Magnetrons, anodes and cathodes therefor

Abstract

To provide a magnetron with a higher output. [Solution] The magnetron 1 comprises an anode 10 having a cylindrical anode shell 11 and a plurality of vanes 12 arranged radially on the inner wall of the anode shell 11, a cathode 20 arranged in the center of the anode 10 along the central axis of the anode shell 11, and a pair of pole pieces 31, 32 arranged opposite each other on both end sides of the anode shell 11, and the anode 10 has a plurality of anode segments 10a, 10b.

Description

[Technical Field]

[0001] The present invention relates to a magnetron, an anode and a cathode therefor. [Background technology]

[0002] Conventionally, magnetrons are used to generate microwaves. It is conceivable that these microwaves could be used as a means of electrifying chemical plants in order to achieve carbon neutrality. For example, in a naphtha cracker, to use microwaves as a heating method, a continuous wave output of several tens of megawatts is required. However, currently available commercially available oscillators have an output of only around 100 kW, which means that an installation of around 100 oscillators would be necessary. Summary of the Invention [Problem to be solved by the invention]

[0003] If the output per unit could be increased, the number of oscillators required could be significantly reduced, so in order to use microwaves as a heating method, it is desirable to develop oscillators with higher output.

[0004] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetron with a higher output, or an anode or cathode therefor. [Means for solving the problem]

[0005] In order to achieve the above object, a magnetron according to one aspect of the present invention is a magnetron comprising: an anode having a cylindrical anode shell, a plurality of vanes arranged radially on the inner peripheral wall of the anode shell; a cathode arranged in the center of the anode along the central axis of the anode shell; and a pair of pole pieces arranged opposite each other on both end sides of the anode shell, wherein the anode has a plurality of anode segments.

[0006] In the magnetron according to one aspect of the present invention, the anode may be formed by joining a plurality of anode segments together.

[0007] In the magnetron according to one aspect of the present invention, the plurality of anode segments may be formed by dividing the anode along a plane perpendicular to the central axis of the anode shell.

[0008] In the magnetron according to one aspect of the present invention, each of the plurality of vanes may have a flow passage therein through which a liquid coolant flows.

[0009] In the magnetron according to one aspect of the present invention, the anode may further include an annular strap that electrically connects every other one of the plurality of vanes.

[0010] In the magnetron according to one aspect of the present invention, the cathode may be arranged coaxially with the anode.

[0011] Moreover, the anode of the magnetron according to one aspect of the present invention has a cylindrical anode shell and a plurality of vanes radially provided on the inner peripheral wall of the anode shell, and the anode has a plurality of anode segments.

[0012] Furthermore, a method for manufacturing an anode of a magnetron according to one aspect of the present invention includes a step of manufacturing a plurality of anode segments formed by dividing an anode having a cylindrical anode shell and a plurality of vanes arranged radially on the inner peripheral wall of the anode shell, and a step of manufacturing an anode by joining the plurality of anode segments. [Effects of the Invention]

[0013] The magnetron according to one aspect of the present invention allows for a larger anode, which in turn allows for greater power output. [Brief explanation of the drawings]

[0014] [Figure 1]FIG. 1 is a cross-sectional perspective view showing the configuration of a magnetron according to an embodiment of the present invention; [Figure 2] FIG. 4 is a perspective view showing a plurality of anode segments according to the embodiment; [Figure 3] FIG. 10 is a diagram showing a refrigerant flow passage provided in the vane according to the embodiment; [Figure 4] FIG. 3 is a perspective view showing a cathode according to the embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0015] The magnetron according to the present invention will be described below using embodiments. In the following embodiments, components with the same reference numerals are the same or equivalent, and repeated description may be omitted. The magnetron according to this embodiment can increase output. In this embodiment, a magnetron having a directly heated cathode and generating a continuous wave for use in a microwave heating device or the like will be described.

[0016] Fig. 1 is a cross-sectional perspective view of a magnetron 1 according to this embodiment, Fig. 2 is a perspective view showing a plurality of anode segments 10a and 10b into which an anode 10 is divided, Fig. 3 is a diagram showing a liquid refrigerant flow passage 14 provided inside a vane 12, and Fig. 4 is a perspective view of a cathode 20. Note that Fig. 3 is a view of one vane 12 as seen from a direction perpendicular to the surface direction of the vane 12.

