JPH0456372A - Method and apparatus for controlling carbon dioxide gas laser - Google Patents

Abstract

PURPOSE:To immediately stop a cross discharge and to restart a discharge by stopping the discharges of all discharge tubes by an OR circuit when a discharge current or high frequency power becomes a reference value or higher in even one of a plurality of discharge tubes. CONSTITUTION:An output of a discharge current detector 29 is input to a delay circuit 34, and the output of the circuit 24 and an output from a reference value setter 35 are input to a comparator 36. The output of the circuit 36 is input to an OR circuit 37 and an OR circuit of the other discharge tube of a control block 41. An output from a comparator of the other discharge tube of the block 41 is input to the circuit 37. The output of the circuit 37 is input to an inhibit circuit in a discharge controller 38. When cross discharge currents 43, 44 flow, the output of the detector 29 exceeds a reference value level 42 of the setter 35, the output of the comparator 36 becomes an H level, and a tube 28 is deenergized. Discharge is again started after a time set by the circuit 34.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and device for controlling a carbon dioxide laser, and more particularly to a method and device for controlling cross-discharge recovery in DC-excited and high-frequency excited carbon dioxide lasers. .

BACKGROUND OF THE INVENTION FIG. 3 shows the structure of a conventional high-speed axial-flow DC-excited carbon dioxide laser oscillator. In FIG. 3, a discharge tube 1.2 made of a dielectric material such as glass is provided with discharge electrodes 3, 4.

The discharge electrodes 3 and 4 are supplied with the output of a DC high voltage power supply 5.6, for example, a voltage of about 16 kV DC and 80 mA. Discharge tube] In the discharge space inside 1.2, discharge occurs in the directions of arrows A and B.

A rear mirror (total reflection mirror) 7 and an output mirror (partial reflection mirror) 8 are fixedly arranged at both ends of the discharge space within the discharge tube 1.2, and constitute an optical resonator. Laser output 9 is taken out from output mirror 8 .

The laser gas in the discharge tubes 1 and 2 is circulated through an air pipe 10, and the gas whose temperature has risen through a blower 11 that circulates the discharge and laser gas is cooled by a heat exchanger 12.13. Ru.

4 and 5 show electrical equivalent circuits of the discharge tubes 1 and 2 in the carbon dioxide laser oscillator shown in FIG. 4 and 5, the discharge current detection circuit 14
．． A CT (current transformer) or a shunt resistor is used for L5, and the insertion locations of the discharge current detection circuits 14 and 15 are different between FIGS. 4 and 5. That is, in Fig. 5, unlike Fig. 4, the ground sides (cathode sides) of the high-voltage power supplies 5 and 6 are partially insulated by inserting an insulating collar into the cathode holder mounting screw, and the ground wires can be taken separately. This is how it was done.

The discharge voltage of discharge tube 1 is Ve+, and the discharge voltage of discharge tube 2 is V
es, the equivalent internal impedance of discharge tube 1 is 21, the equivalent internal impedance of discharge tube 2 is 22, the voltage across the non-discharge section is V e 1-2, and the equivalent internal impedance of the non-discharge section is 21-2, then the cross A discharge occurs and Ve+
>Ve2, an excessive discharge current flows from the high-voltage power supply 5 into the discharge tube 2 through the equivalent internal impedance Z1-2 of the non-discharge part, and in some cases, the discharge tube 1 turns off, and this state is continued and maintained. Sometimes.

In this case, the discharge current detection circuit 14 or 15 can detect that the discharge has become a cross discharge and the discharge current has increased, but if the circuit configuration is as shown in FIG. 5, the cross discharge can be detected more reliably. be able to. That is, V
If 2+>Ve2, this can be detected by the discharge current detection circuit 15 in FIG.

Problems to be Solved by the Invention As described above, in the conventional carbon dioxide laser oscillator, when the discharge tube is composed of multiple discharge tubes such as two, four, or six, the high voltage applied to each discharge tube is connected to the ground side. is in electrical continuity through the oscillator housing, and the positive side of the high voltage is commonly connected through the gas in the non-discharge section if each discharge tube is electrically high impedance to each other in the non-discharge section. It is connected. When feedback control of the discharge current is performed in a region where the discharge current is high, the non-discharge area discharges due to fluctuations in the discharge current, one discharge tube may go out, and excessive current flows to other discharge tubes. This will cause a cross discharge to occur.

