WO2022163643A1

WO2022163643A1 - Laser oscillator and laser processing device provided with same

Info

Publication number: WO2022163643A1
Application number: PCT/JP2022/002653
Authority: WO
Inventors: 雄太黒崎
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2021-01-28
Filing date: 2022-01-25
Publication date: 2022-08-04
Also published as: JPWO2022163643A1

Abstract

This laser oscillator 40 is provided with: bypass switches 421-423 provided between first and second nodes N1, N2 and connected in parallel to each other and in parallel to a laser diode 41; and a control unit 43 which continuously executes, in the following order, control A for turning ON only the bypass switch 421 and turning OFF the bypass switches 422, 423, control B for turning OFF all of the bypass switches 421-423 and causing a supply current to flow to a laser diode LD, and control C for turning OFF the bypass switches 421, 423 and turning ON only the bypass switch 422.

Description

LASER OSCILLATOR AND LASER PROCESSING APPARATUS INCLUDING THE SAME

The present disclosure relates to a laser oscillator including a laser diode and a bypass switch connected in parallel with the laser diode, and a laser processing apparatus including the same.

Patent Document 1 discloses a laser oscillator including a laser diode connected between first and second nodes and a current source for supplying a supply current between the first and second nodes, Disclosed is a bypass switch connected in parallel with the laser diode between first and second nodes. In this laser oscillator, it is possible to switch between the supply current to the laser diode and the bypass switch by switching the bypass switch on and off.

Japanese Patent No. 6577575

By the way, in Patent Document 1, when the laser diode emits light (laser light) for a predetermined continuous light emission time, the switching operation from on to off and the switching operation from off to on are performed for one bypass switch as described above. It is necessary to perform at time intervals corresponding to the continuous light emission time. However, if one bypass switch is turned on and off at short intervals, the response of the bypass switch or the drive circuit for the bypass switch cannot keep up, and the bypass switch enters a half-on state, resulting in damage due to excessive heat generation. There is fear. Therefore, the continuous light emission time of the laser diode cannot be shortened very much.

The present disclosure has been made in view of this point, and its purpose is to make it possible to shorten the continuous emission time of a laser diode.

To achieve the above objectives, the present disclosure provides a laser diode comprising a laser diode connected between first and second nodes and a current source providing a supply current between said first and second nodes. an oscillator, a plurality of bypass switches connected between the first and second nodes, in parallel with the laser diode and in parallel with each other; and at least one first bypass of the plurality of bypass switches. first control for turning on only a switch to stop the laser output of the laser diode, second control for turning off all of the plurality of bypass switches and allowing the supply current to flow through the laser diode, and among the plurality of bypass switches a control unit for continuously executing third control in this order to turn on only at least one second bypass switch different from the first bypass switch to stop the laser output of the laser diode; It is characterized by

As a result, different bypass switches are switched on and off at the start and end of the second control. Therefore, even if the switching operation at the start of the second control is not completely finished, the second control is finished. Can start time switching. Therefore, the time for the second control can be set shorter and the continuous light emission time of the laser diode can be shortened compared to the case where the switching operation is performed with respect to the common bypass switch.

According to the present disclosure, the continuous emission time of the laser diode can be shortened.

FIG. 1 is a schematic diagram showing the configuration of a laser processing apparatus including a laser oscillator according to Embodiment 1 of the present disclosure. FIG. 2 is a circuit diagram of a laser oscillator according to Embodiment 1 of the present disclosure. FIG. 3 is a timing chart explaining the operation of the laser oscillator according to Embodiment 1 of the present disclosure. FIG. 4 is a timing chart explaining the operation of the controller of the laser oscillator according to the second embodiment of the present disclosure. FIG. 5 is a view corresponding to FIG. 4 of the third embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings. The following description of preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its applicability or its uses.

(Embodiment 1)
FIG. 1 shows the configuration of a laser processing apparatus 100. As shown in FIG. This laser processing apparatus 100 is used for cutting a work W, welding processing, and the like. A laser processing apparatus 100 includes a laser processing head 10 , a manipulator 20 , a controller 30 , a laser oscillator 40 according to Embodiment 1 of the present disclosure, and an optical fiber 90 .

The laser processing head 10 irradiates the work W with the laser light LB from the optical fiber 90 . The manipulator 20 has the laser processing head 10 attached to its tip and moves the laser processing head 10 . The controller 30 controls operations of the laser processing head 10 , operations of the manipulator 20 , and laser oscillation of the laser oscillator 40 . The laser oscillator 40 emits a laser beam LB to the optical fiber 90 by oscillation. The optical fiber 90 passes the laser beam LB emitted by the laser oscillator 40 and guides it to the laser processing head 10 . The laser processing head 10 emits laser light LB that has passed through an optical fiber 90 . With such a configuration, the laser processing apparatus 100 operates the laser processing head 10 and the manipulator 20 to irradiate the workpiece W with the laser beam LB emitted from the laser oscillator 40 along a desired trajectory.

