JP2012079966A - Fiber laser processing device and laser diode power supply unit for excitation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber laser processing device capable of completely detecting an open failure and short-circuit failure in a laser diode for excitation with a small-scale and low-cost device configuration without need for an isolation amplifier.SOLUTION: In a pump LD power circuit 50, a switching control section 66 switching-controls a switching element 54 connected between a pump LD 36(38) and a DC power supply 52 by a pulse duration modulation (PWM) control system and meets or approximates a current value of a driving current Irunning through the pump LD 36(38) with/to a preset value. A duty monitoring section 68 monitors a duty of a switching operation of the switching element 54 and detects an open failure or a short-circuit failure in the pump LD 36(38) based on the duty.

Description

  The present invention relates to a fiber laser processing apparatus that performs desired laser processing by irradiating a workpiece with laser light generated by a fiber laser, and an excitation laser diode power supply apparatus that can be used for the fiber laser processing apparatus.

  Conventionally, in a fiber laser processing apparatus, a laser diode (LD) is often used as a light source for exciting a laser oscillation or amplification optical fiber (for example, Patent Documents 1 and 2).

  In general, a power supply circuit for driving this type of excitation LD has a DC power supply for supplying power to the excitation LD and a switching element connected between the DC power supply and the excitation LD. The switching element is subjected to switching control by a pulse width modulation (PWM) method, so that a desired drive current flows through the excitation LD. As a result, the excitation LD oscillates and outputs the excitation light with power corresponding to the current value of the drive current. In particular, in a high-power fiber laser processing apparatus, a large drive current of usually several tens of amperes or more is passed through the excitation LD, and high-power excitation light of several tens of watts or more is generated from the excitation LD.

  As described above, the pumping LD used in the fiber laser processing apparatus is indispensable for the generation of the fiber laser light. However, the pumping LD is not only worn and deteriorated with time, but also suddenly opens (opens) or shorts ( (Short circuit) may cause failure. Many of such open faults or short faults are caused by heat generated in the excitation LD. For example, a PN junction in the active region may be short-circuited by being destroyed by heat. Alternatively, when the solder melts between the excitation LD and the surrounding connection terminals, the soldering connection (electrical connection) may be broken, leading to an open failure.

  In any case, if the pumping LD causes an open failure or short-circuit failure during laser processing, the power of the processing laser beam becomes completely unintentional. Need to stop. Furthermore, it is necessary to prompt the user (on-site worker or the like) to replace the excitation LD parts.

  In this regard, the conventional excitation LD power supply apparatus monitors the voltage between the terminals (anode terminal / cathode terminal) of the excitation LD through an isolation amplifier in order to detect a failure of the excitation LD. When the voltage between the terminals is abnormally high, it is regarded as an open failure, and when the voltage between the LD terminals is abnormally low, it is regarded as a short circuit failure.

US Pat. No. 6,275,250 JP 2009-248157 A

  The conventional pumping LD power supply device has a problem that the number of parts is large and the cost is high by using an isolation amplifier for detecting the failure of the pumping LD as described above. In addition, since the pumping LD terminal is directly connected to the isolation amplifier, if the isolation amplifier fails, the pumping LD is affected by it and the pumping light cannot be oscillated normally. There is also a disadvantage.

  In order to detect a failure of the excitation LD, there is a conventional method of monitoring a drive current flowing through a load circuit including the excitation LD. In this method, when the excitation LD causes an open fault, no current flows through the load circuit, so that the fault can be detected correctly. However, when a short circuit failure occurs in the excitation LD, the current normally flows through the load circuit by feedback control, so that the short circuit failure cannot be detected.

  The present invention solves the above-mentioned problems of the prior art, and ensures that open and short failures of the pumping laser diode can be ensured by a small-scale and low-cost device configuration without requiring an isolation amplifier. Provided are a laser diode power supply device for excitation that can be detected and a fiber laser processing device using the same.

  A first pumping laser diode power supply apparatus of the present invention is a pumping laser diode power supply apparatus for driving a laser diode that generates pumping light used for a fiber laser in a fiber laser processing apparatus, Obtained from a DC power source for supplying a current, a switching element connected between the DC power source and the laser diode, a drive current measuring unit for measuring a current value of the drive current, and the drive current measuring unit A switching control unit that controls a switching operation of the switching element by a pulse width modulation control method so that a current measurement value matches or approximates a current setting value, and the laser diode to detect an open failure or a short-circuit failure. A duty monitoring unit for monitoring the duty of the switching operation; A.

  In the above device configuration, as long as the laser diode functions normally, if the current value of the drive current changes in a direction that increases with respect to the current setting value, the ratio of the switching-on period of the switching element, that is, the duty is increased. As the value increases, the current value of the drive current increases. Further, when the current value of the drive current changes in the direction of decreasing with respect to the current setting value, the ratio of the switching-on period of the switching element, that is, the duty becomes small, and the current value of the drive current decreases.

  However, when an open failure occurs in the laser diode, the current value of the drive current decreases rapidly, and the feedback control of the PWM method is not effective for this, and the ratio of the switching-on period of the switching element, that is, the duty is remarkably large. Become. In addition, when a laser diode causes a short-circuit failure, the current value of the drive current increases abruptly, and the PWM feedback control becomes ineffective, and the ratio of the switching-on period of the switching element, that is, the duty is significantly reduced. Become.

  The duty monitoring unit monitors the duty of the switching operation and detects the state where the duty is abnormally large or the state where the duty is abnormally small as described above, and the laser diode has caused an open failure or a short failure. Detect that.

  A second pumping laser diode power supply device according to the present invention is a pumping laser diode power supply device for driving a laser diode that generates pumping light used for a fiber laser in a fiber laser processing device, A laser power obtained from a direct-current power supply for supplying power, a switching element connected between the direct-current power supply and the laser diode, and a laser power measuring unit for measuring the power of laser light generated from the fiber laser A switching control unit that controls a switching operation of the switching element by a pulse width control modulation method so that a measured value matches or approximates a laser power setting value; and the detection for detecting an open fault or a short fault of the laser diode. Switching operation duty And a duty monitor for viewing.

