JPH0883572A - Magnetron - Google Patents

Abstract

PURPOSE: To facilitate heat diffusion, and realize a long service life and downsizing by inserting/engaging a capacitor constituting a leakage radio wave restraining filter circuit in/with negative electrode leads. CONSTITUTION: A through hole 304 is formed in a central part of a dielectric 301, and an electrode 303 by metallizing processing is formed on the outer periphery, and is fixed by silver brazing to a metallic disk 302 grounded through a sealing part 42. An electrode by metallizing processing is also formed on an inner wall of the through hole 304, and negative electrode leads 23 and 24 penetratingly pass by coming into contact with this inside electrode. The negative electrode leads 23 and 24 are directly fitted to the dielectric 301, and a capacitor is constituted by using the negative electrode leads 23 and 24 as electrodes. This capacitor constitutes a leakage radio wave restraining filter circuit, and penetratingly passes in contact through the negative electrode leads 23 and 24. Then, since efficient heat diffusion is performed through the negative electrode leads 23 and 24 from a negative electrode filament 1, a heat radiating mechanism can be downsized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetron used for microwave application equipment, and in particular, has a structure with improved heat dissipation characteristics and withstand voltage characteristics of a capacitor constituting a filter circuit for noise prevention. For improved magnetron.

[0002]

2. Description of the Related Art Since a magnetron efficiently generates a high frequency output, it has been widely applied to a radar device, a medical device, a cooking device such as a microwave oven, and other microwave application devices in the field.

This type of magnetron includes a main body having a resonant cavity set in a vacuum atmosphere, a high frequency output section, and the like.
A filter circuit is provided for suppressing leaked radio waves in the power supply section that supplies power to the main body section.

A cathode filament is coaxially installed at the center of the resonance cavity. Cathode leads are connected to both ends of the cathode filament and led out to the outside. The cathode lead is used for heating the cathode filament from the outside. It is supplying power.

Further, the filter circuit includes two choke coils each having one end connected in series to each of the two cathode leads in a filter case installed outside a main body in which a resonance cavity is installed. It is composed of each choke coil and a capacitor connected in parallel.

[0006] In the conventional capacitor of this type, it is general that it is connected to an external power source by penetrating the inside and outside of the housing wall of the filter case accommodating the filter circuit.

FIG. 9 is a vertical cross-sectional view for explaining a conventional magnetron structure. 1 is a cathode filament, 2 is an anode vane, 3 is an anode cylinder, 4 and 4'are permanent magnets, 5 is a magnetic pole, and 6 is a yoke. , 7 is an antenna lead, 8 is an antenna, 9 is a choke portion, 10 is an antenna cover, 11 is a cylindrical insulator, 12 is an exhaust pipe support, 21 and 21 'are upper and lower end shields, and 23 and 24 are cathodes. Reed, 2
5 is an input side ceramic, 26 is a cathode terminal, 27 is a spacer, 28 is a sleeve, 31 is a choke coil, 32 is a feedthrough capacitor, 33 is a filter case, 34 is a lid, 4
1 is an upper seal part, 43 is a metal gasket, 44 is an upper yoke, and 45 is a cooling fin.

In FIG. 1, a plurality of anode vanes 2 are radially formed around the cathode filament 1.
The anode vane 2 is fixed to the anode cylinder 3 by brazing or is integrally formed by extrusion molding or the like.

Above and below the anode cylinder 3, magnetic poles 5 and 5'made of a ferromagnetic material such as soft iron and a cylindrical permanent magnet 4 are provided.
4'is installed. The magnetic flux generated from the permanent magnets 4 and 4 ′ passes through the magnetic poles 5 and 5 ′ and enters the working space formed between the cathode filament 1 and the anode vane 2, and gives a necessary DC magnetic field in the axial direction.

The yoke 6 constitutes a magnetic circuit through which the magnetic flux of the permanent magnets 4 and 4'passes, and the yoke 6, the permanent magnets 4 and 4'and the magnetic poles 5 and 5'constitute a magnetic circuit. .

The electrons emitted from the cathode filament 1 having a negative high voltage are affected by the electric field and the DC magnetic field and form a high frequency electric field in each anode vane 2 while making a circular motion.

Further, the cathode leads 23 and 24 are arranged from the cathode filament 1 side to the sealing part 42 and the input side ceramic 25.
It is penetrated through and is directly drawn to the outside.

FIG. 10 is a plan view for explaining the details of the anode structure portion, and 61 is a first strap ring,
Reference numeral 62 is a second strap ring, and the same parts as those in FIG. 9 are designated by the same reference numerals.

In the figure, the anode vanes 2 and 2'are provided in the direction of the center 0 from the inner wall of the anode cylinder 3, and are arranged radially when viewed from the axis passing through the center 0.

The anode vanes 2 and 2'include a first strap ring 61 composed of two annular bodies having different diameters.
And every other one is tied by the second strap ring 62.

FIG. 11 is a perspective view of a strap ring having a large diameter and a strap ring having a small diameter, and FIG. 12 is a partial sectional view of one anode vane.

As shown in FIGS. 11 and 12, a small diameter strap ring 61 contacts the anode vane 2, but a large diameter strap ring does not contact. Therefore, the large-diameter strap ring 62 comes into contact with the adjacent anode vanes (2 ′) (not shown), and the small-diameter strap ring does not come into contact.

Then, the anode vanes 2 and 2'shown in FIG.
An antenna lead 7 for guiding a high frequency (microwave) is attached to one of them by silver brazing or the like.

The high frequency electric field generated in the anode vane 2 (2 ') is guided to the antenna 8 by the antenna lead 7.
It is emitted to the outside from the antenna cover 10 that protects the antenna 8.

The antenna 8 is integrally formed with a choke portion 9 for preventing unnecessary radiation. The cathode filament 1 for generating electrons is generally made of tungsten containing a small amount of thorium oxide (ThO ₂ ) in consideration of electron emission characteristics, processability, and the like.

The upper end shield 21 and the lower end shield 21 'are supported by cathode leads 23 and 24, respectively. These end shields 21,
21 'and the cathode leads 23 and 24 are generally made of molybdenum (Mo) from the viewpoint of heat resistance and workability.

The two cathode leads 23 and 24 are supported by the input side ceramic 25. These cathode leads 23 and 24 are brazed together with the cathode terminal 26 to the input side ceramic 25 so as to keep vacuum tightness.

When vibration, impact or the like is applied to the magnetron having such a structure, the cathode leads 23 and 24 vibrate,
Moreover, since the manner of vibration differs between the cathode leads 23 and 24, mechanical stress may be generated in the cathode filament 1 and the cathode filament 1 may be broken.

In order to prevent this, a spacer 27 is installed near the lower end shield 21 'so as to penetrate and hold the cathode leads 23 and 24. Due to the effect of the spacer, even if the cathode lead vibrates, the movements of the cathode leads 23 and 24 due to the vibration are substantially the same, so that it is possible to prevent stress from being applied to the cathode filament. The sleeve 28 is for supporting the spacer 27 at a predetermined position.

The cathode terminal 26 is connected to the choke coil 31, and the choke coil 31 is connected to the filter case 33 of the input section.
Is connected to the through capacitor 32, which is connected to the power supply.

The cathode terminal 26 and the choke coil 31 are
Generally, they are connected by welding, and the choke coil 31 and the feedthrough capacitor 32 are also generally connected by welding.

Here, the choke coil 31 and the feedthrough capacitor 32 form a low-pass filter when the outside is seen from the inside of the magnetron, and the high-frequency electric field generated in the working space between the cathode filament 1 and the anode is outside. Prevents radiation.

The input side ceramic 25 has a seal part 42.
And engage with the anode cylinder 3 while maintaining vacuum tightness via
The output side ceramic 11 is engaged with the anode cylinder 3 via the seal component 4 while maintaining vacuum tightness.

The yoke 44 is electrically connected to the seal component 41 via the metal gasket 43, and the seal component 41 is
Has the same potential as the anode cylinder 3. Therefore, the yoke 44 has the same potential as the anode cylinder 3. The yoke 44 and the yoke 6 are generally connected by caulking.

The anode of the magnetron becomes high in temperature due to heat radiation from the cathode filament 1 and heat generated by collision of electrons with the anode vane 2 (2 '). When the temperature of the anode becomes high, the magnetic characteristics of the magnet are changed, and the peripheral devices of the magnetron are adversely affected. The cooling fins 45 are provided to counter this problem.

Generally, during operation of the magnetron, cooling air is sent to the cooling fins 45 by a fan installed in a microwave oven or the like.

FIG. 13 is a view of the input portion of the magnetron shown in FIG. 9 as viewed from the bottom, and the same parts as those in FIG. 9 are designated by the same reference numerals.

As shown in the figure, the feedthrough capacitor 32 is mounted through the side wall of the filter case 33 and connected to the choke coil 31.

FIG. 14 is a partially cutaway view for explaining the structure of the feedthrough capacitor. Reference numeral 151 is an insulating cover, and 152 is a dielectric which forms a capacitor together with the electrodes 153 and 156. The electrode 156 also serves to attach the feedthrough capacitor 32 to the filter case 33. Although the electrodes 153 appear to be separated in the figure, they are integrally connected to the terminal 154 in another cross section.

Reference numeral 155 denotes a silicon tube which covers the terminal 154, and insulates the terminal 154 and the electrode 156 together with the resin 157. The terminal 154 is connected to the choke coil 31, and the other end of the choke coil faces the ground via the capacitor.

FIG. 15 is a circuit diagram showing an example of a drive circuit for driving the magnetron, and 231 is a magnetron.

In the figure, the switching power supply unit 20
The DC power supply 201 that supplies DC power to the power supply 9 includes a commercial AC power supply 203 and a full-wave rectifier 205. A filter 207 composed of a reactor and a capacitor is connected to the DC output terminal of the full-wave rectifier 205, but this filter 207 is not for smoothing the rectified current, but for the audio frequency included in the oscillating current to be an AC power source. This is to prevent leakage through the side and thus to avoid generation of radio waves.

The switching device 209 is the transistor 2
11, the ON signal generating circuit and the driving circuit repeat the ON-OFF operation. And the switching device 209
Includes a damper diode 215 connected in anti-parallel to the transistor 211 and a resonance capacitor 213 connected in parallel.

The power supply device is a step-up transformer 217 having a primary winding 219 and three secondary windings 221, 223 and 225.
have. The primary winding 219 of the step-up transformer 217 is connected to the filter 207 via the switching device 209, and the capacitor 213 and the primary winding 219 form a series resonance circuit.

The secondary winding 221 is connected to the magnetron 231 through a voltage doubler rectifier composed of a capacitor 227 and a high voltage diode 229. The current detector 223 is used to detect the load current flowing through the magnetron 231.

The secondary winding 225 is provided for producing a heater current for heating the cathode of the magnetron 231, and the other secondary winding 223 is provided with a magnetic flux in the core of the step-up transformer 217 for producing an output voltage. Acts as a winding for detecting changes. Further, the output current of the secondary winding 224 is rectified and used as a power source of the control circuit.

The load current flowing through the magnetron detected by the current detector 233 is used as an average value by the averaging circuit 249, and the difference from the setting value of the output setting device 251 is used as the average value by the synchronizing pulse generator 235 via the amplifier 257. Is added and given to the ON signal generator 237 as a control signal.

The secondary winding 223 is for producing a voltage for output feedback. After the waveform is shaped by the waveform shaping circuit 243, it is delayed by a predetermined time by the delay circuit 245 to control the ON signal generating circuit 237. Given as a signal.

The output of the secondary winding 224 is the auxiliary power supply 2
The signal is supplied to 47, is rectified, and is used as a power source for a control circuit or the like.

Here, a high voltage of several KV is usually applied to the filament and the anode of the magnetron 231.

In the figure, 232 is a waveguide, 234 is a microwave oven cooking chamber, and the microwave oscillated by the magnetron 231 is supplied to the cooking chamber 234 through the waveguide 232. .

The magnetron power supply is not limited to the switching power supply as described above, and a general commercial power supply can be used as it is. The commercial AC power supply is boosted by a high voltage transformer, and a half-wave voltage doubler composed of a capacitor and a high voltage diode is used. Rectify with a rectifier circuit, etc. to make a high voltage source for the magnetron.

The magnetron power supply using the general commercial power supply as it is is not limited to the half-wave voltage doubler rectifier circuit described above.
A known full-wave rectifier circuit can also be used.

The disclosure of the prior art relating to this type of feedthrough capacitor is given in Japanese Utility Model Publication No. 57-5650.
No. 4 publication can be cited.

[0050]

In the magnetron according to the above-mentioned prior art, the cathode lead for supplying electric power to the cathode filament penetrates the lower seal component 42 and the input side ceramic 25 and is directly connected to the choke coil 31. ing.

The cathode leads 23 and 24 and the input side ceramic 25 are sealed by the respective cathode leads 23 and 24 on the choke coil 31 side of the input side ceramic 25.
The cathode terminals 26 and 26 'are independently installed in the.

In such a structure, the cathode filament 1
The heat from is transmitted mainly to the cathode leads 23 and 24, is transmitted to the input side ceramic 25 at the cathode terminals 26 and 26 ', and is radiated to the outside.

Therefore, the cathode leads 23 and 24 in the vacuum atmosphere are always in a high temperature state, and it is difficult to efficiently radiate the heat of the magnetron cathode part by utilizing the heat dissipation structure of the main body part. In a magnetron having a filter structure with a built-in capacitor that installs a capacitor in a vacuum atmosphere as disclosed in Japanese Patent Laid-Open No. 21539,
There is a problem that the temperature of the capacitor rises and the frequency characteristic becomes unstable, and a temperature of the filter case portion rises.

Further, in the above-mentioned conventional structure, the unwanted radiation propagating from the magnetron cathode part is suppressed by the low-pass filter including the choke coil and the capacitor mounted outside the magnetron tube. Since a high voltage is applied in the atmosphere to a capacitor made of a dielectric material, the capacitor has a structurally sufficient insulating property, and is complicated and large.

This capacitor generally has a structure as shown in FIG. 14, but in terms of reliability, the dielectric 15 is used.
There are problems such as the dielectric breakdown of No. 2 and the occurrence of creepage of the insulating cover 151.

On the other hand, the regulation of the unnecessary radiation emitted from the cathode portion of the magnetron is required to be strict, and in order to meet this, it is necessary to increase the capacitance of the capacitor. However, in order to increase the capacitance of the capacitor, it is not possible to reduce the distance between the electrodes of the dielectric due to the problem of withstand voltage, and eventually the capacitor becomes larger and the magnetron itself becomes larger. There was a problem.

The object of the present invention is to solve the above-mentioned problems of the prior art, to facilitate the heat dissipation of the cathode lead to suppress the temperature rise in a vacuum atmosphere, and to provide a capacitor which constitutes a filament for preventing unnecessary radiation. An object of the present invention is to provide a magnetron that secures a sufficient electrostatic capacity and has a long life and a small size.

[0058]

In order to achieve the above object, the present invention provides: The cathode lead is terminated at the input ceramic portion to be thermally connected to the ceramic, and the cathode lead is externally connected to an external lead-out of another member at the termination portion, and the dielectric is placed in the magnetron tube, that is, in a vacuum atmosphere. Place inside. Inside the magnetron tube is 10 ^-5 to 10 ^-8 (To
rr), the degree of vacuum is maintained, and in view of the withstand voltage, the conventional insulating structure is not required and only the dielectric is provided.

2. Electrodes are provided on both sides of the dielectric, one end of the electrode being a cathode lead and the other end being at ground potential.

3. A hole for penetrating the cathode lead is provided at approximately the center of the dielectric electrode surface to form a penetrating capacitor structure.

4. Since the permittivity of the dielectric has a negative temperature coefficient, it is a position in the magnetron tube where the temperature rise is small, specifically, the end face side of the cathode lead filament side or the input ceramic side supporting the cathode lead. A dielectric is placed on.

In the cathode structure having the above, the electrostatic capacity can be obtained at the cathode portion in the vacuum tube, and at the same time the function equivalent to that of the conventionally arranged condenser disposed in the atmosphere can be obtained. It is possible to avoid fluctuations in the capacitance of the capacitor due to temperature rise, and to significantly improve reliability with respect to defective withstand voltage, and further, with respect to capacitor burnout and the like due to defective withstand voltage.

That is, in the first aspect of the present invention, a cathode filament supported by upper and lower end shields and a plurality of vanes surrounding the cathode filament and coaxially arranged to form a resonance cavity are provided. An anode cylinder having, and an upper seal part and a lower seal part that are joined to the anode cylinder to seal the resonance cavity in vacuum,
One end is connected to both ends of the cathode filament to support the cathode filament and two cathode leads for supplying a heating current, and an input fixed to the lower sealing part to hold the two cathode leads. At least a side ceramic, and the input ceramic has two recesses for supporting the cathode lead on the cathode filament side and two through-holes penetrating to the outside at different positions of the recesses. Side of the side ceramics, which is installed on the side of the cathode filament and penetrates the other end of the cathode lead to fit into the recess, and the cathode filament through the two through holes of the input side ceramic. Recesses formed so as to bulge toward the cathode filament side that respectively supports two external lead-outs inserted from the side Has two electrically independent terminal plates each having a portion, and electrically connects the cathode lead and the external lead-out via each of the two terminal plates. It is characterized in that a capacitor constituting a filter circuit for suppression is inserted and engaged.

A second invention according to claim 2 is the above first invention.
In the invention, the capacitor has a tubular insulator and an electrode formed on the outer periphery of the tubular insulator, and the cathode lead is made to contact and penetrate the inner periphery of the tubular insulator. To do.

A third invention according to claim 3 is the first invention.
In the invention, the capacitor has a tubular insulator and electrodes on the outer and inner circumferences of the tubular insulator, and the cathode lead is brought into contact with the electrode on the inner circumference of the tubular insulator. It is characterized by According to a fourth aspect of the present invention, in the capacitor according to the first aspect of the present invention, at least one of the disk-shaped insulator and the two cathode leads on both sides of the disk-shaped insulator are made to correspond to each other. In addition to having the electrodes formed separately, two through holes are formed in the disk-shaped insulator so as to penetrate the two cathode leads, respectively.

A fifth invention according to claim 5 is the fourth invention.
The capacitor according to the invention has a disk-shaped insulator and electrodes formed separately on both surfaces of the disk-shaped insulator so as to form a pair corresponding to each of the two cathode leads. Through holes are formed in the insulator so as to penetrate the cathode leads, and one of the electrode pairs is electrically connected to the cathode leads.

A sixth invention according to claim 6 is the fifth invention.
The invention is characterized in that one of the electrode pairs formed separately on both surfaces of the disk-shaped insulator is connected to the cathode lead via a terminal plate.

[0068]

According to the above-mentioned inventions, the heat dissipation of the cathode lead is facilitated, the temperature rise in the vacuum atmosphere is suppressed, and a sufficient capacitance is secured for the capacitor which constitutes the filament for preventing unnecessary radiation. Moreover, it is possible to provide a magnetron having a long life and a small size. Also, because the cathode lead can be shortened, effective materials for the cathode lead are saved.

The capacitor forming the filter for the magnetron must have a function of ensuring suppression of unnecessary radiation in the 0.5 MHz to 30 MHz band.

In order to efficiently suppress the unwanted radiation in the above band, a feedthrough type capacitor has been conventionally required and adopted.

According to each of the above-mentioned inventions, since the structure is a penetration type capacitor structure in which the cathode lead is penetrated and engaged with the central part of the dielectric, the performance can be obtained at the same level as the conventional one.

On the other hand, in terms of reliability, 10 ^-4 to 10
^{Since the} dielectric is placed in a vacuum of ^-8 (Torr), the withstand voltage is significantly improved.

Therefore, unlike the conventional capacitor used in the atmosphere, the dielectric filling resin and the accessory parts such as the case for securing the creeping withstand voltage are not required, so that the magnetron is downsized and has a long life. And cost reduction are achieved.

[0074]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a main part for explaining a first embodiment of a magnetron according to the present invention, in which 1 is a cathode filament, 21 is an upper end shield, 21 'is a lower end shield, and 23 and 24 are cathode leads. , 23 ', 24' are external leads, 25 is an input ceramic, 261, 261 '
Is a cathode terminal, 42 is a seal part, 301 is a hollow cylindrical dielectric, and 302 is a metal disk.

In the same figure, the cathode filament 1 has upper and lower end shields 2 at both ends, as in the above embodiment.
1, 21 'are joined to the upper and lower end shields 2
1, 21 'are supported by cathode leads 23, 24. The other end of each of the cathode leads 23 and 24 is connected to the input side ceramic 25 by silver brazing and is connected to the cathode terminal plates 261 and 261.
It is fixed at 61 '.

The cathode leads 23 and 24 are electrically connected to the cathode terminal plates 261 and 261 'and are connected to the choke coil 31 (FIG. 9) by external leads 23' and 24 'extending from the input ceramic 25. There is.

The hollow cylindrical dielectric 301 that constitutes the capacitor is engaged with the cathode leads 23 and 24. Electrodes formed by metallization or the like are formed on the outer peripheral portion of the hollow cylindrical dielectric 301, and are connected to the seal component 42, which is at earth potential, through the metal disk 302.

FIG. 2 is a schematic perspective view for explaining the structure of the capacitor according to the first embodiment of the present invention, in which 303 is a metallized electrode and 304 is a through hole.

A through hole 304 is formed in the center of the dielectric 301, an electrode 303 is formed by metallization on the outer periphery, and is fixed to a metal disk 302 that is grounded via a seal component 42 by silver brazing or the like. To be done.

Further, an electrode is formed by metallization on the inner wall of the through hole 304, and the cathode leads 23, 24 penetrate by coming into contact with the inner electrode.

Instead of providing the electrodes by the metallizing process on the inner peripheral wall of the hollow cylindrical dielectric body 301, the cathode leads 23 and 24 are directly fitted to the dielectric body 301 to form the cathode leads. You may comprise a capacitor as an electrode.

According to this embodiment, since the heat dissipation of the cathode lead is efficiently performed and the dielectric is arranged in vacuum, the withstand voltage is remarkably improved, and the dielectric filling resin and
Since no accessory such as a case for securing the creeping withstand voltage is required, the magnetron can be made smaller, have a longer life, and have a lower cost.

FIG. 3 is a sectional view of an essential part for explaining a second embodiment of the magnetron according to the present invention, in which the same reference numerals as in the above embodiment correspond to the same parts, and 311 is a disk-shaped dielectric material, and 3 is a disk-shaped dielectric material.
Reference numeral 12 is a metal disk, 313, 314 (314 ′) are electrodes formed by metallization, 315 is a through hole, and 42 is a seal component.

In the same figure, as in FIG. 1, the cathode filament 1 has upper and lower end shields 21, 2 at both ends thereof.
1 ', and the upper and lower end shields 21 and 2
1'is supported by cathode leads 23 and 24. The other end of each of the cathode leads 23, 24 is connected to the input side ceramic 25 by silver soldering.
It is fixed at.

The cathode leads 23 and 24 are electrically connected to the cathode terminal plates 261 and 261 'and connected to the choke coil 31 (FIG. 9) by external leads 23' and 24 'extending from the input ceramic 25. There is.

Disk-shaped dielectric 31 that constitutes a capacitor
1 is engaged with the cathode leads 23 and 24. The upper surface and the lower surface of the disk-shaped dielectric 311 are divided into lower surfaces so that electrodes formed by metallization or the like correspond to the cathode leads 23 and 24 and form a pair of upper and lower electrodes. The upper electrode 313 is a metal disk. It is connected to the seal component 42 which is grounded via 312.

Then, the electrodes 314, 314 'on the lower surface side
Are divided by the cathode terminal plates 261 and 261 ′ corresponding to the cathode leads 23 and 24, respectively.
Electrically connected to.

FIG. 4 is a schematic perspective view illustrating the structure of a capacitor according to the second embodiment of the present invention. 313 is a metallization electrode on the upper surface side, 314 and 314 'are metallization electrodes on the lower surface side, 315 and 315'. Is a through hole.

Through holes 315, 315 'for penetrating the cathode leads 23, 24 are formed in the dielectric 311 and an electrode 313 is formed by metallization on the upper surface side, and a silver disk is formed on the metal disk 312 connected to ground. It is fixed by attachment.

Similarly, on the lower surface side, electrodes 314 and 314 ′ formed by the metallizing process are similarly formed on the cathode leads 23 and 24.
Corresponding to the electrode 313, the cathode leads 23, 2 are divided by the cathode terminal plates 261 and 261 ′ that are in contact with the electrodes 314 and 314 ′.
4 is electrically connected. Through holes 315, 315 '
Cathode leads 23 and 24 penetrate each of them without contact.

Also in this embodiment, similarly to the previous embodiment, the heat dissipation of the cathode lead is efficiently performed, and the dielectric is arranged in a vacuum, so that the withstand voltage is remarkably improved and the dielectric Since the filling resin and accessories such as a case for securing the creeping withstand voltage are not required, the magnetron can be downsized, the service life can be shortened, and the cost can be reduced.

FIG. 5 shows a first magnetron according to the present invention.
6A and 6B are structural views of a main part for better explaining the second embodiment, wherein FIG. 7A is a sectional view and FIG. 7B is a sectional view taken along the line AA of FIG.

In the figure, 1 is a cathode filament, 2
1 is the upper end shield, 21 'is the lower end shield, 2
3 and 24 are cathode leads, 23 'and 24' are external leads, 25 is an input ceramic, 261 and 261 'are cathode terminals, and 42 is a seal component.

The cathode filament 1 is the upper end shield 2
1 and the lower end shield 21 'are installed in a coil shape, and the upper end shield 21 and the lower end shield 2 are
Cathode leads 23 and 24 fixed to 1'are erected and supported on an input side ceramic 25.

The input side ceramic 25 is fixed to the lower end of a seal component 41 having openings at the top and bottom. On the upper surface side (cathode filament side) of the input side ceramic 25,
Two recesses 25a, 2 supporting the cathode leads 23, 24
5a 'and two through holes 25b, 25b' penetrating to the outside at positions different from the respective recesses, and the other end of the cathode leads 23, 24 is made to penetrate to the cathode filament 1 side of the input side ceramic 25. The recesses 25a, 2
5a ′ and two external lead-outs 23 ′, 24 ′ which are inserted from the side opposite to the cathode filament 1 through the two through holes 25b, 25b ′ of the input side ceramic 25, respectively. Recessed portions 26b, 26 formed so as to respectively support and bulge toward the cathode filament side
Two electrically independent terminal plates 261 and 2 having b ′ and
61 '.

Then, the above two terminal plates 261 and 26
The cathode leads 23 and 24 are electrically connected to the external lead-out leads 23 ′ and 24 ′ via 1 ′, respectively. The two terminal plates 261 and 261 'seal the space between the cathode leads 23 and 24 and the input side ceramic 25, and are closely fixed by brazing or the like so as to facilitate heat transfer between them.

FIG. 6 illustrates the sealing structure of the terminal plate, the cathode lead and the input side ceramics, taken along the line BB in FIG. 5B.
It is sectional drawing which followed the line.

As can be seen from the figure, the cathode lead 24 and the external lead 24 'are discontinuous, and both of them are the terminal board 2
It is electrically connected at 61. The same applies to the cathode lead 23.

With this structure, the length of the cathode leads 23, 24 can be made shorter than in the conventional case, the material cost thereof can be reduced, and the heat from the cathode filament 1 can be generated in the vacuum atmosphere side of the input side ceramic 25. Because it is transmitted directly,
This heat is transmitted to the main body through the seal component 42 (see FIG. 5) and radiated from the heat dissipation structure of the main body. 7A and 7B are explanatory views of specific dimension examples of the magnetron according to the present invention and the magnetron according to the related art. FIG. 7A shows a conventional magnetron, and FIG. 7B shows cathode lead portions of the magnetron according to the present invention.

The figure is a dimensional example of a magnetron used in a household microwave oven which is a general application object. In the conventional magnetron of (a), the lower end shield 21 'and the input side ceramic 25 are Connection distance is about 4
While it is 0 mm, it is about 21.5 mm in the magnetron according to the present invention in (b).

FIG. 8 is an explanatory view of the temperature gradient in the length direction of each cathode lead of the conventional magnetron described in FIG. 7 and the magnetron according to the present invention. The characteristics of the cathode structure A are shown in FIG. And the characteristics of the cathode structure B correspond to those of the magnetron shown in FIG.

In the same figure, in the cathode structure A in which the cathode lead penetrates the input side ceramic and extends directly to the outside, when the temperature at the lower end shield reference point B shown in FIG. 7 is 950 ° C. The temperature of the cathode lead at the connection point B between the cathode lead and the input side ceramic is 190 ° C., and the temperature of the cathode lead on the vacuum atmosphere side of the input side ceramic is 540 ° C., which is a considerably high temperature.

On the other hand, in the cathode structure B in which the cathode lead does not penetrate the input side ceramic, when the temperature at the lower end shield reference point B is 950 ° C. as in the above, the cathode lead and the input side ceramic are It can be seen that the temperature of the cathode lead at the connection point C is 250 ° C., and the heat dissipation of the cathode lead is efficiently performed.

Therefore, even if a capacitor is installed in the magnetron having the cathode structure B in the internal atmosphere, the characteristics of the capacitor do not change.

As described above, according to this embodiment, the heat dissipation efficiency of the cathode lead is improved and the material of the cathode lead can be saved.

Each of the capacitors of the above-mentioned embodiments is
Since the cathode leads 23 and 24 through which the unwanted radiation propagates form a so-called penetration type capacitor that penetrates the dielectric, excellent filter characteristics can be obtained.

Although ceramics having excellent heat resistance is used as the material of the dielectric material constituting the above-mentioned capacitor, since this dielectric constant has a negative temperature coefficient, it is necessary to suppress the decrease of the dielectric constant. It is preferable that the dielectric is disposed on the input side ceramic 25 side.

Since this dielectric is arranged in a vacuum atmosphere, it is advantageous in terms of withstand voltage, the distance between electrodes can be reduced, and the capacitance can be easily secured.

Needless to say, the present invention is not limited to the magnetrons of the type described in the above embodiments, but can be applied to other types of magnetrons.

[0111]

As described above, according to the present invention,
The heat dissipation of the cathode lead is efficiently performed, and the dielectric having the electrode is arranged in the vacuum atmosphere of the magnetron,
Moreover, since the cathode type penetrates the dielectric, the magnetron having the following effects can be obtained.

(1) Since heat is efficiently dissipated from the cathode filament through the cathode lead, the heat dissipation mechanism can be downsized, and a magnetron with a small size as a whole can be obtained.

(2) A tolerance can be obtained in the withstand voltage design, and the dielectric can be miniaturized. As a result, the desired capacitance is easily obtained.

(3) Only the dielectric itself is provided, which is more cost effective than the conventional capacitor.

(4) Further, there is no damage such as burning of the capacitor caused by defective withstand voltage, and reliability can be improved.

(5) The disposition structure of the dielectric material also has a cathode lead supporting function, and can be expected to improve the filament breakage strength.

(6) Due to the feedthrough capacitor type structure, excellent filter performance for preventing unnecessary radiation of the magnetron can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part for explaining a first embodiment of a magnetron according to the present invention.

FIG. 2 is a schematic perspective view illustrating the structure of the capacitor according to the first embodiment of the present invention.

FIG. 3 is a sectional view of an essential part for explaining a second embodiment of the magnetron according to the present invention.

FIG. 4 is a schematic perspective view illustrating the structure of a capacitor according to a third embodiment of the present invention.

FIG. 5 is a first and second magnetron according to the present invention.
It is a principal part structural drawing for demonstrating an Example better.

FIG. 6 is a cross-sectional view taken along line BB in FIG. 5B for explaining the sealing structure of the terminal plate, the cathode lead and the input side ceramic.

FIG. 7 is an explanatory diagram of specific dimension examples of the magnetron according to the present invention and the magnetron according to the related art.

8 is an explanatory diagram of a temperature gradient in the length direction of each cathode lead of the conventional magnetron described in FIG. 7 and the magnetron according to the present invention.

FIG. 9 is a vertical cross-sectional view illustrating a conventional magnetron structure.

FIG. 10 is a plan view for explaining details of an anode structure portion.

FIG. 11 is a perspective view of a strap ring having a large diameter and a strap ring having a small diameter.

FIG. 12 is a partial cross-sectional view of one anode vane.

FIG. 13 is a view of the input section of the magnetron shown in FIG. 9 as viewed from below.

FIG. 14 is a partial cutaway view illustrating the structure of a feedthrough capacitor.

FIG. 15 is a circuit diagram showing an example of a drive circuit for driving a magnetron.

[Explanation of symbols]

 1 Cathode Filament 2 Anode Vane 3 Anode Cylinder 4, 4'Permanent Magnet 5 Magnetic Pole 6 Yoke 7 Antenna Lead 8 Antenna 9 Choke Part 10 Antenna Cover 11 Cylindrical Insulator 12 Exhaust Pipe Support 21,21 'Upper and Lower End Shield 23 , 24 cathode lead 23 ', 24' external lead 25 input ceramic 25a, 25a 'recess 25b, 25b' through hole 261,261 'cathode terminal plate 27 spacer 28 sleeve 31 choke coil 32 feedthrough capacitor 33 filter case 34 lid 41 Upper Seal Component 42 Seal Component 43 Metal Gasket 44 Upper Yoke 45 Cooling Fin 303 Metallized Electrode 304 Through Hole 25a Terminal Plate 311 Disc-shaped Dielectric 312 Metal Disc 313, 314, 314 'Electrode 315, 3 5 'through-hole.

Claims (6)

[Claims] 1. A cathode filament supported by upper and lower end shields, an anode cylinder having a plurality of vanes that surround the cathode filament and are coaxially arranged to form a resonance cavity, and are joined to the anode cylinder. An upper sealing part and a lower sealing part for sealing the resonance cavity in a vacuum; two cathode leads for supporting the cathode filament by connecting one end to both ends of the cathode filament and supplying a heating current; At least an input side ceramic fixed to the lower sealing part and holding the two cathode leads, two recesses for supporting the cathode lead on the cathode filament side and the recesses are provided on the input side ceramic. Has two through holes penetrating to the outside at different positions, and the cathode filament of the input side ceramic Side of the cathode lead and the other end of the cathode lead that fits into the recess, and the two through holes of the input side ceramic are inserted from the side opposite to the cathode filament. It has two electrically independent terminal plates each having two recessed portions formed so as to bulge toward the cathode filament side that supports the two external lead-outs, and the two terminal plates are connected through each of the two terminal plates. A magnetron in which a cathode lead and the external lead-out are electrically connected to each other, wherein a capacitor constituting a filter circuit for suppressing leaked radio waves is inserted and engaged with the cathode lead. 2. The capacitor according to claim 1, wherein the capacitor has a cylindrical insulator and an electrode formed on the outer periphery of the cylindrical insulator, and the cathode lead is contact-pierced through the inner periphery of the cylindrical insulator. A magnetron characterized by being made possible. 3. The capacitor according to claim 1, wherein the capacitor has a tubular insulator and electrodes on the outer and inner circumferences of the tubular insulator, and the cathode is provided on the electrode on the inner circumference of the tubular insulator. A magnetron characterized in that leads are made to penetrate therethrough. 4. The capacitor according to claim 1, wherein the capacitor has a disk-shaped insulator and electrodes formed by dividing at least one of the two disk-shaped insulators so as to correspond to each of the two cathode leads. A magnetron, characterized in that the disk-shaped insulator is formed with two through-holes for penetrating the two cathode leads, respectively. 5. The capacitor according to claim 4, wherein the capacitor has a disc-shaped insulator and electrodes formed separately on both surfaces of the disc-shaped insulator so as to correspond to each of the two cathode leads. A through hole for penetrating the cathode lead is formed in the insulator of each electrode pair, and one of the electrode pair is electrically connected to the cathode lead. . 6. The magnetron according to claim 5, wherein each of the pair of electrodes formed separately on both surfaces of the disk-shaped insulator is connected to the cathode lead via the terminal plate.