JPS645839Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The invention consists of a high-frequency attenuator provided on the door side of a microwave heating device, and a radio wave absorbing member provided on the main body side, a part of which functions as a resonator. This invention relates to an improvement in the radio wave leakage prevention structure of a microwave heating device that effectively prevents radio wave leakage by combining the following.

(Prior Art) Conventionally, Utility Model Publication No. 1555/1983 is known as a structure for preventing radio wave leakage from the door portion of a microwave heating device called a microwave oven. This means that the inner surface of the door that can be opened and closed at the opening of the heating chamber is brought into contact with the opening of the heating chamber when closed, and that an odd number multiple of λ/4 (λ: wavelength in air) is placed inside the door. A high-frequency attenuator is formed, and a frame-shaped radio wave absorber is provided on the heating chamber side facing the door side periphery. And this actual public school 51-
The configuration of No. 1555 attempts to attenuate radio waves that are about to leak from the high-frequency attenuator on the door side through the gap between the door and the opening of the heating chamber by transmitting them through the radio wave absorber. Therefore, the radio wave absorber portion does not have a structure that resonates with the microwaves generated by the magnetron of the microwave heating device.

(Problem that the invention aims to solve) By the way, recently, satellite broadcasting has been put into practical use, and the harmonic components (12G
Hz) has become a problem. Therefore, there is a need for effective radio wave leakage prevention measures that also take into account the prevention of leakage of harmonic components.

(Means for Solving the Problems) In view of the above points, the present invention provides a heating chamber with approximately λ/4 (λ: wavelength in air) inside the frame of the door that can be opened and closed with respect to the opening of the heating chamber. In addition to forming an odd-numbered high-frequency attenuator, a flat radio wave absorbing member is provided on the eave-like surface perpendicular to the opening end surface of the heating chamber and facing the side surface of the door, and a portion of the material absorbs the microwaves generated by the microwave heating device. On the other hand, by configuring a resonator that is an integral multiple of approximately λ'/2 (λ': the wavelength in the radio wave absorbing member), we aim to further improve the radio wave leakage prevention performance, and not only the fundamental wave but also the The object of the present invention is to provide a radio wave leakage prevention structure for a microwave heating device that is capable of improving performance against harmonics having short wavelengths that are close to integral multiples of the fundamental wave.

(Example) Hereinafter, an example of the radio wave leakage prevention structure of the microwave heating device according to the present invention will be described with reference to the drawings.

In the figure, 1 is a heating chamber of a microwave heating device, and a door 2 is provided to the front opening of the heating chamber 1 so as to be openable and closable. The periphery of the door 2 is a frame-shaped part 3
The frame-shaped portion 3 faces the opening end surface 4 of the heating chamber 1 at a minute interval. The space inside the frame portion 3 constitutes a high frequency attenuator 5 having an odd number multiple of λ/4 (λ: wavelength in air) of the fundamental wave of the magnetron of the microwave heating device.
The high-frequency attenuator 5 opens on the opening end surface 4 side of the heating chamber, and the high-frequency attenuator 5 Distance from the approximate center point B of the opening
L ₁ is also an odd multiple of λ/4, and the high-frequency attenuator 5 on the door side and the distance L ₁ between points A and B constitute a radio wave maze of λ/2 as a whole, that is, a chain attenuator. ing. In other words, the electric field at point A is set to be the maximum, and the electric field at point B is set to be maximum.

Further, an eave-like surface 9 that is perpendicular to the opening end surface 4 and facing the door side surface 8 is formed on the microwave heating apparatus main body side, that is, integrated with the heating chamber 1. A flat radio wave absorbing member 10 is arranged and fixed on this eave-like surface 9. Here, a radio wave leakage passage constituted by a gap between the door inner surface 7 and the opening end face 4 of the heating chamber, and a radio wave leakage passage constituted by a door side surface 8 orthogonal thereto and an eave-like surface 9 on the heating device main body side. When point C, which corresponds to the intersection (L _- shaped intersection) with The position of the flat radio wave absorbing member 10 is set so that it exists inside the flat radio wave absorbing member 10 . Here, the material of the radio wave absorbing member 10 is a mixture of ferrite powder, carbonyl iron powder, or both, and a resin or rubber, or a mixture thereof with carbon powder added thereto.

