Screw element of a ball screw mechanism

Abstract

A screw element of a ball screw mechanism includes a lead screw which, at an axial end, is joined to a rod element using a friction welding process. In order to improve the friction-welded joint, prior to the friction welding process, the lead screw has a circumferential groove on the end face facing the rod element.

Claims

1. A screw element of a ball screw mechanism, comprising a lead screw, which is joined at an axial end to a rod element, wherein: a first end face of the lead screw and a second end face of the rod element are integrally bonded to each other by a friction welding process, and the lead screw prior to performing the friction welding process has an annular groove extending circumferentially on the first end face, a radial outer-most extent of the annular groove arranged radially inwardly of an outer surface of the first end face of the lead screw, and the rod element has an outer-most diameter at its second end face facing toward the lead screw which is less than or equal to an inner diameter of the annular groove, the inner diameter defined by a radial inner-most extent of the annular groove.

2. The screw element as claimed in claim 1, wherein the annular groove has a V-shape in a radial cross section, and wherein a radial thickness of the annular groove increases toward the end face.

3. The screw element as claimed in claim 1, wherein a space of the annular groove existing prior to the friction welding process is at least partly filled with material of the lead screw or with material of the rod element after performing the friction welding process.

4. The screw element as claimed in claim 1, wherein the rod element consists essentially of stainless steel.

5. The screw element as claimed in claim 4, wherein the steel of the rod element has a carbon content of less than 1.2%.

6. The screw element as claimed in claim 1, wherein the lead screw consists essentially of hardened steel.

7. The screw element as claimed in claim 6, wherein the lead screw consists essentially of 16MnCr5.

8. The screw element as claimed in claim 1, wherein it is part of an exhaust gas recirculation system of a motor vehicle.

9. The screw element as claimed in claim 8, wherein the rod element is connected to a valve of the exhaust gas recirculation system and activates it.

10. The screw element as claimed in claim 1, wherein an opening of the annular groove faces the rod element.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The figures present an exemplary embodiment. There are shown:

(2) FIG. 1 a side view of a screw element, comprising a lead screw and a rod element, which is joined to the lead screw by friction welding,

(3) FIG. 2 a side view of the lead screw, shown in partial cross section, and an end segment of the rod element prior to making the friction welded connection, and

(4) FIG. 3 a side view of the screw element, shown in partial cross section, after making the friction welded connection.

DETAILED DESCRIPTION

(5) FIG. 1 shows a screw element 1 of a ball screw mechanism, comprising a lead screw 2, which is joined to a rod element 3 by means of friction welding. The rod element 3 is secured by said friction welding process to an end face 4 of the lead screw 2.

(6) The lead screw 2 comprises on its outer circumference at least one ball groove, in which balls 7 run, as schematically indicated in FIG. 3.

(7) In order for the friction welded connection between the lead screw 2 and the rod element 3 to be stable in the above explained sense, the lead screw 2 has a configuration as represented in FIG. 2 before performing the friction welding process.

(8) Accordingly, an annular groove 5 is machined into the end face 4 of the lead screw 2, said annular groove running in the circumferential direction and having a V-shape in the radial cross section according to one possible embodiment of the proposed solution, as can be seen in FIG. 2. The diameter of the rod element d corresponds substantially to the inner diameter D of the annular groove 5 at the end face 4, as shown in FIG. 2.

(9) The annular groove 5 is preferably worked by a turning process into the lead screw 2.

(10) When performing the friction welding process, the lead screw 2 and the rod element 3 are pressed against each other in the axial direction, while at the same time a relative rotary movement is created between the two components. The friction welding process, which is known in itself, results in the connection shown in FIG. 3.

(11) Accordingly, it can be seen that material of both the lead screw 2 and the rod element 3 which has been melted by the friction welding process goes into the originally existing space of the annular groove 5.

(12) A certain axial region is available for the friction welding process, as indicated by reference number 6 in FIG. 3.

(13) The axial end of the rod element 3 may have a slightly conical region, besides a cylindrical segment, as indicated in FIG. 2.

(14) With the proposed solution, a stable connection can be produced between the rod element 3 and the lead screw 2, resulting from a ductile connection of the materials of the two components. Accordingly, an advantageously durably stable connection is assured between the two components.

(15) The shape of the annular groove 5—a V in the exemplary embodiment—may naturally also have other configurations, which can be used advantageously.

(16) In regard to the dimensioning of the annular groove 5, it should be pointed out that the size relations in FIG. 2 are not drawn true to scale and an advantageous configuration of the dimensions of the geometrical magnitudes is assumed here.

LIST OF REFERENCE NUMBERS

(17) 1 Screw element 2 Lead screw 3 Rod element 4 End face of lead screw 5 Annular groove 6 Possible region available for the friction welding 7 Ball d Diameter of the rod element D Inner diameter of the annular groove