JPH02174282A - Gas laser oscillator - Google Patents

Abstract

PURPOSE:To realize savings in volume and weight and to improve pointing stability and beam property by constituting a blower by a plurality of turbo blowers which are connected in series. CONSTITUTION:High frequency discharge is applied instead of d.c. discharge. Metal electrodes 4, 5 are attached onto a periphery of a discharge tube 1. The metal electrode 4 is grounded and the metal electrode 5 is connected to a high frequency power source 6. A high frequency voltage is applied between the metal electrodes 4, 5 from the high frequency power source 6. High frequency glow discharge thereby develops inside the discharge tube 1 and laser excitation is carried out. Turbo blowers 15, 150 are connected in series instead of a Roots blower. Efficiency of a turbo blower of this type is much higher than that of a Roots blower and allows neglect of compression heat; therefore, a cooler 7 at a following stage can be omitted. An axial-flow CO2 type laser oscillator of laser output of about 1kW can be formed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-output gas laser oscillation device such as a carbon dioxide (Cow) gas laser device for processing, and particularly to a gas laser oscillation device that forcibly circulates laser gas.

[Conventional technology]

Recent carbon dioxide (Cot) gas laser oscillators can obtain high output and have good quality laser beam characteristics, and are now widely used for laser processing such as cutting metal or non-metallic materials, welding metal materials, etc. It's coming. In particular, C.N.
As a CNC laser processing machine combined with C (numerical control device), it is rapidly developing in the field of cutting complex shapes at high speed and with high precision.

A conventional carbon dioxide (Co□) gas laser oscillation device will be described below with reference to the drawings.

FIG. 4 is a diagram showing the configuration of a carbon dioxide (COZ) gas laser oscillation device according to the prior art. An optical resonator consisting of an output coupling mirror 2 and a total reflection mirror 3 is installed at both ends of the discharge tube l. Two high-frequency discharge electrodes, an anode 41 and a cathode 5I, are attached to the side branch of the discharge tube 1. A DC power supply section 61 is connected between the anode and the cathode. The DC power supply unit 61 is composed of a DC power supply and a ballast resistor. A DC high voltage is applied between the anode and the cathode by the DC power supply section 61. At that time, a DC glow discharge is generated in the discharge tube 1 due to the application, and laser excitation is performed. The optical axis of the laser beam inside the discharge tube I is indicated by 13, and the optical axis of the laser beam taken out from the output coupling mirror 2 is indicated by 14.

When starting up such a gas laser oscillation device, first, the entire gas inside the device is exhausted by the vacuum pump 12. Then, the valve 11 is opened, a predetermined flow rate of laser gas is introduced from the gas cylinder 10, and the gas pressure within the apparatus reaches a predetermined value. Thereafter, evacuation by the vacuum pump 12 and introduction of supplementary gas by the valve 11 continue, and part of the laser gas is continuously replaced with fresh gas while the gas pressure inside the apparatus is maintained at a specified value. This prevents gas contamination within the device.

Furthermore, in FIG. 4, a roots blower 9 circulates the laser gas within the apparatus to cool it. In carbon dioxide (CO2) gas lasers, about 20% of the injected electrical energy is converted into laser light, and the rest is consumed for gas heating. However, according to theory, the laser oscillation gain is proportional to the -(3/2) power of the absolute temperature T, so in order to increase the oscillation efficiency, it is necessary to forcibly cool the laser gas. In this device, the laser gas passes through the discharge tube 1 at a flow rate of 100 m/s, flows in the direction shown by the arrow, and is guided to the cooler 8. The cooler 8 mainly removes heating energy due to discharge from the laser gas. The roots blower 9 then compresses the cooled laser gas. The compressed laser gas is guided to the discharge tube 1 via the cooler 7. This is because the compression heat generated by the Roots blower 9 is removed by the cooler 7 before being guided to the discharge tube 1 again. Since these coolers 7 and 8 are well known, detailed explanation will be omitted.

In direct current discharge, as the current density increases, plasma uniformity is lost, streamers are more likely to form, and oscillation efficiency decreases. To prevent this, turbulence is created to ensure uniformity of discharge. For this purpose, in direct current discharge, a throttle I7 is installed at the gas injection port to the discharge tube 1.

