DE19947104C2 - Method and apparatus for laser welding - Google Patents

Description

The present invention relates to a laser welding method and a laser welding device, and in particular a Laser welding method and a laser welding device, at which a laser welding beam relative to a welding line is moved, where to be welded, according to the The preambles of claims 1 and 3.

Such a laser welding method or such Laser welding device is already known for example from DE 42 17 705 A1 known. This method is already the Focal point of a laser source in the direction of the welding depth in Oscillation. From the document DE 40 33 166 A1 is already a method and a device known, wherein a pulsed laser beam to a CW laser beam with the help a beam coupler is coupled. The two rays are focused together. From the document GB 217 57 37 A is already known, in addition to a YAG laser one To provide CO2 laser. From the post-published DE 199 33 825 A1, it is already known, the Foci of two laser beams depending on one Adjust sensor signal.

Laser welding is performed by using a laser beam at a welding position of a metal to be welded  is used. Laser welding was for the reason developed that laser welding with a very low Width can be performed.

The conventional laser welding is carried out by that the laser beam focal point on a welding start position the welding position is placed, and a relative movement the laser output unit or the to be welded Object is carried out. This became the focal point the welding laser beam to a predetermined welding depth set the object to be welded.

In the above-described laser welding is a Keyhole formed on the object to be welded,  and in this keyhole becomes material from which the Subject is melted to the keyhole too fill, whereby the welding is completed. In which conventional laser welding, however, are keyholes, which are formed along a weld line, unstable, and their dimensions are not the same.

In this case, a blow hole or a bubble is attached to the welding position produces what the welding strength impaired.

The object of the present invention is therefore in the Providing a laser welding process and a Laser welding device, with which stable keyholes can be generated along a weld line.

According to the invention, this object is achieved by the features of Claims 1 and 3 solved.

To achieve the above-described advantage is in the present invention, a welding laser beam relative moved along a welding position while holding the Focus of the welding laser beam in the direction of Sweat depth can swing.

In the above-described laser welding method become two welding laser beams at a welding position used. In addition, it is possible the Vibration cycles of the welding laser beams in the direction of Weld depth to select identical. In addition, that will Welding with the welding laser beams with an identical Vibration cycle carried out in the direction of the weld depth.  

In the above-described laser welding method is welding along a welding line, while focussing in the direction of the weld depth swinging.  

In general, the keyhole changes along the Welding line depending on the material and the thickness an object to be welded, as well as in Dependence on the laser intensity. This Keyhole change can be cyclic. This cyclical Change can be caused by the cyclical change of Welding laser beams are compensated.

If in a trial or an investigation a Keyhole fluctuation cycle has exposed to Turn off a resonance of the vibration cycle of Schwingungsbeaufschlagungseinheit on a different Value to be set.

Alternatively, it is also possible the Keyhole fluctuation cycle and the oscillation cycle of Vibration applying unit to the same value adjust and then if the dimensions of the Keyhole increase, the depth of the Welding laser beam chosen lower. That way you can Fluctuations are compensated, causing the welding condition is stabilized.

Furthermore, according to the present invention, a Laser welding device for performing welding for Provided while a relative movement of Welding laser beams is performed on a Welding position are used, the device comprising: a welding laser output unit for emitting a laser beam for welding; a beam collection optical system for collecting the welding laser beam at the welding position, wherein the optical system is a Schwingungsbeaufschlagungseinheit  having the focal point of the welding laser beam in Directed to the welding depth vibrated.

The above-described laser welding device has on: two such welding laser output units for respective emission of a laser beam for welding; two the beam collection optical systems according to the Welding laser output units; and a controller for controlling the operation of the Schwingungsbeaufschlagungseinheiten the Strahlsammeloptiksysteme, wherein the control a Cycle union function, which ensures that the vibration cycles of the vibration applying units become identical.

Furthermore, the beam collection optical system can Welding laser beam vibration centers at different Set positions in the direction of the weld depth, and can the controller is a phase equalization function which ensures that the phase difference of the Vibration applying device set to zero becomes.

Furthermore, the amplitudes of the Vibration application units for the Beam collection system selected identically.

Furthermore, it is preferable that the Vibration application units variable mirrors each having repeated in the concave, plane, and convex state can be offset to the Reflect welding laser beam.  

In the above-described laser welding device when welding, send the welding laser output units Welding laser beams passing through the Beam collection optical system collected at the welding start position become.

