JP3409967B2 - Manufacturing method of impregnated cathode - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing an impregnated cathode used in an electron tube.

[0002]

2. Description of the Related Art Impregnated cathodes are used in cathode ray tubes such as color cathode ray tubes. Then, this impregnated cathode serves as an electron beam source. An example of a conventional impregnated cathode will be described below with reference to FIG.

FIG. 5 shows a perspective view of an example of a conventional impregnated cathode. The columnar matrix 1 is coated with a matrix-coated component 2 which is a cup-shaped metal component.
The matrix 1 is an electron emission electrode. The matrix 1 of this conventional example has a diameter of about 1 mm and a height of about 0.
It is 5 mm. The matrix-coated component 2 is provided to minimize evaporation of the electron emissive agent from the matrix 1 when the impregnated cathode operates within the electron tube. This matrix 1 is fixed to a cylindrical cathode sleeve 3 via support wires 4. This cathode sleeve 3
A heater for heating is built in inside. And
The combined body of the matrix 1 and the cathode sleeve 3 via the supporting wire 4 is fixed to the fixing ring 11. This fixing is performed by joining each tip of the support wire 4 to the fixing ring 11. The impregnated cathode constructed as described above can be fixed to an electron gun (not shown) by connecting the fixing ring 11 to a glass holder (not shown).

The matrix 1 is formed by impregnating the pores of a heat-resistant porous substrate such as W with an electron emitting substance made of, for example, an alkaline earth oxide containing BaO as a main component.
The matrix coating component 2 and the cathode sleeve 3 are made of Mo,
It is formed of a refractory metal such as W or Ta, or an alloy of two or more kinds of these metals. Support line 4 is W, M
It is formed of a refractory metal such as o, Ta, or Re, or an alloy of two or more kinds of these metals.

Resistance welding is used to join the matrix 1 and the cathode sleeve 3 through the support wire 4.
Resistance welding is also used to join the tip of the support wire 4 and the fixed ring 11.

The resistance welding will be specifically described below. Conventionally, for resistance welding of metal parts constituting these impregnated cathodes, a commercial frequency 6 obtained from a single-phase AC power source was used.
The current was applied for one cycle of a 0 Hz sine wave. The impregnated cathode has an operating temperature of 1000 ° C. or higher, which is extremely high. Therefore, a refractory metal is generally used for the metal parts used for the impregnated cathode. Welding of these refractory metals requires large thermal energy. Actually, a current having a peak value of about 1300 to 1600 A was applied during welding. FIG. 6 shows an example of the relationship between the time T of the current waveform during welding and the current value I. In the example of this figure, the peak value of the current is 1600 A, and the time for one cycle is 1/60 ms.

[0007]

However, the above-mentioned conventional method for manufacturing an impregnated cathode has the following problems. (1) When a high peak current of about 1300 to 1600 A is applied during welding, the electron emissive agent melt-impregnated in the matrix is thermally decomposed, causing thermal diffusion to the electron emission surface exposed to the atmosphere. was there. When such a cathode is used for an electron tube, the electron emission characteristic may be deteriorated or the electron beam may not be extracted. (2) Also, as described above, 1300 to 1600 during welding.
When a current having a high peak value of about A is applied, the joint may be excessively heated, and a splash of the metal melt may occur. When the splash occurs, the splash becomes a foreign substance in the tube in the cathode ray tube, which causes a high-pressure defect and a defective clogging of the shadow mask. (3) If the welding current is kept small, the above problems can be solved. However, in this case, the tensile strength of the joint portion of each component is remarkably reduced, and sometimes another problem of not being welded occurs. (4) In resistance welding, the welding current is likely to fluctuate due to variations in contact resistance due to variations in the contact state of the welded portion and variations in pressurization. If the welding current becomes extremely small,
Sufficient welding strength will not be secured. (5) Further, since resistance welding is performed by bringing the electrode into contact with the work, heat during welding is also accumulated at the contact point and the electrode. Therefore, wear occurs on the contact surface of the electrode with the work. The greater the wear of the electrodes, the greater the variation in the contact resistance. Therefore, there is a problem that the variation in welding quality increases as the number of products produced increases. For this reason, it is necessary to shorten the energization time while requiring a large current for welding the high melting point metal.

The present invention solves the above problems, and provides a method for producing an impregnated cathode capable of preventing the deterioration of electron emission characteristics and ensuring a necessary tensile strength in a welded portion. To aim.

[0009]

In order to achieve the above object, in the method for producing an impregnated cathode of the present invention, a portion including a bottom portion of a matrix formed of a porous substrate impregnated with an electron emitting material is coated. By performing resistance welding while sandwiching a support wire supporting the matrix-coated component and the cathode sleeve between the bottom surface of the matrix-coated component and the top surface of the cathode sleeve that houses the heater therein, A method for manufacturing an impregnated cathode in which a bottom surface of a matrix-coated component and a top surface of the cathode sleeve are simultaneously joined via a support wire, wherein a pulse-like current having an energization time of 2 to 9 ms during the resistance welding A current is supplied at least twice, and a pause time is provided between the end of the energization of the pulsed current and the start of the next energization .
The energizing direction is the first time from the cathode sleeve side to the mat
On the lix side, the second time from the matrix side to the shadow
It is characterized by the pole sleeve side .

According to the above-mentioned method, since the joint portion is not excessively heated, the electron emission material melt-impregnated in the matrix is thermally decomposed and surface-diffused on the electron emission surface. It is possible to prevent a splash from occurring. Further, since a large current that can weld a high-melting point metal can be applied, necessary tensile strength can be secured. Moreover, since the quality can be stabilized as described above, the yield can be improved and the manufacturing cost can be reduced as compared with the case of the conventional method. In addition,
Variation in tensile strength can be reduced. The rest time is preferably 30 to 200 ms.

In the method of manufacturing the impregnated cathode, it is preferable that the pulsed current is applied twice and the peak value of the first pulsed current is smaller than the peak value of the second pulsed current.

According to the above method, the contact resistance between the works can be stabilized by suppressing the first pulsed current to be low. For this reason, the fluctuation of the pulsed current in the second welding in which substantial welding is performed is small, and the variation in tensile strength can be reduced.

In the method of manufacturing the impregnated cathode, if the first peak value of the pulsed current is I1 and the second peak value is I2, 1100A≤I2≤1400A.
Within the range, it is preferable to satisfy the relationship of 0.16I2 ≦ I1 ≦ 0.5I2.

[0014]

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the method for producing an impregnated cathode of the present invention will be described below with reference to the drawings. Figure 1
FIG. 3 is a schematic view showing an example of a method for manufacturing an impregnated cathode of the present invention.

The matrix 1 is formed by impregnating a W porous substrate with an electron emitting agent. Portions other than the electron emission surface 8 of the matrix 1 are covered with a cup-shaped matrix coating component 2 made of Mo. Inside the cylindrical cathode sleeve 3 having a diameter of 1.5 mm, a stainless pin 7 having a diameter of about 1.4 mm is inserted. Cathode sleeve 3
Is made of Mo and has a bottom surface portion (a top surface portion in FIG. 1). On the top surface of the cathode sleeve 3, a W alloy support wire 4 having a diameter of 0.05 mm is arranged in a cross shape. On top of that, the previously assembled matrix with cups is arranged. That is, in this state, the support line 4 is
It is sandwiched between the bottom surface of the matrix-coated component 2 and the top surface of the sleeve 3.

Next, in the welding process, first, the diameter is 1 m.
m of the copper electrode 5 in the shape of a cylinder is attached to the matrix 1
It is applied to the electron emission surface 8 of. Similarly, the electrode 6 is applied to the cathode sleeve 3. In this state, resistance welding is performed while applying pressure to the electrodes 5 and 6 in the direction of arrow 10. The pressure during pressurization is 3.
0 to 5.5 kg / mm ² is preferable. During resistance welding,
A welding current is supplied by the welding power source 9. Cathode sleeve 3
The plate thickness of the welded portion is 0.12 mm, and the plate thickness of the welded portion of the matrix-coated component 2 is 0.4 mm. According to the welding method, the bottom surface of the matrix-coated component 2 and the top surface of the cathode sleeve 3 can be simultaneously joined via the support wire 4.

The waveform of the welding current during the welding is shown in FIG. The energization is divided into the first time and the second time. The first energization energizes a pulsed rectangular wave of 5 ms. The direction of the energizing current is from the cathode sleeve 3 to the matrix 1. After the end of the first energization, a pause time of 160 ms is taken. For the second energization, 5 ms pulse-shaped rectangular wave
The welding is completed by energizing in the opposite direction to the first time.

Next, the setting of the crest value of the pulsed current at the time of welding will be specifically described with reference to experimental results. In this experiment, the welding current is the same as that shown in FIG.
Is the same as that shown in. FIG. 3 shows the experimental results of the relationship between the peak value I2 of the pulsed current for the second time and the tensile strength F when the peak value I1 of the pulsed current for the first time is fixed to 300A. This figure shows I2 from 1200A to 1
The measurement results (the number of samples is 10) of the tensile strength F when changed to 600 A are entered. The line 12 is a line connecting the minimum values of the tensile strength F at each crest value. The line 13 is a line connecting the maximum values of the tensile strength F at each crest value. Therefore, the distance between the line 12 and the line 13 in the vertical direction shows the variation in the tensile strength F. The wider the spacing, the greater the variation in tensile strength F.

FIG. 4 shows the peak value I of the second pulsed current.
2 shows the relationship between the peak value I1 of the pulsed current for the first time and the tensile strength F when 2 is fixed to 1200A. This figure shows
The measurement result of the tensile strength F when I1 is changed from 200 A to 600 A (the number of samples is 10) is entered. The line 14 is a line connecting the minimum values of the tensile strength F at each crest value. The line 15 is a line connecting the maximum values of the tensile strength F at each crest value. As in the case of FIG. 3, line 12
If the distance between the line and the line 13 in the vertical direction increases, the tensile strength F
The variability of will also increase.

The tensile strength F was obtained by the tensile strength test described below. In this test, first, the center portion of a Ni alloy ribbon having a length of about 30 mm is laser-welded on the electron emission surface 8 of the matrix 1 which was prototyped. Both ends of this ribbon are joined by resistance welding to form a ring shape. Next, the entire cathode sleeve 3 is fixed with a jig. In this state, a hook of a tensile load measuring device is hooked on the ring-shaped Ni alloy ribbon to pull the ring-shaped ribbon at a constant speed.
The maximum load obtained by the test was defined as the tensile strength F.

From the results shown in FIGS. 3 and 4, the tensile strength F
Shows that 10N is secured. The range of the tensile strength F at each peak value is about 10 to 14 N, and the variation is almost constant. Further, in all of the experiments, the appearance was good with no foreign matter or the like generated on the electron emission surface 8 of the matrix after welding. The tensile strength by welding using a conventional alternating current was in the range of 2 to 10N.
Therefore, according to the method of the present invention, the tensile strength is improved and the variation in the tensile strength is reduced. When the tensile strength is 3 N or less, when the impregnated cathode is used in, for example, a color cathode ray tube, the welded portion may come off due to vibration from the speaker. If the welded part comes off, it becomes a defective product. If such defective products occur frequently, the yield will deteriorate and the cost will increase. According to the method of the present invention, a tensile strength of 10 N is ensured, so such a defective product does not occur, and the yield can be improved and the manufacturing cost can be reduced as compared with the case of the conventional method.

Further, an experiment in which I1 and I2 were changed was added. The experimental conditions are the same as in the above experiment. The results of this additional experiment and the results of the above experiment are summarized in the following (1).
In the range of I1 and I2 shown from (1) to (4), the result was good. The good result means that the tensile strength F is 10 N or more and no foreign matter is generated on the electron emission surface 8. The thickness of the cathode sleeve 3 is 0.03 to 0.2 mm, the thickness of the covering component 2 is 0.02 to 0.1 mm, and the linear shape of the support wire 4 is 0.03 to 0.1 mm. Equivalent results are obtained. (1) I2 = 1100A, I1 = 100 to 600A (2) I2 = 1200A, I1 = 100 to 600A (3) I2 = 1300A, I1 = 200 to 700A (4) I2 = 1400A, I1 = 200 to 700A The result can be expressed as a mathematical expression as follows. 1
Within the range of 100A ≦ I2 ≦ 1400A, 0.1
6I2 ≦ I1 ≦ 0.5I2 That is, if I1 and I2 that satisfy the above formula are set, the tensile strength F after welding is 10
When it is N or more, an impregnated cathode in which no foreign matter is generated on the electron emission surface 8 can be obtained.

In the above experiment, the energization direction of the pulsed current was set from the sleeve side to the matrix side at the first time and from the matrix side to the sleeve side at the second time. Further experiments were conducted to examine the difference in the experimental results due to the difference in the energizing direction. In this experiment, I1 was 300A and I2 was 1200A. Tensile strength is 10 to 1 when the direction of pulsed current is changed from the sleeve side to the matrix side for the first time and from the matrix side to the sleeve side for the second time.
It was 4N. On the other hand, under the same conditions, when the polarities of the first and second currents were set to other combinations, the tensile strength was 7 to 12N. Therefore, it is understood that the variation in tensile strength can be reduced by changing the energizing direction of the pulsed current from the sleeve side to the matrix side for the first time and from the matrix side to the sleeve side for the second time.

Even if the number of times of energization was 3, the welding quality was not affected. Therefore, it is not particularly necessary to make it three times or more. In case of only one pulse current,
There was a large variation in tensile strength. Therefore, by providing the pause time and suppressing the first pulse current to be low, the contact resistance between the works becomes stable. Therefore, the fluctuation of the energizing current becomes small, and the fluctuation of the tensile strength is suppressed.

The rest time is a constant value of 160 m in the above experiment.
Although a good result was obtained as s, the first conduction current was 10
In the case of 0 A, the rest time was 60 ms and the variation in tensile strength was the smallest. The first energizing current is 600A
In that case, the variation in tensile strength was the smallest at 180 ms. Therefore, it can be seen that the optimum value of the pause time is different if the first energization current value is different. Specifically, depending on the first energizing current value, the rest time is 30 to
It is preferable to set a value that minimizes the variation in tensile strength within the range of 200 ms.

If the energization time is set to 10 ms or more,
The electron emitting material in the matrix was thermally decomposed and blown to the electron emitting surface. On the other hand, welding was not possible when the energization time was set to 1 ms. Therefore, it is preferable to set the energization time to 2 to 9 ms.

[0028]

As described above, according to the method of manufacturing an impregnated cathode of the present invention, a pulsed current is applied at least twice during resistance welding, and after the completion of the application of the pulsed current,
By providing a predetermined rest time before the start of the next energization, the necessary tensile strength can be secured, and a good quality impregnated cathode in which no foreign matter is generated on the electron emission surface can be obtained.

Further, the variation of the tensile strength can be reduced by changing the energizing direction of the pulsed current from the sleeve side to the matrix side for the first time and from the matrix side to the sleeve side for the second time.

Further, since the quality can be stabilized as described above, the yield can be improved and the manufacturing cost can be reduced as compared with the conventional method.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of a welding current waveform in the manufacturing method of the present invention.

FIG. 3 is a diagram showing the relationship between the second pulsed current and the tensile strength in the manufacturing method of the present invention.

FIG. 4 is a diagram showing the relationship between the first pulsed current and the tensile strength in the manufacturing method of the present invention.

FIG. 5 is a perspective view of an example of a conventional impregnated cathode.

FIG. 6 is a diagram showing an example of a welding current waveform in a conventional manufacturing method.

[Explanation of symbols]

1 matrix 2 Matrix coated parts 3 cathode sleeve 4 support line 5 Pressure electrode 6 electrodes 7 pin 8 Electron emission surface 9 welding power source 10 Pressing direction 11 fixing ring

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsuyuki Yamashita 1-1 No. 1 Sachimachi, Takatsuki City, Osaka Prefecture Matsushita Electronic Industrial Co., Ltd. (56) Reference JP-A-1-232635 (JP, A) JP-A 6-162916 (JP, A) JP-A-87744 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 9/04

Claims (3)

(57) [Claims] 1. A space between a bottom surface of a matrix-coated component that covers a portion including a bottom surface of a matrix formed of a porous substrate impregnated with an electron emitting material and a top surface of a cathode sleeve that houses a heater therein. By performing resistance welding in a state where a support wire for supporting the matrix-coated component and the cathode sleeve is sandwiched, the bottom surface portion of the matrix-coated component and the top surface portion of the cathode sleeve are simultaneously joined via the support wire. A method for manufacturing an impregnated cathode, comprising conducting a pulsed current having a conduction time of 2 to 9 ms at least twice during the resistance welding, and from the end of conduction of the pulsed current to the start of the next conduction. A quiescent time is provided between the first and second pulse current directions.
From the cathode sleeve side to the matrix side, the second time is the front
A method for producing an impregnated cathode, wherein the matrix side is the cathode sleeve side . 2. The method for producing an impregnated cathode according to claim 1, wherein the pulsed current is applied twice, and the peak value of the first pulsed current is smaller than the peak value of the second pulsed current. 3. The first peak value of the pulsed current is I
Assuming that the peak value of the first and second times is I2, 1100A ≦ I2
Within the range of ≦ 1400A, 0.16I2 ≦ I1 ≦
The method for producing an impregnated cathode according to claim 2, wherein the relationship of 0.5I2 is satisfied.