JP2019149506A - Gas laser oscillator and gas laser processing apparatus - Google Patents

Abstract

To accurately determine whether a state of discharge generated between electrodes is normal or not.SOLUTION: A gas laser oscillator includes: a transformer 5 for boosting high frequency voltage generated in inverter units 3, 4; an upper side electrode 6 and a lower side electrode 7 for discharging electricity in laser gas by high frequency high voltage boosted by the transformer 5; a housing 8 for storing the upper side electrode 6 and the lower side electrode 7 and laser gas; a differential current detection unit 11 including a current transformer 12 arranged on the secondary side of the transformer 5 and capable of detecting a current flowing into the housing 8 by generating electrical discharge between at least one of the upper side electrode 6 and the lower side electrode 7 and the housing 8 and outputting a detection signal; and a threshold determination unit 21 for determining whether a state of discharge generated between the upper side electrode 6 and the lower side electrode 7 is normal or not by comparing a detection signal outputted from the differential current detection unit 11 with a threshold previously stored in its unit.SELECTED DRAWING: Figure 1

Description

The present invention relates to a gas laser oscillator and a gas laser processing apparatus that generate a laser beam by applying a high frequency high voltage to a pair of electrodes to discharge-excite a laser gas supplied between the electrodes.

In the gas laser oscillator, a laser gas is supplied between a pair of electrodes constituting the gas laser oscillator, and the laser gas is discharged and excited by a high frequency high voltage applied between the electrodes.
Here, a high frequency high voltage obtained by boosting the high frequency voltage output from the inverter circuit on the secondary side of the transformer is applied between the electrodes.

The laser gas is filled in the casing of the gas laser oscillator. However, when air or the like leaks into the casing due to negative pressure or laser gas deteriorated by discharge accumulates in the casing, the discharge between the electrodes becomes unstable. When unstable discharge proceeds, a discharge is generated between the electrode and the casing of the gas laser oscillator, in addition to the main discharge between the electrodes.

When such abnormal discharge that generates discharge between the electrode and the casing proceeds, the electrode may be damaged and the gas laser oscillator may be stopped. As a countermeasure, an abnormal discharge current flowing between the secondary side of the transformer that supplies a high frequency high voltage applied between the electrodes and the housing of the gas laser oscillator is detected as an abnormal discharge detection function, and the detected value is detected between the electrodes. A technology that multiplies a rectangular wave signal for control of an inverter circuit that supplies a high frequency high voltage to be applied, removes an AC component from the multiplication result, and as a result, determines whether or not abnormal discharge has occurred from the obtained numerical value. It is disclosed.

JP 2010-251411 (page 9, FIG. 1)

Conventionally, in order to detect an abnormal discharge current flowing between the electrode and the housing, a neutral point is provided on the secondary side of the transformer, and the ground between the neutral point and the housing is grounded using an earth wire, Although the earth current flowing through the earth wire is detected, depending on the earthing condition of the earth wire, another earth current other than the earth current to be detected may be superimposed and detected, resulting in a decrease in detection accuracy or other current that is not to be detected. There is a problem in that it is not possible to accurately determine whether or not the state of discharge generated between the electrodes is normal due to erroneous detection.

The present invention has been made to solve the above-described problems, and an object thereof is to accurately determine whether or not the state of discharge generated between electrodes is normal.

In the gas laser oscillator according to the present invention, a transformer that boosts the high-frequency voltage generated in the inverter section, a pair of electrodes that discharge in the laser gas by the high-frequency high voltage boosted by the transformer, and a housing that stores the electrode and the laser gas. Body, and a current transformer installed on the secondary side of the transformer, detects the current flowing in the case when discharge occurs between at least one of the electrodes and the case, and outputs a detection signal And a threshold value determination unit that determines whether or not a state of discharge generated between the electrodes is normal by comparing a detection signal output from the difference current detection unit with a threshold value stored in advance in the differential current detection unit. And having.

The present invention includes a differential current detection unit that detects a current flowing through a housing when a discharge occurs between at least one of the electrodes and the housing, and the differential current detection unit is provided on the secondary side of the transformer. It has a current transformer installed. As a result, the abnormal discharge current that occurs between the pair of electrodes when the discharge is abnormal can be taken out as a detection signal from the differential current detector, so that there is no false detection and the state of the discharge generated between the electrodes is normal. Whether or not can be determined with high accuracy.

