Method and apparatus for laser-welding at least two conductor pieces, and assembly of at least two integrally bonded conductor pieces

Abstract

The invention relates to a method and an apparatus for laser-welding at least two conductor pieces (10, 16) as well as to an assembly of at least two integrally bonded conductor pieces (10, 16).

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 11, and a device for laser welding at least two conductor pieces having the features of claim 12.

[0004] The welding of conductor pieces using a laser beam is known from the prior art. In this case, a molten pool which extends over all of the conductor pieces to be welded can be created using a laser beam. For this purpose, the laser beam is moved back and forth between the individual conductor pieces. The disadvantage of this is that there is 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 which is dissipated in the gap is not available for the welding process.

[0005] Alternatively, a melt pool can be created on each of the individual conductor sections to be welded together. For this purpose, a laser beam can bounce back and forth between the individual conductor sections or melt pools. The separate melt pools on the individual conductor sections grow and merge (if sufficiently large) into a single melt pool. The disadvantage of this is that switching between the individual melt pools leads to longer downtimes.

[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. The conductor pieces, when arranged in a stator and electrically connected to one another, can be used to generate a magnetic field which is required for the operation of the electrical machine.

[0009] The conductor pieces can be so-called "hairpins," which have two elongated (essentially parallel) legs connected to each other by 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.

[0010] The procedure includes the following steps:

[0011] Providing an elongated first conductor piece having a first end portion and a first end face.

[0012] 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.

[0013] Generating a first laser spot on the first end face to create a first melt pool .

[0014] Generating a second laser spot on the second end face to create a second melt pool. The first laser spot and the second laser spot are generated simultaneously. The first melt pool and the second melt pool then combine (if sufficiently large) to form a single melt pool.

[0015] The conductor pieces can be arranged on circular paths in a stator, whereby the conductor pieces with their

[0016] End sections protrude from the stator. The end sections protruding from the stator can be aligned parallel to one another, in particular oriented along an axial direction of the stator.

[0017] The first laser spot and / or the second laser spot each have a core region and a ring region. The average laser power density in the core region is higher than the 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, e.g., oval or elliptical.

[0018] This prevents a laser spot from being moved across a gap between the two end faces. This ensures 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. Furthermore, the downtime caused by switching the laser beam between the individual melt pools is avoided or reduced.

[0019] In addition, this allows targeted energy to be introduced, thus optimizing mixing in the respective melt bath. This can prevent or at least reduce the formation of spatter and / or pores.

[0020] According to a further development, the method may comprise the steps of: moving the first laser spot on the first end face.

[0021] Alternatively or additionally, moving the second laser spot on the second end face. The first laser spot and / or the second laser spot can be moved using a scanner optics.

[0022] The scanner optics may comprise at least one ultralight mirror. The scanner optics may have an image ratio of 1.7:1.

[0023] The first laser spot can only be moved along the first end face. The second laser spot can only be moved along the second end face. In other words, the first laser spot or the second laser spot cannot be moved beyond the respective end face.

[0024] By moving the laser spots, the desired shape of the melt pool can be achieved. The energy can be introduced into the conductor piece material in a targeted manner. By moving the laser spots exclusively on the respective end faces, no laser power is lost, for example, through radiation into the gap between the end faces, and it can be used entirely for the welding process. In addition, interaction between the laser and the material outside the respective end face (welding or process zone) is avoided.

[0025] According to a further development of the method, the first laser spot and / or the second laser spot can each be moved back and forth along a straight line. The straight line can be aligned, in particular, parallel to one of the edges of the respective end face. It is also conceivable for the first laser spot and / or the second laser spot to each be moved back and forth along a path that is at least partially curved.

[0026] This allows the energy to be distributed more effectively across the respective end face. Furthermore, a more uniform melt pool can be created on each end face. Furthermore, the use of scanner optics, particularly with at least one ultra-lightweight mirror, can further reduce downtime.

