JP2006049121A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetron capable of minimizing cost increase while reducing line noise.
SOLUTION: A plurality of anode vanes 10 have a flat portion 10A at a center of a tip portion opposed to each cathode 3, and from the flat end 10A toward both ends in the axial direction from an anode cylinder fixed end. The length to the tip is gradually shortened to provide a tapered portion 10B cut into a tapered shape.
[Selection] Figure 1

Description

  The present invention relates to an improvement of a magnetron used in a high frequency utilization device or the like.

  Conventionally, a technique for reducing line noise generated in a magnetron has been proposed (see, for example, Patent Document 1).

FIG. 12 is a longitudinal sectional view showing a part of the anode cylinder of the magnetron disclosed in Patent Document 1 described above. In FIG. 12, this magnetron is equipped with a coiled cathode 3 along the axial center of an anode cylinder 1 in which a plurality of anode vanes 2 (only one is visible in this figure) are arranged radially. In addition, metal cylinders 4 and 5 are disposed at both ends of the cathode 3. The cylindrical body 4 on the input side of the cathode 3 is fixed to the lower end hat 6, and the cylindrical body 5 on the output side of the cathode 3 is fixed to the upper end hat 7. These cylindrical bodies 4 and 5 are inwardly located in the range of 1/8 to 1/4 of the axial length of the vane tip from the position corresponding to the tip corner of the anode vane 2 at the position of each opening end. Each is extended.
These cylindrical bodies 4 and 5 suppress the spread of electrons emitted from the cathode 3, and by providing these at both ends of the cathode 3, line noise can be reduced.

  FIG. 13 is a waveform diagram showing a noise level of 1 GHz or less when the cylindrical bodies 4 and 5 are provided at both ends of the cathode 3 based on the actual measurement results, and FIG. 14 does not provide the cylindrical bodies 4 and 5. It is a wave form diagram which shows the noise level of 1 GHz or less in the case. As is clear from these figures, when the cylindrical bodies 4 and 5 are provided, line noise can be reduced in the 30 MHz to 200 MHz band as compared with the case where the cylindrical bodies 4 and 5 are not provided.

Japanese Patent Publication No. 4-77412

  However, in the conventional magnetron according to the above publication, since the cylindrical bodies are provided at both ends of the cathode for reducing line noise, the provision of these increases the number of parts, and the man-hours due to the complexity of assembly. However, there is a problem that the cost increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetron that can suppress an increase in cost while reducing line noise.

The above object is achieved by the following configuration.
(1) A cylindrical anode cylinder, a cathode disposed on the central axis of the anode cylinder, and a plurality of radial anodes disposed on the inner wall surface of the anode cylinder toward the cathode. The anode vane in which the shape of the tip portion facing the cathode is cut into a taper shape that gradually shortens the length from the anode cylinder fixed end to the tip portion from substantially the center in the axial direction toward at least one end portion It is characterized by comprising.

(2) In the magnetron described in (1) above, each of the anode vanes may be characterized in that a cutting dimension at the one end of the tip is set to 0.25 mm or less.

(3) In the magnetron according to the above (1) or (2), each anode vane has a flat portion parallel to the tip portion in the axial direction, and the length of the flat portion is 3 mm or less. It may be characterized by being set.
(4) The high-frequency utilization apparatus includes the magnetron described in any one of (1) to (3) above.

According to the above magnetron, in the central portion in the axial direction of the working space where the orthogonal electromagnetic field is held, electrons emitted from the cathode move for fundamental oscillation, and the magnetic field has an inclination in the axial direction. At least one end portion of both end portions has a larger anode diameter (that is, a longer distance from the cathode), thereby suppressing the fundamental oscillation motion.
In addition, since the taper is formed in the shape cut toward the anode cylinder fixed end, the high-frequency electric field intensity at the end becomes gentle and is similar to the sink region (unstable region). As a result, line noise can be reduced in the same manner as when the cylindrical bodies are provided at both ends of the cathode. Further, since the cylindrical body is not required, the number of parts does not increase, and a significant man-hour for assembly is not required. In other words, line noise can be reduced at a minimum cost by only man-hours for processing the shape of the tip portion of each anode vane.

  According to the above-described high-frequency utilization device, since an inexpensive magnetron with low line noise is provided, noise countermeasure parts such as a coil and a capacitor need only have a small capacity, and the cost can be reduced correspondingly.

Hereinafter, a magnetron according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a vertical partial sectional view showing the periphery of a cathode according to an embodiment of a magnetron according to the present invention. Since the portions other than the cathode portion shown in this figure are the same as those in FIG. 12, the same portions and the same portions are referred to with the same reference numerals.

