Heat resistant hot plate for microwave appliances

Abstract

A heating appliance includes: a housing having an inner wall having an inner surface defining a cooking chamber for heating food; a microwave heating source configured to generate microwave radiation for heating the food; and a thermally resistive heating plate disposed in an opening defined in the inner wall. The thermally resistive heating plate has a substrate having an inner surface aligned with the inner surface of the inner wall and a bottom surface opposite the inner surface. The thermally resistive heating plate includes a thermally resistive coating disposed on the bottom surface, the thermally resistive coating being configured to generate heat when an electric current is applied, such that the heat is transferred from the thermally resistive coating, the microwave heating source, or both through the substrate to the cooking chamber, and the substrate is permeable to microwave radiation to allow microwave emission through the substrate.

Description

Technical Field

[0001] This application relates to a cooking appliance, and more specifically to a thermally resistive heating coating in a microwave heating appliance. Background Technology

[0002] An oven is a heating appliance used for food preparation, having an outer shell that defines a cavity forming a cooking chamber therein. An oven includes a heating mechanism for cooking food placed inside the cooking chamber; this heating mechanism is variable in different types of ovens, and two or more types of heating mechanisms can be combined in a combination oven. Common types of ovens include electric ovens (which include conduction / conventional and convection ovens), gas ovens, toasters, and microwave ovens. The heating mechanisms of these ovens vary, some including those within the cooking chamber itself (e.g., conventional ovens) or within the outer shell (e.g., convection ovens), such that energy or heat is transferred to the cooking chamber or food. Heating mechanisms in electric ovens include electric coils (circulated via a fan in a convection oven) to heat the cooking chamber, heating mechanisms in gas ovens include burning natural gas to heat the cooking chamber, and heating mechanisms in microwave ovens include electromagnetic radiation from strong radio waves from a device such as a magnetron to heat the food itself. Heating appliances referred to as combination ovens may include one or more of the above-mentioned heating mechanisms. Summary of the Invention

[0003] According to one or more embodiments, a heating appliance includes: a housing having an inner wall having an inner surface defining a cooking chamber for heating food; a microwave heating source configured to generate microwave radiation for heating the food; and a thermally resistive heating plate disposed in an opening defined in the inner wall. The thermally resistive heating plate has a substrate having an inner surface aligned with the inner surface of the inner wall and a bottom surface opposite the inner surface. The thermally resistive heating plate includes a thermally resistive coating disposed on the bottom surface, the thermally resistive coating being configured to generate heat when an electric current is applied, such that the heat is transferred from the thermally resistive coating, the microwave heating source, or both through the substrate to the cooking chamber, and the substrate is permeable to microwave radiation to allow microwave emission through the substrate.

[0004] According to at least one embodiment, the microwave efficiency of the thermal resistance heating plate can be from 20% to 80%. In at least one embodiment, the thermal resistance heating plate may further include an insulating layer, wherein the thermal resistance coating is located between the insulating layer and the substrate. In another embodiment, the insulating layer may be a ceramic material. In one or more embodiments, the thermal resistance heating plate may include electrical contacts on the bottom surface to connect the thermal resistance coating to a power supply. In some other embodiments, the electrical contacts may be silver. In at least one embodiment, the thermal resistance coating may include a coating matrix in which active filler is dispersed. In another embodiment, the active filler may include single-walled or multi-walled carbon nanotubes. In some embodiments, the coating matrix may be a ceramic phosphate material. Furthermore, in some embodiments, the active filler may be from 0.001% by weight to 30% by weight of the thermal resistance coating. In at least one embodiment, the thickness of the thermal resistance coating may be from 0.2 nm to 300 μm. In one or more embodiments, the substrate may be a glass-ceramic substrate having a microwave transmittance of 30% to 75%.

