JPS6261289A - Induction heating cooking device - 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 This invention relates to an induction cooking device (hereinafter referred to as an electromagnetic cooking device) that applies electromagnetic induction technology.

Conventional technology In order to best connect the conventional induction cooker with the pot, the bottom diameter of the most commonly used pot (approximately 15 m to 22 cm)
) The outer diameter of the heating coil was selected to match.

Problems to be Solved by the Invention However, in the conventional configuration, if the heating coil has a diameter smaller than the diameter of the bottom of the pot, the electrical coupling will not change, but only the area outside the heating coil will be heated, resulting in uneven temperature at the bottom of the pot.
It is inconvenient for cooking.

However, on the other hand, there are some types of cooking, such as teppanyaki, that require a large heating area, making it difficult to obtain appropriate performance for a variety of cooking menus.

Against this background, pots for induction cooktops 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. Not at all.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide an induction heating cooker that can switch the heating area.

Means for Solving the Problems The technical means of the present invention for solving the above-mentioned problems is to arrange a plurality of heating coils and provide a changeover switch for the heating coils. The system selectively operates the heating coil of the heating coil, and switches to drive the large-diameter heating coil or both heating coils at the bottom of a large pot.By shielding the inductive coupling between both heating coils, the inactive coil The purpose is to reduce the induced voltage generated between the terminals of the switch and relax the rating of the changeover switch.5. Function The function of this technical means is as follows.

That is, when only a single heating coil is selectively connected by the switch means, the heating operation is performed in the same manner as before, and the heating is efficiently combined with the diameter of the pot bottom, allowing use with maximum efficiency and minimum temperature unevenness.

The selector switch needs to have a rating for the current flowing through the heating coil, but since there is a shield between the two heating coils and no electromagnetic inductive coupling occurs, the voltage at the resting coil terminal is low, so a small voltage rating is sufficient. .

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

In FIG. 1, a filter circuit consisting of a capacitor 3.6 and a choke coil 4 is connected to the DC output terminal of the rectifier 2 connected to the AC power supply 1.
A heating coil 6a is provided at both ends of the heating coil 6a.

6b and resonant circuit of resonant capacitor 7 and diodes 8 and 3
An anti-parallel circuit of an I transistor 9, which is a 1' conductor switching element, is connected to perform high frequency operation.

Switch to row 1b for heating coil 6a with a large outer diameter.

When the switch 10 is connected and the switch 1o is closed, the two heating coils 6a and 6b are driven simultaneously by the transistor 9. 2 when switch 1° is closed
While the two heating coils 6a and 6b are driven simultaneously, when the switch 1° is opened, only the heating coil 6b, which has a smaller outer diameter, is driven, and the effective area to be heated can be changed. The human power comparison means 5Q includes a current transformer 11 for detecting the input terminal, a shunt resistor 12 thereof, and a diode 1.
3, a smoothing capacitor 14, and a discharge resistor 15 to convert the current-to-voltage detected voltage to the voltage dividing resistor 16, 17'T:2 and the reference voltage.An operational amplifier 18 increases the error by 5×2 [1] The configuration is such that voltage-to-current conversion is performed by an emitter follower of an NPN transistor 19 and an emitter resistor 20 connected to the output terminal, and a control signal is output to an oscillation circuit 25 at the next stage.

The variable frequency oscillation circuit 25 includes a voltage comparator 30, a timer capacitor 29, a charging resistor 28, a discharging resistor 31,
Resistors 26, 27° 33 that generate the reference voltage, and two diodes 32.3 that separate the reference voltage circuit and the timer circuit.
A relaxation oscillator circuit consisting of 4, a resistor 35, 36° 37 connected to its output terminal, and a switching transistor 3
8, the pulse amplification circuit is supplied to the base terminal of transistor 9 as a drive signal.

