EP3419121B1 - Method for making an electrical connection and an ultrasonic welding system - Google Patents

Description

area

The invention relates to a method for producing an electrical connection and an ultrasonic welding system which is suitable for carrying out the method.

background

In the automotive sector, electrical cables are frequently installed with a stranded conductor consisting of a multiplicity of metal wires, which is surrounded by a jacket of insulating material. In order to be able to install such lines in production effectively and in a time-saving manner, the lines are provided at their ends with electrical contact elements, which are also referred to as "terminals". The contact elements are in particular connected by ultrasonic welding to the electrical conductor of the line. For this purpose suitable ultrasonic welding equipment (in short: "welding system") are known in the art. They usually consist of a sonotrode and an anvil, between which the objects to be welded are positioned and welded together by means of high-frequency vibration under pressure. This method has prevailed particularly in electrical lines having a conductor which is made of stranded strands. When welding the contact element is pressed with a so-called side shifter on the anvil of the welding system. The surface of the anvil is profiled, for example with projecting ribs, to improve the mechanical contact with the contact element and the anvil. On the other side of the contact element of the stranded electrical conductor is pressed by means of the sonotrode on the contact element and set in vibration. The conductor is firmly welded to the contact element.

From the US 6,142,838 For example, an electrical contact element with a connection region for the connection of an electrical conductor and a contact region is known. The electrical conductor is connected by ultrasonic welding to the connection area, which has a surface structure.

The present invention is based on the general object to improve the quality of welded joints between electrical conductors and contact elements.

Summary of the invention

• Erzeugen einer Oberflächenstruktur auf dem Kontaktelement, die an eine Oberflächenstruktur auf einem Amboss einer Ultraschallschweißanlage so angepasst ist, dass der Amboss und das Kontaktelement jeweils eine Oberflächenstruktur, die komplementär zueinander ausgebildet sind, aufweisen;
• Auflegen des Kontaktelementes auf den Amboss der Ultraschallschweißanlage, so dass die Oberflächenstruktur des Kontaktelementes mit der Oberflächenstruktur des Ambosses in Eingriff kommt; und
• Anschweißen des elektrischen Leiters an das Kontaktelement.

To achieve this object, the invention proposes a method for producing an electrical connection by ultrasonic welding between an electrical conductor and a contact element according to a first aspect. The method comprises the following steps:

• Producing a surface structure on the contact element which is adapted to a surface structure on an anvil of an ultrasonic welding system such that the anvil and the contact element each have a surface structure that is complementary to one another;
• Placing the contact element on the anvil of the ultrasonic welding system, so that the surface structure of the contact element engages with the surface structure of the anvil; and
• Welding the electrical conductor to the contact element.

The method of the invention has the advantage that the inter-engaging surface structures on the contact element and the anvil prevent the contact element from vibrating upon welding to an extent that could compromise the quality of the weld. As a result, improved quality of the weld is achieved, especially with aluminum pipes.

According to a second aspect, the invention proposes an ultrasonic welding system with an ultrasonic welding system, which has a sonotrode and an anvil, and with a contact element for an electrical line. The anvil and the contact element each have a surface structure that is complementary to each other. The surface structures improve the mechanical contact between the contact element and the anvil of the ultrasonic welding machine.

In an advantageous embodiment, the anvil has at least one rib with a triangular cross-section. Accordingly, the contact element is provided with as many grooves with a triangular cross section as the anvil has ribs, wherein the included between the flanks of a groove angle is smaller than the included between the edges of a rib angle. This embodiment has the advantage that the ribs rest only along two lines along the grooves, whereby play between anvil and contact element is avoided.

In a comparable embodiment, the locations of the ribs and grooves are reversed, i. the anvil has grooves while the contact element is provided with ribs. But even in this embodiment, the included between the flanks of a groove angle is smaller than the included between the edges of a rib angle.

According to a development of the ultrasonic welding system according to the invention, the surface structures of the anvil and contact elements come into engagement with one another such that a positive connection between the anvil and the contact element is produced.

Due to the positive connection between the anvil and the contact element while on the contact element, an electrical line in the
Ultrasonic welding is achieved, it is achieved that the contact element does not vibrate, whereby an improved quality of the weld, especially in aluminum pipes, is achieved.

Advantageously, an electrical contact element with a connection region for the connection of an electrical conductor by ultrasonic welding and with a contact region in connection with the invention can be used. The terminal region has a surface structure that allows for improved mechanical contact with the anvil of an ultrasonic welding machine.

It is particularly expedient if the surface structure of the electrical contact element is designed to be complementary to a surface structure of an anvil of an ultrasonic welding system. By means of the mutually complementary surface structures, an exclusion between the anvil of the ultrasonic welding system and the contact element is achieved. The positive engagement prevents vibration of the contact element during welding, which could be detrimental to the quality of the weld.