When the laser focal points move relative to each other along the Welding line, the foci are through the Vibration applying units with a predetermined Cycle in the direction of the welding depth vibrated. As a result, a ripple of the welding depth counteracted, which occurs without vibrations, and becomes the Welding state stabilized.

Here it is possible, as already related to the welding laser method has been described when the Keyhole fluctuation cycle from a trial or a trial Investigation is known to turn off the resonances the Schwingungsbeaufschlagungseinheit on a different Cycle set.

Alternatively, it is also possible the Keyhole fluctuation cycle and the oscillation cycle of Schwingungsbeaufschlagungseinheit to choose the same, and the Set the depth of the welding laser beam lower when the Keyhole gets bigger. This is the same Ripples from each other, causing the welding condition is stabilized.

The invention will be described below with reference to the drawing illustrated embodiments explained in more detail, from which further benefits and features emerge. It shows:  

Fig. 1 shows a structure of a laser welding device according to an embodiment of the present invention;

Fig. 2 shows a change of a reflection surface of a variable mirror 41 ( 61 ) shown in Fig. 1; FIG. 2A shows a concave reflecting surface, FIG. 2B shows a plane reflecting surface, and FIG. 2C shows a convex reflecting surface;

Fig. 3 is a block diagram of a control system of the laser welding apparatus shown in Fig. 1;

Fig. 4 welding laser beams whose focal points are vibrated at an identical frequency, with identical phase, and identical amplitude;

Fig. 5 shows welding laser beams whose focal points are oscillated with identical frequency and identical amplitude, but with a phase difference of half a cycle; and

Fig. 6 is a block diagram of a laser welding device which can mix two laser beams coaxially.

A laser welding apparatus 10 according to the present invention performs relative movement of the welding laser beams along a welding line on an object 100 to be welded. The welding laser device 10 comprises: two welding laser output units 1 and 2 for emitting a welding laser beam A and B, respectively; two beam focusing optical systems 4 and 6 for adjusting the focal points of the welding laser beams A and B at a welding position; a beam collecting case 5 for holding the laser output units 1 and 2 and the two beam focusing optical systems 4 and 6 ; a movement stage 7 for supporting and feeding the object 100 to be welded in the direction "e" along the welding positions.

The welding laser output units 1 and 2 are mounted on the top of the beam collecting case 5 so that the jet emitting direction faces downward. These welder laser output units 1 and 2 use YAG lasers. The welding laser output units emit laser beams which are applied via the respective beam focusing optical system 4 or 6 to the welding position of the object 100 to be welded. In this laser welding device 10 , the object 100 to be welded is transported through the movement stage 7 . However, it is also possible to hold the object to be welded 100 while the entire beam collecting housing 5 is moved.

Each of the beam focusing optical systems 4 and 6 comprises: a variable mirror 41 , 61 as a vibrating unit for vibrating the foci of the welding laser beams A, B in the direction "f" of the welding depth (see Fig. 3); and a collecting mirror 42 , 62 for applying the welding laser beams A, B reflected by the variable mirrors 41 , 61 to the object to be welded 100 .

Each of the variable mirrors 41 , 61 has a reflection surface 41 a, 61 a for reflecting the welding laser beam A and B, respectively. These reflection surfaces 41 a and 61 a are flexible, and behind the respective reflection surface 41 a and 61 a, a piezoelectric element 41 b and 61 b is provided.

When a voltage applied to the piezoelectric elements 41 b, is applied b 61, the piezoelectric elements 41 expand b, 61 b and contract together, whereby a print or a train on the reflecting surfaces 41 a and is applied 61 so that the Reflection surfaces assume a convex, planar, or concave state. Fig. 2A shows the reflection surface 41 a ( 61 a) in the convex state. In this state, the reflected beam is collected, and the focal length due to the condensing mirror 42 ( 62 ) becomes shorter. Fig. 2B shows the reflection surface 41 a ( 61 a) in the planar state. In this state, the reflected beam is reflected as it is, and the focal length becomes longer due to the condensing mirror 42 ( 62 ) than in FIG. 2A. Fig. 2C shows the reflection surface 41 a ( 61 a) in the convex state. In this state, the reflected beam is scattered, and the focal length becomes longer due to the condensing mirror 42 ( 62 ) than in FIG. 2B.

Therefore, this variable mirrors 41 and 61 their reflecting surfaces 41 a and 61 a thereby vibrate that an oscillating voltage to the piezoelectric elements 41 b and b is applied 61st As a result, the foci of the welding laser beams A and B can be vibrated.

