JPH0221539A - Cathode composition for magnetron - Google Patents

Abstract

PURPOSE:To reduce the amount of micro liquid component leaking out of the device by making a resonance element act as a resonance type filter of a high impedance to a specific component. CONSTITUTION:At the middle parts of a pair of lead wires 4 and 5, a resonance element 16 to surround the parts is provided. The resonance element 16 consists of a ring-form body 17 of a high dielectric constant, an inner side conductive film 18 provided on the inner peripheral surface, and an outer side conductive film 19 provided on the outer peripheral surface, and a part of the outer side conductive film 19 is soldered to a metal tube body 7. As a result, the ring-form resonance element 16 acts as a resonance type filter of a high impedance. Consequently, a specific high-frequency component of the leaking micro liquid can be trapped selectively and attenuated, and the filter circuit can be simplified by utilizing the electrostatic capacity of the resonance element 16.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a cathode structure of a magnetron used in microwave heating equipment such as a microwave oven.

2. Description of the Related Art Generally, a magnetron used in microwave heating equipment such as a microwave oven has a cathode structure as shown in FIG. This cathode structure includes a spiral cathode body 1 made of thorium tungsten, a pair of metal end hats 2 and 3 provided at both ends thereof, and each end hat 2,
A pair of lead wires 4 and 5 extending from 3, an insulator 6 that forms a stem together with the lead wires 4 and 5, and an insulator 6
and an eyelet-shaped metal tube body 7 whose one open end surface is brazed. The flange portion 7a on the other open end surface of the metal tube body 7 is hermetically sealed to the anode tube body 9 so as to cover the magnetic pole piece 8 provided thereon.

On the other hand, one end of a choke coil 11 is connected to each of a pair of cathode terminals 10 attached on the outer end surface of the insulator 6, and the other end of each choke coil 11 is connected to a feedthrough capacitor 12 having a high withstand voltage. It is connected to the center electrode 13. Then, the metal shield case 14 with the capacitor 12 fixed to the side wall is connected to the insulator 6 and the choke coil 1.
Covers 1. Reference numeral 15 indicates a yoke constituting the external magnetic circuit.

In the magnetron configured in this way, L is configured by a choke coil 11 and a capacitor 12.
Since the C filter circuit and the shield case 14 prevent the microwave components leaked through the lead wire 4.5 from leaking out of the device, it is possible to prevent communication interference due to the leaked microwaves.

Problems to be Solved by the Invention However, since the leaked microwave contains several harmonic components that are considered to be the fundamental wave component of the excavated microwave, it is difficult to reliably and efficiently prevent these leaks from outside the device. is extremely difficult. In addition, the LC filter circuit is held at cathode potential and the shield case is held at anode potential (ground), so when using a particularly long choke coil, a relatively large shield case is required to prevent sparks between the two. These have become a factor that hinders miniaturization and cost reduction of the device.

Means for Solving the Problems A cathode assembly according to the present invention includes a spiral cathode body, a pair of end hats provided at both ends of the cathode body, a pair of lead wires extending from each end hat, and a spiral cathode body. an insulator that forms a stem together with the lead wire; a metal tube having one open end surface hermetically sealed to the insulator and a flange portion to be sealed to the anode cylinder body on the other open end surface; and a resonant element coupled to the lead wire at least in a high frequency manner. The resonant element includes a ring-shaped high dielectric constant material located within the metal tube and through which the lead wire is inserted, and at least a pair of conductive films attached to both end surfaces or inner and outer circumferential surfaces of the high dielectric constant material. It consists of

Function: In the cathode structure configured in this manner, the specific component of the microwave that is about to leak to the stem side through the lead wire resonates with the resonant element and is attenuated. Since it acts as a high impedance resonant filter, it is possible to reduce microwave components leaking out of the device through the stem. Further, by utilizing the capacitance of the resonant element, it is possible not only to downsize or eliminate the feedthrough capacitor of the LC filter circuit, but also to downsize the shield case.

Embodiments Next, the present invention will be explained along with embodiments shown in the drawings.

The cathode structure shown in FIG. 1 differs from the conventional cathode structure shown in FIG. 15 in that a resonant element 16 surrounding the core is provided at the midsection of each of the pair of lead wires 4.5. be. As shown in FIG. 2, the resonant element 16 includes a ring-shaped high dielectric constant material 17 and an inner conductive film 18 attached to its inner peripheral surface.
and an outer conductive film 19 attached to the outer peripheral surface, and a portion of the outer conductive film 19 is brazed to the metal tube body 7. The high dielectric constant body 17 is made of ceramic having a dielectric constant ε of 30 to 90, and the pair of conductive films 18 and 19 are made of a two-layer structure in which a plating layer is provided on a metallized layer. In addition, the inner conductive film 18 does not contact and is separated from the lead wire inserted through the resonant element, but is coupled to the lead wire in terms of high frequency.

In the embodiment shown in FIG. 3, the inner conductive film of the resonant element 16 is brazed to a lead wire inserted through the resonant element, and the outer conductive film is separated from the metal tube 7.

Further, in the embodiment shown in FIG. 4, the inner conductive film of the resonant element 16 is separated from the lead wire inserted through the resonant element, and the outer conductive film is connected to the metal tube through the metal piece 20. 7 is connected. Furthermore, in the embodiment shown in FIG. 5, the inner conductive film of the resonant element 16 is connected to the lead wire inserted through the resonant element via the metal tube 21, and the outer conductive film is connected to the metal tube body 7. Separated.

In either configuration, the specific component of the microwave that leaks from the resonant cavity inside the anode cylinder to the stem insulator 6 side using the lead wire 4.5 as a transmission path is resonated and trapped by the resonant element 16, and is attenuated. I will do it. However, as mentioned above, leakage microwaves contain fundamental wave components and several-order harmonic components, so it is of course necessary to use a resonant element with characteristics (size) that correspond to the wavelength of the component you want to attenuate. be.

In the embodiment shown in FIG. 6, a resonant element 22 formed as shown in FIG. 7 is incorporated. The resonant element 22 consists of a ring-shaped high dielectric constant body 23 and conductive films 24 and 25 attached to one end face and the other end face of the ring-shaped high dielectric constant body 23. The conductive film 24 on the upper face is connected to the lead wire through a metal piece 26. The conductive film 25 on the lower surface is connected to the metal tube body 7 via a metal plate 27.

In this case, the resonant element 22 is connected to the lead wire and the metal tube in a direct current manner, so it provides the same attenuation effect as described above to the leaking microwaves, and its capacitance acts as a capacitor. As a result, conventional feedthrough capacitors can be downsized or eliminated.

In the embodiment shown in FIG. 8, a resonant element 22 provided on the inner surface of the stem insulator 2 is coupled to the lead wire at high frequency. In the embodiment shown in FIG. 9, the conductive film on the upper surface of the resonant element 22 is hermetically brazed to the lead wire through the eyelet-shaped metal piece 28, and the conductive film on the lower surface is connected to the metal tube 7. The stem insulator 6 is airtightly brazed to the stem insulator 6 via a metal plate 29. In this case, the lead wire extension portion is hermetically sealed on the inner surface of the stem insulator 6, so in addition to the above-mentioned effects, the seismic support strength of the cathode body can be increased.

In the embodiment shown in FIG. 10, three resonant elements 2 stacked in three stages are used to increase the attenuation rate of leaked microwaves.
2 is arranged around each lead wire, and the conductive film on the upper surface of the uppermost resonant element is connected to the lead wire via a metal piece 30.
The conductive film on the lower surface of the lowest resonant element is connected to the metal tube 7 via a metal plate 31. Furthermore, in the embodiment shown in FIG. 11, three resonant elements 22a having different outer diameters and plate thicknesses are used.
, 22b, and 22c are stacked in three stages, so various components of the leaked microwave can be trapped and attenuated.

In the embodiment shown in FIG. 12, a conductor 32 is interposed between two resonant elements 22 stacked in two stages, and this conductor 32 is brought into contact with the lead wire, while the lower resonant element The conductive film on the lower surface is connected to the metal tube body 7 via a metal plate 31.

The resonant element 33 in the embodiment shown in FIG. 13 is composed of a high dielectric constant material 35 having two through holes 34a and 34b, and conductive films 36 and 37 attached to both end faces of the high dielectric constant material 35, and one through hole. The lead wire 4 is connected to 34a, and the lead is connected to the other through hole 34b! s5 are inserted through each other.

The resonant element 38 in the embodiment shown in FIG.
．． 41, and a pair of lead wires 4,
5 is inserted through it.

Effects of the Invention Since the present invention is configured as described above, the ring-shaped resonant element acts as a high-impedance resonant filter, and selectively traps and attenuates specific high-frequency components of leaked microwaves. be able to. In addition, by using the capacitance of the resonant element, it is possible not only to downsize or eliminate the feedthrough capacitor in the LC filter circuit, but also to downsize the shield case due to the simplification of the filter circuit. becomes.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a cathode structure in which the present invention is implemented, FIG. 2 is a partially cutaway perspective view of a resonant element incorporated in the cathode structure, and FIGS. 3 to 6 are respectively other embodiments of the present invention. FIG. 7 is a partially cutaway perspective view showing other shapes of the resonant element, and FIGS. 8 to 12 are side sectional views of essential parts of other embodiments of the present invention. , Figures 13 and 14
The figures are respectively perspective views of main parts of other embodiments of the present invention, and
FIG. 5 is a side sectional view showing a conventional cathode assembly and its attached circuit members. 1... Cathode body, 2.3... End hat, 4゜5... Lead wire, 6... Stem anode insulator, 7... etc. Figure ku ku ku size Q tsuha-11 fufne 2.3--1en y haso Y Complete diagram @IQ diagram Figure 14

Claims (1)

[Claims] A spiral cathode body, a pair of end hats provided at both ends of the cathode body, a pair of lead wires extending from each end hat, an insulator that forms a stem together with the lead wires, and the same insulator. a metal tube body having one open end face hermetically sealed to the body and a flange portion to be sealed to the anode cylinder body on the other open end face; and a resonant element coupled at least in a high frequency manner to the lead wire. The resonant element comprises a ring-shaped high dielectric constant material located within the metal tube and through which the lead wire is inserted, and at least A cathode assembly for a magnetron characterized by comprising a pair of conductive films.