JPS5813938A - High frequency heater - Google Patents

Abstract

PURPOSE:To clearly perform egg cooking in a titled heater adapted to automatically cook the egg cooking such as cooking of CHAWANMUSHI by controlling total heating time according to the output of humidity detecting means during weak operation of high frequency output at the time of heating in the egg cooking. CONSTITUTION:When cooking a CHAWANMUSHI is selected, a signal IN is fed to a menu selector 18 and a cook start signal STA is generated, a switch 16 is closed by a relay drive circuit 15, and the maximum power high frequency radio wave is emitted by a magnetron 2 to the food 6 to be heated during the time T1. When the prescribed time T1 stored and set in advance in a heating pattern memory selector 19 elapses, a contact 21 is opened by the circuit 15, and the high frequency power is shifted to the weak operation. Thereafter, when the food 6 is substantially solidified to the state of slightly generating steam and a humidity sensor 8 detects the variation in the humidity, the contact 16 is opened by the circuit 15, and the heating is finished.

Description

Detailed Description of the Invention The present invention relates to a so-called automatic high-frequency heating device that cooks food using high-frequency heating, detects the cooking state of the food, and automatically determines the heating time. The heating time of food at high frequency is determined by various quantities such as the initial temperature, amount, final temperature, specific heat, and high frequency energy absorption rate of the food to be heated. Conventionally, the heating time setting method for microwave ovens was for the user to set the time determined based on the type and amount of food to be heated using a timer. Therefore, the initial temperature of the food, etc. was not taken into consideration, leading to cooking errors. It was difficult to use, as it was easy to cause problems, and the heating time had to be calculated and set each time the quantity changed.

In recent years, in order to improve these shortcomings, so-called automatic microwave ovens have been developed that use a sensor that detects the cooking progress of food and a control circuit mainly based on a microcomputer to automatically set and complete the cooking time. is also becoming the mainstream of microwave ovens. Automatic microwave ovens use various sensors to detect changes in relative humidity, food temperature, odor, gas, etc. that occur when food is heated, and are now capable of automatically cooking only certain items. However, it has not been possible to automate egg dishes, which have traditionally had a high failure rate in microwave ovens.

Hereinafter, with reference to FIGS. 1 to 4, the operating principle and the transition of cooking heating when cooking chawan mushi, a typical egg dish, in a conventional automatic microwave oven will be explained.

In Figure 1, 1 is a transformer for driving the magnetron 2, 3 and 4 are capacitors and diodes that constitute a rectifier circuit, 6 is a heating chamber, and 6 is the food to be heated, the result of microwave heating. The humid air generated from the heated object 6 is exhausted from the exhaust lower. A humidity sensor 8 having characteristics as shown in FIG. 2 is installed in the exhaust passage of the exhaust lower, and the voltage across a resistor 9 connected in series with the humidity sensor is used as a humidity detection signal. 1o is the standard signal source,
11 is a preamplifier, 12 is a minimum value detection and holding circuit, and 13 is a subtraction circuit for detecting an increase in humidity from the minimum value, which outputs a signal C proportional to (mu-B). Figure 3 (
When it is made to correspond to IL), mu is a changing humidity signal,
B is the lowest value hmin, and Δh is C. 14 is a voltage comparison circuit which compares the deviation signal C with a reference voltage vh and generates an output signal when C exceeds vh. This time is T in FIG. 16 is a voltage comparison circuit 14
This is a drive circuit for the contact 16, which is driven by the output signal of the contact 16 and turns the power supply source ON and OFF when cooking starts and stops. (STm) is a cooking start signal, and when STm is input, the contact 16 closes and opens when T in FIG. 3 has elapsed. In other words, when the object 6 to be heated is heated by the high frequency generated by the magnetron 2 and air is generated, the humid air is exhausted.The humidity sensor 8 detects this air and controls the respective control circuits 11, 12, 1.
According to 3°14.16, when the increase in the detected voltage from the lowest value exceeds vh, the contact 16 opens and heating is automatically terminated. Next, the transition of cooking heating will be explained in detail. First, as heating begins, the temperature of the tea steamed liquid, which is the object to be heated 6, rises steadily.High frequency waves have the characteristic of being absorbed from the periphery of the object to be heated, so rapid heating due to high frequency waves causes the temperature to rise steadily. In the zone, the VC temperature increases further than in the E zone.

Next, heating progresses further, and during T2, E
The temperature of the zone reaches 70'C to 90C, and steam gradually begins to be generated as shown in FIG. 3(b). However, during this time 1
The detection signal (h) shown in (a) continues to fall. This is because the relative humidity of the air passing through the exhaust lower continues to decrease due to the temperature increase in the magnetron 2, heating chamber 6, etc. as the high output operation continues.

