JPH09171776A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the magnetron which does not depend on each joint where a shield case shielding the side of a cathode terminal and a shield case lid are over lapped each other so as to be only caulked, but surely makes joints electrically by working parts, and thereby can surely prevent noise from leaking. SOLUTION: The magnetron is so constituted that a filter is connected with the cathode terminal of a magnetron main body 11, and the filter and the portion of the cathode terminal are covered with a shield case 1 and a shield case closure 2. In this case, the shield case 1 is joined to the shield case closure 2 by caulking bar rings 1a provided for the end part of the shield case 1, and concurrently the portion of a through hole 1b formed by the bar rings 1a at the end part of the shield case 1 is blocked by the folding part of the shield case closure 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron used for microwave heating equipment such as a microwave oven and radar. More specifically, the present invention relates to a magnetron in which a filter is provided on the cathode terminal side in order to suppress noise generated during operation of the magnetron, and the filter portion is covered by a shield case to reduce noise.

[0002]

2. Description of the Related Art In a magnetron, a microwave having a predetermined oscillation frequency (fundamental wave), for example, 2450 MHz is oscillated and taken out from an output antenna. In addition to the microwave having a predetermined frequency, a microwave of several hundred kHz to several tens GHz is used. Noise is generated and leaks from the cathode terminal. When this noise leaks from the magnetron, it leaks as it is from the microwave oven and the like using the magnetron, which interferes with reception of radio, television, satellite communications, and the like. Therefore, in order to prevent these noises, a filter composed of a capacitor and a choke coil (not shown) is provided on the cathode terminal side to cut off the noise on the line,
As shown in (a) and (b), noise radiated in the air covered by the shield case 1 and the shield case lid 2 is prevented from leaking to the outside. In addition,
In FIG. 5, 11 is a magnetron body which is a vacuum tube portion in which a cathode and an anode are concentrically arranged inside, 12 is an output portion thereof, 13 is a magnet provided on each of an input side and an output side, and 14 is its A yoke forming a magnetic path, 15
Is a cooling fin attached to the outer periphery of the anode shell.

Inside the main body of the magnetron, particularly harmonics, which are integral multiples of the fundamental wave, are easily generated. Of the harmonics, the 5th harmonic (5 times the fundamental wave 2450 MHz, 1
2.25 GHz) also matches the frequency band of satellite broadcasting,
There is a demand for noise suppression, and regulations are becoming more stringent, especially in Europe.

As a conventional noise suppressing means, as described above, the filter connected to the cathode terminal prevents noise on the low frequency side, and the shield case 1 prevents the noise of high frequency radiated from the cathode terminal. It also prevents leakage. Therefore, the shield case 1 and the shield case lid 2 are also joined together so as to prevent unnecessary radio waves from leaking.

A conventional method of joining the shield case 1 and the shield case lid 2 is, for example, as shown in FIG. 5B, a flange portion 1c is provided at an end of the shield case 1 and the flange portion 1c is used as the shield case. The cover 2 covers the entire circumference so as to be covered by the tip of the lid 2, and the shield case 1
The end and the end of the shield case lid 2 are caulked intermittently over the entire circumference by a large number of grooves 4 (see FIG. 5A) to crimp.

[0006]

As described above, the conventional shield case and the shield case lid are joined by overlapping the shield case and the shield case lid and intermittently crimping only by pressure welding. That is, no processing is performed on the parts, and the parts are superposed on each other and rely only on the pressure contact force due to the shape of the caulking jig. Therefore, the parts are inexpensive, but the caulking strength varies due to dimensional tolerances of the parts and variations in the plate thickness of the parts. Further, the jig shape is deformed due to the wear of the jig, and the caulking strength is changed. As a result, the joining force of the caulked portion decreases depending on the location. Also, both the shield case and the shield case lid are easily deformed because they are made of thin steel such as about 0.4 mm, and if they are joined only by caulking, the elastic force (springback) and external pressure of the material itself after caulking. Deformation may occur due to factors such as gaps.

