DEVICE FOR WELDING BAR-SHAPED ELECTRICAL CONDUCTORS AND SONOTRODE FOR SUCH A DEVICE

Description

[0001] The present invention relates to a device for welding rod-shaped electrical conductors according to the preamble of claim 1 (see e.g. US 2006 / 169388 A1).

[0002] Devices of the type mentioned above have a compression chamber that serves to create an ultrasonic weld between the connection areas of conductors. In practice, electrical conductors with widely varying diameters in their connection areas are joined using the same device. The conductors are handled in a substantially uniform manner, regardless of the different diameters of the connection areas, such that the connection areas are placed in the open compression chamber. After the compression chamber is closed, a contact area is created between the working surface of the sonotrode and at least the lower connection area of ​​two conductors arranged one above the other in a stacked configuration. The contact area depends on the diameter of the connection area.

[0003] To transmit the ultrasonic vibrations from the sonotrode to the connection areas, the working surface is provided with a profiled surface design, such that profiled protrusions extend across the working surface transversely to the longitudinal axis of the sonotrode. Particularly with very small diameter connection areas of the conductors, it has been found that the profiled protrusions can lead to excessive mechanical stress on the connection areas, which manifests itself in the finished weld joint as not achieving the optimal possible joint strength.

[0004] US Patent 2006 / 169388 A1 discloses a sonotrode paired with a suitably designed anvil for joining surfaces or plate-shaped materials, wherein a non-uniformly designed working surface of the sonotrode, which has a profile reduced to an edge area of ​​the working surface, serves to reduce the stress on the materials to be joined in their edge areas.

[0005] US Patent 2015 / 288123 A1 relates to an ultrasonic welding device with a compression chamber and a sonotrode that limits the compression chamber in one axial direction. The sonotrode has a working surface which, in a central area, has a surface structure that is at least non-uniform and which has a surface design that differs from that of the contact zone formed by the rest of the working surface.

[0006] JP 2014 179435 A discloses a sonotrode by which an angled end of a flat contact conductor can be connected to a terminal surface, wherein a reduced mechanical stress on the conductor is to be enabled by a profiling of a working surface of the sonotrode that decreases towards the angled end.

[0007] US 2004 / 020580 A1 describes a sonotrode that enables a connection of a flat cable to a busbar.

[0008] The present invention is therefore based on the objective of proposing a device for welding rod-shaped electrical conductors, which enables an effective reduction of the notch effect when a wire conductor is subjected to ultrasonic vibrations in a compression chamber.

[0009] To solve this problem, the device according to the invention has the features of claim 1.

[0010] In the device according to the invention, the special contact zone is arranged adjacent to the limiting element, such that the special contact zone is formed on a working surface edge parallel to the limiting element.

[0011] The device according to the invention enables the production of ultrasonic welding connections between electrical conductors with medium and large wire diameters as well as with small and very small wire diameters using one and the same device or one and the same sonotrode.

[0012] According to the invention, by differentiating the design of the working surface or by dividing the working surface into a contact zone intended for contacting with medium and large wire diameters and a special contact zone intended for contacting with small and smallest wire diameters, optimal ultrasonic stimulation of different wire diameters is achieved with one and the same device or one and the same sonotrode.

[0013] This makes it possible for the special contact zone to be fully effective in small welding connectors, preventing damage to the wires or conductors caused by the profile protrusions, whereas conductors with larger diameter wires essentially have contact with the "normal" profile in the contact zone of the working surface, allowing greater forces to be transmitted.

[0014] Thus, the smallest and small conductor cross-sections can be supplied with a "softened" profile of the working surface in the special contact zone, and medium and large conductor cross-sections with the "sharp" profile in the contact zone, in order to enable equally optimal connection strengths regardless of the conductor cross-section.

[0015] According to the invention, the special contact zone is arranged adjacent to the limiting element, so that in a closed compression chamber, in which the sliding element is displaced in the y-axis direction as far as the intermediately arranged connection areas of the conductors allow, the desired arrangement of the connection areas in the special contact zone is established.

[0016] This is particularly the case if, according to the invention, the special contact zone is formed on a working surface edge of the sonotrode that is parallel to the limiting element.

