JP2013042000A - Gas laser oscillator with laser gas pressure control function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser gas pressure control device capable of controlling a laser gas pressure at a higher speed than a conventional control.SOLUTION: A laser oscillator 10 comprises a gas container 12, a CV 14 capable of adjusting a flow rate of laser gas to be supplied to the gas container 12 by a change of an aperture, a primary gas pressure sensor 16 for detecting a primary side gas pressure of the CV 14, a secondary gas pressure sensor 18 for detecting a secondary side gas pressure of the CV 14, a vacuum pump 20 for suctioning and exhausting the gas from the gas container 12, a gas pressure control part 22 for controlling the gas pressure in the gas container 12, and a data table storage part 24. The data table storage part 24 stores: a first data table storing a relationship of a CV differential pressure, the aperture of the CV 14, and the flow rate of the gas supplied to the gas container 12; and a second table data storing a relationship of the secondary side gas pressure of the CV 14 and the flow rate of the exhaust gas from the gas container 12.

Description

  The present invention relates to a gas laser oscillator having a laser gas pressure control function, and more particularly to a gas laser oscillator capable of performing gas pressure control at a higher speed than conventional gas pressure control.

  Normally, in a gas laser oscillator, laser oscillation is performed by controlling the laser gas pressure in the container to a desired value. For example, Patent Literature 1 discloses a gas pressure control device that controls the gas pressure in a gas tank. Here, an integrated signal and a proportional signal are obtained from a difference signal between a gas pressure command value and a detected gas pressure in a discharge tube. Is calculated and output, and when the detected pressure reaches the command pressure, the integrated value is reset, so that control with good responsiveness is possible without being affected by the unsteady state.

  Further, Patent Document 2 discloses a substrate processing apparatus that performs a plurality of processing steps in a reduced-pressure processing chamber to which a processing gas is supplied. Here, processing gas pressures corresponding to the plurality of processing steps are calculated. It is said that the processing gas pressure can be controlled to the target value continuously in a short time by using an arithmetic control mechanism having a plurality of arithmetic tables.

JP-A-7-38179 JP 2011-44446 A

  In the conventional control, the gas pressure is monitored, and the gas pressure is controlled by PID control of the operation voltage of the control valve so that the value approaches the gas pressure set value. In other words, the control voltage command of the control valve is controlled by the proportional amount of the difference between the set gas pressure and the gas pressure monitor value, the time integral amount of the difference, and the time differential amount of the difference. However, in the conventional control, the set gas pressure and the gas pressure monitor value are compared, and it is not possible to give the optimal control valve opening command at any given time. There is a problem that it takes a long time to converge to a certain range.

  As another gas pressure control method, when the pressure control is performed by adjusting the supply gas flow rate only by the opening of the control valve, the primary pressure of the control valve fluctuates due to fluctuations in the original pressure or gas pipe pressure loss. However, it is difficult to obtain a desired flow rate.

  When the gas pressure fluctuates, such as when changing the laser output, if the laser gas pressure does not immediately fall within the desired gas pressure, the discharge of the laser gas will not be stable, leading to instability of the laser light output. Further, at the time of laser oscillation start operation, after the gas pressure is changed, laser oscillation is performed after the gas pressure reaches a certain range. Therefore, if the gas pressure control is slow, the laser oscillation start operation is delayed. For these reasons, it is desired that the control of the gas pressure be faster.

  The technique described in Patent Document 1 is designed to reset the integral element in the gas pressure control of PI control. However, since it is still PI control, it is optimal for controlling to the set gas pressure. It is difficult to always obtain the correct control valve opening.

  The technique described in Patent Document 2 performs optimum gas pressure control for each process by having an operation table for optimum valve control with respect to the set pressure in each process of the substrate processing in the substrate processing apparatus. Is. However, this is control with PID control in mind, and the calculation table is a calculation table for PID control.

  Therefore, an object of the present invention is to provide a gas laser oscillator that enables laser gas pressure control faster than conventional control.

