JP2010244712A - Magnetron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetron which has a low manufacturing cost and excellent manufacturability, and is not adversely affected by characteristics. <P>SOLUTION: Radial grooves 36 are extended from a cathode fixing part 32 and formed on a surface of an electron working space s of an input-side end hat 30 jointed by brazing to the cathode fixing part 32 having a central opening 31 and a spiral-shaped cathode 12 in this central opening 31, and then, used as: a storing/stopping part of a pasty brazing material coating the surface; and a flow passage through which the molten brazing material formed by heating flows into the cathode fixing part 32. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a magnetron used in a microwave heating apparatus such as a microwave oven.

  A general magnetron for a microwave oven that oscillates a 2450 MHz band radio wave includes an anode cylinder and a plurality of vanes. The vanes are arranged radially extending in the central axis inside the anode cylinder. The vanes are connected to each other in the circumferential direction by a pair of large and small diameter strap rings brazed to the upper and lower ends of the vane. A spiral cathode is disposed along the central axis of the anode cylinder to form an electron working space surrounded by the cathode and the free ends of the plurality of vanes. Both ends of the spiral cathode are fixed to the output side end hat and the input side end hat, respectively. These end hats support the cathode and shield the electron working space.

  Usually, during the operation of the magnetron, the temperature of the spiral cathode becomes 1800 ° C. or more, so that a high melting point metal such as Mo 2 is used for the output side and input side end hats. In addition, the spiral cathode and the output side and input side end hats are joined together by a brazing material. As a high melting point brazing material, a sintered body having a Ru-Mo composition (Patent Document 1) or Ru powder and Mo powder is used as a binder. In many cases, a paste-like brazing material mixed in (1) is used. The spiral cathode by melting the brazing material and each end hat are joined by high-frequency heating, and each is mechanically and electrically joined.

  Various methods are used to install the brazing material. For example, in the case of a sintered body, a brazing material formed in a ring shape is inserted and installed in the cathode junction of the input side end hat. In some cases, shrink fitting or laser welding is performed. Also, in the case of paste-like brazing material, there are many examples where it is applied directly to the cathode junction, but if the brazing material adheres to a location other than the junction on the cathode surface, there are problems such as cathode fusing during operation and reduced yield strength against vibration shock. For example, a taper or chamfer is provided on the input side end hat side to facilitate application (Patent Document 2). In addition, there is a method of melting and overlaying a brazing alloy (Patent Document 3).

Japanese Utility Model Publication No.54-131466 Japanese Patent Laid-Open No. 08-293265 No. 2,556,019

  When using a sintered brazing material, a ring-shaped brazing material is inserted into the cathode joint of the input side end hat, but it is very narrow and thin, making automatic insertion by a machine difficult. . In addition, when it is tilted at the time of insertion, the cathode may float and become defective. In order to avoid such a problem, temporary fixing to the end hat may be performed in advance, but the cost increases because the number of processes increases. In the first place, the cost of the sintered body is higher than that of the paste-like brazing material, so that there is a problem that the cost difference further increases.

  On the other hand, a paste-like brazing material is less expensive than a sintered body, but it is difficult to apply it with a dispenser or the like with high accuracy. For this reason, as described above, a taper or the like is provided on the end hat to facilitate application, but such a difference in shape greatly affects the characteristics of the magnetron. For example, even if the overall end hat height is the same, the length of the cathode is increased by the taper, so that the resistance value is increased, and the cathode current is lower than that of the conventional case, so that the amount of emitted electrons is reduced. On the other hand, if the end hat height is changed and the cathode lengths are made equal, the working space becomes smaller and the load stability becomes worse.

  In addition, when the taper portion is large, the cathode reverse impact also increases, which causes a problem that the life of the magnetron is shortened. This is considered to be due to the influence of the electric field distribution being different from the electrons rebounding from the tapered portion.

The present invention solves the above-described problems, and provides a magnetron that is low in cost, has good manufacturability, and has no adverse effect on characteristics.

The present invention includes an anode cylinder that extends in a cylindrical shape along a central axis and has one end as an output side and the other end as an input side having an insulating stem in which a center cathode lead and a side cathode lead are implanted;
A plurality of vanes extending from the inner surface of the anode cylinder toward the central axis;
A helical cathode disposed on the central axis and forming an electron action space with the vane;
An output side end hat fixed to one end of the spiral cathode and supported by the center cathode lead and located on the output side;
In a magnetron comprising an input side end hat fixed to the other end of the spiral cathode and supported by the side cathode lead and positioned on the input side,
The input-side end hat is formed in an annular body having a central opening through which the center cathode lead passes, and is formed on the surface of the electron action space and in the central opening to join the other end of the spiral cathode. And a plurality of radial grooves formed radially extending from the cathode fixing portion on the surface on the electron action space side, arranged on the surface on the electron action space side, and melted by heating. A magnetron is obtained in which the brazing material flows into the cathode fixing portion through the radial groove.