[0017] According to the invention, the contact zone has a surface design with profile elevations extending in the third axial direction, which at least partially in the area of ​​the special contact zone have a special profile cross-section that differs from the profile cross-section in the contact zone.

[0018] A particularly simple implementation of the special contact zone is possible because, according to the invention, the special profile cross-section has a reduced profile height compared to the standard profile cross-section.

[0019] Preferably, the reduced profile height is formed by flattening or rounding off a profile tip of the profile cross-section, so that, particularly in the case of flattening, the special contact zone can be formed by partial material removal following the production of the working surface of the sonotrode.

[0020] Preferably, the special contact zone has at least in a central area extending in the first axial direction a special contact section symmetrical to a symmetry axis running parallel to the third axial direction, wherein in a particularly easy-to-manufacture embodiment the special contact zone is symmetrical over its entire length.

[0021] A contact zone arranged symmetrically in the working surface becomes possible if the axis of symmetry is formed by a central axis of the working surface running parallel to the third axis direction, whereby such an embodiment is particularly advantageous for producing a through connection between two conductors, in which the connection areas of the conductors to be connected extend in an overlapping arrangement across the central axis in opposite directions.

[0022] Experiments have shown that the achievable connection quality, especially of overlapping conductors extending in opposite directions, has a particularly positive effect if at least one profile elevation formed in the area of ​​the axis of symmetry extends over the entire width of the working surface and is preferably constant, i.e., if the special contact zone is divided into two sub-zones by the constantly formed profile elevation in the longitudinal direction of the sonotrode or in the direction of the x-axis.

[0023] It is also particularly advantageous if the special contact zone extends only over a portion of the contact zone in the first axial direction.

[0024] If the special contact zone is arranged asymmetrically to a central axis of the working surface running parallel to the third axis direction, the device is particularly suitable for creating a connection between overlapping connection areas of two conductors that extend in the same direction.

[0025] Furthermore, if the special contact zone is arranged to be shifted towards one end of the working surface, the design of a sub-area of ​​the contact zone for forming the special contact zone can be limited to a small, external working surface area, thereby simultaneously defining an "insertion side" of the sonotrode working surface, i.e. the side of the sonotrode working surface on which the insertion of the connecting areas of the conductors to be joined into the compression space takes place.

[0026] Preferably, the special contact zone has a width in the third axis direction that is less than 2 mm.

[0027] It is particularly preferred if the special contact zone has a width in the third axial direction of less than 1.5 mm. In special cases, particularly when very small wire diameters are to be joined together, it has proven advantageous if the special contact zone has a width in the third axial direction of less than 1 mm.

[0028] To solve the problem underlying the invention, the sonotrode can have a working surface which, in a special contact zone designed as a sub-area of ​​the working surface, which can serve to impart ultrasonic vibrations to at least one connection area of ​​an electrical conductor, has a surface design that differs from a contact zone formed by the rest of the working surface.

[0029] Preferably, the special contact zone extends in the direction of a longitudinal axis of the sonotrode.

[0030] It is particularly preferred if the special contact zone is formed on a working surface edge of the sonotrode.

[0031] If the contact zone has a surface design with profile elevations running transversely to the longitudinal direction of the sonotrode, which in the area of ​​the special contact zone have a special profile cross-section that differs from the profile cross-section in the contact zone, the design of the special contact zone can be carried out in a particularly simple manner.

[0032] It is particularly preferred if the special profile cross-section has a reduced profile height compared to the standard profile cross-section.

[0033] Furthermore, it is preferred if the reduced profile height is formed by a flattening or rounding of a profile tip of the profile cross-section.

[0034] Preferably, the special contact zone has, at least in a central area extending in the direction of the longitudinal axis, a special contact section that is symmetrical to an axis of symmetry running parallel to a transverse axis.

[0035] In a particularly preferred embodiment, the special contact zone is symmetrically designed over its entire length.

[0036] If the axis of symmetry is formed by a central axis of the working surface running parallel to the transverse axis, the sonotrode is particularly suitable for creating a connection between connection areas of conductors that extend in opposite directions.

[0037] Preferably, at least one profile elevation formed in the region of the axis of symmetry extends over the width of the working surface, wherein the profile elevation is particularly preferably constant.

