JPH1055880A - Device and method for judging kind of material to be heated by induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time for judging kind of the material to be heated by judging whether a material to be heated is a small load or not, or judging whether a container is a magnetic container or a non-magnetic container in the condition that the frequency is fixed. SOLUTION: When the operation is started, a control unit 5 selects the judgment frequency, and outputs the switch control signal CS2 for operating a heating unit 20. When the current of an ordinary power source AC is detected and the corresponding voltage Va is input to the control unit 5, the control unit 5 reads this voltage value Va, and in the case of the voltage value Va at 1.2V or less, the material 3 to be heated is judged as a small load, and the drive of an inverter INV is stopped. In the case of the voltage value at 1.2V or more, the input voltage value Vb is read out and judged whether the input voltage value Vb exceeds 1.8V or not, and in the case of the input voltage value at 1.8V or less, a judgment whether the voltage value Vb exists in a range at 0.75-1.0V or not is performed, and in the case of yes, the material 3 to be heated is judged as a strong magnetic container, and a switch SW is maintained in the ON-condition, and the strong magnetic container is heated by a magnetic mode.

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, and more particularly, to a type of an object to be heated (small utensil objects) with a fixed frequency.
, Magnetic container, and non-magnetic container), the heating can be stopped if the object to be heated is a small object, and the above-described containers can be heated using a frequency compatible with the magnetic container and the non-magnetic container. The present invention relates to an apparatus and a method for determining the type of an object to be heated in an induction heating cooker.

[0002]

2. Description of the Related Art Conventionally, in an apparatus for judging the type of an object to be heated in an induction heating cooker, as shown in FIG. 4, a rectifier BD for rectifying a normal power supply AC and smoothing the rectified voltage. Inductor L1 and capacitor C1
Rectifying / smoothing unit 1 having an inverter and an inverter INV for switching a commercial power supply AC rectified by a drive signal DS.
And two upper and lower output terminals H and L of the inverter INV.
One terminal is connected to the other, and the other terminal is connected between two capacitors C2 and C3 connected to each other, a common terminal of the capacitors C2 and C3, and an intermediate output terminal M of the inverter INV. A heating unit 2 including a working coil L for heating the placed object 3 to be heated;
A current detecting unit 4 for detecting a current of the common power supply AC applied to the rectifying / smoothing unit 1 and converting the current value into a voltage value; and a type of the heating target 3 based on an output voltage value of the current detecting unit 4. And outputs a control signal CS. The control signal CS of the control unit 5 controls the inverter IN of the heating unit 2.
And an inverter drive unit 6 that outputs a drive signal DS for driving V.

Further, the resonance frequency of the heating unit 2 is determined by the following equation based on the inductance of the working coil L and the capacitance of each of the resonance capacitors C1 and C2.

[0004]

(Equation 1)

[0005] The operation of the apparatus for judging the type of the object to be heated in the conventional induction heating cooker thus constructed is as follows. First, when the user presses a start key (not shown) in a state where the object to be heated 3 is placed on the working coil L, the normal power supply AC is supplied to the induction heating cooker and the control unit 5 performs control. A signal CS is output to the inverter driving unit 6, which outputs a high-frequency driving signal DS to the inverter INV of the heating unit 2, and
The NV switches on and off the commercial power supply AC rectified from the rectification / smoothing unit 1 by switching.

In this case, if it is assumed that the resonance frequency of the heating unit 2 determined from the above equation is 25 kHz, the control unit 5 controls the frequency of the heating unit 2 at the initial stage of operation of the induction heating cooker. A control signal CS is set to 30 kHz. At this time, the current of the service power supply AC is detected from the current transformer CT, and the current detection unit 4 outputs a predetermined voltage corresponding to the magnitude of the current of the service power supply AC to the control unit 5.
And the control unit 5 stores the voltage value as data.

Next, the control unit 5 receives and stores the changing output voltage value of the current detection unit 4 while outputting the control signal CS for causing the switching frequency of the inverter INV to be slightly lower than 30 kHz. . By repeating such a process, the frequency of the heating unit 2 becomes 28 kHz.
z, the control unit 5 averages the voltage values input and stored so far, determines whether the object to be heated 3 is a small object or a magnetic container, and determines whether the object to be heated is a small object. In the case of, all the operations are stopped and the above-mentioned accessory is not heated, and if it is determined that the magnetic container is a magnetic container, an appropriate frequency is selected to heat the magnetic container. At this time, the accessory is a magnetic material such as a spoon or a knife.

