JPS6258159B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas regeneration device for a gas laser.
More specifically, the present invention relates to a gas regeneration device that extends the time during which the gas composition of a sealed CO ₂ laser is maintained, thereby reducing the laser gas replenishment rate and reducing running costs.

CO ₂ laser uses a mixed gas of CO ₂ , N ₂ , and He gas as a laser medium and pumps it by gas discharge, but gas deterioration occurs due to electrochemical phenomena caused by electric discharge, so it is necessary to replace the gas or use a gas regeneration device. Requires. Normal gas regeneration equipment has a limited gas regeneration capacity, so gas regeneration and some fresh gas replenishment are used in combination. This is related to the airtightness of the system. FIG. 1 shows a diagram of the flow of gas when a gas regeneration device is used. This diagram focuses only on gas pressure and volume rather than the gas regeneration function. In Fig. 1, 1 is a pump, 2 is a gas regeneration system, and 3 is a flow rate controller.The area from pump 1 to flow rate controller 3 (indicated by diagonal lines) has a pressure _P1 determined by the back pressure of pump 1. and its volume is V ₁ .

Other areas including the laser head 4 are under pressure.
P ₂ and volume V ₂ . The pressure P ₂ is determined by the balance between the capacity of the pump 1 and the conductance of the flow rate controller 3. Now, the laser gas is moving in the direction shown by the arrow. The pressure P ₁ is selected to be a slightly high pressure close to 1 atmosphere. The pressure _P2 is a parameter related to the laser action and is chosen from the laser operating point and is 20~
It is normally maintained at a constant pressure within 50 torr. If this system has sufficient gas regeneration ability, the laser gas in the closed system shown by this closed loop will continue to oscillate for a long time indefinitely as a sealed gas. However, the actual encapsulation time is limited by vacuum leaks throughout the closed system. Vacuum leaks tend to occur in the head section 4, which is under negative pressure, and in this case, outside air such as atmospheric components is mixed in, and N ₂ and O ₂ are mixed into the laser gas as impurities. The initial amount of laser gas filled is
P ₁ V ₁ + P ₂ V ₂ , for example, P ₁ = 760 torr, P ₂ =
When 40 torr, V ₁ = 7000 c.c., and V ₂ = 3000 c.c., the amount is 256×10 ⁴ torr·cc. For this, about
Suppose there is a leak of 10 torr cc/sec. Although this leak occurs in the laser head 4, it does not directly increase the pressure of the gas within the laser head 4. The gas pressure in the head 4 is determined by the balance between the conductance of the flow controller 3 and the exhaust capacity of the pump. Instead, this increases the amount of gas in the entire closed system, resulting in a decrease in output. In the inventor's experimental example, the output starts to decrease approximately 8 hours after gas is filled.
The leak amount after 8 hours is 10 torr.cc/sec x 8 hours = 288000 Torr.cc, so the ratio to the total gas amount determined earlier reaches approximately 11.2%. The laser gas initially contains about 20% N ₂ and about 3% O ₂ due to the dissociation of CO ₂ , so a small amount of atmospheric components will not affect the output, but as this amount increases, it will The impact cannot be ignored.

FIG. 2 shows the change in laser power as a function of time after fresh gas injection. As can be seen from the figure, the laser output begins to show a slight decreasing trend after 8 hours. After 8 hours have elapsed, the gas can be replaced again to continue laser oscillation, but in mass production factories such as the automobile industry, this gas replacement operation every 8 hours is not desirable. The present invention is intended to make it possible to extend this encapsulation time.

Since the mixing rate of atmospheric components due to leakage is constant, the greater the amount of gas sealed in the closed system, the diluted the impurity concentration. Ltorr the incidence of that leak.
If cc/sec, the amount of impurities after time t will be Lt. Assuming that the output starts to decrease when the ratio between this and the enclosed laser gas amount P ₁ V ₁ +P ₂ V ₂ reaches a constant value, the time t is given by the following equation.

Lt/P ₁ V ₁ + P ₂ V ₂ = (1) To increase the amount of gas enclosed in the system, either increase the gas pressure or increase the volume, but the gas pressure is related to the laser action. Therefore, it cannot be increased arbitrarily; therefore, it is only necessary to increase the volume under as high a pressure as possible. Therefore, the volume of pressure P ₁ is increased by ΔV. If the enclosing time is thereby extended to t', then Lt'/P ₁ (V ₁ +ΔV)+P ₂ V ₂ = (2) holds true. From equations (1) and (2), the extension rate of the enclosing time t′/
The calculation of t is as follows.

