JPH0221690Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a microwave oven that automatically controls heating by detecting the gas concentration generated from heated food using a gas sensor.

Conventionally, a microwave oven has been proposed that includes a heating control means that uses a gas sensor to set an initial heating time and an additional heating time and stops the microwave when the food is in an optimal finished state. Specifically, for example, warming food 1 (rice, soup), warming 2
Classify the heated foods into groups such as (side dishes, rice bowls), Preparation 1 (leaf vegetables), Preparation 2 (root vegetables), etc., and calculate the output voltage of the gas sensor to achieve the optimal initial heating state for each of these heated food groups. The values have been set experimentally, and to briefly explain them with reference to the drawings, Figure 1 shows the basic circuit of the gas sensor, and Figure 2 shows the output characteristics of the gas sensor for a particular group of heated foods. As an example, reference numeral 1 denotes a gas sensor formed by connecting a resistor 2 in series, and a DC power source E is applied to both ends of the gas sensor. This gas sensor 1
It uses a semiconductor whose main component is SnO ₂ and takes advantage of the property that the conductivity of the SnO ₂ semiconductor changes due to gas adsorption.The resistance value decreases due to gas adsorption, and the potential difference between both ends of the gas sensor is output.
I'm taking out _VG . t ₁ is the initial heating time, Kt ₁ is the additional heating time obtained by multiplying the initial heating time t ₁ by a certain constant K, and is the time until the output voltage V ₁ of the gas sensor 1 is reached when the optimal initial heating state is reached. Additional heating time Kt ₁ is determined by t ₁ and heating is automatically controlled. Note that V ₀ is the output voltage of the gas sensor 1 at the end of the oven cleaning cycle, which is executed for about ten seconds after the start of heating.

However, the output voltage V ₁ of the gas sensor 1 may differ depending on the type of material used for cooking even among the specific heated food groups shown in FIG. "Simmered" B belongs to the same classification as a simmered dish, but as shown in Figure 3, the time required to reach the optimal initial heating state does not reach a constant value, and in "Simmered Potato" A, it is t ₁ '' , “Mackerel stew in miso”
In B, it was t ₁ ', and there was a considerable time difference between the two. In other words, the output voltage of gas sensor 1
If the value of V ₁ is determined to be the optimal initial heating time for "boiled potatoes" and the initial heating is finished and the transition is made to additional heat, "Saba Misoni" B becomes overheated, and "Saba Misoni" becomes "Saba Misoni". When B was determined as the optimal initial heating time, there was a problem that "Imono Korogoshi" A was not heated.

The present invention has been developed in view of the above points, and it is possible to determine the upper and lower limits of the initial heating time when the time required to reach the optimum initial heating state is different among heated foods of the same classification. A certain initial heating time is set between the two, and the output voltage of the gas sensor detected when this certain initial heating time is reached and the preset voltage at which the optimum initial heating state of the heated food group is reached. The initial heating time was set based on the results of the comparison, and variations in heating were eliminated to improve the finished state.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 4 is an electrical circuit diagram of a main part of a microwave oven showing an embodiment of the present invention, and FIG. 5 is an output characteristic diagram of a gas sensor.

FIG. 6 is a flowchart showing the operation of the embodiment of the present invention.

FIG. 7 is a functional block diagram showing the function realizing means of the present invention.

In the figures, parts having the same functions as those of the conventional example are designated by the same reference numerals and explained.

A thermistor 3 is connected to a DC power source E via a resistor 4, and detects the temperature inside the oven (not shown) using an output voltage V _T. The output voltage V _G of the gas sensor 1 and the output voltage V _T of the thermistor 3 are connected to independent A/D converters 5 and 6, respectively, and inputted to the CPU of the microcomputer 8 via an interface 7. In addition to the CPU, the microcomputer 8 has built-in ROM and RAM for storing cooking sequence programs, measurement data such as heating temperature and heating time, and the like. 9
uses the heating key 10 to classify the food into heating food groups such as Warming 1 (rice, soup), Warming 2 (side dishes, rice bowls), Preparation 1 (leaf vegetables), Preparation 2 (root vegetables), etc., and perform the desired cooking. This is an operation panel equipped with operation keys such as a cooking menu key for selective cooking, and all key signals from these operation keys are also input to the microcomputer 8 via the interface 7 mentioned above. Reference numeral 11 denotes an NPN transistor connected to the interface 7, and a microwave driving relay 12 is connected to the collector. 13 is a contact point of the microwave driven relay 12, which is connected from the interface 7.
When a high level signal is output to the NPN transistor 11, the heating relay 12 is energized to close this contact, and the AC power source 14 is supplied to the magnetron 16 via the high voltage transformer 15.
Note that 17 is a door switch that is closed when the oven door (not shown) is closed.

