JPH0518834Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) This invention relates to a magnetron for a microwave oven, and particularly relates to a high voltage input terminal fixed to a shield box thereof. (Prior Art) In a microwave oven magnetron, a negative high voltage and heating power for a filament cathode are applied from the cathode input stem side. For a magnetron used in a household microwave oven, this input has an anode voltage of 4 kV, an anode current of 300 mA, a filament voltage of 3.15 V, and a filament current of 10 A.
It is. Conventionally, a through-type high voltage capacitor using a ceramic high dielectric element has been generally used as a high voltage terminal for introducing such a high voltage and large current. This uses a feedthrough high-voltage capacitor that serves as the input terminal to have a capacitance of several hundred pF, and together with a choke coil, it forms an LC filter to suppress noise generated in the magnetron. By the way, the withstand voltage characteristics of high dielectric elements to which high voltage is applied are particularly important, and generally the high dielectric elements are coated with insulating resin to protect the interface, but this has a large impact on the manufacturing process. , quality control of withstand voltage is extremely difficult. For this reason, efforts have recently been made to simplify the structure of high-voltage input terminals as much as possible. As long as a high dielectric material is used, there is a limit to its simplification, and as an extremely simplified example, a configuration can be considered in which a thin layer of insulating resin supports high voltage and forms capacitance. (Problem to be solved by the invention) Conventional magnetrons for general microwave ovens have a structure in which two feedthrough capacitors are formed by the flange part of a common ground electrode, and these are attached to a shield box as a high voltage input terminal. It is. Therefore,
Although some ground potential electrodes can be made common, assembly of each electrode becomes complicated. Molding is used to integrate the plurality of electrodes and insulating resin that are the components of the high-voltage input terminal. In this case, since the coefficient of thermal expansion of the resin is considerably larger than that of the electrode metal, there is a risk that the resin will crack due to heat cycles or the like. This danger is especially great when the resin is subjected to tensile stress. In particular, in microwave oven magnetrons, the input conductors, such as the chiyoke coil and shield box, reach high temperatures during operation, and the input terminals attached to these may also reach temperatures of over 100°C. Therefore, the resin used therein needs to have sufficient heat resistance. If a mold is used to construct the insulating resin, it is necessary to provide the high voltage input terminal with sufficient capacitance, so making the insulating resin a thin layer will improve the microscopic structure of the insulating resin after molding. becomes difficult to maintain. In addition to being subject to mechanical stress, it is also relatively difficult to suppress the generation of voids and the like to fully demonstrate the withstand voltage performance of the insulating resin material itself. Also known is a structure in which two single feedthrough capacitors are arranged in a shield box and their respective mounting flanges are individually fixed to the box wall by screws or caulking. However, with such a structure, the number of man-hours for attaching the shield box to the shield box increases, and mass productivity is lacking. This idea solves the above-mentioned inconveniences,
In addition to simplifying the structure of each high voltage input terminal,
It is an object of the present invention to provide a magnetron for a microwave oven equipped with a high-voltage terminal in which a plurality of terminals are integrated with sufficient mechanical strength. [Structure of the invention] (Means for solving the problem) In this invention, the mounting flanges of each ground potential electrode of a plurality of high voltage input terminals are partially attached to each other so that the mounting surfaces are flat. This is a magnetron for microwave ovens that is pressure welded and integrated. (Function) According to this invention, each high-voltage input terminal can be made into a simple structure, and the mounting flange portions of multiple ground potential electrodes are integrated with sufficient mechanical strength and attached to the shield box. It is possible to obtain a magnetron for a microwave oven that is easy to mount and does not cause undesired radio wave leakage from the mounting surface. (Example) An example will be described below with reference to the drawings. Note that the same parts are represented by the same symbols. In this magnetron, as shown in FIG. 1, a radiator 12 is fixed to the outer periphery of an anode cylinder of an oscillating section main body 11, and a ring-shaped permanent magnet 13 is stacked on the anode cylinder. A ferromagnetic yoke 14 is provided surrounding this magnet, and a shield box 16 covering the input stem portion 15 of the oscillation section body is fixed thereon. shield box 16
Inside, the cathode input terminal 17 of the stem portion is connected to one end 19a of the chiyoke coil, that is, the inductor 18, and the other end 19b is connected to the U-shaped end 21a of the center conductor 21 of the high voltage input terminal 20.
