Patent Application
20220159794
The disclosure relates to an induction cooking device and a respective method.
Although applicable to any inductive heating apparatus, the present disclosure will mainly be described in conjunction with induction cookers.
In modern cookers energy, and therefore heat, may be transferred to the respective cooking vessel inductively. To this end, an induction coil may be provided under the cooking surface and an alternating field may be generated with the induction coil. The varying magnetic field will then induce a current flow in the bottom surface of the cooking vessel. The current flow will generate heat in the bottom of the cooking vessel and the cooking goods in the cooking vessel will heat up accordingly.
The induction coil and the bottom of the cooking vessel may be seen as a kind of coupled inductances. This means that the magnetic properties of the cooking vessel influence the inductance of the induction coil. It is known that different cooking vessels may comprise different magnetic properties. Therefore, the control of the induction coil is usually adapted to accommodate the different types of cooking vessels.
For example, the modulation, i.e., frequency, amplitude or the like, of the current through the induction coil may be changed in induction cookers. Further, algorithms may be used to detect the pot type and size, and the modulation and switching algorithm may be selected according to a detected pot type and size.
However, these control algorithms require complex computations.
Accordingly, there is a need for providing a simplified control of induction cookers.
The above stated problem is solved by the features of the independent claims. It is understood, that independent claims of a claim category may be formed in analogy to the dependent claims of another claim category.
Accordingly, it is provided:
An induction cooking device for heating a cooking vessel, the induction cooking device comprising a cooking surface comprising a cooking hob, an induction coil, a driving circuit electrically coupled to the induction coil, and a coil mount that is arranged under the cooking hob, wherein the induction coil is arranged on the coil mount and wherein the coil mount is configured to dynamically adapt the distance between the induction coil and the cooking surface based on a temperature of the induction coil and/or at least a component of the driving circuit, wherein the coil mount is configured to increase the distance between the induction coil and the cooking surface with increasing temperature of the induction coil and/or the at least one component of the driving circuit.
Further, it is provided:
A method for operating an induction cooking device with an induction coil and a driving circuit for heating a cooking vessel, the method comprising operating the induction coil with the driving circuit, and dynamically adapting the distance between the induction coil and the cooking surface based on a temperature of the induction coil and/or the at least one component of the driving circuit, wherein the distance is increased with increasing temperature of the induction coil and/or the at least one component of the driving circuit.
The present disclosure is based on the finding that different types of cooking vessels may comprise strongly varying ferromagnetic properties. Further, the present disclosure is based on the finding that the distance between the induction coil and the cooking vessel defines the impact of the ferromagnetic properties of the cooking vessel on the induction coil.
Usually, a parallel LC circuit is used to drive the induction coil of an induction cooking device. It is understood, that the term parallel LC circuit may refer to a circuit where the induction coil is the “L” component and a parallel capacitor is provided as the “C” component. The minimum driving current is required if the parallel LC circuit is operated at its' resonant frequency. Further, with a low magnetic coupling between the induction coil and the cooking vessel the impedance of the parallel LC circuit will be lower and the current through the parallel LC circuit will be higher. It is understood, that although not explicitly mentioned, the driving circuit may comprise such a parallel LC circuit and a respective control and switching arrangement.
The present disclosure especially takes into account that cooking vessels with poor ferromagnetic properties cause heterogeneous, irregular and increased current flows in the induction coil and the driving circuit. Such irregular current transitions cause major negative effects in the semiconductor. For example, they cause switching irregularities and loss of outline. Such effects in turn cause losses in the semiconductors and the semiconductors heat up.
The present disclosure therefore provides the coil mount that dynamically adapts the distance between the induction coil and the cooking surface, and therefore the cooking vessel. The coil mount increases the distance between the induction coil and the cooking surface with increasing temperature of the induction coil and/or at least a component of the driving circuit. The term “at least a component” of the driving circuit may, e.g., refer to one or more of the switches in the driving unit that drive the current through the induction coil.
