JPH0773813A - Magnetron - Google Patents

Abstract

PURPOSE:To reduce the sound pressure generated from the element body of a through type capacitor. CONSTITUTION:A magnetron concerned is equipped with a filter circuit comprising two choke coils 131, whose one-side ends are serially connected with external leadout leads 123, 124 supporting a cathode filament 101, and a through type capacitor 132 to be connected parallel with the other ends of the two choke coils. The through capacitor 132 is configured with an element body of dielectric porcelain material meeting the condition sq. rt. xsiS<=50, where xsiS is dielectric constant. Thereby the sound pressure of sonic waves generated from the element body of through capacitor can be reduced while the required withstand voltage characteristics and electrostatic capacitance are maintained, which can be achieved without enlarging the size of through capacitor constituting the filter circuit.

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 more particularly to a magnetron which suppresses the intensity of vibrating sound, that is, the sound pressure due to elemental electrostriction of a feedthrough capacitor which constitutes the filter circuit. .

[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 is provided with a main body having a resonance cavity, a high frequency output section, and the like, and a filter circuit for suppressing leaked radio waves in a power supply section for supplying electric power to the main body.

The above filter circuit supports two filaments installed inside the resonance cavity, and two choke coils each having one end connected in series to each of the two external lead-outs for supplying electric power to the filament. It is composed of a feedthrough capacitor connected in parallel to the other end of the choke coil.

The feedthrough capacitor penetrates the inside and outside of the housing wall of the filter case that houses the filter circuit and is connected to an external power supply.

As a disclosure of the prior art relating to this type of feedthrough capacitor, Japanese Utility Model Publication No. 57-5650.
No. 4 publication can be cited.

[0007]

A feedthrough capacitor that constitutes a filter circuit provided in a magnetron uses a high dielectric constant porcelain material as its material. During operation of the magnetron, several kV is placed between the terminals of this feedthrough capacitor.
An alternating high voltage of _pp is applied.

Therefore, the porcelain forming the feedthrough capacitor vibrates due to the electrostriction phenomenon and generates a sound wave having a large sound pressure. This sound wave becomes noise and is radiated to the surroundings, which makes the use uncomfortable.

In order to reduce the occurrence of the electrostriction, a material having a low dielectric constant may be used as a material forming the feedthrough capacitor. However, if a material having a low dielectric constant is used as a material,
Since the capacitance becomes small, it is necessary to make the electrode interval of the feedthrough capacitor small or make the electrode area large in order to secure the required capacitance.

However, when the electrode spacing is reduced, the withstand voltage characteristic is deteriorated, and when the electrode area is increased, the size of the feedthrough capacitor itself is increased, which is an obstacle to downsizing the magnetron.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to increase the size of the feedthrough capacitor that constitutes the filter circuit, while maintaining the required withstand voltage characteristics, and from the element body of the feedthrough capacitor. An object of the present invention is to provide a magnetron that reduces the sound pressure of generated sound waves.

[0012]

To achieve the above object, the present invention provides two choke coils each having one end connected in series to each of two external lead-outs for supporting a filament, and each choke. In a magnetron provided with a filter circuit consisting of a feedthrough capacitor connected in parallel to the other end of the coil, the feedthrough capacitor is a dielectric ceramic body of √ξ _s ≤50, where relative permittivity is ξ _s. It is characterized by being configured.

Further, according to the present invention, two choke coils each having one end connected in series to each of the two external lead-outs supporting the filament, and a feedthrough capacitor connected in parallel to the other end of each choke coil are provided. In a magnetron provided with a filter circuit consisting of, the feedthrough capacitor is formed of a dielectric ceramic body of √ξ _s ≦ 50, where the relative dielectric constant is ξ _s, and its capacitance C is 1
It is characterized in that it is set to 00 to 300 pF.

Further, according to the present invention, two choke coils each having one end connected in series to each of the two external lead-outs supporting the filament, and a feedthrough capacitor connected in parallel to the other end of each choke coil are provided. In a magnetron provided with a filter circuit consisting of, when the relative permittivity of the feedthrough capacitor is ξ _s , √ξ _s ≦ 50
Of the dielectric porcelain body, the capacitance C thereof is C = 100 to 300 pF, and the inductance L of the choke coil is L≈1 μH. As the dielectric ceramic body having the relative permittivity √ξ _s ≦ 50, for example, a BaTiO ₃ -based material having √ξ _s ≈70 can be adopted.

