JP2012084630A - Fiber laser processing device and laser diode for excitation power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exhibit the optical output from a laser diode for excitation fully while securely preventing failure due to an overcurrent in a laser diode for excitation power supply device used in a fiber laser processing device.SOLUTION: A pump LD power supply circuit 50 has a DC power supply 52 which supplies power to a pump LD 36(38), and a switching element 54 connected in series between the DC power supply 52 and the pump LD 36(38). A current sensor 62 is attached to a current path (a conductor) through which a driving current Iflows. In order to protect the pump LD 36(38) from an excessive driving current I, the pump LD power supply circuit 50 is further provided with a driving current monitoring unit 66 which monitors the driving current Ibased on the nature each of a normal rated current Iand an absolute maximum rated current I.

Description

  The present invention relates to a fiber laser processing apparatus that performs desired laser processing by irradiating a workpiece with a light beam obtained by amplifying seed light in an optical fiber, and an excitation laser diode power supply apparatus that can be used therefor .

  Recently, fiber laser processing apparatuses that perform desired laser processing by irradiating a workpiece with laser light generated by a fiber laser have become widespread. Among them, a fiber laser processing apparatus of the MOPA (Master Oscillator Power Amplifier) method has been attracting attention.

  In the MOPA system, an optical fiber with a rare earth element such as Yb added to the core is used as an active fiber for laser amplification, and seed light with a relatively low output generated by a seed laser is inserted into the core of the active fiber from one end. By pumping the core with excitation light while propagating to the other end, the seed light is amplified or converted into a high-power processing light beam in the core, and the beam mode is high in light / light conversion efficiency. Has features such as being stable.

  Conventionally, in a MOPA fiber laser processing apparatus, a laser diode (LD) is often used as a light source for exciting an active fiber (for example, Patent Document 1).

  In the MOPA type fiber laser processing apparatus, for example, when marking is performed, the excitation LD stops the oscillation output of the excitation light once drawing of one continuous stroke is completed, and drawing of the next stroke is performed. When started, the oscillation output of the excitation light is resumed, and this series of timings differs depending on the marking pattern. That is, the oscillation output of the excitation light lasts for an arbitrary time according to the length of the drawing stroke, and is interrupted for an arbitrary time according to the separation distance between successive strokes. Further, the power or peak power of the excitation light is changed as needed according to the material of the workpiece and the marking specifications.

  However, in general, the current that can be passed through the LD has an allowable limit or rating. That is, when a current exceeding the rated current flows, the LD is broken or operational reliability is not guaranteed. Therefore, the conventional excitation LD power supply device for driving the excitation LD immediately cuts off the drive current when the current value of the drive current supplied to the excitation LD exceeds the monitored value (rated current value). Or try to take safety measures such as restricting.

US Pat. No. 6,275,250

  In recent years, there are an increasing number of excitation LDs available on the market having two types of rated currents, a normal rated current and an absolute maximum rated current. Here, the normal rated current is a rated current that means that it should not be exceeded for a predetermined period of time or longer, if it exceeds even a little. On the other hand, the absolute maximum rated current is a rated current which means that it should not be exceeded instantaneously under any use conditions.

  However, the conventional excitation LD power supply device uses only one of the normal rated current and the absolute maximum rated current as a monitored value, and immediately when the drive current supplied to the excitation LD exceeds the monitored value, I was trying to take such safety measures. For this reason, when the normal rated current is selected as the monitoring value, there is a limitation that the performance (particularly the light output) of the excitation LD cannot be fully exhibited. On the other hand, when the absolute maximum rated current is selected as the monitoring value, it is overlooked that the drive current exceeding the normal rated current continuously flows for the predetermined time or more, and the excitation LD is likely to fail. was there.

  The present invention solves the above-mentioned problems of the prior art, and makes it possible to sufficiently exhibit the optical output of the laser diode for excitation and to reliably prevent failure due to overcurrent. A laser diode power supply device and a fiber laser processing device using the same are provided.

  An excitation laser diode power supply apparatus according to the present invention is an excitation laser diode power supply apparatus for driving a laser diode that generates excitation light in a fiber laser processing apparatus, and is a DC power supply for supplying power to the laser diode. A current control element connected between the DC power supply and the laser diode, a control unit for controlling the drive current supplied to the laser diode through the current control element, and detecting a current value of the drive current Based on an output signal of the current sensor, a first monitoring unit that monitors whether or not the current value of the drive current exceeds a first monitoring value, and an output signal of the current sensor, A second monitoring unit that monitors whether the current value of the driving current has maintained a value equal to or greater than a second monitoring value for a set time or more.

