JPH0765730A - Magnetron - Google Patents

Abstract

PURPOSE:To restrain the temperature rise of a strap ring and prevent the crack or fracture thereof without sustaining any increase in cost by maintaining the size of a vane at the end of an anode cylinder larger than at the end of a cathode in a tube axis direction. CONSTITUTION:This magnetron has a plurality of vanes 2 radially projected from the internal surface of an anode cylinder toward an axial center and electrically shortcircuited alternately via strap rings 3 and 4. The size H of the vane 2 at the end of the anode cylinder is made larger than the size (h) at the end of a cathode along a tube axis direction. According to this construction, the thermal resistance of the vane 2 can be lowered, and the use of an expensive material for the rings 3 and 4 is not required, thereby avoiding an increase in cost. Also, a temperature difference between the external surface of the anode cylinder and the secured sections of the rings 3 and 4 can be reduced to alleviate thermal deformation stress, thereby enabling the crack or fracture of the rings 4 and 4 to be prevented during intermittent operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron, and more particularly to its anode part.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIGS.

A magnetron is widely used as a microwave oscillation source for a microwave oven, etc., and its structure is such that a plurality of vanes 2 are formed on the inner peripheral surface of an anode cylinder 1 which constitutes a part of a vacuum envelope, as shown in FIG. Are arranged in a radial pattern, and the vanes are connected to each other by strap rings 3 and 4.

At both ends of the anode cylinder 1, pole pieces 5 and 6 made of a magnetic material and metal cylinders 7 and 8 forming a part of the vacuum envelope are fixed. One metal cylinder 7
Is an insulating cylindrical body 9 made of ceramics and a cylindrical metal body.
10 are fixed in order.

Inside these, a central conductor 11 having one end fixed to one of the vanes 2 and the other end fixed to the cylindrical metal body 10 is arranged, and the anode cylinder 1 is also provided. A cathode part 12 for emitting thermoelectrons is arranged at the axis center of.
Among them, the anode cylinder 1, the vane 2, the strap ring 3,
Oxygen-free copper, which is excellent in electrical conductivity and thermal conductivity even when the temperature rises and emits little gas, is used for the center conductor 4 and the central conductor 11.

However, in the magnetron having the above-mentioned structure, when it is used in a microwave oven or the like, its oscillation efficiency greatly changes depending on the load of food or the like placed in the heating chamber of the microwave oven. Especially in the empty cooking state where no load is applied, the oscillation efficiency becomes almost zero, and all the microwave power sent from the magnetron into the microwave heating chamber returns, so-called total reflection state where all microwave power is heated inside the magnetron. It is consumed as a loss.

At this time, the end portion of the vane 2 on the cathode side becomes the highest temperature and receives a large heat shock. Especially, since the strap rings 3 and 4 are fixed to the end of the vane 2 on the cathode side, the temperature is high, and the vane 2 is a free end because the anode cylinder 1 is cooled by air cooling or the like. While the strap rings 3 and 4 are thermally expanded in the direction, the strap rings 3 and 4 are subjected to severe thermal deformation stress due to the thermal expansion toward the anode cylinder 1 side. However, there is a problem in that the cracks and fractures lead to changes in oscillation frequency and unstable operation.

As a conventional technique for solving the above problems, a method of improving the heat resistance of the strap ring itself has been used.

As a technique for improving the heat resistance of the strap ring itself, as disclosed in JP-A-63-143722, a precipitation-hardening type metal obtained by adding 1% or less of zirconium to oxygen-free copper, and JP-A-58-58. It was effective to use a molybdenum material, which is a heat-resistant metal having a small thermal expansion disclosed in Japanese Patent Publication No. 54771.

However, the above-mentioned prior art has the following drawbacks. In other words, when changing the material, silver brazing and zirconium-containing oxygen-free copper and molybdenum used as brazing materials are used when brazing in a reducing atmosphere such as hydrogen when assembling the anode assembly consisting of the anode cylinder, vane and strap ring. However, in both cases, surface treatment such as nickel or copper plating is required, which is an unnecessary factor of cost increase.

[0011]

SUMMARY OF THE INVENTION Therefore, in the present invention, the magnetron which suppresses the temperature rise of the strap ring without the problem of unnecessary cost increase and prevents the strap ring from cracking or breaking due to thermal stress relaxation during intermittent operation. The challenge is to provide.