t'/t=1+P ₁ /ΔV/P ₁ V ₁ +P ₂ V ₂ (3) As mentioned above, if P ₁ = 760 torr and P ₂ = 40 torr, P ₂ can be ignored compared to P ₁ . In this case, t'/t=1+ΔV/V ₁ (4). If ΔV is equal to V ₁ , the enclosing time is 2
It can be extended twice. ΔV can be created by increasing the internal volume of the gas regeneration device, and in particular, by using a gas reservoir. At this time, it not only helps to extend the sealing time, but also has the effect of eliminating the pulsating flow of the circulation pump, which eliminates the pulsating flow of pressure within the laser head, thereby preventing fluctuations in the output. If the gas filling time is extended, once the gas is filled, there is no need to control the gas pressure over the subsequent laser operation time, which simplifies operation, and the output is kept at a constant value during that time. It's convenient. Such an effect can also be obtained by preventing leakage in the entire system, but in that case, the cost of the equipment increases due to the improved airtightness. Since the present invention performs the same function without increasing the cost of the device, it is highly effective in various respects such as simplifying the operation of the device, stabilizing the output, and reducing running costs.

FIG. 3 shows an embodiment of the present invention. In the figure, the same parts as in FIG. 1 are denoted by the same reference numerals. 5 is a safety valve for the entire gas regeneration system. A hollow gas reservoir 6 may be installed within the gas regeneration device 2 or before or after the gas regeneration device 2.
The internal volume ΔV of the gas reservoir 6 can be selected from ΔV=(N-1)V ₁ from N=1+ΔV/V ₁ (5), where N is the extension ratio of gas filling time. That is, in order to double the enclosing time, it is only necessary to select ΔV=V ₁ . Since it is more effective to set the installation position in the region _P1 , it should be installed anywhere from the vacuum pump 1 to the flow rate controller 3. In this case, if it is installed in the area after the safety valve 5 up to the flow rate controller 3, the gas in the gas reservoir 6 cannot be replaced with the laser gas when filling the gas, making it impossible to fill the entire system with laser gas correctly, so avoid this area. is preferable. The closer the pump is to the vacuum pump 1, the more contaminated it is by oil vapor. The installation method can be installed in parallel or in series with the gas flow, but if it is in parallel,
During gas filling, it takes a longer time to replace the gas in the gas reservoir 6 with the laser gas, which increases gas consumption. From this point of view, series installation is desirable. Figure 4 shows the structure of some gas reservoirs. Figure a shows a spherical gas reservoir, which is durable, but convection occurs when gas is filled in the gas reservoir, so replacing the gas takes time and consumes a lot of gas. Figure b shows a columnar shape, and the time required for gas replacement is somewhat shortened. The tube shown in Figure c is a helical hollow glass tube, and although it has a large volume, the gas flow does not involve convection, so the replacement time is minimal.

FIG. 5 shows an example of the structure of a gas reservoir having an oil vapor trap function. Oil vapor can be removed by traps or filters, but if it is not completely removed, oil vapor will cause the following problems. First, when it adheres to the catalyst surface, it weakens the activity of the catalyst, thereby reducing the gas regeneration ability. Second, it adheres to the surface of optical components, reducing their performance and strength. The gas reservoir shown in FIG. 5 can also have this oil vapor removal function. That is, gas containing oil vapor moves upward from below, and when it passes through the constriction, it is cooled by adiabatic expansion, so that the vapor condenses into liquid form and can be removed from the gas. The shaded area shown in the figure is solidified fluid oil that drips downward and returns into the pump.

As described above, according to the present invention, since the gas filling time is extended, it has advantages such as improved laser operability, reduced running costs, and improved output stability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional laser gas regeneration device, FIG. 2 is a laser output characteristic diagram of the laser gas regeneration device of FIG. 1, FIG. 3 is a block diagram of a laser gas regeneration device according to an embodiment of the present invention, and FIG. Figure a,
Figures b, c and 5 are diagrams showing the structure of a hollow gas reservoir used in the present invention. 1...Vacuum pump, 2...Gas regeneration system, 3...
Flow rate controller, 4...laser head, 5...safety valve, 6...hollow gas reservoir.

Claims (1)

[Claims] 1. A vacuum pump that recovers used laser gas from the laser head, a gas regeneration system that regenerates the laser gas that has passed through the vacuum pump into the original laser gas, and a gas regeneration system that controls the flow rate of the regenerated laser gas and supplies it to the laser head. A laser gas regeneration device characterized in that flow rate controllers are arranged in series, and a hollow gas reservoir having a volume larger than the volume of the gas path is disposed in a gas path leading from the vacuum pump to the flow rate controller. 2. The laser gas regeneration device according to claim 1, wherein the hollow gas reservoir has an oil trap function.