JPH05258850A - Induction-heated cooking apparatus - Google Patents

Abstract

PURPOSE:To confirm whether a pot is affiliated with a cooking apparatus or not via the input current and oscillation frequency in the induction-heated cooking apparatus used in the general household. CONSTITUTION:An induction-heated cooking apparatus is provided with a current measuring circuit 9, an oscillating circuit 2e, and a pot judging means 10, the material of a pot 5 is confirmed by the pot judging means 10 via the input current Iin and oscillation frequency, and heating is stopped for a different pot. A coil switching means 6 is provided, heating coils 3, 4 are switched to confirm the size of the pot 5, and heating is stopped for a pot having a different size. Satisfactory cooking can be invariably performed with the correct pot 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker having a pan detecting means used in ordinary households.

[0002]

2. Description of the Related Art FIG. 3 shows a block diagram of a conventional induction heating cooker, and FIG. 4 shows a relational diagram of a small object detecting operation for determining whether or not a pan is suitable for an induction heating system in a conventional induction heating cooker.

In FIG. 3, reference numeral 21 is a commercial AC power supply, and high frequency power supply 22 is a rectifying circuit 22a for rectifying the commercial AC power supply 21, a smoothing capacitor 22b for smoothing the output of the rectifying circuit 22a, and a resonance capacitor 22c. It is composed of a switching element 22d and an oscillating circuit 22e which generates a high frequency voltage by turning on / off the switching element 22d at high speed.

Reference numeral 23 denotes a heating coil for conducting induction heating by passing a high frequency current from the high frequency power source 22.
4 is a pan heated by induction heating, which is installed on the ceramic plate 25.

Reference numeral 26 is a temperature detecting means, which is composed of a thermistor 26a which is a temperature detecting element and a temperature detecting circuit 26b which converts a change in resistance value of the thermistor into temperature. The temperature detecting means 26 measures the temperature of the pot 24 via the ceramic plate 25. Reference numeral 27 is a control unit that controls the output of the high frequency power source 22 by changing the frequency of the oscillation circuit 22e. The control means 27 controls the electric power for heating so that the pot 24 has a predetermined temperature arbitrarily set by the user based on the input of the temperature detection means 26.

Reference numeral 28 is a voltage measuring circuit for measuring a voltage (hereinafter abbreviated as Vce) applied between the collector and emitter of the switching element 22d, and 29 is a current (hereinafter abbreviated as Iin) input to the high frequency power source 22. It is a current measuring circuit for measuring. 30 indicates whether or not the pot 24 placed on the ceramic plate 25 is a pot suitable for the induction heating method, depending on the ratio of Vce measured by the voltage measuring circuit 28 and Iin measured by the current measuring circuit 29. It is an accessory detection means for determining whether or not 24 is placed.

Next, in the above structure, the small object detecting means 3
The operation of determining whether or not the pot is proper according to 0 will be described with reference to FIG.

Generally, in the induction heating method, a large resonance current flows through the heating coil 23 and the resonance capacitor 22c by turning on / off the switching element 22d at high speed. At that time, when the magnetic flux generated from the heating coil 23 passes through the ceramic plate 25 and is absorbed by the pan 24, the eddy current generated in the pan 24 causes the pan 24 itself to generate heat. When the on time of the switching element 22d is lengthened to increase Iin, the heating coil 23
A large amount of magnetic flux is generated from the above and is absorbed by the pot 24 to increase the heating power. The control means 27 uses this Iin as a current measuring circuit 29.
The oscillation circuit 22e is controlled so that Iin becomes a predetermined input current, that is, a predetermined input power. Further, generally, when heating a pot of the same material, increasing this Iin also increases Vce.

At this time, the amount of the magnetic flux absorbed in the pot 24 and the amount of heat generated by the eddy current are determined by the material of the pot 24. If the pot 24 is not present or the pot is not suitable for induction heating, the magnetic flux is Is not absorbed in the pan and Iin does not increase, so the ratio of Iin to Vce falls within the range of small object load in FIG. The small object detection means 30 starts heating and starts heating coil 23.
When Iin and Vce are within the small load range shown in FIG. 4 when the magnetic flux is generated from the magnetic flux, the heating is stopped by outputting to the control means 27.

[0010]

However, the above-mentioned FIG.
In the configuration of the conventional induction heating cooker shown in FIG. 2, the input of electric power is unstable depending on the material of the pot 24, and the ceramic plate 2 is controlled even when the temperature of the pot 24 is controlled to a predetermined temperature.
Since the temperature of the pan 24 is indirectly measured via 5, the temperature of the pan 24 cannot be properly controlled depending on the contact state between the pan 24 and the ceramic plate 25 and the size of the pan 24, and the cooking temperature required by the user is It had a drawback that it could not be realized.

SUMMARY OF THE INVENTION The first object of the present invention is to provide an induction heating cooker capable of cooking with a predetermined pot whose material is always clear and under proper temperature control.

[0012] A second object of the present invention is to provide an induction heating cooker which can always perform good cooking with a pan of a predetermined size.

