JPS6025874B2 - High frequency heating device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a high frequency heating device equipped with a waveguide.

In general, microwave ovens, which are high-frequency heating devices, have heat absorption characteristics such as the fact that most of the food being cooked is in a high-density state in the center, and the thickness of the center is large. Taking this into consideration, one of the essential conditions is to increase the temperature distribution around the center of the heating chamber and to make the temperature distribution around the center of the heating chamber uniform.

This idea was made in view of the above circumstances,
The purpose is to achieve a good temperature distribution in the heating chamber according to the heat absorption characteristics of the object to be heated, even though it has an extremely simple configuration, and to achieve optimal heating without uneven heating of the object to be heated. The purpose of the present invention is to provide an excellent high-frequency heating device. Embodiments of the present invention will be described below with reference to the drawings.

In FIGS. 1, 2, and 3, reference numeral 1 denotes a main body of a microwave oven, on the front of which a door 2 is supported so as to be freely openable and closable, and an operation panel 3 is provided.

A heating chamber 4 is disposed within the main body 1 corresponding to the door 2, and a shelf board 5 for stacking food to be cooked is provided within the heating chamber 4. Further, a rectangular waveguide 6 is fixed to the ceiling surface within the heating chamber 4, and one end of this waveguide 6 penetrates the side wall of the heating chamber 4 and is led out to the outside of the heating chamber 4. A high frequency generator such as a magnetron 7 is provided on the outer peripheral surface of one end of the waveguide 6, and an antenna 7a of the magnetron 7 is introduced into the waveguide 6.
Furthermore, a waveguide 6 corresponding to the central part of the heating chamber 4
The tube wall has orthogonal excitation ports 10a, 10b on its bottom wall 6a.
, 10c, orthogonal excitation ports 10d, 10e, 1 on both side walls 6b
0f is formed.

In addition, parallel excitation ports 11a and 11b are formed in the bottom wall 6a of the tube bottom of the waveguide 6 corresponding to the vicinity of the central portion of the heating chamber 4, and parallel excitation ports 11c and 11d are formed in both side walls 6b.
In this case, if the internal wavelength of the high frequency wave emitted from the magnetron 7 in the waveguide 6 is input g, then each of the above excitation rows oa, 10b, Ioc, 10d, 10e, 10f, 10
a, lib, 11c, and 11d are formed sequentially at a distance of n·^g/2 (n is a positive integer) from the high frequency generation source, that is, the antenna 7a, and are in a good matching state (no phase shift occurs). (and SWR=1.5 or less)
is ensured. In addition, the orthogonal excitation ports 10a, 10
b, 10c, 10d, 10e, and 10f have shapes substantially orthogonal to the tube wall current direction, and parallel excitation ports 11a, 11
b, 11c, and 11d have shapes substantially parallel to the tube wall current direction. Here, FIG. 4 shows the state of the high frequency electric field E and magnetic field within the waveguide 6.

That is, the strength of the electric field E is maximum at a position at a distance of n·in g/2 from the antenna 7a. Further, according to the right-handed screw rule, the tube wall current 1 in the lower wall 6a and both side walls 6b flows from the loop of the magnetic field fi as shown in FIG. Therefore, the high frequency waves emitted from the magnetron 6 are guided to the upper part of the heating chamber 4 by the waveguide 6 and supplied into the heating chamber 4 from each excitation port of the waveguide 6.

In this case, each excitation port is located at a position where the strength of the high-frequency electric field E is maximum and constant, so that high-frequency energy is efficiently supplied into the heating chamber 4. In this case, the orthogonal excitation ports 10a, lob, 10c, 10d, 10e, 1
The shape of 0f greatly cuts the tube wall current, and therefore the high frequency energy supplied to the center of the heating chamber 4 becomes very large. On the other hand, parallel excitation ports 11a, 11
The shapes of b, 11c, and 11d cut the tube wall current to a small value, so that the high frequency energy supplied to the vicinity of the center of the heating chamber 4 does not become very large. However, 1
When conducting an experiment in which 00 cc of water (initial water temperature 20±2°C) was heated for 2 minutes, the temperature at the center 0 of the heating chamber 4 was high, and the temperature at the center P, Q around the center was high, as shown in Figures 6 and 7.
, R, and S each have a uniform temperature lower than the temperature of the center part ○.

