Method and apparatus for laser welding at least two conductive pieces, and assembly of at least two integrally joined conductive pieces

Abstract

The present invention relates to a method and apparatus for laser welding at least two conductive pieces (10, 16), and to an assembly of at least two integrally joined conductive pieces (10, 16).

Description

Background Art

[0001] The present invention relates to a method for laser welding at least two conductor pieces including the features recited in claim 1, an assembly of at least two conductor pieces integrally joined to each other including the features recited in claim 11, and an apparatus for laser welding at least two conductor pieces including the features recited in claim 12.

[0002] Welding of conductor pieces by a laser beam is known from the prior art. The laser beam can be used to generate a weld pool that spreads over the entire range of all the conductor pieces to be welded. For this purpose, the laser beam is moved back and forth between the individual conductor pieces. The drawback is that there are gaps between the conductor pieces to be welded, and the laser beam necessarily moves over these gaps. As a result, radiation can enter the gaps and interact with the material outside the weld zone (process zone). The interaction between the material outside the weld zone (e.g., conductor pieces) and the laser beam is not desirable. Furthermore, the energy diverted into the gaps cannot be utilized in the welding process.

[0003] Instead, the weld pool can be generated on each of the individual conductor pieces to be welded to each other. For this purpose, the laser beam can jump back and forth between the individual conductor pieces or the molten pools. The individual weld pools on the individual conductor pieces grow and fuse (when large enough) to form a common weld pool. The drawback is that the switching between the individual molten pools lengthens the non-productive time.

[0004] Object of the Invention Therefore, an object of the present invention is to provide a method and an apparatus for laser welding at least two conductor pieces, and an assembly of at least two conductor pieces integrally joined to each other, in which the above-mentioned drawbacks are eliminated.

[0005] Summary of the Invention The above object is achieved by a method for laser welding at least two conductor pieces having the features recited in claim 1.

[0006] Conductive pieces can be conductive elements and can be made of metal (e.g., copper). Conductive pieces can be placed within the stator of an electromachine. Conductive pieces can be designed for assembly within the stator of an electromachine. When placed within the stator and electrically connected to one another, conductive pieces can be used to generate the magnetic field required for the operation of the electromachine.

[0007] The conducting piece can be called a "hairpin," which has two elongated (substantially parallel) legs connected to each other by a connector. The shape of the hairpin is usually corresponding to a hairpin. In other words, the hairpin has a (substantially) U-shape. The conducting piece may also be called a "special pin," which has only one leg. Combinations of "hairpins" and "special pins" are also conceivable. The conducting piece can have a rectangular cross-section.

[0008] This delicious, A step of providing an elongated first conductor piece having a first end and a first end face, A step of providing a second conductor piece having an elongated end and a second end face, wherein the first end face is positioned adjacent to the second end face, A step of generating a first laser spot on a first end face and generating a first weld pool, The process includes the steps of generating a second laser spot on a second end face and generating a second weld pool. The first and second laser spots are generated simultaneously. The first and second weld pools then fuse together (if they are of sufficient size) to form a common weld pool.

[0009] Conductor pieces can be arranged on a circular path within the stator, with the ends of the conductor pieces protruding from the stator. The ends protruding from the stator can be oriented parallel to each other, and in particular, oriented in the axial direction of the stator.

[0010] The first laser spot and / or the second laser spot each have a core region and a ring region. The average laser power density of the core region is greater than the average laser power density of the ring region. The core region can be circular in shape. The ring region can be annular in shape. Other geometric configurations of the core region and / or ring region are also possible, for example, oval or elliptical.

[0011] This prevents the laser spot from moving through the gap located between the two end faces. This prevents any radiation from being directed into the gap. This prevents the laser radiation from interacting with material outside the welding or process zone. All of the laser energy can be used for the welding process. In addition, the unproductive time that would result from switching the laser beam between individual molten pools is avoided or reduced.

[0012] Furthermore, this allows for the introduction of energy using a targeted method, thereby optimizing the mixing within the weld pool. This prevents or at least reduces splashing and / or pore formation.

[0013] According to one further development, the method is: The procedure may include moving a first laser spot on a first end face. Alternatively, or in addition, moving a second laser spot on a second end face. The first laser spot and / or the second laser spot may be moved by a scanner optical unit.

[0014] The scanner optical unit may include at least one ultralight mirror. The scanner optical unit may have a reproduction ratio of 1.7:1.

[0015] The first laser spot can be moved only on the first end face. The second laser spot can be moved only on the second end face. In other words, neither the first nor the second laser spot can be moved beyond their respective end faces.

