EP0089838B1 - Four à micro-ondes avec circuit de contrôle - Google Patents

Four à micro-ondes avec circuit de contrôle Download PDF

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Publication number
EP0089838B1
EP0089838B1 EP83301543A EP83301543A EP0089838B1 EP 0089838 B1 EP0089838 B1 EP 0089838B1 EP 83301543 A EP83301543 A EP 83301543A EP 83301543 A EP83301543 A EP 83301543A EP 0089838 B1 EP0089838 B1 EP 0089838B1
Authority
EP
European Patent Office
Prior art keywords
monitor
circuit
power
switch
fuse
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
EP83301543A
Other languages
German (de)
English (en)
Other versions
EP0089838A1 (fr
Inventor
Isao Matsumoto
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.)
Sharp Corp
Original Assignee
Sharp Corp
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 Sharp Corp filed Critical Sharp Corp
Publication of EP0089838A1 publication Critical patent/EP0089838A1/fr
Application granted granted Critical
Publication of EP0089838B1 publication Critical patent/EP0089838B1/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
    • H05B6/66—Circuits
    • H05B6/666—Safety circuits

Definitions

  • the present invention relates to a microwave oven having a monitor circuit.
  • Such a monitor circuit is needed in a microwave oven to prevent microwaves from accidentally being scattered from the cavity of the microwave oven. This could otherwise occur when an interlock door switch becomes faulty.
  • Different countries all around the world impose safety standards which require microwave ovens to be provided with such monitor circuits.
  • Fig. 1 shows a known monitor circuit for a microwave oven.
  • the circuit comprises a commercial power source 1, a house main power fuse 2, an AC plug 3, and a microwave oven main fuse 4 rated at about 6-16 A.
  • a first interlock switch 5, which is closed when a latch door is closed, is connected in series with the main fuse 4 and with a primary winding of a high voltage transformer 9 via relay terminals 8 of a relay 7 included within a touch control circuit 6.
  • a second interlock switch 10 is connected between the primary winding of the transformer 9 and the AC plug 3.
  • the first and the second interlock switches 5 and 10 are connected in series with the primary winding of the transformer 9.
  • a monitor switch 11 is connected in series with a monitor resistor 12. This switch 11 is mechanically opened when the latch door is closed, and closed when the door is opened.
  • the terminal of the monitor switch 11 remote from the monitor resistor 12 is connected to a point between the main fuse 4 and the first interlock switch 5.
  • the monitor resistor 12 is connected to the primary winding of the transformer 9.
  • Two terminals 13 and 14 are provided as power input terminals for the touch control circuit 6 which is electronically operated.
  • the terminal 13 is connected to the AC plug 3 via the main fuse 4, and the terminal 14 is directly connected to the AC plug 3.
  • Power is supplied to the touch control circuit 6 by way of a power transformer 15.
  • a rectifier 16 is connected for converting AC power to DC power.
  • the touch control circuit 6 uses DC power from the rectifier 16 for controlling the microwave oven.
  • a conventional microwave generating circuit including a high voltage condenser 17, a high voltage diode 18, a magnetron 19 and the like are connected to the secondary winding of the transformer 9.
  • the monitor resistor 12 is needed.
  • the value of the microwave oven main fuse 4 is not fixed, but rather is variable from one country to another and may be rated at anything from 6-16 A. Depending upon this fuse rating, it may happen that the monitor current can reach such a magnitude that the house main fuse 2 is not adequately protected by the fuse 4 so that it may blow despite the provision of the monitor resistor 12. This is contrary to normal safety standards, which demand that the house main fuse 2 should not be blown when the monitor circuit is operated.
  • said self-holding relay is maintained energized by a current which no longer flows through said monitor circuit.
  • United States patent specification US-A-4054769 discloses a short-circuiting monitor circuit for a microwave oven.
  • a heat-responsive electrical resistance element is connected in the monitor circuit and normally holds closed mechanically an additional protector switch which is in series with the main door switch. In the event of failure of the main door switch, the short circuiting current which flows in the monitor circuit causes the resistance element to fail, and the protector switch opens.
  • a microwave oven having a door interlock switch connected in series with a power utilization circuit of the oven, said interlock switch being arranged to be opened upon opening of a door of the oven; a monitor circuit connected in parallel with said power utilization circuit and including a monitor switch which is arranged to be closed upon opening of a door of the oven; and a power control circuit which is connected to a point on the monitor circuit so that said power control circuit is powered continuously by current which flows in a part of the monitor circuit, said power control circuit being responsive to the cutting of the power supplied thereto by way of said part of the monitor circuit to disable the power utilization circuit; said monitor circuit being connected across power supply terminals coupled to said power utilisation circuit so that if the interlock switch fails to open when the oven door opens, causing power to be applied to said terminals while said-monitor switch is closed, the current flowing through the monitor circuit causes a monitor fuse which is connected in said part of the monitor circuit, to blow, thereby to cut the power supply to said power control circuit and thereby disable the
