • the program continues by forming a parameter A, the block 22, which is defined by the formula: where f - is an empirically obtained function, t 1 , M and T1 have the previously mentioned meanings and k is a scale factor.
  • the value of the parameter A is an indication on how difficult it is to heat the food; the smaller A is the more difficult it is to heat the object.
  • the constants X , y and z are empirically determined in such manner that the power P is adapted to the load in each individual operation case.
  • a parameter V is determined, which parameter is defined as the maximal weight decrease per time unit, i.e. the weight decrease rate at temperature equilibration and for the selected power. This is effected in the block 31 in Fig. 5.
  • a measuring procedure takes place, which leads to final heating and switching-off of the oven.
  • This is in first hand effected by means of the weight decrease rate, which is determined intermittently with a time interval of t v , e.g. 20 seconds, the blocks 32 and,33.
  • the running time t' from foregoing weight measurement is determined and the question "is t' equal to t?" is made.
  • the program proceeds to the block 44 where the final time t ⁇ is determined according to the formula: where f ,,is an empirically determined function of t and t 1 and s, r are scale factors.
  • the block 45 according to the formula; where f"' is an empirically determined function of M and a is a scale factor.
  • the question "is t equal to t ⁇ ?" is made in the block 46. As long as the answer in the block 46 is "no" the final heating continues with the determined power. When the answer in the block 46 is "yes” then the heating is interrupted, the block 47, and the oven returns to the ready state.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Electric Ovens (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)
EP19860201243 1985-07-18 1986-07-15 Procédé pour chauffer dans un four et four à micro-ondes appliquant le procédé Expired EP0209201B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8503510A SE452838B (sv) 1985-07-18 1985-07-18 Forfarande for uppvermning av livsmedel i ugn samt mikrovagsugn for utforande enligt forfarandet
SE8503510 1985-07-18

Publications (2)

Publication Number Publication Date
EP0209201A1 true EP0209201A1 (fr) 1987-01-21
EP0209201B1 EP0209201B1 (fr) 1991-05-02

Family

ID=20360923

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19860201243 Expired EP0209201B1 (fr) 1985-07-18 1986-07-15 Procédé pour chauffer dans un four et four à micro-ondes appliquant le procédé

Country Status (4)

Country Link
EP (1) EP0209201B1 (fr)
JP (1) JPS6266025A (fr)
DE (1) DE3679000D1 (fr)
SE (1) SE452838B (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0359976A1 (fr) * 1988-09-02 1990-03-28 Matsushita Electric Industrial Co., Ltd. Dispositif de chauffage automatique avec capteur de poids
US6489596B2 (en) * 2001-01-09 2002-12-03 Li-Tsan Chu Quantitative cooking device
EP1437921A2 (fr) * 2003-01-11 2004-07-14 Samsung Electronics Co., Ltd. Four à micro-ondes et sa méthode de commande
WO2005016026A1 (fr) * 2003-08-15 2005-02-24 Koninklijke Philips Electronics N.V. Procede de determination de l'instant ou un aliment est pret, dans un processus de preparation d'aliments

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02110217A (ja) * 1988-10-18 1990-04-23 Matsushita Electric Ind Co Ltd 加熱装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3138026A1 (de) * 1980-09-24 1982-05-06 Raytheon Co Mikrowellenofen und verfahren zu seiner steuerung
EP0070728A1 (fr) * 1981-07-20 1983-01-26 Matsushita Electric Industrial Co., Ltd. Procédé et appareil pour décongeler par chauffage à haute fréquence
US4447693A (en) * 1979-09-06 1984-05-08 Litton Systems, Inc. Power controlled microwave oven
US4508948A (en) * 1984-01-16 1985-04-02 Amana Refrigeration, Inc. Microwave cooking method

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5847934A (ja) * 1981-09-14 1983-03-19 Mitsubishi Electric Corp 高周波加熱装置
JPS58150717A (ja) * 1982-03-02 1983-09-07 Mitsubishi Electric Corp 加熱調理装置
JPS58153023A (ja) * 1982-03-09 1983-09-10 Mitsubishi Electric Corp 加熱調理装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4447693A (en) * 1979-09-06 1984-05-08 Litton Systems, Inc. Power controlled microwave oven
DE3138026A1 (de) * 1980-09-24 1982-05-06 Raytheon Co Mikrowellenofen und verfahren zu seiner steuerung
EP0070728A1 (fr) * 1981-07-20 1983-01-26 Matsushita Electric Industrial Co., Ltd. Procédé et appareil pour décongeler par chauffage à haute fréquence
US4508948A (en) * 1984-01-16 1985-04-02 Amana Refrigeration, Inc. Microwave cooking method

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0359976A1 (fr) * 1988-09-02 1990-03-28 Matsushita Electric Industrial Co., Ltd. Dispositif de chauffage automatique avec capteur de poids
US4970374A (en) * 1988-09-02 1990-11-13 Matsushita Electric Industrial Co., Ltd. Automatic heating appliance with weight sensor
US6489596B2 (en) * 2001-01-09 2002-12-03 Li-Tsan Chu Quantitative cooking device
EP1437921A2 (fr) * 2003-01-11 2004-07-14 Samsung Electronics Co., Ltd. Four à micro-ondes et sa méthode de commande
EP1437921A3 (fr) * 2003-01-11 2007-01-03 Samsung Electronics Co., Ltd. Four à micro-ondes et sa méthode de commande
WO2005016026A1 (fr) * 2003-08-15 2005-02-24 Koninklijke Philips Electronics N.V. Procede de determination de l'instant ou un aliment est pret, dans un processus de preparation d'aliments

Also Published As

Publication number Publication date
JPS6266025A (ja) 1987-03-25
SE452838B (sv) 1987-12-14
DE3679000D1 (de) 1991-06-06
EP0209201B1 (fr) 1991-05-02
SE8503510D0 (sv) 1985-07-18
SE8503510L (sv) 1987-01-19

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