[0013]

Means for Solving the Problems To achieve the first object, the first means for solving the problems of the present invention is a pan suitable for an induction heating system for cooking, and a pan at the bottom of the pan. One or more heating coils arranged in a direction, a rectifying circuit for rectifying a commercial AC power source, a smoothing capacitor for smoothing the rectified voltage, a resonance capacitor connected in parallel with the heating coil, and a high frequency current This switching element is turned on and off.
An oscillating circuit for turning off, a high frequency power supply for heating the pot by induction heating by supplying a high frequency current to the heating coil, a current measuring circuit for measuring a current flowing in the rectifying circuit, and an oscillation of the high frequency power supply. Control means for controlling the heating output of the high-frequency power source by changing the on-time of the switching element of the high-frequency power source by outputting to the circuit, and the oscillating circuit for the input current value measured by the current measuring circuit. If the ON time of the switching element is within a predetermined time range peculiar to the pan, the pan discriminating means for outputting an output to the control means to stop heating is provided.

A second problem solving means for achieving the second object is to select a predetermined heating coil when the induction heating cooker shown in the first problem solving means has a plurality of heating coils. The coil switching means for energizing only the selected heating coil is provided, and the oscillating circuit is used for the input current value measured by the current measuring circuit with the coil switching means energizing only the predetermined heating coil. If the ON time of the switching element is not within the predetermined time range peculiar to the pan, the pan discriminating means outputs an output to the control means to stop the heating.

[0015]

According to the first problem solving means of the present invention, the on-time of the switching element of the high frequency power supply is controlled by outputting the current to the current measuring circuit for measuring the current flowing in the rectifier circuit of the high frequency power supply and the oscillation circuit of the high frequency power supply. By changing the output of the high-frequency power source to control the pan to reach a predetermined temperature by changing it, the ON time of the switching element by the oscillating circuit is set to a predetermined value with respect to the input current value measured by the current measuring circuit. If the pot does not fall within the specified time range, the control means outputs the signal to stop the heating, so if you try to cook with a material other than the specified saucepan. Since the ON time of the switching element with respect to the input current value is out of the predetermined time range, the pan discriminating means prevents heating.

In the second means for solving the problem, by providing the coil switching means, the heating area is changed only by a predetermined coil among the plurality of heating coils to perform heating, and the switching element of the switching element corresponding to the input current value at that time is changed. The size of the pan is determined by checking whether the on-time is within a predetermined time range, and if the size is other than the predetermined pan, heating cannot be performed.

[0017]

The above embodiment will be described below with reference to the drawings.

FIG. 1 shows a block diagram of an induction heating cooker according to first and second embodiments of the present invention. In the figure, 1 is a commercial AC power supply, and a high frequency power supply 2 is a rectifier circuit 2a that rectifies the commercial AC power supply, a smoothing capacitor 2b that smoothes the rectified voltage, a resonance capacitor 2c, and a switching element 2d.
And an oscillation circuit 2e that generates a high frequency voltage by turning on / off the switching element 2d at high speed.

Reference numeral 3 is a first heating coil, 4 is a second heating coil, and these two heating coils 3 and 4 are located below the pot 5 at a predetermined distance from the bottom of the pot 5 and the center of the pot 5 is placed. They are arranged symmetrically with respect to. The first heating coil 3 and the second heating coil 4 are connected in parallel to the resonance capacitor 2c of the high frequency power supply 2. Reference numeral 6 is a coil switching means for disconnecting the second heating coil 4 from the circuit. The operation of the coil switching means 6 selects whether the entire surface of the pan 5 is heated by using the two heating coils 3 or 4, or the half surface of the pan 5 is heated by only the first heating coil 3.

Reference numeral 7 is a thermistor 7 of a temperature detecting element arranged in contact with the bottom surface of the pot 5 to measure the temperature of the center of the range of the pot 5 heated by the first heating coil 3.
It is a temperature detecting means constituted by a and a temperature detecting circuit 7b for converting a change in resistance value of the thermistor 7a into temperature. Reference numeral 8 is a control means for controlling the output of the high frequency power supply 2 by changing the frequency of the oscillation circuit 2e. The control means 8 controls the electric power for heating so that the pan 5 has a predetermined temperature arbitrarily set by the user based on the input of the temperature detection means 7. Generally, in order to increase the heating power, the ON time of the switching element 2d is lengthened by the oscillation circuit 2e. A current measuring circuit 9 measures an input current to the high frequency power source 2 (hereinafter abbreviated as Iin), that is, heating power. Then, when the ON time of the switching element 2d is lengthened, a large amount of magnetic flux is generated from the first heating coil 3 and the second heating coil 4, and the pan 5
Is absorbed in the heating power and the heating power increases, that is, Iin increases. The control means 8 measures this Iin by the current measuring circuit 9, and controls the ON time of the switching element 2d by the oscillation circuit 2e so that Iin becomes a predetermined input current, that is, a predetermined input power.