Each of the collecting mirrors 42 and 62 is a parabolic mirror whose cross section is a parabola and whose focal length is set to 254 mm. The collecting mirrors are fixed to the beam collecting case 5 so as to reflect the welding laser beams A and B on the object 100 to be welded, which is fixed to the moving stage 7 .

These collecting mirrors 42 and 62 collect the welding laser beams A and B almost at the same welding position. Strictly speaking, however, the directions of the collecting mirrors 42 and 62 are set so that the focal points of the welding laser beams A and B (at the vibration center) are slightly spaced in the direction f of the welding depth (1 to 5 mm). Therefore, the focal point of the welding laser beam A is slightly lower than the focal point of the welding laser beam B.

Further, the welding laser beams A and B reflected by the collecting mirrors 42 and 62 , respectively, have almost identical feeding directions, namely, actually approximately vertical to the upper surface of the object to be welded (although slightly oblique in Fig. 1).

In addition, the distances from the object to be welded to the converging mirrors 42 and 62 are set to the above-mentioned focal distance.

The beam collecting housing 5 is formed as a box having an opening at the top and bottom. In the upper opening 5 a, the welding laser output units 1 and 2 are provided. The lower opening 5 b is disposed at a position opposite to the object to be welded 100 on the movement stage 7 . The welding laser beams A and B, which are reflected by the collecting mirror 42 and 62 , respectively, are applied to the object 100 to be welded through this opening 5 b.

Furthermore, the beam collecting housing 5 is supported by support members 51 which are indicated by double-dotted, dashed lines, so that the two ends of the housing 5 are supported on the movement stage 7 . The support members 51 support the beam collecting housing 5 so that it can be moved in the vertical direction and forward and backward.

The movement stage 7 has a table 71 , on which the object to be welded is placed; and a fixing unit 72 having a clamping arrangement for fixing the object 100 to be welded. The table 71 is supported on a guide rail 73 so that the object 100 to be welded can be moved along the welding positions. The table 71 is thus engaged with the guide rail 73 so that the table 71 can move along the guide rail 73 .

Furthermore, a Bewegungsbeaufschlagungseinheit (not shown) is provided in the vicinity. The object to be welded 100 , which is placed on the table 71 , is moved at a predetermined speed in the direction "e". It should be noted that the object 100 to be welded is placed on the table 71 so that the feed direction matches the arrangement of the welding positions.

Further, as shown in FIG. 3, the laser welding device 10 has a controller 8 for controlling the operation of the variable mirrors 41 and 61 of the collection optical systems 4 and 6 . This control unit 8 comprises: a vibration generator 81 for receiving an external input and for generating a vibration waveform having a predetermined frequency; an interface 82 for converting the waveform to an output; and a controller 83 for receiving said signal and for applying an oscillating voltage to the piezoelectric element 41b (61b) of the variable mirror 41 (61).

The vibration generator 81 includes: a cycle equalization function that makes the vibration cycles of the variable mirrors 41 and 61 equal; and a phase equalization function that makes the oscillation cycle phase difference of the variable mirrors 41 and 61 equal to zero. Furthermore, the oscillation generator 81 has an amplitude equalization function which ensures that the amplitudes of the reflection surfaces 41 a and 61 a of the variable mirrors 41 and 61 via the controller 83 are identical.

This vibration generator has an operation field (not shown) with which an oscillation frequency and a vibration amplitude can be input. The frequency and the amplitude can be entered according to the material and the thickness of the object to be welded. When a certain frequency value and a certain amplitude value are input, the above-described functions work so that the foci of the welding laser beams A and B oscillate at a welding position in the direction "f" of the welding depth while maintaining an identical interval ( FIG. 4).

Next, the operation of the above-described laser welding device 10 will be described.

First, an article to be welded 100 is placed on the movement stage 7 and fixed there so that the arrangement of the welding positions is adapted to the direction of the guide rails 73 . Further, the beam collecting case 5 is disposed using a welding position adjusting mechanism so that the welding laser beams A and B are directed to a welding position of the object 100 . In addition, a frequency value and an amplitude value are input to the vibration generator 81 .

Next, the discharge of the welding laser beams A and the welding laser output units 1 and 2 is started simultaneously with the start of the movement of the object 100 at the movement stage 7 . In this way, the welding laser beams A and B are simultaneously applied along the welding positions for performing the welding operation.