Short description of the drawing

• Fig. 1 eine perspektivische Ansicht eines herkömmlichen Kontaktelementes;
• Fig. 2A einen Amboss einer Ultraschallschweißanlage;
• Fig. 2B eine Profilplatte für den Amboss aus Figur 2; und
• Fig. 3 eine perspektivische Ansicht eines erfindungsgemäßen Kontaktelementes;
• Fig. 4 eine elektrische Leitung, die an das Kontaktelement aus Figur 3 angeschweißt ist; und
• Fig. 5 ein Flussdiagramm zur Veranschaulichung des erfindungsgemäßen Verfahrens.

The invention will be explained in more detail by way of example with reference to embodiments with reference to the accompanying figures. Show it

• Fig. 1 a perspective view of a conventional contact element;
• Fig. 2A an anvil of an ultrasonic welding machine;
• Fig. 2B a profile plate for the anvil FIG. 2 ; and
• Fig. 3 a perspective view of a contact element according to the invention;
• Fig. 4 an electrical line that goes out to the contact element FIG. 3 welded on; and
• Fig. 5 a flowchart illustrating the method according to the invention.

The same or similar elements are provided in the figures with the same or similar reference numerals.

embodiment

FIG. 1 schematically shows a contact element 10 in a perspective view. The contact element 10 is divided into a connection region 11 and a contact region 12. The connection region 11 is formed flat and provided for the connection of an electrical conductor. The contact region 12 has a substantially round cross-section and is intended for connection to electrical components or devices, for example in an automobile. The connection area 11 has two main surfaces, of which in FIG. 1 only the main surface 13 is visible. Both main surfaces have a smooth surface. On the non-visible main surface, an electrical conductor is welded in an ultrasonic welding device, while the main surface 13 is in contact with an anvil of a welding system during the welding process.

FIG. 2A shows in a perspective view from the side an anvil 20 of a welding system. For clarity, a belonging to the welding system sonotrode in FIG. 2A not shown, which serves to generate the vibrations necessary for welding. On the anvil 20, a support surface 21 is visible, on which an electrical contact element 10 is placed and positioned by means of an insertion mask 22. The support surface 21 of the anvil 20 is provided with a surface structure with respect to FIG. 2B will be explained in more detail. The anvil including the surface structure is made in one piece. Furthermore, the welding system on a side slide, not shown, whose function will be explained below.

In an alternative embodiment, the anvil 20 is constructed in two parts and has a main body and a support plate 23 arranged thereon, which in FIG. 2B is shown. In this alternative embodiment, the support plate 23 forms the support surface 21 FIG. 2A , The support plate 23 is provided with a bore 24 which receives a mounting screw for mounting the support plate 23 on the base body of the anvil. The support plate 23 is provided in particular with a surface structure 26, which in the in FIG. 2B illustrated embodiment of ribs 27 is formed, which have a triangular cross-section. The ribs, which are the in FIG. 2A form surface structure are similar to those in FIG. 2B illustrated ribs.

When welding a stripped end of an electrical line is placed on the terminal portion 11 of the contact element 10 and pressed with the sonotrode on the contact element and welded. The side shifter is used during welding to keep the contact element 10 as quiet as possible, so that caused by the vibrations introduced by the sonotrode friction between the contact element and the conductor, whereby the welding between the contact element and the conductor is brought about. In addition, the side shifter limits the movement of the (stranded) wires during welding when welding a stranded stranded conductor.

In practice, during the welding into the initially smooth surface of the connection region, the profile or the surface structure 26 of the anvil 20 is impressed to a certain extent. It happens, however, that a reliable fixation of the contact element is not always guaranteed, especially when welding an aluminum line. The reason is that the contact element 10 begins to oscillate at the beginning of the welding process, when the surface structure 26 of the anvil 20 is not yet impressed in the smooth surface 41. The result is impermissible fluctuations in the quality of the weld.

To remedy this problem, the present invention proposes a FIG. 3 shown improved contact element 30 with a terminal portion 31 and a contact portion 32 before. Unlike the in FIG. 1 Contact element 10 shown is the connection region 31 of the contact element 30 on the in FIG. 3 provided on the upper side with grooves 33 which form a complementary to the surface structure 26 of the anvil 20 surface structure. The contact region 32 corresponds to the contact region 12 of the contact element 10.

At the in FIG. 3 illustrated concrete embodiment, the surface structure is formed by grooves 33 having a triangular cross-section which extend transversely to a longitudinal axis 34 of the contact element 30. In the in FIG. 1 illustrated embodiment, four grooves 33 are shown. In other embodiments, however, more or less grooves 33 may be provided. Moreover, in other embodiments, the grooves 33 are also formed with a different cross-section, for example, with a rectangular cross section or a semicircular cross section. The grooves are different from the illustration in FIG. 1 Also not limited to a direction transverse to the longitudinal axis 34, but may also be parallel to the longitudinal axis 34 or in any other direction. It should also be mentioned that the surface structure can be formed not only by depressions in the connection region 31 of the contact element 30, but also by elevations. Finally, in other exemplary embodiments, it is also possible for the structural elements (grooves or elevations) to also cross over one another, for example, to cross over at a right angle.

