JPS59207597A - 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] It relates to a high-frequency heating device that has a function to measure the temperature change caused by heating the food, and specifically measures the temperature change accompanying the heating of the food as a change in the degree of absorption of the high-frequency signal turtle wave in the heating chamber, and heats the food. This may be related to the high-frequency heating device 4 that controls the temperature.In general, in high-frequency heating devices such as the Hiji range that heats food using high-frequency waves excited by a magnetron, which is a high-frequency heating source, 2, 450MH7, high-frequency radio waves are used to heat food; for example, when heating and defrosting frozen food (/c), high-frequency energy is used to heat the food intermittently to prevent rapid heating. However, in order to actually achieve the desired degree of thawing, it is necessary to predict the heating time in advance according to the type, quantity, and weight of the frozen food, set it on a timer, and then reach the specified time. There is a method to stop the heating by stopping the magnetron oscillation.However, if you actually defrost the food using this method, the time required to defrost will vary depending on the temperature of the frozen food, so it may result in over-defrosting or under-defrosting. was the norm.

For this reason, there has been a demand for highly accurate 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 the food and to detect changes in the amount of radio wave absorption corresponding to temperature changes of the food, that is, the induced tK loss of the food. There is a means to control the heating of frozen foods by utilizing the temperature dependence of In this method, it is very important to select a specific resonance frequency so that the amount of radio wave absorption changes according to the temperature change IC of the food, and if the selection is incorrect, there is a drawback that sufficient thawing detection cannot be performed.

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 cross-sectional view of a high-frequency heating device equipped with a food thawing detection function according to the present invention. In the figure, 1 is a heating chamber mainly made of metal.

A door (not shown) that can be opened and closed is provided in the front of the wall surface 2. Inside the heating chamber 1, food 6, which is an object to be heated, is placed on a saucer 4. The saucer 4 is rotated by a cutting board rotated by a motor 5, and the food 7 is uniformly heated by high frequency. 7 is a magnetron which 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 foods 3. 10 is a resistance heating element.

Reference numeral 11 is a sweep oscillator used for heating food in an oven or grill, and sweeps and oscillates a high-frequency signal radio wave necessary for detecting frozen food. Reference numeral 12 denotes an impedance matching device, which is used to selectively determine the resonant frequency for measurement and to adjust the reception level of No. 4. 16 is a coaxial filter, and the 2,450 MH2 high frequency heating radio wave oscillated by the magnetron leaks into the signal system and space through the electric wire, causing noise and failure of the signal components:
To avoid bowing, and to selectively allow signal radio waves to pass through. This is a so-called 15-band filter. Also, 14 is attached with 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.

The signal radio waves in this resonant state exhibit a co-possession state due to the influence of the internal structure, etc., and the signal radio waves in this resonance state change at a certain rate depending on the change in dielectric loss caused by the temperature change of the food placed in the heating chamber. After being absorbed, it reaches the receiving loop antenna 16, is received, is sent to the detection circuit 17, and is converted into a DC voltage.
Furthermore, the amplifier circuit 18! 2 DC amplified, this is 1l
The signal is sent to the microcomputer 20 via the A/D converter 19, which converts it into a control signal. The microcomputer 20 has a two-rotation detection section 21. Of the rotation period of the mounting table detected by the rotation period detection step groove 23 composed of the photointerrupter 22, several signals are captured per rotation, and the average value of the signals or the maximum value of (d) is calculated. It is calculated to be a signal when the 4+bt table rotates once, and when this production signal reaches a preset value, the magnetron's drive and activation and the oscillator's oscillation are stopped.

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

When a high-frequency radio wave is swept and oscillated with a certain sweep width from the sweeper 11 and a signal radio wave is radiated into the heating chamber 1 by the transmitting antenna 15 iC, there are many resonance frequencies within the heating chamber 1. can be confirmed. In other words, if we observe the female wave output waveforms at these resonant frequencies.

As shown in FIG. 224, the waveform has many peaks, and by taking this out and measuring it as the reception level 4, the temperature of the two foods can be measured indirectly.

However, the detection outputs of these various resonance frequencies, and n, are not all dependent on the temperature dependence of the dielectric loss of the food (corresponding to C-r).

Only a few resonant frequencies within a certain frequency band change the female wave output and the dielectric loss of the food.

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

FIG. 3 is a characteristic diagram showing the relationship between detection output and food temperature depending on the resonance frequency. In the figure, the reception number 25 changes in accordance with the temperature of the food, and reaches its minimum when the temperature of the food is around 0°C, so defrosting can be performed by detecting this point. However, the reception signals 26 and 27 do not correspond to the food temperature and exhibit irregular fluctuations, so they 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 frequency5.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.

But in any case out of these resonant frequencies.

It is necessary to select and use the receiving number 4 that corresponds to the temperature. Therefore, it is necessary to select a preferable resonant frequency by measuring the reception signal No. 4 while the food is actually heated. In fact, in the case of this microwave oven, there are two frequency bands, such as 1,170.1230 MHz, and the initial objective of the present invention can be achieved by using frequencies within the limited range of 900 to 1.500 MHz. .

As mentioned above, the present invention is a means for transmitting a high-frequency signal radio wave into a heating chamber, and transmitting a phenomenon in which the resonant frequency generated inside the heating chamber is changed in accordance with the temperature of the food. By selecting and using a specific resonant frequency, it is possible to provide a high frequency adder having a 'A freezing detection function with a high degree of filtration.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a high frequency heating device showing an embodiment of the present invention, and FIGS. 2 and 6 are characteristic diagrams illustrating the present invention. 1... Heating chamber. 3. Food. 7. Madaitron. 11...Sweep oscillator. 12... Impedance matching box. 15... Transmission antenna. 16...Antenna for receiving one word. 20...Microcomputer. Applicant: Hitachi Heat Appliances Co., Ltd. Figure 1 Figure 2 Figure 3 -75-10-50510/j5 Humidity ('C)

Claims (1)

[Scope of 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 excavator (ii) that generates weak high-frequency radio waves with a frequency different from the oscillation frequency of the high-frequency heating source; r a transmitting antenna (1) that transmits the radio waves of the oscillator to the heating chamber at a constant output;
5) A receiving antenna (1/) that receives the radio waves transmitted from the transmitting antenna, and a conversion that converts the level change of the radio signal level received by the receiving antenna due to radio wave absorption by food into a control signal. (19) A high-frequency heating device equipped with a mechanism for measuring the temperature of the food based on the output of the converter, characterized by transmission and reception.