JPH0340341A - Magnetron for microwave oven - Google Patents

Abstract

PURPOSE:To prevent displacement of an anode vane with a radiation fin fitted, by restricting to a certain extent the tapered part to be formed on the peripheral wall of an anode cylinder for the purpose of pressure fitting of the radiation fin. CONSTITUTION:A radiation fin 14 is inserted into an anode cylinder 21 from its top opening and jointed to a tapered surface 22 formed on the anode cylinder 21 from its top to a below part. The taper length P alongside the outer wall of this anode cylinder shall cover from the top of the anode cylinder to the neighborhood of the top of an anode vane 12 installed inside of the anode cylinder. Accordingly the anode cylinder 21 does not generate decrease in the outer wall strength in the vane 12 securing part due to tapering. Even though the radiation fin 14 is pressure fitted, therefore, the vane 12 refrains from displacing, so that fitting of the radiation fin will never impair the oscillation characteristic of the magnetron.

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 particularly to an improvement in its anode structure.

(Prior Art) The anode portion of a magnetron for a microwave oven has conventionally generally been constructed as shown in FIG. That is, on the inside of an anode cylinder 11 made of copper, for example, ten plate-shaped anode vanes 12 also made of copper are fixed by soldering. This anode cylinder is assembled with the necessary parts and then evacuated. Further, a tapered surface 13 is previously formed on the outer circumferential wall of the anode cylinder 11 in a range S from one open end to a position corresponding to the other end of the vane 12 by cutting. This tapered surface 13 is necessary so that the heat dissipating fins 14 made of aluminum can be easily and tightly press-fitted onto the outer periphery of the anode cylinder after evacuation. The radiation fin 14 has a short cylindrical portion 15 formed in the center of a rectangular plate to be press-fitted onto the outer periphery of the anode cylinder. The inner diameter of the short cylindrical portion 15 is smaller than the maximum outer diameter of the anode cylinder, and the short cylindrical portion 15 is formed to have a size that allows it to be tightly fixed mechanically and thermally by press-fitting. Usually, about 4 to 6 heat dissipation fins are stacked.

(Problem to be Solved by the Invention) According to such a conventional structure, the tapered surface of the anode cylindrical outer peripheral wall is formed in a region extending almost completely beyond the vane position from one open end, so that the heat dissipation fin Although press-fitting is easy, it has been confirmed that the following inconveniences occur. That is, as the heat dissipation fins are repeatedly press-fitted a predetermined number of times, the anode cylinder deforms inward at the vane corresponding position, and the distances rl and r2 between the upper and lower surfaces of the inner end of the vane 12 and the central axis become uneven. Moreover, the size becomes smaller than the original size, and the oscillation characteristics tend to deteriorate. In particular, in recent years, there has been a trend to reduce the wall thickness of anode cylinders more and more from the viewpoint of resource conservation, and such inconveniences can no longer be ignored.

The present invention solves the above-mentioned disadvantages, and provides a magnetron for a microwave oven in which the oscillation characteristics are not deteriorated due to deformation of the anode cylinder or displacement of the anode vane without impairing the ease of press-fitting the radiation fins. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) This invention provides an outer circumferential wall of an anode cylinder from the vicinity of the open end where the radiation fins are press-fitted to the vicinity of the position corresponding to the anode vane end close to this. This is a microwave oven magnetron formed into a tapered shape.

(Function) According to the present invention, since the tapered surface is formed only on the opening side at one end of the anode cylindrical outer circumferential wall, it is easy to press-fit the radiation fins, and the anode cylindrical wall in the area corresponding to the vane position is easy to press-fit. Since the anode cylinder has a uniform thickness, there is little deformation of the anode cylinder due to the press-fitting of the fins, and therefore almost no displacement of the vane inner end surface occurs. This suppresses deterioration of oscillation characteristics.

(Example) Examples thereof will be described below with reference to the drawings.

In addition, the same parts are designated by the same symbols.

As shown in FIG. 1, from the vicinity of the open end 21a into which the radiation fins 14 are press-fitted into the anode cylinder 21,
A region P corresponding to the anode vane end 12a close to this
A tapered surface 22 is formed on the outer peripheral wall of the anode cylinder. The anode structure of this example is disclosed in Japanese Patent Application Laid-Open No. 62-8124.
This is similar to that described in Publication No. 3. That is, the anode vane 12 is mechanically clamped by a plurality of pairs of embossments 23 that protrude from the outside to the inside at a predetermined position of the anode cylinder, and is further fixed by soldering.

The tapered surface 22 is formed up to the position of the embossed recess 23a. Note that at both open ends of the anode cylinder, there are stepped portions 24a for attaching pole pieces (not shown).
.

24b, and a short tapered portion 24 for forming a welding allowance.
c is formed. The anode cylinder 21 is formed to have a uniform thickness except for the region of the outer peripheral tapered surface 22. After the anode is assembled and evacuated in this way, the radiation fins 14 are press-fitted from the tapered surface 22, and several fins are laminated and fixed.

This causes almost no deformation of the anode cylindrical wall at the position of the anode vane, and therefore almost no displacement of the inner end surface of the vane.

In the embodiment shown in FIG. 2, a tapered surface 25 for vane insertion is formed on the inner surface of the anode cylinder on the opposite side to the anode cylinder outer peripheral tapered surface 22 for press-fitting the radiation fins. The anode structure of this embodiment has a structure in which the vane is fixed to the inner wall of the anode cylinder by soldering. The figure shows the state in which the vane is installed. A vane positioning jig 26 is placed in the center, and the vane 12 is radially positioned using the tapered surface 25 from the bottom of the drawing.
Attach to. The tapered surface 25 is formed in a region Q up to the vane, and has a diameter that increases in substantially the same direction as the fin press-fitting tapered surface 22. The anode cylinder wall in the region corresponding to the location of the vane 12 then remains of uniform thickness.

In this embodiment as well, it is easy to attach the vane or the radiation fin to the anode cylinder, and deformation of the anode cylinder wall at the vane position and displacement of the inner end surface of the vane are suppressed.

[Effects of the Invention] As explained above, according to the present invention, it is easy to press-fit the radiation fins, and there is almost no deformation of the anode cylindrical wall corresponding to the vane position, so no displacement of the inner end surface of the vane occurs. Deterioration of oscillation characteristics is suppressed.

[Brief explanation of drawings]

FIG. 1 is a half-assembled cross-sectional view showing a single-cusp embodiment of the present invention, FIG. 2 is a half-assembled cross-sectional view showing another embodiment of the present invention, and FIG. 3 is a half-assembled cross-sectional view showing a conventional structure. . 21...Anode cylinder, 12...Vane, 14...Radiation fin, 22...Tapered surface, P...Tapered region.

Claims (1)

[Claims] In a microwave oven magnetron comprising an anode cylinder, a plurality of anode vanes fixed to the inside of the anode cylinder, and heat dissipation fins press-fitted and stacked on the outer periphery of the anode, the anode cylinder has the above-mentioned A magnetron for a microwave oven, characterized in that an outer circumferential wall from the vicinity of the opening end of the anode cylinder where the radiation fins are press-fitted to the vicinity of the position corresponding to the anode vane end close thereto is formed in a tapered shape.