EP3187025A1

EP3187025A1 - Induction heating cooker cooking utensil positioning safety arrangement

Info

Publication number: EP3187025A1
Application number: EP14756065.0A
Authority: EP
Inventors: Serdar Gokhan DOGANAY; Selcuk SOYYIGIT; Yasin Sedat Yirmili
Original assignee: Arcelik AS
Current assignee: Arcelik AS
Priority date: 2014-08-29
Filing date: 2014-08-29
Publication date: 2017-07-05
Also published as: WO2016029959A1

Abstract

The present invention relates to a system for the operation of an induction heater cooker by which a cooking utensil can be temporarily position-locked during cooking operation. The present invention more particularly relates to an induction heating cooker (1) comprising a plurality of cooking zones (4) with at least one induction coil (2) effective in that heat energy is induced within a magnetically responsive cooking container placeable above the induction coils (3), the induction heating cooker (1) further comprising a pan detection circuit for detecting position of a pan on a cooking zone (4) surface of the induction heating cooker (1).

Description

INDUCTION HEATING COOKER COOKING UTENSIL POSITIONING SAFETY ARRANGEMENT

The present invention relates to a system for the operation of an induction heater cooker by which a cooking utensil can be temporarily position-locked during cooking operation.
It is well-known that an induction heating cooker operates based on the process of heating a ferromagnetic material by electromagnetic induction where eddy currents are to be induced and resistance provides heat dissipation within the ferromagnetic material, i.e. a cooking vessel in the form of a pot or pan.
By induction heating, high-frequency alternating current is passed through a coil upon which a magnetic field of the same frequency is induced. The internal resistance of the pan causes heat dissipation due to Joule effect and energy transfer is interrupted once the pan is removed from the cooktop. The energy efficiency of induction heating cookers is considerably high since there is no transfer of heat energy between the hob and the cookware and heat energy lost in the air is minimal.
A resonant converter in an induction heater circuit topology typically consists of a capacitor, an inductor and resistance. To this end, when power is supplied to the resonant tank, electric energy is stored in the inductor and transferred to the capacitor. Resonance therefore occurs while the inductor and the capacitor involve in energy exchange. The resonant converter can be a half-bridge series resonant converter or a quasi-resonant converter. In order to drive the resonant inductor generating magnetic field and in turn inducing eddy currents on the skin depth of a cooking vessel, a high-frequency power switch such as an IGBT is accordingly used.
Among others, a prior art publication in the technical field of the invention may be referred to as US2012261424, which discloses methods and devices for securing an item of cookware to the burner of a stove top by use of magnetism. It is suggested that the magnet(s) may be permanent magnets or electromagnets. The cookware may comprise a permanent magnet disposed on or in the base of the cookware. The burner comprises a magnetic material such as steel or iron. The magnetic material may be in the grate of the cook top, in the electric coil of an electric burner, in the surface of a smooth-top stove top, or any other component of the cook top which is in close proximity to the bottom of the cookware when it is placed on the cooking surface. When the cookware is placed on the stove top, the magnetic field of the permanent magnet creates a force on the magnetic material biasing the cookware against the stove top and securing the cookware to the cook top.
The present invention, on the other hand, addresses the situation where a cooking utensil such as a pot or pan being set on the induction coils slides sideways so as to move towards outside of the cooking zone. This may especially become an issue if the respective cooking utensil is a lightweight one, which can then slide more easily. This can also occur when a cheaper and magnetically non-permeable utensil such as for instance a pan having an aluminum base with a steel layer is used. The situation may be facilitated by vibrations generated by fluids inside the cooking container or the container may displace when the user stirs the ingredients in the container. This effect is more pronounced in the case of induction heating cookers having a cooktop with a smooth top surface for example as in the case of vitro-ceramic glass surfaces.
To this end, the present invention provides an effective system by which a number of drivable retaining devices are disposed to ensure correct positioning of a cooking utensil on a cooking zone such that the utensil being heated maintains a predetermined position during operation of the induction heating cooker.
The present invention provides a plurality of distinct drivable retaining devices in the form of selectively operated position retaining means movable relative to the cooking utensil when induction coils in associated with a cooking zone are energized and released to a parking position when the cooking operation is terminated.
Therefore, the present invention is devised under the recognition that retaining position of the retaining devices with regard to the cooking utensils should be temporarily preserved in such manner that the user can easily lift the cooking utensil without necessarily having to turn off the induction heating cooker in the event the cooking operation is terminated.
The present invention provides a system for the operation of an induction heating cooker enabling temporary retaining of the cooking utensils on the cooking zone, as provided by the characterizing features defined in Claim 1.
Primary object of the present invention is to provide a system for the operation of an induction heating cooker by which a cooking utensil’s locked position during cooking operation is releasable upon termination of such operation.
The present invention proposes an induction heating cooker with at least one drivable retaining device. The latter is an electromechanical mechanism moving a magnet closer to a cooking zone surface for position locking of a cooking container in a temporary manner. A plurality of magnets are therefore placeable below the cooking zone to be moved up and down between operative and parking positions relative to the lower side of a cooking zone surface. The displacement is effectuated along the surface normal direction of the cooking zone surface.
The magnets are automatically activatable when an induction coil is energized and taken back to the original positions when power supply is interrupted. A plurality of magnets can be disposed in evenly distributed magnet slots along concentric circular lines of different induction coils which may also have sub-coils. The magnets can be selectively moved up to attract the cooking container in a certain direction to be centered on a cooking zone. The decision as to the specific magnets to be driven is processed by an electronic control unit according to the information obtained by a pan detection circuit.
Accompanying drawings are given solely for the purpose of exemplifying an induction heating cooker, whose advantages over prior art were outlined above and will be explained in brief hereinafter.
The drawings are not meant to delimit the scope of protection as identified in the Claims, nor should they be referred to alone in an effort to interpret the scope identified in the Claims without recourse to the technical disclosure in the description of the present invention.
Fig. 1 demonstrates a general perspective view of an induction heating cooker housing according to the present invention.
Fig. 2 demonstrates a general perspective view of the upper part of the induction heating cooker with drivable retaining devices according to the present invention.
Fig. 3 demonstrates a side view of the induction heating cooker with drivable retaining devices according to the present invention.
The following numerals are assigned to different part numbers used in the detailed description:

Induction heating cooker
Heating cooker housing
Induction coil
Cooking zone
Magnet slot
Drivable retaining device
Driving means
Magnet

The present invention proposes an induction heating cooker (1) having a plurality of induction coils (3). A power circuit in relation with each induction coil (3) provides that heat energy is induced within a magnetically responsive cooking container or pan placed above the induction coils (3) of the heating cooker housing (2).
The induction heating cooker (1) may comprise a plurality of induction resonant inverters supplied with a source of AC voltage. A half-wave or full-wave bridge rectifier may be connected between the AC source and power stage of the resonant inductor depending on the topology of the power circuit. The resonant inductor is conventionally connected between the output of the rectifier and a power switching part. The resonant capacitor is parallel to the resonant inductor and an anti-parallel diode is connected in parallel in the power switching part. The induction resonant inverters of the induction heating cooker (1) may conventionally comprise AC signal filtering circuits. The power switch may be an insulated gate bipolar transistor (IGBT) driven by a known power switch driving circuit.
To detect cookware presence on a vitro-ceramic glass surface of the induction heating cooker (1) and also to detect its position accurately, a known pan detection circuit sensing cookware positioning can be used. Such a pan detection circuit can monitor the resonant current or the IGBT voltage. An electronic circuit that generates an output at the moment which the anti-parallel diode starts conduction can be used; a charge detection circuit can detect the zero-cross of the current of the anti-parallel diode.
The present invention proposes a drivable retaining device (6) for an induction heating cooker (1). According to the present invention, at least one magnet (8) placed below a cooking zone (4) positioned relative to the lower side of a vitro-ceramic glass surface, is movable to retain a cooking utensil in operative position.
When power is delivered to the respective induction coils (3), power will be simultaneously delivered to a driving means (7) repositioning a respective magnet (8) relative to the lower side of cooking surface. In other words, the driving means (7) move a respective magnet (8) nearer to the cooking surface so as to displace the same along the surface normal direction of the cooking surface. This produces the effect that the magnet (8) locks the operative position of the cooking utensil during cooking and prevents the same from moving towards outside of a cooking zone (4). Therefore, the accurate position of the cooking utensil is ensured during cooking.
A plurality of magnets (8) being activated whenever the associated induction coils (3) are energized remain at the operative position during the cooking operation is in process. When the cooking operation is terminated or alternatively when the magnets (8) are manually deactivated for example by a switch means, they automatically retract to a parking position with a substantially reduced magnetic attraction effect. In this case, as the locking effect is removed, the user can easily take and lift the cooking utensil.
In accordance with the invention, the function of the driving means (7) can be performed by a solenoid which moves a magnet (8) up or down with regard to the cooking zone (4) surface. As is known to the skilled worker, the solenoid itself is a mechanical device using an electromagnet to perform the movement function.
The magnets (8) can be disposed in a central portion of the induction coils (3) or in magnet slots (5) evenly distributed along a circular peripheral line so as to be displaceable along the axis perpendicular to the cooking zone (4) surface. Concentric induction coils (3) can be used so as to have different peripheral lines with distributed magnets (8) by which a cooking zone (4) with two distinct induction coils (3) combined into a heating zone with concentrically disposed induction coils (3) is created. Each induction coil (3) can be comprised of a plurality of separately powerable sub-coils. The magnets (8) can be permanent magnets or electromagnets electrically coupled with a power supply.
