JPS6339815B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides only a single cooking key for heating instructions instead of setting keys for each type of cooking.
The present invention relates to a microwave oven that determines the type of food based on the rate of change of the terminal voltage of a gas sensor and determines when the food is automatically cooked.

<Prior Art> Conventionally, a microwave oven that uses a sensor to automatically determine the cooking finish of food is equipped with a plurality of keys corresponding to the type of cooking, and the cooking finish temperature is preset for each key.

In response, the present inventor has developed a system that eliminates the need for setting keys for each type of cooking by determining the type of food based on the rate of change in the terminal voltage of the gas sensor, and calculating and setting the finished cooking temperature of the food. Invented a microwave oven with automatic heating method. The present invention was invented in connection with the invention of this "automatic heating" type microwave oven.

First, we will explain the principle of the "automatic heating" method.

FIG. 7 shows how the terminal voltage V _G of the gas sensor 7 changes over time depending on the type of food being cooked. Let V _T1 be the sensor terminal voltage after time T ₁ has elapsed from the start of heating, and V _T2 be the sensor terminal voltage after time T ₂ has elapsed from the start of heating, and calculate this ratio V _T2 /V _T1 . This value will vary depending on the type of food. shows the difference. For example, when T ₁ = 30 seconds and T ₂ = 40 seconds, it is less than 0.9 for sake sake, and 0.9 or more for side dishes and rice bowls.
0.95, the preparation wrapped in wrap film is
The range is greater than 0.9 to 1.0. In this way, the type of food is determined from the magnitude of the value of V _T2 /V _T1 . On the other hand, if it is determined to be sake sake, the gas sensor detection level V _CS shown in the figure is set, and if it is determined to be a side dish or rice bowl, the gas sensor detection level V _DS shown in the figure is set, and further,
If it is determined that it is preparation, the gas sensor detection level _VHS is set. These gas sensor detection levels V _CS , V _DS , and V _HS are terminal voltages of the gas sensor 7 for stopping heating.

<Problems to be Solved by the Invention> By the way, food preparation is usually divided into "leaf vegetables" and "root vegetables," and automatic finishing microwave ovens with multiple cooking keys for each type of cooking are commonly available on the market. , for cooking preparations, "preparation 1" for leafy vegetables and "preparation 2"
In other words, two cooking keys are provided, one for root vegetables and one for root vegetables. The reason for this is that leafy vegetables such as spinach, Chinese cabbage, and cabbage are sufficiently boiled and softened when the heating temperature reaches close to 100°C, completing the preparation, but root vegetables such as potatoes, sweet potatoes, carrots, and daikon radish Even when the heating temperature reaches close to 100℃, the inside of the meat is not yet soft, and if you stop heating at this point, the inside will be hard and uncooked. Therefore, in order to soften the inside, heating must be continued, which is called "carryover heating." On the other hand, when leaf vegetables reach a detection level, it is necessary to immediately stop heating them to avoid overcooking. For this purpose, we have two cooking keys, one for leafy vegetables and one for roots.
Two types of heating signals stored in the ROM are selectively read out using each cooking key.

On the other hand, in the microwave oven of the above-mentioned "automatic heating" method, as shown in Figure 8, "leafy vegetables"
In both cases of root vegetables, if heating is stopped when the gas sensor terminal voltage V _G reaches the detection level V _HS , there is a problem in the case of root vegetables that the heating is insufficient and the cooking is incomplete. . This point will be explained in detail below based on the research results of the present inventor.

Fig. 9 shows actual measurement data of the time change of the gas sensor terminal electrons when a root vegetable and a leaf vegetable are both wrapped in plastic wrap and heated in a microwave oven, as is usually done. Based on this data, both exhibit similar characteristic changes until the temperature inside the wrap rises to nearly 100℃ after heating begins, but after the wrap ruptures due to strong vapor pressure at close to 100℃, gas and moisture leak outside. It has become clear that there is a significant difference in the rate of change when the sensor voltage suddenly changes due to divergence between "leaf vegetables" and "root vegetables." In other words, "leaf vegetables" are fresher and have a higher moisture content than root vegetables.
Because the surface area is large, the level changes rapidly and the amount of change is large. In contrast, "root vegetables" have been harvested for some time, have an epidermis, and have a relatively small surface area and low water content. Since the level is low, the rate of change in level is slow and the amount of change is small. The circle mark in the figure indicates the optimal point for stopping heating for "leaf vegetables" and "root vegetables." As is clear from this figure, in the case of "root vegetables," the gas sensor terminal voltage V _G is detected. Even after reaching level V _HS , it is necessary to continue heating for the required time.