At this time, pressure loss occurs near this throttle 17. In order to obtain a gas flow that overcomes this pressure loss, a device with a high compression ratio such as the Roots blower 9 is used.

[Problem to be solved by the invention]

However, the above conventional technology has the following problems.

First, since the Roots blower is a positive displacement blower that rotates at a low speed, it is excessive in size and weight, making the gas laser oscillation device itself oversized.

Second, a considerable amount of vibration is generated from the roots blower 9, which adversely affects the bowing stability of the laser beam.

These problems can be avoided by employing a turbo blower instead of the Roots blower, but the turbo blower has a problem in that when the amount of air blown is increased, the compression ratio is extremely reduced. This will be explained using drawings. FIG. 5 is a diagram showing the air blowing characteristics of a normal Roots blower and a turbo blower. The horizontal axis shows the compression ratio, and the vertical axis shows the displacement. In the case of a gas laser oscillation device with a laser output of IKW, a compression ratio of 1.75 and an air flow rate of 225 liters and 7 seconds are required. Therefore, as can be seen from FIG. 5, the Roots blower is sufficient to obtain this blowing characteristic. However, in the case of a turbo blower, although the displacement reaches a predetermined value, the compression ratio is significantly insufficient.

The present invention has been made in view of these points, and it is an object of the present invention to provide a gas laser oscillation device that is small and lightweight, and has excellent pointing stability and beam characteristics.

provided.

[Effect]

By using a high-speed rotation turbo blower as a blower for laser gas circulation, the blower itself can be downsized and vibrations caused by rotation can be reduced. Furthermore, since a plurality of turbo blowers are connected in series, the compression ratio and displacement can be made sufficiently large.

[Means to solve the problem] In order to solve the above problems, the present invention is comprised of a discharge tube that excites the laser by gas discharge, an optical resonator that causes laser oscillation, and a gas circulation device that forcibly cools the laser gas using a blower and a cooler. In gas laser oscillation equipment, A gas laser oscillation device characterized in that the blower is composed of a plurality of turbo blowers connected in series, 〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a configuration diagram of an embodiment of a laser oscillation device of the present invention. Since the same components as in FIG. 4 are given the same reference numerals, only the different parts will be explained here.

In this embodiment, high frequency discharge is used instead of direct current discharge. Metal electrodes 4 and 5 are attached to the outer periphery of the discharge tube 1. The metal electrode 4 is grounded, and the metal electrode 5 is connected to a high frequency power source 6.

A high frequency voltage is applied between the metal electrodes 4 and 5 from a high frequency power source 6. As a result, a high frequency glow discharge is generated in the discharge tube 1, and laser excitation is performed.In this embodiment, turbo blowers 15 and 150 are connected in series instead of the Roots blower.

Since this type of turbo blower has much higher efficiency than the Roots blower, the heat of compression can be ignored, so the cooler 7 in the latter stage can be omitted. Although not shown in the figure, it may of course be provided. By adopting such a configuration, an axial flow type carbon dioxide (COz) gas laser oscillation device with a laser output of about IKW can be realized.

As is clear from Figure 5, the compression ratio is 1.75, and the air flow rate is 2.
In order to obtain 25 liters/second, the compression ratio per turbo engine needs to be the square root of 1.75, or 1.33. Further, the flow rate at that time is approximately 300 liters/second, which sufficiently exceeds the required value. Therefore, by connecting two turbo blowers in series, it is possible to obtain a gas laser oscillation device with a sufficiently large compression ratio and air flow rate. Furthermore, by employing a turbo blower, the entire gas laser oscillation device can be made smaller and lighter, and vibration and pulsation are eliminated, making it possible to obtain laser beam oscillation characteristics with excellent pointing stability and high-speed output stability. Although the present embodiment has been described in the case of high frequency discharge, it can be similarly used in the case of direct current discharge.

Next, an example of the configuration of the turbo blowers 15 and 150 is shown in FIG. Although centrifugal blades 16 are shown here, turbocharger blades used in automobiles, ships, and aircraft engines may be used instead. Since these turbo blades are mass-produced, they are superior in both performance and price.

