JPH0454137B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an automatic high-frequency heating device that can be used when defrosting and cooking frozen foods in a high-frequency heating device such as a microwave oven.

2. Description of the Related Art In general, thawing of frozen foods by microwave heating is completed in an extremely short time, resulting in good quality after thawing, and has been put to practical use more widely than ever before.
Here, we will be talking about the so-called thawing cooking method, which raises the temperature of foods such as frozen cooked foods and frozen vegetables such as Mikkusu Vegetables by heating them directly after thawing them.

Conventionally, such defrosting cooking methods generally involve heating with a constant high-frequency output from defrosting to cooking. Then, using a cooking sensor such as a humidity sensor or a gas sensor, it detects when the heating of the food is completed and automatically ends the cooking. This thawing cooking method requires less heating time, but on the other hand, cold spots tend to appear in the center of the food, and homogeneity is impaired in areas that begin to melt early and areas that begin to melt slowly, resulting in a mushy finish. I had a problem with getting used to it.

In order to improve the above-mentioned problems, a structure has been proposed in which thawing and cooking are automatically performed sequentially (Japanese Patent Application No. 114970/1982). In this system, the first half of defrosting is controlled by a weight sensor, and the second half of cooking is controlled by a gas sensor, and the defrosting is divided into four small modes to improve the defrosting quality.

Problems to be Solved by the Invention However, in such a thawing cooking method, since the thawing in the first half of heating is controlled by a weight sensor, there is a lot of variation in food temperature at the end of thawing, and the food temperature in the second half of cooking is Even if K value control (additional heat control) is applied to the process, there is a problem that the finish will be uneven.
This point will be explained in detail.

FIG. 6 shows the thawing cooking sequence described in Japanese Patent Application No. 114970/1982. Figure 6a shows the microwave heating pattern, Figure 6b shows the temperature rise of each part of the food, and Figure 6b shows the temperature rise of each part of the food.
Figure c shows the change in absolute humidity within the heating chamber. The thawing cycle consists of four small modes T ₁ to _{T 4} , T ₁ is full power, T ₂ is rest, T ₃ is medium power, and T ₄ is low power, and the temperature of each part of the food is as shown in figure b. It is controlled so that it changes as follows. That is, the frozen food passes through the zone of maximum ice crystal formation within a short period of time, and the microwaves are intermittent so that no boiling occurs on the surface, and the carried-over heating is used to thaw the food.

Next, in the cooking cycle, the power is returned to full power and the food is heated until the cooking sensor reaches a predetermined heating state, for example, until it is confirmed that the absolute humidity in the heating chamber has changed by a predetermined change Δh.
If this humidity detection point is P, then based on the heating time _T5 to reach point P during the cooking cycle,
The additional heat time is calculated by KT ₅ (K: constant). In other words, the total heating time is T ₀ =(1+K)T ₅ . This is a method called K value control (additional heat control) that is commonly used in automatic cooking using sensors.

By the way, the T ₁ to T ₄ times of the thawing cycle are each calculated based on the weight of the food. For example, if the weight of food is W, then T ₁ = K ₁ W, T ₂ =
Calculated as K ₂ W, T ₃ = K ₃ W, and T ₄ = K ₄ W. This is because the dielectric loss of frozen food is constant regardless of the material. In other words, if meat or vegetables are frozen, the thawing time can be determined solely by weight. Therefore, if the weight of the food can be accurately detected and the temperature of the frozen food is always the same, the food can be thawed effectively.

However, in order to accurately detect the weight of food, it is generally necessary to perform a "tare" process in which the weight of the container is subtracted, which is extremely troublesome in operation.
The temperature of frozen foods also varies greatly depending on the capacity of the freezer and whether the food is immediately taken out of the freezer or left out for a while.

Regarding the former, a method of estimating the food weight from the correlation between the total weight W ₀ of the food and container and the food weight W is an excellent method in terms of operation, and this method is basically adopted in the present invention. FIG. 5 shows this correlation, where each point indicates the relationship between the total weight W ₀ and the food weight W when various frozen foods are placed in various containers. It can be seen that there is a correlation between the two, W = 0.35W ₀ . Therefore, the thawing time in each mode mentioned above can be calculated without the troublesome process of subtracting the weight of the container.
It can be calculated from the total weight W ₀ . For example, T ₁ = K ₁ W = K ₁
×0.35W ₀ =K ₁ ′W ₀ (K ₁ ′: constant). Although this method is very superior in terms of operation, the error increases as the data deviates from this correlation straight line, leading to cases of over-decompression or under-decompression.

On the other hand, in the latter case, normally well-frozen foods are −20
It shows around ℃, but the temperature rises rapidly as soon as it is taken out of the freezer. For example, when frozen korotsuke is left indoors for 15 minutes, the food temperature drops to -20℃.
The temperature rose to 10℃. This shows that there is a considerable difference in temperature at the end of the thawing cycle between food purchased at the supermarket and cooked immediately after returning home, and food left in the freezer for several days or more.

Therefore, the detection time _T5 from the start of the cooking cycle to the humidity detection will vary greatly due to the above two factors. If it is over-thawed, T ₅ will be shorter, and if it is not thawed, it will be longer. When this unstable _T5 was multiplied by the K value and additional heat was applied, the variation in the finish became large.

The present invention solves these conventional problems and provides an automatic high-frequency heating device that realizes a thawing cooking sequence with little variation in finished product.

Means for Solving the Problems The automatic high-frequency heating device of the present invention includes a weight sensor and a cooking sensor, and the control unit uses both sensors to sequentially heat the object to be heated, and the control unit sequentially heats the object during thawing and heating. The total operating time of the microwave is counted and the additional heating time is calculated based on this.

Function The automatic high-frequency heating device of the present invention counts or calculates only the microwave operating time out of the thawing time calculated according to the weight of the object to be heated, and adds the detection time during the cooking cycle to this. Determine the additional heating time by multiplying by the K value. This allows thawing and cooking to be performed without being affected by the weight or starting temperature of the food.

Embodiment An automatic high-frequency heating device according to an embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, the automatic high-frequency heating device according to the present invention includes a main body 1 containing a heating chamber, a door body 2 that freely opens and closes the opening of the heating chamber, and an operation panel 3 that inputs various commands. It is formed by A thawing/cooking key 4 is arranged on the operation panel 3 for instructing thawing/cooking of frozen food.

FIG. 3 is a block diagram showing one embodiment of such an automatic high-frequency heating device. Commands input from the thawing/cooking key 4 on the operation panel 3 are decoded by the control section 5. Then, the control unit 5 starts defrosting and cooking the frozen food, which is the object to be heated 7 placed in the heating chamber 6 . The heating is controlled by being supplied with power via a driver 8 to a magnetron serving as high frequency generating means 9.

The weight sensor 10 detects the weight of the object to be heated 7 on the mounting plate 11 . Further, the cooking sensor 12 is realized by a humidity sensor, a gas sensor, etc.
It detects when cooking is complete by reacting to the steam and gas emitted by the cooker. Reference numeral 14 represents an exhaust guide, and reference numeral 16 represents a motor that rotates the mounting plate 11 to improve uneven heating.

Note that the weight sensor 10 may employ a capacitance method or a strain gauge method to detect the amount of displacement of the mounting plate 11, or a vibration method to measure the natural frequency.

Further, as the cooking sensor 12, a relative humidity sensor "Hyumi Ceram" manufactured by Matsushita Electric, a similar absolute humidity sensor "Neo Huyumi Ceram", a gas sensor #813 manufactured by Figaro, etc. can be used.

FIG. 1 is a heating pattern for thawing cooking showing an embodiment of the present invention. FIG. 1a shows the microwave output, FIG. 1b shows the temperature rise of various parts of the food being heated, and FIG. 1c shows the amount of steam generated from the food being heated.

Heating consists of three modes. First, in _{T1 ,} the microwave is heated at full power, and the time is _calculated based on the detected total weight _W0 ( _{K1 :} constant).
Calculated by In this _T1 mode, the temperature of the frozen food is raised all at once until the surface partially reaches 40 to 60 degrees Celsius. As shown in Figure 1b, at the end of T ₁ mode, the surface temperature is partially raised to 40 to 60°C to the point where local "boiling" occurs, so to speak, and then in the next T ₂ mode. The standing effect of can also be enhanced. At this time, the internal temperature of the food is still -2 to -3°C, and in this state the mode shifts to _T2 mode.

In _T2 mode, the microwave power is reduced to around 180 Watts and carryover heating is performed. _T2
Similar to _T1 , the time is also calculated by _T2 = _{K2W0 ( K2} : constant). In T ₂ mode, there is a large temperature difference between the surface and the inside, so the temperature moves quickly and T ₂
At the end of the mode, the internal ice is completely thawed. Although the power in the _T2 mode may be simply stopped, the total heating time can be shortened by setting the power to a low output of about 90 to 250 watts as in this embodiment. With this level of output, there is not enough energy to further advance the boiling process, but it is effective in defrosting the inside (see Figure 1b).

In this embodiment, the defrosting cycle is simplified into two modes, _T1 and _T2 , but it is of course possible to have four modes as in the conventional example shown in FIG.

Now, once the food is defrosted in this way, the next step is to proceed to the cooking cycle using the cooking sensor. Here, a cooking sensor such as a humidity sensor or a gas sensor is used to count the time _T3 until a time point P when a predetermined amount of steam Δh is detected from the food. Then, when the point P is reached, additional time is calculated. The additional time T ₄ is determined by the following formula.

T ₄ =K ₁ (T ₁ +K ₂ T ₂ +T ₃ ) Here, K ₁ and K ₂ are each constants. K ₁ is a cooking constant, and a value such as 0.2 is selected depending on the food. K ₂ is the power factor, depending on the average power in T ₂ mode, e.g. full power
600 watts, and if the _T2 mode is 180 watts, a ratio of 0.3 between the two is selected. In other words, K ₂ T ₂ calculates the on-time of intermittent microwaves.

