JP2011233659A - Laser oscillation device and laser beam machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable laser oscillation device by suppressing the occurrence of an abnormal voltage in a high-voltage power supply owing to a defect of a gas mixture ratio or the like, and preventing an overvoltage from damaging a semiconductor rectification element.SOLUTION: A laser oscillation device includes: a laser-launch directing unit for deciding a timing of launching an output laser light from a laser resonator; a current value-setting unit for outputting a preset current value signal according to an output signal of the laser-launch directing unit; and comparison-control means for comparing an output signal of the current value-setting unit and a current value output signal of a current detection unit. In the laser oscillation device, when the output signal of the current value detection unit is smaller than a predetermined current value, a pulse width of a pulse-width calculation means is restricted to a short one by an output signal of a maximum pulse switching means, whereby the occurrence of an abnormal voltage which would be caused in a boosting transformer unit is suppressed, and the breakdown of a semiconductor rectification element is prevented.

Description

  The present invention relates to a laser oscillation device and a laser processing machine provided with an overvoltage protection circuit in a high voltage power supply for laser oscillation.

  The configuration of a conventional laser oscillation device will be described with reference to FIG.

  A current value command is output from the current value setting unit 78 based on the output signal of the irradiation command unit 79 that determines the timing of irradiation of the output laser light. The current value command and the current value output signal of the current detector 73 are compared by the comparison control means 77 and then output to the pulse width calculation means 76.

  In the pulse width calculation means 76, the voltage signal of the comparison control means 77 is converted into a pulse signal whose pulse width is modulated at a constant frequency, and a switching control element such as a power semiconductor of the inverter unit 75 is driven by the pulse signal, so that the step-up transformer A high-frequency AC voltage is supplied to the unit 74.

  In the step-up transformer unit 74, the AC voltage is boosted and converted into a DC high voltage by a semiconductor rectifier such as a high-voltage diode, and supplied to the laser resonator 71 via the current detection unit 73.

  On the other hand, the output signal of the current detection unit 73 is fed back to the comparison control unit 77, and feedback control is performed so that a stable current is supplied to the laser resonator 71. Then, the output laser beam 72 is irradiated from the laser resonator 71 for the command time of the irradiation command unit 79.

  Since the switching type high voltage power source used in laser oscillators and the like controls the output voltage by pulse width modulation, the relationship between the pulse width of the high voltage power source and the generated voltage is as shown in FIG. The generated voltage increases as the width increases.

  In the case of a discharge load such as a gas laser oscillation device, if a gas leak due to loosening of a tightening part such as a gas pipe joint or a vacuum leak occurs due to secular change in the gas circulation path, a laser gas mixing ratio failure occurs, causing a temporary discharge. An abnormal discharge state in which the start voltage increases and discharge cannot be started may occur. The generated voltage of the high-voltage power supply at the time of abnormal discharge sometimes increases from about 2 to 3 times as compared with the voltage when the discharge is normal.

  Also, when an abnormality such as opening of the current feedback control loop or opening of the load due to poor wiring connection occurs, the output voltage of the high voltage power supply is monitored, and when the overvoltage occurs, the driving of the switching control element is stopped, In some cases, the semiconductor rectifying element in the step-up transformer is protected from overvoltage breakdown.

  As described above, an invention having an overvoltage protection function for protecting the semiconductor of the step-up transformer unit and the inverter unit from an overvoltage generated by a load side abnormality such as a load impedance abnormality such as a laser gas mixing ratio defect or a control system abnormality due to a disturbance is provided. It is known (see, for example, Patent Document 1).

  In the invention described in Patent Document 1, a control signal that is inversely proportional to the input voltage is input to the pulse width modulator, and the output voltage is controlled by controlling the maximum pulse width of the pulse width modulator to a constant value. Although the overvoltage of the output voltage can be suppressed against the fluctuation of the input voltage, it is not sufficient for overvoltage protection due to abnormalities such as opening of the current feedback control loop and opening of the load due to poor wiring connection.

JP-A 64-55071

  In such a conventional laser oscillation device, when a laser gas mixing ratio failure occurs due to vacuum leak or gas leak, the discharge start voltage temporarily rises, and it may not be possible to start discharge in the discharge tube. There was a problem of accelerating the breakdown of the semiconductor rectifier element and the deterioration of the semiconductor rectifier element that rectifies the AC voltage of the step-up transformer section and rectifies the AC voltage of the boost transformer section by the abnormal voltage generated in the boost transformer section .

