JPS59207596A - High frequency heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] This relates to a high-frequency heating device that is equipped with a function to control temperature changes associated with food heating VC, and high-frequency waves in the heating chamber as changes in the absorption degree of wave waves. 1] and relates to a high-frequency zero-heat device that controls the heating of food.

In general, high-frequency heating devices such as electronic renos that heat food using high-frequency energy excited by a high-frequency heating source, the McNetron, oscillate high-frequency radio waves of 2,450 MHz excited by the Magnetron to heat the food. For example, when heating frozen food to thaw it, it is common to use high-frequency energy to heat it intermittently, avoiding rapid heating and heating slowly. However, in order to actually obtain the desired degree of thawing (C), the heating time is predicted in advance according to the type, quantity, and weight of the frozen food, and the timer is set. When the predetermined time is reached, the oscillation of the Macnetron is stopped and the heating is stopped. However, when actually thawing using this method, the time required to defrost differs depending on the initial temperature of the frozen food, so there is usually an excess or deficiency in y;s freezing. There has been a demand for automatic control of defrosting.

One of the improved thawing detection means that overcomes the shortcomings of the conventional technology is to emit radio waves of a specific frequency to foods and detect changes in the amount of radio wave absorption corresponding to temperature changes of the foods, that is, the dielectric loss of the foods. There is a means to control the heating of frozen foods by utilizing the temperature dependence of In this method, it is important to select a specific resonance frequency so that the amount of radio wave absorption changes according to the temperature change of the food, and if the selection is incorrect, there is a drawback that sufficient thawing detection may not be possible. .

The present invention eliminates the drawbacks of such prior art and regulates the requirements for optimal defrost detection.

The present invention will be explained below by way of an example.

FIG. 1 is a side view of a high-frequency heating device equipped with a food thawing detection function according to the present invention. In the figure, reference numeral 1 denotes a heating chamber made of metal, and a door (not shown) that can be opened and closed is disposed in front of a wall surface 2. The filter is placed on the saucer 4. The saucers 4 are rotated by a quadruple placing table 6 which is rotated by a motor 5, and each food item 6 is uniformly heated by high frequency. 7 is heated by a magnetron, and radiates high-frequency radio waves through a waveguide 8 into the heating chamber 1 from an excitation port 9 to perform high-frequency heating of the food 7. 10 is a resistance heating element, which is used for heating two foods in an oven or on a grill. Reference numeral 11 denotes a sweep oscillator that sweeps and oscillates a high frequency signal radio wave necessary for decompression detection. Reference numeral 12 denotes an impedance matching device, which is used to selectively determine the resonant frequency for measurement and to maximize the level of the received signal 4, as will be described later. 13 is a coaxial filter, which is excavated by a magnetron.
, a so-called band that prevents 450 MH2 high-frequency heating radio waves from leaking into the signal system or space through electric wires and causing noise or destruction of signal components, and selectively allows signal radio waves to pass through. It is a blocking filter. 14 is still a connector.

Here, the high frequency signal radio waves transmitted from the loop antenna 15 are transmitted within the heating chamber within the heating chamber dimensions.

It exhibits a resonance state under the influence of the internal structure, etc., and the signal radio waves in this resonance state are absorbed at a certain rate depending on the change in dielectric loss caused by the temperature change of the food placed in the heating chamber. It reaches the receiving loop antenna 16 and is received,
The voltage A is sent to the detection circuit 17 and converted into a DC voltage, and then roughly DC amplified by the amplifier circuit 18 and converted into a control signal.
The signal is sent to the microcomputer 2o via the /D converter 19.

The microcomputer 2o has a nine rotation detection section 21. 1 of the rotation periods of the mounting table detected by the rotation period detection mechanism 23 of the 1z mounting table composed of the photo interrupter 22.
Captures several signals per rotation.

The average value or maximum value of the signal is calculated and used as a signal when the mounting table rotates once, and when this detection signal reaches a preset value, driving of the magnetron and excavation of the oscillator are stopped.

