JP2000107876A - Laser beam welding method and laser beam welding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a stable key hole along a weld line, to reduce a blow hole/bubble and to prevent welding strength from lowering at a continuous traveling welding time by moving a laser beam along a place to be welded while vibrating a focus position of a laser beam for welding in the welding depth direction. SOLUTION: It is preferable that laser beams are simultaneously irradiated from two directions and two vibration frequencies in the welding depth direction are made equal. A phase difference of the vibration frequencies of two laser beams are set to zero, the center position of vibration of each laser beam is set to a different position. By collecting first/second laser beams A, B from welding laser beam output parts 1, 2 with beam collecting optical systems 4, 6, an object 100 to be welded is machined. The focus positions of the laser beams A, B are vibrated by modified mirrors 41, 61 (vibration energizing means) of the beam collecting optical systems 4, 6, the vibration switches the reflection face switched to a concave/convex face with a piezo element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser welding method and a laser welding apparatus, and more particularly, to a laser welding method and a laser welding method in which a welding laser beam is relatively moved along a welding line which is a portion to be welded. Related to the device.

[0002]

2. Description of the Related Art In laser welding, a laser beam is applied to a portion to be welded, such as a metal plate, which is a workpiece to be welded, and welding can be performed with a narrow welding width. Its development is underway.

[0003] In conventional laser welding, the focus of a welding laser beam is positioned at a welding start position of a portion to be welded, and the laser output is adjusted so that the focal position relatively moves along a welding line at the portion to be welded. This is performed by moving the means or the workpiece. At this time, welding was performed at a constant welding depth (depth along the direction in which melting proceeds from the laser irradiation surface of the workpiece) at the focal position of the welding laser beam.

[0004]

In the above laser welding, a keyhole is formed on the laser irradiation surface of the workpiece,
The material constituting the object to be welded is melted inside, the welded portion is filled, and welding is performed. However, in the conventional laser welding, a keyhole may be generated unstably along a welding line (a line along a portion to be welded). That is, when the workpiece moves relatively to the welding laser beam, the size of the keyhole changes, and the size does not become constant.

[0005] In such a case, blowholes or bubbles may be generated in the welded portion at the time of welding, and there is a possibility that the welding strength may be reduced.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser welding method and a laser welding apparatus which can solve the disadvantages of the prior art and, in particular, can produce a stable keyhole along a welding line during continuous moving welding. Aim.

[0007]

In order to achieve the above object, according to the present invention, there is provided a laser welding method in which a welding laser beam is relatively moved along a portion to be welded. Is made to vibrate in the welding depth direction to perform welding.

In the laser welding method, the welding laser beam may be simultaneously irradiated from two directions, and the welding cycle may be made equal in the welding depth direction of each of the welding laser beams. The welding may be performed by setting the phase difference of the oscillation cycle of the welding laser beam to 0 and setting the center position of the oscillation of each welding laser beam to a different position in the welding depth direction. Further, the welding may be performed by equalizing the amplitudes of the respective welding laser beams in the welding depth direction.

In the above laser welding method, when the focal position of the laser moves relative to the work to be welded along the portion to be welded, the focal position is moved at a constant cycle to the welding depth (weld depth). Welding is performed by vibrating the object from the laser irradiation surface in a direction (depth along the direction in which melting proceeds).

In general, the change of the keyhole along the welding line may be based on a certain period that fluctuates under the influence of the material, thickness, laser intensity and the like of the workpiece.
By fluctuating the welding laser beam at regular intervals, it positively interferes with the periodic changes of the keyhole,
The welding state is stabilized.

At this time, if the fluctuation period of the keyhole is known by a test or investigation, in order to avoid resonance, the known wave period and the vibration period of the vibration urging means are set to different periods. May be set.

Alternatively, the cycle of the fluctuation of the keyhole and the cycle of the vibration of the vibration urging means are set to be equal to each other, and the depth of the welding laser beam is reduced in accordance with the increase of the keyhole. The wave of the fluctuation is eliminated, and the welding state is stabilized.

