Laser power supply control device and laser processing device

Abstract

To provide a laser power supply control device enabling adjustment even in a case where pulse energy cannot be adjusted to settle in an energy target range with a conventional method.SOLUTION: A laser power supply includes a charging power supply for generating DC link voltage, and a high frequency power supply including an H bridge circuit, to which the DC link voltage is applied and for generating high frequency current from the DC link voltage. A voltage duty command part of a laser power supply control device controls the charging power supply and the high frequency power supply by adjusting a voltage target value of the DC link voltage and a duty ratio command value for driving the H bridge circuit so that a measurement value of pulse energy of the pulse laser beam outputted from a pulse laser oscillator to which the high frequency current is supplied settles in an energy target range.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a laser power control device and a laser processing device.

Background Art

[0002] A laser processing device that performs drilling on a printed circuit board using a pulsed laser beam includes a laser power supply, a laser oscillator, and a processing machine. The laser power supply includes a rectifier, a charging power supply, and a high-frequency power supply (see Patent Document 1, etc.). A laser power control device controls the laser power supply. The charging power supply boosts the DC voltage rectified by the rectifier to generate a DC link voltage. The DC link voltage is applied to the high-frequency power supply. The high-frequency power supply pulsewise generates a high-frequency current from the DC link voltage. The high-frequency current is supplied to a pulsed laser oscillator serving as a load.

[0003] The pulsed laser beam output from the pulsed laser oscillator is input to the processing machine, and laser processing is performed. As the pulsed laser oscillator, for example, a carbon dioxide laser oscillator is used. By fixing the pulse width of the high-frequency current and adjusting the DC link voltage, the energy per pulse (pulse energy) of the pulsed laser beam is adjusted.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The DC link voltage is adjusted within a voltage adjustment range that is equal to or lower than the voltage upper limit value and equal to or higher than the voltage lower limit value. Also, a current upper limit value is set for the high-frequency current, and the adjustment is performed under the condition that the high-frequency current does not exceed the current upper limit value.

[0006] When the operating environment or conditions of the laser processing apparatus change (for example, the state of the laser medium gas), the pulse energy fluctuates. In this case, by changing the DC link voltage within the adjustment range, the target pulse energy can be obtained. However, when the amount of change in the operating environment or conditions of the laser processing apparatus becomes small, the target pulse energy may not be obtained even if the DC link voltage is changed within the adjustment range.

[0007] An object of the present invention is to provide a laser power control device that enables adjustment even when it is not possible to perform adjustment to keep the pulse energy within the energy target range by a conventional method. Another object of the present invention is to provide a laser processing apparatus equipped with this laser power control device.

Means for Solving the Problems

[0008] According to one aspect of the present invention, A laser power control device for controlling a laser power source having a charging power source that generates a DC link voltage and a high-frequency power source that includes an H-bridge circuit to which the DC link voltage is applied and that generates a high-frequency current from the DC link voltage, A voltage duty command unit is provided that controls the charging power source and the high-frequency power source by adjusting a voltage target value of the DC link voltage and a duty ratio command value for driving the H-bridge circuit so that a measured value of the pulse energy of a pulse laser beam output from a pulse laser oscillator to which the high-frequency current is supplied falls within an energy target range.

[0009] According to another aspect of the present invention, The charging power source that generates the DC link voltage, The high-frequency power source that applies the DC link voltage, generates the high-frequency current, and inputs it to the pulse laser oscillator, And the laser power control device A laser processing apparatus provided with is provided.

Effects of the Invention

[0010] Even when the pulse energy cannot be kept within the target range even by adjusting the DC link voltage, it may be possible to keep the pulse energy within the target range by adjusting the duty ratio command value.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

DETAILED DESCRIPTION OF THE INVENTION

[0012] A laser power supply control device and a laser processing device according to an embodiment will be described with reference to FIGS. 1 to 11.

[0013] FIG. 1 is a schematic block diagram of a laser processing device equipped with a laser power supply control device 20 according to the present embodiment. The laser processing device includes a laser power supply 10, a pulse laser oscillator 40, a processing machine 50, a control power supply 15, and a laser power supply control device 20. A high-frequency current I is pulse-supplied from the laser power supply 10 to the pulse laser oscillator 40. RF As the pulse laser oscillator 40, a gas laser oscillator, for example, a carbon dioxide laser oscillator, is used. The pulse laser oscillator 40 includes a pair of discharge electrodes 41. When a high-frequency current I is supplied to the pulse laser oscillator 40, discharge occurs between the pair of discharge electrodes 41, and a pulse laser beam Lp is output. RF The pulse laser beam Lp output from the pulse laser oscillator 40 enters the processing machine 50. Most of the pulse laser beam Lp that has entered the processing machine 50 is reflected by the partial mirror 51 and enters the workpiece 60 via the beam scanner 52 and the condenser lens 53. The workpiece 60 is held by the movable stage 54. The movable stage 54 moves the workpiece 60 in two directions parallel to the processed surface and in a direction perpendicular to the processed surface under the control from the processing machine control unit 59.

