JPH0517790Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Purpose of the Invention] (Field of Industrial Application) This invention relates to a magnetron for a microwave oven, and particularly relates to an improvement in the structure of its cathode support structure.

(Prior Art) A conventional cathode support structure of a magnetitron for an electron lens is formed by fixing both ends of a filament cathode wound into a coil to a pair of end hats either directly or via an end tip. A pair of cathode support rods made of molybdenum (Mo) are fixed to both end hats, and these cathode support rods pass through each through hole of the ceramic stem and are hermetically fixed to the terminal plate that is hermetically soldered to the outer surface. .
Further, a metal container constituting a part of the vacuum container is hermetically sealed to the upper end surface of the ceramic stem. In this conventional structure, the cathode support rod made of Mo is hermetically connected to the lower end of the stem and extended to the outside, so it is quite long, the parts cost is relatively high, and it is difficult to provide sufficient cathode support strength. Hard to get. In addition, it is difficult to make an airtight connection between the Mo material and the Kovar (trade name) terminal, and the airtight solder joint becomes hot due to conduction heat from the cathode, making it difficult to achieve high reliability in this joint. be.

On the other hand, as shown in Japanese Patent Laid-Open No. 56-132747, a structure for improving this point is proposed, in which the airtight joint between the ceramic stem and each cathode support rod faces the cathode side of the stem, that is, the vacuum region. A structure in which the sides are soldered in an airtight manner using a joining ring is also known. In this case, the cathode support rod is simply linear with respect to the through hole of the stem, and since the support rod is easy to rotate, there are disadvantages such as the need for a jig to regulate the position of the support rod.

Therefore, a part of the present invention was previously published in Japanese Patent Application No. 194103/1983, in which a concave groove communicating with the through hole was formed at the outer end of the ceramic stem, and a part of the external connection lead connected to the cathode support rod was formed. We proposed a structure in which it is bent and tightly joined within this groove.

(Problems to be Solved by the Invention) By the way, it has been confirmed that the conventional structure as described above has the advantage that rotation of the cathode lead is prevented and mechanical strength is also improved. However, considering the process of forming a relatively thin through hole or a thin groove connected to the ceramic stem in this way, the through hole is drilled by press molding, so a large force is applied to the mold, resulting in damage to the mold. is likely to occur. Thus, there are disadvantages in mass production.

This invention solves the problems of the conventional structure as described above, makes it easier to assemble the ceramic stem and cathode support rod, and prevents damage to the mold when drilling through holes in the ceramic stem in mass production. The present invention provides a magnetron for a microwave oven.

[Structure of the invention] (Means for solving the problem) This invention has a ceramic stem with a diameter larger than the inner diameter of the through hole on the outside air side surface of the ceramic stem through which the external connection lead electrically connected to the cathode passes. This is a magnetron for a microwave oven, in which a concave groove of the same size is formed continuously with the through hole, and a part of an external connection lead is bent and housed in the concave groove.

(Function) According to this invention, it is easy to assemble the ceramic stem and the cathode support rod, and the concentrated load on the mold is alleviated, especially when drilling through holes in the ceramic stem in mass production, and press forming This can reliably prevent damage to the mold. In this way, a microwave oven magnetron with excellent mass productivity can be obtained.

(Example) An example will be described below with reference to the drawings. Note that the same parts are represented by the same symbols.

The embodiment shown in FIGS. 1 to 5 has the following configuration. First, each reference numeral shown in FIG. 1 represents the following parts. 11 is an anode structure, 12 is an anode cylinder, 13 is an anode vane, 14
is a strap ring, 15 is a pole piece, 16 is
17 represents a metal container on the cathode stem side, 17 represents a ceramic stem, 18 and 19 represent a pair of through holes formed in the stem, and 20 and 21 represent a pair of external connection leads inserted into these through holes.

Therefore, the ceramic stem 17 has a generally cylindrical component structure, and has a ring-shaped recess 22 on one surface (the lower surface in the figure), and the inner surface of the ring-shaped recess 22 is connected to the bonded metal plate. There are two approximately semicircular metal plate joining surfaces 23 on the left and right for joining, a slit 24 is formed between them to provide insulation, and the outer peripheral surface is a metal container joining surface for joining metal containers. It is assumed to be surface 25. Both of these joint surfaces 23 and 25 are formed so as to be located on the same plane perpendicular to the central axis. Further, cathode support rod fitting holes 26 and 27 having a predetermined depth are formed diagonally lined up with the through hole. Further, on the other surface (the upper surface in the figure), elongated external connection lead storage grooves 28 and 29 are formed continuously from each through hole and have the same width as the through hole and extend in opposite directions.