When cross discharge occurs, fluctuations and decreases in laser output, burnout of discharge tube O-rings, destruction of switching elements, etc. occur. In particular, when oscillating in pulse mode, if a high current twice as high as in CW (continuous) mode is injected, the frequency of occurrence of these failures increases.

In addition, in both CW mode and pulse mode, if the rise time of the discharge start voltage varies widely due to variations in the discharge start voltage and the control system, the potential difference in the non-discharge area will increase, and if one discharges first, then the other The voltage of the discharged discharge tube becomes the discharge sustaining voltage, and the voltage of other discharge tubes does not reach the discharge starting voltage, and cross discharge may occur without discharge.

Further, even if the laser oscillator is evacuated several times after being opened to the atmosphere, if the humidity in the atmosphere is high, moisture will adhere to the waste path, and cross discharge is likely to occur in this case as well.

Further, cross discharge is likely to occur when a vacuum leak occurs.

If cross discharge occurs, immediately stop oscillation and
After stopping the system, it is necessary to restart it. Also, when cross discharge occurs, it is extremely dangerous and the power must be turned off.

Such loss discharge is greatly related to laser machining defects, lower machine operating rates, and lower reliability, and countermeasures have been an important issue in this technical field.

The present invention solves these conventional problems, and aims to provide a carbon dioxide laser control method and apparatus that can immediately stop cross discharge and restart discharge.

Means for Solving the Problems In order to achieve the above object, the present invention detects the magnitude of the discharge current or high frequency power in each discharge tube, compares each output with a reference value, and calculates the magnitude of the discharge current or high frequency power for a certain discharge tube. The comparison output is logically summed with the comparison outputs of all other discharge tubes, and when the magnitude of the discharge current or high-frequency power of a certain discharge tube exceeds a reference value, the discharge of all discharge tubes is stopped. This is what I did.

The present invention also provides an on-time or off-time delay circuit before the plurality of comparator circuits.

According to the present invention, with the above configuration, when the discharge current or high frequency power of even one of the plurality of discharge tubes exceeds a reference value, the OR circuit stops the discharge of all the discharge tubes, so cross discharge disappears. It is the same as turning off the power.

In addition, by providing a delay circuit for on time or off time with different time constants before the comparator circuit and setting the time to a consistent value, it is possible to restart discharge after an appropriate time after the discharge tube stops discharging. This makes it possible to prevent laser processing defects and lower operating rates.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1st
The figure shows a control block of a carbon dioxide laser control device in one embodiment of the present invention, and FIG. 2 shows the output waveform at the time of cross discharge recovery in one embodiment of the present invention.

In Fig. 1, 21 is a three-phase 200V commercial power supply, 22 is a rectifier, 23 is a smoothing capacitor, 24 is an inverter circuit with a full bridge connection of power MO8-FETs, 25 is a high-voltage transformer, 26 is a rectifier, and 27 is a A high voltage capacitor, 28 is a discharge tube of a laser oscillator, and 29 is a C
This is a discharge current detection circuit such as a T (current transformer) or shunt resistor.

Further, 30 is a laser power setting circuit, 31 is a laser power detection circuit, 32 is a first error amplifier circuit, and 33 is a second error amplifier circuit.
34 is an on-time or off-time delay circuit, 35 is a reference value setting circuit, 36 is a comparator circuit, 37 is an OR circuit, 38 is a discharge control circuit (PWM (f
M)), 39 is a driver circuit. 40 is the discharge tube 28
The control block 41 is a control block for performing a so-called SD (shutdown) operation for the other discharge tubes.

Next, the operation of the above embodiment will be explained. In FIG. 1, a three-phase 200 V AC voltage from a commercial power supply 21 is rectified by a rectifier 22 and then smoothed by a smoothing capacitor 23, and the smoothed DC voltage is supplied to an inverter circuit 24. The inverter circuit 24 drives a high voltage transformer 25 , and the secondary voltage of the high voltage transformer 25 is rectified by a rectifier 26 and then smoothed by a high voltage capacitor 27 . This smoothed DC high voltage is applied to the discharge tube 28 , and the discharge current flowing through the discharge tube 28 is detected by a discharge current detection circuit 29 .