  In the above device configuration, as long as the laser diode is functioning normally, if the fiber laser beam power changes in the direction of increasing with respect to the laser power setting value, the ratio of the switching-on period of the switching element, that is, the duty cycle Increases and the current value of the drive current increases. Further, when the power of the fiber laser light changes in a direction that becomes lower than the laser power setting value, the ratio of the switching-on period of the switching element, that is, the duty becomes small, and the current value of the drive current decreases.

  However, when an open failure occurs in the laser diode, the current value of the drive current decreases sharply, and the power of the fiber laser light rapidly decreases. On the other hand, the PWM feedback control becomes ineffective, and the switching element The ratio of the switching-on period, that is, the duty is remarkably increased. In addition, when the laser diode causes a short circuit failure, the current value of the drive current increases abruptly, and the power of the fiber laser light increases rapidly. The ratio of the switching-on period, that is, the duty is remarkably reduced.

  The duty monitoring unit monitors the duty of the switching operation and detects the state where the duty is abnormally large or the state where the duty is abnormally small as described above, and the laser diode has caused an open failure or a short failure. Detect that.

  In a preferred aspect of the present invention, the duty monitoring unit sets a duty upper limit value, and when the duty of the switching operation exceeds the duty upper limit value, reports that the laser diode has caused an open failure. Output. More preferably, when the duty monitoring unit sets the first determination time limit and the state where the duty of the switching operation exceeds the duty upper limit value continues for the first determination time limit, the laser diode causes an open failure. It is determined that

  In another preferred embodiment, the duty monitoring unit sets a duty lower limit value, and outputs a report that the laser diode has a short fault when the duty of the switching operation divides the duty lower limit value. . More preferably, when the duty monitoring unit sets the second determination time limit and the state where the duty of the switching operation divides the duty lower limit value continues for the second determination time limit, the laser diode causes a short failure. It is determined that

  In a preferred aspect of the present invention, the switching control unit compares the measured value with the set value and generates an error signal indicating the comparison error, and switching based on the error signal. And a control signal generation unit that generates a binary pulse width modulation control signal to be supplied to the element. Then, the duty monitoring unit compares the level of the error signal with the first reference value corresponding to the duty upper limit value, and determines from the comparison result whether the duty of the switching operation is larger than the duty upper limit value. To do. Alternatively, the duty monitoring unit compares the pulse width of the pulse width modulation control signal with the first reference value corresponding to the duty upper limit value, and based on the comparison result, whether or not the duty of the switching operation is larger than the duty upper limit value. Determine whether.

  In another preferred embodiment, the switching control unit compares the measured value with the set value to generate an error signal representing the comparison error, and the switching element based on the error signal. And a control signal generation unit that generates a binary pulse width modulation control signal to be supplied to the control unit. Then, the duty monitoring unit compares the level of the error signal with the second reference value corresponding to the duty lower limit value, and determines from the comparison result whether the duty of the switching operation is smaller than the duty lower limit value. Alternatively, the duty monitoring unit compares the pulse width of the pulse width modulation control signal with the second reference value corresponding to the duty lower limit value, and from the comparison result, determines whether the duty of the switching operation is smaller than the duty lower limit value. Determine whether.

  The first fiber laser processing apparatus of the present invention has a seed light source for generating seed light and a core to which at least Yb is added as a rare earth element, and the seed light is put into the core from an input end, An optical fiber for amplification that amplifies by stimulated emission while propagating the seed light toward the output end, an excitation laser diode that generates excitation light for exciting the core of the optical fiber for amplification, and the excitation laser A pumping laser diode power supply device of the present invention for lighting and driving the diode, an optical coupler for optically coupling the seed light source and the pumping laser diode to an input end of the amplification optical fiber, and the amplification A laser irradiation unit for condensing and irradiating a workpiece with a pulsed laser beam emitted from an output end of an optical fiber, and the excitation laser diode power supply device Ri wherein when the notification is output and a control unit stopping the seed light source and the excitation laser diode power supply in response to the notification.

  A second fiber laser processing apparatus according to the present invention includes an oscillation optical fiber having a core containing a light emitting element and a clad surrounding the core, and a pair of optically opposed optical fibers through the core of the oscillation optical fiber. A resonator mirror, an excitation laser diode that generates excitation light for exciting the core of the amplification optical fiber, and an excitation laser diode power supply device of the present invention for lighting and driving the excitation laser diode; When the notification is output from the laser irradiation unit that focuses and irradiates the laser beam output from the resonator mirror toward the processing point of the workpiece, and the excitation laser diode power supply device, And a controller that stops the pumping laser diode power supply device in response.

  Since the first and second fiber laser processing apparatuses include the pumping laser diode power supply device of the present invention, the pumping laser diode can appropriately cope with an open failure or a short-circuit failure. Yes, the reliability of the apparatus can be improved.

  According to the pumping laser diode power supply device of the present invention, due to the configuration and operation as described above, an open failure and a short failure of the pumping laser diode can be achieved with a small-scale and low-cost device configuration without requiring an isolation amplifier. Can be reliably detected.

  According to the fiber laser processing apparatus of the present invention, it is possible to take appropriate measures against the open failure and short-circuit failure of the excitation laser diode by the configuration and operation as described above, and improve the reliability of the apparatus. Can be made.

It is a figure which shows the structure of the fiber laser processing apparatus by one Embodiment of this invention. It is a figure which shows an example of the marking pattern in the marking process of the said fiber laser processing apparatus. It is a figure which shows the waveform and timing of each part in the said marking process. It is a figure which shows the structure of the pump LD power supply circuit used with the said fiber laser processing apparatus. It is a figure which shows the circuit structure of the switching control part and duty monitoring part which are contained in the said pump LD power supply circuit. It is a figure which shows the waveform of each part in the switching operation of the said switching control part. It is a figure which shows the waveform of each part for demonstrating one effect | action of the said duty monitoring part. It is a figure which shows the waveform of each part for demonstrating one effect | action of the said duty monitoring part. It is a figure which shows the circuit structure of the duty monitoring part in one modification. It is a figure which shows the structure of the fiber laser processing apparatus in one modification.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a configuration of a MOPA (Master Oscillator Power Amplifier) type fiber laser processing apparatus according to an embodiment of the present invention. This fiber laser processing apparatus includes a seed light generation unit 10, first and second amplification optical fibers (hereinafter referred to as "active fibers") 12 and 14, and a laser irradiation unit 16 as isolators 18, 20, and 22 and optical coupling. Optically cascaded through the devices 24 and 26.

