Microwave heating device

Abstract

The present invention provides a microwave heating apparatus that can suppress the incidence of microwaves emitted from one microwave radiating section into other microwave radiating sections without providing partitions to separate each microwave radiating section. [Solution] A microwave heating apparatus according to one aspect of the present disclosure comprises a heating chamber for housing an object to be heated, and a plurality of microwave radiating units for radiating microwaves into the heating chamber, wherein the plurality of microwave radiating units have frequency characteristics in which the frequencies at which reflection loss is minimized are different from each other.

Description

Technical Field

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[0001] The present disclosure relates to a microwave heating device.

Background Art

[0002] Conventionally, a microwave heating device including a first antenna and a second antenna that radiate microwaves from the bottom surface of a heating chamber toward the inside of the heating chamber has been known (see, for example, Patent Document 1). In the microwave heating device disclosed in Patent Document 1, a partition wall is provided between the first antenna and the second antenna to suppress microwaves radiated from one antenna from entering the other antenna.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] <B In the microwave heating device disclosed in Patent Document 1, a partition wall is required to suppress microwaves radiated from one microwave radiation unit (one antenna) from entering the other microwave radiation unit (the other antenna).

[0005] Therefore, an object of one aspect of the present disclosure is to provide a microwave heating device that can suppress microwaves radiated from one microwave radiation unit from entering the other microwave radiation unit without providing a partition wall separating each microwave radiation unit.

Means for Solving the Problems

[0006] A microwave heating apparatus according to one aspect of the present disclosure comprises a heating chamber for housing an object to be heated, and a plurality of microwave radiating units for radiating microwaves into the heating chamber, wherein the plurality of microwave radiating units have frequency characteristics in which the frequencies at which reflection loss is minimized are different from each other. [Brief explanation of the drawing]

[0007] [Figure 1] This is a perspective view of a cooking appliance. [Figure 2] This is a perspective view of a cooking appliance with the door open. [Figure 3] This is a schematic diagram showing the internal structure of a cooking appliance. [Figure 4] This is a cross-sectional view of a cooking appliance. [Figure 5] This figure shows the frequency characteristics of the reflection loss of each microwave radiation section. [Figure 6] This is a top view showing the arrangement of the two microwave radiation units. [Figure 7] This is a top view showing the arrangement of four microwave radiation units in a modified example of a heating appliance. [Figure 8] This figure shows the frequency characteristics of the reflection loss of each microwave radiating element in a modified cooking appliance. [Modes for carrying out the invention]

[0008] The embodiments of this disclosure will be described below with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0009] In this embodiment, a cooking appliance, which is an example of a microwave heating device, will be described. The cooking appliance uses electromagnetic waves with a frequency of 2.4 GHz to 2.5 GHz, which is in the UHF band, to perform dielectric heating of the object to be heated, such as food. However, the frequency of the electromagnetic waves used in the microwave heating device of this disclosure is not limited to this.

[0010] (First Embodiment) Referring to Figures 1 and 2, the overall configuration of the first embodiment of the cooking appliance 10 will be described. Figure 1 is a perspective view of the cooking appliance 10. Figure 2 is a perspective view of the cooking appliance 10 with the door 12 open. In the following description, the side on which the opening 11a of the cooking appliance body 11 is provided will be referred to as the front, the opposite side as the rear, the side on which the cooking appliance body 11 is placed will be referred to as the bottom, and the opposite side as the top.

[0011] The heating appliance 10 comprises a cooking appliance body 11 and a door 12. The cooking appliance body 11 has a heating cooking function. The cooking appliance body 11 has an opening 11a on its front. The door 12 is provided so as to be able to open and close the opening 11a of the cooking appliance body 11. The door 12 comprises a viewing window 12a that allows the interior to be seen from the outside, a display unit 12b that can display various information, an operating unit 12c that can accept various operations, and a gripping unit 12d for opening and closing the door 12.

[0012] The internal structure of the cooking appliance 10 will be explained using Figures 3 and 4. Figure 3 is a schematic diagram showing the internal structure of the cooking appliance 10. Figure 4 is a cross-sectional view of the cooking appliance 10.

[0013] As shown in Figure 3, the cooking appliance 10 comprises a heating chamber 20, a microwave generating unit 30, a microwave radiating unit 40, a conductive member 50 (see Figure 4), a control unit 100, and a storage unit 110.

[0014] The heating chamber 20 is a space that accommodates the object to be heated F1 through the opening 11a. The heating chamber 20 is a space enclosed by the upper wall 21, the lower wall 22, the left wall 23, the right wall 24, and the rear wall 25. The heating chamber 20 becomes a closed space when the opening 11a is closed by the door 12. The heating chamber 20 is formed of metal members except for the lower wall 22.

[0015] The lower wall portion 22 is configured as a transmission portion that transmits microwaves. The lower wall portion 22 is formed of a member that transmits microwaves, such as glass, ceramic, neoseram, resin, etc. Further, the lower wall portion 22 functions as a heat-resistant plate on which the object to be heated F1 is placed.

[0016] In this embodiment, the entire lower wall portion 22 is configured as a transmission portion, but it is not limited to this, and a part of the lower wall portion 22 may be configured as a transmission portion. Also, in this embodiment, the lower wall portion 22 is configured as a transmission portion, but it is not limited to this, and any wall portion (for example, the upper wall portion 21, the lower wall portion 22, the left wall portion 23, the right wall portion 24, the rear wall portion 25, etc.) constituting the heating chamber 20 may be configured as a transmission portion.

[0017] The microwave generation unit 30 generates microwaves for heating the object to be heated F1 in the heating chamber 20. In this embodiment, two are provided corresponding to the number of microwave radiation units 40. The microwave generation unit 30 is disposed inside the cooker main body 11, for example, below the transmission portion (lower wall portion 22) of the heating chamber 20.

[0018] The microwave radiation unit 40 radiates the microwaves generated by the microwave generation unit 30 toward one surface (in this embodiment, the lower wall portion 22) of the heating chamber 20. The microwave radiation unit 40 is, for example, a planar antenna. In this embodiment, two microwave radiation units 40 are provided.

[0019] The conductive member 50 acts on the microwaves radiated by the microwave radiation unit 40 to adjust the electric field strength in the heating chamber 20. The conductive member 50 is a flat plate having an elongated shape. The conductive member is formed of a metal material such as copper or aluminum. Unlike the microwave radiation unit 40, the conductive member 50 is non-powered.

[0020] The conductive member 50 is provided between the transmission part (lower wall part 22) and the microwave radiation part 40 (see FIG. 4). Specifically, the conductive member 50 is fixed to the lower surface of the lower wall part 22 by an adhesive member such as a polyimide tape or a tape mainly made of polyimide so as to overlap a part of the radiation element 41 described later when viewed from the vertical direction. Two conductive members 50 are provided corresponding to the number of microwave radiation parts 40. Note that the cooking heater 10 includes the conductive member 50, but is not limited thereto, and may not include the conductive member 50.

[0021] The control unit 100 controls the cooking heater 10. The control unit 100 realizes various functions by reading and executing various programs stored in the storage unit 110. The control unit 100 is composed of, for example, one or more CPUs (Central Processing Unit) or dedicated processors.

[0022] The control unit 100 is connected to various components of the cooking heater 10. The control unit 100 is connected to, for example, each microwave generation unit 30. The control unit 100 controls the frequency of each microwave generation unit 30 (oscillation unit 31 described later) based on the opening / closing result of the door 12, the temperature inside the heating chamber 20, the instruction received by the operation unit 12c, etc.

[0023] The storage unit 110 stores various programs and various data necessary for the operation of the cooking heater 10. The storage unit 110 is, for example, a flash memory.

[0024] The specific configuration of the microwave generation unit 30 will be described using FIG. 3.

[0025] The microwave generation unit 30 includes an oscillation unit 31, an amplification unit 32, a circulator 33, and a terminator 34.

[0026] It The oscillation unit 31 generates high-frequency power with a frequency of 2.4 GHz or more and 2.5 GHz or less. The oscillation unit 31 has, for example, a voltage-variable frequency variable function.

[0027] The amplification unit 32 amplifies the high-frequency power output by the oscillation unit 31. The amplification unit 32 is positioned between the oscillation unit 31 and the circulator 33. The amplification unit 32 may amplify the high-frequency power using a single amplifier unit, or it may amplify the high-frequency power in steps using multiple amplifier units.

[0028] The circulator 33 separates the high-frequency power output from the amplifier 32 from the reflected wave power from the microwave radiation unit 40. The circulator 33 controls the propagation of microwaves, for example, by using a magnet. The circulator 33 outputs the high-frequency power output from the amplifier 32 to the microwave radiation unit 40 and outputs the reflected wave power input to the microwave radiation unit 40 to the terminator 34.

[0029] The terminator 34 has one end connected to the circulator 33 and the other end connected to ground. The terminator 34 includes a termination resistor 34a and converts the reflected wave power output by the circulator 33 into heat.

[0030] The specific configuration of the microwave radiation unit 40 will be explained using Figure 4.

[0031] As shown in Figure 4, the heating appliance 10 further comprises a housing section 26 and a ground plate 27.

[0032] The housing section 26 is located below the transmissive section (lower wall section 22) and houses the microwave radiation section 40. The housing section 26 is a space surrounded by the lower wall section 22 and a wall surface formed by a metal member.

[0033] The ground plate 27 is positioned along the bottom of the housing section 26. The ground plate 27 is formed in a flat shape. The ground plate 27 is made of a metal material such as copper. The ground plate 27 has a rectangular shape when viewed from above. The ground plate 27 is grounded.

[0034] The microwave radiating section 40 is provided in the housing section 26 facing the transmissive section (lower wall section 22). In this embodiment, the direction in which the microwave radiating section 40 and the lower wall section 22 face each other is the vertical direction.

[0035] The two microwave radiating units 40 are provided in the housing unit 26 with a gap between them on the left and right sides. Hereinafter, of the two microwave radiating units 40, the microwave radiating unit 40 (radiating element 41) on the right side of Figure 4 will also be referred to as the first microwave radiating unit 40A (first radiating element 41A), and the microwave radiating unit 40 (radiating element 41) on the left side of Figure 4 will also be referred to as the second microwave radiating unit 40B (second radiating element 41B).

[0036] The microwave radiation unit 40 has a radiating element 41. The radiating element 41 is formed in a flat plate shape. The radiating element 41 is made of a metallic material such as copper. The radiating element 41 has a rectangular shape when viewed from above (see Figure 6).

[0037] The radiating element 41 is positioned vertically apart from the lower wall 22. The radiating element 41 is supported, for example, by a plurality of support columns provided on the ground plate 27. A power supply cable 43 is connected to the radiating element 41. The outer conductor of the power supply cable 43 is connected to the ground plate 27 and is at ground potential. The inner conductor of the power supply cable 43 is connected to the power supply point P1 (see Figure 6) of the radiating element 41.

[0038] The radiating element 41 is rectangular when viewed from above, but it is not limited to this shape; it may also be polygonal, circular, or elliptical. In addition, the microwave radiating section 40 may include a dielectric material placed between the radiating element 41 and the ground plate 27, in addition to the radiating element 41.

[0039] Furthermore, although the microwave radiation section 40 is provided opposite the lower wall section 22, it is sufficient that it can radiate microwaves toward one side of the heating chamber 20. For example, it may be provided opposite the upper wall section 21, the left wall section 23, the right wall section 24, or the rear wall section 25. In this case, the corresponding upper wall section 21, left wall section 23, right wall section 24, or rear wall section 25 is formed as a transmissive section.

[0040] Figure 5 illustrates the frequency characteristics of the return loss of the microwave radiation unit 40.

[0041] Figure 5 shows the frequency characteristics of the reflection loss of each microwave radiation unit 40 (each radiation element 41). Figure 5 mainly shows the reflection loss in a predetermined frequency band (in this embodiment, a frequency band of 2.4 GHz to 2.5 GHz), and the reflection loss is expressed in dB (decibels). The reflection loss represents the ratio of the reflected wave power to the incident wave power (high frequency power) in the microwave radiation unit 40.

[0042] As shown in Figure 5, the frequency characteristics of the reflection loss of the first microwave radiator 40A and the second microwave radiator 40B differ mainly in the frequency at which the reflection loss is minimized.

[0043] The first microwave radiating unit 40A has a frequency characteristic in which the reflection loss is minimized at frequency f1 within a predetermined frequency band. Specifically, the first microwave radiating unit 40A has a frequency characteristic in which the reflection loss decreases from the low frequency side towards frequency f1 within a predetermined frequency band, and increases from frequency f1 towards the high frequency side.

