JPS6398939A - Magnetron - Google Patents

Abstract

PURPOSE:To maintain a high output efficiency and to restrict the unnecessary radiation from the input/output part, by providing a pair of strap rings connected alternately to the inside of plural vanes, and an antenna lead with one end connected to the strap ring with the smaller diameter. CONSTITUTION:A pair of strap rings 40 and 41 with different diameters arranged inside vanes 39 and connected alternately to the vanes 39, an output antenna 46 arranged in the axial direction of an anode cylinder 38, and an antenna lead 42 with one end connected to the strap ring 41 with the smaller diameter and with the other end extended up to the output antenna 46, are provided. By providing the strap rings inside the vanes, the electric field in the antenna lead extending space can be formed in a good shape, and the unnecessary radiation to the output side can be restricted. And, since the antenna lead is arranged in a highly dense electric field space through the strap rings, the combination with the microwave energy can be made larger sufficiently, and a high output efficiency is relized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to magnetrons, and more particularly to improved anode structures and output structures that suppress unnecessary radiation from magnetron input/output sections.

BACKGROUND OF THE INVENTION With the rapid spread of microwave ovens in recent years, the technology of microwave ovens has been relentlessly pursued in order to meet the demands and goals of both demand and supply, such as smaller size, lighter weight, and lower price. Considering the above circumstances, the magnetron installed in this microwave oven has been made smaller, lighter, more efficient, and has lower noise.
There is a demand for lower prices. The structure of a conventional general magnetron is shown in FIG. In the figure, 1 is an anode cylinder, 2 is a plurality of vanes arranged inside the anode cylinder, and 3 is arranged on both ends of the vane in the axial direction of the anode cylinder tube, alternately with the plurality of vanes every other vane. A strap ring consisting of two pairs of connected rings, 4 is an antenna lead, one end of which is connected to any one of a plurality of vanes at a desired position, and a coupling hole of a pole piece 5 provided at the end of the anode cylinder. 6 and extends to an output antenna section 7 whose other end is arranged in the axial direction of the anode cylindrical tube. This antenna lead 4
is cut at the same time as the exhaust pipe 8, which serves as an exhaust path when evacuating the inside of the anode cylinder, and is integrally connected and fixed to the exhaust pipe at the cut portion of the exhaust pipe, as shown in the figure.

The cathode section 9 is composed of a spiral filament arranged concentrically with the anode cylinder at the center of the anode cylinder, and end hats 10 and 11 are arranged at both ends of the helical filament. Each end hat is connected to a support lead 12, 13 arranged in the axial direction of the anode cylinder tube. Each support lead is silver-copper soldered to a cathode stem 14 made of a ceramic material disposed on the end face of the anode cylinder opposite to the output antenna part, and this cathode stem is connected via a silver-copper brazed cathode side tube 15. The anode is fixedly assembled on the end face of the anode cylinder. 16 is the pole piece on the cathode stem side, 17.18
19, 20 are permanent magnets, 21 are heat dissipation fins press-fitted into the anode cylindrical tube, 22 and 23 are yoke forming a magnetic circuit, 24 is a core choke coil, 25 is a feedthrough capacitor, and 26 is a filter box.

One way to increase the magnetron output efficiency in such a conventional magnetron structure is to connect the antenna lead to the vane as close to the center of the anode cylinder as possible. By the way, as is clear from the structure of the conventional magnetron, since a strap ring is disposed at the end on the vane side, the connection position is limited due to the structure. In addition, considering the second characteristic, the electromagnetic field distribution in the space near where the strap ring is placed is extremely disordered, as will be described later, so the antenna lead should be connected to the vane to prevent unnecessary radio waves from coupling with the antenna lead. In a connection structure in which the mf anode is moved toward the inner wall of the cylinder, the efficiency decreases. In other words, it is difficult to say that the conventional magnetron structure satisfies both high output efficiency and suppression of unnecessary radiation at the same time.

