JPH03295191A - Microwave oven - Google Patents

Abstract

PURPOSE:To precisely discriminate a no-load state and a light-load state and prevent no-load damage to a magnetron equipment by fitting a temperature detecting element near an anode having the largest temperature rise. CONSTITUTION:A thermistor 17 is provided in contact with or near an anode 9, it is inserted between a cooling fan 13 from the side where the cooling air flows out, and it is fitted by the coupling of a coupling hole provided on the cooling fan i3 end a projection provided on the thermistor 17. The thermistor 17 is kept in contact with the downstream section of the anode 9 not blown with the wind W from a cooling fin 6 directly, and the temperature of a magnetron 4, i.e., the temperature of the anode 9, can be precisely detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a structure for mounting a temperature sensing element for detecting an abnormal temperature rise in a magnetron in order to prevent damage to a microwave oven.

(b) Conventional technology An overtemperature rise prevention thermostat attached to the outer shell of the magnetron detects an abnormal temperature rise in the magnetron and stops the magnetron's oscillation to prevent damage to the equipment.
It is disclosed in Japanese Utility Model Publication No. 57-8640. In such a structure, heat generated at the anode is transferred to the overheat prevention thermostat via the yoke and the cooling fins.

However, the cooling fins are cooled by the air blowing from the cooling fan, and the temperature of the cooling fins becomes much lower than that of the anode.

In such a case, the difference in temperature detected by the overheating prevention sensor between heating in a no-load state with no food in the heating chamber and heating in a light-load state with a small amount of food in the heating chamber becomes small.
If the temperature is set to a temperature that reliably prevents damage to the equipment due to heating under no-load conditions, the over-temperature prevention thermometer will operate even if the room temperature is high under light load conditions. A problem arises in that food cannot be heated.

(The problem that Hano's invention aims to solve is to accurately distinguish between a no-load state where there is no food in the heating chamber and a light-load state where there is a small amount of food) based on the temperature of the magnetron, and equipment such as the 7-Danetron will be damaged during the no-load state. To prevent undesired heating from stopping under light load conditions.

(d) Means for solving the problem A heating chamber that accommodates an object to be heated, a magnetron that supplies high frequency waves to the heating chamber, a cooling fan that cools the magnetron, and a temperature detection element that detects the temperature of the magnetron. and the temperature sensing element is mounted close to or in contact with the anode of the magnetron.

(e) Effect The difference in detected temperature increases between heating in a no-load state and heating in a light-load state.

(f) Example FIG. 1 shows the configuration of the microwave oven of the present invention.

1 is a microwave oven exterior frame; 2 is a heating chamber that houses food to be heated; 3 is a door that opens and closes the opening of the heating chamber; 4 is a magnetron that supplies microwaves into the heating chamber 2; 5 is the above-mentioned A high-voltage transformer supplies high voltage to the magnetron 4; 6 is a cooling fan that forcibly cools the magnetron 4, high-voltage transformer 5, etc.; 7 is a duct that guides cooling air after cooling the magnetron 5 into the heating chamber 2. be.

The structure of the magnetron 4 is shown in FIGS. 2 to 4. 9 is an anode having a resonant cavity; 10 is a donut-shaped permanent magnet provided at both ends of the anode; 11 is an anode 9;
12 is a microwave output antenna, 13 is an anode cooling fin, 14 is a filter box provided in the cathode part, 15 is a cathode connection terminal, and 16 is an air volume. The air volume adjustment plate 16 is made of a non-magnetic material such as aluminum that does not adversely affect the magnetic circuit of the magnetron, and is provided at the cooling air inlet of the magnetron 4 facing the cooling fan 6. By adjusting the amount of air passing through the cooling fins 13, the magnetron output and
The temperature rise value of the anode 9 that occurs for each model is adjusted, and a detection temperature circuit is commonly used. Reference numeral 17 denotes a thermistor for detecting the temperature of the anode 9. The thermistor 17 is provided in contact with or close to the anode 9, and is inserted between the cooling fins 13 from the side from which the cooling air flows out.
The thermistor 17 is attached by engaging an engagement hole provided in the thermistor 3 with a protrusion provided in the thermistor 17.

In this case, the thermistor 17 is connected to the wind W from the cooling fan 6.
The temperature of the magnetron 4 and the temperature of the anode 9 are detected accurately, and the difference in temperature between no-load heating and light-load heating is determined by the cooling fan. It is large and is not affected by wind etc. from 6. Incidentally, when the thermistor 17 is placed upwind of the anode 9, the temperature difference between the top and bottom becomes smaller.

An example of the relationship between the temperature detected by the thermistor 17 having such a configuration and the room temperature is shown in FIG.

The solid line P indicates the detected temperature during heating in a no-load state, and the solid line Q indicates the detected temperature during heating in a light-load state.
The temperature difference during heating under light load conditions is as large as approximately 70°C, so if the thermistor set temperature is set to T1, even if the room temperature reaches 40°C during heating under light load conditions, the detected temperature will be the set temperature T, light load heating will not be stopped undesirably.

Incidentally, when the magnetron temperature is detected by attaching a thermistor to the outer shell of the magnetron as in the past, the temperature will be as shown by broken line R when heating under no load, and as shown as broken line S when heating under light load. Therefore, the difference in detected temperature due to heat between both jaws is small, about 30°C. Therefore, if the thermistor set temperature is set to T, if the room temperature becomes high during light load heating, the detected temperature will exceed the set temperature and the light load heating will be stopped undesirably.

FIG. 6 shows another embodiment of the configuration for mounting the thermistor, in which a folded portion 18 is provided on the portion of the cooling fin 13 in contact with the anode 9, and the thermistor 17 is sandwiched between the folded portion 18 and mounted.

(g) Effects of the invention Proximity to the anode, where the temperature rise is greatest in the magnetron,
Or, since the temperature detection element is attached in contact with the sensor, there is a large temperature difference between heating in no-load condition and in light-load condition, and it is possible to accurately distinguish between no-load condition and light-load condition. It is possible to prevent equipment such as a magnetron from being damaged, and to suppress undesired stopping of heating under light load conditions.

[Brief explanation of the drawing]

The drawings relate to a microwave oven according to an embodiment of the present invention, and FIG. 1 is an external perspective view, FIG. 2 is a front view of the magnetron, FIG. 3 is a sectional view taken along line A-A in FIG. 2, and FIG. 4 is a third view. BB line sectional view of
FIG. 5 is a temperature characteristic diagram showing the relationship between the temperature detected by the thermistor and the room temperature, and FIG. 6 is a partially enlarged view of another embodiment showing the attachment of the thermistor. 2... Heating chamber 4... Magnetron 6... Cooling fan 9... Anode 17... Temperature sensing element.

Claims (1)

[Claims] (1) A heating chamber for accommodating an object to be heated, a magnetron for supplying high frequency waves to the heating chamber, a cooling fan for cooling the magnetron, and a temperature detection element for detecting the temperature of the magnetron; A microwave oven characterized in that the element is attached close to or in contact with the anode of the magnetron.