Magnetron and apparatus that uses microwaves

A magnetron includes: an anode tube; and cooling fins placed on a periphery of the anode tube and arranged along a central axis of the anode tube. Each of the cooling fins includes at least two sets of fins formed by cutting a part of the cooling fin, and performing different bending works on the cut portions, respectively, so as to form a region where the cooling fins are dense and a region where the cooling fins are sparse, when viewed in a flowing direction of a cooling medium which cools the anode tube through the cooling fins. The at least two sets of fins are bent at bending angles such that intervals of the cooling fins in the region where the cooling fins are dense are ½ or less of placement intervals of the cooling fins.

This application is a 371 application of PCT/JP2010/006989 having an international filing date of Nov. 30, 2010, which claims priority to JP2009-272337 filed Nov. 30, 2009, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a magnetron and an apparatus that uses microwaves, and more particularly to a magnetron which is to be used in an apparatus that uses microwaves, such as a microwave oven.

BACKGROUND ART

In a conventional magnetron 100 disclosed in Patent Document 1, as shown in FIG. 6, cooling fins 105 extending from fin plates 104 that are attached at predetermined intervals to an anode tube 102 in which permanent magnets 101 are disposed at the ends thereof are evenly placed over the whole region R (in FIG. 6, the broken-line frame), thereby improving the heat dissipation efficiency of the cooling fins 105.

RELATED ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

In the case where cooling fins are configured by a plurality of fins having the same shape, when the number of fins constituting the cooling fins is simply increased in order to reduce the temperature of a magnetron, however, the gaps between the plurality of fins constituting the cooling fins are narrowed. In the magnetron 100 of Patent Document 1, when the cooling fins 105 are evenly placed in the region R through which the cooling air passes, particularly, gaps S in a yoke 103 are reduced, and the air resistance is increased. Therefore, the amount of cooling air which passes between the fins 105 is reduced, and the heat dissipation efficiency of the cooling fins 105 is lowered (see FIG. 1 of Patent Document 1).

An object of the invention is to provide a magnetron and apparatus that uses microwaves which can improve cooling efficiency by forming a region where cooling fins are sparse and a region where cooling fins are dense when the cooling fins are viewed in a flowing direction of a cooling medium of the magnetron.

Means for Solving the Problem

The present invention provides a magnetron including: an anode tube in which permanent magnets are disposed at both ends thereof; and a plurality of cooling fins which are placed on a periphery of the anode tube, and which are arranged along a central axis of the anode tube, wherein each of the plurality of cooling fins includes at least two sets of fins which are formed by cutting a part of the cooling fin, and performing different bending works on the cut portions, respectively, so as to form a region where the cooling fins are dense and a region where the cooling fins are sparse, when viewed in a flowing direction of a cooling medium which cools the anode tube through the plurality of cooling fins, and wherein the at least two sets of fins are bent at bending angles such that intervals of the cooling fins in the region where the cooling fins are dense are ½ or less of placement intervals of the cooling fins.

In the magnetron described above, when viewed in the flowing direction of the cooling medium which cools the anode tube through the plurality of cooling fins, in the region where the cooling fins are sparse, the fin of one of the at least two sets of fins and a part of the fin of another set are placed on a same plane.

In the magnetron described above, when viewed in the flowing direction of the cooling medium which cools the anode tube through the plurality of cooling fins, in the region where the cooling fins are dense, a direction of the bending work on the fin of the one of the at least two sets of fins is different from a direction of the bending work on the fins of another set.

Further, the present invention provides an apparatus that uses microwaves including the magnetron described above.

Advantages of the Invention

The magnetron and the apparatus that uses microwaves of the invention can improve cooling efficiency of a magnetron by forming a region where cooling fins are sparse and a region where cooling fins are dense when the cooling fins are viewed in a flowing direction of a cooling medium of the magnetron.

MODE FOR CARRYING OUT THE INVENTION

Referring toFIG. 1, the configuration of a magnetron1of the embodiment of the invention will be described.FIG. 1is a view of the whole configuration of the magnetron1of the embodiment of the invention. The magnetron1of the embodiment has: an anode tube2which has permanent magnets4at the ends in the longitudinal axis direction; a plurality of cooling fins10which are placed on the periphery of the anode tube2at substantially regular intervals along the longitudinal direction of the anode tube2; and a magnetic yoke3in which the plurality of permanent magnets4, the anode tube2, and the plurality of cooling fins10are disposed. The cooling fins10have a function of cooling the magnetron1which is heated to a high temperature during operation. The magnetron1of the embodiment of the invention can be used in an apparatus that uses microwaves, such as a microwave oven.