[0005] According to one or more embodiments, a heating appliance includes: a housing having an inner wall having an inner surface defining a cooking chamber for heating food; a microwave heating source configured to generate microwave radiation for heating the food; and a thermal resistance heating plate disposed in an opening defined in the inner wall, the thermal resistance heating plate having: a substrate having an inner surface aligned with the inner surface of the inner wall and a bottom surface opposite the inner surface. The thermal resistance heating plate further includes a thermal resistance coating disposed on at least a portion of the bottom surface, the thermal resistance coating comprising a coating matrix in which active filler is dispersed, the thermal resistance coating being configured to generate heat when an electric current is applied, such that the heat is transferred from the thermal resistance coating, the microwave heating source, or both, through the substrate to the cooking chamber, and the microwave heating source being located in the housing to emit microwave radiation through the substrate.

[0006] According to at least one embodiment, the inner wall may be the bottom wall or top panel defining the cooking chamber. In at least one embodiment, the inner wall may be a side wall defining the cooking chamber. In some other embodiments, the inner wall may include opposing side walls, and the heating appliance may include a corresponding thermal resistance heating plate in each of the opposing side walls defining the cooking chamber.

[0007] According to one or more embodiments, a method of forming a heating appliance includes: providing a housing having an inner wall having an inner surface defining a cooking chamber for heating food; applying a thermally resistive coating to a surface of a substrate to form a thermally resistive heating plate; and positioning the thermally resistive heating plate in an opening defined in the inner wall such that microwave radiation can be transmitted through the substrate to the cooking chamber. An inner surface of the substrate opposite the bottom surface is flush with the inner surface of the inner wall to define the cooking chamber.

[0008] According to at least one embodiment, the method may further include applying metal interconnects to the surface to form electrical contacts for the thermal resistance heating plate prior to applying the thermal resistance coating. In at least one embodiment, applying the thermal resistance coating includes depositing the thermal resistance coating on the substrate and curing the thermal resistance coating. In some other embodiments, the thermal resistance coating may comprise single-walled or multi-walled carbon nanotubes dispersed in a coating matrix. Attached Figure Description

[0009] Figure 1 This is a schematic front view of a heating appliance according to one embodiment;

[0010] Figure 2 This is a schematic diagram of a thermal resistance heating plate for a heating appliance according to one embodiment;

[0011] Figures 3A to 3B It is a schematic front view of a heating appliance according to other embodiments; and

[0012] Figure 4 This is a schematic front view of a heating appliance according to another embodiment. Detailed Implementation

[0013] As requested, detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely examples of the invention that may be embodied in various alternative forms. The drawings are not necessarily drawn to scale; some features may be enlarged or minimized to show details of specific components. Therefore, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art to apply the invention in different ways.

[0014] According to one or more embodiments, a heating appliance for cooking food, such as a microwave oven or combination oven having at least a microwave heat source, includes a cooking chamber defined by cavity walls in a housing. At least one of the cavity walls defines a corresponding opening in which a thermally resistive heating plate is disposed. The thermally resistive heating plate includes a thermally resistive coating disposed on a substrate, the substrate being microwave-transmissible to radiate microwave radiation from the microwave heat source into the cooking chamber. The substrate is also thermally conductive to allow the thermally resistive coating to generate heat to heat the cooking chamber. The thermally resistive heating plate may be located within one or more cavity walls and may include an insulating layer sandwiching the thermally resistive coating between the insulating layer and the substrate to protect the housing.

[0015] See Figure 1 This diagram shows a perspective view of a heating appliance 100 according to one embodiment. The heating appliance 100 is shown and described with reference only to relevant general components and is not intended to be limiting, as the heating appliance 100 includes other components and features for operation not shown or described herein but contemplated for inclusion in the heating appliance 100. The heating appliance 100 includes a housing 110 having inner sidewalls 112, a base 111, and a top plate 113, which together define a cooking chamber 120. The housing 110 also has an outer surface 116 exposed to the external environment. The heating appliance 100 includes a door 114 having an open position for providing passage to the cooking chamber 120 and a closed position for sealing the cooking chamber 120 to isolate it from the external environment. The dimensions of the cooking chamber 120 are based on dimensions suitable for kitchen appliances and for storing food to be cooked, and may include components for optimizing space and food cooking, such as a turntable (not shown) or shelves (not shown). The heating appliance 100 can draw power from an external power source (not shown), such as an electrical plug and socket connection. The heating appliance 100 can be connected to a power supply via any suitable power cable and may include any other components, such as, but not limited to, a power inverter, transformer, voltage converter, etc., to supply the required power to the heating appliance 100. The input can be any suitable input based on the appliance 100. For example, the voltage input could be 120V, and the maximum power could be 1600W.

