JP2011119458A - Gas laser oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas laser oscillator for preventing the leakage of cooling liquid. <P>SOLUTION: This gas laser oscillator is provided with: a wind tunnel container 50 into which laser gas is encapsulated; a discharging electrode 100 formed so as to face the wind tunnel container 50 and equipped with a pair of dielectric electrodes 1a and 1b partially formed with electrodes; and cooling channels 8 embedded in the dielectric electrodes 1a and 1b, and is configured to generate discharging in a space between electrode formation parts by applying a voltage to the electrodes of a pair of dielectric electrodes 1a and 1b, and to cool the dielectric electrodes 1a and 1b by making a cooling liquid pass through the cooling channels 8, wherein the cooling channels 8 of the dielectric electrodes 1a and 1b are embedded in the dielectric parts of the electrode formation parts and the dielectric parts of the dielectric electrodes corresponding to the downstream side of laser gas from the discharging space between the electrode formation parts, and the cooling channels 8 are formed of resin or metal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a gas laser oscillation device used in a laser processing machine, and particularly relates to a cooling structure for the discharge electrode.

  As a conventional gas laser oscillating device, a dielectric path is provided by providing a cooling path at least partially comprising a dielectric and a metal electrode inside the dielectric electrode, and flowing the coolant to directly cool the dielectric electrode. A technique for suppressing the thermal stress (partial thermal expansion) and preventing deformation and destruction of the dielectric electrode is disclosed (for example, Patent Document 1).

Japanese Utility Model Publication No. 5-38931 (summary and Fig. 1)

Usually, the dielectric used in the gas laser oscillation apparatus is glass or ceramics. Since these are brittle materials, they may be broken by thermal stress due to temperature distribution. In Patent Document 1, a cooling path is formed in the dielectric of the dielectric electrode. For this reason, the dielectric is well cooled and the generation of thermal stress is small.
However, if the coolant flow rate decreases or the coolant pressure increases due to an erroneous operation or failure, the dielectric breaks down and the coolant leaks. In the gas laser oscillation device, a discharge electrode is installed in a wind tunnel container (gas container). The leaked coolant is partially vaporized to fill the wind tunnel container.

This is a significant problem. For example,
(1) The dielectric electrodes of the high-voltage discharge electrode are short-circuited, and the power supply means (laser power supply) fails.
(2) A lot of cost and time are required to clean and dry the wind tunnel container.
(3) The inside of the wind tunnel container is corroded and needs to be replaced.
(4) Coolant enters the vacuum pump for gas replacement and breaks down.
Etc. This dielectric breakdown cannot be avoided due to its physical properties (brittleness, thermal expansion coefficient, Young's modulus, fracture strength, bending strength, etc.). Therefore, the conventional electrode cannot avoid the occurrence of this defect (destruction).
In addition, since the corner portion has an acute angle in the cross-sectional shape of the cooling path, it becomes a crack propagation starting point of a dielectric that is a brittle material, and repeated fatigue failure or delayed failure may occur. Further, the dielectric portion corresponding to the upstream side of the laser gas is cooled by the coolant and is cooled by the cooled laser gas. Therefore, since the temperature distribution becomes large during discharge, the probability of destruction is increased.

  The present invention has been made to solve the above-described problems, and can prevent the leakage of the coolant even when the dielectric electrode is destroyed due to an abnormal operating state of the gas laser oscillation device. An object is to obtain a gas laser oscillation device.

A gas laser oscillating device according to the present invention includes a wind tunnel container in which a laser gas is enclosed, a discharge electrode having a pair of dielectric electrodes provided facing each other in the wind tunnel container, each of which is formed with electrodes. A power supply means for applying a voltage between the electrodes of the pair of dielectric electrodes, and a cooling path embedded in the dielectric electrode, and applying a voltage to the electrodes of the pair of dielectric electrodes. In the gas laser oscillation device configured to generate a discharge in a space between each electrode forming portion and to cool the dielectric electrode by passing a cooling liquid in the cooling path, the cooling path for the dielectric electrode is an electrode. The dielectric portion of the forming portion and the dielectric portion of the dielectric electrode corresponding to the downstream side of the laser gas from the discharge space between the electrode forming portions are respectively embedded, and the cooling path is formed of resin or metal. One in which the.

  According to the gas laser oscillation device of the present invention, leakage of the coolant can be prevented even when the dielectric electrode is destroyed due to an abnormal operating state of the gas laser oscillation device.

