Method and device for the laser welding of at least two conductor pieces, and arrangement of at least two conductor pieces integrally connected to one another

Abstract

The invention relates to a method for the laser welding of at least two conductor pieces (10, 16), and to an arrangement of at least two conductor pieces (10, 16) integrally connected to one another.

Description

[0001] Title: Method and device for laser welding at least two conductor pieces, as well as arrangement of at least two conductor pieces bonded together

[0002] Description

[0003] The invention relates to a method for laser welding at least two conductor pieces having the features of claim 1, an arrangement of at least two conductor pieces connected to one another in a materially bonded manner having the features of claim 12, and a device for laser welding at least two conductor pieces having the features of claim 13.

[0004] The welding of conductor sections using a laser beam is known from the prior art. A laser beam can be used to create a molten bath that extends across all conductor sections to be welded. For this purpose, the laser beam is moved back and forth between the individual conductor sections. This creates a molten bead that connects all conductor sections to be welded.

[0005] In order to reduce the process time, the laser power is usually increased. The disadvantage of this is that the increase in laser power is limited because the local heat input can otherwise lead to an asymmetric formation of the molten metal bead. An asymmetrical molten metal bead tends to tilt, which leads to a poorer welding result. In addition, this can be accompanied by an increase in spatter, particularly at the beginning of the process. A further disadvantage is that there is usually a gap between the conductor pieces to be welded, across which the laser beam is inevitably moved. This can allow radiation to enter the gap and interact with material outside the welding zone (process zone). Interaction of the laser beam with material (e.g. the conductor piece) outside the welding zone is undesirable. In addition, the energy that is dissipated in the gap is not available for the welding process.

[0006] It is therefore an object of the present invention to provide a method and a device for laser welding at least two conductor pieces and an arrangement of at least two conductor pieces connected to one another in a materially bonded manner, wherein the above disadvantages are eliminated.

[0007] The above object is achieved by a method for laser welding at least two conductor pieces having the features of claim 1.

[0008] The conductor pieces can be electrically conductive elements, in particular made of metal (e.g. copper). The conductor pieces can be arranged in a stator of an electrical machine. The conductor pieces can be designed for arrangement in a stator of an electrical machine. If they are arranged in a stator and electrically connected to one another, the conductor pieces can be used to generate a magnetic field which is required for the operation of the electrical machine. The conductor pieces can be so-called "hairpins", which have two elongated (essentially parallel) legs that are connected to one another by means of a connecting section. The shape of the hairpins usually corresponds to a hairpin. In other words, a hairpin has a (essentially) U-shape.The conductor pieces can also be so-called "special pins," which have only one leg. A combination of "hairpins" and "special pins" is also conceivable. The conductor pieces can have a rectangular cross-section.

[0009] The procedure includes the following steps:

[0010] Providing an elongated first conductor piece having a first end portion and a first end face.

[0011] Providing an elongated second conductor piece having a second end portion and a second end face. The first end face is arranged adjacent to the second end face.

[0012] The conductor pieces can be arranged on circular paths in a stator, with the conductor pieces protruding from the stator with their end sections. The end sections protruding from the stator can be aligned parallel to one another, in particular oriented along an axial direction of the stator.

[0013] Generating at least two, in particular at least four, laser spots on the first end face and / or on the second end face. The laser spots each have a core region and a ring region. An average laser power density in the core region is higher than an average laser power density in the ring region. The core region can be circular. The ring region can be ring-shaped. Other geometric configurations of the core region and / or the ring region are also conceivable, for example oval or elliptical.

[0014] Moving the laser spots. The laser spots can be moved across the first end face and / or the second end face. In doing so, the laser spots create a common molten pool that extends at least partially, in particular completely, across the first end face and the second end face.

[0015] This allows the heat input to be distributed more evenly across the end faces of the conductor pieces' end sections, allowing for more laser power to be used. This reduces downtime and thus the process time. Furthermore, the melting of the end faces is evened out, allowing for greater gap tolerance and an overall more stable process result with fewer spatter and / or pores. By evening out the heat input, a more uniform melt pool can be created, resulting in a more uniform, more symmetrical melt bead.

[0016] According to a further development, the procedure may include the step :

[0017] Moving the laser spots each along a path. For this purpose, each laser spot can be moved on its own path. It is also conceivable for the laser spots to be moved along a common path. The respective path can extend over the first end face and the second end face. In other words, the respective path can extend over both end faces. This means that in particular the laser spots are moved over both end faces. The laser spots can be moved over the gap between the first end face and the second end face. The respective path can be designed to be straight, circular and / or elliptical, at least in sections, in particular completely. Other geometric designs of the respective path are also conceivable (e.g. rectangular, semicircular, etc.). At least two paths, in particular all paths, can be oriented parallel to one another.

