JP2612111B2 - Grid type electron gun and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grid type electron gun used for a microwave tube or the like, which can control an electron beam flow, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a diagram showing a conventional grid type electron gun shown in FIG.
FIG. 4 is a longitudinal sectional view of FIG. In the figure, 1 is a cathode that emits an electron beam, 2 is a shadow grid arranged close to the cathode 1, 3 is a control grid that controls the electron beam flow 5, and 4 is an anode that accelerates the beam. The two grids 2 and 3 are formed radially and concentrically from the center and spherically, and are supported outside the circumference. In particular, the shadow grid 2 is welded and fixed at the cathode outer peripheral welding portion 6.

Next, the operation will be described. Thermoelectrons generated from the heated cathode 1 are extracted by an electric field created between the cathode 1 and the control grid 3. The accelerated electron flow passes through the control grid 3 and is further accelerated toward the anode 4, resulting in an effective electron beam current 5. A shadow grid 2 is provided so as to approach the surface of the cathode 1 and create a shadow of the electron flow on the control grid 3 so that the electron flow generated from the cathode 1 does not collide with the control grid 3. ing. Each of the grids 2 and 3 is generally made of a high melting point metal such as molybdenum, and is aligned with high precision.

The amount of the electron beam flow 5 extracted from the cathode 1 is determined by the voltage applied to the anode 4 and the control grid 3 and the arrangement dimensions of the cathode 1, the shadow grid 2, the control grid 3 and the anode 4. You.
In particular, the dimension between the grid and the cathode is important.
Since the shadow grid 2 is arranged at a position very close to the cathode 1, the amount of the electron beam flow 5 changes greatly when the distance from the cathode 1 changes.

[0005]

Since the conventional grid type electron gun is constructed as described above, during operation, the stress due to thermal expansion concentrates on the shadow grid 2 and the control grid 3 toward the center. , Causing deformation and disrupting the electron beam flow. In particular, the shadow grid 2 is the cathode 1
, The temperature rises and it is easy to deform. The deformation occurs in the direction in which the shadow grid 2 moves away from the cathode 1 at the center of the cathode, thereby causing the cathode to be hidden, thereby causing a problem that the amount of the electron beam flow 5 is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a grid-type electron gun in which the deformation of the shadow grid 2 is less likely to occur and a method of manufacturing the same.

[0007]

According to a first aspect of the present invention, there is provided a grid-type electron gun, wherein a grid supported at a peripheral portion by a cathode is further provided on an outer peripheral end thereof with the same material as that of the grid material or with a thermal expansion coefficient. With a fixing metal ring made of a small material.

Further, in the manufacturing method according to the second aspect of the present invention, the fixing metal ring is inserted into the outer peripheral end of the grid by press-fitting and shrink fitting at a high temperature, and then brazed or welded. It is to join.

[0009]

In the grid type electron gun according to the first aspect of the present invention, the outer peripheral end of the grid is fixed by a fixing metal ring made of a material having the same or a smaller coefficient of thermal expansion as the material of the grid. Slightly, the deformation of the shadow grid in the direction away from the cathode does not occur, and even if it occurs, the deformation is in the direction in which the shadow grid 2 and the cathode 1 approach. For this reason, a grid-type electron gun having stable characteristics can be obtained.

Further, according to the method of the present invention, the press-fitting and shrink-fitting at a high temperature eliminates the loosening of the fixing metal ring at a high temperature and reduces the thermal stress in the outward direction of the grid. It can be pressed down, and the fixing metal ring is joined to the grid and the cathode by brazing or welding, so that the holding of the grid by the fixing metal ring is ensured.

[0011]

【Example】

Embodiment 1 FIG. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a cathode, 2 denotes a shadow grid, and a cathode outer peripheral welding portion 6 is welded and fixed. 7a is a fixing metal ring brazed to the outer peripheral end of the grid 2. 3 is a control grid for controlling the electron beam flow 5, 4 is an anode, and 8 is a beam forming electrode.