<Purpose of the Invention> The present invention was made in view of the above-mentioned technical problems of microwave ovens of the "automatic heating" method that omit a large number of cooking setting keys. The purpose of the present invention is to provide a microwave oven that can further distinguish between "leaf vegetables" and "root vegetables" based on changes in terminal voltage, and set an appropriate heating time for each type. be.

<Means for Solving the Problems> In order to achieve the above object, the microwave oven of the present invention includes a heating instruction switch that is commonly used regardless of the type of food to be heated, and an on-operation of this switch. A switching means for supplying driving power to the microwave generator, a gas sensor provided in the exhaust passage of the heating chamber, a timing means for measuring the heating time after the heating instruction switch is turned on, and the timing means A food discriminating means for discriminating the food being heated based on the rate of change in the output signal of the gas sensor within a certain period of time after a predetermined time has elapsed from the start of measured heating, and corresponding to the type of food discriminated by the food discriminating means. a detection level setting means for setting a doneness detection level of the gas sensor; and a detection level setting means for setting a doneness detection level of the gas sensor; a time calculation means for calculating the time from a level higher than the above detection level to the detection level from a measurement result of the time measurement means; a comparison means for comparing the output of the time calculation means with a reference value; and a comparison result by the comparison means. The additional heat time is calculated by multiplying the heating time from the start of heating measured by the time measuring means until the output signal of the gas sensor reaches the detection level by an additional heat constant determined in advance according to the above. The gist of the present invention is to include a calculation means and a switching control means for keeping the switching means in the ON state for the calculated additional heating time.

<Function> With the above configuration, when the food discriminating means determines that the food being heated is "preparation" from the rate of change of the output signal of the gas sensor, the time calculating means determines that the output signal of the gas sensor is The time from the level to the finish detection level is calculated and detected. This time is compared with a reference value by a comparison means to determine whether it is a "leaf vegetable" or a "root vegetable." Based on this determination result, the additional heating time is calculated and set, and additional heating is performed for that set time. . Therefore, in a microwave oven of the "automatic heating" method that has only a single heating instruction switch, it is necessary to heat only the necessary time for both "leaf vegetables" and "root vegetables" when preparing food. Can be done.

<Example> Hereinafter, preferred examples of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows an external front view of an embodiment of the present invention.

On the operation panel 1, an "automatic heating" key 2 and a heating key 3 are arranged. Well, it is also possible to combine keys 2 and 3 into one.

FIG. 3 shows a sectional view of an embodiment of the present invention.

A blower 5 is provided on one side of the oven 4, and a gas sensor 7 and a thermistor 8 are provided at an exhaust port 6 on the other side. The resistance value of the gas sensor 7 changes depending on the concentration of exhaust gas generated from the food, and the resistance value of the thermistor 8 changes depending on the temperature of the exhaust gas that 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. 1 shows a circuit diagram of an embodiment of the present invention.

The gas sensor 7 is connected to the DC power supply 11 via the load resistance R _L1 , and the thermistor 8 is connected to the DC power supply 11 via the load resistance R _L2 , and the terminal voltage V _G of the gas sensor 7 and the terminal voltage V _T of the thermistor 8 are independently A-D converted. equipment 12, 13, and input/output interface 1
4 and is input to the CPU of the microcomputer 15. In addition to the CPU, the microcomputer 15 includes a ROM for storing programs, RAM, and an electronic clock. Key signals on the operation panel 1 are also input to the microcomputer 15 via the interface 14. The magnetron 9 is driven by a commercial AC power supply 16 via a contact 18 of a microwave drive relay 17, a door switch 19, a step-up transformer 20, and the like. 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 23 is operated by the interface 14, the transistor 21 or the transistor 25 according to a command from the CPU.
controlled via.

Next, the operation of the embodiment of the present invention will be explained with reference to the characteristic diagram of FIG. 4, the time chart of FIG. 5, and the flow chart of FIG. 6.

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 a command from the CPU, the magnetron 9 oscillates, and heating begins [Flow A]. The terminal voltage VT ₁ of the gas sensor when time T ₁ has elapsed from the start of heating is stored in RAM [Flow B]. Furthermore, the terminal voltage V _T2 of the gas sensor when time T ₂ has elapsed from the start is stored in the RAM [Flow C]. Therefore, the calculation unit in the CPU calculates the ratio V _T2 /V _T1 of the two [Flow D]. Then, as explained in Fig. 7, this value
The type of food is determined from the size of V _T2 /V _T1 [Flow E], and if the value of V _T2 /V _T1 is smaller than 0.9, it is determined that it is sake sake and the gas sensor detection level is determined.
V _CS is set [flow N], and if it is in the range greater than 0.95 and up to 1.0, it is determined that it is food preparation, and the second finished detection is performed at the same level as the detection level V _HS shown in Figure 8. Set level V _S2 and a first finish detection level V _S1 higher than this finish detection level V _S2 by a predetermined value [Flow F],
If the value is between 0.9 and 0.95, it is determined that it is a side dish or a rice bowl, and the detection level V _DS is set [Flow P]. And when the detection level V _CS or V _DS is set,
Measure the gas sensor terminal voltage V _G and check it until it reaches the detection level V _CS or V _DS [Flow O] or [Flow Q], and check the detection level V _CS.
Alternatively, when V _DS is reached, the driving of the microwave generator is stopped [Flow U], and the cooking is finished [Flow V].

