EP2578058A1

EP2578058A1 - Induction heating cooker

Info

Publication number: EP2578058A1
Application number: EP11723480.7A
Authority: EP
Inventors: Haluk Karatas
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2010-06-07
Filing date: 2011-06-07
Publication date: 2013-04-10
Anticipated expiration: 2031-06-07
Also published as: WO2011154373A1; EP2578058B1; CN102918926A; CN102918926B

Abstract

The present invention relates to an induction heating cooker (1) comprising more than one induction coil (2), providing the cooking container of ferromagnetic feature placed thereon to be heated by the magnetic field it generates, an upper plate (3) disposed above the induction coils (2), produced from a material like glass or ceramic, more than one circuit board (4) providing the induction coils (2) to be energized, more than one switching element (5) like IGBT or diode bridge connected to the circuit boards (4) carrying high value electric current and overheated due to effect of the current and a lower plate (6) disposed at the underside of the upper plate (3), whereon the circuit boards (4) are arranged horizontally side by side at intervals, an axial type fan (8) disposed in an opening (7) arranged on the lower plate (6), and a heat sink (10) disposed over the opening (7) to be concentric with the fan (8) and surrounding the fan (8).

Description

INDUCTION HEATING COOKER

The present invention relates to an induction heating cooker the electronic elements carrying high current of which are cooled.
The induction heating cooker functions according to the principle of heating a cast iron or steel ferromagnetic cooking container by the magnetic field effect generated by the induction coil. The energy efficiency of induction heating cookers is considerably high since the heat required for cooking is not generated in the gas or electric burners on the cooker but directly in the cooking container. In order to drive the induction coils that generate magnetic field, great amount of electric current is passed through electronic switching elements such as the IGBT (Insulated Gate Bipolar Transistor) or the diode bridge on the circuit board and therefore the said switching elements are excessively heated. Apart from these, the electronic elements like the capacitor and relay on the circuit board can also be overheated. An effective cooling system is required so that all the elements on the circuit board can operate safely. In state of the art, the switching elements carrying high current and where the most overheating is observed are cooled by being connected to a heat sink and by delivering air thereto by means of a fan. In induction heating cookers, the fan and the heat sink need to be disposed in the narrow volume between the upper plate wherein the induction coil is located and the supporting lower plate disposed below, the capacities of the fan and the heat sink are insufficient for providing the necessary cooling efficiency. Moreover, operating the fan used for cooling at high speed results in increase of noise.
In the state of the art European Patent Application No. EP2028912, a heat sink unit used in an induction heating cooker is explained which provides the power arrangement to be cooled and which is disposed between the power arrangement and the heating arrangement.
In the state of the art Japanese Patent Application No. JP2006302915, a heat sink that is used in an induction heating cooker is explained, providing the overheated electronic elements to be cooled by means of a fan. In order to prevent noise from increasing in the induction heating cooker, the rotational speed of the fan is reduced. Furthermore, the fan and the heat sink are disposed inside a chamber housing, providing effective air current passage from the heat sink.
In the state of the art Japanese Patent Application No. JP2007234623, a two-piece heat sink that is used in an electromagnetic cooking device is explained, providing the overheated electronic elements to be cooled by means of a fan, the tip surfaces of the cooling fins of which extend towards each other.
The aim of the present invention is the realization of an induction heating cooker having a heat sink which provides the electronic elements carrying high current and overheated to be effectively and quietly cooled.
In the induction heating cooker realized in order to attain the aim of the present invention, explicated in the first claim and the respective claims thereof, the circuit boards providing control of the induction coils are arranged horizontally side by side at intervals on the lower plate below the induction coils and an opening is located on the lower plate in the region corresponding to between the circuit boards.
An axial type fan is disposed at the opening and the fan blows the air sucked from the outside to between the lower plate and the upper plate through the opening.
A heat sink is disposed over the opening on the lower plate so as to surround the fan and be concentric with the fan.
The two opposite lateral sides of the heat sink extend over the circuit boards and the cooling fins located on the sides are seated on the circuit boards.
The heat sink is closed by a cap that covers the upper side of the fan, the middle portion facing the fan of which is concave and that distributes the air blown upwards from the opening to the sides in the radial direction. The cap directs the air coming from the fan to the cooling fins at the lateral sides of the heat sink, from the cooling fins to the circuit boards and towards the lower sides of the cooling surfaces on the opposite sides of the heat sink whereon the switching elements are disposed.
In an embodiment of the present invention, the heat sink comprises two air guides, extending symmetrically from the front and rear sides to the center of the heat sink, configured as a V shaped recess and the arms of which forming the V shape direct the air blown by the fan to the sides, under the cooling surfaces on the sides and to the cooling fins.
In another embodiment of the present invention, the heat sink comprises separators disposed on the lower surface of the cap and extending in the radial direction towards the center of the heat sink from the cooling fins on the right and left sides.
In another embodiment of the present invention, the separators extend from the cooling fins towards the center of the heat sink, up to the ring that defines the border of the dome shaped concave region on the cap.
In another embodiment of the present invention, the separators at the heat sink have cut-outs at their end portions that extend towards the center of the heat sink, providing a fan with a wide diameter size to be arranged in the middle of the separators.
In another embodiment of the present invention, the diode bridge which is the most heating switching element is disposed at the center portion of each cooling surface on two opposite lateral sides of the heat sink and the IGBT’s are disposed at the sides of the diode bridge which are switching elements heating less than the diode bridge.
In the induction heating cooker, the circuit boards and the switching elements connected to the circuit boards are cooled effectively in the narrow volume between the upper plate and the lower plate, they are prevented from overheating and safety is increased. Furthermore, the axial fan which is lower in cost and operates with less noise than the radial fans can be used.
The induction heating cooker 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 induction heating cooker.
Figure 2 – is the schematic view of an induction heating cooker in another embodiment of the present invention.
Figure 3 – is the perspective view of the heat sink used in an induction heating cooker.
Figure 4 – is the top view of the circuit boards and the heat sink disposed between the circuit boards that are used in an induction heating cooker.
The elements illustrated in the figures are numbered as follows:

Induction heating cooker
Induction coil
Upper plate
Circuit board
Switching element
Lower plate
Opening
Fan
Cap
Heat sink
Cooling surface
Cooling fin
Air guide
Separator
Cut-out

The induction heating cooker (1) comprises an upper plate (3) made of a material like glass or ceramic, more than one induction coil (2) disposed under the upper plate (3), providing the cooking container of ferromagnetic feature disposed thereon to be heated by the magnetic field it generates, more than one circuit board (4) providing the induction coils (2) to be energized, more than one switching element (5) like IGBT (Insulated Gate Bipolar Transistor) or diode bridge connected to the circuit boards (4) and carrying high value electric current, overheating due to effect of the current and a lower plate (6) disposed at the underside of the upper plate (3), whereon the circuit boards (4) are arranged horizontally, side by side at intervals.
The induction heating cooker (1) of the present invention comprises,
-a circular opening (7) arranged on the lower plate (6) between the circuit boards (4),
-an axial type fan (8) disposed in the opening (7) so as to rotate around the axis passing from the center (M) of the opening (7), blowing the air sucked from the underside of the lower plate (6) through the circuit boards (4) to between the lower plate (6) and the upper plate (3) and
- a heat sink (10) having a cap (9), configured symmetrically with respect to the center (M) of the circular opening (7), disposed over the opening (7) to be concentric with the fan (8) and surrounding the fan (8), the two opposite lateral sides (K) of which lie over the circuit boards (4), cover the upper side of the fan (8) and direct the air the fan (8) blows upwards through the opening (7) in the vertical direction to the switching elements (5) and the circuit boards (4) at the lateral sides (K) thereof by distributing it to the sides in the horizontal direction.
The heat sink (10) comprises two cooling surfaces (11) formed by chamfering all along the opposite lateral sides (K), onto which the switching elements (5) are attached and more than one cooling fin (12), disposed below the cooling surfaces (11), arranged parallel to each other and seated on the upper surface of the circuit boards (4). The cap (9) directs the air blown by the fan (8) to the cooling surfaces (11) and the cooling fins (12) on the lateral sides (K).
In an embodiment of the present invention, the middle portion of the cap (9) covering the heat sink (10) which faces the fan (8) is conical or dome shaped, the air blown upwards through the opening (7) by the fan (8) is directed to below the cooling surfaces (11) and the cooling fins (12) at the opposite lateral sides (K) by lowering the turbulence losses (Figure 1, Figure 2).
In another embodiment of the present invention, the lower surface of the cap (9) facing the fan (8) is concave (Figure 1, Figure 2).
Four induction coils (2) are disposed in the induction heating cooker (1) and two circuit boards (4) providing the induction coils (2) to be supplied with high value current are used. Each of the circuit boards (4) controls two induction coils (2). Two circuit boards (4) are arranged horizontally, side by side, at intervals on the lower plate (6) and the fan (8) is disposed in the opening (7) between two circuit boards (4) on the lower plate (6). The fan (8) blows the air sucked from under the lower plate (6) upwards and the concave lower surface facing the fan (8) of the cap (9) covering upper side of the fan (8) directs towards the opposite lateral sides (K) of the heat sink (10) in parallel direction to the lower plate (6) by distributing the air blown upwards by the fan (8) in the horizontal direction. The air distributed by the cap (9) in the heat sink (10) in the radial direction, passes between the cooling fins (12) under the cooling surfaces (11) and sweeps the upper surfaces of the circuit boards (4) at the right and left sides of the heat sink (10). Thus, the air blown by the fan (8) cools both the switching elements (5) attached to the cooling surfaces (11) and also the other electronic elements disposed on the circuit boards (4) like the capacitor and relay.
