JP2000023830A - Electromagnetic induction heating rice cooker and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the subject cooker according to the kinds of a device by allowing a reference value storing means to store plural reference values for detecting the presence/absence of a pot, selecting a reference value by each kind of the device and comparing the reference value and the voltage of a smoothing capacitor so as to correctly judge the presence/absence of the pot. SOLUTION: When the pot 7 is present, since the power consumption of a heating coil 5 is large, the voltage of the smoothing capacitor 3 does not keep its smoothing state and almost becomes AC components, thereby current flows through a high-pass capacitor 18. On the other hand, when the pot 7 is absent, since the power consumption of the heating coil 5 is small, the voltage of the smoothing capacitor 3 is nearly in the smoothing state and the AC components are few, thereby the current hardly flows through the high-pass capacitor 18. Consequently, when the pot 7 is present, the output of a voltage detecting means 11 becomes high, but to the contrary, when the pot 7 is absent, the output of the means 11 becomes low. Thus, the presence/absence of the pot 7 can be detected corresponding to whether the output of the means 11 is higher or lower than a prescribed reference value by setting the specified reference value.

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 rice cooker having a no-load detecting means for detecting the presence or absence of a pot, and a method of manufacturing the same.

[0002]

2. Description of the Related Art An electromagnetic induction heating type rice cooker in which a high-frequency current flows through a heating coil to generate a high-frequency magnetic field, an eddy current flows through a pan on the heating coil, and the pot itself is heated by Joule heat due to the eddy current, It is widely known as an alternative to gas and heater heating systems. However, because the resonance of the heating coil and the resonance capacitor is used to generate a high-frequency current, if heating is performed without setting the pan, or if the object is caught and heated without the pan being set properly, In addition, the resistance of the resonance circuit may be reduced, and an overcurrent may flow through the power transistor to cause damage.

In order to prevent this, a conventional electromagnetic induction heating rice cooker is provided with a no-load detecting means for detecting the presence or absence of a pan, and the heating is stopped when the pan is not set properly. . As no-load detection means,
There is a method of detecting based on the input current flowing through the inverter circuit and a method of detecting based on the voltage of the smoothing circuit.

FIG. 6 is a block diagram showing the configuration of a conventional electromagnetic induction heating rice cooker for detecting the presence or absence of a pot by detecting the voltage of a smoothing capacitor. In the figure, 1 is an AC power supply, 2 is a rectifier circuit, and 3 is a smoothing capacitor for smoothing the output of the rectifier circuit 2. The current smoothed by the smoothing capacitor 3 is input to a resonance circuit including a resonance capacitor 4 and a heating coil 5 connected in parallel to the resonance capacitor 4. Reference numeral 6 denotes a power transistor, which generates a eddy current in the pan 7 placed above the heating coil 5 by flowing a high-frequency current through the resonance circuit and heats the pan.

[0005] Reference numeral 8 denotes a temperature sensor for detecting the temperature of the lower portion of the pan 7, and 9 denotes temperature detecting means for detecting the temperature based on a signal from the temperature sensor 8. Reference numeral 10 denotes a reference value storage unit that stores a voltage level (reference value) when the pan 7 is not present, 11 denotes a voltage detection unit that detects the voltage of the smoothing capacitor 3, and 12 denotes an output value of the voltage detection unit 11 and a reference value storage unit. This is a no-load detecting means for comparing the reference value stored in 10 with the reference value to determine the presence or absence of the pan 7. A control unit 13 controls the power transistor driving unit 14 based on outputs from the temperature detection unit 9 and the no-load detection unit 12. The power transistor driving means 14 turns on and off the power transistor 6.
To control heating.

FIG. 7 is a flowchart showing the operation of this conventional electromagnetic induction heating rice cooker. When the rice cooking control is started (S22), energization of the heating coil 5 is started by driving the power transistor 6, but when it is detected that the heating coil 5 is energized (S23), the no-load detecting means 12 smoothes. The voltage of the capacitor 3 is compared with a reference value (S
24) If it is determined that there is no pot, a signal corresponding thereto is output to the control means 13, and the control means 13 controls the power transistor driving means 14 to stop energizing the heating coil 5 (S25). .

