Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
  • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
  • B23K26/073—Shaping the laser spot
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/20—Bonding
  • B23K26/21—Bonding by welding

Definitions

• the present disclosure relates to a laser welding method and a laser welding apparatus.
• Patent Document 1 proposes a technique for simultaneously controlling the welding speed and the output of the laser beam at least one of the start and end of welding to secure the penetration depth and prevent perforation.
• Patent Documents 2 to 4 an optical fiber having a two-layer core and a movable mirror that changes the optical path of the laser light are used to change the beam profile of the laser light emitted from the optical fiber. techniques have been proposed.
• the structure of workpieces to be laser-welded has diversified, and the shape, heat capacity, or material of the workpiece may change in a complicated manner along the welding line irradiated by the laser beam.
• Patent Documents 2 to 4 do not disclose any welding method for workpieces whose shape, heat capacity, or material changes.
• the present disclosure has been made in view of this point, and the object thereof is a laser welding method and a laser welding apparatus capable of suppressing the occurrence of perforations and insufficient penetration when laser welding works that change in shape, heat capacity, or material. is to provide
• a laser welding method irradiates a work with a laser beam transmitted through an optical fiber, and welds the work along a predetermined welding line at a predetermined welding speed.
• the method wherein the optical fiber has at least a first core located axially and a third core located radially outside the first core and coaxial with the first core.
• the work has a region in which at least one of shape, heat capacity and material changes continuously or discontinuously along the path along the weld line, and the laser beam is At least either before or after welding the region, or at least after reaching the region, the workpiece is continuously or intermittently irradiated, and the laser beam is directed to the optical fiber during welding of the workpiece.
• the beam profile of the laser light emitted from the optical fiber is gradually changed by adjusting the incident position to at least either before or after welding the region, or at least after reaching the region. .
• a laser welding apparatus includes a laser oscillator that emits a laser beam, an optical fiber that transmits the laser beam, an optical path changing mechanism that causes the laser beam to enter the optical fiber, and the a laser head for irradiating a laser beam toward a workpiece, wherein the optical fiber is radially outside the first core and coaxial with the first core provided in the axial center; and a third core provided in the work, wherein at least one of the shape, heat capacity and material of the work changes continuously or discontinuously during the course along the predetermined weld line
• the laser beam is irradiated to the workpiece continuously or intermittently at least one of before and after welding the area, or at least after reaching the area, and the optical path
• the change mechanism is configured to change an incident position of the laser light incident on the optical fiber by changing an optical path of the laser light, and to change the position of the laser light incident on the optical fiber during welding of the workpiece.
• FIG. 1 is a schematic configuration diagram of a laser welding apparatus according to Embodiment 1.
• FIG. FIG. 2 is a cross-sectional view taken along line II-II of FIG.
• FIG. 3 is a schematic diagram for explaining the definition of the beam diameter of laser light.
• FIG. 4 is a schematic diagram explaining the irradiation area of the laser beam along the weld line.
• FIG. 5 is a diagram showing an example of a beam profile of laser light emitted from an optical fiber.
• FIG. 6 is a schematic cross-sectional view of a work.
• FIG. 7 is a diagram showing temporal changes in the control voltage of the piezo actuator.
• FIG. 8 is a diagram showing changes in welding speed over time.
• 9 is a perspective view of a first work according to Modification 1.
• FIG. 1 is a schematic configuration diagram of a laser welding apparatus according to Embodiment 1.
• FIG. 2 is a cross-sectional view taken along line II-II of FIG.
• FIG. 10A is a top view of a second work according to Modification 1.
• FIG. FIG. 10B is a side view of the sixth member;
• FIG. 10C is a schematic cross-sectional view taken along line XC-XC of FIG. 10A.
• FIG. 10D is a schematic cross-sectional view along line XD-XD in FIG. 10A.
• FIG. 11 is a schematic cross-sectional view of a third work according to Modification 1.
• FIG. FIG. 12 is a diagram showing temporal changes in the control voltage of the piezo actuator according to the second embodiment.
• FIG. 13 is a diagram showing temporal changes in beam diameter of laser light.
• FIG. 14 is a diagram showing temporal changes in the power density of laser light at the central portion of the weld bead.
• FIG. 15 is a diagram showing temporal changes in the power density of laser light at the side edge portion of the weld bead.
• 16 is a schematic plan view of a weld bead according to Embodiment 2.
• FIG. 17A is a cross-sectional view along line XVIIA-XVIIA of FIG. 16.
• FIG. 17B is a cross-sectional view along line XVIIB-XVIIB of FIG. 16.
• FIG. 17C is a cross-sectional view along line XVIIC-XVIIC of FIG. 16.
• FIG. FIG. 18 is a schematic plan view of a weld bead for comparison.
• 19A is a cross-sectional view taken along line XIXA-XIXA of FIG. 18.
• FIG. 19B is a cross-sectional view along line XIXB-XIXB of FIG. 18.
• FIG. 19C is a cross-sectional view along line XIXC-XIXC of FIG. 18.
• FIG. 20 is a diagram showing temporal changes in the control voltage of the piezo actuator according to Modification 2.
• FIG. 21 is a diagram showing temporal changes in the power density of laser light at the central portion of the weld bead.
• FIG. 22 is a diagram showing another time change of the control voltage of the piezo actuator.
• FIG. 23 is a diagram showing still another time change of the control voltage of the piezo actuator.
• FIG. 24 is a schematic configuration diagram of a laser welding device according to Embodiment 3.
• FIG. 25 is a schematic diagram showing periodic changes in the beam profile of laser light emitted from an optical fiber.
• FIG. 26 is a schematic cross-sectional view of another optical fiber.
• 27A and 27B are schematic diagrams for explaining the depression of the workpiece formed at the welding end point.
• FIG. 1 shows a schematic configuration diagram of a laser welding apparatus according to this embodiment.
• the laser welding device 100 has a laser oscillator 10, an optical coupling unit 20, a focusing unit 30, an optical fiber 40, a laser head 50, a stage 60, and a robot 70.
• the traveling direction of the laser beam LB emitted from the laser head 50 to the workpiece 200 is called the Z direction
• the traveling direction of the laser beam LB from the optical coupling unit 20 toward the light collecting unit 30 is called the X direction.
• a direction intersecting with the X direction and the Z direction is sometimes called a Y direction.
• Work 200 is composed of a plurality of members to be welded.
• the laser oscillator 10 has a plurality of laser modules 11 and a laser beam combiner 12 .
• the laser beams emitted from the plurality of laser modules 11 are synthesized by the laser beam combiner 12 and emitted as one laser beam LB.
• the wavelength of the laser beam LB is in the range of 900 nm to 1000 nm, but it is not particularly limited to this and can take other values as appropriate.
• the optical coupling unit 20 has a folding mirror 22 and an optical path changing mechanism 23 inside a housing 21 .
• the folding mirror 22 is fixedly arranged inside the housing 21 and reflects the laser beam LB toward the optical path changing mechanism 23 .
• the laser oscillator 10 is arranged inside the housing 21 in the example shown in FIG. 1 , it may be arranged outside the housing 21 .
• the optical path changing mechanism 23 has a mirror 24 , a piezo stage 25 and a piezo actuator 26 .
• the mirror 24 reflects the laser beam LB reflected by the folding mirror 22 toward the condenser lens 32 of the condenser unit 30 .
• the mirror 24 is integrally attached to the piezo stage 25 and the piezo actuator 26 is attached to the piezo stage 25 .
• the piezo stage 25 and the mirror 24 are tilted about an axis parallel to the Y direction, and the optical axis of the laser beam LB reflected by the mirror 24 is changed within a predetermined range.
• the folding mirror 22 can be omitted.
• the condensing unit 30 has a condensing lens 32 , a shutter 33 and a beam damper 34 inside a housing 31 .
• the condenser lens 32 collects the laser beam LB reflected by the mirror 24 of the optical path changing mechanism 23 and makes it enter the optical fiber 40 .
• the shutter 33 is configured to be movable between inside and outside the optical path of the laser beam LB, and opens and closes the optical path of the laser beam LB according to a predetermined control signal. When the shutter 33 is arranged in the optical path of the laser beam LB, the laser beam LB reflected by the shutter 33 enters the beam damper 34 and is converted into heat.
• the condensing unit 30 is provided with a condensing position adjusting portion (not shown).
