JPH0235899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a microwave oven that automatically cooks food based on a heating sequence in which heating is intermittently performed using microwaves while blowing air inside the oven.

<Prior art> Conventionally, in microwave ovens that automatically cook using microwave heating, microwaves are generated and stopped for a certain period of time while blowing air inside the oven to perform heating intermittently. A finish sensor detects water vapor generated from the food and controls the finish. However, since air is blown inside the oven during heating control, water vapor generated from the food is diffused and distributed uniformly inside the oven, making it impossible for the finish sensor to detect minute amounts of vaporized substances. It was hot. For example, when cooking ``chawanmushi'' in a conventional microwave oven, eggs are heated at 60° to 80°C.
Since it solidifies at a temperature of , microwave heating is performed in that temperature range, but in that temperature range, only a small amount of water vapor is generated from ``chawanmushi'', and the chawanmushi container is usually covered with aluminum foil to obtain a uniform finish. As a result, the amount of water vapor generated is extremely small. Therefore, it takes time for the finishing sensor to detect the steam generated from the chawanmushi, and the chawanmushi becomes overheated, resulting in a problem called "sudachi". Also,
In order to be able to detect such minute changes in the amount of water vapor, if the detection level of the finished sensor is made shallow, there is a problem in that the detection accuracy decreases due to the influence of noise such as radio wave leakage.

<Objective of the Invention> The object of the present invention is to solve the above-mentioned conventional problems, and to provide a method for blowing air into the oven during the time period during which microwaves are not generated in the microwave heating sequence after reaching a certain detection level. The purpose of this invention is to provide a microwave oven that can improve the accuracy of detecting water vapor and the like by a finish sensor and automatically cook food using an optimal microwave heating sequence.

<Structure of the Invention> The microwave oven of the present invention intermittently performs heating using microwaves while blowing air inside the oven, and during this time, a finish sensor detects water vapor generated from the food, and the output level of the finish sensor is detected. A microwave oven that automatically cooks food by performing microwave heating until it reaches a set finish level, comprising a storage means for storing the finish level for each type and number of foods to be cooked, and a type of food to be cooked. and a setting means for setting an optimal finish level among the finish levels stored in the storage means according to the number of pieces, an air blowing stop means for stopping air blowing to the oven during a time when microwaves are not generated, and the air blowing means and a comparison means for comparing the output level of the finish sensor with the finish level set by the setting means when the air blowing is stopped by the stop means, and the output of the finish sensor is determined by the comparison by the comparison means. It is characterized in that heating cooking by microwave is ended when the level reaches the finished level.

That is, as shown in FIG. 5, the blowing stop means detects the stop timing of the drive signal in the magnetron drive section, and outputs a signal to the blower fan drive section to stop the drive of the blower fan. The setting means selects a finish level corresponding to the type and number of foods to be cooked from among the plurality of finish levels stored in the storage means, and sets it in the comparison means. The comparison means compares the output level of the finishing sensor with the finishing level set by the setting means at the timing given by the blowing stop means,
When the two match, a cooking end signal is output to the magnetron drive section. The timing given to the comparison means from the blowing stop means is the same as the output timing of a signal to the blower fan drive section to stop driving the blower fan. Therefore, in the intermittent drive of the magnetron, the blower fan stops while the magnetron is stopped, and during this period, the comparison means compares the output level of the finish sensor and the finish level set by the setting means.

<Example> FIGS. 1A and 1B are structural diagrams of a microwave oven viewed from the top side or the front side, respectively.

The microwave oven of this embodiment performs automatic cooking using both microwave heating and heater heating. Microwaves generated by the magnetron 1 are sent into the oven 5 through a waveguide 2 placed on the ceiling of the oven 5. Inside the oven 5 is provided a turntable 3 on which food 4 is placed and rotated by a rotational drive device (not shown). The outside air sucked in through the suction port 7 by the blower fan 6 is supplied into the oven 5 through the duct 8 through the suction port 9 provided on the upper side of the oven 5 . Air supplied by the blower fan 6 is guided to an exhaust duct 10 through an exhaust hole 11 provided in the ceiling of the oven 5, and is exhausted to the outside through an exhaust port 12. In this example, an absolute humidity sensor 13 is used as a finished sensor for detecting water vapor generated from the food 4 due to heating, and the absolute humidity sensor 13 is installed inside the exhaust duct 10.

A schematic circuit diagram of the microwave oven control section is shown in FIG. 2.