[0014]

[0015] ​The beam scanner 52 receives control from the processing machine control unit 59 and moves the beam spot on the surface of the workpiece 60 to be processed by scanning the pulsed laser beam Lp. As the beam scanner 52, for example, a galvanometer scanner can be used. The condenser lens 53 condenses the pulsed laser beam Lp onto the surface of the workpiece 60 to be processed. As the condenser lens 53, for example, an fθ lens can be used. In addition, if necessary, a beam expander, an aperture, an attenuator, etc. may be arranged in the beam path.

[0016] The workpiece 60 is, for example, a printed circuit board, and drilling is performed within the scan range by moving the beam spot of the pulsed laser beam Lp by the beam scanner 52. By operating the movable stage 54 and sequentially arranging the areas to be processed on the surface of the workpiece 60 within the scan range of the beam scanner 52, the entire surface of the workpiece 60 is processed.

[0017] A part of the power of the pulsed laser beam Lp incident on the partial mirror 51 passes through the partial mirror 51 and is incident on the power meter 55. The power meter 55 measures the average power of the pulsed laser beam. A part of the pulsed laser beam Lp incident on the power meter 55 is scattered, and a part of the scattered light is incident on the photodetector 56. The photodetector 56 has a response speed that can follow the waveform of each laser pulse of the pulsed laser beam Lp. As the photodetector 56, for example, a HgCdTe (MCT) sensor can be used. The photodetector 56 can detect the instantaneous value of the power of the laser pulse, that is, the pulse waveform. The detection value Det regarding the power of the pulsed laser beam by the power meter 55 and the photodetector 56 is input to the laser power control device 20.

[0018] Next, the configuration of the laser power supply 10 will be described. The laser power supply 10 includes a rectifier 11, a charging power supply 12, and a high-frequency power supply 13. The rectifier 11, the charging power supply 12, and the high-frequency power supply 13 operate in response to operation commands Com1, Com2, and Com3 from the laser power control device 20, respectively.

[0019] A three-phase alternating current is supplied from an external alternating current power supply 70 to a rectifier 11. The direct current rectified by the rectifier 11 is supplied to a charging power supply 12. The charging power supply 12 boosts the input direct current voltage to generate a DC link voltage V DC . DC is applied to a high-frequency power supply 13. The high-frequency power supply 13 converts the direct current supplied from the charging power supply 12 into a high-frequency current I RF and supplies it to a pulse laser oscillator 40 in a pulsed manner.

[0020] A control power supply 15 converts the alternating current power supplied from the alternating current power supply 70 into direct current power and supplies the direct current power to a laser power supply control device 20. In addition, direct current power is also supplied from the control power supply 15 to the rectifier 11, the charging power supply 12, and the high-frequency power supply 13.

[0021] The laser power supply control device 20 includes a voltage duty command unit 20A, an efficiency calculation unit 20B, and a control mode setting unit 20C. The laser power supply control device 20 includes, for example, a CPU, a memory, etc. The functions of the voltage duty command unit 20A, the efficiency calculation unit 20B, and the control mode setting unit 20C are realized, for example, by the CPU executing a program stored in the memory.

[0022] When the laser power supply control device 20 gives an operation command Com1 to the rectifier 11, a voltage is applied from the alternating current power supply 70 to the rectifying circuit of the rectifier 11. The laser power supply control device 20 gives operation commands Com2 and Com3 to the charging power supply 12 and the high-frequency power supply 13, respectively, according to an excitation command Sig_e and a simmer command Sig_s given from a processing machine 50. Thereby, the laser power supply 10 operates, and a high-frequency current I RF is supplied to the pulse laser oscillator 40 in a pulsed manner.

[0023] When an excitation command Sig_e is given to the laser power supply control device 20, the laser power supply 10 outputs a high-frequency current I RFis supplied to the pulse laser oscillator 40. As a result, the pulse laser oscillator 40 outputs a pulse laser beam Lp. When a simmer command Sig_s is given to the laser power control device 20, the pulse width of the output high-frequency current I RF becomes short, and only the laser medium gas is excited, and the pulse laser beam Lp is not output.

[0024] FIG. 2 is a schematic equivalent circuit diagram of the rectifier 11. A three-phase alternating current is input from the AC power supply 70 to the three-phase full-wave rectifier circuit 11C via the electromagnetic contactor 11B. The electromagnetic contactor 11B is on-off controlled by an operation command Com1 from the laser power control device 20. An inrush current prevention circuit 11A is connected to the electromagnetic contactor 11B. In FIG. 2, an example in which the inrush current prevention circuit 11A is connected in parallel to the electromagnetic contactor 11B is shown, but the inrush current prevention circuit 11A may be connected in series to the electromagnetic contactor 11B.

[0025] A smoothing capacitor 11D is connected to the output node of the three-phase full-wave rectifier circuit 11C. A voltage sensor 11E is connected between the terminals of the smoothing capacitor 11D. The output current from the three-phase full-wave rectifier circuit 11C is supplied to the charging power supply 12. A current sensor 11F is inserted into the current path of the output current from the three-phase full-wave rectifier circuit 11C. The measured value of the voltage by the voltage sensor 11E and the measured value of the current by the current sensor 11F are input to the laser power control device 20.