• the optical fiber 40 is connected to the condensing unit 30 and the laser head 50 and transmits the laser beam LB incident from the condensing unit 30 to the laser head 50 .
• the structure of the optical fiber 40 will be detailed later.
• the laser head 50 has an optical system (not shown) such as a collimation lens and a condensing lens therein.
• the workpiece 200 is laser welded.
• a laser emission port of the laser head 50 is covered with a protective glass (not shown).
• the stage 60 is configured to hold the work 200 and move relative to the laser head 50 .
• the robot 70 is configured to hold the laser head 50 and move the laser head 50 to a desired position.
• the laser welding device 100 also has an optical path control section 91 , a stage control section 92 , a robot control section 93 and a laser control section 94 .
• the optical path control section 91 is electrically connected to a drive mechanism (not shown) for the piezo actuator 26 and the shutter 33 and controls the operation of the piezo actuator 26 and the opening/closing operation of the shutter 33 .
• the tilting range of the optical path changing mechanism 23 changes according to the magnitude of the control voltage applied from the optical path control unit 91 to the piezo actuator 26, and as will be described later, the incident position P of the laser beam LB into the optical fiber 40 is changed by can be changed.
• the piezoelectric actuator 26 and the driving mechanism of the shutter 33 may be controlled by separate control units.
• the stage control unit 92 is electrically connected to the stage 60, and configured to control the relative movement of the stage 60 with respect to the laser head 50, in other words, the relative position of the stage 60 with respect to the laser beam LB incident on the workpiece 200. It is for example, the stage controller 92 can move the stage 60 along the XY plane. Alternatively, the stage 60 can be rotated around an axis parallel to the Z direction.
• the robot control unit 93 is electrically connected to the robot 70 and configured to control the motion of the robot 70 . Note that the stage 60 and the robot 70 may be controlled by the same control section.
• the stage control unit 92 and the robot control unit 93 are interlocked to operate both the robot 70 and the stage 60 .
• the robot controller 93 operates the robot 70 to move the laser head 50 and irradiate the surface of the workpiece 200 with the laser beam LB along the welding line WL (see FIG. 6).
• the welding line WL is an imaginary line when representing the welding portion to which the workpiece 200 is welded as one line.
• the stage 60 is also operated by the stage controller 92 at the same time as the robot 70 . By doing so, the irradiation range of the laser beam LB can be expanded.
• the stage control section 92 and the robot control section 93 may be interlocked to operate both the robot 70 and the stage 60 .
• the laser beam LB may be moved along the welding line WL by moving only the stage 60 by the stage control unit 92 .
• the laser control unit 94 is connected to the power supply 81 connected to the laser oscillator 10 and the laser oscillator 10, and controls the timing and period of output start and output stop of the laser light LB, and the output of the laser light LB. is configured to
• control cycle of the robot 70 by the robot control unit 93 can be synchronized with the control cycle of the laser light LB by the laser control unit 94 .
• the operation of the robot 70 and the output of the laser beam LB which will be described later, can be changed in synchronization with each other.
• the welding speed Vw and the output of the laser beam LB can be changed synchronously.
• the control period of the piezo actuator 26 by the optical path control section 91 can be synchronized with the control period of the laser beam LB by the laser control section 94 . By doing so, the beam profile of the laser beam LB and the output of the laser beam LB can be changed in synchronization.
• control period of the robot 70 by the robot control section 93 can be synchronized with the control period of the piezo actuator 26 by the optical path control section 91 .
• the welding speed Vw and the beam profile of the laser beam LB can be changed in synchronism.
• the above-described functions of the optical path control unit 91, the stage control unit 92, the robot control unit 93, and the laser control unit 94 are realized by executing a predetermined welding program on their respective hardware.
• the hardware is mainly composed of a CPU (Central Processing Unit) and memory.
• a host controller not shown
• an execution command based on a welding program executed by the host controller changes the optical path It is transmitted to each of the control unit 91, the stage control unit 92, the robot control unit 93, and the laser control unit 94, and executes predetermined processing.
• the optical path controller 91, the stage controller 92, the robot controller 93, and the laser controller 94 may be integrated into one controller.
• FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, showing the cross-sectional structure of the optical fiber 40. As shown in FIG.
• the optical fiber 40 has first to third cores 41, 43, 45, first to third clads 42, 44, 46, and a protective coating 47, which are made of quartz except for the protective coating 47.
• the first core 41 is arranged at the axial center of the optical fiber 40 and has a circular cross-sectional view.
• the third core 45 is provided outside the first core 41 and coaxial with the first core 41 in the radial direction of the optical fiber 40 (Y direction and Z direction in FIG. 2), and has a ring shape in cross section. be.
• the second core 43 is provided between the first core 41 and the third core 45 in the radial direction of the optical fiber 40 and coaxially with the first core 41 and the third core 45, and has a ring shape in cross section. be.
• the first clad 42 is provided coaxially with the first core 41 in contact with the outer peripheral surface of the first core 41 and the inner peripheral surface of the second core 43, respectively, and has a ring shape in cross section.
• the second clad 44 is provided coaxially with the first core 41 in contact with the outer peripheral surface of the second core 43 and the inner peripheral surface of the third core 45, respectively, and has a ring shape in cross section.
• the third clad 46 is provided coaxially with the first core 41 in contact with the outer peripheral surface of the third core 45, and has a ring shape in cross section.
• the refractive index of the first core 41 is set higher than that of the first clad 42 .
• the refractive index of the second core 43 is set higher than the respective refractive indices of the first clad 42 and the second clad 44 .
• the refractive index of the third core 45 is set to be higher than the respective refractive indices of the second clad 44 and the third clad 46 .
• each of the first to third clads 42, 44, 46 is doped with a predetermined amount of fluorine.
• the refractive index of the third clad 46 is lower than the respective refractive indices of the first clad 42 and the second clad 44 . By doing so, it is possible to suppress leakage of the laser beam LB from the third core 45 to the third clad 46 .
• the protective film 47 is made of synthetic resin, for example, and mechanically protects the first to third cores 41, 43, 45 and the first to third clads 42, 44, 46 made of quartz, and protects the optical fiber 40 from To prevent leakage of a laser beam LB and leakage of light into an optical fiber 40 from the outside.
• FIG. 3 is a schematic diagram for explaining the definition of the beam diameter of the laser beam
• FIG. 4 is a schematic diagram for explaining the irradiation area of the laser beam along the weld line.
• the "welding speed Vw” means the traveling speed of the laser beam LB along the welding line WL of the workpiece 200 (see FIG. 6, for example).
• the welding speed Vw corresponds to the speed at which the robot 70 moves the laser head 50 emitting the laser beam LB along the welding line WL while the stage 60 holding the workpiece 200 is stationary.
• the welding speed Vw corresponds to the speed at which the stage 60 holding the workpiece 200 is moved relative to the laser head 50 while the laser head 50 is stationary while emitting the laser beam LB.
• the "beam diameter ⁇ " of the laser beam LB is the beam waist that is the position where the laser beam LB emitted from the optical fiber 40 is most constricted. is the diameter of the cross section.
• the beam diameter ⁇ corresponds to the spot diameter of the laser beam LB when the flat surface of the workpiece 200 is irradiated with the laser beam LB.
• the "power density PD" is a value obtained by dividing the output power of the laser beam LB by the spot area Sp of the laser beam LB irradiated onto the workpiece 200 (see (b) of FIG. 3). Also, if the output of the laser beam LB is LP, the relationship between the power density PD and the beam diameter ⁇ of the laser beam LB satisfies the relationship shown in Equation (1).
• the "energy density ED" of the laser beam LB is a value obtained by multiplying the output of the laser beam LB by the irradiation time T of the laser beam LB and dividing the value by the irradiation area S of the laser beam LB.
• the irradiation area S corresponds to the area of the surface of the workpiece 200 irradiated with the laser beam LB over the welding line WL. In the example shown in FIG. 4, if the length along the weld line WL is Lw, the irradiation area S is expressed by Equation (2).
• Equation (3) the energy density ED satisfies the relationship shown in Equation (3).
• FIG. 5 shows an example of a beam profile of laser light emitted from an optical fiber. Note that the beam profile of the laser beam LB shown in FIG. 5 is simplified and illustrated. For convenience of explanation, only the one-dimensional beam profile in the X direction is shown, but in reality, the beam profile has a similar shape in the Y direction as well. Also, in FIG. 5, when the output of the laser beam LB incident on the optical fiber 40 is set to a predetermined output value, the maximum value of each light intensity is normalized to 1 to show the beam profile. Also, the width of the beam profile measured at the position where the light intensity is 1/e 2 corresponds to the beam diameter ⁇ described above.