  In the above device configuration, when the excitation laser diode has two types of rated currents, the normal rated current and the absolute maximum rated current, the first monitoring value is selected in light of the absolute maximum rated current, and the normal rating is selected. By selecting the second monitoring value and set time in light of the current, the drive current can be prevented from exceeding the absolute maximum rated current even momentarily, and the drive current has exceeded the normal rated current. However, it is possible to prevent the state from continuing for a predetermined time related to the normal rated current. As a result, the optical output of the excitation laser diode can be fully exerted, and failure due to overcurrent can be reliably prevented.

  According to a preferred aspect of the present invention, when the first monitoring unit detects that the current value of the drive current exceeds the first monitor value, the first monitoring unit is configured to turn off or decrease the drive current. 1 overcurrent detection signal is generated. In this case, the control unit preferably cuts or reduces the drive current through the current control element in response to the first overcurrent detection signal.

  According to another preferable aspect, the second monitoring unit is configured to turn off or decrease the drive current when the current value of the drive current has exceeded the second monitor value for a set time or longer. A second overcurrent detection signal is generated. In this case, the control unit preferably cuts or reduces the drive current through the current control element in response to the second overcurrent detection signal.

  In a preferred aspect, the first monitoring value is set to a value lower than the maximum rated current of the laser diode, and the second monitoring value is set to a value that is the same as or close to the normal rated current of the laser diode. .

  According to a preferred aspect, the second monitoring unit converts the output signal of the current sensor at a cutoff frequency corresponding to the set time, the output signal of the low-pass filter, and the second monitoring value. A comparator that compares the corresponding reference value and conditionally generates a second overcurrent detection signal according to the magnitude relationship.

  According to another preferable aspect, the second monitoring unit compares the output signal of the current sensor corresponding to the drive current with the reference value corresponding to the second monitored value, and outputs the magnitude relationship thereof. A comparator that generates a signal, a timer that counts the set time from when the current value of the drive current exceeds the second monitoring value based on the output signal of the comparator, and when the timer counts the set time, And a determination circuit that conditionally generates a second overcurrent detection signal in accordance with the output signal of the comparator.

  According to a preferred aspect, the current control element is a switching element. And a control part carries out switching control of a switching element with a fixed frequency by a pulse width control system.

  According to another preferred aspect, the current control element is a drive transistor having an amplification function. And a control part gives an analog control signal to the control terminal of a drive transistor.

  A fiber laser processing apparatus according to a first aspect of the present invention is a MOPA type fiber laser processing apparatus, comprising: a seed light source for generating seed light; and a core added with at least Yb as a rare earth element, An optical fiber for amplification that amplifies by stimulated emission while introducing seed light into the core from the input end and propagating the seed light toward the output end, and excitation light for exciting the core of the optical fiber for amplification An excitation laser diode for generating light, an excitation laser diode power supply device of the present invention for lighting and driving the excitation laser diode, the seed light source and the excitation laser diode at the input end of the amplification optical fiber An optical coupler that optically couples, and a light beam with a pulse waveform that exits from the output end of the amplification optical fiber is focused on the workpiece. And an optical beam irradiation unit for morphism.

  A fiber laser processing apparatus according to a second aspect of the present invention is a MOPA type fiber laser processing apparatus, comprising: a seed light source for generating seed light; and a core to which at least Yb is added as a rare earth element, A first amplifying optical fiber that amplifies by stimulated emission while introducing seed light into the core from the input end and propagating the seed light toward the output end, and a core of the first amplifying optical fiber. A first pumping laser diode for generating pumping light for pumping, a pumping laser diode power supply device of the first invention for lighting and driving the pumping laser diode, the seed light source, and the first light source A first optical coupler that optically couples the pumping laser diode to the input end of the first amplification optical fiber, and at least Yb as a rare earth element A light beam of the first-stage amplification pulse from the output end of the first amplification optical fiber is introduced into the second core from the input end, and the first stage A second amplification optical fiber that amplifies the light beam of the amplification pulse by stimulated emission while propagating the light beam and outputs a light beam of the second-stage amplification pulse from the output end, and a second of the second amplification optical fiber A second pumping laser diode for generating second pumping light for pumping the core, and a pumping laser diode power supply device according to the second invention for driving and lighting the second pumping laser diode; A second optical coupler for optically coupling the output terminal of the first amplification optical fiber and the second pumping laser diode to the input terminal of the second amplification optical fiber; From the output end of the optical fiber for amplification And an optical beam irradiation unit for irradiating light collecting the light beam of the second stage amplification pulses to the workpiece.

