JPH02275222A - High frequency heating device - Google Patents

Abstract

PURPOSE:To maintain stable control performance through a long period of time without receiving adverse effect induced by oily moisture parts of food or leak waves from a cabinet by laying out a dielectric plate between a heating chamber space and an antenna and installing at least one of a microwave detection circuit and a control circuit to a single printed board. CONSTITUTION:Radio waves transmitted from a high frequency oscillator 1 are supplied to a high frequency heating chamber 3 by way of a wave guide 3, thereby heating food 4 in a cabinet. The high frequency electric field in the cabinet is converted into DC by a detection circuit 8 from an antenna 7 in a recessed part 6 by way of a dielectric plate 5 faced in the cabinet. A detection signal is introduced into a control circuit 9 and connected with a power supply circuit 10 for the high frequency oscillator 1. A part covered with two point chain lines is mounted on a single printed board. The control circuit 9 is designed to control the power supply circuit 10 for the high frequency oscillator 1 based on an inflection point of a detection signal level when frozen food is heated or changes in amplitude comprising several Hz band of low frequency element. The recessed part 6 is covered with the dielectric plate 5 in its open hole, thereby preventing the oily moisture scattered from the food from being adhered directly on the antenna 7.

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 conventional technology, as shown in Jikai Publication No. 59-210759, a high-frequency heating source is activated by detecting the change in dielectric constant of the food that changes depending on the degree of heating of the object (hereinafter referred to as food). What controls is shown.

Problems to be Solved by the Invention In such conventional methods, since the target is food, a lot of moisture and oil scatters inside the refrigerator during heating, and this interposes between the antenna and the ground plane, greatly impairing the detection characteristics. The challenge was to change.

Means for Solving the Problems In order to solve the problems, the present invention adopts a configuration in which a dielectric plate is interposed between the heating chamber space and the antenna, and
At least part of the microwave detection circuit and control circuit,
It is constructed on a single printed circuit board.

Effects According to the present invention, oil and water scattered from food are not directly interposed between the antenna and the ground plane, and a part of the control circuit is mounted on the same printed circuit board as the detection circuit. It becomes possible to control a high-frequency heating source with stable characteristics.

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 in the refrigerator. The high frequency electric field inside the refrigerator is converted into direct current by a detection circuit 8 from an antenna 7 which faces the inside of the refrigerator in a recess 6 via a dielectric plate 5. The detected signal is guided to the control circuit 9 and connected to the power supply circuit IO of the high frequency oscillator 1. The portion surrounded by the two-dot chain line 11 is mounted on one printed circuit board.

FIG. 2 shows an example of how the printed circuit board including the antenna 7, the detection circuit 8, and part of the control circuit 9 is mounted. An antenna 7, an operational amplifier 12, and the like are mounted on the printed circuit board 11. FIG. 3 shows a circuit diagram on the printed circuit board 11, and FIG. 4 shows an actual layout diagram.

In the figure, the detection circuit 8 includes an antenna 7 and a resistor 13.15.
, a diode 16, and a capacitor 17, and a differential amplifying and smoothing circuit that is a part of the control circuit 9 is connected to the operational amplifier 12.
, resistor 18.19.20.21.22, capacitor 23
It consists of Since the voltage across the resistor 15 is directly connected to a part of the control circuit 9 on one printed circuit board 11, it is converted to a small impedance by the operational amplifier 12, so it is less susceptible to the effects of leakage waves from the microwave oven, etc. configuration can be realized. The opening of the recess 6 is covered with a dielectric plate 5 to prevent oil and moisture scattered from the food from directly adhering to the antenna 7. FIG. 5 shows an example of the time change of the detection signal (2) when the frozen food is heated. The amplitude and level change characteristically from the point (a1) of the completion of thawing and the point (b) of the start of boiling.
The circuit 9 controls the power supply circuit 10 of the high frequency oscillator 1 based on the inflection point of the level of V and the amplitude change consisting of a low frequency component in the several Hz band based on the signal (2).

Usually, expensive materials such as Teflon are used for micro source detection.
The printed circuit board and the control circuit use an inexpensive printed i-board made of epoxy, but in the present invention, since the transmission power is small and the change in the detected signal is large, for example, both the detection circuit and the control circuit are made of a single piece of epoxy. This can be realized using a printed circuit board.

Effects of the Invention According to the present invention, it is possible to realize a high-frequency heating device that is not adversely affected by oil and moisture in food products, leakage waves from inside the refrigerator, etc., and can guarantee stable control performance over a long period of time.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a high-frequency heating device according to an embodiment of the present invention, Fig. 2 is a sectional view showing the installation of a printed circuit board of the same device, and Figs. 3 and 4 are circuit diagrams on the same printed board. and an actual layout diagram, and FIG. 5 is a waveform diagram of the detected signal. ■・・・High frequency oscillator, 3・・・Heating chamber,
5... Dielectric plate, 6... Concavity, 7...
...Antenna, 8...Detection circuit, 9...
...Control circuit, 10...Power supply circuit, 11...
····Printed board. Agent's name Patent attorney Shigetaka Awano Haka 18 Figure/-11 Minami Jl > ff Fuyuenho 3--Ga Kei- 5--Issei t#, Kei 7--Antenna 8--Part 1 District? - 苧j immediate circuit, ノ() ---t;

Claims (1)

[Claims] Radio waves from a high-frequency oscillator using power supplied from a power supply circuit are supplied into the heating chamber, and a dielectric plate is arranged between the heating chamber and an antenna facing the heating chamber and insulated from the heating chamber. Further, at least part of a detection circuit and a control circuit are disposed on one printed circuit board, the radio wave received by the antenna is DC detected by the detection circuit, and the detected signal is connected to the control circuit and the power supply circuit. High frequency heating device.