  In order to achieve the above object, the first invention of the present application includes a gas container for storing laser gas, a control valve capable of adjusting a gas flow rate of laser gas supplied to the gas container by adjusting an opening degree, A gas pressure sensor for detecting the pressure on the primary side and the secondary side, a vacuum pump for sucking and exhausting laser gas from the gas container, and a gas pressure control unit for controlling the pressure of the laser gas in the gas container, The gas pressure control unit stores a relationship between a differential pressure between the primary side gas pressure and the secondary side gas pressure, an opening degree of the control valve, and a supply gas flow rate into the gas container. A first data table; and second table data storing a relationship between the gas pressure and the exhaust gas flow rate on the secondary side, and a secondary side detected by an apparatus for detecting the pressure on the secondary side. By dividing the difference between the gas pressure value and the set gas pressure value by the value of the volume of the gas container by a certain time, a gas amount change rate required to approach the set gas pressure after the certain time is obtained, There is provided a gas laser oscillator for obtaining an opening degree of the control valve from the gas amount change rate and the first and second data tables.

  In a second aspect based on the first aspect, the gas pressure control unit is based on a deviation between a gas pressure value predicted by calculation after a certain time and a monitored gas pressure value after starting the gas pressure control. And a laser oscillator that feedback-controls the gas pressure by correcting the data in the first and second data tables.

  A third invention provides a gas laser according to the second invention, wherein when the correction amount from the initial value of the table data exceeds a predetermined range, the gas pressure control method is switched or an alarm signal is output to the outside. Provide an oscillator.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, when changing the laser output, a valve pressure is predicted so as to predict an increase in pressure caused by an increase in gas temperature and cancel the change in advance. A gas laser oscillator is provided for controlling the above.

  According to a fifth invention, in any one of the first to fourth inventions, a device for monitoring the gas temperature is provided on the primary side of the control valve, and the gas temperature on the primary side of the control valve is detected. A gas laser oscillator that corrects data in the first data table by multiplying the first data table by a ratio of the absolute temperature at the time of creation of the data table 1 and the absolute temperature on the primary side of the control valve to the first data table. provide.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects, an apparatus for monitoring the temperature in the gas container is provided, and the absolute temperature at the time of creating the first data table and the second data table is provided. And a gas laser oscillator that corrects the first and second data tables by multiplying the first data table and the second data table by a ratio of the absolute temperature in the gas container, respectively.

  According to a seventh invention, in any one of the first to sixth inventions, an exhaust valve capable of changing an exhaust gas flow rate is provided in a pipe for sucking gas from the gas container by the vacuum pump. A gas laser oscillator is provided that increases the exhaust gas flow rate when the pressure is greater than a set value.

  According to the present invention, a gas pressure sensor is provided not only on the secondary side of the control valve but also on the primary side, and a gas amount change rate (= supply gas flow rate−exhaust gas flow rate) table with respect to the valve differential pressure and opening degree. By storing the data, it is possible to perform valve opening control that provides an optimal gas amount change rate sequentially. In addition, it is possible to adjust the valve opening at which a desired gas amount change rate is obtained. By calculating the amount of gas change required to reach the set gas pressure and controlling the valve, this is not possible with conventional PID control. Possible high-speed gas pressure control becomes possible.

  Even if there is a difference between the actual flow rate and the table data of the supply gas flow rate and the exhaust gas flow rate due to changes in gas temperature, gas composition errors, changes in opening due to aging of the control valve, etc. The table data is corrected by feedback control, and appropriate control of the valve opening becomes possible.

  When the correction amount from the initial value of the table data exceeds a predetermined range, by changing the control method or outputting an alarm, it is possible to cause a change in gas temperature, gas composition error, or aging of the control valve. Even if the opening degree changes, the gas pressure can be controlled and the laser oscillator can be protected.

  By controlling the valve to cancel the expected gas pressure fluctuation at the time before the delay time against the response delay caused by the gas temperature rise that occurs during the gas pressure control, it is possible to increase the speed. Gas pressure control is possible.