[0007]

As described above, in the conventional electromagnetic induction heating rice cooker, the presence or absence of the pot is detected by comparing the voltage of the smoothing capacitor with the reference value stored in the reference value storage means. However, this reference value was constant regardless of the model. Therefore, if the material, diameter, rated current, etc. of the pan differs depending on the model, the current flowing through the heating coil will change. In some cases, it stopped.

In order to eliminate the erroneous judgment, the reference value must be changed for each model. However, when one reference value is stored in one reference value storage means as in the prior art,
It was necessary to use reference value storage means having different reference values for each model. In particular, in the case of rice cookers, it is necessary to provide a plurality of models with different rice cooking capacities, such as pot material and "5 cook" or "1 sho cook," in order to meet the user's function and price needs. However, if the reference value storage means that stores different reference values for each model is used, productivity is poor,
There was a problem that development costs, development time, and development personnel were required.

The present invention has been made in order to solve such a problem. One reference value storage means stores a plurality of reference values for detecting the presence or absence of a pot, and each model matches the model. By allowing you to select a reference value,
An object of the present invention is to obtain an electromagnetic induction heating rice cooker capable of performing control according to a model, and to improve the productivity of the electromagnetic induction heating rice cooker.

[0010]

An electromagnetic induction heating rice cooker according to a first aspect of the present invention includes a heating coil for inductively heating a pot, a circuit for supplying a high-frequency current to the heating coil, and detecting the presence or absence of the pot. Reference value storage means for storing a plurality of reference values, model selection means for outputting a model identification signal, and a model from the plurality of reference values stored in the reference value storage means based on the model identification signal of the model selection means. No load detecting means for detecting the presence or absence of a pot by calling a reference value corresponding to the reference value and comparing the called reference value with an electric signal of the circuit.

According to a second aspect of the present invention, there is provided a method of manufacturing an induction heating rice cooker, comprising: a heating coil for inductively heating a pot; a circuit for supplying a high-frequency current to the heating coil; No-load detecting means for detecting the presence or absence of a pot by comparing the value, a reference value storage means for storing the reference value, a method of manufacturing an electromagnetic induction heating rice cooker, wherein the reference value storage means Store multiple reference values,
At the time of manufacture, a reference value corresponding to a model to be manufactured is selected from the plurality of reference values.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing a configuration of an electromagnetic induction heating rice cooker according to the present invention. In the figure, the same or corresponding parts as those of the conventional electromagnetic induction heating rice cooker described above are denoted by the same reference numerals, and description thereof is omitted. In this embodiment, a plurality of reference values different for each model are stored in the reference value storage means 10. Reference numeral 15 denotes a sequence storage unit that stores the low heat conduction rate, the rice cooking completion temperature, and the like. Since the low heat conduction rate and the like need to be changed according to the thickness of the pot, the rice cooking capacity, and the like, different rice cooking sequences are stored for each model. Have been. Reference numeral 16 denotes a model selection means for selecting a reference value or a rice cooking sequence suitable for the model from the reference value storage means 10 and the sequence storage means 15.

FIG. 2 is a circuit diagram showing an example of the circuit of the voltage detecting means 11. In the figure, reference numeral 18 denotes a high-pass capacitor connected to the smoothing circuit, which passes only the AC component of the voltage of the smoothing capacitor 3 and blocks the DC component. When there is a pot, the power consumption of the heating coil 5 is large,
Since the voltage of the smoothing capacitor 3 is not maintained in a smooth state and almost becomes an AC component, a current flows through the high-pass capacitor 18. On the other hand, when there is no pot, the power consumption of the heating coil 5 is small, and the voltage of the smoothing capacitor 3 becomes almost smooth and the AC component is small.
Almost no current flows through. High pass capacitor 18
Flows through the voltage dividing resistors 19 and 20. Since the voltage generated by the voltage dividing resistors 19 and 20 is an AC voltage, only the voltage on the positive side is taken out by the diode 21, the voltage generated by the capacitor 22 is smoothed, converted to a constant voltage, and output.