The laser oscillator 40 includes a laser diode (LD) 41, a current source 50, three bypass switches 421 to 423, and a controller 43, as shown in FIG.

A laser diode 41 is connected between the first and second nodes N1 and N2. The laser diode 41 has its cathode side directed toward the second node N2.

A current source 50 supplies a supply current between the first and second nodes N1 and N2. Specifically, the current source 50 includes an AC power supply 51, a first rectifier circuit 52, an inverter circuit 53, a capacitor 54, an isolation transformer 55, a second rectifier circuit 56, and a reactor 57. there is

The first rectifier circuit 52 converts the power supply voltage output from the AC power supply 51 into a DC voltage and outputs it from a pair of output nodes ON1 and ON2. The first rectifier circuit 52 is composed of, for example, a diode bridge.

The inverter circuit 53 generates a first AC voltage according to the voltages of the output nodes ON1 and ON2 of the first rectifier circuit 52 . Specifically, the inverter circuit 53 includes a first upper arm switching element 53a and a first lower arm switching element 53b connected in series between a pair of output nodes ON1 and ON2 of the first rectifier circuit 52. , and a second upper arm switching element 53c and a second lower arm switching element 53d connected in series between a pair of output nodes ON1 and ON2 of the first rectifier circuit 52 . A freewheeling diode 53e is connected in parallel to each of the switching elements 53a to 53d.

The capacitor 54 is connected between the first rectifier circuit 52 and the inverter circuit 53 in parallel with the first rectifier circuit 52 and the inverter circuit 53 . A capacitor 54 is connected between a pair of output nodes ON1 and ON2 of the first rectifier circuit 52 .

The isolation transformer 55 converts the first AC voltage output by the inverter circuit 53 into a second AC voltage. The isolation transformer 55 has a primary coil 55a and a secondary coil 55b. The voltage of the primary coil 55a becomes the first AC voltage, and the voltage of the secondary coil 55b becomes the second AC voltage. The primary coil 55a connects a connection point between the first upper arm switching element 53a and the first lower arm switching element 53b and a connection point between the second upper arm switching element 53c and the second lower arm switching element 53d. connected between

The second rectifier circuit 56 generates a DC supply current based on a second AC voltage based on the first AC voltage. Specifically, the second rectifier circuit 56 has first and

second diodes

56a and 56b. The anode of the first diode 56a is connected to one end of the secondary coil 55b, and the anode of the second diode 56b is connected to the other end of the secondary coil 55b. The cathodes of the first and

second diodes

56a, 56b are connected to the first node N1.

Thus, the inverter circuit 53 and the second rectifier circuit 56 are insulated by the isolation transformer 55 .

The reactor 57 is connected between the middle portion of the secondary coil 55b and the second node N2.

The three bypass switches 421-423 are connected in parallel with the laser diode 41 and in parallel with each other between the first and second nodes N1 and N2. Freewheeling diodes 421a to 423a are connected in parallel to these bypass switches 421 to 423, respectively.

The control unit 43 controls on/off of the bypass switches 421 to 423 based on a pulse instruction indicating a period during which the laser diode 41 emits light (laser emission, laser oscillation (stimulated emission)). Specifically, the control unit 43 performs control A to turn on only the bypass switch 421 among the plurality of bypass switches 421 to 423 and turn off the bypass switches 422 and 423, and control B to turn off all the bypass switches 421 to 423. , a control C for turning on only the bypass switch 422 out of the bypass switches 421 to 423 and turning off the bypass switches 421 and 423, the control B, turning on only the bypass switch 423 out of the bypass switches 421 to 423, and The control D for turning off the bypass switch 421 and the bypass switch 422 and the control B are continuously and repeatedly executed in this order. The control unit 43 executes control B for a period corresponding to the period indicated by the pulse instruction. When the bypass switch 421 is regarded as a first bypass switch, the bypass switch 422 constitutes a second bypass switch different from the first bypass switch, the control A is the first control, and the control B is the second control. , and control C correspond to the third control. When bypass switch 422 is regarded as a first bypass switch, bypass switch 423 constitutes a second bypass switch, control C corresponds to first control, control B corresponds to second control, and control D corresponds to third control. .

