JPH08191751A - Electromagnetic induction heating jar rice boiler - Google Patents

Abstract

PURPOSE: To provide an electromagnetic induction heating jar rice boiler in which the erroneous judgment of presence of an inner pan by the temperature rise of an equipment body is never caused with an inexpensive structure. CONSTITUTION: The outputs of an inner pan detecting circuit 6 for detecting the presence of an inner pot 5 and a temperature sensor 9 for detecting the equipment internal temperature are inputted to a microcomputer 8, the microcomputer 8 changes the threshold of judgment level for the presence or absence of the inner pot 5 to the input from the inner pot detecting circuit 6 according to the output value (temperature) of the temperature sensor 9, and the temperature sensor 9 for detecting the equipment internal temperature is used also as a temperature sensor used for the control of rice boiling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic induction heating jar rice cooker having an inner pot detection circuit for detecting the presence or absence of an inner pot.

[0002]

2. Description of the Related Art In a conventional general electromagnetic induction heating jar rice cooker, when the heating operation is performed without inserting the inner pot or with the inner pot being pulled out to some extent, the switching operation of the switching element is disturbed. Since the loss increases and the switching element is destroyed, in order to prevent these, an inner pot detection circuit that detects the presence of the inner pot is provided, and the heating operation is not performed when the inner pot is not set properly. There is. This method uses the fact that the current flowing in the heating coil becomes smaller than the normal value when the inner pot is not set correctly, and a current transformer is installed to detect the current flowing in the heating coil. When the input value is below a certain threshold, the heating operation is not performed.

However, in recent years, in order to reduce the cost, a method has been considered in which the presence or absence of the inner pot is detected without using a current transformer, that is, without detecting the current. FIG. 5 shows an example of a circuit of this system. The voltage at the point A of the inner pot detection circuit 6 for preventing the switching element 4 from being destroyed is the inner pot 5
It changes as shown in FIG. That is, in the state where the inner pot 5 is not present (the load is light), the current flowing to the heating coil 3 side is small, so that the voltage at the point A becomes substantially smooth due to the capacitor 2.

On the other hand, when the inner pot 5 is normally set, the current flowing to the heating coil 3 side is large.
The voltage at point A does not maintain a smooth state and drops to 0 V, resulting in a full-wave rectified voltage waveform of the AC power supply 1. The inner pot detection circuit 6 shown in FIG. 5 is provided so that this voltage change can be input to the microcomputer 8, and the voltage change of the charge / discharge of the capacitor 7 is replaced and input to the microcomputer 8. The voltage due to the charging / discharging of the capacitor 7 gradually increases as the inner pot 5 is removed from the state where the inner pot 5 is normally set, and when the inner pot 5 is completely removed, the microcomputer 8 Power supply voltage of 5V. The microcomputer 8 sets a certain threshold value, and it is judged that there is no inner pot 5 above the threshold voltage and there is an inner pot 5 below.

[0005]

Since the inner pot detecting circuit 6 of the conventional electromagnetic induction heating jar rice cooker utilizes the charge / discharge of the capacitor 7, the temperature characteristic of the capacitor 7 is likely to affect the temperature. As shown in FIG. 3, the voltage input to the microcomputer 8 is the input voltage E5 at room temperature, and the input voltage E5 at 50 ° C. when the temperature inside the container rises due to rice cooking.
It becomes 4. Therefore, depending on how the microcomputer 8 sets the threshold value for determining whether or not the inner pot is present, there is a possibility that a mistaken determination that the inner pot 5 has disappeared during rice cooking may result in a phenomenon in which rice cannot be cooked.

To solve this problem, a capacitor having good temperature characteristics should be used, but there was a problem that it was expensive and costly.

Japanese Patent Laid-Open No. 2-154706 and the like have a circuit configuration slightly different from that described above, but are provided with an inner hook detection circuit for detecting the presence or absence of an inner hook and a small object load detection circuit for detecting that a small object load is applied. Similarly, there are some that do not activate the heating operation when it is determined that there is no inner pot, but no consideration is given to the rise in temperature inside the bowl due to rice cooking.

It is an object of the present invention to provide an electromagnetic induction heating jar rice cooker in which the temperature of a threshold value is corrected and the reliability of an inner pot detection circuit is improved.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is an inner pot, a heating coil for inductively heating the inner pot, and an inner pot detection circuit for detecting the presence or absence of the inner pot. In addition, in the electromagnetic induction heating jar rice cooker that has a microcomputer that controls the equipment, inputs the signal of the inner pot detection circuit to the microcomputer, and stops heating according to the input level, with a temperature sensor used for controlling rice cooking A temperature sensor that detects the temperature inside the body is also connected to the microcomputer, and the microcomputer changes the threshold value of the judgment level of the presence or absence of the inner pot for the input from the inner pot detection circuit according to the output value (temperature) of this temperature sensor. It was supposed to be.

