JPH09129149A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-noise magnetron giving no interference to the radio, television, or communication when a microwave oven is used at the home with high quality at a low cost. SOLUTION: This magnetron is provided with an anode cylinder 1, a cathode 7, a stem, multiple anode vanes 2, a microwave guiding antenna lead 9, an output section, and a pair of opposite magnetic pole pieces constituted of a stem side magnetic pole piece 6 and an output section side magnetic pole piece 5. The shape of the stem side magnetic pole piece 6 is made different from the shape of the output section side magnetic pole piece 5 in a pair of magnetic pole pieces so that the magnetic field strength difference in the center axis direction on the end faces of the anode vanes 2 is within the range of 10% or below on the stem side in the action space 8 surrounded by the cathode 7 and the tips on the center axis side of multiple anode vanes 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron used for microwave heating equipment such as a microwave oven and radar. More specifically, the present invention relates to a magnetron that suppresses noise generation during operation of the magnetron and achieves low noise.

[0002]

2. Description of the Related Art FIG. 7 is an explanatory view of a main part of a main body of a magnetron for microwave output 800 W which is generally used in a household microwave oven or the like. The magnetron is used in the frequency band of 2450 MHz. In FIG. 7, 1 is a cylindrical anode cylinder, 2 is a plurality of anode vanes radially arranged on the inner peripheral surface of the anode cylinder 1, and 3 is a pressure equalizing ring (inner strap ring) having a small diameter. ), 4 is a pressure equalizing ring (outer strap ring) having a large diameter, and 5
Is a pole piece on the output side, 6 is a pole piece on the stem side, 7 is a cathode (filament) arranged on the central axis of the anode vane 2, and 8 is on the central axis of the anode cylinder 1. so,
Moreover, it is an action space of the magnetic force line surrounded by the tips of the cathode 7 and the anode vane 2 (on the side of the central axis). Further, the anode part is composed of the anode cylinder 1, the anode vane 2, and the equalizing ring 3 having a small diameter and the equalizing ring 4 having a large diameter that connect every other one of the anode vanes 2 so as to have the same potential. .

There is an even number of small cavities surrounded by the two anode vanes 2 and the inner peripheral wall of the anode cylinder 1. The plurality of small cavities collectively form a resonance cavity of the magnetron. In order to stably oscillate in the π mode, the phases of the small cavities are shifted by π radians.

A pair of magnetic pole pieces 5 and 6 made of a magnetic material are provided at both open ends of the anode cylinder 1. The output side tubular component 10 is connected to the pole piece 5,
An input side tubular part 11 is connected to the pole piece 6, and the anode cylindrical body 1, the output side tubular part 10 and the input side tubular part 11 are connected.
The space sealed by and is kept in a vacuum state.

Further, a magnetic field is concentrated in the working space 8 by a magnet (not shown) provided outside the magnetron body, and an orthogonal electrostatic magnetic field is formed together with the high voltage applied between the anode part and the cathode 7.

In the magnetron having the above-described structure, the electrons emitted from the cathode 7 are rotated in the circumferential direction by the orthogonal electrostatic magnetic field and approach the anode vane 2, and form an electron cloud to convert energy in the resonance cavity. To be done. As a result, microwaves are induced in the resonance cavity, and are radiated into the interior of a microwave oven or the like by the microwave-leading antenna leads 9 electrically connected to one of the anode vanes 2.

In the magnetron having the above-mentioned conventional structure,
The magnetic field strength in the working space 8 becomes non-uniform in the axial direction of the anode vane 2. That is, since the magnetic force lines between the magnetic pole pieces 5 and 6 draw an arc and travel from one magnetic pole piece to the other magnetic pole piece, at the center of the gap between the magnetic pole pieces 5 and 6, the side of the anode vane 2 outside the working space 8 is located. Or it deviates to the cathode 7 side.
FIG. 9A shows frequency characteristics around the fundamental wave when the above-mentioned conventional magnetron is used, and FIG. 9B shows
The magnetic field strength difference in the central axis direction at the end face of the anode vane is shown. As shown in FIG. 9B, the distribution of the magnetic field strength on the end side (the output side end or the stem side end) of the anode vane 2 in the central axis direction is about 16% stronger than the magnetic field strength of the central portion. Has become. In addition, as shown in FIG. 9A, side lobes indicating multiple oscillation are confirmed around the main lobe that is the fundamental wave.

