JPS5826626B2 - Yuudou Kanetsuchiyoriki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an induction heating cooker that utilizes induction heating, and particularly to a temperature control device for the pot.

In addition to conventional induction heating cookers, when there is an abnormality, when the cabinet is closed, when the pot is not placed on the cooker, or when a pot that is unsuitable for use is placed, and even when the temperature of the pot is low. In situations such as when the temperature of the pot became abnormally high, the protection device was activated and the heating current was cut off, but the temperature of the pot could not be controlled.

The present invention adds a pot temperature control function to the conventional function, and uses the fact that the impedance of the induction heating excitation winding, which also serves as temperature detection, changes depending on the pot temperature.

First, a temperature detection method of a temperature sensor of a conventional commercial frequency type induction heating cooker will be described.

FIG. 1 is a sectional view showing the structure of the induction heating cooker, in which 1 is a pot, 2 is a support leg, 3 is a top plate made of a non-magnetic material with low electrical conductivity, and 4 is a top plate made of a non-magnetic material with low electrical conductivity. 5 is a main excitation winding, 6 is a yoke, and 7 is a box.

Moreover, FIG. 2 shows an equivalent circuit of the excitation winding 5 of the induction heating cooker, and in this FIG. includes a capacitor, and for the circuit current of equivalent circuit 11, 9
This is a special price circuit of an excitation winding 5 in which a current with an advanced phase of 00 flows.

Furthermore, 13 is an equivalent representation of the leakage inductance L1 of the excitation winding 5 that does not include a capacitor, and 1
4 equivalently represents the DC resistance R1.

In addition, 15 equivalently represents the inductance L2 of the pot, and 16 equivalently represents the Joule loss caused by the eddy current as resistance R2.

These leakage inductance L1, DC resistance R1, inductance L2, and resistance R2 are connected in series.

On the other hand, in the equivalent circuit 12, 17 is the leakage inductance L3 of the main excitation winding 5 of the circuit including the capacitor, 18 is its DC resistance R3, and 19 is the inductance L4 of the pot 1.
, 20 is an equivalent representation of the resistance R4 due to Joule loss caused by the eddy current, and 21 is the capacitor C inserted into the equivalent circuit 12.
It is 1.

Long ago, when the temperature of the pan 1 in FIG. 1 rose, the inductance 15.19 in FIG. 2 increased and the resistance 16.20 also increased.

On the other hand, the relationship between the terminal voltage of capacitor 21 and the temperature of steel 1 is shown in Figure 3 [the horizontal axis shows the temperature of pot 1, and the vertical axis shows the temperature of capacitor 2
The terminal voltage of 1 is taken and shown.

].

As is clear from FIG. 3, when the temperature of the pot 1 rises, the terminal voltage of the capacitor 21 also rises.

Also, the relationship between the current I of the equinodal circuit 11 and the temperature of the pot 1 is the fourth
Figure [The horizontal axis shows the temperature of the pot 1, and the vertical axis shows the current of the equinodal circuit 11.

].

It can be seen from FIG. 4 that as the temperature of the pot 1 rises, the current in the equinodal circuit 11 decreases.

It has been conventionally known that by using these relationships, it is possible to protect the upper plate 3, magnetic pole 4, excitation winding 5, etc. in FIG. 1 when the temperature of the pot 1 becomes abnormally high.

Here, a method of detecting the current of the isotonic circuit 11 and the voltage of C121 of the isotonic circuit 12 corresponding to the temperature of the pot 1 will be specifically described.

As a means of detecting the current of the above-mentioned equinodal circuit, a method of inserting a current detection inductor 66 in series as shown in FIG. 5 and detecting the terminal voltage with a voltmeter 70, and a method as shown in FIG. Alternatively, there is a method of inserting a low current detection resistor 67 in series and detecting the terminal voltage with a voltmeter 70.

FIG. 7 shows a method of detecting the terminal voltage of the capacitor C121 of the equinodal circuit 12 using the voltmeter 70.