The central control circuit 20 includes a CPU, ROM, and RAM, and controls cooking in the microwave according to a heating sequence program stored in the ROM.
Operation panel 22 provided on the front plate of the microwave oven body
A food selection key for selecting and specifying the food to be cooked and a heating key 24 for instructing the start of heating are arranged. The food selection keys include a chawanmushi key 23 for specifying chawanmushi cooking. The number of pieces of each food item can be specified using this food selection key. The finish of cooking differs depending on the type and number of foods, but by detecting the amount of vaporized substances such as water vapor generated from the food with the absolute humidity sensor 13, the results can be adjusted depending on the type and number of foods. Control the finish. The detection level of the absolute humidity sensor 13 at the time of finishing each food is determined in advance by the above RAM as the finishing level.
are set in advance for each type and number of foods.

The absolute humidity sensor 13 is an open type thermistor.
A bridge circuit 14 connected in parallel with a series circuit of R ₁ and a sealed thermistor R ₂ and a series circuit of resistors R ₃ and R ₄ , an output terminal A of the bridge circuit 14,
and an amplifier 15 whose input terminals are connected to B.

A current control resistor is connected to the input terminal of the bridge circuit 14.
A DC power supply 16 is connected via Rs. As food is heated, water vapor, gas, etc. generated from the food gradually increase, and the resistance value of the thermistor _R1 changes. When the resistance value of the thermistor _R1 changes, the output voltage between the output terminals A and B changes, so the detection signal of the absolute humidity sensor 13 obtained as the output voltage of the amplifier 15 changes. In this way, the output level of the absolute humidity sensor 13 changes as the time elapses for heating the food, and outputs a detection signal according to the heating state at that time. Absolute humidity sensor 1
The output voltage Va of No. 3 is given to the central control circuit 20 via the A/D converter 17 and an interface (I/F) 21. Further, the output terminal A is connected to the interface 21 via the A/D converter 18, and changes in the voltage across the thermistor _R1 are applied to the central control circuit 20. The magnetron 1 generates microwaves to heat the food in the oven 5, and is turned on and off by being connected to or cut off from the power supply by turning on and off a relay 26. The heater 19 is a heat source for oven cooking, and receives current supply when the relay 27 is turned on. The blower fan 6 is turned on and off when the power is connected or cut off by turning on and off the relay 26 . On/off control of the relays 25 to 27 is performed by control signals given from the central control circuit 20 via the interface 21.

Heating control when cooking chawanmushi using the microwave oven having the above configuration will be explained with reference to FIGS. 3 and 4.

FIG. 3 is a flowchart from microwave cooking to oven cooking in the case of cooking chawanmushi. Furthermore, FIG. 4A is an output voltage-cooking time characteristic diagram showing an example of changes in the output level of the absolute humidity sensor 13 in the case of chawanmushi cooking, and FIG. 4B is for explaining the heating sequence of microwave heating in the same chawanmushi cooking. This is a time chart.

The chawanmushi is placed in the oven 5, and the chawanmushi key 23 and the heating key 24 are pressed to start cooking the chawanmushi. The number of chawanmushi is specified by pressing the chawanmushi key corresponding to the number. When the heating key 24 is pressed, the interface 2
1, the heating start signal is input to the central control circuit 20 via step n1 (hereinafter referred to as step n1).
ni is simply called ni. ) Clean the oven 5. This cleaning is performed by turning on the blower fan 6 and blowing air into the oven 5 for a certain period of time. The cleaning process is performed for a certain period of time, for example, 16 seconds, regardless of the type and number of foods. After finishing the cleaning, the magnetron 1 is driven for a certain period of time while the inside of the oven 5 is kept in a blowing state to perform microwave heating at "microwave high" (n2). This high microwave heating is performed for (60+2N) seconds depending on the number of chawanmushi (N).
When the microwave heating at high microwave power is completed, the magnetron 1 is driven intermittently to proceed to microwave heating at low microwave heating (n3). This microwave heating at a low range is performed intermittently with a duty according to the number of chawanmushi. i.e.
The magnetron 1 is driven for (4+2N) seconds within 20 seconds to perform microwave heating. Blower fan 6 is on even during microwave heating on low range.
Air is provided within the oven 5. By heating the chawanmushi with microwaves on high and low microwaves, the chawanmushi is preheated and gradually begins to vaporize, such as water vapor, and moves to a state where the absolute humidity sensor 13 can detect vaporized substances.

After performing microwave heating at a low temperature in the microwave for a certain period of time, a process (n4 to n9) is performed in which vaporized substances are detected by the absolute humidity sensor 13 and heating is controlled. When you finish microwave heating on low heat and after that
The microwave and air blowing are stopped for 16 seconds, and the microwave is generated and air is blown to the oven 5 for the next 7 seconds.While microwave heating is performed intermittently at a constant duty, when the air blowing is stopped, the absolute humidity sensor is 13 to detect vaporized substances. Immediately after completing microwave heating at a low level in the microwave, the microwave and air blowing are stopped (n6, n7), and the first absolute humidity sensor 13 detects vaporized substances (n8). At this time, the output level of the absolute humidity sensor 13 is _V1 as shown in FIG. 4A.