  According to the present invention, application is easy while using a relatively low cost paste-like brazing material, and there is almost no substantial difference in cathode length or large change in electric field distribution, so there is no adverse effect on characteristics. . In addition, the input side end hat is usually a sintered product of heat-resistant metal such as Mo, and the groove on the surface can be integrally formed with a mold, so that the manufacturing cost can be equal to the conventional one, and the groove is provided. Since there is only a small amount of Mo or the like, the material and parts costs can be reduced.

The longitudinal cross-sectional view of the magnetron of Embodiment 1 of this invention. The perspective view which shows the input side end hat of Embodiment 1. FIG. Sectional drawing which shows the input side end hat of Embodiment 1. FIG. FIG. 2 is a plan view and a cross-sectional view of an input side end hat according to the first embodiment. Sectional drawing which shows the input side end hat of Embodiment 2. FIG. FIG. 6 is a plan view showing an input side end hat according to a third embodiment. FIG. 6 is a plan view showing an input side end hat according to a fourth embodiment. FIG. 9 is a plan view showing an input side end hat according to a fifth embodiment. FIG. 9 is a plan view showing an input side end hat according to a sixth embodiment. The top view which shows the input side end hat of Embodiment 7. FIG.

  Next, embodiments of the present invention will be described with reference to the drawings.

  The first embodiment of the present invention is a magnetron for a microwave oven that generates a fundamental wave in the 2450 MHz band. As shown in FIG. 1, an oscillation unit body 10 that generates a high frequency is an anode cylinder 11 and a tube axis in the anode cylinder 11. It is composed of a spiral cathode 12 positioned at the central axis m, a plurality of vanes 13 forming a cavity resonator, and the like. The vanes 13 are provided radially on the inner surface of the anode cylinder 11 toward the spiral cathode 12, and one end thereof is fixed to the anode cylinder 11. The free end 13a at the other end forms an inscribed circle, and an electron action space s is formed between the cathode and the cathode. Every other vane 13 is connected by a common strap ring 14. Pole pieces 15 and 16 are fixed to upper and lower opening end surfaces of the anode cylinder 11 in the figure. An output unit 18 is provided above the pole piece 15 provided on the upper end surface of the anode cylinder, and an input unit 25 is provided below the pole piece 16 provided on the lower end surface of the anode cylinder.

  The output unit 18 is a part of the container, and includes a cylindrical metal sealing body 19 with a flange and a ceramic cylinder 20, a metal exhaust pipe 21, and the like joined to the upper end surface 11 a of the anode cylinder 11 via a pole piece 15. Has been. The metal sealing body 19, the insulating cylinder 20, and the metal exhaust pipe 21 are hermetically joined by an annular brazing material (not shown), and an antenna lead 22 extends in the direction of the central axis m in the inner space. One end of the antenna lead 22 is electrically connected to one of the anode vanes 13, extends through the pole piece 15 in the direction of the central axis m, and the other end is crimped and fixed at the sealing position of the metal exhaust pipe 21. ing.

  The spiral cathode 12 is formed by winding a filament such as thorium tungsten in a coil shape, and applies a current to emit thermoelectrons to the electron action space s. End hats 17 and 30 are fixed to both ends of the spiral cathode 12.

  The end hats 17 and 30 are made of a heat-resistant metal such as Mo, and are arranged adjacent to the through holes 15a and 16a provided in the funnel-shaped bottom portions of the upper and lower pole pieces 15 and 16, respectively. The terminal serves as a shield that conducts current and flows through the spiral cathode 12. The output side end hat 17 is referred to as an output side end hat, and the end hat 30 disposed on the input side is referred to as an input side end hat.

  The input unit 25 is disposed on the lower end surface 11 b of the anode cylinder 11 via the pole piece 16. That is, the flange portion 26a of the cylindrical metal seal 26 with the flange is sealed to the lower end surface 11b of the anode cylinder 11 to form a part of the container, and the columnar insulating stem 27 is airtight on the lower end surface of the cylindrical wall. It is sealed and configured.