Further, according to the present invention, in a laser welding apparatus which relatively moves a welding laser beam along a portion to be welded, a welding laser output section for emitting a welding laser beam, a welding laser beam, A focusing beam optical system that focuses the laser beam in accordance with the focal position of the laser beam, wherein the focusing beam optical system includes a vibration biasing unit that vibrates the focal position of the welding laser beam in the welding depth direction. It has a configuration of preparing.

The laser welding apparatus has two welding laser output units, has a converging beam optical system individually corresponding to each welding laser output unit, and vibrates each converging beam optical system. Control means for controlling the operation of the urging means may be provided, and the control means may have a cycle uniforming function for equalizing the vibration cycle of each vibration urging means.

In addition, the converging beam optical system sets the center position of the vibration of each welding laser beam to a different position in the welding depth direction, and the control means controls the vibration period of each vibration urging means. A configuration having a phase equalizing function of setting the phase difference to 0 may be adopted.

Furthermore, it is desirable to set the amplitude of the vibration of each vibration urging means of each of the condensed beam optical systems to be uniform.

In any configuration, it is preferable that the above-mentioned vibration urging means has a variable mirror for a welding laser beam having a reflecting surface which is repeatedly switched between a concave surface and a convex surface at a constant period.

In the laser welding apparatus described above, a welding laser beam is emitted from the welding laser output section, and is focused by the focusing beam optical system at the welding start position of the portion to be welded.

When the focal position of the laser moves relative to the workpiece along the portion to be welded, the focal position is periodically moved by the vibration urging means to the welding depth (the workpiece to be welded). (Depth along the direction in which melting progresses from the laser irradiation surface) to positively interfere with the welding depth wave generated in a non-vibration state, thereby stabilizing the welding state.

At this time, as in the case of the above-described laser welding method, if the fluctuation period of the keyhole is known by a test or inspection, the known wave period and vibration are used to avoid resonance. The cycle of the vibration of the urging means may be set to a different cycle.

Alternatively, the cycle of the fluctuation of the keyhole and the cycle of the vibration of the vibration urging means are set to be equal to each other, and the depth of the welding laser beam is reduced when the keyhole becomes large, so that the mutual depth can be reduced. The wave of the fluctuation is eliminated, and the welding state is stabilized.

The present invention seeks to achieve the above-described objects by the above-described configurations.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

The present embodiment, as shown in FIG. 1, is a laser welding apparatus 10 which relatively moves a welding laser beam along a portion to be welded of a workpiece 100, and comprises a first and a second laser welding apparatus. The two welding laser output units 1 and 2 for emitting the two welding laser beams A and B, respectively, and the respective focal positions of the welding laser beams A and B are respectively focused on the welded portion. Two condensing beam optical systems 4 and 6, each welding laser output unit 1 and 2, and each condensing beam optical system 4 and 6
And a moving stage 7 that holds the workpiece 100 and conveys the workpiece 100 in a direction e along the location to be welded.

The welding laser output units 1 and 2 are fixedly mounted on the upper end of the beam focusing case 5 with the laser emitting direction facing downward. A YAG laser is used for each of the laser output units 1 and 2 for welding. The output beams of the welding laser output units 1 and 2 are applied to the welding position on the workpiece 100 being moved via the respective converging beam optical systems 4 and 6. This laser welding device 10
In the above, the workpiece 100 is moved by the moving stage 7, but the workpiece 100 may be fixed and the entire beam focusing case 5 may be moved.

Inside the beam focusing case 5 and below each of the welding laser output sections 1 and 2, there are provided focused beam optical systems 4 and 6, respectively. Optical system for each focused beam 4, 6
Are variable mirrors 41, 61 as vibration urging means for vibrating the focal positions of the welding laser beams A, B in the welding depth direction f, and the welding lasers reflected by the variable mirrors 41, 61, respectively. The focusing mirrors 42, which reflect the beams A and B toward the welded portion of the workpiece 100, respectively.
62.