On the other hand, when the value of V _T2 /V _T1 is determined to be greater than 0.95 and within the range of 1 and is determined to belong to food preparation, the terminal voltage V _G of the gas sensor 7 as shown in FIG. Measure the time _{T Y1 or} T _K1 required for T Check whether _G has reached the second finish detection level [Flow L], and if it has reached this second finish detection level V _S2 , the second detection level
The time T _Y2 or T _K2 required to reach V _S2 is measured and also stored in the RAM [Flow H]. Therefore, the CPU reads out the two times stored in the RAM and calculates the difference ΔT between them [Flow I].

△T = (T _Y2 - _{T Y1} ) or (T _K2 - T _K1 ) This difference △T is compared to see if it is larger or smaller than a predetermined reference value △T _K written in the ROM with the program. [Flow J] For example, it is determined whether the vegetables are "leaf vegetables" or "root vegetables."
If it is determined NO in flow J, that is, if it is determined that it is a leafy vegetable, for example, the additional heat constant
N _K = 0.1 [flow R], and in flow J
If the root vegetable is determined to be YES, the additional heat constant N _K is set to, for example, 1 [Flow K].

According to experiments, when V _S1 and V _S2 are set appropriately, △T = 2 to 5 seconds for leafy vegetables, 30 to 50 seconds for root vegetables, and △T _K = 17 seconds. Once set, it was possible to reliably distinguish between "leaf vegetables" and "root vegetables." Based on the setting of such an additional thermal constant N _K ,
Foods identified as “leaf vegetables” have a gas sensor voltage of V _G
After reaches the level V _S2 , furthermore, (0.1×T _Y2 )
After a slight additional heat [flow T], heating is stopped, and the food that is determined to be "root vegetables" is further heated for a longer time (1×T _K2 ) [flow M] after reaching V _S2 . will be stopped.

As a modified embodiment of the present invention, instead of the time difference ΔT in the above embodiment, the time change rate of the output voltage of the sensor is calculated, and the additional thermal constant N _K is determined by distinguishing its magnitude.
may be determined.

<Effects of the Invention> As detailed above, according to the microwave oven of the present invention, a microwave oven of the "automatic heating" method uses a gas sensor as a detection element to automatically finish the food by operating a single heating instruction switch. In this system, the type of food in food preparation can be determined from the rate of change in the output voltage of the gas sensor, and an additional heat constant can be set according to the type to compensate for the lack of heating time, allowing for better control of food finish. It can be carried out.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 is an external front view thereof, Fig. 3 is a vertical sectional view of Fig. 2, and Figs. 4 and 5 explain the operation of Fig. 1. FIG. 6 is a flowchart of FIG. 1, FIG. 7 is a characteristic diagram for explaining the principle of food types in the present invention, and FIGS. FIG. 2 is a characteristic diagram for explaining the problem to be solved. 2... Automatic heating key (heating instruction switch), 7... Gas sensor, 9... Magnetron (microwave generator), 15... Microcomputer, 21... Transistor (switching means).

Claims (1)

[Claims] 1. A heating instruction switch that is commonly used regardless of the type of food to be heated, a switching means that supplies driving power to the microwave generator when the switch is turned on, and a gas sensor installed in the exhaust passage of the heating chamber. and a timer for measuring the heating time after the heating instruction switch is turned on, and a rate of change in the output signal of the gas sensor within a certain period of time after a predetermined period of time has elapsed from the start of heating as measured by the timer. a food discriminating means for discriminating the food being heated by the food discriminating means; a detection level setting means for setting a finished detection level of the gas sensor in accordance with the type of food discriminated by the food discriminating means; When the type of food is determined to be prepared food, the time required for the output signal of the gas sensor to reach the finished detection level from a level higher than the finished detection level by a predetermined value is calculated from the measurement result of the timing means. a time calculation means; a comparison means for comparing the output of the time calculation means with a reference value; additional heating time calculation means for calculating additional heating time by multiplying the heating time until the output signal of the gas sensor reaches the finish detection level; and switching for maintaining the on state of the switching means for the calculated additional heating time. A microwave oven comprising a control means.