1 is a schematic cross-sectional configuration diagram of a general gas laser oscillation device. It is a schematic front block diagram of the gas laser oscillation apparatus of FIG. FIG. 5 is a cross-sectional view taken along line AA in FIG. 4, showing the discharge electrode according to Embodiment 1 of the present invention. FIG. 4 is a cross-sectional view taken along the line BB in FIG. 3, showing the dielectric electrode in the first embodiment. FIG. 4 is a top view of FIG. 3 showing the dielectric electrode in the first embodiment. 3 is a three-side view of a cooling path in the first embodiment. 7 is a cross-sectional view showing a dielectric electrode in a second embodiment. FIG. FIG. 9 is a cross-sectional view showing a dielectric electrode in a third embodiment. FIG. 9 is a cross-sectional view showing a dielectric electrode in a fourth embodiment. FIG. 10 is a cross-sectional view showing a dielectric electrode in a fifth embodiment. FIG. 10 is a cross-sectional view showing a dielectric electrode in a sixth embodiment. FIG. 10 is a sectional view showing a dielectric electrode in a seventh embodiment.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional configuration diagram showing a general gas laser oscillation device 200. FIG. 2 is a schematic front view of the gas laser oscillator 200 of FIG. The positional relationship of FIG. 2 with respect to FIG. 1 can be understood from the X, Y, and Z axes shown together with FIGS. In FIG. 1, a discharge electrode 100 is installed in a wind tunnel container 50. The discharge electrode 100 includes first and second dielectric electrodes 1a and 1b provided to face each other with a discharge space 55 interposed therebetween. Before and after the discharge space 55, laser resonance mirrors (total reflection mirror 5 and partial transmission mirror 6 in FIG. 2) are provided. Further, a high frequency high voltage is applied to the discharge electrode 100 from the power source 10 which is a power supply means. The laser gas is excited in the discharge space 55 by this high frequency high voltage. The light emitted by this discharge is resonated by the laser resonance mirrors 5 and 6 and output as laser light L from the partial transmission mirror 6. The high-temperature gas flow 54 that has been discharge-heated in the discharge space 55 is guided to the gas duct 51 and cooled by the heat exchanger 52, and the cooled gas flow 56 is sent again to the discharge space 55 by the blower 53. This gas circulation cooling prevents “the oscillation efficiency decreases when the laser gas temperature is high”.

FIG. 3 is a cross-sectional view showing the discharge electrode in the first embodiment. 4 is a cross-sectional view of the dielectric electrode of FIG. 3 taken along the line BB. 3 is a cross-sectional view taken along line AA in FIG. FIG. 5 is a top view of the dielectric electrode of FIG. FIG. 6 is a three-side view (plan view, right side view, front side view) of the cooling path 8 of the dielectric electrode 1a. In addition, in the subscripts a and b, “a” represents a portion of the dielectric electrode on the upper side of the discharge electrode, and “b” represents a portion of the dielectric electrode on the lower side of the discharge electrode. The discharge electrode 100 will be described with reference to FIG. The discharge electrode 100 is composed of first and second dielectric electrodes 1a and 1b provided to face each other with a discharge space 55 interposed therebetween. A high frequency high voltage is applied to the metal electrodes 2a and 2b from a power source (feeding means) 10. The discharge space 55 is filled with a laser (oscillation) gas of about 100 Torr, and the power energy from the power source is effectively converted into discharge energy.

Next, the configuration of the dielectric electrode 1a will be described with reference to FIGS. A cooling path 8a is embedded in the dielectric of the dielectric electrode 1a. The cooling path 8 (or the inner wall of the cooling path) at a position corresponding to the discharge space 55 of the cooling path 8a is formed of a circular metal tube made of a conductive material, and a dielectric portion corresponding to the discharge space 55 of the dielectric electrode 1a. It is in close contact with. This metal tube becomes the metal electrode 2a (metal cooling path). The other cooling path 8a (or the inner wall of the cooling path) is made of a tubular resin (resin cooling path 9a) and is in close contact with the dielectric portion of the dielectric electrode 1a. That is, the resin cooling paths 9a and 9b are in close contact with the dielectric portion corresponding to the downstream side of the laser gas from the discharge space between the electrodes 2a and 2b forming portions of the dielectric electrodes 1a and 1b. As shown in FIGS. 5 and 6, the coolant 7 flows into the injection hole 13 of the cooling path 8, passes through the cooling path 8 a, and flows out from the discharge hole 14. Further, there is a power supply unit 15 for applying a voltage to the metal electrode 2a, and a power supply 10 for applying a high frequency high voltage is connected thereto.

