JPS6243092A - Electromagnetic induction heating cooker - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electromagnetic induction cooking device using an electromagnetic induction method.

Conventional technology This type of electromagnetic induction heating cooker has been designed with the bottom diameter of the most commonly used pot (approximately 1
The outer diameter of the heating coil was selected to match the diameter of the heating coil (5 Cffl to 22 cm).

Problems to be Solved by the Invention However, with the conventional configuration, if the heating coil has a diameter smaller than the diameter of the pot bottom, the electrical coupling will not change, but since only the area of the heating coil will be heated, temperature unevenness will occur at the bottom of the pot. It was inconvenient for cooking. However, on the other hand, there are some types of cooking that require a large heating area, such as teppanyaki, and appropriate performance cannot be obtained for a variety of cooking menus. Against this background, pots for electromagnetic induction cooking devices such as clad pots made of aluminum or other materials have appeared in order to improve heat conduction, but the pots themselves are expensive and there is still no way to solve the problem. has not yet been reached.

Instead, it is conceivable to provide multiple heating coils and change the heating area by arbitrarily turning on and off these heating coils with a switch, but in this case, the inductance of the heating coil will increase due to switching of the switch. Because of the wide variation, the circuit operating state changed, and the input power fluctuated widely. As a result, even when multiple heating coils are driven, the input changes more widely than when a single coil is operated, making it impossible to prevent poor cooking due to insufficient input or overloading the power supply due to excessive input, which results in a small pot. It could not be used for a wide range of purposes, from small pots to large pots.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide an electromagnetic induction cooking device that can be used in a wide range of applications from small pots to large pots and can perform induction heating cooking.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to arrange a plurality of heating coils and provide a changeover switch for the heating coils. The operation of the switching element is controlled by comparison means that compares the input power with a reference value to prevent excessive input.

action The effect of this technical means is as follows.

That is, when only a single heating coil is selectively connected by the switch means, υB thermal operation is performed as before,
By efficiently combining heating with the pot bottom diameter, it can be used with maximum efficiency and minimum temperature unevenness. Next, when other heating coils are additionally connected by switching means, the inductance of the heating coil changes widely and the input fluctuates widely due to changes in the circuit operating state, so compare the input power with the reference value. The drive of the switching element is controlled according to the error. As a result, even when multiple heating coils are driven, there is no large change in input compared to when a single coil is operated, and it is possible to prevent poor cooking due to insufficient input or overload of the power supply due to excessive input. It can be used in a wide range of ways, from pots to large pots.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

In FIG. 1, a filter circuit consisting of capacitors 3 and 5 and a choke coil 4 is connected to the DC output terminal of a rectifier 2 connected to an AC power source 1.
There are heating coils 62L at both ends.

6b, a resonant capacitor 7m, a resonant circuit of 7b, a diode 8, and an antiparallel circuit of a transistor 9, which is a semiconductor switching element, are connected in series.

If a switch 1o is connected in parallel to the heating coil 6a and the switch 10 is open, then the two heating coils 6a and 6b are connected in series and excited by the transistor 9 at the same time; Heating coils 6a, 6
Since the total inductance of b is doubled, switch 1
By connecting the resonant capacitors 7a and 7b in series and reducing the number by about half, the change in the overall oscillation wave number is reduced. When the switch 1o is open, the two heating coils ea and sb are simultaneously driven, but when the switch 10 is closed, only the heating coil 6b is driven, and the effective area to be heated can be switched. The input comparison means 5o includes a current transformer 11 for detecting the input current, a shunt resistor 12 thereof, a diode 13, and a smoothing capacitor 14.
The detected voltage, which is current-voltage converted by the discharge resistor 16, is compared with the reference voltage determined by the voltage dividing resistors 16 and 17. The error is amplified by the operational amplifier 18, and the NPN transistor 19 and the -r i vine connected to the output terminal are amplified. The emitter follower of the resistor 20 performs voltage-to-current conversion, and outputs a control signal to the oscillation circuit 25 at the next stage.