  • a microwave oven having a door interlock switch connected in series with a power utilization circuit of the oven, said interlock switch being arranged to be opened upon opening of a door of the oven; a monitor circuit connected in parallel with said power utilization circuit, and including a monitor switch which is arranged to be closed upon opening of the door of the oven and a current-limiting resistor in series with said monitor switch; and a power control circuit which includes a touch key panel and a power transformer the primary winding of which is connected to a point on the monitor circuit so that the power control circuit is continuously powered by current which flows through said primary winding and through a part of said monitor circuit, which part excludes the monitor switch and the current-limiting resistor, said control circuit being responsive to the cutting of power supply thereto to open the contact of a power switch connected in series with the power utilization circuit; said monotor circuit being connected across power supply terminals coupled to said power utilization circuit so that if the interlock switch fails to open when the oven door opens, causing power to be applied to said terminal
  • a monitor fuse 20 is connected to a power side terminal of the microwave oven main fuse 4 and the monitor switch 11.
  • the current capacity of thus fuse 20 is about 0.5-1 A which is much less than that of the main fuse 4 of about 6-16 A.
  • a connection point between the monitor fuse 20 and the monitor switch 11 is connected to the input terminal 13 of a power input circuit such as the power transformer 15 in the touch control circuit 6.
  • the monitor switch 11 is connected to the AC plug 3 having three terminals via the monitor resistor 12 and the second interlock switch 10.
  • a touch key panel 21 is provided for key operations for the touch control circuit 6.
  • a .CPU 22 is provided within the touch control circuit 6 for controlling the operations of the microwave oven.
  • An NPN transistor 23 is connected to the CPU 22 via a drive circuit 24.
  • a cook start relay 25 is connected at the collector side of this transistor 23.
  • Relay terminals 26 are related to the cook start relay 25.
  • the relay terminals 26 are connected to the primary winding of the high voltage transformer 9 and to the first interlock switch 5 coupled to the microwave oven main fuse 4.
  • the monitor switch 11 is mechanically opened when the latch door is closed, and mechanically closed when this door is opened.
  • the first and the second interlock switches 5 and 10 are mechanically closed when the latch door is closed, and mechanically opened when this door is opened.
  • the interlock switches 5 and 10 function to allow the power supply to the - remaining portions of this circuit only when the latch door is tightly closed.
  • a foodstuff is disposed within the microwave oven and the latch door is closed. Responsive to this operation, the monitor switch 11 is opened, and the first and the second interlock switches 5 and 10 are closed, respectively.
  • a cooking start key 21 in the touch key panel 21 is operated to input a cooking start signal into the CPU 22.
  • the cooking start signal is inputted into the CPU 22 and outputted into the NPN transistor 23 via the drive circuit 24.
  • the NPN transistor 23 is made conductive to supply power energy to the cooking start relay 25, so that the cooking start relay terminals 26 are closed.
  • the commercial power is supplied from the AC plug 3 into the high voltage transformer 9 through the main fuse 4, the first interlock switch 5, the cooking start relay terminals 26, and the second interlock switch 10.
  • the magnetron 19 is energized with a high voltage to generate microwave. Through the monitor fuse 20, the commercial power is supplied to the power transformer 15 in the touch control circuit 6 to operate the CPU 22.
  • the second interlock switch 10 fails so that it cannot open.
  • the monitor switch 11 is closed, so that the power energy is momentarily supplied from the AC plug 3 into the monitor fuse 20, the monitor switch 11, the monitor resistor 12, and the second interlock switch 10 as indicated with an arrow B.
  • the monitor fuse 20 is blown.
  • the input terminal 13 of the power transformer 15 in the touch control circuit 6 is made open so that the touch control circuit 6 no longer receives power.
  • the cooking start relay 25 also becomes deenergized, so that the cooking start relay terminals 26 are opened.
  • the primary winding of the high voltage transformer 9 is thereby isolated from the power source, and the magnetron can no longer generate microwaves. Therefore, the microwave leakage from the oven cavity can be prevented.
  • the monitor fuse 20 is permitted to blow when the second interlock switch 10 cannot be opened due to damage.
  • the power supply to the touch control circuit 6 can be cut to stop energization of the magnetron 19.
  • the oven main fuse 4 is not cut.
  • a line leading to the monitor fuse 20, the monitor switch 11, and the monitor resistor 12 is connected to the power source side of the main fuse 4.
  • this line leading to the monitor fuse 20 is connected to the point between the main fuse 4 and the first interlock switch 5, namely, to the side including the high voltage transformer 9.
  • the monitor fuse 20 can blow to permit the cooking start relay terminals 26 to open.
  • the monitor fuse 20 also serves as a fuse for protecting against short- circuiting in the secondary circuit of the cooking control circuit 6. Since the touch control circuit 6 consumes an approximately-constant current, the resistance of the monitor resistor 12 for limiting a current can be freely selected.
  • the first interlock switch 5 is not damaged, so that it operates successfully without any problem of failure. If necessary, an additional monitor circuit can be provided for protecting the first interlock switch 5.

