Connecting element, current-collecting device and associated production method

Abstract

A connecting element for at least two energy storage cells, having a metal sheet for the electrical connection of the energy storage cells. The metal sheet has at least two perforations for the uptake in each perforation of at least a part of an energy storage cell. Two lugs provided on the metal sheet project into the perforations.

Claims

1. A connecting element, comprising: at least two metal sheets cohesively joined together for the electrical connection of at least two energy storage cells, wherein the at least two metal sheets have at least two perforations for the uptake in each case of at least a part of an energy storage cell, wherein two lugs provided only on one metal sheet of the at least two metal sheets project into each of the perforations, wherein the two lugs project radially into the perforation facing each other, wherein the perforations are designed in such a way that an air gap is formed between the energy storage cells and the perforations of the connecting element upon connection therewith so that an electrical insulation between the energy storage cells and the connecting element is formed with the air gap when the lugs melt due to a current, and wherein the air gap is formed to have a predetermined width between the energy storage cells and the perforations upon connection therewith, wherein the at least two metal sheets cohesively joined together, for which the at least two perforations thereof are arranged coaxially with the predetermined width of the air gap, wherein at least one metal sheet of the at least two metal sheets has a plurality of recesses for reducing mechanical stresses in the at least two metal sheets, and wherein the at least two metal sheets are composed of different metals, and the plurality of recesses reduce the mechanical stresses caused by a bimetal effect.

2. The connecting element according to claim 1, wherein the lugs are produced in one piece with the one metal sheet of the at least two metal sheets.

3. The connecting element according to claim 1, wherein at least one lug has at least one depression.

4. The connecting element according to claim 3, wherein the lug has a protrusion on a side of the lug that lies opposite to the depression.

5. The connecting element according to claim 1, wherein at least one lug has at least one constriction of its cross section.

6. The connecting element according to claim 1, wherein at least one lug projects into the perforation with the formation of at least two radii.

7. The connecting element according to claim 1, the at least two metal sheets comprise at least a first metal sheet and a second metal sheet, each with the perforation that is arranged coaxial to the perforation of the other, wherein the two lugs that project into the perforation are provided only on the second metal sheet.

8. The connecting element according to claim 1, wherein at least a part of a metal sheet is coated.

9. A current-collecting device comprising at least two energy storage cells and at least one connecting element according to claim 1, wherein the current-collecting device pertains to an entire assembly of a battery pack connected by the at least one connecting element.

10. The current-collecting device according to claim 9, wherein the lugs are produced from the same material as the surface of the energy storage cell or are coated therewith.

11. A method for the production of a current-collecting device according to claim 9, comprising the following steps: introducing the at least one part of the energy storage cells into the perforations and contacting the lugs with the energy storage cells; contacting each of the lugs with a tip of a conductor; and applying an electrical voltage between the conductor tips in order to join at least a part of the lugs to the energy storage cells.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) Additional advantages and details of the invention will be explained below based on exemplary embodiments with reference to the drawings. The drawings are schematic representations and show:

(2) FIG. 1 a perspective excerpt from a connecting element according to the invention;

(3) FIG. 2 a top view onto an excerpt from a current-collecting device according to the invention;

(4) FIG. 3 an excerpt from the current-collecting device according to the invention in a lateral cross section along the cutting line in FIG. 2;

(5) FIG. 4 an excerpt of a current-collecting device according to the invention with floating lugs in a lateral cross section;

(6) FIG. 5 a top view onto an excerpt from a connecting element according to the invention with S-shaped lugs;

(7) FIG. 6 a top view onto an excerpt from a connecting element according to the invention with two constricted lugs; and

(8) FIG. 7 a top view onto an excerpt of a connecting element according to the invention with two separate metal sheets.

DETAILED DESCRIPTION OF THE DRAWING

(9) FIG. 1 shows a perspective excerpt from a connecting element 1 for the electrical connection of energy storage cells 2. The energy storage cells are not shown in FIG. 1 for reasons of clarity.

(10) The connecting element 1 comprises two metal sheets 3, 4, each of which have two perforations 5, 6. The connecting element 1 may comprise, of course, a plurality of perforations 5, 6 in metal sheets 3, 4, for example, depending on the number of energy storage cells 2 to be connected.

(11) The metal sheet 3 is cohesively connected to the metal sheet 4 at the joining site 7. The metal sheets 3, 4 are composed of different metals in this example of embodiment. The metal sheet 3 has lugs 8, which are produced in one piece from the metal sheet 3. The metal sheet 3, and also the metal sheet 4, were produced by punching out. The lugs 8 project into the perforation 5 of the metal sheet 3. According to this exemplary embodiment, the lugs project radially into the perforations 5. The perforations 5, 6 of the connecting element 1 in each case are arranged coaxially. Only two perforations 5, 6 are visible in this case due to the limited excerpt from the connecting element 1 that is shown in FIG. 1.

(12) It is further shown in FIG. 1 that the lugs 8 have a depression 10 on their upper side. The depression 10 is designed for the purpose of accommodating the tips of conductors, by which the lugs 8 are contacted during the production process.

(13) FIG. 2 shows an excerpt onto a current-collecting device 11 in a top view. The current-collecting device 11 in this exemplary embodiment has several energy storage cells 2, which are introduced into the perforations 5 of the connecting element 1 of FIG. 1. In order to produce material equality between the lugs 8 and the tops of the energy storage cells 2, the bottoms of lugs 8, thus the side that is facing the energy storage cells 2, are coated. In particular, nickel-plated steel strip has been found to be suitable here as material for the coating.

(14) It is also shown in FIG. 2 that an air gap 14 is formed between the energy storage cells 2 and the perforations 5. The air gap 14 in this case provides an electrical insulation between the energy storage cells 2 and the perforations 5 of the connecting element 1, thus the metal sheet 3.

(15) FIG. 3 shows a lateral cross section in the direction of the sectioning plane III-III from FIG. 2 through a part of a current-collecting device 15. The current-collecting device 15 comprises the connecting element 1 from FIG. 1 and a plurality of energy storage cells 2. In this partial excerpt, which is shown in FIG. 3, only the region around one energy storage cell 2 is illustrated for reasons of clarity. In this lateral cross section, the lugs 8 that are formed in one piece with the metal sheet 3 and project into the perforations 5, 6, which are arranged coaxial to one another, can be recognized.

(16) The lugs 8 have protrusions 16 on the side lying opposite to the depressions 10. The connecting element 1 is welded to the top of the energy storage cell 2 by means of these protrusions. Probes, which are not shown in greater detail, were introduced into the depressions 10 for this purpose and an electrical voltage was applied between them. Due to the flow of current resulting therefrom, through the lugs 8, over the top of the energy storage cell 2, at least parts of the lugs were melted and welded to the top of the energy storage cell 2. A cohesive connection of the protrusions 16 to the energy storage cell 2 was achieved thereby. This is particularly advantageously produced for the current-collecting device 15 by a material equality between the metal sheet 3 and the energy storage cell 2.

(17) Further, the air gap 14 between the connecting element and the energy storage cell 2 is visible in FIG. 3. The double arrow 17 indicates the width of the air gap 14.

(18) The air gap 14 makes possible an electrical insulation of the energy storage cell 2 from the connecting element 1. In the exemplary embodiment shown in FIG. 3, the air gap 14 is sufficiently large, so that an electrical insulation remains ensured if the lugs 8 melt due to a current that is greater than the maximum admissible current.

(19) The lugs 8 in this case assume an implicit safety backup function. If the current exceeds a maximum admissible limit value, then the lugs 8 heat up due to the electrical resistance to such an extent that they melt and the electrical connection between energy storage cell 2 and connecting element 1 is interrupted. This is only possible, however, as long as the size of the air gap 14 is sufficient. If the air gap 14 is too small, a bridging of the air gap cannot be excluded, even with a molten lug 8. A solution for an air gap 14 that is too narrow is shown in FIG. 4.