During assembly, the metal plate joint surface 23 and the metal container joint surface 25 located on the same surface of the stem 17 are
molybdenum (Mo)-manganese (Mn) on the entire surface.
Apply the paste. When applying this paste, the fact that both joint surfaces are on the same plane and there are no obstacles such as protrusions between the two joint surfaces is used to apply the paste in one time, for example, by applying a screen. These can be coated over the entire surface. After drying this, it is placed in an inert gas heating furnace at about 1400°C and sintered to form a so-called metallized layer. Next, the bonded metal plates 30, 31 and the metal container 16 are
Each corresponding joint surface is hermetically soldered with silver solder. As the material for these joining metal plates 30 and 31, a metal such as Kovar (trade name) or Fe-Ni-Cr alloy, which has a coefficient of thermal expansion similar to that of the ceramic stem and is easily soldered through a metallized layer, is used. Ru. Each bonded metal plate 30, 31 has
A pair of external connection leads 20 and 21 made of metal rods such as copper or iron are passed through respective through holes and are hermetically connected by soldering at the through holes. These leads 20, 21
pass through the through holes 18 and 19 of the stem, respectively, and bent portions 20a and 21a are formed at corresponding positions near the ends of the stem. These bent portions are fitted into external connection lead storage grooves 28 and 29 formed continuously in each through hole, so that they hardly rotate in the circumferential direction.

a pair of cathode support rods 34 that support the coiled filament cathode 32 and the end hat 33;
35 is similarly fitted into an adjacent through hole formed in each joining metal plate 30, 31 and brazed to it, and each hole 26 of a predetermined depth has a lower end portion extending downwardly formed in the stem. 27, and is mechanically stabilized and locked and positioned.

The tip of each external connection lead 20, 21 is
In addition to being bent as described above, the stem is extended to protrude outward, and an inductor 36 is attached to the tip of the stem.
The leading ends 37a of the lead wires 37 are intertwined and both ends are connected by a welded portion 38. Note that the inductor 36 is formed by winding a lead wire coated with insulation around a ferrite core 39 into a coil shape. In this way, it is connected to an external power supply circuit. In this way, each cathode support rod 3
4, 35 and each external connection lead 20, 21,
They are electrically connected via connection metal plates 30 and 31, respectively. And each cathode support rod 34, 35
is only connected to the bonded metal plate and has no relation to the vacuum-tight bonding of the ceramic stem, and the bonded metal plate to which the external connection lead is bonded is vacuum-tightly bonded at the through-hole portion of the stem. Further, the open end surface of a metal container 16, which constitutes a part of the vacuum container, is similarly hermetically soldered to the outer circumferential surface of the ceramic stem. The ring-shaped recess 22 on the inner surface of the stem, whose interior is a vacuum area, is designed to absorb high voltage during magnetron operation, which is applied between the bonded metal plate that has the same potential as the cathode and the metal container that has the same potential as the anode structure. It is formed to have sufficient creepage distance and clearance to electrically insulate it from voltage.
Since these insulation distances are in a vacuum, relatively short dimensions are sufficient. The central slit 24 also ensures electrical insulation between the two joining metal plates to which the filament heating voltage is applied. This allows Mo
The length of the cathode support rod made of ceramic can be shortened considerably and the cost of parts can be reduced because it is sufficient to measure approximately from the end hat position to the inner surface of the ceramic stem.
Furthermore, since the soldering and fixing of the cathode support rod and the joint metal plate is not directly related to the vacuum tight connection, there is no need for Ni plating or the like on the surface of the cathode support rod. Since the vacuum-tight joint is obtained by soldering between the metal plate and the external connection lead and the metallized layer of the ceramic stem, it is possible to use a material that is easy to solder to ceramic as the metal plate.
Moreover, a highly reliable airtight joint can be obtained. Furthermore, since the heat conducted from the cathode through the Mo cathode support rod does not directly reach the airtight soldered joint between the ceramic and the metal plate, damage to the airtight joint is also suppressed from this point of view.

