JP2008108657A - Magnetron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetron in which noise in a low frequency band of 30 MHz or lower can be reduced without deteriorating load stability due to phases, and the accuracy of an assembling dimension can be secured without increasing the number of components. <P>SOLUTION: A coil-shape filament 3 is arranged between an input side end hat 62 and an output side end hat 7 supported by a cathode support rod 8. The input side end hat 62 has a tapered boss 62 extending in an action space direction with a small diameter and has further a small-diameter boss 62b having a step at its tip. The small-diameter boss 62b of the input side end hat 62 and one end 3a of the filament 3 are adhered and the other end 3b is adhered to a boss 7a of the end hat 7. Here, a free length part F in a tube axial direction forming an electron emission part of the filament 3 that is not adhered to the end hats 62 and 7 is arranged so as to be displaced to the output side with respect to the tube axial direction H of a plate-shaped vane 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetron with reduced noise used in a high frequency utilization device or the like.

  A conventional magnetron will be described with reference to the drawings.

  FIG. 8 is a longitudinal sectional view showing a working space portion in which electrons of a magnetron in a conventional product move. In this magnetron, a plurality of plate-like vanes 2 (only two are visible in this figure) are arranged radially inside the anode cylinder 1, and these plate-like vanes 2 are formed by pressure equalizing rings 9, 10, 11, 12. Are connected every other. By connecting the pressure equalizing rings 9, 10, 11, 12 every other piece in this way, the magnetron oscillates stably in the π mode. Along the axial center of the anode cylinder 1, a coil 13 including a coiled filament 3, a pair of end hats 6, 7 and a cathode support rod 8 is provided. The filament 3 is made of tungsten containing 1 to 2% of thorium, and is devised to reduce the work function and to easily emit electrons by carburizing the surface. Further, the pair of end hats 6 and 7 are disposed at both ends of the filament 3 in the tube axis direction so as to prevent electrons from leaking in the tube axis direction, and are fixed to the end portions 3 a and 3 b of the filament 3. Here, since the end portions 3a and 3b of the filament 3 fixed to the end hats 6 and 7 are not carburized, the work function is high and hardly emits electrons. The electron emitting portion that actually emits electrons is a filament. 3 is an axial free length region that is carburized in 3 and is not fixed to the end hats 6 and 7.

  In such a magnetron, a technique for reducing noise generated in the magnetron has been conventionally proposed (for example, see Patent Document 1).

  FIG. 9 is a longitudinal sectional view showing a part of the anode cylinder of the magnetron disclosed in Patent Document 1. In this magnetron, in addition to the configuration shown in FIG. 8, metal cylindrical bodies 4 and 5 are arranged at both ends of the cathode 13. The input side cylindrical body 4 of the cathode 13 is fixed to the input side end hat 6, and the output side cylindrical body 5 of the cathode 13 is fixed to the output side end hat 7. These cylindrical bodies 4 and 5 suppress the spread of electrons radiated from the filament 3, and since the magnetron is equipped with these cylindrical bodies 4 and 5, noise in the 30 MHz to 200 MHz band is remarkably increased. Can be reduced.

FIG. 10 is a waveform diagram showing a noise level of 1 GHz or less in a conventional product actually measured by the inventors of the present application and not including these cylindrical bodies 4 and 5 shown in FIG. Certainly, in the conventional product in which no cylindrical body is provided, noise is particularly large at 200 MHz or less, and as described in Patent Document 1, noise reduction in the 30 MHz to 200 MHz band is significant. I understand that.
Japanese Patent Publication No. 4-77412

  In general, a magnetron swirls around the cathode by the force generated by the electrostatic field applied between the cathode and the anode and the Lorentz force generated by the static magnetic field applied in the tube axis direction. I am circling around. The electrons are bunched by the natural vibration of the plurality of resonators formed by the plate-shaped vane, the anode cylinder, and the pressure equalizing ring to form an electron bundle. Then, an induced current flows through the plate-shaped vane by the rotation of the electron bundle, resonates, and is converted into microwave energy.

  The shape of the electron flux depends on the intensity of the microwave electric field determined by the load coupled to the magnetron, and has a great influence on the oscillation frequency. Furthermore, if the intensity of the microwave electric field is strong and the electron bundle becomes sharp due to the influence, the noise level increases due to the interaction of the pushed-in electrons. FIG. 12 shows the noise level when the phase is changed.

  In addition, noise that propagates through power lines and noise that is radiated into the space is considered to be mainly generated at the tube axis direction end of the working space where the electric field and magnetic field are distorted and the orthogonal electromagnetic field cannot be maintained. Yes.