Here, the input comparison means 50 using the operational amplifier 18 and the oscillation circuit 25 applying the voltage comparator 30 are both commonly used and well-known circuits, so a detailed operation explanation will be omitted, but the basic To summarize only the operation, current transformer 11
Compare the detected input current with the set value, and if the input current is greater than the reference value - ! - The collector current of the transistor 19 rises in accordance with the error amount, bypassing the current from the voltage dividing resistors 26 and 27 that determine the oscillation cycle in the oscillation circuit 26 and shortening the cycle, so the conduction time of the transistor 9 is shortened and the heating coil 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 oscillation frequency is operated to match the reference value. In this way, the heating coil 6
It is possible to automatically track the frequency so that it becomes the input set for switching between a and 6b. In the embodiment, the input comparison means using an arithmetic amplifier rlJ circuit and a relaxation oscillation circuit using a voltage comparator have been explained, but the same effect can be obtained with other technical means such as a differential amplifier rj] circuit or a multi-pipe rake circuit. can. Further, although the current transformer is used as the input power detection means in this embodiment, it is also possible to detect the terminal voltage or current value of the transistor 9 as long as there is a correlation with the input power.

7 bae.

Now, assuming that the heating coil 6b has a smaller outer diameter, an annular shield link 90 is disposed around its outer periphery to prevent electromagnetic induction to the heating coil 6a.

Therefore, even if the switch 10 is open, no induced voltage is generated between the terminals of the heating coil 6a, and a large withstand voltage (approximately 1 kV or more) is not required between the contacts of the switch 10.

FIG. 2 shows a shield link 90 and two heating coils 6a,
An example of the arrangement of eb is shown. The heating coil support plate 91 is made of a non-metallic heat-resistant material, on which two heating coils 6a and 6b having different outer diameters are arranged approximately concentrically, and the two heating coils 6a and 6b are arranged approximately concentrically. A shield ring 90 made of metal such as aluminum or copper is arranged between them. With this arrangement, the magnetic field generated by the inner heating coil 6b will not leak to the outside of the ring 9o due to the annular current induced in the shield link 90. No induced voltage is generated. In the above embodiments, concentric coils have been described, but the effect is the same even with square heating coils and shield members, and the same transistor 9 as the eccentric component. Capacitor 3゜5.7, choke coil 4, rectifier 2, 8
and a frequency conversion circuit 100 consisting of a control circuit 4o,
The second frequency conversion circuit 101 connected to the commercial power supply 1 drives the heating coils 6b and 6a, respectively.
). Here, it is assumed that the changeover switch 1° is connected in series to the heating coil 6a. In this example, 2
one heating coil 6a.

6b are connected to different frequency conversion circuits and therefore have different phases and frequencies, but are electromagnetically separated by the shield ring 90, so both heating coils can be driven without mutual interference. I can do it. Therefore, even when applying a large input to a large heated area, the input can be shared among multiple frequency converters, and safe operation can be achieved. In addition, Figures 4 and 5
Go to figure 9 - Two circular or square heating coils ea as shown.
, sb may be provided eccentrically.

Effects of the Invention In the present invention, since a shield member is disposed between a plurality of heating coils, mutual interference and electromagnetic induction coupling between the heating coils can be prevented, and as a result, the following effects are achieved. It is something.

(1) Since there is no mutual interference between the heating coils, the operation is stable, even though the operating state of the heating coil, such as the operating frequency, is affected by the operation of other coils.

(2) The induced voltage applied to the switching means for switching the connection of the heating coil can be reduced.

(3) Since there is no mutual interference between a plurality of heating coils, if each heating coil is driven by a separate frequency conversion circuit, a large amount of power can be applied to a large area, and the power density does not change.

(4) It becomes possible to safely change the heating area, and it becomes possible to use various pots in the most appropriate condition.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an induction heating cooker according to an embodiment of the present invention, FIG. 2 is a structural diagram showing the configuration of a shield member, and FIG.
The figure is a circuit diagram of an induction heating cooker according to another embodiment of the present invention, and FIGS. 4 and 6 are external perspective views of two eccentric heating coils, 36a, 6b... heating coils. , 9. Transistor, 1°-・Selector switch, 90
-...- Shield Link. Name of agent: Patent attorney Toshio Nakao and 1 other person/θ
0- Round table change narrowing 4 /θ7---O2 round J Ne U1 change again Fig. 3 Fig. 4

Claims (1)

[Claims] A plurality of heating coils each including a first heating coil having a small outer diameter and a second heating coil having a large outer diameter, a switching means for exciting the heating coil, and a connection between the heating coil and the switching means. An induction heating cooker comprising a switch means for switching, the first heating coil being disposed inside the outer periphery of the second heating coil, and having a shield means between the two heating coils.