JP3363619B2 - Magnetron - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron.
More specifically, the present invention relates to a magnetron that ensures electrical insulation between leads supporting a filament and between the leads and an anode portion. 2. Description of the Related Art A main part of a magnetron conventionally used in a microwave oven or the like is composed of a cathode part 10, an anode part 20, and an output part 30, as shown in FIG. . The cathode section 10 is supported by a top lead 12 and an end lead 13 via end hats 14a and 14b provided with a filament 11 at both ends, respectively. The top lead 12 and the end lead 13 respectively support an anode section. At the same time, it is fixed to a stem 16 which becomes a part of the vacuum tube wall. Since a voltage is applied to the top lead 12 and the end lead 13 from outside the wall of the vacuum tube, the top leads 12 and the end leads 13 are fixed to flange metals 17 and 18 (see FIG. 4) fixed on the stem 16 by brazing or the like. And is electrically connected to an external lead 19 penetrating the stem 16 via the The anode section 20 is configured such that vanes 22 are radially provided on the inner periphery of an anode cylinder 21 so as to surround the filament 11, and a strap ring 23 for electrically connecting every other vane 22 is provided. Have been. At both ends of the anode cylinder 21, magnetic pole pieces 24 and 25 are provided for concentrating the magnetic field of the externally provided magnet in the working space between the filament 11 and the tip of the vane 22. The microwave power generated in the anode section 20 is extracted to the outside from an output section 30 formed of an output antenna 31 and an antenna ceramic 32 connected to the vane 22. The section where the stem 16 is fixed to the top lead 12 and the end lead 13 has a structure as shown in a sectional view and a plan view as shown in FIGS. As shown in FIG. 4, the flange metal 17, 1 brazed to the stem 16 on the surface of the stem 16 by a silver brazing material or the like.
8, a top lead 12 and an end lead 13 are fixed by brazing or the like. A stem metal 15 holding the anode section 20 is simultaneously brazed to the surface of the stem 16, and the stem metal 15 and the stem 16 form a part of a vacuum tube wall. Since the stem metal 15 is electrically connected to the anode section 20 and the top lead 12 and the end lead 13 are connected to the filament 11 to form a cathode section, 3 to 5 kV (a magnetron switch is connected) 10k for several seconds before the magnetron current starts to flow without being turned on and the filament 11 is heated
As shown in FIG. 4, a circular concave is formed on a stem 16 made of an insulating material such as ceramics to prevent short-circuiting due to brazing material during brazing and to withstand high pressure over a short distance. The groove 16a and the linear concave groove 16b between the flange metals 17 and 18 are provided to increase the creeping distance to prevent high-voltage discharge. However, during operation of the magnetron, the temperature of the filament 11 becomes as high as about 1800 ° C., so that the end hats 14 a and 14 b and the two leads 12 and 14 near the filament.
The temperature of 13 also becomes high, and conductive materials such as nickel and brazing material, which are those materials, scatter and adhere to the surface of the stem 16. As a result, even if the creepage distance is increased by providing the concave grooves 16a and 16b, discharge is likely to occur through the conductive substance scattered and attached from the vicinity of the filament. Therefore, as shown in FIG.