  A fiber laser processing apparatus according to a third aspect of the present invention optically opposes an oscillation optical fiber having a core containing a light emitting element and a clad surrounding the core via the core of the oscillation optical fiber. A pair of resonator mirrors, a pumping laser diode that generates pumping light for pumping the core of the amplification optical fiber, and a pumping laser diode power supply device of the present invention for lighting and driving the pumping laser diode And a laser irradiation unit for condensing and irradiating the laser beam output from the resonator mirror toward a processing point of the workpiece.

  The fiber laser processing apparatus according to the first, second, and third aspects can sufficiently exhibit the optical output of the excitation laser diode and reliably cause a failure due to an overcurrent by the excitation laser diode power supply apparatus of the present invention. Therefore, the processing capability and reliability of laser processing can be improved.

  According to the pumping laser diode power supply apparatus of the present invention, the optical output of the pumping laser diode can be fully exerted and the pumping laser diode can be appropriately protected from overcurrent by the configuration and operation as described above. can do.

  Moreover, according to the fiber laser processing apparatus of this invention, the processing capability and reliability of laser processing can be improved by the above structures and operations.

It is a block diagram which shows the structure of the fiber laser processing apparatus in one Embodiment of this invention. It is a figure which shows the circuit structure of the pump LD power supply device by one Example in the said fiber laser processing apparatus. It is a block diagram which shows the structure in the LD electric current monitoring part integrated in the said pump LD power supply device. It is a circuit diagram which shows the structural example of the 1st and 2nd monitoring part contained in the said LD electric current monitoring part. It is a figure which shows the meaning on the waveform of the 2nd monitoring value and setting time in a 2nd monitoring part. It is a figure which shows one effect | action in a 2nd monitoring part. It is a figure which shows one effect | action in a 2nd monitoring part. It is a figure which shows one effect | action in a 2nd monitoring part. It is a block diagram which shows another structural example of a 2nd monitoring part. It is a figure which shows one effect | action in the 2nd monitoring part of FIG. It is a figure which shows the circuit structure of the pump LD power supply device by another Example. It is a block diagram which shows the structure of the fiber laser processing apparatus in another embodiment of this invention.

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

  FIG. 1 shows the configuration of a MOPA fiber laser processing apparatus according to an embodiment of the present invention. This fiber laser processing apparatus includes a seed light generator 10, first and second amplification optical fibers (hereinafter referred to as “active fibers”) 12, 14, and a light beam irradiation unit 16, and isolators 18, 20, 22 and light. Optically cascaded via couplers 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 light beam 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 or a vent mirror 40, and receives the received light beam LB. Is condensed and applied to a desired position on the surface of the workpiece W on the stage 42. For example, when marking is performed, a galvano scanner is mounted on the light beam irradiation unit 16.

  The main control unit 44 includes a microcomputer connected to an input device 46 such as a keyboard or a mouse, a display (not shown), and the like. Based on a control program stored in a memory, the main control unit 44 and each unit in the above-described device and the entire device. Take control.

  When marking is performed in this MOPA type fiber laser processing apparatus, 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. 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.

  In this way, while the seed light and the pump light propagate through the active fiber 12, absorption of the pump light spectrum and stimulated emission of the seed light spectrum are repeatedly performed in the Yb-doped core, and a desired power is output from the output end of the active fiber 12. The seed light that has been amplified up to (for example, 200 W peak power), that is, the light beam of the first-stage amplified pulse is emitted.

  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 light beam irradiation unit 16 through the collimator 39 and the vent mirror 40 as a processing light beam LB, for example. It is done.

The light beam 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 light beam LB is condensed and applied to a desired position on the surface of the workpiece W on the stage 42. Laser processing applied to the surface of the workpiece W is typically marking processing for drawing characters, figures, etc., but other surface removal processing such as trimming is also possible.
The

  In this MOPA type fiber laser processing apparatus, the pumps LD 36 and 38 used for pumping the first and second active fibers 12 and 14 are pump LD power sources under the control of the main control unit 44 (control signal PC). Driven by circuit 50.