• control voltage V applied from the optical path control unit 91 to the piezo actuator 26
• the mirror 24 of the optical path changing mechanism 23 is tilted by a predetermined amount around the axis parallel to the Y direction. This changes the optical axis of the laser beam LB reflected by the mirror 24 .
• the incident position of the laser beam LB entering the optical fiber 40 is changed.
• P see FIG. 2; hereinafter sometimes simply referred to as incident position P
• the incident position P of the laser beam LB with respect to the optical fiber 40 the amount of the laser beam LB incident on the core of the optical fiber 40 is changed, and the cores of the optical fiber 40 (first core 41, second It is possible to change the ratio of the laser light LB to the output of the laser light LB incident on the second core 43 and the third core 45).
• the output of the laser beam LB corresponds to the total incident amount of the laser beam LB incident on the optical fiber 40 .
• the beam profile of the laser light LB emitted from the optical fiber 40 (hereinafter sometimes simply referred to as the beam profile of the laser light LB) can be changed.
• the ratio of the laser light LB incident on the core of the optical fiber 40 to the output of the laser light LB is the ratio of each core of the optical fiber 40 ( It corresponds to the ratio of the incident amount of the laser LB incident on the first core 41, the second core 43, and the third core 45).
• the output of the laser beam LB corresponds to the total incident amount of the laser LB with which the optical fiber 40 is irradiated.
• the ratio of the laser light LB incident on the core of the optical fiber 40 to the output of the laser light LB can be changed.
• the laser beam LB is incident on the axial center of the optical fiber 40 and is transmitted to the first core 41.
• the layout relationship of each optical component is defined inside the laser welding apparatus 100 . Let the incident position P in this case be P0 (see FIG. 2).
• control voltage V When the control voltage V is changed from V0 to V1 (>V0), to V2 (>V1), to V3 (>V2), as shown in FIG. changed to P2 and P3.
• pattern 1 may be called a top hat shape.
• the beam profile of the laser beam LB has a smaller peak at the position corresponding to the second core 43 as shown in pattern 3 in FIG. It has a bimodal shape with peaks appearing at corresponding positions. In practice, the distribution has ring-shaped peaks on the XY plane.
• pattern 1 has a shape wider than pattern 0 in the X and Y directions.
• pattern 2 is wider than pattern 1
• pattern 3 is wider than pattern 2 in the X and Y directions.
• the spot diameter increases in order of pattern 0 ⁇ pattern 1 ⁇ pattern 2 ⁇ pattern 3.
• voltages V1, V2, and V3 are 3.6 V, 6 V, and 9 V, respectively, but are not particularly limited to this. It can be changed as appropriate according to the type, size, etc. of the piezo actuator 26 .
• the mirror 24 and the piezo stage 25 may tilt around an axis parallel to the X direction.
• FIG. 6 shows a schematic cross-sectional view of the work
• FIG. 7 shows the time change of the control voltage of the piezo actuator
• FIG. 8 shows the time change of the welding speed.
• the workpiece 200 has a structure in which a first member 201 and a second member 202 each having a corner portion are superimposed.
• the first member 201 and the second member 202 are made of iron, for example.
• a gap exists in a cross-sectional view at the corner portion CR of the work 200 indicated by the dashed line in FIG. 6 (hereinafter, simply referred to as the corner portion CR).
• 202 are superimposed in close contact with each other without a gap. Therefore, when irradiating the laser beam LB, the first member 201 at the corner portion CR can be substantially regarded as one sheet of plate material. Therefore, when the same amount of heat is applied, the temperature of the first member 201 increases at the corner portion CR more than at other portions. Therefore, burn-through and perforation of the first member 201 are likely to occur.
• the beam profile of the irradiated laser beam LB and the welding speed Vw are changed between the corner CR and other locations, thereby making the workpiece 200 perforated and penetrated. Shortages can be prevented. This will be further explained.
• the output of the laser beam LB incident on the optical fiber 40 is kept constant.
• the laser beam LB is continuously irradiated to the workpiece 200 over the welding line WL.
• the continuous path of the welding line WL continuously irradiated with the laser beam LB includes, as will be described later, a corner portion as an area where the shape and heat capacity of the workpiece 200 continuously change. CR is included.
• the control voltage V to be applied is fixed at V1.
• the welding speed Vw is fixed at Vw3 shown in FIG.
• the laser beam LB when the laser beam LB is advanced along the welding line WL along the welding direction WD, the laser beam LB reaches the point A at time ta. At point A, a gap begins to form between the first member 201 and the second member 202. At time tb, the gap becomes maximum at point B where the laser beam LB reaches. Then, the laser beam LB reaches the point C, and the first member 201 and the second member 202 come into contact with each other without a gap. Therefore, as described above, the heat capacity of the corner CR, that is, from the vicinity of the point A to the vicinity of the point C is different from that of other portions, and the heat capacity varies within the corner CR. In other words, it can be said that the corner portion CR is a region where the shape and heat capacity of the workpiece 200 change continuously.
• the distances in the welding direction WD from point A (time ta) to point B (time tb) and from point B (time tb) to point C (time tb) are each 10 mm. Further, when the welding speed is 3.0 m/min, the moving time in each of the above sections is 200 msec.
• the control voltage V is continuously and gradually increased from around time ta so that the control voltage V applied to the piezoelectric actuator 26 reaches V3 at time tb. From time tb, the control voltage V applied to the piezo actuator 26 is lowered continuously and gradually so that the control voltage V reaches V1 again at time tc. After that, the control voltage V is fixed at V1.
• the tilting range of the optical path changing mechanism 23 changes according to the magnitude of the control voltage V applied from the optical path control unit 91 to the piezo actuator 26, thereby changing the incident position P of the laser beam LB to the optical fiber 40. , the beam profile of the laser light LB can be changed.
• V1 is 6 V and V3 is 9 V
• welding is performed in the sections from point A (time ta) to point B (time tb) and from point B (time tb) to point C (time tb).
• the absolute value of the average degree of change of the control voltage V by 3 V, which changes continuously and gradually, is 0.015 V/msec.
• the average degree of change of the control voltage V continuously and gradually is 0.075 V/5 msec in absolute value.
• the range of the average degree of change in which the control voltage V is changed continuously and gradually is preferably 0.05 to 0.1 V/5 msec in absolute value.
• the average degree of change that changes continuously and gradually near V1 (points A and C) and near V3 (point B) is calculated as follows: ), the average degree of change, which changes continuously and gradually, is relatively moderate. good too.
• the welding speed Vw may be changed continuously in conjunction with the change in the control voltage V. Specifically, the welding speed Vw is continuously and gradually reduced from the vicinity of the time ta so that the welding speed Vw reaches the speed Vw1 ( ⁇ Vw3) at the time tb. The welding speed Vw is continuously and gradually increased from the time tb so that the welding speed Vw reaches the speed Vw3 again at the time tc. After that, the welding speed Vw is fixed at the speed Vw3. However, when the corner portion CR reappears on the weld line WL, it goes without saying that both the control voltage V and the welding speed Vw are changed.
• Vw1 is 3 m / min
• Vw3 is 5 m / min
• point A time ta
• point B time tb
• point B time tb
• point C time tb
• the average degree of change (acceleration) that continuously and gradually changes the welding speed Vw that changes at an average welding speed of 4 m / min is absolute value is 444 mm/(sec) 2 .
• the range of the average degree of change (acceleration) in which the welding speed Vw is changed continuously and gradually is preferably, for example, 300 mm/(sec) 2 to 500 mm/(sec) 2 in absolute value.
• the workpiece 200 is welded as described below.
• the first member 201 and the second member 202 need to be bridged and welded so as to fill the gap. For this reason, for example, it is conceivable to increase the output of the laser beam LB at the corner portion CR. However, in this case, the workpiece 200 may be perforated.
• the temperature of the first member 201 is likely to rise, it is conceivable to reduce the output of the laser beam LB at the corner portion CR.
• the second member 202 at the corner CR is irradiated with the laser beam LB in a slightly defocused state. For this reason, the power density PD may become too low, and the first member 201 and the second member 202 may not be welded.