Furthermore, in FIG. 8, in order to increase the detection sensitivity when detecting the terminal voltage of the capacitor C121 of the equinodal circuit 12 shown in FIG. Inductance L522, resistor R523, capacitor C with the same ratio as the ratio
This figure shows a bridge configured using a simulated circuit 25 consisting of 224 circuits, which is detected by a voltmeter 10.

Therefore, it is possible to control the temperature using these detection methods.

The present invention specifically proposes this.

Next, as an embodiment of the present invention, an induction heating cooker equipped with a temperature control device for the pot 1 constructed using the above-described temperature control circuit 11 will be described.

FIG. 9 is a block diagram of an embodiment of an induction heating cooker equipped with a pot temperature control device according to the present invention.

In FIG. 9, 50 is a main switch, 51 is a temperature detection voltage changeover switch, 52 is an excitation voltage changeover switch, 53 is a comparison voltage generator, 54 is a comparison voltage changeover switch, 55 is a step-down transformer, and 56 is a temperature detection switch. 57 is a comparator; 5 is a temperature detection voltage generator that detects a current change in accordance with an impedance change due to a temperature change in the excitation winding 5 for induction heating;
8 is a switch changeover drive circuit, and 5 is an excitation winding for induction heating which also serves as temperature detection.

1. When the main switch 50 is turned on, the step-down transformer 55
A low voltage is generated on the secondary side of the

At this time, the switches 51, 52, and 54 are both turned to the low voltage side.

The secondary voltage of the step-down transformer 55 is not large enough to heat the pot 1, and when this low voltage is applied, it is detected whether the temperature of the pot 1 is lower than the set minimum temperature by the impedance change of the winding described earlier. do.

First, the impedance change of the excitation winding 5 is extracted by the temperature detection voltage generator 56, and compared by the comparator 57 with the set lower limit value output from the comparison voltage generator 53 when a low voltage is applied.

Therefore, if the temperature of the pot 1 is lower than the set lower limit temperature, the switches 51, 52 and 54 are both switched to the high pressure side.

As a result, a high voltage is applied to the excitation winding 5, so that the pot 1 is heated.

When high voltage is applied, if the temperature of the pan 1 exceeds the set upper limit temperature, and if the temperature detection voltage output from the temperature detection voltage generator 56 exceeds the set upper limit value output from the housing comparison voltage generator 53, Again, switches 51, 52 and 53 are switched,
A low voltage is applied and heating is interrupted.

The subsequent operations repeat the operations described above.

FIG. 10 shows an example of a circuit diagram created according to the block diagram of FIG. 9.

However, the phase advance capacitor 66 21 is a current detection inductor that outputs a current change according to an impedance change due to a temperature change of the induction heating excitation winding 5 as a voltage change.

The operation is as described in FIG.

It should be noted that, in actual configuration, the detected voltage is affected by fluctuations in the power supply voltage.

The detected voltage also changes due to a change in the winding resistance due to a rise in the temperature of the winding.

Therefore, it is necessary to change the comparison voltage in response to changes in these detection voltages.

FIG. 11 shows a specific example of compensating for this power supply voltage fluctuation and winding temperature rise.

That is, in FIG. 11, 60 is a power supply voltage proportional DC voltage changeover switch, 61 is a winding temperature detection voltage changeover switch, 62 is a power supply voltage proportional voltage generator, 64 is a power supply proportional voltage rectifier, and 65 is a servo star, etc. This is a temperature-sensitive element whose resistance changes depending on the winding temperature.

Therefore, the power supply proportional voltage rectifier 64 compensates for power supply voltage fluctuations.
, is mainly achieved by the power supply voltage proportional voltage generator 62,
To compensate for the winding temperature rise, a winding temperature detection voltage generator 63,
This is mainly performed by the temperature sensing element 65.

As described above, according to the present invention, the excitation winding for induction heating is also used for temperature detection, so it is possible to easily adjust the temperature of the pot without causing a significant increase in cost. The effect can be with dogs.