It is a block diagram of the gas laser oscillator which shows Embodiment 1 of this invention. It is a block diagram of the main circuit of the gas laser oscillator which shows Embodiment 1 of this invention. It is a block diagram of the current-voltage conversion circuit which shows Embodiment 1 of this invention. It is a block diagram of the threshold value determination circuit which shows Embodiment 1 of this invention.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a gas laser oscillator showing a first embodiment of the present invention. In FIG. 1, an inverter circuit 3 and an inverter control circuit 4 constitute an inverter unit. The inverter circuit 3 receives the DC voltage rectified and smoothed by the rectifying circuit 2 that receives the AC power supply 1 and rectifies and smoothes it, and converts it into a high-frequency voltage. The inverter control circuit 4 generates a PWM-controlled rectangular wave signal of the inverter circuit 3 and outputs the rectangular wave signal to the inverter circuit 3. The transformer 5 boosts the high-frequency voltage output from the inverter circuit 3 and converts it to a high-frequency high voltage. A high frequency high voltage on the secondary side of the transformer 5 is applied between the upper electrode 6 and the lower electrode 7, and a discharge is generated between the upper electrode 6 and the lower electrode 7. The housing 8 stores the upper electrode 6, the lower electrode 7, laser gas, and the like. The housing 8 is connected to the ground wire 9 and grounded. In addition, although not included in the figure, there are a reflecting mirror for laser oscillation, an output mirror, laser light, a blower for supplying a laser gas between upper and lower electrodes, a vacuum pump for exhausting the laser gas, and the like.

The differential current detection unit 11 detects an abnormal discharge current that flows between the upper electrode 6 or the lower electrode 7 and the housing 8 other than the discharge current that flows between the upper electrode 6 and the lower electrode 7, and converts the current value into a voltage value. This voltage value is output as a detection signal. The threshold value determination unit 21 uses the threshold value for determining whether or not the state of discharge generated between the upper electrode 6 and the lower electrode 7 stored in advance is normal and the detection signal output from the differential current detection unit 11. By comparing, it is determined whether or not the state of discharge generated between the upper electrode 6 and the lower electrode 7 is normal.

FIG. 2 is a configuration diagram of the main circuit of the gas laser oscillator showing the first embodiment of the present invention. The differential current detection unit 11 detects an abnormal discharge current flowing between the upper electrode 6 or the lower electrode 7 and the housing 8 corresponding to the difference between the discharge current flowing through the upper electrode 6 and the discharge current flowing through the lower electrode 7. Current transformer 12 and a current-voltage conversion circuit 13. The primary side of the current transformer 12 is connected to the secondary side of the transformer 5 in series with the upper electrode 6 and the lower electrode 7, and the primary side of the current transformer 12 has a number of winding turns. The neutral point is grounded so as to be divided into two equal parts. Further, the halved windings are configured such that the polarities are reversed by the current flowing in the bisected windings. The secondary side of the current transformer 12 is connected to the current-voltage conversion circuit 13, and the current-voltage conversion circuit 13 converts the current generated on the secondary side of the current transformer 12 into a voltage, which A voltage corresponding to an abnormal discharge current flowing between the electrode 6 or the lower electrode 7 and the housing 8 is output as a detection signal.

Thus, on the secondary side of the transformer 5, the differential current detection unit 11 equipped with the current transformer 12 for detecting an abnormal discharge current flowing between the upper electrode 6 or the lower electrode 7 and the housing 8. And a detection signal output from the differential current detection unit 11 is generated between the upper electrode 6 and the lower electrode 7 that are preset in the threshold determination circuit 22 built in the threshold determination unit 21. It is determined by a threshold value for determining whether or not the state of discharge to be performed is normal.

Next, a threshold determination procedure in the threshold determination unit 21 will be described. As shown in FIG. 2, the secondary terminal 51a of the transformer 5 is connected to the upper electrode 6, and the current flowing through the upper electrode 6 is ia. The secondary terminal 52a of the transformer 5 is connected to the lower electrode 7, and the current flowing through the lower electrode 7 is ib.

