JPS63146326A - Magnetron for electronic oven and manufacture thereof - Google Patents

Abstract

PURPOSE:To control dislocation between both center shafts of the anode and the cathode and improve their mechanical strength, by fastening a part of mating faces between a pole piece and a flat flange part of a metallic vessel by means of welding. CONSTITUTION:A pole piece 23 and a flat flange part 18a of a metallic vessel 18 are fitted in an aperture end of an anode cylinder 11, and the whole circumference is caulked tight as in an arrow F with uniform force at the same time. And, the whole circumference is joined together airtightly in a vacuum manner by means of arc welding. With this joining, the center shaft of a cathode supporting body structure 15 is congruently locked to that of the anode cylinder 11. Thus, respective parts can be assembled in a state of having them accurately positioned. And especially, since the flat flange part 18a proximate to the root of a cylinder part of the metallic vessel 18 is tightly welded to the pole piece 23, such a possibility that the cathode is eccentric to the anode is brought to almost nothing, so that mechanical strength is improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetron for a microwave oven and a method for manufacturing the same, and particularly relates to a combination structure of an anode cylinder and a cathode support structure and an assembly thereof. Regarding the method.

(Prior Art) The structure of a conventional microwave oven magnetron and the method of assembling its anode cylinder and cathode support structure are shown in FIG.

In the figure, reference numeral 11 indicates a copper anode cylinder;
2 is a plurality of copper anode vanes, 13 is a pair of strap rings, 14 is an output antenna lead, 15 is a cathode support structure, 16 is a ceramic stem thereof, 11 is a cathode external terminal, 18 is a metal container, and 18a is a flat flange thereof. 18b is the cylindrical portion thereof, 19 is a pair of rod-shaped cathode supports, 20.21 is a pair of end shields, 22
23 is a cathode made of a coiled filament, and 23 is a funnel-shaped pole piece made of iron.

When assembling the anode cylinder 11 and the cathode support structure 15, first, place the first positioning jig 24 and the second jig 25 in the center at the lower end opening of the anode cylinder 11 that houses the anode vane 12. Fit together.

The thin cylindrical portion 25a of the second jig 25 is inserted into the inner end of the anode vane 12 so as to be in close contact therewith. Next, the pole piece 23 is fitted, and the cathode support structure 15 is then fitted.
is mounted so that the cathode 22 is positioned inside the cylindrical portion 25a of the second jig 25. Then, the open end of the anode cylinder is caulked and fixed as shown by arrow F, and each member is fixed. Thereafter, arc welding torches (not shown) are placed close to each other at the position of arrow F, and the entire circumference is hermetically sealed by arc welding.

(Problems to be Solved by the Invention) According to such a conventional structure of a magnetron for a microwave oven, the connection portion between the anode cylinder 11, the pole piece 23, and the cathode support structure 15 is completely separated as shown in FIG. Only the circumferential arc welded part B. However, since the ceramic stem 16 and the terminal 17 have a structure that protrudes far outward from the welding part B, undesirable stress in the lateral direction as shown by the arrow H is applied when connecting the connector to the terminal 11. There is. Then, the anode cylinder 11
The central axis 0 of the cathode support structure deviates slightly from the central axis C of the cathode supporting structure, and an angle θ is created between the two.

As a result, the coaxial positional relationship between the working space side end surface of the anode vane 12 and the cathode 22 is disturbed, leading to deterioration of the firing characteristics and, in extreme cases, a short circuit between the electrodes. Further, one of the flat flange portions 18a of the metal container 18 rises from the surface of the pole piece 23, creating a gap Q between the two, resulting in a magnetic path from the permanent magnet stacked on the flat flange portion to the working space. There is also a risk that the magnetic resistance of the magnet will increase, resulting in a decrease in efficiency. Note that reference numeral 19a in the figure indicates a ceramic spacer that maintains the two cathode supports at a constant interval.

A proposal for preventing such eccentricity of the cathode is disclosed in, for example, Japanese Utility Model Application Publication No. 55-31239. It has a tapered part formed near the lower end of the cylindrical part of the metal container. However, such a structure has the disadvantage that the magnetic coupling area between the permanent magnet and the pole piece becomes small, resulting in a decrease in magnetic efficiency.

On the other hand, according to the assembly method shown in FIG. 8, a part of the welding current flows from the pole piece through the thin cylindrical portion 25a of the central positioning jig. In mass production, when welding current flows through this jig cylindrical portion 25a during repeated manufacturing, this portion generates heat and expands. For this reason, the fit between the jig and each part gradually becomes tighter, resulting in a decrease in dimensional accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetron for a microwave oven that eliminates the above-mentioned disadvantages, suppresses changes in the coaxial positional relationship between an anode and a cathode, and does not cause a decrease in dimensional accuracy, and a method for manufacturing the same. .

