JPS5956389A - 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 Field of Industrial Application The present invention relates to a high-frequency heating device that includes a high-frequency heating device and a heater heating device.

Conventional configurations and their problems With the oscillation of microcomputers, cost reductions, and the development of various sensors, microwave ovens that can automatically adjust have appeared. Microwave ovens that detect and automatically cook food have been in the spotlight.

On the other hand, cooking appliances that are equipped with both a high-frequency heating device and a heating device that uses a heater as a heat source are becoming common. Under these circumstances, when trying to automate cooking using high-frequency heating in a cooking device equipped with a heater heating device, and then heating the heater, the current humidity sensor does not detect steam generated by the food. Even if changes in humidity can be detected, it is impossible to detect up to a certain amount of change.
By wrapping the food or using a special lid applicator, the generation of steam from the food is temporarily suppressed, and when it approaches the boiling point, the steam is released. A method of detection and control is adopted.

Therefore, the methods described above that require wrapping or lids have drawbacks such as the wrap melting due to heating by the heater and the lid having to be removed midway through (before heating with the heater). As a result, automation from high-frequency heating to heater heating was delayed.

However, a method has been devised that allows a large change in relative humidity to be obtained by starting high-frequency heating after pre-operating the heater to force the temperature in the heating chamber to a constant low humidity state. A method has been proposed that automates high-frequency heating without using a lid, and then manually heats the heater.

In this type of system, the heater is turned off after the preliminary operation is completed, so the internal temperature can be kept constant, that is, the humidity can be kept low for a limited period of time, so the heated load can be heated quickly and the steam can be released in a short period of time. It is limited to light loads. Therefore, when using this method to cook food that requires a large load, such as roast beef, it is important to avoid situations where the temperature inside the refrigerator is not constant (the temperature inside the refrigerator is lower than the temperature at the end of the preliminary operation). Since the humidity must be detected when the relative humidity is high and the amount of change in humidity is small, stable detection cannot be performed. In addition, if the surrounding environment in which the device is used is highly humid, the amount of change in relative humidity after the heater is turned off will be large, resulting in disadvantages such as the inability to obtain the specified amount of change for detecting vapor from food. have.

Purpose of the Invention The present invention accurately detects the time it takes for the relative humidity to reach a certain amount of change due to water vapor emitted from the food by keeping the temperature of the exhaust gas discharged from the heating chamber constant and detecting the humidity. In particular, the purpose is to achieve continuous cooking and defrosting using high-frequency heating without using plastic wrap or special containers for foods, and also to perform targeted heating with a heater after automatic cooking using high-frequency heating. . In addition, the purpose of the heating device of the present invention is to automatically perform heater heating after automatic defrosting by high-frequency heating. A temperature sensor and a humidity sensor are provided near the exhaust port, and the heater is controlled in accordance with the detection signal of the temperature sensor to keep the exhaust temperature constant, and the food is emitted from the food in the snow near the exhaust port. Detecting the steam with a humidity sensor, and calculating with a microcomputer the time until the relative temperature reaches a predetermined amount of change based on the steam emitted from the food,
The device is configured to cook the food or defrost the frozen food according to a heating pattern determined for each type of food using this time as a function, and is capable of automatically heating and cooking not only general food but also frozen food. It is.

Description of examples An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows an automatic microwave oven according to an embodiment of the present invention, which has an operating section 1 and a door 2 on the front, and an outside air exhaust port 3 at one corner of the top plate.

FIG. 2 shows a front view of the operating unit 1. When no cooking program is set, the time is always displayed on the display unit 4. To set the time display, the clock switch 5 can be input using the numeric keys 6. For normal manual cooking (high frequency heating), after selecting high frequency output using the power key, press the number key 6.
Enter an arbitrary time and press the start key 8 to start cooking. In manual cooking using heater heating, after selecting the heating temperature using the heater key 9, an arbitrary time is input using the numeric keys 6, and cooking is started using the start key 8. The keys shown in 10 and 11 are the automatic cooking key (high-frequency heating → variable cooking of heater heating) by humidity sensor control, which is the key point of the present invention, and the automatic defrosting key (after high-frequency heating thawing → heater heating cooking). By tapping these keys, a number corresponding to the type of food, such as A1, will be displayed on the display 4, and by pressing the start key 8, cooking or defrosting will be automatically started. The keys shown at 12 and 13 are the automatic cooking key 12, which only performs high-frequency heating under humidity sensor control, and the movement defrost key 13.The cancel key shown at 14 is used to temporarily stop cooking, or This key is used to cancel a program.