[0027] According to a further development of the method, the first laser spot and / or the second laser spot can each be moved along a circular or elliptical path. Other (closed) paths, such as rectangular, square, triangular, etc., are also conceivable.

[0028] This allows the laser power to be better distributed across the respective end face. Furthermore, a more uniform melt pool can be created on each end face.

[0029] According to a further development of the method, the first laser spot and the second laser spot can be moved identically on the respective end faces. The two laser spots can be moved simultaneously and / or in the same manner. The two laser spots can be moved along the same trajectories.

[0030] This allows for the same possible

[0031] Melt baths are created. This leads to the most uniform fusion possible of the two melt baths and to the most uniform possible combined melt bath.

[0032] According to a further development of the method, the first laser spot and / or the second laser spot can each be moved at a distance from an edge of the first star surface and / or second end face. The distance of the first laser spot and / or the second laser spot from the respective edge of the first end face and / or second end face can in particular be at least the diameter of the first laser spot or the second laser spot. In other words, the respective laser spot is always arranged at a distance of at least one (own) laser spot diameter from the nearest edge of the respective end face.

[0033] This ensures that the first laser spot and / or the second laser spot are always completely positioned on the respective end face and that no laser power reaches outside the respective end face.

[0034] According to a further development of the method, the first laser spot and the second laser spot can be generated using an optical multifiber. The optical multifiber can be designed as a 2-in-1 fiber. The first laser spot and the second laser spot can be identical. In particular, the two laser spots can have (essentially) identical beam properties.

[0035] The 2-inch fiber can have a fiber core diameter of 50 pm (micrometers) and a fiber ring diameter of 200 pm. A laser with a beam quality of SPP (beam parameter product) of less than or equal to 4 mm*mrad (millimeters * milliradians) can be used to generate the laser spots.

[0036] The laser for generating the laser spots can be designed as an NIR (Near InfraRed) laser with a power of greater than or equal to 4 kW (kilowatts), in particular 8 kW.

[0037] This allows the generation of the first laser spot and the second laser spot to be implemented as simply as possible.

[0038] According to a further development of the method, the first laser spot and the second laser spot can be generated by means of two laser beams guided parallel to one another.

[0039] The first laser spot and the second laser spot can be generated using two partial beams, with a first partial beam generating the first laser spot and a second partial beam generating the second laser spot. The two partial beams can be generated from a common laser beam, e.g., using an optical beam splitter, wedge plate, etc.

[0040] This allows the generation of the first laser spot and the second laser spot, which are identical in design, to be implemented as simply as possible.

[0041] According to a further development, the procedure may include the following steps:

[0042] Varying, in particular oscillating, the average laser power density of the first laser spot, its core region and / or its ring region. Equally conceivable is a continuous shift of the average laser power density from the ring region to the core region, in particular at the start of the welding process. Furthermore, a continuous shift of the average laser power density from the core region to the ring region, in particular at the end of the welding process, is conceivable. In other words, an intensity ramp (increase in the (average) intensity) of the laser power can be run between the core region and the ring region.

[0043] Alternatively or additionally, varying, in particular oscillating, the average laser power density of the second laser spot, its core region and / or its ring region. Equally conceivable is a continuous shift of the average laser power density from the ring region to the core region, in particular at the start of the welding process. Furthermore, a continuous shift of the average laser power density from the core region to the ring region, in particular at the end of the welding process, is conceivable. In other words, an intensity ramp (increase in the (average) intensity) of the laser power can be run between the ring region and the core region.

[0044] This can prevent or at least reduce the formation of pores and / or splashes when processing times are short.

[0045] According to a further development, the procedure may include the step :

[0046] Determining the position of the first laser spot and / or the second laser spot on the respective end face. This can be implemented using an optical sensor. 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.

[0047] 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.

[0048] 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 a method according to the above statements. In particular, the materially bonded connection is a welded connection.

[0049] With regard to the advantages that can be achieved, reference is made to the relevant explanations of the method. The measures described in connection with the method and / or those explained below may serve to further refine the arrangement.

[0050] The above object is achieved by a device for laser welding at least two conductor pieces having the features of claim 12.