  The seed light generator 10 includes a seed laser diode (hereinafter referred to as “seed LD”) 30, a seed LD power supply circuit 32 that drives the seed LD 30 with a pulse waveform current to generate pulse oscillation, and a seed LD 30. And an LD temperature control unit 34 for controlling the temperature. The seed LD 30 is configured as a fiber coupling LD.

  The optical coupler 24 provided between the seed light generator 10 and the first active fiber 12 includes a plurality of, for example, three input ports 24IN (1), 24IN (2), 24IN (3) and one output port 24OUT. And have. A seed LD 30 is connected to the first input port 24IN (1) through the isolator 18. An excitation LD (hereinafter referred to as “pump LD”) 36 for exciting the core of the first active fiber 12 is connected to the second input port 24IN (2). The third input port 24IN (3) is an expansion port, and another pump LD 36 (not shown) can be connected thereto. The input port of the active fiber 12 is connected to the output port 24OUT.

  The seed light generation unit 10, the isolator 18, and the optical coupler 24 constitute a seed light injection unit for the first active fiber 12. Further, the pump LD 36 and the optical coupler 24 constitute a pumping light injection unit for the first active fiber 12.

  The first active fiber 12 has a core made of quartz to which at least Yb ions are added and a clad made of, for example, quartz surrounding the core coaxially, and the total length (fiber length) is selected to be, for example, 3 to 15 m. It is. The gain of the first active fiber 12 (first stage amplifier) can be adjusted, for example, in the range of 10 to 40 dB by the total output of the pump LD 36.

  The optical coupler 26 provided between the first active fiber 12 and the second active fiber 14 includes a plurality of, for example, seven input ports 26IN (1), 26IN (2) to 26IN (7) and one output port. 26 OUT. The output terminal of the first active fiber 12 is connected to the first input port 26IN (1) via the isolator 20. Pumps LD 38 for exciting the core of the second active fiber 14 are connected to the second to fifth input ports 26IN (2) to 26IN (5), respectively. The sixth and seventh input ports 26IN (2) and 26IN (7) are vacant ports, but a pump LD can be added as necessary. The input port of the second active fiber 14 is connected to the output port 26OUT.

  Similarly to the first active fiber 12, the second active fiber 14 also has a core made of quartz to which at least Yb is added, and a clad made of, for example, quartz surrounding the core coaxially. For example, 3-15 m. The gain of the second active fiber 14 (second stage amplifier) can be adjusted in the range of, for example, 10 to 40 dB by the total output of the pump LD38.

  The laser irradiation unit 16 receives a processing light beam LB having a pulse waveform extracted from the output end of the second active fiber 14 via an optical transmission system such as a collimator 39 and a vent mirror 40, and receives the received light beam LB. A desired position on the surface of the workpiece W on the stage 42 is condensed and irradiated. For example, when marking is performed, a galvano scanner is mounted on the laser irradiation unit 16.

  The main control unit 44 includes a microcomputer connected to a touch panel 46 having an input unit 46a such as a keyboard or a mouse and a display unit 46b such as a display. The main control unit 44 includes each unit in the apparatus described above based on a control program stored in a memory. Control the entire device.

  In the fiber laser processing apparatus, when marking is performed, the seed light generation unit 10 generates a desired pulse width (for example, 0.1 to 200 ns) and a desired pulse width of seed light (LD light) having a predetermined wavelength. It is configured to output at a peak power (for example, 10 to 100 mW) and a desired repetition frequency (for example, 20 to 500 kHz). The repetition frequency can be configured to output in the range of 10 kHz to 1 MHz. The seed light having a pulse waveform output from the seed light generator 10 is injected into the core of the first active fiber 12 via the isolator 18 and the optical coupler 24.

  On the other hand, the pump LD 36 is configured to output continuous wave (cw) excitation light having a predetermined wavelength. The continuous wave excitation light output from the pump LD 36 is injected into the core of the first active fiber 12 through the optical coupler 24.

  In the first active fiber 12, the seed light propagates in the axial direction toward the fiber output end while being confined by total reflection at the interface between the core and the clad. On the other hand, the excitation light propagates in the active fiber 12 in the axial direction while being confined by total reflection at the cladding outer peripheral interface, and optically excites Yb ions in the core by crossing the core many times during the propagation.

  Thus, while the seed light and the pumping light propagate through the active fiber 12, absorption of the pumping light spectrum and stimulated emission of the seed light spectrum are repeatedly performed in the Yb-doped core, and a desired value is output from the output end of the active fiber 12. The seed light amplified to have power (for example, 200 W peak power), that is, the light beam of the first stage amplified pulse is output.

  The light beam of the first stage amplified pulse that has exited from the output end of the first active fiber 12 is injected into the core of the second active fiber 14 via the isolator 20 and the optical coupler 26. On the other hand, continuous wave (cw) excitation light from the pump LD 38 is injected into the core of the second active fiber 14 via the optical coupler 26.

  Also in the second active fiber 14, only the light beam to be amplified is different, that is, the seed light is replaced with the first-stage amplified light beam, so that light amplification by the stimulated emission mechanism similar to that of the first active fiber 12 is performed. The second stage amplification pulse light beam having a desired power (for example, 20 kW peak power) is emitted from the output end of the active fiber 14.

  In this way, the light beam of the second-stage amplification pulse extracted from the output end of the second active fiber 14 is sent to the laser irradiation unit 16 via the collimator 39 and the vent mirror 40 as the processing laser light LB, for example. .

  The laser irradiation unit 16 includes a galvano scanner for marking and an fθ lens. The galvano scanner has a pair of movable mirrors capable of swinging in two directions orthogonal to each other. Under the control of the control unit 44, the galvano scanner is synchronized with the pulse oscillation operation of the seed light generation unit 10. By controlling the direction to a predetermined angle, the processing laser beam LB is condensed and applied to a desired position on the surface of the workpiece W on the stage 42. The laser processing applied to the surface of the workpiece W is typically a marking processing for drawing characters, figures, and the like, but other surface removal processing such as trimming is also possible.

  2 and 3 show an example of marking processing in this fiber laser processing apparatus.