  Also, when an abnormality such as opening of the current feedback control loop or opening of the load due to poor wiring connection occurs, the output voltage of the high voltage power supply is monitored, and when the overvoltage occurs, the driving of the switching control element is stopped, The overvoltage protection circuit that protects the semiconductor rectifier element of the step-up transformer unit from overvoltage breakdown has a tendency to cause frequent malfunctions due to changes in the surrounding environment and external noise when the transient response is accelerated, and frequently stops. Moreover, if the transient response is slowed down, the output voltage rises before the protection circuit operates. Therefore, in order to protect the semiconductor rectifier element of the step-up transformer unit from destruction, an expensive semiconductor rectifier element with high withstand voltage is required. There was also a problem.

  As a result, the breakdown voltage of the semiconductor rectifier that converts the AC voltage of the step-up transformer to DC voltage may increase due to an increase in the discharge start voltage due to a poor laser gas mixing ratio, or the response of the output voltage monitoring device of the high-voltage power supply. Therefore, there is a problem that the use of a rectifying element having a high withstand voltage and the occurrence of malfunction are caused by the characteristics.

  SUMMARY OF THE INVENTION The present invention solves the above-described problems, and an object of the present invention is to provide a laser oscillation device that includes an overvoltage protection circuit that limits the maximum pulse width of an inverter unit by current detection and that is capable of stable laser output.

  In order to solve the above-described problem, a laser oscillation apparatus according to a first aspect of the present invention is preset by an irradiation command unit that determines the timing of irradiating output laser light from a laser resonator, and an output signal of the irradiation command unit. A current value setting unit that outputs the current value signal, a comparison control unit that compares the output signal of the current value setting unit and the current value output signal of the current detection unit, and the output signal of the comparison control unit as a pulse width A pulse width calculation means for conversion, an inverter section for switching the control element by a pulse signal of the pulse width calculation means, and an output signal of the inverter section is converted into a direct current high voltage to the laser resonator via a current detection section A step-up transformer for supplying electric power, and maximum pulse width switching means for switching a pulse width with a detection signal of the current detection unit, wherein the detection signal of the current detection unit has a predetermined current value Narrow pulse width in the case of full, also those having a maximum pulse width switching means for controlling the maximum pulse width of the control element of the inverter unit by switching a wide pulse width when it exceeds a predetermined current value.

  This configuration limits the maximum pulse width of the control element of the inverter unit by switching to a narrow pulse width when the detection signal of the current detection unit is less than a predetermined current value, thus causing abnormal discharge in the discharge tube and poor wiring contact An abnormal voltage generated in the step-up transformer unit due to such causes can be suppressed, and breakdown of the high-voltage wiring, rectification element of the step-up transformer unit, and element deterioration can be prevented.

  Further, the laser oscillation device of the present invention is the laser oscillation device of the first invention, wherein the maximum pulse width switching means compares the detection signal of the current detection unit with a predetermined current value setting signal. A pulse width setting unit in which a plurality of pulse widths are set in advance, a pulse width switching unit that switches the pulse width of the pulse width setting unit according to an output signal of the current value determination unit, and an output of the pulse width switching unit A pulse width limiter that controls the pulse width of the pulse width calculation means to be limited by a signal.

  In addition to the same effects as described above, this configuration speeds up and simplifies the process of limiting the pulse width to the pulse width calculation means by switching the plurality of pulse widths of the pulse width setting unit with the detection signal of the current detection unit. Therefore, accurate operation with good repeatability becomes possible and reliability is improved.

  Furthermore, the laser oscillation device of the present invention is the laser oscillation device of the first invention, wherein a current value determination unit that compares a detection signal of the current detection unit and a predetermined current value setting signal, and a current value setting unit A pulse width calculation unit that calculates a pulse width according to a current value command, a pulse width switching unit that switches a pulse width of the pulse width calculation unit according to an output signal of the current value determination unit, and an output signal of the pulse width switching unit And a pulse width limiter for controlling the pulse width of the pulse width calculation means so as to limit the pulse width.

