Method for joining components by means of at least one weld seam

Abstract

The invention relates to a method for joining components (2, 3) by means of at least one weld (S). According to the invention, defects in a produced weld (S) are detected. If at least one defect is present, a laser transmission welding process is carried out in a post-processing step of the weld (S), wherein at least one laser beam (L) is guided through a region of a first component (2) that is transparent to the laser beam (L) onto the weld (S) located in a contact area of ​​the components (2, 3), and the weld (S), or the weld (S) and the second component (3), or the weld (S) and both components (2, 3) are at least partially melted.At least after melting, a defined post-processing joining pressure (NF) is applied to the components (2, 3) so that the components (2, 3) are pressed against each other in the molten area and the weld seam (S) and / or the second component (3) is compressed in the molten area by a predetermined post-processing settling distance (NW). Subsequently, the molten area is cured while maintaining the post-processing joining pressure (NF). The invention further relates to a component arrangement (5).

Description

[0001] The invention relates to a method for joining components by means of at least one weld seam. The invention further relates to a component assembly produced by such a method.

[0002] From WO 2015 / 055419 A1, a method for producing a battery housing is known, wherein the method comprises the following method steps: providing a battery housing which is formed from a composite material which has a thermoplastic matrix and a fiber fabric, fiber fabric or metal sheet or metal grid arranged in the thermoplastic matrix; arranging a cover on the battery housing; melting a connecting region between the battery housing and the cover in regions by means of a laser beam device; exerting mechanical pressure on the cover during melting, wherein the pressure presses the cover against the battery housing; and subsequently solidifying the connecting region to connect the cover to the battery housing.

[0003] The invention is based on the object of providing a novel method for joining components by means of at least one weld seam and a novel component arrangement produced by means of such a method.

[0004] The object is achieved according to the invention by a method which has the features specified in claim 1 and by a component arrangement which has the features specified in claim 8.

[0005] Advantageous embodiments of the invention are the subject of the subclaims.

[0006] In the method for joining components by means of at least one weld seam, defects are detected according to the invention in a weld seam produced by means of a first laser transmission welding process between two components each formed at least partially from a thermoplastic material. If at least one defect is present, a second laser transmission welding process is carried out in post-processing of the weld seam, wherein at least one laser beam is guided through a region of a first component that is transparent to the laser beam onto the weld seam located in a contact region of the components, and the weld seam or the weld seam and the second component or the weld seam and both components is / are at least partially melted.At least after melting, a defined post-processing joining pressure is applied to the components, so that the components are pressed against each other in the melted area, and the weld seam and / or the second component in the melted area are compressed by a specified post-processing set distance. The melted area is then cured while maintaining the post-processing joining pressure.

[0007] In a laser transmission welding process, the components are welded together using a quasi-simultaneous welding process. The laser beam heats a weld contour "virtually simultaneously." The simultaneously applied joining pressure melts the thermoplastic material, compressing the components to a defined set point. Once the set point is reached, the joining pressure is maintained for a short time to allow cooling in the weld area. This creates a material-to-material bond across the entire joining surface.

[0008] However, in such a laser transmission welding process, defects in the produced weld seam can occur due to deviations in the components, for example due to manufacturing tolerances, and / or due to process parameters and / or process conditions and / or damage, which can lead to leaks in the area of ​​the weld seam and in a component arrangement comprising the components.

[0009] This process enables the advantageous and reliable reworking of defective weld seams, ensuring that these defects are reliably sealed. Furthermore, an accepted height tolerance and the resulting gaps in the welding area of ​​the joining partners can be increased. This allows the weld seam and, consequently, the component assembly to be sealed. Using this process, it is possible to reduce the reject rate in the production of component assemblies, resulting in savings in material, effort, energy, time, and costs. During reworking, stresses created during the melting of the original weld seam and the subsequent compression during the original welding process are released and compensated.

[0010] In one possible embodiment of the method, in the first laser transmission welding method, the first component is positioned on the other component such that the components touch in the contact area. Subsequently, at least one laser beam is guided through the area of ​​the first component that is transparent to the laser beam onto an area of ​​the second component located in the contact area, and this area is at least partially melted. By conducting heat from the melted area of ​​the second component, the first component is also at least partially melted in the contact area. At least after melting, a defined joining pressure is applied to the components such that the first component is pressed against the second component in the melted area and at least the second component is compressed by a predetermined setting distance in its melted area.The molten area is then cured while maintaining the joining pressure. The laser transmission welding process enables the creation of the weld seam through non-contact energy application, whereby no mechanical or oscillating stress is generated on the joining partners by the energy input. Only a small heat-affected zone is created by a locally limited energy input, so that thermal stress on sensitive component areas can be minimized. Furthermore, no surface markings are created by the welding process, and there is considerable design freedom for the components to be welded. Furthermore, the laser transmission welding process is characterized by good automation and integration into series production, and it also allows for the welding of pre-assembled components.Furthermore, the weld seam is characterized by a good external appearance, for example for use in visible areas.

[0011] In another possible embodiment of the method, the laser beam parameters and / or the post-processing joining pressure are / are selected during post-processing such that the post-processing settling distance is smaller than the settling distance generated by the initial joining pressure. This minimizes changes in the dimensions of the component arrangement resulting from post-processing.

[0012] In a further possible embodiment of the process, the joining pressure is maintained for a predetermined period of time during the hardening of the molten area carried out after the first laser transmission welding process in order to enable complete cooling and hardening of the weld seam while minimizing defects.

[0013] In a further possible embodiment of the process, the post-processing joining pressure is maintained for a predetermined period of time during the hardening of the area melted during the post-processing in order to enable complete cooling and hardening of the reworked weld seam without defects.

[0014] In another possible embodiment of the process, the period for maintaining the post-processing joining pressure is selected to be longer than the period for maintaining the joining pressure. This can further minimize the risk of defects occurring.

[0015] In another possible embodiment of the process, the post-processing joining pressure is maintained for a period of more than 10 seconds, for example, for a period of 15 seconds, 20 seconds, 25 seconds, or 30 seconds. Such a period has proven particularly effective for minimizing defects within the weld seam.

[0016] The component assembly according to the invention comprises at least two components, wherein the components are connected by means of a weld seam reworked using a method described above. Due to the rework of the weld seam, the component assembly is designed to be media-tight in this area and thus exhibits a minimal leakage rate.

[0017] In one possible embodiment of the component arrangement, it is designed as a battery housing for an electrical energy storage device, with one of the components being a cover and the other a housing body closed by the cover. The battery housing is media-tight due to the post-processing of the weld seam and thus has a minimal leakage rate, which can be, for example, 5.4 * 10 -5 mbar * l / s. This makes it possible to store a temperature control medium in the battery housing without it leaking out. Due to its tightness and minimized leakage rate, the battery housing advantageously meets the requirements of a helium leak test required for its use.

[0018] In another possible configuration of the component arrangement, additional components coupled to openings in the battery housing, such as additional covers, media connections, electrical connections, etc., can be coupled to the battery housing in a particularly reliable, media-tight manner using weld seams created and reworked using the aforementioned method. It is also possible for the components themselves to be produced in a media-tight manner from multiple sub-elements using this method.

[0019] Embodiments of the invention are explained in more detail below with reference to the drawings. In the drawings: Fig. 1 schematically shows a device for connecting components by means of at least one weld seam, Fig. 2 schematically shows a sectional view of a section of two components, Fig. 3 schematically shows a sectional view of a further section of the components according to Fig. 2, Fig. 4 schematically shows a sectional view of a section of two components, Fig. 5 schematically shows a sectional view of a further section of the components according to Fig. 4 and Fig. 6 schematically shows a sequence of a method for joining components by means of a weld seam.

[0020] Corresponding parts are provided with the same reference numerals in all figures.

[0021] Fig. 1 shows a possible embodiment of a device 1 for connecting components 2, 3 formed at least in sections from thermoplastic material by means of at least one joint produced in a laser transmission welding process and in Fig. 6 weld seam shown in more detail S.

[0022] The device 1 comprises a scanner optics 1.1-1.2, a web plate 1.3, a pressure stamp 1.4, a tool carrier 1.5 and a linear drive 1.6.