Next, the operation of the first embodiment will be described. When a high frequency high voltage is applied between the metal electrodes 2a and 2b by the power supply 10 with the laser gas 56 flowing in the discharge space 55, silent discharge occurs in the discharge space 55 via the dielectric electrodes 1a and 1b. When silent discharge occurs, laser oscillation occurs in a resonance mirror composed of the total reflection mirror 5 and the partial transmission mirror 6 shown in FIG. 2 in a direction (X direction) orthogonal to the electric field direction (Z direction) of the silent discharge. Occurs, and the laser beam L is output from the partial transmission mirror 6. When silent discharge occurs, the temperature of the dielectric portions of the dielectric electrodes 1a and 1b in contact with the metal electrodes 2a and 2b rises due to silent discharge and dielectric loss.

At this time, the coolant 7 supplied from the coolant pump (not shown) to the injection hole 13 of the coolant path 8 is supplied to the inside of the coolant paths 8a and 8b. The metal electrodes 2 a and 2 b are directly cooled by the cooling liquid 7. Moreover, although the dielectric part which touches a silent discharge space becomes high temperature by discharge, it is indirectly cooled by the metal electrodes 2a and 2b which are cooling paths. Further, the dielectric portion downstream of the silent discharge space is heated by the high-temperature laser gas flow 54, but is indirectly cooled by the resin cooling paths 9a and 9b. Therefore, the dielectrics of the portions of the dielectric electrodes 1a and 1b do not become high temperature, and are not deformed or destroyed due to the difference in thermal expansion.

Here, when the supply pressure of the cooling liquid 7 rises abnormally or the flow of the cooling liquid 7 stops due to a failure of the cooling liquid pump, a thermal stress is generated due to the temperature distribution, and the dielectric electrodes 1a and 1b. The dielectric may be deformed or destroyed. However, in the first embodiment, the cooling path 8 or the inner wall of the cooling path is made of a metal or a resin, so that the metal material or the resin material has a coefficient of thermal expansion and a Young's coefficient compared to a dielectric material that is a brittle material. Since the stress generated at the same temperature difference is much smaller due to the rate relationship, it does not break. For example, alumina ceramics (thermal expansion coefficient 0.000008, Young's modulus 400 GPa) as a dielectric, aluminum (thermal expansion coefficient 0.000023,
The stress generated at the same temperature difference can be compared by the product of the thermal expansion coefficient and the Young's modulus, assuming that the modulus (Young's modulus is 70 GPa) and polycarbonate (thermal expansion coefficient is 0.000065, Young's modulus is 2.3 GPa). Therefore, as an approximate ratio of stress, “alumina ceramics” vs. “aluminum” vs. “polycarbonate” is “320” vs. “161” vs. “15”.

In addition, since a metal material has a fatigue limit and can be designed so as not to be destroyed, a dielectric material, which is a brittle material, has a probability distribution of failure base points, and may possibly break someday. Therefore, it is assumed that dielectric breakdown is unavoidable. If a metal material or a resin material that does not cause breakdown even at a temperature distribution at the same position is used, the coolant does not leak even if the dielectric breaks. Further, the cross-sectional shape of the metal electrode 2a to which the high frequency high voltage is applied is circular. Thereby, there is no acute angle part where the electric field concentrates on the metal electrode 2a. On the other hand, heat generation and temperature rise are often caused by dielectric loss in the electric field concentration part. Therefore, in the first embodiment, compared to the flat metal electrode disclosed in Patent Document 1, the probability of breakdown of the dielectric electrode due to thermal stress caused by electric field concentration is low.

  Moreover, the cross-sectional shape of the cooling path was circular. As a result, there is no sharp corner where stress is concentrated. On the other hand, the cooling path is a portion where the temperature distribution changes most rapidly. That is, the thermal stress is large. However, in the first embodiment, since there is no stress concentration portion that becomes a base point of fracture, the possibility of repeated fatigue fracture or delayed fracture is low. Further, the cooling path is not provided in the dielectric portion corresponding to the upstream side of the laser gas from the discharge space between the dielectric electrode forming portions. Thereby, only the laser gas flow (cooled gas flow) 56 is cooled in this portion. Therefore, the temperature is higher than when the cooling effect of the coolant acts. On the other hand, since the dielectric part corresponding to the laser gas downstream side from the discharge space 55 is in contact with the heated laser gas, it becomes high temperature. Therefore, in the first embodiment, since the temperature distribution of the dielectric can be relaxed, the probability of destruction of the dielectric electrode due to thermal stress is low.