[0016] The heating appliance 100 includes at least one heating mechanism (not shown) for cooking food placed inside the cooking chamber 120. The heating mechanism consists of a heating element located on the outer surface 116 (e.g., Figure 1 User input is activated at the control panel 118 on the door 114 (not shown) or door 114 (not shown). Depending on the specific type of heating appliance 100, the heating mechanism may be located within the housing 110 or within the cooking chamber 120. The heating mechanism may be activated via microwave radiation from any suitable microwave generating mechanism (such as, but not limited to, one or more magnetrons or solid-state devices). Although the heating appliance 100 may be referred to as microwave oven 100, and Figure 1A microwave oven is described herein, but this is not intended to be limiting, and other types of heating appliances, such as ovens that combine a microwave generating mechanism for microwave heating with another heating mechanism (e.g., an electric coil and / or gas), are also contemplated as heating appliance 100. Therefore, heating appliance 100 can be any suitable household appliance for cooking food, such as, but not limited to, ovens, microwave ovens, toasters, etc., making the features described herein suitable for oven or microwave oven applications where microwaves are present in the cooking chamber 120. Figure 1 In the illustrated embodiment, the heating appliance 100 is microwave-based, such that the heating mechanism can be a microwave generating device disposed in the housing 110 in any suitable manner (e.g., between the sidewall 112, top plate 113, or base 111 and outer surface 116). Microwave radiation is generated by the microwave generating device and transmitted via any suitable mechanism (such as a waveguide, coaxial cable, or stripline) supplying the microwave radiation to one or more feed ports (depending on the design) that open into the cooking chamber 120 to heat food placed therein.

[0017] According to various embodiments, the heating appliance 100 includes one or more thermally resistant heating plates 200, which are incorporated into at least a portion of one or more corresponding surfaces forming a cooking chamber 120, such as a base 111 (e.g., Figure 1 (shown schematically in the diagram), inner wall 112 (as shown in the diagram) Figures 3A to 3B (as shown in the image) and top plate 113 (as shown in the image) Figure 4 (as shown in the figures) or combinations thereof, hereinafter collectively referred to as cavity wall 130. Furthermore, heating plate 200 may be incorporated as at least part of one or more of cavity walls 130 (e.g., at least part of one or more of inner wall 112, top plate 113, or base 111). In some embodiments, cavity wall 130 may be a metal wall. Various embodiments will be commonly referred to using similar reference numerals in the following figures.

[0018] The thermal resistance heating plate 200 is incorporated into the corresponding cavity wall 130 of the cooking chamber 120 (e.g., Figure 1 The base 111 in Figures 3A to 3B The side wall 112 and Figure 4 The thermal resistance heating plate 200 is located within the opening 135 defined in the top plate 113 of the cavity wall 130, such that the thermal resistance plate 200 is flush with the cavity wall 130. In some embodiments, the thermal resistance plate 200 can be removed from the opening 135, allowing for easy replacement and / or maintenance. The thermal resistance heating plate 200 provides efficient heating for convection heating of the cooking chamber 120, while also providing a microwave-transmitting wall for microwave heating.

