Patent Publication Number: US-11665793-B2

Title: Cooking appliance

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. 119 and 365 to Korean Patent Application No. 10-2020-0022579, filed on Feb. 24, 2020, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a cooking appliance. 
     BACKGROUND 
     Various types of cooking appliances are used to heat food at home or in restaurants. For example, various cooking appliances may include a microwave oven, an induction heating type electric stove, and a grill heater. 
     The microwave oven may use electromagnetic radiation in a microwave frequency range to vibrate molecules in food to thereby generate heat to quickly heat food. 
     The induction heating type electric stove may heat an object to be heated by using electromagnetic induction. Specifically, the induction heating type electric stove may generate eddy current in an object made of a metal component by using a magnetic field generated around a coil by a high frequency power of a predetermined magnitude. The object may be heated by the eddy current. 
     The grill heater may heat food by radiation or convection of infrared heat as the infrared heat passes through the food. 
     As the number and types of cooking appliances increase, the cooking appliances may occupy a large area in the living space. Thus, in some cases, a multi-purpose cooking appliance may include a plurality of heating modules. In some cases, a cooking appliance may a plurality of heating methods simultaneously to cook food. For example, a cooking appliance may simultaneously use a microwave and an induction heating coil heat source. 
     In some cases, a user may place a separate conductor tray for heating the induction heating coil by the microwave. In some cases, it may not be possible to heat a type of vessel (for example, a nonmagnetic vessel) in addition to a separate conductor tray with an induction heating coil heat source. 
     In some cases, a cooking appliance may have a complex structure, which may increase the manufacturing cost. For example, the cooking appliance may include a separate sensor part for determining whether the conductor tray is mounted thereon because, when the conductor tray is not mounted, the microwave and the induction heating coil heat source may not be used at the same time. 
     SUMMARY 
     The present disclosure describes a composite cooking appliance having a plurality of heat sources. 
     For example, the present disclosure describes a cooking appliance having a microwave (MW) heating module and an induction heating (IH) module together. In some examples, the MW heating module and the IH module may simultaneously heat an object to be heated. 
     The present disclosure also describes a cooking appliance for heating the object by operating the MW heating module and the IH module simultaneously regardless of the material of the object. 
     According to one aspect of the subject matter described in this application, a cooking appliance includes a housing that defines a cavity therein, a door connected to the housing and configured to open and close the cavity, a microwave (MW) heating module configured to emit microwaves into the cavity, and an induction heating (IH) module configured to emit a magnetic field towards the cavity. The IH module includes a working coil that is configured to generate the magnetic field and a thin film that is disposed between the cavity and the working coil. 
     Implementations according to this aspect may include one or more of the following features. For example, the housing may include a plate that defines the cavity, the plate having at least a portion in contact with the thin film. The thin film may be coated on an entire upper surface of the plate or an entire lower surface of the plate. In some examples, the thin film may be in contact with a portion of an upper surface of the plate or a portion of a lower surface of the plate, where the plate may define a plurality of holes. In some examples, the plurality of holes may be defined in a region of the plate in contact with the thin film. In some examples, none of the plurality of holes is defined in a region of the plate outside of the thin film. 
     In some implementations, the IH module further may include a cover that covers the thin film. For example, the thin film may cover the upper surface of the plate. In some examples, the thin film may cover the lower surface of the plate. 
     In some implementations, the plate may include a first plate made of a glass material and covered by the thin film, and a second plate made of an iron material. In some examples, the first plate may be disposed laterally inside the second plate. In some examples, the second plate may be flush with the first plate. 
     In some implementations, the IH module further may include a heat insulating material disposed between the working coil and the thin film. In some examples, the MW heating module may include a magnetron configured to generate the microwaves, and a waveguide configured to guide the microwaves to the cavity. 
     In some implementations, the IH module may be configured to provide the magnetic field to a first surface defining the cavity, and the MW heating module may be configured to supply the microwaves to the cavity through a second surface defining the cavity. In some examples, the first surface may be a bottom surface facing the cavity, and the second surface may be at least one of surfaces other than the bottom surface. 
     In some implementations, the cooking appliance may further include a grill heater configured to supply radiant heat to the cavity through a third surface defining the cavity. In some implementations, a skin depth of the thin film may be greater than a thickness of the thin film. 