On the other hand, the rotation speed of the electrons is determined by the value of the ratio E / B of the electric field strength E and the magnetic field strength B in the orthogonal electrostatic magnetic field, and the non-uniform distribution of B also makes the rotation speed of the electrons non-uniform. , Causing multiple oscillations. The frequency deviation at the time of this multiple oscillation becomes noise leaking from the cathode side terminal of the magnetron to the outside, which interferes with the reception of radio, television, etc., or the frequency of the multiple oscillation itself interferes with communication. . In order to deal with this problem, as shown in FIG. 8, the flat portions 5a and 6a of the surfaces of the magnetic pole pieces 5 and 6 facing the anode vane 2 are enlarged to make the center of the end face of the anode vane 2 in the working space 8 Reducing the magnetic field strength difference at the end portions in the axial direction is disclosed in JP-A-63-110527 and JP-A-1-274341.

[0009]

However, as described above, the pole piece having a relatively large wall thickness (for example, 1.6 mm) is used.
In the bending process for forming the facing surface flat portions 5a and 6a of each of 5 and 6, it is possible to prevent the deformation of the output side tubular component 10 that is mounted and connected on the pole piece and has a relatively small thickness. Therefore, there is a problem that the inner diameter of the flat portion of the pole piece on the side to be attached to the anode cylinder cannot be increased to about 20 mm or more. Furthermore, in order to reduce the amount of use of relatively expensive magnets, in order to improve the utilization efficiency for the magnetic force of the magnets in the magnetic circuit,
The inner diameter of the flat portion of the pole piece cannot be increased.

A pressure equalizing ring 4 having a large diameter on the anode cylinder side.
Since the angles θ ₁ and θ _{2 of the} conical inclined part that is the connection part between the inner diameter side of the flat part and the outer diameter side of the small diameter flat part on the facing surface side of the pole piece are close to right angles, It becomes difficult to form the hole 5d through which the antenna lead 9 penetrates in the inclined portion of the piece 5. Further, at the time of assembly, it is difficult to penetrate the antenna lead 9 into the hole 5d to hinder the assembling property, or the positional relationship between the hole 5d and the antenna lead 9 becomes unstable, and microwave (fundamental wave) transmission is performed. It may affect the characteristics.

Further, by averaging the magnetic field strength in the working space, the inclination of the magnetic field lines at both ends in the central axis direction in the working space becomes large. Therefore, the orthogonal electrostatic magnetic field that forms the basis of the oscillation principle of the magnetron is used. Cannot be formed. That is, since the thermoelectrons emitted from the cathode deviate from the action space and flow into the pole pieces to melt the pole pieces, there is a problem that vacuum breakage due to gas release occurs and oscillation is stopped. This problem often occurs in the output side magnetic pole piece on the antenna lead side, which is particularly susceptible to the microwave reflection on the load side.

The present invention has been made to solve the above problems, and even if a microwave oven or the like is used at home,
It is an object of the present invention to provide a low-noise magnetron that does not interfere with radio, television, communication, etc., at low cost and with high quality.

[0013]

The magnetron of the present invention comprises (a) an anode cylinder, (b) a cathode, (c) a stem, (d) a plurality of anode vanes, and (e) a microwave guide. What is claimed is: 1. A magnetron comprising: an antenna lead for output; (f) an output part; and (g) a pair of magnetic pole pieces that are opposed to each other and include a magnetic pole piece on the stem side and a magnetic pole piece on the output side. b) is arranged on the central axis of the anode cylinder (a), and the stem (c) is fixed to one end of the anode cylinder (a) to support and fix the cathode (b). The anode vanes (d) are radially arranged on the inner peripheral surface of the anode cylinder (a), and the antenna lead (e) is connected to one of the anode vanes and extends outward. Cage,
The output part (f) is fixed to the other end of the anode cylinder to enclose the antenna lead to form a microwave transmission and radiation part, and the pair of magnetic pole pieces (g) is the anode cylinder. (A) is arranged at both open ends and has a flat portion at a portion connected to both open ends of the anode cylinder (a), and a flat portion is provided toward the anode vane (d). Of the pair of magnetic pole pieces (g), the magnetic pole piece on the output side of the pair of magnetic pole pieces (g) is connected to one of the anode vanes (d).
Of the action space of the magnetic force line formed by being surrounded by the cathode (b) and the tips of the plurality of anode vanes (d) on the central axis side. On the stem side, the shape of the magnetic pole piece on the stem side is set to the shape of the magnetic pole piece on the output side so that the difference in magnetic field strength in the direction of the central axis at the end face of the anode vane (d) is in the range of 10% or less. Are different from each other to form the pair of magnetic pole pieces (g).

