Fastening element for friction welding and method for friction welding a fastening element onto a planar workpiece

Abstract

An assembly includes a workpiece and a fastening element. The fastening element is configured to drill a hole in the workpiece and allow the fastening element to be friction-welded to the workpiece.

Claims

1. An assembly comprising: a workpiece defining a hole; and a fastening element comprising a head portion including an end face disposed above and facing a surface of the workpiece, a shaft extending from the end face of the head portion and disposed in the hole of the workpiece, and a cutting device disposed at an end of the shaft away from the head portion, wherein the end face of the head portion extends radially from the shaft, a friction weld being formed between the end face of the head portion and the surface of the workpiece to join the fastening element to the workpiece, the head portion being completely disposed outside the hole.

2. The assembly according to claim 1, wherein the fastening element is friction-welded to the workpiece along an annular surface of the head portion surrounding the shaft.

3. The assembly according to claim 1, wherein the workpiece is welded to only the end face of the head portion of the fastening element.

4. The assembly according to claim 1, wherein the shaft is disposed in the hole in the workpiece.

5. The assembly according to claim 1, wherein the workpiece has a top surface that is friction-welded to the head portion and a bottom surface opposing the top surface, the shaft being exposed from the bottom surface of the workpiece.

6. The assembly according to claim 5, wherein the shaft extends beyond the bottom surface of the workpiece.

7. The assembly according to claim 1, wherein the cutting device is disposed at a free end of the shaft.

8. The assembly according to claim 1, wherein the fastening element defines a through bore extending along a central axis of the fastening element.

9. The assembly according to claim 8, wherein the fastening element further includes an internal thread on an inner surface of the through bore.

10. The assembly according to claim 1, wherein the head portion, the shaft, and the cutting device are one piece.

11. An assembly comprising: a workpiece defining a hole; and a fastening element including a head portion, a shaft, and a cutting device attached to an end of the shaft away from the head portion, the head portion being disposed completely above outside the hole of the workpiece and including an end face facing a surface of the workpiece, the shaft extending from the end face of the head portion and disposed in the hole of the workpiece, wherein a friction weld is formed between the end face of the head portion and the surface of the workpiece to join the fastening element to the workpiece.

12. A method for attaching a fastening element to a workpiece, comprising: rotating the fastening element against a surface of the workpiece, the fastening element comprising a head portion including an end face disposed above and facing a surface of the workpiece, a shaft extending from the end face of the head portion, and a cutting device disposed at an end of the shaft away from the head portion, the end face extending radially from the shaft; drilling, by the fastening element, a hole in the workpiece while inserting the shaft of the fastening element into the hole of the workpiece until the end face of the head portion of the fastening element is in contact with the surface of the workpiece; and friction-welding the end face of the head portion to the surface of the workpiece to join the fastening element to the workpiece, the head portion being completely disposed outside the hole.

13. The method according to claim 12, further comprising inserting the shaft into the hole to expose the shaft from another surface of the workpiece opposing the surface that is friction-welded to the head portion.

14. The method according to claim 12, wherein the hole in the workpiece is a through hole.

15. The assembly according to claim 1, wherein the friction weld is disposed completely outside the hole.

Description

DRAWINGS

(1) In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

(2) FIG. 1 shows a schematic sectional view of a fastening element according to the teachings of the present disclosure,

(3) FIG. 2 shows a schematic plan view of a nut head of the fastening element according to FIG. 1,

(4) FIG. 3 shows a sectional view of the fastening element according to FIG. 1 in a first process step of a friction welding procedure according to the teachings of the present disclosure,

(5) FIG. 4 shows a sectional view of the fastening element according to FIG. 1 in a second process step of the friction welding procedure according to the teachings of the present disclosure, and

(6) FIG. 5 shows a sectional view of the fastening element according to FIG. 1 in a third process step of the friction welding procedure according to the teachings of the present disclosure.

(7) The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

(8) The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

(9) FIG. 1 shows a schematic sectional view of a fastening element 1 according to the present disclosure. FIG. 2 shows a plan view of the fastening element 1 according to FIG. 1. A fastening element 1 of this kind may also be referred to as a friction welding nut. This fastening element 1, or this friction welding nut, can be welded onto a workpiece 2 by means of a friction welding procedure, as illustrated in FIGS. 3 to 5.

(10) In the friction welding procedure, the fastening element 1 is pressed against the workpiece 2 and rotated. The resulting friction heat causes the fastening element 1 and/or the workpiece 2 to melt, at least in the region of the contact faces, so that, after the end of the rotary movement and the subsequent cooling and solidification of the melts of both components, a welded connection is established.

(11) The welded-on fastening element 1 provides a possibility for fastening further components to the workpiece 2, which are for example screwed to the workpiece 2 by means of a screw connection with the fastening element. For example, this can be desired in the case of thin-walled sheet-metal parts since the small wall thickness of such parts makes it difficult or impossible to introduce threaded bores.