     According to another aspect, a cooking appliance includes a housing that defines a cavity configured to receive an object, a magnetron that is configured to generate microwaves and that is configured to heat the object by the microwaves, a waveguide configured to guide the microwaves to the cavity, a working coil that is configured to generate a magnetic field and that is configured to, based on the object being a magnetic object, heat the object by induction, and a thin film that is disposed between the cavity and the working coil and that is configured to, based on the object being a nonmagnetic object, induce current by the working coil to thereby heat the object. 
     Implementations according to this aspect may include one or more of the following features or the features described above. For instance, the waveguide may be configured to guide the magnetic field to an upper portion of the cavity, and the thin film may be disposed vertically below the cavity, and the working coil is disposed vertically below the thin film. 
     In some implementations, where the thin film of the cooking appliance passes through the magnetic field generated by the working coil and blocks the microwaves, the MW heating module and the IH module may be driven simultaneously. 
     In some implementations, the IH module may heat both the magnetic body and the nonmagnetic body through a thin film, and thus the IH module can heat the object regardless of the disposition position and the type of the object. In some examples, the cooking applicant may not include a sensor for detecting a separate tray, a sensor for detecting the material of the object, or the like. 
     In addition to the above-described effects, additional effects of the present disclosure will be described together with the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view illustrating an example of a cooking appliance. 
         FIG.  2    is a control block diagram illustrating an example of a cooking appliance. 
         FIG.  3    is a sectional view illustrating an example of a cooking appliance. 
         FIGS.  4  and  5    are views illustrating examples of equivalent circuits formed by one or both of an example thin film and an example object to explain a change in electrical impedance according to a type of the object. 
         FIG.  6    is a sectional view illustrating an example of a cooking appliance. 
         FIG.  7    is a sectional view illustrating an example of a cooking appliance. 
         FIG.  8    is a sectional view illustrating an example of a cooking appliance. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, exemplary implementations 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 the same or similar components. 
     Hereinafter, one or more examples of a cooking appliance will be described. 
       FIG.  1    is a perspective view illustrating an example of a cooking appliance. 
     The cooking appliance  1  may include a housing  2  and a door  3  connected to the housing  2 . 
     A cavity  4  may be defined in the housing  2 , and the cavity  4  may be a cooking chamber. The cavity  4  may be a cooking space configured to receive an object to be heated. 
     In some implementations, an input interface  50  may be disposed on an outer surface of the housing  2 . The input interface  50  may receive an input for operating the cooking appliance from the user. 
     The cavity  4  can be opened or closed by the door  3 . The door  3  may be attached to the front portion of the housing  2  so that the door can be opened and closed. The door  3  can open and close the cavity  4 . A window  31  may be formed in the door  3 . The user can check the inside of the cavity  4  through the window  31  when the cavity  4  is closed. The window  31  will be described in detail with reference to  FIG.  3   . 
     The cavity  4  may be formed with first to fifth surfaces and may be opened or closed according to the position of the door  3 . A first surface of the cavity  4  is a bottom surface  41 , a second surface thereof is a ceiling surface  43  (see  FIG.  3   ), a third surface thereof is a rear surface  45  (see  FIG.  3   ), a fourth surface and a fifth face may be both side surfaces. Both side surfaces may be in contact with the bottom surface  41 , the ceiling surface  43 , and the rear surface  45 , respectively. One of both side surfaces  42  may be formed close to the door  3  and the other may be formed close to the input interface  50 . 
       FIG.  2    is a control block diagram illustrating an example of a cooking appliance. 
     The cooking appliance  1  may include an input interface  50 , a power supply unit  60 , an IH module  70 , a MW heating module  80 , and a processor  100 .  FIG.  2    is an example for convenience of description, and the cooking appliance  1  may further include other components in addition to the components illustrated in  FIG.  2    or may omit some of the components illustrated in  FIG.  2   . 
     The processor  100  may control the overall operation of the cooking appliance  1 . The processor  100  may control each of the input interface  50 , the power supply unit  60 , the IH module  70 , and the MW heating module  80 . The processor  100  may control the IH module  70  and the MW heating module  80  so as to operate the cooking appliance  1  according to the input received through the input interface  50 . For example, the processor  100  may include an electric circuit, an integrated circuit, a controller, or the like. 
     The input interface  50  may receive various inputs to operate the cooking appliance  1 . For example, the input interface  50  may receive an operation start input or an operation stop input of the cooking appliance  1 . In some examples, the input interface  50  may receive an input for driving the IH module  70  or input for driving the MW heating module  80 . In some examples, the input interface  50  may include a button, a dial, a touch pad, a knob, a switch, or the like. 
