Abstract:
A magnetron includes an anode cylinder which has a cylindrical shape with both ends opened and which includes a plurality of vanes radially provided on an inner wall surface thereof, a pair of pole pieces positioned in openings of the both ends of the anode cylinder, and metal sleeves. The metal sleeves are positioned outside the pair of pole pieces and configured to air-tightly seal the anode cylinder. Each of the metal sleeves includes a cylinder part, a flange part continuous with the cylinder part, and a plurality of protrusions provided on a portion in which the cylinder part continues with the flange part.

Description:
This application is a 371 application of PCT/JP2009/007217 having an international filing date of Dec. 24, 2009, which claims priority to JP2009-046643 filed on Feb. 27, 2009, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a magnetron and a microwave utilization device, and particularly to the magnetron used in the microwave utilization device such as a microwave oven. 
     BACKGROUND ART 
     In a magnetron  90  disclosed in Patent Document 1, a metal sealing body  80  (hereinafter called a metal sleeve  80 ) is joined to an anode cylinder.  FIG. 5  is a diagram showing the metal sleeve  80  of the magnetron  90  in related art. As shown in  FIG. 5 , the metal sleeve  80  includes a flange part  81  contacting a pole piece  84  (hereinafter called a pole piece  84 ), a cylinder part  82  continuous with the flange part  81 , and a folded-back part  83  which continues from the cylinder part  82  and which is folded back inside the tube. 
     The cylinder part  82  includes a concentric first cylinder part  82   a , a second cylinder part  82   b  having the same central axis as the central axis of the metal sleeve  80 , and a taper part  82   c  continuous with the first cylinder part  82   a  and the second cylinder part  82   b.    
     The first cylinder part  82   a  continues with the second cylinder part  82   b  through the taper part  82   c  in which an inside diameter changes gradually. An inside diameter φ1 of the first cylinder part  82   a  is smaller than an inside diameter φ2 of the second cylinder part  82   b . Also, the inside diameter φ2 of the second cylinder part  82   b  of the metal sleeve  80  is formed in about the same dimension as an inside diameter D of a falling part of the pole piece  84 . 
     Patent Document 1: JP-A-2005-050572 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, in the metal sleeve  80  of the magnetron  90  shown in  FIG. 5 , when the inside diameter of the cylinder part  82  is smaller than the inside diameter D of the falling part  84   a  of the pole piece  84  because of variations in manufacture, application of a high pressure in the case of handling or assembly of a microwave output part concentrates on the metal sleeve  80  and the cylinder part  82  of the metal sleeve  80  tends to sink in a recess of the pole piece  84 . Then, there was a problem of degrading basic characteristics of the magnetron  90  when the cylinder part  82  of the metal sleeve  80  sinks toward the falling part  84   a  of the pole piece  84 . Also, in the metal sleeve  80 , the inside diameter of the cylinder part  82  is gradually changed by providing the cylinder part  82  with the taper part  82   c . As a result, there was also a problem of increasing a manufacturing cost. 
     An object of the invention is to provide a magnetron and a microwave utilization device capable of preventing performance degradation of the magnetron itself by preventing a cylinder part of a metal sleeve from sinking toward a falling part of a pole piece even when subjected to a high pressure in the case of handling or assembly. 
     Means for Solving the Problem 
     The invention provides a magnetron including: an anode cylinder which has a cylindrical shape with both ends opened and which includes a plurality of vanes radially provided on an inner wall surface thereof; a pair of pole pieces positioned in openings of the both ends of the anode cylinder; and metal sleeves which are positioned outside the pair of pole pieces and configured to air-tightly seal the anode cylinder and each of which includes a cylinder part, a flange part continuous with the cylinder part, and a plurality of protrusions provided on a portion in which the cylinder part continues with the flange part. 
     By the configuration described above, sinking of the cylinder part of the metal sleeve in a recess of the pole piece can be decreased since deformation of the portion in which the cylinder part of the metal sleeve continues with the flange part becomes small even when subjected to an external force in the case of handling or assembly of the magnetron. 
     In the magnetron, an inside diameter D 1  of the cylinder part of the metal sleeve is constant over an entire length of the cylinder part of the metal sleeve. 
     According to the configuration described above, the inside diameter D 1  of the cylinder part of the metal sleeve can be made smaller than an inside diameter of a cylinder part of a metal sleeve of a related-art magnetron. As a result, an annular magnet can be decreased and the lower-cost annular magnet can be used. 