  By correcting the error in the gas flow rate caused by the temperature change of the supply gas, the gas flow rate can be accurately controlled even if the temperature of the supply gas changes.

  Even if the gas temperature changes depending on the oscillation state of the laser, the pressure can be controlled more accurately.

  By providing a bypass valve for exhaust and a valve with variable opening, the exhaust speed is increased only when necessary, and the gas pressure control is performed even when the gas pressure is higher than the set gas pressure while suppressing the amount of gas consumed. Can be fast.

It is a figure which shows schematic structure of the principal part of the laser oscillator concerning the 1st Embodiment of this invention. It is a graph which shows the relationship between CV differential pressure | voltage and a supply gas flow rate. It is a graph which shows the relationship between the gas pressure in a container, and an exhaust gas flow rate. It is a graph explaining an example of the control method of gas pressure. It is a flowchart which shows an example of the control procedure of gas pressure. It is a graph explaining the other example of the control method of gas pressure. It is a flowchart which shows the other example of the control procedure of gas pressure. It is a graph explaining the further another example of the control method of gas pressure. It is a figure which shows schematic structure of the principal part of the laser oscillator which concerns on the 2nd Embodiment of this invention. 10 is a graph showing the relationship between the valve opening of the exhaust valve of FIG. 9 and the exhaust gas flow rate.

  FIG. 1 is a diagram showing a schematic configuration of a main part of a gas laser oscillator 10 according to the first embodiment of the present invention. The laser oscillator 10 includes a gas container 12 that contains laser gas, and a control valve (hereinafter abbreviated as CV) that can adjust the gas flow rate of the laser gas to be supplied from a laser gas supply source (not shown) to the gas container 12 by changing the opening. ) 14, a primary gas pressure sensor 16 that detects the laser gas pressure on the primary side (upstream side) of the CV 14, and a secondary gas pressure sensor 18 that detects the laser gas pressure on the secondary side (downstream side) of the CV 14. In the example shown, it is arranged in the gas container 12), a vacuum pump 20 that sucks and exhausts laser gas from the gas container 12, a gas pressure control unit 22 that controls the laser gas pressure in the gas container 12, and a data table storage unit 24 that will be described later. Is provided. An orifice 26 may be provided between the gas container 12 and the vacuum pump 20.

  The data table storage unit 24 is related to the differential pressure (CV differential pressure) between the primary gas pressure and the secondary gas pressure of the CV 14, the opening of the CV 14, and the supply gas flow rate to the gas container 12. And the second table data storing the relationship between the gas pressure on the secondary side (inside the gas container 12) of the CV 14 and the exhaust gas flow rate from the gas container 12. Further, the control unit 22 divides the value obtained by multiplying the difference between the secondary gas pressure value detected by the secondary gas pressure sensor 18 and the set gas pressure value by the volume value of the gas container 12 by a predetermined time, A gas amount change rate necessary to asymptotically approach the set gas pressure after the predetermined time is obtained, a valve opening for obtaining the gas amount change rate is calculated based on the first and second data tables, and the valve The opening degree of the CV 14 is adjusted and controlled so as to be the opening degree.

  The first data table can be generated from data collected at the time of laser gas supply using the primary gas pressure sensor 16 and the secondary gas pressure sensor 18. Further, the second data table can be generated from data collected using the secondary gas pressure sensor 18 when the laser gas is exhausted from the container 12. The data table storage unit 24 may have a function of generating the first and second data tables, or may have only a function of storing the data table generated by other means.