As shown in FIG. 2, for example, the marking pattern of the letter “A” is formed by drawing a continuous first stroke of f ₁ → f ₂ and drawing a continuous second stroke of f ₃ → f _4. . Here, during the period (t _{1 to} t ₂ ) and (t _{3 to} t ₄ ) for drawing the first and second strokes, as shown in FIG. Excitation light is output to generate the processing laser beam LB, and the galvano scanner swings and scans the movable mirror. However, during the period of f ₂ → f ₃ (t _{2 to} t ₃ ) indicated by the dotted line in FIG. 2, the seed LD 30 and the pumps LD 36 and 38 stop the light emission operation, and the seed light, the excitation light, and thus the processing laser light LB. Is not output, the galvano scanner swings and scans the movable mirror. As described above, the pumps LD 36 and 38 generate excitation light during the period in which each stroke is drawn.

  In this fiber laser processing apparatus, each of the pumps LD 36 and 38 used for pumping the first and second active fibers 12 and 14 is supplied with a pump LD power supply circuit 50 according to a control signal from the main control unit 44 and a set value PC. Driven by.

  On the other hand, when the pumps LD 36 and 38 have an open (open circuit) failure or a short (short circuit) failure, a notification AR to that effect is sent from the pump LD power supply circuit 50 to the main control unit 44. When the main control unit 44 receives the notification AR from the pump LD power supply circuit 50 during the laser processing, the main control unit 44 immediately stops the laser processing or takes a compensation measure to continue the laser processing, and displays the display unit 46b of the touch panel 46. The failure status is communicated to the user (on-site worker, etc.). At that time, identification information for specifying the pump LD 36 (38) in which the failure has occurred can also be displayed.

  Hereinafter, the configuration and operation of the pump LD power supply circuit 50 in this embodiment will be described.

As shown in FIG. 4, the pump LD power supply circuit 50 is connected in series between a DC power supply 52 for supplying power to the pump LD36 (38), and the DC power supply 52 and the pump LD36 (38). Switching element 54 and choke coil 56. Further, a smoothing capacitor 58 is connected in parallel with the DC power supply 52, and a flywheel diode 60 is connected in parallel with the choke coil 56 and the pump LD 36 (38), and a current path (conductor) through which the drive current I _d flows. For example, a current sensor 62 composed of a Hall element is attached. The drive current measurement circuit 64 calculates, for example, a current effective value as the current measurement value MI _d of the drive current I _d based on the output signal of the current sensor 62, and a switching control unit described later using the drive current measurement value MI _d as a feedback signal. 66.

  The DC power source 52 is composed of, for example, an AC-DC converter, a DC-DC converter, or a battery, and stably outputs a DC voltage at a certain level. The switching element 54 is a transistor having a high response speed, such as a field effect transistor (FET).

The switching control unit 66 performs on / off control of the switching element 54 at a constant frequency of, for example, 20 kHz to 300 kHz by a switching control signal S _PWM of a pulse width modulation (PWM) control method. During the period when the switching element 54 is switched on, the drive current I _d flows in a closed circuit including the DC power supply 52, the switching element 54, the choke coil 56, and the pump LD 36 (38). During the period in which the switching element 54 is switched off, the electromagnetic energy accumulated in the choke coil 56 becomes the drive current I _d and flows back through the pump LD 36 (38) and the flywheel diode 60.

Thus, while the switching element 54 is performing the switching operation, the direct current drive current I _d continuously flows through the pump LD 36 (38), and the light corresponding to the current value of the drive current I _d from the pump LD 36 (38). LD light having an output is generated as excitation light.

In the PWM control, the switching control unit 66 receives the drive current setting value (current control signal) PC _A from the main control unit 44 and the drive current measurement value (feedback signal) MI _d from the drive current measurement circuit 64.

For example, when marking processing is performed, once drawing of one continuous stroke is finished, once the switching operation of the switching element 54, that is, driving of the pump LD 36 (38) is stopped, and drawing of the next stroke is started, The switching operation of the switching element 54, that is, the driving of the pump LD 36 (38) is resumed. The duration and / or pause time of the drive current I _d (that is, excitation light) supplied to the pump LD 36 (38) is arbitrarily variable in accordance with the drive time control signal PC _t given from the main control unit 44 to the switching control unit 66. It has come to be.

  The pump LD power supply circuit 50 in this embodiment monitors the duty of the switching operation of the switching element 54 controlled by the switching controller 66, and detects the open failure or short-circuit failure of the pump LD 36 (38) based on the duty. A monitoring unit 68 is provided.

  FIG. 5 shows the configuration of the switching control unit 66 and the duty monitoring unit 68.

The switching control unit 66 includes an error amplifier 70, a triangular wave generation circuit 72, a comparator 74, and a gate circuit 76. The error amplifier 70, the driving current measurements from the drive current measuring circuit 64 together with the (feedback signal) MI _d is inputted, the drive current setting value from the main control unit 44 (FIG. 1) (current control signal) PC _A Is entered. The error amplifier 70 is composed of, for example, a differential amplifier, compares the drive current measurement value MI _d with the drive current set value PC _A, and has an error signal ER having a voltage level corresponding to the comparison error (MI _d −PC _A ). Is output.

  The triangular wave generation circuit 72 receives a clock signal CK of 20 kHz to 300 kHz for PWM from the clock circuit 78, and outputs a triangular wave signal (or sawtooth wave signal) KM synchronized with the clock signal CK.

The comparator 74 inputs the error signal ER from the error amplifier 70 and the triangular wave signal KM from the triangular wave generating circuit 72 to both input terminals (−) and (+), respectively, so that the levels of the levels of both input signals ER and KM are related to each other. Accordingly, a binary output signal is generated as a PWM control signal S _PWM that has a logical value L when ER> KM and a logical value H when ER ≦ KM.

The PWM control signal S _PWM output from the comparator 74 is given to the control terminal of the switching element 54 through a gate circuit 76 formed of an AND circuit. The switching element 54 is turned off when the PWM control signal S _PWM is a logical value L, and is turned on when the PWM control signal S _PWM is a logical value H.

The gate circuit 76 inputs the drive time control signal PC _t from the main control unit 44 (FIG. 1), to allow the output of the PWM control signal S _PWM when the control signal PC _t is logical value H, the control signal When _PCt is a logical value L, the output of the PWM control signal S _PWM is prohibited or forcibly stopped.

