JPH03156882A - High-frequency heating device - Google Patents

Abstract

PURPOSE:To prevent a short circuit between an antenna and the ground due to the oil and water scattered from food by providing the antenna near an opening provided on a heating chamber wall, and insulating a printed board from the heating chamber wall for the DC current. CONSTITUTION:Radio waves sent from a high-frequency oscillator 1 are fed to a high-frequency heating chamber 3 via a wave guide 2 to heat the food 4 in the heating chamber 3. The electric field in the heating chamber 3 is directly detected by a detecting circuit 8 having an antenna 7 insulatedly fitted to a heating chamber wall. The circuit 8 is insulated from the heating chamber wall for the DC current, and the radio waves received by the antenna 2 are DC-detected. The antenna 6 is fixed to a printed board with a support, and the opening 6 is covered by a dielectric plate 5. The oil and moisture scattered from the food 4 can be prevented from sticking to the antenna 7 and the circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high-frequency heating device that detects the intensity of radio waves inside a refrigerator such as a microwave oven and controls a high-frequency heat source such as a magnetron.

Conventional technology In the prior art, as shown in Japanese Patent Application Laid-Open No. 59-26759, a high-frequency heating source is developed by detecting the change in dielectric constant of the food (hereinafter referred to as food), which changes depending on the degree of heating of the object (hereinafter referred to as food). What controls the is shown.

Problems to be Solved by the Invention In this conventional method, since the target is food, a lot of water and oil scatters inside the refrigerator during heating, and these are interposed between the antenna and the ground plane of the detection circuit. Therefore, there was a problem of thickening (changing) the detection characteristics.The object of the present invention is to prevent a short circuit between the antenna and the ground due to oil scattered from food.

Means for Solving the Problems In order to solve the problems, the present invention provides an opening in the wall facing the heating chamber, a dielectric plate on the heating chamber side of the opening, and an antenna on the opposite side. A configuration is adopted in which a mounted detection circuit is arranged, and the detection circuit and the heating chamber wall are installed in a DC-insulated manner.

Effect: According to the present invention, oil and water splashed from food are not directly interposed between the antenna and the ground plane.

Embodiment FIG. 1 is a block diagram showing a high frequency heating device of the present invention. Radio waves emitted from the high frequency oscillator 1 are supplied to the high frequency heating chamber 3 via the waveguide 2 and heat the food 4 inside the refrigerator. The electric field inside the refrigerator is directly detected via the dielectric plate 5 and the heating chamber opening 6 by a detection circuit 8 equipped with an antenna 7 installed insulated from the heating chamber wall. The detected signal is guided to a control circuit 9 and connected to a power supply circuit 10 of the high frequency oscillator 1.

FIG. 2 shows an example of the mounting configuration of the detection circuit 8 in a front view A and a sectional view B. The detection circuit 8 includes an antenna 7, a microstrip line land 13, resistors 14, 15, 16,
A diode 17 and a capacitor 18 are connected on a printed board. An antenna 7 is disposed through an opening 6 formed in the heating chamber wall, and the printed board is fixed by a support 20 for DC insulation from the heating chamber wall.

A lead wire 19 connects the detection circuit 8 and the control circuit 9. The opening 6 is covered with a dielectric plate 22 to prevent oil and moisture scattered from the food from directly adhering to the antenna 7 and the detection circuit 8.

In addition, since the ground plate of the microstrip line system that constitutes the detection circuit 8 is installed insulated from the heating chamber wall, in the case of a configuration in which the ground plate is connected to the heating chamber wall, oxidation of the metal surface Compared to other methods, where there is a concern that stable contact cannot be maintained over a long period of time, stable performance can be ensured. Furthermore, if the configuration of the embodiment is adopted, the detection circuit 8 can be easily thermally insulated from the heating chamber wall, so stable performance can be ensured in this respect as well.

FIG. 3 shows an example of how the detected signal Vs changes over time. The signal change when heating frozen food indicates the completion of thawing (a)
The amplitude and level change characteristically from the point (b1) of the start of boiling. Based on this signal VS, the control circuit 9 determines the inflection point of the level of Vs and the amplitude containing the low frequency component of the z band (Equation 1). Based on the changes, the radio wave circuit 10 of the high frequency oscillator 1 is controlled according to a control algorithm determined at the time of design or setting.

Effects of the Invention According to the present invention, it is possible to achieve stable control performance for long-term use with a simple configuration without causing a short circuit between the antenna and the ground (ground plate) due to the scattering of food oil and water. It is.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the configuration of a high-frequency heating device according to an embodiment of the present invention, Fig. 2A is a front view of the detection circuit of the same device, Fig. 2B is a sectional view of the same, and Fig. 3 is a diagram of the detection output of the same. FIG. 1...High frequency oscillator, 3...Inside heating chamber, 5...Dielectric plate, 6...Open hole, 7
...Antenna, 8...Detection circuit, 9.
... Control circuit, 10 ... Power supply circuit.

Claims (1)

[Claims] Radio waves generated by the power supplied from the power supply circuit are supplied into the heating chamber, an antenna is provided near the opening made in the heating chamber wall, a dielectric plate is interposed between the antenna and the heating chamber space, and the above-mentioned A high-frequency heating device in which the radio waves received by the antenna are DC-detected by a detection circuit that is DC-insulated from the heating chamber wall, and the detected signal is connected to a control circuit and a power supply circuit.