     The power supply unit  60  may receive power from an external power source for operation of the cooking appliance  1 . The power supply unit  60  may supply power to the input interface  50 , the IH module  70 , the MW heating module  80 , the processor  100 , and the like. In some examples, the power supply unit  60  may be a commercial power supply, an electric circuit, a regulator, a rectifier, or the like. 
     The IH module  70  may provide the heat source of the induction heating method to the cavity  4 . The IH module  70  may emit a magnetic field towards the cavity  4 . 
     The IH module  70  may generate a magnetic field through the working coil to directly or indirectly heat an object to be heated in the cavity  4 . 
     Specifically, the IH module  70  may include at least some or all of the working coil, the thin film, the cover, the heat insulating material, and the ferrite. In some implementations, the IH module  70  may further include an inverter or the like, but for the convenience of description, a detailed description thereof will be omitted. 
     The working coil can generate a magnetic field. The working coil may directly heat an object (that is, a magnetic body) that is magnetic, and indirectly heat an object (that is, a nonmagnetic body) that is not magnetic through the thin film. 
     The working coil may heat an object by an induction heating method, and the working coil may be provided to overlap the thin film in a longitudinal direction (that is, a vertical direction or an up and down direction). 
     The thin film passes through a magnetic field generated in the working coil and may not pass the microwave generated in the MW heating module  80 . 
     The thin film may have a skin depth deeper than the thickness of the thin film. The thin film may shield the microwaves. The thin film may heat a nonmagnetic body of an object. 
     The thin film may be disposed between the cavity  4  and the working coil. Between the cavity  4  and the working coil, a thin film, a heat insulating material, and the like may be further disposed. 
     The thin film may be disposed to be in contact with a plate forming one surface of the cavity  4 . The thin film may be coated on a cover to be described later. 
     The thin film may be provided to overlap the working coil in the longitudinal direction (that is, in the vertical direction or the up and down direction), thereby being capable of heating the object regardless of the disposition position and type of the object. 
     In addition, the thin film may have at least one property of magnetic and nonmagnetic (that is, magnetic, nonmagnetic, or both magnetic and nonmagnetic). 
     In addition, the thin film may be formed of, for example, a conductive material (for example, aluminum) and may be formed in a shape in which a plurality of rings having different diameters from each other are repeated, but is not limited thereto. In other words, the shape, size, or the like of the thin film may vary. 
     The thin film may be made of a material other than the conductive material or may be formed in another shape. However, for convenience of description, it will be described on the assumption that the thin film is made of a conductive material in an implementation of the present invention. 
     The thin film can be coated on the cover. 
     The cover may cover the thin film. The cover may protect the thin film from the outside. 
     Specifically, when an object is directly placed on the thin film, or when food in the object overflows into the thin film, the thin film may be worn or contaminated. Thus, the cover may cover the thin film so that the thin film is protected from these problems. 
     The cover may be formed of a nonmetallic component so that the magnetic field can pass through the cover. The cover may be composed of a glass material (for example, ceramic glass). 
     The cover may be formed of a component having heat resistance to the heat of the object, the heat of the thin film, and the like. In particular, the thin film may be heated to a temperature close to about 600 degrees and may be formed of a material which can withstand such high temperatures. 
     The cover can dissipate the heat of the thin film. The cover may diffuse heat while hot heat generated in the thin film is transferred to the cover. 
     A heat insulating material may be disposed between the thin film and the working coil. The heat insulating material can be mounted on an upper portion of the working coil. The heat insulating material may block the generated heat from being transferred to the working coil while the thin film or the object is heated by the driving of the working coil. 
     In other words, when the thin film or the object is heated by electromagnetic induction of the working coil, heat of the thin film or the object is transferred to the cover or the plate, and the heat of the cover or the plate is transferred to the working coil again to damage the working coil. By blocking the heat from being transferred to the working coil in this way, the heat insulating material can prevent the damage of the working coil by heat, and furthermore, the heating performance of the working coil can be prevented from being lowered. 
     The ferrite may be mounted below the working coil to block a magnetic field generated downward when the working coil is driven. 
     The MW heating module  80  may provide microwaves to the cavity  4 . The MW heating module  80  may emit microwaves into the cavity  4 . 
