JP5055872B2 - Magnetron - Google Patents

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. 10 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, and 12 every other piece, 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. 11 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 of FIG. 10, metal cylinders 4 and 5 are disposed at both ends of the cathode 13. The cylindrical body 4 on the input side of the cathode 13 is fixed to the end hat 6 on the input side, and the cylindrical body 5 on the output side of the cathode 13 is fixed to the end hat 7 on the output side. 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. 12 is a waveform diagram showing a noise level of 1 GHz or less in the conventional product which is not provided with the cylindrical bodies 4 and 5 shown in FIG. Certainly, in the conventional product in which no cylindrical body is provided, the 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. 13 shows the noise level when the phase is changed.

  In addition, noise propagating through power lines and noise radiated into space are thought to be mainly generated at the end of the working space in the tube axis direction 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. In addition, the oscillation efficiency of the magnetron tended to decrease. 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 its purpose is to reduce noise in a low frequency band of 1 GHz or less without deteriorating load stability due to phase. Another object of the present invention is to provide a magnetron capable of suppressing a decrease in oscillation efficiency and ensuring the accuracy of assembly dimensions without increasing the 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. a filament is set, includes a pair of end hats provided in a position on the cathode supporting rod to sandwich the filament in the axial direction, disposed opposite the tube axis direction dimension of the electron emission portion of said filament The tube axis in the vicinity of the plate-shaped vane is set to be shorter than the dimension of the plate-shaped vane in the tube axis direction, and the electron emission portion of the filament is biased in the tube axis direction and is opposed to the electron emission portion The directional magnetic field strength is substantially uniform.

  (2) In the magnetron described in (1) above, when the maximum value of the magnetic field strength in the tube axis direction in the vicinity of the plate-shaped vane facing the electron emission portion is (Bmax) and the minimum value is (Bmin), (Bmin ) / (Bmax) is preferably 0.9 to 1.0.

  (3) In the magnetron according to the above (1) or (2), the shape of the pair of pole pieces disposed at both side opening ends of the anode cylinder is formed in order to form the tube axis direction magnetic field strength. It may be different.

(4) In the magnetron described in (3) above, a through hole formed in the center of the small-diameter flat portion of the pole piece is formed larger on the electron emission portion side of the cathode biased in the tube axis direction. May be.

(5) In the magnetron according to the above (3), the diameter of the small flat portion of the pole piece may be formed larger on the electron emission portion side of the cathode biased in the tube axis direction.

(6) In the magnetron described in (3) above, the height of the pole piece in the tube axis direction may be higher on the electron emission portion side of the cathode biased in the tube axis direction.

(7) In the magnetron according to the above (1) or (2), the distance between the pole piece and the plate-shaped vane is formed larger on the electron emission side of the cathode biased in the tube axis direction. It may be.

  (8) The high-frequency utilization apparatus includes the magnetron described in any one of (1) to (7) above.

  According to such a configuration, noise in a low frequency band of 1 GHz or less can be reduced without deteriorating load stability due to phase, and a decrease in oscillation efficiency can be suppressed, and the assembly dimensions can be reduced without increasing the number of components. Accuracy can be secured.

According to the magnetron described in (1) above, since the carburized filaments are arranged to be deviated with respect to the tube axis direction, electrons are not emitted from the portion where the cathode filaments do 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 considered to be strongest at the tube axial center of the resonator, that is, the center of the plate-shaped vane in the tube axial direction. However, since the electron emission distribution is biased , the position where electrons are emitted The intensity of the microwave electric field at is weaker than when it is not biased , and the influence of electrons from the microwave electric field is reduced. Furthermore, by forming the magnetic field strength in the tube axis direction in the vicinity of the plate-shaped vane facing the electron emitting portion almost uniformly, the electron drift velocity due to the action of the electrostatic field and the static magnetic field is kept almost constant, and the electron flux is also It converges almost uniformly. For these reasons, noise in a low frequency band of 1 GHz or less can be reduced, and a decrease in oscillation efficiency can be suppressed.

In addition, unlike conventional magnetrons in which a cylindrical body is provided at each end of the cathode, only the arrangement of the electron emission section itself is deviated , so that an 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 ratio (Bmax) / (Bmin) between the maximum value (Bmax) and the minimum value (Bmin) of the magnetic field strength in the tube axis direction in the vicinity of the plate-shaped vane facing the electron emission portion. ) In the range of 0.9 to 1.0, it is possible to significantly reduce noise in a wide band while suppressing a decrease in the oscillation efficiency of the magnetron.