  In view of these facts, in the technique disclosed in Patent Document 1, a cylindrical body is provided so that electrons emitted at the end in the tube axis direction cannot move.

  However, in the technique disclosed in Patent Document 1, although noise in the 30 MHz to 200 MHz band can be reduced, a noise filter (not shown) configured by a coil, a capacitor, or the like attached to a conventional magnetron. However, attention has not been paid to a band of 30 MHz or less which is difficult to suppress. Further, in an experiment conducted by the inventors of the present invention based on the technique disclosed in Patent Document 1, the electrostatic field distribution in the working space is changed by arranging the cylindrical bodies 4 and 5 in the working space. The load stability due to the phase tended to deteriorate significantly. Furthermore, in the technique disclosed in Patent Document 1, the cylindrical bodies 4 and 5 are fixed to the end hats 6 and 7, but the end hats 6 and 7 are separate parts. In addition to increasing the number of points, it is difficult to ensure the accuracy of the assembly dimensions.

  The present invention has been made in view of the above-mentioned knowledge in order to solve the above-mentioned problems, and the object thereof is to reduce noise in a low frequency band of 30 MHz or less without degrading load stability due to phase. And it is providing the magnetron which can ensure the precision of an assembly dimension, without increasing a number of parts.

  The above object is achieved by the following configuration.

  (1) A magnetron according to the present invention includes a cylindrical anode cylinder in which a plurality of plate-shaped vanes are arranged radially toward the central axis, and a cathode support rod disposed on the central axis of the anode cylinder. And a pair of end hats provided at positions on the cathode support rod that sandwich the cathode in the axial direction, and the electron emission portion of the cathode is arranged displaced in the tube axis direction. In addition, the input-side end hat of the pair of end hats has a boss portion with a small diameter extending in the direction of the working space, and has a step at the tip of the boss portion to form a narrower diameter small boss portion. A small-diameter boss portion of the input-side end hat and one end portion of the filament constituting the cathode are fixed, and the other end portion of the filament is fixed to the boss portion of the output-side end hat. It is characterized by that.

  (2) In the magnetron according to the above (1), the boss portion of the input side end hat extends in a taper shape with a small diameter in the working space direction.

  (3) The high-frequency utilization apparatus includes the magnetron described in (1) or (2) above.

  According to such a configuration, it is possible to reduce noise in a low frequency band of 30 MHz or less without deteriorating load stability due to phase, and it is possible to ensure the accuracy of assembly dimensions without increasing the number of components.

  According to the magnetron described in the above (1), since the carburized filaments are displaced with respect to the tube axis direction, electrons are not emitted from the portion where the cathode filament does not face the plate-shaped vane, and noise is generated. The emission of unwanted electrons due to the is suppressed. Furthermore, the microwave electric field strength is thought to be strongest at the tube axial center of the resonator, that is, the plate axial center of the plate-shaped vane. However, since the electron emission distribution is displaced, the position where electrons are emitted. The intensity of the microwave electric field at is weaker than when it is not displaced, and the influence of electrons on the microwave electric field is reduced. Therefore, noise in a low frequency band of 30 MHz or less can be reduced. In addition, unlike conventional magnetrons in which a cylindrical body is provided at each end of the cathode, it is only necessary to displace the arrangement of the electron emitters, so that the increase in the number of parts can be prevented and assembly can be performed in the same manner as in the past. Sufficient accuracy can be secured. Further, since the working space dimension in which the electrons can move is not different from the conventional one, the load stability due to the phase does not deteriorate.

  According to the magnetron described in (2) above, the load stability is improved because the electric field distribution does not change abruptly due to the shape of the boss portion of the input side end hat and the diffusion of electrons in the axial direction is suppressed. .

  According to the high frequency utilization device described in (3) above, noise can be reduced in a frequency band of 30 MHz or less, so that noise countermeasure parts such as coils and capacitors can be of a small capacity, and the cost can be reduced accordingly. Can be planned.

  Hereinafter, a magnetron according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a partial longitudinal sectional view showing a cathode portion of a magnetron according to Embodiment 1 of the present invention. Since the configuration other than the cathode portion shown in this figure is the same as that of the conventional magnetron shown in FIG. 8, the configuration common to FIG. 8 is denoted by the same reference numeral.