Here we will discuss signal radio waves and their forms in more detail.

When the sweep oscillator 11 sweeps and oscillates high-frequency radio waves with a certain sweep width, and the signal radio waves are radiated into the heating chamber 1 by the transmitting antenna 15, the presence of many resonant frequencies within the heating chamber 1 can be confirmed. In other words, if we observe the detection output waveforms of these resonant frequencies.

As shown in FIG. 2, the waveform has many peaks, and by taking this out as the receiving level 4 and opening it, it is possible to indirectly measure the temperature of the 5 foods.

However, the detection output (d) of these various resonance frequencies was examined in detail in 1111, and it was found that not all of them correspond to the temperature dependence of dielectric loss of food.

Only a slight resonant frequency within a certain frequency band (the only difference is the detection output and the dielectric loss change of the food).

In other words, it was confirmed that the detection output changes in response to changes in food temperature.

FIG. 3 is a characteristic diagram showing the relationship between the detection output of the resonant frequency and the food temperature. In the figure received No. 4 25! -1° Changes in response to food temperature 9 Food temperature is near 0°C i/r
Since g is the minimum, M freezing can be produced by detecting this point. Shikaji Ukego 26 and 27 do not correspond to food temperature and show irregular fluctuations.

Cannot be used for temperature measurement. The reason why the received signal No. 4 exhibits such a complicated change is presumed to be due to the generation conditions of the resonant frequency. In other words, the fundamental resonance frequency is determined by the dimensions of the heating chamber, and the higher-order resonance frequency is about twice this fundamental resonance frequency9.It is thought that this is due to the impedance of the circuit system containing the food, etc., but under what conditions does the resonance frequency occur when the food It is unclear whether this changes in response to temperature.

However, in any case, it is necessary to select and utilize one of these resonance frequencies whose reception number 4 corresponds to the warm helmet. Therefore, reception when the food is actually heated 4
The desired resonant frequency must be selected by measuring the signal. In addition, as a result of actually measuring this, the value of the C pile resonance frequency corresponding to the reception number 4 and the food temperature is 1,170 in the case of a microwave oven with a volume of approximately = t # = # cubic. 1230M
H2, etc., and it is preferable to use at least one or more of these frequencies for measurement.

As described above, the present invention is a means for transmitting a high frequency signal radio wave into a heating chamber, and measuring the phenomenon in which the reception signal No. 4, which converts the resonance frequency generated inside the heating chamber, changes in response to the temperature of food Z-1. By selecting and using one of the specific resonant frequencies that changes in response to the food temperature, it is possible to provide a high-frequency heating device with highly accurate defrosting and detection functions.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a stomach of a high-frequency heating device showing one embodiment of the present invention, and FIGS. 2 and 6 are characteristic diagrams for explaining the present invention. 1. Heating chamber. 6. Food. 7. Magnetron. 11...Sweep/oscillator. 12... Impedance matching box. 15... Transmission antenna. 16...Receiving antenna. 20...Microcomputer. Applicant: Hitachi Thermal Appliance Law Company Figure 1 Figure 2 Figure 3 -15-10-5θ 51θ 15 Crystal Humidity (H)

Claims (1)

[Claims] A heating chamber (1) surrounded by metal, and a high-frequency heating source (7) for high-frequency heating food stored in the heating chamber. An oscillator (11) that oscillates weak high-frequency radio waves with a frequency different from the oscillation frequency of the high-frequency heating source, and a transmitting antenna (1S) that transmits the radio waves of the oscillator to the heating chamber. A receiving antenna (16) that receives radio waves transmitted from the transmitting antenna; l A converter (19) that converts the amount of change in level of the received signal received by the receiving antenna due to radio wave absorption by food into a control signal; + A device equipped with a mechanism for controlling the heating of the food based on the output of the converter,
A high-frequency heating device characterized in that at least one of the four receiving signals which detects the resonant frequency generated in the heating chamber by the above-mentioned news agency waves changes in accordance with the temperature of the food, and heating is controlled based on this.