On the other hand, the other terminal 51b via the winding of the secondary side terminal 51a of the transformer 5 is connected to the primary side terminal 61a of the current transformer 12, and the winding of the secondary side terminal 52a of the transformer 5 is connected. The other terminal 52b is connected to the primary side terminal 62a of the current transformer 12.

When the discharge is normal, the current ia flowing to the upper electrode 6 through the secondary terminal 51a of the transformer 5 flows to the lower electrode 7 through the discharge space between the upper electrode 6 and the lower electrode 7, ib. Since the lower electrode 7 is connected to the secondary terminal 52a of the transformer 5, the current flowing through the secondary terminal 52a of the transformer 5 is transferred to the secondary terminal 52b of the transformer 5 via the winding. Then flows to the primary side terminal 62a of the current transformer 12. The current flowing through the primary side terminal 62a of the current transformer 12 flows through the winding to the primary side terminal 62b of the current transformer 12, and then flows into the primary side terminal 61b of the current transformer 12. The current flowing through the primary side terminal 61 b of the current transformer 12 flows through the winding to the primary side terminal 61 a of the current transformer 12, and then flows through the secondary side terminal 51 b of the transformer 5. And it flows from the secondary side terminal 51b of the transformer 5 to the secondary side terminal 51a of the transformer 5 through the winding, and then flows to the upper electrode 6 again.

The number of winding turns when current flows from the primary side terminal 62a of the current transformer 12 to the primary side terminal 62b, and when current flows from the primary side terminal 61b of the current transformer 12 to the primary side terminal 61a. The number of turns of the winding is divided into two equal parts with the grounding point of the neutral point grounding as a boundary. Further, the winding direction of the halved winding is such that when a current flows from the primary side terminal 62a of the current transformer 12 to the primary side terminal 62b, and when the current flows from the primary side terminal 61b of the current transformer 12 to the primary side. In the case where a current flows through the side terminal 61a, the halves of the windings are set to have different polarities. Thus, 51a, 51b, 52a, 52b which are the secondary side terminals of the transformer 5, the discharge space between the upper electrode 6 and the lower electrode 7, and 61a which is the primary side terminal of the current transformer 12. 61b, 62a, 62b, a closed circuit is formed. When the discharge is normal, ia = ib is established on the primary side of the current transformer 12, and the current ia and the current ib are Since the polarities of the halved windings are opposite to each other due to the respective flows, no induced electromotive force is generated on the secondary side of the current transformer 12 as a result. No current flows on the secondary side.

When the discharge is abnormal, the primary terminal 61b is grounded between the primary terminal 61a and the primary terminal 62a of the current transformer 12, and the upper electrode 6 and the lower electrode 7 When the abnormal discharge current flowing between the casings 8 is ic, the abnormal discharge current ic flows into the ground wire connected to the primary side terminal 61b of the current transformer 12. As described above, when the discharge is abnormal, the secondary terminals 51a, 51b, 52a, 52b of the transformer 5, the discharge space between the upper electrode 6 and the lower electrode 7, and the current transformer 12 The abnormal discharge current ic flows into the closed circuit formed between the primary terminals 61a, 61b, 62a, and 62b at the primary terminal 61b of the current transformer 12.

When the discharge is normal, the current ia flowing through the upper electrode 6 and the current ib flowing through the lower electrode 7 have the same current value, and thus ia−ib = 0, but the upper electrode 6 and the lower electrode 7 are not connected to the housing. When the abnormal discharge current ic flowing between the bodies 8 is generated, that is, when the discharge is abnormal, the current ia flowing through the upper electrode 6 is the current ib flowing through the lower electrode 7, the upper electrode 6, the lower electrode 7, and the housing. 8 is the sum of the abnormal discharge currents ic flowing between 8 and ia−ib = ic. At this time, an abnormal discharge current ic corresponding to the difference between the current ia and the current ib generated by considering the polarities of the windings through which the current ia and the current ib flow is substantially present on the primary side of the current transformer 12. Generated as a heavy load current. As a result, an induced electromotive force induced by the abnormal discharge current ic is generated on the secondary side of the current transformer 12, and a differential current ix flows on the secondary side of the current transformer 12.