     The MW heating module  80  may include a magnetron positioned outside the cavity  4  in the housing  2  to generate microwaves, and a waveguide for guiding microwaves generated from the magnetron to the cavity  4 . 
     In some implementations, as shown in  FIG.  2   , the cooking appliance  1  may include only the IH module  70  and the MW heating module  80 . In some implementations, the cooking appliance  1  may further include a grill heater module or device. 
     The grill heater module may supply radiant heat so as to heat food received in the cavity  4 . The grill heater module may include a heating unit having an infrared heating wire and allow to generate radiation or convection of the infrared heat generated from the heating unit to the cavity  4 . 
     For instance, in some implementations, the cooking appliance  1  may include an IH module  70 , a MW heating module  80 , and a grill heater module, and the IH module  70  may emit a magnetic field towards the first surface of the cavity  4 , the MW heating module  80  may supply microwaves to the cavity  4  through the second surface of the cavity  4 , and a grill heater module may supply radiant heat to the cavity  4  through the third surface of the cavity  4 . 
     Hereinafter, a case where the cooking appliance  1  includes the IH module  70  and the MW heating module  80  will be described. 
       FIG.  3    is a sectional view illustrating an example of a cooking appliance. 
     The door  3  can open and close the cavity  4 . A window  31  may be formed in the door  3 , and the window  31  may include a window unit  32  and a shielding unit  33 . 
     The window unit  32  may be formed of a transparent material or a translucent material. The user can see inside the cavity  4  through the window unit  32 . The outer surface of the window unit  32  may face the outside of the cooking appliance  1 , and the inner surface of the window unit  32  may face the inside of the cooking appliance  1 . 
     The shielding unit  33  may be mounted on the inner surface of the window unit  32 . The shielding unit  33  may block the microwaves of the cavity  4  from moving out of the cooking appliance  1  through the door  3 . 
     The shielding unit  33  may be an iron net. A plurality of shielding holes  33   a  may be formed in the shielding unit  33 , and the shielding holes  33   a  may have a size larger than that of a wavelength of visible light and smaller than that of a wavelength of microwaves. Therefore, the user can see the inside of the cavity  4  through the shielding hole  33   a , and microwaves do not pass through the shielding hole  33   a.    
     The housing  2  may be provided with a plate  110  that has a first surface (for example, bottom surface  41 ) facing the cavity  4 , and at least one of the plate  110  is in contact with the thin film  120 . The IH module  70  may emit a magnetic field towards the first surface of the cavity  4 . The first surface may define or face a bottom portion of the cavity  4 . 
     In some implementations, the thin film  120  may be coated on the entire upper surface of the plate  110  or the entire lower surface of the plate  110 . In  FIG.  3   , it is assumed that the thin film  120  is coated on the entire lower surface of the plate  110 , but since this is only an example for convenience of description, the coating of the thin film is not limited thereto. 
     In some examples, the plate  110  may be made of a nonmetallic component so that the magnetic field passes through the plate. The plate  110  may be made of a glass material (for example, ceramic glass). In some implementations, the plate  110  may be a cover that covers the thin film while forming the first surface  41  of the cavity  4 . Therefore, in some cases, the plate  110  may have characteristics equivalent to those of the cover. 
     In addition, the horizontal sectional area size of the thin film  120  may be the same as the horizontal sectional area size of the plate  110 . Therefore, the first surface of the cavity  4  may block the movement of the microwave by the thin film  120 . 
     The heat insulating material  130  may be disposed below the thin film  120 , the working coil  140  may be disposed below the heat insulating material  130 , and the ferrite  150  may be disposed below the working coil  140 . 
     The working coil  140  generates a magnetic field during driving, and when an object made of a magnetic body is placed in the cavity  4 , the magnetic field may induce eddy current through the thin film  120  to the object. When an object made of a nonmagnetic body is placed in the cavity  4 , the magnetic field generated by the working coil  140  induces eddy current in the thin film  120 , and then the plate  110  may heat the object by heat generated in the thin film  120  and diffused into the plate  110 . 
     The characteristics and configuration of the thin film will be described in more detail. 
       FIGS.  4  and  5    are views illustrating examples of equivalent circuits formed by one or both of an example thin film and an example object to explain a change in electrical impedance according to a type of the object. 
     For example, the thin film may be made of a material having low relative permeability. 
     Specifically, when the relative permeability of the thin film is low, the skin depth of the thin film may be deep. Here, the skin depth means the current penetration depth from the material surface, and the relative permeability may be inversely related to the skin depth. Accordingly, the lower the permeability of the thin film, the deeper the skin depth of the thin film. 