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

As shown in FIG. 2, the pump LD power supply circuit 50 is connected in series between a DC power supply 52 for supplying power to the pump LD 36 (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 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 control unit 64 controls the oscillation output duration and the peak power of the pump LD 36 (38) in accordance with the control signal PC from the main control unit 44. For example, the switching element 54 is set to a constant high level by a pulse width control (PWM) method. Switching control with frequency. During the period when 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. Yes.

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.

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. At that time, according to the control signal PC, the current value and / or the duration of the drive current I _d supplied to the pump LD 36 (38) can be varied at any time.

However, the drive current I _d that can be passed through the pump LD 36 (38) has an allowable limit, that is, a rating. The pump LD 36 (38) used in this MOPA type fiber laser processing apparatus has two types of rated currents, that is, a normal rated current I _RS and an absolute maximum rated current I _RM . Here, the normal rated current I _RS is not rated if it exceeds a little, but it is a rated current that means it should not exceed the predetermined time T _S continuously. In particular, this type of LD may not fail even if the energization is continued within the predetermined time T _S exceeding the normal rated current I _RS as long as the time interval equal to or longer than the predetermined time T _G (for example, 10 ms) is provided. Confirmed by the inventor. On the other hand, the absolute maximum rated current I _RM is a rated current meaning that it should not be exceeded instantaneously under any use condition.

The pump LD power source circuit 50, in order to protect the pump LD36 (38) from an excessive driving current I _d, the drive current I _d usually light of the respective properties of the rated current I _RS and the absolute maximum rated current I _RM A drive current monitoring unit 66 for monitoring is provided.

The drive current monitoring unit 66 receives a voltage signal (drive current detection signal) MI _d representing the current value of the drive current I _d from the current sensor 62, and drives the drive current in light of the normal rated current I _RS and the absolute maximum rated current I _RM. When it is determined that I _d is excessive, the binary output signal is lowered to, for example, the L level, and this is used as the overcurrent detection signal ES ₋ . Control unit 64, overcurrent detection signal ES from the driving current monitoring unit 66 _- when is generated, in response thereto, so that off the drive current I _d to stop the switching operation of the switching element 54.

As shown in FIG. 3, the drive current monitoring unit 66 includes a first monitoring unit 68 for absolute maximum rated current and a second monitoring unit 70 for normal rated current. The first monitoring unit 68 monitors whether or not the drive current I _d is excessive in light of the absolute maximum rated current I _{RM. If} it is determined that the drive current I _d is excessive, the first monitoring unit 68 detects the L level output signal as the first over current. The signal ES ₁₋ is generated. On the other hand, the second monitoring unit 70 monitors whether or not the drive current I _d is excessive in light of the normal rated current I _RS, and if it is determined that the drive current I _d is excessive, the second monitoring unit 70 outputs the L level output signal to the second over current. The detection signal ES _2- is generated. When either the first overcurrent detection signal ES ₁₋ or the second overcurrent detection signal ES ₂₋ is generated, an L level overcurrent detection signal ES ₋ is output from the output circuit 72 formed of an AND gate. It is like that.

  FIG. 4 shows circuit configurations of the first monitoring unit 68 and the second monitoring unit 70 in one embodiment.

The first monitoring unit 68 includes a first reference value generation unit 74 and a first comparator 76. The first reference value generator 74, a resistor divider, the desired ratio A ₁ for a constant supply voltage V _BB (However, 0 <A 1 _<1) the divided voltage A1 * V _BB having It is generated as a first reference value K ₁ corresponding to the first monitoring value I _K1 . Here, the first monitoring value I _K1 is in light of the absolute maximum rated current I _RM (eg, 200 A) of the pump LD 36 (38), and preferably is a current value (eg, 195 A) somewhat lower than the absolute maximum rated current I _RM. To be elected.

The comparator 76 is composed of an operational amplifier, and the first reference value K ₁ from the first reference value generator 74 is input to the non-inverting input terminal (+), and the output of the current sensor 62 is input to the inverting input terminal (−). A signal (drive current detection signal) MI _d is input, and an output signal of H level is generated when MI _d ≦ K ₁ , and L when MI _d > K ₁ , according to the magnitude relationship between the two input signals. A level output signal is generated as the first overcurrent detection signal ES _1- . The output terminal of the comparator 74 is connected to the H level power supply voltage V _BB via the pull-up resistor 78.

