JP2001274485A - Gas laser oscillation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas laser oscillation device which maintains a glow discharge stably, which stabilizes a laser output and which can obtain high- quality machining capability. SOLUTION: In the gas laser oscillation device, a gas pipe route used to circulate a laser gas is provided, electrodes are arranged in parts of the pipe route, the laser gas is discharge stimulated by a high-voltage power supply connected to the electrodes, a means which detects and controls a discharge current in a discharge space is provided, a part of the circulating laser gas is discharged to the outside of the gas pipe route, a laser gas in the same amount as its discharge amount is supplied newly to the gas pipe route, and an optical resonator which emits a laser beam is provided. The oscillation device is constituted in such a way that the supply amount of the laser gas is controlled according to the change in the vibration rate of the discharge current due to a change or the like in the composition ratio of the laser gas, that the glow discharge is maintained stably, that the laser output is stabilized and that the high-quality machining performance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas laser oscillation device.

[0002]

2. Description of the Related Art A conventional gas laser oscillation device will be described below. FIG. 2 shows a conventional gas laser oscillation device. In FIG. 2, 1 is a blower, 2 is a discharge tube, 3,
Reference numeral 4 denotes an electrode installed near the discharge tube 2. 5 is the electrode 3,
A high voltage power supply connected to 4, and 6 is a discharge space. 7 is a total reflection mirror, 8 is a partial transmission mirror, 9 is a heat exchanger, 10 is a laser beam extracted from the partial transmission mirror 8, 11 is a laser gas pipe, 12 is a laser gas, 13 is a vacuum pump, 14 is a laser gas cylinder, 15a Is a supply flow regulator, 15b is a discharge flow regulator, 16 is a laser output detector, 17 is a discharge current detector, 18 is a discharge current control unit, 20 is a signal line,
1 is a pressure detector, and 22 is a laser gas supply amount control unit.

The operation of the gas laser oscillating device configured as described above will be described. The laser gas 1 is passed through the laser gas pipe 11 by the blower 1 and
Force circulation of 2. The electrodes 3 and 4 are installed inside the laser gas circulation system near the discharge tube 2. At this time, a high voltage is applied to the discharge space 6 from the electrodes 3 and 4 connected to the high-voltage power supply 5, and the electrodes 3 and 4 grow inside the discharge tube 2. Generates discharge.
The discharge current flowing in the discharge space is detected by the discharge current detector 17 and a signal is sent to the discharge current control unit 18.

[0004] A very small amount of laser beam is extracted from the total reflection mirror 7 and is irradiated on a laser output detector 16 to monitor the laser output, and the laser output setting set by the discharge current control unit 18 is performed. The discharge current is controlled to be equal to the value. The laser output detector 16 uses a thermocouple to output a voltage corresponding to the emitted laser beam output. For example, a photodetector such as a photodiode or a cds cell may be used in addition to the thermocouple. It is possible.

[0005] Since the laser gas 12 is compressed and discharged from the blower 1 and becomes high temperature, it is cooled by the heat exchanger 9 arranged on the downstream side of the blower 1. Also, the laser gas 12 after passing through the discharge space 6 is cooled similarly because the discharge energy is applied and the temperature of the laser gas 12 becomes high.

[0006] Laser gas 1 excited by glow discharge
The laser beam 2 oscillates and the laser beam is amplified while reciprocating between the total reflection mirror 7 and the partial transmission mirror 8 to be in a resonance state.
From this resonance state, a part of the laser beam between the total reflection mirror 7 and the partial transmission mirror 8 is taken out of the resonator as a laser beam 10 from the partial transmission mirror 8, and this laser beam 10 is used for processing such as metal cutting and welding. Used.

[0007] A part of the laser gas 12 is taken out of the laser oscillation device by the vacuum pump 13 through the discharge flow rate regulator 15b and discarded. Discarded laser gas 1
By supplying the same amount of new laser gas from the cylinder 14 to the inside of the laser oscillation device through the supply flow regulator 15a, the internal pressure is maintained constant. The internal pressure is detected by the pressure detector 21, and a signal is sent to the laser gas supply control unit 22. A signal is supplied to the supply flow controller 15 through the driver 19 so that the pressure becomes a preset value in the laser gas supply amount controller 22.
(a) Both or one of the laser gas supply amount and discharge flow rate regulator 15b is controlled to keep the pressure constant. In the conventional example shown in FIG. 2, only the discharge flow rate regulator 15a is controlled to adjust the pressure. At this time, the discharge amount of the laser gas from the vacuum pump 13 controlled by the supply flow controller 15a and the discharge flow controller 15b is fixed to a constant value.

The laser gas 12 receives discharge energy when passing through the discharge space 6. Although the composition of the laser gas 12 is composed of various gases, a part of the composition is dissociated by the discharge energy. The dissociated gas then returns to its original composition through the reverse process. This dissociation and the reverse process become equilibrium with the passage of time, and a certain amount of dissociated gas is present in the gas piping path. Since the dissociated gas is different from the original composition of the laser gas 12, the glow discharge becomes unstable and becomes a local arc discharge, which has an adverse effect such that the oscillation rate of the discharge current increases.