connected by welding. The high voltage input terminal 20 includes an inner high potential electrode 22 made of a metal cylinder with a bottom connected to the center conductor, an outer ground potential electrode 23 made of a metal cylinder coaxially arranged at a predetermined interval on the outside thereof, and It has an insulating resin part 24 that covers the space between the electrodes and the outer periphery of the ground potential electrode. As shown in FIG. 2, this high-voltage input terminal has mounting flanges 25, 25 extending in the horizontal direction of each ground potential electrode of the two terminals 20, which are integrally connected to each other and fitted into the through hole 16a of the shield box. installed and electrically and mechanically connected and fixed. Note that the reference numeral 25a indicates a portion where both the flange portions 25, 25 are joined by a method described later, and 26, 26
... represents a through hole for mounting. The outer end portion 21b of the center conductor 21 is a flat plate-shaped Faston terminal portion, and is used as an input terminal of this magnetron. The high-voltage input terminal 20 has a capacitance of about several tens of pF, and together with the inductor 18 constitutes an LC filter that suppresses undesirable noise leaking from the input side. In order to obtain sufficient creepage withstand voltage characteristics, the insulating resin part 24 has an outer cylindrical sheath part 27 surrounding the fiston terminal part and an inner cylindrical sheath part 27 surrounding the central conductor extension part inside the box. It has a sheath part 28. Furthermore, ring-shaped grooves 29 and 30 are formed in each sheath to further increase the creepage distance. Next, the configuration of the high voltage input terminal 20 will be explained in accordance with a preferred assembly order. First, each electrode component as shown in FIG. 3 is prepared. The center conductor 21 is made by bending the main part of an iron plate of a predetermined length into a U-shape in cross section, and leaving one end of the plate as a faston terminal part 21b. U-shaped end 21
A through hole 21c for inserting the end portion 19b of the inductor is formed in a portion near a. Since the center conductor has a U-shape and a non-rotationally symmetrical shape, it is possible to suppress positional changes in the rotational direction between the Faston terminal portion 21b and the ground potential electrode 23 and to stably position them during resin molding, which will be described later. Serve as positive for. Furthermore, by forming the center conductor in a U-shape, the mechanical strength of the center conductor is also improved. Further, an inner high potential electrode 22 having a cylindrical shape with a bottom is prepared by deep drawing an iron plate using a press. This high potential electrode 22 has a square through hole 22a formed at its bottom, into which the center conductor 21 is inserted. In addition to being positioned coaxially with each other, the bottom through hole 22a of the high potential electrode 22 and the U-shaped end 21d on the Faston terminal side of the center conductor are electrically and mechanically coupled by welding. These are then tinned. Note that the burrs on the ends of each electrode are
To improve withstand voltage, remove by tumbling etc. before plating. On the other hand, an outer cylindrical ground potential electrode 23 having a mounting flange portion 25 is prepared by deep drawing an iron plate using a press. The flange portion 25 has 3
Through holes 26, 26... are bored in each corner. This outer electrode 23 is plated with nickel. Next, as shown in FIG. 4, each electrode component is positioned using a mold (not shown). The outer ground potential electrode 23 is coaxially arranged on the outer side of the inner high potential electrode 22 at an interval of, for example, about 1 mm. The mold (not shown) has a shape such that the insulating resin portion forms the outer surface shown in each drawing. And regarding the insulating resin mold,
Resin is injected as shown by the arrow S1 from pinpoint gates P with a diameter of 0.9 mm in the mold provided at three locations on the circumference surrounding the Faston terminal portion 21b.
The insulating resin is preferably an engineering plastic such as polybutylene terephthalate (PBT) resin containing about 30% by weight of glass fibers. The resin injected at equal pressure in the direction of gravity advances in the axial direction as shown by arrow S2 and simultaneously in the circumferential direction as shown by arrow S3 in the area around the Faston terminal portion. As a result, an outer cylindrical sheath portion 27 surrounding the Faston terminal portion 21b is formed. The space for forming the outer cylindrical sheath portion 27 also serves as a runner for running resin in the circumferential direction during injection molding. That is, this makes it possible to flow the resin to each part involved in maintaining dielectric strength voltage in a state similar to simultaneous injection from the ring-shaped gate. Note that the outer cylindrical sheath portion 27 has a height of, for example, 5 to 6 mm.
mm, and the end width is 1.3 mm. Furthermore, the injected resin flows to the root part of the Faston terminal part 21b, and inside as shown by arrows S4 and S5.
It flows into the gap between the outer cylindrical electrodes 22 and 23 and into the outer circumferential space of the outer electrode 23 at approximately equal pressure.
Further, the resin that has passed through the gap between the inner and outer cylindrical electrodes 22 and 23 flows into the region of the inner cylindrical sheath 28 as indicated by arrow S6. In this way, the shape and arrangement of each electrode are such that the basic flow of the insulating resin is vector-wise in one direction. As a result, the occurrence of voids, etc. is particularly suppressed, and the withstand voltage performance of the insulating resin material itself can be fully demonstrated. Note that the rectangular flange portion 25 of the ground potential electrode 23 extends laterally from the insulating resin portion and is exposed to the outside. In this way, a high voltage input terminal 20 as shown in FIGS. 6 and 7 is obtained. For example, inner high potential electrode 2
The diameter of the electrode 2 is 10 mm, the gap between the inner and outer electrodes is 1 mm as described above, the axial length of the overlapping electrodes 22 and 23 is 13 mm, and the length of the outer cylindrical sheath 27 is 6 mm.
The outer diameter of the inner cylindrical sheath part 28 is 16 mm, and the length is 15 mm.
mm, the relative dielectric constant of PBT is about 4, so the capacitance between the two electrodes is about 20 pF. The withstand voltage was over 20kV at AC voltage. In particular, the insulating resin is used in the portion 24a that forms capacitance.