• the control voltage V is set to V3 so that the beam profile of the laser beam LB gradually approaches the pattern 3 shown in FIG.
• the spot diameter of LB is expanded continuously and gradually.
• the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is made lower than at locations other than the corner portion CR.
• the welding speed Vw is set to a low value of Vw1 to secure the amount of heat applied to the workpiece 200 per unit time.
• the welding speed Vw is gradually increased from Vw1 to Vw3 to suppress an increase in welding time.
• the control voltage V applied to the piezo actuator 26 is gradually lowered from V3 to V1 to change the beam profile of the laser beam LB so as to gradually approach pattern 1 shown in FIG.
• the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is increased.
• the spot diameter of the laser beam LB is gradually reduced, the maximum value of the power density PD of the laser beam LB is increased, and the amount of heat applied to the workpiece 200 and the penetration depth are ensured.
• the moving speed of the robot 70 may be changed, or only the moving speed of the stage 60 may be changed. Also, the moving speeds of the robot 70 and the stage 60 may be changed.
• the welding speed Vw and the beam profile may be controlled to change synchronously. In executing this, it is preferable to synchronize the control cycle of the robot 70 by the robot control unit 93 with the control cycle of the piezo actuator 26 by the optical path control unit 91, as described above.
• the control period of the optical path control section 91 and the control period of the robot control section 93 may not be completely synchronized. It suffices if the emission start timing of the laser beam LB and the operation start timing of the robot 70 are synchronized. After a predetermined time has elapsed since the laser beam LB was emitted and the robot 70 started to move, the optical path control unit 91 tilts the piezo actuator 26 to change the beam profile of the laser beam LB.
• the optical path control unit 91 calculates the moving distance of the tip of the robot 70 based on the time from when the robot 70 started to move and the information on the welding speed Vw. When the moving distance reaches a preset distance, the optical path control unit 91 tilts the piezo actuator 26 to change the beam profile of the laser beam LB.
• the methods described above can be properly used depending on the shape of the workpiece 200 and the like.
• the method of changing the beam profile of the laser beam LB after the lapse of a preset time is easy to control. It is easy to use when the distance for changing the beam profile of the laser beam LB is short.
• the actual shape of the workpiece 200 visually recognized by the welding operator is not associated with the timing and period of control, it lacks accuracy in changing the beam profile of the laser beam LB with respect to the desired position of the workpiece 200. Sometimes.
• the method of changing the beam profile of the laser beam LB based on the positional information of the tip of the robot 70 can be performed in conjunction with the teaching work of the robot 70, for example.
• the welding operator can visually recognize the position of the tip of the robot 70 with respect to the actual shape of the workpiece 200 . Therefore, the beam profile of the laser beam LB can be reliably and easily changed with respect to a desired position on the workpiece 200 .
• the control itself since it is necessary to frequently transmit data from the robot controller 93 to the optical path controller 91 according to the motion of the robot 70, the control itself becomes complicated.
• the method of changing the beam profile of the laser beam LB after the robot 70 moves a preset distance also allows the welding operator to visually recognize the position of the tip of the robot 70 with respect to the actual shape of the workpiece 200 . Therefore, the beam profile of the laser beam LB can be reliably and easily changed with respect to a desired position on the workpiece 200 . However, the accuracy may be lower than that based on the position information of the tip of the robot 70 .
• the complexity of the control is intermediate between changing the beam profile of the laser light LB based on the positional information of the tip of the robot 70 and changing the beam profile of the laser light LB after a preset time has elapsed. degree.
• the laser welding method according to the present embodiment irradiates the workpiece 200 with the laser beam LB transmitted through the optical fiber 40, and moves along the welding line WL in the welding direction WD at the welding speed Vw. to weld the workpiece 200 with.
• the optical fiber 40 includes a first core 41 provided in the axial center, a third core 45 provided radially outside the first core 41 and coaxial with the first core 41, and a third core 45 provided radially outside the first core 41. It has at least a second core 43 provided between 41 and the third core 45 and coaxially with the first core 41 and the third core 45 .
• the workpiece 200 has a region where the shape and heat capacity change, in this case, a corner portion CR, in the course along the weld line WL.
• the laser beam LB is continuously applied to the workpiece 200 before and after the corner portion CR, in this case, over the welding line WL.
• the beam profile of the laser light LB emitted from the optical fiber 40 is gradually changed before and after welding the corner portion CR by adjusting the incident position P of the laser light LB to the optical fiber 40 during welding of the workpiece 200. . From another point of view, by changing the ratio of the laser beam LB incident on the first to third cores 41, 43, 45 during welding of the workpiece 200, before and after welding the corner CR, The beam profile of the emitted laser light LB is gradually changed.
• the beam profile of the laser light LB emitted from the optical fiber 40 and applied to the work 200 can be gradually changed during welding of the work 200 .
• the laser oscillator 10 can be operated at an output close to the maximum output, for example, an output of about 90%, so that the utilization efficiency of the laser oscillator 10 can be improved. That is, since the laser beam LB can be output at a high level with respect to the operating cost of the laser oscillator 10, it is possible to suppress an increase in the cost of laser welding.
• the workpiece 200 may be continuously irradiated with the laser beam LB at least one of before and after welding the region.
• the beam profile of the laser beam LB does not necessarily have to change gradually both before and after welding the region where the shape of the work 200 changes or the region where the heat capacity of the work 200 changes.
• the beam profile of the laser beam LB may be gradually changed at least either before or after welding the region.
• At least one of before and after welding the area where the shape of the work 200 changes or the area where the heat capacity of the work 200 changes, or at least after reaching the area, continuously and gradually change the beam profile of the laser beam LB. is preferable, and by doing so, the generation of spatters can be suppressed.
• the welding speed Vw and the output of the laser beam LB The first core It is preferable to continuously and gradually change the ratio of the laser beam LB incident on 41. By doing so, the welding speed Vw and the beam profile of the laser beam LB are continuously and gradually changed. be able to. Also, the welding speed Vw and the beam profile of the laser beam LB can be changed in synchronism. In addition, it is possible to realize laser welding in which the occurrence of spatter is suppressed while suppressing the occurrence of perforation and insufficient penetration of the workpiece 200 .
• the control voltage V and the welding speed Vw are synchronized and changed at the same time, the welding speed Vw and the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB are continuously changed.
• the welding speed Vw and the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is continuously controlled within a range in which the occurrence of perforations in the workpiece 200 and insufficient penetration can be suppressed. and may be changed gradually.
• the laser beam incident on the first core 41 with respect to the output of the laser beam LB is higher than when welding a location (first location) having a larger heat capacity than the corner portion CR. It is preferable to irradiate the laser beam LB with the ratio of LB reduced, and by doing so, laser welding in which the occurrence of spatter is suppressed while suppressing the occurrence of perforation and insufficient penetration of the work 200. can be realized.
• a laser welding apparatus 100 includes a laser oscillator 10 that emits a laser beam LB, an optical fiber 40 that transmits the laser beam LB, an optical path changing mechanism 23 that causes the laser beam LB to enter the optical fiber 40, and a light and a laser head 50 for irradiating the workpiece 200 with the laser beam LB transmitted through the fiber 40 .
• the optical fiber 40 has at least the first to third cores 41, 43, 45 having the arrangement relationship described above.
• the optical path changing mechanism 23 is configured to change the incident position P of the laser light LB entering the optical fiber 40 by changing the optical path of the laser light LB. In addition, the optical path changing mechanism 23 adjusts the incident position P of the laser light LB to the optical fiber 40 during welding of the workpiece 200 so as to gradually change the beam profile of the laser light LB emitted from the optical fiber 40. is configured to
• the present embodiment at least one of before and after welding a region where the shape and heat capacity of the work 200 change, or at least after reaching the region, laser light emitted from the optical fiber 40 and irradiated to the work 200
• the LB beam profile can be gradually changed. As a result, it is possible to suppress the occurrence of perforations and insufficient penetration in the work 200 whose shape and heat capacity change in the middle.
• the optical path changing mechanism 23 includes a mirror 24 that deflects the laser beam LB toward the optical fiber 40, a piezo actuator (actuator) 26 that changes the angle of the mirror 24 with respect to the incident direction of the laser beam LB, and operations of the piezo actuator 26. and an optical path control unit 91 for controlling.
• the optical path control unit 91 is configured to adjust the incident position P of the laser beam LB to the optical fiber 40 by operating the piezo actuator 26 to change the angle of the mirror 24 .