[0019] See Figure 2 The thermal resistance heating plate 200 includes a substrate 210 having an inner surface 212 facing the cooking chamber 120 and a bottom surface 214 on the underside of the substrate 210 opposite to the inner surface 212. The thermal resistance heating plate 200 also includes a thermal resistance coating 220 disposed on the bottom surface 214 of the substrate 210, and an insulating layer 230 disposed on the thermal resistance coating 220, sandwiching the thermal resistance coating 220 between the insulating layer 230 and the substrate 210. The substrate 210 can be any suitable thermal shock resistant material and has a melting point higher than the operating temperature reached by the thermal resistance coating 220. For example, the substrate 210 can be glass, ceramic, glass-ceramic, or metallic. For example, the substrate 210 can be any suitable material, including but not limited to glass (e.g., soda-lime, borosilicate, silica, etc.) and glass-ceramic (e.g., lithium aluminum silicate, etc.). The substrate 210 can be a colored, tinted, or transparent glass or glass-ceramic material for aesthetic purposes. The substrate material is selected to withstand temperatures up to 700°C without expansion or compromise of structural integrity, and may have a coefficient of thermal expansion of 0.5 to 0 at temperatures up to 700°C. Furthermore, substrate 210 may be a suitable material with sufficient thermal conductivity to transfer heat through the substrate material to the cooking chamber 120 when heat is generated by the thermal resistance coating 220 (located on the outside compared to the cooking chamber 120). In some embodiments, the thermal conductivity is at least 0.5 W / mK for heating the cooking chamber 120. In other embodiments, the thermal conductivity of the substrate material is 1 to 2 W / mK. Substrate 210 may have any suitable thickness to transfer heat to the cooking chamber 120 and form at least a portion of the cavity wall 130, and in some embodiments may have a thickness of 1 mm to 8 mm, in other embodiments 2 mm to 7 mm, and in still other embodiments 2.5 mm to 6.5 mm. In some examples, substrate 210 may be 3 mm to 4 mm thick. The substrate 210 allows microwave wavelengths to be at least partially transmitted through its thickness, enabling the microwave generating device to transmit microwave radiation through the glass substrate 210 and reach the cooking chamber 120. This allows the thermally resistive heating plate 200 to serve as an entry point for microwave emission into the cooking chamber 120. Therefore, the microwave transmittance of the substrate 210 can be 30% to 75% in some embodiments, 40% to 70% in others, and 45% to 60% in still others.

[0020] See again Figure 2A thermal resistance coating 220 is coated on the bottom surface 214 of the substrate 210 and exhibits thermal resistance properties when an electric current is applied through the thermal resistance coating 220. For example, the thermal resistance coating 220 may include conductive filler particles (e.g., metal oxide particles, or graphite or carbon nanomaterials such as nanotubes, spheres, or flakes) dispersed in a ceramic matrix (e.g., alumina, silica, phosphate, etc.), wherein the conductive filler particles are active substances for heating. In some embodiments, the thermal resistance coating 220 may also include other fillers, such as thickeners or dispersants, such as silica, for aiding deposition or film formation. The thermal resistance coating 220 is sandwiched between the substrate 210 and the insulating layer 230. The thermal resistance coating 220 may be electrically connected in any suitable manner (in... Figure 2 The electrical connection 225 (shown as electrical connection 225) is used, such as, but not limited to, via silver paste, copper connectors, or other wiring, bus, or interconnection, to allow current to flow through the thermal resistance coating 220 to generate heat. In one or more embodiments, the electrical connection 225 is located on opposite sides of the resistance heating plate 200 to allow current to flow from one electrical connection 225 to the other through the heating plate 200, such that heat is generated in the thermal resistance coating 220 and transferred via the substrate 210 to the cooking chamber 120. The electrical connection 225 may be sandwiched between the substrate 210 and the insulating layer 230 and located on either side of the thermal resistance coating 220 to allow current to flow through it.

[0021] In one or more embodiments, as previously described, the thermal resistance coating 220 includes a coating matrix in which active fillers are dispersed to provide resistance heating to the cooking chamber 120 via the substrate 210. The active fillers within the thermal resistance coating 220 act as ohmic resistors that generate heat when electricity is applied to the thermal resistance heating plate 200, thus providing heat for conduction through the glass-ceramic substrate 110 to cookware articles thereon. In some embodiments, the active fillers may be single-walled or multi-walled carbon nanotubes, graphite particles, or metal oxide particles. Based on the wet loading in the coating used for deposition, in some embodiments the loading concentration of the active fillers is from 0.001 wt% to 30 wt%, in other embodiments it is from 0.01 wt% to 10 wt%, and in yet another embodiment it is from 0.10 wt% to 5.0 wt%. The average size of each active filler (based on the maximum particle size) may be from 0.2 nm to 300 μm in some embodiments, from 5 nm to 250 μm in other embodiments, and from 25 nm to 200 μm in yet another embodiment. In some embodiments, the thermal resistance coating 220 may include other fillers in the coating matrix, such as, but not limited to, bulk fillers, corrosion inhibitors, etc., including but not limited to silica particles. Furthermore, in one or more embodiments, the coating matrix of the thermal resistance coating 220 is a ceramic matrix with antioxidant properties at high temperatures (i.e., up to 500 degrees Celsius), such as, but not limited to, aluminum phosphate, silicon phosphate, magnesium phosphate, silicates, or combinations thereof. In embodiments where the ceramic matrix is ​​aluminum phosphate, the liquid pH of the coating matrix can be from 2 to 8.