On the other hand, the output of the laser power setting circuit 30 and the output of the laser power detection circuit 31 that detects the magnitude of the laser power are input to the first error amplifier circuit 32. The output of the first error amplifier circuit 32 and the aforementioned discharge current detection circuit 2
9 is input to the second error amplifier circuit 33, and the output of the second error amplifier circuit 33 is input to the discharge control circuit 38.
is input. The discharge control circuit 38 has a built-in inhibit circuit called SD (shutdown), and the output of the discharge control circuit 38 is input to the driver circuit 39.
The output of the driver circuit 39 drives the power Mo1-FET of the impark circuit 24.

The output of the discharge current detection circuit 29 is also input to the delay circuit 34, and the output of the delay circuit 34 and the output from the reference value setting circuit 35 are input to the comparator circuit 36. The output of the comparator circuit 36 is input to an OR circuit 37 and an OR circuit of another discharge tube (not shown) of the control block 41. Further, the logical sum circuit 37 includes a control block 41
The output from the comparator circuit of the other discharge tube is input. The output of the OR circuit 37 is then input to an inhibition circuit within the discharge control circuit 38.

Although FIG. 1 shows the case where there are two discharge tubes, in the case of four discharge tubes, control blocks 40 and 41 representing one discharge tube are used.
A total of 4 blocks are required. Furthermore, when there are four discharge tubes, the OR circuit 37 requires four people to operate.

The level of the reference value setting circuit 35 is set at 20 to 30% of the level during normal discharge in both the CW mode and the pulse mode, and the level can be selected depending on the CW mode or the pulse mode. As shown in Figure 2, cross discharge occurs and the cross discharge current is 43.4
4 flows, the output of the discharge current detection circuit 29 exceeds the reference value level 42 of the reference value setting circuit 35, the output of the comparator circuit 36 becomes H level, and the output of the driver circuit 39 to the inverter circuit 24 through the discharge control circuit 38. The output is cut off and the discharge tube 28 is turned off. And delay circuit 3
When the output of the comparator circuit 36 becomes L level after the time set in 4, discharging is started again to perform a so-called SD operation. The extinguishing and discharging of the discharge tubes 28 in the control block 40 and the extinguishing and discharging of the discharge tubes in the control block 41 are performed simultaneously. Note that even if the discharge tube is composed of four or more, even if only one discharge tube performs the SD operation to turn off the light, the cross discharge will be transferred to the other discharge tubes, so the present embodiment As such, the cross discharge cannot be recovered unless the SD operation is performed for each discharge tube.

In this way, according to the embodiment, the discharge current of each of the plurality of discharge tubes is detected, and if the discharge current of even one of them exceeds the reference value, the discharge of all the discharge tubes is stopped, Since the discharge of all the discharge tubes is restarted after the set time, cross discharge can be extinguished without turning off the power supply, and problems caused by cross discharge can be eliminated.

The above embodiment is an example in which the present invention is applied to a DC excitation type carbon dioxide laser control device. However, the present invention also involves injecting high frequency output into a discharge tube and generating laser light from a waste medium excited by the high frequency discharge. The present invention can be similarly applied to a high-frequency excitation type carbon dioxide gas laser control method and apparatus having a plurality of discharge tubes, and similar effects can be obtained. In this case, the "discharge current" of the discharge tube in the above embodiment shall be read as "high frequency power", and the "discharge current detection circuit" shall be read as "high frequency power detection circuit".

Effects of the Invention As described above, according to the present invention, the magnitude of the discharge current or high-frequency power in each discharge tube is detected and each output is compared with a reference value, and the comparative output of one discharge tube is compared with that of another discharge tube. By calculating the logical sum with the comparative outputs of all discharge tubes, the discharge of all discharge tubes is stopped when the magnitude of the discharge current or high-frequency power of a certain discharge tube exceeds a reference value. Fluctuations and decreases in output, discharge tube zero
Problems such as burnout of links, destruction of switching elements, etc. can be eliminated.

Further, according to the present invention, since the on-time or off-time delay circuit is provided before the comparator circuit, the discharge can be restarted immediately after a certain period of time has passed after the discharge of the discharge tube has stopped, thereby preventing laser processing defects. It is possible to provide a highly reliable carbon dioxide gas racer control method and device that can prevent a decrease in the operating rate.