[0017] The magnetron 1 according to this embodiment includes an anode 10 having a cylindrical anode shell 11 and a plurality of vanes 12 radially arranged on the inner peripheral wall of the anode shell 11, a cathode 20 provided in the center of the anode 10, and a pair of pole pieces 31 and 32 provided opposite both end sides of the anode shell 11, and may further include an output unit 40 that outputs microwaves generated in the resonant cavity of the anode 10 to the outside. In this embodiment, the direction of the central axis of the cylindrical anode shell 11 may be simply referred to as the axial direction, the circumferential direction of the anode shell 11 may be simply referred to as the circumferential direction, and the radial direction of the anode shell 11 may be simply referred to as the radial direction.

[0018] The frequency band of the microwaves generated by the magnetron 1 according to this embodiment may be, for example, around 433.92 MHz, 500 MHz, 915 MHz, 2.45 GHz, or 5.8 GHz, or may be any other frequency band within the range of 300 MHz to 300 GHz. The output of the magnetron 1 is preferably, for example, 100 kW or more, more preferably 500 kW or more, even more preferably 1 MW or more, and even more preferably 10 MW or more. The output of the magnetron 1 may be, for example, 100 kW to 100 MW, 500 kW to 80 MW, 1 MW to 60 MW, or 10 MW to 50 MW.

[0019] The vanes 12 radially arranged on the inner peripheral wall of the anode shell 11 may each extend in the radial direction so as to provide a space in which the cathode 20 can be placed at the center of the anode shell 11. The vanes 12 may be, for example, flat. The number of vanes 12 included in the anode 10 is not particularly limited as long as it is plural. However, as described below, if every other vane 12 is connected by a strap 13, an even number may be provided. The anode shell 11 and the vanes 12 may each be made of a metal such as copper. In the anode 10, a resonant cavity is formed between adjacent vanes 12. The anode 10 is preferably designed so that a resonant cavity corresponding to a desired microwave frequency is formed. The axial length of the resonant cavity may be, for example, equal to or less than half the wavelength of the generated microwave, and typically may be approximately 0.1 to 0.2 times the wavelength. The radial length of the vanes 12 may be, for example, approximately ¼ the wavelength of the generated microwave.

[0020] The anode 10 may further include, for example, an annular strap 13 electrically connecting every other one of the plurality of vanes 12. The annular strap 13 may be arranged, for example, concentric with the anode shell 11. The strap 13 may be connected, for example, to the upper or lower part of the vane 12, or to the joint between the vane segments 12a and 12b (described later). The strap 13 may also be electrically connected to the vane 12 at, for example, a recess 15 provided in the vane 12 as shown in FIG. 3. By electrically connecting every other one of the plurality of vanes 12 along the circumferential direction using the strap 13, the magnetron 1 oscillates in the π mode. As shown in FIG. 2, when the anode 10 has ten vanes 12 along the circumferential direction, i.e., the first to tenth vanes 12, the anode 10 may have, for example, first straps 13a electrically connected to the first vane 12, the third vane 12, the fifth vane 12, the seventh vane 12, and the ninth vane 12, respectively, and second straps 13b electrically connected to the second vane 12, the fourth vane 12, the sixth vane 12, the eighth vane 12, and the tenth vane 12, respectively.

[0021] Each of the vanes 12 may have a flow passage 14 therein through which a liquid coolant flows, as shown in FIGS. 1 and 3 . The coolant may flow through the flow passage 14, for example, as indicated by the arrows in FIG. 3 . By flowing the coolant through the flow passage 14 in this manner, the vanes 12 can be cooled more efficiently than when air-cooling fins are provided on the outer circumferential surface of the anode shell 11. Note that electrons emitted from the cathode 20 impinge on the end 12c of the vane 12 on the cathode 20 side, heating the end 12c. Such heating becomes more pronounced as the output of the magnetron 1 increases. Therefore, in a high-output magnetron 1, it is preferable to cool the vanes 12 using a liquid coolant, which cools the vanes 12 more efficiently than air-cooling fins. Since the cathode 20 side of the vane 12, i.e., the left side in FIG. 3, is heated more by electrons emitted from the cathode 20, it is preferable that the flow passage 14 is provided so as to pass through the inside of the vane 12 near the cathode 20, as shown in FIG. 3. Therefore, the flow passage 14 may be formed, for example, across the vane segments 12a and 12b described below, as shown in FIG. 3. The liquid refrigerant circulating through the flow passage 14 may be, for example, water or another liquid refrigerant. When the flow passage 14 is provided inside the vane 12, the magnetron 1 may further include, for example, a heat exchanger (not shown) that cools the refrigerant discharged from the flow passage 14 of the vane 12 and a pump (not shown) for circulating the liquid refrigerant, and the refrigerant cooled by the heat exchanger may be returned to the flow passage 14 by the pump.

[0022] As shown in FIG. 2, the anode 10 according to this embodiment may be formed by joining a plurality of anode segments 10a, 10b formed by dividing the anode 10. That is, the anode 10 may have a plurality of anode segments 10a, 10b. In this embodiment, the anode 10 is mainly described as being divided into two segments, but the anode 10 may be divided into three or more segments. From the viewpoint of facilitating the manufacture of the anode 10, it is preferable that the number of segments is small. In this embodiment, the anode 10 is mainly described as being divided into a plurality of anode segments 10a, 10b along a plane perpendicular to the central axis of the anode shell 11, but the anode 10 may be divided into a plurality of anode segments at other positions.

[0023] By configuring the anode 10 from multiple anode segments 10a, 10b in this way, it becomes easier to increase the size of the anode 10. For example, although there is a limit to the size of the anode 10 that can be manufactured by machining or other methods, by manufacturing multiple anode segments 10a, 10b separately and then joining them, it is possible to manufacture an anode 10 of a size that cannot be manufactured as a single unit. Using a larger anode 10 allows for greater output from the magnetron 1. This is because, with a high-output magnetron 1, the anode 10 is prone to temperature rise, but by increasing the size of the anode 10, this temperature rise can be easily suppressed. Furthermore, while it is possible to reduce the microwave frequency when increasing the output of the magnetron 1, a larger anode 10 is required to reduce the frequency.

[0024] The cathode 20 is provided in the center of the anode shell 11 along the central axis of the anode shell 11. Preferably, the cathode 20 is arranged so that its longitudinal direction is along the central axis of the anode shell 11. In this manner, the cathode 20 may be arranged coaxially with the anode 10. In order to generate high-power, continuous-wave microwaves, a directly heated cathode 20 is typically used. As shown in FIG. 4 , for example, the directly heated cathode 20 may have a filament 21, end hats 22 and 23, and a cathode lead 24. The directly heated cathode 20 can use a metal filament 21 with a high melting point and high thermal conductivity, which reduces the influence of back heat caused by electron back bombardment and is therefore suitable for generating high-power, continuous-wave microwaves. The diameter of the cylindrical gap near the central axis of the anode shell 11 in which the cathode 20 is housed may be, for example, approximately half the radial length of the vane 12. A larger diameter gap is undesirable because it requires a higher applied voltage. As described above, a directly heated cathode 20 is typically used, but an indirectly heated cathode 20 may also be used. As an example, a dispenser-type hot cathode made of porous tungsten impregnated with barium oxide or the like is difficult to handle due to runaway electron emission caused by backbombardment and the slow temperature control response characteristic of indirectly heated cathodes. However, it can handle large currents at relatively low temperatures and can increase current density to improve output. Therefore, it may be used as the cathode 20 in some cases.

[0025] The filament 21 may be, for example, a metal wire wound in a spiral shape around a cathode lead 24 for power supply. Because the filament 21 becomes hot when microwaves are generated, it is preferable that the material of the filament 21 be, for example, tungsten or thoriated tungsten, which can withstand such high temperatures. The cross section of this wire perpendicular to the longitudinal direction may be, for example, circular, as shown in FIG. 1. End hats 22 and 23 may be provided at both axial ends of the filament 21. For example, the filament 21 and the cathode lead 24 may be electrically connected at the position of the end hat 23. The cathode lead 24 may support the filament 21 and apply a voltage to the filament 21. For example, the filament 21 and another lead for power supply may be electrically connected at the position of the end hat 22. When microwaves are generated, a voltage is applied across the filament 21 to heat it, and a high voltage is applied between the filament 21 and the anode 10, causing the filament 21 to emit thermoelectrons at a high temperature.