  In addition to the same effects as described above, this configuration provides a pulse width calculation unit that calculates the maximum pulse width of the switching control element according to the current value command of the current value setting unit. The optimum setting can be made, the protection performance against overvoltage is increased, and the reliability can be further improved.

  Furthermore, the laser oscillation device of the present invention is the above-described laser oscillation device of any of the above inventions, a processing table for placing a workpiece, a driving unit for moving at least one of the movement of the processing table and the laser beam condensing unit, A numerical control means for controlling the driving means and a laser oscillation device for generating laser light are provided.

  In addition to the effects similar to the above, the laser oscillation device is comprehensively controlled by the numerical control means, thereby improving the reliability of laser processing and preventing the introduction of defective products of the workpiece.

  As described above, the present invention restricts the gate pulse width of the switching control element of the inverter unit when the output current value from the step-up transformer unit to the laser resonator is less than a predetermined current value, thereby causing a discharge abnormality in the discharge tube. By suppressing the abnormal voltage that sometimes occurs in the step-up transformer section, it is possible to prevent dielectric breakdown of the rectifier element and element deterioration of the step-up transformer section. In addition, it is possible to prevent an abnormal feedback signal due to disconnection of the wiring of the current detection unit and an overvoltage due to a failure of the current detection unit, thereby stabilizing the laser output and improving the reliability.

Block diagram of Embodiment 1 of the laser oscillation apparatus of the present invention Detailed block diagram of maximum pulse width switching means in embodiment 1 of the present invention Detailed block diagram of maximum pulse width switching means in embodiment 1 of the present invention Relationship diagram between pulse width and generated voltage when maximum pulse width is limited in the embodiment of the present invention The block diagram of the laser processing machine in embodiment of this invention Block diagram of a conventional laser oscillator Relationship diagram between pulse width and generated voltage of high voltage power supply

  Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS.

(Embodiment 1)
FIG. 1 is a block diagram of a laser oscillation apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the laser oscillation device according to the first embodiment includes a laser resonator 1, an output laser beam 2, a current detection unit 3, a step-up transformer 4, an inverter unit 5, a pulse width calculation unit 6, and a comparison control unit 7. , Current value setting unit 8, irradiation command unit 9, and maximum pulse switching means 10.

  The operation of the laser oscillation apparatus configured as described above will be described.

  In this laser oscillation device, a current value command is output from the current value setting unit 8 based on the output signal of the irradiation command unit 9 that determines the timing of irradiating the output laser beam. The current value command and the current value output signal of the current detector 3 are compared by the comparison control means 7 and then output to the pulse width calculation means 6. In the pulse width calculation means 6, the voltage signal of the comparison control means 7 is converted into a pulse signal of pulse width modulation with a constant frequency and output to the inverter unit 5. In the inverter unit 5, a control element such as a power semiconductor is subjected to switching control to supply an AC voltage to the step-up transformer unit 4. In the step-up transformer unit 4, an AC voltage is converted into a DC high voltage output signal by a transformer and a high-voltage rectifying element, and is supplied to the laser resonator 1 via the current detection unit 3. On the other hand, the output signal of the current detection unit 3 is fed back to the comparison control unit 7 and feedback controlled so that a stable current is supplied to the laser resonator 1.

  Further, the output signal of the current detector 3 is input to the maximum pulse width switching means 10, and when the output signal of the current detector 3 is less than a predetermined current value, the output pulse width of the pulse width calculator 6 is set in advance. It is switched to select the maximum pulse width of the narrow state that has been done. Further, when a predetermined current value is exceeded, the maximum pulse width is switched to a wide state.

  When the output current from the step-up transformer 4 to the laser resonator 1 is not detected by the current detector 3, the pulse width from the pulse width calculator 6 to the inverter 5 is expanded to the maximum pulse width for current feedback control. The output voltage of the step-up transformer unit 4 increases to the maximum voltage.

  When the output signal of the current value detection unit is less than the predetermined current value, the abnormal voltage generated in the step-up transformer unit is suppressed by limiting the pulse width of the pulse width calculation unit 6 to be short with the output signal of the maximum pulse switching unit 10. Therefore, it is possible to prevent dielectric breakdown of the high voltage wiring, breakdown of the rectifying element of the step-up transformer section, and element deterioration.

