JP2003077401A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent discharge generated between a junction part of a stem insulating body with a cylindrical metal container and cathode leads. SOLUTION: A cathode 13 with a filament 14 arranged at a center axis part of an anode 18 is supported by a pair of cathode leads 17, a pair of magnetic pole pieces 19 with a through-hole 19a formed at around the center are arranged at both ends of the anode 8, an opening 24b at one end of a cylindrical metal container 24 is joined airtightly with a junction face formed at a stem insulating body 21, a circular brim part 24c set in extension at the side of the cathode leads 17 is formed at the opening 24b, and a bottom face 26a of the stem insulating body 21 is to be covered with the brim part 24c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron mounted on a microwave oven or the like for generating microwaves.

[0002]

2. Description of the Related Art The cathode part of a conventional magnetron for a microwave oven is disclosed, for example, in Japanese Examined Patent Publication No. 7-62979 (H0).
1J 23/14, H01J 9/24, H01J
23/12), both ends of a filament made of thorium tungsten are fixed to a pair of end hats, and a cathode lead made of molybdenum (Mo) is fixed to the end hats. . These cathode leads are extended to the outside through the through holes of the stem insulator, and on the metallized surface of the outer periphery of the stem insulator, a cylindrical metal container fixed to one end of the anode is formed by a brazing material or the like. It is brazed. A pair of magnetic pole pieces having a through hole formed in the central portion is arranged at both ends of the anode to guide the magnetic force of a magnet (not shown) to the vicinity of the filament.

In the magnetron having such a structure, the cylindrical metal container which is integrally joined to the anode is generally set to the ground potential, while the cathode composed of the filament and the cathode lead has a negative voltage of, for example, 4 kV. Applying a voltage to apply a magnetic field to the cathode shaft,
When an electric current is applied to emit electrons from the filament, the electrons swirl, and the swirling electrons oscillate in synchronization with the high-frequency electric field of the anode to emit microwaves. During this oscillating operation, metal substances such as thorium and tungsten are evaporated from the surface of the filament.Thus, these metal substances pass through the through holes of the pole pieces and adhere to the bottom surface of the stem insulator, causing a tubular metal The insulation resistance between the joint surface of the container and the cathode lead was gradually lowered.

In a microwave oven using a leakage transformer, when the power is turned on without preheating the filament, a no-load voltage of 8 to 10 kV is applied to the magnetron at an initial stage where electrons are not emitted from the filament. If the insulation resistance between the joint surface of the cylindrical metal container and the cathode lead is reduced, discharge will occur between the joint surface of the cylindrical metal container and the cathode lead through the bottom surface of the stem insulator, and surge voltage will be generated. There was a problem of inducing and destroying high voltage parts.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetron capable of reliably preventing a discharge generated between a joint portion of a cylindrical metal container of a stem insulator and a cathode lead.

[0006]

According to the present invention, a cylindrical metal container whose one end opening is hermetically joined to an anode to form a part of a vacuum container, and a through hole is formed at both ends of the anode and substantially in the center. A magnetron having a pair of magnetic pole pieces, a pair of cathode leads supporting a cathode having a filament disposed on the central axis of the anode, and a stem insulator having a through hole through which the cathode lead penetrates. There, the other end opening of the cylindrical metal container is airtightly joined to the joining surface formed around the stem insulator, and the other end opening has a circumferential shape extending toward the cathode lead side. It is characterized in that the collar portion is formed.

With the above structure, when a negative voltage, for example, a high voltage of 4 kV is applied to the cathode, a magnetic field is applied to the cathode shaft, and further, a current is supplied to emit electrons from the filament, the electrons are swirled. , The swirling electrons oscillate in synchronization with the high frequency electric field of the anode, and microwaves are emitted.

During the oscillation operation, even if a metal material such as thorium or tungsten, which is a raw material component of the filament, evaporates from the surface of the filament,
Since the bottom surface of the stem insulator is covered by the collar portion, it becomes difficult for metal objects such as thorium and tungsten to adhere to the bottom surface, and the insulation resistance between the joint surface of the tubular metal container and the cathode lead is reduced. The decrease can be suppressed. Therefore, in the initial stage where electrons are not emitted from the cathode, even if a no-load voltage of 8 to 10 kV is applied to the cathode, the discharge generated between the joint surface of the cylindrical metal container and the cathode lead is prevented. can do.