[0018] The laser spots can be positioned in a fixed arrangement relative to one another while moving across the end faces. The laser spots can be held in a fixed position relative to one another. The distances between the laser spots can be kept constant. It is also conceivable that the distances between the laser spots can be varied or changed, in particular continuously.

[0019] The laser spots can be positioned in a fixed arrangement. The arrangement of laser spots can be moved translationally along a common path. Alternatively, the arrangement of laser spots can be rotated around an axis, particularly an optical axis, while moving along a (common) path.

[0020] This allows the heat input to be distributed more evenly over the first

[0021] frontal surface and the second frontal surface. According to a further development, the method may comprise the step:

[0022] Moving the laser spots each along a path, wherein the respective path extends exclusively over the first end face or the second end face. In other words, the respective path can extend exclusively over the first end face or exclusively over the second end face. For this purpose, each laser spot can be moved on its own path. In particular, the respective path does not extend over the gap between the two end faces. This means that the individual laser spots can each be moved exclusively over the first end face or exclusively over the second end face. In particular, the laser spots are not moved over the gap between the two end faces. The respective path can be designed to be straight, circular and / or elliptical, at least in sections, in particular completely. Other geometric designs of the respective path are also conceivable (e.g. rectangular, semicircular, etc.).) . At least two orbits, in particular all orbits, can be oriented parallel to each other .

[0023] This prevents one of the laser spots from being moved across a gap between the two end faces. This means that no radiation is directed into the gap. This prevents interaction of the laser radiation with material outside of a welding or process zone. The entire laser energy can be used for the welding process. According to a further development of the method, the laser spots can be moved using scanner optics. The scanner optics can have an imaging ratio of 1.7:1.

[0024] Alternatively, it is conceivable that the laser spots are generated using a fixed optics system. It is conceivable that the laser spots are moved by moving the fixed optics system.

[0025] This allows the movement of the laser spot to be implemented using simple means.

[0026] According to a further development of the method, at least two, in particular all, laser spots can be designed identically. It is also conceivable that at least two, in particular all, laser spots can be designed differently.

[0027] This can simplify the generation of the individual laser spots and / or even out the energy distribution.

[0028] According to a further development of the method, the ring regions of at least two, in particular all, laser spots can overlap one another.

[0029] Due to the overlap of the ring areas, the energy input can be further optimized.

[0030] According to a further development of the method, the core regions of at least two, in particular of all, laser spots can be arranged at a distance from one another. The distance between the laser spots can be at least 20% of the diameter of the laser spots. Core regions of at least two, in particular of all, laser spots can be arranged so as not to overlap one another. In other words, the core regions preferably do not overlap.

[0031] Due to the spaced core areas, the energy intensities can be distributed over a larger area and thus the energy input can be further optimized.

[0032] It is conceivable that at least two, in particular all, laser spots can be arranged at a distance from one another. At least two, in particular all, laser spots can be arranged so as not to overlap one another. In other words, the laser spots preferably do not overlap.

[0033] The core regions and / or the ring regions of at least two, in particular all, laser spots can be arranged at a distance from one another. The ring regions of at least two adjacent laser spots can touch each other (at their respective outer diameters) (have at least one common point).

[0034] It is conceivable that at least two, in particular all, laser spots, whose core regions and / or ring regions can be arranged to overlap one another. For example, the ring regions of at least two (adjacent), in particular all, laser spots can overlap one another. It is conceivable that a ring region of a laser spot overlaps the core region of an adjacent laser spot.

[0035] This allows the energy input to be distributed as optimally as possible over a corresponding area. According to a further development of the method, at least two, in particular all, laser spots can be generated using an optical multifiber. The optical multifiber can be designed as a 2-in-1 fiber. At least two, in particular all, laser spots can be identical. In particular, the laser spots can have (essentially) identical beam properties.

[0036] The 2-in-1 fiber can have a fiber core diameter of 50 pm (micrometers) and a fiber ring diameter of 200 pm.

[0037] To generate the laser spots, a laser with a beam quality of SPP (beam parameter product) less than or equal to 4 mm*mrad (millimeters * milliradians) can be used.

[0038] To generate the laser spots, a NIR (Near InfraRed) laser (multi-mode) with a power of greater than or equal to 4 kW (kilowatts), in particular greater than 8 kW, preferably 12 kW, can be used.

[0039] Alternatively, a laser with a wavelength in the visible range (VIS laser), particularly green or blue, can be used.

