JPH10255672A - Multipolar electron tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the dispersion of the operating characteristic, particularly voltage amplification factor, and uniformize quality even when a cathode filament and a grid electrode are assembled without keeping the positional relation in the peripheral direction constant by spirally winding the lateral support wire of the grid electrode fixed to grid vertical wires in the reverse direction to the spiral winding direction of the cathode filament. SOLUTION: A cathode filament 23 is spirally wound prescribed times at the prescribed pitch interval Pf with the prescribed spiral outside radius around a center support 21 arranged on the center axis. A grid electrode 24 is constituted of 24 grid vertical wires 25 arranged at uniform intervals on the circumference of a circle regulated with the prescribed radius Rs, for example, and one lateral support wire 26 spirally wound in the reverse direction to the spiral winding direction of the cathode filament 23 on the outer periphery of the vertical wires 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multipole electron tube having a helical direct-heating cathode filament, at least one cage control grid electrode, and a cylindrical anode.

[0002]

2. Description of the Related Art For example, a transmission tube, which is a kind of multipolar electron tube, is provided with a cathode for emitting thermoelectrons, a cylindrical anode for capturing thermoelectrons emitted from the cathode, and a cathode disposed between the cathode and the anode. And at least one control grid electrode for controlling the amount of thermal electrons passing therethrough. And as the cathode,
A directly heated filament in which a metal wire made of thorium-tungsten is spirally wound is generally used. In addition, a cage-type grid electrode is generally used as a control grid electrode, in which a number of fine molybdenum wires are arranged in a vertical direction, that is, in a direction parallel to the tube axis, and these vertical wires are welded to a horizontal support wire wound in a bundle. Have been.

As such a multipole electron tube, Japanese Utility Model Publication No. 38
The structures described in Japanese Unexamined Patent Publication Nos. 2768 and 41-16896 are well known. That is, the structure disclosed in the former publication is shown in FIGS.
As shown in (c), the cathode support 11 arranged on the tube axis
1 is provided with a helical direct-heated cathode filament 112 fixedly supported. And this cathode filament 1
A control grid electrode 113 is disposed coaxially around the reference numeral 12. The grid electrode 113 has a large number of vertical lines 114 made of tungsten fine wires, and horizontal support lines 115 wound in a spiral shape so as to bundle these vertical lines.
The horizontal support line 115 is a metal line thicker than the vertical line 114, and is welded at an intersection with the vertical line, and has a function of mechanically stably supporting the vertical line and preventing deformation. A cylindrical anode 116 surrounding the filament and the grid electrode and also serving as a part of the vacuum container is arranged.

[0004] On the other hand, the latter, ie, Jikken Sho 41-
In the structure described in Japanese Patent No. 16896, as shown in FIG. 4, several or more horizontal support lines 115 are wound in a direction perpendicular to the tube axis. In this structure, a horizontal support line 115 which is rounded to a predetermined diameter is prepared, fitted at predetermined intervals around a vertical line, and each intersection must be welded. There is.

On the other hand, in the former structure, it is only necessary to continuously wind about one or two horizontal lines 115 around a vertical line and weld each intersection, so that the manufacturing can be relatively simplified. However, conventionally, as shown in FIG. 3, the spiral winding direction of the cathode filament 112 and the spiral winding direction of the horizontal support line of the grid electrode are made the same,
Spiral winding pitch interval (P
f) and the spiral winding pitch interval (Ps) of the lateral support line of the grid electrode are made equal or almost equal.

[0006]

According to such a conventional structure, as shown in FIGS. 5 and 6, the spiral winding of the cathode filament 112 and the spiral winding of the horizontal support line of the grid electrode are formed. The operating characteristics, particularly the voltage amplification factor (μ), vary greatly as shown by the dotted line (R) depending on the degree of overlap as viewed from the lateral direction substantially corresponding to the direction in which the thermoelectron flow proceeds.