In the switching operation of the PWM control system as described above, for example, when the current value of the drive current I _d changes in a direction that becomes smaller than the drive current set value PC _A , an error signal is obtained as shown in FIG. The level of ER (MI _d −PC _A ) decreases, and the H level period PW of the PWM control signal S _PWM increases as shown in (b) of FIG. As a result, the ratio of the switching-on period of the switching element 54, that is, the duty increases, and the current value of the drive current I _d increases as shown in FIG. 6C. Thus, the current value of the drive current I _d again matches or approximates the drive current set value PC _A.

Further, when the current value of the drive current I _d changes in a direction that increases with respect to the drive current set value PC _A , although not shown in the figure, the above-described feedback loop mechanism of the PWM control system works, so that the drive current I _d current is reduced, and so again equal or close to the drive current setpoint PC _a.

  In this embodiment, as described above, the error signal ER and the duty are in an inversely proportional relationship, and the duty decreases as the error signal ER increases, and the duty increases as the error signal ER decreases. However, as a modification, the proportional relationship may be such that the duty increases as the error signal ER increases, and the duty decreases as the error signal ER decreases.

  Next, the configuration and operation of the duty monitoring unit 68 (FIG. 5) will be described. The duty monitoring unit 68 includes a setting unit 80, comparators 82 and 84, an OR circuit 86, and a counter circuit 88.

Setting unit 80 receives a set value PC _D required to detect the open failure and short circuit failure of the main control unit 44 (FIG. 1) from the pump LD 36 (38). The set value PC _D, include duty limit DU, the duty limit value DL and determined timed period DT.

  Here, the duty upper limit value DU is selected to be, for example, a value of 80% duty in view of the characteristic that the duty of the switching operation is significantly increased in the switching control unit 66 when the pump LD 36 (38) has an open failure. . The duty lower limit DL is selected to be, for example, a value of 20% in view of the characteristic that the duty of the switching operation is significantly reduced in the switching control unit 66 when the pump LD 36 (38) has a short fault. The determination time limit DT is, for example, in view of the characteristic that when the pump LD 36 (38) has an open failure or a short failure, the switching control unit 66 maintains an abnormally large or small duty state. It is chosen to be 10 cycles long on a clock basis. Incidentally, when the clock CK is 100 kHz, the time of 10 cycles is 0.1 msec.

The setting unit 80 gives a first reference value ER _DU having a voltage level corresponding to the duty upper limit value DU to one input terminal (+) of the comparator 82, and a second reference having a voltage level corresponding to the duty lower limit value DL. The value ER _DL is given to one input terminal (−) of the comparator 84, and the count value N _DT corresponding to the determination time limit DT is given to the preset terminal (P) of the counter 88.

The comparators 82 and 84 receive the error signal ER generated in the switching control unit 66 at the other input terminals (−) and (+), respectively. One comparator 82 has a binary value that is a logical value L when ER ≦ ER _{DU and} a logical value H when ER> ER _DU , depending on the magnitude relationship between the levels of both input signals ER and ER _DU. the output signal generated as a duty limit exceeded monitor signal DM _U. The duty limit exceeded monitor signal DM _U is applied to the set terminal of the counter 88 via the OR circuit 86 (S) and reset terminal (R).

The other comparator 84 has a binary value that becomes a logical value L when ER ≦ ER _{DL and} a logical value H when ER> ER _DL , depending on the level relationship between both input signals ER and ER _DL. Is output as a monitor signal DM _L below the lower limit of the duty. The monitor signal DM _L below the lower limit of duty is also supplied to the set terminal (S) and the reset terminal (R) of the counter 88 via the OR circuit 86.

The counter 88 receives the clock signal CK from the clock circuit 78 at the clock terminal (C), and counts the clock signal CK while inputting the logic value H signal to the set terminal (S) and the reset terminal (R). When the count value reaches the preset value _NDT , a signal having a logic value H is output from the output terminal (Q). The output signal of this logical value H is given to the main control unit 44 as the notification AR. The count operation is stopped and the count value is returned to the initial value or held at the initial value while the logical value L is input to the set terminal (S) and reset terminal (R). It has come to be.

  The operation of the duty monitoring unit 68 will be described with reference to FIGS. 7A and 7B.

In the fiber laser processing apparatus (FIG. 1), it is assumed that one of the pumps LD 36 (38) suddenly causes a short failure during laser processing. In that case, in the pump LD power supply circuit 50 that drives the pump LD 36 (38), the current of the drive current I _d that has been normal so far (that is, coincident with or approximate to the drive current set value PC _A ). The value increases rapidly due to a short circuit of the pump LD 36 (38).

In the PWM control feedback loop mechanism provided in the pump LD power supply circuit 50, the drive current measurement value MI _d increases as the drive current I _d increases, and as a result, the level of the error signal ER as shown in FIG. 7A. Increases, and the ratio of the pulse width (period of logical value H) PW of the PWM control signal S _PWM , that is, the duty decreases. The duty output from the comparator 84 when the duty divides the duty lower limit value (for example, 20%), that is, when the error signal ER becomes larger than the second reference value ER _DL (time point t _{p in} FIG. 7A). The monitor signal DM _L below the lower limit changes from the logical value L to the logical value H until then. Incidentally, in the comparator 82, since the level of the first reference value ER _DU is considerably lower, in this scene is constantly ER> ER _DU, the duty limit exceeded monitor signal DM _U maintains the logical value L.

As described above, when the monitor signal DM _L less than the lower limit of the duty output from the comparator 84 changes from the logical value L to the logical value H, the counter 88 starts counting the clock signal CK in response thereto. In this case, since the increase in the drive current I _d is caused by a short circuit failure of the pump LD 36 (38), the feedback control (PWM control) in the direction of decreasing the duty as described above is continued. Thus, the counter 88 counts up to the preset value N _DT, and outputs a notification AR logical value H from the output terminal (Q).

Next, as another case, it is assumed that any pump LD 36 (38) suddenly causes an open failure during laser processing. In this case, in the pump LD power supply circuit 50 that drives the pump LD 36 (38), the current of the drive current I _d that has been normal so far (that is, coincident with or approximate to the drive current set value PC _A ). The value is rapidly reduced by opening or shutting off the pump LD 36 (38).