• the incident position P of the laser beam LB to the optical fiber 40 is possible to easily adjust during welding of the workpiece 200 with a simple configuration.
• This makes it possible to easily change the beam profile of the laser beam LB emitted from the optical fiber 40 and applied to the work 200 while the work 200 is being welded.
• the piezo actuator 26 has a high response speed to the control signal, the incident position P of the laser beam LB to the optical fiber 40 can be changed in a short time.
• the beam profile of the laser beam LB can be changed in a short time.
• the laser welding apparatus 100 further includes a robot 70 that holds the laser head 50 and moves the laser head 50 in the welding direction WD, and a robot controller 93 that controls the operation of the robot 70 .
• the robot control unit 93 may control the robot 70 so that the laser beam LB is irradiated along the welding line WL at a predetermined welding speed Vw. Note that the welding speed Vw is constant or varies continuously.
• the robot control unit 93 By providing the robot control unit 93 in this way, the laser beam LB can be easily advanced along the welding line WL. Also, the welding speed Vw can be easily adjusted.
• the laser welding apparatus 100 further includes a stage 60 that holds the workpiece 200 and a stage controller 92 that controls the relative movement of the stage 60 with respect to the laser head 50 .
• the stage controller 92 may control the stage 60 so that the laser beam LB is irradiated along the welding line WL at a predetermined welding speed Vw. Note that the welding speed Vw is constant or varies continuously.
• the stage control unit 92 By providing the stage control unit 92 in this manner, the laser beam LB can be easily advanced along the welding line WL. Also, the welding speed Vw can be easily adjusted. As described above, the stage control unit 92 and the robot control unit 93 may control the operations of the stage 60 and the robot 70 to cause the laser beam LB to travel along the welding line WL. Also in this case, the welding speed Vw can be easily adjusted.
• the workpiece 200 is welded while the output of the laser beam LB incident on the optical fiber 40 is kept constant.
• the power of the laser beam LB may be changed. In this case, it is preferable to change the welding speed Vw and the output of the laser beam LB continuously and synchronously.
• the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is changed.
• the beam profile of the laser beam LB may be changed continuously.
• the control of the laser oscillator 10 and the power supply 81 by the laser control unit 94 is simplified.
• FIG. 9 shows a perspective view of a first work according to this modification.
• FIG. 10A shows a top view of the second work
• FIG. 10B shows a side view of the sixth member.
• 10C shows a schematic cross-sectional view taken along line XC-XC of FIG. 10A
• FIG. 10D shows a schematic cross-sectional view taken along line XD-XD of FIG. 10A.
• FIG. 11 shows a schematic cross-sectional view of the third work.
• the same reference numerals are given to the same portions as in Embodiment 1, and detailed description thereof will be omitted.
• the work 200 to which the laser welding method and laser welding apparatus 100 of the present disclosure are applied is not limited to the structure shown in FIG. 6, and can have various structures.
• the workpiece 200 may have a structure in which a T-shaped third member 203 in plan view is superimposed on a plate-shaped fourth member 204 .
• the third member 203 consists of a first portion 203a and a second portion 203b.
• the first portion 203a extends from the center of the second portion 203b in a direction crossing the longitudinal direction of the second portion 203b.
• the plate thickness of the second portion 203b is thicker than the plate thickness of the first portion 203a when viewed from above. Therefore, the welded portion between the second portion 203b and the fourth member 204 has a larger heat capacity than the welded portion between the first portion 203a and the fourth member 204.
• the heat capacity of a portion 203c where the first portion 203a and the second portion 203b intersect, that is, the welded portion between the T-shaped intersection portion and the fourth member 204 is approximately intermediate the heat capacities of the two welded portions described above. value.
• the third member 203 and the fourth member 204 are laser-welded by irradiating the laser beam LB along the outer shape of the third member 203 in plan view.
• the beam profile of the laser beam LB is gradually narrowed, so that the workpiece 200 is perforated. It is possible to realize laser welding in which the occurrence of spatter is suppressed while suppressing insufficient penetration and penetration.
• the beam profile of the laser beam LB is gradually widened, thereby causing perforation of the workpiece 200. It is possible to realize laser welding in which the occurrence of spatter is suppressed while suppressing insufficient penetration and penetration.
• the laser welding method shown in this embodiment is also useful when the workpiece 200 has the structure shown in FIGS. 10A to 10D.
• the workpiece 200 has a structure in which the side surface of the fifth member 205 and the side surface of the sixth member 206 are butted against each other. Laser welding is performed along the butting surfaces of the fifth member 205 and the sixth member 206 .
• the fifth member 205 is a flat member.
• the sixth member 206 has a shape in which two partitions are provided inside a box-shaped member. Specifically, when the sixth member 206 is viewed from the side, the plate-like portions 206a, 206a facing each other and the other plate-like portions 206b, 206b facing each other form a square annular frame. . Also, two plate-like portions 206c, 206c are provided inside the frame with a space therebetween. When viewed from the side, the plate-like portion 206c is provided substantially parallel to the plate-like portion 206b.
• the portion where the plate-like portion 206c abuts against the fifth member 205 has a larger heat capacity than the other portions. That is, the welded portion shown in FIG. 10D has a larger heat capacity than the welded portion shown in FIG. 10C.
• the workpiece 200 shown in FIG. 10A periodically changes in shape and heat capacity along the weld line WL. Therefore, by gradually and periodically changing the beam profile of the laser beam LB in correspondence with this change, the generation of a hole in the workpiece 200 and insufficient penetration are suppressed, and the generation of spatter is suppressed. Welding can be realized.
• the laser welding method and laser welding apparatus 100 of the present disclosure are also applied when the material of the workpiece 200 changes along the welding line WL.
• the workpiece 200 has a structure in which a seventh member 207 and an eighth member 208 each made of aluminum are superimposed, and a ninth member 209 made of die-cast aluminum is placed in the middle of the eighth member 208. It may be an intercalated structure.
• the seventh to ninth members 207 , 208 , 209 are each made of the same aluminum, but the ninth member 209 has a larger heat capacity than the seventh member 207 and the eighth member 208 .
• the 11 has a discontinuous change in material quality and heat capacity at the boundary between the eighth member 208 and the ninth member 209 along the weld line WL. At least either before or after the vicinity of the boundary between the eighth member 208 and the ninth member 209 is welded, or at least after reaching the region, the beam profile of the laser beam LB is gradually changed. As a result, it is possible to realize laser welding that suppresses the occurrence of spatter while suppressing the occurrence of holes in the workpiece 200 and insufficient penetration.
• the workpiece 200 of the present disclosure has a region where the shape, heat capacity, or material changes continuously or discontinuously along the path along the weld line WL. Furthermore, the workpiece 200 has at least one region in which the shape, heat capacity, or material changes continuously or discontinuously in at least one path along the weld line WL.
• the laser welding method of the present disclosure adjusts the incident position P of the laser beam LB to the optical fiber 40 during welding of the workpiece 200, and at least either before or after welding the region, or at least after reaching the region. , gradually change the beam profile of the laser light LB emitted from the optical fiber 40 .
• the laser welding apparatus 100 of the present disclosure adjusts the incident position P of the laser light LB to the optical fiber 40 during welding of the workpiece 200, and gradually changes the beam profile of the laser light LB emitted from the optical fiber 40. configured to change.
• the laser welding method and laser welding apparatus 100 of the present disclosure can be applied not only to the work 200 shown in the first embodiment, but also to the work 200 having a complicated shape and the work 200 involving changes in material as shown in this modification. As a result, it is possible to realize laser welding in which the occurrence of spatter is suppressed while suppressing the occurrence of perforation and insufficient penetration of the workpiece 200 .
• the beam profile of the laser beam LB, the welding speed Vw, the output of the laser beam LB, the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB in other words, the beam profile of the laser beam LB is continuously It is the same as described in the first embodiment that it is preferable to change quickly and gradually. Also, as in the first embodiment, it is preferable to change the welding speed Vw and the output of the laser beam LB continuously and synchronously. In this case, it is more preferable to continuously and synchronously change the beam profile of the laser beam LB and the output of the laser beam LB.
• the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is reduced. As in the first embodiment, it is preferable to irradiate the laser beam LB in this state.
• the robot 70 moves the laser head 50 along the welding line WL
• the movement locus of the laser head 50 corresponding to the welding line WL is stored in advance in the robot control unit 93 .