Therefore, if a cooking vessel with poor ferromagnetic properties is used, the induction coil and the driving circuit will heat up due to increased operating currents. This increase in temperature will cause the coil mount to lower the induction coil and increase the distance between cooking vessel and induction coil.
The increasing separation of the cooking vessel from the induction coil leads to a reduction of the impedance of the parallel LC circuit and to an increase of the current in the parallel LC circuit. However, the current irregularities caused by the cooking vessel with poor ferromagnetic properties are also reduced. The current irregularities caused by such a cooking vessel with poor ferromagnetic properties influence the temperature of the induction coil and the driving circuit more than the increasing current due to the reduced impedance. Therefore, the overall temperature of the induction coil and/or of the driving circuit is reduced by increasing the distance between the induction coil and a cooking vessel with poor ferromagnetic properties. After increasing the distance, the current flow is more regular and the semiconductor temperature is therefore positively influenced by the fact that the cooking vessel is spaced apart more from the induction coil.
With the present disclosure it is therefore possible to regulate the temperature of the induction coil and/or the driving circuit with a simple mechanical construction, i.e., the coil mount. The present disclosure requires no complex control algorithms to adapt the induction cooking device to the type of cooking vessel.
It is understood, that the term induction coil may refer to a single coil or to a group or plurality of coils that are provided for a single cooking hob. Further, it is understood, that the induction cooking device may comprise more than one cooking hob and respective induction coils. A single driving circuit may be provided per induction coil or group of induction coils. Alternatively, a single driving circuit may be provided for all induction coils in the induction cooking device.
Further embodiments of the present disclosure are subject of the further subclaims and of the following description, referring to the drawings.
In an embodiment, the coil mount may comprise a movable carrying structure configured to carry the induction coil, and a number, i.e., one or more, of actuators configured to change the distance of the movable carrying structure from the cooking surface.
The carrying structure may, e.g., comprise non-ferromagnetic components, like, e.g., plastic clips or the like, that may accommodate the induction coil. It is understood, that the carrying structure may, e.g., be provided integrally with the induction coil. The carrying structure may, e.g., be injection molded around the induction coil.
The actuator may, e.g., be coupled to a structure of the induction cooking device and the carrying structure. The structure of the induction cooking device may be seen as a kind of base or bearing for the actuators.
In another embodiment, the actuators may comprise a flexible body and a phase change material provided in the flexible body.
The flexibly body may, e.g., be a body that expands and contracts easily. Such a body may, e.g., be made of rubber or other plastics. The flexibly body may be filled with a phase change material. The term “phase change material” refers to materials that at least soften with increasing temperature.
It is understood, that the actuators may be thermally coupled to the induction coil and/or the respective component(s) of the driving circuit. To this end, the mechanical arrangement and the position of the actuators in the induction cooking device may put the actuators in direct contact with the induction coil and/or the respective component(s) of the driving circuit. In addition or as alternative, heat transfer elements, like, e.g., pieces of cooper or heat pipes or the like may also be provided between the induction coil and/or the respective component(s) of the driving circuit.
Therefore, if the induction coil and/or the respective component(s) of the driving circuit heat up, the heat will be transferred to the actuators and the phase change material in the actuators will change its' phase or at least soften with respect to lower temperatures. If the phase change material softens, the weight of the induction coil will push down on the actuators and the induction coil will be lowered.
With the help of phase change materials, a totally passive or mechanical arrangement may be provided for dynamically controlling the distance of the induction coil to the cooking surface.
In yet another embodiment, the phase change material may comprise salt hydrates and/or paraffins and/or bio-based phase change materials.
Salt hydrates consist of inorganic salts and water. Their melt point temperatures range between 15° C. and 80° C. The advantages of salt hydrates are low material costs, high latent heat storage capacity, precise melting point, high thermal conductivity and inflammability.