  FIG. 2 is a diagram for explaining a method for measuring the flow rate from the CV 14 and a method for obtaining a desired supply gas flow rate. When filling the gas container 12 with the laser gas through the CV 14, assuming that the gas temperature is constant, the flow rate from the CV 14 is the difference between the primary side pressure and the secondary side pressure of the CV 14 (CV differential pressure), It is uniquely determined from the valve opening. If the valve opening is constant, the gas flow rate is determined by the CV differential pressure. When a gas container 12 with a known volume is filled with gas at a constant valve opening, the CV differential pressure for a certain valve opening is calculated from the relationship shown in FIG. 2 and the differential value of the CV differential pressure and the gas pressure curve in the gas container 12. And the gas supply amount can be obtained. As shown in FIG. 2, by obtaining the relationship between the CV differential pressure and the gas flow rate for a plurality of valve openings, the valve opening for obtaining a desired gas flow rate can be obtained for any CV differential pressure. . In FIG. 2,% represents the valve opening, and V in parentheses represents the operating voltage of the CV 14 corresponding to each opening.

  Here, when an electromagnetic coil type control valve is used as CV14, hysteresis may occur in the valve opening with respect to the operating voltage due to the influence of the residual magnetic polarization of the iron core used internally. Correction shall be performed. On the other hand, when the valve opening degree is controlled using a servo motor that performs position feedback control, the valve opening degree can be accurately controlled, and hysteresis consideration is unnecessary.

  FIG. 3 is a diagram for explaining a method of measuring the exhaust gas flow rate from the gas container 12. The measurement of the exhaust gas flow rate from the exhaust valve provided in the gas container 12 is obtained from the differential value of the exhaust curve during gas exhaust and the volume of the gas container 12 as in FIG. The primary pressure of the exhaust valve is the gas pressure in the container 12, and the secondary pressure is the primary pressure of the vacuum pump 20. When the exhaust capacity of the vacuum pump 20 is large, the secondary pressure can be approximated to be constant regardless of the flow rate. That is, it can be approximated that the flow rate of the exhaust gas is uniquely determined from the gas pressure in the container 12 as shown in FIG.

  FIG. 4 is a diagram for explaining a gas pressure control method, and FIG. 5 is a flowchart for explaining the control method. The rate of change of the gas amount (gas mass) in the container is obtained from the difference between the supply gas flow rate and the exhaust gas flow rate. The supply gas flow rate is obtained in FIG. 1, and the exhaust gas flow rate is obtained in FIG. The change in the gas pressure P in the container is uniquely determined from the rate of change of the gas amount, the volume of the gas container, and the gas equation of state. However, the gas temperature is assumed to be constant. In order to obtain a desired rate of change of the gas amount in the container, the exhaust gas flow rate with respect to the gas pressure at that time is obtained from FIG. 3, and the necessary supply gas flow rate with respect to the CV differential pressure at that time is obtained from FIG. Therefore, the valve opening required for this is obtained, and the CV is controlled so as to be the valve opening.

  In FIG. 4, the valve opening degree at which the gas flow rate approaches the gas pressure setting value most after time T (several milliseconds to several seconds) is obtained by calculation from the table data of the supply gas flow rate and the exhaust gas flow rate shown in FIGS. 2 and 3. Then, the CV is controlled so that the valve opening degree is obtained. The calculation of the valve opening and the valve opening control are repeated every predetermined gas pressure monitoring period.

Specifically, first, the difference between the current gas pressure value in the container and the set gas P ₀ is calculated (step S1 in FIG. 5). For example, in a time T _a, the difference between the container gas pressure P ₁ and the set gas pressure P ₀ becomes [Delta] P. Next, a gas amount change rate A that becomes the set gas pressure P ₀ after ΔT ₁ is calculated (step S2 in FIG. 5), and the current exhaust gas flow rate B is calculated from the data table of the gas pressure and exhaust gas flow rate in the gas container. Is calculated (step S3 in FIG. 5). Further, a supply gas flow rate C (= A−B) for obtaining a gas amount change rate A when the exhaust gas flow rate is B is calculated (step S4 in FIG. 5), and CV differential pressure and supply gas flow rate data are calculated. From the table, the valve opening at which the gas supply amount closest to the supply gas flow rate C is obtained is obtained, and the CV is operated and controlled so as to be the valve opening (step S5 in FIG. 5). Thereafter, after waiting for a time corresponding to a predetermined gas pressure monitoring cycle, the processing after step S1 is repeated (step S6 in FIG. 5).