• This work is called teaching.
• the position information of the area where the shape of the work 200 is changed is acquired, and this information is also stored in the robot control section 93 .
• the workpiece 200 is welded along the welding line WL.
• the beam profile of the laser beam LB is continuously and gradually changed at least either before or after welding the region where the shape of the workpiece 200 changes, or at least after reaching the region. By doing so, it is possible to realize laser welding in which the occurrence of spatter is suppressed while the occurrence of perforation and insufficient penetration of the workpiece 200 is reliably suppressed.
• FIG. 12 shows the change over time of the control voltage of the piezoelectric actuator according to this embodiment
• FIG. 13 shows the change over time of the beam diameter of the laser light
• FIG. 14 shows the time variation of the laser light power density at the central portion of the weld bead
• FIG. 15 shows the time variation of the laser light power density at the side edge portion of the weld bead.
• the laser welding method and laser welding apparatus 100 shown in the present embodiment change the beam profile of the laser beam LB at least before and after welding a region where the shape of the workpiece 200 changes, or at least after reaching the region. It is different from the configuration shown in the first embodiment in that it is changed gradually and gradually. Specifically, the beam diameter ⁇ and the power density PD of the laser light LB are changed periodically. In addition, in this embodiment, the output of the laser beam LB incident on the optical fiber 40 is kept constant.
• the peak value in this case is V3 and the base value is V0.
• the period during which the control voltage V is V3 and the period during which it is V0 are the same, and the duty ratio, which is the ratio of these periods, is set to one.
• the frequency of the control voltage V is 200 Hz, but is not particularly limited to this, and can be appropriately changed according to the shape and material of the workpiece 200 .
• the beam profile of the laser beam LB is periodically and continuously changed from pattern 0 to pattern 3 and from pattern 3 to pattern 0 shown in FIG. change to That is, the optical path changing mechanism 23 is configured to periodically change the incident position P of the laser beam LB incident on the optical fiber 40 .
• the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is determined between a predetermined ratio R1 (hereinafter referred to as first ratio R1) and a ratio lower than the first ratio R1 (
• first ratio R1 hereinafter referred to as first ratio R1
• the laser welding is performed by periodically switching to the second ratio R2).
• the beam diameter ⁇ of the laser light LB periodically changes from ⁇ 0 to ⁇ 3 (> ⁇ 0) and from ⁇ 3 to ⁇ 0, as shown in FIG. do.
• the power density PD of the laser beam LB irradiated to the workpiece 200 also periodically changes. 300 (see FIG. 16) differs between the central portion and the side edge portions.
• the power density PD of the laser beam LB at the central portion of the weld bead 300 changes from PD3 to PD2 ( ⁇ PD3).
• the power density PD of the laser beam LB at the side edge portion of the weld bead 300 changes from PD1 to PD0 ( ⁇ PD1).
• the power density PD of the laser beam LB at the central portion of the weld bead 300 changes from PD3 to PD2
• the power density PD of the laser beam LB at the side edge portion of the weld bead 300 changes from PD0 to PD1.
• PD1 may be the same value as PD2, or may be different.
• the voltages V0, V1, V2, and V3 are the same values as those shown in the first embodiment.
• the beam diameters ⁇ 0, ⁇ 1, ⁇ 2 and ⁇ 3 are 500 ⁇ m, 1000 ⁇ m, 1500 ⁇ m and 2000 ⁇ m, respectively.
• the power densities PD0, PD1, PD2 and PD3 are respectively 0 W/cm 2 , 1.59 ⁇ 10 5 W/cm 2 , 1.59 ⁇ 10 5 W/cm 2 and 2.55 ⁇ 10 6 W/cm 2 . be.
• these values are appropriately changed according to the shape, material, heat capacity, and the like of the workpiece 200 .
• the beam diameter ⁇ and the power density PD of the laser light LB are periodically changed at least either before or after welding the region where the shape of the workpiece 200 changes, or at least after reaching the region. Therefore, the shape of the weld bead 300 formed on the workpiece 200 can be improved. This will be further explained.
• FIG. 16 shows a schematic plan view of a weld bead according to this embodiment.
• 17A is a cross-sectional view along line XVIIA-XVIIA in FIG. 16
• FIG. 17B is a cross-sectional view along line XVIIB-XVIIB in FIG. 16
• FIG. 17C is a cross-sectional view along line XVIIC-XVIIC in FIG. each shown.
• FIG. 18 shows a schematic plan view of a weld bead for comparison.
• 19A is a cross-sectional view along line XIXA-XIXA in FIG. 18
• FIG. 19B is a cross-sectional view along line XIXB-XIXB in FIG. 18,
• FIG. 19C is a cross-sectional view along line XIXC-XIXC in FIG. each shown.
• the workpiece 200 shown in FIGS. 16, 17A to 17C, 18 and 19A to 19C is a plate material made of aluminum.
• the amount of heat applied to the workpiece 200 is also periodically changed. Heat accumulation on the workpiece 200 is reduced.
• the width of the weld bead 300 can be made constant, and the width of the weld bead 300, that is, the side edges can be aligned. can.
• the penetration depth is constant and stabilized throughout the weld bead 300 along the welding direction WD.
• the work 200 can be irradiated with the laser beam LB while ensuring the heat input balance between the central portion and the side edge portions of the weld bead 300. Controllability of the shape of 300 can be improved.
• the beam diameter ⁇ and the power density PD of the laser light LB are obtained by a simple method of driving only the optical path changing mechanism 23 while keeping the output of the laser light LB incident on the optical fiber 40 constant. can be changed periodically. This simplifies control.
• the heat capacity of the work 200 also depends on the size of the work 200 itself. That is, when the size of the work 200 is small, the heat capacity of the work 200 is also small. Therefore, the laser welding method and laser welding apparatus 100 of the present embodiment are also useful when laser welding a work 200 having a small size.
• the control voltage V may be changed periodically between V1 and V3.
• the beam profile of the laser beam LB becomes pattern 1 shown in FIG. 5, that is, a top hat shape.
• the beam profile of the laser beam LB is pattern 0, not only is the spot diameter of the laser beam LB widened, but also the amount of heat input at the periphery of the spot can be increased.
• the keyhole may become unstable and the amount of spatter generated may increase.
• the laser welding method shown in this embodiment is useful. If the work 200 is made of pure aluminum, it has a low absorptivity for the laser beam LB and an oxide film is formed on the surface. Therefore, even if the laser beam LB is irradiated, it is difficult to easily form a molten pool and, by extension, a keyhole. In addition, since no molten pool is formed, the surface maintains a high reflectance of the laser beam LB.
• the absorption rate of the laser beam LB increases in the molten pool. Also, the laser beam LB is multiple-reflected within the keyhole. These things make it easier for the workpiece 200 to melt at once.
• the cycle of increasing the power density PD of the laser beam LB to melt the workpiece 200 and the cycle of decreasing the power density PD of the laser beam LB to suppress excessive melting of the workpiece 200 are performed. repeat. By doing so, a constant penetration depth can be easily obtained for the workpiece 200 having a high reflectance of the laser beam LB.
• the output of the laser beam LB may be changed in a pulsed manner.
• the laser beam LB can be output at a high level at the peak of the pulse with respect to the operation cost of the laser oscillator 10, so that the increase in the cost of laser welding can be suppressed.
• FIG. 20 shows the change over time of the control voltage of the piezo actuator according to this modification
• FIG. 21 shows the change over time of the power density of the laser light at the central portion of the weld bead.
• FIG. 22 shows another change over time of the control voltage of the piezo actuator
• FIG. 23 shows still another change over time of the control voltage of the piezo actuator.
• the change over time of the control voltage V shown in FIG. 20 is such that the base value of the control voltage V increases stepwise for a predetermined period from the start of welding. change and differ. Note that the peak value of the control voltage V is constant at V3.
• the base value of the control voltage V is changed stepwise from V0 to V1, but it is not particularly limited to this.
• the base value V of the control voltage V may be changed stepwise from V0 to a value between V1 and V2.
• the power density PD of the laser beam LB with which the workpiece 200 is irradiated also changes with time.
• the power density PD of the laser beam LB is decreased stepwise from PD3 to PD2.