Joining by simply stacking and caulking is
Since many of these unstable elements are held, stable electrical connection between them cannot be obtained. As a result, there is a problem that a long gap is formed in front of and behind the place where the caulking is insufficient, the electromagnetic waves of unnecessary radiation leak, and it interferes with other electronic devices as noise.

The present invention solves such a problem and does not rely on the joining of the shield case and the shield case lid for shielding the cathode terminal side only by superposing and caulking them, but by reliably processing the parts, the electric It is an object of the present invention to provide a magnetron that can be securely joined to prevent noise leakage.

[0009]

A magnetron according to the present invention is a magnetron in which a filter is connected to a cathode terminal of a magnetron body, and a portion of the filter and the cathode terminal is covered by a shield case and a shield case lid. The shield case and the shield case lid are joined by caulking a burring provided at an end portion of the shield case, and a through hole portion of the shield case end portion by the burring is a folded portion of the shield case lid. Is blocked by.

Even if the burring is a piercing burring, the same effect is obtained, and the burring formation cost is low, which is preferable.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the magnetron of the present invention will be described with reference to the drawings.

FIG. 1 is a side view of a magnetron of the present invention, FIGS. 2 and 3 are enlarged explanatory views and enlarged sectional explanatory views of a burring caulking portion between a shield case and a shield case lid, and FIG. 4 is a burring caulking portion. It is explanatory drawing of other forms.

The magnetron of the present invention has the same structure as the conventional magnetron with respect to the magnetron body which is the vacuum tube part and the filter part connected to the cathode terminal, and the description thereof will be omitted. 1 to 4, the same parts as those in FIG. 5 are designated by the same reference numerals. The present invention is characterized by the structure of the joint portion between the shield case 1 and the shield case lid 2 that shields the cathode terminal of the magnetron body 11 and the filter portion connected to the cathode terminal.

The shield case 1 of the present invention is provided with a burring 1a on its end side, as shown in FIGS. The burring 1a is, as shown in FIG.
The shield case lid 2 is a protrusion that has a through hole 1b in the central portion integrally formed at the end of the side wall of the shield case 1.
After the cutout portion 2a of the tip portion is inserted around the projection portion, the tip of the projection portion can be fixed by being caulked to the outside. Therefore, the tip of the shield case lid 2 is provided with a cut 2a for escaping the burring 1a of the shield case 1. This cut 2a is
They are provided at the same pitch as the pitch of the burring 1a, and these pitches are formed to have a size of ¼ or less of the wavelength of the electromagnetic wave for which leakage is to be suppressed, as will be described later. The burring 1a is formed by forming a box body of the shield case 1 by drawing and then moving a plurality of punches laterally from the inside of the box body to the outside. The burring 1a can be easily formed by forming the burring 1a in the state of the plate material, punching out four side surface portions of the shield case 1, and then bending the side surface portions to form a box body by welding etc. The case 1 can be formed.

Further, as shown in the sectional view of FIG. 3, the tip portion of the shield case lid 2 is formed with a folded portion 2b so as to be in close contact with the inside of the shield case 1. The depth H at which the folded portion 2b is folded back is equal to the burring 1a.
The shield case lid 2 is formed to have a depth that closes the through-hole 1b. Further, when the flange portion 1c is formed at the end portion of the shield case 1, the recess 2c is formed at the tip portion of the shield case lid 2 so as to cover the flange portion 1c.

In order to assemble a magnetron using the shield case 1 and the shield case lid 2 formed in this way, after mounting a choke coil and a capacitor constituting a filter inside the shield case 1, the shield case lid 2 is attached. Cover. At this time, the burring 1a of the shield case 1 is fitted into the notch 2a of the shield case lid 2 for assembly. After that, one of the jigs (punch) is applied to the folded-back portion 2b of the shield case lid 2 and the burring 1a is crushed so that the shield case 1 and the shield case lid 2 are securely electrically connected and fixed (FIG. 3).
reference).