Thus, the first monitoring unit 68 generates the first overcurrent detection signal ES ₁₋ when detecting that the drive current I _d flowing through the pump LD 36 (38) exceeds the first monitoring value I _K1. It is like that. When the first overcurrent detection signal from the first monitoring portion 68 ES _1-is generated, so that the cutting drive current I _d controller 64 immediately stops the switching operation of the switching element 54. At that time, if there is a certain time delay from when the drive current I _d exceeds the first monitoring value I _K1 to when the drive current I _d is cut off, the drive current I _d must be absolute during this time delay. The first monitoring value I _K1 is preferably selected so that the maximum rated current I _RM is not exceeded.

Thus, the drive current I _d does not exceed the absolute maximum rated current I _RM instantaneously. Therefore, the drive current I _d supplied to the pump LD 36 (38) can always be kept below the absolute maximum rated current I _RM .

  The second monitoring unit 70 includes a second reference value generation unit 80, a low-pass filter 82, and a second comparator 84.

Here, the second reference value generating unit 80 is formed of a resistance voltage dividing circuit, and a divided voltage A ₂ having a desired ratio A ₂ (where 0 <A ₂ <1) with respect to a constant power supply voltage V _BB . * generating a V _BB as the second reference value K ₂ corresponding to the second monitoring value I _K2. Here, the second monitoring value I _K2 is in light of the normal rated current I _RS (eg, 100 A) of the pump LD 36 (38), and is preferably the same as or close to the normal rated current I _RS (100 A). To be elected.

The low-pass filter 82 is configured as an RC filter circuit including, for example, a resistor 86 and a capacitor 88, and in light of the predetermined time T _S (for example, 1 ms) related to the normal rated current I _RS , preferably from the predetermined time T _S. Has a cut-off frequency or delay time constant corresponding to a somewhat shorter set time T _S ′ (eg, 0.95 ms).

Low-pass filter 82 inputs the driving current detection signal MI _d from the current sensor 62, the signal MI _d the set time T _S 'signal was blunted at the cutoff frequency or the delay time constant corresponding to the MI _d' Is output.

That is, as shown in FIG. 5, when a drive current I _d having a peak value equal to the second monitoring value I _K2 is supplied to the pump LD 36 (38) in drawing a certain stroke, the energization start time t ₀ is started. At the time t _S when the set time T _S ′ has elapsed, the output signal MI _d ′ of the low-pass filter 82 rises to near the second reference value K ₂ and saturates at that level.

The comparator 84 is composed of an operational amplifier, and the second reference value K ₂ from the second reference value generator 80 is input to the non-inverting input terminal (+), and the low-pass filter 82 is input to the inverting input terminal (−). An output signal MI _d ′ is input, and an output signal of H level is generated when MI _d ′ <K _{2, and} an L level signal is output when MI _d ′ ≧ K ₂ , depending on the magnitude relationship between the two input signals. The output signal is generated as the second overcurrent detection signal ES _2- . The output terminal of the comparator 84 is connected to the H level power supply voltage V _BB via the pull-up resistor 90.

When the drive current I _d having a peak value equal to the second monitoring value I _K2 as described above is supplied to the pump LD 36 (38), the time t when the set time T _S ′ has elapsed from the start time t _{0 of} energization. _{At S} , the output signal MI _d ′ of the low-pass filter 82 rises to near the second reference value K ₂ at the saturation level, and the second overcurrent detection signal ES ₂₋ is generated from the comparator 84. When the second overcurrent detection signal from the second monitoring portion 70 ES _2-is generated, the control unit 64 is adapted to turn off the drive current I _d to stop the switching operation of the switching element 54. At this time, even if there is a time lag from when the set time T _S ′ has elapsed until the drive current I _d is cut off, the predetermined time T _S related to the normal rated current I _RS of the pump LD 36 (38) is reduced. It is preferable to select the set time T _S ′ so as not to exceed.

As another example, as shown in FIG. 6, it is assumed that a drive current I _d having a peak value lower than the second monitoring value I _K2 is supplied to the pump LD 36 (38). In this case, the output signal MI _d ′ of the low-pass filter 82 does not reach the second reference value K ₂ at the time t _S when the set time T _S ′ has elapsed from the start time t _{0 of} energization. No second overcurrent detection signal ES _2- is generated from 84.

As another example, as shown in FIG. 7, it is assumed that a drive current I _d having a peak value lower than the first monitoring value I _{K1 and} higher than the second monitoring value I _K2 is supplied to the pump LD 36 (38). . In this case, the energization start time point t ₀ 'output signal MI _d of the low-pass filter 82 before the expiration of' the set time T _S may exceed the second reference value K _2, the comparator 84 at that time t _e Accordingly, the second overcurrent detection signal ES _2- is generated, and the drive current I _d is cut off.