More specifically, FIG. 5A shows a case where the helical winding of the cathode filament 112 and the helical winding of the horizontal support wire 115 of the grid electrode are viewed from the horizontal direction, that is, the direction perpendicular to the tube axis. Schematically shows a case where both windings are assembled in a state where they are just overlapped. In this case, the winding of the cathode filament 112 and the horizontal support line 1 of the grid electrode
The gap (G) between the fifteen windings and the horizontal direction is zero (G = 0).

In the voltage amplification factor (μ) of the electron tube assembled in this manner, thermoelectrons emitted from the cathode filament are suppressed most through the horizontal support lines 115 of the grid electrode. The lowest voltage amplification factor (μ) corresponding to (G = 0) on the horizontal axis was μ ≒ 17 in the prototype three-pole transmitter tube. In this state, the temporarily determined specific position in the circumferential direction of the cathode filament 112 is Y,
The same specific position of the grid electrode is shown as Z in FIG.

Next, FIG. 5 (5b) shows a case where the grid electrode 113 is positioned by being turned clockwise by 90 degrees when viewed from above while the position of the cathode filament 112 is kept as it is, and then assembled. Therefore, the cathode filament 112
The specific position Z of the grid electrode is 90 degrees clockwise with respect to the specific position Y described above. in this case,
The gap (G) between the winding of the cathode filament 112 and the adjacent winding of the horizontal support line 115 of the grid electrode corresponds to １ ／ of the pitch interval (Pf, Ps) of both windings, and (G =
0.25 · Pf). The voltage amplification factor (μ) of the thus assembled electron tube is represented by (G = 0.
Μ ≒ 20, corresponding to 25).

Further, as shown in FIG. 5 (5c), when the specific position Z of the grid electrode 113 is advanced by 180 degrees clockwise with respect to the specific position Y of the cathode filament 112, the assembly is performed. The gap G between the windings corresponds to one half of the pitch (Pf, Ps) between the windings (G = 0.
5 · Pf). The voltage amplification factor (μ) of the thus assembled electron tube was μ ≒ 24, corresponding to (G = 0.5) on the horizontal axis in FIG.

For this reason, in the conventional structure in which the spiral winding direction of the cathode filament and the spiral winding direction of the horizontal support line of the grid electrode are wound in the same direction, the gap (G) between the two windings is reduced. By adjusting, there is an advantage that the operating characteristics (voltage amplification factor μ) of the electron tube can be arbitrarily set to some extent, but in mass production of the same type of electron tube,
Even if the positioning of the cathode filament and the grid electrode in the circumferential direction is slightly shifted, there is a disadvantage that the characteristics are varied and an irregular electron tube is manufactured. Therefore, there is a problem in mass-producing electron tubes of good quality.

The present invention solves the above-mentioned disadvantages of the conventional structure, and operates in a mass production of the same type of electron tube even if the positional relationship between the cathode filament and the grid electrode in the circumferential direction is not fixed. It is an object of the present invention to provide a multi-electrode tube in which the characteristics, especially the voltage amplification factor (μ), are small and the quality is uniform.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a direct-heated cathode filament for electron emission in which metal wires are spirally wound at a predetermined pitch, and a plurality of vertical grid lines arranged around the cathode filament. And a multi-electrode tube having at least one grid electrode spirally wound and having a horizontal support line fixed to the grid vertical line, and a cylindrical anode located on the outer periphery of the grid electrode. The horizontal support wire is a multi-pole electron tube spirally wound in a direction opposite to the spiral winding direction of the cathode filament.

In the multipole electron tube of the present invention, the spiral winding pitch interval (Ps) of the horizontal support line of the grid electrode is
It is characterized by being at least 0.8 times the pitch interval (Pf) of the spiral winding of the cathode filament.

Further, the multipole electron tube according to the present invention is characterized in that the horizontal support lines of the cathode filament and the grid electrode are each formed of a single metal wire. Still further, in the multipolar electron tube of the present invention, the ratio (Ds / Df) of the diameter (Ds) of the horizontal support line of the grid electrode to the diameter (Df) of the metal wire of the cathode filament is 0.8 or less. It is characterized by the following.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a three-pole transmission tube having an operating characteristic of, for example, 30 MHz and 6 kW high-frequency oscillation output used in a high-frequency induction heating device such as a high-frequency sewing machine. In this transmission tube, a copper cylindrical anode 13 also serving as a part of a vacuum vessel is hermetically bonded to a cathode stem 11 via a ceramic insulating cylinder 12. A radiation fin 14, an exhaust pipe 15, and an exhaust pipe protection cap 16 are fixed to the anode 13.