     In the magnetron, the inside diameter D 1  of the cylinder part of the metal sleeve is smaller than an inside diameter D 2  of a falling part of the pole piece. 
     In the magnetron, the pole piece includes a flat surface part contacting a lower surface of the metal sleeve, a funnel-shaped part continuous with the flat surface part, and a plurality of projections which define a same flat surface together with the flat surface part and which are formed by cutting and raising the funnel-shaped part, and the plurality of projections and the flat surface part contact the lower surface of the metal sleeve. 
     By the configuration described above, the projections of the pole piece can support the flange part of the metal sleeve even when the inside diameter D 1  of the cylinder part of the metal sleeve is smaller than the inside diameter D 2  of the falling part of the pole piece. 
     In the magnetron, the pole piece includes a flat surface part contacting a lower surface of the metal sleeve, a funnel-shaped part continuous with the flat surface part, and a nonmagnetic structure which defines a same flat surface together with the flat surface part and which are joined to the funnel-shaped part, and the same flat surface defined by the flat surface part and the nonmagnetic structure contacts the lower surface of the metal sleeve. 
     By the configuration described above, the nonmagnetic structure can support the flange part of the metal sleeve even when the inside diameter D 1  of the cylinder part of the metal sleeve is smaller than the inside diameter D 2  of the falling part of the pole piece. 
     Also, the invention provides a microwave utilization device including the magnetron. 
     Advantages of the Invention 
     According to the magnetron and the microwave utilization device according to the invention, performance degradation of the magnetron can be prevented by preventing the cylinder part of the metal sleeve from sinking in the falling part of the pole piece even when subjected to a high pressure in the case of handling or assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a magnetron  1  of an embodiment of the invention. 
         FIG. 2  is a perspective view of a cylinder part and a flange part of a metal sleeve  14 A of the output side in the embodiment of the invention. 
         FIG. 3  is a partially sectional view of a modified example of the magnetron  1 . 
         FIG. 4  is a perspective view of a pole piece  12 A of the modified example of the magnetron  1 . 
         FIG. 5  is a diagram showing a metal sleeve  80  of a magnetron  90  in related art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the invention will hereinafter be described with reference to the drawings. 
     (First Embodiment) 
       FIG. 1  is a sectional view of a magnetron  1  of an embodiment of the invention. As shown in  FIG. 1 , the magnetron  1  according to the present embodiment includes a magnetic yoke  10 , an anode cylinder  11 , a pole piece  12 A inserted into an upper end opening of the anode cylinder  11 , a pole piece  12 B inserted into a lower end opening of the anode cylinder  11 , a metal sleeve  14 A of the output side air-tightly coupled to the upper end opening of the anode cylinder  11 , the metal sleeve  14 A with which the pole piece  12 A is covered, a metal sleeve  14 B of the input side air-tightly coupled to the lower end opening of the anode cylinder  11 , the metal sleeve  14 B with which the pole piece  12 B is covered, a doughnut-shaped annular magnet  13 A placed on an upper surface of the inside of the magnetic yoke  10  so as to be inserted into the metal sleeve  14 A of the output side just over the anode cylinder  11 , and a doughnut-shaped annular magnet  13 B placed on a lower surface of the inside of the magnetic yoke  10  so as to be inserted into the metal sleeve  14 B of the input side just under the anode cylinder  11 . 
     As shown in  FIG. 1 , a plurality of cooling fins  16  are fitted into an outer peripheral surface of the anode cylinder  11 . A plurality of vanes  17  are radially arranged on an inner peripheral surface of the anode cylinder  11 . In addition, only one vane  17  is shown in  FIG. 1 . 
     A cathode structural body  18  is arranged in the center of the anode cylinder  11 . Space surrounded by the cathode structural body  18  and the vanes  17  forms an active space inside the anode cylinder  11 . 
     The pole piece  12 A and the pole piece  12 B are formed in a funnel shape by squeezing processing etc. of a plate material of a magnetic body with low magnetic resistance such as iron. Referring to  FIG. 1 , the pole piece  12 A formed in the funnel shape includes a first flat surface part  32  contacting a lower surface of a flange part of the metal sleeve  14 A of the output side described below, and a funnel-shaped part  33  continuous with the first flat surface part  32 . 
     Also, a falling part (the portion in which the first flat surface part  32  continues with the funnel-shaped part  33 ) formed in the funnel shape of the pole piece  12 A has an inside diameter D 2  from the central axis as shown in  FIG. 1 . The inside diameter D 2  of the falling part of the pole piece  12 A is set larger than an inside diameter D 1  of a cylinder part  21  of the metal sleeve  14 A of the output side described below. 