For example, in a typical 2 kw CO ₂ laser oscillator, the temperature of the coolant is 10 ° C., the temperature of the cooled gas stream 56 is 20 ° C., and the temperature of the hot gas stream 54 is 100 ° C. The temperature of the dielectric portion is generally 100 ° C. Here, if the dielectric part on the upstream side of the laser gas is not cooled, the dielectric part on the upstream side of the laser gas becomes 20 ° C., which is the same as the gas temperature. However, when the dielectric portion upstream of the laser gas is cooled with the cooling liquid, the temperature of the cooled gas flow 56 is low, so that the amount of heat absorption is small and is approximately 10 ° C. Therefore, the temperature distribution difference of the dielectric is 80 ° C. for the former and 90 ° C. for the latter. That is, the probability of destruction of the latter (in the case where the dielectric part upstream of the laser gas is cooled with the cooling liquid) is increased.

As described above, in the operation of the laser processing machine, even if the dielectric electrode is broken, a gas laser oscillation device that is less damaged and has a low probability of destruction, that is, a high-quality gas laser oscillation device can be realized. Further, even if a significant stress acts on the dielectric material and the dielectric material, which is a brittle material, is damaged, the coolant does not leak into the wind tunnel container. That is, the failure of the gas laser oscillation device can be limited only to the electrodes. Therefore, since the gas laser oscillation device can be restored only by exchanging the electrodes, a gas laser oscillation device that can be restored earlier can be obtained.
Further, if the cooling path embedded in the dielectric part of the electrode forming part is formed of a conductive material and a voltage is applied to the cooling path from the power feeding means, as in the case of only a flat electrode. Since there is no electric field concentration, heat generation due to dielectric loss can be kept low, and the probability of thermal strain breakdown can be reduced.
Further, a cooling path is not formed in the dielectric portion corresponding to the laser gas upstream side of the discharge space of the dielectric electrode. Therefore, the stress that causes the dielectric to break can be relaxed, and the probability of electrode breakage can be reduced.

Embodiment 2. FIG.
FIG. 7 is a sectional view showing a dielectric electrode in the second embodiment. As the conductive electrode 2a, a flat electrode is provided in the dielectric, and is brought into contact with the circular metal tube to supply power to the circular metal tube and the flat electrode. In this way, if a flat electrode is used, the electric field distribution in the discharge space 55 becomes more uniform. For example, in order to reduce the spatial and temporal fluctuation of the laser light, the laser gas flow velocity distribution may be made uniform at the same time as the second embodiment. Also in the second embodiment, since the power is supplied to the circular metal tube of the cooling path 8, the effect of reducing the concentration of the electric field inside the dielectric works effectively.

Embodiment 3 FIG.
FIG. 8 is a sectional view showing a dielectric electrode in the third embodiment. As the conductive electrode 2a, a flat electrode is provided in the dielectric body, is not in contact with the circular metal tube, and supplies power to the metal tube and the flat electrode. Thus, if a flat electrode is used, the electric field distribution in the discharge space 55 is
It becomes more uniform. For example, in order to reduce the spatial and temporal fluctuations of the laser light, the laser gas flow velocity distribution may be made uniform simultaneously with the third embodiment. Also in the third embodiment, since the power is supplied to the circular metal tube of the cooling path 8, the effect of reducing the concentration of the electric field inside the dielectric works effectively.

Embodiment 4 FIG.
FIG. 9 is a cross-sectional view showing a dielectric electrode in the fourth embodiment. As the conductive electrode 2a, a plate-like electrode is provided in a dielectric body and directly supplied with power, and the cooling path is entirely formed of a tubular resin. In this way, if a flat electrode is used, the electric field distribution in the discharge space 55 becomes more uniform. For example, in order to reduce the spatial and temporal fluctuations of the laser light, the laser gas flow velocity distribution may be made uniform simultaneously with the fourth embodiment. Also in Embodiment 4, since the cross section of the cooling path is circular, the effect of mitigating thermal stress concentration in the cooling path is effective.

Embodiment 5 FIG.
FIG. 10 is a sectional view showing a dielectric electrode in the fifth embodiment. As the conductive electrode 2a, a plate-like electrode is provided on the surface of the dielectric plate 21, and is adhered to the surface of the dielectric of the dielectric electrode 1a by the adhesive layer 22, and power is supplied directly to the plate-like electrode. And all the cooling paths 8 are formed with the tubular resin. If flat electrodes are used in this way, the electric field distribution in the discharge space 55 becomes more uniform. Further, since the process of forming the electrode in the dielectric is simplified, the cost can be kept low. Also in Embodiment 5, since the cross section of the cooling path is circular, the effect of mitigating thermal stress concentration in the cooling path is effective.