FIG. 4 shows the electric field distribution on the vane side end face of a conventional magnetron anode structure measured by the present inventors. In the figure, 27 is the inner surface of the anode cylinder, 28 and 29 are vanes facing each other within the anode cylinder, 30 to 33 are strap rings, and 34 is a portion to which an antenna lead is connected. From the figure, it can be seen that in the conventional structure in which the strap ring is placed at the end on the vane side, the electric field is greatly disturbed near the strap ring. It is also recognized that a certain amount of electric field exists in the space formed between the opposing vanes and into which the cathode portion is inserted and loaded. This indicates that a part of the microwave energy generated within the anode cylinder is combined with the cathode part, and it is thought that this disturbs the movement of electrons emitted from the cathode part. It is thought that unnecessary radiation toward the cathode stem side 1 is promoted.

By the way, as a structure for making the magnetron smaller and lighter, a structure in which the output antenna section is provided in a direction perpendicular to the axis of the anode cylindrical tube is considered. Such a structure was developed in Japanese Patent Application Laid-Open No. 56-39.
This is shown in Publication No. 43.

However, the strap ring structure disclosed in this publication is considered to be arranged on both end faces of the vane like two chains, and is not a structure for suppressing unnecessary radiation.

Meanwhile, Beverly D, ump f @ 1
A unique magnetron structure is disclosed in US Pat. No. 4,310,786 by et al. The main feature of this structure is the support structure for the cathode section. That is, the cathode section is supported by a pair of pole pieces.

The second feature is a structure in which a pair of strap rings are arranged at the center of the vane in the axial direction of the anode cylindrical tube. The present inventors measured the electric field distribution at the vane side end of an anode structure in which such a strap ring is arranged inside the vane, and obtained the following results.

This electric field distribution characteristic is shown in FIG. In the same figure, 35
is the inner wall of the anode cylinder, and 36 and 37 are a pair of strap rings. There are two major differences in characteristics between this structure and conventional anode structures. The first point is that the electric field distribution on the vane side end face is orderly, and the second point is that the electric field distribution is symmetrical with respect to the tube axis, and the electric field strength in the space between the opposing vanes. This is because the coupling of microwave energy to the cathode part is weak. That is, it is thought that if such an anode structure is used, the movement of electrons will be less likely to be disturbed by microwaves, and the suppression of unnecessary radiation that is coupled to the cathode portion and leaks will be significantly improved.

By the way, the output structure disclosed in the above-mentioned US patent, that is, the microwave energy derivation structure in which one end of the antenna lead is looped and the tip thereof is connected to the vane has the following disadvantages. That is, the inner cone increases the output efficiency of the magnetron to the efficiency achieved by the conventional output derivation structure shown in FIG. The reason for this is due to the pair of strap ring structures. In other words, to determine the resonant frequency of a small resonant cavity formed between adjacent vanes and the inner surface of the anode cylinder, the inductance Lr and capacitance CP of the cavity when no strap ring is used, as is well known.
and the capacitance Cs caused by strapping loading. Further, the ratio of Cr and Cs needs to be set to an appropriate ratio from the viewpoint of oscillation mode separation. In other words, in order to obtain with a pair of straps the capacitance value conventionally obtained with two pairs of strap rings, it is necessary to increase the length of the strap ring disposed within the small resonant cavity. In other words, the diameter of the strap ring is required to be larger than that of the conventional method. For this reason, the connection position of the antenna lead to the vane is moved closer to the inner wall surface of the anode cylinder than in the past, resulting in weaker coupling and lower efficiency. If you dare to improve the efficiency using conventional technology, you can make the antenna lead longer, but from the above, increasing the length can only be achieved outside the anode cylinder, so as a result, it means lengthening the output antenna part. Therefore, it is necessary to go against the trend of miniaturization or to create an impractical configuration.

Problems to be Solved by the Invention As mentioned above, according to the conventional magnetron structure, when the strap rings are arranged on both end faces of the vane, the output efficiency is increased.The connection position of the antenna lead vane is on the strap ring. Due to the close proximity of the strap ring, there is a problem that it is likely to combine with the disordered electric field distribution near the strap ring and cause unnecessary radiation.On the other hand, when the strap ring is placed inside the vane, the conventional structure has the problem that the output efficiency decreases. there were.

The present invention solves these conventional problems and provides a compact magnetron that maintains high output efficiency and suppresses unnecessary radiation from the input/output section.

