HK1187190B - High-frequency heating device - Google Patents

Description

High-frequency heating device

Technical Field

The present invention relates to a high-frequency heating apparatus, and more particularly to a high-frequency heating apparatus in which heating unevenness of an object to be heated is suppressed.

Background

As a conventional high-frequency heating apparatus, there has been proposed a high-frequency heating apparatus including: "is provided with: a heating chamber for accommodating an object to be heated; a high-frequency oscillator for oscillating a high-frequency wave for heating an object to be heated in the heating chamber; a waveguide for guiding the high-frequency wave oscillated from the high-frequency oscillator to the heating chamber; and an antenna for diffusing the high-frequency wave propagated from the waveguide into the heating chamber, wherein the antenna includes a plate for emitting the high-frequency wave, and an antenna shaft (antennacraft) having one end disposed in the waveguide and the other end connected to the plate for propagating the high-frequency wave from the waveguide to the plate, and the plate and the antenna shaft are connected by a conductive path branched from the antenna shaft upper portion 2 ".

Patent document 1: japanese patent laid-open publication No. 2009-170335 (page 3, FIG. 4)

Disclosure of Invention

The high-frequency heating apparatus described in patent document 1 has the following configuration: the high-frequency transmission plate is provided with a heating chamber which is provided in a substantially rectangular parallelepiped shape, a high-frequency oscillator which oscillates high-frequency waves, a waveguide tube which propagates the high-frequency waves, and an antenna which propagates the high-frequency waves in the waveguide tube into the heating chamber, and the upper surface of the antenna is provided with an installation plate which can protect the antenna and an object to be heated.

The antenna includes a flat plate portion for emitting a high-frequency wave, and an antenna shaft having one end disposed in the waveguide and the other end connected to the flat plate for propagating the high-frequency wave of the waveguide to the flat plate, and the flat plate and the antenna shaft are connected by a conductive path branched from the antenna shaft upper portion 2. According to this antenna structure, since a strong electric field can be emitted over a wide area on the antenna panel, it is effective to heat an object to be heated relatively uniformly.

However, on the other hand, in the conductive path portion connected to the flat plate portion that emits the high-frequency wave, a large current is likely to flow from the waveguide via the antenna shaft, and therefore the conductive path portion may have stronger microwave radiation characteristics than the flat plate portion. Therefore, as a result, there are concerns about a disadvantage that heating just above the conductive path in the center of the heating chamber becomes too strong, and a disadvantage that deterioration such as metal oxidation is accelerated due to resistance heat generation in the conductive path portion.

The present invention has been made to solve the above-described problems, and provides a high-frequency heating apparatus capable of more uniformly propagating a high-frequency wave oscillated from a high-frequency oscillator into a heating chamber.

The high-frequency heating apparatus of the present invention includes: a heating chamber for accommodating an object to be heated; a high-frequency oscillator for oscillating a high-frequency wave for heating an object to be heated; a waveguide for guiding the high-frequency wave oscillated from the high-frequency oscillator; an antenna shaft for propagating a high-frequency wave in the waveguide; a flat plate-like antenna coupled to the antenna shaft, disposed substantially in parallel to the bottom of the heating chamber, and configured to diffuse high-frequency waves into the heating chamber; and a rotation driving unit that rotates the antenna via the antenna shaft, wherein the antenna includes: a first antenna having an opening formed in a conductor coupled to the antenna shaft as a first radiation section; a first conductive path and a second conductive path which are branched 2 times from the first antenna; and a second antenna having a flat plate portion connected to the first and second conductive paths as a second radiation portion.

According to the present invention, the first conductive path and the second conductive path are connected from the antenna shaft as the feeding portion via the first antenna having the first radiation portion. Therefore, electric field concentration on the first and second conductive paths can be suppressed, and deterioration of the conductive paths can be suppressed.

Further, since a strong electric field is radiated from the first radiation portion to a relatively narrow range and an electric field of an intermediate intensity is radiated from the second radiation portion to a relatively wide range, the high-frequency wave oscillated from the high-frequency oscillator can be more uniformly propagated into the heating chamber.

