JP2011198725A - Magnetron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetron structure capable of thinning plate thickness of an anode cylinder.SOLUTION: An anode 11 for oscillating microwaves has an anode cylinder 14, and a plurality of vanes 21 joined with an inner wall of the anode cylinder by separating from end faces 24, 25 and projected at a radial shape in a tube-axis direction. A non-magnetic cylindrical auxiliary anode 50 for supporting positioning of pole pieces 30, 31 in a tube-axis direction is fitted and arranged between the end faces 24, 25 at an input section 12 side and an output section 13 side of the inner wall of the anode cylinder 14, and the vanes 21; and metal sealing bodies 15, 16 at the input section 12 side and the output section 13 side are airtightly joined with the end faces 24, 25 of the anode cylinder by holding the pole pieces 30, 31 together with the auxiliary anode 50.

Description

  The present invention relates to a magnetron used in a microwave heating apparatus such as a microwave oven.

  In general, as shown in FIG. 5, a magnetron for a microwave oven includes an anode unit 100 that is a microwave oscillating unit, an input unit 101 that supplies power, and an output unit 102 that extracts the oscillated microwave out of the tube. The input unit 101 is arranged on one side and the output unit 102 is arranged on the other side along the tube axis around the anode unit 100. The input part 101 and the output part 102 are joined in a vacuum-tight manner by an anode cylinder 103 in the anode part and cylindrical metal sealing bodies 104 and 105. The input unit includes a ceramic stem and a cathode rod 107 planted on the stem, and a spiral cathode 108 is held at the tip of the rod. The output part pulls out the antenna rod 110 coaxially extended from the anode vane 109 on the tube axis through the ceramic insulating cylinder.

  In the anode part 100, a plurality of vanes 109 are radially arranged inside the anode cylinder 103 toward the tube axis. A spiral cathode 108 is arranged on the tube axis so as to face the inner end of the vane. At both ends of the anode cylinder 103, substantially funnel-shaped pole pieces 111 and 112 are sandwiched and fixed between the end face of the anode cylinder and the metal sealing bodies 104 and 105 (see Patent Document 1).

  The arrangement of the joint portion and pole piece between the anode cylinder 103 of the conventional magnetron and the metal sealing body 104 will be described with reference to FIG. The anode cylinder is made of oxygen-free copper, and ring-shaped step portions 113 are formed on both end faces of the cylinder, and the outer peripheral portion 114 is thinned. The thickness of the cylinder 103 is, for example, 2 mm, and the thickness of the outer peripheral portion 114 of the end surface is 1 mm. The pole piece 111 is made of a soft iron magnetic material, and the diameter of the outermost edge 115 of the funnel matches the inner diameter of the outer peripheral wall 114 of the end surface of the anode cylinder. A ring-shaped step 116 is formed on the metal sealing body side of the outermost edge 115, and the outermost peripheral edge 118 of the flange portion 117 of the cylindrical metal sealing body 104 is fitted to the step 116. This structure is similar to the input / output unit.

  The pole pieces 111 and 112 are fitted to the end surfaces of the anode cylinder and positioned with respect to the axial direction and the circumferential direction by the step 113 of the anode cylinder, and the metal sealing bodies 104 and 105 are positioned by the pole pieces. The outer peripheral wall 114 of the end surface of the anode cylinder is melted by arc welding or the like and is placed on the metal sealing bodies 104 and 105 in the direction of the arrow 122 and fixed to each other. In general, in the magnetron having the structure as shown in FIG. 6A, the necessary conditions for the anode part constituted by the anode cylinder, the vane, the strap ring, etc. are non-magnetic, have good electrical conductivity, and have thermal conductivity. For example, copper and copper alloys are often used as materials that satisfy these conditions.

  In particular, when the parts are joined by brazing using a continuous hydrogen furnace, oxygen-free copper having a low oxygen content that does not cause hydrogen embrittlement is selected.

JP 2002-197984 A

  Resource savings and recent material surges are demanding reductions in material usage and costs for magnetrons, but as mentioned above, a considerable amount of copper and copper alloys are used in the anode part. Attempts have been made to change to other materials or downsize.

  However, changing the anode part to other materials has various problems in manufacturing as well as electrical and thermal constraints, and is currently difficult to put into practical use.

  For example, in recent years aluminum used in electric wires, etc. is inexpensive, non-magnetic and has a relatively high conductivity, but it has a low melting point, strength, and problems of bonding with other metals. Application is difficult. In other fields, there are cases where a clad material bonded with dissimilar metals is used for cost reduction, but it is difficult to use as a magnetron anode due to the same problems as described above.

