DE102021002040A1 - Welding device and method for joining a first workpiece to a second workpiece by laser welding - Google Patents

Abstract

The invention relates to a method and a welding device (30) for connecting a first workpiece (12) to a second workpiece (14) by laser welding. The welding device (30) is designed to apply a laser beam (18) to the workpieces (12, 14) and has an output device (22) of an optical coherence tomograph (20). The output device (22) is designed to output a measuring beam (32) of the coherence tomograph (20). A size (28) of a gap (26) formed between the workpieces (12, 14) during laser welding can be detected by means of the measuring beam (32). The coherence tomograph (20) has at least one deflecting mirror (34) which is designed to deflect the measuring beam (32). By means of the at least one deflecting mirror (34), the respective narrow sides (36, 38) of the workpieces (12, 14) arranged so as to overlap one another at least in regions can be acted upon by the measuring beam (32). At the same time, a broad side (40) of one of the workpieces (12), which adjoins the narrow side (36) of this workpiece (12), can be acted upon by the laser beam (18).

Description

The invention relates to a welding device for joining a first workpiece to a second workpiece by laser welding. The welding device is designed to apply a laser beam to the workpieces and has an output device of an optical coherence tomograph. The output device is designed to output a measuring beam of the coherence tomograph. A size of a gap formed between the workpieces during laser welding can be detected by means of the measuring beam. The coherence tomograph has a deflecting mirror which is designed to deflect the measuring beam. The invention also relates to a method for connecting a first workpiece to a second workpiece by laser welding by means of such a welding device.

The DE 10 2016 010 508 A1 describes a device for laser welding which has an optical coherence tomograph. The width of a gap between two workpieces is recorded by means of the coherence tomograph, while a fillet weld is formed on the workpieces arranged so as to overlap one another by means of a laser beam from the device. Here, the measuring beam is coupled coaxially into the laser beam serving as the processing beam. Both the laser beam and the measuring beam are aligned inclined to a broad side of the workpieces arranged in an overlapping manner and therefore impinge on the fillet weld at an angle from above.

A disadvantage here is the fact that with this device the possibilities of monitoring the gap or joint gap are relatively limited.

Furthermore, the DE 10 2013 112 244 B4 a device for laser welding, in which a laser beam is directed onto the end faces or narrow sides of workpieces arranged so as to overlap one another. At the same time, the welding process and the joining quality are recorded by means of a thermal imaging camera.

With this method, the welding process can only be monitored while welding is being carried out or immediately after welding, since the thermal imaging camera only then provides evaluable thermal images.

The object of the present invention is to create a welding device of the type mentioned at the beginning, which enables improved monitoring of the gap, and to specify a correspondingly improved method.

This object is achieved by a welding device with the features of claim 1 and by a method with the features of claim 8. Advantageous configurations with expedient developments of the invention are specified in the dependent patent claims and in the following description.

The welding device according to the invention for connecting a first workpiece to a second workpiece by laser welding is designed to apply a laser beam to the workpieces. The welding device has an output device of an optical coherence tomograph, the output device being designed to output a measuring beam of the coherence tomograph. A size of a gap formed between the workpieces during laser welding can be detected by means of the measuring beam. The coherence tomograph has at least one deflection mirror which is designed to deflect the measuring beam. Here, by means of the at least one deflection mirror, the respective narrow sides of the workpieces arranged overlapping with one another at least in some areas can be acted upon by the measuring beam, with the laser beam being able to be applied to a broad side of one of the workpieces at the same time. The broad side adjoins the narrow side of this workpiece, on whose broad side the laser beam strikes when the welding device is in operation.

In other words, the at least one deflection mirror is arranged next to the at least partially overlapping workpieces that the measuring beam can be directed onto the narrow side or front side of the first workpiece, onto the gap and onto the narrow side or front side of the second workpiece by means of the at least one deflecting mirror . In this way, on the one hand, the size of the gap can be monitored very well during the laser welding process itself.

It is also possible to monitor the size of the gap or joint gap before the laser welding process is started. This in turn makes it possible to adapt the laser welding process to the size of the gap or joint gap. For example, if a larger or wider joint gap is present, a laser beam with a greater power can be directed onto the mutually overlapping workpieces than if the joint gap or gap is comparatively narrow or narrow.

It is also advantageously possible to rework or change the gap before the workpieces are exposed to the laser beam, for example by aligning or realigning the workpieces accordingly to each other. In this way, it can be ensured in particular that the joint gap is particularly narrow if this is advantageous for the welding process. The latter is the case, for example, when workpieces in the form of arresters from battery cells designed as lithium-ion cells are to be welded to one another by means of the welding device.

However, it can also be the case that a gap or joint gap of a certain size is explicitly desired. This is the case, for example, when galvanized workpieces or components are to be connected to one another by welding. Because then the gap or joint gap formed between the workpieces serves as a degassing gap.

In both cases, the welding device enables the gap or joint gap to be set as desired before the actual start of the laser welding process in order either to ensure an almost gap-free arrangement of the workpieces on top of one another or to provide the joint gap of the desired size.

This is due to the fact that an improved monitoring of the gap can be carried out by means of the coherence tomograph having the at least one deflection mirror. The at least one deflection mirror enables particularly precise detection of the size of the gap, since the measuring beam deflected by the at least one deflection mirror is directed onto the narrow sides of the workpieces that overlap with one another.

By means of the welding device it can therefore be achieved in an advantageous manner that rejects of workpieces connected to one another by laser welding are particularly largely reduced.

Furthermore, trends can be recognized very quickly and easily, for example by monitoring the size of the respective gaps or joint gaps when connecting respective components or workpieces over a plurality of laser welding processes carried out one after the other on the respective workpieces. In this way it is possible to react very quickly to such trends and, in particular, corrective action can be taken.

If, for example, it turns out that when laser welding processes are carried out one after the other, increasingly larger gaps occur between the workpieces or joining partners connected to one another in each of the laser welding processes, it can be deduced from this that an alignment of the workpieces with respect to one another is increasingly deteriorating in the preparation of the respective laser welding process. This can be recognized very quickly by means of the welding device, so that a correction or post-correction can be made.

The output device can be designed as a scanning device or scanner or OCT scanner which is attached, for example flanged, to the welding device.

The OCT scanner can receive the OCT measurement signal via a light guide, which is then directed as the measurement beam onto the narrow sides of the workpieces. Further components of the optical coherence tomograph such as a sensor device with a reference arm, a spectrometer and the like as well as a control device for controlling the components of the coherence tomograph can be located at a different location than the welding device and in particular even in a different room than the welding device. For example, the output device can be connected via the light guide to a measuring beam source of the coherence tomograph which, like the sensor device and the control device, can be accommodated in a switch cabinet or the like.

In the method according to the invention for connecting a first workpiece to a second workpiece by laser welding by means of a welding device, the workpieces are acted upon by a laser beam provided by the welding device. An output device of an optical coherence tomograph outputs a measuring beam. A size of a gap formed between the workpieces during laser welding is recorded by means of the measuring beam. The coherence tomograph has at least one deflecting mirror which deflects the measuring beam. In this case, by means of the at least one deflection mirror, the respective narrow sides of the workpieces which at least regionally overlap with one another are acted upon by the measuring beam. Subsequently and / or at the same time, a broad side of one of the workpieces, which adjoins the narrow side of this workpiece, is acted upon by the laser beam.

The gap or joint gap can therefore be monitored in particular by means of the measuring beam before the workpieces are exposed to the laser beam. The monitoring can also be continued in an advantageous manner while the laser beam connects the workpieces by means of the laser welding.

The advantages and preferred embodiments described for the welding device according to the invention also apply to the method according to the invention and vice versa.

Further advantages, features and details of the invention emerge from the following description of preferred exemplary embodiments and on the basis of the drawing (s). The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the combination specified, but also in other combinations or on their own, without the scope of the Invention to leave.

• 1 stark schematisiert das Verbinden zweier miteinander überlappender Werkstücke miteinander durch Laserschweißen mittels einer ersten Schweißvorrichtung; und
• 2 das Verbinden der beiden Werkstücke miteinander mittels einer verbesserten Schweißvorrichtung, wobei ein Umlenkspiegel einen Messstrahl auf Schmalseiten beziehungsweise Stirnseiten der Werkstücke lenkt, während der Laserstrahl auf eine Breitseite des in 2 oberen Werkstücks auftrifft; und
• 3 stark schematisiert ein zweidimensionales Bild, welches sich beim Abtasten der Schmalseiten der Werkstücke gemäß 2 entlang einer Scanlinie ergibt.

Show:

• 1 highly schematized the joining of two overlapping workpieces to one another by laser welding by means of a first welding device; and
• 2 connecting the two workpieces to one another by means of an improved welding device, a deflection mirror directing a measuring beam onto narrow sides or front sides of the workpieces, while the laser beam onto a broad side of the in 2 hits the upper workpiece; and
• 3rd highly schematized a two-dimensional image, which is shown when the narrow sides of the workpieces are scanned 2 results along a scan line.

