JPS593646B2 - How to control a cooking oven - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects the cooking state of food in a cooking oven such as a microwave oven, electric oven, or gas oven.
The present invention relates to a control method that enables proper heating.

In general, the heating time of a microwave oven depends on the initial temperature of the food, its weight,
It is determined by various quantities such as final temperature, specific heat, and absorbed energy.

However, conventional methods for setting the heating time of microwave ovens have been to set a time determined based on the type and amount of food to be heated.

The relationship between heating time for each item and amount is determined in advance based on the results of heating experiments.

Therefore, when heating any food, it is not possible to set the heating time without considering not only the item but also the amount of the food.

In addition, this method does not take into account the specific heat of the food, the initial temperature of the food, and the final temperature of the food among the various quantities that contribute to determining the heating time. However, the drawback was that cooking and heating mistakes were more likely to occur.

The present invention solves the problems of the conventional heating time setting method and provides a control method that can realize a cooking oven that is easy to operate.

In other words, it is equipped with a temperature sensor that measures the humidity that rises due to water vapor generated from the food being heated, and a heating element that increases the temperature near the sensor. The temperature near the humidity sensor is increased by gradually increasing By measuring the relative humidity of each specified increase, the cooking state of each food item can be detected in the same manner regardless of the amount of the food item.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings showing embodiments in which the present invention is applied to a microwave oven.

FIGS. 1 and 2 show curves of changes in relative humidity, which increases due to water vapor generated when food is heated in a microwave oven, with respect to heating time.

Curves A, B, C and D each show the change in relative humidity for the same item and amount of food but under different ambient conditions.

Curves A and B in Figure 1 represent the relative temperature change when the ambient absolute humidity is the same but the ambient temperature is different, and curves C and D in Figure 2 represent the relative temperature change when the ambient temperature is the same but the ambient absolute humidity is different. Shows relative humidity changes at different times.

In this way, even for the same food item and the same amount, the relative humidity differs in the initial state due to differences in the ambient absolute humidity and ambient temperature near the humidity sensor. It cannot be detected by relative humidity.

The present invention solves this problem by increasing the temperature near the humidity sensor during the initial stage of food heating until the relative humidity near the humidity sensor falls to a specified relative humidity level. This method will be explained with reference to FIG. 3 and subsequent figures.

In Fig. 3, 1 is the heating chamber of the microwave oven, 2 is the food to be heated, 3 is a blower fan, 4 is a magnetron, 5 is a humidity sensor, 6 is a heating element that heats the vicinity of the sensor 5, and 7 is a humidity amplifier. , 8 is a cooking state detection circuit, and 9 is a heating element control circuit, which shows a basic configuration diagram of the method of the present invention.

Furthermore, FIG. 4 shows a partial detailed diagram for explaining in detail the cooking state detection circuit 8 and heating element control circuit 9 in FIG. , 12 is a magnetron driver connected to the magnetron 4 through its output terminal 13.

Also, 14 is a humidity comparator, H is a set humidity matching relay, 15
is the heating switch, 16 is the charging resistor, 17 is the discharging resistor, h is the break contact of the set humidity matching relay H, 1
8 is an integrating circuit consisting of a DC amplifier 19 and a charging capacitor 20, 21 is a heating element current generator, and its output terminal 22
It is connected to the heating element 6 through.

Next, the operation will be explained.

First, the humidity sensor 5 detects the relative humidity increased by water vapor emitted from the food 2 heated by the magnetron 4, and the detected signal voltage is amplified by the humidity amplifier 7 to obtain a voltage output proportional to the detected relative humidity.

This voltage output passes through the output terminal 10 of the humidity amplifier 7 and is compared with a reference voltage Co by a humidity comparator 14, and when the voltage falls below this reference voltage, a relay H is driven.

On the other hand, the heating switch 15 is switched to the lower side at the same time as heating of the food starts.