The dimensions of the grooves 33 are chosen so that they are complementary to the ribs 27 on the support plate 23. This means in particular that when placing the contact element 30 on the support surface of the anvil 20 of the ultrasonic welding system each one of the ribs 27 comes with a groove 33 into engagement. In this way, a positive connection between the anvil 20 and the contact element 30, which creates a Swinging of the contact element 10 during the welding process largely prevented or at least greatly reduced compared to a conventional contact element 10, which rests on the anvil 20 at the beginning of the welding process with a smooth surface.

The nature of the surface structures does not matter for the realization of the invention. It is crucial that the surface structures are formed so that a positive connection between the contact element and the anvil 20 of the welding system is possible. Concretely, this means, for example, that when the ribs 27 of the platen 23 have a rectangular cross section, the grooves 33 in the contact member 30 also have a rectangular cross section.

In an advantageous exemplary embodiment of the invention, in which the in FIG. 2B shown ribs 27 and in FIG. 3 shown grooves 33, each having a triangular cross-section, it has proved to be advantageous if the included between the flanks of a groove 33 angle is smaller than the included between the flanks of a rib 27 angle. The difference may for example be 0.5 ° to 10 ° and in particular 0.5 ° to 5 °. This embodiment has the advantage that the ribs rest only along two lines along the grooves, whereby play between anvil and contact element is avoided.

For other cross-sections, the geometry of the surface structure is otherwise adjusted to achieve the stated advantage. For example, in ribs having a semicircular cross-section, the diameter of the ribs is made larger than the diameter of the grooves. The difference in diameter is for example between 0.05 mm to 1.0 mm and in particular between 0.05 mm to 0.5 mm.

In the FIG. 4 a welded to the contact element 30 line 40 is shown. The lead has an insulating jacket 41 and a conductor 42 made of a plurality of wires. A stripped end of the Line 40 is welded to the contact element by ultrasonic welding.

The individual steps for producing the ultrasonic welding connection between the conductor 42 and the contact element 30 are shown in a flowchart in FIG FIG. 5 illustrated. First, a surface structure is produced on each contact element 30, which is adapted to a corresponding surface structure 26 on the anvil 20 of the ultrasonic welding system (step 51). In practice, it will be so that a sufficient number of appropriately prepared contact elements 30 is provided. That is, the contact elements 30 are not made individually for each electrical weld, although that is basically possible of course. A contact element 30 is placed on the anvil 20 of the ultrasonic welding machine so that the surface structure of the contact element 30 engages with the surface structure 26 of the anvil 20 (step 52). Then, the electrical conductor 42 to be connected is placed on the connection region 31 of the contact element 30 and then pressed with the sonotrode and vibrated so that a welding of the electrical conductor 42 takes place with the contact element 30. (Step 53)

LIST OF REFERENCE NUMBERS

10

contact element

11

terminal area

12

contact area

13

main area

20

anvil

21

bearing surface

22

Sideshift

23

platen

24

drilling

26

surface structure

27

ribs

30

contact element

31

terminal area

32

contact area

33

grooves

34

longitudinal axis

40

management

41

insulating coat

42

ladder

51-53

steps

Claims (5)

1. Method for producing an electrical connection by ultrasonic welding between an electrical conductor (42) and a contact element (30), the method comprising the steps of:

   - generating a surface structure (33) on the contact element, which is so adapted to a surface structure (26, 27) on an anvil (20) of an ultrasonic welding machine that the anvil (20) and the contact element (30) each comprises a surface structure (26, 27, 33) that is complementary to the other;

   - placing the contact element (30) on the anvil of the ultrasonic welding system, so that the surface structure (33) of the contact element (30) engages with the surface structure (26, 27) of the anvil (20); and

   - welding of the electrical conductor (42) to the contact element (30).
2. Ultrasonic welding system with an ultrasonic welding plant, comprising a sonotrode and an anvil (20) and with a contact element (30) for an electrical line (40), characterized in that the anvil (20) and the contact element (30) each comprise a surface structure (26, 27, 33) that is complementary to the other.
3. Ultrasonic welding system according to claim 2, characterized in that the anvil (20) has at least one rib (27) with a triangular cross-section and wherein the contact element (30) has as many grooves (33) with a triangular cross-section as the anvil (20) has ribs (27), and wherein the angle included between the flanks of a groove (33) is smaller than the angle included between the flanks of a rib (27).
4. Ultrasonic welding system according to claim 2, characterized in that the anvil (20) has at least one groove with a triangular cross-section, and wherein the contact element (30) has as many ribs with a triangular cross-section as the anvil (20) has grooves, and wherein angle included between the flanks of a groove is smaller than the angle included between the flanks of a rib.
5. Ultrasonic welding system according to one of claims 2 to 4, characterized in that the surface structures (26,27; 33) of the anvil (20) and the contact element (30) engage each other to produce a positive connection between the anvil (20) and contact element (30).

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