Turbo blade 16 is mechanically coupled to shaft 17 . A rotor 19 is attached to the shaft 17,
The rotor 19 and stator 20 constitute a motor. The motor is in a housing 1 separate from the laser gas housing.
It is installed in 8. The turbo blade 16 is rotated by this motor at a high speed of about 100,000 RPM. Turbo blades 16 having a diameter of 50 to 100 mm are generally widespread, but blades with a diameter of 30 to 300 mm can also be used. The driving rotation speed at that time is in the range of about 30,000 to 300,000 RPM. These rotate at a sufficiently high speed and therefore have a smaller volume inversely proportional to the rotational speed than the low-speed Roots blowers. In the turbo propeller as in this embodiment, it is particularly necessary to prevent resonance vibrations that occur when the turbo blades rotate at high speed. To achieve this, the embodiment shown in FIG. 2 uses ball bearings. The inner rings 22 and 23 of the bearing are fixed to the shaft 17. In this embodiment, the axis of rotation of the shaft 17 is perpendicular to the ground, but it may be parallel.

The outer rings 26 and 27 of the bearing are fixed to sleeves 28 and 29. Balls 24 and 25 are arranged between the inner rings 22 and 23 and the outer rings 26 and 27. Although only four balls are shown in the drawing, there are actually balls that are not shown in the drawing. Sleeves 2 and 29 are not fixed to bearing housings 34 and 35. This is because sleeves 28 and 29 are connected to housings 34 and 35.
This is because the following dangers will occur if the In other words, when the rotational speed of the shaft 17 is gradually increased, the rotational speed of a zero-rotating body that encounters primary, secondary, and tertiary critical speeds will become dangerous due to centrifugal force if the rotational balance is not perfect. There is a possibility of destruction when passing the speed. - The tertiary critical speed for boat fishing can be designed to be sufficiently high compared to the normal rotation speed, but it is necessary to safely pass the primary and secondary critical speeds.

Additionally, it is a design challenge to eliminate the need for extremely high precision rotational balancing and housing machining.

Therefore, in this embodiment, the sleeves 28 and 29 and the bearing housings 34 and 35 are not fixed to each other, but there is a gap between them.
Create a gap of 0 to 100 μm and apply grease 36 there.
and 37 are filled. Greases 37 and 38 damp the vibrations occurring in sleeves 28 and 29 due to their inelastic effects. In the figure, this grease 36 and 3
7 is indicated by diagonal lines 0 In this embodiment, the bearing is located in the laser gas, but since contamination of the laser gas must be avoided, a grease with a low vapor pressure is used as the damper material. Furthermore, in order to prevent the grease from scattering, the grease existing area is covered with O-rings 30 and 31, and
Each pair of numerals 32 and 33 isolates them from the outside.

Although an example using a ball bearing is shown here, a sliding bearing may also be used.

In addition, by adopting this type of damper structure, there is a gap of several tens of microns between the sleeve and the bearing housing, so when machining the housing, the ultra-precision finishing that was previously required is no longer necessary, resulting in an economical effect. . Furthermore, it is possible to eliminate destruction caused by resonance phenomena, which is inevitable in high-speed rotating bodies.

With this configuration, the laser gas is drawn from the cooler 8 to the laser turbo blower 15 (150) as shown by the arrow 81, and the laser gas is sucked into the laser turbo blower 15 (150) as shown by the arrow 71.
(150) and is discharged to the discharge tube 1. The cooling water coil 21 is for cooling the heat generated by the motor.

The turbo prowers 15 and 150 shown in FIGS. 2 and 2 are applied to a laser oscillation device with an output of about IKW, but larger turbo blades may be used to further increase the output, but the cost is the same. It is desirable to use wings. FIG. 3 shows the structure of a turbo blower with a laser output of about 2 kW. In the figure, the bearings of the turbo blower 15 (150) are the same as in FIG. 2, so they are omitted. Note that the arrow 82 in the figure
and 83 are connected from the cooler 8 to the laser turbo blower 15 (1
50) shows the direction in which the laser gas flows.

