Microwave heating device and grill pan

Abstract

To provide a microwave heating device controlling calorific distribution of a grill tray: and to provide a grill tray.SOLUTION: Microwave heating devices (2, 102) are respectively provided with: housings (4, 104) respectively having heating chambers (8, 108); microwave generating devices (16, 116); waveguide structures (18, 118) respectively supplying microwaves to the heating chambers (8, 108); and grill trays (10, 110) where wave absorbers (14, 114) are respectively mounted. The grill trays (10, 110) are respectively provided with: metal base materials (120) respectively disposed on upper surface sides with respect to the wave absorbers (14 114); metal plates (122) respectively disposed on lower surface sides with respect to the wave absorbers (14, 114), extending in a first direction in plan view, and forming a first slit (126A) and a second slit (126B) on positions spaced in a second direction orthogonal to the first direction; and metal elements (24, 124) respectively connected to the lower surfaces of the metal plates (122) at positions between the first slit (126A) and the second slits (126B) and having a component extending in the first direction and a component extending downwards.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a microwave heating device and a grill plate used in the microwave heating device.

Background Art

[0002] Conventionally, a microwave heating device that places an object to be heated, such as food, in a heating chamber and heats it with microwaves is known (see, for example, Patent Document 1).

[0003] The microwave heating device of Patent Document 1 has a grill heating mode in which a grill plate is placed in a heating chamber and the object to be heated is heat-transferred and heated on the grill plate. In the grill heating mode, by controlling the direction of the rotating antenna, more appropriate heating is performed according to the state of the object to be heated (for example, the frozen state).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the ferrite provided on the grill plate is heated by microwaves, the heat generation distribution of the ferrite tends to be non-uniform, and when the object to be heated is grill-heated using the grill plate, the heating distribution of the object to be heated also tends to be non-uniform. It can be said that there is room for improvement in controlling the heat generation distribution of the grill plate.

[0006] Therefore, an object of the present disclosure is to solve the above problems and to realize a microwave heating device and a grill plate that can control the heat generation distribution of the grill plate.

Means for Solving the Problems

[0007] To achieve the above objective, the microwave heating apparatus of the present disclosure comprises a housing having a heating chamber, a microwave generator for generating microwaves, a waveguide structure for supplying microwaves generated by the microwave generator to the heating chamber, and a grill plate disposed in the heating chamber and provided with a radio wave absorber, wherein the grill plate comprises a metal base material disposed on the upper side with respect to the radio wave absorber, a metal plate disposed on the lower side with respect to the radio wave absorber, each extending in a first direction in a plan view and forming a first slit and a second slit at positions spaced apart in a second direction perpendicular to the first direction, and a metal element connected to the lower surface of the metal plate at a position between the first slit and the second slit, and having a component extending in the first direction and a component extending downward.

[0008] Furthermore, the grill pan of this disclosure is a grill pan used in the heating chamber of a microwave heating apparatus, and comprises: a radio wave absorber; a metal base material disposed on the upper side of the radio wave absorber; a metal plate disposed on the lower side of the radio wave absorber, which extends in a first direction in a plan view and forms a first slit and a second slit at positions spaced apart in a second direction perpendicular to the first direction; and a metal element connected to the lower surface of the metal plate at a position between the first slit and the second slit, and having a component extending in the first direction and a component extending downward. [Effects of the Invention]

[0009] According to this disclosure, the heat distribution of the grill pan can be controlled. [Brief explanation of the drawing]

[0010] [Figure 1] Schematic perspective view of the microwave heating apparatus according to the embodiment (with the door closed) [Figure 2] Schematic perspective view of the microwave heating apparatus according to the embodiment (with the door open) [Figure 3] Schematic front view of the microwave heating apparatus of the embodiment (with the door omitted) [Figure 4]A schematic front view showing a microwave heating device modeled after the microwave heating device of the embodiment. [Figure 5] Plan view of the grill plate of the modeled microwave heating device, seen from below. [Figure 6] A perspective view showing an enlarged view of the surrounding structure of a metal element. [Figure 7] Front view showing an enlarged view of the surrounding structure of the metal element. [Figure 8] Front view showing a further enlarged view of the surrounding structure of the metal element. [Figure 9] A table classifying the relationship when the direction of the incident microwave field and the direction of the slit are changed. [Figure 10] The table shows the analysis results of the magnetic field distribution generated inside the ferrite when microwaves are supplied, in the model configuration based on the combination of waveguide structure orientation and slit orientation shown in Figure 9. [Figure 11] Table showing analysis results when using a model with varying metal plate widths. [Figure 12] A graph showing the magnetic field strength and the number of locations where the magnetic field strength was observed when the width of the metal plate was changed. [Figure 13] Table showing analysis results when using a model with varying spacing between metal plates. [Figure 14] A graph showing the magnetic field strength and the number of locations where the magnetic field strength was observed when the distance between metal plates was changed. [Figure 15] Table showing analysis results when the height and width of the metal element are changed. [Figure 16] Table showing analysis results when the height and width of the metal element are changed. [Figure 17] This table shows the analysis results when the height of the metal element is set to a minute height and the width of the metal element is changed. [Figure 18A] This diagram shows a model configuration of a microwave heating device having a grill pan without metal elements. [Figure 18B] Figure 18A shows the analysis results regarding the magnetic field intensity distribution generated in ferrite when microwaves are supplied using the microwave heating device shown. [Figure 19A] Showing the model configuration of a microwave heating device having a grill plate provided with two metal elements [Figure 19B] A diagram showing the analysis result regarding the intensity distribution of the magnetic field generated in a ferrite when microwaves are supplied using the microwave heating device shown in Fig. 19A [Figure 20] A longitudinal sectional view showing the analysis result when only the first metal element shown in Fig. 19A is loaded and the second metal element is not loaded [Figure 21] A longitudinal sectional view showing the analysis result when only the second metal element shown in Fig. 19A is loaded and the first metal element is not loaded [Figure 22A] A schematic front view showing an example of the shape variation of a metal element [Figure 22B] A schematic front view showing an example of the shape variation of a metal element [Figure 22C] A schematic front view showing an example of the shape variation of a metal element [Figure 22D] A schematic front view showing an example of the shape variation of a metal element [Figure 22E] A schematic front view showing an example of the shape variation of a metal element [Figure 22F] A schematic front view showing an example of the shape variation of a metal element [Figure 22G] A schematic front view showing an example of the shape variation of a metal element [Figure 22H] A schematic front view showing an example of the shape variation of a metal element [Figure 22I] A schematic front view showing an example of the shape variation of a metal element [Figure 22J] A schematic front view showing an example of the shape variation of a metal element

Embodiments for Carrying Out the Invention

[0011] According to a first aspect of the present invention, a cooking appliance is provided comprising: a housing having a heating chamber; a microwave generator for generating microwaves; a waveguide structure for supplying microwaves generated by the microwave generator to the heating chamber; and a grill plate disposed in the heating chamber and provided with a radio wave absorber, wherein the grill plate comprises: a metal base material disposed on the upper side relative to the radio wave absorber; a metal plate disposed on the lower side relative to the radio wave absorber, which in a plan view extends in a first direction and forms a first slit and a second slit at positions spaced apart in a second direction perpendicular to the first direction; and a metal element connected to the lower surface of the metal plate at a position between the first slit and the second slit, and having a component extending in the first direction and a component extending downward.