The present invention is a so-called inverter power supply for switching the commercial power supply at high speed to obtain a required voltage by a high frequency transformer as the power supply of the magnetron having the above-mentioned structure.
Alternatively, it is characterized by using a rectifier circuit that directly rectifies and boosts the commercial AC power source to generate an anode voltage.

[0016]

With the above-described configuration of the present invention, the feedthrough capacitor element body can be formed while maintaining the required withstand voltage characteristics and the required capacitance without increasing the size of the feedthrough capacitor that constitutes the filter circuit. It is possible to provide a magnetron in which the sound pressure of generated sound waves is reduced.

That is, in the feedthrough capacitor which constitutes the LC filter for suppressing the noise electric wave leaking from the cathode terminal of this type of magnetron, the dielectric porcelain which is the body of the capacitor is provided at the center thereof. The penetrating portion is connected between the high voltage side cathode terminal (lead) and the ground side cathode terminal. Then, the high voltage side cathode terminal and the ground side cathode terminal are separated by an insulating resin.

The dielectric ceramic body constituting the feedthrough capacitor has a high voltage (for example, 4 kV) when the magnetron operates.
_Since an alternating voltage of _pp ) is applied, a sound is generated due to the electrostriction phenomenon of the porcelain body. That is, when an electric field is applied to the dielectric ceramic body, dielectric polarization occurs, and mechanical distortion / vibration causes acoustic noise. It is known that this sound pressure is proportional to the square of the applied electric field strength.

On the other hand, when the electric field strength is constant, the sound pressure is expressed by the following equation.

[0020]

[Equation 1]

Here, S: sound pressure K _P : electromechanical coupling coefficient _fr : resonance frequency D: diameter of dielectric ceramic ξ _O : dielectric constant of vacuum ξ _S : relative dielectric constant of dielectric ceramic P: dielectric ceramic From the above equation, it can be seen that the sound pressure is proportional to the square root of the relative permittivity ξ _S of the dielectric ceramic. That is, in order to suppress the sound pressure due to the electrostriction phenomenon to a low level, a dielectric body having a small relative permittivity ξ _S may be adopted.

On the other hand, when the relative permittivity is reduced, the electrostatic capacity of the capacitor is also reduced. To correct this, the size of the dielectric ceramic is reduced, specifically, the distance between the electrodes of the ceramic body. Or it is necessary to increase the size of the element body so that the size of the element body becomes large so that the electrode area becomes large.

According to the present invention, by adopting the configuration described in the above claims, the required withstand voltage characteristics and the required capacitance can be maintained without increasing the size of the feedthrough capacitor that constitutes the filter circuit. It is possible to provide a magnetron in which the sound pressure of the sound wave generated from the element body of the feedthrough capacitor is reduced.

[0024]

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

FIG. 1 is a sectional view for explaining the structure of one embodiment of a magnetron according to the present invention, in which 2 is a lower magnet, 3 is a lower yoke, 4 is a lower seal part, and 41 is a flange shape of the lower seal part 4. Seal material, 6 is a filter case, 8
Is an input side ceramic, 101 is a cathode filament, 10
2 is an anode vane, 103 is an anode cylinder, 104 is an upper magnet, 105 is a pole piece, 107 is an antenna lead, 108 is an antenna, 109 is an exhaust pipe, 110 is an antenna cover, 111 is a cylindrical insulator, 112 is an exhaust pipe. Supports, 121 is an upper end shield, 122 is a lower end shield, 123 and 124 are cathode leads, 126 is a cathode terminal, 127 is a spacer, 128 is a sleeve, 13
1 is a choke coil, 132 is a feedthrough capacitor, 134
Is a lid, 141 is an upper seal part, 143 is a metal gasket, 144 is an upper yoke, and 145 is a cooling fin.