[0008]

However, in the conventional apparatus for judging the type of the object to be heated in the induction heating cooker constructed as described above, the frequency is varied within a range not including the resonance frequency to change the frequency. Since the voltage value that is changed corresponding to the frequency to be heated is continuously input and the type of the object to be heated is determined by averaging them, there is an inconvenience that the determination time is long.

In order to heat a non-magnetic container having a lower surface resistance than a magnetic container, the above resonance frequency of 25 kHz is required.
Although a higher frequency (for example, about 80 kHz) should be used, the non-magnetic container cannot be heated because the number of turns of the working coil is fixed.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus and a method for judging an object to be heated in an induction heating cooker capable of judging the type of an object to be heated in a short time with a fixed switching frequency of an inverter. It is intended to provide.
Another object of the present invention is to detect a current of a common power supply AC applied to a rectifier / smoothing unit and a current applied to a working coil from an inverter of a heating unit while the switching frequency of the inverter is fixed, and to detect them. An object of the present invention is to provide an apparatus and a method for determining the type of an object to be heated of an induction heating cooker that can determine the type of the object to be heated in a short time based on the supplied current and form a resonance frequency suitable for each container.

In order to achieve the above object, in the apparatus for judging the type of the object to be heated in the induction heating cooker according to the present invention, a rectifying / smoothing unit 1 for rectifying and smoothing a normal power supply AC, and an inverter. (INV), a capacitor, a working coil, and a switch (SW). The heating unit 20 selectively changes the connection between the working coil and the capacitor according to the switch drive signal (DS2) and selectively heats the object 3 to be heated.
A first current detector 4 for detecting the current of the common power supply AC applied to the rectifier / smoothing unit 1 and converting the current to a voltage (Va); and detecting a current flowing to the working coil of the heating unit 20. The second current detector 70 converts the current into a voltage (Vb), the voltage (Va) output from the first current detector 4 and the voltage (Vb) output from the second current detector 70. Then, the voltage (Va, Vb) is compared with a preset reference voltage value, the type of the object to be heated by the working coil of the heating unit 20 is determined, and the heating unit 20 is controlled. A control unit 5 for outputting a command, and an inverter drive signal (DS1) for driving the inverter (INV) of the heating unit 20 according to the control command of the control unit 5
And a switching drive signal (D) to the heating unit 20 according to a control command of the control unit 5.
S2) and a switch driving unit 80 that outputs S2).

In the method for judging the type of the object to be heated in the induction heating cooker according to the present invention for achieving the above object, the first step of heating the object to be heated by the small object judging frequency is inputted. The current of the AC power supply AC is detected, a voltage proportional to the magnitude of the current is read, and the
A second step of detecting a current applied to the working coil L from V and reading a voltage proportional to the magnitude of the current, and comparing the two voltages read in the second step with a preset reference value, respectively. The object to be heated is a small object, or a magnetic container,
And a third step of determining whether the container is a non-magnetic container,
When it is determined that the object to be heated is a small object, all operations are stopped and the object to be heated is not heated, and the object to be heated is a magnetic container,
And a fourth step of changing the connection of the heating unit when it is determined that the container is a non-magnetic container.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In the apparatus for judging the type of the object to be heated in the induction heating cooker according to the present invention, as shown in FIG.
A smoothing unit 1; an inverter (INV) for switching the voltage of the service power supply AC rectified and smoothed by the inverter drive signal DS1; and an inverter 2 connected in series between an upper terminal H and a lower terminal L of the inverter (INV). Capacitors C2 and C3, working coils L2 and L3 and capacitor C4 connected in series between the intermediate terminal M of the inverter (INV) and the connection point of each of the capacitors C2 and C3, and the working coil L3 and capacitor C
And a switch SW connected in parallel to the heating unit 2
0, a current of the common power supply AC applied to the rectifying / smoothing unit 1, a first current detecting unit 4 for converting the detected current to a voltage (Va), and an inverter (INV) of the heating unit 20. ) Detects a high-frequency current flowing through the working coil L2, converts the detected current into a voltage (Vb), a voltage (Va) output from the first current detection unit 4 and a voltage (Va). Upon receiving the voltage (Vb) output from the second current detection unit 70, the heating unit 20 determines whether the object to be heated is a small object or a magnetic container and a non-magnetic container. Inverter control signal C for switching the inverter (INV) of section 20
A control unit 5 that outputs S1 and outputs a switch control signal CS2 for controlling on / off of a switch SW of the heating unit 20, and an inverter control signal CS1 of the control unit 5
An inverter driving unit 6 that outputs an inverter driving signal DS1 to an inverter (INV) of the heating unit 20;
A switch driving unit 80 that outputs a switching drive signal DS2 to the switch SW of the heating unit 20 according to the switch control signal CS2 of the control unit 5.

The first current detecting section 4 includes a first current transformer CT1 for detecting a current of the common power supply AC applied to the rectifying / smoothing section 1, and a common power supply detected from the first current transformer CT1. A first current / voltage conversion unit 41 that converts an AC current into an AC voltage; a first rectification / smoothing unit 42 that rectifies and smoothes the converted AC voltage; and divides the rectified and smoothed voltage to divide it. And a first partial pressure section 43 for supplying the control section 5.

The current detecting section 70 is connected between the intermediate terminal M of the inverter (INV) of the heating section 20 and the working coil L2.
Current transformer CT2 for detecting a high-frequency current flowing through
A second current / voltage converter 71 that converts a high-frequency current detected from the second current transformer CT2 into an AC voltage;
A second rectifying / smoothing unit 72 for rectifying and smoothing the converted AC voltage; and a second voltage dividing unit 73 for dividing the rectified and smoothed voltage and supplying the divided voltage to the control unit 5. ing.

FIG. 2 shows the operation of the apparatus for judging the type of the object to be heated in the induction heating cooker according to the present invention thus constructed.
This will be described with reference to FIG. First, when the object to be heated 3 is placed on the working coil L and the user presses a start key (not shown), a normal power supply AC is supplied to the induction heating cooker and the control unit 5 transmits a switch control signal. CS2 is output to the switch drive unit 80, and the switch drive unit 80 outputs the switching drive signal DS2 to the switch S of the heating unit 20.
Output to W In this case, the state in which the switch SW is turned on is referred to as "magnetic mode", and the state in which the switch SW is turned off is referred to as "non-magnetic mode". The following table is shown.

[0017]

[Table 1]

As can be seen from the above table, the elements involved in heating the object 3 in the magnetic mode are the working coil L2 and the two capacitors C2 and C3. Next, the control unit 5 outputs the inverter control signal CS1 to the inverter driving unit 6, and the inverter driving unit 6 outputs the inverter driving signal DS1 to the inverter (INV) of the heating unit 20.

Here, the inverter control signal CS1
Is a control signal for determining whether or not the object to be heated 3 is a small object load. The frequency of the heating unit 20 generated by the control signal CS1 is between the resonance frequency of the magnetic mode and the resonance frequency of the non-magnetic mode. In the present invention, when the resonance frequency of the magnetic mode is 30 kHz and the resonance frequency of the non-magnetic mode is 80 kHz, the frequency of the heating unit 20 is determined to be 50 kHz, and the frequency of 50 kHz is determined as the “determination frequency. ".

Next, the inverter (INV) is switched by the inverter drive signal DS1 to heat the object 3 mounted on the working coil L2, and the high-frequency current flowing through the working coil L2 is detected by a second current detection. The current of the commercial power supply AC is detected from the second current transformer CT2 of the first current detector 4 at the same time as the current of the service power supply AC is detected from the second current transformer CT2 of the section 70.

The current detected from the first current transformer CT1 of the first current detector 4 is converted to an AC voltage by a first current / voltage converter 41, and the first rectifier / smoothing unit 42
And a plurality of resistors R of the first voltage dividing section 43.
The voltage is divided (Va) by R3, R4, and R5 and input to the control unit 5. In addition, the second current detector 70
The high-frequency current detected from the current transformer CT2 is
The voltage is converted into an AC voltage by the current / voltage converter 71, rectified and smoothed by the second rectifier / smoothing unit 72, divided by a plurality of resistors R7 and R8 of the second voltage divider 72, and divided (Vb). Input to the unit 5.

FIG. 2 is a table showing the voltage values input to the control unit 5 according to the type of the object to be heated and the size of the object to be heated used in the present invention. The type and size in the table are as follows. This is an experimental value when a heated object is heated. That is, the type of the object to be heated is a ferromagnetic vessel (ferro magnetic vessel).
ssel) and non-ferro magnetic vesse
l) magnetic container and triple bottom container (three plybottom ve
ssel), and the size of the object to be heated is divided into 7cm, 8cm and 9cm in diameter of the bottom of each container, and the object to be heated whose diameter of each container is 8cm or less is small. Judge.