In an embodiment of the present invention, the heat sink (10) comprises more than one air guide (13) disposed on the front and rear sides thereof, which guide the air blown by the fan (8) towards the lateral sides (K) (Figure 3, Figure 4).
In another embodiment of the present invention, the heat sink (10) comprises two V shaped air guides (13) that extend symmetrically from the front and rear sides thereof towards the center (M) (Figure 3, Figure 4).
In another embodiment of the present invention, the heat sink (10) comprises more than one separator (14), disposed at the lower surface of the cap (9), extending from at least one cooling fin (12) on the right and left lateral sides (K) towards the center (M) in the radial direction. The separators (14) provide the air blown upwards by the fan (8) and distributed sideways in the radial direction by means of the cap (9), to be distributed homogeneously under the cooling surfaces (11) and to the cooling fins (12) and the switching elements (5) attached to the cooling surfaces (11) and the other elements on the circuit boards (4) to be effectively cooled.
In yet another embodiment of the present invention, the separators (14) extend from the cooling fins (12) towards the center (M) up to the ring (S) that defines the border of the dome shaped region at the cap (9) (Figure 3, Figure 4). Thus, a volume is gained in the heat sink (10) between the separators (14) wherein the fan (8) can be placed. In this embodiment, since the fan (8) is disposed in the heat sink (10) between the separators (14), the distance between the lower plate (6) and the upper plate (3) is not required to be increased for positioning of the fan (8).
In yet another embodiment of the present invention, the heat sink (10) comprises more than one cut-out (15) at the end portions of the separators (14) extending towards the center (M) and which provides a fan (8) with a wide diameter size to be disposed in the middle of the separators (14) (Figure 2, Figure 3).
In an embodiment of the present invention, in the induction heating cooker (1), the diode bridge which is the most heating switching element (5) is disposed at the center portion of each cooling surface (11) of the heat sink (10) and the IGBT’s, which are switching elements (5) heating less than the diode bridge, are disposed at the sides of the diode bridges (Figure 4). Thus, the diode bridge, which is the most heating switching element (5), is cooled effectively by being connected to the heat sink (10) at the nearest position to the fan (8).
In the induction heating cooker (1), the circuit boards (4) and the switching elements (5) connected to the circuit boards (4) are cooled effectively in the narrow volume between the upper plate (3) and the lower plate (6) and prevented from overheating. The heat sink (10), due to its configuration, allows the use of the axial type fan (8) with low volumetric flow, the cost of the fan (8) and the noise generated during operation of the fan (8) are decreased. Furthermore, since the fan (8) and the heat sink (10) are disposed one into the other, less amount of space is occupied between the lower plate (6) and the upper plate (3).
It is to be understood that the present invention is not limited by the embodiments disclosed above and a person skilled in the art can easily introduce different embodiments. These should be considered within the scope of the protection postulated by the claims of the present invention.