The magnetron of the present invention comprises (a) an anode cylinder, (b) a cathode, (c) a stem, (d) a plurality of anode vanes, and (e) an antenna for deriving a microwave. A magnetron comprising a lead, (f) an output part, and (g) a pair of magnetic pole pieces facing each other composed of a magnetic pole piece on the stem side and a magnetic pole piece on the output side, wherein the cathode (b) is The stem (c) is arranged on the central axis of the anode cylinder (a), and the stem (c) is fixed to one end of the anode cylinder (a) to support and fix the cathode (b). (D) is radially arranged on the inner peripheral surface of the anode cylinder (a), and the antenna lead (e) is connected to one of the anode vanes and extends outward, The output part (f) is fixed to the other end of the anode cylinder (a), and Lead surrounding the (e) forms a microwave transmission and radiation portion, the pair of pole pieces (g)
Is disposed at both open ends of the anode cylinder (a) and has a flat portion at a portion connected to both open ends of the anode cylinder (a), and faces toward the anode vane (d). Of the pair of magnetic pole pieces (g), the magnetic pole piece on the output side of the pair of magnetic pole pieces penetrates the antenna lead for microwave derivation connected to one of the anode vanes. A hole is provided in the inclined portion to allow the magnetic field strength in the central axis direction at the end face of the anode vane in the action space of the magnetic force line formed by the cathode (b) and the antenna lead (e). For equalization, the shape of the facing portion of the pair of magnetic pole pieces (g) is made to be a shape that is displaced either in a tapered shape or a curved shape toward the inclined portion side opposite to the facing portion. It is characterized by

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 10 is a diagram showing the maximum value of the magnetic field strength deviation at the central axial direction central portion and the axial end portion of the conventional anode vane end surface in the working space, and the radiation levels other than the fundamental wave. As shown in FIG. 10, when the maximum value of the magnetic field strength deviation is about 5 to 10%, the radiation level other than the fundamental wave is as low as about 25 to 30%, but the magnetic field strength deviation is 10%.
Above%, radiation levels other than the fundamental wave rise sharply. Therefore, in the present invention, in order to reduce the radiation level other than the fundamental wave, the shapes of the pole piece on the output side and the pole piece on the stem side are adjusted so that the magnetic field strength deviation is less than 10%. To do.

Next, one embodiment of the magnetron of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a part of one embodiment of the magnetron of the present invention, FIG. 2 is a sectional view showing a magnetic pole piece of another embodiment of the magnetron of the present invention, and FIG. 3 is shown. It is a figure which shows the frequency characteristic of the fundamental wave periphery of the magnetron of FIG. 1, and the figure which shows the deviation with respect to the magnetic field intensity of the central part in the central-axis direction in the anode vane end surface.

In FIG. 1, the same parts as those in FIG. 7 are designated by the same reference numerals. Reference numeral 5 is a pole piece on the output side and 6 is a pole piece on the stem side, both of which are made of a ferromagnetic material such as iron. A magnetic pole piece is formed by pressing a plate-shaped magnetic pole piece material into a die for ordinary pressing. The thickness of the pole piece material is 1.6 mm, 5a and 6a are the first flat portions of the pole pieces facing each other having a small diameter, and the diameters thereof are 12.0 mm for D5a and 15.0 mm for D6a, respectively. Therefore, the stem side magnetic pole piece 6a is configured to be larger than the output side magnetic pole piece 5a. 5b, 6
b is the anode cylinder 1 and the thin tubular parts 10, 1
A second flat portion having a large diameter for connecting with 1, and D
Both 5b and D6b are, for example, 20.0 mm, and 5c
And 6c are the first flat portion 5a, 6a and the second flat portion 5b,
6b is a conical inclined portion that connects 6b. 5d is a hole for penetrating the antenna lead 9, and has, for example, an elliptical shape with a short axis of 5.0 mm and a long axis of 10.0 mm. 6e
Is a hole provided to penetrate the cathode 7, and its diameter D6e is 9.2 mm. 5e is a hole which has the same shape as the hole 6e and is provided in order to obtain a magnetic field distribution which is substantially symmetrical with respect to the central axis in the working space, and the diameter D5e is D6.
It is equal to e and is 9.2 mm. θ ₁ is the second flat portion 5
is an angle of the inclined portion 5c with respect to b, θ ₂ is an angle of the inclined portion 6c with respect to the second flat portion 6b, θ ₁ is, for example, 64 °, θ ₂ is, for example, 75 °, and D5a <D6a,
And there is a relation of θ ₁ <θ ₂ . Also, the holes 5e and 6e
Is also provided for exhausting gas in the anode cylinder.

The magnetic field strength difference in the direction of the central axis in the working space at the end face of the anode vane of the magnetron shown in FIG. 1 is shown in FIG.
(B). At the stem side end using the same pole piece as before, the deviation from the magnetic field strength at the center is 8%.
Since it is averaged on the stem side, multiple oscillation on the stem side can be reduced.

At the end of the pole piece 5 on the output side, the diameter of the first flat portion 5a is small (1
Since it is formed (about 2.0 mm), the inclination of the magnetic force is small, and even if it is affected by the distortion of the microwave electric field, it does not deviate from the action space 8 of the thermoelectrons. In the stem-side pole piece 6, the inclination of the magnetic force becomes large, but since it is far from the antenna lead 9, there is no influence of the distortion of the microwave electric field, and the thermoelectrons do not deviate from the working space 8.

When the frequency characteristic around the fundamental wave of the magnetron shown in FIG. 1 is compared with the frequency characteristic of the conventional magnetron shown in FIG. 7 shown in FIG. 3A, side lobes around the main lobe caused by multiple oscillation are found. You can see that it is suppressed.

Further, according to the magnetron of FIG. 1, since the same pole piece as the conventional one can be used as the pole piece 5 on the output side having the hole 5d for penetrating the antenna lead 9, There is no adverse effect on the penetrating work, workability equivalent to the conventional one can be secured, and unnecessary cost increase does not occur.

In the above embodiment, the diameter D6a of the first flat portion 6a of the pole piece 6 facing the pole piece 5 is set to the first flat portion 6a of the pole piece 5.
Although it is formed larger than the flat portion 5a, the same effect can be obtained even if the shape is as shown in FIG. 2 (b) or (c). That is, as compared with the pole piece 6 of this embodiment,
As shown in FIG. 2B, even if the first flat portion 6a has a curved shape that approaches the second flat portion 6b as it goes in the direction of the hole 6e, the degree of bending can be adjusted. The magnetic field distribution in the working space 8 can be made uniform. Further, as shown in FIG. 2C, the first flat portion 6
Even if a has a linear inclination in the direction of the hole 6e, the magnetic field distribution in the action space 8 can be made uniform by adjusting the inclination.

Another embodiment of the present invention will be described with reference to FIG. FIG. 4 is a sectional explanatory view showing a part of another embodiment of the magnetron of the present invention, FIG. 5 is a sectional view showing a magnetic pole piece of still another embodiment of the magnetron of the present invention, and FIG. 4 is a diagram showing frequency characteristics around the fundamental wave of the magnetron of No. 4 and a diagram showing deviation with respect to magnetic field strength at the central portion in the central axis direction on the end face of the anode vane. 4, the same parts as those in FIG. 1 are designated by the same reference numerals.

