WO2017093173A1

WO2017093173A1 - An inductive coil unit

Info

Publication number: WO2017093173A1
Application number: PCT/EP2016/078972
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 (1) that is suitable to be used in all-surface induction cookers comprising a top plate (2) whereon cooking containers suitable for induction heating are placed, and comprises a plurality of adjacent coils (3) that are produced from conductive wire or wires coated with non-conducting material and that magnetically interact with each other.

Description

AN INDUCTIVE COIL UNIT

The present invention relates to an inductive coil unit suitable to be used in induction heating cookers, especially in all-surface induction 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 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. In the state of the art there are a large number of embodiments 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 to be transferred per unit cooking container is desired to be increased then the number of coils also has to be decreased. On the contrary, if the position and geometry of the cooking container is desired to be detected on the entire surface, lower amount of power can be provided to small diameter cooking containers since the number of coils has to be decreased this time. One of the most important problems encountered in optimizing these values is the loss generated in the coils especially by high powers and thermal management.

In the state of the art, one of the important problems is that the base of the cooking container cannot be heated homogeneously in especially circular coil structures since a certain region at the base of the cooking container is heated, the middle portion of the coil windings being the center, which is also known as the “corona effect”.

One of the most important problems in all-surface embodiments developed and formed by using more than one coil instead of a single coil, is to optimize the magnetic interaction between the coils. In the state of the art embodiments, coil solutions with generally circular or quadrilateral coils arranged side by side are used. Using circular solutions leads to the corona effect and also causes the magnetic coupling between coils to be low. On the other hand, while the quadrilateral solutions are the most suitable solution with regards to magnetic coupling, these solutions can be weaker in transferring power to small diameter pots.

In the all-surface induction heating cookers, in the case the adjacent coils operate at the same time, the efficiency of the cooker decreases and the cooking container thereon can be heated by consuming more power. Moreover, since more current is needed in order to heat the cooking container as required, electrical elements resistant to more current are used in the power circuit and thus production costs increase. In order to prevent this, induction heating cookers are produced wherein the distance between the coils is longer and/or the geometry of the coils is circular so that the coils affect one another less.

In the state of the art, in embodiments wherein circular, rectangular or hexagonal coils (3’) are used, the coils (3’) are stacked in a trigonal manner, thus the coils (3') are arranged so as to be closest to each other (Figure 1, Prior Art). In Figure 1, the state of the art circular coils (3’) are arranged on a induction heating cooker top plate (2’) in a trigonal manner. In other words, the centers of each three adjacent coils (3’) form a triangle. In this embodiment, no coil can be disposed especially at the areas close to the corners of the induction heating cooker, thus dead spaces are formed and the entire surface of the induction heating cooker cannot be efficiently used. The same problem arises with the coils (3’) arranged in a hexagonal, quadrilateral and trigonal manner.

In the state of the art United States of America 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 winded one with the other are explained.

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

The inductive coil unit realized in order to attain the aim of the present invention, explicated in the first claim and the respective claims thereof comprises rectangular coils with linear sides and rounded or chamfered corners. The coils are disposed on the induction heating cooker top plate in a coupled or quadrilateral manner so that the centers thereof are in alignment. The distance between the straight sides of the coils that are adjacent and parallel to each other is at most as much as the projection length of the coil at the side of the top plate and the length of one straight side of each coil is more than half the projection length of the coil at the side of the top plate. Similarly, the total of the lengths of the straight sides of each coil is more than half the total side length of the coil together with the corners.

In an embodiment of the present invention, the corners of each coil in the inductive coil unit are rounded with a predetermined radius of curvature and the length of each straight side of the coil is more than twice the radius of curvature.

In another embodiment of the present invention, at least one of the rounded corners of the coil is produced with a different radius of curvature than the other corners. For example, the opposite corners in the center of a group of four coils are rounded with a larger radius of curvature than the other corners.

In an embodiment of the present invention, the corners of each coil in the inductive coil unit are chamfered in a predetermined size and the length of each straight side of the coil is more than twice the size of the chamfer.

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 the trigonal coil arrangement on the top plate of an induction heating cooker in the prior art.

Figure 2 – is the schematic view of the quadrilateral coil arrangement on the top plate of an induction heating cooker in the embodiment of the present invention.

Figure 3 – is the schematic view of the quadrilateral coil arrangement on the top plate of an induction heating cooker whereon a control panel is disposed.