(20) FIG. 4 shows a current-collecting device 18 that comprises two metal sheets 3, 4, wherein the metal sheet 3 has lugs 8 that project into the perforation 5. Here, the air gap 14, which is indicated by the double arrow 17, is designed narrower than in the current-collecting device 15 of FIG. 3, for example. In order to ensure an electrical safety backup function of the lugs 8, the latter are designed as a floating fuse. For this purpose, the lugs 8 have an elevation 19, by which they project out from the plane of the metal sheet 3. The elevation 19 is designed in this case as a radius. By an oppositely curved radius 20, the lugs 8 are conducted back into the plane of the metal sheet 3, so as to come into contact with the energy storage cell 2. Upon a melting of lugs 8 due to a current that is too high through the current-collecting device 18, the implicit electrical safety backup function remains ensured.

(21) FIG. 5 shows a top view onto an excerpt from a connecting element 21. In the excerpt, the connecting element has two lugs 8, which project into the perforation 5 with the formation of two radii 22, 23. The lugs 8 are produced here in one piece by punching out from the metal sheet 3. The lugs 8 form a safety fuse due to their S-shaped configuration. The connecting element 21 comprises a single metal sheet that is composed of the same material as that of the energy storage cells 2, in order to obtain a cohesive connection. Of course, the connecting element 21 has a plurality of perforations 5 that are not visible due to the limited excerpt.

(22) FIG. 6 shows a top view onto an excerpt of a connecting element 24. The connecting element 24 has lugs 8 that project into the perforation 5. In this case, only one perforation 5 is illustrated due to the limited excerpt. The lugs 8 have constrictions 25 that reduce the cross section of the lugs 8. Due to this constriction 25, the electrical resistance in the region of the constriction 25 increases. Thus, a type of predetermined breaking point is formed that melts when an admissible current value is exceeded and thus ensures an implicit safety fuse function.

(23) It is also shown in FIG. 6 that the connecting element 24 has recesses 26 that are provided for reducing mechanical stresses in metal sheet 3 of the connecting element 24. The connecting element 24 comprises two metal sheets 3, 4, which are joined to one another and are produced from different metals. In order to avoid or to decompose the mechanical stresses that may be produced by the bimetal effect, the recesses 26 are provided in metal sheet 3.

(24) Of course, it is possible to combine in any way all of the properties and features of the connecting elements or current-collecting devices shown individually in FIGS. 1 to 6. Thus, for example, it is possible to form constrictions 25 with the elevations 19 and also with the formation of radii 22 or 23 in a connecting element 1, 12, 21 or 24 having one metal sheet 3 or a plurality of metal sheets 3, 4, 13, and to provide recesses 26.

(25) FIG. 7 shows a top view onto an excerpt from an alternative embodiment to the embodiments shown in FIGS. 1 to 6. A connecting element 27 that comprises a first metal sheet 28 and a plurality of second metal sheets 29 is illustrated in FIG. 7. The perforations 5 of the second metal sheets 29 are disposed coaxial to the perforations 6 of the first metal sheet 28. In this case, the second metal sheets 29 are formed as circular metal sheets with the perforation 5 that has lugs 8. A form deviating from the spherical shape is also possible, of course. In this case, the shape of the perforations 5, 6 and of the second metal sheets 29 can be adapted to the shape of the energy storage cells 2. Due to the formation of the second metal sheets 29 as individual sheets, the bimetal effect and the mechanical stresses in the connecting element 27 resulting therefrom are clearly reduced.

(26) Even if this is not explicitly illustrated in FIG. 7, it is also possible, of course, to design lugs 8 of the second metal sheets 29 analogously to the embodiments shown in FIGS. 3 to 6. Further, in all of the figures, the number of perforations 5, 6, as well as the number of metal sheets 3, 4, 28, the number of second metal sheets 29, and the dimensioning of the metal sheets 3, 4, 28, 29 are given by way of example, and can, of course, be selected as desired.