[0026] A pair of pole pieces 31, 32 are provided facing each other at both axial ends of the anode shell 11. A magnetic field is applied in the axial direction by this pair of pole pieces 31, 32. As an example, the pole pieces 31, 32 may be disk-shaped. Furthermore, one of the pole pieces, for example, the pole piece 31, may have a hole in the center of the disk shape through which the cathode lead 24 can pass, as shown in FIG. 1 . A microwave leakage prevention mechanism, such as a choke structure, may be provided to prevent microwaves from leaking between the hole in the pole piece 31 and the cathode lead 24. The pole pieces 31, 32 may be made of, for example, a magnet or a magnetic substance. Furthermore, in FIG. 1 , electromagnets (not shown) may be disposed on the upper surface of the pole piece 31 and the lower surface of the pole piece 32, for example. An axial magnetic field may be generated by these electromagnets. The magnetic field between the pair of pole pieces 31, 32 and the electric field between the anode 10 and cathode 20 cause the electrons emitted from the filament 21 to perform a circular orbital motion, inducing high-frequency vibrations that resonate in the resonant cavity of the anode 10, and the interaction between these high-frequency vibrations and the electrons sustains powerful high-frequency vibrations.

[0027] 1, the output section 40 may have an antenna 41 that radiates microwaves in response to high-frequency vibrations generated in the resonant cavity of the anode 10, and an antenna cap 42 that surrounds the antenna 41. The antenna 41 may be coupled to the vane 12, as shown in FIG.

[0028] The magnetron 1 may further include an input unit (not shown) that generates a voltage for heating the filament 21 and a high voltage to be applied between the anode 10 and the cathode 20. The input unit may further supply power to electromagnets arranged near the pole pieces 31 and 32.

[0029] Next, a description will be given of a method for manufacturing the anode 10. The method for manufacturing the anode 10 may include, for example, a step of manufacturing a plurality of anode segments 10a, 10b, and a step of joining the plurality of anode segments 10a, 10b to manufacture the anode 10.

[0030] In the process of manufacturing the multiple anode segments 10a, 10b, the multiple anode segments 10a, 10b may be manufactured, for example, by machining a metal block such as by cutting, by cutting a metal block by wire cutting, by punching or punching in a press process, or by other methods. From the viewpoint of manufacturing larger anode segments, it is preferable to manufacture the anode segments by machining or wire cutting.

[0031] The anode segment 10a may have, for example, an anode shell segment 11a formed by dividing the anode shell 11 and a plurality of vane segments 12a formed by dividing each of the plurality of vanes 12. Similarly, the anode segment 10b may have, for example, an anode shell segment 11b and a plurality of vane segments 12b. In the anode segment 10a, the anode shell segment 11a and the plurality of vane segments 12a may be integrally formed by, for example, machining or wire cutting. The same applies to the anode segment 10b.

[0032] In the process of manufacturing the anode 10, the anode 10 may be manufactured by joining multiple anode segments 10a, 10b together, for example, by brazing. For example, it is preferable to join multiple anode segments 10a, 10b together so that two anode shell segments 11a, 11b are joined together to form one anode shell 11, and two vane segments 12a, 12b are joined together to form one vane 12. The same applies when the anode 10 is divided into three or more anode segments.

[0033] The method for manufacturing the anode 10 may further include, for example, a step of forming the flow passages 14 in the anode segments 10a, 10b prior to the step of manufacturing the anode 10. In the step of forming the flow passages 14, for example, the flow passages 14 may be formed in the anode shell segments 11a, 11b and the vane segments 12a, 12b by drilling or other methods. When joining the multiple anode segments 10a, 10b, it is preferable that the joining be performed so that the flow passages 14 of the two joined vane segments 12a, 12b for each of the multiple vanes 12 are connected. To prevent refrigerant leakage at the joints of the flow passages 14, for example, brazing or electron beam joining from the inside may be performed. Furthermore, if the anode shell segments 11a, 11b and the vane segments 12a, 12b are made of copper, holes may be drilled in the anode shell segments 11a, 11b, and the vane segments 12a, 12b. Then, copper pipes may be inserted into the holes, and copper pieces may be filled into the gaps between the holes and the copper pipes. The copper pipes may then be pressure-welded from the inside, i.e., explosively welded. Forming the flow channel 14 in this manner can prevent refrigerant leakage at the joints between the vane segments 12a, 12b and increase the contact area between the refrigerant and the vane segments 12a, 12b. While FIG. 3 illustrates a case in which the flow channel 14 is formed across the vane segments 12a, 12b, the flow channel 14 may also be formed so as not to span the vane segments 12a, 12b. That is, a first flow channel may be formed in the vane segment 12a, and a second flow channel may be formed in the vane segment 12b, and the first and second flow channels may not be connected. By doing so, when joining the anode segments 10a, 10b, an additional step for preventing the refrigerant from leaking from the joint between the two is not required.