Each of the deformable mirrors 41, 61 is located at the end of the welding laser beams A, B of the welding laser output units 1, 2 in the emission direction, and has a reflection surface 41a, 61a. Each of these reflecting surfaces 41a,
61a is flexible, and each of the variable mirrors 41, 6
1 and behind each of the reflecting surfaces 41a and 61a,
Piezo elements 41b and 61b are provided respectively.

Since these piezo elements 41b and 61b expand and contract by application of a voltage, each reflecting surface 41b
a and 61a are pulled or pressed from behind to deform into a concave, flat or convex state. FIG. 2A shows a state in which the reflecting surfaces 41a and 61a are concave. In this case, the reflected light is collected, and the focal length of the collecting mirrors 42 and 62 is reduced. FIG. 2B shows a state in which the reflecting surfaces 41a and 61a are flat. In this case, the laser light is reflected as it is,
The focal length by the condenser mirrors 42 and 62 is longer than in the case of FIG. FIG. 2C shows the reflection surfaces 41a and 61a.
Indicates a convex surface state. In this case, the reflected light is diffused, and the focal length by the condenser mirrors 42 and 62 becomes longer than that in the case of FIG.

Therefore, these variable mirrors 41, 61
By applying an oscillating voltage to each of the piezo elements 41b and 61b, the respective reflecting surfaces 41a and 61a can be vibrated, and the positions of the focal points where the welding laser beams A and B are collected are vibrated. It has become possible.

Each of the above condenser mirrors 42 and 62 is a parabolic mirror whose reflection surface has a sectional shape along a parabola, and its focal length is set to 254 [mm]. These are fixedly mounted on the beam focusing case 5 at the respective destinations of the welding laser beams A and B reflected by the variable mirrors 41 and 61, respectively. , B are reflected on the workpiece 100 fixed on the moving stage 7.

Each of these condensing mirrors 42 and 62 condenses each of the welding laser beams A and B at substantially the same location of the object 100 to be welded.
2 and 62, each welding laser beam A,
The focal position of B (the focal position is vibrated by each of the deformable mirrors 41 and 61, but the position that becomes the center of the vibration) is on the line along the welding depth direction f and somewhat on the line The direction of each of the condenser mirrors 42 and 62 is set so as to be shifted (the shift amount is 1 to 5 [mm]). That is, the focal position of the welding laser beam A is set to be slightly lower than the focal position of the welding laser beam B.

The traveling directions of the welding laser beams A and B reflected by the condensing mirrors 42 and 62 coincide with the welding vibration direction f (a direction substantially perpendicular to the upper surface of the workpiece 100). The direction of each of the condenser mirrors 42 and 62 is set as described above (in FIG. 1, both are drawn in an inclined manner for convenience of illustration, but are actually in a vertical direction).

The distance from the above-mentioned welded portion to each of the condenser mirrors 42 and 62 is set so as to be approximately the above-mentioned focal length.

Next, the beam condensing case 5 is a box having an open upper and lower part, and the upper opening 5a is provided with the laser output units 1 and 2 for welding as described above. The lower opening 5b is provided at a position facing the workpiece 100 on the moving stage 7, and the welding laser beams A and B reflected by the condensing mirrors 42 and 62 described above are used for the welding. The workpiece 100 is irradiated through the opening 5b.

The beam condensing case 5 is supported by a supporting member 51 shown by a two-dot chain line so that both ends are positioned on the moving stage 7.
Has a focus position adjustment mechanism (not shown) for holding the beam condensing case 5 so as to be able to move up and down so as to be separated from and close to the moving stage 7 and to be able to reciprocate in the front and back directions on the paper.