[0026] FIG. 3 is a schematic equivalent circuit diagram of the charging power supply 12. The DC-DC converter 12A includes a reactor 12B, a boost switching element 12QH, a buck switching element 12QL, and a freewheeling diode 12F. A direct current is supplied from the rectifier 11 to the DC-DC converter 12A. The driver 12E on-off controls the boost switching element 12QH and the buck switching element 12QL based on an operation command Com2 from the laser power control device 20.

[0027] A bank capacitor 12C is connected between the output nodes of the DCDC converter 12A. When the boosting switching element 12QH is turned on and off, the voltage applied from the rectifier 11 is boosted, and a charging current I CHG flows through the bank capacitor 12C. As a result, the bank capacitor 12C is charged and the voltage between the terminals rises. By adjusting the time for which the boosting switching element 12QH is turned on, the reach voltage value of the DC link voltage V DC can be changed. In other words, the laser power control device 20 adjusts the time for which the boosting switching element 12QH is turned on according to the target value of the DC link voltage V DC (hereinafter referred to as the voltage target value V DCT ).

[0028] A voltage sensor 12D is connected between the terminals of the bank capacitor 12C. The voltage sensor 12D measures the voltage between the terminals of the bank capacitor 12C, that is, the DC link voltage V DC output from the charging power supply 12. The measured value of the DC link voltage V DC is input to the laser power control device 20. The DC link voltage V DC is applied to the high-frequency power supply 13.

[0029] FIG. 4 is a schematic equivalent circuit diagram of the high-frequency power supply 13. The high-frequency power supply 13 includes an H-bridge circuit 13A, a transformer 13C, and an H-bridge circuit driver 13D. The DC link voltage V DC is applied to the input node of the H-bridge circuit 13A from the charging power supply 12.

[0030] The H-bridge circuit 13A includes four switching elements 13Q1, 13Q2, 13Q3, and 13Q4. The switching elements 13Q1 and 13Q3 are connected in series, and the DC link voltage V DC is applied to this series circuit. Similarly, the switching elements 13Q2 and 13Q4 are connected in series, and the DC link voltage V DCis applied. The switching elements 13Q1 and 13Q2 are each connected to the input node on the high voltage side, and the switching elements 13Q3 and 13Q4 are each connected to the input node on the low voltage side. A freewheeling diode 13W is connected to each of the four switching elements 13Q1, 13Q2, 13Q3, and 13Q4.

[0031] A primary coil of the transformer 13C is connected between the interconnection point of the switching elements 13Q1 and 13Q3 and the interconnection point of the switching elements 13Q2 and 13Q4. A secondary coil of the transformer 13C is connected to the pulse laser oscillator 40. The wiring connecting the transformer 13C and the pulse laser oscillator 40 has an inductive component L.

[0032] An operation command Com3 is input from the laser power control device 20 to the H-bridge circuit driver 13D, and the H-bridge circuit driver 13D performs on / off control of the four switching elements 13Q1, 13Q2, 13Q3, and 13Q4 based on the operation command Com3.

[0033] Specifically, a forward conduction state in which the switching elements 13Q1 and Q4 are set to on and the switching elements 13Q2 and 13Q3 are set to off, an off state in which all the switching elements 13Q1 to 13Q4 are set to off, a reverse conduction state in which the switching elements 13Q2 and Q3 are set to on and the switching elements 13Q1 and 13Q4 are set to off, and the off state are repeated in a plurality of cycles with four states in one cycle as a period, so that the direct current supplied from the charging power source 12 is converted into a high-frequency current. The ratio of the time of the forward conduction state and the reverse conduction state for one cycle is called the duty ratio.

[0034] The high-frequency current output from the H-bridge circuit 13A is voltage-converted by the transformer 13C, and the high-frequency current I RF is supplied to the pulse laser oscillator 40. When the duty ratio increases, the current value of the high-frequency current I RF , for example, the amplitude increases. Conversely, when the duty ratio decreases, the high-frequency current I RFThe current value decreases. Thus, by adjusting the duty ratio, the high-frequency current I RF can have its current value changed.

[0035] The current sensor 13B measures the current value of the high-frequency current output from the H-bridge circuit 13A. The measured value of the high-frequency current is input to the laser power control device 20. The measured value by the current sensor 13B corresponds one-to-one with the current value of the high-frequency current I RF supplied from the transformer 13C to the pulse laser oscillator 40. Therefore, it can be said that the current sensor 13B is measuring the current value of the high-frequency current I RF . Incidentally, the current sensor 13B may be inserted on the secondary coil side of the transformer 13C to directly measure the current value of the high-frequency current I RF .