  An output side end hat is fixed to the upper end of the spiral cathode 12. A center cathode lead 40 is fixedly attached to the output end hat 17 so as to be implanted in the stem 27 and extend through the center opening of the input end hat 30 and the center of the spiral cathode. An input side end hat 30 is fixed to the lower end of the spiral cathode. A side cathode lead 41 implanted in the insulating stem 27 is fixed to the input side end hat 30. That is, the side cathode lead 41 is joined to the lower surface of the input side end hat 30. The spiral cathode 12 is supported by these cathode leads 40 and 41 and is electrically drawn out from the insulating stem 27 to the outside.

  As shown in FIGS. 2 to 4, in the present embodiment, the input side end hat 30 is formed of an annular body and has a center opening 31, and a center cathode lead 40 (FIG. 1) extending along the center axis m. ) Can be penetrated in a non-contact manner, and a concave-shaped cathode fixing portion 32 that receives and brazes the lower end 12b of the cathode filament 12a on the upper surface 33 side that is the electron action space s side of the central opening 31 is provided. Is formed. That is, an annular flange 32a is formed on the lower surface side of the central opening 31 to form a stopper that receives the cathode filament lower end 12b.

  An upper surface 33 of the input-side end hat 30 forms a surface substantially perpendicular to the central axis m, and a circumferential groove 34 for retaining the paste-like brazing material is provided on the upper surface 33. A bank 35 is formed between the circumferential groove 34 and the cathode fixing portion 32, and a plurality of radial grooves 36 connecting the circumferential groove and the cathode fixing portion are formed at equal intervals along the bank circumference. Is provided. The radial groove 36 is a flow path through which the brazing material melted at a high temperature flows from the circumferential groove to the cathode fixing portion.

The dimensions of the input-side end hat 30 are, for example, when the pole piece 16 has an opening diameter pi of 9.0 mm, the spiral cathode 12 has an outer diameter f of 3.97 mm, and a filament diameter of 0.5 mm.
Outer diameter e: 7.2 mm,
Cathode fixing part 32 inner diameter b of opening 31: 3.97 mm,
Annular flange 33 inner diameter a: 3.5 mm,
Circumferential groove 34 inner diameter c: 4.7 mm,
Circumferential groove 34 outer diameter d: 5.5 mm,
Circumferential groove 34 depth 0.2 mm,
Radial groove 36 width 0.2 mm,
The radial groove 36 has a depth of 0.2 mm.

  At the time of manufacturing, when fixing the cathode and the end hat, a paste-like brazing material (for example, Ru-Mo) is applied to an arbitrary position of the circumferential groove 34 and dried, followed by high-frequency induction heating. The brazing material melted by the high frequency induction heating flows through the groove 34 to the cathode fixing portion 32, and once contacts the cathode filament 12a, the brazing material flows over the entire circumference.

  It is necessary to set appropriate values for the width and depth of the groove depending on the dimensions of the cathode and the end hat. Since the flow of brazing material is also affected by the output of high frequency induction heating, etc., it is difficult to define the groove size and the amount of brazing material applied, but both the width and depth of the groove in terms of the current magnetron dimensions 0.5 mm or less is desirable and hardly affects the characteristics. In addition, although the cross section of the circumferential groove | channel and the radial groove | channel was made into the rectangular shape, even if it is other shapes, such as semicircle shape, the same effect is obtained.

    Further, in the present embodiment, there is only one circumferential groove, but a plurality of circumferential grooves may be provided as long as the characteristics and the production of the end hat are not affected in the same manner as described above.

  As shown in FIG. 5, the second embodiment is such that the bottom surface 34 a of the circumferential groove that holds the paste-like brazing material is inclined toward the cathode fixing part 32, and has the effect of facilitating the flow of the brazing material. . In the drawing, the bottom surface is continuously inclined from the circumferential groove 34 to the cathode fixing portion. However, even if only the radial groove 36 is inclined, a certain effect can be obtained.

  In the third embodiment, as shown in FIG. 6, a wide portion 37 is partially formed in the circumferential groove 34, and the circumferential groove and the radial groove of the first embodiment are integrated so that a part of the wide portion 37 is a cathode. The structure is open to the fixing portion 32. If the opening is excessively widened, the pastelow material flows excessively to the cathode fixing part, and therefore the numerical aperture is adjusted to prevent this.

  A fourth embodiment will be described with reference to FIG. In the following drawings, the same reference numerals as those in Embodiment 1 indicate the same configuration. In the above-described embodiment, the circumferential groove is provided for the retention of the applied paste-like brazing material, but the retention portion may not be a circumference. In this embodiment, the circumferential groove of the first embodiment is divided into radial grooves 361 to form a dividing groove 341. The dividing groove 341 also has a function of storing a paste-like brazing material that is a viscous liquid, and has a configuration in which a high-temperature molten brazing material flows from the radial groove to the cathode fixing portion 32.