  In addition, material thickness reduction, diameter reduction, axial shortening, and the like have been performed in order to reduce the size of the anode portion, but in any case, the influence on the characteristics and heat dissipation is great. As shown in FIG. 6B, particularly in the case of the anode cylinder 103 having the largest volume, the effect of thinning the material is great, but not only the characteristics and heat dissipation but also the problem due to the strength reduction is caused.

  After being exposed to high temperature by a continuous hydrogen furnace to brane vanes, straps, and antenna rods during the manufacturing process, the entire anode part is very soft and requires careful handling. Thinning is very difficult because it receives a lot of external force in the process.

  For example, when the plate thickness of the anode cylinder 103 is halved from 2 mm in FIG. 6A to 1 mm as shown in FIG. 6B, when the pole piece 111 is fitted to the end face step 113 of the anode cylinder, The end face 120 is deformed to the outside due to the external force and thermal expansion during arc welding, and only the outer diameter around the end face 120 is 0.3 to 0 at the maximum from the center as shown by the broken line 119 in FIG. The problem is that it becomes larger by about 4 mm and becomes a drum shape as a whole.

  In this case, deformation should be prevented by increasing the clearance between the anode cylinder 103 and the pole piece 111. However, if the clearance is too large, alignment with the anode part such as axial alignment cannot be performed, which adversely affects the characteristics. For this reason, it is necessary to make the clearance management width very small, which is not practical.

  In addition, there is a problem that a large external force is applied when the radiator is pressed into the anode cylinder 103. However, in the case of the above drum shape, the radiator is too widened by the end surface portion 120 having a large outer diameter. Further, the contact with the outer wall of the anode cylinder is deteriorated, and there is a problem that the anode cylinder is not cooled.

  Furthermore, since the plate thickness of the welded part 121 is also reduced by the reduction of the plate thickness, the possibility of poor welding is increased. Even if the structure is greatly changed in order to solve the above problems, the degree of freedom of change is low due to the reduced thickness, which not only causes problems in welding with metal seals, but also in equipment and processes. Major changes are also required and are not easy.

  The present invention solves the above-mentioned drawbacks, can reduce the expensive copper by reducing the plate thickness of the anode cylinder without causing major deformation, does not affect the positioning of the pole piece, and has a significant manufacturing process. The present invention provides a magnetron that can also perform hermetic joining of the relevant parts without change.

  The present invention includes an anode portion that oscillates microwaves, an input portion that is disposed on one end surface portion via an input-side pole piece and an input-side metal seal and includes a cathode stem, and an output-side pole piece and an output on the other end surface portion. In the magnetron arranged along the tube axis with the output part including the antenna arranged via the side metal sealing body, the anode part is joined to the anode cylinder and the inner wall of the anode cylinder apart from the end face part, and the tube A plurality of vanes projecting radially in the axial direction are provided, and the pole piece is positioned and supported in the tube axis direction between the end face portions on the input portion side and the output portion side of the inner wall of the anode cylinder and the vanes. A nonmagnetic cylindrical auxiliary anode is disposed, and the metal sealing body on the input portion side and the output portion side sandwiches the pole piece together with the auxiliary anode, and is airtightly bonded to the end face portion of the anode cylinder. In the magnetron, characterized in that they are.

  According to the present invention, an auxiliary anode that is nonmagnetic and relatively strong even at high temperatures is press-fitted inside the anode cylinder, and the auxiliary anode has a positioning function in the axial direction and circumferential direction of the pole piece, Further, since the pole piece is not directly fitted to the anode cylinder and an external force is not applied only to the end portion, the drum-shaped deformation is not caused because it is also used for reinforcing the anode cylinder whose strength is lowered. Further, since the anode cylindrical end portion can be left as it is, it is unlikely to cause a defect as in the conventional case.

The sectional view of the magnetron of one example of the present invention. The cross-sectional schematic which shows the principal part of one Embodiment of this invention. The cross-sectional schematic which shows the principal part of one Embodiment of this invention. (A) is a perspective view which shows the auxiliary anode of one Embodiment of this invention, (b) is a perspective view which shows the modification of an auxiliary anode. The schematic sectional drawing of the magnetron explaining a comparative example. The schematic sectional drawing explaining the anode end surface part of a prior art example (a) and a comparative example (b).

