JP7004591B2 - Gas laser oscillator and gas laser processing equipment - Google Patents

Description

The present invention relates to a gas laser oscillator and a gas laser processing apparatus that generate laser light by discharging and exciting a laser gas supplied between the electrodes by applying a high frequency and high voltage to a pair of electrodes.

In the gas laser oscillator, 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 fills the housing of the gas laser oscillator, but if air or the like leaks into the housing due to negative pressure, or if the laser gas deteriorated by discharge accumulates in the housing, the discharge between the electrodes becomes unstable. When an unstable discharge progresses, a discharge is generated between the electrode and the housing of the gas laser oscillator, in addition to the main discharge between the electrodes.

If an abnormal discharge occurs between the electrode and the housing, the electrode may be damaged and the gas laser oscillator may stop. As a response, the abnormal discharge current flowing between the secondary side of the transformer that supplies the 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 this detected value is used between the electrodes. A technology that multiplies the control rectangular wave signal of the inverter circuit that supplies the high voltage and high voltage to be applied, removes the AC component from the multiplication result, and determines whether or not an abnormal discharge has occurred from the obtained numerical value. It has been disclosed.

Japanese Unexamined Patent Publication No. 2010-2514111 (Page 9, Fig. 1)

Conventionally, in order to detect an abnormal discharge current flowing between an electrode and a housing, a neutral point is provided on the secondary side of the transformer, and the neutral point and the housing are grounded using a ground wire. The ground current flowing through the ground wire is detected, but depending on the grounding state of the ground wire, another ground current other than the ground current you want to detect may be superimposed and detected, resulting in reduced detection accuracy or a current other than the one you want to detect. There is a problem that it is erroneously detected and it is not possible to accurately determine whether or not the state of the discharge generated between the electrodes is normal.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention 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 the electrodes and the laser gas are stored . It is equipped with a grounded housing and a transformer installed on the secondary side of the transformer, and detects the current flowing through the housing by generating a discharge between at least one of the electrodes and the housing. By comparing the differential current detection unit that outputs the detection signal and the detection signal output from the differential current detection unit with the threshold value stored in advance in itself, it is determined whether or not the state of the discharge generated between the electrodes is normal. It has a threshold determination unit and a threshold determination unit. The primary side of the current transformer is connected to the secondary side of the transformer in series with the electrode, and is grounded at the neutral point so that the number of turns of the winding on the primary side of the current transformer is divided into two equal parts. The winding divided into two equal parts is characterized in that the polarities are opposite to each other due to the current flowing in the winding.

The present invention has a differential current detection unit that detects the current flowing through the housing by generating a discharge between at least one of the electrodes and the housing, and the differential current detection unit is located on the secondary side of the transformer. It is equipped with a current transformer to be installed. As a result, the abnormal discharge current generated between the pair of electrodes when the discharge is abnormal can be taken out as a detection signal from the differential current detection unit, so that false detection is eliminated and the state of the discharge generated between the electrodes is normal. It becomes possible to accurately determine whether or not it is.

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. 1 is a block diagram of a gas laser oscillator showing the first embodiment of the present invention. In FIG. 1, the inverter circuit 3 and the inverter control circuit 4 constitute an inverter unit. The inverter circuit 3 inputs the AC power supply 1 and inputs the rectified and smoothed DC voltage by the rectifying circuit 2 to convert the rectified and smoothed DC voltage into a high frequency voltage. The inverter control circuit 4 generates a PWM-controlled square wave signal of the inverter circuit 3, and outputs this square wave signal to the inverter circuit 3. The transformer 5 boosts the high frequency voltage output by the inverter circuit 3 and converts it into 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. Further, the housing 8 is connected to the ground wire 9 and is grounded. In addition, although not included in the figure, there are a reflector for oscillating a laser, an output mirror, a laser beam, a blower for supplying a laser gas between the 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 flowing between the upper electrode 6 and the lower electrode 7 and the housing 8 other than the discharge current flowing between the upper electrode 6 and the lower electrode 7, and determines the current value as a voltage value. And output this voltage value as a detection signal. The threshold value determination unit 21 uses a 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 a detection signal output from the difference current detection unit 11. By comparing, it is determined whether or not the state of the discharge generated between the upper electrode 6 and the lower electrode 7 is normal.

FIG. 2 is a block diagram of a main circuit of a 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, which corresponds to the difference between the discharge current flowing through the upper electrode 6 and the discharge current flowing through the lower electrode 7. It is composed of a 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 winding number of turns. It is grounded at the neutral point so that it is divided into two equal parts. Further, the windings divided into two equal parts are configured so that their polarities are opposite to each other due to the current flowing in the windings divided into two equal parts. The secondary side of the current transformer 12 is connected to the current-voltage conversion circuit 13, and the current generated on the secondary side of the current transformer 12 is converted into a voltage by the current-voltage conversion circuit 13, and the current generated on the secondary side of the current transformer 12 is converted into a voltage. A voltage corresponding to the abnormal discharge current flowing between the electrode 6 or the lower electrode 7 and the housing 8 is output as a detection signal.

As described above, on the secondary side of the transformer 5, the differential current detection unit 11 is equipped with a current transformer 12 for detecting the abnormal discharge current flowing between the upper electrode 6 and the lower electrode 7 and the housing 8. Is installed, and a detection signal output from the differential current detection unit 11 is generated between the upper electrode 6 and the lower electrode 7 preset in the threshold determination circuit 22 built in the threshold determination unit 21. Judgment is made by the threshold value for judging whether or not the state of the discharged discharge is normal.