In order to alleviate such a phenomenon, the amount of dissociated gas existing in the gas pipe path may be reduced.
The amount of dissociated gas present in the laser gas 12 is determined in a state where the amount of dissociated gas and the amount of gas returned in the reverse process are in equilibrium. Therefore, as described above, a part of the laser gas 12 containing the dissociated gas is taken out of the laser oscillation device by the vacuum pump 13 and discarded. By supplying the same amount of new laser gas 12 as the discarded laser gas into the inside of the laser oscillation device, the amount of dissociated gas present in the gas piping path has been reduced.

[0010]

However, in the above configuration, when the gas laser oscillation device is used for a long period of time, glow discharge cannot be performed due to the effects of abrasion of the electrodes 3 and 4 due to discharge, adhesion of impurities on the inner surface of the discharge tube 2, and the like. It was easy to be stable. In addition, the glow discharge is unstable due to impurities such as the lubricating oil of the gear portion of the blower 1 mixed into the path of the gas pipe 11 due to an increase in clearance due to the deterioration of the laser gas in the blower 1 and the seal portion between the gear chambers over time. Had become. In addition to such deterioration of the components of the gas laser oscillation device, the occurrence of the dissociation of the laser gas facilitates the transition of the glow discharge to the arc discharge, and the phenomenon that the discharge current oscillation rate increases with time has occurred. The increase in the oscillation rate of the discharge current causes an increase in the laser output and the variation rate of the laser beam mode, and when used for metal cutting, adversely affects processing such as an increase in the roughness of the cut surface. As described above, the discharge current vibration factor is an important factor in performing processing such as metal cutting and welding, and the increase in the vibration frequency has caused the deterioration of the quality of the processed product and the occurrence of defects.

In the gas laser oscillator immediately after the start of use and after operation for several thousand hours, the supply amount of the laser gas required to suppress the discharge current oscillation is different. However, in conventional laser gas oscillators, the gas supply amount is fixed, so if the gas supply amount is adjusted to the state immediately after the start of use, the discharge current becomes unstable after thousands of hours of operation, causing machining defects. In addition, when the state is adjusted to the state after the operation for several thousand hours, there is a problem that the gas supply amount is unnecessarily large immediately after the start of use and the running cost increases.

Conventionally, there has also been a control method for increasing the supply amount of laser gas in response to a decrease in the laser output. However, this method does not detect an increase in the discharge current oscillation rate, and thus prevents machining defects. Was impossible.

There is a demand from users who use the gas laser oscillation device to maintain stable processing quality for a longer period of time, but it has been difficult to realize the conventional gas laser oscillation device for the above-described reasons.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a low-cost running gas laser oscillation device capable of maintaining stable machining quality for a longer period of time.

[0015]

In order to achieve this object, a gas laser oscillation device according to the present invention comprises a blower for circulating a laser gas, and a gas piping for circulating the laser gas. An electrode is disposed on a part of the laser gas, and the laser gas is discharge-excited by a high-voltage power supply connected to the electrode, and has means for detecting and controlling a discharge current flowing through a discharge space. A gas laser oscillating device equipped with an optical resonator that emits laser light by discharging laser gas to the outside of the piping path and newly supplying the same amount of laser gas into the gas piping path. The laser gas supply amount is controlled according to the fluctuation of the current oscillation rate.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has a structure in which the supply amount of laser gas is controlled in accordance with a change in the discharge current oscillation rate due to a change in the composition ratio of the laser gas or the like. When it increases, the laser gas supply amount is increased, thereby providing an effect of suppressing an increase in the vibration rate. For this reason, it is possible to prevent processing defects at the time of metal cutting using a laser beam, which are caused by an increase in the discharge current oscillation rate.

The operation of the embodiment of the present invention will be described below with reference to FIG. The description of the same components as in the conventional example is omitted.

In FIG. 1, the signal from the discharge current detector 17 is transmitted through the discharge current control unit 18 to the discharge current vibration detector 2.
3 is sent. The discharge current vibration detector 23 measures the vibration rate of the discharge current, and sends information on the vibration rate to the laser gas supply amount control unit 22.
The laser gas supply amount is set to an optimum value in the laser gas supply amount control unit 22 according to the measured vibration rate, and a signal of the set laser gas supply amount is sent to the driver 19, and the driver 19 supplies the supply flow rate regulator 15a, A configuration is provided in which the discharge flow rate regulator 15b is driven to adjust the laser gas supply amount. For this reason, when the discharge current vibration rate changes, it is detected by the discharge current detector 17, and the laser gas supply amount can be changed by the flow regulator 15 through the driver 19. Discharge current detector 17
Use elements such as a CT and a resistor.