  As shown in FIG. 8, the fifth embodiment has a pattern in which a plurality of radial grooves 362 are arranged in a small semicircular loop on the upper surface 33 of the input side end hat 30 and arranged in the circumferential direction of the cathode fixing portion. The vicinity of the loop top portion 362a serves as a retaining portion for the paste-like brazing material, and the loop leg portion 362b serves as a flow passage for the brazing material.

  In the sixth embodiment, as shown in FIG. 9, only the radial grooves 363 are formed on the upper surface 33 of the end hat. The radial grooves 363 are extended from the inner peripheral edge of the cathode fixing portion 32 to near the outer periphery of the end hat so as not to reach the outer peripheral edge 33a, and a portion of the radial grooves has a function of retaining paste-like brazing material.

  The radial groove is narrowed to form a large number of grooves (24 in the drawing) to form a retaining portion. The paste-like brazing material applied to the upper surface 33 stops on the surface without flowing to the outer periphery 33 a of the end hat or the cathode fixing part 32. By the high frequency induction heating, the binder of the paste is evaporated, the Ru-Mo powder is melted and flows to the cathode fixing portion 32 where the cathode filament is inserted, and the cathode filament is brazed to the cathode fixing portion.

  Embodiment 7 is shown in FIG. In this embodiment, the extending direction of the radial groove 364 is a pattern in which the radial direction r is inclined to the radial direction r of the upper surface of the end hat and further bent in the circumferential direction. According to this pattern, the groove can be formed longer than the pattern of the sixth embodiment. The groove 364 of this embodiment has both functions of a paste-like brazing material retaining portion and a molten brazing material flow path. Since the groove length can be sufficiently extended, formation of the retaining portion is easy.

  In Embodiments 3 to 7, the bottom surface of the radial groove is formed in parallel with the top surface, that is, the surface on the electron action space side, but the molten brazing material flows into the cathode fixing portion by increasing the groove depth toward the cathode fixing portion. It can also be made easier.

  As mentioned above, although this invention was demonstrated by embodiment, it cannot be overemphasized that a various deformation | transformation is possible in the range which does not deviate from the range of this invention.

DESCRIPTION OF SYMBOLS 10 ... Oscillator main part 11 ... Anode cylinder 12 ... Spiral cathode 15, 16 ... Pole piece 17 ... Output side end hat 18 ... Output part 22 ... Antenna lead 25 ... Input part 27 ... Insulation stem 30 ... Input side end hat 31 ... Center opening 32 ... cathode adhering portion 33 ... upper surface (surface on the electron action space side)
34 ... Circumferential groove 35 ... Bank 36 ... Radial groove m ... Center axis s ... Electron action space

Claims (4)

An anode cylinder extending in a cylindrical shape along the central axis and having one end as an output side and the other end as an input side having an insulating stem in which a center cathode lead and a side cathode lead are implanted;
A plurality of vanes extending from the inner surface of the anode cylinder toward the central axis;
A helical cathode disposed on the central axis and forming an electron action space with the vane;
An output side end hat fixed to one end of the spiral cathode and supported by the center cathode lead and located on the output side;
In a magnetron comprising an input side end hat fixed to the other end of the spiral cathode and supported by the side cathode lead and positioned on the input side,
The input-side end hat is formed in an annular body having a central opening through which the center cathode lead passes, and is formed on the surface of the electron action space and in the central opening to join the other end of the spiral cathode. And a plurality of radial grooves formed radially extending from the cathode fixing portion on the surface on the electron action space side, arranged on the surface on the electron action space side, and melted by heating. A magnetron, wherein the brazed material flows into the cathode fixing part through the radial groove.   2. The magnetron according to claim 1, wherein a bottom surface of the radial groove is inclined toward the cathode fixing portion. The input-side end hat is formed on the surface of the annular body on the electron action space side and is formed between at least one circumferential groove on which a brazing material is disposed, and between the cathode fixing portion and the circumferential groove. A plurality of radial grooves provided so as to communicate the cathode adhering portion and the circumferential groove on the bank, and the molten brazing material disposed in the circumferential groove passes through the radial groove to form the cathode. 3. The magnetron according to claim 1, wherein the magnetron flows into the fixing portion. The magnetron according to claim 3, wherein the circumferential grooves and the bottom surfaces of the radial grooves are inclined toward the cathode fixing portion.

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