Thus, there is a pot and the smoothing condenser 3
When the change in the voltage is large, the output of the voltage detecting means 11 is high because the AC component is large. Conversely, when there is no pot and the change in the voltage of the smoothing capacitor 3 is small, the AC component is small. Since the output of the means 11 is low, it is possible to set a predetermined reference value and detect the presence or absence of the pot based on whether the output of the voltage detection means 11 is higher or lower than the reference value. The method of detecting the presence or absence of the pan is not limited to this, and a signal having a different level depending on the presence or absence of the pan, such as an input current to the inverter circuit, may be detected and compared with a predetermined reference value. The voltage detecting means 11 and the input current detecting means correspond to the load signal output means.

Here, if the size of the pot and the rated current are different depending on the type of rice cooker, the voltage detecting means 1 when there is no load is used.
Since the output of No. 1 is also different, it is necessary to set a reference value for detecting the presence or absence of a pan separately for each model. For example, in a rice cooker having a large cooking capacity and a large pot diameter, the number of windings of the heating coil is large, so that current does not easily flow when there is no load.
Therefore, the reference value needs to be set low. Further, a rice cooker having a large rated current has a large current when there is no load, and therefore, it is necessary to set a high reference value. Further, it is necessary to change the reference value depending on the material of the pot.

FIG. 3 is a circuit diagram of the model selection means 16. In the figure, 25 is a microcomputer, and 26 is a control power supply for supplying power to this circuit. 27 is the first
When the first switch 27 is closed, the current from the control power supply 26 is input to the port P1 of the microcomputer 25, and the port P1 goes to the "H" level. Reference numeral 28 denotes a second switch. When the second switch 28 is closed, a current from the control power source 26 is supplied to the port P2 of the microcomputer 25.
, And the port P2 becomes “H” level. The voltage levels of the ports P1 and P2 serve as signals for identifying the model. Reference numeral 29 denotes a first resistor, and 30 denotes a second resistor. When the first switch 27 or the second switch 28 is opened, the port P1 or the port P2 of the microcomputer 25 is opened.
To the “L” level.

As shown in FIG. 4, four types A, B, C, and D are selected according to the combination of the input voltage levels of the ports P1 and P2, and a rice cooking sequence and a reference value corresponding to each type are selected. can do. Here, ON and OFF of the first switch 27 and the second switch 28 are as follows.
It is set for each model when the rice cooker is manufactured.

Next, the operation of the cooker will be described with reference to the flowchart of FIG. When the control power supply 26 is turned on (S1), the port P1 and the port P
2 are detected (S2, S5, S8). When both the port P1 and the port P2 are at the “L” level, (S
2), it is determined that the model is A, and the sequence storage unit 1
5 calls a rice cooking sequence A corresponding to the model A (S3). Further, the reference value A corresponding to the model A is called from the reference value storage means 10 (S4). Thereafter, when rice cooking is started by operating a rice cooking key or the like (S13), when the heating coil 5 is energized (S14), the no-load detecting means 12 compares the output of the voltage detecting means 11 with the reference value A, and detects the detected voltage. Is smaller than the reference value A (S15), it is determined that there is no pot 7, and the heating is stopped (S16).

In step 5 (S5), the microcomputer 2
When the port P1 of port No. 5 detects the "H" level and the port P2 of "L" level, the type is determined to be B, and the rice cooking sequence B corresponding to the type B is called from the sequence storage means 15 (S6). ), Reference value storage means 10
Calls the reference value B corresponding to the model B (S7).
Thereafter, as in the case of the above-described model A, the heating coil 5
When power is supplied to the power supply (S14), the no-load detecting means 12 compares the output of the voltage detecting means 11 with the reference value B. If the detected voltage is smaller than the reference value B (S15), it is determined that the pot 7 is not present. To stop heating (S16).