[0022] The thermal resistance coating 220 may have any suitable resistance based on its composition to achieve the desired heat generation based on the heating requirements of the cooking chamber 120. In some embodiments, the resistance of the thermal resistance coating 220 may be 10 to 50 Ω, in other embodiments it is 1.0 to 35 Ω, and in still other embodiments it is 20 to 30 Ω. In some embodiments, the thermal resistance coating 220 may reach a maximum temperature of about 400°C to 600°C when an current is applied, in other embodiments it is 450°C to 550°C, and in still other embodiments it is 475°C to 525°C. In one or more embodiments, the heating slope of the thermal resistance coating may be 45°C to 250°C per minute, in other embodiments it is 50°C to 200°C per minute, and in still other embodiments it is 55°C to 150°C per minute. Furthermore, in some embodiments, the heating slope of the thermal resistance coating may be 75°C to 250°C per minute, in other embodiments it is 85°C to 200°C per minute, and in still other embodiments it is 95°C to 150°C per minute. The thermal resistance coating 220 can be applied to the base surface 214 in any suitable pattern, or to at least a portion of the base surface 214 (e.g., symmetrical or asymmetrical patterns, such as stripes, checkerboard patterns, line segments, etc.). Therefore, the thermal resistance coating 220 can provide customized heating based on the cooking chamber 120. In some embodiments, the thermal resistance coating 220 can be a thin film layer, such that the thermal resistance film layer is up to 100 micrometers thick upon curing. In other embodiments, the thickness of the thermal resistance coating 220 can be thicker than that defined as a thin film layer, and can have a thickness in the range of mm. The thickness of the thermal resistance coating 220 is 15 nm to 1.75 mm in some embodiments, 20 nm to 1.5 mm in others, and 25 nm to 1 mm in still others. In still others, the thickness of the thermal resistance coating 220 can be 25 nm to 500 nm, 25 nm to 450 nm in others, and 25 nm to 425 nm in still others. In at least one embodiment, after deposition, the thickness of the wet thermal resistance coating can be 25 to 75 micrometers, and in other embodiments, it is 40 to 60 micrometers. In at least one embodiment, after curing, the thickness of the dry thermal resistance coating 220 is 10 to 50 micrometers, in other embodiments 15 to 45 micrometers, and in yet another embodiment 20 to 40 micrometers. Although in Figure 2The thermal resistance coating 220 is shown as a single layer, but the thermal resistance coating 220 may comprise any number of layers to produce the desired heating, and the single-layer depiction is not intended to be limiting. For example, the thermal resistance coating 220 may comprise two or more layers forming the thermal resistance coating of that thickness. Thus, each layer of the thermal resistance coating 220 may independently be a thin film having a thickness of up to 100 micrometers or up to 1.75 mm. Furthermore, the aggregate layers of the thermal resistance coating 220 may have a thickness of up to 1.75 mm, with each layer having a different thickness.