Claims (6)

1. Four à micro-ondes comportant un interrupteur de verrouillage de porte (10) connecté en série avec un circuit d'utilisation de courant (9) du four, l'interrupteur de verrouillage (10) pouvant être ouvert pendant l'ouverture d'une porte du four; un circuit de contrôle (11, 12, 20) connecté en parallèle avec le circuit d'utilisation de courant (9) et comprenant un interrupteur de contrôle (11) qui se ferme lors de l'ouverture d'une porte du four, et un circuit de commande de courant (6) qui est connecté à un point du circuit de contrôle (11, 12, 20) tel que le circuit de commande de courant (6) soit alimenté continuellement par du courant qui passe dans une partie du circuit de contrôle, le circuit de commande de courant (6) réagissant à la coupure du courant qui lui est fourni par l'intermédiaire de la dite partie du circuit de contrôle en désactivant le circuit d'utilisation de courant (9); le circuit de contrôle étant connectée à des bornes d'alimentation de courant couplées au circuit d'utilisation de courant (9), de sorte que si l'interrupteur de verrouillage (10) ne s'ouvre pas lorsque la porte du four s'ouvre, provoquant l'application de courant aux bornes pendant que l'interrupteur de contrôle (11) est fermé, le courant passant par le circuit de contrôle fait sauter un fusible de contrôle (20) qui est connecté dans la dite partie du circuit de contrôle, ce qui coupe l'alimentation électrique du circuit de commande de courant (6) et désactive ainsi le circuit d'utilisation de courant (9), le fusible de contrôle (20) étant d'une valeur inférieure à celle d'un autre fusible (4) connecté en série avec le circuit d'utilisation de courant (9).
2. Four à micro-ondes suivant la revendication 1, dans lequel le circuit de commande de courant (6) comprend un transformateur de courant (15) dont l'enroulement primaire est connecté au dit point du circuit de contrôle.
3. Four à micro-ondes suivant la revendication 1 ou 2, dans lequel l'une des bornes d'alimentation de courant est disposée entre une source de courant de secteur et l'autre fusible (4).
4. Four à micro-ondes suivant la revendication 1 ou 2, dans lequel l'une des bornes d'alimentation de courant est située entre l'autre fusible (4) et un autre interrupteur de verrouillage de porte (15) qui peut être actionné pour se fermer lorsque la porte est fermée et qui est connecté en série avec le circuit d'utilisation de courant (9).
5. Four à micro-ondes suivant l'une quelconque des revendications précédentes, dans lequel le fusible de contrôle (20) a une valeur comprise entre 0,5 et 1 A.
6. Four à micro-ondes comportant un interrupteur de verrouillage de porte (10) connecté en série avec un circuit d'utilisation de courant (9) du four, l'interrupteur de verrouillage (10) s'ouvrant lors de l'ouverture d'une porte du four; un circuit de contrôle (11, 12, 20) connecté en parallèle avec le circuit d'utilisation de courant (9) et comprenant un interrupteur de contrôle (11) qui se ferme lors de l'ouverture de la porte du four et une résistance limiteuse de courant (12) en série avec l'interrupteur de contrôle; et un circuit de commande de courant (6) qui comprend un panneau de touches à effleurement (21) et un transformateur de courant (15) dont l'enroulement primaire est connecté à un point du circuit de contrôle (11, 12, 20) tel que le circuit de commande de courant (6) soit continuellement alimenté par du courant qui traverse l'enroulement primaire et une partie du circuit de contrôle, cette partie excluant l'interrupteur de contrôle (11) et la résistance limiteuse de courant (12), le circuit de commande de courant (6) réagissant à la coupure de son alimentation de courant en ouvrant le contact d'un interrupteur d'alimentation (26) connecté en série avec le circuit d'utilisation de courant (9); le circuit de contrôle (11, 12, 20) étant connecté aux bornes d'alimentation de courant couplées au circuit d'utilisation de courant (9), de sorte que si l'interrupteur de verrouillage (10) ne s'ouvre pas lorsque la porte du four s'ouvre, appliquant ainsi du courant aux bornes pendant que l'interrupteur de contrôle (11) est fermé, le courant de court-circuit traversant le circuit de contrôle fait sauter un fusible de contrôle (20) qui est connecté dans la dite partie du circuit de contrôle, coupant donc l'arrivée de courant à l'enroulement primaire et ainsi l'alimentation de courant du circuit de commande de courant (6), le fusible de contrôle (20) étant d'une valeur inférieure à celle d'un autre fusible (4) connecté en série avec le circuit d'utilisation de courant (9), le fusible de contrôle (20) conduisant également du courant qui traverse l'enroulement primaire, de manière à offrir une protection contre les courts-circuits dans le circuit de commande de courant (6).
EP83301543A 1982-03-19 1983-03-18 Four à micro-ondes avec circuit de contrôle Expired EP0089838B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP4021282U JPS58142892U (ja) 1982-03-19 1982-03-19 電子レンジのモニタ−回路
JP40212/82U 1982-03-19