[0038] If the special contact zone extends only over a portion of the contact zone in the direction of the longitudinal axis, the formation of the special contact zone can be limited to the actual overlap area of ​​the conductors resulting from the overlapping arrangement of the connection areas.

[0039] In particular, for the purpose of creating a connection between connection areas of two conductors extending in the same direction, it is advantageous if the special contact zone is arranged asymmetrically to a central axis of the working surface running parallel to the transverse axis.

[0040] Preferably, the special contact zone is arranged towards one end of the work surface.

[0041] In a preferred embodiment of the sonotrode, the special contact zone has a width in the direction of the transverse axis that is less than 2 mm.

[0042] It is particularly advantageous if the special contact zone has a width in the direction of the transverse axis that is less than 1.5 mm, and furthermore, in the case of conductors with particularly small diameters, it is advantageous if the special contact zone has a width in the direction of the transverse axis that is less than 1 mm.

[0043] Preferred embodiments of the device and the sonotrode are explained in more detail below with reference to the drawing.

[0044] They show: Fig. 1 an open compression chamber of an ultrasonic welding device in a front view with two connection areas of conductors to be welded together arranged one above the other in a stack arrangement; Fig. 2 the in Fig. 1 depicted dense area in closed configuration; Fig. 3 a sonotrode in isometric representation with two connection areas arranged in a special contact zone to create a through node; Fig. 4 a sonotrode in isometric representation with two connection areas arranged in a special contact zone for the production of an end node; Fig. 5 a work surface in Fig. 3 The sonotrode shown in an enlarged view has a special contact zone formed on a working surface edge in a first embodiment; Fig. 6 a work surface in Fig. 3 The sonotrode shown in an enlarged view with a special contact zone formed on a working surface edge in a second embodiment; Fig. 7 a work surface in Fig. 3 The sonotrode shown in an enlarged view with a special contact zone formed on a working surface edge in a third design form; Fig. 8 a schematic representation of the arrangement of the in Fig. 6 The connection areas shown on the special contact zone in a sectional view according to section line VIII - VIII in Fig. 4 .

[0045] The Fig. 1 und 2 Figure 1 shows the essential elements of a compression chamber 18, adjustable in cross-section (i.e., adjustable in height and width), which serves to accommodate connection areas 26, 27 of conductors 28, 29 extending in a first axial direction (x-axis). The compression chamber 18 is bounded in a second axial direction (z-axis) on two opposite sides by a working surface 19 of a sonotrode 16 transmitting ultrasonic vibrations and a counter surface 20 of an anvil 21 movable in a third axial direction (y-axis). In the third axial direction, the compression chamber 18 is bounded on two opposite sides by a boundary surface 22 of a sliding element 23 movable in the y-axis direction and a boundary surface 24 of a boundary element 25, which, like the anvil 21, is movable in the z-axis direction.

[0046] At the in Fig. 1 In the illustrated embodiment of the compression chamber 18, two connection areas 26, 27 of conductors 28, 29 to be connected to each other by means of the sonotrode 16 are arranged one above the other in a stacked arrangement on the working surface 19 of the sonotrode 16, wherein Fig. 1 the connection areas 26, 27 immediately after insertion into the opened compression chamber 18.

[0047] Fig. 2 Figure 1 shows the compression chamber 18 in the closed configuration, in which the components limiting the compression chamber 18, namely the sonotrode 16, the anvil 21, the sliding element 23 and the limiting element 25, are moved against each other in such a way that the compression chamber 18, now reduced in volume, forms a shape 40 which, when the connection areas 26, 27 of the conductors 28, 29 are subjected to mechanical vibrations of the sonotrode 16, enables compression and connection of the connection areas 26, 27 to form a weld node in a friction welding process.

[0048] As from the Fig. 1 und 2 As can be seen, the working surface 19 has a contact zone 30 and a special contact zone 31, whereby in the present case the connection areas 26, 27 of the conductors 28, 29 have such a small cross-section that the connection area 26 of the lower conductor 28 rests exclusively in the special contact zone 31 of the working surface 19. After transferring the compaction space into its in Fig. 2 In the closed configuration shown, and with the activation of the sonotrode 16 for the execution of ultrasonic vibrations, the transmission of the ultrasonic vibrations to the connection area 26 only occurs in the area of ​​the special contact zone 31.