[Brief explanation of the drawing]

Fig. 1 is a control block diagram of a carbon dioxide scum laser control device showing an embodiment of the present invention, Fig. 2 is a diagram showing the discharge current and the output waveform of the comparator circuit during cross discharge recovery in an embodiment of the present invention; Figure 3 is a schematic perspective view showing the configuration of a conventional DC-excited carbon dioxide laser oscillator, Figures 4 and 5
This figure is a diagram showing an electrical equivalent circuit of the discharge tube in the apparatus shown in FIG. 3. 21... Commercial power supply, 22... Rectifier, 23... Smoothing capacitor, 24... Inverter circuit, 25...
High voltage transformer, 26... Rectifier, 27... High voltage capacitor, 28... Discharge tube, 29... Discharge current detection circuit, 30... Laser power setting circuit, 31... Laser power detection circuit, 32...first error amplifier circuit,
33... Second error amplifier circuit, 34... Delay circuit, 35... Reference value setting circuit, 36... Comparator circuit, 37... OR circuit, 38... Discharge control circuit, 39... Driver circuit, 40.41... Control block for causing the discharge tube to perform SD operation. Name of agent: Patent attorney Masahiro Kura Go Figure 3 Figure 4 Figure 5

Claims (8)

[Claims] (1) In a DC-excited carbon dioxide laser control method equipped with a plurality of discharge tubes that applies a DC high voltage to the discharge tube and generates laser light from a gas medium excited by DC glow discharge, the discharge current of each discharge tube is Detect the magnitude of each discharge tube, compare each output with the reference value, take the logical sum of the comparison output for one discharge tube and the comparison output for all other discharge tubes, and calculate the discharge current of a certain discharge tube. A carbon dioxide laser control method characterized by controlling the discharge of all discharge tubes to be stopped when a reference value is exceeded. (2) In a high-frequency excitation type carbon dioxide laser control method equipped with a plurality of discharge tubes in which high-frequency output is injected into the discharge tube and laser light is generated from a gas medium excited by the high-frequency discharge, the high-frequency power of each discharge tube is The high-frequency power of a certain discharge tube is determined to be the reference value. 1. A gas laser control method characterized by controlling the discharge of all discharge tubes to be stopped when the value exceeds the limit. (3) In a DC-excited carbon dioxide laser control device equipped with a plurality of discharge tubes that applies a DC high voltage to the discharge tubes and generates laser light from a gas medium excited by DC glow discharge, the discharge current of each discharge tube a plurality of discharge current detection circuits that respectively detect the magnitude of the discharge current; a reference value setting circuit that sets a reference value of the discharge current; and a plurality of discharge current detection circuits that respectively compare the outputs of the respective discharge current detection circuits and the reference value setting circuit. Prohibition of oscillating/stopping the discharge of each discharge tube by inputting a comparator circuit, multiple OR circuits that OR a certain comparator circuit and all other comparator circuits, and the output of each of the OR circuits. A carbon dioxide laser control device comprising a discharge control circuit having a circuit. (4) Claim (3) characterized in that an on-time or off-time delay circuit is provided before the plurality of comparator circuits.
) described carbon dioxide laser control device. (5) The carbon dioxide laser control device according to claim (3) or (4), further comprising means for switching the reference value of the reference value setting circuit between continuous mode and pulse mode. (6) In a high-frequency excitation type carbon dioxide laser control device equipped with a plurality of discharge tubes that injects high-frequency output into the discharge tube and generates laser light from a gas medium excited by the high-frequency discharge, the high-frequency power of each discharge tube is a plurality of high-frequency power detection circuits that respectively detect the high-frequency power, a reference value setting circuit that sets a reference value of the high-frequency power, and a plurality of comparator circuits that respectively compare the outputs of the respective high-frequency power detection circuits and the reference value setting circuit. , a plurality of logical sum circuits that logically OR a certain comparator circuit with all other comparator circuits, and an inhibition circuit that inputs the output of each of the logical sum circuits and oscillates/stops the discharge of each discharge tube. A carbon dioxide laser control device comprising a discharge control circuit. (7) Claim (6) characterized in that an on-time or off-time delay circuit is provided before the plurality of comparator circuits.
) described carbon dioxide laser control device. (8) The carbon dioxide laser control device according to claim (6) or (7), further comprising means for switching the reference value of the reference value setting circuit between continuous mode and pulse mode.