[0016] By moving the laser spot, the desired shape of the weld pool can be achieved. Energy can be specifically introduced into the conductive material. By moving the laser spot only over each end face, for example, there is no loss of laser power due to radiation into gaps between end faces, and the power can be fully used for the welding process. Furthermore, interaction between the laser and the material outside the end face (welding or process zone) is avoided.

[0017] Further development of the method allows the first laser spot and / or the second laser spot to be moved back and forth along a straight line. The straight line can be oriented, in particular, to be parallel to one of the edges of the end face.

[0018] Furthermore, it is conceivable that the first laser spot and / or the second laser spot can each be moved back and forth along a path that is at least partially curved.

[0019] This allows for more efficient energy distribution across the end face. In addition, a more uniform weld pool can be created on the end face. Furthermore, using a scanner optical unit, especially one with at least one ultralight mirror, can further reduce unproductive time.

[0020] Further developments of the method allow the first laser spot and / or the second laser spot to be moved along a circular or elliptical path, respectively. Other (closed) paths, such as rectangles, squares, triangles, etc., are also conceivable.

[0021] This allows the laser power to be distributed more efficiently across the end face. In addition, it enables the creation of a more uniform weld pool on the end face.

[0022] Further development of the method allows the first and second laser spots to be moved similarly on their 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 movement path.

[0023] This allows for the creation of molten pools that are as similar as possible at the two end faces. This results in the fusion of the two weld pools being as uniform as possible, and the common weld pool being as uniform as possible.

[0024] Further development of the method allows the first laser spot and / or the second laser spot to be moved by a distance from the edge of the first and / or second end face. The distance of the first and / or second laser spot from the edge of the first and / or second end face can, in particular, be the size of at least the diameter of the first or second laser spot. In other words, each laser spot is always positioned at a distance of at least one (its own) laser spot diameter from the nearest edge of the end face.

[0025] This ensures that the first laser spot and / or the second laser spot are always perfectly positioned on their respective end faces, and that no laser power leaks outside the end faces.

[0026] Further development of the method allows the first and second laser spots to be generated by optical multifibers. These optical multifibers can be designed as 2-in-1 fibers. The first and second laser spots can be identical. In particular, the two laser spots can have (substantially) identical beam characteristics.

[0027] The 2-in-1 fiber can have a core diameter of 50 μm (micrometers) and a ring diameter of 200 μm.

[0028] To generate the laser spot, a laser having a beam quality with a BPP (beam parameter product) of 4 mm*mrad (millimeter*milliradian) or less can be used.

[0029] The laser for generating the laser spot can be designed as a NIR (near-infrared) laser having an output of 4 kW (kilowatts), particularly 8 kW or more.

[0030] Thereby, the first laser spot and the second laser spot are generated as simply as possible.

[0031] According to a further development of the method, the first laser spot and the second laser spot can be generated using two laser beams guided parallel to each other.

[0032] The first laser spot and the second laser spot can be generated using two partial beams having a first partial beam for generating the first laser spot and a second partial beam for generating the second laser spot. The two partial beams can be generated from a common laser beam, for example, by an optical beam splitter, a wedge plate, or the like.

[0033] Thereby, it is made possible to generate the same first laser spot and second laser spot as simply as possible.

[0034] According to a further development, the method The process may include steps of varying, in particular, the average laser power density of the first laser spot, its core region, and / or its ring region, especially by vibrating it. Furthermore, it is conceivable that the average laser power density may shift continuously from the ring region to the core region, especially at the start of the welding process. Moreover, a continuous shift of the average laser power density from the core region to the ring region is also conceivable, especially at the end of the welding process. In other words, a laser power intensity gradient (an increase in (average) intensity) can be implemented between the core region and the ring region.

[0035] Alternatively, or in addition, the average laser power density of the second laser spot, its core region and / or its ring region, is varied, particularly by causing it to vibrate. Furthermore, it is conceivable that the average laser power density may shift continuously from the ring region to the core region, particularly at the start of the welding process. Moreover, a continuous shift of the average laser power density from the core region to the ring region is also conceivable, particularly at the end of the welding process. In other words, a laser power intensity gradient (an increase in (average) intensity) can be implemented between the ring region and the core region.

[0036] This makes it possible to prevent or at least reduce the formation of pores and / or splashes during a short process time.

[0037] According to one further development, the method is: The procedure may include the step of determining the positions of a first laser spot and / or a second laser spot on the end face. This can be carried out by an optical sensor. The optical sensor may be camera-based. The optical sensor may be designed as a camera. Alternatively, the sensor may be designed as an interferometry-based sensor system.

[0038] This enables the detection and / or monitoring of the laser spot's position. Therefore, any potential misalignment of the laser spot can be recorded and / or corrected. This ensures and enables consistent quality monitoring of welded joints.

