JPH0680244U - Cathode structure - Google Patents

Abstract

(57) [Summary] [Purpose] To speed up the starting of electron tubes and the like, and to save the power used for cathode heating means. [Structure] Radiant heat from a cathode or a heating means for the cathode is reflected by a heat shield plate having a curved surface to reach the cathode.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a cathode assembly used for an electron tube or the like.

[0002]

[Prior art]

 Conventionally, there has been a cathode assembly of this type as shown in FIG. Fig. 4 shows a schematic cross-section of what is used in a general electron tube. Reference numeral 1 is a cathode, for example, a porous tungsten sintered body, in which an electron emissive material composed of a mixture of barium oxide, calcium oxide, aluminum oxide, etc. is melted. It is formed by impregnation. Reference numeral 2 is a heater for heating the cathode, and 3 is a cathode sleeve for supporting the cathode 1 and housing the heater 2 therein, which is made of Mo (molybdenum), Re (rhenium), or the like.

Although not shown, the cathode 1 is directly brazed to the cathode sleeve 3 with a high melting point alloy raw material such as Mo-Ru (molybdenum-rudenium) or Mo-Ni (molybdenum-nickel). Or, after brazing the cathode 1 to a cap (not shown), the cap is welded to the cathode sleeve 3 by resistance or laser. Such a cathode assembly is placed in an airtight container (not shown) containing vacuum or gas, with the surface corresponding to the upper surface of the cathode 1 in the figure facing the anode (not shown) in the same airtight container. It is arranged.

Generally, in a cathode assembly used in an electron tube or the like, the cathode and the heater are separated from each other in order to maintain electrical insulation, and therefore the cathode is heated by radiant heat from a heater. Be done.

[0005]

[Problems to be solved by the device]

 However, in the structure as described above, the radiant heat emitted from the heater 2 does not reach only the cathode 1, but most of them heat the cathode sleeve 3, and the radiant heat reflected there is downward and upward in many directions. I ran away and had very poor thermal efficiency. Therefore, there is a problem that it takes a long time to raise the temperature of the cathode 1 to a temperature required for electron emission of the cathode 1 and that the heater power must be increased in order to compensate for poor thermal efficiency. It was

[0006]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the cathode assembly according to the present invention has a heat shield plate having a curved surface, and the heat shield plate has a curved surface other than the surface facing the anode of the cathode and a heating means. It is arranged so as to face the heat generating portion. Further, the self-heating type cathode assembly has a heat shield plate having a curved surface, and the heat shield plate is arranged with the above curved surface facing the surface of the cathode excluding the surface facing the anode. It is configured as follows.

[0007]

[Action]

 With this configuration, the radiant heat from the heater, which escapes in multiple directions without going to the cathode side, is reflected to the cathode side by the curved surface of the heat shield plate, and the radiant heat is efficiently supplied to the cathode side. To do. In addition, the radiant heat radiated by the temperature rise of the cathode itself is reflected by the curved surface of the heat shield plate and supplied again to the cathode.

[0008]

【Example】

FIG. 1 is a view showing a cathode assembly according to an embodiment of the present invention, which shows a conceptual shape for easy understanding, and is different in size and shape from an actually created one. is there. In the figure, the same reference numerals as those in FIG. 4 denote the same or corresponding parts, 4 denotes a cathode support, and 5 denotes a heat shield plate. The upper surface of the cathode 1 in the figure is the surface facing the anode (not shown). As shown in FIG. 1, the heater 2 is formed of a well-known tungsten wire or the like, has a coil-shaped heat generating portion, and is arranged so that the cathode 1 can be heated with a predetermined gap kept from the cathode 1. The heat shield plate 5 has a curved surface, and has, for example, a rotational quadric surface shape, a spherical surface shape, a rotational parabolic surface shape, etc. as shown in FIG. It reflects well. This heat shield plate is made of molybdenum (Mo), rhenium (Re), rhenium molybdenum (Re-Mo), tantalum (Ta), etc., which is punched out with a press or the like, formed, or sintered by a method such as tungsten (W). Etc. can be formed. At the time of molding, although not shown in the drawings, for ease of assembly, a portion that can be engaged with the cathode support 4 and a light-transmission or slit through which the heater 2 is inserted to avoid contact with the heater 2 are provided as appropriate. Is possible. Further, the engageable portions, the light transmission, the slits, etc. may be formed by machining. Further, the heater 2 may be coated with aluminum oxide (Al ₂ O ₃ ) by electrodeposition or the like to ensure electrical insulation from the heat shield plate 5.

The heat shield plate 5 or the set of the heat shield plate 5 and the heater 2 thus obtained is welded to the cathode support 4 or the assembly of the cathode support 4 and the cathode 1 by welding a resistor or a laser. It is assembled by attachment.

