JPH0531796Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention uses a grip-type thermionic emission cathode for an electron beam welding machine, in particular a cylindrical hexaboride cathode chip, to stably obtain a uniform and large current electron beam. This invention relates to a grip-type thermionic emission cathode for electron beam welding machines.

In the present invention, the notch provided in the cathode chip is one having a surface parallel to the central axis of the cathode chip at a position opposite to the central axis on the side surface of the cathode chip.

Conventionally, high melting point metals such as tungsten and tantalum have been used as cathodes for electron beam processing equipment such as electron beam welding machines, electron beam cutting machines, electron beam melting equipment, or electron beam exposure machines, and electron beam analysis equipment such as electron microscopes. However, recently these high melting point metals have been replaced by boride cathodes.

Boride cathodes are excellent cathodes because they have a longer lifespan, higher radiation current density, higher brightness, and better stability than conventional high-melting point metal cathodes. Since the current value obtained at the cathode is relatively small, on the order of several μA to several tens of μA, it is currently not used in all of the above-mentioned devices in some electron beam application equipment.

In the conventional grip type thermionic emission cathode shown in FIGS. 1 and 2, a prismatic LaB ₆ cathode chip 21 is supported with elastic conductivity via prismatic exothermic graphite members 22 and 23. The conductive supports 24 and 25 are pressed by the bodies 24 and 25 and held by surface contact, and the conductive supports 24 and 25 are connected to terminal electrodes,
The exothermic graphite members 22, 23 are energized and heated so that the LaB ₆ cathode chip reaches an operating temperature of 1400 to 1600°C. Therefore, since the cathode chip and the exothermic graphite member are sandwiched by surface contact, the shape of the LaB ₆ cathode chip is preferably a square prism, but this is preferable from the perspective of the emitted electron beam. do not have. The reason for this is that since the electron emitting surface 26 of the cathode chip is square, each corner 27a, 27b, 27 of the end thereof is square.
A strong electric field is concentrated at c and 27d, and the beam shape becomes stronger at the four corners as shown in Figure 3, and the intensity distribution becomes a complicated shape as shown in Figure 4.
This is because a uniform electron beam cannot be obtained.

FIG. 5 shows the cathode chip 21 in FIG. 2, in which the tip of the rectangular prism is formed into a conical shape, and the electron emitting surface 31 is improved into a circular shape, but as shown in FIG. Although the shape is good, the intensity distribution becomes as shown in FIG. 7, and even with this, the influence of the conical surface 32 remains and a uniform electron beam cannot be obtained.

Even when the conventional grasping type thermionic emission cathode shown in Figures 1 to 7 above is used in a welding machine that requires a cathode current value greater than 50 mA, it exhibits sufficiently satisfactory performance. I couldn't.

The present invention aims to solve these drawbacks and provides a grip-type thermionic emission cathode for an electron beam welding machine that can stably obtain a uniform and large-current electron beam. It is something.

That is, the present invention provides a thermionic emission cathode in which a cathode chip and a conductive support are pressed and integrated through a heat-generating graphite member, in which the shape of the cathode chip is cylindrical with a flat electron emitting surface. and a cutout portion having a surface in contact with a plane of the graphite member is formed on the side surface thereof, and the plane of the cutout portion and the plane of the graphite member are connected to each other. This is a grip-type thermionic emission cathode for electron beam welding machines.

The present invention will be further explained in detail below with reference to the drawings.

FIG. 8 is a perspective view of a grip-type thermionic emission cathode for an electron beam welding machine according to an embodiment of the present invention.

As shown in FIGS. 8 and 9, the cathode chip 41
consists of a cylindrical LaB ₆ whose electron-emitting surface is flat, and it is attached to a heat-generating graphite member 4.
2 and 43, a notch 49 is provided so as to be brought into close contact with each other in a plane. Further, the exothermic graphite members 42 and 43 are configured to be pressed by elastic conductive supports 44 and 45 to grip the cathode chip 41.