[0012] According to a second aspect of the present invention, a plurality of metal plates are provided spaced apart in the second direction, and the first slit and the second slit are each formed by the gaps between the plurality of metal plates, providing a heating cooker as described in the first aspect.

[0013] According to a third aspect of the present invention, the heating appliance according to the first or second aspect is provided, wherein the metal element is a metal plate extending parallel to the first direction.

[0014] According to a fourth aspect of the present invention, the length of the metal element from a first end connected to the metal plate to a second end opposite to the first end is an odd multiple of 1 / 6 to 1 / 3 wavelength of the microwaves generated by the microwave generator, thereby providing a heating cooker according to any one of the first to third aspects.

[0015] According to a fifth aspect of the present invention, the heating appliance is provided according to any one of the first to fourth aspects, wherein the metal element has a first portion extending downward from the metal plate and a second portion connected to the first portion and extending in a direction different from that of the first portion.

[0016] According to a sixth aspect of the present invention, the second part is longer than the first part, providing a cooking appliance according to the fifth aspect.

[0017] According to a seventh aspect of the present invention, a heating appliance according to the fifth or sixth aspect is provided, wherein a bent portion is formed at the connection point between the first and second parts.

[0018] According to the eighth aspect of the present invention, the first and second parts extend orthogonally to each other, providing a heating appliance as described in the seventh aspect.

[0019] According to the ninth aspect of the present invention, a heating cooker is provided according to any one of the fifth to eighth aspects, wherein the height of the first part is 2 mm or less, and the length of the second part is an odd multiple of 1 / 6 to 1 / 3 wavelength of the microwaves generated by the microwave generator.

[0020] According to a tenth aspect of the present invention, the metal element extends in a straight line from a first end connected to the metal plate to a second end opposite to the first end, providing a heating cooker according to any one of the first to ninth aspects.

[0021] According to an eleventh aspect of the present invention, the metal element overlaps the first slit in a plan view, providing a heating appliance according to any one of the first to tenth aspects.

[0022] According to a twelfth aspect of the present invention, the waveguide structure provides a heating cooker according to any one of the first to eleventh aspects, wherein microwaves are supplied to generate an electric field direction along the second direction in a plan view.

[0023] According to a thirteenth aspect of the present invention, the present invention provides a cooking appliance according to any one of the first to twelfth aspects, wherein the metal element is an inverted F-type antenna.

[0024] According to a fourteenth aspect of the present invention, the present invention provides a heating cooker according to any one of the first to thirteenth aspects, wherein the metal element comprises a first metal element provided corresponding to the first slit and a second metal element provided corresponding to the second slit.

[0025] According to a 15th aspect of the present invention, the waveguide structure supplies microwaves such that an electric field direction is generated along the second direction in a plan view, and the first metal element and the second metal element are spaced apart in the second direction, the spacing being an integer multiple of one wavelength of microwaves generated by the microwave generator, the present invention provides a heating cooker according to the 14th aspect.

[0026] According to a sixteenth aspect of the present invention, the waveguide structure supplies microwaves such that an electric field direction is generated along the second direction in a plan view, and the first metal element and the second metal element are spaced apart in the first direction, the spacing being an integer multiple of one wavelength of microwaves generated by the microwave generator, the present invention provides a heating cooker according to the fourteenth or fifteenth aspect.

[0027] According to a 17th aspect of the present invention, a heating appliance is provided according to any one of the 14th to 16th aspects, wherein the first metal element and the second metal element have different dimensions.

[0028] According to an 18th aspect of the present invention, a grill plate for use in the heating chamber of a microwave heating apparatus is provided, comprising: a radio wave absorber; a metal base material disposed on the upper side of the radio wave absorber; a metal plate disposed on the lower side of the radio wave absorber, which extends in a first direction in a plan view and forms a first slit and a second slit at positions spaced apart in a second direction perpendicular to the first direction; and a metal element connected to the lower surface of the metal plate at a position between the first slit and the second slit, and having a component extending in the first direction and a component extending downward.

[0029] Hereinafter, exemplary embodiments of the microwave heating apparatus and grill pan relating to this disclosure will be described with reference to the attached drawings. This disclosure is not limited to the specific configurations of the embodiments described below, but includes configurations based on similar technical ideas.

[0030] (Embodiment) First, a microwave heating apparatus according to one embodiment of this disclosure will be described with reference to Figures 1 to 3.

[0031] Figures 1 and 2 are schematic perspective views of the microwave heating apparatus 2 according to the embodiment, and Figure 3 is a schematic front view of the microwave heating apparatus 2. Figure 1 shows the door 6 in the closed state, Figure 2 shows the door 6 in the open state, and Figure 3 shows the state with the door 6 omitted.

[0032] The microwave heating device 2 shown in Figures 1 to 3 is a cooking appliance (a so-called "microwave oven") for heating and cooking the food to be heated P shown in Figures 2 and 3 using microwaves. The food to be heated P is, for example, meat such as fish, beef, pork, or chicken.

[0033] In Figures 1 to 3, the depth direction (front-to-back direction) of the microwave heating device 2 is defined as the X-axis direction, the width direction (left-to-right direction) as the Y-axis direction, and the height direction (up-down direction) as the Z-axis direction.

[0034] As shown in Figures 1 and 2, the microwave heating device 2 comprises a housing 4 and a door 6.

[0035] The housing 4 is a component that constitutes the outer frame of the microwave heating device 2. As shown in Figure 2, the housing 4 has a heating chamber 8 inside, which is opened and closed by a door 6. The heating chamber 8 is a space for heating the object to be heated P, and a grill plate 10 shown in Figure 3 can be placed there. The grill plate 10 is not shown in Figure 2.

[0036] The grill plate 10 is a component for transferring heat to the object to be heated P by placing it on its upper surface. The grill plate 10 can be inserted into and removed from the heating chamber 8, and multiple rails 12 are provided on the inner wall of the housing 4 that constitutes the heating chamber 8. In the example shown in Figure 3, there are three levels of rails 12 arranged vertically, and the grill plate 10 is shown hooked onto the middle rail 12.