Further, since the inner peripheral edge portion of the collar portion is located inside the through hole of the magnetic pole piece,
Even if a metal substance such as thorium or tungsten that evaporates from the surface of the filament penetrates through the through hole of the pole piece, the collar portion protrudes inside the central hole of the pole piece and the bottom surface of the stem insulator is exposed. Since the metal object does not adhere to at least the bottom surface outside the through hole, the discharge can be prevented between the joining surface of the cylindrical metal container and the cathode lead.

Further, the stem insulator is characterized in that a recess is formed between the joint surface and the cathode lead, so that the creepage distance between the joint surface of the cylindrical metal container and the cathode lead is reduced. Insulation resistance increases due to longer length,
It is possible to prevent discharge that occurs between the joining surface of the cylindrical metal container and the cathode lead.

Further, a cylindrical metal container whose one end opening is airtightly joined to the anode to form a part of a vacuum container, and a pair of magnetic pole pieces arranged at both ends of the anode and having a through hole formed substantially in the center, A magnetron comprising a pair of cathode leads for supporting a cathode in which a filament is arranged on a central axis portion of the anode, and a stem insulator having a through hole through which the cathode lead penetrates. The other end opening is airtightly joined to the joint surface formed around the stem insulator, and a recess is formed between the joint surface and the cathode lead, and the other end opening of the cylindrical metal container is formed. A bent portion that intervenes in the recess is formed.

With the above structure, even if a metal such as thorium or tungsten evaporates from the surface of the filament, the bent portion covers the wall surface of the recess, so that the wall is covered with the metal material such as thorium or tungsten. It becomes difficult to adhere and it is possible to suppress a decrease in insulation resistance between the joint surface of the cylindrical metal container and the cathode lead. Therefore, in the initial stage where electrons are not emitted from the cathode,
Even when a no-load voltage of 8 to 10 kV is applied to the cathode, it is possible to prevent discharge that occurs between the joint surface of the cylindrical metal container and the cathode lead.

Further, since the bent portion is close to the bottom surface of the recess, the bent portion covers the entire wall surface of the recess, and metal objects do not adhere to the wall surface. It is possible to reliably prevent discharge that occurs between the joining surface of the cylindrical metal container and the cathode lead.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Regarding the first embodiment of the present invention,
It will be described in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view of an essential part of a magnetron showing a first embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the essential part, FIG. 3 is a lateral view of the essential part, and FIG. FIG. 5 is a top view of the stem insulator, and FIG. 5 is a view showing another embodiment of the stem insulator.

Reference numeral 1 is a magnetron body which is a bipolar vacuum tube covered with a yoke 2 and a radiation fin 3.

Reference numeral 4 is a capacitor 5 for suppressing noise.
And the case where the choke coil 6 is built in.
A lid 7 is attached in close contact with the opening so that noise does not leak outside.

Reference numeral 8 denotes a magnetron anode, which is made of oxygen-free copper and constitutes an anode cylinder 9 which constitutes a part of the vacuum wall of the main body 1, and which is radially formed on the inner circumference of the anode cylinder 9. An even number of vanes 10 are provided, and every other one of the vanes 10 is connected by a small diameter (inner) inner strap ring 11 and a large diameter (outer) outer strap ring 12 to oscillate in a stable π mode. Is configured.

Reference numeral 13 denotes a cathode in which both ends of a filament 14 formed of about 1% thorium and the rest of tungsten are sandwiched by a top hat 15 and an end hat 16, and the cathode 13 has a pair of cathode leads 17.
Supported by.

Reference numeral 18 is an annular permanent magnet disposed above and below the anode 8.

Reference numeral 19 denotes a magnetic pole piece having a through hole 19a formed in the center thereof. The magnetic pole piece 19 is arranged below the permanent magnet 18, and the tip of the vane 10 and the cathode 13 are arranged.
The magnetic field of the permanent magnet 18 is concentrated in the working space between and.