FIG. 3 shows a front sectional view of the heating chamber 16 showing the cooling air circulation path.
The food enters the heating chamber 15 through the intake port 18 of the heating chamber 15, is heated by the heater 2o together with the water vapor emitted from the food 19, is discharged from the exhaust port 21 of the heating chamber 15, and is sent to the humidity sensor 22 and temperature sensor 23. It passes through and is discharged to the outside from an external exhaust port 3 provided at the top of the body.

Fig. 4 shows the humidity sensor 22, which is composed of a refresh heater 22-a and a detection element 22-b. It has a refreshing function of increasing the surface temperature to burn off dirt 9 and always maintaining constant humidity characteristics of the sensing element 22-b.

FIG. 5 shows a circuit diagram of an automatic microwave oven main body according to an embodiment of the present invention.
5, the low voltage transformer 26 is always connected,
Power is supplied to the control section 27. The input/output relationship of the control unit 27 includes a display unit 4 that displays the time when the microwave oven is not in use, and displays the cooking contents and remaining cooking time when cooking.
, a keyboard 28 for inputting time settings, cooking menus, and cooking time, a temperature sensor 23 for detecting the temperature of the exhaust section near the exhaust port 21, and a temperature sensor 29 for detecting the internal temperature during cooking with the heater. (not shown in FIG. 3), a humidity sensing element 22-b for detecting the temperature of the exhaust section
, a refresh heater 22-a for removing dirt from the humidity detection element 22-b, a power relay 31 for opening and closing the power supply to the heating heater 20, high-voltage transformer 3Q, etc., and a temperature controller for keeping the exhaust part temperature constant at 9-' degrees. A temperature control relay 3 for controlling the heater 20 intermittently according to the signal from the sensor 23 or the signal from the temperature sensor 29 to keep the internal temperature constant.
2. Controls all of the following, including the high-voltage reed switch 33 that intermittents the oscillation of the magnetron 17 and controls the high-frequency output, as well as a buzzer (not shown) that notifies the end of cooking and informs the input status. A microcomputer in section 27 performs control.

Further, 34, 35, and 36 are a first latch switch, a second latch switch, and a short switch that operate in conjunction with the door 2, and the role of the short switch 36 is to open the door 2 when the first latch switch 34 is in an abnormal state such as welding. In such a case, the fuse 25 is blown to ensure a safe failure.

As a power source for the magnetron 17, a high voltage on the secondary side of a high voltage transformer 30 is rectified by half-wave voltage doubler using a capacitor 37 and a diode 38, and is supplied via a high voltage reed switch 33.

The operation of this automatic microwave oven will be explained below.

FIG. 6 shows the humidity detection characteristics when automatic cooking is performed. Since the humidity sensing element 22-b is sensitive to relative humidity and exhibits negative resistance characteristics at temperatures of 160° C. or higher,
The refresh temperature can be kept constant by checking the resistance value of the humidity sensing element 22-b during refresh. In the case of automatic cooking or automatic defrosting, a refresh operation is performed immediately after the start, and then the humidity detection state is entered. In Figure 6, at one point at the start, the indoor
The relative humidity of the surrounding air is shown, and at the same time, the temperature of the exhaust section is read by the temperature sensor 23. Based on the read exhaust temperature, the exhaust temperature to be controlled is determined. The reason why it is necessary to maintain a high exhaust temperature is that if the relative humidity of the indoor air is high, it cannot contain any more water vapor from the food. In other words, it becomes saturated and the amount of change in humidity cannot be determined. For example, indoor snow ambient temperature is 20℃1
oo%, if the food is heated to 50°C by the heater 20, the relative humidity will be approximately 20%, and for this reason, it is possible to further contain 70 g/m' of water vapor generated from the food. Humidity sensor 2 up to m'
2 can be detected.

Other reasons for keeping the exhaust temperature high are heaters 2 OK.
Therefore, after starting to control the exhaust gas temperature to a certain constant temperature, the lowest value of relative humidity is memorized and the change in relative humidity is obtained to detect food vapor. If the control temperature of the exhaust gas is exceeded due to a rise in temperature or a rise in the temperature of electrical parts, etc., control becomes uncontrollable, so the exhaust temperature is kept high in advance to increase the margin for humidity detection.