The microwave and air blowing are stopped for 16 seconds, and the absolute humidity sensor 13 detects vaporized substances. If the output level at that time does not reach the finishing level V ₂ set in advance for chawanmushi, the next microwave is started. Heat for 7 seconds. This finishing level _V2 is determined by the RAM of the central control circuit 20 as described above.
This value is set in advance for each type and number of foods, and is read from the RAM in response to input from the food selection key on the operation panel 22. During this microwave heating, air is blown (n4, n5),
Comparison processing of the output level of the absolute humidity sensor 13 is not performed. In this way, microwave heating is performed intermittently at a constant duty, and when microwave heating is not performed, the air blowing is stopped and the output level of the absolute humidity sensor 13 is compared with the finished level _V2 ,
When the output level of the absolute humidity sensor 13 reaches the finishing level _V2 , the microwave heating is ended (n9). After the output level of the absolute humidity sensor 13 reaches the finishing level _V2 , the oven heating sequence is started (n10), and the oven heating is performed by the heater 19 for a certain period of time without driving the magnetron 1, and the cooking of the chawan mushi is completed. .

By the above operation, microwave heating is controlled until the output level of the absolute humidity sensor 13 reaches the finish level _V2 , but when the microwave is off,
In addition, the output level of the absolute humidity sensor 13 when the air blowing is stopped is compared with the finished level _V2 . Therefore, when detecting vaporized substances using the absolute output sensor 13, there is no need to be affected by noise due to leakage of microwaves, and it is possible to detect minute amounts of water vapor generated from steamed egg custard.
Moreover, since the air blowing into the oven 5 is stopped when the microwave is turned off, vaporized substances from the chawanmushi are not diffused and diluted, and as a result, the concentration of vaporized substances introduced into the exhaust duct 10 increases and is detected. Improves accuracy. Further, since the finish level _V2 compared with the output level of the absolute humidity sensor 13 is set according to the type and number of foods to be cooked, the cooking state of the foods is strictly maintained. Since vaporized substances can be detected with high precision as described above, intermittent microwave heating can be performed while accurately grasping the heating state of chawanmushi, allowing optimal cooking without overheating.

<Effects of the Invention> As described above, according to the present invention, air blowing into the oven is stopped during the time when microwaves are not generated, and at that time, it is determined whether the finish level has been reached based on the output level of the finish sensor. Since intermittent microwave heating is performed, the food is not affected by microwave leakage, and vapors generated from the food are not diffused, making it possible to detect vaporized substances with high precision. Cooking becomes possible. Therefore, even when the number of steamed egg custards is small, for example, the minute amount of water vapor generated by heating can be detected and the food can be cooked optimally without overheating.

[Brief explanation of drawings]

Figure 1 shows a structural diagram of a microwave oven that is an embodiment of the present invention, Figure A is a structural diagram seen from the top, Figure B is a structural diagram seen from the front, and Figure 2 is a control diagram of the microwave oven. Figure 3 is a flowchart up to oven heating when cooking "chawanmushi" using the microwave oven, and Figure 4A is an absolute humidity sensor when cooking chawanmushi using the same microwave oven. FIG. 4B is a time chart for explaining the microwave heating sequence in the case of chawanmushi cooking. Also, the fifth
The figure is a functional block diagram of the present invention. 1... Magnetron, 5... Oven, 6... Blower fan, 13... Absolute humidity sensor, 20... Central control circuit.

Claims (1)

[Scope of Claims] 1. Heating is performed intermittently using microwaves while blowing air inside the oven, and during this time, water vapor etc. generated from the food is detected by a finish sensor, and the output level of the finish sensor is set to a set finish level. In a microwave oven that automatically cooks food by performing microwave heating until the temperature reaches the desired temperature, a storage means for storing the finish level according to the type and number of foods to be cooked, and a storage means for storing the finish level according to the type and number of foods to be cooked; a setting means for setting an optimal finish level among the finish levels stored in the storage means; an air blowing stop means for stopping air blowing to the oven during a time period during which microwaves are not generated; and the air blowing stopping means. and a comparison means for comparing the output level of the finish sensor and the finish level set by the setting means when air blowing is stopped, and the output level of the finish sensor is determined to be equal to the finish level by comparison by the comparison means. A microwave oven that finishes cooking using microwaves when the temperature reaches .