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

First, when the heating key 10 is pressed, the input signal is sent to the CPU 8 via the interface 7.
With the microwave output stopped, a cleaning cycle is executed in which the blower fan (not shown) is rotated for about ten seconds to exhaust the residual gas inside the oven. The terminal voltage is V ₀ . After that, a command signal is sent from the CPU 8 to the interface 7 to turn on the microwave drive relay 12.
The energy is sent to the NPN transistor 11 through the oscillator, causing the magnetron 16 to oscillate, and microwave heating is started. Then, the initial heating output voltage V ₁ corresponding to a specific cooking menu is stored in the ROM in advance, and the output voltage V of the gas sensor 1 after a certain period of time t ₁ ° has passed after the end of the cleaning cycle is stored, and the output voltage is By comparing and determining the voltage _V1 and the output voltage V, as in the case of "Saba Misoni" B, if V< _V1 , the process moves to the "YES" step, and the initial heating ends at this point, and the result is stored in advance. Multiply t ₁ ° by the constant K and apply additional heat for a time of Kt ₁ ° to complete cooking. By the way, like in "boiled potatoes" A, after a certain period of time t ₁゜ has passed, V>
If V ₁ , move to the "NO" step, continue the initial heating, and end the initial heating only when V<V ₁ , and add the elapsed time t ₁ '' at this point multiplied by the constant K mentioned above. Set the heat time to run additional heat and complete cooking.

In this way, if there is a certain range of initial heating times that give the optimum initial heating state for the same group of heated foods, then the approximate average of these times can be set as a certain period of time.
By comparing the output voltage of the gas sensor during this certain period _of time with the output voltage of the gas sensor in the optimal initial heating state corresponding to each cooking menu, it is possible to When the initial heating time t ₁ ″ is relatively long, the initial heating is continued without shifting to additional heat even after a certain period of time t ₁゜, preventing underheating and reaching the optimal heating state. can be transitioned from to additional heat.

As explained above, the present invention reduces the initial heating time t ₁ ″ of the food that requires the longest initial heating time and the shortest initial heating time among the heated food groups that require approximately the same heating time. The output voltage V of the gas sensor after a certain initial heating time t ₁゜ such that t ₁ ′ < t ₁゜ < t ₁ ″ has elapsed with respect to the initial heating time t ₁ ′ of the food, Output voltage V ₁ of the gas sensor set in advance when the optimum initial heating state corresponding to a certain cooking menu is reached
means for comparing and determining the magnitude of the gas sensor, and additional heat in response to the output of the comparing and determining means such that the output voltage of the gas sensor becomes V<V ₁ after the predetermined initial heating time t ₁ ° has elapsed. Since we have provided a means for executing this, cooking menus with different initial heating times within the same heated food group can be classified into the same category, and the initial heating time can be determined based on the output voltage of the gas sensor when a certain period of time has elapsed. Since it can be controlled, for cooking menus where the initial heating tends to be left unheated, the initial heating is reliably continued until the optimum initial heating state corresponding to the menu is achieved, which has a great effect on improving the finish of heated foods. It has a high practical value.

[Brief explanation of drawings]

Figure 1 shows the basic circuit of the gas sensor, Figure 2 is an example of the output characteristic diagram of the gas sensor, Figure 3 is the output characteristic diagram of the gas sensor corresponding to the cooking menu, and Figure 4 shows the implementation of the present invention. FIG. 5 is an output characteristic diagram of the gas sensor according to the present invention, FIG. 6 is a flowchart showing an outline of the operation of the present invention, and FIG. 7 is a diagram showing the main parts of a microwave oven according to the present invention. FIG. 1...Gas sensor, 7...Interface, 8...Microcomputer, 9...Operation panel, 10...Heating key, 12...Microwave drive relay, 16...Magnetron, V ₁ ...Specific cooking Initial heating output voltage corresponding to the menu,
t ₁ ″, t ₁ ′...Upper and lower limits of the optimal initial heating time for the same heated food group, t ₁゜...a certain time such that t ₁ ′<t ₁゜<t ₁ ″, V...time t ₁ Gas sensor output voltage after ゜.

Claims (1)

[Claim for Utility Model Registration] In addition to being equipped with a gas sensor that detects the concentration of gas emitted from food, there is also a selection key on the operation panel for cooking menus that classify food into heated food groups that require approximately the same heating time. In the microwave oven equipped with the above, among the heated food groups that require approximately the same heating time, the food that requires the longest initial heating time and the _shortest initial heating time are For the initial heating time t ₁ ′ of the food, t ₁ ′<
The output voltage V of the gas sensor after the elapse of a certain initial heating time t ₁゜ such that t ₁゜ < t ₁ ″, and the optimal initial temperature corresponding to the heated food group selected by the cooking menu key. means for comparing and determining the magnitude of the output voltage V _{1 of} the gas sensor set in advance when the heating state is reached; V<V ₁
and means for applying additional heat in response to the output of the comparison and determination means.