Publications (2)

Publication Number Publication Date
EP0089838A1 EP0089838A1 (fr) 1983-09-28
EP0089838B1 true EP0089838B1 (fr) 1989-02-01

Family

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EP83301543A Expired EP0089838B1 (fr) 1982-03-19 1983-03-18 Four à micro-ondes avec circuit de contrôle

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EP (1) EP0089838B1 (fr)
JP (1) JPS58142892U (fr)
AU (1) AU557262B2 (fr)
DE (1) DE3379147D1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103175237A (zh) * 2013-03-27 2013-06-26 福州高奇智芯电源科技有限公司 微波炉及其自适应功率输出控制方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3288234B2 (ja) * 1996-11-29 2002-06-04 株式会社東芝 加熱調理器

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4054769A (en) * 1976-03-04 1977-10-18 The Tappan Company Microwave oven interlock switch safety

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE30248E (en) * 1974-08-03 1980-04-01 Amana Refrigeration, Inc. Safety interlock system for microwave ovens
JPS57154789A (en) * 1981-03-20 1982-09-24 Matsushita Electric Ind Co Ltd High frequency heater

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4054769A (en) * 1976-03-04 1977-10-18 The Tappan Company Microwave oven interlock switch safety

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103175237A (zh) * 2013-03-27 2013-06-26 福州高奇智芯电源科技有限公司 微波炉及其自适应功率输出控制方法
CN103175237B (zh) * 2013-03-27 2015-07-15 福州高奇智芯电源科技有限公司 微波炉及其自适应功率输出控制方法

Also Published As

Publication number Publication date
JPS58142892U (ja) 1983-09-26
AU557262B2 (en) 1986-12-18
EP0089838A1 (fr) 1983-09-28
AU1255083A (en) 1983-09-22
DE3379147D1 (en) 1989-03-09

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