WO2017093174A1

WO2017093174A1 - An inductive coil unit

Info

Publication number: WO2017093174A1
Application number: PCT/EP2016/078977
Authority: WO
Inventors: Hilmi Volkan Demir; Emre UNAL; Erdal GONENDIK; Veli Tayfun KILIC; Namik Yilmaz; Metin OZTURK; Ulas OKTAY
Original assignee: Arcelik Anonim Sirketi; Innovel Danismanlik Ve Imalat Sanayi Ticaret Limited Sirketi
Priority date: 2015-12-01
Filing date: 2016-11-28
Publication date: 2017-06-08

Abstract

The present invention relates to an inductive coil unit (3) that is suitable to be used in the all-surface induction heating cookers comprising a top plate (4) whereon a cooking container suitable to be induction heated is placed, and comprising an inner coil (1) that has circular windings and an outer coil (2) that has quadrilateral windings, that surrounds the inner coil (1) concentrically, which together form a magnetic field on the surface thereof by being driven with alternative current of the same frequency.

Description

AN INDUCTIVE COIL UNIT

The present invention relates to an inductive coil unit suitable to be used in induction heating cookers.

In the state of the art, inductive coils used for wireless power transfer especially for induction heating are known. In these embodiments, power is created with the joule effect on the resistance produced as a result of the penetration depth determined by the frequency of the alternative currents of the electromagnetically inducted eddy currents of a coil generating high frequency magnetic field on a conductive metal cooking container (pot, pan etc.) having ferromagnetic features. The desired power adjustment for the suitable cooking container can be realized by changing the frequency of the alternative current. In order to use an induction heating cooker, the cooking container desired to be heated has to be electrically conductive and produced from low density carbon steel, cast iron and magnetic inoxidizable materials with ferromagnetic features. In the induction heating cookers, a certain number of coils are positioned under a glass surface so as to form the heating surface. There are a large number of embodiments in state of the art wherein the coils are positioned in various configurations. In these embodiments, one or more than one coil designed to be one within the other at the regions determined by serigraphy on the glass surface heats a single cooking container. One of the problems encountered in the state of the art is to form coil structures that accommodate best with the cooking container that are produced in very different diameters and shapes and from different materials.

Another problem with the state of the art induction heating cookers is the necessity to operate the high power and large diameter coils together with smaller diameter coils in the most efficient manner. Moreover, as the size of the cooking container increases, the power to be transferred to the cooking container also increases. For example, if the power desired to be transferred per the unit cooking container is increased, the number of coils has to be decreased but the size of the coil and the number of windings have to be increased. On the contrary, if the position and geometry of the cooking container is desired to be detected on the whole surface of the cooker, this time the number of coils should be increased but the dimensions have to be decreased. Increasing the number of coils and decreasing the dimensions result in not being able to transfer the desired power especially to small diameter cooking containers.

One of most important problems in the solutions developed relating to all-surface embodiments created by using more than one coil instead of a single coil, is to optimize the magnetic interaction, in other words the magnetic coupling between the coils. In the state of the art embodiments, coil solutions with generally circular or quadrilateral coils arranged side by side are used. Although the circular coils are suitable for small diameter cooking containers, only certain regions for example the periphery and the places close to the center can reach the desired temperature due to the “corona” effect and the cooking container cannot be heated homogeneously. Moreover, the desired power cannot be transferred to large diameter cooking containers since the magnetic coupling between the coils disposed side by side is low. The quadrilateral coils can be weaker than the circular coils in transferring energy to small diameter cooking containers.

In the state of the art United States Patent No. US6498325, the coils are connected in parallel or series and are driven as a group.

In the state of the art European Patent No. EP2048914, circular and oblong coils that are wound one within the other are explained.

The aim of the present invention is the realization of an inductive coil unit suitable to be used in the induction heating cookers, especially in the all-surface induction cookers.

In the inductive coil unit suitable to be used in induction heating cookers realized in order to attain the aim of the present invention, explicated in the first claim and the respective claims thereof, the inner coil of the inductive coil unit is wound in a circular manner and the outer coil in a quadrilateral manner. Thus, high power is transferred by the coils wound in different shapes and the power per coil decreases. Since the power per coil is decreased, the impedance of the inductive coil unit increases and since less current passes through the inductive coil unit, the number of windings, in other words the amount of conductive material decreases.

In another embodiment of the present invention, the inner and outer coils in the inductive coil unit are formed by winding a single wire. In this embodiment, the inner and outer coils are electrically connected in series and can be driven by a single power source.

In another embodiment of the present invention, the inner and outer coils in the inductive coil unit are driven by two separate power sources at the same phase.

In another embodiment of the present invention, the inner and outer coils are driven by two separate power sources with 180° electrical phase difference such that the applied current directions are opposite to one another.

In another embodiment of the present invention, the outer coil has quadrilateral windings of which the radii of curvature of the corners increase from the outside inwards.

In another embodiment of the present invention, one or more than one ferrite is disposed on one surface of the inductive coil unit.