[0044] The second microwave radiator 40B has a frequency characteristic in which the reflection loss is minimized at frequency f2 within a predetermined frequency band. Specifically, the second microwave radiator 40B has a frequency characteristic in which the reflection loss decreases from the low frequency side towards frequency f2 within a predetermined frequency band, and increases from frequency f2 towards the high frequency side. Frequency f2 is higher than frequency f1.

[0045] Based on the above, the first microwave radiation unit 40A has the characteristic of being able to efficiently radiate microwaves at frequency f1, which minimizes reflection loss, while being less able to absorb microwaves at frequency f2, which has high reflection loss.

[0046] In contrast, the second microwave radiation unit 40B has the characteristic of being able to efficiently radiate microwaves at frequency f2, which minimizes reflection loss, while being less likely to absorb microwaves at frequency f1, which has high reflection loss.

[0047] Therefore, when microwaves of frequency f1 are emitted from the first microwave radiating unit 40A and microwaves of frequency f2 are emitted from the second microwave radiating unit 40B, the first microwave radiating unit 40A can efficiently emit microwaves of frequency f1 while suppressing the incidence of microwaves of frequency f2 emitted from the second microwave radiating unit 40B. Similarly, the second microwave radiating unit 40B can efficiently emit microwaves of frequency f2 while suppressing the incidence of microwaves of frequency f1 emitted from the first microwave radiating unit 40A.

[0048] As described above, since the microwaves radiated from one microwave radiation unit 40 can be prevented from being incident on other microwave radiation units 40, the temperature rise and damage of the microwave generation unit 30 caused by the increased amount of heat converted when reflected wave power is incident on the terminator 34 can be suppressed. In addition, since the reflected wave power incident on the terminator 34 can be reduced, a decrease in the heating efficiency of the heating chamber 20 can be suppressed.

[0049] In the following section, we will use Figure 6 to explain the specific configuration for making the frequency characteristics of each microwave radiating unit 40 different. Figure 6 is a top view showing the arrangement of two microwave radiating units 40 (radiating elements 41).

[0050] In this embodiment, the frequency characteristics of each microwave radiating section 40 are changed by making the dimensions of each radiating element 41 different from those of the others.

[0051] As shown in Figure 6, the two radiating elements 41 have different lengths in the polarization direction when viewed from the vertical direction. The polarization direction is determined based on the feed point P1 of the radiating element 41. Specifically, the polarization direction is the direction in which the center P2 of the radiating element 41 and the feed point P1 of the radiating element 41 are aligned when viewed from the vertical direction. Specifically, the polarization direction of the first radiating element 41A is in the front-to-back direction, and the polarization direction of the second radiating element 41B is in the left-to-right direction.

[0052] As shown in Figure 6, the polarization length A1 of the first radiating element 41A is greater than the polarization length B1 of the second radiating element 41B. This modifies the frequency characteristics so that the frequency f1 at which the reflection loss of the first microwave radiating unit 40A is minimized is lower than the frequency f2 at which the reflection loss of the second microwave radiating unit 40B is minimized. Therefore, it is possible to suppress the incidence of microwaves radiated from one microwave radiating unit 40 into the other microwave radiating unit 40.

[0053] Furthermore, as shown in Figure 6, the polarization directions of the first radiating element 41A and the second radiating element 41B are arranged orthogonally. Specifically, the polarization direction of the first radiating element 41A is in the front-to-back direction, and the polarization direction of the second radiating element 41B is in the left-to-right direction. By staggering the polarization directions of each radiating element 41 in this way, interference between microwaves radiated from one microwave radiating unit 40 and microwaves radiated from other microwave radiating units 40 can be suppressed. Therefore, it is possible to suppress the incident of microwaves radiated from one microwave radiating unit 40 on other microwave radiating units 40.

[0054] In this configuration, the polarization directions of the first radiating element 41A and the second radiating element 41B are arranged orthogonally, but this is not the only option; any configuration in which the polarization directions of the first radiating element 41A and the second radiating element 41B intersect is acceptable.