Drawings

Fig. 1 is a schematic sectional view of a main part of a heating cooker according to an embodiment.

Fig. 2 is a perspective view of a main part of a heating cooker according to the embodiment.

Fig. 3 is a perspective view of a main portion of the bottom surface of the heating chamber of the heating cooker according to the embodiment.

Fig. 4 is a top view of an antenna of the heating cooker of the embodiment.

Fig. 5 is a top view of an antenna of the heating cooker of the embodiment.

Fig. 6 is a schematic view of propagation of high-frequency waves on an antenna of a heating cooker according to the embodiment.

Fig. 7 is a transition diagram of a surface current on an antenna plate of a heating cooker according to the embodiment.

Fig. 8 is a schematic diagram illustrating an electric field distribution when the antenna of the embodiment rotates.

Fig. 9 is a top view illustrating another antenna of the embodiment.

Fig. 10 is a top view of an antenna of a conventional heating cooker.

Description of the reference numerals

1: a main body; 2: a heating chamber; 3: an operation panel; 4: a door; 5: a door visual recognition window; 6: a high-frequency transmission plate; 7: an object to be heated; 8: a temperature detection device; 9: a base plate; 9 a: a shaft hole; 10: an antenna chamber; 11: a high-frequency oscillator; 12: a waveguide; 12 a: a shaft hole; 20: an antenna; 21: a shaft connecting portion; 22: an antenna shaft; 23: an antenna motor; 30: a first radiation unit; 31: a slot antenna; 31 a: a conductor part; 31 b: a slit hole; 31 c: an edge; 32: a slot antenna; 32 a: a conductor part; 32 b: a slit hole; 32c, the ratio of: an edge; 40: a second radiation unit; 41: an antenna panel; 42: a conductive path; 42 a: a connection point; 42 b: a connection point; 43: a conductive path; 43 a: a connection point; 43 b: a connection point; 100: linearly polarized waves; 101: a circularly polarized wave.

Detailed Description

Detailed description of the preferred embodiments

In the present embodiment, a heating cooker used in a home or the like will be described as an example of a high-frequency heating apparatus.

Fig. 1 is a schematic sectional view of a main part of a heating cooker according to an embodiment. Fig. 2 is a perspective view of a main part of a heating cooker according to the embodiment. Fig. 3 is a perspective view of a main portion of the bottom surface of the heating chamber of the heating cooker according to the embodiment. The antenna shown in fig. 3 is a characteristic structure of the heating cooker of the present embodiment.

As shown in fig. 1, a heating chamber 2 is provided inside a main body 1 of the heating cooker, and a door 4 and an operation panel 3 are provided on a front surface of the main body 1.

The heating chamber 2 is formed of a substantially rectangular parallelepiped frame body having an open front surface. A high-frequency transmission plate 6 is detachably provided at the bottom of the heating chamber 2, and the high-frequency transmission plate 6 functions as a mounting table for an object 7 to be heated stored in the heating chamber 2. The high-frequency transmission plate 6 is made of, for example, ceramic that transmits high-frequency waves. The operation panel 3 receives various input operations from a user, such as an instruction to start heating, setting of heating time, and setting of a target heating temperature. The door 4 is openably and closably attached to the main body 1, and is provided with a door viewing window 5 formed of glass with a perforated metal plate interposed therebetween. The cooking state of the object 7 accommodated in the heating chamber 2 can be confirmed through the door viewing window 5.

As shown in fig. 2, a high-frequency oscillator 11 that oscillates a high-frequency wave for heating an object 7 to be heated, and a waveguide 12 that guides the high-frequency wave oscillated from the high-frequency oscillator 11 to the heating chamber 2 are provided in the main body 1. The high-frequency oscillator 11 provided at the bottom of the heating chamber 2 of the main body 1 is a magnetron which oscillates high-frequency waves.

An antenna chamber 10 for housing an antenna 20 is formed between the bottom plate 9 of the heating chamber 2 and the high-frequency transmission plate 6. The antenna 20 is used to diffuse the microwave oscillated from the high-frequency oscillator 11 into the heating chamber 2. An antenna motor 23 for rotating the antenna 20 is attached to the antenna 20.

The temperature detection device 8 provided in the heating chamber 2 is, for example, an infrared sensor that measures the temperature of the object 7 based on infrared rays emitted from the object 7.

The heating cooker includes a control unit (not shown) including a control circuit for controlling the driving of the high-frequency oscillator 11, the antenna motor 23, and the like in accordance with an input from the operation panel 3. The control unit has the following functions: the output of the high-frequency oscillator 11 is controlled in accordance with the temperature detected by the temperature detection device 8, and the antenna motor 23 is rotated/stopped at a predetermined timing. In this way, by rotating and stopping the antenna 20 by the antenna motor 23, the state of irradiation of the microwave to the object 7 is changed, and the object 7 can be heated uniformly and at high speed.

Here, a propagation system of the high frequency wave radiated from the high frequency oscillator 11 to the object 7 via the antenna 20 will be described.

A magnetron as the high-frequency oscillator 11 oscillates a high-frequency wave of 2.45GHz in, for example, a microwave oven (microwaveoven) for home use. For example, a household microwave oven oscillates a high frequency wave with an output of about 1000W to 200W.

The high-frequency wave oscillated by the high-frequency oscillator 11 propagates through a space in the waveguide 12 formed by closing a conductor.

The structure is as follows: the shaft hole 12a of the waveguide 12 and the shaft hole 9a of the bottom plate 9 of the heating chamber 2 are provided at positions corresponding to each other, and the high-frequency wave propagating through the space in the waveguide 12 propagates through the shaft hole 12a and the shaft hole 9a into the heating chamber 2.

However, when only the shaft holes 12a and 9a are provided, the high-frequency waves do not efficiently flow into the heating chamber 2. Therefore, a conductive metal antenna shaft 22 is coaxially coupled to the shaft of the antenna motor 23 and inserted into the shaft holes 12a and 9a, and a flat plate-like antenna 20 connected to one end of the antenna shaft 22 is disposed in the antenna chamber of the heating chamber 2. In this configuration, the high-frequency wave propagating through the waveguide 12 is converted into a surface current in the antenna axis 22 of the antenna 20. The current obtained by the conversion flows on the surface of the antenna 20, and a magnetic field is excited by the current accompanying a temporal change in the current due to the high-frequency wave, and an electric field is generated by the excited magnetic field. The electromagnetic waves are radiated by increasing and decreasing the time change of the magnetic field and the electric field with the phase of the high-frequency wave.

That is, since a current flows on the surface of the antenna 20, the state of the high-frequency wave propagating from the flat plate portion of the antenna 20 into the heating chamber 2 changes according to the flow pattern of the surface current in the temporal change (phase change) of the high-frequency wave. Thus, it can be said that a high-frequency wave can be generated from a wide area on the flat plate by causing a current flowing through the antenna surface and a temporal change in the current in a wider area. In this way, the transmission efficiency is improved by propagating the high-frequency wave into the heating chamber 2 through the antenna shaft 22 and the antenna 20.

Here, a conventional antenna is described. Fig. 10 is a top view of a conventional antenna. In the conventional example, the path of the current is branched by 2 from the shaft connecting portion 66, and the shaft connecting portion 66 is a coupling portion coupled to an antenna shaft (not shown) serving as a current source for supplying the current to the antenna 60. The following method is adopted: the branched currents are merged as independent currents on the antenna plate 63 shown in a disk shape in fig. 10 via a conductive path 64 extending from the shaft connecting portion 66 to the paper surface and bent once to the antenna plate 63, and a conductive path 65 extending from the shaft connecting portion 66 to the paper surface and bent twice to the antenna plate 63. In the conventional example, a high-frequency current from the lower side of the paper surface via the conductive path 64 and a high-frequency current from the right side of the paper surface via the conductive path 65 are vectorially combined, and various currents are caused to flow in the antenna plate 63, so that an effect of diversifying the distribution of the generated electromagnetic wave is obtained.

However, according to the study of the present invention, in the antenna of the conventional example, since the current flows through the conductive paths 64 and 65 to the antenna plate 63, electromagnetic waves of a level that cannot be ignored are generated.

The conductive paths 64 and 65, which are fine paths having a smaller surface area than the antenna plate 63, tend to have a larger current to ground due to their small surface areas, and the energy per unit area (power density) emitted as electromagnetic waves becomes larger.

That is, the portions directly above the conductive paths 64 and 65 from the antenna shaft as the power feeding portion to the vicinity of the shaft are relatively easily heated, resulting in uneven heating.

The antenna 20 of the present embodiment is configured in view of the conventional example described above. Fig. 4 is a top view of the antenna of the heating cooker of the embodiment, and is a view for explaining the antenna 20 structurally.

First, the antenna 20 will be described from the structural side.

As shown in fig. 4, the antenna 20 is formed of a conductor in a flat plate shape as a whole and is connected to the antenna shaft 22. The antenna 20 is disposed so that its flat surface is substantially parallel to the bottom surface of the heating chamber 2, and is housed in the antenna chamber 10.

The antenna 20 includes: the two slot antennas 31 and 32 (both are collectively referred to as a first antenna), a disk-shaped antenna plate 41 (a second antenna), a conductive path 42 (a first conductive path) connecting the antenna plate 41 and the slot antenna 31, and a conductive path 43 (a second conductive path) connecting the antenna plate 41 and the slot antenna 32. A shaft connecting portion 21 for vertically coupling an antenna shaft 22 is provided at a central portion of the antenna 20. The antenna 20 rotates about the shaft connecting portion 21 in a substantially horizontal direction, thereby equalizing the high-frequency waves applied to the object 7 to achieve uniform heating.

The slot antennas 31 and 32 have slit holes 31b and 32b (opening portions) formed in the conductor portions 31a and 32a, respectively, and having a rectangular shape or an arc shape. The slit antennas 31 and 32 use the slit holes 31b and 32b as radiation portions of high-frequency waves. In particular, when the length of the slit holes 31b and 32b is approximately 1/2 of the use wavelength, resonance occurs, and intense high-frequency waves can be emitted. The slot antennas 31 and 32 have substantially fan-shaped outer shapes, and conductive paths 42 and 43 are connected to sides 31c and 32c corresponding to the radii of the fan-shaped outer shapes. In the present embodiment, the two slot antennas 31 and 32 are arranged symmetrically about the shaft connection portion 21, which is the center portion of the antenna 20.

The antenna panel 41 is a radiation unit capable of radiating high-frequency waves as described later. In the present embodiment, the antenna plate 41 is disk-shaped and is disposed in a substantially sector-shaped region sandwiched between the slot antenna 31 and the slot antenna 32 on the same plane. The diameter of the antenna plate 41 is a length slightly shorter than the length of the side 31c of the slot antenna 31. The antenna panel 41 is connected to the first antenna by a conductive path 42 and a conductive path 43 branched from the first antenna 2. In the present embodiment, the antenna panel 41 is connected to one slot antenna 31 through a conductive path 42 and to the other slot antenna 32 through a conductive path 43.

The conductive path 42 and the conductive path 43 are connected to the antenna plate 41 at positions shifted by substantially 90 ° from the center of the antenna plate 41 in the same plane. Further, the apparatus is configured to: the distance L2 from the connection point 43a of the conductive path 43 and the antenna plate 41 to the shaft connection portion 21 is longer than the distance L1 from the connection point 42a of the conductive path 42 and the antenna plate 41 to the shaft connection portion 21. With this configuration, in the present embodiment, when the connection point between the side 31c of the slot antenna 31 and the conductive path 42 is the connection point 42b and the connection point between the side 32c of the slot antenna 32 and the conductive path 43 is the connection point 43b, the distance from the connection point 42b to the shaft connecting portion 21 is shorter than the distance from the connection point 43b to the shaft connecting portion 21.