The cathode stem 11 has a pair of cathode filament terminals 17, 18 and a grid electrode terminal plate 19,
They are fixed electrically insulated from each other. A rod-shaped center support 21 for supporting the filament and supplying a heating current is fixed to one cathode filament terminal 17, and a similar side support 21 is fixed to the other cathode filament terminal 18. Then, the tip portions 23a, 23a of the directly heated cathode filament 23 for thermionic emission wound spirally are attached to the tip portions of the pair of columns 21, 22, respectively.
23b are each more electrically and mechanically connected and supported by welding.

A cage-shaped cylindrical grid electrode 24 is coaxially arranged around the cathode filament 23 at a predetermined interval. The grid electrode 24 is composed of a number of grid vertical lines 25 arranged at predetermined intervals on a circumference of a circle defined by a predetermined radius, and spirally wound around the grid vertical lines, and The intersection with the line 25 has a lateral support line 26 welded. Grid electrode 24
Is fixed to a grid support cylinder 27 at the lower end in the figure, and is fixed to a grid support ring 28 at the upper end in the figure. Note that the grid support cylinder 27 is connected to the cathode stem 11.
Are fixed to the grid electrode terminal plate 19.

FIG. 2 is an enlarged view of a main part of the cathode filament and the grid electrode. The cathode filament 23 is a tungsten (W) alloy wire containing a small amount of thorium (Th) having a diameter (Df) of about 1 mm. This is shown in FIG.
As shown in the figure, the center support 21 disposed on the central axis
Is spirally wound a predetermined number of times so as to have a predetermined spiral outer radius (Rf) and a predetermined pitch interval (Pf). The number of turns (N
f) is arbitrarily set in the range of, for example, 8 to 10, depending on the characteristics required for the transmission tube.

As shown in FIG. 2B, the grid electrodes 24 include, for example, 24 grid vertical lines 25 arranged at equal intervals on the circumference of a circle defined by a predetermined radius (Rs).
A single horizontal support wire 26 wound spirally in the opposite direction to the rotation direction of the spiral winding of the cathode filament 23 is provided around the outer circumference of these vertical lines. The intersections between the grid vertical lines 25 and the horizontal support lines 26 are connected by, for example, welding.

The grid vertical line 25 is a molybdenum wire having a diameter of, for example, 0.4 mm, and the horizontal support line 26 has a diameter (Ds) of, for example, equal to or 1.0 to 2.0 times that of the vertical line 25. It is also a molybdenum wire. Also, in order not to unnecessarily obstruct the passage amount of the electron beam, the ratio (Ds / Df) of the diameter (Ds) of the horizontal support line of the grid electrode to the diameter (Df) of the metal wire of the cathode filament is used. Is
It is selected so as to be 0.8 or less, more preferably 0.5 or less.

The horizontal support line 26 of the grid electrode
The direction of the spiral winding is opposite to the direction of the spiral winding of the cathode filament 23. In addition, this horizontal support line 2
The helical winding pitch interval (Ps) of 6 is also used so as not to unnecessarily obstruct the passage amount of the electron beam.
Spiral winding pitch interval of cathode filament 23 (P
f) 0.8 times or more, more preferably 1.0 times or more.

According to this embodiment, the number of places where the helical winding of the cathode filament 23 and the horizontal support line 26 of the grid electrode overlap as viewed from the sideways direction is determined in the circumferential direction between the filament and the grid electrode. Is substantially constant irrespective of the degree of displacement. Therefore, even if the filament and the grid electrode are misaligned in assembly, the probability that the thermoelectrons emitted from the cathode filament are blocked by the grid electrode in the process of traveling toward the cylindrical anode is almost constant. Compared with the characteristic (R) of the conventional structure, the voltage amplification factor (μ) of the embodiment of the present invention is indicated by the symbol (T) in FIG.
As indicated by, it was almost constant at μ ≒ 23, and there was almost no variation.