Next, the configuration of the cooling fins10will be described with reference toFIG. 2(a) andFIG. 2(b).FIG. 2(a) is a perspective view of one cooling fin10(after a bending work).FIG. 2(b) is a plan view of one cooling fin10(before the bending work). In the magnetron1of the embodiment, six cooling fins10are placed at regular intervals along the longitudinal direction of the anode tube2.

The cooling fin10shown inFIG. 2(a) is a thin aluminum plate, and configured by: a body portion10cin which the anode tube2is inserted through a hole10ddisposed inside of it; a cylindrical portion10ewhich is disposed along the hole10dof the body portion10c; and a plurality of fins10a,10bwhich are formed by forming cuts in a part of the body portion10c. The plurality of fins10a,10bconstitute a part of the body portion10c, and, as shown inFIG. 2(a), one cooling fin10is formed by forming parallel cuts extending a predetermined distance from a pair of sides of the cooling fin10, and applying a bending work to a plurality of places in portions where the cuts are formed. In the magnetron1of the embodiment, the plurality of fins10a,10bwhich are formed in one cooling fin10are bent by different bending works. In the whole magnetron1of the embodiment, therefore, each of the six cooling fins10is configured by two sets of fins which are bent by different bending works.

The bending works which are applied respectively to the plurality of fins10a,10bwill be described with reference toFIGS. 2(a) and2(b).FIG. 2(b) is a plan view of one cooling fin10before the bending work. An cutting work is performed on one side of the cooling fin10along cut lines C1ofFIG. 2(b), and division into four fins10ahaving a width Wa, and two fins10bhaving a width Wb is performed. The widths Wa, Wb of the plurality of fins10a,10bare arbitrary. Different bending works are performed on the four fins10abelonging to one set, and the two fins10bbelonging to the other set along bending lines L1, L2, L3, respectively.

Here, the magnetron1of the embodiment has one feature that, in the case where the bending directions (obliquely upward or obliquely downward) and angles (αa1, αb1) of the bendings of the plurality of fins10a,10balong the bending lines L1are adequately set, when the cooling fins10are attached to the anode tube2and the cooling fins10are viewed in the flowing direction of a cooling medium (in the embodiment, air) of the magnetron1, division into a region where the plurality of fins10a,10bare dense, and that where the plurality of fins10a,10bare sparse is performed (seeFIG. 3).

In the bending lines L1, the four fins10abelonging to the one set are bent at the predetermined angle αa1, toward an obliquely upward direction (inFIG. 2(b), the direction from the depth side of the sheet to the front side). In the bending lines L2, then, parts of the fins10ain the ranges from the bending line L2to the bending line L3are bent at a predetermined angle αa2, toward an obliquely downward direction (inFIG. 2(b), the direction from the front side of the sheet to the depth side). The predetermined angle αa2is set so that, when the cooling fin10is viewed in the flowing direction of the cooling medium (in the embodiment, air) of the magnetron1, parts of the fins10ain the ranges from the bending lines L2to the bending lines L3, and those of the fins10bin the ranges from the bending lines L2to the bending lines L3are overlap with one another (inFIG. 3, see a region R1). In the bending lines L3, then, the fins are bent at a predetermined angle αa3, toward an obliquely downward direction (inFIG. 2(b), the direction from the front side of the sheet to the depth side).

In the bending lines L1, the two fins10bbelonging to the other set are bent at the predetermined angle αb1, toward an obliquely downward direction (inFIG. 2(b), the direction from the front side of the sheet to the depth side). In the bending lines L2, then, parts of the fins10bin the ranges from the bending line L2to the bending line L3are bent at a predetermined angle αb2, toward an obliquely upward direction (inFIG. 2(b), the direction from the depth side of the sheet to the front side). The predetermined angle αb2is set so that parts of the fins10ain the ranges from the bending lines L2to the bending lines L3, and those of the fins10bin the ranges from the bending lines L2to the bending lines L3are overlap with one another (inFIG. 3, see the region R1). In the bending lines L3, then, the fins are bent at a predetermined angle αb3, toward an obliquely upward direction (inFIG. 2(b), the direction from the depth side of the sheet to the front side) so as to extend along the magnetic yoke3.

Then, six cooling fins10which are bent in the above-described method are prepared, and the cooling fins10are attached to the anode tube2so that the anode tube2is inserted into the holes10d. As shown inFIG. 1, at this time, end portions of the six cooling fins10which are bent in the bending lines L3at the predetermined angle are fixed in a state where the end portions are pressed against the inside of the magnetic yoke3.