  Next, embodiments of the present invention will be described with reference to the drawings. 1A to 4A show a magnetron 10 for a microwave oven according to an embodiment of the present invention. Centering on the anode section 11 that oscillates the microwave of 2450 MHz band, the input section 12 that feeds power along the tube axis m to one end face thereof, and the microwave oscillated from the anode section along the tube axis to the other end face An output unit 13 is provided to take out the outside of the tube. The input unit 12 and the output unit 13 are joined in a vacuum-tight manner by an anode cylinder 14 of an anode part and cylindrical metal sealing bodies 15 and 16. The input unit 12 includes a ceramic stem 17 and a cathode rod 18 planted on the stem, and holds a spiral cathode 20 at the tip of the rod. The output part draws out the antenna rod 22 coaxially extended on the tube axis from the anode vane 21 through the ceramic insulating cylinder 23.

  The anode cylinder is made of oxygen-free copper, and has a structure that does not support the pole pieces at both end faces as a thin cylindrical body. A plurality of plate-shaped vanes 21 made of the same material and projecting radially from the both ends 24 and 25 of the anode cylinder are radially projected and arranged on the inner wall toward the tube axis m, and upper and lower sides 211 (FIG. 2). Every other piece is connected by a pair of large and small diameter strap rings 26, 27 brazed to (see). In the electron action space surrounded by the inner end faces of the plurality of vanes, the spiral cathode 20 is disposed on the axis of the anode cylinder, that is, the tube axis, and both ends thereof are the input end hat 28 and the output end hat 29, respectively. It is fixed to.

  More specifically, on both end face portions 24 and 25 of the anode cylinder, a substantially funnel-shaped output side pole piece 31 and an input side pole piece 30 for guiding magnetic flux to the electron action space are opposed to each other across the electron action space. The pole pieces 30 and 31 are fixed in contact with the inner walls of the end surface portions 24 and 25 of the anode cylinder 14 through cylindrical metal sealing bodies 15 and 16, respectively.

  An output side ceramic insulating cylinder 23 constituting an output portion is joined to the upper end of the output side metal sealing body, and an exhaust pipe 33 is joined to the upper end thereof.

  Further, the antenna rod 22 derived from one vane extends through the output piece 13 through the pole piece 31, and the tip is clamped and fixed to the exhaust pipe 33. The cap 34 covers the entire exhaust pipe. Yes. A ceramic stem 17 constituting the input portion 12 is joined to the lower end of the other input side metal sealing body 15. A support rod 18 joined to a relay plate (not shown) joined to the ceramic stem 17 is connected to both ends of the spiral cathode 20 via two end hats 28 and 29.

  Further, an input terminal 39 that penetrates the input side ceramic and is led out of the tube is also joined to the relay plate. A plurality of cooling radiators 40 are press-fitted into the outer periphery of the anode cylinder 14.

  Annular permanent magnets 41 and 42 are fitted on the metal sealing bodies 15 and 16 above the output side pole piece 31 and below the input side pole piece 30. Further, a magnetic yoke 43 for forming a magnetic path is disposed so as to surround the anode cylinder, the cooling radiator, and the permanent magnet.

  A filter box 44 is disposed outside the stem 17 on the input side, and a coil 45 and a feedthrough capacitor 46 forming a filter circuit are connected to an input terminal 39 led out from the stem.

  Next, the anode part will be described in detail. A plurality of vanes 21 of the same oxygen-free copper are radially arranged inside the anode cylinder 14 made of oxygen-free copper having a thickness of 1 mm, and a pair of large and small strap rings brazed to the upper and lower ends 211 of the vanes. 26 and 27 are connected every other sheet.

An austenitic stainless steel with a thickness of 1.0 mm having the same outer diameter as that of the anode cylinder 14 as shown in FIG. A cylindrical auxiliary anode 50 made of steel (Fe74-Cr18-Ni8, SUS304) is press-fitted. One end surface 51 of the auxiliary anode receives the pole piece, and the other end surface 52 contacts the vane side 211. The material is more rigid than the copper anode cylinder, and the difference in expansion coefficient from the anode cylinder is preferably within a range of ± 50% relative to the anode cylinder. In the present embodiment, the thermal expansion coefficients are equivalent to 16.8 × 10 ^{6 for} oxygen-free copper and 16.7 × 10 ⁶ for SUS304.

  In the magnetron for a microwave oven, when the anode cylinder is formed of only oxygen-free copper, the thickness is limited to 2 mm. However, in this embodiment, the anode cylinder has a thickness of 1 mm and the holding anode has a thickness of 1 mm. The thickness of can be halved. The plate thickness of the anode cylinder can be set to about 0.5 mm when the outer diameter of the cylinder is about 40 mmφ.