In this way, with the extremely simple configuration of just forming orthogonal excitation ports and parallel excitation ports on the tube wall of the waveguide 6, it is possible to obtain a favorable temperature distribution state in the heating chamber according to the heat absorption characteristics of the food to be cooked. This enables good cooking of the food to be cooked without uneven heating.

By the way, in the past there is a method of providing a reflector or a starvation fan to eliminate heating unevenness, but the present invention has an extremely simple structure as described above, so it is more economical than the case of providing a reflector or a starvation fan. In addition, it is characterized by being able to make maximum use of the volume of the heating chamber 4. In the above embodiment, each excitation port is provided at a distance of n·^g/2 from the antenna 7a, but it is also possible to provide a stud in the waveguide 6 to ensure a good matching state. For example, it is also possible to change the position of the excitation port.

However, in this case, it should be taken into consideration in advance that not only does the cost increase, but also there are secondary problems such as the generation of sparks on the stamp due to the strong electric field. In addition, this invention is not limited to the above embodiments,
For example, the number of excitation ports may be adjusted as necessary, and it is also possible to provide a partition plate in the heating chamber 4 to prevent steam or residue from the food to be cooked from entering each excitation port. , various modifications can be made without changing the gist.

As described above, according to the present invention, an orthogonal excitation port having a shape substantially orthogonal to the tube wall current direction is provided in the tube wall of the waveguide corresponding to the central portion of the heating chamber, and Since a parallel excitation port having a shape substantially parallel to the direction of the tube falling current is provided on the wall of the waveguide corresponding to the waveguide, it is possible to obtain a good temperature distribution state in the heating chamber according to the heat absorption characteristics of the object to be heated. This makes it possible to provide an excellent high-frequency heating device that can optimally heat the object without uneven heating.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is an external perspective view, FIG. 2 is a schematic diagram showing the inside, and FIG. 3 is a cross-sectional view taken along the line A-A' in FIG. 2. The configuration diagram as seen in the direction of the arrow, Figure 4 is a diagram showing the distribution of the high frequency heron magnetic field in the waveguide, Figure 5 is a diagram showing the flow of the wall current in the waveguide, Figures 6 and 7 are It is a figure which shows the result of investigating the temperature distribution state in a heating chamber by experiment. 4... Heating chamber, 6... Waveguide, 7...
...High frequency generator (magnetron), 7a...
...High frequency source (magnetron antenna), 10
a, 1ob, 10c, 10d, 10e, 10f...
Orthogonal excitation ports, 11a, 11b, 11c, 11d...
Parallel excitation port, 1...Tube wall current. Figure O 2 Prisoner 3 Crab Om Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. In a high-frequency heating device equipped with a waveguide that guides high-frequency waves emitted from a high-frequency generator to an upper part of a heating chamber, a bottom wall and a side wall of the waveguide corresponding to the center portion of the heating chamber Orthogonal excitation ports each having a shape substantially perpendicular to the tube wall electrode direction are provided, and parallel excitation ports each having a shape substantially parallel to the tube wall current direction are provided on the bottom wall and side wall of the waveguide corresponding to the central portion of the heating chamber. A high-frequency generator characterized in that excitation ports are provided and high-frequency waves are supplied into the heating chamber from these excitation ports. 2. The position of each of the excitation ports in the waveguide is located at a distance of n·λg/2 (n is an integer, and λg is the internal wavelength of the high frequency wave in the waveguide) from the high frequency source as the starting point. A high frequency heating device according to claim 1.