  FIG. 2 shows a detailed block diagram of the maximum pulse width switching means in Embodiment 1 of the present invention. The detailed operation of the maximum pulse switching means will be described with reference to FIG.

  As shown in FIG. 2, the maximum pulse width switching means in the first embodiment includes a pulse width limiting unit 31, a pulse width switching unit 32, a current value determination unit 33, and a pulse width setting unit 34.

  The inverter unit 5 is supplied with an AC voltage from the three-phase AC power source 21 by a rectifying / smoothing circuit including a rectifier of the three-phase rectifying unit 22 and a capacitor of the smoothing unit 23. A current detector 3 such as a current transformer (CT) is provided between the step-up transformer unit 4 and the laser resonator 1, and a voltage signal proportional to the output current of the step-up transformer unit 4 is detected. The voltage signal proportional to the output current of the step-up transformer unit 4 output from the current detection unit 3 is feedback-controlled by the comparison control means 7 and simultaneously compared with a predetermined set value by the current value determination unit 33, and the current detection unit When the output signal No. 3 is less than the predetermined set value, the pulse width switching unit 32 switches so as to select a narrow pulse width of the pulse width setting unit 34. In addition, when the output signal of the current detection unit 3 exceeds a predetermined current value, switching is performed so as to select a wide pulse width.

  The pulse width limiting unit 31 is configured to limit the output pulse width of the pulse width calculation means 6 by the output signal of the pulse width switching unit 32, and the pulse width selected by the pulse width switching unit 32 is set as the maximum pulse width. It comes to control.

  With this configuration, the process of limiting the pulse width to the pulse width computing means is speeded up and simplified by switching a plurality of pulse widths of the pulse width setting section with the detection signal of the current detection section, and accurate and repeatable and accurate. Operation is possible and reliability can be improved.

  FIG. 3 shows a detailed block diagram of the maximum pulse width switching means in the first embodiment of the present invention. The detailed operation of the maximum pulse switching means will be described with reference to FIG.

  As shown in FIG. 3, the maximum pulse width switching means in the first embodiment includes a pulse width limiting unit 31, a pulse width switching unit 32, a current value determination unit 33, and a pulse width calculation unit 35.

  The voltage signal from the current detection unit 3 proportional to the output current of the step-up transformer unit 4 is feedback-controlled by the comparison control means 7 and simultaneously compared with a predetermined set value by the current value determination unit 33, and the output of the current detection unit 3 When the signal is less than a predetermined set value, the pulse width switching unit 32 switches so as to select a narrow pulse width of the pulse width calculation unit 35. In addition, when the output signal of the current detection unit 3 exceeds a predetermined current value, switching is performed so as to select a wide pulse width.

  The pulse width calculation unit 35 calculates a pulse width proportional to the output signal of the current value command of the current value setting unit 8, and widens the pulse width as the current value command becomes larger, so that the switching control element of the inverter unit 5 The maximum pulse width is configured to be optimally set according to the current value command.

  The pulse width limiting unit 31 is configured to limit the output pulse width of the pulse width calculation means 6 by the output signal of the pulse width switching unit 32, and the pulse width selected by the pulse width switching unit 32 is set as the maximum pulse width. It comes to control.

  With this configuration, it is possible to set the maximum pulse width optimally according to the current value command by providing a pulse width calculation unit that calculates the maximum pulse width of the switching control element according to the current value command. And the reliability can be further improved.

  FIG. 4 shows the relationship between the pulse width and the generated voltage when the maximum pulse width is limited in the first embodiment of the present invention.

  The relationship between the pulse width of the control element of the inverter unit 5 and the generated voltage of the step-up transformer unit 4 is as shown in FIG. 4 in a proportional relationship in which the generated voltage increases as the pulse width increases. However, when the current feedback signal from the current detection unit 3 is not fed back to the comparison control means due to discharge abnormality of the discharge tube or disconnection of the wiring, the switching control is performed with the maximum pulse width as shown in FIG. 4 without the maximum pulse width limitation. Since the element is driven, the generated voltage rises to V1, which may cause dielectric breakdown of the high voltage rectifier element due to an excessive voltage.

  When limiting the maximum pulse width by the maximum pulse width switching means of the present invention, the generated voltage is limited to V2 as shown in FIG. 4 with the maximum pulse width limited, and the generated voltage at the time of abnormal discharge can be suppressed. Deterioration of the element can be prevented.