The movable magnets (8) according to the present invention may also alternatively be used to effectuate correct positioning of the cooking utensil as will be delineated hereinafter. In this case, a plurality of magnets (8) can be selectively driven to carry the utensil to the correct cooking position on the respective cooking zone (4). To this end, an electronic control unit of the induction heating cooker (1) can selectively actuate certain driving means (7) according to the current placement information obtained by the pan detection circuit. It is therefore possible to actuate a position-based selection of certain driving means (7) so that associated magnets (8) are approached to the cooking zone (4) surface whereby a sliding movement is generated to help reposition the utensil. As a specific example, if the pan detection circuit determines, through induction coils (3), that a certain area of the circular cooking zone (4) is not covered by the cooking utensil standing above, magnets (8) disposed within the projection of the uncovered area but closest to the covered area can be activated to help move the utensil. Therefore, an automatic centering and correct positioning function can be performed. The sensing capability of the pan detection circuit will improve in case each induction coil (3) comprises of a plurality of separately powerable sub-coils. Also a plurality of magnets (8) under the cooking zone (4) will improve the centering effect.
In a nutshell, the present invention proposes an induction heating cooker (1) comprising a plurality of cooking zones (4) with at least one induction coil (3) effective in that heat energy is induced within a magnetically responsive cooking container placeable above the induction coils (3), the induction heating cooker (1) further comprising a pan detection circuit for detecting position of a pan on a cooking zone (4) surface of the induction heating cooker (1).
In one embodiment of the present invention, the induction heating cooker (1) comprises at least one drivable retaining device (6) comprising a magnet (8) in association with a cooking zone (4) and adapted to be operable so as effectuate operative position locking of a cooking container in an interrupted manner.
In a further embodiment of the present invention, the magnet (8) is placeable below a cooking zone (4) positioned relative to lower side of a cooking zone (4) surface.
In a still further embodiment of the present invention, a driving means (7) is disposed to reposition the magnet (8) relative to the lower side of the cooking zone (4) surface.
In a yet still further embodiment of the present invention, the driving means (7) is adapted to move a magnet (8) nearer to the cooking surface (4) so as to displace the same along the surface normal direction of the cooking zone (4) surface.
In a yet still further embodiment of the present invention, the magnet (8) is automatically activatable when an induction coil (3) forming part of a cooking zone (4) in association with the magnet (8) is energized.
In a yet still further embodiment of the present invention, the magnet (8) remains activated in operative position during a cooking period the induction coil (3) is energized.
In a yet still further embodiment of the present invention, the magnet (8) is automatically retracted to a parking position with a substantially reduced magnetic attraction effect upon termination of the cooking period.
In a yet still further embodiment of the present invention, the driving means (7) comprises a solenoid which moves the magnet (8) in opposite directions with regard to the cooking zone (4) surface.
In a yet still further embodiment of the present invention, a plurality of magnets (8) are disposed in magnet slots (5) in an evenly distributed manner along circular lines.
In a yet still further embodiment of the present invention, concentric induction coils (3) are provided having different peripheral lines with distributed magnets (8).
In a yet still further embodiment of the present invention, each induction coil (3) comprises of a plurality of separately powerable sub-coils.
In a yet still further embodiment of the present invention, a plurality of magnets (8) are selectively drivable to carry a cooking container to a correct cooking position on a cooking zone (4).
In a yet still further embodiment of the present invention, an electronic control unit of the induction heating cooker (1) selectively actuates driving means (7) according to current placement information obtained by the pan detection circuit.
In a yet still further embodiment of the present invention, the magnets (8) are selectively drivable in a sequential manner while the cooking container is displaced in a centering direction. Therefore, magnets (8) in the uncovered area can be sequentially driven because the uncovered area progressively shrinks; the individual magnets (8) closest to the covered area dynamically change.
In a yet still further embodiment of the present invention, the magnets (8) are permanent magnets or electromagnets.
Therefore, an effective system for fixing operative position of a cooking utensil during induction cooking is proposed. After completion of the cooking operation, removal of the cooking utensil is facilitated by way of taking magnets (8) away from the cooking zone (4). Further, an induction heating cooker (1) with a centering and positioning system is proposed by which a cooking utensil’s initial non-centered position can be changed.