The antenna plate 41 is disposed in a sector region sandwiched between the substantially sector-shaped slot antenna 31 and the slot antenna 32, and conductive paths 42 and 43 connecting the antenna plate 41 and the slot antennas 31 and 32 are connected to sides 31c and 32c of the slot antennas 31 and 32. With such an arrangement, the conductive paths 42 and 43 can be formed linearly without being bent, and the path length of the conductive paths 42 and 43 can be shortened.

Next, the functional side of the antenna 20 will be described. Fig. 5 is a top view of the antenna of the embodiment, and is a diagram for functionally explaining the antenna 20. Fig. 6 is a schematic view of propagation of high-frequency waves on an antenna of a heating cooker according to the embodiment, and fig. 7 is a transition diagram of surface currents on an antenna plate of the heating cooker according to the embodiment.

The functional side of the antenna 20 is explained with reference to fig. 5, 6, and 7.

As shown in fig. 6, high-frequency waves are radiated from the slot antennas 31 and 32 by linearly polarized waves 100 whose planes intersecting the slot holes 31b and 32b are flat. The slit holes 31b and 32b that radiate the high-frequency wave are referred to as first radiation portions 30. The areas above the slot antennas 31 and 32 are referred to as strong electric field areas F (see fig. 5) having strong electric fields. In the present embodiment, by providing two slit antennas 31 and 32 capable of radiating strong high-frequency waves, the radiation efficiency from the antenna 20 can be improved, and the heating efficiency of the object 7 can be improved.

Next, electric field radiation from the antenna panel 41 will be described.

When the conductive paths 42 and 43 are regarded as current sources with respect to the antenna plate 41, the geometric current sources are introduced with their arrangement shifted by 90 °, so that the vector of the surface current on the antenna plate 41 significantly changes, and high-frequency waves can be radiated in all directions.

The high-frequency waves introduced into the antenna plate 41 are set so that the distances (L1, L2) from the antenna axis 22 as the introduction position are different from each other, and currents with phases shifted by 90 ° can be introduced. By synthesizing the introduced currents, a circularly polarized wave 101 capable of circularly radiating a high electric field can be generated. The antenna panel 41 is referred to as a second radiation portion 40.

Here, the principle of generation of a circularly polarized wave will be described with reference to fig. 7. Fig. 7 is a diagram showing currents flowing through the antenna plate 41, the solid lines showing currents flowing through the antenna plate 41, and the broken lines showing currents flowing in and out from the respective conductive paths. In addition, the length of the dotted line indicates the magnitude of the current.

The current excited by the high-frequency wave oscillates in such a manner that the direction of flow is reversed for each phase by 90 ° (oscillate). For example, the incident current from the conductive path 43 flowing from the lower side of the paper surface of the phase 0 ° flows downward greatly, but the current becomes small as the phase becomes the phases 22.5 ° and 45 °, and then the direction of the current flow starts to be reversed, and the current flows in the opposite direction at the phase 90 ° with the same magnitude as the phase 0 °.

The combination of the currents flowing from the lower side of the drawing and from the right side is, as shown by the solid line on the antenna plate 41, a direction in which the currents flow is changed sequentially for each phase as a combined current. As a result, the direction of the current flowing on the antenna panel 41 rotates by one turn during the phase change by 180 °.

That is, the electromagnetic wave generated in the direction perpendicular to the paper surface in accordance with the movement of the current moves the strong electric field portion in a ring shape in accordance with the phase.

As shown in fig. 6, by the circularly polarized wave 101 emitted from the antenna plate 41, although it is weaker than the energy emitted from the slot antenna 31, a high frequency wave having a medium level of energy can be emitted. This high-frequency wave tends to be relatively strong particularly at the end of the antenna panel 41 where current easily flows. The outer peripheral end of the disk portion of the antenna plate 41 is referred to as a medium electric field region G (see fig. 5) having a medium electric field strength.

