KR19980070512A - Multipolar Electron Tube - Google Patents

Abstract

The present invention relates to a multipolar electron tube, wherein the spiral winding direction of the cathode filament 23 and the spiral winding direction of the lateral support line 26 of the grid electrode 24 are wound in a spiral in opposite directions to each other, thereby operating characteristics such as voltage amplification factor. It is characterized by providing a multipolar electron tube with low dispersion and consistently high quality.

Description

Multipolar Electron Tube

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

In one type of conventional multipole electron tube, for example, a transmission tube is a cathode that emits hot electrons, a cylindrical anode that captures hot electrons emitted from the cathode, and at least one disposed between these cathodes and the anode to control the passage of hot electrons. It has a control grid electrode. In addition, as the cathode, a series of filaments wound in a spiral shape of a metal wire made of thrium-tungsten is generally used. In addition, as the control grid electrode, a cage-shaped grid electrode welded to a horizontal support line wound with thin lines of a plurality of molybdenum arranged in the longitudinal direction, that is, a direction parallel to the tube axis, is generally used.

As such a multipole electron tube, the structures described in Japanese Unexamined Patent Application Publication No. 38-2768 and Japanese Unexamined Patent Application Publication No. 41-16896 are well known. That is, the structure disclosed in the former publication is a spiral columnar cathode filament 112 fixedly supported by a cathode support 111 arranged on a tube axis, as shown in Figs. 3A, 3B, and 3C. ). The control grid electrode 113 is disposed coaxially around the cathode filament 112. The grid electrode 113 has a plurality of vertical lines 114 made of fine tungsten wires and a horizontal support line 115 wound in a coarse spiral shape so as to bind these vertical lines. The lateral support line 115 is a metal line thicker than the vertical line 114, and is welded at the intersection with the vertical line to mechanically support the vertical line and have a function of preventing deformation. Then, the cylindrical anode 116 serving as a part of the vacuum container is arranged to surround these filaments and grid electrodes.

On the other hand, in the latter structure, that is, the structure described in JP 41-16896, several or more transverse support lines 115 are wound vertically with respect to the tube axis as shown in FIG. This structure has a problem in that manufacturing is complicated because a horizontal lateral support line 115 having a predetermined diameter is prepared and sandwiched at predetermined intervals around the vertical line to weld each intersection.

On the other hand, the former structure can be relatively simplified because only one or two lateral support lines 115 can be wound around the vertical line to weld each intersection. However, in the related art, 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 in the same direction, and the spiral winding pitch interval of the cathode filament 112 is the same. Pf and the spiral winding pitch interval Ps of the lateral support line of the grid electrode are equal or almost equal.

According to such a conventional structure, as shown in Figs. 5 and 6, the side immediately corresponding to the direction in which the hot electron flow between the spiral winding of the cathode filament 112 and the spiral winding of the horizontal support line of the grid electrode proceeds. According to the overlapping state seen from the direction, the operating characteristics, in particular, the voltage amplification ratio mu greatly changes as indicated by the dotted line R. FIG.

That is, FIG. 5 (a) shows both windings exactly when the spiral winding of the cathode filament 112 and the helical winding of the lateral support line 115 of the grid electrode are immediately lateral, that is, perpendicular to the tube axis. The case where it was assembled in the superimposed state is shown typically. In this case, the gap G which is shifted when viewed from the right side direction between the winding of the cathode filament 112 and the winding of the lateral support line 115 of the grid electrode is 0 (G = 0).

The voltage amplification factor (μ) of the electron tube thus assembled is controlled at (G = 0) of the horizontal axis of the characteristic graph shown in FIG. 6 since hot electrons emitted from the cathode filament are most controlled to pass through the horizontal support line 115 of the grid electrode. The smallest voltage amplification factor (mu) was the corresponding one, and in the test-produced three-pole transmitter tube, it was mu ≒ 17. The temporary specified specific position of the negative electrode filament 112 in this state in the circumferential direction is Y and the same specific position of the grid electrode is shown in FIG.

Next, FIG. 5B illustrates a case where the position of the cathode filament 112 remains the same, and the grid electrode 113 is rotated 90 degrees clockwise from the top to determine and position the assembled electrode.

Therefore, the specific position Z of the grid electrode with respect to the specific position Y of the cathode filament 112 is a position advanced 90 degrees clockwise. In this case, the gap G between the winding of the cathode filament 112 and the adjacent winding of the lateral support line 115 of the grid electrode corresponds to 1/4 of both winding pitch intervals Pf, Ps, and (G (= 0.25 Pf). The voltage amplification factor (μ) of the electron tube thus assembled was μ 은 20 with respect to (G = 0.25) in the horizontal axis of FIG. 6.