Claims

An induction heating cooker (1) comprising a plurality of cooking zones (4) with at least one induction coil (3) effective in that heat energy is induced within a magnetically responsive cooking container placeable above the induction coils (3), the induction heating cooker (1) further comprising a pan detection circuit for detecting position of a pan on a cooking zone (4) surface of the induction heating cooker (1), characterized in that at least one drivable retaining device (6) comprising a magnet (8) in association with a cooking zone (4) and adapted to be operable so as effectuate operative position locking of a cooking container in an interrupted manner.
An induction heating cooker (1) as in Claim 1, characterized in that the magnet (8) is placeable below a cooking zone (4) positioned relative to lower side of a cooking zone (4) surface.
An induction heating cooker (1) as in Claim 2, characterized in that a driving means (7) is disposed to reposition the magnet (8) relative to the lower side of the cooking zone (4) surface.
An induction heating cooker (1) as in Claim 3, characterized in that the driving means (7) is adapted to move a magnet (8) nearer to the cooking surface (4) so as to displace the same along the surface normal direction of the cooking zone (4) surface.
An induction heating cooker (1) as in Claim 3 or 4, characterized in that the magnet (8) is automatically activatable when an induction coil (3) forming part of a cooking zone (4) in association with the magnet (8) is energized.
An induction heating cooker (1) as in Claim 5, characterized in that the magnet (8) remains activated in operative position during a cooking period the induction coil (3) is energized.
An induction heating cooker (1) as in Claim 6, characterized in that the magnet (8) is automatically retracted to a parking position with a substantially reduced magnetic attraction effect upon termination of the cooking period.
An induction heating cooker (1) as in Claim 3, 4 or 6, characterized in that the driving means (7) comprises a solenoid which moves the magnet (8) in opposite directions with regard to the cooking zone (4) surface.
An induction heating cooker (1) as in Claim 1, 3, 4 or 6, characterized in that a plurality of magnets (8) are disposed in magnet slots (5) in an evenly distributed manner along circular lines.
An induction heating cooker (1) as in Claim 9, characterized in that concentric induction coils (3) are provided having different peripheral lines with distributed magnets (8).
An induction heating cooker (1) as in Claim 9 or 10, characterized in that each induction coil (3) comprises of a plurality of separately powerable sub-coils.
An induction heating cooker (1) as in Claim 9, 10 or 11, characterized in that a plurality of magnets (8) are selectively drivable to carry a cooking container to a correct cooking position on a cooking zone (4).
An induction heating cooker (1) as in Claim 12, characterized in that an electronic control unit of the induction heating cooker (1) selectively actuates driving means (7) according to current placement information obtained by the pan detection circuit.
An induction heating cooker (1) as in Claim 12 or 13, characterized in that the magnets (8) are selectively drivable in a sequential manner while the cooking container is displaced in a centering direction.
An induction heating cooker (1) as in any preceding Claims, characterized in that the magnets (8) are permanent magnets or electromagnets.