Method for forming a straight wire section into a bent, cross-section-modulated busbar blank and pressing device for this purpose

Abstract

The invention relates to a method for forming a straight wire section (14) into a cross-sectionally modulated busbar blank (20) bent in a bending plane by means of a press device, wherein the straight wire section (14) is first bent in the bending plane to form a bent wire section (14), then arranged in an engraving (12) of a lower die (10) aligned parallel to the bending plane and finally, by means of an upper die (18) positioned perpendicular to the bending plane onto the lower die (10), is cross-sectionally formed at least section by section according to a shape predetermined by the engraving (12) and the upper die (18). The invention is characterized in that the two steps of bending and cross-sectional forming are carried out within a common stroke of the press device. The invention further relates to a pressing device for carrying out such a method.

Description

[0001] The invention relates to a method for forming a straight wire section into a cross-sectionally modulated busbar blank bent in a bending plane by means of a press device, wherein the straight wire section is first bent in the bending plane to form a bent wire section, then arranged in an engraving of a lower die aligned parallel to the bending plane and finally, by means of an upper die positioned perpendicular to the bending plane onto the lower die, is cross-sectionally formed at least section by section according to a shape specified by the engraving and the upper die.

[0002] The invention further relates to a pressing device for forming a straight wire section into a bent, cross-sectionally modulated busbar blank, comprising - a press drive performing a vertical movement, - a lower die with an engraving that is longer than it is wide and - an upper die which is positively coupled to the vertical movement of the press drive and can be positioned perpendicularly to the lower die.

[0003] Such a method and such a pressing device are known from DE 10 2021 201 194 A1.

[0004] High currents flow to power high-performance electric traction motors for motor vehicles. These are typically conducted via so-called busbars. A busbar is essentially a rigid metallic conductor with a relatively large cross-section. The notorious lack of space in automotive engineering means that such busbars often have to have curved and angled shapes. To avoid local current peaks and thus local heating of the busbars, the bending shape and cross-sectional modulation must be very precisely coordinated, which can lead to highly complex designs.

[0005] From the aforementioned generic German patent DE 10 2021 201 194 A1, a method and a pressing tool are known by means of which a bent and cross-sectionally modulated busbar blank can be produced from a straight wire section. The term "busbar blank" is to be understood here as meaning that further, downstream processing steps may be necessary to manufacture a usable busbar, but are not necessarily required. The previously known pressing tool is a multi-station pressing tool which has at least one bending station and one cross-sectional forming station. During a first vertical stroke of the pressing tool, a two-dimensionally bent wire section is produced from a straight wire section of a predetermined length. The straight wire section is bent in a bending plane that is vertical during said processing step.By means of subsequent, further bending steps in a perpendicular direction, the resulting busbar blank can be further formed into a three-dimensionally bent structure. However, in the context of the inventive method or the inventive press device, only bending in a bending plane, i.e., the production of a two-dimensionally bent wire section, is initially relevant. The bending station of the known press tool comprises a multi-part lower die and a similarly multi-part upper die, which are brought into contact with each other in a known manner during a press stroke, so that the wire section is bent without any significant change in cross-section. At the same rate as the press device, the bent wire section is then transferred to a cross-sectional forming station of the same press device. There, it is inserted into the engraving of a lower die, which is aligned parallel to the bending plane.The bent wire section lies in the engraving of the lower die in such a way that its bending plane is aligned parallel to the surface of the lower die. The bent wire section extends further longitudinally than laterally in the bending plane or engraving, but this is merely to be understood as a definition of the "length" or "width" of the bent wire section.

[0006] In a further press stroke, an upper die of the cross-sectional forming station is then moved perpendicularly onto the lower die, thereby flattening at least part of the bent wire section. The resulting shape of the cross-sectionally modulated, bent wire section depends on the shape defined by the engraving and the upper die.

[0007] A disadvantage of the known method and press is the time and design effort involved in transferring the workpiece between the individual stations. This not only leads to additional costs due to time constraints, but can also result in significant scrap or even damage to the tool if the transfer fails.

[0008] The object of the present invention is to provide a cost-effective and safer operating method or a corresponding pressing device.

[0009] This problem is solved in conjunction with the features of the preamble of claim 1 by carrying out the two steps of bending and cross-sectional forming within a common stroke of the press device.

[0010] The problem is further solved in conjunction with the features of the preamble of claim 7 by comprising a plurality of bending blocks arranged in the width direction on both sides of the engraving, which are positively coupled to the vertical movement of the press drive and can be moved towards the engraving by sliding on the surface of the lower die and can be retracted outside the circumference of the lower die.

[0011] Preferred embodiments of the invention are the subject of the dependent patent claims.

[0012] The basic idea of ​​the invention is to perform the two essential forming steps, namely the bending and the cross-sectional forming steps, not simultaneously, but nevertheless within a single press stroke. This is possible with a combination tool featuring appropriate positive guides, as explained in more detail below.

[0013] The invention enables a doubling of the production speed, since the two steps that previously required two machine cycles or press strokes can now be carried out in just one machine cycle or within a single combined press stroke. Furthermore, the transfer of the workpiece between two spatially separated processing stations is eliminated, thus avoiding a corresponding risk of errors.

[0014] In detail, the preferred embodiment of the method according to the invention is carried out by the sequence of the following steps in the order mentioned: - Placing the straight wire section on the lower die in such a way that the straight wire section rests in places on wall areas of the lower die and in places spans areas of the engraving, - parallel to the lower die, feeding bending blocks on both sides to bend the straight wire section and transform it into the bent wire section so that it falls into the engraving when the bending blocks are subsequently retracted, - Retracting the bending blocks outside the lower die circumference and - Positioning an upper die.

[0015] In this embodiment of the inventive method, the lower die thus has a dual function. Firstly, it serves as a support for the straight wire section during the bending step. Secondly, it serves, in a manner known in principle, as an engraved lower die for the cross-sectional forming step. This is made possible in particular by the fact that, unlike in the prior art, the bending plane of the wire section is already oriented parallel to the lower die during the bending step. The straight wire section, which is naturally longer than the bent wire section, can be positioned on the lower die such that at least its ends protrude beyond the engraving and rest on wall areas of the lower die. Additionally, the straight wire section will regularly also rest on wall areas of the lower die that are bypassed by the bent wire section.Bending blocks are then applied to the securely positioned, straight wire section from both sides (in the width direction). These blocks clamp the wire section between them and simultaneously bend it in the bending plane, parallel to the lower die surface. The resulting bent wire section then "floats," held by the bending blocks, above the engraving, to which it is now conformed to the shape insofar as it can be positioned within it. When the bending blocks are retracted, the clamping of the wire section is released, and it falls into the engraving. If, as preferably provided, the bending blocks are then retracted beyond the circumference of the lower die, sufficient space is available for the upper die to be fed in perpendicularly to the lower die.

[0016] Those skilled in the art will understand that the movement of the bending blocks on the one hand and the upper die on the other must be precisely coordinated so that the described steps can be carried out in the described sequence. This can be achieved, for example, by electronically coordinated control of different motors. In the preferred embodiment of the invention, however, the movement of the bending blocks and the movement of the upper die are positively coupled to a vertical movement of a press drive of the press device. This positive coupling can be realized, for example, by means of wedges, cams, levers, and / or springs. While such a mechanical positive coupling may be complex to design, once set up, it is extremely robust and produces reproducible results over long service lives.

[0017] In a further development of the invention, the straight wire section is fixed by means of fixing elements before bending, with the fixing elements being retracted outside the circumference of the lower die when the bending blocks are advanced. For the press device according to the invention, this means that it further comprises a plurality of fixing elements by means of which the straight wire section can be fixed in such a way that it spans sections of the lower die wall and sections of the engraving. In other words, in this embodiment of the invention, the straight wire section is not simply placed on the lower die but is additionally fixed there by means of said fixing elements. For example, these fixing elements can be implemented in the form of clamping jaws that engage at both ends of the straight wire section.At these positions, they do not collide with the bending blocks, which are advanced laterally. The fixing elements serve to securely hold the straight wire section until it is clamped by the bending blocks. From this point onward, i.e., during the actual bending of the wire section, the fixing elements are no longer needed and can be retracted outside the die circumference so as not to obstruct the subsequent cross-sectional forming step. Preferably, the movement of the fixing elements is achieved with the vertical movement of the press drive of the pressing device, in particular by means of wedges, cams, levers, and / or springs.

[0018] Further features and advantages of the invention will become apparent from the following detailed description and the drawings.

[0019] They show: Fig. 1: a first step of an embodiment of the method according to the invention, Fig. 2: a second step of said embodiment of the method according to the invention, Fig. 3: a third step of said embodiment of the method according to the invention, Fig. 4: a fourth step of said embodiment of the method according to the invention, Fig. 5: a fifth step of said embodiment of the method according to the invention, Fig. 6: a sixth step of said embodiment of the method according to the invention, Fig. 7: a first embodiment of a busbar blank produced according to the invention, Fig. 8: a second embodiment of a busbar blank produced according to the invention as well as Fig. 9: a third embodiment of a busbar blank produced according to the invention.

[0020] Identical reference symbols in the figures indicate identical or analogous elements.

[0021] Fig. Figure 1 shows, in a highly schematic form, a lower die 10 of a press device according to the invention. At the same time, it represents Fig. Figure 1 represents a first step of an embodiment of the method according to the invention, namely the provision of an empty lower die 10. The lower die 10 has, in particular, an engraving 12, i.e., a recess which at least partially defines the shape for a subsequent die in the context of Fig. specifies the press or cross-sectional forming step described in section 6.

[0022] In the next, in Fig. In the illustrated process step 2, a straight wire section 14, which has been previously cut to a predetermined length, is placed on the lower die. Specifically, the placement is such that areas of the straight wire section 14 rest on the wall of the lower die 10, while other areas of the straight wire section 14 span the engraving 12. In the illustrated embodiment, in particular, both ends and the central area rest on the wall of the lower die 10.