     In some implementations, the skin depth of the thin film may be deeper than the thickness of the thin film. For example, where the thin film has a thin thickness (for example, 0.1 μm˜1,000 μm thickness) and the skin depth of the thin film is deeper than the thickness of the thin film, the magnetic field generated by the working coil may pass through the thin film to transfer to the object, and thus the eddy current can be induced in the object. 
     In some cases, when the skin depth of the thin film is shallower than the thickness of the thin film, it may be difficult for the magnetic field generated by the working coil to reach the object. 
     In other cases, when the skin depth of the thin film is deeper than the thickness of the thin film, the magnetic field generated by the working coil may reach the object. In other words, in the implementation of the present disclosure, since the skin depth of the thin film is deeper than the thickness of the thin film, the magnetic field generated by the working coil passes through the thin film and is mostly transferred to the object and exhausted, and thus the object can be primarily heated. 
     In some examples, where the thin film has a thin thickness as described above, the thin film may have a resistance value to be heated by the working coil. 
     Specifically, the thickness of the thin film may be inversely related to the resistance value (that is, the surface resistance value) of the thin film. For example, as the thickness of the thin film becomes thinner, the resistance value (that is, the surface resistance value) of the thin film becomes larger. The thin film may be thinly coated to change characteristics into a load that can be heated by current. 
     For example, the thin film may have a thickness from 0.1 μm to 1,000 μm, but the thickness of the thin film is not limited thereto. 
     Since the thin film having such characteristics exists to heat the nonmagnetic material, the impedance characteristics between the thin film and the object may be changed according to whether the object disposed in the cavity  4  is a magnetic body or a nonmagnetic body. 
     An example case, where the object is a magnetic body, is described as follows. 
     When the object which is magnetic is placed in the cavity  4  and the working coil is driven, the resistance component R 1  and the inductor component L 1  of the object which is magnetic as illustrated in  FIG.  4    can form an equivalent circuit together with the resistance component R 2  and the inductor component L 2  of the thin film. 
     In this case, the impedance (that is, impedance composed of R 1  and L 1 ) of the object which is magnetic in the equivalent circuit may be smaller than the impedance of the thin film (that is, impedance composed of R 2  and L 2 ). 
     Accordingly, when the equivalent circuit as described above is formed, the size of the eddy current I 1  applied to the object which is magnetic may be larger than the size of the eddy current I 2  applied to the thin film. Accordingly, most of the eddy current generated by the working coil is applied to the object, so that the object can be heated. 
     In other words, when the object is a magnetic body, since the above-described equivalent circuit is formed and most of the eddy currents are applied to the object, the working coil can directly heat the object. 
     In some examples, where some eddy current is also applied to the thin film so that the thin film is slightly heated, the object may be slightly indirectly heated by the thin film. In some cases, the degree to which the object is indirectly heated by the thin film is not significant as compared with the degree to which the object by the working coil is directly heated. 
     An example case, where the object is a nonmagnetic body, is described as follows. 
     When an object, which is not magnetic, is disposed in the cavity  4  and the working coil is driven, an impedance may not exist in the object which is not magnetic and impedance may exist in the thin film. In other words, the resistance component R and the inductor component L may exist only in the thin film. 
     Therefore, when an object to be heated which is not magnetic is disposed in the cavity  4  and the working coil is driven, as illustrated in  FIG.  5   , the resistance component R and the inductor component L of the thin film can form an equivalent circuit. 
     Accordingly, the eddy current I may be applied only to the thin film, and the eddy current may not be applied to the object which is not magnetic. More specifically, the eddy current I generated by the working coil is applied only to the thin film so that the thin film can be heated. 
     In some examples, when the object is a nonmagnetic body since the eddy current I is applied to the thin film and the thin film is heated, the object may be indirectly heated by the thin film heated by the working coil. 
     As discussed above, regardless of whether the object is a magnetic body or a nonmagnetic body, the object may be directly or indirectly heated by one heat source referred to as a working coil. For example, when the object is a magnetic body, the working coil directly heats the object, and when the object is a nonmagnetic body, the thin film heated by the working coil may indirectly heat the object. 
     The thin film  120 ,  220 ,  320 , and  420  according to various implementations of the present disclosure to be described below may have the above-described characteristics. 