[0039] The above objective is further achieved by an assembly of at least two conductive pieces integrally joined to one another, having the features of claim 11. The integral joint is produced by the method described above. In particular, the integral joint is a welded joint.

[0040] For the advantages that can be achieved thereby, refer to the relevant description of the method. The measures described in relation to the method and / or the measures described below can be used to further construct the assembly.

[0041] The above objective is achieved by an apparatus for laser welding at least two conductive pieces having the features of claim 12.

[0042] The apparatus comprises at least one laser source. 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, in particular, a circular core region and, in particular, an annular ring region. In this example, the average laser power density of the core region is greater than the average laser power density of the ring region.

[0043] The apparatus has a control device for controlling the apparatus. The apparatus and / or the control device are configured to perform the methods described above. The control device may be designed as a computer.

[0044] For the advantages that can be achieved thereby, refer to the relevant description of the method. The measures described in relation to the method and / or the measures described below can be used to further configure the apparatus.

[0045] A computer-readable storage medium is proposed that, when executed by a computer, contains commands that cause the computer to perform the method described above. For the advantages that can be achieved thereby, see the relevant description of the method. The measures described in relation to the method and / or the measures described below can be used to further configure the storage medium.

[0046] When executed by a computer, a computer program is proposed that includes commands to cause the computer to perform the method described above. For the advantages that can be achieved thereby, refer to the relevant description of the method. The measures described in relation to the method and / or the measures described below can be used to further constitute the computer program.

[0047] A data carrier signal is proposed to characterize and / or transmit the computer program described above. The data carrier signal can be received, for example, via an optional data interface of the computer. Refer to the relevant description of the computer program for the advantages that can be achieved thereby. The measures described in relation to the computer program and / or the measures described below can be used to further constitute the data carrier signal. [Brief explanation of the drawing]

[0048] Further features, details, and advantages of the present invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. In the drawings, [Figure 1] A schematic perspective view of an end section having two end faces of a conductive piece, with laser spots positioned on each end face, is shown. [Figure 2] Figure 1 shows a schematic top view of the laser spot.

[0049] In the following descriptions and diagrams, corresponding components and elements share the same reference numerals. For clarity, not all reference numerals are reproduced in every diagram.

[0050] A method according to the present invention for laser welding at least two conductive pieces 10, 16 is described below with reference to Figures 1 and 2.

[0051] This delicious, A step of providing an elongated first conductor piece 10 having a first end 12 and a first end face 14, The step includes providing an elongated second conductor piece 16 having a second end 18 and a second end face 20. In this example, the ends 12, 18 and the two end faces 14, 20 are arranged adjacent to each other. There is a gap 15 between the two end faces 14, 20.

[0052] In this example, the conductor pieces 10 and 16 have a rectangular cross-section. Therefore, in this example, the two end faces 14 and 20 also have a rectangular shape. In this example, each of the two end faces 14 and 20 has four edges 38, which represent the outer boundary of the end faces 14 and 20 in each example.

[0053] After providing two end faces 14 and 20, a first laser spot 22 is generated on the first end face 14 to create a first weld pool 24. A second laser spot 26 is generated on the second end face 20 to create a second weld pool 28 (see Figure 1).

[0054] The first laser spot 22 and the second laser spot 26 are generated simultaneously. The first weld pool 24 and the second weld pool 28 grow and fuse together to form a common weld pool (not shown).

[0055] In this example, 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). The average laser power density of the core region is greater than the average laser power density of the ring region 32. In other words, the laser intensity of the core region 30 is greater than the laser intensity of the ring region 32.

[0056] In this example, the first laser spot 22 is moved only on the first end face 14. In this example, the second laser spot 26 is moved only on the second end face 20. This prevents the first laser spot 22 and the second laser spot 26 from moving across the gap 15. In this example, the movement of the two laser spots 22 and 26 is performed by a scanner optical unit (not shown in this specification).

[0057] The first laser spot 22 and the second laser spot 26 can each be moved back and forth along the straight line 34. Movement along the straight line 34 is shown in Figure 1 by double arrows.

[0058] Alternatively, the first laser spot 22 and the second laser spot 26 can move along an elliptical path 36. The elliptical path 36 is schematically shown in Figure 1 by a dashed line. Paths of other geometric shapes are also conceivable.

[0059] The first laser spot 22 and the second laser spot 26 can be moved similarly on their respective end faces 14 and 20. In other words, the two laser spots 22 and 26 can be moved in the same direction at the same speed.