What is particularly important in the present invention is that the cathode chip uses a cylindrical one with a flat electron emitting surface, and when viewed from the electron emitting surface 46, a prismatic exothermic graphite member is in surface contact with the upper part. In order to do this, a notch having a plane parallel to the axial direction of the cathode chip is provided, and the plane of the notch is brought into contact with the plane of the graphite member and pressed by a conductive support.

In the present invention, the cutout is not only cut to the lower end of the cathode chip as shown in FIGS. 8 and 9, but also a cutout that is large enough to allow the end of the exothermic graphite member to be inserted into the side surface of the cathode chip. It may be a piece with only a notch cut out. By forming the cathode chip into a cylindrical shape with a flat electron-emitting surface, the surface area of the side surface is approximately 80% of that of a prismatic chip, making it possible to reduce the power consumption required for heating by approximately 20%. For example, the power consumption required to heat a conventional 2 mm square x 3.5 m long LaB ₆ prismatic cathode chip to operating temperature was 38 W, whereas
If a cylindrical cathode with a length of 3.5 mm is used, 31 W is enough to heat the device to the operating temperature.

As mentioned above, the cylindrical cathode of the present invention with a flat electron emitting surface is mounted on an electron beam welding machine, and the accelerating voltage is
Beam current value 150mA when used at 50KV
I was able to take it. The shape of the electron beam generated from the tip electron emitting surface 46 of the cathode chip is circular as shown in FIG. 10, and its intensity distribution is homogeneous as shown in FIG. 11. Welding was easy.

In addition, the cathode of the present invention is superior in terms of stability; in contrast to the conventional structure, which simply holds a prism plane, the cathode tip tilts when heated and cooled, causing the electron beam to emit light. However, according to the present invention, since the cathode chip has a notch, the cathode chip and the exothermic graphite member are well engaged, and the inclination of the chip is reduced.

[Brief explanation of the drawing]

1 to 7 show a conventional example, and FIGS. 8 to 11 show an embodiment of the present invention. FIG. 1 is a front view of a conventional gripping type cathode, FIG. 2 is an enlarged perspective view of the cathode chip gripping portion of FIG. 1, and FIG. 3 is a diagram of the shape of the electron beam emitted from the cathode of FIG. 2. Figure 4 is an intensity distribution diagram of the electron beam emitted from the cathode in Figure 2;
Figure 5 is a perspective view of a cathode different from Figure 2, Figure 6 is a diagram of the shape of the electron beam emitted from the cathode in Figure 5, and Figure 7 is the intensity of the electron beam emitted from the cathode in Figure 5. Distribution diagram, FIG. 8 is a perspective view of the grip type thermionic emission cathode for an electron beam welding machine of the present invention, FIG. 9 is a side view of the cathode chip of FIG. 8, and FIG.
FIG. 11 is a diagram showing the shape of the electron beam emitted from the cathode shown in the figure, and FIG. 11 is an intensity distribution diagram of the electron beam emitted from the cathode shown in FIG. Code, 21... Cathode chip, 22, 23... Graphite member, 24, 25... Conductive support,
26...Electron emission surface, 27a, 27b, 27c,
27d... Corner of cathode chip, 31... Electron emission surface, 32... Conical surface, 41... Cylindrical cathode chip, 42, 43... Graphite member, 44, 4
5... Conductive support, 46... Electron emission surface, 49
...Notch.

Claims (1)

[Scope of utility model registration request] In a thermionic emission cathode in which a cathode chip and a conductive support are pressed and integrated through a heat-generating graphite member, the shape of the cathode chip is cylindrical with a flat electron-emitting surface, and the side surface thereof has a cylindrical shape. A grip type heat for an electron beam welding machine, characterized in that a notch is formed with a surface that is in contact with a plane of a graphite member, and the plane of the notch is in contact with the plane of the graphite member. Electron emitting cathode.