KR20000025074A - Cathode structure of microwave oven magnetron - Google Patents

Abstract

PURPOSE: A cathode is provided to reduce a thermal deformation despite a temperature gradient by mounting a plate of a Mo material having a thermal expansion coefficient inside a cathode. CONSTITUTION: A heater generates heat with an application of an electric power. A cathode (80) is adjacently disposed to the heater. A first grid is adjacently disposed over the cathode(80). An input cavity is surrounded by a choke structural body mounted between the cathode(80) and the first grid. An output cavity is surrounded by a second grid mounted over an anode and the first grid. A radiation part is formed on the output cavity to radiate a microwave. The cathode(80) is structured with a first Ni plate(81), a first Mo plate(82), a second Mo plate(83), and a second Ni plate(84).

Description

Gritron cathode of microwave generator for microwave oven

The present invention relates to ultra-high frequency oscillators for microwave ovens, and more particularly, to the structure of a gritron cathode.

The microwave oven uses a magnetron driven by a high voltage of 4KV as an ultra-high frequency oscillator. This magnetron is a kind of bipolar vacuum tube that generates microwaves, the structure of which is shown in FIG.

That is, as shown in FIG. 1, the magnetron is provided with a power input unit, a heater, an input cavity and an output cavity, and a feedback rod in a filter box covered with a lower portion thereof, and an antenna in the anode is installed in a bracket. The inside of the filter box and the antenna part of the anode are designed to maintain a vacuum.

Here, the cathode is disposed on the upper surface of the heater to be heated to a high temperature as the heater generates heat to emit hot electrons.

The input cavity is a space surrounded by a cathode, a first grid, and a choke structure. The cathode is a ring-shaped disk having a hole formed in the center thereof, and the first grid disposed at regular intervals on the top of the cathode is applied with a bias voltage. Electrons emitted from the cathode are controlled and connected to the input cavity.

In this case, the choke structure is disposed between the cathode and the first grid because the first grid and the cathode are electrically insulated, that is, the direct current must be shielded, and the surface current forming the microwave inside the input cavity must be energized. .

On the other hand, the output cavity disposed in the upper portion of the input cavity is installed so as to face the upper portion of the first grid of the input cavity, the second grid that the surface current is induced while electrons passing through the first grid and protrudes downward from the bottom surface It refers to a space surrounded by the formed anode. In this space, electrons focused on the input cavity are densely modulated, accelerated by the potential difference between the first and second grids, and microwaves are formed by the surface current induced in the second grid. A plurality of cooling fins are stacked on the anode for dissipating the decelerated electron beam to radiate heat.

The first grid and the second grid are made of metal and have the same shape as the cathode corresponding to the cathode, and a plurality of slots cut along the radial direction from the center are formed at predetermined intervals along the circumferential direction.

Therefore, the electrons connected to the input cavity are densely modulated by the automatic shielding function of the bias power of the first grid to pass through the first grid, and when an operating voltage is applied between the input and output cavities that are insulated from each other, a potential difference is generated therebetween. As a result, electrons passing through the first grid are accelerated to pass through the second grid so that surface current flows through the output cavity.

As a result, microwaves are formed in the output cavity, which passes through the center of the anode and radiates through an antenna provided in the output cavity. For this purpose, the antenna coupling end is located in the output cavity.

Meanwhile, a feedback rod for feeding back a part of the microwaves formed in the output cavity to the input cavity is installed at the center between the input and output cavities to amplify and resonate the power of the microwave.

The magnetron as described above has a cathode made of a Ni plate, and an activation material is coated on the upper surface. Therefore, the cathode rises to about 850 ° C. at the electron emission surface at the electron emission surface, and becomes relatively lower than 750 ° C. at both ends, so that a temperature gradient occurs between the electron emission surface and the tip.

Therefore, when the magnetron is operated for a long time, a problem occurs that the cathode is thermally deformed by the temperature gradient. This is because the cathode has Ni with a thermal expansion coefficient of 17.3 × 10 ⁻⁶ mm / mm · ° C.

As such, when the cathode is thermally deformed to come into contact with the grid, the cavity is deformed to change the resonant frequency and the electromagnetic field, resulting in a defect in which microwaves are not generated.

Accordingly, the present invention has been made to solve the problem of the cathode of the conventional magnetron, the object of the present invention is to provide a structure of the gritron cathode to prevent malfunction by reducing the amount of thermal strain to facilitate the emission of electrons and the cavity. .

The present invention for achieving the above object is laminated to the first grid and the cathode adjacent to the first grid in a multi-layered plate, the inner layer plate is made of a material with a low coefficient of thermal expansion, the outer plate to cover the activation It is possible that this material is made of Ni material.

Therefore, the present invention is to prevent or suppress the deformation of the entire cathode because the plate of the inner layer constituting the cathode has a low coefficient of thermal expansion due to the small coefficient of thermal expansion.