In the example shown in FIG. 4, the time t = T _a previously the largest state valve opening is, t = T _a subsequent opening of the valve is less than the maximum. The time t = T _a later, more control period interval of the valve opening is less than relative [Delta] T _1, exponentially as the gas pressure curve showing the gas pressure P is expressed by the following formula (1) Curve asymptotically approaching the set gas pressure value P ₀ .
P≈P ₀ − (P ₀ −P ₁ ) exp {(T _a −t) / ΔT ₁ } (1)

  FIG. 6 is a diagram illustrating a feedback method when there is a difference between the calculated gas pressure after a lapse of a certain time from the opening of the valve and the actual gas pressure, and FIG. 7 illustrates the feedback method. It is a flowchart to explain. Since steps S11 to S16 in FIG. 7 may be the same as steps S1 to S6 in FIG. 5, detailed description thereof is omitted.

As shown in FIG. 7, in step S < _b > 17 subsequent to step S < _b > 16, it is determined whether the elapsed time from the start of processing is a time that is an integral multiple of ΔT ₂ that is predetermined as a period for correcting the data table of the supply gas flow rate. If it is not an integral multiple, the process returns to step S11. If it is an integral multiple, the process proceeds to step S18. In step S18, the actual gas change amount with respect to the calculated gas change amount ΔD _a after ΔT ₂ hours from a certain reference time (T _{0 in} FIG. 6) is ΔD _b , and further the calculated exhaust gas after ΔT ₂ hours. When the exhaust gas amount calculated based on the actual gas pressure is ΔE _b with respect to the gas amount ΔE _a , the calculated supply gas amount ΔS _a is obtained by the following equation (2), and after ΔT ₂ hours A gas supply amount ΔS _b calculated based on the measured gas pressure is obtained by the following equation (3).
ΔS _a = ΔD _a + ΔE _a (2)
ΔS _b = ΔD _b + ΔE _b (3)

Next, ΔS _b / ΔS _a is multiplied by the value of the data table of the supply gas flow rate every ΔT ₂ period to perform feedback by correcting the table data. Here, ΔT ₂ may be equal to or different from ΔT _{1 in} FIG.

FIG. 8 is a diagram for explaining another example of the feedback method. As another feedback method, when the actual gas pressure change is ΔP _b with respect to the calculated gas pressure change amount ΔP _a after ΔT ₂ hours with respect to the reference time T ₀ , the difference (ΔP _b− ΔP _a ) × V / ΔT ₂ is corrected by adding the value in the data table of the supply gas flow rate. Alternatively, as another correction method, (ΔP _a / ΔP _b ) may be corrected by multiplying the table data of the supply gas flow rate and the exhaust gas flow rate to perform feedback control.

Here, calculation of the calculated gas pressure change amount ΔP _a after ΔT ₂ hours will be described. Assuming that the control time interval of the valve opening is ΔT ₃ = ΔT ₂ / N (N is a natural number), and the gas flow rate calculated at time T is F (T), the gas change amount after ΔT ₃ is F (T) Since xΔT ₃ , the gas change amount ΔD after ΔT ₂ is expressed by the following equation (4).
ΔD = ΣF (T ₀ + k × ΔT ₃ ) × ΔT ₃ (k = 0 to N) (4)
If the gas change amount ΔD is obtained, it is possible to obtain a gas pressure change amount [Delta] P _a using state equation of the known container volume and gas. Note that the gas temperature approximates to be constant.

  FIG. 9 shows a hardware configuration of a laser oscillator 10 ′ according to the second embodiment. The second embodiment is different from the first embodiment described in FIG. 1 in that an exhaust valve 28 capable of changing an exhaust gas flow rate is provided in a pipe between the gas container 12 and the vacuum pump 20. In the illustrated example, the exhaust valve 28 is arranged in parallel with the orifice 26 (so as to bypass the orifice 26). When the gas pressure in the container 12 is higher than the set gas pressure, the exhaust valve 28 can increase the flow rate of the exhaust gas, thereby speeding up the gas pressure control while suppressing the consumption gas flow rate. .