Similarly, when the port P1 of the microcomputer 25 is at the "L" level and the port P2 is at the "H" level, it is determined that the type is the model C, and the sequence C and the reference value C are called (S
9, S10), the presence or absence of a pan is determined based on the reference value C,
Both port P1 and port P2 of microcomputer 25 are "H"
In the case of the level, it is determined that the type is the model D, and the sequence D and the reference value D are called (S11, S12).

As described above, a plurality of reference values are stored in the reference value storage means 10 so that a reference value suitable for each model can be selected for each model. And control according to the model can be performed. In addition, one kind of reference value storage means can be used for a plurality of types of electromagnetic induction heating rice cookers, so that development cost, development time,
The number of development personnel can be reduced, and productivity can be improved.

[0022]

According to the electromagnetic induction heating rice cooker according to the first invention, the presence or absence of a pot can be accurately determined for each model, and control can be performed according to the model.

According to the method of manufacturing an electromagnetic induction heating rice cooker according to the second invention, a plurality of reference values for detecting the presence or absence of a pot are stored in the reference value storage means, and the reference value corresponding to the model manufactured at the time of manufacturing is stored. Since the value is selected, productivity is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electromagnetic induction heating rice cooker according to the present invention.

FIG. 2 is a circuit diagram of a voltage detecting means of the electromagnetic induction heating rice cooker according to the present invention.

FIG. 3 is a circuit diagram of a model selecting means of the electromagnetic induction heating rice cooker according to the present invention.

FIG. 4 is a diagram showing a pattern for selecting a model of the electromagnetic induction heating rice cooker according to the present invention.

FIG. 5 is a flowchart showing the operation of the electromagnetic induction heating rice cooker according to the present invention.

FIG. 6 is a block diagram illustrating a configuration of a conventional electromagnetic induction heating rice cooker.

FIG. 7 is a flowchart showing the operation of a conventional electromagnetic induction heating rice cooker.

[Explanation of symbols]

1 AC power supply, 3 smoothing capacitor, 5 heating coil,
Reference Signs List 6 power transistor, 7 pot, 10 reference value storage means, 11 voltage detection means, 12 no-load detection means, 16
Model selection means.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuaki Moriwa 1728-1 Komaeda, Hanazono-cho, Osato-gun, Saitama F-term in Mitsubishi Electric Home Equipment Co., Ltd. (Reference) 3K051 AA02 AA08 AB04 AB05 AC03 AC07 AC33 AD28 AD40 BD02 BD24 CD39 4B055 AA02 AA09 BA09 BA12 BA29 CA62 CC06 CC17 CC18 GA04 GB29 GB32 GC13 GC34 GD01 GD02

Claims (2)

[Claims] 1. A heating coil for inductively heating a pan, current supply means for supplying a high-frequency current to the heating coil, load signal output means for outputting a signal of a different level depending on the presence or absence of the pan, and detection of the presence or absence of the pan Reference value storage means for storing a plurality of reference values for performing the operation, a model selection means for outputting a model identification signal, and a plurality of reference values stored in the reference value storage means based on the model identification signal of the model selection means. And a no-load detecting means for detecting the presence or absence of the pan by comparing the called reference value with the signal of the load signal output means. 2. A heating coil for inductively heating a pan, a circuit for supplying a high-frequency current to the heating coil, and a no-load detecting unit for detecting the presence or absence of the pan by comparing an electric signal of the circuit with a predetermined reference value. A method of manufacturing an electromagnetic induction heating rice cooker, comprising: a detection unit, and a reference value storage unit that stores the reference value, wherein a plurality of reference values are stored in the reference value storage unit, A method for manufacturing an electromagnetic induction heating rice cooker, comprising selecting a reference value corresponding to a model to be manufactured from the values.