     As described above, since the IH module  70  of the cooking appliance  1  may heat both magnetic body and nonmagnetic body, regardless of the disposition position and type of the object, the object can be heated. Accordingly, since the user may place the object on any heating region on the cavity  4  without having to grasp whether the object is a magnetic body or a nonmagnetic body, ease of use can be improved. 
     In some implementations, the cooking appliance  1  may include the MW heating module  80  and the IH module  70  to heat the object placed on the cavity  4  together. 
     The MW heating module  80  may be installed close to any one of the second to fifth surfaces of the cavity  4 . For example, the MW heating module  80  may supply microwaves to the cavity  4  through the second surface of the cavity  4 , where the second surface may be the ceiling surface  43 , which is only exemplary. In other words, the second surface may be at least one of the other surfaces except for the surface from which the magnetic field is emitted by the IH module  70 . Hereinafter, it is assumed that the second surface is the ceiling surface  43 . 
     The MW heating module  80  may include a magnetron  81 , a waveguide  83 , and a cooling fan  90 , and the waveguide  83  may have one side connected to the magnetron  81  and the other side connected to the cavity  4 . At least one slot  83   a  through which microwaves pass may be formed on the ceiling surface  43  of the cavity  4 . The cooling fan  90  may be installed around the magnetron  81  to cool the magnetron  81 . 
     The object and the food placed in the cavity  4  may be heated by the IH module  70  and the MW heating module  80 . 
       FIGS.  6  and  7    are sectional views illustrating examples of a cooking appliance. 
     Since the characteristics of the door  3 , the thin film, the MW heating module  80 , and the like except for the structure and the shape of the first surface  41  of the cavity  4  and the IH module  70  are same as described with reference to the first implementation, duplicate descriptions will be omitted. In other words, since the method in which the magnetic field generated by the working coil  240  or  340  heats the object is the same as described in the first implementation, duplicate descriptions will be omitted. 
     Referring to  FIGS.  6  and  7   , the housing  2  may include a plate that defines a first surface facing the cavity  4  (for example, the bottom surface  41 ), and at least one of the plate is in contact with the thin film  220  or  320 . The IH module  70  may emit a magnetic field towards the first surface  41  of the cavity  4 . In this case, the IH module  70  may further include a cover  210  or  310  on which the thin film  220  or  320  are coated. Since the cover is described in detail above, duplicate descriptions will be omitted. 
     In some implementations, the thin film  220  or  320  may be disposed in contact with a portion of the upper surfaces of the plate  201  or  301  or a portion of the lower surfaces of the plate  201  or  301 , and the plate  201  or  301  may be formed with a plurality of holes  201   a  or  301   a . Specifically, in the second implementation, as illustrated in  FIG.  6   , the thin film  220  is disposed to be in contact with a portion of the lower surface of the plate  201 , and, in the third implementation, as illustrated in  FIG.  7   , the thin film  320  may be disposed to be in contact with a portion of the upper surface of the plate  201 . As such, when the thin film  220  or  320  are disposed to be in contact with the plate  201  or  301 , the thin film  220  or  320  may block gaps between the plurality of holes  201   a  or  301   a  and the thin film  220  or  320 , and thus the microwaves may be completely blocked from moving toward the working coil  240  or  340  through gaps between the plurality of holes  201   a  or  301   a  and the thin film  220  or  320 . 
     In some examples, the plate  201  or  301  may be made of an iron material so that microwaves are blocked, and the plurality of holes  201   a  or  301   a  can be defined so that the magnetic field generated in the working coil  240  or  340  can move to the cavity  4 . 
     The plurality of holes  201   a  or  301   a  may have a size through which a magnetic field generated by the working coil  240  or  340  can pass. In some cases, where not only a magnetic field but also a microwave pass through the plurality of holes  201   a  or  301   a , the microwave may heat the working coil  240  or  340 . In some examples, the thin film  220  or  320  may be disposed to be in contact with the plate  201  or  301 , particularly the region of the plate  201  or  301  in which the plurality of holes  201   a  or  301   a  are formed. Accordingly, the magnetic field generated in the working coil  240  or  340  may move to the cavity  4  through the plurality of holes  201   a  or  301   a  and the thin film  220  or  320 , and the microwaves in the cavity  4  may be completely blocked from being moved to a direction of the working coil  240  or  340  by the thin film  220  or  320 . 
