JPH04242096A - High frequency heating device - Google Patents

Abstract

PURPOSE:To prevent a high frequency heating device from being operated and heated with no food materials in. CONSTITUTION:Electric waves emitted out of a high frequency oscillator 1 are received by an antenna 7 via a joint hole 6 provided for the side surface of a heating chamber so as to be detected by a detection circuit 8. The condition of a heating chamber is judged by detecting the output of the detection circuit 8 by at least, either one of a detection output judging means 9 and a detection output change rate judging means 10. When it is judged that a cooker is heated with its heating chamber emptied, a power supply circuit is opened. In this invention, the condition of heating with its heating chamber emptied is detected by primarily effective electric waves, accuracy is thereby high, and it can be judged in a short time whether or not the cooker is heated with its heating chamber emptied. This can thereby prevents a food resting table from being damaged due to heating with the heating chamber emptied.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. 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 power source such as a magnetron. In particular, the present invention relates to a method for preventing so-called "dry-baking operation" in which the refrigerator is operated without any food or other load inside the refrigerator.

0002

2. Description of the Related Art Conventionally, as a method of preventing "dry firing operation", a configuration has been used in which a temperature rise in a magnetron is detected using a temperature detection circuit or the like and the power supply is controlled.

0003

[Problems to be Solved by the Invention] In the conventional method, for example, when applied to a commercial microwave oven (output 1 to 1.5 KW), the detection response time is long, so it is necessary to There was a problem that the stand could be destroyed by radio wave heating. SUMMARY OF THE INVENTION An object of the present invention is to provide a configuration for detecting a dry firing state with high accuracy.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a high frequency oscillator that oscillates high frequency waves using electric power supplied from a power supply circuit, and a heating device to which high frequency radio waves oscillated from the high frequency oscillator are supplied. a coupling hole provided in the wall of the heating chamber; an antenna provided near the coupling hole and configured integrally with a detection circuit; and a detection output determination means for determining the output from the detection circuit and a detection output change rate determination unit. The heating chamber is configured to include a control circuit that determines the state of the heating chamber by at least one of the means and controls the power supply circuit.

Further, in the above configuration, the power supply circuit is opened when the detected output value is larger than a preset value by the detected output determining means.

Furthermore, the detection output change rate determining means controls opening and closing of the power supply circuit by comparing the detection output change rate with a preset value.

[0007]

[Function] With the above-described configuration, the present invention can accurately grasp changes in the radio wave condition within the heating chamber and control the power supply in accordance with the input and output of the detection circuit.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a high frequency heating device of the present invention. The output radio waves 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 dielectric plate 5 prevents cooking scatterings and exhaust gas from becoming an antenna 7.
This is a shielding plate that prevents intrusion into the environment. Radio waves inside the refrigerator are detected into direct current by a detection circuit 8 with an antenna 7 via a coupling hole 6 provided in the heating chamber wall. The detected DC signal is connected to a radio wave circuit 12 via a control circuit 11 having a detection output determination means 9 and a detection output change rate determination means 10. Figure 2 shows the index of food (meat) temperature and radio wave absorption rate, ε.
The relationship between r tan δ is shown. When heating from room temperature (20° C.), the absorption rate increases as the temperature of the food increases.

FIG. 3 shows an example of the detection output when different types of foods are heated. (a) is a small food, (b) is a large food, and (c) is a case of fried chicken. The small waveform change is a change in response to the movement of the turntable. There is a tendency for the detection output to decrease as the amount of radio waves absorbed by food increases. The characteristics of the detected output waveform during grilling are that compared to when there is food, the detected output is large and shows small waveform changes, and the detected output fluctuations due to heating time are small. The detection output determination means compares the value of the detection output with a preset output value and/or a peak value, and determines whether or not there is a dry firing state based on the magnitude of the value. As can be seen from FIG. 3, this determination can be made in a short time. Further, the detection output change rate determination means compares the time change rate of the detection output with a preset value, and determines whether or not there is a dry firing state based on the magnitude of the value. Although this determination takes time, it is useful for determining whether the amount of cooking is small or whether the food is dry-cooked.

When the control circuit 11 determines that dry baking is occurring based on these characteristics, it controls the power supply circuit 12 to open the power supply, thereby preventing the destruction of the food table or the magnetron 1.
can prevent negative effects on the lifespan of

As mentioned above, in the past, the dry firing state was detected by the temperature rise value due to the secondary effect, but in the present invention, it is detected by radio waves due to the primary effect, so it is highly accurate and can be detected in a short time. It is possible to detect whether or not there is a dry firing condition.

[0013]

As described above, according to the present invention, the dry baking state can be detected with high accuracy and responsiveness, so that damage to the food mounting table due to dry baking can be prevented.

[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.

[Figure 2] Temperature characteristic diagram of radio wave absorption rate of food

[Figure 3] Detection output diagram when changing the type of food

[Explanation of symbols]

A High frequency heating device 1 High frequency oscillator (magnetron) 3 Heating chamber 6 Binding hole 7 Antenna 8 Detection circuit 9 Detection output determination means 10 Detection output change rate determination means 11 Control circuit 12 Power supply circuit

Claims (2)

[Claims] Claims 1: A high-frequency oscillator that oscillates high-frequency waves using electric power supplied from a power supply circuit; a heating chamber to which the high-frequency radio waves oscillated from the high-frequency oscillator are supplied; a coupling hole provided in the wall of the heating chamber; The state of the heating chamber is determined by an antenna provided near the coupling hole and configured integrally with a detection circuit, and an output from the detection circuit using at least one of a detection output determination means and a detection output change rate determination means. A high-frequency heating device comprising a control circuit that controls the power supply circuit. Claim 2: The value of the detection output is determined by the detection output determination means.
2. The high-frequency heating device according to claim 1, wherein the power supply circuit is opened when the value is larger than a preset value.