In this embodiment, the rotation axis of the shaft is arranged parallel to the ground. That is, the turbo prower shown in FIG.
and 16b are attached. With this configuration, two turbo blades can be rotated with one set of bearing and drive motor, which is advantageous in terms of cost. Rotor 19 and stator 20
Configure the motor with. Here, by placing the turbo blades on the same shaft, load fluctuations in the thrust direction are canceled out, the thrust load becomes extremely small, stability is improved, and the lifespan is also extremely long.

Although ball bearings have been described in the above embodiments, rolling bearings or roller bearings may also be used. Furthermore, a ceramic bearing using ceramic as the bearing material may be used. Further, the turbo blowers shown in FIGS. 2 and 3 may be connected in series.

〔Effect of the invention〕

As explained above, the present invention has the advantage that the gas laser oscillator can be made smaller and lighter, and also that vibration and pulsation can be eliminated, and beam characteristics such as bowing stability and high-speed stability of output can be improved.

[Brief Description of the Drawings] Fig. 1 is a diagram showing the structure of a gas laser oscillation device with a laser output of about IKW, which is an embodiment of the present invention, and Fig. 2 is a diagram showing the structure of the laser turbo blower shown in Fig. 1. , Fig. 3 is a diagram showing the structure of another embodiment of a laser turbo blower, Fig. 4 is a diagram showing the overall configuration of a conventional carbon dioxide (Co□) gas laser oscillation device, and Fig. 5 is a diagram showing the structure of a conventional roots blower and a turbo blower. FIG. 3 is a diagram showing air blowing characteristics. 1-・・−・−・−−−−m−・Discharge tube 2−・−−−
--- Output coupling mirror 3 --- Total reflection mirror 4.5 --- --- High-frequency discharge electrode 6 ---
～・−・−・−High frequency power supply 7.8・・−・・・−・−・Cooler 9−・・・・−・−・−・Roots blower 10−・・・・−・−・・−・・-Gas cylinder IL--
−−−・・−・−・Valve 12−・−・−・−・−・−・Vacuum pump 13−・−−
-1--・--・Intra-cavity laser beam optical axis 14...
・・・・−・−・Extracavity laser beam optical axis 15.1
50---・---・Turbo blower 16.16 a
, l 6 b----------1 turbo blade 17-
・−・−−−−・−・Aperture 18−・−・−・・−・−Drive system housing 19−−・−
・−・・−・−Electric motor rotor 20−−−−−・−・・−
・-Electric motor stator 21-------Cooling water coil 23--Bearing inner ring 25--Ball 27--・--1--・・・・Bearing outer ring 29, −・−・−・・Sleeve 31.32.33−・・・−−−−−0−ring 35−
−−−−−−・・−・−Bearing housing 37・−・
−・−・−−−−−−Grease 40−・・−・−・−・
Sleeve 51 - - - - DC discharge electrode 61 -
・−・−・・−・DC power supply section 22. 24. 26. 28. 30. 34. 36. 39. 41, G81 Patent Applicant Fanuc Co., Ltd. Agent Patent Attorney Takeshi Hattori Figure 2 Figure 3 Compression Ratio Figure 5

Claims (5)

[Claims] (1) A gas laser oscillation device comprising a discharge tube that excites the laser by gas discharge, an optical resonator that causes laser oscillation, and a gas circulation device that forcibly cools the laser gas using a blower and a cooler, wherein the blower is A gas laser oscillation device comprising a plurality of turbo blowers connected in series. (2) The gas laser oscillation device according to claim 1, wherein laser excitation is performed by high-frequency gas discharge. (3) The turbo blower is composed of a shaft having a turbo blade at its tip, a pair of bearings that support the shaft, and a motor for rotating the shaft, and the bearing has an oil film damper. A gas laser oscillation device according to claim 1. (4) The gas laser oscillation device according to claim 3, wherein the rotational axis direction of the shaft is parallel to the ground. (5) The gas laser oscillation device according to claim 3, characterized in that two turbo blades are provided so that thrust loads in opposite directions are applied to the shaft.