Reference numeral 20 is an external terminal made of a metal alloy or the like,
The external terminal 20 is inserted through the cathode lead 17,
It is airtightly joined to a stem insulator 21, which will be described later, by brazing, and thermoelectrons are emitted from the filament 14 by feeding power from the external terminal 20. Since the temperature of the filament 14 at this time is as high as about 1800 ° C., metal substances such as thorium and tungsten are evaporated from the surface of the filament 14 during operation.

Reference numeral 21 is a high heat resistant stem insulator made of alumina ceramic or the like, and the cathode lead 17 is inserted into a pair of through holes 21a formed in the stem insulator.

Reference numeral 21b denotes a notched portion formed in an inclined shape on the edge portion of the stem insulator 21, and the notch portion 21b is detected by a detection sensor 22 so that the external terminal 20 is positioned. There is. With this configuration, the external terminal 20 can be positioned in a non-contact manner. Therefore, in the case of trouble, an abnormal force is applied to the external terminal 20 to cause the external terminal 20 to contact the external terminal for positioning. Since the terminal 20 is not deformed, it is possible to reliably supply power to the external terminal 20. Further, in order to be detected by the detection sensor 22, the notch 21
In addition to the structure of b, the groove 23 may be formed in the edge portion of the stem insulator 21 as shown in FIG.

In the reference numeral 24, one end opening 24a is joined to the anode 8 and the other end opening 24b is connected to the stem insulator 21.
It is a tubular metal container that is joined by brazing to the joining surface 25 formed on the periphery of and is hermetically joined. And
At the other end opening portion 24b, a circumferential flange portion 24c extending toward the cathode lead 17 side is formed.
The inner peripheral edge portion of 4c is made to project inward from the through hole 19a of the magnetic pole piece 19. With this configuration, even if a metal substance such as thorium or tungsten evaporates from the surface of the filament 14 and enters from the through hole 19a, the collar portion 24c covers the bottom surface 26a of the recess 26 described later, A metal substance such as thorium or tungsten is unlikely to adhere to the bottom surface 26a, so that a decrease in insulation resistance is suppressed.

Reference numeral 26 is a joining surface 2 of the cylindrical metal container 24.
5 is a circular concave portion formed between the cathode lead 17 and the cathode lead 17, and the concave portion 26 increases the creepage distance between the joining surface 25 of the cylindrical metal container 24 and the cathode lead 17, The discharge generated between the joint surface 25 of the metal container 24 and the cathode lead 17 can be suppressed.

With the above-described structure, when a negative voltage, for example, a high voltage of 4 kV is applied to the cathode 13 and power is supplied from the external terminal 20 so that a current of about 10 A flows to the filament 14, the permanent magnet Electrons emitted from the filament 14 are swirled by the magnetic field from 18, and the swirling electrons oscillate in synchronization with the high frequency electric field of the anode 8 to emit microwaves.

Even if a metal substance such as thorium or tungsten evaporates from the surface of the filament 14 during operation, since the flange portion 24c covers the bottom surface 26a of the stem insulator 21, the bottom surface 26a It becomes difficult for metal objects such as thorium and tungsten to adhere to the joint surface 25 of the cylindrical metal container 24 and the cathode lead 17.
It is possible to suppress a decrease in insulation resistance between them. Therefore,
In the initial stage in which electrons are not emitted from the cathode 13, even if a no-load voltage of 8 to 10 kV is applied to the cathode 13, the joining surface 25 of the cylindrical metal container 24 and the cathode lead 17 through the bottom surface 26a. It is possible to prevent the electric discharge that occurs between and.

Further, even if a metal substance such as thorium or tungsten that evaporates from the surface of the filament 14 enters through the through hole 19a of the magnetic pole piece 19, the collar portion 24
Since the inner peripheral edge of c projects to the inside of the through hole 19a and covers the bottom surface 21a of the stem insulator 21, at least the bottom surface 21a outside the through hole 19a is prevented from adhering a metal object, The cylindrical metal container 24
It is possible to prevent the discharge generated between the joint surface 25 and the cathode lead 17.