     The plurality of holes  201   a  or  301   a  are formed in a region A 1  of the plate  201  or  301  overlapping the cover  210  or  310  or the thin film  220  or  320  in the vertical direction, and holes  201   a  or  301   a  may not be formed in a region A 2  of the plate  201  or  301  which does not overlap the cover  210  or  310  or the thin film  220  or  320  in the vertical direction. 
     A region A 1  of the plate  201  or  301  overlapping the cover  210  or  310  or the thin film  220  or  320  in the vertical direction may be a heating region in which the object is placed. A region A 2  of the plate  201  or  301  which does not overlap the cover  210  or  310  or the thin film  220  or  320  in the vertical direction may be an unheated region. As such, when the plurality of holes  201   a  or  301   a  are formed only in a portion of the plate  201  or  301  since the thin film  220  or  320  need not be disposed until the unheated region, the manufacturing cost can be reduced and the manufacturing process can be reduced by reducing the number of holes  201   a  or  301   a.    
     In an implementation, holes may be formed in the unheated region, but in this case, the holes in the unheated region may be formed to have a smaller size than the wavelength of the microwave. 
     In some implementations, as illustrated in  FIG.  6   , since the upper surface of the plate  201  is flat, there is an advantage in that the object is easily received. 
     In some implementations, as illustrated in  FIG.  7   , since the plurality of holes  301   a  are covered by the thin film  320 , and the thin film  320  is covered by the cover  310 , there is an advantage that, even if food overflows in the object, the thin film  320 , the working coil  340 , and the like are securely protected, and the ease of cleaning is secured. 
       FIG.  8    is a sectional view illustrating an example of a cooking appliance. 
     Similarly, since, except for the structure, the shape, or the like of the first surface  41  of the cavity  4  and the IH module  70 , the characteristics of the door  3 , the thin film, the MW heating module  80 , and the like are the same as described with reference to the first implementation, duplicate descriptions thereof will be omitted. In other words, since the method in which the magnetic field generated by the working coil  440  heats the object or the like is the same as described in the first implementation, duplicate descriptions thereof will be omitted. 
     Referring to  FIG.  8   , the housing  2  may include plates  410  and  411  that define a first surface of the cavity  4  (for example, the bottom surface  41 ), and at least a portion of the plates may be in contact with the thin film  420 . For example, the plate  410  may be disposed laterally inward relative to the plate  411 , be flush with the plate  411 , and define the first surface facing the cavity  4 . 
     The plates  410  and  411  may be formed of a first plate  410  made of glass material coated with the thin film  420  and a second plate  411  made of iron material. The IH module  70  may emit a magnetic field towards the first surface  41  of the cavity  4 . 
     The first plate  410  may be disposed inside the second plate  411 . The region where the first plate  410  is formed may be a heating region, and the region where the second plate  411  is formed may be an unheated region. 
     In some examples, the first plate  410  may serve as a cover. 
     The thin film  420  may be coated on the lower surface of the first plate  410 . The horizontal sectional area size of the thin film  420  may be less than or equal to the horizontal sectional area size of the first plate  410 . 
     The first plate  410  may be made of a nonmetallic component such that the magnetic field passes through the cover as described above. The first plate  410  may be made of a glass material (for example, ceramic glass). The first plate  410  may be formed of a component having heat resistance to the heat of the object, the heat of the thin film  420 , and the like. The first plate  410  may disperse the heat of the thin film  420 . 
     As described with reference to the first to fourth implementations, the cooking appliance  1  disposes a thin film between the cavity  4  and the working coil  140 ,  240 ,  340 , or  440 , and thus there is an advantage that the IH module  70  and the MW heating module  80  can heat the object or the food together while minimizing the problem of breakage of the IH module  70  due to the microwave. In other words, the thin film is a protective device of the IH module  70  and can heat the object. 
     In some implementations, the cooking appliance may heat an object regardless of the material, position, or the like of the object, and the user may not use only a predetermined tray. In some examples, the cooking appliance may not include a sensor for sensing the material of the object. 
     The above description is merely illustrative of the technical idea of the present disclosure, and various modifications and changes may be made thereto by those skilled in the art without departing from the essential characteristics of the present disclosure. 
     Therefore, the implementations of the present disclosure are not intended to limit the technical spirit of the present disclosure but to illustrate the technical idea of the present disclosure, and the technical spirit of the present disclosure is not limited by these implementations. 
     The scope of protection of the present disclosure should be interpreted by the appending claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present disclosure.