[0023] To create the weld seam S, the component 2, for example a cover for a battery housing, is arranged together with the component 3, for example a housing element for the battery housing, on the tool carrier 1.5 in such a way that the components 2, 3 are already positioned in a desired later position. The pressure stamp 1.4 is arranged on the component 2. The web plate 1.3 is arranged above the pressure stamp 1.4. For example, the pressure stamp 1.4 is fastened to the web plate 1.3. By means of the linear drive 1.6, a Fig. 6, the joining pressure F shown in more detail is applied to the components 2, 3 and at least one laser beam L is generated by means of the scanner optics 1.1-1.2.

[0024] In order to weld the components 2, 3 together in a quasi-simultaneous welding process, the laser beam L is guided through a region of the component 2 that is transparent to this region to a region of the component 3 that is in the contact area with the component 3 and has a high degree of absorption for the laser beam L, so that this region is at least partially melted. By heat conduction from the melted region of the component 3, the component 2 is also at least partially melted in the contact area. The laser beam L is guided in such a way that it melts a welding contour “quasi completely simultaneously”. Due to the simultaneously applied joining pressure F, a melting of at least the thermoplastic material of the component 3 is realized, whereby at least the component 3 is melted up to a defined, also in Fig. 6. After reaching the settling distance W, the joining pressure F is maintained for a defined period of time to allow cooling and hardening of the thermoplastic material in the weld area. Thus, the weld S creates a material-to-material connection across the entire joining surface between components 2, 3.

[0025] The component 2, designed, for example, as a cover, is welded to the component 3, for example, to close an opening formed on an upper side of the component 3, designed, for example, as a housing element for the battery housing. In a manner not shown in detail, a further component, also designed as a cover, can additionally be welded to the housing element in the same way at an opening formed on an underside of the housing element.

[0026] Furthermore, other components not shown in detail can also be welded to components 2, 3 in a manner analogous to the described laser transmission welding process.

[0027] The Fig. 2 to 5 show sectional views of sections of different embodiments of by means of an analogous to the description of Fig. 1 laser transmission welding process of components to be welded 2, 3.

[0028] The component 2 is transparent to the laser beam L, at least in the contact area with the component 3. The component 3 has a high absorption coefficient for the laser beam L in the contact area with the component 2.

[0029] In all embodiments, it is provided to connect a flat side of the component 2 with a front side of the component 3 by means of a weld seam S produced in the laser transmission welding process, as shown schematically in the Fig. 2 to 5.

[0030] Fig. 6 shows a sequence of a possible embodiment of a method for connecting components 2, 3 by means of a weld seam S. The sequence can also be transferred analogously to the production of weld seams S of other components.

[0031] In a first method step V1, the components 2, 3 are positioned such that the components 2, 3 touch each other in a contact area.

[0032] Subsequently, in a second process step V2, analogous to the description of Fig. 1 a laser transmission welding process is carried out, whereby the joining pressure F and a power P of the laser beam L are adjusted such that the settling distance W is achieved. The joining pressure F is, for example, 3.5 N / mm 2 up to 5 N / mm 2 , for example 4 N / mm 2The settling distance W is, for example, 0.3 mm to 0.5 mm, for example, 0.4 mm. After reaching the settling distance W, the joining pressure F is maintained for a defined period of, for example, 5 seconds to 7 seconds, for example, 6 seconds, to allow the thermoplastic material in the weld area to cool and harden.

[0033] During the production of the weld seam S, defects in the produced weld seam S may arise due to deviations in the components 2, 3 and / or due to process parameters and / or process conditions and / or damage, which may lead to leaks in the area of ​​the weld seam S and in the component arrangement 5 comprising the components 2, 3.

[0034] To eliminate these defects, it is planned to first identify them. This can be done, for example, using leak tests, such as a helium leak test, or imaging techniques, such as X-rays.

[0035] If defects have been identified, at least a second laser transmission welding process is carried out in a further process step V3 in a post-processing of the weld seam.

[0036] For this purpose, the component arrangement 5 is positioned in particular in the same device 1 in which the original laser transmission welding process was carried out.