Figure 4 – is the schematic view of a coil having square windings with rounded corners.

Figure 5 – is the schematic view of a coil having square windings with chamfered corners.

Figure 6 – is the schematic view of an inductive coil unit comprising the coils having the rectangular windings with rounded corners on the top plate of an induction heating cooker.

Figure 7 – is the schematic view of an inductive coil unit comprising the coils having the rectangular windings with chamfered corners on the top plate of an induction heating cooker.

Figure 8 – is the schematic view of an inductive coil unit comprising the coils with the corners being rounded in the same radius of curvature on the top plate of an induction heating cooker.

Figure 9 – is the schematic view of an inductive coil unit comprising the coils with the opposite corners being rounded in a larger radius of curvature than the other corners on the top plate of an induction heating cooker.

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

Inductive coil unit
Top plate
Coil

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

L-straight: Length of the straight sides of the coil excluding the corners

L-projection: Projection length of the coil together with the corners on the side of the top plate

Dx: Virtual straight lines parallel to each other in the “X” direction on the plane of the top plate

Dy: Virtual straight lines parallel to each other and perpendicular to the “Dx” straight lines in the “Y” direction on the plane of the top plate

R: Radius of curvature of the rounded corner of the coil

L-chamfer: Projection length of the chamfer shape at the corner of the coil on the side of the top plate

H: Distance between the opposite corners of two coils in rectangular form with rounded sides arranged in diagonal position.

The inductive coil unit (1) is suitable to be used in all-surface induction cookers, comprising a top plate (2) whereon cooking containers suitable for induction heating are placed, and comprises adjacent coils (3) that are produced from conductive material preferably from copper wire or wires coated on the outside by electrically non-conducting material, that magnetically interact with each other and that have rectangular windings, linear sides with a certain length (L-straight) and linear or non-linear corners.

The inductive coil unit (1) of the present invention comprises the coils (3)

- wherein the distance between the straight sides of the coils (3) that are adjacent and parallel to each other is at most as much as the projection length (L-projection) of the coil (3) at the side of the top plate,

- wherein the length (L-straight) of a single straight side of the coil (3) is more than half the projection length (L-projection) of the coil (3) together with the corners at the side of the top plate (2) or the total of the lengths (L-straight) of the straight sides of the coil (3) is more than half the total side length of the coil (3) together with the corners, and

- wherein the coils (3) are arranged in a coupled or quadrilateral manner with the centers thereof overlapping with the junction points of at least two virtual straight lines (Dx) parallel to each other and at least two virtual straight lines (Dy) perpendicular to the said straight lines (Dx) such that the centers of the coils (3) align in the direction of two horizontal axes (X, Y) perpendicular to each other, defining the plane of the top plate (2) (Figure 2).

In the said quadrilateral arrangement, when the centers of the coils (3) in each group of four coils (3) arranged side by side and one below the other in the direction of two axes (X, Y), one vertical, one horizontal, on the top plate (2) are joined, a square or a rectangle is obtained.

By arranging the coils (3) in the inductive coil unit (1) of the present invention in a quadrilateral manner, the total usable area on the plane of the top plate (2) is enabled to be shown in a clear, smooth and simple manner. In comparison to the state of the art trigonal arrangement with the same number of coils (3), the quadrilateral arrangement provides the coverage of a larger active or efficient area on the plane of the top plate (2). In comparison to the state of the art trigonal arrangement with the same number of coils (3), the quadrilateral arrangement provides that the same power is obtained by driving less current. The quadrilateral arrangement provides increase in efficiency and enables the amount of electric current applied to the power electronic circuit components to be decreased, thus enables the said components of the power electronic circuit to function for a longer time and in a safer manner. In the quadrilateral arrangement, the coil (3) being produced in a rectangular, preferably square form increases the length of tangent thereof to another adjacent coil (3). Thus, the load contribution generated from the magnetic interaction between the coils is enabled to be increased, in other words more power is obtained from the coils (3) with the same amount of current.

In an embodiment of the present invention, the inductive coil unit (1) comprises the coils (3) with the corners being rounded in a predetermined radius of curvature (R) (Figure 4). In this embodiment, the length (L-straight) of each straight side of the coil (3) is more than twice the radius of curvature (R) (L-straight> 2R). The production process is facilitated by rounding the corners of the coils (3) in square or rectangular form. Moreover, in the coils (3) which are diagonal with respect to each other, the distance between the corners is increased such that the undesired magnetic interaction is decreased and the power provided by the inductive coil unit (1) is increased.