It should be noted that the repeated control that repeats control A, control B, control C, control B, control D, and control B is interrupted for the reason of stopping the current supply by the current source 50 or switching the pulse current output to the DC output. In this case, the bypass switches 421 to 423 to be selected are reset when resuming the repetitive control, and the same bypass switches 421 to 423 that were turned on immediately before the interruption may be turned on. good too.

In addition, the control unit 43 controls the supply of current by the current source 50 by switching on and off the four switching elements 53a to 53d of the inverter circuit 53 of the current source 50.

The control unit 43 is composed of, for example, a microcomputer or FPGA. Between the control unit 43 and the bypass switches 421 to 423, an isolation circuit (photocoupler, pulse transformer, etc.) is provided to transmit signals from the control unit 43 to the bypass switches 421 to 423 while electrically isolating them from each other. may be provided. Further, in order to switch the bypass switches 421 to 423 at high speed, a drive circuit may be provided between the control unit 43 and the bypass switches 421 to 423 to increase the current supply capability.

Next, the operation of the laser oscillator 40 configured as described above will be described with reference to FIG. In the example of FIG. 3, the control unit 43 performs the following control based on the pulse instruction indicating the period during which the laser diode 41 emits light (laser light emission).

First, the control unit 43 causes the current source 50 to supply current, turns off all of the bypass switches 421 to 423, and executes control B to supply current mainly to the laser diode 41. At timing t1 , the bypass switch 421 is switched from off to on, and execution of control A is started. This causes the supply current to flow through the bypass switch 421 and the current flowing through the laser diode 41 to decrease. Therefore, the laser output of the laser diode 41 stops. It should be noted that the current flowing through the laser diode 41 at this time may be decreased to the extent that the laser output of the laser diode 41 is stopped, that is, less than a predetermined threshold, and does not necessarily have to become 0A.

Next, at timing t2 after the period T11 has elapsed from timing t1, the control unit 43 turns off the bypass switch 421 and starts executing control B again. As a result, the supply current mainly flows through the laser diode 41, and the laser diode 41 outputs laser light.

After that, at timing t3, the control unit 43 turns on the bypass switch 422 and starts executing control C. This causes the supply current to flow through the bypass switch 422 and the current flowing through the laser diode 41 to decrease. Therefore, the laser output of the laser diode 41 stops. Note that the current flowing through the laser diode 41 at this time may also be decreased to the extent that the laser output of the laser diode 41 is stopped, that is, less than a predetermined threshold, and does not necessarily have to be 0A.

Next, at timing t4 when period T12 has passed from timing t3, the control unit 43 turns off the bypass switch 422 and starts executing control B again. As a result, the supply current mainly flows through the laser diode 41, and the laser diode 41 outputs laser light.

After that, at timing t5, the control unit 43 turns on the bypass switch 423 and starts executing control D. This causes the supply current to flow through the bypass switch 423 and the current flowing through the laser diode 41 to decrease. Therefore, the laser output (laser emission) of the laser diode 41 stops. Note that the current flowing through the laser diode 41 at this time may also be decreased to the extent that the laser output of the laser diode 41 is stopped, that is, less than a predetermined threshold, and does not necessarily have to be 0A.

Further, at timing t6 after the period T13 has passed from timing t5, the control unit 43 turns off the bypass switch 423 and starts executing control B again. As a result, the supply current mainly flows through the laser diode 41, and the laser diode 41 outputs laser light.

After that, at timing t7, the control unit 43 turns on the bypass switch 421 and starts executing control A again. This causes the supply current to flow through the bypass switch 421 and the current flowing through the laser diode 41 to decrease. Therefore, the laser output of the laser diode 41 stops.

Furthermore, at timing t8 when period T14 has passed from timing t7, the control unit 43 turns off the bypass switch 421 and starts executing control B again. As a result, the supply current mainly flows through the laser diode 41, and the laser diode 41 outputs laser light.

In this manner, the control unit 43 continuously and repeatedly executes control A, control B, control C, control B, control D, and control B in this order, thereby supplying a pulse current to the laser diode 41 and intermittently supplying the pulse current to the laser diode 41 . light (laser light).

In addition, since the bypass switches 421 to 423 are switched on and off differently at the start and end of the control B, even if the switching operation at the start of the control B is not completely completed, switching operation can be initiated. Therefore, the time for control B can be set shorter and the continuous light emission time of the laser diode 41 can be shortened compared to the case where the switching operation is performed for the common bypass switch. For example, the duration of control B may be shortened, and the waveform of the current flowing through the laser diode 41 during control B may be triangular. In addition, since the continuous light emission time of the laser diode 41 can be set short, it is possible to finely control the amount of heat applied to the welded portion per unit time.