     The metal sleeve  14 A of the output side includes the cylinder part  21 , a flange part  22  and a plurality of protrusions (ribs)  23 . As compared with a configuration of the metal sleeve  80  of the magnetron  90  of the related art, the cylinder part  21  of the metal sleeve  14 A of the output side in the embodiment corresponds to the cylinder part  82  of the metal sleeve  80  of the magnetron  90  of the related art. 
     In addition, the metal sleeve  14 A of the output side has a folded-back part (not shown) which continues with the cylinder part  21  and is folded back toward the inside of the metal sleeve  14 A itself of the output side like the related art. 
     Next, a configuration of the metal sleeve  14 A of the output side of the magnetron  1  will be described with reference to  FIG. 2 .  FIG. 2  is a perspective view of the cylinder part and the flange part of the metal sleeve  14 A of the output side in the first embodiment. In addition, the metal sleeve  14 B of the input side has the same configuration as the metal sleeve  14 A of the output side of the magnetron  1 , so that the explanation is omitted. 
     As shown in  FIG. 2 , the metal sleeve  14 A of the output side includes the cylinder part  21  having the same central axis as the central axis of the anode cylinder  11 , the flange part  22  and the plurality of protrusions (ribs)  23 . 
     The cylinder part  21  of the metal sleeve  14 A of the output side has the same central axis as the central axis of the anode cylinder  11 , and the inside diameter of the cylinder part  21  is D 1 . Also, the cylinder part  21  has the constant inside diameter D 1  over the entire length of the cylinder part  21 . Also, the inside diameter D 1  of the cylinder part  21  of the metal sleeve  14 A of the output side is set smaller than the dimension D 2  of the falling part of the pole piece  12 A. 
     The flange part  22  of the metal sleeve  14 A of the output side is air-tightly coupled to the anode cylinder  11  at the outer peripheral end of the flange part  22 . 
     The protrusions (ribs)  23  of the metal sleeve  14 A of the output side are formed on an outer peripheral surface (side of the annular magnet  13 A) of the portion in which the cylinder part  21  of the metal sleeve  14 A of the output side continues with the flange part  22  of the metal sleeve  14 A of the output side. The portion in which the cylinder part  21  of the metal sleeve  14 A of the output side continues with the flange part  22  of the metal sleeve  14 A of the output side is, in other words, the portion in which the cylinder part  21  rises from the flange part  22  of the metal sleeve  14 A of the output side. 
     By providing the protrusions (ribs)  23  on the outer peripheral surface of the portion in which the cylinder part  21  continues with the flange part  22  in the metal sleeve  14 A of the output side as described above, strength of the cylinder part  21  of the metal sleeve  14 A of the output side increases. As a result, the magnetron  1  according to the embodiment can prevent the cylinder part  21  from sinking in the falling part of the pole piece  12 A even when subjected to an external force in the case of handling or assembly of the magnetron  1  and an external force after the assembly. Therefore, basic characteristics of the magnetron  1  according to the embodiment can be prevented from degrading. 
     According to the magnetron  1  according to the embodiment, the cylinder part  21  of the metal sleeve  14 A of the output side is not pushed into the side formed in the funnel shape of the pole piece  12 A even when subjected to the external force in the case of handling or assembly of the magnetron  1  and the external force after the assembly. Further, deformation of the flange part  22  of the metal sleeve  14 A of the output side becomes small, so that basic performance of the magnetron  1  becomes resistant to degradation. Also, the cylinder part  21  of the metal sleeve  14 A of the output side has the same inside diameter with respect to the central axis of the anode cylinder  11 , so that cost can be reduced. 
     Also, according to the magnetron  1  according to the embodiment, the magnetron in which variations in basic characteristics of the magnetron  1  are reduced can be provided at low cost. Further, a low-cost microwave utilization device with high reliability can be obtained by using the magnetron  1  according to the embodiment. 
     In addition, instead of the protrusions (ribs)  23  provided on the flange part  22  of the metal sleeve  14 A of the output side, the protrusions (ribs) may be formed on an inner peripheral surface (side of the pole piece  12 A) of the portion in which the cylinder part  21  of the metal sleeve  14 A of the output side continues with the flange part  22 . The inner peripheral surface (side of the pole piece  12 A) of the portion in which the cylinder part  21  of the metal sleeve  14 A of the output side continues with the flange part  22  does not include a surface of contact between the flange part  22  and the pole piece  12 A. The protrusions (ribs)  23  are not provided on the surface of contact between the flange part  22  and the pole piece  12 A. 