The burring 1a formed at the end of the shield case 1 has, for example, an outer diameter of about 3 to 5 mm, a through hole at the center of about 2 to 4 mm, and a height of about 2 to 4 mm. It is formed continuously over the entire circumference of the end portion at intervals. Also, the distance between the burrings 1a should be set to 1/4 or less of the wavelength of the electromagnetic wave that is intended to prevent leakage, even if there is a gap between the shield case 1 and the shield case lid 2 during caulking, that electromagnetic wave It is preferable because leakage can be prevented. Specifically, in current magnetrons for microwave ovens, electromagnetic wave leakage of 12.25 GHz, which is the fifth harmonic, is strictly regulated as noise of high frequency. It is preferable that the interval be 6 mm or less.

Since the shield case 1 and the shield case lid 2 of the present invention are joined by caulking the burring 1a provided at the end of the shield case 1 as described above, the caulking portion is There is no peeling and a large gap of 1/4 wavelength or more does not occur, and electrical connection is ensured over the entire circumference, and leakage of unnecessary radio waves is suppressed. Further, in the present invention, since the through hole 1b portion of the burring 1a is closed by a part of the shield case lid 2, leakage of unnecessary radio waves is prevented more reliably. That is, the diameter of the through hole 1b of the burring 1a is about 3 mm, and 12.25 of the 5th harmonic wave, which is a problem of electromagnetic wave leakage, is a problem.
Compared with the 1/4 wavelength of GHz, there is little electromagnetic wave leakage, but a slight electromagnetic wave leakage can occur even in a small gap, and the burring 1a is continuously provided and the phase of the electromagnetic wave in each through hole 1b is increased. It is possible to completely prevent the possibility that electromagnetic waves may leak when a continuous flow occurs and electromagnetic waves may leak.

As described above, the burring 1a has a shape in which the through hole 1b is preliminarily formed in the central portion and then the projection is formed, and the tip of the projection is aligned at a constant height. The burring 1a is for fixing the shield case lid 2 by crushing the tip thereof, and does not necessarily have a clean shape. Therefore, as shown in FIG. 4, the piercing burring 1d in which the tip end of the protrusion is jagged may be formed by crimping while forming the protrusion without forming the through hole 1b in advance. Further, a burring in which the tip is closed like a bag without the through hole being formed may be used.

[0020]

As described above, according to the present invention, since the shield case for shielding the cathode terminal side and the shield case lid are connected by caulking the burring, the dimensional variation and deformation of each component are caused. Does not become a problem, and the connection can be ensured, and a gap of a predetermined value or more does not occur due to the elastic force after caulking or the pressure from the outside. Further, since the through hole portion of the burring is closed by the folded portion of the shield case lid, electromagnetic wave leakage from the through hole cannot occur at all. As a result, leakage of high-frequency electromagnetic waves such as harmonics of the fundamental wave can be suppressed, and a low noise magnetron can be obtained.

Further, since the shield case lid is fixed by being sandwiched by caulking the burring, stable fixing can be obtained, the fixing does not loosen even when used for a long time, and the electromagnetic wave leakage is prevented. The reliability is greatly improved.

[Brief description of the drawings]

FIG. 1 is a side view illustrating an embodiment of a magnetron of the present invention.

FIG. 2 is a side view for explaining the caulking portion of the shield case and the shield case lid of FIG.

3 is a cross-sectional explanatory view of a caulking portion of the shield case and the shield case lid of FIG.

FIG. 4 is a side view of a caulking portion of another embodiment of the magnetron of the present invention.

FIG. 5 is a side view of a conventional magnetron.

[Explanation of symbols]

 1 shield case 1a burring 1b through hole 1d piercing burring 2 shield case lid 2a notch 2b folded part 11 magnetron body

Claims (2)

[Claims] 1. A magnetron in which a filter is connected to a cathode terminal of a magnetron body, and a portion of the filter and the cathode terminal is covered by a shield case and a shield case lid, wherein the shield case and the shield case lid include: A magnetron that is joined by caulking a burring provided at the end of the shield case, and a through hole portion of the end of the shield case due to the burring is closed by a folded portion of the shield case lid. 2. The magnetron according to claim 1, wherein the burring is a piercing burring.