Therefore, the voltage output of the humidity amplifier 7 is applied to the integrating circuit 18 through the output terminal 10, the lower contact of the heating switch 15, the charging resistor 16, and the break contact of the set humidity matching relay H. The capacitor 20 is gradually charged by the voltage output.

This charging voltage is applied to the heating element current generator 21, and the heating element current generated here is passed through the output terminal 22 to the heating element 6.
The ambient temperature of the humidity sensor 5 increases as the charging voltage increases.

Due to this -L increase in the ambient temperature, the relative humidity near the humidity sensor decreases in the early stage of food heating.

FIG. 5a shows the change in temperature near the humidity sensor as the heating time elapses.

Moreover, FIG. 5 shows the change in relative humidity measured by the humidity sensor with respect to the elapse of heating time.

In both figures a and b, curves A and B represent the changes in ambient temperature and ambient relative humidity when the ambient absolute humidity is the same, the ambient temperature is different, and the ambient temperature is not heated by the heating element.

On the other hand, curve E represents the change in ambient temperature and ambient relative humidity when the surroundings are heated by the heating element, respectively.

That is, when heating the vicinity of the humidity sensor in the early stage of food heating, the ambient temperature increases rapidly, as shown by curve E in FIG. 5, compared to curves A and B when no heating is performed.

Therefore, the ambient relative humidity around the humidity sensor rapidly decreases.

and relative humidity as shown.

When the voltage output of the humidity amplifier 9 reaches e.

decreases to As mentioned above, this voltage output is further reduced to the reference voltage e of the humidity comparator 14.

When the difference voltage between the voltage output and the reference voltage is exceeded, the difference voltage between the voltage output and the reference voltage is amplified by the humidity comparator 14 and drives the set humidity matching relay H.

Then, the break contact of relay H opens and the circuit is cut off, so that charging of charging capacitor 20 is stopped.

The output of the integrating circuit holds the voltage value when charging is stopped.

Therefore the relative humidity level increases.

After reaching the holding voltage, the heating element current generator 21
In addition to this, the heating element current generated here is also held and continues to flow through the heating element 6.

This heating current increases the ambient relative humidity near the humidity sensor, excluding the effects of temperature and humidity caused by food heating.

The value is chosen to maintain an ambient temperature that is maintained at .

However, in reality, by heating the food,
As shown by curve E in FIG. 5, the ambient temperature rises and the relative humidity also rises due to the water vapor generated from the heated food.

Furthermore, the voltage output of the humidity amplifier 7 via the terminal 10 is applied to the heating time controller 11.

When the relative humidity detected by the humidity sensor reaches the relative humidity level h shown in FIG. 5, the voltage output reaches e.

When this relative humidity exceeds hl and the voltage output exceeds the reference voltage e1 of the heating time controller 11, the difference voltage between the voltage output and the reference voltage is amplified by the heating time controller 11, and the magnetron driver 12 join.

Then, for example, the output of the magnetron driver 12 is stopped, the operation of the magnetron is stopped, and the heating of the food is completed.

In this way, the cooking state detection circuit 8 consisting of the heating time controller 11 and the magnetron driver 12 can detect the cooking state of the food and heat the food for an appropriate time.

Note that when the heating switch 15 is returned to its original position, it is switched to the upper side and one end of the discharge resistor 17 is connected to the ground.

Also, at this time, the relative humidity near the humidity sensor 5 is measured.

1] even after the food is removed from the oven.

Therefore, as can be seen from the above operation, the set humidity matching relay H is not operating.

Then, the contact of the relay returns to its original state and closes the circuit, so the charging capacitor 20 of the integrating circuit 18 is discharged to the ground through the contact 11, the discharging resistor 17, and the upper contact of the heating switch, and the holding voltage of the integrating circuit is It returns to zero, the heater current also stops, and all parts return to their original state.

FIG. 6 is an psychrometric diagram with temperature on the horizontal axis and relative humidity on the vertical axis, with absolute humidity as a parameter.