[Structure of the Invention] (Means for Solving the Problems) This invention provides a part of the mating surface between the funnel-shaped pole piece and the flat flange portion of the metal container covering the same, particularly preferably a radius of the mating surface of both. This is a magnetron for a microwave oven in which a part of the inner side of the direction midway is integrally fixed by welding.

The assembly method is characterized by first positioning the flat flange of the metal container of the cathode support structure and the pole piece using a positioning jig, and then positioning a part of the mating surface between the flat flange and the pole piece. They are fixed together by welding, and then the assembly structure of the cathode support structure and pole piece is aligned with the open end of the anode cylinder.
The opening end of the anode cylinder and the outer peripheral edge of the metal container flange are hermetically connected.

(Function) According to the present invention, the relatively inner side of the mating surface between the pole piece and the flat flange portion of the metal container of the cathode support structure covering the pole piece is fixed by welding, so that the central axis of the anode and the center of the cathode Misalignment with the shaft is suppressed and mechanical strength is high. Also, high precision assembly is possible.

(Example) An example will be described below with reference to the drawings. Identical parts are designated by the same reference numerals.

First, the main parts of the completed state will be explained with reference to FIGS. 1 and 2.

This magnetron is connected to a flat flange portion 18 of a metal container 18.
A portion of the contact surface of the funnel-shaped pole piece 23 with the flat surface 230 is welded and fixed integrally at four locations on the circumference. The welding fixation portion between the pole piece 23 and the flat flange portion 18a is provided at a position relatively close to the cylindrical portion 18a of the metal container, inside the radial middle of the mating surfaces thereof. Note that the flat flange portion 18a
Four small protrusions 18c, 118c, . . . are formed near the middle in the radial direction to form a heat-insulating gap between the ring-shaped permanent magnet (not shown) stacked on top of the ring-shaped permanent magnet. ing. The welding fixing portion is formed inside these small protrusions 180, that is, at a position closer to the tube axis.

Next, a preferred method of assembling this magnetron will be explained.

First, as shown in FIG. 3, each component and positioning jig are prepared. The cathode support structure 15 has a ceramic stem 16 hermetically sealed to the upper end opening of the cylindrical portion 18a of the metal container 18 as shown in the figure.
A pair of cathode supports 19 and terminals 17 are fixed to 6. A pair of end shields 20, 21 and a coiled filament cathode 22 are fixed to the tip of the cathode support 19.

Four small protrusions 18c are formed on a portion of the flat flange portion 18 of the metal container.

On the other hand, the first outer jig 24 is made of a copper alloy, and the second inner jig 25 made of molybdenum is disposed inside thereof. Then, the funnel-shaped pole piece 23 is attached to both jigs 24.
Attach it to 25. The center through hole 23a of the pole piece is connected to the thin cylindrical portion 25 of the second jig 25, which is formed to have a predetermined size.
It is tightly fitted to the outer periphery of a. Further, the flat portion 23b of the pole piece is placed on the upper surface 24a of the first jig 24. Then, as shown in FIG. 4, the cathode support structure 15 is attached from above while its end shield 20.21 is tightly fitted inside the cylindrical portion 25a of the second sleeper. In this state, the pole piece 23 and the cathode support structure 15 are accurately positioned at their central portions.

Next, one of the welding electrodes 27, 27 connected to the resistance welding device 26 is connected to the flat flange portion 18 of the metal container.
Simultaneously contacts 4 locations around the entire circumference of a. The welding electrode 27 is located relatively inside the flat flange portion 18a, that is, the cylindrical portion 18b.
contact at a position close to . Note that the other welding electrode is connected to the first outer jig 24.

Then, while applying pressure evenly to all the welding electrodes in the direction of arrow P, the relay set is energized to weld. At this time, almost all of the welding current flows through the outer first jig 24. In this way, the pole piece and the flat flange of the metal container are 4
It is fixed integrally by spot welding in several places.

Next, each jig is removed, and the pole piece 23 and the flat flange portion 18a of the metal container are fitted into the open end of the seven-node cylinder 11 without using the jig, as shown in FIG.
Caulk and fix the entire circumference at the same time with equal force as shown by arrow F.

Then, the entire circumference is vacuum-tightly joined by arc welding. Thereby, the central axis of the cathode support structure 15 is fixed to coincide with the central axis of the anode cylinder 11. In this way, each part can be assembled with accurate positioning.

In particular, the flat flange near the base of the cylindrical part of the metal container is welded and fixed to the pole piece at several points, so even if stress is applied from the outside to the stem or cathode terminal, the cathode will not be connected to the anode. Eccentricity is almost eliminated and mechanical strength is increased. In this way, dimensional accuracy does not deteriorate and oscillation characteristics do not deteriorate. Also,
The flat flange portion of the metal container can be configured to have a relatively large area, and the area of magnetic contact with the ring-shaped permanent magnet stacked thereon can be increased. Therefore, there is no possibility that the magnetic utilization efficiency will decrease.

