JPH0237647A - Lc filter structure for magnetron - Google Patents

Abstract

PURPOSE:To miniaturize a shield case by providing a pair of capacitors using the side wall of the case as one electrode and two conductive plates juxtaposed on the inner surface of the side wall through dielectric layers as the other electrodes, and extending the respective conductive plates in overlapped relation via the dielectric layers. CONSTITUTION:On the inner surface of the side wall 1a of a shield case 1, first and second conductive plates 12 and 13 are juxtaposed through dielectric layers 10 and 11, thereby constituting first and second capacitors using the side wall 1a as one electrode and the plates 12 and 13 as the other electrodes. The first and second conductive plates 12 and 13 have extending portions 12a and 13a in overlapped relation via dielectric layers 16 and 17. Accordingly, there are provided a third capacitor between the extending portion 12a of the plate 12 and the plate 13, and a fourth capacitor between the extending portion 13a of the plate 13 and the plate 12 so that the third and fourth capacitors are connected in parallel with the first and second capacitors. Therefore, the capacitors with a relatively large electrostatic capacity can be constituted, and yet the shield case can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to an LC filter structure used in microwave heating equipment such as a microwave oven, in other words, to prevent microwaves leaking from a resonance cavity of a magnetron through a lead wire for leading out a cathode terminal. This invention relates to an LC filter structure for a magnetron for preventing equipment leakage.

BACKGROUND ART In general, the above-mentioned LC filter structure consists of a shield case that is attached to a frame-shaped yoke constituting the external magnetic circuit of a magnetron and held at an anode potential, and a pair of LC filters housed within the shield case. It consists of a choke coil and a pair of feedthrough capacitors attached to the side wall of the shield case, and the cathode filament of the magnetron reaches a cathode heating power source via the choke coil and the center electrode of the feedthrough capacitor. Since the outer electrode of the capacitor is connected to the shield case, the filter circuit in which the magnetron is T1, the capacitor is 01, and the York coil is L has the wiring shown in FIG.

The capacitor of such an LC filter structure was developed in U.S. Pat.
By using a configuration such as that disclosed in Japanese Patent No. 09261, etc., it is possible to reduce costs and downsize the shield case. In the capacitor in this case, as shown in FIG. 5, the side wall 1a of the shield case 1 serves as one electrode, and first and second conductive plates are arranged in parallel on the inner surface of the side wall 1a with a dielectric layer 2 in between. 3.4 becomes the other electrode, and the first and second conductive plates 3, 4 are connected to the side wall 1.
A is connected to a pair of lead wires 5 and 6 that pass through A without touching each other, and one end of each lead wire and the magnetron 7 are connected to each other.
A choke coil 9 is connected between the cathode terminal 8 and the cathode terminal 8 .

Problems to be Solved by the Invention However, when trying to obtain a capacitor with a capacitance comparable to a conventional feedthrough capacitor with such a configuration, the side wall area of the shield case cannot be reduced much, and it is difficult to miniaturize the shield case. subject to restrictions. Therefore, an object of the present invention is to provide an LC filter structure that can constitute a capacitor with a relatively large capacitance while utilizing the side wall of a relatively small shield case.

Means for Solving the Problems According to the present invention, the (11I!) wall of the shield case to be connected to the anode of the magnetron is used as one electrode, and the a pair of capacitors having first and second conductive plates as other electrodes;
a pair of lead wires that penetrate the shield case without contacting the case and are respectively connected to the first and second electrodes; and a pair of lead wires that are located within the shield case and have one end connected to the pair of lead wires; and a pair of choke coils each having its other end connected to the cathode filament of the magnetron,
Each of the first and second conductive plates has extended portions that overlap each other with a dielectric layer interposed therebetween.

Effect With this configuration, in addition to the first and second capacitors having the side wall of the shield case as one electrode and the first and second conductive plates as the other electrode, the first conductive plate serves as one electrode. Third and fourth capacitors each having a second conductive plate as an electrode are laminated, and the third and fourth capacitors are connected in parallel to the first and second capacitors. Therefore, it is possible to achieve both the configuration of the LC filter circuit having a relatively large capacitance and the miniaturization of the shield case.

Example Next, the present invention will be explained with reference to embodiments shown in the drawings.

As shown in FIG.
The first and second conductive plates 12.13 are arranged in parallel with 0.11 in between, and the side wall 1a is used as one electrode, and the first and second conductive plates 12.
The first and second conductive plates 12 and 13 are the other electrodes.
The first and second conductive plates 1 are connected to the point where the capacitor is formed and to the pair of lead wires 14 and 15 that pass through the side wall 1a of the shield case 1 without contacting the same case 1.
2, 13 are connected to each other, and each lead wire 14.
15 are connected to the cathode terminals of the magnetron via choke coils 9, as in the conventional case. However, the first and second conductive plates 12.13, as shown in FIG. Different from the configuration.

In such a configuration, the extension portion 12 of the first conductive plate 12
A third capacitor is formed between the extension portion 13a of the second conductive film 13 and the first conductive plate 12, and a fourth capacitor is formed between the extension portion 13a of the second conductive film 13 and the first conductive plate 12. When the first and second capacitors are C and the third and fourth capacitors are Cs, an LC filter circuit with connections as shown in FIG. 3 is obtained, and the third and fourth capacitors are
The first and second capacitors are connected in parallel.

Effects of the Invention As described above, according to the present invention, a capacitor with a relatively large capacitance can be constructed while utilizing the side wall of a relatively small shield case, thereby reducing the cost of filter circuit components and downsizing the shield case. can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view of an LC filter device embodying the present invention, Fig. 2 is a perspective view of the main parts of the device, Fig. 3 is an equivalent circuit diagram of the device, and Fig. 4 is a conventional magnetron. FIG. 5 is a partially cutaway perspective view of the LC filter device. 1...Shield case, 1a...Side wall, 9...Choke coil, 10, 11.16.
17...Dielectric layer, 12a, 13a...
・Extension part. Name of agent: Patent attorney Shigetaka Awano and one other famous sword (A1 Figure on the sticker -1-7 Head tumor)

Claims (1)

[Claims] A pair of electrodes, in which the side wall of the shield case to be connected to the anode of the magnetron is used as one electrode, and the first and second conductive plates arranged in parallel on the inner surface of the side wall with a dielectric layer interposed therebetween are used as the other electrode. a capacitor, a pair of lead wires that pass through the shield case and are connected to the first and second electrodes, respectively, without contacting the shield case; and a pair of lead wires that are located inside the shield case and connected to the pair of lead wires. One end,
and a pair of choke coils whose other ends are respectively connected to the cathode filament of the magnetron, and the first and second conductive plates each have extension portions that overlap each other via a dielectric layer. An LC filter structure for a magnetron characterized by: