JPH0221541A - Manufacturing method of filter case for magnetron - Google Patents

Abstract

PURPOSE:To prevent the leakage of electromagnetic wave by providing eaves-shaped flange portion on the whole periphery of the aperture of a case, and the 1st recessed groove and the 2nd recessed groove on the whole periphery of the cover of the case. CONSTITUTION:A case 5 and the cover 10 of which are contacted to each other at the upper inside portion of the aperture of the case and the outer surface of the 1st recessed groove 10a on the cover, and at the three layers portion 12 consisting of the surface 5c of the flange portion provided on the upper end of the side wall of the case and the bottom surface and the outer side wall of the 2nd recessed groove 11 on the cover 10, and these two contact surfaces are nearly perpendicular to each other. Therefore the bending work of the outer side wall of the 2nd recessed groove 11 to the inner bottom side (to the rear surface side of the flange) or the pressing work to the three layers portion 12 have negligible effect to the side wall of the case, and the shield effect of the leading out portion of the feeder with a through capacitor can be suitably kept. In addition, at the three layers portion 12 the contact surfaces are two layers of the upper and the lower. Thereby the contact of the cover 10 to the case 5 at the engaging portion can be properly kept to improve the shield effect even for the 5th harmonic wave.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to a metal structure that houses a low-pass filter provided in contact with the outside of the cathode of a magnetron tube to supply power to the cathode while preventing leakage of microwaves. This invention relates to a sealing structure that prevents even the fifth harmonic of microwaves from leaking from the openings of both covers when the lid of a magnetron filter case consisting of a housing and a lid is placed over the housing.

[Prior Art] A magnetron used in a household microwave oven has a metal casing that houses a low-pass filter that is in contact with the outside of the cathode of the tube to supply power to the cathode while preventing leakage of microwaves. A filter case consisting of a lid is attached to the filter case, but in recent years regulations have required that even the fifth harmonic of microwaves be reliably shielded, so it is necessary to tightly seal the filter case housing and the cover of the lid. has become necessary.

[Problems to be Solved by the Invention] When attempting to obtain a satisfactory shielding effect by the filter case, a problem arises when a gap occurs at the fitting portion between the casing and the lid, especially a gap whose length exceeds a predetermined value. Therefore, by intermittently caulking the fitting part, it is possible to prevent a large gap from forming in the fitting part, but since the casing and lid are made of relatively thin metal plates, It is said that it is difficult to always obtain a satisfactory shielding effect because it is easy to warp or deform when pressure is applied from the outside, and also because the fitting part tends to loosen due to warping or deformation due to its own elasticity. There was an interlayer.

As a countermeasure to this problem, Japanese Utility Model Application Publication No. 62-88359 discloses that a concave groove having a U-shaped cross section that is inserted into the open edge of the casing and bent in a zigzag shape together with the open edge is provided on the outer peripheral edge of the lid. It is stated that the following shall be provided. However, if this is done, the edge of the opening of the metal casing that connects to the side surface on which the feedthrough capacitor is mounted is also bent in a zigzag manner, so that the part where the feedthrough capacitor is mounted is affected by this bending and becomes uneven.

A problem arises in that a gap is created between the feedthrough capacitor and the chassis plate (earth plate), and as a result, it is difficult to always obtain a satisfactory shielding effect.

The present invention does not have the problems of the above-mentioned conventional countermeasure techniques, and
It is an object of the present invention to provide a filter case that has high adhesion between the peripheral edge of the housing opening of the filter case and the cover eyelid part of the lid, and has a sufficiently good microwave shielding effect even against the fifth harmonic. .

[Means for Solving the Problems] In order to achieve the above object, in the present invention, an eave-shaped portion extending outward at a substantially right angle is provided on the entire periphery of the opening of the casing, and the outside of the groove is provided on the entire periphery of the lid. A first concave groove whose wall surface fits and contacts the inner surface of the upper end of the entire periphery of the casing opening, and the outer wall is shared as the inner wall of the husband itself, and the eaves-shaped portion on the periphery of the casing contacts the bottom surface of the groove. After the lid is placed over the opening of the casing in the manner described above, the outer wall of the second groove is inserted at a substantially right angle to the inner bottom side. It was decided to form a three-layer laminated part by bending it into contact with the back surface of the eave-like part of the casing, and sandwiching the eave-like part together with the bottom surface at the bent part.

In order to further improve the adhesion between the layers of this three-layer laminated part,
Even better results can be obtained if pressure is applied perpendicularly to the laminated surface of the three-layer laminated portion to bend the laminated portion in a wave-like manner along the periphery of the housing.

[Function] If the above-mentioned measures are taken, the casing and the lid will be connected to the upper end of the opening side wall of the casing and the outer wall surface of the first groove of the lid, and the projecting surface of the upper end of the casing side wall and the first groove of the lid. The bottom surface of the second groove contacts the three-layer stacked part formed by the outer surface, and these two contact surfaces are approximately orthogonal to each other, so the inner bottom surface side of the outer surface of the second groove (the projecting surface of the casing) The influence of the bending work to the rear surface side) and the pressurizing work to the three-layer laminated portion hardly spread to the side wall surface of the case, and the shielding state of the feeder lead-out portion by the one-through capacitor is maintained well. Moreover, in the 3M laminated part, the contact surfaces are double layered on the upper and lower sides. Therefore, the close contact between the lid and the housing of the filter case according to the present invention is extremely good, and the shielding effect is naturally good.

