JPH04245190A - High frequency heater - Google Patents

Abstract

PURPOSE:To facilitate the control of highly accurate heating, which includes the thawing of frozen food, by observing the change of the high frequency power transmitted inside a waveguide and grasping the progress condition of the heating of food and controlling the heating. CONSTITUTION:A directional coupler 5 detects the components of incident and reflectional direction of the high frequency power transmitted inside a waveguide 4, which couples a heating chamber 1 with a magnetron 3, and also a controller 6 observes especially the change of the reflected power, which remarkably changes accompanying the progress of the heating, among the detected directional components, and controls heating operation such as that it stops the heating when there is specified change.

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 controls the heating operation by observing the progress of heating food.

0002

[Prior Art] A high-frequency heating device that controls the heating of food by measuring the surface temperature of the food with an infrared temperature sensor and also measuring the internal temperature of the food with a temperature probe is proposed, for example, as proposed in Japanese Utility Model Application Publication No. 86807/1983. It is known as.

0003

[Problems to be Solved by the Invention] First, regarding the infrared temperature sensor in the conventional device described above,
There is a problem in that the accuracy of temperature detection decreases due to dirt on the sensor, and it is also greatly affected by the position where the food is placed.

[0004] Furthermore, regarding heating and defrosting of frozen foods, there is a problem that it is extremely difficult to perform inexpensive and highly accurate temperature detection because the temperature range is originally a low amount of infrared radiation. There is also the problem that changes in food quality cannot be accurately captured when the food temperature does not rise even after heating time has elapsed, such as when food passes through the eutectic region, which is the thawing temperature range.

[0005] Furthermore, temperature probes have a problem in that temperature detection itself is difficult because they cannot be inserted into hard foods such as frozen foods.

[0006]

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and a directional coupler is attached to a waveguide connecting a magnetron and a heating chamber, so that transmission within the waveguide is prevented. The system detects the incident and reflected components of the high-frequency power generated by the heating process, determines the degree of heating of the food based on changes in the detected value as the heating progresses, and controls the heating operation when a predetermined change is observed.

[0007]

[Operation] As heating progresses, the dielectric properties of the food change. Therefore, the detected value of the transmission power detected by the directional coupler also changes accordingly. When a predetermined change occurs in the detected value, the control device controls the heating by, for example, stopping the oscillation operation of the magnetron.

[0008]

[Embodiment] An embodiment of the present invention will be explained with reference to FIG. 1
is a metal heating chamber that stores food, and 2 is this heating chamber 1.
This is a high-frequency power feed port installed in the ceiling wall of the building. 3 is a magnetron, and 4 is a waveguide for transmitting the high frequency power generated by the magnetron 3 to the high frequency power feed port 2 of the heating chamber 1 described above. Reference numeral 5 denotes a directional coupler, which is installed at a predetermined position on one wall of the waveguide so as to obtain a predetermined output signal level, and which combines the incident power component and reflected power component of the high-frequency power transmitted within the waveguide 4. It detects and outputs respective detection signals. Reference numeral 6 denotes a control device that observes the output signal of the directional coupler 5 that changes as the heating progresses, and outputs a signal for performing control such as stopping the heating operation when a predetermined change occurs. It is something to do. This control device 6 may observe changes in both incident power and reflected power of the signal output from the directional coupler 5, but changes in the reflected power as heating progresses are particularly noticeable. In view of this, attention is focused only on reflected power. Reference numeral 7 denotes a high frequency power supply device for driving the magnetron 3, whose operation is controlled in response to a control signal from the control device 6 described above. Reference numerals 8 and 9 indicate a saucer and food placed in the heating chamber 1.

[0009] In one embodiment configured as described above,
The high frequency power generated by the magnetron 3 is supplied into the heating chamber 1 through the waveguide 4 and heats the stored food 9. At this time, the reflected power is transmitted back through the waveguide 4. As the heating progresses, the dielectric properties of the food 9 begin to change. The control device 6 observes the signal related to the reflected power among the signals detected and output by the directional coupler 5 from the start of this heating. In this case, the directional coupler 5
The output signal changes only in response to increases in temperature and changes in the properties of the food, and does not change due to other influences. Therefore, even if the food temperature does not rise despite the passage of time, such as when the food temperature passes through the eutectic region around 0 degrees C, which is the thawing temperature, the frozen state, the eutectic state, and the ice This means that it is possible to accurately detect the state in which the

First, the control device 6 stores the signal of the reflected power component output by the directional coupler 5 at the start of heating. When heating progresses and it is observed that a predetermined change has occurred in the output signal of the directional coupler 5 with respect to the above-mentioned stored value, that is, it is determined that the temperature, properties, etc. of the food have reached a predetermined state. When this occurs, a signal is output to the next-stage high-frequency power source 7 to stop the operation of the magnetron 3, thereby controlling the heating of the food.

[0011]Although not described in detail, it is possible to incorporate a weight measuring device to provide food weight information to the control device and improve the accuracy of heating control without any particular difficulty.

0012

As described above, according to the present invention, a directional coupler detects a change in the power transmitted in the waveguide that changes as heating progresses, that is, a change in power that changes only due to a change in the dielectric properties of the food. However, the heating operation is controlled when the control device observes a predetermined change depending on the degree of heating.
High-precision heating control including thawing processing of frozen foods is facilitated.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts showing an embodiment of the present invention.

[Explanation of symbols]

1 Heating chamber 3 Magnetron 4 Waveguide 5 Directional coupler 6 Control device 7 High frequency power supply device

Claims (2)

[Claims] 1. A heating chamber 1 that stores food 9, a magnetron 3 that generates high-frequency power, a high-frequency power supply device 7 that drives the magnetron, and a waveguide 4 that couples the heating chamber and the magnetron. A directional coupler 5 is attached to a predetermined position on one wall of this waveguide to detect an input/reflection direction component of high frequency power transmitted within the waveguide and output a detection signal. A high-frequency heating device comprising: a control device that outputs a signal to the high-frequency power supply device to control driving of the magnetron when a predetermined change occurs in the output signal. 2. The high-frequency heating according to claim 1, wherein the control device controls the high-frequency power supply device by observing a signal regarding a reflected power component among the directional components detected by the directional coupler. Device.