[0055] In this embodiment, the frequency characteristics of each microwave radiating section 40 are changed by changing the length of each radiating element 41 in the polarization direction, but this is not limited to this. For example, each microwave radiating section 40 may further include a dielectric, and the frequency characteristics of each microwave radiating section 40 may be changed by changing the dielectric constant of the dielectric of each microwave radiating section 40.

[0056] Furthermore, although the cooking appliance 10 is equipped with two microwave radiating units 40, it is not limited to this and may be equipped with three or more microwave radiating units 40. In this case, the three or more microwave radiating units 40 should have frequency characteristics in which the frequencies at which reflection loss is minimized are different from each other.

[0057] The following describes the heating process performed by the control unit 100. The memory unit 110 has in advance stored the frequency characteristics of each microwave radiating unit 40, more specifically, the frequency f1 corresponding to the first microwave radiating unit 40A and the frequency f2 corresponding to the second microwave radiating unit 40B.

[0058] When the control unit 100 receives a heating instruction from the operation unit 12c, it controls each microwave generator 30 (oscillator 31) so that the frequency of the microwaves emitted from each microwave radiating unit 40 becomes the corresponding frequency. Specifically, the microwave generator 30 is controlled so that the microwaves emitted from the first microwave radiating unit 40A have a frequency of f1, and the microwave generator 30 is controlled so that the microwaves emitted from the second microwave radiating unit 40B have a frequency of f2. As a result, as described above, it is possible to suppress the incident of microwaves emitted from one microwave radiating unit 40 on other microwave radiating units 40, thereby suppressing the temperature rise and damage of the microwave generator 30 while suppressing a decrease in the heating efficiency of the heating chamber 20.

[0059] A modified example of the cooking appliance will be described using Figure 7. Figure 7 is a top view showing the arrangement of the four microwave radiating units 140 (radiating elements 141) in a modified example of the cooking appliance. In this modified example, the cooking appliance differs from the first embodiment in that it is equipped with four microwave radiating units 140 (radiating elements 141).

[0060] As shown in Figure 7, each microwave radiating unit 140 (radiating element 141) has a rectangular shape when viewed from above. The four microwave radiating units 140 (radiating elements 141) are arranged in a line around the center of the housing unit 26 when viewed from above. In the following, of the four microwave radiating units 140 (radiating elements 141), the microwave radiating unit 140 (radiating element 141) in the upper right of Figure 7 will also be referred to as the first microwave radiating unit 140A (first radiating element 141A), the microwave radiating unit 140 (radiating element 141) in the upper left of Figure 7 will also be referred to as the second microwave radiating unit 140B (second radiating element 141B), the microwave radiating unit 140 (radiating element 141) in the lower left of Figure 7 will also be referred to as the third microwave radiating unit 140C (third radiating element 141C), and the microwave radiating unit 140 (radiating element 141) in the lower right of Figure 7 will also be referred to as the fourth microwave radiating unit 140D (fourth radiating element 141D).

[0061] As shown in Figure 7, the four radiating elements 141 have different polarization lengths when viewed from above. Specifically, the polarization length A1 of the first radiating element 141A is greater than the polarization length B1 of the second radiating element 141B. The polarization length B1 of the second radiating element 141B is greater than the polarization length C1 of the third radiating element 141C. The polarization length C1 of the third radiating element 141C is greater than the polarization length D1 of the fourth radiating element 141D.

[0062] As described above, by making the polarization direction lengths of each radiating element 141 different from each other, the frequency characteristics of each microwave radiating section 140 are changed, similar to the first embodiment.

[0063] As shown in Figure 7, the polarization direction of each radiating element 141 is arranged to be perpendicular to the polarization direction of the adjacent radiating element 141. Specifically, the polarization direction of the first radiating element 141A is in the front-to-back direction, and the polarization directions of the two adjacent radiating elements 141 (the second radiating element 141B and the fourth radiating element 141D) are arranged to be in the left-to-right direction. The polarization direction of the second radiating element 141B is in the left-to-right direction, and the polarization directions of the two adjacent radiating elements 141 (the first radiating element 141A and the third radiating element 141C) are arranged to be in the front-to-back direction. This suppresses interference between microwaves radiated from one microwave radiating unit 140 and microwaves radiated from other microwave radiating units 140 adjacent to the first microwave radiating unit 140. Therefore, it is possible to suppress the incident of microwaves emitted from one microwave radiation unit 140 on other microwave radiation units 140 adjacent to that one microwave radiation unit 140.

[0064] Furthermore, the polarization direction of each radiating element 141 only needs to be arranged so as to intersect with the polarization direction of at least the adjacent radiating element 141. For example, the polarization directions of the four radiating elements 141 may be arranged to be different from each other.

[0065] Furthermore, although each radiating element 141 is rectangular when viewed from above, it is not limited to this and may be circular, elliptical, or polygonal in shape, for example.

[0066] For example, if the four radiating elements 141 are circular in shape, the polarization direction is defined as the direction in which the center of each radiating element 141 aligns with the power supply point, and the length of the polarization direction can be changed by changing the length of the circle in the radial direction. Alternatively, the four radiating elements 141 may be arranged so that their polarization directions intersect with those of adjacent radiating elements 141.

[0067] In the following section, the frequency characteristics of the return loss of each microwave radiating unit 140 in a modified example of a cooking appliance will be explained using Figure 8. Figure 8 is a diagram showing the frequency characteristics of the return loss of each microwave radiating unit 140 (each radiating element 141). Figure 8 mainly shows the return loss in a predetermined frequency band (in this embodiment, a frequency band of 2.4 GHz to 2.5 GHz), and the return loss is expressed in dB (decibels).

[0068] As shown in Figure 8, of the multiple microwave radiating units 140, half of the microwave radiating units 140 (the first microwave radiating unit 140A and the second microwave radiating unit 140B) have frequencies in the range of 2.4GHz to 2.45GHz where the reflection loss is minimized, and these frequencies are different from each other. The remaining microwave radiating units 140 (the third microwave radiating unit 140C and the fourth microwave radiating unit 140D) have frequencies in the range of 2.45GHz to 2.5GHz where the reflection loss is minimized, and these frequencies are different from each other.

[0069] Specifically, the frequency f1 at which the reflection loss of the first microwave radiator 140A is minimized is, for example, 2.4 GHz; the frequency f2 at which the reflection loss of the second microwave radiator 140B is minimized is, for example, 2.433 GHz; the frequency f3 at which the reflection loss of the third microwave radiator 140C is minimized is, for example, 2.466 GHz; and the frequency f4 at which the reflection loss of the fourth microwave radiator 140D is minimized is, for example, 2.5 GHz. In this embodiment, the frequencies f1, f2, f3, and f4 are values ​​that are equally spaced within the range of 2.4 GHz to 2.5 GHz.

[0070] As described above, in the frequency band of 2.4 GHz to 2.5 GHz used in heating cookers, by widening the interval between the frequencies at which the reflection loss of each microwave radiating unit 140 is minimized, the incidence of microwaves from other microwave radiating units 140 can be suppressed in each microwave radiating unit 140. Furthermore, in the frequency band of 2.4 GHz to 2.5 GHz, by evenly separating the frequencies at which the reflection loss of each microwave radiating unit 140 is minimized, the incidence of microwaves from other microwave radiating units 140 can be further suppressed in each microwave radiating unit 140.

[0071] In the above configuration, the microwave heating device (cooker 10) comprises a heating chamber 20 for accommodating the object to be heated F1, and a plurality of microwave radiating units 40 that radiate microwaves into the heating chamber 20. The plurality of microwave radiating units 40 have frequency characteristics in which the frequencies at which reflection loss is minimized are different from each other.

[0072] This prevents microwaves emitted from one microwave radiating unit 40 from being incident on other microwave radiating units 40, thereby suppressing the temperature rise and damage of the microwave generating unit 30 that would result from an increase in the amount of heat converted when reflected wave power is incident on the terminator 34. In addition, since the reflected wave power incident on the terminator 34 can be reduced, a decrease in the heating efficiency of the heating chamber 20 can be suppressed.

[0073] The multiple microwave radiating units 40 include a first microwave radiating unit 40A and a second microwave radiating unit 40B that radiate microwaves toward one surface (lower wall 22) of the heating chamber 20. The first microwave radiating unit 40A has a flat plate-shaped first radiating element 41A facing the surface (lower wall 22). The second microwave radiating unit 40B has a flat plate-shaped second radiating element 41B facing the surface (lower wall 22). The first radiating element 41A and the second radiating element 41B have different lengths in the polarization direction when viewed from a first direction (up and down direction) facing the surface (lower wall 22). As a result, the first microwave radiating unit 40A and the second microwave radiating unit 40B can have frequency characteristics in which the frequency at which reflection loss is minimized is different from that of the first microwave radiating unit 40A and the second microwave radiating unit 40B.