In addition, as shown in Fig. 5 (c), when the specific position Z of the grid electrode 113 is assembled 180 degrees clockwise with respect to the specific position Y of the cathode filament 112, it is assembled. The gap G between the two windings corresponds to 1/2 of the winding pitch gaps Pf and Ps, and is (G = 0.5 · Pf). In addition, the voltage amplification factor (μ) of the assembled electron tube was μ ≒ 24 corresponding to (G = 0.5) in the horizontal axis of FIG. 6.

Therefore, 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 operating characteristics of the electron tube (voltage amplification factor) are controlled by adjusting the gap G between the windings of the two windings. μ) can be arbitrarily set to some extent, and in mass production of the same kind of electron tube, the characteristics are dispersed by only a slight shift in the circumferential positioning between the cathode filament and the grid electrode. There is a problem that an electron tube is manufactured. Therefore, there is a problem in mass production of consistently good quality electron tubes.

The present invention solves the problems of the conventional structure as described above, in the mass production of the same type of electron tube, even if assembled without uniformity in the circumferential positional relationship between the cathode filament and the grid electrode, operating characteristics, in particular voltage amplification factor ( It aims at providing the multipolar electron tube with few dispersion | distribution of (mu), and consistently high quality.

1 is a longitudinal sectional view showing the 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;

2 is an enlarged view of an essential part showing a cathode filament and a grid electrode of the electron tube shown in FIG. 1;

3 is a schematic structural diagram showing an example of a conventionally known electron tube;

4 is a longitudinal sectional view of an essential part showing another example of a conventionally known electron tube;

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

FIG. 6 is a graph showing a comparison of fluctuation characteristics of the voltage amplification ratios of the electron tubes shown in FIGS. 1 and 3.

* Explanation of symbols for main parts of the drawings

13: positive pole 23: negative electrode filament

24: grid electrode 25: grid vertical line

26: grid horizontal support line

Ps: Spiral winding pitch spacing of grid transverse support

Pf: spiral winding pitch spacing of cathode filament

Ds: diameter of lateral support line of grid electrode

Df: diameter of metal wire of cathode filament

According to the present invention, a direct-type cathode filament for emitting electrons wound in a spiral shape at a predetermined pitch, and a plurality of grid vertical lines disposed in an outer circumference of the cathode filament, and a lateral support line fixed to the grid vertical line at the same time In a multipolar electron tube having at least one grid electrode having a cylindrical shape and a cylindrical anode positioned at an outer circumference of the grid electrode, the horizontal support line of the grid electrode is wound in a spiral shape in a direction opposite to the spiral winding direction of the cathode filament. to be.

Further, the multipolar electron tube of the present invention is characterized in that the spiral winding pitch spacing Ps of the lateral support line of the grid electrode is 0.8 times or more of the spiral winding pitch spacing Pf of the cathode filament.

In addition, the multipolar electron tube of the present invention is characterized in that both the cathode filament and the horizontal support line of the grid electrode are composed of a single metal line.

The multipolar electron tube of the present invention is characterized in that the ratio (Ds / Df) of the diameter (Ds) of the horizontal support line of the grid electrode and the diameter (Df) of the metal line of the cathode filament is 0.8 or less.

Embodiment of the Invention

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail with reference to 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, a high frequency oscillation output of 30 MHz, 6 kW, used in a high frequency dielectric heating apparatus such as a high frequency machine. The transmission tube is hermetically joined to the cathode stem 11 by a cylindrical cylindrical anode 13 serving as a part of a vacuum container through a ceramic insulating cylinder 12. The heat radiation fin 14, the exhaust pipe 15, and the exhaust pipe protection cap 16 are fixed to the anode 13.

A pair of the negative electrode filament terminals 17 and 18 and the grid electrode terminal plate 19 are electrically insulated from and fixed to the positive electrode stem 11. A rod-shaped center support 21 for fixing the filament and supplying heating current is fixed to one cathode filament terminal 17, and the same side support 22 is fixed to the other cathode filament terminal 18. It is. Each tip 23a, 23b of the hot electron emission direct thermal cathode filament 23 wound spirally on each tip of the pair of struts 21, 22 is welded and electrically and mechanically supported. .

A basket-shaped cylindrical grid electrode 24 is arranged coaxially at a predetermined interval around the cathode filament 23. The grid electrodes 24 are wound around a plurality of grid vertical lines 25 arranged at predetermined intervals on a circle circumference defined by a predetermined semi-diameter, spirally wound around the grid vertical lines, and each vertical line 25 and Has an lateral support line 26 welded at its intersection point. The lower end of the grid electrode 24 is fixed to the grid support cylinder 27, and the upper end is fixed to the grid support ring 28. In addition, the grid support cylinder 27 is fixed to the grid electrode terminal plate 19 of the cathode stem 11.