However, as shown in FIG. 8, even when the drive current I _d having the same high peak value is supplied to the pump LD 36 (38), the original duration T _f is changed from the energization start time t ₀ to the time t _e . When it is shorter than the time until it reaches, since the output signal MI _d ′ of the low-pass filter 82 does not exceed the second reference value K ₂ , the second overcurrent detection signal ES ₂₋ is generated from the comparator 84. Absent.

As described above, the second monitoring unit 70 detects the second overcurrent when the current value of the drive current I _d flowing through the pump LD 36 (38) has maintained a value equal to or greater than the second monitor value I _K2 for the set time T _S ′. A detection signal ES _2- is generated. When the second overcurrent detection signal from the second monitoring portion 70 ES _2-is generated, the control unit 64 is adapted to turn off the drive current I _d to stop the switching operation of the switching element 54.

Thus, even if the drive current I _d becomes equal to or higher than the normal rated current I _RS (100 A), the state does not last for a predetermined time (1 ms) or longer. Therefore, the drive current I _d supplied to the pump LD 36 (38) can be always maintained within acceptable limits of normal rated current I _RS.

As described above, the pump LD 36 (38) used in this embodiment is energized within a predetermined time T _S exceeding the normal rated current I _RS if a time interval equal to or longer than a predetermined time T _G (for example, 10 ms) is available. It has been confirmed by the present inventor that no trouble occurs no matter how many times are repeated. The time management of the predetermined time _TG is preferably performed by software in the main control unit 44 to the control unit 64.

The pump LD power supply circuit 50 according to this embodiment includes the drive current monitoring unit 66 having the above-described configuration and function, so that the optical output of the pump LD 36 (38) can be sufficiently exerted, and excessive driving is performed. The pump LD 36 (38) can be properly protected from the current I _d .

  Further, the MOPA fiber laser processing apparatus of this embodiment drives the pump LD 36 (38) by the pump LD power supply circuit 50 as described above, so that the processing capability and reliability in surface removal processing such as marking and trimming are improved. Can be made.

  As mentioned above, although one suitable embodiment of the present invention was described, the above-mentioned embodiment does not limit the present 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, another embodiment as shown in FIG. 9 is possible for the second monitoring unit 70 of the drive current monitoring unit 66. The second monitoring unit 70 in this embodiment includes a comparator 92, a timer 94, an OR gate 96, and a latch circuit 98.

The comparator 92 is composed of an operational amplifier, and receives the second reference value K ₂ from the second reference value generator (not shown) at its inverting input terminal (−) and low-pass at its non-inverting input terminal (+). -The output signal MI _d ′ of the filter 82 is input, and an output signal of L level is generated when MI _d ′ <K ₂ , and when MI _d ′ ≧ K ₂ , depending on the magnitude relationship between the two input signals. Generates an H level output signal. The output terminal of the comparator 92 is connected to the input terminal of the timer 94 and to the data input terminal (D) of the timer 94.

The timer 94 is composed of, for example, a mono-multi, and when an H level output signal is generated from the comparator 92, the timer 94 responds to the rising edge and has an H level having a pulse width of a predetermined time, that is, the set time T _S ′. A pulse is output. The output terminal of the timer 94 is connected to the clock terminal (CL) of the latch circuit 98 via the OR gate 96.

The latch circuit 98 is composed of, for example, a D-type flip-flop circuit, and takes in the signal input to the data input terminal (D) at that time in response to the falling edge of the pulse input to the clock terminal (CL). The inverting output terminal (Q ₋ ) outputs a signal having an inverse logical value to the input signal. That is, the latch circuit 98 detects the second overcurrent at the L level from the inverting output terminal (Q ₋ ) according to the output signal (H / L level) of the comparator 92 when the timer 94 measures the set time T _S ′. It functions as a judgment circuit that conditionally generates the signal ES _2- .

FIG. 10 shows an example of the operation of the second monitoring unit 70 in this embodiment. For example, it is assumed that a drive current I _d having a peak value lower than the first monitoring value I _{K1 and} higher than the second monitoring value I _K2 is supplied to the pump LD 36 (38). In this case, an H level output signal is generated from the comparator 84, and an H level pulse is generated from the timer 94 in response thereto. When the set time T _S 'elapses, that is, at the falling edge of the timer output pulse, the H-level output signal of the comparator 84 is taken into the latch circuit 98 and is output from the inverting output terminal (Q ₋ ) of the latch circuit 98. An L level output signal is generated as the second overcurrent detection signal ES _2- .