The above-described moving stage 7 has a mounting table 71 on which an object to be welded is mounted on its upper part.
A fixing means 72 having a vise structure for fixing the workpiece 100 is provided above. The mounting table 71 is held on a guide rail 73 for transporting the workpiece 100 along the location to be welded. That is, the mounting table 71 is movably engaged along the guide rail 73, and a moving urging means (not shown) for moving the mounting table is provided near the mounting table 71. With such a configuration,
The workpiece 100 on the mounting table 71 is conveyed along the direction e at a constant speed externally input. When the workpiece 100 is fixed on the mounting table 71, the workpiece 100 is fixed so that the transport direction coincides with the direction along the welding location.

Further, although not shown in FIG. 1, the laser welding apparatus 10 is, as shown in FIG. 3, a control means 8 for controlling the operation of the above-mentioned variable mirrors of the condensing beam optical systems 4, 6. It has. The control means 8 includes a vibration waveform generating means 81 that receives an external input and creates a vibration waveform at an arbitrary frequency, an interface 82 that converts the vibration waveform into a signal, and outputs the signal.
A controller 83 for applying an oscillating voltage to the piezo elements 41b of the first and the first 61 (the variable mirror 61 is not shown in FIG. 3)
And a configuration including:

The vibration waveform generating means 81 has a period equalizing function for equalizing the vibration periods of the variable mirrors 41 and 61 and a phase difference between the vibration periods of the variable mirrors 41 and 61 of 0.
And a phase equalizing function for setting the phase uniformity. Further, the vibration waveform generating means 81 is provided with an amplitude equalizing function for equalizing the amplitudes of the reflecting surfaces 41a and 61a of the variable mirrors 41 and 61 via the controller 83.

The vibration waveform generating means 81 has an operation panel (not shown) for inputting a vibration frequency and an amplitude, and can input a frequency and an amplitude corresponding to a material and a thickness of a workpiece. When such a numerical value is input, the focus of each of the welding laser beams A and B vibrates in the welding depth direction f while maintaining a uniform interval at the welded position by the above functions (FIG. 4). ).

The operation of the laser welding apparatus 10 will be described below.

First, the workpiece 10 is placed on the moving stage 7.
0 is fixed so that the direction of the welded portion coincides with the direction of the guide rail 73. Further, the beam focusing case 5 is positioned by the welding position adjusting mechanism so that the respective welding laser beams A and B are irradiated onto the welding position. Further, a predetermined frequency and amplitude are input to the vibration waveform generating means 81.

Next, the outputs of the welding laser beams A and B from the welding laser output units 1 and 2 and the movement of the workpiece 100 by the moving stage 7 are simultaneously started. Thereby, the laser beams A and B for welding are simultaneously irradiated along the welded portion, and welding is performed.

At the time of such welding, the focal position of each of the welding laser beams A and B oscillates at a position to be welded while maintaining a uniform interval on a straight line along the same welding vibration direction (see FIG. 3). ) Welding is performed.

Thus, even if the keyhole changes along the welding line during welding, the focal positions of the welding laser beams A and B fluctuate at a constant period along the welding depth direction f. It positively interferes with the periodic change of the keyhole, and stabilizes the welding state.

If tests and investigations show that the keyhole fluctuates based on a certain period due to the influence of the material, thickness, laser intensity and the like of the workpiece 100, resonance is avoided. Therefore, a cycle different from the known cycle of the wave may be input to the vibration waveform generating means 81.

Alternatively, the cycle of the fluctuation of the keyhole and the cycle of the vibration of each of the deformable mirrors 41 and 61 are set to be equal, and the depth of the welding laser beams A and B is adjusted in accordance with the size of the keyhole. By making it shallow, the waves of mutual fluctuation may be canceled out to stabilize the welding state.

The above-described condensing mirrors 42 and 62
Is set so that the vibration centers of the oscillating focal points of the respective welding laser beams A and B are slightly displaced along the welding depth direction f, but they may be set so that these focal positions coincide. . In this case, the waveform generator 81 described above includes:
In place of the phase equalizing function, it is desirable to provide a phase difference setting mechanism that sets the phase difference of the oscillation cycle of each of the variable mirrors 41 and 61 to π (shifts by a half cycle). Thus, welding is performed while the focal positions of the welding laser beams A and B alternately move up and down (FIG. 5).

