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DE-102024132566-A1 - Thread-forming and/or hole-forming fastening element, method for inserting a fastening element, vehicle battery and motor vehicle

DE102024132566A1DE 102024132566 A1DE102024132566 A1DE 102024132566A1DE-102024132566-A1

Abstract

The invention relates to a thread-forming and/or hole-forming fastening element 10, comprising an elongated shaft extending between a first and a second shaft end, wherein the elongated shaft has a tip 14, a threaded section 12, a retaining section 18 and a head, wherein the tip 14 is arranged at the first shaft end and is configured to produce a hole by softening material of a workpiece 30, 32, wherein the head is arranged at the second shaft end and has on its outer side a drive area 16 configured to receive a rotary drive force, and the head has an annularly undercut area 44 on one side facing the tip 14, wherein the threaded section 12 is provided between the tip 14 and the head, and wherein the retaining section 18 is provided between the threaded section 12 and the head, and an annular sealing element 20 is arranged around the retaining section 18 and is held captive thereto.

Inventors

  • Rainer Bolch
  • Norbert Hornbostel

Assignees

  • AUDI AKTIENGESELLSCHAFT

Dates

Publication Date
20260513
Application Date
20241108

Claims (10)

  1. Thread-forming and/or hole-forming fastening element (10), comprising: - an elongated shaft extending between a first shaft end and a second shaft end, wherein - the elongated shaft has a tip (14), a threaded section (12), a retaining section (18), and a head, - the tip (14) is located at the first shaft end and is configured to produce a hole by softening material of a workpiece (30, 32), - the head is located at the second shaft end, has on its outer surface a drive area (16) configured to receive a rotary drive force, and the head has an annular undercut area (44) on one side facing the tip (14), - the threaded section (12) is provided between the tip (14) and the head, and - the retaining section (18) is provided between the threaded section (12) and the head; and - an annular sealing element (20) arranged around the retaining section (18) and held securely on the retaining section (18).
  2. Fastening element (10) according to Claim 1 , wherein the sealing element (20) has an outer diameter that is greater than or equal to or up to 1 mm smaller than the maximum outer diameter of the head of the fastening element, and/or has an inner diameter that is smaller than the largest diameter of the threaded section (12) in order to retain the annular sealing element (20) in a position below the head by positive locking.
  3. Fastening element (10) according to Claim 1 or 2 , wherein the sealing element (20) is made of aluminium and/or the sealing element (20) is rotatably held on the shaft.
  4. Fastening element (10) according to one of the preceding claims, wherein the annular undercut area (44) is configured to receive material of the workpiece (30, 32) and of the annular sealing element (20) that has flowed into the workpiece (30, 32) during the insertion of the fastening element (10) and that is generated by a deformation of the annular sealing element (20) during the insertion of the fastening element (10) into the workpiece (30, 32).
  5. Fastening element (10) according to one of the preceding claims, wherein the tip (14) of the elongated shaft comprises a rounded end.
  6. A method for inserting a fastener (10) according to any of the preceding claims, comprising the steps of: - joining an upper workpiece part (30) to a lower workpiece part (32) to form the workpiece (30, 32), - inserting the fastener (10) into an assembly device, - placing the assembly device onto the workpiece (30, 32), - driving the fastener (10) to bring the material of the workpiece (30, 32) into a flowable state at a location of insertion of the fastener (10), and - inserting the fastener (10) into the workpiece (30, 32) at the location of the flowable state, wherein the assembly device is configured to at least partially surround the head of the fastener (10) and to hold down the workpiece (30, 32) during insertion.
  7. Procedure according to Claim 6 , wherein the mounting device is placed on the workpiece (30, 32) by means of a holding force in the range of 100 N and 1500 N, preferably in the range of 100 N to 500 N.
  8. Procedure according to Claim 6 or 7 , wherein the upper workpiece part (30) is a battery cover and/or the lower workpiece part (32) is a frame component of a vehicle battery.
  9. vehicle battery comprising a battery cover having at least one fastening element (10) which is attached by means of the method according to one of the Claims 6 until 8 has been introduced.
  10. motor vehicle, in particular electric vehicle, with the vehicle battery after Claim 9 .