  1, in the magnetron of the present embodiment, a coiled filament 3 is disposed between an input side end hat 61 and an output side end hat 7 supported by a cathode support bar 8. In particular, in the present embodiment, the input-side end hat 61 has a large-diameter boss portion 61a that is thicker than the shape in FIG. 8 extending into the working space, and the small-diameter boss portion 61b and the end portion 3a of the filament 3 are It is fixed. The output-side end hat 7 has the same shape as the conventional one, and the boss 7a and the end 3b of the filament 3 are fixed. Here, the dimension of the free length portion F in the tube axis direction that is not fixed to the end hat 61 and the end hat 7 of the filament 3, that is, capable of emitting electrons, is set to the tube axis direction dimension H of 9.5 mm. The plate-shaped vane 2 is set to about 75% of the plate-shaped vane 2 and the position of the tube axis direction free length portion F forming the electron emission portion is displaced to the output side.

  In this way, by shortening the electron emitting portion in the tube axis direction and displacing it in the tube axis direction with respect to the working space, electron emission at the end portion in the tube axial direction of the working space where the orthogonal electromagnetic field cannot be maintained is on one side. It is suppressed. As a result, the amount of electron emission can be adjusted while minimizing the electron movement at the end of the working space in the tube axis direction, which mainly causes noise propagating through the power line and noise radiated into the space. Thus, noise over a wide band can be reduced as compared with the case where the cylindrical bodies shown in the prior art are provided on both sides of the cathode without degrading the load stability due to the phase. In addition, the number of parts can be reduced as compared with the case where a cylindrical body is provided, and the accuracy of assembly dimensions can be sufficiently ensured.

  Here, an experimental result of measuring a microwave oscillation signal performed by the inventors of the present application for verification is shown.

  FIG. 2 shows that the dimension of the tube axis direction free length F constituting the electron emission portion of the magnetron, which is the present embodiment, is set to about 75% of the dimension H of the plate vane 2 in the tube axis direction, and the output side FIG. 3 is a waveform diagram showing a noise level of 30 MHz or less when the phase is displaced, and FIG. 3 shows a noise level at each phase when the voltage standing wave ratio (VSWR) is changed to VSWR≈1.5. FIG. In FIG. 3, the horizontal axis indicates the insertion position of the slag tuner used for the measurement. Since the in-tube wavelength of the waveguide used in the experiment is about 140 mm, it returns to the same position at about 70 mm of the half wavelength. Further, FIG. 4 shows the noise of the magnetron when the dimension of the free length portion F in the tube axis direction forming the electron emission portion is changed while the electron emission portion is not displaced with respect to the tube axis direction of the plate-shaped vane. FIG. 5 is a diagram showing changes in the level. FIG. 5 shows changes in the oscillation efficiency and noise level of the magnetron when the electron emitting part is displaced to the output side and the dimensions of the tube axis free length part F forming the electron emitting part are changed. FIG.

  As is apparent from FIG. 2, in the case of the present embodiment, the noise level of 30 MHz or less is reduced as compared with the noise level characteristic of the conventional product in which the cylindrical body shown in FIG. 11 is not provided.

  Further, as is clear from FIG. 3, in the case of the present embodiment, the noise fluctuation due to the phase is suppressed lower than the noise level characteristic of the conventional product in which the cylindrical body shown in FIG. 12 is not provided at all. .

  As is clear from FIG. 4, with respect to the position of the electron emission portion, the dimension of the free length portion F in the tube axis direction constituting the electron emission portion is set as it is without being displaced with respect to the tube axis direction of the plate-shaped vane. Even if it is changed, the noise level hardly changes, but as is apparent from FIG. 5, when it is displaced to the output side, if the dimension of the tube axis free length portion F forming the electron emitting portion is changed, the noise level is also changed. Change. Therefore, in order to reduce the noise level, it is effective to displace the electron emission portion with respect to the tube axis direction of the plate-shaped vane.

  On the other hand, as is apparent from FIG. 5, the dimension of the tube axis direction free length F constituting the electron emission part is 50% or more of the dimension H of the plate-shaped vane 2 in the tube axis direction. 70% or more can be secured. This is mainly because the electron motion in the center of the working space contributes to the oscillation efficiency of the magnetron. Further, as apparent from FIG. 5, the noise level can be suppressed to 80 dB or less as long as it is 80% or less with respect to the dimension H in the tube axis direction of the plate-shaped vane 2.

(Embodiment 2)
FIG. 6 is a partial vertical cross-sectional view showing the cathode portion of the magnetron according to the second embodiment of the present invention. Since the configuration other than the cathode portion shown in this figure is the same as that of the conventional magnetron of FIG. 8 described above, it is omitted, and the same reference numerals are given to the configurations common to FIGS.

  In FIG. 6, the magnetron of the present embodiment is obtained by changing the shape of the large-diameter boss portion of the input side end hat in FIG.

  FIG. 7 shows the relationship between the load stability (MoB [mA]) of the magnetron and the outer diameter D of the large-diameter boss portion 61a of the input-side end hat 61 in FIG.