Identical or functionally identical elements are provided with the same reference symbols in the figures.

In 1 is a very schematic representation of a welding device 10 shown, which for joining a first workpiece 12th with a second workpiece 14th is formed by laser welding. The welding device 10 includes laser welding optics 16 , which in the operation of the welding device 10 a laser beam 18th or a process laser beam onto the two workpieces that are arranged overlapping with one another in the present case 12th , 14th directs or focuses.

The welding device 10 is with an optical coherence tomograph 20th coupled, which in 1 is only shown in a highly schematic manner. Is also highly schematic in 1 an output device in the form of a scanner 22nd of the optical coherence tomograph 20th shown. The present on the welding device 10 attached output device 22nd gives a measuring beam 24 from which in 1 is shown. Further components of the optical coherence tomograph 20th such as a sensor device with a reference arm, a spectrometer and the like as well as a control device for controlling the components of the coherence tomograph 20th are not shown in more detail in the figures for reasons of clarity.

The modes of operation of an optical coherence tomograph or the method of optical coherence tomography (OCT = optical coherence tomography) is known per se and, for example, in US Pat DE 10 2016 010 508 A1 explained.

Optical coherence tomography is based on the basic principle of interference from light waves. In this case, a measuring beam source (not shown) of the coherence tomograph is used 20th generated measuring light by means of a (not shown) beam splitter of the coherence tomograph 20th into the optical measuring beam 24 and an optical reference beam (not shown). The measuring beam 24 passes through a measuring arm (not shown) and then hits the workpiece to be monitored or machined, according to 1 for example on the workpiece 12th . On the workpiece 12th becomes the measuring beam 24 at least partially reflected and returned to the beam splitter (not shown).

The optical reference beam (not shown) passes through a reference arm (not shown) and is at least partially reflected at one end of the reference arm. The reflected optical reference beam is also returned to the beam splitter. A superposition of the reflected optical measuring beam 24 and the reflected optical reference beam is then detected by means of a detector (not shown) of the coherence tomograph 20th detected in order to obtain height information at the location of the workpiece or about the location of the workpiece to which the measuring beam is pointing 24 hits.

How out 1 can be seen, is between the two mutually overlapping workpieces 12th , 14th A gap 26th trained, its size 28 or thickness using the coherence tomograph 20th should be monitored.

At the in 1 shown welding device 10 , in which an overlap weld of the workpieces 12th , 14th is carried out, is a check of the possibly occurring gap 26th by means of the measuring beam 24 not easily possible.

A monitor of the size 28 of the gap 26th however, it is advantageous. Namely, there are processes in which the provision of the gap 26th or joint gap is explicitly desired. This applies, for example, when the gap 26th as a degassing gap when welding workpieces designed as galvanized components 12th , 14th serves.

However, there are also many laser welding processes in which, if possible, a gap-free joint should be achieved in order to achieve a stable and easily reproducible welding process enable. This applies, for example, if the workpieces shown here by way of example are involved 12th , 14th are arresters of battery cells designed in particular as lithium-ion cells. In such cases, it is beneficial if by monitoring the size 28 of the gap 26th it can be ensured that the gap 26th is as narrow as possible or as far as possible not at all.

For example, when welding the arresters of the battery cells of a lithium-ion battery, the cycle times are very short. Therefore, it is desirable to have a very rapid inline detection of the size 28 of the gap 26th during the lap welding of the workpieces 12th , 14th can be made.

Out 1 it can be seen that the in 1 shown welding device 10 difficult is the measuring beam 24 to capture the size 28 of the gap 26th to use. Because that in 1 upper component or workpiece 12th blocks optical access to the in 1 lower component or workpiece 14th .

In 2 is one in terms of size monitoring 28 of the gap 26th improved welding device 30th shown, which also use the laser optics or laser welding optics 16 to generate the laser beam 18th as well as the output device 22nd of the optical coherence tomograph 20th having. Even with this welding device 30th is from the output device 22nd a measuring beam 32 output which from an in 2 measuring beam source, not shown in detail, of the optical coherence tomograph 20th provided.

At the in 2 shown welding device 30th however, the measuring beam can 32 self-sufficient or independent of the laser beam used as the processing laser 18th are issued or deflected. In other words, occurs accordingly 2 the measuring beam 32 at a different angle in the area of the laser welding optics 16 from the output device 22nd out than the laser beam 18th . The measuring beam 32 is also then placed on a deflecting mirror 34 directed, which is to the side next to the components or workpieces 12th , 14th is arranged.