[0037] The grill pan 10 incorporates a ferrite 14 as an electromagnetic wave absorber. The ferrite 14 has the function of generating heat in response to the electromagnetic field of microwaves supplied from below. As the ferrite 14 generates heat, the entire grill pan 10 heats up, transferring heat to the object P placed on the grill pan 10 from below. The material of the ferrite 14 may be, for example, a mixture of rubber and metal powder such as iron or magnesium, or it may contain metal powder such as nickel.

[0038] Below the heating chamber 8, a microwave generator 16, a waveguide structure 18, and a control unit 20 are provided.

[0039] The microwave generator 16 is a device that generates microwaves, for example, microwaves with a frequency of 300 MHz to 300 GHz. A magnetron is used as the microwave generator 16. The waveguide structure 18 is a structure for supplying microwaves generated by the microwave generator 16 to the heating chamber 8, and has a waveguide 50 capable of transmitting microwaves and a rotating antenna 52 connected to the waveguide 50. The rotating antenna 52 has the function of rotating about a rotation axis 54 extending in the Z-axis direction, for example, and can change the direction of the electric field and magnetic field generated by the microwaves. The waveguide structure 18 supplies microwaves of 1 W, 2.45 GHz, TE10 mode to the heating chamber 8. The control unit 20 is a component that controls the components of the microwave heating device 2, such as the microwave generator 16, and is configured with, for example, a microcomputer.

[0040] An electric heater 22 is provided inside the heating chamber 8. The electric heater 22 is a heating means located in the heating chamber 8 and has the function of radiating heat to the object to be heated P from above.

[0041] The microwave heating device 2 having the above configuration has a grill heating mode in which the object to be heated P is grilled using the grill plate 10. In grill heating mode, with the grill plate 10 on which the object to be heated P is placed placed on the rail 12, the control unit 20 operates the microwave generator 16 and the electric heater 22. When the microwave generator 16 operates, microwaves are supplied to the heating chamber 8 through the waveguide structure 18, and the ferrite 14 of the grill plate 10 is heated by the electromagnetic field of the microwaves, causing the entire grill plate 10 to heat up. As a result, the object to be heated P is heated by heat transfer from below. Furthermore, when the electric heater 22 operates, the object to be heated P is heated by radiation from above. In this way, the object to be heated P can be grilled (baked) from both above and below.

[0042] One challenge in firing is that standing waves in the magnetic field acting inside the ferrite 14 cause the heat generation distribution of the ferrite 14 to become uniform, resulting in uneven firing of the heated object P. Therefore, in this application, we have devised a technique to equalize the magnetic field distribution by attaching a metal element 24 to the lower surface of the grill plate 10 and making it function as a quarter-wavelength resonator, thereby increasing the magnetic field near the nodes in the magnetic field distribution inside the ferrite 14. A model for explaining this technique and an electromagnetic field analysis using the model will be described below.

[0043] First, Figures 4 to 7 show a model configuration of the microwave heating device 2 of the embodiment. In the following analysis, the object to be heated P was always assumed to be frozen tuna.

[0044] Figure 4 is a schematic front view showing a microwave heating device 102 modeled after the microwave heating device 2 of the embodiment; Figure 5 is a plan view of the grill plate 110 of the microwave heating device 102 viewed from below; and Figures 6 and 7 are a perspective view and a front view, respectively, showing enlarged views of the peripheral configuration of the metal element 124.

[0045] The microwave heating device 102 comprises a housing 104, a grill pan 110, a microwave generator 116, and a waveguide structure 118. These components correspond to the housing 4, grill pan 10, microwave generator 16, and waveguide structure 18 in the microwave heating device 2 of the embodiment, respectively. Note that the rotating antenna in the waveguide structure 118 is not shown in the illustration.

[0046] The grill plate 110 comprises a ferrite 114, which is an electromagnetic wave absorber, as well as a base material 120, a plurality of metal plates 122, and a metal element 124.

[0047] The base material 120 is a plate-shaped member positioned on the upper side (+Z axis direction) relative to the ferrite 114, and is made of metal as a radio wave shielding member that does not transmit microwaves. By providing the base material 120, the transmission of microwaves supplied from below upward is prevented.

[0048] As shown in Figure 5, the base material 120 is provided with multiple slots 121. The slots 121 are notches formed on the outer circumference of the base material 120, creating a gap between them and the inner wall of the housing 104 that constitutes the heating chamber 108. In the example shown in Figure 5, a total of four slots 121 are provided. Each slot 121 has a shape that extends in the Y-axis direction in a plan view, and has the function of transmitting the microwave magnetic field above the grill plate 110 when an electric field along the X-axis direction is incident from the waveguide structure 118. By providing the slots 121, it becomes possible to directly heat the object to be heated P with microwaves without going through the ferrite 114 of the grill plate 110.

[0049] The metal plate 122 is a plate-shaped member positioned on the underside (-Z axis direction) relative to the ferrite 114, and is made of metal, similar to the base material 120. Multiple metal plates 122 are arranged side by side, and each metal plate 122 has an elongated shape in plan view. As shown in Figure 5, each metal plate 122 has a strip shape in which the dimension in the X axis direction is longer than the dimension in the Y axis direction, and is arranged in the Y axis direction with its longer sides adjacent to each other.

[0050] As shown in Figures 6 and 7, a gap is provided between two adjacent metal plates 122, forming a slit 126. Each of the multiple slits 126 extends parallel to the longitudinal direction (X-axis direction) of the metal plate 122. By providing multiple slits 126, the metal plates 122 are arranged at a spacing I, and when an electric field is incident from the waveguide structure 118 along the Y-axis direction, the slits 126 also have the function of transmitting the magnetic field of microwaves supplied from below upwards. By providing multiple slits 126, even when multiple metal plates 122 are provided on the lower surface of the ferrite 114, it is possible to heat the ferrite 114 of the grill plate 110 with the magnetic field of microwaves.

[0051] In Figure 5, the position of the waveguide structure 118 in the XY plane is shown by a dotted line, and the direction of the electric field of the microwaves supplied by the waveguide structure 118 is illustrated in (a). In the example shown in Figure 5(a), the direction of the electric field of the microwaves propagating in the heating chamber 108 is set in the Y-axis direction, which is the width direction of the microwave heating device 102. The direction in which the aforementioned slit 126 extends (X-axis direction) is perpendicular in a plan view to the direction of the electric field of the microwaves supplied from the waveguide structure 118 (Y-axis direction). Therefore, even if multiple metal plates 122 are provided on the underside of the ferrite 114, the magnetic field of the microwaves can be transmitted through the slit 126 to the interior of the ferrite 114.