[0034] Next, a method for generating microwaves using the magnetron 1 according to this embodiment will be described. First, an axial magnetic field is generated by electromagnets arranged adjacent to the pole pieces 31 and 32. A voltage is applied to the filament 21 of the cathode 20 to heat the filament 21, and a high voltage is applied between the anode 10 and the cathode 20 to cause thermions to be emitted from the heated filament 21. The electrons emitted from the filament 21 undergo a rotating and orbiting motion due to the magnetic and electric fields, inducing high-frequency vibrations that resonate in the resonant cavity of the anode 10. The interaction between these high-frequency vibrations and the electrons sustains powerful high-frequency vibrations. Microwaves corresponding to the high-frequency vibrations generated in the resonant cavity in this way are radiated via the antenna 41 of the output unit 40.

[0035] As described above, according to the magnetron 1 of this embodiment, the anode 10 is configured to be composed of a plurality of anode segments 10a, 10b, which makes it easy to increase the size of the anode 10 of the magnetron 1. In this way, by increasing the size of the anode 10, the output of the magnetron 1 can be increased.

[0036] Furthermore, by circulating a liquid refrigerant through the flow passages 14 provided inside the vanes 12, the vanes 12 can be cooled more efficiently, and the vanes 12 can be prevented from becoming too hot in a high-output magnetron 1. Furthermore, by providing the flow passages 14 so as to pass through the inside of the vanes 12 near the cathode 20, the areas that are particularly susceptible to heating by electrons emitted from the cathode 20 can be cooled efficiently.

[0037] Although the present embodiment has been described primarily with reference to a case where the filament 21 is made of a single wire, the filament 21 may also be made of a twisted wire of multiple wires. In this case, the filament 21 may also be made, for example, by spirally winding this twisted wire around the cathode lead 24. In the twisted wire, it is preferable that the multiple wires are twisted so that they are not electrically connected. In this way, by making the filament 21 of a twisted wire of multiple wires, the current flowing through each wire can be reduced.

[0038] Furthermore, the above-described embodiments are merely examples for specifically implementing the present invention, and are not intended to limit the technical scope of the present invention. The technical scope of the present invention is defined by the claims, not by the description of the embodiments, and is intended to include modifications within the literal scope of the claims and within the scope of equivalent meanings. [Explanation of symbols]

[0039] 1 magnetron 10 anodes 10a, 10b Anode segments 11 Anode shell 12 vanes 13 Strap 14 Distribution path 20 cathode 31, 32 pole pieces

Claims

1. an anode having a cylindrical anode shell and a plurality of vanes radially provided on an inner peripheral wall of the anode shell; a cathode provided at the center of the anode along the central axis of the anode shell; a pair of pole pieces provided opposite each other on both end sides of the anode shell; A magnetron comprising: the anode has first and second anode segments, and a plurality of vane segments of the first anode segment and a plurality of vane segments of the second anode segment are joined together; The vanes each have a passage therein through which a liquid refrigerant flows.

2. 2. The magnetron of claim 1, The anode has a third anode segment.

3. The magnetron of claim 1, The first and second anode segments are formed by dividing the anode along a plane perpendicular to the central axis of the anode shell.

4. 4. The magnetron according to claim 1, The anode further includes an annular strap electrically connecting every other one of the plurality of vanes.

5. an anode of a magnetron, a cylindrical anode shell; a plurality of vanes radially provided on the inner peripheral wall of the anode shell; and the anode has first and second anode segments, and a plurality of vane segments of the first anode segment and a plurality of vane segments of the second anode segment are joined together; The vanes each have a passage therein through which a liquid refrigerant flows.

6. 1. A method for manufacturing an anode of a magnetron, comprising: a step of manufacturing first and second anode segments obtained by dividing an anode having a cylindrical anode shell and a plurality of vanes radially provided on an inner peripheral wall of the anode shell; a step of manufacturing the anode by joining a plurality of vane segments of the first anode segment and a plurality of vane segments of the second anode segment; Including, The vanes each have a passage therein through which a liquid refrigerant flows.

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