JPH0815116B2 - High frequency heating equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-frequency heating device for high-frequency dielectrically heating an object to be heated.

2. Description of the Related Art Generally, a microwave oven, which is a high-frequency heating device for high-frequency dielectrically heating an object to be heated, uniformly radiates radio waves from a magnetron, which is a high-frequency oscillator, to the object to be heated, and the result of cooking and heating food such as the object to be heated is achieved. Equipped with means to improve. This means has heretofore been generally used. A stirrer method and a stirrer method in which a high-frequency electric field in the heating chamber is temporally changed by rotating or moving an electric wave stirring blade (stirrer blade) made of a conductor in the heating chamber 3, 4 and 5
It is a turntable system as shown in the figure. In FIG. 3, a magnetron 1 which is a high frequency oscillator is coupled to a waveguide 4 provided on a top surface 3 of a heating chamber 2. The electric field in the waveguide 4 travels in the waveguide 4 in the direction of the arrow in the figure in the case of the TE ₁₀ mode which is very general in a rectangular waveguide that varies depending on the excited mode. An opening 5 serving as a radiation port of radio waves into the heating chamber is provided in a portion of the top surface 3 facing the waveguide 4, and supplies high frequency energy to a water load 6 placed in the heating chamber. An example of the high-frequency electric field distribution in the heating chamber is determined by the resonance mode of the heating chamber, which is a resonator of high-frequency radio waves, depending on the dimensions of the heating chamber 2, the positional relationship between the heating chamber 2 and the opening 5, etc., as shown by the broken line in the figure. It Therefore, as a method for uniformly heating the water load 6 which is the object to be heated within a fixed mode existing in the heating chamber, the water load 6 placed in the heating chamber is rotated and moved one by one into different high frequency electric fields. For this purpose, a tray 8 is provided which rotates the object to be heated by applying a rotational force from a motor 7 provided outside the heating chamber.

FIG. 4 shows the waveguide 4 provided on the side surface of the heating chamber, and is otherwise the same as FIG.

In FIG. 5, the side wall surface 9 forming the heating chamber 2 is partially projected outward, and the magnetron 1 is directly coupled to the heating chamber 2 at this protruding portion, which has no waveguide. Is.

Problems to be Solved by the Invention However, such a conventional high-frequency heating device has the following problems.

In FIG. 3, the resonance mode in the heating chamber changes depending on the shape and size of the heating chamber and the object to be heated, and the rotating saucer is 8
The high-frequency radio wave propagating through the waveguide 4 travels in this resonance mode by the direct radiation of the portion close to the opening 5 due to the directivity of the radio wave. Radiant heating is weakened. Therefore, the heating state of the water load 6 becomes uneven due to a difference in the vertical direction. In FIG. 4, a high frequency radio wave from the magnetron 1 propagates through the waveguide 4 and is radiated into the heating chamber through the opening 5. However, the waveguide 4 and the heating chamber 2 can be easily matched in impedance. Due to the inclination provided to eliminate the discontinuity of the characteristic impedance of No. 4, since it has directivity toward the top surface 3, in addition to the dimensions of the heating chamber, the opening 5 and the top surface 3 which is the main reflection surface in the heating chamber The heating state of the water load 6 is largely influenced by the distance between the two and the shape of the top surface 3.

In FIG. 5, the high-frequency radio wave from the magnetron 1 is unstable and irregular in its excitation mode as compared with the coupling in the waveguide. This is because the magnetron 1 is directly coupled to the load impedance as a resonator of the heating chamber 2 including the water load 6 and excited. Therefore, the difference in load conditions (object to be heated) such as shape and amount of load and the shape of the protruding part equivalently change the load impedance of the resonator, and the radiation state of high-frequency radio waves greatly changes. It is difficult to uniformly heat various objects to be heated. As described above, in the high-frequency heating device having the uniform heating means called the turntable system, the structure for supplying the high-frequency radio wave from the magnetron 1 provides (1)
Directivity of high frequency radio waves, (2) resonance mode in the heating chamber,
(3) The load impedance to the oscillator changes intricately, and the impedance matching between the oscillator and the heating chamber containing the object to be heated improves the efficiency and improves the heating characteristics for supplying uniform high-frequency energy to the object to be heated. It was extremely difficult to realize together.

The present invention solves such conventional problems, and provides a high-frequency heating device having a simple structure, good uniform heating performance, and good heating efficiency.

Means for Solving the Problems A high-frequency heating apparatus according to the present invention includes a heating chamber having a substantially box-like shape, an object mounting table for rotating an object to be heated in the heating chamber, a high-frequency oscillator, and a waveguide. The waveguide is arranged on a surface other than the wall surface of the heating chamber on which the object mounting table is located and the wall surface facing it, and the waveguide wall facing the heating chamber side of the waveguide is projected in a substantially truncated cone shape. A circular hole is provided in the waveguide wall on the central axis of the part and penetrates this hole, and a substantially cylindrical radiating antenna made of a conductor held by a dielectric is provided in the waveguide wall or the heating chamber wall, The waveguide and the heating chamber are electrically coupled by a radiation antenna.

Action The high-frequency heating device of the present invention allows the object to be heated to be seen from the radiation port by providing the radiation port of the high-frequency oscillator on the wall of the heating chamber other than the plane above the rotation axis of the object mounting table provided in the heating chamber. Since the load impedance changes almost in proportion to the reaching distance, the radiation wave energy distribution can be obtained by rotating the object mounting table in concentric circles centered on the rotation axis on each virtual plane on the rotation axis. . Further, a truncated cone-shaped protrusion is provided on the heating chamber wall of the waveguide, a hole and a radiation antenna penetrating the hole are provided at the center of the protrusion, and the protrusion is an outer conductor,
By providing the coaxial electric field coupling section with the radiation antenna as the inner conductor, the electric field of the high frequency radio wave radiated from the waveguide to the heating chamber is parallel to the radiation antenna axis because the radiation antenna has the characteristics of a dipole antenna. Moreover, it is possible to give a substantially uniform radiation pattern to a radial plane centered on the axis. It is well known that matching between the oscillator and the waveguide is easy by adjusting the characteristic impedance by changing the short-circuit surface, width, and height of the waveguide with the conventional technique. The impedance matching between the oscillator and the waveguide is performed by changing the shape of the truncated cone and the diameter of the center hole, and the ratio of the length of the radiating antenna on the heating chamber side to the length inside the waveguide. Is very easy, and impedance matching, that is, each component changed by pursuit of efficiency does not have any adverse effect on uniform heating.

Example A high-frequency heating apparatus according to an example of the present invention will be described below with reference to the drawings.

FIG. 1 is a front sectional view showing the structure of a high-frequency heating device according to the present invention. In FIG. 1, a heating chamber 10 is provided on the front surface for loading and unloading a ceiling plate 11, a U-shaped plate 12 having left and right side surfaces and a bottom surface formed integrally, a rear plate (not shown), and a heated object 13. And a door (not shown). The object to be heated 13 is placed on the object to be heated table 15 rotating on the bottom surface by a motor 14 provided outside the heating chamber. The magnetron 16, which is a high frequency oscillator, is provided with the output section antenna 18 inserted in the rectangular waveguide 17, and the high frequency radio wave oscillated by the magnetron 16 propagates in the tube.
On the other hand, the wall surface of the waveguide 17 that faces the heating chamber 10 (which also serves as the right side surface of the heating chamber at the same time) has a coupling protrusion 19 that is a portion that protrudes in a substantially truncated cone shape. A coupling hole 20 is provided at the center. The radiating antenna 21 is provided so as to penetrate the coupling hole 20, one of which is a waveguide.
17 is inserted into the transmission path, and the other is held in the space newly formed in the heating chamber 10 by the coupling projection 19 by the radiation port cover 22 made of a heat-resistant dielectric.

The high-frequency radio wave traveling in the waveguide 17 is supplied to the heating chamber 10 as a secondary radiator by the simple coaxial conversion structure using the radiation antenna 21 as an inner conductor and the coupling hole 20 as an outer conductor. . Therefore, since the heating chamber radiation port for high-frequency radio waves is provided on the wall surface orthogonal to the rotation axis of the object-to-be-heated mounting table 15, the distance between the radiation port and the object-to-be-heated 13 is elapsed with the rotation of the object-to-be-heated mounting table. As a result, the respective parts are collectively averaged and the high frequency energy due to the load impedance due to the direct radiation is made uniform. Further, the radiation antenna 21 eliminates the directivity of the radio waves traveling through the waveguide 17, and is extremely uniform parallel to the radiation antenna 21 similar to the radiation pattern of the parabolic antenna in combination with the shape of the coupling protrusion 19. Excellent radiation characteristics can be obtained. FIG. 2 is a perspective view of essential parts showing the waveguide and the coupling portion of the present invention, and the same parts are designated by the same reference numerals. A coupling hole 23 for fixing the radiation port cover 22 is provided around the coupling projection 19 of the waveguide 17, but its size is extremely small in order to prevent unnecessary leakage of high frequency radio waves.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) Since the center axis of rotation of the object-to-be-heated mounting table and the heating chamber radiation port for high-frequency radio waves are orthogonal to each other, when the object-to-be-heated mounting table is rotated, the direct radiated wave energy of the high-frequency wave can be most uniformized.

(2) Since the radiation port to the heating chamber of the waveguide has a coaxial structure having a substantially truncated cone shape, horizontal and extremely uniform radiation characteristics can be obtained in the secondary radiation antenna.

(3) When the oscillator supplies high-frequency radio waves to the heating chamber through a waveguide, the position of the oscillation tube and the position of the radio wave emission port can be arbitrarily selected, and moreover, when matching the load impedance to operate the oscillator optimally. The heating efficiency is excellent because it can be freely adjusted by the coupling degree by the radiation antenna.

(4) Since the elements that determine the rotation of the object mounting table and the radiation pattern of the radio wave emission port, which are uniform heating means, and the elements of the impedance matching means for improving the heating efficiency can be configured separately, both performances can be achieved. It is possible to realize a high-frequency heating device that combines both.

[Brief description of drawings]

FIG. 1 is a front sectional view of a high-frequency heating apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view of main portions of a waveguide and a coupling portion of the high-frequency heating apparatus, FIGS. 3, 4, and 5. The figure is a front sectional view of a conventional high-frequency heating device. 10 ... Heating chamber, 15 ... Heated object mounting table, 16 ... Magnetron, 17 ... Waveguide, 19 ... Coupling protrusion, 20 ... Coupling hole,
21 …… Radiating antenna.

Claims (1)

[Claims] 1. A substantially box-shaped heating chamber for housing an object to be heated, and a table for placing an object to be heated for rotating the object in the heating chamber.
A high-frequency oscillator and a waveguide for propagating high-frequency radio waves from the high-frequency oscillator to the heating chamber, and the waveguide is provided on a surface other than the wall surface of the heating chamber on which the object mounting base is located and the wall surface facing the heating chamber wall. A tube is arranged and a waveguide wall facing the heating chamber side of the waveguide is projected in a substantially truncated cone shape, and a circular hole is provided in the waveguide wall on the central axis of this projection, and A waveguide antenna or heating chamber wall is provided with a substantially cylindrical radiating antenna made of a conductor held by a dielectric on the waveguide wall or the heating chamber wall, and the waveguide and the heating chamber are electrically coupled by the radiating antenna. High frequency heating device.