From the cooking start point a in the figure, the heating heater 2Q and the tri-refresh heater 22-a are energized, and the refresh heater 22-& is integrally provided very close to the humidity sensing element 22-b. Humidity sensing element 22-b
The relative humidity of the surrounding air drops rapidly and reaches point b, where the relative humidity is close to the zero coefficient.

When the snow ambient temperature exceeds 100°C, the humidity detection element 22-
Since b exhibits negative resistance characteristics, it reaches the 0 point when the temperature reaches around 600°C. Thereafter, when the power supply to the refresh heater 22-a is cut off and the temperature drops to 150° C. or lower, the air surrounding the humidity sensing element 22-b becomes dry and reaches point d. However, the relative humidity from point b to point d is expressed by a characteristic shown by a straight line connecting point b and point d. Thereafter, the snow surrounding the humidity sensing element 22-b is cooled, and in the state before the heater 20 is continuously energized and the exhaust temperature is controlled to be constant, the temperature returns to point e, and the exhaust temperature begins to be further controlled. When the oscillation start point f is reached, the magnetron 17 starts oscillating and at the same time starts counting the time until vapor detection.

From point a, the starting point, to point f, the oscillation start point, the heater 20 is continuously energized to speed up reaching the first point, and after point f, it is stopped depending on the oscillation status of the magnetron 17, which is intermittently oscillated. At times, the heater 20 is turned on, and at the time of oscillation, the heater 20 is turned off, and the temperature control relay 32 controls the exhaust temperature.

The humidity detection method is to store all the lowest values of relative humidity that occur after point f, count the time until a predetermined amount of change in relative humidity is reached, and automatically detect the humidity based on this. Proceed with cooking.

The humidity change characteristics shown in the figure are 7.2kL3k for beef 1.
, respectively, when cooking.

Characteristic curves shown in h and f. Alternatively, it indicates the amount of change in relative humidity for determining the reference detection time T1 which is a function of the heating program, and this varies depending on the type of food and the control temperature of the exhaust gas. This is because the amount of saturated water vapor varies depending on the temperature, and even if the same weight of water evaporates from food, the amount of change in relative humidity will vary. In addition, as shown in the figure, the standard detection time T1 for the weight of food is such that the larger the change in relative humidity, the more clearly the difference appears, and the more stable it becomes, so the relative humidity at one point should always be kept as low as possible. It is important to start cooking with A heating program for cooking roast beef, for example, using the reference detection time T1 detected in this manner is as follows.

The high frequency output is set to medium output (600W) until steam is detected, and after the steam is detected, control of the exhaust temperature is stopped and heating is continued at the same output for a time of T2=TIX2.

After 72 hours, change the high frequency output to medium to low (350W)
and heat for 73 hours. The calculation method for 73 hours varies depending on the detected T1 time, and when TI≦5 (minutes),
T3=TI X2 (minutes), when T1≦5C minutes), T
3=10-1-TIX5 (minutes). This is a program that was experimentally determined when medium-finishing roast beef.The above programs all use high-frequency output for heating, but T3 of the above program
-T3-heater heating (instead of medium-low power (350W))
Heater 1.2KW.

It is also possible to set the temperature inside the refrigerator to 150°C.

Also, during T1, only high frequency output is used, and for heating after detection,
High frequency heating (130W) and heater heating (heater 1.2K)
It is also possible to adopt a heating pattern in which heating is performed alternately.

FIG. 7 shows the humidity detection characteristics when frozen beef is thawed. The process up to point f when the heater 2Q reaches a predetermined exhaust gas control temperature is the same as in the case of automatic cooking described above, but in the case of automatic defrosting, the temperature of the exhaust section detected at the start of cooking On the other hand, control is performed without setting the temperature too high.

This is because the temperature of the food is low, so the temperature of the exhaust part does not naturally rise due to increases in the temperature of electrical parts until steam is detected, and only extremely small changes in relative humidity due to staleness are detected. This is because there is no need to lower the humidity at point f.

However, in order to shorten the cooking time, the heating heater 2o is operated continuously up to point f to speed up the arrival time, and after point f, the heating heater 2o During oscillation, the temperature control relay 32 controls the exhaust temperature while turning off the power to the heater 2°. Therefore, the humidity rises all at once to point f, and then the magnetron 17 starts oscillating from point f, so that heat is added, and m
It becomes stationary towards a point. The lowest value of relative humidity is detected after point J, and when the amount of change reaches point j, the reference detection time T1 is obtained. After steam is detected, the temperature control relay 32 is opened and the exhaust temperature is not controlled, as in the case of automatic cooking.