[0012]

The present invention is directed to an anode cylinder,
A plurality of vanes that are arranged on the inner peripheral surface of the anode cylinder and radially protrude toward the axis, a strap ring that electrically short-circuits the vanes alternately, and a strap ring that are arranged at the axis of the anode cylinder. In a magnetron having a cathode, the dimension of the anode cylinder side end is larger than the dimension of the cathode side end of the vane in the tube axis direction, and further, at least the output side edge of the vane and the input side edge. One edge is formed in a taper shape.

[0013]

In the magnetron according to the present invention, the space formed by the vane, the anode cylinder, and the mortar-shaped pole piece can be effectively used to reduce the thermal resistance of the vane, so that the temperature of the strap ring can be increased without unnecessary cost increase. Since the rise can be suppressed and the thermal deformation stress can be relieved, the strap ring can be prevented from cracking or breaking during intermittent operation.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a sectional view of an essential part of an embodiment of the present invention, but the description of the same parts as those of the conventional structure will be omitted.

2a and 2b are the anode cylinder 1 side of the vane 2,
Anode cylinder 1, vane 2 and mortar-shaped pole piece 5,
A dimension expansion portion formed by utilizing a wider space on the side of the anode cylinder 1 in the space formed by 6 and projecting in the tube axial direction, H
Is the dimension of the anode cylinder side end in the expanded tube axis direction,
h is the dimension of the cathode side end which is not enlarged, and H> h
Have a relationship. The strap rings 3 and 4 are set and arranged so as to have substantially the same axial dimension as the protruding portions 2a and 2b.

FIG. 2 is a sectional view of the essential part of another embodiment.
Is an output side edge of the vane 2, 14 is an input side edge, and these both edges are formed in a taper shape as shown in FIG. 2 to further reduce the influence of thermal resistance.

In the magnetron of the present invention having the above-mentioned structure, the thermal resistance of the vane 2 can be reduced by enlarging a part of the dimension in the tube axis direction, and the cathode of the vane 2 which determines the operating characteristics can be reduced. Since the size of the anode inner diameter portion formed by the side tip portion can be made equal to that of the conventional one, it does not adversely affect the conventional operating characteristics, and the strap ring is attached to the outer peripheral surface of the anode cylinder 1 which regulates the operating temperature of the magnetron. The temperature difference between the fixed portions 3 and 4 is reduced to reduce the thermal deformation stress, and the strap ring 3 at the time of intermittent operation,
It is intended to prevent cracks and fractures of No. 4.

Further, since oxygen-free copper can be used as the material for the strap rings 3 and 4 as in the prior art, it is not necessary to use oxygen-free copper or molybdenum containing zirconium as in the prior art, and unnecessary cost increase is not caused.

FIG. 3 shows the effect of one embodiment of the present invention. This is a plot of the time until the deviation of the oscillation frequency with respect to the anode temperature reaches 10 MHz (estimated time until the strap ring cracks or breaks) when the magnetron is operated intermittently under certain specific conditions. is there. It can be seen that the anode temperature can be increased about twice as long as the anode temperature is the same as that of the conventional magnetron, and the anode temperature can be increased by about 50 ° C. at the same time.

[0021]

As described above, the magnetron according to the present invention uses the space which has never been used in the past to achieve the function which was conventionally achieved only by changing the material of the component, and the tube axis of the vane. By partially enlarging the directional dimension, it is possible to achieve a reduction in thermal resistance, which leads to unnecessary cost increase and does not change the operating characteristics, so it is harsh, such as when cooking with a microwave oven. It is possible to provide a high-quality magnetron which prevents the strap ring from cracking or breaking even under various usage conditions.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part according to an embodiment of the present invention.

FIG. 2 is a sectional view of an essential part according to another embodiment of the present invention.

FIG. 3 is a graph showing the effect of one embodiment of the present invention.

FIG. 4 is a sectional view of the body of a conventional magnetron.

FIG. 5 is a cross-sectional view of a main part of a conventional magnetron.

[Explanation of symbols]

 1 Anode cylinder 2 Vanes 3, 4 Strap ring 12 Cathode part 13 Output side edge 14 Input side edge h Cathode side edge dimension H Anode cylinder side edge dimension

Claims (2)

[Claims] 1. An anode cylinder, and a plurality of vanes arranged on an inner peripheral surface of the anode cylinder and radially protruding toward an axis.
In a magnetron having a strap ring that electrically short-circuits the vanes alternately and a cathode portion arranged at the axial center of the anode cylinder, the anode cylinder side is closer to the cathode side end of the vane in the tube axis direction. A magnetron with a large end size. 2. The magnetron according to claim 1, wherein at least one of the output side edge and the input side edge of the vane is formed in a taper shape.