Further, the stem insulator 20 has the recess 26 between the joint surface 25 and the cathode lead 17.
Is formed, the creepage distance between the joint surface 25 of the cylindrical metal container 24 and the cathode lead 17 is increased, and the insulation resistance is increased, so that the joint surface 25 of the cylindrical metal container 24 is increased.
It is possible to more reliably prevent discharge that occurs between the cathode lead 17 and the cathode lead 17.

Next, a second embodiment of the present invention will be described with reference to the drawings. The same components as those in the first embodiment described above are designated by the same reference numerals and the description thereof will be omitted.

FIG. 6 is a vertical cross-sectional view of the essential parts of the second embodiment of the present invention.

Reference numeral 27 denotes one end opening portion 27a joined to the anode 8 and the other end opening portion 27b for the stem insulator 21.
It is a tubular metal container that is joined by brazing to the joining surface 25 formed on the periphery of and is hermetically joined.

27c is formed on the cylindrical metal container 27 and extends from the other end opening 27b to the bottom surface 26 of the recess 26.
The bent portion 27c is a bent portion that is bent close to a.
Are formed so as to cover the entire wall surface 26b of the recess 26. With this configuration, even if a metal substance such as thorium or tungsten evaporates from the surface of the filament 14, the bent portion 27c has the wall surface 26b of the recess 26.
Since it covers the entire surface, no metal such as thorium or tungsten adheres to the wall surface 26b, so that the insulation resistance between the joint surface 25 of the cylindrical metal container 27 and the cathode lead 17 can be prevented from lowering. ing.

With the above structure, even when a metal substance such as thorium or tungsten evaporates from the surface of the filament 14 during operation, the bent portion 27c has the concave portion 26c.
Since it covers the wall surface 26b, it becomes difficult for metal objects such as thorium and tungsten to adhere to the wall surface 26b, and a decrease in insulation resistance can be suppressed. Therefore, in the initial stage where electrons are not emitted from the cathode 13,
Even if a no-load voltage of 8 to 10 kV is applied to the cathode 13, it is possible to prevent discharge that occurs between the joint surface 25 of the cylindrical metal container 27 and the cathode lead 17.

Further, since the bent portion 27c is close to the bottom surface 26a of the recess 26, the entire wall surface 26b of the recess 26 is covered with the bent portion 27c.
It is possible to prevent a metal substance from adhering to the wall surface 26b, and it is possible to reliably prevent a discharge generated between the joining surface 25 of the cylindrical metal container 27 and the cathode lead 17.

[0037]

According to the first aspect of the present invention, a pair of magnetic pole pieces arranged at both ends of the anode and having a through hole formed substantially in the center, and a cathode having a filament arranged on the central axis portion of the anode are supported. A pair of cathode leads and a stem insulator formed with a through hole through which the cathode lead penetrates, and the other end opening of the cylindrical metal container is hermetically sealed to a joint surface formed around the stem insulator. Since a circumferential flange extending toward the cathode lead side is formed at the other end opening of the filament, even if a metal substance such as thorium or tungsten evaporates from the surface of the filament, the stem insulation The bottom surface of the body is covered with the brim portion, and it becomes difficult for metal objects such as thorium and tungsten to adhere to the bottom surface, and a decrease in insulation resistance is suppressed. Therefore, in the initial stage where electrons are not emitted from the cathode, even if a no-load voltage of 8 to 10 kV is applied to the cathode, the discharge generated between the joint surface of the cylindrical metal container and the cathode lead is prevented. There are effects such as being able to.

According to the second aspect of the present invention, since the inner peripheral edge portion of the collar portion is located inside the through hole of the magnetic pole piece, metal substances such as thorium and tungsten that evaporate from the surface of the filament are not formed. Even if the brim penetrates through the through hole of the pole piece, the collar portion projects to the inside of the through hole of the pole piece and covers the bottom surface of the stem insulator, and at least the bottom surface outside the through hole has metal. Since no substance is attached, it is possible to prevent an electric discharge from occurring between the joint surface of the cylindrical metal container and the cathode lead.

According to the third aspect of the present invention, the stem insulator has the concave portion formed between the joint surface and the cathode lead. Therefore, the creeping surface between the joint surface of the cylindrical metal container and the cathode lead is formed. The longer the distance, the higher the insulation resistance,
There is an effect that it is possible to surely prevent the discharge generated between the joining surface of the cylindrical metal container and the cathode lead.