Concave groove 2 formed on the outer end of the ceramic stem
The width dimensions of the through holes 8 and 29 are larger than the inner diameter dimensions of the respective through holes 18 and 19. In this embodiment, the groove is made up of a continuous groove including a circular groove a with a large diameter and an elongated groove b whose width is wider than the through hole but smaller than the circular groove. Bent portions 20a, 2 of external connection leads
1a extends outwardly along these grooves and is substantially housed within the grooves. As a result, even if an external force is applied to each external connection lead, this external connection lead is mechanically locked in the concave groove of the stem, so there is almost no undesirable rotation during manufacturing. is almost prevented there, and thus no external force is directly applied to the cathode, and there is little risk of deformation or breakage of the cathode. Furthermore, since the soldering surfaces of the ceramic stems are located on the same plane, the metallized layer can be formed in a single step, simplifying the manufacturing process.

In each of the above-mentioned embodiments, as a connection structure between the joining metal plate and the external connection lead, a through hole or an eyelet with a through hole is formed in the connection metal plate, and the end of the external connection lead is inserted into this to create an airtight seal. Although it is soldered, it is not limited thereto. In other words, for example, the bonded metal plate does not have a through hole for the external connection lead to pass through, but is hermetically soldered to the peripheral surface of the through hole of the ceramic stem, and the external connection lead is attached to the surface of the bonded metal plate on the side of the stem through hole. Electrical connections may be made by welding or brazing. According to this, the connection portion between the bonded metal plate and the external connection lead is not related to vacuum tight connection, so reliability is further improved. In this case, it is also possible to form a recess in the bonded metal plate when viewed from the atmosphere side, and insert the tip of the external connection lead into the recess for connection.

Furthermore, this invention may have a structure in which the above structure is applied to at least one of the plurality of cathode support rods.

The embodiment shown in FIGS. 6a and 6b has grooves 28 and 29 formed on the outer end surface of the ceramic stem 17.
, which is continuous with the through holes 18 and 19 and has a circular shape with a larger diameter outward. The shape of the groove is relatively simple, and the ceramic stem is easy to manufacture.

In the embodiment shown in FIGS. 7a and 7b, one long groove 2 is continuous so as to span two through holes.
8.29. It is also simpler in shape and easier to manufacture from ceramics.

In the embodiment shown in FIGS. 8a and 8b, continuous grooves 28 and 29 extending across the through hole are formed to extend to the outer circumferential side of the ceramic stem. This also has a simpler shape and makes the ceramic stem even easier to manufacture.

The embodiment shown in FIGS. 9a and 9b has grooves 28 and 29 formed on the outer end surface of the ceramic stem 17.
However, the through holes 18 and 19 are continuous with concentric grooves and slits are formed in opposite directions. According to this, the mold for press-molding the ceramic stem can be made less susceptible to concentrated loads, and is suitable for mass production.

[Effects of the invention] As explained above, according to this invention, the rotation of the cathode external connection lead can be prevented, so that the ceramic stem and the cathode support rod can be easily assembled. In addition, the concentrated load on the mold when drilling a through hole in a ceramic stem in mass production is alleviated, and breakage of the mold during press molding can be reliably prevented. In this way, a microwave oven magnetron with excellent mass productivity can be obtained.

[Brief explanation of drawings]

Fig. 1 is a vertical sectional view of the main part showing an embodiment of the present invention, Fig. 2 is a top view of the main part, Figs. 3 to 5 are perspective views of the main part, and Fig. 6 a and b are the main parts. Top views and vertical sectional views of main parts showing other embodiments of this invention, Figures 7a and b, Figures 8a and b, and Figure 9.
Figures a and b are a top view and a vertical cross-sectional view of essential parts, respectively, showing still another embodiment of this invention. 11 ... Anode structure, 32... Cathode, 1
6... Metal container, 17... Ceramic stem, 1
8, 19...Through hole, 20, 21...Cathode external connection lead, 20a, 21a...Bend portion, 2
8,29...concave groove.

Claims (1)

[Claims for Utility Model Registration] A cylindrical metal container that is hermetically sealed to a part of an anode structure and constitutes a part of a vacuum container; a cathode disposed at the central axis of the anode structure; and an opening in the metal container. a ceramic stem whose ends are hermetically sealed and a plurality of through holes are formed in the axial direction; and an external connection which is electrically connected to the cathode and extends to the outside through the through holes of the ceramic stem. In a microwave oven magnetron having a reed, a concave groove having a dimension larger than the inner diameter of the through hole is formed on the outside air side surface of the ceramic stem, and is continuous with the through hole. A magnetron for a microwave oven, characterized in that a part of the connection lead is bent and housed.