JPS6015112B2 - microwave oven - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave oven, and more particularly to a safety device for the microwave oven.

In a conventional microwave oven, as shown in FIG. 1, an AC input power supply voltage is applied to a high frequency generating means 3 through one main electric wire 1 and the other main electric wire 2, and a control rectifier element 4 such as a triac is connected to the main electric wire 1. and further includes a control circuit unit 5 for supplying an operating signal to the control rectifier 4, and outputs an operating signal from the control circuit unit 5 in conjunction with the operation of the cooking button, and the control rectifier 4 generates a high frequency generator 3. The duty
I was in control.

However, in this type of microwave oven, if the device is operated for a long time with no load, or if the device is used in an extremely hot place, the control rectifying element 4 may overheat and break down, resulting in constant conduction. In this state, when the door is closed, the door switch 6 and latch switch 7 are closed, and the monitor switch 8 is opened, so that undesired high frequency oscillation occurs even if the cooking button (not shown) is not operated to start cooking. When oscillation starts and the abnormality is not noticed and oscillation continues for a long time, there is a drawback that the life of the magnetron 9, high voltage transformer 10, etc. is shortened.

This invention has been made in view of this point, and one implementation thereof will be explained below. In Figure 2, 11 is a power plug, 12
13 is one main electric wire, 13 is the other main electric wire, and 14 is a high frequency generating means to which an AC input power supply voltage is applied through one main electric wire 12 and the other main electric wire 13.

The high frequency generating means 14 includes a high voltage transformer 15 and a capacitor 16 connected in series to the secondary winding of the high voltage transformer 15.
and a magnetron 1 which is applied with a high voltage generated by a diode 17 and parts 15, 16, and 17 and which oscillates at a high frequency.
It is formed from 8 mag. 19 is a current fuse; 20 is a latch switch that is closed by the latch when the door (not shown) and the microwave oven body (not shown) with a built-in high-frequency heating chamber are latched to each other; and 21 is a door opener. The door switch 22 is a monitor switch that is turned off when the door is opened and turned on when the door is closed, and is turned off when the door is closed and turned on when the door is opened. , a large current is generated through the latch switch 20 and the monitor switch 22 to melt the current fuse 19 and prevent various accidents from occurring. 23 is a controlled rectifier consisting of a triac or the like;
24 is a control circuit unit for supplying the operating signal Vs to the control rectifier 23, 25 is a normally closed race switch connected to short-circuit the Ryoo electric wires 12 and 13 after the control rectifier 23, and 26 is a control circuit. The normally closed IJ race switch 25 is excited by the operating signal Vs output from the circuit section 24.
27 is a blower motor for cooling the magnetron, and 28 is a heating chamber illumination lamp.

The control circuit section 24 is provided with a cooking start switch, a timer, etc. (not shown), and starts outputting the operation signal Vs shown in FIG. The output of the operating signal Vs is stopped.

Therefore, the control rectifying element 23 is turned on and off as shown by Vm in FIG. 3B based on the operating signal Vs, thereby controlling the duty of the high frequency generating means 14. In conjunction with the operation of the control rectifying element 23, the relay coil 26 is energized and the normally closed race switch 25 is turned on and off as shown in FIG. 3c. In the above configuration, if the control rectifying element 23 is destroyed and becomes conductive, the main electric wires 12 and 13 are short-circuited to each other through the normally closed IJ race switch 25, which is turned on in a non-energized state, and a large current flows. Fuse 19 is blown.

Therefore, high frequency oscillation is not continued undesirably, so that the life of the magnetron 18, high voltage transformer 15, etc. is not shortened, and accidents such as the occurrence of flames are prevented. FIG. 4 shows a part of another embodiment.

In another embodiment, the first signal supply line 29 and the second signal supply line 30 are independently connected to the control circuit section 24',
An on-off signal Vs' shown in FIG. 5a is supplied to the control rectifier element 23 through the first signal supply line 29, and an on-off signal Vs'' shown in FIG. Here, the off time X of the excitation signal Vs'' of the relay coil 26 is set to be longer than the normal time Y of the control rectifying element 23. Therefore, the control rectifier 23 is turned on after a short delay time after the relay switch 26 is turned off, and is turned off a short time before the relay switch 25 is turned off. At the same time, there is no risk of conduction, and therefore the circuit is prevented from malfunctioning and causing a short circuit. Note that other embodiments have the same configuration as the one embodiment described above. Since this invention is configured as described above, if the control rectifier is destroyed and conductive, the electrical circuit is short-circuited by the normally closed switch after the control rectifier and the current fuse is blown, thereby ensuring the safety of the Noriko range device. It has the following effects.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of a conventional example, Fig. 2 is a schematic electric circuit diagram of an embodiment of the present invention, Fig. 3 is an explanatory diagram of the operation of the same embodiment, and Fig. 4 is a summary of another embodiment. FIG. 5 is an explanatory diagram of the operation of another embodiment. 12... One main electric wire, 13... Other main electric wire, 14... High frequency generation means, 19.
...Current fuse, 23...Control rectifier, 24, 24'...Control circuit section, 25...Normally closed switch, Vs, Vs'...Operation signal . Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. In a microwave oven in which a high frequency generation means is connected to a power source via a control rectifying element, and the element is turned on by a signal from a control circuit section, power from the power source is supplied to the high frequency generation means. A normally closed switch is connected in parallel to the higher frequency generating means, and a fuse is connected in series to the switch on the side of the power source from the switch, and the circuit section is configured to turn on at least the element after the start of cooking. The microwave oven is characterized in that the circuit unit turns off a switch when outputting a signal from the microwave oven.