In the figure, a plurality of anode vanes 102 are radially formed around the cathode filament 101. The plurality of anode vanes 102 is the anode cylinder 1.
No. 03 is fixed by brazing or the like, or is integrally formed with the anode sillunder 103 by extrusion molding or the like.

A cylindrical upper magnet 104 is installed on the upper part of the anode cylinder 103, and a cylindrical lower magnet 2 is installed on the lower part. Magnetic fluxes from the upper magnet 104 and the lower magnet 2 pass through the pole pieces 105. As a result, a necessary DC magnetic field is generated in the vertical direction (tube axis direction) with respect to the working space formed between the cathode 101 and the anode vane 102. The lower yoke 3 and the upper yoke 144 pass the magnetic flux from the magnet.

The cathode filament 101 has a negative high potential (4
kV _PP ). That is, the cathode filament 101 is connected to the choke coil 131 via the two cathode leads 123 and 124, the other end of the choke coil is connected to the feedthrough capacitor 132, and the terminal of the capacitor 132 has a negative high potential. Is connected to a filament transformer (described later).

A dielectric ceramic is used as an element body of the feedthrough capacitor 132, and the material of this dielectric ceramic is a conventional BaTiO ₃ system (√ξ _S ≈70, capacitance C = 50).
0pF) instead of the present invention,
Electrostrictive sound can be suppressed without impairing the characteristics of the LC filter.

In such a structure, the electrons emitted from the cathode filament 101 form a high-frequency potential in each anode vane 102 while oscillating under the influence of a DC magnetic field to oscillate a high frequency (microwave). . The oscillated microwave is transmitted through the antenna lead 107 to the antenna 1
It is output from 08.

FIG. 2 is a plan view showing details of only the anode part of the magnetron shown in FIG.
02 and 102 ′ are provided in the direction of the center O from the inner wall of the anode cylinder 103, and are arranged radially when viewed from the axis passing through the center O.

The anode vanes 102, 102 'are the first strap ring 1 made of two annular bodies having different diameters.
61 and the second strap ring 162 are connected to each other.

FIG. 3 is a perspective view for explaining the strap ring in FIG. 2, and the first strap ring 161 is shown.
Is a strap with a small diameter, and the second strap ring 162 is a strap with a large diameter.

FIG. 4 is an explanatory view of the essential part of the anode vane portion of the magnetron shown in FIG. 1, in which the anode vane 102 is brought into contact with the first strap ring 161 having the small diameter,
The second strap ring 162 having a large diameter does not contact,
In addition, the adjacent anode vanes 102 have a second
Of the first strap ring 161 and the second strap ring 16 are arranged such that the first strap ring 161 having a small diameter is in contact with the first strap ring 161 and the first strap ring 161 having a small diameter is not in contact therewith.
2 are alternately joined to every other anode vane 102.

Further, one of the anode vanes 102 is shown in FIG.
As shown in, the antenna lead 107 for deriving a high frequency is brazed and planted.

The antenna lead 107 set up in the anode vane 102 is inserted through the magnetic pole piece 105 enclosed in one opening side of the anode cylinder 103, and at the end of the seal component 141 which is a metal sealing body. Airtightly sealed cylindrical insulator 1
11 and a cup-shaped exhaust pipe support 112 brazed to the outer circumference of the exhaust pipe 109 is brazed to one end of the cylindrical insulator 111.

The exhaust pipe 109 is vacuum-exhausted inside the magnetron pipe, and then is cut off together with the antenna lead 107.
The antenna cover 110 is press-fitted and fixed to the exhaust support 112 to protect its tip. Here, the recessed portion 109a formed by cutting off the exhaust pipe 109 and the antenna lead 107 serves as a choke portion for blocking unnecessary radio wave radiation.

Cathode filament 101 for generating electrons
In general, tungsten containing a trace amount of thorium oxide (ThO ₂ ) is used. In order to improve electron emission characteristics, a carbonized layer (W ₂ C) is formed on the surface of the cathode.

The cathode 101 is supported by engaging the upper end shield 121 and the lower end shield 122 with a high melting point brazing material such as ruthenium-molybdenum eutectic alloy.

The upper end shield 121 and the lower end shield 122 have cathode leads 123 and 12, respectively.
Supported by 4. These end shields 1
From the viewpoint of heat resistance and workability, molybdenum (Mo) is generally used for 21, 122 and the cathode leads 123, 124.

Further, a getter is attached to the upper surface of the upper end shield to evaporate the getter material when the cathode filament 101 is heated, maintain the vacuum degree of the oscillation space, and maintain stable operation characteristics for a long period of time. To do.

The two cathode leads 123 and 124 are supported by the input side ceramic 8, and the cathode leads 123 and 124 are brazed together with the cathode terminal 126 to the input side ceramic 8 so as to keep vacuum tightness. .

When vibration or shock is applied to the magnetron, the cathode leads 123 and 124 vibrate, and the manner of vibration differs between the cathode leads 123 and 124.
01 may cause mechanical stress to cause the cathode 101 to be disconnected. To prevent this, the spacer 127 is used. Even if the cathode leads 123 and 124 vibrate due to the action of the spacer 127, the movements of the cathode leads 123 and 124 due to the vibration are substantially the same, so that the stress applied to the cathode 101 can be reduced. The sleeve 128 is for supporting the spacer 127 at a predetermined position.

The cathode terminal 126 is connected to the choke coil 131, the choke coil 131 is connected to the feedthrough capacitor 132 to which the filter case 6 of the input section is attached, and the feedthrough capacitor 132 is connected to the power supply. Cathode terminal 126
The choke coil 131 and the choke coil 131 are generally connected by welding. The choke coil 131 and the feedthrough capacitor 132 are also generally connected by welding.

Here, the choke coil 131 and the feedthrough capacitor 132 form a low-pass filter when the power supply side is viewed from the inside of the magnetron. This is the cathode 1
01 generated in the working space between the anode cylinder 103 and the anode cylinder 103, the cathode 101 and the cathode leads 123, 1
This is to prevent radiation to the outside through 24.

FIG. 5 is a plan view of the filter case portion of the input portion of the magnetron shown in FIG.
The choke coil 131 is connected to the cathode terminal 126, the choke coil 131 is connected to the feedthrough capacitor 132 having the input filter case 6 attached thereto, and the feedthrough capacitor 132 is connected to a power supply (not shown).

FIG. 6 is a fragmentary sectional view for explaining the structure of the feedthrough capacitor, in which 151 is an insulating cover, 152 is a dielectric, and 153 and 156 are electrodes.

In the figure, the dielectric 152 is the electrode 15
A capacitor is formed with 3,156. Electrode 156
Has a role of attaching the feedthrough capacitor 132 to the filter case 6. Although the electrodes 153 are shown as separated in the lower left part of the figure, they are integrally connected to the terminal 154 in other cross sections.

Reference numeral 155 denotes a silicon tube, which covers the terminal 154 and plays a role of insulation from the electrode 156, and a cushioning material (damper) for preventing the adhesion between the resin 157 and the dielectric 152 from being impaired. Become. Also, 151a
Is a stopper that has a function of dividing the stress generated in the resin 157 and prevents the resin from moving. And
The terminal 154 is connected to the choke coil 131, and the other end of the choke coil 131 faces the ground via the capacitor.

In this embodiment, a SrTiO ₃ -based high dielectric constant material of √ξs≈42 is used as the dielectric ceramic body constituting the dielectric 152. Since the size of the dielectric porcelain body is the same as the conventional one (BaTiO ₃ system material with √ξs≈70), it does not lead to increase in withstand voltage characteristics and feedthrough capacitor, but the capacitance C is BaTiO 3. _{For 3} series materials,
While it is 500 pF, it is 180 to 300 pF in the case of the SrTiO ₃ based material.

On the other hand, the choke coil which constitutes this LC filter has an inductance L of 1 μH.

As shown in FIG. 1, the cathode leads 123 and 124 are connected in series with one end of the choke coil 131, and the other end of the choke coil 131 faces the ground via the capacitor 132.

The filter case 6 of the input section is sealed by the lid 134 to prevent the high frequency (microwave) from being radiated to the outside.

The input side ceramic 8 is a collar-shaped seal portion 4
Anode cylinder 10 via lower sealing part 4 with
3, which is engaged in a vacuum-tight manner with the output side ceramic 111
The anode cylinder 103 through the upper seal part 141.
It is engaged while maintaining a vacuum tightness.

The upper yoke 144 is electrically connected to the upper seal part 141 via the metal gasket 143. This sealing part 141 is the anode cylinder 10.
It has the same potential as 3. Therefore, the upper yoke 14
4 has the same potential as the anode cylinder 103.

FIG. 7 is a top view of the magnetron. The upper yoke 144 and the lower yoke 3 (FIG. 1) are generally connected by caulking.

FIG. 8 is a side view showing the appearance of the magnetron as seen from the yoke side. The antenna 108 is an upper seal part 141 with a cylindrical insulator 111 interposed therebetween.
It is connected to the antenna lead described in FIG. 1 through 44. Below the lower yoke 3, a filter case 6 is joined and fixed by the structure described in each of the embodiments. Reference numeral 132 is a feedthrough capacitor.

FIG. 9 is a front view for explaining the appearance of the magnetron as seen from the cooling fin side.

The anode of the magnetron becomes high in temperature due to heat radiation from the cathode filament 101 described in FIG. 1 and heat generated by electrons colliding with the cathode vanes 102. 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 145 are for dissipating this heat generation.

FIG. 10 is an explanatory view of the shape of the cooling fin.
(A) is a plan view, (b) is a side view seen from the arrow A direction of (a), (c) is a side view seen from the arrow B direction of (a).

In the figure, the cylindrical portion 145a is fitted with the anode cylinder 103 in FIG. In FIG. 9, FIG.
Five cooling fins shown in are used.

Generally, at the time of operation of the magnetron, a cooling fan installed in an applied device such as a microwave oven
Cooling air is blown to the cooling fins.

FIG. 11 is a circuit diagram for explaining an example of a magnetron drive circuit. In FIG. 11, 231 is a magnetron.

This example uses a so-called inverter power supply, which is a switching power supply for obtaining a required voltage by high-speed switching a commercial AC power supply as a magnetron power supply, and a DC power supply 201 for supplying DC power to the switching power supply 209. Is a commercial AC power source 203 and a full-wave rectifier 2
It is composed of 05.

A filter 207 composed of a reactor and a capacitor is connected to the DC output terminal of the full-wave rectifier 205. This filter 207 is not for smoothing the rectified current, but for high-frequency noise included in the oscillated current. Is prevented from leaking through the AC power supply side, which prevents the propagation of interfering waves.

The switching power supply device 209 includes a transistor 211, and is turned on and off by a drive circuit 241 driven by an on signal of an on signal generation circuit 237 controlled by a synchronization pulse generated by a synchronization pulse generator 235. .

The switching power supply device 209 includes a damper diode 21 connected in antiparallel to the transistor 211.
5 and a resonance capacitor 213 connected in parallel.

This switching power supply device 209 comprises a primary winding 219, secondary windings 221, 223 and 224, 225.
Connected to the step-up transformer 217, the primary winding 219 is connected to the filter 207 via the switching power supply 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 233 detects the load current flowing through the magnetron, and the averaging circuit 249 adds the difference from the set value of the output setter 251 as an average value to the sync pulse from the sync pulse generator 235 via the amplifier 257. It is given to the ON signal generator 237 as a control signal.

The secondary winding 225 is provided for heating the filament of the magnetron 231, and the other secondary winding 223 is for producing a voltage for output feedback, and the waveform is generated by the waveform shaping circuit 243. After being molded, the delay circuit 245 delays the signal for a predetermined time and supplies it as a control signal for the ON signal generation circuit 237.

The secondary winding 224 is supplied to the auxiliary power source 247, rectified and 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.

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

FIG. 12 shows an example of a circuit in which a general commercial power source is used as it is as a magnetron power source. 203 is a commercial AC power source, 217 'is a high voltage transformer, 219' is a primary winding, 221 'and 225' are secondary windings. Line 227 'is a capacitor, 229' is a high voltage diode, 231 is a magnetron.

In the figure, a primary winding 219 'of a high voltage transformer 217' is connected to a commercial AC power source 203, and a secondary winding 221 'is a capacitor 227' and a high voltage diode 2.
29 'is connected to the half-wave voltage doubler rectifier circuit.

The secondary winding 225 'is a magnetron 2
The heater is heated by an electric current that is connected to the heater terminal 31 to apply a required voltage to the heater.

The capacitor 22 of the half-wave voltage doubler rectifier circuit
The connection point between 7'and the high voltage diode 229 'is connected to one of the heater terminals and a negative anode voltage is applied. Then, one of the secondary windings 225 'is connected to the anode of the magnetron 231 and the ground.

The magnetron power source using the general commercial power source 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.

FIG. 13 is a conceptual diagram for explaining a concrete example in which the magnetron of the above-described embodiment according to the present invention is applied to a microwave oven. Reference numeral 301 is a microwave oven cooking chamber, and a heated object 303 is set from a door 302. . 304 is a magnetron, 305 is an antenna, 306 is a magnetron power supply, 3
07 is a cooling fan, 308 is cooling air, 309 is a waveguide,
310 is a stirrer.

In the figure, the microwave generated by the magnetron 304 is supplied from the antenna 305 through the waveguide 309 to the cooking chamber 301 in which the object 303 to be heated is set. The stirrer 310 rotates in the cooking chamber 301 and diffuses microwaves so that the object 303 to be heated is uniformly heated.

The cooling fan 307 is for blowing the cooling air 308 to the magnetron 304 to cool the magnetron 231.

The sound pressure of the feedthrough capacitor in the above-described embodiment of the present invention is 40 dB in the feedthrough capacitor using the conventional BaTi ₃ system material, whereas √ξs
By using the SrTiO ₃ -based material with ≈42, it becomes 24 dB, which can be suppressed to about 60%.

FIG. 14 is an explanatory view showing the measurement result of the terminal noise level of the magnetron using the feedthrough capacitor according to the present invention in comparison with the conventional magnetron, in which a is the noise level of the feedthrough capacitor of the above embodiment. (B) shows the noise level of the feedthrough capacitor using the conventional BaTiO ₃ system, and (c) shows the regulation value by the Electrical Appliance and Material Control Law. As shown in the figure, using the SrTiO ₃ system material of this embodiment, the capacitance C was changed from the conventional value of 500 to 180 to 300 pF.
However, it can be seen that the terminal noise level (a) in the range of the oscillation frequency of 0.5 to 30 MHz exhibits substantially the same characteristics as the conventional (b).

As described above, according to this embodiment, it is possible to obtain a highly reliable magnetron which solves the problems of the prior art.

The present invention is not limited to the structure described in each of the above embodiments, but the optimum relative permittivity ξs for suppressing the electrostrictive sound without impairing the leaky radio wave blocking characteristics of the LC filter.
Needless to say, various modifications can be made without departing from the technical idea of the present invention.

[0086]

As described above, according to the present invention,
A dielectric ceramic body having a relative permittivity √ξ _s ≦ 50 is used as the dielectric material of the feedthrough capacitor, and the inductance forming the LC filter is set to L≈1 μH, so that the required filter characteristics are not impaired. The electrostrictive sound level generated from the feedthrough capacitor of the magnetron can be reduced.

As described above, according to the present invention, it is possible to solve the above-mentioned drawbacks of the prior art and provide a magnetron having an excellent function.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a structural example of one embodiment of a magnetron according to the present invention.

FIG. 2 is a plan view illustrating details of only an anode portion of a magnetron.

FIG. 3 is a perspective view illustrating a strap ring of a magnetron.

FIG. 4 is an explanatory view of a main part of an anode vane portion of a magnetron.

FIG. 5 is a plan view of a filter case portion when the input portion of the magnetron is viewed from below.

FIG. 6 is a fragmentary sectional view illustrating the structure of a feedthrough capacitor of a magnetron.

FIG. 7 is a top view of the magnetron.

FIG. 8 is a side view showing the appearance of the magnetron as seen from the yoke side.

FIG. 9 is an explanatory diagram of cooling fins of the magnetron.

FIG. 10 is an explanatory view of a cooling fin shape of the magnetron.

FIG. 11 is a circuit diagram illustrating a drive circuit example of a magnetron.

FIG. 12 is an example of a circuit in which a general commercial power source is used as it is as a magnetron power source.

FIG. 13 is a conceptual diagram illustrating a specific example in which a magnetron is applied to a microwave oven.

FIG. 14 is an explanatory diagram showing the measurement result of the terminal noise level of the magnetron using the feedthrough capacitor according to the present invention in comparison with the conventional magnetron.

[Explanation of symbols]

 2 Lower magnet 3 Lower yoke 4 Lower sealing part 41 Collar-shaped sealing material of lower sealing part 4 Filter case 8 Input side ceramic 101 Cathode filament 102 Anode vane 103 Anode cylinder 104 Upper magnet 105 Magnetic pole piece 107 Antenna lead 108 Antenna 109 Exhaust pipe 110 Antenna Cover 111 Cylindrical Insulator 112 Exhaust Pipe Support 121 Upper End Shield 122 Lower End Shield 123,124 Cathode Lead 126 Cathode Terminal 127 Spacer 128 Sleeve 131 Choke Coil 132 Through Capacitor 134 Lid 141 Upper Seal Part 143 Metal Gasket 144 Upper yoke 145 Cooling fin.

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[Procedure amendment]

[Submission date] June 30, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Further, according to the present invention, two choke coils each having one end connected in series to each of two external lead-outs for supporting the filament, and a feedthrough capacitor connected in parallel to the other end of each choke coil are provided. consisting of the magnetron having a filter circuit, the feedthrough capacitor, when the relative dielectric constant and ξ _s, √ξ _s ≦ 50
Of the dielectric porcelain body, the capacitance C thereof is C = 100 to 300 pF, and the inductance L of the choke coil is L≈1 μH. As the dielectric porcelain body having the relative permittivity √ξ _s ≦ 50, for example, a SrTiO ₃ system material having √ξ _s ≈42 can be adopted.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0083

[Correction method] Change

[Correction content]

FIG. 14 is an explanatory diagram showing the measurement result of the terminal noise level of the magnetron using the feedthrough capacitor according to the present invention in comparison with the conventional magnetron, where a is the noise level of the feedthrough capacitor of the above embodiment, (B) shows the noise level of the feedthrough capacitor using the conventional BaTiO ₃ system, and (c) shows the regulation value by the Electrical Appliance and Material Control Law. As shown in the figure, using the SrTiO ₃ system material of this embodiment, the capacitance C was changed from the conventional value of 500 to 180 to 300 pF.
As well, the terminal noise level in range of the oscillation frequency 0.5~30MH _Z (a) is seen to exhibit a substantially same characteristics as the conventional (b). In addition, below 100 pF
Then, the terminal noise level becomes large, which causes a problem in use.

Claims (4)

[Claims] 1. A filter comprising two choke coils each having one end connected in series to each of two external lead-outs for supporting a filament, and a feedthrough capacitor connected in parallel to the other end of each choke coil. In a magnetron provided with a circuit, when the feedthrough capacitor has a relative permittivity of ξ _s , √
A magnetron constituted by a dielectric ceramic body of ξ _s ≦ 50. 2. A filter comprising two choke coils each having one end connected in series to each of two external lead-outs supporting a filament, and a feedthrough capacitor connected in parallel to the other end of each choke coil. In a magnetron provided with a circuit, when the feedthrough capacitor has a relative permittivity of ξ _s , √
A magnetron, which is composed of a dielectric porcelain body of ξ _s ≦ 50 and has a capacitance C of 100 to 300 pF. 3. A filter comprising two choke coils each having one end connected in series to each of two external lead-outs supporting a filament, and a feedthrough capacitor connected in parallel to the other end of each choke coil. In a magnetron provided with a circuit, when the feedthrough capacitor has a relative permittivity of ξ _s , √
A magnetron characterized by being constituted by a dielectric porcelain body of ξ _s ≦ 50, having a capacitance C of C = 100 to 300 pF and an inductance L of the choke coil being L≈1 μH. 4. The magnetron according to claim 1, wherein a rectifier circuit for rectifying and boosting a commercial AC power source as it is to generate an anode voltage is used as a power source of the magnetron configured as described above.