Next, the threshold value determination procedure in the threshold value determination unit 21 will be described. As shown in FIG. 2, the secondary side terminal 51a of the transformer 5 is connected to the upper electrode 6, and the current flowing through the upper electrode 6 is ia. Further, 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 defined as 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 via the current transformer 12 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, and the current flows to the lower electrode 7. It becomes 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 flows to the secondary terminal 52b of the transformer 5 via the winding. It flows and then flows to the primary 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 to the primary side terminal 61b of the current transformer 12. The current flowing through the primary side terminal 61b of the current transformer 12 flows through the winding to the primary side terminal 61a of the current transformer 12, and then flows to the secondary side terminal 51b of the transformer 5. Then, it flows from the secondary side terminal 51b of the transformer 5 to the secondary side terminal 51a of the transformer 5 via the winding, and flows to the upper electrode 6 again.

The number of windings when a current flows from the primary terminal 62a of the current transformer 12 to the primary terminal 62b, and when a current flows from the primary terminal 61b of the current transformer 12 to the primary terminal 61a. The number of windings of the winding is configured to be bisected with the grounding point of the neutral point grounding as a boundary. Further, the winding direction of the winding divided into two equal parts is the case where a current flows from the primary side terminal 62a of the current transformer 12 to the primary side terminal 62b and the case where the current flows from the primary side terminal 61b of the current transformer 12. When a current flows through the side terminal 61a, the polarities of the windings divided into two equal parts are set so as to be different from each other. As described above, 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 primary terminal of the current transformer 12 61a. , 61b, 62a, 62b, a closed circuit is formed, and 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 established. Since the polarities of the windings divided into two equal parts are opposite to each other due to their respective flows, as a result, no induced electromotive force is generated on the secondary side of the current transformer 12, and the current transformer 12 2 No current flows to the next side.

When the discharge is abnormal, the primary side terminal 61b is grounded at the neutral point between the primary side terminal 61a and the primary side terminal 62a of the current transformer 12, and the upper electrode 6 and the lower side electrode 7 are connected to each other. When the abnormal discharge current flowing between the housings 8 is ic, the abnormal discharge current ic flows into the ground wire connected to the primary terminal 61b of the current transformer 12. As described above, when the discharge is abnormal, the secondary terminals of the transformer 5 are 51a, 51b, 52a, 52b, 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 side terminals 61a, 61b, 62a, and 62b at the primary side 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, so that ia-ib = 0. When an 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 or the lower electrode 7, and the housing. It is the sum of the abnormal discharge currents ic flowing between 8 and ia-ib = ic. At this time, on the primary side of the current transformer 12, 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 each flow is substantially present. It is generated as a 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 the current to the voltage by the current-voltage conversion circuit 13, and the upper electrode 6 and the lower electrode 7 are combined with the threshold determination unit 21. It is output as a detection signal of a voltage corresponding to the abnormal discharge current ic flowing between the bodies 8. The threshold value determination unit 21 has a 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 a detection output by the current-voltage conversion circuit 13. The signals are compared, and if the detected signal is larger than the threshold value, it is determined to be an abnormal discharge.

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

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

As described above, according to the first embodiment of the present invention, the primary side of the current transformer 12 is connected in series with the upper electrode 6 and the lower electrode 7 and is connected to the secondary side of the transformer 5. The windings on the primary side of the current transformer 12 are grounded at the neutral point so that the number of turns is divided into two equal parts, and the polarities of the two equal parts are reversed 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, so that false detection is eliminated and the discharge generated between the electrodes is eliminated. It becomes possible to accurately determine whether or not the state of is normal.

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

Further, by applying the gas laser oscillator shown in the first embodiment of the present invention to the gas laser processing apparatus, a defective processing product which has been produced by performing laser processing in spite of the occurrence of abnormal discharge in the past. Can be eliminated as much as possible, so 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 diodes, 32 resistors, 41 comparators, 42 threshold setting circuits, 51a, 51b, 52a, 52b secondary terminal, 61a, 61b, 62a, 62b Primary side terminal.

Claims (3)

A transformer that boosts the high-frequency voltage generated in the inverter section,
A pair of electrodes that discharge in the laser gas due to the high frequency and high voltage boosted by the transformer,
A grounded housing for storing the electrodes and the laser gas, and
A current transformer installed on the secondary side of the transformer is provided, and a current flowing through the housing is detected by generating a discharge between at least one of the electrodes and the housing, and a detection signal is transmitted. The output differential current detector and
A threshold value determination unit that determines whether or not the state of discharge generated between the electrodes is normal by comparing the detection signal output from the difference current detection unit with a threshold value stored in advance in itself.
Have,
The primary side of the current transformer is connected to the secondary side of the transformer in series with the electrode, and the number of windings of the winding on the primary side of the current transformer is divided into two equal parts. A gas laser oscillator characterized in that the winding is grounded to a sex point and divided into two equal parts so that the polarities are opposite to each other due to a current flowing in the winding . The gas laser oscillator according to claim 1 , wherein the gas laser oscillator is controlled by inputting an output signal from the threshold value determination unit to the inverter unit. A gas laser processing apparatus comprising the gas laser oscillator according to claim 1 or 2 .

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