The differential current ix generated on the secondary side of the current transformer 12 when the discharge is abnormal is converted from current to voltage by the current-voltage conversion circuit 13, and the threshold determination unit 21 is connected to the upper electrode 6 and the lower electrode 7 and the housing. A detection signal of a voltage corresponding to the abnormal discharge current ic flowing between the bodies 8 is output. The threshold determination unit 21 determines whether or not the state of discharge generated between the upper electrode 6 and the lower electrode 7 stored in advance is normal, and the detection output from the current-voltage conversion circuit 13. The signals are compared, and if the detection signal is greater than the threshold value, it is determined that the discharge is abnormal.

FIG. 3 is a configuration diagram of the current-voltage conversion circuit showing the first embodiment of the present invention. On the secondary side of the current transformer 12, diodes 31a to 31d and a resistor 32 are connected. When the discharge is abnormal, the differential current ix output from the current transformer 12 is rectified by the diodes 31a to 31d, and the resistor 32 Is converted into a voltage and output to the threshold value determination unit 21 as a detection signal.

FIG. 4 is a configuration diagram of a threshold determination circuit showing the first embodiment of the present invention. The threshold determination circuit 22 is mainly composed of a comparator 41. A threshold voltage Vref is set in advance by a threshold setting circuit 42, and the detection signal and threshold voltage output from the current-voltage conversion circuit 13 with the threshold voltage Vref as a threshold. Vref is compared by a comparator to determine whether or not the state of discharge generated between the electrodes is normal.

Thus, according to the first embodiment of the present invention, the primary side of the current transformer 12 is connected to the secondary side of the transformer 5 in series with the upper electrode 6 and the lower electrode 7, and The neutral point is grounded so that the number of windings of the primary side winding of the flow device 12 is divided into two equal parts, and the two divided windings are reversed in polarity by the current flowing in the windings. It is configured. As a result, when the discharge is abnormal, the abnormal discharge current ic flowing between the upper electrode 6 or the lower electrode 7 and the housing 8 can be taken out as a detection signal. It is possible to accurately determine whether or not the state is normal.

Further, according to the first embodiment of the present invention, the threshold determination unit 21 includes the threshold determination circuit 22, and the detection signal input to the threshold determination circuit 22 is output as an interlock signal, or the threshold determination The detection signal input to the unit 21 can be output as a monitor signal. For example, by feeding back the output interlock signal or monitor signal to the inverter control circuit 4, the input to the laser oscillator can be immediately cut off, and the electrode failure can be prevented and maintained.

Furthermore, by applying the gas laser oscillator shown in Embodiment 1 of the present invention to a gas laser processing apparatus, defective processing products that have been produced by laser processing in the past even though abnormal discharge has occurred. Therefore, productivity can be improved.

1 AC power supply, 2 rectifier circuit, 3 inverter circuit, 4 inverter control circuit, 5 transformer, 6 upper electrode, 7 lower electrode, 8 housing, 9 ground wire, 11 differential current detector, 12 current transformer, 13 Current / voltage conversion circuit, 21 threshold determination unit, 22 threshold determination circuit, 31a to 31d diode, 32 resistor, 41 comparator, 42 threshold setting circuit, 51a, 51b, 52a, 52b secondary terminal, 61a, 61b, 62a, 62b Primary side terminal.

Claims (4)

A transformer that boosts the high-frequency voltage generated in the inverter unit;
A pair of electrodes for discharging in the laser gas by the high frequency high voltage boosted by the transformer;
A housing for storing the electrode and the laser gas;
A current transformer provided on the secondary side of the transformer, and detecting a current flowing in the housing by generating a discharge between at least one of the electrodes and the housing; A differential current detector to output,
A threshold determination unit that determines whether or not a state of discharge generated between the electrodes is normal by comparing a detection signal output from the differential current detection unit with a threshold stored in advance in the detection signal;
A gas laser oscillator. The primary side of the current transformer is connected in series with the electrode to the secondary side of the transformer, and the number of turns of the primary side winding of the current transformer is divided in half. 2. The gas laser oscillator according to claim 1, wherein the windings that are grounded at a sex point and are divided into two equal parts are configured to have opposite polarities by currents flowing in the windings. The gas laser oscillator according to claim 2, wherein the gas laser oscillator is controlled by inputting an output signal from the threshold determination unit to the inverter unit. A gas laser processing apparatus comprising the gas laser oscillator according to any one of claims 1 to 3.

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