  FIG. 10 is a graph showing the relationship between the valve opening and the exhaust gas flow rate when the exhaust valve 28 of FIG. 9 is a variable valve. Since the exhaust valve 28 is arranged in parallel with the orifice 26, the exhaust gas flow rate does not become zero even if the valve opening of the exhaust valve 28 is 0%.

  In the first and second embodiments, the control unit 22 switches the gas pressure control method when the correction amount from the initial value of the first or second table data exceeds a predetermined range, An alarm signal may be output to the outside. Further, when changing the laser output, the control unit 22 may predict an increase in pressure caused by an increase in gas temperature and control the CV so as to cancel out the change in advance.

  An apparatus (not shown) for monitoring the gas temperature is provided on the primary side of the CV14, detects the gas temperature on the primary side of the CV14, the absolute temperature at the time of creating the first data table, and the primary side of the CV14 The data in the first data table may be corrected by multiplying the first data table by the absolute temperature ratio.

  In addition, a device (not shown) for monitoring the temperature in the gas container 12 is provided, and the ratio between the absolute temperature at the time of creating the first data table and the second data table and the absolute temperature in the gas container 12 is The first and second data tables may be corrected by multiplying the first data table and the second data table, respectively.

  In the present invention, instead of PI control, control is performed by quantitatively calculating the amount of gas change necessary to reach the set gas pressure, so that the optimum opening of the control valve can always be obtained. The pressure can be controlled at high speed. The present invention is not PID control but quantitatively controls the gas flow rate to control the gas pressure.

  As described above, the flow rate of the laser gas supplied from the CV is determined by the differential pressure between the primary pressure and the secondary pressure of the CV and the opening of the CV if the gas temperature is approximated to be constant. In the present invention, the relationship between the opening and differential pressure of the CV and the gas flow rate is prepared and stored in advance as table data. If the exhaust capacity of the exhaust pump and the pipe diameter to the exhaust valve are sufficiently large and the gas temperature is approximated, the gas flow rate exhausted from the exhaust valve is approximately determined by the pressure in the gas container. The relationship between the gas pressure in the container and the exhaust gas flow rate is prepared and stored as table data. By using these two table data, it is possible to obtain the opening degree of a valve necessary for obtaining a desired gas amount change rate (= supply gas flow rate−exhaust gas flow rate).

  Here, if the gas temperature is approximated to be constant, the supply gas flow rate is obtained from the differential value of the gas pressure (secondary pressure) change curve and the volume of the container when only gas supply is performed without exhausting. Can do. Further, if the time change of the primary pressure and the secondary pressure is measured at a plurality of valve openings, table data of the gas supply amount with respect to the valve opening can be created. Further, the exhaust gas flow rate can be obtained from the differential value of the gas pressure curve and the volume of the container when only gas is exhausted without supplying gas in the same manner as described above. Table data can be created. These data can be automatically measured using a computer or the like, and table data can be automatically created. It should be noted that the data adjacent to each other in the table data is interpolated by a straight line, an appropriate curve, or a three-dimensional coordinate system by a plane or an appropriate curved surface.

  In the gas pressure control, the control valve opening that gives the gas change rate that is closest to the gas pressure set value after a certain time with respect to the difference between the current gas pressure and the set gas pressure is calculated from the table data. Control. By performing this calculation and control of the control valve at every gas pressure monitoring period, the gas pressure can be controlled at high speed.

  Note that the deviation between the gas pressure after a certain time predicted by the calculation and the actual gas pressure monitored can be controlled by feedback to the table data of the supply gas flow rate and the exhaust gas flow rate, or the control valve opening directly It is also possible to control by feedback. At this time, if the feedback value deviates from a predetermined range, it may be determined that there is some component failure or abnormality and an alarm state may be set, or the conventional PID control may be switched.