In FIG. 1, the magnetron of the present embodiment includes a plurality of anode vanes (only two are shown in FIG. 1) arranged radially toward the cathode 3 on the inner wall surface of the anode cylinder 1 (see FIG. 12). Each anode vane 10 has a flat portion 10A parallel to the axial direction, with the tip portion on the opposite side of the anode cylinder fixed end being substantially in the center in the axial direction, The flat part 10A is cut into a taper shape that gradually shortens the length dimension from the anode cylinder fixed end to the tip part toward both ends (upper and lower edges) in the axial direction. In addition, the part formed in this taper shape is called the taper shape part 10B.
The cathode 3 is fixed by a cathode support bar 11 and upper and lower end hats 12 and 13, and the cylindrical bodies 4 and 5 as shown in FIG. 12 are omitted.

  In the magnetron having such a configuration, the shape of the tip portion of each anode vane 10 has a flat portion 10A at the center and is formed with a tapered portion 10B cut toward both ends. At the central portion in the axial direction of the working space where electrons are held, the electrons emitted from the cathode 3 move for fundamental oscillation, and the anode diameter increases at both axial ends where the magnetic field is inclined ( That is, the distance from the cathode 3 is increased), and therefore the fundamental oscillation is suppressed. In addition, since the tapered portion 10B is formed, the high-frequency electric field strength at both ends becomes moderate, and the state is similar to the sink region (unstable region). As a result, the line noise can be reduced equivalent to the case where the cylindrical bodies 4 and 5 (see FIG. 12) are provided at both ends of the cathode 3 described in the conventional example. Further, since the cylindrical bodies 4 and 5 are not required, the number of parts does not increase, and a significant man-hour for assembly is not required. That is, the line noise can be reduced at a minimum cost only by man-hours for processing the tip portion of each anode vane 10.

  Here, in the experiment conducted by the present inventor, it has been found that the level of line noise varies depending on the dimension H of the flat portion 10A of the anode vane 10 and the cut dimension D of the tapered portion 10B.

FIG. 2 is a graph showing the relationship between the dimension H of the flat portion 10A at the tip portion of the anode vane 10 and the load stability, and FIG. 3 shows the cut dimension D of the taper portion 10B at the tip portion of the anode vane 10 and the load stability. It is the graph which showed this relationship. In each graph, the horizontal axis is the dimension (mm), and the vertical axis is the current value (mA).
The dimension H of the flat portion 10A is 6 mA or less, and the current value indicating the stability is approximately 600 mA. Moreover, the current value which shows stability falls hundreds of tens mA, whenever the cutting dimension D of the taper-shaped part 10B becomes larger by 0.1 mm. From these figures, it can be said that the dimension H of the flat portion 10A is preferably 6 mm or less, and the cutting dimension D of the tapered portion 10B is preferably 0.25 mm or less.

4 to 6 are waveform diagrams showing noise levels when the cut dimension D of the tapered portion 10B is fixed to 0.2 mm and the dimension H of the flat portion 10A is changed. The axial dimension of the anode vane 10 is 9.5 mm. FIG. 7 shows a noise level in the conventional anode vane 2 (see FIG. 12) which is given for comparison and in which the tip portion is not processed at all. In each case, the horizontal axis represents frequency (MHz) and the vertical axis represents noise level (dB).
As shown in FIG. 6, when the dimension H of the flat portion 10A is 3.17 mm, the noise is larger than that in the conventional case of FIG. Further, in the dimension H = 2.38 mm of the flat portion 10A shown in FIG. 5, the noise is smaller than the dimension H = 3.17 mm of the flat portion 10A in FIG. 6, and the dimension H = 1 of the flat portion 10A in FIG. At 19 mm, the noise is smaller than the dimension H = 2.38 mm of the flat portion 10A in FIG. Considering these results, the dimension H of the flat portion 10A is 3 mm or less, and noise can be reduced.

Next, FIG. 8 shows the line noise phase (VSWR (VSWR ()) in each microwave oscillation frequency band when the cut dimension D of the tapered portion 10B is 0.2 mm and the dimension H of the flat portion 10A is 1.19 mm. Voltage Standing Wave Ratio) = 4) and noise level measurement results are shown. For comparison, FIG. 9 shows the measurement results of the line noise phase and noise level in the conventional anode vane 2 (see FIG. 12) in which the tip portion is not processed at all. In each of the above drawings, the microwave oscillation frequency band was set to 0.3 to 0.5 MHz, 0.5 to 5 MHz, and 5 to 30 MHz.
As shown in FIG. 8, in the present invention, the noise level is within approximately 30 to 50 dB in all frequency bands, but in the conventional anode vane 2 shown in FIG. 9, the noise level is within 35 to 60 dB. The noise reduction effect according to the present invention can be understood.

  As described above, according to the magnetron of the present embodiment, the tip portion facing each cathode 3 of each of the plurality of anode vanes 10 is formed in a tapered shape with a flat portion 10A in the center. A reduction in line noise equivalent to that obtained when the cylindrical bodies 4 and 5 (see FIG. 12) are provided at both ends of the cathode 3 in FIG. In addition, since the cylindrical bodies 4 and 5 are omitted, the number of parts does not increase, and the number of man-hours required for assembly does not increase, so that an increase in cost can be minimized.