[0052] Figure 5(a) illustrates the case where the microwave electric field direction is along the Y-axis, but the microwave electric field direction can also be changed to the X-axis direction by changing the orientation of the rotating antenna of the waveguide structure 118, for example. In that case, the microwave magnetic field can be transmitted above the grill plate 110 through the aforementioned slot 121 extending in the Y-axis direction, allowing the object to be heated P to be directly heated by microwaves.

[0053] The metal element 124 is a metal component provided to locally strengthen the electromagnetic field of microwaves supplied from below. The metal element 124 is attached to the lower surface of the metal plate 122 and electrically connected to the metal plate 122. By providing the metal element 124, it is possible to strengthen the magnetic field near the nodes of the magnetic field distribution generated inside the ferrite 114, thereby controlling the heat distribution of the grill plate 110.

[0054] The metal element 124 shown in Figures 4 to 7 is composed of a plate-shaped metal plate extending parallel to the X-axis direction, and its cross-section (YZ cross-section) viewed along the X-axis direction has an L-shape. As shown in Figures 6 and 7, the metal element 124 has a first part 128 and a second part 130. The first part 128 is the part that is connected to the lower surface of the metal plate 122 and extends downward, and the second part 130 is the part that is connected to the lower end of the first part 128 and extends horizontally. The first part 128 and the second part 130 are perpendicular to each other, and a bent portion 131 (Figure 6) is formed at the connection point between the first part 128 and the second part 130.

[0055] As shown in Figure 6, the metal element 124 has a height h, a width w, and a depth d. The height h is the length of the metal element 124 along the Z-axis, the width w is the length of the metal element 124 along the Y-axis, and the depth d is the length of the metal element 124 along the X-axis. The height h corresponds to the length of the first part 128, and the width w corresponds to the length of the second part 130.

[0056] In a metal element 124 of this shape, by setting the sum of the height h, which is the length of the first part 128, and the width w, which is the length of the second part 130, to approximately 1 / 4 wavelength of the microwaves supplied by the waveguide structure 118, and by arranging it near the slit 126A between the metal plates 122, the metal element 124 can function as a so-called "1 / 4 wavelength resonator" or "inverted F antenna".

[0057] The effects of the metal element 124 will be explained using Figure 8.

[0058] Figure 8 is a schematic front view showing an enlarged view of the peripheral configuration of the metal element 124.

[0059] When microwaves are supplied to the heating chamber 8 from the waveguide structure 118 described above, an electromagnetic field of microwaves is generated in the heating chamber 8, creating a standing wave inside the chamber. In this state, by placing the metal element 124 having the dimensions described above near the slit 126A, the metal element 124 functions as an antenna with a quarter-wavelength resonator, and a strong current flows on the surface of the metal element 124. In Figure 8, the current flowing on the surface of the metal element 124 and the metal plate 122A to which the metal element 124 is connected is represented by arrows.

[0060] In the state shown in Figure 8, current flows from the top surface of the second part 130 toward the side surface of the first part 128, and current is transmitted to the bottom surface of the metal plate 122A. Since there is a slit 126A between the metal plate 122A and the adjacent metal plate 122B, current does not travel to the adjacent metal plate 122B, and current flows sequentially from the bottom surface to the side surface and then to the top surface of the metal plate 122A. In Figure 8, the illustration of currents flowing in other locations is omitted. When microwaves are continuously supplied, currents in the direction shown in Figure 8 and currents in the opposite direction to those shown in Figure 8 occur alternately.

[0061] As shown in Figure 8, by providing a slit 126A to interrupt the flow of current along the Y-axis, the current flowing on the surface of the metal element 124 can be routed to the upper surface 129 of the metal plate 122A. The magnetic field generated by the current flowing on the upper surface 129 of the metal plate 122A acts to strongly heat up region A of the ferrite 114 near the upper surface 129 of the metal plate 122A. This allows for localized heating of region A near the metal element 124, making it possible to control the heat distribution of the grill pan 110.

[0062] The analysis results for the microwave heating device 102 shown in Figures 4 to 8 will be explained below using Figures 9 to 17.

[0063] First, the relationship between the electric field direction of the microwaves supplied by the waveguide structure 118 and the direction of the slit 126 will be explained using Figures 9 and 10.

[0064] Figure 9 is a table classifying the relationship when the direction of the incident microwave field and the direction of the slit 126 (slit direction) are changed. Figure 9 shows schematic bottom views of the grill plate 110 when the "arrangement angle of the waveguide structure" is combined in three patterns and the "slit direction" in two patterns.

[0065] Regarding the "arrangement angle of the waveguide structure," the waveguide structure 118 is shown when it is tilted at angles of 45 degrees and 90 degrees in a plan view, with the angle of the waveguide structure 118 at 0 degrees as the reference. When the arrangement angle of the waveguide structure 118 is 0 degrees, the direction of the incident electric field is upward on the plane of the paper (+X axis direction), whereas when the arrangement angle of the waveguide structure 118 is 90 degrees, the direction of the incident electric field is to the right on the plane of the paper (+Y axis direction).

[0066] "Slit direction" refers to the orientation of slit 126 when viewed from above. In the upper pattern, the orientation of slit 126 is horizontal (Y-axis direction), so it is labeled "horizontal," and in the lower pattern, the orientation of slit 126 is vertical (X-axis direction), so it is labeled "vertical."

[0067] Figure 10 is a table showing the analysis results of the magnetic field distribution generated inside the ferrite 114 when microwaves are supplied, in a model configuration based on the combination of the orientation of the waveguide structure 118 and the orientation of the slit 126 shown in Figure 9. In this model, the microwave heating device 102 is configured without a metal element 124, and a model configuration (Figure 18A) in which multiple metal plates 122 are provided on the lower surface of the ferrite 114 was analyzed to determine the strength of the magnetic field generated in the central cross section (XY cross section) in the height direction of the ferrite 114.

[0068] For the analysis software, we used ANSYS HFSS.

[0069] Figure 10 shows the angular relationship between the incident electric field direction and the slit direction as "orthogonal," "45 degrees," and "parallel." As shown in Figure 10, when the incident electric field direction and the slit direction are "parallel," there is not a large difference in the magnetic field strength, whereas when the angles are "45 degrees" and "90 degrees," a large difference in the magnetic field strength is observed. In particular, when the incident electric field direction and the slit direction are "orthogonal," a large difference in the magnetic field strength is observed, resulting in a magnetic field distribution similar to that of a conventional configuration in which the ferrite 114 directly absorbs the microwave electromagnetic field without the metal plate 122.