  In general, there are communication delays and other response delay factors until the gas pressure actually changes in response to a valve control command from the control unit. In the case of feedback control, more accurate control is possible if control is performed in consideration of the delay. In addition, if the gas pressure fluctuation range is predicted in advance, such as a change in gas pressure due to a change in gas temperature when the laser output is changed, the valve opening required to obtain the desired gas change rate can be known. In consideration of the response delay, it is also possible to perform feedforward control so that the gas change rate is adjusted in advance so as to cancel the predicted gas pressure change.

  When the exhaust valve opening is fixed, if the exhaust valve opening is large, the exhaust speed is large, but in order to keep the gas pressure constant, it is necessary to increase the supply gas flow rate. There is a problem that the amount increases. Conversely, if the opening of the exhaust valve is set small, the amount of gas consumed by the laser oscillator will be small, but the exhaust speed will be small, so if the gas pressure is greater than the set gas pressure, the time to reach the set gas pressure will be reduced. There are many problems. If the opening degree of the exhaust valve is also variable, the gas pressure control can be speeded up even when the gas pressure is higher than the set gas pressure while suppressing the consumption gas amount by increasing the exhaust speed only when necessary.

10, 10 'Laser oscillator 12 Gas container 14 Control valve 16 Primary gas pressure sensor 18 Secondary gas pressure sensor 20 Vacuum pump 22 Control unit 24 Data table storage unit 26 Orifice 28 Exhaust valve

Claims (7)

A gas container containing a laser gas;
A control valve capable of adjusting the gas flow rate of the laser gas supplied to the gas container by adjusting the opening;
A gas pressure sensor for detecting the pressure on the primary side and the secondary side of the control valve;
A vacuum pump for sucking and exhausting laser gas from the gas container;
A gas pressure control unit for controlling the pressure of the laser gas in the gas container,
The gas pressure control unit stores a relationship between a differential pressure between the primary side gas pressure and the secondary side gas pressure, an opening degree of the control valve, and a supply gas flow rate into the gas container. A first data table; and second table data storing a relationship between the gas pressure and the exhaust gas flow rate on the secondary side, and a secondary side detected by an apparatus for detecting the pressure on the secondary side. By dividing a value obtained by multiplying the difference between the gas pressure value and the set gas pressure value by the value of the volume of the gas container by a certain time, a gas amount change rate required to approach the set gas pressure after the certain time is obtained, A gas laser oscillator for obtaining an opening degree of the control valve from the gas amount change rate and the first and second data tables.   The gas pressure controller starts the gas pressure control, and the data in the first and second data tables is based on a deviation between the gas pressure value predicted by calculation after a certain time and the gas pressure value monitored. The laser oscillator according to claim 1, wherein the gas pressure is feedback-controlled by correcting.   3. The gas laser oscillator according to claim 2, wherein when the correction amount from the initial value of the table data exceeds a predetermined range, the gas pressure control method is switched or an alarm signal is output to the outside.   The gas laser oscillator according to any one of claims 1 to 3, wherein when the laser output is changed, a pressure increase caused by a rise in gas temperature is predicted, and the valve is controlled in advance so as to cancel the change. .   A device for monitoring the gas temperature is provided on the primary side of the control valve, detects the gas temperature on the primary side of the control valve, detects the absolute temperature when the first data table is created, and the primary side of the control valve. 5. The gas laser oscillator according to claim 1, wherein the data in the first data table is corrected by multiplying the first data table by an absolute temperature ratio. 6.   A device for monitoring the temperature in the gas container is provided, and a ratio of the absolute temperature in the creation of the first data table and the second data table and the absolute temperature in the gas container is compared with the first data table and the second data table. The gas laser oscillator according to claim 1, wherein the first and second data tables are corrected by multiplying the second data table.   An exhaust valve capable of changing an exhaust gas flow rate is provided in a pipe for sucking gas from the gas container by the vacuum pump, and the exhaust gas flow rate is increased when a pressure in the gas container is larger than a set value. The gas laser oscillator according to any one of 1 to 6.

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