In FIG. 4, the diameters D5a and D6a of the first flat portion are both 14.0 mm, for example, and the first flat portion 5a is inclined toward the hole 5e. Similarly to the first flat portion 5a, the first flat portion 6a is also inclined toward the hole 6e (see FIGS. 4 and 5 (a)). The taper allowances 5t and 6t of the magnetic pole piece 5 on the output side and the magnetic pole piece 6 on the stem side are both 0.5 mm, for example, and the second flat portion 5b of the magnetic pole piece 5 and the second flat portion of the magnetic pole piece 6 are each. Both the diameters D5b and D6b of the flat portion 6b are, for example, 22.0 mm. The diameter D6e of the hole 6e is, for example, 9.2 mm, and the diameter D5e of the hole 5e provided to obtain a symmetrical magnetic field distribution having substantially the same shape as the hole 6e is 9.
It is 2 mm, which is equal to the diameter D6e. Here, as in FIG. 1, the holes 5e and 6e are also provided for exhausting gas in the anode cylinder. The angle θ ₁ of the inclined portion 5c with respect to the flat portion 5b, and the inclined portion 6c with respect to the flat portion 6b
The angle θ ₂ is 71 °, for example. As described above, unlike the embodiment shown in FIG. 1, the magnetic field strength in the central axis direction can be improved by making the flat portion of each of the stem side pole piece and the output side pole piece have a taper allowance. It can be made almost uniform.

FIG. 6B shows the difference in magnetic field strength in the central axis direction in the working space at the end surface of the anode vane according to this embodiment.
Shown in The magnetic field strength in the central axis direction at the end surface of the anode vane 2 is 16%, whereas the magnetic field strength at both the output side end surface and the stem side end surface is 8%, which is 16% of the conventional value shown in FIG. 9B. In comparison, since they are made substantially uniform, it is possible to reduce multiple oscillations due to the difference in magnetic field strength in the central axis direction.

The frequency characteristics around the fundamental wave of the magnetron of this embodiment are shown in FIG. 6 (a). As compared with the frequency characteristics of the conventional magnetron shown in FIG. 9A, it can be seen that side lobes around the main lobe due to multiple oscillation are suppressed.

Further, the hole 5b through which the antenna lead penetrates
And the angle of the inclined portion 5c of the pole piece 5 on the output side is 71
Since the antenna leads are made shallower, the work of penetrating the antenna leads will be easier than before, and the quality of the products will not be deteriorated due to the deterioration of the fundamental wave characteristics due to the variations in the work.

In the magnetron of the above embodiment shown in FIG. 4, the same effect can be obtained even if the pole pieces 6 are formed in the shapes shown in FIGS. 5 (b) and 5 (c). That is, as compared with the pole piece 6 of the present embodiment, as shown in FIG. 5B, a curved shape that approaches the second flat portion 6b as the first flat portion 6a moves toward the hole 6e. However, by adjusting the degree of curvature, it is possible to make the magnetic field distribution in the action space 8 of the pole piece uniform while keeping the angle of the inclined portion 5c of the pole piece 5 shallow. It goes without saying that the pole piece 5 is formed in the same shape as the pole piece 6.
Further, as shown in FIG. 5C, even if the first flat portion 6a is linearly inclined (tapered) in the direction of the hole 6e and has a flat portion at its tip, The magnetic field distribution in the working space 8 can be made uniform by adjusting the inclination.

[0030]

According to the magnetron of the present invention, the end surface of the anode vane is located on the stem side in the working space of the magnetic force lines formed by being surrounded by the cathode and the tips on the central axis side of the plurality of anode vanes. So that the magnetic field strength difference in the direction of the central axis is within 10% or less, the shape of the pole piece on the stem side is made different from the shape of the pole piece on the output side to form the pair of pole pieces. Therefore, the magnetic field distribution of the magnetron can be made uniform without increasing the manufacturing cost and degrading the quality.

Further, since the shape of the facing portion of the pole piece is changed to the shape of being tapered or curved toward the side of the inclined portion opposite to the facing portion, the manufacturing cost is increased and the quality is lowered. It is possible to make the magnetic field distribution of the magnetron uniform. Further, it is possible to provide the magnetron in which the multiple oscillation due to the non-uniformity of the magnetic field distribution is reduced and the noise is suppressed.

Therefore, when the microwave oven using the magnetron of the present invention is used at home, noise will not be introduced into radios, televisions, communications and the like.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a part of an embodiment of a magnetron of the present invention.

FIG. 2 is a cross-sectional view showing a pole piece on the stem side related to the magnetron of the present invention.

FIG. 3 is a diagram showing frequency characteristics around a fundamental wave of the magnetron shown in FIG. 1 and a diagram showing a deviation with respect to a magnetic field strength at a central portion in the central axis direction at an end face of an anode vane.

FIG. 4 is a sectional view showing a part of another embodiment of the magnetron of the present invention.

FIG. 5 is a cross-sectional view showing a magnetic pole piece on the stem side related to the magnetron of the present invention.