As shown in FIG. 2, when the ferromagnetic container has a voltage (Va) of about 1.2 (V) or more and a voltage (Vb) of about 0.75 (V) or more, In the case of a heavy bottom container, the voltage (Va) is about 1.2 (V) or more,
b) is about 1.8 (V) or more, and in the case of a non-ferromagnetic container, the voltage (Va) is about 1.45 (V) or more and the voltage (Vb) is about 2.1 (V) or more. When the diameter of the bottom of each container is 8
It is judged that it is cm or more.

Accordingly, the ferromagnetic container and the triple bottom container have a voltage (Va) of 1.2
(V), and the non-ferromagnetic container sets the voltage (Vb) to 1.8.
(V). When the reference voltage is not reached, the object to be heated is determined to be a small object. After the small object is determined, the type of the container is determined by the voltage (Vb). As described above, the control unit 5 determines the type of the object to be heated based on the input voltage values (Va) and (Vb) based on the reference voltage values in FIG. 2, and the process will be described with reference to FIG. Then it is as follows.

FIG. 3 is a flowchart showing a process of determining the type of the object to be heated in the induction heating cooker according to the present invention. First, when the user presses the start key to start the operation of the apparatus of the present invention (S1), the control unit 5 selects a "judgment frequency" (S2), and the heating unit 2 is selected based on the judgment frequency.
0 to output a switch control signal CS2.

Next, the current of the commercial power supply AC is detected,
When the corresponding voltage (Va) is input to the control unit 5, after reading the voltage value (Va) (S4), the control unit 5 checks whether the voltage value (Va) is 1.2 (V) or more. Is determined (S5), and if it is smaller than 1.2 (V), the object to be heated 3 is determined to be a small object load (S14), the drive of the inverter (INV) is stopped, and the operation of the apparatus according to the present invention is performed. Interrupt.
On the other hand, when the voltage value (Va) is not more than 1.2 (V),
If it is not smaller than 1.2 (V), it is determined as an error, and the voltage value (Va) is read again.

If the voltage value (Va) is 1.2 (V)
If so, the input voltage value (Vb) is read (S6), and it is determined whether or not the voltage value (Vb) is 1.8 (V) or more (S8). Vb) is 1.8
(V), the voltage value (Vb) becomes 0.75 again.
It is determined whether the temperature is within a range larger than (V) and smaller than 1.0 (V) (S10). If the temperature is outside the above range, the object to be heated 3 is determined to be a small object. It is determined that the heating object 3 is a ferromagnetic container (S13), the switch SW is kept on (S15), and the ferromagnetic container is heated in the magnetic mode.

The voltage value (Vb) is 1.8 (V).
If it is above (S8), the voltage value (Vb) is again 1.8.
It is determined whether the temperature is within a range larger than (V) and smaller than 2.1 (V) (S9).
It is determined that the container is a double bottom container (S12), a switching control signal CS2 for turning off the switch SW is output (S16), and the triple bottom container is heated in the non-magnetic mode.

If the voltage value (Vb) is 1.8 (V)
Outside the range of greater than 2.1 (V),
It is determined that the object to be heated 3 is a non-ferromagnetic container (S11),
The switch SW is kept on (S15), and the non-ferromagnetic container is heated in the magnetic mode.

[0030]

As described above, in the apparatus and method for judging the type of the object to be heated in the induction heating cooker according to the present invention, the object to be heated with the frequency fixed is a small object. In order to determine whether the object is a magnetic container or a non-magnetic container, it is possible to shorten the time for determining the type of the object to be heated.

Further, after judging the type of the object to be heated, the magnetic container and the non-magnetic container having different resistances, magnetic permeability and surface resistance are classified, and the object to be heated can be heated using an appropriate frequency. There is.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an apparatus for determining the type of an object to be heated in an induction heating cooker according to the present invention.

FIG. 2 is a table showing detection voltage values of types and sizes of objects to be heated used in the present invention.

FIG. 3 is a flowchart illustrating a method of determining a type of an object to be heated in the induction heating cooker according to the present invention.

