JPH05190102A - Magnetron - Google Patents

Abstract

PURPOSE:To provide a magnetron for a microwave oven and the like which can reduce line noises generated in association with multiple oscillation to thereby prevent acoustic devices such as a radio set, TV set and the like from being subjected to bad influence. CONSTITUTION:Anode vanes 2 are arranged radially toward the central axis from the inner circumferrential face of an anode cylinder 1. At both axial ends of the cathode 7 side anode vane 2, projections 2a, 2b are formed in a manner as protruding from the inscribed circle dia. of the anode vane 2 defined by an operation theory to the cathode 7 side.

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 microwave ovens and radar. More specifically, it relates to a magnetron that suppresses noise during operation of the magnetron and achieves low noise.

[0002]

2. Description of the Related Art FIG. 7 shows a sectional view of an anode structure of a magnetron generally used in a microwave oven or the like. In the figure, the anode cylinder 1 has a plurality of radially arranged anode vanes 2 on its inner peripheral surface, and an even number of small cavities surrounded by the two anode vanes 2 and the peripheral wall of the anode cylinder 1. Individually formed, and the whole thereof forms a resonance cavity of the magnetron.
Since the magnetron normally oscillates in π mode, each small cavity oscillates with a phase shift of π radian. Therefore, in order to stabilize the oscillation of the magnetron, every other anode vane is connected by equalizing rings 3 and 4 having a small diameter and a large diameter so as to have the same potential.

A pair of magnetic pole pieces 5 and 6 are disposed at both open ends of the anode cylinder 1, and a cathode 7 and an anode disposed on the central axis of the anode cylinder 1 and facing the anode vane 2. Magnetic force is supplied by a magnet (not shown) so as to form an orthogonal electrostatic magnetic field together with the DC voltage applied to the working space 8 between the vane 2.

In the magnetone having such a structure, the electrons radiated from the cathode 7 are rotated in the circumferential direction by the orthogonal electrostatic magnetic field to approach the anode vane 2 and are converted into energy in the form of an electron cloud into a resonant cavity. It In this case, the diameter φ _{c of the} cathode 7 and the inscribed circle diameter φ _a of the tip of the anode vane 2
Is determined by the theory of operation so that the motion of electrons is just converted into energy in the resonant cavity, and in the usual case, φ _a is formed with the same size from end to end in the axial direction of the anode vane 2, and therefore The cathode 7 side end is linearly formed.

In the above-described conventional magnetron, 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 line between the magnetic pole pieces 5 and 6 draws an arc and goes 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, it deviates from the working space 8 toward the anode vane 2 side or the anode 7 side. for that reason,
As for the strength of the magnetic field in the working space 8, the axial end portion side of the anode vane 2 has a stronger distribution than the central portion.

On the other hand, the rotation speed of the electron 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-uniformity of B causes the non-uniform rotation speed of the electron.
It causes multiple oscillations. There is a problem that the frequency deviation at the time of this multiple oscillation becomes line noise leaking from the cathode side terminal of the magnetron to the outside, and interferes with reception of a radio or the like.

To solve this problem, as disclosed in Japanese Patent Laid-Open No. 63-110527, Japanese Patent Laid-Open No. 1-27434, etc., as shown in FIG.
It is considered that the flat portions 5a and 6a on the facing surface of 6 are made large to reduce the magnetic field strength at the axial end portion of the anode vane in the working space.

[0008]

However, if the average value of the magnetic field strength is made uniform in this way, the direction of the magnetic force lines in the working space tends to be inclined with respect to the axial direction. It becomes impossible to form an electromagnetic field, line noise of different frequencies (AM band) due to non-uniform electron density is generated, main oscillation is destabilized, oscillation efficiency is reduced, and other basic characteristics are adversely affected. Wall thickness (eg 1.6mm
It is difficult to bend the flat part of the magnetic pole piece in),
There is a problem that the manufacturing cost increases.

In view of such circumstances, it is an object of the present invention to provide a magnetron which does not generate noise in AM or FM radio even when a microwave oven or the like is used at home.