  As is clear from FIG. 7, the outer diameter of the large-diameter boss portion 61a of the input-side end hat 61 is improved in the load stability of the magnetron when the diameter is small.

  Therefore, in the present embodiment, as shown in FIG. 6, the input-side end hat 62 has a tapered boss portion 62a extending with a small diameter in the working space direction, and is formed at the tip of the tapered boss portion 62a. A boss portion 62b having a smaller diameter and having a step is formed, and the boss portion 62b with a small diameter of the input side end hat 62 and one end portion 3a of the filament 3 constituting the cathode are fixed.

  The other end portion 3 b of the filament 3 is fixed to the boss portion 7 a of the output side end hat 7, and the tube axis direction free length portion F forming the electron emission portion of the filament 3 is relative to the tube axis direction portion H of the plate-shaped vane 2. Are displaced to the output side.

  By displacing the electron emission part in this way with respect to the tube axis direction, electron emission from one of the end parts that are mainly noise components due to nonuniform magnetic and electric fields is suppressed, so unnecessary electrons Is suppressed and line noise is reduced.

  In addition, the shape of the large-diameter boss part of the input side end hat is tapered so that the diameter becomes smaller in the working space direction, so that the electric field distribution does not change rapidly and the axial direction of the electrons. Since the diffusion to the load can be suppressed, the load stability is improved.

  Furthermore, since the punching strength is improved in press molding of the input side end hat, mass production becomes possible.

  As described above, according to the magnetron of the present embodiment, a conventional product in which no cylindrical body is provided, or a cylindrical body 4, by displacing the electron emitting portion in the working space in the tube axis direction. The noise in the 30 MHz to 200 MHz band can be reduced as well as the noise in the lower frequency band of 30 MHz or less as compared with the case where the equivalent of 5 is provided on both sides of the cathode 3.

  In addition, when the magnetron of the present embodiment is used in a high-frequency device such as a microwave oven, noise can be reduced in the same manner as described above, so that noise countermeasure parts such as coils and capacitors need only have a small capacity. Cost reduction can be achieved.

  The magnetron according to the present invention can be applied to uses that use a magnetron, such as a microwave oven, a microwave generator, and a high-frequency utilization device using the device.

Partial sectional view of the magnetron according to the first embodiment of the present invention. Waveform diagram showing a noise level of 30 MHz or less in the magnetron of FIG. The graph which shows the change of the noise level by the phase change in the magnetron of FIG. The graph which shows the change of the noise level of a magnetron when the dimension of the tube-axis direction free length part F which comprises an electron emission part is changed with the electron emission part arrange | positioned in the center. A graph showing changes in the oscillation efficiency and noise level of the magnetron when the dimension of the tube-axis-direction free length F forming the electron emission portion is changed by displacing the electron emission portion to the output side Partial sectional view of a magnetron according to a second embodiment of the present invention The graph which shows the relationship of the load stability of a magnetron with respect to the external dimension of the large diameter boss | hub part of the input side end hat in the magnetron of FIG. Longitudinal sectional view showing a part of a conventional anode cylinder without any cylindrical body A longitudinal sectional view showing a part of an anode cylinder of a magnetron provided with a cylinder on the input / output side of a conventional cathode end Waveform diagram showing a noise level of 1 GHz or less in the magnetron of FIG. Waveform diagram showing a noise level of 30 MHz or less in the magnetron of FIG. The graph which shows the change of the noise level by the phase change in the magnetron of FIG.

Explanation of symbols

2 Plate-shaped vane 3 Filament 3a, 3b End of filament 7 Output side end hat 7a Boss portion 8 Cathode support rod 13 Cathode 61, 62 Input side end hat 61a Large diameter boss portion 61b, 62b Small diameter boss portion 62a Tapered boss Part

Claims (3)

A cylindrical anode cylinder in which a plurality of plate-shaped vanes are radially arranged toward the central axis, a cathode provided by a cathode support rod on the central axis of the anode cylinder, and the cathode A pair of end hats provided at positions on the cathode support rod sandwiched in the axial direction, the electron emission portions of the cathode being displaced in the tube axis direction, and the pair of end hats The input side end hat has a boss portion with a small diameter in the direction of the working space, and has a step at the tip of the boss portion to form a narrower small diameter boss portion. A small-diameter boss portion and one end portion of a filament constituting the cathode are fixed, and the other end portion of the filament is fixed to a boss portion of an output side end hat. 2. The magnetron according to claim 1, wherein a boss portion of the input-side end hat extends in a taper shape with a small diameter in a working space direction. A high frequency utilization apparatus comprising the magnetron according to claim 1.

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