In the PWM control feedback loop mechanism provided in the pump LD power source circuit 50, the drive current measured value MI _d abruptly decreases in response to a sharp decrease in the drive current I _d, whereby as shown in FIG. 7B The level of the error signal ER decreases, and the ratio of the pulse width (period of logical value H) PW of the PWM control signal S _PWM , that is, the duty increases. The duty output from the comparator 82 when the duty exceeds the duty upper limit value (for example, 80%), that is, when the error signal ER becomes smaller than the first reference value ER _DU (time point t _{p in} FIG. 7B). the upper limit exceeded monitor signal DM _U is changed to a logical H from logic value L to it. Incidentally, in the comparator 84, since the level of the second reference value ER _DL is considerably higher in this situation is constantly ER <ER _DU, monitor signal DM _L less than the duty limit maintains the logical value L.

As described above, the duty limit exceeded monitor signal DM _U of logical value H from the comparator 82 is output, it is the counter 88 in response to start the operation (counting operation) for counting the clock signal CK to it. In this case, the significant decrease in the drive current I _d as described above is caused by the open failure of the pump LD 36 (38). Therefore, the feedback control (PWM control) in the direction of increasing the duty as described above is continued. As a result, the counter 88 counts up to the preset value N _DT (determination time limit DT), and outputs a notification AR of the logical value H from the output terminal (Q).

  As described above, when a sudden open failure or short-circuit failure occurs in the pump LD 36 (38), the notification AR that informs the failure status from the duty monitoring unit 68 of the pump LD power supply circuit 50 that drives the pump LD 36 (38). Is output. This notification AR is sent to the main control unit 44 (FIG. 1).

Even if the pump LD 36 (38) is functioning normally without failure, the duty may divide the duty lower limit value (20%) or exceed the duty upper limit value (80%) in the switching operation. However, it is instantaneous, and the duty immediately returns to the steady dynamic range (20% to 80% in the above example) by the action of the PWM control feedback loop mechanism. Thus, during normal operation, the duty limit exceeded monitor signal DM _U or duty lower than the monitor signal DM _L of logic value H from the comparator 82 is outputted, the counter 88 starts counting (clock) of the clock CK Even so, before the determination time limit DT elapses, the monitor signal DM _U (DM _L ) returns from the logic value H to the logic value L, and the counter 88 is reset. Therefore, the notification AR is not generated by mistake.

  When the main control unit 44 receives the notification AR from any of the pump LD power supply circuits 50, as one aspect, the main control unit 44 stops the LD drive operations of all the pump LD power supply circuits 50 and the seed LD power supply circuit 32 in the apparatus, That is, the pumping light oscillation output operation of all pumps LD 36 (38) and seed LD 32 in the apparatus is stopped, and laser processing is stopped. As a cause of the stop, it is displayed that one of the pumps LD 36 (38) has caused an open failure or a short failure. At that time, the pump LD 36 (38) in which the failure has occurred can be specified and displayed.

As another aspect, the main control unit 44 stops only the pump LD power supply circuit 50 that is driving the failed pump LD 36 (38) and stops all the remaining pump LD power supply circuits 50 without stopping the laser. It is also possible to continue or continue processing. In this case, the drive current set value PC _A is adjusted in each of the LD power supply circuits 50 that are continuously used so that the remaining pumps LD 36 (38) compensate for the pumping light of the pump LD 36 (38) that is missing due to the failure. It may be. Alternatively, it is possible to use a spare pump LD 36 (38) and a pump LD power supply circuit 50 connected to the expansion port. Of course, in this case as well, the faulty pump LD 36 (38) may be specified and prompted to replace the part.

  As described above, the pump LD power supply circuit 50 in this embodiment does not require an isolation amplifier, and instead, an open failure of the pump LD 36 (38) is performed by the duty monitoring unit 68 having a small and low-cost circuit configuration. In addition, it is possible to reliably detect a short circuit failure.

  In addition, the fiber laser processing apparatus according to this embodiment includes the pump LD power supply circuit 50 having the above-described configuration and function, so that even if any of the pump LDs 36 (38) causes an open failure or a short-circuit failure, the fiber laser processing device is suitable. And the reliability of the apparatus can be greatly improved.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above does not limit this invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and technical scope of the present invention.

For example, in the above embodiment, the setting unit 80 of the duty monitoring unit 68 sets the first and second reference values ER _DU and ER _DL having voltage levels corresponding to the duty upper limit value DU and the duty lower limit value DL, respectively, and switching The error signal ER output from the error amplifier 70 of the control unit 66 is compared with the first and second reference values ER _DU and ER _DL by the comparators 82 and 84. From the comparison result, the duty of the switching operation is determined as the duty upper limit. Whether or not it is larger than the value DU and whether or not it is smaller than the duty lower limit DL is determined.

As another example, as shown in FIG. 8, the setting unit 80 sets first and second reference values PW _DU and PW _DL having pulse widths corresponding to the duty upper limit value DU and the duty lower limit value DL, The pulse width (logical value H period) PW of the PWM control signal S _PWM output from the comparator 74 of the switching control unit 66 is measured or monitored by the pulse width measuring unit 90, and the measured pulse width or the monitored value PW is pulse width. The comparators 92 and 94 compare the first and second reference values PW _DU and PW _DL with each other. From the comparison result, it is determined whether the duty of the switching operation is larger than the duty upper limit value DU and the duty lower limit value DL. It is also possible to determine whether it is small or not.

  The above embodiment relates to the MOPA fiber laser processing apparatus. However, the present invention can be applied to any fiber laser processing apparatus, for example, a fiber laser processing apparatus as shown in FIG.

  This fiber laser processing apparatus is a laser processing machine that can be suitably used for laser processing using, for example, laser welding using a long-pulse fiber laser beam, and mainly includes a fiber laser oscillator 100, an excitation LD 102, an excitation LD power supply circuit 104, and fiber transmission. The system 106 includes a laser emitting unit 108, a main control unit 110, a touch panel 112, and the like.

  The fiber laser oscillator 100 includes an oscillation optical fiber (hereinafter referred to as “oscillation fiber”) 114 and a pair of optical resonator mirrors 116 and 118 that are optically opposed to each other via the oscillation fiber 114. ing.