[0070] As can be seen from the results shown in Figure 10, even when multiple metal plates 124 are provided on the underside of the ferrite 114, the same magnetic field distribution as when the metal plates 124 are not provided is generated by making the incident electric field direction and the slit direction intersect and perpendicular to each other.

[0071] Next, we will explain the analysis results regarding the relationship between the width w of the metal plate 122 and the magnetic field strength generated in the ferrite 114 using Figures 11 and 12.

[0072] Figure 11 is a table showing the analysis results when analyzing a model in which the width w (strip width) of the metal plate 122 is varied in four patterns. In this analysis, the magnetic field strength generated in the XY cross-section of the ferrite 114 was analyzed for three patterns in which the width w of the metal plate 122 was "1 mm", "10 mm", and "20 mm", and for one pattern in which the metal plate 122 was not provided.

[0073] Figure 12 is a graph showing the magnetic field strength (horizontal axis, unit: A / m) and the number of locations where the magnetic field strength was observed (vertical axis, unit: none) for three patterns where the width w of the metal plate 122 was "1 mm", "10 mm", and "20 mm".

[0074] As shown in Figure 11, the difference in magnetic field strength in the XY cross-section of the ferrite 114 is similar in all patterns. As shown in Figure 12, the variation in magnetic field strength is small in all patterns with different widths w of the metal plate 122, and a similar strength distribution is observed.

[0075] The results shown in Figures 11 and 12 indicate that the width w of the metal plate 122 has little effect on the magnetic field strength in the XY cross-section of the ferrite 114.

[0076] Next, we will explain the analysis results regarding the relationship between the distance I between the metal plates 122 and the magnetic field strength generated in the ferrite 114 using Figures 13 and 14.

[0077] Figure 13 is a table showing the analysis results when analyzing a model in which the spacing I (strip spacing) between metal plates 122 is varied in four patterns. In this analysis, the magnetic field strength generated in the XY cross-section of the ferrite 114 was analyzed for three patterns in which the spacing I between metal plates 122 was "1 mm", "10 mm", and "20 mm", and for one pattern in which no metal plates 122 were provided.

[0078] Figure 14 is a graph showing the magnetic field strength (horizontal axis, unit: A / m) and the number of locations where the magnetic field strength was observed (vertical axis, unit: none) for three patterns where the distance I between the metal plates 122 was "1 mm", "10 mm", and "20 mm".

[0079] As shown in Figure 13, the difference in magnetic field strength is similar in all patterns, appearing in the XY cross-section of the ferrite 114. As shown in Figure 14, the variation in magnetic field strength is small in all patterns with different spacing I between the metal plates 122, and a similar strength distribution is observed.

[0080] The results shown in Figures 13 and 14 indicate that the spacing I between the metal plates 122 has little effect on the magnetic field strength in the XY cross-section of the ferrite 114.

[0081] Next, we will explain the analysis results when microwaves are supplied to a model configuration similar to the microwave heating device 102 having the metal element 124 shown in Figures 4 to 8, using Figures 15 and 16.

[0082] Figures 15 and 16 are tables showing the analysis results when the height h and width w of the metal element 124 are changed, respectively. Figures 15 and 16 show the magnetic field intensity distribution in the YZ cross-section of the metal element 124 when viewed along the X-axis direction in which the metal element 124 extends. In this analysis, the wavelength of the microwaves supplied by the microwave generator 116 was set to approximately 120 mm.

[0083] In Figure 15, the height h was varied in four patterns: "10mm", "20mm", "30mm", and "40mm", and the width w was similarly varied in four patterns: "10mm", "20mm", "30mm", and "40mm", resulting in a total of 16 patterns being analyzed.

[0084] In Figure 16, the height h was varied in five patterns: "10mm", "15mm", "20mm", "25mm", and "30mm", and the width w was similarly varied in five patterns: "10mm", "15mm", "20mm", "25mm", and "30mm", resulting in a total of 25 patterns being analyzed.

[0085] As shown in Figures 15 and 16, it can be seen that in the range of width w approximately 10 mm to 20 mm and height h approximately 10 mm to 40 mm, the magnetic field strength in the inner region surrounded by the metal element 124 is relatively greater than the magnetic field strength in other areas.

[0086] Here, the metal element 124 is considered to function as a "quarter wavelength resonator" with a length of 1 / 4 wavelength (approximately 30 mm) relative to one wavelength (approximately 120 mm) of microwaves. By setting the total length = width w + height h of the metal element 124 in the YZ cross-section to a length that approximates 1 / 4 wavelength (approximately 30 mm) of microwaves, the resonator and antenna function of the metal element 124 can be enhanced.

[0087] Based on the above results, the length (width w + height h) of the metal element 124 in the YZ cross-section may be set to an odd multiple within the range of 1 / 6 to 1 / 3 of the microwave wavelength (20 mm to 40 mm, approximately ±30% of 1 / 4 wavelength). This makes it easier for the metal element 124 to locally increase the heat generation of the ferrite 114, and allows for precise control of the heat distribution of the grill plate 110.

[0088] Figure 17 is a table showing the analysis results when the height h of the metal element 124 is set to a small height (2 mm in this case) and the width w is varied. Figure 17 shows the magnetic field intensity distribution in the YZ cross-section of the metal element 124 when viewed along the X-axis direction in which the metal element 124 extends. In this analysis, the wavelength of the microwaves supplied by the microwave generator 116 was set to approximately 120 mm.

[0089] In Figure 17, the analysis was performed by varying the width w in a total of six patterns: "10mm", "20mm", "30mm", "40mm", "50mm", and "60mm".

[0090] As shown in Figure 17, it can be seen that the magnetic field strength is greatest in the inner region surrounded by the metal element 124 when the width w is 30 mm.

[0091] As mentioned above, the metal element 124 is thought to function as a "quarter-wavelength resonator," and by setting the height h of the metal element 124 to a small, negligible length, and then approximating the width w of the YZ cross-section of the metal element 124 to a value that approximates a quarter-wavelength of microwaves (approximately 30 mm), it is thought that the resonator and antenna function of the metal element 124 can be enhanced.

[0092] Based on the above results, the height h of the metal element 124 may be set to, for example, 2 mm or less, and the width w of the metal element 124 may be set to an odd multiple within the range of 1 / 6 to 1 / 3 of the microwave wavelength (20 mm to 40 mm, approximately ±30% of 1 / 4 wavelength). This makes it easier for the metal element 124 to locally increase the heat generation of the ferrite 114, and allows for precise control of the heat distribution of the grill plate 110.

[0093] Figure 18A shows a model configuration of a microwave heating device 2000 having a grill plate 2002 without metal elements, and Figure 18B shows the analysis results regarding the intensity distribution of the magnetic field generated in the ferrite 114 when microwaves are supplied using the microwave heating device 2000.