[0023] Furthermore, the thermally resistive coating 220 reflects microwave radiation, thus preventing indirect and unwanted heat generation in the heating plate 200 when the heating appliance operates solely for microwave heating. In some embodiments, the microwave efficiency of waves passing through the coated substrate (i.e., the thermally resistive heating plate 200) can be 20% to 80%, and in other embodiments 30% to 70%, and in still other embodiments 40% to 60%, depending on the pattern of the coating. The thermally resistive coating 220 has low or no absorption of microwave radiation and is therefore reflective. In one or more embodiments, the thermally resistive coating 220 alone may have a reflectivity of 95% to 100% for microwave radiation, in other embodiments 96% to 100%, and in still other embodiments 97% to 100%. Regarding microwave radiation penetration, the thermally resistive coating 220 has an absorption rate of 0% to 5% for microwaves in some embodiments, 0% to 2.5% in others, and 0% to 1% in still other embodiments. The absorption rate of the thermally resistive coating 220 is a measure of the material's effectiveness in absorbing radiant energy. Typically, substrate 210 transmits microwaves more effectively than thermal resistance coating 220, thereby allowing microwave emissions to be directed into cooking chamber 120.

[0024] See again Figure 2The insulating layer 230 is a coating matrix material that provides thermal insulation between the housing 110 of the appliance 100 and the thermally resistive heating plate 200, and also provides electrical insulation to the coating 220. The insulating layer 230 can be selected based on the substrate type. In some embodiments, the insulating layer 230 can be a material similar to the ceramic material of the coating matrix. In other embodiments, the material of the insulating layer 230 can be another ceramic (alumina, alumina-titanium dioxide, cordierite), or it can be a high-temperature resistant resin, such as a silicone-based high-temperature resistant resin. Although shown as a single layer, the insulating layer 230 can include any suitable number of protective layers and / or combinations of insulating and / or layer materials to sandwich the thermally resistive coating 220 between the insulating layer 230 and the substrate 210. The insulating layer 230 facilitates heat transfer in the direction of the substrate 210. The insulating layer 230 can be of any suitable thickness to protect the thermally resistive coating 220 on the bottom side (located on the top side relative to the substrate 210) and to protect the appliance housing 110 from heat. In some embodiments, it can be 0.1 mm to 0.5 mm thick; in others, 0.25 mm to 0.45 mm thick; and in still others, 0.3 mm to 0.4 mm thick. In some embodiments, although not shown, the thermally resistive heating plate 200 may optionally include additional coatings on the inner surface 212 of the substrate 210 facing the cooking chamber 120. For example, the substrate 210 includes an easy-to-clean coating 240 on the inner surface 212, which has hydrophobic or oleophobic properties (e.g., a water or oil contact angle of at least 90 degrees) to reduce the adhesion of food or chemicals to the easy-to-clean coating 240.

[0025] Although Figure 1 In the diagram, opening 134 is shown in the base 111 defining the cooking chamber 120, but the thermal resistance heating plate 200 may be incorporated into other cavity walls 130, or any combination of cavity walls 130. Furthermore, the thermal resistance heating plate 200 may be incorporated into a portion of a respective cavity wall 130. For example, in some embodiments, the thermal resistance heating plate 200 may form 30% to 100% of the cavity wall 130, in other embodiments 50% to 95% of the wall 130, and in still other embodiments 75% to 90% of the wall. See also Figures 3A to 3B The thermal resistance heating plate 200 is included in the side wall 112. Figure 3A ) and above a portion of the height of the sidewall 112 ( Figure 3B In other implementation schemes, such as Figure 4 As shown, the thermal resistance heating plate 200 may be incorporated as at least part of the top plate 113. Although not shown in the figure, the thermal resistance heating plate 200 may be present on one or more cavity walls 130, and the thermal resistance heating plate 200 is depicted as incorporated in a particular location without being intended to be limiting.

[0026] Therefore, the thermal resistance heating plate 200 generates heat through thin-film thermal resistance heating, which allows the heating plate 200 to reach a high temperature in a short time, while avoiding microwave absorption to ensure effective heating of the food in the cooking chamber 120.