In addition, the temperature control method described here is 0N-OF.
In addition to F control, a method of controlling the voltage applied to the excitation winding,
Alternatively, a method of controlling the phase angle of the excitation current flowing through the excitation winding may be considered, but neither of these methods is beyond the scope of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of the induction heating cooker, FIG. 2 is an equivalent circuit diagram of the excitation winding of the induction heating cooker, and FIG.
The figure is a characteristic diagram showing the relationship between the terminal voltage of the capacitor and the temperature of the copper in an induction heating cooker. Figure 4 is the relationship between the temperature of the current pair of the main excitation winding without a capacitor in Figure 2. 5 is a schematic circuit diagram showing a method of inserting a current detection inductor L666 in series and detecting the current of the other circuit 11 as its terminal voltage, and FIG. 6 is a characteristic diagram showing the other circuit 11. A schematic circuit diagram showing a method of detecting the current of the circuit 11 as the terminal voltage by inserting a current detection low resistance 67 in series, and FIG. 7 shows a method of detecting the terminal voltage of the capacitor C1 of the other circuit 12. 8 is a schematic circuit diagram showing an improved method of increasing the detection sensitivity of the method shown in FIG. 7. FIG. 9 is a schematic circuit diagram showing a method for controlling the temperature of a pot according to an embodiment of the present invention. Block diagram of an induction cooker with the device,
FIG. 10 is a specific circuit diagram thereof, and FIG. 11 is a circuit diagram showing another embodiment of the present invention. In the figure, 1 is a pot, 2 is a support leg, 3 is an upper plate, 4 is a magnetic pole, 5 is a main excitation winding, 6 is a yoke, 7 is a box body, and 11 is an old main excitation winding including a capacitor. 900 for the current of other circuits such as 5 and 12 including capacitors and other circuits 11.
Main excitation winding 5 through which a phase-advanced current flows
13 is the main excitation winding 5 which does not include a capacitor.
The equivalent leakage inductance L1.14 is its equivalent flow resistance R1, 15 is the equivalent inductance of the pot L2.16 is the equivalent resistance R of the Joule loss component caused by the eddy current.
2,17 is the equivalent leakage inductance L3 of the excitation winding of the circuit including the capacitor.18 is its equivalent current resistance R3,1
9 is the equivalent inductance L4 of the pot 1, 20 is the equivalent resistance R4 due to Joule loss caused by the eddy current, 21 is the phase advancing capacitor, 22, 23, 24 are the inductance L5 and resistance R in the simulated circuit of the other circuit 12, respectively.
5, capacitances C2 and 25 are simulation circuits of other circuits 12, 50 is a main switch, 51 is a temperature detection voltage changeover switch, 52 is an excitation voltage changeover switch, 53 is a comparison voltage generator, 54 is a comparison voltage changeover switch, 55 is a step-down transformer, 56 is a temperature detection voltage generator, 57 is a comparator, 58 is a switch changeover drive circuit, 59 is an excitation winding, 60 is a power supply voltage proportional DC voltage changeover switch, 61 is a winding temperature detection voltage changeover switch , 62 is a power supply voltage proportional voltage generator, 6
3 is a winding temperature detection voltage generator, 64 is a power supply proportional voltage rectifier, 65 is a temperature sensing element whose resistance changes depending on the winding temperature, such as a thermistor, 66 is a current detection inductor L6 of other circuits 11, 67 is an etc. This is the current detection resistor R6 of the other circuit 11. In addition, in the figures, the same numbers indicate the same or corresponding parts, respectively.

Claims (1)

[Claims] 1. An excitation winding for induction heating, which also serves as temperature detection, is placed at a predetermined distance from the metal pot that is the object to be measured;
When the temperature of the metal pot changes, the temperature of the metal pot is detected by the change in impedance of the excitation winding for induction heating, which also serves as temperature detection, and the temperature of the metal pot is controlled according to the detection result. An induction heating cooker characterized by: