Cooking appliance

Abstract

A cooking appliance is disclosed. According to at least one embodiment of the present disclosure, the cooking appliance may include: a top plate on which an object to be heated is placed; a plurality of working coils for heating the object to be heated; an inverter for applying current to each of the working coils; and a controller for controlling the operation of the inverter so that the object to be heated is heated through each of the working coils. In this case, the at least one working coil is a PCB working coil including a plurality of turns, wherein the turns may have uneven spacing.

Description

[Technical Field]

[0001] The present disclosure relates to a cooking appliance. More specifically, the present disclosure relates to a cooking appliance including a working coil that maximizes heating efficiency and a cooking appliance that heats an object to be heated using a PCB working coil.[Background Art]

[0002] Various cooking appliances are used to heat food in homes and restaurants. While gas ranges, which use gas as fuel, have been widely used in the past, devices that heat objects to be heated, such as cooking vessels like pots, using electricity instead of gas, have recently become widespread.

[0003] Methods for heating objects using electricity are broadly categorized into resistance heating and induction heating. Electrical resistance heating involves passing current through a metal resistance wire or a non-metallic heating element, such as silicon carbide, to heat the object (e.g., a cooking vessel) by transferring the heat generated through radiation or conduction. Induction heating, on the other hand, involves applying a predetermined amount of high-frequency power to a coil. This magnetic field, generated around the coil, generates eddy currents in the metal object, thereby heating the object itself.

[0004] Recently, induction heating has been primarily used in cooking appliances.

[0005] Research is also being conducted to apply PCB working coils to cooking appliances. However, PCB working coils suffer from significant overheating issues, which can compromise the stability of the cooking appliance. Therefore, a solution is needed.[Disclosure of the Invention][Technical Problem]

[0006] The present disclosure provides a cooking appliance including a working coil that maximizes heating efficiency through the arrangement of the working coil.

[0007] The present disclosure provides a cooking appliance that heats a subject matter using a Printed Circuit Board (PCB) working coil.

[0008] In particular, the present disclosure provides a cooking appliance including a PCB working coil with various structures or patterns to reduce heat generation, which is a problem when operating at high frequencies.[Technical Solution]

[0009] A cooking appliance according to at least one of the various embodiments of the present disclosure may include: a top plate on which an object to be heated is placed; a plurality of working coils that heat the object to be heated; an inverter that applies current to each of the working coils; and a controller that controls the operation of the inverter so that the object to be heated is heated through each of the working coils. In this case, the at least one working coil is a PCB working coil including a plurality of turns, and the spacings between the turns may not be uniform.

[0010] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the spacings between the turns of the PCB working coil may increase as the distance between the turns approaches the center point of the PCB working coil.

[0011] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the PCB working coil may be divided into a plurality of sections from a center point to an outermost edge, and each section may include at least one turn.

[0012] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the plurality of sections may include a first section in which the spacing between turns does not change and a second section in which the spacing between turns changes.

[0013] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the spacing between turns in the first section may be greater than that in the second section.

[0014] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the first section may be a section closer to the center point than the second section.

[0015] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the width of each turn of the PCB working coil may not be uniform.

[0016] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the width of each turn of the PCB working coil may be wider as it gets closer to the center point.

[0017] In a cooking appliance according to at least one of the various embodiments of the present disclosure, each turn of the PCB working coil includes a plurality of unit coils, and the spacing between the unit coils of the plurality of unit coils included in the turn may not be uniform depending on the position of the turn.

[0018] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the spacing between the unit coils of the plurality of unit coils included in the turn may be wider as the position of the turn gets closer to the center point of the PCB working coil.

[0019] In a cooking appliance according to at least one of the various embodiments of the present disclosure, each turn of the PCB working coil includes a plurality of unit coils, and the number of unit coils included in the turn may vary depending on the position of the turn.

[0020] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the number of unit coils included in each turn of the PCB working coil may increase as the number of coils increases closer to the center point of the PCB working coil.

[0021] In a cooking appliance according to at least one of the various embodiments of the present disclosure, each turn of the PCB working coil may include a plurality of unit coils, and the width of each unit coil included in the turn may vary depending on the position of the turn.

[0022] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the width of each unit coil included in each turn of the PCB working coil may increase as the number of coils of the unit ...

[0023] In a cooking appliance according to at least one of the various embodiments of the present disclosure, the working coil comprises a plurality of layers of PCB working coils, and the PCB working coils in each layer may differ from each other in at least one of the turn-to-turn spacing, turn width, and the spacing and number of unit coils included in each turn.[Effects of the Invention]

[0024] In accordance with at least one of the various embodiments of the present disclosure, heating efficiency can be maximized by maximizing the heat loss of a heated object.

[0025] In accordance with at least one of the various embodiments of the present disclosure, heating efficiency can be maximized by controlling a concentrated heating area of the heated object.

[0026] In accordance with at least one of the various embodiments of the present disclosure, a cooking appliance can heat a heated object using a PCB (Printed Circuit Board) working coil.

[0027] According to at least one of the various embodiments of the present disclosure, there is an effect of ensuring stable operation of a cooking appliance by reducing heat generation, which is particularly problematic when operating at high frequencies, and at the same time preventing malfunctions of the cooking appliance that may occur due to heat generation.[Brief description of the drawings]

[0028] FIG. 1 is a perspective view illustrating a cooking appliance according to an embodiment of the present disclosure. FIG. 2 is a perspective view illustrating a cooking appliance and a cooking vessel according to an embodiment of the present disclosure. FIG. 3 is a cross-sectional view of a cooking appliance and a cooking vessel according to an embodiment of the present disclosure. FIG. 4 is a circuit diagram of a cooking appliance according to an embodiment of the present disclosure. FIG. 5 is a cross-sectional view illustrating a cooking appliance and a heated object according to an embodiment of the present disclosure. FIG. 6 is a cross-sectional view illustrating a cooking appliance and a heated object according to another embodiment of the present disclosure. FIG. 7 is a diagram illustrating output characteristics of a cooking appliance according to an embodiment of the present disclosure. FIG. 8 is a diagram illustrating an example of a working coil. FIGS. 9 and 10 are diagrams illustrating the magnetic path length along each turn of the magnetic path. FIG. 11 is a graph illustrating the magnetic path length of each turn of the working coil. FIG. 12 is a graph illustrating the current density of an object to be heated. FIG. 13 is a diagram illustrating an example of the area-specific heat loss (EM-Loss) of an object to be heated by a uniform working coil. FIG. 14 is a diagram illustrating the shape of a working coil according to a first embodiment of the present disclosure. FIG. 15 is a graph illustrating the magnetic path length of each turn of the working coil. FIG. 16 is a graph illustrating the current density of an object to be heated. FIG. 17 is a diagram illustrating an example of the area-specific heat loss (EM-Loss) of a heated object heated by a reverse-type working coil. FIG. 18 is a diagram illustrating the shape of a working coil according to a second embodiment of the present disclosure. FIG. 19 is a graph illustrating the magnetic path length of each turn of the working coil. FIG. 20 is a graph illustrating the current density of the heated object. FIG. 21 is a diagram illustrating an example of the area-specific heat loss (EM-Loss) of a heated object heated by a forward-type working coil. FIG. 22 is a diagram illustrating a PCB working coil. FIG. 23 is a diagram illustrating the turn-to-turn spacing according to an embodiment of the present disclosure. FIG. 24 is a diagram illustrating a turn-to-turn spacing according to another embodiment of the present disclosure. FIGS. 25 to 27 are diagrams illustrating a PCB working coil with turns arranged according to embodiments of the present disclosure. FIGS. 28 to 29 are diagrams illustrating a PCB working coil with turns arranged according to embodiments of the present disclosure. FIG. 30 is a diagram illustrating the internal configuration of turns within the PCB working coil of FIG. 22. FIGS. 31 to 34 are diagrams illustrating unit coils constituting one layer of one turn of FIG. 30. FIGS. 35 and 36 are diagrams illustrating the unit coil configuration for the multi-layer of FIG. 30. FIG. 37 is a diagram illustrating the turn spacing relative to oz according to one embodiment of the present disclosure. FIG. 38 is a diagram illustrating the change in resistance relative to the number of turns according to one embodiment of the present disclosure. FIG. 39 is a diagram illustrating the case where the number of twists is varied when changing from an inner turn to an outer turn according to one embodiment of the present disclosure. [Best Mode]

[0029] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate identical or similar components.

[0030] The suffixes "module" and "unit" used in the following description are assigned or used interchangeably solely for the convenience of writing the specification, and do not inherently have distinct meanings or roles.

[0031] In the following description, "connection" between components includes not only direct connection of the components but also indirect connection through at least one other component, unless otherwise specified.

[0032] Hereinafter, a cooking appliance and its operating method according to an embodiment of the present disclosure will be described. Meanwhile, the cooking appliance in the present disclosure may be, but is not limited to, an induction heating cooktop.

[0033] FIG. 1 is a perspective view illustrating a cooking appliance according to an embodiment of the present disclosure.

[0034] Referring to FIG. 1, a cooking appliance 1 according to an embodiment of the present disclosure may include a case 25, a cover plate 20, and a working coil (WC). The cooking appliance 1 may further include an intermediate material (IM).

[0035] The working coil (WC) may be installed in the case 25.

[0036] In addition to the working coil (WC), various devices related to driving the working coil (WC) may be installed in the case 25. Such devices may include, for example, at least one of a power supply unit (110, see FIG. 4) configured to provide AC power, a rectifier unit (120, see FIG. 4) configured to rectify the AC power into DC power, an inverter unit (140, see FIG. 4) configured to convert the rectified DC power into a resonant current through a switching operation and supply the resonant current to the working coil (WC), and a control module (not shown) configured to control operations of the devices within the cooking appliance 1.

[0037] The cover plate 20 is coupled to an upper portion of the case 25, and may include a top plate portion 15 on an upper surface of which an object to be heated (not shown), such as a cooking vessel, is placed.

[0038] The top plate 15 may be made of a glass material, such as ceramic glass, but this is merely an example. The material of the top plate 15 according to the embodiment of the present disclosure may vary.

[0039] In addition, the top plate 15 may be equipped with an input interface (not shown) that transmits user input to a control module (not shown) for the input interface. The input interface may be equipped at a location other than the top plate 15.

[0040] The input interface is a module for receiving user input, such as a desired heating intensity or an operating time of the cooking appliance 1, and may be implemented with a physical button or a touch panel. The input interface may further be equipped with a power button, a lock button, a power level adjustment button (+, -), a timer adjustment button (+, -), a charging mode button, etc. The control module for the input interface may transmit user input to the aforementioned control module (e.g., a control module for an inverter). The aforementioned control module may control the operation of various devices (e.g., a working coil (WC)) based on the user input, and thus, detailed descriptions thereof will be omitted.

[0041] Whether the working coil (WC) is driven and the heating intensity (i.e., heating power) can be visually displayed in a burner shape on the top plate 15. The burner shape can be displayed by an indicator (not shown) comprising a plurality of light-emitting elements (e.g., LEDs) provided within the case 25.

[0042] The working coil (WC) is installed within the case 25 and can heat the object to be heated.

[0043] The operating status of the working coil (WC) can be controlled by the aforementioned control module (not shown). For example, when the object to be heated is placed on the top plate 15, the working coil (WC) can be driven by the control module.

[0044] The working coil (WC) can directly heat a magnetic object (i.e., a magnetic material) and indirectly heat a non-magnetic object (i.e., a non-magnetic material) via an intermediate material (IM).

[0045] The working coil (WC) may heat an object to be heated by an induction heating method, and may be provided so as to overlap the intermediate material (IM) in a vertical direction (i.e., vertically or in an up-down direction).

[0046] While FIG. 1 illustrates a single working coil (WC) being installed in the case 25, this is not limiting. That is, multiple working coils (WC) can be installed in the case 25. The intermediate material (IM) can be installed in correspondence with the working coil (WC).

[0047] An intermediate material (IM) may be installed on the top plate 15. The intermediate material (IM) may be coated on the top plate 15 to heat a non-magnetic material among the heated objects. The intermediate material (IM) may be inductively heated by a working coil (WC).

[0048] The intermediate material (IM) may be formed on the upper or lower surface of the top plate 15. For example, the intermediate material (IM) may be installed on the upper surface of the top plate 15 as illustrated in FIG. 3, or on the lower surface of the top plate 15 as illustrated in FIG. 4.

[0049] The intermediate material (IM) may be provided so as to overlap at least a portion of the working coil (WC) in a vertical direction (i.e., a vertical direction or an up-down direction). Therefore, the working coil (WC) and the intermediate material (IM) can heat the object to be heated, regardless of its type or placement.

[0050] The intermediate material (IM) can have at least one of magnetic and non-magnetic properties (i.e., magnetic, non-magnetic, or both magnetic and non-magnetic).

[0051] The intermediate material (IM) may be made of a conductive material, such as aluminum (Al), but is not limited thereto. In other words, the intermediate material (IM) may be made of a material other than a conductive material.

[0052] In FIG. 1, the intermediate material (IM) is illustrated as having a shape consisting of multiple rings of different diameters, but this is not limited thereto and may have other shapes.

[0053] In FIGS. 1, 5, and 6, a single intermediate material (IM) is illustrated, but multiple intermediate materials (IM) may be present.

[0054] Referring to FIG. 2, a cooking vessel may be positioned above a cooking appliance 1, and the cooking appliance 1 may heat the cooking vessel positioned above.

[0055] First, a method by which the cooking appliance 1 heats the cooking vessel will be described.

[0056] As illustrated in FIG. 2, the cooking appliance 1 may generate a magnetic field 22 so that at least a portion of the magnetic field passes through the cooking vessel. If the material of the cooking vessel contains an electrical resistive component, the magnetic field 22 may induce an eddy current 30 in the cooking vessel. This eddy current 30 heats the cooking vessel itself, and this heat is conducted or radiated to the interior of the cooking vessel, thereby cooking the contents of the cooking vessel.

[0057] On the other hand, if the material of the cooking vessel does not contain an electrical resistive component, an eddy current 30 does not occur. Therefore, in this case, the cooking appliance 1 cannot heat the cooking vessel.

[0058] Therefore, the cooking vessel that can be heated by the cooking appliance 1 may be a metal vessel, such as a stainless steel vessel, an enamel vessel, or a cast iron vessel.

[0059] Next, a method for generating a magnetic field 22 by the cooking appliance (1) will be described.

[0060] As illustrated in FIG. 3, the cooking appliance 1 may include at least one of a top plate 15, a working coil (WC), and a ferrite core 45.

[0061] The top plate 15 may be configured to support a cooking vessel. That is, the cooking vessel may be positioned on the upper surface of the top plate 15. A heating zone for heating the cooking vessel may be formed on the top plate 15.

[0062] The top plate 15 may be formed of a reinforced glass ceramic material composed of various minerals. Accordingly, the top plate 15 can protect the cooking appliance 1 from external impacts, etc.

[0063] Furthermore, the top plate 15 can prevent foreign substances such as dust from entering the cooking appliance 1.

[0064] A working coil (WC) may be located below the top plate 15. This working coil (WC) may or may not be supplied with current to generate a magnetic field 22. Specifically, current may or may not flow to the working coil (WC) depending on the on / off state of the internal switching element of the cooking appliance 1.

[0065] When current flows through the working coil (WC), a magnetic field 22 is generated, and this magnetic field 22 may encounter the electrical resistance component contained in the cooking vessel to generate an eddy current 30. The eddy current 30 heats the cooking vessel, thereby cooking the contents of the cooking vessel.

[0066] In addition, the heating power of the cooking appliance 1 can be controlled depending on the amount of current flowing through the working coil (WC). For example, the greater the current flowing through the working coil (WC), the more the magnetic field 22 is generated, which in turn increases the magnetic field passing through the cooking vessel, thereby increasing the heating power of the cooking appliance 1.

[0067] The ferrite core 45 is a component for protecting the internal circuit of the cooking appliance 1. Specifically, the ferrite core 45 acts as a shield to block the influence of the magnetic field 22 generated from the working coil (WC) or an external electromagnetic field on the internal circuit of the cooking appliance 1.

[0068] To this end, the ferrite core 45 may be formed of a material having a very high permeability. The ferrite core 45 serves to guide the magnetic field flowing into the interior of the cooking appliance 1 so that it does not radiate but flows through the ferrite core 45. The movement of the magnetic field 22 generated in the working coil (WC) by the ferrite core 45 may be as illustrated in FIG. 2.

[0069] Meanwhile, the cooking appliance 1 may further include other components in addition to the top plate 15, the working coil (WC), and the ferrite core 45 described above. For example, the cooking appliance 1 may further include an insulating material (not illustrated) positioned between the top plate 15 and the working coil (WC). That is, the cooking appliance according to the present disclosure is not limited to the cooking appliance 1 illustrated in FIG. 3.

[0070] FIG. 4 is a circuit diagram of a cooking appliance 1 according to an embodiment of the present disclosure.

[0071] Referring to FIG. 4, the cooking appliance 1 may include some or all of a power supply unit 110, a rectifier unit 120, a DC link capacitor 130, an inverter unit 140, a working coil (WC), and a resonant capacitor 160.

[0072] The power supply unit 110 may receive an external power source, for example, an AC (Alternating Current) power source, and supply it to the rectifier unit 120.

[0073] The rectifier unit 120 is an electrical device that converts AC to DC, converts AC voltage supplied through the power supply unit 110 into DC voltage, and supplies the converted voltage to the DC terminals 121.

[0074] The output terminal of the rectifier 120 may be connected to both DC terminals 121. The DC terminals 121 may be referred to as the "DC link." The voltage measured at both DC terminals 121 is referred to as the "DC link voltage."

[0075] The DC link capacitor 130 functions as a buffer between the power supply 110 and the inverter 140. Specifically, the DC link capacitor 130 may maintain the DC link voltage converted by the rectifier 120 and supply it to the inverter 140.

[0076] The inverter 140 may switch the voltage applied to the working coil (WC) so that a high-frequency current flows through the working coil (WC). The inverter 140 may apply current to the working coil (WC). The inverter unit 140 may include a relay or a semiconductor switch that turns on or off the working coil (WC). For example, the semiconductor switch may include an Insulated Gate Bipolar Transistor (IGBT) or a Wide Band Gap (WBG) element. The WBG element may include silicon carbide (SiC) or gallium nitride (GaN). The inverter unit 140 drives the semiconductor switch to cause a high-frequency current to flow through the working coil (WC), thereby forming a high-frequency magnetic field in the working coil (WC).

[0077] The working coil (WC) may include at least one working coil (WC) that generates a magnetic field for heating the object to be heated (HO). The working coil (WC) may or may not have a current flowing therethrough depending on whether the switching element is driven. When current flows through the working coil (WC), a magnetic field is generated. The working coil (WC) generates a magnetic field as the current flows, thereby heating the object to be heated (HO).

[0078] One end of the working coil (WC) may be connected to a connection point of a switching element of the inverter unit 140, and the other end may be connected to a resonant capacitor 160.

[0079] The switching element is driven by a driving unit (not shown), and the switching time output from the driving unit is controlled so that the switching elements alternately operate, thereby applying a high-frequency voltage to the working coil (WC). Since the on / off times of the switching elements applied from the driving unit (not shown) are gradually compensated, the voltage supplied to the working coil (WC) can change from a low voltage to a high voltage.

[0080] The resonant capacitor 160 can resonate with the working coil (WC).

[0081] The resonant capacitor 160 may be a component that acts as a buffer. The resonant capacitor 160 controls the saturation voltage rise rate during the turn-off of the switching element, thereby affecting energy loss during the turn-off time.

[0082] FIG. 5 is a cross-sectional view illustrating a cooking appliance 1 and an object to be heated (HO) according to an embodiment of the present disclosure.

[0083] FIG. 6 is a cross-sectional view illustrating a cooking appliance 1 and an object to be heated (HO) according to another embodiment of the present disclosure.

[0084] Referring to FIGS. 5 and 6, a cooking appliance 1 according to an embodiment of the present disclosure may further include at least some or all of a heat insulating member 35, a shielding plate 45, a support member 50, and a cooling fan 55.

[0085] The heat insulating member 35 may be provided between the top plate 15 and the working coil (WC).

[0086] Specifically, the heat insulating member (35) may be mounted below the top plate (15), and a working coil (WC) may be disposed below the heat insulating member.

[0087] This heat insulating member 35 can block the heat generated when the intermediate material (IM) or the object to be heated (HO) is heated by the operation of the working coil (WC) from being transferred to the working coil (WC).

[0088] That is, when the intermediate material (IM) or the object to be heated (HO) is heated by the electromagnetic induction of the working coil (WC), the heat of the intermediate material (IM) or the object to be heated (HO) is transferred to the top plate 15, and the heat of the top plate 15 is then transferred back to the working coil (WC), potentially damaging the working coil (WC).

[0089] As described above, the heat insulating member (35) may block heat transferred to the working coil (WC), thereby preventing the working coil (WC) from being damaged by heat, and further preventing degradation of heating performance of the working coil (WC).

[0090] For reference, although not a required component, a spacer (not shown) may be installed between the working coil (WC) and the heat insulating member 35.

[0091] Specifically, the spacer (not shown) may be inserted between the working coil (WC) and the heat insulating member 35 to prevent direct contact between the working coil (WC) and the heat insulating member 35. Accordingly, the spacer (not shown) can block heat generated when the intermediate material (IM) or the object to be heated (HO) is heated by the operation of the working coil (WC) from being transferred to the working coil (WC) through the heat insulating member 35.

[0092] That is, the spacer (not shown) can partially share the role of the heat insulating member 35, thereby minimizing the thickness of the heat insulating member 35, thereby minimizing the spacing between the object to be heated (HO) and the working coil (WC).

[0093] Furthermore, multiple spacers (not shown) may be provided, and the multiple spacers may be spaced apart from each other between the working coil (WC) and the heat insulating member 35. Accordingly, air drawn into the case 25 by the cooling fan 55, described below, may be guided to the working coil (WC) by the spacer (not shown).

[0094] That is, the spacer (not shown) guides the air drawn into the case 25 by the cooling fan 55 so that it can be appropriately delivered to the working coil (WC), thereby improving the cooling efficiency of the working coil (WC).

[0095] The shielding plate 45 is mounted beneath the working coil (WC) to block the magnetic field generated downward when the working coil (WC) is driven. The shielding plate 45 may be made of ferrite.

[0096] Specifically, the shielding plate 45 can block the magnetic field generated downward when the working coil (WC) is driven, and can be supported upward by the support member 50.

[0097] The support member 50 is installed between the lower surface of the shielding plate 45 and the lower plate of the case 25 to support the shielding plate 45 upward.

[0098] Specifically, the support member 50 can indirectly support the heat insulating member 35 and the working coil (WC) upward by supporting the shielding plate 45 upward, thereby ensuring that the heat insulating member 35 is in close contact with the top plate 15.

[0099] As a result, the spacing between the working coil (WC) and the object to be heated (HO) can be maintained at a constant level.

[0100] For reference, the support member 50 may include, for example, an elastic body (e.g., a spring) for supporting the shielding plate 45 upward, but is not limited thereto. Furthermore, the support member 50 is not an essential component and may be omitted from the cooking appliance 1.

[0101] A cooling fan 55 may be installed inside the case 25 to cool the working coil (WC).

[0102] Specifically, the cooling fan 55 may be driven and controlled by the aforementioned control module and may be installed on the side wall of the case 25. Of course, the cooling fan 55 may be installed in a location other than the side wall of the case 25. However, for convenience of explanation, the embodiment of the present disclosure will be described as an example where the cooling fan 55 is installed on the side wall of the case 25.

[0103] Furthermore, as illustrated in FIGS. 5 and 6, the cooling fan 55 can draw in air outside the case 25 and deliver it to the working coil (WC), or draw in air (particularly, hot air) inside the case 25 and discharge it outside the case 25.

[0104] Through this, efficient cooling of components inside the case 25 (particularly, the working coil (WC)) is possible.

[0105] Furthermore, as described above, air outside the case 25 delivered to the working coil (WC) by the cooling fan 55 can be guided to the working coil (WC) by the spacer. Accordingly, direct and efficient cooling of the working coil (WC) is enabled, thereby improving the durability of the working coil (WC) (i.e., improving durability by preventing heat damage).

[0106] The intermediate material (IM) may be a material having a resistance value that can be heated by the working coil (WC) .

[0107] The thickness of the intermediate material (IM) may be inversely proportional to the resistance value (i.e., surface resistance value) of the intermediate material (IM). That is, the thinner the intermediate material (IM), the higher the resistance value (i.e., surface resistance value) of the intermediate material (IM). Therefore, the intermediate material (IM) may be thinly installed on the top plate 15 and thus may be characterized as a heatable load.

[0108] For reference, the intermediate material (IM) according to the embodiments of FIGS. 5 and 6 may have a thickness of, for example, 0.1 µm to 1,000 µm, but is not limited thereto.

[0109] An intermediate material (IM) having such characteristics is provided to heat a non-magnetic material, and the impedance characteristics between the intermediate material (IM) and the object to be heated (HO) may vary depending on whether the object to be heated (HO) placed on the top plate 15 is a magnetic material or a non-magnetic material.

[0110] The following describes a case where the object to be heated (HO) is a magnetic material.

[0111] The resistance component (R1) and the inductance component (L1) of the object to be heated (HO) form an equivalent circuit together with the resistance component (R2) and the inductance component (L2) of the intermediate material (IM). At this time, the impedance of the magnetic object to be heated (HO), that is, the impedance composed of R1 and L1, may be smaller than the impedance of the intermediate material (IM), that is, the impedance composed of R2 and L2. Accordingly, the magnitude of the eddy current (I1) applied to the magnetic object to be heated (HO) may be greater than the magnitude of the eddy current (I2) applied to the intermediate material (IM). As a result, most of the eddy current generated by the working coil (WC) is applied to the object to be heated (HO), so that the object to be heated (HO) can be heated. That is, when the object to be heated (HO) is a magnetic material, the aforementioned equivalent circuit is formed, and most of the eddy current is applied to the object to be heated (HO), such that the working coil (WC) can directly heat the object to be heated (HO).

[0112] Next, the case where the object to be heated is a non-magnetic material will be described as follows.

[0113] When a non-magnetic object to be heated (HO) is placed on the top plate 15 and the working coil (WC) is driven, there is no impedance in the non-magnetic object to be heated (HO), but impedance may exist in the intermediate material (IM). That is, only the intermediate material (IM) may have a resistance component (R) and an inductor component (L). Accordingly, when a non-magnetic object to be heated (HO) is placed on the top plate 15 and a working coil (WC) is driven, the resistance component (R) and the inductor component (L) of the intermediate material (IM) can form an equivalent circuit. Accordingly, an eddy current (I) may be applied only to the intermediate material (IM), and no eddy current may be applied to the non-magnetic object to be heated (HO). More specifically, the eddy current (I) generated by the working coil (WC) may be applied only to the intermediate material (IM), so that the intermediate material (IM) can be heated. That is, when the object to be heated (HO) is a non-magnetic material, an eddy current (I) is applied to the intermediate material (IM) to heat the intermediate material (IM), and the non-magnetic object to be heated (HO) can be indirectly heated by the intermediate material (IM) heated by the working coil (WC). In this case, the intermediate material (IM) can be the main heating source.

[0114] In summary, regardless of whether the object to be heated (HO) is a magnetic material or a non-magnetic material, the object to be heated (HO) can be directly or indirectly heated by a single heat source called the working coil (WC). That is, when the object to be heated (HO) is a magnetic substance, the working coil (WC) directly heats the object to be heated (HO), and when the object to be heated (HO) is a non-magnetic substance, the intermediate material (IM) heated by the working coil (WC) can indirectly heat the object to be heated (HO).

[0115] Next, FIG. 7 is a diagram illustrating the output characteristics of a cooking appliance according to an embodiment of the present disclosure.

[0116] First, the Q factor (quality factor) may be a value indicating the sharpness of resonance in a resonant circuit. Therefore, in the case of a cooking appliance 1, the Q factor is determined by the inductance value of the working coil (WC) included in the cooking appliance 1 and the capacitance value of the resonant capacitor 160. The resonance curve differs depending on the Q factor. Therefore, the cooking appliance 1 has different output characteristics depending on the inductance value of the working coil (WC) and the capacitance value of the resonant capacitor 160.

[0117] FIG. 7 illustrates an example of a resonance curve according to the Q factor. Generally, the larger the Q factor, the sharper the curve shape, and the smaller the Q factor, the broader the curve shape.

[0118] The horizontal axis of the resonance curve may represent frequency, and the vertical axis may represent output power. The frequency at which maximum power is output on the resonance curve is called the resonant frequency (f0).

[0119] Generally, the cooking appliance 1 uses the frequency in the region to the right of the resonant frequency (f0) of the resonance curve. Furthermore, the cooking appliance 1 may have preset minimum and maximum operating frequencies at which it can operate.

[0120] For example, the cooking appliance 1 may operate at a frequency between the minimum operating frequency (fmin) and the maximum operating frequency (fmax). In other words, the operating frequency range of the cooking appliance 1 may range from the maximum operating frequency (fmax) to the minimum operating frequency (fmin).

[0121] For example, the maximum operating frequency (fmax) may be the maximum switching frequency of the IGBT. The IGBT maximum switching frequency may refer to the maximum frequency at which the IGBT switching element can operate, taking into account factors such as the withstand voltage and capacity. For example, the maximum operating frequency (fmax) may be 75 kHz.

[0122] The minimum operating frequency (fmin) may be approximately 20 kHz. In this case, since the cooking appliance 1 does not operate at an audible frequency (approximately 16 Hz to 20 kHz), noise from the cooking appliance 1 can be reduced.

[0123] The above-described maximum operating frequency (fmax) and minimum operating frequency (fmin) are merely exemplary and are not limiting.

[0124] Upon receiving a heating command, the cooking appliance 1 may determine the operating frequency based on the heating power level set in the heating command. Specifically, the cooking appliance 1 may adjust the output power by lowering the operating frequency as the set heating power level increases, and increasing the operating frequency as the set heating power level decreases. That is, when a heating command is received, the cooking appliance 1 can perform a heating mode in which it operates within the operating frequency range according to the set heat power.

[0125] In the following description, the cooking vessel may be an object to be heated (HO).

[0126] FIG. 8 is a drawing illustrating an example of a working coil.

[0127] The working coil (WC) may be formed of a plurality of turns (T). For example, the working coil (WC) may be formed of ten turns (T). The plurality of turns (T) may include first to tenth turns (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10). However, this is merely an example, and the number of turns (T) forming the working coil (WC) is not limited thereto.

[0128] The first turn (T1) may be the turn closest to the center of the working coil (WC) among the ten turns (T). In addition, the tenth turn (T10) may be the turn furthest from the center of the working coil (WC) among the ten turns (T).

[0129] When the working coil (WC) is formed of ten turns (T), the turns may be the first to tenth turns (T1, T2, T3, T4, T5, T7, T8, T9, T10) in order from the turn closest to the center of the working coil (WC) to the turn furthest from the center.

[0130] Each turn (T) of the working coil (WC) may be formed to have a predetermined distance (dn) from other adjacent turns. The spacing (dn) between each turn of the working coil (WC) may include a first spacing to a ninth spacing (dn1, dn2, dn3, dn4, dn5, dn6, dn7, dn8, dn9). However, this is merely an example, and the number of spacings (dn) between each turn may vary depending on the number of turns (T).

[0131] The first spacing (dn1) may be the spacing between the first turn (T1) and the second turn (T2). Additionally, the ninth spacing (dn9) may be the spacing between the ninth turn (T9) and the tenth turn (T10).

[0132] When the working coil (WC) is formed of 10 turns (T), the spacing (dn) between each turn may be the first to ninth spacings (dn1, dn2, dn3, dn4, dn5, dn6, dn7, dn8, dn9) in order from the closest spacing to the farthest spacing from the center of the working coil (WC).

[0133] As illustrated in FIG. 8, the spacing (dn) between each turn of the working coil (WC) can be formed equally. The first to ninth spacings (dn1, dn2, dn3, dn4, dn5, dn6, dn7, dn8, dn9) can all be formed equally.

[0134] A working coil (WC) having a uniform spacing (dn) between each turn of the working coil (WC) can be a uniform working coil (WC1).

[0135] However, in the case of the uniform working coil (WC1), there is a problem in that the magnetic field is not concentrated on the object to be heated (HO), making it difficult to maximize heating efficiency.

[0136] The strength of the magnetic field generated in the working coil (WC) may vary depending on the average magnetic flux length of the working coil (WC).

[0137] The average magnetic flux length of the working coil (WC) may be the average of the magnetic path lengths of each turn (T).

[0138] The magnetic path of each turn (T) of the working coil (WC) will be described with reference to FIGS. 9 to 13.

[0139] FIGS. 9 and 10 are diagrams illustrating the magnetic path length according to the magnetic path of each turn.

[0140] FIG. 9 is a diagram illustrating the magnetic path length of one of the multiple turns (T) forming the working coil (WC). Furthermore, FIG. 10 illustrates the magnetic path length of a turn further from the center of the working coil (WC) than the turn illustrated in FIG. 9.

[0141] The magnetic flux generated in each turn (T) of the working coil (WC) can flow along a magnetic path (MP).

[0142] The magnetic permeability of air may be lower than that of metal. Therefore, when the magnetic path (MP) includes air, the magnetic path length may be longer than when the magnetic path (MP) includes no air. When the magnetic path (MP) includes only metal, it may have a minimum magnetic path length.

[0143] The right magnetic path (lright) of FIG. 9 includes only the heated object (pot) made of metal. In contrast, the right magnetic path (lright) of FIG. 10 includes both the heated object (pot) made of metal and air.

[0144] Accordingly, the length of the right magnetic path (lright) of FIG. 10 is longer than the length of the right magnetic path (lright) of FIG. 9. Therefore, the total magnetic path length of FIG. 10 is longer than the total magnetic path length of FIG. 9.

[0145] That is, the farther a turn (T) is from the center of the working coil (WC), the longer its magnetic path length.

[0146] On the other hand, the closer a turn (T) is to the center of the working coil (WC), the smaller its diameter, so that the opposing magnetic fluxes generated by the turn (T) can cancel each other out. Accordingly, the portion of the magnetic path (MP) of the turn (T) passing through the metal object to be heated (HO) may be reduced.

[0147] For a different reason, the closer a turn (T) is to the center of the working coil (WC), the longer its magnetic path length.

[0148] Next, with reference to FIG. 11, the magnetic path length of each turn (T) of the working coil (WC) will be described.

[0149] FIG. 11 is a graph illustrating the magnetic path length of each turn of the working coil.

[0150] Specifically, FIG. 11 is a graph illustrating the magnetic path length (MPL) for each of the multiple turns of the uniform working coil (WC1) illustrated in FIG. 8.

[0151] Referring to FIG. 11, the magnetic path lengths of the magnetic fields generated by the fifth turn (T5) and the sixth turn (T6) are the shortest. From this, it can be seen that among the multiple turns (T), the turn whose distance from the center of the working coil (WC) is the median has the shortest magnetic path length.

[0152] Meanwhile, based on the fifth turn (T5) and the sixth turn (T6), the magnetic path length increases as the distance between the center of the working coil (WC) and a turn increases. Furthermore, based on the fifth turn (T5) and the sixth turn (T6), the magnetic path length also increases as the distance between the center of the working coil (WC) and a turn decreases.

[0153] Thus, the closer or farther the distance between the center of the working coil (WC) and the turns (T), the longer the magnetic path length of the turns (T). Accordingly, the average magnetic flux length of the working coil (WC) also increases.

[0154] Meanwhile, the strength of the magnetic field generated by the working coil (WC) or each turn (T) of the working coil (WC) can be calculated using the following Equation 1:

[0155] According to Equation 1, the magnetic field (H) is H = N ⋅ I peak l N , the number of turns I peak , input peak current l , average magnetic flux length MPL 1 proportional to the number of turns (N) and the input peak current (Ipeak), and inversely proportional to the average magnetic flux length (l) or magnetic path length (1).

[0156] That is, the strength of the magnetic field (H) generated by the working coil (WC) is weaker as the average magnetic flux length (l) increases. Alternatively, the strength of the magnetic field (H) generated by the working coil (WC) is stronger as the average magnetic flux length (l) decreases.

[0157] Furthermore, the strength of the magnetic field (H) generated by each turn (T) of the working coil (WC) is weaker as the magnetic path length (l) increases. Alternatively, the strength of the magnetic field (H) generated by each turn (T) of the working coil (WC) is stronger as the magnetic path length (l) decreases.

[0158] Therefore, the strength of the magnetic field (H) generated by the first turn (T1) and the tenth turn (T10) may be the weakest. Furthermore, the strength of the magnetic field (H) generated by the fifth turn (T5) and the sixth turn (T6) may be the strongest.

[0159] Meanwhile, the current density (J) of the object to be heated (HO) may be proportional to the strength of the magnetic field (H).

[0160] In this regard, a description will be given with reference to FIG. 12.

[0161] FIG. 12 is a graph illustrating the current density of the heated object.

[0162] Specifically, FIG. 12 illustrates the current density (J) of the object to be heated (HO) heated by the uniform working coil.

[0163] FIG. 12 is a graph illustrating the current density (J) of an object to be heated (HO) as a function of the distance from the center of the object to be heated (HO) with a radius of, for example, 110 mm.

[0164] Referring to FIG. 12, the current density (J) has a maximum value at a point where the distance from the center of the object to be heated (HO) is, for example, approximately 55 mm. Meanwhile, the current density (J) decreases as the distance from the center of the object to be heated (HO) increases.

[0165] Meanwhile, the higher the current density (J) of the object to be heated (HO), the higher the heat loss.

[0166] Next, with reference to FIG. 13, the heat loss by region of the object to be heated (HO) will be described.

[0167] FIG. 13 is a diagram illustrating an example of the heat loss (EM-Loss) by region of an object to be heated (HO) heated by a uniform working coil.

[0168] When the object to be heated (HO) is heated by a uniform working coil (WC1), the regions of the bottom surface of the object to be heated (HO) can be divided into a first region (A1), a second region (A2), a third region (A3), a fourth region (A4), and a fifth region (A5).

[0169] Among the regions of the object to be heated (HO), the region with the greatest heat loss may be the concentrated heating region.

[0170] Referring to the example of FIG. 13, the third region (A3) of the object to be heated (HO) has the greatest heat loss. In other words, the concentrated heating region may be the third region (A3).

[0171] Furthermore, the heat loss of the third region (A3) may be approximately 5^10 [W / m^3]. That is, the maximum heat loss of the object to be heated (HO) may be approximately 5^10 [W / m^3].

[0172] Meanwhile, the third region (A3) may be a region including a point whose distance from the center of the object to be heated (HO) is approximately 55 mm. Alternatively, the third region (A3) may be a region where at least a portion of the fifth turn (T5) or the sixth turn (T6) is positioned below. Alternatively, the third region (A3) may be a point where at least a portion of the fifth spacing (dn5) is positioned below.

[0173] As described in FIGS. 8 to 13, the maximum heat loss of the object to be heated (HO) may vary depending on the arrangement of the plurality of turns (T) forming the working coil (WC).

[0174] In addition, depending on the arrangement of the plurality of turns (T) forming the working coil (WC), the location or size of the area where the object to be heated (HO) has the maximum heat loss may be different.

[0175] Accordingly, the present disclosure aims to provide a working coil (WC) that maximizes heating efficiency by increasing the maximum heat loss of an object to be heated (HO).

[0176] Furthermore, the present disclosure aims to provide a working coil (WC) that maximizes heating efficiency by controlling the size or location of an area of an object to be heated (HO) with maximum heat loss.

[0177] The present disclosure aims to provide a cooking appliance 1 that enhances the maximum heat loss of an object to be heated (HO).

[0178] Furthermore, the present disclosure provides a cooking appliance 1 that controls the size or location of an area of an object to be heated (HO) with maximum heat loss.

[0179] To this end, the spacing (dn) between turns (T) forming the working coil (WC) of the cooking appliance 1 according to an embodiment of the present disclosure may be nonuniform.

[0180] First, the working coil of the cooking appliance 1 according to the first embodiment of the present disclosure will be described with reference to FIGS. 14 to 17.

[0181] FIG. 14 is a drawing illustrating the shape of the working coil according to the first embodiment of the present disclosure.

[0182] The working coil (WC2) of FIG. 14 may be a working coil having the same outer and inner circumferential diameters as the uniform working coil (WC1) of FIG. 8. In addition, the working coil (WC2) of FIG. 14 may be a working coil formed of the first to tenth turns (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10) like the uniform working coil (WC1) of FIG. 8.

[0183] However, unlike the uniform working coil (WC1) of FIG. 8, the spacing (dn) between each turn of the working coil (WC2) of FIG. 14 may not be uniform.

[0184] Specifically, the spacing (dn) between each turn of the working coil (WC2) may decrease as a distance from the center of the working coil (WC) increases. A working coil in which the spacing (dn) between each turn decreases as it moves away from the center of the working coil may be a reverse-type working coil (WC2).

[0185] The spacing (dn) between each turn of the working coil (WC2) may decrease by a predetermined distance as it moves away from the center of the working coil (WC).

[0186] For example, the predetermined distance may be 0.5 mm. Accordingly, when the first spacing (dn1) is 4.5 mm, the second spacing (dn2) may be 4.0 mm, the third spacing (dn3) may be 3.5 mm, the fourth spacing (dn4) may be 3.0 mm, the fifth spacing (dn5) may be 2.5 mm, the sixth spacing (dn6) may be 2.0 mm, the seventh spacing (dn7) may be 1.5 mm, the eighth spacing (dn8) may be 1.0 mm, and the ninth spacing (dn9) may be 0.5 mm.

[0187] Accordingly, the equivalent inductance (Leq) may be 6.92 µH, which is 38.12% larger than a case in which the uniform working coil (WC1) is included. Additionally, the equivalent resistance (Req) of the cooking appliance 1 may be 348.2 mΩ, which is 38.09% greater than in which the uniform working coil (WC1) included.

[0188] As the equivalent inductance (Leq) and equivalent resistance (Req) increase, the resonant current decreases, which may reduce switching loss. As switching loss decreases, heating efficiency may increase.

[0189] Meanwhile, according to an embodiment, the spacing (dn) between each turn of the working coil (WC2) may decrease by a predetermined ratio as the distance increases from the center of the working coil (WC).

[0190] For example, the predetermined ratio may be 10%. Accordingly, when the first spacing (dn1) is 10.0 mm, the second spacing (dn2) may be 9.0 mm. Additionally, the third spacing (dn3) may be 8.1 mm.

[0191] Next, the magnetic path length and average magnetic flux length of each turn (T) of the reverse-type working coil (WC2) will be described.

[0192] FIG. 15 is a graph illustrating the magnetic path length of each turn of the working coil.

[0193] Specifically, FIG. 15 illustrates the magnetic path length (MPL_asy_re) for each turn (T) of the reverse-type working coil (WC2). Additionally, FIG. 15 illustrates the magnetic path length (MPL) for each turn (T) of the uniform working coil (WC1).

[0194] The average magnetic flux length of the working coil (WC) may be the average of the magnetic path lengths of each turn (T).

[0195] From FIG. 15, it can be deduced that the average magnetic flux length of the reverse-type working coil (WC2) is shorter than the average magnetic flux length of the uniform working coil (WC1).

[0196] As described above, the shorter the average magnetic flux length of the working coil (WC), the stronger the magnetic field generated from the working coil (WC). Therefore, the magnetic field generated from the reverse-type working coil (WC2) may be stronger than the magnetic field generated from the uniform working coil (WC1).

[0197] Accordingly, the heating efficiency of the reverse-type working coil (WC2) may be higher than that of the uniform working coil (WC1).

[0198] Next, the current density of the object to be heated (HO) heated by the reverse-type working coil (WC2) will be described.

[0199] FIG. 16 is a graph illustrating the current density of the object to be heated.

[0200] Specifically, FIG. 16 illustrates the current density (Asy_reverse_Mag_J) of the object to be heated (HO) heated by the reverse-type working coil (WC2). Furthermore, FIG. 16 illustrates the current density (Space_Mag_J) of the object to be heated (HO) heated by the uniform working coil (WC1).

[0201] Referring to FIG. 16, when the object to be heated (HO) is heated by the reverse-type working coil (WC2), the current density reaches a maximum at a point approximately 75 mm away from the center of the object to be heated (HO). Meanwhile, the current density decreases as it moves away from a point about 75 mm away from the center of the object to be heated (HO).

[0202] Meanwhile, when the object to be heated (HO) is heated by a uniform working coil (WC1), the current density has a maximum value at a point about 55 mm away from the center of the object to be heated (HO).

[0203] That is, the current density of the object to be heated (HO) heated by the reverse working coil (WC2) has a maximum value at a point further from the center of the working coil (WC) than the current density of the object to be heated (HO) heated by the uniform working coil (WC1).

[0204] In addition, the maximum current density of the object to be heated (HO) heated by the reverse-type working coil (WC2) may be a value that is 7.9% higher than the maximum current density of the object to be heated (HO) heated by the uniform working coil (WC1).

[0205] Next, referring to FIG. 17, the heat loss by region of the object to be heated (HO) heated by the reverse-type working coil (WC2) will be described.

[0206] FIG. 17 is a diagram illustrating an example of the heat loss (EM-Loss) by region of the object to be heated by the reverse-type working coil.

[0207] When an object to be heated (HO) is heated by a uniform working coil (WC1), the bottom surface of the object to be heated (HO) can be divided into a first region (B1), a second region (B2), a third region (B3), a fourth region (B4), and a fifth region (B5).

[0208] The region of the object to be heated (HO) with the greatest heat loss may be a concentrated heating region.

[0209] Referring to the example of FIG. 17, the third region (B3) of the object to be heated (HO) has the greatest heat loss. In other words, the concentrated heating region may be the third region (B3).

[0210] Additionally, the heat loss of the third region (B3) may be approximately 6^10[W / m^3]. That is, the maximum heat loss of the object to be heated (HO) may be approximately 6^10 [W / m^3].

[0211] As described above in FIG. 13, when the object to be heated (HO) is heated using the uniform working coil (WC1), the maximum heat loss of the object to be heated (HO) may be approximately 5^10 [W / m^3].

[0212] That is, the maximum heat loss of the object to be heated (HO) heated by the reverse working coil (WC2) is greater than the maximum heat loss of the object to be heated (HO) heated by the uniform working coil (WC1).

[0213] Meanwhile, the third region (B3) may be a region including a point whose distance from the center of the object to be heated (HO) is approximately 75 mm. Alternatively, the third region (B3) may be a region where at least a portion of the sixth turn (T6) and the seventh turn (T7) are positioned below. Alternatively, the third region (B3) may be a region where at least a portion of the sixth spacing (dn6) is positioned below.

[0214] As described above in FIG. 13, when the object to be heated (HO) is heated using the uniform working coil (WC1), the concentrated heating region may be a region that includes a point at a distance of about 55 mm from the center of the object to be heated (HO).

[0215] That is, the concentrated heating region of the object to be heated (HO) heated by the reverse working coil (WC2) may be formed further from the center of the working coil (WC) than the concentrated heating region of the object to be heated (HO) heated by the uniform working coil (WC1).

[0216] Accordingly, the object to be heated (HO) can be heated intensively over a larger radius than when using a uniform working coil (WC1), thereby evenly heating the load of the object to be heated (HO). In particular, the lower portion of the load can be evenly heated in the horizontal direction.

[0217] Summarizing FIGS. 15 to 17, the cooking appliance 1 according to the first embodiment of the present disclosure can increase the heat loss of the object to be heated (HO).

[0218] Accordingly, the cooking appliance 1 according to the first embodiment of the present disclosure can maximize heating efficiency.

[0219] Next, with reference to FIGS. 18 to 21, a working coil of a cooking appliance 1 according to a second embodiment of the present disclosure will be described.

[0220] FIG. 18 is a drawing illustrating a shape of a working coil according to a second embodiment of the present disclosure.

[0221] The working coil (WC3) of FIG. 18 may be a working coil having the same outer diameter and inner diameter as the uniform working coil (WC1) of FIG. 8. In addition, the working coil (WC3) of FIG. 18 may be a working coil formed of first to tenth turns (T1, T2, T3, T4, T5, T6, T7, T8, T9, T10) like the uniform working coil (WC1) of FIG. 8.

[0222] However, unlike the uniform working coil (WC1) of FIG. 8, the spacing (dn) between each turn of the working coil (WC3) of FIG. 18 may not be uniform.

[0223] Specifically, the spacing (dn) between each turn of the working coil (WC3) may increase as a distance from the center of the working coil (WC) increases. A working coil in which the spacing (dn) between each turn increases as it moves away from the center of the working coil may be a forward-type working coil (WC3).

[0224] That is, the spacing between each turn (T) of the working coil (WC3) may increase as it moves away from the center of the working coil (WC3).

[0225] For example, the predetermined spacing may be 0.5 mm. Accordingly, when the first spacing (dn1) is 0.5 mm, the second spacing (dn2) may be 1.0 mm, the third spacing (dn3) may be 1.5 mm, the fourth spacing (dn4) may be 2.0 mm, the fifth spacing (dn5) may be 2.5 mm, the sixth spacing (dn6) may be 3.0 mm, the seventh spacing (dn7) may be 3.5 mm, the eighth spacing (dn8) may be 4.0 mm, and the ninth spacing (dn9) may be 4.5 mm.

[0226] Accordingly, the equivalent inductance (Leq) may be 5.28 µH, which is 5.4% larger than in a case in which the uniform working coil (WC1) is included. Additionally, the equivalent resistance (Req) of the cooking appliance 1 may be 270.69 mΩ, which is 7.35% greater than when including a uniform working coil (WC1).

[0227] As the equivalent inductance (Leq) and equivalent resistance (Req) increase, the resonant current decreases, which may reduce switching loss. As switching loss decreases, heating efficiency may increase.

[0228] Meanwhile, according to an embodiment, the spacing between each turn (T) of the working coil (WC3) may increase by a predetermined ratio as the distance increases from the center of the working coil (WC3).

[0229] For example, the predetermined ratio may be 10%. Accordingly, when the first spacing (dn1) is 10.0 mm, the second spacing (dn2) may be 11.0 mm. Additionally, the third spacing (dn3) may be 12.1 mm.

[0230] Next, the magnetic path length and average magnetic flux length of each turn (T) of the forward-type working coil (WC3) will be described.

[0231] FIG. 19 is a graph illustrating the magnetic path length of each turn of the working coil.

[0232] Specifically, FIG. 19 illustrates the magnetic path length (MPL_asy_fo) of each turn (T) of the forward-type working coil (WC3). Additionally, FIG. 19 illustrates the magnetic path length (MPL) of each turn (T) of the uniform working coil (WC1).

[0233] The average magnetic flux length of the working coil (WC) may be the average of the magnetic path lengths of each turn (T).

[0234] From FIG. 19, it can be deduced that the average magnetic flux length of the forward-type working coil (WC3) is shorter than the average magnetic flux length of the uniform working coil (WC1).

[0235] As described above, the shorter the average magnetic flux length of the working coil (WC), the stronger the magnetic field generated from the working coil (WC). Therefore, the magnetic field generated from the forward-type working coil (WC3) may be stronger than the magnetic field generated from the uniform working coil (WC1).

[0236] Accordingly, the heating efficiency of the forward-type working coil (WC3) may be higher than that of the uniform working coil (WC1).

[0237] Next, the current density of the object to be heated (HO) heated by the forward-type working coil (WC3) will be described.

[0238] FIG. 20 is a graph illustrating the current density of a heated object.

[0239] Specifically, FIG. 20 illustrates the current density (Asy_forward_Mag_J) of an object to be heated (HO) heated by a forward-type working coil (WC3). Additionally, FIG. 20 illustrates the current density (Space_Mag_J) of an object to be heated (HO) heated by a uniform working coil (WC1).

[0240] Referring to FIG. 20, when the object to be heated (HO) is heated by the forward-type working coil (WC3), the current density has a maximum value at a point about 30 mm away from the center of the object to be heated (HO). Meanwhile, the current density decreases as the distance from the center of the object to be heated (HO) increases from about 30 mm.

[0241] Meanwhile, when the object to be heated (HO) is heated by the uniform working coil (WC1), the current density has a maximum value at a point about 55 mm away from the center of the object to be heated (HO).

[0242] That is, the current density of the object to be heated (HO) heated by the forward working coil (WC3) has a maximum value at a point closer to the center of the working coil (WC) than the current density of the object to be heated (HO) heated by the uniform working coil (WC1).

[0243] In addition, the maximum current density of the object to be heated (HO) heated by the forward working coil (WC3) may be a value that is 8.5% higher than the maximum current density of the object to be heated (HO) heated by the uniform working coil (WC1).

[0244] Next, with reference to FIG. 21, the heat loss by region of the object to be heated (HO) heated by the forward-type working coil (WC3) will be described.

[0245] FIG. 21 is a diagram illustrating an example of the heat loss (EM-Loss) by region of the object to be heated by the forward-type working coil.

[0246] When the object to be heated (HO) is heated by the forward-type working coil (WC3), the regions of the bottom surface of the object to be heated (HO) can be divided into a first region (C1), a second region (C2), a third region (C3), a fourth region (C4), and a fifth region (C5).

[0247] Among the regions of the object to be heated (HO), the region with the greatest heat loss may be the concentrated heating region.

[0248] Referring to the example of FIG. 21, the third region (C3) among the regions of the object to be heated (HO) experiences the greatest heat loss. In other words, the concentrated heating region may be the third region (C3).

[0249] In addition, the heat loss of the third region (C3) may be approximately 6^10 [W / m^3]. In other words, the maximum heat loss of the object to be heated (HO) may be approximately 7^10 [W / m^3].

[0250] As described above in FIG. 13, when the object to be heated (HO) is heated using a uniform working coil (WC1), the maximum heat loss of the object to be heated (HO) may be approximately 5^10 [W / m^3].

[0251] That is, the maximum heat loss of the object to be heated (HO) heated by the forward-type working coil (WC3) is greater than the maximum heat loss of the object to be heated (HO) heated by the uniform working coil (WC1).

[0252] Meanwhile, the third region (C3) may be a region including a point whose distance from the center of the object to be heated (HO) is approximately 30 mm. Alternatively, the third region (C3) may be a region where at least a portion of the fourth turn (T4) and the fifth turn (T5) is positioned below. Alternatively, the third region (C3) may be a region where at least a portion of the fourth spacing (dn4) is positioned below.

[0253] As described above in FIG. 13, when heating an object to be heated (HO) using a uniform working coil (WC1), the concentrated heating region may be a region including a point whose distance from the center of the object to be heated (HO) is approximately 55 mm.

[0254] That is, the concentrated heating region of the object to be heated (HO) heated by the forward-type working coil (WC3) may be formed closer to the center of the working coil (WC) than the concentrated heating region of the object to be heated (HO) heated by the uniform working coil (WC1).

[0255] Accordingly, the load can be heated more evenly than when using the uniform working coil (WC1). In particular, the load can be heated evenly in the vertical direction.

[0256] Summarizing FIGS. 18 to 21, the cooking appliance 1 according to the second embodiment of the present disclosure can increase the heat loss of the object to be heated (HO) by including a forward-type working coil (WC3).

[0257] Accordingly, the cooking appliance 1 according to the second embodiment of the present disclosure can maximize heating efficiency.

[0258] Meanwhile, the shape of the working coil (WC) included in the cooking appliance 1 of the present disclosure is not limited to the first and second embodiments, and may include any shape in which the spacing between each turn (T) is not uniform.

[0259] That is, at least one of the spacings between each turn of the working coil (WC) may be different from the remaining spacings. Alternatively, the spacings between each turn of the working coil (WC) may be different from each other.

[0260] In addition, the turn spacing between the center of the working coil (WC) and the first reference turn and the turn spacing between the first reference turn and the second reference turn forming the outermost portion of the working coil may be different from each other.

[0261] Specifically, the turn spacing between the first turn and the second reference turn may be narrower than the turn spacing between the center of the working coil (WC) and the first reference turn.

[0262] Alternatively, the turn spacing between the first turn and the second reference turn may be wider than the turn spacing between the center of the working coil (WC) and the first reference turn.

[0263] Hereinafter, the present disclosure will be described, particularly using a PCB (Printed Circuit Board) working coil as an example, as the aforementioned working coil (WC).

[0264] The PCB working coil may also be referred to as a PCB pattern coil, but the scope of the present disclosure should not be construed as being limited by such terminology.

[0265] A cooking appliance employing a PCB working coil is described as follows.

[0266] In the case of a PCB working coil with a pattern having a fixed (or equal) spacing (or interval), the magnetic field is concentrated internally, resulting in significant heat generation, which in turn affects the operation of the PCB working coil or the cooking appliance 1.

[0267] In particular, when the PCB working coil operates at a high frequency, the aforementioned heat generation problem can be exacerbated. Furthermore, in the case of a PCB working coil, the heat generation problem tends to be more severe the closer it is to the center.

[0268] The present disclosure provides a cooking appliance including a PCB working coil, and discloses a PCB working coil that generates less heat than conventional ones even when operating at high frequencies, and a cooking appliance 1 including (or employing) such a PCB working coil.

[0269] In order to reduce heat generation even when operating at high frequencies, the PCB working coil according to the present disclosure can utilize various methods, such as PCB pattern structures, arrangements, and shapes.

[0270] The present disclosure discloses a PCB working coil that can reduce heat generation generated in the PCB working coil during high frequency operation by lowering the magnetic flux affecting the windings, disposing the current density asymmetrically (e.g., asymmetrical arrangement of DC resistances), and designing the turn-to-turn spacing to be nonuniform.

[0271] A cooking appliance 1 according to at least one of the various embodiments of the present disclosure may include a top plate 15 on which an object to be heated (HO) is placed, a plurality of working coils (WCs) that heat the object to be heated (HO), an inverter 140 that applies current to each of the working coils (WC), and a controller that controls the operation of the inverter 140 so that the object to be heated (HO) is heated through each of the working coils (WC).

[0272] If the cooking appliance 1 employs multiple working coils (WCs) rather than one, at least one of the multiple working coils (WC) may be a PCB working coil.

[0273] The PCB working coil may include one or more turns.

[0274] Each turn may be a bundle of one or more unit coils.

[0275] If the PCB working coil is composed of multiple turns, the spacing (or distance) between each turn may be uniform. In this case, even if the spacing between turns is uniform, the configuration of each turn may be different from that of other turns.

[0276] According to an embodiment, if the PCB working coil is composed of multiple turns, the spacing between at least one turn may be different from that between other turns, i.e., the spacing between turns may not be uniform. Even in this case, the configuration of each turn may be the same as or different from that of other turns.

[0277] Hereinafter, a PCB working coil according to various embodiments of the present disclosure is disclosed. In this case, the PCB working coil (WC) is composed of multiple turns. For convenience of explanation, the number of turns is set to six (T1 to T6) as an example.

[0278] FIG. 22 is a drawing illustrating a PCB working coil.

[0279] (a) of FIG. 22 illustrates a top view of a PCB working coil composed of multiple turns (T1-T6).

[0280] The PCB working coil can be divided into a heated region and a non-heating region. However, this division is for convenience of explanation only, and the present disclosure is not limited to such division.

[0281] The heated region may refer to a region in which turns (T1-T6) are arranged. On the other hand, the non-heating region may refer to a region that is not a heated region, i.e., a region where turns (T1-T6) are not arranged. In other words, the region between turns can be considered a non-heating region. This non-heating region may also include a central region where no turns are arranged. The central region may include a center point (c). Here, the center point (c) may be an arbitrarily defined concept for describing components of various PCB working coils configured according to the present disclosure.

[0282] The present disclosure will hereinafter be described using a circular PCB working coil as an example, but it should be noted that the present disclosure is not limited thereto. For example, the PCB working coil may also have a polygonal shape, such as an oval, rectangle, or square.

[0283] Meanwhile, (b) of FIG. 22 may be a cross-sectional view of the dotted box portion representing a portion of the PCB working coil illustrated in (a) of FIG. 22.

[0284] Referring to (b) of FIG. 22, it can be seen that the PCB working coil has turns (T1-T6) having a predefined turn width (tw) arranged at a predefined spacing (dn12-dn56).

[0285] For example, the first turn (T1) is a turn arranged at the position closest to the center point (c), i.e., the innermost portion of the PCB working coil, and may have a first turn width (tw1). The second turn (T2) is a turn arranged at a position following the first turn (T1) and may have a second turn width (tw2). In this case, the spacing between the first turn (T1) and the second turn (T2) may be named dn12, and its value may be determined in advance. The third turn (T3) is a turn positioned next to the second turn (T2) and may have a third turn width (tw3). At this time, the spacing between the second turn (T2) and the third turn (T3) may be designated as dn23, and its value may be determined in advance. The fourth turn (T4) is a turn positioned next to the third turn (T3) and may have a fourth turn width (tw4). At this time, the spacing between the third turn (T3) and the fourth turn (T4) may be designated as dn34, and its value may be determined in advance. The fifth turn (T5) is a turn positioned next to the fourth turn (T4) and may have a fifth turn width (tw5). At this time, the spacing between the fourth turn (T4) and the fifth turn (T5) can be named dn45, and its value can be determined in advance. The sixth turn (T6) is a turn located at the furthest position from the center point (c), i.e., the outermost portion of the PCB working coil, and can have a sixth turn width (tw6). At this time, the spacing between the fifth turn (T5) and the sixth turn (T6) can be named dn56, and its value can be determined in advance.

[0286] As described above, the configuration of the PCB working coil according to the present disclosure can adjust factors, such as the turn spacing (dn), the turn width (tw), the spacing (ds) between unit coils within a turn, and the number of strands of the unit coil within a turn, in order to resolve the heat generation problem.

[0287] FIG. 23 is a diagram illustrating a turn-to-turn spacing according to an embodiment of the present disclosure.

[0288] In the graphs (a) and (b) of FIG. 23, the vertical axis may represent the turn-to-turn spacing (dn), and the horizontal axis may represent the number of turns (e.g., T1-T6). Meanwhile, the graphs of (a) and (b) of FIG. 23 describe the turn-to-turn spacing relative to the number of turns according to oz. Here, oz may represent, for example, the thickness of a PCB working coil. While (a) and (b) of FIG. 23 illustrate graphs of 3 oz to 6 oz as examples, 2 oz may also be included. However, when a high current is used, 3 oz or more may be preferred.

[0289] Referring to (a) of FIG. 23, it can be seen that as the number of turns increases, the turn-to-turn spacing decreases. At this time, the decrease in the turn-to-turn spacing may be linear.

[0290] Also, in (a) of FIG. 23, it can be seen that the turn-to-turn spacing decreases with respect to the number of turns for each oz.

[0291] Referring to (a) of FIG. 23, the number of turns on the horizontal axis, 1, may represent T1, 2 may represent T2, 3 may represent T3, 4 may represent T4, 5 may represent T5, and 6 may represent T6.

[0292] Therefore, interpreting the graph of (a) of FIG. 23, the turn-to-turn spacing may narrow as the distance from the center point (c) of the PCB coil (500) increases (from T1 to T6). Conversely, the turn-to-turn spacing may widen or increase as the distance from the center point (c) of the PCB coil (500) increases (from T6 to T1).

[0293] (b) of FIG. 23 is the opposite of (a) of FIG. 6. In other words, when interpreting the graph of (b) of FIG. 23, the turn spacing may increase as the distance from the center point (c) of the PCB coil (500) increases (from T1 to T6).

[0294] FIG. 24 is a diagram illustrating the turn spacing according to another embodiment of the present disclosure.

[0295] The basic description of the graphs of (a) and (b) of FIG. 24 is the same as the basic description of the graphs of (a) and (b) of FIG. 23 described above. Therefore, overlapping content will be omitted, and the differences from (a) and (b) of FIG. 23 described above will be mainly described below.

[0296] While the turn-to-turn spacing increases and decreases linearly with respect to the number of turns in the graphs (a) and (b) of FIG. 23 described above, referring to (a) and (b) of FIG. 24, the turn-to-turn spacing may not varies linearly (increasing or decreasing) with respect to the number of turns.

[0297] The turn-to-turn spacing in the graphs (a) and (b) of FIG. 24 may include non-linear sections.

[0298] Alternatively, referring to (a) and (b) of FIG. 24, the slope indicating the increase and decrease in the turn-to-turn spacing with respect to the number of turns may include sections where the slope changes and sections where the slope does not change.

[0299] Meanwhile, referring to the graphs illustrated in (a) and (b) of FIG. 24, there may be multiple sections where the slope indicating the increase and decrease in the turn-to-turn spacing with respect to the number of turns changes. In this case, the slopes in each section may be different from each other.

[0300] Referring to the graph illustrated in (a) of FIG. 24, it can be seen that the turn-to-turn spacing relative to the number of turns does not change until a certain turn and then gradually decreases (negative slope) after that turn.

[0301] Referring to the graph of (a) of FIG. 24, the turn-to-turn spacing does not change between T1 and T3. That is, the turn-to-turn spacings between T1 and T2 and between T2 and T3 may be the same (or equal). Meanwhile, it can be seen that the turn-to-turn spacing between T3 and T4 changes in a first step. The turn-to-turn spacing between T3 and T4 may differ from the turn-to-turn spacings between previous turns (the turn-to-turn spacings between T1-T2 and T2-T3). In addition, it can be seen that the turn-to-turn spacings between T4 and T5 and the turn-to-turn spacings between T5 and T6 also change in a second step. For example, the turn-to-turn spacing between T4 and T5 may differ not only from the turn-to-turn spacing between T3 and T4, but also from the turn-to-turn spacings between T1-T2 and T2-T3. Furthermore, the turn-to-turn spacing between T5 and T6 may differ from the turn-to-turn spacing between T4 and T5 described above.

[0302] On the other hand, referring to the graph illustrated in (b) of FIG. 24, the turn-to-turn spacing relative to the number of turns remains constant until a certain turn, but gradually increases (positive slope) thereafter.

[0303] In the graph of (b) of FIG. 24, the turn-to-turn spacings between T1 and T2 and between T2 and T3 may remain constant. In other words, the turn-to-turn spacings between T1 and T2 and between T2 and T3 may be identical. Meanwhile, the turn-to-turn spacing between T3 and T4 changes in a first step. The turn-to-turn spacing between T3 and T4 may be different from the turn-to-turn spacing between previous turns. That is, the turn-to-turn spacing between T3 and T4 may be increased compared to the turn-to-turn spacings between T1-T2 and T2-T3. It can be seen that the turn-to-turn spacing between T4 and T5 and the turn-to-turn spacing between T5 and T6 also change in a second step. At this time, the turn-to-turn spacing between T4 and T5 and the turn-to-turn spacing between T5 and T6 may be different from the turn-to-turn spacings between previous turns. That is, the turn-to-turn spacing between T4 and T5 and the turn-to-turn spacing between T5 and T6 may be increased compared to the turn-to-turn spacing between T1-T2 and T2-T3 as well as the turn-to-turn spacing between T3-T4. In addition, the turn-to-turn spacing between T5 and T6 may also be different from the turn-to-turn spacing between T4 and T5 described above.

[0304] The following FIGS. 25 to 27 illustrate embodiments with reference to the graph of (a) of FIG. 23, but are not necessarily limited thereto.

[0305] In each drawing, as described above, T1 represents the turn closest to the center point (c) (i.e., the innermost turn), and T6 represents the turn furthest from the center point (c) (i.e., the outermost turn).

[0306] In the following drawings, all factors not specifically mentioned may be assumed to be the same. For example, FIG. 25 only mentions the turn-to-turn spacing, and the remaining turn widths, the width of unit coils within a turn, the spacing between unit coils, and the number of unit coils may be assumed to be the same.

[0307] FIGS. 25 to 27 are drawings illustrating PCB working coils in which turns are arranged according to embodiments of the present disclosure.

[0308] First, (a) of FIG. 25 illustrates a top view of a PCB coil composed of six turns (T1-T6), and (b) of FIG. 25 illustrates a cross-sectional view of the turns within the dotted box illustrated in (a) of FIG. 25.

[0309] Referring to (a) and (b) of FIG. 25, a PCB working coil constructed with reference to the graph illustrated in (a) of FIG. 23 can be illustrated.

[0310] In this case, the turn width (tw) of each turn (T1-T6) constituting the PCB working coil may be the same.

[0311] As shown in the graph illustrated in (a) of FIG. 23, as the number of turns increases, the turn spacing decreases, as illustrated in (b) of FIG. 25.

[0312] In other words, referring to (b) of FIG. 25, it can be seen that the turn-to-turn spacing (dn12) between T1 and T2 is relatively larger than the turn-to-turn spacing (dn23) between T2 and T3. Similarly, it can be seen that dn23 is relatively larger than the turn-to-turn spacing (dn34) between T3 and T4, the turn-to-turn spacing (dn45) between T4 and T5, and the turn-to-turn spacing (dn56) between T5 and T6. That is, the turn-to-turn spacing gradually decreases relative to the number of turns, and dn12 > dn23 > dn34 > dn45 > dn56.

[0313] Next, FIG. 26 illustrates an embodiment in which the turn-to-turn spacing (dn) within the PCB working coil is uniform, but the turn width (tw) is adjusted.

[0314] In (a) of FIG. 26, a PCB working coil having six turns (T1-T6) is illustrated, and in (b) of FIG. 26, a cross-sectional view of the turns within the dotted box illustrated in (a) of FIG. 26 is illustrated.

[0315] Referring to (a) and (b) of FIG. 26, it can be seen that the turn spacing (dn) of T1-T6 is the same.

[0316] At this time, it can be seen that the turn width (tw) of each turn (T1-T6) is different.

[0317] Referring to (b) of FIG. 26, the turn width (tw1) of T1 may be different from the turn width (tw2) of T2 to the turn width (tw6) of T6.

[0318] Specifically, the turn width (tw1) of T1 may be a relatively larger value than the turn width (tw2) of T2 to the turn width (tw6) of T6. And the turn width (tw2) of T2 may be a relatively larger value than the turn width (tw3) of T3 to the turn width (tw6) of T6. From these characteristics, it can be seen that tw1 > tw2 > tw3 > tw4 > tw5 > tw6. In a similar concept, the turn width (tw6) of T6, which is the outermost turn, may have the smallest turn width among all turns of the PCB working coil, and conversely, the turn width (tw1) of T1, which is the innermost turn, may have the largest turn width among all turns of the PCB working coil. In this case, the turn widths of the remaining turns between T1 and T6 may be arbitrary (for example, a tw value between tw1 and tw6).

[0319] Even if the turn widths of each turn constituting the PCB working coil in (b) of FIG. 26 are different, the number of unit coils constituting one turn may or may not be the same for each turn.

[0320] Next, FIG. 27 illustrates an embodiment in which both the turn width and the turn-to-turn spacing of each turn within a PCB working coil are adjusted.

[0321] (a) of FIG. 27 illustrates a PCB working coil having six turns (T1-T6), and (b) of FIG. 27 illustrates a cross-sectional view of the turns within the dotted box illustrated in (a) of FIG. 27.

[0322] Referring to (a) and (b) of FIG. 27, the turn-to-turn spacings of T1-T6 are all different, and the turn widths of each turn may also be different.

[0323] Referring to (b) of FIG. 27, the turn width (tw1) of T1 may be different from the turn width (tw2) of T2 to the turn width (tw6) of T6.

[0324] The turn spacing (dn12) between T1 and T2 may be different from the turn spacing (dn23) between T2 and T3 and the turn spacing (dn56) between T5 and T6. That is, it can be seen that dn12 > dn23 > dn34 > dn45 > dn56.

[0325] The turn width (tw1) of T1 may be a relatively larger value than the turn width (tw2) of T2 and the turn width (tw6) of T6. That is, it can be seen that tw1 > tw2 > tw3 > tw4 > tw5 > tw6.

[0326] Meanwhile, even if the turn width and the turn-to-turn spacing of each turn constituting the PCB working coil in (b) of FIG. 27 are different, the number of unit coils constituting one turn may or may not be the same for each turn.

[0327] The PCB working coil according to each embodiment illustrated in FIGS. 25 to 27 has the advantage of further reducing heat generation compared to, for example, the PCB working coil illustrated in FIG. 22. In addition, the stable operation of the PCB working coil can be ensured through the reduction of heat generation, which can ultimately contribute to the stable operation of the cooking appliance.

[0328] In addition, the PCB working coil according to each embodiment illustrated in FIGS. 25 to 27 can increase the operating time of the PCB working coil by reducing the heat generation phenomenon compared to the PCB working coil illustrated in FIG. 22, which can ultimately contribute to extending the service life of the cooking appliance.

[0329] The embodiments illustrated in FIGS. 25 to 27 described above are based on the content of (a) of FIG. 23, but an embodiment based on the content of (b) of FIG. 23 is also possible, and such content can also be included in the present disclosure.

[0330] FIGS. 28 to 29 describe the embodiment(s) with reference to the graph of (a) of FIG. 24.

[0331] FIGS. 28 to 29 are drawings illustrating a PCB working coil in which turns are arranged according to embodiments of the present disclosure.