[0036] Next, the functions of the laser power control device 20 will be described. The voltage duty command unit 20A sends an operation command Com2 to the charging power supply 12 (Fig. 3), thereby performing on / off control of the boost switching element 12QH (Fig. 3) so as to bring the DC link voltage V DC close to the voltage target value V DCT . Furthermore, by sending an operation command Com3 to the high-frequency power supply 13 (Fig. 4), the duty ratio for operating the H-bridge circuit 13A is specified to operate the H-bridge circuit 13A. Let the duty ratio specified by the operation command Com3 be the duty ratio command value D C .

[0037] The voltage duty command unit 20A adjusts the voltage target value V DCT and the duty ratio command value D C so that the pulse energy of the pulse laser beam Lp output from the pulse laser oscillator 40 falls within the energy target range. The pulse energy of the pulse laser beam Lp can be obtained from the detected value Det of the photodetector 56 (Fig. 1). Incidentally, the pulse width is fixed at a constant value.

[0038] The efficiency calculation unit 20B calculates the efficiency (e.g., energy efficiency) of the laser power supply 10. Since the pulse energy of the pulse laser beam Lp output from the pulse laser oscillator 40 is adjusted to fall within the energy target range, it can be said that the smaller the power input to the charging power supply 12, the higher the efficiency. For example, the input power to the charging power supply 12 is calculated from the measured value of the voltage sensor 11E of the rectifier 11 (Fig. 2) and the measured value of the current sensor 11F. It can be said that the smaller this input power, the higher the efficiency.

[0039] The control mode setting unit 20C sets the control mode according to an input from the user. The control modes include, for example, a high-efficiency mode, a low-current mode, and a high-current mode.

[0040] Fig. 5 is a timing chart of various signals generated in the laser processing apparatus equipped with the laser power supply control device 20 according to this embodiment. The plurality of timing charts shown in Fig. 5 are, in order from the top, the excitation command Sig_e, the simmer command Sig_s, an operation command (hereinafter sometimes referred to as a duty command) Com3 for commanding the duty, the high-frequency current I RF , the charging current I CHG , the DC link voltage V DC , and the schematic waveform of the pulse laser beam Lp.

[0041] The processing control unit 59 (Fig. 1) periodically sends out the simmer command Sig_s. The rising edge of the simmer command Sig_s corresponds to a command to start supplying the high-frequency current I RF to the pulse laser oscillator 40, and the falling edge of the simmer command Sig_s corresponds to a command to stop supplying the high-frequency current I RF to the pulse laser oscillator 40. The voltage duty command unit 20A (Fig. 4) sends out the duty command Com3 to the high-frequency power supply 13. Thereby, the high-frequency power supply 13 operates the H-bridge circuit 13A based on the commanded duty ratio command value D C . As an example, the duty ratio command value D C is set to 0.72.

[0042] High-frequency current I based on the chirp command Sig_s RF is supplied to the pulsed laser oscillator 40 (Fig. 1), and the laser medium gas is excited. At this time, the pulsed laser beam Lp is not output. The high-frequency current I RF is output, whereby the DC link voltage V DC decreases.

[0043] The rising edge (time t1) of the excitation command Sig_e corresponds to the command to start excitation, and the falling edge (time t2) corresponds to the command to stop excitation. When the laser power control device 20 (Fig. 4) receives the command to start excitation, it sends a duty command Com3 to the high-frequency power supply 13. For example, the duty ratio command value D C is commanded to be 0.80 by the duty command Com3.

[0044] When the H-bridge circuit driver 13D (Fig. 4) of the high-frequency power supply 13 receives the duty command Com3, it turns on and off the four switching elements 13Q1 to 13Q4 of the H-bridge circuit 13A with the commanded duty ratio command value D C . As a result, the high-frequency current I RF is supplied to the pulsed laser oscillator 40, and the laser pulse of the pulsed laser beam Lp rises with a slight delay.

[0045] When the command to stop excitation is notified (time t2), the laser power control device 20 stops the operation of the high-frequency power supply 13. As a result, the output of the high-frequency current I RF stops, and the laser pulse falls. The laser pulse rapidly rises, shows a maximum value, and then gradually decreases after a predetermined time has elapsed from time t1, for example.

[0046] When the laser power control device 20 receives a command to start or stop excitation, it operates the charging power supply 12 (Fig. 3). Specifically, the boosting switching element 12QH is turned on for a predetermined time and then turned off. During the time when the boosting switching element 12QH is on, the current flowing through the current path consisting of the reactor 12B from the rectifier 11 and the boosting switching element 12QH increases. When the boosting switching element 12QH turns off (time t3), a charging current I flows through the freewheeling diode 12F connected to the reactor 12B and the bucking switching element 12QL to the bank capacitor 12C. As a result, the DC link voltage V CHG rises. DC

[0047] The laser power control device 20 adjusts the conduction time of the boosting switching element 12QH according to the voltage target value V DCT . For example, when the voltage target value V DCT increases, the conduction time of the boosting switching element 12QH is lengthened. Conversely, when the voltage target value V DCT decreases, the conduction time of the boosting switching element 12QH is shortened.