[0040] This allows the generation of the first laser spot and the second laser spot to be implemented as simply as possible.

[0041] According to a further development, the method may comprise the step of varying, in particular oscillating, the average laser power density of at least one laser spot, its core region, and / or its ring region. It is conceivable that the average laser power density of several, in particular all, laser spots, their respective core regions, and / or their respective ring regions can be varied, in particular oscillated.

[0042] Varying (or oscillating) the average laser power density can be implemented particularly during the welding process. The total laser power can be varied or oscillated during the welding process.

[0043] This allows the degree of mixing in the melt pool to be increased or adjusted as desired, further homogenizing the energy input.

[0044] According to a further development of the method, at least two, in particular all, laser spots can be generated using a single laser beam. The individual laser beams can be guided parallel to each other.

[0045] At least two, but in particular all, laser spots can be generated using partial beams. The partial beams can be generated from a single laser beam, e.g., using an optical beam splitter, wedge plate, etc. The partial beams can be guided parallel to each other.

[0046] This makes it possible to create laser spots, which are identically designed, as simply as possible.

[0047] The method may comprise the step of: determining the position of the laser spots on the respective

[0048] Frontal surface. An optical sensor can be used for this purpose. The optical sensor can be camera-based. The optical sensor can be designed as a camera. Alternatively, the sensor can be designed as an interferometric-based sensor system.

[0049] This allows for position detection and / or position control of the respective laser spot. Any possible position deviation of the respective laser spot can be recorded and / or corrected. This ensures and controls consistent quality of the welds.

[0050] According to a further development, the procedure may include the step :

[0051] Moving the laser spots in a rotational movement around an optical axis.

[0052] This allows the degree of mixing in the melt bath to be increased or adjusted as desired. This allows the energy input to be further homogenized.

[0053] The above object is further achieved by an arrangement of at least two conductor pieces connected to one another in a materially bonded manner, having the features of claim 11. The materially bonded connection is produced by means of a method according to the above statements. In particular, the materially bonded connection is a welded connection. With regard to the advantages that can be achieved thereby, reference is made to the relevant statements on the method. The measures described in connection with the method and / or those explained below can serve to further refine the arrangement.

[0054] The above object is achieved by a device for laser welding at least two conductor pieces having the features of claim 13.

[0055] The device comprises at least one laser source. The laser source is configured to generate at least two, in particular at least four, laser spots. The laser spots each have a, in particular circular, core region and a, in particular annular, ring region. An average laser power density in the core region is higher than an average laser power density in the ring region.

[0056] The device has a control device for controlling the device. The device and / or the control device are configured to carry out the method according to the above statements. The control device can be embodied as a computer.

[0057] With regard to the advantages that can be achieved thereby, reference is made to the relevant explanations of the method. The measures described in connection with the method and / or those explained below can be used to further configure the device. A computer-readable storage medium is proposed, comprising instructions which, when executed by a computer, cause the computer to carry out the method in accordance with the above explanations. With regard to the advantages that can be achieved thereby, reference is made to the relevant explanations of the method. The measures described in connection with the method and / or those explained below can be used to further configure the storage medium.

[0058] A computer program is proposed, comprising instructions which, when executed by a computer, cause the computer to carry out the method as described above. Regarding the advantages thereby achievable, reference is made to the relevant explanations of the method. The measures described in connection with the method and / or those explained below can be used to further refine the computer program.

[0059] A data carrier signal is proposed that characterizes and / or transmits the computer program according to the above statements. The data carrier signal can be received, for example, via an optional data interface of a computer. Regarding the advantages that can be achieved thereby, reference is made to the relevant statements regarding the computer program. The measures described in connection with the computer program and / or those explained below can be used to further configure the data carrier signal.

[0060] Further features, details and advantages of the invention emerge from the wording of the claims and from the following description of embodiments based on the

[0061] Drawings showing:

[0062] Fig. 1 schematically shows a perspective view of end sections with end faces of two conductor pieces, wherein four laser spots are moved on the end faces according to a first embodiment;

[0063] Fig. 2 schematically shows a perspective view of end sections with end faces of two conductor pieces, wherein four laser spots are moved on the end faces according to a second embodiment;

[0064] Fig. 3 schematically shows a perspective view of end sections with end faces of two conductor pieces, wherein four laser spots are moved on the end faces according to a third embodiment and

[0065] Fig. 4 shows a schematic plan view of a laser spot.

[0066] In the following description and in the figures, corresponding components and elements have the same

[0067] Reference symbols. For the sake of clarity, not all reference symbols are shown in all figures.