Embodiment 6 FIG.
FIG. 11 is a sectional view showing a dielectric electrode in the sixth embodiment. The cross-sectional shape of the cooling path 8 (the conductive cooling path 2 and the resin cooling path 9) is not limited to a circular shape because the corners are arc-shaped. As shown in FIG. 11, for example, the outer shape is a square shape, the inner shape is a circle, the outer shape and the inner shape are both a square shape, or an oval shape, and the desired cooling performance may be obtained. . When the outer shape or the inner shape is a quadrilateral shape, the corners are formed as smoothly as possible. By making the corner portion of the cross-sectional shape of the cooling path into an arc shape, the stress concentration at the corners can be reduced in the thermal stress caused by the temperature difference between the heated dielectric and the cooling path wall surface. Therefore, the probability of thermal strain breakdown can be reduced.

Embodiment 7 FIG.
FIG. 12 is a cross-sectional view showing a dielectric electrode in the seventh embodiment. In the first embodiment, the number of the cooling paths 8 is one. However, as in the seventh embodiment, a multi-branch structure may be used at both ends. In this case, it is possible to design the cooling liquid flow rate by changing the cross-sectional shape of each cooling path 8 so as to obtain a desired cooling performance. Therefore, the temperature distribution of the dielectric electrode 1a can be more relaxed.

In the embodiment, the arrangement interval of the cooling paths is not fixed, and may be set so as to relax the temperature distribution of the dielectric electrodes 1a and 1b. That is, it is only necessary to make the cooling path of the dielectric electrodes 1a and 1b where the temperature rises drastically dense and change the cooling capacity by making the other parts sparse so that the temperature rise of the dielectric becomes uniform. Therefore, the thermal deformation of the dielectric becomes uniform, the generated thermal stress is reduced, and the dielectric is not deformed or broken due to the difference in thermal expansion, so that the reliability of the discharge electrode (gas laser oscillation device) can be improved.
In the embodiment, the cooling path 8 is provided so as to be orthogonal to the direction in which the laser gas flow 56 flows.

1 dielectric electrode, 2 conductive (metal) electrode,
DESCRIPTION OF SYMBOLS 5 Total reflection mirror 6 Partial transmission mirror 7 Coolant 8 Cooling path 9 Resin cooling path 10 Power supply 13 Injection hole 14 Discharge hole 15 Feed part 21 Dielectric board 22 Adhesive layer 50 Wind tunnel container 51 Gas duct 52 Heat exchanger 53 Blower 54 Hot gas Flow 55 Discharge space 56 Cooled gas flow 100 Discharge electrode 200 Gas laser oscillator

Claims (6)

A wind tunnel container filled with laser gas,
A discharge electrode having a pair of dielectric electrodes provided facing each other in the wind tunnel container, each of which is formed with an electrode;
Power supply means for applying a voltage between the electrodes of the pair of dielectric electrodes;
A cooling path embedded inside the dielectric electrode,
A gas laser configured to apply a voltage to the electrodes of the pair of dielectric electrodes to generate a discharge in a space between the respective electrode forming portions, and to cool the dielectric electrodes by passing a coolant through the cooling path. In the oscillation device,
The dielectric electrode cooling path is embedded in the dielectric part of the electrode forming part and the dielectric part of the dielectric electrode corresponding to the downstream side of the laser gas from the discharge space between the electrode forming parts, respectively. A gas laser oscillation device characterized in that the cooling path is formed of resin or metal.   The gas laser oscillation apparatus according to claim 1, wherein a cooling path embedded in a dielectric part of the electrode forming part is formed of a conductive material, and a voltage is applied to the cooling path from the power feeding unit.   3. The gas laser oscillation device according to claim 2, wherein the electrode of the electrode forming portion includes the cooling path made of a conductive material and a flat electrode.   2. The gas laser oscillation apparatus according to claim 1, wherein the cooling path of the dielectric electrode is made of a resin material, and the electrode of the electrode forming portion is made of a flat electrode.   The gas laser oscillation device according to any one of claims 1 to 4, wherein a corner portion of a cross-sectional shape of the cooling path is formed in an arc shape.   6. The gas laser oscillation apparatus according to claim 1, wherein no cooling path is provided in the dielectric portion corresponding to the upstream side of the laser gas from the discharge space of the electrode forming portion.

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