[0060] In this example, when the first laser spot 22 and the second laser spot 26 are moved, the distance to the edges 38 of the end faces 14 and 20 is always maintained. This distance is at least the size of one diameter to the edges 38 of the laser spots 22 and 26. In other words, the first laser spot 22 and the second laser spot 26 are each at least one diameter from the (nearest) edge 38 of the end faces 14 and 20. In other words, in this example, the first laser spot 22 always has a distance to the nearest edge 38 of the first end face 14 that is at least the size of one diameter of the first laser spot 22. Therefore, in this example, the second laser spot 26 always has a distance to the nearest edge 38 of the second end face 20 that is at least the size of one diameter of the second laser spot 26.

[0061] The first laser spot 22 and the second laser spot 26 are similarly designed in this example (see Figure 2). The two laser spots 22 and 26 can be generated by optical multifibers, in particular by 2-in-1 fibers (not shown).

[0062] The two laser spots 22 and 26 can be generated by two laser beams guided parallel to each other. The two parallel-guided laser beams can be designed in particular as partial beams of a common laser beam (not shown), which are preferably generated by a beam splitter.

[0063] 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, made to vibrate. It is also conceivable that an intensity gradient can be implemented from the core region 30 to the ring region 32 (or vice versa). In other words, the average laser intensity can be continuously increased from the core region 30 to the ring region 32 (e.g., at the end of the welding process) and / or decreased (e.g., at the start of the welding process).

[0064] In particular, for position monitoring and control, it is also conceivable to determine the positions of the first laser spot 22 and / or the second laser spot 26 on each end face 14, 20. This can be done by an optical sensor (not shown).

Claims

1. A method for laser welding at least two conductive pieces (10, 16), - A step of providing an elongated first conductor piece (10) having a first end (12) and a first end face (14), - A step of providing an elongated second conductor piece (16) having a second end (18) and a second end face (20), wherein the first end face (14) is positioned adjacent to the second end face (20), - A step of generating a first laser spot (22) on the first end face (14) to generate a first weld pool (24), - A method comprising the step of generating a second laser spot (26) on the second end face (20) to generate a second weld pool (28), wherein the first laser spot (22) and the second laser spot (26) are generated simultaneously, and the first weld pool (24) and the second weld pool (28) subsequently fuse to form a common weld pool, wherein the first laser spot (22) and / or the second laser spot (26) each have a particularly circular core region (30) and a particularly annular ring region (32), and the average laser power density of the core region (30) is greater than the average laser power density of the ring region (32).

2. The method described above is - A step of moving the first laser spot (22) in particular only on the first end face (14), and / or The method according to claim 1, comprising the step of moving the second laser spot (26) particularly on the second end face (20), wherein the first laser spot (22) and / or the second laser spot (26) are moved by a scanner optical unit.

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

6. The method according to any one of claims 2 to 5, characterized in that, in each case, the first laser spot (22) and / or the second laser spot (26) are moved at a certain distance from the edge (38) of the first end face (14) and / or the second end face (20), and in particular, the distance between the laser spots (22, 26) and the edge (38) of the end faces (14, 20) is the size of at least one diameter of the laser spots (22, 26).

7. The method according to any one of claims 1 to 6, characterized in that the first laser spot (22) and the second laser spot (26) are generated by optical multifibers, in particular by 2-in-1 fibers, and in particular, the first laser spot (22) and the second laser spot (26) are identical.

8. The method according to any one of claims 1 to 7, characterized in that the first laser spot (22) and the second laser spot (26) are generated by two laser beams guided parallel to each other.

9. The method described above is - A step of changing the average laser power density of the first laser spot (22), the core region (30) of the first laser spot and / or the ring region (32) of the first laser spot, particularly a step of vibrating it, and / or The method according to any one of claims 1 to 8, characterized by comprising the step of changing, in particular the step of vibrating, the average laser power density of the second laser spot (26), the core region (30) of the second laser spot and / or the ring region (32) of the second laser spot.

10. The method described above is - The method according to any one of claims 1 to 9, characterized in that it includes the step of determining the position of the first laser spot (22) and / or the second laser spot (26) on each end face (14, 20) in particular by an optical sensor.

11. An assembly of at least two conductive pieces (10, 16) integrally joined together, wherein the integral joint is generated by the method described in any one of claims 1 to 10.

12. An apparatus for laser welding at least two conductive pieces (10, 16), - A laser source configured 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 particularly circular core region (30) and a particularly annular ring region (32), and the average laser power density of the core region (30) is greater than the average laser power density of the ring region (32), - An apparatus comprising a control device for controlling the apparatus, wherein the apparatus and / or the control device are configured to perform the method according to any one of claims 1 to 10.

13. A computer-readable storage medium containing a command, wherein, when the command is executed by a computer, the computer causes the computer to perform the method according to at least one of claims 1 to 10.

14. A computer program including a command, wherein, when the computer program is executed by a computer, the command causes the computer to perform the method according to at least one of claims 1 to 10.

15. A data carrier signal for transmitting and / or characterizing the computer program described in claim 14.

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