JPH0415413A - High frequency heater - Google Patents

Abstract

PURPOSE:To realize stable thawing of food in a simple structure by providing an opening of a long hole having 1/4 or less of one wavelength in size at the wall of a heating chamber, directly detecting a radio wave received by an antenna provided in the vicinity of the opening, and controlling the output of high frequency radiating means. CONSTITUTION:An opening 10 of a long hole having 1/4 or less of one wavelength of an oscillation frequency of a magnetron 3 in size is formed at the upper wall of a heating chamber 2. In this structure, high frequency not absorbed to food in the chamber is leaked from the opening 10, received by an antenna 6, and detected by detecting means 7. Control means 9 controls drive means 8 according to a signal of the detecting means. Thus, food can be stably and simply thawed without fail irrespective of placing way of the food in the chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high-frequency heating device for achieving automated defrosting of food products.

BACKGROUND OF THE INVENTION Conventionally, as an example of automating the thawing state of this type of high-frequency heating device (hereinafter referred to as a microwave oven), there has been an example of automating the thawing state of food as seen in Japanese Patent Application Laid-Open No. 59-207595. This was indirectly grasped from the relationship between the temperature dependence of the dielectric loss of and the detected output signal of the detection means in the oscillation frequency band of the high-frequency radiation means. That is, the seventh
As shown in the figure, l is food, 2 is a heating chamber, 3 is a high-frequency radiation means (hereinafter referred to as a magnetron), 4 is a transformer for operating the magnetron 3, 5 is a cooling fan that cools the magnetron 3, and 6 is a cooling fan for cooling the magnetron 3. This is a needle-shaped antenna installed inside the heating chamber. 7 is a detection means, 8 is a drive means for varying the high frequency power of the magnetron 3, and 9 is a control means for controlling the drive means 8 according to a signal from the detection means to adjust the output of the high frequency power.

The method of determining the amount of load on food 1 is that when food 1 is in the state of ice crystals at around -18°C, the dielectric loss is small and the high frequency power absorbed by food 1 is small, so it is relatively detected by the antenna. The signal becomes larger. This detected signal has an inversely proportional relationship with the load amount of the food 1 in the heating chamber 2, and the output of the magnetron 3 is controlled by determining the load amount based on the value of the signal.

Thawing of food was achieved through such control.

Problems to be Solved by the Invention However, in the above configuration, the antenna 6
Since the antenna 6 is placed inside the heating chamber, there is a problem in that it is difficult to manage high frequency variations in the signal line connecting the antenna 6 and the detection means 7.

Furthermore, depending on how the food 1 is placed in the heating chamber 2 (center or edge of the heating chamber 2), the electric field distribution around the food changes greatly. As such, the signal value of the detection means 7 may vary greatly.

Therefore, an object of the present invention is to realize stable thawing of food with a simple configuration.

Means for Solving the Problems In order to solve the above problems, the present invention provides an antenna provided near the opening made in the wall of the heating chamber, and a detection means that is integrated with the antenna and performs DC detection of radio waves received by the antenna. , the shape of the opening is an elongated hole, and the size of the opening is a quarter wavelength or less.

According to the present invention, radio waves that are not absorbed by the food leak through the openings made in the heating chamber and can be easily detected by the detection means.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings. Note that the component parts are the same as in the conventional example, and the same parts are given the same numbers.

FIG. 1 is a partial configuration diagram showing an opening 10 made in the upper wall soil of a heating chamber 2 of a high-frequency heating device according to an embodiment of the present invention. By making the shape of the opening 10 an elongated hole and making its dimension 1 shorter (for example, 15) than the 174 wavelength (approximately 30) of the oscillation frequency (2450 MHz) of the magnetron 3, 500 watts can be supplied into the heating chamber 2. The large output power does not leak from the aperture 10, and only a small amount of radio waves leak. Furthermore, by making the shape an elongated hole, unlike previous needle-shaped antennas that detect at one point, the detection means detects minute leaking radio waves, so they can be received by multiple antennas. This corresponds to the fact that it can be detected stably.

FIG. 2 is an overall configuration diagram of a high-frequency heating device according to an embodiment of the present invention, as seen from the top.

2 is a heating chamber, 3 is a magnetron, 4 is a transformer for operating the magnetron 3, 5 is a cooling fan that cools the magnetron 3, and 6 is an antenna, which is shorter than the 174 wavelength of the oscillation frequency (2450 MHz) of the magnetron 3. It is integrated with the detection means. 7 is a detection means, 8 is a drive means for varying the high frequency power of the magnetron 3, 9
is a control means (in the present invention, a microcomputer) which controls the drive means 8 according to the signal from the detection means and adjusts the output of high frequency power.

