JPH03238784A - induction heating cooker - Google Patents

Abstract

PURPOSE:To make a temperature distribution on the bottom of a pan uniform by periodically switching a switch portion of each terminal of a heating coil by a control means. CONSTITUTION:A heating coil 1 is provided with a plurality of intermediate taps 12, 13, while a switching means 17 for periodically and sequentially switching the taps 12, 13 provided on the heating coil 1 is provided so as to sequentially switch the desired taps 12, 13 of the heating coil 1. Thus a distribution of a high frequency magnetic field can be periodically changed so that a temperature distribution of an entire pan bottom can be uniform and constantly stable thermal power can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an induction cooking device using electromagnetic induction heating.

BACKGROUND OF THE INVENTION In recent years, induction cooking devices that utilize electromagnetic induction heating have become widely used, and demands for improved cooking performance have been increasing.

In recent years, induction heating cookers of this type have been equipped with a pot holder 22 on the upper surface of an outer casing 21, a pot 23 is placed on top of the casing 21, and an inverter circuit 24 supplies a high frequency current to a heating coil. 26, the resulting high-frequency magnetic field generates an eddy current in the pot 23, and the pot 23 is heated by the eddy current loss. As shown in FIG. 6, the heating coil 26 is often wound approximately evenly in a circular shape.

Problems to be Solved by the Invention In such a conventional induction heating cooker, the heating coil 25
As shown in Fig. 6, the high-frequency magnetic field distribution generated in the coil is concentrated in the center between the center and the end of the coil, and the heat generation at the bottom of the pot 23 corresponding to that position is also strong. occurs. Therefore.

Especially when cooking in a frying pan, uneven cooking occurred, and the cooking performance was not satisfactory. The present invention is intended to solve the above-mentioned problems, and aims to make the temperature distribution at the bottom of the pot uniform and to always stabilize the heating power.

Means for Solving the Problems In order to achieve the above object, the present invention provides a heating coil with a plurality of intermediate taps, and a switching means for periodically and sequentially switching the taps provided on the heating coil. It is used as a solution.

Effect of the Invention The present invention uses the above-mentioned problem-solving means to change the high-frequency magnetic field distribution generated from the heating coil in sequence by sequentially switching arbitrary taps of the heating coil, thereby adjusting the strength or weakness of the amount of heat generated at the bottom of the pot. You can evenly distribute the temperature across the bottom of the pot.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 3.

In FIG. 1, an inverter circuit 2 that supplies high-frequency current to a heating coil 1 includes semiconductor switching elements 3. Flywheel diode 4. Resonant capacitor 6, high frequency pipe capacitor 6, high frequency block check coil 7, and commercial power supply 8 are connected to the starting terminal 1o and the winding end terminal 11.
and intermediate tap terminals 12 and 13 are provided. The intermediate tap terminals 12 and 13 are arranged so that when any taps are short-circuited, the inductance is approximately the same in any combination. The contact device 14 is the heating coil 1
Of the both end terminals 10.11 and the intermediate tap terminal 12.13, any one of the terminals 10.12, 12.13, or 11 and 13 is sequentially short-circuited. The control circuit 15 supplies a timing means 16 for supplying ON/OFF signals to the semiconductor switching element 3 and a signal for periodically short-circuiting each terminal in the contact device 12 to the contact device 1.
4.

To explain the operation in the above configuration, the timing means 16 of the control circuit 15 supplies on/off signals to the semiconductor inverting element 3 to operate the inverter circuit 2,
A high frequency current is supplied to the heating coil 1, and the heating coil 1 generates a high frequency magnetic field.

A pot (not shown) is heated by induction. At this time, the switching means 17 sequentially switches each contact of the contact device 14, and periodically switches the heating coil 1 to the connection shown in FIG. 3(a), Φ)t(C). Figure 3(a) shows the case where the terminals 10 and 12 of the heating coil 1 are short-circuited, and $
3 in the figure) is short-circuited between terminals 12 and 13.
Figure (C) shows a case where terminals 11 and 13 are short-circuited. In this case, by setting the inductance between the terminals 11 and 12 of the heating coil 1 to the same value in each case, stable operation can be obtained without changing the resonance frequency with the resonance capacitor 5. In this way, the current distribution flowing through the heating coil 1 can be changed, and the high frequency magnetic field distribution can be changed.

As described above, according to the induction heating cooker of the embodiment of the present invention,
By operating the contact device 14 in response to a signal from the switching means 17 and periodically switching the switching parts of each terminal of the heating coil 1, it is possible to change the high-frequency magnetic field distribution generated from the heating coil 1. The peak part of the heat generating part can be changed periodically.

The temperature distribution throughout the pothole area can be made uniform. In the above embodiment, each terminal is connected to each other, but it is also possible to switch between the terminals.

Effects of the Invention As is clear from the above embodiments, according to the present invention, the high frequency magnetic field distribution generated from the heating coil can be changed, and the peak part of the heat generating part generated at the bottom of the pot can be periodically varied. Therefore, it is possible to equalize the temperature distribution over the entire bottom of the pot, and at the same time, it is possible to always obtain stable heating power, thereby providing an induction heating cooker suitable for frying pan cooking.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an induction heating cooker according to an embodiment of the present invention;
Figures 2 (a) and (b) are a plan view and longitudinal sectional view of the same heating coil, respectively, Figures 3 (a), (b), and (C) are terminal connection diagrams of the same heating coil, respectively, and Figure 4 is a conventional FIG. 5 is a plan view of the heating coil of the conventional induction heating cooker, and FIG. 6 is a high-frequency magnetic field strength distribution diagram of the heating coil. 1°゛°゛°° heating coil, 2... inverter circuit, 3... semiconductor switching element, 10.
... Winding start terminal, 11 ... Winding end terminal, 12 ... Middle tag terminal, 13 ......
・Intermediate tap terminal, 16... Control circuit, 17.
...Switching means.

Claims (1)

[Claims] an inverter circuit that supplies high-frequency current to the heating coil;
The semiconductor switching element of the inverter circuit is turned on,
The heating coil is wound into a flat plate and has a plurality of intermediate taps in the middle thereof, and the control circuit controls each terminal of the intermediate tap of the heating coil and the winding start and winding end. An induction heating cooker comprising a switching means for switching any one of the terminals of the heating coil, wherein the control means periodically switches a switching part of each terminal of the heating coil.