(12) The fastening element 1 has a nut head 3 and a cutting device 4. An outer contour of the nut head 3 has a key face, for example a hexagonal nut, as shown in the plan view according to FIG. 2. The nut head 3 can be of any size or have any key width. Equally, the outer contour of the nut head 3 can be designed as a square nut or any other known nut shape, or equally may have a cylindrical outer contour.

(13) The nut head 3 has a through-bore 5 which extends along a longitudinal central axis 6 (FIG. 1) of the fastening element 1. The through-bore 5 has an internal thread 7 so that a screw can be screwed into the through-bore 5. The internal thread 7 can be provided either partially or completely along the length of the through-bore 5. In some variations, the internal thread 7 is formed in the through-bore 5 in the region of the nut head 3.

(14) The cutting device 4 is provided on an end side 8 of the nut head 3. A friction welding face 9 is formed on this end side 8. This friction welding face 9 serves to establish the friction-welded connection between the fastening element 1 and the workpiece 2. The friction welding face 9 can be formed either directly by the end side 8 of the nut head 3, or it is possible for a welding component 10, which forms the friction welding face 9, to be provided on the end side 8. The welding component 10 can for example be arranged in the form of a welding ring or annular ring on the end side 8. Providing the welding component 10 makes it possible to use different materials for the nut head 3 and the friction welding face 9. The friction welding face 9 can be designed in the form of a circular ring or a segment on the end side 8, and surrounds the cutting device 4.

(15) The cutting device 4 provided on the end side 8 of the nut head 3 is designed as a cylindrical cutting shaft 11. This cutting shaft 11 extends along the longitudinal central axis 6 from the nut head 3, and has a free end portion 12 at the opposite end from the nut head 3. Multiple cutting elements 13 are arranged at the end portion 12 of the cutting shaft 11. In at least one variation the lateral face of the cutting shaft 11 has a smooth surface. The fastening element 1, or at least the cutting shaft 11, can furthermore be provided with a coating, for example a coating for corrosion protection.

(16) As illustrated in FIG. 1, the cutting shaft 11 is designed as a hollow cylinder. Thus, in some variations the through-bore 5 extends through both the nut head 3 and the hollow-cylindrical cutting shaft 11. In at least one variation the hollow-cylindrical cutting shaft 11 has an internal diameter which corresponds to the internal diameter of the through-bore 5 in the nut head 3. In such a variation the external diameter of the hollow-cylindrical cutting shaft 11 is designed to be smaller than the diameter or key width of the nut head 3.

(17) An end edge 14 is formed on the end portion 12 of the hollow-cylindrical cutting shaft 11. The cutting elements 13 are created or formed on the end edge 14. The cutting elements 13 are arranged along the end edge 14 in the form of a ring or a ring segment, and in some variations designed in the shape of saw teeth. Alternatively, the cutting elements 13 can be designed as cutting segments and provided at a distance from one another on the end edge 14.

(18) By virtue of this configuration, the hollow-cylindrical cutting shaft 11 forms a hole saw, core drill or drill crown. This creates a self-cutting fastening element 1 or a self-cutting friction welding nut. This self-cutting fastening element 1 makes it possible to introduce a drilled hole 15 into the workpiece 2 (i.e., to drill the hole 15 into the workpiece 2) and to friction weld the fastening element 1 to the workpiece 2 in one process step.

(19) The process steps of this combined drilling and friction welding procedure, with the fastening element 1, are illustrated in FIGS. 3 to 5. The fastening element 1 is accommodated by a tool 16 and is placed, with the end edge 14 and the cutting elements 13 provided thereon, against a surface 17 of the workpiece 2, as illustrated schematically in FIG. 3. The tool 16 can be a motor-driven rotary device.

(20) The tool 16 imparts, to the fastening element 1, a rotational movement R about the longitudinal central axis 6, and presses the fastening element 1 against the surface 17 with a force F oriented toward the workpiece 2. Owing to the rotational movement R of the fastening element 1, the cutting elements 13 provided on the end edge 14 execute a rotating cutting motion by means of which the drilled hole 15 is introduced into the workpiece 2.

(21) Once the drilled hole 15 has been introduced into the workpiece 2, the force F moves the fastening element 1 further in the direction of the workpiece 2 until the friction welding face 9 of the end side 8 bears against the surface 17 of the workpiece 2 and a contact face is formed. This is shown in FIG. 4.

(22) Owing to the rotational movement R of the fastening element 1 and the resulting friction heat, the friction welding face 9, or the welding component 10, and/or the surface 17 of the workpiece 2 are/is melted in the region of the contact face. After ending of the rotational movement R and the subsequent cooling and solidification of the melt of the friction welding face 9, or of the welding component 10, and/or of the workpiece 2, a strong friction-welded connection 18 is established between the fastening element 1 and the workpiece 2.

(23) Unless otherwise expressly indicated herein, all numerical values indicating mechanical/thermal properties, compositional percentages, dimensions and/or tolerances, or other characteristics are to be understood as modified by the word about or approximately in describing the scope of the present disclosure. This modification is desired for various reasons including industrial practice, material, manufacturing, and assembly tolerances, and testing capability.

(24) As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean at least one of A, at least one of B, and at least one of C.

(25) The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.