[0048] The voltage target value V DCT and the duty ratio command value D C are determined by actually operating the laser power supply 10 and the pulse laser oscillator 40 at various voltage target values V DCT and duty ratio command values D C and measuring the pulse energy. This adjustment may be performed, for example, during the initial adjustment after the assembly of the laser processing apparatus, during the warm-up operation, etc. Next, with reference to Figs. 6 and 7, the method for setting the voltage target value V DCT and the duty ratio command value D C will be described.

[0049] Figs. 6 and 7 show the relationship between the load impedance Z as seen from the high-frequency power supply 13 (Fig. 1) side to the pulse laser oscillator 40 side, and the voltage target value V DCT for keeping the pulse energy within the energy target range, and the high-frequency current I RF ​It is a graph showing the current value. The horizontal axis represents the load impedance Z, the vertical axis of the upper graph represents the voltage target value V DCT and the vertical axis of the lower graph represents the high-frequency current I RF of the current value.

[0050] Duty ratio command value D C When the load impedance Z increases under the condition that the duty ratio command value D is fixed at D1, in order to keep the pulse energy constant, as shown by the solid line in FIGS. 6 and 7, the voltage target value V DCT must be increased. According to the evaluation experiment by the inventor of the present application, when the voltage target value V DCT is increased so that the pulse energy is kept constant, as shown in the lower graphs of FIGS. 6 and 7, it is found that the current value of the high-frequency current I RF decreases.

[0051] Also, as shown by the broken line in FIG. 7, when the duty ratio command value D C is increased from D1 to D2, the voltage target value V DCT for keeping the pulse energy within the energy target range decreases. This is because increasing the duty ratio command value D C causes the high-frequency current I RF to increase. According to the evaluation experiment by the inventor of the present application, under the condition of keeping the pulse energy constant, the high-frequency current I C when the duty ratio command value D is D2 is RF found to be larger than the high-frequency current I C when the duty ratio command value D is D1. RF

[0052] The voltage target value V DCT is adjusted within the voltage adjustment range RV between the voltage upper limit value V UL and the voltage lower limit value V LL . Also, a current upper limit value I RF is set for the high-frequency current I UL , and the voltage target value V RF and the duty ratio command value D UL are adjusted so that the high-frequency current I DCT does not exceed the current upper limit value I​C is adjusted. The voltage target value V DCT is adjusted within the voltage adjustment range, and the duty ratio command value D C is adjusted within the duty ratio adjustment range, but if the high-frequency current I RF does not become equal to or less than the current upper limit value I UL the adjustment results of the voltage target value V DCT and the duty ratio command value D C are determined to be adjustment failures.

[0053] When the load impedance Z is Z1, the voltage target value V DCT is set to V1, and the pulse energy is within the energy target range. The current value of the high-frequency current I RF at this time is denoted as I1. Hereinafter, control when the load impedance Z increases due to environmental changes in the pulse laser oscillator 40, deterioration of the laser medium gas, etc. will be described.

[0054] As shown in FIG. 6, when the load impedance Z increases from Z1 to Z2, if the voltage target value V DCT is maintained at V1, the high-frequency current I RF decreases from I1 to I 12 . Since the high-frequency current I RF decreases, the pulse energy also decreases. In order to increase the pulse energy to the energy target range, the voltage target value V DCT is gradually increased as indicated by the white arrow, and the pulse energy is measured.

[0055] When the voltage target value V DCT is increased to V2 equal to or less than the voltage upper limit value V UL , the pulse energy is within the energy target range. At this time, the current value of the high-frequency current I RF also increases to I2 equal to or less than the current upper limit value I UL as indicated by the white arrow. When it is confirmed that the measured value of the pulse energy is within the energy target range, the laser power control device 20 (FIG. 1) sets the voltage target value V DCT to V2. In actual laser processing, the voltage target value V DCTIt is performed under the condition of being set to V2.

[0056] As shown in FIG. 7, when the load impedance Z rises from Z1 to Z3, the voltage target value V DCT is maintained at V1, the high-frequency current I RF decreases from I1 to I 13 . Since the high-frequency current I RF decreases, the pulse energy also decreases. In order to increase the pulse energy to the energy target range, while maintaining the duty ratio command value D C at D1, the voltage target value V DCT is gradually increased and the pulse energy is measured.

[0057] In the example shown in FIG. 7, even if the voltage target value V DCT is increased to the voltage upper limit value V UL as indicated by the white arrow, the pulse energy does not fall within the energy target range. That is, the voltage target value V C shown by the solid line when the duty ratio command value D DCT is D1 is not reached. At this time, the high-frequency current I RF rises to I 3_D1 as indicated by the white arrow. Since the voltage target value V DCT cannot be set to exceed the voltage upper limit value V UL , while maintaining the voltage target value V DCT at V UL , the duty ratio command value D C is gradually increased as indicated by the hatched arrow and the pulse energy is measured. As the duty ratio command value D C increases, the high-frequency current I RF also increases as indicated by the hatched arrow.