     In addition, a position of the protrusion (rib)  23  of the metal sleeve  14 A of the output side is not particularly limited as long as the position is in the outer peripheral surface of the portion in which the cylinder part  21  of the metal sleeve  14 A of the output side continues with the flange part  22  of the metal sleeve  14 A of the output side. 
     In addition, the protrusions (ribs)  23  provided on the side of the annular magnet  13 A in the portion in which the cylinder part  21  of the metal sleeve  14 A of the output side continues with the flange part  22  may be extended to the vicinity of an outer peripheral part of the flange part  22  of the metal sleeve  14 A of the output side. 
     (Modified Example) 
     Next, a modified example of the magnetron  1  according to the embodiment will be described. The modified example of the magnetron  1  differs from the magnetron  1  according to the first embodiment in a configuration of a pole piece. A configuration of a pole piece  12 A in the modified example of the magnetron  1  will be described with reference to  FIGS. 3 and 4 .  FIG. 3  is a partially sectional view of the modified example of the magnetron  1 .  FIG. 4  is a perspective view of the pole piece  12 A of the modified example of the magnetron  1 . In addition, a pole piece  12 B has the same configuration as the pole piece  12 A, so that the explanation is omitted. 
     Referring to  FIGS. 3 and 4 , the pole piece  12 A formed in a funnel shape includes a plurality of projections  31 , a flat surface part  32 , and a funnel-shaped part  33  continuous with the flat surface part  32 . Referring to  FIG. 3 , an upper surface of the flat surface part  32  contacts a lower surface of a flange part  22  of a metal sleeve  14 A of the output side. Also, referring to  FIG. 4 , the plurality of projections  31  formed by cutting and raising the funnel-shaped part  33  of the pole piece  12 A define a same flat surface together with the flat surface part  32 , and upper surfaces of the projections  31  contacts the lower surface of the flange part  22  of the metal sleeve  14 A of the output side. At least a cylinder part  21  of the metal sleeve  14 A of the output side is positioned over the plurality of projections  31 . As a result, the plurality of projections  31  can prevent the cylinder part  21  of the metal sleeve  14 A of the output side from sinking toward a falling part of the pole piece  12 A. 
     According to the modified example of the magnetron  1  according to the embodiment, the cylinder part  21  of the metal sleeve  14 A of the output side is reinforced with the plurality of projections  31  contact the lower surface of the flange part  22  of the metal sleeve  14 A of the output side. As a result, the cylinder part  21  of the metal sleeve  14 A of the output side is not pushed into the side formed in the funnel shape of the pole piece  12 A even when subjected to an external force in the case of handling or assembly of the magnetron and an external force after the assembly. Further, deformation of the flange part  22  becomes small, so that basic performance of the magnetron becomes resistant to degradation. Also, the cylinder part  21  of the metal sleeve  14 A of the output side has the same inside diameter with respect to the central axis of an anode cylinder  11 , so that cost can be reduced. 
     In addition, in the modified example of the magnetron  1  according to the embodiment, the projections  31  are formed by cutting and raising the funnel-shaped part  33  of the pole piece  12 A, but are not limited to this. For example, the same flat surface with the flat surface part  32  may be defined by joining a nonmagnetic structure different from the pole piece  12 A to the funnel-shaped part  33  without cutting and raising the funnel-shaped part  33  of the pole piece  12 A and may contact a lower surface of the metal sleeve  14 A of the output side. 
     By the configuration described above, the nonmagnetic structure can support the flange part of the metal sleeve even when an inside diameter D 1  of the cylinder part of the metal sleeve is smaller than an inside diameter D 2  of the falling part of the pole piece. Also, by the configuration described above, an influence on a magnetic circuit constructed of the pole piece  12 A, an annular magnet  13 A and a magnetic yoke  10  can be minimized. 
     The invention has been described in detail with reference to the specific embodiment, but it is apparent to those skilled in the art that various changes or modifications can be made without departing from the spirit and scope of the invention. 
     The present application is based on Japanese patent application (Patent Application No. 2009-046643) filed on Feb. 27, 2009, and the contents of the patent application are hereby incorporated by reference. 
     Industrial Applicability 
     A magnetron and a microwave utilization device according to the invention have an effect of providing the low-cost magnetron for preventing deformation of a metal sleeve of the magnetron and preventing degradation of basic characteristics, and are useful as the microwave utilization device such as a microwave oven.