JPH0746568B2 - Magnetron - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron mainly used in a microwave oven, and more particularly to improvement of a cooling structure for preventing a temperature rise of a permanent magnet.

2. Description of the Related Art Ferrite-based magnets, which are easy to construct and inexpensive in circuit configuration, are widely used for the excitation system of magnetrons, which are microwave sources of microwave ovens. However, the ferrite magnet has poor heat resistance, and the heat generation of the magnetron tube lowers the magnetic flux density in the working space, resulting in a decrease in efficiency. Therefore, a large radiating fin is required. With the recent widespread use of microwave ovens, there has been a demand for downsizing and cost reduction of magnetrons, and a small radiating fin structure is desired.

As a means for solving this, for example, there is one disclosed in Japanese Utility Model Publication No. 54-121757.

FIG. 4 is a cross-sectional view of a magnetron showing an example of the
FIG. 5 is an enlarged cross-sectional view of the main parts of FIG. In the drawings, 1 is an anode body having a cathode 2 and a vane 3 inside, 4 is a stem for supporting the cathode, 5 is a pair of permanent magnets provided to face each other in the tube axis direction of the anode body, and 6 is a magnetic flux of the permanent magnet. To a working space 7, a pair of magnetic poles for guiding the working space 7, a yoke forming a magnetic path, 9
Is an output antenna, and a high frequency output is taken out through the antenna lead 10. 11 is a radiation fin for radiating the heat from the anode body 1, 12 is a focusing ring for guiding the magnetic flux of the permanent magnet 5 to the magnetic pole 6, 13 is arranged in contact with the focusing ring 12, and is formed by a yoke 8. It is an auxiliary cooling fin that extends into the duct space, and dissipates the conduction heat from the anode body 1 to the permanent magnet 5.
Reference numeral 14 denotes a stem side tube, and the leads 15 and 16 form a coaxial choke. Reference numeral 17 denotes a filter case containing a feedthrough capacitor 18 therein, which suppresses unnecessary radiation from the cathode side.

In the above structure, the heat generated from the anode body 1 during the magnetron oscillation is conducted to the heat radiation fins 11 provided in close contact therewith, and is radiated by the cooling air from the forced air cooling fan (not shown). On the other hand, heat conduction and radiant heat through the magnet 6 and the focusing ring 12 act on the permanent magnets 5 provided at both ends of the anode body 1, but the heat due to the heat conduction is absorbed by the auxiliary cooling fins 13 and radiated to the atmosphere, Radiant heat is also reflected by the auxiliary cooling fins 13. Therefore, the temperature of the permanent magnet 5 can be reduced.

Problems to be Solved by the Invention However, the above-mentioned conventional magnetron has the following problems in practical use.

(1) Since the auxiliary cooling fin 13 is arranged so as to extend in the duct space formed by the yoke 8 and is sandwiched by the focusing ring 12 and the permanent magnet 5, the heat dissipation area of the auxiliary cooling fin 13 is increased. It is necessary, and the auxiliary cooling fins 13 are deformed due to high temperature and come into contact with the permanent magnets 5.
Temperature rises.

(2) The coaxial choke structure provided on the side of the stem 4 becomes complicated, leading to an increase in manufacturing cost.

As a result, a large cooling fin 11 is required in spite of providing the auxiliary cooling fin 13, and the magnetron is downsized.
Cost reduction was not achieved.

Means for Solving the Problems The present invention has been made in view of the above-mentioned conventional example, and is capable of efficiently dissipating heat of a permanent magnet and providing an unnecessary radiation suppressing means on a part of a heat dissipation fin of the permanent magnet. Thus, it is an object of the present invention to provide a compact and low-cost magnetron by downsizing the cooling fin and simplifying the structure for suppressing unnecessary radiation.