Since the sheath parts 27 and 28 that ensure the creepage distance and the outer cover part 24b that covers the outer electrode are integrally formed of a single resin, phenomena such as deterioration of withstand voltage due to peeling at the boundary of different materials can be avoided. Therefore, a high voltage input terminal with stable quality can be obtained. Furthermore, by using PBT or the like as the insulating resin, stable performance can be maintained up to about 120°C. As a result of various attempts, we were able to obtain withstand voltage characteristics close to the limit withstand voltage of the material by appropriately adjusting the resin molding conditions. Next, as shown in FIG. 8, the same two high-voltage input terminals 20 , 20 manufactured as described above are connected to each other, with the side of each flange portion 25, 25 on which one through hole 25 is formed. Partially overlapped, pressure welding electrode 3
1 and 32 and pressurize them as shown by arrow F while applying electricity to perform pressure welding. In this way, two series of high-voltage input terminals are completed in which the surfaces of the respective flange portions 25 are aligned on the same plane and integrated as shown in FIGS. 2 and 9. This integral joint portion is designated by the reference numeral 25a. In addition, by welding both flanges after resin molding, the positioning accuracy of the high potential electrode and the ground potential electrode, which are related to dielectric strength, can be assembled independently and filled with resin, resulting in a highly reliable high voltage input terminal. is obtained. Furthermore, it becomes easy to press each ground potential electrode individually. This pair of high-voltage input terminals has six through-holes 2 for mounting.
6 is provided, so it is fixed to the shield box by caulking or the like. As a result, the shield box and the flange portion of the high-voltage input terminal are brought into closer contact with each other, eliminating the possibility of radio wave leakage. In the embodiment shown in FIG. 10, the sides 25b, 25b of the ground potential electrode flange portions 25, 25 of the two high voltage input terminals 20 are formed into a crank shape, and are pressure welded while facing each other. It is integrated. The mutual welding portion is likewise designated by the reference numeral 25a. This makes it clear which sides of each flange portion should be joined, and facilitates automated mechanization of assembly. In the embodiment shown in FIGS. 11 and 12, a cut is made partially in the center of one side of the mounting flange 25 of each high voltage input terminal 20 , and one of the cuts is bent by approximately the thickness of the plate. 25b is formed. Then, the two high voltage input terminals 20 and 20 having the same configuration are placed so that the sides on which the bent portions are formed face each other, and the bent portion 25b of one terminal 20 is
and the flat portion 25c of the other terminal 20 are placed one on top of the other, and both are pressure welded and integrated. As a result, a microwave oven magnetron having a high-voltage input terminal with even higher mechanical strength can be obtained. [Effects of the invention] As explained above, according to this invention, each high-voltage input terminal can be made into a simple structure with sufficient withstand voltage performance, and the flange portion for mounting multiple ground potential electrodes can be made simple. It is possible to obtain a microwave oven magnetron that is integrated with sufficient mechanical strength, is easy to attach to a shield box, and does not cause undesired radio wave leakage from the attachment surface.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view of the main part showing an embodiment of this invention, Fig. 2 is a front view of the main part, Fig. 3 is a perspective view of each electrode before assembly, and Fig. 4 is the state when filled with resin. 5 is a front view, FIG. 6 is a vertical sectional view after resin filling, FIG. 7 is a front view, FIG. 8 is a side view showing the integrated state, and FIG. 9 is a side view showing the integrated state. FIG. 10 is a front view of main parts showing another embodiment of the invention, and FIGS. 11 and 12 are perspective views and front views of main parts showing still other embodiments. 11... Oscillator main body, 15... Stem part, 16
...Shield box, 18...Inductor, 2
0... High voltage input terminal, 21... Center conductor, 22...
...Cylindrical high potential electrode, 23...Cylindrical ground potential electrode, 24...Insulating resin part, 25...Flange part,
25a... joint part, 25b... bending part, 27,
28...Cylindrical sheath part.

Claims (1)

[Claims for Utility Model Registration] (1) A high-potential electrode made of a metal cylinder to which an input center conductor passes through the inside and is electrically connected, and a high-potential electrode arranged close to and separated from the outside of the cylindrical high-potential electrode. A high voltage input terminal has a ground potential electrode having a cylindrical part and a mounting flange part extending in the horizontal direction, and an insulating resin integrally molded to cover between the two electrodes and the outside of the ground potential electrode. In a microwave oven magnetron in which a plurality of magnetrons are fixed to a shield box covering an input stem portion of the magnetron, the flange portions for attaching the ground potential electrodes of each of the high voltage input terminals shall be partially welded to each other and integrated. A magnetron for microwave ovens featuring (2) The mounting flange portion of each high-voltage input terminal is formed into a crank shape on one side, and the crank-shaped portions face each other and are welded together. . (3) The mounting flange portion of each high voltage input terminal has a bent portion partially bent by approximately the thickness of the plate on one side, and the sides where this bent portion is formed face each other and are joined. A magnetron for a microwave oven according to claim 1, which is a utility model registered as claimed in claim 1.