[0023] In a next, in Fig. In the process step 3 shown, bending blocks 16 are placed on the straight wire section 14 on both sides and parallel to the surface of the lower die 10 in the width direction of the straight wire section 14. Fig. Figure 3 shows the moment when the bending blocks 16 clamp the straight wire section 14 between them, but do not yet perform any bending deformation on it. In special embodiments of the invention, in which the straight wire section 14 is fixed by means of fixing elements not shown in the figures, particularly in the region of its ends, in addition to its support on the lower die 10, said fixing elements can be retracted from this point onward and, in particular, moved outside the circumference of the lower die. Fixing the straight wire section 14 is then no longer necessary thanks to the clamping by the bending blocks.

[0024] Fig. Figure 4 shows a further process step in which the bending blocks 16 are first moved further in order to cause a bending deformation of the wire section 14, and are then moved back again, in particular to outside the lower die circumference.

[0025] This situation is in Fig. Figure 5 shows that by retracting the bending blocks 16, the now bent wire section 14 loses its fixation and falls under the influence of gravity into the engraving 12, into which it now fits due to the bending deformation it has undergone.

[0026] Last, in Fig. In the process step shown in Figure 6, an upper die 18 of a generally known design is positioned perpendicularly onto the lower die 10 to effect a cross-sectional deformation of the bent wire section 14. The resulting shape of the busbar blank 20 depends on the shape of the engraving 12 and the upper die 18. Examples of busbar blanks 20 shaped according to the invention are shown in the Fig. 7 to 9 illustrated.

[0027] The busbar blank according to Fig. Section 7 is pressed flat to a uniform thickness along its entire length. This represents the simplest form of cross-sectional modulation. In the illustrated embodiment, the cross-section is only laterally tapered in the central region.

[0028] In the embodiment of Fig. 8. In the central area, an additional thickening (or a flattening in the adjacent areas) is provided in the vertical direction.

[0029] In the embodiment of Fig. 9 The busbar blank has two flat pressed end areas and an undeformed middle area with the original, round cross-section of the wire blank.

[0030] Naturally, the embodiments discussed in the detailed description and shown in the figures represent only illustrative examples of the present invention. In light of this disclosure, a wide range of variations is available to the person skilled in the art. Reference symbol list 10 Lower die 12 Engraving 14 wire section 16 Bending block 18 Upper gun 20 busbar blanks QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2021 201 194 A1 [0003, 0005]

Claims

[1] Method for forming a straight wire section (14) into a cross-sectionally modulated busbar blank (20) bent in a bending plane by means of a press device, wherein the straight wire section (14) is first bent in the bending plane to form a bent wire section (14), then arranged in an engraving (12) of a lower die (10) aligned parallel to the bending plane and finally, by means of an upper die (18) positioned perpendicular to the bending plane onto the lower die (10), is cross-sectionally formed at least section by section according to a shape specified by the engraving (12) and the upper die (18), characterized by that the two steps of bending and cross-sectional forming are carried out within a common stroke of the press device. [2] Method according to claim 1, characterized by the following steps: - Placing the straight wire section (14) on the lower die (10) such that the straight wire section (14) rests in places on wall areas of the lower die (10) and in places spans areas of the engraving (12), - parallel to the lower die (10), bending blocks (16) are fed on both sides to bend the straight wire section (14) and transform it into the bent wire section (14) so ​​that it falls into the engraving (14) when the bending blocks (16) are retracted, - Retracting the bending blocks (16) outside the lower die circumference and - Inserting an upper die (18). [3] Method according to claim 2, characterized by , that the movement of the bending blocks (16) and the movement of the upper die (18) are positively coupled with a vertical movement of a press drive of the press device. [4] Method according to claim 3, characterized bythat the forced coupling is realized by means of wedges, cams, levers and / or springs. [5] Method according to any of the preceding claims, characterized by , that the straight wire section (14) is fixed by means of fixing elements before bending, wherein the fixing elements are retracted outside the lower die circumference when the bending blocks (16) are brought into position. [6] Method according to claim 5, characterized by , that the movement of the fixing elements is positively coupled to the vertical movement of the press drive of the press device. [7] Pressing device for forming a straight wire section (14) into a bent, cross-sectionally modulated busbar blank (20), comprising - a press drive performing a vertical movement, - a lower die (10) with an engraving (12) that is longer than it is wide and - an upper die (18) which is positively coupled to the vertical movement of the press drive and can be positioned perpendicularly on the lower die (10), characterized by , that furthermore a plurality of bending blocks (16) arranged in the width direction on both sides of the engraving (12) are included, which are positively coupled to the vertical movement of the press drive and can be moved on the surface of the lower die (10) towards the engraving (12) and can be retracted outside the circumference of the lower die. [8] Pressing device according to claim 7, characterized by that the forced coupling is realized by means of wedges, cams, levers and / or springs. [9] Pressing device according to one of claims 7 to 8, characterized by , that furthermore a plurality of fixing elements are included, by means of which the straight wire section (14) can be fixed in such a way that it spans in places wall areas of the lower die (10) and in places areas of the engraving (12). [10] Pressing device according to claim 9, characterized by , that the fixing elements are positively coupled to the vertical movement of the press drive in such a way that they are retracted outside the lower die circumference when the bending blocks (16) are fed in.

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