The groove 16a is covered with a tip portion 15a extending further from the brazing portion with the stem 16 of the fragile metal 1
The conductive material is prevented from adhering into the concave groove 16a by overlapping on the grooves 7 and 18. As described above, the concave groove 16a between the stem metal 15 and the flange metals 17 and 18 is covered with the flange metals 17 and 18 and the tip end 15a of the stem metal 15 to form a cathode. Can prevent the dielectric breakdown between the anode and the anode, but as the use time increases, the dielectric breakdown between the cathode and the anode easily occurs, the dielectric breakdown is not completely prevented, and the life is shortened, There is a problem that reliability is reduced. An object of the present invention is to provide a magnetron which can solve such a problem and can prevent insulation breakdown under high voltage even when used for a long time. The inventor of the present invention has conducted intensive studies to improve the tendency that high-voltage insulation breakdown is likely to occur with the passage of operation time and reliability is reduced. Flange metal scattered from near the broken filament 1
It has been found that dielectric breakdown occurs through the conductive substance attached to the concave groove 16b between the grooves 7 and 18 (see FIG. 5). That is, only a voltage of about 3 V, which is the voltage between both ends of the filament, is applied between the flange metals, and the problem of dielectric breakdown does not occur, and a conductive substance may adhere to the stem, but will be described later in detail. As described above, when the flange metal is brazed, the brazing material may partially hang down into the groove, and the flange metal and the conductive substance attached to the groove are electrically connected to each other through the hanged brazing material, thereby forming the groove. Since the creepage distance between the conductive material and the stem metal is smaller than the creepage distance between the flange metal and the stem metal, it has been found that dielectric breakdown easily occurs. Therefore, the groove between the flange metals is also covered with the flange metal to prevent the conductive substance scattered from the vicinity of the filament from adhering to the insulating stem, thereby preventing the dielectric breakdown. A magnetron according to the present invention comprises a filament, a top lead and an end lead electrically connected to both ends of the filament and supporting the filament, a part of the vacuum tube wall supporting the top lead and the end lead and supporting the filament. A first flange metal and a second flange metal which are respectively fixed to the filament side of the stem and electrically connect the top lead and the end lead to the external lead. A first flange metal, a second flange metal, a stem metal and the first flange metal, wherein the first flange metal, the second flange metal, and the stem metal are fixed and electrically connected to the anode portion and electrically connected to the anode portion to form a part of a vacuum tube wall; Metal and second
The flange metal is provided so as to overlap with each other via the space. According to the magnetron of the present invention, in addition to the groove between the stem metal and the first and second flange metals, the groove between the first flange metal and the second flange metal can be formed. Since the stem metal is completely covered with the first flange metal and the second flange metal, the surface of the stem is covered with either the stem metal or the flange metal in a plan view, and the vicinity of the filament which has become hot. The conductive material scattered from the surface adheres only to the surface of the flange metal or the stem metal, does not adhere to the stem made of an insulating material, and does not cause dielectric breakdown. Next, the magnetron of the present invention will be described with reference to the drawings. FIG. 1 is a sectional explanatory view of a stem portion of an embodiment of the magnetron of the present invention, and FIG. 2 is a plan view thereof. FIG.
3 to 5, the same reference numerals denote the same parts as those shown in FIGS. The magnetron of the present invention comprises a filament 11 as shown in FIG. 3, a top lead 12 and an end lead 13 electrically connected to both ends of the filament 11 to support the filament 11, and a top lead 12 And a stem 16 that supports the end lead 13 and forms a part of the vacuum tube wall, and is fixed to the filament 16 side of the stem 16, and electrically connects the top lead 12, the end lead 13, and the external lead 19 to each other. A first flange metal 17 and a second flange metal 18 connected to the
As shown in FIGS. 1 and 2, in the input stem portion of the magnetron, which is fixed around the anode 6 and is electrically connected to the anode portion and comprises a stem metal 15 constituting a part of the vacuum tube wall. Flange metal 17 and second
Not only between the flange metal 18 and the stem metal 15, but also between the first flange metal 17 and the second flange metal 18, the flange metals 17 and 18 are provided so as to overlap with each other via a space. It has special features. That is, the flange metals 17 and 18 are formed large so as to travel to the groove 16b side, and one flange metal 18 is formed by bending into the groove 16b.
As shown in the plan view of FIG. 2, when viewed from the filament 11 side, the stem 16 includes the first flange metal 17, the second flange metal 18, and the tip 15 of the stem metal 15.
