JPS6145535A - Magnetron - Google Patents

Abstract

PURPOSE:To improve a filter and reduce high-frequency noise produced by modulation of 60MHz-250MHz low frequencies with fundamental waves by providing an inductance in which a coil is wound around an annular magnetic body in a shield box. CONSTITUTION:A heater electrode 10, feedthrough capacitor 7, inductor, and ceramic support body 9 are provided in a shield box 5 and the inductor is comprised by winding two coils 11 around an annular ferrite 13 that is provided almost on the same axis as the ceramic support 9. In addition, the two coils 11 are wound so that magnetic fields generated from flowing current I1 and I2 can be offset each other. Consequently, a stable and high value of inductance can be obtained to configure a high performance low-pass filter along with the feedthrough capacitor. As a result, the leak of 60MHz-250MHz low frequency noise resulting from the ion oscillation of an electron and such can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the construction of magnetrons. Magnetrons are highly efficient microwave oscillator tubes that are widely used in microwave ovens and the like. A magnetron is a type of traveling wave amplifier, which oscillates not only the fundamental wave but also harmonics at the same time. On the other hand, as seen in satellite broadcasting and the like, systems that utilize weak frequencies in the harmonic region of magnetrons have appeared and are expected to increase in the future.

Therefore, in order for high-frequency heating devices such as microwave ovens to coexist with new media communication systems, magnetrons also need measures to reduce harmonics.

Configuration of conventional example and its problems Figure 1 is an external view of a magnetron. 1 is an antenna that emits microwaves, 2 and 2' are frames for mounting on equipment, 3 and 3' are magnets, and 4 is an A radiation fin 5 formed of an aluminum plate or the like is a shield box that blocks leakage of radio waves from the microwave oscillation power supply section of the magnetron, and is sealed with a lid 6. 7 is a feedthrough capacitor, and 8 is the microwave power supply lead wire (terminal).
It is.

Conventionally, when generating a fundamental wave, an open magnetic path type inductance was used to prevent the leakage of low frequency noise of 60MHz to 250MHz caused by ion vibration of electrons, etc., but due to variations due to installation etc., sufficient performance could not be achieved. Ta.

FIG. 2 shows a conventional example inside the shield box shown in FIG.

A heater electrode 10 is provided on the ceramic support 9, and an inductor having a coil 11 wound around a ferrite rod 12 is provided between the heater electrode and the feedthrough capacitor. In this configuration, the inductor is installed near the shield box made of a magnetic material such as an iron plate, so the magnetic resistance changes depending on the installation distance between the ferrite rod and the shield box.
There was a drawback that a stable inductance value could not be obtained.

Purpose of the Invention The present invention particularly provides a fundamental frequency of 2450 among harmonic components.
The improvement of the low-frequency filter reduces the high-frequency noise generated when the low frequency of 60 MHz to 250 MHz is modulated with the fundamental wave, which is caused by the ion vibration of electrons accompanying the generation of radio waves by the MHz magnetron.

Part 1 of the Invention The present invention improves a filter by providing an inductance in which a coil is wound around an annular magnetic material in a shielding box.

DESCRIPTION OF EMBODIMENTS FIG. 3 shows an embodiment of the present invention. In the present invention, two coils are wound around one annular ferrite 13 provided approximately coaxially with the ceramic support. Another feature is that the coils are wound in a direction that cancels out the magnetic field generated by each coil current.

The magnetic fields generated by the coil currents II and 12 are indicated by arrows A and 12 correspondingly.

According to this configuration, the magnetic resistance is determined by the annular ferrite 13 and is less influenced by nearby magnetic bodies. In addition, the heater current is large and magnetic saturation of ferrite is likely to occur, but by adjusting the winding direction of the coil, the magnetic fields cancel each other out, resulting in a stable inductance value.

Effects of the Invention According to the present invention, in addition to the ability to obtain a stable inductance value and configure a high-performance low-pass filter together with a feedthrough capacitor, the present invention has the following effects.

■ Compared to the conventional open magnetic circuit method, the closed magnetic circuit method makes use of the high relative magnetic permeability of ferrite, which has the effect of saving resources by reducing the number of coil turns and reducing the size of the ferrite.

■ No special insulating support is required because the ferrite can be held in space using the rigidity of the coil.

■　For the same reason as ■, the shield box can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is an external view of a conventional magnetron, FIG. 2 is a diagram showing the inside of a conventional shield box, and FIG. 3 is a diagram showing the inside of a shield box according to an embodiment of the present invention. 5... Shield box, 7... Feedthrough capacitor, 9... Ceramic support, 10...
... Heater electrode, 11 ... Coil, 13 ...
...--Cyclic ferrite. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1

Claims (1)

[Claims] A heater electrode, a feedthrough capacitor, an inductor, and a ceramic support are provided in a shield box, and the inductor is constructed by winding two coils around a ring-shaped ferrite provided approximately coaxially with the ceramic support, and further includes two coils. is a magnetron that is wound so that the magnetic fields generated by flowing current cancel each other out.