[0048]

As described above, according to the present invention, even when the keyhole changes along the welding line during welding and becomes unstable, the focal position of the welding laser beam is shifted in the welding depth direction. Therefore, the welding state is positively interfered with the periodic change of the keyhole, thereby stabilizing the welding state.

Therefore, there is provided an unprecedented excellent laser welding method and laser welding apparatus capable of reducing blowholes and bubbles generated in a welded portion at the time of welding and effectively avoiding the influence of a decrease in welding strength. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a laser welding apparatus according to the present invention.

FIGS. 2A and 2B are diagrams showing changes in the reflecting surface of the variable mirror disclosed in FIG. 1, wherein FIG. 2A shows a state in which the reflecting surface is concave, and FIG. 2B shows a state in which the reflecting surface is flat; The state is shown in FIG.
(C) shows a state in which the reflection surface is convex.

FIG. 3 is a block diagram showing a control system of the laser welding apparatus disclosed in FIG.

FIG. 4 is an explanatory view showing each welding laser beam whose focal position oscillates at the same frequency, the same phase, and the same amplitude.

FIG. 5 is an explanatory diagram showing each welding laser beam whose focal position oscillates in a state where the phase is shifted by a half cycle at the same frequency and the same amplitude.

[Explanation of symbols]

 1, laser output unit for welding 4, 6 optical system for condensed beam 8 control means 10 laser welding device 41, 61 variable mirror (vibration biasing means) 41a, 61a reflection surface 100 workpiece A first welding Laser beam for welding B Second laser beam for welding

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B23K 26/06 B23K 26/06 Z

Claims (9)

[Claims] 1. A laser welding method in which a welding laser beam is relatively moved along a portion to be welded, wherein the welding is performed by vibrating a focal position of the welding laser beam in a welding depth direction. Laser welding method. 2. The welding according to claim 1, wherein the welding laser beam is simultaneously irradiated from two directions, and welding is performed while making the oscillation cycle of each welding laser beam in the welding depth direction equal. Laser welding method. 3. The welding is performed by setting the phase difference of the vibration cycle of each of the welding laser beams to 0 and setting the center position of the vibration of each of the welding laser beams to a different position in the welding depth direction. The laser welding method according to claim 2, wherein: 4. The laser welding method according to claim 2, wherein the welding is performed while equalizing the amplitude of each of the welding laser beams in the welding depth direction. 5. A laser welding apparatus which relatively moves a welding laser beam along a portion to be welded, comprising: a welding laser output section for emitting the welding laser beam; and a focus of the welding laser beam. A converging beam optical system for converging a position in accordance with the position to be welded, wherein the converging beam optical system vibrates a focal position of the welding laser beam in a welding depth direction. A laser welding apparatus comprising: 6. A laser beam output unit for welding, comprising: a plurality of laser output units for welding; wherein said optical system for converging beams individually corresponds to each of said laser output units for welding; 6. The laser welding apparatus according to claim 5, further comprising control means for controlling operation of the urging means, wherein the control means has a period uniforming function for equalizing the vibration periods of the respective vibration urging means. 7. The converging beam optical system sets a center position of the vibration of each of the welding laser beams at a different position in the welding depth direction, and the control unit controls the vibration of each of the vibration urging units. 7. The laser welding apparatus according to claim 6, further comprising a phase equalizing function of setting a phase difference of a period to zero. 8. The laser welding apparatus according to claim 6, wherein the amplitude of the vibration of each of the vibration urging means is set to be uniform. 9. A welding mirror according to claim 5, wherein said vibration urging means includes a variable mirror for said welding laser beam, said mirror having a reflecting surface which is repeatedly switched between a concave surface and a convex surface at a constant period. 9. The laser welding apparatus according to 7 or 8.