In another embodiment of the present invention, according to the current to be used to drive the inductive coil unit (1) and the placement thereof on the top plate (2), at least one of the rounded corners of the coils (3) is produced with a different radius of curvature (R) than the other corners, in other words with a different amount of corner roundness than the other corners.

In a version of this embodiment, the inductive coil unit (1) comprises at least one coil (3) group composed of four coils (3) and the corners of the coils (3) facing each other at the center of each group of four coil (3) are produced by being rounded with a larger radius of curvature than the other corners (Figure 9). Thus, the corners of the diagonal coils (3) that are preferably driven by a current with the same phase are moved away from each other and the magnetic interaction therebetween is decreased. Since the opposite corners of the coils (3) disposed at diagonal positions with respect to each other on the top plate (2) of an induction heating cooker are rounded, the 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.

In another embodiment of the present invention, the inductive coil unit (1) comprises the coils (3) that are arranged in a quadrilateral manner on the top plate (2) and that have the corners which are chamfered in a predetermined value (L-chamfer) (Figure 5). In this embodiment, the length (L-straight) of each straight side of the coil (3) is more than twice the chamfer value (L-chamfer) (L-straight> 2*L-chamfer).

In another embodiment of the present invention, the inductive coil unit (1) is suitable to be used in the all-surface induction heating cookers comprising a control panel (C) thereon and comprises two coils (3) each at the regions of the top plate (2) remaining at the left and right of control panel (C) (Figure 3). By means of the quadrilateral arrangement of the present invention, the empty spaces around the control panel (C) on the top plate (2) are used by disposing the coils (3) thereon and thus the entire surface area of the top plate (2) excluding the control panel (C) is enabled to be used efficiently.

By means of the present invention, in the all-surface induction heating cookers, with the same number of coils (3) more area on the surface of the top plate (2) can be used efficiently with respect to the state of the art embodiments, providing ease of production while defining clearer usable area lines for the user and enabling more power to be transferred to the cooking containers.

Claims

An inductive coil unit (1) suitable to be used in all-surface induction cookers that comprises a top plate (2) whereon cooking containers suitable for induction heating are placed, and comprising adjacent coils (3) that magnetically interact with each other and that have rectangular windings, linear sides with a certain length (L-straight) and linear or non-linear corners, characterized in that

- the distance between the straight sides of the coils (3) that are adjacent and parallel to each other is at most as much as the projection length (L-projection) of the coil (3) at the side of the top plate,

- the length (L-straight) of a single straight side of the coil (3) is more than half the projection length (L-projection) of the coil (3) together with the corners at the side of the top plate (2) or the total of the lengths (L-straight) of the straight sides of the coil (3) is more than half the total side length of the coil (3) together with the corners, and

- the coils (3) are arranged in a coupled or quadrilateral manner with the centers thereof overlapping with the junction points of at least two virtual straight lines (Dx) parallel to each other and at least two virtual straight lines (Dy) perpendicular to the said straight lines (Dx) such that the centers of the coils (3) align in the direction of two horizontal axes (X, Y) perpendicular to each other, defining the plane of the top plate (2).
An inductive coil unit (1) as in Claim 1, comprising the coils (3) with the corners thereof being rounded in a predetermined radius of curvature (R), characterized by the coils (3) of which the length (L-straight) of each straight side is more than twice the radius of curvature (R).
An inductive coil unit (1) as in Claim 1 or 2, characterized by the coils (3) of which at least one of the rounded corners is produced with a different radius of curvature (R) than the other corners.
An inductive coil unit (1) as in Claim 3, characterized by the coils (3) of which the corners the coils (3) facing each other at the center of each group of four coils (3) are produced by being rounded with a larger radius of curvature (R) than the other corners.
An inductive coil unit (1) as in Claim 1, comprising the coils (3) with the corners thereof being chamfered in a predetermined value (L-chamfer), characterized by the coils (3) of which the length (L-straight) of each straight side is more than twice the chamfer value (L-chamfer).
An inductive coil unit (1) as in Claim 1, that is suitable to be used in the all-surface induction heating cookers comprising a control panel (C) on the top plate (2), characterized by at least two coils (3) each at the regions of the top plate (2) remaining at the left and right of control panel (C).