In the inductive coil unit of the present invention, by using less material in the unit area, a larger number of windings are obtained, energy efficiency is increased and cost is decreased.

The inductive coil unit realized in order to attain the aim of the present invention is illustrated in the attached figures, where:

Figure 1 – is the schematic view of an inductive coil unit.

Figure 2 – is the schematic view of the inductive coil units situated on the top plate of the induction heating cooker together with the magnetic members.

Figure 3 – is the schematic view of an inductive coil unit having the outer coil with rounded corners.

Figure 4 – is the schematic view of an inductive coil unit of which the inner and outer coils are driven by separate power sources.

Figure 5 – is the schematic view of the inductive coil units situated on the top plate of an induction heating cooker having the outer coil with rounded corners.

Figure 6 - is the schematic view of an inductive coil unit of which the radii of curvature of the corners increase from the outside inwards.

Figure 7 - is the schematic view of an inductive coil unit and a magnetic member in an embodiment of the present invention.

The elements illustrated in the figures are numbered as follows or given letter references and the references are explained below:

Inner coil
Outer coil
Inductive coil unit
Top plate
Magnetic member

X, Y: Horizontal axes that determine the plane of the induction heating cooker top plate.

K: Power source

H: Distance between the opposite corners of two outer coils with rounded and quadrilateral sides disposed in a diagonal position.

The inductive coil unit (3) is suitable to be used in induction heating cookers especially in all-surface induction cookers comprising a top plate (4) whereon a cooking container suitable to be induction heated is placed, and comprises an inner coil (1) and an outer coil (2) that are arranged one within the other concentrically, that are produced from conductive material, preferably from copper wire or wires coated on the outside with non-conducting material and that form magnetic fields by being driven with an alternative current of the same frequency.

The inductive coil unit (3) of the present invention comprises the inner coil (1) that is disposed in the inner portion thereof and that has circular windings and the outer coil (2) that is disposed at the outer portion, that surrounds the inner coil (1) and that has quadrilateral, for example square windings (Figure 1).

When the inductive coil unit (3) of the present invention is drive with alternative current, the current passes through the inner coil (1) with circular windings and the outer coil (2) with quadrilateral windings and creates a magnetic field in the same frequency as the alternative current, thus providing power transfer. In the inductive coil unit (3), in the center portion of the quadrilateral outer coil (2), which does not contribute to the said power yield, the inner coil (1) with circular windings is disposed. By winding the inner coil (1) in a circular manner, ease of production is provided, the number of windings can be increased and cost advantage is maintained by using less material in the unit area. Furthermore, the circular inner coils (1) transfer power to the small diameter cooking containers placed on the induction heating cooker more efficiently than the outer coils (2) having entirely quadrilateral windings. In the inductive coil unit (3) of the present invention, the advantages of the quadrilateral outer coil (2) in magnetic coupling, power gain and defining the usage area limits clearly and the advantage of the circular inner coil (1), disposed within the outer coil (2), in transferring power to the small diameter cooking container efficiently are obtained.

In an embodiment of the present invention, the inner coil (1) and the outer coil (2) are produced by winding a single uninterrupted conductive wire. The inner coil (1) and the outer coil (2) are electrically connected to each other in series and are driven by a single power source (K) at the same phase.

In another embodiment of the present invention, the inner coil (1) and the outer coil (2) are driven by two separate power sources (K) at the same phase. In this embodiment, when for example 5000 Watt power is desired to be obtained from the inductive coil unit (3), instead of using one power source (K) providing 5000 Watt, two separate power sources (K) each 2500 Watt that supply the inner coil (1) and the outer coil (2) are used thus the current transmitting elements of the power source (K) are prevented from overheating and malfunctioning, thereby increasing its life span (Figure 4).

In another embodiment of the present invention, the inner coil (1) and outer coil (2) are driven by two separate power sources (K) with 180° electrical phase difference such that the applied current directions are opposite to one another. In this embodiment, the directions of the currents applied on the quadrilateral outer coil (2) and the circular inner coil (1) are opposite, and the magnetic coupling between the outer side of the inner coil (1) and the inner side of the outer coil (2) wherein the inner coil (1) is disposed shows strengthening effect on one another and maximum power is obtained from the inductive coil unit (3) (Figure 4).

In another embodiment of the present invention, apart from being in the same frequency, the inner coil (1) and the outer coil (2) are driven by separate power sources (K) electrically independently from one another.

In another embodiment of the present invention, in the inductive coil unit (3) the outer coil (2) has quadrilateral windings with rounded corners (Figure 3). While the outer coil (2) having the quadrilateral windings with rounded corners is produced, first the outer coil (2) is wound circularly than is compressed from four corners towards the center, thus providing the quadrilateral configuration with rounded corners. Since the opposite corners of the coils (3) disposed at diagonal positions with respect to each other on the top plate (4) of an induction heating cooker are rounded, the diagonal corners through which current passes preferably in the same direction and the same phase are moved away from each other a certain distance (H) and the diagonally positioned corners are prevented from adversely affecting each other (Figure 5).