1 is a cross-sectional view of a conventional microwave oven for microwave oven,

2 is an enlarged view of a portion “A” of FIG. 1;

3 is a cross-sectional view showing the structure of a gritron cathode according to the present invention.

※ Explanation of code for main part of drawing

10: power input unit 20: heater

30: input cavity 40: output cavity

50: feedback rod 60: anode

70: antenna 80: cathode

81,84: Ni plate 82,83: Mo plate

90: first grid 100: second grid

110: choke structure

Hereinafter, the structure of the cathode 80 of the ultra-high frequency oscillator according to the present invention will be described in detail with reference to the accompanying drawings.

Ultra-high frequency oscillator according to the present invention, as shown in Figure 1, the power input unit 10, the heater 20, the input cavity 30 and the output cavity 40, the feed back in the filter box covered with a lower cover The rod 50 is installed, and the antenna 70 in the anode 60 is installed in the bracket. The inside of the filter box and the antenna part of the anode are designed to maintain a vacuum.

Here, the cathode 80 is disposed on the upper surface of the heater 20 to be heated to a high temperature as the heater 20 generates heat to emit hot electrons.

As shown in FIG. 3, the cathode 80 is formed by sequentially stacking a plurality of plates. In other words, the first Ni plate 81, the first Mo plate 82, the second Mo plate 83, and the second Ni plate 84 are laminated and joined from each other in the bottom portion.

Accordingly, the Mo plates 82 and 83 have a relatively smaller coefficient of thermal expansion than the Ni plates 81 and 84, so that the temperature gradient generated between the center and the tip during electron emission is reduced, resulting in less thermal deformation and thus the Ni plate in the outer layer. It is to prevent thermal deformation.

The input cavity 30 is a space surrounded by the cathode 80, the first grid 90, and the choke structure 110, and the cathode 80 has a multi-layered shape with a ring having a hole formed in the center thereof. The first grid 90 disposed at regular intervals above the cathode 80 is applied with a bias voltage to control and connect electrons emitted from the cathode 80 to the input cavity 30.

In this case, the first grid 90 and the cathode 80 are electrically insulated, that is, the direct current must be shielded, and the surface current forming the microwaves in the input cavity 30 must be energized. 110 is disposed between the cathode 80 and the first grid 90.

Meanwhile, the output cavity 40 disposed above the input cavity 30 is installed to face the upper portion of the first grid 90 of the input cavity 30 so that electrons passing through the first grid 90 pass through the surface. It refers to a space surrounded by the second grid 100, from which current is induced, and an anode on which protrusions projecting downward from the bottom surface are formed. In this space, the electrons focused on the input cavity 30 are densely modulated and accelerated by the potential difference between the first grid 90 and the second grid 100, and by the surface current induced in the second grid 100. Microwaves are formed. A plurality of cooling fins are stacked on the anode for dissipating the decelerated electron beam to radiate heat.

The first grid 90 and the second grid are made of metal and have the same shape as the cathode 80 corresponding to the cathode 80, and a plurality of slots cut along the circumferential direction at a predetermined interval along the circumferential direction are formed. It is formed.

Therefore, the electrons connected to the input cavity 30 are densely modulated by the automatic shielding function of the bias power supply of the first grid 90 to pass through the first grid 90, where the input and output cavities 30 and 40 are insulated from each other. When an operating voltage is applied therebetween, a potential difference is generated therebetween, and electrons passing through the first grid 90 are accelerated to pass through the second grid 100 so that a surface current flows in the output cavity 40.

As a result, microwaves are formed in the output cavity 40 and the microwaves penetrate through the center of the anode and are radiated through an antenna provided in the output cavity 40. To this end, the antenna coupling end is located in the output cavity 40.

On the other hand, in the center between the input and output cavities 30 and 40, a feedback rod 50 for feeding back part of the microwave formed in the output cavity 40 to the input cavity 30 is installed to amplify and resonate the power of the microwave .

As described above, the ultra-high frequency oscillation apparatus of the present invention is provided with a plate made of Mo material having a low coefficient of thermal expansion inside the cathode, so that even if a temperature gradient occurs between the center and both ends, the thermal strain is reduced, thereby reducing the amount of cathode deformation. The failure of contacting the grid will not occur.

Claims (1)

A power source input unit 10, a heater 20 for generating heat by receiving power from the power source input unit 10, a cathode 80 disposed adjacent to the heater 20, and a cathode disposed adjacent to the cathode 80; An input cavity 30 which is surrounded by a first grid 90, a choke structure provided between the cathode 80 and the first grid 90, and a second grid provided on the anode and the first grid 90 ( Part of the microwave formed in the output cavity 40 is installed between the output cavity 40 surrounded by the 100, the radiating means for radiating the microwave formed in the output cavity 40 and the input and output cavity (30, 40) In the microwave microwave tube including a feedback means for feeding back to the input cavity 30, The cathode 80 is a microwave oven, characterized in that the first Ni plate 81, the first Mo plate 82, the second Mo plate 83, the second Ni plate 84 is sequentially stacked The cathode structure of the microwave oscillator tube.