Although not shown in FIG. 2, a dielectric material is provided between the aperture 10 and the detection means 7 to prevent the detection means from being contaminated by food from the heating chamber 2.

With these configurations, high-frequency waves that are not absorbed by the food in the heating chamber leak through the openings, are received by the antenna 6, and are detected by the detection means 7.
The wave is detected by

FIG. 3 is a circuit diagram of the detection means 7 for detecting the oscillation signal of the magnetron 3. 11 is a 50 ohm resistor, 12 is a detection diode (for example, a Schottky barrier diode), 13, 14 is a resistor, and 15 is a capacitor. These detect the high frequency power that is not absorbed by food in the oscillation frequency band of the magnetron 3, and calculate the voltage. DC detection is performed as Vs.

FIG. 4 is a diagram in which the detection means 7 is composed of a microstrip line.

Copper foil patterns 17, 18, 19, 20, 21 are etched on a dielectric double-sided copper-clad substrate 16 having a certain dielectric constant ER. The copper foil portion 17 forms the 50 ohm wire in FIG.
3.24 indicates continuity.

The antenna 6 also has a detection means 7 with copper foil on the opposite side 22 of the board.
Similarly, the copper foil portion 17 is electrically connected to the copper foil portion 25 through the through hole 25.

By configuring the detection means 7 on the microstripe line, it is easy to optimally design the length of the line according to the frequency band to be detected, and since this is done by etching, the detection dimensional accuracy is improved. This is the second thing to do.

FIG. 5 is a characteristic diagram that does not show the signal level of the detection voltage Vs with respect to the weight of the food (frozen minced meat) immediately after the start of thawing. It can be seen from the figure that there is a large difference in the detected voltage immediately after the start of defrosting, depending on the weight of the food. This is because when the weight of the food is small, less high frequency waves are absorbed and relatively more high frequency waves are detected by the antenna 6.

Furthermore, it has been confirmed that when the aperture 10 is formed of a long hole, a stable signal voltage of the detection means 7 can be detected depending on the way the food is placed in the heating chamber 2.

Unlike needle-shaped antennas that detect dirt at a single point, the detection means detects tiny leaking radio waves that are not absorbed by the food.

In the present invention, the shape of the elongated hole is rectangular, but the shape is not limited to one embodiment of the present invention, and may be a rounded elongated hole or an oblong shape.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

A high frequency wave in the frequency band of the high frequency radiation means is emitted by an antenna installed near the opening in the heating chamber wall, a detection means that is integrated with the antenna and detects the radio waves received by the antenna, and a detection means that detects the radio waves received by the antenna. Since the hole is long and the size of the opening is less than 1/4 wavelength, stable signal detection is possible regardless of how the food is placed in the heating chamber, and thawing can be easily automated without failure. It can be achieved.

[Brief explanation of the drawing]

11 is a partial plan view showing the opening made in the heating chamber of a high-frequency heating device according to an embodiment of the present invention, FIG. 2 is a configuration diagram of the device, and FIG. 3 is a circuit diagram of the detection means of the device. , Fig. 4 is a plan view of the detection means of the same device configured on a substrate, Fig. 5 is a characteristic diagram of the signal of the detection means with respect to food weight during thawing of the same device, and Fig. 6 is a diagram of the conventional high-frequency heating device. The configuration diagram of the main body, FIG. 7, is a characteristic diagram of the signal of the conventional detection means with respect to the weight of the food. 1... Food, 2... Heating chamber, 3...
... High frequency radiation means, 6... Antenna, ■.
...Detection means, 9...Control means, 10.
...Open hole. Name of agent: Patent attorney Shigetaka Awano t ty) Can diagram diagram tjiO Q0 6shiO amount (υ

Claims (1)

[Claims] A heating chamber into which food is taken out and taken out, a high frequency radiation means for feeding high frequency power into the heating chamber, a control means for controlling the high frequency radiation means, an antenna provided near an opening made in the wall of the heating chamber, and the antenna. The control means includes a detection means for direct current detection of radio waves received by the antenna, and a dielectric interposed between the opening and the detection means, and the control means uses the signal of the detection means to generate the high frequency radiation means. A high-frequency heating device in which the output of the aperture is controlled, the shape of the aperture is an elongated hole, and the dimension of the aperture is 1/4 wavelength or less.