In another embodiment of the present invention, the outer coil (2) has quadrilateral windings of which the corner roundness (corner radius of curvature) increases from the outside inwards (Figure 6). The roundness of the corners of the outermost winding in the second coil (2) is in the minimum value with respect to the dimensions thereof and has almost pointed corners. The roundness of the corners of the innermost winding in the second coil (2) is in the maximum value having almost a circular shape. Instead of winding the entire second coil (2) in a quadrilateral manner, winding circularly by increasing the radius of curvature together with the adjacent coils towards the center where positive power contribution is less, enables the coil (2) to be wound in a more compact manner and also less material is used than entirely quadrilateral windings. In this embodiment of the present invention, the point where power contribution ends with respect to the amplitude of current is calculated and if winding is necessary after that point, which this can be required depending on the desired power and the inductance value, the windings continue in a circular manner instead of quadrilateral. Accordingly, without sacrificing efficiency, cost is decreased by using less wire than a completely quadrilateral coil.

In another embodiment of the present invention, the inductive coil unit (3) comprises at least one magnetic member (5), for example ferrite, that is produced from ferromagnetic or ferromagnetic material and that enables the magnetic field to be directed towards the cooking container (Figure 2, Figure 7).

In another embodiment of the present invention, the inductive coil unit (3) comprises more than one, for example 8, bar-shaped magnetic members (5) that extend from the center of the circular inner coil (1) up to the outer sides and corners of the outer coil (2) in the radial direction and are arranged equidistantly all around on one surface thereof (Figure 2).

In another embodiment of the present invention, the inductive coil unit (3) comprises a magnetic member (5) that covers the entirety of one surface of the inner coil (1) and the outer coil (2), that has a hole at the center with the same size as the gap at the center of the circular inner coil (1), the outer side of the magnetic member (5) matching the contour of the outer coil (2) (Figure 7).

In the inductive coil unit (3) of the present invention, the magnetic coupling improving effect of the outer coil (2) having quadrilateral windings and the advantage of determining the lines of the cooking area more clearly for the user and the advantage of the inner coil (1) with circular windings transferring power especially to small diameter cooking containers with high efficiency with minimum amount of conductive wire are provided together and ease of production is provided.

The inductive coil units (3) arranged under the top plate (4) of the all-surface induction cooker provides that the cooking containers are heated on the entire surface of the induction cooker regardless of the dimensions of the heated cooking containers. By means of the inner coils (1) with circular windings, small diameter (for example 7 cm.) containers are enabled to be heated effectively and maximum power is transferred to the cooking containers with circular bases. By means of the high magnetic coupling between the outer coils (2) with quadrilateral windings, more power is obtained by the same current and the leakage magnetic fields that affect the user are minimized.

Claims

An inductive coil unit (3) that is suitable to be used in induction heating cookers especially in all-surface induction cookers comprising a top plate (4) whereon a cooking container suitable to be induction heated is placed, and comprises an inner coil (1) and an outer coil (2) that are arranged one within the other concentrically, that are produced from conductive wire or wires coated on the outside with non-conducting material and that form magnetic fields by being driven with an alternative current of the same frequency, characterized by the inner coil (1) that is disposed in the inner portion and that has circular windings and the outer coil (2) that is disposed at the outer portion, that surrounds the inner coil (1) and that has quadrilateral windings.
An inductive coil unit (3) as in Claim 1, characterized by the inner coil (1) and the outer coil (2) that are produced by winding a single uninterrupted conductive wire, that are electrically connected in series and driven by a single power source (K) at the same phase.
An inductive coil unit (3) as in Claim 1, characterized by the inner coil (1) and the outer coil (2) that are driven by two separate power sources (K) at the same phase.
An inductive coil unit (3) as in Claim 1, characterized by the inner coil (1) and the outer coil (2) that are driven by two separate power sources (K) with 180° electrical phase difference such that the applied current directions are opposite to one another.
An inductive coil unit (3) as in Claim 1, characterized by the inner coil (1) and the outer coil (2) that are driven electrically independently from one another..
An inductive coil unit (3) as in Claim 1, characterized by the outer coil (2) having the quadrilateral windings with rounded corners.
An inductive coil unit (3) as in Claim 6, characterized by the outer coil (2) having the quadrilateral windings of which the corner radius of curvature increases from the outside inwards.
An inductive coil unit (3) as in any one of the above claims, characterized by at least one magnetic member (5) that is disposed on one surface thereof and that is produced from ferromagnetic or ferromagnetic material.
An inductive coil unit (3) as in Claim 8, characterized by a plurality of bar-shaped magnetic members (5) that extends from the center of the circular inner coil (1) up to the outer sides and corners of the outer coil (2) in the radial direction and that are arranged equidistantly all around on one surface.
An inductive coil unit (3) as in Claim 8, characterized by a magnetic member (5) that covers the entirety of one surface of the inner coil (1) and the outer coil (2), that has at the center a hole with the same size as the gap at the center of the circular inner coil (1), the outer side of the magnetic member (5) matching the contour of the outer coil (2).