[0051] The device comprises at least one laser source.

[0052] The laser source is configured to simultaneously generate a first laser spot and a second laser spot. The first laser spot and / or the second laser spot each have a core region, in particular a circular one, and a ring region, in particular a ring-shaped one. The average laser power density in the core region is higher than the average laser power density in the ring region.

[0053] 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.

[0054] With regard to the advantages that can be achieved, 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 device.

[0055] A computer-readable storage medium is proposed, comprising instructions which, when executed by a computer, cause the computer to carry out the method as described above. Regarding the advantages thus achieved, 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.

[0056] 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.

[0057] 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.

[0058] Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. They show:

[0059] Fig. 1 schematically shows a perspective view of end sections with end faces of two conductor pieces, with a laser spot being arranged on each of the end faces and

[0060] Fig. 2 shows a schematic plan view of a laser spot according to Figure 1.

[0061] In the following description and in the figures, corresponding components and elements bear the same reference symbols. For the sake of clarity, not all reference symbols are shown in all figures.

[0062] The method according to the invention for laser welding at least two conductor pieces 10, 16 is explained below with reference to Figures 1 and 2.

[0063] The procedure includes the following steps:

[0064] Providing an elongated first conductor piece 10 with a first end portion 12 and a first end face 14.

[0065] Providing an elongated second conductor piece 16 with a second end section 18 and a second end face 20. In this 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.

[0066] The conductor sections 10, 16 have a rectangular cross-section in this case. Thus, the two end faces 14, 20 also have a rectangular shape. The two end faces 14, 20 each have four edges 38, each of which forms an outward boundary of the respective end faces 14, 20.

[0067] After the two end faces 14, 20 have been prepared, a first laser spot 22 is generated on the first end face 14 to create a first melt pool 24. A second laser spot 26 is generated on the second end face 20 to create a second melt pool 28 (see Figure 1). The first laser spot 22 and the second laser spot 26 are generated simultaneously. The first melt pool 24 and the second melt pool 28 grow and combine to form a common melt pool (not shown).

[0068] In this case, the first laser spot 22 and the second laser spot 26 each have a circular core region 30 and an annular ring region 32 (see Figure 2). An average laser power density in the core region 30 is higher than an average laser power density in the ring region 32. In other words, the laser intensity in the core region 30 is higher than the laser intensity in the ring region 32.

[0069] In this case, the first laser spot 22 is moved exclusively on the first end face 14. The second laser spot 26 is moved exclusively on the second end face 20. This prevents the first laser spot 22 and the second laser spot 26 from being moved across the gap 15. The movement of the two laser spots 22, 26 is implemented in this case by means of a scanner optics (not shown).

[0070] The first laser spot 22 and the second laser spot 26 can each be moved back and forth along a straight line 34. The movement along the straight line 34 is indicated in Figure 1 by a double arrow.

[0071] Alternatively, the first laser spot 22 and the second laser spot 26 can be moved along an elliptical path 36. The elliptical path 36 is indicated schematically in Figure 1 by means of a dashed line. Paths with other geometric shapes are also conceivable. The first laser spot 22 and the second laser spot 26 can be moved identically on the respective end faces 14, 20. In other words, the two laser spots 22, 26 can be moved at the same speed in the same direction.

[0072] When moving the first laser spot 22 and the second laser spot 26, a distance from an edge 38 of the respective end face 14, 20 is always maintained. In this case, the distance is at least one diameter of the respective laser spot 22, 26 from the edge 38. In other words, the first laser spot 22 and the second laser spot 26 are each at least one (own) diameter away from the (nearest) edge 38 of the respective end face 14, 20. In other words, the first laser spot 22 is always at a distance from the nearest edge 38 of the first end face 14 that is at least one diameter of the first laser spot 22. Accordingly, the second laser spot 26 in the present case always has a distance from the nearest edge 38 of the second end face 20 which is at least one diameter of the second laser spot 26.