At this time, the amount of magnetic flux absorbed by the pot 5 and the amount of heat generated are determined by the material of the pot 5, so that when a pot other than the predetermined pot 5 is placed, even if the pot can be heated. Since the amount of absorbed magnetic flux is different, the ON time of the switching element 2d is different for the same current value of Iin as in the case of the predetermined pot 5. Figure 2 shows the relationship of this operation.
Shown in. That is, the pan determining means 10 determines whether or not the pan 5 is a predetermined pan based on the relationship between Iin and the ON time of the switching element 2d as shown in FIG.
In FIG. 2, the pot 5 is not placed in the range of small load, or the pot 5 that cannot be heated by the induction heating method is placed. In the range of the improper pot, it is suitable for heating by the induction heating method, but is not a pot of a predetermined material.

Further, in the first embodiment, the case where the number of heating coils is two is shown, but the coil switching means 6
Needless to say, the same applies to the case where there is one heating coil that does not require the above, or the case where there are three or more heating coils that require a plurality of coil switching means 6.

Next, in the second embodiment of the present invention, the coil switching means 6 is provided in the first embodiment, and the second heating coil 4 is disconnected from the high frequency power source 2 by this function,
Again, the relationship between Iin and the ON time of the switching element 2d is measured and the pan discriminating means 10 discriminates whether or not it is an appropriate predetermined pot 5. At this time, when a pan made of the same material as the predetermined pan 5 and having a different size, for example, a small pan that is biased toward the second heating coil 4 side is placed, the first heating coil 3 is switched by switching the coil. When heating is performed using only the above, the relationship between Iin and the ON time of the switching element 2d is in the range of small load, and it is determined that the pot is not appropriate.

Further, in the second embodiment, the case where the number of heating coils is two is shown, but it goes without saying that the same applies when the number of heating coils is three or more.

[0025]

As described above, according to the first aspect of the present invention, by providing the pan discriminating means, the pan having a predetermined size suitable for the construction of the induction heating cooker of the present invention is provided. Also, when pots of different materials are placed, the pot discriminating means determines that the pots are inappropriate and stops heating. Therefore, there is no problem such as conventional pots with inappropriate materials placed and proper temperature control cannot be achieved and sufficient cooking performance cannot be obtained, and induction heating that can obtain good cooking performance with proper temperature control A cooker can be provided.

Further, according to the second invention, by further providing the coil switching means, even if the material of the pot is suitable for the induction heating of the present invention, the pot of a size different from the predetermined size is placed. In the case of the heating, the pan discriminating means stops the heating. Therefore, in the same manner, there is no problem that an inappropriate pot is placed and proper temperature control cannot be performed and sufficient cooking performance is not obtained, and good cooking performance can always be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an induction heating cooker according to first and second embodiments of the present invention.

FIG. 2 is an induction heating cooker Ii according to the first and second embodiments.
The figure for demonstrating the relationship of the ON time of an n-switching element.

FIG. 3 is a block diagram of a conventional induction heating cooker.

FIG. 4 is an Iin showing a small object detection operation of the induction heating cooker.
-Vce relationship diagram

[Explanation of symbols]

 1 Commercial AC Power Supply 2 High Frequency Power Supply 2a Rectifier Circuit 2b Smoothing Capacitor 2c Resonance Capacitor 2d Switching Element 2e Oscillation Circuit 3 First Heating Coil (Heating Coil) 4 Second Heating Coil (Heating Coil) 5 Pan 6 Coil Switching Means 8 Control Means 9 Current measuring circuit 10 Pan discriminating means

Claims (2)

[Claims] 1. A pan suitable for an induction heating system for cooking, one or more heating coils horizontally arranged at the bottom of the pan, a rectifying circuit for rectifying a commercial AC power source, and a rectified circuit after rectification. A smoothing capacitor for smoothing a voltage, a resonance capacitor connected in parallel with the heating coil, a switching element for performing an on / off operation for generating a high frequency current, and an oscillation circuit for turning on / off this switching element, A high-frequency power source that heats the pot by induction heating by applying a high-frequency current to the heating coil, a current measurement circuit that measures the current flowing in the rectifier circuit, and an output circuit to the oscillation circuit of the high-frequency power source to output the high-frequency power source. Control means for controlling the heating output of the high-frequency power source by changing the on-time of the switching element, and the input measured by the current measuring circuit. If the ON time of the switching element by the oscillating circuit with respect to the current value is not within the predetermined time range specific to the pan, induction provided with a pan determination means for outputting to the control means to stop heating Heating cooker. 2. The induction heating cooker according to claim 1,
A plurality of heating coils are provided, and a coil switching means for selecting a predetermined heating coil from the plurality of heating coils and energizing only the selected heating coil is provided, and only the predetermined heating coil is provided by the coil switching means. If the ON time of the switching element by the oscillating circuit is not within the predetermined time range peculiar to the pan with respect to the input current value measured by the current measuring circuit in the energized state, the pan discriminating means causes the control means to operate. An induction heating cooker that outputs and stops heating.