Claims

An induction heating cooker (1) comprising an upper plate (3) made of a material like glass or ceramic, more than one induction coil (2) disposed under the upper plate (3), providing the cooking container of ferromagnetic feature to be heated by the magnetic field it generates, more than one circuit board (4) providing the induction coils (2) to be energized, more than one switching element (5) like IGBT or diode bridge connected to the circuit boards (4), carrying high value electric current and overheated due to effect of the current and a lower plate (6) disposed at the underside of the upper plate (3), whereon the circuit boards (4) are arranged horizontally, side by side at intervals, characterized by - a circular opening (7) arranged on the lower plate (6) between the circuit boards (4), - an axial type fan (8) disposed in the opening (7), blowing the air sucked from underside the lower plate (6) through the circuit boards (4) to between the lower plate (6) and the upper plate (3) and - a heat sink (10) comprising a cap (9), configured symmetrically with respect to the center (M) of the opening (7), disposed over the opening (7) to be concentric with the fan (8) and surrounding the fan (8), the two opposite lateral sides (K) of which lie over the circuit boards (4), cover the upper side of the fan (8) and direct the air the fan (8) blows upwards through the opening (7) in the vertical direction to the switching elements (5) and the circuit boards (4) at the lateral sides (K) thereof by distributing it to the sides in the horizontal direction.
An induction heating cooker (1) as in Claim 1, characterized by the heat sink (10) comprising two cooling surfaces (11) formed by chamfering all along the opposite lateral sides (K) thereof, whereon the switching elements (5) are attached and more than one cooling fin (12) disposed below the cooling surfaces (11), arranged parallel to each other and seated on the upper surfaces of the circuit boards (4).
An induction heating cooker (1) as in Claim 1 or 2, characterized by the heat sink (10) comprising the cap (9), the middle portion facing the fan (8) of which is conical or dome shaped.
An induction heating cooker (1) as in Claim 3, characterized by the heat sink (10) comprising the cap (9), the lower surface facing the fan (8) of which is concave.
An induction heating cooker (1) as in any one of the above Claims, characterized by the heat sink (10) comprising more than one air guide (13) disposed on the front and rear sides thereof, which guide the air blown by the fan (8) towards the lateral sides (K).
An induction heating cooker (1) as in Claim 5, characterized by the heat sink (10) comprising two V shaped air guides (13) that extend symmetrically from the front and rear sides thereof towards the center (M).
An induction heating cooker (1) as in any one of the above Claims, characterized by the heat sink (10) comprising more than one separator (14), extending from the cooling fins (12) towards the center (M) in the radial direction.
An induction heating cooker (1) as in Claim 7, characterized by the separators (14) that extend from the cooling fins (12) towards the center (M), up to the ring (S) that defines the border of the dome shaped region at the cap (9)
An induction heating cooker (1) as in Claim 7 or 8 , characterized by the heat sink (10) comprising more than one cut-out (15) disposed at the end portions of the separators (14) extending towards the center (M).
An induction heating cooker (1) as in any one of the above Claims, characterized by the heat sink (10) wherein the diode bridge, which is the most heating switching element (5), is disposed at the center portion of each cooling surface (11) and the IGBT’s, which are switching elements (5) heating less than the diode bridge, are disposed at the sides of the diode bridge.