EP0209201B1 - Verfahren zum Erhitzen in einem Herd und Mikrowellenherd zur Durchführung des Verfahrens - Google Patents

Verfahren zum Erhitzen in einem Herd und Mikrowellenherd zur Durchführung des Verfahrens Download PDF

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Publication number
EP0209201B1
EP0209201B1 EP19860201243 EP86201243A EP0209201B1 EP 0209201 B1 EP0209201 B1 EP 0209201B1 EP 19860201243 EP19860201243 EP 19860201243 EP 86201243 A EP86201243 A EP 86201243A EP 0209201 B1 EP0209201 B1 EP 0209201B1
Authority
EP
European Patent Office
Prior art keywords
heating
weight
food
cooking
block
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.)
Expired
Application number
EP19860201243
Other languages
English (en)
French (fr)
Other versions
EP0209201A1 (de
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/de
Application granted granted Critical
Publication of EP0209201B1 publication Critical patent/EP0209201B1/de
Expired 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
    • 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 of automatically cooking food in an oven in which a signal representative of at least one parameter indicative of the extent to which cooking has been completed is fed back to a device controlling a source of the energy employed in cooking, the weight of the food being cooked being measured as cooking proceeds.
  • DE-C2-32 05 124 a microwave oven is described in which during cooking at several time intervals the weight of the food is measured and compared with a calculated final or desired weight in order to control the process. Such a weighing measurement only is not sufficient for a reliable control of the cooking process. Therefore to compensate for intervening factors sensors are located in the inlet and outlet air paths of the cooking chamber, the signals therof being used for additional control of the process.
  • the object of the present invention is to improve the above described method in which use is made only of weight sensing to control the process.
  • the method is characterized in that the weight decrease rate of the food is the parameter fed back to the control device.
  • the weight decrease rate is a very reliable parameter for sensing the condition of the food. For example, the weight decrease will 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 convection inwardly is small. The surface temperature then does not need to be 100°C because the power balance due to convective and evaporative surface cooling can occur earlier.
  • a final heating power and time are initiated when said weight decrease rate reaches a predetermined level. Initiating the final heating is inhibited if the running heating time is greater than a predetermined heating time.
  • a further embodiment of the invention is characterized in that after starting an initial heating power another parameter representing the difficulty of heating said food based upon the time required for said weight to reach a predetermined weight is determined, said parameter being used for the selection of a heating power for continued heating.
  • the invention also relates to a microwave oven for carrying out the above described method comprising a microwave source for feeding microwave energy into the oven cavity where the food to be cooked is placed, a weighing device for weighing the food inside the cavity and delivering an analogue signal indicative of the measured weight, an analogue-to-digital converter for converting the analogue signal into a digital signal, characterized in that it comprises a control device responsive to said digital signal for controlling the microwave source in respect of power level and/or remaining cooking time in dependence on the weight decrease rate of the food as cooking proceeds.
  • Figure 1 shows the power balance during heating in a microwave oven
  • Figure 2 shows the corresponding power balance in case of cooking, i.e. when the temperature no longer increases
  • Figure 3 shows some curves of the weight decrease for different food products as function of the time in case of heating in microwave oven
  • Figure 4 shows a basic block diagram for a microwave oven according to the invention
  • Figure 5 shows a flow diagram for the process in case of automatic control of a microwave oven according to the principles of the invention.
  • Fig. 1 showing the power balance during heating at a temperature of 40°C
  • P0 represents supplied power
  • P1 represents the evaporative losses
  • P2 represents the convective losses
  • P3 represents losses due to heating of the 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 power 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 of cooking (about 100°C)
  • P0 again represents supplied power
  • P1' represents the evaporative losses
  • P2' the convective losses.
  • the utilized power in the food is zero including loss 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.
  • Fig. 3 shows some curves over the weight decrease S as a function of the time t in some different heating cases.
  • the curve 1a relates to about 400 g water or soup in an open pan
  • the curve 1b the same quantity in a covered pan
  • the curve 2 relates to the same quantity of compact food, such as pudding, in a covered pan
  • the curve 3 relates to a larger quantity (1000 g) of compact food.
  • the initial temperature in all cases is normal room temperature and the oven is a microwave oven with about 600 W output power.
  • heating process can be interrupted immediately (the temperature is ca. 65°C).
  • the heating time can be elongated with ca. 30% which results in a final temperature of 75°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 basic 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 continuously measures the weight of the introduced food.
  • the scale which may be of strain gauge type, 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 heating or cooking process is according to the invention controlled with signals derived from the weight indicating signal delivered by the scale D.
  • 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, the heating or cooking process is controlled such that an 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 a desired function.
  • a microprocessor or the like which is pre-programmed to perform a 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 “taring" 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 manual heating. This is because small quantities should not be heated automatically. If the answer is "no” then the process continues and a parameter T1, representing the initial temperature of the food is set, in block 16.
  • T1 which is set by means of buttons on the keyboard can,for example, assume one of three values representing "freezer temperature”, "refrigerator temperature” and "room temperature", respectively.
  • the desired process is selected, in block 17, also by means of buttons on the keyboard. For the selection in block 17 there are for example two alternatives: “heating” and "cooking".
  • the heating process is then started by pushing a start button, in 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, in block 19.
  • the absolute decrease of weight M-M p is determined and the following question "is M-M p larger than 2 g ?" is made, M p being the weight of the food during the heating. If the answer to the question in the block 20 is "no" then repeatedly a new calculation of the absolute decrease of weight M-M p and comparison with the absolute value 2 g is effected.
  • A f (t1/M + k T1) where f is an empirically obtained function, t1, 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 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 equilibrium 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 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 the foregoing weight measurement is determined and the question "is t' equal to tv?" is made. If the answer "no" then the time measurement continues.
  • t s f'' (s . t + r . t1) where f '' is an empirically determined function of t and t1 and s , r are scale factors.
  • P s f''' (s . M) where f ''' is an empirically determined function of M and s is a scale factor.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Electric Ovens (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)