The cathode support 4 can be formed from a rod whose main component is tungsten (W), molybdenum (Mo), etc., and the method of attaching to the cathode is by screwing, brazing, welding, etc. In the case of an impregnated type cathode, a concave portion is formed when the refractory metal such as tungsten (W) is compression-molded, and the cathode support 4 is fitted into the concave portion, followed by the sintering step. There is a method of fixing by utilizing the contraction of the cathode (base) 1 in 1.

FIG. 2 shows another embodiment of the present invention, in which the same reference numerals as those in FIG. 1 or 4 show the same or corresponding parts. Figure 2 also shows a conceptual shape. As shown in FIG. 2, by forming the heat shield plate 5 large, it is possible to increase the area where the radiant heat is reflected and further improve the thermal efficiency. In this case, the effect of reflecting the radiant heat of the negative electrode 1 and reaching the cathode 1 again can be expected.

FIG. 3 is a diagram showing an example in which the present invention is applied to a self-heating type cathode used in a discharge tube. In the figure, the same reference numerals as those in FIG. 1, FIG. 2 or FIG. Indicates the same or equivalent. This figure also shows a conceptual shape. A high voltage is applied as a trigger to an anode (not shown) and the cathode 1. Ions ionized by this high voltage (discharge start) collide with the cathode 1 with high energy and heat it. Next, electrons are emitted from the heated cathode 1 and the electrons are ionized to stabilize the discharge (maintain discharge). The cathode 1 in which the discharge is stable is heated by the collision of ions, but the heating by these ions is limited. If the amount of heat dissipated by the cathode 1 exceeds the amount of heat generated by the ions, the temperature of the cathode will drop and the discharge will stop. With the configuration shown in FIG. 3, heat radiation from the cathode 1 can be reduced, and stable discharge can be maintained. In addition, it takes only a short time from the start of discharge to a stable state, and the trigger power can be reduced.

Although the embodiments have been described in detail above, if it is particularly necessary to prevent the electron emissive material evaporated from the cathode from adhering to the heater in order to prevent the generation of dark current in the gap between the cathode and the heater, The one end of the heater may be set to the same potential as the cathode, and the gap between the heating portion and the cathode may be appropriately set in relation to the voltage drop in the heating portion of the heater. Further, when it is desired to suppress the evaporation of the electron emissive material, a brazing material may be deposited or a deposition layer of a refractory metal may be provided except at least the surface portion of the cathode required for electron emission.

Further, the present invention is arbitrary with respect to demand, and various modifications are possible. For example, in the illustrated embodiment, the cathode, the heating part of the heater, and the heat shield plate are all disposed at the position where they overlap, but they may be disposed at three sides and the radiant heat from the heater or the cathode is a heat having a curved surface. Anything that reflects on the shield plate and reaches the cathode does not depart from the present invention. For that purpose, the cathode support does not need to be rod-shaped, and the heat shield plate need not be one. Further, the heat shield plate only needs to have a curved portion for reflecting radiant heat in a part thereof, and the heat generating portion of the heating means such as a heater is not a coil shape but has a double spiral shape like the conventional example. It may be a mosquito coil shape.

[0015]

[Effect of device]

 According to the present invention, the curved surface of the heat shield plate reflects the radiant heat from the heating means such as the heater to reach the cathode. Therefore, it is possible to provide the cathode with thermal energy which has not contributed to the heating of the cathode. The thermal efficiency is improved. Further, the heat shield plate can also reflect the radiation heat from the cathode to reach the cathode again, so that the thermal efficiency can be further improved. Further, it is possible to reduce the electric power used for the heating means of the cathode, to speed up the starting of the electron tube and the like, and particularly to reduce the amount of trigger current applied in the discharge tube. Further, by arranging the cathode, the heat generating portion of the heating means, and the heat shield plate having the curved surface so as to overlap each other, it is possible to obtain a compact cathode assembly having the above-mentioned effects.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a schematic view showing another embodiment of the present invention.

FIG. 3 is a schematic view showing still another embodiment of the present invention.

FIG. 4 is a schematic view showing an example of a conventional cathode assembly.

[Explanation of sign]

 1 cathode 2 heater 3 cathode sleeve 4 cathode support 5 heat shield plate

Claims (2)

[Scope of utility model registration request] 1. A cathode structure having a cathode, a support for supporting the cathode, and a heat generating portion of a heating means for heating the cathode, comprising a heat shield plate having a curved surface, the heat shield plate comprising: A cathode assembly, wherein the curved surface is disposed toward a surface of the cathode excluding a surface facing the anode and a heat generating portion of the heating means. 2. A self-heating type cathode assembly, comprising a cathode and a support for supporting the cathode, the cathode assembly having a heat shield plate having a curved surface, and the heat shield plate having the curved surface. Is disposed so as to face the surface of the cathode other than the surface facing the anode.