When the phase of the current flowing in the antenna plate 41 is shifted by 90 °, for example, a means of changing the positions and lengths of the conductive paths 42 and 43 by analyzing and confirming the current by electromagnetic field simulation software or the like can be adopted.

Fig. 8 is a schematic diagram illustrating an electric field distribution when the antenna of the embodiment rotates. The electric field distribution when the antenna 20 is rotated will be described with reference to fig. 5 and 8.

First, as shown in fig. 5, a trace C indicates a trace at the center of the strong electric field region F of the slot antennas 31 and 32 when the antenna 20 is rotated. The trajectories near the outer end and the inner end of the medium electric field region G of the antenna plate 41 when the antenna 20 is rotated are referred to as a trajectory D and a trajectory E, respectively.

As shown in fig. 8, since the strong electric field region F enhances the electric field in the region of the track C by rotating the antenna 20, the electric fields in the portions directly above the slot antennas 31 and 32 tend to be enhanced concentrically. Therefore, the object 7 to be heated which is extremely close to the antenna 20 placed directly above the slot antennas 31 and 32 is also heated with the same tendency. Further, since the medium electric field region G enhances the electric field in the region between the tracks D and E by rotating the antenna 20, the electric field in the portion directly above the antenna plate 41 also tends to be enhanced concentrically.

As described above, when the antenna 20 is rotated, the strong electric field region F forms the loop-shaped electric field region F1 having a relatively narrow range, and the medium electric field region G forms the loop-shaped electric field region G1 having a relatively wide range. Since the strong electric field region F and the middle electric field region G are different in range and position from each other, the electric field region F1 in the form of a loop based on the strong electric field region F overlaps with the electric field region G1 in the form of a loop based on the middle electric field region G, but the electric field region F1 does not coincide with the electric field region G1. Since the electric field is radiated from the circumferential tracks D and E simultaneously with the track C in the rotating area directly above the antenna 20, the electric field is radiated from a wide range in the rotating area of the antenna 20. Since the electric field is emitted from a wide range, an efficient and uniform temperature rise effect can be provided to the object 7 to be heated. For example, when only the slot antennas 31 and 32 are provided, the heating element is not present at a position shifted from the track C, and the heating is relatively weak. However, by providing the antenna plate 41 as the second radiation portion as in the present embodiment, it is possible to achieve uniform heating as compared with the case where the slot antennas 31 and 32 are only provided.

As described above, the present embodiment includes: slot antennas 31 and 32, each having a first radiation section 30 formed as slit holes 31b and 32b formed in conductor sections 31a and 32a coupled to the antenna shaft 22; conductive paths 42 and 43 branched 2 from the slot antennas 31 and 32; and a second antenna having the antenna plate 41 connected to the conductive paths 42 and 43 as a second radiation portion.

In the present embodiment, since the conductive path 42 and the conductive path 43 are connected from the antenna shaft 22 as the feeding portion via the first antenna (slot antennas 31 and 32), the conductive paths 42 and 43 can be formed shorter than the conductive paths 64 and 65 of the antenna shown in the conventional example, electric field radiation from the same portion is hardly generated, and the disadvantage that heating is locally increased can be suppressed. Therefore, electric field concentration in the conductive paths 42 and 43 can be suppressed, and deterioration of the conductive paths 42 and 43 can be suppressed.

Further, a strong electric field is radiated from the slot antennas 31 and 32 connected to the antenna shaft 22 to a relatively narrow range above the slot holes 31b and 32b, and an electric field of an intermediate intensity is radiated from the antenna plate 41 to a relatively wide range. By providing the radiation portions having different electric field strengths in this manner, the intensity of electric field radiation on the antenna 20 can be varied. For example, by making the ranges of electric field radiation of the first radiation portion 30 and the second radiation portion 40 different, there is an effect of changing the intensity of electric field radiation on the antenna 20. Further, by adjusting the ranges and the arrangement of the first radiation portion 30 and the second radiation portion 40, the intensity of the electric field radiation on the antenna 20 can be further uniformized.