From the above, the K value is multiplied by the above formula to the total microwave on time including the thawing cycle, so even if the cooking time T ₃ changes due to the influence of the weight or the starting temperature of the food, , can perform stable additional heat.

Next, the control program of the microcomputer, which is the control section, will be explained using the flowchart shown in FIG. FIG. 4 is a flowchart showing the thawing cooking sequence. First, the thawing cooking key input is decoded and 4A is entered.
4B where the weight of the food W ₀ is measured. T ₁ time and T ₂ time are then calculated based on this.
4C. and 4D, where various flags and counters are initialized.

Next, when the start key input is decoded, 4E,
4F with microwave turned on, 4G with _T1 flag set. The clock is counted sequentially, and when 1 second has passed, it is 4H, T _1. After checking the flag 4I, T ₁
4J with daily time increments. and T ₁
It is checked whether the time has counted up or not, and the _T1 time reduction process continues until the time has counted up.

When the _T1 time has elapsed, the _T1 flag is reset, the 4L and _T2 flags are set, and the mode shifts to the 4M and _T2 mode.

By checking the _T2 flag 4N, the _T2 mode processing routine is entered. First, in order to control the microwave intermittently, the ON/OFF register counts and relays are controlled on and off according to the contents4.
Then, in 4P, the T ₂ time is reduced, and in 4Q, it is checked whether the T ₂ time has been counted up.

When the _T2 time has elapsed, the _T2 flag is reset 4R, the microwave is turned on again 4S, the intermittent output ends, and full power is reached. Then it shifts to _T3 mode.

In T ₃ mode, the HUM flag is checked first, 4T,
Initially this is not set, so T ₃ time is counted up 4U. The cooking sensor then checks whether a humidity change exceeding a certain threshold value Δh has been detected, and continues counting _T3 times until a 4V humidity change is detected.

If a temperature change of more than Δh is detected, here
HUM flag set 4W, additional heat time T ₄
is 4X calculated by the following formula.

T ₄ =K ₁ (T ₁ +K ₂ T ₂ +T ₃ ) It has already been described that K ₂ is selected so that the cumulative value of on-time among T ₂ times can be calculated. However, when the microwave is intermittent, the effective output value changes depending on the length of on-time and the length of one intermittent cycle, so K ₂ may be selected according to this effective output value. For example, it is conceivable to choose K ₂ to be 0.
At this time, the time at full power that is effective for heating
Additional heat time is calculated for the sum of T ₁ and T ₃ .

When the HUM flag is set, additional heat control will occur and the 4Y will be reduced at the _T4 time mentioned above. Eventually, when the T ₄ time counts up, 4Z, power is turned off 4a, and cooking ends 4b.

Effects of the Invention As described above, the automatic high-frequency heating device of the present invention has
Equipped with a weight sensor and a cooking sensor, the food is first thawed at high output based on the weight of the food, then carried over heating at low output based on the weight, and then again at high output with the cooking sensor to ensure that the food is heated to a predetermined level. The system detects the point at which the state occurs, calculates or counts the total on-time of the microwave including defrosting, and multiplies this by the K value to generate additional heat. Allows for thawing cooking with small temperature differences without any low-temperature parts. Furthermore, even if the sensor detection time during the cooking cycle fluctuates due to the weight or starting temperature of the food, stable additional heat can be applied.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing a heating pattern of an automatic high-frequency heating device in an embodiment of the present invention;
Fig. 2 is a perspective view of the main body, Fig. 3 is a block diagram showing the same configuration, Fig. 4 is a control flowchart of the microcomputer that is the control section, Fig. 5 is a graph showing the relationship between total weight and food weight, and Fig. 6 is a graph showing the relationship between total weight and food weight. The figure is a time chart showing the heating pattern of conventional thawing cooking. 4... Thawing cooking key, 5... Control unit, 6... Heating chamber, 7... Item to be heated, 9... High frequency generation means,
10... Weight sensor, 12... Cooking sensor.

Claims (1)

[Claims] 1. A heating chamber in which an object to be heated is placed, a high frequency generating means coupled to the heating chamber, a control unit controlling power supply to the high frequency generating means, a weight sensor detecting the weight of the object to be heated, The control unit includes a cooking sensor that detects the heating state of the object to be heated, and a key that commands thawing and cooking of frozen food, and when the key is operated, the control unit controls the heating state of the object detected using the weight sensor. Based on the weight, defrosting is performed at full power for a time T ₁ with a certain high frequency power, then defrosting is continued for a time T ₂ with a reduced high frequency power, and then the high frequency power is increased and the cooking sensor is activated. The time T ₃ required for the object to be heated to reach a predetermined heating state is calculated using K 2 T 2, which is the product of _the time T ₁ and time T ₂ required for thawing by a certain constant K _{2 ,} and then the object to be heated. time until it reaches the specified heating state
An automatic high-frequency heating device configured to control the time K ₁ (T ₁ +K ₂ T 2 +T 3 ), which is obtained by taking the sum of T 3 and further multiplying by a certain constant K ₁ (T _{1 +} K 2 T ₂ +T ₃ ), as an additional heating time.