The heating pattern obtained from the results of a cooking experiment when thawing frozen beef using T1 obtained in this manner is as shown below.

Heating is performed at low output (180W) from point f to vapor detection, and after vapor detection, it switches to T2 or T3. T1 is 1
If it is less than 5 minutes, T2 is skipped and goes to T3, and the heat retention output (
70W) for T3=TI (minutes) to complete thawing. Also, if T1 exceeds 15 minutes, low output (18
After heating for T2-(TI-16)X2 (minutes) at 0W), move to T3 and set the heat retention output (70W) to 73 = 15+
Heat for (T1-15)×2 (minutes) to complete thawing. This method can not only be applied to thawing other frozen foods, but also be able to automate everything from thawing to cooking in one hour by combining it with other high-frequency outputs or heaters as a function of T1 time. becomes.

Effects of the Invention As stated above, according to the present invention, the relative humidity is detected by keeping the exhaust temperature constant using the heating heater installed in the heating chamber, so it is possible to accurately determine the amount of change in humidity. I can do it,
By using the humidity detection time at this time, it is possible to automate the cooking, thawing, and thawing-to-cooking of many types of foods.In addition, there is no need to use plastic wrap or special containers, so food It is possible to provide a high-frequency heating device that is easy to use, without impairing the appearance or taste of foods, or eliminating the risk of cooking failure or overheating or ignition of foods due to misuse. The effects will be explained in detail below.

(1) By detecting relative humidity at room temperature, it is possible to accurately determine the amount of change in relative humidity due to steam from food. You can know the weight and capacity of. Therefore, by using this time as a function and cooking according to the respective heating patterns for each type of food, it becomes possible to perform automatic cooking in a good manner.

(2) When thawing frozen food, it is sensitive to changes in relative humidity due to extremely small amounts of steam emitted from a part of the food, so frozen food can be successfully thawed without overheating.

(3) By keeping the exhaust temperature constant, it is less affected by the indoor environment, and by installing a heater inside the heating chamber, the relative humidity inside the heating chamber can always be kept low, allowing for condensation due to food vapor. It is possible to eliminate the risk of malfunction due to

This allows the amount of change in relative humidity caused by water vapor emitted from food to be set from low humidity to high humidity, making it possible to successfully determine the characteristics of the amount of water vapor generated for different heating times depending on the type and weight of food. becomes.

(4) Automation of high frequency heating to heater heating, or automation of high frequency heating to alternate heating of heater heating and high frequency heating, or high frequency heating after thawing by high frequency heating. Furthermore, automatic cooking with a good finish can be achieved by selecting a heating pattern suitable for various types of foods, such as automatic cooking in which heater heating is performed and automatic heating patterns that are suitable for various types of food.

[Brief explanation of drawings]

Fig. 1 is an external perspective view of an automatic microwave oven showing an embodiment of the present invention, Fig. 2 is a front view of the operating section thereof, Fig. 3 is a front sectional view of the heating chamber section, and Fig. 4 is the same humidity level. FIG. 6 is an external perspective view of the sensor, FIG. 6 is a circuit diagram of the control device, and FIGS. 6 and 7 are humidity characteristic diagrams when beef is cooked and thawed. 1o・・・Automatic high frequency/heater heating key, 11・°
°・°・Auto defrost/heater heating key, 12...
Mechanical cooking key, 13・°°・°・Auto defrost key, 15・
... Heating storage, 17 ... Magnetron (high frequency oscillator), 18 ... Intake port, 20 ...
...Heater, 21...Exhaust port, 22...
... Humidity sensor, 23 ... Temperature sensor, 27
...Control unit, 32...Temperature control relay, T
I...Reference detection time. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] A heating chamber for storing food, a high-frequency oscillator for supplying high-frequency power into the heating chamber, a heater heating device for heating the food in the heating chamber, and a microcomputer for controlling the high-frequency oscillator and the heater heating device. a control circuit; a temperature sensor that detects the temperature of the atmosphere in the heating chamber or the exhaust section of the heating chamber; and a humidity sensor that detects humidity; the heater heating device is controlled by the detection signal of the temperature sensor; While maintaining the inside of the heating chamber at a constant temperature, the humidity sensor detects the amount of change in humidity in the atmosphere, detects the time until a predetermined amount of change in humidity is reached, and uses this time as a function of the amount of change in humidity in the atmosphere. A high-frequency heating device configured to control the high-frequency oscillator and the heater heating device by a control circuit.