[0094] As shown in Figure 18B, the high and low periods of magnetic field strength appear along the Y-axis direction, which is the direction of the microwave electric field. In the example shown in Figure 18B, two nodes 200A and 200B and three antinodes 202A, 202B, and 202C are indicated. The distance L1 between two adjacent nodes 200A and 200B was approximately one microwave wavelength (about 120 mm).

[0095] Figure 19A shows a model configuration of a microwave heating device 3000 having a grill plate 3002 with metal elements 3004A and 3004B provided at positions corresponding to nodes 200A and 200B shown in Figure 18B, respectively. Figure 19B shows the analysis results regarding the intensity distribution of the magnetic field generated in the ferrite 114 when microwaves are supplied using the microwave heating device 3000.

[0096] As shown in Figure 19A, the metal element 3004A is provided at a position corresponding to the slit 3006A of the metal plate 122, and the metal element 3004B is provided at a position corresponding to the slit 3006B of the metal plate 122.

[0097] As shown in Figure 19B, by placing metal elements 3004A and 3004B at positions corresponding to nodes 200A and 200B shown in Figure 18B, the magnetic field strength around metal elements 3004A and 3004B was improved. This made it possible to uniformize the heat generation distribution of ferrite 114 along the Y-axis.

[0098] Based on the above results, when multiple metal elements 3004A and 3004B are provided at intervals along the Y-axis direction (electric field direction), the spacing L2 between the metal elements 3004A and 3004B may be set to an integer multiple of one microwave wavelength. This improves the magnetic field strength at positions corresponding to nodes 200A and 200B in the magnetic field strength distribution generated in the XY cross-section inside the ferrite 114, bringing it closer to the magnetic field strengths of antinodes 202A, 202B, 202C, etc.

[0099] Figure 20 is a longitudinal section (YZ section) showing the analysis results when only metal element 3004A, as explained in Figure 19A, is loaded and metal element 3004B is not loaded, and Figure 21 is a longitudinal section (YZ section) showing the analysis results when only metal element 3004B is loaded and metal element 3004A is not loaded.

[0100] As shown in the results in Figures 20 and 21, it can be seen that the magnetic field strength in the inner region surrounded by metal elements 3004A and 3004B is relatively higher than in other regions. This indicates that by providing metal elements 3004A and 3004B, the magnetic field strength can be locally increased, and the heat generation distribution of the ferrite 114 can be controlled with high precision.

[0101] Returning to Figure 18B, in addition to the high and low periods of magnetic field strength appearing along the Y-axis direction, which is the direction of the microwave electric field, high and low periods of magnetic field strength are also appearing along the X-axis direction, which is perpendicular to the Y-axis direction. In the example shown in Figure 18B, the distance L3 between antinode 202C and its neighbor antinode 202D is approximately one microwave wavelength (about 120 mm), similar to the distance L1.

[0102] When multiple metal elements are arranged in a plan view with spacing along the X-axis direction perpendicular to the Y-axis direction (electric field direction), the spacing between the metal elements may be set to an integer multiple of one microwave wavelength. This makes it possible to equalize the strength of the magnetic field generated in the XY cross-section inside the ferrite 114.

[0103] When multiple metal elements are provided, the dimensions of each metal element do not necessarily have to be the same; they may be made to differ in size. This makes it possible to change the heat generation distribution of the ferrite 114 in various ways.

[0104] Next, the shape variations of the metal element 124 will be explained using Figures 22A to 22J.

[0105] Figures 22A to 22J are schematic front views showing examples of shape variations of the metal element 124.

[0106] The metal element 224 shown in Figure 22A, like the metal element 124 shown in Figures 4 to 7, has an L-shape and comprises a first portion 228 and a second portion 230 that are orthogonal to each other. The fact that the first portion 228 and the second portion 230 are orthogonal to each other, similar to the first portion 128 and the second portion 130 shown in Figures 6 and 7, makes it easier to predict the effect of strengthening the electromagnetic field in the region inside the metal element 224.

[0107] The second portion 230 shown in Figure 22A extends to a position that overlaps with the slit 126 when viewed along the Z-axis (arrow B1). This is thought to increase the effect of strengthening the electromagnetic field around the metal element 224 compared to the case where it does not overlap with the slit 126. Similarly, in the metal elements shown in Figures 22B to 22J, the metal elements also extend to a position that overlaps with the slit 126 when viewed along the Z-axis.

[0108] Unlike metal elements 124 and 224, the metal element 324 shown in Figure 22B has a shape that extends in a straight line. The metal element 324 extends in a straight line from the first end 326 connected to the metal plate 122A to the second end 328 on the opposite side. With this configuration, the metal element 324 can be manufactured with a simple structure.

[0109] The metal element 424 shown in Figure 22C, like the metal elements 124 and 224, has a bent shape in the middle. However, unlike the metal elements 124 and 224, the first part 428 and the second part 430 are not perpendicular to each other, forming an obtuse angle inward.

[0110] The metal element 524 shown in Figure 22D has a bent shape such that the first part 528 and the second part 530 form an obtuse angle inward, but the first part 528 is not perpendicular to the metal plate 122A, but extends inclined downward.

[0111] Unlike the metal element 524 shown in Figure 22D, the metal element 624 shown in Figure 22E has a bent shape such that the first portion 628 and the second portion 630 form an acute angle inward. The first portion 628 of the metal element 624 extends inclined diagonally downward in the direction away from the slit 126.

[0112] The metal element 724 shown in Figure 22F has a third portion 732 in addition to a first portion 728 and a second portion 730 which are orthogonal to each other. The third portion 732 is connected to the tip of the second portion 730 and extends upward toward the metal plate 122.

[0113] The metal element 824 shown in Figure 22G has a linear first portion 828 and a smooth, curved second portion 830. The second portion 830 is smoothly curved so as to be convex downward from the tip of the first portion 828.

[0114] The metal element 924 shown in Figure 22H extends continuously in a smoothly curved manner from the first end 926 connected to the metal plate 122A to the second end 928 on the opposite side.

[0115] The metal element 1024 shown in Figure 22I has a curved first portion 1028 and a straight second portion 1030. The second portion 1030 extends horizontally from the tip of the first portion 1028.

[0116] The metal element 1124 shown in Figure 22J has an L-shape, similar to the metal element 124 shown in Figures 4 to 7, and has a first part 1128 and a second part 1130 that are orthogonal to each other. Unlike the metal element 124, the metal element 1124 has a length, i.e., height h, of the first part 1128 that is longer than the length, i.e., width w, of the second part 1130.

