JP3247750B2 - Vacuum arc ignition device and vacuum arc ignition method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vacuum arc processing apparatus and a method for igniting a vacuum arc in the apparatus. More specifically, the present invention relates to a vacuum arc processing apparatus in which a cathode is processed by a vacuum arc and a method for igniting a vacuum arc, and more particularly to a vacuum arc processing apparatus and a method for igniting a vacuum arc, wherein the cathode runs continuously.

[0002]

2. Description of the Related Art Vacuum arc technology is a technology widely used for vacuum circuit breakers, which are electric circuit components. In recent years, attempts have been made to apply a vacuum arc to a material process. That is, there are vapor deposition, ion plating and removal of an oxide film.

In the material process, it is desired to continuously supply and process a material in order to improve productivity. In a vacuum arc process, when a material to be processed is used as a cathode and the cathode travels, a problem of movement control of the cathode point occurs. That is, the arc is extinguished when the cathode spot moves with the object to be processed and moves away from the anode. The speed at which the cathode spot moves relative to the workpiece is the theoretical upper limit of the line speed of the process. When the cathode surface is metal, the upper limit of the line speed is about 5 m / s.

The present inventors have attempted to descale the cathode surface by a vacuum arc using a mechanical contact method in which an ignition electrode having the same potential as the anode is instantaneously brought into contact with the cathode to ignite the vacuum arc. That is, a metal whose surface was oxidized was used as the cathode. At this time, the upper limit of the line speed is 0.5 m / s
It has been found that the arc is extinguished beyond this limit. In other words, the arc maintenance limit speed becomes slower when the scale is present than when the metal surface is present. Further, in this method, there is a disadvantage that the properties of the cathode surface become rough because the ignition electrode is in mechanical contact.

[0005] The present inventors first attempted an intermittent ignition method in a mechanical contact method. The method of locally heating the cathode surface was also studied. Although these attempts have had some success in increasing the critical speed, they have not been successful in certainty in maintaining the ignition arc at high speeds, for example, 1 m / s.

[0006]

SUMMARY OF THE INVENTION The present inventors have studied the application of a high-frequency high-voltage application method used for igniting a DC arc to the ignition of a vacuum arc. That is, an attempt was made to apply a high-frequency high voltage to an ignition electrode placed near the cathode to ignite a vacuum arc between the cathode and the anode. This method was expected to have the advantages of being able to ignite the arc continuously and not impairing the surface properties of the cathode, unlike the mechanical contact method. However, only the glow discharge was turned on near the ignition electrode, and the vacuum arc was not ignited.

In view of the above-mentioned circumstances, the present invention provides an apparatus and method for continuously igniting a vacuum arc by a high-frequency high-voltage application method and maintaining the vacuum arc without extinguishing the arc regardless of the running speed and surface properties of the object. The purpose is to provide.

[0008]

Means for Solving the Problems The present inventors have conducted various experiments and studies to achieve the above object, and as a result, have reached the present invention. The present inventors have attempted to ignite the arc by changing the pressure in order to examine why the high-frequency high-voltage application method capable of igniting the arc at atmospheric pressure cannot ignite the arc under a vacuum of several Pa, for example. As a result, it was found that when the pressure was high, for example, several hundred Pa or more, corona discharge occurred from the tip of the ignition electrode, thereby causing an arc between the cathode and the anode. It was also found that as the pressure decreases, corona discharge becomes more difficult. This phenomenon was found to be the low-pressure behavior of Paschen's law. That is,
The curve of Paschen's law, in which the ignition voltage of corona discharge depends on the pressure P / distance d, falls to the right when P / d is small, and rises to the right after passing through the minimum value. Although the region of several Pa is a region in which the ignition voltage is lowering to the right of the curve, it has been found that a higher voltage is required for the ignition voltage than when the pressure is higher.

Further, the inventors of the present invention have observed well the glow discharge that occurs when corona discharge does not occur. As a result, it is found that the lamp is lit not only near the ignition electrode but also near the exposed portion of the high-frequency high voltage. Noticed. That is, the high-frequency high-voltage exposed portion is a terminal or the like of a connection portion of the high-frequency high-voltage circuit. Furthermore, he noticed that one electrode of the glow discharge was an exposed part of the high-frequency high-voltage part including the ignition electrode, and the other electrode was a metal vacuum vessel at the ground potential. Furthermore, when observing these glow discharges, the glow discharge at a position electrically close to the high frequency high voltage power supply is
It has been found that it is brighter than a glow discharge at an electrically distant position such as an ignition electrode. That is, the inventors noticed that the discharge energy was used for the glow discharge at a position near the high-frequency high-voltage power supply, and only the attenuated voltage was transmitted to the distant ignition electrode.

Further, the present inventors have observed the movement of the cathode spot with high-speed video in order to clarify the cause of the vacuum arc being easily extinguished when the cathode runs continuously. When the cathode was stationary, it was observed that the cathode spot runs around the entire surface of the cathode near the anode. In addition, it has been found that the total number of simultaneously existing cathode spots is kept substantially constant even if one cathode spot is divided into two cathode spots or the cathode spot disappears spontaneously.

On the other hand, it has been found that when the cathode travels, the cathode spots gather in the downstream portion together with the movement of the cathode in the cathode traveling direction and hardly exist in the upstream portion. In particular, when the speed of the cathode was high, it was observed that even when the vacuum arc was ignited, the cathode spot flowed downstream and was extinguished with the travel of the cathode. At this time, it has been found that if a vacuum arc is continuously ignited in the upstream part, the arc becomes difficult to extinguish.

The invention of the present application has been made based on the above-mentioned experiments and studies. The first invention is to form a vacuum arc between a cathode and an anode with a high-frequency high-voltage ignition electrode placed near the cathode. In a vacuum arc ignition device for ignition, a high-frequency high-voltage lead component from a vacuum vessel wall to an ignition electrode is coated with an insulating material, and an exposed portion of the high-frequency high voltage in the vacuum vessel is limited to the ignition electrode. I do.

A second aspect of the present invention is the vacuum arc ignition device according to the first aspect, further comprising means for supplying a gas near the ignition electrode.

A third invention is characterized in that, in the vacuum arc ignition device of the second invention, a vacuum arc is ignited by applying a high frequency high voltage to an ignition electrode while supplying gas by gas supply means. And

According to a fourth aspect of the present invention, when a vacuum arc is ignited between a cathode and an anode running continuously by the vacuum arc ignition device of the first invention, an ignition electrode is provided upstream of the center of the anode. It is characterized by being installed.

[0016]

First, referring to FIG. 1 showing a vacuum arc processing apparatus and FIG. 2 showing an enlarged view of an ignition electrode 3 shown in FIG.
The second invention will be described. In the first invention, the ignition electrode 3 is provided between the cathode 1 and the anode 2. These are all contained in the vacuum container 4. The cathode 1 is connected to the negative electrode of the DC power supply 5 via a terminal on the vacuum vessel wall, and the anode 2 is similarly connected to the positive electrode of the DC power supply 5 via the terminal on the vacuum vessel wall. The ignition electrode 3 is connected to a high frequency high voltage power supply 7 by a high frequency high voltage lead 6. The high-frequency high-voltage power supply 7 generates a high frequency of tens of thousands of volts by, for example, a Tesla coil method, and has a frequency of, for example, several kHz, but is not limited thereto. The other output terminal of the high-frequency high-voltage power supply 7 is connected to the cathode 1, but may be connected to the ground.

The conductor portion of the high-frequency high-voltage lead 6 that reaches the ignition electrode 3 must be covered with an insulator. This is because a glow discharge occurs between the high-frequency high-voltage exposed conductor and the metal vacuum vessel 4. As an insulator for coating, for example, a fluororesin is desirable. For the same reason, when guiding the high-frequency high-voltage lead 6 into the vacuum vessel 4, it is desirable that no terminal is provided in the vacuum vessel 4. For example, when an attempt is made to provide a terminal in the vacuum vessel 4, it is necessary to coat the terminal with an insulating material, but this coating operation is extremely troublesome. Therefore, as shown in FIG. 2, the high-frequency high-voltage leads 6 are passed through the through holes in the wall of the vacuum vessel 4, and these gaps are filled with a solidified vacuum sealant commercially available under the trade name of "Tall Seal". Therefore, it is desirable to install the terminal outside the vacuum vessel 4. Here, the distance between the terminal and the vacuum vessel 4 needs to be maintained so that corona discharge or the like does not occur. Note that a high-frequency high-voltage power supply 7 may be used to directly introduce the high-frequency high-voltage lead 6 coated with an insulator into the vacuum vessel 4 to apply a high-frequency high voltage to the ignition electrode 3 without providing a terminal.

The second and third aspects of the present invention will be described with reference to FIG. FIG. 3 shows details of one installation mode of the ignition electrode 3. The ignition electrode 3 is a conductor itself obtained by stripping a covering insulator of the high-frequency high-voltage lead 6. As a means for supplying gas, a gas introduction pipe 8 made of an insulator is used.
It is desirable to add a gas discharge pipe 9 for determining the gas discharge direction. Here, the discharge port of the gas discharge tube 9 is desirably directed toward the cathode 1. This is because a vacuum arc is ignited by a corona discharge caused by a high-frequency high voltage between the ignition electrode 3 and the cathode 1. For the same reason, the insulator-coated high-frequency high-voltage lead 6 is integrated with the gas introduction pipe 8 and the gas discharge pipe 9, and all the introduced gas is discharged from the tip of the gas discharge pipe 9 into the vacuum vessel. Is desirable. If there is a gap between the high-frequency high-voltage lead 6 and the tube and gas leaks, a corona discharge or a glow discharge is generated between the ignition electrode 3 and the vacuum vessel 4 or the like, and between the cathode 1 and the ignition electrode 3. This is because no corona discharge occurs. By applying a high-frequency high voltage to the ignition electrode 3 of FIG. 3 while flowing gas from the gas inlet tube 8, the pressure in the gas discharge tube is relatively high even if the pressure in the vacuum vessel 4 is several Pa, and the corona discharge The ignition voltage is reduced, and corona discharge is facilitated.

The gas inlet tube 8 and the gas outlet tube 9 are preferably made of an insulating material such as glass. This is because, when the surface is carbonized with a fluororesin or the like, a discharge runs on the surface and corona discharge between the surface and the cathode 1 hardly occurs. Although the diameter and length of the gas introduction pipe 8 and the gas discharge pipe 9 are not specified, it is preferable that the diameter of the gas discharge pipe 9 is small. This is because it is possible to increase the pressure in the gas discharge tube 9 with a small gas flow rate to easily cause corona discharge. This makes it possible to reduce the gas consumption and the capacity of the evacuation system.

The fourth invention will be described with reference to FIG. Here, the cathode 1 runs and is continuously processed. In FIG. 4, the region where the vacuum arc stands by the shielding plate 10 is limited to a portion surrounded by the shielding plate 10, the anode 2 and the cathode 1. When the conductor roll or the like, which is a means for flowing the arc current from the cathode 1, is sufficiently far from the anode 2, the shielding plate 10 is not necessary, but the means for flowing the arc current from the cathode 1 is the anode 2.
When the temperature is close to the above, a shielding plate is required to prevent the arc from flying directly from the anode 2 to the means. The anode center is a geometric center that divides the upstream and downstream of the travel of the cathode 1. When the anode 2 is not symmetrical between the upstream part and the downstream part, the area of the anode 2 defines the center of the anode. When the cathode 1 travels, the ignition electrode 3 needs to be installed upstream of the center of the anode. This is because the cathode point, which is indispensable for vacuum arc processing, has a low moving speed, and moves at substantially the same speed as the cathode 1 when the running speed of the cathode 1 is high.

Therefore, it disappears away from the anode 2. In particular, when the arc region is limited by the shielding plate 10, the cathode spot disappears downstream of the shielding plate 10. Therefore, by installing the ignition electrode 3 upstream of the center of the anode and igniting continuously, it is possible to supplement the cathode spot that is generated at the upstream and disappears at the downstream.

Hereinafter, embodiments of the present invention will be described.

[0023]

【Example】

Example 1 The apparatus shown in FIGS. 1 and 2 was used. The cathode 1 to be processed is a stainless steel plate after hot rolling. In this case, the thickness of the oxide layer on the surface is about 5 μm. When the vacuum arc is ignited, the arc voltage is 28
V and the arc current is 400A. The result when the high-frequency high-voltage lead 6 before the present invention is exposed in the vacuum vessel is also shown for comparison.

First, the vacuum arc was not ignited without operating the DC power supply 5 and the state of discharge from the ignition electrode was observed while changing the pressure. The high frequency high voltage power supply 7 was operated under the atmospheric pressure. Here, a corona discharge occurred between the ignition electrode 3 and the cathode 1. A vacuum was often applied here. When the high-frequency high-voltage lead 6 was exposed on the way, the corona discharge disappeared at several hundred Pa and transited to glow discharge. On the other hand, in the device of the present invention, 2
Corona discharge was maintained even when the pressure was reduced to Pa.

Next, the pressure was reduced to several Pa, the DC power supply 5 was operated, and then the high frequency high voltage power supply 7 was operated. When the high-frequency high-voltage lead 6 was exposed on the way, only a glow discharge occurred between the ignition electrode 3 and the exposed portion of the high-frequency high-voltage lead 6 and the vacuum vessel 4, but no vacuum arc was ignited.
On the other hand, in the apparatus of the present invention, the vacuum arc was ignited simultaneously with the operation of the high-frequency high-voltage power supply 7.

Example 2 The apparatus shown in FIG. 1 was used. The cathode 1 to be processed is a stainless steel plate after hot rolling. In this case, the thickness of the oxide layer on the surface is about 5 μm.
m. When the vacuum arc is ignited, the arc voltage is 28V and the arc current is 400A. The degree of vacuum is several Pa. A comparison was made using the ignition electrode shown in FIG. 2 and the ignition electrode shown in FIG. The procedure was as follows: the vacuum was reduced to several Pa, the DC power supply 5 was operated, and then the high-frequency high-voltage power supply 7 was operated. When the ignition electrode shown in FIG. 3 was used, Ar was supplied as a gas at a flow rate of 10 sccm.

When the ignition electrode shown in FIG. 2 was used, it was not possible to reignite after the vacuum arc had been sufficiently counted. At this time, corona discharge or glow discharge was carried out from the insulation covering the high-frequency high-voltage lead 6 to a vacuum vessel or the like. This was presumed to be due to the fact that the deposited material adhered to the surface of the covering insulator of the high-frequency high-voltage lead 6 by maintaining the vacuum arc, and the high-frequency high voltage was supplied to the attached material.

When the ignition electrode shown in FIG. 3 was used, re-ignition was easy even after maintaining the vacuum arc for the total counting time.

Example 3 The apparatus shown in FIG. 4 was used. The cathode 1 to be processed is a stainless steel plate after hot rolling. In this case, the thickness of the oxide layer on the surface is about 5 μm.
m. When the vacuum arc is ignited, the arc voltage is 28V and the arc current is 400A. The degree of vacuum is several Pa. A comparison was made using the ignition electrode shown in FIG. 2 and the ignition electrode shown in FIG. The procedure was as follows: the vacuum was reduced to several Pa, the DC power supply 5 was operated, the cathode was run at a constant speed, and then the high-frequency high-voltage power supply 7 was operated. When the ignition electrode shown in FIG. 3 was used, Ar was supplied as a gas at a flow rate of 10 sccm.

When both the ignition electrode of FIG. 2 and the ignition electrode of FIG. 3 were used, the vacuum arc was stably maintained up to the cathode traveling speed of 1 m / s. When the electrode shown in FIG. 2 was used, the critical speed of the cathode, at which the vacuum arc was stably maintained, decreased over time. On the other hand, FIG.
When the electrode was used, the arc could be stably maintained at a running speed of 1 m / s even after 10 hours.

[0031]

According to the present invention, there is provided an apparatus and a method for continuously igniting a vacuum arc by a high-frequency high-voltage application method and maintaining the vacuum arc without extinguishing the workpiece regardless of the running speed and surface properties of the object. As a result, the vacuum arc can be used industrially, and as a result, the present invention has become extremely large in contributing to industrial development.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a vacuum arc ignition device of the present invention.

FIG. 2 is a schematic sectional view of an ignition electrode of the vacuum arc ignition device of the present invention.

FIG. 3 is a schematic sectional view of an ignition electrode of the vacuum arc ignition device of the present invention.

FIG. 4 is a schematic sectional view of the vacuum arc ignition device of the present invention, (a) is a side sectional view, and (b) is a top sectional view.

[Explanation of symbols]

1: Cathode (object to be processed) 2: Anode 3: Ignition electrode 4: Vacuum container 5: DC power supply 6: High-frequency high-voltage lead 7: High-frequency high-voltage power supply 8: Gas introduction tube 9: Gas discharge tube 10: Sealing plate 11: Anode center

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 14/00-14/58 C23C 16/00-16/56 H01L 21/203-21/205 H05H 1/00-1 / 54 JICST file (JOIS)

Claims (4)

(57) [Claims] 1. A vacuum arc igniter for igniting a vacuum arc between a cathode and an anode with a high-frequency high-voltage ignition electrode placed near a cathode, wherein a high-frequency high-voltage lead component from the vacuum vessel wall to the ignition electrode is provided. A vacuum arc igniter, which is covered with an insulating material, and a high-frequency high-voltage exposed portion in a vacuum vessel is limited to an ignition electrode. 2. The vacuum arc ignition device according to claim 1, further comprising means for supplying gas near the ignition electrode. 3. A vacuum arc ignition method according to claim 2, wherein the vacuum arc is ignited by applying a high frequency high voltage to an ignition electrode while supplying gas by gas supply means in the vacuum arc ignition device of claim 2. 4. When a vacuum arc is ignited between a cathode and an anode running continuously by the vacuum arc ignition device according to claim 1, an ignition electrode is provided upstream of the center of the anode. Vacuum arc ignition device.