JPS58110929A - Microwave heating apparatus - Google Patents

Abstract

PURPOSE:To prevent over-rise of the surface temperature of a frozen food and to enable to achieve semi-thawing of the frozen food automatically in a short while, by measuring the surface temperature of the frozen food, and controlling the output of a microwave heating apparatus according to the surface temperature thus detected. CONSTITUTION:The surface temperature of a frozen food 2 put in a heating chamber 1 is detected by a detector 10, and a controller 11 controls the effective output of a high-frequency oscillator 5 at least in three stages of P1, P2 and P3 according to the surface temperature of the frozen food detected by the detector 10. That is, in the first stage of thawing of a frozen food, the oscillator 5 is made to operate at its maximum effective output P1 until the surface temperature of the frozen food is raised to a first predetermined reference temperature T1. In the second stage of thawing, the effective output of the osicllator 5 is controlled at P2 until the surface temperature is lowered to a second reference temperature T2. In the third stage, the effective output of the oscillator 5 is controlled at P3. In the above control, the following relationships, P1>P3>P2>=0 and T1>T2, are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to an automatic defrosting function of a high-frequency heating device.

In general, when thawing perishable frozen foods, for example, when thawing fish for sashimi or frozen meat to the extent that the wrapper can pass through, the surface temperature of the food is 6°C to 1'.
It is necessary to thaw at a temperature below O'C and to such an extent that only a slight frozen state remains in the center. This kind of thawing is called half-thawing.

Conventionally, when performing the above-mentioned half-thawing in a microwave oven, heating was done with a low constant radio wave output of about 200W as shown in Figure 1, but the surface temperature in that case is as shown in Figure 1. As shown in curve a, over 10'C and 15°C to 20'C
This results in so-called overheating. Furthermore, setting the heating time often depends on experience, and if the setting is incorrect, there is a problem that the surface may be boiled or failures may occur, such as not fully thawing the food.

Furthermore, in order to suppress the rise in surface temperature, it is possible to reduce the radio wave output, but this poses the problem of taking a long time.

Furthermore, the rate of increase in surface temperature also changes depending on the size of the frozen food, so even if the radio wave output is optimized for a frozen food of 1oo9, for example, it will be too strong for a 5oop. .

As a method to solve these problems, a method has been proposed in which the surface temperature at the end of thawing is measured and thawing is completed, but as can be understood from Fig. 1, the surface temperature a
As long as heating is carried out in such a way that the core temperature is 1°C or more higher than the core temperature, it is meaningless to detect the end of thawing based on the surface temperature, and it is difficult to accurately control the temperature. , the present invention solves the problems of the prior art.
By measuring the surface temperature of the frozen food and controlling the radio wave output based on the surface temperature, the surface temperature of the frozen food is prevented from rising excessively, and the frozen food is automatically half-thawed in a short time. I can do it. It is an object of the present invention to provide an automatic defrosting microwave oven.1. In order to achieve the above objects, the present invention provides a heating chamber for storing frozen food, and a jiffy frozen food stored in the heating chamber. a surface temperature detector that detects the temperature of the surface portion of the heating chamber; a high frequency oscillator that supplies power to the inside of the heating chamber with a high frequency oscillator; a1) is equipped with a control unit that controls the effective output of the product in at least three stages of preset Pl, P2, and P5; First predetermined temperature T1 with a predetermined detected value
Heating is performed at effective output P1, which is approximately the maximum output of the high-frequency oscillator, until the temperature reaches T2, and then in the second stage, the effective output is set at P2 until the detected surface temperature value decreases to a second predetermined temperature T2, Then, in the third stage, the effective output PS is set, and the high frequency heating device is configured to perform control that satisfies the relationships P+ > P3 > P2 ≧ 0 and TI > T2, making it possible to perform more reliable automatic defrosting with fewer failures. At the same time, the thawing and heating time can be shortened.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 2, a microwave oven with an automatic defrosting function is shown. 1 is a heating chamber for storing and heating frozen foods; 2 is a frozen food placed on a screen 4 placed on a saucer 3;

A magnetron 5 is a high frequency oscillator that supplies high frequency power into the heating chamber 1. Reference numeral 6 denotes an infrared radiation thermometer that measures the surface temperature of the frozen food 2. In front of the infrared radiation thermometer, a chopper 8 driven by a motor 7 is installed. By intermittent infrared rays emitted from the surface of the frozen food 20 by the chopper 8, the infrared radiation thermometer 6 can detect the surface temperature of the frozen food. ”-Light distribution external radiation thermometer6. The motor 7, chopper 8, and hole 9 constitute a surface temperature sensor a:÷10. Reference numeral 11 denotes a restraining section having a restraining circuit E1, which detects the surface temperature 1. : The surface temperature of the tableware measured by No. 10 is input, and other inputs such as a start switch (not shown) are input manually, and the control described in detail below is performed to turn on the magnetron and the cooling fan (not shown). (not shown) and other microwave ovens.