[Embodiment] FIG. 2 is a cross-sectional view of an embodiment of the present invention before the cover is placed on the casing, when each of them stands alone (however, the casing is fixed to the magnetron main body). Cathode side magnetic pole part 2 of magnetron 1
One end of the annular permanent magnet 3 stacked on top is magnetically coupled to the magnetic pole part 2, and the other end is coupled to the other magnetic pole part of the magnetron 1 via a frame-shaped yoke 4. A stem portion 6 (cathode terminal side metal sealing member 6a and cathode side insulator 6b), which is a cathode terminal lead-out portion of the magnetron 1, and a chain are contained in a metal casing 5 fixed on the outer end surface of the frame-shaped yoke 4. A choke coil 8 having one end connected to the cathode terminal 7 of the section is housed. Further, a feedthrough capacitor 9 is provided on the side surface 5a of the housing 5.
The chassis plate 9a of the capacitor and the side surface 5a are fixed by eyelets.

A choke coil 8 is connected to the through conductor of this feedthrough capacitor 9.
the other end is connected. The open end of the casing 5 is bent outward and terminated (terminal end or overhang 5
c).

On the other hand, a metal lid 10 that covers the opening of the housing 5 has a first groove 10a having a U-shaped cross section on its outer periphery, and further has an outer surface 10d of the first groove. A second groove 11 serving as an inner surface is provided on the outside of the first groove, and in the final stage of assembling the magnetron, the opening end protrusion 5c of the casing 5 and a part of the side surface 5a are covered. 10 second grooves 11. After that, the housing 5 with the outer surface 10b of the groove 11 inserted into the groove 11
The projecting portion 5C is bent so as to contact the back surface of the projecting portion 5c, and the projecting portion 5C is connected to the bottom surface 10c of the groove 11 and the outer surface 10.
b to form the three-layer uAf section 12 shown in FIG. FIG. 1 is a diagram showing a state in which a filter element and the like housed inside have been removed for the sake of simplicity, a lid 10 has been placed on the housing 5, and the lid 10 has been brought into close contact with the lid 10 as in the experiment. When bending the outer surface 10b of the second groove 11, creases tend to occur at the four corners of H due to excess meat at the ends of the outer surface 10b. It is necessary to consider the processing jig so that there are no large and long gaps between the parts. However, although a mild steel plate is normally used as the material metal, it is a well-known and easy-to-process material, so such processing is not difficult as long as care is taken.

In order to improve the state of close contact between each surface of the three-layer laminated portion 12, pressure is applied by sandwiching the laminated portion from a direction perpendicular to the laminated surfaces with corrugated tools that engage with each other, and the laminated portion is moved along the periphery of the casing as shown in FIG. 1a. If the layers are bent in a wave-like manner as shown in FIG. 1, even if gaps are formed, contact portions are reliably formed at short intervals, so that a good shielding effect can be reliably obtained.

[Effects of the Invention] As explained above, according to the present invention, the side surface of the casing of the filter case is not deformed, and a long and wide gap does not occur at the fitting part of the casing and lid. Therefore, leakage of electromagnetic waves can be suppressed even after long-term use, and a good shielding effect can be obtained while using a relatively thin metal plate material. Furthermore, since the side surface of the casing is not deformed, the state in which the chassis plate of the feedthrough capacitor is in close contact with the casing side surface is not impaired, and mass productivity is improved.

[Brief explanation of the drawing]

Figure 1 shows a state in which the lid is placed on the housing and the cover is in close contact with the cover, and Figure 1a is a diagram showing the state in which the three-layer laminated portion at the end of the housing and the lid is bent into a waveform to further improve the close contact. FIG. 2, which shows an improved state, is a partially sectional view of an embodiment of the present invention. 1... Magnetron, 5... Housing, 5c... Housing opening end overhang, 8... Choke coil. DESCRIPTION OF SYMBOLS 10... Lid, 10a... 1st groove, 11... 2nd 1 Figure 1c

Claims (1)

[Claims] 1. A filter case for a magnetron consisting of a metal casing and a lid that houses a low-pass filter provided in contact with the outside of the cathode of a magnetron tube to supply power to the cathode while preventing leakage of microwaves. A first recessed groove is provided on the entire periphery of the casing opening extending outward at a substantially right angle, and on the entire periphery of the lid, the outer wall surface of the groove is fitted into contact with the inner surface of the upper end of the entire periphery of the casing opening. , a second recessed groove that shares the outer wall as the inner wall of the husband itself and is inserted and fitted until the eave-shaped portion on the periphery of the housing contacts the bottom surface of the groove, and the lid is placed in the opening of the housing. After covering the periphery as shown above,
The outer wall of the second groove is bent inward at a substantially right angle toward the bottom surface, and brought into contact with the back surface of the eave-like portion of the housing, and the three-layer laminated portion sandwiching the eaves-like portion together with the bottom surface at the bent portion. A filter case for a magnetron characterized by a formed structure. Claim 1, in which pressure is applied perpendicularly to the laminated surface of the two- or three-layer laminated portion to bend the laminated portion in a wavy manner along the periphery of the housing.
Filter case for magnetron described in section.