Next, the conditions of the plurality of fins10a,10bwhen the cooling fins10are attached to the anode tube2and the cooling fins10are viewed in the flowing direction of the cooling medium (in the embodiment, air) of the magnetron1will be described with reference toFIG. 3.FIG. 3is an enlarged view of main portions of the magnetron1. InFIG. 3, for the sake of description, the cooling fins10in the left half ofFIG. 1will be described. InFIG. 3, the fins10aoverlap with one another in the depth direction, and fins10awhich cannot be seen due to overlapping are not illustrated. In the figure, it is assumed that the cooling medium flows in the direction from the front side of the sheet to the depth side. For the sake of description, in order to distinguish each of the fins10a,10bof the six cooling fins10, the fins10aare denoted inFIG. 3as the fins10a-1, . . . ,10a-6starting from the top. Similarly, the fins10bare denoted inFIG. 3as the fins10b-1, . . . ,10b-6starting from the top.

As shown inFIG. 3, when the cooling fins10attached to the anode tube2are viewed in the flowing direction of the cooling medium of the magnetron1, portions in which the fins10a-1, . . . ,10a-6constituting a group Ga are bent toward an obliquely upward direction at the predetermined angle αa1, and the fins10b-1, . . . ,10b-6constituting a group Gb are bent toward an obliquely downward direction at the predetermined angle αb1are dense in a region R2shown inFIG. 3.

The angles of the bendings of the cooling fins10shown inFIG. 3will be described with reference toFIG. 4.FIG. 4is a view illustrating placement intervals of the cooling fins10. InFIG. 4, for the sake of description, only the fins10a-1,10a-2,10b-1,10b-2which are shown inFIG. 3are shown.

In the magnetron1of the embodiment, as shown inFIG. 4, the bending angles αa1, αb1at which the plurality of fins10a,10bare bent in the bending lines L1are set to, for example, 114°. In the magnetron1of the embodiment, the interval P1between cooling fins10which are placed along the longitudinal direction of the anode tube2, and which are adjacent to each other is set to 3 mm, and, in cooling fins10which are adjacent to each other along the longitudinal direction of the anode tube2, the interval Pa2between the fin10a-1of one cooling fin and the fin10a-2of the other cooling fin is set to one half of the interval P1or 1.5 mm. Similarly, the interval Pb2between the fin10b-1and the fin10b-2is set to a half of the interval P1or 1.5 mm. As shown inFIG. 3, therefore, it is possible to form a region where the plurality of fins10a,10bare dense.

In the magnetron1of the embodiment, here, the bending angles αa1, αb1are set to 114°. However, the angles are not limited to this value. When the bending angles αa1, αb1are set in the range from 101° to 127°, a region where the plurality of fins10a,10bare dense can be formed in the region R2as shown inFIG. 3. In the magnetron1of the embodiment, moreover, the intervals Pa2, Pb2(seeFIG. 4) of the fins which are adjacent to each other along the longitudinal direction of the anode tube2are set to 1.5 mm. However, the intervals are not limited to this value. When the intervals Pa2, Pb2are set to one half or less of the interval P1, a region where the plurality of fins10a,10bare dense can be formed in the region R2as shown inFIG. 3.

When the cooling fins10attached to the anode tube2are viewed in the flowing direction of the cooling medium of the magnetron1, the portions in which the fins10a-1, . . . ,10a-6constituting the group Ga are bent toward an obliquely upward direction at the predetermined angle αa2, and the fins10b-1, . . . ,10b-6constituting the group Gb are bent toward an obliquely downward direction at the predetermined angle αb2are uncrowded or sparse in the region R1shown inFIG. 3. In the region R1shown inFIG. 3, the intervals of the plurality of fins10a,10bconstituting the cooling fins10are wide, and, when the cooling fins10attached to the anode tube2are viewed in the flowing direction of the cooling medium of the magnetron1,10a-4,10a-5, and10a-6in the fins constituting the group Ga, and10b-1,10b-2, and10b-3in the fins constituting the group Gb are placed on a substantially same plane. In the region R1shown inFIG. 3, therefore, the effective area of the portion where the gaps of the plurality of fins10a,10bconstituting the cooling fins10are wide is increased, and the airflow resistance difference with respect to a space portion surrounding the permanent magnets4can be reduced. Therefore, the amount of the cooling medium (in the embodiment, air) which passes between the cooling fins10is increased, and the cooling efficiency of the magnetron1is improved.

Similarly with the region R1shown inFIG. 3, in a region R3in which a bending work is not performed, and which is a region in the vicinity of the anode tube2, the fins10a-1, . . . ,10a-6constituting the group Ga, and the fins10b-1, . . . ,10b-6constituting the group Gb are uncrowded or sparse.

In the magnetron1of the embodiment, therefore, regions where the plurality of fins10a,10bare sparse and dense when the cooling fins10attached to the anode tube2are viewed in the flowing direction of the cooling medium of the magnetron1can be formed economically and easily simply by using the plurality of cooling fins10having the same shape, and performing the cutting and bending works on each cooling fin10.

Next, the flow of the cooling medium (air) which passes through gaps between the cooling fins10in the magnetron1of the embodiment will be described with reference toFIG. 5.FIG. 5is a view schematically showing the flow (in the figure, the arrows) of the cooling medium (air) which passes through gaps between the cooling fins10. As shown inFIG. 5, for the cooling medium (air), the region R2(inFIG. 5, the hatched portions) where the fins10a-1, . . . ,10a-6constituting the group Ga and the fins10b-1, . . . ,10b-6constituting the group Gb are crowded can be deemed as a barrier which impedes the flow of the cooling medium (air). Therefore, the cooling medium (air) which passes through the region R3impinges on the region R2which can be deemed as a barrier, and then flows to the rear side of the anode tube2.

In the magnetron1of the embodiment, therefore, the regions where the plurality of fins10a,10bare sparse and dense when the cooling fins10attached to the anode tube2are viewed in the flowing direction of the cooling medium of the magnetron1are formed, whereby the reduction of the amount of the cooling medium which passes between the plurality of fins10a,10bcan be suppressed as a whole, and the cooling efficiency of the magnetron1can be improved. In the magnetron1of the embodiment, furthermore, a diffusion phenomenon that the cooling medium which passes through the region R3escapes from the anode tube2can be prevented from occurring by the region R2which can be deemed as a barrier. Therefore, the cooling efficiency of the magnetron1can be further improved.

In the magnetron1of the embodiment, as described above, simply by adequately bending at least two places of the plurality of fins10a,10bconstituting the cooling fins10having the same shape, the plurality of fins10a,10bare caused to be dense in the region R2shown inFIG. 3, but to be sparse in the regions R1, R3shown inFIG. 3when the cooling fins10attached to the anode tube2are viewed in the flowing direction of the cooling medium of the magnetron1. When the portion (inFIG. 3, the region R2) where the gaps between the fins of the plurality of fins10a,10bconstituting the cooling fins10are extremely small is disposed, therefore, the portion (inFIG. 3, the regions R1, R3) where the gaps between the fins of the plurality of fins10a,10bconstituting the cooling fins10are wide is ensured, whereby the effective area of the portion where the gaps between the plurality of fins10a,10bconstituting the cooling fins10are wide is increased, and the airflow resistance difference with respect to the space portion surrounding the permanent magnets4can be reduced. Therefore, the amount of the reduction of the cooling medium (in the embodiment, air) which passes between the cooling fins10is suppressed, and the cooling efficiency of the magnetron1is improved.

In the magnetron1of the embodiment, with respect to the portion (inFIG. 3, the region R1) where the intervals of the plurality of fins10a,10bconstituting the cooling fins10are wide when the magnetron1is viewed in the flowing direction of the cooling medium (in the embodiment, air), fins in which a group (the group Ga) in which upward bending is performed in the region R2shown inFIG. 3, and a group (the group Gb) in which downward bending is performed in the region R2shown inFIG. 3are on a substantially same plane are disposed, whereby the effective area of the portion where the gaps between the plurality of fins10a,10bconstituting the cooling fins10are wide is increased, and the airflow resistance difference with respect to the space portion surrounding the permanent magnets4can be reduced. Therefore, the reduction of the amount of the cooling medium (in the embodiment, air) which passes between the cooling fins10is suppressed, and the cooling efficiency of the magnetron1is improved.

In the magnetron1of the embodiment, moreover, the cooling medium (air) which passes through the region R3impinges on the region R2which can be deemed as a barrier, and then flows to the rear side of the anode tube2. Therefore, the cooling efficiency of the magnetron1can be further improved.

In the magnetron1of the embodiment, it has been described that the cooling fins10are thin aluminum plates. However, the invention is not limited to this.

Although various embodiments of the invention have been described, the invention is not limited to the matters disclosed in the above-described embodiment. In the invention, it is expected that those skilled in the art will change or apply the matters based on the description in the description and the well-known technique, and such a change or application is included in the range to be protected.

The application is based on Japanese Patent Application (No. 2009-272337) filed Nov. 30, 2009, and its disclosure is incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The magnetron and the apparatus that uses microwaves have advantages of improving cooling efficiency of a magnetron by forming a region where cooling fins are sparse and a region where cooling fins are dense when the cooling fins are viewed in a flowing direction of a cooling medium of the magnetron, and are useful as a microwave oven or the like.