[0027] According to one or more embodiments, a method is provided for forming a heating appliance having a thermally resistive heating plate. The method includes preparing the thermally resistive heating plate by depositing metal interconnects on a substrate. Deposition can be performed by any suitable method, including but not limited to thermal spraying or screen printing. Deposition can be based on a desired pattern formed. The metal interconnects can be formed using silver paste or silver-copper paste. After depositing the metal interconnects, the method includes curing the metal interconnects at a temperature between 50 and 500 degrees Celsius in some embodiments and between 100 and 350 degrees Celsius in other embodiments. The method also includes applying a thermally resistive coating to the bottom surface of the substrate and curing the coating. Application can be based on a pattern of metal interconnects connecting the thermally resistive coating to a power supply. The thermally resistive coating can be applied by any suitable method, including but not limited to screen printing, stencil printing, or other deposition methods. In at least one embodiment, the coating can be cured at a temperature between 200 and 500 degrees Celsius, and in other embodiments at a temperature between 300 and 400 degrees Celsius. In some embodiments, curing can last from 1 to 70 minutes in an oven or furnace, and in other embodiments from 20 to 35 minutes. In some embodiments, the metal connecting wires and thermal resistance coating may be applied prior to the curing step, allowing the curing step to be a single step following coating deposition. The cured thermal resistance heating plate is then deposited within an opening in the cavity wall of the heating appliance, wherein the top surface (opposite to the bottom surface) of the substrate is flush with the cavity wall. Thus, a heating appliance is provided that allows thermal resistance heating of the cooking chamber via the thermal resistance coating and through thermal conduction via the substrate, as well as through the microwave transmittance of the substrate material, to allow microwave emission through the substrate into the cooking chamber.

[0028] Therefore, according to various embodiments, a heating appliance includes a thermally resistive heating plate embedded in an opening in at least one wall defining a cooking chamber to generate heat via thin-film thermal resistance heating. This allows the heating plate to reach high temperatures quickly while avoiding microwave absorption to ensure effective heating of food within the cooking chamber. The thermally resistive heating plate includes a substrate having a top surface facing the cooking chamber, the substrate being transmissive to allow microwave emission and thermally conductive to allow heat transfer. A thermally resistive heating coating is coated on the bottom surface of a glass-ceramic substrate, the thermally resistive heating coating being electrically connected to a power supply. When an electric current is applied, the resistive properties of the thermally resistive coating generate heat, which is conducted through the glass-ceramic substrate to the cooking chamber. Furthermore, the heating appliance may include an insulating layer on the surface of the thermally resistive coating opposite to the glass-ceramic substrate to improve heating in the direction of the glass-ceramic substrate.

[0029] Unless otherwise expressly stated, all numerical values ​​in this disclosure should be understood to be modified by the word “about.” The terms “substantially,” “generally,” or “about” may be used herein and may modify disclosed or claimed values ​​or relative characteristics. In such cases, “substantially,” “generally,” or “about” may mean that the value or related characteristic it modifies differs from that value or related characteristic by ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% (e.g., regarding transparency as measured by opacity). Practice within the specified numerical range is generally preferred. Furthermore, unless expressly stated to the contrary, describing a group or class of materials in conjunction with this disclosure as suitable or preferred for a given purpose implies that a mixture of any two or more members of that group or class may also be suitable or preferred.

[0030] As mentioned in the accompanying drawings, the same reference numerals may be used herein to refer to the same parameters and components or similar modifications and substitutions thereof. For the purposes of this description, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and their derivatives will be used in connection with this disclosure, as in Figure 1 Orientation. However, it should be understood that various alternative orientations may be adopted in this disclosure unless explicitly stated to the contrary. It should also be understood that the specific devices and processes shown in the drawings and described in the following specification are merely exemplary embodiments of the inventive concept defined in the appended claims. Therefore, specific dimensions and other physical characteristics relating to the embodiments disclosed herein should not be considered limiting unless otherwise clearly stated in the claims. The drawings mentioned herein are schematic, and their related views are not necessarily drawn to scale.

[0031] While exemplary embodiments have been described above, these embodiments are not intended to describe all possible forms of the invention. Rather, the language used in this specification is descriptive rather than limiting, and it should be understood that various changes may be made without departing from the spirit and scope of the invention. Furthermore, features of various implementation embodiments may be combined to form other embodiments of the invention.