Further, since the two slot antennas 31 and 32 are provided, the center of gravity during rotation is stable, and the planar portion of the antenna 20 is less fluctuated during rotation, so that the operation is stable. The slot antennas 31 and 32 are provided at positions symmetrical to the axial connection portion 21, which is the center of the antenna 20. This makes it possible to separate the slot antenna 31 and the slot antenna 32 from each other. Therefore, interaction of the high-frequency waves radiated from the slot antennas 31 and 32 can be suppressed, and the high-frequency waves can be efficiently radiated from the slot antennas 31 and 32. In this way, high-frequency wave transmission with stable center of gravity and high efficiency can be achieved by the two slot antennas 31, 32.

In the present embodiment, the trajectory of the first radiation unit 30 when the antenna 20 is rotated is different from the trajectory of the second radiation unit 40. That is, as shown in fig. 8, the ring-shaped electric field region F1 of the strong electric field region F of the first radiation unit 30 overlaps with the ring-shaped electric field region G1 of the medium electric field region G of the second radiation unit 40, but the two electric field regions do not coincide with each other. Therefore, the electric field can be radiated over a wide range on the antenna 20, and thus uneven heating can be suppressed.

In the present embodiment, a circularly polarized wave in which the radiation electric field vector changes periodically is radiated in the second radiation unit 40. Therefore, the direction of the microwave incident on the object 7 can be diversified, and the effect of suppressing uneven heating can be enhanced.

In the above embodiment, the slit hole 31b and the slit hole 32b are described as an example in which they are located on the same radius, but they may be arranged at positions shifted from each other in the radial direction. In this case, the slit holes 31b and 32b need to have the same slit length, and thus the fan-shaped angles are different from each other, which has the effect of further suppressing uneven heating.

In this case, in order to balance the weight, the length of the slit hole having a large fan-shaped angle in the radial direction may be shorter than the length of the other slit hole in the radial direction.

In the above embodiment, the two slot antennas 31 and 32 are provided, but a configuration in which one slot antenna (first antenna) is provided is also possible. Fig. 9 is a top view illustrating another antenna of the embodiment. When the antenna 20 shown in fig. 9 is compared with the antenna shown in fig. 4, there is a difference in the point where the antenna 20 shown in fig. 9 does not have the slit hole 31 b. For example, if two slit antennas are provided, the heating may be too strong, and one slit antenna 32 may be provided as shown in fig. 9, and the high-frequency wave may be radiated only from the slit hole 32b, thereby making the heating more uniform. Further, three or more slot antennas may be provided. Further, a plurality of openings may be provided in one slot antenna (first antenna) to form a plurality of radiation portions. Further, a plurality of second radiation portions may be provided.

In addition, the high-frequency heating of the present invention can be combined with the radiation heater, which is not shown, being provided on the top surface of the heating chamber, the hot air heater being provided on the rear surface, or the steam generating device being provided. In addition, heating control including power stop can be performed according to the finish state of the object to be heated by using a temperature detection device or the like provided in the heating chamber.

Claims (20)

1. A high-frequency heating device is characterized by comprising:

a heating chamber for accommodating an object to be heated;

a high-frequency oscillator for oscillating a high-frequency wave for heating an object to be heated;

a waveguide for guiding the high-frequency wave oscillated from the high-frequency oscillator;

an antenna shaft for propagating a high-frequency wave in the waveguide;

a flat plate-like antenna coupled to the antenna shaft and disposed in parallel to a bottom of the heating chamber, for diffusing a high-frequency wave into the heating chamber; and

a rotation driving unit that rotates the antenna via the antenna shaft,

wherein the antenna comprises:

a first antenna having at least one opening formed in a conductor coupled to the antenna shaft as a first radiation section;

a first conductive path and a second conductive path which are branched 2 times from the first antenna; and

and a second antenna which is a plate antenna and which emits a circularly polarized wave by feeding electricity to the flat plate portion connected to the first and second conductive paths as a second radiation portion via the antenna axis, the conductor portion of the first antenna, and the first and second conductive paths.