According to a fourth aspect of the present invention, a pair of magnetic pole pieces arranged at both ends of the anode and having a through hole formed substantially in the center thereof, and a pair of cathodes having a filament arranged on the central axis portion of the anode are supported. Of the cathode lead and a stem insulator having a through hole through which the cathode lead penetrates, and the other end opening of the cylindrical metal container is airtightly joined to a joint surface formed around the stem insulator. Since a concave portion is formed between the joining surface and the cathode lead, and a bent portion that intervenes the other end opening of the cylindrical metal container into the concave portion is formed, thorium, tungsten, etc. are formed from the surface of the filament. Even if the metal object of the above is evaporated, the wall surface of the recess is covered with the bent portion, and it becomes difficult for metal objects such as thorium and tungsten to adhere to the wall surface, and the decrease of the insulation resistance is suppressed. It is. Therefore, in the initial stage where electrons are not emitted from the cathode, even if a no-load voltage of 8 to 10 kV is applied to the cathode, the discharge generated between the joint surface of the cylindrical metal container and the cathode lead is prevented. There are effects such as being able to.

According to the fifth aspect of the present invention, since the bent portion is brought close to the bottom surface of the recessed portion, the entire wall surface of the recessed portion is covered with the bent portion, and the metal object adheres to the wall surface. Since it does not occur, it is possible to reliably prevent the discharge generated between the joint surface of the cylindrical metal container and the cathode lead.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part of a magnetron showing a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a main part of a magnetron showing a first embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of the relevant part.

FIG. 3 is a lateral view of the same main part.

FIG. 4 is a top view of the stem insulator.

FIG. 5 is a view showing another embodiment of the stem insulator.

FIG. 6 is a longitudinal sectional view of an essential part in a second embodiment of the present invention.

[Explanation of symbols]

24a One end opening 5 anode 24 Tubular metal container 19a Through-hole of pole piece 19 pole pieces 14 filament 13 cathode 17 Cathode lead 21 Stem insulator 24b Opening on the other end 25 Bonding surface 24c collar part 26 recess 27c Bent section

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[Procedure amendment]

[Submission date] June 10, 2002 (2002.6.1)
0)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Continued front page    (72) Inventor Satoshi Nakai             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. (72) Inventor Noriyuki Okada             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. (72) Inventor Kazuki Miki             2-5-3 Keihan Hondori, Moriguchi City, Osaka Prefecture             Within Yo Denki Co., Ltd. F term (reference) 5C029 HH03

Claims (5)

[Claims] 1. A cylindrical metal container whose one end opening is hermetically joined to an anode to form a part of a vacuum container, and a pair of magnetic pole pieces arranged at both ends of the anode and having a through hole formed substantially in the center thereof. A magnetron comprising a pair of cathode leads for supporting a cathode in which a filament is arranged on a central axis portion of the anode, and a stem insulator having a through hole through which the cathode lead penetrates. The other end opening is airtightly joined to the joining surface formed around the stem insulator, and the other end opening is formed with a circumferential flange extending toward the cathode lead side. And magnetron. 2. The magnetron according to claim 1, wherein an inner peripheral edge portion of the collar portion is located inside a through hole of the magnetic pole piece. 3. The magnetron according to claim 1, wherein the stem insulator has a recess formed between the joint surface and the cathode lead. 4. A cylindrical metal container whose one end opening is airtightly joined to the anode to form a part of a vacuum container, and a pair of magnetic pole pieces arranged at both ends of the anode and having a through hole formed at substantially the center thereof. A magnetron comprising a pair of cathode leads for supporting a cathode in which a filament is arranged on a central axis portion of the anode, and a stem insulator having a through hole through which the cathode lead penetrates. The other end opening is airtightly joined to the joint surface formed around the stem insulator, a recess is formed between the joint surface and the cathode lead, and the other end opening of the cylindrical metal container is A magnetron, characterized in that a bent portion that intervenes in the recess is formed. 5. The magnetron according to claim 4, wherein the bent portion is close to the bottom surface of the recess.