A portion of such a plate-shaped radio wave absorbing member 10 having a length L ₃ toward the exit direction of the radio wave leakage passage when viewed from point C preferably has a length of at least λ/4 or more, and when viewed from point C direction, that is, the length L ₄ in the depth direction recessed inside the opening end surface 4
The part is λ'/2 (λ': wavelength in the radio wave absorbing material)
The resonator structure has a length that is an integral multiple of .

Note that the thickness of the flat radio wave absorbing member 10 is 1
Approximately 4 mm to 4 mm is appropriate. In addition, the heating chamber surface 6,
The opening end surface 4 and the eaves-shaped surface 9 are made of a conductor such as a metal plate, and the door 2 is also made of a conductor such as a metal plate.

(Function of the embodiment) In the configuration of the above embodiment, a high frequency attenuator of an odd multiple of λ/4 is formed in the frame portion 3 of the door 2, and a contact point between the heating chamber inner surface 6 and the inner surface 7 of the door 2 is formed. Since the length _L1 of the radio wave leakage path from A to point B at the opening position of the high-frequency attenuator 5 is set to an odd multiple of λ/4 to form a so-called chiyoke attenuator, leakage radio waves toward point C are formed. can be significantly reduced. Furthermore, the corner part of the radio wave leakage path that is bent in an L shape on the extension of points A and B is set as point C where the electric field is minimum (that is, the magnetic field is maximum), and the flat radio wave absorbing member 10 is arranged at the point C. , by generating a standing wave of leakage radio waves by a resonator structure having an integral multiple of the portion λ'/2 of the length L ₄ of the flat radio wave absorbing member, and drawing the leakage radio waves into this portion and attenuating them. It is possible to reduce leakage radio waves from point C toward the exit of the radio wave leakage path between the door side surface 8 and the eaves-like surface 9 to the extent possible. Furthermore, the radio waves heading toward the exit are attenuated by transmission at a length L ₃ of the radio wave absorbing member 10, which has a length of λ/4 or more. As a result, the final leakage of radio waves can be suppressed as much as possible. Indeed, when considering the operation with respect to harmonic components of the magnetron of the microwave heating device, the length of the radio wave absorbing member 10 is
The portion of L ₄ that is an integer multiple of λ'/2 has the advantage that it can resonate with harmonics as well as the fundamental wave and provide sufficient attenuation. As a result, it is possible to achieve a good leakage prevention function even for harmonic components.

(Effect of the invention) As explained above, according to the radio wave leakage prevention structure of the microwave heating device of the invention, approximately λ/4
In addition to forming a high frequency attenuator that is an odd number multiple of (λ: wavelength in air), a flat radio wave absorbing member is provided on the eave-like surface perpendicular to the opening end surface of the heating chamber and facing the side surface of the door, and a part of the radio wave absorbing member is By configuring a resonator that is an integral multiple of approximately λ'/2 (λ: wavelength in the radio wave absorbing member) for the microwave generated by the microwave heating device, the radio wave leakage prevention performance is further improved. can be achieved.

[Brief explanation of the drawing]

The figure is a sectional view of an embodiment of the radio wave leakage prevention structure of the microwave heating device according to the present invention. 1... Heating chamber, 2... Door, 3... Frame-shaped part, 4...
...Opening end face, 5...High frequency attenuator, 9...Eave shaped surface, 10...Plate-shaped radio wave absorbing member.

Claims (1)

[Scope of utility model registration request] A door is provided at the opening of the heating chamber so that it can be opened and closed, and the inner surface of the door is opposed to the end surface of the opening of the heating chamber when the door is closed.
A high frequency attenuator having an odd multiple of approximately λ/4 (λ: wavelength in air) is formed inside the frame-shaped portion of the door, and an eave-like attenuator is formed perpendicular to the end surface of the opening of the heating chamber and facing the side surface of the door. A flat radio wave absorbing member is arranged on the surface, and the middle portion of the flat radio wave absorbing member is arranged at an electric field minimum position that is approximately an odd number times λ/4 away from the electric field maximum position which is the opening end of the high frequency attenuator. , the first portion of the radio wave absorbing member extending on the side opposite to the side surface of the door when viewed from the minimum electric field position has an arbitrary length, and the radio wave absorbing member extending on the opposite side of the first portion with respect to the minimum electric field position. A radio wave leakage prevention structure for a microwave heating device, characterized in that the second portion of the member is set to have a length that is an integral multiple of approximately λ'/2 (λ': wavelength within the radio wave absorbing member).