To explain the locus of the temperature and humidity conditions in the operation explanation above on this psychrometric diagram, if the heating of the food has the same absolute humidity and the initiality of curves A and B in Fig. 1 where the temperature is different, then the 6th The relative humidity changes from points a and b in the figure due to heating of the heating element and reaches point e, where the relative humidity increases.

The relative humidity further increases until the point f becomes .

Also, curve C in Figure 2 where the temperature is the same and the absolute humidity is different.
In the case of the initial values of and D, the relative humidity changes from points C and d in FIG. 6 due to heating of the heating element and reaches g and point k, and the relative humidity increases.

The relative humidity further changes to points l and m where the relative humidity becomes hl.

In this way, even when the ambient temperature and humidity are different, the relative humidity level can be specified by heating control using the heating element.

By providing a function to lower the relative humidity to a certain level, reproducibility is improved so that the relative humidity changes always follow the E curve for the same food.

Therefore, the same cooking state can be obtained depending on the food at the specified relative humidity level h1, which can be used to detect proper heating.

As can be seen from the above explanation of the operation, even if the amount of food differs as shown in FIG. 7, if heating is completed at the relative humidity level h0, proper heating can be achieved with each food being in the same cooking state.

That is, when reheating 30 grams of grilled fish and 60 grams of grilled fish, the time required for the relative humidity level to reach HL is approximately 1:2.

In addition, as shown in Figure 8, when reheating cold rice, it is heated until the relative humidity level reaches a relatively high level such as h2, and when that level is reached, the heating is stopped. Proper heating is possible.

On the other hand, when reheating milk, proper heating is achieved by stopping heating at a relatively low relative humidity level such as h3.

As is clear from the above description, according to the present invention, proper heating can be performed by specifying only the relative humidity level determined for each food, which is a characteristic of the heating state of the food.

Therefore, it is possible to omit the operation of setting the amount of food as in a conventional microwave oven, and the heating state of the food is detected by the relative humidity level, and the heating time is determined accordingly, so the initial temperature of the food can be adjusted. There is no need to correct the heating time due to differences.

Further, there is no need to correct the heating time depending on the difference in output capacity of the magnetron.

Just set the foods or food groups with the same relative humidity level to be detected.

Therefore, compared to conventional microwave ovens, not only is it possible to create a microwave oven that is easier to operate and can cook accurately, but there is no need to adjust the heating time depending on the output capacity of the microwave oven. There is no need to prepare a timer according to the output capacity.

In other words, it has many advantages such as being able to rationalize manufacturing.

Note that the present invention is not limited to the above-mentioned embodiments, but can be easily applied to other general cooking ovens.

[Brief explanation of drawings]

FIGS. 1 and 2 are graphs of changes in relative humidity in a mortar and heating time under different ambient conditions for the same food item and amount; FIG. 3 is a block diagram showing the entire embodiment of the present invention;
Fig. 4 is a detailed diagram of the cooking state detection circuit and heater control circuit of Fig. 3, Fig. 5a is a temperature change curve near the humidity sensor as the heating time elapses, and Fig. 5 shows the humidity sensor as the heating time elapses. Change curve diagram of relative humidity measured by
Fig. 6 is an psychrometric diagram of relative humidity versus temperature with absolute humidity as a parameter; Fig. 7 is a relative humidity change curve of different amounts of food in a cooking oven according to the invention; Fig. 8 is a cooking oven according to the invention. FIG. 3 is a relative humidity change curve diagram of different foods in an oven. 5...Humidity sensor, 6...Heating element.

Claims (1)

[Claims] 1.Equipped with a humidity sensor that measures the humidity increased by water vapor generated from the food to be heated, and a heating element for increasing the temperature near this sensor, the current value applied to the heating element at the initial stage of heating the food is gradually increased to raise the temperature near the humidity sensor, and the heating element energizing current value when the humidity in that area reaches the specified relative humidity level is maintained and continues to flow until the temperature near the specified relative humidity level is increased. A method for controlling a cooking oven, characterized in that a similar cooking state is detected for each food item, regardless of the amount thereof, by measuring the relative humidity of a specified increase.