[0010]

The magnetron according to the present invention comprises an anode cylinder, a cathode arranged on the central axis of the anode cylinder, and a plurality of radially arranged inner peripheral surfaces of the anode cylinder. A magnetron having an anode vane and a pair of magnetic pole pieces arranged at both opening end portions of the anode cylinder, wherein an inscribed circle of the anode vane determined in advance by theory of operation at both axial end portions of the anode vane. It is characterized in that a protruding portion protruding from the diameter toward the cathode side is formed.

[0011]

According to the present invention, since the protruding portion is formed on the cathode side on the axial end side of the anode vane having a strong magnetic field in the working space, the distance between the cathode and the anode is narrowed and the electric field distribution is centered. Become stronger than the division. Therefore, the rotation speed of electrons determined by the ratio E / B of the electric field E and the magnetic field B becomes strong at the end portion of the strong magnetic field B, and the value of E / B does not change much at the central portion and the end portion, and the speed is almost constant. Therefore, a stable frequency oscillation can be obtained. As a result, the multiple oscillation can be suppressed, and the generation of line noise due to the frequency deviation due to the multiple oscillation can also be suppressed. In this case, the size of the central part of the anode vane is the size determined by the theory of operation, and the main oscillation part is not affected at all and the basic characteristics such as output are not impaired.

[0012]

The present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional explanatory view of an anode portion which is an embodiment of the present invention. In FIG. 1, 1 to 8 are the same parts as in FIG. 7, 2a and 2b are protrusions formed at both ends of the anode vane 2 on the cathode side, H is the axial length of the anode vane 2, and h is the anode. Axial length of the protrusions 2a, 2b of the vane 2, Y is an axial length of a portion of the anode vane 2 without the protrusions 2a, 2b, and L is a protrusion length of the protrusions 2a, 2b toward the cathode side. Is. Further, φ _a is an inscribed circle diameter of the tip of the anode vane 2 on the cathode 7 side, which is the inner diameter of the anode, and φ _b is an inscribed circle diameter where the protrusion is provided, and φ _b = φ _a −2L. Further, φ _c is the outer diameter of the cathode 7.

As described above, according to the present invention, in order to correct the non-uniform rotation speed of electrons due to the strong magnetic field B at both axial ends of the working space 8, the protrusions 2 are provided at both ends of the anode vane 2.
The purpose is to form a and 2b, strengthen the electric field E, and keep E / B constant to prevent generation of noise due to nonuniform electron velocity. Therefore protrusions 2a, 2b of the dimensions h, a magnetron having various the L, and particularly 0.5 MH _Z band and FM band radio frequency band to be at home problem 100
The occurrence of line noise in the MH _Z band was investigated. As being representative of the magnetron for microwave oven as the type of the magnetron, the oscillation frequency is 2450MH _Z, (10 pieces in the number of anode vanes 2) anode 10 dividing the anode voltage is 4.0 kV, the magnetic field strength of about 1800 gauss By design, H = 9.0 mm, outer diameter of cathode 7 φ _c = 4.0 mm, φ _a = 9.0 mm, and h / H is 0, 10, 20,
30, 40, 50% and L is 0.1mm, 0.2mm, 0.3mm
3 were manufactured, and the results are shown in FIGS.

In FIG. 3, the horizontal axis represents h / H × 100 (%)
The noise level at 100 MHz _Z band on the vertical axis (dB), showed L as a parameter. From this result, the noise in the 100MHz _Z band is the smallest when h / H is 20%, the preferable range is 5 to 25%, and the smallest L is 0.2mm and 0.15 to 0.3. It has been found that mm is a preferred range.

[0015] FIG. 4 is shown in similar view to Figure 3 the noise level at 0.5 MH _Z band. From this result, h / H is 0
It was found that 20% had low noise with respect to any L, and a preferable range was up to about 25%.

From the results of both, even in the 0.5MH _Z band, 100
To reduce noise even in the MH _Z band, h / H is 20% and L = 0.
2mm is the best, and the preferable range is h / H of 5-25
%, L was found to be in the range of 0.15 to 0.3 mm.

