JPS5840431A - Microwave range - Google Patents

Abstract

PURPOSE:To control the titled microwave range so as not to superheat in the event that food is bread, by a method wherein a kind of food is discriminated by a gas sensor, a detection level of gas sensor output corresponding to the kind of the food is set up and a detection level for thermistor output is set up to every kind of the hood. CONSTITUTION:A microcomputer 15 which applies stop instructions of heating to a driving electric power source of a microwave generator 9 is provided according to an input signal from a heat sensitive element 8 and a gas sensor 7 and a built-in program. A kind of food in a heating chamber is discriminated by a time variation rate of output of the sensor 7, a detection level for scheduled time for completion of heating based on the sensor 7 is set up according to the kind of the food, and a detection level for scheduled time for completion of heating based on the heat sensitive element 8 is set up according to each kind of the above food. Heating is suspended unconditionally when the output of the sensor 7 is arrived at the detection level only for food which is discriminated that the time variation rate of the output of the sensor 7 is the smallest.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave oven, and more specifically, to a microwave oven that determines the type of food based on the time change in the terminal voltage of a gas sensor and makes decisions when automatically cooking and finishing the food. Regarding.

Conventionally, microwave ovens that use sensors to automatically determine the doneness of food are equipped with a plurality of keys corresponding to the type of cooking, and each key has a preset cooking temperature.

On the other hand, the present inventor has proposed that the type of food is determined based on the time change of the terminal voltage of the gas sensor, and the finished cooking temperature of the food is calculated and set, thereby eliminating the need for setting keys for each type of cooking. Invented a microwave oven with an ``automatic heating'' method. The present invention was invented in connection with the invention of the microwave oven of the "automatic heating" method. First, the principle of the "automatic heating" method will be explained.

FIG. 1 shows how the terminal voltage Va of the gas sensor 7 changes with time depending on the type of food being cooked. The terminal voltage of the sensor after a time T has elapsed from the start of heating is VT, and the terminal voltage of the sensor after a time T has elapsed is VT, and these ratios show a significant difference. For example, TI=
At 30 seconds, T = 40 seconds, the VT is 0.9 or less for sake paulownia, 0.9 to 0.95 for side dishes and Imono, and VT for bottom wrapped in cling film.

Rae is 0.95 to 1.0. In this way, the type of food is determined based on the magnitude of the value of v town, and the detection level of VG at which heating should be stopped is VH8°VDS, V
S8 can be set.

However, if the type of food is determined based only on the terminal voltage VG of the gas sensor and the detection levels VH8, VDS, and V3B are determined, the food may heat up faster than the proper finish due to forgetting to wrap it, variations in gas sensor characteristics, etc. There is a risk that it may stop. In order to prevent this, the present invention further determines the type of food by the gas sensor and sets the detection level by the thermistor to stop heating accordingly, and when both the gas sensor and thermistor reach the detection level, a heating stop command is issued. We also propose a control method that outputs . Although this method generally results in good cooking, the types of food to be actually cooked are miscellaneous, and there are exceptions that do not conform to the above-mentioned standard pattern.

One example is food that rapidly generates gas with a small load.
For example, there is heating of bread. When "bread" is heated in a microwave oven, as shown by the solid line in Figure 2, there is no change in the sum of the gas sensor outputs at the beginning of heating, but after about 40 seconds, gas is suddenly generated and the gas sensor output decreases. As shown by the dotted line in FIG. 2, the output of the thermistor at this time decreases at a more or less constant slope, and there is no noticeable change in the output even if the pan suddenly generates gas.

If the food "bread" is not heated immediately when this gas is generated, the shape of the bread will shrink and the taste will deteriorate.
It becomes hard. Therefore, it is preferable to cut off the heating when the output of the gas sensor starts to change rapidly.

As is clear from the comparison between Fig. 1 and Fig. 2, heating of "bread" belongs to the type of "preparation" in Fig. 1. Preparation usually involves wrapping food and handling loads of approximately 200 grams or more, and the heating stop level is determined along this line. On the other hand, bread is not wrapped and has a small load of 200 grams or less. Also, while some overheating is allowed in preparation, there is a strict rule that overheating bread is not allowed.

The present invention has been made based on the above research, and it uses a gas sensor to determine the type of food and sets the detection level of the gas sensor output accordingly, and also sets the detection level of the thermistor output for each type of food. When the output of the gas sensor reaches the detection level only for the food for which the rate of change over time of the gas sensor output is determined to be the smallest in the automatic finishing microwave oven using one cooking key according to the control method to be set. , is characterized in that it is configured to unconditionally issue a heating stop command even if the output of the thermistor has not yet reached the detection level.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows an external front view of an embodiment of the present invention.

An "automatic heating" key 2 and a heating key 6 are arranged on the operation panel 1. Note that it is also possible to combine the keys 2 and 6 into one.

FIG. 4 shows a sectional view of an embodiment of the present invention.

A blower 5 is provided on the open 4p side, and a gas sensor 7 and a thermistor 8 are provided on the exhaust port 6 on the other side. The resistance value of the gas sensor 7 changes in accordance with the concentration of exhaust gas generated from the food, and the resistance value of the thermistor 8 changes in accordance with the exhaust gas temperature, which increases as the food is heated. In the figure, 9 is a magnetron that emits microwaves, and 10 is a heater that heats food by infrared rays.

FIG. 5 shows a circuit diagram of an embodiment of the present invention.