[0068] The method according to the invention for laser welding at least two conductor pieces 10, 16 is explained below with reference to Figures 1 to 4.

[0069] The method comprises the steps of: providing an elongated first conductor piece 10 with a first end section 12 and a first end face 14.

[0070] Providing an elongated second conductor piece 16 with a second end portion 18 and a second end face 20.

[0071] In the present case, the end sections 12, 18 and the two end faces 14, 20 are arranged adjacent to one another. A gap 15 is arranged between the two end faces 14, 20.

[0072] The conductor sections 10, 16 have a rectangular cross-section in the present case. Thus, the two end faces 14, 20 also have a rectangular shape. The two end faces 14, 20 each have four edges 17, which each form an outward boundary of the respective end faces 14, 20.

[0073] After the two end faces 14, 20 have been provided, four laser spots 22 are generated on the end faces 14, 20.

[0074] In the present case, the laser spots 22 each have a circular core region 24 and an annular ring region 26 (cf. Figure 4). In this case, an average laser power density in the core region 24 is higher than an average laser power density in the ring region 26. In other words, the laser intensity in the core region 24 is higher than the laser intensity in the ring region 26. The laser spots 22 are moved over the two end faces 14, 20. The laser spots 22 thereby generate a common molten bath 28. The common molten bath 28 extends at least partially over the first end face 14 and the second end face 20. A molten bead is then formed from the common molten bath 28 and connects the two end sections 12, 18 to one another in a materially bonded manner.

[0075] The four laser spots 22 are arranged spaced apart from one another in the present case. In other words, the laser spots 22 do not overlap. It is also conceivable that the laser spots 22, their ring regions 26 and / or their core regions 24 may overlap. It is conceivable that the ring regions 26 of the laser spots 22 may overlap, with the core regions 24 being arranged spaced apart from one another.

[0076] The four laser spots 22 can be moved by means of a scanner optics (not shown). It is also conceivable for the four laser spots 22 to be generated by means of a fixed optics, wherein the fixed optics can be moved to move the laser spots 22.

[0077] In this case, all four laser spots 22 are identical.

[0078] The four laser spots 22 can be generated by means of an optical multi-fiber, in particular a 2-in-1 fiber (not shown).

[0079] The laser spots 22 can each be generated by means of a laser beam. The laser beams can be guided parallel to one another. The parallel laser beams can, in particular, be designed as partial beams, preferably generated by means of a beam splitter, of a common laser beam (not shown).

[0080] The average laser power density of the laser spots 22, or their core regions 24 and / or their ring regions 26, can be varied, in particular oscillated. It is also conceivable to apply intensity ramps from the core region 24 to the ring region 26 (or vice versa). In other words, the average laser intensity can be continuously increased (e.g., at the end of the welding process) and / or decreased (e.g., at the beginning of the welding process) from the core region 24 to the ring region 26.

[0081] It is also conceivable that the position of the laser spots 22 on the end faces 14, 20 is determined, particularly for position monitoring and control. This can be implemented using an optical sensor (not shown).

[0082] Figure 1 illustrates a movement of the laser spots 22 according to a first embodiment.

[0083] In this case, the laser spots 22 are moved clockwise. Counterclockwise movement is also conceivable.

[0084] The four laser spots 22 are arranged in a rectangular (square) arrangement in the present case. It is conceivable that this arrangement can be rotated during the movement of the laser spots 22, in particular about an optical axis. It is also conceivable that the four laser spots 22 can be moved translationally. In particular, the relative position of the laser spots 22 to one another can be fixed or not changed. In the present case, the four laser spots 22 are each moved along a path 30. In other words, each of the four laser spots 22 is moved along its own path 30. The four paths 30 are indicated in Figure 1 by means of only a dashed line for the sake of clarity.

[0085] In this case, the paths 30 overlap. It is also conceivable that the paths 30 do not overlap.

[0086] The tracks 30 extend in a circular manner over the first end face 14 and the second end face 20. It is conceivable that the tracks 30 each have an elliptical extension.

[0087] In the present case, the laser spots 22 are also moved across the gap 15. Due to the spaced-apart arrangement of the laser spots 22, not all of the laser spots 22 enter the gap 15 at the same time. In other words, at least one laser spot 22 is always arranged, at least in part, on the first end face 14 or on the second end face 20.