The control unit 64 receives the second overcurrent detection signal ES _2- from the second monitoring unit 70 and cuts the drive current I _d, and then connects the clock terminal (CL) of the latch circuit 98 via the OR gate 96. A reset pulse is applied, and the inverted output of the latch circuit 98 is returned to the H level.

  In the embodiment described above, in the pump LD power supply circuit 50, the switching element 54 is connected between the DC power supply 52 and the pump LD 36 (38), and this is used as the current control element. However, instead of the switching element 54, for example, as shown in FIG. 11, the driving transistor 100 can be used as a current control element. The drive transistor 100 in the configuration example of FIG. 11 is composed of, for example, an NPN-type bipolar transistor, and forms a collector-grounded analog amplifier circuit. Note that the drive transistor 100 is not limited to a bipolar transistor, and a field effect transistor (FET) or the like can be preferably used.

In the above embodiment, when the overcurrent detection signal ES ₋ is generated from the drive current monitoring unit 66, the control unit 64 cuts the drive current I _d through the current control element (switching element 54, drive transistor 100). . However, the drive current I _d may be reduced at a constant rate or to a constant level without turning off. The drive current monitor section 66 from the overcurrent detection signal ES _- when is generated, the control unit 64 or the current control element works separate interlock circuit or safety circuit off or drive current I _d, or You may make it reduce.

The first overcurrent detection signal ES ₁₋ generated from the first monitoring unit 68 and the second overcurrent detection signal ES ₂₋ generated from the second monitoring unit 70 are individually controlled by the control unit 64 or the interlock circuit. You may make it give to.

Incidentally, by feeding back the output signal (driving current detection signal) MI _d of the current sensor 62 to the control unit 64, the control unit 64 so that the driving current measurement value matches the setting value and controls the switching element 54 or the driving transistor 100 A configuration is also possible.

  In the MOPA fiber laser processing apparatus (FIG. 1) of the above embodiment, the second active fiber 14 is continuously connected to the first active fiber 12 to form a two-stage amplifier. However, the second active fiber 14 may be omitted to form a single-stage (single) amplifier, or the third active fiber may be connected to the subsequent stage of the second active fiber 14 to form a three-stage amplifier. Is also possible.

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

  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 is a long-pulse 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 also be taken.

  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. A fiber laser beam FB having a 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 includes a DC power supply 52, a switching element 54, a current sensor 62, a control unit 64, and the like (see FIG. 2).

In this case, in order to perform a power feedback control, the control unit 64 in the excitation LD power source circuit 104 inputs the laser output measurement value M _FB from the laser output measuring circuit 136 as a feedback signal, from the main control unit 44 A reference value or set value of the laser power related to the fiber laser beam FB is input, and a PWM switching control signal is generated.

The excitation LD power supply circuit 104 also includes a drive current monitoring unit 66 (FIGS. 2 to 4) similar to that in the above embodiment, and has the same characteristics as the above, and the properties of the normal rated current and the absolute maximum rated current are the same. Based on the above, the optical output of the excitation LD 102 can be fully exhibited, and the excitation LD 102 can be appropriately protected from an excessive driving current I _d .

  Also, since the fiber laser processing apparatus of this embodiment drives the pumping LD 102 by the pumping LD power supply circuit 104 as described above, laser processing using a long pulse fiber laser beam, for example, processing capability and reliability in laser welding. Can be improved.

  The fiber laser processing apparatus of the present invention is not limited to surface removal processing such as marking and welding processing, but can also be used for other laser processing such as drilling and cutting.

DESCRIPTION OF SYMBOLS 10 Seed light generation part 12 1st active fiber 14 2nd active fiber 16 Light beam irradiation part 30 Seed LD
32 LD power supply circuit for seed 36,38 Pump LD
DESCRIPTION OF SYMBOLS 50 Pump LD power supply circuit 52 DC power supply 54 Switching element 62 Current sensor 64 Control part 66 Drive current monitoring part 68 1st monitoring part 70 2nd monitoring part 100 Drive transistor 104 LD power supply circuit for excitation

Claims (15)