[0058] As the high-frequency current I RF increases, the pulse energy falls within the energy target range. At this time, the voltage target value V DCT is equal to the voltage upper limit value V UL . The current value of the high-frequency current I RF at this time is I 3_D2is marked. When it is confirmed that the measured value of the pulse energy falls within the energy target range, the laser power control device 20 (Fig. 1) sets the voltage target value V DCT to the voltage upper limit value V UL . The actual laser processing is performed under the condition that the voltage target value V DCT is set to the voltage upper limit value V UL .

[0059] In the example shown in Fig. 7, the voltage target value V DCT is set to the voltage upper limit value V UL . However, if the duty ratio command value D C is made larger than D2, even if the voltage target value V DCT is set lower than the voltage upper limit value V UL , the pulse energy can be kept within the energy target range. That is, there are multiple combinations of the voltage target value V DCT and the duty ratio command value D C for keeping the pulse energy within the energy target range.

[0060] Fig. 8 is a graph for explaining an appropriate combination of the voltage target value V DCT and the duty ratio command value D C . The horizontal axis represents the load impedance Z, the vertical axis of the upper graph represents the voltage target value V DCT , and the vertical axis of the lower graph represents the current value of the high-frequency current I RF . The upper graph in Fig. 8 shows the voltage target value V C when the duty ratio command value D U is fixed at the upper limit value D L , and when it is fixed at the lower limit value D DCT . The voltage target value V C when the duty ratio command value D U is fixed at the upper limit value D DCT is lower than the voltage target value V C when the duty ratio command value D L is fixed at the lower limit value D DCT .

[0061] When the load impedance Z is Z2, if the duty ratio command value D C is the upper limit value DU The voltage target value V when DCT is V 2U and V 2U is the voltage lower limit value V LL or more. The duty ratio command value D C is the lower limit value D L The voltage target value V when DCT - is V 2L and V 2L is the voltage upper limit value V UL or less. Therefore, as shown by the white arrow, the voltage target value V DCT can be set within the range of V 2U or more and V 2L or less. The voltage target value V DCT is V 2U , V 2L The high-frequency current I when RF The current values are I 2U and I 2L respectively. Both of these are the current upper limit value I UL or less.

[0062] When the load impedance Z is Z1, the duty ratio command value D C is the upper limit value D U The voltage target value V when DCT is V 1U and V 1U is the voltage lower limit value V LL less than. The duty ratio command value D C is the lower limit value D L The voltage target value V when DCT is V 1L and V 1L is the voltage upper limit value V UL or less. Therefore, as shown by the white arrow, the voltage target value V DCT can be set within the range of V LL or more and V 1L or less. The voltage target value V DCT is V LL , V 1L The high-frequency current I when RF The current values are I 1LL and I 1L respectively. Both of these are the current upper limit value I UL or less.

[0063] When the load impedance Z is Z3, the duty ratio command value D C is at the upper limit value D U and the voltage target value V DCT is V 3U and V 3U is the voltage lower limit value V LL or higher and the voltage upper limit value V UL or lower. The duty ratio command value D C is at the lower limit value D L and the voltage target value V DCT is V 3L and V 3L is higher than the voltage upper limit value V UL Therefore, as indicated by the white arrow, the voltage target value V DCT is V 3U or higher and V UL or lower. The voltage target value V DCT is V 3U , V UL and the high-frequency current I RF at that time has current values of I 3U and I 3UL respectively. Both of these are below the current upper limit value I UL .

[0064] As shown in FIG. 8, an appropriate voltage target value V for keeping the pulse energy within the energy target range DCT can be selected from within a certain range. In the example shown in FIG. 7, the highest voltage upper limit value V DCT within the selectable range of the voltage target value V UL is selected.

[0065] When the load impedance Z increases up to Z4, even if the duty ratio command value D C is changed within the range between the lower limit value D L and the upper limit value D U , the voltage target value V that can keep the pulse energy within the energy target range DCTcannot be found. In such a case, the voltage duty command section 20A of the laser power control device 20 notifies the user that the voltage duty ratio cannot be adjusted appropriately. For example, the user is notified that the voltage duty ratio cannot be adjusted appropriately by generating an alarm, displaying a message, or the like.

[0066] In FIG. 8, for the entire range of candidate values of the voltage target value V DCT the current value of the high-frequency current I RF is equal to or less than the current upper limit value I UL For a part of the range of candidate values of the voltage target value V DCT if the current value of the high-frequency current I RF is equal to or greater than the current upper limit value I UL then the voltage target value V RF when the current value of the high-frequency current I UL exceeds the current upper limit value I DCT may be excluded from the range of candidates. Also, if the current value of the high-frequency current I DCT exceeds the current upper limit value I RF for the entire range of candidate values of the voltage target value V UL then the voltage duty command section 20A notifies the user that the voltage duty ratio cannot be adjusted appropriately.

[0067] Next, with reference to FIGS. 9 to 11, the method for setting the voltage target value V DCT will be described when the control mode set in the control mode setting section 20C (FIG. 1) is each of the high-efficiency mode, the high-current mode, and the low-current mode.