The deflection mirror 34 reflects the measuring beam 32 thus from the side onto the joining partners in the form of the workpieces lying flat on top of one another 12th , 14th .

Accordingly, in operation of the welding device 30th or in the operation of the optical coherence tomograph 20th a narrow side 36 of the in 2 upper workpiece 12th and a narrow side 38 of the in 2 lower workpiece 14th by means of the deflection mirror 34 with the measuring beam 32 applied.

In contrast, the laser beam hits 18th on a broadside 40 of the in 2 upper workpiece 12th . This broadside 40 borders on the narrow side 36 of the in 2 upper workpiece 12th at. In particular, the laser beam 18th perpendicular to the broad side 40 of the upper workpiece 12th be directed while by means of the deflection mirror 34 the narrow sides 36 , 38 the two workpieces shown here by way of example 12th , 14th with the measuring beam 32 be applied.

The ones with the OCT system or with the coherence tomograph 20th coupled welding device 30th is therefore scanner-based or enables the front or narrow sides to be scanned or scanned 36 , 38 of the workpieces arranged in an overlapping manner 12th , 14th .

The measuring beam 32 or OCT measuring beam can initially use the same beam path as the laser beam used as the processing laser 18th run through. In particular by mirrors or similar deflection devices of the OCT scanner or the output device 22nd however, the measurement position can be scanned locally around the processing laser. This makes it possible to use the next to the components or workpieces 12th , 14th arranged deflection mirror 34 a line or scan line 42 (compare 2 ) to be scanned, using the OCT scanner or the output device 22nd a respective measuring point along the scan line 42 can be moved.

Accordingly, the size 28 of the gap 26th from this side of the two workpieces 12th , 14th comprehensive workpiece stack or component stack can be recorded very easily and reliably. Because that in 2 upper workpiece 12th does not interfere with the measuring beam 32 or does not obstruct the measuring beam 32 .

The present is the coherence tomograph 20th trained to do this, the narrow sides 36 , 38 of the workpieces 12th , 14th and the gap 26th with the measuring beam 32 to be scanned selectively. The corresponding line or scan line 42 is in 2 shown schematically.

By the edges and the end faces 36 , 38 of the workpieces 12th , 14th including the gap 26th between these two joining partners along the scan line 42 can be scanned or scanned, the gap 26th be reworked if necessary. Such post-processing can be carried out, for example, if the width or size 28 of the gap 26th lies outside a specified tolerance.

By scanning or scanning the narrow sides 36 , 38 and the gap 26th , becomes a two-dimensional image 44 a side view of the joining partners created, which is shown in 3rd is shown schematically. The picture 44 according to 3rd provides the means of the coherence tomograph 20th the welding device 30th captured OCT signals when scanning along the scan line 42 according to 2 represent.

In the two-dimensional picture 44 corresponds to a first line 46 a thick one 48 of the in 2 upper joining partner, i.e. the first workpiece 12th . A second line corresponds in an analogous manner 50 in the picture 44 a thick one 52 of the in 2 lower joining partner, i.e. the second workpiece 14th . By measuring an interruption in the OCT signals between the joining partners, the size 28 of the gap 26th be determined.

In a manner not shown in greater detail here, the coherence tomograph 20th a plurality of deflection mirrors 34 have, by means of which the size 28 of the gap 26th at a plurality of monitoring points of the workpieces arranged so as to overlap with one another at least in some areas 12th , 14th is detectable.

For example, respective deflecting mirrors 34 on several sides of the work pieces 12th , 14th comprehensive component stack are arranged. In this way it is possible to change the size 28 of the gap 26th not just in one place, but in several places around the stack of components.

The deflecting mirror, which is only shown schematically here, is preferably 34 designed in such a way that it is suitable for the wavelength of the optical coherence tomograph 20th provided measuring beam 32 is designed.

It is also possible as the at least one deflection mirror 34 or the like deflector to use a spherical concave mirror. In this way it can be achieved that the detector of the coherence tomograph 20th captured OCT signals are at the same level.

As explained above, by means of the OCT scanner or the output device 22nd the scan line 42 over the next to the component assembly or next to the workpieces 12th , 14th arranged deflection mirror 34 be scanned.