  According to the magnetron described in the above (3), the tube in the vicinity of the plate-shaped vane facing the electron emission portion is made different by making the shapes of the pair of pole pieces arranged at the opening ends on both sides of the anode cylinder. The magnetic field strength in the axial direction can be formed almost uniformly, and noise in a wide band can be greatly reduced while suppressing a decrease in the oscillation efficiency of the magnetron.

According to the magnetron described in (4) above, the through hole formed in the center of the small-diameter flat portion of the pole piece is formed larger on the electron emission portion side of the cathode that is biased in the tube axis direction. As a result, it is possible to significantly reduce noise in a wide band while suppressing a decrease in the oscillation efficiency of the magnetron.

According to the magnetron described in the above (5), the diameter of the small flat portion of the pole piece is formed larger on the side of the electron emitting portion of the cathode that is biased in the tube axis direction, thereby oscillating the magnetron. Noise in a wide band can be greatly reduced while suppressing a decrease in efficiency.

According to the magnetron described in (6) above, the height of the pole piece in the tube axis direction is formed higher on the electron emission portion side of the cathode biased in the tube axis direction. The noise in the wide band can be greatly reduced while suppressing the decrease in the noise.

According to the magnetron described in (7) above, the distance between the pole piece and the plate-shaped vane is formed larger on the electron emission portion side of the cathode biased in the tube axis direction. The magnetic field intensity in the vicinity of the plate-shaped vane facing the portion can be formed substantially uniformly, and noise in a wide band can be greatly reduced while suppressing a decrease in the oscillation efficiency of the magnetron.

  According to the high-frequency utilization device described in (8) above, noise can be reduced in a frequency band of 1 GHz or less, so that noise countermeasure parts such as coils and capacitors need only have a small capacity, and the cost is 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 vertical partial sectional view showing an action space portion in which electrons of a magnetron according to Embodiment 1 of the present invention move. In this figure, the same reference numerals are assigned to components common to FIG.

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 boss portion 61a having a larger diameter than the shape in FIG. 10 extending into the working space, and a boss portion 61b having a smaller diameter and the end portion 3a of the filament 3 are formed. It is fixed. The output-side end hat 7 has the same shape as the conventional one, and the boss portion 7 a and the end portion 3 b of the filament 3 are fixed to each other. Here, the dimension of the free length portion 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 performing electron emission, is set by setting the tube axis direction dimension H to 9.5 mm. It is set to about 75% of a certain plate-shaped vane 2, and the position of the tube-axis-direction free length portion F constituting the electron emission portion is biased toward the output side. Further, the diameter 14a of the through hole formed in the center of the pole piece 14 arranged on the output side is φ11.5 mm, and the diameter 15a of the through hole formed in the center of the pole piece 15 arranged on the input side is It is set to φ9.0mm.

In this way, by shortening the electron emitting portion in the tube axis direction and biasing it in the tube axis direction with respect to the working space, electron emission at the end portion in the tube axis 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. Furthermore, by making the diameter of the through-hole formed in the center of the pole piece different between the input side and the output side, the magnetic field strength in the working space where the electrons move is almost uniform, and the cylindrical body is placed on both sides of the cathode. Therefore, the number of parts can be reduced as compared with the case of providing the assembly dimension, and the accuracy of the assembly dimension can be sufficiently secured.

  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 biases the further, Fai11.5Mm the diameter 14a of the output side pole piece central opening, a waveform diagram showing the following noise levels 1GHz when the diameter 15a of the input side pole piece central opening was φ9.0mm FIG. 3 is a diagram showing the noise level in each phase when the phase is changed with the voltage standing wave ratio (VSWR) being VSWR≈1.5. In FIG. 3, the horizontal axis indicates the insertion position of the slag tuner used for the measurement. Since the waveguide wavelength (not shown) used in the experiment is about 140 mm, it returns to the same position at about 70 mm of the half wavelength. FIG. 4 is a diagram showing the magnetic field strength in the vicinity of the plate-shaped vane 2 at this time. FIG. 5 shows the relationship between the oscillation efficiency and the ratio (Bmin) / (Bmax) of the maximum value (Bmax) and the minimum value (Bmin) of the magnetic field strength in the tube axis direction in the vicinity of the plate-shaped vane 2 facing the electron emission portion. FIG.

  As is apparent from FIG. 2, in the case of the present embodiment, the noise level of 1 GHz or less, particularly 30 MHz or less, is reduced as compared with the conventional product not provided with the cylindrical body shown in FIG.

  Further, as is apparent from FIG. 3, in the case of the present embodiment, the noise fluctuation due to the phase is suppressed as compared with the conventional product in which the cylindrical body shown in FIG. 13 is not provided at both ends of the cathode. .