It is formed so as to be completely covered with a and not to be exposed. Therefore, even if the filament 11 becomes high temperature and the conductive substance is scattered from the filament 11 and its vicinity, the flange metal 17, 18 or the stem metal 15
It adheres only to the top, does not adhere to the stem 16, and since the respective metals 17, 18, and 15 overlap through the space, the insulation in the space is maintained. There is no dielectric breakdown between the stem metals 15. In the present invention, the first flange metal 17 and the second
Although the concave groove 16b between the flange metal 18 is covered so as not to be exposed, as described above, between the first flange metal 17 and the second flange metal 18, the AC voltage, which is the voltage between both ends of the filament, is originally used. The application of only about 3 V does not cause a problem of dielectric breakdown due to the adhesion of the conductive substance. However, the inventor of the present invention has conducted intensive studies in order to solve the problem that the problem of dielectric breakdown during high voltage is likely to occur as the operation time elapses, and as a result, FIG. In addition, flange metal 17, 18
When brazing is performed, the brazing material 41 may drop into the concave groove 16b at any place, in which case, the flange metal 17 and the bottom surface of the concave groove 16b are electrically connected. . If the conductive material adheres to the bottom surface of the groove 16b in this state, the range of C in FIG. 6 becomes a range in which the dielectric breakdown easily occurs due to the conductive material, and the creepage distance that can maintain the clean insulation is shown in FIG. Range. This creepage distance D
Is shorter than the creeping distance E between the flange metals 17 and 18 and the stem metal 15, and the dielectric breakdown easily occurs via the creeping distance D. Therefore, flange metal 17, 1
Even if the insulation between the metal 8 and the stem metal 15 in the vicinity can be maintained, when the conductive material is attached to the concave groove 16b between the flange metals 17 and 18, the solder material 41 and the conductive material attached portion C pass through. And stem metal 15 and flange metal 1
Insulation breakdown occurs between 7 and 18. The present invention has been made based on this finding. In the magnetron according to the present invention, as shown in FIG. 1, one end of one of the flange metals (the second flange metal 18 in the example of FIG. 1) covers the concave groove 16b between the flange metals 17, 18. By extending the portion and bending it into the concave groove 16b, it overlaps with the first flange metal 17 as viewed from above. Therefore, as shown in the top view of FIG. 2, when viewed from the filament side, the stem 16 is not exposed, and the first flange metal 1
7, the second flange metal 18 and the tip 15a of the stem metal 15 completely cover the conductive material scattered from the cathode portion on any one of the metals, and the insulating stem formed by the scattered conductive material. 16 can be prevented from dielectric breakdown. The overlap portion between the first flange metal 17 and the second flange metal 18 is not limited to the structure shown in FIG. 1, and one flange metal may be bent at a right angle to provide a step. Further, a structure in which the groove is bent upward without bending into the concave groove 16b may be used. According to the magnetron of the present invention, since the entire surface of the stem on the filament side is covered with the flange metal or the stem metal and there is no exposed portion, even if the conductive material scatters from the filament side. Dielectric breakdown between the flange metal and the stem metal, that is, between the anode and the cathode can be prevented without being attached to the stem surface. As a result, stable characteristics can be maintained even when used for a long time, and a highly reliable magnetron can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory sectional view of a stem portion of an embodiment of a magnetron of the present invention. FIG. 2 is a top view of FIG. FIG. 3 is a partially cutaway explanatory view of a magnetron. FIG. 4 is an explanatory sectional view of a stem portion of a conventional magnetron. FIG. 5 is a top view of FIG. 4; FIG. 6 is a sectional view taken along line AA of FIG. 5; [Description of Signs] 12 Top lead 13 End lead 15 Stem metal 15a Tip 16 Stem 17 First flange metal 18 Second flange metal

Claims (1)

(57) Claims 1. A filament, a top lead and an end lead electrically connected to both ends of the filament and supporting the filament, and supporting the top lead and the end lead, respectively. A stem constituting a part of a vacuum tube wall, a first flange metal and a second flange metal respectively fixed to the filament side of the stem and electrically connecting the top lead and the end lead to an external lead, respectively; In the input stem portion of the magnetron, which is fixed around the stem and is electrically connected to the anode portion and which constitutes a part of the vacuum tube wall, the stem portion includes the first flange metal, the second flange metal, and the stem metal. And the first and second flange metals are empty. Magnetron thus provided so as to overlap each via.