[0117] As illustrated in Figures 22A to 22J, the shape of the metal element can be varied in various ways, as long as it functions as an antenna that locally increases the magnetic field strength inside the ferrite 114. The metal element having such a function can be one that has a component extending in the X-axis direction in which the slit 126 extends, and a component extending downwards.

[0118] Returning to Figure 8, the metal element 124 is positioned between the two slits 126A and 126B. The first end 160 of the metal element 124 is connected to the metal plate 122A, while the second end 162 is terminated below the metal plate 122A and at a position shifted in the Y-axis direction relative to the connection point (first end 160) and closer to the slit 126A. This makes it possible to enhance the microwave electromagnetic field using the slit 126A.

[0119] When positioning the metal element 124 in a location corresponding to the slit 126A, the metal element 124 can be connected to the lower surface of the metal plate 122A that forms the slit 126A, and the metal element 124 can be bent or curved toward the side where the slit 126A exists.

[0120] As described above, the microwave heating device 102 (microwave heating device 2) of this embodiment comprises a housing 104 (housing 4) having a heating chamber 108 (heating chamber 8), a microwave generator 116 (microwave generator 16) that generates microwaves, a waveguide structure 118 (waveguide structure 18) that supplies microwaves generated by the microwave generator 116 to the heating chamber 108, and a grill plate 110 (grill plate 10) arranged in the heating chamber 108 and provided with ferrite 114 (ferrite 14), and the grill plate 110 is opposite to the ferrite 114 The device comprises a metal base material 120 (base material 20) positioned on the upper side, a metal plate 122 positioned on the lower side relative to the ferrite 114, which extends in the X-axis direction (first direction) in a plan view and forms a first slit 126A and a second slit 126B at positions spaced apart in the Y-axis direction (second direction) perpendicular to the X-axis direction, and a metal element 124 connected to the lower surface of the metal plate 122 at a position between the first slit 126A and the second slit 126B, and having a component that extends in the X-axis direction (first direction) and a component that extends downward (Z-axis direction).

[0121] With this configuration, supplying microwaves from the waveguide structure 118 to the heating chamber 108 allows the metal element 124 to function as an antenna, strengthening the electric and magnetic fields around the metal element 124 and locally changing the heating distribution of the ferrite 114. This makes it possible to control the heat distribution of the grill plate 110.

[0122] Furthermore, in the microwave heating apparatus 102 of this embodiment, multiple metal plates 122 are provided spaced apart in the Y-axis direction (second direction) perpendicular to the X-axis direction (first direction), and the first slit 126A and the second slit 126B are formed by the gaps between the multiple metal plates 122. With this configuration, slits 126 can be created simply by arranging the metal plates 122 at intervals without any processing.

[0123] Furthermore, in the microwave heating device 102 of this embodiment, the metal element 124 is a metal plate extending parallel to the X-axis direction (first direction). With this configuration, the metal element 124 can be constructed with a simple structure.

[0124] Furthermore, in the microwave heating device 102 of this embodiment, the total length of the metal element 124, consisting of the first part 128 and the second part 130, that is, the length from the first end connected to the metal plate 122 to the second end opposite the first end, is an odd multiple of 1 / 6 to 1 / 3 wavelength of the microwaves generated by the microwave generator 116. With this configuration, the effect of strengthening the electric and magnetic fields around the metal element 124 is improved.

[0125] Furthermore, in the microwave heating device 102 of this embodiment, the metal element 124 has a first portion 128 extending downward from the metal plate 122 and a second portion 130 connected to the first portion 128 and extending in a different direction from the first portion 128. With this configuration, the shape of the metal element 124 can be varied in various ways.

[0126] Furthermore, in the microwave heating device 102 of this embodiment, the second part 130 is longer than the first part 128. With this configuration, the effect of strengthening the electric and magnetic fields around the metal element 124 is improved by limiting the height h of the space surrounded by the metal element 124.

[0127] Furthermore, in the microwave heating device 102 of this embodiment, a bent portion 131 is formed at the connection point between the first portion 128 and the second portion 130. With this configuration, the effect of strengthening the electric and magnetic fields around the metal element 124 becomes easier to predict compared to the case where the metal element has a smooth shape.

[0128] Furthermore, in the microwave heating device 102 of this embodiment, the first part 128 and the second part 130 extend orthogonally to each other. With this configuration, the metal element 124 can be constructed with a simple structure, and the effect of strengthening the electric and magnetic fields around the metal element 124 becomes easier to predict.

[0129] Furthermore, in the microwave heating device 102 of this embodiment, the height h of the first part 128 is 2 mm or less, and the length (width w) of the second part 130 is an odd multiple of 1 / 6 to 1 / 3 wavelength of the microwaves generated by the microwave generator 116. With this configuration, by making the height h of the first part 128 sufficiently small, the height dimension of the metal element 124 can be substantially ignored, and by controlling the horizontal dimension of the metal element 124 according to the length (width w) of the second part 130, the effect of strengthening the electric and magnetic fields around the metal element 124 can be easily predicted.

[0130] Furthermore, in the microwave heating device 102 of this embodiment, the waveguide structure 118 supplies microwaves in such a way that it generates an electric field direction along the Y-axis direction (second direction) which is perpendicular to the X-axis direction (first direction) in a plan view. With this configuration, the slit 126 extending in the X-axis direction (first direction) interrupts the current flowing along the Y-axis direction (second direction), making it easier to obtain the effect of locally strengthening the magnetic field around the slit 126.

[0131] Furthermore, in the microwave heating device 102 of this embodiment, the metal element 124 is an inverted F-type antenna. With this configuration, the effect of strengthening the electric and magnetic fields is enhanced.

[0132] Furthermore, in the microwave heating device 3000 of this embodiment, the slits 3006A and 3006B have a first slit 3006A and a second slit 3006B, and the metal elements 3004A and 3004B have a first metal element 3004A provided in correspondence with the first slit 3006A and a second metal element 3006B provided in correspondence with the second slit 3006B. With this configuration, by providing multiple metal elements 3004A and 3004B, the heat generation distribution of the ferrite 114 can be varied in various ways.

[0133] Furthermore, in the microwave heating device 102 of this embodiment, the waveguide structure 118 supplies microwaves in such a way that it generates an electric field direction along the Y-axis direction (second direction) which is perpendicular to the X-axis direction (first direction) in a plan view. The first metal element 124A and the second metal element 124B are arranged with a gap L2 in the Y-axis direction (second direction), and this gap L2 is an integer multiple of one wavelength of the microwaves generated by the microwave generator 116. With this configuration, "nodes" in the heat distribution of the ferrite 114 appear approximately every one wavelength along the Y-axis direction (second direction). By arranging multiple metal elements 124A and 124B at this gap, it becomes easier to arrange each metal element 124A and 124B at each node, thereby making the heating distribution more uniform.