As shown in Fig. 4, the foci of the welding laser beams A and B oscillate while maintaining a predetermined interval on the line along the welding vibration direction.

Even if the keyholes along the weld line This has been changed by the cyclical modification of the Focal points of the welding laser beams A and B in direction "f" the welding depth compensated. This will be a stable Welding process achieved.

In a case where the keyholes fluctuate periodically according to the material and the thickness of the object 100 or the laser intensity, it is possible to cancel a resonance to input a cycle (a periodicity) different from the known cycle of the keyhole, into the vibration generator.

Alternatively, it is possible to set the vibration cycle of the variable mirrors 41 and 61 to be identical to the keyhole fluctuation cycle, and then, as the keyhole becomes larger, to make the depth of the welding laser beams A and B smaller so as to achieve a stable welding operation.

It should be noted that the above-described collecting mirrors 42 and 62 are set so that the welding laser beams A and B have vibration centers at different depths. However, it is also possible to adjust the collecting mirrors 42 and 62 so that the foci are at the same position. In this case, the oscillation generator 81 preferably has a phase difference adjusting mechanism instead of the phase equalizing function, so that the oscillation cycles of the variable mirrors 41 and 61 are shifted from each other by π (half a cycle). In this way, the welding is performed so that the foci of the welding laser beams A and B are alternately moved up and down ( Fig. 5).

As described above, according to the present Invention, even if a keyhole change which leads to instability of the Welding process leads this through the periodic Fluctuations of the focal points of the welding laser beams in Direction of welding depth compensated.  

As a result, blow holes and bubbles can be reduced, the be generated at the welding position, causing a sinking the sweat intensity is switched off.

Claims (5)

A laser welding method of performing a welding operation while relatively moving a welding laser beam along a welding position to be welded, wherein the focal point of the welding laser beam is vibrated in the direction of the welding depth, characterized in that
two welding laser beams (A, B) are simultaneously applied to the welding position, and the welding laser beams perform the welding operation with an identical vibration cycle in the direction of the welding depth, either
the phase difference of the oscillation cycles of the two welding laser beams (A, B) is set to zero, and the oscillation center positions of the two welding laser beams (A, B) are set at different positions in the direction of the welding depth, or
the vibration center positions of the two welding laser beams (A, B) are set at the same position in the direction of the welding depth and the vibration cycles are shifted from each other by π. 2. Laser welding method according to claim 1, characterized in that the Welding laser beams (A, B) welding with identical Amplitudes in the direction of the weld depth.   A laser welding apparatus for performing a welding operation while performing a relative movement of welding laser beams used at a welding position, the apparatus comprising:
a welding laser output unit ( 1 , 2 ) for emitting a laser beam (A, B) for welding;
a beam collection optical system ( 42 , 62 , 41 , 61 ) for collecting the welding laser beam at the welding position, the system having a vibration applying unit that vibrates the focus of the welding laser beam in the direction of the welding depth,
characterized in that the device comprises
two welding laser output units ( 1 , 2 ) for respectively emitting a laser beam (A, B) for welding;
two of the beam collection optical systems ( 42 , 62 , 41 , 61 ) corresponding to the welding laser output units; and
a controller ( 8 ) for controlling the operation of the vibration applying units of the beam collecting optical systems ( 42 , 62 , 41 , 61 ), the controller ( 8 ) having a cycle equalizing function to make the vibration cycles of the vibration applying units identical, either
the beam collecting optical systems ( 41 , 61 , 42 , 62 ) are set so that the oscillation center positions of the welding laser beams (A, B) are at different positions in the direction of the welding depth, and in that the controller ( 8 ) has a phase equalizing function by the phase difference of the oscillation cycles set the oscillation loading units to zero, or
in that the oscillation center positions of the two welding laser beams (A, B) are at the same position in the direction of the welding depth and the controller ( 8 ) has a phase shifting function to set the phase difference of the vibration cycles of the vibration applying units to π. 4. Laser welding device according to claim 3, characterized in that the controller ( 8 ) has an amplitude equalization function for adjusting the vibration amplitudes of the Schwingungsbeaufschlagungseinheiten to the identical value. A laser welding apparatus according to any one of claims 3 or 4, characterized in that each of the vibration applying units ( 41 , 61 , 42 , 62 ) includes a variable mirror ( 41 , 61 ) having a reflection surface repeatedly set to three states, namely convex, even, and concave.