JPS6347033Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a microwave oven equipped with an overheating prevention circuit that detects an overheating state and switches to a weak output.

Conventionally, as a test item included in the technical standards of the Electrical Appliances and Materials Control Law for microwave ovens,
There is a test in which water is heated by repeatedly turning it off for minutes, and when this test is actually conducted, the temperature of each part of the microwave oven increases to a degree higher than that in actual use (normal cooking conditions). In response to this, designs have been made using components with sufficiently high heat resistance. Therefore, parts with excellent heat resistance must be used, which poses a problem in reducing costs.

The present invention was developed in view of the above points, and when inspecting overheating conditions using components that are heat resistant enough to be used in actual use, it is difficult to detect overheating conditions. By automatically switching the output of the microwave oven to a weak output, the overheating state does not persist under severe conditions that would not occur in actual use.

In order to achieve the above-mentioned purpose, the present invention uses an intermittent switch that is connected to the primary side of the high-voltage transformer that supplies power to the magnetron and turns on and off at predetermined intervals to monitor the temperature of the magnetron and the core temperature of the high-voltage transformer. This is characterized by the fact that thermostats operated by the following are connected in parallel.

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

FIG. 1 is a main part power supply circuit diagram of a microwave oven showing an embodiment of the present invention, in which 1 is a commercial AC power supply;
2 and 3 are not shown, but are latch switches that turn on when the microwave oven door is opened, 4 is a timer switch, and 5 is a first intermittent switch that turns ON and OFF using a cam rotated by a motor. , 6 is a second on/off switch connected in series to the first on/off switch 5, and 7 is the timer switch 4 and the second on/off switch 6.
It is a high voltage transformer that is connected to the primary side.
Although not shown, a rectifier circuit and a magnetron are connected to the secondary side. 8 is a strong/weak switch connected in parallel to the first intermittent switch 4 for switching between strong and weak microwave output;
Strong output when ON, weak output when OFF. Also,
Reference numeral 9 denotes a thermostat connected in parallel to the second intermittent switch 6, which detects the temperature of the magnetron, the core temperature of the high-voltage transformer, etc. so that it is turned on in normal use and turned off in overheating conditions. installed in position.

Next, to briefly describe the operation of the embodiment of the present invention having the above configuration, first, a beaker of water 2 is placed in the heating chamber of the microwave oven and the door (not shown) is closed. Latch switch 2 and second latch switch 3 are turned on. Then, assuming that the timer switch 4, the heating switch (not shown), and the strength changeover switch 8 are turned on to use the power source for high-power operation, the thermostat 9 is turned on.
is on, the first intermittent switch 5
Regardless of the on/off operation of the second intermittent switch 6, these first and second intermittent switches 5,
Since a power/weak switch 8 and a thermostat 9 are connected in parallel to 6, a completely continuous power supply is applied to the primary side of the high-voltage transformer, and microwave heating due to strong output is performed. It is done.

At this time, the first on/off switch 5 and the second on/off switch 6 repeat the on/off operation by cams that rotate with different periods and duties, respectively. Now, if high-output operation continues for an abnormally long time in this state, the temperature of the magnetron and the core temperature of the high-voltage transformer will rise, resulting in an overheating state, and the thermostat 9 will be activated and shut off.
becomes. Therefore, the commercial AC power supply 1 is applied to the primary side of the high voltage transformer 7 via the second intermittent switch 6, and the average output changes from strong to weak due to intermittent operation by the second intermittent switch 6. Since the temperature can be switched to , it is possible to suppress the temperature rise of each part of the microwave oven. That is,
It is possible to use parts with low heat resistance, which reduces costs.

In addition, even if the output of the microwave oven becomes slightly weak due to overheating due to long-term use, there is no practical problem as long as the heating is stopped when the finished product is detected by a sensor.

On the other hand, when the strength changeover switch 8 is turned off, power is supplied via the first intermittent switch 5, and desired low output operation can be performed during normal use.

In addition, in the case of the test according to the technical standards of the Electrical Appliance and Material Control Law mentioned above, the strength changeover switch 8 is turned on.

FIG. 2 is a power supply circuit diagram of the main parts of a microwave oven showing another embodiment of the present invention, and parts having the same functions as those in FIG. . Reference numeral 10 denotes an intermittent switch which is turned on and off at predetermined intervals by a cam (not shown), and a series circuit 11 consisting of a strength changeover switch 8 and a thermostat 9 is connected in parallel. in this case,
Turn the strong/weak switch 8 above to the strong output side.
When it is turned on, it will be in strong operation, but when it is turned off, the above-mentioned intermittent switch 10 will repeatedly turn on and off, resulting in a weak output, which can prevent overheating. Therefore, the intermittent switch 10 is a switch that sets a low output during normal use, and a switch that turns off the thermostat 9 and switches from a strong output to a weak output to prevent overheating when an overheating test is performed. It is also used as.

As explained above, the present invention detects the temperature rise of components such as high-voltage transformers and magnetrons, and switches the microwave output from strong to weak at a predetermined temperature. When the microwave oven reaches an overheating state due to harsh use that would be unimaginable in actual use, the output automatically switches from strong to weak, and the temperature of each part does not exceed the specified temperature. Since there is no need to use parts that are of a slightly excessive quality in terms of heat resistance, it is possible to reduce the weight and size of the high-voltage transformer by reducing the wire diameter of the winding, for example. Therefore, it is of high practical value, as it can be designed using parts that are suitable for actual use, and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a power supply circuit diagram of a main part of a microwave oven showing an embodiment of the present invention, and FIG. 2 is a power supply circuit diagram of a main part of a microwave oven showing another embodiment of the invention. 4...Timer switch, 5,6,10...Intermittent switch, 7...High voltage transformer, 8...Strength/weakness selector switch, 9...Thermostat.

Claims (1)

[Scope of Claim for Utility Model Registration] A microwave oven that changes the microwave output by controlling the magnetron on and off using an intermittent switch, which detects the temperature rise of parts that make up the microwave oven, such as a high-voltage transformer and magnetron, and A microwave oven characterized by being equipped with a thermostat that switches the microwave output from strong to weak.