[0134] Furthermore, in this embodiment, the microwave heating device 102 supplies microwaves to the waveguide structure 118 so as to generate an electric field direction along the Y-axis direction (second direction) which is perpendicular to the X-axis direction (first direction) in a plan view. The first metal element and the second metal element are arranged with a gap in the X-axis direction (first direction), and this gap is an integer multiple of one wavelength of the microwaves generated by the microwave generator 116. With this configuration, "nodes" in the heat distribution of the ferrite 114 appear approximately every one wavelength in both the X-axis direction (first direction) and the Y-axis direction (second direction). By arranging multiple metal elements 124 at this gap, it becomes easier to arrange each metal element at each node and make the heating distribution uniform.

[0135] Furthermore, in the microwave heating device 102 of this embodiment, the first metal element 124A and the second metal element 124B have different dimensions. With this configuration, it is possible to change the heat generation distribution of the ferrite 114 in various ways.

[0136] Furthermore, the grill plate 110 used in the heating chamber 108 of the microwave heating device 102 of this embodiment comprises a ferrite 114 (radio wave absorber), a metal base material 120 positioned on the upper side relative to the ferrite 114, a metal plate 122 positioned on the lower side relative to the ferrite 114 and forming a slit 126 extending in the X-axis direction (first direction) in a plan view, and a metal element 124 connected to the lower surface of the metal plate 122 and provided at a position corresponding to the slit 126, having a component extending in the X-axis direction (first direction) and a component extending downward.

[0137] With such a grill plate 110, the same effects as the microwave heating device 102 of the embodiment can be achieved.

[0138] Although the invention of this disclosure has been described above with reference to the embodiments described above, the invention of this disclosure is not limited to the embodiments described above. For example, in the embodiments, the case in which the grill pan 110 comprises ferrite 114, base material 120, metal plate 122, and metal element 124 has been described, but the invention is not limited to this case and may also comprise other members, for example, a coating member may be further provided.

[0139] Furthermore, although the embodiment described a case where the radio wave absorbing member used as a heat source for the grill plate 110 is ferrite 114, the invention is not limited to this case, and any material capable of generating heat through a microwave electromagnetic field may be used as the radio wave absorbing member.

[0140] While this disclosure is adequately described in relation to preferred embodiments with reference to the accompanying drawings, various variations and modifications will be obvious to those skilled in the art. Such variations and modifications should be understood as being included within the scope of the invention as defined in the attached claims. Furthermore, variations in combinations and sequences of elements in each embodiment can be realized without departing from the scope and spirit of this disclosure.

[0141] By appropriately combining any of the above embodiments and various modifications, the effects of each can be achieved. [Industrial applicability]

[0142] This disclosure is applicable to microwave heating devices used for cooking meat and other food ingredients. [Explanation of symbols]

[0143] 2.102 Microwave heating device 4,104 cabinets 8, 108 Heating chamber 10, 110 Grill Pan 14, 114 ferrite 16, 116 Microwave generator 18, 118 Waveguide structure 20, 120 Base material 122 Metal plate 126 slits

Claims

1. A housing having a heating chamber, A microwave generator that generates microwaves, A waveguide structure that supplies microwaves generated by the microwave generator to the heating chamber, The heating chamber is arranged in a grill pan equipped with an electromagnetic wave absorber, The aforementioned grill pan is A metal base material positioned on the upper side of the aforementioned radio wave absorber, A metal plate positioned on the lower side of the radio wave absorber, having a first slit and a second slit formed at positions spaced apart in a second direction perpendicular to the first direction, respectively, in a plan view, A cooking appliance comprising a metal element connected to the lower surface of the metal plate at a position between the first slit and the second slit, and having a component extending in the first direction and a component extending downward.

2. The heating appliance according to claim 1, wherein a plurality of the metal plates are provided spaced apart in the second direction, and the first slit and the second slit are each formed by the gaps between the plurality of metal plates.

3. The heating appliance according to claim 1, wherein the metal element is a metal plate extending parallel to the first direction.

4. The heating appliance according to claim 1, wherein the length of the metal element from a first end connected to the metal plate to a second end opposite to the first end is an odd multiple of 1 / 6 to 1 / 3 wavelength of the microwaves generated by the microwave generator.

5. The heating appliance according to claim 1, wherein the metal element has a first portion extending downward from the metal plate and a second portion connected to the first portion and extending in a direction different from that of the first portion.

6. The heating appliance according to claim 5, wherein the second part is longer than the first part.

7. A bent portion is formed at the connection point between the first portion and the second portion, as described in claim 5.

8. The heating appliance according to claim 7, wherein the first part and the second part extend perpendicularly to each other.

9. The heating appliance according to claim 5, wherein the height of the first part is 2 mm or less, and the length of the second part is an odd multiple of 1 / 6 wavelength to 1 / 3 wavelength of the microwaves generated by the microwave generator.

10. The heating appliance according to claim 1, wherein the metal element extends in a straight line from a first end connected to the metal plate to a second end opposite to the first end.

11. The heating appliance according to claim 1, wherein the metal element overlaps the first slit in a plan view.

12. The heating cooker according to claim 1, wherein the waveguide structure supplies microwaves such that an electric field direction is generated along the second direction in a plan view.

13. The heating appliance according to claim 1, wherein the metal element is an inverted F-type antenna.

14. The heating appliance according to claim 1, wherein the metal element comprises a first metal element provided corresponding to the first slit and a second metal element provided corresponding to the second slit.

15. The waveguide structure supplies microwaves in such a way that it generates an electric field direction along the second direction in a plan view. The heating cooker according to claim 14, wherein the first metal element and the second metal element are arranged with an interval between them in the second direction, and the interval is an integer multiple of one wavelength of microwaves generated by the microwave generator.

16. The waveguide structure supplies microwaves in such a way that it generates an electric field direction along the second direction in a plan view. The heating cooker according to claim 14, wherein the first metal element and the second metal element are arranged with an interval between them in the first direction, and the interval is an integer multiple of one wavelength of microwaves generated by the microwave generator.

17. The heating appliance according to claim 14, wherein the first metal element and the second metal element have different dimensions.

18. A grill plate used in the heating chamber of a microwave heating device, Radio wave absorber, A metal base material positioned on the upper side of the aforementioned radio wave absorber, A metal plate positioned on the lower side of the radio wave absorber, having a first slit and a second slit formed at positions spaced apart in a second direction perpendicular to the first direction, respectively, in a plan view, A grill plate comprising a metal element connected to the lower surface of the metal plate at a position between the first slit and the second slit, and having a component extending in the first direction and a component extending downward.

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