[0332] (a) of FIG. 28 illustrates a top view of a PCB coil composed of six turns (T1-T6), and (b) of FIG. 28 illustrates a cross-sectional view of the turns within the dotted box illustrated in (a) of FIG. 28.

[0333] Referring to (a) and (b) of FIG. 28, a PCB working coil constructed with reference to the graph illustrated in (a) of FIG. 24 can be illustrated.

[0334] Here, it is assumed that the turn widths (tw) of each turn (T1-T6) constituting the PCB working coil are all the same.

[0335] As illustrated in the graph illustrated in (a) of FIG. 24, as the number of turns increases, the turn spacing (dn) may vary, as illustrated in (b) of FIG. 28. At this time, in (a) of FIG. 23, it can be seen that the turn-to-turn spacing (dn) linearly decreases as the number of turns increases, whereas in (a) of FIG. 24, the turn-to-turn spacing (dn) nonlinearly decreases as the number of turns increases. Here, nonlinearity may indicate that there exist both sections in which the turn-to-turn spacing (dn) changes and sections in which it does not change, as described above.

[0336] Referring to (a) of FIG. 24 and (b) of FIG. 28, the turn-to-turn spacing (dn12) between T1 and T2 may be equal to the turn-to-turn spacing (dn23) between T2 and T3. Therefore, dn12 and dn23 may correspond to the non-changing sections described above. However, dn12 and dn23 may have relatively larger values compared to the turn-to-turn spacing between T3 and T4 (dn34), the turn-to-turn spacing between T4 and T5 (dn45), and the turn-to-turn spacing between T5 and T6 (dn56).

[0337] The next changing spacing is that dn34 may have a relatively larger value compared to dn45 and dn56. And dn45 may have a relatively larger value compared to dn56.

[0338] Next, FIG. 29 illustrates an embodiment of adjusting both the turn width and the turn-to-turn spacing of each turn within a PCB working coil, referring to (a) of FIG. 24.

[0339] (a) of FIG. 29 illustrates a PCB working coil having six turns (T1-T6), and (b) of FIG. 29 illustrates a cross-sectional view of the turns within the dotted box illustrated in (a) of FIG. 29.

[0340] Referring to (a) and (b) of FIG. 29, the turn-to-turn spacing (dn) of T1-T6 may not be the same, and the turn widths of T1-T6 may also not be the same.

[0341] Referring to (b) of FIG. 29, the turn width (tw1) of T1 may be different from the turn width (tw2) of T2 to the turn width (tw6) of T6.

[0342] Referring to (b) of FIG. 29, the turn width (tw1) of T1 is the same as the turn width (tw2) of T2, but may be different from the turn width (tw3) of T3 to the turn width (tw6) of T6.

[0343] tw3 may be different from tw4 to tw6. Tw4 may be different from tw5 to tw6. Tw5 may be different from tw6.

[0344] While (a) of FIG. 24 defines the turn spacing relative to the number of turns, the turn spacing in (a) of FIG. 24 may alternatively be defined in terms of turn width. In other words, the turn-to-turn spacing may also decrease nonlinearly relative to the number of turns.

[0345] The above may be applied equally or similarly to the graphs of (a) and (b) of FIG. 23 and (b) of FIG. 24.

[0346] Referring to (a) of FIG. 24 and (b) of FIG. 29, the turn-to-turn spacing (dn) between T1 and T6 may be identical to the turn-to-turn spacing (dn) of T1 to T6 illustrated in (b) of FIG. 28 described above.

[0347] Even though the turn widths and turn-to-turn spacings of each turn constituting the PCB working coil in (b) of FIG. 29 are different, the number of unit coils constituting each turn may or may not be the same.

[0348] The PCB working coil according to each embodiment illustrated in FIGS. 28 and 29 has the advantage of further reducing heat generation compared to, for example, the PCB working coil illustrated in FIG. 22, thereby ensuring stable operation of the PCB working coil. This ultimately contributes to improved stability of the cooking appliance 1.

[0349] Furthermore, the PCB working coil according to each embodiment illustrated in FIGS. 28 and 29 has the advantage of further reducing heat generation compared to, for example, the PCB working coil illustrated in FIG. 22, thereby increasing the operating time of the PCB working coil. This ultimately contributes to extended lifespan of the cooking appliance 1.

[0350] Meanwhile, although not illustrated, the opposite of the content illustrated in FIGS. 28 and 29 is also possible. For example, the embodiments of FIGS. 28 and 29 may configure the PCB working coil in the opposite manner to that illustrated based on the contents of (b) of FIG. 24, and such contents may also be included in the present disclosure.

[0351] If FIGS. 25 to 29 described above have been described in terms of the PCB working coil unit, FIGS. 30 to 36 below will describe one turn among the plurality of turns constituting the PCB working coil as an example.

[0352] FIG. 30 is a drawing illustrating the internal configuration of turns within the PCB working coil (WC) 500 of FIG. 22.

[0353] The internal configuration of each turn constituting the PCB working coil may or may not be identical. However, for convenience of explanation, the internal configurations of the turns constituting the PCB working coil are assumed to be identical in the present disclosure.

[0354] For convenience of explanation, two turns (Tn and Tn+1, where n is a natural number) are illustrated in FIG. 30.

[0355] As described above, the internal configurations of Tn and Tn+1 are assumed to be identical. Therefore, in FIG. 30, the (n+1)th turn, Tn+1, has the same internal configuration as the (n)th turn, Tn, and thus only a portion of the internal configuration is illustrated, with the remainder omitted.

[0356] A single turn (e.g., Tn) may have a multi-layer structure. For convenience of explanation, only two layers (L1, L2) are illustrated in FIG. 30, but the present disclosure is not limited thereto.

[0357] Meanwhile, each layer of the turn (Tn) may be interconnected through via holes, but is not limited thereto.

[0358] Each layer of the turn (Tn) may be configured to include multiple unit coils (e.g., L1 (s1-s8), L2 (s9-s15)).

[0359] For convenience of explanation, the following embodiments will be described using one layer (L1) as an example. However, the present disclosure is not limited thereto, and the same or similar content applied to L1 may also be applied to other layers, such as L2.

[0360] In the present disclosure, the spacing between turns (e.g., between Tn and Tn+1) is referred to as the inter-turn spacing.

[0361] In FIG. 30, a total of eight unit coils (s1-s8) can be arranged in the L1 layer. The spacing between unit coils is referred to as ds and described. The width (or the width) of one unit coil is referred to as ws and described.

[0362] FIGS. 31 to 34 are drawings illustrating unit coils constituting one layer of one turn of FIG. 30.

[0363] In FIG. 30, the spacing (ds) between unit coils constituting the L1 layer of Tn is exemplified as being uniform (or fixed, constant, etc.), and the width (ws) of each unit coil is also the same.

[0364] Meanwhile, FIGS. 31 and 32 illustrate unit coils (s1-s8) constituting the L1 layer of Tn.

[0365] Referring to FIGS. 31 and 32, for example, the widths (ws) of the eight unit coils are all equal, but the spacing (ds) between the unit coils is not uniform.

[0366] In this case, FIGS. 31 and 32 may both represent the L1 layer of the same turn (e.g., T1).

[0367] Alternatively, FIGS. 31 and 32 may each represent the L1 layer of different turns. In this case, for example, FIG. 31 may represent the L1 layer of T1, and FIG. 32 may represent the L1 layer of T6. It should be apparent that other turns may be used in place of the aforementioned T1 and T6.

[0368] First, referring to FIG. 31, the spacing between the unit coils constituting the L1 layer of Tn may be different.

[0369] Specifically, the spacing (ds1) between s1 and s2 is different from the spacing (ds2) between s2 and s3. In this case, ds1 may be greater than ds2. The spacing (ds2) between s2 and s3 is different from the spacing (ds3) between s3 and s4. In this case, ds2 may be greater than ds3. The spacing (ds3) between s3 and s4 is different from the spacing (ds4) between s4 and s5. In this case, ds3 may be greater than ds4. The spacing (ds4) between s4 and s5 is different from the spacing (ds5) between s5 and s6. In this case, ds4 may be greater than ds5. The spacing between s5 and s6 (ds5) is different from the spacing between s6 and s7 (ds6). In this case, ds5 may be greater than ds6. The spacing between s6 and s7 (ds6) is different from the spacing between s7 and s8 (ds7). In this case, ds6 may be greater than ds7.

[0370] The spacing between s7 and s8 (ds7) may be the smallest value among the spacings between unit coils (ds) in the L1 layer. Conversely, the spacing between s1 and s2 (ds1) may be the largest value among the spacings between unit coils (ds) in the L1 layer.

[0371] In the above, the spacing between any two unit coils may not be identical to the spacing between the other two unit coils.

[0372] Alternatively, the spacing between any two unit coils may match the spacing between the other two unit coils.

[0373] FIG. 32 illustrates the opposite case of FIG. 31.

[0374] That is, referring to FIG. 32, the spacing between the unit coils constituting the L1 layer of Tn may be different.

[0375] Specifically, the spacing (ds1) between s1 and s2 is different from the spacing (ds2) between s2 and s3. In this case, ds1 may be smaller than ds2. The spacing (ds2) between s2 and s3 is different from the spacing (ds3) between s3 and s4. In this case, ds2 may be smaller than ds3. The spacing (ds3) between s3 and s4 is different from the spacing (ds4) between s4 and s5. In this case, ds3 may be smaller than ds4. The spacing between s4 and s5 (ds4) is different from the spacing between s5 and s6 (ds5). In this case, ds4 may be smaller than ds5. The spacing between s5 and s6 (ds5) is different from the spacing between s6 and s7 (ds6). In this case, ds5 may be smaller than ds6. The spacing between s6 and s7 (ds6) is different from the spacing between s7 and s8 (ds7). In this case, ds6 may be smaller than ds7.

[0376] The spacing between s1 and s2 (ds1) may be the smallest value among the spacings between unit coils (ds) in the L1 layer. Conversely, the spacing between s7 and s8 (ds7) may be the largest value among the spacings between unit coils (ds) in the L1 layer.

[0377] In the above, the spacing between any two unit coils may not match the spacing between the other two unit coils.

[0378] Alternatively, the spacing between any two unit coils may match the spacing between the other two unit coils.

[0379] Referring to FIGS. 33 and 34, for example, the widths (ws) of all eight unit coils are equal, but the spacing (ds) between the unit coils is not uniform.

[0380] In this case, FIGS. 33 and 34 may both represent the L1 layer of the same turn (e.g., T1).

[0381] Alternatively, FIGS. 33 and 34 may each represent the L1 layer of different turns. In this case, for example, FIG. 33 may represent the L1 layer of T1, and FIG. 34 may represent the L1 layer of T6. It is self-evident that other turns can be used instead of the aforementioned T1 and T6.

[0382] First, referring to FIG. 33, the unit coils constituting the L1 layer of Tn and the spacing between the unit coils (ds1-ds7) may be the same.

[0383] However, the width (ws) of each unit coil may be different.

[0384] Specifically, the width (ws1) of s1 is different from the width (ws2) of s2. In this case, ws1 may be larger than ws2. The width (ws2) of s2 is different from the width (ws3) of s3. In this case, ws2 may be larger than ws3. The width (ws3) of s3 is different from the width (ws4) of s4. In this case, ws3 may be larger than ws4. The width of s4 (ws4) is different from the width of s5 (ws5). In this case, ws4 may be larger than ws5. The width of s5 (ws5) is different from the width of s6 (ws6). In this case, ws5 may be larger than ws6. The width of s6 (ws6) is different from the width of s7 (ws7). In this case, ws6 may be larger than ws7. The width of s7 (ws7) is different from the width of s8 (ws8). In this case, ws7 may be larger than ws8.

[0385] The width of s8 (ws8) may be the smallest value among the widths (ws) of the unit coils of the L1 layer. Conversely, the width of s1 (ws1) may be the largest value among the widths (ws) of the unit coils of the L1 layer.

[0386] In the above, the width (ws) of a unit coil may not match the width (ws) of the other remaining unit coils.

[0387] Alternatively, the width (ws) of a unit coil may match the width (ws) of at least one unit coil among the remaining unit coils.

[0388] FIG. 34 illustrates a case where the spacing (ds) between the adjacent unit coils in FIG. 33 are different. That is, in FIG. 34, not only is the spacing (ds) between the two unit coils different, as illustrated in FIG. 31, but also the width (ws) of each unit coil is different, as illustrated in FIG. 33.