2. The high-frequency heating apparatus according to claim 1,

at least two of the first antennas are coupled to the antenna shaft,

the first conductive path is connected to one of the first antennas, and the second conductive path is connected to the other of the first antennas.

3. The high-frequency heating apparatus according to claim 1 or 2,

a trajectory of rotation defined by the first radiation unit when the antenna shaft is rotated is different from a trajectory of rotation defined by the second radiation unit.

4. The high-frequency heating apparatus according to claim 1 or 2,

the radiation device is provided with one or both of the first radiation part and the second radiation part.

5. The high-frequency heating apparatus according to claim 3,

the radiation device is provided with one or both of the first radiation part and the second radiation part.

6. The high-frequency heating apparatus according to claim 1,

a pair of first antennas configured to be symmetrical about a coupling portion coupled to the antenna shaft,

the first conductive path is connected to one of the first antennas, and the second conductive path is connected to the other of the first antennas.

7. The high-frequency heating apparatus according to claim 6,

a trajectory of rotation defined by the first radiation unit when the antenna shaft is rotated is different from a trajectory of rotation defined by the second radiation unit.

8. The high-frequency heating apparatus according to claim 6,

the radiation device is provided with one or both of the first radiation part and the second radiation part.

9. The high-frequency heating apparatus according to any one of claims 1, 2, 6, 7, 8,

a distance from a coupling portion coupled to the antenna shaft to a connection point of the flat plate portion and the first conductive path and a distance from a coupling portion coupled to the antenna shaft to a connection point of the flat plate portion and the second conductive path are made different.

10. The high-frequency heating apparatus according to claim 3,

a distance from a coupling portion coupled to the antenna shaft to a connection point of the flat plate portion and the first conductive path and a distance from a coupling portion coupled to the antenna shaft to a connection point of the flat plate portion and the second conductive path are made different.

11. The high-frequency heating apparatus according to claim 4,

a distance from a coupling portion coupled to the antenna shaft to a connection point of the flat plate portion and the first conductive path and a distance from a coupling portion coupled to the antenna shaft to a connection point of the flat plate portion and the second conductive path are made different.

12. The high-frequency heating apparatus according to any one of claims 1, 2, 6, 7, 8,

the first conductive path and the second conductive path are connected to positions geometrically staggered by 90 ° with respect to the center of the flat plate portion.

13. The high-frequency heating apparatus according to claim 3,

the first conductive path and the second conductive path are connected to positions geometrically staggered by 90 ° with respect to the center of the flat plate portion.

14. The high-frequency heating apparatus according to claim 4,

the first conductive path and the second conductive path are connected to positions geometrically staggered by 90 ° with respect to the center of the flat plate portion.

15. The high-frequency heating apparatus according to claim 9,

the first conductive path and the second conductive path are connected to positions geometrically staggered by 90 ° with respect to the center of the flat plate portion.

16. The high-frequency heating apparatus according to any one of claims 1, 2, 6, 7, 8,

the phase of the high-frequency wave incident from the first conductor path to the second radiation portion is shifted by 90 ° from the phase of the high-frequency wave incident from the second conductor path to the second radiation portion.

17. The high-frequency heating apparatus according to claim 3,

the phase of the high-frequency wave incident from the first conductor path to the second radiation portion is shifted by 90 ° from the phase of the high-frequency wave incident from the second conductor path to the second radiation portion.

18. The high-frequency heating apparatus according to claim 4,

the phase of the high-frequency wave incident from the first conductor path to the second radiation portion is shifted by 90 ° from the phase of the high-frequency wave incident from the second conductor path to the second radiation portion.

19. The high-frequency heating apparatus according to claim 9,

the phase of the high-frequency wave incident from the first conductor path to the second radiation portion is shifted by 90 ° from the phase of the high-frequency wave incident from the second conductor path to the second radiation portion.

20. The high-frequency heating apparatus according to claim 12,

the phase of the high-frequency wave incident from the first conductor path to the second radiation portion is shifted by 90 ° from the phase of the high-frequency wave incident from the second conductor path to the second radiation portion.