[0037] Subsequently, by means of the device 1 in the second laser transmission welding process, at least one laser beam L is guided through the region of the component 2 that is transparent to the laser beam L onto the weld seam S located in the contact area of ​​the components 2, 3, while applying a post-processing joining pressure NF to the components 2, 3, so that the weld seam S or the weld seam S and the component 3 or the weld seam S and both components 2, 3 is / are at least partially melted. The joining pressure F and a power P of the laser beam L are adjusted such that a post-processing settling distance NW is achieved. The post-processing joining pressure NF is, for example, 3.5 N / mm 2 up to 5 N / mm 2 , for example 4 N / mm 2The post-processing settling distance NW is, for example, 0.15 mm to 0.2 mm, for example, 0.17 mm. After reaching the post-processing settling distance NW, the post-processing joining pressure NF is maintained for a defined period of time, for example, more than 10 seconds, for example, 12 seconds, 15 seconds, or 20 seconds, to allow complete cooling and curing of the thermoplastic material in the weld area.

[0038] The features and advantages described herein with respect to a method for joining components may also relate to the component arrangement described herein and vice versa. List of reference symbols 1 device 1.1 Scanner optics 1.2 Scanner optics 1.3 Multi-wall sheet 1.4 Printing stamp 1.5 Tool carrier 1.6 Linear drive 2 component 3 Component 5 Component arrangement F Joining pressure L laser beam NF post-processing joining pressure NW post-processing setting path P Performance S Weld seam V1 to V3 process step W setting path QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2015 / 055419 A1

[0002]

Claims

[1] Method for joining components (2, 3) by means of at least one weld seam (S), characterized by , that - Defects are detected in a weld seam (S) produced by means of a first laser transmission welding process between two components (2, 3) each formed at least partially from a thermoplastic material, - if at least one defect is present in a post-processing of the weld seam (S), a second laser transmission welding process is carried out, wherein at least one laser beam (L) is guided through a region of a first component (2) that is transparent to the laser beam (L) onto the weld seam (S) located in a contact region of the components (2, 3), and the weld seam (S) or the weld seam (S) and the second component (3) or the weld seam (S) and both components (2, 3) is / are at least partially melted, - at least after melting, a defined post-processing joining pressure (NF) is applied to the components (2, 3) so that the components (2, 3) are pressed against each other in the melted area and the weld seam (S) and / or the second component (3) in the melted area are / is compressed by a predetermined post-processing setting distance (NW), and - the melted area is cured while maintaining the post-processing joining pressure (NF). [2] Method according to claim 1, characterized by that in the first laser transmission welding process - the first component (2) is positioned on the further component (3) so that the components (2, 3) touch each other in the contact area, - subsequently, at least one laser beam (L) is guided through the region of the first component (2) that is transparent to the laser beam (L) onto a region of the second component (3) located in the contact region, and this region is at least partially melted, - the first component (2) is at least partially melted in the contact area by heat conduction from the melted area of ​​the second component (3), - at least after melting, a defined joining pressure (F) is applied to the components (2, 3) so that the first component (2) is pressed against the second component (3) in the melted area and at least the second component (3) is compressed in its melted area by a predetermined setting distance (W), - the melted area is cured while maintaining the joining pressure (F). [3] Method according to one of the preceding claims, characterized bythat in the post-processing parameters of the laser beam (L) and / or the post-processing joining pressure (NF) are / is selected such that the post-processing setting path (NW) is smaller than the setting path (W) generated by means of the joining pressure (F). [4] Method according to claim 2 or 3, characterized by that during the curing of the molten area carried out after the first laser transmission welding process, the joining pressure (F) is maintained for a predetermined period of time. [5] Method according to one of the preceding claims, characterized by that the post-processing joining pressure (NF) is maintained for a specified period of time during the curing of the area melted during post-processing. [6] Method according to claim 5, characterized by that the period for maintaining the post-processing joining pressure (NF) is chosen to be longer than the period for maintaining the joining pressure (F). [7] Method according to claim 5 or 6, characterized by that the maintenance of the post-processing joining pressure (NF) is carried out for a period of more than 10 s. [8] Component arrangement (5) comprising at least two components (2, 3), wherein the components (2, 3) are connected by means of a weld seam (S) reworked in a method according to one of the preceding claims. [9] Component arrangement (5) according to claim 8, designed as a battery housing for an electrical energy storage device, wherein one of the components (2) is a cover and the other component (3) is a housing body closed by means of the cover.

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