Claims (6)

  1. Verfahren zum automatischen Kochen von Nahrung in einem Ofen, in dem ein Signal, das für wenigstens einen Parameter repräsentativ ist, der eine Anzeige ist für das Ausmaß, in dem das Kochen fortgeschritten ist, zu einer Vorrichtung zurückgeführt wird, die eine zum Kochen verwendete Energiequelle steuert, wobei das Gewicht der zu kochenden Nahrung beim Kochen gemessen wird, dadurch gekennzeichnet , daß die Gewichtsabnahmegeschwindigkeit der Nahrung der zur Steuervorrichtung zurückgeführte Parameter ist.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet , daß eine schlußendliche Heizleistung und Heizzeit eingeschaltet werden, wenn die genannte Gewichtsabnahmegeschwindigkeit einen vorbestimmten Pegel erreicht.
  3. Verfahren nach Anspruch 2, dadurch gekennzeichnet , daß das Einschalten der schlußendlichen Heizung gesperrt wird, wenn die laufende Heizzeit länger ist als eine vorbestimmte Heizzeit.
  4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß die genannte vorbestimmte Heizzeit auf einem Anfangsgewicht der Nahrung und auf einer vorher fortgesetzten Heizleistung basiert wird.
  5. Verfahren nach Anspruch 1, dadurch gekennzeichnet , daß nach dem Starten einer Anfangsheizleistung ein anderer Parameter bestimmt wird, der die Schwierigkeit der Erhitzung der genannten Nahrung darstellt, und zwar basiert auf der für dieses Gewicht erforderlichen Zeit zum Erreichen eines vorbestimmten Gewichts, wobei dieser Parameter zum Wählen einer Heizleistung für fortgesetztes Erhitzen verwendet wird.
  6. Mikrowellenherd zum Durchführen des Verfahrens nach einem der Ansprüche 1 bis 5 mit einer Mikrowellenquelle zum Einspeisen von Mikrowellenenergie in einen Ofenraum, in dem die zu kochende Nahrung hingestellt ist, mit einer Wägevorrichtung zum Wägen der Nahrung in dem Raum und zum Liefern eines analogen Signals, das das gemessene Gewicht angibt, mit einem Analog-Digital-Wandler zum Umwandeln des analogen Signals in ein Digitalsignal, dadurch gekennzeichnet , daß der Herd eine Regelvorrichtung aufweist, die auf das genannte digitale Signal reagiert zur Regelung der Mikrowellenquelle in bezug auf Leistungspegel und/oder restliche Kochzeit abhängig von der Gewichtsabnehmegeschwindigkeit der Nahrung während des Kochvorgangs.
EP19860201243 1985-07-18 1986-07-15 Verfahren zum Erhitzen in einem Herd und Mikrowellenherd zur Durchführung des Verfahrens Expired EP0209201B1 (de)

Applications Claiming Priority (2)

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

Publications (2)

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

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Application Number Title Priority Date Filing Date
EP19860201243 Expired EP0209201B1 (de) 1985-07-18 1986-07-15 Verfahren zum Erhitzen in einem Herd und Mikrowellenherd zur Durchführung des Verfahrens

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EP (1) EP0209201B1 (de)
JP (1) JPS6266025A (de)
DE (1) DE3679000D1 (de)
SE (1) SE452838B (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4970374A (en) * 1988-09-02 1990-11-13 Matsushita Electric Industrial Co., Ltd. Automatic heating appliance with weight sensor
JPH02110217A (ja) * 1988-10-18 1990-04-23 Matsushita Electric Ind Co Ltd 加熱装置
US6489596B2 (en) * 2001-01-09 2002-12-03 Li-Tsan Chu Quantitative cooking device
KR100499024B1 (ko) * 2003-01-11 2005-07-01 삼성전자주식회사 전자레인지 및 그 제어방법
EP1656035A1 (de) * 2003-08-15 2006-05-17 Koninklijke Philips Electronics N.V. Verfahren zur bestimmung des endzeitpunktes in einem verfahren zur herstellung eines nahrungsmittels

Family Cites Families (7)

* 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
CA1183907A (en) * 1980-09-24 1985-03-12 Wesley W. Teich Heating time coupling factor for microwave oven
JPS5816667A (ja) * 1981-07-20 1983-01-31 Matsushita Electric Ind Co Ltd 高周波加熱による解凍方法
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
US4508948A (en) * 1984-01-16 1985-04-02 Amana Refrigeration, Inc. Microwave cooking method

Also Published As

Publication number Publication date
SE8503510D0 (sv) 1985-07-18
DE3679000D1 (de) 1991-06-06
SE452838B (sv) 1987-12-14
SE8503510L (sv) 1987-01-19
EP0209201A1 (de) 1987-01-21
JPS6266025A (ja) 1987-03-25

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