• the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is set to a predetermined ratio R3 (hereinafter referred to as a third ratio R3) at the welding start point of the workpiece 200, and a predetermined laser welding is performed so as to gradually decrease to a ratio lower than the third ratio R3 (hereinafter referred to as a fourth ratio R4) until the welding length of .
• a predetermined ratio R3 hereinafter referred to as a third ratio R3
• a predetermined laser welding is performed so as to gradually decrease to a ratio lower than the third ratio R3 (hereinafter referred to as a fourth ratio R4) until the welding length of .
• the peak value of the control voltage V is constant at V3
• the value of the power density PD of the laser beam LB at the side edge portion of the weld bead 300 is also substantially constant.
• the heating of the workpiece 200 is insufficient immediately after the start of welding.
• the laser beam LB has a steep beam profile like pattern 0 shown in FIG.
• the penetration depth becomes deeper, and as described above, the width of the weld bead 300 may expand more than a predetermined width.
• the temperature in a small area of the work 200 rises sharply from a low temperature state, which may increase the frequency of spatter generation.
• the welding speed Vw is set to a predetermined value or more while the power density PD of the laser beam LB is suppressed to a predetermined value or less, insufficient penetration of the workpiece 200 may occur at the welding start point, resulting in poor welding. There is Moreover, there is a possibility that the shape of the weld bead 300 at the welding start point may be disturbed.
• the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is increased, and the power of the laser beam LB at the central portion of the weld bead 300 is increased.
• density PD By doing so, it is possible to secure the penetration depth at the welding start position and to suppress the shape of the weld bead 300 from being disturbed.
• gradually decreasing the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB it is possible to prevent the workpiece 200 from being heated more than necessary at the central portion of the weld bead 300. , the penetration depth and the shape of the weld bead 300 can be stabilized.
• the width of the weld bead 300 can be made constant, as in the second embodiment. Also, the edges of the weld beads 300 can be aligned. Also, the generation of spatter can be suppressed.
• the power density PD of the laser beam LB at the side edge portion of the weld bead 300 is reduced at the timing when the power density PD of the laser beam LB is decreased at the center portion of the weld bead 300. is increasing. This will be further explained.
• the penetration depth may gradually increase along the weld line WL.
• the width of weld bead 300 may gradually widen.
• the amount of heat input to the workpiece 200 can be periodically reduced by periodically varying the beam profile of the laser beam LB.
• the aforementioned problems caused by the heat trapped inside the workpiece 200 propagating to the surroundings that is, the gradual increase in the penetration depth and the gradual increase in the width of the weld bead 300 can be prevented. can be suppressed.
• the weld bead 300 can be formed so that the penetration depth and width are constant.
• the method of changing the state of heat input to the work 200 between the welding start point of the work 200 and other welding points is not limited to the example shown in FIG.
• the aforementioned duty ratio may be changed. That is, the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is the first period T1 in which the ratio is the above-described first ratio R1, and the duty ratio of the second period T2 in which the above-described second ratio R2 is The ratio (T1/(T1+T2) or T2/(T1+T2)) may be gradually changed. In addition, in the example shown in FIG. 20, the period (T1+T2) is kept constant.
• T1>T2 immediately after the start of welding of the work 200, and in the next cycle, while maintaining the relationship of T1>T2, the first period T1 is shortened from the previous cycle, Also, the second period T2 is lengthened. This process is repeated until the first period T1 and the second period T2 have substantially the same value.
• the width of the weld bead 300 can be made constant, and the width of the weld bead 300 can be made uniform.
• the method shown in this modified example is not applied only when welding of the workpiece 200 is started.
• the method shown in this Modification can be applied according to the heat capacity change, shape change, and material change of the work 200 during welding of the work 200 .
• the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is changed in at least two consecutive cycles.
• the ratio of the laser beam LB incident on the first core 41 to the output of the laser beam LB is the second
• the duty ratio between the first period T1, which is the 1 ratio R1, and the second period T2, which is the second ratio R2, is gradually changed.
• the penetration depth and the shape of the weld bead 300 can be stabilized.
• the width of the weld bead 300 can be made constant, and the width of the weld bead 300 can be made uniform.
• control voltage V may be controlled as shown in FIG. Note that times ta, tb, and tc shown in FIG. 21 are the same as those shown in FIG. Also, the first period T1 has the same value as the second period T2.
• control voltage V is periodically varied between V1 and V2 until time ta.
• the peak value of control voltage V is increased stepwise from V2 to V3.
• the time average of the power density PD of the laser beam LB can be lowered according to the increase in the gap. That is, an appropriate amount of heat input can be ensured for portions of the workpiece 200 where the heat capacity gradually decreases.
• the peak value of control voltage V is decreased stepwise from V3 to V2.
• the time average of the power density PD of the laser beam LB can be increased according to the reduction in the gap, and an appropriate amount of heat input can be ensured for the portion of the workpiece 200 where the heat capacity gradually increases.
• the control voltage V is periodically varied between V1 and V2.
• the welding speed Vw is changed in accordance with the change in the control voltage V and thus the power density PD of the laser beam LB during the control of the control voltage V shown in the second embodiment and this modified example.
• the power of the laser beam LB incident on the optical fiber 40 may be changed.
• FIG. 24 shows a schematic configuration diagram of a laser welding apparatus according to this embodiment
• FIG. 25 schematically shows periodic changes in the beam profile of laser light emitted from an optical fiber.
• a laser welding apparatus 100 of this embodiment shown in FIG. 24 differs from the laser welding apparatus 100 of Embodiment 1 shown in FIG. 1 in that it has a first laser oscillator 10 and a second laser oscillator 13 .
• the first laser oscillator 10 is the same as the laser oscillator 10 shown in FIG. 1, and is connected to the first power supply 81 and the laser control section 94 .
• the first power supply 81 is the same as the power supply 81 shown in FIG.
• the optical path of the first laser beam LB1 emitted from the first laser oscillator 10 is also the same as the optical path of the laser beam LB shown in FIG.
• the second laser oscillator 13 is arranged inside the housing 21 like the first laser oscillator 10 and is connected to the second power supply 82 and the laser control section 94 . Therefore, the output of the second laser beam LB2 emitted from the second laser oscillator 13 is controlled independently of the output of the first laser beam LB1.
• the second laser beam LB2 has the same wavelength as the first laser beam LB1. At least one of the first laser oscillator 10 and the second laser oscillator 13 may be arranged outside the housing 21 .
• the second laser beam LB2 is directly incident on the condenser lens 32, and is condensed by the condenser lens 32 on the incident end surface of the optical fiber 40, specifically the third core 45.
• the incident angle or the incident position of the second laser beam LB2 to the condenser lens 32 is adjusted so that the incident position of the second laser beam LB2 on the incident end face of the optical fiber 40 does not overlap with the incident position of the first laser beam LB1.
• a second shutter 35 is arranged in the focusing unit 30 so as to be movable between inside and outside the optical path of the second laser beam LB2.
• the second shutter 35 operates in conjunction with the first shutter 33 which is movable between the inside and outside of the optical path of the first laser beam LB1.
• the laser welding method shown in Embodiment 2 and the modified example can be executed more finely and accurately.
• the beam profile of the first laser beam LB1 periodically changes from pattern 1 to pattern 3 and from pattern 3 to pattern 1 shown in FIG. do.
• the second laser beam LB2 is periodically incident on the third core 45 during laser welding. That is, the laser beam LB that is incident on the optical fiber 40 and emitted from the optical fiber 40 includes the first laser beam LB1 and the second laser beam LB2.
• the beam profile of the laser beam LB changes periodically as shown in FIG.
• the control voltage V is V1
• the peak caused by the second laser beam LB2 is superimposed on the outer edge of the pattern 1 caused by the first laser beam LB1, as shown on the left side of FIG.
• the output of the second laser beam LB2 is controlled by the laser controller 94 so that the period during which the second laser beam LB2 is incident on the third core 45 coincides with the period during which the control voltage V is V1.
• the output of the second laser beam LB2 is controlled by the laser controller 94 so that the beam profile of the laser beam LB has the shape shown on the left side of FIG. That is, the second laser beam LB2 is set to have an output lower than that of the laser beam LB or a power density lower than the power density PD of the laser beam LB.
• the beam profile of the laser beam LB is pattern 3 due to the first laser beam LB1.
• the spot diameter of the laser beam LB can be expanded more than in the case shown in Modification 2, and the power density PD of the laser beam LB irradiated to the workpiece 200 can be changed to increase the spot size.