[0073] The first laser spot 22 and the second laser spot 26 are identical in this case (see Figure 2). The two laser spots 22, 26 can be generated using an optical multifiber, in particular a 2-in-1 fiber (not shown).

[0074] The two laser spots 22, 26 can be generated by means of two laser beams guided parallel to one another. The two parallel laser beams can, in particular, be configured as partial beams of a common laser beam (not shown), which are preferably generated by means of a beam splitter.

[0075] The average laser power density of the first laser spot 22 and / or the second laser spot 26, or their core regions 30 and / or their ring regions 32, can be varied, in particular oscillated. It is also conceivable for intensity ramps to be applied from the core region 30 to the ring region 32 (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 30 to the ring region 32.

[0076] It is also conceivable that the position of the first laser spot 22 and / or the second laser spot 26 on the respective end face 14, 20 is determined, in particular for position monitoring and control. This can be implemented by means of an optical sensor (not shown).

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 a first laser spot (22) on the first end face (14) to create a first melt pool (24); Generating a second laser spot (26) on the second end face (20) in order to generate a second melt pool (28), wherein the first laser spot (22) and the second laser spot (26) are generated simultaneously, wherein the first melt pool (24) and the second melt pool (28) subsequently combine to form a common melt pool, wherein the first laser spot (22) and / or the second laser spot (26) each have a, in particular circular, core region (30) and a, in particular annular, ring region (32), wherein an average laser power density in the core region (30) is higher than an average laser power density in the ring region (32).

2. Method according to claim 1, characterized in that the method comprises the steps: Moving the first laser spot (22), in particular exclusively, on the first end face (14), and / or Moving the second laser spot (26), in particular exclusively, on the second end face (20), in particular wherein the first laser spot (22) and / or the second laser spot (26) are moved by means of a scanner optics.

3. Method according to claim 1 or 2, characterized in that the first laser spot (22) and / or the second laser spot (26) are each moved back and forth along a straight line (34).

4. Method according to claim 1 or 2, characterized in that the first laser spot (22) and / or the second laser spot (26) are each moved along a circular or elliptical path (36).

5. Method according to claim 3 or 4, characterized in that the first laser spot (22) and the second laser spot (26) are moved identically on the respective end faces (14, 20).

6. Method according to one of claims 2 to 5, characterized in that the first laser spot (22) and / or the second laser spot (26) is / are each moved at a distance from an edge (38) of the first end face (14) and / or the second end face (20), in particular wherein the distance between the respective laser spot (22, 26) and an edge (38) of the respective end face (14, 20) is at least one diameter of the respective laser spot (22, 26).

7. Method according to one of the preceding claims, characterized in that the first laser spot (22) and the second laser spot (26) are generated by means of an optical multifiber, in particular a 2-in-1 fiber, in particular wherein the first laser spot (22) and the second laser spot (26) are identical.

8. Method according to one of the preceding claims, characterized in that the first laser spot (22) and the second laser spot (26) are generated by means of two laser beams guided parallel to one another.

9. Method according to one of the preceding claims, characterized in that the method comprises the steps: Varying, in particular oscillating, the average laser power density of the first laser spot (22), its core region (30) and / or its ring region (32) and / or Varying, in particular oscillating, the average laser power density of the second laser spot (26), its core region (30) and / or its ring region (32).

10. Method according to one of the preceding claims, characterized in that the method comprises the step: Determining the position of the first laser spot (22) and / or the second laser spot (26) on the respective end face (14, 20), in particular by means of an optical sensor.

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

12. Device for laser welding at least two conductor pieces (10, 16) comprising: a laser source which is set up to simultaneously generate a first laser spot (22) and a second laser spot (26), wherein the first laser spot (22) and / or the second laser spot (26) each have a, in particular circular, core region (30) and a, in particular annular, ring region (32), wherein an average laser power density in the core region (30) is higher than an average laser power density in the ring region (32), 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 10.

13. 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 10.

14. 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 10.

15. A data carrier signal that transmits and / or characterizes the computer program according to claim 14.

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