  Further, when the magnetron of the present embodiment is used in a microwave oven, noise countermeasure parts such as a coil and a capacitor need only have a small capacity, and the cost can be reduced accordingly.

  In the above embodiment, the flat portion 10A is formed at the tip of the anode vane 10. However, as described above, as the dimension H of the flat portion 10A is shortened, noise can be reduced. The flat portion 10A is omitted, that is, the tip of the anode vane has a mountain shape with the central portion protruding toward the cathode, so that the load equivalent to the case where the flat portion 10A is provided as shown in FIG. Further noise reduction can be achieved while ensuring stability. However, since the electric field concentration occurs in the protruding central portion, the anode vane deteriorates.

  10 and 11 are partial vertical cross-sectional views showing the periphery of the cathode of another embodiment of the magnetron according to the present invention. Except for the shape of the tip portion of the anode vane shown in these figures, it is the same as the magnetron shown in FIG. 1 and is omitted, and the same reference numerals are given to the parts common to FIG.

  In FIG. 10, the magnetron of the present embodiment is such that the tip portion of the anode vane 20 is directed from the anode cylinder fixed end toward the one end (upper edge) facing the output side of the cathode 3 from the substantially center in the axial direction. A taper-shaped portion 20B cut into a tapered shape that gradually shortens the length dimension to the portion is formed, and a tip portion excluding the taper-shaped portion 20B is provided on a flat portion 20A that is parallel to the axial direction. Yes.

On the other hand, in FIG. 11, the magnetron of the present embodiment has an end portion (lower end edge) where the tip portion of the anode vane 30 faces the input side of the cathode 3 from the approximate center in the axial direction opposite to the above embodiment. ) Toward the tip end portion of the anode cylinder, and the tip portion excluding the taper portion 30B is axially formed. Are provided on a flat portion 30A parallel to the surface.
In any of these cases, the high-frequency electric field strength is moderated while suppressing the fundamental oscillation motion in the tapered portions 20B and 30B. As a result, it is possible to reduce the line noise equivalent to when the cylindrical bodies 4 and 5 are provided at both ends of the cathode 3 shown in the prior art. In addition, since the number of parts does not increase and a large number of man-hours for assembly are not required, the line noise can be reduced at a minimum cost.

  It can be applied to applications using magnetrons such as microwave ovens.

It is a fragmentary sectional view of the vertical direction which shows the cathode periphery by one Embodiment of the magnetron concerning this invention. It is a graph which shows the relationship between the anode vane front-end | tip flat part dimension of the magnetron of FIG. 1, and load stability. It is a graph which shows the relationship between the anode vane notch part dimension of the magnetron of FIG. 1, and load stability. It is a wave form diagram which shows a noise level when changing the flat part dimension of a magnetron. It is a wave form diagram which shows a noise level when changing the flat part dimension of a magnetron. It is a wave form diagram which shows a noise level when changing the flat part dimension of a magnetron. It is a wave form diagram which shows the noise level of the conventional magnetron. It is a graph which shows the measurement result of the noise level in the different frequency band of a magnetron. It is a graph which shows the measurement result of the noise level in the different frequency band of the conventional magnetron. It is a fragmentary sectional view of the vertical direction which shows the cathode periphery by other embodiment of the magnetron concerning this invention. It is a fragmentary sectional view of the vertical direction which shows the cathode periphery by other embodiment of the magnetron concerning this invention. It is a longitudinal cross-section which shows a part in the anode cylinder of the conventional magnetron which provided the cylindrical body in the both ends of the cathode. It is a wave form diagram which shows the noise level in the conventional magnetron of FIG. It is a wave form diagram which shows the noise level in the conventional magnetron which does not provide a cylindrical body in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Anode cylinder 3 Cathode 10, 20, 30 Anode vane 10A, 20A, 30A Flat part 10B, 20B, 30B Tapered part 11 Cathode support bar 12 Upper end hat 13 Lower end hat

Claims (4)

A cylindrical anode cylinder;
A cathode disposed on a central axis of the anode cylinder;
A plurality of radial shapes are arranged on the inner wall surface of the anode cylinder toward the cathode, and the shape of the tip portion facing each of the cathodes is the anode cylinder fixed end from the approximate center in the axial direction to at least one end portion. An anode vane cut into a tapered shape that gradually shortens the length from the tip to the tip,
A magnetron comprising:   2. The magnetron according to claim 1, wherein each of the anode vanes has a notch dimension set to 0.25 mm or less at the one end of the tip portion.   Each said anode vane has a flat part parallel to an axial direction in the front-end | tip part, The length dimension of this flat part is set to 3 mm or less, The Claim 1 or Claim 2 characterized by the above-mentioned. The magnetron described.   A high-frequency utilization apparatus comprising the magnetron according to any one of claims 1 to 3.

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