[0010]

With the above-described configuration, even if a capacitor having particularly good temperature characteristics is not used, the microcomputer can be operated according to the output value (temperature) of the temperature sensor when the temperature inside the bowl rises during rice cooking. Change the threshold value of the judgment level of the presence or absence of the inner hook for the input from the hook detection circuit,
Even if there is a rise in the input voltage from the inner pot detection circuit due to a rise in temperature, it is possible to prevent a false determination that there is no inner pot.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block circuit diagram of an electromagnetic induction heating jar rice cooker to which an embodiment of the present invention is applied, FIG. 2 is a voltage waveform curve at point A in FIG. 1, and FIG. 3 is an inner pot detection in the circuit. FIG. 4 is a voltage waveform diagram of the circuit, and FIG. 4 is a program flow chart of the microcomputer in the circuit.

In the figure, reference numeral 1 is an AC power supply, which is a DC power supply rectified by a rectification circuit and smoothed by a smoothing circuit having a capacitor 2, a heating coil 3 and a switching element 4.
Are supplied to the inverter circuit consisting of The inverter circuit heats the inner pot 5 for cooking rice by generating a high-frequency magnetic field with the heating coil 3. Reference numeral 6 denotes an inner pot detection circuit for detecting the presence or absence of the inner pot 5. The voltage at the point A on the DC power supply side between the capacitor 2 and the heating coil 3 is used as the charging / discharging voltage of the capacitor 7 and is built in the microcomputer 8 for A / D conversion. Input to the terminal of the instrument. Reference numeral 9 is a temperature sensor, and its voltage is input to a terminal of another A / D converter of the microcomputer 8. The microcomputer 8 controls the drive circuit 10 which drives the switching element 4 based on these inputs. Further, a stabilized power supply circuit 11 that supplies the AC power supply 1 with 5 V, which is the power supply voltage of the microcomputer 8,
Is connected.

With the above structure, the microcomputer 8 A / D-converts the charge / discharge voltage of the capacitor 7 and compares it with the threshold value set on the program to determine the presence or absence of the inner pot 5. Further, the temperature from the temperature sensor 9 is similarly A / D converted to recognize the temperature, and the rice cooking control is performed by this temperature. The temperature sensor 9 used for this rice cooking control is also used, and the threshold value for determining the presence or absence of the inner pot 5 is changed according to the detected temperature. This program flow chart is shown in FIG.

In this example, the judgment level of "no inner pot" is changed when the temperature input by the temperature sensor 9 is 50 ° C, 200 when it is less than 50 ° C, and 23 when it is 50 ° C or more.
The program is set to 0. The temperature of the body rises with the start of rice cooking, and the voltage input to the microcomputer 8 from the inner pot detection circuit 6 also rises due to the influence of the temperature characteristic of the capacitor 7. Although it approaches a voltage equivalent to 200, it is usually 50 ° C.
At a voltage of about 190.

However, it is possible that the voltage becomes equal to or higher than 200 due to variations in parts, and there is a possibility that rice cooking may stop. Therefore, by changing the threshold value for determining “no inner pot” to 230 when 50 ° C. is detected, a margin can be provided between it and the actual voltage of the inner pot detection circuit 6, and rice cooking is stopped. It is possible to prevent the trouble of doing.

[0016]

According to the present invention, a temperature sensor for detecting the temperature inside the body is also connected to the microcomputer, which is also used as a temperature sensor used for controlling the cooking of rice, and the microcomputer outputs the temperature value (temperature). By changing the threshold value of the judgment level of the presence or absence of the inner pot for the input from the inner pot detection circuit, even if the temperature inside the bowl rises during rice cooking It is possible to provide an electromagnetic induction heating jar rice cooker capable of surely detecting the inner pot at low cost without the need of using a capacitor having particularly good temperature characteristics.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an electromagnetic induction heating jar rice cooker showing an embodiment of the present invention.

FIG. 2 is a diagram showing a voltage waveform curve at point A in the same circuit.

FIG. 3 is a voltage waveform diagram of an inner hook detection circuit in the same circuit.

FIG. 4 is a program flowchart of a microcomputer in the same circuit.

FIG. 5 is a block circuit diagram of a conventional electromagnetic induction heating jar rice cooker.

[Explanation of symbols]

 5 Inner kettle 6 Inner kettle detection circuit 8 Microcomputer 9 Temperature sensor

Claims (2)

[Claims] 1. An inner pot, a heating coil for inductively heating the inner pot, an inner pot detection circuit for detecting the presence or absence of the inner pot, and a microcomputer for controlling the equipment. The signal of the inner pot detection circuit is controlled by a microcomputer. In an electromagnetic induction heating jar rice cooker that inputs heat to an input device and stops heating according to the input level, a temperature sensor (9) that detects the temperature inside the body is connected to the microcomputer (8), and the microcomputer (8) uses this temperature sensor ( Output value (temperature) of 9)
The electromagnetic induction heating jar rice cooker is characterized in that the threshold value of the determination level of the presence or absence of the inner pot (5) is changed with respect to the input voltage from the inner pot detection circuit (6). 2. The electromagnetic induction heating jar rice cooker according to claim 1, wherein the temperature sensor (9) for detecting the temperature inside the body is also used as a temperature sensor used for controlling rice cooking.