[0049] As illustrated by the dashed representation of connection areas 32, 33, which have a significantly larger cross-section compared to connection areas 26, 27, such large cross-section connection areas 32, 33 would mostly lie on the contact zone 30 of the working surface 19 and only with a relatively small proportion in the special contact zone 31.

[0050] As can be seen from the depictions in the Fig. 3 bis 7 As can be seen, the working surface 19 has a profiled surface design with profiled protrusions 34 that extend across the working surface 19 transversely to the longitudinal axis L of the sonotrode 16. In special contact zones 31, 50, 51, 52 formed along a working surface edge 35, the profiled protrusions 34 are at least partially provided with a special profile cross-section 36, which differs from a profile cross-section 37 of the profiled protrusions 34 in the area of ​​the contact zone 30.

[0051] In the case of the in the Fig. 3 bis 7 In the illustrated embodiments, the special profile cross-section 36 has a reduced profile height compared to the profile cross-section 37, which is formed by a flattening 38 of a profile tip 39 formed on the profile cross-section 37 in the area of ​​the contact zone 30. The flattening 38 thus creates a "softened" profile in the special contact zone 31, so that the corresponding Fig. 3 and 4 The lower connection area 26 is subjected to comparatively less mechanical stress when subjected to vibration by the sonotrode 16 in the longitudinal direction of the sonotrode 16 than would be the case when the connection area 26 is subjected to the "sharper" profile cross-section 37 of the profile elevations 34 in the contact zone 30.

[0052] Fig. 3 The arrangement of the conductors 28, 29 for creating a through-junction is shown, with the sonotrode 16 on the working surface 19 with a Fig. 5 The special contact zone 50 is shown enlarged. Fig. 4 The arrangement of the ladders 28, 29 for producing an end node is shown, with the sonotrode 16 on the working surface 19 with a Fig. 7 The special contact zone 52 is shown enlarged.

[0053] Fig. 5 Figure 1 shows the formation of the special contact zone 50 with a special contact section 53 extending in the direction of the longitudinal axis L and symmetrically formed with respect to an axis of symmetry S, which is arranged parallel to a transverse axis Q, which in this case is arranged at a right angle to the longitudinal axis L. Since in this case the axis of symmetry S coincides with the central axis M of the working surface 19, the special contact zone 50 is thus symmetrically formed over its entire length.

[0054] Unlike the one in Fig. 5 The special contact zone 50 shown in the diagram indicates that Fig. 6 The special contact zone 51 shown, located in the area of ​​the axis of symmetry S, which in this case again coincides with the central axis M of the working surface 19, features a profile projection 34 extending along the axis of symmetry S. This profile projection has a constant cross-sectional area 37 and extends over the entire width B of the working surface 19. This results in two special contact sections 54 and 55 separated from each other by the central profile projection 34. It has been found that, due to the "central tooth" thus formed by the continuous profile projection 34, the conductors 28 and 29 to be connected are arranged according to the following configuration: Fig. 3 a particularly high "peel strength" of the through-node can be achieved.

[0055] Fig. 7 shows the configuration of a special contact zone 52, which is particularly suitable for forming an end node, wherein the end node is formed by the Fig. 4 The relative arrangement of the connection areas 26, 27 shown on the work surface 19 is provided in the special contact zone 52.

[0056] How Fig. 7 As shown, the special contact zone 52 is arranged asymmetrically to the central axis M of the working surface 19, which extends parallel to the transverse axis Q (running at a right angle to the longitudinal axis in this case). The special contact zone 52 is displaced towards a working surface end 56, which in this case is located at a free sonotrod end 57. As can be seen in particular from Fig. 4 It is evident that an insert side E is thus defined, such that it is the one in Fig. 7 The depicted formation or arrangement of the special contact zone 52 in the working surface 19 offers the connection areas 26, 27 to be connected to each other to form an end node, with reference to the illustration of the sonotrode 16 in Fig. 4 from left to right of the work surface 19 of the sonotrode 16, or into the Fig. 1 und 2 to introduce the densely populated area 18 shown.