(Embodiment 2)
FIG. 4 is a timing chart illustrating the operation of the controller 43 of the laser oscillator 40 according to Embodiment 2 of the present disclosure. In Embodiment 2, the laser oscillator 40 has only two

bypass switches

421 and 422 and does not have the bypass switch 423 .

The control unit 43 outputs a first clock signal with a duty ratio of 50% for switching the bypass switch 421 on and off. Bypass switch 421 turns on when the first clock signal is at high level, and turns off when the first clock signal is at low level. That is, the control unit 43 switches the bypass switch 421 on and off when switching the level of the first clock signal.

In addition, the control unit 43 further outputs a second clock signal for switching the bypass switch 422 on and off. Bypass switch 422 turns on when the second clock signal is at high level and turns off when the second clock signal is at low level. That is, the control unit 43 switches the bypass switch 422 on and off when switching the level of the second clock signal. The second clock signal is obtained by delaying the phase of the signal obtained by inverting the first clock signal (the signal indicated by the broken line in FIG. 4) by the phase corresponding to the continuous light emission time of the laser diode 41 . The periods and duty ratios of the first and second clock signals are equal to each other. The phases of the first and second clock signals are different from each other.

The first and second clock signals are signals that switch (periodically) between high level and low level at a specific cycle. The first and second clock signals are generated by dividing or multiplying a clock signal generated by a timing device such as a crystal oscillator. Alternatively, the first and second clock signals are switched to high level and low level at a specific period by counting the time by the signal generated by dividing or multiplying the clock signal generated by the timing device. may be generated. Alternatively, the clock signal given from the outside of the laser processing apparatus 100 may be directly output by the controller 43 as the first and second clock signals. The first and second clock signals do not include non-periodic signals, eg, signals whose levels are switched when an aperiodically occurring event occurs.

In the example of FIG. 4, in period T21, the control unit 43 performs first control to turn on the bypass switch 421 and turn off the bypass switch 422 to stop the laser output of the laser diode 41. FIG. Next, in a period T22 that continues from the period T21, the control unit 43 performs second control in which both (all) of the bypass switches 421 and 422 are turned off and the supply current is mainly supplied to the laser diode 41. FIG. Next, in a period T23 that continues from the period T22, the controller 43 performs third control to turn off the bypass switch 421 and turn on the bypass switch 422 to stop the laser output of the laser diode 41. FIG. The second control time corresponds to the phase difference between the first and second clock signals.

Other configurations are the same as in Embodiment 1, so detailed description thereof will be omitted.

Therefore, according to the second embodiment, since the control signals used to control the bypass switches 421 and 422 are the first and second clock signals with the same period, the light emission interval of the laser diode 41 can be easily controlled to be constant.

Since two clock signals with the same cycle and different phases are used to control the bypass switches 421 and 422, the function of outputting the two clock signals is provided, and the phase difference between the two clock signals can be detected by the user. When a microcomputer that can be set by the control unit 43 is employed as the signal generation source of the control unit 43, the continuous light emission time of the laser diode 41 can be easily adjusted simply by setting the phase of the clock signal.

(Embodiment 3)
FIG. 5 is a timing chart illustrating the operation of the controller 43 of the laser oscillator 40 according to Embodiment 3 of the present disclosure. In Embodiment 3, the laser oscillator 40 has only two

bypass switches

421 and 422 and does not have the bypass switch 423 .

The control unit 43 outputs a first clock signal that switches the bypass switch 421 on and off. Bypass switch 421 turns on when the first clock signal is at high level, and turns off when the first clock signal is at low level. That is, the control unit 43 switches the bypass switch 421 on and off when switching the level of the first clock signal.

In addition, the control unit 43 further outputs a second clock signal with a duty ratio of 50% for switching the bypass switch 422 on and off. Bypass switch 422 turns on when the second clock signal is at high level and turns off when the second clock signal is at low level. That is, the control unit 43 switches the bypass switch 422 on and off when switching the level of the second clock signal.

Here, the first clock signal is a signal obtained by inverting the second clock signal (the signal indicated by the broken line in FIG. 4) with a duty ratio of less than 50%. Therefore, the duty ratios of the first and second clock signals are different from each other. The periods of the first and second clock signals are equal to each other. Also, the fall of the second clock signal coincides with the rise of the first clock signal.

In the example of FIG. 5, in period T31, the control unit 43 performs the first control to turn on the bypass switch 421 and turn off the bypass switch 422 to stop the laser output of the laser diode 41 . Next, in a period T32 that follows the period T31, the control unit 43 performs second control in which both (all) of the bypass switches 421 and 422 are turned off and the supply current is mainly supplied to the laser diode 41. FIG. Next, in a period T33 that continues from the period T32, the controller 43 performs third control to turn off the bypass switch 421 and turn on the bypass switch 422 to stop the laser output of the laser diode 41 . The second control time corresponds to the difference between the duty ratios of the first and second clock signals.