Paraffins, typically, are derived from petroleum and have a waxy consistency at room temperature. Their melt point temperatures range between −8° C. and 40° C. They have good thermal storage capacity and are proven to freeze without supercooling.
Bio-based phase change materials, PCMs, are organic compounds derived from animal fat and plant oils. Their melt point temperatures range between −40° C. and 151° C. The most common bio-based PCMs are derived from fatty acids and have higher efficiency than salt hydrates and petroleum-based phase change material.
In a further embodiment, the actuators may comprise electromechanical actuation elements and respective driving circuits.
As alternative to a passive control as suggested above, electromechanical actuation elements may be used to allow a fine-grained control of the distance of the induction coil from the cooking surface.
The electromechanical actuation elements may, e.g., comprise linear actuators or any other type of electrical motor and mechanical arrangement that allow positioning the induction coil or the movable carrying structure with respect to the cooking surface.
In another embodiment, the induction cooking device may comprise a distance control unit and a temperature sensor that is configured to measure the temperature of the induction coil and/or the at least one component of the driving circuit and that is coupled to the distance control unit. The distance control unit may be configured to control the actuators based on a temperature measured by the temperature sensor.
It is understood, that the distance control unit may, e.g., be a dedicated distance control unit. Such a dedicated control unit may, e.g., comprise a microcontroller or the like with respective drivers, e.g., switches or transistors, for the actuators. Further, position sensors may be provided that indicate to the control unit the distance of the carrying structure from the cooking surface.
As alternative, the distance control unit may also, e.g., be integrated into another control unit in the induction cooking surface. The distance control unit may, e.g., be integrated into a control unit or controller of the driving circuit.
The temperature sensor may be a single temperature sensor, e.g., provided at the switches of the driving circuit or at the induction coil. Further, multiple temperature sensors may be provided, e.g., at the driving circuit and at the induction coil.
Further, additional switches like, e.g., end switches may be provided at the minimum and maximum movement range or position of the movable carrying structure.
In a further embodiment, the temperature sensor may comprise an indirect temperature sensor, especially a current sensor.
As alternative to the above, the temperature may, e.g., be derived from other system values, like, e.g., the current through the induction coil. This current may, e.g., be measured anyway with a current sensor in the driving circuit.
For example, a specific current threshold value may be determined and the carrying structure may be lowered if the current threshold value is exceeded by the measured current. If the measured current is lower than the current threshold value, the distance between the carrying structure and the cooking surface may be set to a minimum value.
For a more complete understanding of the present disclosure and advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings. The disclosure is explained in more detail below using exemplary embodiments which are specified in the schematic figures of the drawings, in which:
In the figures like reference signs denote like elements unless stated otherwise.
During operation of the induction cooking device 100, the coil mount 105 dynamically adapts the distance between the induction coil 102 and the cooking surface 101 based on a temperature of the induction coil 102 and/or at least a component of the driving circuit 103, e.g., switching element 104. If the temperature of the induction coil 102 and/or at least a component of the driving circuit 103 increases, e.g., to more than a predefined threshold, the coil mount 105 increases the distance between the induction coil 102 and the cooking surface 101, and vice versa.
This means, that if a specific temperature in the driving circuit 103 or the induction coil 102 is exceeded, the induction coil 102 will be lowered. It is understood, that the coil mount 105 may be configured such that lowering starts at a temperature that is not achieved under normal operating conditions, but only with cooking vessels that comprise inferior ferromagnetic properties. This temperature may, e.g., be determined experimentally during development or design of the induction cooking device 100.
The carrying structure 210 carries the induction coil 202 and is mechanically coupled to the flexible bodies 211, 212, which are positioned under the carrying structure 210. As already explained above, the phase change materials 213, 214 may become soft or liquid when they are heated up to a specific temperature. If the phase change material 213, 214 becomes soft, the flexible bodies 211, 212 may be compressed by the weight of the carrying structure 210 and the induction coil 202. Alternatively, the phase change materials 213, 214 may expand when liquifying and may therefore expand the flexible bodies 211, 212 sideways, therefore contracting them vertically. To this end, the top and bottom of the flexible bodies 211, 212 may be non-flexible.
The embodiment of
The distance control unit 316 controls the electromechanical actuation element 315 based either on a temperature measured by the temperature sensor 317 or based on a current measured by the current sensor 318, or both. If the temperature or the current or both exceed a predetermined threshold value, the distance control unit 316 may control the electromechanical actuation element 315 to lower the induction coil 302 with respect to the cooking surface 301.
The current through the switching element 304 and the induction coil 302 influences the temperature of the switching element 304 and the induction coil 302. The current sensor 318 in this embodiment may therefore be seen as an indirect temperature sensor.
For sake of clarity in the following description of the method-based
The method comprises operating S1 the induction coil 102, 202, 302 with the driving circuit 103, 203, 303, and dynamically adapting S2 the distance between the induction coil 102, 202, 302 and the cooking surface 101, 201, 301 based on a temperature of the induction coil 102, 202, 302 and/or the at least one component of the driving circuit 103, 203, 303, wherein the distance is increased with increasing temperature of the induction coil 102, 202, 302 and/or the at least one component of the driving circuit 103, 203, 303.
The step of adapting S2 may comprise moving a movable carrying structure 210, 310 that carries the induction coil 102, 202, 302 with a number of actuators.
Moving the movable carrying structure 210, 310 may be performed especially with two different options.
For example, a flexible body 211, 212 and a phase change material 213, 214 provided in the flexible body 211, 212 may be arranged such that when the phase change material 213, 214 heats up, the flexible body 211, 212 deforms and lowers the carrying structure 210, 310. The phase change material 213, 214 may comprise salt hydrates and/or paraffins and/or bio-based phase change materials 213, 214.
As alternative, moving the movable carrying structure 210, 310 may be performed with electromechanical actuation elements 315 and respective driving circuits 103, 203, 303. To this end, the temperature of the induction coil 102, 202, 302 and/or the at least one component of the driving circuit 103, 203, 303 may be measured and moving may comprise controlling the electromechanical actuation elements 315 based on the measured temperature. The temperature may be measured with a dedicated temperature sensor or with an indirect temperature sensor 317. The indirect temperature sensor 317 may, e.g., comprise a current sensor 318. The carrying structure 210, 310 may be lowered if a predefined current threshold value is exceeded by a current measured by the current sensor 318. If the measured current is lower than the current threshold value, the carrying structure 210, 310 may, e.g., be positioned in the position nearest to the cooking surface 101, 201, 301. As alternative, a linear relationship may be established between temperature/current and the distance.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations exist. It should be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.
The present disclosure provides an induction cooking device 100, 200, 300 for heating a cooking vessel 150, 250, 350, the induction cooking device 100, 200, 300 comprising a cooking surface 101, 201, 301 comprising a cooking hob 106, an induction coil 102, 202, 302, a driving circuit 103, 203, 303 electrically coupled to the induction coil 102, 202, 302, and a coil mount 105 that is arranged under cooking hob 106, wherein the induction coil 102, 202, 302 is arranged on the coil mount 105 and wherein the coil mount 105 is configured to dynamically adapt the distance between the induction coil 102, 202, 302 and the cooking surface 101, 201, 301 based on a temperature of the induction coil 102, 202, 302 and/or at least a component of the driving circuit 103, 203, 303, wherein the coil mount 105 is configured to increase the distance between the induction coil 102, 202, 302 and the cooking surface 101, 201, 301 with increasing temperature of the induction coil 102, 202, 302 and/or the at least one component of the driving circuit 103, 203, 303.
This application is the U.S. national phase of PCT Application No. PCT/EP2019/056463 filed on Mar. 14, 2019, the disclosure of which is incorporated in its entirety by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/056463 | 3/14/2019 | WO | 00 |