The pumping LD 102 is driven to emit light by a pulsed drive current I _d supplied from the pumping LD power supply circuit 104, and pulsed LD light used for laser pumping (pumping) in the fiber laser oscillator 100, that is, pumping light MB. Is output. The number of LD elements constituting the LD 102 is arbitrary, and an array structure or a stack structure can be adopted.

  The optical lens 120 in the fiber laser oscillator 100 condenses and enters the excitation light MB from the LD 102 onto one end face of the oscillation fiber 112. The optical resonator mirror 116 disposed between the LD 102 and the optical lens 120 transmits the excitation light MB incident from the LD 102 side, and totally reflects the oscillation light beam incident from the oscillation fiber 114 side on the optical axis of the resonator. The coating is made to do.

  The oscillation fiber 114 has a core doped with a rare earth element and a clad surrounding the core coaxially. The core is used as an active medium, and the clad is used as a propagation optical path of excitation light. The excitation light MB incident on one end face of the oscillation fiber 114 as described above propagates in the oscillation fiber 114 in the axial direction while being confined by total reflection at the outer peripheral boundary surface of the cladding, and the core passes through the core several times during the propagation. Crossing the light also photoexcites the light emitting element in the core. Thus, an oscillating light beam having a predetermined wavelength is emitted from both end faces of the core in the axial direction, and this oscillating light beam travels back and forth between the optical resonator mirrors 116 and 118 many times, and is amplified by resonance. The pulsed fiber laser beam FB having the predetermined wavelength is extracted from the optical resonator mirror 118.

  The optical lens 122 in the fiber laser oscillator 100 collimates the oscillating light beam emitted from the end face of the oscillating fiber 114 into parallel light, passes it through the optical resonator mirror 118, reflects off the optical resonator mirror 118, and returns. The oscillating light beam is condensed on the end face of the oscillating fiber 114. Further, the excitation laser beam MB that has passed through the oscillation fiber 114 passes through the optical lens 122 and the optical resonator mirror 118 and is then folded back toward the side laser absorber 126 by the folding mirror 124. The fiber laser light FB output from the optical resonator mirror 118 passes straight through the folding mirror 124, and then passes through the beam splitter 128 before entering the laser incident portion 130 of the fiber transmission system 106.

The beam splitter 128 reflects a part (for example, 1%) of the incident fiber laser beam FB in a predetermined direction, that is, a light receiving element for power monitoring, for example, a photodiode (PD) 132 side. A condensing lens 134 that condenses the reflected light from the beam splitter 128 or the monitor light R _FB may be disposed in front of the photodiode (PD) 132.

The photodiode (PD) 132 photoelectrically converts the monitor light R _FB from the beam splitter 128 and outputs an electrical signal (laser output measurement signal) representing the laser output (laser power) of the fiber laser light FB. The laser output measurement circuit 136 obtains the laser output measurement value M _FB of the fiber laser light FB by analog signal processing based on the output signal of the photodiode 132. The laser output measurement value M _FB obtained by the laser output measurement circuit 136 is given to the excitation LD power supply circuit 104 as a feedback signal for power feedback control.

  The fiber laser beam FB that passes straight through the beam splitter 128 and enters the laser incident portion 130 is first folded in a predetermined direction by the vent mirror 138, and then condensed by the condensing lens 142 in the incident unit 140 and transmitted through the fiber. The light is incident on one end face of a transmission optical fiber (hereinafter referred to as “transmission fiber”) 144 of the system 106. The transmission optical fiber 144 is made of, for example, an SI (step index) fiber, and transmits the fiber laser light FB incident in the incident unit 140 to the emission unit 146 of the laser emission unit 108. The emission unit 146 includes a collimator lens 148 that collimates the fiber laser light FB emitted from the end surface of the transmission fiber 52 into parallel light, and a condensing lens 150 that condenses the parallel fiber laser light FB at a predetermined focal position. have.

When laser welding is performed, the drive current I _d whose waveform is controlled by the excitation LD power supply circuit 104 is supplied (injected) to the LD 102, and the LD 102 corresponds to the waveform of the drive current I _{d in} the fiber laser oscillator 100. The pumping light MB having the output waveform is supplied (injected) to the oscillation fiber 104, and the fiber laser oscillator 100 oscillates and outputs the fiber laser beam FB having a laser output waveform corresponding to the LD output waveform. The waveform-controlled fiber laser beam FB is focused and irradiated on the welding point or welding line of the workpiece W via the laser incident part 130, the fiber transmission system 106, and the laser emitting part 108. At the welding point or welding line, the workpiece material is melted by the energy of the fiber laser beam FB, and solidifies after the pulse irradiation to form a nugget.

In this fiber laser processing apparatus, the present invention can be applied to the excitation LD power supply circuit 104. The excitation LD power supply circuit 104 may have the same configuration as the pump LD power supply circuit 50 in the above embodiment, and the laser output measurement value _MFB obtained by the laser output measurement circuit 136 matches or approximates the set value. As described above, the switching operation of the switching element 54 is controlled by the PWM control method.

In this case, the laser output measurement value M _FB from the laser output measurement circuit 136 and the laser output set value PC _P from the main control unit 110 are input to the error amplifier 70 (FIGS. 5 and 8) of the switching control unit 66. The The error amplifier 70 compares the laser output measurement value M _FB with the laser output set value PC _P and outputs an error signal ER having a voltage level corresponding to the comparison error (M _FB −PC _P ). The comparator 74 inputs the error signal ER from the error amplifier 70 and the triangular wave signal KM from the triangular wave generating circuit 72 to both input terminals (−) and (+), respectively, so that the levels of the levels of both input signals ER and KM are related to each other. Accordingly, a binary output signal is generated as a PWM control signal S _PWM that has a logical value L when ER> KM and a logical value H when ER ≦ KM.

  The excitation LD power supply circuit 104 is also provided with a duty monitoring unit 68 similar to that in the above embodiment. Therefore, when a sudden open failure or short-circuit failure occurs in the LD 102, a notification AR notifying the failure status is sent from the duty monitoring unit 68 in the excitation LD power supply circuit 104 to the main control unit 110.