The gas sensor 7 is connected to a thermistor 8 via a load resistor RL.
is connected to the DC power supply 11 via a load resistor RL, and the terminal voltage VG of the gas sensor 7 and the terminal voltage VT of the thermistor 8 are connected to independent A-D converters 12, 15 and an input/output interface 14, respectively. The data is then input to the CPU of the microcomputer 15. Microcomputer 1
5 is a ROM, R, which stores programs, etc. in addition to the CPU.
A.M.

It also has a built-in electronic clock. Key signals on the operation panel 1 are also input to the microcomputer 15 via the interface 14. Magnetron 9 is a commercial AC power source 1
6, it is driven via the contact 18 of the microwave drive relay 17, the door switch 19, the step-up transformer 20, etc. The heater 10 is driven by a commercial AC power source 16 via a contact 24 of a heater drive relay 23 and a door switch 19. The microwave drive relay 17 or the heater drive relay 26 is controlled via the interface 14, the transistor 21, or the transistor 25 according to a command from the CPU.

Next, the operation of the embodiment of the present invention will be explained.

When you press the "Automatic heating" key 2 and then the heating key 3, the CPU receives the input signal, the microwave drive relay 17 is excited by the CPU's command, the magnetron 9 oscillates, and the heating starts. It begins. Time T from start of heating
, the terminal voltage VT of the gas sensor after elapsed time is stored in RAM.
to be memorized. Furthermore, the terminal voltage VT of the gas sensor when a time T has elapsed from the start is stored in the RAM. So CVT.

A calculation section within the CPU calculates the ratio VT between the two - and the value VT as described with respect to FIG.

Determine the type of food from the size of 〒 and determine the optimal finish level V
H8, VD8. Determine VSB.

Similar to the gas sensor, the detection level of the thermistor is set to a different value depending on the type of food. That is, 1,000F<(1
If you are using the hot route (g), set the thermistor detection level TBS to 55'C, as shown in Figure 9, and if you are using the warm route, set the thermistor detection level TH8 to nearly 100°C. Then, when both the terminal voltage vG of the gas sensor 7 and the terminal voltage VT of the thermistor 8 reach the optimum finishing level, VT.

Stop heating for the first time. However, only for the "preparation" route with the highest value of OK, when the output of the gas sensor reaches that detection level, heating will stop unconditionally regardless of the output level of the thermistor.

Figure 6 shows the case of normal preparation according to this example.
It shows temporal changes in the output voltage VG (solid line) of the gas sensor and the output voltage VT (dotted line) of the thermistor. T after starting heating
1 and T, thermistor output voltage VT, , VT
Since the ratio of
Heating is stopped regardless of whether or not the detection level THs has been reached.

FIG. 7 shows the cooking of "bread" according to this embodiment. The thermistor output voltage V'r of T and T after the start of heating
Since the ratio of , , V'r, is almost 1, it is determined that the route is "preparation", and the detection levels VH8 and TH8 are set as in the case of Fig. 6, but the output voltage VG of the gas sensor suddenly changes. Since it quickly reaches the detection level VH19, at that time - thermistor output voltage V?
has not yet reached the detection level TH8FC, but heating will stop regardless of that. In this way, both normal preparation and bread can be heated well.

As a modified embodiment of the present invention, an infrared sensor or a temperature sensor may be used instead of the thermistor.

According to the present invention, by simply pressing one "auto heating key", the computer selects a heating program according to the type of food and controls the food for optimal finishing, thereby simplifying operations for the user. In addition, even if the gas sensor reaches the detection level earlier than the original heating stop point for various reasons, heating will not be stopped (as long as the thermistor terminal voltage VT has not reached the finishing level), so there is no possibility of accidentally stopping it early. A proper finish can always be obtained. Furthermore, even if the food is bread, do not overheat it (
Able to cook properly.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram explaining the principle of food types in the present invention, Fig. 2 is a characteristic diagram explaining the problem to be solved by the present invention, Fig. 3 is an external front view of an embodiment of the present invention, and Fig. 4 is a characteristic diagram explaining the principle of food types in the present invention. FIG. 3 is a longitudinal sectional view, and FIG. 5 is a circuit diagram of an embodiment of the present invention. FIGS. 6 and 7 are characteristic diagrams illustrating the operation of the embodiment of the present invention. 1... Operation panel 2... Automatic heating key 7... Gas sensor 8... Thermistor 9... Macnetron 10...・Heater 12.13...A-D converter 14...Interface 15...Microcomputer patent applicant
Sharp Corporation Agent Patent Attorney Nishi 1) Arata

Claims (1)

[Claims] A switching means for controlling the driving power source of the microwave generator, a heat-sensitive element and a gas sensor provided in the exhaust passage of the heating chamber, a heating instruction switch commonly used for different types of food, and the heat-sensitive element and the gas sensor. It has a microcomputer that issues a heating stop command to the drive power source of the microwave generator according to the input signal from the sensor and a built-in program, and determines the type of food in the heating chamber based on the temporal rate of change in the output of the gas sensor. The detection level at the scheduled end of heating by the gas sensor is set according to the type, and the detection level at the scheduled end of heating by the heat-sensitive element is set according to each type, and the output of the gas sensor is set. When the output of the gas sensor reaches the detection level only for food determined to have the smallest rate of change over time, a heating stop command is issued unconditionally regardless of the output of the thermistor. microwave oven.