Hereinafter, the operation in the configuration shown in "-" will be explained based on FIG.

In the figure, curve d represents the change in surface temperature, and curve e represents the change in temperature at the center.

First, a safety check is carried out according to conventional operating procedures, such as making sure that the door of heating chamber 1 is closed.

After that, press the defrost start switch (not shown) and
Start defrosting and heating. At this time, the surface temperature measuring device 1o
By measuring the surface temperature of the frozen food 2 and confirming that it is below -2°C or another predetermined temperature, it is confirmed that the frozen food 2 is placed. Then, thawing is started, and first, heating is started with the effective radio wave output set to Pl. This P
By setting l to the maximum output of the magnetron 6, the entire defrosting time can be shortened. While heating with this output P1, the surface temperature of the frozen food 2 is continuously measured, and this surface temperature is determined in advance. Heating is continued at this effective radio wave output P1 until the predetermined temperature T1 is reached.

This predetermined temperature T1 is desirably set to 6°C or less. The temperature of the surface of frozen food 20 rises relatively quickly,
As shown in the figure, the temperature in the center remains in the range of 15°C to 0°C, consuming the energy absorbed as heat of melting of the ice. This period is called the first stage.

Then, when the surface temperature reaches T1, the effective radio wave output is changed to P2 by 9 times at time tτ1, and the second stage is entered.

At this stage, the surface temperature, which has risen by 1- to T+, is lowered again by the heat absorption 11 inside the frozen food 2, and waits for it to drop to the second predetermined constant temperature T2. Therefore, T1', > T2 and P2 < PI, and P2 is preferably zero, that is, a force that stops radio wave oscillation.1. It is desirable to set the second predetermined temperature T2 to a fairly low temperature of about 2' (~-3℃).Also, at the beginning of the second stage, there is a large temperature difference between the surface and the inside, so can speed up heat conduction.

When the surface temperature reaches the second predetermined temperature T2, the third
stage, the effective radio wave output is P3, and heating is performed. Here, P3<PI, so the temperature rise on the surface is gradual.
Increase by 1. The actual (IJ'+l+) wave output in the third stage is preferably about 300 W to 100 W, and since the overall temperature rise is gradual, the temperature difference between the center and the surface can be kept relatively small.

Thawing ends when the surface temperature reaches a predetermined temperature T3.

In addition, in the third stage, several temperature settings are set, and when each stage is reached, the effective radio wave output is set to 300W, for example.
By changing from 2ooW to 1oOW, even better decompression can be achieved.

As described above, according to this embodiment, the radio wave output is increased in the first stage to provide a large amount of energy, thereby shortening the entire defrosting time. Also, since the surface temperature is monitored, it is possible to prevent the surface temperature from rising too high.

Therefore, it becomes possible to defrost food in a short time while keeping the surface temperature low, which was previously said to be difficult to achieve.

Next, FIG. 4 shows another embodiment, in which the effective radio wave output P3 in the third stage is output intermittently.

In FIG. 4, from the start of thawing until the surface temperature reaches the first predetermined temperature T1, the maximum output P
The fourth step of heating is the same as in the example of FIG. At the 21st floor in the hole, the radio wave oscillation of the magnetro/6 is stopped when the surface width H91 of the frozen food 20 drops to the second predetermined temperature T2, that is, P2 in the above-described embodiment shown in FIG. − This is the case of 〇. Now, the surface temperature is T2
When it reaches low 1, it moves to the third stage. The features of this embodiment are:
The third stage is the control of magnetron 6. 111
In the first embodiment, the radio wave output P5 of the magnetron 6 is set to P3.
Although continuous oscillation was performed with a constant output as <Pl, in this example, in order to obtain the radio wave output of P5, the time toff
The oscillation of the magnetron 6 is stopped for a time t, and then the oscillation of the magnetron 6 is stopped for a time t.
By making the magnetron 5 oscillate while it is on,
The oscillation of the magnetron 6 is repeatedly stopped periodically.