Claims

1. A heating appliance, the heating appliance comprising: The housing has an inner wall that has an inner surface defining a cooking chamber for heating food; A microwave heating source configured to generate microwave radiation for heating the food; as well as A thermal resistance heating plate is disposed in an opening in a sidewall defined in an inner wall, the thermal resistance heating plate having: a substrate having an inner surface aligned with the inner surface of the inner wall and a bottom surface opposite to the inner surface; and a thermal resistance coating disposed on the bottom surface, the thermal resistance coating being configured to generate heat when an electric current is applied. The heat is transferred from the thermal resistance coating, the microwave heating source, or both through the substrate to the cooking chamber, and the substrate is permeable to microwave radiation to allow microwave emission through the substrate.

2. The heating appliance as claimed in claim 1, wherein the microwave efficiency of the thermal resistance heating plate is 20% to 80%.

3. The heating appliance of claim 1, wherein the thermal resistance heating plate further comprises an insulating layer, wherein the thermal resistance coating is located between the insulating layer and the substrate.

4. The heating appliance of claim 3, wherein the insulating layer is a ceramic material.

5. The heating appliance of claim 1, wherein the thermal resistance heating plate includes electrical contacts on the bottom surface to connect the thermal resistance coating to a power supply.

6. The heating appliance of claim 5, wherein the electrical contacts are silver.

7. The heating appliance of claim 1, wherein the thermal resistance coating comprises a coating matrix in which active fillers are dispersed.

8. The heating appliance of claim 7, wherein the active filler comprises single-walled or multi-walled carbon nanotubes.

9. The heating appliance of claim 7, wherein the coating matrix is ​​a ceramic phosphate material.

10. The heating appliance of claim 7, wherein the active filler is 0.001% to 30% by weight of the thermal resistance coating.

11. The heating appliance of claim 1, wherein the thickness of the thermal resistance coating is from 0.2 nm to 300 micrometers.

12. The heating appliance of claim 1, wherein the substrate is a glass-ceramic substrate having a microwave transmittance of 30% to 75%.

13. A heating appliance, the heating appliance comprising: The housing has an inner wall that has an inner surface defining a cooking chamber for heating food; A microwave heating source configured to generate microwave radiation for heating the food; as well as A thermal resistance heating plate is disposed in an opening defined in an inner wall, the thermal resistance heating plate having: a substrate having an inner surface flush with the inner surface of the inner wall and a bottom surface opposite to the inner surface; And a thermal resistance coating disposed on at least a portion of the bottom surface, the thermal resistance coating comprising a coating matrix in which active fillers are dispersed, the thermal resistance coating being configured to generate heat when an electric current is applied. The heat is transferred from the thermal resistance coating, the microwave heating source, or both through the substrate to the cooking chamber, and the microwave heating source is located in the housing to emit microwave radiation through the substrate.

14. The heating appliance of claim 13, wherein the inner wall is the bottom wall or top plate defining the cooking chamber.

15. The heating appliance of claim 13, wherein the inner wall is a side wall defining the cooking chamber.

16. The heating appliance of claim 13, wherein the inner wall comprises opposing sidewalls, and the heating appliance comprises a respective thermal resistance heating plate in each of the opposing sidewalls defining the cooking chamber.

17. A method of forming a heating appliance, the method comprising: A housing is provided, the housing having an inner wall having an inner surface defining a cooking chamber for heating food; A thermal resistance coating is applied to the bottom surface of the substrate to form a thermal resistance heating plate; as well as The thermal resistance heating plate is positioned in an opening in the side wall defined in the inner wall, so that microwave radiation can pass through the substrate and be transmitted to the cooking chamber. The inner surface of the substrate opposite the bottom surface is flush with the inner surface of the sidewall to define the cooking chamber.

18. The method of claim 17, further comprising applying metal connecting wires to the surface to form electrical contacts for the thermal resistance heating plate prior to applying the thermal resistance coating.

19. The method of claim 17, wherein applying the thermal resistance coating comprises depositing the thermal resistance coating on the substrate and curing the thermal resistance coating.

20. The method of claim 19, wherein the thermal resistance coating comprises single-walled or multi-walled carbon nanotubes dispersed in a coating matrix.

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