Next, the axial length H of the anode vane 2 corresponding to h / H of 20% is H = 9.0 mm, the axial length h of the protrusions 2a and 2b is h = 1.8 mm, and therefore the inscribed circle diameter is dimension Y of a portion corresponding to phi _a is, Y = H-2h = 5.4mm , projecting portion 2a, in the protrusion length L = 0.2 mm to the cathode side of the 2b, and oscillation waveform by magnetron formed in the specification of the aforementioned The measurement result is shown in FIG. The protrusion 2a on the conventional anode vane 2;
Compared to FIG. 9 showing the oscillation waveform of the magnetron without the 2b As is apparent, in the magnetron according to an embodiment of the present invention, multiple oscillation of high output level in addition to the oscillation frequency of 2450MH _Z (f ₀₎ It can be seen that the frequency (f ₁ ) is not shown and noise due to the frequency deviation (f ₀ −f ₁ ) cannot occur. On the other hand, 2370MH in the conventional magnetron shown in FIG. 9 _Z, 2320MH _Z, also near 2550MH _Z have cracks oscillation waveform table, the noise in the vicinity of 100 MHz _Z is the difference between 2450MH _Z is the original oscillation frequency generated It turns out easy.

Furthermore by magnetron formed in the above dimensions are examples of the present invention to measure the noise level at 0.15~1000MH _Z, shown in FIG. 6 in comparison with the conventional magnetron. In FIG. 6, P is the noise level of the magnetron according to the embodiment of the present invention, Q is the noise level of the conventional magnetron without protrusions, and R is the flat portion of the conventional magnetic pole piece to reduce noise. It shows the noise level of the magnetron. As apparent from FIG. 6, with the noise in the vicinity noise Q in 100 MHz _Z conventional magnetron has occurred is eliminated, the noise of conventional pole pieces around noise in R 100 MHz _Z shape change by safe products However, on the other hand,
0.3 ~ 1.5MH and _Z neighborhood noise which occurs in is solved in the present invention, it can be seen that the noise in the entire region of 0.15～1000MH _Z band is reduced.

In the above-described embodiments, the example of the projecting portion having a rectangular cross section has been described, but the purpose is to strengthen the electric field at the end portion where the magnetic field is strong and to make the E / B uniform. Therefore, it suffices that the electric field is strengthened evenly at the ends, and the projections 2a and 2b having a tapered shape as shown in FIG. 2 may be used instead of the rectangular shape, and the projections may be formed as concave or convex surfaces. You can also

[0020]

As described above, according to the present invention, since the protrusions are formed on the cathode side at both axial ends of the anode vane, the rotation speed of the electrons can be made uniform in the entire working space.
Multiple oscillations can be prevented, and line noise due to frequency deviation can be significantly reduced.

Further, since the protrusions are formed only on both ends of the anode vane and the central portion has the original design dimensions, characteristics such as oscillation output do not change and the basic characteristics of the magnetron and the manufacturing cost are not adversely affected. Does not reach.

As a result, even if the microwave oven or the like is used at home, there is an effect that a comfortable living environment can be constructed without causing noises on the radio and television.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a magnetron anode portion which is an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of an anode vane portion which is another embodiment of the present invention.

FIG. 3 is a diagram showing the noise level in the 100 MHz _Z band when the size of the protrusion of the anode vane according to the present invention is changed.

FIG. 4 is a diagram showing a noise level in a 0.5 MHz _Z band when the size of the protruding portion of the anode vane according to the present invention is changed.

FIG. 5 is a diagram showing an oscillation waveform of a magnetron according to an embodiment of the present invention.

FIG. 6 is a diagram showing noise levels of a magnetron according to an embodiment of the present invention and a conventional magnetron.

FIG. 7 is an explanatory cross-sectional view showing a structure of an anode part of a conventional magnetron.

FIG. 8 is an explanatory cross-sectional view showing the structure of the anode part of another conventional magnetron.

FIG. 9 is a diagram showing an oscillation waveform of a conventional magnetron.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anode cylinder 2 Anode vanes 2a, 2b Projection parts 5, 6 Pole piece 7 Cathode

Claims (1)

[Claims] 1. An anode cylinder, a cathode arranged on a central axis of the anode cylinder, a plurality of anode vanes radially arranged on an inner peripheral surface of the anode cylinder, and both openings of the anode cylinder. A magnetron having a pair of magnetic pole pieces arranged at the ends, wherein both end portions in the axial direction of the anode vane have protrusions protruding toward the cathode side from the inscribed circle diameter of the anode vane determined in advance by theory of operation. A magnetron characterized by being formed.