Means for Solving the Problems In order to solve the above problems, the magnetron of the present invention includes a pair of strap rings arranged inside a plurality of vanes and alternately connected to every other vane, and the strap rings. It has a structure including an antenna lead whose one end is connected to a strap ring having a smaller diameter.

Function: With the above configuration, the small diameter strap ring placed in the high density microwave energy space essentially behaves like an antenna lead, which can increase the coupling with the microwave energy, resulting in high output efficiency. It is something.

Example An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of a main part of a magnetron showing an embodiment of the present invention, and FIG. 2 is a perspective view of the main part.

In the figure, 38 is an anode circular part, 39 is a plurality of vanes disposed inside the anode cylinder, 40 and 41 are disposed on the same plane approximately in the center of the anode cylinder tube in the axial direction, and 40 and 41 are arranged on the same plane and are connected to a plurality of vanes. A pair of strap rings 42 of different diameters are connected alternately and alternately, 42 is an antenna lead, and one end is connected to a strap ring 41 of a smaller diameter approximately in the center of adjacent vanes of a plurality of vanes, and this connection point A curved portion 45 is provided which curves on the opposite side to the pole piece 43 from the end surface of the anode cylinder to the coupling hole 44 provided in the pole piece 43 attached from the end surface of the anode cylinder. A section is provided to extend concentrically inside an exhaust pipe 47 which is a component of the output antenna section 46 arranged in the axial direction of the anode cylindrical tube. The figure shows an assembly configuration diagram that occurs after the bleed pipe and the antenna lead are cut together, and one end of the antenna lead is also fixed as shown in the figure. 48 is a pole piece attached from the other end of the anode cylinder, 49 is an antenna side tube, 50 is a side tube made of ceramic material and is a component of the output antenna section, and 51 is an antenna cap.

In the second configuration, by arranging the strap ring inside the vane, the electric field distribution in the space in which the antenna lead extends can be made orderly, and unstable radiation toward the output side can be suppressed. Furthermore, since the antenna lead is arranged in a high-density electric field space via the strap ring, the coupling with microwave energy can be sufficiently increased, and high output efficiency can be obtained.

The antenna lead connected to the small-diameter strap ring has a part extending from this connection position to some extent in the axial direction of the anode cylinder tube. It is also possible to connect one end directly to the strap ring using a curved portion that creates a gap. Further, the shape of the antenna lead may be a round bar, a plate, or a round bar with a part of the plate shape.

Effects of the Invention As described above, the magnetron of the present invention provides the following effects.

(1) By directly connecting the antenna lead to the strap ring placed in the high-density electric field space inside the vane, high output efficiency can be achieved while suppressing unnecessary radiation.

(2) The antenna lead is provided with a bent or curved portion to prevent deformation of the strap ring caused by the antenna lead being pushed toward the anode cylinder due to the change in volume of the antenna lead that occurs when it is cut integrally with the exhaust pipe. The antenna lead can sufficiently absorb the stress generated when cutting the exhaust pipe, prevent deformation of the strap ring, and provide a highly reliable magnetron.

(3) By arranging a strap ring inside the vane, unnecessary radiation toward the cathode stem side can be sufficiently suppressed.

[Brief explanation of the drawing]

4 is a sectional view of a conventional magnetron, FIG. 4 is an electric field distribution diagram in a conventional anode assembly, and FIG. 5 is an electric field distribution diagram in an anode assembly of the present invention. 3rd... Anode cylinder, 39... Vane,
40...Large diameter strap ring, 41...
...Small diameter strap ring, 42...Antenna lead, 46...Output antenna section. Name of agent: Patent attorney Toshio Nakao and one other person
Large diameter t Strap ring 4/- Discretionary small 9 Fig. 2 Fig. 3 Fig. 4 Fig. 5

Claims (1)

[Claims] a plurality of vanes arranged radially within the anode cylinder; a pair of strap rings with different diameters arranged inside the vanes and connected to the vanes alternately; and an output arranged in the tube axis direction of the anode cylinder. A magnetron having an antenna part and an antenna lead having one end connected to the strap ring having a small diameter and the other end extending to the output antenna part.