To achieve this object, the present invention provides an anode body, a choke member fixed to a power supply line to the cathode, a sealing body that seals one end of the anode body, and a yoke that constitutes a magnetic path of a magnet. And a cylindrical wall fitted to the protruding cylinder of the filter case between the magnet and the sealing body, and the cylindrical wall and the choke member constitute a coaxial choke. Magnet cooling fins are provided, both ends of the magnet cooling fins are brought into contact with the yoke, and an air layer is formed between the magnets and the magnet cooling fins.

Action With this configuration, the conductive heat from the anode body is radiated from the magnet cooling fins to the atmosphere and also to the yoke, so that the heat radiation efficiency is improved. Further, the magnet cooling fins are in contact with the yoke and are fixed, so that they have an effect of preventing thermal deformation. Further, since the coaxial choke is constituted by the choke member and the cylindrical wall of the magnet cooling fin, leakage of electromagnetic noise generated from the cathode side during operation of the magnetron to the outside is prevented. That is, it has an effect of suppressing unnecessary radiation.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a main part of a magnetron according to the present invention, FIG.
FIG. 3 is an enlarged cross-sectional view of an essential part of FIG. 1, and FIG. 3 is a perspective view of a magnet cooling fin.

In the drawing, 20 is a cathode 21, an anode body having a plurality of vanes 22 forming a resonance cavity, 23 is a power supply line 24 to the cathode 21,
25, a dielectric 26, a stem supporting a choke member 27 welded and fixed to the power supply line 24, 28 is a conductive sealing body provided between the anode body 20 and the stem 23 and sealing one end of the anode body 20. ,
29a and 29b are a pair of permanent magnets provided to face each other in the tube axis direction,
Reference numeral 30 is a pair of magnetic poles for focusing the magnetic flux of the permanent magnet 29 into the working space 31, 32 is a yoke that constitutes the magnetic path of the permanent magnets 29a, 29b, and 33
Is a filter case in which the protruding cylinder 34 is provided on the anode body 20 side, 35 is a magnet cooling fin having a cylindrical wall 36 that fits into the protruding cylinder 34 and forms a coaxial choke with the choke member 27, and has an L-shaped end portion. Is formed in contact with the yoke 32, and a plurality of protrusions 37 are provided at the portion where the permanent magnet 29a abuts.
Forming eight. 39 is an output antenna section provided in a direction perpendicular to the tube axis, 40 is a cooling fin fitted and fixed to the anode body 20, and 41 is a second sealing body for sealing the other end of the anode body 20. A plurality of protrusions 42 are provided and an air layer 43 is formed. Reference numeral 44 denotes a second magnet cooling fin provided in the center with a magnetic plate 45 in contact with the permanent magnet 29b, which is sandwiched between the flange 46 provided on the magnetic plate 45 and the permanent magnet 29b and has an L-shaped end. It is molded and fixed in contact with the yoke 32. In the above configuration, the heat generated from the anode body 20 during magnetron oscillation is conducted to the cooling fin 40 which is closely fitted and fixed, and is radiated by the cooling air from the forced air cooling fan (not shown). On the other hand, at the same time, the permanent magnets 29a and 29b arranged at both ends of the anode body 20 are likely to transfer heat by heat conduction and radiant heat through the magnetic pole 30 and the sealing plates 36 and 41. Here, the heat conduction to the permanent magnet 29a is absorbed by the magnet cooling fin 35 having a low heat resistance because the air layer 38 is provided, and the heat is radiated to the atmosphere by the forced air cooling and is also conducted to the yoke 32 for efficient cooling. . As an example, as a result of comparison between the case where the magnet cooling fins having the same surface area are contacted with the yoke 32 and the case where the yoke 32 is not contacted, the temperature of the permanent magnet 29a can be reduced by about 8%. Further, since the ends of the magnet cooling fins 35 are in contact with the yoke 32, the magnet cooling fins 35 will not be deformed even when subjected to a heat cycle due to long-term use. On the other hand, since the radiant heat covers the heat generating side of the permanent magnet 29a by the magnet cooling fin 35 integrally provided with the cylindrical wall 36, the amount of radiation to the permanent magnet 29a can be reduced. Further, the cylindrical wall 36 provided on the magnet cooling fin 35 is provided with a protruding cylinder of the filter case 33.
A type of coaxial choke is formed with the choke member 27 for fitting into the 34. As a result, electromagnetic noise generated from the cathode side during magnetron oscillation is prevented from leaking to the outside through the power supply line 24. That is, there is an effect of suppressing unnecessary radiation. Therefore, the structure of the unnecessary radiation suppressing means can be simplified.

Further, the heat conduction to the permanent magnet 29b side is reduced due to the formation of the air layer 43, and further conducted to the second magnet cooling fin 44 through the magnetic plate 45 to be air-cooled and the yoke 32.
And is efficiently cooled, and the radiation amount of radiation heat can be reduced by the magnetic plate 45 and the second magnet cooling fins 44. Since the output antenna section 39 is provided in the direction perpendicular to the tube axis, the permanent magnet 29b can be made solid and miniaturization of the permanent magnet 29b can be achieved. Since the layer 43 can be formed and a means for preventing radiant heat can be arranged over the entire surface, the heat insulating effect of the permanent magnet 29b can be enhanced. Further, since the magnetic plate is provided in contact with the permanent magnet 29b, there is an effect that the increase in the magnetic gap due to the provision of the second magnet cooling fins 44 made of a non-magnetic material is prevented and the permanent magnet 29b can be downsized. .

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) Since a coaxial choke is configured by a part of the magnet cooling fin, that is, the cylindrical wall and the choke member, it is possible to prevent electromagnetic noise generated from the cathode side during operation of the magnetron from leaking to the outside through the power supply line, and unnecessary radiation. It is possible to realize a magnetron with less energy consumption. Further, this can simplify the structure of the unwanted radiation suppressing means.

(2) Since the cylindrical wall is provided between the permanent magnet and the sealing body, radiation heat from the anode to the permanent magnet can be reduced. Further, since both ends of the magnet cooling fin are held in contact with the yoke, the magnet cooling fin is not deformed and comes into contact with the permanent magnet even when subjected to a heat cycle due to long-term use. Further, since the air layer is formed between the permanent magnet and the magnet cooling fin, the heat of the anode is effectively radiated by the magnet cooling fin. As a result, the heat dissipation efficiency is improved and a small cooling fin structure can be realized, so that the magnetron can be downsized.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a magnetron showing an embodiment of the present invention, FIG. 2 is a partially enlarged sectional view of FIG. 1, FIG. 3 is a perspective view of the same magnet cooling fin, and FIG. FIG. 5 is a sectional view of a magnetron showing an example, and FIG. 5 is an enlarged view of the same. 20 …… Anode body, 21 …… Cathode, 22 …… Bain, 23 …… Stem, 24 …… Power supply line, 27 …… Choke member, 28 …… Sealing body, 29a …… Permanent magnet, 30 …… Magnetic pole, 32 ... Yoke, 33
...... Filter case, 34 ...... Projection cylinder, 35 ...... Magnet cooling fins, 36 ...... Cylinder wall, 38 ...... Air layer.

Claims (1)

[Claims] 1. An anode body having a cathode and a vane inside,
A stem supporting the cathode, a choke member fixed to a power supply line to the cathode, a sealing body provided between the anode body and the stem and sealing one end of the anode body, and the anode body. And a pair of magnetic poles and permanent magnets provided to face each other in the tube axis direction, a yoke forming a magnetic path, and a filter case having a projecting cylinder, and the filter between the permanent magnet and the sealing body. A magnet cooling fin that has a cylindrical wall fitted to the protruding cylinder of the case and that constitutes a coaxial choke with the cylindrical wall and the choke member is provided, and both ends of the magnet cooling fin are brought into contact with the yoke. A magnetron having a structure in which an air layer is formed between the permanent magnet and the magnet cooling fin.