FIG. 4 is a block diagram showing an apparatus for determining the type of a heated object in a conventional induction heating cooker.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rectification / smoothing part 20 ... Heating part 3 ... Heated object 4 ... 1st current detection part 5 ... Control part 6 ... Inverter drive part 70 ... Second current detection part 80 ... Switch drive part INV ... Inverters C1-C4 ... Capacitors L1 to L3 Working coil CT1 First current transformer CT2 Second current transformer

Claims (9)

[Claims] 1. A rectifying / smoothing unit (1) for rectifying and smoothing a commercial power supply (AC), an inverter (INV), a capacitor, working coils (L2, L3), and a switch (SW). The connection between the working coil and the capacitor is changed by the drive signal (DS2) to selectively heat the object to be heated (3), and a normal power supply (AC) applied to the rectifying / smoothing unit (1). ), A first current detector (4) for converting the current into a voltage (Va), and a current flowing through a working coil (L2) of the heating unit (20). Second to convert to (Vb)
A current detector (70); a voltage (Va) output from the first current detector (4); and a voltage (Vb) output from the second current detector (70).
Is received, the voltage (Va, Vb) is compared with a preset reference voltage value, and the object to be heated by the working coil of the heating unit is a small object or a magnetic container, A control unit (5) that determines whether the container is a non-magnetic container and outputs a control command to the heating unit (20); and an inverter (INV) of the heating unit (20) according to the control command of the control unit (5). An inverter drive section (6) for outputting an inverter drive signal (DS1) for driving the motor; and the heating section (20) according to a control command of the control section (5).
And a switch drive unit (80) for outputting a switching drive signal (DS2) to the induction heating cooker. 2. The heating unit (20) includes a normal power supply (A) rectified and smoothed by an inverter drive signal (DS1).
C) an inverter (INV) for switching a voltage;
Two capacitors (C2, C2) connected in series between an upper terminal (H) and a lower terminal (L) of the inverter (INV).
C3) and an intermediate terminal (M) of the inverter (INV).
And the working coil (L2, L3) and the capacitor (C4) connected in series between the connection points of the capacitors (C2, C3), and the switch () connected in parallel to the working coil (L3) and the capacitor (C4). S
2. The apparatus for judging the type of an object to be heated of the induction heating cooker according to claim 1, wherein the apparatus comprises: W). 3. The reference value set by the controller (5) is a voltage value obtained by conducting an experiment in advance based on the size of the bottom surface of the container to be heated. 1
An apparatus for judging the type of an object to be heated in the induction heating cooker according to Item 1. The controller (5) sends a switch control signal (CS2) for turning on a switch (SW) when determining that the object to be heated is a magnetic container, to the switch driver (8).
0), and when it is determined that the object to be heated is a non-magnetic container, the switch control signal (CS
The apparatus for determining the type of the object to be heated of the induction heating cooker according to claim 2, wherein 2) is output to the switch driving unit (80). 5. The object to be heated by the induction heating cooker according to claim 4, wherein the magnetic container is a ferromagnetic container and a non-ferromagnetic container, and the non-magnetic container is a triple bottom container. Device to determine the type of 6. A first step of heating an object to be heated at a small object judging frequency, detecting an input current of an alternating current power supply (AC), reading a voltage proportional to the magnitude of the current, and reading the voltage.
A second step of detecting a current applied to the working coil (L2) and reading a voltage proportional to the magnitude of the current, and comparing the two voltages read in the second step with a preset reference value, respectively. And a third step of determining whether the object to be heated is a small object or a magnetic container and a non-magnetic container. If it is determined that the object to be heated is a small object, all operations are stopped to stop the operation. And heating the heating object is stopped, and when it is determined that the object to be heated is a magnetic container and a non-magnetic container, a fourth step of changing the connection of the heating unit is sequentially performed. A method to determine the type of object to be heated by the machine. 7. The small object judgment frequency in the first stage is higher than a resonance frequency for heating the magnetic container and lower than a resonance frequency for heating the non-magnetic container. Item 7. A method for judging the type of an object to be heated in the induction heating cooker according to Item 6. 8. The method according to claim 6, wherein the preset reference value in the third step is a voltage value obtained by conducting an experiment in advance based on the size of the bottom surface of the container of the object to be heated.
3. The method for judging the type of an object to be heated of the induction heating cooker according to item 1. 9. The object to be heated in the magnetic mode is a ferromagnetic container and a non-ferromagnetic container, and the object to be heated in the non-magnetic mode is a triple bottom container. 3. The method for judging the type of an object to be heated of the induction heating cooker according to item 1.