FIG. 6 is a diagram showing frequency characteristics around a fundamental wave of the magnetron of the present invention, and a diagram showing deviation with respect to magnetic field strength at the central portion in the central axis direction at the end face of the anode vane.

FIG. 7 is a sectional view showing a part of an example of a conventional magnetron.

FIG. 8 is a sectional view showing a part of a conventional magnetron.

FIG. 9 is a diagram showing a frequency characteristic around a fundamental wave of a conventional magnetron and a diagram showing a deviation with respect to a magnetic field intensity at a central portion in a central axis direction on an end face of an anode vane.

FIG. 10 is a diagram showing a relationship between a maximum value of a magnetic field strength deviation and a radiation level other than a fundamental wave.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode cylinder 2 Anode vane 3 Pressure equalizing ring 4 Pressure equalizing ring 5 Magnetic pole piece 6 Magnetic pole piece 7 Cathode 8 Working space 9 Antenna lead

Claims (2)

[Claims] 1. (a) Anode cylinder, (b) Cathode,
(C) stem, (d) multiple anode vanes, (e)
A magnetron comprising: an antenna lead for deriving a microwave; (f) an output portion; and (g) a pair of magnetic pole pieces that are opposed to each other and include a stem side magnetic pole piece and an output side magnetic pole piece. The cathode (b) is arranged on the central axis of the anode cylinder (a), and the stem (c) is fixed to one end of the anode cylinder (a) to support and fix the cathode (b). And the anode vane (d) is the anode cylinder (a).
Are radially arranged on the inner peripheral surface of the antenna, the antenna lead (e) is connected to one of the anode vanes and extends outward, and the output part (f) is formed on the anode cylinder. The pair of magnetic pole pieces (g) is fixed to the other end to surround the antenna lead to form a microwave transmission and radiation part, and the pair of magnetic pole pieces (g) are arranged at both open ends of the anode cylinder (a). In addition, a flat portion is provided at a portion connected to both opening ends of the anode cylinder (a), and the protrusion is conically projected toward the anode vane (d) via an inclined portion. Among the pieces (g), the pole piece on the output side has a hole for allowing the microwave lead-out antenna lead (e) connected to one of the anode vanes (d) to pass through. On the central axis side of the cathode (b) and the plurality of anode vanes (d). On the stem side of the working space surrounded by the ends, the magnetic pole on the stem side is set so that the magnetic field strength difference in the direction of the central axis on the end face of the anode vane (d) is within 10%. A magnetron, characterized in that the pair of magnetic pole pieces (g) is formed by making the shape of the magnetic pole piece different from the shape of the magnetic pole piece on the output side. 2. (a) Anode cylinder, (b) Cathode,
(C) stem, (d) multiple anode vanes, (e)
A magnetron comprising: an antenna lead for deriving a microwave; (f) an output portion; and (g) a pair of magnetic pole pieces that are opposed to each other and include a stem side magnetic pole piece and an output side magnetic pole piece. The cathode (b) is arranged on the central axis of the anode cylinder (a), and the stem (c) is fixed to one end of the anode cylinder (a) to support and fix the cathode (b). And the anode vane (d) is the anode cylinder (a).
Are radially arranged on the inner peripheral surface of the antenna, the antenna lead (e) is connected to one of the anode vanes and extends outward, and the output portion (f) is the anode cylinder. The antenna lead (e) is fixed to the other end of (a) to enclose the antenna lead (e) to form a microwave transmitting and radiating portion, and the pair of magnetic pole pieces (g) are provided on both sides of the anode cylinder (a). A flat portion is provided at a portion that is arranged at the opening end portion and is connected to both opening end portions of the anode cylinder (a), and protrudes in a conical shape toward the anode vane (d) via an inclined portion. Among the pair of magnetic pole pieces (g), the magnetic pole piece on the output side is provided with a hole in the inclined portion for penetrating the microwave lead-out antenna lead connected to one of the anode vanes. Formed by the cathode (b) and the antenna lead (e). The interaction space, the magnetic field intensity in the central axis direction of the end face of the anode vane to average that,
A magnetron characterized in that the shape of the facing portions of the pair of magnetic pole pieces (g) is tapered or curved toward the inclined portion side opposite to the facing portions.