In addition, as shown in FIG. 4, the position in the tube axis direction that takes the minimum value of the magnetic field strength in the tube axis direction is biased toward the output side as compared with the conventional product that does not have the cylindrical body shown in FIG. I understand. As shown in FIG. 14, the maximum value (Bmax) = 0.200 [T] and the minimum value (Bmin) of the magnetic field strength in the tube axis direction in the vicinity of the plate-shaped vane 2 facing the electron emission portion of the conventional product without any cylindrical body. = 0.166 [T] and the ratio (Bmin) / (Bmax) = 0.83, but as is apparent from FIG. 4, in the case of the present embodiment, the plate-shaped vane facing the electron emission portion 2 The maximum value (Bmax) = 0.173 [T] and the minimum value (Bmin) = 0.165 [T] of the magnetic field strength in the tube axis direction at the vicinity of 2 and the ratio (Bmin) / (Bmax) = 0.95 In the space where the electrons move, the electron drift speed determined by the electric field strength and the magnetic field strength becomes almost constant, and the noise level of 1 GHz or less can be suppressed.

Further, as is clear from FIG. 5, the ratio (Bmin) / (Bmax) of the maximum value (Bmax) and the minimum value (Bmin) of the magnetic field strength in the tube axis direction at the position in the vicinity of the plate-shaped vane 2 facing the electron emission portion. By setting it to 0.9 to 1.0, it becomes possible to suppress a decrease in oscillation efficiency. This is because the motion space that contributes to oscillation in the tube axis direction is widened by making the magnetic field strength at the electron emitting portion position substantially constant.

(Embodiment 2)
FIG. 6 is a vertical partial sectional view showing an action space portion in which electrons of the magnetron according to the second embodiment of the present invention move. In this figure, the same reference numerals are assigned to components common to those in FIG.

6, in the magnetron of the present embodiment, a coiled filament 3 is arranged between an input side end hat 61 and an output side end hat 7 supported by a cathode support rod 8. In particular, in the present embodiment, the input-side end hat 61 has a boss portion 61a having a larger diameter than the shape in FIG. 10 extending into the working space, and a boss portion 61b having a smaller diameter and the end portion 3a of the filament 3 are formed. It is fixed. The output-side end hat 7 has the same shape as the conventional one, and the boss portion 7 a and the end portion 3 b of the filament 3 are fixed to each other. 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 biased toward the output side. Further, the diameter 24a of the small diameter flat portion of the pole piece 24 arranged on the output side is set to φ18.0 mm, and the diameter 25a of the small diameter flat portion of the pole piece 25 arranged on the input side is set to φ14.0 mm. ing.

In this way, by shortening the electron emitting portion in the tube axis direction and biasing it in the tube axis direction with respect to the working space, electron emission at the end portion in the tube axis direction of the working space where the orthogonal electromagnetic field cannot be maintained is on one side. It is suppressed. This minimizes electron motion at the tube axis direction end of the working space, which mainly causes noise, while adjusting the total electron emission amount without degrading the load stability due to phase. The 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. Further, by making the small-diameter flat portion formed in the center of the pole piece different between the input side and the output side, the magnetic field strength in the tube axis direction in the working space in which electrons move is substantially uniform, as shown in FIG. As in the first embodiment, the ratio (Bmin) / (Bmax) of the maximum value (Bmax) and the minimum value (Bmin) of the magnetic field strength in the tube axis direction in the vicinity of the plate-shaped vane 2 facing the electron emission portion is 0. Compared with a conventional product that does not have a cylindrical body at all, the noise level of 1 GHz or less is reduced and the noise fluctuation due to the phase is kept low while suppressing a decrease in oscillation efficiency.

(Embodiment 3)
FIG. 8 is a partial cross-sectional view in the vertical direction showing an action space where the electrons of the magnetron according to the third embodiment move. In this figure, the same reference numerals are assigned to components common to FIG.

In FIG. 8, the magnetron of the present embodiment has the same positional relationship between the plate-shaped vane 2, the cathode 23 and the small-diameter flat portions of the pole pieces 34 and 35 as in the first embodiment. The distance between the end of the anode cylinder 1 and the plate-shaped vane 2 is biased along the tube axis direction so that the output-side distance L1 is larger than the input-side distance L2.

Even with this configuration, the tube axis direction magnetic field strength in the working space in which electrons move is substantially uniform as in the first and second embodiments, and the tube axis in the vicinity of the plate-shaped vane 2 facing the electron emission portion. The ratio (Bmin) / (Bmax) of the maximum value (Bmax) and the minimum value (Bmin) of the directional magnetic field can be set to 0.9 to 1.0.