In other words, since the magnetro/6 oscillates at its maximum output P1 for a period of time ton, the surface temperature decreases relatively quickly.
rise The oscillation then stops for a period of time toff, so that the surface temperature decreases. Compared to the case shown in Figure 3, the surface temperature of the dust becomes higher while the magnetron 6 is oscillating, so the temperature difference between the surface and the inside (1) increases, and while the oscillation is stopped, the temperature increases from the surface to the inside. Furthermore, if the start of the third stage is delayed by the toff time, that is, the oscillation of the magnetron is stopped, when the magnetron 15 actually starts oscillating, the surface temperature is lower than the predetermined temperature T2 of the second stage, so the temperature difference between the predetermined temperatures T1 and T2 can be set relatively small compared to the example in FIG. It is also possible to use a comparator with hysteresis.Also, one period of the third stage (t
If the effective radio wave output at (off + ton) is P's, On P'3 = -------P 1 toff + ton, so if you choose the ratio of time ton and toff,
An effective radio wave output P's similar to that shown in FIG. 3 can be obtained. In experiments, better thawing results were obtained when the time ton was set to 3 seconds or more.

According to the above two embodiments, the following effects can be obtained.

(1) Since the maximum output P1 of the radio wave oscillator is applied in the first stage, the defrosting time is shortened. At this time, when the surface 1Vli degree reaches the first predetermined value, radio waves are emitted at +:,iy4)](
Since the output of the device is set to the minimum (including when stopped), there is no excessive rise in surface temperature.

(2) In the second stage, the output of the radio wave oscillator is lowered to lower the surface temperature, and this is continued until the surface TA, X degrees reach the second predetermined value T2, so that the surface temperature is Thermal energy can be transferred to the center, and the surface temperature can be lowered. Furthermore, since the surface IT;A degree at the end of the first stage, that is, at the beginning of the second stage, is considerably higher than that at the center, heat can be quickly conducted from the surface to the inside.

(3) In the third stage, the radio wave output is reduced, so it is possible to freeze the mattress while keeping the temperature difference between the surface and the inside small.

(4) Furthermore, as shown in Figure 4, by setting P3 in the third stage to oscillation and stopping of Pl, pulsations in the temperature of table m1 occur, so compared to the case without pulsations, heat conduction from the surface to the inside is reduced. can be done faster.

As described above, according to the present invention, by heating the first stage at maximum output and automatically measuring when the frozen food has reached a predetermined temperature, it is possible to thaw and heat the frozen food without weighing it. can. In addition, automatic defrosting and heating is possible by setting the output of the second stage to the lowest level, and then heating to a predetermined temperature in the third stage with an output higher than that of the second stage and lower than that of the first stage. An object of the present invention is to provide an excellent high-frequency heating device that can shorten the time required for thawing and does not overheat the surface of food.

[Brief explanation of the drawing]

Fig. 1 is a temperature change characteristic diagram of food during thawing using a conventional high-frequency heating device, Fig. 2 is a side sectional view of a high-frequency heating device which is an embodiment of the present invention, and Fig. 3 is a diagram showing the temperature change characteristics of food during thawing using the same device. FIG. 4 is a temperature change characteristic diagram of food, which is a diagram showing temperature change of food in another embodiment of the present invention. 1...Heating chamber, 2...Frozen food, 6.
...High frequency oscillation a:), 6'''''' Table 1rl
l IAA I'f r! l, 10 ”'”' fE
tffi jfF, degree 1 output a 11... control (1 part, Pl, P2.P5...... effective output of high □□□ wave oscillation 8g T1.T2.・・・・・・Predetermined j
71A' (R: + Name of agent Benyo 11: Toshio Nakao and 1 other person Figure 1 Figure 2 Figure 3 @r 1735 Figure 4

Claims (2)

[Claims] (1) A heating chamber that stores frozen food, a surface temperature detector that detects the temperature of the surface of the frozen food stored inside the heating chamber, and a high-frequency oscillator that supplies high frequency power to the inside of the heating chamber. and Pl, P2 ., which set the effective output of the high frequency oscillator in advance according to the temperature of the surface portion detected by the surface temperature detector. P3, and in the first stage when the frozen food is thawed, until the surface temperature detection value of the frozen food reaches a predetermined first predetermined temperature T1. teeth,
Heating is performed at an effective output P1, which is approximately the maximum output of the high frequency oscillator, and then, in a second stage, the effective output is set to P2 at a trench where the detected surface temperature value decreases to a second predetermined temperature T2,
Next, in the third stage, the effective output is set to P3, and the high-frequency heating apparatus is configured to perform a control that satisfies the following relationships: P+>P'322P2;H20 and T1-T2. (2) In the third stage, the maximum output P1 is output in a disconnected manner to become the effective output P3.
Ice range: The high-frequency heating device according to item 1.