In the embodiment shown in FIGS. 6 and 7, the positioning jig 24
．． 25 are electrically insulated with an insulating cylinder 28 interposed between them, and are assembled. Outside jig 2
4 is formed with a tapered portion 24a into which the funnel-shaped pole piece 23 is tightly fitted.
3, and the respective parts are aligned in the same manner as in the previous embodiment, and resistance welding is performed by passing a current between the rod-shaped welding electrode 21 and the outer jig 24 to which the welding electrode is connected.

According to this embodiment, no welding current flows through the thin cylindrical portion 25a involved in positioning the pole piece and the cathode. Therefore, thermal expansion of the thin-walled cylindrical portion, which requires high precision, does not occur, and even higher precision assembly is possible. Thereafter, it is joined to the anode structure in the same manner as described above.

[Effects of the Invention] As explained above, according to the present invention, the relatively inner side of the mating surface between the flat flange of the metal container of the cathode support structure and the pole piece is fixed by welding, so that the central axis of the anode and Misalignment with the central axis of the cathode is suppressed,
Mechanical strength is also improved. Therefore, there is less risk of deterioration of the oscillation characteristics, and the risk of electrical short circuit between electrodes is eliminated.

Further, according to the manufacturing method of the present invention, there is no fear that the accuracy of assembling the cathode support structure and the pole piece will deteriorate. Furthermore, by preventing welding current from flowing through the jig portion that contacts the cathode and end shield, heat generation and expansion of the jig will not occur.

Therefore, highly accurate assembly is possible.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of main parts showing one embodiment of the present invention;
The cause is the cross-sectional view at 2-2 in Fig. 1, Fig. 3 is an exploded longitudinal sectional view showing the initial state of assembly, Fig. 4 is a longitudinal sectional view of the main part showing the subsequent state, and Fig. 5 is the same. 6 and 7 are exploded sectional views and assembled state diagrams showing other embodiments of the present invention, and FIG. 8 is a main part showing the conventional assembly process. FIG. 9 is a longitudinal sectional view showing the structure. DESCRIPTION OF SYMBOLS 11... Anode cylinder, 12... Anode vane, 15... Cathode support structure, 16... Ceramic stem, 18... Metal container, 18a... Flat flange part, 18b... Cylindrical part , 22... cathode,
23... Pole piece, D... Welding fixed part, 24.
25... Jig, 26... Welding It! ! device, 27.
...Welding electrode. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 91!0

Claims (4)

[Claims] (1) An anode cylinder having a plurality of anode vanes, a plurality of anode vanes provided inside the anode cylinder, a funnel-shaped pole piece fixed to the open end of the anode cylinder, and this pole piece. A metal container in which the outer periphery of a flat flange portion is hermetically sealed to the open end of the anode cylinder, a ceramic stem hermetically sealed to the end of the cylindrical portion of the metal container, and a ceramic stem held by the ceramic stem. In a microwave oven magnetron comprising a cathode support extending inside the anode vane and a coiled filament cathode connected to the cathode support, the pole piece and a flat flange of a metal container covering the pole piece A magnetron for a microwave oven, characterized in that a part of the mating surface with the part is integrally fixed by welding. (2) The magnetron for a microwave oven according to claim 1, wherein the welded and fixed portion between the pole piece and the flat flange portion is located inside the radial middle of the mating surfaces thereof. (3) an anode cylinder having a plurality of anode vanes, a plurality of anode vanes provided inside the anode cylinder, a funnel-shaped pole piece fixed to the open end of the anode cylinder, and this pole piece. A metal container in which the outer periphery of a flat flange portion is hermetically sealed to the open end of the anode cylinder, a ceramic stem hermetically sealed to the end of the cylindrical portion of the metal container, and a ceramic stem held by the ceramic stem. In the method for manufacturing a magnetron for a microwave oven comprising a cathode support extending inside the anode vane and a coiled filament cathode connected to the cathode support, the coiled filament cathode is connected to the cathode support in advance. A cathode support structure is prepared in which a cylindrical portion of a metal container having a flat flange portion is hermetically joined to the stem, the cathode support body is supported by a ceramic stem, and the metal container of the cathode support structure is The flat flange portion and the pole piece are positioned using a positioning jig, a part of the mating surface of the flat flange portion and the pole piece is fixed together by welding, and then the open end of the anode cylinder is fixed. A magnetron for a microwave oven, characterized in that the assembly structure of the cathode support structure and the pole piece is aligned in the position, and in that state, the open end of the anode cylinder and the outer periphery of the metal container flange are hermetically connected. Production method. (4) The method for manufacturing a magnetron for a microwave oven according to claim 3, wherein the step of welding and fixing the pole piece and the flat flange portion includes welding the pole piece and the flat flange portion at a position inside the radial middle of their mating surfaces.