  When receiving the notification AR from the excitation LD power supply circuit 104, the main control unit 110 stops the LD drive operation of the excitation LD power supply circuit 104, stops the oscillation output operation of the fiber laser light FB, and stops the laser processing. To do. As a result, it is possible to prevent laser processing defects caused by the open failure or short-circuit failure of the LD 102.

  If the cause of the failure of the excitation LD to be used is always determined to be either an open failure or a short failure, the duty monitoring unit only needs to be able to detect only the most likely open failure or short failure. It is also possible.

DESCRIPTION OF SYMBOLS 10 Seed light generation part 12 1st active fiber 14 2nd active fiber 16 Laser irradiation part 30 Seed LD
32 LD power supply circuit for seed 36,38 Pump LD
44 Main Control Unit 50 Pump LD Power Supply Circuit 52 DC Power Supply 54 Switching Element 62 Current Sensor 64 Drive Current Measuring Circuit 66 Switching Control Unit 68 Duty Monitoring Unit

Claims (12)

An excitation laser diode power supply device for driving a laser diode that generates excitation light used for a fiber laser in a fiber laser processing apparatus,
A DC power supply for supplying power to the laser diode;
A switching element connected between the DC power source and the laser diode;
A drive current measurement unit for measuring a current value of the drive current;
A switching control unit that controls the switching operation of the switching element by a pulse width modulation control method so that a current measurement value obtained from the drive current measurement unit matches or approximates a current setting value;
A pumping laser diode power supply apparatus comprising: a duty monitoring unit that monitors a duty of the switching operation in order to detect an open failure or a short failure of the laser diode. An excitation laser diode power supply device for driving a laser diode that generates excitation light used for a fiber laser in a fiber laser processing apparatus,
A DC power supply for supplying power to the laser diode;
A switching element connected between the DC power source and the laser diode;
Switching operation of the switching element by a pulse width control modulation method so that a laser power measurement value obtained from a laser power measurement unit that measures the power of laser light generated from the fiber laser matches or approximates a laser power setting value A switching control unit for controlling
A pumping laser diode power supply apparatus comprising: a duty monitoring unit that monitors a duty of the switching operation in order to detect an open failure or a short failure of the laser diode.   The duty monitoring unit sets a duty upper limit value, and outputs a notification that the laser diode has an open failure when the duty of the switching operation exceeds the duty upper limit value. The laser diode power supply for excitation according to claim 2.   The duty monitoring unit sets a first determination time limit time, and when the duty of the switching operation exceeds the duty upper limit value continues for the first determination time limit time, the laser diode causes an open failure. The pumping laser diode power supply device according to claim 3, wherein the excitation laser diode power supply device is determined to have occurred.   The duty monitoring unit sets a duty lower limit value, and when the duty of the switching operation divides the duty lower limit value, outputs a report that the laser diode has a short fault. 5. The excitation laser diode power supply device according to claim 4.   The duty monitoring unit sets a second determination time limit, and when the duty of the switching operation divides the duty lower limit value continues the second determination time limit, the laser diode causes a short fault. The pumping laser diode power supply device according to claim 5, wherein the excitation laser diode power supply device is determined to have occurred. The switching control unit compares the measured value with the set value, generates an error signal representing the comparison error, and binary signals to be supplied to the switching element based on the error signal. A control signal generation unit for generating a pulse width modulation control signal,
The duty monitoring unit compares the level of the error signal with a first reference value corresponding to the duty upper limit value, and from the comparison result, determines whether the duty of the switching operation is greater than the duty upper limit value. Determine
The laser diode power supply for excitation according to claim 3 or 4. The switching control unit compares the measured value with the set value, generates an error signal representing the comparison error, and binary signals to be supplied to the switching element based on the error signal. A control signal generation unit for generating a pulse width modulation control signal,
The duty monitoring unit compares the pulse width of the pulse width modulation control signal with a first reference value corresponding to the duty upper limit value, and from the comparison result, the duty of the switching operation is less than the duty upper limit value. Determine if it is larger,
The laser diode power supply for excitation according to claim 3 or 4. The switching control unit compares the measured value with the set value, generates an error signal representing the comparison error, and binary signals to be supplied to the switching element based on the error signal. A control signal generation unit for generating a pulse width modulation control signal,
The duty monitoring unit compares the level of the error signal with a second reference value corresponding to the duty lower limit value, and based on the comparison result, determines whether the duty of the switching operation is smaller than the duty lower limit value. judge,
The excitation laser diode power supply device according to claim 5 or 6. The switching control unit compares the measured value with the set value to generate an error signal representing a comparison error, and a binary pulse to be supplied to the switching element based on the error signal A control signal generation unit for generating a width modulation control signal,
The duty monitoring unit compares the pulse width of the pulse width modulation control signal with a second reference value corresponding to the duty lower limit value, and from the comparison result, the duty of the switching operation is less than the duty lower limit value. Determine if it is small,
The excitation laser diode power supply device according to claim 5 or 6. A seed light source for generating seed light;
An amplification optical fiber having a core to which at least Yb is added as a rare earth element, the seed light entering the core from the input end, and being amplified by stimulated emission while propagating the seed light toward the output end;
An excitation laser diode that generates excitation light for exciting the core of the amplification optical fiber;
The excitation laser diode power supply device according to any one of claims 3 to 6, wherein the excitation laser diode is driven to be lit.
An optical coupler for optically coupling the seed light source and the excitation laser diode to an input end of the amplification optical fiber;
A laser irradiation unit for condensing and irradiating a workpiece with a laser beam having a pulse waveform that is output from the output end of the amplification optical fiber;
And a control unit that stops the seed light source and the excitation laser diode power supply device in response to the notification when the notification is output from the excitation laser diode power supply device. An optical fiber for oscillation having a core containing a light emitting element and a clad surrounding the core;
A pair of resonator mirrors optically opposed via the core of the oscillation optical fiber;
An excitation laser diode that generates excitation light for exciting the core of the amplification optical fiber;
The excitation laser diode power supply device according to any one of claims 3 to 6, wherein the excitation laser diode is driven to be lit.
A laser irradiator for condensing and irradiating the laser beam output from the resonator mirror toward a processing point of the workpiece;
And a controller that stops the excitation laser diode power supply in response to the notification when the notification is output from the excitation laser diode power supply.

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