The gap 26th can also be measured in a different way than by corresponding control of the OCT scanner. This is because it is additionally or alternatively possible that the OCT scanner or the output device 22nd the measuring beam 32 on the deflection mirror 34 aligns and the measuring beam 32 then there stands still while the deflecting mirror 34 moves or is moved.

This also has the consequence that the measuring beam 32 or OCT measuring beam over the component end faces or the narrow sides 36 , 38 of the overlapping arranged workpieces 12th , 14th is directed. A corresponding movement device of the coherence tomograph 20th which are used to move the at least one deflection mirror 34 is trained is in 2 by a double arrow 54 illustrated.

Overall, the examples show how the size can be measured in a particularly simple way 28 of the gap 26th or joint gap in the case of an overlap welded connection of the workpieces 12th , 14th by means of the optical coherence tomograph 20th using the at least one deflection mirror 34 can be done.

List of reference symbols

10

Welding device

12th

workpiece

14th

workpiece

16

Laser welding optics

18th

laser beam

20th

Coherence tomograph

22nd

Output device

24

Measuring beam

26th

gap

28

size

30th

Welding device

32

Measuring beam

34

Deflection mirror

36

Narrow side

38

Narrow side

40

Broadside

42

Scan line

44

picture

46

line

48

thickness

50

line

52

thickness

54

Double arrow

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102016010508 A1 [0002, 0028]
• DE 102013112244 B4 [0004]

Claims (8)

Welding device for connecting a first workpiece (12) to a second workpiece (14) by laser welding, the welding device (30) being designed to apply a laser beam (18) to the workpieces (12, 14) and an output device (22) an optical coherence tomograph (20), the output device (22) being designed for outputting a measuring beam (32) of the coherence tomograph (20), the measuring beam (32) being used to determine a size (28) of a temperature between the workpieces (12 , 14) formed gap (26) can be detected, and wherein the coherence tomograph (20) has at least one deflecting mirror (34) which is designed to deflect the measuring beam (32), characterized in that by means of the at least one deflecting mirror (34) respective Narrow sides (36, 38) of the workpieces (12, 14) arranged so as to overlap one another at least in some areas can be acted upon by the measuring beam (32), with e A broad side (40) of one of the workpieces (12), which adjoins the narrow side (36) of this workpiece (12), can be acted upon by the laser beam (18). Welding device according to Claim 1 , characterized in that the welding device (30) is designed to direct the laser beam (18) essentially perpendicular to the broad side (40), while the narrow sides (36, 38) of the workpieces ( 12, 14) can be acted upon with the measuring beam (32). Welding device according to Claim 1 or 2 , characterized in that the coherence tomograph (20) is designed to scan the narrow sides (36, 38) of the workpieces (12, 14) and the gap (26) with the measuring beam (32) at specific points. Welding device according to one of the Claims 1 to 3rd , characterized in that the coherence tomograph (20) is designed to provide a two-dimensional image (44) of the narrow sides (36, 38) of the workpieces (12, 14) and of the gap (26) formed between the workpieces (12, 14) create. Welding device according to Claim 4 , characterized in that the coherence tomograph (20) is designed to determine the size (28) of the gap (26) from the two-dimensional image (44). Welding device according to one of the Claims 1 to 5 , characterized in that the coherence tomograph (20) has a plurality of deflection mirrors (34) by means of which the size (28) of the gap (26) can be detected at a plurality of monitoring points of the workpieces (12, 14) which are arranged overlapping at least in some areas . Welding device according to one of the Claims 1 to 6th , characterized in that the coherence tomograph (20) comprises a movement device for moving the at least one deflection mirror (34), wherein the movement device is designed to move the deflection mirror (34) to move the narrow sides (36, 38) of the workpieces (12, 14) and scan the gap (26) with the measuring beam (32). Method for joining a first workpiece (12) to a second workpiece (14) by laser welding by means of a welding device (30), the workpieces (12, 14) being acted upon by a laser beam (18) provided by the welding device (30), and an output device (22) of an optical coherence tomograph (20) outputting a measuring beam (32), the measuring beam (32) being used to detect a size (28) of a gap (26) formed between the workpieces (12, 14) during laser welding , and wherein the coherence tomograph (20) has at least one deflection mirror (34) which deflects the measuring beam (32), characterized in that, by means of the at least one deflection mirror (34), respective narrow sides (36, 38) of the workpieces which are at least partially overlapping (12, 14) are acted upon by the measuring beam (32), and then and / or at the same time a broad side (40) of one of the workpieces (12) which is attached to d he narrow side (36) of this workpiece (12) is adjacent to which the laser beam (18) is applied.

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