2 is an enlarged view of a main part of the cathode filament and the grid electrode. The negative electrode filament 23 is a tungsten (W) alloy wire containing a trace amount of thri (Th) having a diameter Df of about 1 mm. As shown to Fig.2 (a), it wound around the center strut 21 arrange | positioned on the center axis | shaft in predetermined spiral so that it may become predetermined spiral outer half diameter Rf and predetermined pitch spacing Pf. . The number of turns Nf of the negative electrode filament 23 is arbitrarily set according to the characteristics required for the transmission tube in the range of, for example, 8 to 10.

As shown in Fig. 2B, the grid electrode 24 includes grid vertical lines 25 arranged at equal intervals, for example, on a circle circumference defined by a predetermined radius Rs, and the vertical lines of these vertical lines. It consists of one lateral support line 26 wound in a spiral shape opposite to the rotation direction wound by the spiral of the cathode filament 23 on the outer periphery. And the intersection of each grid vertical line 25 and the horizontal support line 26 is joined by welding, for example.

The grid longitudinal line 25 is a molybdenum wire having a diameter of, for example, 0.4 mm, and the transverse support line 26 has a molybdenum wire having a diameter Ds equal to, or for example, in the range of 1.0 to 2.0 times the vertical line 25. to be. Also, in order not to disturb the passing amount of the electron beam undesirably, the ratio (Ds / Df) of the diameter (Ds) of the horizontal support line of the grid electrode to the diameter (Df) of the metal line of the cathode filament is 0.8 or less, more preferably. Select it to be 0.5 or less.

The spiral winding direction of the horizontal support line 26 of the grid electrode is opposite to the spiral winding direction of the cathode filament 23. Further, the spiral winding pitch spacing Ps of the lateral support line 26 is 0.8 times or more of the spiral winding pitch spacing Pf of the cathode filament 23 in order not to be unnecessarily obstructed much of the passage of the electron beam. More preferably, it is 1.0 times or more.

According to this embodiment, the number of places where the spiral winding of the cathode filament 23 viewed from the side direction and the horizontal support line 26 of the grid electrode overlap with each other is related to the degree of positional shift in the circumferential direction between these filaments and the grid electrode. Almost constant. Therefore, even if there is a positional misalignment between the filament and the grid electrode, the probability that the hot electrons radiated from the cathode filament are blocked by the grid electrode in the process of moving toward the cylindrical anode is almost constant, and the characteristics of the conventional structure of FIG. Compared to R), the voltage amplification factor (μ) in the case of the present invention was almost constant at μ23, as indicated by the symbol (T) in Fig. 6, and there was little dispersion.

In this way, when the multipolar electron tube is manufactured by assembling a large amount, almost uniform operating characteristics, particularly voltage amplification (μ), can be obtained without precisely matching the position in the circumferential direction between the cathode filament and the grid electrode. Therefore, the assembly process of an electron tube can be simplified.

The present invention can also be applied to a multipole electron tube in which two or more grid electrodes are arranged coaxially, and the above advantages can be obtained if the structure of at least one grid electrode is the above-described configuration.

In addition, although the said Example is comprised by the line which wound the negative electrode filament in one spiral shape, it is not limited to this, You may comprise by the line which wound in a double spiral shape as shown in FIG.3 (b). In addition, the horizontal support line of the grid electrode is not limited to the single winding, but may be wound in a double helix as shown in FIG.

In this case, however, the winding pitch spacing Pf or Ps of the cathode filament or grid lateral support line is defined as the average value of the pitch spacings of adjacent windings, which are visible in the lateral direction, including all the windings for each. 1 and 2, the winding pitch interval Pf or Ps in the case of winding in a single line is also defined as the average value of all winding pitch intervals.

As described above, according to the present invention, since the spiral winding direction of the negative electrode filament and the lateral winding spiral winding direction of the grid electrode are opposite to each other, the magnitude of the positional displacement in the circumferential direction between the negative electrode filament and the grid electrode is correlated. Almost constant operating characteristics, in particular voltage amplification, are obtained. In this way, a small dispersion of operating characteristics and a consistently high quality electron tube can be mass produced at low cost.

Claims (4)

An electron-emitting linear cathode filament wound in a spiral shape at a predetermined pitch, a plurality of grid longitudinal lines disposed in an outer circumference of the cathode filament, and a lateral support line wound in a spiral shape and fixed to the grid vertical line A multipolar electron tube having at least one grid electrode and a cylindrical anode positioned at an outer circumference of the grid electrode, And the horizontal support line of the grid electrode is wound in a spiral shape in a direction opposite to the winding direction of the cathode filament. The method of claim 1, And the spiral winding pitch spacing Ps of the lateral support line of the grid electrode is 0.8 times or more of the spiral winding pitch spacing Pf of the cathode filament. The method of claim 1, The transverse support lines of the cathode filament and the grid electrode are each composed of a single metal line. The method of claim 1, And the ratio (Ds / Df) of the diameter (Ds) of the horizontal support line of the grid electrode to the diameter (Df) of the metal line of the cathode filament is 0.8 or less.