[0057] Fig. 8 illustrates the arrangement of the lower connection area 26 on the in Fig. 6 The special contact zone 51 shown is characterized by a width b that extends in a direction transverse to the longitudinal axis L of the sonotrode 16 or in the longitudinal direction of the profile projections 34, corresponding to the diameter d of the connection area 26, which in this case is formed from seven individual wires 40 or conductors. In the illustrated embodiment, the diameter of the individual wires 40 is approximately 0.158 mm, so the diameter of the connection area 26 is approximately 0.5 mm.

[0058] The width b of the special contact zone 51 is in this case chosen to be slightly wider than the diameter of the connection area 26, so that it is ensured that the connection area 26 has contact with the working surface 19 of the sonotrode 16 exclusively in the area of ​​the special contact zone 51.

Claims

1. A device for welding rod-shaped electrical conductors (28, 29), the device comprising a compression space (18) for receiving two connection regions (26, 27) of the conductors (28, 29) to be connected, the connection regions (26, 27) extending in a first axial direction (x-axis), the compression space (18) being defined by a working surface (19) of a sonotrode (16), which transmits ultrasonic vibrations, and a counterface (20) of an anvil (21) at two opposite sides in a second axial direction (z-axis) and by a boundary surface (22) of a slider element (23), which is displaceable in a third axial direction (y-axis), and a boundary surface (24) of a boundary element (25) on two opposite sides in the third axial direction (y-axis), the working surface (19) of the sonotrode having a surface configuration, which differs from a contact zone (30) formed by the remaining working surface (19), in a special contact zone (31, 50, 51, 52), which is a section of the working surface (19) of the sonotrode (16) and serves to subject at least one connection region (26, 27) to ultrasonic vibrations, the contact zone (30) having a surface configuration comprising profile elevations (34) which extend in the third axial direction (y-axis) and at least some of which have a special profile cross-section (36) in the area of the special contact zone (31, 50, 51, 52) which differs from the profile cross-section (37) in the contact zone (30) in that the special profile cross-section (36) has a reduced profile height h compared to the profile cross-section (37), characterized in that the special contact zone is disposed adjacent to the boundary element in such a manner that the special contact zone is formed on a working surface edge (35) of the sonotrode (16) parallel to the boundary element.

2. The device according to claim 1, characterized in that the reduced profile height h is formed by a flattened portion (38) or a rounded portion of a profile peak (39) of the profile cross-section (37).

3. The device according to claim 1 or 2, characterized in that at least in a middle portion extending in the first axial direction (x-axis), the special contact zone (50, 51) has a special contact portion (53, 54, 55) which is symmetric with respect to an axis of symmetry S running parallel to the third axial direction (y-axis).

4. The device according to claim 3, characterized in that the special contact zone (50, 51) is symmetric across its entire length.

5. The device according to claim 3 or 4, characterized in that the axis of symmetry S is formed by a centerline M of the working surface, said centerline M running parallel to the third axial direction (y-axis).

6. The device according to any one of claims 3 to 5, characterized in that the special contact zone (51) is discontinuous.

7. The device according to claim 6, characterized in that at least one profile elevation (34) formed in the area of the axis of symmetry S extends across the entire width B of the working surface (19).

8. The device according to any one of the preceding claims, characterized in that the special contact zone (31, 50, 51, 52) extends across only part of the length of the contact zone (30) in the first axial direction (x-axis).

9. The device according to claim 8, characterized in that the special contact zone (52) is asymmetrical with respect to a centerline M of the working surface (19), said centerline M running parallel to the third axial direction (y-axis).

10. The device according to claim 9, characterized in that the special contact zone (52) is disposed toward a working surface end (56).

11. The device according to any one of the preceding claims, characterized in that the special contact zone (31, 50, 51, 52) has a width of less than 2 mm in the third axial direction (y-axis).

12. The device according to claim 11, characterized in that the special contact zone (31, 50, 51, 52) has a width of less than 1.5 mm in the third axial direction (y-axis).

13. The device according to claim 12, characterized in that the special contact zone (31, 50, 51, 52) has a width of less than 1 mm in the third axial direction.