  The axial length L of the auxiliary anode accurately regulates the distance between the vane side 211 and the vane side surfaces 301 and 311 of the pole piece, and the auxiliary anode is disposed between them, so that the input / output side pole piece 30, 31 is fitted with the auxiliary anode 50 and positioned with respect to the axial direction and the circumferential direction. On the opposite side of the pole pieces 30 and 31, cylindrical sealing metal bodies 15 and 16 on the input and output sides are installed. Ribs 151 and 161 are formed on the outermost edge of the non-land portion of the metal sealing body so as to be fitted around the outer edge of the pole piece. In this state, the anode cylindrical end face part 25 is melted in the direction of the arrow in FIG.

  As a result, the anode cylinder 14 and the pole pieces 30 and 31 are not directly fitted to each other and are positioned by the auxiliary anode, so that the anode cylinder end portion 25 is not significantly deformed. Therefore, defects due to deformation of the anode cylinder do not occur.

  Non-magnetic chrome nickel steel, such as SUS304, is not inexpensive as a material, but uses less and does not require treatment such as plating, leading to a reduction in total cost.

  In this embodiment, the annular step 53 is provided on the inner wall side of the end face 51 that receives the pole piece of the auxiliary anode and the pole pieces 30 and 31 are positioned. However, the step may be provided by providing a step on the pole piece side.

  FIG. 4B shows a modification of the auxiliary anode. The auxiliary anode 50 may be a simple cylindrical shape as shown in FIG. 4A. However, the other end surface 52 in contact with the vane side 211 is provided with a slit 54 corresponding to the vane as shown in FIG. When extending to the center of the cylinder, the auxiliary anodes on both sides of the input / output unit are brought into contact with each other, so that the reinforcing effect is further improved. Even if the slit 54 is deep enough to be engaged with the vane, rotation in the circumferential direction can be restricted, so that stronger support is realized. In this modification, a step is not formed on the end face that receives the pole piece, but a step is formed on the pole piece side.

  In this embodiment, the auxiliary anode is press-fitted after brazing the vane or strap. This is because in normal brazing, each part is brazed by being put into a hydrogen atmosphere furnace, and therefore, when an auxiliary anode made of a different material such as SUS304 is pressed before brazing, hydrogen embrittlement occurs. As long as the auxiliary anode is made of a material that does not cause hydrogen embrittlement and satisfies other conditions, it may be press-fitted before brazing or, in some cases, brazed. Further, since the auxiliary anode is disposed in the vacuum envelope, it is not limited by the envelope conditions.

10: Magnetron, 11: Anode section, 12: Input section, 13: Output section, 14: Anode cylinder, 15, 16: Metal seal, 17: Ceramic stem, 18: Cathode rod, 20: Cathode, 21: Bain 211: Bain side, 22: Antenna rod, 24, 25: End face part, 26, 27: Strap ring, 30: Input side pole piece, 31: Output side pole piece, 39: Input terminal, 40: Radiator, 41, 42: permanent magnet, 50: auxiliary anode, 51, 52: (auxiliary anode) end face

Claims (5)

An anode section that oscillates microwaves, an input section that includes a cathode stem disposed on one end face through an input pole piece and an input metal seal, and an output pole piece and output metal seal on the other end. In the magnetron arranged along the tube axis, the output part including the antenna arranged through the body,
The anode part has a plurality of vanes that are joined to the anode cylinder and the inner wall of the anode cylinder at a distance from the end face part and project radially from the tube axis direction,
A non-magnetic cylindrical auxiliary anode for positioning and supporting the pole piece in the tube axis direction is disposed between the end surface portion on the input portion side and the output portion side of the inner wall of the anode cylinder and the vane, and the input portion side The magnetron is characterized in that the metal sealing body on the output portion side is airtightly joined to the end face portion of the anode cylinder with the pole piece sandwiched with the auxiliary anode.   The magnetron according to claim 1, wherein inner walls of the anode cylinder have the same diameter, and the input side and the output side pole pieces are not supported in the tube axis direction.   The magnetron according to claim 1, wherein the auxiliary anode is a metal having a thermal expansion coefficient equivalent to that of the anode cylinder and high rigidity at high temperature.   The magnetron according to any one of claims 1 to 3, wherein the anode cylinder is copper and the auxiliary anode is chromium nickel steel.   The magnetron according to claim 1, wherein the auxiliary anode has a slit that engages with the vane on an end surface that abuts the vane.

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