An excitation laser diode power supply device for driving a laser diode that generates excitation light in a fiber laser processing apparatus,
A DC power supply for supplying power to the laser diode;
A current control element connected between the DC power source and the laser diode;
A control unit for controlling the drive current supplied to the laser diode through the current control element;
A current sensor for detecting a current value of the drive current;
A first monitoring unit that monitors whether the current value of the drive current exceeds a first monitoring value based on an output signal of the current sensor;
A pumping laser diode power supply apparatus comprising: a second monitoring unit that monitors whether a current value of the driving current has maintained a value equal to or greater than a second monitoring value for a set time or longer based on an output signal of the current sensor; .   The excitation laser diode power supply device according to claim 1, wherein the first monitoring value is higher than the second monitoring value.   When the first monitoring unit detects that the current value of the driving current exceeds the first monitoring value, the first monitoring unit outputs a first overcurrent detection signal to cut or reduce the driving current. The pumping laser diode power supply device according to claim 1, which is generated.   4. The excitation laser diode power supply device according to claim 3, wherein the control unit cuts or reduces the drive current through the current control element in response to the first overcurrent detection signal. 5.   5. The excitation laser diode power supply device according to claim 3, wherein the first monitoring value is set to a value lower than a maximum rated current of the laser diode.   The second monitoring unit includes a second overcurrent for turning off or reducing the drive current when the current value of the drive current has maintained a value equal to or greater than the second monitor value for the set time or longer. The laser diode power supply for excitation according to claim 1 or 2, which generates a detection signal.   The pumping laser diode power supply device according to claim 6, wherein the control unit cuts or reduces the drive current through the current control element in response to the second overcurrent detection signal.   8. The excitation laser diode power supply device according to claim 6, wherein the second monitoring value is set to a value that is the same as or close to a normal rated current of the laser diode. The second monitoring unit includes:
A low-pass filter for smoothing the output signal of the current sensor at a cutoff frequency corresponding to the set time;
A comparator that compares the output signal of the low-pass filter with a reference value corresponding to the second monitoring value and conditionally generates the second overcurrent detection signal according to the magnitude relationship thereof. Item 9. The laser diode power supply for excitation according to any one of Items 1 to 8. The second monitoring unit includes:
A comparator that compares an output signal of the current sensor corresponding to the drive current and a reference value corresponding to the second monitoring value, and generates an output signal representing the magnitude relationship;
A timer circuit that counts the set time from when the current value of the drive current exceeds the second monitoring value based on the output signal of the comparator;
A determination circuit that conditionally generates the second overcurrent detection signal according to an output signal of the comparator when the timer circuit measures the set time. A laser diode power supply device for excitation as described in 1. The current control element is a switching element;
The control unit performs switching control of the switching element at a constant frequency by a pulse width control method.
The laser diode power supply for excitation according to any one of claims 1 to 10. The current control element is a drive transistor having an amplification function,
The control unit provides an analog control signal to a control terminal of the drive transistor.
The laser diode power supply for excitation according to any one of claims 1 to 10. 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 pumping laser diode power supply device according to any one of claims 1 to 12, for lighting and driving the pumping laser diode,
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 MOPA type fiber laser processing apparatus, comprising: a light beam irradiation unit that focuses and irradiates a workpiece with a light beam having a pulse waveform that is output from an output end of the amplification optical fiber. A seed light source for generating seed light;
A first amplification light 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 Fiber,
A first excitation laser diode that generates excitation light for exciting the core of the first amplification optical fiber;
The first pumping laser diode power supply device according to any one of claims 1 to 12, for lighting and driving the first pumping laser diode;
A first optical coupler that optically couples the seed light source and the first excitation laser diode to an input end of the first amplification optical fiber;
A second core to which at least Yb is added as a rare earth element, and the light beam of the first-stage amplified pulse from the output end of the first amplification optical fiber enters the second core from the input end A second amplification optical fiber that amplifies by stimulated emission while propagating the light beam of the first-stage amplification pulse and emits the light beam of the second-stage amplification pulse from the output end;
A second pump laser diode for generating second pump light for pumping a second core of the second amplification optical fiber;
The second pumping laser diode power supply device according to any one of claims 1 to 12, for driving and driving the second pumping laser diode.
A second optical coupler for optically coupling the output end of the first amplification optical fiber and the second excitation laser diode to the input end of the second amplification optical fiber;
And a light beam irradiating unit for condensing and irradiating the workpiece with the light beam of the second-stage amplification pulse emitted from the output end of the second amplification optical fiber. 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 pumping laser diode power supply device according to any one of claims 1 to 12, for lighting and driving the pumping laser diode,
And a laser irradiation unit for condensing and irradiating the laser beam output from the resonator mirror toward a processing point of the workpiece.

Images