  In the laser oscillation device having the above configuration, each component is provided with a control element and controlled in each signal processing or each configuration. However, the laser oscillation device is provided with a CPU connected to each configuration. You may make it control each process collectively.

  FIG. 5 shows a block diagram of the laser beam machine in the embodiment of the present invention.

  The laser beam machine has a machining table 62 on which the workpiece 61 is placed, a driving unit 63 that moves at least one of the movement of the machining table 62 or the condensing unit 67 that collects laser light, and a numerical value that controls the driving unit 63. The control unit 64, the laser oscillation device 65, and the laser beam path 66 are configured.

  The laser beam emitted from the laser oscillation device 65 is transmitted through a laser beam path 66 constituted by a folding mirror or the like, condensed by the condensing means 67, irradiated onto the workpiece 61, and machining is started. At the same time, a command is output to the driving means 63 by the numerical control means 64, and the workpiece 61 is machined by operating at least one of the machining table 62 or the light collecting means 67.

  According to the laser processing machine, the generation of abnormal voltage due to fluctuations in the discharge load is prevented, the semiconductor rectifying element of the high voltage circuit is prevented from being broken or damaged, and the laser beam output power can be stably irradiated. . Furthermore, since the laser oscillation device is comprehensively controlled by the numerical control means, it is possible to improve the reliability of laser processing and to prevent defective products from being mixed into the workpiece.

  The laser oscillation device of the present invention is useful for preventing damage to the semiconductor rectifying element due to overvoltage and improving the stability of laser output and long-term reliability.

DESCRIPTION OF SYMBOLS 1 Laser resonator 2 Output laser beam 3 Current detection part 4 Step-up transformer part 5 Inverter part 6 Pulse width calculating means 7 Comparison control means 8 Current value setting part 9 Irradiation command part 10 Maximum pulse width switching means 21 Three-phase AC power supply 22 3 Phase rectification unit 23 Smoothing unit 31 Pulse width limiting unit 32 Pulse width switching unit 33 Current value determination unit 34 Pulse width setting unit 35 Pulse width calculation unit

Claims (4)

An irradiation command unit that determines the timing of irradiating the output laser beam from the laser resonator, a current value setting unit that outputs a current value signal preset by an output signal of the irradiation command unit, and an output signal of the current value setting unit A comparison control means for comparing the current value output signal of the current detection unit, a pulse width calculation means for converting the output signal of the comparison control means into a pulse width, and a control element is switched by the pulse signal of the pulse width calculation means An inverter unit, a step-up transformer unit that converts an output signal of the inverter unit into a DC high voltage and supplies power to the laser resonator via a current detection unit, and a maximum that switches a pulse width by a detection signal of the current detection unit Pulse width switching means, and a narrow pulse width when the detection signal of the current detection unit is less than a predetermined current value, and a wide pulse width when the detection signal exceeds a predetermined current value Laser oscillation apparatus characterized by having the maximum pulse width switching means limited to the maximum pulse width of the control element of the inverter section by switching. The maximum pulse width switching means includes a current value determination unit that compares a detection signal of the current detection unit with a predetermined current value setting signal, a pulse width setting unit in which a plurality of pulse widths are set in advance, and the current A pulse width switching unit for switching the pulse width of the pulse width setting unit according to the output signal of the value determining unit, and a pulse width limiting unit for controlling the pulse width of the pulse width calculating means to be limited by the output signal of the pulse width switching unit The laser oscillation device according to claim 1, wherein: The maximum pulse width switching means includes a current value determination unit that compares a detection signal of the current detection unit with a predetermined current value setting signal, and a pulse that calculates a pulse width according to a current value command of the current value setting unit A pulse width switching unit that switches a pulse width of the pulse width calculation unit according to an output signal of the current value determination unit, and a pulse width of the pulse width calculation unit that is limited by an output signal of the pulse width switching unit. The laser oscillation device according to claim 1, further comprising a pulse width limiting unit that controls the laser. A laser beam is generated from a processing table on which a workpiece is placed, a driving unit that moves at least one of a movement of the processing table and a laser beam condensing unit, a numerical control unit that controls the driving unit, and a laser beam. A laser processing machine comprising the laser oscillation device according to any one of 3 above.

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