The inner diameter of the fixing metal ring 7a is slightly (several μ) larger than the outer diameter of the outer peripheral end of the shadow grid 2.
The fixing metal ring 7a is assembled at a high temperature with the shadow grid 2 inserted, and then fixed by brazing or welding. The material of the fixing metal ring 7a is the same molybdenum as that of the shadow grid 2, or a material having a smaller thermal expansion coefficient than molybdenum.

Next, the operation will be described. Thermions generated from the heated cathode 1 are extracted by an electric field created between the cathode 1 and the control grid 3. The accelerated electron stream passes through the control grid 3 and is further accelerated toward the anode 4, resulting in an effective electron beam stream 5. The shadow grid 2 has a role of forming a shadow of the electron flow on the control grid 3 by approaching the surface of the cathode 1 so that the electron flow generated from the cathode 1 does not collide with the control grid 3.

Although the thermal deformation in the shadow grid 2 leads to a change in the electron beam flow 5, a fixing metal ring made of a material having the same or a smaller coefficient of thermal expansion as the material of the grid, for example, tungsten, is provided on the outer peripheral end thereof. 7a is fixed, the thermal deformation is small, the deformation of the shadow grid in the direction away from the cathode does not occur, and even if it occurs, the deformation is in the direction in which the shadow grid 2 and the cathode 1 approach each other. The grid type electron gun has stable characteristics without a decrease in the beam flow 5.

The inner diameter of the fixing metal ring 7a is
The outer diameter of the shadow grid 2 is smaller than the outer diameter of the outer peripheral edge by several μm and is shrink-fitted. Even if the shadow grid 2 becomes hot during use, this relationship does not change. By joining the fixing metal ring 7a, the grid 2 and the cathode 1, the holding of the grid 1 by the fixing metal ring 7a is ensured.

Embodiment 2 FIG. Further, in the above embodiment, the case where the fixing metal ring 7a is provided only in the shadow grid 2 has been described. However, as shown in FIG. 2, the control grid 3 is also made of a material having the same or smaller thermal expansion coefficient than the grid material. With the fixing metal ring 7b made of, for example, tungsten, both grids 2 and 3
Thermal deformation is small, and no deformation occurs in the direction in which both grids 2 and 3 move away from the cathode.
3 and the cathode 1 are deformed in the approaching direction, and a grid type electron gun with more stable characteristics can be obtained.

[0017]

As described above, according to the first aspect of the present invention, since the fixing metal ring is provided at the outer peripheral end of the grid, the shadow grid is prevented from being deformed by thermal stress in the direction away from the cathode. Thus, there is an effect that a highly reliable grid type electron gun having stable characteristics can be obtained.

According to the second aspect of the present invention, the fixing metal ring is inserted into the outer peripheral end of the grid by press fitting and shrink fitting at a high temperature and brazed or welded.
The above effects are further ensured.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a grid type electron gun according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a grid type electron gun according to another embodiment of the present invention.

FIG. 3 is a partially sectional perspective view showing a conventional grid-type electron gun.

FIG. 4 is a longitudinal sectional view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cathode 2 Shadow grid 4 Anode 7a Metal ring for fixing (for shadow grid) 7b Metal ring for fixing (for control grid)

Claims (2)

(57) [Claims] 1. A cathode having a spherical electron emission surface, a plurality of grids disposed at a predetermined distance from the cathode, and beams respectively disposed at a predetermined distance from the grid. In a grid-type electron gun including a molded electrode and an anode, the grid-type electron gun is made of a material having the same or a smaller coefficient of thermal expansion as the material of the grid, and a shadow grid or another grid of the plurality of grids is fixed at an outer peripheral end. A grid-type electron gun, comprising: a metal ring for fixing. 2. A step of inserting the metal ring for fixing into the outer peripheral end of the grid by press-fitting and shrink fitting at a high temperature, and connecting the metal ring for fixing, the grid and the cathode by brazing or welding. And a joining step.