[0389] That is, referring to FIG. 34, the spacing (ds) between the unit coils constituting the L1 layer of Tn and the width (ws) of each unit coil may be different.

[0390] Specifically, the spacing (ds1) between s1 and s2 is different from the spacing (ds2) between s2 and s3. In this case, ds1 may be smaller than ds2. The spacing (ds2) between s2 and s3 is different from the spacing (ds3) between s3 and s4. In this case, ds2 may be smaller than ds3. The spacing between s3 and s4 (ds3) is different from the spacing between s4 and s5 (ds4). In this case, ds3 may be smaller than ds4. The spacing between s4 and s5 (ds4) is different from the spacing between s5 and s6 (ds5). In this case, ds4 may be smaller than ds5. The spacing between s5 and s6 (ds5) is different from the spacing between s6 and s7 (ds6). In this case, ds5 may be smaller than ds6. The spacing between s6 and s7 (ds6) is different from the spacing between s7 and s8 (ds7). In this case, ds6 may be smaller than ds7.

[0391] The spacing (ds7) between s7 and s8 may be the smallest value among the spacings (ds) between unit coils in the L1 layer. Conversely, the spacing (ds1) between s1 and s2 may be the largest value among the spacings (ds) between unit coils in the L1 layer.

[0392] In the above, the spacing between any two unit coils may not be identical to the spacing between the other two unit coils.

[0393] Alternatively, the spacing between any two unit coils may be identical to the spacing between the other two unit coils.

[0394] Furthermore, the width (ws1) of s1 is different from the width (ws2) of s2. In this case, ws1 may be larger than ws2. The width (ws2) of s2 is different from the width (ws3) of s3. In this case, ws2 may be larger than ws3. The width of s3 (ws3) is different from the width of s4 (ws4). In this case, ws3 may be larger than ws4. The width of s4 (ws4) is different from the width of s5 (ws5). In this case, ws4 may be larger than ws5. The width of s5 (ws5) is different from the width of s6 (ws6). In this case, ws5 may be larger than ws6. The width of s6 (ws6) is different from the width of s7 (ws7). In this case, ws6 may be larger than ws7. The width of s7 (ws7) is different from the width of s8 (ws8). In this case, ws7 may be larger than ws8.

[0395] The width of s8 (ws8) may be the smallest value among the widths (ws) of the unit coils of the L1 layer. Conversely, the width (ws1) of s1 may be the largest value among the widths (ws) of the unit coils of the L1 layer.

[0396] In the above, the width (ws) of a unit coil may not match the widths (ws) of the other unit coils.

[0397] Alternatively, the width (ws) of a unit coil may match the width (ws) of at least one of the remaining unit coils.

[0398] FIGS. 35 and 36 are drawings illustrating the unit coil configuration for the multi-layer of FIG. 30.

[0399] FIGS. 31 to 34 disclose the configuration of unit coils belonging to the L1 layer of the multi-layer of Tn illustrated in FIG. 30.

[0400] The disclosures of FIGS. 31 to 34 described above can be applied identically or similarly to layers other than the L1 layer of Tn illustrated in FIG. 30.

[0401] In other words, the unit coil configurations of each layer constituting one turn (Tn) may be identical.

[0402] According to another embodiment, the unit coil configurations of each layer constituting one turn (Tn) may not be identical. For example, at least one layer among the plurality of layers constituting one turn (Tn) may not have the same unit coil configuration as at least one other layer. Conversely, at least one layer among the plurality of layers constituting one turn (Tn) may have the same unit coil configuration as at least one other layer.

[0403] For convenience, the L1 layer and the L2 layer of T1 are illustrated in FIGS. 35 and 36.

[0404] First, referring to FIG. 35, the configuration (arrangement, spacing, width, etc.) of the unit coils (s1-s8) of the L1 layer and the configuration (s9-s15) of the unit coils of the L2 layer are identical.

[0405] On the other hand, referring to FIG. 36, the configuration (arrangement, spacing, width, etc.) of the unit coils (s1-s8) of the L1 layer and the configuration (s9-s15) of the unit coils of the L2 layer are not identical.

[0406] FIGS. 35 and 36 are examples for explaining the similarity or difference in configuration between each layer in a multi-layer, and are not limited to the detailed configuration (arrangement, spacing, width, etc.) of each layer.

[0407] FIG. 37 is a diagram illustrating a turn-to-turn spacing relative to oz according to an embodiment of the present disclosure.

[0408] (a) of FIG. 37 illustrates that the pattern-to-pattern spacing can be determined for each oz (i.e., PCB thickness), and accordingly, the turn-to-turn spacing of each pattern can also be determined based on oz.

[0409] Compared to the minimum spacing determined by oz in the past, according to the present disclosure, the turn-to-turn spacing can be at least twice the conventional manufacturing limit.

[0410] Meanwhile, (b) of FIG. 37 illustrates that the minimum spacing in oz can be increased by multiples of the oz when moving inward from the outer turn based on the center point.

[0411] For example, if the outer turn spacing is 0.3 mm based on a 3oz standard, the inner turn spacing can be designed to be increased by a multiple (e.g., a turn-index-based multiple) of the minimum spacing.

[0412] However, this is merely an example and may not be limited to the content of FIG. 37 described above.

[0413] FIG. 38 is a diagram illustrating a change in resistance versus the number of turns according to an embodiment of the present disclosure.

[0414] The resistance versus the number of turns can be designed to vary linearly or non-linearly.

[0415] FIG. 38 is a diagram illustrating that the turn spacing can be increased and the inner and outer winding cross-sectional areas can be made asymmetrical.

[0416] (a) of FIG. 38 illustrates that the pattern width of the inner turn increases toward the outside. Since the resistance of the outer turns is greater than that of the inner turns, the resistance can be reduced, which can be expected to improve pattern loss.

[0417] (b) and (c) of FIG. 38 are diagrams illustrating how the resistance of the inner turns and the outer turns change nonlinearly, for example, in a step-like fashion.

[0418] Meanwhile, (d) of FIG. 38 is a diagram illustrating how the pattern width of the inner turns decreases as they move outward. Referring to FIG. 38(d), the internal magnetic field can be reduced, which can be expected to improve heat generation in the inner PCB pattern (reducing the resistance of the inner turns).

[0419] However, the numerical values in (a) to (d) of FIG. 38 are arbitrarily selected for convenience of explanation and are not limited thereto.

[0420] FIG. 39 is a diagram illustrating a case where the number of twists is varied when changing from an inner turn to an outer turn according to one embodiment of the present disclosure.

[0421] (a) of FIG. 39 illustrates a case where twisting is not applied to overlap magnetic fields between adjacent windings, while (b) of FIG. 39 illustrates a case where twisting is applied to minimize the area of twisting with adjacent windings, thereby reducing magnetic field overlap.

[0422] (c) of FIG. 39 is a diagram illustrating that the number of twists can be varied for both internal and external turns.

[0423] (d) of FIG. 39 illustrates a case where the number of twists changes nonlinearly as the number of turns increases. For example, the number of twists decreases up to a certain number of turns, but remains constant after that number of turns without changing. While (d) of FIG. 39 illustrates a linear decrease, the decrease is not necessarily limited to this case and may also decrease nonlinearly.

[0424] In contrast to the aforementioned (d) of FIG. 39, (e) of FIG. 39 illustrates that as the number of turns increases, the number of twists may change nonlinearly. For example, the number of turns may not change until a certain number of turns is reached, but may increase after that number of turns. Although (e) of FIG. 39 illustrates a linear increase, the present disclosure is not necessarily limited thereto and may increase nonlinearly.

[0425] The present disclosure may also include embodiments in which the contents illustrated in FIGS. 22 to 36 described above are combined within a combinable range.

[0426] Meanwhile, the present disclosure may adjust the number of strands within a single turn constituting a single PCB working coil by referring to at least one drawing and the technical concepts contained in the description thereof among the contents illustrated in FIGS. 22 to 36 described above. Here, the number of strands may refer to the number of unit coils. For example, Tn may have m strands (where m is a natural number), and Tn+1 may have m+k strands (where k is a natural number). K may or may not have a linear value depending on the variation of n. Meanwhile, Tn may have m strands (where m is a natural number), and Tn+1 may have m-p strands (where p is a natural number). P may or may not have a linear value depending on the variation of n.

[0427] Similarly, if a single turn is composed of multiple layers, the aforementioned content may also apply to each layer. That is, even if they belong to the same turn, the composition of each layer may or may not be identical.

[0428] In addition, adjusting the number of strands as described above may affect other factors.

[0429] In addition, when the cooking appliance 1 includes multiple working coils to form each burner, at least one of the plurality of working coils may be a PCB working coil. In this case, the PCB working coil may be configured according to at least one of the aforementioned FIGS. 22 to 39.

[0430] Meanwhile, when the cooking appliance 1 includes multiple working coils to form each burner, at least two of the plurality of working coils may be PCB working coils. In this case, each PCB working coil may be configured according to at least one of the aforementioned FIGS. 22 to 39. However, each PCB working coil may not have the same configuration.

[0431] Meanwhile, when the cooking appliance 1 includes multiple PCB working coils, the sizes of the respective PCB working coils may be different. For example, the distance between the center point of each PCB working coil and the outermost turns may be different.

[0432] The above description merely exemplifies the technical concepts of the present disclosure. Those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present disclosure.

[0433] Therefore, the embodiments disclosed in this disclosure are intended to illustrate, rather than limit, the technical concepts of the present disclosure. These embodiments do not limit the scope of the technical concepts of the present disclosure.

[0434] The scope of protection of this disclosure should be construed according to the claims below, and all technical concepts within the scope equivalent thereto should be construed as being included within the scope of the rights of this disclosure.[Industrial Applicability]

[0435] The present disclosure relates to a cooking appliance including a working coil that maximizes heating efficiency and a cooking appliance that heats a heated object using a PCB working coil, and has industrial applicability.

Claims

1. A cooking appliance comprising: a top plate portion on which an object to be heated is placed; a plurality of working coils configured to heat the object to be heated; an inverter configured to apply current to each of the working coils; and a controller configured to control an operation of the inverter such that the object to be heated is heated through each of the working coils, wherein at least one of the working coils is a PCB working coil including a plurality of turns, and a spacing between the turns is non-uniform.

2. The cooking appliance according to claim 1, wherein the spacing between the turns of the PCB working coil increases as the turns are closer to a center point of the PCB working coil.

3. The cooking appliance according to claim 1, wherein the PCB working coil is divided into a plurality of sections from a center point to an outermost portion, and each of the sections includes at least one turn.

4. The cooking appliance according to claim 3, wherein the plurality of sections includes a first section in which the spacing between the turns does not change, and a second section in which the spacing between the turns changes.

5. The cooking appliance according to claim 4, wherein the first section has a larger spacing between the turns than the second section.

6. The cooking appliance according to claim 5, wherein the first section is a section closer to the center point than the second section.

7. The cooking appliance according to claim 1, wherein widths of the turns of the PCB working coil are non-uniform.

8. The cooking appliance according to claim 7, wherein the widths of the turns of the PCB working coil become wider as the turns are closer to the center point.

9. The cooking appliance according to claim 1, wherein each turn of the PCB working coil includes a plurality of unit coils, and a spacing between the unit coils included in the turn is non-uniform depending on a position of the turn.

10. The cooking appliance according to claim 9, wherein as the position of the turn is closer to the center point of the PCB working coil, the spacing between the unit coils included in the turn is larger.

11. The cooking appliance according to claim 1, wherein each turn of the PCB working coil includes a plurality of unit coils, and a number of the unit coils included in the turn differs depending on a position of the turn.

12. The cooking appliance according to claim 11, wherein the number of the unit coils included in each turn of the PCB working coil increases as the turn is closer to the center point of the PCB working coil.

13. The cooking appliance according to claim 1, wherein each turn of the PCB working coil includes a plurality of unit coils, and widths of the unit coils included in the turn differ depending on a position of the turn.

14. The cooking appliance according to claim 13, wherein the widths of the unit coils included in each turn of the PCB working coil become wider as the turn is closer to the center point of the PCB working coil.

15. The cooking appliance according to claim 1, wherein the working coil includes a plurality of layers of PCB working coils, and the PCB working coils of the plurality of layers differ from each other in at least one of a spacing between turns, a turn width, a spacing between unit coils included in each turn, and a number of unit coils included in each turn.

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