[0068] FIG. 9 is a flowchart showing the procedure for determining the voltage target value V DCT when the control mode is set to the high-efficiency mode. First, the voltage duty command section 20A (FIGS. 3 and 4) of the laser power control device 20 adjusts the voltage target value V DCT and the duty ratio command value D C to extract the condition under which the pulse energy falls within the energy target range (step SA1). Specifically, the voltage target value V DCT and the duty ratio command value D CAs extraction is performed for the range indicated by the white arrow.

[0069] Next, for each combination of the voltage target value V DCT and the duty ratio command value D C the physical quantity reflecting the efficiency of the laser power supply 10 is calculated (step SA2). For example, the DC power supplied from the rectifier 11 to the charging power supply 12 is calculated.

[0070] Next, the voltage duty command unit 20A adopts, as the operating condition, the combination of the voltage target value V DCT and the duty ratio command value D C at which the efficiency is the highest (step SA3). For example, the combination of the voltage target value V DCT and the duty ratio command value D C at which the DC power supplied from the rectifier 11 to the charging power supply 12 is the smallest is adopted as the combination with the highest efficiency.

[0071] FIG. 10 is a flowchart showing the procedure of the method for determining the voltage target value V DCT when the control mode is set to the high current mode. Similar to step SA1 of the flowchart shown in FIG. 9, the voltage duty command unit 20A of the laser power supply control device 20 (FIGS. 3 and 4) adjusts the voltage target value V DCT and the duty ratio command value D C to extract the condition under which the pulse energy falls within the energy target range.

[0072] Next, from among the extracted combinations, the condition under which the current value of the high-frequency current I RF is the largest is adopted as the operating condition (step SB3).

[0073] FIG. 11 is a flowchart showing the procedure of the method for determining the voltage target value V DCT when the control mode is set to the low current mode. Similar to step SA1 of the flowchart shown in FIG. 9, the voltage duty command unit 20A of the laser power supply control device 20 (FIGS. 3 and 4) adjusts the voltage target value V DCTand duty ratio command value D C Adjust them to extract the conditions under which the pulse energy falls within the energy target range.

[0074] Next, from among the extracted combinations, the condition under which the current value of the high-frequency current I RF is minimized is adopted as the operating condition (step SC3).

[0075] Next, the excellent effects of the above embodiments will be described. In the above embodiments, during the initial adjustment after the assembly of the laser processing machine, during the warm-up operation, etc., the voltage target value V DCT and duty ratio command value D C can be automatically adjusted. Thereby, the adjustment time of the laser processing apparatus can be shortened. Further, even when changes occur in the environment where the laser processing apparatus is placed, deterioration of the laser medium gas, etc., the operation can be continued while keeping the pulse energy within the energy target range.

[0076] Also, in the above embodiments, when the load impedance fluctuates due to disturbances such as environmental fluctuations and deterioration of the laser medium gas, in order to keep the pulse energy within the energy target range, in addition to the adjustment of the voltage target value V DCT the duty ratio command value D for driving the H-bridge circuit 13A of the high-frequency power supply 13 C is also adjusted. For this reason, it is possible to find appropriate conditions for keeping the pulse energy within the energy target range even in the range of the load impedance Z that could not be adjusted only by adjusting the voltage target value V DCT . By performing processing with the pulse energy within the energy target range, the processing quality can be stabilized.

[0077] When the voltage target value V DCT and duty ratio command value D C are adjusted within the duty ratio adjustment range but the pulse energy cannot be kept within the energy target range, the user is notified that the adjustment of the voltage duty ratio cannot be performed, so the user can immediately notice an abnormality in the apparatus.

[0078] By setting the control mode to the high-efficiency mode in the control mode setting unit 20C (Fig. 1), energy-saving processing can be performed. Also, when the control mode is set to the low-current mode or the high-current mode, the current value of the high-frequency current I can be decreased or increased under the condition that the pulse energy is the same. When the current value of the high-frequency current I changes, the pulse waveform of the pulsed laser beam Lp shown in Fig. 5 changes. When the pulse waveform changes, the shape of the processed hole changes. The processing conditions can be selected so that the shape of the hole to be formed approaches the target shape. RF of the current value can be decreased or increased. When the current value of the high-frequency current I RF changes, the pulse waveform of the pulsed laser beam Lp shown in Fig. 5 changes. When the pulse waveform changes, the shape of the processed hole changes. The processing conditions can be selected so that the shape of the hole to be formed approaches the target shape.

[0079] Next, a modification of the above embodiment will be described. In the above embodiment, as described with reference to Figs. 6 and 7, when the measured value of the pulse energy deviates from the energy target range, the duty ratio command value D C is fixed and the voltage target value V DCT is changed. When the measured value of the pulse energy does not fall within the energy target range even when the voltage target value V DCT is changed within the voltage adjustment range, the duty ratio command value D C is changed.