Therefore, according to the third embodiment, since the control signals used to control the bypass switches 421 and 422 are the first and second clock signals having the same period, the light emission interval of the laser diode 41 can be easily controlled to be constant.

In addition, since two clock signals having the same cycle and different duty ratios are used to control the bypass switches 421 and 422, it has a function of outputting the clock signals, and the duty ratio of the clock signals can be set by the user. When a microcomputer is employed as the signal generation source of the control section 43, the continuous emission time of the laser diode 41 can be easily adjusted simply by setting the duty ratio of the clock signal.

Although only one laser diode 41 is provided in the first to third embodiments, a plurality of laser diodes 41 may be provided in series between the first and second nodes N1 and N2.

In the first embodiment, the laser oscillator 40 is provided with the three bypass switches 421 to 423, and in the second and third embodiments, the laser oscillator 40 is provided with the two

bypass switches

421, 422. Four or more bypass switches may be provided.

In the first to third embodiments, only one bypass switch 421 to 423 is turned on in the first control and the third control. may That is, if the first and second bypass switches do not overlap (if they are different), not only one but also a plurality of first and second bypass switches may be provided. That is, at least one each of the first and second bypass switches is provided.

In the second embodiment, the first and second clock signals have the same duty ratio of 50%. However, the first and second clock signals may have different duty ratios. It may be greater than 50% or less than 50%. In addition, the laser diode 41 may generate two types of continuous light emission time, which may adversely affect the processing quality, but the sum of the duty ratios of the first and second clock signals may be set to a value smaller than 100%. .

Further, in Embodiments 1 to 3 described above, the continuous light emission time of the laser diode 41 may be adjusted according to the processing state during processing of the workpiece W with the laser beam LB. For example, the continuous emission time of the laser diode 41 is set to be shorter when the amount of spatter generation equal to or greater than a predetermined amount is detected by the amount of spatter detection means, compared to when the amount of spatter generation less than the predetermined amount is detected. may In Embodiments 2 and 3, the continuous light emission time of the laser diode 41 can be adjusted by adjusting at least one of the duty ratio and phase of the first and second clock signals.

Further, in the third embodiment, the duty ratio of the second clock signal is 50%. may be adjusted.

In the third embodiment, the falling edge of the second clock signal coincides with the rising edge of the first clock signal. There may be periods during which both the first and second clocks are at high level.

As described above, the present disclosure has the highly practical effect of shortening the continuous light emission time of the laser diode, so it is extremely useful and highly industrially applicable.

10 laser processing head
40 laser oscillator
41 laser diode
50 current source
90 optical fiber
N1, N2 second node
100 laser processing equipment
421-423 bypass switch
LB laser light

Claims

a laser diode connected between the first and second nodes;
a current source that supplies a supply current between the first and second nodes,
a plurality of bypass switches connected in parallel with the laser diode and in parallel with each other between the first and second nodes;
a first control for turning on at least one first bypass switch among the plurality of bypass switches to stop the laser output of the laser diode; turning off all the plurality of bypass switches to supply the current to the laser diode; and third control for turning on at least one second bypass switch different from the first bypass switch among the plurality of bypass switches to stop the laser output from the laser diode. A laser oscillator, further comprising: a control section for sequentially executing the laser oscillator.
The laser oscillator according to claim 1,
The control unit switches on and off the first bypass switch when the level of a first clock signal that periodically switches between a high level and a low level is switched, and the second bypass switch that periodically switches between a high level and a low level. switching on and off the second bypass switch when switching the level of the clock signal of
the periods of the first and second clock signals are equal to each other, and the phases of the first and second clock signals are different from each other;
The laser oscillator, wherein the second control time is a time corresponding to the phase difference between the first and second clock signals.
The laser oscillator according to claim 1,
The control unit switches on and off the first bypass switch when the level of a first clock signal that periodically switches between a high level and a low level is switched, and the second bypass switch that periodically switches between a high level and a low level. switching on and off the second bypass switch when switching the level of the clock signal of
the periods of the first and second clock signals are equal to each other, and the duty ratios of the first and second clock signals are different from each other;
The laser oscillator, wherein the time for the second control is a time corresponding to a difference in duty ratio between the first and second clock signals.
a laser oscillator according to any one of claims 1 to 3;
an optical fiber through which the laser beam emitted by the laser oscillator passes;
and a laser processing head that emits a laser beam that has passed through the optical fiber.