[0074] The first radiating element 41A and the second radiating element 41B are arranged so that their polarization directions intersect when viewed from the first direction (up and down direction). This suppresses interference between the microwaves radiated from the first microwave radiating unit 40A and the microwaves radiated from the second microwave radiating unit 40B.

[0075] Of the multiple microwave radiating units 40, half of them have a frequency within the range of 2.4 GHz to 2.45 GHz at which reflection loss is minimized, and these frequencies are different from each other. The remaining microwave radiating units 40 have a frequency within the range of 2.45 GHz to 2.5 GHz at which reflection loss is minimized, and these frequencies are different from each other. In this way, in the frequency band of 2.4 GHz to 2.5 GHz used in cooking appliances, by widening the interval between the frequencies at which reflection loss is minimized for each microwave radiating unit 40, the incidence of microwaves from other microwave radiating units 40 can be suppressed for each microwave radiating unit 40.

[0076] The microwave heating device (cooker 10) further comprises a plurality of microwave generating units 30 connected to each of a plurality of microwave radiating units 40, which generate microwaves, and a control unit 100 that controls the frequency of each of the plurality of microwave generating units 30. The control unit 100 controls each of the plurality of microwave generating units 30 so that the frequency of the microwaves radiated from each of the plurality of microwave radiating units 40 is the frequency that minimizes the reflection loss corresponding to each of the plurality of microwave radiating units 40.

[0077] This disclosure is not limited to the embodiments described above, and various modifications are possible. For example, the configurations shown in the embodiments above can be replaced with configurations that are substantially the same, that produce the same effects, or that can achieve the same purpose. Furthermore, some or all of the embodiments of this disclosure may be used in combination. [Explanation of Symbols]

[0078] 10 Cooking appliance (microwave heating device), 20 Heating chamber, 22 Lower wall (one side of the heating chamber), 30 Microwave generator, 40 Microwave radiator, 40A First microwave radiator, 40B Second microwave radiator, 41A First radiating element, 41B Second radiating element, 100 Control unit, F1 Object to be heated

Claims

1. A heating chamber for containing the object to be heated, The heating chamber comprises a plurality of microwave radiating units that radiate microwaves, A microwave heating device in which the plurality of microwave radiating units have frequency characteristics in which the frequencies at which reflection loss is minimized are different from each other.

2. The plurality of microwave radiating units include a first microwave radiating unit and a second microwave radiating unit that radiate microwaves toward one surface of the heating chamber. The first microwave radiation unit has a flat plate-shaped first radiation element facing the one surface, The second microwave radiation section has a flat plate-shaped second radiation element facing the first surface, The microwave heating apparatus according to claim 1, wherein the first radiating element and the second radiating element have different lengths in the polarization direction when viewed from a first direction facing the one surface.

3. The microwave heating apparatus according to claim 2, wherein the first radiating element and the second radiating element are arranged so that their polarization directions intersect when viewed from the first direction.

4. Of the plurality of microwave emitting units, Half of the microwave radiating sections have frequencies within the range of 2.4 GHz to 2.45 GHz at which the reflection loss is minimized, and these frequencies are different from each other. The microwave heating apparatus according to any one of claims 1 to 3, wherein the remaining microwave radiating portion has a frequency within the range of 2.45 GHz to 2.5 GHz at which the reflection loss is minimized, and the frequencies of the remaining microwave radiating portion are different from each other.

5. Each of the aforementioned plurality of microwave radiating units is connected to a plurality of microwave generating units that generate microwaves, The system further comprises a control unit that controls the frequency of each of the plurality of microwave generating units, The microwave heating apparatus according to any one of claims 1 to 3, wherein the control unit controls each of the plurality of microwave generating units so that the frequency of the microwaves emitted from each of the plurality of microwave emitting units is the frequency that minimizes the reflection loss corresponding to each of the plurality of microwave emitting units.

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