[0080] Conversely, when the voltage target value V DCT is fixed and the duty ratio command value D C is changed, and the measured value of the pulse energy does not fall within the energy target range even when the duty ratio command value D C is changed within the duty ratio adjustment range, the voltage target value V DCT may be changed. Or, a plurality of combinations of the voltage target value V DCT and the duty ratio command value D C may be prepared in advance, the laser power supply 10 may be operated under the conditions of each of the plurality of prepared combinations, and the pulse energy may be measured.

[0081] In FIGS. 6 and 7, the case where the load impedance Z increases from Z1 to Z2 or Z3 and the pulse energy becomes lower than the energy target range has been described. However, there may also be a case where the load impedance Z decreases and the pulse energy becomes higher than the energy target range. In this case, the voltage target value V DCT should be searched while decreasing it from the current voltage target value to an appropriate voltage target value V DCT . If the pulse energy is still higher than the energy target range even when the voltage target value V DCT is decreased to the voltage lower limit value V LL , the duty ratio command value D C should be decreased.

[0082] The above-described embodiments and modified examples are illustrative, and it goes without saying that partial substitution or combination of the configurations shown in the embodiments and modified examples is possible. The same operational effects due to the same configurations in the embodiments and modified examples will not be sequentially mentioned for each of the embodiments and modified examples. Furthermore, the present invention is not limited to the above-described embodiments and modified examples. For example, it will be obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

Description of Reference Numerals

[0083] 10 Laser power supply 11 Rectifier 11A Inrush current prevention circuit 11B Electromagnetic contactor 11C Three-phase full-wave rectifier circuit 11D Smoothing capacitor 11E Voltage sensor 11F Current sensor 12 Charging power supply 12A DCDC converter 12B Reactor 12C Bank capacitor 12D Voltage sensor 12E Driver 12F Freewheeling diode 12QH Boost switching element 12QL Buck switching element 13 High-frequency power supply 13A H-bridge circuit 13B Current sensor 13C Transformer 13D H-bridge circuit driver 13Q1, 13Q2, 13Q3, 13Q4 Switching elements 13W Freewheeling diode 15 Control power supply 20 Laser power control device 20A Voltage duty command section 20B Efficiency calculation section 20C Control mode setting section 40 Pulse laser oscillator 41 Discharge electrode 50 Processing machine 51 Partially transmissive mirror 52 Beam scanner 53 Condensing lens 54 Moving stage 55 Power meter 56 Photodetector 59 Processing machine control section 60 Workpiece 70 AC power supply

Claims

1. A laser power supply control device for controlling a laser power supply having a charging power supply that generates a DC link voltage of direct current and a high-frequency power supply that includes an H-bridge circuit to which the DC link voltage is applied and that generates a high-frequency current from the DC link voltage, the voltage duty command unit that controls the charging power supply and the high-frequency power supply by adjusting a voltage target value of the DC link voltage and a duty ratio command value for driving the H-bridge circuit so that a measured value of pulse energy of a pulse laser beam output from a pulse laser oscillator to which the high-frequency current is supplied falls within an energy target range.

2. The laser power supply control device according to claim 1, wherein the voltage duty command unit adjusts the voltage target value and the duty ratio command value on the condition that the voltage target value falls within a voltage adjustment range of the DC link voltage.

3. The laser power supply control device according to claim 2, wherein the voltage duty command unit adjusts the voltage target value and the duty ratio command value on the condition that a current value of the high-frequency current does not exceed a preset current upper limit value.

4. The laser power supply control device according to claim 2 or 3, wherein the voltage duty command unit adjusts the duty ratio command value when the pulse energy of the pulse laser beam output from the pulse laser oscillator does not fall within the energy target range even if the voltage target value is adjusted within the voltage adjustment range with the duty ratio command value being fixed.

5. The laser power supply control device according to claim 4, wherein the voltage duty command unit adjusts the voltage target value within the voltage adjustment range and adjusts the duty ratio command value within a duty ratio adjustment range, and when the pulse energy of the pulse laser beam output from the pulse laser oscillator does not fall within the energy target range, notifies that adjustment of the voltage duty ratio is not possible.

6. Further, An efficiency calculation unit that calculates the efficiency of the laser power supply, A control mode setting unit for setting a control mode, and is provided with, When the control mode set in the control mode setting unit is the high-efficiency mode, the voltage duty command unit adjusts the voltage target value and the duty ratio command value so that the efficiency of the laser power supply becomes the highest. The laser power supply control device according to any one of claims 1 to 3.

7. When the high-current mode is set in the control mode setting unit, the voltage duty command unit adjusts the voltage target value and the duty ratio command value so that the current value of the high-frequency current becomes the largest. The laser power supply control device according to claim 6.

8. When the control mode set in the control mode setting unit is the low-current mode, the voltage duty command unit adjusts the voltage target value and the duty ratio command value so that the current value of the high-frequency current becomes the smallest. The laser power supply control device according to claim 6.

9. The charging power supply that generates the DC link voltage, The high-frequency power supply to which the DC link voltage is applied, generates the high-frequency current, and inputs it to the pulse laser oscillator, The laser power supply control device according to any one of claims 1 to 3, and a laser processing apparatus including the same.

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