JPS6121836Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a microwave oven, and particularly to a microwave oven equipped with a door seal structure that prevents leakage of electromagnetic waves.

Microwave ovens are widely used in general households,
Various electromagnetic wave leakage countermeasures are taken to prevent electromagnetic waves emitted from the magnetron from leaking outside the heating chamber.

Figure 1 shows a conventional example of a door seal structure that prevents electromagnetic waves from leaking from a gap 3 between an oven wall 1 and a door 2 of a microwave oven. A branch path 6 is formed between the metal wall 5 and the metal wall 5 arranged and fixed in the cavity 4 . The total length of this branch path 6 is designed so that there is a path length difference of λ/2 with respect to the total length of the straight path from the branch point A to the confluence B of the gap 3.
Here, λ indicates the wavelength of electromagnetic waves emitted from the magnetron.

With this design, there will be a phase difference of 180° between the electromagnetic waves that go straight from point A to point B through gap 3 and the electromagnetic waves that arrive from point A through branch 6 and arrive at point B. Both electromagnetic waves cancel each other out, and the leakage waves disappear.

However, the above-mentioned cancellation phenomenon is caused by (2a+b)-(b)=2a=λ/2 for electromagnetic waves incident in a direction perpendicular to the axis XX of the metal wall 5 as illustrated in FIG. ...(1) is completely established, but for electromagnetic waves incident from the oblique direction θ with respect to the axis X-X, (2a+b)-c≠2a ...(2), so The phase difference of electromagnetic waves
There is an inconvenience that the angle deviates from 180° and uncancelled electromagnetic waves leak to the outside of the oven.

The present invention was devised to eliminate the above-mentioned disadvantages of the conventional apparatus. A contact piece is provided between the oven cavity and the oven wall, and at the rising part of this contact piece there is a channel that is divided into a branch path and a straight path. By providing a slit opening in the longitudinal space of the yoke cavity, a microwave oven is provided in which only electromagnetic waves having a direction component orthogonal to the aforementioned axis X-X are introduced into the yoke cavity and are canceled out and annihilated. This is what we are trying to provide.

The details of the present invention will be described below with reference to the embodiments shown in FIG. 3 and subsequent figures.

In FIG. 3, the front surface of an oven wall 1 forming a heating chamber 7 of a microwave oven is openably and closably closed by a door 2 provided with an inner barrier 2a, an outer barrier 2b, and a shielding screen 2c. A metal wall 5 in the shape of a hollow rectangular tube is disposed within a metal wall cavity 4 provided on the inner surface near the peripheral edge of the door, and is fixed by a holder 8 made of a dielectric material.

A contact piece 9 having an inclined rising portion 9a is arranged between the cheese cavity 4 and the oven wall 1, one end of which is fixed to the metal wall 5 via a holder 10 made of dielectric material, and the other end is fixed to the metal wall 5 via a holder 10 made of a dielectric material. The end is directly fixed to the entrance of the chiyoke cavity 4 by welding or the like.

As shown in FIG. 4, a plurality of narrow slits 9b are bored in the rising portion 9a of the contact piece 9 in parallel. These slits open in the longitudinal space of the choke cavity, which is divided into a branch path and a straight path, and allow electromagnetic waves S incident from a direction parallel to the length direction to pass through as they are, but electromagnetic waves incident from an oblique direction pass through them. It functions as an attenuator for T and blocks its transmission. Therefore, the electromagnetic waves after passing through these slits only have a component in the direction perpendicular to the axis X-X of the metal wall 5, and since equation (1) strictly holds, the confluence point B
The cancellation of the leakage electromagnetic waves is completed and the leakage electromagnetic waves disappear.

FIG. 5 shows a modification of the contact piece used in the present invention, in which a dielectric cover 11 is attached to the surface of the contact piece 9 to improve the appearance.

Further, FIG. 6 shows an example in which the dielectric material 12 is filled over almost the entire length of the branch path 6. In this way, the propagation speed υ of electromagnetic waves in the dielectric is expressed as υ = (μ・ε) ^-1/2 , where μ: magnetic permeability and ε: permittivity, so fill it with a dielectric material with a large permittivity. By doing so, it is possible to obtain the necessary phase difference even if the path length of the branch passage 6 is shortened, and it is possible to eliminate the disadvantage that the door becomes thick in order to obtain the necessary path length difference. Alternatively, as shown in FIG. 7, it is also possible to form the branch passage 6 into a V-shaped structure and easily form the choke cavity 4 and the metal wall 5 by drawing.

As described above, according to the present invention, the slit 9b provided in the contact piece 9 rectifies the electromagnetic waves just before branching into the branching path and the straight path. It is possible to prevent the path length difference of the electromagnetic waves that have passed from deviating from λ/2, and it is possible to reduce leakage electromagnetic waves due to the canceling effect of electromagnetic waves having a phase difference. In addition, by filling the branch path with a dielectric material having an appropriate dielectric constant, the apparent path length can be shortened, the thickness of the door can be reduced, or manufacturing costs can be reduced by adopting a V-shaped branch path. It becomes possible to aim at reduction.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the door seal structure of a conventional microwave oven, Fig. 2 is a diagram explaining its principle, Fig. 3 is a sectional view illustrating the door seal structure of the microwave oven of the present invention, and Fig. 4 5 is a perspective view showing one embodiment of the contact piece in the microwave oven of the present invention;
The figure is a perspective view showing another embodiment of the contact piece, FIG. 6 is a sectional view showing another embodiment of the door seal structure of the microwave oven of the present invention, and FIG. It is a sectional view showing a modification of a metal wall. 1...Oven wall, 2...Door, 3...Gap (straight path), 4...Cyoke cavity, 5...Metal wall, 6...Divergent path, 7...Heating chamber, 8...Holding Tool, 9...Contact piece, 9a...Rising portion, 9b...
slit, 10... holder, 11... dielectric cover, 12... dielectric material.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A metal chiyoke cavity is provided on the inner surface of the periphery of a door that can be opened and closed in the front side of the oven wall, and a branch path and a straight path are formed in this chiyoke cavity. In a microwave oven configured such that the path length difference is approximately λ/2 with respect to the wavelength λ of the electromagnetic wave, the electromagnetic wave leaking from the gap between the oven wall and the door is divided into the branch path and the straight path. A contact piece having a plurality of rectifying slits opening into the longitudinal space of the bit.
A microwave oven characterized by being installed between a chiyoke cavity and an oven wall. 2. The microwave oven according to claim 1 of the utility model registration, characterized in that a dielectric cover is provided on the surface of the contact piece. 3. The microwave oven according to claim 1 or 2, wherein a dielectric material is filled in a branch path formed in the cavity. 4. The microwave oven according to claim 3 of the utility model registration, characterized in that the branching path is V-shaped.