[0088] Figure 2 illustrates a movement of the laser spots 22 according to a second embodiment. The second embodiment differs from the first embodiment shown in Figure 1 in the following:

[0089] The four laser spots 22 are moved along a common, in this case circular, path 30. The laser spots 22 are arranged equidistantly (or evenly) distributed along the common path 30. Figure 3 illustrates a movement of the laser spots 22 according to a third embodiment. The third embodiment differs from the first embodiment shown in Figure 1 in the following:

[0090] The four laser spots 22 are each moved along a, in this case circular, path 30. The paths 30 each extend only on the first end face 14 or on the second end face 20.

[0091] In the present case, two tracks 30 run on the first end face 14 and two further tracks 30 run on the second end face 20. In the present case, the tracks 30 do not extend over the gap 15.

[0092] The tracks 30 do not intersect or touch each other. The tracks 30 are spaced apart from each other.

[0093] Since the paths 30 do not extend across the gap 15, the respective laser spots 22 are also not moved across the gap 15. Thus, two laser spots 22 are moved exclusively on the first end face 14 and two further laser spots 22 are moved exclusively on the second end face 20.

[0094] In particular, the laser spots 22 are always kept at a distance from the edges 17. The laser spots 22 can be kept at a distance from the gap 15. This can prevent (or at least reduce the probability of) a laser spot 22 entering the gap 15.

[0095] Figure 4 schematically shows a plan view of a laser spot 22. This can be a laser spot 22 from one of Figures 1 to 3.

Claims

Patent claims 1. A method for laser welding at least two conductor pieces (10, 16) comprising the steps: Providing an elongated first conductor piece (10) with a first end portion (12) and a first end face (14); Providing an elongated second conductor piece (16) having a second end portion (18) and a second end face (20), wherein the first end face (14) is arranged adjacent to the second end face (20); Generating at least two, in particular at least four, laser spots (22) on the first end face (14) and / or the second end face (20); wherein the laser spots (22) each have a, in particular circular, core region (24) and a, in particular annular, ring region (26), wherein an average laser power density in the core region (24) is higher than an average laser power density in the ring region (26); Moving the laser spots (22), wherein the laser spots (22) produce a common melt pool (28) which extends at least partially, in particular completely, over the first end face (14) and the second end face (20).

2. Method according to claim 1, characterized by the step: Moving the laser spots (22) along a path (30), wherein the respective path (30) extends over the first end face (14) and the second end face (20), in particular wherein the respective path (30) is at least partially rectilinear, circular and / or elliptical.

3. Method according to claim 1, characterized by the step: Moving the laser spots (22) each along a path (30), wherein the respective path (30) extends exclusively over the first end face (14) or the second end face (20), in particular wherein the respective path (30) is at least partially rectilinear, circular and / or elliptical.

4. Method according to one of the preceding claims, characterized in that the laser spots (22) are moved by means of a scanner optics.

5. Method according to one of the preceding claims, characterized in that at least two, in particular all, laser spots (22) are identical.

6. Method according to one of the preceding claims, characterized in that the ring regions (26) of at least two, in particular all, laser spots (22) overlap one another.

7. Method according to one of the preceding claims, characterized in that the core regions (24) of at least two, in particular of all, laser spots (22) are arranged at a distance from one another, in particular wherein the distance between the laser spots (22) is at least 20% of a laser spot diameter.

8. Method according to one of the preceding claims, characterized in that at least two laser spots (22), in particular all laser spots (22), are generated by means of an optical multifiber, in particular a 2-in-1 fiber.

9. Method according to one of the preceding claims, characterized in that the method comprises the step: Varying, in particular oscillating, the average laser power density of at least one laser spot (22) of its core region (24) and / or its ring region (26).

10. Method according to one of the preceding claims, characterized in that at least two, in particular all, laser spots (22) are each generated by means of a laser beam, wherein the laser beams are guided parallel to one another.

11. Method according to one of the preceding claims, characterized in that the method comprises the step: Moving the laser spots (22) in a rotational movement around an optical axis.

12. Arrangement of at least two conductor pieces (10, 16) connected to one another in a materially integral manner, wherein the materially integral connection is produced by means of a method according to one of the preceding claims.

13. Device for laser welding at least two conductor pieces (10, 16) comprising: a laser source which is set up to generate at least two, in particular at least four, laser spots (22), wherein the laser spots (22) each have a, in particular circular, core region (24) and a, in particular annular, ring region (26), wherein an average laser power density in the core region (24) is higher than an average laser power density in the ring region (26), a control device for controlling the device, wherein the device and / or the control device are set up to carry out the method according to one of claims 1 to 11.

14. A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to at least one of claims 1 to 11.

15. A computer program comprising instructions which, when the computer program is executed by a computer, cause the computer to carry out the method according to at least one of claims 1 to 11.

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