Description

The invention relates to a thread-forming and/or hole-forming fastening element, a method for inserting the fastening element, a vehicle battery and a motor vehicle. It is known to fasten a battery cover to a battery housing using a flow-drilling screw. The cover is coated, for example, with a cathodic dip coating (e-coating) and, for example, in the case of a screw connection with an M5 thread, has an opening (pre-drilled hole) of approximately 8 mm in diameter at the point where the screw is to be inserted. When inserting the screw, it is first positioned centrally in the opening and placed onto the workpiece. A rotation of the screw generates frictional heat, and once the battery housing material has heated sufficiently, the screw is driven into the housing to hold the battery cover in place by the screw head, which rests on the battery cover. This flow-drilling connection method has the advantage that no pre-drilled opening or hole needs to be provided, and no thread needs to be pre-drilled. Furthermore, the flow-drilling screw connection has the advantage that the screw can be loosened again. This distinguishes flow-hole forming screw connections from, for example, rivet connections. When inserting the flow-drilling (thread-forming and/or hole-forming) screw, material from the battery frame is forced upwards (towards the penetrating screw). This can result in the screw being positioned off-center in the opening, even if it is fully tightened. Consequently, the required seal may not be achieved, or may be insufficient. This process therefore poses significant risks regarding sealing. To achieve a seal nonetheless, an additional sealant can be applied over the screw heads, for example, using a polymer. However, this necessitates additional steps to ensure the battery cover is sealed. Furthermore, an additional sealant over the screw head makes it more difficult to loosen the connection again, for example, during maintenance, and to reseal it afterward. Particularly in automotive manufacturing, high production volumes create considerable problems that require a solution. Furthermore, if the flow-drilling screw is positioned off-center relative to the opening, rising material may be forced between the battery cover and the battery frame, thus lifting the battery cover from the battery frame. This can lead to unwanted leakage and the formation of an undesirable volume between the battery cover and the battery frame, potentially making the connected components (the battery cover and the battery frame) susceptible to corrosion. It is also known in the prior art to use screws with a recess or annular undercut in the underside of the fastener head, designed to receive rising material. Using a screw with such a recess allows the flow-drilling screw to be inserted directly into the un-pre-drilled battery cover and the underlying battery frame. This eliminates the step of creating the opening, and screw positioning can be performed with greater tolerances and, in a machine-based process, also more quickly, since the screw does not need to be aligned with the opening. However, more material protrudes upwards (against the direction of screw insertion) (also known as top mushrooming), and the volume of the undercut (also known as axial undercut) should be dimensioned such that the screw head can still rest securely and completely on the top of the battery cover. Since the amount of material protruding upwards can vary slightly with each screw, and the insertion angle can also differ, two basic possibilities arise: - On the one hand, the volume of the undercut may be too large. In this case, the upper mushrooming can be accommodated in the undercut, but in this case, an air volume is usually trapped under the screw head, which can promote corrosion. - On the other hand, the volume of the undercut may be too small. This can lead to the screw head not sitting completely flush with the workpiece surface after final tightening, because the screw tightens too early when screwing into the mushroomed material, thus compromising the tightness of the connection. Furthermore, when using a fastener with an undercut head, it can happen that a screw is not inserted perfectly perpendicularly. Such an angular error can lead to a leak in the screw connection, as the screw head does not sit completely flush against the workpiece surface. Furthermore, the head of the fastening element can damage the paintwork and/or coating of the upper part of the workpiece (the battery cover), which can make the connected workpieces susceptible to corrosion. For example, the printed material reveals this. DE 10 2010 044 887 A1 A connection area between two components, where the first component has an entry side and the second component an exit side, the two components are connected by a joining element with a head and a structured, tapered shaft. A contact surface of the head is adjacent to the entry side of the first component, and the shaft extends