• Heat input at the periphery can be increased.
• the shape of the molten pool and the keyhole can be stabilized, and the occurrence of spatter can be suppressed.
• the penetration depth and the shape of the weld bead 300 can be stabilized.
• the width of the weld bead 300 can be made constant, and the width of the weld bead 300 can be made uniform.
• the output of the first laser beam LB1 and the output of the second laser beam LB2 can be independently controlled.
• the power density PD of the laser beam LB in other words, the input heat amount can be independently controlled at the central portion and the side edge portions of the weld bead 300 formed on the workpiece 200 .
• the sizes of the keyhole and the molten pool can be appropriately set according to changes in the shape of the work 200, changes in the heat capacity of the work 200, or changes in the material of the work 200, and their shapes can be stabilized.
• the shape of the weld bead 300 can be stabilized, and the shape of the weld bead 300 can be uniformed.
• the laser welding method according to this embodiment includes the following configurations.
• the laser beam LB includes a first laser beam LB1 and a second laser beam LB2 having a lower output than the laser beam LB or a lower power density than the power density PD of the laser beam LB.
• the first laser beam LB1 is incident on the first core 41, and the second laser beam LB2 is incident on the third core 45, respectively.
• the beam profile of the laser beam LB emitted from the optical fiber 40 is changed.
• the laser welding apparatus 100 further includes a laser control section 94 that controls outputs of the first laser beam LB1 and the second laser beam LB2 emitted from the first laser oscillator 10 and the second laser oscillator 13, respectively. ing.
• the optical path control unit 91 changes the power density PD of the laser light LB emitted from the optical fiber 40 by changing the incident position of the first laser light LB1 on the optical fiber 40 .
• the first laser beam LB1 is incident on the first core 41, and the second laser beam LB2 is incident on the third core 45, respectively.
• the laser control unit 94 may periodically turn on and off the second laser oscillator 13 .
• the laser control unit 94 is configured to change the beam profile of the laser light LB emitted from the optical fiber 40 by causing the second laser light LB2 to enter the third core 45 at predetermined intervals. ing.
• the second shutter 35 may be periodically opened and closed by the optical path control section 91 .
• the optical path control unit 91 is configured to change the beam profile of the laser light LB emitted from the optical fiber 40 by causing the second laser light LB2 to enter the third core 45 at predetermined intervals. ing.
• the second laser beam LB2 may be continuously output within a range that does not greatly affect laser welding. In that case, by setting the control voltage V to V3, in the beam profile of the laser beam LB, the peak due to the second laser beam LB2 is superimposed on the pattern 3 due to the first laser beam LB1.
• the second laser beam LB2 may be reflected by the optical path changing mechanism 23 and then incident on the condenser lens 32 . Also in this case, the incident position of the second laser beam LB2 on the incident end face of the optical fiber 40 is made different from the incident position of the first laser beam LB1. For example, the incident angle of the second laser beam LB2 with respect to the optical path changing mechanism 23 is made different from the incident angle of the first laser beam LB1.
• the first laser beam LB1 emitted from the first laser oscillator 10 may be partially branched between the return mirror 22 and the optical path changing mechanism 23 and used as the second laser beam LB2.
• a new embodiment can be created by appropriately combining the constituent elements shown in Embodiments 1 to 3 and Modifications 1 and 2. For example, it is possible to apply the laser welding method shown in the second embodiment to various workpieces 200 shown in the first modification.
• the workpiece 200 has a region in which at least one of the shape, heat capacity and material changes continuously or discontinuously in the course along the weld line WL.
• the workpiece 200 may be continuously irradiated with the laser beam LB at least either before or after welding the region, or at least after reaching the region.
• the laser beam LB is applied to the workpiece 200 at least either before or after welding the region, or at least after reaching the region, in a pulsed manner, in other words, intermittently.
• intermittently irradiating the workpiece 200 with the laser beam LB means not only irradiating the laser beam LB in a pulsed manner, but also the weld bead formed in the welded portion in the shape of a plurality of intermittent stitch-like seams. It may also include irradiating with a laser beam LB so as to form.
• the optical fiber 40 has a so-called three-layer core structure, in which the first to third cores 41, 43, and 45, is described as an example. core.
• the optical fiber 40 may have a structure having a first core 41 and a third core 45 or a structure having a first core 41 and a second core 43 .
• the beam profile of the laser beam LB can be changed during the welding of the workpiece 200 by changing the incident position P of the laser beam LB to the optical fiber 40 by the optical path changing mechanism 23 .
• Embodiments 1 to 3 and Modifications 1 and 2 when there is a region in which the shape of the work 200 changes in the path along the welding line WL, at least one of the front and rear of the region, or at least in the region An example is shown in which the beam profile of the laser beam LB is gradually changed after the peak is reached.
• the timing "at least after reaching the area” means immediately after reaching the area where the shape of the workpiece 200 changes, or after a predetermined time has passed after reaching the area. Includes timing.
• the laser welding method and laser welding apparatus 100 of the present disclosure are also useful in the following cases.
• FIG. 27 shows a schematic diagram for explaining the depression of the work formed at the welding end point.
• the illustration of the weld bead 300 is omitted in FIG. 27 .
• the amount of heat input to the workpiece 200 changes abruptly when the irradiation of the laser beam LB ends at the welding end point.
• the front along the weld line WL is not heated, heat tends to accumulate in the vicinity of the welding end point, increasing the temperature difference between the molten pool (not shown) and its surroundings. This occurs even when the shape, heat capacity, and material of the work 200 do not change during the course of the weld line WL.
• a recess 200a (see the broken line in FIG. 27) is formed in the workpiece 200 near the welding end point due to a rapid temperature change. There is The formation of the recess 200a impairs the appearance of the welded portion. In addition, there is a risk of attachment failure when attaching the welded workpiece 200 to another component.
• the laser welding device 100 to gradually change the beam profile of the laser beam LB before reaching the welding end point, the above problems can be eliminated or reduced.
• the beam of the laser beam LB is emitted from a predetermined position before reaching the welding end point that is the terminal end of the welding line WL. Gradually change the profile. In this case, the beam diameter ⁇ of the laser light LB is gradually increased.
• the output or power density PD of the laser light LB may be gradually decreased in synchronism with the change in the beam diameter ⁇ of the laser light LB.
• the unsteady period includes at least a predetermined period immediately after the start of welding of workpiece 200 and another predetermined period immediately before the end of welding.
• the penetration depth of the workpiece 200 can be ensured by narrowing the beam profile of the laser beam LB and increasing the power density PD.
• the beam profile of the laser beam LB is widened to widen the melting range of the workpiece 200, thereby reducing the planar size and depth of the recess 200a.
• the steady period is the period during which the workpiece 200 is welded, excluding the steady period described above. That is, the steady period excludes at least a predetermined period immediately after the start of welding of the workpiece 200 and another predetermined period immediately before the end of welding.
• the beam profile of the laser beam LB is gradually narrowed. Furthermore, the output of the laser beam LB is reduced to make the power density PD less than or equal to a predetermined value. By doing so, it is possible to suppress excessive heat accumulation in the workpiece 200 and form the weld bead 300 having a constant width.
• the laser welding method of the present disclosure is useful because it can weld workpieces that change in shape, heat capacity, or material without causing perforation or insufficient penetration.
• laser oscillator (first laser oscillator) 11 laser module 12 laser light combiner 13 second laser oscillator 20 optical coupling unit 21 housing 22 folding mirror 23 optical path changing mechanism 24 mirror 25 piezo stage 26 piezo actuator (actuator) 30 condensing unit 31 housing 32 condensing lens 33 shutter (first shutter) 34 beam damper 35 second shutter 40 optical fiber 41 first core 42 first clad 43 second core 44 second clad 45 third core 46 third clad 47 protective coating 50 laser head 60 stage 70 robot 81 power source (first power source) 82 second power supply 91 optical path control unit 92 stage control unit 93 robot control unit 94 laser control unit 100 laser welding device 200 workpiece 200a recesses 201 to 209 first to ninth members 300 welding bead

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• 2023
  • 2023-02-01 JP JP2023578584A patent/JPWO2023149458A1/ja active Pending
  • 2023-02-01 WO PCT/JP2023/003173 patent/WO2023149458A1/ja not_active Ceased
  • 2023-02-01 CN CN202380019475.2A patent/CN118742409A/zh active Pending

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