Further, in the latter half of the period T2, the temperature in the D zone shows an even steeper rising curve. This phenomenon is unique to egg dishes. In other words, proteins such as hopoalpmin and lipovitellin, which are the main components contained in eggs, have a temperature of about 66℃~
It has the property of solidifying at 72°C. For example, chawanmushi is generally made by mixing eggs and soup stock at a ratio of 1:3 to 1:4 and heating it with seasonings, but the coagulation temperature is 76°C to 86°C.
It is ℃. The egg liquid in zone D that has reached this temperature is completely solidified, the convection that had been occurring in the container 17 until then completely stops, and the temperature rises even more rapidly. In addition, as mentioned above, even though a small amount of steam is generated, there is no increase in relative humidity, so
The heating operation continues without any rise in the detection signal curve. Next, when the heating progresses to between Ts 0, the upper 2
The temperature in zone D rises to around 100℃, and a large amount of steam is rapidly generated.
This greatly exceeds the cause of the decrease in relative humidity due to the rise in temperature of the internal air, which is detected as an increase in the detection signal Δh', and the heating operation is automatically terminated. Heated object 6 at this point
The D zone is intense, erect, extremely hard and coagulated, with a bad texture. Originally, when miso soup is reheated, it does not solidify even when the temperature approaches the boiling point, so the temperature is relatively uneven due to heat conduction by convection until the end.And when you eat it, you can mix it and drink it. There are a lot of them, so there is no particular problem. In addition, when cooking raw vegetables, etc., the food is wrapped in plastic wrap and heated, so the steam fills the gaps between the vegetables in the plastic wrap and heats the whole thing, which prevents uneven heating and allows for the heating and detection described above. I was able to cook without any problems. However, for egg dishes such as chawanmushi, the cooking end temperature is
It is necessary to maintain the temperature at a low temperature where the amount of steam and gas produced is relatively small, the allowable range of the above-mentioned end temperature is extremely small, and furthermore, since it solidifies around 80℃, it blocks convection and causes uneven heating. Conventional automatic microwave ovens were unable to automatically cook the food, as it required many difficult conditions such as the possibility of large amounts of gas being generated.

The present invention aims to automate egg cooking, which was thought to be impossible with the automatic microwave oven described above, by fully considering the unique characteristics of egg cooking, steam and relative humidity, and the characteristics of the microwave oven itself. This was made possible by devising patterns and control circuits, and will be explained below with reference to FIGS. 4 to 6.

In FIG. 6, the basic elements for detecting the steam of the heated object 6 are 1, 2, 3, 4, 5, 7, 8, 9 degrees, 10 degrees.
The functions of 11, 12, 13, 14, 16, and 16 are the same as in the conventional example, so detailed explanation will be omitted. In the figure, 18 is a menu selection circuit for selecting a target cooking item;
19 is a heating pattern storage selection circuit, which also serves as a timer circuit. (IN) is a menu selection signal. Further, 20 is a second capacitor, and 21 is a second capacitor 2.
0, and is turned on and off by a signal from the relay drive circuit 16. 22 is a magnetron cooling fan.The transition of the heating operation will be explained by referring to FIG. To (
S'l'A) signal to the menu selection circuit 18 and
When sent to the relay drive circuit 16, a high frequency wave of 600 W, which is the highest output, is immediately irradiated to the heated object 6 for a period of time T1 in FIG. The temperature is set to stop before the temperature reaches 76°C to 86°C. Next, when a certain period of time T1 preset in the heating turn memory selection circuit 19 has elapsed, a signal is sent to the relay drive circuit 16, the second contact 21 is opened, and the high frequency output shifts to weak operation. . Now, I would like to pay attention to the amount of steam generated by the detection signal and the temperature of the food being cooked during low output operation. First, the detection signal followed a large downward slope during high output operation, but when it changed to low output operation, it decreased. It's almost stable. This is because the temperature rise in the magnetron 2 and the heating chamber 6 is small and the temperature is almost saturated due to the cooling effect of the cooling fan 22, so there is no change in relative humidity. In addition, since the food 6 is not solidified and is gradually heated by low output operation, sufficient convection occurs within the container 17, and the temperature difference between the D zone and the two zones decreases.

As the heating operation progresses further, when the overall temperature of the food 6 reaches 76°C to 86°C, it solidifies and generates a small amount of steam.At this time, the relative humidity in the heating chamber 6 becomes stable. Due to the generation of a small amount of steam from cooking food 6,
The change increases and is detected as an increase in the detection signal Δh. This detection signal rise Δh sends a signal to the relay drive circuit 16 to open the first contact 16 and end the heating. Steam can be detected reliably, and egg dishes such as egg custard, which have traditionally had many failures, can be automatically cooked, and can be done without failure with extremely simple operations. In addition, high output operation is performed until the temperature of the food solidifies, and then automatically shifts to low output operation, which shortens the overall cooking time and realizes automatic heating of delicious egg dishes without uneven heating. Ru. It should be noted that each of the aforementioned control circuits can be mostly processed by the microcontroller 13 that has become rapidly popular in recent years, and does not result in an increase in cost.
The automation of egg dishes, which was an extremely difficult cooking item, was achieved by devising a heating turn program and a control circuit that are compatible with the unique characteristics of egg dishes, making it extremely useful.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a conventional high-frequency heating device;
The figure is a humidity sensor characteristic diagram, Figure 3 a, b. 0, (1 is a diagram showing each operating characteristic of a conventional example, FIG. 4 is a cross-sectional view showing a food to be cooked, FIG. 6 is a block diagram of a high-frequency heating apparatus showing an embodiment of the present invention, and FIG. 6a. b, c, and d are diagrams showing the same operating characteristics. 6... Heated object, 8... Humidity sensor, 9... Resistor, 14... ...Voltage comparison circuit. Name of agent: Patent attorney Toshio Nakao and one other person
11 0 rail 2 Figure 1 , l:1. H (%) Figure 13 4f! !

Claims (2)

[Claims] (1) A heating chamber that houses an object to be heated, a high-frequency generating means for high-frequency heating of the object to be heated, a detection means for detecting changes in humidity, etc. in the heating chamber, and a signal detector for the detection means. It has an output control means for controlling the high frequency output and a cooking item selection means, and it is possible to select a heating operation pattern of the high frequency output set in advance according to the target cooking item,
When cooking and heating an egg dish, the high-frequency heating device determines the detection signal of the detection means during operation with a weak output compared to the maximum high-frequency output, and controls the total heating time. (2) The high-frequency heating apparatus according to claim 1, further comprising a control means for performing high-output operation at least in the initial stage of heating when cooking eggs.