JPS6136078Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a safety device against microwave leakage of a high frequency heating device having a power transformer for microwave oscillation.

In a conventional high-frequency heating device, such as a microwave oven, in which the object to be heated is placed inside a heating chamber and the microwaves are trapped inside to heat the object, the microwave is emitted when the door is opened. To prevent leakage, door switches are installed at two locations to cut off the power supply to the microwave oscillation circuit on the electrical circuit. Furthermore, as shown in FIG. 1, a short switch 1 is provided to detect a welding failure of the door switch A2 and blow out a fuse 3. This is to provide double safety against microwave leakage by cutting off the power supply with door switch A2 and door switch B4, and short switch 1 is provided to more reliably achieve this purpose. . However, with this configuration, when one end 5-a of the primary coil of the transformer 5 has a ground fault, power is supplied to the microwave oscillation circuit even if the door is opened, and microwaves are generated and leaked from the door. do. This means that the power supply voltage is passed through the fuse 3, timer switch 6, and short switch 1 to one end 5-b of the primary coil of the transformer 5.
This is because it is applied to the other end 5-a of the primary coil of the transformer 5 via the grounded part.

The present invention solves the above-mentioned conventional drawbacks and aims to improve the safety of a high-frequency heating device against leakage of microwaves.

In order to achieve the above object, the present invention includes a transformer that supplies power to a microwave oscillation circuit, a door switch A, a door switch B, a short switch, and a fuse, which are respectively linked to opening and closing of the door, and the fuse, the door switch B, The primary coil of the transformer and the door switch A are connected in series in that order to form a main circuit, and the short switch is connected between the fuse and the door switch B, and between the door switch A and the primary coil of the transformer. The door switch B has a normally open contact and a normally closed contact, and is configured to close the main circuit when the door is closed, and short-circuit both ends of the primary coil of the transformer when the door is opened. When the door is opened when one end of the primary coil of the transformer has a ground fault, a short circuit current flows through the fuse and the short switch, the fuse is blown, and no power is supplied to the microwave oscillation circuit. This has the effect that there is no wave leakage.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 2 is a sectional view of a main part of a high-frequency heating device according to an embodiment of the present invention. In the figure, 15 is a heating chamber into which the object to be heated is placed, 7 is a door through which the object to be heated is taken in and out, 8 is a magnetron that oscillates microwaves, and 9
1 is a waveguide that guides microwaves from the magnetron 8 to the heating chamber 15; 5 is a transformer that generates a high voltage to be supplied to the magnetron; 10 is a capacitor that doubles and rectifies the high voltage generated by the transformer 5 together with a diode; 11 is a door Door switch pins A and 12 operate the door switch A2 in conjunction with the door 7, and door switch pins B and 13 operate the door switch B4 in conjunction with the door 7, respectively. The short switch 1 closes the door 7 when the door 7 is opened.
It is designed to open when closed. The door switch A2 is provided so that it opens when the door 7 is opened and closes when the door 7 is closed. Door switch B3
has a normally closed contact and a normally open contact, and when the door 7 is opened, the normally closed contact is closed and the normally open contact is opened, and when the door 7 is closed, the normally closed contact is opened and the normally open contact is closed. It is provided in FIG. 3 is an electrical circuit diagram of the high frequency heating device of the embodiment shown in FIG. In the figure, fuse 3, timer switch 6, normally closed terminal 4-a of door switch B4, door switch B
4 common terminal 4-b, the primary coil of the transformer 5,
The door switches 2 are connected in series to form a main circuit. The short switch 1 is connected between a lead wire that connects the timer switch 6 and the normally open terminal of the door switch B4, and a lead wire that connects the door switch A2 and the primary coil of the transformer 5.
Common terminal 4-b of door switch B4 is transformer 5
A door switch B4 is connected to one end 5-a of the primary coil of
The normally closed terminals 4-c of the transformer 5 are connected to the other end 5-b of the primary coil of the transformer 5, respectively.

The operation of the above configuration will be explained below. When the door 7 is opened and the object to be heated is placed in the heating chamber 15 and the door 7 is closed, the electric circuit opens the shot switch 1, closes the door switch A2, and closes the normally open contact of the door switch 4. When the timer switch 6 is turned on, voltage is supplied to the primary coil of the transformer 5, the magnetron 8 oscillates, and microwaves are supplied to the heating chamber 15 through the waveguide 9, and the microwaves are generated by the heating chamber 15. The heated object is heated. When the time has elapsed, the timer switch 6 is opened by the timer motor 14 to end the heating. Suppose that one end 5-a of the transformer 5 has a short circuit to the chassis 16 through the iron core of the transformer 5. At this time, if door 7 is opened and timer switch 6 is turned on, fuse 3, time switch 6, short switch 1, and door switch B4 are
A short circuit is formed through the normally open terminal 4-c of the door switch B4, the common terminal 4-b of the door switch B4, one end 5-a of the transformer 5, the iron core of the transformer 5, the chassis 16, and the earth, and the fuse 3 blows. Therefore, no microwave is generated, and even if the door 7 is closed, it does not operate.
Also, if the other end 5-b of the transformer 5 is grounded, the fuse 3 will be blown in the same manner as described above, making the device inoperable.

In this way, according to this embodiment, one of the transformers 5
If a ground fault occurs at one end of the secondary coil, the fuse 3 will not be fused and microwave leakage will not be caused, and the user will be able to know that there is a malfunction and can promptly repair it.

As described above, according to the present invention, the following effects can be obtained.

(1) It is safe because microwaves will not leak outside the heating chamber even in the event of a single failure such as a ground fault at one end of the primary coil of the transformer.

(2) When the above-mentioned failure occurs, the fuse is blown and the equipment is rendered inoperable, allowing the user to know that the failure has occurred, and when another failure occurs, causing a double failure. Safety can be prevented.

(3) The above effect can be achieved by adding a normally closed contact and a lead wire to the conventionally configured door switch B, so that the cost increase can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of a conventional high-frequency heating device, FIG. 2 is a sectional view of a main part of a high-frequency heating device according to an embodiment of the present invention, and FIG. 3 is a diagram of the same electric circuit. 1...Short switch, 2...Door switch A, 3...Fuse, 4...Door switch B, 5
...Transformer, 5-a... One end of the primary coil of the transformer, 5-b... One end of the primary coil of the transformer, 6... Timer switch, 7... Door, 8...
... Magnetron, 9 ... Waveguide, 10 ... Capacitor, 11 ... Door switch pin A, 12 ... Door switch pin B, 13 ... Door arm, 14 ...
...Timer motor, 15... Heating chamber, 16... Chassis, 4-a... Normally open terminal of door switch B,
4-b... Common terminal of door switch B, 4-c...
...Normally closed terminal of door switch B.

Claims (1)

[Scope of utility model registration request] It includes a transformer that supplies power to a microwave oscillation circuit, a door switch A, a door switch B, a shot switch, and a fuse that are respectively linked to the opening and closing of the door, the fuse, the door switch B, the primary coil of the transformer, and the door switch A. are connected in series in that order to form a main circuit, and the short switch is connected between the fuse and the door switch B, and between the door switch A and the primary coil of the transformer, and the short switch is connected between the fuse and the door switch B, and between the door switch A and the primary coil of the transformer. The high frequency heating device has a normally open contact and a normally closed contact, and has a structure in which the main circuit is closed when the door is closed, and both ends of the primary coil of the transformer are short-circuited when the door is opened.