The variable frequency excavation circuit 25 includes a voltage comparator 30° timer capacitor 29, its charging resistor 28 and discharging resistor 31,
Resistors 26, 27゜33 that generate a reference voltage, two diodes 32.3 that separate the reference voltage circuit and the timer circuit.
A relaxation oscillation circuit consisting of 4, a resistor 35, 36°3 connected to its output terminal, and a switching transistor 3
8, the pulse output of which is supplied to the base terminal of transistor 9 as a drive signal.

Here, the input comparison means 60 using the arithmetic intensifier 18 and the excavation circuit 25 applying the voltage comparator 3o are both commonly used and well-known circuits, so a detailed explanation of their operation will be omitted, but the basic To summarize only the operation, current transformer 11
The input current detected by is compared with the set value, and if the input current is larger than the reference value, the collector current of the transistor 19 increases according to the error amount, and the excavation circuit 25 determines the oscillation period by the voltage dividing resistor 28.27. Since the period is shortened by bypassing the current, the conduction time of the transistor 9 is shortened and the resonant frequency of the heating coil is shifted, so that the input current decreases and matches the reference value.

When the input current is lower than the reference value, the oscillation frequency is lowered by the opposite operation to the above, and the operation is made to match the reference value. In this way, the input comparison means 50 and the oscillation circuit 2
6, the heating coil ea
, 6b can be automatically tracked to match the input set for switching.

Although this embodiment has been described using an input comparison means using an operational amplifier and a relaxation excavation circuit using a voltage comparator, similar effects can be obtained using other technical means such as a differential amplifier circuit or a multivibrator.

1. Although a current transformer is used as a means for detecting input power, there is no problem in detecting the terminal voltage or current value of the transistor 9 as long as there is a correlation with the input power.

FIG. 2 shows another embodiment in which another heating coil is switched, in which a second heating coil 6a is connected in parallel to a constantly connected heating coil 8b via a switch 1o. Although the connection of the heating coil and the connection location of the shared camera capacitor 7 are different from the embodiment shown in FIG. 1, the operation is exactly the same. FIG. 3 shows another embodiment of the connection of the heating coil. N heating coils (sa, eb, ., 6N) are connected to N changeover switches (1oa, 10b, 6N) corresponding to the connection points of X and Y in Figure 2.

1ON), and the larger the number of N, the more widely the heating section can be controlled.

FIG. 4 is an external view of an electromagnetic induction cooking device to which this embodiment is applied, and corresponds to FIG. 1. A pattern corresponding to the two heating coils ea and sb is printed on the large top plate 53, and in the configuration shown in FIG.
If the heating coil 6a is also activated at the same time, a large heating area (indicated by a large oval in FIG. 4) can be obtained.

In addition, the heating output adjustment knob 62 in FIG. 4 is one regardless of the changeover switch 1o, and for example, the
By replacing 7 with a variable resistor and interlocking with knob 52, it is possible to set the desired output level.

Effects of the Invention The present invention can arbitrarily switch between a plurality of heating coils to arbitrarily select and set the portion/area to be heated, and has the following effects.

■Appropriate heating area can be selected for pots with various bottom diameters, so heating can always be done efficiently.

■Being able to change the heating area with the same amount of human power means being able to change the density of heating energy, making it possible to apply the rated input to even small-diameter containers, providing a power density that cannot be obtained with gas, etc. That is, small volumes (for example, heating a cup of water) can be heated extremely quickly.

■It is also possible to freely change the power consumption ratio between each heating coil (for example, by changing the coil diameter), and thereby it is also possible to freely provide a heat retention area and a heating area.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an electromagnetic induction cooking device according to an embodiment of the present invention, Fig. 2 is a circuit diagram showing another embodiment of the invention, and Fig. 3 is a circuit diagram showing another coil connection method. 4 are external perspective views of the electromagnetic induction cooking device of this embodiment. 6... Heating coil, 9... Transistor, 1°... Switch, 4o... Control device, 6o... Input comparison means,

Claims (1)

[Claims] It comprises a plurality of heating coils, a switch means for switching connections of these heating coils, and a switching element for exciting the heating coils, the switching element being controlled by the output of an input comparison means for comparing input power with a reference value. Electromagnetic induction heating cooker.