Thus, when assembling and manufacturing a large number of multi-pole electron tubes, even if the positions of the cathode filament and the grid electrode in the circumferential direction are not adjusted with high accuracy, almost uniform operating characteristics, particularly the voltage amplification factor (μ), are obtained. Is obtained. Therefore, the assembling process of the electron tube can be simplified.

The present invention can be applied to a multipolar electron tube in which two or more grid electrodes are coaxially arranged. If the structure of at least one grid electrode has the above-described structure, the above-described advantages can be obtained. You can enjoy.

In the above-described embodiment, the cathode filament is constituted by one spiral winding.
However, the present invention is not limited to this, and may be constituted by a double spiral winding as shown in FIG. Further, the horizontal support wire of the grid electrode is not limited to a single wire winding, but may be a double spiral winding as shown in FIG. 3C, or may have more windings.

However, in these cases, the winding pitch interval (Pf or Pf) of the cathode filament or grid lateral support line is used.
s) is defined, for each, as the average value of the pitch spacing of adjacent windings as viewed from the side, including all of the windings. In addition, the winding pitch interval (Pf or Ps) in the case of a single winding as shown in FIGS. 1 and 2 is defined by an average value of all winding pitch intervals.

[0028]

As described above, according to the present invention, the spiral direction of the cathode filament and the spiral direction of the horizontal support wire of the grid electrode are opposite to each other. Irrespective of the magnitude of the positional deviation in the circumferential direction, substantially constant operating characteristics, particularly a voltage amplification factor, can be obtained. In this way, it is possible to mass-produce low-cost electron tubes with small variations in operating characteristics and high quality.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a structure of an electron tube having a spiral cathode filament and a cage grid electrode to which an embodiment of the present invention is applied.

FIG. 2 is an enlarged view of a main part showing a cathode filament and a grid electrode of the electron tube shown in FIG.

FIG. 3 is a schematic structural view showing an example of a conventionally known electron tube.

FIG. 4 is a longitudinal sectional view of a main part showing another example of a conventionally known electron tube.

FIG. 5 is a schematic diagram showing a winding relationship between a cathode filament and a horizontal support line of a grid electrode in the electron tube shown in FIG. 3;

FIG. 6 is a graph showing a comparison between fluctuation characteristics of a voltage amplification factor of the electron tube shown in FIGS. 1 and 3;

[Explanation of symbols]

 23: cathode filament, 24: grid electrode, 25: grid vertical line, 26: grid horizontal support line, 13: anode, Ps: spiral winding pitch interval of grid horizontal support line, Pf: spiral winding of cathode filament Pitch interval, Ds: diameter of horizontal support line of grid electrode, Df: diameter of metal wire of cathode filament.

Claims (4)

[Claims] 1. A direct-heating cathode filament for electron emission in which a metal wire is spirally wound at a predetermined pitch, and a plurality of grid vertical lines arranged around the outer periphery of the cathode filament and spirally wound. At least one grid electrode having horizontal support lines secured to grid vertical lines;
A multi-electrode tube comprising: a tubular anode positioned on the outer periphery of the grid electrode; wherein the lateral support lines of the grid electrode are spirally wound in a direction opposite to the spiral winding direction of the cathode filament. And a multipolar electron tube. 2. The spiral winding pitch interval (Ps) of the horizontal support line of the grid electrode is at least 0.8 times the spiral winding pitch interval (Pf) of the cathode filament. Multipole electron tube. 3. The multipole electron tube according to claim 1, wherein each of said cathode filament and said horizontal support line of said grid electrode is constituted by a single metal wire. 4. The diameter (D) of a lateral support line of the grid electrode.
s) and the diameter (Df) of the metal wire of the cathode filament
The multipole electron tube according to claim 1, wherein a ratio (Ds / Df) of the multipole electron tube is 0.8 or less.