Next, the operation of the embodiment of the present invention will be described. First, when the power supply is turned on, the blower 1 is activated to suck and exhaust the laser gas 12, circulate the laser gas through the laser gas pipe 11, and to the discharge tube 2. In this state, a high voltage is applied between the electrodes 3 and 4 arranged in the discharge tube 2 from the high voltage power supply 5 to generate a glow discharge inside the discharge tube 2. The laser light emitted by exciting the laser gas 12 by the glow discharge reciprocates between the total reflection mirror 7 and the partial transmission mirror 8 and oscillates.

A very small amount of a laser beam is extracted from the total reflection mirror 7 and is irradiated on a laser output detector 16 to monitor the laser output.
The discharge current is controlled so as to be equal to the set laser output set value.

A part of the laser gas 12 is taken out of the laser oscillation device by the vacuum pump 13 through the discharge flow rate regulator 15b and discarded. The internal pressure is maintained constant by supplying the same amount of new laser gas 12 as the discarded laser gas 12 from the cylinder 14 to the inside of the laser oscillation device through the supply flow regulator 15a.

The supply amount of the laser gas 12 is controlled by a laser gas supply amount control unit 22. A signal related to the vibration rate of the discharge current is sent from the discharge current vibration detector 23 to the laser gas supply control unit 22, and the laser gas supply control unit 22 controls to increase the supply amount of the laser gas when the vibration rate increases.

FIG. 3 shows the laser output fluctuation rate with respect to the discharge current oscillation rate. As described above, when the discharge current oscillation rate increases, the laser output oscillation rate also increases. FIG. 4 shows a change in the cut surface roughness Rz when machining mild steel 12 mm with respect to the laser output vibration rate (CW2).
kw). As can be seen from FIG. 4, the increase in the laser output vibration rate increases the cut surface roughness. 3 and 4, it can be seen that an increase in the discharge current vibration rate causes an increase in the roughness of the cut surface of the processed product, thereby lowering the quality.

Conventionally, a constant laser gas has always been supplied irrespective of the discharge current oscillation rate. On the other hand, in the present embodiment, the deterioration of the glow discharge due to the dissociated gas is prevented by supplying the laser gas according to the discharge current oscillation rate. Therefore, stable glow discharge can be maintained for a long period of time, and it becomes possible to suppress discharge current oscillation and laser output fluctuation and prevent machining quality from deteriorating. FIG. 5 shows a change in the discharge current oscillation rate with respect to the use time of the gas laser oscillation device. Curve A is a conventional example, and curve B is the present embodiment. In the conventional example, since the vibration rate gradually increases, the processing quality is deteriorated. On the other hand, in the example of the present invention, since the discharge current oscillation rate is stable, high-quality machining performance can be maintained for a long period of time.

[0025]

As described above, according to the present invention, a blower for circulating a laser gas and a gas piping for circulating the laser gas are provided, and an electrode is disposed in a part of the piping. Means for discharging and exciting the laser gas by means of a high-voltage power supply connected to the electrode, detecting and controlling a discharge current flowing through the discharge space, and discharging a part of the circulating laser gas to the outside of the gas piping path; A gas laser oscillating device comprising an optical resonator that newly supplies the same amount of laser gas into the gas pipe path and emits laser light,
A configuration that controls the supply of laser gas in accordance with fluctuations in the discharge current oscillation rate due to changes in the composition ratio of the laser gas, etc., and realizes a gas laser oscillation device that can stabilize the laser output and maintain high-quality processing performance for a long time. It has the effect that it has.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a gas laser oscillation device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional gas laser oscillation device.

FIG. 3 is a correlation diagram between a general discharge current vibration rate and a laser output vibration rate.

FIG. 4 is a correlation diagram between a general laser output vibration rate and a cut surface roughness Rz.

FIG. 5 is a correlation diagram between the gas laser oscillation device usage time and the discharge current vibration rate in the conventional gas laser oscillation device and the gas laser oscillation device of the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 blower 2 discharge tube 3 electrode 4 electrode 5 high voltage power supply 6 discharge space 7 total reflection mirror 8 partial transmission mirror 9 heat exchanger 10 laser beam 11 laser gas pipe 12 laser gas 13 vacuum pump 14 cylinder 15a supply flow regulator 15b discharge flow regulation Device 16 Laser output detector 17 Discharge current detector 18 Discharge current control unit 19 Driver 20 Signal line 21 Pressure detector 22 Laser gas supply amount control unit 23 Discharge current vibration detector

Claims (1)

[Claims] 1. A blower for circulating a laser gas, a gas piping path for circulating the laser gas, an electrode disposed in a part of the piping path, a high-voltage power supply connected to the electrode, and a discharger. A means for detecting and controlling the discharge current flowing through the space, and discharging a part of the circulating laser gas to the outside of the gas pipe route, newly supplying the same amount of laser gas into the gas pipe route as the laser beam, A gas laser oscillating device comprising: an optical resonator that emits laser light; and controlling a laser gas supply amount according to a change in a discharge current oscillation rate.