(Embodiment 4)
FIG. 9 is a partial cross-sectional view in the vertical direction showing an action space where the electrons of the magnetron according to the fourth embodiment move. In this figure, the same reference numerals are assigned to components common to FIG.

  In FIG. 9, the magnetron of the present embodiment has the same positional relationship between the plate-shaped vane 2 and the cathode 23 as in the first embodiment, but the distance L3 between the pole piece 44 on the output side and the plate-shaped vane 2 is set as follows. The input side pole piece 45 and the plate-shaped vane 2 are configured to be larger than the distance L4.

  Even with this configuration, the tube axial direction magnetic field strength in the working space in which electrons move is substantially uniform as in the first, second, and third embodiments, and the tube in the vicinity of the plate-shaped vane facing the electron emitting portion is provided. The ratio (Bmin) / (Bmax) of the maximum value (Bmax) and the minimum value (Bmin) of the axial magnetic field can be set to 0.9 to 1.0.

  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 1 GHz 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 figure which shows the magnetic field intensity of the plate-shaped vane vicinity in the magnetron of FIG. The figure which shows the relationship between the ratio of the maximum value (Bmax) and the minimum value (Bmin) of the magnetic field strength in the tube axis direction near the plate-shaped vane facing the electron emission portion in the magnetron of FIG. Partial sectional view of a magnetron according to a second embodiment of the present invention The figure which shows the magnetic field intensity of the plate-shaped vane vicinity in the magnetron of FIG. Partial sectional view of a magnetron according to a third embodiment of the present invention Partial sectional view of a magnetron according to a fourth embodiment of the present invention. 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. 10 is a graph showing a change in noise level due to a phase change in the magnetron of FIG. The figure which shows the magnetic field intensity of the vicinity of the plate-shaped vane in the magnetron of FIG.

DESCRIPTION OF SYMBOLS 1 Anode cylinder 2 Plate-shaped vane 3 Filament 3a, 3b End part of filament 6,61 Input side end hat 61a, 61b Boss part 7 Output side end hat 7a Boss part 8 Cathode support rod 13,23 Cathode 14,15 , 24, 25, 34, 35, 44, 45 Pole pieces 14a, 15a Diameters of through holes formed in the center 24a, 25a Diameters of small flat portions F Tube axis free length portions H forming electron emission portions H Plate shape Dimension of vane tube axis direction L1 Distance from the end of the anode cylinder on the output side to the plate-shaped vane L2 Distance from the end of the anode cylinder on the input side to the plate-shaped vane L3 From the pole piece on the output side to the plate-shaped vane Distance L4 Distance from the pole piece on the input side to the plate-shaped vane

Claims (8)

A cylindrical anode cylinder in which a plurality of plate-shaped vanes are radially arranged toward the central axis, a filament disposed by a cathode support rod on the central axis of the anode cylinder, and the filament A pair of end hats provided at positions on the cathode support rod sandwiched in the axial direction;
The tube-axis direction dimension of the electron emission portion of the filament is set to be shorter than the tube-axis direction dimension of the plate-shaped vane disposed so as to face each other, and the electron emission portion of the filament is disposed offset in the tube axis direction. The magnetron is characterized in that the magnetic field strength in the tube axis direction in the vicinity of the plate-shaped vane opposite to the electron emission portion is substantially uniform. The ratio of (Bmin) / (Bmax) is 0.9 when the maximum value of the magnetic field strength in the tube axis direction in the vicinity of the plate-shaped vane facing the electron emission portion is (Bmax) and the minimum value is (Bmin). The magnetron according to claim 1, wherein the magnetron is -1.0. The shape of a pair of pole piece arrange | positioned in the both-ends opening part of the said anode cylinder is differed in order to form the said tube axial direction magnetic field strength, The Claim 1 or Claim 2 characterized by the above-mentioned. Magnetron. In the pair of pole pieces disposed at both ends of the anode cylinder, a through-hole formed in the center of the small-diameter flat portion of the pole piece is biased in the tube axis direction. The magnetron according to claim 3, wherein the emission part side is formed larger. 4. The magnetron according to claim 3, wherein the diameter of the small flat portion of the pole piece is formed larger on the side of the electron emission portion of the cathode that is biased in the tube axis direction. 4. The magnetron according to claim 3, wherein the height of the pole piece in the tube axis direction is higher on the electron emission side of the cathode biased in the tube axis direction. 5. The distance between the pole piece and the plate-shaped vane is formed larger on the electron emission portion side of the cathode biased in the tube axis direction. Magnetron. A high-frequency utilization apparatus comprising the magnetron according to any one of claims 1 to 7.

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